JP2009274772A - Duplicate feed detecting device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a duplicate feed detecting device capable of reducing erroneous detection of duplicate feeding of sheets in a plurality of ultrasonic wave sensors arranged on a conveyance passage as well as suitably detecting presence/absence of the sheets. <P>SOLUTION: The duplicate feed detecting device performs sheet detection and detects duplicate feeding, which means two or more sheets are overlapped and conveyed, by using a plurality of the ultrasonic wave sensors. In the duplicate feed detecting device, when a sheet on the conveyance passage is detected by one of a plurality of ultrasonic wave transmitters 102a-102c (for example, the ultrasonic wave transmitter 102a) and an ultrasonic wave receiver (the ultrasonic wave receiver 103a) arranged on a position opposite to the ultrasonic wave transmitter (the ultrasonic wave transmitter 102a), the detecting device controls to increase the pulse number of ultrasonic wave transmitting pulse to the ultrasonic wave transmitter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an apparatus having a function of mounting a plurality of sheets, separating and conveying the sheets one by one, and particularly using an ultrasonic sensor to convey two or more sheets while being stacked. The present invention relates to a multifeed detection apparatus and method for detecting

  Some scanners, printers, copiers, printing machines, ATMs (Automated Teller Machines), and the like are equipped with a plurality of sheets such as originals and checks, and have a function of separating and conveying the sheets one by one. In an apparatus having such a function, there may be a case where double feeding is performed where only one sheet is transported while part or all of two or more sheets are overlapped. The function to detect is needed. As a mechanism for detecting double feeding of a sheet, a multifeed detection device using an ultrasonic sensor including an ultrasonic transmitter and an ultrasonic receiver is widely used. An example of a double feed detection device using an ultrasonic sensor is shown in FIG.

  In FIG. 7, 2 is an ultrasonic transmitter that transmits ultrasonic waves, and 3 is an ultrasonic receiver that receives ultrasonic waves transmitted from the ultrasonic transmitter 2. These constitute an ultrasonic sensor, and are installed at positions facing each other across the conveyance path of the sheet 1 so that the ultrasonic wave transmitted through the sheet 1 to be detected can be received.

  The control unit 4 supplies an ultrasonic transmission signal to the drive unit 5, and a pulse signal for transmitting an ultrasonic wave from the drive unit 5 is output to the ultrasonic transmitter 2. The ultrasonic transmitter 2 transmits a 300 kHz ultrasonic wave upon receiving a pulse signal. The ultrasonic wave transmitted from the ultrasonic transmitter 2 hits the sheet 1 and the ultrasonic receiver 3 receives the ultrasonic wave transmitted through the sheet 1. The ultrasonic receiver 3 outputs an ultrasonic reception signal that changes in accordance with the intensity of the received ultrasonic wave. The signal amplifier 6 amplifies the ultrasonic reception signal output from the ultrasonic receiver 3 and outputs the amplified signal to the A / D converter 7. The A-D converter 7 converts the ultrasonic reception signal amplified by the signal amplifier 6 into a digital signal and outputs the digital signal to the signal analysis unit 8. The signal analyzer 8 analyzes the digitized ultrasonic reception signal output from the A / D converter 7. Then, when the control unit 4 determines that double feeding is performed based on the analysis result of the signal analysis unit 8, the control unit 4 performs processing for notifying the device or the user of the device that double feeding has occurred.

  In the double feed detection device described above, a level determination method is performed in which the signal analysis unit 8 analyzes a change in the amplitude of the ultrasonic reception signal output from the ultrasonic receiver 3 to detect double feed. In this level determination method, first, the ultrasonic wave receiver 3 receives the ultrasonic wave that has passed through the sheet 1, and the amplitude of the ultrasonic wave reception signal output from the ultrasonic wave receiver 3 is amplified by the signal amplifier 6 in advance. It is compared with the set double feed judgment threshold. The amplitude of the ultrasonic reception signal when the sheet 1 is double-fed is smaller than the double-feed determination threshold when the sheet 1 is normally conveyed one by one, because the attenuation amount of the ultrasonic wave becomes large. Become. Therefore, the double feed of the sheet 1 can be detected by comparing the amplitude of the ultrasonic reception signal output from the ultrasonic receiver 3 and amplified by the signal amplifier 6 with the double feed determination threshold in the signal analysis unit 8. Is possible.

In addition, in order to adjust the ultrasonic reception signal output from the ultrasonic reception means to a constant value regardless of changes in external factors, a transmission control means for controlling the characteristics of the ultrasonic waves transmitted by the ultrasonic transmission means is provided. A feed detection device has been proposed (see, for example, Patent Document 1).
JP 2004-231404 A

  However, in a multifeed detection device provided with ultrasonic sensors at a plurality of locations, an ultrasonic receiver other than the ultrasonic receiver disposed at a position opposite to the ultrasonic wave transmitted by each ultrasonic transmitter is received. Mutual interference may occur, and erroneous detection of double feeding may occur. In addition, as the installation interval of the plurality of ultrasonic sensors is narrower, the mutual interference of the ultrasonic waves is relatively increased, and erroneous detection of double feeding is likely to appear remarkably.

  On the other hand, if a certain ultrasonic transmitter is stopped in order to suppress such mutual interference of ultrasonic waves, a sheet detecting means for determining whether or not the sheet passes through the installation position is separately required. It leads to up.

  The present invention has been made in view of the above problems, and can reduce erroneous detection of sheet double feeding in a plurality of ultrasonic sensors arranged on a conveyance path and appropriately detect the presence or absence of a sheet. An object of the present invention is to provide an apparatus and method for detecting a double feed.

  In order to achieve the above object, the multifeed detection device according to claim 1 includes ultrasonic transmission means disposed at a plurality of locations on a conveyance path in which a sheet is conveyed, and conveyance of each of the ultrasonic transmission means to the ultrasonic transmission means. Ultrasonic wave receiving means arranged at positions facing each other across the road, and ultrasonic waves transmitted by the ultrasonic wave transmitting means and transmitted through the sheet are received by each of the ultrasonic wave receiving means facing the ultrasonic wave transmitting means. And a double feed detection unit that detects double feed by analyzing the ultrasonic reception signal that is output, and in the double feed detection device capable of detecting double feed at a plurality of locations in the transport path, When the sheet of the conveyance path is detected by any ultrasonic transmission means of the ultrasonic transmission means and the ultrasonic reception means disposed at a position facing the ultrasonic transmission means, the ultrasonic transmission means Control the characteristics of transmitted ultrasonic waves And, characterized in that it comprises a control means for the ultrasonic wave transmission means disposed in a position facing the ultrasonic wave receiving means for increase the intensity of the ultrasonic reception signal output.

  In order to achieve the above object, the multi-feed detection method according to claim 7 includes ultrasonic transmission means disposed at a plurality of locations on a conveyance path through which the sheet is conveyed, and the conveyance to each of the ultrasonic transmission means. Ultrasonic wave receiving means arranged at positions facing each other across the road, and ultrasonic waves transmitted by the ultrasonic wave transmitting means and transmitted through the sheet are received by each of the ultrasonic wave receiving means facing the ultrasonic wave transmitting means. And a double feed detection unit capable of detecting double feed by analyzing the ultrasonic reception signal outputted and detecting double feed at a plurality of locations on the transport path. When the sheet of the conveyance path is detected by an arbitrary ultrasonic transmission unit among the plurality of ultrasonic transmission units and an ultrasonic reception unit disposed at a position facing the ultrasonic transmission unit, Ultra transmitted from ultrasonic transmission means Controls wave characteristics, characterized in that the ultrasonic wave transmission means disposed in a position facing the ultrasonic wave receiving means for increase the intensity of the ultrasonic reception signal output.

  According to the present invention, it is possible to reduce erroneous detection of double feeding of sheets in a plurality of ultrasonic sensors arranged on a conveyance path on which a sheet is conveyed, and to appropriately detect the presence or absence of a sheet.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram illustrating a configuration of main functional units of the double feed detection device according to the first embodiment of the present invention.

  The double feed detection device 1000 is an ultrasonic device that combines an ultrasonic transmitter and an ultrasonic receiver for double feed in which a sheet 101 to be transported is partially or wholly overlapped in an apparatus such as a scanner. Detect using a sensor. In the present embodiment, a sheet 101 made of paper such as a document, banknote, or check is described as a conveyance target. However, the present invention is not limited to this, and other materials such as a film may be used.

  Reference numerals 102a, 102b, and 102c denote ultrasonic transmitters that transmit ultrasonic waves. Reference numerals 103a, 103b, and 103c denote ultrasonic receivers that receive the ultrasonic waves transmitted from the ultrasonic transmitters 102a, 102b, and 102c.

  The ultrasonic receivers 103a, 103b, and 103c are installed so as to face the ultrasonic transmitters 102a, 102b, and 102c across the conveyance path of the sheet 101 so that the ultrasonic waves that have passed through the sheet 101 can be received. Specifically, the ultrasonic transmitter 102a and the ultrasonic receiver 103a are arranged on a substantially straight line across the conveyance path. Similarly, the ultrasonic transmitter 102b and the ultrasonic receiver 103b, and the ultrasonic transmitter 102c and the ultrasonic receiver 103c are also arranged on a substantially straight line across the conveyance path. Thereby, the ultrasonic waves transmitted from the ultrasonic transmitters 102a, 102b, and 102c pass through the sheet 101 and reach the ultrasonic receivers 103a, 103b, and 103c and are received.

  In the present embodiment, the arrangement position of the ultrasonic transmitter 102a and the ultrasonic receiver 103a is the position a, the arrangement position of the ultrasonic transmitter 102b and the ultrasonic receiver 103b is the position b, the ultrasonic transmitter 102c and the ultrasonic wave. The arrangement position of the receiver 103c is assumed to be position c. The distances between the position a and the position b and the position b and the position c are 60 mm in a direction substantially orthogonal to the transport direction. In the present embodiment, a configuration in which ultrasonic sensors are arranged at three positions a, b, and c will be described. However, the number of arrangement positions is not limited to this. Further, the intervals between the position a and the position b, and the position b and the position c differ depending on the apparatus, and are not limited to 60 mm.

  When the sheet 101 exists in the conveyance path, the ultrasonic waves transmitted from the ultrasonic transmitters 102a, 102b, and 102c pass through the sheet 101 and are received by the ultrasonic receivers 103a, 103b, and 103c. On the other hand, when the sheet 101 does not exist in the conveyance path, the ultrasonic waves transmitted from the ultrasonic transmitters 102a, 102b, and 102c are received as they are by the ultrasonic receivers 103a, 103b, and 103c.

  A control unit 105 can supply a pulse signal having a frequency substantially equal to the resonance frequency of the ultrasonic sensor to the driving units 104a, 104b, and 104c as an ultrasonic transmission signal. In the present embodiment, the resonance frequency of the ultrasonic sensor is 300 kHz. The pulse signal supplied by the control unit 105 is, for example, a digital ON-OFF signal that repeats ON / OFF at 300 kHz for several cycles over a certain period of time. This is generally called a burst wave, and the burst wave is transmitted once at intervals of several hundred μsec to several msec. Further, the control unit 105 can control the change of the time interval for transmitting the burst wave and the number of pulses of the burst wave.

  Reference numerals 104 a, 104 b, and 104 c denote drive units that output ultrasonic transmission pulses to the ultrasonic transmitters 102 a, 102 b, and 102 c in accordance with pulse signals from the control unit 105. The ultrasonic transmission pulse is obtained by amplifying a pulse signal with an amplification circuit in the drive units 104a, 104b, and 104c in order to drive the ultrasonic transmitters 102a, 102b, and 102c to transmit ultrasonic waves.

  Reference numeral 106 denotes a signal amplifier that amplifies the ultrasonic reception signals output from the ultrasonic receivers 103a, 103b, and 103c. The sheet 101 on the conveyance path blocks between the ultrasonic transmitters 102a, 102b, and 102c and the ultrasonic receivers 103a, 103b, and 103c. Then, the ultrasonic waves transmitted from the ultrasonic transmitters 102a, 102b, and 102c are attenuated and become weak before reaching the ultrasonic receivers 103a, 103b, and 103c. The amplitudes of the ultrasonic reception signals output from the ultrasonic receivers 103a, 103b, and 103c are weak. Therefore, the signal amplifier 106 amplifies the ultrasonic reception signal and raises it to a signal amplitude that allows determination of double feed detection.

  Reference numeral 107 denotes an A-D converter, which converts the amplified ultrasonic reception signal (analog signal) output from the signal amplifier 106 into a digital signal and outputs the digital signal to the CPU 108 which is a signal analysis unit. Note that the A-D converter 107 may be built in the CPU 108.

  The CPU 108 analyzes the ultrasonic reception signal digitized by the A / D converter 107 and outputs the double feed determination result of the sheet 101 to the control unit 105. The control unit 105 can output the double feed determination result of the CPU 108 to an external device (not shown). Note that the control unit 105 may be built in the CPU 108.

  Reference numeral 109 denotes a storage unit that holds various setting values in the multifeed detection apparatus 1000. Specifically, the storage unit 109 has a time interval for transmitting a burst wave, the frequency of a pulse signal, the number of pulses of the burst wave, a double feed detection level (hereinafter referred to as “double feed detection threshold”), and the presence of a sheet. A setting value such as a non-existence detection level (hereinafter referred to as “sheet detection threshold”) is held. Note that the storage unit 109 may be built in the CPU 108.

  The CPU 108 monitors the amplitude (hereinafter referred to as “signal intensity”) of the digitized ultrasonic reception signal, and performs double feeding of the position a, the position b, and the position c based on a change in the magnitude of the signal intensity. Can be detected individually.

  Further, the CPU 108 monitors the signal intensity, and can individually detect the presence / absence of the sheet 101 at the position a, the position b, and the position c based on the change in the signal intensity. For example, the signal strength when the sheet 101 is not interposed between the ultrasonic transmitters 102a, 102b, and 102c and the ultrasonic receivers 103a, 103b, and 103c is set as the first signal strength. The signal strength when only one sheet 101 is interposed between the ultrasonic transmitters 102a, 102b, 102c and the ultrasonic receivers 103a, 103b, 103c is defined as the second signal strength. The signal strength when the two sheets 101 are interposed between the ultrasonic transmitters 102a, 102b, and 102c and the ultrasonic receivers 103a, 103b, and 103c (when double-fed) is defined as a third signal strength. The first signal strength, the second signal strength, and the third signal strength are measured in advance. Then, between the first signal strength and the second signal strength is stored in the storage unit 109 as a sheet detection threshold, and between the second signal strength and the third signal strength as a double feed detection threshold. . As a result, the CPU 108 refers to the sheet detection threshold value stored in the storage unit 109, detects the sheet 101 by the ultrasonic sensors arranged at the position a, the position b, and the position c, and determines whether the sheet is present or absent. judge. Further, the CPU 108 refers to the double feed detection threshold held in the storage unit 109 and detects whether the sheet 101 is one sheet or a plurality of sheets by each ultrasonic sensor arranged at the positions a, b, and c. Determine whether there is a double feed. Note that the sheet detection threshold and the double feed detection threshold can be individually set for each of the position a, the position b, and the position c.

  Next, a method for suppressing the mutual interference of ultrasonic waves by a plurality of ultrasonic sensors in the multifeed detection apparatus 1000 of FIG. 1 will be described.

  FIG. 2 is a diagram for explaining a method of suppressing the mutual interference of ultrasonic waves between the ultrasonic transmitters 102a, 102b, 102c and the ultrasonic receivers 103a, 103b, 103c in FIG.

  In FIG. 2, the ultrasonic waves output from the ultrasonic transmitters 102a, 102b, and 102c are referred to as ultrasonic waves 201a, 201b, and 201c. Conventionally, when a plurality of ultrasonic sensors are provided as shown in the figure, when the sheet 101 exists at the position a, the ultrasonic receiver 103a transmits ultrasonic waves in addition to the ultrasonic wave 202 that has been weakened through the sheet 101. Mutual interference that receives 201b and the ultrasonic wave 201c occurs. Due to such mutual interference of ultrasonic waves, the accuracy of sheet detection and double feed detection at the position a is lowered, and there is a possibility that erroneous detection occurs.

  In order to suppress the mutual interference between the ultrasonic waves in the situation of FIG. 2, the intensity of the ultrasonic waves 201b and 201c at the position where there is no sheet (positions b and c in the illustrated example) is smaller than that of the ultrasonic wave 201a. Just keep it. That is, for ultrasonic sensors that have not yet detected the presence of a sheet among a plurality of ultrasonic sensors, ultrasonic waves with weak intensity suitable for determination of the presence or absence of a sheet are transmitted. Then, when the sheet is detected, the ultrasonic wave is changed to a strong ultrasonic wave suitable for double feed detection. In the present embodiment, for example, the control unit 105 sets the number of pulses of the pulse signal supplied to the driving unit 104a that is required to transmit a high-intensity ultrasonic wave to 10 pulses. The number of pulses of the ultrasonic burst wave transmitted from the ultrasonic transmitter 102a is assumed to be 10. On the other hand, the number of pulses of the pulse signal supplied to the drive units 104b and 104c is set to 1 pulse in order to keep the weak intensity ultrasonic wave transmitted. The number of ultrasonic burst waves transmitted from the ultrasonic transmitters 102b and 102c is one. By performing such control, mutual interference in which the ultrasonic receiver 103a receives the ultrasonic waves 201b and 201c transmitted from the ultrasonic transmitters 102b and 102c can be suppressed. Note that even if the intensity of the ultrasonic wave 201a transmitted from the ultrasonic transmitter 102a is high, the ultrasonic wave is attenuated when passing through the sheet 101, so the ultrasonic receivers 103b and 103c receive the ultrasonic wave 202 transmitted through the sheet 101. Mutual interference does not occur.

  Due to the characteristics of the ultrasonic sensor, if the number of pulses of the pulse signal supplied to the drive unit is increased, the signal intensity also increases proportionally, and if the number of pulses is decreased, the signal intensity decreases proportionally. Even if the number of pulses increases by a predetermined number or more, there is a limit to the conversion between the electrical energy of the ultrasonic transmission pulse and the vibration energy of the transmitted ultrasonic wave, and the transmission intensity of the ultrasonic wave reaches its peak. No longer grows. This depends on the characteristics of the ultrasonic sensor used.

  Next, an example of a control process for executing the above-described method for suppressing the mutual interference of ultrasonic waves will be described with reference to the flowchart of FIG.

  FIG. 3 is a flowchart illustrating an example of a control process for executing a method for suppressing the mutual interference of ultrasonic waves in the multifeed detection apparatus 1000.

  First, in step S601, the control unit 105 adds ultrasonic transmission pulses from the driving units 104a to 104c to the ultrasonic transmitters 102a to 102c to transmit ultrasonic waves. At this time, the number of pulses of the pulse signal supplied from the control unit 105 to the drive units 104a to 104c is the number of pulses reflecting the result of the previous sheet detection determination (steps S603 to S612).

  Next, in step S602, the ultrasonic receivers 103a, 103b, and 103c output ultrasonic reception signals to the signal amplifier 106 in accordance with the intensity of the received ultrasonic waves. Then, the CPU 108 acquires the ultrasonic reception signal as the signal intensity from the signal amplifier 106 via the AD converter 107. At this time, the CPU 108 acquires the signal strengths at the positions a, b, and c. Note that the CPU 108 can average each of the digital data of each signal intensity using data acquired a plurality of times as necessary. By this averaging, it is possible to stabilize the control when the data fluctuates, particularly in a transient state such as the leading edge / rear edge of the sheet.

  In step S603, the CPU 108 performs the sheet detection determination at the position a, and compares the acquired signal strength at the position a with a preset sheet detection threshold value. As described above, the CPU 108 refers to the sheet detection threshold value stored in the storage unit 109 and detects the sheet 101 by the ultrasonic sensor arranged at the position a, and determines the presence / absence of the sheet. When it is determined that there is a sheet, the control unit 105 changes the setting so as to increase the ultrasonic wave at the position a (step S604). On the other hand, when it is determined that there is no sheet, the control unit 105 outputs the ultrasonic wave at the position a. The setting is changed so as to be weakened (step S605). In the first embodiment, when the setting is changed so as to increase the ultrasonic wave at the position a, the number of pulses of the pulse signal supplied from the control unit 105 to the drive unit 104a is 10 pulses. On the other hand, when the setting is changed so as to be weakened, the number of pulses of the pulse signal supplied to the driving unit 104a is set to one pulse.

  In step S606, the CPU 108 performs sheet detection determination at the position b, and compares the acquired signal strength at the position b with a preset sheet detection threshold value. As described above, the CPU 108 refers to the sheet detection threshold value stored in the storage unit 109 and detects the sheet 101 by the ultrasonic sensor arranged at the position b, and determines the presence / absence of the sheet. When it is determined that there is a sheet, the control unit 105 changes the setting to increase the ultrasonic wave at the position b (step S607). On the other hand, when it is determined that there is no sheet, the ultrasonic wave at the position b is weakened. The setting is changed so as to be performed (step S608). In the first embodiment, when the setting is changed to increase the ultrasonic wave at the position b, the number of pulses of the pulse signal supplied from the control unit 105 to the drive unit 104b is set to 10 pulses. On the other hand, when the setting is changed so as to be weakened, the number of pulses of the pulse signal supplied to the driving unit 104b is set to one pulse.

  In step S609, the CPU 108 performs sheet detection determination at the position c, and compares the acquired signal strength at the position c with a preset sheet detection threshold value. As described above, the CPU 108 refers to the sheet detection threshold value stored in the storage unit 109 and detects the sheet 101 by the ultrasonic sensor arranged at the position c to determine the presence / absence of the sheet. When it is determined that there is a sheet, the control unit 105 changes the setting to increase the ultrasonic wave at the position c (step S610). On the other hand, when it is determined that there is no sheet, the ultrasonic wave at the position c is weakened. The setting is changed so as to be performed (step S611). In the first embodiment, when the setting is changed so as to increase the ultrasonic wave at the position c, the number of pulses of the pulse signal supplied from the control unit 105 to the driving unit 104c is 10 pulses. On the other hand, when the setting is changed so as to be weak, the number of pulses of the pulse signal supplied to the drive unit 104c is set to 1 pulse. The number of pulses of the pulse signal supplied to the driving units 104a to 104c may be increased or decreased by one pulse or several pulses instead of the control performed by switching to 10 pulses or 1 pulse as described above. .

  Next, in step S612, the control unit 105 performs a process of reflecting the setting change of the ultrasonic characteristic, and reflects the result of the setting change in steps S603 to S611 on the characteristic of the ultrasonic wave to be transmitted next. Here, the characteristics of the ultrasonic wave that is to be strengthened or weakened are not limited to the number of pulses of the pulse signal supplied to the drive unit. For example, as described in each embodiment described later, the pulse width of the pulse signal supplied to the drive unit, the amplitude of the ultrasonic transmission pulse supplied to the ultrasonic transmitter, and the frequency of the ultrasonic wave transmitted by the ultrasonic transmitter It may be. Note that an upper limit value and a lower limit value are set as values to be changed in the process of reflecting the setting change of the ultrasonic characteristics in step S612. In particular, the lower limit value is a set value that provides a signal intensity that can reliably detect the sheet.

  In addition, the setting change range may be set at a time in the process of changing the setting to increase or decrease the ultrasonic wave in steps S604, S605, S607, S608, S610, and S611. In the above-described example, the number of pulses of the pulse signal supplied to the drive unit is one of 10 pulses, but the number of pulses to be changed at a time is set to an arbitrary value from 1 pulse to 9 pulses, for example. It may be settable.

  In addition, in another embodiment to be described later, if the object to be changed is an ultrasonic frequency, the frequency to be changed at a time may be set with a lower limit of, for example, 10 kHz. Further, the pulse width that is changed at a time as long as the pulse width of the pulse signal supplied to the drive unit may be set, for example, with T / 10 as a lower limit. Furthermore, the drive amplitude that is changed at a time as long as the amplitude of the ultrasonic transmission pulse supplied to the ultrasonic transmitter may be set with 1 V as a lower limit, for example.

  In step S613, the CPU 108 performs double feed detection determination at the position where the sheet is present, and compares the signal strength acquired at the position where it is determined that there is a sheet with a preset double feed detection threshold. As described above, the CPU 108 refers to the double feed detection threshold value stored in the storage unit 109 and detects whether the sheet 101 is one sheet or a plurality of sheets by the ultrasonic sensors arranged at the positions a, b, and c. Then, the presence / absence of double feeding is determined. Note that this double feed detection determination can be performed simultaneously with the sheet detection determination in steps S603, S606, and S609.

  In some cases, it is preferable to have a time lag before the determination result of the double feed detection determination in step S613 is finalized. For example, the determination of the presence / absence of sheets at positions a, b, and c is inaccurate during a transient state or during a certain period including a transient state, the determination of the double feed determination result is suspended or not double fed Can be determined.

  When the sheet detection threshold value in the sheet detection determination in steps S603, S606, and S609 is substantially the same as the signal intensity, the processing for increasing the ultrasonic wave due to the presence determination of the sheet and the ultrasonic wave due to the determination regarding the absence of the sheet are weakened. There is a risk of repeating the process to be repeated many times. For this reason, two types of threshold values are provided: a sheet detection threshold value when determining that there is no sheet in the presence of a sheet, and a sheet detection threshold value when determining that there is a sheet in the absence of a sheet. That is, the sheet detection threshold value has a hysteresis. As a result, stable processing can be performed even when the sheet detection threshold value and the signal intensity are comparable.

  According to the first embodiment, when the sheet of the conveyance path is detected by one of the plurality of ultrasonic transmitters and the ultrasonic receiver disposed at a position facing the ultrasonic transmitter, Control is performed to increase the number of ultrasonic transmission pulses supplied to the ultrasonic transmitter. On the other hand, when the sheet is not detected, control is performed to reduce the sheet. When the sheet is detected by the ultrasonic transmitter and the ultrasonic receiver, the number of ultrasonic transmission pulses to be supplied to other ultrasonic transmitters among the plurality of ultrasonic transmitters is reduced. You may control to.

  By performing the control described above, it is possible to suppress the mutual interference of ultrasonic waves in a plurality of ultrasonic sensors arranged on the conveyance path, reduce erroneous detection of double feeding of sheets, and appropriately detect the presence or absence of sheets. Can be done.

[Second Embodiment]
The multifeed detection device according to the second embodiment of the present invention has the same configuration (FIGS. 1 and 2) as that of the multifeed detection device 1000 according to the first embodiment. About the part similar to the form of, the description is abbreviate | omitted using the same code | symbol. Only differences from the first embodiment will be described below.

  In the first embodiment, in order to maintain the accuracy of the double feed determination while suppressing the mutual interference, the number of pulses of the signal to the ultrasonic transmitter is increased for the ultrasonic wave at the position determined to have a sheet or no sheet. Or the setting was changed to make it stronger or weaker by decreasing. In the second embodiment, the intensity of the ultrasonic wave at the position where it is determined that there is no sheet is weakened by shifting the frequency of the ultrasonic wave transmitted from the ultrasonic transmitter from the resonance frequency, and it is determined that there is a sheet. At the set position, the setting is changed so as to become stronger by approaching the resonance frequency.

  FIG. 4 is a diagram showing the ultrasonic transmission frequency and the ultrasonic transmission / reception efficiency when the ultrasonic transmission / reception efficiency is 100% at the resonance frequency of 300 kHz. In the illustrated example, it is assumed that both the ultrasonic transmitter and the ultrasonic receiver have a resonance frequency of 300 kHz.

  Reference numeral 301 denotes the resonance frequency of the ultrasonic wave transmitted from the ultrasonic transmitters 102a to 102c. When the frequency of the ultrasonic wave deviates from the resonance frequency of 300 kHz, the ultrasonic wave transmission / reception efficiency tends to decrease. The resonance frequency of the ultrasonic sensor depends on the structure of the ultrasonic sensor, and is a total of the ultrasonic transmission efficiency and the ultrasonic reception efficiency of the ultrasonic sensor. The conversion efficiency between electrical energy and ultrasonic vibration energy is maximized at the resonance frequency.

  If the frequency of the pulse signal supplied from the control unit 105 to the drive units 104a to 104c is equal to the resonance frequency, the conversion efficiency between the electric energy and the vibration energy of the ultrasonic wave is maximized as shown in FIG. Then, by controlling the frequency of the pulse signal supplied by the control unit 105 to be equal to the resonance frequency, the signal intensity received and output by the ultrasonic receivers 103a to 103c is maximized. When the frequency of the pulse signal supplied from the control unit 105 to the driving units 104a to 104c deviates from the resonance frequency, the conversion efficiency between the electric energy and the vibration energy of the ultrasonic wave is lowered. Therefore, the control unit 105 controls the frequency of the pulse signal supplied to the drive units 104a to 104c, so that the amplitude (signal intensity) of the ultrasonic reception signal received and output by the ultrasonic receivers 103a, 103b, and 103c is increased. Control to make it smaller is possible. Also, it is possible to control to increase the amplitude of the ultrasonic reception signal by bringing the frequency of the pulse signal deviating from the resonance frequency closer to the resonance frequency.

  In order to suppress the mutual interference of the ultrasonic waves, the drive units 104b and 104c are configured such that the oscillation frequency of the ultrasonic transmission signal at the position without the sheet (positions b and c in the illustrated example) is shifted from the resonance frequency of 300 kHz to 500 kHz. The frequency of the pulse signal supplied to the is controlled. Thereby, the transmission efficiency of the ultrasonic waves transmitted from the ultrasonic transmitters 102b and 102c is lowered. At the same time, the reception efficiency of the ultrasonic receiver with respect to 500 kHz ultrasonic waves also decreases, and the total ultrasonic transmission / reception efficiency decreases at each of the positions b and c.

  Naturally, the ultrasonic waves from the ultrasonic transmitters 102b and 102c received by the ultrasonic receiver 103a at the position a are also reduced from the ultrasonic transmitters at other positions in the position a where the sheet is present because the reception efficiency decreases. It is possible to suppress mutual interference of ultrasonic waves. Note that the ultrasonic transmission frequency may be shifted from the resonance frequency either in the direction of increasing the frequency or in the direction of decreasing the frequency. Further, even if the intensity of the ultrasonic wave transmitted from the ultrasonic transmitter 102a is strong, it is sufficiently attenuated when passing through the sheet, so that the ultrasonic receivers 103b and 103c receive the ultrasonic wave transmitted from the ultrasonic transmitter 102a. Mutual interference will not occur.

  A method of suppressing the mutual interference of ultrasonic waves in the second embodiment will be described with reference to FIG. Only the processing different from the first embodiment will be described.

  In step S604, the control unit 105 changes the setting so as to increase the ultrasonic wave at the position a. In the second embodiment, when the setting is changed so as to increase the ultrasonic wave at the position a, the frequency of the ultrasonic wave transmitted from the ultrasonic transmitter 102a is set as shown in FIG. Resonance frequency with highest efficiency or close to resonance frequency. In step S605, the control unit 105 changes the setting so as to weaken the ultrasonic wave at the position a. In the second embodiment, when the setting is changed so as to weaken the ultrasonic wave at the position a, the frequency of the ultrasonic wave transmitted from the ultrasonic transmitter 102a is set to a frequency shifted from the resonance frequency, or the present Away from the resonant frequency.

  In steps S607 and S610, as in step S604, the frequency of the ultrasonic wave transmitted from the ultrasonic transmitter 102a is set to the resonance frequency or close to the resonance frequency. In steps S608 and S611, as in step S605, the frequency of the ultrasonic wave transmitted from the ultrasonic transmitter 102a is set to a frequency that deviates from the resonance frequency or is further away from the resonance frequency than at present.

  According to the second embodiment, when a sheet on the conveyance path is detected by one of a plurality of ultrasonic transmitters and an ultrasonic receiver disposed at a position facing the ultrasonic transmitter, The frequency of the ultrasonic wave transmitted from the ultrasonic transmitter is controlled so as to approach the resonance frequency. On the other hand, when the sheet is not detected, control is performed to keep away from the resonance frequency. In addition, when the sheet is detected by the ultrasonic transmitter and the ultrasonic receiver, the frequency of the ultrasonic wave transmitted from the other ultrasonic transmitters among the plurality of ultrasonic transmitters is kept away from the resonance frequency. You may control to.

  By performing the control described above, it is possible to suppress the mutual interference of ultrasonic waves in a plurality of ultrasonic sensors arranged on the conveyance path, reduce erroneous detection of double feeding of sheets, and appropriately detect the presence or absence of sheets. Can be done.

  Note that by adding a band-pass filter circuit that cuts off frequencies away from 300 kHz between the ultrasonic receivers 103a, 103b, and 103c and the signal amplifier 106, it is possible to further increase or decrease the frequency effect.

[Third Embodiment]
The multifeed detection device according to the third embodiment of the present invention has the same configuration (FIGS. 1 and 2) as that of the multifeed detection device 1000 according to the first embodiment. About the part similar to the form of, the description is abbreviate | omitted using the same code | symbol. Only differences from the first embodiment will be described below.

  In the third embodiment, the setting is changed so that the ultrasonic wave at the position determined as having no sheet is weakened by narrowing the pulse width of the pulse signal supplied from the control unit to the driving unit. Also, the setting is changed so as to increase the intensity of the ultrasonic wave at the position where it is determined that there is a sheet.

  FIG. 5 is a diagram showing the waveform of a pulse signal supplied from the control unit to the drive unit, where (a) is a pulse width of a normal pulse signal, and (b) is transmitted at a position where it is determined that there is no sheet. The pulse width of the pulse signal when the intensity of the ultrasonic wave is weakened is shown.

  The intensity of the ultrasonic reception signals received and output by the ultrasonic receivers 103a to 103c can also be reduced by controlling the pulse width per cycle of the pulse signals supplied from the control unit 105 to the driving units 104a to 104c. It is possible.

  The method for controlling the pulse width of the pulse signal supplied to the drive unit is to change the H time or L time of the pulse signal while fixing the time T of one cycle. For example, as shown in FIGS. 5A and 5B, the normal pulse signal is (H time) / (1 period time) = 1/2, and it is determined that there is no sheet. The pulse signal at this time is controlled so that (time of H) / (time of one cycle) = 1/4. Although the case where the pulse width is halved has been described, the present invention is not limited to this. On the other hand, when it is determined that there is a sheet, the control opposite to the above is performed to increase the intensity of the ultrasonic reception signal.

  A method for suppressing mutual interference of ultrasonic waves in the third embodiment will be described with reference to FIG. Only the processing different from the first embodiment will be described.

  In step S604, the control unit 105 changes the setting so as to increase the ultrasonic wave at the position a. In the third embodiment, when the setting is changed to increase the ultrasonic wave at the position a, the pulse width of the pulse signal supplied from the control unit 105 to the drive unit 104a is as shown in FIG. If it is not the normal pulse width, it is returned to it or made wider than it is now. In step S605, the control unit 105 changes the setting so as to weaken the ultrasonic wave at the position a. In the third embodiment, when the setting is changed so as to weaken the ultrasonic wave at the position a, the pulse width of the pulse signal supplied from the control unit 105 to the drive unit 104a is as shown in FIG. In addition, the pulse width is made narrower than the normal pulse width or decreased from the present time.

  In steps S607 and S610, similarly to step S604, the pulse width of the pulse signal supplied from the control unit 105 to the drive units 104b and 104c is returned to the normal pulse width or made wider than the current pulse width. On the other hand, in steps S608 and S611, as in step S605, the pulse width of the pulse signal supplied from the control unit 105 to the driving units 104b and 104c is narrower than the normal pulse width or smaller than the current pulse width.

  According to this embodiment, when a sheet on the conveyance path is detected by one of a plurality of ultrasonic transmitters and an ultrasonic receiver disposed at a position facing the ultrasonic transmitter, the ultrasonic wave is detected. Control is performed to widen the pulse width of the pulse signal supplied to the drive unit for driving the transmitter. On the other hand, when no sheet is detected, control is performed to reduce the sheet. In addition, when a sheet is detected by the ultrasonic transmitter and the ultrasonic receiver, a pulse is supplied to another drive unit for driving another ultrasonic transmitter among the plurality of ultrasonic transmitters. You may control so that the pulse width of a signal may be narrowed.

  By performing the control described above, it is possible to suppress the mutual interference of ultrasonic waves in a plurality of ultrasonic sensors arranged on the conveyance path, reduce erroneous detection of double feeding of sheets, and appropriately detect the presence or absence of sheets. Can be done.

[Fourth Embodiment]
The multifeed detection device according to the fourth embodiment of the present invention has the same configuration (FIGS. 1 and 2) as that of the multifeed detection device 1000 according to the first embodiment. About the part similar to the form of, the description is abbreviate | omitted using the same code | symbol. Only differences from the first embodiment will be described below.

  In the fourth embodiment, the setting is changed so that the ultrasonic wave at the position determined as having no sheet is weakened by reducing the amplitude of the ultrasonic wave transmission pulse supplied from the drive unit to the ultrasonic wave transmitter. To do. Also, the setting is changed so as to increase the ultrasonic wave at the position where it is determined that there is a sheet.

  FIG. 6 is a diagram showing the waveform of an ultrasonic wave transmission pulse supplied from the drive unit to the ultrasonic wave transmitter, where (a) shows the amplitude of a normal ultrasonic wave transmission pulse, and (b) shows that there is no sheet. The amplitude of the ultrasonic transmission pulse when the ultrasonic wave transmitted at the position is weakened is shown.

  By controlling the drive amplitude of the ultrasonic transmission pulses supplied from the drive units 104a to 104c to the ultrasonic transmitters 102a to 102c, the transmission intensity of the ultrasonic waves can be adjusted, and the ultrasonic receivers 103a to 103c receive the signals. It is possible to reduce the output signal intensity.

  As shown in FIG. 6 (a), the drive amplitude is controlled by driving the ultrasonic transmitter at 24V when it is determined that there is no sheet. It controls to weaken the output of the ultrasonic wave itself. For example, a method of switching and using power sources having different voltages is possible. Although the case where the amplitude of the ultrasonic transmission pulse is changed from 24 V to 5 V has been described, the present invention is not limited to this.

  A method for suppressing mutual interference of ultrasonic waves in the fourth embodiment will be described with reference to FIG. Only the processing different from the first embodiment will be described.

  In step S604, the control unit 105 changes the setting so as to increase the ultrasonic wave at the position a. In the fourth embodiment, when the setting is changed to increase the ultrasonic wave at the position a, the amplitude of the ultrasonic wave transmission pulse supplied from the drive unit 104a to the ultrasonic wave transmitter 102a is shown in FIG. As shown in FIG. 5, the normal amplitude is set or the amplitude is increased from the current level. In step S605, the control unit 105 changes the setting so as to weaken the ultrasonic wave at the position a. In the third embodiment, when the setting is changed to weaken the ultrasonic wave at the position a, the amplitude of the ultrasonic wave transmission pulse supplied to the ultrasonic wave transmitter 102a is as shown in FIG. , Make the amplitude smaller than the normal amplitude or decrease the amplitude smaller than the present.

  In steps S607 and S610, similarly to step S604, the amplitudes of the ultrasonic transmission pulses supplied from the driving units 104b and 104c to the ultrasonic transmitters 102b and 102c are set to normal amplitudes, or the amplitudes are increased from the current levels. . On the other hand, in steps S608 and S611, similarly to step S605, the amplitude of the ultrasonic transmission pulse supplied from the driving units 104b and 104c to the ultrasonic transmitters 102b and 102c is made smaller than the normal amplitude or smaller than the current amplitude. Decrease the amplitude.

  According to the fourth embodiment, when the sheet of the conveyance path is detected by one of the plurality of ultrasonic transmitters and the ultrasonic receiver disposed at a position facing the ultrasonic transmitter, Control is performed so as to increase the amplitude of the ultrasonic transmission pulse supplied to the ultrasonic transmitter. On the other hand, when no sheet is detected, control is performed to reduce the sheet. When the sheet is detected by the ultrasonic transmitter and the ultrasonic receiver, the amplitude of the ultrasonic transmission pulse supplied to the other ultrasonic transmitters among the plurality of ultrasonic transmitters is reduced. You may control to.

  By performing the control described above, it is possible to suppress the mutual interference of ultrasonic waves in a plurality of ultrasonic sensors arranged on the conveyance path, reduce erroneous detection of double feeding of sheets, and appropriately detect the presence or absence of sheets. Can be done.

  The control unit 105 combines at least two of the number of pulses of the burst wave, the oscillation frequency of the ultrasonic wave, the pulse width of the pulse signal applied to the driving unit, and the amplitude of the ultrasonic transmission pulse described in each of the above embodiments. And may be controlled. By controlling two or more of the four methods at the same time, it is possible to more effectively control the amplitude of the ultrasonic reception signal and suppress the mutual interference of the ultrasonic waves.

  Although the pulse signal supplied by the control unit 105 is a burst wave, it is not limited to a burst wave. Even in a configuration in which an ultrasonic wave transmission pulse is always added to an ultrasonic wave transmitter to continuously transmit an ultrasonic wave, mutual control of the ultrasonic wave is achieved by controlling the ultrasonic wave transmission frequency, the ultrasonic pulse width, and the ultrasonic drive amplitude. Interference can be suppressed.

  In the first to fourth embodiments, the multifeed detection device including three ultrasonic sensors has been described. However, the number of ultrasonic sensors is not limited to this.

  The object of the present invention can also be achieved by executing the following processing. That is, a storage medium that records a program code of software that realizes the functions of the above-described embodiments is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus is stored in the storage medium. This is the process of reading the code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Moreover, the following can be used as a storage medium for supplying the program code. For example, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM or the like. Alternatively, the program code may be downloaded via a network.

  Further, the present invention includes a case where the function of the above-described embodiment is realized by executing the program code read by the computer. In addition, an OS (operating system) running on the computer performs part or all of the actual processing based on an instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, a case where the functions of the above-described embodiment are realized by the following processing is also included in the present invention. That is, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

It is a figure which shows the structure of the main function parts of the double feed detection apparatus which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the suppression method of the mutual interference of the ultrasonic wave of the ultrasonic transmitter of FIG. 1, and an ultrasonic receiver. It is a flowchart which shows an example of the control processing for performing the suppression method of the mutual interference of the ultrasonic wave in a double feed detection apparatus. It is a figure which shows an ultrasonic transmission frequency and ultrasonic transmission / reception efficiency when the ultrasonic transmission-reception efficiency is 100% at a resonance frequency of 300 kHz. It is a figure which shows the waveform of the pulse signal supplied to a drive part from a control part, (a) is the pulse width of a normal pulse signal, (b) is the intensity | strength of the ultrasonic wave transmitted at the position determined to be no sheet | seat. The pulse width of the pulse signal when weakening is shown. It is a figure which shows the waveform of the ultrasonic transmission pulse supplied to an ultrasonic transmitter from a drive part, (a) is an amplitude of a normal ultrasonic transmission pulse, (b) is transmitted in the position determined to have no sheet | seat. The amplitude of the ultrasonic transmission pulse when weakening the ultrasonic wave is shown. It is a figure which shows an example of the conventional double feed detection apparatus using an ultrasonic sensor.

Explanation of symbols

102a, 102b, 102c Ultrasonic transmitters 103a, 103b, 103c Ultrasonic receivers 104a, 104b, 104c Driving unit 105 Control unit 106 Signal amplifier 107 AD converter 108 CPU
109 storage

Claims (7)

Ultrasonic transmission means disposed at a plurality of locations on a conveyance path through which the sheet is conveyed, ultrasonic reception means disposed at positions facing each of the ultrasonic transmission means across the conveyance path, and the ultrasonic wave The ultrasonic wave transmitted by the sound wave transmitting unit and transmitted through the sheet is received by each of the ultrasonic wave receiving units facing the ultrasonic wave transmitting unit, and the ultrasonic reception signal output and analyzed, thereby detecting the double feed. In a double feed detection device having a feed detection means and capable of detecting multiple feeds at a plurality of locations on the transport path,
When a sheet on the conveyance path is detected by an arbitrary ultrasonic transmission unit of the plurality of ultrasonic transmission units and an ultrasonic reception unit disposed at a position facing the ultrasonic transmission unit, the ultrasonic wave It is characterized by comprising control means for controlling the characteristics of the ultrasonic wave transmitted from the transmitting means and increasing the intensity of the ultrasonic reception signal output by the ultrasonic receiving means arranged at a position facing the ultrasonic transmitting means. Double feed detection device.   The control means detects a sheet on the conveyance path by an arbitrary ultrasonic transmission means of the plurality of ultrasonic transmission means and an ultrasonic reception means arranged at a position facing the ultrasonic transmission means. When there is not, control the characteristic of the ultrasonic wave transmitted from the ultrasonic transmission unit, and weaken the intensity of the ultrasonic reception signal output by the ultrasonic reception unit arranged at a position facing the ultrasonic transmission unit The multifeed detection device according to claim 1.   The multifeed detection device according to claim 1, wherein the control unit performs control so as to change a number of ultrasonic transmission pulses supplied to the ultrasonic transmission unit.   The multifeed detection apparatus according to claim 1, wherein the control unit performs control so as to change a frequency of an ultrasonic wave transmitted from the ultrasonic wave transmission unit.   The multifeed detection device according to claim 1 or 2, wherein the control means performs control so as to change a pulse width of a pulse signal supplied to a driving means for driving the ultrasonic wave transmission means.   The multifeed detection device according to claim 1, wherein the control unit performs control so as to change an amplitude of an ultrasonic transmission pulse supplied to the ultrasonic transmission unit. Ultrasonic transmission means disposed at a plurality of locations on a conveyance path through which the sheet is conveyed, ultrasonic reception means disposed at positions facing each of the ultrasonic transmission means across the conveyance path, and the ultrasonic wave The ultrasonic wave transmitted by the sound wave transmitting unit and transmitted through the sheet is received by each of the ultrasonic wave receiving units facing the ultrasonic wave transmitting unit, and the ultrasonic reception signal output and analyzed, thereby detecting the double feed. In the double feed detection method of the double feed detection device having a feed detection means and capable of detecting multiple feeds at a plurality of locations on the transport path,
When a sheet on the conveyance path is detected by an arbitrary ultrasonic transmission unit of the plurality of ultrasonic transmission units and an ultrasonic reception unit disposed at a position facing the ultrasonic transmission unit, the ultrasonic wave Double feed detection characterized by controlling the characteristics of the ultrasonic wave transmitted from the transmitting means and increasing the intensity of the ultrasonic reception signal output by the ultrasonic receiving means arranged at a position facing the ultrasonic transmitting means Method.

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