JPH1010881A - Both sides image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently maintain a transporting performance of recording paper and the transferring performance of a toner image, in the case of simultaneously transferring the toner image on both front and rear sides of the recording paper. SOLUTION: This device makes respective toner image of several picture on an original either front and rear side severally formed on synchronous position of the respective periphery on the photoreceptor drum 10 and the toner image receptor 15, holds the photoreceptor drum 10 which is made as a small diameter drum of 10 to 50mm radial in press contact with respect to the toner image reception body 15 so as to form a nip part N of 1 to 6mm depth (n). Thus, the recording paper P transported while held in close contact with the toner image receptor 15 is transported without causing slippage in a transfer area on the nip part N, the excellent transfer performance is realized, and the separation from the drum surface is facilitated by suppressing curvature (r) of the belt surface to be small.

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 exposing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier to both sides of a transfer material. The present invention relates to an electrophotographic double-sided image forming apparatus such as a machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, in double-sided copying, an image on one side formed on an image carrier is transferred and fixed on a transfer material, and this is temporarily stored in a two-sided reversing paper feeder, and the image bearing is again performed. A method has been adopted in which a transfer material is fed from a double-sided reversing sheet feeder in synchronization with an image formed on the body, and an image on the other surface is transferred and fixed onto the transfer material.

In this double-sided copying apparatus, as described above, the transfer of the transfer material, such as feeding to the two-sided reversing paper feeder and passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low. And so on. On the other hand, after forming a toner image on both surfaces of a transfer material according to JP-B-49-37538, JP-B-54-28740, JP-A-1-44457 and JP-A-4-214576, fixing is performed once. Things have been suggested.

[0004]

As is well known, an image forming apparatus for forming a two-sided image using the above-described two-sided reversing sheet feeder requires a long processing distance for transferring a transfer material, so that it takes much processing time for copying. Further, since the transfer material is heated twice for fixing the image, there is a problem that paper quality is damaged.

The inventor of the present invention has previously provided two image bearing means and two transfer means to transfer a toner image to both sides of a transfer material and to simultaneously fix the transfer material having toner images on both sides. A study was made on an apparatus that performs double-sided copying, and a double-sided image forming apparatus capable of significantly increasing the processing speed of double-sided copying was realized.

However, a drum-shaped photosensitive member and a belt-shaped intermediate transfer member are used as the two image bearing means, and a toner image of a surface image of a document is formed on the drum surface of the photosensitive member to perform intermediate transfer. Since the transfer material is transferred onto the transfer material that is transported linearly by the body, if the adhesion of the transfer material to the drum surface is weak, the transfer material floats from the drum surface, causing image misregistration or poor transfer. On the other hand, if the adhesion is too strong, there is a problem that the transfer material wraps around the drum surface after transfer and the separability deteriorates.

The present invention has solved and improved the above points,
An object of the present invention is to provide a double-sided image forming apparatus which is excellent in both transferability to a transfer material and transportability while preventing image displacement and winding.

[0008]

An object of the present invention is to provide a first image carrying means for carrying a toner image formed by a toner image forming means, and a transfer of the toner image carried by the first image carrying means. A second image holding means for holding the transferred toner image on the surface, a first transfer means for transferring the toner image carried on the first image holding means to a surface of a transfer material, Second transfer means for transferring the toner image carried on the second image carrying means to the back surface of the transfer material, and toner image carried on the first image carrying means by the first transfer means Is transferred to the front surface of the transfer material, and the toner image carried by the second image carrying means is transferred to the back surface of the transfer material by the second transfer means, and is transferred to both surfaces of the transfer material. Image formation having a fixing unit for fixing a damaged toner image Wherein the first image carrier is a drum-shaped image carrier, the second image carrier is a belt-shaped toner image receiver, and the image forming body has a radius of curvature of 10 to 50 mm, The nip forming portion formed by contact of the image forming body has a depth of 1 to 6 mm, and is formed by a double-sided image forming apparatus (the invention according to claim 1) and a toner image forming unit. A first image carrying means for carrying the transferred toner image, a second image carrying means for carrying the toner image carried on the first image carrying means, and carrying the transferred toner image on the surface; A first transfer unit for transferring the toner image carried by the first image carrying unit to a front surface of a transfer material; and a toner image carried by the second image carrying unit to a back surface of the transfer material. Second transfer means for transferring, and the first transfer means Transfers the toner image carried by the first image carrying means to the surface of the transfer material, and transfers the toner image carried by the second image carrying means by the second transferring means. And a fixing unit for transferring the toner image transferred to both sides of the transfer material and fixing the toner images transferred to both surfaces of the transfer material, wherein the first image bearing unit comprises a plurality of drum-shaped image forming bodies. The second image bearing means is a belt-shaped toner image receiving member, wherein the image forming member has a radius of curvature of 10 to 50;
mm, a plurality of nip forming members abutting from the back side of the toner image receiving body between the toner image receiving body and the toner image receiving body formed by the abutting of the image forming body. Is achieved by a double-sided image forming apparatus (the invention according to claim 3), wherein the nip portion has a depth of 1 to 6 mm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the present invention, the structure and functions of a document image reading apparatus for reading images on the front and back of a document will be described with reference to FIG.

Image data of a document input to the image forming apparatus of the present invention is read by, for example, an image reading apparatus 50A provided separately from the apparatus main body shown in FIG.

In the case of the above-described image reading apparatus 50A, the originals D are stacked in a page order from the lower side with the front surface facing downward, and the lowermost original D is directed to the transport path 53 by the operation of the discharge belt 51A and the separating roller 52. It is carried out.

The conveyed original document D is retracted to the position shown by the broken line without the guide plate G biased to the position shown by the solid line, and is placed on the transparent platen glass 55 via the transport belt 54. The document is fed, and is temporarily stopped at the document reading position with the back face down.

An image of the back surface of the document D on the platen glass 55 is composed of a first mirror unit 56 including an illumination lamp and a first mirror constituting a scanning optical system, and a second V-shaped second mirror unit 56.
Second mirror unit 57 including a mirror and a third mirror
Of the first mirror unit 56 at the speed V and the speed V / 2 in the same direction by the second mirror unit.
Is read by the moving exposure of the camera, and an image is formed on the image sensor CCD by the projection lens L. The back side image formed on the image pickup device CCD is temporarily stored in the image memory (I) as image data, and is also output as an electric signal to an exposure unit to be described later to form a latent image on the photoreceptor. The finished toner image is transferred by a transfer device, and a back side image is formed on a toner image receiving body described later.

When the reading of the back side image is completed in the image reading device 50A, the original D is turned upside down through the reverse feeding path 58 by the temporary reverse rotation of the transport belt 54, and again passed through the transport path 53 to the transport belt 54. And is temporarily stopped at the document reading position with the surface facing downward.

The original image on the platen glass 55 is read by the above-described scanning optical system and temporarily stored as image data in the image memory (II) and output to the exposure unit as an electric signal. A surface image on the photoconductor is formed.

The back side image formed on the toner image receiver and the front side image formed on the photoreceptor are transferred to the front and back of a first recording sheet fed from a sheet feeding cassette, and are transferred to the front and back sides. The copy cycle for the sheet is completed. The recording paper holding the front toner image and the rear toner image is fixed by a fixing device, and is discharged onto a tray outside the apparatus with the front and back turned upside down.

When copying the second and subsequent sheets, the image of the original D is not read, and the image data from the image memory (I) is output so that the back side image and the image data from the image memory (II) are output. By outputting the image data, a front side image is formed, and the front side image and the back side image are respectively transferred to the front and back of each of the second and subsequent recording sheets fed from the sheet feeding cassette. The recording paper holding the front toner image and the rear toner image is fixed by a fixing device, and is stacked in a page order on the recording paper discharged first with the front side down.

On the other hand, in the original reading device 50A, the originals D, for which the image reading has been completed, are stacked on the tray 60 via the discharge rollers 59 by the operation of the transport belt 54 with the front surface facing down, in order from the bottom. Paper is discharged as follows.

Next, a basic image forming process of a double-sided image forming apparatus which receives image data of the front and back of a document obtained by the image reading apparatus and records images on the front and back of a transfer material will be described with reference to FIG.

Reference numeral 10 denotes a small-diameter photosensitive drum serving as first image bearing means, which is formed by applying an OPC photosensitive member on the drum, and is driven and rotated clockwise in a grounded state.
Numeral 11 denotes a scorotron charger, which in the present embodiment negatively and uniformly charges the peripheral surface of the photosensitive drum 10 by corona discharge by a grid and a corona charging wire maintained at a predetermined potential, thereby giving a potential _VH .

After the photosensitive drum 10 is charged, the image data of the back side image of the document is input to the laser writing device 12 from the memory (I) as a signal, and the formation of a latent image is started.

The laser writing device 12 is a polygon mirror 12 which rotates using a laser diode (not shown) as a light source.
A, the main scanning is performed via the fθ lens 12B and the reflecting mirror 12C, and the sub-scanning is performed by the rotation of the photosensitive drum 10 to form a latent image on the photosensitive drum 10. In this embodiment the latent image becomes lower V _L absolute value than V _H potential at the exposed portion is formed.

On the peripheral surface of the photosensitive drum 10, there is provided a developing unit 13 containing a developer such as a monochrome, for example, a black toner and a magnetic carrier, and the latent image is rotated by rotation of a developing sleeve 13A holding the developer. Reversal development is performed on the image. The developer is transported to the developing area while being regulated to an appropriate layer thickness on the developing sleeve 13A, and has a negative polarity by a negative DC voltage _VDC applied between the developing sleeve 13A and the photosensitive drum 10. The toner is adhered to the latent image portion having the potential _VL on the photosensitive drum 10 side to perform visualization.

The toner image of the back side image of the original formed on the photosensitive drum 10 is applied with a DC voltage having a polarity opposite to that of the toner by the transfer unit 14 as the first transfer unit, and the second image holding unit Is transferred to the peripheral surface of the toner image receiver 15. The toner image receiver 15 has a thickness of 0.5 to 2.
An endless rubber belt of 0 mm, a semiconductive substrate of silicon rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹² Ω · cm, and a thickness of 5 to 10 μm as a toner filming prevention layer outside the rubber substrate. And a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-0.5 thickness instead of rubber belt base
mm semiconductive polyester, polystyrene, polyethylene, polyethylene terephthalate, or the like can also be used. The toner image receiving member 15 is driven by the driving roller 15B and the driven roller 1 by pressing the tension roller 15A.
5C, and is circulated counterclockwise in synchronization with the peripheral speed of the photosensitive drum 10 by the rotation of the drive roller 15B in a state where the peripheral surface thereof is in contact with the photosensitive drum 10. The drive roller 15B and the driven roller 15C are grounded.

After the transfer of the photosensitive drum 10 to the toner image receiving member 15 is completed, the cleaning device 100 removes and cleans the residual toner, and subsequently, the scorotron charger 11 applies a potential of V _{H to} the photosensitive drum 10 to write the laser. The formation and transfer of the toner image of the back side image of the document are continuously performed by the exposure scanning of the device 12.

When the formation and transfer of the toner image on the entire back surface image are completed by a plurality of rotations of the photosensitive drum 10, the image data of the front surface image of the original is called from the memory (II) and input as a signal, and the photosensitive drum is input. The formation of a toner image of a surface image on the surface 10 is started.

The toner image of the front side image is synchronized with the toner image of the back side image formed on the toner image receiving body 15 formed earlier, and the photosensitive drum is formed by the same process as that for forming the toner image of the back side image. 10 is formed. The image data is converted so that the toner image of the front surface image formed at this time becomes a mirror image of the toner image of the rear surface image formed earlier.

The recording paper is carried out of the paper feed cassette 16 in parallel with the formation of the toner image of the front surface image, and is synchronized with each toner image on the photosensitive drum 10 and the toner image receiver 15 by the operation of the timing roller 17. Fed.

The recording paper is charged to the same polarity as the toner by the paper charger 18, is adsorbed on the toner image receiving body 15, and is fed integrally therewith, and is transferred onto the upper surface of the photosensitive drum 10 by the transfer unit 14. The toner image of the image is transferred.

Next, the recording paper is charged to the opposite polarity to the toner in the back transfer unit 19 provided as the second transfer means, and the toner image of the back image on the toner image receiver 15 is transferred to the lower surface thereof.

The recording paper on which the toner images have been transferred to both the upper and lower surfaces is thus neutralized by the neutralizer 20 and the toner image receiving member 15
And is fed to the fixing device 21 so that the fixing roller 2
The toner is heated from both upper and lower surfaces by the nipping and transporting of the pressure roller 1 </ b> A and the pressure roller 21 </ b> B to fuse the toner, and then discharged onto the tray 23 via the discharge roller 22.

Photosensitive drum 10 after transfer of toner image
In the cleaning device 100, the residual toner is removed, while the toner image receiving body 15 is cleaned of the residual toner by the cleaning device 150 in which the blade 150A is pressed, so as to prepare for the formation of the toner image of the backside image of each subsequent document.

(Embodiment 1) An embodiment of the invention according to claims 1 and 2 will be described with reference to FIGS.

The toner image receiving member 15 is tensioned by the pressure contact of a tension roller 15A, and the photosensitive drum 1 is placed on the belt peripheral surface facing the transfer device 14.
The nip portion N is formed by abutting the peripheral surfaces of the toner images 0 to form a transfer area of the toner image from the photosensitive drum 10 to the toner image receiver 15.

The toner image receiving body 15 is a paper charger 1
8, the recording paper P closely contacted on the toner image receiving body 15 is conveyed in the transfer area without causing a gap between the recording paper P and the peripheral surface of the photosensitive drum 10 to efficiently convert the toner image of the surface image. Good transfer is made. After passing the transfer area, the recording paper P
Are separated from each other without adhering to the peripheral surface of the photosensitive drum 10 due to the adhesive force of the toner or the like, and the toner image receiving member 1
The toner image of the back side image is transferred to the back side of the recording sheet P by being conveyed integrally to the back side transfer unit 19 and subjected to corona discharge having a polarity opposite to that of the toner of the back side image.

The transferability of the recording paper P and the transferability of the toner image within the transfer area, the separability of the recording paper P from the drum surface after passing through the transfer area, and the disturbance of the toner image on the toner image receiver 15 are as follows. However, the present inventors largely depend on the form and size of the nip portion N, and the present inventor has focused on this point and tried to consider experimentally. As a result, the radius of curvature R of the photosensitive drum 10 is 10 to 50 mm, that is, the diameter is 20 to 50 mm.
By setting the depth n of the nip portion N in the range of 1 to 6 mm corresponding to the range of 100 mm, the toner image on the toner image receiving body 15 is not disturbed and the transportability of the recording paper P is ensured. It was confirmed that good toner image transferability was obtained. Further, at the downstream end of the nip portion N, the toner image receiving member
Of the toner image receiving member 15 is greatly reduced.
From this, it was found that the recording paper P was not peeled off and that the separation property of the recording paper P from the drum surface was good. That is, when the radius of curvature of the photosensitive drum 10 is 10 mm or less, the recording paper P is strongly bent in the transfer area, so that the toner image on the photosensitive drum 10 and the toner image on the toner image receiver 15 are disturbed. When the radius of curvature is 50 mm or more, the recording paper P tends to wind around the photosensitive drum 10 after the transfer process, and tends to float once away from the toner image receiver 15,
Disturbance of the toner image on the image forming body and the toner image on the toner image receiving body 15 was observed. When the depth n of the nip portion N is 1 mm or less, insufficient pressure bonding is likely to cause poor transfer.
It is recognized that the recording paper P after transfer is separated from the toner image receiving body 15 at a distance of not less than mm, the toner image of the rear surface image is disturbed, and the image quality is reduced.

The width of the nip forming portion is preferably 5 to 30 mm. If the width is small, transfer failure at the contact portion is apt to occur, and the pressing with the recording paper becomes uneven, so that the toner image receiving body is easily wrinkled. On the other hand, if the width is wide, a contact depth is required, and there is a problem that the conveyance path of the recording paper becomes largely bent. Further, the toner image on the toner image receiver is also easily disturbed.

(Embodiment 2) An embodiment of the invention according to claims 3 to 6 will be described with reference to FIGS.

The apparatus shown in FIG. 4 is a color image forming apparatus of the type in which front and back images of a document are formed on both sides of recording paper by superposing a plurality of monochrome images.

The toner image receiver 15 as a second image carrier
The image forming unit 10Y forms yellow (Y), magenta (M), cyan (C), and black (K) toner images on one side opposite to the tension roller 15A, respectively.
10M, 10C and 10K are arranged in parallel from the upstream side of the conveyance, that is, from the right.

The toner image receiver 15 is made of silicon rubber or urethane rubber of 10 ⁸ to 10 ¹² Ω · cm.
And a 0.5 to 2.0 m thick two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is applied to the outside of the rubber substrate as a toner filming preventing layer.
m endless rubber belt is used.

Each of the image forming units includes a photosensitive drum 10 as a first image bearing unit having the same shape and a corona charger 11, an exposure optical system 12, and a developing unit 1 disposed on the peripheral surface thereof.
3 and the cleaning device 100, and in the process of rotating each of the photoconductor drums 10 a plurality of times in the clockwise direction, a uniform potential is applied to the photoconductor on the peripheral surface by the discharge of the corona charger 11 so that a uniform The photoreceptor applied with the potential forms an electrostatic latent image by exposure of the exposure optical system 12, and the latent image is visualized by a developing unit 13 to sequentially form a toner image of a specific color.

After the photosensitive drum 10 is charged, each exposure optical system 1
2 shows Y, M, C, and K of the back side image of the original from the memory.
Image data of four colors (black) is sequentially input as signals with a delay of a predetermined time, and the formation of a latent image on each photosensitive drum 10 is started.

The above-mentioned exposure optical system 12 is, for example, a linear type in which a plurality of LEDs (light emitting diodes) as image exposure light emitting elements arranged in the main scanning direction in parallel with the axis of the photosensitive drum 10 are arranged. It is composed of a light emitting element and a selfoc lens (trade name) as an equal magnification imaging element.

The latent images formed on the respective photosensitive drums 10 are reversely developed by respective developing units 13 containing a developer of a specific color, so that the latent images are yellow (Y), magenta (M), cyan (C) and black. The toner image on each of the photosensitive drums 10 which forms the toner image of (K) and is conveyed synchronously is transferred onto the peripheral surface of the toner image receiver 15 by each of the transfer units 14 as a first transfer unit. When a voltage having a polarity opposite to that of the toner is applied, the toner image is sequentially superimposed and transferred to form a color toner image.

After the transfer to the toner image receiving member 15 is completed, the respective photosensitive drums 10 are cleaned by removing the residual toner by the respective cleaning devices 100, and subsequently, the electric potential is applied by the charger 11 and the respective exposure optical systems 12 are successively applied.
, The formation of the toner image of the back side image of the document is continued.

When the formation and transfer of the toner image on the entire back surface image are completed by a plurality of rotations of the photosensitive drum 10, after a predetermined time has elapsed, image data of the front surface image of the original is input as a signal, and each photosensitive drum 10 On the upper side, formation of toner images of four colors of Y, M, C, and K (black) of the surface image is started with a delay of a predetermined time.

The toner image of the front surface image is synchronized with the toner image of the rear surface image formed on the toner image receiving body 15 previously formed, and the respective photosensitive images are formed by the same process as that for forming the toner image of the rear surface image. It is formed on the body drum 10.
The image data is converted so that the toner image of the front surface image formed at this time becomes a mirror image of the toner image of the rear surface image formed earlier.

The recording paper is carried out of the paper supply cassette 16 in parallel with the formation of the toner image of the front surface image, and is synchronized with each toner image on the photosensitive drum 10 and the toner image receiver 15 by the operation of the timing roller 17. Fed.

The recording paper is charged to the same polarity as the toner by the paper charger 18, electrostatically attracted to the toner image receiving body 15, and fed integrally, and is formed on the photosensitive drum 10 in each image forming section. The transferred toner images of the respective specific colors are sequentially superimposed and transferred by applying a transfer voltage having a polarity opposite to that of the toner from the back side of the recording paper by each transfer unit 14 as a first transfer unit, and the surface is transferred to the upper surface thereof. The color toner image of the image is recorded.

Next, the recording paper is corona-charged to the opposite polarity to that of the toner in the back transfer unit 19 as the second transfer means, and the toner image of the back image on the toner image receiver 15 is transferred to the lower surface of the recording paper. Thus, the color toner images on the front and back of the document are recorded on the upper and lower surfaces of the recording paper.

The toner image receiver 15 has a driven rotatable nip roller 30 on a belt surface at a fixed position corresponding to an intermediate point between the photosensitive drums 10 or at a fixed position before and after the photosensitive drum 10 is sandwiched. A nip portion N is formed between the photosensitive drum 10 and the toner image receiving member 15 for each image forming unit so as to be in contact with each other.
5 is formed.

The toner image receiving member 15 is a paper charger 1
The recording paper closely contacted by the discharge of No. 8 is conveyed into the transfer area without causing a gap between the recording paper and the peripheral surface of the photosensitive drum 10 to efficiently transfer the toner image of the surface image.
After passing through the transfer area, the toner image is separated without adhering to the peripheral surface of the photosensitive drum 10 due to the adhesive force of the toner or the like, and is transported integrally with the toner image receiving body 15 to the next image forming unit. After the repetition, the toner image is conveyed to the backside transfer unit 19 to perform corona discharge having a polarity opposite to that of the toner, thereby transferring the toner image of the backside image on the toner image receiver 15 to the lower surface of the recording paper.

The transferability of the recording paper P and the transferability of the toner image in the transfer area, the separability of the recording paper P from the drum surface after passing through the transfer area, and the disturbance of the toner image on the toner image receiver 15 are as follows. The inventor of the present invention has attempted to consider experimentally by paying attention to this point, which largely depends on the shape and size of the nip portion N. As a result, for the photosensitive drum 10, the radius of curvature R1 is 10 to 50 mm, that is, the diameter is 20 to 1 mm.
By setting the depth n of the nip portion N to be 1 to 6 mm and the width b to be 5 to 30 mm in accordance with the range, the toner image on the toner image receiving body 15 can be reliably disturbed. It was confirmed that excellent transferability of the recording paper P and good transferability of the toner image were obtained. That is, when the radius of curvature of the photosensitive drum 10 is 10 mm or less, the recording paper P is strongly bent in the transfer area, so that the toner image on the photosensitive drum 10 and the toner image on the toner image receiver 15 are disturbed. If the radius of curvature is 50 mm or more, the recording paper P tends to wind around the photosensitive drum 10 after the transfer step or tends to float once away from the toner image receiving body 15, so that the toner image on the image forming body or the toner image receiving Disturbance of the toner image on the body 15 was observed. The depth n of the nip portion N is 1 mm
In the following, transfer failure was apt to occur due to insufficient pressure bonding, and it was recognized that the transfer paper P was separated from the toner image receiving body 15 and the toner image of the back side image was disturbed and the image quality was deteriorated in the case of 6 mm or more. Further, the width b of the nip forming portion is 5 to 30 mm.
When the width b is smaller than 5 mm, transfer failure at the contact portion is likely to occur, and the pressing with the recording paper becomes uneven.
The toner image receiver is likely to wrinkle. On the other hand, the width b is 30 mm
If it is wider, a contact depth is required, and there is a problem that the recording paper transport path becomes largely bent, and the toner image on the toner image receiver is easily disturbed. Further nip N
At the downstream end of the recording paper P, the radius of curvature r of the toner image receiving body 15 that has been in close contact with the toner image receiving body 15 due to the electrostatic force at the time of transfer is greatly suppressed. The separation property from the drum surface was also good, and it was found that the recording paper P after the transfer was in a state of being continuously adhered to the toner image receiver 15. The radius of curvature R of the nip roller 30 is maintained in order to maintain the conveyance of the recording paper P between the image forming units.
2 is required to be larger than the radius of curvature r of the toner image receiving body 15 at the downstream end of the nip portion N and to be 10 mm or more, and to set the radius of curvature R2 of the nip roller 30 to 10 mm.
mm, the leading edge of the recording paper is
Away from the image, resulting in a decrease in image quality. The driving roller 15B, the driven roller 15C, and the nip roller 30 are grounded.

Further, the recording paper P on which the transfer of the toner image has been completed
Is subjected to static elimination by the static eliminator 20 and is separated horizontally from the belt surface at the curved surface of the toner image receiver 15 formed by the driving roller 15B. It was confirmed that good results were obtained with the separation from the belt surface by taking the range of up to 35 mm. That is, when the diameter φ of the curved surface portion is 35 mm or more, the recording paper is likely to be poorly separated from the belt surface. There was a tendency for performance to decrease.

[0056]

According to the present invention, the respective images on the front and back of the original are formed on the respective image carrying means, and are simultaneously transferred with a high transfer rate without any deviation from the front and back of the transfer material, and the transfer of the transfer material is also good. As a result, a double-sided image forming apparatus that efficiently records a high-quality image is provided. In particular, according to the first and second aspects of the present invention, a double-sided image forming apparatus dedicated to monochrome images is provided.
According to the third to seventh aspects of the present invention, a two-sided color image forming apparatus capable of forming a color image is realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image reading apparatus.

FIG. 2 is a sectional configuration view of a monochrome double-sided image forming apparatus.

FIG. 3 is a main part diagram of a monochrome double-sided image forming apparatus.

FIG. 4 is a cross-sectional configuration diagram of a color double-sided image forming apparatus.

FIG. 5 is a main part view of a color double-sided image forming apparatus.

[Explanation of symbols]

 10Y, 10M, 10C, 10K Image forming unit 10 Photoconductor drum 11 Charger (scorotron charger) 12 Laser writing device (exposure optical system) 13 Developing device 14 Transfer device 15 Toner image receiver 16 Feeding cassette 17 Timing roller Reference Signs List 18 paper charger 19 backside transfer unit 20 static eliminator 21 fixing device 30 nip roller 100, 150 cleaning device N nip part n (nip) depth b (nip) width

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadayoshi Ikeda 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Inventor Akira Matsubara 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Invention Person Masakazu Fukuchi 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation

Claims (7)

[Claims] A first image carrying means for carrying the toner image formed by the toner image forming means; and a toner image carried by the first image carrying means is transferred. A second image carrying means carried on the surface; a first transferring means for transferring the toner image carried on the first image carrying means onto a surface of the transfer material; and a carrying means carried on the second image carrying means. Second transfer means for transferring the toner image formed on the back surface of the transfer material, and transferring the toner image carried on the first image carrying means to the front surface of the transfer material by the first transfer means. And fixing the toner image carried by the second image carrying means to the back surface of the transfer material by the second transfer means, and fixing the toner images transferred to both surfaces of the transfer material. Means, the first image forming apparatus comprising: The image bearing means is a drum-shaped image forming body,
Is a belt-shaped toner image receiving member, wherein the image forming member has a radius of curvature of 10 to 50 mm, and a depth of a nip portion of the toner image receiving member formed by abutting of the image forming member. A double-sided image forming apparatus having a thickness of 1 to 6 mm. 2. The double-sided image forming apparatus according to claim 1, wherein the width of the nip forming portion is 5 to 30 mm. 3. A first image carrying means for carrying a toner image formed by a toner image forming means, and a toner image carried by the first image carrying means is transferred. A second image carrying means carried on the surface; a first transferring means for transferring the toner image carried on the first image carrying means onto a surface of the transfer material; and a carrying means carried on the second image carrying means. Second transfer means for transferring the toner image formed on the back surface of the transfer material, and transferring the toner image carried on the first image carrying means to the front surface of the transfer material by the first transfer means. And fixing the toner image carried by the second image carrying means to the back surface of the transfer material by the second transfer means, and fixing the toner images transferred to both surfaces of the transfer material. Means, the first image forming apparatus comprising: The image carrying means comprises a plurality of drum-shaped image forming bodies, the second image carrying means is a belt-shaped toner image receiving body, and the image forming body has a radius of curvature of 10 to 50 mm.
Having a plurality of nip forming members abutting from the back side of the toner image receiving body between the toner image receiving body and the toner image receiving body formed by the abutting of the image forming body A double-sided image forming apparatus, wherein a depth of a nip portion is 1 to 6 mm. 4. The double-sided image forming apparatus according to claim 3, wherein the width of the nip portion is 5 to 30 mm. 5. The nip forming member has a radius of curvature of 10 m.
The double-sided image forming apparatus according to claim 3, wherein m is at least m. 6. A curvature of a nip portion of the toner image receiving member formed by contact of the image forming member is larger than a curvature of a nip portion of the toner image forming member formed by pressing the nip forming member. 3. The method of claim 3, wherein
6. The double-sided image forming apparatus according to claim 5. 7. The double-sided image forming apparatus according to claim 3, wherein the toner image receiving body has a radius of curvature of 7.5 to 17.5 mm at a separation position of the transfer material. .