Image forming apparatus

Abstract

To securely leave a sheet to a first position where a first sheet detecting part detects the sheet when finishing another discharge mode to discharge the sheet to a loading part.SOLUTION: A control part of an image forming apparatus when a discharge part is unavailable and a second conveyance passage is available, executes another mode to discharge a plurality of sheets (752, 753, 754, 755) present in the image forming apparatus to a loading part and finishes the other mode in the state of leaving the sheets to a first position (P1). The control part, during executing the other discharge mode, discharges a preceding sheet present in the first position (P1) to the loading part when a second sheet detecting part detects that a following sheet is present in a second position (P2).SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that forms an image on a sheet. [Background technology]

[0002] In image forming devices such as printers, copiers, and multifunction peripherals, when a sheet jam occurs, the location of the jammed paper is displayed to the user, and the user is notified to remove the jammed sheet. Furthermore, when a sheet jam occurs, if a sheet other than the jammed sheet is being transported through the transport path of the image forming device and transport of that sheet is stopped, that sheet is left behind inside the image forming device, and the user must remove it. Particularly when the transport path of the image forming device is long, the number of sheets being transported when a jam occurs increases, and many sheets are left behind, increasing the user's workload. Therefore, a device has been proposed that, when a paper jam occurs, transports the paper to a branched transport path branching off from the transport path that was transporting the paper, and then ejects the paper from the branched transport path into a jammed paper storage box (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-220966 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a configuration in which, when a paper jam occurs, sheets that were scheduled to be discharged from the discharge section are discharged and stacked in another location (hereinafter referred to as the "stacking section") as described in the above-mentioned Patent Document 1, providing a sensor to detect the sheets in the stacking section would hinder cost reduction. Therefore, a method has been considered in which a sensor located in the sheet transport path near the stacking section is used, and by stopping the sheet at the sensor's detection position, the sensor detects that the sheet is present in the stacking section and notifies the user to remove the sheet from the stacking section. However, a paper jam can also occur when the sheet is transported toward the stacking section, and if the sheet cannot be transported to the sensor's detection position, the sensor's detection cannot be used to notify the user to remove the sheet.

[0005] Therefore, an object of the present invention is to provide an image forming device that can more reliably leave a sheet at the first position where the first sheet detection section detects the sheet when ending a separate discharge mode in which the sheet is discharged to a stacking section. [Means for solving the problem]

[0006] One aspect of the present invention is a printing apparatus including an image forming unit that forms an image on a sheet, a discharge unit that discharges the sheet on which the image has been formed by the image forming unit to the outside, a first conveying path that conveys the sheet on which the image has been formed by the image forming unit to the discharge unit, a second conveying path that branches off from the first conveying path at a first branching unit, a sheet conveying unit that conveys the sheet on the second conveying path, a stacking unit that stacks the sheets discharged from the second conveying path, a first sheet detecting unit that detects a sheet at a first position on the second conveying path, and a second sheet detecting unit that detects a sheet at a second position on the second conveying path that is closer to the image forming unit than the first position. and a control unit that, when the discharge unit is unavailable and the second transport path is available, executes a separate discharge mode in which multiple sheets inside the device are discharged to the stacking unit, and ends the separate discharge mode with the sheet left at the first position, wherein, when the second sheet detection unit detects that there is a subsequent sheet at the second position using the sheet transport unit during execution of the separate discharge mode, the control unit discharges the preceding sheet at the first position to the stacking unit and transports the subsequent sheet at the second position to the first position. [Effects of the Invention]

[0007] According to the present invention, when the separate discharge mode in which the sheet is discharged onto the stacking section is terminated, the sheet can be more reliably left at the first position where the first sheet detection section detects the sheet. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing a control configuration of the image forming apparatus according to the present embodiment. [Figure 3] 5 is a time chart showing the reversing operation in the reversing unit according to the present embodiment. [Figure 4] 5 is a flowchart showing control of a printing operation according to the present embodiment. [Figure 5]10 is a flowchart showing the control of the operation for determining the number of sheets to be evacuated in the discharge process according to the present embodiment. [Figure 6] 6 is a flowchart showing control of a retreat discharge operation in the discharge process according to the present embodiment. [Figure 7] (a) A diagram showing the position of the stuck paper when a paper jam occurs during the discharge process. (b) A diagram showing the state where the discharge of the stuck paper has started during the discharge process. (c) A diagram showing the state where the stuck paper has been discharged to the evacuation section during the discharge process. (d) A diagram showing the state where the last stuck paper has stopped at the detection position of the reversal / duplex transport guide sensor during the discharge process. [Figure 8] FIG. 6 is a schematic diagram showing the position of paper when a paper jam occurs. [Figure 9] (a) is a diagram showing the state where the preceding paper has stopped at the first position, (b) is a diagram showing the state where the succeeding paper has been transported to the second position, (c) is a diagram showing the state where the preceding paper has started to be ejected, and (d) is a diagram showing the state where the transport of the succeeding paper has started. [Figure 10] FIG. 10 is a diagram showing an example of a notification screen. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are shown by way of example, and the present invention is not limited to the following embodiments.

[0010] [Image forming device] First, the structure of an image forming apparatus according to this embodiment will be described. FIG. 1 is a schematic diagram showing an image forming apparatus according to this embodiment. In FIG. 1, image forming apparatus 100 is a color laser printer, and is roughly composed of an image output unit 100P as the apparatus main body, a reader unit 104 arranged above image output unit 100P, and an operation unit 105. When operated via operation unit 105, image output unit 100P forms an image by copying an image of a document read by reader unit 104. Alternatively, image output unit 100P forms an image based on image data recorded on a hard disk drive or the like (not shown) or image data input from an external interface (not shown).

[0011] The image output section 100P includes an image forming unit 10, a feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, an inverting unit 50, a double-sided conveying unit 60, a discharge conveying unit 70, a control unit 80, and a retracting section 90. In the image forming apparatus 100, the image forming unit 10, the intermediate transfer unit 30, and the fixing unit 40 constitute an image forming section 100A that forms an image on a paper P as a sheet.

[0012] The image forming unit 10 includes four image forming stations a to d arranged side by side in the horizontal direction. The four image forming stations a to d have the same configuration. That is, each of the image forming stations a to d includes a photosensitive drum 11 a to 11 d as an image carrier that is axially supported at its center and driven to rotate. The photosensitive drums 11 a to 11 d each rotate in the direction indicated by the arrow in FIG. 1. Primary charging devices 12 a to 12 d, optical systems 13 a to 13 d, developing devices 14 a to 14 d, and cleaning devices 15 a to 15 d are arranged facing the outer circumferential surfaces of the photosensitive drums 11 a to 11 d along the rotation direction.

[0013] The primary charging devices 12a-12d apply a uniform amount of charge to the surfaces of the corresponding photosensitive drums 11a-11d. The optical systems 13a-13d expose the corresponding photosensitive drums 11a-11d to light beams, such as laser beams, modulated according to a recording image signal, forming electrostatic latent images on the photosensitive drums 11a-11d. The developing devices 14a-14d, each containing yellow, cyan, magenta, and black toner, supply the toner to the electrostatic latent images formed on the corresponding photosensitive drums 11a-11d to form and visualize toner images. The toner images formed on the photosensitive drums 11a-11d are transferred to the intermediate transfer belt 31 so as to be superimposed on each other, forming a color image, by applying a predetermined transfer voltage to primary transfer rollers 35a-35d of the intermediate transfer unit 30 (described later). The cleaning devices 15a to 15d scrape off residual toner that has not been transferred to the intermediate transfer belt 31 and remains on the photosensitive drums 11a to 11d, respectively, to clean the surfaces of the photosensitive drums 11a to 11d.

[0014] The feeding unit 20 includes a cassette 21 that stores paper P as sheets or recording paper, and a pickup roller 22 that feeds paper P from the cassette 21. The feeding unit 20 also includes a manual feed tray 97 and a manual feed pickup roller 96 that feeds paper P from the manual feed tray 97. The feeding unit 20 also includes a registration roller pair 26, a separable pre-registration roller pair 27, a plurality of conveyance roller pairs 23 that convey paper P fed from the cassette 21 to the registration roller pair 26, and a conveyance path 24. A registration sensor 28 that detects the presence or absence of paper P is disposed upstream of the registration roller pair 26 on the conveyance path 24. A pre-secondary transfer sensor 29 is also disposed downstream of the registration roller pair 26 on the conveyance path 24.

[0015] The cassette 21 is provided with a sensor as a size detector that detects the size of the paper P stored in the cassette 21. The registration sensor 28 and the pre-secondary transfer sensor 29 are examples of transport sensors, and as shown in FIG. 2, the cassette 21 has a plurality of transport sensors 106 that monitor the paper position.

[0016] In addition, in this embodiment, the conveying path refers to a space that is physically contacted by the paper P (sheet) and is partitioned by a conveying guide that serves as a guide section that guides the paper P in the conveying direction. The conveying path along which the sheet is conveyed is configured by a guide member, and therefore may also be referred to as a guide section that guides the sheet being conveyed.

[0017] The pickup roller 22 feeds out the paper P from the cassette 21, and the fed paper P is transported to the registration roller pair 26 by the transport roller pair 23. On the other hand, when feeding the paper P from the manual feed tray 97, the manual feed pickup roller 96 feeds out the paper P from the manual feed tray 97, and the fed paper P is transported to the registration roller pair 26 by the pre-registration roller pair 27. The registration roller pair 26 feeds the paper P towards the secondary transfer area Te of the intermediate transfer unit 30, which will be described later, in accordance with the timing for forming an image.

[0018] The intermediate transfer unit 30 includes an intermediate transfer belt 31. The intermediate transfer belt 31 is rotatably stretched by a drive roller 32, a tension roller 33, and a secondary transfer inner roller 34. The drive roller 32 transmits a driving force to the intermediate transfer belt 31. The tension roller 33 applies an appropriate tension to the intermediate transfer belt 31. A secondary transfer outer roller 36 is disposed opposite the secondary transfer inner roller 34 across the intermediate transfer belt 31. The contact area between the secondary transfer inner roller 34 and the secondary transfer outer roller 36 forms a secondary transfer area Te. Primary transfer rollers 35a to 35d are disposed opposite the photosensitive drums 11a to 11d, respectively, with the intermediate transfer belt 31 interposed therebetween. The contact areas between the photosensitive drums 11a to 11d and the primary transfer rollers 35a to 35d form primary transfer areas Ta to Td, respectively. A cleaning device 37 is disposed opposite the tension roller 33 with the intermediate transfer belt 31 interposed therebetween. The cleaning device 37 cleans the image forming surface of the intermediate transfer belt 31 .

[0019] The fixing unit 40 includes a fixing roller 41a and a pressure roller 41b that is pressed by the fixing roller 41a. The fixing roller 41a includes a heat source such as a halogen heater inside. The pressure roller 41b may also include a heat source. A conveyance path 43 of the fixing unit 40 includes a pair of pre-fixing rollers 42 that conveys the paper P into the nip between the fixing roller 41a and the pressure roller 41b.

[0020] The discharge / conveyance unit 70 includes an inner discharge roller pair 71, an outer discharge roller pair 72 as a discharge section, a flapper 73 as a first branch section, and a first conveyance path including a conveyance path 74, a conveyance path 75, and a conveyance path 76. The inner discharge roller pair 71 conveys the paper P on which the image has been thermally fixed by the fixing unit 40. The outer discharge roller pair 72 as a discharge section discharges the paper P toward the outside of the apparatus main body. The flapper 73 as the first branch section is a branching mechanism that switches the conveyance destination of the paper P to the conveyance path 74 or the conveyance path 75 using a reversing / double-sided flapper solenoid 95. In other words, it switches the conveyance destination of the paper P between the direction of the reversing unit 50 (described below) and the direction of the outer discharge roller pair 72.

[0021] In this embodiment, the conveying path 74 constitutes a first conveying path that conveys the paper P conveyed from the image forming unit 100A to the pair of external discharge rollers 72 as a discharge unit. Further, the conveying path 75 branching off from the conveying path 74 constitutes a second conveying path that conveys the paper P conveyed from the image forming unit 100A to the evacuation unit 90 as a stacking unit, which will be described later. Further, the conveying path 76 branching off from the conveying path 75 constitutes a fourth conveying path that conveys the paper P reversed by the reversing unit 50 as a reversing unit to the pair of external discharge rollers 72 as a discharge unit.

[0022] The reversing unit 50, which serves as a sheet conveying section or reversing section, includes a first reversing / duplexing roller pair 51A (first roller) and a second reversing / duplexing roller pair 51B (second roller) serving as a first conveying section. The reversing unit 50 also includes a conveying path 52 serving as a second conveying path and a discharge flapper 53 serving as a third branching section. The reversing unit 50 also includes a reversing / duplexing flapper 54 serving as a second branching section and a reversing / pull-in roller pair 55 serving as a second conveying section. The reversing unit 50 also includes a reversing / duplexing sensor 91 serving as a second sheet detecting section, a reversing / duplexing conveying guide sensor 92 serving as a first sheet detecting section, a reversing / duplexing drive motor 93 serving as a first drive source, and a reversing / pull-in drive motor 99 serving as a second drive source.

[0023] The first reversing / duplexing roller pair 51A and the second reversing / duplexing roller pair 51B are driven by a reversing / duplexing drive motor 93 and are configured to be rotatable in both forward and reverse directions. The reversing / pushing roller pair 55 is driven by a reversing / pushing drive motor 99 and is similarly configured to be rotatable in both forward and reverse directions. In other words, the first reversing / duplexing roller pair 51A and the second reversing / duplexing roller pair 51B and the reversing / pushing roller pair 55 can transport paper P transported from the image forming unit 100A in a first direction A toward the retraction unit 90, or in the opposite second direction B.

[0024] The discharge flapper 53 is a branching mechanism that switches the destination of the paper P that has been reversed in the transport path 52 to the transport path 76 that branches off from the transport path 52 by the reverse / duplex flapper solenoid 95 during reverse discharge. In other words, it switches the destination of the paper P to the direction of the outer discharge roller pair 72 of the discharge transport unit 70. The reverse / duplex flapper 54 is a branching mechanism that is driven by the reverse / duplex flapper solenoid 95 and switches the destination of the paper P to the direction of the transport path 62 that branches off from the transport path 52, which will be described later, during a double-sided print job. The reverse / duplex flapper 54 switches the destination of the paper P to the direction of each duplex transport roller pair 61 of the duplex transport unit 60.

[0025] The reverse / double-sided sensor 91 detects the presence or absence of paper P at a second detection position 91A between the reverse / double-sided flapper 54 and the first reverse / double-sided roller pair 51A in the transport direction of paper P, and detects the leading and trailing ends of paper P during reverse discharge and double-sided printing. That is, the reverse / double-sided sensor 91 detects a sheet at a second position P2 (see FIG. 9(b)) where paper P can be transported by the reverse pull-in roller pair 55. In other words, the second position P2 can be said to be a position where paper P can be transported by the reverse pull-in roller pair 55.

[0026] Furthermore, the reversing / duplex conveying guide sensor 92 detects the presence or absence of paper P at a first detection position 92A between the second reversing / duplex roller pair 51B and the retraction section 90. In other words, the reversing / duplex sensor 91 is located upstream of the reversing / duplex conveying guide sensor 92 in the first direction A, which is the conveying direction of paper P, and is disposed on the image forming section 100A side. The reversing / duplex conveying guide sensor 92 also detects a sheet at a first position P1 (see FIG. 9(b)) where the sheet can be conveyed by either the first reversing / duplex roller pair 51A or the second reversing / duplex roller pair 51B. In other words, the first position P1 can be said to be a position where paper P can be conveyed by the first reversing / duplex roller pair 51A and the second reversing / duplex roller pair 51B.

[0027] The double-sided conveying unit 60 includes a pair of double-sided conveying rollers 61 for conveying the paper P, and a conveying path 62 as a third conveying path for re-conveying the paper P reversed by the reversing unit 50 to the image forming section 100A.

[0028] The control unit 80 incorporates a CPU 111 as a control section. The CPU 111 controls the various mechanisms in the above-mentioned units to perform various operations.

[0029] The evacuation section 90 is configured to evacuate the leading edge (trailing edge after inversion) of the sheet P inverted by the reversing unit 50, and is configured to be able to evacuate sheets that have become stuck in the transport path when a paper jam occurs, as will be described later. That is, the evacuation section 90 is connected to the transport path 52 of the reversing unit 50 and is provided so as to be close to the reversing unit 50. The evacuation section 90 includes a paper stopper 90Y and a paper stopper 90X. The leading edge of the sheet P in the transport direction that is discharged into the evacuation section 90 abuts against the paper stopper 90Y. The paper stopper 90X abuts against the other end of the sheet P that has bounced off after abutting against the paper stopper 90Y, thereby stopping the sheet P.

[0030] Next, the control configuration of image forming apparatus 100 will be described. FIG. 2 is a block diagram showing the control configuration of the image forming apparatus of FIG. 1. In FIG. 2, image forming apparatus 100 includes a CPU 111 as a control unit. CPU 111 is connected to operation unit 105, image memory 107, ROM 108, and RAM 112. CPU 111 is also connected to reverse / duplex drive motor 93, reverse / duplex flapper solenoid 95, reverse / duplex sensor 91, and reverse / duplex conveyance guide sensor 92. CPU 111 is also connected to pickup motor 94, manual pickup motor 98, reverse retraction drive motor 99, and conveyance sensor 106. CPU 111 centrally controls each unit of image forming apparatus 100 and executes various processes by loading various programs stored in ROM 108 into RAM 112.

[0031] The operation unit 105 includes a key operation unit having various keys, accepts various operation inputs (single-sided / double-sided printing mode, reverse discharge mode, paper size, paper basis weight, number of prints, etc.) to the key operation unit by the user, and outputs the input operation signals to the CPU 111. The operation unit 105 is provided with a display unit for notifying the user of various information. The operation unit 105 is also provided with a setting unit for the user to set the size of the paper P. The image memory 107 is a storage unit that temporarily stores information such as image data received from an external device. The ROM 108 is a storage unit that is dedicated to reading information.

[0032] The pickup motor 94 receives a drive signal from the CPU 111 to drive the pickup roller 22 and feed the paper P from the cassette 21. In addition, the manual feed pickup motor 98 receives a drive signal from the CPU 111 to drive the manual feed pickup roller 96 and feed the paper P from the manual feed tray 97.

[0033] The reverse / duplex sensor 91 is, for example, an optical sensor equipped with a light-emitting element and a light-receiving element. It detects the presence, trailing edge, and leading edge of a sheet P being conveyed by the reversing unit 50 at a second detection position 91A on the conveying path 52, and outputs the detection results to the CPU 111. That is, the optical sensor has a light-emitting element that irradiates light onto the sheet in the retraction section and a light-receiving element that receives light reflected from the sheet. The optical sensor detects whether a sheet is present at the second detection position 91A on the conveying path 52, which is the detection position of the reverse / duplex sensor 91, and outputs the detection results to the CPU 111. The CPU 111, upon receiving the detection results, expands and stores the detection results in the RAM 112. Similarly, the reverse / duplex conveying guide sensor 92 is, for example, an optical sensor equipped with a light-emitting element and a light-receiving element. This optical sensor also detects the presence, trailing edge, and leading edge of a sheet P being conveyed by the reversing unit 50 at a first detection position 92A on the conveying path 52, and outputs the detection results to the CPU 111.

[0034] The reverse pull-in drive motor 99 receives information necessary for driving, such as a CW / CCW rotation signal and a drive start signal, from the CPU 111, and drives the reverse pull-in roller pair 55. Similarly, the reverse / duplex drive motor 93 receives information necessary for driving, such as a CW / CCW rotation signal and a drive start signal, from the CPU 111, and drives the reverse / duplex roller pair 51. The reverse / duplex flapper solenoid 95 operates the reverse / duplex flapper 54 to switch the destination of the paper P.

[0035] [Image formation operation] Next, the operation of the image forming apparatus 100 according to this embodiment will be described. When an operation start signal for starting the image forming operation is issued, first, the pickup roller 22 feeds out the paper P one sheet at a time from the cassette 21. Next, the conveyance roller pair 23 guides the paper P along the conveyance path 24, conveying the paper P through the pre-registration roller pair 27 to the registration roller pair 26. At this time, the registration roller pair 26 is stopped. The paper P that comes into contact with the stopped registration roller pair 26 forms a loop (flexure), thereby correcting any skew of the paper P. Thereafter, the registration roller pair 26 starts rotating in synchronization with the timing at which an image is formed by the image forming unit 10. The timing at which the registration roller pair 26 starts rotating is set so that the paper P and the toner image transferred from the image forming unit 10 onto the intermediate transfer belt 31 are aligned in the secondary transfer area Te.

[0036] Meanwhile, in the image forming unit 10, when an operation start signal for starting an image forming operation is issued, the toner image formed on the photosensitive drum 11d located most upstream in the rotation direction of the intermediate transfer belt 31 through the above-described process is transferred to the intermediate transfer belt 31. That is, a high voltage for transfer is applied to the primary transfer roller 35d disposed opposite the photosensitive drum 11d, so that the toner image formed on the photosensitive drum 11d is transferred to the intermediate transfer belt 31 in the primary transfer region Td.

[0037] The toner image transferred onto the intermediate transfer belt 31 is transported to the next primary transfer region Tc. An image is formed on the photosensitive drum 11c with a delay compared to the time it takes for the toner image to be transported between the image forming units, and the toner image on the photosensitive drum 11c is transferred in registration onto the previous toner image transferred onto the intermediate transfer belt 31. Thereafter, the same process is repeated, and the four color toner images formed on the photosensitive drums 11d to 11a are transferred onto the intermediate transfer belt 31 so as to be superimposed on each other.

[0038] Thereafter, when the paper P enters the secondary transfer area Te and comes into contact with the intermediate transfer belt 31, a high voltage is applied to the outer secondary transfer roller 36 in time with the passage of the paper P. When a high voltage is applied to the outer secondary transfer roller 36, the toner image formed on the intermediate transfer belt 31 is transferred to the surface of the paper P. The paper P onto which the toner image has been transferred is transported by the transport path 43 to a nip portion between the fixing roller 41a and the pressure roller 41b of the fixing unit 40. The toner image is then fixed to the surface of the paper P by the heat and nip pressure of the fixing roller 41a and the pressure roller 41b.

[0039] The paper P with the fixed toner image is sent out by the pair of inner discharge rollers 71. During single-sided printing or after printing on the back side during double-sided printing, the flapper 73 operates to guide the paper P toward the conveyance path 74 where the pair of outer discharge rollers 72 are located, and the pair of outer discharge rollers 72 discharges the paper P from the image output unit 100P to the outside. On the other hand, during a reverse discharge job or when an image is formed on the back side of the paper P after printing on the front side of a double-sided printing job, the flapper 73 operates to guide the paper P toward the conveyance path 75 where the reversing unit 50 is located.

[0040] The paper P drawn into the reversing unit 50 is drawn into the conveying path 52 by the reversing and drawing-in roller pair 55, the first reversing and double-sided roller pair 51A, and the second reversing and double-sided roller pair 51B. Then, when the rear end of the paper P is detected by the reversing and double-sided sensor 91, the conveying of the paper P is temporarily stopped. After that, in the case of reverse discharge, the reversing and drawing-in roller pair 55, the first reversing and double-sided roller pair 51A, and the second reversing and double-sided roller pair 51B rotate in the reverse direction, and the discharge flapper 53 is operated to convey the paper P along the conveying path 76 toward the external discharge roller pair 72. The paper P conveyed to the external discharge roller pair 72 is discharged outside the image output section 100P.

[0041] On the other hand, in the case of a double-sided printing job, the paper P is conveyed in the direction of the conveying path 62 where the double-sided conveying unit 60 is located by the operation of the reversing / double-sided flapper 54. The paper P guided to the conveying path 62 of the double-sided conveying unit 60 is conveyed by the pair of double-sided conveying rollers 61 and merges with the conveying path 24 of the feeding unit 20 used for front-side printing. An image is then formed on the back side of the paper P through a process similar to that for front-side printing. In this way, the paper P with images formed on both sides is then discharged to the outside of the image output section 100P by the pair of external discharge rollers 72.

[0042] [Operation of Reversing Unit 50] 3 is a timing chart of the reverse / duplex sensor 91, reverse / duplex drive motor 93, reverse retraction drive motor 99, and reverse / duplex flapper solenoid 95 in a reverse / duplex print job. In Fig. 3, when paper P is first transported into the reverse unit 50, the reverse / duplex flapper solenoid 95 (i.e., the reverse / duplex flapper 54) is in the home position (HP). That is, the reverse / duplex flapper solenoid 95 is OFF, and the reverse / duplex flapper 54 is switched to a position that forms a flow path facing downward (first direction A) in Fig. 1 for transporting paper P to the transport path 52.

[0043] In this state, the CPU 111 outputs a drive ON signal and a rotation direction CW signal to the reverse / double-sided drive motor 93 and the reverse / pull-in drive motor 99. These signals rotate the reverse / pull-in roller pair 55, the first reverse / double-sided roller pair 51A, and the second reverse / double-sided roller pair 51B, and downward transport of the paper P in the first direction A begins.

[0044] After time t1 from when the reverse / duplex drive motor 93 and reverse / retract drive motor 99 start to drive, the reverse / duplex sensor 91 detects the leading edge of the sheet of paper P and turns ON. After that, after time t2, the reverse / duplex sensor 91 detects the trailing edge of the sheet of paper P and turns OFF. After time t3 from when the reverse / duplex sensor 91 detects the trailing edge of the sheet of paper P, the drive of the reverse / duplex drive motor 93 and reverse / retract drive motor 99 stops. This stops the rotation of the reverse / retract roller pair 55, the first reverse / duplex roller pair 51A, and the second reverse / duplex roller pair 51B.

[0045] During the time t4 during which the reverse / duplex drive motor 93 is stopped, the reverse / duplex flapper solenoid 95 is turned ON, and the reverse / duplex flapper 54 switches to the direction in which it guides the paper P to the transport path 62 of the duplex transport unit 60. With the reverse / duplex flapper solenoid 95 in the ON state, the CPU 111 outputs a drive ON signal and a rotation direction CCW signal to the reverse / duplex drive motor 93. In response to these signals, the paper P is transported in the second direction B by the first reverse / duplex roller pair 51A and the second reverse / duplex roller pair 51B, and is transported toward the duplex transport unit 60.

[0046] After the reverse / duplex drive motor 93 starts to rotate, the reverse / duplex sensor 91 detects the leading edge of the sheet P t5 later. After detecting the leading edge, the reverse / duplex sensor 91 detects the trailing edge of the sheet P t6 later and turns OFF. After the reverse / duplex sensor 91 turns OFF, the drive of the reverse / duplex drive motor 93 stops and the rotation of the reverse / duplex roller pair 51 stops t8 later. After the drive of the reverse / duplex drive motor 93 stops, the reverse / duplex flapper solenoid 95 turns OFF and the reverse / duplex flapper 54 returns to its initial state, forming a flow path for transporting the sheet P in the first direction A.

[0047] [Paper ejection process when a paper jam occurs] Next, a case where a paper jam occurs in the pair of external discharge rollers 72 and the conveying path 74, or in a processing device such as a finisher, binding device, or cutting device connected to the conveying path 74 will be described. In other words, the discharge process when the pair of external discharge rollers 72 and the conveying path 74 become unusable and the conveying paths 75 and 52 are usable will be described with reference to FIGS.

[0048] (Outline of the ejection process) First, an overview of the operation of retracting paper P (hereinafter referred to as "retained paper Pt") retained inside image forming apparatus 100 to retract section 90 when a paper jam such as the one described above occurs will be described with reference to Figure 7. Figure 7(a) is a diagram showing the position of the retained paper when a paper jam occurs during discharge processing, and Figure 7(b) is a diagram showing the state when discharge of the retained paper has begun during discharge processing. Also, Figure 7(c) is a diagram showing the state when the retained paper has been discharged to the retract section during discharge processing, and Figure 7(d) is a diagram showing the state when the last retained paper has stopped at the detection position of the reversing / duplex conveying guide sensor during discharge processing.

[0049] First, we will roughly explain the operation when a paper Pt is stuck in the transport path 75 and transport path 52 from the fixing unit 40 to the reversing / duplex sensor 91 of the reversing unit 50. As shown in FIG. 7A, when a paper jam occurs that disables the outer discharge roller pair 72 and the transport path 74, the stuck paper Pt is stuck in the transport path 75 and transport path 52. In this case, as shown in FIG. 7B, the stuck paper Pt in the transport path 75 and transport path 52 is transported in the first direction A (downward in the figure) by the inner discharge roller pair 71, the reversing pull-in roller pair 55, the first reversing / duplex roller pair 51A, and the second reversing / duplex roller pair 51B. Then, as shown in FIG. 7C, all the stuck paper Pt sent to the second reversing / duplex roller pair 51B is ejected to the evacuation section 90 and stacked. This prevents stuck paper Pt from being left scattered in various places when a paper jam occurs, simplifying the user's recovery work.

[0050] Incidentally, the evacuation section 90 is not provided with a sensor or the like for detecting the presence or absence of paper P for the purpose of reducing costs, etc. Therefore, if all of the retained sheets Pt are discharged to the evacuation section 90 as shown in FIG. 7(c), it may not be possible to detect whether or not there are retained sheets Pt in the evacuation section 90. For example, if the power is turned off and the RAM 112 is erased, there is a risk that the sensor will not be able to detect the retained sheets P. Therefore, as shown in FIG. 7(d), the last sheet of the retained sheets Pt is stopped at the detection position (first detection position 92A) of the reversing / duplex conveying guide sensor 92 on the conveying path 52. In this way, even if the retained sheets P in the evacuation section 90 cannot be detected, the retained sheets P can be detected by the reversing / duplex conveying guide sensor 92, and the user can be notified that there are retained sheets P in the evacuation section 90 and the reversing unit 50. However, if a paper jam occurs again and the retained paper Pt cannot be stopped at the detection position of the reverse / duplex conveying guide sensor 92, it may not be possible to detect the retained paper P and to issue such a notification. Therefore, in this embodiment, the discharge process is performed as follows.

[0051] (Details of ejection process when paper jam occurs) Next, in this embodiment, a paper jam occurs during a printing operation, and the discharge process for discharging the accumulated paper Pt to the evacuation section 90 will be described using FIGS. 4, 5, 6, 8, 9, and 10. FIG. 4 is a flowchart showing control of the printing operation according to this embodiment. FIG. 5 is a flowchart showing control of the operation for determining the number of sheets to be evacuated in the discharge process according to this embodiment, and FIG. 6 is a flowchart showing control of the evacuation and discharge operation in the discharge process according to this embodiment. FIG. 8 is a schematic diagram showing the position of paper when a paper jam occurs. FIG. 9(a) is a diagram showing a state in which the preceding paper has stopped at the first position, and FIG. 9(b) is a diagram showing a state in which the succeeding paper has been transported to the second position. FIG. 9(c) is a diagram showing a state in which the discharge of the preceding paper has begun, and FIG. 9(d) is a diagram showing a state in which the transport of the succeeding paper has begun. Finally, FIG. 10 is a diagram showing an example of a notification screen.

[0052] <Printing operation> 4, when a print job is input by operating the operation unit 105, for example, the CPU 111 starts controlling the printing operation. Then, first, it monitors whether a paper jam has occurred (S1), and while a paper jam has not occurred (N in S1), it repeats this monitoring until the final sheet of paper has been output to the outside (N in S2). Thereafter, when no paper jam has occurred (N in S1) and the final sheet of paper in the print job has been output to the outside (Y in S2), the printing operation ends.

[0053] On the other hand, if a paper jam is detected during printing (Y at S1), the process proceeds to step S3, where a process for discharging the retained paper Pt to the evacuation section 90 is executed when a paper jam occurs. This discharge process can be considered a separate discharge mode in which paper inside the device is discharged to the evacuation section 90, separate from the mode in which normal discharge is performed from the pair of external discharge rollers 72 when no paper jam has occurred. The discharge process of step S3 will be described in detail later. Thereafter, the process proceeds to step S4, where a screen indicating a paper jam is displayed on the operation unit 105, such as a screen as shown in FIG. 10 , urging the user to remove the retained paper Pt stacked in the evacuation section 90, and the printing operation is interrupted or terminated.

[0054] <Discharge processing> When the discharge process of step S3 above is started (when the discharge process of step S3 is being executed), CPU 111 proceeds to step S11, as shown in Fig. 5. In step S11, of the sheets of paper remaining inside image forming apparatus 100, those sheets of paper to be evacuated to evacuation section 90 and those sheets of paper to be stopped in place without being evacuated are sorted. In other words, when a paper jam occurs, CPU 111 executes a process for determining whether or not to evacuate each sheet of paper to evacuation section 90. The order in which it is determined whether or not to evacuate each sheet of paper to evacuation section 90 is the order in which the sheets are scheduled to be discharged, which is the order of sheets of paper 751, 752, 753, 754, and 755 in the example shown in Fig. 8.

[0055] Specifically, CPU 111 manages the position of retained paper inside image forming apparatus 100 based on the elapsed time since detection by each transport sensor. When transport sensor 106 located near pair of external discharge rollers 72 serving as a discharge section detects a paper jam in retained paper 751, CPU 111 determines that retained paper 751 is not to be transported to evacuation section 90 because it has passed through the branching section (flapper 73) of transport path 75 to evacuation section 90. On the other hand, CPU 111 determines that retained paper 752, 753, 754, and 755 are to be transported to evacuation section 90, and performs transport to evacuation section 90 as described below.

[0056] In step S11, CPU 111 generates data in RAM 112 for counter N, which represents the number of sheets remaining in the apparatus, and executes loop processing by repeating this process until counter N reaches 0 in step S12. That is, in this loop processing, the data in counter N is decremented by -1 for each process in step S16, and processing for N sheets is executed by determining whether counter N is greater than 0 in step S12. In accordance with the example in Figure 8, when processing for stuck paper 751 is executed, counter N=5, for stuck paper 752 counter N=4, for stuck paper 753 counter N=3, for stuck paper 754 counter N=2, and for stuck paper 755 counter N=1. When processing for stuck paper 755 is completed, counter N=0 (N in S12) and the loop processing ends.

[0057] 8, the CPU 111 first sets the counter N for the number of retained sheets to 5, generates data for the counter M for the number of saved sheets in the RAM 112, and sets the initial value of the counter M for the number of saved sheets to 0 (S11). Since N>0 in step S12 (Y in S12), the CPU 111 determines that there is paper to be processed, and executes loop processing.

[0058] In step S13, CPU 111 determines whether the retained paper is to be retracted to retraction section 90 or not, based on the determination conditions in the example of FIG. 8 as described above. If CPU 111 determines that the retained paper is to be discharged to retraction section 90 (e.g., retained paper 752, 753, 754, 755 in FIG. 8) (Y in S13), it increments counter M for the number of retained sheets by +1 (S14). On the other hand, if CPU 111 determines in step S13 that the retained paper is not to be retracted (e.g., retained paper 751 in FIG. 8) (N in S13), it stops the retained paper in place (S15). In the example of FIG. 8, retained paper 751 is stopped by stopping pair of outer discharge rollers 72 (see FIG. 1). Next, in step S16, CPU 111 decrements counter N for the number of retained sheets by -1, and returns to step S12. In step S12, when counter N is no longer > 0 and judgment has been completed for all the retained sheets (N in S12), step S17 judges whether the counter M for the number of sheets to be evacuated is > 0 (i.e., whether there are any retained sheets to be evacuated). If the counter M for the number of sheets to be evacuated is > 0 and there are retained sheets to be evacuated, the process proceeds to step S21 in Fig. 6. If there are no retained sheets to be evacuated, the process proceeds to step S18, where the discharge process ends.

[0059] As described above, the counter M for the number of sheets to be evacuated is set by executing the flowchart shown in Fig. 5, that is, the control of the operation for determining the number of sheets to be evacuated is completed. When the control of the operation for determining the number of sheets to be evacuated in Fig. 5 is completed, the control shifts to the control of the evacuation and discharge operation for discharging the sheets to the evacuation section 90 shown in Fig. 6.

[0060] 6, when the CPU 111 proceeds to step S21, it first turns off the reversing / duplexing flapper solenoid 95. That is, in order to transport the retained paper to the retraction section 90 via the reversing unit 50, it switches the flapper 73 so that the destination is the transport path 75. Next, in step S22, it drives the reversing pull-in drive motor 99 CW to rotate the reversing pull-in roller pair 55, thereby starting transport of the retained paper in the reversing unit 50. Then, in step S23, it acquires the drive start time T_ON, which is the timing at which transport started.

[0061] Next, it is determined whether the reverse / duplex sensor 91 is ON (S24). If the reverse / duplex sensor 91 is not ON (N in S24), it is determined whether Tj time has elapsed since the drive start time T_ON (S25). The Tj time is set to a value greater than the value obtained by dividing the transport distance from the transport start position to the reversing unit 50 until the reverse / duplex sensor 91 turns ON by the transport speed. If Tj time has not elapsed since the drive start time T_ON (N in S25), the process returns to step S24 and repeats the determination of whether the reverse / duplex sensor 91 is ON. If the reverse / duplex sensor 91 turns ON before Tj time has elapsed since the drive start time T_ON (Y in S24), it is determined that a paper jam did not occur in the reversing unit 50 before the retained paper reached the reverse / duplex sensor 91 and that the retained paper was transported normally. Then, the process proceeds to step S26 and subsequent steps. On the other hand, if the reverse / double-sided sensor 91 is not ON and the time Tj has elapsed since the drive start time T_ON (Y in S25), it is determined that a paper jam occurred in the reversing unit 50 before the retained paper reached the reverse / double-sided sensor 91. If a paper jam occurs in this way, the retained paper cannot be discharged to the evacuation section, and therefore this discharge process is terminated.

[0062] When the retained paper is transported and the reverse / double-sided sensor 91 is turned ON, the reverse / retraction drive motor 99 is stopped, and the reverse / retraction roller pair 55 is stopped (S26). As a result, the retained paper to be discharged to the retraction section 90 is temporarily stopped at the second position P2 (see FIG. 9(b)) that can be detected by the second detection position 91A of the reverse / double-sided sensor 91 before it reaches the first reverse / double-sided roller pair 51A. By stopping the retained paper at this second position P2, the retained paper is prevented from being transported even if the first reverse / double-sided roller pair 51A rotates.

[0063] Next, the reverse / duplex drive motor 93 starts to drive in the clockwise direction, rotating the first reverse / duplex roller pair 51A and the second reverse / duplex roller pair 51B (S27). Here, it is determined whether the reverse / duplex conveying guide sensor 92 is already ON (S28). If the reverse / duplex conveying guide sensor 92 is ON (Y in S28), it is determined that the preceding retained sheet is already waiting in front of (near) the retraction section 90 on the conveying path 52. In this case, the preceding retained sheet waiting at the first position P1 (see FIG. 9B) detected by the first detection position 92A of the reverse / duplex conveying guide sensor 92 must be ejected before the succeeding retained sheet at the second detection position 91A (second position P2) of the reverse / duplex sensor 91 can be conveyed. Therefore, the process proceeds to step S29 while the first reverse / duplex roller pair 51A and the second reverse / duplex roller pair 51B are still rotating.

[0064] In step S29, the process waits until the reverse / duplex conveying guide sensor 92 turns OFF (N in S29). If the reverse / duplex conveying guide sensor 92 turns OFF (Y in S29), it is determined that the rotation of the first reverse / duplex roller pair 51A and the second reverse / duplex roller pair 51B has caused the preceding retained paper to be discharged to the evacuation section 90. Therefore, the counter M for the number of evacuated sheets is decremented by -1.

[0065] In this way, if there is already a preceding retained sheet in front of the evacuation section 90, it is possible to discharge the preceding retained sheet into the evacuation section 90 after confirming that the succeeding retained sheet has approached the transport path of the evacuation section 90. Then, once the preceding retained sheet has been discharged into the evacuation section 90, the reversing and retracting drive motor 99 starts to be driven CW, and the pair of reversing and retracting rollers 55 starts to rotate (S31). This causes the succeeding retained sheet waiting at the second position P2 to start being transported toward the first position P1.

[0066] On the other hand, in step S28, if the reverse / duplex conveying guide sensor 92 is OFF (N in S28), there is no preceding retained paper, so the reverse pull-in drive motor 99 is driven CW to start rotating the reverse pull-in roller pair 55 (S31), which similarly starts conveying the retained paper waiting at the second position P2 toward the first position P1.

[0067] Next, the process waits until it is determined whether the reverse / duplex conveying guide sensor 92 has turned ON (N in S32). If the reverse / duplex conveying guide sensor 92 has turned ON (Y in S32), the reverse / duplex drive motor 93 is stopped, thereby stopping the reverse / duplex roller pair 51 (S33). This allows the retained paper to be stopped at the first position P1 that can be detected by the first detection position 92A of the reverse / duplex conveying guide sensor 92, meaning that the following retained paper is set as the preceding retained paper.

[0068] Next, it is determined whether the counter M for the number of retracted sheets is 1 (S34). If the counter M for the number of retracted sheets is not 1 (N in S34), the retained sheet currently stopped at the detection position of the reversing / duplex conveying guide sensor 92 is not the last sheet yet to be discharged among the retained sheets that can be discharged, so the process returns to step S23 and repeats the same control. If the counter M for the number of retracted sheets is 1 (Y in S34), the retained sheet currently stopped at the detection position of the reversing / duplex conveying guide sensor 92 is the last sheet yet to be discharged among the retained sheets that can be discharged, so the discharge process ends. This allows the discharge process to end with the last sheet of the retained sheets remaining stopped at the first position P1.

[0069] <Movement of retained paper due to main discharge process> Next, the behavior of the retained sheets during the discharge process described above will be explained using Figures 9(a) to 9(d). When this discharge process is executed, the retained sheets 752 to 755 begin to be transported to the reversing unit 50 in order to be discharged to the retraction section 90. First, as shown in Figure 9(a), retained sheet 752, which is the first to be discharged, stops at first position P1, where it can be detected by first detection position 92A of reversing / duplex conveying guide sensor 92 (S21 to S27, N in S28, S31 to S33). Next, as shown in Figure 9(b), while retained sheets 753 to 755 are transported to the reversing unit 50, retained sheet 753, which is discharged into the retraction section 90 after retained sheet 752, reaches second position P2, where it can be detected by second detection position 91A of reversing / duplex sensor 91 (S23, Y in S24).

[0070] The fact that the retained sheet 753 has reached the reverse / double-sided sensor 91 means that the retained sheet 753 has been transported normally without jamming and has approached the retained sheet 752 at first position P1. As a result, even if the preceding retained sheet 752 has been discharged, the succeeding retained sheet 753 can be transported to first position P1. Therefore, as shown in FIG. 9C, the discharge of the preceding retained sheet 752 begins (transport starts) (Y in S28, S29, S30). After the discharge of the retained sheet 752 has progressed to a certain extent, transport of the succeeding retained sheet 753, which was at second position P2, is resumed (transport starts) toward first position P1 (S31, S32), as shown in FIG. 9D. As a result, the leading retained paper 752 is discharged to the retraction section 90, and the trailing retained paper 753 becomes the retained paper leading to the retained paper 754, and is stopped at the first position P1 (S33).

[0071] Similarly, the following retained paper 754 is transported to the reversing unit 50, and the relationship between retained paper 752 and retained paper 753 in FIG. 9(a) becomes the relationship between retained paper 753 and retained paper 754. When retained papers 752 to 755 are transported sequentially in this manner, if the preceding retained paper reaches first position P1 when the following retained paper is transported to the reversing unit 50, that retained paper is temporarily stopped. After that, the following retained paper is transported into the reversing unit 50 without any problems, and after confirming that it has been detected by the reversing / double-sided sensor 91, the preceding retained paper is discharged to the evacuation section 90. By repeating these operations, the retained paper is sequentially discharged while the retained paper remains at first position P1.

[0072] The discharge process (S3) ends with retained paper 755, the last paper, remaining at first position P1. At this time, CPU 111, in response to detecting retained paper 755 at first position P1 by reversing / duplex conveying guide sensor 92, displays a screen such as that shown in Fig. 10 on operation unit 105. That is, the user is notified to remove retained paper 752-754 discharged to retraction section 90 and retained paper 755 remaining in reversing unit 50 (S4). The user is prompted to remove the retained paper by viewing the display of Fig. 10.

[0073] As described above, in a configuration in which the retraction section 90 does not have a sensor for detecting paper, suppose that a further paper jam occurs while the retained paper is being discharged to the retraction section 90. Even in this state, one of the retained sheets can be left at the first position P1, which is located immediately in front of (near) the retraction section 90, and the retained paper can be reliably left at the first position P1. This solves the problem of not being able to notify the user to remove the retained paper when a further paper jam occurs, and makes it possible to reliably notify the user to remove the retained paper.

[0074] [Possibilities for other embodiments] In the embodiment described above, the preceding retained paper is stopped temporarily at the first position P1, and conveyance of the succeeding retained paper begins when the succeeding retained paper reaches the second position P2. This allows the preceding retained paper to be discharged only after the succeeding retained paper has been reliably conveyed to the second position P2. However, this is not limiting, and the preceding retained paper may be configured to stop only when the succeeding retained paper cannot be detected. This allows the discharge process of the retained paper to be completed more quickly.

[0075] In addition, in this embodiment, the following stuck paper is detected at the second position P2, and the conveyance of the following stuck paper is started after the conveyance of the preceding stuck paper has started. This reliably prevents the following stuck paper from catching up with and interfering with the preceding stuck paper. However, the conveyance of the preceding stuck paper and the following stuck paper may start simultaneously, and further, the conveyance of the following stuck paper may start earlier than the conveyance of the preceding stuck paper, as long as the following stuck paper does not catch up with the preceding stuck paper. This allows the discharge process of the stuck paper to be completed more quickly.

[0076] In addition, in the present embodiment, when the transport path 74 is unavailable, the retained paper is discharged to the evacuation section 90, which evacuates the paper to be reversed by the reversing unit 50. However, this is not limited to this, and the discharge process of this embodiment can be performed in the same way in a case where there are multiple discharge destinations for paper, such as when there are multiple discharge trays, and when one transport path is unavailable, another available transport path is used for discharge.

[0077] Furthermore, in the present embodiment, the sheets have been described as paper or retained paper, but the type of sheet may be any type and is not limited to paper as a material.

[0078] In addition, in the present embodiment, the image forming apparatus has been described as a full-color electrophotographic type, but it is not limited to this, and any type of image forming apparatus may be used, such as a monochrome printer, an inkjet printer, etc. Furthermore, although the image forming apparatus has been described as being equipped with a discharge section and a stacking section, a processing apparatus such as a finisher, a punching device, a binding device, or a folding device may also be equipped with a discharge section and a stacking section. In this case, the image forming apparatus can be considered to be equipped with a processing apparatus.

[0079] The present disclosure can also be realized by providing a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0080] 50...Reversing unit (sheet conveying section, reversing section) / 51A...First reversing / duplex conveying roller pair (first conveying section, first roller) / 51B...Second reversing / duplex conveying roller pair (first conveying section, first roller) / 52...Conveying path (second conveying path) / 53...Discharge flapper (third branching section) / 54...Duplex flapper (second branching section) / 55...Reversing pull-in roller pair (second conveying section, second roller) / 62...Conveying path (third conveying path) / 72...External discharge roller (discharge section) / 73...Flapper (first branching section) / 74...Conveying path (first conveying path) / 75...Conveying path ( 2nd conveyance path) / 76... conveyance path (4th conveyance path) / 90... evacuation section (loading section) / 91... reversing / duplex sensor (2nd sheet detection section) / 92... reversing / duplex conveyance guide sensor (1st sheet detection section) / 93... duplex drive motor (first drive source) / 99... reversing / retraction drive motor (second drive source) / 100... image forming device / 100A... image forming section / 105... operation section (display section) / 111... CPU (control section) / A... first direction / B... second direction / P... paper (sheet) / P1... first position / P2... second position / S3... discharge process (separate discharge mode)

Claims

1. an image forming unit that forms an image on a sheet; a discharge section that discharges a sheet on which an image has been formed by the image forming section to the outside; a first conveying path that conveys a sheet on which an image is formed by the image forming unit to the discharge unit; a second conveying path branched off from the first conveying path at a first branching portion; a sheet conveying unit that conveys the sheet in the second conveying path; a stacking section for stacking the sheets discharged from the second conveying path; a first sheet detection unit that detects a sheet located at a first position of the second transport path; a second sheet detection unit that detects a sheet located at a second position upstream of the first position in a sheet conveying direction in the second conveying path; a control unit that executes a separate discharge mode in which a plurality of sheets inside the device are discharged to the stacking unit when a paper jam occurs during sheet conveyance, and ends the separate discharge mode in a state in which the sheets are left at the first position, When the second sheet detection unit detects that there is a subsequent sheet at the second position during execution of the separate discharge mode, the control unit causes the sheet conveying unit to discharge the preceding sheet at the first position to the stacking unit and convey the subsequent sheet at the second position to the first position.

1. An image forming apparatus comprising:

2. The control unit, during execution of the separate discharge mode, stops the conveyance of the preceding sheet when the first sheet detection unit detects that the preceding sheet has been conveyed to the first position, and resumes the conveyance of the preceding sheet at the first position and discharges it to the stacking unit when the second sheet detection unit detects that a subsequent sheet is at the second position.

2. The image forming apparatus according to claim 1,

3. a reversing unit that is disposed on the second conveying path, conveys the sheet on which the image is formed by the image forming unit in a first direction, and then conveys the sheet in a second direction opposite to the first direction, thereby reversing the sheet; the sheet conveying unit is the inversion unit, the stacking unit is a retracting unit that retracts a leading end of the sheet in the first direction to be inverted by the inverting unit, 3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. a third conveying path that branches off from the second conveying path at a second branching portion and conveys the sheet that has been inverted by the inverting portion back to the image forming portion; The inversion portion is a first conveying section disposed downstream of the second branching section in the first direction and capable of conveying a sheet in the first direction and the second direction; A first driving source that drives the first transport unit; a second conveying section disposed in the second conveying path upstream of the second branching section in the first direction and capable of conveying a sheet in the first direction; a second drive source that drives the second transport unit, the first position is a position where the sheet can be transported by the first transport unit, the second position is a position where the sheet can be transported by the second transport unit; 4. The image forming apparatus according to claim 3.

5. a fourth conveying path that branches off from the second conveying path at a third branching portion and conveys the sheet that has been inverted by the inverting portion to the discharge portion; the second transport section is disposed downstream of the third branch section in the first direction and is capable of transporting the sheet in the second direction to the fourth transport path; 5. The image forming apparatus according to claim 4.

6. The first conveying unit is a first roller disposed downstream of the second branch portion in the first direction; a second roller disposed downstream of the first roller in the first direction and configured to discharge the sheet onto the stacking portion; 6. The image forming apparatus according to claim 4, wherein the image forming apparatus is a multi-color image forming apparatus.

7. A display unit for displaying an image is provided, and after the separate discharge mode is stopped, in response to detection of a sheet by the first sheet detection unit, the control unit causes the display unit to display a message prompting the user to remove the sheets stacked on the stacking unit.

7. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: a first fixing member;

8. The control unit executes the separate discharge mode when the discharge unit is unavailable and the second conveying path is available.

8. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:

Images