JP2016179868A - Paper feeding device and control program of paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeding device and a control program of the paper feeding device capable of suppressing the occurrence of double feeding and accompany-feeding.SOLUTION: An image forming apparatus as a paper feeding device includes: a pair of conveyance rollers RB; a separation roller 11; and a handling roller 12. The image forming apparatus conveys a paper sheet by stopping rotation driving of the pair of conveyance rollers RB and rotationally driving the separation roller 11 so as to abut a front end of the paper sheet on the pair of conveyance rollers RB. The image forming apparatus conveys the paper sheet by rotationally driving the pair of conveyance rollers RB and the separation roller 11 when a rear end of the paper sheet passes the separation roller 11 after the front end of the paper sheet is abutted when the occurrence of double feeding is not detected. The image forming apparatus conveys the paper sheet by rotationally driving the pair of conveyance rollers RB and stopping rotation driving of the separation roller 11 when the rear end of the paper sheet passes the separation roller 11 after the front end of the paper sheet is abutted when the occurrence of double feeding is detected.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sheet feeding device and a control program for the sheet feeding device. More specifically, the present invention relates to a paper feeding device that can accurately transport paper and a control program for the paper feeding device.

  An MFP (Multifunction Peripheral) has a scanner function, a copying function, a function as a printer, a facsimile function, a data communication function, and a server function.

  An image forming apparatus (image recording apparatus) such as an MFP, a printer, a copier, or a facsimile, an image reading apparatus, and the like are equipped with a paper feeding device. The image forming apparatus is required to have reproducibility of the input image, and the image reading apparatus is required to be reproducible for the original image. In order to improve the reproducibility of an input image or a document image, a paper feeding device capable of accurately transporting paper is required.

  When the image forming apparatus prints an image on a sheet, the conventional sheet feeding apparatus conveys the sheet by the following operation.

  The sheet feeding device is a separation unit configured by a separation roller and a separating unit, and separates one sheet from a plurality of sheets stacked on a sheet feeding tray and introduces the sheet into the sheet feeding device. The paper feeding device abuts the leading end of the introduced paper against the nip of the stopped pair of registration rollers.

  Next, the paper feeding device continuously rotates the loop forming roller set on the upstream side of the registration roller pair, thereby forming a loop of a predetermined loop amount on the paper between the registration roller pair and the loop forming roller. Form. As a result, the inclination generated in the sheet during conveyance on the upstream side in the conveyance direction with respect to the registration roller pair is corrected.

  Thereafter, the paper feeding device stops the separation roller, and conveys the paper by the registration roller pair and the reading roller. An image is formed when the sheet passes through an image forming position provided on the downstream side of the pair of registration rollers.

  When the image reading apparatus reads an image of a document, the paper feeding device conveys the document by the same operation as described above, and reads the image when the document passes through the image reading position.

  Each conveyance unit that conveys paper, such as a separation roller, a separation unit, a registration roller, or a reading roller, is connected to another conveyance unit that is adjacent on either the upstream side or the downstream side as the conveyance of the paper or the document proceeds. Deliver paper between. When the paper or document is transferred between the two transport units, the load torque received by the paper from the transport unit varies, and the transport speed of the paper or document temporarily varies. If the paper transport speed fluctuates during image formation on the paper, the quality of the image will be degraded. Further, if the document transport speed fluctuates during the reading of the document image, the quality of the scanned image is degraded. Therefore, it is important to suppress fluctuations in the conveyance speed when the paper or document is transferred between the conveyance units.

  Here, when the transport unit has a role of merely transporting paper, such as a pair of registration rollers and a pair of reading rollers, the transport speed can be adjusted by adjusting the pressure contact force such as separation of the transport roller pair. Variation can be suppressed relatively easily. On the other hand, when the conveyance unit is a separation unit that separates a single sheet or document from a plurality of sheets or documents, it is difficult to suppress variations in conveyance speed in the same manner as other conveyance units. is there. For the separation roller and the separation unit constituting the separation unit, the frictional force between the separation roller and the separation unit and the frictional force between each of the separation roller and the separation unit and the paper or the document need to be set appropriately. Because there is.

  In recent years, a torque limiter system is being adopted as a paper or document separation system in a paper feeder from the viewpoint of reliability and cost performance. This method is a method in which a roller with a torque limiter using a torsion coil spring is used as the winding part. In the torque limiter method, when only one sheet or document enters the nip of the separation unit, the torque limiter is loosened and the rolling roller follows the sheet or document and rotates forward. On the other hand, when two or more sheets or originals enter the nip of the separation unit, the slip torque of the torque limiter overcomes the frictional force between the sheets or between the originals, and the second or subsequent sheets or originals are generated by the torque limiter sliding torque. Remains in the nip of the separator.

FIG. 18 is a graph showing the relationship between the sheet conveyance amount at the reading position and the variation rate of the sheet conveyance speed when the document is conveyed without taking measures to suppress the variation in the conveyance speed. 17 and 18 show the results when A4 size paper having a basis weight of 80 g / m ² is conveyed at a conveyance speed of 160 mm / s.

  Referring to FIG. 18, when a document is transported without taking measures to suppress fluctuations in the transport speed of the separation unit, when the trailing edge of the sheet passes through the nip of the separation unit (area A2 in FIG. 18), the sheet is It is released from the back tension (force in the direction opposite to the conveying direction) received from the winding section, and the conveying speed fluctuates greatly. As a result, when the paper feeding device is mounted on the image forming apparatus, the toner images of the respective colors are displaced, and the image formed on the paper is significantly stretched or shrunk. Further, when the paper feeding device is mounted on the image reading device (in the case of an ADF (Auto Document Feeder)), there is a shift in an image pattern captured by a reading element such as a CCD (Charge Coupled Device). Occurs, and the reproducibility of the original image is greatly deteriorated.

  The image reading apparatus includes a plurality of reading elements for each color of R (red), G (green), and B (blue) for reading an image of a color document. Reading element groups for reading RGB colors are arranged at regular intervals along the document transport direction. Each of a plurality of reading elements (a plurality of reading elements for reading the same color) constituting one reading element group is arranged at regular intervals along a direction perpendicular to the document transport direction. Since there is a difference in the time when the document passes through the reading element groups for each color of RGB, the passage time difference is corrected based on the document transport speed. For this reason, when the conveyance speed fluctuates, pixels of each color of RGB that should originally overlap are shifted in the conveyance direction, and the color reproducibility of the original image is greatly deteriorated.

  When the paper or document separation method is a torque limiter method, the back tension applied to the paper is released when the rear end of the paper or document passes through the nip of the separation unit. As a result, the fluctuation of the conveyance speed is particularly large. This back tension is caused by the restoring force of the deformed rubber material on the surface of the rolling roller and the biasing force of the torsion coil spring of the torque limiter biased in the loosening direction following the paper.

  Conventional paper feeders are disclosed in, for example, Patent Documents 1 and 2 below. Patent Document 1 below discloses a document reading apparatus that transports a fed document to a document reading position after a conveyance resistance is applied by a separation roller. This document reading apparatus is provided with a load torque that is configured to give a load torque as a conveyance resistance to the roller and to change the magnitude of the load torque. In this document reading apparatus, the load torque by the load torque generating mechanism at the start of feeding is set to the first value. In this document reading apparatus, the load torque is reduced from the first value until the leading end of the fed document passes through the registration nip on the downstream side of the separation roller and reaches the document reading position. Change to the second value. Thereby, the conveyance resistance by the roller is reduced.

  Patent Document 2 below discloses a technique for transmitting a driving force to the pickup roller and the separating plate when the vicinity of the rear end of the document conveyed on the document conveying path passes between the separating roller and the separating plate. Has been. According to this technique, the tension of the original between the separating roller and the registration roller is reduced.

JP 2013-180894 A JP 2005-035739 A

  The following has been proposed as a measure for suppressing a decrease in reproducibility due to a change in the conveyance speed caused by the separation unit. The first policy is to increase the distance from the image forming position or the image reading position to the nip of the separation unit, rather than the length along the conveyance direction of frequently used paper or originals. According to this measure, since the rear end of the sheet passes through the nip of the separation unit before the front end of the sheet reaches the image forming position or the image reading position, the reproducibility is deteriorated due to the conveyance speed variation caused by the separation unit. Can be suppressed. However, in the first measure, the conveyance path of the paper or the document becomes long, resulting in an increase in the size of the apparatus. In the first measure, it is difficult to handle all lengths of paper or originals that can be passed.

  The second strategy is to increase the inertia (moment of inertia) of the conveyance unit other than the separation unit, such as the registration roller pair and the reading roller pair, or increase the frictional resistance at the bearing unit of the conveyance unit other than the separation unit. By doing this, it is a measure to prevent the fluctuation of the conveyance speed in the separation unit from being transmitted to the downstream side. However, in the second policy, the load for driving the conveyance unit other than the separation unit is increased, and a larger amount of power is required.

  The third method is a method in which a loop (sag) is formed between the registration roller pair and the separation unit by driving the separation roller of the separation unit when the trailing edge of the document passes through the nip of the separation unit. . In this measure, fluctuations in the conveyance speed are absorbed by the loop, so that fluctuations in the conveyance speed at the separation unit can be prevented from being transmitted downstream, and fluctuations in the conveyance speed of the paper can be suppressed. . However, depending on the use environment and the type of paper, there are cases where double feeding or carry-in occurs due to the driving of the separation roller. In this case, there is a problem that double-feed or carry-in cannot be eliminated.

  SUMMARY An advantage of some aspects of the invention is to provide a sheet feeding device and a sheet feeding device control program capable of suppressing fluctuations in the conveyance speed.

  Another object of the present invention is to provide a paper feeding device and a control program for the paper feeding device that can suppress the occurrence of double feeding and accompanying feeding.

  A sheet feeding device according to one aspect of the present invention includes a conveyance roller pair that conveys a sheet by being driven to rotate, and a loop that conveys the sheet by being driven to rotate more upstream of the conveyance path than the pair of conveyance rollers. The forming roller, the separation unit that applies a force in the direction opposite to the paper conveyance direction on the upstream side of the conveyance path with respect to the conveyance roller pair, and the rotation drive of the conveyance roller pair is stopped and the loop is formed. By conveying the paper by rotating the roller, the abutting means that abuts the front end of the paper against the pair of conveyance rollers, the detecting means for detecting the presence or absence of occurrence of double feeding, and the occurrence of double feeding by the detecting means Is detected, when the trailing edge of the paper passes the loop forming roller after abutting the front edge of the paper with the abutting means, each of the conveying roller pair and the loop forming roller is rotated. When the occurrence of double feeding is detected by the first conveying unit that conveys the sheet by driving and the detecting unit, the trailing end of the sheet pushes the loop forming roller after abutting the front end of the sheet by the abutting unit. A second transport unit that transports the paper by rotating the transport roller pair and stopping the rotational drive of the loop forming roller when passing.

  Preferably, in the sheet feeding device, the size of the loop when the detection unit does not detect the occurrence of double feeding, and when the trailing edge of the paper passes the loop forming roller, The size of the loop formed on the paper between the two is the size of the loop when the detection means detects the occurrence of double feed, and is conveyed when the trailing edge of the paper passes the loop forming roller It is larger than the size of the loop formed on the paper between the roller pair and the loop forming roller.

  Preferably, in the paper feeding device, the loop forming roller is in contact with the winding portion.

  Preferably, in the above-described paper feeding device, when the detection unit detects the occurrence of double feeding, the second transport unit transports the paper in contact with the loop forming roller in the paper transport direction. The sheet that comes into contact with the sheet stays on the upstream side of the conveyance path with respect to the nip between the loop forming roller and the separating section.

  Preferably, the sheet feeding device further includes a clutch unit that allows rotation of the loop forming roller in a conveyance direction in a state where rotation driving is stopped.

  Preferably, in the sheet feeding device, the clutch unit is a one-way clutch that does not allow rotation in a direction opposite to the conveyance direction of the loop forming roller.

  Preferably, in the sheet feeding device, the first conveying unit rotates the loop forming roller between the time when the front end of the sheet is abutted by the abutting unit and the time when the rear end of the sheet passes the loop forming roller. Stop and resume.

  Preferably, in the sheet feeding device, the first conveying unit continues the loop forming roller from the time when the front end of the sheet is abutted by the abutting unit until the rear end of the sheet passes the loop forming roller. Rotation drive.

  Preferably, in the paper feeding device, the webbing unit forms the paper or the loop when the frictional force between the webbing roller in contact with the loop forming roller and the paper or the looping roller and the papering roller reaches a predetermined value or more. Including a torque limiter that moves the roller and follows the roller.

  Preferably, in the sheet feeding device, the detection unit detects presence or absence of occurrence of double feeding based on a rotation state of the roller.

  Preferably, the sheet feeding device further includes a rotating unit that follows the rotation of the rolling roller, and a sensor that irradiates the rotating unit with light and receives reflected light, and the detection means is based on the reflected light received by the sensor. To detect the occurrence of multiple feeds.

  Preferably, the sheet feeding device further includes a rotating unit that rotates integrally with the roller and a sensor that irradiates the rotating unit with light and receives reflected light, and the detection means detects reflected light received by the sensor. Based on this, the presence or absence of double feed is detected.

  Preferably, the paper feeding device further includes a rotating unit that is coaxial with the whirling roller and rotates independently of the whirling roller, and a sensor that irradiates light to the rotating unit and receives reflected light. The presence / absence of occurrence of double feed is detected based on the reflected light received at.

  Preferably, in the sheet feeding device, the transport roller pair is rotationally driven by rotating one of the two rollers constituting the transport roller pair and following the other.

  A control program for a sheet feeding device according to another aspect of the present invention includes a pair of conveyance rollers that conveys a sheet by being rotated, and a sheet that is rotated by being driven upstream of the conveyance roller pair on the upstream side of the conveyance path. This is a control program for a paper feeding device that includes a loop forming roller to be transported and a separation unit that applies a force in a direction opposite to the paper transport direction on the upstream side of the transport path from the pair of transport rollers. The rotation of the transport roller pair is stopped and the loop forming roller is rotated to transport the paper, so that the front end of the paper abuts the transport roller pair, and whether double feeding has occurred. If the detection step does not detect the occurrence of double feed in the detection step, the rear end of the paper is looped after the front end of the paper is abutted in the abutment step. When detecting the occurrence of double feed in the first transport step and the detection step of transporting the paper by rotating and driving each of the transport roller pair and the loop forming roller when passing the roller, in the abutting step Second transport for transporting the paper by rotating the transport roller pair and stopping the rotational drive of the loop forming roller when the rear edge of the paper passes the loop forming roller after the front edge of the paper is abutted Let the computer execute the steps.

  According to the present invention, it is possible to provide a sheet feeding device and a sheet feeding device control program capable of suppressing fluctuations in the conveyance speed. In addition, it is possible to provide a sheet feeding device and a sheet feeding device control program capable of suppressing the occurrence of double feeding and accompanying feeding.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure of ADF1 in one embodiment of this invention. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a first operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 10 is a diagram illustrating a second operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 10 is a diagram for explaining a third operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 10 is a diagram illustrating a fourth operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 10 is a diagram for explaining a fifth operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 10 is a diagram illustrating a sixth operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 10 is a diagram illustrating a seventh operation of the image forming apparatus when a sheet is conveyed in the ADF 1 in the embodiment of the present invention. FIG. 20 is a diagram for describing a modification example of the sixth operation of the image forming apparatus when a sheet is conveyed in the ADF in the embodiment of the present invention. It is sectional drawing which shows typically the 1st structure of sensor SE in one embodiment of this invention. It is a perspective view which shows typically the 2nd structure of sensor SE in one embodiment of this invention. It is sectional drawing which shows typically the 3rd structure of sensor SE in one embodiment of this invention. It is a perspective view which shows typically the 3rd structure of sensor SE in one embodiment of this invention. 6 is a flowchart illustrating an operation of the image forming apparatus when transporting a sheet in an embodiment of the present invention. 6 is a graph showing a relationship between a sheet conveyance amount at a reading position and a fluctuation rate of a sheet conveyance speed when double feeding occurs. 5 is a graph showing a relationship between a sheet conveyance amount at a reading position and a variation rate of a sheet conveyance speed when a document is conveyed without taking a measure for suppressing variation in conveyance speed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In the following embodiment, a case where a paper feeding device is mounted on an image forming apparatus will be described. Examples of the image forming apparatus include an MFP, a printer, a copier, and a facsimile. The paper feeding device may be mounted on the image reading device instead of the image forming device.

  [Configuration of Image Forming Apparatus]

  FIG. 1 is a cross-sectional view showing a configuration of an image forming apparatus according to an embodiment of the present invention.

  Referring to FIG. 1, an image forming apparatus (an example of a paper feeding device) in the present embodiment includes an ADF 1, a toner image forming unit 210, a fixing device 220, a paper feeding cassette 230, and a paper transporting unit 240. , And scanner 250.

  The ADF 1 is provided in the upper part of the image forming apparatus. A detailed configuration of the ADF 1 will be described later.

  The toner image forming unit 210 combines four color images by a so-called tandem method, and forms a color image on a sheet. The toner image forming unit 210 includes a photoconductor 211 provided for each color of C (cyan), M (magenta), Y (yellow), and K (black), and a developing device 212 that forms a toner image on the photoconductor 211. The image forming apparatus includes an intermediate transfer belt 213 to which a toner image is transferred (primary transfer) from the photosensitive member 211, a transfer roller 214 for transferring an image from the intermediate transfer belt 213 to a sheet (secondary transfer) at the image forming position P1, and the like.

  The fixing device 220 includes a pressure roller 221 and a heating roller 222. The fixing device 200 conveys the sheet on which the toner image is formed between the pressure roller 221 and the heating roller 222 while heating and pressing the sheet. As a result, the fixing device 200 melts the toner adhering to the paper and fixes it on the paper to form an image on the paper.

  The paper feed cassette 230 stores paper for forming an image. There may be a plurality of paper feed cassettes 230.

  The paper transport unit 240 includes a separation unit 241, a transport roller pair 242, a discharge roller pair 243, and the like. The separation unit 241 separates one sheet from a plurality of sheets stored in the sheet feeding cassette 230 and feeds the sheet to the transport path TR. The separation unit 241 includes a separation roller 241a and a rolling roller 241b. The transport roller pair 242 transports the paper along the transport path TR. The discharge roller pair 243 discharges the sheet on which the image is formed to the discharge tray 261.

  The scanner 250 is disposed between the ADF 1 and the paper discharge tray 261. The scanner 250 includes an IR (Infrared) module 251 and the like. The IR module 251 includes a lamp 252 for irradiating the original with light and an image sensor 253 for receiving reflected light from the original. The IR module 251 reads an image of a document and acquires the image data.

  FIG. 2 is a cross-sectional view showing a configuration of ADF 1 in one embodiment of the present invention.

  Referring to FIG. 2, ADF 1 conveys a sheet (original) that is an object of image reading by scanner 250 to image reading position P0. The ADF 1 has a U-shaped transport path TR. The ADF 1 includes a separation roller (feed roller) 11 (an example of a loop forming roller), a separating roller 12 (an example of a separating unit), registration rollers 13 and 14 (an example of a conveying roller pair), and reading rollers 15 and 16. A pair of discharge rollers 17, a paper feed tray 31, a paper discharge tray 32, and a sensor SE.

  The separation roller 11 and the rolling roller 12 constitute a separation unit RA. The registration rollers 13 and 14 constitute a transport roller pair RB. The separation unit RA conveys the sheet upstream of the conveyance path TR with respect to the conveyance roller pair RB. The outer peripheral surfaces of the separation roller 11 and the separating roller 12 and the registration rollers 13 and 14 have a high coefficient of friction.

  The separation roller 11 and the separating roller 12 are opposed to each other across the transport path TR, and are in contact with each other. Each of the separation roller 11 and the separating roller 12 conveys a sheet by being rotationally driven in the sheet conveyance direction (forward rotation direction). Each of the separation roller 11 and the separation roller 12 separates one sheet from a plurality of sheets stored in the sheet feed tray 31, and rotates while sandwiching the sheets, thereby transporting the separated sheets along the transport path TR. . The separating roller 12 is urged in a rotation direction (reverse direction) opposite to the paper transport direction, and applies a force in a direction opposite to the paper transport direction to the contacting paper.

  The friction coefficient between the surface of the separation roller 11 and the paper is preferably higher than the friction coefficient between the papers. The friction coefficient between the surface of the roller 12 and the paper is preferably higher than the friction coefficient between the papers.

  The registration rollers 13 and 14 are opposed to each other across the transport path TR and are in contact with each other. Each of the registration rollers 13 and 14 is driven to rotate in the normal rotation direction to convey the paper. Each of the registration rollers 13 and 14 conveys the sheet in the conveyance direction along the conveyance path TR by rotating while sandwiching the sheet.

  The transport unit RB may be driven to rotate by rotating one of the registration rollers 13 and 14 and driving the other. The transport unit RB may be rotationally driven by rotationally driving both the registration rollers 13 and 14.

  The reading roller 15 is disposed between the transport roller pair RB and the image reading position P0. The reading roller 16 is disposed between the image reading position P0 and the discharge roller pair 17. Each of the reading rollers 15 and 16 conveys the sheet along the conveyance path TR by rotating while sandwiching the sheet with the wall portion 20. Each of the reading rollers 15 and 16 conveys the sheet so that the sheet passes through the image reading position P0 on each of the upstream side and the downstream side of the conveyance path TR of the image reading position P0.

  The discharge roller pair 17 is disposed on the most downstream side of the transport path TR. The discharge roller pair 17 discharges the paper to the paper discharge tray 32.

  The sensor SE detects the double feed or the carry of the paper in the vicinity of the nip of the separation unit RA.

  FIG. 3 is a block diagram showing a configuration of the image forming apparatus according to the embodiment of the present invention.

  Referring to FIG. 3, the image forming apparatus includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a network I / F 104, an image reading unit 105, and the like. , An operation panel 106, an auxiliary storage device 107, an image forming unit 108, a double feed detection unit 109, a conveyance control unit 110, a paper feed motor 111, a registration motor 112, and a conveyance motor 113. .

  The CPU 101, the ROM 102, the RAM 103, the network I / F 104, the image reading unit 105, the operation panel 106, the auxiliary storage device 107, the image forming unit 108, the double feed detection unit 109, and the conveyance control unit 110 are each connected by a bus or the like. Are connected to each other. The conveyance control unit 110 and each of the paper feed motor 111, the registration motor 112, and the conveyance motor 113 are connected to each other.

  The CPU 101 controls the operation of the entire image forming apparatus. The CPU 101 performs processing based on the control program.

  The ROM 102 stores a control program executed by the CPU 101 and various tables.

  A RAM 103 is a working memory for the CPU 101, and temporarily stores data relating to various jobs.

  The network I / F 104 transmits and receives various types of information to and from external devices through the network.

  The image reading unit 105 reads an image of a document and creates image data thereof.

  The operation panel 106 includes a display panel that displays various types of information and a detection unit that detects an input operation to the display panel.

  The auxiliary storage device 107 stores various information such as image data.

  The image forming unit 108 forms an image on a sheet.

  The double feed detection unit 109 uses the sensor SE to detect the occurrence of paper double feed and carry-in.

  The conveyance control unit 110 controls the conveyance of the paper by controlling on / off of each of the paper feed motor 111, the registration motor 112, and the conveyance motor 113. The paper feed motor 111 rotates the separation roller 11. The registration motor 112 rotates the registration roller 13. The transport motor 113 rotationally drives other rollers (such as the reading rollers 15 and 16 and the discharge roller pair 17).

  [Operation of Image Forming Apparatus]

  Next, the operation of the image forming apparatus when transporting paper in the ADF according to the present embodiment will be described. In FIGS. 4 to 11, for convenience of explanation, the transport route TR is shown as a straight line. The arrow AR1 indicates the paper transport direction, and the arrow AR2 indicates the direction opposite to the paper transport direction. An arrow indicating the direction of rotation is attached to the rotationally driven roller, and an arrow is not attached to the roller whose rotational drive is stopped.

  4 to 10 are diagrams for explaining the operation of the image forming apparatus when a sheet is conveyed in the ADF 1 according to the embodiment of the present invention.

  Referring to FIG. 4, the user places a plurality of paper sheets as originals on paper feed tray 31 and receives an instruction to execute a scan job or a copy job through operation panel 106. When receiving an instruction to execute a scan job or a copy job, the image forming apparatus rotates the separation roller 11 in the normal rotation direction. As a result, the image forming apparatus introduces one sheet SH among the plurality of sheets stored in the sheet feed tray 31 into the ADF 1 by the separation unit RA. The image forming apparatus transports the paper SH along the transport path TR.

  The rotational torque when the separation roller 11 is rotationally driven is larger than the force with which the roller 12 is urged in the reverse direction. Therefore, when no multi-feed or follow-up occurs, the paper SH is transported in the transport direction, and the separation roller 12 is rotated following the separation roller 11. At this time, the rolling roller 12 applies a back tension that is a force in a direction opposite to the transport direction (direction indicated by arrow AR2) to the paper SH transported in the transport direction (direction indicated by arrow AR1). On the other hand, the frictional force between the two sheets is smaller than the force with which the separation roller 11 is urged in the reverse direction. Therefore, when double feed or follow-up occurs, the rolling roller 12 does not follow the separation roller 11. The paper that comes into contact with the separation roller 11 is conveyed in the conveyance direction, and the paper that has been double-fed or carried away remains in the nip of the separation part RA due to the back tension received from the rolling roller 12.

  Referring to FIG. 5, when the sheet SH is introduced into the ADF 1, the image forming apparatus stops the rotation driving of the transport roller pair RB. The front end of the sheet SH conveyed by the rotationally driven separation roller 11 is abutted against the stopped conveyance roller pair RB. Accordingly, the image forming apparatus forms a loop (slack) RP1 on the sheet SH between the separation unit RA and the transport roller pair RB, and aligns the front end of the sheet SH in a direction perpendicular to the transport path TR.

  Referring to FIG. 6, the image forming apparatus starts to rotate the transport roller pair RB in the normal rotation direction after a predetermined time has elapsed since the sheet SH is abutted against the transport roller pair RB, and the separation roller 11 rotates. Stop driving. The loop RP1 of the paper SH is eliminated (the sagging disappears).

  Referring to FIG. 7, in the image forming apparatus, when the sensor SE does not detect the occurrence of double feed or follow-up immediately before the rear end of the paper SH passes through the RA nip (separation roller 11), the transport roller Together with the pair RB, the separation roller 11 is rotationally driven in the normal rotation direction (rotation drive of the separation roller 11 is resumed). The separation roller 11 only needs to be rotationally driven when the trailing edge of the paper passes through the separation roller 11, and the timing of the rotational drive is arbitrary. Accordingly, the image forming apparatus forms a new loop RP2 on the sheet SH between the separation unit RA and the transport roller pair RB. In addition, it is preferable that the paper conveyance speed by the separation roller 11 at this time is faster than the paper conveyance speed by the conveyance roller pair RB.

  Before the rear end of the sheet SH passes through the nip of the separation portion RA, the front end of the sheet SH passes the image reading position P0, and reading of the image on the sheet SH is started. When the rear end of the sheet SH passes through the nip of the separation unit RA, the image forming apparatus is reading an image on the sheet SH at the image reading position P0.

  When the trailing edge of the sheet SH passes through the nip of the separation unit RA, the sheet SH is released from the back tension received from the separating roller 12, and the conveyance speed of the trailing end of the sheet SH increases rapidly. However, the rapid increase in the conveyance speed due to the release from the back tension is alleviated by the loop RP2. As a result, it is possible to suppress fluctuations in the conveyance speed during reading of the image on the sheet SH.

  Referring to FIG. 8, the image forming apparatus stops the rotation driving of separation roller 11 after a predetermined time has elapsed since the rotation driving of separation roller 11 was started. Accordingly, the image forming apparatus transports the sheet SH in the transport direction using the transport roller pair RB in a state where the transport by the separation unit RA is stopped. The loop RP2 of the paper SH is eliminated.

  Referring to FIG. 9, in the image forming apparatus, when the sensor SE detects the occurrence of double feed or follow-up immediately before the trailing edge of the sheet SH passes through the nip of the separation unit RA, the image forming apparatus While the sheet SH is conveyed by rotational driving, the rotational driving of the separation roller 11 is not started but is stopped. Thereby, the paper SH that contacts the separation roller 11 receives a force in the transport direction indicated by the arrow AR1 from the transport roller pair RB. On the other hand, the paper OS (paper that has been multi-fed or carried forward) that contacts the paper roller 12 receives back tension from the paper roller 12 in the direction indicated by the arrow AR2. This back tension is due to, for example, the restoring force of a spring of a torque limiter provided on the roller 12.

  In the case of FIG. 9, no loop is formed on the paper SH between the transport roller pair RB and the separation roller 11. In other words, in the case of FIG. 9, the size of the loop (the amount of deflection of the paper between the transport roller pair RB and the separation roller 11) is smaller than the loop RP2 of FIG.

  Referring to FIG. 10, the paper SH that contacts the separation roller 11 is transported in the transport direction by the force received from the transport roller pair RB. On the other hand, the paper OS is separated from the paper SH by the force received from the separation roller 12, and remains on the upstream side of the transport path from the nip of the separation unit RA or the nip of the separation unit RA.

  FIG. 11 is a modified example of the operation of the image forming apparatus shown in FIG.

  Referring to FIG. 11, when the sensor SE does not detect the occurrence of double feeding or carry-in, the image forming apparatus abuts the sheet SH against the transport roller pair RB, and then the trailing end of the sheet SH pushes the separation roller 11. Until it passes, the separation roller 11 may be continuously rotated so that the loop RP1 is not eliminated. Thereby, in this case, fluctuations in the conveyance speed due to release from the back tension are alleviated by the loop RP1.

  [Detailed sensor configuration]

  Subsequently, the configuration of the sensor SE in the present embodiment will be described. The sensor SE has, for example, one of the first to third configurations shown below.

  FIG. 12 is a cross-sectional view schematically showing a first configuration of the sensor SE in one embodiment of the present invention.

  Referring to FIG. 12, the sensor SE of the first configuration detects the occurrence of double feed or follow-up based on the rotation state of the roller 12, and includes a reflection sensor 21 and a speed detection roller 22 (rotation). Part of an example). The speed detection roller 22 has a roller shape and is in contact with the rolling roller 12 so as to follow the rotation of the rolling roller 12. A black and white pattern BW is formed on the outer peripheral surface of the speed detection roller 22. The black and white pattern BW is a pattern in which white patterns and black patterns are alternately formed at regular intervals along the rotation direction of the speed detection roller 22.

  The reflection sensor 21 irradiates the outer peripheral surface of the speed detection roller 22 with light and receives the reflected light. The change in the amount of reflected light received by the reflection sensor 21 reflects the change in the black-and-white pattern of the reflection portion at the speed detection roller 22. Based on the reflected light received by the reflection sensor 21, the image forming apparatus grasps the rotational state of the speed detection roller 22 and the rolling roller 12, and detects the occurrence of double feeding or carry-in. For example, the image forming apparatus detects the occurrence of double feed or carry-over when the rotation speed of the separation roller 12 is extremely low with respect to the conveyance speed serving as a reference of the paper or when the separation roller 12 is stopped. .

  FIG. 13 is a perspective view schematically showing a second configuration of the sensor SE in one embodiment of the present invention.

  Referring to FIG. 13, the sensor SE of the second configuration detects the occurrence of double feed or follow-up based on the rotation state of the roller 12, and includes a reflection sensor 21.

  The image forming apparatus further includes a torque limiter 33 provided on the rotation shaft 12 a of the separating roller 12 and a one-way bearing 34 (an example of a clutch unit) provided on the rotation shaft 11 a of the separation roller 11.

  The torque limiter 33 rotates integrally with the rolling roller 12. The torque limiter 33 includes a torsion coil spring (not shown). The torque limiter 33 urges the rolling roller 12 in the reverse direction by the elastic force of the torsion coil spring.

  When only one sheet is interposed in the nip of the separation unit RA, or when there is no sheet in the nip of the separation unit RA, a large force for rotating the separation roller 12 in the forward rotation direction (between the separation roller 11 and the sheet) The frictional force between the paper or the separation roller 11 and the separation roller 12 reaches a predetermined value or more. In this case, the torsion coil spring of the torque limiter 33 is loosened (the elastic force of the torsion coil spring is weakened), and the rolling roller 12 rotates following the separation roller 11 that rotates in the forward direction. On the other hand, when a plurality of sheets are present in the nip of the separation portion RA, the frictional force between the sheet and the separating roller 12 becomes less than a predetermined value, and the biasing force of the torsion coil spring of the torque limiter 33 becomes larger. As a result, the separating roller 12 is not driven by the separating roller 11 that rotates in the forward direction, but stops together with the paper that contacts.

  The torque limiter 33 functions as the speed detection roller 22. That is, a black and white pattern BW is formed on the outer peripheral surface of the case of the torque limiter 33. The reflection sensor 21 irradiates the outer peripheral surface of the speed detection roller 22 with light and receives the reflected light. The image forming apparatus detects the occurrence of double feed or follow-up from the change in the amount of reflected light received by the reflection sensor 21. The configuration of the reflection sensor 21 and the method for detecting the occurrence of double feeding or follow-up using the reflection sensor 21 are the same as in the first configuration, and therefore description thereof will not be repeated.

  The one-way bearing 34 is engaged with the separation roller 11 and allows rotation of the separation roller 11 in the forward rotation direction in a state where the rotation drive is stopped. Further, the one-way bearing 34 does not allow the separation roller 11 to rotate in the reverse direction. The separation roller 11 passes through the nip of the separation portion RA by the action of the one-way bearing 34 when the paper is conveyed by the forward rotation driving of the transport roller pair RB when the forward rotation driving is stopped. Follow the paper to be printed. By providing the one-way bearing 34, the connection between the separation roller 11 and the drive system is disconnected, and the back tension (force pulling toward the upstream side of the transport path) on the paper can be reduced.

  14 and 15 are diagrams schematically showing a third configuration of the sensor SE in one embodiment of the present invention. 14 is a cross-sectional view, and FIG. 15 is a perspective view.

  Referring to FIGS. 14 and 15, the sensor SE of the third configuration detects the occurrence of double feed or carry-on based on the sheet conveyance state, and includes a reflection sensor 21, a speed detection roller 22, and the like. Is included.

  The speed detection roller 22 includes a large diameter part (paper contact part) 22a and a small diameter part (speed index part) 22b. The large-diameter portion 22 a has substantially the same radius as that of the rolling roller 12 and is provided coaxially with the rotating shaft 12 a of the rolling roller 12. The large-diameter portion 22a can rotate around the rotation shaft 12a independently of the rolling roller 12. The large-diameter portion 22a is rotated by a frictional force between the large-diameter portion 22a and the sheet passing through the nip of the separation portion RA. The outer peripheral surface of the large diameter portion 22a has a high coefficient of friction.

  The small diameter portion 22b has a smaller radius than the large diameter portion 22a, and is provided coaxially with the rotating shaft 12a of the roller 12. The small diameter portion 22b rotates integrally with the large diameter portion 22a. The small diameter portion 22b comes into contact with the sheet passing through the nip of the separation portion RA. A black and white pattern BW is formed on the outer peripheral surface of the small diameter portion 22b. The reflection sensor 21 irradiates the outer peripheral surface of the small diameter portion 22b with light and receives the reflected light. The image forming apparatus detects the occurrence of double feed or follow-up from the change in the amount of reflected light received by the reflection sensor 21.

  The image forming apparatus further includes a torque limiter 33 provided on the rotation shaft 12a of the roller 12 and a one-way bearing 34 (an example of a one-way clutch) provided on the rotation shaft 11a of the separation roller 11. The configuration and operation of the torque limiter 33 and the one-way bearing 34, the configuration of the reflection sensor 21, and the method for detecting the occurrence of double feed or follow-up using the reflection sensor 21 are the same as those in the first or second configuration. The description will not be repeated.

  According to the sensor SE having the first to third configurations described above, the configuration can be simplified and the cost can be reduced by using the speed detection roller. The image forming apparatus may include a sensor having a configuration other than the first to third configurations described above as a sensor for detecting double feeding or accompanying feeding. The image forming apparatus may be provided with a sensor for detecting double feed or follow-up using ultrasonic waves (see, for example, Japanese Patent Application Laid-Open No. 2007-276976), and the speed of the surface of the paper roller or paper to be conveyed is determined. A sensor for direct measurement may be provided.

  [Flowchart showing operation of image forming apparatus]

  Next, a flowchart illustrating the operation of the image forming apparatus when conveying a sheet will be described.

  FIG. 16 is a flowchart showing the operation of the image forming apparatus when transporting a sheet in one embodiment of the present invention. In this flowchart, it is assumed that the paper feed motor 111 is configured by a stepping motor, and the drive of the paper feed motor 111 is controlled based on a pulse signal indicating the drive amount (rotation amount) of the stepping motor.

  Referring to FIG. 16, the CPU 101 of the image forming apparatus determines whether a drive request for the separation roller 11 has been received (S101). The CPU 101 repeats the process of step S101 until it is determined that the drive request for the separation roller 11 has been received.

  If it is determined in step S101 that the drive request for the separation roller 11 has been received (YES in S101), the CPU 101 rotates the separation roller 11 by driving the paper feed motor 111 to rotate forward (S103). As a result, a loop is formed on the sheet between the separation unit RA and the transport roller pair RB (S105). Next, the CPU 101 determines whether or not a request for driving the registration roller 13 has been received (S107). The CPU 101 repeats the process of step S107 until it is determined that a request for driving the registration roller 13 has been received.

  If it is determined in step S107 that a request to drive the registration roller 13 has been received (YES in S107), the CPU 101 drives each of the paper feed motor 111 and the registration motor 112 in the normal direction, thereby separating the separation roller 11 and the registration roller 13. Each of these is rotated (S109).

  Here, in step S109, the separation roller 11 is rotated together with the registration roller 13 on the assumption that the front end of the sheet is not in the nip of the transport roller pair RB, and the front end of the sheet is in the nip of the transport roller pair RB. This is because only a small amount of paper is conveyed by the separation unit RA. Next, the CPU 101 determines whether or not the driving amount of the paper feed motor 111 has reached the pulse PA (S111). The pulse PA is the number of pulses indicating the displacement of the paper feed motor 111 necessary for conveying the above-mentioned minute amount of paper. The CPU 101 repeats the process of step S111 until it is determined that the driving amount of the paper feed motor 111 has reached the pulse PA.

  If it is determined in step S111 that the drive amount of the paper feed motor 111 has reached the pulse PA (YES in S111), the CPU 101 stops the drive of the paper feed motor 111 (S113) and whether double feed is detected or not. Is determined (S115).

  If it is determined in step S115 that double feeding has been detected (YES in S115), the CPU 101 carries the paper downstream of the carrying roller pair RB without driving the paper feed motor 111. Then, the process ends. In this case, the CPU 101 does not drive the paper feed motor until the next paper is fed.

  If it is determined in step S115 that double feed is not detected (NO in S115), the CPU 101 determines whether or not it is the timing immediately before the trailing edge of the sheet passes through the nip of the separation portion RA (S117). The CPU 101 repeats the processing of step S117 until it is determined that the timing immediately before the trailing edge of the sheet passes through the nip of the separation unit RA.

  In step S117, when it is determined that the trailing edge of the sheet is just before the nip of the separation unit RA (YES in S117), the CPU 101 drives the sheet feeding motor 111 to rotate forward, thereby separating the separation roller 11. Is rotated (S119). As a result, a loop is formed on the sheet between the separation unit RA and the conveyance roller pair RB, and fluctuations in the conveyance speed when the rear end of the sheet passes through the nip of the separation unit RA can be suppressed.

  Next, the CPU 101 determines whether or not the driving amount of the paper feed motor 111 has reached the pulse PB (S121). The pulse PB is the number of pulses indicating the displacement of the paper feed motor 111 necessary to form a loop having a required size on the paper. The CPU 101 repeats the process of step S121 until it is determined that the driving amount of the paper feed motor 111 has reached the pulse PB.

  When it is determined in step S121 that the driving amount of the paper feed motor 111 has reached the pulse PB (S121). The CPU 101 stops driving the paper feed motor (S123) and ends the process.

  As an embodiment different from the above, in step S109, the rotation speed of the separation roller 11 may be set slower than the rotation speed of the registration roller, and the processes in steps S111 and S113 may be omitted. In this embodiment, when double feed is not detected (NO in S115), the loop formed in step S105 is maintained without being eliminated. If double feed is detected (YES in S115), the drive of the paper feed motor is stopped and the next paper feed motor drive request is awaited.

  [Effect of the embodiment]

  According to the above-described embodiment, when double feeding does not occur, the image forming apparatus causes the trailing edge of the sheet to be rolled while the loop is formed on the sheet between the transport roller pair RB and the separation roller 11. The conveying roller pair RB and the separation roller 11 are driven to rotate forward so as to pass. As a result, a rapid increase in the sheet conveyance speed when released from the back tension from the winding roller 12 is suppressed by the loop.

  When double feeding occurs, the image forming apparatus conveys the sheet by the conveying roller pair RB while stopping the forward rotation of the separation roller 11. In this case, since the paper to be conveyed is not in contact with the separating roller 12, the conveyed paper is only subjected to a small frictional force with the double-fed paper and is received by the conveyed paper. The back tension itself is reduced. As a result, as shown in FIG. 17, the fluctuation in the conveyance speed when the trailing edge of the sheet passes through the nip of the separation unit (area A1 in FIG. 17) becomes small.

  As a result of suppressing the rapid increase in the sheet conveyance speed, in an image forming apparatus equipped with a sheet feeding device, it is possible to suppress a decrease in image quality and improve the reproducibility of an input image. In an image reading apparatus equipped with a paper feeding device, it is possible to suppress the deterioration of the quality of a read image and improve the reproducibility of a document image.

  In addition, when double feeding occurs, the image forming apparatus stops the forward rotation driving of the separation roller 11, and therefore, due to the action of the separation roller 11 and the separating roller 12, double feeding is performed regardless of the use environment and the type of paper. It is possible to suppress the occurrence of transport.

  [Others]

  The paper feeding device of the present invention conveys a sheet (original) to be imaged to the image reading position P0, and also conveys a sheet to be imaged to the image forming position P1. It may be. In this case, the operation of the separation roller 11 may be performed by the separation roller 241a, the operation of the separation roller 12 may be performed by the separation roller 241b, and the operation of the conveyance roller pair RB may be performed by the conveyance roller pair 242.

  In the above-described embodiment, the case where the loop forming roller is in contact with the winding portion has been described. However, the loop forming roller is arranged at a distance from the winding portion on the downstream side of the conveying path from the winding portion. May be. In this case, a roller different from the loop forming roller that contacts the winding portion may be provided.

  The separating section may be any one that applies a force in the direction opposite to the sheet conveyance direction to the sheet. In addition to the case where the winding portion is constituted by a roller as described above, the winding portion may be constituted by a stationary member (pad) having a high friction coefficient.

  The above-described embodiments can be combined as appropriate. For example, a one-way clutch or a torque limiter provided together with the sensor having the second configuration shown in FIG. 13 may be applied together with the sensor having the first configuration.

  The processing in the above-described embodiment may be performed by software or by using a hardware circuit. It is also possible to provide a program for executing the processing in the above-described embodiment, and record the program on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, or a memory card and provide it to the user. You may decide to do it. The program is executed by a computer such as a CPU. The program may be downloaded to the apparatus via a communication line such as the Internet.

  The above-described embodiment is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 ADF (Auto Document Feeder)
11, 241a Separation roller 11a Separation roller rotation axis 12,241b Separation roller 12a Separation roller rotation axis 13,14 Registration roller 15,16 Reading roller 17 Discharge roller pair 20 Wall 21 Reflection sensor 22 Speed detection roller 22a Speed detection roller Large diameter portion 22b Small diameter portion of speed detection roller 31 Paper feed tray 32,261 Paper discharge tray 33 Torque limiter 34 One-way bearing 101 CPU (Central Processing Unit)
102 ROM (Read Only Memory)
103 RAM (Random Access Memory)
104 Network I / F
DESCRIPTION OF SYMBOLS 105 Image reading part 106 Operation panel 107 Auxiliary storage device 108 Image formation part 109 Double feed detection part 110 Conveyance control part 111 Paper feed motor 112 Registration motor 113 Conveyance motor 200 Fixing device 210 Toner image formation part 211 Photoconductor 212 Developing device 213 Intermediate Transfer belt 214 Transfer roller 220 Fixing device 221 Pressure roller 222 Heating roller 230 Paper feed cassette 240 Paper transport unit 241 Separation unit 242, RB Transport roller pair 243 Discharge roller pair 250 Scanner 251 IR (Infrared) module 252 Lamp 253 Image sensor A1 , A2 Area in the graph AR1 Paper transport direction AR2 Direction opposite to paper transport direction BW Black and white pattern OS Double-feed or accompanying paper P0 Image reading Position P1 image forming position RA separation unit RP1, RP2 loop SE sensors SH sheet TR conveying path

Claims (15)

A pair of transport rollers for transporting paper by being driven to rotate;
A loop forming roller that conveys paper by being rotationally driven on the upstream side of the conveying path from the conveying roller pair;
A separation unit that applies a force in a direction opposite to the paper conveyance direction on the upstream side of the conveyance path from the conveyance roller pair;
Abutting means for stopping the rotational driving of the transport roller pair and transporting the paper by rotationally driving the loop forming roller, thereby abutting the front end of the paper against the transport roller pair;
A detecting means for detecting the presence or absence of occurrence of double feeding;
When the detection unit does not detect the occurrence of double feeding, the conveying roller pair and the loop forming roller are rotated when the trailing edge of the paper passes the loop forming roller after the front edge of the paper is abutted by the abutting means. First conveying means for conveying paper by driving;
When the detection unit detects the occurrence of double feed, the conveying roller pair is driven to rotate and the loop is formed when the rear end of the paper passes the loop forming roller after the front end of the paper is abutted by the abutting means. A sheet feeding device comprising: a second transport unit configured to transport a sheet by stopping the rotation of the roller.   This is the size of the loop when the detection means does not detect the occurrence of double feed, and is formed on the paper between the pair of conveyance rollers and the loop forming roller when the trailing edge of the paper passes the loop forming roller. The size of the loop is the size of the loop when the detection means detects the occurrence of double feeding. When the trailing edge of the paper passes the loop forming roller, the loop between the conveying roller pair and the loop forming roller is The paper feeding device according to claim 1, wherein the paper feeding device is larger than a size of a loop formed on the paper in between.   The paper feeding device according to claim 1, wherein the loop forming roller is in contact with the winding portion.   When the detection unit detects the occurrence of double feed, the second transport unit transports the paper in contact with the loop forming roller in the paper transport direction, and the separation unit forms the paper in contact with the separation unit in a loop formation. The sheet feeding device according to claim 3, wherein the sheet feeding device is allowed to stay on the upstream side of the conveyance path with respect to the nip between the roller and the separating unit.   The sheet feeding device according to any one of claims 1 to 4, further comprising a clutch unit that allows rotation of the loop forming roller in a state where rotation driving is stopped in a conveyance direction.   The sheet feeding device according to claim 5, wherein the clutch unit is a one-way clutch that does not allow rotation in a direction opposite to a conveyance direction of the loop forming roller.   The first conveying unit stops and restarts the rotational driving of the loop forming roller between the time when the front end of the sheet is abutted by the abutting unit and the time when the rear end of the sheet passes the loop forming roller. The sheet feeding device according to any one of 1 to 6.   The first transport unit continuously drives the loop forming roller to rotate until the rear end of the sheet passes through the loop forming roller after the front end of the sheet is abutted by the abutting unit. The sheet feeding device according to any one of claims 6 to 6. The whispering part
A rolling roller in contact with the loop forming roller;
9. A torque limiter that includes a torque limiter that causes the roller to follow the movement of the paper or the loop forming roller when the frictional force between the paper or the loop forming roller and the roller reaches a predetermined value or more. A paper feeding device according to any one of the above.   The sheet feeding device according to claim 9, wherein the detection unit detects presence or absence of occurrence of double feed based on a rotation state of the roller. A rotating part that follows the rotation of the roller,
A sensor that irradiates the rotating part with light and receives reflected light;
The sheet feeding device according to claim 10, wherein the detection unit detects presence or absence of occurrence of double feed based on reflected light received by the sensor. A rotating part that rotates integrally with the roller,
A sensor that irradiates the rotating part with light and receives reflected light;
The sheet feeding device according to claim 10, wherein the detection unit detects presence or absence of occurrence of double feed based on reflected light received by the sensor. A rotating part that is coaxial with the roller and rotates independently of the roller,
A sensor that irradiates the rotating part with light and receives reflected light;
The sheet feeding device according to claim 9, wherein the detection unit detects presence or absence of occurrence of double feeding based on reflected light received by the sensor.   The sheet feeding device according to any one of claims 1 to 13, wherein the transport roller pair is rotationally driven by rotating one of two rollers constituting the transport roller pair and following the other. A pair of transport rollers for transporting paper by being driven to rotate;
A loop forming roller that conveys paper by being rotationally driven on the upstream side of the conveying path from the conveying roller pair;
A control program for a sheet feeding device including a separation unit that applies a force in a direction opposite to a sheet conveyance direction on a sheet upstream of a pair of conveyance rollers,
An abutting step of stopping the rotational driving of the transport roller pair and transporting the paper by rotationally driving the loop forming roller, thereby abutting the front end of the paper against the transport roller pair;
A detection step for detecting the presence or absence of occurrence of double feed;
When the detection step does not detect the occurrence of double feed, when the trailing edge of the paper passes the loop forming roller after hitting the front edge of the paper in the bumping step, each of the conveying roller pair and the loop forming roller is rotated. A first transport step for transporting the paper by driving;
When the double feed is detected in the detection step, when the rear end of the paper passes the loop forming roller after hitting the front edge of the paper in the hitting step, the conveyance roller pair is driven to rotate and the loop is formed. A control program for a sheet feeding device that causes a computer to execute a second transport step for transporting a sheet by stopping rotation of a roller.