JP2007078917A - Sheet post processing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image of high photographic image quality without decreasing productivity regarding image formation. <P>SOLUTION: A sheet post processing apparatus 1b is installed on a downstream side of an image forming apparatus body 1a carrying out the image formation to a sheet. The sheet post processing apparatus 1b is provided with: a fixing and processing apparatus 26 pressurizing and heating again the sheet P with the image formed on it, transporting it on a fixing belt 34, and then cooling and peeling the sheet P from a fixing belt 34 by cooling it; a sheet cutting apparatus 27 carrying out cutting of the sheet P downstream of the fixing and processing apparatus 26; and a control means adjusting transporting speed of the sheet P. The control means makes control so that transporting speed v3 of the sheet P after being cooled and peeled, is faster than transporting speed v2 of the sheet P in the fixing and processing apparatus 26. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet post-processing apparatus that performs a quality-enhancing process such as a photographic image by performing a cutting process and a re-fixing process on an image-formed sheet, and an image forming apparatus using the same.

  In recent years, color copying, high quality, and miniaturization of copying machines and printers have rapidly progressed, and color image forming apparatuses such as color copying machines and color printers for public use have become widespread. On the other hand, with the widespread use of digital still cameras, there is a desire to hard copy video shot with digital still cameras using a color printer or the like.

  When taking a picture with a digital still camera and outputting the taken picture as a hard copy of photographic quality, it is desirable that the outputted picture is high gloss. However, in order to give gloss to the finished image, processing that is basically different from that of a color image such as a black-and-white image or a graphic formed by a commonly used image forming apparatus is required.

  In view of this, there is a device in which a device for outputting an image of high smoothness and high gloss photographic image quality is provided as a separate unit from the image forming device (see, for example, Patent Document 1). In addition, there is an image forming apparatus that cuts the edge portion of a sheet on which no image is formed, and discharges the image to a target size in order to make a photographic quality image a borderless image (see Patent Document 2).

JP-B-4-31393 JP2004-109860

  However, when the sheet is cut to a desired size, particularly when the sheet is cut in a direction perpendicular to the sheet conveyance direction, the conveyance of the sheet is temporarily stopped, the sheet is cut, and the sheet is conveyed again. It is necessary to repeat the operation. For this reason, when cutting sheets continuously, the sheet interval of the conveyed sheets is sufficiently set so that the next sheet does not overlap the sheet that has been stopped for cutting (see FIG. 4). It must be free (see FIG. 5). For this reason, there is a problem that the original productivity of the image forming apparatus is lowered.

  Further, in order to maintain the original productivity of the image forming apparatus, the sheet conveyance speed may be increased. However, if the sheet conveyance speed is too high in an apparatus that outputs an image with high smoothness and high gloss photo quality. The time for performing pressurization, heating and cooling in the apparatus is shortened. For this reason, there has been a problem that a sufficiently smooth and high gloss photographic image quality cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to obtain a high-quality photographic image without reducing productivity related to image formation.

  In order to achieve the above object, a typical configuration of the present invention is to pressurize a sheet on which an image has been formed again in a sheet post-processing apparatus disposed on the downstream side of an image forming apparatus main body that forms an image on a sheet. And a fixing processing device that heats, conveys the fixing belt, cools and separates from the fixing belt by cooling, and a sheet cutting device that cuts the stopped sheet downstream of the fixing processing device, Control means for adjusting the sheet conveyance speed, the control means so that the sheet conveyance speed after the cooling and peeling is faster than the sheet conveyance speed in the fixing processing apparatus. It is characterized by being controlled.

  The present invention also includes a fixing processing device that fixes an image on a sheet while conveying a sheet on which an image has been formed, a sheet cutting device that cuts a stopped sheet downstream of the fixing processing device, A sheet to be cut by the sheet cutting device is conveyed on the downstream side of the fixing processing apparatus, and when the sheet is cut by the sheet cutting apparatus, the sheet is stopped and at a speed faster than the sheet conveying speed in the fixing processing apparatus. And conveying means capable of conveying the sheet.

  As described above, since the sheet conveyance speed after the fixing processing apparatus is faster than the sheet conveyance speed in the fixing processing apparatus, productivity associated with image formation is not reduced. In addition, since the sheet conveyance speed in the fixing processing apparatus can be reduced, high-quality photographic image quality can be obtained.

  An embodiment of an image forming apparatus 1 including the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view schematically showing a schematic configuration of an image forming apparatus 1 of the present embodiment, and FIG. 2 is a cross-sectional view schematically showing a schematic configuration of a sheet post-processing apparatus 1b. In the description, after describing the schematic configuration of the image forming apparatus 1, the configuration and operation of the image forming apparatus main body 1a, the configuration and operation of the sheet post-processing apparatus 1b, and finally the operation and effect of the present invention will be described. To do.

(Schematic configuration of the image forming apparatus 1)
As shown in FIG. 1, the image forming apparatus 1 is configured by assembling a sheet post-processing apparatus 1b to an image forming apparatus main body 1a.

  In the image forming apparatus main body 1a, the image is read by the optical reading system 10, the image read by the developing device 3 is used as a toner image, the toner image is transferred to the conveyed sheet, and the toner image is fixed by the fixing device 15. . This forms a toner image on the sheet.

  On the other hand, the sheet post-processing device 1b temporarily holds the sheet on which the image is formed by the buffer device 25, re-fixes the sheet so as to obtain a high-gloss photographic image by the fixing processing device 26, and the sheet cutting device 27 performs the sheet fixing. The edge is cut to obtain an edgeless image. Thereby, in the sheet post-processing apparatus 1b, the post-processing is performed so that the image formed by the image forming apparatus main body 1a is a borderless photographic image.

  Next, the configuration of the image forming apparatus main body 1a and the sheet post-processing apparatus 1b will be described in detail.

(Configuration and operation of image forming apparatus main body 1a)
First, as shown in FIG. 1, an image forming apparatus main body 1a includes, from above, a document processing device 12 that conveys a document, an optical reading system 10 that reads image information of a document, and an image forming unit 9 that forms a toner image. A sheet feeding unit 13 for feeding the sheet P, and a fixing device 15 for fixing the toner image on the sheet P.

  The document processing device 12 and the optical reading system 10 read an image of a document. The document processing apparatus 12 includes a placement unit 12a for placing a document and a conveyance belt 12b. The optical reading system 10 includes a CCD 10a and a reading unit 10b.

  With this configuration, the document placed on the placement unit 12a passes over the reading unit 10b while being conveyed by the conveyance belt 12b. The CCD 10a transmits the image read in this process as digital information to the exposure unit 11 described later.

  The image forming unit 9 uses an image obtained by the CCD 10a as a toner image. As shown in FIG. 1, the image forming unit 9 is formed around an image carrier (hereinafter referred to as a drum 2) and the drum 2, and includes a developing device 3, a transfer unit 5, a cleaning device 6, a charge removing unit 7, a primary unit. A charger 8 and an exposure unit 11 are provided. As the image carrier, for example, a drum-shaped electrophotographic photosensitive member or a belt-shaped electrophotographic photosensitive member can be used.

  The sheet feeding unit 13 is a unit that feeds or re-feeds the sheet P to the transfer unit 5. On the upstream side of the transfer unit 5 in the sheet conveying direction, a feeding cassette 13a for stacking sheets P, a main body path 13b for conveying the sheets P, a manual tray 13c for feeding special sheets such as OHT and thick sheets to the image forming unit. Is disposed. Further, on the downstream side of the transfer unit 5 in the sheet conveyance direction, a refeed conveyance path 17 that guides a sheet to be refed, a reversal path 18 that reverses the sheet, and a duplex path 19 that conveys the reversed sheet to the developing device. Is placed.

  As a means for conveying the sheet in the sheet feeding unit 13, the registration roller 20 that conveys the sheet P to the drum 2, the inner discharge roller 21 that conveys the fixed sheet P, and the sheet P to the sheet discharge unit 16. And an outer discharge roller 22 for conveying. A discharge unit flapper 23 that switches the sheet conveyance path between the sheet discharge unit 16 and the refeed conveyance path 17 is disposed immediately downstream of the fixing device 15 and upstream of the sheet discharge unit 16.

  With this configuration, when a toner image is formed on the drum 2, the drum 2 is first uniformly charged by the primary charger 8. Next, the exposure unit 11 exposes image information from the optical reading system 10 onto the drum 2 to form an electrostatic latent image. The developing device 3 supplies developer to the electrostatic latent image (the developer in the present embodiment is a two-component magnetic toner), whereby the electrostatic latent image is visualized as a toner image.

  The remaining developer and other deposits adhere to the drum 2 and are removed by the cleaning device 6. Further, since charges remain on the drum 2, the charge remaining on the drum 2 is discharged by the charge removing unit 7. In this way, the operation of charging the drum 2 uniformly by the primary charger 8 is repeated again.

  On the other hand, from the sheet feeding unit 13, the sheets P stacked and stored in the feeding cassette 13a or the tray 13c pass through the main body path 13b and are conveyed to the registration rollers 20. The registration roller 20 sends out the sheet P in synchronization with the image formation timing.

  Then, the toner image on the drum 2 is transferred by the transfer unit 5 to the sheet P fed from the sheet feeding unit 13 in this way. The transferred toner image is heated and pressurized by the fixing device 15 and fixed to the sheet P.

  Thereafter, the sheet P is normally conveyed to the sheet discharge unit 16 by the inner discharge roller 21 and the outer discharge roller 22. On the other hand, when an image is formed on both sides and only one side is formed, the sheet P is guided by the discharge unit flapper 23 in the direction of the refeed conveyance path 17, the reversing path 18, the double-sided path 19, and the like. . Thereby, image formation is performed also on the back surface.

(Configuration and operation of sheet post-processing apparatus 1b)
In the sheet post-processing apparatus 1b, post-processing is performed using the buffer device 25, the fixing processing device 26, and the sheet cutting device 27 so that the image formed in the image forming apparatus main body 1a is a borderless photographic image. Next, this will be described in detail.

  The buffer device 25 includes a plurality of conveying rollers 28, a guide unit 29 that guides the sheet, and a sheet detection sensor 30 that detects the sheet.

  The fixing processing device 26 includes a fixing roller 31, a peeling roller 32 disposed on the downstream side of the fixing roller 31, and a stretching roller 33 below the peeling roller 32. A fixing belt 34 is stretched around these three rollers. A pressure roller 36 is disposed at a position facing the fixing roller 31 with the fixing belt 34 interposed therebetween. The fixing roller 31 and the pressure roller 36 are pressed against each other to form the nip portion 35. Further, a cooling device 37 for cooling the fixing belt is provided on the downstream side of the fixing roller 31 in the direction of arrow C in which the fixing belt 34 circulates and on the upstream side of the peeling roller 32. Next, each means will be specifically described.

  As the fixing roller 31, a metal core 31b having a built-in heating halogen lamp 31a covered with an elastic body layer such as silicone rubber and further a release layer may be used. . However, it is not limited to this. In addition, aluminum or SUS can be used for the metal core 31b from the viewpoint of thermal conductivity, strength, and the like.

  In the pressure roller 36, a metal core bar 36b in which a halogen lamp 36a for heating is built is covered with an elastic body layer and a release layer.

  The peeling roller 32 is preferably made of metal. In view of peeling the sheet P from the fixing belt 34, a cylindrical member is desirable. However, the present invention is not limited to this. That is, as long as the running performance of the fixing belt 34 is not hindered, it is not necessary to be a rotating body, and for example, a fixing member may be used.

  The cooling device 37 is called a heat sink, and is formed of a box-shaped member having metal fins with good thermal conductivity inside. An auxiliary member that presses from the opposite side of the surface where the fixing belt 34 contacts the cooling device 37 may be provided. With this configuration, the adhesion between the cooling device 37 and the fixing belt 34 can be improved. Instead of the heat sink, a heat pipe type cooling device that exchanges heat by flowing water or the like, or a water cooling type cooling device in which cooling water circulates between the heat exchanger may be used.

  The sheet cutting device 27 is disposed downstream of the fixing processing device 26 in the sheet conveying direction. A straight blade cutting unit (first cutting means) 38 that cuts the sheet P in a direction orthogonal to the conveyance direction of the sheet P, and a sheet P in a direction parallel to the conveyance direction of the sheet P downstream of the linear blade cutting unit 38. And a round blade cutting part (second cutting means) 39 for cutting. Further, below the straight blade cutting part 38 and the round blade cutting part 39, there is a chip storage box 43 for storing chips. Next, each means will be specifically described.

  The straight blade cutting part 38 is composed of a movable blade 40 and a fixed blade 41.

  The movable blade 40 includes a cutting blade 40a and a cutting blade 40b. The fixed blade 41 is disposed so as to contact the cutting blades on both sides of the movable blade 40. The movable blade 40 repeats approaching and separating from the fixed blade 41 by driving means (not shown).

  The round blade cutting part 39 is composed of a plurality of rotary cutters 42.

  The rotary cutter 42 is disposed so as to cut the sheet in a conveying direction at a predetermined position. A chip guide portion 42a is disposed downstream of the rotary cutter 42 in the transport direction. The chip guide part 42a guides the chips so that the chips cut by the rotary cutter 42 are dropped downward.

  A chip storage box 43 for storing chips is installed below the straight blade cutting section 38 and the round blade cutting section 39.

  Further, the sheet cutting device 27 is provided with rollers for conveying a plurality of sheets. A registration roller 44 that corrects the skew of the sheet is disposed upstream of the straight blade cutting unit 38 in the conveyance direction, and a conveyance roller 45 is disposed between the linear blade cutting unit 38 and the round blade cutting unit 39 to convey the round blade cutting unit. A discharge roller 46 for discharging the sheet is disposed on the downstream side in the direction. Further, a conveyance roller 47 is disposed on the upstream side of the registration roller 44 in the conveyance direction.

  The sheet cutting device 27 is provided with sensors for detecting a plurality of sheets. A sheet detection sensor 48 for detecting the sheet is arranged on the upstream side in the conveyance direction of the registration roller 44, and a sheet leading edge detection sensor 49 for detecting the leading edge of the conveyed sheet is arranged on the downstream side in the conveyance direction of the registration roller 44. Has been.

  In addition, the sheet cutting device 27 is provided with a discharge tray 50 on which the sheets P that have undergone re-fixing and cutting processing are stacked downstream of the discharge roller 46 in the conveying direction. Further, a sheet rear end detection sensor 52 that detects that the belt has been completely cooled and separated from the fixing belt 34 of the belt fixing device, and a guide plate 51 that guides the sheet to each roller are provided.

  In the sheet cutting device 27, the distance between the sheet separation position of the peeling roller 32 of the fixing processing device 26 and the sheet cutting position in the linear blade cutting unit 38 of the sheet cutting device 27 is larger than the maximum length in the conveyance direction of the sheet P to be conveyed. It is arranged to be long.

  With the above configuration, the sheet post-processing apparatus 1b shown in FIG. 2 operates as follows. FIG. 3 shows a relationship between the time and the position of the sheet P in the present embodiment. Note that a driving unit that drives each unit and a control unit that controls the driving unit control the conveyance speed of the sheet P by a control unit (not shown) provided in the sheet post-processing apparatus 1b. Specifically, based on the detection result of the sheet detection means sensor 48, the drive of the conveyance means composed of the registration roller 44, the conveyance roller 47, the discharge roller 46, etc., the operation of the movable blade 40, the rotary cutter 42, etc. The control means controls. This control means also controls the operations of the buffer device 25 and the fixing processing device 26. Note that a control unit for controlling the sheet post-processing apparatus 1b as described above may be provided in the image forming apparatus main body 1a.

  The sheet P on which an image is formed by the image forming apparatus main body 1 a is conveyed from the discharge unit 16 to the buffer device 25. Here, the conveyance speed at which the sheet P is conveyed from the image forming apparatus main body 1a is v1. When the sheet detection sensor 30 of the buffer device 25 detects the sheet, the conveyance roller 28 stops rotating. For this reason, the conveyance of the sheet P is stopped.

  After a predetermined time, the transport roller 28 rotates again. At this time, the transport roller 28 transports the sheet at a transport speed v2 that is slower than the transport speed v1. Then, the sheet is conveyed into the fixing processing device 26.

  The sheet P conveys a multi-color toner image toward the fixing belt 34 and is sandwiched between nip portions 35 of the fixing roller 31 and the pressure roller 36. In the nip portion 35, the toner image on the sheet P is heated and melted, and the molten toner image is pressurized. Thereafter, the sheet P is conveyed while being in close contact with the fixing belt 34, and a plurality of color toner images are cooled and solidified by the cooling device 37. Then, the sheet P is peeled from the fixing belt 34 by the peeling roller 32 using the waist.

  In this way, the sheet P that has passed through the nip portion 35 is conveyed while being in close contact with the fixing belt 34. As described above, since the heating time can be extended on the fixing belt 34, the multi-color toner image can be sufficiently melted, and the smoothness can be ensured by being brought into close contact with the belt surface. The sheet P heated for a predetermined time is cooled by the cooling device 37 from the back side of the fixing belt 34 to solidify the multi-color toner image, and then peeled off by the peeling roller 32. For this reason, it can peel, maintaining high glossiness.

  The sheet P that has been re-fixed by the fixing processing device 26 and has been given glossiness and smoothness is conveyed to the sheet cutting device 27.

  When the sheet detection sensor 48 detects the sheet, the sheet P is conveyed by a predetermined distance so as to form a loop by the registration rollers 44, and the conveyance of the sheet is temporarily stopped. The sheet is conveyed again at the conveyance speed v2 while maintaining the alignment.

  When the sheet leading edge detection sensor 49 detects the leading edge of the sheet P, the sheet P is conveyed by a predetermined distance according to the size to be cut. Note that the subsequent transport speeds are all transport speeds v3 that are faster than the transport speed v2. Thereafter, the conveyance of the sheet P is stopped.

  When the sheet P stops, the movable blade 40 contacts and separates from the fixed blade 41 in the straight blade cutting portion 38. Thereby, the sheet P is cut at a predetermined position in a direction orthogonal to the sheet conveying direction. Further, the sheet is conveyed again for a predetermined distance in accordance with the size for cutting the sheet, and the conveyance is stopped and cut. The sheet cutting device 27 repeats this sheet cutting operation once or a plurality of times. FIG. 3 shows an example in which the cutting operation is performed three times.

  When the sheet cutting operation in the straight blade cutting unit 38 is completed, the sheet P is conveyed to the round blade cutting unit 39 by the conveying roller 45. The sheet P is cut in a direction parallel to the sheet conveying direction by a rotary cutter 42 arranged in accordance with the size to be cut by the round blade cutting unit 39.

  The cut sheet P is discharged out of the apparatus by the discharge roller 46 and stacked on the discharge tray 50. At this time, after stopping at the registration roller 44, the transport speed v3 when transported again is faster than the transport speed v2 at the fixing processing device 26.

  In the present embodiment, a linear blade cutting unit having a movable blade 40 moving in the vertical direction and a fixed blade 41 is used as a cutting means arranged in a direction orthogonal to the sheet conveying direction and cut. However, it is not limited to this. As a cutting unit that cuts a sheet in a direction orthogonal to the sheet conveyance direction, for example, a rotary cutter may reciprocate in a direction orthogonal to the sheet conveyance direction to cut the sheet.

  In this embodiment, the sheet conveyance speed is increased from v2 to v3 before and after the registration roller 44, but the position where the sheet conveyance speed is increased is not limited to this. Any position where the trailing edge of the sheet is not on the fixing belt 34 may be used. That is, the sheet conveyance speed may be increased after the trailing edge of the sheet passes the cooling separation position of the belt fixing device. For example, by using the sheet trailing edge detection sensor 52 in FIG. 2, the trailing edge of the conveyed sheet is cooled and peeled off, and the sheet trailing edge detection sensor 52 detects the sheet trailing edge to increase the sheet conveyance speed. May be. Alternatively, the sheet may be conveyed at a speed v2 before being cut by the movable blade 40 and the fixed blade 41, and may be controlled to increase the sheet conveyance speed after being cut by the movable blade 40 and the fixed blade 41. In this case, not only the leading end side of the cut sheet but also the trailing end side is conveyed at a speed higher than the speed v2.

  When the sheet cutting operation is performed only once, the position where the sheet conveyance speed is increased must be upstream of the sheet cutting position in the sheet conveyance direction. That is, when the sheet cutting operation is performed only once, the sheet gap does not increase even if the sheet conveying speed is increased after the sheet cutting. For this reason, it does not contribute to the improvement of productivity.

(Operation and effect of the present invention)
The following operations and effects can be obtained by the above configuration and operation.

  In the present embodiment, the sheet conveyance speed v2 in the fixing device 26 is slower than the sheet conveyance speed v1 in the buffer device 25. However, since the sheet conveying speed v3 in the sheet cutting device 27 is sufficiently faster than the sheet conveying speed v2, as shown in FIG. 3, it is not necessary to reduce the conveying speed in order to increase the sheet interval. For this reason, the original productivity of the image forming apparatus main body 1a is not lowered.

  In the present embodiment, the buffer device 25 is mounted, and the conveyance speed v2 in the fixing processing apparatus can be sufficiently slowed without reducing the productivity of the image forming apparatus main body 1a. For this reason, heating, pressurization, and cooling of the sheet in the fixing processing device 26 can be performed slowly. As a result, high smoothness and high gloss on the surface of the sheet P can be further achieved.

  Further, in the present embodiment, the sheet cutting device 27 is configured such that the distance between the sheet separation position of the peeling roller 32 of the fixing processing device 26 and the sheet cutting position of the linear blade cutting unit 38 of the sheet cutting device 27 is It is arranged to be longer than the maximum length in the transport direction. Thus, even if the sheet stops at the straight blade cutting unit 38 in order to cut the leading edge of the sheet, the trailing edge of the sheet passes the sheet separation position of the peeling roller 32 of the fixing processing device 26. For this reason, the trailing edge of the sheet does not stop conveying on the belt 34 of the fixing processing device 26, and the high smoothness and high glossiness of the sheet are not partially impaired.

  In this embodiment, the sheet post-processing apparatus 1b is detachable from the image forming apparatus main body 1a. However, the present invention is not limited to this. For example, the functions of the sheet post-processing apparatus 1b may be integrated into the image forming apparatus main body 1a.

1 is a cross-sectional view schematically showing a schematic configuration of an image forming apparatus 1 according to an embodiment. Sectional drawing which showed typically schematic structure of the sheet | seat post-processing apparatus 1b. The figure which shows the relationship between time and the position of the sheet | seat P in this embodiment. The figure which shows the relationship between the time in the past, and the position of a sheet | seat. The figure which shows the relationship between the time in the past, and the position of a sheet | seat.

Explanation of symbols

P ... sheet, 1 ... image forming apparatus, 1a ... image forming apparatus main body, 1b ... sheet post-processing apparatus, 2 ... drum (image carrier), 15 ... fixing device, 16 ... sheet discharge section, 22 ... outer discharge roller, 25 ... Buffer device, 26 ... Fixing processing device, 27 ... Sheet cutting device, 28 ... Conveying roller, 29 ... Guide unit, 32 ... Peeling roller, 34 ... Fixing belt, 37 ... Cooling device, 38 ... Straight blade cutting unit, 39 ... round blade cutting part, 40 ... movable blade, 40a ... cutting blade, 40b ... cutting blade, 41 ... fixed blade, 42 ... rotary cutter, 44 ... registration roller, 45 ... transport roller, 47 ... transport roller, 48 ... sheet detection Sensor, 49 ... sheet leading edge detection sensor, 50 ... discharge tray, 52 ... sheet trailing edge detection sensor

Claims (11)

In the sheet post-processing apparatus disposed on the downstream side of the image forming apparatus main body that performs image formation on the sheet,
A fixing processing device that pressurizes and heats the image-formed sheet again, conveys the sheet on the fixing belt, and cools and separates the sheet from the fixing belt by cooling;
A sheet cutting device for cutting the sheet in a stopped state downstream of the fixing processing device;
Control means for adjusting the sheet conveyance speed,
The sheet post-processing apparatus is characterized in that the control means controls the sheet conveying speed after the cooling separation to be higher than the sheet conveying speed in the fixing processing apparatus.   2. The sheet post-processing apparatus according to claim 1, wherein the predetermined position at which the sheet conveyance speed is increased after the sheet is cooled and peeled is upstream of the cutting position of the sheet cutting apparatus in the conveyance direction. . A roller for aligning the sheet upstream of the sheet cutting device in the sheet conveying direction;
The sheet post-processing apparatus according to claim 1, wherein the control unit increases a sheet conveyance speed at the position of the roller. The sheet cutting device has a fixed blade and a movable blade disposed in a direction orthogonal to the sheet conveying direction,
The sheet post-processing apparatus according to any one of claims 1 to 3, wherein the sheet is cut one by one by the fixed blade and the movable blade while the sheet is stopped.   The sheet cutting by the fixed blade and the movable blade is performed at a plurality of locations on one sheet, and the sheet is stopped every time the sheet is cut by the fixed blade and the movable blade. Sheet post-processing device.   4. The sheet post-processing apparatus according to claim 1, wherein the sheet cutting device is a rotary cutter that reciprocates in a direction orthogonal to a sheet conveyance direction. 5.   The sheet cutting device includes: a first cutting unit that cuts a sheet in a direction orthogonal to the sheet conveyance direction; and a second cutting unit that cuts the sheet in a direction parallel to the sheet conveyance direction. The sheet post-processing apparatus according to any one of claims 1 to 6,   The sheet post-processing apparatus according to claim 7, wherein the second cutting unit is disposed downstream of the first cutting unit in the sheet conveyance direction. A buffer device between the image forming apparatus main body and the fixing processing apparatus;
9. The control unit according to claim 1, wherein the control unit controls a sheet conveyance speed in the buffer device to be slower than a sheet conveyance speed in the fixing processing apparatus. Sheet post-processing device. A fixing device that fixes an image on the sheet while conveying the image-formed sheet;
A sheet cutting device for cutting the sheet in a stopped state downstream of the fixing processing device;
A sheet to be cut by the sheet cutting device is conveyed on the downstream side of the fixing processing apparatus, and when the sheet is cut by the sheet cutting apparatus, the sheet is stopped and at a speed faster than the sheet conveying speed in the fixing processing apparatus. A sheet post-processing apparatus, comprising: a conveying unit capable of conveying the sheet. In an image forming apparatus having an image forming apparatus main body for performing image formation and a sheet post-processing apparatus disposed on the downstream side of the image forming apparatus main body,
The image forming apparatus according to claim 1, wherein the sheet post-processing apparatus is the sheet post-processing apparatus according to claim 1.

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