JPH04125665A - Image forming device - Google Patents

Abstract

PURPOSE:To allow a transfer material to be exactly attracted and held at a prescribed position on the carrying sheet of a transfer drum by forming both the elastic ring of the transfer drum of a transfer device and the abutting roller of a conductive roller being a transfer material sucking means with an elastic material which has a high frictional force. CONSTITUTION:Not only the elastic ring of a transfer drum 6A but also the abutting roller to a conductive roller 20 abutted on this are formed with the rubber material of the elastic material which has the high frictional force. Therefore, the high friction can be obtained between them, and the conductive roller 20 can be rotated by smoothly following the transfer drum 6A at the same speed without sliding. Also, the conductive roller 20 can be abutted on a transfer material carrying sheet 6a by relaxing a shock at the time of abutment. Thus, a transfer material P can be exactly attracted and held at the prescribed position on the carrying sheet 6a, and the disturbance of an electrostatic latent image on a photosensitive drum 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and in particular to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus. The present invention relates to an image forming apparatus that electrostatically transfers an image onto a transfer material held on a member to obtain an image on the transfer material.

[Undeveloped and 1] For example, in color electrophotographic copying, a toner image is formed on an image carrier using an electrophotographic method, and then the toner image is transferred onto a transfer material using a transfer device equipped with a transfer drum.
An image is obtained on a transfer material.

The transfer device is equipped with the above-mentioned transfer drum as a transfer material holder, and the transfer drum has a transfer material carrying sheet usually made of a high resistance film as a flexible transfer material carrying member between both end frames of the cylinder. It is wrapped in a shape. The transfer material is supplied to the transfer drum of the transfer device, and by applying electrostatic adsorption force between the transfer material carrying sheet and the transfer material, it is attracted and held onto the transfer material carrying sheet and wound onto the transfer drum. (Refer to Japanese Patent Application Laid-Open No. 55-32079).

In a transfer device that holds a transfer material using this electrostatic adsorption method, the transfer material is sandwiched between the transfer material holding sheet at the transfer material adsorption position where the transfer material is adsorbed and held on the transfer material holding sheet of the transfer drum, and the inside is charged with a corona charge for adsorption. A conductor roller is placed on the outside facing the transfer material, and is movable into and out of contact with the transfer material. The transfer material is attracted to the transfer material carrying sheet by applying an electric charge with a polarity opposite to that of the toner constituting the toner image on the image carrier using a corona charger and a conductive roller.
Retained.

By the way, normally, the leading edge of the transfer material adsorbed and held on the transfer material carrying sheet is detected, and this is used as an image formation signal to form an image on the image carrier, and the toner image formed on the image carrier is The position of the transfer material and the transfer material on the transfer material carrying sheet are matched at the transfer position.

To explain the above positional relationship, let L be the circumference of the image carrier between the n light position on the image carrier and the transfer position, and let L be the circumference of the image carrier between the n light position on the image carrier and the transfer position, and the distance between the sensor position that transmits the image forming signal and the toner image transfer position. Measure the circumference of the carrier sheet.

Assuming that the circumference of the carrier sheet between the transfer material adsorption position and the toner image transfer position is L3, the distances LL, , L, between the above-mentioned transfer positions, adsorption positions, etc. are used to calculate L. There was a relationship such as +=L, l<L a.

However, in recent years, miniaturization of equipment has become important in the copying machine market, and the transfer material supply section has also become smaller.
The direction is to place it close to the image carrier.

If the transfer material supply section is arranged in this way, it is necessary to provide the transfer material suction position close to the transfer position, and the relationship between the transfer position and suction position described above is as follows: Ll = La > t, a becomes.

In the above case, image formation is already started on the image carrier before the transfer material is attracted and held by the carrier sheet. Therefore, in order to match the positions of the toner image on the image carrier and the transfer material on the carrier sheet at the transfer position, the leading edge of the transfer material adsorbed and held on the transfer material carrier sheet is detected and detected. Unlike the case where an image is formed on an image carrier using the image forming signal as an image forming signal, it is necessary to reliably attract and hold the transfer material at a predetermined position on the carrier sheet.

If there is any misalignment or variation in the suction position of the transfer material, the toner image and the transfer material will not match, resulting in variations in alignment (registration) in the image obtained by transferring the toner image onto the transfer material, and further transfer If there is a large deviation or variation in the material suction position, not only will the toner image be transferred onto the carrier sheet and stain it, but also the transfer material will not be separated properly at the rear transfer material separation section, resulting in a so-called jam. Cause.

Further, since fog toner on the image carrier is transferred onto the carrier sheet and further transferred to the conductive roller, it is necessary to attach a cleaning member to the conductive roller to remove the toner. As a result, the rotational load on the conductor roller increases,
A problem arises in that the contact force of the conductive roller must be increased in order to cause the conductive roller to follow the carrier sheet.

However, when the conductive roller is brought into contact with the carrier sheet to adsorb the transfer material, an electrostatic latent image is being formed on the image carrier, and the contact force of the conductive roller is reduced. , the impact of the contact is transmitted to the image carrier through the carrier sheet, causing disturbances in the electrostatic latent image on the image carrier.

Therefore, in view of the above-mentioned current situation, it is an object of the present invention to securely adsorb and hold a transfer material at a predetermined position on a holding sheet wrapped around a transfer drum of a transfer device, thereby forming a toner image on an image carrier. An object of the present invention is to provide an image forming apparatus which can obtain a high-quality image without variation in alignment on the transfer material by transferring the image onto the transfer material, and which also enables miniaturization of the apparatus.

for The above object is achieved by an image forming apparatus according to the present invention.

In summary, the present invention provides a flexible transfer material holding member that is wound around a transfer material holding member of a transfer device by applying an electric charge to the transfer material using a suction means that can freely move toward and away from the transfer material holding member of a transfer device. electrostatically adsorbing and holding the transfer material, and transferring the toner image formed on the image carrier that is in contact with the transfer material holder onto the transfer material held on the transfer material holding member. , in the image forming apparatus for obtaining an image on the transfer material, elastic members are provided at both ends of the transfer material holder, and the transfer material holder and the image carrier are brought into contact with each other via the elastic members; The image forming apparatus is characterized in that a contact member made of an elastic material having a large frictional force is provided at a position of the suction means corresponding to the elastic member of the transfer material holder.

According to one aspect of the present invention, the suction means includes a conductive roller, and when the contact member abuts the elastic member of the front transfer material holder, the conductor roller holds the front transfer material. It follows the rotation of the body and rotates at the same speed. Further, a cleaning member is provided for cleaning at least one of the elastic member of the transfer material holder and the contact member of the suction means.

look up Examples of the present invention will be described in detail below.

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention.

In FIG. 1, 1 is a photosensitive drum as an image carrier;
The photosensitive drum 1 is pivotally supported at its center and rotated in the direction of the arrow. Around the photosensitive drum 1, a primary charger 2, an optical system 3, and a developing device 4 are arranged opposite to the photosensitive drum 1 in the direction of rotation thereof.
, a pre-transfer charger 4° are arranged.

The primary charger 2 applies a uniform primary charge to the photosensitive drum 1, and the optical system 3 applies a color-separated optical image or an optical image equivalent thereto to the surface of the photosensitive drum 1 at a predetermined timing.
Forms an electrostatic latent image. The optical system 3 uses a laser beam scanning device or the like. Further, the developing device 4 includes the photosensitive drum 1
It is equipped with four developing units 4M, 4C14Y, and 4B, each of which contains magenta toner, cyan toner, yellow toner, and black toner as developers. The developing device 4 has a developing device containing toner of a color corresponding to the electrostatic latent image formed on the photosensitive drum 1 facing the photosensitive drum 1;
Toner from the opposing developing device electrostatically flies onto the surface of the photosensitive drum 1 and adheres to the electrostatic latent image on the photosensitive drum 1, and the electrostatic latent image is developed and visualized as a toner image.

Further, around the photosensitive drum 1, as shown in FIG. 1, a static eliminator 27 for removing static charges on the surface of the photosensitive drum 1 and a cleaning blade 28 for removing toner are provided.

Further, on the right side of the photosensitive drum 1, a transfer device 6 is installed.
A is provided so as to be slightly away from the surface of the photosensitive drum 1.

As shown in FIG. 4, the transfer drum 6A has a transfer material carrying sheet 6a wrapped in a cylindrical shape between both cylindrical end frames 6b. is ensured by elastic rings 6c on both end frames 6b that come into contact with the photosensitive drum 1. A gear 6d that meshes with the gear lc of the photosensitive drum 1 (see FIG. 3) is provided on the outer side of one of the end frames 6b of the transfer drum 6A. The gear 6d and the like will be described later.

Inside the transfer material carrying sheet 6a of the transfer drum 6A, as shown in FIG. An adsorption corona charger 19 is disposed at a position upstream of 6 in the rotational direction. A conductive roller 20 is provided on the outside of the carrier sheet 6a, facing the corona charger 19, as a suction means.

At a position on the downstream side in the rotational direction of the transfer drum 6A from the transfer position, charge eliminating corona dischargers 10 and 11 are provided on the outside and inside of the transfer material carrying sheet 6a, respectively, and the transfer material P is disposed downstream thereof. Pressing rollers 12 and 13 are provided to separate the sheet from the carrier sheet 6a, and a separating blade 14 is provided near the pressing rollers 12 and 13, respectively. If necessary, a corona discharger 29 is installed near the separation blade 14,
By performing AC corona discharge, when the transfer material P after which the toner images of multiple colors have been transferred is separated from the carrier sheet 6a, the toner image on the transfer material P is prevented from being disturbed by peeling discharge. It can be prevented.

When the transfer material P is separated from the carrier sheet 6a by the separation blade 14, it is conveyed to the fixing roller pair 18 via the conveyor 17 nearby, and is transferred onto the transfer material P at the transfer position by the fixing roller pair 18. The toner image transferred to is fixed.

At a position on the downstream side of the separation blade 14 in the rotational direction of the transfer drum 6, there is a brush roller 15 on the outside of the transfer material 6a for cleaning toner adhering to the outer surface (transfer material holding surface) of the carrier sheet 6a. If necessary, a corona discharger or a brush type static eliminator 16 for removing toner adhesion force (residual Coulomb force and van der Waals force) is provided inside the carrier sheet 6a.

In FIG. 1, the symbol L1 is the circumference of the photosensitive drum l between the exposure position by the optical system 3 on the photosensitive drum l and the toner image transfer position by the transfer charger 7, and L2 is the circumferential length of the photosensitive drum l which transmits the image forming signal. L indicates the same length of the carrying sheet 6a between the sensor position and the toner image transfer position, and L indicates the circumferential length of the carrying sheet 6a between the transfer material adsorption position and the toner image transfer position.

In this image forming apparatus, the transfer material supply section is made smaller for the purpose of downsizing the apparatus, and accordingly, the transfer material suction position is also located close to the transfer position, and the The above distance is between L2. Using L, the relationship Ll = L* > Lm is established.

In the image forming apparatus with the above configuration, the surface of the photosensitive drum 1 is uniformly and primarily charged by the primary charger 2, and an optical system 3 is applied to the surface of the photosensitive drum 1 to form an optical image that has first passed through, for example, a green filter. When the light is irradiated, an electrostatic latent image consisting mainly of the magenta component of the light image is formed. In synchronization with the above-described feeding of the electrostatic latent image due to the rotation of the photosensitive drum 1, the developing device 4 moves in a tangential direction with respect to the photosensitive drum 1, and transfers the developing device 4M containing magenta toner to the photosensitive drum 1. Opposingly, the electrostatic latent image on the photosensitive drum 1 is developed with magenta toner, thereby forming a magenta toner image. The magenta toner image is transferred onto the transfer material P by the transfer device 6.

When the transfer of the magenta toner image is completed, the toner remaining on the surface of the photosensitive drum 1 is neutralized by the static eliminator 27 and cleaned by the blade 28, thereby cleaning the surface of the photosensitive drum 1. Then, in the same way, cyan, yellow,
Image formation in black color is performed.

On the other hand, the transfer material P to which the magenta toner has been transferred moves as the transfer drum 6 rotates while being attracted and held by the carrier sheet 6a, and passes between the corona dischargers 10 and 11. During this passage, the corona discharger 10.11
is not operated, and the pressing rollers 12 and 13 are also not activated.
a, and the brush roller 15 and the corona discharger or brush static eliminator 16 are also separated from the carrier sheet 6a. Further, the operation of the corona charger 19 and the contact of the conductive roller 20 with the transfer material P are completed before the leading edge of the toner image on the transfer material P reaches the positions of the corona charger 19 and the conductive roller 20. , when the transfer material P passes between these, no charge for adsorption is applied to the transfer material P.

As a result of the above, the transfer material P is transferred to the corona discharger 10 without disturbing the toner image carried thereon by Coulomb force.
11, it passes between the corona charger 19 and the conductive roller 20, and is then sent to the transfer position again.

Thereafter, the cyan toner image, yellow toner image, and black toner image are transferred in the same manner.

Now, the transfer material suction section in the transfer device in the image forming apparatus of the present invention will be explained in detail.

In FIG. 1, the transfer material P is fed from a paper feed section (not shown), and is placed in front of the transfer device 6 by a pair of registration rollers 21a, 21.
b, the transfer drum 6A is sent out at the same timing as the peripheral speed of the transfer drum 6A and at the same speed as the peripheral speed of the transfer drum 6A. At this time, the conductive roller 20 is brought into contact with the carrier sheet 6a.

The conductive roller 20 is rotatably attached to the tip of the lower guide 30 of the pair of upper and lower transfer material guides 34 and 30 provided between the transfer drum 6A and the pair of registration rollers 21a and 21b. .

The lower guide 30 is swingably supported around a fulcrum shaft 31 at its base end, and the contact of the conductive roller 20 at the tip with the support sheet 6a is caused by a coil spring 32 attached to the fulcrum shaft 31. This is performed by biasing and displacement of an eccentric cam 33 provided on an upper guide 34 located above the lower guide 30.

The conductive roller 20 that is in contact with the carrier sheet 6a is pressed by the urging force of the coil spring 32 and the carrier sheet 6a.
Due to the frictional force between the transfer drum 6A and the transfer drum 6A, the transfer drum 6A rotates at the same speed.

Further, in the lower guide 30, a cleaning member 36 made of a blade, a brush, etc. is placed in contact with the conductive roller 20 in order to prevent the conductive roller 20 from being contaminated by fog toner transferred via the carrier sheet 6a. It is provided.

The upper guide 34 is rotatably supported by the shaft 35 of the eccentric cam 33, and is biased counterclockwise by its own weight or by a pressure spring (not shown). The biasing force of the upper guide 34 is made sufficiently smaller than the biasing force of the lower guide 30 due to the coil spring 32.

By the above-mentioned upper and lower guides 30 and 34, the transfer material P sent out by the pair of registration rollers 21a and 21b is sent in the direction of the conductive roller 20, and is adsorbed onto the carrier sheet 6a.
Retained. The upper and lower guides 34.30 in FIG. 1 indicate the posture for adsorbing and holding the transfer material P on the carrier sheet 6a, and the upper and lower guides 34.30 in FIG. A retracted posture due to the subsequent displacement of the eccentric cam 33 is shown.

Next, the arrangement of the photosensitive drum, transfer device, and conductive roller in the image forming apparatus of the present invention will be explained with reference to FIG.

The photosensitive drum 1 integrally has flanges of 18% lb that rotate together with the drum shaft 100 at both ends.

A flange cleaner 40 that cleans the peripheral surfaces of both flanges 1a and lb is in contact with the flanges 1a and lb to prevent dirt from floating toner and the like. The above-mentioned transfer drum 6A is applied to the circumferential surfaces of both flanges la and 1b that have been cleaned by the cleaner 40.
The elastic rings 6c on both end frames 6b are in contact with each other to ensure a slight gap between the surface of the photosensitive drum 1 and the carrier sheet 6a.

The transfer drum 6A is driven by meshing a gear lc provided at one flange 1b of the photosensitive drum 1 with a gear 6d provided at a corresponding location on one of the end frames 6b of the transfer drum 6A. .

Now, the conductive roller 20 integrally has contact rollers 22 as contact members at both ends, is rotatably supported by the lower guide 30 via a conductive bearing 37, and the contact rollers 22 are attached to the transfer drum 6A. By coming into contact with the elastic ring 6C, the photosensitive drum 6A is rotated.

According to the present invention, at least the circumferential surface of the abutting roller 22 is formed of an elastic material with a large frictional force, and in this embodiment,
The elastic ring 6C of the transfer drum 6A was made of urethane rubber, and the entire contact roller 22 was made of neoprene rubber.

Further, the conductive roller 20 is preferably formed of metal or conductive rubber, and in this embodiment, the cleaning member 36
In order to enhance the cleaning effect by the conductive roller 2
In order to reduce the rotational load of 0, the conductive roller 20 is made of metal.

As described above, in the present invention, not only the elastic ring 6c of the transfer drum 6A but also the conductive roller 2 that comes into contact with the elastic ring 6c
Since the contact rollers 22 of 0 are also made of rubber, an elastic material with a large frictional force, high friction can be obtained between them, so that the conductive roller 20 can be smoothly moved at the same speed without slipping on the transfer drum 6A. The conductive roller 20 can be rotated following the transfer material carrying sheet 6a, and the impact at the time of contact can be alleviated, and the conductive roller 20 can be brought into contact with the transfer material carrying sheet 6a. Accordingly, the transfer material P can be reliably attracted and held at a predetermined position on the carrier sheet 6a, and the electrostatic latent image formed on the photosensitive drum 1 due to the impact when the conductive roller 20 comes into contact with it can be prevented. It is possible to prevent disturbances from occurring.

Further, the contact positions of the elastic ring 6c of the transfer drum 6A and the contact roller 22 of the 11-piece roller 20 are at both ends thereof, and are sufficiently distant from the image forming area of the photosensitive drum 1 in the axial direction. In addition, since the cleaner member 40 is arranged on the flanges la and 1b at both ends of the photosensitive drum 1, it is possible to prevent the toner from transferring from the flanges 1a and 1b onto the ring 6c of the transfer drum 6A. 6
C allows the conductive roller 20 to be driven with high frictional force via the contact roller 22 stably over a long period of time. It can be made smaller, and the impact caused by contact can be further reduced.

Judging from FIG. 3, it is conceivable that the conductive roller 2.degree. is driven not by the elastic ring 6c of the transfer drum 6A but by the gear 6d. However, according to the inventor's experimental findings, when the conductive roller 2o is brought into contact with the transfer material carrying sheet 6a of the transfer drum 6A, the gear 6d of the transfer drum 6A and the conductive roller 20 (not shown) The tips of the teeth of the gears collide, resulting in a large impact, and due to the pressure angle of the gears 6d, a force acts in the direction of separating the conductive roller 20 from the photosensitive drum 6A, resulting in tooth skipping, causing the conductive roller 20 to move away from the photosensitive drum 6A. It is no longer possible to make the body roller 2o perform a good suction operation for the transfer material P.

Therefore, the conductive roller 2o is driven as in this embodiment.
It is preferable to take the receiver from the elastic ring 6c of the transfer drum 6A.

Standing soy beans■ As explained above, according to the image forming apparatus of the present invention,
The following effects can be obtained.

(1) In addition to the elastic ring of the transfer drum of the transfer device (the contact roller of the conductive roller, which is the transfer material adsorption means, is made of rubber material, an elastic material with a large frictional force, Avoid sliding on the rollers due to high friction (
It can be rotated smoothly and the transfer material can be accurately attracted to a predetermined position on the carrier sheet of the transfer drum.
can be retained.

(2) Since the elastic ring of the transfer drum and the contact roller of the conductive roller are made of elastic material, it is possible to reduce the impact when the conductive roller contacts the transfer drum. It is possible to prevent the electrostatic latent image formed on the photosensitive drum from being disturbed by impact.

(3) The contact position between the elastic ring of the transfer drum and the contact roller of the conductive roller is sufficiently far away from the image forming area of the photosensitive drum in the axial direction, and a cleaner member is attached to the rings at both ends of the photosensitive drum. As a result, the elastic ring can stably drive the conductive roller with high frictional force through the contact roller over a long period of time.

(4) From the above, the position at which the transfer material is attracted to the transfer drum can be brought closer to the transfer position, and therefore the image forming apparatus can be downsized.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is an explanatory diagram showing that the upper and lower guides provided in front of the transfer material adsorption section are in the retracted position. FIG. 3 is a layout diagram showing the arrangement of a photosensitive drum, a transfer device, and a conductive roller of the image forming apparatus shown in FIG. 4 is a perspective view showing a transfer drum of a transfer device provided in the image forming apparatus of FIG. 1. FIG. A a C Photosensitive drum: Transfer device: Transfer drum: Transfer material carrying sheet: Elastic ring: Adsorption corona charger: Conductive roller: Contact roller

Claims (1)

[Scope of Claims] 1) A flexible transfer material holder wound around the transfer material holder of the transfer device by applying an electric charge to the transfer material using a suction means that can be freely moved toward and away from the transfer material holder. The transfer material is electrostatically attracted and held by the member, and the toner image formed on the image carrier in contact with the transfer material holder is transferred onto the transfer material held on the transfer material holding member. In the image forming apparatus for forming an image on the transfer material, elastic members are provided at both ends of the transfer material holder, and the transfer material holder and the image carrier are brought into contact with each other via the elastic members. The image forming apparatus is further characterized in that an abutment member made of an elastic material having a large frictional force is provided at a position of the suction means corresponding to the elastic member of the transfer material holder. 2) The suction means is composed of a conductive roller, and when the abutment member abuts the elastic member of the transfer material holder, the conductive roller is moved by the rotation of the transfer material holder and rotates the same. The image forming apparatus according to claim 1, wherein the image forming apparatus rotates at a high speed. 3) The image forming apparatus according to claim 1, further comprising a cleaning member for cleaning at least one of the elastic member of the transfer material holder and the contact member of the suction means.