JP6292139B2 - Sheet conveying apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a sheet conveying apparatus suitably used for a copying machine, a printer, and the like, and an image forming apparatus including the same.

  In general, an electrophotographic image forming apparatus drives a pair of conveyance rollers while a sheet (sheet) sent from a sheet feeding unit to a conveyance path is abutted against a pair of registration rollers and blocked. Is configured to feed in. As a result, the bending of the leading edge of the paper is corrected. Thereafter, the image forming apparatus is configured to drive the pair of registration rollers at a predetermined timing to transport the paper again.

  However, along with the recent increase in the speed of image formation processing, re-conveyance by a pair of registration rollers may be started in a state where the skew of the paper is not corrected. In this case, there is a problem that the paper is wrinkled when passing between the pair of registration rollers.

  In order to solve the above problems, for example, Patent Document 1 discloses a loop forming roller (conveyance) having a pair of upper and lower registration rollers (a pair of registration rollers) and a pair of upper and lower rollers provided at a plurality of axial positions. A sheet conveying apparatus including a pair of rollers) and a one-way clutch provided on any one of the upper and lower rollers of the loop forming roller is disclosed. This sheet conveying device prevents the paper from being bent by the action of the one-way clutch and prevents the paper from being wrinkled.

JP 09-073310 A

  By the way, the conveying roller pair of the above-described sheet conveying apparatus is formed in a comb shape by providing a plurality of rollers at intervals in the axial direction. When a sheet is conveyed by a pair of comb-shaped conveyance rollers, the sheet is bent at a portion where there is no roller and deformed so as to wave in the axial direction. When a sheet having such undulation is passed between the pair of registration rollers, the undulation portion is crushed and the sheet is wrinkled. However, the sheet conveying apparatus described in Patent Document 1 has not been considered at all for suppressing the corrugation of the paper.

  The generation of wrinkles due to the corrugation of the paper is suppressed, for example, by setting the distance between the conveyance roller pair and the registration roller pair sufficiently long. This is because undulating deformation is alleviated by increasing the sheet conveyance distance. However, the extension of the conveyance distance has a problem that it leads to an increase in the size of the sheet conveyance device and the image forming apparatus including the sheet conveyance device. For this reason, it has been difficult to easily extend the transport distance.

  Further, for example, the corrugation of the paper can be suppressed by changing the rollers constituting the pair of conveying rollers to be long in the axial direction. However, since the roller that is long in the axial direction is more expensive than the small roller that forms a comb-teeth shape, there is a problem that the cost increases. For this reason, it was not possible to easily adopt a roller that is long in the axial direction.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet conveying apparatus for suppressing generation of wrinkles due to sheet undulation and an image forming apparatus including the sheet conveying apparatus.

  In order to achieve the above-described object, a sheet conveying apparatus of the present invention includes a conveying path configured to convey a sheet, a registration roller pair provided in the conveying path, and a conveyance path that is more than the registration roller pair. A pair of conveyance rollers provided on the upstream side, and a guide portion provided so as to bulge from the wall surface of the conveyance path on the upstream side of the conveyance path with respect to the pair of conveyance rollers, and the pair of conveyance rollers A plurality of first rollers fixed to a single conveyance axis at intervals, and a plurality of second rollers provided to face each other so as to form a conveyance nip portion between each of the first rollers, The guide portion is provided between the adjacent first rollers or between the adjacent second rollers, and has a guide surface that is parallel to a tangent line in the conveyance nip portion.

  According to this configuration, the guide portion is provided in a portion where the first roller or the second roller (hereinafter simply referred to as “roller”) does not exist. For this reason, the sheet is nipped by the conveyance nip portion in a portion where the roller is present, and is supported by the guide portion in a portion where the roller is not present. Therefore, the sheet is prevented from being deformed in the axial direction of the pair of transport rollers, and is transported along the transport path in a substantially flat posture. Thereby, the wrinkle of the sheet | seat which generate | occur | produces when a registration roller pair crushes a wavelike part can be prevented. Further, for example, in order to prevent wrinkling of the sheet, it is not necessary to extend the conveyance distance (the distance between the conveyance roller pair and the registration roller pair). Thereby, size reduction of a sheet conveying apparatus can be achieved. Further, for example, it is not necessary to employ an expensive roller that is long in the axial direction in order to suppress the corrugation of the sheet. Thereby, the cost reduction of a sheet conveying apparatus can be aimed at.

  In this case, the conveyance path is formed between the curved inner guide frame and the outer guide frame facing the inner guide frame, and each of the first rollers is formed on the top of the curved portion of the inner guide frame. The guide portion is provided on the inner guide frame between the adjacent first rollers, and is formed to bulge from the top of the curved portion toward the outside of the curved portion, It is preferable that the guide surface is formed in a range between the top of the curved portion and a tangent line in the conveyance nip portion.

  In general, a sheet conveyed on a curved conveyance path is easily bent inside the curved portion. That is, since the sheet bends so as to enter between adjacent first rollers, the sheet is deformed so as to wave in the axial direction of the conveying shaft. So, according to this structure, since the guide part is provided in the top part of the curved part, the corrugation (deflection) of a sheet | seat can be suppressed effectively. Further, the guide surface does not protrude outside the curve from the tangent line at the conveyance nip portion. As a result, the guide unit does not interfere with sheet conveyance, and smooth and appropriate sheet conveyance can be ensured.

  In this case, it is preferable that the guide portion includes a surface member that constitutes the guide surface, and an urging member that urges the surface member toward a tangent to the conveyance nip portion.

  According to this configuration, for example, when a thick sheet is passed through the conveyance path, the thick sheet contacts the guide surface and pushes the surface member against the urging force of the urging member. For this reason, a guide part does not inhibit conveyance of a thick sheet. On the other hand, the thin sheet is restrained from undulating deformation in the axial direction of the pair of transport rollers, and is transported along the transport path in a substantially flat posture. Thereby, the wavy of a thin sheet | seat can be suppressed effectively, ensuring favorable conveyance of a thick sheet | seat.

  In this case, it is preferable that the two first rollers are fixed to the intermediate portion in the axial direction of the transport shaft so as to be separated from each other, and the guide portion is provided between the two first rollers.

  If the guide portion is provided in the entire axial direction, the conveyance path is narrowed by the guide portion, and sheet conveyance failure is likely to occur. In particular, it becomes difficult to appropriately convey a thick sheet. According to this configuration, since the guide portion is provided only in the central portion in the axial direction, it can be suppressed that the guide portion causes a sheet conveyance failure. Thereby, favorable sheet conveyance can be ensured. In addition, the sheet waviness can be effectively suppressed.

  In order to achieve the above object, an image forming apparatus of the present invention includes any one of the above sheet conveying apparatuses.

  According to this configuration, since the guide portion is provided in a portion where the rollers of the pair of transport rollers do not exist, the sheet is supported by the guide portion in a portion where there is no roller. Therefore, it is possible to suppress sheet waviness and to prevent sheet wrinkling that occurs when the registration roller pair crushes the wavy portion. Thereby, a good image forming process can be secured. Further, for example, it is not necessary to extend the conveyance distance in order to prevent sheet wrinkling. Thereby, it is possible to reduce the size of the image forming apparatus. Further, for example, it is not necessary to employ an expensive roller that is long in the axial direction in order to suppress the corrugation of the sheet. Thereby, the cost of the image forming apparatus can be reduced.

  According to the present invention, it is possible to suppress the generation of wrinkles due to the corrugation of the sheet.

1 is an external perspective view showing a multifunction machine according to a first embodiment of the present invention. 1 is a cross-sectional view schematically showing an internal structure of a multifunction machine according to a first embodiment of the present invention. It is sectional drawing which shows typically the sheet conveying apparatus which concerns on 1st Embodiment of this invention. FIG. 3 is a perspective view showing a part of the upstream side of the sheet conveying apparatus according to the first embodiment of the present invention. It is sectional drawing which shows typically the guide part etc. of the sheet conveying apparatus which concerns on 2nd Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
With reference to FIG. 1 and FIG. 2, an overall configuration of a multifunction machine 1 as an image forming apparatus will be described. FIG. 1 is an external perspective view showing the multifunction machine 1. FIG. 2 is a cross-sectional view schematically showing the internal structure of the multifunction machine 1. In the following description, the front side of the sheet of FIG. 2 is the front side (front side) of the multifunction machine 1, and directions are appropriately shown in the drawings.

  As shown in FIG. 1, the multifunction machine 1 includes an image reading device 1 </ b> A and a printing device 1 </ b> B.

  The image reading apparatus 1A is configured to optically read image information of a document. An operation unit 100 including a liquid crystal panel, push buttons, and the like is provided at the front of the image reading apparatus 1A. The user performs various functions of the multifunction device 1 and changes settings by operating the operation unit 100. Although not shown, an automatic document feeder for conveying a document toward the reading position is disposed on the upper surface of the image reading apparatus 1A. Since the image reading apparatus 1A and the automatic document feeder have a known general structure, detailed description thereof is omitted.

  The printing apparatus 1 </ b> B includes a substantially box-shaped apparatus main body 2, upper and lower two paper feed cassettes 3 and 4 provided at the lower part of the apparatus main body 2, and upper and lower two discharge trays 5 provided at the upper part of the apparatus main body 2. 6 are provided. The image reading apparatus 1A described above is supported on the upper surface of the apparatus main body 2 with a space for configuring the two paper discharge trays 5 and 6 interposed therebetween.

  As illustrated in FIG. 2, the printing apparatus 1 </ b> B includes two paper feeding units 10 and 11, a sheet conveying device 12, an image forming unit 13, a fixing device 14, and a control device 15. The two paper feeding units 10 and 11 are provided in the vicinity of the right side of the two paper feeding cassettes 3 and 4. The sheet transport device 12 includes a transport path 50 that extends in the vertical direction from the paper feed cassettes 3 and 4 toward the paper discharge trays 5 and 6. The image forming unit 13 is provided at substantially the center inside the apparatus main body 2. The fixing device 14 is provided on the downstream side of the conveyance path 50. The control device 15 is provided for overall control of each component of the multifunction machine 1.

  Each paper feed unit 10, 11 supplies the paper S stored in each paper feed cassette 3, 4 to the transport path 50. The sheet transport device 12 transports the paper S supplied to the transport path 50 along the transport path 50. A detailed description of each of the paper feeding units 10 and 11 and the sheet conveying device 12 will be described later.

  The image forming unit 13 includes four toner containers 20, an intermediate transfer unit 21, four drum units 22, and an exposure unit 23. The four toner containers 20 are juxtaposed in the left-right direction below the paper discharge tray 5. The intermediate transfer unit 21 is disposed below each toner container 20. The four drum units 22 are disposed below the intermediate transfer unit 21. The exposure unit 23 is disposed below each drum unit 22.

  The four toner containers 20 contain four colors of toner (developer). The intermediate transfer unit 21 includes an intermediate transfer belt 25 that is stretched between a pair of left and right rollers. The intermediate transfer belt 25 travels in the direction of the arrow shown in FIG. 1 by rotationally driving a roller by a drive motor (not shown).

  Each of the four drum units 22 includes a photosensitive drum 30, a charging device 31, a developing device 32, a primary transfer roller 33, and a cleaning device 34. Since the four drum units 22 have the same configuration, only one drum unit 22 will be described below.

  The photosensitive drum 30 is in contact with the lower surface of the intermediate transfer belt 25. The charging device 31, the developing device 32, the primary transfer roller 33, and the cleaning device 34 are arranged around the photosensitive drum 30 in the order of the transfer process. The primary transfer roller 33 is disposed opposite to the photosensitive drum 30 from above with the intermediate transfer belt 25 interposed therebetween. On the right side of the intermediate transfer belt 25, a secondary transfer roller 35 is disposed to form a secondary transfer nip portion 35a.

  The control device 15 includes a CPU, a memory, and the like (not shown). The control device 15 is electrically connected to a control target included in the image reading device 1A or the printing device 1B.

  Here, the operation of the printing apparatus 1B will be described. The control device 15 of the printing apparatus 1B executes image forming processing as follows based on image data input from the image reading apparatus 1A or the like.

  Each charging device 31 charges the surface of each photosensitive drum 30. The exposure unit 23 performs exposure corresponding to the image data (see broken line arrows in FIG. 2) toward each photosensitive drum 30. Thereby, an electrostatic latent image is formed on the surface of each photosensitive drum 30. Each developing device 32 develops the electrostatic latent image using the toner supplied from the toner container 20. As a result, four color toner images are carried on the surfaces of the four photosensitive drums 30. The four toner images are primarily transferred sequentially to the traveling intermediate transfer belt 25 by the respective primary transfer rollers 33 to which a primary transfer bias is applied. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 25.

  On the other hand, the paper S supplied from the paper feed cassette 3 or the like is transported through the transport path 50 and passes through the secondary transfer nip portion 35a. The full-color toner image is secondarily transferred to the paper S by the secondary transfer roller 35 to which a secondary transfer bias is applied. The fixing device 14 fixes the full-color toner image on the paper S. The paper S after the fixing process is discharged to the paper discharge tray 5 or the like. Each cleaning device 34 removes the toner remaining on the surface of each photosensitive drum 30 after the transfer.

  The sheet feeding units 10 and 11 and the sheet conveying device 12 will be described with reference to FIGS. FIG. 3 is a cross-sectional view schematically showing the sheet conveying device 12. FIG. 4 is a perspective view showing a part of the upstream side of the sheet conveying apparatus 12.

  As shown in FIG. 3, the lower paper feed unit 10 includes a pickup roller 40, a paper feed roller 41, and a separating roller 42. Each roller 40-42 is connected to the drive device 16 via a gear train (not shown) or the like. The pickup roller 40 is provided so as to contact the uppermost sheet S of a plurality of sheets S (sheet bundle) stacked in the sheet feeding cassette 3. The paper feed roller 41 is in contact with the upper side of the separating roller 42, and forms a separation nip portion 10 a with the separating roller 42.

  The pickup roller 40 rotates in the direction of the arrow in FIG. 3 and sends the uppermost sheet S of the sheet bundle toward the separation nip portion 10a. Each of the paper feed roller 41 and the separating roller 42 rotates in the direction of the arrow in FIG. 3 and sends the paper S toward the conveyance path 50. Although detailed description is omitted, the separation roller 42 has a function of separating a plurality of sheets S sent out by the pickup roller 40 into one sheet.

  Similarly, the upper paper supply unit 11 includes a pickup roller 45, a paper supply roller 46, and a separating roller 47. A separation nip portion 11 a is formed between the paper feed roller 46 and the separating roller 47. The upper sheet feeding unit 11 is the same as the lower sheet feeding unit 10, and thus detailed description thereof is omitted.

  As shown in FIG. 2, the sheet conveying apparatus 12 includes a conveying path 50, a registration roller pair 51, an upstream conveying roller pair 52, a downstream conveying roller pair 53, and a guide unit 54. ing. The transport path 50 is configured to transport the paper S inside the apparatus main body 2. The registration roller pair 51, the upstream conveyance roller pair 52, and the downstream conveyance roller pair 53 are provided in the conveyance path 50. The guide portion 54 is provided so as to bulge from the wall surface of the conveyance path 50.

  The conveyance path 50 is formed to be curved in a substantially S shape between the paper feeding unit 10 and the fixing device 14. Further, the conveyance path 50 is formed to be curved toward the discharge trays 5 and 6 on the downstream side of the fixing device 14. The transport path 50 is branched up and down on the downstream side of the fixing device 14 (downstream transport roller pair 53) in order to discharge the paper S toward the upper and lower two paper discharge trays 5 and 6. The conveyance path 50 toward the upper discharge tray 6 is connected to a reverse path R that conveys the sheet S when performing duplex printing.

  As shown in FIGS. 3 and 4, the upstream side of the conveyance path 50 (the lower side of the apparatus main body 2) is formed between a curved inner guide frame 55 and an outer cover 58 facing the inner guide frame 55. Has been. The inner guide frame 55 is disposed in the apparatus main body 2, and an exterior cover 58 as an outer guide frame is configured in the lower right portion of the apparatus main body 2. The inner guide frame 55 and the outer cover 58 are mainly formed of a synthetic resin material.

  The inner guide frame 55 forms a transport surface 56 that is convex to the right in front view. As shown in FIG. 4, a plurality of guide ribs 57 are erected on the transport surface 56 of the inner guide frame 55 at predetermined intervals in the front-rear direction. Each guide rib 57 is extended along the conveyance direction (vertical direction). Each guide rib 57 is formed so as to become lower toward the apex portion of the convex conveying surface 56 and disappears at the apex portion.

  As shown in FIGS. 1 to 3, the exterior cover 58 constitutes a part of the outer wall of the apparatus main body 2. The exterior cover 58 is supported by the apparatus main body 2 so as to rotate around a rotation shaft 58a (see FIG. 2) at the lower part of the front and rear ends. A plurality of guide ribs (not shown) are erected on the inner surface of the exterior cover 58 (inside the apparatus main body 2). When the exterior cover 58 is rotated outward (opened), the conveyance surface 56 of the inner guide frame 55 is exposed. On the other hand, the closed exterior cover 58 faces the conveyance surface 56 of the inner guide frame 55 with a gap (see FIG. 3).

  As shown in FIG. 2, the registration roller pair 51 is provided in the conveyance path 50 between the upper sheet feeding unit 11 and the secondary transfer roller 35. As shown in FIG. 3, the registration roller pair 51 includes a driving roller 60 and a driven roller 61.

  The drive roller 60 is disposed on the left side of the conveyance path 50. The driving roller 60 is formed in a cylindrical shape that is long in the axial direction (front-rear direction), and is supported by the apparatus main body 2 so as to rotate around the axis. A driving device 16 is connected to one end of the driving roller 60 in the axial direction via a gear train (not shown). The driven roller 61 is disposed so as to contact the drive roller 60 from the right side. The driven roller 61 is urged toward the driving roller 60 by the compression spring 62 and rotates following the driving roller 60. A resist nip portion N1 is formed between the driving roller 60 and the driven roller 61. The driving roller 60 and the driven roller 61 are formed in a cylindrical shape that is longer in the axial direction than the maximum width of the sheet S to be conveyed.

  As shown in FIGS. 3 and 4, the upstream transport roller pair 52 is provided on the upstream side of the transport path 50 with respect to the registration roller pair 51. Specifically, the upstream-side conveyance roller pair 52 is disposed in a conveyance path 50 that is curved between the upper and lower two sheet feeding units 10 and 11. The upstream transport roller pair 52 includes a pair of front and rear upstream drive rollers 67 and a pair of front and rear upstream driven rollers 68.

  The two upstream drive rollers 67 as the first rollers constitute a comb-tooth roller 65 having a comb-teeth shape. That is, the comb-tooth roller 65 has two upstream drive rollers 67 fixed to a single upstream conveyance shaft 66. The comb-tooth roller 65 (each upstream drive roller 67) is provided inside the top 55b of the curved portion 55a of the inner guide frame 55.

  The upstream conveyance shaft 66 is formed in a rod shape (circular cross section) that is long in the axial direction (front-rear direction). The upstream conveying shaft 66 is supported at both ends by the inner guide frame 55 so as to rotate around the axis. A driving device 16 is connected to one end of the upstream conveyance shaft 66 in the axial direction via a gear train (not shown) or the like. Each upstream drive roller 67 is formed in a roller shape that is extremely shorter than the axial length of the upstream transport shaft 66. The two upstream drive rollers 67 are fixed to an intermediate portion in the axial direction of the upstream transport shaft 66 so as to be separated from each other.

  As shown in FIG. 3, each upstream driven roller 68 as the second roller is formed in a roller shape that is substantially the same as the upstream drive roller 67 described above. Each upstream driven roller 68 is supported on the inner upper portion of the exterior cover 58 so as to rotate around the axis.

  In a state where the exterior cover 58 is closed, the two upstream driven rollers 68 are provided to face each other so as to form a transport nip portion N2 between each upstream drive roller 67. By the way, the paper S may be jammed in the curved conveyance path 50 (curved portion 55a). In this case, the exterior cover 58 is opened to release the transport nip portion N2 and open the upstream side of the transport path 50. As a result, the jammed paper S can be removed (so-called jam processing).

  As shown in FIG. 2, the downstream side conveyance roller pair 53 is provided on the downstream side of the conveyance path 50 with respect to the fixing device 14. The downstream transport roller pair 53 includes a pair of front and rear downstream drive rollers 70 and a pair of front and rear downstream driven rollers 71. A conveyance nip N3 is formed between each downstream drive roller 70 and each downstream driven roller 71. Since the downstream side conveyance roller pair 53 has substantially the same configuration as the upstream side conveyance roller pair 52, detailed description thereof is omitted. Each downstream driven roller 71 is supported by the apparatus main body 2 so as to be rotatable about an axis.

  The drive roller 60, the upstream drive roller 67, and the downstream drive roller 70 are each connected to the drive device 16 via a clutch or the like (not shown), and are rotated / stopped independently. In addition, you may provide a some drive device (motor etc.) for every roller 60,67,70 not only in such a structure.

  As shown in FIGS. 3 and 4, the guide portion 54 is provided integrally with the inner guide frame 55 on the upstream side of the transport path 50 relative to the upstream transport roller pair 52. Specifically, the guide portion 54 is provided at a substantially central portion between a pair of adjacent upstream drive rollers 67 and on the upstream side (lower side) of the upstream conveyance shaft 66. The guide portion 54 is formed so as to bulge from the top portion 55b of the curved portion 55a of the inner guide frame 55 toward the outside of the curved portion 55a. The guide part 54 protrudes from the conveyance surface 56 so as to form a substantially trapezoidal shape when viewed from the front, and is formed in a substantially box shape. A detection sensor 101 that protrudes from the conveyance surface 56 of the inner guide frame 55 is provided above the guide portion 54 (see FIG. 4). The detection sensor 101 detects the paper S before reaching the registration roller pair 51.

  As shown in FIG. 3, the guide portion 54 has a guide surface 75 that is parallel to a tangent L that extends in the transport direction at the transport nip portion N2. The guide surface 75 is formed integrally with the transport surface 56. The guide surface 75 is a front end surface of the guide portion 54 that protrudes in a substantially trapezoidal shape when viewed from the front, and is located slightly closer to the transport surface 56 than the tangent line L. That is, the protrusion amount of the guide portion 54 is set to a range that does not protrude outward from the tangent line L. In addition, the guide surface 75 should just be formed in the range between the inner wall surface (conveyance surface 56) of the curved part 55a, and the tangent L in the conveyance nip part N2. In addition, the guide surface 75 is preferably formed on the tangent L side with respect to the distal end portion of each guide rib 57 of the inner guide frame 55.

  Next, with reference to FIGS. 2 and 3, the conveyance of the paper S by the sheet conveyance device 12 described above will be described. The control device 15 controls the driving device 16 to rotate / stop the rollers included in the paper feeding unit 10 (11) and the sheet conveying device 12 (see arrows in FIG. 3).

  First, the paper S accommodated in the paper feed cassette 3 is sent out to the transport path 50 by the paper feed unit 10. The sheet S is guided by the guide ribs 57 of the inner guide frame 55 and the like, reaches the upstream conveyance roller pair 52, and passes through the conveyance nip portion N2 of the upstream conveyance roller pair 52. The leading edge of the sheet S that has passed through the conveyance nip N2 comes into contact with the registration nip N1 of the stopped registration roller pair 51. The sheet S blocked by the registration nip portion N1 is further transported by the upstream transport roller pair 52. Thereby, the skew of the paper S is corrected.

  At this time, the transported paper S bends toward the inside of the curved transport path 50 (left side in FIG. 3). Therefore, it enters between the pair of upstream drive rollers 67 arranged at intervals in the axial direction, and tries to deform in a wave shape in the axial direction (front-rear direction) of the comb-tooth roller 65. However, in the sheet conveying device 12 according to the first embodiment, the guide portion 54 is disposed between the pair of upstream drive rollers 67. The guide unit 54 supports the sheet S so as not to be greatly deformed inside the curved conveyance path 50. That is, since the guide portion 54 is provided at the top portion 55b of the curved portion 55a of the inner guide frame 55, the wavy (deflection) of the paper S can be effectively suppressed.

  Thereafter, the registration roller pair 51 (drive roller 60) is rotationally driven at the timing when the toner image formed on the intermediate transfer belt 25 reaches the secondary transfer nip portion 35a. The sheet S passes through the registration nip portion N1 and is conveyed toward the secondary transfer nip portion 35a. As described above, the full color toner image is secondarily transferred onto the sheet S conveyed to the secondary transfer nip portion 35a. The sheet S on which the toner image is secondarily transferred passes through the fixing device 14 and the conveyance nip portion N3 of the downstream conveyance roller pair 53 and is discharged to the paper discharge tray 5.

  According to the sheet conveying apparatus 12 according to the first embodiment described above, the upstream conveying roller pair 52 is formed in a comb-like shape, but the guide portion 54 is provided in a portion where each upstream driving roller 67 does not exist. It has been. For this reason, the sheet S is sandwiched by the conveyance nip portion N2 in a portion where the upstream drive roller 67 is present, and is supported by the guide portion 54 in a portion where the upstream drive roller 67 is not present. Therefore, the sheet S is restrained from undulating deformation in the axial direction of the upstream conveying roller pair 52 and is conveyed along the conveying path 50 in a substantially flat posture. Thereby, the wrinkles of the paper S generated by the registration roller pair 51 crushing the wavy portion can be prevented. Furthermore, according to the multifunction machine 1 including such a sheet conveying device 12, a good image forming process can be ensured.

  For example, in order to prevent wrinkling of the paper S, it is not necessary to extend the transport distance (the distance between the upstream transport roller pair 52 and the registration roller pair 51). Thereby, size reduction of the sheet conveying apparatus 12 can be achieved. For example, in order to suppress the undulation of the paper S, it is not necessary to employ an expensive roller that is long in the axial direction. Thereby, the cost reduction of the sheet conveying apparatus 12 can be aimed at. Further, it is possible to reduce the size and cost of the multifunction machine 1 including such a sheet conveying device 12.

  Further, according to the sheet conveying apparatus 12 according to the first embodiment, the guide surface 75 of the guide portion 54 does not protrude outside the curve from the tangent L in the conveying nip portion N2. Thereby, the guide part 54 does not interfere with the conveyance of the paper S, and smooth and appropriate conveyance of the paper S can be ensured.

  If the guide portion is provided in the entire area in the axial direction (front-rear direction), the conveyance path 50 is narrowed by the guide portion, so that the conveyance failure (paper jam) of the paper S is likely to occur. In particular, when a thick sheet S is passed through the curved conveyance path 50 (conveying nip portion N2), a large load is applied to the thick sheet S, and a conveyance defect is likely to occur. In this regard, according to the sheet conveying apparatus 12 according to the first embodiment, since the guide portion 54 is provided only in the central portion in the axial direction, the guide portion 54 is prevented from causing a conveyance failure of the paper S. be able to. Thereby, it is possible to ensure good conveyance of the paper S. Further, the undulation of the paper S can be effectively suppressed.

(Second Embodiment)
Next, a sheet conveying device 80 according to the second embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view schematically showing the guide portion 81 of the sheet conveying apparatus 80. In addition, about the structure similar to above-mentioned 1st Embodiment, the same code | symbol is attached | subjected and the same description is abbreviate | omitted.

  In the sheet conveying apparatus 80 according to the second embodiment, the guide portion 81 is different from that according to the first embodiment. Specifically, the guide portion 81 includes a surface member 82 and a coil spring 84.

  The surface member 82 is a member obtained by separating the guide portion 54 according to the first embodiment from the inner guide frame 55. That is, the surface member 82 is formed in a substantially box shape so as to constitute the guide surface 83. A coil spring 84 as an urging member is connected to the inner guide frame 55 and the surface member 82. The coil spring 84 urges the surface member 82 toward the tangent L in the conveyance nip portion N2 with the inner guide frame 55 as a pedestal.

  According to the sheet conveying apparatus 80 according to the second embodiment described above, for example, when the thick sheet S is passed through the conveying path 50, the thick sheet S comes into contact with the guide surface 83 and resists the biasing force of the coil spring 84. The surface member 82 is pushed in. For this reason, the guide portion 54 does not hinder the conveyance of the thick paper S. On the other hand, the thin paper S is restrained from undulating deformation in the axial direction of the upstream transport roller pair 52 and is transported along the transport path 50 in a substantially flat posture. Since the thin paper S is weaker than the thick paper S, the pushing amount of the surface member 82 is also small. For this reason, the thin paper S is conveyed along the surface member 82 supported by the urging force of the coil spring 84, similarly to the sheet conveying apparatus 12 according to the first embodiment. Accordingly, it is possible to effectively suppress the undulation of the thin paper S while ensuring good conveyance of the thick paper S.

  The sheet conveying device 80 according to the second embodiment employs the coil spring 84 as the biasing member, but instead of this, a rubber, a leaf spring, or the like may be used as the biasing member.

  In the sheet conveying apparatuses 12 and 80 according to the first and second embodiments, since the comb roller 65 is provided on the top 55b of the curved portion 55a of the inner guide frame 55, the guide portions 54 and 81 are adjacent to each other. Although provided between the upstream drive rollers 67, the present invention is not limited to this. For example, when each upstream driven roller 68 is provided at the top 55 b of the curved portion 55 a of the inner guide frame 55, the guide portions 54 and 81 are provided between the adjacent upstream driven rollers 68.

  Two or more upstream drive rollers 67 and upstream driven rollers 68 of the upstream transport roller pair 52 may be provided. In this case, one or more guide portions 54 and 81 may be provided. Similarly, two or more downstream drive rollers 70 and downstream driven rollers 71 of the downstream transport roller pair 53 may be provided.

  In the first and second embodiments, the case where the present invention is applied to the multifunction machine 1 has been described as an example. May be applied.

  The description of the above embodiment shows one aspect of the sheet conveying apparatus according to the present invention and an image forming apparatus including the same, and the technical scope of the present invention is not limited to the above embodiment. . The components in the above embodiment can be appropriately replaced or combined with existing components and the like, and the description of the above embodiment does not limit the content of the invention described in the claims. .

1 MFP (image forming device)
12, 80 Sheet conveying device 50 Conveying path 51 Registration roller pair 52 Upstream conveying roller pair 52 (conveying roller pair)
54, 81 Guide portion 55 Inner guide frame 55a Curved portion 55b Top portion 56 Transport surface (wall surface of transport path)
58 Exterior cover (outer guide frame)
66 Upstream transport axis (transport axis)
67 Upstream drive roller (first roller)
68 Upstream driven roller (second roller)
75, 83 Guide surface 82 Surface member 84 Coil spring (biasing member)
L Tangent N2 Conveying nip S Paper (sheet)

Claims (5)

A conveyance path configured to convey the sheet;
A pair of registration rollers provided in the conveyance path;
A pair of transport rollers provided on the upstream side of the transport path from the pair of registration rollers;
A guide portion provided so as to bulge from the wall surface of the transport path on the upstream side of the transport path from the pair of transport rollers, and
The transport roller pair is
A plurality of first rollers fixed at intervals to a single conveying shaft;
A plurality of second rollers provided facing each other so as to form a conveyance nip portion between each of the first rollers,
The guide portion is provided between the adjacent first rollers or between the adjacent second rollers, and has a guide surface that is parallel to a tangent line in the conveyance nip portion ,
In the sheet conveyance direction, a downstream end portion of the guide surface extends to the conveyance nip portion . The transport path is formed between a curved inner guide frame and an outer guide frame facing the inner guide frame,
Each of the first rollers is provided on the top of the curved portion of the inner guide frame,
The guide portion is provided on the inner guide frame between the adjacent first rollers, and is formed so as to bulge from the top of the curved portion toward the outside of the curved portion,
The sheet conveying apparatus according to claim 1, wherein the guide surface is formed in a range between a top portion of the curved portion and a tangent line in the conveying nip portion. The guide portion is
A surface member constituting the guide surface;
The sheet conveying apparatus according to claim 1, further comprising an urging member that urges the surface member toward a tangent to the conveyance nip portion. The two first rollers are fixed apart from each other at an intermediate portion in the axial direction of the transport shaft,
The sheet conveying device according to claim 1, wherein the guide portion is provided between the two first rollers.   An image forming apparatus comprising the sheet conveying device according to claim 1.

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