JP2017007797A - Sheet conveyance device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance device and an image formation apparatus which can set the optimum shutter pressure in accordance with the basis weight of a conveyed sheet without performing an operation of changing a pulling amount of a spring and the like.SOLUTION: A sheet conveyance unit comprises: a conveyance roller pair 30 which conveys a sheet S; and a shutter part 11 and an auxiliary shutter part 16 which are energized in the direction facing the sheet conveyance direction and feed the sheet to a nip portion N while being in contact with the sheet tip in any of the first load state of giving the first load to the sheet and the second load state of giving the second load larger than the first load to the sheet. A skew correction device 10 includes a movement guide member 21 switching between the first load state and the second load state by the shutter part 11 and the auxiliary shutter part 16 with the pressing force in accordance with the basis weight of the contacting sheet S.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet in an image forming apparatus such as a copying machine, a printer, and a facsimile machine, and an image forming apparatus including the sheet conveying apparatus.

  For example, on the upstream side in the sheet conveyance direction closest to the image forming unit (hereinafter referred to as “upstream side”), a sheet conveyance in which a pair of registration rollers extending in the width direction orthogonal to the sheet conveyance direction and a shutter member are arranged The device is known. This sheet conveying apparatus employs a registration shutter system in which the leading edge of the sheet is brought into contact with a shutter member to correct the skew of the sheet. The shutter member is configured to be swingable between a posture capable of abutting the leading end of the sheet around the rotation axis of the registration roller pair and locking the leading end of the sheet, and a posture capable of passing the sheet. Then, after the sheet has passed, the shutter member is biased by an elastic member such as a spring in a direction returning from a posture capable of passing the sheet to a posture capable of locking the leading end of the sheet.

  In this sheet conveying apparatus, a shutter member is rotatably disposed at a predetermined interval along the axial direction on the rotation shaft of the conveying roller in the registration roller pair, and the leading edge of the sheet conveyed by the upstream conveying roller pair is arranged. It is brought into contact with the abutting surface of the shutter member. Then, a loop is gradually formed in the sheet, and the force with which the leading end of the sheet presses the shutter member increases, and the shutter member is pressed and rotated to retract, and the sheet passes through the shutter member. When the sheet presses and rotates the shutter member, the leading end of the sheet follows the contact surface of the shutter member and is aligned in a direction orthogonal to the sheet conveying direction. In this state, the sheet is conveyed by the registration roller pair so that the skew is corrected and conveyed.

  In this technique, when the pressure (load) by the shutter member facing the sheet conveying direction is constant, the optimum shutter pressure differs depending on whether the sheet basis weight is small or large. Becomes narrower. As a countermeasure, a technique for switching the pressure (load) of the shutter member according to the media has been proposed. In this technique, the shutter pressure is urged by a tension spring, and one of a plurality of hooking portions for locking the tension spring is selected to change the tension amount of the tension spring and switch the load by the shutter member. It is configured. In this technique, the hooking portion of the tension spring is manually switched. However, as an alternative, this can be switched by controlling with an actuator or the like (see Patent Document 1).

Japanese Patent No. 3554145

  In general, in the case of a shutter system that generates a biasing force with a spring, the pressure (load) by the shutter member gradually increases until the shutter member is opened and the leading edge of the sheet is conveyed to the nip portion of the registration roller pair. . When the shutter pressure in a state where the shutter member is waiting is set optimally, the shutter pressure increases from the optimal value while being conveyed to the nip portion of the registration roller pair. For this reason, when the increment is large, there is a concern that the sheet may cause a scratch such as a dent at the leading edge, and that the sheet may not be reliably conveyed to the nip portion of the registration roller pair. For this reason, it is desirable to set the spring so that the shutter pressure does not change as much as possible while the spring multiplier is set as low as possible and the sheet is conveyed from the standby position of the shutter member to the nip portion of the registration roller pair.

  However, when switching the shutter pressure according to the amount of tension of the tension spring as in Patent Document 1, if the spring multiplier of the tension spring being used is set low, it is necessary to widen the interval between the hook portions of the tension spring. It becomes necessary to secure space. Conversely, to minimize the space, it is necessary to set the spring multiplier high, and as described above, while the sheet is conveyed from the standby position of the shutter to the nip portion of the registration roller pair (conveying roller pair). The shutter pressure may increase more than necessary. In the method of switching the shutter pressure by changing the amount of spring tension according to the basis weight of the sheet to be used, when using a sheet having a different rigidity (rigidity) with a difference in basis weight, the optimum shutter pressure is obtained. Cannot be set.

  Accordingly, the present invention provides a sheet conveying apparatus and an image that can be set to an optimum shutter pressure (load) according to the basis weight of the conveyed sheet without performing an operation such as changing the amount of spring tension. An object is to provide a forming apparatus.

  The present invention provides a sheet conveying apparatus, a pair of conveying rollers that convey a sheet, a first load state that is biased in a direction opposite to the sheet conveying direction, and applies a first load to the sheet, and the first load Depending on the basis weight of the abutting sheet and shutter means for feeding the sheet to the nip portion of the pair of conveying rollers while abutting the leading end of the sheet in any of the second load states in which a larger second load is applied to the sheet And switching means for switching between the first load state and the second load state by the shutter means by the pressing force.

  According to the present invention, it is possible to set an optimum shutter pressure (load) according to the basis weight of the conveyed sheet without performing an operation such as changing the amount of spring tension.

1 is a schematic cross-sectional view showing an image forming apparatus according to a first embodiment of the present invention. (A) is a perspective view showing a skew feeding correction device according to the first embodiment, (b) is a cross-sectional view showing initial positions of a shutter and an auxiliary shutter in the skew feeding correction device of (a). (A)-(c) is sectional drawing which shows the state at the time of skew correction of the sheet | seat with a small basic weight in the skew correction apparatus which concerns on 1st Embodiment in steps. (A)-(c) is sectional drawing which shows the state at the time of skew correction of the sheet | seat with a large basic weight in the skew correction apparatus which concerns on 1st Embodiment in steps. It is a side view which shows the skew correction apparatus which concerns on 1st Embodiment in the state seen from the right side of FIG. (A) shows the state where the leading edge of the sheet conveyed obliquely contacts the shutter side abutting surface, and (b) shows the state where the sheet abuts against the shutter side abutting surface and the skew correction is performed. The perspective view which shows the skew feeding correction apparatus which concerns on the 2nd Embodiment of this invention. (A), (b) is sectional drawing which shows the state at the time of skew correction of the sheet | seat with a small basic weight in the skew correction apparatus which concerns on 2nd Embodiment in steps. (A)-(d) is sectional drawing which shows the state at the time of skew correction of the sheet | seat with a large basic weight in the skew correction apparatus which concerns on 2nd Embodiment in steps.

<First Embodiment>
Hereinafter, an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS. The image forming apparatus 100 according to the present embodiment is an image forming apparatus including a sheet conveying device having a skew feeding correction device that corrects the skew feeding of a sheet, such as a copying machine, a printer, a facsimile machine, and a multifunction machine thereof. In the following embodiments, an image forming apparatus provided with a sheet conveying apparatus will be described with reference to an electrophotographic color laser beam printer (printer). FIG. 1 is a schematic cross-sectional view showing the image forming apparatus according to the first embodiment.

  As shown in FIG. 1, the image forming apparatus 100 is conveyed by a sheet feeding unit 110 that feeds a sheet S, a sheet conveying unit (sheet conveying device) 40 that conveys the sheet S, and a sheet conveying unit 40. An image forming unit 140 that forms an image on the sheet S is provided. The image forming apparatus 100 also includes a discharge roller pair 161 that discharges the sheet S on which an image is formed, a discharge tray 170 on which the discharged sheet S is stacked, and an image reading device 49 that can read an image of a document. And a control unit 55 for controlling them.

  The sheet feeding unit 110 includes a sheet feeding cassette 111 that stores sheets S, a feeding roller 50 that feeds sheets S stored in the sheet feeding cassette 111, and a sheet S that is fed by the feeding roller 50. And a separation / conveying section 51 that conveys the sheets while separating them one by one. The paper feed cassette 111 is provided so that it can be pulled out and mounted in the front and back directions in FIG. 1, and paper, OHT, and the like as a sheet S for forming an image are set. The sheet conveyance unit 40 also includes a conveyance roller pair (registration roller pair) 30 that conveys the sheet S conveyed by the separation conveyance unit 51 and a skew that corrects skew of the sheet S conveyed by the conveyance roller pair 30. The line correction apparatus 10 is provided. The skew correction device 10 will be described in detail later.

  The image forming unit 140 includes process cartridges 52Y, 52M, 52C, and 52Bk that form four color images of yellow (Y), magenta (M), cyan (C), and black (Bk), and laser light based on the image information. And a laser scanner unit 142 for irradiating the laser beam. Each of the process cartridges 52Y, 52M, 52C, and 52Bk includes a photosensitive drum 141 on which an electrostatic latent image is formed and a developing unit 143 that develops the electrostatic latent image on the photosensitive drum 141. Since the four process cartridges 52Y to 52Bk have the same configuration except that the colors of the images to be formed are different, description of the process cartridges 52M to 52Bk is omitted.

  The image forming unit 140 includes an intermediate transfer belt 145 to which the toner image on the photosensitive drum 141 is primarily transferred, and a primary transfer roller 144 for primarily transferring the toner image on each photosensitive drum to the intermediate transfer belt 145. This intermediate transfer belt 145 is transported in the direction of arrow A in FIG. Further, the image forming unit 140 includes a secondary transfer roller 132 that secondary-transfers the primary-transferred toner image onto the sheet S, and a fixing unit 150 that heat-fixes the secondary-transferred toner image. Further, a secondary transfer portion is constituted by the secondary transfer nip portion N2 between the intermediate transfer belt 145 whose inner surface is supported by the driving roller 131 and the secondary transfer roller 132 that contacts the intermediate transfer belt 145. . The image forming unit 140, the fixing unit 150, and the secondary transfer nip portion N2 constitute an image forming unit that forms an image on the conveyed sheet.

  Next, a print job (image forming job) by the control unit 55 of the image forming apparatus 100 having the above-described configuration will be described.

  When a print job is started in accordance with settings on an operation unit (not shown), the laser scanner unit 142 is applied to the photosensitive drum 141 based on image information input from the image reading device 49 or an external personal computer (PC). Irradiate with laser light. At this time, the photosensitive drum 141 is charged in advance to a negative potential, and an electrostatic latent image is formed on the photosensitive drum 141 when irradiated with laser light. The electrostatic latent image is reversely developed by the developing unit 143 and negative toner is attached, and yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are formed on the respective photosensitive drums 141. Are formed respectively.

  The toner images of the respective colors formed on the respective photosensitive drums 141 are sequentially superimposed and transferred from the respective photosensitive drums 141 to the intermediate transfer belt 145 by applying a positive bias to the primary transfer roller 144. The four color toner images superimposed and transferred onto the intermediate transfer belt 145 are conveyed to the position of the secondary transfer roller 132 by the rotational drive of the intermediate transfer belt 145.

  In parallel with the toner image forming operation, the sheet S stored in the paper feed cassette 111 is fed one by one to the transport roller pair 120 by the feed roller 50 and the separation transport unit 51, and is inclined by the transport roller pair 120. It is conveyed to the row correction device 10. The skew correction device 10 conveys the sheet S to the secondary transfer nip N2 by the conveyance roller pair 30 while correcting the skew. The sheet S conveyed to the secondary transfer nip N2 is subjected to secondary transfer of the four color toner images on the intermediate transfer belt 145 by applying a positive bias from the secondary transfer roller 132.

  The sheet S to which the toner image has been transferred is conveyed to the fixing unit 150 and heated and pressed by the fixing unit 150 to fix the toner image. The sheet S having a fixed image obtained in this way passes through the post-fixing conveyance unit 160 and is discharged as it is onto the discharge tray 170 via the discharge roller pair 161 in the case of single-sided printing. In the case of double-sided printing, the sheet S having a fixed image on one side is conveyed to the reverse conveying device 180 through a branch by the switching of the switching member 162, sent to the skew feeding correction device 10, and then again. It is sent to the secondary transfer nip portion N2 to form an image on the other surface. That is, the reversed sheet S is conveyed to the reverse conveyance device 180 via the reverse roller pair 163, passes through the reverse conveyance device 180, and passes through the skew feeding correction device 10 to the secondary transfer nip portion N <b> 2 and the fixing. It is conveyed to the section 150 and the like. As a result, the sheet S having fixed images on both sides is discharged onto the discharge tray 170 via the discharge roller pair 161.

[Skewing correction device]
Next, the skew feeding correction device 10 according to the present embodiment will be described in detail with reference to FIGS. 2A is a perspective view showing the skew feeding correction device 10 according to the present embodiment, and FIG. 2B is a shutter portion 11 and an auxiliary shutter portion 16 in the skew feeding correction device 10 according to the present embodiment. It is sectional drawing which shows the initial position (shutter standby position). FIGS. 3A to 3C are cross-sectional views showing in stages the skew correction of a sheet having a small basis weight in the skew correction device 10 according to the present embodiment.

  The skew correction device 10 as the skew correction unit according to the present embodiment is a pair of upstream conveying rollers with respect to the shutter member 12 and the auxiliary shutter member 17 biased in the direction opposite to the sheet conveying direction. A sheet is abutted by 120 and the sheet front ends are aligned to form a loop. At that time, the shutter member 12 and the auxiliary shutter member 17 are opened using the rigidity (rigidity, stiffness) of the sheet, and the sheet is conveyed by the conveying roller pair (registration roller pair) 30 immediately after the shutter. Correct the line.

  That is, as shown in FIGS. 2A and 2B, the skew feeding correction device 10 is conveyed on the upstream side in the sheet conveying direction (the direction of arrow G) of the nip portion N of the conveying roller pair 30. A configuration is provided in which the skew feeding of the sheet S is corrected and fed to the nip portion N. The conveyance roller pair 30 includes a conveyance roller (drive roller) 31 having the shutter unit 11 and a driven roller (conveyance roller) 32 having the auxiliary shutter unit 16 in a state of facing each other in the axial direction.

  The conveyance roller 31 is divided into a plurality (eight in this embodiment) in the width direction (direction of arrow H) orthogonal to the sheet conveyance direction (direction of arrow G), and the frame 34 (see FIG. 5) and is supported so as to be rotatable integrally with the rotating shaft 31a. The driven roller 32 is divided into a plurality (eight in the present embodiment) in the width direction facing the corresponding positions of the transport roller 31 and is rotatably supported by a fixed shaft 33 fixed to the frame 34. ing.

  The shutter portion 11 includes a plurality (six in this embodiment) of shutter members (first shutter members) 12 and two shutter bearing portions 14 that are integrally connected by a shutter connecting member 13. The shutter portion 11 is supported so as to be rotatable about the fixed shaft 33 as the shutter bearing portion 14 is rotatably supported at both ends of the fixed shaft 33. The shutter connecting member 13 is formed long in the axial direction of the fixed shaft 33. The plurality of shutter members 12 are arranged between the driven rollers 32 divided into a plurality.

  The auxiliary shutter portion 16 includes a plurality (six in this embodiment) of auxiliary shutter members (second shutter members) 17 and two auxiliary shutter bearing portions 19 that are integrally connected by an auxiliary shutter connecting member 18. doing. And the auxiliary shutter part 16 is supported so that the auxiliary shutter bearing part 19 can turn at both ends of the rotating shaft 31a, and can turn around the rotating shaft 31a. The auxiliary shutter connecting member 18 is formed long in the axial direction of the rotation shaft 31a. The plurality of auxiliary shutter members 17 are disposed between the transport rollers 31 divided into a plurality of parts. The auxiliary shutter member 17 is provided at a position shifted in the axial direction from the shutter member 12 with respect to the longitudinal direction of the auxiliary shutter portion 16. That is, the auxiliary shutter portion 16 is disposed in a position shifted in the axial direction from the shutter member 12 on the fixed shaft 33 side extending in parallel with the rotation shaft 31a in the axial direction of the rotation shaft 31a.

  Here, when the shutter unit 11 is viewed in the axial direction from one end of the transport roller pair 30, the shutter unit 11 has the fixed shaft 33 as the center of rotation by the shutter biasing spring 15, as shown in FIG. It is biased in the direction of the arrow 15a. Further, when the auxiliary shutter unit 16 is viewed in the axial direction from one end of the conveying roller pair 30, the auxiliary shutter unit 16 rotates the rotation shaft 31a by the auxiliary shutter biasing spring 20, as shown in FIG. The center is biased in the direction of the arrow 20a. The shutter urging spring 15 can be constituted by a torsion coil spring wound around the fixed shaft 33, but can also be constituted by another urging member such as a tension spring. This also applies to the auxiliary shutter urging spring 20.

  A stopper projection 34b shown in FIG. 2B is fixed at a predetermined position of the frame 34. A shutter locking projection 14b that engages with the stopper projection 34b in a direction rotating in response to the biasing force of the shutter biasing spring 15 in FIG. 2B is fixed at a predetermined position of the shutter bearing portion 14. . Further, at another position of the frame 34, a stopper projection 34c shown in FIG. At a predetermined position of the auxiliary shutter bearing 19, an auxiliary shutter locking projection 19 b that engages with the stopper projection 34 c in a direction rotating in response to the biasing force of the auxiliary shutter biasing spring 20 in FIG. 2B is fixed. Has been.

  The shutter member 12 of the shutter unit 11 is restricted from rotating in the direction of the arrow 15a by the contact between the stopper projection 34b on the frame 34 side and the shutter locking projection 14b, and the leading edge of the sheet shown in FIG. Is held in the first posture on the shutter side where it can come into contact. That is, as shown in FIG. 2B, the shutter portion 11 is urged in the direction of the arrow 15a by the shutter urging spring 15 with the fixed shaft 33 as the rotation center. By abutting the shutter locking protrusion 14b and the stopper protrusion 34b, the rotation of the shutter member 12 in the direction of the arrow 15a is restricted, and the shutter member 12 of the shutter 11 is held in the first posture on the shutter side. Is done.

  The auxiliary shutter member 17 of the auxiliary shutter portion 16 is restricted from rotating in the direction of the arrow 20a by the contact between the stopper projection 34c on the frame 34 side and the auxiliary shutter locking projection 19b, and the sheet shown in FIG. It is held in the first posture on the side of the auxiliary shutter that can come into contact with the tip. As shown in FIG. 2B, the auxiliary shutter portion 16 is urged in the direction of the arrow 20a by the auxiliary shutter urging spring 20 with the rotation shaft 31a as the rotation center. By abutting the auxiliary shutter locking projection 19b and the stopper projection 34c, the rotation of the auxiliary shutter 16 in the direction of the arrow 20a is restricted, and the auxiliary shutter member 17 of the auxiliary shutter 16 is provided on the auxiliary shutter side. 1 posture.

  As shown in FIG. 3A, the shutter member 12 rotatably supported by the fixed shaft 33 and the auxiliary shutter member 17 rotatably supported by the rotation shaft 31a are in the first postures. It has a shutter side abutting surface 12a and an auxiliary side abutting surface 17a, which are abutting portions protruding from each other. 3A, the length of the auxiliary side abutting surface (contact portion) 17a from the rotation center of the auxiliary shutter member 17 is the shutter side abutting surface ( The contact portion) 12a is set to be shorter than the length from the rotation center of the shutter member 12.

  The shutter member (first shutter member) 12 has a first posture on the shutter side (FIGS. 3A and 3B, FIGS. 4A and 4B), and a shutter-side first passage through which the sheet passes. It is configured to be movable to two postures (FIGS. 3C and 4C). The auxiliary shutter member 17 is movable between a first posture (FIGS. 3A and 3B) and a second posture (FIG. 4C) on the auxiliary shutter side, and the auxiliary-side abutting surface 17a is provided. The sheet has a shape that allows the leading end of the sheet to pass in accordance with the direction of the sheet that is conveyed in the state where the first posture is held. Therefore, in a state where the auxiliary shutter unit 16 is held in the first posture on the auxiliary shutter side, the auxiliary side abutting surface 17a is the abutting surface of the shutter member 12 held in the first posture on the shutter side. 12a and the conveying roller pair 30 are overlapped in the axial direction.

  The auxiliary side abutting surface 17a in the first posture is located so as to partially overlap the shutter side abutting surface 12a in the first posture. When the shutter member 12 and the auxiliary shutter member 17 are held in their first postures, the shutter side abutting surface 12 a and the auxiliary side abutting surface 17 a are more than the nip portion N of the conveying roller pair 30. Located upstream.

  The shutter member 12 and the auxiliary shutter member 17 are coaxially and rotatably supported by the rollers (respective transport rollers) 32 and 31 of the transport roller pair 30. The shutter member 12 and the auxiliary shutter member 17 are urged with a predetermined urging force toward a first posture in which the abutting surfaces 12a and 17a, which are the abutting portions, can abut against the sheet front end. The shutter member 12 constitutes a first shutter member, and the auxiliary shutter member 17 constitutes a second shutter member.

  The skew feeding correction device 10 described above includes the shutter unit 11 and the auxiliary shutter unit 16 as shutter means, and a movement guide member 21 as switching means. The shutter unit 11 and the auxiliary shutter unit 16 are biased in a direction opposite to the sheet conveying direction (the direction of the arrow G). The shutter unit 11 and the auxiliary shutter unit 16 are either in the first load state (the state shown in FIGS. 3A to 3C) or in the second load state (the state shown in FIGS. 4A to 4C). The sheet is fed to the nip portion N while contacting the leading end of the sheet. The first load state is a state in which a first load is applied to the seat, and the second load state is a state in which a second load greater than the first load is applied to the seat.

  Further, the movement guide member 21 switches between the first load state and the second load state by the shutter portion 11 and the auxiliary shutter portion 16 by a pressing force according to the basis weight of the sheet to be contacted. As shown in FIGS. 2A and 2B, the moving guide member 21 is arranged on the upstream side of the conveying roller pair 30 of the skew feeding correction device 10, and the moving guide member 21 is moved by the conveying roller pair 120 (FIG. 1). The conveyed sheet S is configured to be guided to the shutter unit 11 and the auxiliary shutter unit 16. The moving guide member 21 has rotating shaft portions 21a at both ends extending in the width direction (arrow H direction) orthogonal to the sheet conveying direction, and the rotating shaft portions 21a are attached to the frame 34 (FIG. 5). (See (a) and (b)), it is supported so as to be rotatable (swingable).

  The moving guide member 21 is urged in the direction of the arrow 22a by the guide urging spring 22, and the stopper surface 21c that can come into contact with the stopper portion 34d of the frame 34 is brought into contact with the moving guide member 21, thereby restricting the rotation in the direction of the arrow 22a. Thus, the initial position shown in FIG. The guide urging spring 22 is composed of a compression spring, with one end engaged with a spring support 48 fixed to the image forming apparatus main body 100a side, and the other end opposite to the stopper surface 21c of the moving guide member 21. In contact with the back side. The guide urging spring 22 is not limited to a compression coil spring, but can be constituted by a leaf spring or the like.

  In the skew correction device 10 described above, in the first load state described above, the leading end of the sheet comes into contact only with the shutter-side abutting surface 12a of the shutter member 12 held in the first posture. In the second load state described above, the leading end of the sheet contacts the shutter-side abutting surface 12a and the auxiliary-side abutting surface 17a of both the shutter member 12 and the auxiliary shutter member 17 held in the first posture. Touched.

[Skew correction]
Next, the skew correction operation of the sheet S by the skew correction device 10 will be described in detail with reference to FIGS. FIGS. 4A to 4C are cross-sectional views showing in stages the skew correction of a sheet having a large basis weight in the skew correction device 10 according to the present embodiment. FIG. 5 is a side view showing the skew feeding correction device 10 as viewed from the right side of FIG. 1, and FIG. 5 (a) shows a state where the leading edge of the sheet conveyed obliquely contacts the shutter-side abutting surface. FIG. 5B shows a state in which the sheet is in contact with the shutter-side abutting surface and the skew correction is performed.

  When the sheet S is conveyed downstream by the conveying roller pair 120, the sheet S is guided to the shutter member 12 side of the shutter unit 11 by the moving guide member 21. At this time, when the sheet S is conveyed in a skewed manner, as shown in FIG. 5A, the leading end portion S2 on the preceding side of the sheet S (the right side in FIG. 5A) is first moved to the shutter side. It abuts against the abutting surface 12a. At this time, the leading end portion S3 on the subsequent side (left side in FIG. 5A) of the sheet S is not in contact with the shutter-side abutting surface 12a of the shutter member 12. For this reason, the pushing force of the sheet S cannot exceed the urging force generated by the shutter urging spring 15, and the shutter part 11 cannot be pushed and rotated.

  When the sheet S is further conveyed by the conveying roller pair 120, as shown in FIG. 5B, the leading end portion S2 is aligned in contact with the shutter-side abutting surface 12a, and the following leading end portion is aligned. S3 sequentially contacts and aligns with the plurality of shutter side abutting surfaces 12a. When the sheet S is further conveyed, the sheet S forms a loop as shown in FIG. 3B, and the entire leading edge of the sheet S is shuttered by the strength (rigidity) of the sheet itself. Skew is corrected by contacting the side abutting surface 12a.

  When the sheet S forms a predetermined loop, the pushing force of the sheet S exceeds the urging force (first load) generated by the shutter urging spring 15, and the shutter member 12 rotates in the direction of the arrow 15b. And evacuate. As a result, the leading edge of the sheet S is nipped by the nip portion N of the conveying roller pair 30 and is conveyed downstream in a state where the skew is corrected. When the sheet S is conveyed downstream by the conveying roller pair 30, the shutter member 12 separates the shutter-side abutting surface 12a from the leading edge of the sheet S, and the shutter-side second posture shown in FIG. Retained.

  As described above, when the basis weight of the sheet S is smaller than a predetermined value, even if the sheet S is conveyed obliquely as described above, the entire sheet leading edge follows the plurality of shutter members 12. In contact with each other, a loop is formed and skew is corrected appropriately. However, when the basis weight of the sheet S is larger than a predetermined value and the rigidity (rigidity) of the sheet S is high, the following occurs. That is, when the sheet S is conveyed obliquely, the urging force generated on the shutter member 12 by the shutter urging spring 15 when a part of the leading edge of the sheet abuts against the shutter-side abutting surface 12a ( Exceeds the second load). As a result, the sheet S may be nipped between the conveyance roller pair 30 and conveyed downstream without correcting skew.

  Therefore, in this embodiment, the moving guide member 21 disposed upstream of the shutter member 12 is rotatably supported by the rotation shaft portion 21a on the image forming apparatus main body 100a side, and is urged by the guide urging spring 22. It is arranged so that rotation is possible. Accordingly, even when the basis weight of the sheet S is large, it is possible to reliably correct the skew by providing the auxiliary shutter portion 16.

  When the sheet S is conveyed downstream by the conveying roller pair 120, the sheet S is guided to the shutter member 12 while being in contact with the moving guide member 21 and sliding contact. When the leading edge of the sheet S reaches the movement guide member 21, the relationship between the force Fg that the sheet S rotates the movement guide member 21 and the urging force F22 of the guide urging spring 22 that urges the movement guide member 21. The position of the movement guide member 21 is determined.

  As shown in FIG. 3A, the basis weight of the sheet is less than a predetermined value, and the relationship between the force Fg that the sheet rotates the moving guide member 21 and the biasing force F22 generated by the guide biasing spring 22 is Fg < When F22 is satisfied, it is as follows. That is, the movement guide member 21 is held at the initial position (shutter standby position) shown in FIG. Then, since the leading end portion 21b of the movement guide member 21 guides the sheet S toward the shutter-side abutting surface 12a, the leading end of the sheet reaches the base side 12b of the abutting surface 12a as shown in FIG. To do.

  In the case where the movement guide member 21 is not rotated, when a sheet having a basis weight larger than a predetermined value is conveyed, the rigidity of the sheet S is high. It becomes as follows. That is, in order to obtain a pressing force Fs sufficient to rotate the shutter member 12 when the leading end portion S2 (see FIG. 5A) on the preceding side of the sheet S reaches the shutter-side abutting surface 12a, The sheet S is conveyed downstream without being sufficiently corrected for skew. However, in the present embodiment, since the movement guide member 21 is configured to be rotatable, skew correction is performed even when the basis weight of the sheet S is large, as shown in FIGS. It is possible to do it properly.

  That is, when the sheet S ′ having a large basis weight is conveyed, the relationship between the force Fg ′ that the sheet S ′ rotates the moving guide member 21 and the urging force F22 generated by the guide urging spring 22 is expressed as Fg ′> F22. At that time, it becomes as follows. That is, the movement guide member 21 rotates in the direction of the arrow 22b from the initial position shown in FIG. Thereby, the front end portion 21b of the movement guide member 21 guides the sheet S ′ toward the front end side 12c of the shutter side abutting surface 12a. Therefore, the sheet S ′ is in a region where the shutter-side abutting surface 12a and the auxiliary-side abutting surface 17a overlap in the axial direction of the conveying roller pair 30 (front and back directions in FIG. 4A). To reach.

  When the leading edge of the sheet S ′ hits the area where the shutter side abutting surface 12a and the auxiliary side abutting surface 17a overlap, the following occurs. That is, the force (load) applied to the sheet S ′ from the shutter member 12 and the auxiliary shutter member 17 is a combination of the two spring forces generated by the biasing springs 15 and 20. Thereby, the force Fs required for the sheet S ′ to push the shutter member 12 away can be increased. As a result, as shown in FIG. 4B, it becomes possible to form a loop when the leading edge of the sheet S ′ abuts against the shutter member 12 in the entire width direction, and the sheet S ′ having a basis weight larger than a predetermined value. Even when the sheet is conveyed, the skew can be corrected appropriately.

  When the pressing force of the sheet S ′ exceeds the urging force generated by the shutter urging spring 15 and the auxiliary shutter urging spring 20 when the sheet S ′ forms a predetermined loop, the shutter member 12 moves in the direction of the arrow 15b. The auxiliary shutter member 17 rotates in the direction of the arrow 20b. When the shutter-side abutting surface 12a of the shutter member 12 and the auxiliary-side abutting surface 17a of the auxiliary shutter member 17 are retracted from the conveyance path of the sheet S ′, the sheet S ′ is transported in a state where the skew is corrected. The tip is sandwiched between the pair 30 and conveyed downstream.

  When the sheet S ′ is conveyed downstream by the conveying roller pair 30, the sheet S ′ is separated from the shutter-side abutting surface 12 a and the auxiliary-side abutting surface 17 a, and as shown in FIG. Each of the auxiliary shutter members 17 is in the second posture that allows the sheet S ′ to pass therethrough. Further, when the sheet S ′ passes to the rear end, the shutter member 12 and the auxiliary shutter member 17 are returned to the first posture shown in FIG.

  As described above, in the present embodiment, the movement guide member 21 has the first guide position shown in FIGS. 3A to 3C and the second guide position shown in FIGS. It is configured to be movable. The first guide position is a position for guiding the leading end of the sheet so as to face only the shutter-side abutting surface 12a of the shutter member 12 in a state where both the shutter member 12 and the auxiliary shutter member 17 are held in the first posture. is there. The second guide position is such that both the shutter member 12 and the auxiliary shutter member 17 are held in the first posture, and the shutter side abutting surface 12a and the auxiliary side abutting surface of both the shutter member 12 and the auxiliary shutter member 17 are used. This is the position for guiding the leading edge of the sheet so as to face 17a. Thereby, the advancing direction of the front end of the sheet can be appropriately changed according to the pressing force according to the basis weight of the sheet contacting the moving guide member 21.

  In the present embodiment, the movable guide member 21 is supported so as to be rotatable between the first guide position and the second guide position, and the first guide member 21 is pressed by the pressing force corresponding to the basis weight of the abutting sheet. It is urged | biased by the guide position and the 2nd guide position so that rotation is possible. Thereby, although it is simple structure, the movement guide member 21 can be rotated according to the pressing force according to the basic weight of the sheet | seat to contact | abut, and the advancing direction of a sheet | seat front-end | tip can be changed appropriately.

  According to the present embodiment, the rigidity of the sheet from the initial position to the nip portion N of the conveying roller pair 30 without switching the pulling amount of the auxiliary shutter urging spring 20 and the shutter urging spring 15 that generate the urging force of the shutter pressure. It is possible to set an optimum shutter pressure according to the above. Further, since a configuration for switching the amount of spring tension is not required, the configuration can be simplified.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a perspective view showing the skew feeding correction device 10 according to the present embodiment. FIGS. 7A and 7B are cross-sectional views showing stepwise how the skew correction of a sheet having a small basis weight is corrected in the skew correction apparatus 10 according to the present embodiment. In the present embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and descriptions of components having the same configuration and function are omitted.

  In the first embodiment described above, the movement guide member 21 is rotated with the pressing force corresponding to the basis weight of the sheet to be contacted in a state where the movement guide member 21 is rotatably supported and is urged by the guide urging spring 22. I was moving. And the conveyance direction of the sheet | seat was changed by the front-end | tip part 21b, and it was determined whether the sheet | seat contact | wins the auxiliary side abutting surface 17a. On the other hand, in the present embodiment, a fixed guide member 21 ′ fixed to the image forming apparatus main body 100a side is provided so as not to rotate. Then, by arranging the auxiliary shutter holding member 41 that holds the auxiliary shutter member 17 in the second posture through which the sheet passes, it is determined whether or not the sheet hits the auxiliary side abutting surface 17a of the auxiliary shutter member 17. .

[Configuration of switching means]
In the present embodiment, the fixed guide member 21 ′ and the auxiliary shutter holding member 41 constitute switching means. As shown in FIG. 6, the auxiliary shutter holding member 41 is disposed at a substantially central portion in the longitudinal direction of the fixed guide member 21 ′, and a rotation shaft portion 41 a formed to project from the lower end portion to both ends in the longitudinal direction is attached to the frame 34. It is rotatably supported by being pivotally supported by (see FIG. 5). An opening 24 that is long in the sheet conveying direction is formed at a substantially central portion in the longitudinal direction of the fixed guide member 21 '.

  The fixed guide member 21 ′ is a region where the shutter-side abutting surface 12 a and the auxiliary-side abutting surface 17 a overlap each other in the axial direction of the conveying roller pair 30 (for example, the front and back directions in FIG. 8B). The angle at which the leading end of the sheet is guided is fixed. Further, as shown in FIGS. 7A and 7B, the auxiliary shutter holding member 41 has a shape that is bent in two stages upward from the rotation shaft portion 41a in a side view, and is bent at the first stage. The portion is formed as a protrusion 41 d protruding from the opening 24. Furthermore, the second bent portion is formed as the first locking portion 41b, and the distal end side of the first locking portion 41b is formed as the second locking portion 41c.

  In the auxiliary shutter holding member 41, the lower surface of the first locking portion 41b is biased in the direction of the arrow 43a by the holding member biasing spring 42, and the first locking portion 41b is fixed to the frame 34 side. It is made to contact with the stopper part 34e. Thereby, the rotation of the auxiliary shutter holding member 41 in the direction of the arrow 43a is restricted at a predetermined position, and the auxiliary shutter holding member 41 is held at the initial position shown in FIGS.

  The shutter member 12 of the present embodiment has the same configuration as the shutter member 12 of the first embodiment, but the auxiliary shutter member 17 of the present embodiment is different from the auxiliary shutter member 17 of the first embodiment. That is, in the auxiliary shutter member 17 of the present embodiment, the auxiliary side abutting surface 17a is formed to have the same length as the shutter side abutting surface 12a. Furthermore, the auxiliary shutter member 17 according to the present embodiment is formed as an auxiliary shutter locking portion 17b whose end opposite to the auxiliary side abutting surface 17a protrudes in the direction opposite to the auxiliary side abutting surface 17a. The auxiliary shutter portion 16 is engaged with the auxiliary shutter engaging portion 17b by the second engaging portion 41c of the auxiliary shutter holding member 41 so that the sheet is allowed to pass through the second posture (FIGS. 7A and 7B). ) And FIG. 8A).

  In the present embodiment, the shutter member (first shutter member) 12 and the auxiliary shutter member (second shutter member) 17 are in a first posture (see FIG. 8B) that can contact the sheet front end. It is supported so as to be rotatable (movable) in a second posture (see FIG. 7B) through which the sheet passes.

  Further, the fixed guide member 21 ′ and the auxiliary shutter holding member 41 as switching means are configured to be able to shift between a first guide state and a second guide state. The first guide state is a state where the shutter member 12 is held in the first posture and the auxiliary shutter member 17 is held in the second posture, and the shutter-side abutting surface (contact portion) of the shutter member 12. In this state, the leading end of the sheet is guided toward only 12a. In the second guide state, both the shutter member 12 and the auxiliary shutter member 17 are held in the first posture, and the shutter side abutting surface 12a and the auxiliary side abutting of both the shutter member 12 and the auxiliary shutter member 17 are used. In this state, the leading edge of the sheet is guided toward the surface 17a.

  The auxiliary shutter holding member 41 causes the second shutter member 17 to resist the urging force in the direction opposite to the sheet conveying direction with the protrusion 41d protruding from the opening 24 of the fixed guide member 21 '. Hold in posture. Then, when the protrusion 41d is pushed by the conveyed sheet S ′, the auxiliary shutter member 17 is rotated so as to change to the first posture according to the urging force. The auxiliary shutter holding member 41 is held in the first posture by releasing the auxiliary shutter member 17, and is held in the second posture by locking the auxiliary shutter member 17 with the second locking portion 41c. Accordingly, the fixed guide member 21 ′ and the auxiliary shutter holding member 41 operate as follows in the first guide state in which the auxiliary shutter member 17 is held (locked) in the second posture. That is, the fixed guide member 21 ′ and the auxiliary shutter holding member 41 release the lock when a sheet with a grammage of a predetermined amount or more comes into contact, so that the front end of the sheet comes into contact with the shutter member 12 in the first posture. The auxiliary shutter member 17 is moved to the first posture with a predetermined urging force.

[Skew correction]
Next, the skew feeding correction operation will be described with reference to FIGS. 7A and 7B and FIGS. 8A to 8D. 8A to 8D are cross-sectional views illustrating how the skew correction of the sheet having a large basis weight is corrected in the skew correction device 10 according to the present embodiment.

  In the case of a sheet S having a basis weight smaller than a predetermined value, the auxiliary shutter holding member 41 does not rotate even when the sheet S comes into contact with the protrusion 41d of the auxiliary shutter holding member 41 as shown in FIG. That is, when the relationship between the force Fg for rotating the auxiliary shutter holding member 41 and the biasing force F42 generated by the holding member biasing spring 42 is Fg <F42, the auxiliary shutter holding member 41 is shown in FIG. The initial position shown in a) is held. For this reason, the auxiliary shutter member 17 of the auxiliary shutter unit 16 remains held in the second posture for allowing the sheet to pass therethrough, and the skew correction operation of the sheet S is performed as shown in FIG. 7B. This is performed only by the shutter member 12.

  On the other hand, in the case of a sheet S ′ having a basis weight larger than a predetermined value, when the sheet S ′ comes into contact with the protrusion 41d of the auxiliary shutter holding member 41 as shown in FIG. 8A, the auxiliary shutter holding member 41 rotates. Move. That is, when the relationship between the force Fg for rotating the auxiliary shutter holding member 41 and the biasing force F42 generated by the holding member biasing spring 42 is Fg> F42, the auxiliary shutter holding member 41 rotates. As a result, the auxiliary shutter holding portion 41c in the auxiliary shutter holding member 41 is unlocked by the auxiliary shutter locking portion 17b, so that the second posture is released and is the same as the auxiliary shutter member 17 of the first embodiment. It is rotated and held in the first posture.

  As a result, as shown in FIG. 8B, the leading edge of the sheet S ′ reaches a region where the shutter side abutting surface 12a and the auxiliary side abutting surface 17a overlap. When the leading edge of the sheet S ′ hits this area, the force acting on the leading edge of the sheet from the shutter-side butting surface 12a and the auxiliary-side butting surface 17a is the shutter biasing spring 15 and the auxiliary shutter biasing spring 20 (FIG. 2 ( The two spring forces generated in (b)) are combined biasing forces. As a result, the force required for the leading edge of the sheet S ′ to push away the shutter-side abutting surface 12a can be increased, so that proper skew correction can be performed for the sheet S ′ having a grammage of a predetermined value or more. It becomes possible.

  As shown in FIG. 8C, after the sheet S ′ pushes up the shutter member 12 in the direction of the arrow 15b and pushes up the auxiliary shutter member 17 in the direction of the arrow 20b, the state shown in FIG. That is, when the sheet S ′ passes through the protrusion 41d of the auxiliary shutter holding member 41, the released auxiliary shutter holding member 41 rotates in the direction of the arrow 43a. Accordingly, the second locking portion 41c of the auxiliary shutter holding member 41 locks the auxiliary shutter locking portion 17b in the second posture pushed up by the sheet S ′ while pushing it in the clockwise direction. As a result, the auxiliary shutter holding member 41 and the auxiliary shutter portion 16 are returned to the positions shown in FIG. Then, when the trailing end of the sheet S ′ passes through the conveying roller pair 30, the shutter member 12 released from the sheet S ′ returns to the first posture shown in FIG.

  Also in this embodiment, the rigidity of the sheet can be increased from the initial position to the nip portion N of the conveying roller pair 30 without switching the pulling amounts of the auxiliary shutter biasing spring 20 and the shutter biasing spring 15 that generate the biasing force of the shutter pressure. Accordingly, the optimum shutter pressure can be set. Further, since a configuration for switching the amount of spring tension is not required, the configuration can be simplified.

  In the first and second embodiments, the electrophotographic image forming apparatus 100 has been described. Instead, for example, an inkjet that forms an image on a sheet by ejecting ink liquid from a nozzle. It is also possible to use the image forming apparatus of the type.

  DESCRIPTION OF SYMBOLS 10 ... Skew correction device / 11, 16 ... Shutter part, auxiliary shutter part (shutter means) / 12 ... Shutter member (first shutter member) / 12a ... Shutter side abutting surface (contact part) / 17 ... Auxiliary Shutter member (second shutter member) / 17a ... auxiliary abutting surface (contact portion) / 21 ... moving guide member (switching means) / 21 ', 41 ... fixed guide member, auxiliary shutter holding member (switching means) /30...Conveying roller pair / 40 ... Sheet conveying section (sheet conveying apparatus) / 100 ... Image forming apparatus / 140, 150, N2 ... Image forming section, fixing section, secondary transfer nip section (image forming means) / N ... Nip / S, S '... sheet

Claims (8)

A pair of conveying rollers for conveying the sheet;
Either a first load state that is biased in a direction opposite to the sheet conveyance direction and applies a first load to the sheet, or a second load state that applies a second load greater than the first load to the sheet Shutter means for feeding the sheet to the nip portion of the pair of conveying rollers while abutting the front end of the sheet at
Switching means for switching between the first load state and the second load state by the shutter means by a pressing force according to the basis weight of the sheet that abuts.
A sheet conveying apparatus. The shutter means includes first and second shutter members that are rotatably supported, and are urged by a predetermined urging force toward a first posture in which each contact portion can contact the leading end of the sheet. And
In the first load state, the front end of the sheet is brought into contact with only the contact portion of the first shutter member held in the first posture, and in the second load state. The leading end of the sheet is brought into contact with the contact portions of both the first and second shutter members held in the first posture.
The sheet conveying apparatus according to claim 1. Each of the first and second shutter members is rotatably supported by each conveyance roller of the conveyance roller pair.
The sheet conveying apparatus according to claim 2. The first shutter member is movable between the first posture and a second posture that allows the sheet to pass through,
The second shutter member is movable between the first posture and the second posture, and the contact portion is in a direction of a sheet being conveyed while holding the first posture. According to the shape of the sheet to pass through,
The switching means is
A first guide position for guiding the leading edge of the sheet so as to face only the abutting portion of the first shutter member in a state where both the first and second shutter members are held in the first posture; ,
A second guide for guiding the leading edge of the sheet so as to face the contact portion of both the first and second shutter members in a state where both the first and second shutter members are held in the first posture. A movable guide member movable to the guide position,
The sheet conveying apparatus according to claim 2, wherein the sheet conveying apparatus is a sheet conveying apparatus. The moving guide member is rotatably supported between the first guide position and the second guide position, and the first guide position and the second guide position are pressed by a pressing force according to a basis weight of the sheet to be in contact with. The second guide position is biased so as to be rotatable.
The sheet conveying apparatus according to claim 4. The first and second shutter members are movable between the first posture and a second posture that allows the sheet to pass through,
The switching means is
In a state where the first shutter member is held in the first posture and the second shutter member is held in the second posture, the sheet is directed toward only the contact portion of the first shutter member. A first guide state for guiding the tip;
A second guide for guiding the leading edge of the sheet toward the abutting portions of both the first and second shutter members in a state where both the first and second shutter members are held in the first posture. Configured to be able to transition to the guide state,
The sheet conveying apparatus according to claim 2, wherein the sheet conveying apparatus is a sheet conveying apparatus. The switching means is
In the first guide state in which the second shutter member is locked in the second posture, when a sheet having a basis weight of a predetermined amount or more comes into contact, the lock is released so that the leading end of the sheet is in the first guide state. Moving the second shutter member to the first posture with the predetermined biasing force immediately before coming into contact with the first shutter member in the posture;
The sheet conveying apparatus according to claim 6. A sheet conveying device according to any one of claims 1 to 7,
Image forming means for forming an image on a conveyed sheet,
An image forming apparatus.

Images