JP2009249066A - Sheet conveying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet conveying device and an image forming device capable of reliably positioning sheets in the width direction irrespective of the environment and the kind of the sheets. <P>SOLUTION: A reference member 24 extending in the sheet conveying direction is provided on one end in the width direction of a re-conveying passage through which a sheet S to be re-conveyed to an image forming unit passes, the sheet S is obliquely conveyed by an obliquely conveying roller 16a, and one end of the sheet S is pressed against the reference member 24 to position the sheet S in the width direction. When the sheet S is pressed against the reference member 24 and deflected, the sheet obliquely feeding angle of an obliquely feeding roller 16a is changed to the angle at which the deflection of the sheet S is decreased by an obliquely feeding angle changing unit 15A. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly to a configuration for performing alignment in the width direction of a sheet when conveying a sheet to an image forming unit.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, and fax machines have a sheet conveying apparatus that conveys a sheet to an image forming unit. Further, in the conventional image forming apparatus, an image is formed on the second surface opposite to the first surface of the sheet by inverting the sheet on which the image is formed on the first surface and transporting the sheet again to the image forming unit. There is something to do. Such an image forming apparatus includes a sheet conveying apparatus that reverses the sheet on which the image is formed on the first surface and conveys the sheet again to the image forming unit.

  In such a conventional sheet conveying apparatus, when a sheet on which an image is formed on the first side (front side) is conveyed again to the image forming unit, the sheet is skewed during conveyance and an image is formed on the second side (back side). When doing this, the sheet and image may be misaligned. This is because when the image is formed on the second side, the conveyance path until the image is formed on the sheet is longer than that on the first side. This is because the sheet is slightly shifted during conveyance due to a difference in resistance or the like.

  In order to prevent such sheet misalignment, it is necessary to adjust the position of the sheet so that the image and the sheet coincide after the image is formed on the first side and before the image is formed on the second side. As such a sheet position adjusting method, for example, there is a method in which a reference member is disposed at one end portion in a direction (hereinafter referred to as a width direction) orthogonal to a sheet conveyance direction of a re-conveyance path that conveys a sheet to an image forming unit again. . Then, there is a method of aligning the sheet in the width direction (hereinafter referred to as lateral registration correction) by conveying the sheet while pressing the sheet against the reference member (see Patent Document 1).

JP 2004-161390 A

  However, in such a sheet conveying apparatus and an image forming apparatus equipped with the sheet conveying apparatus, depending on the environment in which the image forming apparatus is installed and the type of sheet used, the sheet is directed toward the reference member during lateral registration correction. There may be a difference in the conveying force for conveying. For this reason, depending on the type, the end of the sheet may not be sufficiently pressed against the reference member.

  Conversely, the sheet end may be damaged by sliding while strongly pressing the end of the sheet against the reference member, or the sheet pressing surface of the reference member may be scraped by the sheet and the sheet may be caught. . As described above, depending on the environment and the type of the sheet, the sheet may not be aligned in the width direction. In such a case, the sheet and the image are not formed when the image is formed on the second side (back side). It will shift.

  Accordingly, the present invention has been made in view of such a current situation, and provides a sheet conveying device and an image forming apparatus that can reliably perform alignment in the width direction of a sheet regardless of the environment and the type of sheet. It is intended to provide.

  The present invention provides a sheet conveying apparatus that conveys a sheet to an image forming unit, a conveying path through which the sheet conveyed to the image forming unit passes, and one end portion in the width direction orthogonal to the sheet conveying direction of the conveying path. A reference member that extends in the sheet conveyance direction, a skew feeding roller that is provided in the conveyance path and that obliquely feeds the sheet toward the reference member so that one side edge of the sheet is pressed against the reference member, and the reference And a skew feeding angle changing section that changes a sheet skew feeding angle of the skew feeding roller to an angle at which the bending of the sheet is reduced when the sheet is bent by being pressed against the member. .

  According to the present invention, when positioning the sheet in the width direction, if the sheet bends, the sheet skew feeding angle of the skew feeding roller is changed to an angle at which the sheet bending is reduced, so that the environment or Regardless of the type of the sheet, the sheet can be reliably aligned in the width direction.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is an overall configuration diagram of a color laser printer which is an example of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 50 denotes a color laser printer, and 51 denotes a color laser printer main body (hereinafter referred to as a printer main body). The printer main body 51 includes an image forming unit 52 that forms an image on a sheet, a sheet feeding unit 8 that feeds the sheet, and a sheet conveyance that conveys the sheet fed from the sheet feeding unit 8 to the image forming unit 52. A unit 9 and a fixing unit 10 for fixing an image formed on the sheet are provided.

  Here, the image forming unit 52 is arranged in the vertical direction, and is provided with a photosensitive drum 1 (1a to 1d) that is an image carrier that carries toner images of four colors of yellow, magenta, cyan, and black, respectively. Yes.

  Further, a charging means 2 (2a to 2d) for uniformly charging the surface of the photosensitive drum along the rotation direction of the photosensitive drum 1, and a laser beam are irradiated on the periphery of the photosensitive drum 1 based on image information. Exposure means 3 (3a to 3d) for forming an electrostatic latent image on the photosensitive drum is provided. Further, around the photosensitive drum 1, a developing means 4 (4a to 4d) for making the toner image adhere to the electrostatic latent image to be visualized, and removing the toner remaining on the surface of the photosensitive drum after the transfer. Cleaning means 6 (6a to 6d) and the like are provided.

  The photosensitive drum 1 as an image carrier is configured by applying an organic optical conductor layer (OPC) to the outer peripheral surface of an aluminum cylinder. The photosensitive drum 1 is rotatably supported at both ends by flanges, and is driven to rotate counterclockwise as indicated by an arrow by transmitting a driving force from a driving motor (not shown) to one end. Is done.

  The charging unit 2 is a conductive roller formed in a roller shape. The charging unit 2 is brought into contact with the surface of the photosensitive drum, and a charging bias voltage is applied to the charging unit 2 by a power source (not shown). Thus, the surface of the photosensitive drum is uniformly charged.

  The developing unit 4 includes toner storage units 4a1, 4b1, 4c1, and 4d1 that store toners of black, cyan, magenta, and yellow, respectively. Further, the developing means 4 is adjacent to the surface of the photoreceptor, and is driven to rotate by a driving unit (not shown), and developing rollers 4a2 and 4b2 that perform development by applying a developing bias voltage from a developing bias power source (not shown). , 4c2, 4d2, etc. In the present embodiment, the photosensitive drum 1, the charging unit 2, the developing unit 4, and the cleaning unit 6 are integrally formed as a cartridge to form a process cartridge 7 (7a to 7d).

  The exposure means 3 has polygon mirrors 3a1, 3b1, 3c1, 3d1, and image light corresponding to an image signal is irradiated from a laser diode (not shown) to the polygon mirrors 3a1, 3b1, 3c1, 3d1. Further, inside the transfer conveyance belt 9a, which is an endless sheet conveyance member for conveying a sheet to be described later, transfer means 5 (5a to 5d) for holding the transfer conveyance belt 9a together with the four photosensitive drums 1 are respectively provided. It is attached.

  Here, these transfer means 5 are connected to a power supply for transfer bias (not shown), and positive charges are applied from the transfer means 5 to the sheet via the transfer conveyance belt 9a. By applying the transfer bias in this manner, the negative color toner images on the photosensitive drum are sequentially transferred onto the sheet in contact with the photosensitive drum 1 to form a multicolor image. ing.

  In this embodiment, a toner pattern is formed on the transfer conveyance belt in order to measure the color misregistration amount. Then, this toner pattern is detected by the toner image detection sensor 20, a color misregistration amount is calculated based on the detection result, and the image forming position is corrected based on the calculation result.

  The paper feed unit 8 includes a paper feed cassette 8a, a multi-feed tray 8b, a multi-feed unit 8c, a registration roller pair 8d, and the like. Here, the paper feed cassette 8a stores a plurality of sheets S and is loaded on the bottom of the printer main body. The multi-feed tray 8b is usually stored in the front of the printer main body. As shown in FIG. 1, the sheet S is opened and stacked.

  When forming an image, first, sheets S are fed one by one from the sheet feeding cassette 8a by the pickup roller 8a1. Thereafter, the sheet S is conveyed to the sheet conveyance unit 9 by the intermediate conveyance roller 8a2 and the registration roller pair 8d that conveys the sheet S at a predetermined timing.

  When the sheets S are fed from the multi-feed tray 8b, first, the sheets S accommodated in the multi-feed tray 8b are fed one by one by the multi-pickup roller 8c1. Thereafter, the sheet S is conveyed to the sheet conveying unit 9 by the multi-conveying roller 8c2 and the registration roller pair 8d. Such separation and conveyance of the sheet S in the feeding cassette 8a and the multi-feed tray 8b are performed by a feeding motor (not shown) provided in the sheet feeding unit 8 via a gear drive train.

  The sheet conveying unit 9 is supported by a driving roller 9b and driven rollers 9c to 9e, and includes a transfer conveying belt 9a as a sheet carrier disposed opposite to all the photosensitive drums 1. . The transfer conveyance belt 9 a electrostatically attracts the sheet S to the outer peripheral surface facing the photosensitive drum 1, and is circulated and moved by a driving roller 9 b so that the sheet S is brought into contact with the photosensitive drum 1. . Then, the sheet S is conveyed to the transfer position by the transfer conveyance belt 9a by being electrostatically attracted to the transfer conveyance belt 9a that circulates in this way, and the toner image on the photosensitive drum is transferred.

  Reference numeral 9f denotes an adsorption roller that is disposed at the most upstream position of the transfer conveyance belt 9a, holds the sheet S together with the transfer conveyance belt 9a, and adsorbs the sheet S to the transfer conveyance belt 9a. When the sheet S is conveyed, a voltage is applied to the suction roller 9f to form an electric field between the oppositely driven roller 9e and the dielectric polarization between the transfer conveying belt 9a and the sheet S. To generate an electrostatic adsorption force between the two.

  The fixing unit 10 applies heat and pressure to the image formed on the sheet to fix the toner image, and includes a fixing belt 10a and an elastic pressure roller 10b. Here, the fixing belt 10a is a cylindrical belt having an electromagnetic induction heat generating layer, and is guided by a belt guide member 10c having a built-in magnetic field generating means including an exciting coil and a T-shaped magnetic core.

  The elastic pressure roller 10b sandwiches the fixing belt 10a and forms a fixing nip portion N having a predetermined width with a predetermined pressure contact force with the belt guide member 10c. When the elastic pressure roller 10b is rotationally driven by a driving means (not shown), the cylindrical fixing belt 10a is rotated accordingly, and the fixing belt 10a is fed by power supply from an excitation circuit (not shown) to the excitation coil. Electromagnetic induction heat is generated.

  Next, an image forming operation of the color laser printer 50 configured as described above will be described.

  First, when the surface of the photosensitive drum 1 uniformly charged by the charging unit 2 is scanned with a laser beam corresponding to the image information irradiated from the exposure unit 3, a latent image is formed on the surface of the photosensitive drum. Is done. Then, the latent image is developed by the developing unit 4 so that toner images of four colors of yellow, magenta, cyan, and black are formed on the surface of the photosensitive drum.

  In parallel with this toner image forming operation, the sheet S accommodated in the paper feed cassette 8a is fed by the pickup roller 8a1 or the sheet S accommodated in the multi-feed tray 8b is fed by the multi-pickup roller 8c1. Sheets are fed one by one. Thereafter, the sheet S is guided to the registration roller pair 8d, and is attracted to the transfer conveyance belt 9a by the registration roller pair 8d in synchronization with the image forming operation, so that the photosensitive drum 1 and the transfer conveyance belt 9a are pressed against each other. It is conveyed to the transfer unit.

  Next, the toner images of the respective colors on the photosensitive drums are transferred to the sheet S thus transported to the transfer unit by the action of the transfer unit 5 disposed in each transfer unit and applied with a voltage having a polarity opposite to that of the toner. The images are sequentially superimposed and transferred on the sheet. The sheet S on which the four color toner images are transferred in this way is separated from the transfer conveyance belt 9a and conveyed to the fixing device 10.

  Next, the sheet S on which an unfixed toner image conveyed from the image forming unit 52 is formed is connected to the fixing belt 10a of the fixing nip N in a state where the temperature of the fixing nip N rises to a predetermined temperature. The image surface is introduced upward with respect to the elastic pressure roller 10b. Then, after the image surface is introduced between the fixing belt 10a and the elastic pressure roller 10b in this way, that is, facing the fixing belt surface, the image surface of the sheet S is in close contact with the outer surface of the fixing belt 10a. In this state, the fixing nip portion N is nipped and conveyed together with the fixing belt 10a.

  In the process of transporting the fixing nip N together with the fixing belt 10a in this way, the sheet S is heated by the electromagnetic induction heat generated by the fixing belt 10a, and the unfixed toner image on the sheet is heated and fixed. As a result, a full-color print image is fixed on the sheet as a permanent image. Next, after the full-color print image is fixed as a permanent image in this way, the sheet S is discharged and stacked on the discharge tray 13 as indicated by the arrow A by the discharge roller pairs 11 and 12.

  By the way, the color laser printer 50 according to the present embodiment is capable of forming images on both sides of the sheet S. When images are formed on both sides of the sheet S, the conveyance path is switched by the switching member 42 before the sheet S is discharged to the discharge tray 13 by the discharge roller pair 11, 12.

  Here, when an image is formed on only one side of the sheet S, the switching member 42 is in a position that does not prevent the discharge of the sheet S discharged from the discharge roller pair 11 and 12 as shown in FIG. When images are formed on both sides of S, the image is rotated downward. As the switching member 42 rotates downward in this manner, the sheet conveyance path is switched from the sheet discharge path R1 to the reverse conveyance path R2 that is the re-conveyance path.

  As a result, the sheet S is nipped and conveyed by the forward / reverse conveying roller 40 and conveyed in the arrow B direction. Thereafter, the sheet passes through the sheet detection sensor 43, and a control unit (not shown) drives the forward / reverse conveyance roller 40 in reverse after a predetermined time based on a detection signal from the sheet detection sensor 43. By this time, the switching member 42 has returned to the position shown in FIG.

  Next, the sheet S is transported to the transport roller 41 by the reverse driving of the forward / reverse transport roller 40, and then disposed on the front of the apparatus main body via the transport roller 41. The reverse transport path R2, the U-turn roller Is conveyed to a sheet conveying device 15 having 17 or the like. Then, the sheet S is conveyed by the sheet conveying device 15 to the registration roller 8d through the reverse conveyance path R2, and then conveyed again to the image forming unit 52 by the registration roller 8d, and image formation is performed on the second surface. Is called.

  By the way, when the sheet S is conveyed again to the image forming unit 52 as described above, if the sheet S is skewed during conveyance, the image may be misaligned with the sheet S when an image is formed on the second surface. For this reason, it is necessary to align the sheet S in the reverse conveyance path R2 and adjust the position of the sheet S so that the image and the sheet S coincide with each other.

  Therefore, in the present embodiment, in order to adjust the position in the width direction of the sheet S, one side end of the sheet S passing through the reverse conveyance path R2 shown in FIG. A reference member 24 is provided that is in pressure contact with the sheet S to align the sheet S in the width direction. Here, the reference member 24 extends in the sheet conveyance direction, and two skew feeding rollers 16 a that obliquely feed the sheet S toward the reference member 24 are provided in the sheet conveyance direction.

  The two skew feeding rollers 16a are rotationally driven by a gear drive train 22 driven by a drive source (not shown). In addition, a rotary roller 23 is in pressure contact with the skew feeding roller 16a by a spring (not shown) so as to rotate following the skew feeding roller 16a.

  By the way, the skew feeding roller 16a is angled with respect to the sheet conveying direction so that one end of the sheet S always comes into pressure contact with the reference member 24 when the sheet S passes through the reverse conveying path R2. Here, if the conveying force applied to the sheet S is too strong, the sheet S slides strongly with the reference member 24, the end of the sheet is damaged, or the reference member 24 is scraped by the sheet S and the sheet S It may adversely affect transportation.

  On the other hand, if the conveyance force is too weak, when passing through the reverse conveyance path R2, the sheet S is conveyed to the U-turn roller 17 without being completely in contact with the reference member 24, and the sheet is printed on the second surface. S and the image are misaligned. For this reason, the conveyance force of the sheet S with respect to the sheet conveyance direction of the skew feeding roller 16a, the skew feeding angle, and the pressing force of the driven roller 23 need to be appropriately set as appropriate.

  For this reason, in the present embodiment, the surface layer material of the skew feeding roller 16a is selected to have a low friction coefficient in the thrust direction of the skew feeding roller 16a while obtaining an appropriate conveying force for the sheet S. Are securely brought into pressure contact with the reference member 24.

  Further, the direction (angle) of the oblique feeding roller 16a for feeding the sheet S obliquely is preferably 0.1 to 1.5 deg with respect to the sheet conveying direction. In the present embodiment, as shown in FIG. did. Further, the pressure contact force of the driven roller 23 is preferably 0.5 to 2.0 N, and in this embodiment, 1.5 N. Accordingly, for example, when the sheet S is thick paper, the driven roller 23 is further retracted, so that the nip pressure with the oblique feeding roller 16a is increased, and the conveying force for obliquely feeding the sheet S toward the reference member is increased. .

  By the way, even if the surface layer material of the oblique feeding roller 16a, the oblique feeding direction (angle) of the oblique feeding roller 16a, and the pressure contact force of the driven roller 23 are set as described above, the use environment and the sheet to be used are already described. Depending on the type, the conveying force of the oblique feeding roller 16a differs. Therefore, in the present embodiment, the oblique feeding angle of the oblique feeding roller 16a is conveyed so that the oblique feeding roller 16a can obtain an optimum conveying force according to conditions such as a use environment and the type of the sheet S to be used. The sheet S can be changed according to the sheet S.

  Next, a configuration for changing the skew feeding angle of the skew feeding roller 16a will be described.

  FIG. 3 is a side view showing the configuration of the skew feeding angle changing portion 15A for changing the skew feeding angle of the skew feeding roller 16a. Here, as shown in FIG. 3, the reference member 24 supports the sheet S sandwiched and conveyed by the pressure contact portion 24 b that slides while the side surface of the sheet S is in pressure contact, and the oblique feeding roller 16 a and the driven roller 23 from below. A support portion 24a is provided as a guide portion for guiding while guiding.

  In FIG. 3, reference numeral 25 denotes a sheet S which is disposed above the support portion 24 a of the reference member 24, and presses the reference member 24 together with the reference member 24 to convey the sheet S sandwiched and conveyed by the oblique feeding roller 16 a and the driven roller 23. It is an upper guide which forms the guide space P which guides to the part 24b. Then, the sheet S conveyed to the reverse conveyance path R2 is guided to the guide space P while being obliquely fed by the oblique feeding roller 16a and the driven roller 23, and finally to the pressure contact portion 24b vertically provided at the end of the support portion 24a. Press contact.

  By the way, after being pressed against the pressure contact portion 24b in this manner and then being obliquely fed by the skew feeding roller 16a and the driven roller 23, the sheet S pressed against the pressure contact portion 24b bends in the guide space as shown in FIG. (Loop) is formed. In the present embodiment, the support portion 24a of the reference member 24 has a curved shape that swells upward, so that when pressed against the pressure contact portion 24b, the sheet S bends upward in the guide space. .

  Here, the upper guide 25, which is a rotating member, can be rotated in the vertical direction by a rotating shaft 25a provided in the printer main body 51. When the sheet S bends upward, the sheet S shows the arrow A. Thus, it is pressed from below and pivots upward with the pivot shaft 25a as a fulcrum. Further, as shown in FIG. 4, the upper guide 25 includes a protrusion 25a having a cam surface c on the upper surface, and when the upper guide 25 is rotated upward, the protrusion 25a is a slanting member that is an interlocking member. The feed rod 26 is pressed.

  An insertion hole (not shown) having an area larger than the cross-sectional area of the roller shaft 16b of the oblique feeding roller 16a is formed in the oblique feeding rod 26, and one end portion of the roller shaft 16b is inserted into the insertion hole. I have to. Further, the oblique feeding rod 26 is slidable on a frame (not shown) provided in the printer main body 51 in the sheet conveying direction indicated by the arrow B. When the oblique feeding rod 26 slides, the oblique feeding roller 16a is inclined. It moves together with the feed rod 26.

  In FIG. 4, reference numeral 28 denotes a bearing that pivotally supports the other end portion of the roller shaft 16b of the skew feeding roller 16a on the drive gear train side, and this bearing 28 is held and fixed on a frame (not shown). Then, when one end of the roller shaft 16b is inserted into the oblique feeding rod 26 and the other end is pivotally supported by the fixed bearing 28, the oblique feeding rod 26 moves in the sheet conveying direction. The roller 16a moves around the bearing 28 in the direction of arrow D. As a result, the skew feeding angle of the skew feeding roller 16a with respect to the sheet conveying direction changes.

  In FIG. 4, reference numeral 27 denotes a spring that presses the oblique feeding rod 26 toward the protruding portion of the upper guide 25. When the sheet S is not in the guide space by the spring 27, when the sheet S is not in contact with the reference member 24, or when the sheet S is not bent enough to push up the upper guide 25. The oblique feeding rod 26 is held at a predetermined position.

  Next, the skew feeding angle changing operation in the skew feeding angle changing unit 15A having such a configuration will be described.

  First, after the sheet S sandwiched and conveyed by the skew feeding roller 16a and the driven roller 23 is brought into pressure contact with the pressure contact portion 24b of the reference member 24, the upper guide 25 pressed by the bent sheet S rotates upward. The protrusion 25 a of the guide 25 presses the oblique feeding rod 26. A cam surface that engages with the cam surface c of the protrusion 25a of the upper guide 25 is formed at one end of the oblique feeding rod 26.

  As a result, the oblique feeding rod 26 slides in the direction opposite to the sheet conveying direction, and accordingly, the oblique feeding roller 16a moves in the direction of arrow D around the bearing 28 on the drive gear train side. When the skew feeding roller 16a moves in this manner, the skew feeding angle of the skew feeding roller 16a with respect to the sheet conveying direction decreases. As a result, the sheet conveying force to the reference member 24 is reduced, and accordingly, the upward deflection of the sheet S in the guide space is reduced.

  When the bending is reduced, the upper guide 25 is lowered in conjunction with this, and when the upper guide 25 is lowered in this way, the oblique feeding rod 26 is returned to the original position by the force of the spring 27. As a result, the skew feeding angle of the skew feeding roller 16a also returns to the original angle, and the conveying force for the sheet S is increased again.

  In this way, in response to the occurrence of the bending of the sheet S, the skew feeding roller 16a presses the sheet S against the reference member 24 while changing the conveying force in the skew feeding direction, in other words, in the reference member direction, whereby the sheet S S can be conveyed while regulating the position in the width direction.

  FIG. 5 is a diagram illustrating the magnitude of the tension of the sheet at the time of forming a bend according to the basis weight of the sheet. In FIG. 5, the horizontal axis represents the basis weight of the sheet, and the vertical axis represents the magnitude of the tension when the sheet is bent.

  Here, as shown in FIG. 5, the tension at the time of flexure formation increases as the thick paper having a larger basis weight increases, and the force pushing up the upper surface 25 of the guide increases. Does not occur.

  For this reason, in the present embodiment, the conveying force (slope feeding force) of the oblique feeding roller 16a is set to a size that allows the thin paper having a relatively small basis weight to be securely brought into pressure contact with the reference member 24. Yes. When a sheet having a large basis weight is passed, an optimum conveying force is obtained by the oblique feed angle changing unit 15A having the above-described configuration.

  As described above, according to the present embodiment, when the sheet is bent when the sheet is aligned in the width direction, the skew feeding angle of the skew feeding roller 16a is an angle at which the sheet bending is reduced. I am trying to change it. Accordingly, an appropriate conveying force can be obtained by the skew feeding roller 16a, and the sheet width direction alignment is performed reliably without damaging the sheet end portion or damaging the guide space including the reference member 24. The sheet can be conveyed as it is.

  With this configuration, the sheet can be reliably aligned in the width direction regardless of the environment and the type of sheet. As a result, there is provided a sheet conveying device 15 and a color laser printer (image forming apparatus) that perform alignment reliably under a wider range of conditions than before with an easy configuration without using electrical components such as sensors. be able to.

  In the above description, the oblique feeding rod 26 slidable in conjunction with the upper guide 25 supports the two oblique feeding rollers 16a. The number of the oblique feeding rollers 16a depends on the number of the sheet feeding rollers 16a. An appropriate selection can be made according to the conveyance speed, the length of the re-conveyance path, and the like. In the description so far, the case where the skew feeding angle changing unit is provided in the reverse conveyance path has been described. However, the present invention is not limited to this, and the skew feeding angle changing unit is used as a sheet as an image forming unit. You may provide in the conveyance path | route to convey.

1 is an overall configuration diagram of a color laser printer that is an example of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a front view illustrating a configuration of a skew feeding angle changing unit provided in the color laser printer. The side view which shows the structure of the said skew feeding angle change part. The perspective view explaining the skew feeding angle change operation | movement of the said skew feeding angle change part. The figure which shows the magnitude | size of the tension | tensile_strength of the sheet | seat at the time of bending formation according to the basic weight of a sheet | seat.

Explanation of symbols

15 sheet conveying device 15A oblique feeding angle changing portion 16a oblique feeding roller 24 reference member 24a support portion 24b pressure contact portion 25 upper guide 26 oblique feeding rod 50 color laser printer 51 color laser printer main body 52 image forming portion P guide space R2 reverse conveying path S sheet

Claims (5)

In a sheet conveying apparatus that conveys a sheet to an image forming unit,
A conveyance path through which a sheet conveyed to the image forming unit passes;
A reference member provided at one end in the width direction orthogonal to the sheet conveyance direction of the conveyance path and extending in the sheet conveyance direction;
A skew feeding roller that is provided in the conveyance path and that obliquely feeds the sheet toward the reference member such that one side end of the sheet comes into pressure contact with the reference member;
And a skew feeding angle changing section that changes a sheet skew feeding angle of the skew feeding roller to an angle at which the bending of the sheet is reduced when the sheet is bent by being pressed against the reference member. Conveying device. The oblique feed angle changing unit is
A rotating member that is pressed and rotated by a sheet bent in pressure contact with the reference member;
The sheet conveyance according to claim 1, further comprising an interlocking member that holds one end of the shaft of the skew feeding roller and moves in the sheet conveyance direction in conjunction with the rotation of the rotation member. apparatus. The reference member, together with the rotating member, forms a space through which a sheet that is obliquely fed by the oblique feeding roller passes, and a guide portion that is provided facing the rotating member, and is suspended from the guide portion. A pressure contact portion that is pressed against the sheet that is obliquely fed by the skew feeding roller,
The sheet conveying apparatus according to claim 2, wherein the guide portion has a shape that swells in the direction of the rotating member.   The conveyance path is a re-conveyance path through which a sheet conveyed again to the image forming unit passes when an image is formed on the second surface opposite to the sheet on which an image is formed on the first surface by the image forming unit. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus.   An image forming apparatus comprising the sheet conveying device according to claim 1.

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