Sheet conveying device and image forming apparatus

Abstract

To reduce change in conveyance speed of a sheet when performing skew correction in a side registration method.SOLUTION: A sheet conveyance device includes: sheet conveying means (50) having a first rotating body (34-4) and a first rotating body moving unit (600) for moving the first rotating body in a state of nipping a sheet in a width direction; skew feeding correcting means (55) having a contact surface (31) which extends along a sheet conveying direction and can be brought into contact with an end part of the sheet; an oblique feed rotating body (32) for moving the sheet so as to approach an abutting surface as the sheet is moved downstream in the sheet conveying direction, where the sheet conveyance device corrects the skew of the sheet; detecting means (60) for detecting a position of an end of the sheet; and control means. In a case where the position of an end part in a width direction of the sheet is a first position before the sheet held by the first rotating body reaches the oblique feed rotating body, the first rotating body is moved by first distance. In a case where the position of the end part in the width direction of the sheet is a second position which is farther from the first position than the abutting surface, the first rotating body is moved by second distance longer than the first distance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a sheet transport device that transports a sheet and an image forming apparatus including the same. [Background technology]

[0002] Conventionally, image forming devices have been used that can correct misalignment of a sheet position in a direction perpendicular to the sheet conveying direction, skew of the sheet, etc., while the sheet is being conveyed. For example, Patent Document 1 discloses a sheet alignment device of a so-called side registration type that conveys the sheet while shifting the width of the sheet toward a reference member by a skew roller, and corrects skew of the sheet by abutting the side edge of the sheet against the reference member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-189355 Summary of the Invention [Problem to be solved by the invention]

[0004] In the side registration method, first, a roller moves the sheet toward a reference member, which moves the sheet in a direction inclined with respect to the sheet conveying direction. Then, when the side edge of the sheet abuts against the reference member, the sheet is slipped between the roller and the sheet, so that the sheet is conveyed along the reference member. In addition, in a direction perpendicular to the sheet conveying direction, the conveying distance of the sheet when it abuts against the reference member varies depending on the position of the end of the sheet relative to the reference member. In this way, if the sheet slips between the roller and the roller, or the conveying distance of the sheet when it abuts against the reference member varies, there is a problem that the conveying speed of the sheet becomes unstable during skew correction, which is a factor that reduces productivity.

[0005] The present invention has been made to solve the above problems, and has an object to reduce changes in the sheet transport speed when performing skew correction in the side registration method. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a sheet conveying device, comprising: a first conveying roller pair that is movable in a width direction perpendicular to a sheet conveying direction while sandwiching a sheet and conveys the sheet; and a second conveying roller pair that is disposed downstream of the first conveying roller pair in the sheet conveying direction, extends along the sheet conveying direction, and conveys the sheet in the width direction. side a reference member having a contact surface capable of contacting an end of the sheet; a pair of skew rollers arranged downstream of the first conveying roller pair in the sheet conveying direction, which sandwich and convey the sheet in a direction inclined with respect to the sheet conveying direction so as to approach and contact the contact surface in the width direction of the sheet as the sheet moves downstream in the sheet conveying direction; a detection means arranged upstream of the first conveying roller pair in the sheet conveying direction, which detects the position of a side end of the sheet in the width direction; and a control means for controlling movement of the sheet in the width direction by the first conveying roller pair, wherein before the sheet is skewed by the skew roller pair, the control means a sheet having a side end portion in the width direction that is located on an opposite side of the contact surface from a predetermined position in the width direction, the sheet being moved to the predetermined position in the width direction by the first conveying roller pair; Based on the detection result of the detection means when a side end of the sheet sandwiched between the first conveying roller pair is at a first position with respect to the contact surface, the first conveying roller pair is moved a first distance in the width direction, and when the side end of the sheet sandwiched between the first conveying roller pair is at a second position farther from the contact surface than the first position, the first conveying roller pair is moved a second distance in the width direction that is longer than the first distance. The sheet conveying device is characterized in that: Effect of the Invention

[0008] According to the present invention, it is possible to reduce a change in the sheet transport speed when performing skew correction in the side registration method. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of a printer according to a first embodiment. [Diagram 2] FIG. 2 is a schematic configuration diagram of a registration unit according to the first embodiment. [Diagram 3] FIG. 13 is a schematic diagram of a conventional registration unit as a reference example. [Figure 4]13 is a diagram showing speed components of a sheet conveyed through a registration unit in a reference example. [Diagram 5] 13A and 13B are diagrams illustrating the relative positions of a sheet conveyed through a registration unit and a reference member in a reference example. [Figure 6] 13 is a plot of the relationship between the change in sheet conveying speed during skew correction and the distance L before skew correction. [Figure 7] 3A and 3B are schematic diagrams showing a cross-sectional configuration of a conveying section of the first embodiment. [Figure 8] FIG. 2 is a perspective view showing a drive configuration of a conveying roller according to the first embodiment. [Figure 9] 1A is a schematic diagram showing a skew correction unit according to a first embodiment as viewed from above, and FIG. [Figure 10] 1A is a perspective view showing a pressure applying configuration of a pressure applying mechanism of the first embodiment, and FIG. [Figure 11] 3A and 3B are schematic diagrams showing a pressurized state and a released state of the pressurizing mechanism of the first embodiment. [Figure 12] FIG. 2 is a perspective view showing an arrangement position of a seat position detection sensor according to the first embodiment. [Figure 13] FIG. 2 is a schematic perspective view of a roller driving mechanism according to the first embodiment. [Figure 14] FIG. 2 is a schematic perspective view of a slide mechanism according to the first embodiment. [Figure 15] 1A is an enlarged perspective view of a pressure release mechanism of the first embodiment; [Figure 16] FIG. 4 is a functional block diagram showing a control configuration of a registration unit according to the first embodiment. [Figure 17] 6 is a flowchart showing the flow of a sheet conveying operation in the registration unit according to the first embodiment. [Figure 18] FIG. 11 is a schematic diagram of a registration unit according to a second embodiment. [Figure 19] FIG. 11 is a functional block diagram showing a control configuration of a registration unit according to the second embodiment. [Figure 20] 10 is a flowchart showing the flow of a sheet conveying operation in a registration unit according to the second embodiment. [Figure 21] FIG. 11 is a schematic diagram of a registration unit according to a third embodiment. [Figure 22] 13A and 13B are diagrams showing the configuration of a reference member moving mechanism according to a third embodiment. [Figure 23] FIG. 11 is a functional block diagram showing a control configuration of a registration unit according to a third embodiment. [Figure 24] 13 is a flowchart showing the flow of a sheet conveying operation in a registration unit according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. EXAMPLES

[0011] <Overall configuration of image forming apparatus> First, a schematic configuration of a printer 1 as an image forming apparatus of the first embodiment will be described. FIG. 1 is a schematic configuration diagram of the printer 1. The printer 1 is a device such as a printer, a copier, a facsimile, and a multifunction machine that forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from a document. The printer 1 is also capable of printing for purposes other than general office use, and can use various sheets such as paper and envelopes, glossy paper, plastic films such as sheets for overhead projectors, and cloth as recording media. The device body 1A of the printer 1 contains a feed cassette 51 that stores sheets S, and an image forming engine 513 that forms an image on the sheets S fed from the feed cassette 51. The image forming engine 513, which is an example of an image forming means, is a tandem-type intermediate transfer type engine unit that includes four image forming units PY, PM, PC, and PK that form yellow, magenta, cyan, and black toner images, respectively, and an intermediate transfer belt 506. The image forming stations PY to PK are electrophotographic units having photosensitive drums 1Y, 1M, 1C and 1K, respectively, which are photosensitive members.

[0012] The image forming units PY to PK have a common configuration except for the different colors of toner used for development. Here, the configuration of the image forming engine 513 and the toner image forming process (image forming operation) will be described using the yellow image forming unit PY as an example. In addition to the photosensitive drum 1Y, the image forming unit PY has an exposure device 511, a development device 510, and a drum cleaner 509. The photosensitive drum 1Y is a drum-shaped photosensitive body having a photosensitive layer on its outer periphery, and rotates in a direction (arrow A in the figure) along the rotation direction (arrow B in FIG. 1) of the intermediate transfer belt 506. The surface of the photosensitive drum 1Y is charged by receiving a charge from a charging means such as a charging roller. The exposure device 511 irradiates a laser beam modulated according to image information, scans the photosensitive drum 1Y by an optical system including a reflecting device 512, and draws an electrostatic latent image on the surface of the photosensitive drum 1Y. The developing device 510 contains a developer containing toner, and supplies the toner to the photosensitive drum 1Y to visualize the electrostatic latent image into a toner image. The toner image formed on the photosensitive drum 1Y is primarily transferred to the intermediate transfer belt 506 at a nip portion (primary transfer portion) between the primary transfer roller 507 and the intermediate transfer belt 506. Residual toner remaining on the photosensitive drum 1Y after transfer is removed by a drum cleaner 509.

[0013] The intermediate transfer belt 506 is wound around a driving roller 504, a driven roller 505, a secondary transfer inner roller 503, and a primary transfer roller 507, and is driven to rotate in a clockwise direction (arrow B) in FIG. 1 by the driving roller 504. The image forming operation described above is carried out in parallel in each image forming portion PY to PK, and four color toner images are transferred in a superimposed manner to form a full-color toner image on the intermediate transfer belt 506. This toner image is transported to the secondary transfer portion T while being supported by the intermediate transfer belt 506. The secondary transfer portion T is configured as a nip portion between the secondary transfer roller 56 and the secondary transfer inner roller 503 as a transfer means. A bias voltage of a polarity opposite to the charge polarity of the toner is applied to the secondary transfer roller 56, and the toner image is secondarily transferred to the sheet S. Residual toner remaining on the intermediate transfer belt 506 after the transfer is removed by a belt cleaner (not shown).

[0014] The sheet S onto which the toner image has been transferred is delivered to a fixing unit 58 by a pre-fixing transport section 57. The fixing unit 58 has a pair of fixing rollers that sandwich and transport the sheet S, and a heat source such as a halogen heater, and applies pressure and heat to the toner image carried on the sheet S. This causes the toner particles to melt and adhere, and the toner image is fixed to the sheet S.

[0015] Next, the configuration and operation of a sheet transport system that feeds the sheet S stored in the feeding cassette 51 and discharges the sheet S on which an image is formed to the outside of the apparatus main body 1A will be described. The sheet transport system includes a sheet feeding section 54, a transport section 50, a skew correction section 55, a branch transport section 59, a reversing transport section 501, and a double-sided transport section 502.

[0016] The feeding cassette 51 is attached to the apparatus main body 1A so as to be removable, and stores the sheets S stacked on a lifting plate 52 which can be raised and lowered. The sheets S are fed one by one by a feeding unit 53. The feeding unit 53 which is a sheet feeding means may be a belt type (see FIG. 1) in which a suction fan attracts the sheet S to a belt member and conveys it, or a friction separation type using a roller or a pad. The sheet S sent out from the feeding unit 53 is conveyed along a feeding path 54a by a pair of conveying rollers, passes through the conveying section 50, and is delivered to the skew correction section 55.

[0017] The sheet S delivered to the skew correction section 55 as the skew correction means of the present disclosure is conveyed toward the secondary transfer section T after skew correction and timing correction are performed in the skew correction section 55. At this time, the registration roller pair 7 included in the skew correction section 55 sends the sheet S to the secondary transfer section T at a timing according to the progress of the image forming operation by the image forming sections PY to PK based on the detection signal of the registration sensor 8. The sheet S on which the toner image is transferred in the secondary transfer section T and the image is fixed by the fixing unit 58 is conveyed to a branch conveying section 59 having a switching member capable of switching the conveying path of the sheet S. When the image formation on the sheet S is completed, the sheet S is discharged by the discharge roller pair to the discharge tray 500 arranged outside the apparatus main body 1A. When an image is formed on the back side of the sheet S, the sheet S is delivered to the double-sided conveying section 502 via the reverse conveying section 501. The reverse conveying section 501 has a reverse roller pair capable of forward and reverse rotation, and switches back the sheet S to deliver it to the double-sided conveying section 502. The double-sided conveying section 502 conveys the sheet S toward the conveying section 50 via a re-conveying path 54b that merges with the feeding path 54a. Then, the sheet S is discharged to the discharge tray 500 after an image is formed on the back side thereof.

[0018] The above configuration is an example of an image forming apparatus, and may be, for example, an image forming apparatus equipped with an inkjet type image forming means instead of an electrophotographic type. Also, there are image forming apparatuses equipped with accessory devices such as an optional feeder and a sheet processing device in addition to the main body equipped with the image forming means, and the configuration of the sheet conveying device described below may be used to convey the sheet S in such accessory devices.

[0019] <Overview of the registration section> Next, the configuration of the registration unit 5 constituting the sheet conveying device will be described with reference to FIG. 2. FIG. 2 is a schematic diagram of the registration unit 5. FIG. 2 shows the configuration of the registration unit 5 when viewed from above the device main body 1A (see FIG. 1). As shown in FIG. 2, the registration unit 5 includes a conveying unit 50 that conveys a sheet in the sheet conveying direction, and a skew correction unit 55 arranged downstream of the conveying unit 50 with respect to the sheet conveying direction. The registration unit 5 also includes a sheet position detection sensor 60 that detects the position of the end of the sheet in the width direction perpendicular to the sheet conveying direction, and a slide mechanism 600 that moves the rollers constituting the conveying unit 50 in the width direction perpendicular to the sheet conveying direction. The conveying unit 50 has at least one set of conveying rollers, and FIG. 2 shows a configuration including conveying rollers 34-1, 34-2, 34-3, and 34-4. In the following description, when it is not necessary to distinguish between the conveying rollers 34-1, 34-2, 34-3, and 34-4, they will be referred to as "conveying rollers 34". The conveying roller 34 sends out the sheet in the sheet conveying direction. In the registration unit 5 of this embodiment, a slide mechanism 600 is provided on the conveying roller 34-4. FIG. 2 illustrates a configuration in which the sheet position detection sensor 60 is disposed between the conveying rollers 34-2 and 34-3. The sheet position detection sensor 60 can be disposed at a position where it can detect the end in the width direction of the sheet being conveyed through the conveying unit 50, for example, between the conveying rollers 34-4 and 34-3, other than the position shown in FIG. 2.

[0020] The skew correction unit 55 includes skew rollers 32-1, 32-2, and 32-3 as skew rotating bodies, a reference member 31, and a pair of registration rollers 7. In the following description, when it is not necessary to distinguish between the skew rollers 32-1, 32-2, and 32-3, they will be referred to as "skew rollers 32." The reference member 31 has a reference surface 301 (see FIG. 9B) extending in the sheet conveying direction, and is disposed on one side of the sheet conveying path in the width direction perpendicular to the sheet conveying direction. The reference surface 301 extends along the sheet conveying direction, and corresponds to a contact surface that can contact one end of the sheet in the width direction, i.e., a side end of the sheet.

[0021] A pre-registration sensor P that detects the passage of a sheet is disposed near the conveying roller 34-4. As the pre-registration sensor P, for example, a reflective photoelectric sensor having a light-emitting portion and a light-receiving portion can be used. In this case, the light emitted by the light-emitting portion is reflected by the sheet that has reached the detection position, and the reflected light is detected by the light-receiving portion, thereby detecting the timing of the sheet passing. In FIG. 2, the pre-registration sensor P is disposed between the conveying roller 34-4 and the oblique feed roller 32-1 in the sheet conveying direction.

[0022] The skew rollers 32-1, 32-2, and 32-3 each rotate about an axis inclined with respect to the width direction. That is, the skew rollers 32-1, 32-2, and 32-3 are arranged parallel to each other so that the tangent direction at the contact portion with the sheet is inclined at an angle α with respect to the sheet conveying direction. Therefore, the skew rollers 32-1, 32-2, and 32-3 rotate in contact with the sheet, thereby moving the sheet so that the sheet approaches the reference surface 301 of the reference member 31 in the width direction as it moves downstream in the sheet conveying direction V. Also, the sheet is moved by the skew rollers 32 so that the sheet approaches the reference surface 301 as it moves downstream in the sheet conveying direction V.

[0023] Here, the skew correction of the sheet by the skew correction unit 55 will be described. The skew correction unit 55 corrects the skew of the sheet by a so-called side registration method. Specifically, the skew correction unit 55 abuts the side end of the sheet, that is, the end of the sheet in the width direction, against a reference member 31 having a reference surface 301 extending along the sheet conveying direction. After the sheet abuts against the reference surface 301, the side end of the sheet is moved along the reference surface 301 to correct the skew of the sheet. Note that the sheet conveying direction is the proceeding direction of the sheet before the sheet approaches the reference member 31 in the skew correction unit 55, and in this embodiment, it refers to the sheet conveying direction by the conveying roller 34 of the conveying unit 50.

[0024] In addition to the pre-registration sensor P, a pre-registration sensor Q that detects the passage of a sheet is also arranged in the skew correction unit 55. The pre-registration sensor Q is arranged downstream of the skew roller 32 and upstream of the registration roller pair 7 in the sheet conveying direction. As with the pre-registration sensor P, the pre-registration sensor Q can be a known sensor such as a reflective photoelectric sensor.

[0025] The registration roller pair 7 is capable of sliding in the width direction perpendicular to the sheet conveying direction while sandwiching the sheet. The registration roller pair 7 moves the sheet, whose side edge has been in contact with the reference surface 301 of the reference member 31, in the width direction to match the position of the image to be transferred in the secondary transfer unit T. As a result, the center of the width direction of the sheet, which has been skew-corrected in the registration unit 5, moves to the designed conveying center of the printer 1. The method of adjusting the position of the sheet and the image formed on the sheet is not limited to this, and for example, a configuration may be adopted in which the width direction positions of the reference member 31 and the registration roller pair 7 are fixed and the main scanning direction position of the toner image formed by the image forming units PY to PK is adjusted.

[0026] Next, a change in the sheet conveying speed during skew correction will be described using the configuration of a conventional registration unit 5A as a reference example. FIG. 3 is a diagram showing a schematic configuration of the conventional registration unit 5A as a reference example. The registration unit 5A is configured by omitting the slide mechanism 600 and the sheet position detection sensor 60 from the registration unit 5 of this embodiment. In other words, the registration unit 5A corresponds to a configuration that does not include a configuration for moving the rollers constituting the conveying unit 50 in the width direction perpendicular to the sheet conveying direction, as compared to the registration unit 5. Therefore, the same reference numerals as in FIG. 2 are used in FIG. 3 for configurations that overlap with the registration unit 5, and overlapping descriptions will be omitted.

[0027] FIG. 4 is a diagram showing the speed components of the sheet conveyed through the registration section 5A. FIG. 5 (A, B) is a diagram showing an example of the relative position between the sheet conveyed through the registration section 5A and the reference member 31. The conventional registration section 5A does not have a configuration for moving the rollers constituting the conveying section 50 in the width direction perpendicular to the sheet conveying direction. Therefore, the sheet is shifted toward the reference member 31 by the skew roller 32 and conveyed along the reference member 31 to correct the skew of the sheet. Here, as shown in FIG. 4, the speed component in the sheet conveying direction of the sheet conveyed through the registration section 5A is speed V1, and the speed component in the direction perpendicular to the sheet conveying direction is speed V2. Also, in FIG. 5 (A, B), the distance between the end of the width direction perpendicular to the sheet conveying direction of the sheet S conveyed through the registration section 5A and the reference member 31 is shown as distance L.

[0028] FIG. 5A shows a case where the end of the sheet S is closer to the reference surface 301 of the reference member 31 than the skew roller 32 in the width direction. FIG. 5B shows a case where the end of the sheet S is farther from the reference surface 301 of the reference member 31 than the skew roller 32 in the width direction. As shown in FIG. 5A, when the distance L is relatively small, the sheet S abuts against the reference member 31 at about the center of the skew correction unit 55 in the sheet conveying direction. On the other hand, as shown in FIG. 5B, when the distance L is relatively large, the sheet S abuts against the reference member 31 at about the end of the skew correction unit 55 in the sheet conveying direction. In other words, when the distance L is relatively small, the sheet S starts to receive frictional resistance from the reference member 31 early, and the distance over which the sheet S receives frictional resistance becomes longer, and as a result, the speed V1 becomes slower. On the other hand, when the distance L is relatively large, the sheet S abuts against the reference member 31 relatively late. As a result, the distance over which the sheet S receives frictional resistance from the reference member 31 becomes relatively short, and the speed V1 becomes faster. In this way, when the sheet is abutted against the reference member 31 to correct the skew of the sheet, the distance L before the skew correction varies, which causes a change in the sheet conveying speed during the skew correction, as shown in FIG. 6. FIG. 6 is a plot of the relationship between the change in the sheet conveying speed during the skew correction and the distance L before the skew correction. As shown in FIG. 6, it has been observed that the speed V1 during the skew correction tends to be faster as the distance L increases. Therefore, it can be said that the variation in the distance L before the skew correction is one of the causes of the variation in the speed V1 during the skew correction. The change in the sheet conveying speed during the skew correction is one of the factors that impair printing productivity.

[0029] The variation in the distance L is due to the way the user sets the sheet and the variation in conveyance during sheet conveyance. In response to this, the present embodiment is provided with a sheet position detection sensor 60 that detects the position of the edge of the sheet in the width direction, and a slide mechanism 600 that moves the rollers constituting the conveyance unit 50 in the width direction. The sheet position detection sensor 60 detects the position of the side edge of the sheet before skew correction and moves the rollers constituting the conveyance unit 50, thereby correcting the variation in the distance L and correcting the skew of the sheet.

[0030] <Conveyor section configuration> The configuration of the conveying unit 50 will be described in detail with reference to Figures 7(A, B) and 8. Figures 7(A) and (B) are schematic diagrams showing the cross-sectional configuration of the conveying unit 50. Figure 8 is a perspective view showing the drive configuration of each conveying roller 34.

[0031] Each of the transport rollers 34-1, 34-2, and 34-3 is composed of a drive roller 13 to which a driving force is input, and a driven roller 14 that rotates following the drive roller 13 (FIGS. 7(A) and (B)). The transport rollers 34 are switchable between a pressurized state (FIG. 7(A)) in which a sheet can be clamped in the nip portion, and a separated state (FIG. 7(B)) in which the nip portion is open. Whether all of the transport rollers 34 are switchable between the pressurized state and the separated state can be determined according to the maximum size of a sheet that the printer 1 can transport.

[0032] The conveying section 50 is provided with a cam mechanism 100 having an eccentric roller 103 as a switching means capable of switching the pressurized state and the separated state of the conveying rollers 34-1, 34-2, and 34-3. The eccentric roller 103 is rotated and driven via gears 105 and 106 by a conveying roller drive motor Md as a drive source, and swings an arm member 101 that abuts against a cam surface on the outer periphery. The arm member 101 is supported to be swingable with respect to the stay member 18 around a swing shaft 102, abuts against the eccentric roller 103 on one side of the swing shaft 102, and supports a driven shaft 20 that is a rotation shaft of the driven roller 14 on the other side. By swinging the arm member 101, the driven rollers 14 appear and disappear from the sheet conveying path formed by a guide member (not shown). Therefore, the positional relationship between the driven roller 14 and the drive roller 13 can be switched by controlling the rotation angle of the eccentric roller 103 via the conveying roller drive motor Md, which is a stepping motor. That is, by controlling the rotation angle of the eccentric roller 103 , the driven rollers 14 can be switched between a separated state in which they are separated from the driving roller 13 and a pressurized state in which they are in pressure contact with the driving roller 13 .

[0033] 8, the drive roller 13 is a rubber roller attached to a drive roller shaft 301A, and is connected to a conveyor roller drive motor Md, which is a drive source, via a belt transmission mechanism 302. The conveyor roller drive motor Md is a stepping motor, and is configured to be able to change the timing of starting and stopping the drive and the drive speed of the drive roller 13 (the peripheral speed of the drive roller 13).

[0034] <Configuration of the skew correction unit> Next, the configuration of the skew correction unit 55 will be described in detail with reference to Fig. 9 to Fig. 11. Fig. 9(A) is a schematic diagram of the skew correction unit 55 viewed from above, and Fig. 9(B) is a schematic diagram showing a cross-sectional configuration of the reference member 31 viewed from the sheet conveying direction V shown in Fig. 9(A). Fig. 10(A) is a perspective view showing the pressing configuration of the pressing mechanism 33, and Fig. 10(B) is a side view thereof. Figs. 11(A) and (B) are schematic diagrams showing the pressed and released states by the pressing mechanism 33.

[0035] As shown in Fig. 9(A), the rotation axes of the skew rollers 32-1, 32-2, and 32-3 are fixed in a state inclined according to the angle α by universal joints 321, 321, and 321, respectively. Each skew roller 32 is connected to a correction roller drive motor Ms, which is a drive source, via a transmission mechanism including the universal joint 321, belt 323, and pulley. The correction roller drive motor Ms is a stepping motor, and the drive speed and the drive start / stop timing can be controlled.

[0036] 9(B), the reference member 31 has a concave cross section consisting of a reference surface 301 against which the side edge of the sheet S abuts, an upper facing surface facing the upper surface of the sheet S, and a lower facing surface facing the lower surface of the sheet S. The reference member 31 is made of die-cast aluminum, and the reference surface 301 is preferably made by machining to improve its accuracy, and further by applying a fluororesin such as PTFE (polytetrafluoroethylene) to the reference surface 301 by electroless nickel processing. This provides a reference surface 301 that is highly flat and has high slipperiness (low frictional resistance against the sheet), thereby improving the accuracy of skew correction of the sheet S.

[0037] As shown in Figs. 10 and 11, the skew correction unit 55 is provided with a pressurizing mechanism 33 that can switch between a pressurized state in which a sheet can be sandwiched and conveyed in a nip portion (sandwich portion) between the skew roller 32-n and the driven roller 331-n facing the skew roller 32-n, and a release state in which the pressurized state is released. The release state is not limited to a state in which the nip portion is open, but also includes a state in which the rollers are in contact with each other with a weaker force than the pressurized state. The pressurized state of the pressurizing mechanism 33 refers to at least one skew roller 32 being in a pressurized state, and the release state of the pressurizing mechanism 33 refers to all skew rollers 32 being in a release state. Here, n is a number obtained by numbering the skew rollers 32 and the driven rollers 331 in order from the upstream of the sheet conveying direction V, and for example, the skew roller 32-1 means the skew roller 32 arranged at the most upstream (n=1). In other words, in the skew correction section 55 of this embodiment, multiple sets of driven rollers 331-n and pressure mechanisms 33 are arranged, with the skew roller 32-n shown in Figures 10 and 11 being replaced with any of the skew rollers 32-1, 32-2, and 32-3.

[0038] As shown in Fig. 10(A) and (B), the pressure mechanism 33 includes an arm member 332, a link member 333, a pressure gear 334, a pressure spring 335, and a driven roller pressure motor Mk-n. The driven roller 331-n is supported by the arm member 332 so as to be rotatable about a driven shaft, and can move in a direction approaching or separating from the oblique feed roller 32-n by the swinging of the arm member 332. The driven roller 331-n in this embodiment rotates along the sheet conveying direction V about an axis extending in the width direction, but may be configured to be disposed on an axis parallel to the corresponding oblique feed roller 32-n. The arm member 332 is connected to the pressure gear 334 via the pressure spring 335 and the link member 333. The pressure gear 334 is connected to the output shaft of the driven roller pressure motor Mk-n, which is a driving source.

[0039] As shown in Fig. 11(A), in the pressurized state, the pressurizing gear 334 rotates counterclockwise in the figure, and the arm member 332 pulled by the pressurizing spring 335 swings counterclockwise around the swing shaft 332a. As a result, the driven roller 331-n is in pressure contact with the oblique feed roller 32-n. On the other hand, as shown in Fig. 11(B), in the released state, the pressurizing gear 334 rotates clockwise in the figure and presses the link member 333, and the link member 333 swings the arm member 332 clockwise. As a result, the driven roller 331-n is separated from the oblique feed roller 32-n, or at least the contact pressure against the oblique feed roller 32-n becomes smaller than in the pressurized state.

[0040] The driven roller pressure motor Mk-n is a stepping motor, and can change the amount of extension of the pressure spring 335 in the pressured state by controlling the rotation angle of the pressure gear 334. That is, the pressure mechanism 33 according to this embodiment can switch between the pressured state and the released state, and change the pressure in the pressured state.

[0041] <Configuration of seat position detection sensor> Next, the configuration of the sheet position detection sensor 60 as the detection means of this embodiment will be described with reference to Fig. 12. Fig. 12 is a perspective view showing the arrangement position of the sheet position detection sensor 60 in the conveying section 50. The sheet position detection sensor 60 includes an optical element such as a CIS (Contact Image Sensor), and is arranged in the same direction as the reference member 31 with respect to the center of the sheet in the width direction in the sheet conveying direction V, and at a position offset in the width direction. This is to detect the position of the side edge of the sheet that abuts against the reference member 31, and can reduce the influence of cutting variations in the sheet width direction. In other words, in this embodiment, the distance L before skew correction can be detected with high accuracy.

[0042] <Slide structure of transport roller> Next, with reference to Fig. 13 to Fig. 15 (A, B), the drive configuration of the conveying roller 34-4 in this embodiment and the configuration of the slide mechanism 600 as a first rotator moving unit that slides the conveying roller 34-4 will be described. Fig. 13 is a schematic perspective view of a roller drive mechanism 800 that drives the conveying roller 34-4. Fig. 14 is a schematic perspective view of the slide mechanism 600 that slides the conveying roller 34-4. Fig. 15 (A) is an enlarged perspective view of a pressure release mechanism 700 that puts the conveying roller 34-4 in a pressurized state or a separated state. Fig. 15 (B) is a cross-sectional view of the pressure release mechanism 700.

[0043] The conveying roller 34-4 is rotationally driven by a roller driving mechanism 800, and configured to be movable by a slide mechanism 600 in a width direction perpendicular to the sheet conveying direction while holding a sheet. The conveying roller 34-4 is also configured to be switchable between a pressurized state in which the sheet is held between the nip of the rollers constituting the conveying roller 34-4 and a separated state in which the rollers are separated from each other. The release state of the conveying roller 34-4 is not limited to a state in which the nip portion is released, but includes a state in which the rollers are in contact with each other with a weaker force than the pressurized state. The conveying roller 34-4 is configured by an upper roller 401 and a lower roller 402 (see FIG. 15). The lower roller 402 is rotatably supported by the frame 201 (see FIG. 15), and the upper roller 401 is rotatably supported by a pressure arm 405 (see FIG. 14). The pressure arm 405 is rotatably fixed by a shaft 201a formed on the frame 201 (see FIG. 14). Upper roller 401 is pressed against lower roller 402 by tension spring 407. Furthermore, roller gear 412 that transmits driving force from roller driving mechanism 800 to lower roller 402 is fixed to one end of lower roller 402 (see FIG. 13).

[0044] As shown in FIG. 13, the roller drive mechanism 800 for rotating the conveying roller 34-4 includes a slide roller drive motor 801, drive gears 802 and 803, and a roller gear 412. The slide roller drive motor 801 is fixed to the frame 201, and the drive of the slide roller drive motor 801 is transmitted to the roller gear 412 via the drive gears 802 and 803. The tooth surface of the drive gear 803 is formed to a length d that is longer than the reciprocating width of the roller gear 412 so that meshing with the roller gear 412 is maintained. The drive gear 802 is rotatably fixed to a fixed shaft 201b of the frame 201, and the drive gear 803 is rotatably fixed to a fixed shaft 201c. The slide roller drive motor 801 rotates in the direction of an arrow A1 in FIG. 13. In this embodiment, a stepping motor is used as the slide roller drive motor 801. With this configuration, the drive force of the slide roller drive motor 801 is transmitted to the roller gear 412, causing the conveying roller 34-4 to rotate.

[0045] As shown in FIG. 14, the slide mechanism 600 that moves the conveying roller 34-4 in the width direction perpendicular to the sheet conveying direction has a slide motor 601 that is fixed to a motor base 602 and screwed to a motor support plate 603. A pulley support plate 604 is screwed above the motor support plate 603 via the slide motor 601. Pulley bases 605 and 606 are fixed to the pulley support plate 604. A pulley shaft 607 is fixed to the pulley base 605, and a pulley shaft 608 is fixed to the pulley base 606 so as to be freely rotatable. Pulleys 609 and 610 are fixed to the pulley shaft 607, and a pulley 611 is fixed to the pulley shaft 608 (see FIG. 13). A pulley 612 is fixed to the tip of the output shaft of the slide motor 601. A timing belt 613 is stretched between the pulleys 609 and 612, and a timing belt 614 is stretched between the pulleys 610 and 611, respectively.

[0046] A holder 415 is rotatably supported by a bearing at the end of the lower roller 402 on the roller gear 412 side. A sensor flag 416 is attached to the holder 415 to detect the home position in the width direction of the upper roller 401 and the lower roller 402 of the conveying roller 34-4. When the upper roller 401 and the lower roller 402 of the conveying roller 34-4 are at the home position, the sensor flag 416 is detected by a sensor 615 provided on the pulley support plate 604. The holder 415 is fixed to the timing belt 614 by a stopper 616 and a screw (not shown). With this configuration, the timing belt 614 is rotated by the drive of the slide motor 601, and the lower roller 402 of the conveying roller 34-4 reciprocates in the width direction perpendicular to the sheet conveying direction in accordance with the rotation of the timing belt 614. Further, the upper roller 401 of the conveying roller 34-4 is engaged with the lower roller 402 by an engagement member (not shown) and reciprocates together with the lower roller 402 in the width direction perpendicular to the sheet conveying direction. In this embodiment, the slide motor 601 is driven based on the detection result of the position of the edge of the sheet in the width direction detected by the CIS 60, and the conveying roller 34-4 moves in the width direction.

[0047] The pressure release mechanism 700, which brings the upper roller 401 and the lower roller 402 of the conveying roller 34-4 into contact with and away from each other, has a pressure release shaft 701 positioned in the frame 201, as shown in FIG. 15(A). The pressure release mechanism 700 also includes cams 702 and 703 (see FIG. 15(B)) fixed to the pressure release shaft 701. As shown in FIG. 15(B), deep groove ball bearings 702a and 703a are press-fitted into the cams 702 and 703 at positions eccentric to their respective rotation centers. As shown in FIG. 15(A), a gear 702b is formed on the cam 702, and the pressure release shaft 70 rotates by transmitting the drive of the pressure release motor 704 via the cam 702.

[0048] The deep groove ball bearing 702a is disposed at a position where it can come into contact with the pressure arm 405, and when the pressure release shaft 701 rotates once, the deep groove ball bearing 702a swings the pressure arm 405 against the biasing force of the spring 407. By swinging the pressure arm 405 in this way, the upper roller 401 and the lower roller 402 can be brought into contact with and separated from each other once. In addition, a pressure arm (not shown) is also provided on the side where the deep groove ball bearing 703a is provided in the axial direction of the pressure release shaft 701. In addition, a sensor flag 703b is formed on the cam 703 (see FIG. 15(B)). The phase of the pressure release shaft 701 is determined by the sensor flag 703b being detected by a sensor 706 fixed to a sensor support plate 705 fixed to the frame 201, and the rotation of the pressure release motor 704 is controlled according to the phase of the pressure release shaft 701. Further, the phases of the cams 702 and 703 are determined so that the sensor flag 703b shields the sensor 706 when the upper roller 401 and the lower roller 402 of the conveying roller 34-4 are in contact with each other.

[0049] <Registration section control configuration> Next, the control configuration of the registration unit 5 will be described with reference to Fig. 16. As shown in Fig. 16, the operation of the registration unit 5 is controlled by a controller 600A mounted on the printer 1. The controller 600A, which is an example of a control means of this embodiment, includes a CPU 601 as a calculation means, a RAM 602 and a ROM 603 as storage means, and an interface (I / O) 604 for an external device or a network.

[0050] The CPU 601 performs control based on information input via the operation unit 400 as a user interface and detection signals from the pre-registration sensor P and the pre-registration sensor Q. The detection signals from the pre-registration sensor P and the pre-registration sensor Q are input to the CPU 601 via AD conversion units 605P and 605Q, respectively. In addition, the detection signal from the sheet position detection sensor 60 is input to the CPU 601 via the AD conversion unit 60C. The CPU 601 loads and executes a program stored in the ROM 603 or the like. The CPU 601 drives and controls a group of motors (Ms, 801, 701, Md, 104d, Mk-n, 601, ...) that are actuators of the registration unit 5 via drivers 606d, 607a, 607b, 607c, 608a, 608b, and 609-n. This allows the CPU 601 to execute each step of the control method described in the flowchart of FIG. 17. The number (n) of driven rollers 331-n corresponds to the number (n) of oblique feed rollers 32-n, and the CPU 601 can independently control whether or not the driven rollers 331-n apply pressure to each oblique feed roller 32 and the magnitude of the pressure.

[0051] <Registration section control method> Next, the sheet conveying operation in the registration unit 5 in the first embodiment will be described with reference to the flowchart in FIG. 17. Also, during execution of the flowchart in FIG. 17, it is assumed that the oblique feed roller 32 is continuously rotated. As described above, the control of the sheet conveying operation in the registration unit 5 in this embodiment is realized by the CPU 601 expanding a program stored in a storage means such as the ROM 603 into the RAM 602 and executing it. Therefore, each step included in the flowchart in FIG. 17 is executed by each unit of the registration unit 5 under the control of the CPU 601. Also, in the flowchart in FIG. 17, the conveying roller 34-4 will be described as a "slide roller" as a first rotating body.

[0052] First, an image forming job is started (S01) in a state where profile information, which is information indicating the characteristics of the sheet S to be image-formed, such as size and number of sheets, is input via the operation unit 400 or the I / O 604. Here, the profile information of the sheet S acquired by the controller 600A via the operation unit 400 or the I / O 604 is information indicating the characteristics of the sheet S, such as the basis weight, rigidity, surface roughness, and material of the sheet S. Then, the pressure of each oblique feed roller 32 is determined based on the information input in S01 (S02). However, the pressure here is the pressure of the driven roller 331-n against each oblique feed roller 32-n, and is a value determined for the oblique feed rollers 32-1, 32-2, and 32-3 based on information previously stored in the ROM 603 or the like. The magnitude of the pressure is, for example, a value set according to the basis weight of the sheet S in this embodiment so that the sheet S can be stably conveyed regardless of the type of the sheet S. Based on the pressure thus determined, the oblique feed rollers 32 start to apply pressure and enter a pressurized state (S03).

[0053] Thereafter, when the image forming operation by the image forming units PY to PK is started (S04), a delay time for starting feeding of the sheet S is counted based on the start timing of the image forming operation (S05), and then the sheet S is fed from the feeding cassette 51 (S06). In the process until the sheet S fed from the feeding cassette 51 reaches the oblique feed roller 32, the sheet position detection sensor 60 detects the position of the edge of the sheet S in the width direction perpendicular to the sheet conveying direction (S07). Then, the CPU 601 determines the position of the edge of the sheet S with respect to the reference surface 301 of the reference member 31 in the width direction based on the position of the edge of the sheet S detected in S07.

[0054] Here, consider the case where the end of the sheet S is closer to the reference surface 301 of the reference member 31 in the width direction than the oblique feed roller 32 (see FIG. 5A), and the case where the end of the sheet S is farther from the oblique feed roller 32 (see FIG. 5B). When the sheet S is in the positional relationship shown in FIG. 5A, the sheet S hits the reference surface 301 at a position between the oblique feed roller 32-1 and the oblique feed roller 32-2. On the other hand, in order to hit the sheet S against the reference surface 301 in the positional relationship shown in FIG. 5B, the sheet S needs to be obliquely fed by the oblique feed roller 32 over a longer distance than in the positional relationship shown in FIG. 5A. Therefore, the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction varies, and the conveying speed of the sheet S when conveying the sheet S along the reference surface 301 also varies (see FIG. 5).

[0055] In contrast, in this embodiment, the sheet S is moved in the width direction according to the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction before the leading edge of the sheet S reaches the oblique feed roller 32. To this end, the movement distance of the slide roller (conveyance roller 34-4) in the width direction is determined according to the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction (S08). For example, when the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction is as shown in FIG. 5(A), the movement distance of the slide roller in the width direction is determined so that the end of the sheet S approaches the reference surface 301 by 12 mm in the width direction. On the other hand, when the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction is as shown in FIG. 5(B), the movement distance of the slide roller in the width direction is determined so that the end of the sheet S approaches the reference surface 301 by 42 mm in the width direction. In this way, when the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction is a first position (for example, FIG. 5(A)), the slide roller is moved a first distance in the width direction. On the other hand, when the position of the end of the sheet S is a second position that is farther from the reference surface 301 than the first position (for example, FIG. 5(B)), the slide roller is moved a second distance in the width direction that is longer than the first distance. In this way, in this embodiment, the variation in the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction is reduced.

[0056] Then, when the sheet S handed over to the slide roller is detected by the pre-registration sensor P (S09 / Y), the stop delay time is counted (S10). When the stop delay time has elapsed, the conveying roller drive motor Md and the slide roller drive motor 801 are stopped (S11). By stopping the conveying roller drive motor Md and the slide roller drive motor 801, the conveying of the sheet S stops with the sheet being sandwiched between the slide rollers. Note that in S09, if the pre-registration sensor P does not detect the sheet S even after a predetermined time has elapsed since the start of feeding (S09 / N), a screen indicating a sheet jam is displayed on the operation unit 400 (S24), and the job ends.

[0057] Then, in S11, the conveying roller drive motor Md and the slide roller drive motor 801 are stopped, and then the grip of the sheet by the conveying rollers 34-3, 34-2, and 34-1 as the third rotating body upstream of the slide rollers is released (S12). Then, the slide rollers are moved in the width direction according to the movement distance in the width direction of the slide rollers determined in S08 (S13). When the slide rollers move in the width direction, the grip of the sheet by the conveying rollers 34-3, 34-2, and 34-1 is released, so that the burden on the sheet S due to the slide movement can be reduced.

[0058] Thereafter, a restart delay time is counted in accordance with the progress of the image forming operation (S14), and the driving of the slide roller drive motor 801 is resumed (S15). Since the timing of restarting the slide roller drive motor 801 is adjusted in accordance with the image forming operation, the variation in the time until the sheet S reaches the pre-registration sensor P is absorbed. Thereafter, a delay time for releasing the pressure applied to the slide rollers is counted (S16), and the upper roller 401 and the lower roller 402 are separated, and the slide rollers are in a separated state (S17). This releases the sheet S from the nip by the slide rollers, and abutment alignment operation is started in which the sheet S is abutted against the reference member 31 to correct the skew.

[0059] When the pressure of the slide roller is released, the sheet S starts to move obliquely with respect to the sheet conveying direction so as to approach the reference member 31 by the conveying force received from the oblique roller 32. That is, the sheet S is conveyed along the tangential direction of the oblique roller 32 inclined with respect to the sheet conveying direction, and is shifted toward the reference surface 301 of the reference member 31. After the pressure of the oblique roller 32 starts in S03, when the pre-registration sensor Q detects the leading edge of the sheet S (S18 / Y), a delay time for releasing the pressure of the oblique roller 32 is counted (S19). Then, after the delay time of S19 has elapsed, the pressure of the oblique roller 32 is released (S20). This delay time is set so that the oblique roller 32 is released after the leading edge of the sheet S enters the nip portion of the registration roller pair 7. If the pre-registration sensor Q does not detect the sheet S within a predetermined time, a screen indicating a sheet jam is displayed on the operation unit 400 (S24), and the job is ended.

[0060] When the sheet S is handed over to the registration roller pair 7 as the position changing means of the present disclosure, the registration roller pair 7 moves in the width direction while transporting the sheet S (S21). As a result, the center position of the sheet S in the width direction perpendicular to the sheet transport direction is positioned to match the center position of the image formed by the image forming units PY to PK. When the sheet S is sent to the secondary transfer unit T, a counter that manages the remaining number K of sheets on which images are to be formed decrements the value K (S22). If the remaining number K is not 0, that is, if there are sheets on which images are to be formed (S23 / N), the above operations (S03 to S23) are repeated. If the remaining number K is 0 (S23 / Y), it is determined that the image forming operation is completed and the job ends.

[0061] In this manner, in this embodiment, the sheet S is moved in the width direction according to the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction before the leading edge of the sheet S reaches the skew roller 32. This makes it possible to reduce the variation in the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction. Therefore, it is possible to suppress the variation in the conveying distance of the sheet S when the sheet S abuts against the reference surface 301, and therefore it is possible to reduce the change in the conveying speed of the sheet S when correcting the skew of the sheet S. EXAMPLES

[0062] <Registration section configuration> In the first embodiment, the configuration in which the slide mechanism 600 is provided on the conveying roller 34-4 arranged at the most downstream of the conveying section 50 in the sheet conveying direction is described. In this embodiment, the configuration in which the slide mechanisms 600a and 600b are provided on the conveying rollers 34-4 and 34-3 on the downstream side of the conveying section 50 in the sheet conveying direction is described. FIG. 18 is a schematic configuration diagram of the registration section 5 of this embodiment. The registration section 5 of this embodiment has the same configuration as the registration section 5 of the first embodiment, except that the slide mechanism 600a is provided on the conveying roller 34-4 and the slide mechanism 600b is provided on the conveying roller 34-3. In addition, the configurations of the slide mechanism 600a as the first rotating body moving section and the slide mechanism 600b as the second rotating body moving section are the same as the slide mechanism 600 of the first embodiment, so that overlapping explanations will be omitted. Note that the slide mechanism 600 may be provided on all of the conveying rollers 34 constituting the conveying section 50.

[0063] <Registration section control configuration> Next, the control configuration of the registration unit 5 of this embodiment will be described with reference to FIG. 19. As shown in FIG. 19, the operation of the registration unit 5 is controlled by a controller 600A mounted on the printer 1. In the control configuration of the registration unit 5 of this embodiment, the same components as those in the first embodiment are given the same reference numerals, and duplicated explanations will be omitted. The CPU 601 drives and controls the motor group (Ms, 801a, 801b, 701a, 701b, Md, 104d, Mk-n, 601a, 601b, ...) which are actuators of the registration unit 5 via drivers 606d, 607a, 607b, 607c, 608a, 608b, 609-n. As a result, each step of the control method described in the flowchart of FIG. 20 can be executed.

[0064] <Registration section control method> Next, the sheet conveying operation in the registration unit 5 in the second embodiment will be described with reference to the flowchart in FIG. 20. In addition, during the execution of the flowchart in FIG. 20, the oblique feed roller 32 is continuously rotated. As described above, the control of the sheet conveying operation in the registration unit 5 in this embodiment is realized by the CPU 601 expanding a program stored in a storage unit such as the ROM 603 into the RAM 602 and executing it. Therefore, each step included in the flowchart in FIG. 20 is executed by each unit of the registration unit 5 according to the control of the CPU 601. In addition, in the flowchart in FIG. 20, the conveying roller 34-4 is referred to as the "first slide roller" and the conveying roller 34-3 is referred to as the "second slide roller". The first rotating body in this embodiment is the conveying roller 34-4, and the second rotating body is the conveying roller 34-3. In the flowchart in FIG. 20, the same steps as those in the sheet conveying operation in the registration unit 5 in the first embodiment are given the same reference numerals as those in FIG. 17, and duplicated explanations will be omitted.

[0065] In the flowchart of FIG. 20, the steps up to S09 are the same as those in the first embodiment. Here, the steps from S101 will be described. When the sheet S delivered to the slide roller is detected by the pre-registration sensor P (S09 / Y), the stop delay time is counted (S101). When the stop delay time has elapsed, the conveying roller drive motor Md and the slide roller drive motors 801a and 801b are stopped (S111). By stopping the conveying roller drive motor Md and the slide roller drive motors 801a and 801b, the conveying of the sheet S stops with the sheet being sandwiched between the first slide roller and the second slide roller. In S09, if the pre-registration sensor P does not detect the sheet S even after a predetermined time has elapsed since the start of feeding (S09 / N), a screen indicating a sheet jam is displayed on the operation unit 400 (S24), and the job ends.

[0066] Then, in S111, the conveying roller drive motor Md and the slide roller drive motors 801a, 801b are stopped, and then the sheet is released from the conveying rollers 34-2, 34-1, which serve as third rotating bodies upstream of the slide rollers (S121). Then, the first slide roller and the second slide roller are moved in the width direction according to the movement distance in the width direction of the slide rollers determined in S08 (S131). When the slide rollers move in the width direction, the sheet is released from the conveying rollers 34-2, 34-1, so that the burden on the sheet S caused by the slide movement can be reduced.

[0067] Thereafter, a restart delay time is counted in accordance with the progress of the image forming operation (S141), and the driving of the slide roller drive motors 801a and 801b is resumed (S151). Since the timing of restarting the slide roller drive motors 801a and 801b is adjusted in accordance with the image forming operation, the variation in the time until the sheet S reaches the pre-registration sensor P is absorbed. Thereafter, a delay time for releasing the pressure state of the first slide roller and the second slide roller is counted (S161), and the first slide roller and the second slide roller are separated (S171). As a result, the sandwiched state of the sheet S by the first slide roller and the second slide roller is released, and abutting alignment operation is started in which the sheet S is abutted against the reference member 31 to correct the skew.

[0068] When the pressure applied to the first and second slide rollers is released, the sheet S starts to move obliquely with respect to the sheet conveying direction so as to approach the reference member 31 due to the conveying force received from the oblique conveying roller 32. That is, the sheet S is conveyed along the tangential direction of the oblique conveying roller 32 inclined with respect to the sheet conveying direction, and is shifted widthwise toward the reference surface 301 of the reference member 31. The steps thereafter are the same as those in the first embodiment, and therefore will not be described.

[0069] In this embodiment, similarly to the first embodiment, the sheet S is moved in the width direction according to the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction before the leading edge of the sheet S reaches the skew roller 32. This makes it possible to reduce the variation in the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction. Therefore, it is possible to suppress the variation in the conveying distance of the sheet S in the state where the sheet S abuts against the reference surface 301, and therefore it is possible to reduce the change in the conveying speed of the sheet S when correcting the skew of the sheet S. In addition, in this embodiment, the sheet S is moved in the state where the sheet S is sandwiched between the conveying rollers 34-4 and 34-3, so that the sheet S can be quickly moved in the width direction even if the sheet has a smooth surface or a large basis weight. EXAMPLES

[0070] In the first and second embodiments, when the sheet S is moved in the width direction, the rollers of the conveying section 50 other than the rollers that sandwich the sheet S and move in the width direction are separated. In recent years, it has been desired that the printer 1 be able to handle sheets (long sheets) that are extremely long in the sheet conveying direction. However, if a configuration is provided to separate the rollers of the conveying section 50 other than the rollers that sandwich the sheet S and move in the width direction when moving a long sheet in the width direction, the configuration of the printer 1 becomes complicated, which may lead to an increase in the size and cost of the device. Therefore, in this embodiment, when the sheet being conveyed through the registration section 5 is a long sheet, the reference member 31 is moved in the width direction to suppress the variation in the distance L before skew correction (see FIG. 4).

[0071] As shown in Fig. 21, in the skew correction of a sheet of normal length described in the first and second embodiments, from the viewpoint of high productivity, it is necessary to convey the sheets by simultaneously contacting the reference member 31 with multiple sheets (sheet S1, sheet S2, ...). Therefore, when a long sheet is being conveyed, even if an attempt is made to move the reference member 31 based on the detection result of the position of the side edge of the long sheet, the reference member 31 cannot be slid because of the presence of sheet S1 that has been conveyed in advance. In contrast, in this embodiment, either the conveying roller 34-4 or the reference member 31 is moved depending on the length of the sheet being conveyed in the sheet conveying direction in the conveying section 50.

[0072] FIG. 21 shows an example in which the slide mechanism 600 of the first embodiment is provided on the conveying rollers 34-4 and 34-3. In addition, the slide mechanism 600 may be provided only on the conveying roller 34-4. In FIGS. 23 and 24, the conveying roller 34-4 is assumed to be provided with the slide mechanism 600, and the conveying roller 34-4 is described as a "slide roller". Even if the conveying rollers 34-4 and 34-3 are each provided with the slide mechanism 600, the skew correction of the sheet can be performed according to the process of FIG. 24. Therefore, in this embodiment, the conveying roller 34-4 is provided with the slide mechanism 600. Note that the configuration other than the reference member moving mechanism 300 that moves the reference member 31 in the width direction is the same as in the first and second embodiments, so that the overlapping description will be omitted.

[0073] <Configuration of the reference member moving mechanism> First, with reference to Figs. 22(A and B), the configuration of the reference member moving mechanism 300 as the abutment surface moving part for moving the reference member 31 in the width direction will be described. As shown in Fig. 22(A), the reference member moving mechanism 300 includes bearing pedestals 303A and 303B fixed on a base part 300A. The bearing pedestals 303A and 303B rotatably support the lead screw 304. As shown in Fig. 22(B), a double row angular ball bearing 305 is press-fitted inside the bearing pedestal 303A. The angular ball bearing 305 is fixed to the lead screw 304 by a lock nut 307 via two spacers 306. Therefore, when the lock nut 307 is tightened with a predetermined torque, the angular ball bearing 305 eliminates backlash, and the lead screw 304 is uniquely positioned with respect to the bearing pedestal 303A. A deep groove ball bearing 308 is fitted inside the bearing pedestal 303B with a predetermined gap. Further, the deep groove ball bearing 308 and the lead screw 304 are fitted together with a predetermined gap, and a C-ring 309 is attached to the tip of the lead screw 304 to prevent the deep groove ball bearing 308 from coming off.

[0074] A nut 310 is rotatably attached to the spline portion 304a of the lead screw 304, and a bracket 311 to which a reference member 31 (see FIG. 21) can be connected is fixed to the nut 310. The lead screw 304 and the nut 310 are ball screws, and a ball (not shown) is incorporated inside the nut 310. This improves the accuracy and reduces noise when moving the reference member 31. A reference member slide motor 313 is connected to the tip portion 304b of the lead screw 304 via a coupling 312, and absorbs the deviation of the rotation center between the reference member slide motor 313 and the lead screw 304. The reference member slide motor 313 is fixed to a motor support plate 314. The reference member moving mechanism 300 configured in this way allows the reference member 31 to slide in the width direction.

[0075] <Registration section control configuration> Next, the control configuration of the registration unit 5 of this embodiment will be described with reference to FIG. 23. As shown in FIG. 23, the operation of the registration unit 5 is controlled by a controller 600A mounted on the printer 1. In the control configuration of the registration unit 5 of this embodiment, the same components as those in the first and second embodiments are given the same reference numerals, and duplicated descriptions will be omitted. The CPU 601 drives and controls the motor group (Ms, 801a, 801b, 701a, 701b, Md, 104d, Mk-n, 601a, 601b, 313, etc.) that are actuators of the registration unit 5 via the drivers 606d, 607a, 607b, 607c, 608a, 608b, 609-n, and 313c. As a result, each step of the control method described in the flowchart of FIG. 24 can be executed.

[0076] <Registration section control method> Next, the sheet conveying operation in the registration unit 5 in the third embodiment will be described with reference to the flowchart in FIG. 24. In addition, during the execution of the flowchart in FIG. 24, the oblique feed roller 32 is continuously rotated. As described above, the control of the sheet conveying operation in the registration unit 5 in this embodiment is realized by the CPU 601 expanding a program stored in a storage unit such as the ROM 603 into the RAM 602 and executing it. Therefore, each step included in the flowchart in FIG. 24 is executed by each unit of the registration unit 5 according to the control of the CPU 601. In addition, in the flowchart in FIG. 24, the conveying roller 34-4 will be referred to as a "slide roller" and described. In the flowchart in FIG. 24, the same steps as those in the sheet conveying operation in the registration unit 5 in the first and second embodiments are denoted by the same reference numerals as those in FIG. 17 and FIG. 20, and duplicated descriptions will be omitted.

[0077] In the flowchart of FIG. 24, the steps up to S11 are the same as those in the first embodiment. Here, the steps from S31 will be described. After stopping the conveying roller drive motor Md and the slide roller drive motor 801 in S11, it is determined whether the length of the sheet in the sheet conveying direction is 762 mm or less based on the information acquired in S01 (S31). If the length of the sheet in the sheet conveying direction is 762 mm or less (S31 / Y), the sheet is released from the grip of the conveying rollers 34-3, 34-2, and 34-1 as the third rotating body upstream of the slide rollers (S32). Then, the slide rollers are moved in the width direction according to the movement distance in the width direction of the slide rollers determined in S08 (S33). When the slide rollers move in the width direction, the grip of the sheet by the conveying rollers 34-3, 34-2, and 34-1 is released, so that the burden on the sheet S due to the slide movement can be reduced.

[0078] Thereafter, a restart delay time is counted in accordance with the progress of the image forming operation (S34), and the driving of the slide roller drive motor 801 is resumed (S35). Since the timing of restarting the slide roller drive motor 801 is adjusted in accordance with the image forming operation, the variation in the time until the sheet S reaches the pre-registration sensor P is absorbed. Thereafter, a delay time for releasing the pressure applied to the slide roller is counted (S36), and the slide roller is placed in a separated state (S37). This releases the sheet S from the clamping state by the slide roller, and abutment alignment operation is started in which the sheet S is abutted against the reference member 31 to correct the skew.

[0079] On the other hand, if the length of the sheet in the sheet conveying direction is longer than 762 mm (S31 / N), the reference member 31 is moved in the width direction by the same distance as the movement distance in the width direction of the slide roller determined in S08 (S38). After that, the slide roller and conveying roller 34 are separated (S39), the sandwiched state of the sheet S in the conveying section 50 is released, and an abutting alignment operation is started in which the sheet S is abutted against the reference member 31 to correct the skew. The steps thereafter are the same as those in the first and second embodiments, and therefore a description thereof will be omitted.

[0080] In this embodiment, when the position of the end of the sheet S with respect to the reference surface 301 of the reference member 31 is as shown in FIG. 5A, the movement distance of the slide roller or the reference member 31 in the width direction is determined so that the end of the sheet S approaches the reference surface 301 by 12 mm in the width direction. On the other hand, when the position of the end of the sheet S with respect to the reference surface 301 of the reference member 31 is as shown in FIG. 5B, the movement distance of the slide roller or the reference member 31 in the width direction is determined so that the end of the sheet S approaches the reference surface 301 by 42 mm in the width direction. In this way, when the position of the end of the sheet S with respect to the reference surface 301 of the reference member 31 in the width direction is the third position (for example, FIG. 5A), the reference member 31 is moved a third distance in the width direction. On the other hand, when the position of the end of the sheet S is a fourth position (for example, FIG. 5B) which is farther from the reference surface 301 than the third position, the reference member 31 is moved a fourth distance in the width direction which is longer than the third distance. Furthermore, when the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction is a fifth position (for example, FIG. 5(A)), the slide roller is moved a fifth distance in the width direction. On the other hand, when the position of the end of the sheet S is a sixth position that is farther from the reference surface 301 than the fifth position (for example, FIG. 5(B)), the slide roller is moved a sixth distance in the width direction that is longer than the fifth distance. In this way, in this embodiment, the variation in the position of the end of the sheet S relative to the reference surface 301 of the reference member 31 in the width direction is reduced.

[0081] Thus, in this embodiment, when the length of the sheet in the sheet transport direction is a second length (e.g., 762 mm or less) that is shorter than a first length (e.g., the length of the registration section 5 in the transport direction (first length)), the transport roller 34-4 is moved in the width direction. On the other hand, when the length of the sheet in the sheet transport direction is the first length, the reference member 31 is switched to be moved in the width direction. Therefore, even when transporting a long sheet, there is no need to provide a configuration that separates the rollers of the transport section 50 over the entire length of the sheet, and it is possible to avoid a complex configuration of the printer 1 and an increase in the size of the device.

[0082] <Other Examples> In the first to third embodiments, a configuration has been described in which the registration unit 5 is provided upstream of the secondary transfer unit T of the printer 1. In addition to this, for example, a configuration similar to the registration unit 5 may be implemented in a post-print device that performs post-processing such as punching and stapling on sheets.

[0083] The present invention can also be realized by supplying a program for implementing one or more of the functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in a computer of the system or device load and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions. [Explanation of symbols]

[0084] 1 printer (image forming apparatus) / 5 registration section (sheet conveying device) / 7 registration roller pair (position changing means) / 31 reference member / 32 skew roller (skew rotating body) / 34-2, 34-1 conveying roller (third rotating body) / 34-3 conveying roller (third rotating body, second rotating body) / 34-4 conveying roller (first rotating body) / 50 conveying section (sheet conveying means) / 55 skew correction section (skew correction means) / 60 sheet position detection sensor (detection means) / 300 reference member moving mechanism (contact surface moving section) / 301 reference surface (contact surface) / 600 slide mechanism (first rotating body moving section) / 600A controller (control means)

Claims

1. a first conveying roller pair that is movable in a width direction perpendicular to a sheet conveying direction while holding the sheet therebetween and conveys the sheet; a reference member disposed downstream of the first conveying roller pair in the sheet conveying direction, extending along the sheet conveying direction, and having a contact surface capable of contacting a side edge of the sheet in the width direction; a pair of skew rollers disposed downstream of the first conveying roller pair in the sheet conveying direction, the pair of skew rollers configured to sandwich and convey the sheet in a direction skewed with respect to the sheet conveying direction so as to approach and come into contact with the contact surface in the width direction of the sheet as the pair of skew rollers moves downstream in the sheet conveying direction; a detection unit disposed upstream of the first conveying roller pair in the sheet conveying direction and configured to detect a position of a side edge of the sheet in the width direction; a control unit that controls the movement of the sheet in the width direction by the first conveying roller pair, the control means, based on a detection result of the detection means, moves the first conveying roller pair a first distance in the width direction when the position of the side end of the sheet held by the first conveying roller pair is a first position with respect to the contact surface, and moves the first conveying roller pair a second distance in the width direction that is longer than the first distance when the position of the side end of the sheet held by the first conveying roller pair is a second position farther from the contact surface than the first position, in order to move the sheet, whose side end position in the width direction of the sheet is located on the opposite side of the contact surface from a predetermined position in the width direction, to the predetermined position in the width direction by the first conveying roller pair before the sheet is obliquely conveyed by the oblique conveying roller pair; A sheet conveying device comprising:

2. the detection unit detects the position of the side edge of the sheet in the width direction before the leading edge of the sheet reaches the first conveying roller pair; 2. The sheet transport device according to claim 1.

3. an upstream conveying roller pair that is disposed adjacent to the first conveying roller pair in the sheet conveying direction and upstream of the first conveying roller pair and that sandwiches and conveys a sheet; a first switching means that is movable between a nip state in which a nip portion is formed between the pair of upstream conveying rollers to nip a sheet and a separation state in which the nip portion of the pair of upstream conveying rollers is separated, The control means controlling the pair of upstream conveying rollers to move between the sandwiching state and the separated state by the first switching means; when the sheet is moved in the width direction by the first conveying roller pair, the first switching means switches the upstream conveying roller pair from the sandwiching state to the separated state, and then the sheet is moved in the width direction by the first conveying roller pair.

2. The sheet transport device according to claim 1.

4. the detection unit is a CIS that detects a side edge of the sheet on one side where the contact surface is disposed with respect to a conveyance center line in a sheet conveyance path of the sheet conveyed by the upstream conveyance roller pair; 4. The sheet transport device according to claim 3.

5. a guide member for guiding a sheet conveyed by the pair of upstream conveying rollers, The CIS is attached to the guide member.

5. The sheet transport device according to claim 4.

6. a second switching means that is movable between a nip state in which a nip portion of the first conveying roller pair is formed to nip a sheet and a separation state in which the nip portion of the first conveying roller pair is separated, The control means controlling the first conveying roller pair to move between the clamping state and the separated state by the second switching means; When the sheet is obliquely fed toward the contact surface by the pair of oblique feed rollers, the second switching means switches the first conveying roller pair from the sandwiching state to the separated state, and then the sheet is obliquely fed by the pair of oblique feed rollers.

2. The sheet transport device according to claim 1.

7. a second conveying roller pair that is movable in a width direction perpendicular to the sheet conveying direction while holding the sheet after being obliquely conveyed by the oblique conveying roller pair and conveys the sheet; a third switching means that is movable between a clamping state in which a nip portion is formed between the pair of oblique feed rollers to clamp a sheet and a separating state in which the nip portion of the pair of oblique feed rollers is separated; The control means controlling the second conveying roller pair and the third switching means; when the second conveying roller pair is moved in the width direction of the sheet, the third switching means moves the oblique conveying roller pair from the sandwiching state to the separated state.

7. The sheet transport device according to claim 6.

8. The sheet conveying device according to claim 1 ; and an image forming unit for forming an image on the sheet conveyed by the sheet conveying device.

1. An image forming apparatus comprising:

9. an upstream conveying roller pair disposed adjacent to the first conveying roller pair in the sheet conveying direction and upstream of the first conveying roller pair, the upstream conveying roller pair being movable in a width direction of the sheet while sandwiching the sheet, and conveying the sheet; The control means Controlling the movement of the upstream conveying roller pair in the width direction of the sheet; moving the sheet in the width direction of the sheet together with the first conveying roller pair and the upstream conveying roller pair; 2. The sheet transport device according to claim 1.

10. The reference member is movable in a width direction of the sheet, The control means Controlling the movement of the reference member in the width direction of the sheet; When the length of the sheet to be conveyed is a first length, before the sheet is skewed by the pair of skew rollers, the first conveying roller pair moves the sheet to a predetermined position in the width direction of the sheet based on a detection result of the detection means; when the length of the conveyed sheet is a second length that is longer than the first length, the reference member is moved in the width direction of the sheet by the same distance as a distance by which the sheet is moved to a predetermined position in the width direction of the sheet by the first conveying roller pair based on a detection result of the detection means; 2. The sheet transport device according to claim 1.

11. the second length is a length of the sheet in the sheet conveying direction of 762 mm; The sheet transport device according to claim 10 .

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