JP2022044866A - Sheet transfer device - Google Patents

Abstract

To set easily and accurately a threshold value for discriminating a double feed of sheets.SOLUTION: A sheet transfer device is provided with: transport means (154, 155) for transporting sheets; transmitting means for transmitting ultrasonic waves toward a transport path (R) of sheets transported by the transporting means; receiving means for receiving ultrasonic waves transmitted from the transmitting means; and control means for determining that the feed is a double feed in which two or more sheets are overlapped (153), based on the intensity and threshold of the ultrasonic waves which is transmitted from the transmitting means toward a sheet transported by the transporting means and which is passed through the sheet received by the receiving means. After the transport means starts transporting sheets, the control means transmits ultrasonic waves to each of the plurality of sheets transported along the transport path by the transmitting means, and sets the threshold on the basis of the intensity of multiple ultrasonic waves that have passed through each of the plurality of sheets received by the receiving means.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sheet transport device for transporting sheets.

In a sheet transporting device that transports sheets such as originals and recording paper, double feeding may occur in which a plurality of sheets are transported in an overlapping state. Double feeding causes jams on sheets, missing images, and blank paper mixed in printed matter. By the way, when ultrasonic waves are transmitted to the sheet, the ultrasonic waves are attenuated by the sheet, so that when the sheet is double-fed, the attenuation of the ultrasonic waves is also large. However, since the attenuation of ultrasonic waves by the sheet changes depending on the type of sheet and the environment such as atmospheric pressure, the detection accuracy is affected by how to set the threshold value for determining whether or not it is double feeding. Occurs.

Therefore, the threshold value is set based on the signal in the state where the seat does not exist between the ultrasonic transmitter and the receiver (first signal) and the signal in the state where the seat exists (second signal). Has been proposed (see Patent Document 1). Further, when ultrasonic waves are applied to the folded sheets, the attenuation rate of the ultrasonic waves is higher in the double-feeding region where the sheets overlap than in the single-feeding region where the sheets do not overlap. Therefore, there has been proposed a method in which an ultrasonic wave is transmitted to a double feed region and a single feed region of a folded sheet to set a threshold value (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2017-39589 Japanese Unexamined Patent Publication No. 2018-39647

Both the above-mentioned Patent Document 1 and the above-mentioned Patent Document 2 are premised on executing a setting mode (adjustment mode) in which a threshold value is set or adjusted by a serviceman or a user himself / herself. Therefore, there is a problem that the work load of the serviceman and the user becomes large. However, even if an ultrasonic wave is transmitted to a sheet after starting a job such as printing and an attempt is made to set a threshold value based on the received value, the value alone is affected by the type of sheet, environment, double feeding, etc. It is difficult to set a threshold value with good detection accuracy without knowing whether or not it is present.

Therefore, an object of the present invention is to provide a sheet transport device capable of easily and accurately setting a threshold value for discriminating double feed of sheets.

In order to solve the above problems, one aspect of the present invention includes a transport means for transporting a sheet and a transmission means for transmitting ultrasonic waves toward a transport path of the sheet transported by the transport means in the sheet transport device. , The receiving means that receives the ultrasonic waves transmitted from the transmitting means and the ultrasonic waves transmitted from the transmitting means toward the sheet conveyed by the conveying means, and passed through the sheet received by the receiving means. A control means for determining that two or more sheets are overlapped with each other based on the intensity and the threshold value of the sound wave is provided, and the control means transmits the sheet after starting the transfer of the sheet by the transfer means. The threshold value is based on the intensity of a plurality of ultrasonic waves transmitted by means to each of a plurality of sheets conveyed in the transport path and passed through each of the plurality of sheets received by the receiving means. It is characterized by setting.

According to the present invention, the threshold value for discriminating the double feed of the sheet can be easily and accurately set.

The schematic block diagram which shows an example of the image formation system of Example 1. FIG. The functional block diagram which shows the control composition of the image forming apparatus of Example 1. FIG. The enlarged view which shows the structure of the double feed detection unit of Example 1. FIG. The block diagram which shows an example of the functional structure of the double feed detection unit of Example 1. FIG. (A) is a model diagram showing the state of ultrasonic wave attenuation in the single feed state, and (B) is a model diagram showing the state of ultrasonic wave attenuation in the single feed state. (A) is a measurement diagram of the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit of the first embodiment, and (B) is the reception timing of the ultrasonic wave, the setting status of the threshold value for the double feed determination, and the setting status of the double feed determination. Explanatory diagram showing the relationship with. The flowchart which shows the flow of the process of setting the threshold value for determining the double feed of the sheet of Example 1. The flowchart for measuring the intensity of the ultrasonic wave passing through the sheet of Example 1. FIG. (A) is a measurement diagram of the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit of the second embodiment, and (B) is an explanatory diagram showing the relationship between the reception timing of the ultrasonic wave and the setting state of the threshold value for double feed determination. (A) is a measurement diagram of the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit of the second embodiment, and (B) is an explanatory diagram showing the relationship between the reception timing of the ultrasonic wave and the setting state of the threshold value for double feed determination. (A) is a measurement diagram of the ultrasonic wave intensity received by the ultrasonic wave receiving unit of Example 1 of Example 2, and (B) is a relationship between the ultrasonic wave reception timing and the setting status of the threshold value for double feed determination. Explanatory drawing to show. The flowchart which shows the flow of the process which sets the threshold value for determining the double feed of the sheet of Example 2.

Hereinafter, exemplary embodiments for carrying out the present invention will be described with reference to the drawings.

<Overall configuration of image formation system>
FIG. 1 is a schematic configuration diagram showing an example of an image forming system 1000 according to this embodiment. The image forming system 1000 includes an image forming apparatus 10 as an example of the sheet conveying device of the present embodiment, and a paper processing apparatus 500 connected to the downstream side of the image forming apparatus 10 in the conveying direction of the sheet S. Has been done. Further, the image forming apparatus 10 includes an image reader 200 for reading the image of the sheet S, a document feeding device 100, and an operation unit 400. The image forming apparatus 10 includes an electrophotographic image forming means 10A and a main control unit 153 that controls the overall operation of the image forming apparatus 10. In the image forming means 10A, the laser beam modulated based on the input video signal is output by the exposure control unit 110. The laser beam output from the exposure control unit 110 is irradiated onto the photosensitive drum 111 while being scanned by the polygon mirror 110a. As a result, an electrostatic latent image corresponding to the scanned laser beam is formed on the photosensitive drum 111. The electrostatic latent image formed on the photosensitive drum 111 is visualized as a toner image by a developer such as toner supplied from the developer 113. As the image forming means 10A, an inkjet type may be used.

Further, the image forming apparatus 10 includes cassettes 114 and 115 as a feeding means for feeding the sheet S, a manual feeding unit 125, and transport rollers 154 and 155 as the transporting means for transporting the sheet S. It is provided. The sheet S is fed from the cassettes 114 and 115, the manual feeding unit 125, and the double-sided transport path 124 at the timing synchronized with the start of irradiation of the laser beam. The fed sheet S passes through the pass sensor 132 and is transported toward the double feed detection unit 140 by the transfer rollers 154 and 155. When it is determined that the sheet S is in the single feed state when passing through the double feed detection unit 140, the sheet S is conveyed between the photosensitive drum 111 and the transfer unit 116. The double feed detection unit 140 includes an ultrasonic wave transmitting unit 130 and an ultrasonic wave receiving unit 131. The details of the double feed detection unit 140 will be described later. The toner image formed on the photosensitive drum 111 is transferred onto the sheet S by the transfer unit 116. The sheet S to which the toner image is transferred is conveyed toward the fixing portion 117. The fixing portion 117 fixes the toner image on the sheet S by heating and pressurizing the sheet S. The sheet S that has passed through the fixing portion 117 is discharged to the paper processing apparatus 500 via the flap member 121 and the discharge roller 118. The paper processing device 500 ejects the sheet tray 501 for ejecting the sheet after processing the sheet ejected from the image forming apparatus 10 and the sheet without processing the sheet ejected from the image forming apparatus 10. It has an escape tray 502. The first discharging part of this embodiment is a seat tray 501, and the second discharging part is an escape tray 502. When the image forming system 1000 is not provided with the paper processing device 500, the image forming apparatus 10 may be provided with a configuration corresponding to the sheet tray 501 and the escape tray 502.

When the sheet S is discharged with the image forming surface facing downward (face down), the sheet S that has passed through the fixing portion 117 is guided to the inversion path 122 by the switching operation of the flap member 121. Then, after the rear end of the sheet S has passed through the flap member 121, the sheet S is switched back and discharged from the image forming apparatus 10 via the discharge roller 118. The sheet S is ejected face-down in order from the first page, such as when forming an image read through the document feeding device 100 or when forming an image based on image information output from a computer. Do it when you do. As a result, the order of the sheets S after ejection becomes the correct page order. Further, when a hard sheet S such as an OHP sheet is fed from the manual feeding unit 125 to form an image, the sheet S is not guided by the inversion path 122 and the image forming surface is turned upward (face-up). ) Is discharged via the discharge roller 118. Further, when forming an image on both sides of the sheet S, the sheet S is guided to the inversion path 122 by the switching operation of the flap member 121 and then transferred to the double-sided transfer path 124. Then, the sheet S guided to the double-sided transfer path 124 is transferred again between the photosensitive drum 111 and the transfer unit 116 at the timing synchronized with the start of irradiation of the laser beam.

<Control configuration of image forming device>
Next, the control configuration of the image forming apparatus 10 will be described with reference to FIG. FIG. 2 is a functional block diagram showing a control configuration of the image forming apparatus 10. The image forming apparatus 10 has a main control unit 153 that controls the whole. The main control unit 153 as a control means of this embodiment includes a CPU (CENTRAL PROCESSING UNIT) 150, a ROM (READ ONLY MEMORY) 151, and a RAM (RANDOM ACCESS MEMORY) 152. In the main control unit 153, the CPU 150 reads out the control program stored in the ROM 151 and performs an operation to control the operation of each unit constituting the image forming apparatus 10. Further, the RAM 152 is used as a work area when the CPU 150 performs an operation.

With such a configuration, the motor 50, the feed control unit 101, the double feed detection unit 140, the path sensor 132, the image reading control unit 201, the image signal control unit 202, and the operation unit 400 are controlled by the main control unit 153. The feeding control unit 101 controls the driving of the document feeding device 100 based on the instruction from the main control unit 153. The image reading control unit 201 performs drive control of the image reader 200 based on an instruction from the main control unit 153. The image signal output from the image reader 200 is transferred to the image signal control unit 202 via the image bus 203. The double feed detection unit 140 is controlled by the main control unit 153, emits ultrasonic waves to the sheet S that has passed through the detection position 132P of the path sensor 132, and receives ultrasonic waves that have passed through the sheet S. Further, the information regarding the received ultrasonic wave is transmitted to the main control unit 153, and it is determined whether or not the sheet S conveyed based on the received waveform of the ultrasonic wave received by the main control unit 153 is in the double feed state. .. The motor 50, which is the drive source of the transfer rollers 154 and 155, is controlled by the main control unit 153. When the seat S is double-fed, the main control unit 153 can control the drive of the motor 50 to stop the transport rollers 154 and 155 to stop the transport of the seat S. The operation unit 400 receives the user's operation and outputs a signal corresponding to the accepted operation to the main control unit 153. Further, the information output from the main control unit 153 is notified to the user via, for example, the display unit of the operation unit 400. Further, for example, when it is determined that the sheet S to be transported is in the double feed state, the information indicating that the sheet S is double feed is notified.

<Structure of double feed detection unit 140>
Next, the configuration of the double feed detection unit 140 will be described with reference to FIG. FIG. 3 is an enlarged view showing the configuration of the double feed detection unit 140. As shown in FIG. 3, the double feed detection unit 140 includes an ultrasonic wave transmitting unit 130 and an ultrasonic wave receiving unit 131. The ultrasonic transmitting unit 130 has an ultrasonic transmitting unit T1 that emits ultrasonic waves, and the ultrasonic receiving unit 131 has an ultrasonic receiving unit T2 that receives ultrasonic waves transmitted from the ultrasonic transmitting unit T1. There is.

The ultrasonic wave transmitting unit T1 as a transmitting means of this embodiment is arranged on one side of the transport path R to which the sheet S is transported, and transmits ultrasonic waves toward the transport path R. Further, the ultrasonic wave receiving unit T2 as a receiving means of this embodiment is arranged on the side opposite to the ultrasonic wave transmitting unit T1 with the transport path R interposed therebetween, and receives the ultrasonic waves transmitted from the ultrasonic wave transmitting unit T1. .. When there is a sheet S in the transport path R, the ultrasonic waves transmitted from the ultrasonic wave transmitting section T1 pass through the sheet S on the transport path R and then reach the ultrasonic wave receiving section T2. Therefore, when there is a sheet S in the transport path R, the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit T2 is higher than the intensity of the ultrasonic waves transmitted from the ultrasonic wave transmitting unit T1 because it has passed through the sheet S. It gets smaller. The strength of the ultrasonic wave received by the ultrasonic wave receiving unit T2 is converted into a voltage amplitude by the A / D converter 5 described later.

Next, the internal configuration of the double feed detection unit 140 will be described with reference to FIG. FIG. 4 is a block diagram showing an example of the functional configuration of the double feed detection unit 140. The double feed detection unit 140 includes an ultrasonic wave transmitting unit 130 for transmitting ultrasonic waves and an ultrasonic wave receiving unit 131. The ultrasonic wave transmitting unit 130 includes an ultrasonic wave transmitting unit T1 and a drive circuit 3. Further, the ultrasonic receiving unit 131 includes an ultrasonic receiving unit T2, an amplifier circuit 4 for amplifying an ultrasonic signal received by the ultrasonic receiving unit T2, and an AD converter 5 for AD-converting ultrasonic waves. ing. Further, the ultrasonic wave receiving unit 131 is provided with an ultrasonic wave control unit 6 that controls the transmission timing of ultrasonic waves from the ultrasonic wave transmitting unit 130 and calculates the peak value of the received ultrasonic waves. The operation of the ultrasonic control unit 6 is controlled by the main control unit 153. In this embodiment, the ultrasonic wave transmitting unit T1 has a natural frequency of 300 KHz. Further, the ultrasonic wave receiving unit T2 has sensitivity to ultrasonic waves having a frequency of 300 KHz, and converts the sound pressure of the received ultrasonic waves into an electric signal.

The ultrasonic waves transmitted from the ultrasonic wave transmitting unit 130 toward the sheet S transported through the transport path R pass through the sheet S and then propagate to the ultrasonic wave receiving unit 131. The ultrasonic wave receiving unit 131 converts the strength of the received ultrasonic wave into a voltage amplitude, and the conversion result is amplified by the amplifier circuit 4. The ultrasonic wave receiving unit 131 AD-converts the signal amplified by the amplifier circuit 4 via the AD converter 5 and outputs the signal to the main control unit 153. Based on the signal received from the ultrasonic wave receiving unit 131, the main control unit 153 determines whether or not two or more sheets S are overlapped and transported in the transport path R, that is, so-called double feed.

<Attenuation of ultrasonic waves>
Next, the state of attenuation of the ultrasonic wave passing through the sheet will be described with reference to FIGS. 5 (A) and 5 (B). FIG. 5A is a model diagram showing the state of ultrasonic wave attenuation in a single feed state in which one sheet is transported to the transport path. FIG. 5B is a model diagram showing the state of ultrasonic wave attenuation in a double feed state in which two or more sheets are stacked and transported on the transport path.

The attenuation of ultrasonic waves by passing through the sheet is affected by the type of sheet and varies depending on, for example, the thickness of the sheet. When the sheet is thin, the ultrasonic wave attenuation is small, and when the sheet is thick, the ultrasonic wave attenuation is large. Further, the attenuation of ultrasonic waves is larger due to the difference in physical properties at the boundary between the air layer and the sheet than the attenuation due to the thickness of the sheet. For example, the attenuation of ultrasonic waves is larger when passing through a sheet in a double feed state (FIG. 5 (A)) than when passing through a sheet in a single feed state (FIG. 5 (A)). B)). This is a phenomenon observed because when the sheet is double-fed, ultrasonic waves pass through the boundary between the air layer and the sheet more times than in the single-fed state. That is, in the double feed state in which a plurality of sheets are stacked and conveyed, the ultrasonic wave is attenuated by the number of overlapping sheets S. Therefore, the amplitude of the ultrasonic wave received by the ultrasonic wave receiving unit T2 is attenuated more in the double feed state (see FIG. 5 (B)) than in the single feed state (see FIG. 5 (A)). Therefore, when ultrasonic waves of the same intensity are transmitted from the ultrasonic wave transmitting unit T1, the amplitude of the ultrasonic waves detected by the ultrasonic wave receiving unit T2 is smaller in the double feeding state than in the single feeding state. As described above, in this embodiment, it is determined whether or not the sheet is double-fed in the transport path by using the difference in the amplitude of the ultrasonic waves received by the ultrasonic wave receiving unit T2, that is, the property related to the intensity of the ultrasonic waves. can do.

<How to set the threshold for double feed judgment>
As described above, the attenuation of ultrasonic waves due to passing through the sheet is affected by the type of sheet, and when the sheet is thin, the attenuation of ultrasonic waves is small, and when the sheet is thick, the attenuation of ultrasonic waves is large. Therefore, it is necessary to set the threshold value of the ultrasonic wave intensity for determining whether the sheet is double-fed or single-fed for each type of sheet. Next, a method of setting the threshold value of the ultrasonic wave for the double feed determination in the present embodiment will be described with reference to FIGS. 6 (A) and 6 (B). FIG. 6A is a measurement diagram of the intensity of ultrasonic waves received by the ultrasonic wave receiving unit 131 when a plurality of sheets of the same type are conveyed to the transport path. FIG. 6B is an explanatory diagram showing the relationship between the reception timing of ultrasonic waves, the setting status of the threshold value for double feed determination, and the setting status for double feed determination.

In this embodiment, when a plurality of sheets of the same type are conveyed, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit 130 to the first three sheets, and the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 is adjusted. Based on this, a threshold value for determining double feeding of sheets is set. Here, as shown in FIG. 6B, since the threshold value for determining the double feed of the sheets is not set for the first to third sheets, the double feed determination is invalidated. There is. Then, when the threshold value for determining the double feed of the sheets is determined, the double feed determination is performed for the outputs of the first to third sheets, and then the fourth and subsequent sheets are determined based on the set threshold value. The double feed judgment is enabled for the sheet.

Hereinafter, a method of setting a threshold value for determining double feeding of sheets will be specifically described with reference to FIG. 6A. For example, after the sheet is set in the cassette 114, the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 in the first job is: 1st sheet: 221 (single feed state), 2nd sheet: 81 (double feed state). ), 3rd sheet: 216 (single feed state). At this time, among the ultrasonic waves passing through the first to third sheets, 221 having the highest intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 is multiplied by 0.5 as a predetermined coefficient 110. Is set as a threshold value. Then, when the threshold value is set, the double feed determination is executed for the first, second, and third sheets of the sheet S using the threshold value. At this time, if the intensities of the ultrasonic waves passing through the first to third sheets are all larger than the threshold value, it is determined that the first to third sheets are single feed. On the other hand, if any of the intensities of the ultrasonic waves passing through the first to third sheets is smaller than the threshold value, it is determined that double feeding has occurred in any of the first to third sheets. .. In the example of FIG. 6A, since the intensity of the ultrasonic wave passing through the second sheet is smaller than the threshold value of 110, it is determined to be double feed. In the example of FIG. 6A, the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 with respect to the fourth and subsequent sheets is the fourth sheet: 214, the fifth sheet: 223, which is larger than the threshold value. Therefore, it is judged to be single delivery.

Here, in the present embodiment, when determining the threshold value for determining the double feed of the sheets, the ultrasonic waves that have passed through each of the plurality of sheets are sequentially received a plurality of times, and the received ultrasonic waves of the plurality of times are received. The setting is made based on the strength, but the number and order may not be particularly limited. For example, a threshold value for determining double feeding of sheets may be set based on the intensity of ultrasonic waves passing through up to the second sheet conveyed by the job. Further, ultrasonic waves may be transmitted to four or more sheets, and a threshold value for determining double feeding of the sheets may be set based on the intensity of the ultrasonic waves passing through each sheet. The smaller the number of sheets for determining the threshold value for determining the double feed of sheets, the smaller the number of sheets for which the double feed determination is invalidated. Therefore, if the double feed occurs before the threshold value for determining the double feed of the sheet is determined, the waste of the sheet can be reduced.

On the other hand, if a threshold value for determining double feeding of sheets is set based only on the intensity of ultrasonic waves passing through the first sheet, it is not possible to set a good threshold value of the system especially when double feeding occurs. However, since the possibility of continuous double feeding is extremely low, if the number of sheets for determining the threshold value for determining the double feeding of sheets is two or more, it is based on the intensity of ultrasonic waves passing through the sheets. Can determine a good threshold for the system. Therefore, the reliability of the double feed determination can be improved. In this embodiment, the threshold is determined from the intensity of the ultrasonic waves passing through the first three sheets in the job. For example, in addition to this, for the fifth sheet of the job, a threshold value for determining the double feed of the sheets based on the immediately preceding three sheets (intensity of ultrasonic waves passing through the second to fourth sheets of the job). May be determined. Further, for the sixth sheet of the job, even if the threshold value for determining the double feeding of the sheets is determined based on the immediately preceding three sheets (the intensity of the ultrasonic waves passing through the third to fifth sheets of the job). good. By doing so, it is possible to determine the threshold value for determining the double feed of the sheet according to the fluctuation of the installation environment (temperature, humidity and atmospheric pressure) of the image forming apparatus 10.

The threshold value for determining the double feeding of the sheets of this embodiment is a value obtained by multiplying the maximum value by 0.5 of a predetermined coefficient among the intensities of the ultrasonic waves passing through the first three sheets transported by the job. This is because, in the experimental data of various types of sheets, the intensity of the ultrasonic wave received by the ultrasonic receiving unit 131 in the double feed state was 50% or less of the intensity of the ultrasonic wave in the single feed state. However, the predetermined coefficient may be set in the range of 0.4 to 0.7 in addition to 0.5. Further, the threshold value for determining the double feed of the sheets is that the difference between the maximum value and the minimum value of the intensity of the ultrasonic waves passing through the first three sheets transported by the job is a predetermined value or more. For example, a threshold value may be set between the maximum value and the minimum value. At this time, for example, when the predetermined value is 100 and the maximum value (first sheet: 221) and the minimum value (second sheet: 81) are set, (maximum value + minimum value) / 2 = (221 + 81) / 2 = 151 may be set as a threshold value for determining the double feed of the sheet.

Next, the flow of the process of setting the threshold value for determining the double feed of the sheet will be described with reference to FIGS. 7 and 8. FIG. 7 is a flowchart showing a flow of processing for setting a threshold value for determining double feeding of sheets in this embodiment. FIG. 8 is a flowchart for measuring the intensity of ultrasonic waves that have passed through the sheet. The flowcharts shown in FIGS. 7 and 8 are processes executed mainly by the main control unit 153.

First, the flow of the process for measuring the intensity of ultrasonic waves will be described with reference to FIG. When the sheet transfer is started, it waits until the sheet is detected by the path sensor 132 (S201). When the tip of the sheet reaches the detection position 132P (see FIG. 3) of the path sensor 132, the path sensor 132 outputs a signal indicating that the sheet is in the transport path R. Next, the pass sensor 132 waits for a predetermined time from the timing when the seat is detected (S202). The predetermined time is the time for the sheet to move to a position where the double feed detection unit 140 can be stably determined to be double feed after the sheet is detected by the pass sensor 132. Specifically, it is determined according to the transport speed of the sheet and the mounting distance from the path sensor 132 to the ultrasonic wave transmitting unit T1 and the ultrasonic wave receiving unit T2 (see FIG. 3). Next, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit T1 (S203). The ultrasonic wave transmitted from the ultrasonic wave transmitting unit T1 acquires the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit T2 from the ultrasonic wave receiving unit 131, and ends this process (S204). The process of measuring the intensity of the ultrasonic wave of FIG. 8 is executed as one step of the flowchart of FIG. 7.

Next, the flow of the process of setting the threshold value for determining the double feed of the sheet will be described with reference to FIG. 7. In FIG. 7, ultrasonic waves are transmitted to the first three sheets transported by the job, ultrasonic waves that have passed through the sheets are received multiple times in order, and settings are made based on the strength of the received multiple ultrasonic waves. Shows the processing when performing.

When the job is started, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit T1 to the first sheet conveyed by the job, and the intensity of the ultrasonic waves is measured according to the flowchart of FIG. 8 (S101). Then, the intensity of the ultrasonic waves is measured for the second and third sheets conveyed by the job according to the flowchart of FIG. 8 in the same manner as for the first sheet (S102, S103). The nth sheet conveyed by the job refers to a sheet that has been fed from the cassettes 114 and 115, the manual feeding unit 125, and the like and has reached the detection position of the pass sensor 132. Next, among the measured values of the ultrasonic waves that have passed through the first to third sheets, the maximum value having the highest ultrasonic wave intensity and the minimum value having the lowest ultrasonic wave intensity are specified. Then, it is determined whether or not the difference between the maximum value and the minimum value is equal to or greater than a predetermined value (S104). When it is determined that the difference between the maximum value and the minimum value in the ultrasonic intensity of the first to third sheets is equal to or more than a predetermined value (S104 / Y), (maximum value + minimum value) / 2 = VthA. Is set as a threshold value (S105). The predetermined value is a predetermined value based on the intensity of ultrasonic waves of 300 KHz passing through one sheet of A4 size plain paper frequently used in the image forming apparatus 10, and is a value determined in advance for each type of sheet. It may be a predetermined value.

On the other hand, when it is determined that the difference between the maximum value and the minimum value in the ultrasonic intensity of the first to third sheets is less than the predetermined value (S104 / N), the maximum value × 0.5 = VthB. Is set as a threshold value (S106). Next, it is determined whether or not any of the ultrasonic intensity of the first to third sheets conveyed by the job is equal to or higher than the threshold value set in S105 or S106 (S107). If any of the ultrasonic intensities of the first to third sheets transported by the job is less than the threshold value set in S105 or S106, multiple sheets are overlapped and transported. (S107 / N).

When it is determined in S104 that the difference between the maximum value and the minimum value in the ultrasonic intensity of the first to third sheets is equal to or more than a predetermined value, the minimum value of the ultrasonic wave is the threshold value set in S104. Is a smaller value than. Therefore, when the difference between the maximum value and the minimum value in the ultrasonic intensity of the first to third sheets is equal to or more than a predetermined value, it can be determined that double feeding of the sheets has occurred. can. When it is determined that the double feed has occurred, the motor 50 is controlled to execute the stop process of stopping the sheet transfer (S108), and the operation unit 400 is notified that the double feed has occurred (S109). ). That is, when the difference between the maximum value and the minimum value in the ultrasonic intensity of the first to third sheets is equal to or more than a predetermined value when setting the threshold value for determining the double feed of the sheets. Is executed. Further, the stop process is not executed until the threshold value for determining the double feed of the sheet is set. It should be noted that the flowchart of FIG. 7 may be executed from the step of S110 described later after the steps such as the removal of the double-fed sheet are performed.

On the other hand, when the intensity of the ultrasonic waves for the first to third sheets transported by the job is equal to or higher than the threshold value set in S105 or S106, one sheet is transported by single feed. Is determined to be. Then, ultrasonic waves are transmitted to the Nth sheet, here the 4th sheet, which is conveyed by the job, and the intensity of the ultrasonic waves passing through the 4th sheet is measured according to the flowchart of FIG. 8 (S110). Then, it is determined whether or not the intensity of the ultrasonic wave passing through the fourth sheet is equal to or higher than the threshold value set in S105 or S106 (S111). If the intensity of the ultrasonic wave passing through the fourth sheet is less than the threshold value set in S105 or S106 (S111 / N), the process proceeds to S108. On the other hand, when the intensity of the ultrasonic wave passing through the fourth sheet is equal to or higher than the threshold value set in S105 or S106 (S111 / Y), and the next page is left in the job (S112 /). Y) returns to S110. If the job does not have the next page (S112 / N), this process ends.

As described above, in this embodiment, ultrasonic waves are applied to each of a plurality of sheets while the sheets are being conveyed by the job, and double feeding occurs based on the intensity of the ultrasonic waves passing through each sheet. A threshold value for determining is set. Therefore, it is not necessary to perform the operation of setting the threshold value in advance for each sheet used in the image forming apparatus 10, and the threshold value for discriminating the double feed of the sheets can be easily set. Further, even if the intensity of the ultrasonic wave is measured on the first sheet, for example, when the intensity is low, it may be caused by the environment such as whether double feeding occurs, the sheet is thick, or the atmospheric pressure is low. I don't know. However, in this embodiment, since the threshold value is set based on the intensity of the ultrasonic waves that have passed through each of the plurality of sheets, the probability that the double feed is continuously generated is extremely low, and the threshold value for discriminating the double feed is accurately set. It is configurable.

Next, a configuration for setting a threshold value for determining the double feed of the sheet according to the second embodiment will be described. Since the configuration of the image forming system 1000 in this embodiment is the same as that in the first embodiment, the description thereof will be omitted. In this embodiment, in order to determine the double feeding of the sheet using the intensity of the ultrasonic wave observed in the state where there is no sheet between the ultrasonic transmitting unit T1 and the ultrasonic receiving unit T2 (hereinafter referred to as “paperless state”). Set the threshold of. Further, in this embodiment, ultrasonic waves are transmitted to the first two sheets transported by the job, respectively, and a threshold value for determining the double feed of the sheets based on the intensity of the ultrasonic waves passing through the respective sheets. To set. At this time, the sheets transported by the job are of the same type. Then, the double feed of the sheets is determined based on the difference between the intensity of the ultrasonic waves passing through the first sheet conveyed by the job and the intensity of the ultrasonic waves passing through the second sheet conveyed by the job. Change the setting method of the threshold value. Further, in this embodiment, ultrasonic waves are transmitted to each of the two sheets, and the threshold value for determining the double feed of the sheets is set again based on the intensity of the ultrasonic waves passing through the sheets. When the difference between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet is less than a predetermined value and one of them is less than the threshold value set without paper. The threshold is reset based on the intensity of the first or second ultrasonic wave, whichever is greater. When the difference between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet is equal to or more than a predetermined value, both the first and second sheets of ultrasonic waves are used. Reset the threshold based on the intensity of.

Hereinafter, a method of setting a threshold value for determining double feeding of sheets in this embodiment will be specifically described with reference to the drawings in order. In FIGS. 9 (A), 9 (B), 10 (A), 10 (B), 11 (A), and 11 (B), the threshold values for determining the double feed of the sheet are set, respectively. The setting method is different. In addition, in FIG. 9A, FIG. 9B, FIG. 10A, FIG. 10B, FIG. 11A, and FIG. 11B, the ultrasonic wave transmitted from the ultrasonic wave transmitting unit T1 is It is assumed that they have the same intensity and frequency.

First, a method of setting the threshold value of the ultrasonic wave for the double feed determination will be described with reference to FIGS. 9 (A) and 9 (B). FIG. 9A is a measurement diagram of the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit 131 when a plurality of sheets of the same type are transported to the transport path, and is the one when the sheets are single-fed. Shows. FIG. 9B is an explanatory diagram showing the relationship between the reception timing of ultrasonic waves and the setting status of the threshold value for double feed determination. In this embodiment, first, as shown in FIG. 9B, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit 130 toward the transport path in the state without paper, and based on the intensity of the ultrasonic waves in the state without paper. Set a threshold for determining double feed of sheets. In FIG. 9B, 130 is set as a threshold value based on the intensity of ultrasonic waves in the state without paper, and it is determined whether or not double feeding of the sheets transported by the job has occurred.

As shown in FIG. 9A, the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit 131 in the job is as follows: 1st sheet: 220, 2nd sheet: 218, 3rd sheet: 223, 4th sheet: 200. Suppose there was. In addition, in FIG. 9A and FIG. 9B, the first to fourth sheets are both conveyed in a single feed state. At this time, the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet are both larger than the threshold value of 130. Further, the difference between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet is less than the predetermined value when the predetermined value is 80. In such a case, in this embodiment, the threshold value set based on the intensity of the ultrasonic wave in the paperless state is used to determine the double feeding of the third and subsequent sheets transported by the job. Continue to be used as the threshold value of.

Next, a method of setting the threshold value of the ultrasonic wave for the double feed determination will be described with reference to FIGS. 10 (A) and 10 (B). FIG. 10A is a measurement diagram of the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit 131 when a plurality of sheets of the same type are conveyed to the transport path, and the sheet is fed alone. Shows. FIG. 10B is an explanatory diagram showing the relationship between the reception timing of ultrasonic waves and the setting status of the threshold value for double feed determination. In this embodiment, first, as shown in FIG. 10B, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit 130 toward the transport path in the state without paper, and based on the intensity of the ultrasonic waves in the state without paper. Set a threshold for determining double feed of sheets. In FIG. 10B, 130 is set as a threshold value based on the intensity of ultrasonic waves in the state without paper, and it is determined whether or not double feeding of the sheets transported by the job has occurred.

As shown in FIG. 10A, the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 in the job is as follows: 1st sheet: 110, 2nd sheet: 114, 3rd sheet: 115, 4th sheet: 108. Suppose there was. In addition, in FIG. 10A and FIG. 10B, the first to fourth sheets are both conveyed in a single feed state. At this time, the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet are both smaller than the threshold value of 130. Further, the difference between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet is less than the predetermined value when the predetermined value is 80. As described above, the degree of attenuation of ultrasonic waves when passing through the sheet increases as the sheet becomes thicker (see FIGS. 5 (A) and 5 (B)). In the case of FIGS. 10 (A) and 10 (B), since the intensity of the ultrasonic wave after passing through the sheet is smaller than that of FIGS. 9 (A) and 9 (B), FIGS. 9 (A) and 9 (B) and FIG. It is clear that the sheet has a larger basis weight than FIG. 9B. That is, in FIGS. 10 (A) and 10 (B), the difference from the intensity of the ultrasonic waves passing through the first and second sheets is less than a predetermined value, and the first and second sheets are The intensity of the ultrasonic waves passing through is smaller than the threshold set based on the intensity of the ultrasonic waves without paper.

In such a case, in this embodiment, the threshold value set based on the intensity of the ultrasonic wave without paper is reset again based on the intensity of the ultrasonic wave passing through the first and second sheets. .. In FIG. 10A, 0.5 is set as a predetermined coefficient for the intensity of the ultrasonic wave passing through the second sheet, which is the maximum value among the intensities of the ultrasonic waves passing through the first or second sheet. The multiplied value of 57 is set again as a threshold value for determining the double feed of the sheet. Then, for the third and subsequent sheets transported by the job, the threshold value is 57, which is a value obtained by multiplying the maximum value of the intensity of ultrasonic waves passing through the second sheet by 0.5 as a predetermined coefficient. The double feed of the sheet is determined as. In the example of FIG. 10A, the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 with respect to the third and subsequent sheets is the third sheet: 115, the fourth sheet: 108, which is larger than the threshold value. Is also determined to be single delivery.

Next, a method of setting the threshold value of the ultrasonic wave for the double feed determination will be described with reference to FIGS. 11 (A) and 11 (B). FIG. 11A is a measurement diagram of the intensity of ultrasonic waves received by the ultrasonic wave receiving unit 131 when a plurality of sheets of the same type are conveyed to the transport path. FIG. 11B is an explanatory diagram showing the relationship between the reception timing of ultrasonic waves and the setting status of the threshold value for double feed determination. In this embodiment, first, as shown in FIG. 11B, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit 130 toward the transport path in the state without paper, and based on the intensity of the ultrasonic waves in the state without paper. Set a threshold for determining double feed of sheets. In FIG. 11B, 130 is set as a threshold value based on the intensity of ultrasonic waves in the state without paper, and it is determined whether or not double feeding of the sheets transported by the job has occurred.

As shown in FIG. 11A, the intensity of the ultrasonic wave received by the ultrasonic wave receiving unit 131 in the job is as follows: 1st sheet: 225, 2nd sheet: 115, 3rd sheet: 228, 4th sheet: 226. Suppose there was. At this time, the intensity of the ultrasonic wave passing through the first sheet is larger than the threshold value of 130. On the other hand, the intensity of the ultrasonic wave passing through the second sheet is smaller than the threshold value of 130. The difference between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet is greater than or equal to the predetermined value when the predetermined value is 80. As described above, the degree of attenuation of ultrasonic waves when passing through the sheet increases as the sheet becomes thicker (see FIGS. 5 (A) and 5 (B)). In the case of FIGS. 11A and 11B, the intensity of the ultrasonic wave passing through the second sheet conveyed by the job is the intensity of the ultrasonic wave passing through the first sheet due to the double feeding of the sheets. It is significantly smaller than. That is, in FIGS. 11A and 11B, double feeding of the sheets occurs when the second sheet is conveyed, and the intensity of the ultrasonic wave passing through the first sheet and the second sheet. The difference from the intensity of the ultrasonic wave passing through the sheet becomes a predetermined value or more.

In such a case, in this embodiment, the threshold value set based on the intensity of the ultrasonic wave without paper is reset again based on the intensity of the ultrasonic wave passing through the first and second sheets. .. In FIG. 11A, 170, which is an intermediate value between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet, is used to determine the double feeding of the sheets. It is set again as the threshold value of. Then, for the third and subsequent sheets transported by the job, the value is intermediate between the intensity of the ultrasonic wave passing through the first sheet and the intensity of the ultrasonic wave passing through the second sheet. The double feed of the sheet is determined with 170 as the threshold value. In the example of FIG. 11A, the intensity of the ultrasonic waves received by the ultrasonic wave receiving unit 131 with respect to the third and subsequent sheets is the third sheet: 228, the fourth sheet: 226, which is larger than the threshold value. Is also determined to be single delivery.

In this embodiment, when determining the threshold value for determining the double feed of the sheets, the ultrasonic waves that have passed through the first and second sheets are received twice in order, and the two received ultrasonic waves are received. Although the setting is made based on the intensity of the sound wave, it is not necessary to limit the setting to these two. For example, a threshold value for determining double feeding of sheets may be set based on the intensity of ultrasonic waves passing through the third and subsequent sheets conveyed by the job. Further, ultrasonic waves may be transmitted to three or more sheets, and a threshold value for determining double feeding of the sheets may be set based on the intensity of the ultrasonic waves passing through each sheet.

Next, the flow of the process of setting the threshold value for determining the double feed of the sheet will be described with reference to FIG. FIG. 12 is a flowchart showing a flow of processing for setting a threshold value for determining double feeding of sheets in this embodiment. In the flowchart of FIG. 12, the process for measuring the intensity of the ultrasonic wave passing through the sheet is the same process as that of the flowchart of FIG. 8, so duplicate description will be omitted. The flowchart shown in FIG. 12 is a process executed mainly by the main control unit 153.

When the job is started, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit T1 before the sheet transfer is started (S301). At this time, the ultrasonic wave receiving unit T2 receives the ultrasonic waves transmitted from the ultrasonic wave transmitting unit T1 without a sheet in the transport path (without paper) (S302). Then, the product of the ultrasonic wave intensity in the paperless state and the predetermined coefficient received in S302 is set as a threshold value (S303, ultrasonic wave intensity in the paperless state × predetermined coefficient = Vth1).

Next, ultrasonic waves are transmitted from the ultrasonic wave transmitting unit T1 to the first and second sheets conveyed by the job, and the intensity of the ultrasonic waves is measured according to the flowchart of FIG. 8 (S304, S305). The nth sheet conveyed by the job refers to a sheet that has been fed from the cassettes 114 and 115, the manual feeding unit 125, and the like and has reached the detection position of the pass sensor 132. Next, from the measured values of the ultrasonic waves passing through the first and second sheets, the maximum value having the highest ultrasonic wave intensity and the minimum value having the lowest ultrasonic wave intensity are specified. Then, it is determined whether or not the difference between the maximum value and the minimum value is less than a predetermined value (S306). The predetermined value is a predetermined value based on the intensity of ultrasonic waves of 300 KHz passing through one sheet of A4 size plain paper frequently used in the image forming apparatus 10, and is a value determined in advance for each type of sheet. It may be a predetermined value.

In S306, when it is determined that the difference between the maximum value and the minimum value in the ultrasonic intensity of the first and second sheets is a predetermined value or more (S306 / N), (maximum value + minimum value). ) / 2 = Vth3 is set as a threshold value (S312). When the difference between the maximum value and the minimum value in the intensity of ultrasonic waves for the first and second sheets is a predetermined value or more, double feeding of the sheets occurs. Therefore, the first and second sheets conveyed by the job are discharged to the escape tray 502 (S313).

When it is determined in S306 that the difference between the maximum value and the minimum value of the ultrasonic wave intensity for the first and second sheets is equal to or more than a predetermined value, the minimum value of the ultrasonic wave is the threshold value set in S303. Is a smaller value than. Therefore, when the difference between the maximum value and the minimum value in the ultrasonic intensity of the first and second sheets is equal to or more than a predetermined value, it can be determined that double feeding of the sheets has occurred. can. Then, when it is determined that the double feed has occurred, the motor 50 is controlled to execute the stop process of stopping the sheet transfer (S314), and the operation unit 400 is notified that the double feed has occurred. (S315). That is, when the difference between the maximum value and the minimum value in the intensity of ultrasonic waves for the first and second sheets is a predetermined value or more when setting the threshold value for determining the double feed of the sheets. Is executed. Further, the stop process is not executed until the threshold value for determining the double feed of the sheet is set. It should be noted that the flowchart of FIG. 12 may be executed from the step of S309 described later after the steps such as the removal of the double-fed sheet are performed.

On the other hand, when it is determined that the difference between the maximum value and the minimum value in the ultrasonic intensity of the first and second sheets is less than the predetermined value (S306 / Y), the first and second sheets are used. It is determined whether or not the intensity of the ultrasonic wave for the sheet of No. 1 is equal to or higher than the threshold value (S307). At this time, since Vth1 is set as a threshold value, when the ultrasonic intensity of the first and second sheets is less than Vth1 (S307 / N), the maximum value × 0.5 = Vth2 is set as the threshold value. Set again (S308). When the intensity of the ultrasonic waves for the first and second sheets is less than Vth1 in S307, the threshold value set in S308 is the intensity of the ultrasonic waves for the first and second sheets. It will be smaller than the maximum and minimum values.

When the intensity of the ultrasonic waves of the first and second sheets is Vth1 or more, that is, the intensity of the ultrasonic waves in the state without paper (S307 / Y), Vth1 is used as the threshold value. Then, ultrasonic waves are transmitted to the Nth sheet, here the third sheet, which is conveyed by the job, and the intensity of the ultrasonic waves passing through the third sheet is measured according to the flowchart of FIG. 8 (S309). Then, it is determined whether or not the intensity of the ultrasonic wave passing through the third sheet is equal to or higher than the threshold value set in S303, S308, or S312 (S310). When the intensity of the ultrasonic wave passing through the third sheet is less than the threshold value set in S303, S308, or S312 (S310 / N), the process proceeds to S314. On the other hand, when the intensity of the ultrasonic wave passing through the third sheet is equal to or higher than the threshold value set in S303, S308, or S312 (S310 / Y), and the next page is left in the job. (S311 / Y), return to S309. If the job does not have the next page (S311 / N), this process ends.

As described above, in this embodiment, ultrasonic waves are irradiated toward the sheet transport path before and during sheet transport, and the weight is based on the intensity of the ultrasonic waves that have passed through each of the plurality of sheets. A threshold value for determining the occurrence of transmission is set. Therefore, it is not necessary to perform the operation of setting the threshold value in advance for each sheet used in the image forming apparatus 10, and the threshold value for discriminating the double feed of the sheets can be easily set. Further, in this embodiment, since the threshold value is set based on the intensity of the ultrasonic wave passing through each of the plurality of sheets, the probability that the double feed is continuously generated is extremely low, and the threshold value for discriminating the double feed is accurately set. It is configurable.

<Other Examples>
In Examples 1 and 2, the image forming apparatus 10 having the image forming means 10A for forming an image on the sheet was described as an example of the sheet conveying apparatus. As other sheet transporting devices, for example, the configurations of Examples 1 and 2 are applied to a device that performs processing such as punching and folding of a sheet and a device that reads an image of a sheet to perform double feeding of the sheet. A threshold value for determination can be set. The image forming system 1000 is also an example of a sheet transfer device.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

10 Image forming device (sheet transporting device) / 10A Image forming means / 153 Main control unit (control means) / 501 Sheet tray (first discharging part) / 502 Escape tray (second discharging part) / 1000 Image forming system (sheet) Transport device) / R transport path / T1 ultrasonic transmitter (transmitting means) / T2 ultrasonic receiver (receiving means)

Claims (9)

The means of transporting the sheet and
A transmitting means that transmits ultrasonic waves toward the transport path of the sheet transported by the transport means, and
A receiving means for receiving ultrasonic waves transmitted from the transmitting means, and a receiving means.
Two or more sheets are overlapped based on the intensity and the threshold value of the ultrasonic waves transmitted from the transmitting means toward the sheet transported by the transporting means and passed through the sheet received by the receiving means. It is equipped with a control means for determining that it is a double feed.
After the sheet is transported by the transporting means, the control means transmits ultrasonic waves to each of the plurality of sheets transported along the transport path by the transmitting means, and the receiving means receives the plurality of sheets. The threshold is set based on the intensity of multiple ultrasonic waves passed through each of the sheets.
A sheet transfer device characterized by this. The control means is a value between the maximum value and the minimum value when the difference between the maximum value and the minimum value is equal to or more than a predetermined value among the intensities of the plurality of ultrasonic waves received by the receiving means. When the difference between the maximum value and the minimum value is less than the predetermined value, the product of the maximum value and the predetermined coefficient is set as the threshold value.
The sheet transporting apparatus according to claim 1. The control means is
When the difference between the maximum value and the minimum value is equal to or greater than a predetermined value among the intensities of the plurality of ultrasonic waves received by the receiving means, the value is set to be between the maximum value and the minimum value. Set a threshold and
The difference between the maximum value and the minimum value is less than the predetermined value, and the maximum value and the minimum value are smaller than the intensity of the ultrasonic wave received by the receiving means when there is no sheet in the transport path. In this case, the threshold value is set so as to be smaller than the maximum value and the minimum value.
The difference between the maximum value and the minimum value is less than the predetermined value, and the maximum value and the minimum value are equal to or higher than the intensity of the ultrasonic wave received by the receiving means when there is no sheet in the transport path. Occasionally, the intensity of ultrasonic waves received by the receiving means in the absence of a sheet in the transport path is set as the threshold value.
The sheet transport device according to claim 1. The control means can execute a stop process for stopping the transfer of the sheet by the transfer means, and executes the stop process when it is determined that the double feed is performed.
The sheet transport device according to claim 2 or 3, wherein the sheet transport device is characterized by the above. The control means does not execute the stop process until the threshold value is set based on the intensity of the plurality of ultrasonic waves.
The sheet transporting apparatus according to claim 4. The control means executes the stop process when the difference between the maximum value and the minimum value is equal to or greater than the predetermined value while setting the threshold value based on the intensity of the plurality of ultrasonic waves. ,
The sheet transporting apparatus according to claim 4. When the stop process is executed, the control means notifies that the double feed is performed.
The sheet transport device according to any one of claims 4 to 6, wherein the sheet transport device is characterized by the above. A first discharging unit from which the sheet conveyed by the conveying means is discharged, and
A second discharge unit, which is arranged at a position different from the first discharge unit and discharges the sheet conveyed by the transfer means, is provided.
When the control means does not execute the stop process, the sheet is discharged to the first discharge section by the transport means, and when the stop process is executed, the sheet is discharged to the second discharge section by the transport means. Stop transporting the sheet after discharging,
The sheet transport device according to any one of claims 4 to 7, wherein the sheet transport device is characterized by the above. An image forming means for forming an image on a sheet conveyed by the conveying means is provided.
The sheet transport device according to any one of claims 1 to 8, wherein the sheet transport device is characterized by the above.

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