Paper discharging device, image forming device, post-processing device, control method, and control program

Abstract

To appropriately load a discharged paper sheet on a tray.SOLUTION: A paper discharging device 100 comprises: a loading tray 231 for receiving a discharged paper sheet P, that is provided in a liftable / descendible manner; and a control part 28 for controlling a lifting / descending position of the loading tray 231 when discharging the paper sheet P, based on a curl amount of the paper sheet P discharged onto the loading tray 231. Thus, positional displacement of the paper sheet P on the loading tray 231 can be suppressed, even when the discharged paper sheet P is curled.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a paper discharge device that discharges paper onto a tray, an image forming apparatus, a post-processing apparatus, a control method, and a control program. [Background technology]

[0002] In image forming devices, paper curls depending on the characteristics of the paper and the printing content. For example, recycled paper tends to curl more. If the paper curls too much, it may kick out paper that has already been ejected when ejecting it onto the tray. In this regard, for example, in Patent Document 1, the position of the paper discharge tray is changed vertically based on the type of paper fed, thereby preventing the transfer paper from curling or stacking improperly on the paper discharge tray. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-188322 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology in Patent Document 1 only considers paper types such as cardboard and OHP, and is therefore unable to address curl factors other than paper type, such as print content, etc. It is desirable to be able to suppress misalignment at the time of ejection due to curling of paper, regardless of the curl factor. The present invention has been made in view of the above circumstances, and has as its object to allow ejected sheets to be stacked suitably on a tray. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides a paper discharge device, a tray that is provided so as to be able to rise and fall and that receives discharged paper; a control unit that controls the elevation position of the tray when the paper is discharged based on the curl amount of the paper discharged to the tray; Equipped with. [Effects of the Invention]

[0006] According to the present invention, the discharged paper can be suitably stacked on the tray. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing the overall configuration of an image forming system according to an embodiment; [Figure 2] FIG. 2 is a block diagram showing a schematic control configuration of the image forming system according to the embodiment. [Figure 3] 4 is a flowchart showing the flow of operations of the image forming apparatus according to the embodiment. [Figure 4] 4 is a flowchart showing the flow of operations of the post-processing device according to the embodiment. [Figure 5] 10 is a flowchart showing a flow of movement control of a stacking tray according to an embodiment. [Figure 6A] 10A and 10B are diagrams for explaining movement control of a stacking tray according to an embodiment. [Figure 6B] 10A and 10B are diagrams for explaining movement control of a stacking tray according to an embodiment. [Figure 6C] 10A and 10B are diagrams for explaining movement control of a stacking tray according to an embodiment. [Figure 7A] 10A and 10B are diagrams for explaining movement control of a stacking tray according to an embodiment. [Figure 7B] 10A and 10B are diagrams for explaining movement control of a stacking tray according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] [Overall configuration of image formation system] FIG. 1 is a diagram showing the overall configuration of an image forming system 1 according to this embodiment. As shown in this figure, the image forming system 1 includes an image forming apparatus 10 and a post-processing apparatus 20.

[0010] The image forming apparatus 10 forms an image on a sheet of paper (print medium) based on print data. Specifically, the image forming apparatus 10 includes an image reading unit 12 and an image forming unit 13.

[0011] The image reading unit 12 reads an image of a document placed on a document table or an automatic document feeder (ADF), not shown, and obtains an image signal. Specifically, the image reading unit 12 scans and exposes the image of the document using the optical system of a scanning exposure device, reads the reflected light using a line image sensor, and obtains an image signal. The image signal undergoes processing such as A / D conversion, shading correction, and compression, and is then transmitted to the main body control unit 18 as image data. Note that the image data is not limited to data read by the image reading unit 12, and may be data received from an external device such as a client terminal.

[0012] The image forming unit 13 forms an image made up of four colors, C, M, Y, and K, on ​​paper in accordance with the pixel values ​​of the four colors of each pixel of the image-processed original image. The image forming unit 13 includes four image creating units 131, an intermediate transfer belt 132, a secondary transfer roller 133, a fixing unit 134, etc.

[0013] The four image forming units 131 are arranged in series (tandem) along the belt surface of the intermediate transfer belt 132, and form images of the respective colors of C, M, Y, and K. Each image forming unit 131 includes an exposure unit 131a, a photosensitive member 131b, a developing unit 131c, a charging unit 131d, a cleaning unit 131e, and a primary transfer roller 131f.

[0014] In each image forming unit 131, first, the photoconductor 131b is charged by the charging unit 131d. Next, a light beam emitted from the exposure unit 131a is scanned over the photoconductor 131b based on image data to form an electrostatic latent image. When the developing unit 131c supplies a color material such as toner and develops the image, an image (toner image) is formed on the photoconductor 131b. Images formed on the photoconductors 131b of the four image forming units 131 are sequentially superimposed and primarily transferred onto the intermediate transfer belt 132 by the respective primary transfer rollers 131f. The intermediate transfer belt 132 is an image carrier that rotates while being wound around multiple rollers. As a result, toner images of each color are formed on the intermediate transfer belt 132. After the primary transfer, the cleaning unit 131e removes color materials remaining on the photoconductors 131b.

[0015] The toner image that has been primarily transferred onto the intermediate transfer belt 132 is secondarily transferred by a pair of secondary transfer rollers 133 onto a sheet of paper fed from the manual feed tray C1 or the paper feed tray C2. The paper onto which the toner image has been secondarily transferred is transported to the fixing unit 134. In the fixing unit 134, the paper is heated and pressed by a fixing roller 134a, thereby fixing the toner image onto the paper. The paper that has passed through the fixing unit 134 is transported to the subsequent post-processing device 20. However, if images are to be formed on both sides of the paper, the paper is transported to a reversing path 135 after passing through the fixing unit 134, where the paper is reversed, and then the paper is fed again to the position of the secondary transfer roller 133.

[0016] FIG. 2 is a block diagram showing a schematic control configuration of the image forming system 1. As shown in FIG. As shown in FIG. 2, the image forming apparatus 10 includes an operation panel 14, a communication unit 15, a curl detection sensor 16, a storage unit 17, and a main body control unit 18 in addition to the above configuration.

[0017] The operation panel 14 includes an operation section that accepts various operations by a user (operator) and a display section that displays various information. The communication unit 15 is connected to a client terminal such as a PC via a network, and transmits and receives various data such as image data and job data.

[0018] The curl detection sensor 16 detects, for example, the amount of curl (warping) of the paper immediately before it is transported to the post-processing device 20, and outputs the result to the main body control unit 18. The curl detection sensor 16 is disposed, for example, downstream of the fixing unit 134 on the paper transport path. Here, at least the curl amount (including the direction) in the paper transport direction is detected. Hereinafter, unless otherwise specified, the "curl amount" refers to the amount of warping in the transport direction. The type of sensor used for curl detection sensor 16 and the method for acquiring the curl amount are not particularly limited. For example, an ultrasonic media sensor may be used to detect the transmittance, reflectance, relative reflectance, basis weight, etc. of the paper, and the curl amount may be estimated based on these values. Other conventionally known curl detection (estimation) techniques may also be used as appropriate. The location of curl detection sensor 16 is not particularly limited, and it may be located in post-processing device 20, for example.

[0019] The storage unit 17 is a memory configured by, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The storage unit 17 stores various programs and data, and also functions as a work area for the main body control unit 18. The main body control unit 18 is configured by, for example, a CPU (Central Processing Unit) and controls the entire image forming system 1 including the post-processing device 20. Specifically, the main body control unit 18 loads a program stored in advance in the storage unit 17 based on, for example, the operation content of the operation panel 14, and executes various processes in cooperation with the loaded program.

[0020] [Configuration of post-processing device] The post-processing device 20 performs post-processing such as stapling, punching, and sorting on the sheets conveyed from the image forming device 10 . As shown in FIG. 1, the post-processing device 20 includes a conveying mechanism 21, a stacking tray (main tray) 231, a sub-tray 232, a punching unit 24, a staple mechanism 25, and a detection sensor .

[0021] The conveying mechanism 21 includes registration rollers 211, intermediate rollers 212, a switch 216, sub-discharge rollers 213, storage rollers 214, main discharge rollers 215, and a paddle 219. Each roller forms a pair and sandwiches and conveys a sheet.

[0022] The transport mechanism 21 transports the paper transported from the image forming apparatus 10 along transport paths R1, R2, and R3. Specifically, a sheet of paper from the image forming apparatus 10 is first transported along transport path R1 by registration rollers 211 and intermediate rollers 212. When transport path R2 is selected by switch 216, the sheet of paper enters transport path R2 from transport path R1 and is discharged onto sub-tray 232 by sub-discharge rollers 213.

[0023] When the conveying path R3 is selected by the switch 216, the sheet enters the conveying path R3 from the conveying path R1, is conveyed along the conveying path R3 by the containing rollers 214, and reaches the main discharge rollers 215. In a post-processing mode other than the staple mode in which staple binding is performed, the main discharge rollers 215 rotate with the pair of rollers in pressure contact, and discharge the paper onto the stack tray 231.

[0024] In the staple (online staple) mode, the paddle 219 drops the paper onto the staple mechanism 25 below. In this case, the pair of main discharge rollers 215 separate and stop rotating, so that the paper is no longer constrained by either roller once it passes the storage roller 214. When the rotating paddle 219 comes into contact with the paper in this state, the paper is forcibly dropped onto the staple mechanism 25 (processing tray 250).

[0025] The stacking tray 231 corresponds to an example of a tray according to the present invention, and is disposed downstream of the transport path R3 to receive sheets transported along the transport path R3. The stacking tray 231 protrudes from the side of the main body of the post-processing device 20, and supports, on its upper surface, sheets discharged from the sheet discharge position E of the main body of the post-processing device 20. The stacking tray 231 is supported so as to be movable in the vertical direction (liftable) within a predetermined range below the sheet discharge position E on the transport path R3. The sub-tray 232 is provided to protrude from the upper surface of the main body of the post-processing device 20, and receives the sheets conveyed along the conveying path R2.

[0026] The punch unit 24 is disposed between the registration rollers 211 and the intermediate rollers 212, and punches holes in the paper that has been registered at the position of the registration rollers 211. The punched paper is discharged to the sub-tray 232.

[0027] The stapling mechanism 25 includes a processing tray 250, a stapling section 251, an alignment plate 253, and a bundle carrying-out means 254 (see FIG. 2). The processing tray 250 is disposed below the paddle 219 and receives the sheets dropped onto the paddle 219 . The staple unit 251 stores staples (not shown) and staples into the sheets (bundle) dropped onto the processing tray 250 by the paddle 219 . The alignment plate 253 aligns (aligns) multiple sheets of paper in the paper transport direction (FD direction) and the width direction (CD direction) perpendicular to the transport direction. The alignment plate 253 aligns multiple sheets of paper in both the transport direction and the width direction before post-processing such as stapling by the staple unit 251 is performed. The bundle carrying means 254 carries the sheets stapled by the staple unit 251 and discharges them onto the stack tray 231. The specific configuration of the bundle carrying means 254 is not particularly limited, and may be, for example, a conveyor belt.

[0028] The detection sensors 26 detect paper in each part of the post-processing device 20. In this embodiment, the detection sensors 26 are arranged upstream in the conveying direction of the registration rollers 211 on conveying path R1, upstream in the conveying direction of the sub-discharge rollers 213 on conveying path R2, and upstream in the conveying direction of the storage rollers 214 on conveying path R3. Of these, the last one closest to the paper discharge position E on conveying path R3 is called the discharge sensor 26a. The detection sensor 26 in this embodiment is a transmissive optical sensor. However, the type of the detection sensor 26 is not particularly limited as long as it can detect paper (passing paper), and may be, for example, an ultrasonic sensor, a reflective optical sensor, a touch sensor, or the like.

[0029] 2, in addition to the above configuration, post-processing device 20 includes tray lifting motor 233, upper surface sensor 29U, lower surface sensor 29L, memory unit 27, and control unit 28. Paper discharge device 100 according to the present invention includes stacking tray 231 and control unit 28. The tray lifting motor 233 lifts and lowers the stacking tray 231. In this embodiment, the tray lifting motor 233 is a DC motor.

[0030] The upper surface sensor 29U is disposed at a height position immediately below the paper discharge position E (see FIG. 6A, etc.), detects that the upper surface of the stacking tray 231 (or the paper on the stacking tray 231) is at that height, and outputs the result to the control unit 28. The upper surface sensors 29U are disposed on both sides in the width direction (the direction perpendicular to the paper surface in FIG. 1) of the stacking tray 231. This makes it possible to suitably detect the height position of the highest paper even when the heights of the paper on the stacking tray 231 are different on both sides in the width direction, for example, when a stack of paper is stacked with the stapled portions biased to one side in the width direction. The lower surface sensor 29L is disposed at a height position lower than the upper surface sensor 29U, and detects that the lower surface (lower portion) of the stacking tray 231 is at that height and outputs the result to the control unit 28. In this embodiment, the lower surface sensor 29L is disposed at the lower limit position in the movement range of the stacking tray 231. The lower surface sensor 29L is disposed at the center of the stacking tray 231 in the width direction.

[0031] The storage unit 27 is a memory configured by, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The storage unit 27 stores various programs and data, and also functions as a work area for the control unit . Control unit 28 is configured with, for example, a CPU (Central Processing Unit) and controls the entire post-processing device 20. Specifically, control unit 28 executes various processes based on control commands from main body control unit 18 of image forming apparatus 10, for example, by programs stored in advance in storage unit 27. Further, the post-processing device 20 is supplied with power from the power supply of the image forming device 10 .

[0032] [Image formation system operation] Fig. 3 is a flowchart showing the flow of operations of the image forming apparatus 10. Fig. 4 is a flowchart showing the operations of the post-processing apparatus 20 following the operations of the image forming apparatus 10 in Fig. 3. The printing process in the image forming system 1 is executed by the main body control unit 18 of the image forming apparatus 10 reading out the corresponding program from the storage unit 17 and developing it.

[0033] As shown in FIG. 3, first, the main body control unit 18 controls communication with external devices and the like, and also controls input such as receiving a print job from an external device (step S1).

[0034] Next, the main body control unit 18 performs panel control such as accepting input of a copy job from the operation panel 14 (step S2). At this time, for example, the user sets manual feed tray C1 or paper feed tray C2 from the operation panel 14 and places a document in the document feeder. Then, the user sets various image formation modes on the operation panel 14 and presses the copy start key. The scanned image is saved in the memory unit 17. The main body control unit 18 determines the fixing temperature and speed, development output parameters, transfer output parameters, transport speed parameters, etc. based on the selected paper type, etc. Then, the main body control unit 18 starts the transport drive and starts feeding the selected paper. The types of paper loaded in the manual feed tray C1 and the paper feed tray C2 are preset by a user operation on the operation panel 14. These paper types include, for example, thin paper, regular paper, thick paper 1, thick paper 2, thick paper 3, etc. Information on the paper type includes at least information on the thickness of the paper.

[0035] Next, the main body control unit 18 performs copy control such as image formation and output in the image forming device 10, and forms an image on paper (step S3). At this time, the main body control unit 18 detects various characteristics and the amount of curl of the paper using the curl detection sensor 16. Next, the main body control unit 18 controls communication with the post-processing device 20 to perform predetermined post-processing based on the print job or copy job (step S4).

[0036] At this time, as shown in FIG. 4, the control unit 28 of the post-processing device 20 controls communication with the image forming device 10 (step S5) and controls detection of the paper conveyed from the image forming device 10 (step S6). In the paper detection control, information on at least the type, curl amount, and size of the paper is acquired from the image forming apparatus 10. The acquired information is stored in the storage unit 27. In addition, the control unit 28 acquires information on the post-processing mode from the image forming apparatus 10.

[0037] Next, the control unit 28 controls the conveying mechanism 21 to control the conveyance of the printed paper P (see FIG. 6B) conveyed from the image forming device 10 (step S7). The control unit 28 controls the drive of each roller that conveys the paper P in accordance with the conveyance speed of the image forming device 10. Here, it is assumed that the paper sheets P are transported along a path that leads to the paper sheets P being stapled by the staple mechanism 25 and being discharged onto the stacking tray 231.

[0038] Next, the control unit 28 controls the operations of the post-processing unit (for example, the punch unit 24) and the paddle 219 (step S8). Specifically, the control unit 28 lowers and then rotates the paddle 219 a predetermined time after the discharge sensor 26a detects the sheet P, and stores the sheet P in the processing tray 250. The number of rotations of the paddle 219 is determined depending on the type of sheet P. If the sheet P is plain paper or thin paper, the curl and stiffness (resistance) are small, so the paddle 219 is rotated, for example, twice. On the other hand, if the sheet P is thick paper, the curl and resistance are relatively large, so the paddle 219 is rotated, for example, three times. The rotation speed of the paddle 219 may be adjusted depending on the type of sheet P. For example, if the sheet P is thin paper, the paddle 219 may be rotated relatively slowly.

[0039] Next, the control unit 28 performs finishing control (step S9). In this embodiment, the control unit 28 executes control relating to stapling by the staple mechanism 25. Here, the control unit 28 aligns the sheets P stored in the processing tray 250 one by one in the FD direction and the CD direction using the alignment plate 253. Then, the control unit 28 staples a predetermined number of sheets P using the staple unit 251, and discharges them onto the stack tray 231 using the bundle discharge means 254. Note that the discharge of the sheets P onto the stack tray 231 is performed in conjunction with the movement control of the stack tray 231 in step S10. If the curl of the paper P is large, it may not be possible to align it properly, resulting in misalignment. This is because the weight, rigidity, and surface resistance (coefficient of friction) of the paper vary depending on the type of paper P, and the degree of curl of the paper changes depending on the fixing temperature of the image forming apparatus 10 when the paper is passed through and the ambient humidity, etc., and the behavior of the paper during transport changes. In addition, the behavior of the paper during transport changes depending on the number of sheets of paper stored in the processing tray 250, the image density, the environment in which the device is used, etc., and this can result in misalignment of the paper P (or a stack of sheets) in the processing tray 250 or on the stacking tray 231.

[0040] Next, the control unit 28 controls the movement of the stacking tray 231 onto which the paper sheets P are discharged (step S10). This movement control is executed every time a sheet P is discharged onto the stacking tray 231, regardless of the transport path in the post-processing device 20 or the contents of post-processing. The processing of each step above may be performed for each sheet or set of paper P, or may be performed for each job if the contents are the same within the same job, for example.

[0041] [Loading tray movement control] The movement control of the stacking tray 231 will now be described in detail. 5 is a flowchart showing the flow of movement control of the stacking tray 231. FIGS. 6A to 7B are diagrams for explaining the movement control of the stacking tray 231. In the following explanation, the paper P discharged onto the stacking tray 231 includes both a single sheet and a stack of sheets stapled together by the staple mechanism 25. In either case, the control operation of the stacking tray 231 is basically the same. For the sake of convenience, the following explanation may overlap with the control processes of the image forming apparatus 10 and post-processing apparatus 20 described above. Although not particularly limited, it is assumed that the paper P is once accommodated in the processing tray 250 and then discharged onto the stacking tray 231.

[0042] As shown in FIG. 5, in the movement control of the stacking tray 231, the control unit 28 first determines whether or not a job (copy or print) is started in the image forming apparatus 10 (step T1). When it is determined that the job is not started in the image forming apparatus 10 (step T1; No), the control unit 28 repeats the process of step T1. If the start of the job has been confirmed in any step prior to step S10, step T1 may be omitted.

[0043] On the other hand, if it is determined in step T1 that a job is to be started in image forming apparatus 10 (step T1; Yes), control section 28 drives tray lift motor 233 to lift stack tray 231 (step T2). The stacking tray 231 has a home position at the lower limit of its movement range, and waits at this lower limit position in normal conditions such as when no job is being executed (FIG. 6A).

[0044] Next, the control unit 28 determines whether or not either of the two upper surface sensors 29U has detected the stacking tray 231 (or the sheets P on the stacking tray 231) (step T3). Then, when it is determined that none of the upper surface sensors 29U has detected the stacking tray 231 (or the paper P) (step T3; No), the control unit 28 proceeds to the process of step T2 described above, and further raises the stacking tray 231.

[0045] On the other hand, if it is determined that any of the upper surface sensors 29U has detected the stacking tray 231 (or the paper P) (step T3; Yes), the control unit 28 stops the lifting of the stacking tray 231 (step T4).

[0046] Next, the control unit 28 determines the magnitude of the curl amount of the paper P acquired in step S6 (step T5). Here, the control unit 28 classifies the curl amount of the paper P into multiple levels (for example, three levels: large, medium, and small) based on a preset threshold value, for example. In the case of a paper stack, the largest curl amount of all the paper sheets P included therein is adopted and used for classification.

[0047] Next, the control unit 28 continues the transport control and transports the paper P (step T6). Next, the control section 28 determines whether the curl amount of the discharged paper P is "large" or not based on the result of step T5 (step T7). Then, when it is determined that the magnitude of the curl amount is not "large" (step T7; No), the control unit 28 proceeds to the process of step T11, which will be described later.

[0048] On the other hand, if it is determined in step T7 that the curl amount is "large" (step T7; Yes), the control section 28 drives the tray lifting motor 233 to lower the stacking tray 231 (step T8). Here, for example, when the discharge sensor 26a detects the passage of paper, the stacking tray 231 starts to lower. If the paper P is the first sheet of the job, the stacking tray 231 is lowered before the paper P is discharged onto the processing tray 250.

[0049] Next, the control unit 28 determines whether the stacking tray 231 has been lowered by a predetermined amount (step T9). If it is determined that the stacking tray 231 has not been lowered by the predetermined amount (step T9; No), the control unit 28 proceeds to the process of step T8 described above, and further lowers the stacking tray 231. Here, the "predetermined lowering amount" is a movement amount that targets a predetermined lifting position based on the amount of curl of the paper P. The "predetermined lifting position" is a vertical position that moves downward from the paper discharge position E as the amount of curl of the paper P increases.

[0050] In step T9, if it is determined that the stacking tray 231 has been lowered by the predetermined amount (step T9; Yes), the control unit 28 stops the lowering of the stacking tray 231 (step T10). If the stacking tray 231 reaches the lower limit position detected by the lower surface sensor 29L before the predetermined lowering amount is detected, the stacking tray 231 is stopped at the lower limit position.

[0051] Next, the control section 28 continues the transport control and discharges the sheets P onto the stacking tray 231 (step T11). In this embodiment, the sheet P is discharged from the processing tray 250 onto the stacking tray 231 by the bundle discharge means 254.

[0052] At this time, if the curl amount of the discharged paper P is not "large", the stacking tray 231 is in the lift position detected by the upper surface sensor 29U by the processing of steps T2 to T4. This allows the stacking tray 231 to receive the paper P with a small curl at a height close to the paper discharge position E.

[0053] On the other hand, if the curl amount of the discharged paper P is "large", the stacking tray 231 is at a lift position lowered by a predetermined lowering amount based on the curl amount through the processing of steps T8 to T10. This allows the discharged paper P to be stacked on the stacking tray 231 in an appropriate manner. That is, if the stacking tray 231 is set to a lifting position close to the discharge position E even though the curl of the sheet P is large, the sheet P may kick out the discharged sheets Px (FIG. 6B). In this regard, in this embodiment, if the curl of the sheet P is large, the stacking tray 231 is lowered in accordance with the curl amount. Therefore, even if the curl of the sheet P is large, interference between the sheet P and the discharged sheets Px is suppressed, and misalignment of the sheet P on the stacking tray 231 can be suppressed (FIG. 6C).

[0054] Next, the control unit 28 determines whether or not the discharge of one set of sheets P has been completed (step T12). Here, "one set" of sheets P means a predetermined number of sheets or a bundle of sheets P. If it is determined that the discharge of one set of paper P has not been completed (step T12; No), the process of step T12 is repeated.

[0055] In step T12, if it is determined that the discharge of one set of sheets P has been completed (step T12; Yes), control section 28 drives tray lifting motor 233 to further lower stacking tray 231 (step T13; FIG. 7A). However, if the number of sheets that can be stacked on the stacking tray 231 exceeds the upper limit, the stacking tray 231 is not lowered after the stack is discharged at the end of the job, but is made to wait at the detection position of the upper surface sensor 29U. Also, if none of the upper surface sensors 29U detects the stacking tray 231 (or the paper P), the stacking tray 231 does not need to be lowered.

[0056] Next, the control unit 28 determines whether the job has been completed (step T14). If it is determined that the job has not been completed (step T14; No), the control unit 28 proceeds to the process of step T2 described above. On the other hand, if it is determined that the job has ended (step T14; Yes), the control unit 28 moves the stack tray 231 to the lowest position detected by the lower surface sensor 29L (step T15; FIG. 7B), and ends the process.

[0057] [Technical effect of this embodiment] As described above, according to this embodiment, the lifting position (vertical position) of the stacking tray 231 is controlled based on the amount of curl of the sheets (sheet stack) P discharged onto the stacking tray 231. As a result, even if the discharged paper P is curled, it is possible to prevent the paper P from shifting in position (misalignment) on the stacking tray 231, regardless of the cause of the curl. Therefore, the discharged paper P can be stacked appropriately on the stacking tray 231.

[0058] Furthermore, according to this embodiment, as the curl amount of the paper P increases, the stacking tray 231 moves to a lifting position that is spaced downward from the paper discharge position E. This makes it possible to suitably prevent the paper P from interfering with the already discharged paper Px on the stacking tray 231, even if the paper P to be discharged is curled. Therefore, misalignment of the paper P on the stacking tray 231 can be prevented.

[0059] Furthermore, according to this embodiment, the stacking tray 231 is normally positioned at the lower limit of its movement range, and when the paper P is discharged, it rises to a predetermined lift position below the paper discharge position E, and then descends based on the amount of curl of the paper P. Therefore, when the curl amount of the discharged paper P is small, the stacking tray 231 receives the paper P at a height close to the paper discharge position E, and when the curl amount is large, the stacking tray 231 receives the paper P at a position lowered according to the curl amount. Therefore, regardless of the curl amount of the paper P, the paper P can be suitably stacked on the stacking tray 231.

[0060] [others] The above describes one embodiment of the present invention, but embodiments to which the present invention can be applied are not limited to the above-described embodiment and its variations, and can be modified as appropriate within the scope of the invention.

[0061] For example, in the above embodiment, the actual detected value (estimated value) of the curl amount is used to determine the magnitude of the curl amount. However, in addition to (or instead of) determining the curl amount based on the detected value, the following determination may also be made. - Determine the amount of curl based on the size, type, and basis weight of the paper. For example, thick paper, thin paper, and recycled paper are considered to have a large amount of curl. - Determine the amount of curl depending on whether you are printing on one side or both sides (double-sided printing will result in more curl). - Determine the amount of curl depending on whether you are printing in color or monochrome (color printing will be larger). If the number of sheets passed continuously is greater than the specified number, the curl amount is determined to be large. -Consider the fixing temperature, humidity, and transport speed of the image forming device. - Consider the type of image forming device. If it is a slow model, the curl amount is judged to be large. Furthermore, since a sensor for detecting the amount of curl is often not installed in a low-speed image forming apparatus, in such a case, the magnitude of the amount of curl may be estimated based on the above-mentioned factors that can be detected by a device other than the sensor.

[0062] In the above embodiment, the stacking tray 231 is lowered by a predetermined amount when the curl amount is "large." However, the manner in which the stacking tray 231 is moved is not particularly limited as long as the amount of lowering in step T8 corresponds to the amount of curl. For example, the determination may be made in multiple stages as follows: Curl amount: Large → Loading tray lowering amount: Large (lowering time: Long) Curl amount: Medium → Loading tray lowering amount: Medium (lowering time: Medium) Curl amount: Small → Loading tray lowering amount: Small (lowering time: Short) Curl amount: Zero → Loading tray lowering amount: Zero Alternatively, the amount of lowering of the stacking tray 231 may be continuously made to correspond to the value of the curl amount.

[0063] The direction of the curl may also be taken into consideration when determining the amount of lowering of the stacking tray 231. Specifically, if the curl direction of the sheet P is downward, the lifting position of the stacking tray 231 may be controlled based on the amount of curl of the sheet P. This makes it possible to omit movement control of the stacking tray 231 based on the amount of curl in the case of an upward curl that is unlikely to cause misalignment of the paper P. Therefore, movement control of the stacking tray 231 can be executed efficiently.

[0064] Furthermore, the print interval may be adjusted according to the elevation position of the stacking tray 231, which is moved based on the amount of curl of the paper P. In other words, when the stacking tray 231 is lowered according to the amount of curl of the paper, the greater the amount of lowering, the longer the movement time required. Therefore, the print interval in the image forming apparatus 10 may be adjusted according to the amount of lowering of the stacking tray 231. The print interval is the waiting time from the end of printing one copy until the start of printing the next copy. This makes it possible to prevent a decrease in productivity due to the timing of the lowering of the stacking tray 231 not matching the timing of printing in the image forming apparatus 10.

[0065] In the above embodiment, when the paper is discharged, the stacking tray is first raised to the position of the upper surface sensor and then lowered by an amount corresponding to the amount of curl. However, the stacking tray may not be raised to the position of the upper surface sensor, and the amount of lift from the lower limit position may be controlled based on the amount of curl.

[0066] The alignment members for aligning the sheets include a paddle, an alignment plate, a bundle discharge means, a discharge roller, and a stapler. When alignment is imperfect with one of the alignment members, the post-processing operations of the other alignment members may be changed.

[0067] In the above embodiment, the paper discharge device according to the present invention is provided in a post-processing device separate from the image forming apparatus. However, the paper discharge device according to the present invention may also be provided in the image forming apparatus. Furthermore, the image forming system according to the above embodiment can be considered an image forming apparatus if the functions of the image forming apparatus and the post-processing device are integrated. Furthermore, the paper discharge device according to the present invention is not limited to post-processing devices or image forming apparatuses, but can be widely applied to paper discharge devices that discharge paper that may curl. [Explanation of symbols]

[0068] 1. Image forming system 10 Image forming device 13 Image forming unit 16 Curl detection sensor (curl detection means) 18 Main unit control section 20 Aftertreatment device 21 Transport mechanism 25 Stapling mechanism (post-processing section) 26 Detection sensor 26a Emission sensor 28 Control Unit 29L Bottom sensor 29U Top sensor 100 Paper ejection device 215 Main discharge roller (discharge means) 231 Loading tray (tray) 233 Tray lift motor 250 processing trays 254 Bundle delivery means (discharge means) E Paper ejection position P paper Px Ejected paper

Claims

1. a tray that is provided so as to be able to rise and fall and that receives discharged paper; a control unit that controls the elevation position of the tray when the paper is discharged based on the curl amount of the paper discharged to the tray; A paper discharge device comprising:

2. the control unit moves the tray to a lifting position that is spaced downward from a paper discharge position where the paper is discharged as the curl amount of the paper increases. The paper delivery device according to claim 1 .

3. The control unit When the curl amount of the paper is a first magnitude, the tray is controlled to a first lifting position; When the curl amount of the paper is a second size larger than the first size, the tray is controlled to a second lifting position that is lower than the first lifting position. The paper delivery device according to claim 2 .

4. The control unit The tray is normally positioned at the lower limit of its range of movement, When the paper is discharged, the tray is raised to a predetermined lift position below the paper discharge position, and then lowering the tray based on the amount of curl of the paper; The paper delivery device according to claim 2 .

5. the control unit controls the lifting position of the tray based on the amount of curl of the paper when the curl direction of the paper is downward. The paper delivery device according to claim 1 .

6. the control unit adjusts the print interval in accordance with the elevation position of the tray, which is moved based on the amount of curl of the paper. The paper delivery device according to claim 1 .

7. an image forming unit that forms an image on the paper; a curl detection means for detecting the curl amount of the paper; The paper discharge device according to any one of claims 1 to 6, An image forming apparatus comprising:

8. a post-processing section that performs post-processing on the paper on which the image is formed; The paper discharge device according to any one of claims 1 to 6, a discharge means for discharging the paper from the post-processing section to the tray; A post-processing device comprising:

9. A method for controlling a paper discharge device having a tray that can be raised and lowered and that receives discharged paper, comprising: a control unit that controls the elevation position of the tray when the paper is discharged based on the curl amount of the paper discharged to the tray; Control method.

10. A control program for a paper discharge device having a tray that can be raised and lowered and that receives discharged paper, causing the computer to function as a control unit that controls the elevation position of the tray when the paper is discharged onto the tray based on the amount of curl of the paper; Control program.

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