JP2006298598A - Double feeding detection device and double feeding detection method of sheet-like member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double feeding detection device and a double feeding detection method of a sheet-like member for achieving high precision without relying on unevenness of ultrasonic transmitting and receiving elements and change of the environment. <P>SOLUTION: This double feeding detection device is provided with an ultrasonic transmitting part 8 for transmitting ultrasonic waves arranged on one side across a conveyance face on which the sheet-like member P is conveyed, an ultrasonic receiving part 9 provided on the other side of the ultrasonic transmitting part 8 across the conveyance face and receiving ultrasonic waves from the ultrasonic transmitting part 8, an ultrasonic wave output level detection part 17 for detecting output level of ultrasonic wave received by the ultrasonic receiving part 9, and an ultrasonic wave variable means 16 for changing output level of ultrasonic waves transmitted by the ultrasonic transmitting part 8 based on output level of ultrasonic waves detected by the ultrasonic wave output level detection part 17 and/or central frequency of ultrasonic waves. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-feed detection device for a sheet-like member such as a sheet or a document in a paper feeding mechanism or an automatic document feeding mechanism used in an image scanner device, a digital copying machine, a printer, etc., and particularly using an ultrasonic sensor. The present invention relates to a multi-feed detection device for a sheet-like member capable of detecting multi-feed with high accuracy and a detection method thereof.

  Copiers and image scanner devices for image reading include a paper feeding device and an automatic document feeder for supplying paper to an image reading unit. In these paper feeders and automatic document feeders, it is necessary to prevent double feeding so that two or more sheets overlap and are not fed out simultaneously.

  As a mechanism for detecting double feeding of sheets, recently, a mechanism using ultrasonic waves has become widespread in various fields. For example, there is one described in (Patent Document 4), and an outline thereof is shown in FIG.

  The multifeed detection device described in this public information is intended for detection of banknotes, and faces each other across the conveyance lines of banknotes 51 and 52 as shown in the schematic diagram of the conventional multifeed detection device in FIG. An ultrasonic transmitter 53 and an ultrasonic receiver 54 are arranged, and a waveform analyzer 55 to which an output signal of the ultrasonic receiver 54 is input is provided.

  The ultrasonic wave transmitted from the ultrasonic transmitter 53 passes through the banknote 51 and is received by the ultrasonic receiver 54 as an ultrasonic signal. Then, it is input as an output voltage to the waveform analyzer 55 and analyzed as an output signal as shown in FIG. 13B, which shows an output waveform on the receiving side in the conventional double feed detection device. Since the ultrasonic wave from the ultrasonic transmitter 53 is attenuated and received by the ultrasonic receiver 54 when passing through the banknote 51, the range of the area A of one banknote 51 is set as a reference signal output. And since the attenuation amount of an ultrasonic wave will increase when the area | region B part where the banknote 51 and the banknote 52 overlapped passes, it analyzes as an output signal of the range of B in FIG.13 (b). Accordingly, by detecting the difference between the reference output signal and the attenuated output signal, it is possible to detect double feeding between the bills 51 and 52.

  Such ultrasonic double sheet detection is similarly employed in the field of preventing double sheet feeding in printers, copiers and printing machines, as described in, for example, (Patent Document 5).

In short, double-feed detection of paper using ultrasonic waves is in advance set based on the ultrasonic wave reception intensity when one sheet passes, and the reception intensity of the actually detected signal is higher than this reference value. The basic idea is that it is judged to be double feed when it is low.
JP 2004-231403 A JP 2005-15121 A JP 2004-231404 A Japanese Patent Laid-Open No. 4-129852 Japanese Utility Model Publication No. 1-115647.

  However, the sensitivity, resonance frequency, and directivity of actual ultrasonic transmission / reception elements vary greatly during manufacture, and the sensitivity and detection timing vary greatly depending on the temperature environment. Even if the thickness of the paper to be passed in advance, such as paper, is determined even if the received intensity is compared between when one thick original passes and when two thin originals pass It becomes difficult to uniquely determine.

  In particular, when using different types of originals such as image scanners, there is a wide range of thickness of sheet-like material such as paper to be passed and the transmittance of ultrasonic waves accompanying it, so it is possible to efficiently and reliably double feed. It has become more difficult to detect.

  In order to solve the above-described problem, the sheet-like member multifeed detection apparatus and the multifeed detection method of the present invention are arranged on one side of the conveyance surface on which the sheet-like member is conveyed. The ultrasonic wave transmitting unit and the ultrasonic wave transmitting unit are provided on the other side of the conveyance surface, the ultrasonic wave receiving unit receiving ultrasonic waves from the ultrasonic wave transmitting unit, and the ultrasonic wave received by the ultrasonic wave receiving unit An ultrasonic output level detection unit for detecting the output level of the ultrasonic wave, and an ultrasonic output level or an ultrasonic center frequency transmitted by the ultrasonic wave transmission unit based on an ultrasonic output level detected by the ultrasonic output detection unit This configuration has an ultrasonic variable section that can vary the sensitivity, resonance frequency, directivity, and other variations of the ultrasonic transmission / reception element, and the effects of sensitivity and detection timing fluctuations depending on the temperature environment. Suppress And one in which it is possible to obtain a double-feed detection device and detection method of the sheet-like member to allow efficient detection with high accuracy.

  The multi-feed detection device and multi-feed detection method for a sheet-like member according to the present invention have the above-described configuration, and are sensitive to temperature environments regardless of variations in sensitivity, resonance frequency, directivity, and the like of ultrasonic transmission / reception elements. And highly accurate and efficient double feed detection that suppresses the influence of detection timing fluctuations.

  According to the first aspect of the present invention, an ultrasonic wave transmitting unit that transmits ultrasonic waves and is disposed on one side of a conveyance surface on which a sheet-like member is conveyed, An ultrasonic receiving unit that is provided on the other side and receives ultrasonic waves from the ultrasonic transmitting unit, an ultrasonic output level detecting unit that detects an output level of ultrasonic waves received by the ultrasonic receiving unit, and an ultrasonic output detection An apparatus for detecting a multi-feed of a sheet member, comprising: an ultrasonic wave variable means for varying an ultrasonic output level and / or an ultrasonic center frequency transmitted by an ultrasonic wave transmission unit based on an ultrasonic wave output level detected by the wave unit Yes, the reception sensitivity can be kept at a constant level by adjusting the transmission level to an appropriate value in advance in order to optimize the reception sensitivity by correcting variations in the reception level of ultrasonic waves, or the transmission frequency can be varied. By most It is possible to select a higher frequency efficiency, has the effect that it is possible to perform efficient detection with high accuracy.

  In the invention according to claim 2 of the present invention, the ultrasonic wave transmitting unit for transmitting ultrasonic waves, which is arranged on one side across the conveyance path through which the sheet-like member is conveyed, and the ultrasonic wave transmitting unit have a conveyance surface. An ultrasonic receiving unit that is provided on the other side and receives ultrasonic waves from the ultrasonic transmitting unit, an ultrasonic output level detecting unit that detects an output level of ultrasonic waves received by the ultrasonic receiving unit, and an ultrasonic output detection Based on the output level of the ultrasonic wave detected by the unit, the output level of the ultrasonic wave transmitted by the ultrasonic wave transmission unit and / or the ultrasonic variable unit for changing the center frequency of the ultrasonic wave, and the variable of the ultrasonic variable unit are controlled. This is a double feed detection device for a sheet member comprising an ultrasonic variable control unit and a storage unit for storing a control value variably controlled by the ultrasonic variable control unit, and corrects variations in ultrasonic reception level to improve reception sensitivity. Appropriate transmission level in advance to optimize It is possible to maintain the reception sensitivity at a constant level by adjusting to a proper value, or to select the frequency with the highest transmission efficiency by changing the transmission frequency, so that highly accurate and efficient detection is performed. Has the effect of being able to.

  In the invention according to claim 3 of the present invention, an ultrasonic wave transmitting unit for transmitting ultrasonic waves, which is disposed on one side of a conveyance path through which the sheet-like member is conveyed, and the ultrasonic wave transmitting unit have a conveyance surface. An ultrasonic receiving unit that is provided on the other side and receives ultrasonic waves from the ultrasonic transmitting unit, an ultrasonic output level detecting unit that detects an output level of ultrasonic waves received by the ultrasonic receiving unit, and an ultrasonic output level A sheet-like member multi-feed detection device comprising an ultrasonic transmission / reception direction variable unit that varies the transmission direction of the ultrasonic transmission unit and / or the reception direction of the ultrasonic reception unit based on the output level detected by the detection unit. Yes, the reception sensitivity can be kept at a constant level by adjusting the transmission level to an appropriate value in advance in order to optimize the reception sensitivity by correcting variations in the reception level of ultrasonic waves, or the transmission frequency can be varied. The most communicated by It is possible to select a frequency higher rate has the effect that it is possible to perform efficient detection with high accuracy.

  In the invention according to claim 4 of the present invention, the ultrasonic wave transmitting unit for transmitting ultrasonic waves, which is disposed on one side of the conveyance path through which the sheet-like member is conveyed, and the ultrasonic wave transmitting unit have a conveyance surface. Ultrasonic wave output unit equipped with an ultrasonic wave reception unit that receives ultrasonic waves from the ultrasonic wave transmission unit, and an ultrasonic wave output level detection unit that detects the output level of ultrasonic waves received by the ultrasonic wave reception unit. The level detection unit detects the output level at regular intervals from the start of ultrasonic transmission by the ultrasonic transmission unit, measures the time until it reaches the reference level, and detects the output level based on the measured time interval Is a sheet feed member double feed detection device that corrects variations in directivity or mounting angle of ultrasonic transmission / reception elements. high It has the effect that it is double feed detection in the state.

  According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect of the present invention, the ultrasonic wave transmitting section and the ultrasonic wave receiving section are the transmitting direction and the receiving direction of the transmitting section and the receiving section. Alternatively, it is a sheet-like member double feed detection device that is movably provided so that both directions can be varied in the radial direction around the attachment axis, and the attachment angle is adjusted to tightly couple the receiver and transmitter. By doing so, it becomes possible to detect double feed in a state where the transmission efficiency is highest.

  According to a sixth aspect of the present invention, in the first, second, fourth or fifth aspect, the ultrasonic variable section adjusts the output level until the output level of the ultrasonic transmission section reaches a predetermined value. This is a double feed detection device that has the effect of being able to correct deviations in double feed detection timing due to environmental temperature fluctuations and the like.

  According to a seventh aspect of the present invention, in the first, second, third, fourth, fifth, or sixth aspect of the invention, the ultrasonic variable section is configured until the output level of the ultrasonic transmission section reaches a predetermined value. This is a multi-feed detection device for sheet-like members that adjusts the output level step by step, and corrects variations in sensitivity or resonance frequency in the ultrasonic transmission element and reception element. In the state where the transmission efficiency on the side is the highest, it is possible to perform double feed detection with low background noise and high detection accuracy.

  The invention according to claim 8 of the present invention has ultrasonic transmission means for transmitting ultrasonic waves across a line for conveying a sheet-like member, and ultrasonic reception means arranged to face the ultrasonic transmission means. A method for detecting the double feed of the sheet-like material based on the output waveform of the ultrasonic wave after passing through the sheet-like member and detecting the output level of the ultrasonic wave transmitted from the ultrasonic wave transmitting means Ultrasonic output level detection means, means for changing the output level of the ultrasonic wave transmitted by the ultrasonic transmission means based on the value detected by the ultrasonic output level detection means, and double feed detection of the sheet-like member for changing the center frequency The device can maintain the reception sensitivity at a constant level by adjusting the transmission level to an appropriate value in advance in order to correct the dispersion of the ultrasonic reception level and optimize the reception sensitivity, or the transmission frequency Variable It is possible to select the frequency having the highest transmission efficiency by Rukoto has the effect that it is possible to perform efficient detection with high accuracy.

  The invention according to claim 9 of the present invention has ultrasonic transmission means for transmitting ultrasonic waves across a line for conveying a sheet-like member, and ultrasonic reception means arranged to face the ultrasonic transmission means. A method for detecting the double feed of the sheet-like material based on the output waveform of the ultrasonic wave after passing through the sheet-like member and detecting the output level of the ultrasonic wave transmitted from the ultrasonic wave transmitting means Ultrasonic output level detecting means, output level varying means for varying the output level of ultrasonic waves transmitted by the ultrasonic transmitting means based on the value detected by the ultrasonic output level detecting means, and center frequency varying means for varying the center frequency A sheet-like member multi-feed detection device comprising: a control means for controlling the output level variable means and the center frequency variable means; and a storage means for storing a control value variably controlled by the control means. In order to correct the bell variation and optimize the reception sensitivity, the transmission sensitivity can be maintained at a constant level by adjusting the transmission level to an appropriate value in advance, or the transmission efficiency can be maximized by changing the transmission frequency. Since it is possible to select a high frequency, it is possible to perform highly accurate and efficient detection.

  According to a tenth aspect of the present invention, in the invention according to the eighth or ninth aspect, the ultrasonic output level detecting means detects the output by sampling at a predetermined interval from the start of transmission of the ultrasonic wave, and the reference level. Is a sheet-like member double feed detection device that measures the time interval until reaching the position and changes the timing of detecting the output by the receiving means according to the time interval, and varies the directivity variation or the mounting angle variation of the ultrasonic transmitting / receiving element. Since the correction is made, the coupling between the receiving means and the transmitting means is made dense, and there is an effect that the double feed can be detected with the highest transmission efficiency.

  According to an eleventh aspect of the present invention, in the invention according to the eighth, ninth or tenth aspect, the ultrasonic wave transmitting means and the ultrasonic wave receiving means are a transmission direction of the transmission means or a reception direction of the reception means or the This is a sheet-type multi-feed detection device that is movable so that both directions can be changed, and corrects variations in the directivity or mounting angle of ultrasonic transmission / reception elements, so that the coupling between the receiving means and the transmitting means is tight. By doing so, there is an effect that double feed detection can be performed with the highest transmission efficiency.

  According to the twelfth aspect of the present invention, the conveying roller feeds the sheet-like member, and the ultrasonic variable unit adjusts the ultrasonic wave transmission level from the ultrasonic wave transmission means until it reaches a specified reception level. A step in which the control unit varies the transmission frequency of the ultrasonic wave in several steps, a step in which the storage unit stores an adjustment value of the transmission level at each transmission frequency of the transmission frequency, and a control unit in the adjustment value in the storage unit More specifically, a method for detecting a multi-feed of a sheet-like member having a step of determining a transmission level and a transmission frequency and a step of detecting a multi-feed of the sheet-like member by a multi-feed determining unit, and correcting variations in the reception level of ultrasonic waves. In order to optimize the reception sensitivity, the transmission sensitivity can be kept at a constant level by adjusting the transmission level to an appropriate value in advance, or the transmission efficiency can be maximized by changing the transmission frequency. It is possible to select a high frequency of, has the effect that it is possible to perform efficient detection with high accuracy.

(Embodiment)
Embodiments of the present invention will be described below.

  FIG. 1 is an external view of an image scanner device including a sheet-like member double feed detection device and a double feed detection method according to an embodiment of the present invention.

  As shown in the figure, the image scanner device comprises a reading unit of an optical system, a main body 1 having a conveyance path for paper P (shown in FIG. 2) as a sheet-like member, and an automatic paper feeder 2 as paper feeding means. Has been. The main body 1 is provided with an operation panel 1a on the front and a control circuit (not shown) for controlling all the components. A collection tray is provided on the upper surface of the main body 1 for receiving the paper P that has been fed from the automatic paper feeder 2 and has been read by the reading unit. FIG. 2 is a schematic view showing a conveyance path of the sheet-like member of FIG.

  The automatic paper feeder 2 has a hopper function for loading the paper P and feeding it to the conveyance path in the main body 1. The paper P is picked up and fed out one by one by the supply roller 3. A pair of a separation roller 4 and a retard roller 5 for preventing double feeding of the paper P is disposed downstream of the supply roller 3, and a conveyance path for the paper P is formed between the roller pair and the collection tray 1b. Has been. A plurality of conveyance rollers 6a and 6b for nipping and conveying the paper P are arranged in the conveyance path of the paper P, and a first scanning sensor 7a and a lower surface for reading a document image on the upper surface of the paper P are disposed in the middle. A second scanning sensor 7b for reading the original image is arranged. One sheet P picked up by the supply roller 3 from the automatic sheet feeder 2 is read by the first and second scanning sensors 7a and 7b while passing through the conveyance path, and then the collection tray 1b. The paper is discharged.

  Further, in the image scanner device, an ultrasonic wave transmission that constitutes a part of a sheet-like member double feed detection device using ultrasonic waves between a pair of separation roller 4 and retard roller 5 and a pair of conveying rollers 6a and 6b. A machine 8 and an ultrasonic receiver 9 are arranged.

  FIG. 3 is a schematic diagram of a double feed detection device according to an embodiment of the present invention.

  In FIG. 3, an ultrasonic transmitter 8 as an ultrasonic transmission means and an ultrasonic receiver 9 as an ultrasonic reception means are arranged opposite to each other across a conveyance path to which a sheet P1 as a sheet-like member is supplied. The ultrasonic transmitter 8 and the ultrasonic receiver 9 are arranged facing each other in the direction orthogonal to the line of the conveyance path as in the prior art, and a controller 10 that executes all the control related to double feed detection. It is connected to the.

  In the present embodiment, a sheet is described as an example of a sheet-like member. However, the present invention is not limited to paper and may be applied to other sheet-like members such as banknotes and films.

  The controller 10 is provided with a circuit for analyzing the output signal by receiving the signal from the ultrasonic receiver 9 and setting the ultrasonic transmission period and transmission time of the ultrasonic transmitter 8. The apparatus structure of the controller in one embodiment of this invention is shown as a schematic block diagram which shows an ultrasonic transmitter and an ultrasonic receiver.

  In FIG. 4, a control unit 11 for controlling the whole is provided, a driving circuit 12 for pulse driving an ultrasonic signal is connected to the ultrasonic transmitter 8, and an amplifier circuit 13 is connected to the ultrasonic receiver 9. Has been. A DA converter 14 that determines the amplitude level of the ultrasonic waveform driven by the drive circuit 12 is provided, and the signal waveform is varied between 200 kHz and 240 kHz with a center frequency of 220 kHz, for example, and input to the drive circuit 12. An ultrasonic generation circuit 16 as an ultrasonic variable means is provided. The output of the amplifier circuit 13 outputs a peak value from which noise and AC components have been removed by an integration circuit 17 as an ultrasonic output level detection unit. Further, this peak value is converted into digital data by the AD converter 18 and detected by the control unit 11.

  As an overall operation of FIG. 4, an ultrasonic wave is transmitted from the ultrasonic transmitter 8 to the ultrasonic receiver 9 based on the input of the signal waveform from the ultrasonic wave generation circuit 16, and according to the transmission coefficient of the sheet material to be passed. The attenuated reception output is input to the control unit 11 as a reception level converted into a digital value by the AD converter 18. The control unit 11 is configured to calculate based on the transmission timing and the attenuation of the output waveform and to output a calculation output for double feed detection by the double feed determination unit. Further, this double feed determination unit (not shown) is controlled by the control unit 11.

  Next, the operation of the sheet-like member double feed detection apparatus and method assembled in this way will be described.

  First, since double feed calibration is performed in order to determine the double feed detection level before paper reading, the operation will be described based on the flowchart of FIG. 6 and the ultrasonic waveform diagram of FIG.

  FIG. 6 is a flowchart for explaining the operation of double feed calibration in the double feed detection apparatus of FIG.

  In the double feed calibration, first, a reference sheet material having a known transmittance is passed (S601).

  Next, the transmission frequency generated by the ultrasonic wave generation circuit 16 is determined. In the first stage, the center frequency of the resonance frequency of the ultrasonic sensor used for the ultrasonic transmitter 8 and the ultrasonic receiver 9 is selected.

(S602)
FIG. 8 shows a sound pressure / frequency characteristic diagram showing the resonance frequency characteristic of the ultrasonic wave transmitting element. In this example, the center frequency of the ultrasonic sensor is 220 kHz, but the half-value width at which the output is halved has a steep characteristic of about ± 10 kHz. As shown in the figure, the center frequency may vary from 200 kHz to 240 kHz for manufacturing reasons.

  As the next step, the transmission output voltage is determined. In the present embodiment, the output voltage can be varied from 0 V to 24 V by varying the value given to the DA converter 14 from 0 to 255.

  Here, a DA value of 80 and a voltage value of 7.5 V are selected as initial values (S603).

  Next, ultrasonic transmission is performed at the specified frequency and voltage. In order to suppress the influence of reflection by the mechanism, ultrasonic wave transmission outputs a burst waveform of several tens of pulses at intervals of several mS as shown in the transmission application waveform of FIG. 7A (S605).

  Since the transmitted ultrasonic wave reaches the ultrasonic receiver 9 after a certain time (after 135 uS in FIG. 7), the reception level is confirmed after the waveform is stabilized (S607).

  As shown in FIG. 7A, the ultrasonic wave transmitted from the ultrasonic transmitter 8 passes through the reference sheet material, the attenuated waveform is received by the ultrasonic receiver 9, and a weak signal of several mV. Is amplified to a level of several volts by the amplifier circuit 13. This signal is detected by the integration circuit 17 as a peak value from which noise and AC components have been removed, and is detected by the control unit 11 as a reception level by the AD converter 18. The reception level is 0 to 1024 at the minimum, and corresponds to the output voltage 0 V to 3 V of the amplifier circuit 13. Here, it is determined that the output level per sheet is 900 or more and the specified level (S608).

  If the reception level is 900 or less, the transmission output voltage is increased by a specified step (20 in this case) until the reception level reaches the specified level (S604).

  Further, when the reception level reaches 900, the transmission frequency and transmission voltage at that time are stored as adjustment values (S609).

  FIG. 7B shows an ultrasonic waveform diagram at this time. By the way, the transmission output adjustment value at this time is 12V (128) and the frequency is 220 kHz.

  When the transmission output is 255 or more and the reception level does not exceed 900 (S606), as will be described later, the transmission frequency is varied at a predetermined step and retries are performed, but the frequency that does not reach the predetermined reception level 900 at all frequency steps. If an adjustment error has occurred, error processing is performed (S613).

  When the center frequency of the ultrasonic sensor to be used is 200 kHz minimum value or 240 kHz maximum value due to manufacturing variations, the sound pressure / frequency characteristics shown in FIG. 8 shows that the output decreases. In this state, the specified reception level cannot be reached no matter how much the transmission output voltage is increased.

  Therefore, after adjustment is performed with the center value of the resonance frequency of the ultrasonic sensor, the same adjustment is repeated for a specified step within a range of variation of the ultrasonic sensor, for example, in increments of 5 kHz, and the transmission frequency and transmission at that time are repeated. The voltage level is stored (S610).

  After adjustment is completed in all frequency steps (S611), the frequency and transmission level with the lowest transmission voltage level are adopted as adjustment values (S612).

  A combination having the lowest transmission voltage and a high reception level has a high transmission coefficient between ultrasonic transmission and reception, and is efficient.

  Thus, the reference sheet material is discharged, the double feed calibration adjustment is completed, and the preparation for executing the operation of performing the double feed detection by using the obtained adjustment value is completed in the actual document reading.

  From here, the operation of the double feed detection device in actual document reading will be described in detail.

  Since the reference sheet material described above is adjusted to a level that secures the output of the original with the largest thickness and the lowest transmittance relative to the thickness of the actually operated original, the normal sheet as shown in FIG. As shown in FIG. 9A, the output when only one sheet of paper P1 is passed becomes a reception level of about 900 or more, and particularly when a thick coated paper or the like is passed, the value is around 900. . Here, when two sheets of P1 and P2 shown in FIG. 5 are stacked, the reception level is 200 or less as shown in FIG. 9B. The thinner the paper, the higher the reception level for double feeding, and the thicker the paper, the lower the reception level for single-sheet feeding. Therefore, the reception level for double-feeding the thickest paper and the thinnest paper is double. The most difficult to distinguish. This level difference is at least about 1: 2 to 1: 1.5, and the reception sensitivity is set by temperature change, transmission level setting, resonance frequency shift of ultrasonic transmitter 8 and ultrasonic receiver 9 and decoupling of coupling. If there is variation, it is obvious that the setting value of the double feed detection level cannot be uniquely determined, and it is easy to erroneously detect, and the importance of the double feed calibration adjustment described above is here.

  Here, if the gain of the amplifier circuit 13 is adjusted by the DA converter 15 shown in FIG. 4, it appears that the same effect can be obtained with respect to erroneous detection, but in practice, it is shown in FIGS. 9 (c) and 9 (d). As shown in FIG. 9D, when the gain of the amplifier circuit is increased as shown in FIG. 9D, the noise level is similarly amplified. It becomes difficult to detect the double feed level below 200. For this reason, it is desirable that the gain of the amplifier circuit 13 be limited to such a level that the control unit 11 detects a temperature change (not shown) and compensates for the overall gain reduction of the receiving circuit. The essence is to determine the double feed detection level after increasing the coupling between the ultrasonic transmitter 8 and the ultrasonic receiver 9 and increasing the SN ratio.

  Next, a second embodiment of the present invention will be described. FIG. 10A shows an attachment portion of the ultrasonic transmitter 8 or the ultrasonic receiver 9 in the second embodiment.

  As shown here, the attachment portion is movable, and the angle can be freely adjusted within a certain range in the radial direction. The user manually adjusts the ultrasonic sensor waveform while checking it on the monitor. Further, it may be connected to a control system so that the angle can be automatically adjusted to each appropriate latitude according to the reception level of the ultrasonic reception sensor. Since the ultrasonic sensor used as shown in the drawing showing the transmission / reception sensitivity directivity of the ultrasonic transmission element of FIG. 11 has high directivity and a half-value width of only ± 3 °, the ultrasonic transmitter is adjusted by adjusting the angle of the mounting portion. The reception level can be increased by adjusting the directivity variation between 8 and the ultrasonic receiver 9 and by tightly coupling them.

  With this configuration, even if the ultrasonic output is set to the maximum value 255 at all frequency steps in the first embodiment, the reception level does not reach the specified value, and error processing is caused by variations in transmission angle or mounting angle. It is possible to avoid an error state.

  Next, a third embodiment of the present invention will be described. 12A shows an ultrasonic wave transmission application waveform, an output from the amplifier circuit 13 and an output waveform (reception level) of the integration circuit 17 when there is no paper P. FIG. Here, the delay from the start of transmission application to the amplifier circuit 13 is 135 uS. This is a sound speed of 340.3 m / S with respect to a distance of 4.5 cm from the ultrasonic transmitter 8 to the ultrasonic receiver 9. Then, it agrees with the calculated value of T1 = 4.5 / 34030 = 132.2 uS. Sampling of the waveform level is started when the waveform is stabilized after a fixed time (in this case, after 50 uS) from detection ON. Here, the output level is sampled every 10 uS, and the detection end (380 uS) is set before sampling is performed 24 times and a reflected wave enters and accurate level detection cannot be performed. The control unit 11 is configured to analyze this waveform and detect double feed.

  However, the speed of sound varies with temperature, for example, 368.1 m / S at 60 ° C., and the delay at this time shifts to T2 = 4.5 / 368100 = 12.2uS. In the application in the apparatus, the internal temperature rises due to the influence of the lamp, the motor, etc., so that a timing shift occurs in the received waveform as shown in FIG.

  Therefore, in the third embodiment of the present invention, the time until the ultrasonic wave is transmitted in the absence of paper and the reception level is periodically sampled and the detection ON start level is reached before the paper is passed through each time. As a program to detect the timing shift and detect the double feed detection by shifting the timing of the double feed detection ON and detection end in the actual paper passing, the double feed detection with high accuracy despite the environmental change Can be done.

  Thus, according to the double feed detection device and the double feed detection method in the embodiment of the present invention, in addition to the conventional double feed detection device, the means for changing the output level of the ultrasonic transmission means and the center frequency are set. By providing means for changing and means for storing each variable level, and providing means for passing a reference sheet material prepared in advance before reading the original, and changing the transmission output and oscillation frequency of the ultrasonic wave The reception sensitivity is set to an appropriate level, the adjustment value at that time is stored in the apparatus, and the double feed detection apparatus during document reading is operated according to the stored adjustment value.

  In addition, regarding the variation in the reception level due to the sensitivity variation of the transmission means and the reception means, the reception sensitivity can be maintained at a constant level by adjusting the transmission level to an appropriate value in advance. Furthermore, when the resonance frequency of the transmission means varies and the appropriate value of the reception level cannot be obtained even if the transmission level is maximized, the frequency with the highest transmission efficiency can be selected by varying the transmission frequency. In addition, since the transmitting means and the receiving means are ultrasonic, the transmission efficiency is greatly reduced and an appropriate value may not be obtained because the directivity is very high even when the mounting angle varies. In such a case, by providing a means for adjusting the mounting angle, and by tightly coupling the receiving means and the transmitting means, it becomes possible to detect double feed in a state with the highest transmission efficiency. For this reason, even with a thick sheet-like member, it is possible to obtain a high S / N reception output with little dark noise, and to realize highly accurate double feed detection.

  In addition, it is a device that detects double feed with an ultrasonic transmitter and an ultrasonic receiver that are provided opposite to the line that conveys the paper, and transmits the reference sheet material as an adjustment value with an appropriate level of transmission output and transmission frequency. This is memorized, and the double feed detection at the time of paper conveyance is performed according to the value. In the present embodiment, it is possible to improve the accuracy of double feed detection by changing only the frequency.

  Furthermore, the reception timing delay is measured, and the detection timing shift due to the environmental temperature change is corrected.

  Furthermore, by providing a mechanical means for adjusting the angle at which the transmitting element and the receiving element face each other, it is possible to suppress poor adjustment due to a decrease in the transmission coefficient due to the directional angle variation in the highly directional ultrasonic element. It becomes like this.

  Further, by transmitting ultrasonic waves before reading a document, monitoring the received waveform, and providing means for correcting the double feed detection timing, it is possible to correct a shift in the double feed detection timing due to environmental changes.

  As described above, according to the present invention, the reference sheet material prepared in advance is provided with means for changing the output level of the means for transmitting ultrasonic waves, means for changing the center frequency, and means for storing each variable level. Is passed before reading the original, and the ultrasonic transmission output and oscillation frequency are varied and the adjustment value is stored in the device. Sensitivity or resonance frequency variation occurs in the ultrasonic transmission and reception elements. Even in such a case, it is possible to correct the variation and to detect double feed with low background noise and high detection accuracy in a state where the transmission efficiency of the transmission side and the reception side is the highest.

  With these configurations, it can be applied to other uses that use ultrasonic transmitters that cause problems such as variations in the center frequency and transmission angle of ultrasonic sensors, mounting errors, and poor detection due to environmental changes. is there.

  The present invention can also be used for a copying machine, a facsimile, an image reading apparatus, and the like that have the above-described configuration and are required to detect double feeding with high accuracy.

FIG. 1 is an external view of an image scanner apparatus including a sheet-like member multifeed detection apparatus and method according to an embodiment of the present invention. Schematic which shows the conveyance path of the sheet-like member of FIG. Schematic of the double feed detection device in one embodiment of the present invention 1 is a schematic block diagram showing an apparatus configuration of a controller according to an embodiment of the present invention including an ultrasonic transmitter and an ultrasonic receiver. FIG. 3 is a schematic diagram of an example in which two sheets are detected in the detection apparatus of FIG. Flowchart for explaining the operation of double feed calibration in the double feed detection device of FIG. Ultrasonic waveform diagram of the double feed detection device during the double feed calibration operation in the double feed detection device of FIG. Sound pressure / frequency characteristic diagram showing resonance frequency characteristics of ultrasonic transmitter Ultrasonic waveform diagram for explaining the double feed detection operation in the double feed detection device and method in the double feed detection device of FIG. The figure which shows the attachment state of the movable ultrasonic transmission / reception device in one embodiment of this invention The figure which shows the transmission and reception sensitivity directivity of the ultrasonic transmission element The figure explaining the influence on the ultrasonic reception waveform by the environmental temperature in one embodiment of this invention, and its correction method (A) Schematic diagram of conventional double feed detection device, (b) Diagram showing output waveform on reception side in conventional double feed detection device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body 1a Operation panel 2 Automatic paper feeder 3 Supply roller 4 Separation roller 5 Retard roller 6a, 6b Conveyance roller 7a 1st scanning sensor 7b 2nd scanning sensor 8 Ultrasonic transmitter (ultrasonic transmission means)
9 Ultrasonic receiver (Ultrasonic receiver)
DESCRIPTION OF SYMBOLS 10 Controller 11 Control unit 12 Drive circuit 13 Amplifier circuit 14, 15 DA converter 16 Ultrasonic wave generation circuit (ultrasonic variable means)
17 Integration circuit (ultrasonic output level detection means)
18 AD converter 51, 52 Banknote 53 Ultrasonic transmitter 54 Ultrasonic receiver 55 Waveform analyzer

Claims (12)

An ultrasonic transmission unit that transmits ultrasonic waves, disposed on one side of the conveyance surface on which the sheet-like member is conveyed;
The ultrasonic wave transmitting unit is provided on the other side across the transport surface and receives an ultrasonic wave from the ultrasonic wave transmitting unit; and
An ultrasonic output level detector that detects an output level of the ultrasonic wave received by the ultrasonic receiver;
An ultrasonic variable unit that varies the output level of the ultrasonic wave transmitted from the ultrasonic wave transmitter and / or the center frequency of the ultrasonic wave based on the output level of the ultrasonic wave detected by the ultrasonic wave output detector. A sheet-like member double feed detection device. An ultrasonic transmission unit that transmits ultrasonic waves, disposed on one side of the conveyance path through which the sheet-like member is conveyed;
The ultrasonic wave transmitting unit is provided on the other side across the transport surface and receives an ultrasonic wave from the ultrasonic wave transmitting unit; and
An ultrasonic output level detector that detects an output level of the ultrasonic wave received by the ultrasonic receiver;
An ultrasonic variable unit that varies the output level of the ultrasonic wave and / or the center frequency of the ultrasonic wave transmitted by the ultrasonic wave transmitter based on the output level of the ultrasonic wave detected by the ultrasonic wave output detector;
An ultrasonic variable control unit for controlling the variable of the ultrasonic variable unit;
A sheet feed member double feed detection device comprising: a storage unit that stores a control value variably controlled by the ultrasonic variable control unit. An ultrasonic transmission unit that transmits ultrasonic waves, disposed on one side of the conveyance path through which the sheet-like member is conveyed;
The ultrasonic wave transmitting unit is provided on the other side across the transport surface and receives an ultrasonic wave from the ultrasonic wave transmitting unit; and
An ultrasonic output level detector that detects an output level of the ultrasonic wave received by the ultrasonic receiver;
Based on the output level detected by the ultrasonic output level detection unit,
An apparatus for detecting double feeding of sheet-like members, comprising: an ultrasonic transmission / reception direction variable unit that varies a transmission direction of the ultrasonic transmission unit and / or a reception direction of the ultrasonic reception unit. An ultrasonic transmission unit that transmits ultrasonic waves, disposed on one side of the conveyance path through which the sheet-like member is conveyed;
The ultrasonic wave transmitting unit is provided on the other side across the transport surface and receives an ultrasonic wave from the ultrasonic wave transmitting unit; and
An ultrasonic output level detector that detects an output level of the ultrasonic wave received by the ultrasonic receiver;
The ultrasonic output level detection unit detects the output level at regular intervals from the start of transmission of ultrasonic waves by the ultrasonic transmission unit and measures the time until both reach the reference level, and based on the measured time interval And a timing for detecting the output level is varied. The ultrasonic transmission unit and the ultrasonic reception unit are movably provided so that the transmission direction and / or the reception direction of the transmission unit and the reception unit can be varied in the radial direction around the mounting axis. The sheet-like member double feed detection device according to claim 1, 2, 3, or 4. The multi-feed detection of a sheet-like member according to claim 1, wherein the ultrasonic variable unit adjusts the output level until the output level of the ultrasonic transmission unit reaches a predetermined value. apparatus. The said ultrasonic variable part adjusts an output level in steps until the output level of the said ultrasonic transmission part reaches a predetermined value, The 1, 2, 3, 4, 5 or 6 characterized by the above-mentioned. Multi-feed detection device for sheet-like members. An ultrasonic wave transmitting means for transmitting an ultrasonic wave across a line for conveying the sheet-like member; and an ultrasonic wave receiving means arranged opposite to the ultrasonic wave transmitting means, and transmitted through the sheet-like member to be attenuated A method for detecting a double feed of a sheet-like material based on an output waveform of a later ultrasonic wave, the ultrasonic output level detecting means for detecting an output level of an ultrasonic wave transmitted from the ultrasonic wave transmitting means, The weight of the sheet-like member is provided with means for changing the output level of the ultrasonic wave transmitted by the ultrasonic wave transmission means and means for changing the center frequency based on the value detected by the ultrasonic output level detection means. Feed detection device. An ultrasonic wave transmitting means for transmitting an ultrasonic wave across a line for conveying the sheet-like member; and an ultrasonic wave receiving means arranged opposite to the ultrasonic wave transmitting means, and transmitted through the sheet-like member to be attenuated A method for detecting a double feed of a sheet-like material based on an output waveform of a later ultrasonic wave, the ultrasonic output level detecting means for detecting an output level of an ultrasonic wave transmitted from the ultrasonic wave transmitting means, Output level varying means for varying the output level of the ultrasonic wave transmitted by the ultrasonic wave transmitting means based on the value detected by the ultrasonic output level detecting means, center frequency varying means for varying the center frequency, and the output level varying means And a control means for controlling the center frequency variable means, and a storage means for storing a control value variably controlled by the control means. The ultrasonic output level detection means detects the output by sampling at a predetermined interval from the start of transmission of ultrasonic waves, measures the time interval until the reference level is reached, and detects the output by the reception means based on the time interval 10. The sheet-like member multifeed detection device according to claim 8 or 9, wherein the timing is variable. The ultrasonic transmission means and the ultrasonic reception means are movable so that the transmission direction and / or the reception direction of the transmission means and the reception means can be varied. The sheet-like member double feed detection device according to claim 10. A step in which the conveyance roller passes the sheet-like member, a step in which the ultrasonic variable unit adjusts an ultrasonic transmission level from the ultrasonic transmission unit until a predetermined reception level is reached, and an ultrasonic variable control unit in the ultrasonic variable unit A step for variably controlling the transmission frequency and output level of the sound wave, a step in which the storage unit stores an adjustment value of the transmission level at each transmission frequency in the transmission frequency, and a transmission level and an adjustment value stored by the control unit A method of detecting a double feed of a sheet-like member, comprising: determining a transmission frequency; and a step of detecting whether or not the double feed of the sheet-like member is detected by a double feed determination unit.

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