JP2017222431A - Sheet transportation device, image reading device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a sheet from being broken during being fed by a simple configuration by detecting if a sheet is transported in a multi-feed state.SOLUTION: An automatic document transportation device 1 includes: a multi-feed sensor 34 for detecting multi-feed of transported sheets; a post-separation sensor 33 for detecting transported sheets; and CPU 151 for determining a state of multi-feed sheets detected by the multi-feed sensor 34 based on a multi-feed detection timing of sheets by the multi-feed sensor 34 and a sheet detection timing by the post-separation sensor 33.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine, a facsimile, or a printer includes an image reading device that reads an image of a document in the apparatus main body, and copies an image of the document on a sheet based on image reading information read by the image reading device. To do. As such an image reading apparatus, there is conventionally known an apparatus provided with an automatic document feeder (ADF) that automatically conveys a document to an image reading unit.

  In an image reading apparatus equipped with an automatic document feeder, there are cases where two or more documents are conveyed to the image reading unit in a double feed state depending on the paper quality, temperature, or humidity of the document from which images are read. . When a document is conveyed in such a double feed state, a paper jam (JAM) or an image reading error may occur, or the document may be damaged.

  On the other hand, Patent Document 1 discloses an image reading apparatus including an automatic document feeder that prevents double feeding of documents. An automatic document conveying device disclosed in Patent Document 1 includes a conveying unit that conveys a sheet, a separating mechanism that separates multi-feed sheets, and a weight that is disposed downstream of the separating mechanism in the sheet conveying direction. And a feed detection sensor. In the automatic document feeder disclosed in Patent Document 1, when a double feed is detected by a double feed detection sensor, the separation capability is increased by changing the pressure contact pressure in the nip of the separation mechanism, and the double feed of the document is performed. Eliminate.

JP, 2015-101457, A

  However, in Patent Document 1, since double feed is detected using only a double feed detection sensor, a so-called complete double feed state in which a plurality of sheets are completely overlapped and a so-called double feed in which a part of a plurality of sheets are overlapped. The double feed state of the sheet such as the state cannot be determined. From this, in order to change the pressure contact pressure of the separation mechanism even during full double feed and try to eliminate double feed, if the staple sheet that is completely double fed or the adhered sheet is conveyed by mistake, Since these sheets are forcibly separated, the sheets may be damaged.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying apparatus that can determine a double feeding state of a sheet being fed and can prevent breakage of the fed sheet with a simple configuration. .

  A sheet conveying apparatus according to the present invention includes a multi-feed detecting unit that detects multi-feed of a conveyed sheet, a sheet detecting unit that detects a conveyed sheet, and a multi-feed detection timing of the sheet by the multi-feed detecting unit. And determining means for determining the state of the double feed sheet detected by the double feed detection means based on the sheet detection timing by the sheet detection means.

  An image reading apparatus according to the present invention includes the sheet conveying apparatus described above and an image reading unit that reads an image of the sheet conveyed by the sheet conveying apparatus.

  An image forming apparatus according to the present invention includes the above-described sheet conveying apparatus and an image forming unit that forms an image on a sheet conveyed by the sheet conveying apparatus.

  According to the present invention, it is possible to prevent the sheet being fed with a simple configuration from being damaged.

1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view of an automatic document feeder according to an embodiment of the present invention. 1 is a block diagram showing a configuration of an automatic document feeder according to an embodiment of the present invention. It is a perspective view of the pressurization separation mechanism in the normal pressurization mode concerning an embodiment of the invention. It is a side view of the cam in the normal pressurization mode concerning an embodiment of the invention. It is a perspective view of the pressurization separation mechanism in the pressurization reduction mode concerning an embodiment of the invention. It is a side view of the cam in the pressurization reduction mode which concerns on embodiment of this invention. It is a perspective view of the pressurization separation mechanism in separation mode concerning an embodiment of the invention. It is a side view of the cam in the separation mode according to the embodiment of the present invention. It is a figure which shows the structure of the pick-up roller which concerns on embodiment of this invention, and its drive system. It is a flowchart which shows the document conveyance control process which concerns on embodiment of this invention. It is a figure which shows the determination result of the double feeding state which concerns on embodiment of this invention. It is a figure which shows the double feed state of the sheet | seat which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Configuration of image forming apparatus>
The configuration of the image forming apparatus 100 according to the embodiment of the present invention will be described in detail with reference to FIG.

  The image forming apparatus according to the present embodiment is, for example, a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, and has an image reading function.

  The image forming apparatus 100 shown in FIG. 1 is exemplified here as a copying machine. Specifically, the image forming apparatus 100 includes the image reading apparatus 2 and an apparatus main body 100A.

  The image reading apparatus 2 is provided on the upper part of the apparatus main body 100A and reads an image of the document D that is a sheet. Specifically, the image reading device 2 includes an automatic document feeder (ADF: auto document feeder) 1 and an image reading unit 2A.

  The automatic document conveying device 1 as a sheet conveying device separates a plurality of documents D stacked on a document tray 3 as a stacking unit by a user one by one, and the separated documents D are illustrated in the automatic document conveying device 1. It is automatically transported to the transport path that does not. The automatic document feeder 1 discharges and stacks the document whose image has been read by the image reading unit 2A onto the discharge tray. Details of the configuration of the automatic document feeder 1 will be described later.

  In the image reading unit 2 </ b> A, the image reading unit 104 receives reflected light of light emitted from a light source (not shown) on the document D conveyed by the automatic document conveying device 1. The image reading unit 2A optically reads the image of the document D from the reflected light received by the image reading unit 104, converts the image into an electrical signal, and creates image data based on the electrical signal. The image reading unit 2A outputs the created image data to the apparatus main body 100A.

  The apparatus main body 100A forms a copy image of the image read by the image reading apparatus 2 on a sheet.

  Specifically, the apparatus main body 100A includes a photosensitive drum 121, a charger 122, an exposure unit 123, a developing unit 124, a transfer charger 125, a separation charger 126, and a cleaner 127. ing. The apparatus main body 100 </ b> A includes a transport unit 128, a fixing device 129, a discharge tray 130, a transport roller 131, a control unit 132, an image forming unit 133, and a registration roller pair 136. Further, the apparatus main body 100A includes sheet placement portions 137a, 137b, 137c, and 137d, a manual feed tray 137e, and feeding rollers 138a, 138b, 138c, and 138d. The photosensitive drum 121, the charger 122, the developing device 124, and the fixing device 129 constitute an image forming unit 133.

  The surface of the photosensitive drum 121 is uniformly charged by the charger 122. When the photosensitive drum 121 is irradiated with laser light corresponding to the image data from the exposure unit 123, the charge charged by the charger 122 in the portion irradiated with the laser light is removed, and the photosensitive drum 121 corresponds to the image data. An electrostatic latent image is formed.

  The charger 122 charges the surface of the photosensitive drum 121 when a predetermined bias voltage is applied.

  The exposure unit 123 operates based on the image data created by the image reading device 2 and forms an electrostatic latent image on the surface of the rotating photosensitive drum 121 by irradiating the surface of the photosensitive drum 121 with laser light. To do.

  The developing device 124 supplies toner to the electrostatic latent image formed on the surface of the photoconductive drum 121 and develops it, and generates a toner image on the surface of the photoconductive drum 121.

  The transfer charger 125 transfers the toner image formed on the surface of the photosensitive drum 121 onto the sheet S.

  The separation charger 126 separates the toner image formed on the surface of the photosensitive drum 121 from the photosensitive drum 121.

  The cleaner 127 cleans the surface of the photosensitive drum 121 on which the toner image is transferred to the sheet S.

  The conveyance unit 128 conveys the sheet S on which the toner image is transferred by the transfer charger 125 toward the fixing device 129.

  The fixing device 129 heats and pressurizes the sheet S to which the toner image conveyed from the conveying unit 128 is transferred, and fixes the toner image on the surface of the sheet S. The fixing device 129 discharges the sheet S on which the toner image is fixed to the discharge tray 130.

  The conveying roller 131 conveys the sheet S fed by the feeding roller 138a, the feeding roller 138b, the feeding roller 138c, or the feeding roller 138d toward the registration roller pair 136.

  The registration roller pair 136 corrects the skew of the sheet S by causing the leading edge of the sheet S to follow the nip when the rotation is stopped. The registration roller pair 136 supplies a sheet S with corrected skew between the photosensitive drum 121 and the transfer charger 125 in synchronization with the timing at which the toner image is formed on the surface of the photosensitive drum 121.

  The sheet placing unit 137a, the sheet placing unit 137b, the sheet placing unit 137c, or the sheet placing unit 137d is provided in the lower part of the apparatus main body 100A and can load sheets S of various sizes.

  The manual feed tray 137e can place sheets S of various sizes.

  The feeding roller 138 a takes out the sheets S loaded in the sheet placement unit 137 a one by one from the sheet placement unit 137 a and conveys the sheets S toward the conveyance roller 131. The feeding roller 138 b takes out the sheets S loaded in the sheet placement unit 137 b one by one from the sheet placement unit 137 b and conveys them toward the conveyance roller 131. The feeding roller 138 c takes out the sheets S loaded in the sheet placement unit 137 c one by one from the sheet placement unit 137 c and conveys the sheets S toward the conveyance roller 131. The feeding roller 138d takes out the sheets S loaded in the sheet placement unit 137d one by one from the sheet placement unit 137d and conveys the sheets S toward the conveyance roller 131.

  The feeding roller 138e takes out the sheets S placed on the manual feed tray 137e one by one from the manual feed tray 137e, and conveys the sheets S toward the registration roller pair 136.

<Configuration of automatic document feeder>
The configuration of the automatic document feeder 1 according to the embodiment of the present invention will be described in detail with reference to FIGS.

  The automatic document feeder 1 includes a pickup roller 4, a feed roller 5, a retard roller 6, a pressure spring 7, a registration roller 8, a registration sensor 9, and a torque limiter 16. Further, the automatic document feeder 1 includes a roller holder 17, a conveyance guide frame 18, a tension spring 19, a cam follower 20, a post-separation sensor 33, a multifeed sensor 34, a CPU 151, a RAM 152, a ROM 153, have. The pressure spring 7, the roller holder 17, the conveyance guide frame 18, the tension spring 19, and the cam follower 20 constitute a pressure separation mechanism 240 that adjusts the pressure of the retard roller 6 against the feed roller 5. . The operation panel 160 is provided in the apparatus main body 100A.

  The pickup roller 4 descends from the standby position and contacts the uppermost document D among the plurality of documents D placed on the document tray 3, and the uppermost document D is moved by the frictional force when rotating. The sheet is fed to the feed roller 5 through the conveyance path of the document D which is a sheet conveyance path.

  The feed roller 5 is rotated to convey the document D fed from the pickup roller 4 toward the registration roller 8 disposed on the downstream side in the conveyance direction via the conveyance path.

  The retard roller 6 which is a sheet separating means is urged by a tension spring 19 and a pressure spring 7 and presses against the feed roller 5 with a predetermined separation pressure to form a nip N. The retard roller 6 is pressed against the feed roller 5 with a predetermined separation pressure to obtain a predetermined separation force for separating the document D being conveyed. The retard roller 6 is driven to rotate by the feed roller 5 via the document D, or rotates so as to transport the document D in the direction opposite to the transport direction via a torque limiter 16 described later.

  When a single document D is conveyed from the pickup roller 4 to the nip N, the retard roller 6 receives a rotational torque exceeding the torque of the torque limiter 16 due to the frictional force generated between the retard roller 6 and the document roller D. The document D is transported in the transport direction.

  The retard roller 6 is reverse to the rotation direction when one or more originals D are conveyed to the nip N when two or more originals D are fed from the pickup roller 4 and conveyed to the nip N. Rotate in the direction to resist passage of the original D other than the uppermost one through the nip N. The retard roller 6 rotates in the reverse direction and pushes back the document D other than the uppermost sheet D in the direction opposite to the transport direction, thereby pushing the document D other than the uppermost sheet D back to the document tray 3 side.

  The pressure spring 7 is provided between the roller holder 17 and the conveyance guide frame 18. The pressure spring 7 biases the roller holder 17 to rotate about the rotation shaft 17j, thereby bringing the retard roller 6 into contact with the feed roller 5 through the roller holder 17 to form the nip N. .

  The registration roller 8 stands by in a stopped state and corrects the skew of the document D by causing the leading end of the document D conveyed by the feed roller 5 to abut the nip in the stopped state. The registration roller 8 starts to rotate in accordance with the reading timing of the document D, and conveys the document D toward the reading area on the glass plate 101 of the image reading unit 2A.

  The registration sensor 9 is disposed between the feed roller 5 and the registration roller 8. The registration sensor 9 detects that the document D conveyed from the feed roller 5 is conveyed to the nip of the registration roller 8.

  The torque limiter 16 is connected to the retard roller 6 and applies a predetermined rotational load torque to the retard roller 6. Specifically, the torque limiter 16 regulates the rotational torque generated by the frictional force in the transport direction of the document D by the feed roller 5 when the document D is not transported. The torque limiter 16 receives the driving force of the drive shaft 15 that rotates in the direction opposite to the conveyance direction of the document D when the document D is held at the nip N. The torque limiter 16 receives the driving force of the drive shaft 15, thereby restricting the rotational torque that causes the original D of the retard roller 6 caused by the frictional force between the original D to be conveyed and the retard roller 6 to be conveyed in the conveying direction. To do.

  The roller holder 17 is supported so as to be rotatable about a rotation shaft 17j, and supports the retard roller 6 so as to be able to contact and separate from the feed roller 5.

  The conveyance guide frame 18 supports the rotation shaft 17j of the roller holder 17, and guides the document D from the document tray 3 to the downstream side in the conveyance direction on the upper conveyance surface.

  The tension spring 19 is attached to the roller holder 17 on the opposite side of the pressure spring 7 with respect to the rotation shaft 17j, and biases the roller holder 17 in a direction opposite to the biasing direction of the pressure spring 7.

  The cam follower 20 is rotatably supported with respect to the conveyance guide frame 18 by a rotation shaft 20j.

  The first cam 21 and the second cam 22 operate by the action of the solenoid SL1. The second cam 22 is disposed coaxially and in parallel with the first cam 21, and operates by the action of the solenoid SL1 to swing the roller holder 17.

  The post-separation sensor 33 that is a sheet detection unit is disposed downstream of the nip N in the conveyance direction of the sheet S. The post-separation sensor 33 detects the document D conveyed on the conveyance path, and outputs the detection result to the CPU 151 described later. The post-separation sensor 33 can detect the leading end of the transported document D in the transport direction.

  The double feed sensor 34 which is a double feed detecting means is arranged at a position where the fed document can be detected at a position on the same line orthogonal to the post-separation sensor 33 and the conveyance direction. The double feed sensor 34 detects a double feed of the document D conveyed on the conveyance path, and outputs an output signal corresponding to the detection result to the CPU 151.

  Here, the double feed sensor 34 is exemplified by an ultrasonic sensor. In the case of an ultrasonic sensor, the double feed sensor 34 includes a transmitting element 34a and a receiving element 34b as shown in FIG. The double feed sensor 34 transmits an ultrasonic signal from the transmitting element 34 a to the document D under the control of the CPU 151, and receives the ultrasonic signal transmitted from the transmitting element 34 a via the document D by the receiving element 34 b. The double feed sensor 34 outputs an output signal having a different attenuation amount to the CPU 151 depending on whether or not the document D received by the receiving element 34b is double fed. For example, the multi-feed sensor 34 outputs to the CPU 151 output signals having different attenuation amounts for one original and two originals fed in multi-feed.

  The document detection sensor 35 detects the document D on the document tray 3 and outputs the detection result to the CPU 151.

  The control unit 132 controls the operation of the automatic document feeder 1 based on a signal input from an operation panel 160 provided in the apparatus main body 100A. Specifically, the control unit 132 includes a CPU 151, a RAM 152, and a ROM 153.

  The CPU 151 serving as a determination unit reads the control program stored in the ROM 153 from the ROM 153 to the RAM 152 and controls the conveyance of the document D and the like. The CPU 151 controls the operation of the drive source 210, the clutch CL1, the clutch CL2, or the clutch CL3 according to the detection results of the document detection sensor 35, the post-separation sensor 33, the double feed sensor 34, or the registration sensor 9. The CPU 151 performs control to start energization or stop energization of the solenoid SL1 or the solenoid SL2 according to the detection result of the document detection sensor 35, the post-separation sensor 33, the double feed sensor 34, or the registration sensor 9.

  The CPU 151 determines the state of the multi-feed original D, which is a multi-feed sheet detected by the multi-feed sensor 34, based on the double feed detection timing of the original D by the multi-feed sensor 34 and the sheet detection timing by the original detection sensor 35. judge. The CPU 151 stops the conveyance of the document D or controls the pressure separation mechanism 240 based on the determination result of the state of the multi-feed document D. The CPU 151 changes the separation force of the retard roller 6 by controlling the pressure separation mechanism 240 and switching the position of the retard roller 6 according to the normal pressure mode, the pressure reduction mode, or the separation mode. The CPU 151 causes the sheet S feeding operation to be executed intermittently and continuously when the document detection sensor 35 detects the sheet S.

  The CPU 151 displays a message such as double feeding of the sheet S on the monitor screen of the operation panel 160 and notifies the user.

  The operation panel 160 detects an operation by the user, outputs a signal corresponding to the detected operation to the CPU 151, and displays a message to the user under the control of the CPU 151.

  The drive source 210 is a drive motor that drives the pickup roller 4, the feed roller 5, or the retard roller 6 under the control of the CPU 151.

  The clutch CL <b> 1 rotates the registration roller 8 or stops the rotation of the registration roller 8 under the control of the CPU 151.

  The clutch CL <b> 2 rotates the pickup roller 4 and the feed roller 5 or stops the rotation of the pickup roller 4 and the feed roller 5 under the control of the CPU 151.

  The clutch CL3 rotates the retard roller 6 or stops the rotation of the retard roller 6 under the control of the CPU 151.

<Operation of automatic document feeder>
The operation of the automatic document feeder 1 according to the embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 5A shows a state in which the pressure separation mechanism 240 of FIG. 4 is viewed from the tension spring 19 side. FIG. 7A shows a state in which the pressure separation mechanism 240 in FIG. 6 is viewed from the tension spring 19 side. FIG. 9A shows a state in which the pressure separation mechanism 240 of FIG. 8 is viewed from the tension spring 19 side. FIG. 5B shows a state in which the pressure separation mechanism 240 of FIG. 4 is viewed from the photosensor 24a and photosensor 24b side. FIG. 7B shows a state in which the pressure separation mechanism 240 of FIG. 6 is viewed from the photosensor 24a and the photosensor 24b side. FIG. 9B shows a state in which the pressure separation mechanism 240 of FIG. 8 is viewed from the photosensors 24a and 24b side.

  In FIG. 10, the retard roller 6 is illustrated downstream of the feed roller 5 in the conveyance direction of the document D for convenience of illustration, but actually, the feed roller 5 is located below the feed roller 5 when viewed from above. It is arranged to overlap.

  As shown in FIGS. 5 (a), 7 (a) and 9 (a), the tension spring 19 is attached to the cross bar 17p of the roller holder 17, and in the direction opposite to the urging direction of the pressure spring 7. The roller holder 17 is urged. The tension spring 19 is attached to a hook hanging portion 20e provided on the rotating end side of the cam follower 20.

  The driving force of the driving source 210 is distributed to the pickup roller 4, the feed roller 5, the retard roller 6, and the registration roller 8 by the gear train 220 shown in FIG.

  The pickup roller 4 moves up and down when the solenoid SL2 rotates the arm 4a around the rotation axis of the feed roller 5. The pickup roller 4 descends when the energization of the solenoid SL2 is started under the control of the CPU 151, and comes into contact with the document D on the document tray 3. The pickup roller 4 rises when the power supply to the solenoid SL <b> 2 is stopped under the control of the CPU 151 and is separated from the document D on the document tray 3.

  The pickup roller 4 rotates in the same conveying direction as the feed roller 5 in conjunction with the rotation of the feed roller 5 by the toothed belt 4 b shown in FIG. 10, and sends the document D from the document tray 3 to the nip N.

  In the normal pressure mode shown in FIGS. 4 and 5, the drive shaft 5a of the feed roller 5 rotationally drives the feed roller 5 so as to transport the document D in the transport direction.

  In the pressurization reduction mode shown in FIGS. 6 and 7, the first cam 21 contacts the rotation end of the cam follower 20 and swings the cam follower 20 with the rotation by the action of the solenoid SL1. As shown in FIG. 7A, the cam follower 20 rotates and changes the length of the tension spring 19 with the rotation of the first cam 21, thereby changing the biasing force of the cam follower 20 by the tension spring 19. . As a result, the pressure applied to the feed roller 5 by the retard roller 6 can be changed with high reproducibility.

  In the separation mode shown in FIGS. 8 and 9, the second cam 22 contacts the cross bar 17p at a predetermined rotation angle on the opposite side of the pressure spring 7 across the rotation shaft 17j of the roller holder 17. The second cam 22 forcibly separates the retard roller 6 from the feed roller 5 by rotating and lifting the roller holder 17 against the urging force of the pressure spring 7.

  Here, in the automatic document feeder 1, when the document D fed in the nip N fails to be separated while the document D is being transported in the normal pressure mode, the document D fed in the nip N It is transported downstream in the transport direction.

  When a plurality of originals D are transported downstream in the transport direction of the nip N, the second and subsequent originals D are skipped, and the value of the read image data Is damaged. When the double-fed original D is separated after passing through the nip N, two overlapping originals are read as one long original, resulting in a reading error. When the above double feed occurs, jamming may occur in the second document D with a high probability, the conveyance of the document D, etc. may be interrupted, and the valuable document D may be broken and damaged.

  On the other hand, when the double feed of the document D is detected by the double feed sensor 34, the CPU 151 releases the pressure force of the tension spring 19 by the pressure separation mechanism 240, and the feed roller 5 and the retard roller 6. The pressure reduction mode in which the contact pressure is reduced is set. As a result, it is possible to avoid a state in which a plurality of documents D are conveyed downstream in the conveyance direction of the nip N in a state where the plurality of documents D are fed.

  The CPU 151 separates the retard roller 6 and the feed roller 5 by the pressure separation mechanism 240 when the double feed sensor 34 detects the double feed again in the pressure reduction mode and the double feed sensor 34 detects the double feed again. And the separation mode shown in FIG.

<Document transport control processing>
The document conveyance control process according to the embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 11 is a flowchart showing the document conveyance control process, FIG. 12 is a diagram showing the determination result of the double feed state, and FIG. 13 is a diagram showing the double feed state of the sheet.

  In S <b> 2 of FIG. 11, “ON” indicates that the document D is detected by the post-separation sensor 33, and “OFF” indicates that the document is not detected by the post-separation sensor 33. In S3 of FIG. 11, “ON” indicates that double feed is detected by the double feed sensor 34, and “OFF” indicates that double feed is not detected by the double feed sensor 34. Further, in S8 of FIG. 11, “ON” indicates that the document D on the document tray 3 is detected by the document detection sensor 35, and “OFF” indicates that the document D on the document tray 3 is not detected by the document detection sensor 35. Show.

  The CPU 151 sets the normal pressurization mode before starting to feed the document D. Thereby, a high nip pressure is set in the nip N. The retard roller 6 rotates following the feed roller 5 by idling the torque limiter 16.

  In this state, first, when the user performs a reading start command operation in a state where the document on the document tray 3 is detected by the document detection sensor 35, the CPU 151 starts conveying the document D for image reading. (S1).

  Next, the CPU 151 determines whether or not the post-separation sensor 33 has detected the document D (determines whether or not the post-separation sensor 33 has been turned on) (S2).

  When the post-separation sensor 33 does not detect the document D (S2: No), the CPU 151 repeats the process of S2.

  On the other hand, when the post-separation sensor 33 detects the document D (S2: Yes), the CPU 151 determines whether or not the double feed sensor 34 detects double feed (whether or not the double feed sensor 34 is turned on). (S3).

  When the multifeed sensor 34 detects double feed (S3: Yes), the CPU 151 double feeds because the multifeed sensor 34 is “ON” and the post-separation sensor 33 is “ON” as shown in FIG. Judge that Thus, the CPU 151 calculates the detection time difference T between the document detection timing when the post-separation sensor 33 detects the document and the double feed detection timing when the double feed sensor 34 detects the double feed. The CPU 151 determines whether or not the calculated detection time difference T is greater than or equal to a predetermined value (S4). Here, the predetermined value is 5 msec.

  When the detection time difference T is less than the predetermined value (S4: No), the CPU 151 determines that a so-called complete double feed state in which most of the two or more originals D shown in FIG. At this time, the CPU 151 determines that the document D cannot be separated, stops the transport of the document D (S5), and ends the document transport control process.

  On the other hand, when the detection time difference T is greater than or equal to a predetermined value (S4: Yes), the CPU 151 is in a so-called double feed state in which a part of two or more documents D shown in FIG. It is determined that the document D can be separated. Accordingly, the CPU 151 adjusts the separation pressure of the retard roller 6 with respect to the feed roller 5 by switching from the normal pressure mode to the pressure reduction mode and changing the position of the retard roller 6 (S6). The separation force is changed and the process proceeds to S7.

  Further, when the multifeed sensor 34 does not detect double feed in the process of S3 (S3: No), as shown in FIG. 12, the multifeed sensor 34 is “OFF” and the post-separation sensor 33 is “ON”. Therefore, it is determined that one document D is being conveyed. Thereby, the CPU 151 determines whether or not the document detection sensor 35 has detected the document D (determines whether or not the document detection sensor 35 has been turned on) (S7).

  When the document detection sensor 35 does not detect the document D (S7: No), the CPU 151 ends the document conveyance control process.

  On the other hand, when the document detection sensor 35 detects the document D (S7: Yes), the CPU 151 returns to the process of S2.

  As shown in FIG. 12, when the multifeed sensor 34 is “ON” and the post-separation sensor 33 is “OFF”, the CPU 151 determines that the apparatus is abnormal, and the multifeed sensor 34 is “OFF”. When the post-separation sensor 33 is “OFF”, it can be determined that the document D is not conveyed.

  The CPU 151 can reliably determine the double feed state of the conveyed document D by the above operation.

  Thus, in the present embodiment, the double feed document D detected by the double feed sensor 34 based on the double feed detection timing of the original D by the double feed sensor 34 and the original detection timing of the post-separation sensor 33. Determine the state. Thereby, it is possible to prevent the document fed with a simple configuration from being damaged.

  In the present embodiment, the configuration and operation when the document D is conveyed in the image reading apparatus 2 have been described. However, the configuration and operation when the sheet S is fed to form an image in the apparatus main body 100A may be used. .

  In the present embodiment, the post-separation sensor 33 and the double feed sensor 34 are provided on the same line in the direction orthogonal to the conveyance direction of the original D. However, the post-separation sensor 33 and the double feed sensor 34 are provided on the original. You may provide in a different position in the conveyance direction of D.

  In this case, for example, the CPU 151 subtracts the time obtained from the distance between the post-separation sensor 33 and the double feed sensor 34 and the conveyance speed of the document D from the detection time difference T calculated in S4 of FIG. Then, the CPU 151 determines a double feed state when a time difference occurs in the subtraction result, and determines a complete double feed state when a time difference does not occur in the subtraction result. As described above, the CPU 151 determines the state of the double-fed document D based on the double-feed detection timing and the document detection timing corresponding to the detection positions of the post-separation sensor 33 and the multi-feed sensor 34.

CL1 clutch CL2 clutch CL3 clutch SL1 solenoid SL2 solenoid 1 automatic document feeder 2 image reading device 2A image reading unit 3 document tray 4 pickup roller 4a arm 4b belt 5 feed roller 5a drive shaft 6 retard roller 8 registration roller 9 registration sensor 10 cleaning device Reference Signs List 14 Discharge tray 15 Drive shaft 16 Torque limiter 17 Roller holder 17j Rotating shaft 17p Crossbar 18 Transport guide frame 20 Cam follower 20e Hook hook 20j Rotating shaft 21 First cam 22 Second cam 33 Post-separation sensor 34 Double feed sensor 34a Transmission Element 34b Receiving element 35 Document detection sensor 100 Image forming apparatus 100A Apparatus main body 101 Glass plate 104 Image reading unit 121 Photosensitive drum 122 Charger 1 DESCRIPTION OF SYMBOLS 23 Exposure part 124 Developing device 125 Transfer charger 126 Separation charger 127 Cleaner 128 Transport unit 129 Fixing device 130 Discharge tray 131 Transport roller 132 Control unit 133 Image forming unit 136 Registration roller pair 137a Sheet placement unit 137b Sheet placement unit 137c Sheet placement unit 137d Sheet placement unit 137e Manual feed tray 138a Feed roller 138b Feed roller 138c Feed roller 138d Feed roller 138e Feed roller 160 Operation panel 210 Drive source 220 Gear train 240 Pressure separation mechanism

Claims (7)

A double feed detecting means for detecting double feed of the conveyed sheet;
Sheet detecting means for detecting a conveyed sheet;
A determination unit for determining a state of the multi-feed sheet detected by the multi-feed detection unit based on a double-feed detection timing of the sheet by the multi-feed detection unit and a sheet detection timing by the sheet detection unit;
A sheet conveying apparatus comprising: The multi-feed detection means and the sheet detection means are arranged in a sheet conveyance path,
The determination means includes
Determining the state based on the double feed detection timing and the sheet detection timing according to a detection position in the sheet conveyance direction of the double feed detection unit and the sheet detection unit;
The sheet conveying apparatus according to claim 1. The determination means includes
When the detection time difference between the double feed detection timing and the sheet detection timing is less than a predetermined value, the conveyance of the sheet being fed is stopped.
3. A sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. Having sheet separating means for separating the conveyed sheet;
The determination means includes
When the detection time difference between the double feed detection timing and the sheet detection timing is a predetermined value or more, the separation force of the separation unit is changed.
The sheet conveying device according to any one of claims 1 to 3, wherein the sheet conveying device is provided. The determination means includes
When the detection time difference between the multi-feed detection timing and the sheet detection timing is less than a predetermined value, it is determined that at least a plurality of sheets are completely overlapped,
The sheet conveying apparatus according to any one of claims 1 to 4, wherein the sheet conveying apparatus is provided. A sheet conveying device according to any one of claims 1 to 5,
Image reading means for reading an image of the sheet conveyed by the sheet conveying device;
An image reading apparatus comprising: A sheet conveying device according to any one of claims 1 to 5,
Image forming means for forming an image on the sheet conveyed by the sheet conveying device;
An image forming apparatus comprising:

Images