Sheet processing device and image forming system

Abstract

In a configuration that uses a loading tray position sensor, an encoder to detect the amount of movement of the loading tray, and a sheet surface detection sensor to detect the sheet surface to determine the presence or absence of a sheet on the loading tray, the system is designed to accurately determine the presence or absence of a sheet when the tray is fully loaded. [Solution] Sheets are discharged onto the loading tray 15, and once it is full, the loading tray 15 is moved until the loading tray HP sensor Sn1 turns on, resetting the encoder clock. Then, the number of clock cycles until the sheet surface detection sensor Sn3 turns on when the sheet is removed from the loading tray 15 is counted.

Description

Technical Field

[0001] The present invention relates to a sheet processing apparatus that performs a predetermined process on a sheet and discharges it, and an image forming system including the same.

Background Art

[0002] In a sheet processing apparatus, a sheet on which an image is formed by an image forming apparatus is subjected to a predetermined process and discharged onto a stacking tray. A conventional sheet processing apparatus includes a sheet surface detection sensor for positioning the stacking tray or the uppermost sheet of the sheets stacked on the stacking tray in a sheet receiving position when no sheet is stacked, a tray position detection sensor for detecting a reference position of the stacking tray, a drive mechanism including a DC motor for raising and lowering the stacking tray, and an encoder provided in a part of the drive mechanism, and manages the position of the stacking tray based on the number of clock pulses of the encoder when the stacking tray moves from the reference position.

[0003] Since the stacking tray performs a lifting operation, the number of clock pulses of the encoder is set to 0 at the reference position, and is added by the clock input during upward movement and subtracted by the clock input during downward movement. Based on the number of clock pulses when the sheet surface detection sensor is turned on in such a configuration, it is determined whether a sheet is stacked on the stacking tray. For example, when the reference position sensor is below the sheet surface detection sensor, if the number of clock pulses when the sheet surface detection sensor is turned on is equal to or greater than a predetermined number of clock pulses, it is determined that "no sheet", and if it is less than the predetermined number of clock pulses, it is determined that "sheet exists" because the upward movement amount of the stacking tray is small. In this sheet processing apparatus, when the sheets on the stacking tray reach a full load state, if it is determined that "no sheet" according to the above configuration, the full load state is released and the next job is executed.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Because the loading tray repeatedly lowers or raises and stops, when the loading tray stops near the edge of the encoder, vibrations or other factors may cause unintended encoder clock inputs. These erroneous clock inputs prevent the system from determining the direction of drive, leading to positional errors. As a result, even if all sheets are removed from the loading tray when it is fully loaded, the number of clocks triggered by the sheet surface detection sensor may fall below a predetermined number, potentially preventing the system from resolving the load because it cannot detect "no sheets." [Means for solving the problem]

[0005] A typical configuration according to the present invention for achieving the above objective comprises: a sheet processing unit for performing a predetermined process on a sheet; a discharge unit for discharging the sheet; a loading unit provided so as to be vertically movable relative to the discharge unit and for loading the sheets discharged by the discharge unit; a reference position detection sensor for detecting the reference position of the loading unit; a sheet surface detection sensor for detecting the height of the upper surface of the loading unit or the top sheet of the sheet bundle loaded on the loading unit; a drive motor for raising and lowering the loading unit; an encoder provided in a drive transmission mechanism that transmits the drive of the drive motor to the loading unit and detects the amount of movement of the loading unit; and a control unit for controlling the operation of the loading unit, wherein the control unit comprises the The sheet processing device is characterized in that, when the loading unit is in a reference position as determined by the reference position detection sensor, the input clock count from the encoder is used as the reference clock count, and the position of the loading unit from the reference position is managed by adding the input clock count input when the loading unit is raised and subtracting the input clock count input when it is lowered. When a sheet is loaded onto the loading unit and it is fully loaded, the loading unit is moved to the reference position and the input clock count is reset to the reference clock count, and then it is determined whether or not a sheet is loaded on the loading unit according to the input clock count when the loading unit moves from the reference position until the sheet surface detection sensor turns on. [Effects of the Invention]

[0006] According to the present invention, in a configuration in which the presence or absence of a sheet on a loading tray is determined using a loading tray position sensor, an encoder for detecting the amount of movement of the loading tray, and a sheet surface detection sensor for detecting the sheet surface, it is possible to accurately determine the presence or absence of a sheet when the tray is fully loaded. [Brief explanation of the drawing]

[0007] [Figure 1] Schematic diagram of the overall configuration of an image forming system equipped with a sheet processing device. [Figure 2] Perspective view of the sheet processing device [Figure 3] Diagram illustrating the configuration of the sheet processing device. [Figure 4] Diagram illustrating sheet alignment and binding operations. [Figure 5] Diagram illustrating the lifting mechanism of the loading tray. [Figure 6] Diagram illustrating the drive mechanism of the seat retaining paddle. [Figure 7] Block diagram of the control configuration of the image forming system [Figure 8] This diagram shows the relationship between the tray lifting motor drive, the output of the seat surface detection sensor, and the encoder clock. [Figure 9] This diagram shows the number of encoder clock cycles when the loading tray moves from its home position until the seat surface detection sensor is activated. [Figure 10] Diagram illustrating the operation to release the full load state. [Figure 11] Diagram illustrating the operation to release the full load state. [Figure 12] Diagram illustrating the operation to release the full load state. [Figure 13] Diagram illustrating the operation to release the full load state. [Modes for carrying out the invention]

[0008] [First Embodiment] Next, a sheet processing apparatus and an image forming system equipped therewith, according to a preferred embodiment of the present invention, will be described with reference to the drawings. Figure 1 schematically shows the overall configuration of an image forming system equipped with a sheet processing apparatus according to an embodiment of the present invention. As shown in the figure, the image forming system C consists of an image forming apparatus A and a sheet processing apparatus B attached thereto. In Figure 1, the left-right direction is called the horizontal direction, the up-down direction is called the vertical direction, the direction of arrow FR in Figure 2 is called the front-to-back direction or the sheet width direction, the side of arrow F is called the front side, and the side of arrow R is called the rear side.

[0009] <Image forming apparatus> Image forming apparatus A consists of an image forming unit A1, a scanner unit A2, and a feeder unit A3. The image forming unit A1 has a feeding section 2, an image forming section 3, and an discharge section 4 inside the apparatus housing 1.

[0010] The feeding unit 2 consists of multiple cassette mechanisms 2a, 2b, and 2c, each storing image forming sheets of different sizes, and feeds sheets of a specified size from the main control unit to the feeding path 2f. Each cassette mechanism 2a, 2b, and 2c is detachably installed from the feeding unit 2 and contains a separation mechanism for separating the sheets one by one and a feeding mechanism for feeding the sheets. The feeding path 2f is provided with transport rollers for feeding the sheets supplied from each cassette mechanism 2a, 2b, and 2c downstream, and pairs of registration rollers at the ends of the path for aligning the leading edges of each sheet.

[0011] In this embodiment, the image forming unit 3 is configured using an electrophotographic method and comprises a rotating photosensitive drum 3a and, arranged around it, a charging roller 3b, an exposure unit 3c, a developer unit 3d, and a cleaner (not shown). The illustrated diagram shows a color printing mechanism, in which the image forming mechanism is provided according to the respective colors: yellow Y, magenta M, cyan C, and black K.

[0012] In image formation, the circumferential surface of the rotating photosensitive drum 3a is uniformly charged by a charging roller 3b, irradiated with light according to an image signal by an exposure device 3c to form an electrostatic latent image, and developed by a developing device 3d to form a toner image. The toner images of each color thus formed are primarily transferred to a rotating intermediate transfer belt 3e to form a color image. In accordance with the timing of image formation, a sheet is sent from a feeding path 2f to a secondary transfer section, and the toner image formed on the intermediate transfer belt 3d is transferred onto the sheet by applying a transfer bias from a secondary transfer roller 3f. The sheet onto which the toner image has been transferred is heated and pressed when passing through a fixing device 5, the toner image is fixed, and the sheet is discharged from a discharge port 4b by a discharge roller 4a and conveyed to a sheet processing device B described later.

[0013] The scanner unit A2 includes a platen 6a on which an image original is placed, a carriage 6b that reciprocates along the platen 6a, a photoelectric conversion element 6c, and a reduction optical system 6d that guides reflected light from the original on the platen 6a by the carriage 6b to the photoelectric conversion element 6c. The photoelectric conversion element 6c photoelectrically converts the optical output from the reduction optical system 6d into image data and outputs it as an electrical signal to the image forming unit 3. Further, the scanner unit A2 can also read a document sheet sent from a feeder unit A3.

[0014] <Sheet Processing Device> Next, the overall configuration of a sheet processing device B that processes the sheet sent from the image forming device A will be described.

[0015] FIG. 2 is a perspective view of the sheet processing device according to the present embodiment, and FIG. 3 is a configuration explanatory diagram of the sheet processing device B. The sheet processing device B includes a device housing 11 provided with an entrance 10 for introducing a sheet from the image forming device A. The device housing 11 is arranged in alignment with the housing 1 of the image forming device A so that the entrance 10 communicates with the discharge port 4b of the image forming device A.

[0016] The discharge unit 4 of the image forming apparatus A of the present embodiment is formed in a space portion (inner space of the body) 4c formed between the image forming unit A1 and the scanner unit A2, and the sheet processing apparatus B is disposed in the space portion 4c.

[0017] The sheet processing apparatus B includes an apparatus frame 11, a sheet conveyance path 12 disposed on the apparatus frame 11, a processing tray 14 disposed downstream of the conveyance path outlet 13, and a stacking tray 15 disposed further downstream thereof. As shown in FIG. 2, a cartridge mounting opening 16 for staple pins, a manual setting portion 17, and a manual operation button 18 are provided on the front side of the apparatus frame 11.

[0018] In addition, the processing tray 14 is provided with a scraping paddle 19 composed of a rubber plate for scraping the sheet into the rear end stopper 21, a rubber knurled belt 20 having a knurling process on the outer peripheral surface, and a sheet rear end stopper 21 and an alignment plate 22 for accumulating the sheets in a bundle shape. Together with this, a staple binding unit 23 for staple-binding the sheet bundle and a non-staple binding unit 24 for binding the sheet bundle without needles are disposed on the processing tray 14.

[0019] (Sheet binding mechanism) The sheet on which an image is formed by the image forming apparatus A is sent from the discharge port 4b of the image forming apparatus to the inlet 10 of the sheet processing apparatus B, and predetermined sheet processing is executed in the sheet processing unit. In the sheet processing unit of the present embodiment, as shown in FIG. 4(a), the sheet P sent from the inlet 10 is conveyed by a conveyance roller 30a which is a sheet conveyance member provided in the sheet conveyance path 12, and is conveyed to the processing tray 14 by a conveyance roller 30b as a sheet conveyance member provided near the conveyance path outlet 13.

[0020] The sheet P, which is transported from the transport path exit 13 to the processing tray 14, is scraped off by the counterclockwise rotating scraping paddle 19 shown in Figure 4(b), and is transported by the counterclockwise rotating knurled belt 20 so that the rear end of the sheet abuts against the sheet rear end stopper 21, and the alignment plate 22 is slid in the sheet width direction to align both sides of the sheet in the width direction.

[0021] After transporting a predetermined number of sheets to the processing tray 14 as described above, the stapling unit 23, which is a processing unit, is operated to perform stapling on the sheet bundle on the processing tray 14. Once the sheets have been stapled, the upper discharge roller 31a of the separated discharge roller pair 31a, 31b moves and nips the sheets on the processing tray 14. Then, as shown in Figure 4(c), the driving force of the discharge motor is transmitted to the lower discharge roller 31b, and the sheets are discharged by the rotating discharge roller pair 31a, 31b and loaded into the loading tray 15, which serves as the sheet loading section. This loading tray 15 is equipped with a tray lifting mechanism that lowers it sequentially according to the amount of sheets loaded.

[0022] (Loading tray lifting mechanism) Figure 5 shows the lifting mechanism (lifting section) for raising and lowering the loading tray 15. As shown in Figure 5, the base 40 of the loading tray 15 is mounted so as to be slidable vertically along a rail (not shown) formed in the device housing 11. A rack section 41 is formed on the tray base 40, and this rack section 41 meshes with a pinion gear 42 provided on the device housing 11. The pinion gear 42 receives driving force from the tray lifting motor M1 via a transmission gear 43 and rotates, causing the rack section 41 to move up and down, thereby raising and lowering the loading tray 15. An encoder 44 that rotates integrally with the pinion gear 42 is attached to it, and the amount of rotation of this encoder 44 can be detected using an encoder sensor Sn2 to control the amount of raising and lowering of the loading tray 15.

[0023] Furthermore, a loading tray HP sensor Sn1 is provided at a predetermined position on the device housing 11 as a reference position detection sensor. This sensor Sn1 detects a sensor flag 45 provided on the tray base 40, thereby enabling the loading tray 15 to be positioned in the home position.

[0024] The loading tray 15 is controlled to move up and down in accordance with the discharge of the sheets, as will be described later. The sheet holding paddle 50 is also controlled to rotate in accordance with the discharge of the sheets and the raising and lowering of the loading tray 15.

[0025] (Seat holding paddle) The sheet-holding paddle 50, acting as a sheet-grabbing member, presses down on the upper surface of sheets loaded onto the loading tray 15, thereby preventing previously loaded sheets from being pushed out by sheets subsequently discharged onto the loading tray 15. This sheet-holding paddle 50 is rotatable coaxially with the lower discharge roller 31b and is also rotatable independently of the lower discharge roller 31b. Furthermore, by rotating the sheet-holding paddle 50 in the counterclockwise direction shown in Figure 3 while in contact with the upper surface of the sheet discharged onto the loading tray 15, the rear end of the sheet can be grabbed towards the upright surface 11a. Repeating this process with each discharge improves the alignment of the sheets in the sheet discharge direction.

[0026] Figure 6(a) is a perspective view showing the drive configuration of the lower discharge roller 31b and the sheet-holding paddle 50.

[0027] The lower discharge roller 31b is driven by the discharge motor M2 via a drive transmission mechanism 32. In the illustrated example, the drive transmission mechanism 32 consists of a pulley and a belt, and transmits the rotational drive of the drive shaft of the discharge motor M2 to the rotation shaft 31b1 of the lower discharge roller 31b. On the other hand, the sheet pressing paddle 50 is driven by the sheet pressing paddle motor M3, which acts as the drive unit, via a drive transmission mechanism 51. In the illustrated example, the drive transmission mechanism 51 consists of a pulley and a belt, and transmits the rotational drive of the drive shaft of the sheet pressing paddle motor M3 to the rotation shaft 52 of the sheet pressing paddle 50.

[0028] The rotating shaft 31b1 of the lower discharge roller 31b is designed so that the rotating shaft 52 of the sheet-holding paddle 50 can pass through its interior, allowing the two sheet-holding paddles 50 located on either side of the lower discharge roller 31b's rotation axis to be mounted on a single rotating shaft 52. The rotating shaft 31b1 of the lower discharge roller 31b is rotatably supported on the rotating shaft 52 of the sheet-holding paddle 50, for example, via a bearing. This allows the lower discharge roller 31b and the sheet-holding paddle 50 to be driven independently by separate motors. In addition to the pulley and belt configuration, the drive transmission mechanisms 32 and 51 may also be configured using other drive transmission members, such as multiple gears.

[0029] As shown in Figure 6(b), the sheet-holding paddle 50 has a fixed portion 50a fixed to the rotating shaft 52 and a plate-shaped paddle portion 50b that serves as an elastic contact portion provided on the fixed portion 50a. The paddle portion 50b extends from the fixed portion 50a fixed to the rotating shaft 52 in a direction perpendicular to the rotating shaft 52. The paddle portion 50b is made of an elastic material such as rubber (for example, ethylene propylene rubber (EPDM) with a hardness of 30±5HS(A) ((old JIS K6301, spring type A))). The sheet-holding paddle 50 configured in this way rotates with the rotation of the rotating shaft 52, and when the paddle portion 50b comes into contact with the sheet on the loading tray 15, it elastically deforms to hold down the rear end of the sheet.

[0030] Furthermore, a sensor flag 53 is provided on the rotation axis 52 of the sheet-holding paddle 50 so as to rotate integrally with the rotation axis 52, and a paddle HP sensor Sn2 capable of detecting the sensor flag 53 is provided in the device housing 11. The position where the paddle HP sensor Sn2 detects the sensor flag 53 becomes the home position of the sheet-holding paddle 50 (Figure 9). Also, the position where the sheet-holding paddle 50 has rotated a predetermined amount after the paddle HP sensor Sn2 detects the sensor flag 53 is the sheet-holding position (Figure 3). Note that the home position is set in the space above the loading tray 15 and does not interfere with other components so that the paddle portion 50b of the sheet-holding paddle 50 does not develop any deformation. For example, when a job is waiting, the sheet-holding paddle 50 is in the home position.

[0031] Here, since the sheet-holding paddle 50 rotates around the rotation axis 52, the paddle portion 60b passes through the processing tray 14. For this reason, as shown in Figure 10, a recess 500 is formed on the processing tray 14 side, through which the paddle portion 50b can pass when the sheet-holding paddle 50 rotates. That is, since the sheet-holding paddle 50 rotates around the rotation axis 52, it rotates counterclockwise in Figure 10 from the loading tray 15 toward the processing tray 14, passes through the processing tray 14 side, and returns to the loading tray 15 again. For this reason, at the downstream end of the processing tray 14 in a predetermined direction, a recess 500 is formed at a position corresponding to the sheet-holding paddle 50 in the width direction, so as to be recessed toward the upstream side in a predetermined direction. Then, when the sheet-holding paddle 50 rotates, the paddle portion 50b passes through the recess 500.

[0032] In this embodiment, the processing tray 14 is provided with a moving mechanism (a rack and pinion mechanism in this embodiment) for moving the alignment plate 271A in the width direction. Since this moving mechanism extends across the width direction, the recess 500 can only be recessed up to the front of the moving mechanism. That is, in this embodiment, the recess 500 cannot be recessed to a depth corresponding to the length of the sheet pressing paddle 50. On the other hand, since the paddle portion 50b of the sheet pressing paddle 50 is elastic, as shown in Figure 10(a), the paddle portion 50b passes through the recess 500 by elastically deforming.

[0033] <Department Head> Next, the control configuration of the image forming system described above will be explained with reference to the block diagram in Figure 7.

[0034] The image forming system of this embodiment includes an image forming control unit 200 of the image forming apparatus A and a sheet processing device control unit (CPU: also called MPU; that is, a chip that integrates the calculation functions of a CPU, not just the calculation part) 100 of the sheet processing device B. The image forming control unit 200 includes a sheet feeding control unit 201 and an input unit 202. The "print mode (straight output)" and "sheet processing mode (sorted output mode or bound output mode)" are set from a control panel 203 provided on the input unit 202.

[0035] The sheet processing control unit 100 operates the sheet processing device B according to the sheet processing mode. This sheet processing control unit 100 is equipped with a ROM that stores the operation program and a RAM that stores control data. The sheet processing control unit 100 also receives signals from various sensors via the various sensor input unit 101, such as the loading tray HP sensor Sn1 that detects the home position of the loading tray 15, the paddle HP sensor Sn2 that detects the home position of the sheet holding paddle 50, the sheet surface detection sensor Sn3 that detects the top surface of the sheet loaded on the loading tray 15, and the encoder sensor Sn4 that detects the rotation of the encoder 44 for managing the amount of movement of the loading tray 15. The sheet surface detection sensor Sn3 detects the sheet loading surface of the loading tray 15, and when a sheet is loaded on the loading tray 15, it detects the position of the top surface of the loaded sheet, and is provided at a predetermined position in the movement area of ​​the loading tray 15. The sheet surface detection sensor Sn3 turns on when it detects a sheet loaded on the loading tray 15, and turns off when it does not detect a sheet. The sheet surface detection sensor Sn3 in this embodiment is a reflective sensor provided on the upright surface 11a.

[0036] Furthermore, the sheet processing apparatus control unit 100 includes a sheet transport control unit 104 that controls the discharge motor M2 which provides driving force to the discharge roller 31b, the transport motor M4 which provides driving force to the transport rollers 30a and 30b, and the like.

[0037] Furthermore, the sheet processing device control unit 100 includes a processing tray control unit 105 that controls the driving of a matching motor that moves the matching plate 22 which performs sheet stacking operations on the processing tray 14, and a motor that rotates the scraping paddle 19 and the knurling belt 20. In addition, the sheet processing device control unit 100 has a stapling control unit 106 that performs stapling operations on the sheet bundles on the processing tray 14.

[0038] Furthermore, the sheet processing control unit 100 also includes a sheet loading control unit 107 that controls the tray lifting motor M1 for raising and lowering the loading tray 15, the sheet pressing paddle motor M3 for operating the sheet pressing paddle 50, and the like.

[0039] The control unit described above controls the execution of sheet processing, such as image formation processing and sheet discharge and loading processing. In this embodiment, it is possible to execute a "straight discharge mode" in which sheets with images formed in the image forming apparatus 1 are discharged one by one onto the loading tray 15 of the sheet processing apparatus B, a "sorted discharge mode" in which sheets are sorted by shifting them in the sheet width direction before discharge, and a "bound discharge mode" in which sheets are bound before discharge.

[0040] First, let's explain the straight discharge mode. When a job in straight discharge mode is received, the sheets with images formed on them by the image forming apparatus A are transported one by one to the sheet processing apparatus B. Once a sheet is handed over to the transport roller pair 30a of the sheet processing apparatus B, it is transported in the transport direction and sequentially handed over to the transport roller pair 30b and the discharge roller pairs 31a, 31b, and discharged onto the loading tray 15. Once a sheet has been discharged onto the loading tray 15, the sheet pressing paddle 50 is rotated to press down on the top surface of the sheet that has been discharged onto the loading tray 15. The above operation is repeated for each sheet until the last sheet has been discharged, at which point the sheet pressing paddle 50 moves to the home position and the job in straight discharge mode is completed.

[0041] Next, the sorting and discharge mode will be explained. When a sorting and discharge mode job is received, the sheets with images formed on them by the image forming apparatus A are transported one by one to the sheet processing apparatus B, similar to the straight discharge mode. The sheets handed over to the transport roller pair 30a are transported in the transport direction, and when the rear end of the sheet (upstream end in the transport direction) passes the transport roller pair 30b, the sheet is shifted in the width direction by the pair of alignment plates 22, and then the sheet is nipped by the discharge roller pair 31a and 31b and discharged to the loading tray 15. Once the sheet is discharged to the loading tray 15, the sheet pressing paddle 50 is rotated to press down on the top surface of the sheet discharged to the loading tray 15. If the sheets are to be sorted in groups of three, the next two sheets are also shifted in the same direction by the alignment plate 22 and discharged, and the next three sheets are shifted in the opposite direction by the alignment plate 22 and discharged. The above operation is repeated one sheet at a time until the last sheet is discharged, at which point the sheet pressing paddle 50 moves to the home position and the straight discharge mode job is completed.

[0042] Next, the stapled output mode will be explained. When a job for the stapled output mode is received, the sheets on which images have been formed in the image forming apparatus A are transported one by one to the sheet processing apparatus B, similar to the straight output mode. The sheets transported to the sheet processing apparatus B are loaded one by one onto the processing tray 14, and a sheet bundle is formed on the processing tray 14. The sheet bundle is stapled by the stapled unit 23, and the sheet bundle is discharged to the loading tray by the discharge roller pair 31a and 31b.

[0043] From the above, in all discharge modes, the sheets are ultimately discharged into the loading tray 15. The loading tray 15 moves up and down with a large number of sheets loaded on it, so there is a limit to the number of sheets that can be loaded. The limit varies depending on the sheet size; in this embodiment, for example, it is 1000 sheets for A4 size and 500 sheets for A3 size. The sheet processing device control unit 100 manages how many of each sheet are loaded in the loading tray based on the input sheet information and job information. Therefore, once 1000 A4 sheets or 500 A3 sheets have been discharged, the tray becomes full, and the next job will not be accepted until all sheets have been removed from the loading tray 15.

[0044] Once all the sheets have been removed from the loading tray 15, the sheet count on the loading tray is reset, and the next job is accepted. This prevents the loading tray 15 from being damaged due to excessive loading of sheets. In this embodiment, the removal of sheets from the loading tray 15 is determined from the number of input clocks of the encoder 44.

[0045] In this embodiment, with no sheet loaded on the loading tray 15, the number of input clocks to the encoder 44 from the state where the loading tray 15 is detected by the loading tray HP sensor Sn1 until the sheet surface detection sensor Sn3 detects the loading tray 15 is set to 50 clocks (Figure 9). In other words, with the sheet surface detection sensor Sn3 off and the loading tray HP sensor Sn1 on, the loading tray 15 is raised, and the encoder sensor Sn4 counts the number of clocks of the encoder 44 from the time the loading tray HP sensor Sn1 turns off until the sheet surface detection sensor Sn3 turns on. If the count is 50 clocks, it is determined that there is no sheet on the loading tray. In this embodiment, if the count is 48 clocks or more, it is determined that there is no sheet. Conversely, if the count is 47 clocks or less, it is determined that there is a sheet.

[0046] In this way, the presence or absence of a sheet on the loading tray 15 is determined by the loading tray HP sensor Sn1, encoder sensor Sn2, sheet surface detection sensor Sn3, and tray lifting motor M1, and this is used as a trigger to release the fully loaded state.

[0047] Here, we will explain the encoder 44 mentioned above. The encoder 44 is used to manage the amount of lifting and lowering of the loading tray, and the encoder sensor Sn4 detects the input of the encoder clock. Figure 8 shows the relationship between the drive of the tray lifting motor M1, the output (on / off) of the sheet surface detection sensor Sn3, and the clock of the encoder 44. In Figure 8, when the sheet surface detection sensor Sn3 is off, the tray lifting motor M1 is driven to raise the loading tray 15, and the encoder 44 rotates, inputting a clock to the encoder sensor Sn4. As a result of the loading tray 15 rising, when the sheet surface detection sensor Sn3 changes from off to on, the tray lifting motor M1 is stopped.

[0048] In this embodiment, regarding the clock detected by the encoder sensor Sn4, it is not possible to determine whether the loading tray 15 is rising or falling based solely on the detection result of the encoder sensor Sn4. Therefore, the control unit, which will be described later, manages the amount of movement when rising and the amount of movement when falling in combination with the drive direction of the loading tray lifting motor 15. Figure 8 shows the state in which the loading tray 15 is rising, indicating that a total of 28 clocks were input: 25 clocks from the start of rising until the tray lifting motor M1 stops, and then 3 clocks after that.

[0049] In this embodiment, even if the tray lifting motor M1 is stopped, the loading tray 15 continues to move due to inertia. Therefore, only two encoder clocks are counted after the tray lifting motor M1 is stopped and used to manage the amount of movement. However, for the third clock and beyond, it is impossible to determine whether the input clocks are due to the actual movement of the loading tray 15 due to inertia, or whether they are clocks that are input even if the loading tray 15 has not moved due to vibrations when the loading tray 15 is stopped. As a result, although the loading tray 15 has actually risen by 27 clocks, it is recorded as having risen by 28 clocks.

[0050] In this embodiment, when the power is turned on, the loading tray 15 is moved to the home position (descended until sensor Sn1 turns on) and the encoder clock is reset. Then, the clock input when the loading tray lifting motor is driven in the direction that raises the loading tray 15 (forward rotation) is added, and conversely, the clock input when the loading tray 15 is driven in the direction that lowers the loading tray 15 (reverse rotation) is subtracted, and the position of the loading tray 15 from the home position is managed according to the current number of clocks.

[0051] In this configuration, the loading tray 15 repeatedly lowers and stops as sheets are loaded and ejected at the sheet receiving position. Once a sheet is removed, it rises until the sheet surface detection sensor Sn3 turns on. Repeating this operation causes the clock input due to vibration when the loading tray 15 stops to be added or subtracted, making correct position management impossible. Therefore, even if all sheets are removed from the loading tray 15 when it is fully loaded, the number of clocks when the loading tray 15 is raised until the sheet surface detection sensor Sn3 turns on may be 47 or less. In that case, even though all sheets have been removed, it may be judged as "sheets present" and the fully loaded state cannot be released.

[0052] If we were to set the threshold for determining the presence or absence of a sheet to 40 clock cycles, we could certainly release the full load state, but at that point, the system would recognize that there was no sheet in the loading tray 15. Therefore, loading sheets until the tray is full again would result in overloading.

[0053] Therefore, in this embodiment, once the tray is fully loaded, the loading tray 15 is moved to the home position to reset the encoder clock. Then, the number of clock cycles until the sheet surface detection sensor Sn3 turns on when a sheet is removed from the loading tray 15 is counted, thereby enabling accurate determination of the presence or absence of a sheet. Furthermore, since the reset is not performed for each job, the next job can be started immediately if the tray is not fully loaded.

[0054] The operation from full load to unloaded state will be explained below using Figures 10 to 13. Figure 10(a) shows the state in which a sheet is being discharged onto the loading tray 15. Since this sheet is, for example, a B4 size sheet, the loading tray 15 becomes full before it reaches the loading tray HP sensor Sn1, which is the lower limit sensor (Figure 10(b)). Once full, the loading tray 15 is lowered until the loading tray HP sensor Sn1 turns on, and the encoder clock is reset (Figure 11(a)). After that, the loading tray 15 is raised until the sheet surface detection sensor Sn3 turns on, and the number of clocks during that time is counted (Figure 11(b)). In this case, since the loading tray drive motor M1 is driven in the forward direction, the input clocks are added together to 12 clocks.

[0055] Figure 12(a) shows a state in which a portion of the sheet on the loading tray 15 has been removed. When the sheet is removed, the sheet surface detection sensor Sn3 turns off, so the loading tray drive motor is driven in the forward direction to raise the loading tray 15 until the sheet surface detection sensor Sn3 turns on (Figure 12(b)). In this case as well, the input clocks are added, and when the sheet surface detection sensor Sn3 turns on, the clock count is 38 clocks. Here, the current clock count is compared with a predetermined number of clocks (48 clocks in this embodiment), which is a threshold for determining the presence or absence of a sheet. Since it is less than 48 clocks, it is determined that there is still a sheet on the loading tray 15, and the fully loaded state continues.

[0056] Figure 13 shows the state after the sheet has been removed from the loading tray 15. When the sheet is removed, the sheet surface detection sensor turns off, so the loading tray drive motor is driven in the forward direction to raise the loading tray 15 until the sheet surface detection sensor Sn3 turns on. In this case as well, the input clocks are added together, and when the sheet surface detection sensor Sn3 turns on, the number of clocks becomes 50, which is more than the predetermined number of 48 clocks, so it is determined that there is no sheet on the loading tray and the full load state is released.

[0057] In this embodiment, by resetting the encoder clock once when the vehicle is fully loaded, it is possible to accurately determine whether or not there is a seat using the encoder 44 for releasing the vehicle from full load.

[0058] In the embodiments described above, the encoder clock is reset when the tray is fully loaded. However, if a clock signal exceeding a certain number of clocks (2 clocks in this embodiment) is input after the loading tray drive motor M1 has stopped when the loading tray 15 stops, the loading tray 15 may be moved to the home position and the encoder clock reset after the job is completed.

[0059] Furthermore, although the above-described embodiment uses the loading tray HP sensor Sn1 as the reference position detection sensor, a separate sensor may be provided, or multiple sensors may be provided to detect the position of the loading tray 15. In that case, when the tray is fully loaded, the loading tray 15 may be moved until the nearest sensor turns on, thereby resetting the encoder clock.

[0060] In the embodiments described above, the sheet processing apparatus B is arranged within the internal space 4c of the image forming apparatus A. However, the sheet processing apparatus of the present invention may be configured, for example, to be mounted on the side of the image forming apparatus. Furthermore, the sheet processing apparatus may be controlled by an image forming control unit 200 provided in the image forming apparatus A. That is, the control unit may be located within the sheet processing apparatus or within the image forming apparatus, as long as it is possible to control the sheet processing apparatus within the image forming system. [Explanation of Symbols]

[0061] A...Image forming apparatus B...Sheet processing device M1 ... Tray lifting motor M2 ... Discharge roller motor M3... Seat-holding paddle motor M4 ... Conveyor motor S...Seat Sn1 ... Loading tray HP sensor Sn2 ... Paddle HP Sensor Sn3 ... Sheet surface detection sensor Sn4… Encoder Sensor 11a...erecting surface 14… Processing tray 15…Loading tray 23… Staple binding unit 31a ... Upper discharge roller 31b ... Lower discharge roller 50...Seat retaining paddle 100 ... Sheet processing device control unit

Claims

1. A sheet processing unit that performs a predetermined process on the sheet, A discharge section for discharging the sheet, A loading section is provided so as to be able to move up and down relative to the discharge section, and loads the sheets discharged by the discharge section, A reference position detection sensor for detecting the reference position of the loading section, A sheet surface detection sensor for detecting the height of the top surface of the loading section or the top sheet of the sheet bundle loaded in the loading section, A drive motor for raising and lowering the loading section, A drive transmission mechanism that transmits the drive of the drive motor to the loading section is provided with an encoder for detecting the amount of movement of the loading section, A control unit that controls the operation of the loading section, Equipped with, The control unit manages the position of the loading unit from the reference position by using the input clock count from the encoder as the reference clock count when the loading unit is raised and subtracting the input clock count when it is lowered, while the loading unit is in the reference position as determined by the reference position detection sensor. When a sheet is loaded onto the loading section and it becomes fully loaded, the loading section is moved to the reference position and the input clock count is reset to the reference clock count. Then, it is determined whether or not a sheet is loaded on the loading section according to the input clock count when the loading section moves from the reference position until the sheet surface detection sensor turns on. A sheet processing apparatus characterized by the following:

2. An image forming unit that forms an image on a sheet, A sheet processing unit that performs predetermined processing on a sheet on which an image has been formed by the image forming unit, A discharge section for discharging the sheet, A loading section is provided so as to be able to move up and down relative to the discharge section, and loads the sheets discharged by the discharge section, A reference position detection sensor for detecting the reference position of the loading section, A sheet surface detection sensor for detecting the height of the top surface of the loading section or the top sheet of the sheet bundle loaded in the loading section, A drive motor for raising and lowering the loading section, A drive transmission mechanism that transmits the drive of the drive motor to the loading section is provided with an encoder for detecting the amount of movement of the loading section, A control unit that controls the operation of the loading section, Equipped with, The control unit manages the position of the loading unit from the reference position by using the input clock count from the encoder as the reference clock count when the loading unit is raised and subtracting the input clock count when it is lowered, while the loading unit is in the reference position as determined by the reference position detection sensor. When a sheet is loaded onto the loading section and it becomes fully loaded, the loading section is moved to the reference position and the input clock count is reset to the reference clock count. Then, it is determined whether or not a sheet is loaded on the loading section according to the input clock count when the loading section moves from the reference position until the sheet surface detection sensor turns on. An image forming system characterized by the following:

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