JP5604376B2 - Paper feeding device and image forming apparatus - Google Patents

Description

 The present invention relates to a sheet feeding device and an image forming apparatus.

  In general, an image forming apparatus such as a copier, a printer, or a multifunction peripheral includes a paper feeding device that feeds paper stored in a paper storage unit one by one. The sheet feeding device is configured to feed one sheet at a time from the top sheet of the sheet bundle to the sheet conveyance path by a sheet feeding roller (also referred to as a pickup roller) that is pressed against the top surface of the sheet bundle and rotates in the sheet feeding direction. However, there may occur a phenomenon in which a plurality of sheets are simultaneously sent out to the sheet conveyance path (hereinafter, this phenomenon is referred to as double feeding).

  In Patent Document 1 below, when a sheet fed from a sheet cassette to a sheet conveyance path by a pickup roller is conveyed to a predetermined position on the sheet conveyance path by the conveyance roller, the conveyance roller is rotated in the reverse direction so that the first sheet Discloses a technique for preventing double feeding of paper by returning the second and subsequent papers, which are conveyed while being overlapped with the paper, to the paper cassette side.

  In addition, a general paper feeding device is arranged on the downstream side of the paper feeding roller and rotates forward in the paper feeding direction, and is opposed to the paper feeding roller, and the rotation shaft is connected with a torque limiter. In many cases, a double feed prevention mechanism including a roller is provided. In this torque limiter, when the number of sheets sandwiched between the conveying roller and the separating roller is one, the separating roller is driven by the conveying roller, while when the number of sheets is plural, the separating roller is stopped (or reversely rotated). When the torque is applied, it is set to rotate backward).

  As described above, when the number of sheets sent to the sheet conveyance path by the sheet feeding roller is one sheet, the separation roller follows the conveyance roller, so that the sheet is moved to the downstream side in the sheet feeding direction (downstream of the sheet conveyance path). On the other hand, when a plurality of sheets are conveyed normally, the first roller on the conveying roller side is normally conveyed to the downstream side in the paper feeding direction by stopping the roll roller (or rotating in reverse). Since the second and subsequent sheets on the side of the separating roller stop at that position (or return to the upstream side in the sheet feeding direction), it is possible to prevent double feeding.

  Even if the double feed prevention mechanism as described above is provided, the occurrence of double feed cannot be prevented 100%. Therefore, conventionally, a double feed detection sensor that detects the physical quantity related to the paper thickness is provided downstream of the double feed prevention mechanism, and a paper jam error occurs when the occurrence of double feed is detected from the output signal. In this case, the user is requested to take a measure against the paper jam, or the image forming operation is interrupted by forcibly discharging the paper.

JP 2006-16182 A

  As described above, conventionally, a paper jam error occurs or an image forming operation is interrupted each time a double feed occurs that cannot be prevented by the double feed prevention mechanism, resulting in a reduction in user work efficiency. It was.

 The present invention has been made in view of the above-described circumstances, and an object of the present invention is to improve the user's business efficiency by suppressing the frequency of occurrence of double feed.

 In order to solve the above-described problems, in the present invention, as a first solution means for the paper feeding device, as a paper double feed prevention mechanism, a feed roller that rotates forward in the paper feeding direction and a reverse feed through a torque limiter are provided. A sheet feeding device that rotates in the reverse direction in the sheet direction and includes a separating roller that follows the conveying roller when a single sheet is fed, and is disposed on the downstream side of the double feed prevention mechanism. A double feed detection sensor for detecting a physical quantity corresponding to the number of sheets, and a double feed occurrence frequency on the downstream side of the double feed prevention mechanism for each job based on an output signal of the double feed detection sensor, and the double feed occurrence And a controller that slows the reverse rotation speed of the roller when the frequency is equal to or higher than a first threshold and restores the reverse rotation speed when the current job is finished.

  According to the present invention, as the second solving means relating to the sheet feeding device, in the first solving means, the control unit is configured to perform the above-described multifeed occurrence frequency when the current job is equal to or more than the first threshold. Decreases the reverse rotation speed of the roller and determines whether the reverse rotation speed of the roller has been reduced in the past job. If not, the reverse rotation speed is restored to the original at the end of the current job. On the other hand, when the speed is slow, the reverse rotation speed is not restored and the user is notified that the productivity is lowered.

  In the present invention, as the third solving means relating to the sheet feeding device, in the second solving means, the control unit is executing a job after a job in which the reverse rotation speed of the roller is not restored. When the double feed occurrence frequency is less than the second threshold value, the reverse rotation speed is restored after the current job is ended. On the other hand, when the double feed occurrence frequency is not less than the third threshold value, the current job is finished. The reverse rotation speed is returned to the original, and the user is notified that the maintenance time of the roller has arrived.

  Further, according to the present invention, as a solving means related to the image forming apparatus, a paper feeding apparatus having any one of the first to third solving means and a toner image is transferred to a paper fed from the paper feeding apparatus. A toner image transfer unit, a fixing unit that fixes the toner image transferred onto the paper, and a paper discharge unit that discharges the paper on which the toner image is fixed.

According to the present invention, based on the output signal of the double feed detection sensor, the double feed occurrence frequency on the downstream side of the double feed prevention mechanism is obtained for each job, and the double feed occurrence frequency is equal to or more than a first threshold value. By reducing the reverse rotation speed of the roller, the success rate of preventing double feed by the double feed prevention mechanism can be increased. As a result, it is possible to reduce the frequency of occurrence of double feeds and improve user work efficiency.
The double feed prevention success rate by the double feed prevention mechanism is greatly affected by the type of paper used for each job (friction force between papers), so for jobs that use slippery (weak frictional) paper. If the frequency of double feed increases, the reverse rotation speed of the roller is reduced at the end of the job, which may reduce the productivity of jobs that use paper with normal friction after that. However, in the present invention, since the reverse rotation speed of the roller is restored when the current job is completed, it is possible to avoid a decrease in productivity in subsequent jobs.

1 is a schematic configuration diagram of a multifunction peripheral A according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a configuration of a sheet feeding device included in the multifunction peripheral A. 6 is a flowchart illustrating a control procedure of a paper feeding operation executed by a control unit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Hereinafter, as an image forming apparatus according to the present invention, a multi-function machine having functions such as a copier, a printer, a scanner, and a facsimile will be described as an example.
FIG. 1 is a schematic configuration diagram of a multifunction peripheral A according to the present embodiment. As shown in FIG. 1, the MFP A includes an operation display unit 1, an image reading unit 2, an image data storage unit 3, a paper transport image forming unit 4, a communication unit 5, and a control unit 6.

   The operation display unit 1 includes operation keys and a touch panel, and functions as a man-machine interface that associates the user with the multifunction peripheral A. The operation display unit 1 outputs an operation instruction of a pressed operation key or an operation button displayed on the touch panel to the control unit 6 and displays various screens on the touch panel based on a control signal input from the control unit 6. indicate.

   Under the control of the control unit 6, the image reading unit 2 reads a surface image (original image) of a document automatically fed by an ADF (Auto document feeder) or a document placed on a platen glass with a line sensor. The document image data is converted into document image data, and the document image data is output to the control unit 6. The image reading unit 2 outputs the document image data to the control unit 6, while the control unit 6 stores the document image data in the image data storage unit 3.

   The image data storage unit 3 is a semiconductor memory, a hard disk device, or the like. Document image data based on a control signal input from the control unit 6 or a print image received by the communication unit 5 from an external client computer (not shown). Data and facsimile image data received from the facsimile apparatus by the communication unit 5 are stored.

   Under the control of the control unit 6, the sheet transport image forming unit 4 transports sheets one by one from the sheet bundle stored in the sheet feeding cassette 44, and puts them on the sheet based on the image data in the image data storage unit 3. An image is formed. As shown in FIG. 1, the sheet transport image forming unit 4 has an image forming unit 41 that forms an image (hereinafter referred to as a toner image) made of toner corresponding to four colors of black, yellow, cyan, and magenta. , Intermediate transfer belt 42, primary transfer roller 43, paper feed cassette 44, paper feed roller 45, double feed prevention mechanism 46, double feed detection sensor 47, registration roller 48, secondary transfer roller 49, fixing roller 50, paper discharge It comprises a roller 51 and a paper discharge tray 52.

   Each image forming unit 41 forms a toner image corresponding to each color of yellow, magenta, cyan, and black. Four image forming units 41 are provided corresponding to each color at predetermined intervals in the horizontal direction when viewed from the front of the multi-function peripheral A. It has been. As shown in FIG. 1, the image forming unit 41 includes a photosensitive drum 41a on which a toner image is formed on the peripheral surface.

   The intermediate transfer belt 42 is an endless belt provided so as to be in contact with each photoconductive drum 41a, and a toner image formed on the peripheral surface of each photoconductive drum 41a is primarily transferred from each photoconductive drum 41a. It is. The primary transfer roller 43 is disposed so as to face each of the photoconductive drums 41a so as to sandwich the intermediate transfer belt 42. The primary transfer roller 43 is rotated from the photoconductive drum 41a by applying a primary transfer voltage to the intermediate transfer belt 42 while rotating. A roller that primarily transfers the toner image to the intermediate transfer belt 42.

    The paper feed cassette 44 is a container that accommodates a sheet bundle PS of a predetermined size such as A4 size or B5 size, and has an opening for exposing at least the uppermost surface of the sheet bundle PS. As shown in FIG. 2, the paper feed roller 45 rotates forward in the paper feed direction while being pressed against the uppermost surface of the paper bundle PS on the paper feed cassette 44, so that the paper P 1 is fed from the top of the paper bundle PS. A roller that feeds the sheet to the sheet conveyance path L one by one. Here, the paper feeding direction refers to the direction in which the paper P is transported along the paper transport path L (the direction of the arrow in the figure).

 Note that a rotation drive mechanism (such as a motor and a speed reduction gear) (not shown) is connected to the rotation shaft of the paper feed roller 45, and the normal rotation operation of this paper feed roller 45 (positive rotation start timing and stop timing). , Rotation speed, and the like) are controlled by the control of the rotation drive mechanism by the control unit 6 (particularly, the application of positive rotation torque by motor control).

 The double feed prevention mechanism 46 is arranged on the downstream side of the paper feed roller 45 (downstream in the paper feed direction) on the paper transport path L, and a plurality of sheets P are simultaneously fed by the paper feed roller 45 to the paper transport path L. When the paper is fed to the printer, that is, when double feed occurs, the first sheet and the second and subsequent sheets P are separated to prevent double feed.

 Specifically, as shown in FIG. 2, the double feed prevention mechanism 46 is disposed opposite to the transport roller 46a that rotates forward in the paper feed direction and the transport roller 46a, and is pressed against the transport roller 46a. It is comprised from the roller 46b reversely rotated in a reverse paper feeding direction via a torque limiter (not shown). A rotation drive mechanism (such as a motor and a reduction gear) (not shown) is connected to the rotation shaft of the transport roller 46a, and the forward rotation operation (forward rotation start timing, stop timing, rotation speed, etc.) of the transport roller 46a is performed. ) Is controlled by the control of the rotation drive mechanism by the control unit 6 (particularly, the application of positive rotation torque by motor control). A configuration in which the rotational force of the paper feed roller 45 is transmitted to the rotation shaft of the transport roller 46a by a belt may be employed.

 On the other hand, a rotation drive mechanism (a motor, a reduction gear, etc.) is connected to the rotation shaft of the rolling roller 46b via a torque limiter (not shown), and the reverse rotation operation (reverse rotation start timing) of the rolling roller 46b. And stop timing, rotation speed, etc.) are controlled by the control of the rotation drive mechanism by the control unit 6 (particularly, application of reverse rotation torque by motor control). Here, the torque limiter of the rolling roller 46b is driven when the sheet P sandwiched between the conveying roller 46a and the separating roller 46b is one (or zero), and the separating roller 46b is driven by the conveying roller 46a (see FIG. 2 (a)), when the paper P is a plurality of sheets, the setting roller 46b is set to rotate reversely (see FIG. 2B).

 On the downstream side of the double feed prevention mechanism 46 on the paper transport path L, a double feed detection sensor 47 for detecting a physical quantity corresponding to the number of sheets P is disposed. The double feed detection sensor 47 includes an ultrasonic transmission unit 47a and an ultrasonic reception unit 47b arranged to face each other so as to sandwich the paper conveyance path L therebetween. The ultrasonic transmission unit 47a transmits the ultrasonic wave S from below the paper conveyance path L to the ultrasonic reception unit 47b. The ultrasonic receiver 47b receives the ultrasonic wave S transmitted from the ultrasonic transmitter 47a, and outputs a voltage signal corresponding to the received intensity to the controller 6.

 The reception intensity of the ultrasonic wave S by the ultrasonic wave receiving unit 47b is the highest when the number of sheets P moving on the downstream side of the double feed prevention mechanism 46 is 0 (no paper state), and decreases as the number of sheets P increases. Become. That is, the reception intensity of the ultrasonic wave S is a physical quantity that changes in accordance with the number of sheets P that move on the downstream side of the double feed prevention mechanism 46. Therefore, the control unit 6 determines that the state of the sheet P moving on the downstream side of the double feed prevention mechanism 46 is 0 sheet state (paper out state) based on the output signal of the double feed detection sensor 47 (ultrasonic receiving unit 47b). It is possible to detect whether it is a single sheet state or a plurality of sheets.

Specifically, the control unit 6 stores in advance the reception intensity of the ultrasonic wave S when the sheet P is one sheet as a reference intensity for comparison, and the multi-feed detection sensor 47 (ultrasonic reception unit 47b). The received intensity (actually measured value) obtained from the output signal is compared with the reference intensity, and if both match, it is determined that there is one sheet P, and if the received intensity (actually measured value) is greater than the reference intensity. If it is determined that there is no paper and the received intensity (actually measured value) is smaller than the reference intensity, it is determined that there are a plurality of sheets P (multiple feed).
Note that various sensors may be used as the double feed detection sensor 47 regardless of the ultrasonic type or the optical type as long as the physical quantity according to the number of sheets P is detected.

 Returning to FIG. 1, on the downstream side of the double feed detection sensor 47 on the paper transport path L, a pair of paper for adjusting the transport timing of the paper P transported from the double feed prevention mechanism 46 to the secondary transfer roller 49. A registration roller 48 is disposed. The pair of registration rollers 48 is composed of two rollers that face each other and rotate in the paper feeding direction while being pressed against each other.

 Note that a rotation drive mechanism (such as a motor and a reduction gear) (not shown) is connected to the rotation shaft of one roller of the registration roller 48, and the other roller is idled. That is, the forward rotation operation (start timing or stop timing of normal rotation, rotation speed, etc.) of one roller is controlled by the control of the rotation drive mechanism by the control unit 6 (particularly, the application of positive rotation torque by motor control), The roller is driven by one roller.

 The secondary transfer roller 49 is a roller that is disposed so as to sandwich the intermediate transfer belt 42 between the opposing transfer rollers and that forms a secondary transfer nip with the intermediate transfer belt 42. The intermediate transfer belt The toner image on 42 is secondarily transferred to the paper P. That is, the secondary transfer roller 49 applies the secondary transfer voltage with the intermediate transfer belt 42 and the paper P sandwiched in the secondary transfer nip, thereby transferring the toner image on the intermediate transfer belt 42 to the paper P. Next transfer.

   The fixing roller 50 includes a heating roller having a heater therein and a pressure roller pressed against the heating roller. The fixing roller 50 sandwiches the paper P on which the toner image is secondarily transferred by the secondary transfer roller 49. Thus, the paper P is heated and pressed to fix the toner image on the paper P. The paper discharge roller 51 discharges the paper P conveyed from the fixing roller 50 to the paper discharge tray 52. The paper discharge tray 52 is a tray that stores the paper P discharged by the paper discharge roller 51.

   The communication unit 5 communicates with an external multifunction peripheral or facsimile apparatus via a telephone line based on a control signal input from the control unit 6, or with a client computer via a local area network. That is, the communication unit 5 has a communication function compliant with a LAN standard such as Ethernet (registered trademark) and a communication function compliant with a facsimile standard such as G3. The communication unit 5 performs e-mail transmission or facsimile transmission / reception, for example.

   The control unit 6 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an interface circuit that transmits and receives various signals to and from the above-described units, and is stored in the ROM. The overall operation of the multifunction device A is controlled based on the control program.

   The above is the overall configuration of the multifunction peripheral A. Among the above-described components, the control unit 6, the paper feed cassette 44, the paper feed roller 45, the double feed prevention mechanism 46, and the double feed detection sensor 47 are the same as those in the present embodiment. 1 constitutes a sheet feeding device. Further, the image forming unit 41, the intermediate transfer belt 42, the primary transfer roller 43, and the secondary transfer roller 49 function as a toner image transfer unit that transfers a toner image onto a sheet P fed from a sheet feeding device. The roller 50 functions as a fixing unit that fixes the toner image transferred onto the paper P, and the paper discharge roller 51 and the paper discharge tray 52 function as a paper discharge unit that discharges the paper P on which the toner image is fixed. To do.

Next, the operation of the multifunction peripheral A configured as described above will be described.
For example, a user who wants to copy a document using the multifunction device A sets the document on the image reading unit 2 and presses the copy start key on the operation display unit 1 to cause the multifunction device A to start a copy operation. . When the copy start key of the operation display unit 1 is pressed by the user, the control unit 6 causes the image reading unit 2 to read the original image and stores the original image data obtained from the image reading unit 2 in the image data storage unit 3. Let

 Then, the control unit 6 controls each image forming unit 41 based on the document image data stored in the image data storage unit 3 to form (develop) each color toner image on the surface of each photoconductive drum 41a. At the same time, the primary transfer voltage is sequentially generated at each primary transfer roller 43 while the intermediate transfer belt 42 is rotated, so that the toner images of the respective colors are sequentially superimposed and transferred onto the intermediate transfer belt 42.

 The control unit 6 controls the paper feeding operation of the paper P by the paper feeding device in parallel with the control of the primary transfer operation of the toner image as described above. Hereinafter, the control procedure of the paper feeding operation executed by the control unit 6 will be described in detail with reference to the flowchart shown in FIG. The control unit 6 controls the paper feeding operation in units of jobs according to the flowchart of FIG. Further, in this embodiment, one job is from when the copy start key is pressed by the user until all document images are printed (formed) on the required number of sheets P and output (discharged). .

 As shown in FIG. 3, the controller 6 controls the paper feed roller 45, the transport roller 46a, and the separation roller 46b to transport the paper P one by one (step S1). Specifically, the control unit 6 controls the rotation driving mechanism of the paper feed roller 45 and the transport roller 46a to generate a positive rotation torque, thereby causing the paper feed roller 45 and the transport roller 46a to rotate forward, and the rolling roller. The rotational drive mechanism 46b is controlled to generate reverse rotational torque.

 Here, as shown in FIG. 2A, when one sheet P is sent out from the sheet bundle PS set in the sheet feeding cassette 44 to the sheet conveying path L by the sheet feeding roller 45, the winding roller 46b. Is rotated following the conveyance roller 46 a, so that one sheet P is normally conveyed downstream of the double feed prevention mechanism 46.

 On the other hand, as shown in FIG. 2B, a plurality of (two in this case) sheets P (P1, P2) are fed from the sheet bundle PS set in the sheet feeding cassette 44 by the sheet feeding roller 45. When the paper roller 46b is fed to L, the first paper P1 on the side of the transport roller 46a is fed by the rotation of the transport roller 46a if the winding roller 46b rotates backward without being driven by the transport roller 46a by the action of the torque limiter. Since the second sheet P2 conveyed to the downstream side in the paper direction and returned to the upstream side in the paper feeding direction is returned to the upstream side in the paper feeding direction, the first sheet P1 and the second sheet P2 can be separated. Yes (multiple feeds can be prevented).

  However, when the frictional force between the first sheet P1 and the second sheet P2 is larger than the frictional force between the separation roller 46b and the second sheet P2, the conveyance roller 46a and the separation roller 46b Although the two sheets P1 and P2 are sandwiched between them, the separation roller 46b is driven by the conveyance roller 46a, and the two sheets P1 and P2 are conveyed downstream of the double feed prevention mechanism 46. There is a possibility of being.

  Therefore, the control unit 6 determines whether or not the sheet P conveyed to the downstream side of the double feed prevention mechanism 46 is in a double feed state based on the output signal of the double feed detection sensor 47 (ultrasonic receiving unit 47b). (Step S2). If “No” in step S 2, that is, if one sheet P (P 1) is normally conveyed downstream of the double feed prevention mechanism 46, the control unit 6 proceeds to step S 6 described later.

  On the other hand, in the case of “Yes” in step S2, that is, when the control unit 6 detects that the sheet P conveyed downstream of the double feed prevention mechanism 46 is in the double feed state, Counting up (incrementing the count value of the number of times of double feeding) is performed (step S3), and it is determined whether or not the number of times of double feeding occurrence C (corresponding to the frequency of double feeding occurrence) is greater than or equal to the first threshold CA (step S4). ).

  If “No” in step S4, the control unit 6 proceeds to step S6, which will be described later, whereas if “Yes” in step S4 (when the number of occurrences of double feed C is equal to or greater than the first threshold value CA). Then, the double feed suppression function is turned on, that is, the reverse rotation speed of the roller 46b is made slower than the initial set value (step S5). As described above, when the reverse rotation speed of the separation roller 46b is slowed, the force to return the second sheet P2 in the reverse sheet feeding direction (the frictional force between the separation roller 46b and the second sheet P2) increases. The success rate of preventing double feed by the double feed prevention mechanism 46 can be increased.

  Then, when it is determined “No” in step S2 or step S4, or after execution of step S5, the control unit 6 determines whether or not the sheet P currently being conveyed is the last sheet (step S5). S6) If “No”, the process returns to Step S1, while if “Yes”, the double feed suppression function is turned off, that is, the reverse rotation speed of the roller 46b is returned to the original initial setting value (Step S6). S7).

 As described above, according to this embodiment, based on the output signal of the double feed detection sensor 47 (ultrasonic receiving unit 47b), the number of occurrences of double feed C (on the downstream side of the double feed prevention mechanism 46 for each job) If the double feed occurrence frequency C is equal to or greater than the first threshold value CA, the reverse rotation speed of the roller 46b is slowed to increase the double feed prevention success rate by the double feed prevention mechanism 46. it can. As a result, it is possible to reduce the frequency of occurrence of double feeds and improve user work efficiency.

 In addition, the success rate of the double feed prevention by the double feed prevention mechanism 46 is greatly influenced by the type of paper P used for each job (friction force between the papers), so the paper P that is slippery (weak friction force) is used. If the frequency of occurrence of double feed increases in the job to be performed, the reverse rotation speed of the roller 46b is slowed at the end of the job, and the productivity in the job using the paper P having the normal friction force thereafter is reduced. In this embodiment, since the reverse rotation speed of the roller 46b is restored when the current job is completed, it is possible to avoid a decrease in productivity in subsequent jobs.

In addition, this invention is not limited to the said embodiment, The following modifications are mentioned.
For example, in the above embodiment, when the number C of occurrences of double feeding in the current job is equal to or greater than the first threshold value CA, the reverse rotation speed of the roller 46b is slowed, and the past job or all of the past several jobs are used. It is determined whether the reverse rotation speed of the roller has been slowed down. If not, the reverse rotation speed is restored at the end of the current job, whereas if it is slow, the reverse rotation speed is not restored. The control unit 6 may be provided with a function for notifying the user that productivity is reduced.
In order to notify the user that the productivity is lowered, a method of controlling the operation display unit 1 to display a screen for notifying the user that the productivity is lowered may be employed.

 Also, during the execution of a job after the job that did not return the reverse rotation speed of the roller 46b to the original, if the double feed occurrence number C is less than the second threshold value CB, the reverse rotation speed is returned to the original at the end of the current job. On the other hand, when the double feed occurrence count C is greater than or equal to the third threshold value CC, the reverse rotation speed is restored to the original value at the end of the current job, and the function for notifying the user that the maintenance time for the roller 46b has arrived is controlled. The part 6 may be provided. The second threshold value CB is set to be smaller than the first threshold value CA, and the third threshold value CC is set to be larger than the first threshold value CA.

In the above-described embodiment, the image forming apparatus including the paper feeding device has been described with reference to the multifunction peripheral A. However, the paper feeding device may be another image forming device such as a copier, a printer, a scanner, or a facsimile machine. Can be applied to.
Further, in the above embodiment, the paper feeding device that feeds the paper P from the paper bundle PS accommodated in the paper feeding cassette 44 is exemplified as the main paper feeding device, but the original paper to be read is fed one by one. The present invention can also be applied to an automatic paper feeder (ADF) for paper.

 A ... multifunction device, 1 ... operation display unit, 2 ... image reading unit, 3 ... image data storage unit, 4 ... paper transport image forming unit, 5 ... communication unit, 6 ... control unit, 41 ... image forming unit, 42 ... Intermediate transfer belt, 43 ... primary transfer roller, 44 ... paper feed cassette, 45 ... paper feed roller, 46 ... transport roller, 47 ... double feed detection sensor, 47a ... ultrasonic transmitter, 47b ... ultrasonic receiver, 48 ... Registration roller, 49 ... Secondary transfer roller, 50 ... Fixing roller, 51 ... Discharge roller, 52 ... Discharge tray, P ... Paper

Claims (4)

As a paper double feed prevention mechanism, a transport roller that rotates in the forward direction in the paper feed direction and a reverse roller in the reverse paper feed direction through a torque limiter, which is driven by the transport roller when a single paper is fed. A paper feeding device comprising a roller,
A double feed detection sensor that is disposed downstream of the double feed prevention mechanism and detects a physical quantity corresponding to the number of sheets;
Based on the output signal of the double feed detection sensor, the double feed occurrence frequency on the downstream side of the double feed prevention mechanism is obtained for each job, and when the double feed occurrence frequency is equal to or higher than a first threshold value, A controller that slows the rotation speed and restores the reverse rotation speed when the current job ends;
A sheet feeding device comprising:   The control unit slows the reverse rotation speed of the rolling roller when the frequency of occurrence of the double feed in the current job is equal to or higher than the first threshold, and slows the reverse rotation speed of the rolling roller in the past job. When the current job is finished, the reverse rotation speed is restored to the original value. When the current job is completed, the reverse rotation speed is not restored to the original value. The paper feeding device according to claim 1, wherein the paper feeding device is notified of a decrease. The control unit, when executing a job subsequent to a job that did not restore the reverse rotation speed of the roller, when the double feed occurrence frequency is less than a second threshold set smaller than the first threshold When the current job is finished, the reverse rotation speed is returned to the original value. On the other hand, when the double feed occurrence frequency is equal to or higher than the third threshold value set larger than the first threshold value , the reverse rotation speed is restored when the current job is finished. The paper feeding device according to claim 2, wherein the user is notified that the maintenance time for the roller has arrived. A paper feeding device according to any one of claims 1 to 3,
A toner image transfer unit for transferring a toner image to a sheet fed from the sheet feeding device;
A fixing unit for fixing the toner image transferred to the paper;
A paper discharge unit for discharging the paper on which the toner image is fixed;
An image forming apparatus comprising:

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