Sheet loading device, sheet loading method, and program

Abstract

To provide a sheet stacking device, a sheet stacking method, and a program capable of determining presence or absence of an abnormality, when a foreign object is placed on a stacking tray that moves in a vertical direction, or when a foreign object is placed in an operating area below the stacking tray, etc.SOLUTION: A sheet stacking device includes: stacking trays 33 and 51 for stacking sheets on which images are formed; driving means 315 for moving the stacking tray upward or downward from a home position and then returning it to the home position; load detection means 300 for detecting a drive load when the drive means moves the stacking tray; distance detection means 300 for detecting a distance from the home position of the stacking tray; and judging means 300 for judging whether there is an abnormality based on a driving direction of the stacking tray, the drive load detected by the load detecting means, and the distance from the home position detected by the distance detecting means.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a sheet stacking device provided in an image forming apparatus such as a multi-functional digital composite machine (MFP) that forms an image on a sheet such as paper, or a post-processing device that performs post-processing such as binding and punching on the sheet conveyed from the image forming apparatus, and further relates to a sheet stacking method and a program.

Background Art

[0002] As a sheet stacking device that receives sheets such as paper discharged from an image forming apparatus or a post-processing device after image formation or post-processing and stacks them in order, a type in which a stacking tray for stacking sheets moves in the vertical direction has been conventionally known. In particular, a type that can stack a large volume of sheets has a wide movable range, and it is easy for the user to reach the operating area.

[0003] In addition, the operating area of the stacking tray may seem like an empty space to the user, and foreign objects such as cardboard and empty boxes may be inadvertently placed in the operating area below the stacking tray. Also, small boxes or heavy objects may be placed on the stacking tray. In such cases, the foreign objects may inhibit the operation of the stacking tray and an error may occur, but conventionally, the exact cause of the error could not be identified.

[0004] Note that Patent Document 1 discloses a stacking device that can detect an abnormality in the driving load of a tray caused by pinching or the like, including a tray, tray vertical movement driving means for moving the tray in the vertical direction, load detection means for detecting the driving load when the tray vertical movement driving means moves the tray in the vertical direction, and abnormality determination means for determining whether an abnormality has occurred in the movement of the tray based on the driving load when the tray rises and the driving load when the tray descends detected by the load detection means.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-200118 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, as described in Patent Document 1 above, detection is only performed when the drive load becomes high, so it cannot detect when lightweight foreign objects are placed on the tray. Furthermore, even if foreign objects are placed in the operating area below the loading tray, detection will not occur unless the drive load becomes high, and even if detection occurs, it will not be possible to determine whether the foreign object in the operating area is the cause.

[0007] This invention has been made in view of the above technical background, and aims to provide a sheet loading device, a sheet loading method, and a program that can determine whether or not there is an abnormality, such as when a foreign object is placed on a loading tray that moves in the vertical direction, or when a foreign object is placed in the operating area below the loading tray. [Means for solving the problem]

[0008] The above objectives will be achieved by the following means. (1) A loading tray for loading sheets on which images have been formed, A drive means for moving the aforementioned loading tray upward or downward from the home position, and then moving it back to the home position, A load detection means for detecting the drive load when the drive means moves the loading tray, Distance detection means for detecting the distance of the loading tray from the home position, A determination means for determining whether or not there is an abnormality based on the driving direction of the loading tray, the driving load detected by the load detection means, and the distance from the home position detected by the distance detection means, A sheet loading device characterized by having the following features. (2) The sheet loading device according to item 1 above, wherein the distance detection means detects the distance from the home position by counting the pulse encoder of the motor which is the driving means. (3) The sheet loading device according to item 1 above, wherein the distance detection means detects the distance from the home position by counting the drive pulses of the pulse motor which is the drive means. (4) Equipped with a distance measuring sensor capable of detecting the distance to the moving loading tray, The sheet loading device according to item 1 above, wherein the distance detection means detects the distance from the home position based on the detection result of the distance measuring sensor. (5) The sheet loading device according to any one of paragraphs 1 to 4 above, wherein the reference value of the drive load for determining whether or not there is an abnormality by the determination means changes according to the distance of the loading tray from the home position. (6) The reference value of the drive load for determining whether there is an abnormality by the determination means is a sheet loading device according to any of paragraphs 1 to 5 above, which changes according to the basis weight and / or size of the sheet. (7) The reference value of the drive load for determining whether or not there is an abnormality by the determination means is: The aforementioned home position is located below the sheet loading device. When the loading tray rises from its home position, the greater the distance of the loading tray from its home position, The aforementioned home position is located above the sheet loading device. The sheet loading device according to item 5 or 6 above, wherein when the loading tray descends from the home position, the amount of reduction decreases as the distance of the loading tray from the home position increases. (8) The load detection means detects the drive load based on the current value of the motor which is the drive means, The sheet loading device according to any one of paragraphs 1 to 7 above, wherein the determination means compares a reference value of the drive load, which is calculated in advance from the distance of the loading tray from the home position and the weight of the sheets loaded on the loading tray, with the drive load detected based on the current value, to determine whether or not there is an abnormality. (9) A lower limit sensor is provided to detect the lower limit position of the loading tray, The sheet loading device according to paragraph 8, wherein if the drive load is greater than a reference value even though the lower limit sensor does not turn on when the loading tray is lowered, the determination means determines that a foreign object is obstructing the loading tray at a position where it has not reached the lower limit sensor, and notifies of the occurrence of an abnormality. (10) The system includes a storage means for storing the position of the loading tray when the determination means determines that there is an abnormality when the loading tray is lowered, The sheet loading device according to any one of paragraphs 1 to 9 above, wherein, after the determination means determines that there is an abnormality, the driving means drives the loading tray using the position stored in the storage means as the lower limit position of the loading tray. (11) The system includes an upper limit sensor for detecting the upper limit position of the loading tray, The sheet loading device according to paragraph 8, wherein if the upper limit sensor turns on when the loading tray is raised, even though the drive load is less than a reference value, the determination means determines that a foreign object has been placed on the loading tray. (12) The system is equipped with an upper limit sensor for detecting the upper limit position of the loading tray, The load detection means detects the drive load from the current value of the motor, which is the drive means. The aforementioned determination means determines that if the drive load is at a normal value when the loading tray starts to rise, but increases rapidly after the start of rising, a foreign object has been placed on the loading tray and notifies the system of the occurrence of an abnormality, as described in any of paragraphs 1 to 11 above. (13) The sheet loading device described in paragraph 9 or 12 above, which determines that there is a malfunction in the sheet loading device if it is determined that there is a malfunction even after executing multiple jobs after notification of the occurrence of the abnormality. (14) A sheet loading device as described in any of paragraphs 9, 12, or 13 above, which notifies of the occurrence of an abnormality or malfunction by displaying it on the control panel, contacting a service technician by means of communication, or transmitting data to a management server. (15) The sheet loading device according to any one of paragraphs 1 to 14 above, wherein the determination of whether or not there is an abnormality by the determination means is performed at least during job processing, during the movement of the loading tray after job processing, or during test mode. (16) A sheet loading device according to paragraph 2 or 3 above, wherein if the loading tray rises due to the removal of a portion of the loaded sheets, the distance of the loaded sheets from the home position after the rise is calculated based on the amount of motor drive for the rise. (17) A loading tray for loading sheets on which images have been formed, A drive means for moving the aforementioned loading tray upward or downward from the home position, and then moving it back to the home position, A sheet loading device equipped with, A load detection step in which the drive means detects the drive load when moving the loading tray, A distance detection step for detecting the distance of the loading tray from the home position, A determination step that determines whether or not there is an abnormality based on the driving direction of the loading tray, the driving load detected by the load detection step, and the distance from the home position detected by the distance detection step, A method for loading sheets, characterized by performing the following: (18) A loading tray for loading sheets on which images have been formed, A drive means for moving the aforementioned loading tray upward or downward from the home position, and then moving it back to the home position, The computer of the seat loading device equipped with A load detection step in which the drive means detects the drive load when moving the loading tray, A distance detection step for detecting the distance of the loading tray from the home position, A determination step that determines whether or not there is an abnormality based on the driving direction of the loading tray, the driving load detected by the load detection step, and the distance from the home position detected by the distance detection step, A program to execute. [Effects of the Invention]

[0009] According to the invention described in the preceding paragraph (1), based on the moving direction of the loading tray that moves upward or downward from the home position, the driving load detected by the load detection means when the driving means moves the loading tray, and the distance from the home position of the loading tray detected by the distance detection means, the presence or absence of an abnormality is determined. Therefore, for example, it is possible to reliably detect an operating area below the loading tray or the presence of foreign matter on the loading tray.

[0010] According to the invention described in the preceding paragraph (2), the distance from the home position can be accurately detected by counting the pulses of the pulse encoder of the motor which is the driving means.

[0011] According to the invention described in the preceding paragraph (3), the distance from the home position can be accurately detected by counting the drive pulses of the pulse motor which is the driving means.

[0012] According to the invention described in the preceding paragraph (4), the distance from the home position can be accurately detected based on the detection result of the distance measuring sensor.

[0013] According to the invention described in the preceding paragraph (5), since the reference value of the driving load for determining the presence or absence of an abnormality changes according to the distance from the home position of the loading tray, it is possible to accurately determine the presence or absence of an abnormality during the operation of the loading tray.

[0014] According to the invention described in the preceding paragraph (6), since the reference value of the driving load for determining the presence or absence of an abnormality changes according to the basis weight and / or size of the sheet, it is possible to accurately determine the presence or absence of an abnormality during the operation of the loading tray.

[0015] According to the invention described in the preceding paragraph (7), the reference value of the driving load for determining the presence or absence of an abnormality is The home position is located below the sheet loading device. when the loading tray rises from the home position, the larger the distance from the home position of the loading tray, the larger it becomes, The home position is located above the sheet loading device. when the loading tray descends from the home position, the larger the distance from the home position of the loading tray, the smaller it becomes.

[0016] According to the invention described in paragraph (8) above, the drive load is detected based on the current value of the motor, which is the driving means, and the drive load detected based on the current value is compared with a reference value of the drive load calculated in advance from the distance of the loading tray from the home position and the weight of the sheets loaded on the loading tray, thereby enabling accurate determination of whether or not there is an abnormality.

[0017] According to the invention described in item (9) above, when the loading tray is lowered, if the lower limit sensor that detects the lower limit position of the loading tray does not turn on, but the drive load is greater than a reference value, it is determined that there is an obstruction at the position where the lower limit sensor of the loading tray does not turn on, and an abnormality is notified, so the user can recognize the abnormality and remove the foreign object.

[0018] According to the invention described in item (10) above, the position where an abnormality is detected when the loading tray is lowered is stored, and after an abnormality is detected, the loading tray is driven with the stored position as the lower limit of the loading tray, so that the loading tray can be operated within an effective range of motion.

[0019] According to the invention described in paragraph (11) above, if the upper limit sensor that detects the upper limit position of the loading tray turns on even though the drive load is less than a reference value when the loading tray is raised, it is determined that a foreign object has been placed on the loading tray.

[0020] According to the invention described in paragraph (12) above, if the drive load detected from the motor current value when the loading tray is raised is at a normal value at the start of the rise, but increases rapidly after the start of the rise, it is determined that a foreign object has been placed on the loading tray, and an abnormality is notified, so the user can recognize the abnormality and remove the foreign object.

[0021] According to the invention described in paragraph (13) above, if an abnormality is still detected after executing multiple jobs following notification of an abnormality, there is a possibility of a malfunction in the sheet loading device, and therefore, notification of the malfunction is issued.

[0022] According to the invention described in paragraph (14) above, notification of an abnormality or malfunction is provided by at least one of the following: display on the control panel, contact with a service technician via communication means, or transmission of data to a management server.

[0023] According to the invention described in paragraph (15) above, the determination of whether or not there is an abnormality is made at least one of the following: during job processing, during the movement of the loading tray after job processing, or during test mode.

[0024] According to the invention described in paragraph (16) above, if the loading tray rises due to the removal of a portion of the loaded sheets, the position after the rise is stored again in the storage means as the position of the loading tray, and a downward movement is performed to accommodate the sheets discharged from this position.

[0025] According to the invention described in paragraph (17) above, abnormalities during the operation of the loading tray, such as the presence of foreign objects in the operating area below the loading tray or on the loading tray, can be reliably detected.

[0026] According to the invention described in paragraph (18) above, the computer of a sheet stacking device, which includes a stacking tray for stacking sheets on which images are formed, and a driving means for moving the stacking tray upward or downward from a home position and then moving it back to the home position, can be made to perform a load detection step for detecting the driving load when the driving means moves the stacking tray, a distance detection step for detecting the distance of the stacking tray from the home position, and a process for determining whether or not there is an abnormality based on the direction of movement of the stacking tray, the detected driving load, and the detected distance from the home position. [Brief explanation of the drawing]

[0027] [Figure 1] This figure shows the configuration of an image forming system according to one embodiment of the present invention. [Figure 2] This is a block diagram showing the electrical configuration of an image forming apparatus. [Figure 3]This flowchart shows the electrical configuration of the aftertreatment device, which is a sheet loading device. [Figure 4] This diagram schematically shows the configuration of the post-processing device. [Figure 5] This figure shows the configuration of a post-processing device according to another embodiment of this invention. [Figure 6] This diagram illustrates the operation of the post-processing device when foreign objects such as cardboard boxes are placed within the movable range below the loading tray. [Figure 7] This diagram illustrates the operation of the post-processing device when a foreign object is placed on the elevator tray. [Figure 8] This is a schematic front view of an image forming apparatus equipped with a post-processing device, which is a sheet lamination apparatus according to another embodiment of the present invention. [Figure 9] This is a schematic, enlarged view of the post-processing device shown in Figure 8. [Figure 10] This table summarizes the estimated causes of malfunctions based on the vertical position of the elevator tray, the direction of the elevator tray's drive, and the drive load status of the drive motor. [Figure 11] This figure shows the location of the elevator tray in Table 10. [Figure 12] This graph shows the relationship between the distance from the home position when the elevator tray 51 is raised and the allowable load range of the drive motor. [Figure 13] This graph shows the relationship between the distance from the home position when the elevator tray is descending and the allowable range of motor load. [Figure 14] This flowchart shows the process by which the after-processing unit detects an abnormality based on the vertical position of the elevator tray (distance from the home position), the direction of the elevator tray's drive, and the state of the drive motor's drive load. [Modes for carrying out the invention]

[0028] Hereinafter, embodiments of this invention will be described based on the drawings.

[0029] Figure 1 shows the configuration of an image forming system 1 according to one embodiment of the present invention. This image forming system 1 comprises an image forming apparatus 2 and a floor-type post-processing device 3 connected to the image forming apparatus 2. In this embodiment, the post-processing device 3 functions as a sheet loading device.

[0030] The post-processing device 3 has the function of bundling multiple sheets (hereinafter referred to as paper) sent from the image forming apparatus 2 and performing stapling using metal needles, punching holes, and saddle stitching. In the example in Figure 1, a stapling processing unit 31 for stapling is located approximately in the center of the post-processing device 3. In the image forming apparatus 2 in Figure 1, the paper is fed from the paper feed tray 21 and transported vertically from below along the sheet transport path 22. The image generated on the intermediate transfer belt 24 by the image forming unit 23 is then transferred to the paper by the transfer roller 25, fixed by the fixing unit 26, and transported to the post-processing device 3. Reference numeral 27 in Figure 1 indicates an image reader, and reference numeral 28 indicates an automatic document feeder (ADF). The configurations of the image forming unit 23, image reader 27, automatic document feeder 28, etc. are well known, so a detailed explanation is omitted.

[0031] The post-processing device 3 stacks the printed paper, which is fed from the image forming apparatus 2, on the paper stack generation unit 32. In this embodiment, a paper feed tray 34 is provided for feeding different paper, such as divider paper as in this example, and mixing it with the printed paper. At predetermined intervals of printed paper transported from the image forming apparatus 2, the divider paper set in the paper feed tray 34 is fed, and a paper stack containing a mixture of printed paper and divider paper is generated on the paper stack generation unit 32.

[0032] The post-processing device 3 stacks the paper transported from the image forming apparatus 2 in the paper stack generation unit 32 and, if necessary, inserts divider paper set in the paper feed tray 34 into the middle, first, or last pages of the stack, generating a paper stack on the paper stack generation unit 32 containing a mixture of printed paper and divider paper. After generating the paper stack according to the user's instructions, the paper stack generation unit 32 performs post-processing, such as stapling, as specified by the user on the paper stack, and then discharges it into the stack tray 33. If no post-processing is performed, the paper with the image formed on it by the image forming apparatus 2 is discharged directly into the stack tray 33.

[0033] The loading tray 33 is movable up and down between an upper limit and a lower limit, as indicated by arrow Y1. It is configured to sequentially load the paper ejected from the post-processing device 3, moving downward according to the amount loaded, and then moving upward when the loaded paper is removed. This will be explained in more detail later.

[0034] Figure 2 is a block diagram showing the electrical configuration of the image forming apparatus 2. As shown in Figure 2, the image forming apparatus 2 includes a control unit 200, a fixed storage device 210, an image reading device 220 (indicated by reference numeral 27 in Figure 1), an operation panel 230, an image output device 240, a printer controller 250, and a network interface (network I / F) 260, a communication interface (communication I / F) 270, a media measurement unit 280, etc., which are connected to each other via a system bus 275.

[0035] The control unit 200 includes a CPU (Central Processing Unit) 201 and a ROM (Read-Only Memory). It includes an ory)202, S-RAM (Static Random Access Memory)203, NV-RAM (Non-Volatile RAM)204, and a clock IC205, etc.

[0036] The CPU 201 comprehensively controls the entire image forming apparatus 2 by executing operation programs stored in ROM 202, etc. For example, it controls functions such as copying, printing, scanning, and facsimile to enable their execution. Furthermore, in this embodiment, when the user instructs the post-processing device 3 to perform post-processing or insert divider paper, the CPU 201 notifies the post-processing device 3 of the post-processing mode and the conditions for inserting divider paper, and also performs communication processing with the post-processing device 3 regarding the transport of printed paper to the post-processing device 3.

[0037] ROM202 stores programs and other data executed by CPU201.

[0038] S-RAM203 serves as a workspace for the CPU201 when executing programs, and temporarily stores programs and data related to program execution.

[0039] NV-RAM204 is a battery-backed non-volatile memory that stores various settings related to image formation.

[0040] The clock IC205 not only measures the time but also functions as an internal timer to measure processing time, etc.

[0041] The fixed storage device 210 consists of a hard disk or the like, and stores programs, various data, etc.

[0042] The image reading device 220 is equipped with a scanner and reads a document placed on a platen glass by scanning it, and converts the read document into image data.

[0043] The control panel 230 is used by the user to give instructions for jobs such as inserting divider paper and to make various settings, and is equipped with a reset key 231, a start key 232, a stop key 233, a display unit 234, and a touch panel 235.

[0044] The reset key 231 is used to reset the settings, the start key 232 is used to start operations such as scanning, and the stop key 233 is pressed to interrupt operations, etc.

[0045] The display unit 234 is, for example, a liquid crystal display device and displays messages and various operation screens, while the touch panel 235 is generated on the screen of the display unit 234 and detects user touch operations.

[0046] The image output device 240 prints the image data of the original document read by the image reading device 220 and the copy image generated from the print data transmitted from the terminal device 3 onto paper and outputs it as a printed document. It consists of the aforementioned image forming unit 23, intermediate transfer belt 24, transfer roller 25, fixing unit 26, etc.

[0047] The printer controller 250 generates a copy image from the print data received via the network interface 260.

[0048] Network I / F260 functions as a communication means for sending and receiving data via a network with external devices such as personal computers, while communication I / F270 is an interface for communicating with the post-processing unit 3.

[0049] The media measurement unit 280 measures media information, which is information about the characteristics of the paper to be printed on. In this embodiment, for example, it measures the paper type, including the paper size, and the basis weight.

[0050] Figure 3 is a flowchart showing the electrical configuration of the post-processing unit 3. As shown in Figure 3, the post-processing unit 3 includes a control unit 300, a fixed storage device 304, the aforementioned staple processing unit 31, a punch processing unit 35, a communication interface (communication I / F) 306, the aforementioned loading tray 33, as well as an upper limit sensor 311, a lower limit sensor 312, a distance measuring sensor 313, a drive circuit 314, a drive motor 315, etc., which are all connected to each other via a system bus.

[0051] The control unit 300 includes a CPU 301, ROM 302, RAM 303, etc. The CPU 301 comprehensively controls the entire post-processing unit 3 by executing operation programs stored in the ROM 302, etc. For example, it communicates with the image forming apparatus 2 and executes post-processing specified by the user. In particular, in this embodiment, it detects the drive load of the drive motor 315 that drives the loading tray 33 based on the current of the drive motor 315, detects the distance of the loading tray 33 from the home position, and performs processing such as determining whether there is an abnormality in the operation of the loading tray 33 based on the direction of movement of the loading tray 33, the detected drive load, and the detected distance from the home position. Details will be described later.

[0052] The fixed storage device 304 consists of a hard disk or the like, and stores programs, various data, etc.

[0053] The punching unit 35 punches holes in the stack of paper. In the example in Figure 3, the stapling unit 31 and the punching unit 35 are shown as post-processing units, but the system is not limited to these.

[0054] Communication I / F306 is an interface for communicating with the image forming apparatus 2.

[0055] The drive motor 315 drives the loading tray 33 to move it up and down, stop it, etc., and the drive circuit 314 is a circuit that drives the drive motor 315.

[0056] The upper limit sensor 311 defines the upper limit position of the loading tray 33, the lower limit sensor 312 defines the lower limit position, and the distance measuring sensor 313 measures the distance to the loading tray 33.

[0057] Figure 4 is a schematic diagram showing the configuration of the post-processing device 3. As mentioned above, the post-processing device 3 is equipped with the aforementioned drive motor 315 as a means of moving the loading tray (hereinafter referred to as the elevation tray) 33 up and down, and this drive motor 315 is located in the upper part of the internal space of the post-processing device 3. A belt 317 is stretched between the drive motor 315 and a driven shaft 316 located in the lower part of the internal space of the post-processing device 3, and the elevation tray 33 is configured to move in conjunction with the belt 317. In other words, when the drive motor 315 is rotated, the belt 317 travels in the direction of arrow Y2 between it and the driven shaft 316, and the elevation tray 33 moves up and down while maintaining its position as the belt 317 travels.

[0058] Furthermore, the post-processing device 3 includes an upper limit sensor 311 that protrudes from the post-processing device 3 at a position close to the paper output opening below the paper feed tray 34, and a lower limit sensor 312 that protrudes from the bottom of the post-processing device 3 into the space below the elevator tray 33.

[0059] The upper limit sensor 311 detects the upper limit position of the elevator tray 33. When the elevator tray 33 rises due to the drive motor 315, it contacts the upper limit sensor 311, and when the sensor 311 turns on, the drive motor 315 stops, and the upward movement of the elevator tray 33 also stops. However, the elevator tray 33 can continue to rise even if it exceeds the upper limit sensor 311. In this embodiment, the upper limit sensor 311 also serves as the home position sensor for the elevator tray 33, and the position where the elevator tray 33 stops upon contact with the upper limit sensor 311 is the home position of the elevator tray 33. Note that a separate home position sensor may be provided in addition to the upper limit sensor 311.

[0060] The lower limit sensor 312 detects the lower limit position of the elevator tray 33. The elevator tray 33 descends when driven by the drive motor 315, and when it comes into contact with the lower limit sensor 312 and the sensor 312 turns on, the drive motor stops, and the downward movement of the elevator tray 33 also stops. Therefore, the elevator tray 33 repeatedly moves up and down between the upper limit sensor 311 and the lower limit sensor 312, but the elevator tray 33 is in a state where it can descend beyond the lower limit sensor 312.

[0061] Furthermore, as shown in Figure 4, a distance measuring sensor 313 is positioned facing upward below the vertically movable range of the elevator tray 33 to measure the distance between it and the elevator tray 33. Based on the distance to the elevator tray 33 measured by the distance measuring sensor 313, the vertical position of the elevator tray 33 can be determined, and the distance of the elevator tray 33 from its home position can be detected.

[0062] Figure 5 shows the configuration of the post-processing device 3 according to another embodiment of the present invention. In this embodiment, similar to the embodiment in Figure 4, an upper limit sensor 311 and a lower limit sensor 312 are provided, but a distance measuring sensor 313 is not provided, and the distance of the elevator tray 33 from the home position is detected based on the amount of motor drive.

[0063] Specifically, a pulse motor such as a stepping motor is used as the drive motor 315, or a DC brushless motor and pulse encoder are used, and the drive pulses of the pulse motor or pulse count of the pulse encoder are performed from the moment the upper limit sensor (home position sensor) 311 changes from ON to OFF, and the distance of the elevator tray 33 from the home position is detected based on the motor drive amount corresponding to the counted pulses.

[0064] Furthermore, to further improve reliability, both detection methods—the pulse counting method used to detect the distance from the home position of the elevator tray 33 as shown in Figure 5, and the distance measurement sensor 313 used to detect the distance from the home position as shown in Figure 4—may be used in combination.

[0065] Furthermore, the detected distance of the elevator tray 33 from its home position, and the corresponding vertical position of the elevator tray 33, are stored in the RAM 303, etc., and are updated whenever the distance or position changes.

[0066] In the post-processing device 3 shown in Figures 4 and 5, the elevator tray 33 is in standby position when no paper is stacked, with the upper limit sensor (home position sensor) 311 turned on. When paper is discharged from the image forming apparatus 2, the elevator tray 33 descends while loading the discharged paper P. As the elevator tray 33 approaches the lower limit position, the amount of paper P loaded increases and the downward load increases. As shown in Figure 5, when the paper P is fully loaded, the lower limit sensor 312 turns on and the paper discharge stops. When the user removes the discharged paper P from the elevator tray 33, the elevator tray 33 rises to the home position and stops and waits at the home position.

[0067] When a portion of the paper P is removed, the elevator tray 33 rises by a distance corresponding to the weight of the removed paper P. In this case, if the distance of the elevator tray 33 from its home position is detected by a pulse counting method of the drive motor 315 or encoder, the distance (position) after rising is calculated from the distance (position) before rising, which is stored in the RAM 303, etc., and the amount of drive of the drive motor 315 corresponding to the pulse count for the rise, and the calculated distance (position) is stored in the RAM 303, etc. After that, it descends as usual according to the amount of paper P loaded.

[0068] The current of the drive motor 315 in the drive circuit 314 is constantly monitored by the control unit 300 of the post-processing device 3. Based on the current of the drive motor 315, the control unit 300 detects the drive load of the drive motor 315 and compares it with a reference value to determine whether there is an abnormality. The reference value of the drive load is calculated in advance according to the distance of the loading tray 33 from the home position and the weight of the sheets loaded on the loading tray 33, and a predetermined numerical range is set as the allowable range. The reference value differs depending on the weight of the sheets because the weight of the sheets differs depending on the type of paper, basis weight, etc., so even if the distance of the loading tray 33 from the home position is the same, the allowable drive load will differ depending on the type of paper, basis weight, etc.

[0069] The control unit 300 compares the detected drive load of the drive motor 315 with a reference value corresponding to the same paper type, basis weight, and distance from the home position as the currently loaded sheet to determine whether there is an abnormality. The paper type and basis weight of the currently loaded sheet are determined based on the paper type and basis weight detected by the media measurement unit 280 of the image forming apparatus 2.

[0070] Next, the operation of the post-processing device 3 when a foreign object such as a cardboard box is placed within the movable range below the elevator tray 33 will be explained with reference to Figure 6. In the example in Figure 6, the post-processing device 3 shown in Figure 5 is used, which detects the distance of the elevator tray 33 from the home position from the motor drive amount obtained by the pulse count of the drive motor 315 or encoder.

[0071] The elevator tray 33 descends in accordance with the ejection and loading of paper P. However, as shown in Figure 6, if a foreign object 40 is placed in the movable range below the elevator tray 33 in a state that interferes with the elevator tray 33 before it reaches the position of the lower limit sensor 312, the descent of the elevator tray 33 will be obstructed by the foreign object 40 and will stop before the elevator tray 33 turns on the lower limit sensor 312. In this case, the current, and thus the load, of the drive motor 315 will increase in an attempt to lower the elevator tray 33. However, the control unit 300 of the post-processing device 3 determines whether the load of the drive motor 315, detected from the current of the drive motor 315, is outside the allowable range of the reference value.

[0072] If the load on the drive motor 315 is significantly larger than the allowable range, the control unit 300 determines that there is a high probability that a foreign object 40 obstructing the operation of the elevator tray 33 is located below the elevator tray 33, and that the foreign object 40 is causing an obstruction at a position where the elevator tray 33 has not yet reached the lower limit sensor 312. Therefore, the control unit 300 stops the drive motor 315 to halt the descent of the elevator tray 33, and notifies the user of the abnormality by displaying a message on the display unit 234 of the operation panel 230 of the image forming apparatus 2, prompting the user to remove the foreign object 40. Note that such notification of an abnormality is not limited to a display on the operation panel 230, and may also be made by contacting a service technician via communication means or by transmitting data to a management server.

[0073] When the user removes the foreign object 40, the image forming apparatus 1 resumes operation, and the elevator tray 33 descends to its normal lower limit position. Alternatively, the stopping position of the elevator tray 33, which is the position where the abnormality occurred, may be stored in memory, and if the foreign object 40 is not removed, the elevator tray 33 may be raised and lowered within its movable range, i.e., between the home position and the position stored in memory. Furthermore, if the abnormality is still determined after executing multiple jobs following notification of the abnormality, it may be determined that the problem is not with the foreign object 40 but with the post-processing device 3, and the occurrence of the malfunction may be notified via the display unit 234. Notification of the occurrence of a malfunction may also be made by contacting a service technician via communication means or by sending data to a management server, rather than by display.

[0074] Thus, if the load on the drive motor 315 increases beyond the allowable value before the elevator tray 33 descends and reaches its maximum distance from the home position, in other words, before it reaches the lower limit position where the lower limit sensor 312 turns on, the system determines that there is a high probability that a foreign object 40 is present that is obstructing the descent of the elevator tray 33, and stops the drive motor 315. This prevents damage to gears and other components that may occur when attempting to forcibly lower the elevator tray 33.

[0075] Next, the operation of the post-processing device 3 when a foreign object 40 is placed on the elevator tray 33 will be explained with reference to Figure 7. In Figure 7, the post-processing device 3 shown in Figure 5 is used, which is of the type that detects the distance of the elevator tray 33 from the home position from the motor drive amount.

[0076] The elevator tray 33 descends from its home position in accordance with the ejection of paper P. However, if a foreign object 40, such as a heavy object, is placed on the elevator tray 33, the paper P will be loaded on top of the foreign object 40, as shown in Figure 7. As a result, the elevator tray 33 reaches the lower limit sensor 312 before loading the specified number of sheets of paper, the lower limit sensor 312 turns on, the drive motor 315 stops, and the elevator tray 33 also stops. On the other hand, the drive load of the drive motor 315 during descent is within the allowable range of a preset standard value in the normal state where no foreign object 40 is present. However, when paper P is loaded on top of the foreign object 40, if the weight of the foreign object 40 is large, the downward load applied to the elevator tray 33 is larger than in the normal state where no foreign object 40 is present, and the load on the drive motor 315 becomes smaller. As a result, the control unit 300 detects that the drive load of the drive motor 315 is small and below the allowable range while the elevator tray 33 is descending.

[0077] In this situation, there is a high probability that a heavy foreign object 40 is loaded on the elevator tray 33. Therefore, after the elevator tray 33 reaches its lower limit, notification is given by displaying a message on the display unit 2343 of the control panel 230, contacting a service technician, or sending data to the management server, prompting the removal of the foreign object 40.

[0078] Thus, if the load on the drive motor 315 when the elevator tray 33 is lowered is less than the allowable range, the system will determine that there is a high probability that a heavy foreign object 40 is loaded on the elevator tray 33 and will notify the user of the abnormality, allowing the user to remove the foreign object 40. Conversely, if the drive load on the drive motor 315 while the elevator tray 33 is lowering is greater than the allowable range, the system may determine that there is a high probability that a lightweight foreign object 40 is loaded on the elevator tray 33 and notify the user.

[0079] In the example shown in Figure 7, the elevator tray 33 is stopped when it reaches the lower limit sensor 312, so the elevator tray 33 operates within its normal range of motion.

[0080] Figure 8 is a schematic front view of an image forming apparatus 2 equipped with a post-processing device 5, which serves as a sheet lamination device according to another embodiment of the present invention. This post-processing device 5 is an inner type incorporated into the image forming apparatus 2, and after performing post-processing such as binding and punching on the paper on which the image has been formed by the image forming apparatus 2, it discharges the paper into a loading tray 51 located at the rear. Furthermore, when post-processing by the post-processing device 5 is not performed, it also functions as a paper discharge tray for discharging the paper on which the image has been formed by the image forming apparatus 2. This loading tray 51 is also configured as an elevator tray that can be raised and lowered vertically, as indicated by the arrow Y3.

[0081] Since the configuration of the image forming apparatus 2 is the same as that shown in Figure 1, a detailed explanation will be omitted.

[0082] Figure 9 is a schematic, enlarged view of the post-processing device 5 shown in Figure 8. In the case of the inner-type post-processing device 5, the home position of the elevator tray 51 is set to the lower limit position for visibility. When the image forming apparatus 2 starts operating, the elevator tray 51 rises from the home position to load the paper P discharged from the discharge port, and then lowers as the number of loaded sheets increases.

[0083] The electrical configuration of the post-processing device 5 is the same as that shown in the block diagram in Figure 3, except that the lower limit sensor 312 is not provided. However, the lower limit sensor 312 may be provided. The lifting and lowering operation of the elevator tray 51 is also performed by the drive motor 315 via the belt 317, similar to the embodiments shown in Figures 4 to 7, although this is not shown in the diagram.

[0084] Furthermore, an upper limit sensor 52 is provided on the upper part of the post-processing device 5, which protrudes toward the elevator tray 51. When the device makes contact with this upper limit sensor 52, the sensor 52 is turned on, and the upper limit position of the elevator tray 51 is detected.

[0085] Furthermore, a distance measuring sensor 53 is positioned below the elevator tray 51 to measure the distance to the elevator tray 51, and the distance of the elevator tray 53 from its home position can be detected based on the distance measured by the distance measuring sensor 53. However, the distance of the elevator tray 51 from its home position may also be detected by counting the pulses of a pulse encoder provided on the drive motor 315, or by counting the drive pulses if a pulse motor is used as the drive motor 315, or the distance from the home position may be detected using both pulse counting and the distance measuring sensor 53.

[0086] As described above, the elevator tray 51 rises from its home position when operation starts, and the paper ejected from the post-processing device 5 is loaded onto it. However, as shown in Figure 9, if a heavy foreign object 40 is placed on the elevator tray 51, the drive load of the drive motor 315 increases by the amount of the foreign object 40 before the elevator tray 51 reaches the upper limit sensor 52. Also, if a heavy foreign object 40 is placed during the rise, the drive load is at a normal value when the elevator tray 51 starts to rise, but increases sharply after the rise begins. Furthermore, if a large foreign object 40 is placed, the foreign object 40 or the paper loaded on the foreign object 40 may interfere with the upper limit member before the elevator tray 51 reaches the upper limit sensor 52, causing the elevator tray 51 to stop. In this case as well, the drive load of the drive motor 315 increases.

[0087] The control unit 300 of the post-processing device 3 determines whether the drive load of the drive motor 315, detected from the current of the drive motor 315, is outside the acceptable range of the reference value. If the drive load is larger than the acceptable range, there is a high possibility that a heavy or large foreign object 40 is present on the elevator tray 51. Therefore, the control unit 300 notifies the user of the abnormality by displaying a message on the display unit 234 or the like, and prompts the user to remove the foreign object 40. Such notification of abnormality is not limited to display on the operation panel 230, but may also be made by contacting a service technician via communication means or by transmitting data to a management server.

[0088] Thus, when the load on the drive motor 315 increases before the elevator tray 41 rises from its home position and the distance of the elevator tray 51 from its home position reaches its maximum, in other words, before the elevator tray 41 reaches the upper limit sensor 52, the control unit 300 determines that there is a high possibility that a heavy object or large foreign object 40 is present on the elevator tray 51 and stops the drive motor 315. This prevents damage to gears and other components that may occur when attempting to forcibly raise the elevator tray 51.

[0089] On the other hand, if a lightweight, bulky foreign object 40 is placed, the load on the drive motor 315 when the elevator tray 51 is raised becomes smaller compared to normal paper loading, resulting in a load below the permissible range. In this case, the control means 300 determines that there is a high probability that a lightweight foreign object 40 is present, and notifies the user of the abnormality by displaying a message on the display unit 234, etc., and prompts the user to remove the foreign object 40.

[0090] If an abnormality is still detected after executing multiple jobs following a notification of an abnormality, it will be determined that there is a problem with the post-processing unit 5, and a notification of the malfunction will be issued.

[0091] Figure 10 is a table summarizing the estimated causes of abnormalities based on the vertical position of the elevator trays 33 and 51, the direction of drive of the elevator trays 33 and 51, and the state of the drive load of the drive motor 315. The vertical position of the elevator trays 33 and 51 corresponds to the distance from the home position calculated from the drive amount of the drive motor 315 based on the pulse count of the drive motor 315 and the encoder, and / or the distance of the elevator trays 33 and 51 from the home position measured by the distance measuring sensors 313 and 53. Furthermore, as shown in Figure 11, the vertical position of the elevator trays 33 and 51 is defined as follows: A is the position when they have risen above the upper limit sensor 311, B is the intermediate position between the upper limit sensor 311 and the lower limit sensor 312, and C is the position when they have descended above the lower limit sensor 312.

[0092] As in Judgment 1, if the position of the elevator trays 33 and 51 is A, the driving direction of the elevator trays 33 and 51 is upward, and the driving load of the drive motor 315 is excessively large and exceeds the allowable range, then it is determined that the upper limit sensors 311 and 52 are damaged. However, even if the upper limit sensors 311 and 52 are damaged, it can be determined from the amount of drive of the drive motor 315 that the elevator trays 33 and 51 are above the upper limit sensors 311 and 52.

[0093] As in Judgment 2, if the position of the elevator trays 33 and 51 is A, the driving direction of the elevator trays 33 and 51 is upward, and the driving load of the drive motor 315 is too small and below the allowable range, then it is determined that the drive series is slipping or the drive motor 315 is damaged.

[0094] As in Judgment 3, if the position of the elevator trays 33 and 51 is A, the driving direction of the elevator trays 33 and 51 is downward, and the driving load of the drive motor 315 is too large and exceeds the allowable range, then it is determined that a foreign object 40 is placed below the elevator trays 33 and 51, and the foreign object 40 is interfering with the lower part of the elevator trays 33 and 51, preventing them from descending. The operation in Case 3 is an irregular operation, and it is conceivable that the foreign object 40 was placed below the elevator trays 33 and 51 while the power was off, causing the elevator trays 33 and 51 to be lifted beyond the upper limit sensor.

[0095] As in judgment 4, if the position of the elevator trays 33 and 51 is A, the driving direction of the elevator trays 33 and 51 is downward, and the driving load of the drive motor 315 is too small and below the allowable range, then it is determined that the drive series is slipping or the drive motor 315 is damaged.

[0096] As in judgment 5, if the position of the elevator trays 33 and 51 is B, the driving direction of the elevator trays 33 and 51 is upward, and the driving load of the drive motor 315 is too large and exceeds the allowable range, then it is determined that a heavy foreign object 40 is loaded on the elevator trays 33 and 51, or that a large foreign object 40 is loaded and the foreign object 40 is interfering with the upper part of the elevator trays 33 and 51, thereby hindering their upward movement.

[0097] As in judgment 6, if the position of the elevator trays 33 and 51 is B, the drive direction of the elevator trays 33 and 51 is upward, and the drive load of the drive motor 315 is too small and below the allowable range, then it is determined that the drive series is slipping, the drive motor 315 is damaged, or a lightweight foreign object 40 is loaded on it.

[0098] As in Judgment 7, if the position of the elevator tray 33 is B, the driving direction of the elevator tray 33 is downward, and the driving load of the drive motor 315 is too large and exceeds the allowable range, it is determined that there is foreign matter placed below the elevator tray 33, and that the foreign matter is interfering with the lower part of the elevator trays 33 and 51 and hindering their downward movement, or that a lightweight foreign object 40 is loaded onto the elevator trays 33 and 51.

[0099] As in judgment 8, if the position of the elevator trays 33 and 51 is B, the driving direction of the elevator trays 33 and 51 is downward, and the driving load of the drive motor 315 is too small and below the allowable range, then it is determined that the drive series is slipping, the drive motor is damaged, or a heavy foreign object 40 is loaded on the elevator trays 33 and 51.

[0100] As in judgment 9, if the position of the elevator tray 33 is C, the driving direction of the elevator tray 33 is upward, and the driving load of the drive motor 315 is too large and exceeds the allowable range, it is determined that a heavy object or large foreign object 40 is placed on the elevator tray 33, that is, the foreign object 40 is interfering with the upper part of the elevator tray 33 and is preventing it from rising. The operation in case 9 is irregular, and it is conceivable that a heavy object or the like, foreign object 40, was placed on the elevator tray 33 with the power off, causing the elevator tray 33 to move downward beyond the lower limit sensor 312.

[0101] As in judgment 10, if the position of the elevator tray 33 is C, the drive direction of the elevator trays 33 and 51 is upward, and the drive load of the drive motor 315 is too small and below the allowable range, then it is determined that the drive series is slipping or the drive motor is damaged.

[0102] As in judgment 11, if the position of the elevator tray 33 is C, the driving direction of the elevator tray 33 is downward, and the driving load of the drive motor 315 is too large and exceeds the allowable range, then it is determined that the lower limit sensor 312 is damaged. However, even if the lower limit sensor 312 is damaged, it can be determined from the amount of drive of the drive motor 315 that the elevator tray 33 has exceeded the lower limit sensor 312.

[0103] As in judgment 12, if the position of the elevator tray 33 is C, the driving direction of the elevator tray 33 is downward, and the driving load of the drive motor 315 is too small and below the allowable range, then it is determined that the drive series is slipping or the drive motor 315 is damaged.

[0104] In this way, the cause of the malfunction can be determined based on the vertical position of the elevator trays 33 and 51 (distance from the home position), the direction of drive of the elevator trays 33 and 51, and the state of the drive load of the drive motor 315.

[0105] However, when the elevator trays 33 and 51 are in the intermediate position B, the value of the drive load of the drive motor 315, which is the criterion for judgment, differs depending on the position of the elevator trays 33 and 51 (distance of the elevator trays 33 and 51 from the home position), as shown in Figures 12 and 13. This is because the closer the elevator trays 33 and 51 are to the lower limit, the greater the weight of the ejected paper P.

[0106] Figure 12 is a graph showing the relationship between the distance from the home position when the elevator tray 51 is raised and the allowable range of the drive load of the drive motor 315.

[0107] As the distance of the elevator tray 51 from its home position increases, the weight of the paper P loaded increases, and therefore the motor load when the elevator tray 51 is raised increases. Consequently, the allowable load range also shifts to a larger range. Furthermore, the motor load also changes depending on the type of paper P loaded. As shown in the example in Figure 12, the allowable load range for A3 size paper with a basis weight of 200g, enclosed by lines L3 and L4, shifts to a larger range compared to the allowable range for A4 size paper with a basis weight of 64g, enclosed by lines L1 and L2.

[0108] Figure 13 is a graph showing the relationship between the distance from the home position when the elevator trays 33 and 51 are lowered and the allowable range of the drive load of the drive motor 315.

[0109] As the distance of the elevator trays 33 and 51 from their home positions increases, the weight of the paper P loaded increases, and therefore the load during descent decreases. Consequently, the allowable load range also shifts to a smaller range. Furthermore, the drive load also changes depending on the type of paper P loaded. As shown in the example in Figure 13, the allowable load range for A3 size paper with a basis weight of 200g, enclosed by lines L7 and L8, is smaller than that for A4 size paper with a basis weight of 64g, enclosed by lines L5 and L6.

[0110] Figure 14 is a flowchart showing the process by which the post-processing units 3 and 5 detect an abnormality based on the vertical position of the elevator trays 33 and 51 (distance from the home position), the direction of drive of the elevator trays 33 and 51, and the state of the drive load of the drive motor 315. This flowchart is executed by the CPU 301 of the post-processing units 3 and 5 operating according to an operation program stored in the ROM 302 or the like.

[0111] In step S101, the position h of the elevator trays 33 and 51, in other words, the distance of the elevator trays 33 and 51 from their home positions is detected, and in step S102, the drive current of the drive motor 315 is converted into the torque value (load) T of the drive motor 315.

[0112] Next, in step S103, the position h of the elevator trays 33 and 51 is checked. If the position h of the elevator trays 33 and 51 is at position A, which is above the upper limit sensor 311, the process proceeds to step S104, and in step S105, the direction of drive of the elevator trays 33 and 51 is checked.

[0113] If the drive direction is upward, proceed to step S106, and then in step S107, determine whether the load on the drive motor 315 is less than the reference minimum value. If it is less than the reference minimum value (YES in step S107), in step S108, determine whether the drive series is slipping or whether the drive motor 315 is damaged.

[0114] If the load on the drive motor 315 is not less than the reference minimum value (NO in step S107), in step S109, it is determined whether the drive load is greater than the reference maximum value. If it is greater than the reference maximum value (YES in step S109), in step S110, it is determined that the upper limit sensor 311 is damaged. If it is not greater than the reference maximum value (NO in step S109), it is determined that no abnormality has occurred, and the system returns to terminate this process.

[0115] If the direction of drive of the elevator trays 33 and 51, as checked in step S105, is downward, the process proceeds to step S111, and further in step S112, it is determined whether the drive load of the drive motor 315 is smaller than the reference minimum value. If it is smaller than the reference minimum value (YES in step S112), in step S113, it is determined whether the drive series is slipping or whether the drive motor 315 is damaged.

[0116] If the load on the drive motor 315 is not less than the reference minimum value (NO in step S112), in step S114, it is determined whether the drive load is greater than the reference maximum value. If it is greater than the reference maximum value (YES in step S114), in step S115, it is determined that there is foreign matter 40 below the elevator trays 33 and 51. If it is not greater than the reference maximum value (NO in step S114), it is determined that no abnormality has occurred, and the process is terminated.

[0117] If the tray position h determined in step S103 is the intermediate position B, proceed to step S116, and then in step S117, check the direction of drive of the elevator trays 33 and 51.

[0118] If the drive direction is upward, the process proceeds to step S118, and further in step S119, it is determined whether the drive load of the drive motor 315 is smaller than the reference minimum value. If it is smaller than the reference minimum value (YES in step S119), in step S120, it is determined whether the drive series is slipping or whether the drive motor 315 is damaged.

[0119] If the drive load of the drive motor 315 is not less than the reference minimum value (NO in step S119), in step S121, it is determined whether the drive load is greater than the reference maximum value. If it is greater than the reference maximum value (YES in step S121), in step S122, it is determined that foreign matter 40 is placed on the elevator trays 33 and 51. If it is not greater than the reference maximum value (NO in step S121), it is determined that no abnormality has occurred, and the system returns to terminate this process.

[0120] If the direction of drive of the elevator trays 33 and 51, as checked in step S117, is downward, proceed to step S123, and further in step S124, determine whether the drive load of the drive motor 315 is smaller than the reference minimum value. If it is smaller than the reference minimum value (YES in step S124), in step S125, determine whether the drive series is slipping, the drive motor 315 is damaged, or a heavy object is loaded.

[0121] If the drive load of the drive motor 315 is not less than the reference minimum value (NO in step S124), in step S126, it is determined whether the drive load is greater than the reference maximum value. If it is greater than the reference maximum value (YES in step S126), in step S127, it is determined that there is foreign matter 40 below the elevator trays 33 and 51, etc. If it is not greater than the reference maximum value (NO in step S126), it is determined that no abnormality has occurred, and the process is terminated.

[0122] If the tray position h determined in step S103 is at position C, which is above the lower limit sensor 312, the process proceeds to step S128, and in step S129, the direction of drive of the elevator trays 33 and 51 is determined.

[0123] If the drive direction is upward, the process proceeds to step S130, and further in step S131, it is determined whether the drive load of the drive motor 315 is smaller than the reference minimum value. If it is smaller than the reference minimum value (YES in step S131), in step S132, it is determined whether the drive series is slipping or whether the drive motor 315 is damaged.

[0124] If the drive load of the drive motor 315 is not less than the reference minimum value (NO in step S131), in step S133, it is determined whether the drive load is greater than the reference maximum value. If it is greater than the reference maximum value (YES in step S133), in step S134, it is determined that foreign matter 40 is placed on the elevator trays 33 and 51. If it is not greater than the reference maximum value (NO in step S133), it is determined that no abnormality has occurred, and the system returns to terminate this process.

[0125] If the direction of drive of the elevator trays 33 and 51, as checked in step S129, is in the downward direction, the process proceeds to step S135, and further in step S136, it is determined whether the drive load of the drive motor 315 is smaller than the reference minimum value. If it is smaller than the reference minimum value (YES in step S136), in step S137, it is determined whether the drive series is slipping or whether the drive motor 315 is damaged.

[0126] If the drive load of the drive motor 315 is not less than the reference minimum value (NO in step S136), in step S138, it is determined whether the drive load is greater than the reference maximum value. If it is greater than the reference maximum value (YES in step S138), in step S139, it is determined that the lower limit sensor 312 is damaged. If it is not greater than the reference maximum value (NO in step S138), it is determined that no abnormality has occurred, and the process is terminated.

[0127] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, although the sheet loading device has been described as being a post-processing device 3, 5, the sheet loading device may also be of a type that does not have a post-processing function and loads the paper discharged from the image forming apparatus 2 onto the elevator trays 33, 51.

[0128] Furthermore, although the control unit 300 has been described as making a determination of whether or not there is an abnormality during job processing, it may also be done during the movement of the loading tray after job processing, or during test mode, or it may be done at least one of the following times: during job processing, during the movement of the loading tray after job processing, or during test mode. [Explanation of symbols]

[0129] 2 Image forming apparatus 3.5 Post-treatment device (sheet loading device) 33, 51 Loading tray (elevator tray) 40 Foreign object 52 Upper limit sensor 53 Distance measuring sensor 230 Control Panel 234 Display section 300 Control Unit 301 CPU 311 Upper limit sensor 312 Lower limit sensor 313 Distance measuring sensor 315 Drive motor 316 Driven axis 317 Belt P paper

Claims

1. A loading tray for loading sheets on which images have been formed, A drive means for moving the aforementioned loading tray upward or downward from the home position, and then moving it back to the home position, A load detection means for detecting the drive load when the drive means moves the loading tray, Distance detection means for detecting the distance of the loading tray from the home position, A determination means for determining whether or not there is an abnormality based on the driving direction of the loading tray, the driving load detected by the load detection means, and the distance from the home position detected by the distance detection means, A sheet loading device characterized by having the following features.

2. The sheet loading device according to claim 1, wherein the distance detection means detects the distance from the home position by counting the pulse encoder of the motor which is the driving means.

3. The sheet loading device according to claim 1, wherein the distance detection means detects the distance from the home position by counting the drive pulses of the pulse motor, which is the drive means.

4. It is equipped with a distance measuring sensor capable of detecting the distance to the moving loading tray, The sheet loading device according to claim 1, wherein the distance detection means detects the distance from the home position based on the detection result of the distance measuring sensor.

5. The sheet loading device according to any one of claims 1 to 4, wherein the reference value of the drive load for determining whether or not there is an abnormality by the determination means changes according to the distance from the home position of the loading tray.

6. The sheet loading device according to any one of claims 1 to 5, wherein the reference value of the drive load for determining whether or not there is an abnormality by the determination means changes according to the basis weight and / or size of the sheet.

7. The sheet loading device according to claim 5 or 6, wherein the reference value of the drive load for determining whether or not there is an abnormality by the determination means is greater when the home position is below the sheet loading device and the loading tray rises from the home position, and is smaller when the home position is above the sheet loading device and the loading tray descends from the home position, and is smaller when the distance of the loading tray from the home position is larger.

8. The load detection means detects the drive load based on the current value of the motor, which is the drive means. The sheet loading device according to any one of claims 1 to 7, wherein the determination means compares a reference value of the drive load, which is calculated in advance from the distance of the loading tray from the home position and the weight of the sheets loaded on the loading tray, with the drive load detected based on the current value, to determine whether or not there is an abnormality.

9. The system includes a lower limit sensor that detects the lower limit position of the loading tray, The sheet loading device according to claim 8, wherein if the drive load is greater than a reference value even though the lower limit sensor does not turn on when the loading tray is lowered, the determination means determines that a foreign object is obstructing the loading tray at a position where it has not reached the lower limit sensor and notifies of the occurrence of an abnormality.

10. The system includes a storage means for storing the position of the loading tray when the determination means determines that there is an abnormality during the lowering of the loading tray. The sheet loading device according to any one of claims 1 to 9, wherein, after the determination means determines that there is an abnormality, the driving means drives the loading tray using the position stored in the storage means as the lower limit position of the loading tray.

11. The aforementioned loading tray is equipped with an upper limit sensor that detects the upper limit position, The sheet loading device according to claim 8, wherein if the upper limit sensor turns on when the loading tray is raised, even though the drive load is less than a reference value, the determination means determines that a foreign object has been placed on the loading tray.

12. The aforementioned loading tray is equipped with an upper limit sensor that detects the upper limit position, The load detection means detects the drive load from the current value of the motor, which is the drive means. The sheet loading device according to any one of claims 1 to 11, wherein the determination means determines that a foreign object has been placed on the loading tray and notifies of the occurrence of an abnormality if the drive load is at a normal value when the loading tray starts to rise, but increases rapidly after the start of rising.

13. The sheet loading device according to claim 9 or 12, wherein the determination means determines that there is a malfunction in the sheet loading device and notifies the occurrence of the malfunction if it is determined that there is a malfunction even after executing multiple jobs after notification of the occurrence of the malfunction.

14. The sheet loading device according to any one of claims 9, 12, or 13, wherein notification of an abnormality or malfunction is provided by displaying it on the control panel, contacting a service technician via communication means, or transmitting data to a management server.

15. The sheet loading device according to any one of claims 1 to 14, wherein the determination of whether or not there is an abnormality by the determination means is performed at least one of the following: during job processing, during the movement of the loading tray after job processing, or during test mode.

16. The sheet loading device according to claim 2 or 3, wherein if the loading tray rises due to the removal of a portion of the loaded sheets, the distance of the loaded sheets from the home position after the rise is calculated based on the amount of motor drive for the rise.

17. A loading tray for loading sheets on which images have been formed, A drive means for moving the aforementioned loading tray upward or downward from the home position, and then moving it back to the home position, A sheet loading device equipped with, A load detection step in which the drive means detects the drive load when moving the loading tray, A distance detection step for detecting the distance of the loading tray from the home position, A determination step that determines whether or not there is an abnormality based on the driving direction of the loading tray, the driving load detected by the load detection step, and the distance from the home position detected by the distance detection step, A method for loading sheets, characterized by performing the following:

18. A loading tray for loading sheets on which images have been formed, A drive means for moving the aforementioned loading tray upward or downward from the home position, and then moving it back to the home position, The computer of the seat loading device equipped with A load detection step in which the drive means detects the drive load when moving the loading tray, A distance detection step for detecting the distance of the loading tray from the home position, A determination step that determines whether or not there is an abnormality based on the driving direction of the loading tray, the driving load detected by the load detection step, and the distance from the home position detected by the distance detection step, A program to execute.

Images