JP2019204057A - Image forming apparatus - Google Patents

Abstract

To remove a numeric value affected from noise from numeric values used for determination of thickness to improve the accuracy in determination of paper thickness.SOLUTION: An image forming apparatus comprises: a sheet conveying unit; a thickness detection unit; a control unit; and a storage unit. The thickness detection unit includes a transmitting unit and a receiving unit. The transmitting unit and the receiving unit are provided to sandwich a sheet conveyance path and allow a sheet to be conveyed therebetween. The control unit causes the transmitting unit to transmit an ultrasonic wave during a detection period. The control unit determines, from a plurality of voltage values acquired through sampling during a thickness detection period, a voltage value to be excluded that is a voltage value having a noise mixed therein. The control unit determines the average value of the voltage values excluding the voltage value to be excluded. The control unit determines the thickness of the sheet to be conveyed on the basis of the average value and data for thickness determination.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus that detects the thickness of a sheet.

  There are image forming apparatuses such as multifunction peripherals, printers, and fax machines. Some image forming apparatuses acquire information on paper using an ultrasonic sensor. An example of such an image forming apparatus is described in Patent Document 1.

  Specifically, Patent Document 1 includes a first roller and a second roller that are arranged opposite to each other across a conveyance path for conveying a sheet, and a transmission sensor that transmits an ultrasonic signal in the shaft of the first roller. Provided within the shaft of the second roller is a receiving sensor that transmits a radio signal when an ultrasonic signal is received, and transmits a radio signal of a predetermined frequency to the transmitting sensor and receives a radio signal transmitted from the receiving sensor. A sheet information measuring device that calculates the thickness of a sheet based on a received radio wave signal of a receiving sensor is described (Patent Document 1: Claims 1 and 5).

JP 2006-264927 A

  An ultrasonic sensor may be used to detect the thickness of the paper. The ultrasonic wave transmitted from the transmission circuit is received by the reception circuit. The receiving circuit outputs a signal based on the received ultrasonic wave. The paper thickness is detected based on the waveform of the signal output from the receiving circuit. However, since detection is performed during paper conveyance, noise may be mixed in the output of the receiving circuit. In addition, vibration due to rotation of a roller or a motor, or vibration of a sheet due to a collision with a guide may cause noise. There is a problem that the thickness of the sheet may not be detected accurately due to noise mixing.

  Patent Document 1 does not describe noise countermeasures. Therefore, the technique described in Patent Document 1 cannot solve the above problem.

  In view of the above problems, the present invention excludes numerical values that are affected by noise from among the numerical values used for determining the thickness, and improves the accuracy of determining the paper thickness.

  An image forming apparatus according to the present invention includes a paper transport unit, a thickness detection unit, a control unit, and a storage unit. The paper transport unit transports paper. The thickness detector includes a transmitter and a receiver. The thickness detector outputs a detection voltage having a magnitude corresponding to the ultrasonic wave received by the receiver. The control unit receives the detection voltage. The storage unit stores thickness determination data for determining the thickness of the sheet. The transmitting unit and the receiving unit are provided so that the sheet is conveyed with the sheet conveying path interposed therebetween. The control unit causes the transmission unit to transmit the ultrasonic wave toward the reception unit during a predetermined thickness detection period. The control unit obtains a voltage value of the detection voltage in a predetermined sampling period shorter than the thickness detection period. The said control part determines the exclusion voltage value which is the said voltage value in which noise mixed among the said several voltage values acquired by sampling of the thickness detection period. The control unit obtains an average value of the voltage values excluding the excluded voltage value among the voltage values acquired during the thickness detection period. The controller determines the thickness of the conveyed paper based on the average value and the thickness determination data. The determination data is data defining a range of the average value corresponding to each sheet thickness.

  According to the present invention, it is possible to exclude a numerical value affected by noise from a numerical value (voltage value) used for determining a thickness (thickness level). The accuracy of the determination of the thickness of the transport sheet can be improved.

1 is an explanatory diagram illustrating an example of an image forming apparatus according to an embodiment. It is a figure which shows an example of the part regarding the paper conveyance which concerns on embodiment. It is a figure which shows an example of the part regarding the paper conveyance which concerns on embodiment. It is a figure which shows an example of the signal processing circuit which concerns on embodiment. It is a figure which shows an example of determination of the thickness of the paper using the thickness detection part which concerns on embodiment. An example of the data for thickness determination which concerns on embodiment is shown. It is a figure which shows an example of the waveform of the voltage value of the voltage for a detection which concerns on embodiment. It is a figure which shows an example of the flow of determination of the exclusion voltage value which concerns on embodiment. It is a figure which shows an example of the determination of the double feed of the paper using the thickness detection part which concerns on embodiment. It is a figure which shows an example of the waveform of the voltage value of the voltage for a detection at the time of double feeding. FIG. 3 is a diagram illustrating an example of a fixing unit and a nip pressure adjusting unit according to the embodiment. It is a figure which shows an example of the fixing temperature data based on embodiment. It is a figure showing an example of nip pressure data concerning an embodiment. 5 is a diagram illustrating an example of control according to the thickness of a sheet in the multifunction peripheral according to the embodiment. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In this description, the multifunction peripheral 100 will be described as an example of the image forming apparatus. The multifunction device 100 conveys and prints the paper. Hereinafter, each element such as configuration and arrangement described in the description of the present embodiment is merely an illustrative example without limiting the scope of the invention.

(Multifunction machine 100)
First, an example of the multifunction peripheral 100 according to the embodiment will be described with reference to FIG. FIG. 1 is an explanatory diagram illustrating an example of a multifunction peripheral 100 according to the embodiment.

  As shown in FIG. 1, the multifunction peripheral 100 includes a control unit 1 and a storage unit 2. The control unit 1 controls each unit of the multifunction device 100. The control unit 1 includes a control circuit 10 and an image processing circuit 11. The control circuit 10 is, for example, a CPU. The control circuit 10 performs calculations and processes related to control. The image processing circuit 11 processes image data. The storage unit 2 includes storage devices such as ROM, RAM, and HDD. The storage unit 2 stores a control program and various data.

  The multifunction device 100 includes an image reading unit 3. The image reading unit 3 reads a set original. The image reading unit 3 generates image data of a document. The original image data is used as printing image data.

  The multifunction machine 100 includes an operation panel 4. The control unit 1 is communicably connected to the operation panel 4. The operation panel 4 includes a display panel 41, a touch panel 42, and hard keys 43 (for example, a start key). The control unit 1 controls display on the display panel 41. The control unit 1 causes the display panel 41 to display a screen and an image. For example, the control unit 1 displays an operation image. The operation image is, for example, a soft key or a button. Based on the output of the touch panel 42, the control unit 1 recognizes the operated operation image. Further, the control unit 1 recognizes the operated hard key 43. Thus, the operation panel 4 receives a user's operation. The control unit 1 recognizes the content of the setting operation performed on the operation panel 4. Further, the control unit 1 causes the display panel 41 to switch display contents in accordance with the operated operation image and the hard key 43. The control unit 1 controls the multifunction device 100 so as to operate as set.

  The multifunction device 100 includes a printing unit 5. The printing unit 5 includes a paper feeding unit 5a, a paper transport unit 6, an image forming unit 5b, and a fixing unit 7. In the case of a print job, the control unit 1 supplies sheets one by one to the sheet feeding unit 5a. The control unit 1 causes the paper transport unit 6 to transport the paper. The control unit 1 causes the image forming unit 5b to form a toner image based on the printing image data using toner. The control unit 1 causes the image forming unit 5b to transfer the toner image onto the transport sheet. The control unit 1 causes the fixing unit 7 to fix the toner image on the sheet. The paper transport unit 6 discharges the printed paper to the discharge tray.

  The multifunction device 100 includes a communication unit 13. The communication unit 13 communicates with the computer 200. The computer 200 is, for example, a PC or a server. The communication unit 13 includes a communication connector and a communication circuit. The communication unit 13 can transmit and receive data with the computer 200.

(Paper transport)
Next, with reference to FIGS. 2 and 3, an example of a portion related to paper conveyance in the multifunction peripheral 100 according to the embodiment will be described. 2 and 3 are diagrams illustrating an example of a portion related to sheet conveyance in the multifunction peripheral 100 according to the embodiment.

  The multifunction machine 100 includes a paper feed unit 5 a and a paper transport unit 6. As shown in FIG. 2, the paper feed unit 5 a includes a paper cassette 51, a paper feed motor 52, and a paper feed rotator 53 (pickup roller). The paper cassette 51 stores a bundle of paper. The sheet feeding rotator 53 is in contact with the accommodated sheet. The sheet feeding motor 52 is driven to rotate the sheet feeding rotating body 53. The sheet is sent out from the sheet cassette 51 by the rotation of the sheet feeding rotator 53. In the case of a print job, the control unit 1 rotates the paper feed motor 52. When printing a plurality of sheets continuously, the control unit 1 repeats the rotation and pause of the paper feed motor 52 to provide a predetermined space between the sheets.

  The paper sent out from the paper supply unit 5 a enters the paper transport unit 6. As shown in FIG. 3, the paper transport unit 6 includes a transport roller pair 61 (corresponding to a transport rotating body pair) and a transport guide 64. The conveyance roller pair 61 rotates and conveys the paper. The conveyance guide 64 guides the conveyance paper. FIG. 3 shows an example of a portion of the paper transport unit 6 that transports from the lower side (paper feeding unit 5a) to the upper side (image forming unit 5b). In FIG. 3, the lower conveying roller pair 61 is an intermediate roller pair 62. In FIG. 3, the upper conveyance roller pair 61 is a registration roller pair 63. The registration roller pair 63 feeds the paper toward the image forming unit 5b.

  The paper transport unit 6 includes one or a plurality of transport motors 60. In the transport motor 60, one or a plurality of transport roller pairs 61 are rotated by driving the transport motor 60. The sheet is conveyed by the rotation of the conveyance roller pair 61. The sheet passes through a sheet conveyance path by the conveyance guide 64. In the case of a print job, the control unit 1 rotates the transport motor 60.

(Thickness detector 8)
Next, an example of the thickness detection unit 8 included in the MFP 100 according to the embodiment will be described with reference to FIGS. FIG. 4 is a diagram illustrating an example of the signal processing circuit 84 according to the embodiment.

  The thickness detector 8 includes an ultrasonic sensor 81 and a signal processing circuit 84. The ultrasonic sensor 81 includes a transmission unit 82 and a reception unit 83. The transmitter 82 and the receiver 83 each include a piezoelectric element. When performing double feed detection, the control unit 1 inputs pulses having a predetermined cycle (frequency) to the transmission unit 82. For example, a pulse of about several tens of kilohertz is input to the transmission unit 82. The piezoelectric element is deformed by applying a voltage (pulse). As a result, the transmitter 82 transmits an ultrasonic wave having the frequency of the input pulse.

  The receiving unit 83 receives the ultrasonic wave radiated from the transmitting unit 82. The piezoelectric element of the receiving unit 83 outputs an electric charge (voltage) corresponding to the intensity of ultrasonic pressure (sound pressure). The receiving unit 83 may include an amplifier circuit that amplifies the output of the piezoelectric element. In other words, the receiving unit 83 may output a voltage (charge) obtained by amplifying the output of the piezoelectric element.

  As shown in FIG. 3, the transmission unit 82 and the reception unit 83 are provided so as to sandwich the conveyance sheet. The ultrasonic transmission surface of the transmission unit 82 and the ultrasonic reception surface of the reception unit 83 face each other. The sheet passes between the transmission unit 82 and the reception unit 83. The transmitting unit 82 and the receiving unit 83 are provided so that the sheet is conveyed between them with the sheet conveying path interposed therebetween. An ultrasonic sensor 81 is provided upstream of the image forming unit 5b in the paper conveyance direction. FIG. 3 shows an example in which an ultrasonic sensor 81 is provided between the paper feeding unit 5a and the image forming unit 5b in the paper transport path.

  The signal processing circuit 84 is a circuit that charges the output (charge) of the receiving unit 83 and generates the detection voltage V1. As shown in FIG. 4, the signal processing circuit 84 includes, for example, a diode D1, a capacitor C1, and a resistor R1. The output of the receiving unit 83 is input to the input terminal (anode) of the diode D1. The output voltage from the output terminal (cathode) of the diode D1 is input to one end of the capacitor C1 and one end of the resistor R1. The other end of the capacitor C1 and the other end of the resistor R1 are connected to the ground. The capacitor C1 stores (charges) the charge output from the receiving unit 83. For example, the terminal voltage of the capacitor C1 is output as the output of the thickness detector 8 (detection voltage V1). The detection voltage V1 is input to the control unit 1.

  The control unit 1 includes an A / D conversion circuit 12 (see FIG. 1). The control unit 1 performs A / D conversion on the input detection voltage V1. Then, the control unit 1 recognizes the magnitude of the detection voltage V1. The A / D conversion circuit 12 may be provided in the thickness detection unit 8, and the A / D conversion circuit 12 may generate digital data indicating the magnitude of the detection voltage V1. In this case, digital data generated by the A / D conversion circuit 12 is input to the control unit 1. The control unit 1 recognizes the magnitude of the detection voltage V1 based on the input digital data.

  The magnitude of the detection voltage V1 increases as the intensity of the received ultrasonic wave increases. The smaller the intensity of the received ultrasonic wave, the smaller the magnitude of the detection voltage V1. The thickness detector 8 outputs a detection voltage V1 having a magnitude corresponding to the ultrasonic wave received by the receiver 83.

(Determination of paper thickness)
Next, an example of determination of the thickness of the sheet using the thickness detection unit 8 according to the embodiment will be described with reference to FIGS. FIG. 5 is a diagram illustrating an example of determination of the sheet thickness using the thickness detection unit 8 according to the embodiment. FIG. 6 shows an example of the thickness determination data D1 according to the embodiment.

  The operation panel 4 can set the thickness (thickness level) of the paper (contained in the paper cassette 51) used for printing. For example, the operation panel 4 accepts selection of the sheet thickness from a plurality of levels such as thick paper, plain paper, and thin paper. The control unit 1 causes the storage unit 2 to store the thickness of the selected paper in a nonvolatile manner. Based on the stored contents of the storage unit 2, the control unit 1 can recognize the set paper thickness.

  However, the sheet thickness set on the operation panel 4 may differ from the sheet thickness actually stored in the sheet cassette 51. For example, although the paper in the paper cassette 51 is changed to a paper having a different thickness, the user may forget to reset the paper thickness on the operation panel 4. For example, if the thickness previously set on the operation panel 4 is plain paper and a new thick paper is set, but the paper thickness is reset on the operation panel 4, it is set on the operation panel 4. The thickness of the printed paper is different from the thickness of the paper that is actually conveyed.

  Therefore, the control unit 1 determines the thickness (thickness level) of the paper during printing. The control unit 1 performs a sheet thickness determination process for each sheet conveyed. Note that the control unit 1 may determine the thickness of only one of the plurality of sheets. In other words, the control unit 1 may perform a paper thickness determination process once for a plurality of sheets.

  The start in FIG. 5 is a point in time when the paper feeding is started. When printing a plurality of sheets continuously, the control unit 1 executes the flowchart of FIG. 5 every time the feeding of one sheet is started.

  First, the control unit 1 causes the transmission unit 82 to start transmitting ultrasonic waves (step # 11). The control unit 1 may cause the transmission unit 82 to transmit ultrasonic waves before the leading edge of the paper reaches between the transmission unit 82 and the reception unit 83. In order to transmit ultrasonic waves from the transmission unit 82, the control unit 1 inputs a pulse signal having a predetermined transmission frequency to the transmission unit 82. For example, the transmission frequency is 20,000 or more Hz.

  Then, the control unit 1 recognizes the start of the thickness detection period T1 (step # 12). The thickness detection period T1 is predetermined. In the thickness detection period T1, the control unit 1 acquires the detection voltage V1 a predetermined number of times at a predetermined sampling period. Therefore, the thickness detection period T1 can be a time obtained by multiplying the predetermined number of times by the sampling period. Therefore, the relationship of thickness detection period T1> sampling period is established.

  The start point of the thickness detection period T1 is set after the leading edge of the paper reaches between the transmission unit 82 and the reception unit 83. In addition, the start point of the thickness detection period T1 is set so that the thickness detection period T1 ends before the sheet passes between the transmission unit 82 and the reception unit 83.

  When the paper reaches between the transmission unit 82 and the reception unit 83, the detection voltage V1 decreases. When the detection voltage V1 drops below a predetermined value after the rotation of the paper feed motor 52 starts, the control unit 1 recognizes that the leading edge of the paper has reached between the transmission unit 82 and the reception unit 83. Good. In this case, the control unit 1 may set the time point when it is recognized that the leading edge of the paper has reached between the transmission unit 82 and the reception unit 83 as the start time point of the thickness detection period T1.

  Further, the control unit 1 may recognize the start of the thickness detection period T1 based on the time elapsed from the start of paper feed (start of rotation of the paper feed motor 52). In this case, the control unit 1 measures the elapsed time from the start of paper feeding. For example, the control circuit 10 measures the elapsed time. The time required for the leading edge of the paper to reach between the transmission unit 82 and the reception unit 83 from the start of paper feeding can be obtained in advance. For example, the required time can be determined by dividing the distance between the front end position on the downstream side in the conveyance direction of the paper set in the paper cassette 51 and the distance between the transmission unit 82 and the reception unit 83 by the specification paper conveyance speed. it can. In this case, the control unit 1 recognizes the time when the elapsed time becomes the required time or the time when the elapsed time becomes a time obtained by adding a predetermined margin to the required time as the start time of the thickness detection period T1. To do.

  Then, the control unit 1 acquires the voltage value of the detection voltage V1 a predetermined number of times at a predetermined sampling period (step # 13). The control unit 1 performs A / D conversion on the analog voltage output from the thickness detection unit 8. For A / D conversion, the control unit 1 includes an A / D conversion circuit 12 (see FIG. 1). Thus, the control unit 1 acquires the voltage value of the detection voltage V1 digitized a predetermined number of times. The control unit 1 stores the voltage value (digital value) obtained by sampling in the storage unit 2.

  For example, a case where the predetermined number is 25 will be described. When the thickness detection period T1 is 10 milliseconds, 10 milliseconds / 25 = 0.4 milliseconds. Since the period is 0.4 milliseconds, the frequency is 2.5 kilohertz (1 ÷ 0.4 milliseconds). In this case, the sampling frequency is 2.5 kHz. The sampling frequency is set based on the predetermined number of times used and the thickness detection period T1.

  Information indicating the variation in the amplitude of the detection voltage V1 in the thickness detection period T1 can be obtained by sampling a predetermined number of times. In other words, the control unit 1 performs envelope detection of the output voltage of the thickness detection unit 8 by sampling a predetermined number of times.

  Then, the control unit 1 determines an excluded voltage value among a plurality of voltage values acquired by sampling in the thickness detection period T1 (step # 14). The excluded voltage value is a voltage value in which noise is mixed. In other words, the excluded voltage value is a voltage value corresponding to the detection voltage V <b> 1 when noise is mixed in the output of the receiving unit 83. Details of the determination of the excluded voltage value will be described later.

  Next, control unit 1 obtains an average value of the voltage values (step # 15). At this time, the control unit 1 excludes the excluded voltage value from the voltage values acquired during the thickness detection period T1. When obtaining the average value, the control unit 1 does not obtain the excluded voltage value. For example, when it is determined that the tenth acquired (sampled) voltage value is the excluded voltage value, the control unit 1 obtains an average value of the voltage values other than the tenth. Then, the control unit 1 determines the thickness of the conveyed paper based on the average value and the thickness determination data D1 (step # 16). Then, this flow ends (END).

  The thickness determination data D1 is data defining a range of an average value corresponding to each sheet thickness (thickness level). The storage unit 2 stores the thickness determination data D1 in a nonvolatile manner. At step # 16, the control unit 1 refers to the thickness determination data D1.

  FIG. 6 shows an example of the thickness determination data D1. FIG. 6 shows thickness determination data D1 when there are three types of paper thickness. In FIG. 6, X means an average value actually obtained. In FIG. 6, X1, X2, and X3 are boundary values for determining the sheet thickness. The thicker the paper, the less the ultrasonic wave that passes through the paper and reaches the receiving unit 83. On the contrary, the thinner the paper, the more ultrasonic waves that pass through the paper and reach the receiving unit 83. Therefore, the magnitude relationship between X1, X2, and X3 is X1 <X2 <X3. Note that the thickness of the sheet may be greater than three stages. The average value range corresponding to each thickness (stage, level) is defined by the thickness determination data D1.

(Determination of excluded voltage value)
Next, an example of determination of the excluded voltage value according to the embodiment will be described with reference to FIGS. FIG. 7 is a diagram illustrating an example of a waveform of a voltage value of the detection voltage V1 according to the embodiment. FIG. 8 is a diagram illustrating an example of a flow of determination of an exclusion voltage value according to the embodiment.

  The horizontal axis in FIG. 7 indicates time. The vertical axis in FIG. 7 indicates the amplitude of the voltage value of the detection voltage V1. The numbers attached to the upper side of the graph in FIG. 7 indicate the order in which voltage values are acquired in the thickness detection period T1. In other words, the numbers on the upper side of the graph indicate the order of the sampled voltages. In FIG. 7, the voltage value sampled fifth is much larger than the other voltage values. The 18th sampled voltage value is much smaller than other voltage values. Noise may suddenly change the magnitude of the detection voltage V1. When the thickness of the sheet is determined using the voltage value of the detection voltage V1 that is affected by noise, there is a risk of erroneous determination.

  Therefore, the control unit 1 determines that the voltage value greatly changed due to noise among the voltage values of the detection voltage V1 is an excluded voltage value. The control unit 1 determines whether or not each voltage value is an excluded voltage value. In the following description, n is a positive integer. N is a number less than a predetermined number.

  Details of step # 14 in FIG. 5 will be described with reference to FIG. The start of FIG. 8 is the time when step # 13 (acquisition of the voltage value of the detection voltage V1 a predetermined number of times) of FIG. 5 is completed.

  First, the control unit 1 substitutes 1 for n (step # 21). Then, control unit 1 determines whether or not the nth voltage value is an exclusion determination value (step # 22). Next, the control unit 1 checks whether or not the maximum value of n (predetermined number of times) has been reached (step # 23). In other words, the control unit 1 confirms whether or not all voltage values have been determined as exclusion determination values. When the determination of all the voltage values has not been completed (No in Step # 23), the control unit 1 adds 1 to n (Step # 24). Then, the flow returns to step # 22. On the other hand, when all the voltage values have been determined (Yes in step # 23), the control unit 1 ends this flow.

  Here, the control part 1 determines whether it is an exclusion voltage value by comparing the nth voltage value with the voltage value which order changes.

  As for the voltage value (voltage value of n = 1) sampled (acquired) for the first time, there is no previous voltage value in the sampling order. Therefore, the control unit 1 obtains the absolute value of the difference between the nth (first) voltage value and the (n + 1) th voltage value acquired by sampling in the thickness detection period T1. When the absolute value exceeds a predetermined allowable value D2, the control unit 1 determines that the n = 1st voltage value is an excluded voltage value.

  As for the last sampled (acquired) voltage value (n = a predetermined number of voltage values), there is no voltage value after the sampling order. Therefore, the control unit 1 obtains the absolute value of the difference between the nth (last) voltage value and the (n−1) th voltage value acquired by sampling in the thickness detection period T1. When the absolute value exceeds a predetermined allowable value D2, the control unit 1 determines that the nth (last) voltage value is an excluded voltage value.

  With respect to the voltage value from the second to the last sampled in order of sampling, there are a voltage value before and after the sampling order of sampling. Therefore, when n = 2 to (predetermined number −1), the control unit 1 calculates the absolute difference between the nth voltage value acquired by sampling in the thickness detection period T1 and the (n−1) th voltage value. A first absolute value that is a value is obtained. In addition, the control unit 1 obtains a second absolute value that is an absolute value of a difference between the nth voltage value acquired by sampling in the thickness detection period T1 and the (n + 1) th voltage value. Then, when both the first absolute value and the second absolute value exceed the allowable value D2, the control unit 1 determines the nth voltage value as an excluded voltage value. In addition, when one or both of the first absolute value and the second absolute value is less than the allowable value D2, the control unit 1 determines that the nth voltage value is not an excluded voltage value.

  Even in the case of n = 2 to (predetermined number −1), the controller 1 determines that the absolute value of the difference between the nth voltage value and the (n + 1) th voltage value exceeds the allowable value D2. The second voltage value may be determined as the excluded voltage value. Alternatively, when the absolute value of the difference between the nth voltage value and the (n−1) th voltage value exceeds the allowable value D2, the control unit 1 determines that the nth voltage value is an excluded voltage value. Also good.

  The allowable value D2 is determined in advance. For example, a plurality of sheets are conveyed, and a change width of the detection voltage V1 during sheet conveyance when there is no noise is measured. Then, the maximum value of the change width obtained by the measurement can be determined as the allowable value D2. The storage unit 2 stores the allowable value D2 in a nonvolatile manner (see FIG. 1). The control unit 1 makes a determination with reference to the allowable value D2 stored in the storage unit 2.

(Determination of double feed)
Next, an example of determination of double feeding of sheets using the thickness detection unit 8 according to the embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a diagram illustrating an example of determination of double feeding of sheets using the thickness detection unit 8 according to the embodiment. FIG. 10 is a diagram illustrating an example of a waveform of a voltage value of the detection voltage V1 at the time of double feeding.

  Double feeding (conveyance in which a plurality of sheets overlap) may occur. For example, a part of the next sheet overlaps with a part of the preceding sheet and may be conveyed. In some cases, two sheets of paper are almost completely overlapped and conveyed.

  Paper jams may occur due to double feeding. Further, when the paper reaches the image forming unit 5b in the double feed state, the contents of one page may be printed across a plurality of sheets. In order to avoid clogging and useless printing, paper conveyance should be stopped immediately when a double feed occurs. In the multi-function device 100, the thickness detector 8 can be used to detect double feeding.

  Here, the thickness detection period T1 can be, for example, about 10 milliseconds. In the multifunction device 100, for example, the minimum size of printable paper is A6. The size of A6 paper is 105 × 148 mm. When the paper transport speed is 300 mm / second, the time from when the leading edge of the A6 paper reaches the transmission unit 82 and the reception unit 83 to the passage is about 0.5 seconds. During about 0.5 seconds, the control unit 1 sets a thickness detection period T1 of 10 milliseconds. Even if the thickness detection period T1 is set after recognizing the arrival of the leading edge of the sheet from the control unit 1 based on the outputs of the transmitting unit 82 and the receiving unit 83, the weight immediately after reaching the ultrasonic sensor 81 at the leading end of the sheet. The occurrence of feeding can be detected.

  In the double feed state, the ultrasonic wave that passes through the paper and is received by the receiving unit 83 is less than that during the transport of the thick paper. And at the time of double feeding, the sudden drop of the detection voltage V1 may be repeated during the thickness detection period T1. The control unit 1 determines whether or not double feeding has occurred based on repeated rapid voltage value reductions.

  The start of FIG. 9 is the time when step # 13 of FIG. 5 (acquisition of the voltage value of the detection voltage V1 a predetermined number of times) is completed. First, the control unit 1 checks whether or not the voltage value has changed from the abnormal value D3 or more to less than the abnormal value D3 in the thickness detection period T1 (step # 31). In other words, the control unit 1 checks whether or not the voltage value of the detection voltage V1 is less than the abnormal value D3.

  The abnormal value D3 is determined in advance. For example, the abnormal value D3 can be determined based on the output (detection voltage V1) of the receiving unit 83 when the double feed occurs. For example, the average value of the voltage value of the detection voltage V1 when the double-fed paper is transported by experiment can be set as the abnormal value D3. The storage unit 2 stores the abnormal value D3 in a nonvolatile manner (see FIG. 1). The control unit 1 performs confirmation by referring to the abnormal value D3 stored in the storage unit 2.

  When there is no change in the voltage value from the abnormal value D3 or more to less than the abnormal value D3 (No in step # 31), the control unit 1 ends the processing relating to this flow (end). When the voltage value changes from the abnormal value D3 or more to less than the abnormal value D3 (Yes in step # 31), the control unit 1 determines the period of the double feed reference time T2 or more among the periods of less than the abnormal value D3. It is confirmed whether or not there is (step # 32). The voltage value may drop instantaneously due to noise. The control unit 1 checks the length of the period less than the abnormal value D3 so as not to erroneously detect the occurrence of double feed.

  When there is no period equal to or longer than the multifeed reference time T2 (No in step # 32), the control unit 1 ends the process related to this flow (end). When there is a period equal to or longer than the double feed reference time T2 (Yes in step # 32), the control unit 1 checks whether there are a plurality of periods equal to or longer than the double feed reference time T2 (step # 33).

  The double feed reference time T2 is predetermined. The double feed reference time T2 can be, for example, a length equal to or longer than two sampling periods of the detection voltage V1. The storage unit 2 stores the multifeed reference time T2 in a nonvolatile manner (see FIG. 1). The control unit 1 performs confirmation by referring to the double feed reference time T2 stored in the storage unit 2.

  When there are not a plurality of periods equal to or longer than the multifeed reference time T2 (No in Step # 33), the control unit 1 ends the process related to this flow (End). When there are a plurality of periods equal to or greater than the double feed reference time T2 (Yes in Step # 33), the control unit 1 determines that the double feed of the paper has occurred (Step # 34).

  When it is determined that double feeding has occurred, the control unit 1 causes the printing unit 5 (the paper feeding unit 5a, the paper conveyance unit 6, the printing unit 5, and the fixing unit 7) to stop the conveyance of the paper. In addition, the control unit 1 causes the display panel 41 to display a message. This message notifies, for example, that a double feed has occurred. In addition, the message may be a content that informs the user that the sheet remaining in the multifunction peripheral 100 should be removed due to the stop of the sheet conveyance.

  FIG. 10 shows an example of the transition of the detection voltage V1 when it is determined that double feed has occurred. In the example of FIG. 10, the detection voltage V1 is temporarily recovered after the first drop of the detection voltage V1 to less than the abnormal value D3. However, the detection voltage V1 drops again below the abnormal value D3. In other words, in the example of FIG. 10, the decrease of the detection voltage V1 to less than the abnormal value D3 is repeated twice. Further, in the example of FIG. 10, the periods less than the two abnormal values D3 are both equal to or longer than the multifeed reference time T2.

(Control based on the judged paper thickness)
Next, an example of control based on the determined sheet thickness in the multifunction peripheral 100 according to the embodiment will be described with reference to FIGS. FIG. 11 is a diagram illustrating an example of the fixing unit 7 and the nip pressure adjusting unit 9 according to the embodiment. FIG. 12 is a diagram illustrating an example of the fixing temperature data D4 according to the embodiment. FIG. 13 is a diagram illustrating an example of the nip pressure data D5 according to the embodiment. FIG. 14 is a diagram illustrating an example of control according to the sheet thickness in the multifunction peripheral 100 according to the embodiment.

  First, the multifunction peripheral 100 includes a fixing unit 7. As shown in FIG. 11, the fixing unit 7 includes a heating rotator 71, a pressure rotator 72, a heater 73, and a fixing motor 74. The heating rotator 71 and the pressure rotator 72 are, for example, rollers. The peripheral surface of the heating rotator 71 and the peripheral surface of the pressure rotator 72 are in contact with each other. The pressure rotator 72 is pressed against the heating rotator 71. The peripheral surface of the heating rotator 71 and the peripheral surface of the pressure rotator 72 form a nip. The heater 73 heats the heating rotator 71. The fixing motor 74 rotates either one or both of the peripheral surface of the heating rotator 71 and the pressure rotator 72. During printing, the control unit 1 rotates the fixing motor 74. The sheet on which the toner image is transferred passes through the nip. Of the surface of the paper, the surface to which the unfixed toner image is transferred is in contact with the heating rotator 71. The sheet is conveyed while being heated and pressurized. The heating rotator 71 and the pressure rotator 72 also function as a pair of conveying rotators.

  In addition, a temperature sensor 75 for detecting the temperature of the heating rotator 71 is provided. The temperature sensor 75 outputs a voltage corresponding to the temperature of the heating rotator 71. The output of the temperature sensor 75 is input to the control unit 1. Based on the output of the temperature sensor 75, the control unit 1 recognizes the temperature of the heating rotator 71. The controller 1 controls ON / OFF (power supply) of the heater 73 so that the heating rotator 71 (recognized temperature) is maintained at the fixing control temperature.

  The storage unit 2 stores the fixing temperature data D4 in a nonvolatile manner. The fixing temperature data D4 is data defining a fixing control temperature that is a temperature of a heating rotating body corresponding to each sheet thickness (thickness level). At the start of printing, the control unit 1 heats the heating rotator. For example, the control unit 1 recognizes the fixing control temperature corresponding to the thickness of the sheet selected on the operation panel 4. When detecting that the temperature reaches the recognized fixing control temperature, the control unit 1 causes the paper feeding unit 5a to start printing.

  FIG. 12 shows an example of the fixing temperature data D4. In FIG. 12, the values of Y1, Y2, and Y3 are temperatures and differ depending on the model of the image forming apparatus. In the multifunction peripheral 100, the fixing control temperature is set higher as the sheet becomes thicker. Therefore, the magnitude relationship is Y1> Y2> Y3.

  In addition, the multifunction peripheral 100 includes a pair of conveying rotating bodies that rotate to convey a sheet. The heating rotator 71 and the pressure rotator 72 of the fixing unit 7 are also a kind of a pair of rotating rotators for conveyance. The transport roller pair 61 provided in the paper transport unit 6 is also a kind of transport rotating body pair. The peripheral surfaces of the pair of transport rotary members are in contact with each other. The control unit 1 rotates each conveying rotator. The paper enters the nip between the peripheral surfaces. The sheet is conveyed by the rotation of each conveying rotator.

  The multi-function device 100 includes a nip pressure adjusting unit 9 that adjusts the nip pressure of the conveying rotating body pair. The nip pressure adjusting unit 9 includes a pressurizing mechanism 91 and a pressure adjusting mechanism 92. The pressurizing mechanism 91 includes, for example, a pressing member that presses one transport rotator against the other transport rotator. The pressure adjustment mechanism 92 includes a nip pressure adjustment motor and an eccentric cam. The cam is in contact with the pressing member. The pressing force of the pressing member varies depending on the rotation angle of the nip pressure adjusting motor (eccentric cam). The control unit 1 can adjust the nip pressure by controlling the rotation angle of the nip pressure adjusting motor (eccentric cam).

  The nip pressure adjusting unit 9 may be provided for all the conveying rotator pairs. In addition, a pressurizing mechanism 91 and a pressure adjusting mechanism 92 may be provided for a part of the transport rotator pairs among the transport rotator pairs provided on the paper transport path. For example, the nip pressure adjusting unit 9 may be provided only for the conveying rotating body pair (the heating rotating body 71 and the pressing rotating body 72) of the fixing unit 7.

  The storage unit 2 stores the nip pressure data D5 in a nonvolatile manner. The nip pressure data D5 is data defining the nip pressure of the conveying rotating body corresponding to each sheet thickness (thickness level). At the start of printing, the control unit 1 causes the nip pressure adjusting unit 9 to adjust the nip pressure. For example, the control unit 1 causes the nip pressure adjustment unit 9 to adjust the nip pressure corresponding to the thickness of the sheet selected on the operation panel 4. After the adjustment, the control unit 1 causes the paper supply unit 5a to start printing.

  FIG. 13 shows an example of the nip pressure data D5. In FIG. 13, the values of Z1, Z2, and Z3 are nip pressures and differ depending on the model of the image forming apparatus. In the multifunction peripheral 100, the nip pressure is reduced as the sheet becomes thicker. Therefore, the magnitude relationship is Z1 <Z2 <Z3.

  Then, the start of FIG. 14 is the time when the thickness of the sheet is determined based on the flowchart of FIG. First, the controller 1 refers to the fixing temperature data D4 and sets the fixing control temperature to a temperature corresponding to the determined sheet thickness (step # 41). Thereafter, the control unit 1 controls ON / OFF of the heater 73 so that the heating rotator 71 is maintained at the fixing control temperature. Even if the thickness of the sheet set on the operation panel 4 is different from the thickness of the sheet being conveyed (determined sheet thickness), the fixing control temperature is set to a temperature corresponding to the thickness of the sheet being conveyed. be able to.

  Next, the control unit 1 refers to the nip pressure data D5 and causes the nip pressure adjustment unit 9 to adjust the nip pressure corresponding to the determined thickness (step # 42). Even if the thickness of the sheet set on the operation panel 4 is different from the thickness of the sheet being conveyed (determined sheet thickness), the nip pressure of one or a plurality of conveying rotating body pairs is set to the sheet size. The size can be adjusted accordingly.

  As described above, the image forming apparatus (multifunction peripheral 100) according to the embodiment includes the paper transport unit 6, the thickness detection unit 8, the control unit 1, and the storage unit 2. The paper transport unit 6 transports paper. The thickness detection unit 8 includes a transmission unit 82 and a reception unit 83. The thickness detector 8 outputs a detection voltage V1 having a magnitude corresponding to the ultrasonic wave received by the receiver 83. The control unit 1 receives the detection voltage V1. The storage unit 2 stores thickness determination data D1 for determining the thickness of the paper. The transmitting unit 82 and the receiving unit 83 are provided so that the sheet is conveyed between them with the sheet conveying path interposed therebetween. The control unit 1 causes the transmission unit 82 to transmit ultrasonic waves toward the reception unit 83 during a predetermined thickness detection period T1. The control unit 1 acquires a voltage value of the detection voltage V1 at a predetermined sampling period shorter than the thickness detection period T1. The control unit 1 determines an excluded voltage value that is a voltage value in which noise is mixed among a plurality of voltage values acquired by sampling in the thickness detection period T1. The control part 1 calculates | requires the average value of the voltage value except an exclusion voltage value among the voltage values acquired in thickness detection period T1. The control unit 1 determines the thickness of the conveyed paper based on the average value and the thickness determination data D1. The determination data is data defining an average value range corresponding to each sheet thickness.

  According to this configuration, it is possible to exclude a numerical value in which noise is mixed (influenced by noise) from a numerical value (voltage value) serving as a reference for calculation for determining the thickness. Information that causes a determination error can be excluded from the information used to determine the thickness of the sheet. Accordingly, the thickness of the paper can be accurately determined.

  The control unit 1 obtains the absolute value of the difference between the nth voltage value acquired by sampling in the thickness detection period T1 and the (n−1) th or (n + 1) th voltage value. When the absolute value exceeds a predetermined allowable value D2, the control unit 1 determines that the nth voltage value is an excluded voltage value. Determining whether or not the nth voltage value is abnormal based on a comparison with a voltage value sampled at time (n−1) or a voltage value obtained by sampling at time (n + 1). it can. It can be determined whether or not noise is mixed in the voltage value acquired in the n-th sampling. A voltage value that is abnormally different from a voltage value acquired by sampling at the previous or next time point can be excluded from the numerical values used for the determination. Accordingly, the thickness of the paper can be accurately determined.

  The control unit 1 obtains a first absolute value that is an absolute value of a difference between the nth voltage value acquired by sampling in the thickness detection period T1 and the (n−1) th voltage value. In addition, the control unit 1 obtains a second absolute value that is an absolute value of a difference between the nth voltage value acquired by sampling in the thickness detection period T1 and the (n + 1) th voltage value. When both the first absolute value and the second absolute value exceed a predetermined allowable value D2, the control unit 1 determines the nth voltage value as an excluded voltage value. When one or both of the first absolute value and the second absolute value is less than the allowable value D2, the control unit 1 determines that the nth voltage value is not an excluded voltage value. Based on the comparison between the voltage value sampled at time (n−1) and the voltage value obtained by sampling at time (n + 1), it can be determined whether or not the nth voltage value is abnormal. . It is possible to accurately determine whether noise is mixed in the nth sampled voltage value. The voltage value corresponding to the detection voltage V1 in which noise is mixed can be excluded from the numerical values used for the determination. Accordingly, the thickness of the paper can be accurately determined.

  The controller 1 checks whether or not there is a change in voltage value from a predetermined abnormal value D3 or more to a value less than the abnormal value D3 within the thickness detection period T1. When there is a change in the voltage value from the abnormal value D3 or more to less than the abnormal value D3, the control unit 1 determines whether or not there is a period longer than the predetermined multifeed reference time T2 among the periods less than the abnormal value D3. Confirm. When there is a period longer than the multifeed reference time T2, the control unit 1 checks whether there are a plurality of periods longer than the multifeed reference time T2. When there are a plurality of periods equal to or longer than the double feed reference time T2, it is determined that the double feed of the paper has occurred. When the voltage value of the detection voltage V1 repeats abnormal drops and rises, it can be determined that a double feed of the paper has occurred.

  The multifunction peripheral 100 (image forming apparatus) includes an image forming unit 5 b and a fixing unit 7. The image forming unit 5b forms a toner image and transfers the toner image formed on the conveyed paper. The fixing unit 7 includes a heating rotator 71 and a heater 73 that heats the heating rotator 71. The fixing unit 7 fixes the toner image by heating the sheet on which the toner image is transferred. The storage unit 2 stores fixing temperature data D4 that defines a fixing control temperature that is a temperature of the heating rotator 71 corresponding to each sheet thickness. At the time of printing, the control unit 1 refers to the fixing temperature data D4 and sets the temperature of the heating rotator 71 to a fixing control temperature corresponding to the determined sheet thickness. The temperature of the heating rotator 71 can be set to a temperature suitable for the thickness of the paper. The temperature of the heating rotator 71 can be maintained at a temperature suitable for printing.

  The multifunction peripheral 100 (image forming apparatus) includes a pair of transport rotators (for example, a heating rotator 71, a pressure rotator 72, and a transport roller pair 61) that rotate and transport the paper. The multi-function device 100 also includes a nip pressure adjusting unit 9 that adjusts the nip pressure between the pair of conveying rotators. The storage unit 2 stores nip pressure data D5 that defines the nip pressure of the conveying rotator corresponding to each sheet thickness. At the time of printing, the control unit 1 refers to the nip pressure data and causes the nip pressure adjustment unit 9 to adjust the nip pressure corresponding to the determined sheet thickness. The nip pressure of the transport rotator can be set to a nip pressure suitable for the thickness of the transport paper. During printing, the nip pressure can be maintained at an appropriate pressure. The nip pressure can be adjusted so that the paper is not jammed or broken.

  The embodiment of the present invention has been described above, but the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

  The present invention is applicable to an image forming apparatus including an ultrasonic sensor.

DESCRIPTION OF SYMBOLS 100 MFP (image forming apparatus) 1 Control part 2 Memory | storage part 5b Image forming part 6 Paper conveyance part 61 Conveyance roller pair (pair of rotary bodies for conveyance)
7 Fixing Unit 71 Heating Rotating Body (Conveying Rotating Body)
73 Heater 8 Thickness detector 82 Transmitter 83 Receiver 9 Nip pressure adjuster D1 Thickness determination data D3 Abnormal value D4 Fixing temperature data D5 Nip pressure data T1 Thickness detection period T2 Double feed reference time V1 Detection voltage

Claims (6)

A paper transport unit for transporting paper,
A thickness detector that includes a transmitter and a receiver, and outputs a detection voltage having a magnitude according to the ultrasonic wave received by the receiver;
A control unit to which the detection voltage is input;
A storage unit for storing data for determining the thickness for determining the thickness of the paper,
The transmitting unit and the receiving unit are provided so as to sandwich a sheet conveyance path and convey a sheet therebetween,
The controller is
During the predetermined thickness detection period, the ultrasonic wave is transmitted to the transmission unit toward the reception unit,
The voltage value of the detection voltage is obtained in a predetermined sampling period shorter than the thickness detection period,
Among the plurality of voltage values acquired by sampling in the thickness detection period, determine an excluded voltage value that is the voltage value mixed with noise,
Among the voltage values acquired during the thickness detection period, obtain an average value of the voltage values excluding the excluded voltage value,
Based on the average value and the thickness determination data, determine the thickness of the conveyed paper,
The image forming apparatus, wherein the determination data is data defining a range of the average value corresponding to a sheet thickness. The controller is
Find the absolute value of the difference between the nth voltage value acquired by sampling in the thickness detection period and the (n-1) th or (n + 1) th voltage value,
The image forming apparatus according to claim 1, wherein when the absolute value exceeds a predetermined allowable value, the nth voltage value is determined as the exclusion voltage value. The controller is
A first absolute value that is an absolute value of a difference between the nth voltage value and the (n−1) th voltage value acquired by sampling in the thickness detection period;
A second absolute value that is an absolute value of a difference between the nth voltage value acquired by sampling in the thickness detection period and the (n + 1) th voltage value is obtained;
When both the first absolute value and the second absolute value exceed a predetermined allowable value, the nth voltage value is determined as the excluded voltage value,
2. The n-th voltage value is determined not to be the exclusion voltage value when one or both of the first absolute value and the second absolute value is less than the allowable value. Image forming apparatus. The controller is
Check whether there was a change in voltage value from a predetermined abnormal value to less than the abnormal value within the thickness detection period,
When there is a change in voltage value from the abnormal value or more to less than the abnormal value, check whether there is a period longer than a predetermined multifeed reference time among the periods less than the abnormal value,
When there is a period longer than the multifeed reference time, check whether there are a plurality of periods longer than the multifeed reference time,
4. The image forming apparatus according to claim 1, wherein when there are a plurality of periods equal to or longer than the multi-feed reference time, it is determined that a double feed of the paper has occurred. An image forming unit that forms a toner image and transfers the toner image formed on the conveyed paper;
A heating rotator and a heater that heats the heating rotator, and a fixing unit that fixes the toner image by heating the paper on which the toner image is transferred,
The storage unit stores fixing temperature data defining a fixing control temperature, which is a temperature of the heating rotator corresponding to each sheet thickness,
When printing
5. The control unit according to claim 1, wherein the controller refers to the fixing temperature data and sets the temperature of the heating rotator to the fixing control temperature corresponding to the determined thickness of the sheet. 2. The image forming apparatus according to item 1. A pair of conveying rotators for rotating and conveying paper;
Including a nip pressure adjusting unit that adjusts the nip pressure between the pair of conveying rotators,
The storage unit stores nip pressure data defining a nip pressure of the conveying rotating body corresponding to each sheet thickness,
When printing
6. The control unit according to claim 1, wherein the control unit causes the nip pressure adjustment unit to adjust the nip pressure corresponding to the determined sheet thickness with reference to the nip pressure data. The image forming apparatus according to claim 1.

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