JP2928296B2 - Double-sided image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided image forming apparatus such as a color copying machine, a color printer, and a color facsimile. A double-sided image forming apparatus for forming an image on both sides of a material is known.

A transfer belt that conveys the transfer material to the transfer position where the visible image of the photoreceptor is transferred is formed so as to be reciprocable, and the transfer material after the surface image is formed is fed backward by the reverse rotation of the transfer belt so that the rear end becomes the front end. A double-sided image forming apparatus for inverting and guiding the transfer material to a transfer position of a photoreceptor is known, for example, from JP-A-59-166 and JP-A-54-24639.

In this conventional apparatus, the transfer material is inverted and guided to the transfer position after image formation on the surface and before fixing, so that the image of the transfer material is rubbed by rollers or guide members in the middle by being transported without being fixed. Therefore, there is a problem that the image is deteriorated and the guide member, the roller and the like are stained.
Further, since the front and rear ends of the transfer material are reversed, it is necessary to provide a device for inverting the double-sided document and guiding it to the exposure position so that the front and rear ends of the back and front images are not reversed. In this case, in the case of a one-sided original, it is necessary for the operator to reverse the front end and the rear end of the original every other sheet and feed the original. Alternatively, the original on the back side must be scanned and exposed in the reverse direction without inverting the original. Therefore, there has been a problem that the operation of the operator is troublesome and the control for adjusting the timing is complicated.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a double-sided image forming apparatus capable of forming a color double-sided image with a simple structure by solving the above-mentioned conventional problems.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention forms a latent image by performing optical writing on a photoreceptor by writing means, develops the latent image by development, and transfers reciprocally by a reciprocable transfer belt. An image forming apparatus that forms an image by superimposing and transferring a visual image of a photoconductor onto a material, wherein a visual image is transferred to a front surface, and a back surface of the transfer material after fixing of the visual image faces the photoconductor. In a double-sided image forming apparatus that returns to the transfer belt via a reversing path curved as described above and forms an image on the back surface,
The image forming apparatus includes a storage unit for storing image data of at least one page of the document. For image formation on the back surface of the transfer material, the transfer material whose front and back are reversed is sent downstream with respect to the transfer position of the transfer belt via the reversing path. When the transfer belt is moved forward after the transfer belt is moved backward and conveyed to the upstream side of the transfer position,
The front end of the one-page image stored in the storage means is sequentially formed from the rear end line to the front end line, with the front end side at the time of forming the front image being the rear end.

[Action]

According to the present invention, the transfer material is reciprocated on the guide plate and the conveyance path by the transfer belt by the reciprocating transfer belt, so that the transfer material is transferred with the color separation image of the photoreceptor superimposed thereon to form a color image. The transfer material after the color image is formed is branched from the guide plate by the switching of the fixing switching claw and transported to the fixing device.
Be established. In the case of single-sided image formation, the sheet is discharged from the fixing device through the discharge path. In the case of double-sided image formation, the transfer material after the image is fixed on the front surface is guided to the reversal path by switching of the reversing switching claw, and is guided on the guide plate. And guided on a conveyor belt. At this time, the transfer material is fed on the transport belt in the opposite direction to that for image formation on the front surface, so that the leading end position of the transfer material is reversed. In other words, the rear end of the transfer material comes to the front end position for image formation on the front surface when forming an image on the back surface.

When forming an image on the back side, a latent image is formed on the photoconductor sequentially from the rear end line to the front end of the one-page image by a storage unit for storing at least one page of image data, and the image based on the latent image is formed. Thus, when the image is transferred to the transfer material, the front and rear images are prevented from being reversed.

〔Example〕

 The details of the present invention will be described based on an embodiment shown in the drawings.

A copying machine as an example of an image forming apparatus utilizing the present invention can be configured as shown in FIG.

In FIG. 1, an image of a document on a contact glass 1 is read by a known reading device 2. For example, an optical signal read by an image sensor 3 of the reading device 2 is changed into an electric signal, and the light in the printer unit 4 is changed. It is sent to the writing unit 5 as a writing signal.

The printer unit 4 is provided with a photoreceptor belt 8 wound around a driving roller 6 and a driven roller 7, and a corona charger 9, a writing position 10 by a writing unit 5 along a traveling path of the photoreceptor belt 8, A developing device 11, a transfer corona charger 12, a cleaning device 13, and a static eliminator 14 are sequentially arranged.

The developing device 11 includes a developing device, for example, a yellow developing device 11a, a magenta developing device 11b, and a cyan developing device 11c, each of which develops with a separated color toner in order to visualize the latent image of the separated color image of the color image. Has a black developing device 11d. Each of the developing units 11a to 11d is provided with a developing roller 15 for adhering toner to the photosensitive belt 8.

A transfer material, for example, a transfer paper 17 is called from a paper feed device, for example, a cassette 16 by a paper feed roller 18,
As a result, the paper is fed in synchronization with the image on the photosensitive belt 8.

Transfer belt as transfer paper transport means for transporting transfer paper
20 is a transfer belt driving roller 21 and a transfer belt driven roller 22
And the switching movement of the contact / separation switching roller 23,
At a transfer position T by the transfer corona charger 12, the transfer belt 20 is formed to be switchable between a contact position where it contacts the photoreceptor belt 8 and a non-contact position where it separates.

The transfer paper 17 fed by the registration roller 19 is placed on the transfer belt 20, and is attracted to the transfer belt 20 by charging by the charge applying means 24 as the suction means. In the example shown in the figure, the transfer paper 17 is transferred along a substantially horizontal transport roller by a transfer belt.
The photoconductor belt 8 is conveyed by the photoconductor 20 and is disposed so as to extend substantially in the vertical direction, but is not limited to this shape.

The transfer belt 20 that transports the transfer paper 17 is neutralized by a neutralization corona discharger 25 on the return side opposite to the transport side,
The transfer belt cleaning device 26 is formed so that the transfer belt 20 can be cleaned.

A transfer path by the transfer belt 20 as transfer paper transfer means,
Alternatively, the fixing path 27 is formed as a branch path upward from an extension of the transport path. A fixing device 28 is formed in the middle of the fixing path 27. On the other hand, an extended portion of the transfer path by the transfer belt 20 is formed as a guide plate 29 for paper leading end guide which also serves as a discharge path. The fixing path 27 and the guide plate 29 are formed so as to be switched by a fixing switching claw 30.

The guide plate 29 can be used as an unfixed discharge path for discharging the transfer paper after transfer without fixing it. When the transfer sheet after the transfer is conveyed to the fixing path 27 which is switched and selected by the fixing switching claw 30, it is fixed by the fixing device 28 and can be discharged to the discharge tray 31 after fixing.

When the transfer paper adsorbed on the transfer belt 20 and conveyed is discharged after the transfer is completed, the transfer paper is transferred by the separation charger 32.
The electricity is removed from the transfer belt 20 and the transfer belt 20, the electrostatic attraction force is removed, and the transfer belt 20 can be separated from the transfer belt 20.

A transfer paper trailing end guide 33 is provided on the side opposite to the discharge path on the side of the transfer belt 20 on which the transfer paper 17 is sucked and conveyed, that is, an extension to the entrance side.
However, in the example of the figure, it is formed below the sheet feeding device 16. An opening 34 is formed in the frame 35 of the printer as a paper re-feeding port in the portion of the transfer paper trailing end guide 33.

FIG. 1 shows an example of a copying apparatus for forming a single-sided guide. In this apparatus, portions related to a fixing device 28 and a guide plate 29 are shown in FIG. 2 in a double-sided image forming apparatus according to the present invention. The configuration is as shown.

In FIG. 2, the reverse transport unit 36 is formed so as to be attachable to the printer unit frame 35. The reverse transport unit 36 has a casing 37 that can be fixed to the machine frame 35, and the casing 37
Inside, a discharge path 38 and an inversion path 39 branched from the discharge path 38 are provided.

In order to mount the reverse transport unit 36, an opening 40 leading to the outlet of the fixing device 28 is formed in the machine frame 35, and the discharge path 38 is formed so as to be connected to the opening 40 when the reverse transport unit 36 is fixed. You.

At that time, a free end 41 of the curved reversing path 39 opens at a position facing the machine casing 35 and can be connected to the guide plate 29.

A reversing switching claw is provided at a branch position between the discharge path 38 and the reversing path 39.
The switch 42 is rotatably supported by a support shaft 42a, and is switched by operation of a solenoid or the like.

A discharge roller 43 is provided in the discharge path 38, and feed rollers 44 and 45 are provided in the reversal path 39.

The casing 37 is provided with a tray 31 ′ for storing the transfer material discharged from the discharge path 36. When the reverse transport unit 36 is mounted, the paper discharge tray 31 provided on the machine frame 35 is removed.

When the reverse transport unit 36 is attached to the machine frame 35, the discharge roller 43 and the feed rollers 44 and 45
For example, it may be configured to be driven and connected to a gear or the like, or may be configured to be driven by a motor or the like built in the casing 37.

A connector for connecting and detaching a power supply, a signal line, and the like to and from the main control plate 46 of the image forming apparatus in accordance with the attachment and detachment of the casing 37 to and from the machine casing 35 can be provided.

When the reverse transport unit 36 is attached, it can be used as a double-sided copying machine. When the reverse transport unit 36 is removed, it can be used as a single-sided copying machine shown in FIG. Therefore, only by preparing the copying machine and the reversing and conveying unit 36 shown in FIG. 1, it is possible to meet the demand for the single-sided copying machine and the demand for the double-sided copying machine.

 The operation of the present device will be described.

When the print switch to ON, the photoreceptor motor controlled based on a signal from the main control board 46, the drive roller 6 is rotated in the clockwise direction in the figure, the photosensitive belt 8 linear velocity V _P in the direction of the arrow To rotate.

At the same time, the start of the first forward transfer belt drive roller 21 is driven by a transfer drive motor, transfer belt 20 is also rotated at a linear velocity of V _F in the left direction of the arrow. It is controlled and driven to rotate under the condition of V _P = V _F.

Photoreceptor belt 8 (hereinafter abbreviated as PC belt) is a static eliminator
At 14, the charge is removed, and the entire surface is uniformly charged by the charger 9, but is processed to satisfy the following conditions. That is, the static eliminator 14
The surface of the PC belt 8 from which the toner has been removed by the cleaning device 13 is irradiated with light or a corona is applied to the surface of the PC belt 8 so that the surface potential of the PC belt is reduced to approximately 0V. In the case of the negative / positive process, the toner adheres to an uncharged portion on the surface of the photoreceptor, so that the entire surface of the PC belt 8 must be uniformly charged by the charger 9. The charger 9 performs uniform charging by corona discharge.
A small amount of ozone is generated by the discharge. This ozone is decomposed in a short time when the discharge is stopped, but may have an adverse effect on the PC belt surface and impair the sharpness of the image. Therefore, air is sent from the rear of the charger 9 by a fan or the like (not shown), or the air is sucked to eliminate the influence of ozone.

An encoder is fixed to the shaft of the drive roller 6, and a rotation detection sensor is provided for the encoder. One detection pulse is output for each rotation of the drive roller 6.

At the timing of the third pulse of the rotation detection sensor, for example, the semiconductor laser (hereinafter abbreviated as LD) of the optical writing unit is controlled and started to drive (here, an example of the LD will be described, but another type of laser, or Other optical writing units such as an LED array and an LCD array may be used). First, optical writing based on yellow (Y) image data is started to form an electrostatic latent image.

The image data is read by, for example, three color separation lights of blue, green, and red, respectively, by a color image reading device 2 installed at the upper part of FIG. 1, and an image is formed based on the intensity level of each separation color light. By performing arithmetic processing, yellow (Y), magenta (M), cyan (C), black (Bk)
Are written image data of each color.

Alternatively, image data output from another color image processing system, for example, a color facsimile, a word processor, a personal computer, or the like may be used. The connection interface for that may be individually handled.

The developing device 11 for visualizing the electrostatic latent image on the PC belt 8 is usually located at a position where the developing roller 15 does not contact the surface of the PC belt 8. Then, only during a period from immediately before the latent image surface of the corresponding color reaches the developing roller position of each color to immediately after passing, the developing units (11a to 11d) of the corresponding color are pressed leftward in FIG. Then, the developing roller 15 is set to a position where the developing roller 15 comes into contact with the photosensitive member surface by a predetermined amount.

At the same time, only the developing device starts driving the developing roller and a portion contributing to the development so as to have the developing function.

First, since a latent image of the Y image is formed, the Y developing unit 11a is brought into contact with and driven on the surface of the photoconductor at a certain timing with respect to the surface to visualize the Y image.

Next, the transfer process is performed. The vertical position of the separation switching roller 23 is switched so that the transfer belt 20 comes into contact with or separates from the PC belt surface at the transfer position (the position of the drive roller 6).

When the printing operation starts, the transfer belt 20 is moved as described above.
Is driven in the direction of the left arrow, and thereafter, the transfer belt contact / separation switching roller 23 is pressed to the upper position to bring the transfer belt 20 into contact with the PC belt 8.

Then, at a predetermined timing, the transfer paper 17 is
Then, the sheet is conveyed by registration rollers 19 at a timing so as to match the image position formed on the surface of the PC belt 8.

The transferred transfer paper 17 is applied with a voltage of a predetermined polarity by the charge applying means 24 and is attracted to the transfer belt 20 charged with a charge of a desired charge density pattern, and is conveyed so that the paper position does not shift during transfer. Is done. The charge applying means 24 is formed by an electrode plate or an electrode roller in contact with the transfer belt 20, and a voltage is applied by a power supply 20 a, for example, an AC power supply (or a DC power supply), and charges are applied to the transfer belt 20 in a striped or checkered pattern. You. In addition, before the transfer of the first color, the entire surface of the transfer belt 20 is uniformly discharged by the discharge corona discharger 25 before the transfer process of the first color. At this time, a cleaning process is also performed by the transfer belt cleaning device 26.

When visualizing the Y image tip has reached the position T ₃ points before a predetermined distance from the transfer position T, the transfer drive motor 36
Forward start signals S ₁ of the is input to a drive control circuit of the transfer drive motor.

However, in ,, S ₁ point in time, there is already in the forward rotation, to continue the forward operation as it is.

S ₁ timing is a time when the leading end of the substantially transfer sheet 17 reaches the position short direction l ₁ of R _T point, namely the transfer position T, Y image leading edge of the PC belt together has, in the transfer position T it is when it reaches the position T _S of the front direction l _1.

This from the Y image data writing start timing, and 4 rotation of the drive roller 6, the time of the rotational further pulse number P ₀ corresponds caused by the photosensitive body drive motor encoder provided on the photoconductor drive motor. During this time, PC belt has moved distance component from the image writing position 10 to the position T _S point.

After a time t ₁ has elapsed from S ₁ point, Y image top, and the transfer sheet tip both move the distance l _1, and reaches the transfer position T, hereinafter, Y image transfer line at the transfer corona charger 12 Will be

At this time, the number of pulses of the photoconductor drive motor encoder at time t ₁ is P ₁ , and the number of pulses of the transfer drive motor encoder is P
Becomes _T1 .

Here, as the resolution of both encoders, if the movement dimensions of the belt per one pulse are the same,
P ₁ = P _T1 , and if the ratio between them is α, P ₁ and P _T1 become values corresponding to the count α.

In this example, a description will be given below on the assumption that P ₁ = P _T1 .

As the Y image transfer process proceeds, the leading end of the transfer paper separates from the transfer belt 20, passes over the fixing switching claw 30 shown by a solid line in the drawing, and advances toward the paper leading end guide plate 29.

Then, the Y image transfer process further proceeds, and when the rear end of the transfer paper having the transfer paper size of 1 _P passes the transfer position T by the distance l ₂ , that is, from the time of S ₁ , the transfer paper becomes l ₁ + l _P + l when the transfer sheet by moving the _second distance is in the position shown by the two-dot chain line in FIG. as shown by 17 '(time t ₁ + t _2), the reverse rotation signal with respect to the transfer drive motor 36 reverses the motor.

Prior to this reverse rotation, the transfer belt contact / separation switching roller 23
Is lowered to the lower position, and the transfer belt 20 is separated from the PC belt surface.

By reverse rotation of the transfer drive motor 36, the transfer sheet 17 and the transfer belt 20 'is quick return at a velocity V _R (> V _F) in the right direction of the arrow.

At this time, time t ₁ + t _{2 is} added to the short return time of time t _3.
During this time, a distance equal to the distance moved to the left is controlled to the right and returned.

At the time of this return, the rear end of the transfer paper separates from the transfer belt and advances toward the paper rear end guide plate 33. Then, the transfer paper returns exactly by a predetermined distance, stops at the dashed-dotted line position (position where the paper leading end position is at the position _RT ) indicated by 17 ", and stands by for transfer of the M image of the second color ( time t ₄₎ to.

On the other hand, in the case of the PC belt 8, the M image of the second color has already been formed even during the transfer of the Y image of the first color. That is,
The formation of the electrostatic latent image of the optical writing by the control and driving of the LD based on the M image data starts when the photoconductor driving roller 6 rotates an integer number of times, for example, four times, from the start of the Y image writing. ing.

Then, the developing device 11 contacts and drives the Y developing device 11b only in the Y image region, and before the M image region of the second color arrives,
The Y developing device 11a is separated from the PC belt surface and the driving is stopped. In this case, instead, the M developing device 11b is brought into contact with and driven on the PC belt surface before the end of the M image area reaches after the Y image area has passed, and only the M image latent image area is visualized into the M image. I do.

Next, when the leading end of the M image reaches the position T _S , that is, as in the case of the Y image of the first color, the drive roller 21 is rotated four times and the pulse number P of the photoconductor driving motor encoder is started from the M image data writing start timing. ₀ to the time of the movement corresponds rotated, the transfer drive motor to enter the forward start signal S ₂ to the control drive circuit.

At the same time or slightly later, the transfer paper belt contact / separation switching roller 23 starts the pressing operation in the upper position direction, and contacts the transfer paper belt at least until the leading end of the transfer paper reaches the transfer position T.

PC belt 8 at time t ₁ from the timing of S _2, as in the case of previous Y image, the number of pulses of the photoconductor drive motor encoder is a P _1, PC belt surface moving distance l _1.

Therefore during even the time t ₁ towards the transfer paper, with launch from the state of zero velocity to V _F (= V _P), the same number of pulses as the number of pulses in the t ₁ hour from S ₁ of the first color during this time P _T1
In this case as well, position control is also performed so that P ₁ = P _T1 and both coincide with each other.

This makes it possible to the leading edge of the transfer sheet is moved l ₁ at time t _1, 1-color Y image and the second color M image is aligned with the transfer paper.

Thereafter, the same process as described above is repeated. That is, M image transfer, transfer paper quick return, C image data writing, C development, C image transfer, transfer paper quick return,
Then, the process proceeds to Bk image data writing, Bk development, and Bk image transfer.

 Next, a description will be given of the steps after the Bk image transfer.

At the time of the Bk image transfer process, the fixing switching claw 30 switches to the position indicated by the dashed line, and the transfer paper during the transfer process is
While being discharged by the paper separator 32, the paper advances in the direction of the transfer path 27, that is, in the direction of the fixing device 28, and even when the rear end of the transfer paper is completed, the transfer drive motor continues to rotate forward and the transfer paper continues to rotate. The color prints conveyed to the left and fixed are transferred directly to the tray 31 in FIG. 1 and the reversing switching claw 42 is switched to the solid line position in FIG. 'Discharged.

At this time, the transfer belt 20 is uniformly charged by applying a charge removing corona from the timing when the rear end portion of the first image area has passed the charge removing corona discharger 25.

Subsequently, when the next image forming repeat operation is performed, the writing of the first sheet of Bk image data is followed by the writing of the Y image data of the second sheet, and the operation control of the transfer paper and the transfer belt is performed. Perform the same operation as from the beginning.

The residual toner is removed from the PC belt 8 by the post-transfer cleaning device 13, the residual charge is removed by the charge remover 14, and the PC belt 8 advances toward the charger 9.

In the case of single-color recording, the developing device for that color is contacted and driven until the predetermined number of sheets is completed, and the transfer belt 20 is driven.
Are kept in contact with the PC belt 8 and
Reference numeral 30 denotes a position where the transfer paper is guided in the direction of the fixing device 28, and is held and performs a recording operation.

Therefore, in the repeat printing, the print creation speed is 4/3 times for the three colors, two times for the two colors, and four times for the single color as compared with the four colors.

Developing colors are not limited to the above four colors, and blue, green, red and other desired colors can be used in combination as needed.

The above is a description of the normal single-color to four-color one-sided image forming operation. Next, the operation of double-sided image formation will be described.

The operation of forming a color image using four colors will not be described because the operation is the same as that described above until an image of four colors on the surface is formed and fixed by the fixing device 28.

A double-sided copying mode is set on the operation display panel 47, and copying of one side on the front side is completed in the same manner as described above, and when forming an image on the back side, the reversal switching claw 42 is indicated by a chain line by a signal from the main control board 46. The transfer paper is switched to the position shown, and the transfer paper is sent to the guide plate 29 through the reversing path 39. Main control plate at the same time or at the same time as the transfer switching claw 42 is switched
Since the fixing switching claw 30 is switched to the position shown by the solid line by the signal from 46, the transfer paper moving on the guide plate 29 is sent onto the transfer belt 20.

When the leading edge of the transfer paper is detected by the paper detection sensor 46 provided on the fixing switching claw 30, a signal is folded through the main control plate 46 to reverse the transfer drive roller 21, and in synchronization therewith, a back surface charge applying means as a suction means 49 AC voltage power supplies 50
When the transfer belt is turned on, electric charges are formed in a predetermined pattern on the transfer belt in the same manner as the charge applying means 24, and the transfer paper is sucked and held, conveyed until the rear end reaches the _RT point, and stopped. Back surface charge applying means 49
Can also be used as a charge applying means for the transfer belt at the time of return during single-sided image formation, or the charge applying means 24 can be omitted and the charge applying means 24 can provide the charge. As the paper detection sensor 48, a sensor used for jam detection, slip detection, and the like during single-sided image formation can be used in common.

The image data writing for the back side image formation is started by the output of the paper detection sensor 48, and the writing of the Y image is started first for a color image. In this case, since the tip is reversed in the reversing path 39, the front end and the rear end are reversed on the front and rear surfaces. Therefore, when writing to the back surface, the image data is stored in a memory for storing one page, and is sequentially written from the rear end line of the image data. Thereby, the front and rear ends of the front and back images can be matched.

The subsequent image forming process can be performed in exactly the same manner as in the above-described single-sided copying except that writing is performed from the trailing end line for one page. When all image formation on the back side is completed, the reversing switching claw 42 is switched to the solid line position, and the transfer paper after fixing is discharged to the tray 31 'through the discharge path 38.

〔effect〕

According to the present invention, when writing data on the back side, by writing the image data for one page from the rear end line by the memory for storing the image data, it is possible to eliminate the inconsistency between the front and rear ends due to the reversal of the transfer paper, and to have a complicated structure. It became possible with a compact device without the need for members.

According to the present invention, the reverse conveyance unit can be easily detached from the machine frame of the image forming apparatus, and the single-sided image forming apparatus can be easily switched to the double-sided one. Further, since it is not necessary to incorporate a dedicated device for both sides, the cost can be reduced because the device is not compact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall schematic diagram of an image forming apparatus utilizing the present invention;
FIG. 2 is a cross-sectional view of a portion related to the reverse transport unit according to the present invention. 5 Writing means 8, Photoreceptor 11 Document device 20, Transfer belt 27 Fixing path 29 Guide plate 30 Fixing switching claw 31, 31 'Tray 36 Reverse transport unit 39 Reversing path, 42 Reversing switching claw 24, 47 Suction means

Continued on the front page (72) Inventor Kenichi Mizuma 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Mitsuru Mamizuka 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Yoshihiro Sakai 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Ricoh (72) Inventor Noriyuki Kimura 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company, Ltd. (56) References JP-A-60-185967 (JP, A) JP-A-62-118366 (JP, A) JP-A-63-22438 (JP, A) JP-A-63-54060 (JP, A) (1) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/00 106 G03G 15/00 303 G03G 21/00 307-540 G03G 15/36 G03G 21 / 02-21/04 G03G 21/14 G03G 21/20 B65H 83/00-85/00

Claims (1)

(57) [Claims] A latent image is formed on a photosensitive member by optical writing by a writing means, the latent image is visualized by development, and the latent image is visualized on a transfer material reciprocated by a reciprocating transfer belt. An image forming apparatus for forming an image by superimposing and transferring an image, wherein a transfer material having a visible image transferred to a front surface and having the fixed visible image fixed thereto is a reverse path curved so that the back surface thereof faces the photosensitive member. A double-sided image forming apparatus for forming an image on the back side by returning the image to the transfer belt via a storage means for storing at least one page of image data of the document; When the transfer material whose front and back are reversed is sent to the downstream side with respect to the transfer position of the transfer belt, and the transfer belt is moved forward after returning the transfer belt to the upstream side of the transfer position,
A two-sided image forming apparatus which sequentially forms images from a rear end line of a one-page image stored in the storage means toward a front end line, with a front end side at the time of front surface image formation being a rear end.