JP2019123603A - Sheet conveying device, control method and program for sheet conveying device - Google Patents

Abstract

To provide a sheet conveying device, a control method and a program for the sheet conveying device, capable of performing double feed detection and basis weight detection easily without complicating control, using one set of ultrasonic sensors.SOLUTION: A sheet conveying device includes: conveying means for conveying sheets; transmitting means for transmitting ultrasonic waves toward a conveying path; receiving means disposed opposite to the transmitting means across the conveying path and receiving ultrasonic waves transmitted from the transmitting means; driving means for driving the transmitting means to transmit ultrasonic waves at a first duty ratio to determine double feeding of the sheets, and driving the transmitting means to transmit ultrasonic waves at a second duty ratio different from the first duty ratio to determine a basis weight of the sheet; and determining unit for determining whether or not the sheet is double fed from a received signal of the first Duty ratio ultrasonic wave detected by the receiving means, and determining the basis weight of the sheet from the received signal of the second duty ratio ultrasonic wave which is irradiated to the sheet and detected by the receiving means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sheet conveying apparatus for conveying a sheet. In particular, a sheet conveying apparatus and a sheet conveying apparatus control method, which use an ultrasonic sensor to determine double feeding in which two or more sheets overlap and are conveyed using an ultrasonic sensor, and determine the characteristics of the sheet using the ultrasonic sensor And the program.

2. Description of the Related Art In recent years, there has been known a technique for detecting double feeding in which two or more originals as sheets are conveyed in a sheet conveying apparatus such as a copying machine. When the document is read by the sheet conveying apparatus in the double feeding state, a problem such as failure to read an image of a necessary document occurs.
In order to prevent such a defect, a double feed detection technique is known which determines a double feed using an ultrasonic sensor.

  In double feed detection using an ultrasonic sensor, the sensor on the transmission side for transmitting the ultrasonic wave and the sensor on the reception side for receiving the ultrasonic wave form one set so that the respective sensors face each other through the document conveyance path. Will be installed. A piezoelectric element is incorporated in the ultrasonic sensor, and a pulse voltage of a predetermined cycle is applied to the piezoelectric element to vibrate the piezoelectric element to emit an ultrasonic wave. The ultrasonic sensor on the receiving side installed at the opposite position through the transport path converts the received ultrasonic wave into an electric signal, and it is determined by the output voltage level whether or not double feeding has occurred.

Further, in recent years, there has been a demand from the user for conveying a thick original by a sheet conveying apparatus. Since a thick original is strong in stiffness, if the thick original is transported at the same speed as a thin original, there is a possibility that a paper jam (jamming) or separation failure may occur.
When a thick original is to be conveyed, the user may select a mode for conveying thick paper from the operation unit, but this causes a load on the user. In addition, it is difficult for the user to determine what kind of document is a thick document.
Therefore, it is necessary to automatically detect the thickness of the document, and to convey the thick document at an optimal transport speed. In order to detect the thickness of the document, there is a method using an ultrasonic sensor as in the double feed detection (see, for example, Patent Document 1).

JP, 2011-37524, A

  In order to detect double feed, the output amplitude of the ultrasonic sensor on the receiving side is large in the case of single feed in which one document is fed and in the case of double feed in which two or more documents are overlapped and fed. The transmitting ultrasonic sensor needs to be set to change. Therefore, for the ultrasonic sensor on the transmission side, the frequency, the voltage, and the duty ratio are set such that the efficiency of the characteristic of the ultrasonic sensor is maximized. Therefore, if the signal input to the transmitting ultrasonic sensor is set for double feed detection and the signal is used for basis weight detection as it is, the amplitude level of the reception signal of the receiving ultrasonic sensor is saturated. There is a possibility that the basis weight can not be detected.

  Specifically, in the case of thin paper having a predetermined thickness or less, the amplitude level of the ultrasonic sensor on the receiving side is saturated with the amplitude of the ultrasonic wave output for double feed detection. That is, there is a problem that coexistence of double feeding detection and basis weight detection can not be performed when double feeding detection and basis weight detection are performed using ultrasonic waves of the same setting.

  In patent document 1, double feeding detection and basis weight detection are compatible by the frequency of an ultrasonic wave changing by double feeding detection and basis weight detection. In double feeding and basis weight detection using an ultrasonic sensor, double feeding and basis weight are determined by the maximum amplitude of the received signal. Therefore, in order to detect double feed and basis weight from the received signal, detection control of the received signal needs to be different between double feed detection and basis weight detection.

For example, if double feeding detection transmits 300 KHz ultrasonic waves, and if basis weight detection sends 200 KHz ultrasonic waves, the frequency of the electrical signal obtained by converting the received ultrasonic waves is also 300 KHz when double feeding detection. When the basis weight is detected, it is 200 KHz.
In such a case, when sampling the reception signal level from the electric signal, the maximum value of the amplitude, the sampling time, and the like need to be different between the double feed detection time and the basis weight detection time. As described above, when the frequency of the ultrasonic wave transmitted in double feed detection and basis weight detection changes, the detection control of the received signal needs to be different, and there is a problem that control becomes complicated.

The present invention has been made to solve the above-mentioned problems.
An object of the present invention is to provide a sheet conveying apparatus capable of easily detecting double feeding and basis weight detection without complicating control using one set of ultrasonic sensors, and a control method and program of the sheet conveying apparatus. It is.

The sheet conveying apparatus of the present invention for achieving the above object has the following configuration.
A conveying means for conveying the sheet, a transmitting means for transmitting an ultrasonic wave toward the conveying path in which the sheet is conveyed, and an opposite to the transmitting means with the conveying path interposed therebetween. A receiving means for receiving an ultrasonic wave, and driving the transmitting means so as to transmit an ultrasonic wave with a first duty ratio for determining double feeding of sheets, and for determining the basis weight of the sheet, Driving means for driving the transmitting means to transmit ultrasonic waves at a second duty ratio different from one duty ratio, and the first duty ratio ultra that is emitted to the sheet and detected by the receiving means Based on the received signal of the sound wave, it is determined whether or not the sheet is double feed, and the basis weight of the sheet is determined from the received signal of the second duty ratio ultrasonic wave which is irradiated to the sheet and detected by the receiving means. Discrimination It has a stage, the sheet conveying apparatus characterized by.

  According to the present invention, double feed detection and basis weight detection can be easily performed using one set of ultrasonic sensors without complicating control.

Side cross-sectional view of a schematic configuration of a sheet conveying apparatus according to an embodiment Schematic control block diagram of sheet conveying apparatus Enlarged sectional view showing the structure near the ultrasonic sensor Diagram showing the principle of double feed detection Detailed circuit diagram of amplifier circuit and AD converter circuit Explanatory drawing of the amplitude detection method of the receiving wave of an ultrasonic wave reception sensor Characteristic diagram of duty ratio of burst wave and ultrasonic sensor output Diagram showing the relationship between basis weight, burst wave Duty ratio and reception level at double feed detection An illustration of the method of double feed detection and basis weight detection Diagram showing the relationship between reception level and basis weight range Flow chart showing control of double feed detection and basis weight detection of sheet conveying apparatus according to an embodiment

  Hereinafter, exemplary embodiments of the present invention will be exemplarily described in detail with reference to the drawings. However, the components described in this embodiment are merely examples, and the scope of the present invention is not limited to them.

FIG. 1 is a side sectional view of a schematic configuration of a sheet conveying apparatus according to an embodiment of the present invention.
In FIG. 1, a sheet conveying apparatus 100 has a function of conveying a document, which is a sheet, and reading an image of the document. The document 102 is stacked on the document tray 101 by the user. A document size detection sensor (not shown) for detecting the size of the document 102 is installed on the document tray 101. Further, a tray document detection sensor S1 for detecting the presence or absence of a tray document is disposed downstream of the document tray 101, and the document 102 is stacked at a position where the document 102 can be fed based on the output of the tray document detection sensor S1. If the apparatus is in operation, it is detected whether the next original 102 is present.

  A paper feed roller 103 is provided downstream of the tray document detection sensor S1. The feed roller 103 is connected to the same drive source (actuator) as the separation transport roller 104, rotates in conjunction with the rotation of the drive source, and feeds the original 102. The sheet feed roller 103 is normally retracted to the upper position, which is the home position, so that the setting operation of the document 102 is not hindered. When the sheet feeding operation is started, the sheet feeding roller 103 descends and contacts the upper surface of the document 102. The paper feed roller 103 is pivotally supported by an arm (not shown), and moves up and down by swinging the arm.

  The separation driven roller 105 is disposed on the opposite side of the separation conveyance roller 104, and is pressed to the separation conveyance roller 104 side. The separation driven roller 105 is formed of a rubber material or the like which has a little friction less than the separation conveyance roller 104, and cooperates with the separation conveyance roller 104 to copy the originals 102 fed by the paper feed roller 103 one by one Roll and feed. The post-separation sensor S2 is a sensor for detecting that the document 102 has passed through the separation driven roller 105 and the separation conveyance roller 104.

  The ultrasonic wave transmission sensor T1 as the transmission means and the ultrasonic wave reception sensor T2 as the reception means are disposed to face each other via the document conveyance path. The ultrasonic wave transmission sensor T1 transmits an ultrasonic wave to the document 102 passing through the document conveyance path sandwiched between these two sensors, and the ultrasonic wave reception sensor T2 receives the ultrasonic wave, thereby overlapping the document 102. And detection of the sheet thickness and sheet type of the original 102 are performed. The registration roller 106 and the registration driven roller 107 align the leading end of the document 102 fed by the separation unit. That is, the leading end of the original 102 abuts against the nip portion of the registration roller 106 and the registration driven roller 107 which are stationary, and the leading end is aligned by causing the original 102 to bend (loop).

  The lead roller 108 and the lead driven roller 109 convey the original 102 toward the flow reading glass 116. A platen guide 110 is disposed on the opposite side of the reading glass 116. The CCD line sensor 126 reads image information of the surface of the document 102 passing on the reading glass 116. When the surface image reading of the document 102 by the CCD line sensor 126 is completed, the read discharge roller 111 and the read discharge driven roller 112 convey the document 102 to the discharge roller 113 side.

  The jump stand 117 scoops the document 102 from the reading glass 116. The paper discharge roller 113 discharges the original 102 onto the paper discharge tray 114. The image reading unit 115 has a lamp 119 for irradiating light to the surface of a reading document, and mirrors 120, 121, and 122 for guiding reflected light from the document 102 to the lens 125 and the CCD line sensor 126. The lamp 119 and the mirror 120 are attached to the first mirror base 123. The mirrors 121 and 122 are attached to the second mirror stand 124.

  The mirror mounts 123 and 124 are coupled to a drive motor (not shown) by wires (not shown), and move parallel to the document mount glass 118 by rotational drive of the drive motor. In addition, a reference white plate 127 serving as a reference of luminance is attached to an end portion of the original table glass 118. Reflected light from the document 102 is guided to a lens 125 via mirrors 120, 121, 122, and is focused on a light receiving portion of a CCD line sensor 126 by the lens 125. The CCD line sensor 126 photoelectrically converts the formed reflected light by the light receiving element, and outputs an electric signal according to the amount of incident light.

FIG. 2 shows a schematic control block diagram of the sheet conveying apparatus 100 according to the present embodiment.
In FIG. 2, a document conveyance motor 202 is for driving conveyance rollers in the sheet conveyance apparatus 100, and is controlled by the CPU 201. The CPU 201 performs detection of the output of the tray original detection sensor S1 and the sensor S2 after separation described above, control of the ultrasonic wave transmission sensor T1, ultrasonic wave reception sensor T2 and the like, control of AD conversion timing of the AD conversion circuit 205, and the like. .

  The ultrasonic wave drive circuit 203, which is a driving means, receives from the CPU 201 a signal for generating a burst wave of a frequency (300 KHz in this embodiment) close to the resonance frequency of the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2. A burst wave having a voltage necessary for driving the ultrasonic wave transmission sensor T1 is output. The ultrasonic wave transmission sensor T1 receives a burst wave from the ultrasonic wave drive circuit 203, and transmits ultrasonic waves toward the ultrasonic wave reception sensor T2. The ultrasonic wave reception sensor T2 receives the ultrasonic wave transmitted by the ultrasonic wave transmission sensor T1, converts the received ultrasonic wave signal into an electric signal, and outputs the electric signal to the amplification circuit 204.

  The amplification circuit 204 amplifies the voltage of the reception signal received from the ultrasonic wave reception sensor T2 and outputs it. The AD conversion circuit 205 performs AD conversion on the reception signal amplified by the amplification circuit 204 according to an AD conversion timing instruction signal output from the CPU 201, and outputs an AD value after AD conversion to the CPU 201. The CPU 201 calculates the amplitude level of the received wave from the output AD value of the AD conversion circuit 205, and determines the presence or absence of double feeding of the conveyed document 102. The memory 206 is for storing the output AD value of the AD conversion circuit 205 and the like.

  FIG. 3 is an enlarged cross-sectional view showing the structure in the vicinity of the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2 which constitute the sheet conveying apparatus. In this embodiment, the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2 are attached at an angle with respect to the document conveyance path 301 on which the document 102 is conveyed. This is because, when the sensors T1 and T2 are attached perpendicularly to the document conveyance path 301, the ultrasonic wave is reflected between the ultrasonic wave receiving sensor T2 and the document 102 when the ultrasonic waves are transmitted at the time of document passing. Is repeated to prevent the accuracy of double feed detection from being deteriorated.

  The ultrasonic wave emitted from the ultrasonic wave transmission sensor T1 passes through the document 102 and propagates to the opposite side, is received by the ultrasonic wave reception sensor T2 and its reception intensity is converted into voltage amplitude. The voltage amplitude is amplified by the amplifier circuit 204, and then AD converted by the AD conversion circuit 205. The CPU 201 determines double feed and basis weight of the document 102 based on the AD value.

The principle of determining "single feed" and "double feed" of a conveyed document using the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2 will be described with reference to FIG.
FIG. 4A shows an input signal waveform to the ultrasonic wave transmission sensor T1 in a state where the document 102 is not present on the document conveyance path 301 sandwiched by the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2 (when no paper is present). And the output waveform of the ultrasonic wave reception sensor T2 are shown. FIG. 4B is an ultrasonic wave transmission sensor in a single-feed state (in the presence of paper) in which one original 102 is present in the document conveyance path 301 sandwiched between the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2. The relationship between the input signal waveform to T1 and the output waveform of ultrasonic wave reception sensor T2 is shown. FIG. 4C shows an ultrasonic wave transmission sensor in a double feeding state (with paper) in which two sheets of the document 102 exist in the document conveyance path 301 sandwiched between the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2. The relationship between the input signal waveform to T1 and the output waveform of ultrasonic wave reception sensor T2 is shown.

  In FIG. 4, “ultrasonic transmission sensor T1 input” is a burst wave that the ultrasonic transmission sensor T1 receives from the ultrasonic drive circuit 203. The “ultrasonic wave reception sensor T2 output” is an output signal obtained by converting the ultrasonic wave received by the ultrasonic wave reception sensor T2 from the ultrasonic wave transmission sensor T1 into an electrical signal. The delay of "ultrasonic wave reception sensor T2 output" with respect to the burst wave of "ultrasonic wave transmission sensor T1 input" is an ultrasonic wave from ultrasonic wave transmission sensor T1 transmitting ultrasonic wave to reception sensor T2 receiving ultrasonic wave It corresponds to the arrival time.

  As compared with the case where the original 102 is not present between both sensors (FIG. 4 (a)), the ultrasonic wave transmits the original 102 when the single original 102 is present between both sensors (FIG. 4 (b)). At the same time, the amplitude of the ultrasonic wave is greatly attenuated. At this time, when there are a plurality of originals (FIG. 4C), the large attenuation occurs a plurality of times, so the amplitude of the ultrasonic wave transmitted through the plurality of originals is one original. It attenuates further compared to. As a result, a difference occurs between the amplitude of the received wave at "single feed" and the amplitude of the received wave at "double feed" (the amplitude at "double feed" is smaller), and based on this difference, Determine the presence or absence of double feed.

  Although the attenuation of ultrasonic waves varies depending on the thickness and type of the original 102, the difference between the attenuation of the number of originals (one or more) is better than the variation of the attenuation depending on the thickness and type of the original 102. Because it is overwhelmingly large, it is possible to determine the presence or absence of double feeding regardless of the thickness and type of the document.

FIG. 5 is a detailed circuit diagram of the amplifier circuit 204 and the AD converter circuit 205 shown in FIG.
The amplification circuit 204 is configured by a plurality of stages of amplification circuits in order to perform large amplification on a minute signal from the ultrasonic wave reception sensor T2. Here, the amplifier circuit 204 is formed of two stages of inverting amplifier circuits 501 and 502 connected in series.
The output of the first-stage inverting amplification circuit 501 of the amplification circuit 204 is input to the paper presence AD converter 504 of the AD conversion circuit 205 through the second-stage inverting amplification circuit 502, and also has two stages. The signal is directly input to the AD converter 503 for no paper without passing through the inverting amplifier circuit 502 of the eye.

  This configuration corrects the change in the attenuation of the ultrasonic wave from the ultrasonic wave transmission sensor T1 to the ultrasonic wave reception sensor T2 which fluctuates depending on the ultrasonic sensor sensitivity variation, the ambient temperature, and the mechanical relative position of the reception sensor and the transmission sensor. “Detection in the absence of a document” is performed. Furthermore, it is for performing “detection in a state where there is no document” for correcting the change of the arrival time of the ultrasonic wave from the ultrasonic wave transmission sensor T1 to the ultrasonic wave reception sensor T2 which fluctuates for the same reason.

  As described above, the attenuation amount of the ultrasonic wave is largely different between the state where the document 102 is not present in the document conveyance path 301 and the state where the document 102 is present. Therefore, when the signal is measured at the same amplification factor, the received signal is saturated (amplitude is too large, exceeding the output voltage range of the amplifier circuit 204 or exceeding the input voltage range of the AD conversion circuit) or crushed (amplitude in any state) Is too small to be buried in the dark noise). As a result, the received wave can not be measured correctly. Therefore, when performing "detection in a state in which the document 102 is not in the document conveyance path 301" for performing the correction, the CPU 201 does not go through the second stage inverting amplification circuit 502, that is, the amplification factor is small. The above correction is performed on the basis of the output AD value of the AD converter 503 when there is no paper.

  Note that it is desirable that the correction of the absence of the document 102 in the document conveyance path 301 be performed immediately before the passage of the document. That is because the ambient temperature of the ultrasonic sensor and the mechanical relative position of the reception sensor and the transmission sensor are almost the same at the time of detection immediately before the passage of the document and at the time of detection of the passage of the document. It is possible to correct the

A method of detecting the amplitude of the output reception signal of the ultrasonic wave reception sensor T2 will be described with reference to FIG.
The AD conversion circuit 205 performs discrete sampling and AD conversion on the reception signal amplified by the amplification circuit 204 from the time when the AD conversion start signal from the CPU 201 is received. The range for discrete sampling and AD conversion is a period of an arbitrary one cycle of the received signal waveform (in this embodiment, one cycle is 3.3 μs because ultrasonic waves are transmitted at 300 KHz). The start timing of the AD conversion at this time is a timing at which the amplitude of the received signal wave becomes maximum (for example, A in FIG. 6).

In order to correctly detect the amplitude of the received waveform, the sampling interval needs to be sufficiently smaller than the ultrasonic wave transmission period. In this embodiment, since the ultrasonic wave transmission sensor T1 transmits an ultrasonic wave of 300 KHz, the cycle is 3.3 μs. For example, when the CPU 201 performs eight samplings with respect to this cycle, the sampling interval is 0.41 μs. Become. As described above, sampling and AD conversion are performed at sufficiently small intervals with respect to the period of the ultrasonic wave, and the CPU 201 obtains the difference between the minimum value and the maximum value among them, and thereby, an arbitrary one wave of the reception wave. Calculate the amplitude.
In the example of FIG. 6, the difference between the minimum value and the maximum value of the eight sampling values A, B, C, D, E, F, G, and H is the amplitude.

The relationship between the burst wave of each duty ratio input to the ultrasonic wave transmission sensor T1 and the signal level of the transmission wave from the ultrasonic wave transmission sensor T1 will be described with reference to FIG.
FIG. 7A is a waveform diagram of a burst wave with a duty ratio of 50% input to the ultrasonic wave transmission sensor T1. For example, assuming that the width of the high level is 50 μs when one cycle T of the burst wave is 100 μs,
Duty ratio = (50 μs / 100 μs) × 100 = 50 (%)
The duty ratio is 50%.

7B shows the case where the width of the High level of the burst wave input to the ultrasonic wave transmission sensor T1 is 40 μs, and the duty ratio is 40%. FIG. 7C shows the case where the width of the high level of the burst wave input to the ultrasonic wave transmission sensor T1 is 30 μs, and the duty ratio is 30%.
In FIG. 7D, the horizontal axis indicates the duty ratio of the burst wave input to the ultrasonic wave transmission sensor T1, and the vertical axis indicates the sensitivity of the output level of the transmission wave from the ultrasonic wave transmission sensor T1.

The ultrasonic wave transmission sensor T1 has a built-in piezoelectric element. When a burst wave is input to the piezoelectric element, electric energy is applied to the piezoelectric element, and the piezoelectric element vibrates to transmit an ultrasonic wave. As shown in FIG. 7D, ultrasonic waves are most efficiently transmitted when the duty ratio of the burst wave input to the ultrasonic wave transmission sensor T1 is 50%. The output signal level of the ultrasonic wave transmission sensor T1 is low even if the duty ratio of the burst wave is higher or lower than 50%.
In this embodiment, as described later, the CPU 201 sets the duty ratio to 50% at which the signal level of the transmission wave becomes highest when performing double feed detection, and when performing basis weight detection, the duty ratio is set to It is set to a value at which the signal level of the transmission wave becomes lower, ie, a value shifted from 50%.

Next, the relationship between the duty ratio of the burst wave and the reception level at the time of basis weight detection and double feed detection will be described using FIG.
FIG. 8A shows the basis weight when the duty ratio of the burst wave to the ultrasonic wave transmission sensor T1 is set to 50%, 30%, and 15% in the case of single-feed transporting one sheet of document. The relationship between (the thickness of the document: horizontal axis) and the reception level characteristic (vertical axis) of the ultrasonic wave reception sensor T2 is shown.

When the duty ratio of the burst wave is 50%, the reception level of the ultrasonic wave receiving sensor T2 changes relatively linearly with respect to the size of the basis weight for an original whose basis weight is larger than a predetermined value. That is, by detecting the reception level, it is possible to determine what the basis weight of the document being conveyed is.
However, in the case of an original whose basis weight is less than a predetermined value, the amount of attenuation of ultrasonic waves transmitted through the original decreases, so the reception level of the ultrasonic wave reception sensor T2 reaches a limit value at which the reception signal can swing and is saturated. Resulting in. That is, when the duty ratio is set to 50%, in the case of a document having a basis weight of a predetermined value or less, the reception level is saturated and the basis weight of the document can not be determined.

  As described above, if the duty ratio of the burst wave is set to a value shifted from 50%, the ultrasonic wave irradiated to the document becomes weak, so even in the case of a document having a relatively small basis weight, the reception level is the basis weight It changes relatively linearly with the size. Therefore, when the duty ratio of the burst wave is set to, for example, 30%, the reception level is relatively linear with respect to the size of the basis weight even in the case of an original having a small basis weight, as compared to the case where it is set to 50%. Change to When the duty ratio of the burst wave is set to a lower value, for example, 15%, the basis weight of the original can be determined even for an original having a smaller basis weight.

  FIG. 8 (b) shows the relationship between the reception level of the ultrasonic wave receiving sensor T2 and the basis weight in the case of single transmission and double transmission, when the duty ratio of the burst wave is set to 50%. When double feed detection is performed, the reception level is small regardless of the basis weight in the double feed state, as described in FIG. On the other hand, in the single-feed state, the reception level of the ultrasonic wave receiving sensor T2 is lower as the basis weight is larger, so when the duty ratio is set to 15%, for example, The latitude of is reduced (see FIG. 8 (a)). Therefore, the risk of erroneously detecting that the document is in the single feed state but in the double feed state is increased. Therefore, in the case of double feed detection for determining single feed / double feed, it is preferable that the duty ratio of the burst wave be set to 50%.

  From the above, it is difficult to detect the basis weight of a document having a small basis weight when performing basis weight detection using the burst wave duty ratio suitable for double feed detection. Therefore, as described above, it is necessary to make the discrimination by making the duty ratio of the burst wave different between the basis weight detection and the double feed detection.

Next, features of the control method of the sheet conveying apparatus of the present embodiment will be described with reference to FIG.
FIG. 9A is a view schematically showing the document transport direction and the operation of irradiating the document with ultrasonic waves. The details are omitted because they overlap with the explanation of FIG.
FIG. 9 (b) shows the portion irradiated for double feed detection and the portion irradiated for basis weight detection when the document is irradiated with ultrasonic waves as shown in the schematic view of FIG. 9 (a). FIG. FIG. 9C shows a burst wave from the ultrasonic wave transmission sensor T1 and an ultrasonic wave corresponding thereto when the double feed detection and the basis weight detection are alternately performed using the ultrasonic wave transmission sensor T1 and the ultrasonic wave reception sensor T2. Fig. 7 schematically shows the reception waveform of the reception sensor T2.

As described above, in the double feed detection, ultrasonic waves are irradiated from the front end side of the document, and it is necessary to immediately stop the feeding of the document when it is detected that the double feed occurs. Since the basis weight detection can not detect the correct basis weight at the time of single feeding of the document, it is performed at timing after the first double feeding detection. Further, in the basis weight detection, since the basis weight does not significantly change in one sheet of document, it is not necessary to always detect from the front end to the rear end of the document. Therefore, basis weight detection is sufficient with sampling at one to three places on the front end side of the document.
Specifically, the ultrasonic wave transmission sensor T1 intermittently irradiates ultrasonic waves of duty ratio for basis weight detection sequentially to a plurality of places of the document, and the ultrasonic wave reception sensor T2 sequentially receives the ultrasonic waves. Then, the CPU 201 averages AD values of reception levels (amplitudes) acquired at a plurality of places sequentially to obtain data in which the variation in detected data per place is corrected, and the basis weight determination is high. Made to accuracy.

Next, how to determine the basis weight will be described.
FIG. 10 is a table showing AD values of reception levels (amplitudes) obtained by measuring as described above for each document of a known predetermined basis weight range. For example, it is shown that the AD value of an original having a basis weight in the range of 180 to 200 gsm is 170 to 180. A high AD value indicates that the amplitude of the received signal is large, and a low AD value indicates that the amplitude is small.

Next, how to identify the basis weight range from the AD value of the reception level (amplitude) obtained by measurement will be described.
In the sheet conveying apparatus 100, data shown in FIG. 10 obtained in an experiment or the like is stored in advance in the memory 206 as a table. Next, the ultrasonic wave transmission sensor T1 transmits an ultrasonic wave of duty ratio for basis weight detection from the ultrasonic wave transmission sensor T1 as described above to the conveyed document to be measured, and the signal level (amplitude) received from the ultrasonic wave reception sensor T2. Get the AD value of The CPU 201 searches which AD value range the obtained AD value belongs to as shown in FIG. 10, obtains the basis weight range corresponding to the searched AD value range, and specifies it as the basis weight range of the conveyed document. Do.

  A specific example of the method of specifying the basis weight range will be described. For example, assuming that the AD value of the reception level (amplitude) obtained by measurement is 200, the CPU 201 searches the data of FIG. 10 stored in the memory 206 for the basis weight range corresponding to the AD value 200. . In this case, since the basis weight range corresponding to the AD value 200 is 120 to 179 gsm, it can be determined that the document of at least the basis weight range has been conveyed.

Next, the sheet discrimination operation in the sheet conveying apparatus 100 according to the present embodiment will be described using the flowchart shown in FIG.
A program operating on the sheet conveying apparatus 100 according to the flowchart is stored, for example, in a ROM (not shown), read out to a RAM (not shown), and executed by the CPU 201. Moreover, in the following description, the code | symbol S shows a step.

  The CPU 201 receives a JOB start signal from the outside, and starts execution of JOB (S101). Next, the CPU 201 drives the ultrasonic wave transmission sensor T1 by the burst wave of the duty ratio for the absence of paper in a state where the document 102 is not present in the document conveyance path 301 (S102). The duty ratio of the burst wave for the absence of paper here may be the same as the duty ratio of the burst wave for double feed detection. An ultrasonic wave is received by the ultrasonic wave receiving sensor T2, and AD0 which is an AD value of the reception level (amplitude) of the burst wave for absence of paper is calculated (S103). Next, the CPU 201 sets a predetermined level for double-feed determination, that is, a threshold value ADth based on the detected value AD0 (S104). The threshold value ADth for discrimination of double feeding is the reception level AD value in the state where there is one document in the document conveyance path 301 shown in FIG. 4B described above, and the document conveyance path shown in FIG. It is appropriately set between the reception level AD value in the state where there are two originals.

Next, the CPU 201 initializes the value N of a basis weight counter (not shown) in the CPU 201 that counts the number of times of basis weight detection (S105). When sheet feeding is started in S106, the process proceeds to the double feed detection flow.
In the double feed detection flow, first, the CPU 201 sets the duty ratio of the burst wave (S107). Although the duty ratio k of the burst wave for double feed detection is set to 50% in this embodiment, the present invention is not limited to this but other arbitrary numerical values capable of double feed detection, for example, a value around 50% may be set. Good. When the duty ratio of the burst wave for double feed detection is set, the CPU 201 outputs a signal for causing the ultrasonic drive circuit 203 to output the burst wave for double feed detection (S108). As a result, the ultrasonic wave transmission sensor T1 is driven to transmit ultrasonic waves. Then, an ultrasonic wave is received by the ultrasonic wave reception sensor T2, and the CPU 201 acquires an AD value AD1 of the reception level (amplitude) (S109).

  Next, the CPU 201 determines whether the acquired AD value AD1 is equal to or more than the predetermined level set in S104, that is, the threshold value ADth for double-feed determination (S110). If AD1 is smaller than a predetermined level, that is, smaller than ADth, the CPU 201 determines that the multi-feed state is set, and stops the conveyance of the document (S121). If AD1 is equal to or greater than ADth, the CPU 201 determines that the single-feed state is set, and advances the process to step S111. The above-described processing from S107 to S110 is a double feed detection flow.

  In S111, the CPU 201 determines whether the value N of the basis weight detection counter is less than a predetermined number (here, 3). If N is less than 3, the process proceeds to a basis weight detection flow, and if N is 3 or more, the CPU 201 determines in S122 that the trailing edge of the document is overlapped with the ultrasonic wave transmission sensor T1 based on the output of the sensor S2. It is determined whether or not it has passed between the sound wave reception sensor T2. If it is determined in S122 that the rear end of the document has not passed, the process returns to S107, and the CPU 201 executes the double feed detection flow again. On the other hand, if it is determined that the rear end of the document has passed, the CPU 201 determines whether or not the next document is present. If the next document is present, the process returns to step S105. The processing of 11 ends.

  In the basis weight detection flow, the CPU 201 first sets the duty ratio k of the burst wave for basis weight detection to 15% (S112). The duty ratio of the burst wave for basis weight detection is not limited to this, and may be set to any other numerical value capable of basis weight detection, for example, a value of around 15%. Next, the CPU 201 outputs a signal for causing the ultrasonic drive circuit 203 to output a burst wave for basis weight detection (S113). As a result, the ultrasonic wave transmission sensor T1 is driven to transmit an ultrasonic wave, and the ultrasonic wave reception sensor T2 receives the ultrasonic wave. The CPU 201 acquires the AD value AD2 of the reception level (amplitude) (S114). Next, in S115, the CPU 201 determines whether the value N of the basis weight detection counter is 1 or not. If the counter value is 1, the CPU 201 stores the AD value AD2 in the memory 206 and adds one to the value N of the basis weight detection counter (S120). Thereafter, the process proceeds to S122.

  On the other hand, if the value N of the basis weight detection counter is determined to be 2 in S115, the CPU 201 determines that the AD value AD2 stored in the memory 206 in S119 when the value N is 1 and the current N is 2 The average value AD2ave of the reception level with the AD value AD2 is calculated (S116). Note that the AD value stored in the memory 206 at this point may be cleared. Next, the CPU 201 refers to the data (FIG. 10) stored as a table in the memory 206 (S117), identifies which range of basis weight the average value AD2ave belongs to, and identifies the original to be discriminated It is determined that it has a basis weight within the specified range (S118). Thereafter, the process proceeds to S122. The above-described processing from S112 to S120 is a basis weight detection flow.

According to the above embodiment, double feeding detection and basis weight detection can be performed by one set of ultrasonic sensors. Furthermore, in basis weight detection, by setting the duty ratio of the burst wave to a value different from the duty ratio in double feed detection, it becomes possible to determine the basis weight of the document in a wide range from thin paper to thick paper.
In the above embodiment, the basis weight detection flow is executed twice, and the basis weight is determined from the average value of the AD value of the reception level (amplitude) obtained there. The basis weight may be determined from the AD value of the obtained reception level (amplitude) with reference to the table of FIG. Alternatively, the basis weight detection flow may be performed three or more times, and the basis weight may be determined from the average value of AD values of the reception level (amplitude) obtained there.

  In the above embodiment, basis weight detection and double feed detection are alternately performed. However, double feed detection is performed after the basis weight detection is performed plural times continuously (or once) on the front end side of the document. You may do so. In this case, after calculating the AD value AD2 of the reception level (amplitude) in the basis weight detection flow, the CPU 201 determines that the AD value AD1 of the reception level (amplitude) is equal to or greater than ADth in the double transmission detection flow and is not double transmission. In this case, the basis weight is determined based on the AD value AD2 calculated in the basis weight detection flow.

Next, document conveyance control and the like according to the determined basis weight will be described.
Optimal design for each basis weight is realized by performing control to increase or decrease the drive current value of an actuator (specifically, a stepping motor) for driving a mechanical member such as a roller that transports a document according to the basis weight. it can. In this case, as compared to control in which the drive current value of the motor is uniformly set to the same current value regardless of the basis weight, the drive current can be set to an optimum drive current according to the basis weight, and hence power consumption can be reduced.

In the case of a document whose determined basis weight is larger than a predetermined basis weight, jamming or the like can be suppressed by reducing the speed of the stepping motor for conveying the document.
On the other hand, in the case of a document whose determined basis weight is smaller than a predetermined basis weight, the read image becomes defective by adjusting the amount of light emitted by the lamp 119 (specifically, the amount of light is too strong) And the phenomenon of reading the image on the back side can be suppressed.

  As described above, the sheet discriminating apparatus according to the present invention includes the transmitting means (the transmitting sensor T1), the receiving means (the receiving sensor T2), the driving means (the ultrasonic wave drive circuit 203), and the determining means (the CPU 201, the memory 206, etc.) ). The transmitting means transmits ultrasonic waves toward the transport path 301 on which the sheet (original) 102 is transported, and the receiving means is disposed to face the transmitting means across the transport path, and the ultrasonic waves transmitted from the transmitting means are transmitted. To receive. The driving means drives the transmitting means to transmit an ultrasonic wave with a first duty ratio for determining double feeding of sheets, and is different from the first duty ratio for determining a basis weight of sheets. The transmitting means is driven to transmit ultrasonic waves at the second duty ratio. The discriminating means discriminates whether or not double feeding of the sheet is performed from the received signal of the ultrasonic wave of the first duty ratio which is irradiated to the sheet and detected by the receiving means, and the sheet is irradiated and detected by the receiving means The basis weight of the sheet is determined from the received signal of the second duty ratio ultrasonic wave.

According to the sheet conveying apparatus of this embodiment configured as described above, double feeding detection and basis weight detection can be easily performed without complicating control using one set of ultrasonic sensors. Become.
The present invention is also applicable to a sheet feeding unit for feeding a sheet used for printing in an image forming apparatus.

(Other embodiments)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

Reference Signs List 100 sheet conveying apparatus 115 image reading unit T1 ultrasonic wave transmission sensor T2 ultrasonic wave reception sensor 201 CPU
203 Ultrasonic drive circuit

Claims (10)

Transport means for transporting the sheet;
Transmitting means for transmitting an ultrasonic wave toward the transport path along which the sheet is transported;
Receiving means disposed opposite to the transmitting means with the transport path interposed therebetween, and receiving ultrasonic waves transmitted from the transmitting means;
A second different from the first duty ratio for driving the transmitting means to emit ultrasonic waves with a first duty ratio for determining double feeding of the sheet and for determining the basis weight of the sheet Driving means for driving the transmitting means to transmit ultrasonic waves at a duty ratio of
It is determined whether or not double feeding of the sheet is performed from the received signal of the ultrasonic wave of the first Duty ratio which is irradiated to the sheet and detected by the receiving means, and the sheet is irradiated and detected by the receiving means Determining means for determining the basis weight of the sheet from the received signal of the ultrasonic wave of the second duty ratio;
A sheet conveying apparatus comprising:   The second judging means judges that the sheet is not double-fed from the reception signal of the ultrasonic wave of the first duty ratio irradiated to the sheet, when the judging means judges that the double feeding of the sheet is not performed. 2. The sheet conveying apparatus according to claim 1, wherein the basis weight of the sheet is determined from a received signal of an ultrasonic wave of Duty ratio.   The discrimination means detects the basis weight of the sheet from the received signal of the ultrasonic wave of the second duty ratio irradiated to the sheet, and then the sheet is irradiated by the sheet and detected by the reception means. The basis weight of the sheet is determined as the basis weight of the sheet when it is determined that double feeding of the sheet is not made from the received signal of the ultrasonic wave of the first Duty ratio. Sheet transport device.   The determination means determines whether or not double feeding of the sheet is made from a received signal by the receiving means of the ultrasonic wave of the first duty ratio irradiated from the transmitting means to the front end side of the sheet. The sheet conveying apparatus according to any one of claims 1 to 3.   The discrimination means determines the basis weight of the sheet from the reception signal by the reception means of the ultrasonic wave of the second duty ratio irradiated from the transmission means to a plurality of places of the sheet. The sheet conveying apparatus according to any one of 1 to 4.   The determination means is based on an average value of reception signals obtained by the reception means sequentially receiving the ultrasonic waves of the second duty ratio sequentially applied from the transmission means to a plurality of places along the sheet conveyance direction. 5. The sheet conveying apparatus according to claim 4, wherein the basis weight of the sheet is determined.   The sheet conveying apparatus according to any one of claims 1 to 6, wherein the second duty ratio is smaller than the first duty ratio.   8. The sheet feeding apparatus according to any one of claims 1 to 7, wherein the discrimination means discriminates double feeding of the sheets when the signal received by the reception means of the ultrasonic wave of the first duty ratio is less than a predetermined level. The sheet conveying device according to item 1. A conveying means for conveying the sheet, a transmitting means for transmitting an ultrasonic wave toward the conveying path in which the sheet is conveyed, and an opposite to the transmitting means with the conveying path interposed therebetween. A control method of a sheet conveying apparatus comprising: receiving means for receiving an ultrasonic wave,
The transmission means is driven to transmit ultrasonic waves at a first duty ratio for determining double feeding of sheets, and ultrasonic waves are transmitted at a second duty ratio for determining basis weight of sheets. A driving step of driving the transmitting means;
It is determined whether or not double feeding of the sheet is performed from the received signal of the ultrasonic wave of the first Duty ratio which is irradiated to the sheet and detected by the receiving means, and the sheet is irradiated and detected by the receiving means Determining a basis weight of the sheet from the received signal of the ultrasonic wave of the second duty ratio;
The control method characterized by having. A program for causing a computer to execute the control method according to claim 9.

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