JP2018122949A - Sheet feeding apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device and image formation apparatus which can accurately detect the height position of a sheet.SOLUTION: A sheet feeding device includes: a light emission part which emits light to a sheet on the uppermost position loaded on a loading surface; a light reception part which receives the light emitted from the light emission part and reflected on the sheet on the uppermost position; and a height detection sensor S1 which detects the height position being the position in the height direction orthogonal to the loading surface of the sheet on the uppermost position loaded on the loading surface on the basis of the light received by the light reception part. The sheet feeding device stops feeding of the sheet by a pickup roller on the basis of the detection result of the height detection sensor S1 after starting feeding of the sheet loaded on the loading surface by the pickup roller.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sheet feeding apparatus that feeds a sheet and an image forming apparatus including the sheet feeding apparatus.

  2. Description of the Related Art In general, an image reading apparatus that is disposed on an upper part of a printer body and reads an image of an original is known. The image reading apparatus feeds an ADF (ADF) that separates originals placed on an original table one by one. Auto Document Feeder). The ADF cannot separate and feed a so-called “bound original” such as a stapled original or a glued original, and the original becomes a wrinkle or torn in a mechanism in the ADF that separates the original. There are things to do. Further, if the bound document is fed as it is without being separated in the ADF, there is a possibility of jamming on the conveyance path.

  Conventionally, a plurality of detection sensors are arranged on both sides in the width direction of the document table, and the light emitted from the light emitting portion of the detection sensor is shielded by the document so as to determine the presence or absence of the bound document. An apparatus has been proposed (see Patent Document 1). The plurality of detection sensors are respectively arranged at different positions in the height direction, and the light emitting portions of the detection sensors respectively irradiate light toward the paper feed roller. Each reflected light reflected on the side surface of the paper feed roller is received by the light receiving portion of each detection sensor.

  By the way, when the bound document is fed by the ADF, only the uppermost sheet of the bound document is fed by a pickup roller provided in the ADF. However, since the uppermost sheet is bound with staples or the like, the uppermost sheet is lifted upward by being fed by the pickup roller. The amount of lift of the sheet is detected by the number of light receiving portions of each detection sensor in which the light emitted from each detection sensor is shielded by the sheet lift and the reflected light cannot be detected. When it is detected that the amount of sheet lift is greater than or equal to a predetermined height, the ADF is stopped and feeding of the bound document is interrupted.

JP 2008-7280 A

  Since the image reading apparatus described in Patent Document 1 has a plurality of detection sensors arranged in the height direction, the height of the sheet corresponding to the position of each detection sensor is detected stepwise. In addition, there is a limit to densely arranging the detection sensors in the height direction. For this reason, there is a limit to the detection accuracy of the uppermost sheet floating, and the detection of the bound original may be delayed, and the sheet may be damaged or jammed.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet feeding apparatus and an image forming apparatus that can accurately detect the height position of a sheet.

  The present invention provides a sheet feeding apparatus, a stacking surface on which sheets are stacked, a feeding unit that feeds the sheets stacked on the stacking surface in a sheet feeding direction, and an uppermost stack stacked on the stacking surface. A light emitting unit that emits light to the sheet, and a light receiving unit that receives light emitted from the light emitting unit and reflected by the uppermost sheet, and the uppermost sheet stacked on the stacking surface Detection means for detecting a height position which is a position in a height direction perpendicular to the stacking surface based on the light received by the light receiving unit, and feeding of the sheets stacked on the stacking surface by the feeding unit And a control unit for stopping sheet feeding by the feeding unit based on a detection result of the detecting unit after starting.

  According to the present invention, in the sheet feeding device, a stacking surface on which the sheets are stacked, a feeding unit that feeds the sheets stacked on the stacking surface in the sheet feeding direction, and the stacking surface stacked on the stacking surface. A moving unit that moves following the uppermost sheet and an encoder that detects a position of the moving unit, and a height direction perpendicular to the stacking surface of the uppermost sheet stacked on the stacking surface After detecting the height position, which is the position of the moving unit, based on the position of the moving unit detected by the encoder, and feeding of the sheets stacked on the stacking surface by the feeding unit, Control means for stopping sheet feeding by the feeding means based on a detection result of the detecting means.

  According to the present invention, the height position of the sheet can be accurately detected based on the amount of light or the position of the moving unit. For example, the binding document can be stopped in a short time after feeding is started. This can prevent the sheet from being damaged or jammed.

1A is an overall schematic diagram illustrating a printer according to a first embodiment, and FIG. 1B is a schematic diagram illustrating an image forming engine. The side view which shows a height detection sensor. (A) is a schematic diagram showing a height detection sensor that is close to the document surface, (b) is a schematic diagram showing a height detection sensor that is far from the document surface, and (c) is a document surface and height detection. The graph which shows the relationship between the distance between sensors, and a sensor output. Explanatory drawing explaining that a float arises in a binding original. The control block diagram which concerns on 1st Embodiment. 6 is a flowchart illustrating a copy operation when a bound document is fed. FIG. 5A is a view of a normal document fed from the width direction, and FIG. 5B is a view of a bound document fed from the width direction. (A) is a graph showing the output of the height detection sensor while feeding a normal document, and (b) is a graph showing the output of the height detection sensor while feeding a bound document. FIG. 4A is a view of a folded document having a fold formed at an end portion when viewed from the width direction, and FIG. 4B is a view of the folded document when viewed from a sheet feeding direction. The perspective view which shows a folded original. 10 is a flowchart showing a copy operation according to the second embodiment. (A) is a graph showing the output of the height detection sensor before feeding the bound document, and (b) is a graph showing the output of the height detection sensor while feeding the bound document. FIG. 10 is an overall schematic diagram illustrating a printer according to a third embodiment. The control block diagram which concerns on 3rd Embodiment. The timing chart explaining the setting timing of a threshold value. It is a side view which shows the height detection sensor which concerns on 4th Embodiment, (a) is the state in which the normal original is loaded, (b) is the state in which the binding original is fed. The perspective view which shows a height detection sensor. (A) is a schematic diagram showing a height detection sensor according to a fifth embodiment that is close to the document surface, and (b) is a schematic diagram showing a height detection sensor that is far from the document surface. (C) is a graph showing the time until light received from the light emitting unit and reflected by the document surface is received by the light receiving unit; (d) is a distance between the document surface and the height detection sensor; The graph which shows the relationship between output. 10 is a flowchart showing a copy operation according to the fifth embodiment. (A) is a graph showing the output of the height detection sensor while feeding a normal document, and (b) is a graph showing the output of the height detection sensor while feeding a bound document. 20 is a flowchart showing a copy operation according to the sixth embodiment. (A) is a graph showing the output of the height detection sensor before document feeding, and (b) is a graph showing the output of the height detection sensor after document feeding.

<First Embodiment>
[overall structure]
First, a first embodiment of the present invention will be described. A printer 100 as an image forming apparatus according to the first embodiment is an electrophotographic laser beam printer. As shown in FIG. 1A, the printer 100 includes a printer main body 70 and an image reading device 10 mounted on the upper portion of the printer main body 70. In the following, the sheet includes, in addition to plain paper, special paper such as coated paper, recording material having a special shape such as envelope or index paper, and plastic film or cloth for an overhead projector. An original is an example of a sheet.

  The printer main body 70 has an image forming engine 60 therein. As shown in FIG. 1B, the image forming engine 60 includes an image forming unit PU as an electrophotographic image forming unit and a fixing device 7. When the start of the image forming operation is instructed, the photosensitive drum 1 as the photosensitive member rotates, and the drum surface is uniformly charged by the charging device 2. Then, the exposure device 3 modulates and outputs a laser beam based on the image data transmitted from the image reading device 10 or an external computer, and scans the surface of the photosensitive drum 1 to form an electrostatic latent image. This electrostatic latent image is visualized (developed) with toner supplied from the developing device 4 and becomes a toner image.

  In parallel with such an image forming operation, a feeding operation for feeding sheets stacked on a cassette (not shown) or a manual feed tray toward the image forming engine 60 is executed. The fed sheet is conveyed in accordance with the progress of the image forming operation by the image forming unit PU. The toner image carried on the photosensitive drum 1 is transferred onto the sheet by the transfer roller 5. The toner remaining on the photosensitive drum 1 after the toner image transfer is collected by the cleaning device 6. The sheet on which the unfixed toner image is transferred is transferred to the fixing device 7 and is sandwiched between the roller pair and heated and pressed. The sheet on which the image is fixed by melting and fixing the toner to the sheet is discharged by a discharge unit such as a discharge roller pair.

[Image reading device]
Next, the image reading apparatus 10 will be described in detail. As shown in FIG. 1A, the image reading apparatus 10 feeds a document loaded on the document tray 21 and discharges it to the discharge tray 32, a reading unit 40 that reads the document conveyed by the ADF 20, It has. An ADF 20 (Auto Document Feeder) as a sheet feeding device is supported by a hinge so as to be rotatable with respect to the reading unit 40 so that the document table glass 41 can be opened. The document D, which is an example of a sheet, may be a blank sheet or may have an image formed on one side or both sides.

  The ADF 20 includes a pickup roller 22 as a feeding unit, a separation driving roller 23 and a separation driven roller 24, a registration roller pair 25, conveyance roller pairs 26 and 30, and a discharge roller pair 31. . The ADF 20 also includes a document presence / absence sensor S21 that detects the document D on the document tray 21, a post-separation sensor S22 that is disposed downstream of the separation drive roller 23 in the sheet feeding direction and detects the document D, and a height detection sensor. S1.

  The reading unit 40 includes a platen glass 28, a jump table 29, a reference white plate 42, a document table glass 41, a first mirror table 43, a second mirror table 44, a lens 45, a CCD line sensor 46, have. A lamp 47 and a mirror 48 are arranged inside the first mirror table 43, and mirrors 49 and 50 are arranged inside the second mirror table 44. The first mirror base 43 and the second mirror base 44 are configured to be movable in the sub-scanning direction which is the left-right direction in the figure by a wire and a drive motor (not shown).

  The image reading apparatus 10 includes a scanning reading mode that scans a document image while feeding the document D loaded on the document tray 21 by the ADF 20, a fixed reading mode that scans a document placed on the document table glass 41, and Thus, image information is read from the document D. The flow-reading mode is selected when the document presence sensor S21 detects the document D stacked on the document tray 21, or when the user explicitly instructs the operation panel or the like of the printer main body 70.

  When the flow-reading mode is executed, the pickup roller 22 supported by an arm (not shown) descends and comes into contact with the uppermost document D on the document tray 21. The documents D are fed by the pickup roller 22 and separated one by one in a separation nip N as separation means formed by a separation driving roller 23 and a separation driven roller 24. The separation drive roller 23 is formed of a rubber material or the like that has slightly less friction than the separation driven roller 24. A torque limiter is disposed in the drive transmission path to the separation driven roller 24, and the separation driven roller 24 is rotated along with the separation driving roller 23 when a single document is fed, and the fed document is fed. It does not rotate when there are two or more sheets. For this reason, the originals can be separated one by one. Note that driving in the direction opposite to the sheet feeding direction may be input to the separation driven roller 24.

  The leading edge and the trailing edge of the document that have passed through the separation nip N are detected by the post-separation sensor S22, and the timing of raising and lowering the pickup roller 22, the driving start and driving stop timing, and the driving start and driving stop timing of the registration roller pair 25 are detected. The standard.

  The leading edge of the conveyed document D hits the registration roller pair 25 in a stopped state, and the skew of the document D is corrected. The document D whose skew has been corrected is conveyed by the registration roller pair 25 and is conveyed toward the platen glass 28 by the conveyance roller pair 26. A platen guide roller 27 is disposed so as to face the platen glass 28, and the platen guide roller 27 guides the document D passing through the platen glass 28 so as not to float from the platen glass 28.

  Then, the image on the surface of the document D is read by the reading unit 40 through the platen glass 28. Specifically, the light of the lamp 47 is irradiated to the document D being conveyed, and the reflected light from the document D is guided to the lens 45 via the mirrors 48, 49, and 50. The light that has passed through the lens 45 is imaged on the light receiving portion of the CCD line sensor 46, undergoes photoelectric conversion, and image information is transmitted to the CPU 81. The reference white plate 42 serves as a reference for the reading luminance of the document D. The document D that has passed through the platen glass 28 is guided to the transport roller pair 30 by the jump table 29 and discharged to the discharge tray 32 by the discharge roller pair 31.

  On the other hand, the fixed reading mode is selected when the apparatus detects the document D placed on the platen glass 41 or when the user explicitly instructs it through the operation panel of the printer main body 70 or the like. In this case, the document D on the document table glass 41 does not move, and the first mirror table 43 and the second mirror table 44 move along the document table glass 41. Then, the document D is scanned with the light emitted from the lamp 47. The image information photoelectrically converted by the light receiving element of the CCD line sensor 46 is transferred to the CPU 81.

[Height detection sensor]
As shown in FIG. 2, the height detection sensor S <b> 1 as detection means is provided on the frame 33 of the ADF 20. More specifically, the height detection sensor S1 is arranged so as to overlap the stacking surface 21a when viewed from the height direction orthogonal to the stacking surface 21a of the document tray 21. In the present embodiment, only one height detection sensor S1 is disposed, but a plurality of height detection sensors S1 may be disposed.

  As shown in FIGS. 3A and 3B, the height detection sensor S <b> 1 receives a light emitting unit S <b> 11 that irradiates light on the topmost document D stacked on the document tray 21 and reflected light from the document D. Light receiving unit S12.

  As shown in FIG. 3A, when the distance H1 between the document surface DS of the document D and the height detection sensor S1 is relatively small, the light receiving unit S12 captures a large amount of light reflected by the document surface DS. Therefore, the amount of light received by the light receiving unit S12 increases. As shown in FIG. 3B, when the distance H2 (H2> H1) between the document surface DS of the document D and the height detection sensor S1 is relatively large, the light receiving unit S12 is reflected by the document surface DS. Therefore, the amount of light received by the light receiving unit S12 becomes small. And the output of height detection sensor S1 is determined according to the magnitude | size of the light quantity which light-receiving part S12 received. That is, the height detection sensor S1 transmits a signal based on the magnitude of the amount of light received by the light receiving unit S12 to the CPU 81 (see FIG. 5), and the distance between the document surface DS and the height detection sensor S1. The relationship with the sensor output is as shown in the graph of FIG. The CPU 81 can detect the height position that is the position in the height direction of the document at the detection position in accordance with a signal corresponding to the sensor output transmitted from the height detection sensor S1. In the present embodiment, the height detection sensor S1 detects the height position on the upstream side in the sheet feeding direction of the document and on one side in the width direction, but the detection position of the document is not limited.

  Here, the principle that the original floats when a so-called “bound original” such as a stapled original or a glued original is fed will be described. The “bound document” in the present embodiment is not limited to a stapled or glued document, but may be a stapleless binding or a bound document. Further, the document bundle is not limited to a document bundle having a plurality of pages, and may be a document in which one document is folded so as to overlap in the height direction.

  As shown in FIG. 4, a document D is fed as a sheet bundle in which the corners of the leading edges of the first sheet D1 as the first sheet and the second sheet D2 as the second sheet are connected by the staple ST. Think about the case. When the document D is fed by the pickup roller 22, the document D abuts against the separation nip N and stops.

  The pickup roller 22 is in contact with the upper surface of the first sheet D1 of the document D, and applies a feeding force to the first sheet D1 even when the leading edge of the document D is stopped at the separation nip N. However, since the first sheet D1 is connected to the stopped second sheet D2 by the staple ST, the pickup roller 22 floats from the vicinity of the staple ST as the pickup roller 22 feeds the first sheet D1. . As described above, when the bound original is fed by the pickup roller 22, a characteristic float or deflection is formed on the first sheet D1.

[Control block]
FIG. 5 is a control block diagram of the CPU 81 as control means. As shown in FIG. 5, a height detection sensor S1, a document presence / absence sensor S21, and a post-separation sensor S22 are connected to the input side of the CPU 81. A pickup motor 84 and a separation drive motor 85 are connected to the output side of the CPU 81 via a motor control unit 83. The pickup motor 84 drives the pickup roller 22, and the separation drive motor 85 drives the separation drive roller 23.

  An operation unit 506 and a memory 82 are connected to the CPU 81. The operation unit 506 has an operation panel, for example, and can start a copy job and make various settings. A memory 82 serving as a storage unit stores a threshold value TH of the output OP2 of the height detection sensor for determining that the document is a bound document.

[Binding document detection]
Next, a copy operation when a bound original is fed will be described with reference to a flowchart shown in FIG. First, as shown in FIG. 6, the CPU 81 determines whether or not a document is stacked on the document tray 21 by the document presence / absence sensor S21 (step S101). When the document is not stacked on the document tray 21 (step S101: No), the CPU 81 does not proceed to the next process and waits until the document is stacked on the document tray 21.

  When it is determined that the document is loaded on the document tray 21 (step S101: Yes), the CPU 81 determines whether or not the start of the copy job is instructed (step S102). If the start of the copy job is not instructed from the operation unit 506 (step S102: No), the CPU 81 does not proceed to the next process and waits until the start of the copy job is instructed.

  When it is determined that the start of the copy job is instructed (step S102: Yes), the CPU 81 feeds the document D by the pickup roller 22 (step S103). Then, the CPU 81 reads the output OP2 during document feeding (sheet feeding) of the height detection sensor (step S104), and the output OP2 sets the threshold value TH as a predetermined height stored in the memory 82 in advance. It is determined whether or not it has been exceeded (step S105).

  At this time, as shown in FIG. 7A, when a normal document that is not a bound document is fed, a characteristic float does not occur as in the case of a bound document. For this reason, as shown in FIG. 8A, the output OP2 of the height detection sensor S1 during document feeding is kept low. Therefore, when a normal document is fed, the output OP2 does not exceed the threshold value TH (step S105: No), and the process proceeds to step S106. In step S106, the CPU 81 determines whether or not the leading edge of the fed document D has passed the post-separation sensor S22. While the leading edge of the document D does not pass the post-separation sensor S22, steps S104 to S106 are performed. repeat.

  When the leading edge of the fed document D passes through the sensor S22 after separation (step S106: Yes), the CPU 81 determines whether or not the fed document D is the final document of the copy job (step S106). S107). When the document presence / absence sensor S21 detects that no document is loaded on the document tray 21, the CPU 81 determines that the document is the final document. If the fed document D is not the final document, the process returns to step S103 to feed the next document, and if it is the final document, the process proceeds to step S108. In step S108, the CPU 81 stops the pickup motor 84 and the separation drive motor 85, and the document feeding is finished.

  Next, as shown in FIG. 7B, when the bound document is fed, the first sheet D1 that is the uppermost document of the document D is lifted as the document D is fed. The height position of the first sheet D1 rises. For this reason, as shown in FIG. 8B, the output OP2 of the height detection sensor S1 increases as the bound original is fed. In step S105, the CPU 81 determines whether or not the output OP2 during document feeding of the height detection sensor exceeds the threshold value TH of the height detection sensor. When the output OP2 of the height detection sensor S1 exceeds the threshold value TH (step S105: Yes), the CPU 81 determines that the bound original is being fed. Then, the CPU 81 stops the pickup motor 84 and the separation drive motor 85, and stops the document feeding (step S108). That is, the CPU 81 stops the pickup motor 84 and the separation drive motor 85 based on the detection result of the height detection sensor S1.

  In the present embodiment, the height position of the uppermost document placed on the document tray 21 is detected based on the amount of light received by the light receiving unit S12. For this reason, it is possible to detect the rising of the document with high accuracy, and it is possible to quickly detect the bound document. For this reason, it is possible to detect the bound original in a short time after the feeding is started, and it is possible to prevent the original from being damaged or jammed.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. The second embodiment has the same basic configuration as the first embodiment, but the operation flow during the copy operation is different. For this reason, about the structure similar to 1st Embodiment, illustration is abbreviate | omitted or attaches | subjects the same code | symbol to a figure and demonstrates.

  In the present embodiment, for example, it is possible to cope with a case where the first original of the bound original is a folded original in which a fold is formed at the end or a curled original in which a curl is formed at the end. . For example, as shown in FIGS. 9A, 9B, and 10, consider a case where a folded document DF in which a fold is formed at the end in the width direction of the document is fed. The folded original document DF is folded below the height detection sensor S1, and the distance between the height detection sensor S1 and the folded original document DF is reduced, so that the folded original document DF is loaded on the original tray 21. The output of the height detection sensor S1 becomes high. Here, the output of the height detection sensor S1 before document feeding (before sheet feeding) is output OP1, and the output of the height detection sensor S1 during document feeding is OP2.

[Binding document detection]
Next, the copy operation according to the present embodiment will be described with reference to the flowchart shown in FIG. 11. However, steps S201 to S202 are the same as steps S101 to S102 described in FIG. In the following description, the copy operation when feeding the binding original whose top document is the folded original DF shown in FIGS. 9 and 10 will be described. However, the type and orientation of the original to be fed are described. It is not limited.

  When it is determined that the start of the copy job has been instructed (step S202: Yes), the CPU 81 reads the output of the height detection sensor S1 before the document D is fed (step S203). That is, as described above, the light emitting unit S11 of the height detection sensor S1 irradiates the topmost document D with light, and the light detection unit S12 receives the light of the reflected light received by the light receiving unit S12. The output OP1 is determined. At this time, since the height detection sensor S1 detects the height position of the folded portion of the folded document DF, as shown in FIG. 12A, the output OP1 of the height detection sensor S1 has a higher value than the normal time. It has become.

  Then, the CPU 81 adds the change amount α as a predetermined value stored in the memory 82 to the output OP1 of the height detection sensor S1 before document feeding, and sets a threshold value TH for the height detection sensor S1. (Step S204). The CPU 81 stores the threshold value TH in the memory 82.

  Next, the CPU 81 feeds the document D by the pickup roller 22 (step S205), and reads the output OP2 during document feeding of the height detection sensor S1 (step S206). Then, the CPU 81 determines whether or not the output OP2 exceeds the threshold value TH (step S207). That is, when the amount of change in the height position detected by any one of the height detection sensors exceeds the amount of change α before and during document feeding, the CPU 81 feeds the bound document. Judge.

  Hereinafter, steps S206 to S210 are the same as steps S104 to S108 shown in FIG. 6 described in the first embodiment, and thus description thereof is omitted. If it is determined in step S209 that the document is not the final document (step S209: No), the process returns to step S203, and the CPU 81 performs processing for setting a threshold value of the document to be fed next.

  As described above, in the present embodiment, the threshold value TH of the height detection sensor S1 is obtained based on the output OP1 of the height detection sensor S1 before document feeding. That is, when a bound document is detected with a fixed threshold, the threshold may be exceeded before the document is fed, or a document that is not a bound document may be detected as a bound document due to a slight change in the document. However, in the present embodiment, the bound original is detected based on the change amount α from the output OP1 before the original feeding regardless of the posture and the floating amount of the topmost original before the original feeding. A bound original can be detected with high accuracy.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. In the third embodiment, the pickup roller is raised and lowered and the drive is turned on and off based on the position of the document to be fed. For this reason, about the structure similar to 2nd Embodiment, illustration is abbreviate | omitted or attaches | subjects the same code | symbol to a figure and demonstrates. In the present embodiment, including the second embodiment, it is necessary to set a threshold value for detecting a bound document for each sheet to be fed. When setting the threshold value, it is necessary that the document is not fed and stopped.

  As shown in FIG. 13, the printer 101 has a drawing roller 90 and a drawing sensor S23 downstream of the post-separation sensor S22 in the sheet feeding direction. As shown in FIG. 14, the height detection sensor S1, the document presence / absence sensor S21, the post-separation sensor S22, the extraction sensor S23, and the position sensor S24 are connected to the input side of the CPU 81. . The pull-out sensor S23 detects the positions of the leading edge and the trailing edge of the fed document D. The position sensor S24 detects the position of the pickup roller 22 in the height direction.

  In addition, a pickup motor 84, a separation drive motor 85, a tray drive motor 91, a pulling motor 92, and a lifting motor 93 are connected to the output side of the CPU 81 via a motor control unit 83. The tray drive motor 91 moves the downstream side of the document tray 21 up and down around a rotation shaft (not shown). The drawing motor 92 rotates or stops the drawing roller 90. The raising / lowering motor 93 raises / lowers the raising / lowering arm 94 which supports the pick-up roller 22 so that raising / lowering is possible. The elevating motor 93 and the elevating arm 94 constitute an elevating mechanism. The driving of the pickup motor 84 and the separation drive motor 85 is transmitted to the pickup roller 22 and the separation drive roller 23, respectively.

  Next, the operation of the printer 101 during document feeding and threshold setting timing will be described. First, when it is detected by the document presence / absence sensor S21 that the user has placed the document D on the document tray 21, the CPU 81 drives the tray drive motor 91 to raise the document tray 21. Then, when the upper surface of the document D comes into contact with the pickup roller 22 that is regulated to be lowered by a stopper (not shown) and the document tray 21 is further raised, the pickup roller 22 is also pushed up by the document D.

  When the position sensor S24 detects that the pickup roller 22 has been raised to the feeding position, the CPU 81 stops the tray drive motor 91. At this time, if the copy button or the like is pressed before the pickup roller 22 is raised to the feeding position and a copy start instruction is issued, it waits for the pickup roller 22 to rise to the feeding position. A threshold value of the detection sensor S1 is set. Since the setting of the threshold value of the height detection sensor S1 has been described in steps S203 and S204 in FIG. 11, the description thereof is omitted here. When a copy start instruction is issued after the pickup roller 22 has moved up to the feeding position, the threshold TH of the height detection sensor S1 is set immediately after the copy start instruction. That is, the threshold setting timing of the height detection sensor S1 is when the pickup roller 22 is in contact with the document D and the pickup roller 22 is stopped.

  When the threshold value TH of the height detection sensor S 1 is set, the CPU 81 drives the pickup motor 84 and feeds the document D by the pickup roller 22. Hereinafter, the raising / lowering of the pickup roller and the turning on / off of the drive after the feeding of the document D is started will be described with reference to the timing chart of FIG. In FIG. 15, the case where the post-separation sensor S22 and the extraction sensor S23 detect the document D is “ON”, and the case where the document D is not detected is “OFF”.

  As shown in FIG. 15, when the post-separation sensor S22 detects the leading edge of the fed document D, the CPU 81 drives the lifting motor 93 to raise the lifting arm 94 at time t1. As a result, the pickup roller 22 is separated from the document D on the document tray 21, and the document D is not fed. The lifting arm 94 stops at a predetermined height. When the pull-out sensor S23 detects the leading edge of the document D at time t2, the CPU 81 stops driving the pickup motor 84. As a result, the driving of the pickup roller 22 and the separation driving roller 23 is stopped, and the fed document D is conveyed by the drawing roller 90.

  Then, the CPU 81 obtains a time t3 for lowering the pickup roller 22 based on the size of the fed document D, particularly the length in the sheet feeding direction. That is, the CPU 81 obtains the time from when the leading edge of the document D is detected by the pull-out sensor S23 to when the trailing edge of the fed document D passes below the pickup roller 22. The size of the document D to be fed is determined from a sensor (not shown) that detects the position of the document tray 21 in the feeding direction, for example.

  At time t3, the pickup roller 22 starts to descend, and at time t4, the pickup roller 22 contacts the upper surface of the second original D. At this time, the pickup roller 22 is not rotating. When the post-separation sensor S22 detects the trailing edge of the document D at time t5, the CPU 81 drives the pickup motor 84 and feeds the second document by the pickup roller 22. From time t1 to time t5 is one pattern from the time when one original is fed to the time when the second original is fed. The control at times t6 and t7 shown in FIG. This is the same as the control at t2.

  The update timing of the threshold value TH for the second and subsequent documents is a period CT between time t4 and time t5. This period CT is when the pickup roller 22 is in contact with the document D and the pickup roller 22 is stopped. By setting the threshold value of the height detection sensor in this period CT, it is possible to suppress a decrease in productivity and detect a bound original with high accuracy.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described. The fourth embodiment is different from the first embodiment only in the configuration of the height detection sensor. For this reason, about the structure similar to 1st Embodiment, illustration is abbreviate | omitted or attaches | subjects the same code | symbol to a figure and demonstrates.

  As shown in FIGS. 16A and 17, a height detection sensor 130 is provided on the frame 33 of the ADF 120. Similar to the height detection sensor S1 of the first embodiment, the height detection sensor 130 is disposed so as to overlap the stacking surface 21a when viewed from the height direction orthogonal to the stacking surface 21a of the document tray 21. .

  As shown in FIG. 17, the height detection sensor 130 includes a lever 96 as a moving unit that rotates following the uppermost document stacked on the document tray 21, and an encoder that detects the rotation angle of the lever 96. As a rotary volume 99. A first gear 98 is rotatably connected to the rotary volume 99, and a second gear 97 is engaged with the first gear 98. The second gear 97 is fixed to the shaft 95, and a lever 96 is fixed to the shaft 95. For this reason, as the lever 96 rotates following the uppermost document, the electrical resistance of the rotary volume changes, and the voltage detected by the CPU 81 changes. The height position of the uppermost document can be detected by this voltage change. That is, the height detection sensor 130 transmits a signal based on the magnitude of the rotation angle of the lever 96 to the CPU 81.

  As shown in FIG. 16B, when the uppermost original of the bound original bound with the staple ST is fed by the pickup roller 22, the uppermost original is lifted and the height of the original is increased. Part of the position rises. Since the lever 96 of the height detection sensor 130 is in contact with the upper surface of the document, the lever 96 rotates upward as the document floats. When the height position of the document detected by the height detection sensor 130 based on the position of the lever 96 exceeds a predetermined threshold, the CPU 81 determines that the fed document is a bound document.

  As described above, in the present embodiment, the height position of the document is detected according to the rotation angle of the lever, not the amount of reflected light from the document. Therefore, it is possible to stably detect the height position of the document regardless of the paper type and basis weight of the document.

  In the fourth embodiment, the height position of the document is detected by the lever 96 that is rotatably supported and the rotary volume 99 that detects the rotation angle of the lever 96. However, the present invention is not limited to this. That is, it is not limited to a pivotable lever, and any device that detects the height position of the document based on the position of the moving unit that moves following the uppermost document can be used. For example, the height position of the document may be detected by detecting the position of the float contacting the upper surface of the uppermost document.

<Fifth embodiment>
Next, a fifth embodiment of the present invention will be described. The fifth embodiment is different from the first embodiment in the flowchart of the detection method of the height detection sensor. About the structure similar to 1st Embodiment, illustration is abbreviate | omitted or attaches | subjects the same code | symbol to a figure and demonstrates.

  As shown in FIGS. 18A and 18B, the height detection sensor S <b> 1 receives a light emitting unit S <b> 11 that emits light to the uppermost document D stacked on the document tray 21, and receives reflected light from the document D. And a light receiving unit S12.

  As shown in FIG. 18C, the height detection sensor S1 emits light from the light emitting unit S11 and outputs a signal based on the time Tr until the light reflected by the document surface DS is received by the light receiving unit S12. . As shown in FIG. 18A, when the distance H1 between the document surface DS of the document D and the height detection sensor S1 is relatively small, the light emitted from the light emitting unit S11 is reflected by the document surface DS. Thus, the time Tr until the light receiving unit S12 receives light is short. As shown in FIG. 18B, when the distance H2 (H2> H1) between the document surface DS of the document D and the height detection sensor S1 is relatively large, the light emitted from the light emitting unit S11 is emitted. The time Tr from reflection on the document surface DS to reception by the light receiving unit S12 is long. That is, the height detection sensor S1 transmits a signal based on the time Tr to the CPU 81 (see FIG. 5), and the relationship between the distance between the document surface DS and the height detection sensor S1 and the sensor output is shown in FIG. It becomes like the graph shown in (d). The CPU 81 can detect the height position that is the position in the height direction of the document at the detection position in accordance with a signal corresponding to the sensor output transmitted from the height detection sensor S1.

  Next, an operation flowchart for feeding a document will be described with reference to FIG. The basic flowchart is the same as FIG. 6 which is the flowchart of the first embodiment, but step S105 in FIG. 6 is changed to step S305 in FIG. In step S305, the CPU 81 determines whether the output of the height detection sensor S1 has fallen below the threshold value TH. As shown in FIG. 7A, when a normal document that is not a bound document is fed, a characteristic float does not occur as in the case of a bound document. For this reason, as shown in FIG. 20A, the output OP2 of the height detection sensor S1 during document feeding is kept high. Therefore, when a normal document is fed, the output OP2 does not fall below the threshold value TH.

  Next, as shown in FIG. 7B, when the bound document is fed, the first sheet D1 that is the uppermost document of the document D is lifted as the document D is fed. The height position of the first sheet D1 rises. For this reason, as shown in FIG. 20B, the output OP2 of the height detection sensor S1 decreases as the bound original is fed. If the output of the height detection sensor S1 falls below a threshold TH as a predetermined height stored in advance in the memory 82 (step S305: Yes), the CPU 81 determines that the bound original is being fed. To do.

  As in the first embodiment, when the distance between the document surface DS of the document D and the height detection sensor S1 is detected based on the amount of light detected by the height detection sensor S1, it is formed on the document D. It is easy to be influenced by the image that is being. For example, there is a possibility that the difference in light quantity between an image that hardly reflects light such as a solid black image and an image that easily reflects light such as a solid white image may increase. In the present embodiment, the distance between the document surface DS of the document D and the height detection sensor S1 is determined based on the time until the light emitted from the light emitting unit S11 of the height detection sensor S1 reaches the light receiving unit S12. Detected. For this reason, it is difficult to be influenced by the image formed on the document D.

<Sixth Embodiment>
Next, a sixth embodiment of the present invention will be described. The sixth embodiment differs from the second embodiment in the detection method of the height detection sensor and part of the flowchart. About the structure similar to 2nd Embodiment, illustration is abbreviate | omitted or attaches | subjects the same code | symbol to a figure and demonstrates. As in the fifth embodiment, the height detection sensor in the present embodiment is based on the time until the light emitted from the light emitting unit S11 of the height detection sensor S1 reaches the light receiving unit S12. The distance between the original document surface DS and the height detection sensor S1 is detected.

  In this embodiment, as in the second embodiment, as shown in FIGS. 9A and 9B and FIG. 10, a folded document DF in which a fold is formed at the end in the width direction of the document is fed. Think about the case. The folded original document DF is folded below the height detection sensor S1, and the distance between the height detection sensor S1 and the folded original document DF is reduced, so that the folded original document DF is loaded on the original tray 21. The output of the height detection sensor S1 becomes low. Here, the output of the height detection sensor S1 before document feeding (before sheet feeding) is output OP1, and the output of the height detection sensor S1 during document feeding is OP2.

  Next, the copy operation according to the present embodiment will be described with reference to the flowchart shown in FIG. 21. Steps S201 to S206 are the same as those in FIG. As shown in FIG. 22A, the CPU 81 subtracts a change amount α as a predetermined value stored in the memory 82 from the output OP1 of the height detection sensor S1 before feeding the document in step S404 to obtain the height. A threshold value TH is set for the detection sensor S1. The CPU 81 stores the threshold value TH in the memory 82. Note that the output OP1 is determined according to the time until the light emitting unit S11 of the height detection sensor S1 irradiates light on the uppermost document D and the light receiving unit S12 receives light as described above. Since the height detection sensor S1 detects the height position of the folded portion of the folded document DF, the output OP1 has a lower value than the unfolded document.

  In step S407, the CPU 81 determines whether or not the output OP2 during document feeding of the height detection sensor S1 has fallen below the threshold value TH. When the bound original is fed, the uppermost original of the original D is lifted as the original D is fed, and as shown in FIG. 20B, the bound original is fed. The output OP2 of the height detection sensor S1 becomes low. That is, when the amount of change in the height position detected by the height detection sensor S1 exceeds the amount of change α before and during document feeding, the CPU 81 determines that the bound document is being fed. To do.

  In the sixth embodiment, the distance between the document surface DS of the document D and the height detection sensor S1 is detected based on the time when the light emitted from the light emitting unit S11 of the height detection sensor S1 reaches the light receiving unit S12. Therefore, it is difficult to be influenced by the image formed on the document D.

  In any of the above-described embodiments, the electrophotographic printer has been described. However, the present invention is not limited to this. For example, the present invention can be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting ink liquid from a nozzle.

  20: Sheet feeding device (ADF) / 21a: Loading surface / 22: Feeding means (pickup roller) / 81: Control means (CPU) / 82: Storage means (memory) / 93, 94: Lifting mechanism (lifting motor) , Elevating arm) / 96: moving part (lever) / 99: encoder (rotary volume) / D1: first sheet (first sheet) / D2: second sheet (second sheet) / N: separating means ( Separation nip) / PU: Image forming means (image forming unit) / S1: Detection means (height detection sensor) / S11: Light emitting part / S12: Light receiving part / TH: Predetermined height, threshold value / α: Predetermined value (Change)

Claims (14)

A loading surface on which sheets are stacked;
A feeding means for feeding the sheets stacked on the stacking surface in a sheet feeding direction;
A light emitting unit that emits light to the uppermost sheet stacked on the stacking surface; and a light receiving unit that receives the light emitted from the light emitting unit and reflected by the uppermost sheet. Detecting means for detecting a height position, which is a position in a height direction perpendicular to the stacking surface of the uppermost stacked sheet, based on light received by the light receiving unit;
Control means for stopping the feeding of the sheet by the feeding means based on the detection result of the detecting means after starting feeding of the sheets stacked on the stacking surface by the feeding means,
A sheet feeding apparatus characterized by that. The detection means detects the height position based on the amount of light received by the light receiving unit,
The sheet feeding apparatus according to claim 1. The detection means detects the height position based on a time until light emitted from the light emitting unit is received by the light receiving unit,
The sheet feeding apparatus according to claim 1. The detection means is disposed so as to overlap the loading surface when viewed from the height direction.
The sheet feeding device according to any one of claims 1 to 3, wherein the sheet feeding device is provided. The light emitting unit irradiates light in the height direction.
The sheet feeding apparatus according to claim 4, wherein the sheet feeding apparatus is a sheet feeding apparatus. A loading surface on which sheets are stacked;
A feeding means for feeding the sheets stacked on the stacking surface in a sheet feeding direction;
The stack of the uppermost sheet stacked on the stacking surface includes a moving unit that moves following the uppermost sheet stacked on the stacking surface, and an encoder that detects a position of the moving unit. Detecting means for detecting a height position which is a position in a height direction perpendicular to the surface based on the position of the moving unit detected by the encoder;
Control means for stopping the feeding of the sheet by the feeding means based on the detection result of the detecting means after starting feeding of the sheets stacked on the stacking surface by the feeding means,
A sheet feeding apparatus characterized by that. The moving unit is rotatably supported,
The encoder detects a rotation angle of the moving unit and transmits a signal based on the rotation angle to the control means.
The sheet feeding apparatus according to claim 6. Comprising storage means for storing a predetermined height;
The control means stops the feeding of the sheet by the feeding means when the height position detected by the detecting means during the sheet feeding by the feeding means is higher than a predetermined height;
The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device. The control means includes: the height position detected by the detection means before feeding the sheet by the feeding means; and the height position detected by the detection means during sheet feeding by the feeding means. If the difference is greater than a predetermined value, stop feeding the sheet by the feeding means;
The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device. An elevating mechanism for elevating the feeding means with respect to the loading surface;
The control means includes the height position detected by the detection means when the feeding means is stopped and the feeding means is in contact with the uppermost sheet stacked on the stacking surface; When the difference between the height position detected by the detection means during the sheet feeding by the feeding means is larger than a predetermined value, the feeding of the sheet by the feeding means is stopped.
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. The control unit sets a threshold value based on a detection result of the detection unit before feeding the sheet by the feeding unit, and the sheet is fed by the feeding unit while the detection unit is higher than the threshold value. When the position is detected, the feeding of the sheet by the feeding unit is stopped.
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. An elevating mechanism for elevating the feeding means with respect to the loading surface;
The control unit updates the threshold when the feeding unit is stopped and the feeding unit is in contact with the uppermost sheet stacked on the stacking surface.
The sheet feeding apparatus according to claim 11. Separating means for separating the sheets fed by the feeding means one by one;
When a sheet bundle having a topmost first sheet and a second sheet connected to the first sheet in the height direction is fed, the feeding unit is By applying a feeding force to the first sheet while the second sheet is stopped, the first sheet is bent.
The detection means detects the height position of the deflection formed in the first sheet;
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. A sheet feeding device according to any one of claims 1 to 13,
Image forming means for forming an image of a sheet fed and read by the sheet feeding device on another sheet,
An image forming apparatus.

Images