JP2005035757A - Sheet handling device and image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet handling device allowing a single sensor to sense the leading edge and the trailing edge of each sheet fed from a sheet stacker and also judge whether the sheets are fed properly one by one or not (i.e., double feed). <P>SOLUTION: The sheet treatment device is equipped with the sheet stacker, a separating means to feed separately the stacked sheets, a resist roller to correct an eventual skew condition of the sheet fed from the separating means, an ultrasonic wave sensor consisting of a wave sending sensor and reception sensor installed between the separating means and the resist roller, and a judging means to make both sensing the leading edge and the trailing edge of the sheet and judging eventual double feed condition of sheets based on the output signal given by the wave reception sensor. The judging means executes a first comparison for sensing the leading edge and the trailing edge of the sheet and a second comparison to be conducted at a timing and with conditions different from in the first comparison for judging the double feed condition of the sheets. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sheet handling apparatus including a sheet separating unit that separates sheets stacked on a sheet stacker one by one and feeds them to the downstream side. In particular, whether or not two or more fed sheets are fed out in a superimposed manner is determined. The present invention relates to a sheet handling apparatus having a function of detecting.

  An image reading apparatus that separates sheets (cut sheets, plastic sheets, etc.) stacked on a sheet stacker one by one and reads an image of each sheet is mounted on a copying machine or a facsimile machine. In a copying machine, sheets (sheets) are separated from a sheet cassette one by one and supplied to a printing unit so that characters and figures are printed on the sheet.

  As described above, reliably separating and feeding out the sheets stacked on the sheet stacker such as a document tray or a paper cassette one by one is extremely important in a sheet handling apparatus that performs a document image reading process, a printing process, and the like. It has become a technical element.

  Therefore, in an automatic document feeder (hereinafter referred to as “ADF”) that feeds sheets one by one from a sheet stacker (sheet feeding tray), the sheets stacked on the sheet stacker are separated one by one. A sheet separation mechanism is provided. Further, in such a sheet conveyance path in the ADF, a plurality of sensors are arranged at various positions for accurate sheet position detection (sheet leading edge and trailing edge detection). Patent Document 1 discloses an example of an ADF having such a sheet separation mechanism.

  In Patent Document 1, a feeding roller 18 that can move up and down to feed a document (sheet) in contact with the uppermost sheet of the sheets stacked on the sheet stacker 11, and a feed that feeds out only one upper surface of the fed document (sheet). A paper roller 19; a separation pad 20 that prevents the second and subsequent originals from being fed; a registration roller 21 that corrects a skew state of the original fed from the paper feed roller 19; An ADF including a registration sensor S5 that is installed between rollers 21 and detects the leading edge and the trailing edge of a sheet is disclosed.

  Even with an ADF having such a separation mechanism, a sheet (especially in the case of a document) stacked on the sheet stacker may be bent at its end, and the sheet separation mechanism as described above is provided. However, the sheets are not necessarily separated and fed out one by one. For this reason, it is necessary to detect whether the sheets are normally fed out one by one or sent out in a state where two or more sheets are overlapped (referred to as “multiple feeding” in the present application).

  Therefore, in the ADF according to the related art having the above-described configuration, an optical sensor for detecting the position of the sheet handled in the sheet feeding path and an ultrasonic sensor for detecting the double feed state of the sheet are provided in different places. The sheet feeding timing control, the sheet length detection, and the double feed detection are performed based on output signals from these sensors.

  As an example of performing double sheet detection using an ultrasonic sensor, Patent Document 2 discloses an ultrasonic transmitter 11 disposed above a moving surface 13 of a detection target 14 and an ultrasonic reception disposed below. The ultrasonic wave propagation axis 10 constituted by the machine 16 is inclined with respect to the moving surface 13 so that a stable amount of ultrasonic waves is measured by the ultrasonic wave receiver 16.

  As another example of detecting a double feed of a sheet using an ultrasonic sensor, Patent Document 3 is installed in a register device provided in a portion that delivers a sheet fed from a sheet feeding unit to a post-processing device. In an ultrasonic type two-sheet detector comprising a wave transmitting sensor 23 disposed below and a wave receiving sensor 24 disposed below with a sheet interposed therebetween, ultrasonic waves are obliquely applied to the sheet to be detected. Discloses a method of detecting two ultrasonic waves.

JP 2001-354339 A Japanese Utility Model Publication No. 6-49567 JP-A-6-72591

  In such a sheet handling apparatus having a sheet double feed detection function, an ultrasonic sensor for performing double feed detection and a sensor for detecting the leading edge or the trailing edge of the sheet to be handled ("Registration sensor 5S" in Patent Document 1). Must be placed individually on the feed path where the installation space is not sufficient.

  Here, when handling a thin sheet that vibrates vertically or flutters when the sheet is thin and travels, in order to accurately detect the double feed state of the sheet, the ultrasonic sensor installation position and the ultrasonic sensor must be used. The timing for capturing the output signal is strictly limited.

  According to the present invention, a single detection unit installed in a feeding path detects double feeding as to whether or not sheets stacked on a sheet stacker are fed one by one, and the leading edge and / or trailing edge of the sheet. An object of the present invention is to provide a sheet handling apparatus capable of performing detection.

  Therefore, the present invention provides a sheet stacker, a separating unit that separates and feeds out the sheets stacked on the sheet stacker, a registration roller that corrects a skew state of the sheet fed from the separating unit, and the separating unit. And an ultrasonic sensor comprising a wave transmission sensor and a wave reception sensor disposed between the registration rollers, and detection of the leading edge and / or trailing edge of the sheet based on an output signal from the wave reception sensor It is an object of the present invention to provide a sheet handling apparatus including a determination unit that performs both determinations. Here, the sheet size (length in the feeding direction) can also be detected by detecting the leading edge and the trailing edge of the sheet.

  For this reason, the determination means performs the first comparison for detecting the leading edge and the trailing edge of the sheet and the timing and conditions different from the first comparison in order to determine the double feed state of the sheet. A second comparison is performed. In this way, by detecting the leading or trailing edge of the sheet and the double feed detection of the sheet under different conditions and timing, both the presence / absence detection of the sheet and the double feed detection of the sheet, which are conventionally performed by a plurality of sensors, are performed. This makes it possible to detect only with a single sensor. Here, the first timing is the time when the leading edge or trailing edge of the sheet has passed the ultrasonic sensor installation position, and the second timing is a predetermined time after the leading edge of the sheet arrives at the registration roller. It can be provided at one or more later times.

  By the way, the wave transmission sensor and the wave receiving sensor are preferably arranged in a state of being inclined with respect to the sheet running surface between the separating unit and the registration roller and facing each other. As a result, even if the sheet surface vibrates up and down while being fed, the amount of ultrasonic waves received by the wave receiving sensor can be stabilized.

  There are a plurality of embodiments of the discrimination means of the present invention. The discriminating means according to the first embodiment includes a comparison circuit that performs the first comparison and the second comparison, and a receiving amplifier that amplifies an output signal of the receiving sensor, In the comparison of the second and the second comparison, the gain of the amplifier is changed and compared.

  The discriminating means according to the second embodiment of the present invention comprises: a comparison circuit that performs the first comparison and the second comparison; and a reception amplifier that amplifies an output signal of the reception sensor. In the first comparison and the second comparison, the comparison is performed by changing the value of the reference value input to the comparison circuit.

  Further, the discriminating means according to the third embodiment of the present invention comprises: a first comparison circuit that performs the first comparison; a second comparison circuit that performs the second comparison; and an output signal of the reception sensor. A first receiving amplifier for amplifying with a predetermined gain, and a second receiving amplifier for amplifying the output signal of the receiving sensor with a gain different from that of the first amplifier.

  Further, the discriminating means according to the fourth embodiment of the present invention comprises a comparison circuit that performs the first comparison and the second comparison, a reception amplifier that amplifies an output signal of the reception sensor, and the transmission circuit. A transmission amplifier that adjusts the level of the ultrasonic wave output from the wave sensor, and in the first comparison and the second comparison, the gain of the transmission amplifier is changed for comparison. To do.

  The discriminating means according to the fifth embodiment of the present invention comprises: a wave receiving amplifier that amplifies the output signal of the wave receiving sensor by a predetermined gain; and an A / D converter that digitally converts the analog output of the wave receiving amplifier. And performing the first comparison and the second comparison based on a digital output signal from the A / D converter.

  The discrimination means according to the first to fifth embodiments described above enables detection of both the leading edge detection and double feed detection of the sheet.

  Here, in the present sheet handling apparatus, when the sheet fed from the separation unit is determined to be double feed by the determination unit according to each of the first to fifth embodiments, the subsequent sheet stacker Stop the sheet supply. As a result, the operator of the sheet handling apparatus is given an opportunity to check the bending of the sheet end and the like to refeed the sheet.

  The present invention further includes a sheet stacker, separation means for separating and feeding out the sheets stacked on the sheet stacker, a registration roller for correcting a skew state of the sheet fed from the separation means, and the registration roller. A conveying unit that conveys the fed sheet to a reading position, an optical reading unit that reads the sheet conveyed to the reading position, and an inclined state with respect to a sheet traveling surface between the separating unit and the registration roller. An ultrasonic sensor comprising a transmitted wave sensor and a received wave sensor, and a discriminating means for both detecting the leading edge and / or trailing edge of the sheet and determining a double feed state based on an output signal from the received wave sensor; An image reading apparatus characterized by comprising:

  The sheet handling apparatus according to the present invention realizes the detection of the double feeding of the sheet and the detection of the leading edge and the trailing edge of the sheet to be fed with a single ultrasonic sensor. Since the ultrasonic sensor can be installed at the optimum position in the sheet, it is possible to accurately detect the double feed of the sheet and the sheet size, and to simplify the structure of the sheet handling apparatus, thereby reducing the cost of the apparatus.

  Further, in the present sheet handling apparatus, since the wave receiving sensor is disposed on the upper side of the sheet traveling surface, it is possible to eliminate the situation where the paper dust or the like of the sheet falls on the sensor surface of the wave receiving sensor. Thus, it is possible to stabilize the accuracy of the sheet leading edge and trailing edge detection and the double feed detection. This is because the transmission sensor has a larger ultrasonic vibration on the sensor surface than the reception sensor, so that the sensor surface is mounted inclined with respect to the plane perpendicular to the direction of gravity. This is because dust such as paper dust easily falls from the sensor surface.

  In addition, it is possible to detect double feed more reliably by continuously determining whether or not the sheet fed from the separating means is double feed before the trailing edge of the sheet passes the registration roller. It was.

  Hereinafter, the details of the present invention will be described based on the drawings.

  FIG. 1 shows a configuration example of an ADF 10 that is one embodiment of a sheet handling apparatus according to the present invention. In FIG. 1, the ADF 10 is mounted on an image reading apparatus 20 and allows a sheet (original) to pass through the upper surface of the platen 12 of the apparatus main body 20. The image reading apparatus 20 irradiates a sheet with light from a light source 21 that constitutes an optical reading unit disposed below the platen 12, and uses a mirror 22 or a prism to reflect the reflected light to a CCD (not shown). By guiding, the image on the sheet is converted into an electric signal in the CCD.

  The image reading device 20 also includes a second platen 13 having an area where the entire surface of the sheet can be placed, and the image of the sheet placed on the upper surface of the platen 13 can be read by opening and closing the ADF 10. ing.

  The ADF 10 includes a sheet stacker 11 on which a plurality of sheets can be placed, a feeding roller 1 that picks up the sheets stacked on the sheet stacker 11 and feeds them downstream, and a sheet fed by the feeding roller 1. Separating means 2 that separates the sheets one by one and feeds them toward the platen 12, a registration roller pair 5 that corrects the skew state of the sheet fed from the separating means 2, and a separation means 2 and a registration roller pair 5. The ultrasonic sensor 3 for detecting the leading and trailing edges of the sheet fed from the separating means 2 and the double feeding state, and the sheet fed from the registration roller pair 5 pass in a state where the sheet is in contact with the upper surface of the platen 12. A first conveying roller pair 6 to be received, a second conveying roller pair 7 that receives the sheet that has passed through the upper surface of the platen 12 and conveys the sheet to the downstream side, and A discharge roller pair 8 to discharge onto the sheet delivery stacker 14 is conveyed from the second conveying roller pair 7, and a.

  In the conventional ADF, a registration sensor is installed on the upstream side of the registration roller pair 5 in order to detect the leading edge of the sheet, and the timing at which the leading edge of the sheet fed from the separating unit 3 arrives at the registration roller pair 5. Was to be detected. However, the ADF according to the present invention does not require such a resist sensor. The leading edge and the trailing edge of the sheet are detected by the ultrasonic sensor 3 and a discrimination unit that processes output signals from the ultrasonic sensor. Since the feeding speed of the registration roller pair 5 is known, it is possible to know the size of the fed sheet (the length in the feeding direction).

  The ultrasonic sensor 3 includes a wave transmission sensor 3 a and a wave reception sensor 3 b, and is installed between the separating unit 2 and the registration roller pair 5. And it is good to arrange | position the ultrasonic sensor 3 in the state which mutually opposed in the state inclined with respect to the sheet | seat running surface if possible. As a result, the amount of ultrasonic waves received by the wave receiving sensor 3b can be stabilized against vibrations of the sheet surface. Further, in the present sheet handling apparatus, the wave transmission sensor 3a is disposed below the seat traveling surface, and the wave receiving sensor 3b is disposed above the seat traveling surface.

  The ADF 10 further includes a switchback path 14 that is switched back in the discharge path from the platen 12 to the discharge stacker 14 and is sent again to the registration roller pair 5 and fed to the upper surface of the platen 12.

  The sheet stacker 11 is inclined above a predetermined angle and is disposed above the discharge stacker 14. The sheet placed on the sheet stacker 11 is regulated by a side guide 24 that regulates the side portion thereof. The sheet is placed in a state where the leading end is pushed in such a manner that the leading end of the sheet comes into contact with the leading end portion 11 a of the sheet stacker 11, and the liftable feeding roller 1 for feeding out the sheet descends and is stacked on the sheet stacker 11. And the sheet is fed downstream (separating means 2 side). At this time, the number of sheets fed out is not necessarily one.

  The separating means 2 feeds the sheet fed from the feeding roller 1 to the downstream side, and prevents the feeding of the second and subsequent sheets on the lower side through only one uppermost sheet. And a separation roller 2b. The separation roller 2b is stopped when the sheet is fed out, thereby preventing the second and lower sheets from being fed out. Accordingly, instead of the separation roller 2b, a non-rotating separation pad may be used.

  The sheet that has passed through the separating means 2 is sent to the next registration roller pair 5 side. The registration roller pair 5 is stopped when the leading edge of the sheet fed from the separating unit 2 hits the registration roller pair 5 and is driven to rotate after a predetermined time after the leading edge of the sheet arrives at the registration roller pair 5. . As a result, the sheet once forms a loop state between the registration roller pair 5 and the separating means 2 and the leading ends thereof are aligned. As a result, the skew state of the sheet is corrected. The timing at which the leading edge of the sheet hits the registration roller pair 5 is detected by the ultrasonic sensor 3. The ultrasonic wave output from the transmission sensor 3a constituting the ultrasonic sensor 3 is received when the leading edge of the sheet enters between the transmission sensor 3a and the reception sensor 3b because the ultrasonic path 3c is obstructed by the sheet. The level of ultrasonic waves received by the sensor 3b is lowered. The determination unit detects the leading edge of the sheet by detecting this timing. Similarly, the rear end of the sheet is a timing at which the level of the ultrasonic wave received by the wave receiving sensor 3b due to the opening of the ultrasonic wave path 3c increases.

  In the present ADF 10, the separation roller 3b constituting the separation means and one drive roller 5a of the registration roller pair 5 are configured to be driven by a single feeding drive motor (not shown). When the feeding drive motor is controlled to rotate in the forward direction, the separation roller 3b is driven to rotate and the registration roller pair 5 is stopped. When the feeding drive motor is controlled to rotate in the opposite direction, the separation roller 3b is stopped and the registration roller is stopped. The pair 5 is rotationally driven.

  In the present ADF, as will be described in detail later, the ultrasonic sensor 3 discriminates the double feed state of the sheet once the sheet forms a loop between the registration roller pair 5 and the separating means 2 and then the registration roller. After the pair 5 is rotationally driven from the stop, this is performed based on the output signal of the wave receiving sensor 3b after the loop state is canceled. This realizes accurate detection of the double feed state of the sheet.

  The sheet fed from the registration roller pair 5 is supplied to the first transport roller pair 6 and is transported by the first transport roller pair 6 so as to run in a state of being in contact with the upper surface of the platen 12. The sheet is optically read by the optical reading means arranged below the sheet.

  In the single-sided reading mode, the sheet on which the image on one sheet surface is optically read is discharged onto the discharge stacker 14 by the second conveying roller pair 7 via the discharge path 23. In this case, it is switched back by the reverse rotation drive of the discharge roller pair 8 and sent out again to the registration roller pair 5 via the switchback path 24. For this reason, a flapper 29 is provided at the intersection of the discharge path 23 and the switchback path 24. The flapper 29 is always urged downward by an urging spring (not shown). When the sheet is sent along the discharge path 23 to the discharge roller pair 8, the flapper 29 is moved upward by the leading end of the discharged sheet. When the sheet is switched back by the discharge roller pair 8, the discharge path 23 is positioned below to close the discharge path 23 and guide the sheet to the switchback path 24. .

  FIG. 2 shows a change in the state of the sheet between the separating unit 2 and the registration roller 5 and the arrangement relationship of the ultrasonic sensors 3.

As described above, the ultrasonic sensor 3 includes the transmission sensor 3 a and the reception sensor 3 b, and face each other in an inclined state with respect to the sheet traveling surface between the separating unit 2 and the registration roller pair 5. Arranged in a state. A wave transmission sensor 3a is disposed below the seat travel surface, and a wave reception sensor 3b is disposed above the seat travel surface. The ultrasonic sensor 3 detects the leading edge and the trailing edge of the sheet P and detects the double feeding state of the sheet. The ultrasonic sensors 3 are arranged in a state of being opposed to each other while being inclined with respect to the sheet running surface. The reason for this is to stabilize the amount of ultrasonic waves received by the wave receiving sensor 3b. If the transmission sensor 3a and the reception sensor 3b are arranged so as to oppose each other at a position perpendicular to the sheet running surface, the amount of ultrasonic reception greatly fluctuates due to slight distortion generated on the sheet surface. End up. This is because the double feed state of the sheet cannot be accurately detected.

  In addition, the wave receiving sensor 3b is disposed above the sheet running surface, because dust and dirt such as paper dust accumulate on the sensor surface that receives the ultrasonic wave, thereby degrading accurate detection of the ultrasonic wave reception amount. It is for preventing.

  FIG. 2A shows a state in which the leading edge of the sheet P fed out from the separating unit 2 blocks the ultrasonic path 3c between the transmission sensor 3a and the reception sensor 3b constituting the ultrasonic sensor 3. Since the ultrasonic path 3c is obstructed by the sheet P, the level of the ultrasonic wave received by the wave receiving sensor 3b is reduced, and the discrimination means can detect the leading edge of the sheet P at the timing of the reduction of the ultrasonic level.

  FIG. 2B shows a state where the sheet has a resist loop. The registration roller pair 5 is controlled to stop when the leading edge of the sheet P fed from the separating unit 2 arrives. For this reason, the sheet P fed out from the separating unit 2 is further pushed out by the separating unit 2 after the leading end of the sheet P hits the registration roller pair 5, thereby forming a loop state. Since the loop shape (diameter) fluctuates or fluctuates, the amount of ultrasonic waves received by the wave receiving sensor 3b is not stable, and this loop shape is not suitable for detecting the double feed state of the sheet. Is appropriate.

  FIG. 2C shows a state in which the sheet P once looped is linearly extended with respect to the running surface between the separating unit 2 and the registration roller pair 5. When a predetermined time elapses after the leading edge of the sheet P hits the registration roller pair 5, the registration roller pair 5 that has been stopped is started. At the same time as the registration roller pair 5 is started, the separation roller 2a constituting the separation means 2 is stopped, so that the loop shape is gradually extended and the loop state is eliminated. This time is the most suitable timing for detecting the double feed state of the sheet P because the amount of ultrasonic waves received by the wave receiving sensor 3b is stabilized. At this time, since the sheet P is nipped by the separating means 2 and the registration roller pair 5, the sheet P does not vibrate up and down or flutter. Furthermore, if the sheet P is in a double feed state, an air gap is generated between the sheets when the loop state shown in FIG. 2C is formed, and the ultrasonic wave is attenuated by this air layer. Therefore, the ultrasonic sensor 3 can accurately detect the double feed state of the sheet.

  FIG. 2D shows a state in which the sheet P is further conveyed downstream by the registration roller pair 5 and the rear end thereof leaves the nip of the separation roller 2. In this state, the sheet P moves up and down around the nip point of the registration roller pair 5 and flutters. Therefore, based on the output signal of the wave receiving sensor 3b at this time, the double feed state of the sheet is determined. It cannot be detected accurately.

  FIG. 2E shows the time when the trailing edge of the sheet passes through the ultrasonic path 3 c between the wave transmitting sensor 3 a and the wave receiving sensor 3 b constituting the ultrasonic sensor 3. Since the ultrasonic path 3c hindered by the sheet P is opened, the level of the ultrasonic wave received by the wave receiving sensor 3b is increased, and the discriminating means can detect the rear end of the sheet at the timing of the increase of the ultrasonic level. it can.

  This ADF control device determines the sheet size (sheet size) from the time from sheet leading edge detection to trailing edge detection, the feeding speed of the registration roller pair 5 and the stopping time of the registration roller pair 5 when the sheet is in registration loop. The length in the feeding direction) can be calculated.

  FIG. 3 is a flowchart for explaining the timing of reading the output signal of the wave receiving sensor 3b constituting the ultrasonic sensor 3. The flowchart of FIG. 3 will be described with reference to FIG.

  The sheet fed from the feeding roller 1 passes through only one uppermost sheet in the separating unit 2 and is sent out to the next registration roller pair 5 side so as to prevent the second and subsequent sheets from being fed out. (S1). It is detected that the leading edge of the sheet has reached a predetermined position by blocking the ultrasonic path of the ultrasonic sensor 3 (S2).

  Next, since the sheet registration roller pair 5 is stopped when the leading edge of the sheet fed from the separating means 2 hits the registration roller pair 5, the sheet forms a loop in the registration roller pair 5 (S3). . The separation roller 2b constituting the separation unit 2 is stopped at this time, and the separation of the sheet is finished (S4).

  Next, the registration roller pair 5 is rotationally driven a predetermined time after the leading edge of the sheet arrives at the registration roller pair 5. As a result, the feeding of the sheet is started (S5), and the loop state formed while the registration roller pair 5 is stopped is canceled for the sheet (S6). Thereby, the skew state of the sheet is also corrected. At this time, the output signal of the wave receiving sensor 3b constituting the ultrasonic sensor 3 is read (S7).

  In this way, the double feed state of the sheet is determined based on the output signal of the wave receiving sensor 3b at the time when the loop state in the registration roller pair 5 of the sheet is eliminated (S8). At that time, the operation of the ADF is stopped (S9). Here, even if the double feeding of the sheets is detected, the reading of the sheets may be continued and a display to that effect may be displayed after the reading of all the sheets is completed.

  Further, when the double feeding of the sheet is not detected, the determination of the double feeding state of the sheet based on the output signal of the wave receiving sensor 3b is performed until the trailing edge of the sheet passes the separating unit 2 (S10). By carrying out continuously (repeating operation of S7 and S8), a more accurate sheet double feed state is detected.

  Then, after the trailing edge of the sheet exits the separating means 5, the trailing edge of the sheet is detected by passing through the ultrasonic optical path of the ultrasonic sensor (S11). Here, since the time from sheet leading edge detection to trailing edge detection is known, the sheet size (the length in the sheet feeding direction) is calculated (S12). Thereafter, the sheet is fed downstream (S13), and the next sheet is continuously fed and separated.

  FIG. 4 shows an example of a timing chart in the control of the image reading apparatus 20 equipped with the ADF 10.

  4, the sheet stacker 11 (FIG. 1) is provided with a sheet placement detection sensor (not shown) for detecting whether or not a sheet is placed, and the sheet is placed on the sheet stacker 11. When the image reading start button of the image reading apparatus 20 is pressed in this state, a sheet feeding start signal rises to start sheet feeding.

  The feeding roller 1 contacts the uppermost sheet on the sheet stacker 11 and feeds the sheet by rotating the feeding driving motor (not shown) in the forward direction in response to the rising edge of the sheet feeding start signal. The separation roller 2a is driven to rotate. At this time, the ultrasonic sensor 3 is also in an operating state.

  When the separation motor 2a starts to rotate in this way, the leading edge of the sheet blocks the ultrasonic path 3c (see FIG. 2A), so that the leading edge of the sheet is detected. The separation roller 3a continues to rotate and stops only for a predetermined time set after the detection of the leading edge of the sheet. During this time, since the registration roller pair 5 is stopped, the sheet is blocked by the registration roller pair 5 to form a loop shape, and the skew state is corrected.

  Thereafter, at a predetermined timing, a feeding drive motor (not shown) is reversely rotated, whereby the registration roller pair 5 starts to rotate. Since the separation roller 2a is stopped simultaneously with the start of the rotation driving of the registration roller pair 5, the sheet loop state (registration loop) is gradually eliminated. Since the registration loop is canceled after a predetermined time has elapsed since the rotation of the registration roller pair 5 is started, the output signal of the wave receiving sensor 3b constituting the ultrasonic sensor 3 is read at that time.

  In the present invention, based on the output signal in this state, it is determined whether or not the sheet is in a double feed state. The output signal of the wave receiving sensor 3b is read continuously until the trailing edge of the sheet leaves the nip of the separating unit 2, so that the double feed state of the sheet is accurately determined.

  Thereafter, the trailing edge of the sheet passes through the ultrasonic path 3c (see FIG. 2E), so the trailing edge of the sheet is detected. Here, the determination means determines the sheet size (sheet) from the time from detection of the leading edge of the sheet to detection of the trailing edge, the feeding speed of the registration roller pair 5 and the stop time of the registration roller pair 5 when the sheet is registered in the registration loop. (The length in the feeding direction) can be calculated.

  Image reading is started a predetermined time after the leading edge of the sheet that has passed through the registration roller pair 5 is detected by a lead sensor 9 (see FIG. 1) disposed upstream of the image reading position, and a CCD (optical reading means). The output signal is taken into the memory. At the same time, the next sheet stacked on the sheet stacker 11 is fed out.

  FIG. 5 is a block diagram showing the control circuit of the discriminating means according to the first embodiment.

  As described above, the ultrasonic sensor 3 includes the transmission sensor 3a and the reception sensor 3b. In the discriminating means according to the first embodiment, the transmission sensor 3a is driven by an amplification circuit 32 that amplifies the ultrasonic signal oscillated by the ultrasonic oscillation circuit 31. Here, the gain (amplification factor) of the amplification circuit 32 that amplifies the ultrasonic signal oscillated by the ultrasonic oscillation circuit 31 can be varied by volume knob or the like. As a result, the output level of the ultrasonic wave emitted from the wave transmission sensor 3a can be freely set, so that variations in sensor (element) sensitivity, the installation angle with respect to the seat running surface, the distance from the wave reception sensor 3b, and the like can be adjusted. it can.

On the other hand, the output signal of the wave receiving sensor 3b is amplified by the amplifier circuit 34, and is smoothed by the integrating circuit having a predetermined time constant after the amplified electrical signal is rectified in the smoothing circuit 35.
Here, the CPU 33 and the amplifier 34 are connected via a D / A converter 38, and the gain of the amplifier 34 can be arbitrarily set by software. The CPU 36 individually sets the gain of the output signal of the wave receiving sensor 3b when detecting the leading edge and trailing edge of the sheet and when detecting double feeding of the sheet. As a result, the single ultrasonic sensor 3 can accurately perform the detection of the leading and trailing edges of the sheet and the double detection of the sheet.

  When detecting the leading edge and trailing edge of the sheet, it is only necessary to detect the presence or absence of the sheet. Therefore, a relatively small first gain value is set. When detecting the double sheet feeding, whether the sheet is one sheet or two or more sheets. Therefore, a relatively large second gain value is set.

  The electrical signal that has passed through the smoothing circuit 36 is compared with a reference value set in advance in the comparison circuit 37. The comparison value output from the comparison circuit 37 is input to the CPU 36, and the leading edge and trailing edge detection of the sheet and the double feed detection of the sheet are performed at different timings and different comparison conditions. As described above, the double feed detection is continuously performed from the time when the loop formation of the sheet is released between the separating unit 3 and the registration roller pair 5 until the trailing edge of the sheet leaves the nip in the separating unit 3. This enables accurate sheet double feed detection.

FIG. 6 is a block diagram showing a control circuit of the discriminating means according to the second embodiment.
The circuit configuration of the wave transmission sensor 3a in the discrimination means of the second embodiment is the same as that of the first embodiment shown in FIG.

  On the other hand, the output signal of the wave receiving sensor 3b is amplified by a predetermined gain defined in advance by the amplifier circuit 34, and the electric signal amplified by the smoothing circuit 35 is rectified and smoothed by an integrating circuit having a predetermined time constant. The The electric signal that has passed through the smoothing circuit 36 is compared with a reference value in the comparison circuit 37.

  Here, the negative input terminals of the CPU 33 and the comparison circuit 37 are connected via a D / A converter 38, and the CPU 36 sets a reference value with which the output signal of the smoothing circuit 35 is compared in the comparison circuit 37. It is configured to be arbitrarily set by software. The CPU 36 individually sets a reference value to be compared with the output signal of the wave receiving sensor 3b when detecting the leading and trailing edges of the sheet and when detecting the double feed of the sheet. As a result, the single ultrasonic sensor 3 can accurately detect the leading and trailing edges of the sheet and the double detection of the sheet. That is, when detecting the leading edge and the trailing edge of the sheet, since the level of the ultrasonic wave received by the wave receiving sensor 3b is relatively high, a relatively large first reference value is set to detect sheet double feed. In this case, since the level of the ultrasonic wave received by the wave receiving sensor 3b is relatively small, the second reference value that is smaller than the first reference value is set.

  The comparison value output from the comparison circuit 37 is input to the CPU 36, and the leading edge and trailing edge detection of the sheet and the double feed detection of the sheet are performed. The double feed detection is continuously performed from the time when the loop formation of the sheet is released between the separating unit 3 and the registration roller pair 5 until the trailing edge of the sheet leaves the nip in the separating unit 3. This enables accurate sheet double feed detection.

FIG. 7 is a block diagram showing a control circuit of the discriminating means according to the third embodiment.
The circuit configuration of the wave transmission sensor 3a in the discrimination means of the second embodiment is the same as that of the first embodiment shown in FIG.

  On the other hand, the output signal of the wave receiving sensor 3 b is first amplified by a predetermined gain set in advance by the first amplifier circuit 34. The output signal of the first amplifier circuit 35 is rectified in the first smoothing circuit 35 and smoothed by an integrating circuit having a predetermined time constant. Then, the output signal of the smoothing circuit 35 is compared with a first reference value preset in the first comparison circuit 37.

  The output signal of the first amplifier circuit 35 is also input to the second amplifier circuit 38 and further amplified by a predetermined gain. The output of the second amplifier circuit 38 is rectified in the second smoothing circuit 39 and smoothed by an integrating circuit having a predetermined time constant. Then, the output signal of the second smoothing circuit 29 is compared with a second reference value different from the first reference value set in advance in the second comparison circuit 40.

  The CPU 36 detects the leading edge and the trailing edge of the sheet based on the input signal from the first comparison circuit 37, and detects the double feed of the sheet based on the output signal from the second comparison circuit 40. The double feed detection is continuously performed from the time when the loop formation of the sheet is released between the separating unit 3 and the registration roller pair 5 until the trailing edge of the sheet leaves the nip in the separating unit 3. This enables accurate sheet double feed detection.

FIG. 8 is a block diagram showing a control circuit of the discriminating means according to the fourth embodiment.
In the discriminating means according to the fourth embodiment, the transmission sensor 3a is driven by an amplification circuit 32 that amplifies the ultrasonic signal oscillated by the ultrasonic oscillation circuit 31. Here, the gain (amplification factor) of the amplification circuit 32 that amplifies the ultrasonic signal oscillated by the ultrasonic oscillation circuit 31 can be freely set by the CPU 36. Therefore, a D / A converter 38 that converts a digital signal output from the CPU 36 into an analog value and inputs the analog signal to the amplifier circuit 32 is connected between the CPU 36 and the amplifier circuit 32. As a result, the CPU can set the output level of the ultrasonic wave output from the wave transmission sensor 3a at the time of detecting the leading edge and the trailing edge of the sheet and at the time of detecting the double feed of the sheet to respective different values. is there. Further, since the output level of the ultrasonic wave emitted from the wave transmission sensor 3a can be freely set, the CPU 36 can vary the sensitivity of the sensor (element), the installation angle with respect to the seat running surface, the distance from the wave receiving sensor 3b, and the like. Can also be adjusted.

  On the other hand, the output signal of the wave receiving sensor 3b is amplified by an amplifier circuit 34 having a predetermined gain, and the electric signal amplified by the smoothing circuit 35 is rectified and smoothed by an integrating circuit having a predetermined time constant.

  The electrical signal that has passed through the smoothing circuit 36 is compared with a reference value set in advance in the comparison circuit 37. The comparison value output from the comparison circuit 37 is input to the CPU 36. When detecting the leading edge and the trailing edge of the sheet, the gain of the amplifier circuit 32 is set to a relatively small value, and when detecting the double feed of the sheet. Sets the gain of the amplifier circuit 32 to a relatively large value. Thus, the single ultrasonic sensor 3 can detect the leading and trailing edges of the sheet and the double feed detection of the sheet. Here, the double feed detection is continuously performed from the time when the loop formation of the sheet is released between the separating unit 3 and the registration roller pair 5 until the trailing edge of the sheet leaves the nip in the separating unit 3. This enables accurate sheet double feed detection.

FIG. 9 is a block diagram showing a control circuit of the discriminating means according to the fifth embodiment.
The circuit configuration of the transmission sensor 3a in the discrimination means of the fifth embodiment is the same as that of the first embodiment shown in FIG.

  On the other hand, the output signal of the wave receiving sensor 3b is amplified by the amplifier circuit 34, and in the smoothing circuit 35, the amplified electric signal is rectified and smoothed by an integrating circuit having a predetermined time constant.

  The analog output signal of the smoothing circuit 35 is digitally converted by the A / D converter 38, and the value of this digital signal is directly read by the CPU 36. In the CPU 33, two comparison reference values (ranges) at the time of detecting the leading and trailing edges of the sheet and at the time of detecting the double feed of the sheet are stored in advance. When the leading edge and trailing edge of the sheet are detected, a comparatively large comparison reference value is compared with the digital signal from the A / D converter 38 described above. At the time of sheet double feed detection, a comparatively small comparison reference value (range) and the digital signal from the A / D converter 38 are compared. The double feed detection is continuously performed from the time when the loop formation of the sheet is released between the separating unit 3 and the registration roller pair 5 until the trailing edge of the sheet leaves the nip in the separating unit 3. This enables accurate sheet double feed detection.

  FIG. 10 shows an example of the waveform of the output signal of the wave receiving sensor 3b together with the reference value when detecting the double feeding state of the sheet, which is more difficult than detecting the leading edge and the trailing edge of the sheet (that is, detecting the presence / absence of the sheet). Is. Similarly, at the time of detecting the leading edge and the trailing edge of the sheet, the level of the output signal of the wave receiving sensor 3b is compared with the reference value.

  Here, FIG. 10A shows the case of only one sheet properly at the time of sheet double feed detection, and FIG. 10B shows the case of the double feed state. FIG. 10A shows that the output value of the wave receiving sensor 3b exceeds the reference value, indicating that only one sheet has been properly fed out. In FIG. 10B, the output of the wave receiving sensor 3b is shown. The value is below the reference value, indicating that the sheet has been double fed.

  In FIG. 10, the waveform of the output signal of the wave receiving sensor 3b is divided into three sections [A], [B], and [C]. Section [A] indicates that the sheet is in a loop state (the state shown in FIG. 2B) and the level of ultrasonic waves received by the wave receiving sensor 3b is unstable. Section [B] indicates a loop state. Indicates that the front and back of the sheet are nipped by the separating means 3 and the registration roller pair 5 (the state shown in FIG. 2C), and the output signal of the wave receiving sensor 3b is stable. In section [C], when the trailing edge of the sheet leaves the separating means 3 (the state shown in FIG. 2D), the trailing edge of the sheet vibrates and the output signal of the wave receiving sensor 3b is slightly unstable. It shows that there is.

  In the present invention, since the sheet double feed state is determined based on the output signal of the wave receiving sensor 3b in the section [B], accurate sheet double feed detection is realized.

  FIG. 11 shows the first embodiment shown in FIG. 5 as an example in which the gain of the amplifier is detected by setting the first gain value at the time of detecting the leading and trailing edges of the sheet and the second gain value at the time of detecting double feed. The example of the control flow which performs the front-end | tip and rear-end detection of a sheet | seat and the double feed detection of a sheet | seat by one ultrasonic sensor using the discrimination means which concerns on an aspect is shown.

  The CPU 36 (FIG. 5) sets the gain of the amplifier circuit 34 stored at a predetermined address in the memory (included in the CPU 36) in advance to the lower first gain value (S21). When the start button of the apparatus is pressed (S22), the sheet feeding control is started, and the CPU 36 monitors the output of the comparison circuit 37 to check whether or not the leading edge of the sheet blocks the ultrasonic path 3c of the ultrasonic sensor 3. This is detected by comparing with the first gain value (S23). After it is determined that the leading edge of the sheet has blocked the ultrasonic path 3c (S24), the sheet forms a registration loop because the leading edge is stopped at the registration roller pair 5 (S25).

  Thereafter, the CPU 36 sets the gain of the amplifier circuit 34 stored at a predetermined address in the memory (included in the CPU 36) to the higher second gain value (S26). Since the registration roller pair 5 is driven to rotate after a predetermined time, the registration loop of the sheet is eliminated (S28). The CPU 36 monitors the output of the comparison circuit 37 (S28), and when the sheet is in the state of FIG. 2C, determines the double feed state of the sheet based on the output signal of the comparison circuit 37 (S29). . At this time, the comparison circuit 37 outputs a comparison signal between the first gain value and the output of the smoothing circuit 35 to the CPU 36. If it is determined that the sheet is double-feed, double-feed processing such as stopping the sheet feeding or stopping the image reading operation is performed (S30), and the control of the apparatus is ended (S31).

  On the other hand, when it is determined that only one sheet is normally fed, the control is continued as it is, and the CPU 36 lowers the gain of the amplifier circuit 34 stored at a predetermined address in the memory (included in the CPU 36) again. One of the first gain values is set (S32). Next, the CPU 36 monitors the output of the comparison circuit 37 and detects whether or not the trailing edge of the sheet blocks the ultrasonic path 3c of the ultrasonic sensor 3 by comparing with the first gain value (S33). If it is determined that the trailing edge of the sheet has blocked the ultrasonic path 3c (S34), the CPU calculates the size of the sheet (S35). The CPU 36 determines from the time from detection of the leading edge of the sheet to detection of the trailing edge, the feeding speed of the registration roller pair 5, the stop time of the registration roller pair 5 when the sheet is registered in the registration loop, and the sheet feeding speed of the registration roller 5. The sheet size (the length in the sheet feeding direction) can be calculated.

  The sheet fed in this way is conveyed onto the platen 12 (FIG. 1) arranged on the downstream side, and the image is read by the optical reading means (S36), and sent to the discharge path 23 side. (S37). The above control is performed until the feeding of all the sheets stacked on the sheet stacker is completed (S38 and S39).

  FIG. 12 shows an example in which the comparison circuit 37 detects the reference value to be compared by setting the first reference value when detecting the leading and trailing edges of the sheet and the second reference value when detecting double feed. 6 shows an example of a control flow for detecting the leading edge and the trailing edge of a sheet and detecting the double feeding of a sheet by one ultrasonic sensor using the determination unit according to the second embodiment shown in FIG.

  The CPU 36 (FIG. 5) sets the reference value input to one input terminal (−) of the comparator 37 stored in advance at a predetermined address of the memory (included in the CPU 36) as the lower first reference value. (S31). When the start button for starting the operation of the apparatus is pressed (S32), the sheet feeding control is started, and the CPU 36 monitors the output of the comparison circuit 37 and the leading edge of the sheet is the ultrasonic path of the ultrasonic sensor 3. It is detected by comparing whether or not 3c is blocked with the first reference value (S33). After it is determined that the leading edge of the sheet has blocked the ultrasonic path 3c (S34), the sheet forms a registration loop because the leading edge is stopped at the registration roller pair 5 (S35).

  Thereafter, the CPU 36 sets the reference value input to the comparison circuit 37 stored at a predetermined address in the memory (included in the CPU 36) to a second reference value higher than the first reference value (S36). Since the registration roller pair 5 is rotated after a predetermined time, the registration loop of the sheet is eliminated (S38). The CPU 36 monitors the output of the comparison circuit 37 (S38), and when the sheet is in the state shown in FIG. 2C, determines the double feed state of the sheet based on the output signal of the comparison circuit 37 (S39). At this time, the comparison circuit 37 compares the output of the smoothing circuit 35 with the second reference value and outputs the comparison result to the CPU 36. If it is determined that the sheet is double-feed, double-feed processing such as stopping the sheet feeding or stopping the image reading operation is performed (S40), and the sheet feeding control or image reading control is performed. The process ends (S41).

  On the other hand, when it is determined that only one sheet has been normally fed, the control is continued as it is, and the CPU 36 is a reference inputted to the comparison circuit 37 stored in a predetermined address of the memory (included in the CPU 36). The value is set again to the lower first reference value (S42). Next, the CPU 36 again monitors the output of the comparison circuit 37 and detects whether or not the trailing edge of the sheet has blocked the ultrasonic path 3c of the ultrasonic sensor 3 by comparing with the first reference value (S43). . When it is determined that the trailing edge of the sheet blocks the ultrasonic path 3c (S44), the CPU calculates the size of the sheet (S45). The CPU 36 determines from the time from detection of the leading edge of the sheet to detection of the trailing edge, the feeding speed of the registration roller pair 5, the stop time of the registration roller pair 5 when the sheet is registered in the registration loop, and the sheet feeding speed of the registration roller 5. The sheet size (the length in the sheet feeding direction) can be calculated.

  The sheet fed in this way is conveyed onto the platen 12 (FIG. 1) arranged on the downstream side, and the image is read by the optical reading means (S46), and sent to the discharge path 23 side. (S47). The above control is performed until the feeding of all the sheets stacked on the sheet stacker is completed (S48 and S49).

  As described above, the sheet apparatus includes a sheet stacker, a separating unit that separates and feeds out the sheets stacked on the sheet stacker, a registration roller that corrects a skew state of the sheet fed from the separating unit, An ultrasonic sensor composed of a transmission sensor and a reception sensor disposed between the separation means and the registration roller, and detection of the leading and trailing edges of the sheet and a double-feed state based on an output signal from the reception sensor And a discriminating means for performing both of the discriminating. Here, the sheet size (length in the feeding direction) can also be detected by detecting the leading edge and the trailing edge of the sheet.

  Therefore, the discriminating means has a timing and conditions different from those in the first comparison for detecting the leading edge and the trailing edge of the sheet and the first comparison in order to discriminate the double feed state of the sheet. Two comparisons are performed. In this way, by detecting the leading edge of the sheet and the double feeding detection of the sheet under different conditions and timing, both the leading edge detection and the multifeed detection that were conventionally performed by a plurality of sensors can be performed by using a single sensor. It made it possible to detect.

  The present invention is applicable not only to an ADF that transports an original sheet to an image reading position, but also to a sheet handling apparatus in general provided in a copying machine that feeds sheets one by one from a sheet stacker and supplies them to a printing unit. Needless to say.

  The sheet handling apparatus according to the present invention includes a sheet separating unit that separates the sheets stacked on the sheet stacker one by one and feeds them downstream, and detects a leading edge and a trailing edge of the sheet, and a sheet double feeding state. Since the present invention relates to a sheet handling apparatus provided with means, it has industrial applicability.

The structural example of ADF which is one aspect of the sheet handling apparatus which concerns on this invention is shown. The change in the state of the sheet between the separating means and the registration roller in the sheet handling apparatus and the arrangement relationship of the ultrasonic sensors are shown. The flowchart for demonstrating the timing which reads the output signal of the wave receiving sensor which comprises an ultrasonic sensor is shown. An example of a timing chart in the control of an image reading apparatus equipped with an ADF is shown. The block diagram of the control circuit which concerns on 1st Embodiment which processes the signal of an ultrasonic sensor is shown. The block diagram of the control circuit which concerns on 2nd Embodiment which processes the signal of an ultrasonic sensor is shown. The block diagram of the control circuit which concerns on 3rd Embodiment which processes the signal of an ultrasonic sensor is shown. The block diagram of the control circuit which concerns on 4th Embodiment which processes the signal of an ultrasonic sensor is shown. The block diagram of the control circuit which concerns on 5th Embodiment which processes the signal of an ultrasonic sensor is shown. A waveform example of the output signal of the wave receiving sensor at the time of sheet double feed detection is shown together with a reference value. An example of a control flow by the discrimination means according to the first embodiment is shown. The example of the control flow by the discrimination | determination means concerning a 2nd embodiment is shown.

Explanation of symbols

1: Feeding roller 2: Separating means 2a: Feeding roller 2b: Separating roller 3: Ultrasonic sensor 3a: Wave sending sensor 3b: Wave receiving sensor 5: Registration roller pair 6: First conveying roller pair 7: Second Conveying roller pair 8: Discharging roller pair 9: Lead sensor 10: ADF (sheet handling device)
12: Platen 13: Second platen 20: Image reading device 36: CPU (component of discrimination means)

Claims (13)

A sheet stacker,
Separating means for separating and feeding out the sheets stacked on the sheet stacker;
A registration roller that corrects a skew state of the sheet fed from the separating unit;
An ultrasonic sensor comprising a transmission sensor and a reception sensor disposed between the separating means and the registration roller;
A sheet handling apparatus comprising: a discriminating unit that performs both of the leading end and / or trailing end detection of a sheet and the determination of a double feed state based on an output signal from the wave receiving sensor. 2. The sheet handling apparatus according to claim 1, wherein the wave transmitting sensor and the wave receiving sensor are disposed in a state in which they are inclined with respect to a sheet traveling surface between the separating unit and the registration roller and face each other. . The discrimination means includes
A first comparison for detecting the leading edge and / or trailing edge of the sheet;
In order to determine the double feed state of the sheet, a second comparison of timing and conditions different from the first comparison,
The sheet handling device according to claim 1, wherein the sheet handling device is executed. The first comparison is performed based on an output signal from the wave receiving sensor when the leading edge or the trailing edge of the sheet passes the installation position of the ultrasonic sensor,
The second comparison is performed based on an output signal from the wave receiving sensor at one or a plurality of time points after a predetermined time has elapsed since the leading edge of the sheet arrived at the registration roller. 3. The sheet handling apparatus according to 3. The determination means includes a comparison circuit that performs the first comparison and the second comparison, and a reception amplifier that amplifies an output signal of the reception sensor,
The sheet handling apparatus according to claim 3 or 4, wherein the first comparison and the second comparison are performed by changing an amplification factor (gain) of the amplifier. The determination means includes a comparison circuit that performs the first comparison and the second comparison, and a reception amplifier that amplifies an output signal of the reception sensor,
The sheet handling apparatus according to claim 3 or 4, wherein the first comparison and the second comparison are performed by changing a value of a reference value input to the comparison circuit. The determination means includes a first comparison circuit that performs the first comparison, a second comparison circuit that performs the second comparison, and a first reception amplifier that amplifies the output signal of the reception sensor with a predetermined gain. And a second receiving amplifier for amplifying an output signal of the receiving sensor with a gain different from that of the first amplifier. The discrimination means adjusts the level of the ultrasonic wave output from the transmission sensor, the comparison circuit that performs the first comparison and the second comparison, the reception amplifier that amplifies the output signal of the reception sensor A transmission amplifier,
5. The sheet handling apparatus according to claim 3, wherein the first comparison and the second comparison are performed by changing a gain of the transmission amplifier. 6. The discriminating means includes: a wave receiving amplifier that amplifies an output signal of the wave receiving sensor by a predetermined gain; and an A / D converter that digitally converts an analog output of the wave receiving amplifier, the A / D converter 5. The sheet handling apparatus according to claim 3, wherein the first comparison and the second comparison are performed based on a digital output signal from. The sheet supply from the sheet stacker thereafter is stopped when the sheet fed from the separating unit by the determining unit is determined to be double feed. The sheet handling device described. A sheet stacker,
Separating means for separating and feeding out the sheets stacked on the sheet stacker;
A registration roller for correcting the skew state of the sheet fed from the separating means;
A conveying means for conveying the sheet fed from the registration roller to a reading position;
Optical reading means for reading the sheet conveyed to the reading position;
An ultrasonic sensor comprising a wave transmission sensor and a wave reception sensor arranged in an inclined state with respect to a sheet running surface between the separation means and the registration rollers;
An image reading apparatus comprising: a determination unit configured to detect both a leading edge and / or a trailing edge of a sheet and a double feed state based on an output signal from the wave receiving sensor. The discrimination means includes
A first comparison for leading and trailing edge detection of the sheet;
In order to determine the double feed state of the sheet, a second comparison of timing and conditions different from the first comparison,
The image reading apparatus according to claim 11, wherein: 13. The image reading apparatus according to claim 12, wherein when the sheet fed from the separating unit is determined to be multi-feed by the determining unit, the image reading of the sheet by the optical reading unit is stopped.

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