JPH11102124A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the securement of the transfer ability and the separability of recording paper on the separation side of a toner image receiving body compatible with the stabilization of driving the belt-like toner image receiving body by separately providing the conductive roller of the toner image receiving body and a driving roller driving the belt-like toner image receiving body. SOLUTION: The conductive roller 14d provided on the side of the toner image receiving body 14a where the recording paper P is separated and the driving roller 14j driving the belt-like toner image receiving body 14a are separately provided. The body 14a is stretched and laid in a state that it is inscribed to the driving roller 14j, the conductive roller 14d, a driven roller 14e and a tension roller 14i, and is rotated counterclockwise as shown by an arrow in figure. The roller 14e is disposed on the supply side of the recording paper P as the transfer material of the body 14a, and the roller 14d is disposed on the separation side of the recording paper P. The roller 14j is provided on the upstream side in the moving direction of the body 14a near the roller 14d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine 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 capable of forming an image on both sides of a transfer material.

[0002]

2. Description of the Related Art Conventionally, in forming a double-sided image, 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 double-sided reversal feeding device, and the image is re-supported. 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 the body, and an image on the other surface is transferred and fixed on the transfer material.

In this double-sided image forming apparatus, as described above,
The transfer of the transfer material, such as feeding to the two-sided reversing feed device or passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low, causing jams and wrinkles of the transfer material. .

On the other hand, JP-B-49-37538, JP-B-54-28740, and JP-A-1-444.
No. 57 and Japanese Unexamined Patent Publication No. 4-214576,
There has been proposed an image forming apparatus that forms a toner image on both surfaces of a transfer material using a first image holding unit and a second image holding unit, and then performs fixing once.

Further, the present inventors have arranged a plurality of sets of toner image forming means including a charging means, an image writing means, a developing means, etc. around a photosensitive drum (first image carrying means). The superimposed color toner image formed on the drum is once collectively transferred to a belt-shaped toner image receiver (second image carrying means) by the first transfer means, and then the superimposed color toner image is again transferred onto the photosensitive drum. A toner image is formed, and a transfer material fed at the same time as the toner image on the photosensitive drum and the toner image on the toner image receiver is charged by a transfer material charging unit and adsorbed on the toner image receiver, The toner image on the photoreceptor drum is transferred as a front image by a first transfer unit to both surfaces of the transfer material conveyed on the toner image receiver, and the toner image on the toner image receiver is printed as a back image. Transcription 2 After transferring the stage, separates the transfer material from the toner image receiving body, is considering an image forming apparatus for forming a double-sided color image the toner image on the transfer material and fixed by a fixing device (fixing unit).

[0006]

In the above-mentioned image forming apparatus, the roller provided on the transfer material supply side and the separation side of the belt-shaped toner image receiving body for conveying the transfer material,
And the tension roller stretches the toner image receiver, but in order to reduce the speed unevenness of the belt-shaped toner image receiver in the transfer material transporting unit between the transfer material supply side and the separation side, A roller provided on the separation side of the transfer material on the downstream side in the moving direction of the toner image receiver is used as a driving roller. Further, a second transfer unit and a transfer material separating unit are provided to face the driving roller, and transfer of the back surface image to the transfer material and separation of the transfer material are performed.

In order to ensure the transfer property of the transfer material in the roller portion of the separation section, it is preferable that the electrical resistivity of the roller be as low as possible, and a metal roller is suitable. However, since the roller of the separation unit is also used for driving, it is preferable to use a material having a large friction with the back surface of the toner image receiving body, for example, a rubber roller. Instead of a metal roller, a conductive rubber roller is used. Since the electrical resistivity of a rubber roller is too high, discharge failure may occur.
A problem arises in that good transferability of the back side image cannot be ensured. Also, when separating the transfer material from the toner image receiver,
Immediately after the transfer, the transfer material is strongly electrostatically attracted to the toner image receiving body, so that there is also a problem that it is very difficult to separate the transfer material.

Therefore, in order to ensure the separation of the transfer material at the roller portion of the separation section, it is effective to perform the curvature separation by reducing the radius of curvature of the roller. Since the angle at which the toner image receiving body is wound around the roller becomes small, there arises a problem that the driving force cannot be secured. In addition, since the role of the second transfer means as a counter electrode is also reduced, a discharge failure is likely to occur and a transfer failure occurs.

As described above, in order to ensure the transferability of the back side image and the separability of the transfer material, it is preferable to use a metal roller having a small roller diameter as the roller of the separation unit. There is a problem that it is difficult to achieve both stability and stability.

The present invention solves the above-mentioned problems, and ensures the transferability and separability of the transfer material on the separation side of the second image bearing means, and stabilizes the driving of the belt-shaped second image bearing means. It is an object of the present invention to provide an image forming apparatus capable of achieving both of the above.

[0011]

An object of the present invention is to provide a first image carrying means for carrying a toner image formed by a toner image forming means, and a transfer of the toner image carried by the first image carrying means. A belt-like second image carrying means for carrying the transferred toner image on the surface and conveying a transfer material; and a second image carrying means for carrying the toner image carried by the first image carrying means. Means or first for transferring to the surface of the transfer material
Transfer means, and a second transfer means for transferring the toner image carried by the second image carrying means to the back surface of the transfer material,
A fixing unit for fixing the toner image transferred to the transfer material, wherein the second image bearing unit is provided at least on a side for supplying the transfer material to the second image bearing unit. Driven roller, a conductive roller provided on a side for separating the transfer material from the second image bearing means, and a conductive roller provided near the conductive roller and upstream in the moving direction of the second image bearing means. This is achieved by an image forming apparatus characterized by being stretched by a driving roller and a tension roller.

[0012]

Embodiments of the present invention will be described below. The description in this section does not limit the technical scope of the claims and the meaning of the terms. The assertive description below shows the best mode, and limits the technical scope of the present invention and the meaning of the terms. It does not do. In the following description of the embodiment, in the transfer area, the surface of the transfer material on the side facing the first image bearing means is the surface, and the other surface of the transfer material, ie, the transfer material on the side facing the second image bearing means The image transferred to the front surface of the transfer material is called a front image, and the image transferred to the back surface of the transfer material is called a back image.

An image forming process and each mechanism of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a color image forming apparatus showing an embodiment of the image forming apparatus according to the present invention. FIG. 2 is a side sectional view of the first image bearing means of FIG. FIG. 3A is a diagram showing a state of forming a toner image in the image forming apparatus according to the present invention, and FIG.
FIG. 3B is a diagram showing a toner image formation state when the back image formed on the image carrying means is transferred onto the second image carrying means. FIG. FIG. 3C is a diagram illustrating a state of forming a toner image when a surface image is formed on the first image carrier in synchronization with the first embodiment, and FIG. 3C is a diagram illustrating double-sided image formation on a transfer material.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as first image bearing means, 11 denotes a scorotron charger as charging means for each color, 12 denotes an exposure optical system as image writing means for each color, and 13 Denotes a developing device which is a developing means for each color;
Reference numeral a denotes a toner image receiving body as a second image carrying means, 14c a primary transfer unit as a first transfer unit, 14g a secondary transfer unit as a second transfer unit, and 150 a transfer material charging unit. A paper charger 160 is a transport unit having a separation claw 210 as a claw member and a spur 162 as a spur member, and 17 is a fixing device as fixing means.

Photosensitive drum 10 as first image bearing means
Is obtained by forming a photosensitive layer such as a transparent conductive layer, an a-Si layer, or an organic photosensitive layer (OPC) on the outer periphery of a cylindrical base formed of a transparent member such as optical glass or transparent acrylic resin. FIG. 1 with the conductive layer grounded.
It is rotated clockwise as indicated by the arrow.

The photosensitive drum 10 is, as shown in FIG.
Flange members 10a and 1 at both ends for engaging and fixing it
The gear G integrated with the flange member 10b is supported by the bearings B1 and B2 fitted to the drum shaft 30 and is rotatably supported by the drum shaft 30 erected and fixed to the apparatus main body. When driven by meshing with the drive gear, it is rotated at a constant speed in a predetermined direction.

A scorotron charger 11, which is a charging unit for each color, an exposure optical system 12, which is an image writing unit for each color, and a developing unit 13, which is a developing unit for each color, form a set of yellow (Y) ), Magenta (M), cyan (C), and black (K) are provided for the image forming processes, and four sets are provided.
Are arranged in the order of Y, M, C, and K with respect to the rotation direction.

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 faces the photosensitive layer of the photosensitive drum 10. And installed
The charging operation (in the present embodiment, negative charging) is performed by corona discharge having the same polarity as that of the toner.
A uniform potential is given to 0. 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 has a line in which a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light arranged in the main scanning direction in parallel with the drum shaft 30 are arranged. An exposure unit composed of an exposure element 12a in the shape of a circle, a light-converging light transmitter (trade name: Selfoc lens array) 12b as an imaging element, and a lens holder 12c, which is attached to the holding member 20. . In addition to the exposure optical system 12 for each color, a transfer simultaneous exposure unit 12d and a uniform exposure unit 12e are attached to the holding member 20, and are housed integrally within the light-transmitting base of the photoconductor drum 10 ( (See FIG. 1). The exposure optical system 12 for each color performs image exposure of the photosensitive layer of the photosensitive drum 10 from the back side in accordance with image data of each color read by a separate image reading device and stored in the memory, and electrostatically exposes the photosensitive layer on the photosensitive drum 10. Form a latent image. As the exposure element 12a, an element in which a plurality of light-emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array can be used. The emission wavelength of the image exposure light emitting element is usually in the range of 780 to 900 nm, which is highly transparent to Y, M, and C toners. 400 to 780 n, which does not have sufficient transparency to the color toner.
The wavelength may be m. In FIG. 2, WA is a lead wire from a light emitting element (LED) for image exposure light.

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 in the forward direction with respect to the rotating direction of the photosensitive drum 10, for example, 0.5 to 1 mm in thickness. , A developing sleeve 131 formed of a non-magnetic stainless steel or aluminum material having an outer diameter of 15 to 25 mm, and a developing casing 138. Yellow (Y), magenta (M), cyan (C), It contains a black (K) one-component or two-component developer. Each of the developing devices 13 is provided with a predetermined gap, for example, 100 to 500 μm, from the photosensitive drum 10 by an abutting roller (not shown).
Is applied, and a non-contact reversal development is performed by applying a developing bias in which a DC voltage and an AC voltage are superimposed on the developing sleeve 131, and a toner image is formed on the photosensitive drum 10. Form.

Toner image receiver 1 as second image bearing means
4a is an endless belt having a volume resistivity of 10 ⁸ to 10 ¹⁵ Ω · cm, for example, a modified polyimide, a thermosetting polyimide,
Conductive material dispersed in engineering plastics such as ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, nylon alloy, etc., thickness 0.1-0.5m
A seamless belt having a two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is preferably formed on the outside of a semiconductive film substrate having a thickness of 5 m as a toner filming preventing layer. In addition to the above, the base material of the belt may have a thickness of 0.3 to 0.3 in which a conductive material is dispersed in silicon rubber or urethane rubber.
A 2.0 mm semiconductive rubber belt can also be used.

The toner image receiving member 14a includes a driving roller 14
j, the conductive roller 14d, the driven roller 14e, and the tension roller 14i are stretched in contact with each other, and rotated counterclockwise as indicated by the arrow in FIG. The driven roller 14e is disposed on the supply side of the recording paper P as a transfer material of the toner image receiver 14a, and the conductive roller 14d is disposed on the separation side of the recording paper P. The driving roller 14j is provided near the conductive roller 14d and on the upstream side in the moving direction of the toner image receiving body 14a. The driven roller 14e and the conductive roller 14d
The portion between the supply side of the recording paper P and the separation side of the recording paper P of the toner image receiver 14a stretched between the recording material P is used as a transfer material transport unit.

According to the rotation direction of the toner image receiver 14a,
Driven roller 14e, conductive roller 14d, drive roller 1
4j, a tension roller 14i, and a driven roller 14e, a conductive roller 14d, and a drive roller 14j.
Is fixedly rotated, and the tension roller 14i is movably supported by elasticity of a spring (not shown) or the like, and is rotated while stretching the toner image receiver 14a. A curvature portion KT is formed at the end of the toner image receiving member 14a on the fixing device 17 side on the separation side due to the curvature of the conductive roller 14d. The drive roller 14j is rotated by a drive motor (not shown), and the toner image receiver 14a is driven and rotated. The conductive roller 14d, the driven roller 14e, and the tension roller 14i are driven to rotate by the rotation of the toner image receiver 14a. The conductive roller 14d is normally driven to rotate, but may be driven to rotate by the same drive source as the drive roller 14j. Belt slack of the rotating toner image receiver 14a is tensioned by the tension roller 14i.
Toner image receiver 14a stretched over conductive roller 14d
The recording paper P, which is the transfer material conveyed by the toner image receiver 14a, is separated by the curvature separation at the curvature portion KT at the end of the fixing device 17 side.

The electrical resistivity of preferably less 10 ⁰ Ω · cm as the conductive small diameter which is grounded is arranged in the separation of the recording sheet P a toner image receiving body 14a of the conductive roller 14d, the conductive It is preferable to use a metal roller. A roller using a highly conductive member other than a metal member can be used. Further, it is preferable that the radius of curvature of the conductive roller 14d is 10 mm or less, and the winding angle with the toner image receiver 14a is 60 ° or more. By setting the radius of curvature to 10 mm or less, the conductive roller 1
The separation of the recording paper P at the curvature portion KT of the toner image receiver 14a formed with the curvature of 4d is facilitated. Further, by setting the winding angle to 60 ° or more, the conductive roller 14
d prevents slippage of the toner image receiver 14a. In particular, slippage when a metal roller is used is prevented.

The driving roller 1 disposed upstream of the conductive roller 14d in the moving direction of the toner image receiving member 14a.
4j has a rubber hardness of 60 to 9 in order to obtain durability and a large driving force by eliminating slippage with the toner image receiver 14a.
It is preferable to use a large-diameter rubber roller of 0 degree (vulcanized rubber physical test method (JIS-K6301, spring type hardness test A type)). It is preferable that the radius of curvature of the drive roller 14j be 10 mm or more and the winding angle with the toner image receiver 14a is 90 ° or more so as to increase the amount of winding of the toner image receiver 14a to prevent slippage.

As described above, the conductive roller 14d provided on the toner image receiving member 14a on the side of separating the recording paper P and the driving roller 1 for driving the belt-shaped toner image receiving member 14a.
4j and the toner image receiving member 14 separately.
As a result, it is possible to ensure both transferability and separability of the recording paper P on the separation side of a, and to stabilize driving of the belt-shaped second image bearing means.

A primary transfer unit 14c as a first transfer unit
Is a corona discharger provided opposite the photosensitive drum 10 with the toner image receiver 14a interposed therebetween, and forms a transfer area 14b between the toner image receiver 14a and the photosensitive drum 10. A DC voltage having the opposite polarity (positive polarity in the present embodiment) to the toner is applied to the primary transfer device 14c.
The toner image on the photosensitive drum 10 is transferred to the toner image receiving member 14a.
The image is transferred onto the upper surface or the surface of the recording paper P as a transfer material. As the primary transfer device 14c, it is also possible to use a brush charger, a roller charger, or the like provided in contact with the back surface of the toner image receiver 14a.

The secondary transfer unit 14g, which is the second transfer unit, is preferably constituted by a corona discharger, and is a small-diameter conductive roller 14d grounded with the toner image receiver 14a interposed therebetween.
And a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to transfer the toner image on the toner image receiver 14 a to the back surface of the recording paper P. The second transfer device 14g preferably electrical resistivity of 10 ⁰
By providing the conductive roller 14d opposite to the grounded conductive roller 14d of Ω · cm or less, stabilization of corona discharge by the secondary transfer device 14g is achieved, and good transferability of the back side image is secured.

The paper charger 150, which is a transfer material charging means, is preferably constituted by a corona discharger, is provided opposite to a driven roller 14e, which is grounded across the toner image receiving member 14a, and has the same polarity as the toner. A DC voltage (in the embodiment, a negative polarity) is applied, and the recording paper P is charged and attracted to the toner image receiver 14a. As the paper charger 150, a paper charging brush, a paper charging roller, or the like can be used in addition to the corona discharger.

The transport section 160 includes a separation claw 21 which is a claw member.
0 and a spur 162 which is a spur member, and is provided between the curvature portion KT of the toner image receiver 14 a and the fixing device 17. By providing the transport section 160 between the toner image receiver 14a and the fixing device 17, the toner image receiver 14a is deformed by the heat of the fixing device 17, or the toner image of the back side image on the toner image receiver 14a is formed. Can be avoided due to the fact that the toner tends to be fused and transfer is difficult, and the toner is fixed on the toner image receiving body 14a.

The separation claw 210, which is a claw member, is provided in the vicinity of the curvature portion KT of the toner image receiver 14a formed by the conductive roller 14d having a small radius of curvature of preferably 10 mm or less. The recording paper P is fixed to a support shaft 215 provided on the upstream side in the transport direction. Separation claw 2
Reference numeral 10 denotes a state in which, when the recording paper P is separated from the toner image receiving body 14a, the leading end of the recording paper P that is to be bent and conveyed along the curvature portion KT of the toner image receiving body 14a is brought into contact with the recording paper P for recording. It assists in separating paper P from toner image receiver 14a.

The spur 162, which is a spur member, is
The recording paper P is provided on the upper surface of the recording paper P so as to be rotatable about a rotation support shaft 165 and separated from the toner image receiver 14a.
The recording paper P is conveyed to the fixing device 17 while the rear side of the recording paper P is guided by a plurality of protrusions provided on the peripheral surface to prevent disturbance of the rear toner image.

The fixing device 17 as a fixing means is constituted by two roller-shaped fixing members, a fixing roller 17a having a heater therein and a pressure roller 17b.
The recording paper P is nipped at the nip T between the a and the pressure roller 17b, and the toner image on the recording paper P is fixed by applying heat and pressure.

Next, the image forming process will be described.

The photosensitive drum 10 is rotated clockwise as indicated by the arrow in FIG. 1 by starting a photosensitive member driving motor (not shown) at the start of image recording, and is also exposed to light by the charging action of a yellow (Y) scorotron charger 11. Body drum 1
Application of a potential to 0 starts.

After the photosensitive drum 10 is applied with a potential, the Y exposure optical system 12 starts image writing with a 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 a 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. A 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 superposed 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. (Toner image forming means).

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.

In the transfer area 14b, the superimposed color toner image, which is the back image formed on the photosensitive drum 10 as the first image carrying means by the above image forming process, is used as the first transfer means 1 The next transfer unit 14c collectively transfers the toner image onto the toner image receiving body 14a as the second image carrying means (FIG. 3A). At this time, uniform exposure may be performed by the simultaneous transfer exposure device 12d provided inside the photoconductor drum 10 so that good transfer is performed.

After the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to charge removal by the photosensitive drum AC charge remover 16, the toner is transferred to a cleaning device 19, which is a first image carrier cleaning means, or is exposed to light. The toner is cleaned by a cleaning blade 19a made of a rubber material in contact with the body drum 10 and collected by a screw 19b in a waste toner container (not shown). 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 serving as the back side image is formed on the toner image receiver 14a as described above, the surface of the photoreceptor drum 10 is continuously formed in the same manner as the above-described color image forming process. A superimposed color toner image serving as an image is formed (FIG. 3B). On this occasion,
The image data is changed so that the front surface image formed on the photoconductor drum 10 is a mirror image of the back surface image formed on the photoconductor drum 10.

With the formation of a surface image on the photosensitive drum 10, recording paper P as a transfer material is sent out by a feed roller 15a from a paper feed cassette 15 as a transfer material storage means, and is used as a transfer material feeding means. Timing roller 1
5b and driven by the timing roller 15b to synchronize the color toner image of the front surface image formed on the photosensitive drum 10 with the color toner image of the rear surface image carried on the toner image receiver 14a. Transfer area 14
b. 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 surface side of the recording paper P, and is attracted to the toner image receiving member 14a and transferred. It is fed to the area 14b. By charging the paper with the same polarity as the toner, the toner is prevented from being attracted to the toner image on the toner image receiving member 14a or the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed.

In the transfer area 14b, a first voltage to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied.
The surface image on the photosensitive drum 10 is collectively transferred to the surface of the recording paper P by the primary transfer device 14c as the transfer means. At this time, the back surface image on the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a. At the time of transfer by the primary transfer unit 14c, a transfer simultaneous exposure unit 12d using a light emitting diode, for example, provided inside the photosensitive drum 10 facing the transfer area 14b so that good transfer is performed. Exposure may be performed.

The recording paper P on which the color toner image has been transferred to the surface thereof is transferred to a secondary transfer unit 14g as a second transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. The sheet is conveyed, and the rear surface image on the peripheral surface of the toner image receiver 14a is collectively transferred to the rear surface of the recording paper P by the secondary transfer device 14g (FIG. 3C).

The recording paper P on which the color toner images are formed on both sides is separated by the curvature of the curvature portion KT of the toner image receiver 14a and the separation claw 210 provided at a predetermined distance from the toner image receiver 14a. The fixing device 17 is separated from the toner image receiving body 14 a and passes through a spur 162 as a fixing unit.
The toner image on the recording paper P is fixed by applying heat and pressure at a nip portion T between the fixing roller 17a and the pressure roller 17b. 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. Further, as shown by a dashed line in FIG. 1, a switching member (not shown) may be provided at the exit of the fixing device 17 so that the sheet is discharged to a tray outside the device without turning over.

The toner remaining on the peripheral surface of the toner image receiving member 14a after the transfer is provided to face the driven roller 14e with the toner image receiving member 14a interposed therebetween, and the toner image receiving member 14 is rotated around the support shaft 142 as a fulcrum. The toner image receiving member is cleaned by a toner image receiving member cleaning device 140 which is a second image carrying means cleaning means having a toner image receiving member cleaning blade 141 capable of contacting and releasing contact with 14a.

Further, the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the photosensitive drum AC static eliminator 16, then the residual toner is removed by the cleaning device 19, and the uniform exposure device 12e before charging is used. The history of the photosensitive drum 10 in the previous image formation is eliminated, and the next image formation cycle is started.

Since the superimposed color toner images are collectively transferred by using the above-described method, the color image on the toner image receiving member 14a is hardly discolored, the toner is scattered or rubbed, and the image deterioration is small. A double-sided color image is formed.

In the above-described embodiment, a paper separating AC static eliminator serving as a transfer material separating means may be provided opposite to the conductive roller 14d. When providing a paper separation AC neutralizer,
Conductive roller 14d is preferably electrical resistivity 10 ⁰ Omega
-Since it is provided facing the conductive roller 14d of not more than cm, the corona discharge by the paper separating AC static eliminator is stabilized, and the better separation of the recording paper P can be secured.

Although the embodiment of the double-sided image forming apparatus has been described with reference to a color image forming apparatus, the present invention is not necessarily limited to this, and the present invention is not limited to this. The present invention is also applied to a double-sided image forming apparatus.

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

[0054]

According to the first aspect, the conductive roller provided on the side of the second image bearing means for separating the transfer material is separated from the drive roller for driving the belt-shaped second image bearing means. To ensure the transferability and separability of the transfer material on the separation side of the second image bearing means, and to improve the belt-like second shape.
And stabilization of the driving of the image bearing means.

According to the second aspect, the second transfer means is provided so as to face the grounded conductive roller,
Corona discharge is stabilized by the second transfer means, and good transferability of the back side image is ensured.

According to the third aspect, good separability by the conductive roller is ensured.

According to the fourth aspect, a good driving force by the driving roller can be obtained.

According to the fifth aspect, the transfer material can be more favorably separated from the second image bearing means.

[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 according to the present invention.

FIG. 2 is a side sectional view of a first image bearing unit of FIG. 1;

FIG. 3 is a diagram illustrating a state of forming a toner image in the image forming apparatus according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14a toner image receiver 14c primary transfer device 14d conductive roller 14e driven roller 14g secondary transfer device 14i tension roller 14j drive roller 17 fixing device 210 separation claw KT Curvature section P Recording paper

Continuing on the front page (72) Inventor Satoshi Haneda 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation

Claims (5)

[Claims] A first image carrying means for carrying the toner image formed by the toner image forming means; and a toner image carried by the first image carrying means is transferred. While supported on the surface,
A belt-shaped second image holding means for conveying a transfer material; and a second image holding means for transferring the toner image held by the first image holding means to the second image holding means.
A first transfer unit that transfers the image on the surface of the transfer material, or a second transfer unit that transfers the toner image carried on the second image support onto the back surface of the transfer material; An image forming apparatus comprising: a fixing unit that fixes a toner image transferred to a transfer material; wherein the second image bearing unit is provided at least on a side that supplies the transfer material to the second image bearing unit. A driven roller, a conductive roller provided on a side for separating the transfer material from the second image bearing means, and a conductive roller provided near the conductive roller and upstream in the moving direction of the second image bearing means. An image forming apparatus, which is stretched by a drive roller and a tension roller. 2. The apparatus according to claim 1, wherein the conductive roller is grounded, and the second transfer unit is provided at a position facing the conductive roller via the second image bearing unit. An image forming apparatus according to claim 1. 3. The radius of curvature of the conductive roller is 10 mm.
3. The image forming apparatus according to claim 1, wherein a winding angle of the conductive roller with the second image bearing unit is set to 60 ° or more. 4. 4. The drive roller according to claim 1, wherein a radius of curvature of the drive roller is 10 mm or more, and a winding angle of the drive roller with the second image bearing means is 90 ° or more.
An image forming apparatus according to claim 1. 5. An image forming apparatus according to claim 1, wherein a claw member is provided near a curvature portion of said second image bearing means formed by said conductive roller.