JP2010006477A - Paper feeder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeder capable of correctly returning a paper medium in the overlapped feeding state clamped by a separation roller into a storage part. <P>SOLUTION: The paper feeder is constituted by: an overlapped feeding detection part for determining whether the paper medium during conveying is in the overlapped feeding based on the output of a supersonic wave sensor; a conveying control part for controlling conveying of the paper medium based on the determination result by the overlapped feeding detection part; a first separation roller, i.e., a separation roller driven by a motor for conveying the paper medium in a feeding direction; and a second separation roller, i.e., a separation roller rotated in a following manner by rotation of the first separation roller rotated in a following manner when torque in the feeding direction exceeding a constant level is applied and rotated in a following manner by small torque in a returning direction as compared with the feeding direction. The conveying control part reverses the rotation of the first separation roller when the overlapped feeding is detected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet feeding device, and more particularly, to an improvement in a sheet feeding device that separates paper media in a storage unit that stores a large number of paper media one by one and sends them to a conveyance path.

  In an image reading apparatus that reads an image from a document or a printing apparatus that prints characters, images, and the like on recording paper, the paper medium is taken out from a storage section that stores a large number of paper media, separated one by one, and then transported to a conveyance path A paper feeding device for sending out is provided. In general, the paper feeding device is configured by a separation roller that separates the paper medium in the storage unit one by one and sends it to a conveyance path, and a plurality of conveyance rollers that convey the paper medium sent by the separation roller. Usually, the separation roller and the conveyance roller are driven by a common motor.

  For example, in an image reading apparatus provided with such a sheet feeding device, there is a problem that when a document is conveyed in a double feed state and an image is read, a reading error such as skipping of the document occurs. there were. In the conventional image reading apparatus, when a double feed occurs during the conveyance of a document, the separation roller and the conveyance roller are stopped, so that the document in the double feed state is conveyed in the double feed state and is read. The operation | movement which prevents this is performed (for example, patent documents 1-4). However, in the conventional image reading apparatus that determines whether or not the document being transported is double-feed and stops the document transport, the transport of the document immediately stops when double-feed is detected. There is a problem in that a finished document is also left in the conveyance path. To take out the original in the transport path and resume reading the original, it is necessary to set the original that has not been read, but the original taken out from the transport path includes the scanned original, It was difficult to determine which original document was read and which original document was not read.

Further, when the conveyance is resumed in order to take out the document left behind due to the conveyance stop due to the occurrence of the multi-feed, the document in the double-feed state is also conveyed, and there is a problem that a paper jam is likely to occur. In view of this, it is conceivable to reverse the separation roller in order to return the double-fed original to the accommodating portion. However, even if the separation roller sandwiching the double-fed original is reversed, there is a problem that the double-fed original does not return correctly.
JP 2007-266767 A JP 2002-2992 A JP-A-8-282870 JP-A-5-294484

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a paper feeding device capable of suppressing a paper medium from being left in a conveyance path when double feeding occurs. That is, an object of the present invention is to provide a paper feeding device that can correctly return a paper medium in a double feeding state sandwiched between separation rollers into a storage unit. In particular, the present invention relates to a paper in a double feed state sandwiched between separation rollers in a non-active retard type paper feeding device in which a separation roller for applying a frictional force in a returning direction to a paper medium in a double feed state is not driven by a motor. An object is to correctly return the medium into the accommodating portion.

  According to a first aspect of the present invention, there is provided a sheet feeding device configured to store a plurality of paper media, a separation unit that separates the paper media in the storage unit one by one, and sends the paper media to a transport path. A sheet feeding device having two or more transport rollers for transporting a paper medium, comprising: a sending unit that sends out an ultrasonic wave; and a detection unit that detects the ultrasonic wave that has passed through the paper medium, and the separating unit Based on the ultrasonic sensor disposed between the separation roller and the conveyance roller closest to the separation unit, and the output of the detection unit, it is determined whether or not the paper medium being conveyed is double feeding. And a conveyance control unit that controls conveyance of the paper medium based on the determination result by the multi-feed detection unit, wherein the separation unit is a separation roller driven by a motor, and the paper medium is A first separation roller for conveying in the feed direction; A separation roller that is driven to rotate by the rotation of the separation roller, and is driven to rotate when a torque in the feed direction exceeding a certain level is applied, and is driven to rotate in a return direction with a smaller torque than the feed direction. The separation controller is configured to reverse the rotation of the first separation roller when the double feed is detected.

  According to such a configuration, the second separation roller is driven to rotate when a torque in the feed direction exceeding a certain level is applied, and is separated to rotate in the return direction with a smaller torque than the feed direction. Since it is a roller, it can be driven and rotated in the return direction when the rotation of the first separation roller is reversed. Therefore, by reversing the rotation of the first separation roller when double feeding is detected, the paper medium in the double feeding state sandwiched between the first separation roller and the second separation roller is correctly returned into the storage unit. Can be made.

  A sheet feeding device according to a second aspect of the present invention includes a cylindrical drum in which, in addition to the above configuration, the second separation roller is driven to rotate by applying a torque in a feeding direction exceeding a certain level from the first separation roller. A support shaft that contacts the inner peripheral surface of the drum and supports the drum, and a one-way clutch that restricts the rotation of the support shaft in the feed direction and rotatably supports the support shaft in the return direction. Configured as follows.

  In addition to the above configuration, the sheet feeding device according to the third aspect of the present invention is configured such that the one-way clutch is fixed so as not to rotate the support shaft in the feed direction.

  In the sheet feeder according to the fourth aspect of the present invention, in addition to the above configuration, the conveyance control unit stops the first separation roller until the paper medium in a double-feed state reaches the conveyance roller, and It is configured to reverse the rotation of the first separation roller after the paper medium preceding the paper medium is carried out. According to such a configuration, the first separation roller is stopped to stop the transport of the paper medium in the double feed state, and the rotation of the first separation roller is performed after the paper medium preceding the paper medium is discharged. Therefore, only the paper medium in the double feed state can be returned to the accommodating portion.

  According to the paper feeding device of the present invention, the second separation roller for urging the paper medium in the return direction is driven to rotate when a feed direction torque exceeding a certain level is applied, and is fed in the return direction. Since the separation roller is driven and rotated with a small torque compared to the direction, it can be driven and rotated in the return direction when the rotation of the first separation roller is reversed. Therefore, by reversing the rotation of the first separation roller when double feeding is detected, the paper medium in the double feeding state sandwiched between the first separation roller and the second separation roller is correctly returned into the storage unit. It is possible to prevent the paper medium from being left in the conveyance path when double feeding occurs.

  FIG. 1 is a diagram illustrating an example of a schematic configuration of an image reading apparatus including a paper feeding device according to an embodiment of the present invention. The image reading apparatus 1 includes a paper feed tray 11, a separation unit 21, an ultrasonic sensor 22, conveyance rollers 17 to 20, document reading units 23 and 24, a paper discharge tray 25, a motor 31, a power transmission unit 32, and a clutch unit 33. Consists of.

  In the image reading apparatus 1, the paper medium is taken out from the paper feed tray 11, separated one by one and sent to the conveyance path A 2, and conveyed in the conveyance path A 2 by the conveyance rollers 17 to 20. Then, the original reading units 23 and 24 read an image from the paper medium, and the read paper medium is discharged into the paper discharge tray 25.

  The paper feed tray 11 is a storage unit for storing a large number of paper media, and is loaded with unread originals A1.

  The separation unit 21 includes a pickup roller 12, a first separation roller 13, and a second separation roller 14, and performs an operation of separating the documents A1 in the sheet feed tray 11 one by one and sending them to the conveyance path A2. Yes. The pick-up roller 12 urges the document A1 in the feed direction to take out the documents A1 in the sheet feed tray 11 one by one, and sends the document A1 from the sheet feed tray 11 to the first separation roller 13 side. It is.

  Here, a large number of documents A1 are stacked on a document table biased upward, and the uppermost document A1 is always in contact with the pickup roller 12 regardless of the stacking amount of the documents A1. And

  The first separation roller 13 and the second separation roller 14 are separation devices for separating the documents A1 sent by the pickup roller 12 one by one and sending them to the conveyance path A2. The first separation roller 13 is a separation roller for conveying the document A1 in the feeding direction.

  The second separation roller 14 is a separation roller for applying a frictional force in the return direction to the paper medium in the double feed state, and is disposed opposite to the first separation roller 13 so as to sandwich the document A1 being conveyed. Yes. That is, the first separation roller 13 is disposed on the upper side of the conveyance path A2, while the second separation roller 14 is disposed on the lower side of the conveyance path A2.

  The second separation roller 14 is provided with a torque limiter so as to be driven to rotate when a torque exceeding a certain level is applied. For example, the second separation roller 14 includes a cylindrical drum that is driven to rotate by applying a torque exceeding a certain level, and a support shaft that is arranged coaxially with the drum and supports the drum by contacting the inner peripheral surface of the drum. Consists of. The drum is held rotatably with respect to the support shaft.

  Here, the first separation roller 13 is driven by a motor 31, whereas the second separation roller 14 is a so-called non-active retard roller that is not driven by a motor.

  Further, the second separation roller 14 is provided with a one-way clutch so that the second separation roller 14 is driven to rotate in the return direction with a smaller torque than in the feed direction. This one-way clutch is a coupler that restricts the rotation of the support shaft in the feed direction and holds the support shaft so that it can rotate in the return direction. For example, the one-way clutch is fixed so as not to rotate the support shaft in the feed direction. In other words, the one-way clutch is a coupler that locks to prevent the spindle from rotating when the drum rotates in the feed direction, and releases the lock to rotate the spindle freely when the drum rotates in the return direction. Yes.

  The ultrasonic sensor 22 is a sensor for detecting whether or not the document A1 being conveyed is in a double feed state using ultrasonic waves, and is disposed between the separation unit 21 and the conveyance rollers 17 to 20. The ultrasonic sensor 22 includes a transmission unit 15 that transmits ultrasonic waves, and a detection unit 16 that detects ultrasonic waves transmitted through the document A1 and outputs detection signals.

  The sending unit 15 is a transmitter that converts an electric pulse signal into ultrasonic vibration and sends it out. The detection unit 16 is a receiver that receives the ultrasonic wave from the transmission unit 15, converts the ultrasonic vibration into an electric signal, and outputs it as a detection signal. The sending unit 15 and the detection unit 16 are arranged so that the ultrasonic wave sent from the sending unit 15 is incident on the document A1 being conveyed in an oblique direction so that the reflected wave does not interfere with the sending unit 15. Has been.

  In the sending unit 15, for example, ultrasonic waves having a frequency of 200 kHz are transmitted at predetermined time intervals in accordance with the conveyance of the document A <b> 1.

  The sending unit 15 and the detection unit 16 are arranged to face each other with the conveyance path A2 interposed therebetween, and the ultrasonic wave sent in one direction from the sending unit 15 propagates in the one direction and enters the detection unit 16. . Here, the ultrasonic sensor 22 is disposed between the first separation roller 13 and the conveyance roller closest to the first separation roller 13 on the conveyance path A2, that is, the most upstream conveyance roller 17. Yes.

  The transport rollers 17 to 20 are rollers for transporting the document A1 in the transport path A2 on the transport path A2 in the feeding direction, and each includes a pair of rollers arranged to face each other so as to sandwich the document A1 being transported. Become. One of the transport rollers 17 to 20 is driven in the feed direction by the motor 31 and the other roller is driven to rotate.

  The conveyance roller 17 is a conveyance roller arranged on the most upstream side, and the document reading unit 23 is arranged between the conveyance roller 17 and the conveyance roller 18 on the downstream side. That is, the transport roller 17 performs an operation of transporting the document A1 sent by the first separation roller 13 and the second separation roller 14 to the document reading unit 23 side.

  A document reading unit 24 is disposed between the conveyance roller 18 and the conveyance roller 19 on the downstream side. The conveyance roller 20 is a conveyance roller arranged on the most downstream side, and performs an operation of conveying the document A1 sent by the upstream conveyance roller 19 into the paper discharge tray 25.

  A roller that is not driven by a motor, for example, a guide roller for regulating paper feeding, is disposed between the separation roller 13 and the ultrasonic sensor 22 or between the ultrasonic sensor 22 and the transport roller 17. May be.

  The document readers 23 and 24 are optical readers that irradiate the document A1 with light and optically read an image from the document A1 to generate image data. Both of them are an exposure light source, a mirror, a condenser lens, and the like. And an image pickup device such as a CCD image sensor.

  The document reading unit 23 is arranged on the upper side of the conveyance path A2 and reads the upper surface of the document A1, whereas the document reading unit 24 is arranged on the lower side of the conveyance path A2 and It is a reading device that reads the lower surface.

  The paper discharge tray 25 is a storage unit for storing the read original A3, and the original A1 sent out by the transport roller 20 is stacked thereon.

  The power transmission unit 32 is a transmission mechanism for transmitting the driving force of the motor 31 to the pickup roller 12, the first separation roller 13, and the transport rollers 17 to 20, and includes a plurality of gears.

  The clutch unit 33 is a coupling mechanism that interrupts transmission of driving force to the pickup roller 12 and the first separation roller 13 as necessary in order to control the timing of paper feeding.

  Here, when the rotation of the motor 31 is reversed and the rotations of the pickup roller 12 and the first separation roller 13 are reversed, the rotations of the transport rollers 17 to 20 are also reversed in conjunction with these separation rollers.

  FIG. 2 is a diagram illustrating an example of an operation at the time of paper feeding in the main part of the image reading apparatus 1 in FIG. 1, and shows a case where there is no paper medium between the separation rollers 13 and 14 and the conveyance roller 17. Has been. In a state where the paper medium is not sandwiched between the first separation roller 13 and the second separation roller 14, the first separation roller 13 and the second separation roller 14 come into contact with each other.

  In this state, a frictional force in the feed direction is applied from the separation roller 13 to the separation roller 14 by the rotation of the separation roller 13 in the feed direction. As a result, torque in the feed direction is applied to the separation roller 14, and when the torque in the feed direction exceeds the upper limit value of the torque limiter in the separation roller 14, the torque limiter slips, and the separation roller 14 moves in the feed direction. Followed rotation.

  In this figure, the clockwise rotation of the separation roller 13 is the rotation in the feed direction, and the counterclockwise rotation is the rotation in the return direction.

  FIG. 3 is a diagram illustrating an example of an operation at the time of paper feeding in the main part of the image reading apparatus 1 in FIG. 1, and shows a case where the separation rollers 13 and 14 sandwich one original A10. In a state where the first separation roller 13 and the second separation roller 14 sandwich the single document A10, the urging force in the feeding direction due to the rotation of the separation roller 13 in the feeding direction causes the separation roller to pass through the document A10. 13 is added to the separation roller 14.

  At this time, if the torque in the feed direction applied to the separation roller 14 by the urging force exceeds the upper limit value of the torque limiter, the separation roller 14 is driven to rotate in the feed direction.

  FIG. 4 is a diagram illustrating an example of an operation at the time of paper feeding in the main part of the image reading apparatus 1 in FIG. 1, in which the separation rollers 13 and 14 sandwich the two originals A11 and A12. Yes. In the state where the first separation roller 13 and the second separation roller 14 sandwich a plurality of paper media, the energizing force in the feed direction due to the rotation of the separation roller 13 in the feed direction passes through these paper media. The separation roller 13 is added to the separation roller 14.

  In the case of a non-active retard roller, the one-way clutch is fixed so as not to contact the inner peripheral surface of the drum and rotate the support shaft that supports the drum in the feed direction.

  For this reason, even when the urging force due to the rotation of the separation roller 13 in the feed direction is applied to the separation roller 14 via the paper medium in the double feed state, the torque in the feed direction applied to the separation roller 14 is not reduced. If the upper limit value of the torque limiter is not exceeded, the torque limiter does not slip and the separation roller 14 stops.

  The upper limit value of the torque limiter is added to the separation roller 14 when there is no document or a single document is sandwiched so that the double feed state can be automatically canceled by the action of the separation rollers 13 and 14. Is determined in advance based on the torque to be applied and the torque applied while two or more documents are sandwiched.

  The upper document A11 moves in the feeding direction by the rotation of the separation roller 13, whereas the lower document A12 stops as the rotation of the separation roller 14 stops. When a double feed occurs, the separation rollers 13 and 14 act to separate the double feed document, and the double feed state is automatically canceled.

  However, when the frictional force between the upper document A11 and the lower document A12 is large, the torque limiter of the separation roller 14 slips, and the lower document A12 moves in the feeding direction together with the upper document A11. It will be. In such a case, the originals A11 and A12 are transported to the downstream transport roller 17 in the double feed state.

  FIG. 5 is a diagram illustrating a configuration example of a main part of the image reading apparatus 1 in FIG. 1, and schematically illustrates an example of the second separation roller 14. The second separation roller 14 is a non-active retard roller with a one-way clutch mechanism, and includes a drum 2, a sleeve 3, and a one-way clutch mechanism 4.

  The drum 2 is a cylindrical rotating body that rotates following the application of torque exceeding a certain level from the first separation roller 13. The sleeve 3 is disposed coaxially with the drum 2 and is a support shaft that supports the drum 2 by contacting the inner peripheral surface of the drum 2, and holds the drum 2 rotatably with respect to the support shaft. A torque limiter is configured using the frictional force between the inner peripheral surface of the drum 2 and the outer peripheral surface of the sleeve 3.

  The one-way clutch mechanism 4 is a device for restricting rotation of the sleeve 3 in the feeding direction, that is, counterclockwise rotation, and holding the sleeve 3 so as to be rotatable in the return direction, that is, clockwise rotation direction. is there. In this example, it is constituted by a fixed shaft portion and a leaf spring which is attached to the inner peripheral surface of the sleeve 3 and meshes with teeth formed on the peripheral surface of the shaft portion.

  In this one-way clutch mechanism, when the drum 2 is driven to rotate in the feed direction, the shaft portion and the sleeve 3 are locked (connected state). On the other hand, when the drum 2 is driven to rotate in the return direction, the lock between the shaft portion and the sleeve 3 is released, and the drum 2 rotates idle.

  FIG. 6 is a diagram showing the operation of the non-active retard roller in the conventional paper feeding device, and shows the case where the rotation of the separation roller is reversed when double feed occurs. In the conventional paper feeder, when the rotation of the separation roller is reversed at the time of occurrence of double feeding, the upper document among the paper media in the double feeding state is returned in the return direction by the urging force by the rotation of the separation roller in the return direction. Moving. On the other hand, the lower document stays at that position due to the frictional force with the retard roller whose rotation is restricted by the built-in torque limiter.

  That is, there is a problem that even if the separation roller is reversed to return the double-fed original to the storage unit, the double-fed original does not return correctly. Further, by continuing the rotation of the separation roller in the return direction, even if the lower document can be returned into the storage unit after the upper document is returned into the storage unit, The leading edge of the document is set at a position upstream of the leading edge of the lower document.

  FIG. 7 is a diagram showing an example of the operation at the time of occurrence of double feeding in the image reading apparatus 1 of FIG. 1, and shows a case where the rotation of the separation roller 13 is reversed. In this image reading apparatus 1, when the double feed is detected, the rotation of the first separation roller 13 is reversed by reversing the rotation of the motor 31.

  At that time, since the sleeve 3 is in a free rotation state by the action of the one-way clutch mechanism 4, the second separation roller 14 is driven to rotate in the return direction by the urging force from the first separation roller 13. As a result, it is possible to correctly return the document in the double feed state sandwiched between the separation rollers 13 and 51 into the paper feed tray 11.

  FIG. 8 is a block diagram showing a configuration example of the paper feed control unit 40 in the image reading apparatus 1 of FIG. The paper feed control unit 40 includes a double feed detection unit 41 that detects double feed based on a detection signal from the ultrasonic sensor 22 and a conveyance control unit 45 that outputs a motor inversion signal based on the detection result. The

  The double feed detection unit 41 includes a threshold storage unit 42, a comparison unit 43, and a double feed discrimination unit 44. Based on the detection signal from the detection unit 16, it is determined whether or not the document A1 being conveyed is double feed. The operation to be performed. Specifically, the comparison unit 43 determines the reception level of the ultrasonic wave based on the detection signal, and compares it with a predetermined threshold value stored in the threshold value storage unit 42. The double feed discriminating unit 44 discriminates whether or not the document A1 being conveyed is in a double feed state based on the comparison result by the comparison unit 43.

  The conveyance control unit 45 performs an operation of controlling the conveyance of the document A1 based on the determination result by the double feed determination unit 44. Specifically, when double feed is detected, first, the clutch unit 33 is controlled, and the pickup roller 12 and the first separation roller 13 are moved until the paper medium in the double feed state reaches the transport roller 17. The operation to stop is performed.

  Then, after the reading of the document preceding the paper medium in the double-feed state is completed and the document is discharged, the rotation of the motor 31 is reversed to pick up the roller 12, the first separation roller 13, and the transport rollers 17˜. An operation of reversing the rotation of 20 is performed.

  Steps S <b> 101 to S <b> 106 in FIG. 9 are flowcharts illustrating an example of an operation during paper feeding in the image reading apparatus 1 in FIG. 1. First, the double feed detection unit 41 detects whether or not the document A1 being conveyed is double feed by acquiring the reception level of the ultrasonic sensor 22 and comparing it with a predetermined threshold (step S101). S102).

  Next, when it is determined that the document A1 being transported is double-feed, the transport control unit 45 immediately stops the pickup roller 12 and the separation roller 13 (step S103).

  Next, the conveyance control unit 45 stops the conveyance of the paper medium in the double feed state by stopping the pickup roller 12 and the separation roller 13, and then completes reading of the paper medium preceding the paper medium, If the paper is discharged, the rotation of the motor 31 is reversed to reverse the rotation of the pickup roller 12, the separation roller 13, and the transport rollers 17 to 20 (steps S104 and S105).

  Next, the conveyance control unit 45 determines whether or not to resume paper feed. When the paper feed is resumed, the process is terminated (step S106).

  According to the present embodiment, since it is determined whether or not the paper medium being transported is a double feed based on the ultrasonic wave that has passed through the paper medium, the paper medium that is being double fed in a completely overlapped state Even so, double feeding can be detected. In addition, the pickup roller 12 and the separation roller 13 are stopped by determining whether or not the feed is double based on the output of the ultrasonic sensor 22 disposed between the separation rollers 13 and 14 and the conveyance roller 17. It is possible to continue transporting the paper medium preceding the paper medium while leaving the paper medium in the double feed state in the transport path A2.

  Furthermore, the second separation roller 14 is driven to rotate when a feed direction torque exceeding a certain level is applied from the first separation roller 13, and the return direction is driven to rotate with a smaller torque than the feed direction. Therefore, when the rotation of the first separation roller 13 is reversed, the separation roller can be driven to rotate in the return direction. Therefore, by reversing the rotation of the first separation roller 13 when double feeding is detected, the paper medium in the double feeding state sandwiched between the first separation roller 13 and the second separation roller 14 is fed. The tray 11 can be returned correctly. In particular, in a non-active retard type paper feeding device in which a separation roller for exerting a frictional force in the return direction on a double-fed paper medium is not driven by a motor, the configuration is simple by providing the separation roller with a one-way clutch mechanism. Thus, in a low-cost paper feeding device, the paper medium in the double feed state sandwiched between the separation rollers can be correctly returned into the storage unit.

  In the present embodiment, the example of the image reading apparatus 1 including the paper feeding device has been described. However, the present invention is not limited to this. For example, the present invention can be applied to a printing apparatus that prints an image on recording paper.

1 is a diagram illustrating an example of a schematic configuration of an image reading apparatus including a sheet feeding device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating an example of an operation at the time of paper feeding in a main part of the image reading apparatus in FIG. FIG. 2 is a diagram illustrating an example of an operation at the time of paper feeding in a main part of the image reading apparatus 1 in FIG. 1, in which the separation rollers 13 and 14 sandwich a single document A10. FIG. 2 is a diagram illustrating an example of an operation at the time of paper feeding in a main part of the image reading apparatus 1 in FIG. 1, in which a separation roller sandwiches two originals A11 and A12. FIG. 2 is a diagram illustrating a configuration example of a main part of the image reading apparatus 1 in FIG. 1, and schematically illustrates an example of a second separation roller 14. It is a figure showing operation of a non-active retard roller in a conventional paper feeder, and shows a case where rotation of a separation roller is reversed when double feed occurs. FIG. 2 is a diagram showing an example of an operation at the time of occurrence of double feed in the image reading apparatus 1 in FIG. 1, and shows a case where the rotation of the separation roller 13 is reversed. FIG. 2 is a block diagram illustrating a configuration example of a paper feed control unit 40 in the image reading apparatus 1 of FIG. 1. 3 is a flowchart illustrating an example of an operation during paper feeding in the image reading apparatus 1 in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reader 2 Drum 3 Sleeve 4 One-way clutch mechanism 11 Paper feed tray 12 Pickup roller 13 First separation roller 14 Second separation roller 15 Sending part 16 Detection part 17-20 Conveyance roller 21 Separation part 22 Ultrasonic sensor 23 , 24 Document reading unit 25 Paper discharge tray 31 Motor 32 Power transmission unit 33 Clutch unit 40 Paper feed control unit 41 Double feed detection unit 42 Threshold storage unit 43 Comparison unit 44 Double feed discrimination unit 45 Transport control unit A1, A3 Document A2 transport Road

Claims (4)

A storage unit that stores a large number of paper media, a separation unit that separates the paper media in the storage unit one by one and sends them to a transport path, and two or more transport rollers that transport the paper medium on the transport path; In a paper feeder having
An ultrasonic sensor comprising a sending unit for sending ultrasonic waves and a detecting unit for detecting the ultrasonic waves transmitted through the paper medium, and disposed between the separating unit and the transport roller closest to the separating unit When,
Based on the output of the detection unit, a double feed detection unit for determining whether or not the paper medium being conveyed is double feed,
A conveyance control unit that controls conveyance of the paper medium based on the determination result by the double feed detection unit;
The separation unit is a separation roller driven by a motor, and a first separation roller for conveying the paper medium in a feeding direction;
A separation roller that is driven to rotate by the rotation of the first separation roller, and is driven to rotate when a torque in the feed direction exceeding a certain level is applied, and is driven to rotate in the return direction with a smaller torque than the feed direction. A second separating roller,
The conveyance control unit reverses the rotation of the first separation roller when double feeding is detected. The second separation roller includes a cylindrical drum that rotates following the application of torque in the feed direction exceeding a certain level from the first separation roller;
A spindle that contacts the inner peripheral surface of the drum and supports the drum;
The sheet feeding device according to claim 1, further comprising a one-way clutch that restricts rotation of the support shaft in a feeding direction and rotatably supports the support shaft in a return direction.   The sheet feeding device according to claim 2, wherein the one-way clutch is fixed so as not to rotate the support shaft in the feeding direction.   The conveyance control unit stops the first separation roller until the paper medium in the double feed state reaches the conveyance roller, and after the paper medium preceding the paper medium is discharged, the first separation roller is stopped. The sheet feeding device according to claim 1, wherein the rotation of the separation roller is reversed.

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