JP2002023507A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which prevents corona dischargers and a transfer material from coming into contact with each other and prevents the transfer material from being caught by those corona dischargers when a reverse-surface toner image on a transfer material discharging means and an intermediate transfer body is transferred to the reverse surface of the transfer material. SOLUTION: This image forming device is characterized in that a spur member is provided adjacently to the upstream side of a transfer material discharging means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copying in which a charging means, an image writing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier onto a transfer material. The present invention relates to an electrophotographic image forming apparatus such as a printer, a facsimile, and the like, and more particularly to an image forming apparatus that forms a toner image on both surfaces of a transfer material.

[0002]

2. Description of the Related Art Conventionally, in double-sided image formation, an image on one side formed on an image carrier is transferred and fixed onto a transfer material, and this is temporarily stored in a two-sided reversal feeding device, and is again carried out. A method has been adopted in which a transfer material is fed from a two-sided reversing feed device in synchronization with an image formed on a body, and an image on the other surface is transferred and fixed on the transfer material.

As described above, in the double-sided image forming apparatus, as described above, the transfer of the transfer material such as feeding to the double-sided reversing feeder and passing through the fixing device twice is performed. It was low and caused the transfer material to jam or wrinkle.

On the other hand, JP-B-49-37538 and JP-B-54-28740, and JP-A-1-44457.
Japanese Patent Application Laid-Open Nos. 4-214576 and 4-214576 propose a method in which a toner image is formed on both surfaces of a transfer material using an image carrier and an intermediate transfer member, and then fixed once.

Further, the present inventors dispose a plurality of sets of toner image forming means including a charging means, an image writing means, a developing means and the like around a photosensitive drum (image carrier), and place the toner image forming means on the photosensitive drum. The formed superimposed color toner image is once transferred onto a belt-shaped intermediate transfer body at one time, and then a superimposed color toner image is formed again on the photoconductor drum, and the toner image on the photoconductor drum and the intermediate transfer body are formed again. The toner image on the photosensitive drum is transferred as a surface image (surface toner image) onto both surfaces of the transfer material which is fed in time with the toner image of the intermediate transfer member and conveyed by the intermediate transfer member. After transferring the toner image as a backside image (backside toner image), the transfer material is separated from the intermediate transfer member by discharging the transfer material, and the toner image on the transfer material is fixed by a fixing unit to form a double-sided color image. JP-image forming apparatus and an image forming method for forming a (one-pass double-sided image forming method) 9-2584
No. 92 and JP-A-9-258516.

[0006]

However, in an image forming apparatus (one-pass double-sided image forming apparatus) for forming an image on both sides of a transfer material using the belt-like intermediate transfer body as described above, a belt-like intermediate transfer is used. The transfer material conveyed over the body rises, and comes into contact with a transfer material static eliminator using a corona discharger or a corona discharger that transfers the backside toner image on the intermediate transfer body to the backside of the transfer material, and the surface on the transfer material The toner image is disturbed or the transfer material is caught by these corona dischargers,
The problem of jams occurs.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and prevents the transfer material from contacting with a corona discharger when transferring the back surface toner image on the transfer material to the back surface of the transfer material. It is a first object of the present invention to provide an image forming apparatus which prevents a transfer material from being caught by these corona dischargers.

An image forming apparatus for forming an image on both sides of a transfer material using the belt-shaped intermediate transfer member,
In the corona discharger for retransferring the backside toner image on the intermediate transfer member to the backside of the transfer material, a voltage having a polarity opposite to the polarity of the toner used (positive polarity in the description of an embodiment described later) is applied to the corona discharger. The backside toner image on the intermediate transfer body is re-transferred to the backside of the transfer material by applying the voltage, but the distance between the side end of the corona discharger on the outlet side of the transfer material and the intermediate transfer body is short, or the discharge width is small. If the toner spreads, the surface toner image is disturbed by the discharge, and the toner of the negative polarity surface toner image on the transfer material converted into the positive polarity adheres to the side of the corona discharger on the outlet side of the transfer material. However, there arises a problem that the corona discharger becomes dirty.

The present invention also solves the above-mentioned problems, and provides a method for discharging a back-side toner image on an intermediate transfer member to the back side of a transfer material, the discharge of the corona discharger, the contamination of the corona discharger and the surface toner. A second object is to provide an image forming apparatus which prevents image disturbance.

In an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-shaped intermediate transfer member,
If the transfer material to which the toner image is transferred has irregularities or wrinkles, and the adhesion between the belt surface of the intermediate transfer body and the transfer material is not good,
A problem arises in that transfer omission occurs when the front and back toner images are transferred. If the adhesion between the belt surface of the intermediate transfer member and the transfer material is not good due to the unevenness of the belt-like intermediate transfer member or the unevenness and wrinkles of the transfer material for transferring the toner image, transfer omission occurs at the time of transfer. The problem arises. When transferring the toner image of the surface image on the photosensitive drum to the transfer material,
Since the transfer is performed in a state where the transfer material is pressed against the photosensitive drum by the intermediate transfer body, unevenness of the intermediate transfer body and unevenness of the transfer material, wrinkles, etc. are not so much a problem, but the back side image on the intermediate transfer body is When the toner image is transferred to the transfer material, the transfer material is not pressed against the intermediate transfer member, and if there is unevenness or wrinkles on the intermediate transfer member or the transfer material, the transfer loss (the back surface toner image (Transfer loss) occurs. This problem also occurs depending on the type of transfer material.

The present invention also solves the above problems, suppresses unevenness and wrinkles of the transfer material during transfer, improves the adhesion between the transfer material and the belt-shaped intermediate transfer body, and improves the toner on both sides. It is a third object of the present invention to provide an image forming apparatus which prevents transfer omission of an image, particularly transfer omission at the time of transferring a toner image of a back side image.

[0012]

The first object of the present invention is to provide an image bearing member for carrying a toner image formed by a toner image forming means, and transferring the toner image on the image bearing member. A belt-like intermediate transfer body that supports and conveys a transfer material while carrying a toner image; and 1 transfers the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material.
A secondary transfer unit for retransferring the toner image on the intermediate transfer member to the back surface of the transfer material; and a transfer material provided near a position where the transfer material is separated from the intermediate transfer member. An image forming apparatus comprising: a transfer material discharging unit that separates the transfer material from the intermediate transfer body; and a fixing unit that fixes a toner image on the transfer material. An image forming apparatus (first invention) characterized by providing a spur member by
A first image carrier for carrying the toner image formed by the toner image forming means, a second image carrier for carrying the toner image formed by the second toner image forming means, and the first image carrier. The toner image on the image carrier is transferred, and the belt-shaped intermediate transfer member that supports the transferred toner image and supports and conveys the transfer material, and the toner image on the first image carrier is transferred to the intermediate image. First primary transfer means for transferring the toner image on the transfer member, second primary transfer means for transferring the toner image on the second image carrier to the surface of the transfer material, and toner on the intermediate transfer member Secondary transfer means for retransferring an image to the back surface of the transfer material;
A transfer material removing unit that is provided near a position where the transfer material is separated from the intermediate transfer body and separates the transfer material from the intermediate transfer body that removes the charge of the transfer material; and fixes a toner image on the transfer material. An image forming apparatus (second invention), wherein a spur member is provided adjacent to an upstream side of the transfer material charge removing means, and a toner image forming means. An image carrier that carries the transferred toner image, a belt-shaped intermediate transfer body that supports the transferred toner image while transferring the toner image on the image carrier, and Primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer member or the transfer material; and secondary transfer means for retransferring the toner image on the intermediate transfer member to the back surface of the transfer material. , The intermediate transfer member A transfer material removing unit that is provided near a position where the transfer material is separated, separates the transfer material from the intermediate transfer body that removes the charge of the transfer material, and a fixing unit that fixes a toner image on the transfer material. An image forming apparatus comprising: a spur member provided between the secondary transfer unit and the transfer material discharging unit; and a first toner image forming unit. A first image carrier for carrying the formed toner image;
A second image carrier for carrying the toner image formed by the toner image forming means, and a toner image on the first image carrier which is transferred to carry the transferred toner image and a transfer material. Belt-like intermediate transfer member that supports and conveys the toner, first primary transfer means that transfers the toner image on the first image carrier to the intermediate transfer member, and toner on the second image carrier Second primary transfer means for transferring an image to the front surface of the transfer material, secondary transfer means for re-transferring the toner image on the intermediate transfer member to the back surface of the transfer material, and transfer from the intermediate transfer member An image provided near a position where the transfer material is separated, the transfer material removing device configured to separate the transfer material from the intermediate transfer body configured to remove the transfer material, and a fixing device configured to fix a toner image on the transfer material. In the forming apparatus, the secondary transfer unit and the transfer material static elimination An image forming apparatus (fourth invention) characterized by providing a spur member between a step and an image carrier for carrying a toner image formed by toner image forming means; A belt-shaped intermediate transfer member that supports the toner image and transfers the toner image, and that supports and conveys the transfer material; and the toner image on the image carrier is a surface of the intermediate transfer member or the surface of the transfer material. Transfer to 1
A secondary transfer means, and a secondary transfer provided downstream of the primary transfer position of the primary transfer means in the moving direction of the transfer material and retransferring the toner image on the intermediate transfer body to the back surface of the transfer material. And a fixing unit for fixing the toner image on the transfer material, wherein a spur member is provided adjacent to the upstream side of the secondary transfer unit. Invention), and a first image carrier for carrying the toner image formed by the first toner image forming means, and a second image carrying the toner image formed by the second toner image forming means A carrier, a belt-shaped intermediate transfer body on which the toner image on the first image carrier is transferred and which carries the transferred toner image, and supports and conveys a transfer material; Transferring the toner image on the body to the intermediate transfer body A first transfer means, said second primary transfer means for the toner image on the second image bearing member is transferred to the surface of the transfer material, the second by a second primary transfer unit 1
A secondary transfer means provided downstream of the next transfer position in the transfer material moving direction to re-transfer the toner image on the intermediate transfer member to the back surface of the transfer material; and fixing the toner image on the transfer material. The image forming apparatus includes a spur member adjacent to the upstream side of the secondary transfer means.

An image bearing member for carrying the toner image formed by the toner image forming means; a toner image transferred onto the image bearing member; carrying the transferred toner image; and supporting and transporting the transfer material. A belt-shaped intermediate transfer body, a primary transfer unit for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material, and the transfer from a primary transfer position by the primary transfer unit An image provided on the downstream side in the material moving direction and having a secondary transfer unit for retransferring the toner image on the intermediate transfer body to the back surface of the transfer material, and a fixing unit for fixing the toner image on the transfer material In the forming device,
An image forming apparatus (seventh invention), wherein a spur member is provided between the primary transfer position and the secondary transfer means, and a toner image formed by the first toner image forming means is provided. A first image carrier for carrying, a second image carrier for carrying the toner image formed by the second toner image forming means, and the toner image on the first image carrier is transferred and transferred A belt-shaped intermediate transfer member that carries the transferred toner image and supports and conveys a transfer material; and a first primary transfer unit that transfers the toner image on the first image carrier to the intermediate transfer member. A second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material; and a second primary transfer position by the second primary transfer unit. The toner image on the intermediate transfer member is provided downstream of the transfer material In an image forming apparatus having a secondary transfer unit for retransferring to a back surface and a fixing unit for fixing a toner image on the transfer material, a spur is provided between the second primary transfer position and the secondary transfer unit. This is achieved by an image forming apparatus (eighth invention) in which a member is provided.

A second object of the present invention is to provide an image bearing member for carrying a toner image formed by a toner image forming means, a toner image on the image bearing member being transferred, and carrying the transferred toner image. A belt-shaped intermediate transfer member that supports and conveys a transfer material; a primary transfer unit that transfers a toner image on the image carrier to the surface of the intermediate transfer member or the transfer material; An image forming apparatus comprising: a secondary transfer unit for retransferring the toner image onto the back surface of the transfer material; and a fixing unit for fixing the toner image on the transfer material. And a corona discharger provided to face the conductive roller with the intermediate transfer member interposed therebetween. The discharge width of the corona discharger is controlled by the intermediate transfer member and the conductive member. Narrower than contact width with roller An image forming apparatus characterized in that (ninth invention), and a first image bearing member for bearing a toner image formed by the first toner image forming means, second
A second image carrier for carrying the toner image formed by the toner image forming means, and a toner material on which the toner image on the first image carrier is transferred. Belt-like intermediate transfer member that supports and conveys the toner, first primary transfer means that transfers the toner image on the first image carrier to the intermediate transfer member, and toner on the second image carrier Second primary transfer means for transferring an image to the surface of the transfer material, secondary transfer means for re-transferring the toner image on the intermediate transfer member to the back surface of the transfer material, and toner image on the transfer material An image forming apparatus having a fixing unit for fixing
The secondary transfer unit includes a conductive roller that stretches the intermediate transfer member, and a corona discharge device provided to face the conductive roller with the intermediate transfer member interposed therebetween. An image forming apparatus (tenth aspect) having a width smaller than a contact width between the intermediate transfer member and the conductive roller, and a toner image forming unit for carrying the toner image formed by the toner image forming unit An image carrier, a belt-shaped intermediate transfer body on which the toner image on the image carrier is transferred and which carries the transferred toner image, and supports and conveys a transfer material; and a toner image on the image carrier. Primary transfer means for transferring the toner image onto the intermediate transfer body or the surface of the transfer material, secondary transfer means for retransferring the toner image on the intermediate transfer body to the back surface of the transfer material, and toner on the transfer material Fixing means for fixing the image In the image forming apparatus, the secondary transfer unit is provided so as to be opposed to the conductive roller via the intermediate transfer member, and a discharge electrode and a shield member. When the closest distance between the discharge electrode and the shield member is d1 (mm) and the closest distance between the discharge electrode and the intermediate transfer member is d2 (mm), d1> d2 And the width of the intermediate transfer member in a region surrounded by an imaginary circle having a radius d1 (mm) centered on the discharge portion of the discharge electrode is determined by the contact width between the intermediate transfer member and the conductive roller. An eleventh aspect of the present invention, a first image bearing member for bearing a toner image formed by a first toner image forming means, and a second toner image forming device Formed by means A second image carrier for carrying the toner image, and a belt-shaped intermediate transfer for transferring the toner image on the first image carrier, carrying the transferred toner image, and supporting and transporting the transfer material Body, first primary transfer means for transferring the toner image on the first image carrier to the intermediate transfer body, and transfer of the toner image on the second image carrier to the surface of the transfer material An image having: a second primary transfer unit for performing transfer; a secondary transfer unit for retransferring the toner image on the intermediate transfer member to the back surface of the transfer material; and a fixing unit for fixing the toner image on the transfer material. In the forming device,
The secondary transfer means, a conductive roller that stretches the intermediate transfer member, a corona discharge device that is provided to face the conductive roller via the intermediate transfer member, and has a discharge electrode and a shield member. When the closest distance between the discharge electrode and the shield member is d1 (mm) and the closest distance between the discharge electrode and the intermediate transfer member is d2 (mm),
d1> d2, and the width of the intermediate transfer member in a region surrounded by an imaginary circle having a radius d1 (mm) centered on the discharge portion of the discharge electrode is defined as the width of the intermediate transfer member and the conductive roller This is achieved by an image forming apparatus (twelfth invention) characterized in that the width is smaller than the contact width.

A third object of the present invention is to provide an image carrier for carrying a toner image formed by a toner image forming means, a toner image on the image carrier being transferred, and carrying the transferred toner image. A belt-shaped intermediate transfer member that supports and conveys a transfer material; a primary transfer unit that transfers a toner image on the image carrier to the surface of the intermediate transfer member or the transfer material; Secondary transfer means for re-transferring the toner image to the back surface of the transfer material; and transferring the toner image from the intermediate transfer body provided near a position where the transfer material is separated from the intermediate transfer body, and for removing the charge of the transfer material. In an image forming apparatus having a transfer material discharging unit for separating a material and a fixing unit for fixing a toner image on the transfer material, a transfer pressure at the time of transferring a toner image from the image carrier to the intermediate transfer member is set to P1.
(N / cm), the transfer pressure when transferring the toner image from the image carrier to the transfer material is P2 (N / cm).
1 <P2.
Invention), and an image carrier that carries the toner image formed by the toner image forming means, and the toner image transferred onto the image carrier, carrying the transferred toner image, and the transfer material A belt-shaped intermediate transfer body for supporting and conveying, a primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material, and a transfer of the toner image on the intermediate transfer body A secondary transfer means for re-transferring to the back surface of the material, and a transfer material provided near a position for separating the transfer material from the intermediate transfer body and separating the transfer material from the intermediate transfer body for removing the charge of the transfer material In an image forming apparatus having a static elimination unit and a fixing unit for fixing a toner image on the transfer material, a transfer pressure at the time of transfer from the image carrier to a central portion of the transfer material is P2 (N / cm). Transfer from carrier to transfer material tip The transfer pressure at P3 (N / cm)
Where P2> P3, an image forming apparatus (a fourteenth invention), and a first image carrier for carrying a toner image formed by the first toner image forming means. A second image carrier that carries the toner image formed by the second toner image forming unit, and a toner image on the first image carrier that is transferred and carries the transferred toner image; A belt-shaped intermediate transfer member that supports and conveys a transfer material; a first primary transfer unit that transfers a toner image on the first image carrier to the intermediate transfer member; A second primary transfer means for transferring the toner image on the surface of the transfer material, a secondary transfer means for retransferring the toner image on the intermediate transfer body to the back surface of the transfer material, The transfer material is provided near the position where the transfer material is separated, and before the transfer material is neutralized. A transfer material discharging means for separating the transfer material from the intermediate transfer member, in an image forming apparatus having a fixing unit for fixing the toner image on the transfer material, wherein the first
The transfer pressure at the time of transferring the toner image by the primary transfer means is P1
(N / cm), when the transfer pressure at the time of transferring the toner image by the second primary transfer unit is P2 (N / cm), P1
<P2, an image forming apparatus (fifteenth invention), a first image carrier for carrying a toner image formed by a first toner image forming unit, and a second toner image A second image carrier for carrying the toner image formed by the forming means, and the toner image on the first image carrier is transferred to carry the transferred toner image and support and transport the transfer material A belt-like intermediate transfer member, a first primary transfer means for transferring the toner image on the first image carrier to the intermediate transfer member, and a toner image on the second image carrier. A second primary transfer unit that transfers the toner image on the front surface of the transfer material, a secondary transfer unit that retransfers the toner image on the intermediate transfer member to the back surface of the transfer material, and separates the transfer material from the intermediate transfer member From the intermediate transfer member that is provided in the vicinity of the In an image forming apparatus having a transfer material discharging unit that separates the transfer material and a fixing unit that fixes a toner image on the transfer material, the image forming apparatus may include a transfer unit that transfers the toner image to the transfer material center by the second primary transfer unit. Transfer pressure to P2 (N / c
m), when the transfer pressure at the time of transfer to the leading end of the transfer material by the second primary transfer means is P3 (N / cm), P2
> P3 is achieved by an image forming apparatus (a sixteenth invention).

[0016]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Further, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning or technical scope of the terms of the present invention. In the following description of the embodiment, the surface of the transfer material supported and conveyed by the intermediate transfer member, the surface on the side facing the image carrier is the front surface, and the other surface, that is, the surface on the side facing the intermediate transfer member is the back surface. That is, an image transferred to the front surface of the transfer material is called a front image, and an image transferred to the back surface of the transfer material is called a back image.

First, claims 1 to 3, claim 7 to 9, claim 13 to 15, claim 19 to 21, claim 25 or 26, claim 29 to 31, of the present invention.
The image forming process and each mechanism of the image forming apparatus according to the first example, which are common to claims 35 to 40 and claims 41 to 43, will be described with reference to FIGS. FIG. 1 is a perspective view of a first embodiment of the present invention.
To 9, claim 13 to 15, claim 19 to 2
1. Cross-sectional structure of a color image forming apparatus showing an embodiment of a first example of an image forming apparatus common to claims 25, 26, 29 to 31, 35 to 40, and 41 to 43 FIG. 2 is a side sectional view of the image carrier of FIG. 1, and FIG. 3 is a diagram showing a toner image forming state in the image forming apparatus of FIG. 1, and FIG.
FIG. 3B is a diagram illustrating a toner image formation state when the back surface image formed on the image carrier is transferred onto a belt-shaped intermediate transfer member. FIG. 3B is a diagram illustrating the back surface image on the belt-shaped intermediate transfer member. FIG. 3C is a diagram illustrating a toner image forming state when a surface image is formed on an image carrier in synchronization with the image forming apparatus, and FIG. 3C is a diagram illustrating double-sided image formation on a transfer material.

In FIG. 1, 10 is a photosensitive drum as an image carrier, 11 is a scorotron charger as a charging unit for each color, 12 is an exposure optical system as an image writing unit for each color, and 13 is an exposure optical system for each color. A transfer device as a belt-like intermediate transfer member; and 14c, a primary transfer device for transferring the toner image on the image carrier onto the surface of the belt-like intermediate transfer member and the transfer material. 14g is a secondary transfer device which is a secondary transfer means for retransferring the toner image on the belt-shaped intermediate transfer member to the back surface of the transfer material.
14m is a static eliminator as a static elimination means, 150 is a paper charger as a transfer material electrification means, 14h is a transfer material static eliminator as a transfer material static elimination means, 160 is a separation claw 210 as a nail member and a spur 162 as a spur member. And a fixing device 17 serving as a fixing unit.

The photosensitive drum 10, which is an image carrier, has a transparent conductive layer, a
A photosensitive layer such as an Si layer or an organic photosensitive layer (OPC), which is rotated at a linear speed of 80 to 400 mm / sec in a clockwise direction indicated by an arrow in FIG. Is done.

The photosensitive drum 10, as shown in FIG.
Flange members 10A and 10 at both ends for engaging and fixing it
The photoconductor driving gear G integrated with the flange member 10B is rotatably supported by bearings B1 and B2 fitted in the main body 0B and supported by the photoconductor drum shaft 30 erected and fixed to the apparatus main body. The drive gear is rotated at a constant speed in a predetermined direction by being driven by being engaged with a drive gear (not shown) on the side.

The toner image forming means for forming a toner image on the image carrier is a scorotron charger 11, which is a charging means.
An exposure optical system 12 serving as an image writing unit and a developing unit 13 serving as a developing unit. These units constitute an image of each color of yellow (Y), magenta (M), cyan (C), and black (K). Four sets are provided for the forming process, and are arranged in the order of Y, M, C, and K with respect to the rotation direction of the photosensitive drum 10 indicated by the arrow in FIG.

The scorotron charger 11, which is a charging means for each color, has a control grid maintained at a predetermined potential and a discharge electrode 11a composed of, for example, a sawtooth electrode. And installed
The charging operation is performed by corona discharge having the same polarity as the toner (the polarity of the toner used in this embodiment is set to minus polarity, and the charging by the scorotron charger 11 serving as a charging unit in this embodiment is performed negatively). 10 is given a uniform potential. As the discharge electrode 11a, a wire electrode or a needle electrode may be used.

Exposure optical system 1 as image writing means for each color
2 indicates that the exposure position on the photosensitive drum 10 is the photosensitive drum 1 with respect to the scorotron charger 11 for each color described above.
It is arranged inside the photoconductor drum 10 so as to be located on the downstream side in the rotation direction of 0. As shown in FIG. 2, each exposure optical system 12 includes a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light (image writing light) arranged in the main scanning direction in parallel with the drum axis 30. Linear exposure elements 12a arranged in an array, and a light converging light transmitter (trade name: Selfoc lens array) 12b as an imaging element
And a lens holder 12c that holds the SELFOC lens array 12b, and is attached to the exposure optical system holding member 20. A transfer simultaneous exposure unit 12d and a uniform exposure unit 12e are attached to the exposure optical system holding member 20 in addition to the exposure optical system 12 for each color. Is done. The exposure optical system 12 for each color writes an image on the photosensitive layer of the photosensitive drum 10 from the back surface in accordance with the image data of each color read by a separate image reading device and stored in the memory. An electrostatic latent image is formed. As the exposure element 12a, besides LED, FL (phosphor emission),
It is also possible to use an array of a plurality of light emitting elements such as EL (electroluminescence) and PL (plasma discharge). The emission wavelength of the light emitting element for the image exposure light (image writing light) is generally in the range of 780 to 900 nm, which is high in transmittance for the Y, M, and C toners. Since it is a method of writing an image from the beginning, a wavelength of 400 to 780 nm shorter than this, which does not have sufficient transparency to the color toner, may be used.
Further, since 80% or more of the image exposure light is absorbed by the photosensitive layer of the photosensitive drum 10, the influence of the reflection and absorption by the color toner on the surface of the photosensitive drum 10 can be neglected. Generally, the development order of the color toner is the toner image or the developing device 1
The order of Y, M, C, and K is preferable from the relationship of color mixture to 3.
In FIG. 2, WA is a light emitting element (LE) for image exposure light.
D).

The developing device 13 as a developing means for each color keeps a predetermined gap with respect to the peripheral surface of the photosensitive drum 10 and rotates at a developing position in the forward direction with respect to the rotation direction of the photosensitive drum 10. The developing casing 13b includes a cylindrical nonmagnetic stainless steel or aluminum material having a diameter of 5 to 1 mm and an outer diameter of 15 to 25 mm, and a developing casing 13b. , Magenta (M), cyan (C) and black (K) one-component or two-component developers. The developing sleeves 13a of the respective developing devices 13 are separated from the photosensitive drum 10 with a predetermined gap, for example, 100 to 500 μm by an abutting roller (not shown). 10 is kept in non-contact with the developing sleeve 13a, and by applying a developing bias in which a DC voltage (in this embodiment, the same polarity as the toner polarity used and a minus polarity) is superimposed on an AC voltage to the developing sleeve 13a, Contact reversal development is performed to form a toner image on the photosensitive drum 10.

Intermediate transfer bell which is a belt-shaped intermediate transfer member
G preferably has a volume resistivity of 10⁹Ω · cm or less
Above, 10¹²Less than Ω · cm, surface resistance is 10⁹-10¹²Ω
/ Cm ^TwoAnd the surface resistance (Ω / cm^Two) Is the volume
Endless bell with a value of 1 to 100 times the resistivity (Ω · cm)
Are modified polyimide, thermosetting polyimide,
Ethylene-tetrafluoroethylene copolymer
Engineering of vinylidene chloride, nylon alloy, etc.
0.1 to 1.0 m thickness of conductive material dispersed in plastic
m on the outside of a semiconductive film substrate, preferably a toner
Fluorine core having a thickness of 5 to 50 μm as a filming preventing layer
Seamless belt with two layers
You. In addition to the base of the intermediate transfer belt 14a,
Disperse conductive material in silicon rubber or urethane rubber
Use a semi-conductive rubber belt with a thickness of 0.5 to 2.0 mm
You can also. Each of the intermediate transfer belts 14a
Drive roller 14 as a roller member for stretching the intermediate transfer member
d, the secondary transfer facing roller 14j, the driven roller 14e,
Stretched between the id roller 14f and the tension roller 14i.
And rotated counterclockwise as indicated by the arrow in FIG. guide
Roller 14f, driven roller 14e, secondary transfer facing roller
14j and the drive roller 14d are rotated at a fixed position,
The transfer roller 14i is moved by the elasticity of a spring (not shown).
It is movably supported and rotated. Not-shown photoconductor drive mode
The drive roller 14d is rotated by the drive from the motor,
The intermediate transfer belt 14a is driven and rotated. Intermediate transfer
Due to the rotation of the belt 14a, the secondary transfer facing roller 14j,
Driven roller 14e, guide roller 14f and tension
The roller 14i is driven to rotate. Intermediate transfer during rotation
Belt slack of belt 14a causes tension roller 14i
I am more nervous. Intermediate transfer belt 14a is driven roller 1
The recording paper P as a transfer material is supplied to a position where
And is conveyed by the intermediate transfer belt 14a. Drive
Setting of the intermediate transfer belt 14a stretched around the moving roller 14d
The intermediate transfer bell is formed at the curvature portion KT at the end of the
The recording paper P is separated from the sheet 14a.

A primary transfer roller 14c, which is a primary transfer means for transferring a toner image on an image carrier to a belt-shaped intermediate transfer member or a surface of a transfer material, using a contact-type transfer roller member, is used. The intermediate transfer belt 14a is provided so as to face the photosensitive drum 10 for each color with the intermediate transfer belt 14a interposed therebetween, and to be in contact with (contact with) the intermediate transfer belt 14a. None). A DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to the primary transfer roller 14c.
The toner image on the photosensitive drum 10 is transferred to the intermediate transfer belt 14a.
The image is transferred onto the upper surface or the surface of the recording paper P as a transfer material. It is also possible to use a corona discharger as the primary transfer means.

A secondary transfer device 1 as a secondary transfer means for retransferring the toner image on the belt-shaped intermediate transfer member to the back surface of the transfer material.
4g is constituted by a corona discharger, and the primary transfer roller 1
4c and the driving roller 14d, the intermediate transfer belt 14
a, a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to record a toner image on the intermediate transfer belt 14a. The image is transferred to the back surface of the paper P.

The static eliminator 14m, which is a static eliminator, is constituted by a corona discharger, and is provided downstream of the primary transfer roller 14c with respect to the moving direction of the intermediate transfer belt 14a in parallel with the primary transfer roller 14c. AC voltage is applied and 1
The charge of the intermediate transfer belt 14a charged by the voltage application of the next transfer roller 14c is eliminated.

The paper charger 150, which is a transfer material charging means, is preferably constituted by a corona discharger, is provided to face a driven roller 14e, which is grounded across the intermediate transfer belt 14a, and has the same polarity as the toner (this embodiment). (In the embodiment, a negative polarity) is applied, and the recording paper P is charged and attracted to the intermediate transfer belt 14a. As the transfer material charging means, in addition to the corona discharger, it is also possible to use a sawtooth electrode, a brush-like or roller-like charger capable of contacting and releasing the contact with the intermediate transfer belt 14a, and the like.

Transfer material static eliminator 14h as transfer material static elimination means
Is constituted by a corona discharger, and the intermediate transfer belt 14a
Of the recording paper P at the end of the fixing device 17 side of the intermediate transfer belt 14
A recording paper conveyed by the intermediate transfer belt 14a is provided in the vicinity of a position where the recording paper is conveyed by the intermediate transfer belt 14a. P is neutralized and separated from the intermediate transfer belt 14a.

The transport section 160 has a separation claw 210 as a transfer material separation assisting means and a spur 162 as a spur member.
The intermediate transfer belt 14a is provided between the fixing device 17 and a curvature portion KT at the end of the intermediate transfer belt 14a on the fixing device 17 side. Transport unit 160
The intermediate transfer belt 14 is heated by the heat from the fixing device 17.
a, the toner image carried on the intermediate transfer belt 14a becomes less likely to be transferred due to fusion, and the toner is prevented from being fixed on the intermediate transfer belt 14a.

The separation claw 210, which is a transfer material separation assisting means, is close to the curvature portion KT of the intermediate transfer belt 14a, and has a predetermined distance from the intermediate transfer belt 14a, preferably 0.1 to 2.0.
When the recording paper P is separated from the intermediate transfer belt 14a, the recording paper P is bent toward the intermediate transfer belt 14a to be conveyed when the recording paper P is separated from the intermediate transfer belt 14a. To assist the curvature separation of the recording paper P.

The spur 162, which is a spur member, is made of an insulating resin material such as polyacetal or polyamide, has a plurality of projections 162a on its peripheral surface, and is provided rotatably about a rotation support shaft 165. The spur 162 guides the back side of the recording sheet P to convey the recording sheet P, prevents the back side toner image of the recording sheet P having the toner image on both sides from being disturbed, and also supplies the recording sheet P to the fixing device 17. The recording paper P is stably conveyed to the fixing device 17 while keeping the entering direction constant.

The separation claw 210 and the spur 162 are disposed on the side opposite to the photosensitive drum 10 with respect to the transfer material conveying surface on the intermediate transfer belt 14a or its extension surface.
It is also possible to provide spurs 162 as spur members on both sides of the transfer material conveying surface or an extension surface thereof.

A fixing device 17 serving as a fixing unit includes a first fixing roller 17a having a heater therein and a second fixing roller 1a.
7b, and by applying heat and pressure while nipping and transporting the recording paper P in a nip portion T between the first fixing roller 17a and the second fixing roller 17b. Then, the toner image on the recording paper P is fixed.

Next, the image forming process will be described. The photosensitive drum 10 is rotated clockwise as indicated by an arrow in FIG. 1 by the start of a photosensitive member drive motor (not shown) at the start of image recording, and at the same time, the yellow (Y) scorotron charger 1
The application of the potential to the photosensitive drum 10 is started by the charging operation of 1.

After the photosensitive drum 10 is applied with a potential, the Y exposure optical system 12 starts image writing by the first color signal, that is, an electric signal corresponding to the Y image data. An electrostatic latent image corresponding to the Y image of the original image is formed on the front surface.

The latent image is reversal-developed in a non-contact state by the Y developing device 13 to form a yellow (Y) toner image on the photosensitive drum 10.

Next, a potential is applied to the photosensitive drum 10 from above the Y toner image by the charging action of the magenta (M) scorotron charger 11, and the second color signal, that is, the M color signal, is applied by the M exposure optical system 12. Image writing is performed by an electric signal corresponding to the image data, and the magenta (M) toner image is superimposed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13. It is formed.

By the same process, the cyan (C) toner image corresponding to the third color signal is further superimposed by the cyan (C) scorotron charger 11, the exposure optical system 12 of C, and the developing device 13 of C. The black (K) toner image corresponding to the fourth color signal is sequentially superimposed thereon by a black (K) scorotron charger 11, an exposure optical system 12 for K, and a developing device 13 for K. A superimposed color toner image of four colors of yellow (Y), magenta (M), cyan (C) and black (K) is formed on the peripheral surface within one rotation of the photosensitive drum 10. .

These Y, M, C and K exposure optical systems 12
Image writing on the photosensitive layer of the photosensitive drum 10 is performed from the inside of the drum through the above-described translucent substrate. Therefore, the writing of the images corresponding to the second, third and fourth color signals is performed without any influence from the previously formed toner image, and is equivalent to the image corresponding to the first color signal. Can be formed.

The superimposed color toner image (backside toner image), which is the backside image formed on the photosensitive drum 10 serving as the image carrier by the above-described image forming process, is transferred to the transfer area (unsigned) of the primary transfer roller 14c. 3), the image is collectively transferred onto an intermediate transfer belt 14a, which is a belt-shaped intermediate transfer member, by a primary transfer roller 14c (FIG. 3).
(A)). At this time, uniform exposure may be performed by the simultaneous transfer exposure device 12d provided inside the photosensitive drum 10 so that good transfer is performed. The charge on the intermediate transfer belt 14a charged by the primary transfer roller 14c is removed by a charge remover 14m serving as an intermediate transfer member discharging means.

The toner remaining on the peripheral surface of the photoconductive drum 10 after the transfer is subjected to static elimination by the photoconductive drum AC static eliminator 16, and then the rotation direction of the photoconductive drum 10 and the transfer area of the primary transfer roller 14c. Photoreceptor cleaning device 1 which is an image carrier cleaning means provided downstream of (no symbol)
The photosensitive member is cleaned by a photosensitive member cleaning blade 19a which comes in contact with the photosensitive member 10 and is made of a rubber material which contacts the photosensitive member drum 10. The toner cleaned by the photoconductor cleaning blade 19a is collected by a screw 19b into a not-shown waste toner container. In addition, the history of the photosensitive drum 10 in the previous image formation on the peripheral surface of the photosensitive drum 10 is eliminated by, for example, exposure by the uniform exposure device 12e before charging using a light emitting diode.

After the superimposed color toner image (backside toner image) serving as the backside image is formed on the intermediate transfer belt 14a as described above, the color image forming process is performed on the photosensitive drum 10 in the same manner as described above. As a result, a superimposed color toner image (surface toner image), which subsequently becomes a surface image, is formed (FIG. 3B). At this time, the image data is changed so that the front surface image formed on the photoconductor drum 10 becomes a mirror image with respect to the rear surface toner image formed on the photoconductor drum 10.

With the formation of the surface toner image on the photosensitive drum 10, recording paper P, which is a transfer material, is sent out by a feed roller 15a from a paper feed cassette 15 which is a transfer material storage means, and a transfer material feed means is provided. Is transported to the timing roller 15b as a color toner image (surface toner image) of the surface image formed on the photosensitive drum 10 by the driving of the timing roller 15b, and the intermediate transfer belt 1
The image is fed to the transfer area (no symbol) of the primary transfer roller 14c in synchronization with the color toner image of the back side image (rear side toner image) carried on 4a. At this time, the fed recording paper P is charged to the same polarity as the toner by a paper charger 150 which is a transfer material charging means provided on the front surface side of the recording paper P, and is attracted to the intermediate transfer belt 14a to be charged to the primary transfer belt. The sheet is conveyed to a transfer area (no reference numeral) of the transfer roller 14c. By charging the paper to the same polarity as the toner, the intermediate transfer belt 1 is charged.
This prevents the toner image on the photosensitive drum 4a and the toner image on the photosensitive drum 10 from being attracted to each other, thereby preventing the toner image from being disturbed.

In the transfer area (no symbol) of the primary transfer roller 14c, a voltage of a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied by the primary transfer roller 14c. The color toner images (surface toner images) are collectively transferred to the surface of the recording paper P. At this time, the color toner image (backside toner image) of the backside image on the intermediate transfer belt 14a is present on the intermediate transfer belt 14a without being transferred to the recording paper P. At this time, a transfer simultaneous exposure unit 12d using, for example, a light emitting diode is provided inside the photosensitive drum 10 to face a transfer area (no reference numeral) of the primary transfer roller 14c so that good transfer is performed. May be performed.
The charge on the intermediate transfer belt 14a charged by the primary transfer roller 14c is removed by a charge remover 14m serving as an intermediate transfer member discharging means.

The recording paper P having the surface transferred with the color toner image is conveyed to a secondary transfer unit 14g to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. By 14g, the color toner image (backside toner image) of the backside image on the peripheral surface of the intermediate transfer belt 14a is collectively retransferred to the backside of the recording paper P (FIG. 3C).

The recording paper P on which the color toner images are formed on both sides is provided with a curvature of the curvature portion KT of the intermediate transfer belt 14a and a transfer material static eliminator 14h as a transfer material static eliminator provided at an end of the intermediate transfer belt 14a. Of the intermediate transfer belt 14a and the separation claw 210 provided on the conveyance unit 160 at a predetermined interval from the intermediate transfer belt 14a.
From the nip portion T between the first fixing roller 17a and the second fixing roller 17b, and is conveyed to the fixing device 17 as a fixing unit through a spur 162 provided in the conveying portion 160. By applying heat and pressure in the portion T, the toner images on the front and back sides of the recording paper P are fixed, and a front surface image of the recording paper P and a back surface image of the rear surface are formed. The recording paper P on which double-sided image recording has been performed is sent upside down, and is discharged by a discharge roller 18 to a tray outside the apparatus.

The toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is transferred to an intermediate transfer member cleaning device 190 which is an intermediate transfer member cleaning means provided opposite to the guide roller 14f with the intermediate transfer belt 14a interposed therebetween. ,
The cleaning is performed by an intermediate transfer member cleaning blade 191a made of a rubber material and abutting on the intermediate transfer belt 14a. The toner cleaned by the intermediate transfer member cleaning blade 191a is supplied to the screw 190b
Is collected in a not-shown waste toner container. During the passage of the back toner image on the intermediate transfer belt 14a, the contact of the intermediate transfer body cleaning blade 191a with the intermediate transfer belt 14a is released.

Further, the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16 and then cleaned by the photosensitive body cleaning device 19 to uniformly remove the toner before charging. The history of the photosensitive drum 10 in the previous image formation is eliminated by the exposure device 12e, and the process proceeds to the next image formation cycle.

Since the superposed color toner images are collectively transferred by using the above-described method, color shift of the color image on the intermediate transfer belt 14a, scattering or rubbing of the toner, and the like are less likely to occur, and the image quality is reduced with less deterioration. Double-sided color image formation is performed.

Next, claims 4 to 6, claims 10 to 12, claims 16 to 18, claims 22 to 24, claims 27 or 28, and claims 32 to 3 of the present invention.
4, Claims 44 to 49, and Claims 50 to 52
An embodiment of the image forming apparatus of the second example common to the first embodiment will be described with reference to FIG. FIG. 4 shows claim 4 of the present invention.
To 6, claim 10 to 12, claim 16 to 1
8, a color showing an embodiment of an image forming apparatus of a second example common to claims 22 to 24, 27 or 28, 32 to 34, 44 to 49, and 50 to 52. FIG. 2 is a cross-sectional configuration diagram of a main part of the image forming apparatus. The members having the same functions and structures as those of the members described in the image forming apparatus of the first example are given the same numbers.

In the image forming apparatus of this embodiment, as shown in FIG. 4, a photosensitive drum 10b as a first image carrier for forming a toner image to be a back image (back toner image) and a front image are formed. A photoconductor drum 10a as a second image carrier for forming a toner image (front toner image) is separately provided, and the back toner image formed on the photoconductor drum 10b has a polarity opposite to that of the toner (in the present embodiment). Is a belt-like intermediate transfer member by a first primary transfer roller 114b, which is a first primary transfer unit to which a voltage of negative polarity is used for the toner to be used, and a positive polarity voltage is applied in the present embodiment. Is transferred onto the intermediate transfer belt 114a,
The recording paper P, which is a transfer material, is supplied onto the intermediate transfer belt 114a between the photosensitive drum 10b and the photosensitive drum 10a by driving the timing roller 15b, which is a transfer material feeding unit, in synchronization with the back surface toner image. , Intermediate transfer belt 114
The recording paper P is electrostatically attracted to the intermediate transfer belt 114a and conveyed by the charging of the paper charger 150, which is a transfer material charging unit provided to face the driven roller 14e with the a interposed therebetween.
The photoconductor drum 1 is conveyed on the transfer material conveyance surface of the intermediate transfer belt 114a and the extension surface thereof, and is synchronized with the conveyance of the recording paper P.
A second primary transfer roller 11 serving as a second primary transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the surface toner image formed on the first toner transfer roller 11a.
4c, the toner image on the back surface on the intermediate transfer belt 114a is applied with a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment).
The secondary transfer unit 14g, which is a secondary transfer unit, re-transfers the image onto the back surface of the recording sheet P to form a front and back toner image on the recording sheet P. The curvature of the curvature portion KT of the transfer belt 114a, the neutralization of the transfer material by the transfer material neutralizer 14h, which is a transfer material neutralization unit provided at the end of the intermediate transfer belt 114a, and to which an AC voltage on which a DC voltage is superimposed is applied. Separating claw 2 provided on the transport unit 160 at a predetermined interval from the transfer belt 114a
10, the spur is a spur member that is separated from the intermediate transfer belt 114a and is a spur member provided in the conveyance unit 160 provided between the fixing unit 17 and the curvature unit KT at the end of the intermediate transfer belt 114a on the fixing device 17 side. 162 to a fixing device 17 as a fixing unit, and the first fixing roller 17
The toner images on the front and back sides of the recording paper P are fixed at a nip portion T between the first fixing roller 17a and the second fixing roller 17b to obtain a double-sided image. The charge of the intermediate transfer belt 14a charged by the first primary transfer roller 114b or the second primary transfer roller 114c is respectively discharged by a neutralizer 114m or a neutralizer 114n as an intermediate transfer member static eliminator provided on the downstream side. Static electricity is removed.

The toner remaining on the peripheral surfaces of the photosensitive drums 10b, 10a after the transfer is transferred to a photosensitive member cleaning device 19 (FIG. (Not shown in FIG. 4), or a photoconductor cleaning blade 19a made of a rubber material that comes into contact with the photoconductor drums 10b and 10a, respectively.
(See FIG. 1, not shown in FIG. 4). The transfer residual toner of the back toner image remaining on the peripheral surface of the intermediate transfer belt 114a after the transfer is an intermediate transfer member cleaning unit provided opposite the guide roller 14f with the intermediate transfer belt 114a interposed therebetween. The body cleaning device 190 is made of a rubber material, and is cleaned by an intermediate transfer body cleaning blade 190a that can be brought into and out of contact with the intermediate transfer belt 114a. The toner cleaned by the intermediate transfer member cleaning blade 191a is collected by a screw 190b into a waste toner container (not shown).

The photosensitive drums 10a and 10b and the intermediate transfer belt 114a in the image forming apparatus of this embodiment are the same as those of the first embodiment.
The same function and structure as those of the photosensitive drum 10 and the intermediate transfer belt 14a described in the image forming apparatus of the example are used. The intermediate transfer belt 114a is stretched while being in contact with a driving roller 14d, a secondary transfer opposing roller 14j, a driven roller 14e, a guide roller 14f, and a tension roller 14i, which are tension roller members serving as intermediate transfer members. It is rotated in the counterclockwise direction indicated by the arrow 4.

Toner image serving as backside image (backside toner image)
On the photosensitive drum 10b as a first image carrier, and a toner image (surface toner image) as a surface image on a photosensitive drum 10a as a second image carrier. The second toner image forming unit to be formed includes the same yellow (Y), magenta (M), cyan (C), and black (K) image forming units as those used in the above-described image forming apparatus. Four sets of scorotron chargers 11 (charging means), an exposure optical system 12 (image writing means), and a developing device 13 (developing means) for the process are composed of the photosensitive drum 10b,
Each of the toner images 10a is used (see FIG. 1 and not shown in FIG. 4) to form a toner image of a back image and a toner image of a front image.

Even when the above-described image forming apparatus is used, since the superimposed color toner images are collectively transferred, color shift of the color image on the intermediate transfer belt 114a, scattering and rubbing of the toner, and the like are less likely to occur, and image deterioration is reduced. A small and favorable double-sided color image is formed.

In each of the above-described examples of the image forming apparatus, the toner image is formed directly on the image carrier. However, an image former is provided separately from the image carrier, and It may be carried on an image carrier. In addition, although a color image forming apparatus has been described as an example of each of the above image forming apparatuses, the present invention is not necessarily limited to this, and a monochrome image formed by a process similar to that described with reference to FIG. It is also applied to a forming apparatus. Further, although the image writing means is provided inside the image carrier, the first image carrier, and the second image carrier, it may be provided outside.

Further, according to the image forming apparatus of the present invention, in addition to the double-sided image forming for forming an image on both sides of the transfer material as described in each of the above-described image forming apparatuses, the image forming apparatus is provided on one side of only the front surface or the back surface of the transfer material. It goes without saying that single-sided image formation for forming an image can also be performed.

Embodiment 1 However, in an image forming apparatus in which an image is formed on both surfaces of a transfer material using the belt-shaped intermediate transfer member as described above, the humidity of the transfer material is increased due to an increase in humidity, and the effect of charging the transfer material by the transfer material charging means is reduced. When the transfer material is no longer useful, the transfer material conveyed on the belt-like intermediate transfer body (intermediate transfer belt) is lifted up (bounces up), and the transfer material static elimination means using a corona discharger and the backside toner image on the intermediate transfer body are used. Is contacted with a secondary transfer means for transferring the toner image to the back surface of the transfer material, and the surface toner image on the transfer material is disturbed, or the transfer material is caught by these corona dischargers, causing a jam. This also depends on the length and thickness of the transfer material.

A method for preventing the transfer material discharging means or the secondary transfer means from contacting or catching with the transfer material to solve this problem will be described with reference to FIGS. FIG.
FIG. 6 is a diagram showing a spur member for preventing the transfer material discharging means and the transfer material from coming into contact with or catching when the transfer material enters the transfer material discharging means. FIG. FIG. 7 is a diagram illustrating a spur member that prevents contact and catch between the transfer material discharging unit and the transfer material when the transfer material is conveyed to the unit. FIG. 8 is a view showing a spur member for preventing contact and catch between the secondary transfer means and the transfer material, and FIG. 8 shows the spur member when the transfer material is transferred from the primary transfer position to the secondary transfer means FIG. 4 is a diagram illustrating a spur member that prevents contact with or catching with a transfer material.

According to FIG. 5 or FIG. 6, FIG.
As described above, after the front surface toner image of the recording paper P is transferred onto the front surface of the recording paper P, the back surface toner image on the intermediate transfer belt 14a (or the intermediate transfer belt 114a) has a polarity opposite to that of the toner ( In the present embodiment, the secondary transfer device 14g to which a voltage having a positive polarity is applied is re-transferred to the back surface of the recording paper P, and the front and back toner images are formed on the recording paper P. The recording paper P on which the color toner images are formed on both sides and conveyed on the transfer material conveying surface has a curvature of the curvature portion KT of the intermediate transfer belt 14a (or the intermediate transfer belt 114a).
The intermediate transfer belt 14a (or the intermediate transfer belt 114
The intermediate transfer is performed by the charge removing operation of the transfer material charge remover 14h provided at the end of (a) and the separation claw 210 provided on the transport unit 160 at a predetermined interval from the intermediate transfer belt 14a (or the intermediate transfer belt 114a). The conveyance unit 160 is provided between the fixing device 17 and the curvature unit KT at the fixing device 17 side end of the intermediate transfer belt 14a (or the intermediate transfer belt 114a), which is separated from the belt 14a (or the intermediate transfer belt 114a). Is transported to the fixing device 17 through a spur 162 provided in the first fixing roller 17a.
At the nip portion T between the recording paper P and the second fixing roller 17b.
The upper and lower toner images are fixed to form a double-sided image. At this time, the recording paper P added to the nip portion T forms a loop between the recording material P and the separation position of the transfer material static eliminator 14h, and the intermediate transfer belt 14a (or the intermediate transfer belt 11).
4a) to the fixing device 17.

In FIG. 5, the transfer material neutralizer 14h is configured as a corona discharger having a discharge wire HWa as a discharge electrode and a shield plate SP1 as a shield member. At the entrance of
In order to prevent the recording paper P from jumping up and coming into contact with or catching on the transfer material static eliminator 14h, or to prevent the recording paper P from contacting the transfer material static eliminator 14h due to a loop, the transfer paper static eliminator 14h is adjacent to the upstream side of the transfer material static eliminator 14h. For example, a spur 162A as a spur member made of an insulating resin material such as polyacetal or polyamide is provided. At this time, as shown in FIG. 5, the recording paper P on the shield plate SP1 of the transfer material static eliminator 14h.
It is preferable to dispose the spur 162A so as to be integrally provided on the entry side of the cartridge, in order to prevent contact and catch at the time of entry and to prevent contact by a loop at the time of fixing.

The amount of jump or loop of the recording paper P varies depending on the length and thickness of the recording paper P, but the amount of the recording paper P on the side of the intermediate transfer belt 14a (or the intermediate transfer belt 114a) of the shield plate SP1 of the transfer material static eliminator 14h. The closest distance between the leading end and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is D1 (mm), which is adjacent to the upstream side of the transfer material static eliminator 14h, and is preferably provided integrally with the transfer material static eliminator 14h. The closest distance between the spur 162A and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is D2 (m
In the case of m), it is more preferable to set D1> D2 in order to prevent the recording paper P from coming into contact with the transfer material static eliminator 14h or being caught by a loop during fixing and a loop during fixing. Experimentally, the closest distance D1 is about 5 to 15 mm, and the closest distance D
As for 2, a range of about 4 to 10 mm is a preferable value.

As described above, the transfer material conveyed on the belt-shaped intermediate transfer member is prevented from rising (jumping up) due to the irregularity of the transfer material entering the transfer material charge removing means, and the transfer material charge removal means and the transfer material are removed. Contact and snagging are prevented,
Disturbance of the surface toner image on the transfer material is suppressed. Further, contact between the transfer material discharging unit and the transfer material due to a loop at the time of fixing is prevented, and occurrence of disturbance of the surface toner image on the transfer material is suppressed.

In FIG. 6, the transfer material charge eliminator 14h is configured as a corona discharger having a discharge wire HWa as a discharge electrode and a shield plate SP1 as a shield member. When the recording paper P jumps up and comes in contact with the transfer material static eliminator 14h during conveyance between the transfer material static eliminator 14h and the transfer material static eliminator 14h, or when the recording paper P contacts the transfer material static eliminator 14h due to a fixing loop. In order to prevent this, a spur 1 as a spur member made of an insulating resin material such as polyacetal or polyamide is provided between the secondary transfer device 14g and the transfer material static eliminator 14h.
62B is provided. At this time, as shown in FIG. 6, a holding plate HP1 as a holding member for a spur member is provided between the secondary transfer device 14g and the transfer material static eliminator 14h, and a spur 162B is provided on the holding plate HP1. Thereby, the secondary transfer unit 14g
It is possible to prevent contact and catch during transfer between the transfer material and the transfer material static eliminator 14h, and to prevent contact due to a loop during fixing.

The holding plate H on which the spur 162B is provided
P1 is configured to be rotatable about the support shaft J1 (a configuration movable with respect to the intermediate transfer belt 14a (or the intermediate transfer belt 114a)), and is positioned at the stopper ST1 to move the spur 162B to a predetermined position. In the case where the recording paper P is jammed due to a jump between the secondary transfer device 14g and the transfer material static eliminator 14h or a contact with the transfer material static eliminator 14h, the dashed line in FIG. As shown, the holding plate HP1 is rotated about the support shaft J1 to
It is preferable that the transport path of the recording paper P by the intermediate transfer belt 14a (or the intermediate transfer belt 114a) be opened so that the jam processing can be performed. Further, the transfer material static eliminator 14h is attached to the holding plate HP1 by the coupling member KB, and the holding plate HP1 and the transfer material static eliminator 14h are integrally opened so that the jam processing can be more easily performed. It is possible.

The amount of jump or loop of the recording paper P varies depending on the length and thickness of the recording paper P. The closest distance between the leading end and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is D1 (mm), and a spur 162B provided between the secondary transfer device 14g and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) The closest distance to the transfer belt 14a (or the intermediate transfer belt 114a) is D3 (mm),
When the closest distance between the secondary transfer device 14g and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is D4 (mm), setting D1> D3 ≧ D4 can be performed by setting the secondary transfer device 14g and the transfer material. Static eliminator 1
4h to prevent contact and snagging during transport,
It is more preferable to prevent contact by a loop during fixing. Experimentally, the closest distance D1 is 5 to 1
The preferred values are about 5 mm, the closest distance D3 is about 3 to 10 mm, and the closest distance D4 is about 3 to 8 mm.

As described above, the transfer material conveyed on the belt-shaped intermediate transfer member between the secondary transfer means and the transfer material charge eliminating means is prevented from rising (jumping) due to the unevenness of the transfer material, and the transfer material charge removal is performed. The contact between the means and the transfer material and the catch of the transfer material are prevented, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed. Also, contact between the transfer material discharging means and the transfer material due to a loop during fixing is prevented,
Disturbance of the surface toner image on the transfer material is suppressed.

According to FIG. 7 or FIG.
As described above, the surface toner image formed on the photosensitive drum 10 (or the photosensitive drum 10a) in synchronization with the conveyance of the recording paper P has the opposite polarity (positive polarity in the present embodiment) to the toner. ) Is applied to the surface of the recording paper P by the primary transfer roller 14c (or the second primary transfer roller 114c) to which the intermediate transfer belt 14 is applied.
a (or the intermediate transfer belt 114a) is re-transferred to the back surface of the recording paper P by a secondary transfer unit 14g to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. The recording paper P on which the front and back toner images are formed on the recording paper P and the color toner images are formed on both sides is transferred to the intermediate transfer belt 14a (or the intermediate transfer belt 1).
The transfer material is separated at a separation position of the transfer material neutralizer 14h provided opposite to the drive roller 14d with the transfer member 14a) interposed therebetween.

In FIG. 7, the secondary transfer device 14g is configured as a corona discharge device having a discharge wire HWa as a discharge electrode and a shield plate SP2 as a shield member. In order to prevent the recording paper P from jumping up and coming into contact with the secondary transfer unit 14g and to prevent the recording paper P from catching up, an insulating resin such as polyacetal or polyamide is provided adjacent to the upstream side of the secondary transfer unit 14g. Spur 162C as spur member made of material
Is arranged. At this time, as shown in FIG.
A spur 1 is placed on the entry side of the recording paper P of the 4 g shield
It is preferable to dispose the 62B integrally so as to prevent contact and catching when entering.

Although the amount of jump of the recording paper P varies depending on the length and thickness of the recording paper P, the end of the shield plate SP2 of the secondary transfer unit 14g on the side of the intermediate transfer belt 14a (or the intermediate transfer belt 114a) and the intermediate position. The closest distance to the transfer belt 14a (or the intermediate transfer belt 114a) is D4
(Mm), a spur 1 that is adjacent to the upstream side of the secondary transfer unit 14g and is preferably provided integrally with the secondary transfer unit 14g.
Assuming that the closest distance between the intermediate transfer belt 62C and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is D5 (mm), setting D4> D5 is equivalent to the secondary transfer unit 14g due to the jumping of the recording paper P when it enters. It is more preferable to prevent contact with and catching. Experimentally, the closest distance D4 is about 3 to 8 mm, and the closest distance D5 is 2 to 6 mm
The degree is in a preferable value range.

As described above, the transfer material conveyed on the belt-like intermediate transfer body is prevented from rising (jumping) due to the unevenness when entering the secondary transfer means. Is prevented, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed.

In FIG. 8, the secondary transfer device 14g is configured as a corona discharge device having a discharge wire HWa as a discharge electrode and a shield plate SP2 as a shield member. (Or the second primary transfer roller 114c), the secondary transfer due to the jump of the recording paper P during the transport between the primary transfer position (or the second primary transfer position) and the secondary transfer unit 14g. In order to prevent the transfer device 14g from contacting or catching, the primary transfer position (or the second primary transfer position) and the secondary transfer device 1
4 g, a spur 162 as a spur member made of an insulating resin material such as polyacetal or polyamide.
D is arranged. At this time, as shown in FIG. 8, a holding plate HP2 as a holding member for the spur member is provided between the primary transfer position (or the second primary transfer position) and the secondary transfer unit 14g, and the holding plate HP2 Is provided with a spur 162D. Thus, it is possible to prevent contact and catch during transport between the primary transfer position (or the second primary transfer position) and the secondary transfer device 14g.

The holding plate H on which the spur 162D is provided
P2 is configured to be rotatable about the support shaft J2 (a configuration movable with respect to the intermediate transfer belt 14a (or the intermediate transfer belt 114a)), and is positioned at the stopper ST2 to move the spur 162D to a predetermined position. The primary transfer position (or the second primary transfer position) and the secondary transfer device 14 are provided.
In the case where the recording paper P is jammed due to a jump between the recording paper P and the secondary transfer unit 14g, as shown by a dashed line in FIG.
, The spur 162D is lifted, and the conveyance path of the recording paper P by the intermediate transfer belt 14a (or the intermediate transfer belt 114a) can be opened, so that the jam processing can be performed. Furthermore, the secondary transfer device 14g is attached to the holding plate HP2 by the coupling member KB, and the holding plate HP2 and the secondary transfer device 14g are integrally opened, so that the jam processing can be performed more easily. It is possible.

Although the amount of jump of the recording paper P varies depending on the length and thickness of the recording paper P, the tip of the shield plate SP2 of the secondary transfer unit 14g on the side of the intermediate transfer belt 14a (or the intermediate transfer belt 114a) and the intermediate position. The closest distance to the transfer belt 14a (or the intermediate transfer belt 114a) is D4
(Mm) Primary transfer position (or second primary transfer position)
When the closest distance between the spur 162D provided between the intermediate transfer belt 14a and the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is D6 (mm), it is possible to set D4> D6 as primary. It is more preferable to prevent the transfer position (or the second primary transfer position) and the secondary transfer device 14g from contacting or catching during transport. Experimentally,
The closest distance D4 is about 3 to 8 mm, and the closest distance D
The preferred range of 6 is about 1 to 5 mm.

As described above, the rising (bounce) of the transfer material conveyed on the belt-shaped intermediate transfer member between the primary transfer means and the secondary transfer means is prevented, and the secondary transfer means is prevented from rising. And the transfer material are prevented from contacting or catching with the transfer material, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed. In addition, the transfer material conveyed on the belt-shaped intermediate transfer member between the second primary transfer means and the secondary transfer means is prevented from rising (jumping up) due to the unevenness of the transfer material. The contact and the catch with the transfer material are prevented, and the occurrence of the disturbance of the surface toner image on the transfer material and the occurrence of the jam of the transfer material are suppressed.

Embodiment 2 In an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-like intermediate transfer member as described above, the back toner image on the intermediate transfer member is retransferred to the back surface of the transfer material. In the secondary transfer means using a corona discharger in this case, a voltage having a polarity opposite to the polarity of the toner to be used is applied to the corona discharger to transfer the backside toner image on the intermediate transfer body to the backside of the transfer material. When the distance between the end of the transfer material outlet side surface of the discharger and the intermediate transfer member is short or the discharge width is wide, the surface toner image is disturbed by the discharge, or the transfer is converted to a positive polarity. The toner of the negative polarity surface toner image on the material adheres to the side surface of the corona discharger on the exit side of the transfer material, and the corona discharger becomes dirty.

In order to solve this problem, the corona discharge device is used to re-transfer the back surface toner image on the intermediate transfer member to the back surface of the transfer material. FIG. 9 shows a method for preventing toner image disturbance.
This will be described with reference to FIG. FIG. 9 is a diagram showing the discharge conditions of the secondary transfer device constituting the secondary transfer means.
FIG. 11 is a diagram showing the position setting of the discharge electrodes of the secondary transfer device constituting the secondary transfer means.
FIG. 4 is a diagram illustrating an arrangement of conductive rollers constituting a next transfer unit and a setting condition of a diameter. Note that the secondary transfer unit in the present embodiment includes a secondary transfer device and a secondary transfer facing roller provided to face each other with the intermediate transfer belt 14a interposed therebetween.

According to FIGS. 9 to 11, the intermediate transfer belt 14a (or the intermediate transfer belt) is provided by a secondary transfer device 14g and a secondary transfer opposing roller 14j provided opposite each other with the intermediate transfer belt 14a interposed therebetween. A secondary transfer means for retransferring the toner image on 114a) onto the back surface of the recording paper P is constituted, and a primary transfer roller 14c and a drive roller 14d
Is provided between The secondary transfer device 14g is a corona discharge device having a discharge electrode formed of a discharge wire HWa. The secondary transfer opposing roller 14j has a volume resistance on the peripheral surface of a conductive core metal (unsigned) such as stainless steel. Is 1
0 ⁶ Ω · cm or less, urethane, rubber hardness such as silicon to form a 10Hs~50Hs (JIS, A rubber hardness) foam rubber layer foamed rubber (unsigned), the foam rubber layer (not numbered) A roller member that is formed as an elastic soft roller having an insulating layer (not numbered) made of, for example, Teflon (registered trademark) coating on the outside (outer peripheral surface), and is a grounded conductive roller. A DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to the discharge wire HWa of the secondary transfer device 14g, and the toner image on the intermediate transfer belt 14a is transferred to the back surface of the recording paper P. As a discharge electrode, FIG.
It is also possible to use a saw-tooth electrode KDa as described later in (B).

A secondary transfer unit 14g using a corona discharger when the back side toner image on the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is re-transferred to the back side of the recording paper P.
As shown in FIG. 9, the discharge conditions of the secondary transfer device 14g to prevent the secondary transfer device 14g from being stained during the discharge by the discharge wire HWa and to prevent the surface toner image from being disturbed at the time of retransfer are as follows. The discharge width L1 (mm) of the discharge wire HWa is set to the intermediate transfer belt 14a (or the intermediate transfer belt 114a).
It is preferable to set the contact width L2 (mm) smaller than the contact width L2 (mm) between the roller and the secondary transfer opposing roller 14j. It is preferable that the discharge width L1 is set in a range of about 1 to 8 mm and the contact width L2 is set in a range of about 2 to 10 mm. Thereby, the intermediate transfer belt 14a (or the intermediate transfer belt 114a)
Intermediate transfer belt 14 of shield plate SP2 due to toner scattering, which is likely to occur when leaving from next transfer opposing roller 14j.
a (or the intermediate transfer belt 114a) side dirt,
In particular, toner is prevented from adhering to the side of the shield plate SP2 on the exit side of the recording paper P.

More specifically, as a shielding member, for example, a mylar sheet MS is provided at both ends of the opening of the shield plate SP2.
The width of the shield plate SP2 is set to be small by controlling the discharge width by sticking, for example, or as shown by a dashed line in FIG.

As shown in FIG. 10A, the closest distance between the discharge wire HWa as a discharge electrode of the secondary transfer device 14g and the shield plate SP2 is d1 (mm), and the discharge wire HWa and the intermediate transfer belt 14a. When the closest distance to the intermediate transfer belt 114a is d2 (mm), d1> d2 is set, and a virtual circle CL having a radius d1 (mm) centered on the discharge portion of the discharge wire HWa is used. The intermediate transfer belt 14a (or the intermediate transfer belt 1)
The width L3 (mm) of the intermediate transfer belt 14a
The position of the discharge wire HWa is set so as to be smaller than the contact width L2 between the (or the intermediate transfer belt 114a) and the secondary transfer opposing roller 14j. The closest distance d1 is 5
It is preferable to set the distance to about 15 mm, the closest distance d2 to about 4 to 8 mm, the width L3 to about 1 to 8 mm, and the contact width L2 to about 2 to 10 mm.
Thus, after the discharge is completed, the intermediate transfer belt 14a
(Or the intermediate transfer belt 114a) is separated from the secondary transfer opposing roller 14j, and the intermediate transfer belt 14a
When the backside toner image on the intermediate transfer belt 114a is re-transferred to the backside of the recording sheet P, the secondary transfer unit 14g using the corona discharger is stained during discharge by the discharge wire HWa of the secondary transfer unit 14g. Also, disturbance of the surface toner image at the time of retransfer is prevented.

As shown in FIG. 10B, a sawtooth electrode KDa is used as a discharge electrode, and the closest distance between the sawtooth electrode KDa as the discharge electrode and the shield plate SP2 is d1.
(Mm), sawtooth electrode KDa and intermediate transfer belt 14a
(Or the closest distance to the intermediate transfer belt 114a) is d
2 (mm), d1> d2, and the intermediate transfer of a region surrounded by an imaginary circle CL having a radius d1 (mm) centered on the discharge portion (the tip of the sawtooth electrode KDa) of the sawtooth electrode KDa. Belt 14
a (or intermediate transfer belt 114a) width L3 (mm)
To the intermediate transfer belt 14a (or the intermediate transfer belt 11).
The same effect can be obtained by setting the position of the saw-tooth electrode KDa so as to be smaller than the contact width L2 between 4a) and the secondary transfer opposing roller 14j. The setting range is preferably the same as described above.

The position of the secondary transfer opposing roller 14j in the above is, as shown in FIG.
j with the intermediate transfer belt 14a and the photosensitive drum 1
0 (or the intermediate transfer belt 114a and the photosensitive drum 10
a) is in contact with the recording paper P and the intermediate transfer belt 14
a (or the intermediate transfer belt 114a) and a virtual plane PL1 passing through a position separated from the intermediate transfer belt 114a.
a (or the intermediate transfer belt 114a) is preferably set so as to protrude toward the outer peripheral surface side.
It is preferable to set the range to about 8 mm.

Further, both ends of the shield plate SP2 and the intermediate transfer belt 14a (or the intermediate transfer belt 114a).
The distance L4 (mm) to the secondary transfer opposed roller 14j is set to, for example, about 5 to 15 mm, and the radius of the secondary transfer opposed roller 14j is set to r1.
(Mm), it is also possible to set d1> r1. As described above, it is preferable that the closest distance d1 (mm) between the discharge electrode of the secondary transfer device 14g and the shield plate SP2 is set to about 5 to 15 mm, and the radius r1 is set to about 4 to 10 mm. As a result, the discharge of the discharge electrode occurs in a narrow area (area) of the secondary transfer facing roller 14j opposed to the intermediate transfer belt 14a (or the intermediate transfer belt 114a), and after the discharge is completed, Since the transfer belt 14a (or the intermediate transfer belt 114a) is separated from the secondary transfer opposing roller 14j, the back toner image on the intermediate transfer belt 14a (or the intermediate transfer belt 114a) is retransferred to the back surface of the recording paper P. Wire HW of the secondary transfer device 14g using a corona discharger
This prevents contamination of the secondary transfer device 14g at the time of discharge due to a and disturbance of the surface toner image at the time of retransfer.

With the above, toner contamination of the secondary transfer means at the time of discharge by the secondary transfer means when retransferring the backside toner image on the intermediate transfer member to the backside of the transfer material is prevented, and the surface toner Image disturbance is prevented.

Embodiment 3 In an image forming apparatus for forming an image on both surfaces of a transfer material using the belt-shaped intermediate transfer member as described above, the transfer material onto which the toner image is transferred has irregularities and wrinkles. If the adhesion between the belt surface of the transfer member and the transfer material is not good, there is a problem that transfer omission occurs during the transfer of the front and back toner images. If the adhesion between the belt surface of the intermediate transfer member and the transfer material is not good due to the unevenness of the belt-like intermediate transfer member or the unevenness and wrinkles of the transfer material for transferring the toner image, transfer omission occurs at the time of transfer. The problem arises. When transferring the toner image of the surface image on the photosensitive drum to the transfer material, the transfer is performed while the transfer material is pressed against the photosensitive drum by the intermediate transfer member. Although the unevenness and wrinkles of the material are not significant, when the toner image of the back side image on the intermediate transfer body is transferred to the transfer material, the transfer material is not pressed onto the intermediate transfer body, and the intermediate transfer body is not pressed. If there is unevenness or unevenness or wrinkles on the transfer material, transfer omission (transfer omission of the backside toner image) occurs. This also occurs depending on the type of the transfer material.

In order to solve this problem, unevenness and wrinkles of the transfer material at the time of transfer are suppressed, the adhesion between the transfer material and the belt-shaped intermediate transfer member is improved, and the transfer of the front and back toner images is prevented. In particular, a method for preventing transfer omission at the time of transferring the toner image of the back side image will be described with reference to FIGS.
FIG. 12 is a view showing a means for applying a transfer pressure to the intermediate transfer body in the image forming apparatus described with reference to FIG. 1 for achieving good adhesion between the transfer material and the belt-shaped intermediate transfer body; FIG. 13 is a view showing an appropriate area of the primary transfer or the second primary transfer by pressing the primary transfer means or the second primary transfer means, and FIG. 14 is a view showing a transfer pressure to the intermediate transfer body. FIG. 15 is a diagram illustrating another example of the application unit, and FIG. 15 is a diagram illustrating a pressing force of the application unit that applies a transfer pressure to the intermediate transfer member in a direction in contact with the image carrier; FIG. 17 is a diagram showing a non-image area at the leading end. FIG. 17 shows an image forming apparatus described with reference to FIG. 4 to an intermediate transfer member for achieving good adhesion between a transfer material and a belt-shaped intermediate transfer member. FIG. 3 is a diagram showing a transfer pressure applying means. In the following description of the present embodiment, the image forming apparatus shown in FIG. 1 will be mainly described. However, those matters also apply to the image forming apparatus shown in FIG.

According to FIGS. 12 to 16, as shown in FIG. 12, a recording sheet P as a transfer material is a color toner image of a surface image formed on the photosensitive drum 10 (this is used in the present embodiment). (Negative polarity of the same polarity as toner polarity)
Is synchronized with the color toner image (minus polarity in the present embodiment) of the rear surface image carried on the intermediate transfer belt 14a, and is fed to the transfer area (no symbol) of the primary transfer roller 14c. In the transfer area (no symbol) of the primary transfer roller 14c, the photosensitive member is driven by the primary transfer roller 14c, which is a primary transfer unit to which a DC voltage having the opposite polarity (positive polarity in this embodiment) to the toner is applied. After the front surface toner image on the drum 10 is collectively transferred to the front surface of the recording paper P, a voltage of the opposite polarity (positive polarity in the present embodiment) to the toner is applied to the back surface toner image on the intermediate transfer belt 14a. Is re-transferred to the back surface of the recording paper P by a secondary transfer device 14g,
The top and bottom toner images are formed on the top.

At this time, when the surface toner image is transferred onto the recording paper P by the primary transfer roller 14c, the recording paper P is sandwiched between the photosensitive drum 10 and the intermediate transfer belt 14a, and the intermediate transfer belt 14a As a result, the recording paper P is
The transfer of the toner image of the surface image onto the recording paper P is performed in a state where the recording medium P is pressed, so that the unevenness of the intermediate transfer belt 14a and the unevenness of the recording paper P do not occur, and the photosensitive drum 1 of the recording paper P
The transfer of the front surface toner image is performed in a state of good adhesion to 0, and transfer omissions and the like are not so noticeable. In particular, when transferring the back surface toner image on the intermediate transfer belt 14a to the recording paper P, Since the recording paper P is conveyed on the intermediate transfer belt 14a in a state where the recording paper P is placed on the intermediate transfer belt 14a, if the recording paper P or the intermediate transfer belt 14a has irregularities or wrinkles, the intermediate transfer The adhesion between the belt 14a and the recording paper P is poor, and the transfer of the backside toner image is lost.

For this reason, the primary transfer roller 14c is formed, for example, of stainless steel or the like on the peripheral surface of a conductive metal core (no symbol) having a central axis PJ1 with a volume resistance of 10 ⁶ Ω · cm or less, urethane or silicon. Rubber hardness of 10Hs-50
A foamed rubber layer (unsigned) is formed from foamed rubber of Hs (JIS, A rubber hardness), and a Teflon coating layer (unsigned) is provided on the outside (outer peripheral surface) of the foamed rubber layer (unsigned) as a measure against contamination. Preferably, the primary transfer roller 1 is formed as a formed elastic conductive roller member.
4c is made elastic, and the photosensitive drum 10 is pressed across the intermediate transfer belt 14a. It is also possible to use a roller-shaped metal member as the primary transfer roller 14c.

If the pressing force (transfer pressure) between the recording paper P and the intermediate transfer belt 14a is increased, the transfer rate is reduced. Therefore, it is preferable to limit the transfer pressure. Temperature 15 ± 5 ℃,
55-6% as transfer material under environmental conditions of 35 ± 10% humidity
FIG. 13 shows the relationship between the transfer pressure (N) and the transfer rate (%) when 0 kg / m ² of plain paper is used. The transfer rate when there is no transfer material (no paper) is shown in FIG. Curve (a)
The transfer rate in the case where the transfer material is present (there is paper) is as shown by the curve (b) in FIG. 13, and the proper area (the transfer proper area) in the case where the transfer material is present is the case where there is no transfer material. From the proper area (transfer proper area) in the case, the primary transfer roller 14
The width is made wider in accordance with the transfer pressure of c (in the image forming apparatus of FIG. 4 described later, the second area in the case where there is paper than the appropriate area of the first primary transfer roller 114b when there is no paper) The appropriate area of the primary transfer roller 114c is widened according to the transfer pressure.) This is pressed by the intermediate transfer belt 14a as a smooth belt-shaped intermediate transfer member. Therefore, when the recording paper P is present, the toner enters the uneven surface of the recording paper P, the proper transfer area is expanded, and the pressing force is increased. It is considered that the higher the value, the better the transfer rate.

Therefore, the transfer pressure at the time of transferring the back toner image from the photosensitive drum 10 to the intermediate transfer belt 14a is
When the transfer pressure at the time of transferring the surface toner image from the photosensitive drum 10 to the recording paper P is 1 (N / cm) and P2 (N / cm), it is preferable to set P1 <P2.

As shown in FIG. 13, experimentally,
Preferably, the transfer pressure P1 is set in a range of 0.1 N / cm ≦ P1 ≦ 0.5 N / cm, and the transfer pressure P2 is set in a range of 0.2 N / cm ≦ P2 ≦ 1 N / cm 2. Has been confirmed.

As shown in FIG. 12, the receiving portions GBa and GB are connected to the central axis PJ1 of the primary transfer roller 14c.
b, the rack LKa guided by the drive motor M1
The rotation of the pinion PNa engaged with the rack LKa through a speed reduction mechanism (not shown) causes the rack L to rotate.
A transfer pressure applying means configured to push Ka upward is used to change the transfer pressure when transferring the front and back toner images.

Since a roller member is used as the primary transfer means, particularly when a roller-shaped metal member is used, the central portion of the roller which comes into contact with the intermediate transfer belt 14a is free, so that as shown in FIG. First, for example, the primary transfer roller 14c is formed in a crown shape having a drum-shaped center portion.
It is preferable that the transfer pressure at the center of the next transfer roller 14c be higher than that at the end.

FIG. 14 shows another example of the means for applying the transfer pressure (pressing pressure). A primary transfer device 14C using a corona discharger is used as the primary transfer device. A holder H which is rotatable about the support shaft J3 and has a pressing blade BOa as a blade member having a tip abutting on the intermediate transfer belt 14a on the opposite side of the support shaft J3.
D may be provided, and a transfer pressure applying means having the same configuration as described above may be coupled to the holder HD, and the transfer pressure applying means may apply the transfer pressure P1 and the transfer pressure P2. In this case as well, as shown in FIG. 15B, a reinforcing member HB is provided at the center of the pressing blade BOa and is brought into contact with the intermediate transfer belt 14a, so that the transfer pressure at the center of the pressing blade BOa is reduced at the end. It is preferable to make it larger.

The appropriate area of the transfer pressure varies depending on the type of transfer material such as the length and thickness of the recording paper P and environmental conditions. Preferably, the means is operated to change the transfer pressure.

As described above, irregularities and wrinkles of the intermediate transfer member are suppressed when the backside toner image is transferred from the image carrier to the intermediate transfer member by the primary transfer means, and the transfer from the image carrier to the transfer material is suppressed. The unevenness and wrinkles of the transfer material during transfer of the surface toner image are suppressed, the adhesion between the transfer material and the belt-shaped intermediate transfer member is improved, and the transfer loss of the front and back toner images, especially the secondary Transfer omission at the time of retransfer of the toner image on the back surface by the transfer means is prevented.

In FIG. 12, if the transfer pressure is too strong during the transfer of the surface toner image from the image carrier to the transfer material,
Since the leading end of the transfer material is wrapped around the image carrier, the transfer pressure when transferring the surface toner image from the photosensitive drum 10 to the recording paper P when transferring from the photosensitive drum 10 to the transfer material central portion Pb. Is P2 (N / cm), and the transfer pressure at the time of transfer from the photosensitive drum 10 to the transfer material tip Pa is P3 (N / c).
When m), it is preferable to set P2> P3.

As described above with reference to FIG. 13, the transfer pressure P2
It has been confirmed that it is preferable to set the range of 0.2 N / cm ≦ P2 ≦ 1 N / cm 2 as the transfer pressure P3. It has been experimentally confirmed that it is preferable to set the value within the range in order to prevent the leading end of the transfer material from being wound around the photosensitive drum 10.

Further, as shown in FIG. 16, a non-image area is provided at the front end portion (the front end portion on the back side) Pc of the recording paper P, and the surface toner image is transferred to the recording paper P by the primary transfer roller 14c. Of the photosensitive drum 10 at the leading end of the recording paper P
It is preferable to prevent winding around.

As described above, when the surface toner image is transferred from the image carrier to the transfer material, the leading end of the transfer material is prevented from winding around the image carrier.

According to FIG. 17, the back toner image on the photosensitive drum 10b as the first image carrier is transferred to the intermediate transfer belt by the first primary transfer roller 114b as the first primary transfer means. After being transferred onto the photoconductor 114a, the recording paper P as a transfer material is formed on the surface of the photosensitive drum 10a as the second image carrier (in this embodiment, a toner having the same polarity as the toner used). (Negative polarity) and the back toner image (negative polarity in the present embodiment) carried on the intermediate transfer belt 114a are synchronized.
The sheet is fed onto the intermediate transfer belt 114a between the photoconductor drum 10b and the photoconductor drum 10a, and is conveyed to the transfer area (no symbol) of the second primary transfer roller 114c, and
In the transfer area (no symbol) of the primary transfer roller 114c, a second primary transfer unit serving as a second primary transfer unit to which a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. After the surface toner image on the photosensitive drum 10a is collectively transferred to the front surface of the recording paper P by the roller 114c, the back surface toner image on the intermediate transfer belt 114a is set to the opposite polarity (positive in the present embodiment) to the toner. (Polarity) voltage is re-transferred to the back surface of the recording paper P by a secondary transfer device 14g, which is a secondary transfer means, to form a front and back color toner image on the recording paper P.

At this time, when the surface toner image is transferred to the recording paper P by the second primary transfer roller 114c, the recording paper P is sandwiched between the photosensitive drum 10a and the intermediate transfer belt 114a, and The surface toner image is transferred onto the recording paper P in a state where the recording paper P is pressed against the photosensitive drum 10a by the transfer belt 114a.
The surface toner image is transferred in a state where the unevenness of the recording paper P and the unevenness of the recording paper P do not occur and the adhesiveness of the recording paper P to the photosensitive drum 10a is good. When the back toner image on the intermediate transfer belt 114a is transferred to the recording paper P, the recording paper P is placed on the intermediate transfer belt 114a and the intermediate transfer belt 114 is
Since the recording paper P is conveyed on the recording paper P, if the recording paper P or the intermediate transfer belt 114a has irregularities or wrinkles, the adhesion between the intermediate transfer belt 114a and the recording paper P is poor, and the transfer of the back side toner image is lost. Occurs.

For this reason, the second primary transfer roller 114c
A volume resistance of 10 ⁶ Ω · c on the peripheral surface of a conductive core metal (no symbol) having a central axis PJ1 of, for example, stainless steel.
m or less, rubber hardness of urethane, silicon, etc. is 10Hs
Forming a foamed rubber layer (unsigned) with foamed rubber of up to 50 Hs (JIS, A rubber hardness), and forming the foamed rubber layer (unsigned)
It is preferable to form a conductive roller member having elasticity in which a Teflon coating layer (no symbol) is formed on the outside (outer peripheral surface) as a countermeasure against contamination, and the second primary transfer roller 114c has elasticity. Intermediate transfer belt 11
The photosensitive drum 10a is pressed with the photosensitive drum 4a interposed therebetween. It is also possible to use a roller-shaped metal member as the second primary transfer roller 114c.

If the pressing force (transfer pressure) between the recording paper P and the intermediate transfer belt 114a is increased, the transfer rate decreases, so it is preferable to limit the transfer pressure. Temperature 15 ± 5
55 ° C as the transfer material under environmental conditions of
The relationship between the transfer pressure (N) and the transfer rate (%) when plain paper of 〜60 kg / m ² is used is the same as described above with reference to FIG. The rate is the same as that shown by the curve (a) in FIG. 13, and the transfer rate when there is a transfer material (with paper) is the same as that shown by the curve (b) in FIG. The appropriate area (transfer appropriate area) of the second primary transfer roller 114c in the presence of paper is made wider in accordance with the transfer pressure than the appropriate area (transfer appropriate area) of the first primary transfer roller 114b. this is,
Intermediate transfer belt 1 as a smooth belt-shaped intermediate transfer body
14a, the recording paper P is
It is considered that the toner enters the concave and convex surface, the appropriate transfer area expands, and the higher the pressing force, the better the transfer rate.

For this reason, the intermediate transfer belt 114a from the photosensitive drum 10b by the first primary transfer roller 114b
The transfer pressure at the time of transfer of the backside toner image to P1 is P1 (N / c
m), the photosensitive drum 10a to the second primary transfer roller 1
When the transfer pressure at the time of transferring the surface toner image onto the recording paper P by 14c is P2 (N / cm), it is preferable to set P1 <P2.

As described above, experimentally, the transfer pressure P1
It is confirmed that it is preferable to set the transfer pressure P2 in the range of 0.1 N / cm ≦ P1 ≦ 0.5 N / cm and the transfer pressure P2 in the range of 0.2 N / cm ≦ P2 ≦ 1 N / cm 2. ing.

As shown in FIG. 17, the first primary transfer roller 114b is coupled to the center axis PJ2 of the first primary transfer roller 114b, and receives the receiving portion GB.
c, the rack LKb guided by GBd is connected to the drive motor M2 through a speed reduction mechanism (not shown), and the pinion PNb meshed with the rack LKb rotates.
The first 1 of a configuration in which the rack LKb is pushed upward.
The transfer pressure applying means of the next transfer means is used to change the transfer pressure when transferring the toner image on the back surface. The rack L coupled to the central axis PJ3 of the second primary transfer roller 114c and guided by the receiving portions GBe and GBf.
Kc is coupled to the drive motor M3 through a speed reduction mechanism (not shown) and meshed with the rack LKc.
With the rotation of, the transfer pressure applying means of the second primary transfer means configured to push up the rack LKc upward is used, and the transfer pressure at the time of transferring the toner image on the surface is changed.

Since a roller member is used as each of the first primary transfer unit and the second primary transfer unit, especially when a roller-shaped metal member is used, the intermediate transfer belt 114 is used.
Since the central portion of the roller abutting on a is free,
In the same manner as described above in (A), for example, the first primary transfer roller 114b and the second primary transfer roller 114c each have a crown shape having a drum-shaped center portion, and
Next transfer roller 114b and second primary transfer roller 114
It is preferable that the transfer pressure at the center of c is higher than at the end.

As described above with reference to FIG. 14, a corona discharger is used as the first primary transfer means and the second primary transfer means, and the first primary transfer means and the first primary transfer means using the corona discharger are used. A transfer pressure applying means for the first primary transfer means and a transfer pressure applying means for the second primary transfer means, each using a blade member, are provided upstream of the second primary transfer means. , The transfer pressure P2 may be applied. In this case as well, as described above with reference to FIG. 15B, a reinforcing member HB is provided at the center of each blade member, and the transfer pressure at the center of the blade member is made larger than that at the end, so that each intermediate member has an intermediate transfer pressure. Preferably, the transfer belt 114a is brought into contact with the transfer belt 114a.

The appropriate area of the transfer pressure also varies depending on the type of the transfer material such as the length and thickness of the recording paper P and the environmental conditions. In addition to operating the transfer pressure applying means, the transfer pressure applying means of the second primary transfer means is operated according to the type of transfer material and environmental conditions to change the respective transfer pressures. Is preferable.

As described above, unevenness and wrinkles of the intermediate transfer body are suppressed when the back side toner image is transferred from the first image carrier to the intermediate transfer body by the first primary transfer means. When the surface toner image is transferred from the second image carrier to the transfer material by the primary transfer means, unevenness and wrinkles of the transfer material are suppressed, and the transfer material and the belt-shaped intermediate transfer body are brought into close contact with each other. The transferability of the toner images on the front and back sides, especially when the toner image on the back side is transferred by the secondary transfer means, is prevented.

In FIG. 17, if the transfer pressure is too high during the transfer of the surface toner image from the second image carrier to the transfer material, the leading end of the transfer material is wrapped around the second image carrier. When the surface toner image is transferred from the photosensitive drum 10a to the recording paper P, the transfer pressure at the time of transfer from the photosensitive drum 10a to the transfer material central portion Pb is P2 (N / cm), and the transfer pressure is from the photosensitive drum 10a. When the transfer pressure at the time of transfer to the material front end portion Pa is P3 (N / cm), it is preferable to set P2> P3.

As described above, it has been confirmed that the transfer pressure P2 is preferably set in the range of 0.2 N / cm ≦ P2 ≦ 1 N / cm, but the transfer pressure P3 is also set to 0.1 N / cm. It has been experimentally confirmed that it is preferable to set the range of /cm≦P3≦0.5 N / cm 2 in order to prevent the leading end of the transfer material from being wound around the photosensitive drum 10a.

Further, in the same manner as described above with reference to FIG. 16, a non-image area is provided in the front end portion (the front end portion on the back side) Pc of the recording paper P, and the non-image area is formed on the recording paper P by the second primary transfer roller 114c. It is preferable to prevent the leading end of the transfer material from winding around the photosensitive drum 10a during the transfer of the surface toner image.

As described above, when the surface toner image is transferred from the second image carrier to the transfer material by the second primary transfer means,
The leading end of the transfer material is prevented from winding around the second image carrier.

[0120]

According to the first to sixth aspects of the present invention, the transfer material conveyed on the belt-shaped intermediate transfer body is prevented from rising (jumping) due to the irregularity of the transfer material entering the transfer material static elimination means. The transfer material is prevented from contacting or being caught by the transfer material discharging means and the transfer material, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed. Further, contact between the transfer material discharging unit and the transfer material due to a loop at the time of fixing is prevented, and occurrence of disturbance of the surface toner image on the transfer material is suppressed.

According to the seventh to twelfth aspects, it is possible to prevent the transfer material conveyed on the belt-shaped intermediate transfer member from being lifted (bounced up) between the secondary transfer means and the transfer material discharging means. As a result, contact and catch between the transfer material discharging means and the transfer material are prevented, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed. Further, contact between the transfer material discharging unit and the transfer material due to a loop at the time of fixing is prevented, and occurrence of disturbance of the surface toner image on the transfer material is suppressed.

In particular, according to the ninth or twelfth aspect, the jamming of the transfer material between the secondary transfer means and the transfer material discharging means is facilitated.

According to the thirteenth to eighteenth aspects, the transfer material conveyed on the belt-like intermediate transfer member is prevented from rising (bounce) due to the sloshing at the time of entering the secondary transfer means, and Contact and catch between the transfer means and the transfer material are prevented, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed.

According to the nineteenth to twenty-first aspects, it is possible to prevent the transfer material conveyed on the belt-shaped intermediate transfer member from being lifted (bounced up) between the primary transfer means and the secondary transfer means. Thus, contact and catch between the secondary transfer means and the transfer material are prevented, and the occurrence of disturbance of the surface toner image on the transfer material and the occurrence of jam of the transfer material are suppressed.

In particular, according to the twenty-first aspect, the jamming of the transfer material between the primary transfer means and the secondary transfer means is facilitated.

According to claims 22 to 24, the second 1
The transfer material conveyed on the belt-shaped intermediate transfer member between the secondary transfer means and the secondary transfer means is prevented from rising (jumping up) due to the unevenness, and the contact between the secondary transfer means and the transfer material is prevented. Snagging is prevented, and occurrence of disturbance of the surface toner image on the transfer material and occurrence of jam of the transfer material are suppressed.

In particular, according to the twenty-fourth aspect, the jamming of the transfer material between the second primary transfer means and the secondary transfer means becomes easy.

According to the twenty-fifth to thirty-fourth aspects of the present invention, it is possible to transfer the toner image on the back surface of the intermediate transfer member to the back surface of the transfer material.
At the time of discharging in the next transfer unit, toner contamination of the secondary transfer unit is prevented, and disturbance of the surface toner image is prevented.

According to the thirty-fifth to thirty-fourth aspects, irregularities and wrinkles of the intermediate transfer member are suppressed when the back side toner image is transferred from the image carrier to the intermediate transfer member by the primary transfer means. During transfer of the surface toner image from the body to the transfer material, irregularities and wrinkles of the transfer material are suppressed, the adhesion between the transfer material and the belt-shaped intermediate transfer body is improved, and Transfer omission, particularly at the time of retransfer of the toner image on the back surface by the secondary transfer means, is prevented.

According to Claims 41 to 43, it is possible to prevent the leading end of the transfer material from being wound around the image carrier when the surface toner image is transferred from the image carrier to the transfer material.

According to claims 44 to 49, the first 1
During transfer of the back toner image from the first image carrier to the intermediate transfer member by the next transfer means, unevenness and wrinkles of the intermediate transfer body are suppressed, and the second image is formed by the second primary transfer means. During transfer of the surface toner image from the carrier to the transfer material, unevenness and wrinkles of the transfer material are suppressed, and the adhesion between the transfer material and the belt-like intermediate transfer body is improved, and the front and back toner images are formed. Transfer missing,
Particularly, transfer omission at the time of transferring the toner image on the back surface by the secondary transfer means is prevented.

According to Claims 50 to 52, the second image carrier at the leading end of the transfer material when the surface toner image is transferred from the second image carrier to the transfer material by the second primary transfer means. Winding around is prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus of a first example.

FIG. 2 is a side sectional view of the image carrier of FIG. 1;

FIG. 3 is a diagram illustrating a toner image forming state in the image forming apparatus of FIG. 1;

FIG. 4 is a cross-sectional view of a main part of a color image forming apparatus showing an embodiment of the image forming apparatus according to a second example.

FIG. 5 is a diagram showing a spur member that prevents the transfer material discharging unit and the transfer material from coming into contact with or catching when the transfer material enters the transfer material discharging unit;

FIG. 6 is a diagram illustrating a spur member that prevents contact and catch between the transfer material discharging unit and the transfer material when the transfer material is transferred from the secondary transfer unit to the transfer material discharging unit.

FIG. 7 is a diagram illustrating a spur member that prevents contact and catch between the secondary transfer unit and the transfer material when the transfer material enters the secondary transfer unit.

FIG. 8 is a diagram showing a spur member for preventing contact and catch between the secondary transfer means and the transfer material when the transfer material is conveyed from the primary transfer position to the secondary transfer means.

FIG. 9 is a diagram showing discharge conditions of a secondary transfer device constituting a secondary transfer unit.

FIG. 10 is a diagram showing a position setting of a discharge electrode of a secondary transfer device constituting a secondary transfer unit.

11 is a diagram showing the arrangement of conductive rollers constituting the secondary transfer means in FIG. 10 and the conditions for setting the diameter.

FIG. 12 is a view showing a means for applying a transfer pressure to the intermediate transfer body in the image forming apparatus described with reference to FIG. 1 for achieving good adhesion between the transfer material and the belt-shaped intermediate transfer body.

FIG. 13 is a diagram illustrating an appropriate area for primary transfer or second primary transfer by pressing a primary transfer unit or a second primary transfer unit.

FIG. 14 is a diagram illustrating another example of a unit that applies a transfer pressure to an intermediate transfer member.

FIG. 15 is a diagram illustrating a pressing force in a direction of contact with an image carrier of a means for applying a transfer pressure to an intermediate transfer member.

FIG. 16 is a diagram illustrating a non-image area at the front end of the back surface of the transfer material.

FIG. 17 is a diagram showing a means for applying a transfer pressure to the intermediate transfer body for achieving good adhesion between the transfer material and the belt-shaped intermediate transfer body in the image forming apparatus described in FIG.

[Explanation of symbols]

10, 10a, 10b Photoreceptor drum 11 Scorotron charger 12 Exposure optical system 13 Developing device 14a, 114a Intermediate transfer belt 14c Primary transfer roller 14C Primary transfer device 14f Guide roller 14g Secondary transfer device 14h Transfer material removing device 14j 2 Next transfer opposed roller 14m, 114m, 114n Static eliminator 15b Timing roller 17 Fixing device 114b First primary transfer roller 114c Second primary transfer roller 150 Paper charger 162, 162A, 162B, 162C, 162D Spur BOa pressing blade HWa Discharge wire KDa Serrated electrode LKa, LKb, LKc Rack MS Mylar sheet M1, M2, M3 Drive motor P Recording paper Pa Transfer material tip Pb Transfer material center Pc Back face tip PNa, PNb, PNc Pinion SP1, SP2 Rudo plate

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) G03G 15/16 G03G 15/16 (72) Inventor Satoshi Haneda 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term ( Reference) 2H028 BA06 BB02 2H032 AA05 AA15 BA09 BA21 BA23 BA28 BA29 DA03 DA04 DA14 2H072 AA32 AA36 AB07 CA01 CA07 CB07 CB08 HB05 JA02 JA03 JC02 JC09 3F049 AA01 AA10 CA03 CA11 LA02 LA05 LA07 LB03

Claims (52)

[Claims] An image bearing member for bearing a toner image formed by a toner image forming means; a toner image on the image bearing member being transferred; and supporting the transferred toner image and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a transfer material for transferring the toner image on the intermediate transfer body to the transfer material. A secondary transfer means for re-transferring to the back surface of the transfer material; and a transfer material removing device provided near a position for separating the transfer material from the intermediate transfer member, for separating the transfer material from the intermediate transfer member for removing the transfer material. And a fixing unit for fixing the toner image on the transfer material, wherein a spur member is provided adjacent to an upstream side of the transfer material neutralization unit. 2. A method according to claim 1, wherein the closest distance between the transfer material discharging means and the intermediate transfer member is D1 (mm), and the closest spur member provided adjacent to the upstream side of the transfer material discharging device and the intermediate transfer member. The image forming apparatus according to claim 1, wherein when the distance is D2 (mm), D1> D2. 3. The transfer material discharging means is a corona discharger having a discharge electrode and a shield member, and a spur member provided adjacent to an upstream side of the transfer material discharging means is provided integrally with the shield member. The image forming apparatus according to claim 1, wherein: 4. A first image carrier for carrying a toner image formed by a first toner image forming means, and a second image carrier for carrying a toner image formed by a second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, A secondary transfer unit that retransfers the toner image on the intermediate transfer member to the back surface of the transfer material; and an intermediate unit that is provided near a position where the transfer material is separated from the intermediate transfer member and removes the charge of the transfer material. A transfer material removing unit configured to separate the transfer material from the transfer body; In the image forming apparatus having a fixing unit that fixes the toner image on the image forming apparatus characterized by providing a spur member adjacent the upstream side of the transfer material discharging means. 5. The closest distance between the transfer material discharging means and the intermediate transfer body is D1 (mm), and the closest distance between a spur member provided adjacent to the upstream side of the transfer material discharging means and the intermediate transfer body is D1 (mm). The image forming apparatus according to claim 4, wherein when the distance is D2 (mm), D1> D2. 6. The transfer material discharging means is a corona discharger having a discharge electrode and a shield member, and a spur member provided adjacent to an upstream side of the transfer material discharging means is provided integrally with the shield member. The image forming apparatus according to claim 4, wherein: 7. An image carrier for carrying a toner image formed by a toner image forming means, a toner image transferred on the image carrier, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a transfer material for transferring the toner image on the intermediate transfer body to the transfer material. A secondary transfer means for re-transferring to the back surface of the transfer material; and a transfer material removing device provided near a position for separating the transfer material from the intermediate transfer member, for separating the transfer material from the intermediate transfer member for removing the transfer material. And a fixing unit for fixing the toner image on the transfer material, wherein a spur member is provided between the secondary transfer unit and the transfer material neutralization unit. . 8. A spur member provided between the secondary transfer unit and the transfer material neutralizing unit, wherein the closest distance between the transfer material neutralizing unit and the intermediate transfer body is D1 (mm), and The distance D3 (mm) and the closest distance D2 (mm) between the secondary transfer means and the intermediate transfer member are: D1> D3 ≧ D4. The image forming apparatus as described in the above. 9. A spur member provided between the secondary transfer means and the transfer material discharging means is movably provided with respect to the intermediate transfer body, and a transfer path of the transfer material by the intermediate transfer body can be opened. 9. The method according to claim 7, wherein
An image forming apparatus according to claim 1. 10. A first image carrier for carrying a toner image formed by a first toner image forming means, and a second image carrier for carrying a toner image formed by a second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, A secondary transfer unit that retransfers the toner image on the intermediate transfer member to the back surface of the transfer material; and an intermediate unit that is provided near a position where the transfer material is separated from the intermediate transfer member and removes the charge of the transfer material. A transfer material neutralizing unit for separating the transfer material from the transfer body; In the image forming apparatus having a fixing unit for fixing the toner image on the wood, the image forming apparatus characterized by providing a spur member between said second transfer means the transfer material discharging means. 11. A method according to claim 1, wherein a closest distance between said transfer material discharging means and said intermediate transfer body is D1 (mm), and a spur member provided between said secondary transfer means and said transfer material discharging means and said intermediate transfer body. 11. When the closest distance is D3 (mm) and the closest distance between the secondary transfer unit and the intermediate transfer body is D4 (mm), D1> D3 ≧ D4. Image forming apparatus. 12. A spur member provided between the secondary transfer means and the transfer material discharging means is movably provided with respect to the intermediate transfer body, and a transfer path of the transfer material by the intermediate transfer body can be opened. The image forming apparatus according to claim 10, wherein: 13. An image carrier for carrying a toner image formed by a toner image forming means, a toner image transferred on the image carrier, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; a primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a primary transfer position by the primary transfer means. A secondary transfer unit provided on the downstream side in the transfer material moving direction and retransferring the toner image on the intermediate transfer body to the back surface of the transfer material; and a fixing unit for fixing the toner image on the transfer material. An image forming apparatus having a spur member adjacent to an upstream side of the secondary transfer unit. 14. The closest distance between the secondary transfer means and the intermediate transfer body is D4 (mm), and the closest distance between the spur member provided adjacent to the upstream side of the secondary transfer means and the intermediate transfer body. 14. The image forming apparatus according to claim 13, wherein when the distance is D5 (mm), D4> D5. 15. The secondary transfer means is a corona discharger having a discharge electrode and a shield member, and a spur member provided adjacent to an upstream side of the secondary transfer means is provided integrally with the shield member. The image forming apparatus according to claim 13, wherein: 16. A first image carrier for carrying the toner image formed by the first toner image forming means, and a second image carrier for carrying the toner image formed by the second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, A second primary transfer unit which is provided downstream of the second primary transfer position in the transfer material moving direction with respect to the second primary transfer position and retransfers the toner image on the intermediate transfer body to the back surface of the transfer material; An image forming apparatus comprising: a transfer unit; and a fixing unit that fixes a toner image on the transfer material. An image forming apparatus according to claim 1, wherein a spur member is provided adjacent to an upstream side of said secondary transfer means. 17. The closest distance between the secondary transfer means and the intermediate transfer body is D4 (mm), and the closest distance between a spur member provided adjacent to the upstream side of the secondary transfer means and the intermediate transfer body. 17. The image forming apparatus according to claim 16, wherein when the distance is D5 (mm), D4> D5. 18. The secondary transfer means is a corona discharger having a discharge electrode and a shield member, and a spur member provided adjacent to an upstream side of the secondary transfer means is provided integrally with the shield member. 18. The image forming apparatus according to claim 16, wherein: 19. An image carrier for carrying a toner image formed by a toner image forming means, a toner image on the image carrier being transferred, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; a primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a primary transfer position by the primary transfer means. A secondary transfer unit provided on the downstream side in the transfer material moving direction and retransferring the toner image on the intermediate transfer body to the back surface of the transfer material; and a fixing unit for fixing the toner image on the transfer material. An image forming apparatus, comprising: a spur member provided between the primary transfer position and the secondary transfer unit. 20. A spur member provided between the primary transfer position and the secondary transfer means, wherein the closest distance between the secondary transfer means and the intermediate transfer body is D4 (mm), and 20. The image forming apparatus according to claim 19, wherein D4> D6 when the closest distance of D6 is D6 (mm). 21. A spur member provided between the primary transfer position and the secondary transfer means is movably provided with respect to the intermediate transfer body, and a transfer path of the transfer material by the intermediate transfer body can be opened. The image forming apparatus according to claim 19, wherein: 22. A first image carrier for carrying the toner image formed by the first toner image forming means, and a second image carrier for carrying the toner image formed by the second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, A second primary transfer unit which is provided downstream of the second primary transfer position in the transfer material moving direction with respect to the second primary transfer position and retransfers the toner image on the intermediate transfer body to the back surface of the transfer material; An image forming apparatus comprising: a transfer unit; and a fixing unit that fixes a toner image on the transfer material. The image forming apparatus according to claim 1, wherein a spur member is provided between the second primary transfer position and the secondary transfer unit. 23. A spur member provided between the second primary transfer position and the secondary transfer unit, wherein the closest distance between the secondary transfer unit and the intermediate transfer body is D4 (mm). 23. The image forming apparatus according to claim 22, wherein D4> D6 when the closest distance to the transfer member is D6 (mm). 24. A spur member provided between the second primary transfer position and the secondary transfer means so as to be movable with respect to the intermediate transfer member, and a transfer path of the transfer material by the intermediate transfer member. 23. The device according to claim 22, wherein the device can be opened.
Or the image forming apparatus according to 23. 25. An image carrier for carrying a toner image formed by a toner image forming means, a toner image transferred on the image carrier, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a transfer material for transferring the toner image on the intermediate transfer body to the transfer material. An image forming apparatus comprising: a secondary transfer unit that retransfers to the back surface of the image forming apparatus; and a fixing unit that fixes the toner image on the transfer material. The secondary transfer unit includes a conductive roller that stretches the intermediate transfer member. And a corona discharger provided to face the conductive roller via the intermediate transfer member, wherein a discharge width of the corona discharger is larger than a contact width between the intermediate transfer member and the conductive roller. It is characterized by narrowing Image forming apparatus. 26. The corona discharger according to claim 25, wherein the corona discharger includes a discharge electrode and a shield member, and a shield member is provided at an opening of the shield member to reduce a discharge width of the corona discharger. The image forming apparatus as described in the above. 27. A first image carrier for carrying a toner image formed by a first toner image forming means, and a second image carrier for carrying a toner image formed by a second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, An image forming apparatus comprising: a secondary transfer unit that re-transfers the toner image on the intermediate transfer member to the back surface of the transfer material; and a fixing unit that fixes the toner image on the transfer material. A conductive roller for stretching the intermediate transfer member, A corona discharger provided to face the conductive roller via a body, wherein a discharge width of the corona discharger is smaller than a contact width between the intermediate transfer body and the conductive roller. Image forming apparatus. 28. The corona discharger according to claim 27, wherein the corona discharger comprises a discharge electrode and a shield member, and a shield member is provided at an opening of the shield member to reduce a discharge width of the corona discharger. The image forming apparatus as described in the above. 29. An image carrier for carrying a toner image formed by a toner image forming means, a toner image transferred on the image carrier, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a transfer material for transferring the toner image on the intermediate transfer body to the transfer material. An image forming apparatus comprising: a secondary transfer unit that retransfers to the back surface of the image forming apparatus; and a fixing unit that fixes the toner image on the transfer material. The secondary transfer unit includes a conductive roller that stretches the intermediate transfer member. And a corona discharger provided facing the conductive roller via the intermediate transfer member and having a discharge electrode and a shield member. The closest distance between the discharge electrode and the shield member is d1.
(Mm), when the closest distance between the discharge electrode and the intermediate transfer member is d2 (mm), d1> d2, and a radius d1 (mm) about the discharge portion of the discharge electrode as a center. The width of the intermediate transfer member in the area surrounded by the circle of
An image forming apparatus, wherein the width is smaller than the contact width between the intermediate transfer member and the conductive roller. 30. An outer peripheral surface of the conductive roller, which is larger than a virtual plane passing through a position where the intermediate transfer member contacts the image carrier and a position where the transfer material separates from the intermediate transfer member. The image forming apparatus according to claim 29, wherein the image forming apparatus protrudes toward an outer peripheral surface of the intermediate transfer body. 31. The conductive roller has a radius of r1 (m
31. The image forming apparatus according to claim 29, wherein when m), d1> r1. 32. A first image carrier for carrying the toner image formed by the first toner image forming means, and a second image carrier for carrying the toner image formed by the second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, An image forming apparatus comprising: a secondary transfer unit that re-transfers the toner image on the intermediate transfer member to the back surface of the transfer material; and a fixing unit that fixes the toner image on the transfer material. A conductive roller for stretching the intermediate transfer member, Provided opposite to the conductive roller through the body, it consists of a corona discharger having a discharge electrode and the shield member, the closest distance of the discharge electrode and the shield member d1
(Mm), when the closest distance between the discharge electrode and the intermediate transfer member is d2 (mm), d1> d2, and a radius d1 (mm) about the discharge portion of the discharge electrode as a center. The width of the intermediate transfer member in the area surrounded by the circle of
An image forming apparatus, wherein the width is smaller than the contact width between the intermediate transfer member and the conductive roller. 33. An imaginary plane passing the outer peripheral surface of the conductive roller through a position where the intermediate transfer member contacts the second image carrier and a position where the transfer material separates from the intermediate transfer member. 33. The image forming apparatus according to claim 32, wherein the image forming apparatus protrudes toward the outer peripheral surface of the intermediate transfer member. 34. The conductive roller has a radius of r1 (m
The image forming apparatus according to claim 32, wherein when m), d1> r1. 35. An image carrier for carrying a toner image formed by a toner image forming means, a toner image transferred on the image carrier, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a transfer material for transferring the toner image on the intermediate transfer body to the transfer material. A secondary transfer means for re-transferring to the back surface of the transfer material; and a transfer material removing device provided near a position for separating the transfer material from the intermediate transfer member, for separating the transfer material from the intermediate transfer member for removing the transfer material. And a fixing unit for fixing the toner image on the transfer material, wherein the transfer pressure at the time of transferring the toner image from the image carrier to the intermediate transfer member is P1 (N / cm). The transfer from the image carrier The transfer pressure at the time of transferring the toner image to the copying material is P2 (N / cm)
Wherein: P1 <P2. 36. The transfer pressure P1 is set in a range of 0.1 N / cm ≦ P1 ≦ 0.5 N / cm, and the transfer pressure P2 is set in a range of 0.2 N / cm ≦ P2 ≦ 1 N / cm. 36. The image forming apparatus according to claim 35, wherein the setting is set to: 37. The image forming apparatus according to claim 35, wherein the transfer pressure is larger at a center portion than at an end portion. 38. The image forming apparatus according to claim 35, wherein a roller member is used as the primary transfer unit, and the primary transfer unit is a unit for applying the transfer pressure. apparatus. 39. An apparatus according to claim 35, wherein said transfer pressure applying means is provided upstream of said primary transfer means.
38. The image forming apparatus according to any one of items 37 to 37. 40. The image forming apparatus according to claim 35, wherein the transfer pressure is changed according to a type of the transfer material. 41. An image carrier for carrying a toner image formed by a toner image forming means, a toner image transferred on the image carrier, carrying the transferred toner image, and supporting a transfer material. A belt-shaped intermediate transfer body to be conveyed; primary transfer means for transferring the toner image on the image carrier to the surface of the intermediate transfer body or the transfer material; and a transfer material for transferring the toner image on the intermediate transfer body to the transfer material. A secondary transfer means for re-transferring to the back surface of the transfer material; and a transfer material removing device provided near a position for separating the transfer material from the intermediate transfer member, for separating the transfer material from the intermediate transfer member for removing the transfer material. And a fixing unit for fixing the toner image on the transfer material, wherein the transfer pressure at the time of transfer from the image carrier to the center of the transfer material is P2 (N / cm). From the body to the tip of the transfer material When the transfer pressure at the time of transfer is P3 (N / cm), P2> P3. 42. The transfer pressure P2 is set in a range of 0.2 N / cm ≦ P2 ≦ 1 N / cm, and the transfer pressure P3 is set in a range of 0.1 N / cm ≦ P3 ≦ 0.5 N / cm. 42. The image forming apparatus according to claim 41, wherein the setting is set to: 43. A non-image area is provided at a front end portion on the back surface side of the transfer material.
An image forming apparatus according to claim 1. 44. A first image carrier for carrying the toner image formed by the first toner image forming means, and a second image carrier for carrying the toner image formed by the second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, A secondary transfer unit that retransfers the toner image on the intermediate transfer member to the back surface of the transfer material; and an intermediate unit that is provided near a position where the transfer material is separated from the intermediate transfer member and removes the charge of the transfer material. A transfer material neutralizing unit for separating the transfer material from the transfer body; A fixing unit for fixing a toner image on a material, wherein a transfer pressure at the time of transferring the toner image by the first primary transfer unit is P1 (N / cm), and the second primary transfer unit is An image forming apparatus wherein P1 <P2 when a transfer pressure at the time of transferring a toner image is P2 (N / cm). 45. The transfer pressure P1 is set in a range of 0.1 N / cm ≦ P1 ≦ 0.5 N / cm, and the transfer pressure P2 is set in a range of 0.2 N / cm ≦ P2 ≦ 1 N / cm. The image forming apparatus according to claim 44, wherein the setting is set to: 46. The image forming apparatus according to claim 44, wherein the transfer pressure is larger at the center than at the ends. 47. A roller member is used as the first primary transfer unit or the second primary transfer unit, and the first primary transfer unit or the second primary transfer unit is controlled by the transfer pressure. The application means is provided.
7. The image forming apparatus according to any one of 6. 48. The apparatus according to claim 44, wherein the transfer pressure applying means is provided at an upstream portion of the first primary transfer means or at an upstream portion of the second primary transfer means. Item 10. The image forming apparatus according to item 1. 49. The image forming apparatus according to claim 44, wherein the transfer pressure is changed according to a type of the transfer material. 50. A first image carrier for carrying the toner image formed by the first toner image forming means, and a second image carrier for carrying the toner image formed by the second toner image forming means. A belt-shaped intermediate transfer body that transfers the toner image on the first image carrier, carries the transferred toner image, and supports and conveys a transfer material; and the first image carrier. A first primary transfer unit for transferring the upper toner image to the intermediate transfer body, a second primary transfer unit for transferring the toner image on the second image carrier to the surface of the transfer material, A secondary transfer unit that retransfers the toner image on the intermediate transfer member to the back surface of the transfer material; and an intermediate unit that is provided near a position where the transfer material is separated from the intermediate transfer member and removes the charge of the transfer material. A transfer material neutralizing unit for separating the transfer material from the transfer body; A fixing unit for fixing a toner image on a material, wherein the transfer pressure at the time of transfer to the center of the transfer material by the second primary transfer unit is P2 (N / cm); The transfer pressure at the time of transfer to the leading end of the transfer material by the primary transfer means is P3 (N
/ Cm), wherein P2> P3. 51. The transfer pressure P2 is set in a range of 0.2 N / cm ≦ P2 ≦ 1 N / cm, and the transfer pressure P3 is set in a range of 0.1 N / cm ≦ P3 ≦ 0.5 N / cm. 51. The image forming apparatus according to claim 50, wherein the setting is set to. 52. A non-image area is provided at a front end portion on the back surface side of the transfer material.
An image forming apparatus according to claim 1.