JP7651882B2 - Sheet stacking device and post-processing device - Google Patents

Description

The present invention relates to a sheet stacking device that stacks discharged sheets and a post-processing device.

Sheet stacking devices are known that stack sheets on which an image has been formed by an image forming device. The sheet stacking device includes, for example, a discharge section (such as a pair of discharge rollers) that discharges sheets, a stacking tray on which the discharged sheets are stacked, and a lifting mechanism that raises and lowers the stacking tray depending on the amount of stacked sheets. Also known is a post-processing device that includes a post-processing section that performs post-processing on sheets on which an image has been formed, and the above-mentioned sheet stacking device that stacks the sheets on which the post-processing has been performed.

In such sheet stacking devices, the top surface of the stacking tray is located lower than the discharge section, so the leading edge of the discharged sheet may droop. In such cases, the sheet may fall onto the stacking tray in a curled state, or the leading edge of the sheet may collide with the stacking tray, causing problems with the discharge and stacking of the sheet. Therefore, it has been proposed to provide a guide member that protrudes in the discharge direction below the discharged sheet (for example, Patent Documents 1 to 4).

JP 2019-147673 A JP 2019-127355 A JP 2000-289909 A JP 2005-263475 A

However, with the inkjet method, the sheet may be transported in a wet state. In that case, it is conceivable that the paper rubs against the guide member, causing the ink to adhere to the guide member. Furthermore, when a highly wettable sheet is used, the frictional resistance is large, so the ink is more likely to adhere to the guide member. This also increases the load during transport.

In consideration of the above circumstances, the present invention aims to provide a sheet stacking device and post-processing device that can reduce friction between a guide member that protrudes in the discharge direction and a sheet.

In order to solve the above problems, the sheet stacking device of the present invention includes a discharge section that discharges sheets, a loading tray on which the sheets discharged by the discharge section are loaded, a blower section that blows air, a guide member that protrudes to a protruding position above the loading tray when the sheets are discharged and contacts the underside of the sheets to guide the discharge of the sheets and retracts to a retracted position upstream of the protruding position in the discharge direction at a predetermined timing, and a control section that controls the movement of the guide member and the blowing of air from the blower section, the guide member having a built-in air duct connected to the blower section and an air outlet that opens on the upper surface and allows air to flow through the air duct, and the control section blows the air toward the underside of the sheets while the sheets are being discharged.

The sheet stacking device may include a detection unit that detects the sheet upstream of the discharge unit in the discharge direction, and the control unit may be configured to control the guide member so that the leading edge of the sheet protrudes to the protruding position at the timing when the leading edge of the sheet is detected by the detection unit.

The control unit may control the blower unit to start blowing air when the leading edge of the sheet is detected by the detection unit.

The control unit may control the guide member to retract to the retracted position when the trailing end of the sheet is detected by the detection unit.

The control unit may control the air blowing unit to stop blowing air when the rear end of the sheet is detected by the detection unit.

The control unit may control the blowing unit to blow air only when the number of sheets discharged by the discharge unit at one time is less than a predetermined number.

The post-processing device according to the present invention is characterized by comprising a post-processing section that performs one or more of the following post-processing processes on the sheet on which an image has been formed: stapling, shifting, and center folding; and a sheet stacking device that stacks the sheet on the stacking tray after the post-processing process has been performed by the post-processing section.

According to the present invention, it is possible to reduce friction between the guide member protruding in the discharge direction and the sheet.

1 is a perspective view showing an external appearance of an image forming system according to an embodiment of the present invention; 1 is a front view showing a schematic internal configuration of a post-processing device according to an embodiment of the present invention; FIG. 2 is a perspective view of a lifting mechanism according to an embodiment of the present invention. 1 is a front view showing a schematic configuration of a sheet stacking device according to an embodiment of the present invention; 1 is a perspective view of a sheet stacking device according to an embodiment of the present invention; 1 is a front view showing a schematic configuration of a sheet stacking device according to an embodiment of the present invention; 1 is a perspective view of a sheet stacking device according to an embodiment of the present invention; 1 is a block diagram showing an electrical configuration of an image forming system according to an embodiment of the present invention. 5 is a flowchart of sheet stacking control according to an embodiment of the present invention.

Below, we will explain an image forming system 100 according to one embodiment of the present invention with reference to the drawings.

First, the overall configuration of image forming system 100 will be described. Figure 1 is a perspective view showing the external appearance of image forming system 100. In the following description, the Fr side in Figure 1 is the front side (front side) of image forming system 100, and the left and right directions will be described based on the direction when image forming system 100 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr respectively indicate top, bottom, left, right, front, and back.

The image forming system 100 includes an image forming device 1 and a post-processing device 110. The image forming device 1 is, for example, a multifunction device including a printer, a scanner, and a document transport device. The document transport device transports a document along a transport path that passes through the reading position of the scanner. The scanner is a flatbed type image scanner that reads a document and generates image data. The printer forms an image on a sheet using an inkjet method, an electrophotographic method, or the like. The post-processing device 110 performs post-processing on the sheet transported from the printer and discharges it.

Next, the configuration of the post-processing device 110 will be described (see Figs. 1 and 2). Fig. 2 is a front view showing a schematic internal configuration of the post-processing device 110. The post-processing device 110 has a roughly rectangular parallelepiped housing 21. An inlet 22 is provided at the top of the right side plate of the housing 21 to receive sheets transported from the image forming device 1.

The left side plate of the housing 21 is provided with a recess 23 recessed to the right. When viewed from the left, the recess 23 is generally rectangular with a long side along the up-down direction and a short side along the front-rear direction. The recess 23 includes a bottom 23B formed to the right of the left side plate, front and rear side walls 23S formed between the front and rear ends of the bottom 23B and the left side plate, an upper wall 23U formed between the upper end of the bottom 23B and the left side plate, and a lower wall 23L formed between the lower end of the bottom 23B and the left side plate.

A discharge section 31 for discharging sheets is provided above the recess 23. A sheet stacking device 120, which will be described later, is provided below the discharge section 31. An upper discharge section 44 is provided on the top plate of the housing 21. A transport path 41 is provided inside the housing 21, which runs from the receiving opening 22 to the discharge section 31, and a branch path 42 is provided that branches off from the transport path 41 and leads to the upper discharge section 44. A transport roller 43 is provided on the transport path 41.

The upper discharge section 44 is equipped with discharge rollers and a discharge port. A fixed-position loading tray 45 is provided to the left of the upper discharge section 44.

The discharge section 31 includes a discharge opening 32 and a discharge roller 33 provided to the right of the discharge opening 32. The discharge roller 33 includes a drive roller 33D driven by a motor (not shown) and a driven roller 33N that follows the drive roller 33D. The drive roller 33D can be pressed against and separated from the driven roller 33N.

Below the conveying path 41, a processing tray 51 (an example of a post-processing section) and a stapler 54 (an example of a post-processing section) are provided. The processing tray 51 is provided so as to incline downward from the discharge port 32 to the right, and a sheet stack to be stapled by the stapler 54 is stacked on it. The left end of the processing tray 51 rotatably supports the driven roller 33N of the discharge roller 33. The stapler 54 is provided to the right of the processing tray 51, and staples the right end of the sheet stack stacked on the processing tray 51 (stapling process). The post-processing section 110 may also be provided with a center-folding device (an example of a post-processing section) that folds sheets in the middle (not shown).

The processing tray 51 is provided with a pair of side fences 52 facing each other in the front-rear direction. The pair of side fences 52 are movable along the sheet width direction (the direction intersecting the discharge direction Y). The pair of side fences 52 move synchronously in a direction approaching each other, thereby aligning the sheets on the processing tray 51 in the width direction. The pair of side fences 52 also move together in the width direction to move the sheet stack in the width direction (shift processing). A sheet receiving plate 53 is provided at the right end of the processing tray 51. The right end of the sheet stack loaded on the processing tray 51 abuts against the sheet receiving plate 53, thereby aligning the sheets in the discharge direction Y.

[Sheet stacking device]
Next, a description will be given of the configuration of the sheet stacking device 120. Fig. 3 is a perspective view of the lifting mechanism 63. Figs. 4 and 6 are front views that typically show the configuration of the sheet stacking device 120. Figs. 5 and 7 are perspective views of the sheet stacking device 120.

The sheet stacking device 120 includes a discharge section 31 that discharges sheets, a stacking tray 61 on which the sheets discharged by the discharge section 31 are stacked, an air blowing section 91 that blows air, a guide member 81 that protrudes to a protruding position P2 above the stacking tray 61 when the sheets are discharged and contacts the underside of the sheets to guide the discharge of the sheets and retracts to a retracted position P1 upstream of the protruding position P2 in the discharge direction at a predetermined timing, and a control section 2 that controls the movement of the guide member 81 and the blowing of air by the air blowing section 91. The guide member 81 has an air duct 93 connected to the air blowing section 91 built in, and has an air outlet 81U that opens on the top surface and flows through the air duct 93. The control section 2 blows air toward the underside of the sheets while the sheets are being discharged.

[Loading tray]
The top surface of the stacking tray 61 is inclined upward toward the downstream side in the sheet discharge direction Y. The stacking tray 61 is provided to the left of the recess 23. Brackets 62 that connect the stacking tray 61 to a belt 66 (described later) are provided at the right end portions of the front and rear side surfaces of the stacking tray 61 (see FIG. 3). Slits (not shown) are formed in the vertical direction at locations of the bottom 23B or side wall 23S of the recess 23 that correspond to the brackets 62, and the brackets 62 pass through the slits.

[Lifting mechanism]
The lifting mechanism 63 (see FIG. 3) includes a drive shaft 64, a driven shaft 65 provided below the drive shaft 64, and a belt 66 provided at two locations, front and rear. The lifting mechanism 63 is provided to the right of the recess 23. Sprockets 64S are provided at two locations, front and rear, of the drive shaft 64, and a drive gear 64G is provided at one end of the drive shaft 64. A driving force is transmitted to the drive gear 64G via a motor and a reduction gear train (not shown). Sprockets 65S are provided at two locations on the driven shaft 65 corresponding to the sprocket 64S of the drive shaft 64. An endless belt 66 with teeth formed on the inner peripheral surface is wound around the sprocket 64S of the drive shaft 64 and the sprocket 65S of the driven shaft 65. A bracket 62 of the stacking tray 61 is fixed to the outer peripheral surface of the belt 66. When a driving force is transmitted to the driving gear 64G, the front and rear belts 66 circulate in the same direction in synchronization, and the loading tray 61 moves up and down as the belts 66 move.

[Upper surface detection section]
An upper surface detection unit 68 is provided on the upper part of the recess 23 of the housing 21 (see FIG. 2). The upper surface detection unit 68 is, for example, a transmission type, a reflection type, or other optical sensor. In the case of the transmission type, a light emitting unit is provided on one of the side walls 23S at the front or rear of the recess 23, and a light receiving unit is provided on the other side wall 23S (not shown). In the case of the reflection type, a light emitting unit and a light receiving unit are provided on one side wall 23S, and a reflector is provided on the other side wall 23S (not shown). In either type, when the height of the upper surface of the stacked sheets (the upper surface of the uppermost sheet) is equal to or higher than the height of the light path of the light emitting unit, the light is blocked by the sheet, and the light receiving unit cannot receive the light. In this case, the upper surface detection unit 68 outputs a first level signal (hereinafter referred to as a light blocking signal). On the other hand, when the height of the upper surface of the stacked sheets is lower than the height of the light path of the light emitting unit, the light is not blocked by the sheet, and the light receiving unit receives the light. In this case, the upper surface detector 68 outputs a second level signal (hereinafter referred to as a light receiving signal).

[Guide member]
The guide member 81 (see FIG. 4) is a cylindrical member having a hollow structure curved in an upwardly convex arc. The cross section perpendicular to the longitudinal direction of the guide member 81 is rectangular. The end of the guide member 81 on the downstream side in the discharge direction Y is closed and formed in a tapered shape. The guide member 81 is provided at two locations in the width direction intersecting with the discharge direction Y (see FIG. 5). The housing 21 is provided with a casing 82 in which the upstream side part of the guide member 81 in the discharge direction Y is accommodated. The guide member 81 is movable between a retracted position P1 (see FIGS. 4 and 5) accommodated in the casing 82 and a protruding position P2 (see FIGS. 6 and 7) protruding above the stacking tray 61. The movements of the two guide members 81 are synchronized. At the protruding position P2, a gap is formed between the end of the guide member 81 on the downstream side in the discharge direction Y and the upper surface of the stacking tray 61.

Rack teeth 81R are formed on the underside of the guide member 81 along the longitudinal direction of the guide member 81. The guide drive unit 84 has a pinion gear 85 that meshes with the rack teeth 81R, a motor 86, and a transmission mechanism 87 that transmits the rotation of the motor 86 to the pinion gear 85. The motor 86 is a stepping motor.

At the retracted position P1, the guide member 81 is placed on the inner surface of the casing 82 and the pinion gear 85 (see FIG. 4). When the pinion gear 85 rotates counterclockwise in FIG. 6 by the drive of the motor 86, the guide member 81 protrudes from the retracted position P1 toward the protruding position P2 (see FIG. 6). A roller 88 having a smaller diameter than the driven roller 33N is provided on the rotation shaft of the driven roller 33N of the discharge roller 33. When the guide member 81 protrudes from the retracted position P1 toward the protruding position P2, the lower surface of the guide member 81 is guided by the roller 88, and at the protruding position P2, the guide member 81 is placed on the pinion gear 85 and the roller 88. When the pinion gear 85 rotates clockwise, the guide member 81 retracts from the protruding position P2 toward the retracted position P1.

The retraction detection unit 75 is, for example, a photointerrupter, and detects the guide member 81 when the guide member 81 blocks the optical path when the guide member 81 is located at the retraction position P1. The retraction position P1 is the home position of the guide member 81.

[Blower section]
A blower 91 is provided at the lower right of the casing 82 (see FIG. 4). The blower 91 includes a blower 92 and an air duct 93. The blower 92 is, for example, a centrifugal fan, an axial fan, or the like. An opening 82A is provided at the right end of the casing 82. An opening 81A is provided at the right end of the guide member 81. The air duct 93 is a tube with a smaller diameter than the hollow portion of the guide member 81, and is inserted into the inside of the guide member 81 through the opening 82A of the casing 82 and the opening 81A of the guide member 81. The right end of the air duct 93 is connected to the blower 92. The length of the air duct 93 is determined so that the left end of the air duct 93 is located inside the guide member 81 even when the guide member 81 moves to the protruding position P2. One or more blower openings 81U are provided on the upper surface of the guide member 81. The position of the air blowing port 81U is determined so that the air blowing port 81U is located downstream of the discharge rollers 33 in the discharge direction Y when the guide member 81 is located at the protruding position P2.

[Sheet detection unit]
A sheet detection unit 76 is provided upstream of the conveyance roller 43 in the discharge direction Y (see FIG. 4). The sheet detection unit 76 is, for example, a transmissive or reflective optical sensor. When the sheet passes the position of the sheet detection unit 76, the sheet blocks light, so that the sheet detection unit 76 outputs a first level signal (hereinafter, referred to as a light-blocking signal). On the other hand, when the sheet does not pass the position of the sheet detection unit 76, the sheet does not block light, so that the sheet detection unit 76 outputs a second level signal (hereinafter, referred to as a light-receiving signal). When the leading end of the sheet (the end on the downstream side in the discharge direction Y) passes the position of the sheet detection unit 76, the light-receiving signal is switched to a light-blocking signal. On the other hand, when the trailing end of the sheet (the end on the upstream side in the discharge direction Y) passes the position of the sheet detection unit 76, the light-blocking signal is switched to a light-receiving signal.

[Electrical configuration]
8 is a block diagram showing an electrical configuration of the image forming system 100. The image forming apparatus 1 is provided with a control unit 2. The control unit 2 includes a calculation unit 2P and a storage unit 2M. The calculation unit 2P is, for example, a central processing unit (CPU). The storage unit 2M includes storage media such as a read only memory (ROM), a random access memory (RAM), and an electrically erasable programmable read only memory (EEPROM). The calculation unit 2P performs various processes by reading and executing a control program stored in the storage unit 2M. The control unit 2 may be realized by an integrated circuit that does not use software.

The control unit 2 is connected to the top surface detection unit 68, the sheet detection unit 76, the lifting mechanism 63, the guide drive unit 84, the air blower unit 91, and the operation unit 19. The operation unit 19 is provided at the top of the front side of the image forming device 1 (see FIG. 1). The operation unit 19 includes a display panel, a touch panel superimposed on the display surface of the display panel, and a keypad adjacent to the display panel (not shown). The control unit 2 displays a screen showing the operation menu of the image forming device 1 and the post-processing device 110 on the display panel, and controls each part of the image forming device 1 and the post-processing device 110 in response to the operations detected by the touch panel and the keypad.

Next, the operation of the sheet stacking device 120 will be described. FIG. 9 is a flow diagram of sheet stacking control. When the image forming system 100 is powered on, the control unit 2 executes sheet stacking control according to the flow diagram of FIG. 6.

First, the control unit 2 determines whether a print job has been started (step S01). If it is determined that a print job has not been started (step S01: NO), the control unit 2 repeats the process of step S01. On the other hand, if it is determined that a print job has been started (step S01: YES), the control unit 2 determines whether the leading edge of the sheet has been detected by the sheet detection unit 76. If it is determined that the leading edge of the sheet has not been detected (step S03: NO), the control unit 2 repeats the process of step S03. On the other hand, if it is determined that the leading edge of the sheet has been detected (step S03: YES), the control unit 2 drives the discharge rollers 33 of the discharge unit 31 (step S05).

Next, the control unit 2 determines whether the discharge unit 31 discharges one sheet at a time (step S07). If it determines that the discharge unit 31 discharges one sheet at a time (step S07: YES), the control unit 2 causes the blower 91 to start blowing air (step S09) and causes the guide member 81 to protrude to the protruding position P2 (step S11).

Specifically, the control unit 27 drives the motor 86 of the guide drive unit 84, and drives the motor 86 a predetermined number of pulses after the retraction detection unit 75 no longer detects the guide member 81, causing the guide member 81 to protrude from the retracted position P1 to the protruding position P2 (see Figs. 6 and 7). The control unit 2 presses the drive roller 33D of the discharge roller 33 against the driven roller 33N, causing the drive roller 33D to rotate in the clockwise direction in Fig. 6. The first sheet is transported along the top surface of the guide member 81 by the transport roller 43 and the discharge roller 33.

Next, the control unit 2 determines whether the rear end of the sheet has been detected by the sheet detection unit 76 (step S13). If it is determined that the rear end of the sheet has been detected, the control unit 2 causes the air blowing unit 91 to stop blowing air and causes the guide member 81 to retreat to the retreat position P1.

Next, the control unit 2 determines whether the print job has ended (step S15). If it determines that the print job has not ended (step S15: NO), the control unit 2 repeats the processes from step S03 onwards. On the other hand, if it determines that the print job has ended (step S15: YES), the control unit 2 repeats the processes from step S01 onwards.

Next, the process from step S21 onwards will be described. In step S21, the control unit 2 executes post-processing specified in the print job. Here, an example will be described in which stapling is executed as post-processing.

After the control unit 2 causes the guide member 81 to protrude from the retracted position P1 to the protruding position P2, it separates the drive roller 33D from the driven roller 33N. The first sheet is transported along the upper surface of the guide member 81 by the transport roller 43.

Next, when the rear end of the sheet passes through the nip of the transport roller 43, the control unit 2 presses the drive roller 33D against the driven roller 33N and rotates the drive roller 33D counterclockwise. The sheet is then switched back and transported to the processing tray 51. The control unit 2 transports the sheet until the rear end of the sheet contacts the sheet receiving plate 53 of the processing tray 51, and then stops the rotation of the discharge roller 33 and separates the drive roller 33D from the driven roller 33N.

Then, the control unit 2 transports the second and subsequent sheets to the processing tray 519 in the same manner as for the first sheet, stops the rotation of the discharge rollers 33, moves the drive roller 33D away from the driven roller 33n, and aligns the widthwise position of the sheets using a pair of side fences 52.

After the control unit 2 transports the number of sheets specified in the print job to the processing tray 51, it retracts the guide member 81 to the retracted position P1, presses the drive roller 33D against the driven roller 33n to clamp the sheet stack, and staples the sheet stack using the staple device 54.

Next, the control unit 2 determines whether the number of sheets in the sheet stack is less than the predetermined number (step S23). If it is determined that the number of sheets in the sheet stack is less than the predetermined number (step S23: YES), the control unit 2 proceeds to processing in step S25. On the other hand, if it is determined that the number of sheets in the sheet stack is equal to or greater than the predetermined number (step S23: NO), the control unit 2 proceeds to processing in step S31.

In step S25, the control unit 2 causes the blower 91 to start blowing air, causes the guide member 81 to protrude to the protruding position P2 (step S27), and causes the drive roller 33D to rotate in a clockwise direction. The sheet stack is discharged along the guide member 81.

Next, the control unit 2 determines whether the rear end of the sheet stack has been detected by the sheet detection unit 76 (step S29). If it is determined that the rear end of the sheet stack has been detected, the control unit 2 causes the blower 91 to stop blowing air and causes the guide member 81 to retreat to the retreat position P1. After the rear end of the sheet stack is discharged, the sheet stack falls onto the stacking tray 61 due to gravity. At this time, the guide member 81 has retreated from above the stacking tray 61 and does not interfere with the falling sheet stack.

Next, the process from step S31 onwards will be described. In step S31, the control unit 2 causes the guide member 81 to protrude to the protruding position P2 and rotates the drive roller 33D in a clockwise direction, and the sheet stack is discharged along the guide member 81.

Next, the control unit 2 determines whether the rear end of the sheet stack has been detected by the sheet detection unit 76 (step S33). If it is determined that the rear end of the sheet stack has been detected, the control unit 2 retracts the guide member 81 to the retract position P1.

According to the sheet stacking device 120 of the present embodiment described above, the device includes a discharge section 31 that discharges sheets, a stacking tray 61 on which the sheets discharged by the discharge section 31 are stacked, an air blowing section 91 that blows air, a guide member 81 that protrudes to a protruding position P2 above the stacking tray 61 when the sheets are discharged and contacts the underside of the sheets to guide the discharge of the sheets, and retracts to a retracted position P1 upstream of the protruding position P2 in the discharge direction at a predetermined timing, and a control section 2 that controls the movement of the guide member 81 and the blowing of air by the air blowing section 91. The guide member 81 has an air duct 93 connected to the air blowing section 91 built in, and has an air blowing port 81U that opens on the upper surface and flows through the air duct 93, and the control section 2 blows air toward the underside of the sheets while the sheets are being discharged. With this configuration, air is blown out from the air blowing port 81U, so that friction between the guide member 81 protruding in the discharge direction Y and the sheets can be suppressed.

Further, according to the sheet stacking device 120 of this embodiment,
The control unit 2 is provided with a detection unit (sheet detection unit 76) that detects the sheet upstream of the discharge unit 31 in the discharge direction Y, and controls the guide member 81 so that it protrudes to the protrusion position P2 at the timing when the leading edge of the sheet is detected by the detection unit, thereby allowing the guide member 81 to protrude at a timing consistent with the passage of the sheet.

In addition, according to the sheet stacking device 120 of this embodiment, the control unit 2 controls the air blowing unit 91 to start blowing air when the leading edge of the sheet is detected by the detection unit, so that air blowing can be started at a timing that coincides with the passage of the sheet.

In addition, according to the sheet stacking device 120 of this embodiment, the control unit 2 controls the guide member 81 to retreat to the retreat position P1 when the trailing end of the sheet is detected by the detection unit, so that the guide member 81 can be retreated at a timing that coincides with the discharge of the sheet.

In addition, according to the sheet stacking device 120 of this embodiment, the control unit 2 controls the air blowing unit 91 to stop blowing air when the rear end of the sheet is detected by the detection unit, so that the air blowing can be stopped at a timing that coincides with the discharge of the sheet.

In addition, according to the sheet stacking device 120 of this embodiment, the control unit 2 controls the blower unit 91 to blow air only when the number of sheets discharged at one time by the discharge unit 31 is equal to or less than a predetermined number, so that energy consumption can be reduced when the effect of blowing air is poor.

The above embodiment may be modified as follows:

In the above embodiment, an example is shown in which the airflow is stopped before the guide member 81 is retracted, but the airflow may be continued until the guide member 81 reaches the retracted position P1, and the airflow may be stopped after the guide member 81 reaches the retracted position P1. This configuration can reduce friction between the guide member 81 and the sheet when the guide member 81 moves from the protruding position P2 to the retracted position P1.

In the above embodiment, an example has been shown in which air is blown only when the number of sheets discharged by the discharge section 31 at one time is less than a predetermined number, but the air volume may be changed depending on the number of sheets discharged by the discharge section 31 at one time. For example, when the number of sheets discharged by the discharge section 31 at one time is equal to or greater than a predetermined number, the air blower 91 may be controlled to blow more air than when the number of sheets discharged is less than the predetermined number. With this configuration, friction between the guide member 81 and the sheets can be suppressed even if the number of sheets discharged by the discharge section 31 at one time increases.

In the above embodiment, an example is shown in which air blowing is started and the guide member 81 is extended when the downstream end of the sheet in the discharge direction Y is detected by the sheet detection unit 76, but the timing for starting air blowing and extending the guide member 81 may be a predetermined time after the downstream end of the sheet in the discharge direction Y is detected by the sheet detection unit 76. In addition, the timing for starting air blowing and the timing for extending the guide member 81 may be different.

In the above embodiment, an example is shown in which the air blowing is stopped and the guide member 81 is retracted when the upstream end of the sheet in the discharge direction Y is detected by the sheet detection unit 76, but the air blowing may be stopped and the guide member 81 is retracted when the upstream end of the sheet in the discharge direction Y is discharged from the discharge unit 31. For example, the air blowing may be stopped and the guide member 81 is retracted a predetermined time after the upstream end of the sheet in the discharge direction Y is detected by the sheet detection unit 76.

2 Control unit 31 Discharge unit 51 Processing tray (post-processing unit)
54 Stapling device (post-processing section)
61 Stacking tray 76 Sheet detection unit (detection unit)
81 Guide member 81U Air outlet 91 Air blowing section 110 Post-processing device 120 Sheet stacking device

Claims (7)

a discharge section for discharging the sheet;
a stacking tray on which the sheets discharged by the discharge unit are stacked;
A blower that blows air;
a guide member that is cylindrical and curved in an upwardly convex arc, has an air outlet on its arc-shaped upper surface, and when the sheet is discharged, protrudes to a protruding position above the stacking tray and contacts the underside of the sheet to guide the sheet from being discharged, and retracts to a retracted position upstream of the protruding position in the discharge direction at a predetermined timing;
an air duct connected to the blower and built into the guide member;
A control unit that controls the extension and retraction of the guide member and the blowing of the blower,
the air blowing port is located downstream of the exhaust portion in the exhaust direction when the guide member is located at the protruding position,
The control unit is configured to blow the air toward a lower surface of the sheet while the sheet is being discharged. a detection unit configured to detect the sheet upstream of the discharge unit in the discharge direction,
2 . The sheet stacking device according to claim 1 , wherein the control unit controls the guide member so that the leading edge of the sheet is projected to the projecting position at a timing when the leading edge of the sheet is detected by the detection unit. The sheet stacking device according to claim 2, characterized in that the control unit controls the blower unit to start blowing air when the leading edge of the sheet is detected by the detector unit. The sheet stacking device according to claim 2 or 3, characterized in that the control unit controls the guide member so that the trailing end of the sheet is retracted to the retracted position when the trailing end of the sheet is detected by the detection unit. The sheet stacking device according to any one of claims 2 to 4, characterized in that the control unit controls the air blowing unit to stop blowing air when the rear end of the sheet is detected by the detection unit. The sheet stacking device according to any one of claims 1 to 5, characterized in that the control unit controls the blowing unit to blow air only when the number of sheets discharged by the discharge unit at one time is less than a predetermined number. a post-processing section that performs one or more of post-processing processes, such as stapling, shifting, and center-folding, on the sheet on which the image is formed;
7. A post-processing apparatus comprising: a sheet stacking device according to claim 1, which stacks the sheets, which have been subjected to the post-processing by the post-processing section, on the stacking tray.

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