JP5089346B2 - Sheet stacking apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet stacking apparatus and an image forming apparatus, and more particularly to an apparatus for stacking a large number of sheets on a sheet stacking unit.

  2. Description of the Related Art In recent years, in image forming apparatuses that form images on sheets, the speed of image formation has been increased due to technological advances, and the discharge of sheets discharged from the main body of the image forming apparatus as the speed of image formation increases. The speed is also increasing. In order to align and stack a large number of sheets discharged at high speed in this way, some conventional image forming apparatuses include a large capacity sheet stacking apparatus.

  By the way, in such a conventional large-capacity sheet stacking apparatus, in order to stack a large amount of sheets on a stacking tray which is an example of a sheet stacking unit, it is necessary to increase the stroke of the vertical driving area of the stacking tray. Occurs. Therefore, there must be no obstacle in the drive area where the stacking tray moves, and space must always be left.

  However, the lower part of the stacking tray tends to be regarded as a dead space for a user who wants to use a narrow space effectively, and serves as a place for supplying supplies such as sheets and toner of the image forming apparatus, and office supplies such as a trash can. Was used as a space to put.

  By the way, when an article such as a sheet is placed below the stacking tray in this way, if the stacking of the sheet is sequentially performed and the stacking tray is lowered, the article becomes an obstacle and the stacking tray cannot be lowered and an error occurs. Or cause the device to malfunction. For this reason, when a large number of sheets are stacked, it is necessary to check whether there is an article below the stacking tray.

  Here, for example, an optical sensor is used to detect whether there is an article as an obstacle below the stacking tray (see Patent Document 1).

  FIG. 12 is a diagram showing a configuration of a conventional sheet stacking apparatus using such an optical sensor. The sheet stacking apparatus C is provided in the sheet processing apparatus B, and includes a sheet discharge tray 12 that is an example of a sheet stacking unit that is movable in the vertical direction for stacking sheets discharged from the image forming apparatus main body A. A reflection type optical sensor 101 is provided below the paper discharge tray 12, and the article 102 is detected by the optical sensor 101.

  In addition, there is a switch that is used to detect whether there is an article that becomes an obstacle below the stacking tray (see Patent Document 2).

  FIG. 13 is a diagram showing a configuration of another conventional sheet stacking apparatus using such a switch. This sheet stacking apparatus is capable of moving in the vertical direction according to the number of discharged sheets stacked. A stacker tray 13 which is an example of a section is provided. The stacker tray 13 includes a fixing member 2 fixed to the bottom surface of the stacker tray 13 and a damper member that is swingably provided with respect to the fixing member 2 and is biased in a direction away from the fixing member 2. 3 is provided.

  The fixing member 2 is provided with a switch 41 that detects that the damper member 3 has reached within a predetermined distance. In FIG. 12, reference numeral 102 denotes an article that becomes an obstacle placed below the stacker tray 13.

  When the stacking amount of sheets increases and the stacker tray 13 descends, the damper member 3 eventually interferes with the article 102. In this case, when the stacker tray 13 is further lowered, the protruding portion 31 provided on the damper member 3 enters the concave portion of the switch 41 and the switch 41 is turned on, thereby confirming that the article 102 is below the stacker tray 13. Can be detected.

JP-A-8-26570 JP 2001-348162 A

  However, in such a conventional sheet stacking apparatus and image forming apparatus, for example, in the sheet stacking apparatus configured to detect an article by the reflection type optical sensor shown in FIG. Therefore, it is affected by the detection of the article. Further, in the case of a reflection type optical sensor, since the range that can be detected is limited, a plurality of optical sensors are required to detect the entire lower area of the paper discharge tray. In this case, not only power consumption and cost increase, but also article detection control becomes complicated.

  On the other hand, in the case of the sheet stacking apparatus configured to detect the article by the switch 41 shown in FIG. 13 described above, the article can be detected by one switch 41, but the stacker tray 13 (the damper member 3) is the article. The presence of an article can be detected only after interference.

  Accordingly, when the switch 41 detects the article 102, the lowering of the stacker tray 13 can be stopped, but it is difficult to immediately stop the main body of the image forming apparatus, so that the image forming operation is continued. Further, there may be a case where a sheet before stacking remains in the sheet stacking apparatus. For this reason, after the stacker tray 13 is stopped, all sheets remaining in the image forming apparatus main body and the sheet stacking apparatus must be discharged onto the stacker tray.

  However, when these sheets are discharged and stacked on the stacker tray, the normal sheet stacking control of lowering the stacker tray in accordance with sheet discharge cannot be performed, so the stackability of the sheets stacked on the stacker tray is not possible. Decreases.

  Therefore, the present invention has been made in view of such a situation, and provides a sheet stacking apparatus and an image forming apparatus capable of stacking sheets on a sheet stacking unit in a state where an article underneath is reliably removed. It is intended to do.

The present invention comprises a liftable sheet stacking portion for stacking sheets, in the sheet stacking device for moving downward the sheet stacking portion with increasing amount of the sheets stacked, the lower side of the sheet stacking portion, movably a detection member provided, detection that detects a biasing means for biasing the sensing member in the direction of the sheet stacking portion, the sensing member has moved downward against the biasing force of the biasing means And when the article having a predetermined weight or more is placed, the detection member moves downward against the urging force of the urging means, and the article having a weight less than the predetermined weight is placed. When the sheet is placed, the article is pressed by the sheet stacking portion that moves downward as the sheet stacking amount increases, so that the article moves downward against the urging force of the urging means , and the detection means before but based on placement of a predetermined weight or more of the articles Upon detecting the movement of the sensing member by the pressing movement and to an article of the sheet stacking portion of the detecting member, characterized by stopping the loading of the sheet to the sheet stacking portion to the detection by said detecting means is released Is.

  As in the present invention, when the detection unit detects the downward movement of the detection member, the lower article is surely removed by stopping the stacking of sheets on the sheet stacking unit until the detection by the detection unit is canceled. In this state, the sheets can be stacked on the sheet stacking unit.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of an image forming apparatus including a sheet stacking apparatus according to a first embodiment of the present invention.

  In FIG. 1, 900 is an image forming apparatus, 901 is an image forming apparatus main body, and an image reading apparatus 951 including a scanner unit 955 and an image sensor 954 is provided on the upper part of the image forming apparatus main body 901. A document feeding device 950 that feeds a document to the platen glass 952 is provided on the upper surface of the image reading device 951.

  Further, an image forming unit 902 that forms an image on a sheet and a double-sided reversing device 953 are provided at the center of the image forming apparatus main body 901. The image forming unit 902 includes a cylindrical photosensitive drum 906, a charger 907, a developing unit 909, a cleaning device 913, and the like. Further, a fixing device 912 and a discharge roller pair are provided on the downstream side of the image forming unit 902. 914 etc. are arranged.

  The image forming apparatus main body 901 is connected to a stacker 100 which is a sheet stacking apparatus for stacking sheets after image formation discharged from the image forming apparatus main body 901. Reference numeral 960 denotes a controller that controls the image forming apparatus main body 901 and the stacker 100.

  Next, an image forming operation of the image forming apparatus main body 901 having such a configuration will be described.

  When an image forming signal is output from the controller 960, a document is first placed on the platen glass 952 by the document feeding device 950, and this document image is read by the image reading device 951. The read digital data is the exposure means. It is input to 908. The exposure unit 908 irradiates the photosensitive drum 906 with light corresponding to the digital data.

  At this time, the surface of the photosensitive drum 906 is uniformly charged by the charger 907. When light is irradiated in this manner, an electrostatic latent image is formed on the surface of the photosensitive drum, and the electrostatic latent image is developed. By developing with the device 909, a toner image is formed on the surface of the photosensitive drum.

  On the other hand, when a paper feed signal is output from the controller 960, the sheets S set in the cassettes 902a to 902d and the paper feed deck 902e are first transported to the registration rollers 910 by the paper feed rollers 903a to 903e and the transport roller pair 904. .

  Next, the sheet S is conveyed by a registration roller 910 to a transfer unit including a transfer separation charger 905 at a timing such that the front end of the sheet and the front end of the toner image on the photosensitive drum 906 are aligned. In this transfer portion, a transfer bias is applied to the sheet S by the transfer separation charger 905, whereby the toner image on the photosensitive drum 906 is transferred to the sheet side.

  Next, the sheet S on which the toner image is transferred is conveyed to the fixing device 912 by the conveying belt 911, and then the toner image is thermally fixed when being nipped and conveyed between the heating roller and the pressure roller of the fixing device 912. The At this time, foreign matters such as residual toner that are not transferred to the sheet on the photosensitive drum 906 are scraped off by the blade of the cleaning device 913. As a result, the surface of the photosensitive drum 906 becomes clear, and the next It can prepare for image formation.

  The fixed sheet is conveyed as it is to the stacker 100 by the discharge roller 914 or is conveyed to the duplex reversing device 953 by the switching member 915, and image formation is performed again.

  FIG. 2 is a block diagram showing the configuration of the controller 960. The controller 960 includes a CPU circuit unit 206. The CPU circuit unit 206 includes a CPU, a ROM 207, and a RAM 208 (not shown). Then, the DF (document feeding) control unit 202, the image reader control unit 203, the image signal control unit 204, the printer control unit 205, the stacker control unit 210, and the operation unit 209 are comprehensively controlled by a control program stored in the ROM 207. Control. The RAM 208 temporarily stores control data and is used as a work area for arithmetic processing associated with control.

  A DF (document feeding) control unit 202 controls driving of the document feeding device 950 based on an instruction from the CPU circuit unit 206. The image reader control unit 203 performs drive control on the scanner unit 955 and the image sensor 954 provided in the image reading apparatus 951, and transfers an analog image signal output from the image sensor 954 to the image signal control unit 204. is there.

  The image signal control unit 204 converts each analog image signal from the image sensor 954 into a digital signal, performs each process, converts the digital signal into a video signal, and outputs the video signal to the printer control unit 205.

  The image signal control unit 204 performs various processes on the digital image signal input from the computer 200 or the external I / F 201 and converts the digital image signal into a video signal to control the printer. This is output to the unit 205. The processing operation by the image signal control unit 204 is controlled by the CPU circuit unit 206.

  The printer control unit 205 drives the exposure unit 908 via an exposure control unit (not shown) based on the input video signal. The operation unit 209 includes a plurality of keys for setting various functions relating to image formation, a display unit for displaying information indicating a setting state, a touch panel 209a which is a notification unit described later, and the like. A key signal corresponding to the operation of each key is output to the CPU circuit unit 206, and corresponding information is displayed on the display unit based on the signal from the CPU circuit unit 206.

  The stacker control unit 210 is mounted on the stacker 100, and performs drive control of the entire stacker by exchanging information with the CPU circuit unit 206. The stacker control unit 210 is connected to a lift motor 800, a top tray lift motor 801, a top tray paper surface detection sensor 129, a full load detection sensor 130, a foreign matter detection sensor 127, a paper surface detection sensor 117, a solenoid (not shown), and the like. . This control content will be described later. Note that the stacker control unit 210 may be integrated into the CPU circuit unit 206 on the image forming apparatus main body 901 side to control the stacker 100 directly from the image forming apparatus main body 901.

  FIG. 3 is a diagram illustrating a configuration of the stacker 100. The stacker 100 includes a top tray 106, which is a sheet stacking unit for stacking sheets discharged from the image forming apparatus main body 901, on the upper surface thereof so as to be movable up and down. The top tray 106 is lowered as the sheet stacking amount increases.

  In addition, the stacker 100 includes a stack unit 100A that is a sheet stacking unit having a stacker tray 112 that is a sheet stacking unit for stacking sheets. Here, the stacker tray 112 of the stack unit 100A is disposed so as to be movable up and down in directions indicated by arrows C and D by a lifting motor 800 (see FIG. 2).

  Further, the stacker 100 includes a first switching member 103 that is driven by a solenoid (not shown) and directs the sheet S conveyed into the stacker to the top tray 106 or the stack unit 100A that is another sheet stacking unit. . In FIG. 3, reference numeral 108 denotes a second switching member, which is driven by a solenoid (not shown) when the sheet discharge destination is a downstream sheet processing device (stacker device) (not shown).

  In FIG. 3, reference numeral 115 denotes a sheet pulling unit which is a pulling unit that pulls the sheet discharged by the discharge roller pair 110 serving as a sheet discharging unit to the stacker tray side. The sheet drawing unit 115 includes a knurled belt 116 that rotates in a clockwise direction and has elasticity for drawing the sheet above the stacker tray, and a leading end stopper 121 that is a bumping unit that positions the sheet in the sheet discharge direction. doing.

  The sheet drawing unit 115 draws the discharged sheet between the knurling belt 116 and the stacker tray 112 by the knurling belt 116 and then abuts against the leading end stopper 121. As a result, the discharged sheets can be stacked while being positioned on the stacker tray 112.

  The sheet retracting unit 115 is attached so as to be movable in the directions of arrows A and B along the slide shaft 118. The sheet retracting unit 115 is driven by an unillustrated retracting unit drive motor and can move to a position corresponding to the sheet size. . Further, a taper surface 115 a is formed on the frame of the sheet retracting unit 115 so as to guide the retracted sheet to the knurled belt 116.

  Reference numeral 117 denotes a paper surface detection sensor provided to keep the distance between the sheet drawing unit 115 and the upper surface of the sheet constant, and a signal from the paper surface detection sensor 117 is input to the stacker control unit 210 (see FIG. 2). . In the present embodiment, the position of the upper surface of the sheet is set below the discharge roller pair 110 so that the leading edge of the succeeding sheet is not caught by the discharge roller pair 110 when the stacked sheets are curled upward. Has been.

  A home position sensor 113 detects the home position of the stacker tray 112 during the initial operation. Further, during the stacking operation, it functions as a paper surface detection sensor for the stacker tray 112. The stacker tray 112 is positioned at a home position where sheets can be stacked as shown in FIG. 3 by the home position sensor 113 when the sheets are discharged.

  Next, the sheet stacking operation of the stacker 100 configured as described above will be described with reference to the flowchart shown in FIG.

  When the sheet is discharged from the image forming apparatus main body 901, the sheet is first conveyed to the inside by the entrance roller pair 101 of the stacker 100 and then conveyed to the first switching member 103. Note that before the sheet is conveyed to the stacker control unit 210, sheet information such as sheet size, paper type, and sheet discharge destination information is preliminarily received from the controller 960 (CPU circuit unit 206) of the image forming apparatus main body 901. Etc. have been sent.

  Here, the stacker control unit 210 determines whether or not the discharge destination of the sheet sent from the controller 960 is the top tray 106 (S301). When the sheet discharge destination is the top tray 106 (Y in S301), the first switching member 103 and the second switching member 108 are switched to the positions indicated by broken lines in FIG. 3 (S302). As a result, the sheet is guided to the conveying roller pair 104, and then discharged to the top tray 106 by the discharging roller pair 105 (S303) and stacked.

  If the sheet discharge destination is not the top tray 106 (N in S301), it is next determined whether or not the sheet discharge destination is the stacker tray 112 (S304). Here, when it is determined that the discharge destination is not the stacker tray 112 (N in S304), for example, when it is determined that the sheet discharge destination is a downstream stacker device (not shown), the first switching member 103 is set to the second broken line position. The switching member 108 is switched to the position indicated by the solid line in FIG. 3 (S306). Thus, the sheet conveyed by the entrance roller pair 101 is conveyed by the conveyance roller pair 102, guided to the exit roller pair 109, and then conveyed to a downstream stacker device (not shown) (S307).

  When the sheet discharge destination is the stacker tray 112 (Y in S304), the first switching member 103 is switched to the position indicated by the solid line (S308). As a result, the sheet is conveyed to the discharge roller pair 110 while being guided by the first switching member 103, and then discharged to the stacker tray 112 (S309).

  Here, before the sheet reaches the discharge roller pair 110, the timing of passage of the leading edge is detected by the timing sensor 111 disposed upstream of the discharge roller pair 110. Thereafter, the sheet is conveyed by the discharge roller pair 110 and abuts against the tapered portion 115a of the sheet drawing unit 115, and is conveyed while being guided to the stacker tray side by the tapered portion 115a and guided to the knurled belt 116. At this time, the sheet comes into contact with the knurled belt 116 by the inertial force when being conveyed, that is, the momentum that has been conveyed.

  Thereafter, the knurled belt 116 causes the sheet to enter between the knurled belt 116 and the stacker tray 112 or the uppermost sheet when the sheets are stacked.

  Next, after the sheets are discharged in this way, alignment in the width direction is performed by moving the alignment plate 119 to the width direction orthogonal to the sheet conveyance direction of the sheet bundle, for example, the front side of the image forming apparatus main body. The aligning plate 119 aligns the sheet bundle and then withdraws in the width direction by a predetermined amount and waits for a new sheet to be conveyed. Thereafter, the sheets are sequentially stacked on the stacker tray 112.

  Here, the stacker control unit 210 constantly monitors the upper surface of the sheets discharged and stacked via the paper surface detection sensor 117. When the distance between the sheet drawing unit 115 (the knurled belt 116) and the upper surface of the stacked sheets becomes narrower than a predetermined amount, the stacker tray 112 is lowered by a predetermined amount. By such control, the interval between the sheet drawing unit 115 (the knurled belt 116) and the upper surface of the stacked sheets can be increased, and the subsequent sheets can be stacked.

  By repeating this operation, sheets are sequentially stacked on the stacker tray 112, and eventually the stacker tray 112 becomes full. The full load of the stacker tray 112 is detected by counting the detection signal of the timing sensor 111, which is a sheet detection unit for detecting the sheet discharged from the discharge roller pair 110, by the stacker control unit 210. Alternatively, the stacker control unit 210 detects the lowering position of the stacker tray and the position of the uppermost sheet.

  When the full stacker tray 112 is detected by such a configuration, the stacker control unit 210 drives the elevating motor 800 to lower the stacker tray 112, and the stacked sheet bundles together with the stacker tray are shown in FIG. Place on the dolly 120 shown. After the stacker tray 112 is stacked in this manner, the sheet bundle SA loaded in the stacker tray 112 can be integrally taken out by taking out the dolly 120 as the take-out means from the stacker 100.

  Thereafter, the sheet bundle SA is removed from the dolly 120, the dolly 120 and the stacker tray 112 are attached to the stacker 100 again, and then the stacker tray 112 is raised. As a result, the stacker tray 112 returns to the state shown in FIG. 3, and a new sheet can be stacked.

  FIG. 6 is a diagram showing the configuration of the upper portion of the stacker 100. In FIG. 6, 100B is the upper surface of the stacker 100. At a position facing the top tray 106 on the upper surface 100B of the stacker 100, a foreign matter detection cover 124, which is a detection member on which an article such as a sheet is placed, is provided so as to be rotatable in the vertical direction about the rotation shaft 125. It has been.

  In FIG. 6, reference numeral 126 denotes a compression spring which is an urging means for urging the foreign object detection cover 124 upward. By urging by the compression spring 126, the foreign object detection cover 124 is pressed against a stopper (not shown) and is held at a position that forms the same surface as the upper portion 100B of the stacker 100.

  Reference numeral 129 denotes a top tray paper surface detection sensor for detecting the interval between the uppermost sheet stacked on the top tray movable in the vertical direction and the discharge roller pair 105, and reference numeral 130 denotes a full load detection sensor. Reference numeral 127 denotes that an article (hereinafter referred to as a foreign object) 128 has been placed on a foreign object detection cover urged counterclockwise about the rotation shaft 125 by a compression spring 126 and the foreign object detection cover 124 has moved. For example, it is a foreign matter detection sensor as a detection means for optically detecting.

  Here, in the present embodiment, the foreign object detection cover 124 rotates downward (clockwise) against the urging force of the compression spring 126 when the foreign object 128 having a predetermined weight or more is placed. It has become. The foreign object detection sensor 127 detects that the foreign object 128 has been placed by detecting the foreign object detection cover 124 that is rotated downward by the load of the foreign object 128 when the foreign object 128 is placed. Although the foreign object detection cover 124 is described as a plate-like member in the present embodiment, the present invention is not limited to this, and may be, for example, a button shape, a rod shape, a spherical shape, or the like. However, it is better to use a plate-like member having a certain area in order to detect in a wide range that the foreign material 128 has been placed.

  Next, the operation at the time of sheet discharge to the top tray 106 of the stacker 100 configured as described above will be described.

  In FIG. 6, the stacker 100 is in a standby state and is waiting for a sheet to be conveyed from the image forming apparatus main body. As described above, when the sheet is discharged to the top tray 106, the sheet is conveyed to the discharge roller pair 105 by the conveyance roller pair 104, and then the sheet is discharged to the top tray 106 by the discharge roller pair 105. Discharged into the stack.

  Thereafter, the sheets are sequentially discharged from the discharge roller pair 105, and when the interval between the uppermost sheet and the discharge roller pair 105 becomes shorter than a predetermined distance, the top tray paper surface detection sensor 129 detects this. Based on the detection signal from the top tray paper surface detection sensor 129, the stacker control unit 210 drives the top tray lifting / lowering motor 801 to lower the top tray 106 by a predetermined amount. As a result, more sheets can be stacked on the top tray, and a large amount of sheets are stacked on the top tray 106 by repeating this operation.

  On the other hand, after that, the sheets are further stacked, and the top tray 106 is lowered to a position indicating that it has become full. When this is detected by the full load detection sensor 130, based on the detection signal from the full load detection sensor 130, the stacker control unit 210 notifies the CPU circuit unit 206 that the top tray 106 is full, and finishes loading. Or pause.

  Incidentally, when the stacker 100 is in operation or in standby, the user may place the foreign object 128 in the operating area of the top tray 106, that is, on the foreign object detection cover 124, as shown in FIG. In this case, the foreign object detection cover 124 rotates clockwise about the rotation shaft 125 due to its own weight (load) of the foreign object 128, and the tip of the foreign object detection cover 124 shields the foreign object detection sensor 127 from light. As a result, the stacker control unit 210 detects that the foreign object 128 has been placed on the foreign object cover 124.

  When it is detected that the foreign object 128 is placed on the foreign object cover 124 as described above, the stacker control unit 210 transmits a signal indicating that the foreign object has been detected to the CPU circuit unit 206. Accordingly, the CPU circuit unit 206 displays, on the touch panel 209a provided on the operation unit 209, that the foreign matter is removed or that the foreign matter has been placed on the stacker, and the image forming operation and the sheet stacker. The conveyance to 100 is stopped.

  When the user viewing this display removes the foreign matter 128 placed on the foreign matter detection cover 124, the foreign matter detection cover 124 is rotated counterclockwise about the rotation shaft 125 by the compression spring 126 as shown in FIG. Rotate. Thereby, the foreign matter detection sensor 127 outputs a signal indicating that the foreign matter has been removed, and based on this signal, the stacker control unit 210 detects that the foreign matter 128 on the foreign matter cover 124 has been removed.

  When it is detected that the foreign material 128 has been removed in this manner, the stacker control unit 210 notifies the CPU circuit unit 206 of this. Further, the CPU circuit unit 206 that has been notified that the foreign matter 128 has been removed restarts the image forming operation and the conveyance of the sheet to the stacker 100.

  By the way, when the user places the foreign object 128 on the foreign object detection cover 124 while the stacker 100 is operating or in the standby state, if the foreign object 128 is light, the foreign object detection cover 124 is loaded with the foreign object 128 as shown in FIG. Still in state. In this case, since the foreign object detection cover 124 does not rotate, the stacker control unit 210 cannot detect that the foreign object 128 has been placed on the foreign object cover 124.

  For this reason, in the present embodiment, the sheet is discharged onto the top tray 106 until the foreign object detection sensor 127 detects that the foreign object 128 has been placed on the foreign object cover 124. When the foreign matter detection sensor 127 detects that the foreign matter 128 has been placed, a display indicating that the foreign matter has been placed on the stacker is performed.

  Next, the foreign object detection operation of the stacker 100 configured as described above will be described with reference to the flowchart shown in FIG.

  First, before discharging a sheet to the top tray 106, it is determined whether the foreign object detection sensor 127 detects a foreign object (S100). If the foreign object detection sensor 127 detects a foreign object (Y in S100), a display to remove the foreign object is displayed (S101).

  If the foreign matter detection sensor 127 has not detected any foreign matter (N in S100), the sheet is discharged onto the top tray 106 as described above, and the stacking of sheets on the top tray 106 is started (S102).

  Thereafter, when a predetermined amount of sheets are stacked and eventually the interval between the uppermost sheet and the discharge roller pair 105 becomes smaller than a predetermined distance, the top tray paper surface detection sensor 129 detects this (Y in S103). Based on the detection signal from the top tray paper surface detection sensor 129, the stacker controller 210 drives the top tray lifting / lowering motor 801 to lower the top tray 106 by a predetermined amount (S104). As a result, more sheets can be stacked on the top tray, and a large amount of sheets are stacked on the top tray 106 by repeating this operation.

  By the way, as shown in FIG. 10, a large amount of sheets S are stacked on the top tray 106, and thereafter, when the top tray 106 is lowered by a predetermined amount based on the detection by the top tray paper surface detection sensor 129, 128 is pressed. As a result, the foreign matter detection cover 124 swings in the clockwise direction about the rotation shaft 125, and the tip of the foreign matter detection cover 124 shields the foreign matter detection sensor 127 accordingly. Then, the foreign matter detection sensor 127 is shielded from light in this way, so that the stacker control unit 210 detects that the foreign matter 128 is placed on the foreign matter cover 124.

  When the foreign object detection sensor 127 detects a foreign object in this manner (Y in S105), the stacker control unit 210 transmits a signal indicating that the foreign object has been detected to the CPU circuit unit 206. Along with this, the CPU circuit unit 206 performs a display to remove the foreign matter on the touch panel provided on the operation unit 209 (S106).

  After the foreign matter 128 interferes with the top tray 106 in this way, even if the top tray 106 further descends, the foreign matter cover 124 can follow and rotate downward. As a result, the sheets can be stacked on the top tray 106 even after the placement of the foreign matter 128 is detected. Thereafter, all the sheets remaining in the image forming apparatus main body and the stacker are stacked. It can be discharged onto the stacker tray while maintaining the above.

  Next, when the user viewing this display removes the foreign matter 128 placed on the stacker 100, the foreign matter detection cover 124 is rotated counterclockwise around the rotation shaft 125 by the compression spring 126 as shown in FIG. And the light shielding by the foreign object detection cover 124 is released. As a result, a signal indicating that the foreign matter has been removed is output from the foreign matter detection sensor 127, and based on this signal, the stacker control unit 210 detects that the foreign matter 128 on the foreign matter cover 124 has been removed.

  Next, when the foreign matter 128 on the foreign matter cover 124 is removed and the foreign matter detection sensor 127 does not detect the foreign matter (N in S105), the stacking of sheets on the top tray 106 is started again. After that, when the full load detection sensor detects the full load or when the job is finished (Y in S107), the stacking of sheets is finished.

  As described above, in this embodiment, when the foreign object detection sensor 127 detects the downward movement of the foreign object cover 124 based on the placement of the foreign object, the detection to the top tray 106 until the detection by the foreign object detection sensor 127 is released. Sheet loading is stopped. In other words, after the foreign matter below the top tray 106 is removed, the sheets are stacked on the top tray 106. As a result, the sheets can be stacked on the top tray 106 in a state where the articles underneath are reliably removed.

  In the present embodiment, as shown in FIG. 11, after determining that the foreign matter has been removed based on a signal from the foreign matter detection sensor 127, the top tray 106 is moved up and down over the entire operation region. That is, after the detection by the foreign matter detection sensor 127 is released, the top tray 106 is temporarily lowered before starting the stacking of sheets on the top tray 106.

  Thereby, it is possible to automatically detect whether or not the foreign matter has been removed. Then, after confirming the presence or absence of foreign matter in this way, the loading onto the top tray 106 is resumed, thereby ensuring more certainty. Sheets can be stacked on the top tray 106 in a state where the articles underneath are reliably removed.

  In the description so far, the configuration has been described in which the foreign object detection cover 124 rotates to detect the foreign object, but the present invention is not limited to this. For example, a foreign object detection cover that moves (lowers) when a foreign object is placed may be used to detect the foreign object by detecting the movement of the foreign object detection cover.

  In the description so far, the case where the touch panel is used as a means for notifying (notifying) that a foreign object has been placed has been described, but the present invention is not limited thereto. For example, it is possible to provide a stacker display unit to display the placement of a foreign object or to notify by voice or the like.

1 is a diagram illustrating a configuration of an image forming apparatus including a sheet stacking apparatus according to a first embodiment of the present invention. FIG. 3 is a control block diagram of a controller provided in the image forming apparatus. The figure which shows the structure of the said stacker. 6 is a flowchart for explaining a sheet stacking operation of the stacker. FIG. 4 is a diagram illustrating a state in which a stacker tray of the stacker is lowered in a full state and the stacked sheet bundles are placed on a dolly. The figure which shows the structure of the upper part of the said stacker. The figure which shows a state when a foreign material is removed from the foreign material detection cover provided in the upper surface of the said stacker. The figure which shows a state when a light foreign material is put on the said foreign material detection cover. The flowchart explaining the foreign material detection operation | movement of the said stacker. The figure explaining the foreign material detection operation of the sheet | seat of the said stacker. The figure explaining the operation | movement which confirms the presence or absence of the foreign material of the said stacker. The figure which shows the structure of the conventional sheet | seat stacking apparatus. The figure which shows the structure of the other conventional sheet stacking apparatus.

Explanation of symbols

100 Stacker 100B Top surface of stacker 106 Top tray 117 Paper surface detection sensor 124 Foreign object detection cover 126 Compression spring 127 Foreign material detection sensor 128 Foreign material 129 Top tray paper surface detection sensor 130 Full load detection sensor 205 Printer control unit 206 CPU circuit unit 209 Operation unit 209a Touch panel 210 Stacker control unit 800 Elevating motor 801 Top tray elevating motor 900 Image forming apparatus 901 Image forming apparatus main body 902 Image forming unit S Sheet SA Sheet bundle

Claims (4)

In a sheet stacking apparatus that includes a sheet stacking unit capable of moving up and down to stack sheets, and moves the sheet stacking unit downward as the sheet stacking amount increases.
Below the sheet stacking portion, and the detecting member is provided to be movable,
Biasing means for biasing the detection member in the direction of the sheet stacking unit;
And a detection means for detecting the detection member that has moved downward against the biasing force of said biasing means,
The detection member moves downward against an urging force of the urging means when an article having a predetermined weight or more is placed, and when an article having a weight less than the predetermined weight is placed, the sheet When the article is pressed by the sheet stacking section that moves downward as the stacking amount increases, the article moves downward against the urging force of the urging means , and the detection means has a predetermined weight or more. When the movement of the detection member based on the placement of the article and the movement of the detection member due to the pressing of the sheet stacking part against the article are detected, the sheet is stacked on the sheet stacking part until the detection by the detection unit is released. A sheet stacking device characterized by stopping the operation. Wherein after the detection by the detection means is released, before starting the loading of sheets to the sheet stacking portion, once Claim 1 Symbol placement of the sheet stacking apparatus, characterized in that lowering the sheet stacking unit. Informing means for informing the placement of the article on the detection member,
3. The sheet stacking apparatus according to claim 1, wherein when the detection unit detects a downward movement of the detection member, the notification unit notifies the placement of the article. An image forming unit that forms an image on a sheet, and a sheet stacking device according to any one of claims 1 to 3 , further comprising a sheet stacking unit that stacks sheets discharged after image formation. An image forming apparatus.

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