JP6934820B2 - Double feed detection device, double feed detection method and control program - Google Patents

Description

The present invention relates to a double feed detection device, a double feed detection method and a control program, and more particularly to a double feed detection device, a double feed detection method and a control program for detecting double feed using an ultrasonic oscillator and an ultrasonic receiver.

A device such as a scanner that conveys a document and reads an image of the conveyed document has a function of detecting whether or not a double feed in which a plurality of documents are overlapped and conveyed has occurred. Generally, a double feed detection device such as a scanner includes an ultrasonic oscillator that outputs ultrasonic waves and an ultrasonic receiver that outputs a signal corresponding to the received ultrasonic waves, and is an ultrasonic receiver when a document is conveyed. Detects double feed based on the signal output by.

A recording material discriminating device having a means for transmitting ultrasonic waves and a means for receiving ultrasonic waves is disclosed (see Patent Document 1). This recording material discriminating device transmits ultrasonic waves a plurality of times from the transmitting means, and each time from the transmission of the drive signal to the transmitting means to the detection of the peak of the ultrasonic wave reception signal received by the receiving means. Based on the difference between the above, it is determined whether or not the recording material is double-fed.

Japanese Unexamined Patent Publication No. 2013-40000

The double feed detection device is desired to detect double feed with higher accuracy.

An object of the present invention is to provide a double feed detection device, a double feed detection method, and a control program capable of detecting double feed with higher accuracy.

The double feed detection device according to one aspect of the present invention is an ultrasonic oscillator that outputs ultrasonic waves and an ultrasonic receiver that is arranged to face the ultrasonic oscillator and outputs an ultrasonic signal corresponding to the received ultrasonic waves. A detection unit that detects the propagation time of ultrasonic waves from the ultrasonic oscillator to the ultrasonic receiver, and a double feed determination unit that determines whether or not double feed has occurred based on the ultrasonic signal and the propagation time. When the signal value of the ultrasonic signal is larger than the first threshold value, the double feed determination unit determines that double feed has not occurred, and the signal value of the ultrasonic signal is smaller than the first threshold value. If it is less than or equal to the threshold value, it is determined that double feeding has occurred, and if the signal value of the ultrasonic signal is less than or equal to the first threshold value and larger than the second threshold value, or if the propagation time is less than or equal to the third threshold value, double feeding Is not generated, and when the propagation time is larger than the third threshold value, it is determined that double feeding has occurred.

The double feed detection method according to one aspect of the present invention includes an ultrasonic oscillator that outputs ultrasonic waves and an ultrasonic receiver that is arranged to face the ultrasonic oscillator and outputs an ultrasonic signal corresponding to the received ultrasonic waves. It is a double feed detection method in a double feed detection device having Including determining whether or not the ultrasonic signal has been performed, if the signal value of the ultrasonic signal is larger than the first threshold value, it is determined that double feeding has not occurred, and the signal value of the ultrasonic signal is higher than the first threshold value. If it is less than or equal to the second threshold, it is determined that double feeding has occurred, and if the signal value of the ultrasonic signal is less than or equal to the first threshold and greater than the second threshold, or if the propagation time is less than or equal to the third threshold. , It is determined that the double feed has not occurred, and when the propagation time is larger than the third threshold value, it is determined that the double feed has occurred.

The control program according to one aspect of the present invention includes an ultrasonic oscillator that outputs ultrasonic waves, an ultrasonic receiver that is arranged to face the ultrasonic oscillator and outputs an ultrasonic signal corresponding to the received ultrasonic waves. It is a control program to be executed by a double feed detection device having The double feed detection device is made to determine whether or not, and when the signal value of the ultrasonic signal is larger than the first threshold value, it is determined that the double feed has not occurred, and the signal value of the ultrasonic signal is If it is less than or equal to the second threshold value that is smaller than the first threshold value, it is determined that double feeding has occurred, and if the signal value of the ultrasonic signal is less than or equal to the first threshold value and greater than or equal to the second threshold value, the propagation time is equal to or less than the third threshold value. When is, it is determined that the double feed has not occurred, and when the propagation time is larger than the third threshold value, it is determined that the double feed has occurred.

According to the present invention, the double feed detection device can detect double feed with higher accuracy.

It is a perspective view which shows the double feed detection apparatus 100 which concerns on embodiment. It is a figure for demonstrating the transport path in the double feed detection apparatus 100. It is a block diagram which shows the schematic structure of the double feed detection apparatus 100. It is a figure which shows an example of the circuit diagram of the peak detection circuit 133. It is a graph which shows the example of each signal generated by ultrasonic waves. It is a figure which shows the schematic structure of the storage device 150 and the CPU 160. It is a flowchart which shows the example of the operation of the document reading process. It is a flowchart which shows the example of the operation of the double feed determination process. It is a figure for demonstrating the characteristic of an ultrasonic signal. It is a figure for demonstrating the characteristic of the propagation time of an ultrasonic wave. It is a graph which shows the relationship between the temperature and altitude, and the signal value of an ultrasonic signal. It is a graph which shows the relationship between the humidity and altitude, and the signal value of an ultrasonic signal. It is a graph which shows the relationship between the temperature and the propagation time of an ultrasonic wave. It is a graph which shows the relationship between the humidity and the propagation time of an ultrasonic wave. It is a graph which shows the relationship between the altitude and the propagation time of an ultrasonic wave. It is a figure which shows the schematic structure of another processing circuit 270.

Hereinafter, the double feed detection device according to one aspect of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to those embodiments, but extends to the inventions described in the claims and their equivalents.

FIG. 1 is a perspective view showing a double feed detection device 100 configured as an image scanner. In the following, the case where the double feed detection device 100 is a document transport device for transporting a document such as paper or a plastic card will be described as an example, but the double feed detection device 100 is a medium such as paper or a plastic card. Any device may be used as long as it is a device for transporting. For example, the double feed detection device 100 may be a facsimile, an inkjet printer, a laser printer, a multifunction printer (MFP, Multifunction Peripheral), or the like.

The double feed detection device 100 is a document transport device, and includes a lower housing 101, an upper housing 102, a document stand 103, an ejection stand 105, an operation button 106, and the like.

The upper housing 102 is arranged at a position covering the upper surface of the double feed detection device 100, and engages with the lower housing 101 by a hinge so that the upper housing 102 can be opened and closed when the document is clogged, when the inside of the double feed detection device 100 is cleaned, or the like. doing.

The platen 103 is engaged with the lower housing 101 so that the original can be placed on it. The platen 103 is provided with side guides 104a and 104b that can move in a direction orthogonal to the document transport direction. Hereinafter, the side guides 104a and 104b may be collectively referred to as side guides 104.

The ejection table 105 is engaged with the lower housing 101 by a hinge so as to be rotatable in the direction indicated by the arrow A1, and holds the ejected document in the open state as shown in FIG. Is possible.

The operation button 106 is arranged on the surface of the upper housing 102, and when pressed, generates and outputs an operation detection signal.

FIG. 2 is a diagram for explaining a transport path inside the double feed detection device 100.

The transport paths inside the double feed detection device 100 are the document detection sensor 111, the feed roller 112, the retard roller 113, the ultrasonic oscillator 115a, the ultrasonic receiver 115b, the first transport roller 116, the first driven roller 117, and the first. It has an image pickup device 119a, a second image pickup device 119b, a second transfer roller 120, a second driven roller 121, and the like. The number of each roller is not limited to one, and the number of each roller may be plural.

The upper surface of the lower housing 101 forms the lower guide 107a of the document transport path, and the lower surface of the upper housing 102 forms the upper guide 107b of the document transport path. In FIG. 2, the arrow A2 indicates the transport direction of the document. In the following, the upstream means the upstream of the document transport direction A2, and the downstream means the downstream of the document transport direction A2.

The document detection sensor 111 has a contact detection sensor arranged on the upstream side of the feeding roller 112 and the retard roller 113, and detects whether or not the document is placed on the document table 103. The document detection sensor 111 generates and outputs a document detection signal whose signal value changes depending on whether the document is placed on the document stand 103 or not.

The ultrasonic oscillator 115a and the ultrasonic receiver 115b are arranged in the vicinity of the document transport path so as to face each other with the transport path in between. The ultrasonic oscillator 115a outputs ultrasonic waves at predetermined intervals. On the other hand, the ultrasonic receiver 115b receives the ultrasonic waves oscillated by the ultrasonic oscillator 115a and passed through the document, and generates and outputs an ultrasonic signal which is an electric signal corresponding to the received ultrasonic waves. Hereinafter, the ultrasonic oscillator 115a and the ultrasonic receiver 115b may be collectively referred to as an ultrasonic sensor 115.

The first image pickup device 119a has a reduction optical system type image pickup sensor including an image pickup element by CCD (Charge Coupled Device) arranged linearly in the main scanning direction. This image sensor reads the back surface of the document, generates an analog image signal, and outputs it. Similarly, the second image pickup device 119b has a reduction optical system type image pickup sensor including a CCD image pickup element linearly arranged in the main scanning direction. This image sensor reads the surface of the document, generates an analog image signal, and outputs it. The first imaging device 119a and the second imaging device 119b may be arranged on one side so as to read only one side of the document. Further, instead of the CCD, a 1x optical system type CIS (Contact Image Sensor) provided with an image sensor using CMOS (Complementary Metal Oxide Semiconductor) can also be used. Hereinafter, the first imaging device 119a and the second imaging device 119b may be collectively referred to as an imaging device 119.

The document placed on the platen 103 is conveyed in the document transfer direction A2 between the lower guide 107a and the upper guide 107b by the feeding roller 112 rotating in the direction of the arrow A3 in FIG. .. The retard roller 113 rotates in the direction of arrow A4 in FIG. 2 when the document is conveyed. When a plurality of documents are placed on the platen 103 due to the functions of the feeding roller 112 and the retard roller 113, only the documents placed on the platen 103 that are in contact with the feeding roller 112 Is separated. As a result, it operates so as to limit the transport of documents other than the separated documents (prevention of double feeding). The feeding roller 112 and the retard roller 113 function as a document separating portion.

The document is fed between the first transport roller 116 and the first driven roller 117 while being guided by the lower guide 107a and the upper guide 107b. The document is fed between the first imaging device 119a and the second imaging device 119b by rotating the first conveying roller 116 in the direction of the arrow A5 in FIG. The document read by the image pickup apparatus 119 is ejected onto the ejection table 105 by the second transport roller 120 rotating in the direction of the arrow A6 in FIG.

FIG. 3 is a block diagram showing a schematic configuration of the double feed detection device 100.

In addition to the above-described configuration, the double feed detection device 100 includes a first image A / D converter 130a, a second image A / D converter 130b, an absolute value signal generation circuit 131, and an ultrasonic A / D converter 132. It further includes a peak detection circuit 133, a drive device 134, an interface device 135, a temperature sensor 136, a humidity sensor 137, a pressure sensor 138, a storage device 150, a CPU (Central Processing Unit) 160, a processing circuit 170, and the like.

The first image A / D converter 130a converts the analog image signal output from the first image pickup apparatus 119a into analog-digital to generate digital image data, and outputs the digital image data to the CPU 160. Similarly, the second image A / D converter 130b analog-digitally converts the analog image signal output from the second image pickup apparatus 119b to generate digital image data, and outputs the digital image data to the CPU 160 and the processing circuit 170. Hereinafter, these digital image data will be referred to as a scanned image. Further, in the following, the first image A / D converter 130a and the second image A / D converter 130b may be collectively referred to as an image A / D converter 130.

The absolute value signal generation circuit 131 generates an absolute value signal obtained by taking the absolute value of the analog ultrasonic signal output from the ultrasonic sensor 115, and outputs the absolute value signal to the ultrasonic A / D converter 132 and the peak detection circuit 133. ..

The ultrasonic A / D converter 132 analog-digitally converts the absolute value signal output from the absolute value signal generation circuit 131 to generate a digital ultrasonic signal, and outputs the digital ultrasonic signal to the CPU 160.

The peak detection circuit 133 detects the peak of the absolute value signal output from the absolute value signal generation circuit 131, generates a peak detection signal indicating the time when the peak occurs, and outputs the peak detection signal to the CPU 160.

The drive device 134 includes one or a plurality of motors, and rotates the feed roller 112, the retard roller 113, the first transfer roller 116, and the second transfer roller 120 by a control signal from the CPU 160 to perform a document transfer operation. conduct.

The interface device 135 has an interface circuit similar to a serial bus such as USB, and is electrically connected to an information processing device (for example, a personal computer, a personal digital assistant, etc.) (not shown) to read images and various information. Send and receive. Further, instead of the interface device 135, a communication unit having an antenna for transmitting and receiving wireless signals and a wireless communication interface device for transmitting and receiving signals through a wireless communication line according to a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network).

The temperature sensor 136 detects the temperature (air temperature) in the double feed detection device 100, and outputs temperature information indicating the detected temperature to the CPU 160.

The humidity sensor 137 detects the humidity in the double feed detection device 100, and outputs humidity information indicating the detected humidity to the CPU 160.

The atmospheric pressure sensor 138 detects the atmospheric pressure in the double feed detection device 100, and outputs the atmospheric pressure information indicating the detected atmospheric pressure to the CPU 160.

The storage device 150 includes a memory device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk and an optical disk. Further, the storage device 150 stores computer programs, databases, tables, etc. used for various processes of the double feed detection device 100. The computer program may be installed in the storage device 150 from a computer-readable portable recording medium using a known setup program or the like. The portable recording medium is, for example, a CD-ROM (compact disk read only memory), a DVD-ROM (digital versatile disk read only memory), or the like. Further, the storage device 150 stores the scanned image.

The CPU 160 operates based on a program stored in the storage device 150 in advance. Instead of the CPU 160, a DSP (digital signal processor), an LSI (large scale integration), or the like may be used. Further, instead of the CPU 160, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programming Gate Array) or the like may be used.

The CPU 160 includes an operation button 106, a document detection sensor 111, a first image pickup device 119a, a second image pickup device 119b, a first image A / D converter 130a, a second image A / D converter 130b, and an ultrasonic A / D conversion. It is connected to a device 132, a peak detection circuit 133, a drive device 134, an interface device 135, a temperature sensor 136, a humidity sensor 137, a pressure sensor 138, a storage device 150, a processing circuit 170, and the like, and controls each of these parts. The CPU 160 performs drive control of the drive device 134, document reading control of the image pickup device 119, and the like, and acquires a scanned image. Further, the CPU 160 performs double feed detection processing and the like based on each signal output from the peak detection circuit 133 and the ultrasonic A / D converter 132.

The processing circuit 170 executes a predetermined image processing on the scanned image output from the scanned image, and stores the scanned image in which the image processing is executed in the storage device 150. A DSP, LSI, ASIC, FPGA, or the like may be used instead of the processing circuit 170.

FIG. 4 shows an example of a circuit diagram of the peak detection circuit 133.

As shown in FIG. 4, the peak detection circuit 133 includes operational amplifiers 142, 147, diodes 143, resistors 144, 146, 148, capacitors 145, and the like. The input terminal 141 is connected to the absolute value signal generation circuit 131, and the output terminal 149 is connected to the CPU 160.

The non-inverting input terminal of the operational amplifier 142 is connected to the input terminal 141, its output terminal is connected to the anode of the diode 143, and its inverting input terminal is connected to the cathode of the diode 143. The cathode of the diode 143 is further connected to one end of the capacitor 145 via a resistor 144. The other end of the capacitor 145 is connected to ground. The cathode of the diode 143 is further connected to ground via a resistor 146. Further, the cathode of the diode 143 is further connected to the non-inverting input terminal of the operational amplifier 147. The inverting input terminal of the operational amplifier 147 is connected to the input terminal 141, the output terminal is connected to the output terminal 149, and is connected to the non-inverting input terminal via a resistor 148.

The diode 143 blocks the flow of current to the output terminal side of the operational amplifier 142. The operational amplifier 142 controls the output voltage so that the potential difference between the non-inverting input terminal and the inverting input terminal becomes 0V, and as a result, raises the voltage dropped due to the forward voltage drop of the diode 143. The capacitor 145 is charged by the input voltage from the input terminal 141, and is discharged according to a constant time constant (= (capacitor value C of the capacitor 145) / (resistance value R1 of the resistor 144 + resistance value R2 of the resistor 146)). The capacitance value C of the capacitor 145 and the resistance value R1 of the resistor 144 are set so as to substantially satisfy the following equations.
f = 1 / (2π ・ R1 ・ C)
Here, f is the (rising) fundamental frequency of the input voltage from the input terminal 141.

The operational amplifier 147 operates as a comparator, and changes the output voltage at the timing when the input voltage from the input terminal 141 becomes smaller than the voltage charged in the capacitor 145. Further, in the peak detection circuit 133, the output voltage of the operational amplifier 147 is positively fed back via the resistor 148. This improves the noise immunity of the peak detection circuit 133, and suppresses erroneous detection of the peak of the input voltage, especially when the SN ratio (signal-to-noise ratio) of the input voltage from the input terminal 141 is small. Will be done.

FIG. 5 is a graph showing an example of each signal (voltage) generated by the double feed detection device 100. The horizontal axis of each graph shown in FIG. 5 indicates time, and the vertical axis indicates signal value.

Graph 500 shown in FIG. 5 shows an example of a drive signal 501 input to the ultrasonic oscillator 115a in order to output ultrasonic waves to the ultrasonic oscillator 115a. As shown in FIG. 5, the drive signal 501 has a signal value of a predetermined number of times (1) at regular intervals between a value that causes the ultrasonic oscillator 115a to output ultrasonic waves and a value that does not cause the ultrasonic oscillator 115a to output ultrasonic waves. In the example shown in FIG. 5, it is a clock signal that changes four times).

Graph 510 shows an example of an absolute value signal 511 in which the absolute value of the ultrasonic signal generated with respect to the ultrasonic wave output according to the drive signal 501 is taken. The absolute value signal 511 is measured at point A in FIG. As shown in FIG. 5, since the ultrasonic waves transmitted by the ultrasonic oscillator 115a reach the ultrasonic receiver 115b after passing through the document, they are propagated to the ultrasonic receiver 115b after the propagation time T1 has elapsed. NS. The ultrasonic receiver 115b accumulates and detects the ultrasonic waves output by the ultrasonic oscillator 115a for each cycle of the drive signal 501. Therefore, the signal value of the absolute value signal 511 gradually increases from the timing P1 at which the ultrasonic wave corresponding to the first cycle of the drive signal 501 is received, and the ultrasonic wave corresponding to the last cycle of the drive signal 501 is received. It gradually decreases from the timing P2.

Graph 520 shows an example of a signal 521 appearing at the output terminal of the operational amplifier 142 of FIG. 4 and a passing signal 522 passing through the diode 143 when the absolute value signal 511 is input to the input terminal 141. As shown in FIG. 5, since the output signal 521 is controlled so that the potential difference between the inverting input terminal signal 522 of the operational amplifier 142 and the non-inverting input terminal signal 511 is 0V, the signal value of the output signal 521 is absolute. The potential is slightly higher than the signal value of the value signal 511 due to the forward voltage drop of the diode 143.

Graph 530 shows an example of the peak hold signal 531 measured at the point C in FIG. 4 when the absolute value signal 511 is input to the input terminal 141. As shown in FIG. 5, even after the signal value of the passing signal 522 starts to decrease at the timing P2, the peak value (maximum value) of the peak hold signal 531 is held and gradually decreases according to a constant time constant.

Graph 540 shows an example of a peak detection signal 541 output from the output terminal 149 when the absolute value signal 511 is input to the input terminal 141. The peak detection signal 541 is measured at point D in FIG. As shown in FIG. 5, the signal value of the peak detection signal 541 remains an undetected value indicating that the peak has not been detected until the timing P2, and becomes a detection value indicating that the peak has been detected at the timing P2. Change.

In this way, the peak detection circuit 133 detects the timing at which the absolute value of the signal value of the ultrasonic signal output by the ultrasonic receiver 115b first becomes the peak value.

FIG. 6 is a diagram showing a schematic configuration of a storage device 150 and a CPU 160.

As shown in FIG. 6, each program such as the control program 151, the image generation program 152, the double feed determination program 153, and the detection program 154 is stored in the storage device 150. Each of these programs is a functional module implemented by software running on the processor. The CPU 160 reads each program stored in the storage device 150 and operates according to each read program, thereby functioning as a control unit 161, an image generation unit 162, a double feed determination unit 163, and a detection unit 164.

FIG. 7 is a flowchart showing an example of the operation of the document scanning process of the double feed detection device 100.

Hereinafter, an example of the operation of the document reading process of the double feed detection device 100 will be described with reference to the flowchart shown in FIG. 7. The operation flow described below is mainly executed by the CPU 160 in cooperation with each element of the double feed detection device 100 based on the program stored in the storage device 150 in advance. The operation flow shown in FIG. 7 is executed periodically.

First, the control unit 161 waits until the operation button 106 for instructing the reading of the document is pressed by the user and the operation detection signal instructing the reading of the document is received from the operation button 106 (step S101). ).

Next, the control unit 161 determines whether or not a document is placed on the document table 103 based on the document detection signal received from the document detection sensor 111 (step S102).

If no document is placed on the platen 103, the control unit 161 returns the process to step S101 and waits until a new operation detection signal is received from the operation button 106.

On the other hand, when the document is placed on the platen 103, the control unit 161 drives the drive device 134 to rotate the feed roller 112, the retard roller 113, the first transfer roller 116, and the second transfer roller 120. The document is conveyed (step S103).

Next, the image generation unit 162 causes the image pickup apparatus 119 to read the conveyed document, and acquires the scanned image via the image A / D converter 130 (step S104).

Next, the image generation unit 162 transmits the read image to an information processing device (not shown) via the interface device 135 (step S105). When not connected to the information processing device, the image generation unit 162 stores the read image in the storage device 150.

Next, the control unit 161 determines whether or not a document remains on the platen 103 based on the document detection signal received from the document detection sensor 111 (step S106).

When a document remains on the platen 103, the control unit 161 returns the process to step S103 and repeats the processes of steps S103 to S106. On the other hand, when no document remains on the platen 103, the control unit 161 ends a series of steps.

FIG. 8 is a flowchart showing an example of the operation of the double feed determination process.

Hereinafter, an example of the operation of the double feed determination process of the double feed detection device 100 will be described with reference to the flowchart shown in FIG. The operation flow described below is mainly executed by the CPU 160 in cooperation with each element of the double feed detection device 100 based on the program stored in the storage device 150 in advance. The operation flow shown in FIG. 8 is executed when the document is conveyed. Further, while the operation flow shown in FIG. 8 is being executed, the control unit 161 inputs the drive signal 501 shown in FIG. 5 to the ultrasonic oscillator 115a at predetermined intervals, and superimposes the drive signal 501 on the ultrasonic oscillator 115a. Output sound waves.

First, the double feed determination unit 163 acquires a digital ultrasonic signal from the ultrasonic sensor 115 via the ultrasonic A / D converter 132 (step S201). The double feed determination unit 163 acquires each ultrasonic signal corresponding to each output ultrasonic wave at predetermined intervals.

Next, the double feed determination unit 163 calculates an average value (hereinafter, referred to as a signal average value) of the signal values of the digital ultrasonic signals acquired in a plurality of predetermined periods (step S202). The double feed determination unit 163 calculates the maximum value of the signal value of each digital ultrasonic signal acquired for each predetermined period, and calculates the average value of each calculated maximum value as the signal average value.

Next, the detection unit 164 detects the propagation time of the ultrasonic wave from the ultrasonic oscillator 115a to the ultrasonic receiver 115b (step S203). The detection unit 164 acquires the timing at which the control unit 161 stops the output of the drive signal 501 (the fall timing D in the last cycle of the drive signal 501 shown in FIG. 5) from the control unit 161 every predetermined period. .. Further, the detection unit 164 acquires the peak detection signal from the peak detection circuit 133 at predetermined intervals, and the timing at which the peak detection signal changes from the undetected value to the detected value (rising edge of the peak detection signal 541 shown in FIG. 5). Acquire timing P2). The detection unit 164 detects the time from the timing D to the timing P2 (time T2 shown in FIG. 5) as the propagation time of the ultrasonic wave. The detected propagation time indicates the time from when the ultrasonic oscillator 115a stops the output of ultrasonic waves to when the absolute value of the signal value of the ultrasonic signal output by the ultrasonic receiver 115b first reaches its peak value. ..

As shown in FIG. 5, the propagation time T2 is substantially the same as the propagation time T1. However, at the timing P1 when the ultrasonic receiver 115b starts receiving ultrasonic waves, the absolute value signal 511 gradually increases, so that the timing P1 when the ultrasonic receiver 115b starts receiving ultrasonic waves is accurately detected. It's difficult. Therefore, it is difficult for the detection unit 164 to accurately detect the end timing of the propagation time T1, and it is difficult for the detection unit 164 to accurately detect the propagation time T1. On the other hand, the absolute value signal 511 has a peak value at the timing P2 when the ultrasonic receiver 115b finishes receiving the ultrasonic waves. Since the peak of the absolute value signal 511 is accurately detected by the peak detection circuit 133, the detection unit 164 can accurately detect the end timing of the propagation time T2 and can accurately detect the propagation time T2. ..

Next, the detection unit 164 calculates the average value of the propagation time of the ultrasonic waves output in a plurality of predetermined periods (hereinafter, referred to as the average value of the propagation time) (step S204). The detection unit 164 calculates the average value of each propagation time detected for each predetermined period as the average value of the propagation time.

Next, the double feed determination unit 163 determines whether or not the calculated signal average value is larger than the first threshold value (step S205). The first threshold is, for example, a signal average value calculated when one sheet of PPC (Plain Paper Copier) paper is conveyed, and when two sheets of thin paper (for example, paper of 0.07 mm or less) are conveyed. It is preset to a value between the calculated signal averages.

When the calculated signal average value is larger than the first threshold value, the double feed determination unit 163 determines that no double feed has occurred (step S206), and returns the process to step S201.

On the other hand, when the calculated signal average value is equal to or less than the first threshold value, the double feed determination unit 163 determines whether or not the calculated signal average value is equal to or less than the second threshold value (step S207). The second threshold value is a value smaller than the first threshold value, and is, for example, a signal average value calculated when two sheets of thin paper are conveyed and a signal average value calculated when two sheets of PPC paper are conveyed. It is preset to a value between the values.

When the calculated signal average value is equal to or less than the second threshold value, the double feed determination unit 163 determines that double feed has occurred (step S208). In that case, the double feed determination unit 163 notifies the user that an abnormality has occurred by means of a speaker (not shown), an LED (Light Emitting Diode), or the like as an abnormality process, and returns the process to step S201. Further, the double feed determination unit 163 may stop the transport of the original as an abnormal process.

If the number of times the signal average value is continuously equal to or less than the second threshold value is less than the second predetermined number, the double feed determination unit 163 does not yet determine that double feed has occurred, and proceeds to step S209. You may migrate. In that case, the double feed determination unit 163 determines that the double feed has occurred only when the number of times that the signal average value is equal to or less than the second threshold value is continuously equal to or greater than the second predetermined number. The second predetermined number is preset to two or more values. As a result, the double feed determination unit 163 can prevent the double feed determination unit 163 from erroneously determining that the double feed has occurred even though the double feed has not occurred.

On the other hand, when the calculated signal average value is larger than the second threshold value, the double feed determination unit 163 determines whether or not the calculated propagation time average value is equal to or less than the third threshold value (step S209). The third threshold value is set in advance to, for example, a value between the average propagation time calculated when the PPC paper is conveyed and the average propagation time calculated when the plastic card is conveyed. The propagation time of the ultrasonic wave changes according to the environment (atmospheric pressure, air temperature, humidity, etc.) in which the double feed detection device 100 is installed. Therefore, the double feed determination unit 163 measures the propagation time of the ultrasonic waves when the double feed detection device 100 is started or at an arbitrary timing when the document reading process is not executed, in a state where the medium is not conveyed. The third threshold value may be set based on the measured propagation time. For example, the double feed determination unit 163 measures the propagation time a plurality of times, calculates the median value of each measured propagation time, and subtracts a predetermined value (for example, 2 μs) from the calculated median value as the third threshold value. Set. As a result, the double feed determination unit 163 can set an appropriate third threshold value according to the environment in which the double feed detection device 100 is installed.

The double feed determination unit 163 processes even when the signal average value is larger than the second threshold value when the number of times the signal average value is continuously equal to or less than the first threshold value is less than the first predetermined number. It may be determined that the double feed has not yet occurred without shifting to step S209. In that case, the double feed determination unit 163 shifts the process to step S209 only when the number of times the signal average value is equal to or less than the first threshold value is continuously equal to or greater than the first predetermined number. The first predetermined number is preset to a value that is two or more and is larger than the second predetermined number. As a result, the double feed determination unit 163 can prevent the double feed determination unit 163 from erroneously determining that the double feed has occurred even though the double feed has not occurred.

When the calculated propagation time average value is equal to or less than the third threshold value, the double feed determination unit 163 determines that the plastic card (resin card) is being conveyed (step S210). Since the separation error rate at the separation unit of the plastic card is very low and the possibility of double feeding is very low, in this case, the double feeding determination unit 163 determines that double feeding has not occurred (step S206). , The process returns to step S201.

On the other hand, when the calculated propagation time average value is larger than the third threshold value, the double feed determination unit 163 determines that the paper is being conveyed (step S211). In this case, the double feed determination unit 163 determines that double feed has occurred (step S208), executes an abnormality process, and returns the process to step S201.

In this way, the double feed determination unit 163 determines whether or not double feed has occurred based on the ultrasonic signal and the propagation time of the ultrasonic waves.

The double feed detection device 100 omits the process of step S202, and whether or not double feed has occurred based on the signal value of one ultrasonic signal, not the average value of the signal values of the plurality of ultrasonic signals. May be determined. Similarly, the double feed detection device 100 may omit the process of step S204 and determine whether or not double feed has occurred based on one propagation time instead of the average value of the plurality of propagation times. ..

Hereinafter, the technical significance of determining whether or not double feeding has occurred based on the ultrasonic signal and the propagation time of the ultrasonic wave will be described.

FIG. 9A is a diagram for explaining the characteristics of the ultrasonic signal.

The vertical axis of FIG. 9A shows the signal value of the ultrasonic signal. In FIG. 9A, the range 901 indicates the range in which the signal value can be taken when one sheet of thin paper is conveyed, and the range 902 indicates the range in which the signal value can be taken when two sheets of thin paper are conveyed. Further, the range 903 indicates a range in which a signal value can be obtained when one sheet of PPC paper is conveyed, and a range 904 indicates a range in which a signal value can be obtained when two sheets of PPC paper are conveyed. Further, the range 905 indicates a range in which a signal value can be taken when a plastic card is being conveyed.

As shown in FIG. 9A, when the signal value is larger than the first threshold value, the double feed determination unit 163 can determine that one sheet of thin paper or PPC paper is being conveyed, and the signal value is equal to or less than the second threshold value. If, it can be determined that two sheets of PPC paper are being conveyed. However, when the signal value is equal to or less than the first threshold value and larger than the second threshold value, the double feed determination unit 163 cannot accurately determine whether the medium being conveyed is two sheets of thin paper or a plastic card.

FIG. 9B is a diagram for explaining the characteristics of the propagation time of ultrasonic waves.

The vertical axis of FIG. 9B shows the propagation time of ultrasonic waves. In FIG. 9B, the range 911 indicates the range in which the propagation time can be taken when the paper is conveyed, and the range 912 indicates the range in which the propagation time can be taken when the plastic card is conveyed.

As shown in FIG. 9B, the double feed determination unit 163 can determine that the paper is being conveyed when the propagation time is greater than the third threshold value, and when the propagation time is equal to or less than the third threshold value, the plastic card. Can be determined to be transported.

ここで、ｃは音波の伝搬速度［ｍ／ｓ］であり、Ｅはヤング率（縦弾性係数）［Ｐａ］であり、ρは密度［ｋｇ／ｍ³］であり、νはポアソン比である。 The relationship between the characteristics of the medium and the propagation velocity of the sound wave when the sound wave is propagated through the medium is shown by the following equation.

Here, c is the sound wave propagation velocity [m / s], E is Young's modulus (longitudinal elastic modulus) [Pa], ρ is the density [kg / m ³ ], and ν is Poisson's ratio. ..

When the medium is paper, Young's modulus is 2.0 × 10 ⁹ [Pa], density is 1160 [kg / m ³ ], and Poisson's ratio is 0.30, so the sound wave propagation velocity is 1500. It becomes [m / s]. On the other hand, if the medium is a plastic card, the Young's modulus is 3.2 × 10 ⁹ [Pa], density of 1400 [kg / m ^3], because Poisson's ratio is 0.38, the propagation of sound waves The speed is 2100 [m / s]. The propagation velocity (sound velocity) of the sound wave when the medium does not exist (when the sound wave propagates in the air layer) is 332 [m / s].

For example, when an ultrasonic wave passes through a path of 1.4 [mm], there is a plastic card having a thickness of 1.4 [mm] in the path, and a thickness of 0.04 [mm], respectively. The difference in propagation time in the presence of two thin sheets of paper will be described. The propagation time of ultrasonic waves passing through a plastic card having a thickness of 1.4 [mm] is as follows.
1.4 [mm] / 2100 [m / s] = 0.7 [μs]
On the other hand, the propagation time of ultrasonic waves passing through two sheets of thin paper having a thickness of 0.04 [mm] and a space (air layer) of 1.32 [mm] is as follows.
(0.04 [mm] x 2) / 1500 [m / s] +1.32 [mm] /332 [m / s] = 4.1 [μs]
As described above, there is a time difference of 3.4 [μs] between each propagation time, and this time difference is large enough to be discriminated by the double feed detection device 100.

That is, by setting the third threshold value to a value between the propagation time of the ultrasonic wave when the plastic card is conveyed and the propagation time of the ultrasonic wave when the paper is conveyed, the double feed determination unit 163 transfers. It is possible to determine whether the medium is a plastic card or paper. Therefore, when the signal value is equal to or less than the first threshold value and is larger than the second threshold value, the double feed determination unit 163 uses the propagation time of the ultrasonic wave to use the propagation time of the ultrasonic wave to make the conveyed medium a plastic card or paper. It is possible to determine whether or not double feeding has occurred.

As described in detail above, the double feed detection device 100 operates according to the flowchart shown in FIG. 8 so that when the signal value of the ultrasonic signal is equal to or less than the first threshold value and larger than the second threshold value, the ultrasonic wave is transmitted. Based on the propagation time, it is determined whether or not double feeding has occurred. Therefore, the double feed detection device 100 can detect the double feed with higher accuracy.

In particular, the double feed detection device 100 erroneously determines that two thin sheets have been conveyed when the plastic card is conveyed, interrupts the transfer of the original, and reduces the work efficiency of the scanning operation. It became possible to suppress it. In addition, the user can perform the scanning work by mixing the paper and the plastic card, and it is possible to improve the convenience of the user. Further, since the double feed detection device 100 does not need to provide a special sensor for detecting the plastic card, it detects that the plastic card has been conveyed while suppressing an increase in the device size and an increase in the device cost. It became possible.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the double feed detection device 100 does not detect the peak of the signal value based on the analog ultrasonic signal (absolute value signal), but detects the peak of the signal value based on the digital ultrasonic signal. You may. In that case, the peak detection circuit 133 is omitted, and instead, the detection unit 164 scans the signal value of the digital ultrasonic signal in time series and detects a decrease in the signal value over a predetermined width to detect the signal. Detect peak values. In this case, since the peak detection circuit 133 is omitted, the double feed detection device 100 can reduce the device size and the device cost. On the other hand, when the peak is detected by the peak detection circuit 133, the double feed detection device 100 can reduce the processing load of the peak detection process by software.

Further, the double feed determination unit 163 may correct the first threshold value, the second threshold value, or the third threshold value based on the temperature, humidity, or atmospheric pressure in the double feed detection device 100.

FIG. 10A shows the temperature and altitude (atmospheric pressure) of the environment in which the double feed detection device 100 is installed and the signal value of the ultrasonic signal output when the double feed detection device 100 is installed in each environment. It is a graph which shows the relationship.

The horizontal axis of FIG. 10A indicates the altitude [km] in which the double feed detection device 100 is installed, and the vertical axis indicates the signal value of the ultrasonic signal. Graph 1001 shows a signal value of an ultrasonic signal when a sheet of PPC paper is conveyed in a state where the temperature of the double feed detection device 100 is 60 ° C. Graph 1002 shows the signal value of the ultrasonic signal when a sheet of PPC paper is conveyed in a state where the temperature in the double feed detection device 100 is 25 ° C. Graph 1003 shows the signal value of the ultrasonic signal when a sheet of PPC paper is conveyed in a state where the temperature in the double feed detection device 100 is 0 ° C. Graph 1004 shows the signal value of the ultrasonic signal when two sheets of PPC paper are conveyed in a state where the temperature in the double feed detection device 100 is 60 ° C. Graph 1005 shows the signal value of the ultrasonic signal when two sheets of PPC paper are conveyed in a state where the temperature in the double feed detection device 100 is 25 ° C. Graph 1006 shows the signal value of the ultrasonic signal when two sheets of PPC paper are conveyed in a state where the temperature in the double feed detection device 100 is 0 ° C.

As shown in FIG. 10A, the lower the temperature in the double feed detection device 100, the more the ultrasonic waves are attenuated, and the lower the signal value of the ultrasonic signal. Therefore, the double feed determination unit 163 acquires the temperature information from the temperature sensor 136, and corrects the first threshold value and the second threshold value so that the lower the temperature indicated in the temperature information, the lower the temperature information. As a result, the double feed determination unit 163 can more accurately determine whether or not double feed of the paper has occurred regardless of the temperature of the environment in which the double feed detection device 100 is installed.

Further, as shown in FIG. 10A, the higher the altitude at which the double feed detection device 100 is installed, that is, the lower the atmospheric pressure in the double feed detection device 100, the more the ultrasonic waves are attenuated, and the signal value of the ultrasonic signal becomes higher. It gets lower. Therefore, the double feed determination unit 163 acquires the atmospheric pressure information from the atmospheric pressure sensor 138, and corrects the first threshold value and the second threshold value so that the lower the atmospheric pressure indicated in the atmospheric pressure information, the lower the atmospheric pressure information. As a result, the double feed determination unit 163 can more accurately determine whether or not double feed of paper has occurred regardless of the altitude of the place where the double feed detection device 100 is installed.

FIG. 10B shows the humidity and altitude (atmospheric pressure) of the environment in which the double feed detection device 100 is installed and the signal value of the ultrasonic signal output when the double feed detection device 100 is installed in each environment. It is a graph which shows the relationship.

The horizontal axis of FIG. 10B shows the altitude [km] in which the double feed detection device 100 is installed, and the vertical axis shows the signal value of the ultrasonic signal. Graph 1011 shows the signal value of the ultrasonic signal when a sheet of PPC paper is conveyed in a state where the humidity in the double feed detection device 100 is 80%. Graph 1012 shows the signal value of the ultrasonic signal when a sheet of PPC paper is conveyed in a state where the humidity in the double feed detection device 100 is 50%. Graph 1013 shows the signal value of the ultrasonic signal when a sheet of PPC paper is conveyed in a state where the humidity in the double feed detection device 100 is 30%. Graph 1014 shows the signal value of the ultrasonic signal when two sheets of PPC paper are conveyed in a state where the humidity in the double feed detection device 100 is 80%. Graph 1015 shows the signal value of the ultrasonic signal when two sheets of PPC paper are conveyed in a state where the humidity in the double feed detection device 100 is 50%. Graph 1016 shows the signal value of the ultrasonic signal when two sheets of PPC paper are conveyed in a state where the humidity in the double feed detection device 100 is 30%.

As shown in FIG. 10B, the signal value of the ultrasonic signal changes according to the humidity in the double feed detection device 100. Therefore, the double feed detection device 100 has a signal value when one sheet of PPC paper is conveyed and a signal value when two sheets of thin paper are conveyed, and two sheets for each humidity in the double feed detection device 100. The signal value when the PPC paper is conveyed is measured in advance and stored in the storage device 150. The double feed determination unit 163 acquires humidity information from the humidity sensor 137, and stores the signal value when one sheet of PPC paper is conveyed, which is stored corresponding to the humidity indicated in the humidity information, and two sheets of thin paper. The first threshold value is corrected so that the value is between the signal value and the signal value when is conveyed. Further, the double feed determination unit 163 stores a signal value when two sheets of thin paper are conveyed and a signal value when two sheets of PPC paper are conveyed, which are stored corresponding to the humidity indicated in the humidity information. The second threshold is corrected so that the value is between. As a result, the double feed determination unit 163 can more accurately determine whether or not double feed of the paper has occurred regardless of the humidity of the environment in which the double feed detection device 100 is installed.

FIG. 11A is a graph showing the relationship between the temperature of the environment in which the double feed detection device 100 is installed and the propagation time of ultrasonic waves when the double feed detection device 100 is installed in each environment.

The horizontal axis of FIG. 11A shows the temperature [° C.] in the double feed detection device 100, and the vertical axis shows the propagation time [μs]. Graph 1101 shows the propagation time when the ultrasonic wave propagates through the plastic card, graph 1102 shows the propagation time when the ultrasonic wave propagates through the PPC paper, and graph 1103 shows the propagation time when the ultrasonic wave propagates through the air. Indicates the propagation time of. As shown in FIG. 11A, the lower the temperature in the double feed detection device 100, the longer the propagation time of the ultrasonic wave. Therefore, the double feed determination unit 163 acquires the temperature information from the temperature sensor 136, and corrects the third threshold value so that the lower the temperature indicated in the temperature information, the higher the temperature information. As a result, the double feed determination unit 163 can more accurately determine whether or not double feed of the paper has occurred regardless of the temperature of the environment in which the double feed detection device 100 is installed.

FIG. 11B is a graph showing the relationship between the humidity of the environment in which the double feed detection device 100 is installed and the propagation time of ultrasonic waves when the double feed detection device 100 is installed in each environment.

The horizontal axis of FIG. 11B shows the humidity [%] in the double feed detection device 100, and the vertical axis shows the propagation time [μs]. Graph 1111 shows the propagation time when the ultrasonic wave propagates through the plastic card, graph 1112 shows the propagation time when the ultrasonic wave propagates through the PPC paper, and graph 1113 shows the propagation time when the ultrasonic wave propagates through the air. Indicates the propagation time of. As shown in FIG. 11B, the lower the humidity in the double feed detection device 100, the longer the propagation time of ultrasonic waves. Therefore, the double feed determination unit 163 acquires humidity information from the humidity sensor 137, and corrects the third threshold value so that the lower the humidity shown in the humidity information, the higher the humidity information. As a result, the double feed determination unit 163 can more accurately determine whether or not double feed of the paper has occurred regardless of the temperature of the environment in which the double feed detection device 100 is installed.

FIG. 11B is a graph showing the relationship between the altitude at which the double feed detection device 100 is installed and the propagation time of ultrasonic waves when the double feed detection device 100 is installed at each altitude.

The horizontal axis of FIG. 11C indicates the altitude [km] in which the double feed detection device 100 is installed, and the vertical axis indicates the propagation time [μs]. Graph 1121 shows the propagation time when the ultrasonic wave propagates through the plastic card, graph 1122 shows the propagation time when the ultrasonic wave propagates through the PPC paper, and graph 1123 shows the propagation time when the ultrasonic wave propagates through the air. Indicates the propagation time of. As shown in FIG. 11C, the higher the altitude at which the double feed detection device 100 is installed, that is, the lower the air pressure in the double feed detection device 100, the longer the ultrasonic wave propagation time. Therefore, the double feed determination unit 163 acquires the atmospheric pressure information from the atmospheric pressure sensor 138, and corrects the third threshold value so that the lower the atmospheric pressure indicated in the atmospheric pressure information, the higher the atmospheric pressure information. As a result, the double feed determination unit 163 can more accurately determine whether or not double feed of paper has occurred regardless of the altitude at which the double feed detection device 100 is installed.

FIG. 12 is a diagram showing a schematic configuration of a processing circuit 270 in the double feed detection device according to another embodiment. The processing circuit 270 includes a control circuit 271, an image generation circuit 272, a double feed determination circuit 273, a detection circuit 274, and the like. Each of these parts may be composed of independent integrated circuits, microprocessors, firmware, and the like.

The control circuit 271 is an example of a control unit. The control circuit 271 transmits a control signal to the drive device 134 to drive the drive device 134 and convey the document.

The image generation circuit 272 is an example of an image generation unit. The image generation circuit 272 acquires a read image from the image pickup device 119 via the image A / D converter 130 and transmits it to an information processing device (not shown) via the interface device 135.

The double feed determination circuit 273 is an example of the double feed determination unit. The double feed determination circuit 273 acquires a digital ultrasonic signal from an ultrasonic sensor 115 via an ultrasonic A / D converter 132, and acquires an ultrasonic propagation time from a detection circuit 274. The double feed determination circuit 273 determines whether or not double feed has occurred based on the ultrasonic signal and the propagation time, and transmits a detection signal indicating the determination result to the CPU 160.

The detection circuit 274 is an example of a detection unit. The detection circuit 274 acquires a peak detection signal from the peak detection circuit 133, detects the propagation time of the ultrasonic wave based on the acquired peak detection signal, and transmits it to the double feed determination circuit 273.

As described in detail above, the double feed detection device can detect double feed with higher accuracy even when the processing circuit 270 is used.

100 Double feed detection device 115a Ultrasonic oscillator 115b Ultrasonic receiver 163 Double feed judgment unit 164 Detection unit

Claims (5)

An ultrasonic oscillator that outputs ultrasonic waves and
An ultrasonic receiver that is arranged to face the ultrasonic oscillator and outputs an ultrasonic signal according to the received ultrasonic waves, and an ultrasonic receiver.
The time from when the ultrasonic oscillator stops the output of the ultrasonic wave until the absolute value of the signal value of the ultrasonic signal output by the ultrasonic receiver first reaches the peak value is determined from the ultrasonic oscillator. A detector that detects the propagation time of the ultrasonic waves to the ultrasonic receiver, and
It has a double feed determination unit that determines whether or not double feed has occurred based on the ultrasonic signal and the propagation time.
The double feed determination unit
When the signal value of the ultrasonic signal is larger than the first threshold value, it is determined that double feeding has not occurred, and it is determined that double feeding has not occurred.
When the signal value of the ultrasonic signal is equal to or less than the second threshold value smaller than the first threshold value, it is determined that double feeding has occurred.
When the signal value of the ultrasonic signal is equal to or less than the first threshold value and larger than the second threshold value, and when the propagation time is equal to or less than the third threshold value, it is determined that double feeding has not occurred, and the propagation is performed. When the time is larger than the third threshold value, it is determined that double feeding has occurred.
A double feed detection device characterized by this. The double feed detection device according to claim 1, wherein the double feed determination unit determines that the plastic card has been conveyed and no double feed has occurred when the propagation time is equal to or less than the third threshold value. .. The ultrasonic oscillator outputs ultrasonic waves at predetermined intervals and outputs ultrasonic waves.
The double feed determination unit determines whether or not double feed of paper has occurred by using the average value of the propagation times of the ultrasonic waves output in a plurality of predetermined periods, according to claim 1 or 2 . The double feed detection device described. Double feed detection in a double feed detection device having an ultrasonic oscillator that outputs ultrasonic waves and an ultrasonic receiver that is arranged opposite to the ultrasonic oscillator and outputs an ultrasonic signal corresponding to the received ultrasonic waves. It ’s a method,
The time from when the ultrasonic oscillator stops the output of the ultrasonic wave until the absolute value of the signal value of the ultrasonic signal output by the ultrasonic receiver first reaches the peak value is determined from the ultrasonic oscillator. Detected as the propagation time of the ultrasonic wave to the ultrasonic receiver,
Including determining whether or not double feeding has occurred based on the ultrasonic signal and the propagation time.
In the above determination
When the signal value of the ultrasonic signal is larger than the first threshold value, it is determined that double feeding has not occurred, and it is determined that double feeding has not occurred.
When the signal value of the ultrasonic signal is equal to or less than the second threshold value smaller than the first threshold value, it is determined that double feeding has occurred.
When the signal value of the ultrasonic signal is equal to or less than the first threshold value and larger than the second threshold value, and when the propagation time is equal to or less than the third threshold value, it is determined that double feeding has not occurred, and the propagation is performed. When the time is larger than the third threshold value, it is determined that double feeding has occurred.
A double feed detection method characterized by this. Control to be executed by a double feed detection device having an ultrasonic oscillator that outputs ultrasonic waves and an ultrasonic receiver that is arranged opposite to the ultrasonic oscillator and outputs an ultrasonic signal corresponding to the received ultrasonic waves. It ’s a program,
The time from when the ultrasonic oscillator stops the output of the ultrasonic wave until the absolute value of the signal value of the ultrasonic signal output by the ultrasonic receiver first reaches the peak value is determined from the ultrasonic oscillator. Detected as the propagation time of the ultrasonic wave to the ultrasonic receiver,
The double feed detection device is made to determine whether or not double feed has occurred based on the ultrasonic signal and the propagation time.
In the above determination
When the signal value of the ultrasonic signal is larger than the first threshold value, it is determined that double feeding has not occurred, and it is determined that double feeding has not occurred.
When the signal value of the ultrasonic signal is equal to or less than the second threshold value smaller than the first threshold value, it is determined that double feeding has occurred.
When the signal value of the ultrasonic signal is equal to or less than the first threshold value and larger than the second threshold value, and when the propagation time is equal to or less than the third threshold value, it is determined that double feeding has not occurred, and the propagation is performed. When the time is larger than the third threshold value, it is determined that double feeding has occurred.
A control program characterized by that.

Images