JP2001013799A - Double-sided image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the biasing or the bending inclination of an intermediate transfer belt caused by long-time carrying of the belt at the time of forming an image and to reduce the deterioration of a photoreceptor occurring because the belt abuts on the photoreceptor. SOLUTION: A belt moving means consisiting of a moving lever 40, an eccentric cam 41 and a microswitch S is provided at the inner periphery part of the belt on the carrying upstream side of a contact between the photoreceptor drum 10 and the intermediate transfer belt 14a, and is constituted so that the belt may abut on the drum 10 or such abutting may be released through a roller 40B at the edge of the lever 40 by switching the rotational angle of the cam 41. At the time of abutting, the drum and the belt can be driven synchronously according to the on-signal of the switch S, and at the time of releasing abutting, the drum and the belt are individually driven according to the off- signal of the switch S, whereby maintenance is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, and a printer for transferring a toner image formed on an image carrier onto a transfer material.
The present invention relates to an image forming apparatus such as an AX, and more particularly to an image forming apparatus capable of forming an image on both surfaces of a transfer material, for example, a transfer material in which a charging unit, an image writing unit, and a developing unit are arranged around an image carrier. The present invention relates to an electrophotographic image forming apparatus capable of forming an image on both sides.

[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.

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 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 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 (image carrier), and provided on the photosensitive drum. After the formed superimposed color toner image is collectively transferred onto a belt-shaped intermediate transfer member temporarily stretched over a plurality of roller members, the superimposed color toner image is formed again on the photoconductor drum, The toner image on the intermediate transfer body and the toner image on the intermediate transfer body are fed in time,
On both sides of the transfer material conveyed by the intermediate transfer body,
After transferring the toner image on the photosensitive drum as a front image and transferring the toner image on the intermediate transfer member as a back image, the transfer material is separated from the intermediate transfer member, and the toner image on the transfer material is fixed. An image forming apparatus and an image forming method for forming a two-sided color image are disclosed in Japanese Patent Application Laid-Open Nos. 9-258492 and 9-258516.

[0006]

However, in the above-described image forming apparatus, if the belt-like intermediate transfer body is left without rotating during non-image formation (at the time of stop), the intermediate transfer during image formation can be performed. Even if the preparatory rotation of the body is performed, the belt cannot be eliminated by the preparatory rotation alone. Problems such as irregularity of the toner image and transfer failure due to unevenness, and deterioration of the photoconductor of the image carrier occur.

The present invention solves the above-mentioned problems, corrects the curl of the belt-shaped intermediate transfer member at the time of stoppage which is not solved only by the preliminary rotation, and transfers the toner image generated by the curl of the intermediate transfer member. It is an object of the present invention to provide an image forming apparatus which prevents toner images from being disturbed or transfer failure due to missing or uneven rotation of an intermediate transfer member and deterioration of a photosensitive member.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide an image carrier, a means for forming a toner image on the image carrier, and an intermediate transfer member which is capable of transferring a toner image and transports a transfer material. Transferring the first toner image formed on the image carrier to one surface of a transfer material via the intermediate transfer member, and transferring the second toner image formed on the image carrier. In a double-sided image forming apparatus for forming an image on both sides of a transfer material by directly transferring the image to the other surface of the material, the image carrier and the intermediate transfer body can be independently driven and controlled, and A double-sided image forming apparatus (invention according to claim 1) comprising a moving means for contacting and releasing contact with the image carrier at the transfer position, and the image carrier and toner on the image carrier. Image forming means and two sets An image forming unit, and an intermediate transfer body which is a means for transferring a toner image and conveying a transfer material, wherein a first image forming unit is provided on one surface of the transfer material fed between the image forming units. A toner image formed by the second image forming unit is transferred directly to the other surface to form an image on both surfaces of a transfer material by using the two-sided image forming apparatus. The image carrier and the intermediate transfer member can be independently driven and controlled, and the intermediate transfer member has a moving means for contacting and releasing contact with the image carrier at a transfer position. (A second aspect of the present invention).

[0009]

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 facing the image carrier in the transfer area is referred to as the front surface, and the other surface of the transfer material, that is, the surface of the transfer material facing the intermediate transfer member is referred to as the back surface. 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.

(Embodiment 1) The structure and image forming process of a double-sided image forming apparatus according to the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view of a color image forming apparatus showing one embodiment of an image forming apparatus common to the claims of the present invention, and FIG. 2 is a side sectional view of the image carrier of FIG. FIG. 3 is a diagram showing a toner image forming state in the image forming apparatus common to the claims of the present invention, and FIG.
FIG. 3 is a view showing a toner image formation state when a back image formed on the image carrier is transferred onto the intermediate transfer body.
FIG. 3B is a diagram illustrating a toner image formation state when a front surface image is formed on the image carrier in synchronization with a back surface image on the intermediate transfer body.

In FIG. 1, 10 is a photosensitive drum as an image carrier, 11 is a scorotron charger as charging means for each color, 12 is an exposure optical system as image writing means for each color, and 13 is an exposure optical system for each color. 14a is an intermediate transfer belt as an intermediate transfer body, 14c is a means for transferring the toner image on the image carrier to the intermediate transfer body, and the toner image on the image carrier is transferred to the surface of the transfer material. A transfer unit as a transfer unit, 14g is a backside transfer unit as a unit for transferring the toner image on the intermediate transfer body to the backside of the transfer material, 14m is a charge remover as a charge removing unit, and 150 is a paper as a transfer material charging unit. Charger, 1
4h is a paper separating AC static eliminator as a transfer material separating means, 160
Is a separation claw 210 as a claw member and a spur 16 as a spur member
Reference numeral 17 denotes a fixing unit which is a fixing unit.

The photosensitive drum 10, which is an image carrier, has a transparent conductive layer, a, on the outer periphery of a cylindrical substrate formed of a transparent member such as optical glass or transparent acrylic resin.
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 1A at both ends for engaging and fixing it
The gear G integrated with the flange member 10B is rotatably supported by the bearings B1 and B2 fitted into the apparatus main body 0B, and is 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.

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

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 (minus charging in the present embodiment) is performed by corona discharge having the same polarity as the toner, and the photosensitive drum 1 is charged.
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 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, and is attached to the holding member 20. The holding member 20 has a transfer simultaneous exposure device 12d in addition to the exposure optical system 12 for each color.
The uniform exposure device 12e is attached to the photosensitive drum 10, and the uniform exposure device 12e is housed inside the light-transmitting substrate of the photosensitive drum 10. The exposure optical system 12 for each color writes an image on the photosensitive layer of the photosensitive drum 10 from the back side 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, in addition to an LED, 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 light emitting element of the image exposure light (image writing light) is usually high for Y, M and C toners.
Although a wavelength in the range of 80 to 900 nm is used, in the present embodiment, since the image is written from the back side, even a wavelength of 400 to 780 nm, which is shorter than this and does not have sufficient transparency to the color toner. Good. 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 order of development of the color toner is preferably Y, M, C, and K from the relation of the color mixture to the toner image and the developing device 13. FIG. 2
In the above, 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 a forward direction with respect to the rotating direction of the photosensitive drum 10, for example, 0.5 to 1 mm in thickness. And a developing casing 131 formed of a cylindrical nonmagnetic stainless steel or aluminum material having an outer diameter of 15 to 25 mm, and a developing casing 138. Inside the developing casing 138, yellow (Y) and magenta ( M), cyan (C) and black (K) one-component or two-component developers. Each developing unit 13
Is maintained in a non-contact state with the photosensitive drum 10 with a predetermined gap, for example, 100 to 500 μm, by an abutting roller (not shown), and applies a developing bias in which a DC voltage and an AC voltage are superimposed on the developing sleeve 131. By doing
Non-contact reversal development is performed to form a toner image on the photosensitive drum 10.

The intermediate transfer belt 14a, which is an intermediate transfer member, has a volume resistivity of 10 ⁸ to 10 ¹² Ω · cm, preferably 10 ^9.
It is an endless belt of 〜１０10 ¹¹ Ω · cm, for example, modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, a thickness of 0.1 to 0.1 conductive material dispersed in engineering plastics such as nylon alloy This is a seamless belt having a two-layer structure in which a 1.0-mm semiconductive film substrate is coated with a fluorine coating having a thickness of 5 to 50 μm, preferably as a toner filming preventing layer. In addition, as the base of the intermediate transfer belt 14a, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber or the like can be used. The intermediate transfer belt 14a includes a driving roller 1 that is a roller member.
4d, a ground roller 14j, a driven roller 14e, a guide roller 14f, and a tension roller 14i.
It is rotated counterclockwise as indicated by the arrow in FIG. The guide roller 14f, the driven roller 14e, the ground roller 14j, and the drive roller 14d are fixedly rotated, and the tension roller 14i is movably supported and rotated by the elastic force of a spring (not shown). The drive roller 14d is rotated by a drive motor (not shown), and the intermediate transfer belt 14d is rotated.
a is driven to rotate. The rotation of the intermediate transfer belt 14a causes the ground roller 14j, the driven roller 14e, the guide roller 14f, and the tension roller 14i to be driven and rotated. The slack of the rotating intermediate transfer belt 14a is tensioned by the tension roller 14i. The recording paper P as a transfer material is supplied to a position where the intermediate transfer belt 14a is stretched around the driven roller 14e, and the intermediate transfer belt 14a
Conveyed by Curvature portion K at the end of fixing device 17 side of intermediate transfer belt 14a stretched around drive roller 14d
At T, the recording paper P is separated from the intermediate transfer belt 14a.

A transfer unit 14c serving as a unit for transferring the toner image on the image carrier to the intermediate transfer body and a unit for transferring the toner image on the image carrier to the surface of the transfer material is provided with a photosensitive member sandwiching the intermediate transfer belt 14a. The corona discharger is provided to face the body drum 10, and forms a transfer area 14 b between the intermediate transfer belt 14 a and the photosensitive drum 10. Transfer device 14
A DC voltage of 4 to 6 kV having the opposite polarity (positive polarity in the present embodiment) to the toner is applied to c, and the toner image on the photosensitive drum 10 is transferred to the intermediate transfer belt 14a or to the recording paper P as a transfer material. Transfer to the surface.

A backside transfer unit 14g, which is a means for transferring the toner image on the intermediate transfer body to the backside of the transfer material, is preferably constituted by a corona discharger, and includes a transfer unit 14c and a driving roller 14d with an intermediate transfer belt 14a interposed therebetween. And 4 to 6 kV of a polarity opposite to that of the toner (positive polarity in the present embodiment).
Is applied to transfer the toner image on the intermediate transfer belt 14a to the back surface of the recording paper P.

The static eliminator 14m, which is a static eliminator, is constituted by a corona discharger. The static eliminator 14m is provided on the downstream side of the transfer unit 14c with respect to the moving direction of the intermediate transfer belt 14a in parallel with the transfer unit 14c. Then, the charge of the intermediate transfer belt 14a charged by the voltage application of the transfer unit 14c is eliminated.

The paper charger 150, which is a transfer material charging means, is preferably formed of a saw-toothed electrode.
A DC voltage of 3 to 5 kV having the same polarity as the toner (minus polarity in this embodiment) is applied to the driven roller 14 e which is grounded with the recording paper P interposed therebetween.
And is adsorbed on the intermediate transfer belt 14a. As the paper charger 150, in addition to the saw-toothed electrode, a corona discharger, a paper charging brush that can be brought into and out of contact with the intermediate transfer belt 14a, a paper charging roller, and the like can be used.

Paper separation AC static eliminator 1 as transfer material separating means
Reference numeral 4h designates a corona discharger, which is provided at an end of the intermediate transfer belt 14a on the side of the fixing device 17 so as to face a driving roller 14d which is grounded with the intermediate transfer belt 14a interposed therebetween. An AC voltage in which a DC voltage having the same polarity as the DC voltage applied to the unit 14g (positive polarity in this embodiment) is applied, and the recording paper P conveyed by the intermediate transfer belt 14a is neutralized to remove the intermediate transfer belt 14a. Separate from

The transport section 160 includes a separation claw 210 as a claw member.
And a spur member 162 serving as a spur member. The spur member 162 is provided between the fixing device 17 and the curvature portion KT at the end of the intermediate transfer belt 14a on the fixing device 17 side. The transport unit 160 includes the fixing device 1
7, the intermediate transfer belt 14a is deformed, the toner image carried on the intermediate transfer belt 14a tends to be fused, and the transfer is difficult.
4a is prevented from sticking to the toner.

The separation claw 210, which is a claw member, approaches the curvature portion KT of the intermediate transfer belt 14a, and
Is fixed to the support shaft 221 at a predetermined interval, preferably 0.1 to 2.0 mm, and when the recording paper P is separated from the intermediate transfer belt 14a, the intermediate transfer belt 1
The leading end of the recording paper P, which is bent and conveyed in the direction 4a, is brought into contact with the recording paper P to assist the separation of the recording paper P.

The spur 162, which is a spur member, has a plurality of protrusions 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 fixes 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 opposite side of the photosensitive drum 10 with respect to the transfer material conveying surface on the intermediate transfer belt 14a or its extension surface. Spurs 16 as spur members are provided on both sides of the transfer material conveying surface or an extension surface thereof.
It is also possible to provide 2.

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, the recording paper P is nipped and conveyed at a nip T between the first fixing roller 17a and the second fixing roller 17b, and heat and pressure are added. Then, the toner image on the recording paper P conveyed through the nip portion T is fixed.

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 simultaneously exposed by the charging action of the 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 a 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 a magenta (M) scorotron charger 11, and a second color signal, that is, an 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, a K exposure optical system 12, and a K developing device 13. 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. .

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, which is the back image formed on the photosensitive drum 10 serving as the image carrier by the image forming process, is transferred to the transfer area 14b.
The transfer unit 14c collectively transfers the image onto an intermediate transfer belt 14a as an intermediate transfer body (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. The charge on the intermediate transfer belt 14a charged by the transfer device 14c is removed by the charge remover 14m.

After 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, the toner enters the cleaning device 19 as an image carrier cleaning means, The toner is cleaned by a cleaning blade 19a made of a rubber material in contact with the toner, and collected by a screw 19b in a toner discharge container (not shown). Further, the peripheral surface of the photosensitive drum 10
For example, a uniform exposure device 12 before charging using a light emitting diode
The history of the photosensitive drum 10 in the previous image formation is eliminated by the exposure by e.

After the superimposed color toner image serving as the back surface image is formed on the intermediate transfer belt 14a as described above, the front surface image is continuously formed on the photosensitive drum 10 in the same manner as the above-described color image forming process. Is formed (FIG. 3B). On this occasion,
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 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 the timing roller 15b is driven to synchronize the color toner image of the front image formed on the photosensitive drum 10 with the color toner image of the rear image carried on the intermediate transfer belt 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 front surface side of the recording paper P, and is attracted to the intermediate transfer belt 14a to be transferred to the transfer area. 14b. By charging the paper with the same polarity as the toner, the toner image is prevented from being attracted to the toner image on the intermediate transfer belt 14a and the toner image on the photosensitive drum 10, thereby preventing the toner image from being disturbed.

In the transfer area 14b, the surface image on the photosensitive drum 10 is collectively transferred to the surface of the recording paper P by the transfer unit 14c to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. You. At this time, the back surface image on the intermediate transfer belt 14a is not transferred to the recording paper P but exists on the intermediate transfer belt 14a. At this time, in order to perform good transfer, uniform exposure is performed by a simultaneous transfer exposure device 12d using a light emitting diode, for example, provided inside the photosensitive drum 10 so as to face the transfer area 14b. You may. The charge on the intermediate transfer belt 14a charged by the transfer device 14c is removed by the charge remover 14m.

The recording paper P on which the color toner image has been transferred to the front side is conveyed to a back side transfer unit 14g to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. The back surface image on the peripheral surface of the intermediate transfer belt 14a is collectively transferred to the back surface of the recording paper P (FIG. 3C).

The recording paper P on which the color toner images are formed on both sides is subjected to the curvature of the curvature portion KT of the intermediate transfer belt 14a and the paper separation AC neutralizer as a transfer material separating means provided at the end of the intermediate transfer belt 14a. 14h, and the conveying unit 160 with a predetermined distance from the intermediate transfer belt 14a.
, The intermediate transfer belt 1
4a, which is separated from the spur 16
2 to a fixing device 17 as a fixing unit, and is conveyed between a nip portion T between a first fixing roller 17a and a second fixing roller 17b, where heat and pressure are added at the nip portion T. The toner image on the recording paper P is fixed. 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 provided opposite to the guide roller 14f with the intermediate transfer belt 14a interposed therebetween, and is applied to the intermediate transfer belt 14a with the support shaft 252 as a rotation fulcrum. The intermediate transfer member is cleaned by an intermediate transfer member cleaning device 250 which is an intermediate transfer member cleaning unit having an intermediate transfer member cleaning blade 251 capable of contacting and releasing contact.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is discharged by a photoreceptor drum AC static eliminator 16 and then cleaned by a cleaning device 19. By 12e, 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, color misregistration of the color image on the intermediate transfer belt 14a, scattering and rubbing of the toner, and the like are less likely to occur, and the image deterioration is reduced. Double-sided color image formation is performed.

As shown in FIG. 4, the photosensitive drum 10 and the intermediate transfer belt 14a use the pulse motors M1 and M2 as dedicated power sources, and have the same peripheral speed via the respective gears G by respective drive controls. It is rotated or transported in the direction indicated by the arrow.

The intermediate transfer belt 14a is provided with a belt moving means at an inner peripheral portion near the transfer position, and the outer peripheral surface of the belt is moved relative to the peripheral surface of the photosensitive drum 10 by the operation of the moving means as shown in FIG. The structure is such that the contact state is established and the contact is released after being separated.

That is, the moving means comprises a pair of moving levers 40, an eccentric cam 41 and a microswitch S which are integrally connected. When the apparatus is in an image forming state, the eccentric cam 41 is not shown. 5A, the moving lever 40 is returned to the bias of the return spring 42, and is kept clockwise about the support shaft 40A. As a result, the intermediate transfer belt 14a is brought into contact with the photosensitive drum 10 by the pressing of the roller 40B at the end of the moving lever 40, and the required width of the transfer portion is 2 mm to 10 m.
A nip N of about m is formed.

The photosensitive drum 10 of the intermediate transfer belt 14a
Is detected when the micro switch S is switched from OFF to ON by the rotation of the moving lever 40, and when the ON signal is input to the control unit, both the pulse monitors M1 and M2 are individually operated. Is prohibited, and is controlled to be driven with the number of pulses synchronized with the start of image formation, thereby enabling image formation and transfer processes.

When the transfer roller is used as the transfer means, the roller 40B can be replaced with the transfer device 14c by using the transfer roller. Therefore, if the transfer roller is used, the intermediate transfer belt 14a and the photosensitive drum 10 can be used. It is preferably provided at a position where the distance d shown in the drawing is 0 to 5 mm on the upstream side of the belt from the contact point, so that the width suitable for transferring an image to the contact point between the belt and the drum is 2 mm to 10 m.
A nip N of about m is formed.

The ground roller 14j has an outer peripheral surface at a top portion higher than a tangent line (indicated by a dashed line) connecting the drive roller 14d and the inner peripheral surface of the intermediate transfer belt 14a in contact with the photosensitive drum 10. h, whereby the contact state with the intermediate transfer belt 14a is maintained even during the operation of the above-described moving means, and functions as a backup roller of the backside transfer unit 14g. The height h depends on the distance between the drive roller 14d and the photosensitive drum 10 and the position of the backside transfer unit 14g, but it is required to be at least 1 mm, and is suppressed to 5 mm or less so as not to impair the flatness. Is desirable.

On the other hand, when the apparatus is not in the image forming state, that is, when the apparatus is at rest or in the standby mode, the eccentric cam 41 is rotated by the angle shown in FIG. The rotation angle is maintained counterclockwise about the shaft 40A as a fulcrum. As a result, the intermediate transfer belt 14a moves the photosensitive drum 1
The contact portion with respect to 0 is released, and the transfer portion is opened. Even if the roller 40B is retracted, the belt can be driven without separating the belt from the roller 40B due to the tension of the tension roller 14i.

The photosensitive drum 10 of the intermediate transfer belt 14a
Release of contact with the pulse motors M1 and M2 is detected when the microswitch S is switched from ON to OFF by the rotation of the moving lever 40, and when the OFF signal is input to the control unit, the synchronous drive control of the pulse motors M1 and M2 is released. In addition, it is possible to individually drive each of them independently.

As a result, with respect to the photosensitive drum 10, the residual potential and the toner image can be removed and cleaned prior to the start of printing, or the pre-rotation including the developing means can be performed at the time of warming up, so that fatigue recovery is performed. You. In addition, the intermediate transfer belt 14a can be rotated in a so-called idling manner to correct the belt curving or the like that occurs during use or during jam processing. Each of the pulse motors can be independently driven at the same time, so that the above-described maintenance on the photosensitive drum 10 and the intermediate transfer belt 14a can be simultaneously performed in parallel.

(Embodiment 2) The structure and image forming process of a two-sided image forming apparatus according to the second aspect of the present invention will be described with reference to FIGS.

In FIG. 6, reference numeral 10 denotes a photosensitive drum as an image carrier, 11 a scorotron charger as a charging unit for each color, 12 an exposure optical system as an image exposure unit for each color,
A developing device 13 is a developing unit for each color, and 14a is an intermediate transfer belt which is an intermediate transfer member.
Reference numeral 14g denotes a secondary transfer unit which is a second transfer unit, 15b denotes a timing roller which is a transfer material supply unit, and 17 denotes a fixing device which is a fixing unit.

A plurality of scorotron chargers 11 and a plurality of exposure optical systems are provided on the peripheral surface of a common photosensitive drum 10 as the first and second image forming members on the downstream side and the upstream side of the upper surface of the intermediate transfer belt 14a. First and second process units 20A and 20B in which a developing unit 12 and a developing unit 13 are arranged are provided.

The photoreceptor drum 10 is formed, for example, by forming a transparent conductive layer, an a-Si layer, an organic photosensitive layer (OPC), etc. on the outer periphery of a cylindrical base formed of a transparent member of optical glass or transparent acrylic resin. A photosensitive layer is formed,
It is rotated clockwise as indicated by the arrow in FIG.

As shown in FIG. 7, the photosensitive drum 10 has flange members 10A and 10A at both ends for engaging and fixing it.
B is rotatably supported by bearings B1 and B2 fitted into flange members 10A and 10B at both ends of a drum shaft 30 erected and fixed to the apparatus main body, and is rotatably supported. Is driven at a constant speed in a predetermined direction by being driven by meshing with a drive gear on the apparatus body side.

A scorotron charger 11, which is a charging unit for each color, an exposure optical system 12, which is an image exposure 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)
Four sets are provided for the image forming process of each color of black and black (K), 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, is attached to the photosensitive drum 10 in a direction orthogonal to the moving direction of the photosensitive drum 10 so as to face the photosensitive drum 10. Has a control grid maintained at a predetermined potential and a discharge electrode made of, for example, a sawtooth electrode, and performs a charging action (a negative charge in the present embodiment) by corona discharge having the same polarity as the toner. A uniform potential is applied to the photosensitive drum 10. Other wire electrodes may be used as the discharge electrodes.

An exposure optical system 12 as an image exposure means for each color
Are arranged inside the photoconductor drum 10 such that the exposure position on the photoconductor drum 10 is located on the downstream side in the rotation direction of the photoconductor drum 10 with respect to the scorotron charger 11 for each color. The exposure optical system 12 includes L as light emitting elements arranged in the main scanning direction in parallel with the axis of the photosensitive drum 10.
It comprises a linear light-emitting element 12a in which a plurality of EDs (light-emitting diodes) are arranged in an array, and a holder (not shown) to which a selfoc lens 12b as an equal-magnification imaging element is attached. Image data of each color read by a separate image reading device and stored in the memory is sequentially read from the memory and input to the exposure unit 12 for each color as an electric signal. As the light emitting device, a device in which a plurality of light emitting devices such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array is used. The emission wavelength of the light emitting element used in this embodiment is preferably in the range of 680 to 900 nm, which is generally high in transmittance for the Y, M, and C toners. Since the image exposure is performed from the back side), the wavelength may be shorter than this, which does not have sufficient transparency for the color toner.

The developing device 13 as a developing means for each color includes
For example, a cylindrical non-magnetic stainless steel having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm, which keeps a predetermined gap with respect to the peripheral surface of the photoconductor drum 10 and rotates in the forward direction with respect to the rotation direction of the photoconductor drum 10, It has a developing sleeve 131 made of aluminum material and a developing casing, and has yellow (Y), magenta (M), cyan (C) and black (K) inside.
Contains a one-component or two-component developer. Each developing unit 13 is kept in non-contact with the photosensitive drum 10 by a contact roller (not shown) with a predetermined gap, for example, 100 to 1000 μm, and has the same polarity as the toner with respect to the developing sleeve 131 (this embodiment). By applying a developing bias in which a DC voltage and an AC voltage having a negative polarity are superimposed, non-contact reversal development is performed, and a toner image is formed on the photosensitive drum 10.

The intermediate transfer belt 14a has a volume resistivity of 10 ^8.
An endless belt having a perimeter to be described later at 〜１０10 ¹² Ω · cm, for example, the outside of a semiconductive rubber belt substrate having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber or the like. Preferably, the seamless belt has a two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is applied as a toner filming preventing layer. As the base of the belt, in addition to this, modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer,
Conductive material dispersed in engineering plastics such as polyvinylidene fluoride and nylon alloy, thickness 0.1
A semiconductive film of ~ 1.0 mm can also be used. The intermediate transfer belt 14a is stretched in contact with a driving roller 14d and a driven roller 14e, and is rotated in a counterclockwise direction indicated by an arrow in FIG.

The primary transfer units 14c and 14c ', which are the first transfer means, are provided opposite to the photosensitive drum 10 with the intermediate transfer belt 14a interposed therebetween.
A transfer area is formed between the photosensitive drum 10 and the photosensitive drum 10. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the primary transfer units 14c and 14c ', and a transfer electric field is formed in a transfer area, whereby a toner image on the photosensitive drum 10 is formed. Is transferred onto the intermediate transfer belt 14a or to the surface of a recording sheet P as a transfer material.

A secondary transfer unit 14g as a second transfer unit
Is provided so as to face a conductive backup roller that is grounded with the intermediate transfer belt 14a interposed therebetween. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the intermediate transfer belt 14a. Is transferred to the back surface of the recording paper P.

Timing Roller 1 as Transfer Material Supply Means
5c feeds a recording sheet P as a transfer material to a transfer area in synchronization with a color toner image of a front surface image on the photosensitive drum 10 or a color toner image of a back surface image on the intermediate transfer belt 14a.

The 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, which fixes the toner image on the recording paper P by applying heat and pressure between the first fixing roller 17a and the second fixing roller 17b.

Next, the image forming process will be described. FIG. 8 is an explanatory diagram showing the image forming process.

In an image reading apparatus separate from the present apparatus, image data of a document image read by an image sensor or image data of an image edited by a computer is Y (yellow), M (magenta), (Cyan) and K (black) are temporarily stored and stored in the memory as image signals for respective colors.

When image recording is started, a gear G provided on the back side flange 10B of the photosensitive drum 10 is rotated through a driving gear (not shown) by starting a photosensitive member driving motor (not shown), and the photosensitive drum 10 is rotated. Is rotated clockwise as indicated by the arrow in FIG. 6, and at the same time, the application of the potential to the photosensitive drum 10 is started by the charging action of the scorotron charger 11 for yellow (Y).

First, the image data on the back side of the original is input to each of the exposure units 12 of the second process unit 20B. In the second process unit 20B, the charging unit 11 and the developing unit 13 act on the photosensitive drum. 10 is 1
During the rotation, a color toner image is formed on the peripheral surface by superimposing the yellow, magenta, cyan, and black toner images. This color toner image is once transferred onto the peripheral surface of the intermediate transfer belt 14a by the transfer device 14c.

The recording paper P as a transfer material is fed from the paper feed cassette 15 in parallel with the formation and transfer of the color toner image on the back side of the original.
Is started by the operation of the feed roller 15a,
The recording paper P is fed to the timing roller 15b via the paper feed path 15d.

The image data of the front side of the document is input to the first process unit 20A with a predetermined time difference between the input of the image data of the back side of the document to the second process unit 20B, and the second process unit. Through the same process as in 20B, the photosensitive drum 10 forms a color toner image by superposition during one rotation. The image data is converted in advance so that each toner image on the front surface of the document formed on the photosensitive drum 10 of the first process unit 20A has a mirror image relationship with the color toner image on the back surface of the document previously formed.

Both the formation of the color toner image on the front surface of the document on the peripheral surface of the photosensitive drum 10 in the first process unit 20A and the position of the color toner image on the back surface of the document transferred onto the intermediate transfer belt 14a described above. Synchronously, the operation of the timing roller 15b is started, and the recording paper P is adjusted in phase with each color toner image on the front and back of the original, so that the front end of the color toner image on the front and back coincides with the front end of the recording paper P. Paper is fed onto the transfer belt 14a.

The recording paper P is conveyed while being in close contact with the intermediate transfer belt 14a by the charging of the paper charger 150. First, the color toner on the surface of the document carried by the photosensitive drum 10 of the first process unit 20A on the upper surface thereof. Image transfer device 1
4c ', and then the color toner image on the back surface of the original on the intermediate transfer belt 14a transferred from the photosensitive drum 10 of the second process unit 20B to the lower surface thereof is retransferred by the transfer device 14g.

The recording paper P on which the color toner image has been transferred on the upper and lower sides, that is, on both front and rear sides, is discharged by the discharger 14h and separated from the peripheral surface of the intermediate transfer belt 14a. After being fused on the sheet, the sheet is discharged onto a tray via a sheet discharge roller 18.

On the other hand, each of the photosensitive drums 10 and the intermediate transfer belt 14a, on which the transfer of the color toner image has been completed, are removed and cleaned by the cleaning device 19 and the intermediate transfer member cleaning device 250, respectively. Prepare for formation and transfer.

The intermediate transfer belt 14a is erected without loosening between the driving roller 14d and the driven roller 14e, and is moved and rotated at a stable peripheral speed by applying an appropriate tension by the urging of the tension roller 14i. You.

Each of the photoconductor drums 10 and the intermediate transfer belt 14a incorporated in each of the above-described process units uses the pulse motors M1 and M2 shown in FIG. 9 as dedicated power sources, and controls the gears G by drive control. And is rotated or conveyed in the direction of the arrow synchronously with the same peripheral speed.

The intermediate transfer belt 14a has a pair of moving means having the same functions as those described in the first embodiment at the inner peripheral portion near each transfer position of each process unit. The peripheral surface of the intermediate transfer belt 14a corresponding to each photosensitive drum 10 is
As shown in FIG. 11, it is in contact with the drum surface, or as shown in FIG. Even if the roller 40B is retracted, the belt can be driven without separating the belt from the roller 40B due to the tension of the tension roller 14i.

The photosensitive drum 10 of the intermediate transfer belt 14a
Is detected by the microswitch S, the photosensitive drums 10 and the intermediate transfer belt 14a can be simultaneously rotated and conveyed at the same peripheral speed by the drive control of the pulse motors M1 and M2. When the contact release state is detected by the microswitch S, the synchronized drive control of the pulse motors M1 and M2 is released, and the photosensitive drum 10 side and the intermediate transfer belt 1 are released.
4a can be individually driven individually or simultaneously.

For the same purpose as in the first embodiment, the roller 40B at the tip of the moving lever 40 is located at a distance d from the contact point between the intermediate transfer belt 14a and the photosensitive drum 10 upstream of the belt conveyance distance of 0 to 0. The ground roller 14j, which is provided at a position of 5 mm and backs up the transfer unit 14g, has a tangential line connecting the driving roller 14d and the inner peripheral surface of the intermediate transfer belt 14a, whose outer peripheral surface is in contact with the photosensitive drum 10 at the top. (Indicated by the dashed line)
It is provided at a position of height h that is 1 to 5 mm higher than that. Further, the backup roller 150 of the paper charger 150 is used.
A is the outer peripheral surface of the top of the roller 40B on the side of the first process unit 20A in the operation position, and the intermediate transfer belt 14 on the side of the second process unit 20B that contacts the photosensitive drum 10.
a of a height h of 1 to 5 mm from a tangent line (shown by a two-dot chain line) connecting the intermediate transfer belt 14a to the intermediate surface of the intermediate transfer belt 14a. , Paper charger 1
Due to the charging of the recording paper P, the recording paper P is brought into close contact with the intermediate transfer belt 14a and is integrally transported to transfer the toner image.

[0085]

According to the first and second aspects of the present invention, it is possible to arbitrarily release the contact state between the drum-shaped image carrier and the belt-shaped intermediate transfer body, and it is possible to realize individual release by independent driving of each. Maintenance or preliminary operation becomes possible,
Further, according to the third and fourth aspects, malfunctions at the time of contact and at the time of contact release are prevented. Further, at the time of contact, a required nip portion is automatically formed, and the resulting images are formed. Thus, a double-sided image forming apparatus capable of stably forming a high-quality image while maintaining the performance function of the carrier and the intermediate transfer member has been provided.

[Brief description of the drawings]

FIG. 1 is a sectional configuration diagram of a color image forming apparatus showing a first embodiment of a two-sided image forming apparatus of the present invention.

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 main part diagram showing a drive system of the image forming unit of FIG. 1;

FIG. 5 is a partial view showing each state of contact and release of the intermediate transfer member of FIG. 1;

FIG. 6 is a sectional view of a color image forming apparatus showing a second embodiment of the double-sided image forming apparatus of the present invention.

FIG. 7 is a side sectional view of the image carrier of FIG. 6;

FIG. 8 is a diagram illustrating a toner image forming state in the image forming apparatus of FIG. 6;

FIG. 9 is a main part diagram illustrating a drive system of the image forming unit in FIG. 6;

FIG. 10 is a main part view showing a contact state of the intermediate transfer member of FIG. 6;

FIG. 11 is a main part view showing a contact release state of the intermediate transfer body of FIG. 6;

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14a intermediate transfer belt 14c, 14c '(primary) transfer device 14d drive roller 14g back (secondary) transfer device 14i tension roller 14j ground roller 15 paper feed cassette 17 Fixing device 40 Moving lever 40B Roller 41 Eccentric cam 42 Return spring M1, M2 Pulse motor S Micro switch

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yotaro Sato 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H028 BA06 BA16 BB02 BC01 2H032 AA02 AA15 BA09 BA18 BA23 BA28 CA04 DA03 DA12 3F049 AA04 DA12 DB02

Claims (5)

[Claims] 1. An image carrier, comprising: an image carrier; means for forming a toner image on the image carrier; and an intermediate transfer body which is a means for transferring the toner image and conveying a transfer material. The first toner image formed thereon is transferred to one surface of the transfer material via the intermediate transfer member, and the second toner image formed on the image carrier is directly transferred to the other surface of the transfer material. In the double-sided image forming apparatus for forming an image on both surfaces of a transfer material, the image carrier and the intermediate transfer member can be independently driven and controlled, and the intermediate transfer member is provided at the transfer position with the image carrier. A double-sided image forming apparatus comprising moving means for contacting and releasing contact. 2. An image forming unit comprising: an image carrier; and a unit for forming a toner image on the image carrier.
A toner image formed by a first image forming unit on one surface of a transfer material fed between the image forming units, the toner image having an intermediate transfer body that is capable of transferring a toner image and conveying a transfer material; In the double-sided image forming apparatus, which transfers the toner image formed by the second image forming unit directly to the other surface to form an image on both surfaces of the transfer material. And the intermediate transfer member is capable of independent drive control, and the intermediate transfer member is provided with moving means for contacting and releasing contact with the image carrier at a transfer position. apparatus. 3. The double-sided image forming apparatus according to claim 1, wherein the image carrier and the intermediate transfer body can be independently driven and controlled in the contact release state. 4. The double-sided image forming apparatus according to claim 1, wherein independent drive control of the image carrier and the intermediate transfer member is prohibited in a contact state. . 5. The double-sided surface according to claim 1, wherein the intermediate transfer body is brought into contact with the image carrier and the nip width in a range of 2 to 10 mm by the moving means. Image forming device.