Sheet inversion device and image forming apparatus

Abstract

To prevent a user from forgetting to remove a stored sheet.SOLUTION: A sheet reversing device 200 includes a pair of reversing rollers 230 that conveys a sheet P in the forward direction when an abnormality occurs during a conveyance of the sheet P and nips the last sheet P by stopping the conveyance of the last sheet P among the sheets P conveyed in the forward direction, a reversing and retreating portion 210 that stores the sheet conveyed in the forward direction by the pair of reversing rollers 230 when a conveyance abnormality occurs, and a conveyance sensor 229 that detects the last sheet P nipped by the pair of reversing rollers 230.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sheet reversing device and an image forming apparatus.

Background Art

[0002] In an image forming apparatus such as a printer, a copier, or a multifunction peripheral, a reversing conveyance mechanism such as a pair of reversing rollers for performing reversing conveyance is provided to reverse a sheet used as a recording material for the purpose of double-sided printing or face-down discharging. In the case of double-sided printing, the sheet reversely conveyed by the pair of reversing rollers is re-fed to the image forming unit through the re-conveyance path for double-sided printing with the first side already image-formed and the second side to be image-formed reversed.

[0003] Patent Document 1 discloses an image forming apparatus having such a reversing conveyance mechanism or a re-conveyance path. When a sheet jam occurs during printing, the image forming apparatus according to Patent Document 1 collects and stores a plurality of sheets remaining in the apparatus in a reversing space provided in the reversing conveyance mechanism, and detects the stored sheets with a detection unit. Then, when the detection unit detects a sheet, the image forming apparatus according to Patent Document 1 displays on a display unit that there are sheets remaining in the reversing space.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, there are cases where the sheets stored in the reversing space cannot be detected by the detection unit. For example, when small-sized sheets are stored outside the detection range of the sensor, or when the stored sheets are curled or skewed and thus outside the detection range, they cannot be detected by the detection unit.

[0006] In the image forming apparatus of Patent Document 1, in such a case, since the sheet accommodated in the inversion space portion cannot be recognized, there is a problem that an operation for prompting the user to remove the sheet left in the apparatus cannot be performed. Further, when the user forgets to remove the sheet, the sheet remains in the apparatus. When the next printing operation is performed with the sheet remaining, there is a problem that the remaining sheet comes into contact with the sheet conveyed during the next printing operation, causing damage to the sheet.

[0007] An object of the present invention is to provide a sheet inversion device and an image forming apparatus capable of preventing forgetting to remove an accommodated sheet.

Means for Solving the Problems

[0008] The sheet inversion device according to the present invention Forward After conveying the sheet in a direction, in the forward and reverse directions The sheet By conveying, the sheet in the conveyance direction Is inverted is caused to An inversion roller pair, a support means for supporting the sheet to convey the sheet conveyed in the forward direction by the inversion roller pair in the reverse direction, and provided upstream or downstream in the forward direction of the inversion roller pair, by the inversion roller pair convey A detection means for detecting the sheet to be sent, and a control means for controlling the conveyance of the sheet by the inversion roller pair based on the detection result by the detection means, a sheet inversion device comprising The sheet feeder - When it occurs during the conveyance of the sheet paper jam When it occurs, the inversion roller pair conveys a plurality of sheets in the forward direction, and the control means The last sheet among the plurality of sheets sheets other than the sheet are discharged to the support means by the pair of reversing rollers, and the last sheet is in a state detected by the detection means, and Clamped by the inversion roller pair is made Controlling the inversion roller pair so as to stop in a state, characterized in that.

Effects of the Invention

[0009] According to the present invention, it is possible to prevent forgetting to remove an accommodated sheet.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described in detail with reference to the drawings.

[0012] (Embodiment 1) <Configuration of the Image Forming Apparatus> The configuration of the image forming apparatus 100 according to Embodiment 1 of the present invention will be described in detail with reference to FIG. 1.

[0013] The image forming apparatus 100 includes a housing 101, a control board storage unit 103, a feeding and conveying unit 110, an optical image processing unit 120, an optical image processing unit 121, an optical image processing unit 122, and an optical image processing unit 123. Further, the image forming apparatus 100 includes a secondary transfer unit 140, an intermediate transfer unit 152, a fixing processing unit 160, a discharging unit 170, an operation unit 180, a sheet reversing device 200, and a duplex conveying mechanism 220.

[0014] The optical image processing unit 120, the optical image processing unit 121, the optical image processing unit 122, the optical image processing unit 123, the secondary transfer unit 140, the intermediate transfer unit 152, the fixing processing unit 160, the discharging unit 170, the sheet reversing device 200, and the duplex conveying mechanism 220 constitute an engine unit. Further, the optical image processing unit 120, the optical image processing unit 121, the optical image processing unit 122, the optical image processing unit 123, the secondary transfer unit 140, and the intermediate transfer unit 152 constitute an image forming unit. The image forming apparatus 100 shown in FIG. 1 is exemplified as a laser beam printer here.

[0015] The housing 101 houses the control board storage unit 103 and the engine unit.

[0016] The control board storage unit 103 houses an engine control unit 103a and a printer controller 103b.

[0017] The engine control unit 103a performs serial communication with the printer controller 103b and controls the operation of the engine unit based on the instruction information input from the printer controller 103b.

[0018] The printer controller 103b expands the image data received from an external computer (not shown) into bit data necessary for image formation, outputs instruction information to the engine control unit 103a, comprehensively controls the engine control unit 103a, and executes a printing job. By executing the printing job, the printer controller 103b outputs image data to the laser scanner units 107 of the optical image processing units 120, 121, 122, and 123, respectively.

[0019] The paper feed and conveyance unit 110 includes a storage 110a and a main conveyance path 190, and conveys the sheet P stored in the storage 110a or the sheet P conveyed from the double-sided conveyance path 202 toward the secondary transfer unit 140.

[0020] The storage 110a stores the sheet P.

[0021] The main conveyance path 190 extends substantially horizontally in FIG. 1. The main conveyance path 190 is a conveyance path that reaches the discharge unit 170 from the paper feed and conveyance unit 110 via the secondary transfer unit 140 and the fixing processing unit 160.

[0022] Each of the optical image processing units 120, 121, 122, and 123 is a station that performs processes of charging, exposure, and development in the electrophotographic process to create a monochromatic visible image (toner image) on the intermediate transfer body 150. Each of the optical image processing units 120, 121, 122, and 123 includes a photosensitive drum 105, a laser scanner unit 107, a semiconductor laser 108, and a reflecting polygon mirror 109. Further, each of the optical image processing units 120, 121, 122, and 123 includes a primary charger 111 and a developing device 112.

[0023] The photosensitive drum 105 is attached to the housing 101 by an attachment member (not shown) and is rotationally driven.

[0024] The laser scanner unit 107 includes a laser driver (not shown) that controls the emission of laser light from the semiconductor laser 108 according to the image data input from the printer controller 103b.

[0025] The semiconductor laser 108 emits laser light to the reflection polygon mirror 109 under the control of the laser driver of the laser scanner unit 107.

[0026] The reflection polygon mirror 109 irradiates the photosensitive drum 105 with the laser light emitted from the semiconductor laser 108, and scans and exposes the photosensitive drum 105 in the main scanning direction with the laser light, thereby forming an electrostatic latent image on the photosensitive drum 105.

[0027] The primary charger 111 uniformly charges the photosensitive drum 105.

[0028] The developing device 112 supplies toner to the electrostatic latent image formed on the surface of the photosensitive drum 105 to form a toner image, thereby visualizing it.

[0029] The secondary transfer unit 140 secondarily transfers the toner image carried on the intermediate transfer member 150 to the sheet P. The secondary transfer unit 140 includes a secondary transfer roller pair 151.

[0030] The secondary transfer roller pair 151 is provided in the main conveyance path 190 and sandwiches the sheet P and the intermediate transfer member 150 conveyed in the main conveyance path 190. The secondary transfer roller pair 151 presses the sheet P against the intermediate transfer member 150 and applies a bias having a characteristic opposite to that of the toner, thereby performing secondary transfer to the sheet P. The secondary transfer roller pair 151 conveys the sheet P that has undergone secondary transfer toward the fixing unit 160.

[0031] The intermediate transfer unit 152 includes the intermediate transfer member 150. A toner image is primarily transferred from the photosensitive drums 105 of the optical image processing units 120, 121, 122, and 123 to the intermediate transfer member 150 to create a full-color toner image.

[0032] The fixing processing unit 160 performs a fixing process on the toner image transferred onto the sheet P conveyed from the secondary transfer roller pair 151 to fix the image on the sheet P, and conveys the sheet P with the image fixed thereto toward the discharge unit 170. The fixing processing unit 160 includes a heating roller 161 and a pressure roller 162 that sandwich and convey the sheet P, and a heat source (not shown) such as a halogen lamp that heats the toner image on the sheet P via the heating roller 161.

[0033] The discharge unit 170 distributes the sheet P with the image fixed thereto conveyed from the fixing processing unit 160 in the conveyance direction. The discharge unit 170 includes a discharge roller pair 171, a reverse entrance roller 172, a first switching flap 173, and a second switching flap 174.

[0034] The discharge roller pair 171 discharges the sheet P conveyed from the fixing processing unit 160 through the main conveyance path 190 to the outside of the image forming apparatus 100.

[0035] The reverse entrance roller 172 conveys the sheet P guided and conveyed by the first switching flap 173 toward the sheet reversing device 200.

[0036] The first switching flap 173, under the control of the engine control unit 103a, guides the sheet P conveyed from the fixing processing unit 160 through the main conveyance path 190 to the discharge roller pair 171 or to the second switching flap 174.

[0037] The second switching flap 174 is provided on the upstream side in the conveyance direction of the sheet P before the reverse conveyance than the reverse entrance roller 172. The second switching flap 174 guides the sheet P conveyed and guided to the first switching flap 173 by the control of the engine control unit 103a to the reverse entrance roller 172. Or, the second switching flap 174 guides the sheet P reversely conveyed from the sheet reversing device 200 to the discharge roller pair 171 when performing face-down discharge by the control of the engine control unit 103a. Here, face-down discharge means discharging the sheet with the surface on which the image is formed facing down in the case of single-sided printing.

[0038] The operation unit 180 includes a display device such as a liquid crystal panel for displaying information, and an input device such as a physical key or a touch panel through which a user can input commands or data to the image forming apparatus 100.

[0039] The sheet reversing device 200 reversely conveys the sheet P when performing double-sided printing on the sheet P or when performing face-down discharge. The sheet reversing device 200 includes a reverse storage unit 210 as a storage means. The details of the configuration of the sheet reversing device 200 will be described later.

[0040] The double-sided conveyance mechanism 220 merges with the feeding conveyance unit 110 on the upstream side in the conveyance direction of the sheet P than the secondary transfer unit 140. The double-sided conveyance mechanism 220 conveys the sheet P reversed by the sheet reversing device 200 to the secondary transfer unit 140 again. The double-sided conveyance mechanism 220 includes a double-sided conveyance path 202 extending in the horizontal direction in FIG. 1.

[0041] Here, as the sheet P used as the recording material, various sheets such as plain paper, recycled paper, glossy paper, coated paper with surface treatment such as resin coating, thin paper, or thick paper can be used. Also, in the present embodiment, a long sheet whose length in the conveyance direction is longer than a general standard size (for example, a sheet longer than 420 mm which is the long side of an A3 sheet) can be used as the recording material.

[0042] Note that the long sheet is not necessarily stored in the storage 110a. For example, it may be set on a hand insertion tray (not shown) that protrudes to the side of the housing 101 and fed one by one from the hand insertion tray to the feeding and conveying unit 110 by a feeding roller (not shown).

[0043] <Configuration of Sheet Inversion Device> The configuration of the sheet inversion device 200 according to Embodiment 1 of the present invention will be described in detail with reference to FIGS. 1 and 2.

[0044] The sheet inversion device 200 includes an upstream conveyance path 201, a duplex conveyance path 202, a duplex conveyance roller 206, an inversion storage unit 210, a conveyance sensor 229, an inversion roller pair 230, and a duplex switching flap 231.

[0045] The upstream conveyance path 201 is a conveyance path through which the sheet P guided by the first switching flap 173 to the inversion inlet roller 172 passes. The upstream conveyance path 201 is provided with conveyance guides 201a and 201b as guide means for guiding the conveyance of the sheet P.

[0046] The duplex conveyance path 202 is a conveyance path through which the sheet P reversely conveyed by the inversion roller pair 230 passes. The duplex conveyance path 202 is provided below the main conveyance path 190. The duplex conveyance path 202 communicates with the confluence portion with the main conveyance path 190 via the duplex conveyance mechanism 220. The duplex conveyance path 202 branches from the upstream conveyance path 201 on the upstream side of the inversion roller pair 230 in the conveyance direction of the sheet P before reverse conveyance. The duplex conveyance path 202 extends in a substantially horizontal direction in FIG. 1.

[0047] The duplex conveyance roller 206 is provided in the duplex conveyance path 202. The duplex conveyance roller 206 conveys the sheet P reversely conveyed by the inversion roller pair 230 and fed into the duplex conveyance path 202 toward the duplex conveyance mechanism 220 via the duplex conveyance path 202.

[0048] The inversion standby unit 210 is provided on the downstream side in the conveyance direction of the sheet P before inversion conveyance with respect to the pair of inversion rollers 230. The inversion standby unit 210 is provided below the duplex conveyance path 202. The inversion standby unit 210 has an arrangement relationship in which it at least partially overlaps with the fixing processing unit 160 and the discharge unit 170 located above the inversion standby unit 210 in the vertical direction. The inversion standby unit 210 is arranged side by side horizontally with the storage 110a of the feeding conveyance unit 110 in FIG. 1.

[0049] The inversion standby unit 210 has a standby area, shown by a broken line in FIG. 2, for temporarily standby a part of the sheet P sent out from the pair of inversion rollers 230 when the pair of inversion rollers 230 inversely conveys the sheet P or the like. This standby area is a conveyance space formed by being surrounded by a guide member 228 including a first bending portion 203, a second bending portion 204, and a third bending portion 205.

[0050] The conveyance sensor 229 as a detection means is provided on the upstream side in the conveyance direction of the sheet P before inversion conveyance with respect to the pair of inversion rollers 230. The conveyance sensor 229 detects the leading end and the trailing end of the conveyed sheet P, thereby detecting the timing of passage of the sheet P, and outputs the detection result to the engine control unit 103a of the control board storage unit 103. The detection result output from the conveyance sensor 229 to the engine control unit 103a is used for control when conveying the sheet P, such as when determining the timing to temporarily stop the conveyance of the sheet P when inversely conveying the sheet P.

[0051] The conveyance sensor 229 uses a reflection type sensor including a light emitting unit and a light receiving unit. When the sheet P has not passed, the light emitted from the light emitting unit does not return to the light receiving unit in the conveyance sensor 229, and when the sheet P is passing, the light emitted from the light emitting unit is reflected by the sheet P and enters the light receiving unit. Thereby, since the light receiving amount of the light receiving unit increases when the sheet P is passing in the conveyance sensor 229, it is possible to detect whether or not the sheet P is passing by detecting the increase in the light receiving amount. The conveyance sensor 229 is provided in the upstream conveyance path 201, and emits light from the light emitting unit toward the inside of the upstream conveyance path 201.

[0052] Generally, when the reflective sensor is separated from the detection object such as the sheet P by a predetermined distance or more, the light reflected from the detection object cannot reach the light receiving unit, making detection impossible. The distance between the transport guides 201a and 201b of the upstream transport path 201 is 2 to 3 mm. The distance between the transport sensor 229 and the transport guide 201b on the opposite side is 4 mm to 5 mm. Thus, the transport sensor 229 is configured to be able to reliably detect the sheet P even when the sheet P is farthest from the transport sensor 229 as it passes near the transport guide 201b. Also, the distance between the transport sensor 229 and the inversion roller pair 230 is approximately 100 mm.

[0053] The inversion roller pair 230 is provided on the downstream side in the transport direction of the sheet P before inversion transport, rather than at the location where the upstream transport path 201 and the duplex transport path 202 merge. The inversion roller pair 230 is connected to a motor that can be driven to rotate forward or backward under the drive control of the engine control unit 103a. When this motor rotates from forward drive to reverse drive or from reverse drive to forward drive, the transport direction of the sheet P can be switched.

[0054] The duplex switching flap 231 is provided at the location where the upstream transport path 201 and the duplex transport path 202 merge. The duplex switching flap 231 guides the sheet P transported from the upstream transport path 201 to the inversion roller pair 230 under the control of the engine control unit 103a, or regulates the backflow of the sheet P that has been reversely transported by the inversion roller pair 230 into the upstream transport path 201.

[0055] <Operation of the Image Forming Apparatus> The operation of the image forming apparatus 100 according to Embodiment 1 of the present invention will be described in detail.

[0056] First, the primary charger 111 charges the photosensitive drum 105.

[0057] Next, each laser scanner unit 107 of the optical image processing unit 120, the optical image processing unit 121, the optical image processing unit 122, and the optical image processing unit 123 emits laser light from the semiconductor laser 108 according to the image data input from the printer controller 103b.

[0058] The laser light emitted from the semiconductor laser 108 is guided to the photosensitive drum 105 via the reflecting polygon mirror 109, and an electrostatic latent image is formed on the surface of the photosensitive drum 105 by exposing the photosensitive drum 105 in the main scanning direction.

[0059] Next, the electrostatic latent image formed on the surface of the photosensitive drum 105 is visualized as a toner image by the toner supplied by the developing device 112.

[0060] Next, the toner image carried on the photosensitive drum 105 is transferred (primary transfer) to the intermediate transfer member 150 provided in the intermediate transfer unit 152 by applying a voltage having a characteristic opposite to that of the toner image to the intermediate transfer member 150.

[0061] At the time of forming a color image, the yellow, magenta, cyan, and black monochromatic toner images formed in each of the optical image processing unit 120, the optical image processing unit 121, the optical image processing unit 122, and the optical image processing unit 123 are sequentially transferred to the intermediate transfer member 150. Thereby, a full-color visible image is formed on the surface of the intermediate transfer member 150.

[0062] Also, while separating the sheets P one by one from the bundle of sheets P stored in the storage 110a, the feeding and conveying unit 110 conveys them in parallel with the above-described toner image creating operation and conveys them to the secondary transfer unit 140.

[0063] Next, the visible image carried on the surface of the intermediate transfer member 150 is transferred (secondary transfer) to the sheet P by the secondary transfer roller pair 151 of the secondary transfer unit 140.

[0064] Next, the sheet P that has passed through the secondary transfer unit 140 is conveyed to the fixing processing unit 160.

[0065] The sheet P conveyed to the fixing processing unit 160 passes through a fixing nip constituted by a heating roller 161 and a pressure roller 162. Then, the toner transferred to the sheet P is heated and melted at the fixing nip and then cooled and solidified. Thereby, an image is fixed on the sheet P.

[0066] The sheet P that has passed through the fixing processing unit 160 is conveyed to the discharging unit 170.

[0067] The conveyance path of the sheet P conveyed to the discharging unit 170 is switched according to whether double-sided printing is performed or not. In the case of single-sided printing, the sheet P is guided by the first switching flap 173 toward the pair of discharging rollers 171 and discharged to the outside of the image forming apparatus 100 by the pair of discharging rollers 171.

[0068] On the other hand, in the case of double-sided printing, the sheet P on which an image is formed on the first side is guided by the first switching flap 173 to the reverse entrance roller 172 and conveyed to the sheet reversing device 200 via the reverse entrance roller 172. The sheet reversing device 200 performs reverse conveyance while temporarily storing the sheet P using the reverse storage unit 210 and conveys it to the double-sided conveyance mechanism 220.

[0069] Next, the double-sided conveyance mechanism 220 conveys the sheet P in a state where the first side and the second side are reversed by the sheet reversing device 200 back to the feeding and conveying unit 110.

[0070] Then, the sheet P conveyed back to the feeding and conveying unit 110 passes through the secondary transfer unit 140 and the fixing processing unit 160, and after an image is formed on the second side, it is discharged to the outside of the image forming apparatus 100 by the pair of discharging rollers 171.

[0071] In this way, an image is formed on the sheet P by being conveyed through the main conveyance path 190.

[0072] <Operation of the Sheet Reversing Device> The operation of the sheet reversing device 200 according to Embodiment 1 of the present invention will be described.

[0073] First, the normal operation of the sheet reversing device 200 will be described in detail with reference to FIGS. 3 to 5.

[0074] The sheet P conveyed from the reversing inlet roller 172 to the sheet reversing device 200 is conveyed through the upstream conveyance path 201 and delivered to the pair of reversing rollers 230 (see FIG. 3).

[0075] When the pair of reversing rollers 230 receives the sheet P from the reversing inlet roller 172, it continues to convey the sheet P in the forward direction A. At this time, a part of the sheet P sent out from the pair of reversing rollers 230 in the forward direction A is stored in the reversing storage unit 210 and is in a stored state.

[0076] A part of the sheet P sent from the pair of reversing rollers 230 to the reversing storage unit 210 is guided while contacting the first bending portion 203, the second bending portion 204, and the third bending portion 205.

[0077] Specifically, the leading end of the sheet P sent downward from the pair of reversing rollers 230 in the conveyance direction is guided by the first bending portion 203 in the direction from the upstream side to the downstream side in the conveyance direction of the sheet P in the double-sided conveyance path 202 (right direction in FIG. 3). Next, the leading end of the sheet P is guided upward by the second bending portion 204.

[0078] In this way, when the long sheet P is reversely conveyed by the pair of reversing rollers 230, the sheet P is retracted in a curved state along the first bending portion 203, the second bending portion 204, and the third bending portion 205 in the reversing storage unit 210.

[0079] The pair of reversing rollers 230 temporarily stops when the trailing end of the sheet P in the forward direction A passes through the double-sided switching flap 231.

[0080] Next, the double-sided switching flap 231 rotates in the direction of arrow B in FIG. 4 under the control of the engine control unit 103a, restricts the backflow of the sheet P to the upstream conveyance path 201, and switches its orientation to guide the sheet P to the double-sided conveyance path 202 (see FIG. 4).

[0081] Next, the pair of reversing rollers 230 reversely drives to switch the conveyance direction of the sheet P from the forward direction A to the reverse direction C and reversely conveys the sheet P. As a result, the sheet P is carried into the double-sided conveyance path 202 and conveyed by the double-sided conveyance rollers 206 (see FIG. 5).

[0082] In the above description, the operation of the sheet reversing device 200 when conveying the reversed sheet P through the double-sided conveyance path 202 has been described. However, the present invention is not limited to this, and the sheet reversing device 200 can also be used when performing face-down discharge. When performing face-down discharge, the sheet P reversely conveyed by the sheet reversing device 200 is guided to the pair of discharge rollers 171 by the second switching flap 174.

[0083] Subsequently, the operation of the sheet reversing device 200 in case of an abnormality will be described in detail with reference to FIGS. 6 to 10.

[0084] In case of an abnormality in the image forming apparatus 100, the reverse standby unit 210 functions as a storage unit for the sheet P.

[0085] When the image forming apparatus 100 detects some abnormality (for example, paper jam of the sheet P or irregular operation) during the image forming operation, it stops part of its operation. Also, the sheet P remaining in the conveyance path between the fixing processing unit 160 and the pair of reversing rollers 230 that can be conveyed to the reverse standby unit 210 without being affected by the above-mentioned abnormality is conveyed toward the reverse standby unit 210. In this case, unlike normal times, even when the sheet P reaches the reverse standby unit 210, the pair of reversing rollers 230 is not reversely rotated, and the sheet P is continuously fed in the forward direction A.

[0086] For example, when a paper jam occurs in the fixing unit 160, all the sheets P remaining in the discharging unit 170 are conveyed toward the reverse standby unit 210. Further, when a paper jam occurs in a plurality of sheets P being conveyed in the discharging unit 170, the sheets P remaining downstream in the conveyance direction of the sheet P from the sheet P in which the paper jam has occurred are conveyed toward the reverse standby unit 210.

[0087] Then, as shown in FIG. 6, the sheets P conveyed toward the reverse standby unit 210 are discharged from the reverse roller pair 230 to the reverse standby unit 210 and collected in the reverse standby unit 210. Since the sheets P that should have been left in a plurality of locations inside the image forming apparatus 100 are collected in one place, the work of the user to remove the sheets P inside the image forming apparatus 100 after the abnormal state can be simplified.

[0088] Further, the reverse roller pair 230 stops the conveyance and holds the sheet (hereinafter referred to as the "last sheet") P that is the last to reach the reverse roller pair 230 among the sheets collected in the reverse standby unit 210 without discharging it to the reverse standby unit 210. Here, the last sheet P is the sheet P that remains most upstream among the sheets P remaining downstream in the conveyance direction of the sheet P from the sheet P in which an abnormality such as a paper jam has been detected.

[0089] Specifically, as shown in FIG. 7, the engine control unit 103a determines the last sheet P (S1). For example, the engine control unit 103a counts the number of sheets P detected by a sensor (not shown) provided upstream in the conveyance direction of the sheet reversing device 200. Then, when the number of sheets P for forming the image input by the operation unit 180 matches the count value, the engine control unit 103a determines that the sheet P with the matching count value is the last sheet P.

[0090] Next, the conveyance sensor 229 detects that the last sheet P has arrived (S2).

[0091] Next, the engine control unit 103a acquires the detection result detected in the operation of step S2 (S3).

[0092] Next, based on the acquired detection result and a predetermined calculation formula, the engine control unit 103a determines deceleration conditions including the timing to decelerate the inversion roller pair 230 and the acceleration during deceleration (S4).

[0093] Next, the engine control unit 103a outputs a signal for decelerating the inversion roller pair 230 according to the determined deceleration conditions to a motor (not shown) that operates the inversion roller pair 230 (S5), and decelerates the inversion roller pair 230.

[0094] Next, the engine control unit 103a stops the rearmost seat P at a predetermined position (S6), and then ends the operation.

[0095] The predetermined position where the rearmost seat P stops is, for example, as shown in FIG. 8, a position where the conveyance sensor 229 can detect the rearmost seat P. Specifically, the predetermined position where the rearmost seat P stops is set such that the rear end portion of the rearmost seat P in the forward direction A is located 10 to 30 mm upstream in the forward direction A from the conveyance sensor 229.

[0096] Even when the seat P is conveyed downstream in the forward direction A more than expected, the above-mentioned predetermined position is a position where the conveyance sensor 229 can surely detect the rearmost seat P. Examples where the seat P is conveyed downstream in the forward direction A more than expected include cases where the diameter of the inversion roller pair 230 is larger than the nominal value, or where the transmission of the signal for controlling the operation of the inversion roller pair 230 is delayed, resulting in the seat P being conveyed downstream in the forward direction A more than expected.

[0097] After the sheet P is clamped by the inversion roller pair 230 by the above operation, when the sheet P is detected by the conveyance sensor 229, the display device of the operation unit 180 performs a display prompting the user to remove the sheet P, such as information indicating that the sheet P remains. Thereby, the user can smoothly perform the operation of removing the sheet P by checking the display on the display device, and can check, for example, whether the sheet P remains in the image forming apparatus 100 after the JAM process. Detect the sheet by the detection means and display information indicating that the sheet remains

[0098] Here, when all the sheets P are stored in the inversion standby unit 210 in the event of an abnormality in the sheet inversion device 200, it is impossible to detect whether the sheets P stored in the inversion standby unit 210 have been removed by the user. Therefore, for example, even if a display prompting the user to remove the sheet P stored in the inversion standby unit 210 is performed on the display unit, if the user does not notice the sheet P remaining in the inversion standby unit 210, the operation of the image forming apparatus can be started.

[0099] When the image forming operation is performed with the sheet P remaining in the inversion standby unit 210, the sheet P during the image forming operation contacts the sheet P remaining in the inversion standby unit 210 when being conveyed to the inversion standby unit 210 and is damaged. As a result, the quality of the finished product of the image forming apparatus deteriorates, or the conveyed sheet P jams due to the resistance at the time of contact.

[0100] To avoid this, it is conceivable to install detection sensors 232a and 232b for detecting the sheet P stored in the inversion standby unit 210, as in the sheet inversion device 300 shown in FIG. 9. However, as shown in FIG. 9, when the sheet P is curled, the distance from the light receiving unit to the sheet P becomes long for the detection sensors 232a and 232b, so that the emitted light does not enter the light receiving unit and the sheet P cannot be detected.

[0101] In addition, the sheet P2 discharged to the inversion standby section 210 may collide with the previously discharged sheet P1. In this case, as shown in FIG. 10, when the sheet P1 is pushed to the back side (the right side in FIG. 10), or when the sheet P2 moves obliquely when viewed from above, the detection sensors 232a and 232b cannot detect the sheets P1 and P2.

[0102] On the other hand, in the present embodiment, the conveyance sensor 229 is provided in the upstream conveyance path 201. Further, since the position of the sheet P conveyed in the upstream conveyance path 201 is regulated by the conveyance guides 201a and 201b, a detectable distance can be maintained by the conveyance sensor 229. Thereby, the image forming apparatus 100 can surely detect the last sheet P by the conveyance sensor 229, and thus can surely recognize that the sheet P remains in the image forming apparatus 100.

[0103] In addition, since the last sheet P is held by the inversion roller pair 230, the conveyance sensor 229 can continue to detect the sheet P until the user removes the sheet P without being inadvertently moved by some user operation.

[0104] In addition, when the conveyance sensor 229 detects the last sheet P, by preventing the operation of the image forming apparatus 100 from returning, it is possible to prevent the user from forgetting to remove the sheet P.

[0105] In addition, in order to remove the last sheet P held by the inversion roller pair 230 from the portion D shown in FIG. 8, at this time, the user will also recognize the sheet P remaining in the inversion standby section 210. From this, it is possible to prevent the user from forgetting to remove the sheets P collected in the inversion standby section 210.

[0106] In this embodiment, when an abnormality occurs during the conveyance of the sheet P, the reverse roller pair 230 conveys the sheet P in the forward direction, stops the conveyance of the last sheet P among the sheets P conveyed in the forward direction, and clamps the last sheet P. Further, the reverse storage unit 210 stores the sheet P conveyed in the forward direction by the reverse roller pair 230 when a conveyance abnormality occurs. Furthermore, the conveyance sensor 229 detects the last sheet P clamped by the reverse roller pair 230. Thereby, it is possible to prevent forgetting to pick up the stored sheet P.

[0107] Also, according to this embodiment, by arranging the reverse storage unit 210 and the storage bin 110a side by side in the horizontal direction, it is possible to suppress an increase in the size of the image forming apparatus 100.

[0108] (Embodiment 2) Since the configuration of the image forming apparatus according to Embodiment 2 of the present invention is the same as that in FIG. 1, the description thereof is omitted. Also, since the operation of the image forming apparatus according to this embodiment is the same as the operation of the image forming apparatus 100 in Embodiment 1 above, the description thereof is omitted.

[0109] <Configuration of Sheet Reversing Device> The configuration of the sheet reversing device 1200 according to Embodiment 2 of the present invention will be described in detail with reference to FIG. 11.

[0110] Note that parts having the same configuration as those in FIG. 2 in FIG. 11 are denoted by the same reference numerals, and the description thereof is omitted.

[0111] The sheet reversing device 1200 includes an upstream conveyance path 201, a duplex conveyance path 202, a duplex conveyance roller 206, a reverse storage unit 210, a conveyance sensor 229, a reverse roller pair 230, a duplex switching flap 231, and a detection sensor 232.

[0112] The detection sensor 232 as a detection means is disposed downstream of the reverse roller pair 230 in the forward direction A and detects the sheet P.

[0113] In the sheet reversing device 1200 having the above configuration, the sheet P can be stopped at a location closer to the sheet reversing standby unit 210. As a result, the portion of the sheet P protruding into the sheet reversing standby unit 210 (portion E in FIG. 11) can be made larger compared to the first embodiment described above, and the user can easily recognize the sheet P being held by the reversing roller pair 230.

[0114] It goes without saying that the present invention is not limited to the above embodiments and can be variously modified without departing from the gist thereof.

[0115] Specifically, in the above-described first and second embodiments, it has been applied to an image forming apparatus equipped with a tandem type and intermediate transfer type electrophotographic mechanism, but it is not limited thereto. For example, it may be applied to an image forming apparatus equipped with a direct transfer type electrophotographic mechanism that transfers the toner image formed on the photoreceptor to the sheet without passing through an intermediate transfer member. Further, not limited to the electrophotographic mechanism, it may be applied to an image forming apparatus equipped with an inkjet printing unit or an offset printing mechanism.

Explanation of Reference Numerals

[0116] 100 Image forming apparatus 103 Control board storage section 103a Engine control section 103b Printer controller 105 Photoconductive drum 107 Laser scanner section 108 Semiconductor laser 110 Feeding and conveying section 111 Primary charger 112 Developing device 120 Optical image development processing section 121 Optical image development processing section 122 Optical image development processing section 123 Optical image development processing section 140 Secondary transfer section 150 Intermediate transfer member 151 Secondary transfer roller pair 152 Intermediate transfer section 160 Fixing processing section 170 Discharge section 171 Discharge roller pair 172 Reverse inlet roller 173 Switching flap 174 Switching flap 180 Operation section 190 Main conveyance path 200 Sheet reversing device 201 Upstream conveyance path 201a Conveyance guide 201b Conveyance guide 202 Duplex conveyance path 203 Bending section 204 Bending section 205 Bending section 206 Duplex conveyance roller 210 Reverse storage section 220 Duplex conveyance mechanism 228 Guide member 229 Conveyance sensor 230 Reverse roller pair 231 Duplex switching flap 232 Detection sensor 1200 Sheet reversing device

Claims

1. A pair of reversing rollers that reverse a conveying direction of a sheet by conveying the sheet in a forward direction and then conveying the sheet in a direction opposite to the forward direction; a support means for supporting a sheet so as to transport the sheet, which is transported in the forward direction by the pair of reversing rollers, in the reverse direction; a detection unit provided upstream or downstream of the pair of reversing rollers in the forward direction, the detection unit detecting a sheet conveyed by the pair of reversing rollers; a control unit that controls conveyance of the sheet by the pair of reversing rollers based on a detection result by the detection unit, When a paper jam occurs during sheet conveyance, the pair of reversing rollers conveys the plurality of sheets in the forward direction, the control means causes the pair of reversing rollers to discharge sheets other than the rearmost sheet of the plurality of sheets onto the support means; controlling the pair of reversing rollers so that the rearmost sheet is stopped in a state where it is detected by the detection means and is sandwiched by the pair of reversing rollers; A sheet inverting device.

2. the support means is a first guide member that contacts a first surface of the sheet to guide the sheet, A second guide member that faces the first guide member and contacts a second surface of the sheet opposite to the first surface to guide the sheet is not provided.

2. The sheet inverting device according to claim 1.

3. A third guide member arranged upstream of the support means in the forward direction and guiding the sheet; a fourth guide member that is disposed at a position opposite to the third guide member, forms a sheet transport path together with the third guide member, and guides the sheet; having The detection means is disposed on the third guide member.

2. The sheet inverting device according to claim 1.

4. The first guide member has a bent portion.

3. The sheet inverting device according to claim 2.

5. The first guide member has a first bent portion and a second bent portion, A long sheet is a sheet whose length in the sheet conveying direction is longer than that of a standard size sheet, When the conveying direction of the long sheet is reversed by the pair of reversing rollers and conveyed, the long sheet is curved along the first bent portion and the second bent portion.

3. The sheet inverting device according to claim 2.

6. The plurality of sheets are sheets downstream in a sheet conveying direction from the sheet in which the paper jam occurred.

2. The sheet inverting device according to claim 1.

7. The rearmost sheet is a sheet located furthest upstream among sheets downstream in a sheet conveying direction from the jammed sheet, 7. The sheet transport device according to claim 6.

8. A conveying roller pair is disposed upstream of the reversing roller pair in a sheet conveying direction, and conveys a sheet toward the reversing roller pair, the forward direction is a direction in which the sheet is transported from the transport roller pair to the reverse roller pair; 2. The sheet inverting device according to claim 1.

9. The detection means is disposed upstream of the pair of reversing rollers in the forward direction.

9. The sheet inverter according to claim 8.

10. an image forming unit that forms an image on a sheet; The sheet inverting device according to claim 1 , which inverts and conveys the sheet on which the image is formed by the image forming unit; An image forming apparatus comprising:

11. A display means for displaying information indicating that a sheet remains in the image forming apparatus when a sheet jam occurs.

11. The image forming apparatus according to claim 10.

12. When a sheet jam occurs, the display means displays information indicating that a sheet remains in the sheet inverting device while the detection means is detecting the rearmost sheet.

12. The image forming apparatus according to claim 11.

13. When transporting a sheet having an image formed on a first surface by the image forming unit to form an image on a second surface opposite to the first surface of the sheet, the pair of reversing rollers transports the sheet in the forward direction and the reverse direction based on a detection result of the detection means.

11. The image forming apparatus according to claim 10.

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