JPH0588588A - Method and device for synthetic image forming - Google Patents

Abstract

(57) [Summary] (Correction) [Construction] The recording sheet is conveyed by the feeding device 6 driven in the forward direction to the reversal conveyance path 94 without passing the transfer position of the photoconductor 18 and transferred to the photoconductor. 18 is rotated in the reverse direction to form an image based on the first image information, and the recording sheet is conveyed in the direction opposite to the first conveying step by the feeding device 6 driven in the opposite direction to record the first image at the transfer position, The photoconductor 18 is rotated in the forward direction to form an image based on the second image information, the recording paper is conveyed by the feeding device 6 driven in the forward direction, the second image is recorded at the transfer position, and the second image is recorded. The paper is conveyed to the fixing device 7 through a substantially linear fixing conveyance path 91, and is ejected after fixing by the fixing device 7. [Effect] A part of the reverse conveyance path for double-sided image formation can also be used as a conveyance path for composite copying, the conveyance path is reduced, the space can be reduced, and the apparatus can be downsized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite image forming method and apparatus for copying machines, laser printers, facsimiles and the like.

[0002]

2. Description of the Related Art In copying machines and the like, an image forming apparatus capable of forming images on both front and back surfaces of a recording sheet or forming a composite image of a plurality of originals on the same side of the recording sheet has been widely known.

Conventionally, as a double-sided image forming apparatus, a reverse conveyance path is disclosed in US Pat. No. 4,098,551.
JP-A-60-8863, JP-B-63-46416
Various proposals have been made according to the publications.

In the conventional image forming apparatus, in order to form a double-sided or composite image, the recording sheet after the first image is formed is returned to the same registration position as before the first image.
Since the conveying path becomes long and the reversing operation of the recording paper itself takes a lot of time, the number of image processed sheets per unit time is reduced during double-sided or composite image formation, and there is a problem in productivity.

To solve this problem, Japanese Examined Patent Publication No. 63-4641
No. 6, it was proposed to shorten the reverse conveyance path. However, since the recording paper before fixing is curvedly conveyed, the toner image is disturbed and the image quality is deteriorated. There are problems that many rollers are required as the device, the structure is complicated, the number of parts is increased, and the cost is increased.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, enables reverse image transfer by a short and simple transfer path, enables double-sided image formation, and enables composite transfer. It is an object of the present invention to provide a compact synthetic image forming method and apparatus capable of preventing the image quality from being disturbed by transporting the recording paper in a substantially linear shape.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by providing an image forming method for transferring an image formed on a photoreceptor by charging, exposing, developing and transferring to a recording paper at a transfer position. A first transporting step of transporting to a reversing transport path branched from a substantially straight fixing transport path that passes through the transfer position by the photoconductor without transferring by a feeding device driven in the forward direction and guides to the fixing device; In the meantime, the first image forming step of reversely rotating the photoconductor to form an image from the first image information, and the recording sheet is conveyed in the opposite direction to the first conveying step by the feeding device driven in the opposite direction and transferred. First in position
A first image recording step of recording an image, and a second image forming step of forming an image from the second image information by rotating the photoconductor in the forward direction,
A second image forming step of recording a second image at a transfer position by conveying the recording paper by a feeding device driven in the forward direction;
Synthetic image formation characterized by a second conveying step of conveying a recording sheet on which a second image is recorded to a fixing device through a substantially linear fixing conveying path, and a fixing step of discharging the recording sheet after fixing by the fixing device. Solved by the method.

Further, the present invention has been made to solve the above-mentioned problems by a photosensitive member on which a toner image is formed by charging, exposing and developing, a transfer device for transferring the toner image from the photosensitive member, and a recording paper after transfer is fixed. Fixing device, a feeding device that feeds the recording paper to the transfer position, a fixing conveyance path that conveys the recording paper in a substantially straight line between the transfer position and the fixing device, and the recording paper after fixing is turned upside down. Double-sided composite image forming apparatus having a reversing conveyance path for conveying the recording paper after fixing to the transfer position, a combination conveyance path for conveying the recording paper after fixing to the transfer position as it is, and a switching means for switching between the reversal conveyance path and the combination conveyance path. In the above, the photoconductor is formed so as to be capable of rotating in the forward and reverse directions, the fixing conveyance path is formed in a substantially linear shape, and the reversal conveyance path is curved in the up-down direction after the fixing device, and is arranged between the fixing device and the transfer position. A curved circulation path that joins the fixing conveyance path The transfer path is formed at the confluence of the fixing conveyance path and the reversing conveyance path, and a switching means is provided for switching and guiding the recording sheet after transfer to the reversing conveyance path side and the fixing conveyance path side. It is also used as a part and is guided to the fixing conveyance path side by the switching means at the time of double-sided image formation, and is guided to the reverse conveyance path side by the switching means at the time of composite image formation.
The image forming apparatus is characterized in that when the image is formed on the screen, the photoconductor is reversed to form an image, and the image can be transferred when passing through the transfer position by the conveyance in the direction opposite to that when forming the first screen.

[0009]

According to the present invention, the first and second images are formed by the forward and reverse rotations of the photosensitive member, respectively, and the recording paper is forwardly and reversely conveyed by the feeding device, and the first image of the composite image formation and the double-sided image formation is formed. The second image and the second image are transferred and recorded on recording papers conveyed in opposite directions, and are sent to a fixing device in a substantially linear short distance by a fixing and conveying path and fixed. When forming a composite image, the recording paper that is normally conveyed before the first image formation is transferred to the composite conveyance path that also serves as a part of the reversal conveyance path that branches to the fixing conveyance path without transferring, The first image is transferred by the photoconductor that rotates in the reverse direction when it is conveyed in the reverse direction, and the second image is then transferred and fixed when it is conveyed in the forward direction. During double-sided image formation, the first image is transferred to the recording paper that is conveyed in the normal direction, is conveyed through a straight fixing conveyance path, is fixed by the fixing device, is reversed by the reverse conveyance path, is inverted upside down, and is reversed. A second image is formed when the image is conveyed, the image is conveyed at the transfer position without transfer by the forward conveyance, and is conveyed to the fixing device through the fixing conveyance path. According to the present invention, it is possible to linearly feed to the fixing device at a short transport distance, and it is possible to reliably prevent image disturbance during transport. The reversing conveyance path guides the recording paper after fixing to the confluence point where it merges with the fixing conveyance path by the circulation path curved in the vertical direction, and the backside transfer can be performed by the photoconductor rotated in reverse, and the reversal conveyance path is very short. Can be formed. Moreover, the composite conveying path can be guided to the reversing conveying path branched from the fixing conveying path by the switching means provided at the confluence.
A part of the reverse conveyance path can be used as both the reverse path for double-sided image formation and the composite conveyance path for composite image formation, reducing the required space and making the device compact.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on the embodiments shown in the drawings.

In FIG. 1, an image forming apparatus 1 includes an original placing table 2 on which an original is placed, for example, a contact glass, and an optical system 3 for reading an image of the original on the contact glass 2.
A process system 4 as an image forming unit that forms an image by exposure by the optical system 3, a feeding device 6 that conveys a recording paper, for example, a transfer paper fed from the feeding device 5 to the process system 4, and a process. And a fixing device 7 for fixing the transfer paper on which the image formed in the system 4 is transferred. On the image forming apparatus 1, it is possible to provide an automatic document feeder (ADF) 8 which automatically and continuously feeds documents onto the contact glass 2.

The optical system 3 includes an exposure lamp 9 for exposing an original document on the contact glass 2, a first mirror 10, a second mirror 11 and a third mirror 1 for sequentially reflecting light reflected from the original document.
2, a lens 13 that receives the reflected light from the third mirror 12, and a fourth mirror 14 and a fifth mirror 15 that sequentially reflect the emitted light from the lens 13 and project it onto the photoconductor 18 of the process system 4. And a sixth mirror 16. Fifth mirror 15
A tiltable seventh mirror 17 is provided between the second mirror and the sixth mirror. When the reflected light from the sixth mirror 16 is projected onto the photoconductor 18, the seventh mirror 17 is retracted out of the optical path as shown by the solid line. When moving and projecting onto the photoconductor 18 at another position, the seventh mirror 17 can be tilted to the operating position indicated by the broken line so as to be located in the optical path, and the reflected light of the seventh mirror 17 can be projected onto the photoconductor 18. To

As shown in FIG. 2, the photosensitive member 18, for example, the photosensitive member belt, is wound around a driving roller 19 having a large diameter and a driven roller 20 having a small diameter, and the driving roller 19 is controlled to rotate in the forward and reverse directions. Can be driven in opposite directions.

The charging charger 21, the eraser 22, the exposure position 23 by the projection light from the optical system 3, the developing device 24, and the transfer charger 2 along the movement path of the photosensitive belt 18.
5, a cleaning device 26, and a discharge lamp 27 are arranged.

Since the photoconductor belt 18 can be switched between forward and reverse movements, it is structurally balanced to arrange each member symmetrically with respect to the center plane connecting the axis of the driving roller 19 and the axis of the driven roller 20. It is convenient because it can be removed.

In the illustrated example, one developing device 24 is arranged on the center surface so as to face the driving roller 19, and one transfer charger 2 is arranged on the center surface so as to face the driven roller 20.
5 are arranged. Only the developing device 24 and the transfer charger 25 are commonly used for forward rotation and reverse rotation.
1, eraser 22, exposure position 23, cleaning device 2
6 is arranged in a symmetrical position with respect to the center plane.

In order to facilitate the distinction, the same parts are designated by the same reference numerals, but those for the reverse rotation are designated by "'".

The paper feeding device 5 is, for example, the first paper feeding cassette 3
It has a first paper feed cassette 32, a second paper feed cassette 32, and a third paper feed cassette 33, and one of the paper feed cassettes is selected and fed.

The recording paper called by the first paper feeding roller 34 is sent from the first paper feeding cassette 31 to the feeding device 6 by the first paper feeding and carrying roller 35 and the second paper feeding and carrying roller 36.

From the second paper feeding cassette 32, the recording paper called by the second paper feeding roller 37 is transferred to the second paper feeding and conveying roller 3.
6 to the feeding device 6.

From the third paper feeding cassette 33, the recording paper called by the third paper feeding roller 38 is transferred to the third paper feeding and conveying roller 3.
It is sent to the feeding device 6 by 9.

As shown in FIG. 3, the feeding device 6 has a feeding belt 42 which is wound around a first roller 40 and a second roller 41 and is supported by a guide roller 45 in the middle thereof. The feeding belt 42 uses a Mylar (trade name) that is easily charged,
The first roller 40 and the second roller 41 are formed as conductive contact type rollers, and a (+) or (-) DC bias voltage is applied thereto. The first roller 40 and the second roller 41 are formed so as to be switchable between forward and reverse driving, and therefore the feeding belt 6 is switchable between forward and reverse. At the time of forward rotation, the first roller 40 serves as a charging roller and a (-) bias voltage is applied thereto. At the time of reverse rotation, the (+) bias voltage is applied thereto, and at the time of reverse rotation, the second roller 41 serves as a charging roller. The bias voltage application polarity is switched so that the first roller 40 functions as a charge eliminating roller.

At the time of normal rotation, the recording paper is attracted and conveyed to the feeding belt 42 charged by the first roller 40, and is separated after transfer. After separation of the recording paper, the residual electrode of the conveyor belt 42 becomes the second
The charge is removed by the roller 41. At the time of reverse rotation, it works in reverse.

Both the first roller 40 and the second roller 41 can be driven by a drive motor, and are driven by the drive motor of the second roller during forward rotation and by the drive motor of the first roller during reverse rotation. The side of the feeding belt 42 that sucks and conveys the recording paper is always the tension side, and consideration should be given so that slack does not occur. The bias voltage is, for example, the first bias 4 during normal rotation.
A (-) voltage is applied to 0 to charge the second roller 41, and a (+) voltage is applied to the second roller 41 to remove the charge. The second roller 4 during reverse rotation
The (-1) voltage is applied to the first roller 40 to charge it, and the (+) voltage is applied to the first roller 40 to remove the charge.

The feeding belt 42 passes between the driven roller 20 and the transfer charger 25 at the transfer position as shown in FIG. 4, and when the transfer is not performed, the transfer charger 25 descends as shown in FIG. 4A. 42 is guided by a guide plate 43 provided on the transfer charger 25 and is separated from the driven roller 20, and the recording paper conveyed by the feeding belt 42 can pass without contacting the photosensitive belt 18. At the time of transfer, as shown in FIG. 4B, the transfer charger 25 rises and the guide plate 43 pushes up the feeding belt 42 to bring it into contact with the photoconductor belt 20, thereby making it possible to reliably bring the recording paper into contact with the photoconductor belt 18. ..

A tension member 44 is provided below the transfer charger 25 in order to prevent fluctuations in the tension of the feeding belt 42 due to the vertical movement of the transfer charger 25. The tension member 44 is interlocked with the vertical movement of the transfer charger 25 so as to keep the tension of the feeding belt, for example, Mylar (trade name), constant during transfer and non-transfer.

In order to facilitate separation of the recording paper after transfer by the transfer charger 25, the driven roller 20 has a diameter as small as possible.

The feeding belt 42 of the feeding device 6 is set such that the conveyance length from the portion supported by the first roller 40 to the transfer position is longer than the maximum double-sided copy size. As shown in FIGS. 2 and 5, the developing device 24 has symmetrical developing casings 51, and a developing roller 52 is rotatably supported at the lower end outlet of the developing casing 51.

An agitating roller 53 is rotatably arranged on the developing roller 52, and agitating paddles 54a and 54b are rotatably supported on opposite sides of the agitating roller 53 in opposite directions.

The developing casing 51 has a toner hopper 55 at the top thereof, and a toner replenishing roller 56 is rotatably arranged at the outlet of the toner hopper 55.
An agitator 57 is arranged in the unit 5.

The toner replenishing roller 56 is provided with a groove substantially parallel to the axis. The toner that has entered the groove is arranged so as to sandwich the toner replenishing roller 56 from both sides, and the inside of the toner hopper 55 is exposed to the outside. The developing casing 51 is scraped off by the sponge 58 that seals against the developing casing 51.
Mixed with the developer inside.

In the toner hopper 55, an agitator 57
The toner is agitated by and is sent to the toner replenishing roller 56. In the developing casing 51, the developer is stirred by the two stirring paddles 54a and 54b and the stirring roller 53,
It is circulated and sent to the developing roller 52.

A magnet is built in the developing roller 52, and the developer after development is attracted onto the developing roller 52 and conveyed above the developing casing 51.

The developing roller 52 is arranged to face the driving roller 19 which drives the photosensitive belt 18. Developing roller 52
The stirring roller 53 and the like are drive-controlled by using an electromagnetic clutch to shorten the development driving time and attempt to extend the life of the developer.

On the photoconductor belt 18, the photo sensor 5
9, the toner concentration is detected, and when the toner concentration becomes low, the toner replenishing clutch is turned on and the agitator 57 and the toner replenishing roller 56 are rotated to replenish the toner.

The developing roller 52 is controlled so as to be in a forward direction (forward rotation direction) at a position facing the moving direction of the photosensitive belt 18 as indicated by an arrow, thereby preventing the uniformity of a solid image and the background stain.

When the moving direction of the photosensitive belt 18 is switched back and forth, the rotating directions of the developing roller 52, the rollers of the developing device 24, the paddles, etc. are also switched so that they are continuous through gears. be able to.

In order to regulate the amount of the developer layer on the developing roller 52 to a certain amount, doctor blades 60 are arranged on both sides of the developing roller 52 and approach the developing roller 52 according to the switching of the rotating direction of the developing roller 52. The operating doctor blade 60 is also configured to be switched between right and left in the figure.

As shown in FIG. 6, two doctor blades 60 are pivotally supported by fulcrums 61 on both sides of the developing roller 52, and both doctor blades 60 are fixed to a shaft 63 concentric with the developing roller 52 by a connecting rod 62. Connected to the arm 64. When the shaft 63 is switched and rotated by a predetermined angle, the shaft 63 is switched between a state in which the shaft 63 is tilted to the right at the time of forward rotation and a state that is tilted to the left at the time of reverse rotation shown in FIG. 6B.

The magnet in the developing roller 52 is also fixed to the shaft 63, and the shaft 6 is aligned with the rotation direction of the developing roller 52.
It is convenient for the formation of developer ears to rotate the main pole angle θ, which is shown as the angle of the main magnet pole with respect to the line toward the center of the drive roller 19, by rotating 3.

The cleaning device for cleaning the residual toner on the photosensitive belt 18 after the transfer is, for example, a cleaning case in which the fur brush 71 and the rubber blade 72 for contacting the photosensitive belt 18 to scrape and remove the toner are used. The toner which is supported by 73 and scraped off is sent by a flicker bar 74 and discharged by a waste toner carrying pipe 75. The rubber blade 72 is supported at a central point so that the left and right pressures are even, and is pressed against the photosensitive belt 18 by a spring.

The fur brush 71 is rotated in the opposite direction to the photosensitive belt 18 at the contact portion to remove toner, and the rubber blade 72 removes foreign matter such as paper dust which is difficult to remove.

Two sets of cleaning devices 26 and 26 'arranged symmetrically are moved corresponding to the switching of the moving direction of the photosensitive belt 18, and one cleaning device 26 or 26'.
Only has a cleaning action on the photoreceptor belt 18.

When the direction of the photosensitive belt 18 is switched, the switching solenoid 76 is reset in FIG.
As shown in FIG. 8B, the clutch arm 87 rotates around the fulcrum 89 to rotate the one-way clutch 88, the cam 77 connected by the one-way clutch 88 makes a half rotation, and the cam follower 78 descends. A lever 79 that supports the cam follower 78 tilts downward, and a shaft 80 that fixes the lever 79 is rotated. The cam follower 78 is constantly pressed against the cam 77 by the action of a spring (not shown) connected via the wire 83.

A lever 81 fixed to a shaft 80 moves an abutment 82 supporting a cleaning case 73 in the direction of the arrow, and the cleaning device 26 is separated from the photosensitive belt 18, in which case a lever 79 and a connecting rod 84 (see FIG. The other abutment connected by 9) moves in the same direction and by the same amount as the abutment 82 shown in the figure, and the other cleaning device 26 contacts the photosensitive belt 18.

Next, when the moving direction of the photosensitive belt 18 is switched, the solenoid 76 is set again, the cam 77 rotates half a turn from the state shown in FIG. 8B to the state shown in FIG. 8A, and the operating cleaning device 26 shifts to the opposite side. Then, the cleaning device 26 ', which is in contact with the photoconductor belt 18 and is in the operating state, is separated from the photoconductor belt 18 and is in the non-operating state.

When the cleaning device 26 is moved, FIG.
As shown in FIG. 2, a backup roller 86 is provided on a member connecting two sets of cleaning devices, for example, a lever 85 connected to a connecting rod 84, and it can be used as a pressing member for pressing the photoconductor belt 18 against the fur brush 71. it can.

Further, as shown in FIG. 10, a positioning member 89
When the cleaning device 26 is moved from the non-operating position shown in FIG. 10A to the operating position shown in FIG. 10B, the pin provided on the casing or the end of the shaft of the fur brush 71 engages with the concave portion of the positioning member 89. The contact pressure of the fur brush 71 and the rubber blade 72 of the cleaning device 26 with respect to the photoconductor belt 18 may be determined.

The fixing conveyance path 9 from the transfer position of the photosensitive belt 18 to the nip with the fixing roller of the fixing device 7.
No. 1 is formed in a substantially linear shape, and the recording paper is conveyed with almost no curvature, and when the recording paper carrying the unfixed toner image is bent, it is prevented from rubbing against the guide member and causing image unevenness. To do.

The feeding conveyor 42 is set to have a length such that the recording sheet is fed to the fixing feeding path 91 after continuing the feeding of the recording sheet after transfer, and when the feeding conveyor 42 is reversed, the feeding conveyor 42 is fed back. The recording paper is surely conveyed by the feeding conveyor 42 and can pass through the transfer position.

The recording paper after fixing is formed so that it can be switched and guided by a second switching claw (not shown) to a paper discharge path 93 discharged to a paper discharge tray 92 and a reversing conveyance path 94. The reversal conveyance path 94 is formed as a curved path that is curved in the up-down direction, that is, in the drawing, in the upward direction, and the exit end thereof joins the fixing conveyance path 91 between the transfer position and the fixing device 7 in a V shape. That is, the outlet end portion of the reverse conveyance path 94 is formed as a branch path for the reverse conveyance path 94. A first switching claw 95 is provided at the confluence,
The recording sheet after transfer sent from the right side of the figure is a lower fixing conveyance path 9 which serves as a first approach path used for fixing.
1 (passage closer to the fixing device) and an upper reversing conveyance passage 94 (passage farther from the fixing device) that acts as a second approaching route that guides before recording the first image during composite image formation. ) Is formed so that switching guidance is possible. The reverse transport path 94 also acts as a composite transport path in the portion near the exit end and extends substantially linearly for a certain length, and the exit end of the reverse transport path 94 formed as a circulating curved path is fixed. It is convenient to form it so as to merge with the transport path 91 in a V-shape.

The exit end of the reversing conveyance path 94, that is, the path on the upper side in the drawing, which is remote from the fixing device, is also used as a guide path during composite image formation (copying), that is, a composite conveyance path.

A registration roller 97 and a second sensor 98 are provided near the confluence point of the reverse conveyance path 94 with the fixing conveyance path 91.

The operation of this device will be described.

Image forming modes include a single-sided mode in which an image of an original is recorded on only one side of a recording sheet, a double-sided mode in which an image of the original is recorded on both sides of the recording sheet, and images of a plurality of originals on one side. There is a composite mode for recording.

In the single-sided mode, even if the original is manually placed on the contact glass 2 in the pressure plate mode, A is automatically set.
Even in the case of the ADF mode in which the paper is fed in the DF, the description is omitted because it is a method that is usually performed. In this case, the photosensitive belt 18 and the feeding belt 42 are driven in the forward direction, and the one charging charger 21, the eraser 22, the exposure position 23, the developing device 24, the transfer charger 25, and the cleaning device 26 are used, and the fixing device 7 is used. The recording sheet fixed by is immediately discharged to the discharge tray 92 by the discharge path 93.

The case of the composite mode will be described.

In the ADF mode, the paper feed clutch is turned on by the print button ON and the original is set on the contact glass 2. In the manual mode, the pressure plate is raised and the original is manually set on the contact glass 2. Lower the pressure plate.

When the print button is turned on, the photosensitive belt 18 is driven to rotate in the reverse direction, the feeding belt 42 is driven to rotate in the forward direction, and one of the paper feeding trays selected by the operation of the paper feeding device 5 is driven. The chart paper is fed.

The transfer charger 25 descends, the recording paper is adsorbed by the feeding belt 42 and conveyed, passes through the transfer position, and the reversing conveyance path 94 is caused by the switching operation of the first switching claw 95.
You will be guided to (second approach road).

When the trailing edge of the recording paper reaches the second registration position, that is, the registration roller 97, the registration roller 97
And the feeding belt 42 is stopped.

During this time, the exposure lamp of the optical system 3 moves to the reverse scan start position to the right in the figure at a predetermined timing to start reverse scan exposure of the original.

After the feeding of the recording paper is stopped, the feeding belt 42 is switched and driven in the reverse direction, and the transfer charger 25 is raised to the transfer operation position by the operation of the solenoid, for example.

Of the two sets of image forming functional parts for charging, exposing, developing, and transferring the photosensitive belt 18, the second set of charging charger 21 ', eraser 22', exposure position 23 ',
The cleaning device 26 'is switched to the operating state, the first charger 21, eraser 22, exposure position 23, and cleaning device 26 are switched to the non-operating state, and the developing device 24 is connected to the developing roller 52 and, if necessary, the stirring roller 53, etc. The rotation direction of each part of can be switched to a suitable direction.

The registration roller 97 is rotated in the forward direction at a timing so that the leading edge of the first image formed on the photoconductor belt 18 and the leading edge of the recording sheet are exactly overlapped, and the recording sheet is charged by the second roller 71. The first image is transferred under the action of the transfer charger 25 at the transfer position while being attracted to and conveyed by the feeding belt 42.

When the trailing edge of the recording paper passes the transfer position, the feeding belt 42 and the photoconductor belt 18 are stopped, and the first
The image transfer is completed.

When the original is manually or changed by the ADF and the print button is turned on again, the photosensitive belt 18 is first rotationally driven in the forward direction, and the image forming functional component is set to the first position.
The set is switched to operate, the exposure scanning for the original is performed in the forward direction, that is, the right direction in the drawing, and the photosensitive member is irradiated with the reflected light from the sixth mirror 16 at the exposure position 23 and the electrostatic latent image. An image is formed and developed.

At the timing when the leading edge of the image on the photosensitive belt 18 and the leading edge of the unfixed recording paper just overlap, the feeding belt 42
Is rotated in the forward direction, and the second image is transferred.

The recording sheet after transfer is guided to the fixing / conveying path 91, that is, the first approaching path by the switching of the first switching claw 95,
The sheet is fixed by the fixing device 7, and the discharge path 9 is fixed by the second switching claw.
It is guided to 3 and discharged.

The above operation is shown in a flow chart in FIG. 11 in the case of manual operation and in FIG. 12 in the case of ADF.

In the double-sided mode, the following operation is performed as an example.

By rotating the photosensitive belt 18 and the feeding belt 42 in the forward direction, the first set of image forming functional parts 21, 22,
When the recording paper on which the image is formed by 23 and 26 and which is attracted and conveyed by the feeding belt 42 charged by the first roller 40 is detected at the first registration position by the first registration sensor 46, the leading end of the recording paper is detected. And once the feeding belt 4
2 stops. When the leading edge of the recording paper is detected by the first registration sensor 46, the optical system 3 and the process system 4 are started. The feeding belt 42 is started to be driven again at the timing when the leading edge of the image on the photoconductor belt 18 and the leading edge of the recording paper are exactly overlapped with each other, and the transfer belt 42 is transferred at the transfer position and is fixed by the first switching claw 95 (fixing conveyance path 91 (first approach path)). When the second registration sensor 98 detects that the second registration claw 93 has reached the second registration position, the second switching claw 93 guides it to the reversing conveyance path 94, and then temporarily stops at a predetermined timing. ..

When the trailing edge of the recording paper passes the transfer position during the transfer of the first screen, the transfer charger 25 is set at a predetermined timing.
The transfer charger 21, eraser 22, and
The developing roller 52 and the cleaning device 26 are turned off, and the photosensitive belt 18 and the developing roller 52 are reversely rotated to prepare for image formation on the back surface.

When the trailing edge of the recording paper passes through the end of the feeding belt 42, the driving of the feeding belt is reversed, and the second roller 41 applies a suction bias to charge the same.

The sequence control of the image forming process is performed on the basis of the time when the photosensitive belt 18 starts to rotate in the reverse direction.

After the photoconductor belt 18 is rotated in the reverse direction, the second set of chargers 21 ', erasers 22',
The exposure position 23 ', the developing device 24 (common to the first group), and the cleaning device 26' are turned on, reverse exposure scanning is performed by the optical system 3, and the photosensitive belt is exposed by the light reflected by the seventh mirror 17. The registration roller 97 is driven at the timing when the leading edge of the image 18 and the leading edge of the recording sheet are exactly overlapped with each other, and the transfer charger 25 is raised to be in the transfer operation state before the leading edge of the recording sheet reaches the transfer position. Is transferred to recording paper.

As soon as the trailing edge of the recording paper passes the transfer position, the transfer charger descends and becomes inoperative, the image forming functional parts are switched to the first set, and the photosensitive belt 18 and the feeding belt 42 are The recording paper is switched to the forward direction, is fixed by the fixing device 7 through the fixing conveyance path 91, and is discharged to the discharge tray 92. The control of double-sided image formation is shown in the flow chart of FIG. A timing chart is shown in FIG. 14 for reference. The timing chart is divided into three diagrams of FIG. 14A, FIG. 14B, and FIG. 14C due to the limitation of the size of the drawings, but the three diagrams are combined to show one timing chart.

The image forming functional component is different from the example shown in FIG.
As shown in FIG. 15, the charging charger 21 and the transfer charger 25 are commonly used, and the eraser 22, the exposure position 23, the developing device 24, and the cleaning device 26 are arranged symmetrically, and instead of the charging charger 21 as shown in FIG. Changing the cleaning device 26 to a common part, as shown in FIG.
It is also possible to change the exposure position 23 in common as shown by 7.

With respect to other members, the same members are designated by the same reference numerals and the description thereof will be omitted.

[0080]

According to the present invention, the recording paper is guided in a substantially straight line both during the formation of the first image and during the formation of the second image and before the transfer. Since a part of the reverse transport path of is also used as the combined transport path when forming a composite image, the transport path is simple, the required space is reduced, the image forming time is shortened, and the device can be made compact. Became.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram of an image forming function unit.

FIG. 3 is an explanatory diagram of a feeding belt.

FIG. 4 is a diagram showing the arrangement of the transfer chargers when A is not in operation and B is in operation.

FIG. 5 is a cross-sectional view of a developing device.

FIG. 6 is a schematic view of a doctor switching mechanism, in which A indicates a forward operation and B indicates a reverse operation.

FIG. 7 is a perspective view of a part of the switching mechanism of the cleaning device.

8A and 8B are diagrams showing the operation of the cam of the switching mechanism, in which A shows the cam rising and B shows the cam descending.

FIG. 9 is a diagram showing a modification of the cleaning device.

FIG. 10 is a modification showing the positioning mechanism of the cleaning device.

FIG. 11 is a flowchart of a pressure plate mode when forming a composite image.

FIG. 12 is a flowchart of an ADF mode when forming a composite image.

FIG. 13 is a flowchart for forming a double-sided image.

FIG. 14A is a part of a timing chart at the time of double-sided image formation.

FIG. 14B is a part of a timing chart at the time of double-sided image formation.

FIG. 14C is a part of a timing chart at the time of double-sided image formation.

FIG. 15 is an explanatory diagram showing another example of the image forming function section.

FIG. 16 is an explanatory diagram showing still another example of the image forming function unit.

FIG. 17 is an explanatory diagram showing another example of the image forming function section.

[Explanation of symbols]

 1 Image Forming Device 2 Contact Glass 3 Optical System 4 Image Forming Unit 5 Paper Feeding Device 6 Feeding Device 7 Fixing Device 8 ADF 18 Photoreceptor 21 Fixing Charger 22 Eraser 23 Exposure Position 24 Developing Device 25 Transfer Charger 26 Cleaning Device 27 Electrification Lamp 42 Feeding Belt 91 Transfer Conveying Path 92 Paper Discharging Tray 94 Reverse Conveying Path

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Hasegawa 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh (72) Inventor Yukitaka Nakazato 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Company Ricoh

Claims (2)

[Claims] 1. An image forming method for transferring an image formed on a photoconductor by charging, exposing, developing, and transferring to a recording sheet at a transfer position, wherein the recording sheet is fed in a forward direction by the photosensitive body. The first conveyance step of conveying the transfer position to the fixing device passing through the transfer position without transfer and branching it to the substantially straight fixing conveyance path, and the reverse rotation of the photosensitive member during the first conveyance step. A first image forming step of forming an image and a first image recording step of recording a first image at a transfer position by conveying a recording sheet in a direction opposite to the first conveying step by a feeding device driven in a reverse direction. And a second rotation that rotates the photoconductor in the forward direction to form an image from the second image information.
An image forming step, a second image forming step of recording the second image at the transfer position by conveying the recording sheet by a feeding device driven in the forward direction, and a substantially linear fixing of the recording sheet recording the second image. A composite image forming method comprising: a second transporting step of transporting to a fixing device via a transport path; and a fixing step of discharging a sheet after fixing by the fixing device. 2. A photosensitive member on which a toner image is formed by charging, exposing, and developing, a transfer device for transferring the toner image from the photosensitive member, a fixing device for fixing the recording paper after the transfer, and a recording paper transfer. A feeding device that feeds the recording paper to the position, and a fixing conveyance path that conveys the recording paper in a substantially straight line between the transfer position and the fixing device,
A reversing conveyance path for reversing the recording paper after fixing to the transfer position, a combination conveyance path for conveying the recording paper after fixation to the transfer position as it is, and a switching means for switching between the reversal conveyance path and the combination conveyance path. In a double-sided composite image forming apparatus having a fixing device, the photoconductor is formed so as to be reversible in the forward and reverse directions, the fixing conveyance path is formed in a substantially linear shape, and the reversal conveyance path is curved in a vertical direction after the fixing device. Is formed as a curved circulation path that joins the fixing conveyance path between the transfer position and the transfer position, and the recording sheet after transfer is switched between the reverse conveyance path side and the fixing conveyance path side at the confluence of the fixing conveyance path and the reverse conveyance path. A switching means for guiding is provided, and the composite conveyance path is also used as a part of the reverse conveyance path. When the double-sided image is formed, it is guided to the fixing conveyance path side by the switching means. When the image is formed on the second screen of the double-sided image type and the composite image formation, the photoconductor is reversed to form an image, and the image is formed by passing in the direction opposite to that of the formation of the first screen when the image is formed on the second conveyance screen. An image forming apparatus, which is capable of transfer.