JP2005350166A - Sheet handling device and double feed sensing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discriminate the overlapped condition of sheets accurately at all times by adjusting properly the output value of a signal emitting element for sensing a double feed of sheets. <P>SOLUTION: A sheet handling device with a function to sense a double feed of sheets includes a sheet feeding stacker 1 to admit placing of sheets thereon, a sheet feeding means to pay out the sheets on the stacker 1 to the specified position, the signal emitting element 6a and a signal receiving element 6b to sense the double feed of sheets located downstream of the sheet feeding means, for example in such a configuration that the wave transmitting element and the wave receiving element of an ultrasonic sensor are installed confronting with the sheets interposed, a sensitivity adjusting means 35 to adjust the output of the signal emitting element 6a through comparison of the sensing value of the signal receiving element 6b with the specified reference value, and a control means for a driving means to drive the sheet feeding means, wherein the sensitivity adjusting means 35 adjusts the output of the signal emitting element 6a in the condition that the driving means is stopped or decelerated to the specified speed. Thereby a specified output value is obtained at all times from the signal receiving element 6b, and stable sensing of double feed can be performed even if the sensibility is deteriorated resulting from the wave transmitting element and wave receiving element being influenced by the environmental temperature or other secular changes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a device that separates sheets such as originals stacked on a stacker one by one and supplies them to an image reading platen or other sheet processing platen, and detects multi-sheet feeding in a path from the stacker to the processing platen. The present invention relates to a sheet handling apparatus having a function.

  In general, a device that supplies a series of sheets such as originals to a processing platen and reads an image on the sheet with the processing platen is widely known for scanners, copiers, facsimiles, and the like, and performs processing such as printing on the sheet with the processing platen. The apparatus is widely used as a printer.

  In such a sheet handling apparatus, it is required to accurately separate the sheets stacked on the stacker one by one and supply them to the processing platen in the correct posture, and in particular, when reading a series of documents sequentially. In addition, there is a risk that a non-feed in which no sheet is supplied to the platen or a double feed in which two or more sheets are supplied in an overlapping manner may cause an erroneous process to be executed in the processing platen. Similarly, when a series of information is printed on the processing platen, the non-feed or double feed of the sheet may be erroneously processed by the processing platen.

  Therefore, it is necessary to detect the sheet from the stacker to the processing platen and interrupt the processing in the platen when non-feeding or double feeding. For example, a sensor for detecting the presence or absence of a sheet is provided in front of the processing platen (upstream side). In many apparatuses, it is determined that the sheet is not fed even if a predetermined time has elapsed from the sheet feed stacker and the processing on the platen is stopped by determining that the sheet is not fed.

  On the other hand, there is a problem that accurate sheet discrimination is difficult with double-feed detection of sheets, and detection elements and discrimination circuits are also expensive. However, in systems where scanners, copying machines, etc. are connected to a network, double-feeding of sheets is critical. The detection is required to be more accurate and less expensive in order to cause general errors.

  It is possible to use a pair of ultrasonic sensors as devices for detecting such double feeding of sheets, for example, Japanese Utility Model Publication No. 6-49567 (Patent Document 1), Japanese Patent Application Laid-Open No. 2000-95390 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2000-95390. No. 2003-17603 (Patent Document 3) and the like. In both devices, a pair of ultrasonic sensors are arranged at positions facing each other across the sheet in the sheet conveyance path, and ultrasonic waves transmitted from the transmitting side sensor (transmitting element) are received on the receiving side sensor (receiving element) ) And the overlapping state of the sheets is determined based on the attenuation amount of the ultrasonic wave transmitted through the sheets.

  As an ultrasonic sensor used for detecting such a sheet, for example, a structure shown in FIG. 2 is known. A piezoelectric vibrating body is embedded in a case such as a metal that covers the outside, a high-frequency voltage is applied to an electrode formed on the piezoelectric vibrating body to excite vibration, and the surface of the case is excited to oscillate ultrasonic waves. . 13 shown in the figure is a resin filled in the case. On the other hand, the receiving element also receives ultrasonic waves with the same structure, the case surface is excited, and the electric vibration generated by the vibration of the piezoelectric vibrating body integrated therewith is output to the outside.

Therefore, since such transmitting and receiving elements vary in the dimensions and shape of the piezoelectric vibrator and the natural frequency of the metal case during the manufacturing process and have individual characteristics, elements within a certain allowable range can be transmitted and received. And as a receiving element, accurate detection cannot be obtained unless combined. Therefore, conventionally, only the elements allowed by measuring the characteristics of the individual elements in the manufacturing process of the ultrasonic sensor are used.
No. 6-49567 JP 2000-95390 A JP 2003-176063 A

  As described above, when detecting a double feed of a sheet, a conventional detecting element such as an ultrasonic sensor is measured and used in the manufacturing process, so the element becomes expensive. If a change occurs in the structure and form, erroneous detection will be caused. Therefore, the detection element must be selected and used within the range that does not affect the detection of the sheet even if temperature or some form change occur with the same characteristics as possible on the transmission side and reception side in the manufacturing process. However, there was a problem that the device was expensive and could not withstand aged use.

  Therefore, the present invention adjusts the variation in the characteristics of the element on the transmission side and the element on the reception side by adjusting the detection element that detects double feeding of the sheet to an appropriate value in a state of being incorporated in the sheet conveyance path. Providing a sheet handling device that is based on knowledge and can always accurately determine the overlapping state of sheets fed from the paper feed stacker to the processing platen without causing erroneous processing in the processing platen. Is the issue.

  The means for solving the above problems will be described. A paper feed stacker for placing sheets, a paper feed means for feeding the sheets on the paper feed stacker to a predetermined processing position, and a sheet on the downstream side of the paper feed means. A transmitting element and a receiving element for detecting the double feed of are arranged. For example, the transmitting element and the receiving element are configured by arranging a transmitting element and a receiving element of an ultrasonic sensor so as to face each other with a sheet interposed therebetween. The sensitivity adjusting means for adjusting the output of the transmitting element by comparing the detection value of the receiving element with a predetermined reference value and the control means of the driving means for driving the paper feeding means are configured as follows. .

  The sensitivity adjusting means adjusts the output of the transmitting element while the driving means is stopped or decelerated to a predetermined speed. The sensitivity adjusting means compares the output value of the receiving element with a predetermined reference value, and changes the power source energy supplied to the transmitting element according to the comparison result. Increase or decrease the power supply amplitude. Thus, a predetermined output value is always obtained from the receiving element, and stable double feed detection is possible even if the detection sensitivity of the transmitting element and the receiving element deteriorates due to environmental temperature or other aging.

  Also, first and second transporting units are arranged at a distance from the paper feed stacker and a predetermined sheet processing position, and a transmitting element and a receiving element are disposed between the first and second transporting units. And a sensitivity adjusting means for adjusting the output of the transmitting element by comparing the detected value of the transmitting element with a predetermined reference value. Based on a sheet leading edge detection signal from a sheet sensor that detects whether or not the sheet from the paper feed stacker has reached the downstream side of the first and second conveying means, the sensitivity adjusting means Adjust the output level. At this time, the first and second conveying units stop driving based on the sheet leading edge detection signal from the sheet sensor, and after the sensitivity adjustment by the sensitivity adjusting unit is completed, the driving is performed again to carry out the sheet at high speed. Control to do.

In addition, the present invention can also achieve the above object by the following method.
An ultrasonic sensor having a conveying step for conveying a sheet on the sheet feeding stacker to a predetermined sheet processing position, and a transmitting element and a receiving element disposed between the sheet feeding stacker and the sheet processing position is used to overlap the sheets. A double feed detecting step for detecting feeding, and a sensor sensitivity adjusting step for changing the output value of the transmitting element by stopping or decelerating the sheet moving between the paper feed stacker and the sheet processing position to a predetermined speed And a sheet discharge step of moving the sheet again after executing the sensor sensitivity adjustment step or carrying out the sheet at a speed higher than the predetermined speed. Further, this adjustment step is executed in a state where the sheet is nipped by at least two conveying means arranged in the front and rear directions in the conveying direction.

  The present invention compares the detection value of the receiving element with a preset reference value when detecting the double feeding of the sheet by arranging a transmitting side element such as an ultrasonic sensor and a receiving side element in the path for conveying the sheet. Sensitivity adjustment means is provided to adjust the output value of the transmitting element, so the output value on the transmitting side can be changed even if there is a difference in the characteristics of the transmitting and receiving elements, errors in the mounting positions of both elements, or changes due to environmental temperature. By adjusting, it becomes possible to detect an appropriate double feed.

  Therefore, even in the case of ultrasonic sensors whose characteristic values tend to be different, the allowable characteristic range is widened, and the manufacturing cost can be reduced. Furthermore, the adjustment of the output value on the transmission side is performed by stopping the conveyance of the sheet such as a test sheet or decelerating to a predetermined speed, so that the output value of the transmission element is not distorted due to variations in the sheet conveyance speed. Have.

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 various sheet handling apparatuses such as an image reading apparatus or a copying machine or a printing machine, which will be described later, and separates and supplies one sheet at a time to a processing platen for image reading and printing. In particular, the present invention relates to an apparatus and a method for detecting an overlap state of sheets in front of a processing position.

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

  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 first and second conveyances arranged in the conveyance guide 3. Means 4 and 5, and a multi-feed detection means 6 disposed between the first conveying means 4 and the second conveying means 5 for detecting the overlapping state of the sheets are provided. Then, the sheets stacked on the stacker 1 are separated one by one by the separating means and fed to the processing position (processing platen 2) by the first and second conveying means 4 and 5, and the image is read and printed at the processing position. A predetermined process such as stamping and stapling is performed, and the paper is discharged to the paper discharge stacker 9.

  The stacker 1 is usually composed of a tray on which a sheet is placed, and an empty sensor S1 for detecting the presence or absence of a sheet and a size sensor S2 for detecting the length of the sheet are appropriately attached according to the apparatus specifications. Separating means for sequentially separating and feeding the uppermost sheet or the lowermost sheet is provided at the tip of the stacker 1.

  This separation means can be implemented by various methods such as a combination of the first conveying roller 4a and friction pad 4b shown in the figure, a combination of a normal rotation roller and a reverse rotation roller, a combination of a paper feed roller and a separation claw (corner separator), Vacuum separation is known, and the present invention can employ any method for separating stacked sheets into one sheet. The illustrated one shows a first conveying roller 4a (which may be a belt) that rotates in the sheet conveying direction and a friction pad 4b that prevents double feeding of the sheet. The sheet separated by the separating unit 4 is fed toward the platen 2, but a registration roller 5 a or a first conveying roller for temporarily waiting the sheet on a conveying path between the separating unit 4 and the platen 2. A conveying roller 8 a that takes over and conveys the sheet from 4 a toward the platen 2 is disposed.

  In the present invention, at least two conveying means are provided between the stacker 1 and the processing platen 2. In the illustrated example, the first conveying roller 4a is set as the first conveying means, and the registration roller 5a is set as the second conveying means. The first and second conveying means 4a and 5a are the smallest sizes to be conveyed. They are arranged at intervals shorter than the sheet length. The registration roller 5 is configured in such a manner that the sheet from the separation roller 4a is curved by a pair of rollers 5a and 5b that are in pressure contact with each other to correct the skew, and then supplied to the platen 2 at a predetermined timing. Has been.

  Therefore, a double feed detection sensor 6 and a sheet sensor 7 for detecting the leading edge of the sheet are arranged between the first and second transport rollers 4 and 5. The double feed detection sensor 6 is configured by arranging a transmitting element (transmitting element 6a) and a receiving element (receiving element 6b) at positions facing each other across the conveyance guide 3, and the sheet sensor 7 receives the light emitting element 7a and the light receiving element. The elements 7b are arranged to face each other. The double feed detection sensor 6 shown in the figure is an ultrasonic sensor, and the transmitting-side transmitting element 6a and the receiving-side receiving element 6b are composed of piezoelectric vibrators having the same structure. 8a is a conveyance roller provided on the conveyance guide 3, and controls the sheet fed to the platen 2 to a predetermined speed.

  Next, the double feed detection sensor 6 is composed of an ultrasonic sensor, and a transmitting element 6a is disposed on the transmitting side and a receiving element 6b is disposed on the receiving side. The transmitting element 6a and the receiving element 6b are composed of piezoelectric vibrators having the same structure as shown in FIG. 2 as an example, and are made of a metal material such as an aluminum alloy in a cylindrical outer casing case 10 such as a ceramic. The piezoelectric vibrating body 11 is built in contact with the case 10 and filled with a synthetic resin 13. Electrode layers are formed on the front and back surfaces of the piezoelectric vibrator 11 by vapor deposition, the lead wire 12 is connected to one of them, and the other is grounded and electrically connected to the case. Accordingly, when a high frequency voltage is applied to the lead wire 12, the piezoelectric vibrating body 11 vibrates at a predetermined frequency, and when the piezoelectric vibrating body 11 is excited, the electromotive force is taken out from the lead wire 12.

A high-frequency power source is connected to the wave transmitting element 6a, and this will be described with reference to FIG.
The apparatus power supply 14 is connected to a high-frequency oscillation circuit 15, which generates a high-frequency voltage of 30 KHZ to 40 KHZ, for example, and then amplifies it by the amplification circuit 16 and supplies it to the wave transmitting element 6 a. Then, the piezoelectric vibrator 11 has its natural frequency set to a predetermined frequency, and an ultrasonic wave is transmitted from the outer casing case 10 by the vibration. The amplification factor of the amplifier circuit 16 is set by the control CPU, and an instruction signal from the CPU is D / A converted and transmitted to the amplifier circuit 16.

  Therefore, the ultrasonic wave emitted from the wave transmitting element 6 a is transmitted to the wave receiving element 6 b via the sheet S of the conveyance guide 3. In the wave receiving element 6b, the case 10 is excited by the ultrasonic wave transmitted through the sheet, and the piezoelectric vibrating body 11 in close contact with the case 10 vibrates. The electromotive force generated by the vibration of the piezoelectric vibrating body 11 is guided from the electrode to the lead wire 12, and the current is output as a detection value proportional to the amplitude of the piezoelectric vibrating body 11.

  The wave receiving element 6b is connected to an amplifier circuit 18 for amplifying the detection current, and the detection current generated in the piezoelectric vibrating body 11 is amplified. A smoothing circuit 19 is connected to the amplifier circuit 18, and the detected current of the amplified wave is averaged by the smoothing circuit 19 configured by an integrating circuit and sent to the comparison circuit 20. The comparison circuit 20 compares the detected current from the smoothing circuit 19 with a preset reference value. This reference value is determined as follows.

  FIG. 4 shows the output value (analog voltage) of the smoothing circuit 19, wherein FIG. 4A shows the output value when one sheet is sent to the conveyance path, and FIG. The output value when the sheet is sent is shown. Therefore, the sheet fed from the stacker 1 is directed from the first conveying roller 4a to the second conveying roller 5a, and A in the drawing is an output in a state where the leading end of the sheet is directed from the first conveying roller 4a to the second conveying roller 5a. The value shows an unstable waveform, and B in the figure shows an output value in a state where the sheet is held by both the first conveyance roller 4a and the second conveyance roller 5a, and becomes a stable waveform. In the figure, C indicates an unstable waveform with an output value in a state where the sheet is held by the second conveying roller 5a and the trailing edge of the sheet is separated from the first conveying roller 4a.

  Therefore, in the region B of the stable waveform, the output value is clearly divided into high and low levels when there is one sheet and when there are two sheets, and the attenuation when the ultrasonic wave passes through the sheet is one. The detection current is small and high, and the amount of attenuation when the sheets overlap two or more is large and the detection current is low. The detection current output from the smoothing circuit in a state where the sheet is supported by the pair of front and rear conveying rollers 4a and 5a is higher than the detection current for one sheet and lower than the detection current for two sheets. Compare with the determined reference value. In this case, since the reference value varies depending on the thickness of the paper to be used, paper quality, and the like, various kinds of paper selected according to the apparatus specifications are obtained by experiments.

  The comparison data from the comparison circuit 20 is transferred to a control CPU (control circuit) 21. The control CPU 21 is connected to size sensors S2 and S3 arranged on the stacker 1, the above-described sheet sensor 7, and a paper discharge sensor arranged on the conveyance guide 3 (not shown). The sheet sensor 7 described above is disposed between the first conveyance roller 4a and the second conveyance roller 5a, and transmits to the control CPU 21 the timing at which the leading edge of the sheet arrives.

  On the other hand, the control CPU 21 is connected to transmit a command signal to the motor drive circuit 22 of the drive motor M that drives the first and second transport rollers 4a and 5a. A power supply 25 is connected to the pulse generator 23 to the motor drive circuit 22 and a pulse current is supplied to the motor drive circuit 22. The drive motor M that receives the power supply 25 is a stepping motor. A counter 24 is connected to the pulse generator 23 to count the pulse current supplied to the drive motor M, and this counter 24 is connected to the control CPU 21.

  An operation for detecting double feeding of sheets in the apparatus having the configuration shown in FIG. 1 will be described with reference to the flowchart shown in FIG.

The control program of the CPU 21 configures the transport control unit 28 as follows, for example.
When the apparatus power supply 14 is turned on, the CPU 21 determines whether there is a sheet on the stacker 1 from the status signal of the empty sensor S1 (F1). When a sheet exists, a start signal is issued to the motor drive circuit 22, and the motor drive circuit 22 supplies a pulse power supply from the power supply 25 to the drive motor M via the pulse generator 23. When the drive motor M is activated (F2), the first conveying roller 4a connected to the motor rotates in the clockwise direction in FIG.

  The sheet is separated one by one by the friction pad 4b in the process of feeding the sheet by the first conveying roller 4a and proceeds to the conveying guide 3, and the leading edge of the sheet passes through the double feed detecting sensor 6 and then the sheet sensor 7 to the second. To the transport means 5. At this time, the second conveying means 5 is placed in a stopped state, the leading edge of the sheet comes into contact with the pressure contact portion of the second conveying rollers 5a and 5b, and is curved in a loop shape. When the leading edge of the sheet reaches the sheet sensor 7, the conveyance control unit 28 starts a timer in response to a detection signal from the sheet sensor 7 (F3), and stops the driving motor M after the time T1 has elapsed (F4).

  Next, the CPU 21 receives a processing start signal from the main apparatus such as image reading and printing as a paper feed instruction signal (F5), and restarts the drive motor M with this signal. In the illustrated example, the transmission mechanism is constituted by a one-way clutch so that the first conveyance roller 4a rotates in the forward direction of the drive motor M and the second conveyance roller 5a rotates in the opposite direction (selective) in the reverse direction.

  Accordingly, when the drive motor M is restarted, the second conveyance roller 5a rotates, and the first conveyance roller 4a stops and the sheet is fed to the conveyance roller 8a side by the second conveyance roller 5a (F6). At the same time, the conveyance control unit 28 of the CPU 21 starts the timer T2 (F7). The timer T2 is set at time T1 <T2 so that the loop of the sheet curved in a loop shape is eliminated. When the predetermined time of the timer T2 has elapsed, the CPU 21 issues a double feed detection instruction signal (F8). Upon receipt of this signal, the detection signal / reference value comparison unit 29 in the CPU 21 receives the double feed comparison data shown in FIG. 3A, and determines the overlapping state of the sheets (F9). This double feed detection (discrimination) is performed when the detection value is lower than the reference value based on the data obtained by comparing the detection value from the wave receiving element 6b with the reference value (LV0 in FIG. 2) in the comparison circuit 20 in advance. Judged as double feed over 2 sheets.

  The detection signal / reference value comparison unit 29 in the configuration shown in the drawing first prevents the detection error when the detection value of the wave receiving element 6b fluctuates due to the vibration of the sheet or other external conditions. After an air layer is formed between two sheets that are bent in a loop shape and overlapped by means 5, double feeding is detected in a state where the loop is eliminated. Further, it is detected that the sheet is nipped between both the first conveying roller 4a and the second conveying roller 5a, and further discriminated by an average value detected by a predetermined distance (length) as the sheet is conveyed. Has been.

  Therefore, when the detection signal / reference value comparison unit 29 determines that the sheet is double-fed, a double-fed process (F10) is executed. In this multi-feed processing, the apparatus is stopped, and the user removes the sheet in the conveyance guide 3 and sets it again on the stacker 1 or carries out the sheet to the paper discharge stacker 9 without performing processing on the processing platen 2. Then, a measure such as displaying the fact (that is, double feeding) on the operation panel is executed. When the detection signal / reference value comparison unit 29 determines that the sheet is normally conveyed (not double-fed), the second conveying roller 5a and the conveying roller 8a send the sheet to the processing platen 2 and execute a predetermined sheet processing (F12). . When the trailing edge of the sheet passes the preceding sheet sensor 7, the CPU 21 detects the state signal, drives the drive motor M (F2), and similarly feeds the next sheet.

  The conveyance roller 8a is connected to a drive motor different from the drive motor M, and feeds the sheet to the processing platen 2 at a predetermined speed. The sheets that have been subjected to the predetermined processing by the processing platen 2 are sequentially stored in the sheet discharge stacker 9, and sheet storage is detected by the sheet discharge sensor provided at the sheet exit end of the sheet discharge stacker 9 (F13). The CPU 21 determines whether or not a series of jobs have been completed based on the status signal of the empty sensor 1 as to whether or not a sheet exists in F1 (F14). When the empty sensor 1 indicates the presence of the next sheet, the CPU 21 issues a paper feed instruction signal (F5) and feeds the next sheet to the processing platen 2.

  The above operation has been described with respect to a general sheet feeding step. However, in the case of a scanner device that sequentially reads an image on a sheet with the processing platen 2, the conveyance control unit 28 executed in the CPU 21 is a drive motor. The speed of M is controlled as follows.

  The conveyance control unit 28 sets the conveyance speeds of the first conveyance unit 4 and the conveyance roller 8a in accordance with the sheet processing conditions by a signal from the scanner device. This transport speed is determined on the scanner device side according to the image reading condition, and the transport speed varies depending on whether the condition is color, monochrome, or the reading resolution is high or low. Generally, color and high resolution are set to high speed, monochrome and low resolution are set to low speed, and the speed is also set to various speeds depending on conditions.

  FIG. 3B shows a sensitivity adjustment circuit (means) 35, which is configured in the CPU 21. The detected value from the wave receiving element 6b is amplified by the amplifier circuit 18, smoothed by the smoothing circuit 19, and compared with the reference value by the comparison circuit 20. In such a circuit configuration, first, the amplification factor 16 for supplying high-frequency power to the transmission element 6a is transmitted from the sensitivity adjustment circuit 35 of the CPU 21 through the D / A converter 17 as an analog voltage value to be amplified. The circuit 16 supplies a high-frequency voltage to the transmission element 6a with the amplitude of the set amplification factor. On the other hand, the detected current from the transmission element 6 a passes through the amplifier circuit 18, and the output value (detected value) from the smoothing circuit 19 is converted into a digital value by the A / D converter 36 and sent to the sensitivity adjustment circuit 35. .

  Therefore, the sensitivity adjustment circuit 35 compares the output value of the wave receiving element 6b with a predetermined reference value (output value / reference value comparison unit 37), and determines the output value according to the comparison result (output value determination unit 39). ). An amplification factor is set (amplification factor setting unit 38) based on the determination result of the output value determination unit 39, and the gain of the amplifier circuit 16 is set via the D / A converter 17.

  Then, a preset amplification factor reference value 41 is read from, for example, a ROM, the gain of the amplifier circuit 16 is set, and an ultrasonic wave is oscillated from the transmission element 6a. Then, the ultrasonic wave that has passed through the test sheet (reference paper) is detected by the wave receiving element 6 b and output from the smoothing circuit 19 to the A / D converter 36 via the amplifier circuit 18. This output value (analog voltage value) is compared with a reference value, and when the output value matches the reference value (a certain range), the amplification factor is stored in the amplification factor memory 40. On the other hand, when the output value does not satisfy the reference value, the output value determination unit 39 sets the amplification factor so that the output value (analog voltage), for example, increases by 0.1 V (amplification factor setting unit 38).

  The output value from the wave receiving element 6b when the predetermined amount is amplified is compared again by the output value / reference value comparison unit 37, and when the values match, the amplification factor is stored in the amplification factor memory 40. When the output value is less than the reference value, the amplification factor is further increased by a predetermined amount, and thereafter the same adjustment is repeatedly performed. When such amplification factor setting reaches a predetermined amplification factor maximum value 42, it is determined that there is an abnormality in the double feed detection system such as the transmitting element 6a and the receiving element 6b, and an error is displayed on the control panel, for example. The operator can continue sheet processing as a system that does not use the repair or double feed detection function.

  In the above embodiment, the reference value for adjusting the amplification factor is, for example, an appropriate (normal) amplification if the output value (analog voltage value) from the smoothing circuit 19 is in the range of 3.5V to 4.0V. The output value (analog voltage value) after smoothing is increased by an increase in the minimum increase in amplification factor (for example, 0.1 V) even when the element (device) used is a combination of products with the highest sensitivity. It is set as a value that does not exceed.

  Next, an operation flow when the sensitivity adjustment for adjusting the amplification factor as described above is executed by the apparatus of FIG. 1 will be described with reference to FIG.

  First, sensitivity adjustment mode setting (F20) is performed. This mode setting is configured such that the user operates a switch on the control panel or automatically executes simultaneously with the initial operation of the main apparatus such as image reading and printing. Then, the CPU 21 determines whether or not a sheet exists on the stacker 1 based on the status signal of the empty sensor S1. In this case, it is determined whether or not a test sheet exists on the stacker 1, and when it exists, the drive motor M is started.

  The drive speed of the drive motor M is set to be the same as the speed for the sheet processing described above. By driving the drive motor M, the sheet on the stacker 1 is fed out, the leading end of the sheet passes through the ultrasonic sensor (double feed detecting means) (F22), and feeding of the test sheet is started (F23). When the leading edge of the sheet reaches the sheet sensor 7 (F24), the CPU 21 starts the timer T1 with the status signal (F25). When the timer T1 elapses for a predetermined time (F26), the drive motor M is stopped and the first transport roller 4a is stopped (F27).

  Next, the drive motor M is restarted in the reverse rotation direction, and the second transport roller 5a is driven (F28). Simultaneously with the activation of the drive motor M, the counter 24 connected to the pulse generator 23 counts power pulses, and the CPU 21 determines whether or not the second conveying roller 5a has conveyed a predetermined amount of sheets. The predetermined amount of sheet conveyance is set so that the sheet curved in a loop shape by the second conveyance roller 5a is in a state of being linearly tensioned.

  Concurrent with the cancellation of the registration loop, the conveyance control unit 28 of the CPU 21 stops the drive motor M or decelerates to a predetermined speed. This stop of the drive motor is to prevent the detection value of the ultrasonic sensor from fluctuating due to the movement of the sheet in the subsequent sensitivity adjustment, and the deceleration to the predetermined speed is the fluctuation and movement of the detection value due to the movement speed. The optimum speed is set from the time when the subsequent sensitivity adjustment is completed in the process. Usually, the speed for adjusting the sensitivity is preferably set to a speed slower than the minimum speed at which the sheet is subjected to the predetermined processing by the processing platen 2.

  Thus, the following sensitivity adjustment is performed in a state where the sheet is slow or decelerated. First, the sensitivity adjustment circuit 35 supplies a high-frequency power source set with a gain reference value 41 to the transmission element 6a (F36). Then, the output value (analog voltage) that has passed through the A / D conversion 36 from the wave receiving element 6b is compared, and when the comparison result matches, the amplification value at that time is stored in the amplification factor memory 40 and the sensitivity adjustment is completed. To do. If the comparison result does not match, the output value determination unit 39 increases the amplification factor by a predetermined amount, and the amplification factor setting unit 38 sets the maximum value of the amplification factor (a range in which the gain of the amplification circuit does not become saturated). If not, the power is supplied from the amplifier circuit 16 to the transmission element 6a.

  When the amplification factor from the output value determination unit 39 exceeds the maximum value, the CPU 21 transmits a failure signal to the main body (F38), and the conveyance control unit 28 drives the conveyance roller 8a at a high speed and discharges the test sheet to the sheet stacker. Unload to 9 (F39). On the other hand, the main body apparatus that has received the failure signal executes the subsequent sheet processing (F40) in the non-use state (non-detection operation mode) of the double feed detection function, or repairs the double feed detection means (F42). Selected by the operator. When the non-detection operation mode is selected, for example, a message indicating that “multiple feed cannot be detected but paper can be fed” is displayed on the control panel to prepare for the aforementioned sheet processing operation (F41).

  After completion of the adjustment (F32) when the appropriate sensitivity is output from the wave receiving element 6b, the sheet of the conveyance guide 3 is driven to the sheet discharge stacker 9 by rotating the conveyance roller 8a at high speed (F33). Then, a display indicating that the adjustment is completed (F34) is displayed on the control panel of the main body apparatus, and the adjustment mode is ended (F35) to prepare for execution of the subsequent sheet processing.

  The proper amplification factor adjusted in this way is stored in the amplification factor memory 40 and used for gain setting of the amplification circuit 16 at the time of sheet feeding thereafter.

  Next, a case where the present invention is implemented in an image reading apparatus will be described. FIG. 8 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. 9 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 adopted. 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 for reading a document sheet via the platen 1112 and a photoelectric conversion element 113 are arranged. As the photoelectric conversion element 113, a CCD or the like is widely known.

  A sheet feeding device C shown in FIG. 9 is installed on the platen 112. In this sheet supply 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 conveyance 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 loaded 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 rotary shaft 119a is rotated in the clockwise direction, the kick roller 118 is lowered onto the paper feed stacker 115, and when the rotary shaft 119a is rotated in the counterclockwise direction, the kick roller 118 is raised to the state shown in the figure. 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, a pair of registration rollers 125a and 125b, a pair of feeding rollers 127a and 127b, a pair of discharge rollers 129, and a pair of paper discharge rollers 130a and 130b are provided in this order in the conveyance path 134, and a sheet is discharged from the paper feed stacker 115. It is conveyed to the stacker 116.

  126 in the figure is a lead sensor for detecting the leading edge of the sheet, and 128 in the figure is a guide for backing up the sheet at the position of the platen 112. Reference numeral 131 denotes a circulation path in which the sheet from the platen 112 is retransmitted to the registration roller pairs 125a and 125b by 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 a 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 a sheet having the same width size.

  Next, FIGS. 11a and 11b show a driving mechanism for the separation roller 119 and the registration roller 125. The kick driving 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, and a conveyance drive motor 141 is shown. Thus, the feeding roller 127, the carry-out roller 129, and the paper discharge roller 130 are driven. 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 tightened to raise the bracket 119b and return to the retracted position in FIG.

  As shown in FIG. 11b, 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 are one-way. The clutch always rotates in one direction by forward and reverse rotation of the motor, and the paper discharge roller 130 rotates forward and backward by forward and reverse rotation of the motor.

  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 paper feed stacker 115, and the subsequent sheet conveyance is controlled by detecting the size of the sheet. 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 feeding 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 detecting means 123 and the sheet sensor 124 are provided.

  A lead sensor 126 is provided in front of the pair of feeding rollers 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 pair of carry-out rollers 129, and detects a leading edge and a trailing edge of the sheet to determine a jam.

  Next, the operation of the above-described apparatus will be described. The apparatus power 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. By the rotation of the paper feed drive motor 140, the kick roller 118 and the separation roller 119 separate the sheet and feed it to the conveyance guide 128 between the feeding separation roller 119 and the registration roller 125, and a sheet sensor 124 (hereinafter referred to as sensor 124). ) Detects the leading edge of the sheet. The timer T1 is actuated from the detection signal at the leading edge of the sheet, and the paper feed drive motor 140 is stopped after a predetermined time.

  In such an operation, the sensor 124 detects the leading edge of the sheet in FIG. Next, in the state (b), the leading edge of the sheet hits the registration roller 125 and curves in a loop. In this state, the set time of the timer T1 ends, and the paper feed drive motor 140 is stopped.

  Next, when a paper feed instruction signal is issued from the control unit of the image reading apparatus A, the paper feed drive motor 140 is restarted in the reverse rotation direction. At the same time, the timer T2 is activated by this sheet feeding instruction signal, the timer T2 cancels the registration loop, and the sheet is supported and conveyed linearly between the separation roller 119 and the registration roller 125. This state is shown in FIG.

  Next, double feed of the sheet is detected by the double feed detection means 123 until the trailing edge of the sheet is separated from the separation roller 119 in the state of FIG. The trailing edge of the sheet thus fed is detected by the sensor 124. 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 sheet detected at the leading edge by the lead sensor 126 reaches the platen 112, the optical mechanism 114 and the photoelectric conversion element 113 perform reading processing as an electrical signal. After this reading process, the sheet is discharged to the paper discharge stacker 116 by the carry-out roller 129 and the paper discharge roller 130. The discharge of the sheet is detected by a paper discharge sensor 145.

  In such a process, the double feed detection means 123 is constituted by an ultrasonic sensor, and is arranged in a path from the separation roller 119 (paper feeding means) to the registration roller 125. The sensitivity adjustment circuit 35 described with reference to FIG. 3A is provided in the transmission element of this ultrasonic sensor, and the smoothed output value (analog voltage) is compared with the reference value in the reception element. ing. Therefore, when a test sheet is set on the paper feed stacker 115 and the sensor sensitivity adjustment mode is instructed from the control panel of the apparatus, the output of the transmitting element is adjusted to the optimum condition according to the operation flow shown in FIG.

Explanatory drawing of the principal part of the sheet | seat handling apparatus which implemented this invention. The schematic structure figure of the double feed detection means which consists of an ultrasonic sensor. It is explanatory drawing of control of the apparatus of FIG. 1, and shows the control circuit of double feed detection. It is explanatory drawing of control of the apparatus of FIG. 1, and shows the circuit of a sensitivity adjustment. Waveform explanatory drawing of the output signal of the ultrasonic sensor of FIG. (A) shows a non-multifeed state. (B) shows a double feed state. The block diagram which shows the control circuit of the apparatus of FIG. The operation | movement flow in the case of performing sensitivity adjustment with the apparatus of FIG. The operation | movement flow in the case of detecting double feeding of a sheet | seat with the apparatus 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. 9 is a detailed explanatory diagram of a document sheet supply unit in the apparatus of FIG. 8. FIG. 10 is a perspective view showing a structure of a paper feed stacker of the apparatus of FIG. 9. Explanatory drawing which shows the drive mechanism of the apparatus of FIG. (A) shows the drive of the paper feed unit. The same (b) shows the drive of a conveyance part. FIG. 9 is an explanatory diagram of an operation state of sheet supply in the apparatus of FIG. 8. (A) to (e) show the sheet conveyance state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stacker 2 Processing platen 3 Conveying guide 4 1st conveying means (separating means)
5 Second conveying means (registration roller)
6 Double feed detection sensor (Double feed detection means)
6a Transmitting element (transmitting element)
6b Receiving element (receiving element)
7 Sheet sensors 8a and 8b Conveying roller 9 Discharge stacker 10 Outer casing 11 Piezoelectric vibrator 12 Lead wire 13 Synthetic resin 14 Device power supply 15 Oscillator circuit 16 Amplifier circuit 17 D / A converter 18 Amplifier circuit 19 Smoothing circuit 20 Comparison Circuit 21 Control CPU
22 motor drive circuit 23 pulse generator 28 transport control unit 29 detection signal / reference value comparison unit 30 sheet processing execution control unit 31 count value / measurement length comparison unit 35 sensitivity adjustment circuit 36 A / D converter 37 output value / reference Value comparison unit 38 Amplification rate setting unit 39 Output value determination unit S1 Empty sensors S2, S3 Size sensor A Image reading device B Image forming device C Sheet supply device 100 Casing 101 Paper cassette 102 Print drum 103 Print head 104 Paper discharge stacker 105 Transport roller 107 Paper discharge roller 108 Storage device 109 Data management control circuit 110 Casing 112 Platen 113 Photoelectric conversion element 114 Optical mechanism 115 Paper feed stacker 116 Paper discharge stacker 117 Empty sensor 118 Kick roller 119 Separating roller 119a Rotating shaft 119b Bra Tsu DOO 120 fixed roller 123 double feed detection unit 124 sheet end detecting means 125a registration roller pair 125b registration roller pair 126 leading sensor 127a feed roller pair
127b Feed roller pair 129 Unload roller pair 130 Discharge roller pair 131 Circulation path 131a Path notch gate 132 Size sensor 133 Side guide (133a, 133b)
134 Transport path 135 Rack 136 Rack 137 Pinion 138 Position sensor 139 Detection piece 140 Paper feed drive motor 141 Transport drive motor 142 One-way clutch 143 One-way clutch

Claims (8)

A paper feed stacker for placing sheets;
A sheet feeding means for feeding a sheet on the sheet feeding stacker to a predetermined processing position;
Driving means for driving the paper feeding means;
A double feed detecting means disposed downstream of the paper feeding means and having a transmitting element and a receiving element for detecting double feeding of sheets;
Sensitivity adjustment means for adjusting the output of the transmitting element by comparing the detection value of the receiving element with a predetermined reference value;
Control means for controlling the conveying speed of the paper feeding means,
The sheet handling apparatus, wherein the sensitivity adjusting means adjusts the output of the transmitting element in a state where the driving means is stopped or decelerated to a predetermined speed by the control means. The transmitting element is an ultrasonic wave transmitting element, and the receiving element is an ultrasonic wave receiving element,
2. The sheet handling apparatus according to claim 1, wherein the sensitivity adjusting means is constituted by an amplifying means for adjusting the amplitude of the transmitting element. A paper feed stacker for placing sheets;
A sheet feeding means for separating sheets on the sheet feeding stacker and feeding them to a predetermined processing position;
First and second conveying means disposed at a distance from each other between the paper feed stacker and the sheet processing position;
A double feed detecting means disposed oppositely between the first and second conveying means and having a transmitting element and a receiving element for detecting double feeding of a sheet;
Sensitivity adjusting means for comparing the detected value of the transmitting element with a predetermined reference value to adjust the output of the transmitting element;
Control means for controlling the transport speed of the first and second transport means,
A sheet sensor for detecting whether or not a sheet from the paper feed stacker has reached the downstream side of the first and second conveying means;
The sheet handling apparatus, wherein the sensitivity adjusting means adjusts the output of the transmitting element based on a sheet leading edge detection signal from the sheet sensor. The control means stops the driving means based on a sheet leading edge detection signal from the sheet sensor,
4. The sheet handling apparatus according to claim 3, wherein after the sensitivity adjustment by the sensitivity adjustment unit is completed, the driving unit is restarted to carry out the sheet. The control means drives the driving means at a predetermined speed based on a sheet leading edge detection signal from the sheet sensor,
4. The sheet handling apparatus according to claim 3, wherein after the sensitivity adjustment by the sensitivity adjustment unit is finished, the driving unit is driven at a high speed to carry out the sheet. A first operation mode in which the first and second conveying means convey a sheet to a sheet processing position at a preset speed and execute a predetermined process;
A second operation mode in which predetermined processing is not performed at the sheet processing position;
4. The sheet handling apparatus according to claim 3, wherein the speed of the first and second transport means is set to be lower than the speed of the first operation mode in the second operation mode. A double feed detection method for detecting whether or not a sheet fed out and fed from a paper feed stacker is double fed,
A transport step for transporting a sheet on the paper feed stacker to a predetermined sheet processing position;
A double feed detection step of detecting double feed of a sheet with an ultrasonic sensor having a transmitting element and a receiving element disposed between the paper feed stacker and the sheet processing position;
A sensor sensitivity adjustment step of changing the output value of the transmitting element by stopping the sheet moving between the sheet feeding stacker and the sheet processing position or decelerating the sheet to a predetermined speed;
A sheet double feed detection method comprising: a sheet discharge step of moving the sheet again after executing the sensor sensitivity adjustment step or discharging the sheet at a speed higher than the predetermined speed.   The multifeed detection method according to claim 7, wherein the adjusting step is executed in a state where the sheet is nipped by at least two conveying units arranged in the front and rear directions in the conveying direction.

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