JP7471809B2 - Sheet stacking device and image forming system - Google Patents

Description

The present invention relates to a sheet stacking device that stacks sheets and an image forming system that forms images on sheets.

Conventionally, image forming systems have been known in which an image forming device performs printing processing on sheets, temporarily places the printed sheets on a processing tray (first stacking section), performs post-processing such as binding and shift discharge processing, and discharges the sheets to a stack tray (second stacking section) (e.g., Patent Document 1). In recent years, an increasing number of such image forming systems have an inkjet image forming section, and systems that perform post-processing on sheets printed using the inkjet method are also known (e.g., Patent Document 2).

JP 2015-16970 A JP 2017-132636 A

However, when forming an image using the inkjet method as in Patent Document 2, if the image ratio is high (for example, printing a full-surface solid image), the friction coefficient of the sheet against other members, sheets, etc. may increase. In this case , when discharging a sheet from the processing tray to the stack tray, the sliding property between the sheet (the sheet discharged to the processing tray at the beginning of a job when forming a sheet bundle) and the stack tray or sheets already placed on the stack tray is poor, and there is a risk of the sheet not being discharged normally and causing a discharge failure. For this reason, it has been conventionally desired to suppress discharge failure based on the image ratio of the sheet.

The present invention aims to provide a sheet stacking device and an image forming system that can appropriately suppress ejection failures according to the image ratio of a sheet, even if the friction coefficient differs depending on the image ratio of the image formed on the sheet when the sheet is ejected from the processing tray to the stack tray.

The sheet stacking device of the present invention is a sheet stacking device that stacks sheets on which an image has been formed by an image forming device, and is equipped with a transport section that transports sheets, a first stacking section that places the sheets transported by the transport section , a discharge section that discharges the sheets placed on the first stacking section, a second stacking section that stacks the sheets discharged by the discharge section, a fan that can blow air against the underside of the sheets being discharged by the discharge section toward the second stacking section , a drive motor that drives the fan, and a control section that controls the drive motor, wherein the control section controls the rotational speed of the drive motor so that when an image ratio of an image formed on a sheet by the image forming device is a first value, the air volume blown against the sheet is a first air volume including an air volume of 0 , and when the image ratio is a second value greater than the first value, the air volume blown against the sheet is a second air volume greater than the first air volume.

Further, a sheet stacking device of the present invention is a sheet stacking device for stacking sheets on which an image has been formed by an image forming apparatus, the sheet stacking device comprising : a transport section for transporting sheets; a first stacking section for stacking the sheets transported by the transport section ; a discharge section for discharging the sheets stacked on the first stacking section; an upstream end in a discharge direction of the sheets by the discharge section being disposed vertically lower than a downstream end of the first stacking section in the discharge direction; a second stacking section for stacking the sheets discharged from the first stacking section by the discharge section; and an air outlet provided between the downstream end of the first stacking section in the discharge direction and the upstream end of the second stacking section in the discharge direction , the image forming apparatus includes an air blowing means for blowing air toward the underside of a sheet being discharged toward the second stacking section by the image forming device, and an air direction changing means for changing the direction of air blowing from the air outlet by the air blowing means, wherein when an image ratio of an image formed on a sheet by the image forming device is a first value, the air direction changing means changes the direction of air blowing from the air outlet by the air blowing means to the sheet inclined at a first angle with respect to the horizontal direction, and when the image ratio is a second value greater than the first value, the air direction changing means changes the direction of air blowing from the air outlet by the air blowing means to the sheet inclined at a second angle greater than the first angle with respect to the horizontal direction.

The image forming system of the present invention is characterized by comprising an image forming device having an image forming unit that forms an image on a sheet, and the above-mentioned sheet stacking device that stacks sheets on which images have been formed by the image forming device.
The image forming system of the present invention further comprises an image forming unit which forms an image on a sheet, a transport unit which transports the sheet on which the image has been formed by the image forming unit, a first stacking unit which places the sheet transported by the transport unit, a discharge unit which discharges the sheet placed on the first stacking unit, a second stacking unit which places the sheet discharged by the discharge unit, a fan capable of blowing air against the underside of the sheet being discharged by the discharge unit toward the second stacking unit, a drive motor which drives the fan, and a control unit which controls the drive motor, wherein the control unit controls the rotational speed of the drive motor so that when an image ratio of an image formed on the sheet by the image forming unit is a first value, the air volume blown against the sheet is a first air volume including an air volume of 0, and when the image ratio is a second value greater than the first value, the air volume blown against the sheet is a second air volume greater than the first air volume.

The sheet stacking device and image forming system of the present invention can appropriately suppress ejection failures according to the image ratio of the sheet, even if the friction coefficient differs depending on the image ratio of the image formed on the sheet when the sheet is ejected from the processing tray to the stack tray.

1 is a schematic diagram of an image forming system according to a first embodiment. FIG. 2 is a schematic diagram of a post-processing unit according to the first embodiment. FIG. 2 is a block diagram showing a control configuration of the first embodiment. 1A to 1D are diagrams for explaining the stack formation process by the post-processing unit of the first embodiment, where (a) is when the sheet is transported to the discharge roller, (b) is when the sheet is discharged to the processing tray, (c) is when the sheet is moved to the sheet end regulating member, and (d) is when the sheet stack is pushed out to the stack tray. 1A and 1B are diagrams for explaining the operation of the blower device in the post-processing unit of the first embodiment, where (a) is a diagram illustrating when the leading edge of the sheet discharged from the discharge rollers protrudes from the processing tray, and (b) is a diagram illustrating when the entire sheet is discharged from the discharge rollers to the processing tray. 1A and 1B are diagrams for explaining the operation of the blower device by the post-processing unit of the first embodiment, in which (a) shows when a sheet stack loaded on the processing tray has been stapled, and (b) shows when the entire stapled sheet stack is about to be discharged from the processing tray by the stack discharge member. 5 is a flowchart showing a procedure of an operation of the blower device according to the first embodiment. FIG. 11 is an enlarged schematic view showing a blower device of the post-treatment unit according to a second embodiment.

First Embodiment
The first embodiment will be described with reference to Figures 1 to 7. First, the schematic configuration of an image forming system according to the present embodiment will be described with reference to Figure 1.

[Image forming system]
1 shows a schematic diagram of the overall configuration of an image forming system 100 according to the present embodiment. As shown in the figure, the image forming system 100 is composed of an image forming apparatus 101 and a sheet processing apparatus 102 provided therewith. The image forming apparatus 101 is composed of a feeding unit 10, an image forming unit 20, and an image reading unit 30. The sheet processing apparatus 102 is composed of an relay transport unit 60 and a post-processing unit 70.

[Image forming apparatus]
First, the image forming apparatus 101 will be described. The feeding unit 10 of the image forming apparatus 101 is provided at the bottom of the image forming apparatus 101 and is composed of a plurality of cassette mechanisms 10a, 10b, 10c, and 10d, each of which stores image forming sheets of different sizes, and a large-capacity cassette 10e. For example, the feeding unit 10 feeds sheets of a size designated by an operator such as a user through an input unit 86 (see FIG. 3) to a feeding path P1. The feeding unit 10 also includes a manual feed tray 10f. Each of the cassette mechanisms 10a, 10b, 10c, and 10d is detachably installed from the apparatus housing 1, and each of them includes a separation mechanism for separating the sheets one by one and a feeding mechanism for feeding the sheets.

A large-capacity cassette 10e and a manual feed tray 10f are connected to the feeding path P1. The large-capacity cassette 10e and the manual feed tray 10f are provided on one side of the device housing 1 (the right side in FIG. 1), and the device housing 1 is provided with corresponding sheet feed ports (feed openings) 16, 17. The large-capacity cassette 10e is configured as an optional unit that stores sheets of a size that are consumed in large quantities. The manual feed tray 10f is configured to be able to feed special sheets such as thick paper sheets, coated sheets, and film sheets that are difficult to separate and feed. In other words, the sheets used in this embodiment include various sheet materials other than plain paper for printing. Examples of sheet materials include paper such as thin paper and thick paper, plastic films such as sheets for overhead projectors, cloth, surface-treated sheet materials such as coated paper, and special-shaped sheet materials such as envelopes and index paper.

The feeding path P1 is provided with a pair of conveying rollers 11 that feeds the sheets supplied from each of the cassette mechanisms 10a, 10b, 10c, 10d and the large-capacity cassette 10e via the feeding paths P1a, P1b, P1e downstream, and a pair of registration rollers 12. The pair of registration rollers 12 is provided at the end of the feeding path P1, and after correcting the skew of the sheet by contacting the leading edge of the sheet (the downstream end in the conveying direction), the sheet is sent toward the image forming unit 20. In addition, the sheet supplied from the manual feed tray 10f is sent to the pair of registration rollers 12 via the feeding path P1f.

Each cassette mechanism 10a, 10b, 10c, 10d and large-capacity cassette 10e is provided with a pickup roller 13, which is an example of a feeding mechanism, and a conveying roller pair 14, which is an example of a separation mechanism, which feed sheets one by one to the feeding path P1. A conveying roller pair 15 is provided near the sheet feed port 17 of the manual feed tray 10f inside the device housing 1, and conveys the sheet manually fed by the user toward the registration roller pair 12.

The image forming unit 20 is provided above the cassette mechanism 10a on the transport path P2, and includes an image forming section 21 having, for example, an inkjet print head. The image forming section 21 is provided at a position facing the transport belt 22 across the transport path P2. The image forming section 21 prints by spraying liquid such as ink onto the sheet that is supported and transported by the transport belt 22 along the transport path P2. In this embodiment, the image forming section 21 is configured with a line head that can simultaneously spray ink over a predetermined range in a direction intersecting the transport direction of the sheet (particularly, the width direction perpendicular to the transport direction).

The image forming unit of the present disclosure is not limited to the inkjet system, and may be, for example, an electrophotographic unit equipped with a rotating photosensitive drum, a light emitter such as a laser light emitter or an LED light emitter arranged around the photosensitive drum, a developing unit, and a cleaner. In this case, a latent image is optically formed on the photosensitive drum by the light emitter, and toner is attached to the latent image by the developing unit. In accordance with the timing of image formation on the photosensitive drum, a sheet is transported to the transport path P2, and a toner image is transferred from the photosensitive drum to the sheet by a transfer charger. A fixing roller arranged downstream of the transfer charger in the sheet transport direction applies heat generated by a heat source such as a halogen heater to the toner image transferred to the sheet to melt the toner. Thereafter, the toner adheres to the sheet as the temperature drops, resulting in an image fixed to the sheet.

The sheet on which the image forming process is performed by the image forming unit 20 is transported to the sheet inversion path P3, the transport path P4 for discharging to the first discharge section 40a, or the transport path P5 for transporting to the relay transport unit 60. The path switching section 23 has a switching member (not shown) that moves depending on the destination of the sheet, and guides the sheet to either the sheet inversion path P3 or the transport paths P4 and P5.

The sheet reversal path P3 is a transport path for reversing the sheet and is used for double-sided printing, or for single-sided printing when the sheet is transported face-down (with the printed side facing down) to the post-processing unit 70 described below.

The transport path P4 is a transport path for discharging the sheet to the first discharge section 40a. When discharging the sheet to the first discharge section 40a, the path switching section 23 transfers the sheet from the transport path P2 to the transport path P4, and the sheet is discharged to the sheet placement surface (placement section) 41 with the printed side of the sheet (the side printed the second time in the case of double-sided printing) facing downwards, face-down. The transport path P4 curves upward (draws an arc) from the approximately horizontal transport path P2 starting from the path switching section 23, and is formed so that the end of the curved section faces the sheet discharge port 24 provided in the device housing 1.

When a sheet is transported to the relay transport unit 60, the path is not switched by the path switching unit 23, and the sheet is transported straight along the transport path P2. Note that when the sheet is transported to the relay transport unit 60, if it is transported face-up (with the printed side of the sheet facing up), the sheet is not inverted by the sheet inversion path P3, and if it is transported face-down, the sheet is inverted using the sheet inversion path P3 before being transported.

The image reading unit 30 is provided above the first discharge section 40a and the transport path P4, and is composed of an image reading section 33 that reads the image of the original document, an original document feed tray 31 on which the original document to be fed is placed, and an original document discharge tray 32 on which the original document read by the image reading section 33 is discharged. The image reading unit 30 photoelectrically converts the original document image read by the image reading section 33 into image data, and outputs the image data to the image forming unit as an electrical signal. The image of the original document may also be read using a platen on which the original document is placed, a carriage that reciprocates along the platen, and the image reading section 33 provided on the carriage.

[Sheet Processing Device]
Next, the sheet processing apparatus 102 will be described. The relay transport unit 60 of the sheet processing apparatus 102 is a unit for transporting the sheet on which the image forming process has been performed by the image forming unit 20 to the post-processing unit 70, and has a path switching section 61. The path switching section 61 switches the transport path between a transport path P5 for discharging the sheet to a stack tray 171 as a second stacking section of the post-processing unit 70 and a transport path P6 for discharging the sheet to a sheet placement surface 71a on the upper surface of the unit housing 71 of the post-processing unit 70. The sheet passing through the transport path P5 is discharged toward the post-processing unit 70 by a discharge roller 62, and the sheet passing through the transport path P6 is discharged toward the sheet placement surface 71a of the post-processing unit 70 by a discharge roller 63. The sheet placement surface 71a of the post-processing unit 70 constitutes the second discharge section 40b of the image forming system 100, and the stack tray 171 constitutes the third discharge section 40c of the image forming system 100.

Whether the sheet processing device 102 outputs the sheet to the stack tray 171 or the sheet placement surface 71a is switched depending on whether post-processing such as stapling is performed on the sheet. In this embodiment, the sheet is output straight to the sheet placement surface 71a, so the mode may be divided so that the sheet is output to the first output section 40a when it is required to output the sheet face down, and to the second output section 40b when it is required to output the sheet face up. Note that if the output rollers 63 provided on the transport path P6 are configured to be movable in the width direction perpendicular to the sheet transport direction, the sheet can be jog-output by shifting it in the width direction in the second output section 40b.

The post-processing unit 70 is a unit that performs post-processing such as binding on the sheets received from the relay transport unit 60. The post-processing unit of this embodiment is equipped with a sheet binding processing mechanism that collates and accumulates the multiple transported sheets to form a sheet bundle and performs a binding process on the sheet bundle.

In this embodiment, a configuration in which an intermediary transport unit 60 is interposed between the image forming apparatus 101 and the post-processing unit 70 is described, but the post-processing unit 70 may be directly connected to the image forming apparatus 101. In other words, the post-processing unit 70 can function as a processing device even as a standalone unit that is not combined with the intermediary transport unit 60. The post-processing unit 70 is also an example of a sheet stacking device that stacks sheets on which images have been formed by the image forming apparatus 101, regardless of whether or not it has a function of performing post-processing on the sheets.

The configuration of the post-processing unit 70 as a sheet stacking device will be described using Figure 2. The post-processing unit 70 has a unit housing 71 in which a sheet supply port 72, a transport path P5, a discharge roller 73 as a discharge means, a processing tray 74 as a first stacking section on which sheets can be stacked, a sheet input member 75, a staple binding processing section 76 as a processing means, a sheet end regulating member 77, a width alignment member 79, and a stack discharge member 78 as a transport means are stored, and a stack tray 171 that can move up and down is provided on the opposite side of the sheet supply port 72.

The stack tray 171 is arranged such that the upstream end in the sheet transport direction by the stack discharge member 78 is vertically lower than the downstream end in the transport direction of the processing tray 74, and can stack sheets transported from the processing tray 74 by the stack discharge member 78. In addition, an air blower 90 is provided between the processing tray 74 and the stack tray 171.

The sheet carrying member 75 is composed of a paddle 75a and a knurled belt 75b, and is a member for transporting a sheet in a direction in which the rear end of the sheet on the processing tray 74 (the upstream end in the transport direction of the sheet transported by the discharge roller 73) hits the sheet end regulating member 77. That is, the sheet received from the image forming device 101 via the relay transport unit 60 and the sheet supply port 72 is transported by the discharge roller 73 and discharged to the processing tray 74 and placed thereon. At this time, the paddle 75a and the knurled belt 75b transport the sheet in the opposite direction to the transport direction by the discharge roller 73, and the end of the sheet hits the sheet end regulating member 77. The sheet end regulating member 77 is located at the upstream end of the processing tray 74 in terms of the sheet discharge direction by the bundle discharge member 78 described later, and can regulate the upstream end of the sheet placed on the processing tray 74. The paddle 75a and the knurled belt 75b are each configured to be movable between a retracted position away from the sheet and an operating position where they rotate in contact with the sheet, and in the operating position they convey the sheet by rotating in the counterclockwise direction in FIG. 2.

The width alignment member (alignment member) 79 is composed of a pair of alignment members that can move in the sheet width direction (the direction intersecting the sheet discharge direction by the bundle discharge member 78 (the direction perpendicular to the sheet discharge direction in this embodiment)) in the post-processing unit 70, and regulates the end position of the sheet placed on the processing tray 74 in the sheet width direction. The width alignment member 79 is configured to be movable between a retracted position away from the side end of the sheet (the edge in the sheet width direction) and an operating position corresponding to the target position (alignment position) when aligning the sheet in the sheet width direction. At least one of the alignment members moves from the retracted position to the operating position while contacting the side end of the sheet, thereby aligning the sheet discharged to the processing tray 74 to the alignment position. Note that it is not necessary for both alignment members to move, and one of the alignment members may be a fixed regulating member with respect to the frame body of the post-processing unit 70, and only the other alignment member may move to perform the sheet width direction alignment operation with respect to the fixed regulating member. Furthermore, the other alignment member does not need to move in contact with the edge of the sheet in the width direction; sheet width alignment is possible by providing a member that can move in the sheet width direction by contacting the top surface of the sheet, or a roller member that transports the sheet in the sheet width direction.

The staple binding processing unit 76 performs a binding process on the sheet bundle aligned and accumulated in the sheet conveying direction and the sheet width direction on the processing tray 74. That is, the staple binding processing unit 76 processes the sheet bundle SB consisting of a plurality of sheets stacked on the processing tray 74. The staple binding processing unit 76 is configured to be movable in the sheet width direction, and can perform a binding process at a corner of the sheet bundle or a predetermined position of the sheet edge that contacts the sheet end regulating member 77. Note that, although a staple binding mechanism using staples is adopted in this embodiment, a stapleless binding mechanism that does not use staples may be adopted, or a staple binding mechanism and a stapleless binding mechanism may be provided on the front side (the front side of the image forming system 100, the front side in FIG. 1) and the rear side (the rear side in FIG. 1) of the post-processing unit 70, respectively, and the staple binding and the stapleless binding may be switched according to the user's settings.

The bundle discharge member 78 is driven by the discharge member drive unit M6 (FIG. 3) and pushes out the rear end edge of the sheet bundle, thereby transporting and discharging the sheet bundle on the processing tray 74 to the stack tray 171. That is, the bundle discharge member 78 transports the sheet bundle SB processed by the staple binding processing unit 76 from the processing tray 74 to the stack tray 171. The bundle discharge member 78 is retracted below the processing tray 74 until the sheet bundle is formed, and is configured to move along the guide member 78a to come into contact with the rear end edge of the sheet bundle and push the sheet bundle toward the stack tray 171 after the sheet bundle is formed on the processing tray 74 (after the binding process, if a binding process is performed). Note that the bundle discharge member 78 can discharge not only the stapled sheet bundle as described above, but also the unstapled sheet bundle.

Figures 4(a) to (d) show the basic procedure of the staple binding process by the post-processing unit 70. As shown in Figure 4(a), the sheet S is delivered from the relay transport unit 60 to the post-processing unit 70. As shown in Figure 4(b), the sheet S is discharged to the processing tray 74 by the discharge roller 73, and the paddle 75a and the knurled belt 75b are lowered to the operating position and contact the sheet S in sequence. As shown in Figure 4(c), the sheet S is moved toward the sheet end regulating member 77. The sheet S, which is aligned in the conveying direction by contacting the sheet end regulating member 77, is aligned in the sheet width direction by the width alignment member 79. This alignment operation is repeated each time one sheet S is discharged, and when the number of sheets to form a sheet bundle are aligned and accumulated, the staple binding processing unit 76 staples the sheet bundle at a predetermined position. Then, as shown in FIG. 4(d), the stack discharge member 78 contacts the rear edge of the sheet stack SB and pushes the sheet stack SB onto the stack tray 171.

The details of the configuration of the discharge rollers 73, processing tray 74, sheet input member 75, staple binding processing unit 76, sheet end regulating member 77, width alignment member 79, and stack discharge member 78 described so far are described in, for example, JP 2015-16970 A, and various post-processing units such as staple binding, stapleless binding, punching (hole punching), and folding can be applied. In addition, the sheets can be shifted in the sheet width direction and discharged to the stack tray 171 without performing the stapling process, which can also be included in the post-processing. When shifting the sheets in the width direction, this can be achieved by changing the alignment position with the width alignment member 79, or by changing the discharge position of the sheets using a mechanism that shifts the discharge rollers 73 in the sheet width direction.

As shown in FIG. 1, the post-processing unit 70 (and relay transport unit 60) of this embodiment is installed on a stand 50 on the side of the image forming apparatus 101. The stand 50 is composed of an installation section 51, legs 52, and an opening 53, and is fixed by hooking a hook member 54 provided on the side of the image forming apparatus 101 into the opening 53. The installation section 51 is provided with a slide rail (not shown), and the post-processing unit 70 is configured to be slidable in the left-right direction of FIG. 1. By moving the post-processing unit 70 (and relay transport unit 60) away from the image forming apparatus 101, a jam can be cleared when a sheet becomes jammed.

When the post-processing unit 70 moves toward the tip of the installation section 51, a force acts on the stand 50 in a counterclockwise direction, but because the legs 52 are supported by the hook members 54 and the side surface 1c of the image forming device 101, the stand 50 does not fall over.

[Discharge Configuration]
In this embodiment, a plurality of discharge sections are provided for discharging the processed sheets. As described above, the first discharge section 40a is a discharge section for discharging the sheet that has been subjected to image formation processing by the image forming section 21 straight in a face-down state, or for discharging the sheet in a face-up state after inverting the sheet in a sheet inversion path P3. The first discharge section 40a is a so-called internal discharge section of the image forming apparatus 101, and is formed of a space partitioned by the standing surface 1a, the ceiling surface 1b, and the placement surface 41 of the apparatus housing 1.

The second discharge section 40b is a discharge section that uses the sheet placement surface 71a on the top surface of the unit housing of the post-processing unit 70, and discharges the sheet that has been image-formed by the image forming section 21 straight in a face-up state, or inverts the sheet in a sheet reversal path P3 and discharges it face-down. In other words, the first discharge section 40a and the second discharge section 40b can be set to discharge in either direction depending on the user's settings, but considering productivity, it is desirable to discharge to the first discharge section 40a in the case of face-down, and to the second discharge section 40b in the case of face-up.

It is also possible to determine whether the sheet is discharged to the first discharge section 40a or the second discharge section 40b depending on the amount of ink adhering to the sheet by the image forming process by the image forming unit 21 (for example, based on information on the image ratio described later). For example, when the image ratio is low, it is not necessary to dry the ink adhering to the sheet, so as described above, the sheet is discharged directly to the first discharge section 40a in the face-down state, and to the second discharge section 40b in the face-up state. However, when the image ratio is high, it is necessary to dry the ink adhering to the sheet, so the sheet is once transported to the sheet inversion path P3 to buy time until discharge, thereby drying the sheet. After the sheet is transported through the sheet inversion path P3, the face-up sheet is discharged to the first discharge section 40a, and the face-down sheet is discharged to the second discharge section 40b. In addition, if a drying member such as a fan is provided in the sheet inversion path P3, the drying effect can be further improved.

The third discharge section 40c is a stack tray 171 of the post-processing unit 70, to which sheets that have been post-processed by the post-processing unit 70 are discharged. This stack tray 171 is configured to be able to rise and fall, and rises and falls according to the amount of sheets stacked. In addition, since the post-processing unit 70 of this embodiment has a mechanism for shifting sheets in the width direction, it is possible to discharge sheets shifted in the width direction on the stack tray 171 without stapling processing.

In this embodiment, the post-processing unit 70 performs the processing described below based on information related to the image ratio. However, for example, a sheet on which an image with a high image ratio that exceeds the limit of the range suitable for processing by the post-processing unit 70 has been formed (for example, a sheet on which a dark colored full-surface solid image or the like is printed) may be discharged to the first discharge section 40a or the second discharge section 40b.

In addition, when post-processing is performed using the post-processing unit 70, productivity is lower than with straight discharge. Therefore, even when executing a productivity-oriented mode, it may be better to discharge to the first discharge section 40a or the second discharge section 40b.

[Control configuration]
3 is a diagram showing the control configuration of the image forming system 100 of this embodiment. The image forming apparatus 101 and the sheet processing apparatus 102 each have a control CPU 81, 87, and can exchange information with each other. The first control CPU 81 of the image forming apparatus 101 is connected to the image formation control section 82, the first drive control section 83, the reading control section 84, and the first signal control section 85. The reading control section 84 acquires image data read by the image reading section 33 of the image reading unit 30, and sends it to the first control CPU 81 as print data. The first control CPU 81 sends the print data received from the reading control section 84 to the image formation control section 82, and the image formation control section 82 controls the image forming section 21 to perform image formation processing. In addition, the first control CPU 81 issues a command to the first drive control section 83 in response to input information (such as detection of a sheet end) from various sensors connected to the first signal control section 85, and controls the conveying drive motor of the roller that conveys the sheet and the switching member drive section to convey the sheet. The first control CPU 81 is also connected to an input unit 86 that inputs information such as the print mode, discharge mode, and post-processing mode from the user, and controls each control unit according to the input information, and also transmits mode information to the second control CPU 87 of the sheet processing device 102.

The input unit 86 is used to set the "image formation mode" and "post-processing mode." The image formation mode includes mode settings such as color or monochrome printing, double-sided or single-sided printing, and image formation conditions such as sheet size, sheet type (sheet basis weight, material, etc.), number of printout copies, and enlarged or reduced printing. The "post-processing mode" is set to, for example, a "printout mode," a "staple binding processing mode," a "eco binding processing mode," or a "jog sorting mode." The illustrated sheet processing device 102 is provided with a "manual binding mode," and in this mode, the binding processing operation for a sheet stack is performed offline, separately from the first control CPU 81 of the image forming device 101.

The second control CPU 87 of the sheet processing device 102 is provided in the post-processing unit 70, and this second control CPU 87 controls the operation of not only the post-processing unit 70 but also the relay transport unit 60. The second control CPU 87 is connected to the second drive control unit 88 and the second signal control unit 89, and issues commands to the second drive control unit 88 in response to input information (such as detection of the sheet edge) from various sensors connected to the second signal control unit 89 to control the operation of the sheet processing device 102. Based on the command from the second control CPU 87, the second drive control unit 88 controls the transport drive motor M1 that drives the rollers that transport the sheet and the switching member drive unit M2 that drives the switching member arranged in the path switching unit 61 of the relay transport unit 60 to transport the sheet. The second drive control section 88 is also connected to a staple drive section M3 that drives the staple binding processing section 76, a width alignment drive section M4 that drives the width alignment member 79, a sweep drive section M5 that drives the paddle 75a and the knurled belt 75b, a discharge member drive section M6 that drives the bundle discharge member 78, and a fan drive motor M7 that drives the fan 91 described below, and controls these drive sections to cause the post-processing unit 70 to perform post-processing operations.

The first control CPU 81 also transfers data such as the post-processing mode, sheet number information (number of sheets to be formed in a bundle), number of copies information, and sheet type information such as the size and thickness of the sheets on which images are formed to the second control CPU 87. In addition, the first control CPU 81 transfers a job end signal to the second control CPU 87 each time the image formation process ends. In addition, in this embodiment, the first control CPU 81 transfers printing information, particularly information related to the image ratio of the sheet (for example, the amount of ink ejected), to the second control CPU 87. In addition to information related to the image ratio of the sheet, the printing information includes image information read by the image reading unit 30, or the amount of ink ejected calculated from the image information, etc.

Here, "image ratio (printing rate)" refers to the ratio of the area of the area where an image is formed to the area of the entire area where an image can be formed on a sheet. For example, a full-surface solid image in which the image forming unit 21 forms an image of maximum density on the entire area where an image can be formed on a sheet has an image ratio of 100%. In the case of an inkjet image forming device, if the image ratio is high, the amount of ink used to form the image on the sheet also increases. In the following explanation, the type of information related to the image ratio used to control operations based on the image ratio is not particularly limited. Examples of information related to the image ratio include a count value obtained by accumulating the amount of ink ejected in the inkjet method, and a count value (video count value) obtained by accumulating a signal specifying the presence or absence of a dot for each pixel in the electrophotographic method.

For example, when an image is formed by the inkjet method, if the image ratio is high, the stiffness of the sheet decreases, the weight increases, and the coefficient of friction with other members and sheets may increase (even if the sheet weight after image formation is the same, the friction coefficient increases for sheets with a high image ratio because a large amount of ink adheres to the sheet. In other words, even if the sheets are the same size, there are thick sheets with a low image ratio and thin sheets with a high image ratio, and even if the sheet weight after image formation is the same, the thinner sheets with a high image ratio are more likely to cause discharge failure due to an increase in the friction coefficient.). For this reason, when a sheet bundle with a high image ratio is formed and post-processed in the processing tray 74 and then discharged to the stack tray 171, large friction occurs between the sheet bundle and the upper surface of the stack tray 171 or between the sheet bundle and the sheets already placed on the stack tray 171. In addition, because the sheet bundle is heavy and has low stiffness, the sheet bundle comes into contact with the processing tray 74 in the stack tray 171 from very close, and the contact area with the stack tray 171 is larger than when the stiffness of the sheet bundle is high. This also generates a large amount of friction between the sheet bundle and the upper surface of the stack tray 171, or between the sheet bundle and sheets already stacked on the stack tray 171. Since sheets with a high image ratio have low rigidity, if the sliding resistance is large, the sheet bundle may not be able to be transported or may bend upward, which may cause a discharge failure of the sheet bundle. Therefore, in this embodiment, when the image ratio is high, the sheet bundle is floated off the stack tray 171 by the air blower 90, thereby reducing the contact area with the upper surface of the stack tray 171 or the sheets stacked on the stack tray 171, and suppressing a discharge failure of the sheet bundle.

[Blower device]
Next, the blower device 90 as the blowing means, which is a characteristic configuration of this embodiment, will be described in detail. As shown in Fig. 2, the blower device 90 is disposed between the processing tray 74 and the stack tray 171 in the unit housing 71, and has a fan 91, a duct portion 92, a nozzle portion 93, and an air outlet 94. The blower device 90 is provided so as to be able to blow air from between the downstream end of the processing tray 74 and the upstream end of the stack tray 171 toward the downstream side in the conveying direction.

The fan 91 is driven by a fan drive motor M7 (see FIG. 3) based on a command signal from the second control CPU 87 (see FIG. 3) and is provided, for example, at the bottom inside the unit housing 71. When driven, the fan 91 draws in air from an intake port 71b provided on the bottom surface of the unit housing 71 and blows it out into a duct portion 92 provided facing upward.

The duct section 92 is provided with a vertical flow path, a fan 91 is disposed at the bottom, and a nozzle section 93 is connected to the upper end. In this embodiment, the duct section 92 is formed with a narrower flow path in the upstream and downstream directions of the sheet conveying direction at the upper part than at the lower part. The nozzle section 93 is provided with a flow path inclined from the top of the duct section 92 in a direction in which the downstream side in the sheet conveying direction is the upper side. The nozzle section 93 opens at a position facing between the processing tray 74 and the stack tray 171 of the unit housing 71, and the opening forms an air outlet 94. The inclination angle of the nozzle section 93 can be set appropriately, and it may be arranged horizontally or with the discharge side inclined downward, as well as arranged with the discharge side inclined upward as in this embodiment.

The operation of the blower device 90 will be described with reference to Figures 5(a) and 5(b) and Figures 6(a) and 6(b). Note that in Figures 5(a) to 6(b), the width alignment member 79 is omitted from the illustration in order to make the sheet S easier to see. As shown in Figure 5(a), the sheet S is delivered from the relay transport unit 60 to the post-processing unit 70, and the leading edge of the sheet S reaches the processing tray 74 by the discharge rollers 73.

Then, as shown in FIG. 5B, the sheet S is placed from the processing tray 74 to the stack tray 171, and the paddle 75a and the knurled belt 75b are lowered to the operating position to move the sheet S in the direction opposite to the conveying direction until it abuts against the sheet end regulating member 77. Once the rear end of the sheet S is abutted against the sheet end regulating member 77 by the paddle 75a and the knurled belt 75b, the paddle 75a and the knurled belt 75b are raised and the width alignment member 79 aligns the sheet in the width direction. At this point, the second control CPU 87 drives the fan 91 to start blowing air.

After that, the sheets are sequentially discharged from the discharge roller 73, and as shown in FIG. 6A, a sheet bundle SB is formed in contact with the sheet end regulating member 77, and the staple binding processing unit 76 staples the sheet bundle SB at a predetermined position. Then, the bundle discharge member 78 contacts the rear end of the sheet bundle SB and pushes the stapled sheet bundle SB to the stack tray 171. At this time, the fan 91 is driven, so that the sheet bundle SB on the stack tray 171 floats up on the side of the stack tray 171 (or the sheets already placed on the stack tray 171) closer to the processing tray 74, thereby reducing the contact area of the sheet bundle SB with the stack tray 171 and reducing the sliding resistance. Therefore, when the sheets are discharged from the processing tray 74 to the stack tray 171, even if the sliding property is poor, discharge failures can be suppressed and smooth discharge can be achieved.

6B, the sheet stack SB is further pushed out, and the air blower 90 stops blowing air just before the upstream end of the sheet stack SB in the transport direction moves from the processing tray 74 to the stack tray 171. That is, the air blower 90 stops blowing air before the upstream end of the sheet transported from the processing tray 74 to the stack tray 171 by the bundle discharge member 78 reaches the downstream end of the processing tray 74. Here, if the air blower 90 continues to blow air even after the upstream end of the sheet moves downstream of the downstream end of the processing tray 74, the upstream end of the sheet stack SB may not be able to fall onto the stack tray 171 because it is blown up by the air blowing. In contrast, in this embodiment, the air blowing is stopped, so the upstream end of the sheet stack SB can fall onto the stack tray 171 and is discharged to the stack tray 171. The timing for stopping the air blowing by the air blowing device 90 can be, for example, by using a timer to stop the air blowing after a predetermined time has elapsed since the discharge member drive unit M6 started driving the bundle discharge member 78, or by providing a sensor capable of detecting that the rear end of the sheet bundle SB has passed a predetermined position on the processing tray 74, and stopping the air blowing based on the sensor detecting the passage of the rear end of the sheet bundle SB. However, it goes without saying that the timing for stopping the air blowing by the air blowing device 90 is not limited to these examples.

Next, the volume of air blown from the blower 90 will be described in detail. For example, if the blower 90 is always blown with an appropriate volume of air for a sheet stack made up of sheets with the highest image ratio, the volume of air may be excessively large for a sheet stack made up of sheets with a low image ratio, and this may cause problems such as the sheet stack being blown downstream on the stack tray 171. Therefore, in this embodiment, the blower 90 is configured so that the second control CPU 87 changes the volume of air based on the image ratio of the image formed on the sheet. For example, if the threshold value of the image ratio is set to 70%, the blower 90 blows air to the sheet at a first volume of air F1 when the image ratio is a first value (e.g., a value less than 70%), and blows air to the sheet at a second volume of air F2 greater than the first volume of air F1 when the image ratio is a second value greater than the first value (e.g., a value equal to or greater than 70%).

When the image ratio is a first value that is relatively small, the frictional resistance of the sheets is not so large, so if the air volume is too large, there is a risk that the sheet stack SB will be swept downstream on the stack tray 171. In this case, the air volume blown onto the sheets is set to a relatively small first air volume F1, and the sheet stack SB is not blown too much, so that it is lifted up by an appropriate amount from the stack tray 171. On the other hand, when the image ratio is a second value that is relatively large, the frictional resistance of the sheets is large, so if the air volume is too small, the sheet stack SB is not lifted up by an adequate amount, so that the sliding resistance cannot be sufficiently reduced. In this case, the air volume blown onto the sheets is set to a relatively large second air volume F2, so that the sheet stack SB is sufficiently blown up, so that it is sufficiently lifted up from the stack tray 171. As a result, an appropriate air volume can be blown according to the weight and frictional resistance of the sheet stack, so that discharge failures can be more appropriately suppressed and smooth discharge can be achieved.

In this embodiment, the shapes of the duct portion 92 and nozzle portion 93 of the air blowing device 90 do not change, so the air volume correlates with the air speed. Also, the sheet transport speed and the time that the sheet is stopped are not changed in order to change the air volume. In other words, the air blowing time is constant. Therefore, in this embodiment, the second control CPU 87 changes the air volume only by changing the rotation speed of the fan drive motor M7 of the fan 91.

Next, the procedure for performing the air blowing process using the air blower 90 after image formation in the image forming system 100 of this embodiment will be described in detail with reference to the flowchart shown in FIG. 7. Here, a case will be described where a plurality of sheets on which images have been formed by the image forming device 101 are bound into a sheet bundle by the sheet processing device 102. After image formation by the image forming device 101, the sheets on which images have been formed are transferred one by one from the relay transport unit 60 to the post-processing unit 70 (step S1), and the leading edge of the sheet S reaches the processing tray 74 by the discharge rollers 73 (see FIG. 5A). The second control CPU 87 of the sheet processing device 102 acquires the image ratio of the sheet sent from the image forming device 101 (step S2).

The second control CPU 87 judges whether the image ratio is less than 70% (step S3). If the second control CPU 87 judges that the image ratio is less than 70% (YES in step S3), it judges that the image ratio is small and blows air from the blower device 90 at the first air volume F1 (step S4). That is, the air volume is small so as not to blow the sheet stack SB on the stack tray 171 too far downstream. Then, the second control CPU 87 moves the sheet to the sheet end regulating member 77 by the paddle 75a and the knurled belt 75b, and the next sheet is handed over from the image forming device 101 (step S5). The second control CPU 87 judges whether the handed over sheet is the last sheet forming the sheet stack (step S6). If the second control CPU 87 determines that the delivered sheet is not the final sheet forming the sheet stack (NO in step S6), it continues blowing air at the first air volume F1 (step S4) while the next sheet is delivered from the image forming device 101 (step S5).

When the second control CPU 87 determines that the delivered sheet is the final sheet forming the sheet bundle (YES in step S6), it executes the binding process by the staple binding processing unit 76 (step S7). Then, the second control CPU 87 drives the bundle discharge member 78 to discharge the bound sheet bundle from the processing tray 74 toward the stack tray 171 (step S8), and stops blowing air from the blower device 90 just before the upstream end of the sheet bundle SB in the transport direction moves from the processing tray 74 to the stack tray 171 (step S9).

On the other hand, if the second control CPU 87 determines that the image ratio is not less than 70% (NO in step S3), it determines that the image ratio is large, and blows air from the blower 90 at the second air volume F2 (step S10). That is, it blows air at a large volume so as to sufficiently lift the sheet stack SB on the stack tray 171. Then, the second control CPU 87 moves the sheet to the sheet end regulating member 77 by the paddle 75a and the knurled belt 75b, and the next sheet is handed over from the image forming device 101 (step S11). The second control CPU 87 determines whether the handed-over sheet is the last sheet forming the sheet stack (step S12). If the second control CPU 87 determines that the handed-over sheet is not the last sheet forming the sheet stack (NO in step S12), it continues blowing air at the second air volume F2 (step S10), and the next sheet is handed over from the image forming device 101 (step S11). Furthermore, if the second control CPU 87 determines that the delivered sheet is the final sheet that will form the sheet stack (YES in step S12), it executes the binding process and subsequent processes (steps S7 to S9) in the same manner as described above.

As described above, according to the sheet processing device 102 of this embodiment, when the sheet stack SB after the binding process is pushed out onto the stack tray 171, the fan 91 is driven, so that the sheet stack SB on the stack tray 171 floats up on the side of the stack tray 171 (or the sheets already placed on the stack tray 171) closer to the processing tray 74, thereby reducing the contact area of the sheet stack SB with the stack tray 171 and reducing the sliding resistance. Therefore, when the sheets are discharged from the processing tray 74 to the stack tray 171, even if the sliding properties are poor, discharge failures can be suppressed and smooth discharge can be achieved.

In addition, according to the sheet processing apparatus 102 of this embodiment, the air blower 90 blows air to the sheets at a first air volume F1 (including 0 air volume) when the image ratio is a first value (e.g., a value less than 70%), and blows air to the sheets at a second air volume F2 greater than the first air volume F1 when the image ratio is a second value greater than the first value (e.g., a value equal to or greater than 70%). This allows an appropriate air volume to be blown according to the weight and frictional resistance of the sheet stack, so that discharge failures can be more appropriately suppressed. That is, even if the friction coefficient differs depending on the image ratio of the image formed on the sheet when the sheet is discharged from the processing tray 74 to the stack tray 171, discharge failures can be appropriately suppressed according to the image ratio of the sheet.

Second Embodiment
Next, the second embodiment will be described in detail with reference to Fig. 8. This embodiment is different from the first embodiment in that the nozzle portion 93 of the blower 90 has an air direction changing portion 95 as an air direction changing means capable of changing the air blowing direction from the blower 90. However, other configurations are the same as those of the first embodiment, so the same reference numerals are used and detailed description is omitted.

The airflow direction changing unit 95 has fins 96, a rotating shaft 97 for rotating the fins 96, and a drive motor (not shown) for rotating the rotating shaft 97. The rotating shaft 97 is provided in approximately the center of the nozzle unit 93 so as to be rotatable with its longitudinal direction being the width direction perpendicular to the conveying direction. The fins 96 are plate-shaped with its longitudinal direction being the width direction perpendicular to the conveying direction, and are provided so as to be able to change the flow path of the air flowing through the nozzle unit 93 in the vertical direction by changing their orientation by rotating the rotating shaft 97. The drive motor is driven by the second control CPU 87.

In this embodiment, when the image ratio of the image formed on the sheet handed over to the sheet processing device 102 is a first value, the air direction changing unit 95 changes the air blowing direction of the air blowing device 90 to a direction inclined at a first angle θ1 with respect to the horizontal direction (solid arrow in FIG. 8). When the image ratio of the image formed on the sheet handed over to the sheet processing device 102 is a second value that is greater than the first value, the air direction changing unit 95 changes the air blowing direction of the air blowing device 90 to a direction inclined at a second angle θ2 with respect to the horizontal direction that is greater than the first angle θ1 (imaginary arrow in FIG. 8).

When the image ratio is a relatively small first value, the frictional resistance of the sheets is not so large, so if the inclination angle of the airflow direction is too large, the sheet stack SB may be lifted too much from the stack tray 171 and may be swept downstream. In this case, the inclination angle of the airflow direction for blowing air onto the sheets is set to a relatively small first angle θ1, and air is blown to the extent that the sheet stack SB does not lift too much, so that the sheet stack SB is lifted up by an appropriate amount from the stack tray 171. On the other hand, when the image ratio is a relatively large second value, the frictional resistance of the sheets is large, so if the inclination angle of the airflow direction is too small, the amount of lift is insufficient and the sliding resistance cannot be sufficiently reduced. In this case, the inclination angle of the airflow direction for blowing air onto the sheets is set to a relatively large second angle θ2, so that sufficient air is blown onto the sheet stack SB and the sheet stack SB is sufficiently lifted up from the stack tray 171. As a result, air can be blown in an appropriate airflow direction according to the weight and frictional resistance of the sheet stack, so that discharge failures can be more appropriately suppressed and smooth discharge can be achieved.

As described above, according to the sheet processing apparatus 102 of the present embodiment, when the image ratio of the image formed on the sheet handed over to the sheet processing apparatus 102 is a first value, the air direction changing unit 95 changes the air blowing direction of the air blowing device 90 to a direction inclined at a first angle θ1 with respect to the horizontal direction (solid arrow in FIG. 8), and when the image ratio of the image formed on the sheet handed over to the sheet processing apparatus 102 is a second value greater than the first value, the air blowing direction of the air blowing device 90 to the sheet is a direction inclined at a second angle θ2 greater than the first angle θ1 with respect to the horizontal direction (imaginary arrow in FIG. 8). This allows air to be blown in an appropriate air blowing direction according to the weight and frictional resistance of the sheet stack, so that discharge failures can be more appropriately suppressed. That is, even if the friction coefficient differs depending on the image ratio of the image formed on the sheet when the sheet is discharged from the processing tray 74 to the stack tray 171, discharge failures can be appropriately suppressed according to the image ratio of the sheet.

<Other embodiments>
In the sheet processing apparatus 102 in each of the above-described embodiments, the case has been described in which the air blowing from the air blowing device 90 is stopped immediately before the upstream end of the sheet bundle SB in the transport direction moves from the processing tray 74 to the stack tray 171, but the invention is not limited to stopping the air blowing. For example, immediately before the upstream end of the sheet bundle SB in the transport direction moves from the processing tray 74 to the stack tray 171, the air blowing may be made smaller than the air blowing volume up to that point without stopping the air blowing.

In addition, in the sheet processing apparatus 102 in each of the above-mentioned embodiments, the image ratio is transmitted from the first control CPU 81 of the image forming apparatus 101 to the second control CPU 87 of the sheet processing apparatus 102, but this is not limited to the above. For example, an image sensor such as a CIS that reads the image of the sheet after image formation may be provided in the image forming apparatus 101 or the sheet processing apparatus 102, and the image ratio may be obtained based on the value read by this image sensor. In this case, for example, even if the first control CPU 81 does not have information regarding the image ratio, the image ratio can be obtained, or the image ratio based on the image actually formed can be obtained. This image sensor is provided on the transport path P5 of the sheet processing apparatus 102 (between the sheet supply port 72 and the discharge rollers 73), and reads the image of the sheet transported on the transport path P5.

In addition, in the sheet processing apparatus 102 in each of the above-mentioned embodiments, a case has been described in which 70% is applied as the threshold value of the image ratio, and the air volume is varied depending on whether the image ratio is less than 70%, but this is not limited to the above. For example, the threshold value is not limited to 70%, and may be an appropriate value between 60% and 80%. Alternatively, the threshold value is not limited to one, and for example, two threshold values, a large and a small, may be provided, and a different air volume may be set for each of three stages, such as when the image ratio is smaller than the small threshold, when it is between the two thresholds, and when it is larger than the large threshold. The number of stages may be four or more, or may change linearly without steps. In addition, in the sheet processing apparatus 102 in each of the above-mentioned embodiments, a case has been described in which the first small air volume F1 is blown when the image ratio is less than 70%, but this is not limited to the above. For example, when the image ratio is less than 70%, the blowing of air may be stopped.

In the above embodiment, a part of the processing executed by the second control CPU 87 may be performed by a processor mounted in a housing other than the housing in which the first stacking unit is mounted, such as the first control CPU 81 of the image forming apparatus 101. In particular, the first control CPU 81 of the image forming apparatus 101 may calculate the volume of air to be blown from the blower 90 based on information related to the image ratio, send the result to the second control CPU 87, and not send the information related to the image ratio itself to the second control CPU 87. In such a configuration, the "sheet stacking device" refers to a device that includes a device main body having a mechanical configuration for stacking sheets (processing tray 74, stack tray 171, etc.) and elements (processor, storage device, etc.) that are electrically connected to the device main body and constitute a control circuit for operating the device main body.

The present invention can also be realized by supplying a program that realizes one or more of the functions of the above-mentioned embodiments to a system or device via a network or storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that realizes one or more functions.

The volume of air from the blower 90 may be changed depending on whether the sheets discharged to the stack tray 171 are single-sided or double-sided. In this case, it is desirable to increase the volume of air from the blower 90 when double-sided printing is performed rather than single-sided printing, even with the same image ratio. Also, even in the case of single-sided printing, if the sheet on the stack tray is face-up and the sheet to be discharged is face-down, the printed surfaces will come into contact with each other, so it is desirable to increase the volume of air from the blower 90 compared to when the sheets are face-down or face-up in succession, even with the same image ratio.

21...image forming section, 70...post-processing unit (sheet stacking device), 73...discharge roller (discharge means), 74...processing tray (first stacking section), 76...stapling processing section (processing means), 78...bundle discharge member (conveying means), 79...width alignment member (alignment member), 90...blower device (blower means), 95...airflow direction changing section (airflow direction changing means), 100...image forming system, 101...image forming device, 171...stack tray (second stacking section), S...sheet.

Claims (8)

A sheet stacking device that stacks sheets on which images are formed by an image forming apparatus,
A conveying unit that conveys a sheet;
a first stacking section for stacking the sheet conveyed by the conveying section ;
a discharge section that discharges the sheets placed on the first stacking section ;
a second stacking section for stacking the sheets discharged by the discharge section ;
a fan capable of blowing air against a lower surface of the sheet discharged by the discharge unit toward the second stacking unit ;
A drive motor that drives the fan;
A control unit that controls the drive motor,
the control unit controls the rotation speed of the drive motor so that , when an image ratio of an image formed on a sheet by the image forming device is a first value, the air volume to be blown onto the sheet is a first air volume including an air volume of 0 , and, when the image ratio is a second value larger than the first value, the air volume to be blown onto the sheet is a second air volume larger than the first air volume.
A sheet stacking device comprising: A sheet stacking device that stacks sheets on which images are formed by an image forming apparatus,
A conveying unit that conveys a sheet;
a first stacking section on which the sheet conveyed by the conveying section is placed ;
a discharge section that discharges the sheets placed on the first stacking section ;
a second stacking portion having an upstream end in a discharge direction of the sheet by the discharge portion disposed vertically lower than a downstream end of the first stacking portion in the discharge direction, the second stacking portion stacking the sheet discharged from the first stacking portion by the discharge portion;
a blowing unit that is provided with an air outlet between a downstream end of the first stacking unit in the discharge direction and an upstream end of the second stacking unit in the discharge direction and that blows air from the air outlet toward a lower surface of the sheet being discharged toward the second stacking unit by the discharge unit ;
and a wind direction changing means for changing the direction of air blown from the air outlet by the air blowing means,
the air direction changing means changes the air blowing direction from the air blowing outlet to the sheet by the air blowing means to a direction inclined at a first angle with respect to the horizontal direction when an image ratio of an image formed on the sheet by the image forming device is a first value, and changes the air blowing direction from the air blowing outlet to the sheet by the air blowing means to a direction inclined at a second angle with respect to the horizontal direction when the image ratio is a second value larger than the first value.
A sheet stacking device comprising: an alignment member that is movable in a width direction perpendicular to a direction in which the sheet is discharged by the discharge unit and that abuts against and aligns a side edge in the width direction of the sheet transported to the first stacking unit by the transport unit ;
the control unit starts blowing air after the sheet discharged to the first stacking unit is aligned in the width direction by the alignment member.
2. The sheet stacking device according to claim 1, wherein the sheet stacking device is a sheet stacking device. the control unit stops blowing air before an upstream end in a discharge direction of the sheet transported from the first stacking unit to the second stacking unit by the discharge unit reaches a downstream end of the first stacking unit in the discharge direction .
4. The sheet stacking device according to claim 1, wherein the sheet stacking device is a sheet stacking device. the control unit reduces the amount of air to be blown to a smaller amount before an upstream end in a discharge direction of the sheet transported from the first stacking unit to the second stacking unit by the discharge unit reaches a downstream end of the first stacking unit in the discharge direction .
4. The sheet stacking device according to claim 1, wherein the sheet stacking device is a sheet stacking device. a processing unit that processes a sheet stack made up of a plurality of sheets placed on the first stacking unit,
The discharge section discharges the sheet stack processed by the processing unit from the first stacking section to the second stacking section.
6. The sheet stacking device according to claim 1, wherein the sheet stacking device is a sheet stacking device. an image forming apparatus including an image forming unit for forming an image on a sheet;
and a sheet stacking device according to any one of claims 1 to 6, which stacks sheets on which images have been formed by the image forming device.
1. An image forming system comprising: an image forming unit that forms an image on a sheet;
a conveying section that conveys a sheet on which an image has been formed by the image forming section;
a first stacking section for stacking the sheet conveyed by the conveying section;
a discharge section that discharges the sheets placed on the first stacking section;
a second stacking section for stacking the sheets discharged by the discharge section;
a fan capable of blowing air against a lower surface of the sheet discharged by the discharge unit toward the second stacking unit;
A drive motor that drives the fan;
A control unit that controls the drive motor,
the control unit controls the rotation speed of the drive motor so that, when an image ratio of an image formed on a sheet by the image forming unit is a first value, the air volume to be blown onto the sheet is a first air volume including an air volume of 0, and, when the image ratio is a second value larger than the first value, the air volume to be blown onto the sheet is a second air volume larger than the first air volume.
1. An image forming system comprising:

Images