JP4353779B2 - Sheet feeding apparatus and image reading apparatus using the same - Google Patents

Description

  The present invention relates to a sheet supply apparatus that sequentially separates sheets on a stacker one by one and feeds them to a processing platen such as image reading and printing, and a sheet double feed detection method that detects a plurality of double feeds during a sheet feeding process. About.

  Conventionally, this type of sheet supply apparatus is widely known as sequentially supplying sheets stacked on a stacker to a processing platen such as a printer, a copying machine, or a scanner. In the process of separating sheets on the stacker one by one with this apparatus and supplying them to the processing platen, if a plurality of sheets are overlapped and sent, the processing platen will perform the wrong processing, and at the same time the sheets are accurately separated It is necessary to detect the double feed before reaching the processing platen and stop the processing or invalidate the processed data such as reading.

  Conventionally, as a method of detecting such double feeding of a sheet, there is known a method of detecting whether one sheet or a plurality of sheets is detected from an ultrasonic wave or a light amount attenuation amount passing through the sheet by an ultrasonic sensor, a photo sensor, or the like. Yes. Patent Document 1 discloses a detection by an ultrasonic sensor. A piezoelectric diaphragm such as piezoelectric ceramics is provided on the transmission (communication) side, and vibration is generated by applying a high-frequency voltage of a predetermined period to the piezoelectric diaphragm. Then send ultrasonic waves. Then, a similar piezoelectric diaphragm is provided at a position facing through the sheet, and the vibration excited by the piezoelectric diaphragm is electrically output to configure the reception (communication) side. Therefore, one sheet or a plurality of sheets are compared by comparing the electric energy applied to the piezoelectric diaphragm (transmitting element) on the transmission side with the electric energy generated on the piezoelectric diaphragm (receiving element) on the receiving side. It is determined whether or not the two overlap.

  In order to detect the overlapping state of sheets with such an ultrasonic sensor, the ultrasonic energy attenuated by the sheet between the transmitting element and the receiving element (output from the receiving element as electric energy) is finely It must be detected and judged accurately. Therefore, conventionally, in order to avoid that the ultrasonic waves emitted from the wave transmitting element are reflected on the sheet surface and return to the wave transmitting element to interfere with each other, for example, in Patent Document 2, the wave is transmitted while being inclined at a predetermined angle with respect to the traveling sheet surface. It has been proposed that the element and the receiving element face each other.

  Japanese Patent Application Laid-Open No. H10-228561 proposes that a wave transmitting element and a wave receiving element are disposed opposite to each other between rollers at the front and rear ends that are separated from each other, and detection is performed with little change in the posture of the sheet. That is, by detecting the double feed while the sheet is nipped by the front and rear rollers and moving in a constant linear posture, it is possible to prevent the sheet from being detected in a state where the leading edge or trailing edge of the sheet is curved or fluttered up and down.

In order to determine the difference between a single sheet and multiple sheets by measuring the amount of transmission of ultrasonic waves or light quantity with respect to the sheet moving at a predetermined speed in this way, reduce the change in the posture of the sheet. It is necessary to measure and smooth the predetermined length (area) of the sheet.
JP-A-10-257595 (FIG. 1) US Patent No. 6212130 Japanese Utility Model Publication No. 6-49567

  In order to correctly detect the overlap of sheets by the above-mentioned ultrasonic sensor and other double feed detection means, it is necessary to continuously detect a certain area of the sheet and smooth the data as a result to prevent detection errors due to noise or the like. However, the following problem occurs when a certain length is continuously detected. When the detection length (area) is set to the same length as the stacker recognition size, for example, when a sheet with a deformed (non-standard) size shorter than this is sent, the trailing edge of the sheet is detached from the conveying means and fluttered. There is a risk of detecting abnormalities and causing abnormal detection. On the other hand, if it is set to be short so that it can be applied to all sheets that assume the detection length, if the sheets are shifted back and forth and overlapped like a scale, this cannot be detected and the processing platen There is a risk of giving it. In order to prevent this, the trailing edge of the conveyed sheet may be detected and the detection length may be changed each time, but the structure for that and the processing of the measured result data become complicated.

  Therefore, the present invention always accurately detects and discriminates the overlap of the sheets fed from the stacker even if a non-standard size irregular-size sheet is fed with a simple structure, or even if the sheet is greatly shifted forward and backward. The main object of the present invention is to provide a sheet feeding apparatus and a double feed detection method that can perform the above-described operation.

The present invention adopts the following configuration in order to achieve the above-described problems.
A stacker for placing the sheet and a sheet size recognition means for discriminating the length in the transport direction of the sheet placed on the stacker are provided. A first conveyance unit is provided on the upstream side of a conveyance guide that reads the sheet from the stacker and guides a sheet to a processing platen such as printing, and a second conveyance unit is disposed on the downstream side. Double feed detection means such as a sonic sensor is arranged. At the same time, a conveyance length detecting means for detecting the length of the sheet from the leading edge to the trailing edge of the sheet conveyed in the conveyance guide is provided, and the conveyance length of the sheet detected by the conveyance length detection means and the above sheet size Sheets based on the comparison result (long or short) from the comparison means for comparing the length in the conveyance direction of the sheet detected by the recognition means and the detection result (one sheet or many sheets) from the multi-feed detection means A discriminating means for discriminating abnormal conveyance is provided.

  With this configuration, when the predetermined area (length) of the leading end or the central portion of the sheet conveyed from the stacker is detected by the double feed detecting means, the sheet is supported by the first and second conveying means and in a stable posture. Whether this is a double feed is detected. Also, when the sheet is double-fed with a large shift forward and backward, the length is detected by the conveyance length detection means, and when it is longer than a predetermined length, it is determined as double-feed.

  Further, the comparison unit can detect the double feed more accurately by comparing the conveyance direction length of the sheet to be conveyed from the sheet size recognition unit with the conveyance length from the conveyance length detection unit.

  The sheet size recognition means is configured to detect the end face of the sheet placed on the stacker by a detection means such as a photo sensor, and the position of the side guide for regulating the side edge of the sheet is detected by the sensor to detect the sheet width from the sheet width. A configuration for calculating the thickness is adopted. It is also possible for the user to input the sheet size from the control panel of the other apparatus and to determine the length in the sheet conveyance direction from this input information.

  The first conveying means is constituted by a separation roller that separates the sheets on the stacker one by one, and the second conveying means is constituted by a registration roller that temporarily stands by the sheet. After the sheet is separated by the separation roller after being configured in this way, the sheet is brought into contact with the stopped registration roller and curved, and then the registration roller is rotationally driven to hold the sheet linearly between the two rollers. The detection unit is configured to detect double feeding. In this way, a plurality of sheets fed in a superimposed manner can form an air layer between the sheets due to the curvature of the sheet (resist loop), and the accuracy of the double feed detection method such as an ultrasonic sensor can be improved.

A sheet end detecting unit configured to bend the leading end of the sheet in a loop by the second conveying unit. The conveyance length detection means is configured to measure the conveyance length from the leading edge to the trailing edge of the sheet by the sheet edge detection means that detects the sheet conveyance amount and the sheet trailing edge of the second conveyance means, The double feed detection means and the sheet edge detection means are arranged in the order of the double feed detection means and then the sheet edge detection means between the first conveyance means and the second conveyance means .

Further, it is preferable that the first and second conveying means and the double feed detecting means are configured as follows. Conveyable sheet minimum size length of a sheet feeding apparatus with respect to (LS), first, the detection length of the double-feed detection means and the distance (L1) of the second conveying means (L3) LS> L1, ( LS-L1 )> L3. With this setting, even when the user sets a non-standard size sheet other than the standard size on the stacker, the sheet is held by the first and second conveying means, and in this state, the double feed detecting means detects the detection length ( Region) L3 is detected, and detection errors can be reduced.

  Further, in the present invention, instead of sheet size recognition means for determining the conveyance direction length of the sheet placed on the stacker, a reference length is set based on the conveyance direction length of the maximum size sheet that can be conveyed in advance, Comparing means for comparing the reference length with the conveying length of the conveying length detecting means, and even if the abnormal conveyance of the sheet is determined based on the comparison result of the comparing means and the detection result of the multifeed detecting means Can achieve the task.

  The present invention compares the double feed detection means for detecting the overlap of sheets such as an ultrasonic sensor during the conveyance process of the sheet from the stacker to the processing platen, and the conveyance length from the leading edge to the trailing edge of the conveyance sheet and the length of the sheet itself. In order to detect the overlap of the sheets with the comparing means, the double feed detecting means or the comparing means surely detects whether the sheets are in close contact with each other in the vertical direction or overlapped with each other.

  Therefore, even when the sheets are conveyed in a broad manner in a wide range, it is possible to reliably detect an abnormality and to prevent erroneous processing on the processing platen.

  In addition, when detecting the overlap state of sheets with a multi-feed detection means such as an ultrasonic sensor, it is possible to reliably detect the sheet while being supported by two front and rear conveying means with a relatively small interval. In the detection of the sheet carried out by being largely shifted forward and backward, more accurate double feed detection can be performed by detecting the sheet by the transport length comparison means.

  The present invention will be described in detail below based on the preferred embodiments shown in the drawings.

  The present invention is used in a sheet supply unit of an image reading apparatus or a copying machine or a printing machine, which will be described later, and separates and supplies sheets one by one to a processing position such as an image reading platen and a printing platen. The present invention relates to an apparatus and a method for detecting a double feed in which two or more sheets overlap each other before a processing position.

  FIG. 1 is an explanatory view of the main part of a sheet feeding apparatus embodying the present invention, FIG. 2 is a schematic structure of a double feed detecting means comprising an ultrasonic sensor, FIG. 3 is an explanatory view of its control circuit, and FIG. It is a chart.

  The apparatus shown in FIG. 1 includes a stacker 1 for stacking and storing sheets, a conveyance guide 3 for guiding sheets from the stacker 1 to a processing platen 2, and at least two first and second conveyances arranged in the conveyance guide 3. Means 4 and 5, and double feed detection means 6 disposed between the first conveyance means 4 and the second conveyance means 5 for detecting the overlap of sheets are provided. The stacker 1 is composed of a tray on which a sheet is placed, and the stacker 1 is provided with a sheet size recognition means 49 for detecting the length of the sheet in the conveyance direction.

  The configuration of the sheet size recognition means 49 is either (1) an input means for the user to input a standard sheet size from the control panel, or (2) a sensor for detecting the standard sheet size on the stacker in the paper transport direction. A plurality of sensor means, (3) a guide detection means for providing a slidable side guide on the sheet end face on the stacker and detecting the position of this guide with a sensor, and the like are employed. An example of this will be described in detail in an image reading apparatus to be described later. FIG. 1 shows a size sensor 50 that detects the trailing edge in the sheet conveyance direction. In the figure, reference numeral 50a denotes a photodiode, and 50b denotes a light receiving element. A plurality of size sensors 50 are arranged on the bottom of the stacker 1, and the positions thereof are arranged so as to be applied to the end of a standard size sheet.

  The stacker 1 is provided with a side guide 51 that is movable in the sheet width direction. The position of the side guide 51 is also detected by a sensor (described later), and the position of the size sensor 50 and the side guide 51 in the sheet longitudinal direction. It is arranged so that the standard size of the sheet is determined by the sensor. Therefore, when the sheet is placed on the stacker 1, the size sensor 50 detects this, and the length of the sheet in the conveyance direction is identified.

  The first conveying means 4 includes a separation roller 4a that separates the sheets on the stacker 1 one by one and feeds them to the processing platen 2, and a friction pad 4b that presses the separation roller 4a. Various separation means are known, and a belt can be used instead of the separation roller 4a, and a reverse rotation roller or a belt can be used instead of the friction pad 4b.

  The second conveying means 5 is composed of a pair of rollers or belts that are in pressure contact with each other. Even in a configuration in which the sheet from the first conveying means 4 is taken over and conveyed, the sheet from the first conveying means 4 as shown in the figure. It may be configured to temporarily wait and convey the sheet toward the processing platen 2 by a sheet feeding timing signal.

  The first and second transport means may be connected to individual drive motors, but may be connected to a drive motor M capable of forward / reverse rotation, and the first transport means 4 for forward rotation and the second transport for reverse rotation. The means 5 is rotated, and the drive mechanism will be described later with reference to FIG.

  The first and second conveying means 4 and 5 rotate in a reciprocal manner in this manner because the first conveying means 4 is composed of a separation roller 4a for separating and feeding the sheets on the stacker 1 to separate the sheets. Then, after the sheet is delivered to the second conveying means 5, the separation roller 4a is stopped so that the subsequent sheet is not fed out. Therefore, the first and second conveying means 4 and 5 may be configured to convey the sheet synchronously in the same direction when arranged in another conveying path different from the separation and registration of the sheet.

  Between the first and second conveying means 4 and 5, a next double feed detecting means 6, a sheet end detecting means 7, and a sheet conveying length detecting means 20 are arranged. The double feed detecting means 6 is an ultrasonic sensor and is composed of a pair of a wave transmitting element 6 a and a wave receiving element 6 b, and is disposed opposite to each other with a sheet traveling along the conveyance guide 3. In the example shown in FIG. 2, the angle α is inclined by 30 to 45 degrees from the normal line N-N orthogonal to the seat running surface.

  The sheet edge detecting means 7 arranges the light emitting element and the light receiving element so as to face each other through a sheet traveling by an optical sensor such as a photodiode.

  The multifeed detecting means 6 and the sheet edge detecting means 7 are located between the first and second conveying means (distance L1). Is arranged at a distance L3 from the first conveying means 4. The sheet conveyance length detection means 20 detects the length in the conveyance direction of the sheet fed by the first and second conveyance means. (1) The rotation amount of one of the first and second conveyance means (2) Drive the conveyance means at a constant speed, calculate the rotation amount of the conveyance means from the drive time, or count the number of drive pulses when using a stepping motor, or (3) No. Any one of the methods of providing an idler roller that is engaged with a sheet that is moved by the first and second conveying means and detecting the rotation amount of the idler roller by an encoder or the like is employed.

  The illustrated one is provided with an encoder 21 having slits formed at equal intervals on the outer periphery of the rotating shaft of the registration roller 5b. The slit is detected by an encode detection sensor 22 such as a photocoupler, and the signal from the encode detection sensor 22 is counter 23. In this case, the amount of rotation of the registration roller 5b is measured by measuring the above, and the conveyance length of the registration roller 5b is calculated from the amount of rotation. Accordingly, the sheet edge detection sensor 7 detects the leading edge of the sheet, and starts the counter 23 at a timing when the leading edge of the sheet is nipped by the registration rollers 5a and 5b with a predetermined timer delay time. The sheet edge detection sensor 7 detects the trailing edge of the sheet, and stops the counter 23 after the expected time (timer time) when the sheet trailing edge reaches the nip point of the registration rollers 5a and 5b. A conveyance length from the front end to the rear end is detected.

  Next, the structure of the double feed detecting means 6 will be described. FIG. 2 shows an example thereof. In a normal ultrasonic sensor, the transmitting element 6a and the receiving element 6b are composed of elements having the same structure, such as metal. A piezoelectric vibrating body 9 such as a piezoelectric ceramic plate is embedded in an elastic resin 10 in an outer casing 8 of the present invention. Electrodes are formed on the front and back surfaces of the piezoelectric vibrating body 9 by vapor deposition. Supply. The illustrated piezoelectric vibrating body 9 is formed in close contact with the outer casing case 8 so that both vibrate together, and one of the lead wires 11 is grounded to the outer casing case 8.

  Therefore, when a high frequency power is supplied from the lead wire 11 on the wave transmitting element 6a side, the piezoelectric vibrating body 9 and the outer casing case 8 in contact with the piezoelectric vibrating body 9 vibrate at a predetermined frequency to emit ultrasonic waves, and the receiving element 6b Then, the piezoelectric vibrator 9 integrated with the vibrator vibrates due to resonance, and electric energy generated in the piezoelectric vibrator 9 is output from the lead wire 11.

  The ultrasonic sensor having such a structure is disposed on the conveyance guide 3 as the double feed detecting means 6 and is connected to the oscillation circuit 12 and the vibration receiving circuit 13 as shown in FIG. The oscillation circuit 12 is composed of a high-frequency oscillation circuit 12a and a power amplification circuit 12b, and the vibration receiving circuit 13 is composed of an amplification circuit 13a composed of a transistor or the like and a smoothing circuit 13b. The high-frequency oscillation circuit 12a generates a high-frequency voltage of 30 KHz to 400 KHz, for example, 200 KHz in the present embodiment, and this signal is powered up by a transistor and applied to the piezoelectric vibrating body 9 from the lead wire 11 and superposed by the piezoelectric vibrating body 9. Oscillates sound waves.

  The ultrasonic wave excites the piezoelectric vibrating body 9 on the wave receiving element side through the sheet and is output as an electrical signal. The input signal from the wave receiving element 6b is amplified by a transistor, rectified by a smoothing circuit 13b, and then smoothed by an integrating circuit such as a capacitor.

  Therefore, when power is supplied to the transmission circuit 12a, ultrasonic vibration of a specific frequency is excited by the piezoelectric vibrating body 9 of the transmission element 6a. As shown in FIG. 2A, the vibrating body 9 emits ultrasonic waves at a high frequency with a constant amplitude (output level LV1). The wave receiving element 6b facing the wave transmitting element 6a receives the ultrasonic wave through the sheet, the piezoelectric vibrating body 9 on the wave receiving element 6b side resonates, and the electric power generated by the vibration is output. At this time, the attenuation of the ultrasonic wave when passing through the sheet differs as shown in FIG. 2 (b) when it is one sheet (output level LV2) and when it is two sheets (output level LV3) in FIG. 2 (c). It becomes.

  The electric energy output in the waveforms (b) and (c) is processed by the amplifier circuit 13a and the smoothing circuit 13b. That is, the vibration wave-shaped electric energy output from the wave receiving element 6b is amplified, rectified, and then smoothed by the smoothing circuit 13b formed of an integrating circuit as an output level as shown in FIGS. 6 (a) and 6 (b) as a reference value ( The level LV0) is compared with a comparison means such as a comparator. FIG. 6A illustrates the output level LV2 when the sheet is conveyed by one sheet, and the detected value is in a state where the A portion forms a registration loop before the sheet leading edge reaches the registration roller pair 5a. The detected value is stable when the sheet is nipped between the separation roller 4a and the registration roller pair 5a, and the detected value is detected when the rear end of the sheet is separated from the separation roller 4a (passes the roller position). Is disturbed. FIG. 6 (b) shows the output level LV3 when two sheets are conveyed while being overlapped, and the A part, the B part and the C part respectively show the above-mentioned states.

  Therefore, when the reference value is set to the level LV0 indicated by the dotted line in the figure, in the stable portion B, the relationship of LV1> LV2> LV0> LV3 is established, and there is one sheet (a) and two sheets (b). It becomes possible to discriminate based on the output result of the comparator, and this reference value is determined as follows. First, conditions such as sheet thickness, paper quality, and conveyance speed are determined based on the operating environment of the device. Under these conditions, the output level of the receiving sensor when the number of sheets is one and two by experiment. The boundary value is obtained and this value is set as the reference value. In this case, since the current of the vibration waveform is output as an analog signal from the wave receiving element 6b, this is amplified and the integrated value is compared with the detected value and the reference value by the integrating circuit, or the output value of the wave receiving element 6b is set. After amplification, the voltage is rectified by a diode or the like, smoothed by a smoothing circuit such as a capacitor, and then the voltage level is compared with a detected value and a reference value, either method is adopted.

  Next, either a high-frequency voltage is instantaneously applied from the oscillation circuit 12a to the transmission element 6a to generate a burst wave or a continuous power supply to generate a continuous wave. In this case, since the output from the wave receiving element 6b is unstable (easy to change due to environmental conditions) in the overlapping state of the sheets, it is preferable to detect the burst wave repeatedly repeatedly intermittently. As shown in FIG. 1, the measurement length L0 when detecting a region with a sheet continuously or intermittently is L5 at the leading edge of the sheet and L4 at the trailing edge of the sheet, as shown in FIG. A region is formed and determined.

  That is, a non-detection length L5 larger than the distance (L1-L2) between the second conveyance unit 5 and the multifeed detection unit 6 is formed at the leading end of the sheet in a relationship of L5 ≧ (L1-L2). This is because the detection is started in a state where the leading end of the sheet is nipped by the second conveying unit 5.

  Next, a non-detection length L4 larger than the distance L2 between the first conveyance unit 4 and the multifeed detection unit 6 is formed at the rear end of the sheet in a relationship of L4 ≧ L2, and the rear end of the sheet is the first conveyance unit. The detection is finished in a state where it is nipped by 4. Sheet double feed detection is performed by setting a measurement length L0 = (minimum size length) − (L4 + L5) in advance, and continuously or intermittently during this interval. In this case, the wave transmitting element 6a transmits ultrasonic waves between the sheet front end L5 and the rear end L4, and the output signal acquired by the wave receiving element 6b is used for the multifeed discrimination between the sheet front end (L5) and the rear end (L4). It may not be used.

  FIG. 4 is a timing chart in the control circuit of FIG. 3 and will be described according to the flowchart of FIG.

  When a sheet is stacked on the stacker 1, the control unit configured by the control CPU 14 activates the drive motor M of the conveying means 4 and 5 in the forward rotation direction in response to a signal detected by the empty sensor 117 (S01). 5ST01).

  With this rotation of the drive motor M, the separation roller 4a constituting the first conveying means 4 rotates in the clockwise direction, and the registration roller pair 5a constituting the second conveying means 5 is placed in a stopped state. The sheet on the stacker 1 is fed to the left in FIG. 1 by the rotation of the separation roller 4a, and reaches the registration roller pair 5a through the double feed detection means 6 and the sheet end detection means 7.

  Next, when the sheet end detecting means 7 detects the leading end of the sheet, the timer T1 is started (S02). This timer T1 issues a stop signal after rotating the separation roller 4a until the leading edge of the sheet reaches the registration roller pair 5a and draws a predetermined loop curved, and stops the drive motor M (see ST02 in FIG. 5).

Therefore, when a paper feed instruction signal S03 is issued from the main body processing apparatus such as an image reading apparatus, the driving motor M is reversed and the timer T2 is started simultaneously. At the same time, the control CPU 14 turns on the power to the oscillation circuit 12 of the ultrasonic sensor in response to the paper feed instruction signal S03. The reverse rotation of the drive motor M rotates the registration roller pair 5a in the clockwise direction so that the sheet is fed to the processing platen 2 side. At this time, the separation roller 4a is placed in a stationary state. The timer T2 cancels the loop at the leading end of the sheet and issues a double feed detection start signal (S04) after the sheet has been linearly supported by the separation roller 4a and the registration roller pair 5a (see ST03 in FIG. 5).
The timers T1 and T2 are respectively constituted by delay circuits that count the reference clock of the control CPU 14 with a counter.

  When receiving the sheet feed instruction signal S03 from the main body apparatus, the control CPU 14 monitors the state of the size sensor 50 of the stacker 1 and recognizes the length of the sheet placed on the stacker 1. The sheet size recognition means 49 is configured to recognize the sheet length corresponding to the position of the sheet on the stacker 1 from the memory table of the ROM 52 and the corresponding sheet length or standard size by a signal from the size sensor 50. (See ST04 in FIG. 5).

  This timer T2 is set to the expected time for the second conveying means 5 to send the sheet by the length (L6 in FIG. 1) that forms a loop for correcting the registration at the leading edge of the sheet, and double feed detection is detected when the timer T2 expires. Start. At this time, the transmitting element 6a is already turned on and emits an ultrasonic wave in a stable state. The opposing receiving element 6b receives an ultrasonic wave that has passed through the sheet and outputs an output corresponding to the state of the sheet. The signal is compared with a predetermined reference value through the amplifier circuit 13a and the smoothing circuit 13b by the comparison circuit 13c (see ST05 in FIG. 5).

  The comparison result is stored in the memory 53 and transferred to the discrimination circuit of the control CPU 14. The control CPU 14 clears the double feed comparison data in the memory 53 in response to the double feed detection start signal S04 when the timer T2 expires. Then, the sheet is sequentially sent to the memory 53 with the data compared by the comparison circuit 13c as it is transferred by the second conveying means 5, and the control CPU 14 calls this comparison data and monitors whether or not the sheet is in a double feed state.

  At the same time, when the drive motor M is restarted, the control CPU 14 detects the sheet feeding amount of the second conveying means 5 corresponding to the measurement length L0. As shown in FIG. 1, the registration roller 5b measures the encoder 21 with a counter 23 and measures the sheet conveyance amount as follows.

  First, the counter 23 starts counting simultaneously with the rotation of the registration roller 5b, and when the sheet is conveyed by the set measurement length L0, the control CPU 14 determines that the detection is finished and finishes reading the comparison data from the memory 53. Next, after the trailing edge of the sheet is detected by the sheet edge detecting means 7, the counter 23 finishes counting when the expected time timer T3 for the trailing edge to reach the registration roller 5b has elapsed (see ST06 in FIG. 5). As a result, the CPU detects the transport length of the transported sheet.

  Therefore, the determination of double sheet feeding by the control CPU 14 is performed as follows. During the process of transferring the sheet between the first and second conveying means 4 and 5, (A) the comparison data from the double feed detecting means 6 and (B) the sheet size recognizing means 49 for a predetermined measurement length L0. The sheet length detected in step 1 is compared with the sheet conveyance length. In (A) above, it is determined whether or not one sheet or a plurality of sheets are overlapped from the comparison data obtained by comparing the output data from the vibration receiving circuit 13 in the comparison circuit unit 13c. The sheet set on 1 is compared with the conveyance direction length from the sheet size recognition means 49 and the conveyance length of the sheet from the counter 23 to determine whether or not the sheets are overlapped in a state where they are displaced forward and backward ( (See FIG. 5 ST07).

  Accordingly, the discriminating means 24 for discriminating abnormal conveyance of the sheet constituted by the control CPU 14 is configured to regard as abnormal conveyance when at least one of the above (A) and (B) detects double feeding of the sheet. .

  In the present invention, the length of the sheet in the conveyance direction has been described with reference to the case where the sheet size recognition unit 49 detects the sheet on the stacker 1. However, the length of the sheet may be set as follows.

  The maximum size sheet that can be conveyed is set as an apparatus specification, and the length in the conveyance direction of the maximum size sheet is stored in the ROM 52 as a setting value. Therefore, the control CPU 14 detects the conveyance length of the sheet by the encoder 21 and the counter 23 described above, compares the conveyance length with a set value called from the ROM 52, and doubles when the conveyance length is larger than the set value. It is configured so as to be determined as a feed (double feed). In addition, for example, the set value is divided into large, medium, and small sections, and the corresponding set value is stored in the ROM 52, and the length of the sheet on the stacker 1 in the conveyance direction is detected by the size sensor 50 to detect the large size. The first set value may be selected for a sheet that is classified into a second size, the second set value may be selected for a sheet that is classified into a medium size, and the third set value may be selected for a sheet that is classified into a small size.

Next, the double feed detection method of the present invention will be described.
(Step 1)
Identifies the length of the sheet in the conveyance direction. The length size of a series of sheets set in the stacker 1 is detected. In the apparatus of FIG. 1, the standard size prepared (stored) in the ROM 52 is selected and specified by detecting the sheet edge by the size sensor 50 provided in the stacker 1. In this step, the length in the sheet conveyance direction is recognized.

(Step 2)
An overlap in the sheet conveyance process is detected to determine whether or not double feeding is performed. In FIG. 1, a sheet conveyed by the first and second conveying means 4 and 5 is detected by a multifeed detecting means 6 such as an ultrasonic sensor, and the output data is compared with a reference value to determine whether or not the multifeed is performed. To do.

(Step 3)
The conveyance length from the leading edge to the trailing edge of the sheet in the conveyance path is measured. In FIG. 1, the transport amount of at least one of the first and second transport means 4 and 5 for transporting the sheet is measured by means such as an encoder 21 and a counter 23.

(Step 4)
The sheet conveyance direction size (length) in step 1 is compared with the sheet conveyance length in step 3. In this case, the two length values are compared by a calculation means such as a CPU.

(Step 5)
Based on the comparison result of step 4 and the comparison result of step 2, a sheet conveyance abnormality is determined.

  When the sheet overlap is detected in step 2 and when the sheet conveyance length is larger than the sheet size length in step 4, it is determined that conveyance abnormality is detected when any of them is detected. In the apparatus shown in FIG.

  Next, a case where the present invention is implemented in an image reading apparatus will be described. FIG. 7 shows a schematic configuration of an image reading apparatus A and an image forming apparatus B provided with the same as a unit, and FIG. 8 shows details of a sheet supply unit of the image forming apparatus B. An image forming apparatus B provided with an image reading apparatus A, which will be described later, includes a printing drum 102 in a casing 100, a paper feed cassette 101 that supplies paper to the printing drum 102, and a developing device that develops and forms toner on the printing drum 102. 108 and a fixing device 104 are incorporated. Reference numeral 103 denotes a print head such as a laser that forms a latent image on the print drum 102. The paper from the paper feed cassette 101 is sent to the print drum 102 by the transport roller 105, and the image formed by the print head 103 is transferred to the fixing device 104. It is fixed by. The sheet on which the image is formed is stored in the sheet discharge stacker 121 from the sheet discharge roller 107. Such an image forming apparatus B is widely known as a printer, and includes a paper feeding unit, a printing unit, and a paper discharge storage unit. Each functional unit is not limited to the above-described structure, and various types such as ink jet printing and silk screen printing are employed. Is possible.

  The print head 103 is electrically connected to a storage device 122 such as a hard disk for storing image data and a data management control circuit 109 for sequentially transferring the stored image data to the print head. Above the image forming apparatus B, the image reading apparatus A is attached as a unit. In the image reading apparatus A, a platen 112 is attached to a casing 110, and an optical mechanism 114 and a photoelectric conversion element 113 for reading a document sheet via the platen are arranged. As the photoelectric conversion element 113, a CCD or the like is widely known.

  A sheet feeding device C shown in FIG. 8 is installed on the platen 112. In the sheet feeding apparatus C, a sheet feed stacker 115 and a sheet discharge stacker 116 are arranged above and below the platen 112, and the sheet from the sheet feed stacker 115 is moved through the U-shaped transport path 134 to the platen 112. Then, it guides to the paper discharge stacker 116. The paper feed stacker 115 is provided with an empty sensor 117 and a size sensor 132 for detecting the presence / absence of a placed sheet, and 133 shown in the figure is a side guide for regulating the side edge of the sheet. The size sensor 132 and the side guide 133 will be described later according to FIG.

  A separation roller 119 and a fixed roller 120 pressed against the separation roller 119 are arranged on the upstream side of the paper feed stacker 115, and a kick roller 118 is attached to a bracket 119b attached to the rotation shaft 119a of the separation roller 119. When the rotating shaft 119a is rotated in the clockwise direction, the kick roller 118 is lowered onto the paper feed stacker 115, and when the rotating shaft 119a is rotated in the counterclockwise direction, the kick roller 118 is raised to the state shown in the drawing (the mechanism will be described later). On the downstream side of the separation roller 119, a multi-feed detection unit 123 that detects the overlapping state of sheets and a sheet end detection unit 124 that detects the leading and trailing ends of the sheet are disposed in the conveyance path 134. In addition, registration rollers 125 a and 125 b, feeding rollers 127 a and 127 b, carry-out rollers 129, and paper discharge rollers 130 are sequentially provided in the conveyance path 134, and a sheet is conveyed from the paper feed stacker 115 to the paper discharge stacker 116. 126 in the figure is a lead sensor for detecting the leading edge of the sheet, and 131 in the figure is a circulation path for retransmitting the sheet from the platen 112 to the registration rollers 125a and 125b through the path cutout gate 131a.

  Next, the side guide 133 and the size sensor 132 will be described with reference to FIG.

  The sheet feed stacker 115 is provided with a pair of left and right side guides 133 (133a, 133b) for regulating the side edges of the sheet, and the side guides are attached to be movable in the sheet width direction. Racks 135 and 136 are integrally provided on the left and right guides 133a and 133b, and meshed with a pinion 137 that is rotatably fixed to the paper feed stacker 115.

  Accordingly, the left and right guides 133a and 133b are moved in the opposite direction by the same amount by the pinion 137. One of the racks 136 is provided with a detection piece 139 made of a protrusion at a position corresponding to the width of the sheet, and the position sensor 138 attached to the bottom surface of the stacker 115 detects the position of the detection piece 139. Yes. The position sensor 138 is configured by a slidac volume, and the resistance value changes depending on the engagement length with the detection piece 139, and the position of the side guide 133 can be detected by the detection output. The stacker 115 is provided with a plurality of size sensors 132 for detecting the trailing edge of the sheet.

  Therefore, the position sensor 138 detects the width direction of the sheet on the stacker 115, and the size sensor 132 determines the sheet size on the stacker 115 for the sheets having the same width size.

  Next, FIGS. 10A and 10B show a driving mechanism of the separation roller 119 and the registration roller 125. The kick roller 118, the separation roller 119, and the registration roller 125 are driven by a paper feed drive motor 140 capable of forward and reverse rotation. The feeding drive motor 141 drives the feeding roller 127, the carry-out roller 129, and the paper discharge roller 130. The paper feed drive motor 140 rotates the kick roller 118 and the separation roller 119 by normal rotation and rotationally drives the registration roller 125 by reverse rotation. At the same time, the paper feed drive motor 140 controls the kick roller 118 to move up and down. The paper feed drive motor 140 transmits only rotation in one direction to the registration roller 125 by the one-way clutch 142 via the belts B1 and B2. At the same time, the paper feed drive motor 140 is connected to the rotating shaft of the separation roller 119 by a one-way clutch 143, and the one-way clutches 142 and 143 are set so as to transmit driving relatively.

  A bracket 119b is supported on the rotating shaft of the separation roller 119 via a spring clutch 144, and the drive is transmitted to the kick roller 118 attached to the bracket 119b by the transmission belt B3. When the paper feed drive motor 140 is rotated in the forward direction, the separation roller 119 and the kick roller 118 are rotationally driven. At the same time, the spring clutch 144 is loosened and the bracket 119b becomes free, and the kick roller 118 is lowered from the raised retracted position in FIG. Touches the sheet on the stacker. When the paper feed drive motor 140 is rotated in the reverse direction, the drive is transmitted to the registration roller 125, and at the same time, the spring clutch 144 is contracted to raise the bracket 119b and return to the retracted position in FIG.

  As shown in FIG. 10B, the transport unit drive motor 141 is connected to the feed roller 127, the carry-out roller 129, and the paper discharge roller 130 via belts B5, B6, and B7, and the feed roller 127 and the carry-out roller 129. Is a one-way clutch that always rotates in one direction by forward and reverse rotation of the motor, and the discharge roller 130 rotates forward and backward by motor forward and backward rotation.

  A sensor for detecting the arrival of the leading edge of the sheet is disposed in the conveyance path 134, and the operation thereof will be described. A plurality of size sensors 132 for detecting a specified size of the set sheet are arranged on the sheet feed stacker 115 to detect the sheet size and control subsequent sheet conveyance. An empty sensor 117 that detects the presence or absence of a sheet on the stacker is provided at the leading end of the sheet feed stacker 115, detects the feeding of the final sheet, and sends a signal to a processing apparatus such as the image reading apparatus A. On the downstream side of the separation roller 119, the above-mentioned double feed detection means 123 and the sheet end detection sensor 124 are provided.

  A lead sensor 126 is provided in front of the feeding roller 127 to notify the image reader of the arrival of the leading edge of the sheet and to determine the starting line for image reading and printing. At the same time, if a sheet is not detected even after a lapse of a predetermined time from the feeding instruction signal of the registration roller 125, the drive motor is stopped as a jam and a warning signal is issued at the same time. A paper discharge sensor 145 is disposed on the downstream side of the carry-out roller 129, and detects the leading edge and the trailing edge of the sheet to determine a jam.

  Next, the operation of the above-described apparatus will be described. FIG. 11 is a flowchart of the operation. The apparatus is turned on and a sheet is set (placed) on the sheet feed stacker 115. With this sheet set, the empty sensor 117 detects the paper presence state and activates the paper feed drive motor 140 (ST100).

  The kick roller 118 and the separation roller 119 separate the sheet by the rotation of the paper feed drive motor 140 and feed the sheet to a conveyance guide 128 between the feeding separation roller 119 and the registration roller 125, and a sheet end detection unit 124 (hereinafter referred to as a sensor 124). ) Detects the leading edge of the sheet (ST101). The timer T1 (see FIG. 4) is operated from the detection signal at the leading edge of the sheet, and the motor 140 is stopped after a predetermined time (ST102).

  In such an operation, in FIG. 12A, the sensor 124 detects the leading edge of the sheet and activates the timer T1. Next, in the state shown in FIG. 6B, the leading edge of the sheet hits the registration roller 125 and curves in a loop shape. In this state, the set time of the timer T1 ends and the motor 140 is stopped. Next, when a paper feed instruction signal is issued from the control unit of the image reading apparatus A, the motor 140 is restarted in the reverse rotation direction (ST103).

  The timer T2 is activated by a paper feed instruction signal. This timer T2 (see FIG. 4) cancels the registration loop, and the sheet is linearly supported and conveyed between the separation roller 119 and the registration roller 125. This state is shown in FIG. 12 (c) (ST104).

  Next, double feed of the sheet is detected by the double feed detecting means 123 until the trailing edge of the sheet is separated from the separation roller 119 in the state of FIG. 12D (ST105). The trailing edge of the sheet thus fed is detected by the sensor 124 (ST106). At the same time as the detection of the trailing edge of the sheet, the leading edge of the sheet is detected by the lead sensor 126 and is fed toward the platen 112 by the feeding roller 127.

  When the leading edge of the sheet detected by the lead sensor 126 reaches the platen 112, the optical mechanism 114 and the photoelectric conversion element 113 perform a reading process as an electric signal (ST107). After the reading process, the sheet is discharged to the discharge stacker 116 by the discharge roller 129 and the discharge roller 130. The discharge of the sheet is detected by the paper discharge sensor 145 (ST108).

  In this process, the sheet conveyance direction and the width direction of the sheet are detected on the sheet feed stacker 115 by the size sensor 132 and the position sensor 138 of the side guide 133, and the length size of the sheet is recognized. The registration roller 125b is provided with the same encoder and counter as described in FIG. 1 so as to detect the rotation amount of the roller, and from the leading edge of the sheet conveyed by the separation roller 119 and the registration roller 125 to the rear. The transport length reaching the end is detected. The transport length and the sheet length size are compared in the same manner as described with reference to FIG. 1, and at the same time, the output signal from the multifeed detecting means 123 is compared with the reference value in the same manner as in FIG. Sending is determined.

Explanatory drawing of the schematic mechanism of the sheet supply apparatus which implemented this invention. FIG. 2 is an explanatory view of the structure of an ultrasonic sensor showing an example of a double feed detection unit in the apparatus of FIG. The block diagram which shows the control circuit of the apparatus of FIG. The timing chart explaining control of the apparatus of FIG. The flowchart explaining control of the apparatus of FIG. Waveform explanatory drawing of the output signal of the ultrasonic sensor of FIG. 1 is an overall explanatory diagram of an image reading apparatus embodying the present invention and an image forming apparatus including the image reading apparatus as a unit; FIG. FIG. 8 is a detailed explanatory diagram of a document sheet supply unit in the apparatus of FIG. 7. The perspective view which shows the structure of the paper feed stacker of the apparatus of FIG. Explanatory drawing which shows the drive mechanism of the apparatus of FIG. The flowchart explaining control of the apparatus of FIG. FIG. 8 is an explanatory diagram of an operation state of sheet supply in the apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stacker 2 Processing platen 3 Conveying guide 4 1st conveying means 4a Separation roller 4b Friction pad 5 2nd conveying means 5a, 5b Registration roller pair 6 Double feed detecting means 6a Wave sending element 6b Wave receiving element 7 Sheet edge detecting means DESCRIPTION OF SYMBOLS 9 Piezoelectric vibrating body 12 Oscillation circuit 12a High frequency oscillation circuit 12b Power amplification circuit 13 Vibration receiving circuit 13a Amplification circuit 13b Smoothing circuit 13c Comparison circuit 14 Control CPU
20 Sheet conveyance length detection means 21 Encoder 22 Encoding detection sensor 23 Counter 24 Discrimination means 49 Sheet size recognition means 50 Size sensor 51 Side guide 52 ROM
117 Empty Sensor M Drive Motor

Claims (9)

A stacker for placing the sheet;
A conveyance guide for guiding the sheet from the stacker to a predetermined processing position;
An upstream first transport means and a downstream second transport means disposed in the transport guide;
Sheet size recognizing means for determining the conveyance direction length of the sheet placed on the stacker;
A multi-feed detecting unit disposed between the first conveying unit and the second conveying unit for detecting an overlap of sheets;
A conveyance length detecting means for detecting a conveyance length from the leading edge to the trailing edge of the sheet conveyed by the conveying means;
A comparison unit that compares the length in the conveyance direction of the sheet from the sheet size recognition unit and the conveyance length from the conveyance length detection unit;
A discriminating means for judging abnormal conveyance of the sheet based on the comparison result of the comparing means and the detection result of the double feed detecting means ;
Sheet end detecting means for curving the leading edge of the sheet in a loop shape by the second conveying means;
With
The conveyance length detection means is configured to measure the conveyance length from the leading edge of the sheet to the trailing edge by the sheet edge detection means for detecting the sheet conveyance amount and the sheet trailing edge of the second conveyance means,
The double feed detection means and the sheet edge detection means are arranged between the first conveyance means and the second conveyance means in the order of the double feed detection means and then the sheet edge detection means. A sheet feeding device. The first conveying means is constituted by a separation roller for separating and supplying sheets on the stacker,
2. The sheet feeding apparatus according to claim 1, wherein the second conveying unit is constituted by a registration roller that temporarily waits for a sheet from the separation roller. The sheet feeding apparatus according to claim 1, wherein the sheet size recognition unit is a sensor unit that detects a sheet end disposed on the stacker. The comparison unit is configured by a calculation unit that compares whether or not the conveyance direction length of the sheet from the sheet size recognition unit coincides with the conveyance length from the conveyance length detection unit. The sheet supply apparatus according to claim 1. A stacker for loading sheets;
A conveyance guide for guiding sheets from the stacker to a predetermined processing platen;
Separating means for separating and feeding the sheets on the stacker;
Registration roller means for conveying the sheet from the separation means to the processing platen;
A multi-feed detecting unit disposed between the separating unit and the conveying unit to detect the overlap of sheets;
A sheet end detecting means for bending the leading end of the sheet in a loop shape by the conveying means;
A conveyance length detecting means for detecting a conveyance length from the leading edge to the trailing edge of the sheet conveyed by the registration roller means ;
A comparison unit that compares the conveyance length of the conveyance length detection unit with a predetermined reference length;
A discriminating means for discriminating abnormal conveyance of the sheet based on the comparison result of the comparing means and the detection result of the double feed detecting means ;
Equipped with a,
The conveyance length detection means is configured to measure the conveyance length from the leading edge of the sheet to the trailing edge by the sheet edge detection means for detecting the sheet conveyance amount and the sheet trailing edge of the registration roller means,
The sheet feeding device, wherein the double feed detecting means and the sheet end detecting means are arranged in the order of the double feed detecting means and then the sheet end detecting means between the separating means and the registration roller means. . 6. The sheet according to claim 5, wherein the reference length is set to a conveyance direction length of a maximum size sheet that can be conveyed, and the sheet is determined to be abnormal conveyance when a comparison result of the comparison unit is longer than the reference length. Feeding device. The sheet feeding apparatus according to claim 5, wherein the conveying unit includes a registration roller for temporarily waiting the sheet. The separating unit and the conveying unit are arranged at a distance position shorter than the conveyance direction length of the smallest sized sheet that can be conveyed, and the multi-feed detecting unit is configured such that the sheet is engaged with the separating unit and the conveying unit. The sheet feeding apparatus according to claim 5 , wherein the sheet feeding apparatus is configured to detect an overlap of the sheet. A platen having photoelectric conversion means for reading an image on a sheet;
A paper feed stacker that supplies sheets to the platen;
A paper discharge stacker for storing sheets from the platen;
A conveyance guide for guiding sheets from the sheet feed stacker to the platen;
An upstream first transport means and a downstream second transport means disposed in the transport guide;
Sheet size recognizing means for determining the conveyance direction length of the sheet placed on the stacker;
A multi-feed detecting unit disposed between the first conveying unit and the second conveying unit for detecting an overlap of sheets;
A conveyance length detecting means for detecting a conveyance length from the leading edge to the trailing edge of the sheet conveyed by the conveying means;
A comparison unit that compares the length in the conveyance direction of the sheet from the sheet size recognition unit and the conveyance length from the conveyance length detection unit;
A determining means for determining abnormality conveyance of the sheet based on the detection result of the comparison result and said double feed detecting means of the comparison means,
Sheet end detecting means for curving the leading edge of the sheet in a loop shape by the second conveying means;
With
The conveyance length detection means is configured to measure the conveyance length from the leading edge of the sheet to the trailing edge by the sheet edge detection means for detecting the sheet conveyance amount and the sheet trailing edge of the second conveyance means,
The double feed detection means and the sheet edge detection means are arranged between the first conveyance means and the second conveyance means in the order of the double feed detection means and then the sheet edge detection means. An image reading apparatus.

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