JP4260595B2 - Ultrasonic double feed detector - Google Patents

Description

  The present invention relates to an ultrasonic multi-feed detection device that detects whether or not sheets are multi-fed when a plurality of stacked sheets are separated and conveyed one by one.

  2. Description of the Related Art Conventionally, sheet handling apparatuses such as a scanner, a printer, a copying machine, a printing machine, and an ATM (Automated Teller Machine) have a mechanism for separating and conveying sheets one by one. However, even if the mechanism tries to convey the sheets one by one, a double feeding phenomenon may occur in which a part of two or more sheets or the whole sheet is conveyed while being overlapped.

  For this reason, in general, a sheet handling apparatus often includes a double feed detection device that detects double feed of sheets. As the double feed detection device, an ultrasonic double feed detection device using ultrasonic waves has been widespread (see, for example, Patent Documents 1 and 2). Hereinafter, an ultrasonic multifeed detection device that detects multifeed of banknotes with ultrasonic waves will be described using a banknote as an example of a sheet.

  FIG. 8 is a schematic diagram of a conventional ultrasonic multifeed detection device 100 that detects multifeed of banknotes P. An ultrasonic transmitter 102 that is an ultrasonic transmitter is configured to transmit ultrasonic waves to the banknote P. An ultrasonic receiver 103 which is an ultrasonic receiving means receives ultrasonic waves transmitted from the ultrasonic transmitter 102. Further, the ultrasonic receiver 103 is disposed at a position facing the ultrasonic transmitter 102 across the conveyance path of the banknote P so that the ultrasonic wave transmitted through the banknote P can be received. The waveform analyzer 108 analyzes the ultrasonic reception signal received by the ultrasonic receiver 103.

  Next, the operation of the double feed detection device 100 shown in FIG. 8 will be described. First, the ultrasonic wave transmitted from the ultrasonic transmitter 102 passes through the bill P and is received by the ultrasonic receiver 103 as a transmitted wave. The ultrasonic receiver 103 outputs an output voltage that changes according to the received intensity of the received ultrasonic wave.

  The waveform analysis means 108 analyzes the change in the output voltage output from the ultrasonic receiver 103 as an ultrasonic reception signal. The waveform analysis unit 108 analyzes changes in the amplitude and phase of the received ultrasonic wave to detect double feeding of banknotes. There are two methods for detecting double feed: a level determination method for detecting double feed from a change in the amplitude of ultrasonic waves, and a phase determination method for detecting double feed from changes in the phase of ultrasonic waves.

  A level determination method will be described. First, after setting the double feed determination threshold in advance, the ultrasonic receiver 103 acquires the amplitude of the ultrasonic wave that has been conveyed through the banknote P and has passed through the banknote P. Since the attenuation amount of the ultrasonic wave is increased, the amplitude of the transmitted ultrasonic wave when the banknote P is double-fed is smaller than the amplitude of the transmitted ultrasonic wave when the banknote P is normally conveyed one by one. Therefore, the ultrasonic double feed detection device 100 detects the double feed of the banknote P by comparing the amplitude of the ultrasonic wave acquired by the ultrasonic receiver 103 with the above-described double feed determination threshold in the waveform analysis unit 108. Can do.

The phase determination method will be described. A predetermined time after the ultrasonic wave is transmitted from the ultrasonic wave transmitter 102, the waveform analyzer 108 holds the phase information of the ultrasonic wave reception signal acquired by the ultrasonic wave receiver 103. The waveform analyzer 108 uses the phase information when the bill P is not present between the ultrasonic transmitter 102 and the ultrasonic receiver 103 as basic phase information, and compares the basic phase information with the current phase information, A double feed of the banknote P is detected.
JP 2003-160257 A JP 2003-176063 A

  In the conventional ultrasonic multifeed detection device, when the end of the sheet passes between the ultrasonic transmission means and the ultrasonic reception means, the ultrasonic waves are irregularly reflected between the sheet and the sheet conveyance path. The ultrasonic wave reception signal was unstable and the double feed detection accuracy was low.

  In addition, since the conventional ultrasonic multifeed detection device needs to adjust the multifeed determination result depending on the shape of the sheet and the conveyance conditions (for example, paper stuck to the binder), the conveyance speed information and the paper from the outside. It is necessary to acquire detection information, and it is difficult to use the ultrasonic multifeed detection device alone.

  The present invention provides an ultrasonic double feed detection device that detects an indefinite state in which the amplitude and phase of a received signal are disturbed, avoids double feed erroneous detection due to the undefined state, and has improved double feed detection accuracy. It is aimed.

  In order to achieve the above object, an ultrasonic double-feed detection device according to the present invention includes an ultrasonic wave transmitting means that is disposed on one side of a sheet conveyance path and emits ultrasonic waves to the sheet, and the other of the conveyance paths. Based on the ultrasonic wave receiving means arranged on the side for receiving the ultrasonic wave of the ultrasonic wave transmitting means and outputting an ultrasonic wave reception signal, and whether the sheet is double-fed based on the waveform of the ultrasonic wave reception signal An ultrasonic reception state determination unit that determines an ultrasonic reception state of the ultrasonic reception unit based on a waveform of the ultrasonic reception signal; and The state determination unit compares the set first threshold value and the second threshold value with the amplitude of the ultrasonic reception signal, and the amplitude is between the first threshold value and the second threshold value. At this time, the determination result of the double feed determination means is invalidated.

  In order to achieve the above object, an ultrasonic double-feed detection device according to the present invention includes an ultrasonic wave transmitting means that is disposed on one side of a sheet conveyance path and emits ultrasonic waves to the sheet, and the other of the conveyance paths. Based on the ultrasonic wave receiving means arranged on the side for receiving the ultrasonic wave of the ultrasonic wave transmitting means and outputting an ultrasonic wave reception signal, and whether the sheet is double-fed based on the waveform of the ultrasonic wave reception signal And comparing the first threshold value and the second threshold value that are set with the amplitude of the ultrasonic reception signal, and the amplitude is the first threshold value and the second threshold value. A conveyance speed detection means for calculating the conveyance speed of the sheet from the time between the threshold value of 2 and the length of the ultrasonic reception area of the ultrasonic reception means, and a sheet detection means for detecting the passage of the sheet And the conveyance speed of the sheet calculated by the conveyance speed detection means The position detection means for detecting the position of the sheet based on the elapsed time after the sheet detection means detects the sheet, the first threshold value, the second threshold value, and the position of the specific part of the sheet are stored. When it is determined that the specific part of the sheet is in the ultrasonic wave reception area based on the storage means, the position of the sheet detected by the position detection means, and the position of the specific part stored in the storage means And an ultrasonic wave reception state determination unit that invalidates the determination result of the double feed determination unit.

  The ultrasonic double feed detection device of the present invention includes amplification means for amplifying an ultrasonic reception signal output from the ultrasonic reception means, and the double feed determination means and the ultrasonic reception state determination means include the amplification means. The ultrasonic reception signal of the ultrasonic reception means is received via the.

  The ultrasonic double feed detection device of the present invention includes amplification means for amplifying an ultrasonic reception signal output from the ultrasonic reception means, and the double feed determination means and the transport speed detection means are provided via the amplification means. The ultrasonic reception signal of the ultrasonic reception means is received.

  In the ultrasonic multifeed detection device of the present invention, the sheet detection means compares the set first and second thresholds with the amplitude of the ultrasonic reception signal, and the amplitude is The sheet is detected by being between the first threshold value and the second threshold value.

  In the ultrasonic double-feed detection device of the present invention, the sheet detection means is a sensor that detects a sheet.

  The ultrasonic double feed detection device of the present invention includes an ultrasonic indeterminate state determination unit that detects an indefinite state in which the amplitude and phase of the ultrasonic reception signal are disturbed, so that it is possible to avoid double feed erroneous detection due to the indefinite state, Double feed can be detected with high accuracy.

  The ultrasonic double-feed detection device of the present invention detects the position of the sheet, and when it is detected that a specific part of the sheet is approaching the ultrasonic wave transmission area, it does not determine multi-feed. It is possible to avoid double feed erroneous detection depending on the state, and to detect double feed with high accuracy. In addition, the sheet conveying speed is detected by using the ultrasonic transmission means and the ultrasonic receiving means, but the sheet moving speed is detected by the apparatus alone without acquiring the conveying speed information from the outside. be able to.

  The ultrasonic multifeed detection device of the present invention is set so as not to determine multifeed unless the multifeed determination of a certain length or more is continued. Variation can be suppressed.

  Since the ultrasonic double feed detection device of the present invention detects an indefinite state in which the amplitude and phase of the ultrasonic reception signal are disturbed from the change in the amplitude of the ultrasonic reception signal, the ultrasonic transmission means and the ultrasonic wave Misdetection of double feed can be avoided without providing sheet detecting means other than the receiving means.

  In the ultrasonic double feed detection device of the present invention, since the position information of the sheet is detected by the sensor, the period during which the amplitude and phase of the ultrasonic reception signal are disturbed is specified, and double feed error is detected. Detection can be avoided.

  The ultrasonic double feed detection device of the present invention can accurately specify a period in which the amplitude and phase of the ultrasonic reception signal are disturbed and can avoid erroneous double feed detection.

  Hereinafter, an ultrasonic double feed detection device according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram of an ultrasonic double feed detection device according to an embodiment of the present invention.

  The ultrasonic double feed detection device 10 is a device that detects double feed of a sheet P conveyed by a sheet conveyance device (not shown) using an ultrasonic sensor.

  Sheets include plain paper, resin sheets that are substitutes for plain paper, cardboard, originals, banknotes, labels, films, and the like, and these are collectively referred to as sheets. In the present embodiment, plain paper (hereinafter simply referred to as “paper”) will be described. However, the present invention is not limited to this.

  Moreover, the numerical value shown by this embodiment is a reference numerical value, Comprising: This invention is not limited to this. Furthermore, the present invention is not limited to the configuration of the present embodiment, and includes configurations such as design changes within a range not departing from the gist of the present invention.

  The ultrasonic transmitter 2 which is an ultrasonic wave generating means is configured to transmit an ultrasonic signal to the paper P when an ultrasonic pulse signal from a drive circuit 5 described later is input.

  The ultrasonic receiver 3 that is an ultrasonic receiving means receives the ultrasonic wave transmitted from the ultrasonic transmitter 2 as it is, or receives the ultrasonic wave that has passed through the paper P, so that the conveyance path 11 of the paper P is received. (Refer to FIG. 4) is disposed at a position facing the ultrasonic transmitter 2 with a sandwich in between.

  The ultrasonic wave transmitted from the ultrasonic transmitter 2 passes through the paper P and is received by the ultrasonic receiver 3 as a transmitted wave. Further, the ultrasonic receiver 3 outputs an output voltage (ultrasonic reception signal) that changes in accordance with the received intensity of the received ultrasonic wave. As described above, when the paper P exists in the transport path 11, the ultrasonic wave transmitted through the paper P is received by the ultrasonic receiver 3, but when the paper P does not exist in the transport path 11, the ultrasonic transmitter 2. Is transmitted as it is by the ultrasonic receiver 3.

  The control device 4 supplies a 200 kHz pulse signal as an ultrasonic transmission signal to the drive circuit 5. The signal is generally called a burst wave, and the burst wave is periodically transmitted once every several ms.

  The drive circuit 5 amplifies the pulse signal supplied from the control device 4 and outputs the ultrasonic pulse signal to the ultrasonic transmitter 2. Accordingly, the ultrasonic transmitter 2 transmits a 200 kHz ultrasonic wave based on the amplified ultrasonic pulse signal. The ultrasonic pulse signal supplied by the control device 4 is a signal for transmitting a 200 kHz pulse signal for several cycles over a certain period of time, for example.

  The amplifier circuit 6 which is an amplifying means amplifies the output signal output from the ultrasonic receiver 3. The reason for amplifying the signal is that when the paper P to be conveyed enters between the ultrasonic transmitter 2 and the ultrasonic receiver 3, the ultrasonic signal transmitted from the ultrasonic transmitter 2 is transmitted to the ultrasonic receiver 3. This is because the signal attenuates before reaching the signal and becomes a very weak signal, and the amplitude of the output signal of the ultrasonic receiver 3 becomes weak accordingly. Therefore, the amplifier circuit 6 amplifies the output signal of the ultrasonic receiver 3 and raises it to a signal amplitude that allows determination of double feed detection.

  A circuit example of the amplifier circuit 6 will be described with reference to FIG. FIG. 2 is a diagram showing a circuit example of the amplifier circuit 6 shown in FIG. As shown in FIG. 2 (a), the amplifier circuit 6 has a plurality of amplifiers 6a (amplification degree is 10 times) connected in series in multiple stages, and is configured to amplify the received signal. The output stage of each amplifier 6a is input to the AD converter 7 respectively. As shown in FIG. 2B, the amplifier circuit 6 may include a plurality of amplifiers 6a to 6e having different amplification factors connected in parallel to amplify the received signal. Also in this case, the outputs of the amplifiers 6a to 6e are input to the AD converter 7, respectively.

  The A-D converter 7 converts the ultrasonic reception signal (analog signal) amplified by the amplifier circuit 6 into a digital signal and outputs the digital signal to the control device 4.

  Next, an example of an ultrasonic waveform transmitted from the ultrasonic transmitter 2 and an exemplary waveform of an ultrasonic wave received by the ultrasonic receiver 3 will be described with reference to FIG. FIG. 3 is a diagram showing an example of an ultrasonic waveform (upper waveform) transmitted by the ultrasonic transmitter 2 shown in FIG. 1 and an example of an ultrasonic waveform (lower waveform) received by the ultrasonic receiver 3. It is.

  t1 [s] indicates the time from when the ultrasonic transmitter 2 transmits the ultrasonic wave to when the ultrasonic receiver 3 receives the ultrasonic wave, depending on the distance between the ultrasonic transmitter 2 and the ultrasonic receiver 3. Different. t2 indicates a range where the ultrasonic reception signal is sampled. Since the waveform information of the ultrasound reception signal acquired by the ultrasound receiver 3 needs to include the maximum value and the minimum value in the amplitude of the ultrasound signal, the AD converter 7 Sampling is performed within a range of one cycle, and an ultrasonic reception signal is acquired. Here, if one period is t2 [s] and the sampling points acquired from one period are n [pieces], the ultrasonic receiver 3 transmits an ultrasonic signal during the time for receiving the nath sampling point. Then, t = t1 + (t2 × na / n) [s].

  In addition to the ultrasonic signal transmitted from the ultrasonic transmitter 2, since the noise signal from the external device is input to the ultrasonic receiver 3, the noise signal is reduced by averaging the time. The above-described time average is a value obtained by obtaining, for example, eight sample values and obtaining the average value. However, in order to avoid the situation of time averaging including spike noise due to static electricity etc., when the value fluctuates significantly compared to the signal amplitude acquired at the previous time at the same sampling point, the value is It is not included in the time average.

  The reason why the ultrasonic wave becomes unstable in an indefinite state will be described with reference to FIG. FIG. 4A shows a state in which the end of the paper P passes between the ultrasonic transmitter 2 and the ultrasonic receiver 3. The paper P passes through the conveyance path 11. The conveyance path 11 is formed by a guide 12.

  The ultrasonic wave transmitted from the ultrasonic transmitter 2 causes irregular reflection by the paper P, the ultrasonic receiver 3 and the guide 12. The ultrasonic waves that have interfered by causing irregular reflection form a complex dense wave, and both the amplitude and phase of the received signal become unstable and are received by the ultrasonic receiver 3.

  FIG. 4B shows a state in which the paper P starts to be applied to the ultrasonic wave reception area 11a. FIG. 4C shows a state where the paper is completely applied to the ultrasonic wave receiving area 11a. The state in which the ultrasonic signal causes irregular reflection is a state between FIG. 4B and FIG. 4C (the state of FIG. 4A), and this state is called an indeterminate state. The ultrasonic reception area 11 a is an area through which an ultrasonic wave emitted from the ultrasonic transmitter 2 and received by the ultrasonic receiver 3 passes.

  The configuration and function of the control device 4 in FIG. 1 will be described with reference to FIG. FIG. 5 is a schematic block diagram of the control device 4 shown in FIG.

  The basic phase information holding unit 41 is configured such that when no paper exists between the ultrasonic transmitter 2 and the ultrasonic receiver 3, the ultrasonic receiver receives a predetermined time from the timing at which the ultrasonic wave is transmitted from the ultrasonic transmitter 2. The phase information of the ultrasonic wave reception signal acquired in 3 is held as basic phase information.

  The phase double feed determination unit 42, which is a double feed determination means, compares the basic phase information in the basic phase information holding unit 41 with the current phase information to determine whether or not double feed is to be performed. This determination method is called a phase determination method.

  The level double feed determination unit 43, which is a double feed determination means, compares the ultrasonic signal amplitude with a threshold value, which will be described later, to determine whether or not double feed. This determination method is called a level determination method. It is sufficient that at least one of the phase double feed determination unit 42 and the level double feed determination unit 43 is provided.

  The indeterminate state determination unit 44, which is an ultrasonic reception state determination unit, is generated when the front end portion and the rear end portion of the paper pass based on the signal level of the ultrasonic receiver 3 that changes depending on the presence or absence of paper. An indefinite state of the ultrasonic signal is detected. If the indeterminate state determination unit 44 determines that the state is indefinite, in order to avoid erroneous detection, the indefinite state determination unit 44 determines that it is not double feed regardless of the determination results of the phase double feed determination unit 42 and the level double feed determination unit 43. ing.

  The conveyance speed detection unit 45, which is a conveyance speed detection means, acquires the signal waveform output from the amplifier circuit output stage with a low amplification factor, and the time from when the paper starts to be applied to the ultrasonic wave reception area 11a until it takes completely. The paper conveyance speed is detected from the external dimensions of the ultrasonic wave transmitting surface 2a of the ultrasonic wave transmitter 2 and the ultrasonic wave receiving surface 3a of the ultrasonic wave receiver 3.

  An indeterminate state determination unit 44 that is an ultrasonic reception state determination unit and also a sheet detection unit is included in the control device 4 and monitors the amplitude of the ultrasonic reception signal output from the ultrasonic receiver 3 to be indefinite. A first indeterminate state determination circuit 44a that determines the state and a second indeterminate state determination circuit 44b that detects the position of the paper and determines the indeterminate state. The undefined state determination unit 44 is configured to avoid double feed erroneous detection based on the undefined state determination result of either one or both of the first and second undefined state determination circuits 44a and 44b. Therefore, the undefined state determination unit 44 only needs to include at least one of the first and second undefined state determination circuits 44a and 44b.

  The operation of the first indeterminate state determination circuit 44a will be described. FIG. 6 is a waveform diagram of an ultrasonic reception signal output from the low amplification stage of the amplifier circuit 6.

  The basic signal waveform A is a waveform of an ultrasonic reception signal when the paper 1 does not exist between the ultrasonic transmitter 2 and the ultrasonic receiver 3 (see FIG. 4B). In selecting the output stage of the amplifier circuit for indeterminate state determination, a signal whose basic signal waveform A is not saturated is selected in order to detect changes in signal amplitude sensitively.

  The current signal waveform B has an edge of paper between the ultrasonic transmitter 2 and the ultrasonic receiver 3, and the ultrasonic signal becomes unstable when the ultrasonic signal becomes unstable (see FIG. 4A). It is a waveform. The signal amplitude at this time is 70% compared with the signal amplitude of the basic signal waveform A. When the paper completely covers between the ultrasonic transmitter 2 and the ultrasonic receiver 3 (see FIG. 4C), the ultrasonic reception signal output from the ultrasonic receiver 3 is stabilized. Further, the signal amplitude at this time is 1% or less as compared with the signal amplitude of the basic signal waveform A.

  The first indeterminate state determination circuit 44a determines the indeterminate state by monitoring the amplitude of the current signal waveform B when there is a paper edge between the ultrasonic transmitter 2 and the ultrasonic receiver 3. It has become.

  The signal amplitude of the current signal waveform B is compared with the signal amplitude of the basic signal waveform A, the signal amplitude value at 95% is set as the first threshold value, and the signal amplitude value at 5% is set as the first threshold value. It is set as a threshold value of 2 and stored in the storage unit 46 which is a storage means. In addition, the storage unit 46 also stores the position of a specific part of paper to be described later. In the present embodiment, when the signal amplitude is a value between the first threshold value and the second threshold value, the indeterminate state determination unit 44 determines that the indefinite state is present. In addition, description of this embodiment does not mean limiting to what was described about control of the control apparatus 4, and each setting value.

  The operation of the second indeterminate state determination circuit 44b will be described. FIG. 7 is a diagram in which a sensor 8 for detecting an indefinite state is provided in the configuration of FIG.

  In order to detect an indefinite state, a sensor 8 for detecting the paper is installed before the paper passes between the ultrasonic transmitter 2 and the ultrasonic receiver 3. The sensor 8 detects the presence / absence of paper according to a control command from the control device 4 and notifies the control device 4 of the presence / absence of paper. The control device 4 receives the paper detection information from the sensor 8 to obtain the position information, and does not determine the double feed when the end of the paper passes between the ultrasonic transmitter 2 and the ultrasonic receiver 3. It is supposed to be controlled.

  Operations of the indeterminate state determination unit 44 and the conveyance speed detection unit 45 will be described.

(Description of the operation of invalidating the double feed determination result of the phase double feed determination unit 42 in a portion having a predetermined length from the end of the sheet)
The first indeterminate state determination circuit 44a compares the signal amplitude of the current signal waveform B with the signal amplitude of the basic signal waveform A, and determines a value between the first threshold value and the second threshold value (the signal amplitude is 95). % Or less and 5% or more), it is determined that the state is indefinite, and the phase double feed determination unit 42 is not allowed to determine double feed.

(Explanation of operation for invalidating phase double feed determination unit 42 double feed determination result in a portion where a hole for binder is formed in a sheet and a portion where paper is pasted at a specific position of the sheet)
When the signal amplitude changes from 95% (see FIG. 4B) to 5% (see FIG. 4C), the paper passes between the ultrasonic transmitter 2 and the ultrasonic receiver 3. It's time. The conveyance speed detection unit 45 divides the outer dimensions of the ultrasonic wave transmission surface 2a of the ultrasonic wave transmitter 2 and the ultrasonic wave reception surface 3a of the ultrasonic wave receiver 3 by the above-described time during which paper passes, thereby determining the conveyance speed. calculate. Note that the description of the present embodiment is not meant to be limited to the description of the control of the control device 4 and each set value. The position detection unit 47, which is a position detection means, uses the conveyance speed obtained by the conveyance speed detection unit 45 and the elapsed time from when the signal amplitude falls between the threshold values 95% and 5%. Find the position. On the other hand, the storage unit 46 stores in advance the position of a specific part of the paper, for example, a section having a hole for a binder or a section where the paper is pasted.

  Thus, the second indeterminate state determination circuit 44b causes the specific part to be placed in the ultrasonic reception area 11a based on the current position information of the paper of the position detection unit 47 and the position of the specific part stored in the storage unit 46. When it arrives, a specific portion of the paper is not allowed to be determined to be double-feed by the phase double-feed determination unit 42. The elapsed time may be an elapsed time after the sensor 8 serving as the sheet detection unit detects the sheet.

  In addition, if the double feed determination of a certain length or more is not continued, the second indeterminate state determination circuit 44b sets the double feed detection determination result to be invalid so that the double feed determination condition due to the change in the conveyance speed is set. It becomes possible to suppress the variation of. The length of the paper can be calculated from the transport speed obtained by the transport speed detector 45 and the time until the paper has passed. By storing the calculated paper length in the storage unit 46 and comparing the lengths of the paper at any time, it is possible to detect double feed based on the length of the paper.

  As described above, the ultrasonic double feed detection device 10 of this embodiment prevents erroneous detection of double feed in an indefinite state in which the end of the paper passes between the ultrasonic transmitter 2 and the ultrasonic receiver 3. be able to. Further, by not determining that double feeding is performed at a specific part of the paper based on the position information, it is possible to prevent erroneous detection in a binder hole or the like. In addition, by using the sheet length calculated from the paper conveyance speed and the conveyance time in accordance with the level determination method and the phase determination method for double-feed detection, double-feed can be detected with high accuracy.

  Each unit illustrated in FIG. 5 may be realized by dedicated hardware. Each unit shown in FIG. 5 is configured by a memory in the control device 4 and a CPU (central processing unit), and a program for realizing the function of each unit is read into the memory and executed to realize the function. It may be.

  The memory is a non-volatile memory such as a hard disk device, a magneto-optical disk device, or a flash memory, a recording medium such as a CD-ROM that can only be read, a volatile memory such as a RAM (Random Access Memory), or It is assumed to be configured by a computer-readable and writable recording medium by a combination of these.

  In FIG. 5, a program for realizing the functions of the processing unit for performing various processes is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read by the CPU in the control device 4 and executed. Each processing may be performed as necessary.

  “Computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) inside the CPU in the control device 4 serving as a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. ) And the like that hold the program for a certain period of time.

  The program may be transmitted from a computer system storing the program in a memory or the like to a memory in the control device 4 via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the memory in the control apparatus 4, and what is called a difference file (difference program) may be sufficient.

  A program product such as a computer-readable recording medium in which the program is recorded can also be applied as an embodiment of the present invention.

It is the schematic of the ultrasonic double feed detection apparatus in embodiment of this invention. FIG. 2 is a diagram illustrating a circuit example of an amplifier circuit illustrated in FIG. 1. (A) is an example of an amplifier circuit. (B) is another example of an amplifier circuit. It is a figure which shows the waveform example (upper waveform) of the ultrasonic wave which the ultrasonic transmitter shown in FIG. 1 transmits, and the waveform example (lower waveform) of the ultrasonic wave which an ultrasonic receiver receives. It is a figure which shows the unstable ultrasonic signal in the state in which the edge of paper is applied between the ultrasonic transmitter and ultrasonic receiver shown in FIG. (A) has shown the state which the edge of paper passes between an ultrasonic transmitter and an ultrasonic receiver. (B) The state where the paper starts to be applied to the ultrasonic transmission / reception path is shown. (C) shows a state in which the paper is completely applied to the ultrasonic transmission / reception path. It is a schematic block diagram of the control apparatus shown in FIG. It is a wave form diagram of an ultrasonic wave reception signal which changes with states of a sheet between an ultrasonic wave transmitter and an ultrasonic wave receiver shown in Drawing 1. It is the figure which added the sensor which detects the state of a sheet | seat to the ultrasonic double feed detection apparatus shown in FIG. It is the schematic of the conventional ultrasonic multifeed detection apparatus.

Explanation of symbols

t1 Ultrasonic pulse arrival time t2 Ultrasound component sampling point acquisition time A Ultrasonic signal waveform example in the absence of a sheet between the ultrasonic transmitter and the ultrasonic receiver B Ultrasonic transmitter and ultrasonic Example of current signal waveform of ultrasonic wave with the edge of the sheet between the sound wave receivers 1 Paper (sheet)
2 Ultrasonic transmitter (Ultrasonic transmitter)
2a Ultrasonic wave transmitting surface 3 Ultrasonic wave receiver (ultrasonic wave receiving means)
3a Ultrasonic wave receiving surface 4 Control device 5 Drive circuit 6 Amplifier circuit (amplification means)
7 A-D converter 8 Sensor (sheet detection means)
DESCRIPTION OF SYMBOLS 10 Ultrasonic double feed detection apparatus 11 Conveyance path 11a Ultrasonic reception area | region 12 Guide 41 Basic phase information holding part 42 Phase double feed determination part (double feed determination means)
43 level double feed judgment unit (double feed judgment means)
44 Indeterminate state determination unit (ultrasonic wave reception state determination means, sheet detection means)
44a First indeterminate state determination circuit 44b Second indeterminate state determination circuit 45 Conveyance speed detection unit (conveyance speed detection means)
46 storage unit (storage means)
47 Position detection unit (position detection means)

Claims (6)

An ultrasonic wave transmitting means disposed on one side of the sheet conveyance path to emit ultrasonic waves to the sheet;
Ultrasonic receiving means arranged on the other side of the conveying path to receive ultrasonic waves of the ultrasonic transmitting means and output ultrasonic reception signals;
Based on the waveform of the ultrasonic reception signal, double feed determination means for determining whether or not the sheet is double fed;
Based on the waveform of the ultrasonic reception signal, an ultrasonic reception state determination unit that determines an ultrasonic reception state of the ultrasonic reception unit, and
The ultrasonic wave reception state determination unit compares the set first threshold value and the second threshold value with the amplitude of the ultrasonic wave reception signal, and the amplitude is the first threshold value and the second threshold value. The ultrasonic double feed detection device, wherein the determination result of the double feed determination means is invalidated between the two. An ultrasonic wave transmitting means disposed on one side of the sheet conveyance path to emit ultrasonic waves to the sheet;
Ultrasonic receiving means arranged on the other side of the conveying path to receive ultrasonic waves of the ultrasonic transmitting means and output ultrasonic reception signals;
Based on the waveform of the ultrasonic reception signal, double feed determination means for determining whether or not the sheet is double fed;
The first threshold value set and the second threshold value are compared with the amplitude of the ultrasonic reception signal, and the time when the amplitude is between the first threshold value and the second threshold value; A conveyance speed detection unit that calculates the conveyance speed of the sheet from the length of the ultrasonic reception area of the ultrasonic reception unit;
Sheet detecting means for detecting passage of the sheet;
Position detection means for detecting the position of the sheet based on the conveyance speed of the sheet calculated by the conveyance speed detection means and the elapsed time after the sheet detection means detects the sheet;
Storage means for storing the first threshold value, the second threshold value, and the position of the specific part of the sheet;
When it is determined that the specific part of the sheet is in the ultrasonic wave reception area based on the position of the sheet detected by the position detection unit and the position of the specific part stored in the storage unit, the multifeed determination Ultrasonic reception state determination means for invalidating the determination result of the means;
An ultrasonic double feed detection device comprising: Amplifying means for amplifying the ultrasonic reception signal output from the ultrasonic reception means,
The double feed determination unit and the ultrasonic reception state determination unit receive an ultrasonic reception signal of the ultrasonic reception unit via the amplification unit,
The ultrasonic double-feed detection device according to claim 1. Amplifying means for amplifying the ultrasonic reception signal output from the ultrasonic reception means,
The double feed determination unit and the conveyance speed detection unit receive an ultrasonic reception signal of the ultrasonic reception unit via the amplification unit,
The ultrasonic double feed detection device according to claim 2. The sheet detection means compares the set first and second threshold values with the amplitude of the ultrasonic reception signal, and the amplitude is determined by the first threshold value and the second threshold value. Detecting the sheet by being between
The ultrasonic double feed detection device according to claim 2. The sheet detecting means is a sensor for detecting a sheet.
The ultrasonic double feed detection device according to claim 2.

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