JP6604316B2 - Sheet stacking apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a sheet stacking apparatus that stacks sheets and an image forming apparatus including the sheet stacking apparatus.

  2. Description of the Related Art Conventionally, a sheet stacking apparatus that discharges an image-formed sheet to a sheet discharge tray is known. Patent Documents 1 and 2 disclose an image forming apparatus including a sheet stacking device including a mechanism for blowing air to a discharged sheet.

JP 2013-136453 A JP 2013-184809 A

  In the techniques described in Patent Documents 1 and 2, the sheets are blown to perform sheet blowing during discharge, thereby preventing the sheets from being attracted and the sheets buckled. However, in this case, since the posture of the sheet at the time of discharging becomes unstable, there is a problem that the stackability of the sheet is likely to deteriorate.

  SUMMARY An advantage of some aspects of the invention is that a sheet stacking apparatus capable of maintaining good alignment of sheets discharged to a sheet stacking unit and an image forming apparatus including the sheet stacking apparatus are provided. The purpose is to provide.

A sheet stacking apparatus according to one aspect of the present invention is a sheet stacking apparatus that stacks sheets, and is disposed in the casing, a sheet stacking unit that is disposed in the casing and stacks sheets, and is rotatable in the casing A plurality of lower discharge rollers that discharge the sheet along a predetermined conveyance direction toward the sheet stacking unit, and a plurality of lower discharge rollers that are rotatably supported by the housing. A plurality of upper discharge rollers that form a nip portion through which the sheet passes, an air flow generation portion that generates an air flow, and a lower portion of the sheets that are discharged from the nip portion toward the sheet stacking portion. An air flow guide portion that guides the air flow toward the facing sheet surface, and the air flow guide portion faces a central portion of the sheet surface in the sheet width direction orthogonal to the conveyance direction. The sky A central exhaust port that blows out the flow, and a pair of side exhaust ports that are arranged on both outer sides in the seat width direction than the central exhaust port and blow out the air flow toward the sheet surface, The exhaust direction of the air flow blown out from the central exhaust port and the pair of side exhaust ports is set so as to rise toward the downstream side in the transport direction so as to intersect the transport direction of the sheet. The air volume blown from the central exhaust port is set to be larger than the air flow blown from the side exhaust port, and the air flow blown from the central exhaust port The exhaust direction of the central exhaust port and the one of the central exhaust port and the one of the one side exhaust port are so as to rise at a larger angle toward the downstream side in the transport direction than the exhaust direction of the air flow blown out from the pair of side exhaust ports. The orientation of the side exhaust port is set for.

  According to this configuration, the airflow guide unit includes at least three exhaust ports that blow out the airflow. The amount of airflow blown from the central exhaust port is larger than the amount of airflow blown from the pair of side exhaust ports. For this reason, the sheet having passed through the nip portion is formed with a bent shape along the conveying direction such that the central portion is convex upward. As a result, the sheet discharged to the sheet stacking unit is stably provided with the waist, and the sheet alignment is stably maintained. Further, since an air layer is formed between the sheets, adsorption (sticking) between the sheets is suppressed.

Further , according to this configuration, the air flow blown from the central exhaust port is blown to the seat surface at a steeper angle than the side exhaust port. For this reason, it becomes easy to form the bending shape in which the center part becomes convex upwards in the conveyance direction on the sheet that has passed through the nip part.

In the above configuration, the sheet stacking unit includes an inclined surface that rises toward the downstream side in the conveyance direction, and the exhaust direction of the airflow blown out from the pair of side exhaust ports is the sheet stacking unit. It is desirable that the direction of the pair of side exhaust ports is set so as to rise at a larger angle toward the downstream side in the transport direction than the inclined surface.

  According to this configuration, the airflow blown from the side exhaust port is prevented from strongly colliding with the inclined surface of the sheet stacking unit before reaching the sheet surface. For this reason, the disturbance of the air flow is unlikely to occur between the discharged sheet and the sheet stacking section, and the sheet alignment is improved.

  In the above configuration, the air flow generation unit starts generating the air flow for spraying the sheet before the leading end of the sheet passes through the nip, and the trailing end of the sheet It is desirable to stop the generation of the air flow before passing through the nip portion.

  According to this configuration, a bent shape can be stably imparted to the leading end portion of the sheet. In addition, since a strong air flow does not collide with the rear end portion of the sheet that has passed through the nip portion, it is possible to suppress stacking failure due to jumping of the rear end portion of the sheet.

  In the above configuration, the air flow generation unit includes a first air flow generation unit and a second air flow generation unit, and the air flow guide unit divides the air flow generated by the first air flow generation unit. A first duct guided to one of the pair of side exhaust ports and the central exhaust port, and an air flow generated by the second air flow generation unit, It is desirable to have a second duct that guides the other side exhaust port among the side exhaust ports and the central exhaust port.

  According to this configuration, an air flow having a large air volume can be blown out from the central exhaust port by joining the air flows of the two air flow generation units. In addition, even when the driving of one air flow generation unit is stopped, the air flow blown out from the central exhaust port can be ensured.

  In the above configuration, the plurality of lower discharge rollers include at least four lower discharge rollers arranged at intervals in the sheet width direction, and the central exhaust port is formed at a central portion in the sheet width direction. Disposed below a region between the two lower discharge rollers that are spaced apart from each other, and the pair of side exhaust ports are located outside the sheet width direction with respect to the two lower discharge rollers It is desirable that they are disposed below the pair of lower discharge rollers disposed adjacent to each other.

  According to this structure, it becomes easy to form convex-shaped bending by spraying a strong airflow from a center exhaust port between two lower discharge rollers. Further, the air flow blown out from the side exhaust port is blown to the downstream side of the region constrained by the pair of lower discharge rollers on the sheet width direction outside of the sheet surface of the sheet. For this reason, skew of the discharged sheet is suppressed.

In the above configuration, the edge in the sheet width direction outside of the pair of side exhaust ports is disposed at the same position in the sheet width direction as the edge in the sheet width direction outside of the pair of lower discharge rollers. The edge of the pair of side exhaust ports on the inner side in the sheet width direction is disposed more inside the sheet width direction than the edge of the pair of lower discharge rollers on the inner side in the sheet width direction. desirable.

  According to this configuration, a part of the air flow blown out from the side exhaust port enters the inside in the seat width direction and merges with the air flow blown out from the central exhaust port. For this reason, it is possible to stably form a bent shape in which the central portion is convex upward in the conveyance direction on the sheet that has passed through the nip portion.

  An image forming apparatus according to another aspect of the present invention includes an image forming unit that forms an image on a sheet, and the sheet stacking apparatus according to any one of the above.

  According to this configuration, the sheet discharged to the sheet stacking unit is stably provided with the waist, and the sheet consistency is stably maintained. Further, since an air layer is formed between the sheets, adsorption (sticking) between the sheets is suppressed.

  According to the present invention, there is provided a sheet stacking apparatus capable of maintaining good alignment of sheets discharged to the sheet stacking unit and an image forming apparatus including the sheet stacking apparatus.

1 is a perspective view illustrating an appearance of an image forming apparatus including a sheet stacking apparatus according to an embodiment of the present invention. 2 is a cross-sectional view schematically showing an internal structure of a main body portion of the image forming apparatus. FIG. 3 is an enlarged perspective view schematically showing an internal structure of the sheet stacking apparatus. FIG. FIG. 4 is a side view illustrating a structure around a sheet stacking unit of the sheet stacking apparatus. It is the schematic which shows the structure of an airflow generation | occurrence | production part and a duct. FIG. 3 is an enlarged cross-sectional view of a sheet stacking apparatus illustrating a state in which an air flow is blown to a sheet. It is a perspective view of a sheet | seat which shows a mode that an airflow is blown on a sheet | seat. FIG. 4 is an enlarged cross-sectional view of a sheet stacking apparatus showing a state in which a discharge failure has occurred in a sheet.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing an appearance of an image forming apparatus S provided with a post-processing apparatus 5 according to an embodiment of the present invention. FIG. 2 schematically shows an internal structure of a main body 1 of the image forming apparatus S. FIG. Here, the main body 1 of the image forming apparatus S is a so-called in-body discharge type monochrome copying machine, but the main body is a color copying machine, a printer, a facsimile machine, or a multifunction machine having these functions. It may be.

  As shown in FIG. 1, an image forming apparatus S includes a main body 1 that performs image forming processing on a sheet, and a sheet or a sheet group that is disposed adjacent to the main body 1 and has undergone image forming processing ( And a post-processing device 5 including a post-processing unit that performs predetermined post-processing on the sheet bundle. The post-processing includes, for example, punch processing for punching a binding hole in a sheet, staple processing for placing staples in a sheet group, intermediate folding processing for folding a sheet, and alignment processing for performing a shift operation and a width alignment operation on the sheet. Etc.

  The main body unit 1 includes a main body housing 100, an image reading unit 2a disposed on the top of the main body housing 100, an automatic document feeder (ADF) 2b disposed on the upper surface of the image reading unit 2a, and an image. And an operation unit 10 attached to the front surface of the reading unit 2a. Inside the main body housing 100 are housed a paper feed unit 3a, a conveyance path 3b, an image forming unit 4a, a fixing unit 4b, and a sheet discharge unit 3c (FIG. 2).

  The operation unit 10 receives input of various settings and operation instructions for the image forming apparatus S from the user. The operation unit 10 includes a numeric keypad unit 11 for setting the number of copies and the like, a start key 12 for receiving an instruction input for executing a copy operation, and a touch panel 13 for displaying various operation keys and guidance. Yes.

  The automatic document feeder 2b automatically feeds a document sheet to be copied toward a predetermined document reading position (a position where the first contact glass 24 is assembled). On the other hand, when the user manually places the document sheet on a predetermined document reading position (position of the second contact glass 25), the automatic document feeder 2b is opened upward. The automatic document feeder 2b includes a document tray 21 on which a document sheet is placed, a document transport unit 22 that transports a document sheet via an automatic document reading position, and a document discharge in which a document sheet after reading is discharged. A tray 23.

  The image reading unit 2a has a box-shaped housing structure, and a first contact glass 24 for reading a document sheet automatically fed from the automatic document feeder 2b and a manually placed document on the upper surface thereof. A second contact glass 25 for reading the sheet is fitted. The image reading unit 2a optically reads an image on a document sheet.

  The paper feed unit 3a in the main body housing 100 includes a plurality of cassettes 31 (as shown in FIGS. 1 and 2, a total of four stages 31A, 31B, 31C, and 31D from above). Each cassette 31 accommodates a plurality of sheets of each size (for example, A type, B type sheet such as A4, B4, etc.) and each type (for example, copy sheet, recycled paper, cardboard, OHP sheet, etc.). Each cassette 31 includes rotationally driven paper feed rollers 32 (a total of four from 32A, 32B, 32C, and 32D from the top in FIG. 2), and feeds the sheets one by one to the transport path 3b during image formation.

  The conveyance path 3 b is a conveyance path for conveying a sheet in the main body casing 100 from the paper feed unit 3 a to the in-body discharge tray 33 or the post-processing device 5. In the conveyance path 3b, a guide plate for guiding a sheet, a conveyance roller pair 34 that is rotationally driven during sheet conveyance (a total of three from 34A, 34B, and 34C from the top in FIG. 2) and a sheet to be conveyed are provided. A registration roller pair 35 is provided that waits in front of the image forming unit 4a and feeds the sheet in accordance with the transfer timing of the formed toner image.

  The image forming unit 4a generates a toner image and transfers it onto the sheet, that is, forms an image on the sheet. The image forming unit 4 a includes a photosensitive drum 41 and a charger 42, an exposure device 43, a developing device 44, a transfer roller 45, and a cleaning device 46 disposed around the photosensitive drum 41.

  The photosensitive drum 41 rotates around its axis, and an electrostatic latent image and a toner image are formed on its peripheral surface. The charger 42 uniformly charges the surface of the photosensitive drum 41. The exposure device 43 has a laser light source and optical system equipment such as a mirror and a lens, and irradiates the peripheral surface of the photosensitive drum 41 with laser light L based on image data of an original image to generate an electrostatic latent image. Form. The developing device 44 supplies toner to the peripheral surface of the photosensitive drum 41 in order to develop the electrostatic latent image formed on the photosensitive drum 41. The transfer roller 45 forms a transfer nip portion together with the photosensitive drum 41 and is given a transfer bias. The toner image on the photosensitive drum 41 is transferred to the sheet passing through the transfer nip portion. The cleaning device 46 includes a cleaning roller and the like, and cleans the peripheral surface of the photosensitive drum 41 after the toner image is transferred.

  The fixing unit 4b fixes the toner image transferred to the sheet P. The fixing unit 4 b includes a heating roller 47 that incorporates a heating element, and a pressure roller 48 that is pressed against the heating roller 47. When the sheet on which the toner image has been transferred passes through the fixing nip formed by the heating roller 47 and the pressure roller 48, the toner is melted and heated, and the toner image is fixed on the sheet. The sheet after the fixing process is sent to the sheet discharge unit 3c.

  The sheet discharge unit 3 c includes an external discharge roller pair 36 </ b> A for sending an image-formed sheet in the direction of the post-processing device 5, and an internal discharge roller pair 36 </ b> B for sending it in the in-body discharge tray 33 direction. Each of the discharge roller pairs 36A and 36B is rotationally driven during the discharge operation, and discharges the sheet to the outside of the apparatus. Further, the sheet discharge unit 3c includes a switching lever 37 that switches a sheet paper conveyance direction. The switching lever 37 rotates and guides the sheet toward the discharge destination designated by the operation unit 10.

  The post-processing device 5 (sheet stacking device) performs a predetermined post-processing on the sheet and then stacks the sheet. The post-processing apparatus 5 includes a post-processing apparatus casing 500 (casing) disposed adjacent to the main body casing 100, and various types of post-processing that are disposed in the post-processing apparatus casing 500 and perform post-processing on the sheet P. And a post-processing unit. FIG. 3 is an enlarged perspective view schematically showing the internal structure of the post-processing device 5.

  The post-processing device 5 includes a shaft 51, a discharge roller 52 (lower discharge roller), a driven roller 53 (upper discharge roller), a main discharge tray 54 (sheet stacking unit), and a sub discharge tray 55. .

  Further, a side surface of the post-processing apparatus housing 500 facing the main body housing 100 is provided with an unillustrated carry-in port for receiving the sheet after the image forming process into the housing 500, and a side surface opposite to the side surface ( The left side) is provided with a main carry-out port and a sub carry-out port for discharging sheets from the housing 500. A main discharge tray 54 and a sub discharge tray 55 are attached to the left side surface of the post-processing device casing 500 in correspondence with the main carry-out port and the sub carry-out port, respectively (FIG. 1).

  The main discharge tray 54 is a tray on which staple processing, shift operation, width adjustment operation, and the like are performed, and sheets or sheet groups discharged by the discharge roller 52 are stacked. The main discharge tray 54 includes an inclined surface that rises toward the downstream side in the conveyance direction of the sheet P.

  The sub discharge tray 55 is a tray on which sheets discharged from the sub carry-out port are stacked. The sub discharge tray 55 is disposed above the main discharge tray 54 at an interval, and sheets are selectively discharged from the main discharge tray 54. The sub discharge tray 55 is mainly used to stack sheets discharged without being subjected to post-processing by the post-processing device 5 or sheets subjected to only punch processing.

  The discharge roller 52 is rotatably supported by the post-processing apparatus main body 500. In the present embodiment, a plurality of discharge rollers 52 arranged at intervals in the sheet width direction are supported by the shaft 51. The shaft 51 is supported by the post-processing apparatus main body 500 by a bearing portion (not shown). The discharge roller 52 conveys the sheet carried into the post-processing apparatus main body 500 from the sheet discharge portion 3 c of the main body 1 toward the main discharge tray 54 along a predetermined conveyance direction (left direction). In the present embodiment, as shown in FIG. 3, four discharge rollers 52 are arranged at intervals in the sheet width direction (front-rear direction). In another embodiment, a plurality of discharge rollers 52 may be arranged, and four or more discharge rollers 52 may be arranged.

  The driven roller 53 is rotatably supported by the post-processing apparatus main body 500 and forms a nip portion through which the sheet passes with the discharge roller 52. In the present embodiment, a plurality of driven rollers 53 are also arranged at intervals along the front-rear direction.

  In order to discharge the sheet to the sub discharge tray 55, the post-processing apparatus main body 500 is further provided with a conveyance roller and a driven roller (not shown).

  The post-processing device 5 further includes a first fan 71 (air flow generation unit), a second fan 72 (air flow generation unit), and a duct 73 (air flow guide unit). FIG. 4 is a side view showing the structure around the main discharge tray 54 of the post-processing device 5. FIG. 5 is a schematic diagram showing the structure of the first fan 71, the second fan 72, and the duct 73. FIG. 6 is an enlarged cross-sectional view of the post-processing device 5 showing a state in which an air flow is blown to the sheet.

  The first fan 71 and the second fan 72 generate an air flow that is blown onto the seat. In the present embodiment, the first fan 71 and the second fan 72 are known sirocco fans. As shown in FIGS. 5 and 6, in the present embodiment, the first fan 71 and the second fan 72 are arranged below the discharge roller 52 in the post-processing apparatus main body 500 with an interval in the front-rear direction. Yes. In FIG. 6, the first fan 71 arranged in front is shown. The second fan 72 is disposed on the rear side of the first fan 71 in FIG. The outlets of the first fan 71 and the second fan 72 are opened upward.

  The duct 73 is disposed inside the post-processing apparatus main body 500 and communicates the first fan 71 and the second fan 72 with the space above the main discharge tray 54. The duct 73 guides the air flow from the nip portion between the discharge roller 52 and the driven roller 53 toward the sheet surface facing downward among the sheets P discharged toward the main discharge tray 54.

  The duct 73 includes a central exhaust port 61, a pair of side exhaust ports 62, a first duct 73J, and a second duct 73K. As shown in FIGS. 3 and 4, the central exhaust port 61 and the side exhaust port 62 are provided on the left side surface of the post-processing apparatus main body 500 below the discharge roller 52 and above the base end portion of the main discharge tray 54. Is arranged.

  The central exhaust port 61 blows out an air flow toward the central portion in the sheet width direction (front-rear direction) orthogonal to the transport direction, among the sheet surfaces of the sheet P discharged by the discharge roller 52. The pair of side exhaust ports 62 are respectively disposed on both outer sides in the sheet width direction (front-rear direction) with respect to the central exhaust port 61, and blow an air flow toward the sheet surface of the sheet P. The direction in which the central exhaust port 61 and the side exhaust port 62 blow the air flow is parallel to the conveying direction of the sheet P as viewed from above. However, as will be described later, the direction in which the central exhaust port 61 and the side exhaust port 62 blow the air flow intersects the conveying direction of the sheet P at a predetermined angle when viewed from the horizontal direction (front-rear direction).

  The arrangement of the central exhaust port 61 and the side exhaust ports 62 will be described in further detail with reference to FIG. As described above, in the present embodiment, the four discharge rollers 52 are arranged. The central exhaust port 61 is disposed below a region between the two discharge rollers 52 that are disposed at a distance from each other at the center in the sheet width direction (front-rear direction). On the other hand, the pair of side exhaust ports 62 are respectively disposed below the pair of discharge rollers 52 disposed adjacent to the outer sides in the sheet width direction with respect to the two discharge rollers 52 on the center side. .

  Further, the edge of the pair of side exhaust ports 62 on the outer side in the sheet width direction is substantially the same position in the sheet width direction as the outer edge of the pair of discharge rollers 52 arranged on the outer side in the sheet width direction. Is arranged. Furthermore, the edge on the inner side in the sheet width direction of the pair of side exhaust ports 62 is located on the inner side in the sheet width direction with respect to the inner edge in the sheet width direction of the pair of discharge rollers 52 disposed on the outer side in the sheet width direction. Has been placed. In other words, as shown in FIG. 4, the sheet width direction inner portions of the pair of side exhaust ports 62 protrude inward from the upper discharge roller 52.

  The first duct 73J divides the air flow generated by the first fan 71, and one of the pair of side exhaust ports 62 (the front side exhaust port 62) and the central exhaust port 61. To each.

  The second duct 73K divides the air flow generated by the second fan 72, and out of the pair of side exhaust ports 62, the other side exhaust port 62 (rear side exhaust port 62) and the central exhaust port. Guide each to 61.

  Note that when a part of the air flow generated by the first fan 71 and the second fan 72 joins, the air volume of the air flow blown from the central exhaust port 61 is blown out from each side exhaust port 62. It is set larger than the air volume of the air flow.

  In the present embodiment, the air flow generated by the first fan 71 and the second fan 72 is thus blown out from the central exhaust port 61 and the pair of side exhaust ports 62. The air flow is blown leftward from the central exhaust port 61 and the side exhaust port 62, but is blown at a predetermined angle with respect to the conveyance direction of the sheet P. The opening length in the width direction (front-rear direction) of the central exhaust port 61 is twice the opening length in the width direction of the side exhaust port 62. Further, the opening length in the height direction (vertical direction) of the central exhaust port 61 is one half of the opening length in the height direction of the side exhaust port 62. Further, the upper end edge of the central exhaust port 61 and the upper end edge of the side exhaust port 62 are disposed at substantially the same height, and the lower end edge of the central exhaust port 61 is disposed above the lower end edge of the side exhaust port 62. ing. With such a structure, as described above, the airflow rate of the airflow blown from the central exhaust port 61 is set to be larger than the airflow rate of the airflow blown from each side exhaust port 62.

  Specifically, the exhaust direction of the airflow blown out from the central exhaust port 61 and the pair of side exhaust ports 62 rises toward the downstream side in the transport direction so as to intersect the transport direction of the sheet P. It has been set (FIG. 3). Furthermore, the angle formed by the exhaust direction of the air flow blown from the central exhaust port 61 and the conveyance direction of the sheet P is such that the exhaust direction of the air flow blown from the pair of side exhaust ports 62 and the conveyance direction of the sheet P The direction of the central exhaust port 61 and the side exhaust port 62 is set so as to be larger than the angle formed by. In other words, the exhaust direction of the air flow blown from the central exhaust port 61 rises at a larger angle toward the downstream side in the transport direction than the exhaust direction of the air flow blown from the pair of side exhaust ports 62. It is set to become. That is, the air flow blown from the central exhaust port 61 collides with the sheet surface of the sheet P at a position closer to the discharge roller 52 than the air flow blown from the side exhaust port 62.

  Further, as described above, the main discharge tray 54 has an inclined surface that rises forward along the conveyance direction of the sheet P. The angle formed between the exhaust direction of the air flow blown from the pair of side exhaust ports 62 and the conveyance direction of the sheet P is larger than the angle formed between the inclined surface of the main discharge tray 54 and the conveyance direction of the sheet P. Thus, the direction of the side exhaust port 62 is set. In other words, the exhaust direction of the air flow blown out from the pair of side exhaust ports 62 is set to rise at a larger angle toward the downstream side in the transport direction than the inclined surface of the main discharge tray 54. ing.

  FIG. 7 is a perspective view of the sheet P showing a state in which an air flow is blown to the sheet P. In FIG. 7, the conveyance direction of the sheet P discharged by the discharge roller 52 and the driven roller 53 is indicated by an arrow DP. FIG. 8 is an enlarged cross-sectional view of the post-processing apparatus 5 showing a state in which a discharge failure has occurred in the sheet P.

  When transported inside the main body 1 and the post-processing device 5 of the image forming apparatus S, the sheet P is easily charged. That is, when the sheet P is discharged by the discharge roller 52 while the sheet surface of the sheet P is charged with static electricity, the leading end of the sheet P is attracted to the main discharge tray 54 as shown in FIG. As a result, the sheet P is not successfully stacked on the main discharge tray 54, and a problem such as a paper jam occurs.

  In the present embodiment, in order to solve such a problem, the duct 73 includes three exhaust ports that blow out an air flow. The blown air flow collides with a sheet surface facing the lower side of the sheet P and enters a space between the sheet P and the main discharge tray 54 as indicated by an arrow DF in FIG.

  The air volume blown from the central exhaust port 61 (arrow D61 in FIG. 7) is larger than the air flow blown from the side exhaust port 62 (arrow D62 in FIG. 7). For this reason, as shown in FIG. 7, the sheet P that has passed through the nip portion is formed with a bent shape along the transport direction so that the central portion is convex upward. As a result, a strong waist is stably imparted to the sheet P discharged to the main discharge tray 54, and the consistency of the sheet P is stably maintained. Further, since an air layer is formed between the sheets P, the adsorption (sticking) between the sheets P is suppressed.

In particular, in the present embodiment, as shown in FIGS. 3 and 7, the exhaust direction of the air flow blown from the central exhaust port 61 is more than the exhaust direction of the air flow blown from the pair of side exhaust ports 62. It is set to rise upward at a large angle toward the downstream side in the transport direction. For this reason,
The air flow blown from the central exhaust port 62 is blown to the seat surface at a steeper angle than the side exhaust port 61. For this reason, it becomes easy to form the bending shape in which the center part becomes convex upwards in the conveyance direction in the sheet P that has passed the nip part.

  Further, the exhaust direction of the air flow blown out from the pair of side exhaust ports 62 is set to rise at a larger angle toward the downstream side in the transport direction than the inclined surface of the main discharge tray 54. . For this reason, the air flow blown out from the side exhaust port 62 is prevented from strongly colliding with the inclined surface of the main discharge tray 54 before reaching the sheet surface of the sheet P. For this reason, air flow is hardly disturbed between the discharged sheet P and the main discharge tray 54, and the alignment of the sheet P is improved.

  In the present embodiment, the first fan 71 and the second fan 72 start generating an air flow before the leading end portion of the sheet P passes through the nip portion between the discharge roller 52 and the driven roller 53. The generation of airflow is stopped before the trailing edge of the sheet P passes through the nip. For this reason, a bending shape can be stably given to the front-end | tip part of the sheet | seat P. FIG. Further, since a strong air flow does not collide with the rear end portion of the sheet P that has passed through the nip portion, it is possible to suppress a stacking failure due to the jumping of the rear end portion of the sheet P.

  In the present embodiment, two fans are provided as shown in FIG. A large air flow can be blown out from the central exhaust port 61 by combining the air flows of the two fans through the duct 73. Further, even when the driving of one fan is stopped, the air flow blown out from the central exhaust port 62 can be ensured.

  Further, as shown in FIG. 4, the central exhaust port 61 is disposed below a region between the two discharge rollers 52 arranged at intervals in the central portion of the four discharge rollers 52 in the sheet width direction. Has been. For this reason, by blowing a strong air flow from the central exhaust port 61 between the two discharge rollers 52, it becomes easy to form a convex bending as shown in FIG.

  Further, the pair of side exhaust ports 62 are disposed below the pair of discharge rollers that are respectively disposed outside the four discharge rollers 52 in the sheet width direction (FIG. 4). For this reason, the airflow blown out from the side exhaust port 62 is blown to the downstream side in the transport direction of the area of the sheet P restrained by the pair of discharge rollers 52 on the outer side in the sheet width direction. For this reason, the discharged sheet P is prevented from wobbling and skewing due to the air flow blown out from the side exhaust port 62.

  Further, the outer edges of the pair of side exhaust ports 62 on the outer side in the sheet width direction are the outer edges of the pair of discharge rollers 52 arranged on the outer side in the sheet width direction (both ends of the four discharge rollers 52). Are arranged at substantially the same position. Further, the inner edges in the sheet width direction of the pair of side exhaust ports 62 are arranged on the inner side in the sheet width direction than the inner edges in the sheet width direction of the pair of discharge rollers 52. In this case, a part of the air flow blown out from the side exhaust port 62 enters the inside in the seat width direction and merges with the air flow blown out from the central exhaust port 61. For this reason, it is possible to stably form a bent shape in which the central portion is convex upward on the sheet P that has passed through the nip portion along the conveying direction.

  The embodiment of the present invention has been described in detail above. According to these configurations, a strong waist is imparted to the sheet P discharged to the main discharge tray 54, and the consistency of the sheet P is stably maintained. Further, since an air layer is formed between the sheets P, the adsorption (sticking) between the sheets P is suppressed. In addition, this invention is not limited to said aspect. The present invention can take, for example, the following modified embodiments.

  (1) In the above embodiment, the post-processing apparatus 5 is used as the sheet stacking apparatus, but the present invention is not limited to this. Other modes may be used as long as the apparatus discharges and stacks the sheet P on which the image is formed.

  (2) In the above-described embodiment, the post-processing device 5 has been described as being provided with one central exhaust port 61 and two side exhaust ports 62, but the present invention is limited to this. is not. For one central exhaust port 61, four side exhaust ports 62 may be provided outside the sheet width direction, and a plurality of side exhaust ports 62 may be further provided.

  (3) Moreover, although the said embodiment demonstrated in the aspect by which 4 pairs of discharge rollers 52 and the driven roller 53 were arrange | positioned, the discharge roller 52 and the driven roller 53 pinch | interpose the center part of a sheet | seat width direction. Two pairs may be arranged at intervals in the front-rear direction. In this case, the central exhaust port 61 may be disposed below the two rollers, and a pair of side exhaust ports 62 may be disposed below the two rollers.

  (4) In the above embodiment, the discharge roller 52 constitutes the lower discharge roller of the present invention, and the driven roller 53 constitutes the upper discharge roller of the present invention. The aspect which comprises the upper discharge roller of invention and the driven roller 53 comprises the lower discharge roller of this invention may be sufficient.

DESCRIPTION OF SYMBOLS 1 Main-body part 2a Image reading part 2b Automatic document feeder 3a Paper feeding part 4a Image forming part 4b Fixing part 5 Post-processing apparatus (sheet stacking apparatus)
51 Shaft 52 Discharge roller (lower discharge roller)
53 Follower roller (upper discharge roller)
54 Main discharge tray (sheet stacking section)
55 Sub-discharge tray 500 Post-processing device housing (housing)
61 Central exhaust port 62 Side exhaust port 71 First fan (air flow generator)
72 Second fan (air flow generator)
73 Duct (air flow guide)
73J 1st duct 73K 2nd duct P sheet S Image forming apparatus

Claims (7)

A sheet stacking device for stacking sheets,
A housing,
A sheet stacking unit disposed in the housing and on which sheets are stacked;
A plurality of lower discharge rollers which are rotatably supported by the housing and discharge the sheets along a predetermined conveyance direction toward the sheet stacking unit;
A plurality of upper discharge rollers that are rotatably supported by the housing above the lower discharge rollers and that form nip portions through which the sheet passes between the lower discharge rollers;
An air flow generator for generating an air flow;
An air flow guide portion for guiding the air flow toward a sheet surface facing downward among the sheets discharged from the nip portion toward the sheet stacking portion;
Have
The air flow guide is
A central exhaust port that blows out the airflow toward the center of the sheet surface in the sheet width direction orthogonal to the conveyance direction;
A pair of side exhaust ports that are arranged on both outer sides in the sheet width direction from the central exhaust port and blow out the airflow toward the sheet surface,
Have
The exhaust direction of the air flow blown out from the central exhaust port and the pair of side exhaust ports is set so as to rise toward the downstream side in the transport direction so as to intersect the transport direction of the sheet. And
The air volume blown from the central exhaust port is set larger than the air flow blown from the side exhaust port ,
The exhaust direction of the air flow blown from the central exhaust port rises at a larger angle toward the downstream side in the transport direction than the exhaust direction of the air flow blown from the pair of side exhaust ports. As described above , the sheet stacking apparatus in which orientations of the central exhaust port and the pair of side exhaust ports are set . The sheet stacking unit is composed of an inclined surface that rises toward the downstream side in the conveyance direction,
The pair of side exhaust air is blown out from the pair of side exhaust ports so that the exhaust direction of the air flow rises at a larger angle toward the downstream side in the transport direction than the inclined surface of the sheet stacking unit. The sheet stacking apparatus according to claim 1, wherein a direction of the side exhaust port is set. The air flow generation unit starts generating the air flow for spraying the sheet before the front end of the sheet passes through the nip, and the rear end of the sheet passes through the nip. before stopping the generation of the air flow, the sheet stacking apparatus according to claim 1 or 2. The air flow generation unit includes a first air flow generation unit and a second air flow generation unit,
The air flow guide is
A first duct that divides the air flow generated by the first air flow generation unit and guides the air flow to one of the pair of side exhaust ports and the central exhaust port;
A second duct for diverting an air flow generated by the second air flow generation unit and guiding the air flow to the other side exhaust port and the central exhaust port of the pair of side exhaust ports;
The has a sheet stacking apparatus according to any one of claims 1 to 3. The plurality of lower discharge rollers include at least four lower discharge rollers arranged at intervals in the sheet width direction,
The central exhaust port is disposed below a region between the two lower discharge rollers disposed at a distance from each other at a central portion in the sheet width direction,
The pair of side exhaust ports are disposed below a pair of the lower discharge rollers that are respectively disposed adjacent to the outer sides in the sheet width direction with respect to the two lower discharge rollers. The sheet stacking apparatus according to any one of 1 to 4 . The edges of the pair of side exhaust ports on the outer side in the sheet width direction are arranged at the same position in the sheet width direction as the edges of the pair of lower discharge rollers on the outer side in the sheet width direction,
The edge in the sheet width direction inside of a pair of the side exhaust ports is disposed on the inner side in the sheet width direction than the edge in the sheet width direction on the pair of lower discharge rollers. 5. The sheet stacking apparatus according to 5 . An image forming unit for forming an image on a sheet;
The sheet stacking apparatus according to any one of claims 1 to 6 ,
An image forming apparatus comprising:

Images