JP2020050493A - Sheet carrier and image processing apparatus - Google Patents

Abstract

To provide a sheet carrier capable of preventing the lowering of sheet transport efficiency and preventing a skew of a sheet, and an image processing apparatus comprising a sheet carrier.SOLUTION: A sheet carrier includes a control section 90 that actuates a solenoid 64 to raise a follower roller 23B1 outside in a widthwise direction D3, displacing the follower roller 23B1 from a pressing position to a release position (S11). The control section 90 then returns an inclination unit 65 to an initial position and corrects a skew of a print sheet P (S16).SELECTED DRAWING: Figure 7

Description

  The present invention relates to a sheet conveying device capable of conveying a sheet, and an image processing apparatus including the sheet conveying device.

  An image forming apparatus such as a printer, a copier, a facsimile, and a multifunction peripheral having these functions is provided with a sheet conveying device that conveys a sheet such as printing paper. A conventional sheet conveying apparatus is provided with a pair of registration rollers for performing a registration operation (also referred to as registration) on a sheet. Here, the registration operation is an operation of applying a conveying force to the sheet in the conveying direction in a state where the leading end of the sheet is abutted on the nip portion of the stopped registration roller pair. By performing this registration operation, the skew of the sheet being conveyed is corrected. Further, it is possible to align the image forming position on the sheet with the transfer position of the image transferred to the sheet.

  Conventionally, as a device for correcting skew of a sheet, a rotative mechanism for rotatably supporting a sheet being conveyed while nipping the sheet is provided, and when skew is detected, skew is detected. 2. Description of the Related Art There is known a sheet conveyance device that rotates a rotation mechanism in a correction direction (see Patent Document 1).

JP 2006-27859 A

  However, in a conventional sheet conveying apparatus that corrects skew by rotating a sheet by a rotating mechanism, when the sheet is rotated, the nip of the sheet is temporarily stopped by a pair of conveying rollers provided before and after the rotating mechanism. Must be canceled. For example, it is necessary to separate one of the drive roller and the driven roller that constitute the transport roller pair from the other roller. In general, a pair of rollers is pressed against each other by an elastic member such as a spring in order to pinch and convey the sheet. Therefore, when the transport roller pair is pressed again after the nip is released, one roller collides vigorously with the other roller by the spring force of the elastic member. In this case, a vibration state occurs in which the pressure contact force of the pair of conveying rollers periodically fluctuates, and until the vibration state converges, the conveyance of the sheet by the pair of conveying rollers becomes unstable, and the sheet tends to be skewed. . Further, if the feeding of the sheet to the pair of conveying rollers is stopped or delayed until the vibration state converges to avoid unstable conveyance, the sheet conveying efficiency is reduced.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet conveying apparatus capable of preventing a reduction in sheet conveying efficiency and preventing skew of a sheet, and an image processing apparatus including the sheet conveying apparatus.

The sheet conveying device according to one aspect of the present invention is provided with at least three pairs of conveying rollers arranged side by side in a width direction orthogonal to the conveying direction, and provided on a downstream side of the conveying roller pair in the conveying direction. Before the entering sheet enters, the sheet rotates from the initial position by an amount of inclination corresponding to the inclination of the sheet, and after the sheet enters, returns to the initial position while holding the sheet, thereby correcting the skew of the sheet. A row correction mechanism.
Of the three transport roller pairs, each roller of the outer transport roller pair located on the outside in the width direction is a pressed position pressed by an elastic force capable of transporting the sheet in the transport direction, and the pressed state is released. Movably supported between the release position.
Further, the sheet conveyance device includes a skew detection unit configured to detect that the sheet conveyed toward the skew correction mechanism by the conveyance roller pair is skewed, A control unit for controlling movement.
The controller moves each roller of the outer transport roller pair to the release position before the skew correction mechanism returns to the initial position when the skew of the sheet is detected by the skew detector. It is configured to be.

  An image processing apparatus according to another aspect of the present invention includes the sheet conveyance device, and performs predetermined image processing using the sheet conveyed by the sheet conveyance device. The predetermined image processing is an image forming processing for forming an image on a sheet or an image reading processing for reading an image from a sheet.

  According to the present invention, it is possible to prevent a reduction in sheet conveyance efficiency and prevent skew of a sheet.

FIG. 1 is a perspective view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 2A and 2B are cross-sectional views illustrating the configuration of the image forming apparatus. FIG. 3 is a block diagram illustrating a configuration of the image forming apparatus. FIG. 4 is a schematic diagram illustrating a configuration of a skew feeding correction mechanism included in the image forming apparatus. 5A and 5B are diagrams illustrating a pair of transport rollers provided in the image forming apparatus, and are side views taken along a line VV in FIG. 4. FIG. 6 is a diagram illustrating a configuration of a sheet correction mechanism included in the image forming apparatus, and is a side view taken along a line VI-VI in FIG. 4. FIG. 7 is a flowchart illustrating an example of a procedure of a sheet correction process performed by a control unit included in the image forming apparatus. FIG. 8 is a diagram for explaining the operation of the conveying roller pair and the sheet correction mechanism provided in the image forming apparatus. FIG. 9 is a diagram for explaining the operation of the pair of conveying rollers and the sheet correction mechanism provided in the image forming apparatus. FIG. 10 is a diagram for explaining the operation of the transport roller pair and the sheet correction mechanism provided in the image forming apparatus. FIG. 11 is a diagram for explaining the operation of the conveying roller pair and the sheet correction mechanism provided in the image forming apparatus. FIG. 12 is a diagram for explaining the operation of the conveying roller pair and the sheet correction mechanism provided in the image forming apparatus. FIG. 13 is a diagram for explaining the operation of the transport roller pair and the sheet correction mechanism provided in the image forming apparatus. FIG. 14 is a diagram for explaining the operation of the pair of conveying rollers and the sheet correction mechanism provided in the image forming apparatus.

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

  FIGS. 1 to 3 are views showing a configuration of an image forming apparatus 10 according to an embodiment of the present invention. FIG. 1 is a perspective view of the image forming apparatus 10. FIG. 2 is a cross-sectional view of the image forming apparatus 10, FIG. 2A is a schematic cross-sectional view, and FIG. 2B is a detailed cross-sectional view. FIG. 3 is a block diagram illustrating a configuration of the image forming apparatus 10. The image forming apparatus 10 is an example of the image processing apparatus according to the present invention. In the following description, the up-down direction D1 is defined based on the state in which the image forming apparatus 10 is installed so as to be usable (the state in FIG. 1), and the front-rear direction D2 is defined with the near side (front side) as the front. A left-right direction D3 is defined when the image forming apparatus 10 is viewed from the near side (front side).

[Image Forming Apparatus 10]
As shown in FIG. 1, the image forming apparatus 10 is a printer that prints an image on printing paper P (an example of a sheet). Note that the image forming apparatus 10 is not limited to a printer having only a printing function. For example, the present invention can be applied to a multifunction peripheral or a copier having various functions such as a printer, a facsimile, and a copier.

  The image forming apparatus 10 prints an image on printing paper P using a printing material such as toner. As shown in FIG. 2, the image forming apparatus 10 mainly includes an electrophotographic image forming unit 18, a fixing unit 19, a sheet feeding device 15, and a skew detection sensor 61 (a skew detection unit of the present invention). An example), a sheet transport unit 23 (an example of the transport unit of the present invention), a sheet correction mechanism 60, a control unit 90 (see FIG. 3) for controlling the image forming apparatus 10 overall, and a sheet discharging unit 21. , Is provided. These are provided inside the housing 14 that forms the cover of the outer frame of the image forming apparatus 10 and the internal frame. In addition, the sheet conveying device of the present invention is realized by the sheet conveying unit 23 and a later-described tilt unit 65 provided in the sheet correcting mechanism 60.

  As shown in FIG. 2, the sheet feeding device 15 is provided at the lowermost part of the image forming apparatus 10. The paper supply device 15 includes a paper supply tray 37, a pickup roller 38, and a paper supply roller pair 39. The paper feed tray 37 accommodates printing paper P on which an image is formed by the image forming unit 18, and is supported by the housing 14. The pickup roller 38 and the sheet feeding roller pair 39 are provided above a front portion of the sheet feeding tray 37. When an instruction signal for starting the feeding operation of the printing paper P is input to the image forming apparatus 10, the pickup roller 38 and the paper feeding roller pair 39 are rotated by the motor, and the printing paper P is fed from the paper feeding tray 37. Is fed. The print paper P fed by the pickup roller 38 is transported by the paper feed roller pair 39 to the curved first transport path 26 formed on the downstream side in the feed direction of the print paper P.

  The first transport path 26 is a curved transport path that is curved upward from the paper feed roller pair 39 and further curved backward. The first transport path 26 is provided with a paper transport unit 23 that transports the printing paper P to the downstream side in the transport direction D11 by receiving a rotational driving force from the first transport motor 56 (see FIG. 3). The printing paper P sent to the first transport path 26 by the paper feeding device 15 is transported to the second transport path 27 through the first transport path 26 by the paper transport unit 23 that is driven to rotate by the first transport motor 56. You.

  The paper transport unit 23 includes a drive roller 23A that is driven to rotate by obtaining a driving force from a first transport motor 56 (see FIG. 3), and a driven roller 23B that is disposed in contact with the outer peripheral surface of the drive roller 23A ( An example of the driven roller of the present invention). The transport roller pair of the present invention is realized by the driving roller 23A and the driven roller 23B.

  As shown in FIG. 4, the paper transport unit 23 has four drive rollers 23A arranged at equal intervals along a left-right direction D3 (corresponding to the width direction of the present invention) orthogonal to the transport direction D11. . Hereinafter, the left-right direction D3 may be referred to as the width direction D3. Each drive roller 23A is fixed to a rotation shaft 47 extending in the width direction D3, and the rotation shaft 47 is rotatably supported by the internal frame 14A of the housing 14. The driving force from the first transport motor 56 (see FIG. 3) is transmitted to the rotating shaft 47. Further, the paper transport unit 23 has four driven rollers 23B (an example of a first roller of the present invention) corresponding to each drive roller 23A. That is, the paper transport unit 23 has four transport roller pairs provided side by side in the width direction D3. Each of the four driven rollers 23B is rotatably supported by two rotation shafts 49 provided on a guide member 26A constituting a transport guide surface outside the first transport path 26. Each rotating shaft 49 is provided so as to be separated in the width direction D3, and two driven rollers 23B are rotatably supported by each rotating shaft 49. The rotation shaft 49 provided on the left side of the center in the width direction D3 corresponds to the first rotation shaft of the present invention, and the rotation shaft 49 provided on the right side of the center in the width direction D3 is the second rotation shaft of the present invention. It corresponds to a rotation axis.

  As shown in FIG. 2B, the driven roller 23B is urged toward the driving roller 23A by a spring 23C. Thus, the driven roller 23B is pressed against the driving roller 23A. When the driving roller 23A is rotationally driven in this state, the driven roller 23B is driven.

  As shown in FIG. 5A, the rotation shaft 49 of the driven roller 23B is rotatably supported by support portions 51A and 51B provided on the guide member 26A. In each rotating shaft 49, an outer shaft end 49A (an example of a first end of the present invention) in the width direction D3 is supported by a support portion 51A, and an inner shaft end 49B in the width direction D3 is a support portion. 51B. The support portions 51A and 51B are urged downward by a spring 23C. That is, the supporting portion 51A rotatably supports the shaft end 49A while biasing the shaft end 49A downward by receiving the spring force of the spring 23C. Further, the support portion 51B rotatably supports the shaft end 49B while biasing the shaft end 49B downward by receiving a spring force of the spring 23C.

  The support portion 51B is fixed to the guide member 26A. Therefore, the two driven rollers 23B2 located on the center side in the width direction D3 are maintained at a pressing position (a position shown in FIG. 5A) described later. On the other hand, the support portion 51A is supported by the guide member 26A so as to be movable in the vertical direction D1. In the present embodiment, the support portion 51A is configured to press the two driven rollers 23B1 located outside in the width direction D3 with a pressing position (a position shown in FIG. 5A) described below and a release position (a position shown in FIG. 5C). (Position shown in FIG. 2).

  In a state where the support portion 51A is disposed at the press-contact position shown in FIG. 5A, the two driven rollers 23B1 located outside in the width direction D3 are at the same height position as the two driven rollers 23B2 located inside. Becomes In this case, the driven rollers 23B1 and 23B2 are elastically urged toward the driving roller 23A by the same spring force (elastic force) by the spring 23C, and the driving roller 23A and the driven roller 23B are pressed by the same spring force. You. This spring force is such an elastic force that the printing paper P can be nipped and transported in the transport direction D11. Note that the driven roller 23B1 and the corresponding driving roller 23A correspond to an outer conveying roller pair of the present invention. In addition, the driven roller 23B2 and the corresponding driving roller 23A correspond to the inner conveying roller pair of the present invention.

  When the support portion 51A is lifted upward from the pressure contact position and moved to the release position shown in FIG. 5B, the driven roller 23B1 is released from the pressure contact with the drive roller 23A. FIG. 5B shows a state in which the driven roller 23B1 is separated from the driving roller 23A at the release position. However, if the driven paper 23B cannot pinch and transport the printing paper P, the driven roller 23B1 is not driven. The surface of 23B1 and the surface of drive roller 23A may be in contact. That is, the surface of the driven roller 23B1 and the surface of the driving roller 23A may be in contact with each other to such an extent that the conveying force of the driven roller 23B1 and the driving roller 23A is not transmitted to the printing paper P. Such a state of contact is a state in which the pressure contact state has been released.

  As shown in FIG. 3, a solenoid 64 is provided inside the housing 14. The solenoid 64 is connected to the control unit 90, and operates by being energized by drive control by the control unit 90. The plunger of the solenoid 64 is connected to the support portion 51A via a link member (not shown). When the solenoid 64 is energized, the plunger operates to move the support portion 51A to the release position. When the energization of the solenoid 64 is released, the plunger is returned to the original position by a tension spring provided on the solenoid 64, and the support portion 51A moves to the pressure contact position.

  A second transport path 27 (see FIG. 2A) is formed inside the housing 14 so as to be continuous with the first transport path 26. The second transport path 27 extends rearward substantially horizontally from the end of the first transport path 26 and reaches the image forming unit 18.

  The skew detection sensor 61 is provided in the second transport path 27. In the second transport path 27, the skew detection sensor 61 is provided downstream of the paper transport unit 23 in the transport direction D11. The skew detection sensor 61 is a pair of reflective optical sensors provided at positions equidistant from the center of the second transport path 27 to the outside in the width direction D3. The reflection type posterior sensor has a light emitting element and a light receiving element, receives reflected light of light emitted from the light emitting element, and outputs a detection signal corresponding to the amount of received light. In the present embodiment, the skew detection sensor 61 is connected to the control unit 90, and detection signals from the respective reflective optical sensors are sent to the control unit 90. The control unit 90 determines whether or not the printing paper P conveyed by the paper conveyance unit 23 is skewed based on a shift in the change of the detection signal sent from each of the pair of reflection-type optical sensors. If so, the inclination direction is determined. Further, the control unit 90 calculates the amount of inclination (the amount of inclination) of the printing paper P based on the amount of deviation of each detection signal. Since such a determination method is conventionally known, a detailed description thereof will be omitted.

  The image forming section 18 is provided at the end of the second transport path 27. The image forming unit 18 performs an image forming process (an example of an image process) for forming a toner image on the printing paper P based on image data input from the outside. Specifically, the image forming unit 18 transfers the toner image onto the printing paper P using the toner. As shown in FIG. 2, the image forming unit 18 includes a photoconductor drum 31, a charging unit 32, a developing unit 33, a transfer unit 35, a cleaning unit 36, and an LSU (Laser Scanner Unit) 34 as an exposure unit. And When the toner is attached to the electrostatic latent image on the photosensitive drum 31 by the developing unit 33 and the toner image is developed on the photosensitive drum 31, the toner image is transported along the second transport path 27 by the transfer unit 35. The image is transferred to the printing paper P that has been processed. Then, the printing paper P on which the toner image has been formed is transported to the third transport path 28 formed downstream of the image forming unit 18 in the transport direction D11 of the printing paper P.

  The third transport path 28 extends rearward from the image forming unit 18 and reaches the fixing unit 19. The printing paper P sent from the image forming section 18 to the third transport path 28 is transported to the fixing section 19 through the third transport path 28. The fixing unit 19 fixes the toner image transferred to the printing paper P on the printing paper P by heat and pressure, and includes a heating roller 41 and a pressure roller 42. The heating roller 41 is heated to a high temperature by a heating means such as an IH heater during the fixing operation. When the printing paper P passes through the fixing unit 19, the toner is heated and melted by the heating roller 41 of the fixing unit 19, and is further pressed by the pressing roller 42. Thereby, the toner image is fixed on the printing paper P, and an image is formed on the printing paper P. The printing paper P on which the image is fixed by the fixing unit 19 is transported to a fourth transport path 29 formed downstream of the fixing unit 19 in the transport direction D11 of the printing paper P.

  The fourth transport path 29 is curved upward from the fixing unit 19, extends straight vertically upward, and is further curved forward to reach the paper discharge port 22. That is, the fourth conveyance path 29 is formed between the fixing unit 19 and the sheet discharge port 22. The fourth transport path 29 is provided with a plurality of discharge roller pairs 24. The discharge roller pair 24 conveys the printing paper P to the downstream side in the conveyance direction D11 by receiving the rotational driving force from the motor. The printing paper P sent to the fourth conveyance path 29 is conveyed upward through the fourth conveyance path 29 by the discharge roller pair 24, and discharged from the paper discharge port 22 on the upper surface of the image forming apparatus 10. It is discharged to the unit 21.

  A resist transport unit 43 is provided in the second transport path 27. The resist transport unit 43 is provided on the second transport path 27 upstream of the image forming unit 18 in the transport direction D11. The resist transport unit 43 receives the rotational driving force from the motor, sends the printing paper P that has reached the resist transport unit 43 to the downstream side in the transport direction D11, and transports the printing paper P to the transfer position in the image forming unit 18. The resist transport unit 43 includes a resist roller 43A that is driven to rotate by obtaining a driving force from a motor, and a rotating roller 43B that is disposed in contact with the outer peripheral surface of the resist roller 43A. The rotating roller 43B is urged toward the registration roller 43A by a spring 43C, whereby the rotating roller 43B is pressed against the registration roller 43A. When the registration roller 43A is driven to rotate in this state, the rotating roller 43B is driven.

  In the present embodiment, as shown in FIG. 4, the resist transport unit 43 has two resist rollers 43A arranged at equal intervals along the left-right direction D3. Each registration roller 43A is fixed to a rotation shaft 45 extending in the left-right direction D3, and this rotation shaft 45 is rotatably supported by the internal frame 14A of the housing 14. The driving force from the motor is transmitted to the rotating shaft 45. Further, the resist transport unit 43 has two rotating rollers 43B corresponding to each resist roller 43A. Each of the rotary rollers 43B is rotatably supported by a support shaft 46 provided on a guide member (not shown) constituting a transport guide surface on the upper side of the second transport path 27.

  The registration roller 43A is provided with an electromagnetic clutch (not shown). The electromagnetic clutch is connected to the control unit 90, and is turned on (engaged) or turned off (disengaged) according to a control signal (ON signal or OFF signal) output from the control unit 90. As a result, the drive transmission path from the motor to the registration roller 43A is cut off or connected. In the present embodiment, the rotational drive of the registration roller 43A is controlled by controlling the electromagnetic clutch by the control unit 90.

  In the second transport path 27, a leading edge detection sensor 62 and an edge detection sensor 63 are provided on the upstream side of the resist transport unit 43 in the transport direction D11.

  The leading edge detection sensor 62 is provided near the center of the second transport path 27 in the width direction D3. The leading edge detection sensor 62 detects the leading edge of the printing paper P that has passed through a sheet correction mechanism 60 described later. The tip detection sensor 62 is, for example, a reflective optical sensor. The tip detection sensor 62 is connected to the control unit 90, and a detection signal from the reflection type optical sensor is sent to the control unit 90. The control unit 90 detects the leading edge of the printing paper P based on a change in the detection signal sent from each of the reflection type optical sensors. Since such a detection method is conventionally known, a detailed description thereof will be omitted.

  The edge detection sensor 63 is arranged on the downstream side in the transport direction D11 from the tip detection sensor 62. The edge detection sensors 63 detect the positions of both ends in the width direction D3 of the printing paper P that has passed the sheet correction mechanism 60 described later. The edge detection sensors 63 are a pair of line sensors provided at positions equidistant from the center of the second conveyance path 27 to the outside in the width direction D3. Each line sensor is composed of a plurality of image sensors arranged in a line along the width direction D3. In the present embodiment, the edge detection sensor 63 is arranged so that the end of the printing paper P in the width direction D3 passes through each line sensor. The edge detection sensor 63 is connected to the control unit 90, and determines the position of the printing paper P in the width direction D3 based on an output signal (density signal) from the line sensor. Specifically, the control unit 90 determines whether the printing paper P is located at the center in the width direction D3, whether the printing paper P is displaced in any direction in the width direction D3, If there is a shift in the width direction D3, it is determined how much the shift amount (lateral shift amount) is. Since such a determination method is conventionally known, a detailed description thereof will be omitted.

[Control unit 90]
The control unit 90 controls the image forming apparatus 10 and controls the operation of a sheet correction mechanism 60 described later. As shown in FIG. 3, the control unit 90 includes a CPU 91, a ROM 92, a RAM 93, a flash memory 94, a motor driver 95, and the like. The control unit 90 is electrically connected to the motors 56, 73, 79, 85, the sensors 61, 62, 63, and the solenoid 64 by signal lines and the like. Each of the motors 56, 73, 79, and 85 is connected to a motor driver 95 of a control unit 90, and is driven and controlled by receiving individual control signals from the motor driver 95.

  By the way, in a conventional sheet conveying device that corrects skew by rotating a sheet by a rotating mechanism, when the sheet is rotated, the nip of the sheet by a pair of conveying rollers provided before and after the rotating mechanism is temporarily stopped. Specifically, it is necessary to separate a pair of rollers constituting the transport roller pair from each other. However, when the rollers are spring-biased, if the transport roller pair is pressed again after the nip is released, one roller collides vigorously with the other roller due to the spring force. In this case, a vibration state occurs in which the pressure contact force of the pair of conveying rollers periodically fluctuates, and until the vibration state converges, the conveyance of the sheet by the pair of conveying rollers becomes unstable, and the sheet tends to be skewed. . Further, if the feeding of the sheet to the pair of conveying rollers is stopped or delayed until the vibration state converges in order to avoid unstable conveyance, the sheet conveying efficiency is reduced.

  In the present embodiment, the control unit 90 performs a sheet correction process according to the flowchart of FIG. This sheet correction process is performed in the image forming apparatus 10 in order to prevent a reduction in the transport efficiency of the printing paper P and prevent skew of the printing paper P. Note that the sheet correction process by the control unit 90 may be realized by an electronic circuit such as an integrated circuit (ASIC, DSP).

[Sheet correction mechanism 60]
As shown in FIG. 2A, the sheet correction mechanism 60 is provided in the second transport path 27. The sheet correction mechanism 60 is provided on the second transport path 27 on the upstream side of the registration transport unit 43 in the transport direction D11 and on the downstream side of the paper transport unit 23 in the transport direction D11. That is, the sheet correction mechanism 60 is provided between the registration transport unit 43 and the paper transport unit 23 on the second transport path 27. Specifically, the sheet correction mechanism 60 is provided between the skew detection sensor 61 and the leading edge detection sensor 62 on the second conveyance path 27.

  As shown in FIG. 6, the sheet correction mechanism 60 includes a tilt unit 65, a slide unit 66, and a second transport motor 79. The tilt unit 65 is an example of the skew feeding correction unit of the present invention.

  Before the skewed printing paper P conveyed by the paper conveyance unit 23 enters the sheet correction mechanism 60, the tilting unit 65 is determined in advance by a tilt amount (tilt amount) corresponding to the tilt of the printing paper P. After the printing paper P enters the sheet correction mechanism 60 and returns to the initial position while nipping the printing paper P, the skew of the printing paper P is corrected. Here, the initial position is a position where the printing paper P can be transported straight to the downstream side in the transport direction D11 by the paper transport unit 80 described later. Further, when the printing paper P conveyed by the paper conveyance unit 23 is displaced in the width direction D3, the slide unit 66 prints in a direction to correct the deviation by the amount of the deviation (a direction opposite to the deviation direction). By moving the paper P, the displacement of the printing paper P in the width direction D3 is corrected.

  As shown in FIGS. 4 and 6, the slide unit 66 has a base frame 67 that is long in the width direction D3. The base frame 67 is movably supported by the inner frame 14B of the housing 14 so as to be movable in the width direction D3. Specifically, the base frame 67 includes a horizontal flat base portion 67A, and a support portion 67B (see FIG. 4) integrally formed at an end on the rear side (right side in FIG. 4) of the base portion 67A. have. The support portion 67B has a shaft portion 68 protruding outward from both ends in the width direction D3 of the base portion 67A. The shaft portion 68 is inserted into a shaft hole formed in the internal frame 14B and supported. I have.

  As shown in FIG. 4, a rack 71 is formed on the rear end surface of the support portion 67B. A pinion gear 72 is meshed with the rack 71. The slide unit 66 includes a second correction motor 73. The pinion gear 72 is attached to an output shaft of the second correction motor 73. Therefore, the control unit 90 can slide the base frame 67 of the slide unit 66 in any of the width directions D3 by controlling the driving of the second correction motor 73.

  As shown in FIG. 4, a projecting piece 69 projecting rightward is formed at the right end of the base frame 67. The right inner frame 14B is provided with an optical sensor 70 capable of detecting the projecting piece 69. The position of the projecting piece 69 is detected by the optical sensor 70. The control unit 90 moves the base frame 67 in the width direction D3 based on a position where the protruding piece 69 is detected by the optical sensor 70 (hereinafter, referred to as a slide reference position).

  Further, a support portion 74 (see FIG. 6) for pivotally supporting a rotation shaft 76 (an example of a rotation fulcrum of the present invention) to be described later is provided at the right end of the base portion 67A.

  The tilting unit 65 includes a rotating frame 75 supported by the base 67A of the base frame 67, and a paper transport unit 80 rotatably supported by the rotating frame 75. The turning frame 75 is a plate-like member formed in a shape elongated in the width direction D3, and a turning shaft 76 extending in the vertical direction D1 is provided at a right end thereof. The rotation shaft 76 is rotatably supported by a support portion 74 (see FIG. 6) provided on the base frame 67.

  A pair of support walls 77 and 78 provided at predetermined intervals in the width direction D3 are provided on the upper surface 75A of the rotating frame 75. The pair of support walls 77 and 78 project upward from the upper surface 75A. The predetermined interval is a length that allows the printing paper P to be transported between the pair of support walls 77 and 78. The paper transport unit 80 is rotatably supported by support walls 77 and 78.

  The paper transport unit 80 is driven to rotate by a second transport motor 79. The paper transport unit 80 transports the print paper P that has entered the sheet correction mechanism 60 to the downstream side in the transport direction D11. The paper transport unit 80 includes a drive roller 80A that is driven to rotate by obtaining a driving force from the second transport motor 79, and a driven roller 80B that is disposed in contact with the outer peripheral surface of the drive roller 80A. A transport roller pair is realized by the driving roller 80A and the driven roller 80B.

  The paper transport unit 80 has four drive rollers 80A arranged at regular intervals in the width direction D3. Each drive roller 80A is fixed to a rotating shaft 81 extending in the width direction D3, and the rotating shaft 81 is rotatably supported by support walls 77 and 78. A second transport motor 79 is fixed to the support wall 78, and is connected to the rotation shaft 81 via an output gear 79A fixed to an output shaft of the second conveyance motor 79 and an input gear 81A fixed to an end of the rotation shaft 81. The rotational driving force is transmitted. The paper transport unit 80 has four driven rollers 80B corresponding to each drive roller 80A. Each of the four driven rollers 80B is rotatably supported by a rotation shaft 82 provided on a guide member that constitutes a transport guide surface on the upper side of the second transport path 27. Two rotating shafts 82 are provided so as to be separated in the width direction D3, and two driven rollers 80B are rotatably supported by each rotating shaft 82.

  The driven roller 80B is urged toward the driving roller 80A by a spring 80C (see FIG. 2B). Thus, the driven roller 80B is pressed against the driving roller 80A. When the driving roller 80A is rotationally driven in this state, the driven roller 80B is driven.

  A first correction motor 85 is attached to the left inner frame 14B. The first correction motor 85 is fixed to the outer surface of the inner frame 14B, and its output shaft 85A extends through the inner frame 14B to the opposite side (right side). A pinion gear 86 is fixed to the tip of the output shaft 85A of the first correction motor 85. At the left end of the upper surface 75A of the rotating frame 75, a rack 87 extending in the front-rear direction D2 is formed. The rack 87 meshes with the pinion gear 86. The rack 87 has parallel teeth arranged in the front-rear direction D2. The control unit 90 can rotate the rotation frame 75 of the tilt unit 65 about the rotation shaft 76 by controlling the driving of the first correction motor 85.

[Sheet correction process]
Hereinafter, an example of the procedure of the sheet correction process executed by the control unit 90 will be described with reference to the flowchart of FIG. 7 while referring to the operation explanatory diagrams of FIGS. 8 to 14. Here, FIGS. 8 to 14 are diagrams for explaining the operation of the transport roller pair of the paper transport unit 23 and the sheet correction mechanism 60, wherein the upper diagram is a plan view and the lower diagram is a side view. In the image forming apparatus 10, before the sheet correction process is performed, it is assumed that the tilt unit 65 is arranged at the initial position and the slide unit 66 is arranged at the slide reference position.

  When an instruction signal indicating the start of an image forming operation is input to the image forming apparatus 10, the motor driver 95 of the control unit 90 drives the first transport motor 56, the second transport motor 79, and the like to perform pickup. The rollers 38, the paper feed roller pair 39, the paper transport unit 23, the paper transport unit 80, the resist transport unit 43, the discharge roller pair, and the like are rotated. Thereby, the printing paper P is taken out from the paper feeding tray 37 and fed to the first transport path 26, and further, the printing paper P is transported to the second transport path 27 by the paper transport unit 23.

  In step S11, the control unit 90 determines whether the printing paper P transported by the paper transport unit 23 is skewed. If it is determined in step S11 that the printing paper P is skewed, in next step S12, the control unit 90 operates the solenoid 64 to raise the driven roller 23B1 outside the width direction D3. Specifically, the driven roller 23B1 is moved from the pressed position to the release position (see FIG. 8).

  In the next step S13, the control unit 90 calculates the inclination direction of the printing paper P and the amount of inclination based on the detection signal of the skew detection sensor 61.

  In step S14, the control unit 90 rotates the tilt unit 65 in accordance with the tilt amount before the printing paper P enters the sheet correction mechanism 60 (see FIG. 9). Specifically, the tilt unit 65 is rotated from the initial position by the tilt amount in a direction opposite to the tilt direction of the printing paper P. Thereafter, when the printing paper P enters the sheet correction mechanism 60, the printing paper P is transported downstream by the paper transport unit 80 in the transport direction D11.

  As shown in FIG. 10, when the leading edge of the printing paper P reaches the leading edge detection sensor 62 and the leading edge of the printing paper P is detected by the control unit 90 (S15), in step S16, the control unit 90 sets the tilt The unit 65 is returned to the initial position (see FIG. 11). That is, the tilt unit 65 is rotated in the direction opposite to that of step S14 by the amount of the tilt. At this time, the upstream side in the transport direction D11 of the printing paper P is nipped only by the transport roller pair of the drive roller 23A and the driven roller 23B2. That is, the sheet is nipped by the pair of transport rollers located on the center side in the width direction D3. Therefore, the printing paper P is in a state where it is easy to rotate around the nip portion between the driving roller 23A and the driven roller 23B2. Therefore, when the tilt unit 65 is rotated to return the tilt unit 65 to the initial position, the printing paper P also rotates in the same direction about the nip between the driving roller 23A and the driven roller 23B2. Thereby, the skew of the printing paper P is corrected.

  When the leading end of the printing paper P reaches the edge detection sensor 63 as shown in FIG. 12, in the next step S17, the control unit 90 determines whether or not the printing paper P is displaced in any of the width directions D3. . If a lateral shift has occurred, the process proceeds to step S18, and the lateral shift amount is calculated. On the other hand, if no lateral displacement has occurred, the process proceeds to step S20.

  In step S18, the control unit 90 calculates the direction of the lateral shift of the printing paper P and the amount of the lateral shift. Thereafter, in step S19, the control unit 90 moves the slide unit 66 in the width direction D3 according to the lateral shift amount (see FIG. 13). Specifically, the slide unit 66 is moved from the slide reference position in the direction opposite to the direction of the lateral shift of the printing paper P by the amount of the lateral shift. Thereby, the lateral displacement of the printing paper P is corrected.

  In step S20, the control unit 90 determines whether the rear end of the printing paper P has passed through the paper transport unit 23. Such a determination can be made based on, for example, a change in the output of the skew detection sensor 61. When it is determined that the rear end of the printing paper P has passed the paper transport unit 23, in step S21, the control unit 90 operates the solenoid 64 to move the driven roller 23B1 outside the width direction D3 to the original position. Lower it (see FIG. 14). Specifically, the driven roller 23B1 is moved from the release position to the pressure contact position.

  Thereafter, in step S22, when the control unit 90 determines that the rear end of the printing paper P has passed the sheet correction mechanism 60, the control unit 90 returns the slide unit 66 to the slide reference position.

  As described above, in the present embodiment, when the inclination unit 65 is returned to the initial position, the outer driven roller 23B1 is disposed at the release position, and the outer driven roller 23B1 is located at the center in the width direction D3. Since the upstream portion of the printing paper P is nipped by the drive roller 23A, when the tilt unit 65 is returned to the initial position for skew correction, the printing paper P also rotates in the same direction. . After that, when the printing paper P is transported and the next printing paper P reaches the paper transport unit 23, the following printing is performed because the driven roller 23B1 on the center side in the width direction D3 and the driving roller 23A are in pressure contact with each other. The sheet P can be appropriately transported in the transport direction D11.

  The sheet correction mechanism 60 includes a slide unit 66 in addition to the tilt unit 65. Therefore, the correction of the skew of the printing paper P and the correction of the lateral displacement of the printing paper P by the slide unit 66 can be performed only by the sheet correction mechanism 60.

  In the above-described embodiment, the configuration in which the paper transport unit 23 has four transport roller pairs arranged in the width direction D3 is illustrated, but the present invention is not limited to this configuration. For example, the paper transport unit 23 may have an even number of transport roller pairs arranged in the width direction D3. In this case, two transport roller pairs located on the center side in the width direction D3 and adjacent in the width direction D3 correspond to the inner transport roller pair of the present invention, and the other transport roller pairs correspond to the outer transport roller pair of the present invention. Is equivalent to

  Further, the paper transport unit 23 may have a configuration in which three transport roller pairs are arranged in the width direction D3, and the transport roller pair inside the width direction D3 is arranged at the center in the width direction D3. In this case, when the skew correction is performed by the tilt unit 65, only the center conveyance roller pair in the width direction D3 is in the pressed state, so that the printing paper P rotates around the nip portion of the conveyance roller pair. It is in a state where it is easy to move. Therefore, when the tilt unit 65 is rotated to return the tilt unit 65 to the initial position, the printing paper P is likely to rotate in the same direction around the nip.

  The paper transport unit 23 may have a configuration in which three or more odd-numbered transport roller pairs are provided in the width direction D3. In this case, one transport roller pair located on the center side in the width direction D3 corresponds to the inner transport roller pair of the present invention, and the other transport roller pairs correspond to the outer transport roller pair of the present invention. With this configuration, when the tilt unit 65 is returned to the initial position, only the transport roller pair located at the center in the width direction D3 is disposed at the pressing position, and the other transport roller pairs are disposed at the release position. Preferably.

10: Image forming apparatus 23: Paper transport unit 23A: Drive roller 23B: Driven roller 23C: Spring 43: Registration transport unit 43A: Registration roller 43B: Rotating roller 43C: Spring 56: First transport motor 60: Sheet correction mechanism 61: Skew detection sensor 62: Tip detection sensor 63: Edge detection sensor 64: Solenoid 65: Inclination unit 66: Slide unit 67: Base frame 67A: Base portion 67B: Support portion 71: Rack 72: Pinion gear 73: Second correction motor 74 : Support portion 75: Rotating frame 76: Rotating shaft 77: Support wall 78: Support wall 79: Second transport motor 79A: Output gear 80: Paper transport unit 80A: Drive roller 80B: Follower roller 80C: Spring 81: Rotation Axis 81A: Input gear 82: rotating shaft 85: first correction motor 85A: output shaft 86: pinion gear 87: Rack 90: control unit

Claims (4)

A transport unit having three or more transport roller pairs arranged side by side in the width direction orthogonal to the transport direction,
Provided downstream of the transport unit in the transport direction, supported rotatably about a predetermined pivot point, and a skew amount corresponding to the skew of the sheet before the skewed sheet enters. A skew correction unit that is rotated from the initial position and corrects the skew of the sheet by returning to the initial position while nipping the sheet after the sheet has entered,
With
Each roller of the inner transport roller pair located on the center side in the width direction of the plurality of transport roller pairs is maintained at a pressure contact position where the rollers are pressed by an elastic force capable of transporting the sheet in the transport direction. Each roller of the outer transport roller pair located on the outer side in the width direction than the transport roller pair is movably supported between the pressed position and a release position where the pressed state is released,
A skew detection unit that detects that the sheet conveyed toward the skew correction unit by the conveyance unit is skewed;
A control unit that controls the movement of each roller of the outer transport roller pair,
The control unit includes:
When the skew detecting unit detects the skew of the sheet, the skew correcting unit is configured to move each roller of the outer conveying roller pair to the release position before returning to the initial position. Sheet transport device. The control unit includes:
2. The sheet conveying device according to claim 1, wherein each roller of the pair of outer conveying rollers is configured to return to the pressing position after the skew feeding correction unit is returned to the initial position. When the transport unit has an even number of the transport roller pairs, and the inner transport roller pairs are two transport roller pairs located on the center side in the width direction,
The first roller on one side of the plurality of transport roller pairs is a driven roller, and each of the driven rollers located between the center in the width direction and one end in the width direction is rotatable by a first rotation shaft. Each of the driven rollers located between the center in the width direction and the other end in the width direction is rotatably supported by a second rotation shaft,
An outer first end in the width direction of each of the first rotation shaft and the second rotation shaft is configured such that each roller of the outer conveyance roller pair can move between the pressing position and the release position. Displaceably supported,
The sheet conveyance device according to claim 1, wherein the control unit moves each roller of the pair of outer conveyance rollers to the release position by displacing the first end.   An image processing apparatus comprising the sheet conveying apparatus according to any one of claims 1 to 3, wherein the image processing apparatus performs predetermined image processing using the sheet conveyed by the sheet conveying apparatus.

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