JP2011132022A - Sheet carrying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrying device which surely prevents such a problem of ruining the accuracy of the skew correction due to the buckling of a sheet and the generation of a loop part, and to provide an image forming device provided with the same. <P>SOLUTION: The sheet carrying device includes: a carrying roller pair 36 which holds the sheet S, which is aligned along a reference plane 31a by a skew correction roller pair 32 and 32a, and carries it in a sheet carrying direction; a nip release mechanism which releases the holding of skew correction roller pair 32 and 32a; further, a nip release mechanism which releases the holding of carrying roller pair 36; and a control part 9 that controls those nip release mechanisms, respectively. The control part 9 effectively removes the buckling, the loop part, etc. caused between the reference plane 31a and the carrying roller pair 36 by releasing the holding by the skew correction roller pair 32 and 32a when the holding conveyance of the aligned sheet S is begun by the carrying roller pair 36. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheet conveyance device having a skew correction unit that corrects skew of a sheet being conveyed, and an image forming apparatus including the sheet conveyance device.

  2. Description of the Related Art Conventionally, some image forming apparatuses such as copiers, printers, and facsimiles include a skew correction unit for adjusting the posture and position of a sheet before the sheet is conveyed to the image forming unit. One of the correction methods of such a skew correction unit is a correction method based on a side registration standard. In this correction method, a reference wall is provided on the side of the sheet conveyance path in parallel with the conveyance direction, a skew feeding roller (width-adjusting roller) is disposed in the sheet conveyance path, and the sheet being conveyed by the skew feeding roller is used as a reference wall. The sheet skew is corrected by abutting the side edge of the sheet against the reference wall.

  However, in the above correction method, the sheet is abutted against the reference wall by the conveying force of the skew feeding roller to correct the skew of the sheet. Therefore, if the conveying force of the skew feeding roller is too strong, the side edge of the sheet is abutted against a thin sheet. When it is bent, it will buckle, leading to jamming of the sheet and deterioration of correction accuracy.

  In view of this, there has been proposed one that suppresses the occurrence of sheet buckling, looped portions, and the like by variably configuring the gap of the guide groove that guides the sheet to the reference wall (see Patent Document 1).

  Further, an image forming apparatus including a conveying roller provided on the downstream side of the skew feeding roller and movable in a width direction orthogonal to the sheet conveying direction, and an alignment device having a side edge detection sensor for detecting a side edge of the sheet. Has been proposed. In this image forming apparatus, when the conveyance roller is moved in the width direction, the movement operation of the conveyance roller is controlled based on the timing when the side edge detection sensor detects the side edge of the sheet. Thereby, even if the buckling of a sheet | seat, a loop-shaped part, etc. generate | occur | produce, a side end position can be match | combined with a reference | standard position (refer patent document 2).

JP 2002-356250 A JP-A-11-189355

  However, with the technique described in Patent Document 1, it is possible to suppress the occurrence of buckling, looped portions, and the like that occur in the sheet, but it is difficult to reliably prevent them. Therefore, in the case of thin paper, if a buckling or loop-shaped part is created with the gap of the guide groove set narrow, there is no space to allow (escape) the buckling or loop-shaped part. There was a risk of causing.

  Further, in the technique disclosed in Patent Document 2, if the buckling or the size of the loop-shaped portion is different between the upstream side and the downstream side between the holding position of the transport roller and the reference wall, the skew cannot be corrected. There was a problem.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides a sheet conveying apparatus capable of reliably preventing problems that impair the accuracy of skew correction due to sheet buckling and loop-shaped portions, and an image forming apparatus including the sheet conveying apparatus. Objective.

  The present invention has a reference surface extending along the sheet conveying direction, and a pair of width adjusting rollers that adjust the width while sandwiching the sheet so that the side edge of the sheet is in sliding contact with the reference surface, In a sheet conveying apparatus including a skew correcting unit that corrects a skew of a sheet, the sheet conveying device is disposed between the reference surface in the width direction orthogonal to the sheet conveying direction and the width adjusting roller pair. A conveying roller pair for nipping the sheet that is width-adjusted on the reference surface and conveying the sheet in the sheet conveying direction; a release unit that releases nipping of the width-adjusting roller pair; and a control unit that controls the release unit. And the control unit controls the release unit so as to release the nipping by the width-adjusting roller pair when conveyance of the sheet subjected to the width-adjusting by the width-adjusting roller pair is started by the conveying roller pair. It is a symptom.

  The present invention also includes a reference surface extending along the sheet conveyance direction, and a pair of width adjusting rollers that adjust the width while sandwiching the sheet so that the side edge of the sheet is in sliding contact with the reference surface. In the sheet conveying apparatus including a skew correcting unit that corrects the skew of the sheet, the width adjusting roller is disposed between the reference surface and the width adjusting roller pair in the width direction orthogonal to the sheet conveying direction. A first conveying roller pair and a second conveying roller pair that nipping and conveying the sheet that has been width-adjusted to the reference surface by a pair, and a first release unit that releases nipping of the width-adjusting roller pair And a second release unit for releasing the clamping of each of the first and second transport roller pairs, and a control unit for controlling the first and second release units, wherein the control unit includes: Width on the reference surface by a pair of width adjusting rollers The second conveying roller pair is released until the first conveying roller pair holds the sheet to be held, and when the sheet is held by the first conveying roller pair, the width adjusting roller pair The nipping is released and the second conveying roller pair is nipped.

  According to the present invention, in the side registration method, even if buckling or a loop-shaped portion occurs when the sheet is abutted against the reference surface, these can be regulated between the reference surface and the pair of conveyance rollers. It becomes possible. For this reason, buckling and a loop-shaped part which arise between a reference plane and a conveyance roller pair can be suppressed to the minimum. After that, by releasing the clamping of the width adjusting roller pair, it is possible to remove the buckling or loop-like portion generated between the reference surface and the conveying roller pair, thereby generating the buckling or loop-like portion. It is possible to perform skew correction with high accuracy even on an easy sheet.

  Further, according to the present invention, in the side registration method, even if buckling or a loop-shaped portion occurs when the sheet is abutted against the reference surface, these are referred to as the reference surface and the first and second conveying roller pairs. It becomes possible to regulate during For this reason, buckling and a loop-shaped part which arise between a reference plane and the 1st and 2nd conveyance roller pair can be suppressed to the minimum. Further, by releasing the clamping of the width-adjusting roller pair, it is possible to remove buckling or a loop-shaped portion or the like generated between the reference surface and the first and second conveying roller pairs. It is possible to perform skew correction with high accuracy even on a sheet that is liable to generate a loop-shaped portion.

1 is a cross-sectional view illustrating a schematic configuration of a color image forming apparatus that is an example of an image forming apparatus including a sheet conveying device according to the present invention. FIG. 3 is a plan view for explaining a configuration of a skew feeding correction device and a conveyance roller provided in the sheet conveyance device according to the first embodiment of the present invention. FIG. 3 is a side view illustrating configurations of a skew feeding correction device and a conveyance roller device provided in the sheet conveyance device of the first embodiment. FIG. 5 is a plan view for explaining operations of the skew feeding correction device and the conveyance roller device according to the first embodiment. The front view explaining operation | movement of the skew feeding correction apparatus and conveyance roller apparatus of 1st Embodiment. The figure which shows the mechanism which spaces apart the driven roller which comprises a conveyance roller from a drive roller. FIG. 3 is a block diagram illustrating a control system of the skew feeding correction device and the conveyance roller device according to the first embodiment. 6 is a flowchart illustrating operations of the skew feeding correction device and the conveyance roller device according to the first embodiment. The figure which shows the mode of the buckling of the sheet | seat by the skew feeding correction apparatus as a comparative example. The figure which shows the structure of the skew feeding correction apparatus and conveyance roller apparatus of 2nd Embodiment which concern on this invention. 9 is a flowchart illustrating operations of the skew feeding correction device and the conveyance roller device according to the second embodiment. The figure which shows the structure of the skew feeding correction apparatus and conveyance roller apparatus of 3rd Embodiment which concern on this invention. 10 is a flowchart illustrating operations of the skew feeding correction device and the conveyance roller device according to the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a color image forming apparatus which is an example of an image forming apparatus including a sheet conveying device according to the present invention.

  As shown in FIG. 1, reference numeral 100 denotes a color image forming apparatus, and the color image forming apparatus 100 includes a color image forming apparatus main body (hereinafter referred to as an apparatus main body) 100A. The color image forming apparatus 100 is classified mainly into a tandem system in which a plurality of image forming units are arranged side by side and a rotary system in which the color image forming apparatus 100 is arranged in a cylindrical shape. Transfer methods are classified into a direct transfer method in which a toner image is directly transferred from a photosensitive drum to a sheet, and an intermediate transfer method in which the toner image is once transferred to an intermediate transfer member and then transferred to a sheet material.

  Here, since the intermediate transfer method does not require the sheet to be held on the intermediate transfer belt unlike the direct transfer method, the intermediate transfer method can cope with a wide variety of sheets such as ultra-thick paper and coated paper. The intermediate transfer method is suitable for realizing high productivity because of the features of parallel processing in a plurality of image forming units and batch transfer of full-color images.

  Hereinafter, the color image forming apparatus 100 will be described as an intermediate transfer tandem system in which four color image forming units are arranged side by side on an intermediate transfer belt. The apparatus main body 100A of the color image forming apparatus 100 is fed with an image forming unit 513, a sheet feeding device 100B that conveys the sheet S, and a toner image formed by the image forming unit 513 from the sheet feeding device 100B. A transfer unit 100C for transferring to the sheet S; Further, the apparatus main body 100A is provided with a sheet conveying apparatus 100D that conveys the sheet S.

  Here, the image forming unit 513 includes a photosensitive drum 508, an exposure device 511, a developing device 510, a primary transfer device 507, a cleaner 509, and the like, which are yellow (Y), magenta (M), cyan (C), and the like. It is composed of a black (Bk) image forming unit. Note that the colors formed by each image forming unit are not limited to these four colors, and the color arrangement order is not limited to this.

  The sheet feeding device 100 </ b> B includes a sheet storage unit 51 that stores the sheets S in a form of being stacked on the lift-up device 52, and a sheet feeding unit 53 that sends out the sheets S stored in the sheet storage unit 51. Yes. Examples of the sheet feeding unit 53 include a method using friction separation by a feeding roller and the like, a method using separation adsorption by air, and the like. Here, an air feeding method is taken as an example.

  The transfer unit 100C includes an intermediate transfer belt 506 that is stretched by rollers such as a driving roller 504, a tension roller 505, and a secondary transfer inner roller 503, and is driven to be conveyed in the direction of arrow B in the drawing. Yes.

  Here, the intermediate transfer belt 506 is to transfer the toner image formed on the photosensitive drum 508 by a predetermined pressure and an electrostatic load bias given by the primary transfer device 507. The intermediate transfer belt 506 is provided with a predetermined pressing force and an electrostatic load bias at a secondary transfer portion formed by the substantially opposite secondary transfer inner roller 503 and secondary transfer outer roller 56. An unfixed image is adsorbed to S.

  The sheet conveyance device 100D includes a conveyance unit 54, a conveyance roller device 50, a skew correction device 55 as a skew correction unit, a registration roller pair 7, a pre-fixing conveyance unit 57, a branch conveyance device 59, a reverse conveyance device 501, and a double-side conveyance. It is comprised from the apparatus 502 grade | etc.,. In addition, the apparatus main body 100A includes a control unit 9 that controls an image forming operation of the color image forming apparatus 100 and a skew feeding correcting operation of the sheet S described later.

  In the color image forming apparatus 100 having such a configuration, when an image is formed, first, the photosensitive drum 508 is rotated in the direction of arrow A in the drawing, and the photosensitive drum 508 is preliminarily rotated by a charging unit (not shown). Charge the surface uniformly. Thereafter, the exposure device 511 emits light to the rotating photosensitive drum 508 based on the transmitted image information signal, and this light is irradiated through the reflecting member 512 and the like as appropriate, whereby the photosensitive drum. An electrostatic latent image is formed on 508. Note that the transfer residual toner slightly remaining on the photosensitive drum 508 is collected by the cleaner 509 and prepared for the next image formation again.

  Next, toner development is performed by the developing device 510 on the electrostatic latent image formed on the photosensitive drum 508 in this manner, and a toner image is formed on the photosensitive drum 508. Thereafter, a predetermined pressure and an electrostatic load bias are applied by the primary transfer device 507, and the toner image is transferred onto the intermediate transfer belt 506. Note that image formation by the Y, M, C, and Bk image forming units of the image forming unit 513 is performed at the timing when the toner image is superimposed on the upstream toner image primarily transferred onto the intermediate transfer belt 506. As a result, a full-color toner image is finally formed on the intermediate transfer belt 506.

  Further, the sheet S is sent out by the sheet feeding unit 53 in accordance with the image forming timing of the image forming unit 513. Thereafter, the sheet S passes through a transport path 54 a provided in the transport unit 54 and is transported to a skew feeding correction device 55 for correcting the positional deviation and skew feeding of the sheet being transported.

  Then, the sheet S on which the positional deviation and skew have been corrected by the skew correction device 55 is conveyed to the registration roller pair 7, and after correcting the timing by the registration roller pair 7, the secondary transfer inner rollers 503 and the second transfer roller 503. It is conveyed to the secondary transfer portion formed by the next transfer outer roller 56. Thereafter, a full color toner image is secondarily transferred onto the sheet S in the secondary transfer portion.

  Next, the sheet S on which the toner image is secondarily transferred in this manner is conveyed to the fixing device 58 by the pre-fixing conveyance unit 57. Then, in this fixing device 58, a predetermined pressurizing force by a substantially opposing roller or belt and a heating effect by a heat source such as a heater are generally applied to melt and fix the unfixed toner image on the sheet S.

  Next, the sheet S having the fixed image obtained in this manner is discharged as it is onto the discharge tray 500 by the branch conveyance device 59. When images are formed on both sides of the sheet S, the sheet is then conveyed to the reverse conveying device 501 by switching a switching flapper (not shown).

  Here, when the sheet S is conveyed to the reverse conveying device 501 as described above, the leading and trailing ends of the sheet S are switched by performing a switchback operation, and conveyed to the re-conveying path R provided in the double-sided conveying device 502. Is done. Thereafter, the sheet is fed from the sheet re-feeding path 54b of the conveyance unit 54 in synchronization with the timing of the sheet S of the subsequent job conveyed from the sheet feeding apparatus 100B, and similarly sent to the secondary transfer unit. Since the image forming process is the same as that of the first side, it is omitted.

  The transport unit 54, the branch transport device 59, the reverse transport device 501, and the double-side transport device 502 are provided with a large number of transport rollers. These conveying rollers are configured to convey the sheet S by rotating the driving roller and the driven roller while the sheet S is sandwiched between the driving roller and the driven roller. In these conveyance rollers, a pressure for nipping the sheet S between the two rollers is set by urging the driven roller toward the driving roller by a biasing member such as a spring (not shown).

<First Embodiment>
Next, the sheet conveying apparatus 100D according to the first embodiment of the present invention will be described. FIG. 2 is a plan view for explaining the configuration of the skew feeding correction device 55 and the transport roller device 50 provided in the sheet transporting device 100D of the present embodiment. FIG. FIG. 4 is a side view showing a configuration of a conveyance roller device 50. In FIG. 2, the illustration of the upper driven roller 322 constituting the skew correction roller pair 32, 32a is omitted so that the drive roller 321 can be easily seen.

  As illustrated in FIG. 2, the sheet conveying apparatus 100 </ b> D includes a skew feeding correction device 55 and a conveying roller device 50. The skew correction device 55 is of a correction method based on a side registration standard that corrects misalignment and skew with reference to the side edge of the sheet S being conveyed. The skew feeding correction device 55 can move in a direction (width direction) orthogonal to the sheet conveyance direction (arrow C direction) according to the size of the sheet S being conveyed and the fixed guide 33 that functions as a conveyance guide for the sheet S. The movable guide 30 is provided. The movable guide 30 has a reference member 31 and a skew correction roller pair 32, 32a and functions to correct the skew of the sheet S. A pair of skew correction roller pairs 32a is disposed upstream of the sheet conveyance direction, and two pairs of skew correction roller pairs 32 are disposed downstream of the skew correction roller pair 32a in the sheet conveyance direction.

  The movable guide 30 has a skew correction roller pair 32, 32a, which is a pair of width-adjusting rollers, and a reference for correcting the skew feeding by the sheet S fed obliquely by the skew correction roller pair 32, 32a. Member 31. The reference member 31 has a reference surface 31a that extends in the sheet conveyance direction and is formed perpendicular to the conveyance surface that conveys the sheet. The skew correction roller pair 32, 32a moves the width of the sheet S while sandwiching the sheet S so that the side edge of the sheet S is in sliding contact with the reference surface 31a. The drive roller 321 in the skew feeding correction roller pair 32, 32a is inclined by an angle α with respect to the sheet conveyance direction (arrow C direction) so that an abutting conveyance component with respect to the reference surface 31a of the reference member 31 is obtained. The movable guide 30 is attached.

  As shown in FIG. 2, the conveyance roller device 50 that is disposed upstream of the skew feeding correction device 55 in the sheet conveyance direction and that conveys the sheet S to the skew correction device 55 includes a plurality of conveyance roller pairs 34. Yes. As shown in FIGS. 3A to 3D, each of the plurality of conveying roller pairs 34 is in contact with and separated from the driving roller 301 that is a lower roller, and the driving roller 301 and the sheet S together with the driving roller 301. It is comprised from the driven roller 14 which is an upper roller which conveys.

  When the driven roller 14 conveys the sheet S conveyed from the conveying unit 54 (see FIG. 1), the driven roller 14 is in a position where it is pressed against the driving roller 301 as shown in FIG. Thus, after being conveyed from the conveyance unit 54, the sheet S is nipped by the plurality of conveyance roller pairs 34 and conveyed to the skew feeding correction device 55.

  Further, as shown in FIGS. 3A to 3D, the skew feeding correction roller pair 32, 32a is in contact with the driving roller 321 positioned on the lower side and the driving roller 321 so as to come into contact with and away from the driving roller 321. 321 and a driven roller 322 that conveys the sheet S.

  In FIG. 2, a pair of conveying rollers (conveying rollers) is provided between the reference surface 31a and the skew correction roller pair 32, 32a in the width direction (left and right direction in FIG. 2) orthogonal to the sheet conveying direction (arrow C direction). 36 is arranged. The pair of conveying rollers 36 sandwiches the sheet S that has been brought close to the reference surface 31a by the skew feeding correction roller pairs 32 and 32a and conveys the sheet S in the sheet conveying direction.

  The registration roller pair 7 includes a driving roller (not shown) and a driven roller that conveys a sheet together with the driving roller while being in pressure contact with the driving roller. Further, the registration roller pair 7 needs to shift the sheet in order to return the skew-corrected sheet to the sheet conveyance reference. In other words, in the present embodiment, the sheet is conveyed so that the center of the conveyance path and the center of the sheet coincide with each other, so that the sheet shifted from the center needs to be returned to the center again because of the skew correction. . Therefore, the registration roller pair 7 is provided so as to be slidable in the width direction perpendicular to the sheet conveyance direction in order to return the sheet to the center while the sheet is sandwiched.

  Next, a control mechanism including the control unit 9 that controls the image forming operation and the sheet skew correction operation of the color image forming apparatus 100 will be described with reference to FIG.

  As one control of the skew correction operation, the control unit 9 includes a nip release mechanism 32A as a first release part (release part) that releases the clamping of the skew correction roller pair 32 and 32a, and a conveyance roller pair 36. The nip release mechanism 36A serving as a second release unit that releases the pinching of each is controlled. The control unit 9 controls to release the nipping by the skew correction roller pair 32, 32a when the sheet S that has been widened by the skew correction roller pair 32, 32a starts to be nipped and conveyed by the conveyance roller pair 36. To do.

  The controller 9 includes a registration roller moving mechanism 7A that slides the registration roller pair 7 in the width direction orthogonal to the sheet conveyance direction, and a nip that releases the nip (clamping) between the driving roller and the driven roller of the registration roller pair 7. The release mechanism 7B is connected. The control unit 9 includes a registration roller driving motor 7C that drives the registration roller pair 7, a sheet passage detection sensor 40 that detects the passage of the sheet, and a nip release mechanism 36A that releases the nip (nip) of the conveyance roller pair 36. And are connected. As shown in FIG. 3A, the sheet passing detection sensor 40 is disposed so as to detect that the sheet S has arrived immediately before the nip portion of the skew feeding correction roller pair 32a.

  Further, the control unit 9 includes a conveyance roller drive motor 36B for driving the conveyance roller pair 36, a nip release mechanism 34A for releasing the nip (clamping) of the conveyance roller pair 34, and a conveyance roller drive motor for driving the conveyance roller pair 34. 34B is connected. Further, the controller 9 includes a nip releasing mechanism 32A for releasing the nip (clamping) of the skew correction roller pair 32, 32a, and a skew correction roller driving motor 32B for driving the skew correction roller pair 32, 32a, respectively. Is connected.

  Here, the nip releasing mechanism 7B for separating the driven roller 14 in the registration roller pair 7 from the driving roller 301 will be described with reference to FIG.

  That is, the nip release mechanism 7B includes an arm member 101 that rotatably supports the driven roller 14 and an eccentric roller 103, as shown in FIG. The arm member 101 is swingably supported by the stay member 18 via the shaft 12 and urges the driven roller 14 in a direction in which the driven roller 14 is pressed against the driving roller 301 by an urging member (not shown). The end of the arm member 101 opposite to the driven roller 14 is pressed (elastically contacted) with the eccentric roller 103 by a biasing member (not shown). The rotation of the stepping motor 104 is transmitted to the eccentric roller 103 via gears 105 and 106.

  In the nip release mechanism 7 </ b> B, when the eccentric roller 103 is rotated by driving the stepping motor 104, the eccentric portion of the eccentric roller 103 presses the end of the arm member 101 opposite to the driven roller 14. As a result, the arm member 101 rotates clockwise from the clamping position (nip position) shown in FIG. 6A with the shaft 12 as a fulcrum, and the driven roller 14 is moved in the same direction as shown in FIG. As shown in b), it is separated from the driving roller 301 (release position).

  The above is the configuration of the nip release mechanism 7B. In the present embodiment, the nip release mechanism 36A for the transport roller pair 36, the nip release mechanism 34A for the transport roller pair 34, and the skew correction roller pairs 32 and 32a. The nip release mechanism 32A is similarly configured.

  Next, operations of the conveyance roller device 50 and the skew feeding correction device 55 having the above-described configuration during sheet conveyance will be described with reference to FIGS. 3 to 5, 8, and 9. 3 is a side view showing the configuration of the skew feeding correction device 55 and the transport roller device 50 provided in the sheet transport device 100D of the present embodiment, and FIG. 4 shows the skew feeding correction device 55 and the transport roller device 50. It is a top view explaining operation | movement of. FIG. 5 is a front view showing operations of the skew feeding correction device 55 and the conveyance roller device 50 according to the present embodiment, FIG. 8 is a flowchart showing operations of the skew feeding correction device 55 and the conveyance roller device 50, and FIG. It is a figure which shows the mode of the buckling of the sheet | seat by the skew correction apparatus 55 as a comparative example.

  In FIG. 8, the controller 9 drives the skew correction roller drive motor 32B to start rotation of the skew correction roller pair 32, 32a, and drives the conveyance roller drive motor 34B to rotate the conveyance roller pair 34. Let it begin. Further, the conveyance roller drive motor 36B is driven to start rotation of the conveyance roller pair 36 (S1).

  Thus, the sheet S fed from the sheet storage unit 51 is sent to the transport roller device 50 via the transport path 54a. At this time, as shown in FIGS. 2, 3A and 4A, the sheet S has a skew roller β with respect to the sheet conveying direction (arrow C direction) (FIG. 2). Even if it is conveyed to 50, it is sent to the skew feeding correction device 55, and skew feeding is corrected as will be described later (FIGS. 5A and 5B).

  In step S2, the control unit 9 determines whether or not the sheet S conveyed by the conveying roller pair 34 has reached the skew correction roller pair 32a based on the detection result of the sheet passing detection sensor 40. As a result, when it is determined that it has arrived, the control unit 9 operates the nip release mechanism 34A to release the nip (clamping) of the transport roller pair 34 (S3). That is, when the sheet S begins to be conveyed by the most upstream skew correction roller pair 32a, the nip of the conveyance roller pair 34 is released (FIG. 3B). Accordingly, the sheet S is conveyed in the sheet conveyance direction by the skew feeding correction roller pairs 32 and 32a in a state where the sheet S is released from the nipping of the conveyance roller pair 34 (FIGS. 3B, 4B, and 4C). 5 (a)). Thus, when the driven roller 14 is separated from the driving roller 301 in the conveying roller pair 34, when the sheet S is obliquely fed by the skew feeding correction roller pair 32, 32a, the sheet S is obliquely fed. It is possible to prevent obstruction by 34.

  At the time of the skew feeding, the sheet S is conveyed to the downstream registration roller pair 7 while being slid in contact with the end surface (side edge) pressed against the reference surface 31a by the skew correction roller pair 32, 32a. The positional deviation in the row and width directions is corrected. In FIG. 5A, in the skew feeding correction device 55 in the present embodiment, a guide member 31b for forming a guide groove 31c into which the sheet S can be inserted on the upper side of the reference surface 31a of the movable guide 30. Is arranged.

  When the sheet S is pressed against the reference surface 31a, if the pressing force is too strong, the sheet S is buckled or looped. Therefore, in the comparative example shown in FIG. 9, buckling and loop-shaped portion L grow in the narrow guide groove 31 c, and the skew correction ability is reduced and the sheet S is jammed. Therefore, in this embodiment, as shown in FIG. 5B, the width of the guide groove 31c, that is, the distance d between the inlet of the guide groove 31c and the reference surface 31a is made shorter than that of the comparative example. Thereby, a large space is allowed between the entrance of the guide groove 31c and the skew correction roller pair 32, 32a in which buckling or a loop-shaped portion L is allowed. In the present embodiment, buckling or loop-like portion L is actively grown in the space, and the excessive pressing force is released, while buckling in the guide groove 31c as shown in FIG. Generation | occurrence | production of the loop-shaped part L can be suppressed. As a result, the sheet S can be sandwiched in the guide groove 31c in which buckling and generation of the loop-shaped portion L are suppressed by a later-described conveyance roller pair 36.

  In step S <b> 4, the control unit 9 determines whether or not the sheet S conveyed while being skew-corrected by the skew correction roller pair 32 and 32 a has reached the conveyance roller pair 36. This determination can be made by a configuration in which a sensor such as the sheet passing detection sensor 40 is arranged to detect the leading edge of the sheet. For example, a predetermined time is measured after the feeding is started by the skew feeding correction roller pair 32a. Thus, it is possible to determine the arrival at the conveyance roller pair 36. During this time, a loop-shaped portion L is formed on the sheet S that is sandwiched between the skew feeding correction roller pairs 32 and 32a and pressed against the reference surface 31a (FIG. 5B).

  In step S4, when the control unit 9 determines that the sheet S has reached the conveying roller pair 36, the control unit 9 operates the nip releasing mechanism 32A to release the nip (clamping) between the skew correction roller pairs 32 and 32a (S5). ). At this time, after the sheet S is nipped by the conveying roller pair 36 that is rotationally driven in the nip state (FIG. 5C), the nipping correction roller pairs 32 and 32a are released (see FIG. 5). 3 (c), FIG. 4 (c), and FIG. 5 (d)), the loop-shaped portion L is released to return to a flat state. The sheet S is conveyed as it is by the conveying roller pair 36.

  That is, when the sheet S reaches the conveyance roller pair 36 and begins to be conveyed (S4), the nipping of the skew correction roller pair 32, 32a is released (S5), as shown in FIG. 5D. The buckling or loop-shaped portion L generated in the sheet S can be released to be planar. At this time, even if the buckling and the loop-shaped portion L that have occurred are different in size between the upstream side and the downstream side, the sheet in the guide groove 31c is released by releasing the clamping of the skew correction roller pair 32, 32a. Since it follows the posture, stable skew correction can be performed. The release timing in step S5 may be performed at the same time as the sheet S starts to be conveyed by the conveying roller pair 36, or may be performed immediately after the sheet S starts to be conveyed by the conveying roller pair 36. As will be described later, the transport roller pair 36 is not limited to the downstream side of the skew feeding correction roller pair 32, and the number of transport roller pairs 36 is not limited to one, and a plurality of pairs may be arranged. In this embodiment, the conveyance roller pair 36 waits for a sheet in a nipped state, but may wait for a sheet in a state where the nip is released in advance by the nip releasing mechanism 36A. In this case, the sheet may be nipped by detecting or predicting that the sheet has entered between the rollers of the conveyance roller pair 36. If comprised in this way, the freedom degree of the installation position of the conveyance roller pair 36 can be raised. That is, the conveyance roller pair 36 can be arranged near the skew feeding correction rollers 32 and 32a, and the sheet feeding correction rollers 32 and 32a feed the sheet obliquely while the sheet passes between the rollers of the conveyance roller pair 36. It becomes possible. Therefore, it leads to size reduction of an apparatus.

  Subsequently, in step S <b> 6, the control unit 9 determines whether or not the sheet S conveyed by the conveyance roller pair 36 has reached the registration roller pair 7. When it is determined that the controller 9 has reached, the controller 9 operates the nip releasing mechanism 36A to release the conveyance roller pair 36 (S7). At the same time, the registration roller moving mechanism 7A is operated to shift the registration roller pair 7 with the sheet S sandwiched therebetween in the width direction orthogonal to the sheet conveying direction (S8) (FIG. 3D, FIG. d)).

  Further, in step S9, it is determined whether or not the sheet S has reached the secondary transfer portion. If it is determined that the sheet S has reached, the control portion 9 operates the nip release mechanism 7B to hold the registration roller pair 7. Release (S10) and end the process.

  As described above, in the present embodiment, when the control unit 9 starts nipping and conveying the sheet S that has been widened by the skew correction roller pair 32 and 32a by the conveyance roller pair 36, the skew correction roller pair 32 and 32a. Control to release the pinching by. For this reason, even if buckling or a loop-shaped portion L occurs when the sheet S is abutted against the reference surface 31a, these can be regulated between the reference surface 31a and the conveyance roller pair 36, and the reference surface 31a and the conveyance portion 36 can be conveyed. The buckling and the loop-shaped portion L generated between the roller pair 36 can be minimized. Thereafter, the buckling or loop portion L generated between the reference surface 31a and the conveying roller pair 36 can be removed by releasing the clamping of the skew feeding correction roller pair 32, 32a. Even in a sheet in which the shape L is likely to be generated, it is possible to perform skew correction with high accuracy.

<Second Embodiment>
Next, a second embodiment according to the present invention will be described with reference to FIGS. FIG. 10 is a diagram illustrating the configuration of the skew feeding correction device and the transport roller device of the present embodiment, and FIG. 11 is a flowchart illustrating the operation of the skew feeding correction device and the transport roller device of the present embodiment. The present embodiment is different from the first embodiment shown in FIGS. 1 to 9 only in that the conveyance roller pair 36a is provided, and the other parts are substantially the same. Are denoted by the same reference numerals, and the description thereof is omitted.

  That is, in this embodiment, as shown in FIGS. 10A and 10B, in addition to the conveyance roller pair 36 that is the first conveyance roller pair on the downstream side in the sheet conveyance direction, the upstream side in the sheet conveyance direction. A conveyance roller pair 36a which is a second conveyance roller pair is disposed. Also in the present embodiment, the conveying roller pair 36, 36a is disposed between the reference surface 31a and the skew correction roller pair 32, 32a in the width direction orthogonal to the sheet conveying direction (arrow C direction). The conveyance roller pairs 36 and 36a sandwich the sheet S that has been narrowed to the reference surface 31a by the skew feeding correction roller pairs 32 and 32a and convey the sheet S in the sheet conveyance direction.

  In the present embodiment, the arrangement of the conveyance roller pair 36 is the same as that in the first embodiment, but the conveyance roller pair 36a includes a skew correction roller pair 32 and a skew correction roller pair 32a in the sheet conveyance direction. It is arranged at the position between. Thereby, it is possible to stabilize the sheet behavior when transporting a sheet that is long in the sheet transport direction or a thick sheet.

  Further, the control unit 9 in the present embodiment releases the nipping of the conveying roller pair 36a until the conveying roller pair 36 nipping the sheet S that is brought closer to the reference surface 31a by the skew correction roller pair 32, 32a. deep. When the sheet S is nipped by the conveying roller pair 36, the nipping mechanism (second releasing unit) 36A releases the nipping of the skew correction roller pair 32, 32a and nipping the conveying roller pair 36a. And the nip release mechanism (first release portion) 32A. In the present embodiment, the conveyance roller drive motor 36B is configured to individually rotate and drive the conveyance roller pair 36 and 36a, and the nip release mechanism 36A is configured to individually clamp and release the conveyance roller pair 36 and 36a. Has been.

  In FIG. 11, the control unit 9 starts to rotate the skew feeding correction roller pair 32, 32a, starts to rotate the transport roller pair 34, and starts to rotate the transport roller pair 36 in the nipped state (S21). In step S22, the nip of the conveying roller pair 36a is released before the sheet S is nipped by the skew feeding correction roller pair 32a, and the sheet S is moved to the skew feeding correction roller based on the detection result of the sheet passing detection sensor 40. It is determined whether or not the pair 32a has been reached.

  When it is determined that the sheet S has reached the skew correction roller pair 32a, the control unit 9 operates the nip release mechanism 34A to release the nip (nip) of the conveyance roller pair 34 (S24). Accordingly, the sheet S is conveyed in the sheet conveyance direction by the skew feeding correction roller pairs 32 and 32a in a state where the sheet S is released from the nipping of the conveyance roller pair 34.

  Further, in step S25, the control unit 9 determines whether the sheet S conveyed while being skew-corrected by the skew correction roller pair 32, 32a has reached the conveyance roller pair 36 or not. When the sheet S reaches the conveyance roller pair 36 and begins to be conveyed by the conveyance roller pair 36, the conveyance roller pair 36a is sandwiched by the operation of the nip release mechanism 36A (S26), and the operation of the nip release mechanism 32A is performed. The holding of the skew correction roller pair 32, 32a is released (S27). The release timing in step S27 may be performed simultaneously with the start of conveyance of the sheet S by the conveyance roller pair 36, 36a, or may be performed immediately after the sheet S begins to be conveyed by the conveyance roller pair 36, 36a.

  In consideration of variation in the position of the conveyed sheet S in the width direction, the position where the reference member 31 is offset so that the sheet S conveyed to the skew feeding correction device 55 does not collide with the reference member 31. Waiting at. Therefore, when the sheet S reaches the registration roller pair 7 and then the conveyance of the sheet S is started by the registration roller pair 7 (S28), the nipping of the conveyance roller pairs 36 and 36a is released (S29), and the registration roller pair 7 Thus, the sheet S is moved in the width direction while being nipped and conveyed (S30). Thereby, the sheet S and the center position of the image on the intermediate transfer belt 506 can be matched.

  Further, in step S31, it is determined whether or not the sheet S has reached the secondary transfer portion. If it is determined that the sheet S has reached, the control portion 9 operates the nip release mechanism 7B to hold the registration roller pair 7. Release (S32). At the same time, the registration roller pair 7 is moved in the opposite direction to that in step S30 to return to the standby state for the next sheet, and the process is terminated.

  Also in the present embodiment having the above configuration, substantially the same effect as that of the first embodiment can be obtained.

<Third Embodiment>
Next, a third embodiment according to the present invention will be described with reference to FIGS. FIG. 12 is a diagram illustrating a configuration of the skew feeding correction device and the conveyance roller device of the present embodiment, and FIG. 13 is a flowchart illustrating operations of the skew feeding correction device and the conveyance roller device of the present embodiment. The present embodiment is different from the first embodiment only in that the conveyance roller pair 36 is eliminated, the conveyance roller pair 36b is provided, and the sheet passage detection sensor 60 is provided. Are substantially the same, the same reference numerals are given to the main parts, and the description thereof is omitted.

  In the present embodiment, the sheet is disposed between the reference surface 31a in the width direction and the skew feeding correction roller pair 32, 32a, and is conveyed as a conveyance roller that sandwiches the sheet that has been brought close to the reference surface 31a and conveys the sheet in the sheet conveyance direction. Roller pairs 36a and 36b are disposed (FIGS. 12A and 12B). The transport roller pair 36a has the same function as that of the second embodiment, but the transport roller pair 36b newly provided in the present embodiment is disposed downstream of the transport roller pair 36a in the sheet transport direction, and the operation thereof is as follows. It is the same as the conveyance roller pair 36a. In the present embodiment, the conveyance roller drive motor 36B is configured to simultaneously rotate and drive the conveyance roller pair 36a and 36b, and the nip release mechanism 36A is configured to simultaneously nipping and releasing the conveyance roller pair 36a and 36b. Yes.

  In this embodiment, the control unit 9 holds the conveyance roller pairs 36a and 36b until the sheet passing detection sensor 60 detects the leading edge of the sheet S that is brought close to the reference surface 31a by the skew correction roller pairs 32 and 32a. Cancel. When the sheet S is detected by the sheet passage detection sensor 60, the nip release mechanism 36A and the nip release mechanism are configured to release the holding of the skew feeding correction roller pair 32, 32a and to hold the conveyance roller pair 36a, 36b. 32A is controlled.

  In FIG. 13, the controller 9 starts rotating the skew correction roller pair 32, 32a and starts rotating the transport roller pair 34 and the transport roller pair 36a, 36b (S31). In step S32, before the sheet S is nipped by the skew correction roller pair 32a, the nip of the conveyance roller pairs 36a and 36b is released, and the sheet S is skewed based on the detection result of the sheet passage detection sensor 40. It is determined whether or not the correction roller pair 32a has been reached.

  When it is determined that the sheet S has reached the skew correction roller pair 32a, the control unit 9 operates the nip release mechanism 34A to release the nip of the transport roller pair 34 (S34). Accordingly, the sheet S is conveyed in the sheet conveyance direction by the skew feeding correction roller pairs 32 and 32a in a state where the sheet S is released from the nipping of the conveyance roller pair 34.

  Further, the control unit 9 determines whether or not the leading edge of the sheet S conveyed while being skew-corrected by the skew correction roller pair 32, 32a is detected by the sheet passage detection sensor 60 (S35). When the leading edge of the sheet S is detected by the sheet passage detection sensor 60, the conveyance roller pair 36a, 36b is held by the operation of the nip release mechanism 36A (S36), and the skew correction is performed by the operation of the nip release mechanism 32A. The clamping of the roller pairs 32 and 32a is released (S37). The release timing in step S37 may be performed at the same time as the sheet S starts to be conveyed by the conveying roller pair 36a, 36b, or may be performed immediately after the sheet S starts to be conveyed by the conveying roller pair 36a, 36b.

  When the sheet S reaches the registration roller pair 7 and then the conveyance of the sheet S is started by the registration roller pair 7 (S38), the nipping of the conveyance roller pairs 36a and 36b is released (S39). While sandwiching and conveying S, it is moved in the width direction (S40). Thereby, the sheet S and the center position of the image on the intermediate transfer belt 506 are matched.

  Further, in step S41, it is determined whether or not the sheet S has reached the secondary transfer portion. Release (S42). At the same time, the registration roller pair 7 is moved in the opposite direction to that in step S40 to return to the standby state for the next sheet, and the process ends.

  In the present embodiment having the above configuration, substantially the same effect as that of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 9 ... Control part, 31a ... Reference surface, 32, 32a ... Width-adjusting roller pair (skew correction roller pair), 32A ... 1st cancellation | release part (nip release mechanism), 36 ... Conveyance roller pair, 1st conveyance roller pair (Conveying roller pair), 36a ... conveying roller pair, second conveying roller pair (conveying roller pair), 36b ... conveying roller pair (conveying roller pair), 36A ... second releasing part (nip releasing mechanism), 55 ... inclined Line correction unit (skew correction device), 100 ... Image forming device (color image forming device), 100D ... Sheet conveying device, 513 ... Image forming unit, C ... Sheet conveying direction, S ... Sheet

Claims (4)

The sheet has a reference surface extending along the sheet conveyance direction, and a pair of width-adjusting rollers for holding the sheet so that the side edge of the sheet is in sliding contact with the reference surface, and skewing the sheet In a sheet conveying apparatus including a skew feeding correction unit for correcting
The sheet is disposed between the reference surface in the width direction orthogonal to the sheet conveyance direction and the width-adjusting roller pair, and sandwiches the sheet that is width-adjusted by the width-adjusting roller pair in the sheet conveyance direction. A pair of transport rollers to transport,
A release portion for releasing the holding of the width adjusting roller pair;
A control unit for controlling the release unit,
The control unit controls the release unit to release the nipping by the width adjusting roller pair when conveyance of the sheet that has been adjusted by the width adjusting roller pair is started by the conveying roller pair. Sheet transport device.   A second release unit for releasing the holding of the conveying roller pair; and the control unit controls the second releasing unit to release the holding of the conveying roller pair by the width adjusting roller pair. The sheet conveying apparatus according to claim 1, wherein the sheet transported sheet is received. A reference surface extending along the sheet conveying direction, and a pair of width-adjusting rollers for holding the sheet so that the side edge of the sheet is in sliding contact with the reference surface, In a sheet conveying apparatus including a skew feeding correction unit for correcting
The sheet is disposed between the reference surface in the width direction orthogonal to the sheet conveyance direction and the width-adjusting roller pair, and sandwiches the sheet that is width-adjusted to the reference surface by the width-adjusting roller pair in the sheet conveyance direction. A first conveying roller pair and a second conveying roller pair for conveying;
A first release portion for releasing the holding of the width adjusting roller pair;
A second release portion for releasing the holding of each of the first and second transport roller pairs;
A control unit that controls the first and second release units,
The controller releases the holding of the second conveying roller pair until the first conveying roller pair holds the sheet that is width-adjusted to the reference surface by the width adjusting roller pair. The sheet conveying apparatus, wherein when the sheet is nipped by one conveying roller pair, the nipping of the width adjusting roller pair is released and the second conveying roller pair is nipped. A sheet conveying device according to any one of claims 1 to 3,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet conveyed by the sheet conveying apparatus.

Images