JP2020128278A - Sheet conveying device and image forming device - Google Patents

Abstract

To appropriately guide a sheet conveyed in a forward direction and the sheet conveyed in an opposite direction, in a branching part to a reverse conveyance path in a main conveyance path, respectively.SOLUTION: A movable guide member 34 is displaceable between a reference position along a main conveyance path 300 and a protruded position protruded to a main conveyance path 300 rather than the reference position. A control unit 8b executes a first control of changing a rotational direction of a second roller pair 31b from a first rotational direction R1 to a second rotational direction R2 and a second control of displacing the movable guide member 34 from the reference position to the protruded position, when it is determined that a reference end 9b which is an end of an upstream side in a forward direction in a sheet 9 exists at a position before passing through a branch position P3 from passing through a first roller pair 31a.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sheet conveying device that conveys a sheet in a forward or backward direction in a curved conveying path and an image forming apparatus including the same.

The image forming apparatus may perform double-sided printing processing. In this case, the sheet conveying device first conveys the sheet in the forward direction along the main conveying path passing through the print position. At that time, the image forming unit forms an image on the first surface of the sheet at the print position.

The electrophotographic image forming unit includes a transfer device that transfers a toner image onto the sheet, and a fixing device that fixes the toner image onto the sheet. The fixing device heats and pressurizes the toner image on the sheet.

Further, the sheet conveying device conveys the sheet in the reverse direction and from the branch position of the main conveying path to the reversing conveying path. The reversal conveyance path extends from the branch position to a merging position in the main conveyance path, which is in a stage preceding the printing position.

Further, the sheet carrying path carries the sheet from the merging position to the main carrying path and again carries the sheet along the main carrying path. At that time, the image forming unit forms an image on the second surface of the sheet at the printing position.

Further, it is known that a mechanism for guiding the sheet in the sheet conveying device includes a fixed main body and a movable rib whose projection height from the main body changes (for example, refer to Patent Document 1).

JP, 2007-99483, A

By the way, a guide member that guides the sheet appropriately guides the sheet conveyed in the forward direction and the sheet conveyed in the reverse direction at a branch portion of the main conveyance path to the reversal conveyance path. Is difficult

For example, it is conceivable that the guide member is arranged so as to project from the opposite side of the main conveyance path to the side where the reverse conveyance path branches to the main conveyance path. In this case, the guide member can appropriately guide the sheet conveyed in the reverse direction to the reverse conveyance path, but is likely to interfere with the conveyance of the sheet in the forward direction.

On the other hand, it is also conceivable that the guide member is arranged in a state along the portion of the main conveyance path where the reverse conveyance path branches. In this case, the guide member may not be able to appropriately guide the sheet conveyed in the reverse direction to the reverse conveyance path, and the sheet may be guided from the branch position to the original path in the main conveyance path. is there.

It is an object of the present invention to appropriately guide a sheet conveyed in a forward direction and a sheet conveyed in a reverse direction at a branch portion of a main conveyance path to a reversal conveyance path, and an image forming apparatus including the same. Is to provide.

A sheet conveying device according to one aspect of the present invention includes a first roller pair, a second roller pair, a third roller pair, a motor, a movable guide member, a drive device, a sheet detection device, and a position specifying device. And a control unit. The first roller pair is arranged in the main transport path and rotates in the first rotation direction to transport the sheet in the first direction along the main transport path. The second roller pair is arranged at a position downstream of the first roller pair in the first direction in the main transport path, and when rotating in the first rotation direction, the second roller pair is moved from the first roller pair to the sheet. Of the sheet in the first direction, and when the sheet rotates in the second rotation direction opposite to the first rotation direction, the sheet is conveyed in the second direction opposite to the first direction. The third roller pair branches from the branch position between the position of the first roller pair and the position of the second roller pair in the main transport path to the first side of the main transport path, and the main transport path. From the second roller pair which is arranged in a reversing conveyance path reaching a merging position on the upstream side in the first direction with respect to the position of the first roller pair, and which rotates in the predetermined direction by rotating in the second rotation direction. The conveyance of the sheet in the second direction is taken over, and the sheet is carried into the reverse conveyance path. The motor rotates the second roller pair in the first rotation direction or the second rotation direction. The movable guide member is disposed on the second side opposite to the first side with respect to the portion between the branch position and the position of the second roller pair in the main transport path, and is disposed in the main transport path. It is supported so as to be displaceable between a reference position along the line and a projecting position projecting to the main transport path from the reference position. The drive device selectively displaces the movable guide member from one of the reference position and the protruding position to the other. The sheet detection device detects the sheet conveyed along the main conveyance path. The position specifying unit specifies the position of the sheet according to the operation status of the first roller pair and the second roller pair and the detection status of the sheet by the sheet detection device. The control unit controls the rotation direction of the second roller pair and the position of the movable guide member by controlling the motor and the driving device. The control unit may be that the reference end, which is an end on the upstream side in the first direction in the sheet, exists at a position after passing the first roller pair and before passing the branch position. A first control that changes the rotation direction of the second roller pair from the first rotation direction to the second rotation direction and the movable guide member is displaced from the reference position to the protruding position. 2 Execute control.

An image forming apparatus according to another aspect of the present invention includes the sheet conveying device, and an image forming unit that forms an image on the sheet conveyed by the sheet conveying device along the main conveying path.

According to the present invention, a sheet conveying apparatus capable of appropriately guiding a sheet conveyed in a forward direction and a sheet conveyed in a reverse direction at an branch portion of a main conveyance path to a reverse conveyance path, and an image forming apparatus including the same It becomes possible to provide.

FIG. 1 is a configuration diagram of the image forming apparatus according to the first embodiment. FIG. 2 is a block diagram showing the configuration of the control device in the image forming apparatus according to the first embodiment. FIG. 3 is a configuration diagram of a main part of the sheet conveying device in the image forming apparatus according to the first embodiment. FIG. 4 is a perspective view of the fixing unit in the image forming apparatus according to the first embodiment. FIG. 5 is a diagram illustrating a main part of the sheet conveying apparatus when the first control and the second control are performed in the image forming apparatus according to the first exemplary embodiment. FIG. 6 is a diagram illustrating a main part of the sheet conveying apparatus when the third control is performed in the image forming apparatus according to the first embodiment. FIG. 7 is a diagram illustrating a main part of the sheet conveying apparatus when the first control and the second control are performed in the image forming apparatus according to the second exemplary embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples of embodying the present invention and do not limit the technical scope of the present invention.

[First Embodiment: Configuration of Image Forming Apparatus 10]
The image forming apparatus 10 according to the first embodiment includes an image forming unit 4 that executes print processing by an electrophotographic method. The printing process is a process of forming an image on the sheet 9. The sheet 9 is a sheet-shaped image forming medium such as paper or resin film.

As shown in FIG. 1, the image forming apparatus 10 includes a sheet conveying device 3, an image forming unit 4, a control device 8, an operating device 8X, a display device 8Y, and the like. Further, the image forming apparatus 10 has therein a main conveyance path 300 and a reversal conveyance path 301, which are conveyance paths for the sheet 9, respectively.

The main conveyance path 300 is a conveyance path that passes through a print position P1 where a toner image is formed on the sheet 9 and a fixing position P2 where the toner image on the sheet 9 is heated and pressed. The reverse conveyance path 301 branches from the branch position P3 at the rear stage of the fixing position P2 on the main conveyance path 300, and joins at the confluence position P4 at the front stage of the print position P1 on the main conveyance path 300.

The sheet conveying device 3 includes a sheet feeding mechanism 30 and a plurality of roller pairs 31. The sheet delivery mechanism 30 delivers the sheet 9 stored in the sheet storage unit 101 to the main transport path 300.

A part of the plural pairs of rollers 31 is arranged in the main conveyance path 300, and another part of the plural pairs of rollers 31 is arranged in the reversal conveyance path 301. The plurality of pairs of rollers 31 arranged in the main transport path 300 transport the sheet 9 along the main transport path 300, and further discharge the sheet 9 from the main transport path 300 onto the discharge tray 102. In the following description, the transport direction of the sheet 9 from the fixing position P2 to the exit of the main transport path 300 via the branch position P3 is referred to as the forward direction.

Further, at least one pair of rollers 31 arranged at the position downstream of the branch position P3 in the main transport path 300 in the forward direction rotates the sheet 9 in the forward direction by rotating in the first rotation direction R1. The sheet 9 is conveyed and rotated in the second rotation direction R2 to convey the sheet 9 in the opposite direction. The reverse direction is the opposite direction to the forward direction. The forward direction is a first direction along the main transport path 300, and the reverse direction is a second direction along the main transport path 300.

The sheet conveying device 3 includes a plurality of motors that rotate a plurality of pairs of rollers 31. Hereinafter, a motor that rotates the second roller pair 31b in the first rotation direction R1 or the second rotation direction R2 is referred to as a target motor 71.

The rotational force of the target motor 71 is transmitted to one of the second roller pair 31b by the gear mechanism 71a.

Further, the plurality of pairs of rollers 31 arranged in the reverse conveyance path 301 conveys the sheet 9 conveyed in the reverse direction from the branch position P3 toward the merge position P4 along the reverse conveyance path 301.

The image forming unit 4 forms an image on the sheet 9 conveyed by the sheet conveying device 3 along the main conveyance path 300. The image forming unit 4 includes an optical scanning unit 40, a photoconductor 41, a charging device 42, a developing device 43, a toner replenishing unit 44, a transfer device 45, a cleaning device 46 and a fixing device 47.

The drum-shaped photoconductor 41 rotates, and the charging device 42 charges the surface of the photoconductor 41. The optical scanning unit 40 scans the charged light beam on the surface of the photoconductor 41 to write an electrostatic latent image on the surface of the photoconductor 41.

By the action of the charging device 42 and the optical scanning unit 40, the electrostatic latent image based on the image data to be printed is formed on the surface of the photoconductor 41.

The developing device 43 develops the electrostatic latent image into a toner image by supplying the toner 90 to the photoconductor 41 on which the electrostatic latent image is formed. By developing the electrostatic latent image, the photoconductor 41 carries the toner image and rotates. The photoconductor 41 is an example of an image carrier.

The transfer device 45 transfers the toner image on the photoconductor 41 to the sheet 9 at the print position P1 on the main transport path 300. The transfer device 45 may be a device that transfers the toner image on the photoconductor 41 to the intermediate transfer belt and then transfers the toner image on the intermediate transfer belt to the sheet 9.

The fixing device 47 includes a heating roller 471 that is heated by a heater, and a pressure roller 472 that presses the sheet 9 against the heating roller 471. The surface layer of the pressure roller 472 is made of an elastic member such as rubber.

The fixing device 47 heats and presses the toner image transferred to the sheet 9 at a fixing position P2, which is a subsequent stage of the print position P1 on the main transport path 300. As a result, the toner image is fixed on the sheet 9.

The cleaning device 46 removes the toner 90 remaining on the surface of the photoconductor 41. The toner replenishing unit 44 replenishes the developing device 43 with the toner 90.

The operation device 8X is an information input device that receives a user operation. The display device 8Y displays various information including images. For example, it is conceivable that the operation device 8X and the display device 8Y are configured by a display panel having a touch panel.

As shown in FIG. 2, the control device 8 includes a CPU (Central Processing Unit) 80, a RAM (Random Access Memory) 81, a secondary storage device 82, and a communication device 83. Note that, instead of the CPU 80, another processor such as a DSP (Digital Signal Processor) may be adopted.

The RAM 81 is a computer-readable volatile storage device. The RAM 81 temporarily stores the program executed by the CPU 80 and the data output and referenced in the process of executing the program by the CPU 80. The RAM 81 is a storage device that can access data faster than the secondary storage device 82.

The secondary storage device 82 is a computer-readable non-volatile storage device. For example, secondary storage device 82 may include flash memory and/or hard disk drives.

The CPU 80 operates as the main controller 8a, the conveyance controller 8b, the print controller 8c, the timer 8d, and the like by executing the program. In the present embodiment, the conveyance control unit 8b and the time counting unit 8d form part of the sheet conveyance device 3.

The main controller 8a controls the display device 8Y and starts processing according to the operation content of the operation device 8X. Further, the main control unit 8a controls the communication device 83 to execute a process of receiving data from the other device and a process of transmitting data to the other device.

The conveyance control unit 8b controls various motors related to the conveyance of the sheet 9 to control the operations of the sheet feeding mechanism 30 and the plurality of roller pairs 31.

The print control unit 8c controls various motors, laser light sources, voltage output circuits, heaters, and the like related to the print processing, so that the optical scanning unit 40, the charging device 42, the developing device 43, the toner replenishing unit 44, and the transfer unit. The operations of the device 45, the cleaning device 46, and the fixing device 47 are controlled.

In the following description, the roller pair 31 arranged between the fixing position P2 and the branch position P3 on the main transport path 300 is referred to as a first roller pair 31a. The first roller pair 31a conveys the sheet 9 in the forward direction along the main conveyance path 300 by rotating in a predetermined direction.

The path length from the fixing position P2 to the position of the first roller pair 31a in the main transport path 300 is shorter than the length of the sheet 9 in the direction along the main transport path 300. Therefore, when a part of the sheet 9 remains at the fixing position P2, the first roller pair 31a takes over the conveyance of the sheet 9 from the fixing device 47 in the forward direction, and further conveys the sheet 9 in the forward direction. To do.

A portion of the main transport path 300 including the branch position P3 is the curved path 300a. The first roller pair 31a is arranged on the curved path 300a.

The reverse conveyance path 301 branches from the branch position P3 of the curved path 300a to the outside of the curved path 300a. In the example shown in FIG. 1, the outside of the curved path 300a in the direction from the branch position P3 to the upstream side in the forward direction of the main transport path 300 is the lower side of the curved path 300a.

Further, the roller pair 31 arranged at the position closest to the branch position P3 on the downstream side of the branch position P3 in the main transport path 300 in the forward direction is referred to as a second roller pair 31b. The branch position P3 is a position between the position of the first roller pair 31a and the position of the second roller pair 31b in the main transport path 300.

In the present embodiment, the second roller pair 31b is a discharge roller pair that discharges the sheet 9 from the main transport path 300 to the discharge tray 102. The path length from the position of the first roller pair 31a to the position of the second roller pair 31b in the main transport path 300 is shorter than the length of the sheet 9 in the direction along the main transport path 300.

Therefore, the second roller pair 31b takes over the conveyance of the sheet 9 in the forward direction from the first roller pair 31a when rotating in the first rotation direction R1. Further, the second roller pair 31b conveys the sheet 9 in the reverse direction when rotating in the second rotation direction R2.

Further, the roller pair 31 arranged at the position closest to the branch position P3 in the reverse conveyance path 301 is referred to as a third roller pair 31c. In the present embodiment, one roller of the first roller pair 31a is the shared roller 311 that also serves as one roller of the third roller pair 31c.

The path length from the position of the second roller pair 31b to the position of the third roller pair 31c in the main transport path 300 is shorter than the length of the sheet 9 in the direction along the main transport path 300.

Therefore, the third roller pair 31c takes over the conveyance of the sheet 9 in the reverse direction from the second roller pair 31b which rotates in the second rotation direction R2 by rotating in the predetermined direction, and reversely conveys the sheet 9. Carry on to the road 301.

When the image forming apparatus 10 executes the one-sided printing process for forming an image only on one side of the sheet 9, the second roller pair 31b rotates only in the first rotation direction R1. As a result, the second roller pair 31b discharges the sheet 9 having the image formed only on one side thereof from the main transport path 300 to the discharge tray 102.

On the other hand, when the image forming apparatus 10 executes the double-sided printing process for forming images on both sides of the sheet 9, the first roller pair 31a first rotates in the first rotation direction R1 and the sheet on which the image is formed on one side. Before 9 is discharged from the main transport path 300, it rotates in the second rotation direction R2.

Then, the third roller pair 31c carries in the sheet 9 conveyed in the opposite direction by the second roller pair 31b to the reverse conveyance path 301. As a result, the sheet 9 is conveyed again along the main conveyance path 300 in a state in which the front and back and front and back are reversed as compared with the case where the sheet 9 is conveyed along the main conveyance path 300 for the first time.

When the sheet 9 passes the print position P1 and the fixing position P2 for the second time, the image forming unit 4 transfers and fixes the toner image on the second surface of the sheet 9. The sheet 9 having the images formed on both sides is discharged to the discharge tray 102 by the third roller pair 31c that rotates in the first rotation direction R1.

As shown in FIG. 1, the sheet conveyance device 3 includes a plurality of sheet detection devices 6 that detect the sheet 9 conveyed along the main conveyance path 300 or the sheet 9 conveyed along the reverse conveyance path 301. Equipped with.

In the example shown in FIG. 1, one of the two sheet detection devices 6 detects the sheet 9 at a position between the merge position P4 and the print position P1 on the main transport path 300. The other of the two sheet detection devices 6 detects the sheet 9 between the fixing position P2 on the main transport path 300 and the position of the first roller pair 31a, and further, the position of the third roller pair 31c on the reverse transport path 301. The sheet 9 is also detected at a position closer to the merging position P4.

The timer unit 8d represents the position of the sheet 9 by measuring the elapsed time after any one of the plurality of sheet detection devices 6 detects the sheet 9 during the operation of the plurality of pairs of rollers 31. Fire a position event.

For example, the time counting unit 8d generates an optical scanning start event indicating that the sheet 9 has reached the position predicted to reach the print position P1 after the elapse of a predetermined time. The optical scanning start event is used to control the optical scanning unit 40 to start writing the electrostatic latent image on the photoconductor 41.

In addition, the timer unit 8d is responsive to the operating statuses of the plurality of roller pairs 31 such as the first roller pair 31a, the second roller pair 31b, and the third roller pair 31c and the detection status of the sheet 9 by the sheet detection device 6. It is an example of a position specifying unit that specifies the position of the seat 9.

Further, the position of the sheet 9 corresponding to the event generated by the time counting unit 8d includes the rotational speeds of the plurality of pairs of rollers 31, the path length of the main transport path 300, the path length of the reverse transport path 301, and the arrangement position of each device. It is a position specified based on. Therefore, the event does not guarantee that the sheet 9 always exists at the position corresponding to the event.

By the way, the guide member for guiding the sheet 9 appropriately moves the sheet 9 transported in the forward direction and the sheet 9 transported in the reverse direction at the branch position P3 of the main transport path 300 to the reverse transport path 301. It is difficult to guide you.

In the following description, the front end and the rear end of the sheet 9 when the sheet 9 is first conveyed along the main conveyance path 300 will be referred to as a first end 9a and a second end 9b, respectively (see FIG. 3). The second end 9b corresponds to the reference end that is the upstream end of the sheet 9 in the forward direction.

For example, it is conceivable that the guide member is arranged so as to project from the opposite side of the main conveyance path 300 where the reversal conveyance path 301 branches to the main conveyance path 300. In this case, the guide member can appropriately guide the sheet 9 conveyed in the reverse direction to the reverse conveyance path 301, but it is likely to interfere with the conveyance of the sheet 9 in the forward direction.

That is, the first end 9a of the sheet 9 may come into contact with the guide member protruding into the curved path 300a, and the sheet 9 may be clogged in the curved path 300a.

On the other hand, it is also conceivable that the guide member is arranged in a state along the part of the main conveyance path 300 where the reverse conveyance path 301 branches. In this case, the guide member cannot properly guide the sheet 9 conveyed in the reverse direction to the reverse conveyance path 301, and the sheet 9 is the original path in the main conveyance path 300 from the branch position P3. There is a risk of being guided toward 31a.

That is, the second end 9b of the sheet 9 may come into contact with the first roller pair 31a, and the sheet 9 may be jammed in the curved path 300a.

As shown in FIG. 3, in the fixing device 47, the heating roller 471 is arranged inside the curved path 300a, and the pressure roller 472 is arranged outside the curved path 300a. In this case, the sheet 9 is likely to curl in the direction in which the second end 9b of the sheet 9 approaches the first roller pair 31a. Further, the sheet 9 may be curled by passing through the curved path 300a.

Therefore, when the sheet 9 has a characteristic of easily curling in the fixing device 47, when the sheet 9 is conveyed in the reverse direction, the second end 9b of the sheet 9 contacts the first roller pair 31a, and the sheet 9 is The phenomenon of clogging in the curved path 300a is more likely to occur.

On the other hand, the sheet conveying device 3 of the image forming apparatus 10 appropriately selects the sheet 9 conveyed in the forward direction and the sheet 9 conveyed in the reverse direction at the branch portion of the main conveying path 300 to the reverse conveying path 301. It is equipped with a structure that can guide to. The configuration will be described below.

[Configuration of Main Parts of Sheet Conveying Device 3]
3, 5 and 6 show the configuration of the main part of the sheet conveying device 3 arranged in the area from the fixing position P2 of the main conveying path 300 to the position of the second roller pair 31b.

As shown in FIG. 3, the sheet conveying device 3 further includes an outer guide member 32, a first inner guide member 33, a movable guide member 34, a second inner guide member 35, and a drive device 72.

The outer guide member 32 is arranged outside the curved path 300a, and the first inner guide member 33, the movable guide member 34, and the second inner guide member 35 are arranged inside the curved path 300a. The outer side and the inner side of the curved path 300a are examples of the first side and the second side of the main transport path 300, respectively.

The first inner guide member 33 is arranged next to the movable guide member 34 in the reverse direction, and the second inner guide member 35 is arranged next to the movable guide member 34 in the forward direction.

The first inner guide member 33 is disposed inside the branch position P3 on the curved path 300a. The movable guide member 34 and the second inner guide member 35 are arranged inside the portion between the branch position P3 and the position of the second roller pair 31b in the curved path 300a.

The guide surface 32a of the outer guide member 32 guides the seat 9 along the curved path 300a on the outer side of the curved path 300a.

The first inner guide portion 33a included in the first inner guide member 33 faces the branch position P3 inside the curved path 300a and guides the seat 9 along the curved path 300a.

The second inner guide portion 34a of the movable guide member 34 guides the seat 9 along the curved path 300a at a position downstream of the first inner guide portion 33a inside the curved path 300a in the forward direction. To do.

The fixing device 47 constitutes a fixing unit 470 together with the outer guide member 32, the movable guide member 34, and the like. FIG. 4 is a perspective view of the fixing unit 470. As shown in FIG. 4, the second inner guide portion 34a is composed of a plurality of ribs arranged in a direction orthogonal to the sheet 9 conveyance direction. The ribs are formed along the conveyance direction of the sheet 9.

The third inner guide portion 35a of the second inner guide member 35 has the seat 9 along the curved path 300a at a position on the inner side of the curved path 300a that is on the downstream side of the position of the second inner guide portion 34a in the forward direction. To guide you.

The movable guide member 34 is supported so as to be displaceable between a reference position along the curved path 300a and a protruding position projecting toward the curved path 300a from the reference position. The movable guide member 34 constitutes the inner side surface of the curved path 300a at the reference position. 3, 4, and 6 show the movable guide member 34 held at the reference position, and FIG. 5 shows the movable guide member 34 held at the protruding position.

More specifically, as shown in FIGS. 3 to 6, the movable guide member 34 has a shaft portion 34b rotatably supported by a pair of side plates 471 included in the fixing unit 470. As a result, the movable guide member 34 can swing about the shaft portion 34b between the reference position and the protruding position.

In the present embodiment, the shaft portion 34b is provided in a portion of the movable guide member 34 on the upstream side of the center portion in the forward direction. Therefore, a portion of the movable guide member 34 on the downstream side in the forward direction with respect to the shaft portion 34b can be displaced between the reference position and the protruding position.

The drive device 72 selectively displaces the movable guide member 34 from one of the reference position and the protruding position to the other under the control of the transport control unit 8b. For example, an actuator such as a solenoid is adopted as the drive device 72.

The conveyance control unit 8b controls the target motor 71 and the drive device 72 to control the rotation direction of the second roller pair 31b and the position of the movable guide member 34.

In the present embodiment, the time counting unit 8d generates a reversal event indicating that the second end 9b of the sheet 9 is in a state after passing the first roller pair 31a and before passing the branch position P3.

Generating the reversal event corresponds to the fact that the time counting unit 8d has specified that the second end 9b of the sheet 9 exists at a position after passing the first roller pair 31a and before passing the branch position P3. To do.

The transport controller 8b executes the first control and the second control when the reversal event occurs. The first control is control for changing the rotation direction of the second roller pair 31b from the first rotation direction R1 to the second rotation direction R2. The second control is control for displacing the movable guide member 34 from the reference position to the protruding position.

In addition, the first control and the second control are simultaneously executed, the second control is executed after the execution of the first control, or the first control is executed after the execution of the second control. It is conceivable that control is executed.

FIG. 3 shows the seat 9 and the movable guide member 34 before the reversal event occurs, and FIG. 5 shows an example of the seat 9 and the movable guide member 34 immediately after the first control and the second control are executed. Indicates.

Before the second control is executed, that is, when the sheet 9 is conveyed in the forward direction along the curved path 300a, the conveyance control unit 8b holds the movable guide member 34 at the reference position. .. As a result, the movable guide member 34 does not hinder the first end 9a of the sheet 9 passing through the curved path 300a from traveling, and the sheet 9 is smoothly guided along the curved path 300a.

Further, by executing the second control, the second end 9b of the sheet 9 conveyed in the reverse direction is moved to the third roller pair 31c rather than the first roller pair 31a by the movable guide member 34 at the protruding position. Will be guided in the direction close to.

Therefore, by adopting the sheet conveying device 3, the sheet 9 conveyed in the forward direction and the sheet 9 conveyed in the opposite direction are appropriately respectively provided at the branch portion of the curved path 300a to the reversal conveying path 301. Be guided.

Further, the conveyance control unit 8b executes the third control when the sheet 9 is conveyed in the reverse direction after the first control and the second control are executed. The third control is control for returning the movable guide member 34 from the protruding position to the reference position.

FIG. 6 shows the seat 9 and the movable guide member 34 before the reversal event occurs, and FIG. 5 shows an example of the seat 9 and the movable guide member 34 immediately after the execution of the third control.

For example, the timer 8d is located at a position where the sheet 9 being conveyed in the reverse direction by the second roller pair 31b comes into contact with the third roller pair 31c after the first control and the second control are executed. Raises a release event indicating that it exists.

Generating the release event means that the sheet 9 being conveyed in the reverse direction by the second roller pair 31b comes into contact with the third roller pair 31c after the first control and the second control are executed. This corresponds to the fact that the time counting unit 8d has specified that the position exists.

Then, the transport control unit 8b executes the third control when the release event occurs.

For example, before the second end 9b of the sheet 9 reaches one of the third roller pairs 31c, and the second end 9b of the sheet 9 is sandwiched in the nip portion of the third roller pair 31c in the timer 8d. At the time of, it is possible to generate the release event.

Alternatively, it is conceivable that the timer 8d causes the release event when the second end 9b of the sheet 9 reaches the nip portion of the third roller pair 31c.

By executing the third control in accordance with the release event, the sheet 9 extends from the movable guide member 34 in a state where the sheet 9 extends over both the nip portion of the second roller pair 31b and the nip portion of the third roller pair 31c. It is avoided that unnecessary pressure is continuously applied to the seat 9. As a result, the seat 9 is prevented from being damaged by the movable guide member 34.

[Second Embodiment]
Next, the sheet conveying device 3A included in the image forming apparatus 10A according to the second exemplary embodiment will be described with reference to FIG. In FIG. 7, the same components as those shown in FIGS. 1 to 6 are designated by the same reference numerals.

The sheet conveying device 3A also has the same configuration as the sheet conveying device 3. Hereinafter, differences between the sheet conveying apparatus 3A and the sheet conveying apparatus 3 will be described.

In the sheet conveying device 3A, the shaft portion 34b is provided in a portion of the movable guide member 34 on the downstream side of the central portion in the forward direction. Therefore, a portion of the movable guide member 34 on the upstream side of the shaft portion 34b in the forward direction can be displaced between the reference position and the protruding position.

The transport control unit 8b of the sheet transport device 3A executes the first control and the second control similarly to the transport control unit 8b of the sheet transport device 3. Further, the conveyance control unit 8b of the sheet conveyance device 3A also executes the third control.

Even when the sheet conveying device 3A is adopted, the same effect as when the sheet conveying device 3 is adopted is obtained.

Further, in the sheet conveying device 3A, a portion of the movable guide member 34 closer to the branch position P3 is displaced from the reference position to the protruding position by the second control. Therefore, even when the vicinity of the second end 9b of the sheet 9 is curled toward the first roller pair 31a, the movable guide member 34 can more reliably guide the second end 9b to the movable guide member 34.

3, 3A: sheet conveying device 4: image forming unit 6: sheet detecting device 8: control device 8X: operating device 8Y: display device 8a: main control unit 8b: conveyance control unit 8c: print control unit 8d: timing unit (position) Specific part)
9: Sheet 9a: First end of sheet 9b: Second end of sheet (reference end)
10, 10A: Image forming apparatus 30: Sheet feeding mechanism 31: Roller pair 31a: First roller pair 31b: Second roller pair 31c: Third roller pair 32: Outer guide member 32a: Guide surface 33: First inner guide member 33a: 1st inside guide part 34: Movable guide member 34a: 2nd inside guide part 34b: Shaft part 35: 2nd inside guide member 35a: 3rd inside guide part 40: Optical scanning unit 41: Photosensitive body 42: Charging device 43: developing device 44: toner replenishing unit 45: transfer device 46: cleaning device 47: fixing device 71: target motor 71a: gear mechanism 72: drive device 80: CPU
81: RAM
82: Secondary storage device 83: Communication device 90: Toner 101: Sheet accommodating section 102: Ejection tray 300: Main transport path 300a: Curved path 301: Reverse transport path 311: Shared roller 471: Heating roller 472: Pressure roller P1 : Print position P2: Fixing position P3: Branch position P4: Merging position R1: First rotation direction R2: Second rotation direction

Claims (7)

A first roller pair which is disposed in the main transport path and transports the sheet in the first direction along the main transport path by rotating in the first rotation direction;
It is arranged at a position downstream of the first roller pair in the first direction in the main conveyance path, and when rotating in the first rotation direction, the first roller pair moves from the first roller pair in the first direction. A second roller pair that takes over the conveyance and conveys the sheet in a second direction opposite to the first direction when rotating in a second rotation direction opposite to the first rotation direction;
From the branch position between the position of the first roller pair and the position of the second roller pair in the main transport path, to the first side of the main transport path to branch the first roller pair in the main transport path. The second direction of the sheet from the second roller pair which is arranged in a reversing conveyance path reaching a merging position on the upstream side of the first direction from the position and rotates in the second rotation direction by rotating in a predetermined direction. A third roller pair that carries over the conveyance to the sheet and carries the sheet into the reverse conveyance path,
A motor that rotates the second roller pair in the first rotation direction or the second rotation direction;
The reference position and the reference along the main conveyance path, which are arranged on the second side opposite to the first side with respect to the portion between the branch position and the position of the second roller pair in the main conveyance path. A movable guide member that is displaceably supported between a projecting position that projects from the position to the main transport path,
A drive device for selectively displacing the movable guide member from one of the reference position and the protruding position to the other;
A sheet detection device for detecting the sheet conveyed along the main conveyance path,
A position specifying unit that specifies the position of the sheet according to the operating status of the first roller pair and the second roller pair and the detection status of the sheet by the sheet detection device;
A control unit that controls the rotation direction of the second roller pair and the position of the movable guide member by controlling the motor and the drive device,
The control unit is
When it is specified by the position specifying unit that the reference end, which is an end on the upstream side in the first direction in the sheet, exists at a position before passing the branch position after passing the first roller pair. First, a first control for changing the rotation direction of the second roller pair from the first rotation direction to the second rotation direction and a second control for displacing the movable guide member from the reference position to the protruding position are executed. , Sheet conveying device. The first roller pair is arranged in a curved path including the branch position in the main transport path,
The reversal conveyance path branches from the branch position of the curved path to the outside of the curved path,
The movable guide member is supported so as to be displaceable between the reference position that constitutes an inner surface of the curved path and the protruding position that protrudes toward the curved path from the reference position. Sheet conveying device. The control unit returns the movable guide member from the projecting position to the reference position when the sheet is conveyed in the second direction after the first control and the second control are executed. The sheet conveyance device according to claim 1 or 2, which further executes control. The control unit is present at a position where the sheet being conveyed in the second direction by the second roller pair comes into contact with the third roller pair after the first control and the second control are executed. The sheet conveying apparatus according to claim 3, wherein the third control is executed when it is specified by the position specifying unit. The movable guide member has a shaft portion that is rotatably supported at a position downstream of a central portion of the movable guide member in the first direction, and is located upstream of the shaft portion in the first direction. The sheet conveying device according to claim 1, wherein the portion is displaceable between the reference position and the protruding position. The sheet transporting device according to claim 1, wherein one roller of the first roller pair also serves as one roller of the third roller pair. A sheet conveying device according to any one of claims 1 to 6,
An image forming apparatus, comprising: an image forming unit that forms an image on the sheet conveyed along the main conveying path by the sheet conveying apparatus.

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