JP2019156584A - Paper feeding apparatus and image forming apparatus provided with the paper feeding apparatus - Google Patents

Abstract

To provide a paper feeding apparatus and an image forming apparatus capable of suppressing a decrease in paper feeding efficiency.SOLUTION: A paper feeding apparatus 4 includes a conveyance control unit. When a double feed detection unit 50 continuously detects the presence of multiple feeds a predetermined number of times, the conveyance control unit executes an evacuation process in which the multi-feed sheet S is guided to an evacuation conveyance path 40g by a switching member 54 and discharged to an evacuation tray 52.SELECTED DRAWING: Figure 2

Description

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

  In general, an image forming apparatus that prints an image on a sheet includes a paper feeding device for supplying the sheet to the main body of the image forming apparatus. This paper feeding device may be mounted as an optional device on the image forming apparatus main body, or may be provided as a standard on the image forming apparatus main body.

  The sheet feeding device is in contact with a sheet feeding cassette for storing sheets, a pickup roller for picking up sheets in the sheet feeding cassette one by one, a sheet feeding roller for feeding sheets to the image forming unit, and a sheet feeding roller. And a separation roller arranged opposite to each other. The separation roller separates the multi-feed sheet by rotating in the opposite direction to the paper feed roller.

  The sheet conveyance path may be provided with a double feed detection unit for detecting the presence or absence of double feed of sheets. For example, in Patent Document 1, the double feed detection unit is provided on the downstream side of the separation roller. The double feed detector detects the presence or absence of double feed by detecting the thickness of the sheet. In this paper feeding device, if the multi-feed sheet separation processing by the separation roller is not performed even after the multi-feed sheet separation processing is executed a plurality of times, the paper feeding operation is stopped and the jam display is performed.

JP 2003-72988 A

  In the paper feeding device disclosed in Patent Document 1, the paper feeding operation is stopped when the double feeding of sheets is not eliminated. If the sheet feeding operation is frequently stopped due to such double feeding of sheets, the sheet feeding efficiency deteriorates.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet feeding device and an image forming apparatus capable of suppressing a decrease in sheet feeding efficiency.

  A sheet feeding device according to the present invention includes a sheet feeding cassette that accommodates sheets, a main conveyance path that guides the sheets in the sheet feeding cassette to a predetermined conveyance destination, and a double conveyance of sheets provided in the main conveyance path. When the presence of double feeding of a sheet is detected by the multi-feed detection unit that detects the presence or absence of the multi-feed detection unit, after the multi-feed sheet is switched back, sheet separation processing is performed on the multi-feed sheet. The sheet separating mechanism that re-feeds the separated sheet from the upstream side of the multi-feed detection unit into the main conveyance path and the outside of the main conveyance path, and eliminates multi-feed by the sheet separation mechanism. A retreat tray for retreating the multi-feed sheet that could not be formed, a retreat conveyance path for branching from the downstream side of the multi-feed detection unit in the main conveyance path to guide the multi-feed sheet to the retraction tray, and a main conveyance path At the connection part with the above-mentioned evacuation conveyance path And a switching member that selectively switches the sheet transport destination to either the main transport path or the retraction tray, and when the presence of multi-feed is detected a predetermined number of times by the multi-feed detector. Includes a conveyance control unit that performs a retraction process of guiding the multi-feed sheet to the retraction conveyance path by the switching member and discharging it to the retraction tray.

  According to the present invention, it is possible to obtain a sheet feeding device and an image forming apparatus that can suppress a decrease in sheet feeding efficiency.

1 is a schematic diagram illustrating an image forming apparatus equipped with a sheet feeding device according to an embodiment. FIG. 3 is an enlarged schematic diagram illustrating a paper feeding device in an enlarged manner. It is explanatory drawing for demonstrating the forward rotation state, reverse rotation state, and separation rotation state of a separation roller pair. FIG. 4 is a block diagram illustrating a configuration of a conveyance control system of a sheet feeding device. 6 is a flowchart illustrating a part of sheet feeding control executed by a control unit. 6 is a flowchart illustrating a part of sheet feeding control executed by a control unit. 6 is a flowchart illustrating a part of sheet feeding control executed by a control unit. 6 is a flowchart illustrating a part of sheet feeding control executed by a control unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiment.

  FIG. 1 is a schematic diagram illustrating an image forming apparatus 1 including a sheet feeding device 4 according to the embodiment. The image forming apparatus 1 includes an image forming apparatus main body 2 and an image reading unit 3 that is fixed to an upper end portion of the image forming apparatus main body 2 and reads a document image to generate image data. In the image forming apparatus main body 2, based on the image data received from the image reading unit 3, a document image is printed on a sheet (paper or a recording material such as OHP). On the side surface of the image forming apparatus main body 2, the paper feeding device 4 that supplies sheets to the image forming apparatus main body 2 is mounted as an optional device. A sheet feeding unit 20 that feeds a sheet for printing is provided as standard at the bottom of the image forming apparatus main body 2.

  The paper feed unit 20 of the image forming apparatus main body 2 has a paper feed cassette (not shown) provided in four stages. A pair of paper feed rollers 21 is provided on the side of each paper feed cassette. Each paper feed roller pair 21 pulls out the sheet S in each paper feed cassette and supplies it to the sheet conveyance path 2 a in the image forming apparatus main body 2. The sheet conveyance path 2 a guides the sheet S supplied from the paper feeding unit 20 or the paper feeding device 4 to a paper discharge tray 22 formed on the upper surface of the image forming apparatus main body 2.

  In the middle of the sheet conveyance path 2a, an image forming unit 23 that transfers and forms a toner image on the sheet S by an electrophotographic method, and a fixing unit that heats and pressurizes the toner image on the sheet S and fixes the toner image on the sheet S. 24. The sheet S that has passed through the fixing unit 24 is discharged to the discharge tray 22 by a discharge roller pair 25.

  Next, details of the sheet feeding device 4 will be described with reference to FIGS. 1 and 2. The sheet feeding device 4 includes a rectangular box-shaped casing 40 and a sheet feeding cassette 41. The paper feed cassette 41 is provided in three upper and lower stages (only the uppermost stage is shown in FIG. 2). Each sheet cassette 41 contains a plurality of sheets S stacked in a bundle. A pair of paper feed rollers 42 is provided on the side of each paper feed cassette 41 to draw out the sheet S in the paper feed cassette and supply it to the main transport path 40a.

  The main transport path 40 a is a single transport path that is used in common among the plurality of paper feed cassettes 41. Each paper feed cassette 41 and the main conveyance path 40a are connected by different introduction conveyance paths 40b. The main transport path 40a allows the sheet S supplied from each paper feed cassette 41 via the introduction transport path 40b to be discharged into a discharge port 40c (predetermined feed) formed on the side wall (left side wall in FIG. 2) of the housing 40. To the paper tip). The paper discharge port 40 c communicates with a paper feed port 2 b (shown only in FIG. 1) formed on the side wall of the image forming apparatus main body 2. The main transport path 40a is connected to the sheet transport path 2a in the image forming apparatus main body 2 through the paper discharge port 40c and the paper feed port 2b (see FIG. 1).

  First to fourth transport roller pairs 43 to 46 are provided on the transport downstream side of the connecting portion 40d (see FIG. 2) with the uppermost introduction transport path 40b in the main transport path 40a. The first to fourth transport roller pairs 43 to 46 are arranged at intervals in this order from the transport upstream side to the transport downstream side.

  Between the first transport roller pair 43 and the second transport roller pair 44, a multi-feed detection sensor 50 (duplicate) that detects the presence or absence of multi-feed of sheets (a state of being transported in a state of being overlapped in the thickness direction). An example of a feed detection unit) is provided.

  The double feed detection sensor 50 includes an ultrasonic transmission unit 50a that transmits ultrasonic waves, and an ultrasonic reception unit 50b that receives ultrasonic waves transmitted from the ultrasonic transmission unit 50a. As the number of overlapping sheets S passing between the ultrasonic transmission unit 50a and the ultrasonic reception unit 50b increases, the attenuation amount of ultrasonic waves transmitted from the ultrasonic transmission unit 50a to the ultrasonic reception unit 50b increases. The double feed detection sensor 50 detects the presence or absence of double feed of the sheet S based on the change in the attenuation amount of the ultrasonic wave.

  A sheet separation mechanism 47 is connected to the upstream side of the first conveyance roller pair 43 in the main conveyance path 40a (downstream side from the connection portion 40d).

  The sheet separation mechanism 47 performs a separation process on the double-fed sheet S (double-fed sheet) to eliminate double-fed. The sheet separation mechanism 47 is provided in the separation conveyance path 40e branched from the vicinity of the upstream side of the first conveyance roller pair 43 in the main conveyance path 40a. The separation conveyance path 40e is inclined upward toward the right side of FIG. The separation conveyance path 40e is provided with a separation tray 51 for temporarily holding the multi-feed sheet S to be separated. A separation roller pair 48 is provided at the end of the separation tray 51 on the main conveyance path 40a side.

  As shown in FIG. 3, the separation roller pair 48 has three states: a forward rotation state, a reverse rotation state, and a separation rotation state. In the forward rotation state, as shown in the upper part of FIG. 3, both the upper roller 48a and the lower roller 48b rotate in the direction in which the sheet S is sent out to the main transport path 40a. In the reverse rotation state, as shown in the middle part of FIG. 3, both the upper roller 48a and the lower roller 48b rotate in a direction in which the sheet S is pulled back from the main conveyance path 40a (a direction in which the sheet S is discharged to the separation tray 51). In the separated rotation state, as shown in the lower part of FIG. 3, the upper roller 48a (one roller) rotates in a direction to send the sheet S to the main transport path 40a, and the lower roller 48b (the other roller) rotates the sheet S. It rotates in the direction of pulling back from the main transport path 40a (direction of discharging to the separation tray 51).

  Returning to FIG. 2, a retreat conveyance path 40 g is connected between the third conveyance roller pair 45 and the fourth conveyance roller pair 46 in the main conveyance path 40 a. The retreat conveyance path 40g is a conveyance path for retreating out of the main conveyance path 40a the sheet S whose double feeding is not eliminated even if the sheet separation process is performed a predetermined number of times by the sheet separation mechanism 47. The evacuation conveyance path 40g branches from the main conveyance path 40a and then extends obliquely upward to the right in FIG. A retraction tray 52 is provided at the upper end of the retraction conveyance path 40g. The evacuation tray 52 is formed by denting a part of the upper surface of the housing 40. Since the evacuation tray 52 is a part of the upper surface of the housing 40, it is exposed to the outside and can be easily accessed by the user. In the middle of the retreat conveyance path 40g, a retraction roller pair 49 for discharging the multi-feed sheet S to the retraction tray 52 is provided.

  Further, a first discharge guide 53 for switching the discharge destination of the sheet S to the separation tray 51 is provided in the vicinity of the connection portion 40f of the main conveyance path 40a with the separation conveyance path 40e. The first discharge guide 53 has a triangular shape when viewed from the sheet width direction and is supported by a fixing pin 53a. The first discharge guide 53 is rotatable between a main conveyance path side position (a position indicated by a solid line in FIG. 2) and a separation tray side position (a position indicated by a two-dot chain line in FIG. 2) with the fixed pin 53a as a fulcrum. It has become. Since the first discharge guide 53 is arranged along the main conveyance path 40 a at the main conveyance path side position, the switched-back sheet S does not go to the separation tray 51. On the other hand, at the separation tray side position, the front end of the first discharge guide 53 blocks the main conveyance path 40 a, so that the switched back sheet S is discharged toward the separation tray 51.

  In addition, a second discharge guide 54 for switching the discharge destination of the sheet S to the retract tray 52 is provided in the vicinity of the connection portion 40h of the main transport path 40a with the retract transport path 40g. The second discharge guide 54 has a triangular shape as viewed from the sheet width direction and is supported by a fixing pin 54a. The second discharge guide 54 is rotatable between a position on the main transport path side (a position indicated by a solid line in FIG. 2) and a position on a retraction tray (a position indicated by a two-dot chain line in FIG. 2) with the fixed pin 54a as a fulcrum. It has become. Since the second discharge guide 54 is arranged along the main conveyance path 40 a at the main conveyance path side position, the sheet S does not go to the retraction tray 52. On the other hand, at the retreat tray side position, the front end of the second discharge guide 54 blocks the main conveyance path 40a, so that the sheet S is discharged toward the retraction tray 52.

  Next, the details of the transport control system of the paper feeding device 4 will be described with reference to FIG. This transport control system includes a control unit 100. The control part 100 is comprised by the microcomputer which has CPU, ROM, and RAM, for example.

  The control unit 100 is electrically connected to the multi-feed detection sensor 50, the sheet detection sensor 55, the roller driving unit 101, and the two electromagnetic solenoids 102 and 103 via signal lines.

  The double feed detection sensor 50 is a sensor that detects the presence or absence of double feed of the sheet S as described above, and outputs a signal corresponding to the presence or absence of double feed to the control unit 100.

  The sheet detection sensor 55 is provided in the connection portion 40h of the main conveyance path 40a with the retreat conveyance path 40g. The sheet detection sensor 55 outputs a detection signal when detecting the sheet S passing through the connecting portion 40h. The sheet detection sensor 55 is configured by, for example, an optical sensor having a light emitting unit and a light receiving unit.

  The roller drive unit 101 includes an electric motor and a clutch. The roller driving unit 101 drives the paper feed roller pair 42, the first to fourth roller pairs 43 to 46, and the separation roller pair 48 based on a signal from the control unit 100.

  When the electromagnetic solenoid 102 is excited by the control unit 100, the first discharge guide 53 is switched from the main conveyance path side position to the separation tray side position (two-dot chain line in FIG. 2). When the excitation of the electromagnetic solenoid 102 is released by the control unit 100, the first discharge guide 53 returns to the main conveyance path side position by its own weight.

  The electromagnetic solenoid 103 is energized by the control unit 100 to switch the second discharge guide 54 from the main transport path side position to the retreat tray side position (see the two-dot chain line in FIG. 2). When the excitation of the electromagnetic solenoid 103 is released by the control unit 100, the second discharge guide 54 returns to the main conveyance path side position by its own weight.

  Next, details of sheet feeding control executed by the control unit 100 will be described with reference to FIGS.

  In step S1, it is determined whether or not the total number of sheets S detected by the sheet detection sensor 55 has reached the set number. If this determination is YES, the process proceeds to step S16 (see FIG. 8), while NO. If so, the process proceeds to step S2. The set number can be set by the user through the operation panel, for example.

  In step S2, the excitation of the electromagnetic solenoids 102 and 103 is released so that both the first discharge guide 53 and the second discharge guide 54 are in the main transport path side position.

  In step S3, the paper feed roller pair 42 and the first to fourth transport roller pairs 43 to 46 are driven in a forward rotation state. Here, the forward rotation state is a state in which the two rollers constituting each of the roller pairs 43 to 46 rotate in a direction in which the sheet S is sent from the upstream side to the downstream side of the main conveyance path 40a.

  In step S4, it is determined whether or not the presence of double feed is detected by the double feed detection sensor 50. If this determination is YES, the process proceeds to step S7 (see FIG. 6). Proceed to S5.

  In step S5, it is determined whether or not there is a sheet S on the separation tray 51. If this determination is YES, the process proceeds to step S15. If NO, the process proceeds to step S6. Note that the determination in step S5 may be performed based on a signal from a sheet detection sensor provided on the separation tray 51, for example.

  In step S6, the sheet S is conveyed to the image forming apparatus main body 2, and the feeding operation of the subsequent sheet S is continued, and then the process returns.

  In step S7 that proceeds when the determination in step S4 is YES, it is determined whether or not the presence of double feed by the double feed detection sensor 50 has been continuously detected a predetermined number of times. If this determination is NO, step S11 is performed. On the other hand, the process proceeds to step S8 if YES (see FIG. 7). Here, “continuously detected a predetermined number of times” means that the presence of double feeding is detected in any process as a result of the process of step S4 being executed a predetermined number of times. The predetermined number of times may be any number as long as it is one or more times, but it is preferably set to 4 to 5 times because the sheet feeding operation is stagnant if it is too much or too little. Further, the predetermined number of times may be set by the user inputting from the operation panel of the image forming apparatus main body 2 or may be the number of times stored in the ROM in advance.

  In step S8, the electromagnetic solenoid 103 is excited to switch the second discharge guide 54 to the retreat tray side position.

  In step S9, the separation roller pair 48 and the first to third transport roller pairs 43 to 45 are driven in a forward rotation state.

  In step S <b> 10, the multi-feed sheet S is discharged to the retraction tray 52 by driving the retraction roller pair 49 in the forward rotation state. The forward rotation state of the retraction roller pair 49 is a state in which the two rollers constituting the retraction roller pair 49 rotate in the direction in which the sheet S is discharged to the retraction tray 52. Then, the process returns after the process of step S10 is completed.

  In step S11 that proceeds when the determination in step S7 is NO, it is determined whether or not the trailing edge of the sheet S has passed through the first discharge guide 53. If this determination is NO, the determination in step S11 is performed. On the other hand, if YES, the process proceeds to step S12. Note that this determination process is easily executed by, for example, calculating the trailing end position of the sheet S based on the rotation speed of the first transport roller pair 43.

  In step S12, the electromagnetic solenoid 102 is excited to switch the first discharge guide 53 to the separation tray side position.

  In step S <b> 13, the first and second transport roller pairs 43 and 44 and the separation roller pair 48 are driven in the reverse rotation state, whereby the sheet S is switched back and discharged to the separation tray 51.

  In step S14, it is determined whether or not the front end of the sheet S (the end on the main conveyance path side of the sheet S and the rear end at the time of switchback) has passed the separation roller pair 48. While the determination in step S14 is continued, if YES, the process proceeds to step S15. This determination process is easily executed by calculating the front end position of the sheet S based on the rotation speeds of the first transport roller pair 43 and the separation roller pair 48 at the time of switchback, for example.

  In step S15, the separation roller pair 48 is driven in the separated state, and the first and second transport roller pairs 43 and 44 are driven in the forward rotation state. Thereby, the separation process of the sheet S held on the separation tray 51 is executed, and the separated sheet S is conveyed downstream along the main conveyance path 40a. After the process of step S15, the process returns to step S3.

  In step S16 (see FIG. 8) that proceeds when the determination in step S2 is YES, the feeding of a new sheet S by the pair of feed rollers 42 is stopped.

  In step S17, the second discharge guide 54 is driven to the retreat tray side position, and all the sheets S remaining in the transport path on the upstream side of the second discharge guide 54 are discharged to the retreat tray 52, and then the end Proceed to

  As described above, when the presence of double feeding is continuously detected a predetermined number of times by the double feed detection sensor 50 (when the determination in step S7 is YES), the control unit 100 removes the double feed sheet S from the second. The paper is guided to the retreat conveyance path 40g by the discharge guide 54 and is discharged to the retreat tray 52 (steps S8 to S10).

  According to this, when the multi-feed is not canceled even after the sheet separation process of the sheet S is executed a predetermined number of times, the multi-feed sheet S is discharged to the retreat tray 52. For this reason, the user does not need to open the exterior cover in the paper feeding device 4 and remove the multi-feed sheet S. Therefore, it is not necessary to stop the paper feeding operation for a long time in order to remove the double feed sheet S. Accordingly, the sheet feeding operation can be continuously executed, and the sheet feeding efficiency of the sheet feeding device 4 to the image forming apparatus main body 2 can be improved.

  In the present embodiment, the main conveyance path 40a is one conveyance path that is used in common among the three sheet feeding cassettes 41. The sheet separation mechanism 47, the double feed detection sensor 50, and the retraction tray 52 include: Regardless of which sheet feeding cassette 41 the sheet S conveyed in the main conveyance path 40a is supplied from, the three sheet feeding cassettes 41 are used in common.

  According to this, since it is not necessary to provide the sheet separation mechanism 47, the double feed detection sensor 50, and the retreat tray 52 for each of the three sheet feeding cassettes 41, it is possible to reduce the number of parts and reduce the cost.

  In the present embodiment, the sheet separation mechanism 47 includes a separation roller pair 48, and drives the upper roller 48a of the separation roller pair 48 in the forward direction to send the sheet S to the main transport path 40a. The sheet separation process is executed by driving the side roller 48b in the reverse direction to pull the sheet S back from the main transport path 40a.

  According to this, it is possible to easily separate the multi-feed sheets S with a simple configuration.

  In the present embodiment, the sheet separation mechanism 47 switches to the separation tray 51 when the double feed detection sensor 50 continuously detects the presence of double feed a predetermined number of times (in the case of YES at step S7). In order to send all the backed multi-feed sheets S into the main conveyance path 40a, the two rollers (the upper roller 48a and the lower roller 48b) constituting the separation roller pair 48 are both rotated in the forward direction (step S9).

  According to this, all the multi-feed sheets S that are difficult to eliminate multi-feed can be reliably sent out into the main conveyance path 40a.

  Even after the sheet saving process (steps S8 to S10) is executed, the control unit 100 does not reach the preset set number of sheets S discharged from the discharge port 40c ( If the determination in step S1 is NO, the sheet S feeding operation is continued without stopping (step S6).

  According to this, even when there is a multi-feed sheet S that is difficult to be separated by the sheet separation mechanism 47, the control unit 100 continues the paper feeding operation without stopping. Accordingly, the sheet feeding efficiency can be significantly improved.

<< Modification of Embodiment >>
In the above-described embodiment, the configuration has been described in which the multi-feed sheet S detected by the multi-feed detection sensor 50 is conveyed to the separation tray 51 to be separated and sent to the main conveyance path 40a. Further, it is possible to provide a sensor for detecting the presence or absence of the sheet S in the separation tray 51 so that the sheets S set on the separation tray 51 are sequentially sent to the main transport path 40a. In this case, the separation roller pair 48 also functions as a paper feed roller pair.

  With this configuration, the separation tray 51 can be used as a paper feed tray without providing a separate paper feed tray. As a result, it is possible to improve the convenience of the user while suppressing the manufacturing cost of the device. Further, the multi-feed sheet S discharged to the evacuation tray 52 can be used after being separated once to improve the separability and then set to the separation tray 51. Therefore, it is possible to easily reuse the multi-feed sheet S without taking time to return the double-feed sheet S to the paper feed cassette 41.

<< Other embodiments >>
In the above-described embodiment, an example in which the paper feeding device 4 is retrofitted as an optional device to the image forming apparatus main body 2 has been described. However, the present invention is not limited to this. The main body 2 may be a standard equipment.

  In the above embodiment, the ultrasonic double feed detection sensor 50 has been described as an example of the double feed detection unit, but the present invention is not limited to this. That is, the double feed detection unit is configured by a pair of rollers that can be separated from each other and a sensor that measures a separation distance between the pair of rollers, and whether or not the sheet S is double fed based on the output of the sensor. You may make it detect.

  As described above, the present invention is useful for a sheet feeding device and an image forming apparatus provided with the sheet feeding device, and is particularly mounted in an image forming apparatus such as a printer, a facsimile, a copying machine, or a multifunction peripheral (MFP). Alternatively, it is useful for a paper feeding device to be mounted.

1: Image forming apparatus 40a: Main transport path 40b: Introduction transport path 40c: Paper discharge port (predetermined transport destination)
40e: Separation conveyance path 40g: Retraction conveyance path 41: Paper feed cassette 47: Sheet separation mechanism 48: Separation roller pair 48a: Upper roller (one roller)
48b: Lower roller (the other roller)
50: Double feed detection sensor (double feed detection unit)
51: Separation tray 52: Retraction tray 54: Second discharge guide (switching member)
100: Control unit S: Seat

Claims (7)

A paper cassette for storing sheets;
A main conveyance path for guiding the sheets in the sheet feeding cassette to a predetermined conveyance destination;
A double feed detector provided in the main transport path for detecting the presence or absence of double feed of sheets;
When the multi-feed detection unit detects the presence of multi-feed of sheets, the multi-feed sheet is switched back, and then a sheet separation process is performed on the multi-feed sheet, and the separated sheet is transferred to the multi-feed sheet. A sheet separation mechanism that re-feeds the main conveyance path from the conveyance upstream side of the feed detection unit;
A retraction tray that is provided outside the main conveyance path and retreats a multi-feed sheet that could not be canceled by the sheet separation mechanism;
A retreat conveyance path that branches from the downstream side of the multifeed detection section in the main conveyance path and guides the multifeed sheet to the retraction tray;
A switching member provided at a connection portion of the main conveyance path with the retraction conveyance path, and selectively switching a sheet conveyance destination to one of the main conveyance path and the retraction tray;
Conveyance control for executing retraction processing for guiding the multifeed sheet to the retraction conveyance path by the switching member and discharging it to the retraction tray when the multifeed detection unit detects the presence of multifeed continuously for a predetermined number of times. A sheet feeding device. The paper feeding device according to claim 1.
A plurality of the paper cassettes are provided,
The main transport path is one transport path that is used in common among the plurality of paper feed cassettes,
The sheet separation mechanism, the multi-feed detection unit, and the evacuation tray are commonly used among the plurality of sheet feeding cassettes regardless of which sheet feeding cassette is used to feed the sheet conveyed in the main conveying path. The paper feeding device that is to be used. The sheet feeding device according to claim 1 or 2,
The sheet separation mechanism has a pair of separation rollers, and drives one roller of the pair of separation rollers in a forward direction for feeding the sheet to the main conveyance path, and the other roller moves the sheet to the main conveyance path. A sheet feeding device that performs the sheet separation process by driving in a reverse direction to pull back from the sheet. The paper feeding device according to claim 3.
The sheet separation mechanism is further provided with a separation tray that is provided outside the main conveyance path and holds the multi-feed sheet after the switchback,
The separation roller pair is provided at the end of the separation tray on the main conveyance path side,
The sheet separation mechanism is configured so that the multi-feed sheet switched back to the separation tray is sent out into the main conveyance path when the multi-feed detection unit continuously detects the presence of multi-feed for a predetermined number of times. A paper feeding device that rotates two rollers constituting a roller pair together in the forward direction. In the paper feeding device according to any one of claims 1 to 4,
The sheet feeding operation is performed when the number of sheets supplied to the predetermined sheet feeding destination has not reached the preset number of sheets even after executing the evacuation process. The paper feeding device to continue without stopping. In the paper feeding device according to any one of claims 1 to 5,
The separation tray is a sheet feeding device that can also be used as a sheet feeding tray on which sheets are set.   An image forming apparatus comprising the paper feeding device according to claim 1.

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