JP2018090404A - Conveyance device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conveyance device which can accurately correct the positional deviation of a sheet by using another detection member even within a range where one detection member does not detect the sheet.SOLUTION: A conveyance device includes: a holding roller which holds a sheet and performs at least any operation of rotation and movement in the sheet width direction; a second CIS which is provided on the upstream side of the holding roller 1 and detects the position of the sheet; and a third CIS which is provided on the downstream side of the holding roller and detects the position of the sheet. The holding roller corrects at least one positional deviation of the positional deviation in the width direction of the sheet on a conveyance path of the sheet and the inclination with respect to the sheet conveyance direction on the basis of the detection result of the sheet by the second CIS and third CIS. The conveyance device stores the past position information of the sheet detected by the third CIS within a range where the second CIS does not detect the position of the sheet and the third CIS detects the position of the sheet. The holding roller corrects the positional deviation of the sheet that is currently conveyed on the basis of the stored position information.SELECTED DRAWING: Figure 17

Description

  The present invention relates to a conveyance device and an image forming apparatus in a copying machine, a printer, a facsimile, or a complex machine including the conveyance device.

  In a conveyance device that conveys a sheet such as a sheet, there may be a problem of sheet positional deviation (skew or lateral deviation) on the conveyance path. A transport device for transporting in a direction is already known.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2006-108152), as shown in FIG. 22, a sandwiching roller 200 that sandwiches the recording medium P and corrects its positional deviation is provided. The first CIS 201 and the second CIS 201 each having a plurality of photosensors arranged in the width direction of the recording medium P as detection means for detecting a positional deviation of the recording medium on the upstream side and the downstream side in the recording medium conveyance direction of the sandwiching roller 200, respectively. Two CIS 202 are provided. Each CIS is provided across the position corresponding to the side edge of the recording medium P, and the lateral displacement amount α of the recording medium P is detected by reading the side edge position of the recording medium P that has entered the CIS. be able to. Further, the skew amount (skew angle) β of the recording medium can be detected from the difference in the side end position of the recording medium P detected by the first CIS 201 and the second CIS 202. Based on the detected displacement amount of the recording medium P, the sandwiching roller 200 rotates or translates in the width direction while sandwiching the recording medium P to correct the displacement amount of the recording medium P. Can do.

  In the above-described detection method of the conveyance apparatus of Patent Document 1, the skew amount of the recording medium is calculated by simultaneously detecting the recording medium by two CISs, and the period during which the skew amount of the recording medium can be detected is recorded. Limited to the period when the media is facing both CIS. For this reason, when a period when the recording medium faces the two CISs is short, such as when a small-size recording medium is conveyed, the correction accuracy deteriorates, or there is no period when the two CISs face each other. In such a case, there is a problem that it cannot be detected by the above method.

  Under such circumstances, the present invention has an object to provide a conveying device that can accurately correct a positional deviation of a sheet using the other detection member even in a range where one detection member does not detect the sheet. .

  In order to solve the above-described problems, the present invention provides a sandwiching member that sandwiches and conveys a sheet to the downstream side, corrects the positional deviation, and is provided upstream of the sandwiching member in the sheet transport direction, In the conveying apparatus provided with an upstream side detection member that detects the position of the sheet and a downstream side detection member that is provided on the downstream side in the sheet conveyance direction of the clamping member and detects the position of the sheet, the clamping member includes the Based on the detection results of the upstream detection member and the downstream detection member, the positional deviation of the sheet is corrected, the upstream detection member does not detect the position of the sheet, and the downstream detection member is the sheet. In the range in which the position of the sheet is detected, the past position information of the sheet detected by the downstream side detection member is stored, and the clamping member is actually transported based on the stored position information. And correcting the positional deviation of.

  In the present invention, in the sheet conveyance process, the upstream side detection member does not detect the sheet, and the downstream side detection member detects the sheet in the range in which the downstream side detection member detects the sheet. Based on this, the sheet conveyance position is corrected. As a result, the detection result of the past sheet can be substituted for the positional deviation in the range not detected by the upstream side detection member, and the positional deviation correction of the sheet can be performed with high accuracy.

1 is a schematic configuration diagram of an image forming apparatus. It is a schematic block diagram of a conveying apparatus. It is sectional drawing which shows the drive mechanism of a clamping roller. It is sectional drawing which shows the moving mechanism of a holding frame. It is sectional drawing which shows the drive mechanism of a clamping roller. It is sectional drawing which shows the structure of a two-stage spline coupling. It is a figure explaining the mode of movement of a holding frame. 5A and 5B are diagrams illustrating a process of paper conveyance and position correction by the conveyance device, in which FIG. 9A is a plan view of the conveyance device, and FIG. FIG. 6 is a diagram illustrating a process of paper conveyance and position correction by a conveyance device. FIG. 6 is a diagram illustrating a process of paper conveyance and position correction by a conveyance device. FIG. 6 is a diagram illustrating a process of paper conveyance and position correction by a conveyance device. FIG. 6 is a diagram illustrating a process of paper conveyance and position correction by a conveyance device. FIG. 6 is a diagram illustrating a process of paper conveyance and position correction by a conveyance device. It is a top view which shows a mode that a small sized paper is conveyed to a conveying apparatus. It is a figure explaining detection of the amount of skew by the 3rd CIS. It is a block diagram regarding the control operation of a conveying apparatus. FIG. 10 is a flowchart of paper position correction using a skew amount of a past paper according to the present exemplary embodiment. FIG. 10 is a diagram illustrating correction of a sheet using a past skew amount of the sheet. FIG. 10 is a flowchart of paper position correction using a skew amount of a past paper according to a different embodiment. It is a top view which shows the conveying apparatus of different embodiment. It is a schematic block diagram of the image forming apparatus of different embodiment. It is a schematic block diagram of the conventional conveying apparatus.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

  In the color image forming apparatus 1 shown in FIG. 1, an image forming unit 2 in which four process units 9Y, 9M, 9C, 9Bk are detachably provided is arranged. Each process unit 9Y, 9M, 9C, 9Bk contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. The configuration is the same except that.

  Specifically, each process unit 9 includes a photosensitive drum 10 that is a drum-like rotating body capable of carrying toner as a developer on the surface, a charging roller that uniformly charges the surface of the photosensitive drum 10, And a developing device for supplying toner to the surface of the photosensitive drum 10.

  An exposure unit 3 is disposed above the process unit 9. The exposure unit 3 is configured to emit laser light based on the image data.

  A transfer unit 4 is disposed immediately below the image forming unit 2. The transfer unit 4 includes a drive roller 13, a secondary transfer counter roller 15, a plurality of tension rollers, an endless intermediate transfer belt 16 stretched around these rollers so as to be able to run around, and a photosensitive drum of each process unit 9. 10 includes a primary transfer roller 17 disposed at a position facing the intermediate transfer belt 16 with respect to 10. Each primary transfer roller 17 presses the inner peripheral surface of the intermediate transfer belt 16 at each position, and a primary transfer nip is formed at a place where the pressed portion of the intermediate transfer belt 16 and each photosensitive drum 10 come into contact. Has been.

  A secondary transfer roller 18 is disposed at a position opposite to the drive roller 13 of the intermediate transfer belt 16 and the drive roller 13 across the intermediate transfer belt 16. The secondary transfer roller 18 presses the outer peripheral surface of the intermediate transfer belt 16, and a secondary transfer nip is formed at a location where the secondary transfer roller 18 and the intermediate transfer belt 16 are in contact with each other.

  The paper feeding unit 5 is located below the image forming apparatus 1 and carries out the paper P from the paper feeding cassettes 19a to 19d serving as a plurality of sheet stacking units that store the paper P as sheets and each of the paper feeding cassettes. The paper feed roller 20 is used.

  In addition to the sheet feeding unit 5, a manual feed tray 40 as a sheet stacking unit is provided. The paper P loaded on the manual feed tray 40 is fed into the apparatus by a manual feed roller 41.

  The transport path 6 is a transport path for transporting the paper P carried out from the paper supply unit 5. On the conveyance path 6, a plurality of conveyance roller pairs are appropriately arranged until reaching a paper discharge unit 8 described later.

  On the conveyance path 6, on the conveyance path 6 on the downstream side in the paper conveyance direction (in the direction of arrow A <b> 2 in FIG. 1, also simply referred to as the conveyance direction) on the conveyance path 6 and on the upstream side with respect to the secondary transfer nip position. A conveyance device 30 is provided that corrects the positional deviation of the paper P and conveys the paper P downstream.

  The fixing unit 7 includes a fixing belt 22 that is heated by a heating source, a pressure roller 23 that can press the fixing belt 22, and the like.

  The paper discharge unit 8 is provided on the most downstream side of the conveyance path 6 of the image forming apparatus 1. The paper discharge unit 8 is provided with a pair of paper discharge rollers 24 for discharging the paper P to the outside and a paper discharge tray 25 for stocking the discharged paper P.

  In addition to the paper discharge path on the most downstream side of the conveyance path 6, a reverse conveyance path 6b branched from the paper discharge roller 24 is provided. The end of the reverse conveyance path 6 b joins the conveyance path 6 at a position upstream of the conveyance device 30 in the conveyance path 6. In the middle of the reverse conveyance path 6b, a plurality of conveyance roller pairs are provided.

  A scanner unit 42 is provided above the image forming apparatus 1. The scanner unit 42 can read an image on the surface of the document placed on the contact glass 43.

  An ADF (automatic document feeder) 44 is provided above the scanner unit 42. The document placed on the document table of the ADF 44 is automatically conveyed to the contact glass 43.

  The basic operation of the image forming apparatus 1 will be described below with reference to FIG.

  In the image forming apparatus 1, when an image forming operation is started, an electrostatic latent image is formed on the surface of the photosensitive drum 10 of each process unit 9Y, 9C, 9M, 9Bk. The image information exposed to each photosensitive drum 10 by the exposure unit 3 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. An electrostatic latent image is formed on each photoconductive drum 10, and toner stored in each developing device is supplied to the photoconductive drum 10 by a drum-shaped developing roller, whereby the electrostatic latent image is visualized. A visible image is formed as a toner image (developer image).

  In the transfer unit 4, the intermediate transfer belt 16 is driven to run in the direction of the arrow A <b> 1 in FIG. Further, each primary transfer roller 17 is applied with a constant voltage or a constant current-controlled voltage having a polarity opposite to the charging polarity of the toner. As a result, a transfer electric field is formed in the primary transfer nip, and the toner images formed on the respective photosensitive drums 10 are sequentially superimposed and transferred onto the intermediate transfer belt 16 in the primary transfer nip.

  On the other hand, when the image forming operation is started, the sheet accommodated in the sheet feeding cassette (for example, the sheet feeding cassette 19a) is rotated in the lower part of the image forming apparatus 1 by the rotation of the sheet feeding roller 20 of the sheet feeding unit 5. P is sent out to the conveyance path 6. The paper P can also be sent out from the manual feed tray 40 to the transport path 6.

  The paper P sent out to the transport path 6 is transported downstream by the transport device 30 and the roller pair on the transport path 6, and its positional deviation is corrected by the transport device 30, so that the secondary transfer roller 18 and the secondary transfer roller 18 are aligned. It is sent to a secondary transfer nip formed between the transfer opposing roller 15. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner images on the intermediate transfer belt 16 are collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

  The sheet P on which the toner image is transferred is conveyed to the fixing unit 7, and the sheet P is heated and pressed by the fixing belt 22 and the pressure roller 23, and the toner image is fixed on the sheet P. Then, the paper P on which the toner image is fixed is separated from the fixing belt 22, transported by a pair of transport rollers, and discharged to a paper discharge tray 25 by a paper discharge roller 24 in the paper discharge unit 8.

  The above description is an image forming operation when a full color image is formed on the paper P. A single color image can be formed using any one of the four process units 9Y, 9C, 9M, and 9Bk. It is also possible to form two or three color images using two or three process units 9.

  Next, a specific configuration of the transport device 30 that transports the paper P to the secondary transfer roller 18 on the downstream side and corrects the positional deviation will be described with reference to FIG.

  As shown in FIG. 2, the conveyance device 30 is provided with a straight conveyance path 6a that is a part of the conveyance path 6 (see FIG. 1). On this linear conveyance path 6a, the sheet P is nipped and conveyed downstream, and the nipping roller 31 as a nipping member for correcting the positional deviation of the sheet P, and the upstream in the conveying direction (arrow A2 direction in the figure). In order from the side, three detection members, a first CIS 32, a second CIS 33 (upstream detection member), and a third CIS 34 (downstream detection member) are provided. The sandwiching roller 31 is provided on the downstream side of the second CIS 33 and on the upstream side of the third CIS 34. In addition, on the upstream side of the first CIS 32 in the conveyance direction, a conveyance roller pair 35 that conveys the paper P is provided. In each CIS, a plurality of photosensors each including a light emitting element such as an LED and a light receiving element such as a photodiode are arranged in parallel in the width direction of the paper P.

  Next, the drive mechanism of the pinching roller 31 and the configuration around it will be described with reference to FIGS.

  As shown in FIG. 3, the sandwiching roller 31 is a roller pair having a plurality of roller portions divided in the width direction, and is driven by a driving roller 31b that is rotationally driven by a first motor 61 as a first driving means, It is comprised with the driven roller 31a rotated with the rotation of the roller 31b. The sandwiching roller 31 is configured to be able to transport the sheet P by rotating in a state where the sheet P is sandwiched.

  The main body frame 70, the base frame 71, the bracket 69, and the like are fixed to each other by screw fastening, and the sandwiching roller 31 is rotatably supported by the holding frame 72.

  The sandwiching roller 31 is formed so as to be able to rotate in an oblique direction (a double arrow W direction in FIG. 2) around the support shaft 73 together with a holding frame 72 as a holding member, and in the width direction (double arrow in FIG. 2). It can be moved in the H direction). Based on the detection result of each CIS, the sandwiching roller 31 moves in any one of the above directions, whereby the skew of the paper P and the positional deviation (lateral deviation) in the width direction can be corrected.

  The holding frame 72 is a sheet metal formed in a box shape, and the shaft portion of the sandwiching roller 31 is inserted into a hole portion formed at both end portions in the width direction via a bearing. The holding frame 72 can move in the width direction with respect to the main body frame 70 and the base frame 71 together with the sandwiching roller 31, and can rotate around the support shaft 73.

  A first drive mechanism including a first motor 61, gear trains 66 and 67, and the like is connected to one end side in the width direction of the drive roller 31b via a two-stage spline coupling 65. The first driving mechanism transmits the rotational driving force of the first motor 61 to the driving roller 31b via the gear trains 66 and 67 and the two-stage spline coupling 65, and rotationally drives the pinching roller 31.

  In addition, an encoder 96 for controlling the rotation speed and rotation timing of the drive roller 31b (the clamping roller 31) is installed on the other end side in the width direction of the drive roller 31b.

  As shown in FIG. 6, the two-stage spline coupling 65 includes a first spline gear 65a, a second spline gear 65b, an intermediate spline gear 65c, a guide ring 65d, and the like.

  The first spline gear 65a is an external gear, and is installed on a rotating shaft 68 that rotates together with one gear 67 of the gear trains 66 and 67 of the first drive means. The rotating shaft 68 is rotatably held by the bracket 69 via a bearing. The second spline gear 65b is an external gear and is installed on the shaft portion of the drive roller 31b.

  The intermediate spline gear 65c is an internal gear and extends in the width direction so as to mesh with the two spline gears 65a and 65b even if the clamping roller 31 (holding frame 72) moves (slides) in the width direction. Has been. Further, the two spline gears 65a and 65b are formed in a crown shape so as to mesh with the intermediate spline gear 65c even when the sandwiching roller 31 (holding frame 72) rotates in an oblique direction. By using such a two-stage spline coupling 65, even if the clamping roller 31 rotates about the support shaft 73 in a substantially horizontal plane direction or slides in the width direction, the frames 69 to 71 of the main body. Thus, the driving force of the first motor 61 fixedly installed on the motor is reliably and accurately transmitted to the driving roller 31b, so that the pinching roller 31 is driven to rotate well.

  The guide ring 65d is a substantially annular stopper member, and prevents the two spline gears 65a and 65b from moving relative to each other in the width direction and falling off the two-stage spline coupling 65. It is respectively installed at both ends in the width direction of 65c.

  Here, as shown in FIG. 5, the holding frame 72 is attached to the frames 69 to 71 via free bearings 95 (ball transfer) as relay support members installed on the frames 69 to 71 (base frame 71) of the apparatus. The base frame 71 is supported so as to be movable in both the width direction and the oblique direction (supported so that it can freely move in a plane perpendicular to the paper surface of FIG. 5).

  The free bearing 95 is a known bearing in which a steel ball 95 a is inserted into the recess of the pedestal 95 b, and the top of the steel ball 95 a makes point contact with the bottom surface of the holding frame 72. The free bearing 95 is configured to support the holding frame 72 at three or more positions with respect to the frames 69 to 71. In the present embodiment, the free bearing 95 corresponds to the four corners on the bottom surface of the holding frame 72 as shown in FIG. Free bearings 95 are fixed to the base frame 71 at positions where the holding frame 72 can be contacted even when the holding frame 72 is slid or rotated to the maximum.

  As described above, the holding frame 72 is supported by the base frame 71 via the free bearing 95, so that even if the holding frame 72 moves in the surface direction relative to the base frame 71, the friction load generated thereby is reduced. It can be made extremely small, and positional deviation correction (skew correction and lateral deviation correction) of the paper P can be performed with high responsiveness and high accuracy.

  As shown in FIG. 3, a support shaft 73 (stud) is fixed to the bottom surface of the holding frame 72 by caulking or the like so as to stand downward on the first drive mechanism side (right side in FIG. 3). ing.

  On the other hand, as shown in FIG. 4, a guide portion 71 a that is a rectangular hole is formed on the ceiling surface of the base frame 71 on the first drive mechanism side.

  As shown in FIGS. 3 and 4, the support shaft 73 is fitted to the guide portion 71 a of the base frame 71 via a guide roller 76 that is rotatably provided on the support shaft 73. The holding frame 72 can slide in the width direction in conjunction with the movement of the support shaft 73 along the guide portion 71 a together with the sandwiching roller 31, and can rotate around the support shaft 73.

  Further, the sandwiching roller 31 is provided with a second drive mechanism for rotating the sandwiching roller 31 about the support shaft 73 to correct the skew of the paper P. As shown in FIG. 3, the second drive mechanism includes a second motor 63, a timing belt 98, a first cam 84, a first tension spring 92 (see FIG. 4) as a first biasing member, a lever member 81, and the like. It is configured.

  As shown in FIG. 3, the second motor 63 is fixed to the base frame 71. A timing belt 98 is wound around a drive pulley installed on the motor shaft of the second motor 63 and a driven pulley installed on the rotation support shaft of the first cam 84. The driving force of the second motor 63 is transmitted to the first cam 84 via the timing belt 98.

  As shown in FIG. 4, the first tension spring 92 and the holding frame 72 are configured so as to urge the holding frame 72 in an obliquely forward direction (a clockwise direction around the support shaft 73 in FIG. 4). It is connected to the base frame 71.

  The lever member 81 is held by the base frame 71 so as to be rotatable about a rotation support shaft 81a, and a cam follower 82 (first roller-shaped member) that contacts the first cam 84 is rotatably installed at one end thereof. On the other end side, an action roller 83 (second roller-shaped member) that abuts against the protrusion 72a of the holding frame 72 is rotatably installed (axially supported).

  The first cam 84 is held by the base frame 71 so as to be rotatable about the rotation support shaft 84a. The first cam 84 urges the holding frame 72 biased in the obliquely forward direction by the first tension spring 92 in the obliquely opposite direction (counterclockwise direction around the support shaft 73 in FIG. 4). It is pushed indirectly through the lever member 81.

  With this configuration, when the second motor 63 is driven, the rotational driving force is transmitted to the first cam 84 via the timing belt 98 as shown in FIG. Try to rotate counterclockwise. By the rotational force of the first cam 84, the lever member 81 is pushed and rotated around the rotation support shaft 81a, whereby the holding frame 72 is pushed by the lever member 81 at the position of the projection 72a, The holding frame 72 rotates to resist the spring force of the first tension spring 92. By the rotation of the holding frame 72, the clamping roller 31 is rotated in the direction of the arrow W in FIG.

  The first cam 84 and the cam follower 82 are always in contact with each other by the spring force of the first tension spring 92. In addition, the protrusion 72 a of the holding frame 72 and the action roller 83 are always in contact with each other, and the holding frame 72 centered on the support shaft 73 depending on the rotation angle (posture in the rotation direction) of the first cam 84. The rotation angle (posture in the rotation direction) is determined. As described above, the cam follower 82 is installed at the contact position between the first cam 84 and the lever member 81, and the action roller 83 is installed at the contact position between the protrusion 72 a and the lever member 81. Since the frictional load generated at the contact position can be extremely reduced, skew correction (skew correction) is performed with high responsiveness and high accuracy.

  As shown in FIG. 3, an encoder wheel 86 is installed on the rotation support shaft 84 a of the first cam 84, and an encoder sensor 87 is fixed at the position of the base frame 71 corresponding thereto. Then, the second motor 63 is controlled based on the detection of the encoder wheel 86 by the encoder sensor 87, the rotation angle of the first cam 84 is adjusted and controlled, and the rotation amount of the holding frame 72 is adjusted.

  Here, the first cam 84 is formed so that its cam curve becomes a constant velocity cam curve. As a result, the amount of change in the rotation angle of the first cam 84 and the amount of change in the rotation angle of the holding frame 72 associated therewith can be made proportional, so that the skew correction control of the paper P can be performed with high accuracy. it can.

  The sandwiching roller 31 is provided with a third drive mechanism for correcting the lateral displacement of the paper P by moving the sandwiching roller 31 in the width direction. As shown in FIG. 3, the third drive mechanism includes a third motor 62, a timing belt 97, a second cam 74, a second tension spring 91 (see FIG. 4) as a second urging member, and the like. .

  As shown in FIG. 3, the third motor 62 is fixed to the base frame 71. A timing belt 97 is wound around a drive pulley installed on the motor shaft of the third motor 62 and a driven pulley installed on the rotation support shaft 74 a of the second cam 74. The driving force of the third motor 62 is transmitted to the second cam 74 via the timing belt 97.

  As shown in FIG. 4, the second tension spring 91 is connected to the holding frame 72 and the base frame 71 so as to bias the holding frame 72 in the positive direction of the width direction (left direction in FIG. 4). .

  The second cam 74 is held by the base frame 71 so as to be rotatable about the rotation support shaft 74a. The second cam 74 pushes the holding frame 72 urged in the forward direction of the width direction by the second tension spring 91 in the opposite direction of the width direction (right direction in FIG. 4). A cam follower 75 is installed (supported) on the support shaft 73 of the holding frame 72 at a position where it abuts on the second cam 74. Further, a guide roller 76 is installed (axially supported) at a position where it abuts on the guide portion 71 a of the support shaft 73.

  With this configuration, when the third motor 62 is driven, the rotational driving force is transmitted to the second cam 74 via the timing belt 97 as shown in FIG. Try to rotate counterclockwise. Due to the rotational force of the second cam 74, the holding frame 72 (clamping roller 31) slides along the guide portion 71a so as to resist the spring force of the second tension spring 91, and the lateral displacement of the paper P is shifted. It is corrected.

  The second cam 74 and the cam follower 75 are always in contact with each other by the spring force of the second tension spring 91, and the width of the support shaft 73 depends on the rotation angle of the second cam 74 (posture in the rotation direction). A moving distance in the direction is determined. As described above, since the second cam 74 and the support shaft 73 are in contact with each other via the cam follower 75, the frictional load generated at the contact position can be extremely reduced. Often done with high accuracy.

  As shown in FIG. 3, an encoder wheel 77 is installed on the rotation support shaft 74 a of the second cam 74, and an encoder sensor 78 is fixed at the position of the base frame 71 corresponding thereto. Then, the third motor 62 is controlled based on the detection of the encoder wheel 77 by the encoder sensor 78, the rotation angle of the second cam 74 is adjusted and controlled, and the amount of movement of the holding frame 72 in the width direction is adjusted.

  Here, the second cam 74 is formed so that its cam curve becomes a constant velocity cam curve. As a result, the amount of change in the rotation angle of the second cam 74 and the amount of change in the movement distance of the holding frame 72 can be proportional to each other, so that the lateral deviation correction control of the paper P can be performed with high accuracy. it can.

  FIG. 7C is a diagram illustrating an example of the operation of the holding frame 72 when the above-described lateral displacement correction and skew correction of the paper P are performed simultaneously.

  As shown in FIG. 7C, when the second motor 63 is driven and the first cam 84 is rotated, the lever member 81 is pushed by the first cam 84 and rotates around the rotation support shaft 81a. As a result, the holding frame 72 is pushed by the lever member 81 at the position of the protrusion 72 a, and the holding frame 72 rotates to resist the spring force of the first tension spring 92. At the same time, when the third motor 62 is driven to rotate the second cam 74, the holding frame 72 slides against the spring force of the second tension spring 91 by the second cam 74. At this time, the action roller 83 of the lever member 81 pushes the protrusion 72a (holding frame 72) while moving on the surface of the protrusion 72a.

  Next, a method of calculating the lateral displacement amount α and the skew amount β on the conveyance path of the paper P by each CIS will be described with reference to FIG.

  As shown in FIG. 2, when each CIS faces the paper P, each CIS detects the position of the side edge Pb of the paper P, whereby an ideal position in the width direction of the side edge of the paper P (parallel line in the figure). L) can be calculated as a lateral displacement amount α (in the illustrated example, a positional displacement amount at the position of the leading edge Pa of the paper P).

  Further, the skew amount β of the paper P is calculated from the difference between the positions of the side edges Pb detected by the two CISs. That is, as shown in FIG. 2, when the paper P is conveyed to a position facing the first CIS 32 and the second CIS 33, the position in the width direction of the side edge Pb is detected by the first CIS 32 and the second CIS 33, respectively. . The position in the width direction of the side end Pb detected by the first CIS 32 is L1, the position in the width direction of the side end Pb detected by the second CIS 33 is L2, and the first CIS 32 and the second CIS 33 measured in advance are used. Is the distance d, the skew amount β can be calculated by tan β = (L2−L1) / d. Note that the lateral displacement amount α and the skew amount β can also be calculated by the second CIS 33 and the third CIS 34 by the same method.

  In the present embodiment, the sandwiching roller 31 has two positional shift amounts calculated as described above, that is, a positional shift amount (horizontal shift amount) in the paper width direction and a tilt (skew amount) with respect to the paper transport direction. Based on this, the positional deviation is corrected. Hereinafter, an operation in which the clamping roller 31 corrects the positional deviation of the paper P will be described with reference to FIGS. As shown in FIG. 8B, a detection sensor 36 for detecting that the paper P has reached the secondary transfer position is provided immediately before the secondary transfer nip.

  As shown in FIGS. 8A and 8B, when the paper P is carried into the transport device 30, first, the transport roller pair 35 sandwiches the paper P and transports it downstream. When the paper P moves to a position facing each CIS, the lateral displacement amount α1 of the paper P is detected.

  When the paper P is conveyed to a position facing the first CIS 32 and the second CIS 33, the skew amount β1 of the paper P is detected by the two CISs by the method described above. Note that the positional deviation amount of the paper P can be obtained by detecting the positional deviation amount of the paper P a plurality of times and statistically processing the detection results, and the detection result of one time is used as the positional deviation amount of the paper P. You can also.

    As shown in FIGS. 9A and 9B, the pinching roller 31 has a rotation center W0 provided at the center in the width direction of the pinching roller 31, and rotates around the center position in the width direction of the paper P. Move. By this rotation operation, the sandwiching roller 31 can correct the skew (inclination with respect to the transport direction) of the sheet P when the sheet P is sandwiched. Further, the sandwiching roller 31 can slide in the width direction of the paper P, and can correct the lateral displacement of the paper P.

  When the positional deviation amount (lateral deviation amount α1 and skew amount β1) of the paper P is calculated by the first CIS 32 and the second CIS 33, the clamping roller 31 corrects the paper P in advance before clamping the paper P. The sheet P is moved in the direction opposite to the direction in which it is moved by the amount of positional deviation of the paper P. Specifically, the clamping roller 31 rotates by an angle β1 in the direction of the arrow W1 and translates by a distance α1 in the direction of the arrow H1 (hereinafter, this operation is referred to as a welcome operation).

  By this pick-up operation, the pinching roller 31 can pinch the paper P in a state of facing the paper P, and the positional deviation of the paper P when the pinching roller 31 pinches the paper P can be reduced as much as possible.

  As shown in FIGS. 10A and 10B, when the paper P is transported to a position facing the sandwiching roller 31, the sandwiching roller 31 sandwiches the paper P, and the transport roller pair 35 moves from the paper P. Separate.

  As shown in FIGS. 11A and 11B, the nipping roller 31 that nipped the paper P corrects the positional deviation of the paper P while conveying the paper P downstream. Specifically, the clamping roller 31 rotates in the direction of the arrow W2 and moves in parallel in the direction of the arrow H2 based on the amount of displacement detected by each CIS. As a result, the paper P moves from the original position (two-dot chain line portion in the figure) to the corrected position (solid line portion in the figure), and the positional deviation is corrected (hereinafter, this operation is referred to as a feeding operation). .

  In this way, the positional deviation of the paper P can be corrected by the pick-up operation and the feeding operation (first correction operation) by the pinching roller 31. Further, by causing the holding roller 31 to pick up in advance, the holding roller 31 after the feeding operation is moved to the reference posture of the holding roller 31 (the posture of the solid line portion in FIG. 11a facing the conveyance path of the paper P). Can be arranged.

  As shown in FIGS. 12A and 12B, when the paper P is conveyed further downstream by the sandwiching roller 31, the paper P faces the third CIS 34. Then, the second CIS 33 and the third CIS 34 detect the lateral displacement amount α2 and the skew amount β2 of the paper P. Based on the positional deviation amount of the paper P, the clamping roller 31 rotates and translates, and the positional deviation of the paper P is corrected again (hereinafter, this operation is referred to as a second correction operation).

  By performing such a second correction operation, the positional deviation of the paper P can be corrected with higher accuracy. That is, in the first correction operation, the positional deviation of the paper P detected by the first CIS 32 and the second CIS 33 before the pick-up operation can be corrected, but the subsequent positional deviation of the paper P can be corrected. Can not. For this reason, by performing the second correction operation after the first correction operation, it is possible to correct the subsequent positional deviation of the paper P, and it is possible to realize highly accurate correction. The main causes of the positional deviation of the paper P after first detecting the positional deviation of the paper P are the conveyance skew of the conveyance roller pair 35, the difference in parallelism with the clamping roller 31, and the clamping roller 31 being the paper. Examples include fluttering of the paper P due to pressure when the P is held, pressure deviation in the width direction of the holding roller 31, conveyance skew of the holding roller 31, and the like.

  During the second correction operation, the positional deviation of the paper P is repeatedly detected by the second CIS 33 and the third CIS 34, and the positional correction amount of the paper P is corrected each time and fed back to the movement amount of the pinching roller 31. That is, as described above, the positional deviation of the paper P also occurs during correction of the position of the paper P (while the paper P is being conveyed), and the positional deviation amount of the clamping roller 31 is detected from moment to moment. By feeding back to this correction amount, it is possible to correct the positional deviation amount to the downstream side in the transport direction of the paper P, and it is possible to realize more accurate correction.

  Then, as shown in FIGS. 13A and 13B, after the second correction operation of the paper P, when the paper P is further conveyed downstream and reaches the secondary transfer position, the sandwiching roller 31 is moved. Separated from the paper P. Then, at the secondary transfer position, the image is transferred to the paper P, and the paper P is further conveyed downstream. At this time, the detection sensor 36 detects the arrival of the paper P at the secondary transfer position, and the transport device 30 shifts to an operation for transporting the next paper.

  As described above, in the conveyance device 30 of this embodiment, during the conveyance process of the paper P, the positional deviation amount of the paper P can be calculated by each CIS, and the positional deviation can be corrected by the clamping roller 31. In particular, in the present embodiment, the conveying device 30 is disposed immediately before the secondary transfer position, so that the positional deviation of the paper P in the secondary transfer nip can be minimized, and the intermediate transfer belt 16 (see FIG. 1). Misalignment of the image transferred from the paper to the paper P can be kept to a minimum.

  By the way, there are various sizes of paper on which the image forming apparatus 1 forms an image, and the transport device 30 is also required to support various sizes of paper. For example, a postcard size paper P1 as shown in FIG.

  When the small-size paper P1 is passed through the conveying device 30, there is a problem that the range in which the positional deviation amount of the paper P can be detected is narrower than that of the large-size paper. That is, as shown in FIG. 14, since the rear end Pc of the paper P passes through the second CIS 33 at an earlier stage than the large paper, the small paper P1 passes through the second CIS 33 and the third CIS 34. The period facing is short. For this reason, in the section where the sheet P reaches the secondary transfer position from the position shown in FIG. 14, the sheet P cannot be detected by the two CISs, and the positional deviation of the sheet P occurring in this section is corrected. Or the number of data of the positional deviation amount of the paper that can be acquired by the second CIS 33 and the third CIS 34 is reduced, which affects the accuracy of the position correction.

  In order to solve the above-described problems, the transport apparatus according to the present embodiment performs the following control when a small-size sheet is transported.

  First, as shown in FIG. 14, after the rear end Pc of the sheet P1 passes through the second CIS 33 (after the sheet P1 is no longer detected by the second CIS 33), the sheet P1 is moved by the third CIS 34 facing the sheet P1. The position of the side end Pb is detected and recorded a plurality of times at regular intervals.

  The skew amount β of the paper P1 can be calculated from a plurality of detection positions having different detection times. Specifically, as shown in FIG. 15, the portion of the side end Pb of the paper P1 that faces (detects) the third CIS 34 at a certain time is positioned at the side end Pb1, and the position in the width direction of the side end Pb1 is positioned. M1 is set, the side end Pb portion of the paper P1 facing the third CIS 34 after t seconds from a certain time is the side end Pb2, the width direction position of the side end Pb2 is the position M, and the conveyance speed of the paper P1 is v Then, the skew amount β of the paper P1 can be obtained by tan β = (M1−M2) / vt. The skew amount β (position information) of the sheet P1 thus obtained is stored in the storage unit of the image forming apparatus.

  Next, when a small-size sheet is passed to the transport device 30, the skew of the sheet that is actually passed is based on the skew amount β (position information of the past sheet) of the sheet P1 described above. Correct the line. In other words, in addition to the first correction operation for the paper that is actually passed through and the second correction operation until the trailing edge of the paper passes through the second CIS 33, this is obtained by detecting the paper transported in the past. Correction based on the amount of skew (hereinafter, simply referred to as the skew amount of the past paper) is performed.

  As the correction amount based on the past skew amount of paper, it is preferable to determine the correction amount by statistically processing a plurality of detection results. As a result, error factors such as individual detection errors can be eliminated, and accurate correction can be performed. Further, the correction amount may be determined by statistically processing data of detection results of a plurality of sheets. As a result, it is possible to eliminate as much as possible the cause of positional deviation peculiar to each sheet, such as the habit of each sheet, and it is possible to perform correction with higher accuracy. However, the skew amount of the past sheet can be detected only once and used as the correction amount. In this case, it is preferable to use the skew amount immediately before the sheet reaches the secondary transfer position. As a result, it is possible to correct the skew amount from when the sheet passes through the second CIS 33 to immediately before reaching the secondary transfer position.

  In this way, in the range in which the paper P cannot be detected by the second CIS 33, the amount of skew of the paper detected by the third CIS 34 in the past is substituted, and the paper P occurs immediately before reaching the secondary transfer position. The positional deviation can be corrected, and correction with higher accuracy becomes possible.

  In the correction using the skew amount of the past sheet (paper), the skew amount of the sheet is stored for each type of sheet (plain paper, cardboard, envelope, etc.), sheet size, and thickness. The correction is preferably performed using the skew amount of the past sheet corresponding to the type, size, and thickness of the sheet that is actually conveyed. As a result, it is possible to correct the positional deviation with a correction amount corresponding to each type of sheet, so that more accurate correction can be performed. In addition, the sheet feeding unit 19a to 19d or the manual feed tray 40 determines which sheet is supplied from the sheet stacking unit, stores past sheet skew amount data for each sheet stacking unit, and actually conveys the sheet. Correction may be performed using past data corresponding to a paper feed cassette or the like on which sheets to be stacked are stacked.

  Further, it is determined whether the sheet that is actually transported is the front side printing or the back side printing, and using the skew amount of the past paper detected in the process of transporting the corresponding printing side, It is preferable to perform skew correction. Since the transport path of the paper is different between the front side transport and the back side transport, the skew amount is also different. Therefore, it is possible to perform correction with higher accuracy by making corrections using different skew amounts. it can.

  The skew amount of the past paper used for correction may be measured by providing a measurement mode for measuring the skew amount in advance. Thereby, the correction using the skew amount of the above-mentioned past paper can be performed from the first paper passed through the transport device. In addition, the sheet that has been passed through first may be used for the subsequent correction by detecting and storing the skew amount without performing the correction using the skew amount of the past sheet. Regarding these methods, it may be set so that the operator can select the presence or absence of the measurement mode by using the operation panel of the image forming apparatus. Also in the measurement mode, a plurality of sheets are conveyed, the skew amount is detected and stored, and the stored plural skew amounts are statistically processed, thereby correcting the correction amount of the currently conveyed sheet. Is preferably determined.

  Further, the skew amount of the past paper used for the correction is the skew amount measured in advance in the measurement mode or the skew amount obtained by measuring the paper passed in the first stage, The skew feeding amount may be detected by the third CIS 34 every time the sheet is conveyed, and the stored skew amount data of the past sheet may be updated each time.

  Each time the control unit of the image forming apparatus detects the opening / closing of the paper feed cassettes 19a to 19d (see FIG. 1), the past skew amount data of the type of paper corresponding to the paper feed cassette is initialized. Also, it is possible to newly set the paper skew amount data to be retrieved. When the paper cassette is opened and closed, there is a high possibility that a new bundle of paper is set in the paper cassette. There is a high possibility that the tendency of the skew amount and the skew direction of the paper will change. For this reason, it is possible to make corrections according to the new paper trend by initializing the skew amount data of the past paper at the timing of opening and closing the paper cassette and setting it to a new one. Can be improved.

  Alternatively, the image forming apparatus may be configured such that the power of the image forming apparatus is once stopped and the skew amount data of the past paper is initialized and newly retrieved at the timing of restart. Even if the paper cassette is opened or closed while the image forming apparatus is turned off, the control unit of the image forming apparatus cannot detect the opening and closing, so when the image forming apparatus is turned off and restarted In this case, a new skew amount can be set.

FIG. 16 is a block diagram illustrating control of operations related to the transport device 30.
As shown in FIG. 16, when the controller 54 outputs a drive signal to the motor driver 55, the motor driver 55 drives each motor provided in the conveyance device 30, and the rotation operation of the nipping roller 31 and the rotation of the conveyance roller pair 35. Drive control such as operation is performed.

  Further, the correction amount of the paper is determined by the arithmetic circuit 53 based on the detection result by each CIS of the transport device 30. In accordance with this correction amount, a drive signal is output from the controller 54, the second motor 63 and the third motor 62 are driven, and the nipping roller 31 is rotated or slid to correct the positional deviation of the paper.

  When the operator operates the operation panel 52, the information is sent to the main body control unit 50 provided on the main body side of the image forming apparatus 1. Specifically, information such as the type of paper used for image formation and the presence / absence of a measurement mode for measuring data of the skew amount of past paper is sent to the main body control unit 50.

  When the image forming operation is started, information such as the size of a sheet used for image formation is referred to, and the data of the skew amount of the past sheet is sent from the storage unit 51 to the controller 54 for the corresponding sheet. . Based on the past skew amount of the paper, the paper position deviation is corrected. Further, the past positional deviation amount of the paper detected by the third CIS 34 is stored in the storage unit 51.

  The main body control unit 50 detects the opening / closing operation of the paper feed cassette 19 and initializes (deletes) the past positional deviation data of the paper stored in the storage unit 51 for the corresponding paper feed cassette 19.

FIG. 17 shows a control flow of the above-described second correction operation of the present embodiment.
As shown in FIG. 17, first, when a print command is issued to the image forming apparatus 1, information on the sheet P (sheet type, size, etc.) carried into the transport apparatus 30 is confirmed by the control unit (step S1). . Then, it is determined whether or not the skew amount data of the past paper suitable for the loaded paper P exists in the storage unit (step S2), and if the past skew amount data exists, The data is referred to from the storage unit, and the target position of the pinching roller 31 is determined based on the skew amount data (step S3).

  Then, the actual skew amount of the sheet P currently conveyed by the second CIS 33 and the third CIS 34 is detected (step S4), and the skew amount is corrected by the rotation operation of the pinching roller 31 (step S5). ). This skew amount detection operation is repeated until the trailing edge Pc of the paper P passes through the second CIS 33. That is, every time the skew amount is detected by the second CIS 33 and the third CIS 34, the rotation amount by the clamping roller 31 is corrected. By this feedback control based on repeated detection, it is possible to correct misalignment of the paper P during the correction operation, and more accurate correction is possible.

  Here, details of the skew correction of the paper P in steps S3 to S6 will be described with reference to FIG. In the example of FIG. 18, the correction amount is determined to be the rotation of the angle β3 in the clockwise direction based on the past skew amount data referred to from the storage unit.

  The right side of FIG. 18 shows the paper P before the second correction operation, and the paper P is inclined counterclockwise by an angle β4 with respect to the transport direction.

  The clamping roller 31 is rotated in the direction of the arrow W2 by the second correction operation, and corrects the skew of the detected paper P. At this time, if there is no data on the skew amount of the past paper, the paper P is rotated to an ideal position facing the transport path. On the other hand, when there is data on the skew amount of the past paper, the paper P is rotated from the ideal position by the determined correction amount. Specifically, as shown in the center of FIG. 18, since the determined correction amount is the rotation of the angle β3 in the clockwise direction, the sheet P is inclined by the angle β3 from the position facing the conveyance path in the clockwise direction. Rotate to the desired position. That is, based on the data of the skew amount of the past paper, the paper P is inclined by the angle β3 counterclockwise from the position after passing the second CIS 33 (see FIG. 14) until it is conveyed to the secondary transfer nip. is assumed. For this reason, the sheet P can be brought closer to the ideal position in front of the secondary transfer roller 18 as shown on the left side of FIG. If it is tilted by the same amount as the other paper, it can be placed in the ideal position).

  As described above, the correction amount determined based on the past skew amount of the sheet is added to the correction amount of the second correction operation (the rotation amount to the ideal position of the sheet) during the second correction operation. Correction is performed. Further, the correction using the past skew amount of the sheet is not limited to the time of the second correction operation, and can be performed at a predetermined timing during the nipping roller 31 nipping the sheet P, such as during the feeding operation.

  Then, as shown in FIG. 17, the paper P that has completed the second correction operation and has passed the second CIS 33 is detected in its positional deviation by the third CIS 34, and the detected data is stored (step S7, S8). The detection by the third CIS 34 is repeated until the paper P reaches the secondary transfer roller 18 (step S9).

  The data of the positional deviation amount of the paper P stored in step S8 is stored as a value obtained by correcting the target movement amount determined in step S2. That is, the sheet P in step S7 is tilted by the skew amount in the direction opposite to the tilt direction based on the past skew amount data of the sheet (second correction operation in step S5). . For example, in the example of FIG. 18, it is inclined clockwise by an angle β3. Therefore, the value excluding the angle β3 is stored in the storage unit as the skew amount of the past sheet.

  When the detection sensor 36 (see FIG. 8b) detects that the paper P has reached the secondary transfer roller 18, the detection of the positional deviation by the third CIS 34 is terminated, and the detection result by the third CIS 34 is statistically processed. Then, a correction value using the past skew amount of the paper is determined (step S10).

  If there is a next paper print command, the transport device proceeds to the next operation (step S11).

  Through the above steps, the transport device 30 can transport the paper to the downstream side while accurately correcting the positional deviation of the paper, even if the paper to be carried in is a small-size paper.

  In the above description, the case where the skew amount of the past paper is updated each time the transport device transports a new paper has been described. On the other hand, FIG. 19 shows a flowchart when the correction amount determined first is used as it is without updating the skew amount of the past paper.

  As shown in FIG. 19, in the flow of the present embodiment, as a point different from the flowchart shown in FIG. 17, when the rear end of the paper P passes through the second CIS 33 (step S <b> 6), the past paper P is skewed. It is determined again whether or not the amount of data exists (step S6b). If there is past skew amount data of the paper P and the correction amount has already been determined, the leading edge of the paper is detected without performing detection and correction amount determination by the third CIS 34 in steps S7 to S10. When the detection sensor 36 detects that has reached the secondary transfer roller (step S7c), the transport device shifts to the next paper transport operation.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  Sheets include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, plastic film, prepreg, copper foil, etc. included.

  As shown in FIG. 20, a pair of skew detection sensors 37 may be provided immediately downstream of the third CIS 34 and immediately before the secondary transfer roller 18. As a result, the skew amount of the sheet P immediately before reaching the secondary transfer nip can be detected. By using this detection result as the skew amount of the past paper and correcting the skew of the currently transported paper, it becomes possible to perform more accurate correction.

  The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a complex machine thereof.

  In the embodiment described above, the present invention is applied to the conveyance device 30 installed in the electrophotographic image forming apparatus 1. However, the present invention is applied to the conveyance device installed in the inkjet image forming apparatus. The present invention can also be applied. Hereinafter, an ink jet image forming apparatus will be described with reference to FIG.

  As shown in FIG. 21, the inkjet image forming apparatus 100 includes a paper feeding unit 110, a transport device 120, an image forming unit 130, a drying unit 140, and a paper discharge unit 150.

  The paper P sent out from the paper supply unit 110 is transported by the transport device 120 and sent out to the image forming unit 130.

  In the image forming unit 130, the paper P is positioned on the cylindrical drum 131 and is conveyed in the direction of the arrow in the drawing by the rotation of the cylindrical drum 131. Then, the paper P is transported to the lower part of the discharge heads 132 for each color at a predetermined timing, and ink of each color is discharged onto the paper P, so that an image is formed on the surface of the paper P.

  The paper P on which the image is formed by the image forming unit 130 is transported to the drying unit 140 to evaporate moisture in the ink, and then discharged by the paper discharge unit 150 to a position where the operator can take it out.

  By applying the above-described configuration of the transfer device of the present invention to the transfer device 120, the same effects as those of the above-described embodiment can be obtained. In other words, the paper P can be transported to the image forming unit 130 side, and the positional deviation of the paper P on the transport path can be accurately corrected, and an image can be formed at the regular position of the paper P.

  Further, in the embodiment described above, the case where correction is performed based on the data of the skew amount of the past paper for the small size paper is shown, but a large size paper may be used.

  Further, in the embodiment described above, the range in which the paper P does not face the second CIS 33 and the second CIS 33 cannot detect the paper P is corrected by using the past skew amount data of the paper by the third CIS 34. To do. However, the correction is not limited to the range in which detection by the second CIS 33 is not possible. For example, correction may be performed using the skew amount data of the past paper by the third CIS 34 within a range in which the detection accuracy by the second CIS 33 is reduced. .

  In the embodiment described above, the storage unit that stores the skew amount of the past paper is provided on the main body side of the image forming apparatus 1, but the storage unit may be provided on the transport device side.

  In the above description, the lateral displacement amount and skew amount of the paper are detected by each CIS and corrected. However, only one positional displacement may be corrected.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 18 Secondary transfer roller 30 Conveying apparatus 31 Nipping roller (nipping member)
32 First CIS
33 Second CIS (upstream detection member)
34 Third CIS (downstream detection member)
19a to d Paper feed cassette (sheet stacking section)
40 Bypass tray (sheet stacking section)

JP-A-2006-108152

Claims (10)

A sandwiching member that sandwiches the sheet and conveys it downstream, and corrects the misalignment;
An upstream side detection member that is provided on the upstream side in the sheet conveyance direction of the clamping member and detects the position of the sheet;
In the conveying apparatus provided with a downstream side detection member that is provided on the downstream side in the sheet conveyance direction of the clamping member and detects the position of the sheet,
The clamping member corrects the positional deviation of the sheet based on the detection results of the upstream detection member and the downstream detection member.
In the range where the upstream detection member does not detect the position of the sheet and the downstream detection member detects the position of the sheet, the past position information detected by the downstream detection member is stored,
The conveying apparatus, wherein the clamping member corrects a positional deviation of a sheet that is actually conveyed based on the stored position information.   The stored position information of the sheet includes a plurality of pieces of position information of a plurality of sheets conveyed in the past, and the clamping member uses the correction amount obtained by statistically processing the plurality of pieces of position information according to the correction amount. The transport apparatus according to claim 1, wherein the positional deviation is corrected.   The clamping member is based on position information of a past sheet having a type, size, or thickness corresponding to at least one of the type, size, and thickness of the sheet that is actually conveyed, The conveying apparatus according to claim 1, wherein a positional deviation of a sheet that is actually conveyed is corrected.   4. The transport apparatus according to claim 1, wherein the correction amount based on the stored sheet position information is updated each time a new sheet is transported. 5. A measurement mode for storing the position information;
5. The conveying device according to claim 1, wherein the clamping member corrects a positional deviation of a sheet that is actually conveyed based on position information stored in the measurement mode. The sheet is supplied from one of a plurality of sheet stacking units that stack sheets.
6. The positional deviation of a sheet that is currently conveyed is corrected based on position information of a past sheet that has been supplied from the same sheet stacking unit as the sheet stacking unit that supplied the sheet that is currently conveyed. The transport apparatus according to item 1. A conveying device provided in an image forming apparatus capable of duplex printing,
For each of the front side printing and the back side printing, the past sheet position information is individually stored,
The said clamping member correct | amends the position shift of the sheet | seat currently conveyed based on the positional information on the past sheet | seat of the printing surface corresponding to the printing surface of the sheet | seat currently conveyed. The conveying apparatus as described in. A conveying device provided in an image forming apparatus capable of forming an image on the sheet,
The sheet is supplied from a sheet stacking unit that can be opened and closed with respect to the image forming apparatus main body.
Each time the sheet stacking unit is opened and closed, the stored past sheet position information is initialized,
The conveying apparatus according to claim 1, wherein the clamping member corrects a positional deviation of a sheet that is actually conveyed based on position information of the sheet after opening and closing. A conveying device provided in an image forming apparatus capable of forming an image on the sheet,
Each time the power of the image forming apparatus is stopped and started, the stored past sheet position information is initialized,
9. The conveying device according to claim 1, wherein the clamping member corrects a positional deviation of a sheet that is actually conveyed based on position information of the sheet after the power supply of the image forming apparatus is stopped and started. .   An image forming apparatus comprising the transport device according to claim 1.

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