JP2000137421A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image rubbing from occurring due to slip at a position where transfer material is separated from an intermediate transfer body at the rear end of the loop of the transfer material because a loop amount gets large by changing the fixing rate of a fixing means in accordance with the size of the transfer material. SOLUTION: In the case of judging that the size of the transfer material to be used is large size based on setting from an operation part and detecting a transfer material housing means, the rotating speed of a 1st and a 2nd fixing rollers 17a and 17b of a fixing device 17 is changed to the fixing rate higher than the ordinary speed of the device 17 by 0.5 to 2.0%. Thus, the loop of recording paper P to be carried so that the loop may be formed as shown by a dotted line is corrected to the loop shown by a solid line and the paper P is carried. In a stage where the paper P passes through the device 17 from its leading edge to the trailing edge, in such a case, its speed is gradually changed to the higher speed. Furthermore, in the case of judging that the size of the transfer material is the ordinary size, the each rotating speed of the 1st and the 2nd fixing rollers 17a and 17b of the device 17 is changed to the oridnary speed again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copying in which a charging means, an image writing means and a developing means are arranged around an image forming body to transfer and fix a toner image formed on the image forming body onto a transfer material. More particularly, the present invention relates 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 double-sided image formation, an image on one side formed on an image forming body is transferred and fixed on a transfer material, and this is temporarily stored in a double-sided reversal feeding device, and is again formed on the image forming body. A method has been adopted in which a transfer material is fed from a two-sided reversing feeding device at the same time as the image formed thereon, and the image on the other surface is transferred and fixed onto 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 Publication No. 4-214576 and the like propose a method in which a toner image is formed on both surfaces of a transfer material using an image forming body and an intermediate transfer body, 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 forming body), and provided on the photosensitive drum. After the formed superimposed color toner image is once transferred to the belt-shaped intermediate transfer body by the first transfer means, the superimposed color toner image is formed again on the photoconductor drum, and the toner on the photoconductor drum is formed. The transfer material fed in time with the image and the toner image on the intermediate transfer body is charged by the transfer material charging means and adsorbed on the intermediate transfer body,
On both sides of the transfer material conveyed by the intermediate transfer body,
The toner image on the photosensitive drum is transferred as a front image by a second transfer unit (using the same one as the first transfer unit), and the toner image on the intermediate transfer body is transferred as a back image by a third transfer unit. Fixing device (fixing means)
The curvature of the roller member provided on the side and stretching the intermediate transfer member,
And an image forming apparatus and an image forming method for separating a transfer material from an intermediate transfer body by static elimination by a transfer material separating unit provided as necessary, and fixing a toner image on the transfer material by a fixing device to form a double-sided color image Is disclosed in JP-A-9-25849.
No. 2 and JP-A-9-258516.

[0006]

However, in a double-sided image forming apparatus for forming a double-sided image by transferring the front and back toner images of the image forming body and the belt-like intermediate transfer body onto a transfer material as described above. After transferring the toner image to the front and back surfaces of the material, the transfer material is separated from the intermediate transfer body, and the fixing means fixes the toner image on the transfer material while nipping and transporting the transfer material by the fixing means. A loop is formed between the entrance of the transfer material and the position where the transfer material is separated from the intermediate transfer member. There is a problem that an image is rubbed due to rubbing with the transfer material, and that the leading end of the transfer material is not uniformly held in the fixing portion and wrinkles are generated in the fixing portion. Further, there is also a problem that an image is rubbed due to a change in the separation position of the transfer material from the intermediate transfer body at the rear end of the loop due to an increase in the loop amount. The loop shape also changes depending on the type of the transfer material, and the above problem is likely to occur particularly when the transfer material is thin paper, which is paper with weak stiffness.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, prevents an increase in the amount of loop when the size of the transfer material is large, and causes an image due to friction between the fixing roller and the transfer material at the entrance of the fixing means at the end of the loop. It is an object of the present invention to provide an image forming apparatus that prevents rubbing and wrinkles in a fixing unit, and also prevents image rubbing caused by a change in a separation position of a transfer material from an intermediate transfer body at a loop rear end.

In particular, when the type of the transfer material is thick paper, which is a paper of strong stiffness, and the size of the transfer material is large, the transfer material may be separated from the intermediate transfer member at the separation position at the rear end of the loop due to an increase in the loop amount. The problem of image rubbing due to slippage occurs. Further, there is also a problem that the rear end of the loop of the transfer material slips and comes into contact with the transfer material separating means provided at the separation position, thereby causing image rubbing.

The present invention solves the above-mentioned problems, and in particular, when the type of the transfer material is thick paper, which is a strong paper, and the transfer material size is large, the loop end of the transfer material due to a large loop amount. It is another object of the present invention to provide an image forming apparatus which prevents image rubbing caused by slipping at a position separated from an intermediate transfer member at the time of printing.

[0010]

The object of the present invention is to form a toner image formed on an image forming member on both sides of a transfer material via an intermediate transfer member, and then form a toner image on both surfaces of the transfer material. The first aspect of the present invention is achieved by an image forming apparatus in which fixing is performed by a fixing unit, wherein a fixing speed of the fixing unit is changed according to a size of the transfer material.

Further, the above object is to form a toner image formed on an image forming member on both sides of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by fixing means. An image forming apparatus according to the present invention is characterized in that the fixing speed of the fixing unit is changed during the passage of the transfer material according to the size of the transfer material (second invention).

[0012] It is another object of the present invention to form a toner image formed on an image forming member on both surfaces of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by fixing means. The third aspect of the present invention is directed to an image forming apparatus that changes the linear velocity of the intermediate transfer member according to the size of the transfer material.

It is another object of the present invention to form a toner image formed on an image forming member on both surfaces of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by a fixing means. An image forming apparatus according to claim 4, wherein the linear velocity of the intermediate transfer body is changed during the passage of the transfer material according to the size of the transfer material (a fourth invention).

It is another object of the present invention to form a toner image formed on an image forming member on both sides of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by fixing means. The fifth aspect of the present invention is achieved by an image forming apparatus, wherein the fixing speed of the fixing unit is changed according to the type of the transfer material.

It is another object of the present invention to form a toner image formed on an image forming member on both surfaces of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by fixing means. An image forming apparatus according to the present invention is characterized in that the fixing speed of the fixing unit is changed during the passage of the transfer material in accordance with the type of the transfer material (a sixth invention).

It is another object of the present invention to form a toner image formed on an image forming member on both sides of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by fixing means. This is achieved by an image forming apparatus, wherein the linear velocity of the intermediate transfer member is changed according to the type of the transfer material (seventh invention).

It is another object of the present invention to form a toner image formed on an image forming member on both sides of a transfer material via an intermediate transfer member, and then fix the toner images on both surfaces of the transfer material by fixing means. An image forming apparatus according to the present invention is characterized in that the linear velocity of the intermediate transfer body is changed during the passage of the transfer material according to the type of the transfer material (an eighth invention).

[0018]

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. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope. In the following description of the embodiment, the surface of the transfer material on the side facing the image forming body in the transfer area is called the front surface, and the other surface of the transfer material, that is, the surface of the transfer material on the side facing the intermediate transfer body is called 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.

An image forming process and each mechanism of an embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a sectional configuration 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 image forming body of FIG. 1, and FIG. FIG. 3A is a diagram illustrating a toner image forming state in the image forming apparatus according to the present invention, and FIG. 3A is a diagram illustrating a toner image forming state when a back surface image formed on an image forming body is transferred onto an intermediate transfer body. FIG. 3B is a diagram illustrating a toner image forming state when a front surface image is formed on an image forming body in synchronization with a back side image on the intermediate transfer body.
FIG. 4C is a diagram illustrating double-sided image formation on a transfer material.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as an image forming body; 11, a scorotron charger as charging means for each color; 12, an exposure optical system as image writing means for each color; The developing device 14a is an intermediate transfer belt which is an intermediate transfer member, and 14c is a first and a second transfer belt.
14g, a backside transfer unit as a third transfer unit, 14m, a neutralizer as a neutralization unit, and 150g.
Is a paper charger which is a transfer material charging means, 14h is a paper separation AC static eliminator which is a transfer material separating means, 160 is a conveying section having a separation claw 210 which is a claw member and a spur 162 which is a spur member, and 17 is a fixing member. It is a fixing device as a means. The image forming process member as described above is used in the image forming process of the image forming apparatus according to the present invention.

Hereinafter, each process member will be described.

The photosensitive drum 10, which is an image forming body, has a transparent conductive layer, a, on the outer periphery of a cylindrical base 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), and a normal speed of an image forming body of, for example, 80 to 250 mm / sec in a clockwise direction indicated by an arrow in FIG. Is rotated at.

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 supported by the bearings B1 and B2 fitted into the drum body 0B and supported rotatably 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) for image forming processes, four sets are provided, and the photosensitive drum 1 indicated by an arrow in FIG.
With respect to the 0 rotation direction, they are arranged in the order of Y, M, C, and 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 saw-tooth 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 surface in accordance with the image data of each color read by a separate image reading device and stored in the memory, and the image is statically placed on the photosensitive drum 10. An electrostatic latent image is formed. Exposure element 12
As a, besides LED, FL (phosphor emission), EL
(Electroluminescence), PL (plasma discharge)
It is also possible to use a plurality of light emitting elements such as those arranged in an array. The light emission wavelength of the light emitting element of the image exposure light (image writing light) is usually in the range of 780 to 900 nm, which is highly transparent to the Y, M, and C toners.
In this embodiment, since the image is written from the back side, the wavelength may be shorter than 400 to 780 nm, which does not sufficiently transmit the color toner. Further, since 80% or more of the image exposure light is absorbed by the photosensitive layer of the photosensitive drum 10, the influence of the reflection and absorption by the color toner on the surface of the photosensitive drum 10 can be neglected. Generally, the development order of the color toner is the toner image or the developing device 1.
The order of Y, M, C, and K is preferable from the relationship of color mixture to 3.
In FIG. 2, WA is a light emitting element (LE) for image exposure light.
D).

The developing unit 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. 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 ¹⁶ Ω · cm, preferably 10 ^9.
It is an endless belt of 〜１０10 ¹² Ωcm, for example, modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, a thickness of 0.1 to 0.1 to which a conductive material is dispersed in engineering plastic 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.
The photosensitive drum 10 is rotated (conveyed) in a counterclockwise direction at a normal speed of the intermediate transfer body, which is the same as the normal speed of the image forming body of the photosensitive drum 10. Guide roller 14f, driven roller 14e,
The earth roller 14j and the driving 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 from a drive motor (not shown), and drives and rotates the intermediate transfer belt 14a. 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 are driven and rotated. Belt slack of the rotating intermediate transfer belt 14a is tensioned by the tension roller 14i. Intermediate transfer belt 14a is driven roller 1
The recording paper P, which is a transfer material, is supplied to a position where it is stretched around 4e, and is conveyed by the intermediate transfer belt 14a. The intermediate transfer belt 1 is fixed at a curvature portion KT at an end of the intermediate transfer belt 14a stretched around the driving roller 14d on the fixing device 17 side.
The recording paper P is separated from 4a.

The transfer device 14c as the first or second transfer means is a corona discharge device provided to face the photosensitive drum 10 with the intermediate transfer belt 14a interposed therebetween. Transfer area 14 between
b is formed. A DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied to the transfer device 14c, and the toner image on the photosensitive drum 10 is transferred to the intermediate transfer belt 1.
4a or onto the surface of the recording paper P as a transfer material.

The back transfer device 14g, which is the third transfer means, is preferably constituted by a corona discharger, and is driven by the transfer device 14c downstream of the transfer device 14c and upstream of the drive roller 14d in the rotation direction of the intermediate transfer belt 14a. Roller 14d
And 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.

The static eliminator 14m, which is a static eliminator, is constituted by a corona discharger.
In the movement direction, an AC voltage, which is provided in parallel with the transfer device 14c on the downstream side of the transfer device 14c as the first and second transfer means and in which a DC voltage of the same polarity or opposite polarity to the toner is superimposed, The charge of the intermediate transfer belt 14a which is applied and charged by the voltage application of the transfer device 14c is removed.

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 with the intermediate transfer belt 14a interposed, and has the same polarity as the toner (this embodiment). (In the embodiment, negative polarity) is applied, and the recording paper P is charged and attracted to the intermediate transfer belt 14a. In addition to the corona discharger, a paper charging brush or a paper charging roller that can abut and release the intermediate transfer belt 14a can be used as the paper charger 150.

Paper separation AC neutralizer 1 as transfer material separating means
Reference numeral 4h denotes a driving roller 14 which is preferably constituted by a corona discharger, and which is grounded to the end of the intermediate transfer belt 14a on the side of the fixing device 17 as required.
d, and an AC voltage obtained by superimposing a DC voltage of the same polarity or opposite polarity to the toner is applied as necessary.
The recording paper P conveyed by the intermediate transfer belt 14a is discharged and separated from the intermediate transfer belt 14a.

The transport section 160 includes a separation claw 210 which is 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, is close to the curvature portion KT of the intermediate transfer belt 14a.
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 projections 162a on its peripheral surface, and is provided rotatably about a rotation support shaft 165. The spur 162 guides the back side of the recording sheet P to convey the recording sheet P, prevents the back side toner image of the recording sheet P having the toner image on both sides from being disturbed, and also 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 positioned between the transfer material conveying surface of the intermediate transfer belt 14a or the extension surface thereof.
It is arranged on the opposite side of the photosensitive drum 10. It is also possible to provide spurs 162 as spur members on both sides of the transfer material conveying surface or an extension surface thereof.

A fixing device 17 serving as a fixing means includes a first fixing roller 17a having a heater therein and a second fixing roller 1a.
7b. The recording paper P is sandwiched by a nip portion T between the first fixing roller 17a and the second fixing roller 17b, and the recording is performed by applying heat and pressure. The toner image on the paper P is fixed. The fixing device 17 conveys the recording paper P at a fixing device normal speed that is the same as the normal speed of the image forming member of the photosensitive drum 10 and the normal speed of the intermediate transfer member of the intermediate transfer belt 14a.

Next, the image forming process will be described.

The photosensitive drum 10 is rotated clockwise as shown by an arrow in FIG. 1 by starting a photosensitive member driving motor (not shown) at the start of image recording, and is simultaneously exposed by a 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 by the first color signal, that is, an electric signal corresponding to the Y image data. An electrostatic latent image corresponding to the Y image of the original image is formed on the front surface.

The latent image is reversal-developed in a non-contact state by the Y developing unit 13, and a yellow (Y) toner image is formed on the photosensitive drum 10.

Next, a potential is applied to the photoreceptor 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. 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. (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.

The superimposed color toner image, which is the back image formed on the photosensitive drum 10 as the image forming body by the above image forming process, is transferred to the transfer area 14b.
By the transfer device 14c as a first transfer unit, the transfer is performed collectively (first transfer) on the intermediate transfer belt 14a as the 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 is transferred to a cleaning device 19 as image forming body 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 side image is formed on the intermediate transfer belt 14a as described above, the front side 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 from a paper feed cassette 15 as a transfer material storage means by a feed roller 15a, and is used as a transfer material feeding means. Timing roller 1
5b, and the timing roller 15b drives the front surface image color toner image formed on the photosensitive drum 10 to synchronize with the back surface image color toner 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 that of the toner by a paper charger 150 which is a transfer material charging means provided on the front side of the recording paper P, and is attracted to the intermediate transfer belt 14a to transfer the recording paper P 14b. By charging the paper with the same polarity as that of the toner, the toner 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, a second 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 (second transfer) to the surface of the recording paper P by the transfer device 14c as the transfer means. 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. Transfer device 1 as second transfer means
At the time of the second transfer by 4c, uniform transfer is performed by a simultaneous transfer exposure unit 12d using a light emitting diode, for example, provided inside the photosensitive drum 10 in opposition to the transfer area 14b so that good transfer is performed. Exposure may be performed. 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 surface is conveyed to a back transfer device 14g as a third transfer means to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. Then, the back surface image on the peripheral surface of the intermediate transfer belt 14a is collectively transferred (third transfer) to the back surface of the recording paper P by the back transfer device 14g (FIG. 3).
(C)).

The recording paper P on which the color toner images are formed on both sides is formed by the curvature of the curvature portion KT of the intermediate transfer belt 14a and the paper as transfer material separating means provided at the end of the intermediate transfer belt 14a as necessary. The spur 162 provided on the transport unit 160 is separated from the intermediate transfer belt 14a by the static elimination action of the separation AC neutralizer 14h and the separation claw 210 provided on the transport unit 160 at a predetermined interval from the intermediate transfer belt 14a. Fixing device 17 as fixing means through
The toner image on the recording paper P is fixed by applying heat and pressure at a nip portion T between the first fixing roller 17a and the second fixing 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.

The toner remaining on the peripheral surface of the intermediate transfer belt 14a after the transfer is provided to face 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 142 as a rotation fulcrum. The intermediate transfer member is cleaned by an intermediate transfer member cleaning device 140 which is an intermediate transfer member cleaning unit having an intermediate transfer member cleaning blade 141 capable of contacting and releasing contact.

The toner remaining on the peripheral surface of the photoreceptor drum 10 after the transfer is subjected to static elimination by the photoreceptor drum AC static eliminator 16 and then cleaned by the cleaning device 19, so that the uniform exposure device before charging is removed. 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 superposed color toner images are collectively transferred by using the above-described method, color shift of the color image on the intermediate transfer belt 14a, scattering or rubbing of the toner, and the like are less likely to occur, and the image deterioration is small and good. Double-sided color image formation is performed.

In the transfer process of the transfer material in the image formation, a loop of the transfer material is formed between the position where the transfer material is separated from the intermediate transfer member and the fixing means. 4 will be described with reference to FIG. 4, and the correction of the loop amount according to the paper thickness of the transfer material will be described with reference to FIG. FIG. 4 is a diagram illustrating the correction of the loop amount according to the size of the transfer material, and FIG. 5 is a diagram illustrating the correction of the loop amount according to the paper thickness of the transfer material.

According to FIG. 4, the recording paper P on which the color toner images are formed on both sides as described above is applied to the intermediate transfer belt 1.
4a, the curvature of the curvature portion KT, the neutralization effect of the paper separation AC neutralizer 14h as a transfer material separating means provided as necessary at the end of the intermediate transfer belt 14a, and a predetermined interval from the intermediate transfer belt 14a. The belt is separated from the intermediate transfer belt 14a by a separation claw 210 provided in the conveyance unit 160, and is conveyed to a fixing device 17 as a fixing unit through a spur 162 provided in the conveyance unit 160. 2 is applied to the nip T between the fixing roller 17b and the toner image on the recording paper P is fixed at the nip T, and the fixing device 17 is conveyed at the fixing device normal speed. A loop of the recording paper P is formed between the transfer material separating position from the transfer material 14a and the entrance of the nip T of the fixing device 17.

The feed speed in the image formation including the feed speed of the fixing device 17 is set to the normal speed, the transfer material size is the normal size, and the recording paper P as the transfer material is, for example, A-size.
When the paper is fed with a transport width of 4 (horizontal) size width, a loop is formed as shown by a solid line in FIG. 4, and the leading end of the loop is smoothly added to the nip portion T, and the trailing end of the loop is from the intermediate transfer belt 14a. Although it is separated smoothly, the transfer material size is large (large size), the conveyance width of the recording paper P is long,
For example, when a recording sheet P having an A-3 (vertical) size width is conveyed, as the recording sheet P is added to the nip portion T, the formed loop becomes larger as indicated by a dotted line in FIG. At the entrance of the nip portion T of the fixing device 17 at the end of the loop, an image is rubbed due to the rubbing between the upper first fixing roller 17a and the recording paper P, or the leading end of the recording paper P is uniformly held in the nip T. This causes wrinkles in the fixing device 17. The above problem is that the transfer material is, for example, 55 to 60 kg / m ^2.
This tendency is particularly evident in thin papers of less than 55 kg / m ² , for example 45 kg / m ² , especially papers with low stiffness.

Therefore, when the transfer material size is large, the loop amount is corrected. If it is determined that the size of the transfer material to be used is large based on settings from an operation unit (not shown) or detection of a transfer material storage unit, the fixing device 17 is used.
Of the first fixing roller 17a and the second fixing roller 17b is 0.5 to 2.0% faster than the normal speed of the fixing device. (Loop difference of about 5 to 6 mm). Thereby, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 4 is corrected to a loop as shown by the solid line in FIG. 4, and the recording paper P is transported. Further, when it is determined that the transfer material size is the normal size, the rotation speed of the first fixing roller 17a and the second fixing roller 17b of the fixing device 17 is changed to the fixing device normal speed again.

When the size of the transfer material to be used is determined to be large based on the setting of the operation unit (not shown) or the detection of the transfer material storage means, the first fixing roller 17a and the second fixing roller of the fixing device 17 are used. The rotation speed of the roller 17b is gradually increased from the normal speed of the fixing device to a faster speed in the process in which the leading edge and the trailing edge of the recording paper P pass through the fixing device 17 (as the recording paper P passes from the leading edge to the trailing edge). Change and go. The change speed gradually increases up to about 2.0% (A
-3 (vertical) size, a loop difference of about 6 mm for a width of 297 mm). Thereby, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 4 is gradually corrected to the loop shown by the solid line in FIG. 4, and the recording paper P is transported. Further, when it is determined that the transfer material size is the normal size, the rotation speed of the first fixing roller 17a and the second fixing roller 17b of the fixing device 17 is changed to the fixing device normal speed again.

Alternatively, if it is determined that the size of the transfer material to be used is large based on the setting from the operation unit (not shown) or the detection of the transfer material storage means, the intermediate transfer belt 14a
The transfer speed (linear speed) of the intermediate transfer member is set at 0.
Intermediate transfer member speed 5 to 2.0% slower (loop difference of about 1.5 to 6 mm for A-3 (length) size width 297 mm)
Change to Thereby, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 4 is corrected to a loop as shown by the solid line in FIG. 4, and the recording paper P is transported. At this time, since the change in the process speed (linear speed) of the toner image forming means described above is slight, only the change in the speed of the intermediate transfer belt 14a as described above may be performed. In particular, it is preferable to simultaneously change the rotation speed (linear speed) of the photosensitive drum 10 described above with reference to FIG. 1 to an image forming body low speed lower than the image forming body normal speed. At this time, the expansion and contraction of the image in the sub-scanning direction is slight and may be left as it is, but it is preferable to cope with this by transferring image data or changing the speed of the scanner. Further, when it is determined that the transfer material size is the normal size, the linear speed of the intermediate transfer belt 14a and the photosensitive drum 10 is changed to the normal speed again.

If the size of the transfer material to be used is determined to be large based on the setting from the operation unit (not shown) or the detection of the transfer material storage means, the conveyance speed (linear speed) of the intermediate transfer belt 14a is set to the intermediate value. From the normal speed of the transfer body, in the process in which the leading edge and the trailing edge of the recording sheet P pass through the fixing device 17 (as the recording sheet P passes from the leading edge to the trailing edge),
Change to a faster speed gradually. Change speed gradually 2.
Slow speed up to about 0% (A-3 (vertical) size width 297m
m, a loop difference of about 6 mm). Thereby, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 4 is gradually corrected to the loop shown by the solid line in FIG. 4, and the recording paper P is transported. At this time, the process speed (linear speed) of the toner image forming means described above,
In particular, it is preferable that the rotational speed (linear speed) of the photosensitive drum 10 is also gradually changed to the same speed as the transport speed (linear speed) of the intermediate transfer member, and gradually reduced. At this time, since the change in the process speed of the toner image forming means is slight,
Although only the speed of the intermediate transfer belt 14a may be changed, the process speed of the toner image forming unit, particularly, the rotation speed of the photosensitive drum 10 should be gradually changed to the same speed as the conveyance speed of the intermediate transfer body. Is preferred. At that time, the expansion and contraction of the image in the sub-scanning direction is slight and may be as it is,
It is preferable to respond by transferring image data or changing the speed of the scanner. Further, when it is determined that the transfer material size is the normal size, the linear speed of the intermediate transfer belt 14a and the photosensitive drum 10 is changed to the normal speed again.

As described above, when the size of the transfer material is large, the loop amount is prevented from increasing, and image rubbing due to rubbing between the fixing roller and the transfer material at the entrance of the fixing means at the leading end of the loop and wrinkles at the fixing portion are prevented. In addition to this, it is possible to prevent image rubbing caused by a change in the separation position of the transfer material from the intermediate transfer member at the rear end of the loop due to an increase in the loop amount.

Further, as shown in FIG. 5, as described above, the recording paper P on which the color toner images are formed on both sides is the same as the curvature of the curvature portion KT of the intermediate transfer belt 14a and the intermediate transfer belt 14
The neutralization operation is performed by the paper separation AC neutralizer 14h as a transfer material separating means provided as necessary at the end portion of the intermediate transfer belt 14a, and the separation claw 210 provided on the transport unit 160 at a predetermined interval from the intermediate transfer belt 14a. , Intermediate transfer belt 14a
And is conveyed to a fixing device 17 as a fixing unit through a spur 162 provided in a conveying unit 160, and is added to a nip portion T between the first fixing roller 17a and the second fixing roller 17b, and the nip portion At T, the toner image on the recording paper P is fixed, and the fixing device 17 is conveyed at the fixing device normal speed. At this time, the transfer material separation position from the intermediate transfer belt 14a and the nip portion T of the fixing device 17 A loop of the recording paper P is formed between the recording paper P and the entrance.

[0065] The fixing device 17 of the feed speed in the image forming comprises feeding speed respectively with normal speed, plain paper or 55 kg / m ² less than thin recording paper P as a transfer material, for example 55~60kg / m ² In the case where the recording paper P is fed with a transfer width of the normal size, for example, the A-4 (horizontal) size width, a loop is formed as shown by a solid line in FIG. T and the rear end of the loop is smoothly separated from the intermediate transfer belt 14a, but the recording paper P as a transfer material weighs 60 kg.
/ M ^2, for example, 70 kg / m ² , which is a thick paper with strong stiffness, a large transfer material size (large size), and a long conveyance width of the recording paper P, for example, an A-3 (vertical) size width When the recording paper P is conveyed, as the recording paper P is added to the nip portion T, the loop formed by the thick transfer material and the size of the transfer material becomes larger as indicated by the dotted line in FIG. The slip of the recording paper P with the intermediate transfer belt 14a at the separation position at the rear end of the loop due to an increase in the loop amount may cause image rubbing of the back side toner image, or the rear end of the loop of the transfer material may slip. To contact the paper separation AC neutralizer 14h provided at the separation position, and the surface toner image is rubbed.

For this reason, when the type of the transfer material is thick paper, which is a strong paper, and the size of the transfer material is large, the loop amount is corrected. The transfer material to be used is thick paper by a paper thickness detection means (not shown) that measures the resistance value and capacity of the transfer material and detects the paper thickness, and by setting from an operation unit (not shown) and detecting the transfer material storage means. If it is determined that the transfer material size is large, the rotation speeds of the first fixing roller 17a and the second fixing roller 17b of the fixing device 17 are set to
Fixing device high speed 0.5 to 2.0% faster than normal fixing device speed (A-3 (vertical) size: 1.5 to 297 mm width)
ル ー プ 6 mm). Thereby, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 5 is corrected to the loop shown by the solid line in FIG. 5, and the recording paper P is transported. Further, when the type of the transfer material is plain paper or thin paper, which is a weak paper, and the size of the transfer material is determined to be the normal size, the first of the fixing device 17 is determined.
The rotational speeds of the fixing roller 17a and the second fixing roller 17b are changed again to the fixing device normal speed.

The paper thickness detecting means (not shown) for measuring the resistance value and capacity of the transfer material and detecting the paper thickness, and the setting from an operation unit (not shown) and the detection of the transfer material storage means, etc.
The type of transfer material used is thick paper, which is strong paper.
If it is determined that the transfer material size is large, the rotation speed of the first fixing roller 17a and the second fixing roller 17b of the fixing device 17 is changed from the normal speed of the fixing device to the fixing device from the front end to the rear end of the recording paper P. In the process of passing through the recording paper P (as the recording paper P passes from the leading edge to the trailing edge), the speed is gradually changed to a higher speed. Change rate gradually 2.0%
The speed is changed to a high speed (loop difference of about 6 mm for A-3 (length) size width of 297 mm). As a result, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 5 is gradually corrected to the loop shown by the solid line in FIG. 5, and the recording paper P is transported. Further, if the type of the transfer material is plain paper or thin paper, which is a weak paper, and the size of the transfer material is determined to be the normal size, the first fixing roller 17 a and the second fixing roller 1
The rotation speed of 7b is again changed to the fixing device normal speed.

Alternatively, it is used by a paper thickness detecting means (not shown) for measuring the resistance value and capacity of the transfer material and detecting the paper thickness, and by setting from an operation unit (not shown) and detecting the transfer material storage means. When it is determined that the type of the transfer material to be used is thick paper, which is a strong paper, and the size of the transfer material is large, the transport speed (linear speed) of the intermediate transfer belt 14a is set to 0.5 to 0.5 to the intermediate transfer body normal speed. 2.0% slower intermediate transfer member speed (1.5 to 1.5% for A-3 (vertical) size width 297 mm)
(Loop difference of about 6 mm). As a result, FIG.
Paper P to be formed and transported as shown by the dotted line in FIG.
Is corrected to a loop indicated by a solid line in FIG. 5, and the recording paper P is conveyed. At this time, since the change in the process speed (linear speed) of the toner image forming means described above is slight, only the change in the speed of the intermediate transfer belt 14a may be performed.
The process speed (linear speed) of the toner image forming means, in particular, FIG.
The rotation speed (linear speed) of the photosensitive drum 10 described above
Is preferably simultaneously changed to a low speed of the image forming body lower than the normal speed of the image forming body. At this time, the expansion and contraction of the image in the sub-scanning direction is slight and may be left as it is, but it is preferable to cope with this by transferring image data or changing the speed of the scanner. Further, when the type of the transfer material is plain paper or thin paper that is a weak paper, and the size of the transfer material is determined to be the normal size, the linear speed of the intermediate transfer belt 14a and the photosensitive drum 10 is changed to the normal speed again. I do.

The paper thickness detecting means (not shown) for measuring the resistance value and capacity of the transfer material to detect the paper thickness, and the setting from an operation unit (not shown) and the detection of the transfer material storage means, etc.
The type of transfer material used is thick paper, which is strong paper.
If it is determined that the size of the transfer material is large, the fixing device 1 moves the conveying speed (linear speed) of the intermediate transfer belt 14a from the normal speed of the intermediate transfer member to the leading edge and the trailing edge of the recording paper P.
7 (as the recording paper P passes from the leading edge to the trailing edge), the speed is gradually changed to a slower speed.
The changing speed is gradually slowed down to about 2.0% (A-3).
(Length: loop difference of about 6 mm for 297 mm width). As a result, the loop of the recording paper P formed and transported as shown by the dotted line in FIG. 5 is gradually corrected to the loop shown by the solid line in FIG. 5, and the recording paper P is transported. At this time, the process speed (linear speed) of the toner image forming means, particularly the rotation speed (linear speed) of the photosensitive drum 10 is also gradually changed to the same speed as the conveyance speed (linear speed) of the intermediate transfer body. It is preferable to go. At this time, since the change in the process speed of the toner image forming unit described above is slight, only the change in the speed of the intermediate transfer belt 14a may be performed, but the process speed of the toner image forming unit, particularly, the rotation speed of the photosensitive drum 10 is also intermediate. It is preferable to gradually change the speed at the same speed as the transfer speed of the transfer body. At this time, the expansion and contraction of the image in the sub-scanning direction is slight and may be left as it is, but it is preferable to cope with this by transferring image data or changing the speed of the scanner. Further, when the type of the transfer material is plain paper or thin paper that is a weak paper, and the size of the transfer material is determined to be the normal size, the linear speed of the intermediate transfer belt 14a and the photosensitive drum 10 is changed to the normal speed again. I do.

As described above, especially when the type of the transfer material is thick paper, which is a strong paper, the loop amount increases when the size of the transfer material is large. Of the surface toner image caused by the slip of the image is prevented. In addition, the rear end of the loop of the transfer material slips, and the image of the back toner image caused by contact with the transfer material separating means provided at the separation position is prevented.

Another embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 6 is a schematic explanatory view of a color image forming apparatus showing another embodiment of the image forming apparatus according to the present invention.

In the image forming apparatus of the present embodiment, as shown in FIG. 6, a photosensitive drum 10b as a first image forming body for forming a toner image (backside toner image) serving as a backside image, and a frontside image. A photoconductor drum 10a, which is a second image forming member for forming a toner image (front toner image), is separately provided, and the back toner image formed on the photoconductor drum 10b has a polarity opposite to that of the toner (in the present embodiment). Is a first transfer unit to which a voltage having a positive polarity is applied.
After the transfer (first transfer) on the intermediate transfer belt 114a, which is an intermediate transfer body, by 4b, the recording paper P, which is a transfer material, is transferred onto the intermediate transfer belt 114a between the photosensitive drums 10b and 10a. Supply the intermediate transfer belt 114
The recording paper P is attracted to and conveyed to the intermediate transfer belt 114a by the charging of the paper charger 150 provided opposite to the opposite ground roller 14k that is grounded with the surface a interposed therebetween, and the surface toner formed on the photosensitive drum 10a After the image is transferred (second transfer) to the surface of the recording paper P by the secondary transfer unit 114c 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 back toner image on the intermediate transfer belt 114a is applied to the back surface of the recording paper P by a tertiary transfer unit 114g which is a third transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. Transfer (third transfer), the front and back toner images are formed on the recording paper P, and the recording paper P on which the color toner images are formed on both sides is transferred to the intermediate transfer belt 14a at the curvature of the curvature portion KT and the intermediate transfer belt 14a. Transcription Paper separation as a transfer material separating means appropriately provided in an end portion of the belt 14a AC discharger 14
h and the separation claw 210 provided on the conveyance section 160 at a predetermined interval from the intermediate transfer belt 14a to separate the transfer section 160 from the intermediate transfer belt 14a.
Is conveyed to a fixing device 17 as fixing means through a spur 162 provided in the recording medium P, and a toner image on the recording paper P is fixed at a nip portion T between the first fixing roller 17a and the second fixing roller 17b. The purpose is to obtain an image.

The photosensitive drums 10a and 10b and the intermediate transfer belt 114a in the image forming apparatus of this embodiment have the same function and structure as those of the photosensitive drum 10 and the intermediate transfer belt 14a described in the image forming apparatus. Can be The intermediate transfer belt 114a is stretched while being in contact with a driving roller 14d, a ground roller 14j, a facing ground roller 14k, a driven roller 14e, a guide roller 14f, and a tension roller 14i, which are roller members. Each of the charge eliminators 114m and 114n, which are charge elimination means, is preferably constituted by a corona discharger.
A DC voltage having the same polarity or opposite polarity as the toner is provided in parallel with the primary transfer unit 114b and the secondary transfer unit 114c after the primary transfer unit 114b and the secondary transfer unit 114c with respect to the moving direction of 14a. A superimposed AC voltage is applied and 1
The charge of the intermediate transfer belt 114a charged by the voltage application of the secondary transfer unit 114b and the secondary transfer unit 114c is eliminated.

A toner image forming means (first toner image forming means) for forming a toner image serving as a back image on the photosensitive drum 10b serving as a first image forming body, and a toner image serving as a front image are formed as a second image. The toner image forming means (second toner image forming means) formed on the photosensitive drum 10a as a forming body includes:
Four sets of developing units 13 (developing means) of yellow (Y), magenta (M), cyan (C), and black (K) and a scorotron charger 11 (charging) similar to those used in the above-described image forming apparatus. Means), and an exposure optical system 12 (image writing means) is used for each of the photosensitive drums 10b and 10a to form a toner image of a back side image and a toner image of a front side image, respectively.

Also in this example, the loop amount is corrected according to the size of the transfer material described with reference to FIG. 4 and the type of the transfer material described with reference to FIG. All the loop amounts are corrected. At this time, the rotation speed (linear speed) of the photosensitive drum 10b as the first image forming body and the photosensitive drum 10a as the second image forming body is rotated at the above-described normal speed of the image forming body. When the transport speed (linear speed) of the intermediate transfer belt 114a is changed to a low speed, it is preferable that the linear speed of the photosensitive drum 10 also rotates at a lower linear speed than the normal speed of the image forming body. When the linear speed of the intermediate transfer belt 114a is gradually reduced, it is preferable that the linear speed of the photosensitive drum 10a is also gradually reduced at the same linear speed as the intermediate transfer belt 114a.

Also in this embodiment, the same effect as described above can be obtained by correcting the loop amount in FIG. 4 or FIG.

Although the color image forming apparatus has been described as an example of each of the above image forming apparatuses, the present invention is not necessarily limited to this, and the same process as described with reference to FIG. 1 or FIG. The present invention is also applied to a monochrome image forming apparatus.

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

[0079]

According to the present invention, when the size of the transfer material is large, the loop amount is prevented from increasing, and the image formed by the friction between the fixing roller and the transfer material at the entrance of the fixing means at the end of the loop is prevented. Rubbing and wrinkling at the fixing unit are prevented, and image rubbing caused by a change in the separation position of the transfer material from the intermediate transfer body at the rear end of the loop due to an increase in the loop amount is prevented.

According to the fifth and eighth aspects, the intermediate transfer at the rear end of the loop of the transfer material due to the increase in the amount of loop when the size of the transfer material is large especially when the type of the transfer material is thick paper, which is a paper with strong stiffness. Image rubbing caused by slipping at a position separated from the body is prevented. In addition, the rear end of the loop of the transfer material slips and the image rubbing caused by contact with the transfer material separating means provided at the separation position is prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus according to the present invention.

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

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

FIG. 4 is a diagram illustrating correction of a loop amount according to a size of a transfer material.

FIG. 5 is a diagram illustrating correction of a loop amount according to a sheet thickness of a transfer material.

FIG. 6 is a schematic explanatory view of a color image forming apparatus showing another embodiment of the image forming apparatus according to the present invention.

[Explanation of symbols]

 10, 10a, 10b Photoconductor drum 11 Scorotron charger 12 Exposure optical system 13 Developing device 14a, 114a Intermediate transfer belt 14c Transfer device 14g Back surface transfer device 14h Paper separation AC neutralizer 14m, 114m, 114n Static neutralizer 17 Fixing device 17a 1 fixing roller 17b second fixing roller 114b primary transfer device 114c secondary transfer device 114g tertiary transfer device P recording paper

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsu Haneda 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation F-term (reference) 2H027 DA32 DC02 DC10 ED16 ED25 EE03 EF09 FA13 ZA07 2H028 BA06 BA16 BB04 2H032 BA09 BA18 BA21 2H033 AA01 AA15 AA46 AA47 BA08 CA16 CA36 9A001 HH34 JJ35 KK42

Claims (8)

[Claims] An image forming apparatus that forms a toner image on both surfaces of a transfer material via an intermediate transfer member on a toner image formed on the image forming body, and then fixes the toner images on both surfaces of the transfer material by a fixing unit; 2. The image forming apparatus according to claim 1, wherein a fixing speed of the fixing unit is changed according to a size of the transfer material. 2. An image forming apparatus, wherein a toner image formed on an image forming member is formed on both surfaces of a transfer material via an intermediate transfer member, and then the toner images on both surfaces of the transfer material are fixed by a fixing unit. The image forming apparatus according to claim 1, wherein a fixing speed of the fixing unit is changed in a process of passing the transfer material according to a size of the transfer material. 3. An image forming apparatus in which a toner image formed on an image forming body is formed on both sides of a transfer material via an intermediate transfer body, and the toner images on both sides of the transfer material are fixed by a fixing unit. 3. The image forming apparatus according to claim 1, wherein a linear velocity of the intermediate transfer body is changed according to a size of the transfer material. 4. An image forming apparatus in which a toner image formed on an image forming body is formed on both sides of a transfer material via an intermediate transfer body, and the toner images on both sides of the transfer material are fixed by a fixing unit. The image forming apparatus according to claim 1, wherein a linear velocity of the intermediate transfer body is changed during a passage of the transfer material according to a size of the transfer material. 5. An image forming apparatus in which a toner image formed on an image forming body is formed on both sides of a transfer material via an intermediate transfer body, and then the toner images on both sides of the transfer material are fixed by a fixing unit. 3. The image forming apparatus according to claim 1, wherein a fixing speed of the fixing unit is changed according to a type of the transfer material. 6. An image forming apparatus in which a toner image formed on an image forming body is formed on both sides of a transfer material via an intermediate transfer body, and the toner images on both sides of the transfer material are fixed by a fixing unit. The image forming apparatus according to claim 1, wherein a fixing speed of the fixing unit is changed in a process of passing the transfer material according to a type of the transfer material. 7. An image forming apparatus for forming a toner image on both surfaces of a transfer material via an intermediate transfer member on a toner image formed on an image forming member, and fixing the toner images on both surfaces of the transfer material by a fixing unit. 3. The image forming apparatus according to claim 1, wherein a linear velocity of the intermediate transfer body is changed according to a type of the transfer material. 8. An image forming apparatus in which a toner image formed on an image forming member is formed on both surfaces of a transfer material via an intermediate transfer member, and the toner images on both surfaces of the transfer material are fixed by a fixing unit. The image forming apparatus according to claim 1, wherein a linear velocity of the intermediate transfer body is changed in a process of passing the transfer material according to a type of the transfer material.