Post-processing device and image forming device including the same

Abstract

To provide a post-processing device which prevents a sheet loaded on a paper discharge tray on the lower side from interfering with a paper discharge tray on the upper side.SOLUTION: A post-processing device 10 includes: a middle stage paper discharge tray 2; a lower stage paper discharge tray 3 positioned below the middle stage paper discharge tray 2; and a paper sensor 20 for transmitting a detection signal by detecting the fact that a distance between an upper surface of a sheet P1 loaded on the lower stage paper discharge tray 3 and a lower surface of the middle stage paper discharge tray 2 becomes equal to or less than a predetermined distance. The middle stage paper discharge tray 2 and the lower stage paper discharge tray 3 can move vertically being independent of each other. The paper sensor 20 includes a paper detection part 21 arranged so as to extend downward from the lower surface of the middle stage paper discharge tray 2. In the case where the paper detection part 21 comes into contact with the upper surface of the sheet P1 loaded on the lower stage paper discharge tray 3, and the distance between the upper surface of the sheet P1 and the lower surface of the middle stage paper discharge tray 2 becomes equal to or less than the predetermined distance, the distance between the middle stage paper discharge tray 2 and the lower stage paper discharge tray 3 is forbidden from being smaller than that.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a post-processing device that performs post-processing on a sheet on which an image has been formed, and an image forming apparatus including the same. [Background technology]

[0002] Conventionally, there is a post-processing device that is provided in conjunction with an image forming unit and performs post-processing, such as stapling, on sheets on which an image is formed by the image forming unit. The sheets on which an image is formed by the image forming unit are transported to the post-processing device via, for example, a relay device, and then discharged from the post-processing device to the outside. The post-processing device has multiple discharge trays for stacking the discharged sheets, for example, two discharge trays arranged vertically. In such a post-processing device, the discharge trays are movable up and down. For example, the lower discharge tray is positioned to match the position of the discharge outlet from which the sheets are discharged to the outside, and the sheets are discharged from the discharge outlet and stacked on the lower discharge tray. When the sheet capacity limit of the lower discharge tray is reached, the lower discharge tray is lowered to a position away from the discharge outlet, and the upper discharge tray is moved to the position of the discharge outlet instead. The sheets are then discharged from the discharge outlet and stacked on the lower discharge tray. When sheets are stacked on the paper output tray, if the top position of the stacked sheets is higher than the position of the paper output outlet, the discharged sheets will not be stacked, so when sheets are stacked on the paper output tray (when sheets are being discharged), the paper output tray moves downward as appropriate to prevent problems with sheet stacking. In this way, by maintaining the top position of the stacked sheets lower than the paper output outlet, sheets are stacked on the paper output tray.

[0003] In such post-processing devices, if a large number of sheets are loaded onto the discharge tray, the weight of the sheets increases, and if the number of sheets loaded exceeds the discharge tray's loading limit, problems such as damage to the discharge tray or problems with the up and down movement of the discharge tray may occur.

[0004] Therefore, for example, the post-processing device described in Patent Document 1 is equipped with a paper output tray with a weight sensor, which allows the load capacity of the paper output tray to be estimated with high accuracy and prevents sheets exceeding the load limit from being loaded on the paper output tray.

[0005] However, the post-processing device described in Patent Document 1 detects the weight of the sheets stacked on the paper discharge tray and processes them, but does not detect the height of the stacked sheets. Although the height can be estimated from the weight of the stacked sheets, the thickness, etc. of the sheets varies depending on the type of sheet, making it difficult to accurately estimate the height of the stacked sheets from the weight of the sheets.

[0006] Therefore, in addition to the post-processing device described in Patent Document 1, a post-processing device has also been proposed that has a sensor for detecting sheets located near the paper discharge outlet. In this post-processing device, the sensor is installed on the side of the post-processing device body where the paper discharge outlet is formed, and the edge of the sheet discharged from the paper discharge outlet and stacked on the paper discharge tray comes into contact with the sensor to detect the height of the stacked sheets, thereby detecting the amount of sheets stacked on the paper discharge tray. This makes it possible to prevent sheets from being stacked on the paper discharge tray beyond the stack limit.

[0007] Furthermore, this post-processing device can detect the height position of sheets stacked on the lower discharge tray, so even if the upper discharge tray is lowered while sheets are stacked on the lower discharge tray, it can prevent the top surfaces of the sheets stacked on the lower discharge tray from interfering with the upper discharge tray. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-59575 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the above-described post-processing device, the force of the discharge of sheets may cause them to be positioned on the discharge tray away from the side of the post-processing device where the discharge outlet is formed. In such cases, the sheets on the discharge tray do not come into contact with the sensor installed on the side of the post-processing device where the discharge outlet is formed, and the height of the sheets stacked on the discharge tray cannot be accurately detected. This poses a problem in that it is not possible to prevent the top surfaces of the sheets stacked on the lower discharge tray from interfering with the upper discharge tray.

[0010] The present disclosure has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a post-processing device that prevents sheets loaded on a lower output tray from interfering with an upper output tray, and an image forming device equipped with the same. [Means for solving the problem]

[0011] A post-processing device according to one aspect of the present disclosure is a post-processing device that performs post-processing on sheets on which images are formed, and includes: a first output tray to which sheets are discharged; a second output tray located below the first output tray to which sheets are discharged; and a paper sensor that detects when the distance between the top surface of a sheet stacked on the second output tray and the bottom surface of the first output tray falls below a predetermined distance so that the sheets stacked on the second output tray do not interfere with the first output tray, and emits a detection signal; the first output tray and the second output tray are movable up and down independently of each other, and the paper sensor has a paper detection unit that is arranged to extend downward from the bottom surface of the first output tray, and when the paper detection unit contacts the top surface of a sheet stacked on the second output tray and the distance between the top surface of the sheet and the bottom surface of the first output tray falls below the predetermined distance, the paper sensor emits the detection signal, and when the detection signal is emitted, the distance between the first output tray and the second output tray is prevented from becoming any smaller.

[0012] This prevents interference between the sheets stacked on the second discharge tray and the first discharge tray, thereby preventing damage to the first discharge tray, the second discharge tray, and the sheets. Furthermore, even if the sheets on the second discharge tray are misaligned, because the upper surface of the sheet is detected, it can be more reliably detected that the upper surface of the sheet and the first discharge tray are too close, preventing damage to the first discharge tray, the second discharge tray, and the sheets.

[0013] In addition, in the above-mentioned post-processing device, the paper detection unit has a shape that branches in two directions, and has an upper detection end that extends upward from the upper surface of the first paper output tray and a lower detection end that extends downward from the lower surface of the first paper output tray, and when the sheet is placed on the first paper output tray and the upper detection end comes into contact with the sheet, the paper sensor detects that the sheet is placed on the first paper output tray, and when the lower detection end comes into contact with the upper surface of the sheet stacked on the second paper output tray and the distance between the upper surface of the sheet and the lower surface of the first paper output tray is less than the specified distance, the paper sensor emits the detection signal.

[0014] This makes it possible not only to detect that the sheets stacked on the second discharge tray and the first discharge tray are too close to each other, but also to detect that a sheet is placed on the first discharge tray.

[0015] In addition, in the above-mentioned post-processing device, the paper detection unit may have an inclined support portion that extends diagonally relative to the sheet discharged to the second discharge tray, and a detection end located at the tip of the inclined support portion, and when the detection end contacts the upper surface of the sheet stacked on the second discharge tray and the distance between the upper surface of the sheet and the lower surface of the first discharge tray becomes less than the specified distance, the paper sensor may emit the detection signal.

[0016] This not only detects when sheets loaded on the second discharge tray are too close to the first discharge tray, but also supports the sheets loaded on the second discharge tray and prevents sheets being discharged onto the second discharge tray from being loaded at an angle (tilted).

[0017] In the above-described post-processing device, the sheet detection unit may be rotatable with respect to the first sheet discharge tray.

[0018] This makes it difficult for the paper detection unit to scratch the top surface of the sheet even when it comes into contact with the sheet, and can prevent the sheet from being deteriorated.

[0019] An image forming apparatus according to one aspect of the present disclosure includes the above-described post-processing device and an image forming unit that forms an image on the sheet.

[0020] This prevents damage to the first and second ejection trays and the sheets. Also, even if the sheets on the second ejection tray are misaligned, the upper surface of the sheets is detected, so it is possible to more reliably detect that the upper surface of the sheets and the first ejection tray are too close to each other, preventing damage to the first and second ejection trays and the sheets. [Effects of the Invention]

[0021] According to the present disclosure, it is possible to provide a post-processing device that prevents sheets stacked on a lower paper output tray from interfering with an upper paper output tray, and an image forming apparatus including the same. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a front view showing a schematic external configuration of an image forming apparatus according to a first embodiment of the present disclosure. [Figure 2] 1 is a perspective view showing a configuration of a post-processing device according to a first embodiment of the present disclosure. [Figure 3]1 is a perspective front view showing a schematic configuration of a post-processing device according to a first embodiment of the present disclosure. [Figure 4] FIG. 2 is an enlarged perspective front view illustrating the configuration of a sheet sensor of the post-processing device according to the first embodiment of the present disclosure. [Figure 5] FIG. 2 is a block diagram showing a control configuration of the post-processing device according to the first embodiment of the present disclosure. [Figure 6] FIG. 2 is a first diagram for explaining the operation of the post-processing device according to the first embodiment of the present disclosure. [Figure 7] FIG. 2 is a second diagram for explaining the operation of the post-processing device according to the first embodiment of the present disclosure. [Figure 8] FIG. 3 is a third diagram for explaining the operation of the post-processing device according to the first embodiment of the present disclosure. [Figure 9] FIG. 4 is a fourth diagram for explaining the operation of the post-processing device according to the first embodiment of the present disclosure. [Figure 10] FIG. 5 is a fifth diagram for explaining the operation of the post-processing device according to the first embodiment of the present disclosure. [Figure 11] 5 is a flowchart showing an example of a control operation of the post-processing device according to the first embodiment of the present disclosure. [Figure 12] FIG. 10 is an enlarged perspective front view illustrating the configuration of a sheet sensor of a post-processing device according to a second embodiment of the present disclosure. [Figure 13] FIG. 10 is a first diagram for explaining the operation of a post-processing device according to a second embodiment of the present disclosure. [Figure 14] FIG. 10 is a second diagram for explaining the operation of the post-processing device according to the second embodiment of the present disclosure. [Figure 15] FIG. 11 is an enlarged perspective front view illustrating the configuration of a sheet sensor of a post-processing device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0024] (First embodiment) The configuration of an image forming apparatus according to a first embodiment of the present disclosure will be described with reference to the drawings. Note that a post-processing device is a part of the image forming apparatus. Fig. 1 is a front view showing a schematic external configuration of the image forming apparatus according to the first embodiment of the present disclosure.

[0025] 1, the image forming apparatus 100 includes an image forming unit 70, a relay device 60, and a post-processing device 10. The image forming apparatus 100 forms an image on a sheet P and discharges the sheet P to the outside. The image forming apparatus 100 can also perform post-processing such as stapling, which binds a plurality of sheets P together.

[0026] The image forming unit 70 has a function of forming an image on a sheet (paper), and is, for example, an MFP (Multifunction Peripheral). An MFP is a multifunction machine that combines the functions of a copier, printer, facsimile, scanner, etc. The image forming unit 70 can, for example, read an image of an original document set by an operator, create image data of the read original document, and form an image based on this image data on a sheet P. It is also possible to output the image data as is to an external device. The image forming unit 70 can also form an image on a sheet P based on image data sent from a printer, or form an image of text or the like on a sheet P based on data sent by facsimile.

[0027] The relay device 60 is a device that relays the sheet on which an image is formed by the image forming unit 70 when it is transported to the post-processing device 10. In other words, the sheet P on which an image is formed by the image forming unit 70 is transported from the image forming unit 70 to the relay device 60, and then from the relay device 60 to the post-processing device 10, and then discharged from the post-processing device 10 to the outside. The relay device 60 is a device that adjusts the positions of the sheet P discharge position of the image forming unit 70 and the sheet P load position into the post-processing device 10 when the heights of these positions are different, for example, so that the sheet P discharged from the image forming unit 70 can be loaded into the post-processing device 10. In other words, the relay device 60 is a device that transports the sheet P from the image forming unit 70 to the post-processing device 10.

[0028] Next, the configuration of the post-processing device 10 according to the first embodiment will be described with reference to the drawings. As described above, the image forming apparatus 100 is equipped with the post-processing device 10. Fig. 2 is a perspective view showing the configuration of the post-processing device according to the first embodiment of the present disclosure. Fig. 3 is a front view showing in perspective the schematic configuration of the post-processing device according to the first embodiment of the present disclosure.

[0029] 2 and 3, the post-processing device 10 includes a post-processing device main body 11, and an upper paper discharge tray 1, a middle paper discharge tray 2, and a lower paper discharge tray 3 onto which sheets P formed to protrude from a side wall surface 12 of the post-processing device main body 11 are discharged. The middle paper discharge tray 2 is provided with a paper sensor 30, which has a paper detection unit 31 extending downward from the underside of the middle paper discharge tray 2.

[0030] Further, provided within the post-processing device body 11 are a pair of conveying rollers 5a, a pair of conveying rollers 5b, a pair of discharge rollers 4, a staple processing section 6, and a conveying tray 7. Further, a side wall surface 12 is formed with a sheet discharge port 8 through which the sheet P is discharged from the post-processing device body 11.

[0031] The conveying rollers 5a convey the sheet P carried into the post-processing device 10 from the relay device 60, and convey it to the conveying rollers 5b. The conveying rollers 5b further convey the sheet P conveyed from the conveying rollers 5a to the discharge rollers 4. As a result, the sheet P is conveyed and discharged as shown in the sheet conveying path S. The post-processing device 10 can also perform stapling to bind multiple sheets P. When stapling is performed, the conveying rollers 5b convey the sheet P so that multiple sheets P to be bound together are stacked on the conveying tray 7.

[0032] The staple processing unit 6 has a function of stacking and stapling a plurality of sheets P. Specifically, when predetermined sheets P are stacked on the conveyance tray 7, the staple processing unit 6 staples the plurality of sheets P stacked on the conveyance tray 7 with staples. Then, the staple processing unit 6 pushes the plurality of stapled sheets P toward the discharge rollers 4.

[0033] When stapling is not performed, the discharge rollers 4 discharge the sheets P conveyed from the conveyance rollers 5b from the paper discharge outlet 8 to the outside of the post-processing device main body 11. When stapling is performed, the discharge rollers 4 discharge the multiple sheets P stapled together by staples and pushed out from the staple processing unit 6 from the paper discharge outlet 8 to the outside of the post-processing device main body 11.

[0034] The upper, middle, and lower paper output trays 1, 2, and 3 each receive a stack of sheets P ejected from the paper output outlet 8. Therefore, they can each move up and down along the side wall surface 12. That is, when a sheet P is ejected to the upper paper output tray 1, the upper paper output tray 1 moves to a position below and near the paper output outlet 8. Similarly, when a sheet P is ejected to either the middle or lower paper output tray 2 or 3, either the middle or lower paper output tray 2 or 3 moves to a position below and near the paper output outlet 8. Furthermore, as the sheets P ejected from the paper output outlet 8 are stacked, their height increases, so the upper paper output tray 1 (middle or lower paper output tray 2 or 3) moves downward sequentially in accordance with the amount of paper ejected from the paper output outlet 8 so that the topmost sheet P of the stack is positioned below the paper output outlet 8.

[0035] The post-processing device 10 also has an offset function, and can execute offset processing to shift the position of the sheet P from the sheet discharge port 8 by a specified unit before discharging the sheet.

[0036] Here, the upper and middle paper ejection trays 1 and 2 are integrally configured and move up and down together. The lower paper ejection tray 3 is not integral with the upper and middle paper ejection trays 1 and 2, and the lower paper ejection tray 3, upper paper ejection tray 1, and middle paper ejection tray 2 move independently of each other.

[0037] In the post-processing device 10 according to the first embodiment, sheets P that have been stapled or offset processed are discharged to the upper discharge tray 1 and the lower discharge tray 3. Sheets P that have not been stapled or offset processed are discharged to the middle discharge tray 2.

[0038] Furthermore, the middle paper output tray 2 has a paper sensor 20, and a paper detection unit 21, which is part of the paper sensor 20, is installed so as to extend downward from the underside of the middle paper output tray 2. The configuration of the paper sensor 20 will now be described with reference to the drawings. Fig. 4 is an enlarged perspective front view for explaining the configuration of the paper sensor of the post-processing device according to the first embodiment of the present disclosure.

[0039] As shown in FIG. 4 , a paper sensor 20 is installed inside the middle paper ejection tray 2, and as described above, the paper detection unit 21 is exposed to the outside from the underside (bottom surface) of the middle paper ejection tray 2. The paper sensor 20 includes the paper detection unit 21, a switch unit 24, a support member 22 connected to the paper detection unit 21, and a support pin 23 that axially supports the support member 22 so that it can rotate freely. The paper detection unit 21 is located at an end of the support member 22, and an end 25 of the support member 22 opposite the paper detection unit 21 can come into contact with the switch unit 24. The switch unit 24 is, for example, a contact-type switch, and the switch unit 24 can transmit an electrical signal when the end 25 comes into contact with or separates from the switch unit 24. Furthermore, since the support member 22 is axially supported by the support pin 23, the paper detection unit 21 can rotate relative to the middle paper ejection tray 2. For example, when the paper detection unit 21 moves upward, the end 25 located on the opposite side of the support member 22 moves downward and moves away from the switch unit 24. When the paper detection unit 21 moves downward, the end 25 moves upward and moves closer to the switch unit 24.

[0040] Because the paper sensor 20 is configured in this way, when the paper detection unit 21 comes into contact with an object located below it and moves upward, the switch unit 24 turns OFF, and when the paper detection unit 21 is not in contact, the switch unit 24 turns ON. Therefore, the paper sensor 20 can detect whether the paper detection unit 21 is interfering with the sheet P located below it.

[0041] As described above, the lower paper output tray 3 is disposed below the middle paper output tray 2. Furthermore, sheets P are stacked on the lower paper output tray 3. In this state, if the middle paper output tray 2 moves downward (descends) and interferes with the sheets P stacked on the lower paper output tray 3, the middle paper output tray 2 or the lower paper output tray 3 may be damaged. Furthermore, problems such as tearing of the sheets P may occur.

[0042] However, in the first embodiment, because the paper sensor 20 is provided, when the middle paper ejection tray 2 moves downward and the paper detection unit 21 comes into contact with the upper surface of the sheet P on the lower paper ejection tray 3, the paper detection unit 21 moves upward, turning off the switch unit 24. As a result, the paper sensor 20 transmits a signal (detection signal) notifying that the paper detection unit 21 and the sheet P have come into contact and that the distance between the upper surface of the sheet P1 and the lower surface of the middle paper ejection tray 2 is equal to or less than a predetermined distance. This stops the downward movement of the middle paper ejection tray 2, thereby preventing problems such as damage to the middle paper ejection tray 2 or the lower paper ejection tray 3 or tearing of the sheet P. Note that the sheet P on the lower paper ejection tray 3 may come into contact with the middle paper ejection tray 2 not only when the middle paper ejection tray 2 moves downward but also when the lower paper ejection tray 3 moves upward (rising). However, even in this case, the movement of the lower paper ejection tray 3 can be stopped by a signal from the paper sensor 20. Furthermore, since the sheet detection unit 21 is rotatable relative to the middle sheet discharge tray 2, even if it comes into contact with the upper surface of the sheet P, it moves smoothly upward and does not damage the upper surface of the sheet P.

[0043] Next, the control configuration of the post-processing device 10 will be described with reference to the drawings. Fig. 5 is a block diagram showing the control configuration of the post-processing device according to the first embodiment of the present disclosure. Details of the configuration of the post-processing device 10 are as described above. Fig. 5 shows only the components of the post-processing device 10 related to the control configuration described below.

[0044] 5, the post-processing device 10 includes a control unit 180, a tray drive device 183, a transport drive device 184, and a paper sensor 20. The control unit 180 can transmit and receive signals to and from each of the tray drive device 183, the transport drive device 184, and the paper sensor 20, and can transmit operation command signals from the control unit 180 to each unit and transmit signals from each unit to the control unit 180.

[0045] The control unit 180 controls the operation of each component of the post-processing device 10 and is responsible for overall control of the post-processing device 10. The post-processing device 10 also transmits and receives signals to and from the image forming unit 70 and the relay device 60 so that the operations of these devices are coordinated.

[0046] The control unit 180 includes a processing unit 181 and a storage unit 182. The control unit 180 includes the 181, which is a microcomputer such as a CPU (Central Processing Unit), and the storage unit 182, which is a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), or a data-rewritable nonvolatile memory.

[0047] A control program for the post-processing device 10 is stored in the storage unit 182. The processing unit 181 controls the operation of various components by loading the control program, which is stored in advance in the ROM of the storage unit 182, onto the RAM of the storage unit 182 and executing it. The RAM of the storage unit 182 provides the processing unit 181 with a work area for working and an area serving as an image memory for storing image data.

[0048] The tray drive device 183 moves the upper paper output tray 1, middle paper output tray 2, and lower paper output tray 3 up and down. Specifically, it is a drive mechanism for transmitting motors, which are the drive sources for driving each tray, and power to each tray. Note that the upper paper output tray 1 and middle paper output tray 2 are configured as an integrated unit, so their operation is the same.

[0049] The transport drive device 184 executes transport of the sheet P in the post-processing device 10. Specifically, it is a motor that is a drive source for driving each roller and a drive mechanism for transmitting power.

[0050] A signal indicating whether or not paper detection unit 21 of paper sensor 20 is in contact with a sheet P or the like is transmitted from paper sensor 20 to control unit 180. Based on the signal from paper sensor 20, control unit 180 controls the operation of upper paper ejection tray 1, middle paper ejection tray 2, and lower paper ejection tray 3. For example, when the operation of lower paper ejection tray 3 is stopped with sheets P stacked on lower paper ejection tray 3, and the upper paper ejection tray 1 and middle paper ejection tray 2 are lowered, if an object is detected in contact with paper detection unit 21 (switch unit 24 is turned OFF), paper sensor 20 transmits a signal to control unit 180, and control unit 180 transmits a control signal to tray drive device 183 to control the operation of upper paper ejection tray 1 and middle paper ejection tray 2 and stop them. This prevents the sheets P stacked on the lower discharge tray 3 from coming into contact with the middle discharge tray 2, and prevents the upper discharge tray 1, middle discharge tray 2, lower discharge tray 3 and the sheets P from being damaged.

[0051] Next, with reference to the drawings, an example of the operation of the upper paper output tray 1, middle paper output tray 2, and lower paper output tray 3 of the post-processing device 10 according to the first embodiment will be described. FIG. 6 is a first diagram for describing the operation of the post-processing device according to the first embodiment of the present disclosure. FIG. 7 is a second diagram for describing the operation of the post-processing device according to the first embodiment of the present disclosure. FIG. 8 is a third diagram for describing the operation of the post-processing device according to the first embodiment of the present disclosure. FIG. 9 is a fourth diagram for describing the operation of the post-processing device according to the first embodiment of the present disclosure. FIG. 10 is a fifth diagram for describing the operation of the post-processing device according to the first embodiment of the present disclosure.

[0052] As shown in Fig. 6, when a sheet P is discharged from the post-processing device 10, it is first discharged to the lower discharge tray 3 before being discharged to the upper discharge tray 1. In the following description of the first embodiment, it is assumed that stapling or offset processing is performed. Therefore, the sheet is not discharged to the middle discharge tray 2.

[0053] When discharge to the lower paper discharge tray 3 is performed, the lower paper discharge tray 3 moves to a position where sheets P discharged from the paper discharge outlet 8 are stacked, and discharge is performed. The lower paper discharge tray 3 is lowered in accordance with the amount of paper discharged from the paper discharge outlet 8, and the tray drive device 183 operates so that the upper surface of sheet P1 formed by stacking multiple sheets P is positioned below the paper discharge outlet 8. When the amount of sheets P1 reaches a predetermined amount, discharge stops, and as shown in FIG. 7, the lower paper discharge tray 3 is lowered with sheets P1 still placed on it, and the tray drive device 183 operates so that the upper paper discharge tray 1 and middle paper discharge tray 2 are also lowered.

[0054] 8, the lower paper discharge tray 3 is lowered to a predetermined position, and the upper paper discharge tray 1 is lowered to a position where the sheets P discharged from the paper discharge outlet 8 are stacked. Then, the sheets are discharged from the paper discharge outlet 8 to the upper paper discharge tray 1. Furthermore, the upper paper discharge tray 1 is lowered in accordance with the amount of paper discharged from the paper discharge outlet 8, and the tray drive device 183 is operated so that the upper surface of the sheet P2 formed by stacking the multiple sheets P is positioned below the paper discharge outlet 8.

[0055] 9, when the paper detection unit 21 comes into contact with the upper surface of the sheet P1, the paper sensor 20 sends a signal to the control unit 180 informing the control unit 180 that the paper detection unit 21 has come into contact with the upper surface of the sheet P1, and the control unit 180 sends a signal to the tray drive device 183 to stop the lowering of the upper paper output tray 1 and the middle paper output tray 2. This stops the lowering operation of the upper paper output tray 1 and the middle paper output tray 2. The control unit 180 also sends a signal to the transport drive device 184 to stop the transport operation of the sheet P and to stop the discharge operation from the paper output port 8. In this case, the operator may be notified by a buzzer, a lamp, or the like.

[0056] Furthermore, when sheets P1 are stacked on the lower discharge tray 3, the force of the sheets being discharged from the discharge outlet 8 may cause the sheets P1 to be stacked at a position away from the post-processing device main body 11. For example, as shown in Fig. 10, the sheets P1 may be misaligned. In such a case, if a sensor is provided on the side wall surface 12 on which the discharge outlet 8 is provided, a part of the sheets P1 may be located away from the side wall surface 12, and therefore the stacking state of the sheets P1 may not be detected correctly.

[0057] However, in the first embodiment, the sheet detection unit 21 is formed to extend downward from the underside of the middle sheet discharge tray 2. Therefore, even if the sheet P1 is shifted to a position away from the post-processing device main body 11 as shown in Fig. 10, the sheet sensor 20 and the upper surface of the sheet P1 come into proper contact, and the sheet sensor 20 can perform detection based on the position of the upper surface of the sheet P1. This makes it possible to reliably detect when the upper surface of the sheet P1 and the lower surface of the middle sheet discharge tray 2 are too close. Specifically, it can detect when the upper surface of the sheet P1 and the lower surface of the middle sheet discharge tray 2 are no more than a predetermined distance apart.

[0058] Next, an example of the control operation of the post-processing device 10 will be described with reference to the drawings. Fig. 11 is a flowchart showing an example of the control operation of the post-processing device according to the first embodiment of the present disclosure.

[0059] 8, when paper is discharged from the paper discharge port 8 to the upper paper discharge tray 1, the tray drive device 183 controls the operation of the upper paper discharge tray 1 and the middle paper discharge tray 2, and the transport drive device 184 controls the transport operation of the sheet P inside the post-processing device main body 11 and the paper discharge operation from the paper discharge port 8. In this state, the processing unit 181 of the control unit 180 determines whether the paper detection unit 21 and the upper surface of the sheet P1 have come into contact and the paper sensor 20 has detected the sheet P1 (step S1). Specifically, it determines whether a signal has been sent from the paper sensor 20.

[0060] If the paper sensor 20 does not detect the sheet P1 (No in step S1), step S1 is repeated. If the paper sensor 20 detects the sheet P1 (Yes in step S1), the tray drive device 183 stops the lowering of the upper discharge tray 1 and the middle discharge tray 2 (step S2). Then, the transport drive device 184 stops the transport operation and the paper discharge operation (step S3), and the process ends.

[0061] The above describes the post-processing device 10 and the image forming apparatus 100 equipped with the post-processing device 10 according to the first embodiment. As described above, the paper detection unit 21 is provided so as to extend downward from the underside of the middle paper output tray 2 located above the lower paper output tray 3. This prevents the upper surface of the sheet P1 from coming too close to the middle paper output tray 2 when the sheet P1 is placed on the lower paper output tray 3. This prevents interference between the sheet P1 and the middle paper output tray 2. Furthermore, even if the sheet P1 placed on the lower paper output tray 3 is misaligned, the upper surface of the sheet P1 can be detected, so it is possible to reliably detect that the upper surface of the sheet P1 has come too close to the middle paper output tray 2. This prevents damage to the upper paper output tray 1, middle paper output tray 2, lower paper output tray 3, or the sheet P1.

[0062] Furthermore, the paper sensor 20 may have a configuration other than that described above, and may be a sensor that has a paper detection section 21 extending downward from the underside of the middle paper output tray 2 and can detect that the upper surface of the sheet P1 and the underside of the middle paper output tray 2 are too close together.

[0063] (Second embodiment) A post-processing device 10 and an image forming device 100 according to a second embodiment of the present disclosure will be described with reference to the drawings. Note that the post-processing device 10 according to the second embodiment has a paper sensor 30, which will be described below, instead of the paper sensor 20, and is otherwise similar to the first embodiment. Therefore, the following describes the configuration and operation of the paper sensor 30, and a description of other aspects will be omitted. Also, the same reference numerals will be used for components similar to those in the first embodiment.

[0064] 12 is an enlarged perspective front view illustrating the configuration of a sheet sensor of a post-processing device according to a second embodiment of the present disclosure. As shown in FIG. 12, in post-processing device 10 according to the second embodiment, sheet sensor 30 is installed inside middle sheet ejection tray 2, with upper detection end 31a exposed to the outside from the upper side (top surface) of middle sheet ejection tray 2 and lower detection end 31b exposed to the outside from the lower side (bottom surface) of middle sheet ejection tray 2.

[0065] The paper sensor 30 includes a paper detection unit 31, a support member 32, and a support pin 33. As with the paper sensor 20, the paper sensor 30 also includes a switch unit for transmitting a signal (detection signal) in response to the operation of the support member 32, but this is not shown in the figure.

[0066] The sheet detection unit 31 has a shape that branches in two directions, up and down. That is, the sheet detection unit 31 has an upper detection end 31a that extends upward from the top surface of the middle sheet discharge tray 2, and a lower detection end 31b that extends downward from the bottom surface of the middle sheet discharge tray 2.

[0067] The support member 32 is connected to the paper detection unit 31 and is rotatably supported by a support pin 33. Therefore, the support pin 33 allows the paper detection unit 31 to also rotate relative to the middle paper discharge tray 2, and the paper detection unit 31 can move up and down. In other words, the lower detection end 31b can come into contact with an object located below it and move upward. Furthermore, when a sheet P3 or the like is placed on the middle paper discharge tray 2, the sheet P3 will come into contact with the upper detection end 31a.

[0068] With this configuration, the paper sensor 30 can detect whether a sheet P or the like is placed on the middle paper ejection tray 2, and whether the middle paper ejection tray 2 and the sheet P1 or the like are too close to each other by contact of the lower detection end 31b with a sheet P1 or the like below the middle paper ejection tray 2. Furthermore, because the paper detection unit 31 (lower detection end 31b) is rotatable relative to the middle paper ejection tray 2, even if it comes into contact with the top surface of the sheet P1, it moves smoothly upward and does not damage the top surface of the sheet P1. Similarly, the upper detection end 31a does not easily damage the sheet P3 placed on the middle paper ejection tray 2.

[0069] An example of the operation of the upper paper ejection tray 1, middle paper ejection tray 2, and lower paper ejection tray 3 of the post-processing device 10 according to the second embodiment will be described with reference to the drawings. Fig. 13 is a first diagram for explaining the operation of the post-processing device according to the second embodiment of the present disclosure. Fig. 14 is a second diagram for explaining the operation of the post-processing device according to the second embodiment of the present disclosure. Note that Figs. 13 and 14 are enlarged views illustrating the periphery of the upper paper ejection tray 1 and middle paper ejection tray 2.

[0070] 13, when sheet P3 formed by stacking multiple sheets P is stacked on middle paper ejection tray 2, upper detection end 31a is pushed downward by sheet P3, causing paper detection unit 31 to move downward. This allows paper sensor 30 to detect that sheet P3 is placed on middle paper ejection tray 2. Note that even when only one sheet P is placed on middle paper ejection tray 2, not multiple sheets, paper sensor 30 can detect that sheet P is placed on middle paper ejection tray 2.

[0071] From this state, the middle paper ejection tray 2 and the upper paper ejection tray 1 descend, and as shown in FIG. 14 , if the sheet P1 placed on the lower paper ejection tray 3 (not shown) and the middle paper ejection tray 2 get too close, the lower detection tip 31b comes into contact with the upper surface of the sheet P1 and is pushed upward, causing the sheet P1 to move. This causes the paper sensor 30 to detect that the upper surfaces of the middle paper ejection tray 2 and the sheet P1 are too close, and the paper sensor 30 sends a signal to the control unit 180 informing it that the lower detection tip 31b has come into contact with the upper surface of the sheet P1. Upon receiving this signal, the control unit 180 sends a signal to the tray drive device 183 to stop the lowering of the upper paper ejection tray 1 and the middle paper ejection tray 2. This stops the lowering of the upper paper ejection tray 1 and the middle paper ejection tray 2. The control unit 180 also stops the conveyance of the sheet P and sends a signal to the conveyance drive device 184 to stop the discharge of the sheet P from the discharge outlet 8.

[0072] As described above, in the post-processing device 10 according to the second embodiment, the sheet detection unit 31 has an upper detection end 31a extending upward and a lower detection end 31b extending downward, and therefore can detect that a sheet P3 (P) is placed on the middle paper ejection tray 2 and can detect that a sheet P1 placed on the middle paper ejection tray 2 is too close to a sheet P1 placed on the lower paper ejection tray 3. This not only makes it possible to detect that a sheet P3 is placed on the middle paper ejection tray 2, but also prevents the upper surface of the sheet P1 from being too close to the middle paper ejection tray 2 when the upper paper ejection tray 1 and the middle paper ejection tray 2 are lowered with a sheet P1 placed on the lower paper ejection tray 3. This prevents damage to the upper paper ejection tray 1, middle paper ejection tray 2, and lower paper ejection tray 3, and to the sheet P1.

[0073] (Third embodiment) A post-processing device 10 and an image forming device 100 according to a third embodiment of the present disclosure will be described with reference to the drawings. Note that the post-processing device 10 according to the third embodiment has a paper sensor 40, which will be described below, instead of the paper sensor 20, and is otherwise similar to the first embodiment. Therefore, the following describes the configuration and operation of the paper sensor 40, and a description of other aspects will be omitted. Also, the same reference numerals will be used for components similar to those in the first embodiment.

[0074] 15 is an enlarged perspective front view illustrating the configuration of a sheet sensor of a post-processing device according to a third embodiment of the present disclosure. As shown in FIG. 15, in post-processing device 10 according to the third embodiment, sheet sensor 40 is installed inside middle sheet discharge tray 2, and sheet detection unit 41 is exposed to the outside from the underside (bottom surface) of middle sheet discharge tray 2.

[0075] The paper sensor 40 includes a paper detection unit 41 and a support pin 43b. The paper detection unit 41 also includes a detection end 42 provided at the tip, an inclined support unit 44, and a support pin 43a that connects the detection end 42 and the inclined support unit 44. As with the paper sensor 20, the paper sensor 40 also includes a switch unit for transmitting a signal (detection signal) in response to the operation of the paper detection unit 41, but this is not shown in the figure.

[0076] The detection end 42 is connected to the inclined support portion 44 by a support pin 43a and is rotatable. The detection end 42 is pivotally supported by the support pin 43a so that it is approximately parallel to or slightly inclined with the sheet P1. The inclined support portion 44 is also provided so as to be inclined with respect to the sheet P1. Specifically, the inclined support portion 44 is inclined downward as it moves away from the side wall surface 12 on which the paper discharge outlet 8 is formed. The inclined support portion 44 is also pivotally supported on the middle paper discharge tray 2 by a support pin 43b.

[0077] Because the paper sensor 40 is configured as described above, when the middle paper output tray 2 and upper paper output tray 1 are lowered from a state in which a sheet P1 is stacked on the lower paper output tray 3, and the lower paper output tray 3, sheet P1, and the middle paper output tray 2 become too close to each other, the detection end 42 comes into contact with the upper surface of the sheet P1 and is pushed upward, causing the paper detection unit 41 to move upward. As a result, the paper sensor 40 detects that the upper surfaces of the middle paper output tray 2 and sheet P1 are too close to each other and sends a signal to the control unit 180. As a result, the control unit 180 sends a signal to the tray drive device 183 to stop the lowering of the upper paper output tray 1 and middle paper output tray 2. This stops the lowering operation of the upper paper output tray 1 and middle paper output tray 2. The control unit 180 also stops the transport operation of the sheet P and sends a signal to the transport drive device 184 to stop the discharge operation from the paper output outlet 8. Furthermore, since the paper detection unit 41 (detection end 42) is rotatable relative to the middle paper discharge tray 2, even if it comes into contact with the upper surface of the sheet P1, it moves smoothly upward and does not damage the upper surface of the sheet P1.

[0078] Note that, since the inclined support portion 44 is provided, the detection end 42 is spaced from the underside of the middle paper discharge tray 2. Therefore, it is not necessary to determine that the middle paper discharge tray 2 and the upper surface of the sheet P1 are too close together just because the detection end 42 comes into contact with the sheet P1. When the detection end 42 moves upward and comes too close to the middle paper discharge tray 2, the paper sensor 40 detects that the middle paper discharge tray 2 and the upper surface of the sheet P1 are too close together, and the lowering operation of the upper paper discharge tray 1 and the middle paper discharge tray 2 and the transport operation of the sheet P can be stopped.

[0079] Furthermore, even if the detection end 42 is in contact with the upper surface of the sheet P1, the sheet P may be discharged from the discharge outlet 8 to the lower discharge tray 3 as long as the middle discharge tray 2 and the upper surface of the sheet P1 are not too close to each other. As described above, the detection end 42 is substantially parallel to or slightly inclined with respect to the upper surface (upper surface of the sheet P1) of the lower discharge tray 3. Because the detection end 42 has such a shape, the detection end 42 supports from above the sheet P (sheet P1) that is discharged and stacked from the discharge outlet 8, thereby preventing the sheet P1 from being stacked out of position or collapsing.

[0080] As described above, the inclined support portion 44 is provided so as to be inclined with respect to the sheet P1. Because the inclined support portion 44 is configured in this manner, when the sheet P is discharged from the discharge outlet 8, it collides with the inclined support portion 44, thereby suppressing the momentum of the discharged sheet, and preventing the sheet P from falling beyond the lower discharge tray 3 or being stacked in a misaligned (tilted) position. Furthermore, because the inclined support portion 44 is inclined, even if the sheet P collides with it, the impact is absorbed, and the sheet P is not damaged.

[0081] As described above, in the post-processing device 10 according to the third embodiment, the paper detection unit 41 has a configuration that extends downward, and therefore can detect when the middle paper output tray 2 and the sheet P1 placed on the lower paper output tray 3 are too close to each other. Therefore, when the upper paper output tray 1 and the middle paper output tray 2 are lowered with the sheet P1 placed on the lower paper output tray 3, it is possible to prevent the top surface of the sheet P1 from getting too close to the middle paper output tray 2. This makes it possible to prevent damage to the upper paper output tray 1, middle paper output tray 2, lower paper output tray 3, and the sheet P1.

[0082] Furthermore, by discharging the paper to the lower paper discharge tray 3 while the paper detection unit 41 is positioned near the paper discharge outlet 8, the sheets P1 stacked on the lower paper discharge tray 3 are stacked stably without tilting or shifting.

[0083] The present disclosure is not limited to the above-described embodiments, but can be implemented in various other forms. Therefore, these embodiments are merely examples in all respects and should not be interpreted as limiting. The scope of the present disclosure is defined by the claims and is not limited in any way by the text of the specification. Furthermore, all modifications and variations within the equivalent range of the claims are within the scope of the present disclosure. [Explanation of symbols]

[0084] 1 Upper output tray 2 Middle output tray (first output tray) 3 Lower output tray (second output tray) 4 Ejection roller 5a, 5b Conveyor rollers 6 Staple processing section 7 Transport tray 8 Paper output slot 10 Aftertreatment device 11 Post-processing device main body 12 Side wall 20 Paper sensor 21 Paper detection unit 22 Support member 23 Support pin 24 Switch section 25 End 30 Paper sensor 31 Paper detection unit 31a Upper detection tip 31b Lower detection tip 32 Support member 33 Support pin 40 Paper sensor 41 Paper detection unit 42 Detector 43a, 43b Support pins 44 Inclined support 60 Relay Device 70 Image forming unit 100 Image forming device 180 Control Unit 181 Processing section 182 Storage section 183 Tray drive unit 184 Conveyor drive device P, P1, P2 seats S Sheet transport path

Claims

1. A post-processing device that performs post-processing on a sheet on which an image is formed, a first discharge tray onto which sheets are discharged; a second discharge tray located below the first discharge tray and onto which sheets are discharged; a paper sensor that detects when the distance between the top surface of the sheets stacked on the second paper ejection tray and the bottom surface of the first paper ejection tray is equal to or less than a predetermined distance, and transmits a detection signal so that the sheets stacked on the second paper ejection tray do not interfere with the first paper ejection tray; the first discharge tray and the second discharge tray are movable up and down independently of each other; the paper sensor has a paper detection section that is arranged to extend downward from the bottom surface of the first paper output tray, When the sheet detection unit comes into contact with an upper surface of the sheet stacked on the second sheet output tray and the distance between the upper surface of the sheet and the lower surface of the first sheet output tray becomes equal to or less than the predetermined distance, the sheet sensor transmits the detection signal; When the detection signal is transmitted, the post-processing device prevents the distance between the first and second paper discharge trays from becoming any smaller.

2. The post-processing device according to claim 1, the sheet detection unit has a shape that branches in two directions and has an upper detection end that extends upward from an upper surface of the first sheet discharge tray and a lower detection end that extends downward from a lower surface of the first sheet discharge tray, When the sheet is placed on the first paper ejection tray and the upper detection end comes into contact with the sheet, the paper sensor detects that the sheet is placed on the first paper ejection tray; A post-processing device characterized in that the paper sensor emits the detection signal when the lower detection end contacts the upper surface of the sheet stacked on the second paper output tray and the distance between the upper surface of the sheet and the lower surface of the first paper output tray becomes less than the specified distance.

3. The post-processing device according to claim 1, the sheet detection unit has an inclined support portion that extends in a direction oblique to the sheet discharged onto the second discharge tray, and a detection end that is located at a tip of the inclined support portion, A post-processing device characterized in that the paper sensor emits the detection signal when the detection end contacts the top surface of the sheet stacked on the second paper output tray and the distance between the top surface of the sheet and the bottom surface of the first paper output tray becomes less than the specified distance.

4. The post-processing device according to claim 1, 4. The post-processing device, wherein the paper detection unit is rotatable with respect to the first paper discharge tray.

5. a post-processing device according to claim 1; an image forming unit that forms an image on the sheet.

Images