JP2012046329A - Skew detection device, sheet transport device using the same, and image reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a skew detection device which can perform sure skew detection with a simple structure, a sheet transport device using the same, and an image reading apparatus.SOLUTION: A transmission-side wave transmission part 102 transmits ultrasonic waves generated by an ultrasonic-wave generation part 101 to transmission-side openings 103A, 103B, 103C. A reception-side wave transmission part 105 transmits ultrasonic waves received by reception-side openings 104A, 104B, 104C to an ultrasonic-wave reception part 106. A first distance L1 is smaller than a second distance L2. The ultrasonic-wave reception part 106 receives the ultrasonic waves received by the reception-side openings 104A, 104B, 104C. The presence of skew of a sheet is determined based on the differences among amplitude values of the ultrasonic waves received by the ultrasonic-wave reception part 106.

Description

  The present invention relates to a skew detection device that detects the presence or absence of skew of a conveyed sheet, a sheet transport device using the skew detection device, and an image reading device.

  Conventionally, there has been proposed a skew detection device that detects the presence or absence of skew of a conveyed sheet using ultrasonic waves. The skew detection device disclosed in Patent Document 1 includes two or more ultrasonic transmission units and two or more ultrasonic reception units. Each of the two or more ultrasonic transmission units transmits ultrasonic waves toward a piece of corrugated cardboard that is an example of a conveyed sheet. Each of the two or more ultrasonic wave reception units receives the ultrasonic waves that are transmitted through the reflected corrugated paper piece or reflected by the corrugated paper piece.

  When a piece of corrugated paper passes over each of the two or more ultrasonic wave receivers, there is a difference in the amplitude value of the ultrasonic wave as compared to when it does not pass. For example, when two or more ultrasonic wave reception units each receive ultrasonic waves that have passed through a piece of corrugated paper that is being conveyed, the amplitude value of the ultrasonic wave is smaller than that during non-passage. That is, the ultrasonic wave is attenuated. The skew detection device of Patent Document 1 detects the presence or absence of skew of a corrugated paper piece from the time difference between two or more ultrasonic wave receiving parts of the passage signal of the corrugated paper piece indicated by this ultrasonic wave.

JP-A-61-206758

  However, since the skew detection device disclosed in Patent Document 1 uses two or more ultrasonic transmission units and an ultrasonic reception unit, when transmitting ultrasonic waves simultaneously from two or more ultrasonic transmission units, Interference between ultrasonic waves occurred. Due to this interference, it has been difficult to perform reliable skew detection. In addition, the skew detection device disclosed in Patent Document 1 transmits ultrasonic waves separately from two or more ultrasonic transmission units, and transmits ultrasonic waves from each ultrasonic transmission unit to two or more ultrasonic waves. It was necessary to receive by each of the receiving units. Therefore, the configuration of the apparatus is complicated.

  The present invention has been made to solve the above-described problems, and has a simple configuration and a skew detection device capable of performing reliable skew detection, and a sheet using the skew detection device. It is an object to provide a transport device and an image reading device.

  In order to achieve the above object, the present invention according to claim 1 is a skew detection device for detecting the presence or absence of skew of a conveyed sheet, comprising: an ultrasonic generator that generates pulsed ultrasonic waves; A plurality of transmission-side openings arranged on a plane parallel to the surface of the sheet and at different positions with respect to an orthogonal direction orthogonal to a conveyance direction in which the sheet is conveyed, A transmission-side transmission unit that is coupled to the ultrasonic generation unit and the plurality of transmission-side openings, and that transmits the ultrasonic waves generated by the ultrasonic generation unit to the plurality of transmission-side openings; and in the orthogonal direction A plurality of reception side openings that are arranged at different positions, face each other across the plurality of transmission side openings and sandwich the sheet, and receive the ultrasonic waves transmitted by the plurality of transmission side openings; Received by the receiving side opening of the An ultrasonic receiver that receives sound waves, a receiver that is coupled to the plurality of reception openings and the ultrasonic receiver, and that transmits the ultrasonic waves received by the reception openings to the ultrasonic receiver A determination unit that determines whether or not the sheet is skewed based on a difference between amplitude values of the ultrasonic waves received by the ultrasonic wave reception unit via the side transmission unit and the plurality of reception side openings; Path lengths of a plurality of paths from the ultrasonic wave generation unit to the ultrasonic wave reception unit via the transmission side transmission unit, the plurality of transmission side openings, and the plurality of reception side openings Are characterized by different lengths.

  According to a second aspect of the present invention, in the first aspect of the invention, one of the plurality of transmission side openings, the transmission side opening, the ultrasonic wave generation unit, and the ultrasonic wave reception unit, The reception-side opening, the ultrasonic wave generation unit, and the ultrasonic wave reception unit, which are arranged at the same position with respect to the orthogonal direction, of the plurality of reception-side openings, It is arranged at the same position.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the transmission-side transmission unit and the reception-side transmission unit extend in the orthogonal direction, and a plurality of the transmission-side openings. Are arranged at the same position with respect to the carrying direction, and the plurality of reception side openings are arranged at the same position with respect to the carrying direction.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, the ultrasonic wave generating portion, the ultrasonic wave receiving portion, and the specific transmission side opening portion disposed at the same position with respect to the orthogonal direction Is arranged on the upstream side of the other transmission side opening in the conveyance direction, and the ultrasonic wave generation unit, the ultrasonic wave reception unit, and the specific reception side arranged at the same position with respect to the orthogonal direction The opening is arranged on the upstream side of the other receiving-side opening in the transport direction, and the time obtained by dividing the distance between the specific transmitting-side opening and the other transmitting-side opening by the speed of sound, The distance between the specific transmission-side opening in the conveyance direction and the other transmission-side opening is equal to the time divided by the conveyance speed of the sheet, and the specific reception-side opening and the other reception The distance to the side opening was divided by the speed of sound. The gap is configured to be equal to a time obtained by dividing a distance between the specific reception side opening in the conveyance direction and the other side opening by the conveyance speed of the sheet. Is.

  The present invention according to claim 5 is the invention according to any one of claims 1 to 4, characterized by comprising at least three transmission side openings and at least three reception side openings. Is.

  According to a sixth aspect of the present invention, in the invention according to the fifth aspect, of the at least three transmission side openings, a distance between two transmission side openings adjacent to each other in the transmission side transmission unit. Among the at least three reception side openings, the distances between the two reception side openings adjacent to each other in the reception side transmission part are respectively the transmission side transmission part and the reception side transmission part. The distance is equal to or more than half the value obtained by multiplying the reverberation time depending on the configuration of the part and the sound speed.

  The present invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the transmission-side transmission unit, the plurality of transmission-side openings, the reception-side transmission unit, and the plurality of the transmission units Each of the reception side openings is constituted by a voice tube.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, further comprising a notifying unit for notifying whether or not the sheet is skewed based on a determination result of the determining unit. To do.

  The present invention according to claim 9 is a sheet conveying device, comprising the skew detection device according to any one of claims 1 to 8 and a conveying unit that conveys the sheet. It is.

  According to a tenth aspect of the present invention, in the invention according to the ninth aspect, the conveying portions are arranged to face each other in a direction intersecting the surface of the sheet, and the sheet is placed in the conveying direction while sandwiching the sheet. A pair of conveying sections that extrude and convey the sheet, wherein the conveying section is positioned between at least two of the plurality of transmitting-side openings and the at least two of the transmitting-side openings; It is located between at least two receiving side openings that receive ultrasonic waves through the transmitting side openings.

  The present invention described in claim 11 is an image reading apparatus, comprising: the sheet conveying apparatus according to claim 9 or 10; and a reading unit that reads an image of the sheet conveyed by the conveying unit. It is a feature.

According to a twelfth aspect of the present invention, in the invention according to the eleventh aspect, the ultrasonic wave is received by the ultrasonic wave reception unit through the plurality of reception side openings and the conveyance speed of the sheet by the conveyance unit. A determination unit that determines a skew angle of the sheet based on a difference in time and a distance from the ultrasonic wave generation unit to each transmission side opening in the transmission side transmission unit;
An image processing unit that corrects an inclination of the image of the sheet based on the skew angle determined by the determination unit.

  According to the skew detection apparatus of the first aspect, the ultrasonic wave generation unit and the plurality of transmission side openings are connected by the transmission side transmission unit. Further, the ultrasonic wave receiving unit and the plurality of reception side openings are connected by the reception side wave transmission unit. Therefore, only by generating an ultrasonic wave from one ultrasonic wave generation unit, the ultrasonic wave is transmitted through the transmission side transmission unit and transmitted from a plurality of transmission side openings. The ultrasonic waves received by the plurality of reception side openings are transmitted through the reception side transmission unit and received by one ultrasonic reception unit. Therefore, it is not necessary to separately transmit ultrasonic waves from a plurality of ultrasonic transmission units, and it is not necessary to receive ultrasonic waves by a plurality of ultrasonic reception units. Therefore, skew detection can be performed with a simple configuration.

  According to the skew detection device according to claim 1, from the ultrasonic wave generation unit to the ultrasonic wave reception unit through the transmission side transmission unit, the plurality of transmission side openings, and the plurality of reception side openings. The path lengths of the plurality of paths are different lengths. Therefore, the time for the ultrasonic waves generated by the ultrasonic wave generation unit to reach the ultrasonic wave reception unit via the plurality of transmission side openings and the plurality of reception side openings is different. Accordingly, it is possible to reduce the possibility of interference between ultrasonic waves and to perform reliable skew detection.

  According to the skew detection device according to claim 2, the ultrasonic wave generated by the ultrasonic wave generator is firstly arranged in the same position as the ultrasonic wave generator and the ultrasonic wave receiver in the orthogonal direction. Transmitted by the transmission side opening. Thereafter, the ultrasonic wave generated by the ultrasonic wave generation unit is transmitted through the transmission side transmission unit and transmitted through the other transmission side opening. The ultrasonic waves transmitted by one transmission side opening arranged at the same position as the ultrasonic wave generation unit and the ultrasonic wave reception unit with respect to the orthogonal direction are the ultrasonic wave generation unit and the ultrasonic wave reception unit with respect to the orthogonal direction. The signal is received by one receiving side opening disposed at the same position. Therefore, the ultrasonic wave that passes through one transmission side opening and one reception side opening arranged at the same position as the ultrasonic wave generation unit and the ultrasonic wave reception unit with respect to the orthogonal direction is transmitted through the path with the shortest path length. I can tell you. Therefore, compared to the case where all of the plurality of transmission side openings and the plurality of reception side openings are arranged at other positions with respect to the orthogonal direction, the time required for transmitting and receiving ultrasonic waves used for skew detection Can be shortened as much as possible.

  According to the skew detection device of claim 3, the transmission-side transmission unit and the reception-side transmission unit extend in the orthogonal direction, and the plurality of transmission-side openings are at the same position with respect to the conveyance direction. The plurality of reception side openings are arranged at the same position with respect to the transport direction. Therefore, since the presence / absence of a sheet can be detected at the same position in the conveyance direction, it is possible to reliably detect skew feeding.

  According to the skew detection device of the fourth aspect, after the ultrasonic wave is transmitted from one transmission side opening disposed at the same position as the ultrasonic wave generation unit and the ultrasonic wave reception unit with respect to the orthogonal direction, The influence on the skew detection accuracy due to the sheet being conveyed during the time from when the ultrasonic wave is transmitted through the transmission side opening can be reduced. Therefore, accurate skew detection can be performed.

  According to the skew detection apparatus of the fifth aspect, at least three transmission side openings and at least three reception side openings are provided. Therefore, compared to a skew detection device having two transmission side openings and two reception side openings, a transmission side opening and a reception side opening that are members for detecting the presence or absence of a sheet Since there are a large number, the skew detection can be performed more reliably.

  According to the skew detection device of the sixth aspect, the reverberation generated in the reception-side transmission unit when the ultrasonic wave is received by the specific reception-side opening among the plurality of reception-side openings is specified. After the reception side opening receives the ultrasonic wave, it does not remain in the reception side transmission unit until the ultrasonic wave is received by the opening adjacent to the specific reception side opening. If reverberation remains until an ultrasonic wave is received by the adjacent reception side opening, the ultrasonic wave received by the adjacent reception side opening and the reverberation are superimposed. If ultrasonic waves and reverberation overlap in this way, the accuracy of skew detection is affected. Therefore, according to the apparatus of the fifth aspect, it is possible to prevent the reverberation from affecting the accuracy of the detected skew detection.

  According to the skew detection device of claim 7, each of the transmission-side transmission unit, the plurality of transmission-side openings, the reception-side transmission unit, and the plurality of reception-side openings is configured by a voice tube. . Therefore, the number of parts is reduced for the transmission side transmission unit, the plurality of transmission side openings, the reception side transmission unit, and the plurality of reception side openings, respectively, as compared with the case where separate components are used. be able to.

  According to the skew detection device of the eighth aspect, it is possible to notify the user of the presence or absence of the skew of the sheet. Therefore, it is possible to notify the user whether or not the sheet has been reliably conveyed without being skewed.

  According to the sheet conveying apparatus of the ninth aspect, it is possible to detect the presence or absence of the skew of the sheet while conveying the sheet. Therefore, the sheet can be reliably conveyed while suppressing the occurrence of skew.

  According to the sheet conveying apparatus of the tenth aspect, the sheet is sandwiched by the conveying unit located between the at least two transmission side openings and the at least two reception side openings. Therefore, the ultrasonic transmission / reception between the specific transmission side opening and the reception side opening that receives the ultrasonic wave transmitted by the specific transmission side opening is performed between the other transmission side opening and the other transmission side opening. It does not interfere with the ultrasonic transmission / reception between the receiving side opening for receiving the ultrasonic wave transmitted by. Therefore, according to the sheet conveying apparatus of the ninth aspect, it is possible to reliably detect skew feeding.

  According to the image reading apparatus of the eleventh aspect, the skew detection can be simultaneously performed in the image reading apparatus that reads the image of the sheet while conveying the sheet. Therefore, it is possible to connect to reliable image reading with the inclination of the image suppressed.

  According to the image reading device of the twelfth aspect, it is possible to correct the inclination of the image of the sheet read by the reading unit based on the skew angle of the sheet determined by the determining unit. Therefore, it is possible to perform reliable image reading while suppressing the inclination of the image.

1 is a perspective view showing an image reading apparatus 1 according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining an internal configuration of the image reading apparatus 1. FIG. 2 is a front view showing a detection unit 10 of the image reading apparatus 1. It is a side view which shows the said detection part. It is explanatory drawing for demonstrating the detection of the sheet | seat PP by the said detection part. It is explanatory drawing for demonstrating generation | occurrence | production, transmission, and reception of the ultrasonic wave by the said detection part. It is explanatory drawing for demonstrating the influence on the detection precision of the sheet | seat PP by superimposition of an ultrasonic wave and reverberation. It is explanatory drawing for demonstrating the skew detection by the said detection part. 2 is a block diagram showing an electrical configuration of the image reading apparatus 1. FIG. 4 is a flowchart showing operation control of the image reading apparatus 1. 6 is a flowchart showing steps SX1 to SX10 in the operation control of the image reading apparatus 1 according to the second embodiment of the present invention. 4 is a flowchart showing steps SX11 to SX13 in the operation control of the image reading apparatus 1. It is a front view which shows the detection part 10 which concerns on one modification of this invention. It is a front view which shows the detection part 10 which concerns on one modification of this invention. It is a front view which shows the detection part 10 which concerns on one modification of this invention. It is a front view which shows the detection part 10 which concerns on one modification of this invention. It is a front view which shows the detection part 10 which concerns on one modification of this invention. It is a front view which shows the detection part 10 which concerns on one modification of this invention. It is a side view which shows the detection part 10 which concerns on one modification of this invention. It is a side view which shows the detection part 10 which concerns on one modification of this invention. It is the top view (A) and front view (B) which show the detection part 10 which concerns on one modification of this invention. It is explanatory drawing for demonstrating the effect which the detection part which concerns on one modification of this invention show | plays.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

[Appearance of image reader]
FIG. 1 is a perspective view showing an appearance of the image reading apparatus 1 of the present embodiment. As illustrated in FIG. 1, the image reading apparatus 1 includes a paper feed tray 2, a reading unit 3, a paper discharge tray 4, a setting unit 5, and a display unit 6. The image reading apparatus 1 according to the present embodiment is a sheet feed scanner that reads a plurality of sheets PP placed on a paper feed tray 2 by a user while being conveyed in a reading unit 3. The image reading apparatus 1 in this embodiment is an example of the skew detection apparatus of the present invention. The image reading apparatus 1 in the present embodiment is an example of a sheet conveying apparatus of the present invention. The image reading apparatus 1 in the present embodiment is an example of the image reading apparatus of the present invention.

  The reading unit 3 pulls the sheet PP placed on the paper feed tray 2 into the reading unit 3. The reading unit 3 conveys the drawn sheet PP from the paper feed tray 2 toward the paper discharge tray 4 inside the reading unit 3. The reading unit 3 reads an image of the conveyed sheet PP inside the reading unit 3.

  The paper discharge tray 4 receives the sheet PP conveyed by the reading unit 3. The setting unit 5 has a power switch and various setting buttons. The display unit 6 is configured by a liquid crystal display. The display unit 6 can display an image read by the reading unit 3. The display unit 6 can display a message “skewing occurrence” indicating the occurrence of skewing of the sheet. The display part 6 in this embodiment is an example of the alerting | reporting part of this invention.

[Internal structure of image reading apparatus]
FIG. 2 is an explanatory diagram for explaining the internal structure of the image reading apparatus 1. As shown in FIG. 2, the image reading apparatus 1 includes a pickup roller 32, a separation pad 33, a detection unit 10, a feeding roller 34, and a feeding driven roller 34 ′ inside the reading unit 3. A conveyance roller 35, a conveyance driven roller 35 ′, a reading sensor 36, a conveyance path 37, a discharge roller 38, a discharge driven roller 38 ′, and the control unit 7 are provided.

  The pickup roller 32 pulls a plurality of sheets PP placed on the paper feed tray 2 into the image reading apparatus 1 by frictional force. The pickup roller 32 is driven by a motor (not shown). The separation pad 33 separates the plurality of sheets PP into one sheet by frictional force. The feeding roller 34 is driven by a motor (not shown) to convey the sheet PP. The feeding driven roller 34 ′ is disposed to face the feeding roller 34. The feeding roller 34 and the feeding driven roller 34 ′ sandwich the sheet PP between the feeding roller 34 and the feeding driven roller 34 ′. The sheet PP is conveyed in the conveyance path 37 by the frictional force between the feeding roller 34 and the feeding driven roller 34 ′. The feed roller 34 in the present embodiment is an example of a transport unit according to the present invention.

  The detection unit 10 detects the conveyed sheet PP. The detection unit 10 is configured by an ultrasonic sensor. The detection unit 10 includes an ultrasonic transmission unit 10A and an ultrasonic reception unit 10B. The ultrasonic transmission unit 10A transmits pulsed ultrasonic waves to the conveyed sheet PP. The ultrasonic receiver 10B receives the ultrasonic waves transmitted by the ultrasonic transmitter 10A. When the sheet PP passes between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B, the ultrasonic wave transmitted through the sheet PP and reaching the ultrasonic reception unit 10B is received by the ultrasonic reception unit 10B. . The detection part 10 in this embodiment is an example of the skew detection apparatus of this invention.

  Thereafter, as shown in FIG. 2, the conveyance direction of the sheet PP conveyed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B is the X-axis direction, and the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B. The sheet PP being conveyed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B on a plane parallel to the surface of the sheet PP conveyed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B. A direction perpendicular to the surface is defined as the Z-axis direction. Therefore, for example, a plane parallel to the surface of the sheet PP conveyed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B is parallel to the XY plane. In the following, “upper” or “front” means the positive direction of the Z-axis indicated by the arrow shown in FIG. 2, and “lower” or “back” shows the same in FIG. It shall mean the negative direction of the Z axis. The definitions of the X-axis direction, the Y-axis direction, and the Z-axis direction are common to other drawings. The X-axis direction in the present embodiment is an example of the transport direction in the present invention. The Y-axis direction in the present embodiment is an example of the orthogonal direction in the present invention.

  The conveyance roller 35 is driven by a motor (not shown) to convey the sheet PP. As shown in FIG. 2, the conveyance roller 35 is disposed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B. The transport driven roller 35 ′ is disposed to face the transport roller 35. The transport roller 35 and the transport driven roller 35 ′ sandwich the sheet PP between the transport roller 35 and the transport driven roller 35 ′. The sheet PP is conveyed in the conveyance path 37 by the frictional force between the conveyance roller 35 and the conveyance driven roller 35 ′. The transport roller 35 and the transport driven roller 35 'will be described later with reference to FIG. The conveyance roller 35 in the present embodiment is an example of the conveyance unit of the present invention.

  The reading sensor 36 includes a pair of contact image sensors (Contact Image Sensor, hereinafter referred to as “CIS”) 36 </ b> A and 36 </ b> B that face each other across the conveyance path 37. The reading sensor 36 reads images on the front and back surfaces of the sheet PP. The reading sensor 36 in the present embodiment is an example of the reading unit of the present invention.

  The discharge roller 38 is disposed on the downstream side of the reading sensor 36 in the conveyance direction of the sheet PP in the conveyance path 37. The discharge driven roller 38 ′ is disposed to face the discharge roller 38. The discharge roller 38 and the discharge driven roller 38 ′ sandwich the sheet PP between the discharge roller 38 and the discharge driven roller 38 ′. The sheet PP is conveyed in the conveyance path 37 by the frictional force between the discharge roller 38 and the discharge driven roller 38 ′. The discharge roller 38 sends the sheet PP conveyed in the conveyance path 37 to the sheet discharge tray 4. The discharge roller 38 is driven by a motor (not shown). The sheet PP is stacked on the paper discharge tray 4.

  The control unit 7 is configured by a computer having a CPU, ROM, RAM, flash ROM, and the like.

[Appearance of detector]
FIG. 3 is a front view showing the appearance of the detection unit 10. FIG. 4 is a side view showing the appearance of the detection unit 10. FIG. 5 is a top view illustrating the appearance of the detection unit 10. However, in FIG. 4, the conveyance roller 35 and the conveyance driven roller 35 ′ are omitted, and only the side surface of the detection unit 10 is shown. Further, in FIG. 5, the ultrasonic wave generation unit 101 which is one configuration of the detection unit 1 is omitted, and the upper surface of the detection unit 10 is illustrated. In FIG. 5, the transmission side openings 103 </ b> A, 103 </ b> B, and 103 </ b> C are indicated by hidden lines because they are disposed below the transmission side transmission unit 102. 3, 4, and 5, the sheet PP is shown together with the detection unit 10.

  As shown in FIGS. 3 and 4, the detection unit 10 includes an ultrasonic transmission unit 10 </ b> A and an ultrasonic reception unit 10 </ b> B. As illustrated in FIG. 3, the ultrasonic transmission unit 10A includes an ultrasonic wave generation unit 101, a transmission-side transmission unit 102, and transmission-side openings 103A, 103B, and 103C. As illustrated in FIG. 3, the ultrasonic receiving unit 10 </ b> B includes reception-side openings 104 </ b> A, 104 </ b> B, and 104 </ b> C, a reception-side transmission unit 105, and an ultrasonic reception unit 106. The ultrasonic generator 101 in the present embodiment is an example of the ultrasonic generator of the present invention. The transmission side transmission unit 102 in the present embodiment is an example of the transmission side transmission unit of the present invention. The transmission side openings 103A, 103B, and 103C in the present embodiment are an example of a plurality of transmission side openings of the present invention. The reception side openings 104A, 104B, and 104C in the present embodiment are examples of a plurality of reception side openings of the present invention. The reception-side transmission unit 105 in the present embodiment is an example of the reception-side transmission unit of the present invention. The ultrasonic receiving unit 106 in the present embodiment is an example of the ultrasonic receiving unit of the present invention.

  The ultrasonic wave generation unit 101 generates ultrasonic waves. The transmission-side transmission unit 102 is connected to the ultrasonic wave generation unit 101 and the transmission-side openings 103A, 103B, and 103C. The transmission-side transmission unit 102 transmits the ultrasonic waves generated by the ultrasonic generation unit 101 to the transmission-side openings 103A, 103B, and 103C. As shown in FIGS. 3 and 5, the transmission-side transmission unit 102 extends in the Y-axis direction. Therefore, the transmission-side transmission unit 102 can transmit the ultrasonic wave generated by the ultrasonic wave generation unit 101 in the Y-axis direction.

  The transmission side openings 103A, 103B, and 103C are arranged at different positions with respect to the Y-axis direction as shown in FIGS. That is, the transmission side openings 103A, 103B, and 103C are arranged at different coordinate positions in the Y-axis direction. As shown in FIG. 5, the transmission side openings 103A, 103B, and 103C are arranged at the same position with respect to the X-axis direction. That is, the transmission side openings 103A, 103B, and 103C are arranged at the same coordinate position in the X-axis direction. As shown in FIG. 3, each of the transmission side openings 103A, 103B, and 103C is arranged with the opening portion directed toward the Z-axis negative direction. In FIG. 3, the sheet PP is conveyed in the positive direction of the X axis between the ultrasonic transmitter 10 </ b> A and the ultrasonic receiver 10 </ b> B with the surface parallel to the XY plane. The transmission-side transmission unit 102 and the transmission-side openings 103A, 103B, 103C are configured by a hollow transmission tube made of a hard plastic material.

  In the present embodiment, the first distance L1 from the ultrasonic wave generation unit 101 to the transmission side opening 103A and the second distance L2 from the ultrasonic wave generation unit 101 to the transmission side opening 103C in the Y-axis direction are respectively the first. The distance L1 = 40 mm and the second distance L2 = 50 mm. Therefore, the first distance L1 <the second distance L2. That is, the first distance L1 and the second distance L2 are different distances.

  The reception side openings 104A, 104B, and 104C receive the ultrasonic waves transmitted through the transmission side openings 103A, 103B, and 103C, respectively. When the sheet PP is conveyed between the transmission side openings 103A, 103B, and 103C and the reception side openings 104A, 104B, and 104C, the reception side openings 104A, 104B, and 104C are respectively transmitted to the transmission side openings 103A, The ultrasonic waves that have reached the reception side openings 104A, 104B, and 104C are received via the 103B and 103C and the sheet PP. As shown in FIG. 3, the reception side openings 104A, 104B, and 104C are arranged at different positions with respect to the Y-axis direction. That is, the receiving side openings 104A, 104B, and 104C are arranged at different coordinate positions in the Y-axis direction. The reception side openings 104A, 104B, 104C are arranged at the same position with respect to the X-axis direction. That is, the receiving side openings 104A, 104B, and 104C are arranged at the same coordinate position in the X-axis direction. As shown in FIG. 3, each of the reception side openings 104A, 104B, and 104C is disposed with the opening portion directed toward the Z axis positive direction.

  The reception side openings 104A, 104B, and 104C are respectively located at the same positions as the transmission side openings 104A, 104B, and 104C with respect to the Y-axis direction. Therefore, the distance from the ultrasonic wave receiving unit 106 to the reception side opening 104A in the Y-axis direction is equal to the first distance L1. The distance from the ultrasonic wave receiving unit 106 to the reception side opening 104C in the Y-axis direction is equal to the second distance L2. Therefore, the distance from the ultrasonic wave receiving unit 106 to the reception side opening 104A in the Y-axis direction is different from the distance from the ultrasonic wave reception unit 106 to the reception side opening 104C.

  The reception-side transmission unit 105 is connected to the reception-side openings 104A, 104B, 104C and the ultrasonic reception unit 106. As shown in FIG. 3, the reception-side transmission unit 105 extends in the Y-axis direction. Therefore, the reception-side transmission unit 105 can transmit the ultrasonic waves received by the reception-side openings 104A, 104B, and 104C in the Y-axis direction. The reception-side transmission unit 105 transmits the ultrasonic waves received by the reception-side openings 104A, 104B, and 104C to the ultrasonic reception unit 106. The ultrasonic receiving unit 106 receives the ultrasonic waves received by the reception side openings 104A, 104B, and 104C. The reception-side transmission unit 105 and the reception-side openings 104A, 104B, and 104C are configured by a hollow transmission tube made of a hard plastic material.

  As shown in FIG. 3, the transmission side opening 103B, the reception side opening 104B, the ultrasonic wave generation unit 101, and the ultrasonic wave reception unit 106 are arranged at the same position with respect to the Y-axis direction.

  As shown in FIG. 4, the ultrasonic transmission unit 10 </ b> A and the ultrasonic reception unit 10 </ b> B are configured such that the sheet PP is between the transmission side openings 103 </ b> A, 103 </ b> B, 103 </ b> C and the reception side openings 104 </ b> A, 104 </ b> B, 104 </ b> C. Are opposed to each other in the Z-axis direction with the sheet PP interposed therebetween. As illustrated in FIG. 4, the ultrasonic transmission unit 10 </ b> A and the ultrasonic reception unit 10 </ b> B are disposed at the same position with respect to the X-axis direction.

  As described above, the first distance L1 from the ultrasonic wave generation unit 101 to the transmission side opening 103A and the second distance L2 from the ultrasonic wave generation unit 101 to the transmission side opening 103C in the Y-axis direction are different distances. is there. Further, the first distance L1 from the ultrasonic wave receiving unit 106 to the reception side opening 104A and the second distance L2 from the ultrasonic wave reception unit 106 to the reception side opening 104C in the Y-axis direction are different distances. Therefore, the path length from the ultrasonic wave generation unit 101 to the ultrasonic wave reception unit 106 via the transmission side transmission unit 102, the transmission side opening 103A, and the reception side opening 104A, and the ultrasonic wave generation unit 101 The path length from the ultrasonic wave generation unit 101 to the transmission side transmission unit 102 through the transmission side transmission unit 102, the transmission side opening 103B, and the reception side opening 104B to the ultrasonic reception unit 106. The path length of the path from the transmitting side opening 103C and the receiving side opening 104C to the ultrasonic wave receiving unit 106 is different.

  As shown in FIG. 3, the transport driven roller 35 'is disposed between the transmission side opening 103A and the reception side opening 104A, the transmission side opening 103B, and the reception side opening 104B. Further, the transport roller 35 is disposed between the transmission side opening 103B and the reception side opening 104B, the transmission side opening 103C, and the reception side opening 104C. When ultrasonic waves are transmitted from the transmission side openings 103A, 103B, and 103C to the sheet PP, the sheet PP vibrates. For example, when ultrasonic waves are transmitted from the transmission side opening 103B to the sheet PP, the vibration of the sheet PP propagates in the Y-axis direction. When the vibration of the sheet PP propagates between the transmission-side opening 103A and the reception-side opening 104A or between the transmission-side opening 103C and the reception-side opening 104C, the ultrasonic attenuation is affected. Therefore, transmission / reception of ultrasonic waves between the transmission side opening 103B and the reception side opening 104B is performed by the transmission side opening 103A and the reception side opening 104A, or the transmission side opening 103C and the reception side opening 104C. Will interfere with the transmission and reception of ultrasonic waves. However, in this embodiment, the transmission-side opening 103A, the reception-side opening 104A and the transmission-side opening 103B, and the reception-side opening 104B, and the transmission-side opening 103B and the reception-side opening 104B The sheet PP is sandwiched between the transport roller 35 and the transport driven roller 35 ′ positioned between the transmission-side opening 103C and the reception-side opening 104C. Therefore, for example, the vibration of the sheet PP due to the ultrasonic wave via the transmission side opening 103B is blocked by the conveyance roller 35 and the conveyance driven roller 35 ′, so that the transmission side opening 103A and the reception side opening 104A And between the transmission side opening 103B and the reception side opening 104B. Therefore, the ultrasonic transmission / reception between the specific transmission side opening and the reception side opening that receives the ultrasonic wave transmitted by the specific transmission side opening is performed between the other transmission side opening and the other transmission side opening. It does not interfere with the ultrasonic transmission / reception between the receiving side opening for receiving the ultrasonic wave transmitted by. Therefore, the image reading apparatus 1 in the present embodiment can perform reliable skew detection.

  The ultrasonic transmission to the sheet PP by the detection unit 10 will be described with reference to FIG. Now, as shown in FIG. 5, the sheet PP is being conveyed in the positive direction of the X-axis. In this case, ultrasonic waves are transmitted to the sheet PP from the transmission side openings 103A, 103B, and 103C while the sheet PP is conveyed in the positive direction of the X axis. Therefore, the ultrasonic wave is transmitted to the sheet PP along the lines LA, LB, and LC indicated by the two-dot chain line in FIG. The ultrasonic waves transmitted along the lines LA, LB, and LC are attenuated when passing through the sheet PP as compared with the case where the ultrasonic waves are not transmitted through the sheet PP. By detecting the attenuation of this ultrasonic wave, it is possible to connect to the skew detection of the sheet PP. That is, as shown in FIG. 5, when the sheet PP is skewed and conveyed in the positive X-axis direction, the sheet PP first passes under the transmission side opening 103C. Therefore, first, the ultrasonic wave transmitted from the transmission side opening 103C is attenuated. Next, the sheet PP passes under the transmission side opening 103B. Therefore, the ultrasonic wave transmitted from the transmission side opening 103B next to the transmission side opening 103C is attenuated. Finally, the sheet PP passes under the transmission side opening 103A. Therefore, the ultrasonic wave finally transmitted from the transmission side opening 103A is attenuated. As described above, the attenuation pattern of the ultrasonic waves transmitted from the transmission side openings 103A, 103B, and 103C is determined according to the skew pattern of the sheet PP. By detecting this attenuation pattern, it is possible to detect the skew of the sheet PP. In the present embodiment, as shown in FIG. 5, the length of the detection unit 10 in the Y-axis direction is such that the sheet PP always passes under the transmission side openings 103A, 103B, and 103C. The sheet guide mechanism of the image reading apparatus 1 that is set and not shown is configured.

  With reference to FIG. 6, transmission / reception of ultrasonic waves by the above-described detection unit 10 will be described. In FIG. 6A, the horizontal axis indicates a time TM during which ultrasonic waves are generated by the ultrasonic wave generation unit 101. In FIG. 6A, the vertical axis indicates the amplitude AM of the ultrasonic wave generated by the ultrasonic wave generation unit 101. In FIG. 6B, the horizontal axis is a diagram showing the time TM during which ultrasonic waves are transmitted from the transmission side openings 103A, 103B, 103C. In FIG. 6B, the vertical axis represents the amplitude AM of the ultrasonic wave transmitted from the transmission side openings 103A, 103B, 103C. In FIG. 6C, the horizontal axis indicates the time TM during which the ultrasonic wave is received by the ultrasonic wave receiving unit 106. In FIG. 6C, the vertical axis represents the amplitude AM of the ultrasonic wave received by the ultrasonic wave receiving unit 106. However, (C) in FIG. 6 shows that when the sheet PP is not interposed between the transmission side openings 103A, 103B, and 103C and the reception side openings 104A, 104B, and 104C, ultrasonic waves are transmitted from the transmission side openings 103A, The amplitude AM of the ultrasonic wave received by the ultrasonic wave receiving unit 106 when transmitted from the 103B and 103C to the reception side openings 104A, 104B and 104C is shown. In FIGS. 6A, 6B, and 6C, the time TM is indicated by a common time axis, and the amplitude AM is indicated by the same unit. Therefore, for example, time TG1 shown in FIG. 6A and time TG1 shown in FIGS. 6B and 6C are the same time TM.

  As shown in FIG. 6 (A), the pulsed ultrasonic waves generated by the ultrasonic wave generator 101 at times TG1 and TG2 are first superposed at times TT1 and TT2 as shown in FIG. 6 (B). It is transmitted from the transmission side opening 103B located on the Z-axis negative direction side of the sound wave generation unit 101. Hereinafter, for example, the time from the time TG1 to the time TG2 is expressed as “time TG1 to TG2”. The ultrasonic wave travels through the transmission-side transmission unit 102. Since the first distance L1 <the second distance L2, the ultrasonic wave transmitted through the transmission-side transmission unit 102 is then transmitted from the transmission-side opening 103A at times TT3 to TT4 as shown in FIG. The Thereafter, the ultrasonic wave is transmitted from the transmission-side opening 103C at times TT5 to TT6. As described above, the distance from the ultrasonic wave generation unit 101 to the transmission side openings 103A, 103B, and 103C in the transmission side transmission unit 102 is different, so that the transmission side opening is not required without controlling the transmission timing of the ultrasonic waves. The timing at which ultrasonic waves are transmitted from the units 103A, 103B, and 103C can be shifted. The pulse width of the pulsed ultrasonic wave generated by the ultrasonic wave generation unit 101 is such that the ultrasonic waves transmitted from the transmission side openings 103A, 103B, and 103C do not overlap as shown in FIG. Is preset. The set value of the pulse width is a value determined by the first distance L1 and the second distance L2.

  The ultrasonic waves transmitted from the transmission side opening 103B at time TT1 to TT2 are received by the reception side opening 104B. The ultrasonic wave received by the reception side opening 104B is received by the ultrasonic wave receiving unit 106 at times TR1 and TR2, as shown in FIG. The ultrasonic waves transmitted from the transmission side opening 103A at the times TT3 to TT4 shown in FIG. 6B are received by the reception side opening 104A. The ultrasonic wave received by the reception side opening 104A is transmitted through the reception side transmission unit 105 and is received by the ultrasonic reception unit 106 at times TR3 to TR4. The ultrasonic waves transmitted from the transmission side opening 103C at the times TT5 to TT6 are received by the reception side opening 104C. The ultrasonic wave received by the reception side opening 104C is transmitted through the reception side transmission unit 105 and received by the ultrasonic reception unit 106 at times TR5 to TR6. In this way, the distance from the ultrasonic receiving unit 106 to the receiving side openings 104A, 104B, and 104C in the Y-axis direction is different, so that the receiving side opening 104A, The timing at which the respective ultrasonic waves received by the 104B and 104C are received by the ultrasonic receiving unit 106 can be shifted. That is, the ultrasonic waves received by the reception side openings 104 </ b> A, 104 </ b> B, and 104 </ b> C do not overlap when received by the ultrasonic wave receiving unit 106. Therefore, it is possible to detect the skew of the conveyed sheet PP without the need to control the transmission timing of the ultrasonic waves.

  The ultrasonic wave generation unit 101 generates an ultrasonic wave next to the ultrasonic wave generated at the time TG1 to TG2 at the time TG3 to TG4. The time interval PR from when the ultrasonic wave is generated at the previous time TG1 to TG2 to when the ultrasonic wave is generated at the later time TG3 to TG4 is as shown in FIGS. 6 (A) and 6 (C). In addition, when the time P1 between the time points TT2 to TT3, the time P2 between the time points TT4 and TT5, and the time PS between the time points TG1 and TG2, the PR> 2 × (3 × PS + P1 + P2) is set in advance. Is set. The preset time interval PR is stored in advance in the ROM included in the control unit 7. Since the time PS is an ultrasonic vibration time, if the frequency of the ultrasonic wave is a frequency FR, PS = (the wave number of the ultrasonic wave generated by one transmission) / FR is satisfied. The time PS + P1, which is the sum of the time PS and the time P1, is from when the ultrasonic wave generated by the ultrasonic wave generation unit 101 is transmitted from the transmission side opening 103B until it is transmitted by the transmission side opening 103A. It's time. Accordingly, the time PS + P1 shown in FIG. 6B satisfies PS + P1 = L1 / SS because the distance from the ultrasonic wave generation unit 101 to the transmission side opening 103A is the distance L1 when the sound speed is the sound speed SS. . Similarly, the time PS + P2 from when the ultrasonic wave generated by the ultrasonic wave generation unit 101 is transmitted by the transmission side opening 103A until it is transmitted by the transmission side opening 103C is from the ultrasonic wave generation unit 101 to the transmission side opening. It is determined by the difference between the distance L1 to the portion 103A and the distance L2 from the ultrasonic wave generator 101 to the transmission side opening 103C. That is, the time PS + P2 shown in FIG. 6B satisfies PS + P2 = (L2−L1) / SS. On the other hand, the time taken for the ultrasonic wave received by the reception side opening 104B to be received by the ultrasonic wave reception unit 106 and the time period until the ultrasonic wave received by the reception side opening 104A is received by the ultrasonic wave reception unit 106. The time difference is PS + P1 (= L1 / SS). In addition, the time taken for the ultrasonic wave received by the reception side opening 104A to be received by the ultrasonic wave reception unit 106 and the time period until the ultrasonic wave received by the reception side opening 104C is received by the ultrasonic wave reception unit 106. The time difference is time PS + P2 = (L2−L1) / SS. Therefore, in FIG. 6C, as shown at times TR1 to TR3, the ultrasonic wave generated from the ultrasonic wave generation unit 101 is transmitted through the transmission side opening 103B and the reception side opening 104B. The signal received by the ultrasonic receiving unit 106 via the transmission side opening 103A and the reception side opening 104A is delayed by 2 × (PS + P1) with respect to the signal received at 106. In FIG. 6C, as shown at times TR1 to TR5, the ultrasonic wave generated from the ultrasonic wave generating unit 101 is transmitted through the transmitting side opening 103B and the receiving side opening 104B. The signal received through the transmission side opening 103C and the reception side opening 104C is delayed by 2 × (PS + P1) + 2 × (PS + P2) = 2 × (2 × PS + P1 + P2) with respect to the signal received at 106. . Furthermore, in FIG. 6C, as shown at times TR5 to TR6, time PS is required to complete the reception of the signal received through the transmission side opening 103C and the reception side opening 104C. . Accordingly, the time interval PR at which the ultrasonic wave is generated by the ultrasonic wave generation unit 101 is set to satisfy PR> 2 × (3 × PS + P1 + P2) as shown in FIG. The ultrasonic wave receiving unit 106 prevents the ultrasonic wave derived from the ultrasonic wave generated at the previous time TG1 to TG2 and the ultrasonic wave derived from the ultrasonic wave generated at the subsequent time TG3 to TG4 from being received in an overlapping manner. be able to. Accordingly, it is possible to detect the skew of the sheet PP being conveyed reliably.

  The first distance L1 and the second distance L2 are half the values obtained by multiplying the reverberation time depending on the configurations of the transmission-side transmission unit 102 and the reception-side transmission unit 105 and the sound speed. This is the distance. The reverberation time depends on the configurations of the transmission-side transmission unit 102 and the reception-side transmission unit 105, that is, the material and structure of the voice tube. In the detection unit 10 of the present embodiment, the reverberation time is 200 μs. In the present embodiment, the sound velocity is a sound velocity of 331.5 m / s under the slowest condition of 0 ° C. under a temperature range of 0 ° C. to 40 ° C. that is assumed as a condition for using the image reading apparatus 1. Accordingly, since the first distance L1 = 40 mm and the second distance L2 = 50 mm, the first distance L1 and the second distance L2 are 33.15 mm (= 200 μs × 331.5 m / s ÷ 2) <L1 <L2 Meet. When the first distance L1 and the second distance L2 satisfy 33.15 mm <L1 <L2, it is possible to prevent the skew detection accuracy of the sheet PP conveyed due to reverberation from being affected. That is, the reverberation generated in the reception-side transmission unit 105 when an ultrasonic wave is received by a specific opening of the reception-side openings 104A, 104B, and 104C is generated after the specific opening receives the ultrasonic waves. The ultrasonic wave is not left in the reception-side transmission unit 105 until the ultrasonic wave is received by the openings adjacent to each other in the specific opening. As shown in FIG. 7, when reverberation remains until an ultrasonic wave is received by an adjacent opening, the ultrasonic wave and reverberation received by the adjacent openings overlap each other. When the ultrasonic wave and the reverberation are superposed in this way, the skew detection accuracy of the conveyed sheet PP is affected as described below. That is, due to superimposition of the ultrasonic wave and reverberation, the amplitude of the ultrasonic wave increases or decreases. Therefore, the superimposition of the ultrasonic wave and the reverberation hinders the determination accuracy when determining whether or not the sheet PP is skewed. However, when the first distance L1 and the second distance L2 satisfy 33.15 mm <L1 <L2, it is possible to prevent the skew detection accuracy of the conveyed sheet PP from being affected by reverberation.

  The relationship between the skew of the sheet PP and the amplitude value of the ultrasonic wave received by the ultrasonic wave reception unit 106 will be described with reference to FIG. 8A to 8D are explanatory diagrams for explaining the positional relationship between the sheet PP conveyed in the positive X-axis direction and the transmission-side openings 103A, 103B, and 103C. 8A to 8D is a case where the sheet PP and the transmission side openings 103A, 103B, and 103C are positioned as shown on the left side of the paper in FIGS. 8A to 8D. FIG. 6 is a diagram illustrating ultrasonic waves received by the ultrasonic receiving unit 106. 8A to 8D, the configuration of the reception side openings 104A, 104B, 104C, etc., which is one configuration of the detection unit 10, is omitted. Thereafter, as shown in FIGS. 8A to 8D, the presence of the sheet PP below each of the transmission side openings 103A, 103B, and 103C indicates that the transmission side openings 103A, 103B, and 103C It is described that the sheet PP is interposed between each of the reception side openings 104A, 104B, and 104C.

  As shown in FIG. 8A, when the sheet PP is not interposed between the transmission side openings 103A, 103B, 103C and the reception side openings 104A, 104B, 104C, the reception side openings 104A, 104B. , 104C, the ultrasonic waves received by the ultrasonic receiving unit 106 are not attenuated. As shown in FIG. 8B, when the sheet PP is interposed only between the transmission side opening 103C and the reception side opening 104C, the ultrasonic wave reception unit 106 passes through the reception side opening 104C. Only the received ultrasound is attenuated. As shown in FIG. 8C, when the sheet PP is interposed between the transmission-side openings 103B and 103C and the reception-side openings 104B and 104C, the sheet PP exceeds the reception-side openings 104B and 104C. The ultrasonic wave received by the sound wave receiving unit 106 is attenuated. As shown in FIG. 8D, when the sheet PP is interposed between the transmission side openings 103A, 103B, 103C and the reception side openings 104A, 104B, 104C, the reception side openings 104A, 104B. , 104C, all ultrasonic waves received by the ultrasonic receiver 106 are attenuated. As described above with reference to (A) to (D) of FIG. 8, when skew occurs in the sheet PP, the sheet is received by the ultrasonic receiving unit 106 through the reception side openings 104A, 104B, and 104C. A difference occurs in the amplitude value of the ultrasonic wave. That is, when no skew occurs, the ultrasonic wave received by the ultrasonic wave receiving unit 106 via the receiving side openings 104A, 104B, and 104C is uniformly attenuated when the sheet is interposed, and the sheet non- When intervening, all do not attenuate uniformly. However, when skew occurs in the sheet PP, there is a difference in whether or not the ultrasonic wave received by the ultrasonic wave receiving unit 106 through the reception side openings 104A, 104B, and 104C is attenuated. The image reading apparatus 1 assumes that skew has occurred in the sheet PP when there is a difference in the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit 106 via the receiving side openings 104A, 104B, and 104C. judge. The skew determination is performed by the control unit 7 shown in FIG. The control part 7 in this embodiment is an example of the determination part of this invention.

[Electrical configuration of image reading apparatus]
With reference to FIG. 9, an electrical configuration related to skew detection in the electrical configuration of the image reading apparatus 1 will be described. FIG. 9 is a diagram illustrating an electrical configuration related to skew detection in the electrical configuration of the image reading apparatus 1. As shown in FIG. 9, the control unit 7 includes a CPU 71, a RAM 72, a ROM 73, a drive signal generation unit 74, an amplification unit 75, a sample hold circuit 76, an AD conversion unit 77, and a bus 78. Prepare.

  The CPU 71 is an arithmetic processing device that executes various functions provided in the image reading apparatus 1 by executing various information processing programs. The RAM 72 is an area for temporarily storing various data such as ultrasonic amplitude data received by the ultrasonic receiver 106 and image data of the sheet PP read by the reading sensor 36. The ROM 73 stores various information processing programs executed by the CPU 71. The ROM 73 stores the time interval PR, the time P1, the time P2, the time PS, the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit 106 when not passing through the sheet PP (hereinafter referred to as “threshold”), and the like. Various data are also stored. The ROM 73 is configured by a flash memory that is a nonvolatile memory. The CPU 71, RAM 72, and ROM 73 are respectively connected to a data communication bus 78, and transmit and receive various types of information via the bus 78. The bus 78 is connected to the setting unit 5 and the display unit 6. When the CPU 71 determines that the skew has occurred, command information for notifying the display section 6 of the occurrence of the skew is supplied via the bus 78.

  The drive signal generation unit 74 generates a drive signal for driving the ultrasonic transmission unit 10A. The drive signal generation unit 74 supplies the generated drive signal to the ultrasonic transmission unit 10A. The ultrasonic transmission unit 10A generates ultrasonic waves based on the supplied drive signal. As illustrated in FIG. 3 and the like, the ultrasonic transmission unit 10A transmits the generated ultrasonic waves toward the ultrasonic reception unit 10B. When the sheet PP is conveyed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B, the ultrasonic wave is attenuated and received by the ultrasonic reception unit 10B.

  The amplifying unit 75 amplifies the ultrasonic analog signal received by the ultrasonic receiving unit 10B. The sample hold circuit 76 samples the peak value of the ultrasonic analog signal amplified by the amplification unit 75. The sample hold circuit 76 temporarily holds the sampled values in association with the predetermined time points TS1, TS2, and TS3 during the time PS shown in FIG. The predetermined time points TS1, TS2, and TS3 are obtained by the CPU 71 each time an ultrasonic wave is received by the ultrasonic wave receiving unit 106 based on the data of the time interval PR, the time P1, the time P2, and the time PS stored in the ROM 73. It is determined. The time points TS1, TS2, and TS3 correspond to the time points at which the ultrasonic wave reception unit 106 receives ultrasonic waves through the reception side openings 104B, 104A, and 104C, respectively. By sampling and temporary holding by the sampling hold circuit 76, the amplitude of the ultrasonic wave received by the ultrasonic wave receiving unit 106 is determined in association with the time point when the ultrasonic wave is received by the ultrasonic wave receiving unit 106. The AD converter 77 converts the ultrasonic analog data temporarily held by the sample hold circuit 76 into digital data. The RAM 72 temporarily stores the ultrasonic data converted into digital data by the AD conversion unit 77 in association with the time when the ultrasonic wave is received by the ultrasonic receiving unit 106. That is, as shown in FIG. 6C, the RAM 72 generates three ultrasonic waves derived from one ultrasonic wave generated by the ultrasonic wave generation unit 101 at each time interval PR, respectively, at time points TS1, TS2, and Store in association with TS3.

[Image reader operation control]
Hereinafter, operation control of the image reading apparatus 1 will be described with reference to FIG. FIG. 10 is a flowchart showing operation control of the image reading apparatus 1. A series of operation control is executed by the CPU 71 shown in FIG. When the user presses the power switch of the setting unit 5, a power ON command is supplied from the setting unit 5 to the CPU 71. When a power-on command is supplied to the CPU 71, the image reading apparatus 1 starts to be driven. When driving of the image reading apparatus 1 is started, detection of the sheet PP by the detection unit 10 and image reading of the sheet PP by the reading sensor 36 are started. When the driving of the image reading apparatus 1 is started, the analog signal of the ultrasonic wave received by the ultrasonic wave receiving unit 10B is amplified by the amplifying unit 75. When the amplification is performed, the sample hold circuit 76 performs sampling and temporary holding of the peak value of the amplified ultrasonic analog signal. When sampling and temporary holding are performed, the analog analog data of the ultrasonic wave temporarily held by the sample hold circuit 76 is converted into digital data by the AD conversion unit 77. The ultrasonic data converted into digital data is temporarily stored in the RAM 72 in association with the time points TS1, TS2, and TS3. The following series of operation control is processing executed by the CPU 71 thereafter.

  In the process shown in FIG. 10, three ultrasonic data received by the ultrasonic receiving unit 106 and stored in the RAM 72 at the time interval PR after one ultrasonic wave is generated by the ultrasonic generating unit 101 are stored. It is read from the RAM 72 together with the time points TS1, TS2, and TS3 (S1).

  The read ultrasonic data is compared with the threshold value of the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit 106 when not passing through the sheet PP stored in the ROM 73. Specifically, it is determined whether one or two of the three ultrasonic data values is less than the threshold value stored in the ROM 73 (S2). If it is determined that all three ultrasonic data are greater than or less than the threshold stored in the ROM 73 (S2: No), the process proceeds to S4.

  When it is determined that the value of one or two of the three ultrasonic data is less than the threshold stored in the ROM 73 (S2: Yes), the occurrence of skew is notified (S3). Specifically, command information for notifying the display unit 6 of the occurrence of skew is supplied via the bus 78. The display unit 6 displays a message “occurrence of skew” based on the supplied command information. In order to notify the occurrence of skew when one or two of the three ultrasound data values are determined to be less than the threshold value, the skew is applied to the sheet PP as soon as possible. It is possible to notify that the occurrence has occurred. When the occurrence of skew is notified, the process proceeds to S4.

  When the process moves to S4, it is determined whether or not all the processes of the operation control of the image reading apparatus 1 are finished (S4). Specifically, it is determined whether or not a power OFF command is supplied from the setting unit 5. If it is determined that all the processes are not completed (S4: No), the process returns to S1. If it is determined that all the processes are finished (S4: Yes), all the processes shown in FIG. 10 are finished.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

  In the first embodiment, when the image reading apparatus 1 determines in S2 shown in FIG. 10 that one or two ultrasonic data values out of three ultrasonic data values are less than the threshold value. In S3, the occurrence of skew is reported. However, the present invention is not limited to this, and for example, as described below, skew correction of a sheet image read may be performed instead of notification of skew occurrence or in conjunction with notification of skew occurrence.

  Hereinafter, operation control of the image reading apparatus 1 according to the present embodiment will be described with reference to FIGS. 11 and 12. 11 and 12 are flowcharts showing operation control of the image reading apparatus 1 in the present embodiment. A series of operation control is executed by the CPU 71 shown in FIG.

  In the process shown in FIG. 11, first, various flags and various counts are initialized (SX0). After that, the three ultrasonic data stored in the RAM 72 are read from the RAM 72 together with the time (SX1).

  The read ultrasonic data is compared with the threshold value of the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit 106 when not passing through the sheet PP stored in the ROM 73. Specifically, it is determined whether one or two of the three ultrasonic data values is less than the threshold stored in the ROM 73 (SX2).

  If it is determined that one or two of the three ultrasonic data values is less than the threshold value stored in the ROM 73 (SX2: Yes), whether the determination end flag is set or not. It is judged (SX3). The determination end flag is a flag indicating that the skew angle has already been determined. By using the determination end flag for the process, it is possible to prevent the process for determining the skew angle from being repeated even though the skew angle has already been determined.

  If it is determined that the determination end flag is not set (SX3: No), the number of ultrasonic transmissions is incremented (SX4). When the ultrasonic transmission count is incremented, the process proceeds to SX11 shown in FIG. If it is determined that the determination end flag is set (SX3: Yes), the process proceeds to SX11 shown in FIG.

  If it is determined in SX2 that any data is less than the threshold value or more than the threshold value (SX2: No), it is determined whether the determination end flag is set (SX5). If it is determined that the determination end flag is not set (SX5: No), the skew angle is determined (SX6). Note that “determining” includes both obtaining a specific numerical value based on the obtained data and determining a specific numerical value from a judgment criterion such as a table based on the obtained data.

  The skew angle determination process in SX6 will be described in detail. The skew angle θ of the sheet PP due to the skew of the sheet PP shown in FIG. In Equation 1, the deviation Xd is the deviation Xd in the X-axis direction of the sheet PP due to the skew of the sheet PP shown in FIG.

(Equation 1)
θ = tan ⁻¹ {Xd / (L1 + L2)}

  As shown in FIG. 8, the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit 106 changes as the sheet PP is conveyed in the X-axis direction. The deviation Xd shown in Equation 1 is the time Tcd from the position in the X-axis direction shown in FIG. 8B to the position in the X-axis direction shown in FIG. In this case, it is expressed by Formula 2. In Expression 2, the conveyance speed Vf is a speed at which the sheet PP is conveyed between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B. The conveyance speed Vf is set in advance by maintaining the rotation speed of the conveyance roller 34 and the conveyance roller 35 at a set speed. The conveyance speed Vf is stored in the ROM 73 in advance.

(Equation 2)
Xd = Vf * Tcd

  The time Tcd in Formula 2 is the time interval PR as shown in FIG. 6 as the ultrasonic wave generation cycle by the ultrasonic wave generation unit 101, and the number of times the ultrasonic wave is transmitted by the ultrasonic wave transmission unit 10A during the time Tcd. When the number of ultrasonic transmissions is n, it is expressed by Equation 3.

(Equation 3)
Tcd = n * PR

  Substituting Equation 2 and Equation 3 into Equation 1 yields Equation 4.

(Equation 4)
θ = tan ⁻¹ {n * Vf * PR / (L1 + L2)}

  In Formula 4, the conveyance speed Vf, the time interval PR, the distance L1, and the distance L2 take preset values and are stored in the ROM 73. The number of ultrasonic transmissions n is determined by being incremented in SX4. In SX6, the number of ultrasonic transmissions n in Equation 4 is substituted into Equation 4, so that the skew angle θ is determined. Whether the sheet PP is tilted in the positive Y-axis direction or in the negative Y-axis direction can be detected in SX2 based on which of the three data values is less than the threshold value. . The skew direction of the sheet PP is reflected as a positive / negative sign of the skew angle θ in SX6.

  When the skew angle is determined, the count of the number of ultrasonic transmissions n is reset (SX7). That is, the number of ultrasonic transmissions n incremented in SX4 is returned to the initial value 0.

  When the count of the number of ultrasonic transmissions n is reset, a determination end flag is set (SX8). When the determination end flag is set in SX8, the sheet PP is further conveyed in the X-axis positive direction from the position shown in FIG. 8D, and passes between the ultrasonic transmission unit 10A and the ultrasonic reception unit 10B. In this case, it is possible to prevent the skew angle from being determined once more. When the determination end flag is set, the process proceeds to SX11 shown in FIG.

  In SX5, when it is determined that the determination end flag is set (SX5: Yes), it is determined whether all three ultrasonic data values are equal to or greater than the threshold (SX9). If it is determined that all the threshold values are exceeded (SX9: Yes), the determination end flag is lowered (SX10). If it is determined that all are not equal to or greater than the threshold (SX9: No), the process proceeds to SX11 shown in FIG.

  When the process moves to SX11 shown in FIG. 12, it is determined whether the image reading is completed (SX11). Specifically, it is determined whether the image of the sheet PP detected by the detection unit 10 has been read by the reading sensor 36 shown in FIG.

  When it is determined that the image reading is completed (SX11: Yes), the inclination of the read image is corrected based on the skew angle θ determined in SX6 shown in FIG. 11 (SX12). Specifically, a process of rotating the read image based on the skew angle θ is performed. When image tilt correction is performed, the process proceeds to SX13. If it is determined that the image reading is not completed (SX11: No), the process proceeds to SX13.

  When the process proceeds to SX13, it is determined whether or not all the processes of the operation control of the image reading apparatus 1 are finished (SX13). Specifically, it is determined whether or not a power OFF command is supplied from the setting unit 5. If it is determined that all the processes are not finished (SX13: No), the process returns to SX1 shown in FIG. When it is determined that all the processes are finished (SX13: Yes), all the processes shown in FIGS. 11 and 12 are finished.

(Modification)
The present invention is not limited to the first and second embodiments, and various modifications can be made without departing from the spirit of the present invention. An example of the modification will be described below. In the modifications shown below, the same configurations as those in the first and second embodiments will be described with the same numbers.

  In the first and second embodiments, the detection unit 10 includes three transmission-side openings, that is, transmission-side openings 103A, 103B, and 103C, and reception-side openings 104A, 104B, and 104C, and three reception-side openings. And had. However, the present invention is not limited to this, and the detection unit may include, for example, two transmission-side openings 203A and 203B and two reception-side openings 204A and 204B as in the detection unit 10 illustrated in FIG. 13A. Good. Further, as in the detection unit 10 illustrated in FIG. 13B, any number of transmission side openings 303A to 303N and reception side openings 304A to 304N may be provided. However, as in the detection unit 10 illustrated in FIG. 13A, when only two transmission-side openings 203A and 203B and two reception-side openings 204A and 204B are provided, when a small sheet is conveyed, 2 There is a possibility that the sheet does not pass between one of the two transmission openings and the two reception openings. In the case of a skew detection device having only two transmission openings and two reception openings, if the sheet does not pass between one opening, it cannot be determined whether the sheet is skewed. Therefore, according to the detection unit 10 in the first and second embodiments and the detection unit 10 shown in FIG. 13B, since it includes at least three transmission side openings and at least three reception side openings, it is small. Even when the sheet is conveyed, the possibility that the sheet passes between at least two transmission side openings and at least two reception side openings becomes higher. Therefore, accurate skew detection can be performed.

  In the first and second embodiments, as shown in FIG. 5, the Y-axis direction of the detection unit 10 ensures that the sheet PP always passes under the transmission side openings 103A, 103B, and 103C. The sheet guide mechanism of the image reading apparatus 1 (not shown) is configured. However, the present invention is not limited to this, and the image reading apparatus 1 may be configured as follows. That is, the user uses the setting unit 5 to specify the sheet size, the sheet placement position, and the like. Based on this user designation, any two of the transmission side openings 103A, 103B, 103C and the reception side openings 104A, 104B, 104C, and two reception side openings Skew determination is made based on the via ultrasonic waves. By configuring the image reading apparatus 1 in this way, the sheet can be reliably detected even when a small sheet is conveyed. Further, when a small sheet is conveyed, it is possible to reduce the possibility of erroneously determining that the sheet is skewed even though the sheet is not skewed.

  In the first and second embodiments, the transmission-side transmission unit 102 and the reception-side transmission unit 105 extend in the Y-axis direction as shown in FIG. However, the present invention is not limited to this. For example, the transmission parts 402Z and 405Z extending in the Z-axis direction, such as the transmission parts 402 and 405 shown in FIG. 13C and the transmission parts 502 and 505 shown in FIG. , 502Z, 505Z and portions 402Y, 405Y, 502Y, 505Y extending in the Y-axis direction. Further, for example, like the wave transmission portions 602 and 605 shown in FIG. 13E, the wave transmission portion includes portions 602Z and 605Z extending in the Z-axis direction and portions 602YZ and 605YZ extending in an oblique direction on the YZ plane. You may have.

  In the first and second embodiments, the ultrasonic wave generation unit 101 is disposed on the Z axis positive direction side of the transmission side openings 103A, 103B, and 103C, and the ultrasonic wave reception unit 106 includes the reception side opening 104A, 104B and 104C were arranged on the Z axis negative direction side. However, the present invention is not limited to this. For example, as illustrated in FIG. 13F, the ultrasonic wave generation unit 701 is arranged on the Y axis negative direction side of the transmission side openings 103A, 103B, and 103C, and the ultrasonic wave reception unit 706 The side openings 104A, 104B, 104C may be arranged on the Y axis negative direction side. Similarly, the ultrasonic wave generation unit 701 is arranged on the Y axis positive direction side of the transmission side openings 103A, 103B, and 103C, and the ultrasonic wave reception unit 706 is arranged on the Y axis positive direction of the reception side openings 104A, 104B, and 104C. It may be arranged on the side.

  In the first and second embodiments, the ultrasonic transmitter 10A and the ultrasonic receiver 10B are arranged at the same position with respect to the X-axis direction as shown in FIG. However, the present invention is not limited to this, and the ultrasonic transmission unit and the ultrasonic reception unit include, for example, a transmission side opening 803C and a reception side opening like the ultrasonic transmission unit 800A and the ultrasonic reception unit 800B illustrated in FIG. The line EL connecting the portion 804C may be arranged so as to obliquely intersect the surface of the sheet PP. In this case, the line connecting the transmission side opening and the reception side opening other than the transmission side opening 803C and the reception side opening 804C may be disposed so as to obliquely intersect the surface of the sheet PP. Note that “intersecting diagonally” indicates that the reflected waves of the ultrasonic waves intersect at an angle so as not to return to the ultrasonic wave transmitting unit 800A. For example, this intersection angle may be set from geometric conditions such as the opening size of the transmission side opening, the distance from the reflecting sheet, or the reflection state of the reflected wave. By configuring the detection unit as shown in FIG. 14, the ultrasonic wave transmitted from the transmission side opening and reflected by the sheet does not return to the transmission side opening again. Therefore, it is possible to prevent the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit from becoming unstable due to the influence of the reflected wave. Therefore, compared to the case where the transmission side opening and the reception side opening are arranged so that the line connecting the transmission side opening and the reception side opening is orthogonal to the sheet to be conveyed, the sheet is more reliable. Can be connected to the detection of skew.

  In the first and second embodiments, the detection unit 10 is a transmission type detection unit that detects the skew of the sheet PP based on the presence or absence of attenuation of the ultrasonic wave that occurs when the ultrasonic wave passes through the sheet PP. there were. However, the present invention is not limited to this. For example, the detection unit 10 has a reflection type that detects the skew of the sheet PP based on the ultrasonic wave detected when the ultrasonic wave is reflected by the sheet PP as shown in FIG. It may be a detection unit. The detection unit 10 illustrated in FIG. 15 includes an ultrasonic transmission unit 900A and an ultrasonic reception unit 900B provided to be located on one side of the sheet PP. At least one transmission side opening not shown in FIG. 15 is arranged on the Y axis negative direction side of the transmission side opening 903C shown in FIG. At least one receiving side opening not shown in FIG. 15 is arranged on the Y axis negative direction side of the receiving side opening 904C shown in FIG. As shown in FIG. 15, the ultrasonic wave receiving unit 900B receives the ultrasonic wave transmitted by the ultrasonic wave transmitting unit 900A and reflected by the sheet PP. That is, an ultrasonic wave having an amplitude value greater than 0 is detected. On the other hand, when the sheet PP does not pass, the ultrasonic waves are not reflected by the sheet PP. When the ultrasonic wave is not reflected by the sheet PP, the ultrasonic wave is not received by the ultrasonic wave receiving unit 900B. That is, an ultrasonic wave having an amplitude value of 0 is detected. When skew occurs in the sheet PP, it is determined whether or not an ultrasonic wave is received by the ultrasonic wave receiving unit 106 via the reception side opening 904C and other reception side openings. The image reading apparatus 1 skews the sheet PP when there is a difference in the amplitude value of the ultrasonic wave received by the ultrasonic wave receiving unit 106 via the reception side opening 904C and the other reception side opening. What is necessary is just to determine with having occurred.

  In the first and second embodiments, the transmission-side transmission unit 102 and the reception-side transmission unit 105 extend in the Y-axis direction, that is, the direction orthogonal to the conveyance direction. In the first and second embodiments, the transmission side openings 103A, 103B, and 103C are arranged at the same position with respect to the X-axis direction, that is, the transport direction. In the first and second embodiments, the reception side openings 104A, 104B, and 104C are arranged at the same position with respect to the transport direction. The sheet PP is also conveyed during the time from when the ultrasonic wave is transmitted from the transmission side opening 103B to when the ultrasonic wave is transmitted from the transmission side opening 103A. Accordingly, as shown in FIG. 17A, when the sheet PP is conveyed without being skewed, ultrasonic waves are transmitted from the transmission side openings 103A, 103B, 103C to the sheet PP at a certain time interval PR. The transmission points PA, PB, and PC are at different positions with respect to the X-axis direction. The locations PA, PB, and PC to which ultrasonic waves are transmitted are positions in the X-axis direction that serve as a reference for detecting whether or not the sheet PP is skewed. Therefore, if the locations PA, PB, and PC where the ultrasonic waves are transmitted are at different positions with respect to the X-axis direction, the accuracy of skew detection is affected.

  In view of the problems of the first and second embodiments, the transmission-side transmission unit may be V-shaped like a transmission-side transmission unit 1002 shown in FIG. The transmission side openings 103A, 103B, and 103C are arranged at different positions in the X-axis direction, as shown in FIG. The transmission side openings 103A and 103C are arranged on the downstream side of the transmission side opening 103B in the X-axis direction. As shown in FIG. 16B, the ultrasonic wave generation unit 101 is located above the transmission side opening 103B. The reception-side transmission unit 1005 has the same shape as the transmission-side transmission unit 1002. The three reception side openings 104A, 104B, and 104C are arranged below the transmission side openings 103A, 103B, and 103C, respectively. The three reception side openings 104A, 104B, and 104C are open toward the upper side. As shown in FIG. 16B, the ultrasonic wave receiving unit 106 is positioned below the reception side opening 104B. The distance L1 from the ultrasonic wave generation unit to the transmission side opening 103A in the transmission side transmission unit 102 and the distance L2 from the ultrasonic wave generation unit to the transmission side opening 103C in the transmission side transmission unit 102 are shown in FIG. The distance is different as shown in A).

  In the modification shown in FIG. 16, the detection unit 10 satisfies L1 / SS = X1 / Vf when the distance between the transmission side opening 103B and the transmission side opening 103A in the X-axis direction is a distance X1. It is configured as follows. In the modification shown in FIG. 16, the detection unit 10 satisfies L2 / SS = X2 / Vf when the distance between the transmission-side opening 103B and the transmission-side opening 103C in the X-axis direction is a distance X2. It is configured as follows. Note that the sound velocity SS is the ultrasonic sound velocity SS as in the first and second embodiments. The conveyance speed Vf is the conveyance speed Vf of the sheet PP as in the first and second embodiments.

  The detection unit 10 is configured to satisfy L1 / SS = X1 / Vf. Therefore, the sheet PP is conveyed in the X-axis direction by a distance X1 during a time L1 / SS from when the ultrasonic wave is transmitted from the transmission side opening 103B to when the ultrasonic wave is transmitted from the transmission side opening 103A. . Similarly, the detection unit 10 is configured to satisfy L2 / SS = X2 / Vf. Therefore, the sheet PP is conveyed in the X-axis direction by the distance X2 during the time L2 / SS from when the ultrasonic wave is transmitted from the transmission side opening 103B to when the ultrasonic wave is transmitted from the transmission side opening 103C. . Therefore, as shown in FIG. 17B, when the sheet PP is conveyed without being skewed, ultrasonic waves are transmitted from the transmission side openings 103A, 103B, 103C to the sheet PP at the time interval PR. The locations PA, PB, and PC to be used are at the same position with respect to the X-axis direction. Therefore, skew detection can be performed with high accuracy. Further, as shown in FIG. 5 and Formula 1, the skew angle is determined based on the deviation Xd in the X-axis direction of the sheet PP due to the skew of the sheet PP. Therefore, the locations PA, PB, and PC where the ultrasonic waves are transmitted are at the same position with respect to the X-axis direction, so that the deviation Xd can be determined with high accuracy. Accordingly, the skew angle can be determined with high accuracy, and the inclination of the image can be corrected with high accuracy. In the modification shown in FIG. 16, the skew angle determination and the image inclination correction may be performed according to the flowcharts shown in FIGS.

  In the first and second embodiments, the ultrasonic generator 101 and the ultrasonic receiver 106 are arranged at the same position in the Y-axis direction. However, the present invention is not limited to this, and for example, the ultrasonic wave generation unit 101 and the ultrasonic wave reception unit 106 may be arranged at positions shifted from each other in the Y-axis direction within a range that does not interfere with skew detection. .

  In the first and second embodiments, the transmission-side transmission unit 102 and the transmission-side openings 103A, 103B, and 103C, the reception-side transmission unit 105, and the reception-side openings 104A, 104B, and 104C are hard. It consisted of a hollow tube made of plastic material. However, not limited to this, for example, the transmission-side transmission unit and the reception-side transmission unit may be configured by solid elements that are not hollow.

  In the first and second embodiments, the sheet feed scanner has been described as an example of the image reading apparatus. However, the present invention is not limited to this, and for example, even a reading unit of a multifunction machine with a FAX and an automatic conveyance function may be used. Good. Further, the detection unit may be used for skew detection in the paper feed mechanism of the printing press.

  In the first and second embodiments, the reception side openings 104A, 104B, and 104C are located at the same positions as the transmission side openings 103A, 103B, and 103C, respectively, in the Y-axis direction. However, the present invention is not limited to this, and for example, the reception side openings 104A, 104B, and 104C may be displaced from the transmission side openings 103A, 103B, and 103C by about 0.1 mm in the Y-axis direction. That is, the reception side openings 104A, 104B, and 104C only need to be positioned at positions that can receive at least the ultrasonic waves transmitted from the transmission side openings 103A, 103B, and 103C in the Y-axis direction.

  In the first and second embodiments, the image reading apparatus 1 notifies the occurrence of double feeding by the display unit 6 when the skew of the sheet is detected. May be notified, or the reading operation may be stopped halfway.

  In the first and second embodiments, the image reading apparatus 1 determines whether skew has occurred in the sheet PP. However, the present invention is not limited to this. For example, the detection unit 10 may include a determination unit, and the detection unit 10 may determine whether or not skew has occurred in the sheet PP.

  In the first embodiment, the image reading apparatus 1 includes the conveyance roller 35. However, the present invention is not limited to this, and the image reading apparatus 1 may include, for example, a pair of conveying belts opposed in the Z-axis direction instead of the conveying roller 35. In other words, the conveyance unit arranged between at least two transmission side openings and between the at least two reception side openings conveys the sheet by pushing the sheet in the conveyance direction while sandwiching the sheet. Any part can be used. Further, the image reading apparatus 1 includes a conveyance unit that is disposed between at least two transmission side openings as represented by the conveyance roller 35 and that is disposed between at least two reception side openings. However, it does not have to be provided.

  For example, the detection unit 10 may include sound absorbing materials at both ends in the Y-axis direction of the transmission-side transmission unit 102 and the reception-side transmission unit 105 in order to reduce reverberation.

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 10 Detection part 10A Ultrasonic transmission part 10B Ultrasonic reception part 36 Reading sensor 33 Separation pad 101 Ultrasonic wave generation part 102 Transmission side transmission part 103A, 103B, 103C Transmission side opening part 104A, 104B, 104C Reception side Opening part 105 Receiving side wave transmission part 106 Ultrasonic wave receiving part 7 Control part 71 CPU
72 RAM
73 ROM
76 Sample hold circuit

Claims (12)

A skew detection device that detects the presence or absence of skew of a conveyed sheet,
An ultrasonic generator that generates pulsed ultrasonic waves;
A plurality of transmission side openings for transmitting the ultrasonic waves, arranged on different planes on a plane parallel to the surface of the sheet and orthogonal to a conveying direction in which the sheet is conveyed;
A transmission-side transmission unit coupled to the ultrasonic generation unit and the plurality of transmission-side openings, and transmitting the ultrasonic waves generated by the ultrasonic generation unit to the plurality of transmission-side openings;
A plurality of reception-side openings arranged at different positions with respect to the orthogonal direction, facing the plurality of transmission-side openings and sandwiching the sheet, and receiving the ultrasonic waves transmitted by the plurality of transmission-side openings. And
An ultrasonic receiver for receiving the ultrasonic waves received by the plurality of receiving side openings;
A reception-side transmission unit coupled to a plurality of reception-side openings and the ultrasonic reception unit, and transmitting the ultrasonic waves received by the plurality of reception-side openings to the ultrasonic reception unit;
A determination unit that determines the presence or absence of skew of the sheet based on a difference in amplitude value of the ultrasonic wave received by the ultrasonic wave reception unit through the plurality of reception side openings,
The path lengths of the plurality of paths from the ultrasonic wave generation unit to the ultrasonic wave reception unit via the transmission side transmission unit, the plurality of transmission side openings, and the plurality of reception side openings are different. A skew detection device characterized by a length. One of the plurality of transmission side openings, the transmission side opening, the ultrasonic wave generation unit, and the ultrasonic wave reception unit are arranged at the same position with respect to the orthogonal direction,
One of the plurality of reception side openings, the reception side opening, the ultrasonic wave generation unit, and the ultrasonic wave reception unit are arranged at the same position with respect to the orthogonal direction. The skew detection device according to Item 1. The transmission-side transmission unit and the reception-side transmission unit extend in the orthogonal direction,
The plurality of transmission side openings are arranged at the same position with respect to the transport direction,
The skew detection device according to claim 1, wherein the plurality of reception side openings are arranged at the same position with respect to the transport direction. The ultrasonic wave generation unit, the ultrasonic wave reception unit, and the specific transmission side opening arranged at the same position with respect to the orthogonal direction are arranged upstream of the other transmission side opening in the transport direction. And
The ultrasonic wave generation unit, the ultrasonic wave reception unit, and the specific reception side opening arranged at the same position with respect to the orthogonal direction are arranged upstream of the other reception side opening in the transport direction. And
The time obtained by dividing the distance between the specific transmission-side opening and the other transmission-side opening by the speed of sound is between the specific transmission-side opening and the other transmission-side opening in the transport direction. Is equal to the time obtained by dividing the distance by the sheet conveyance speed, and the time obtained by dividing the distance between the specific reception-side opening and the other reception-side opening by the sound velocity is a specific value in the conveyance direction. 3. The skew detection according to claim 2, wherein the skew detection is configured to be equal to a time obtained by dividing a distance between the reception side opening and the other side opening by a conveyance speed of the sheet. apparatus.   The skew detection device according to claim 1, comprising at least three transmission side openings and at least three reception side openings.   Of the at least three transmission side openings, the distance between the two transmission side openings adjacent in the transmission side transmission part, and among the at least three reception side openings, the reception side transmission The distance between two reception side openings adjacent to each other in the unit is obtained by multiplying the reverberation time and the sound speed depending on the configuration of the transmission side transmission unit and the reception side transmission unit, respectively. 6. The skew detection device according to claim 5, wherein the distance is equal to or greater than a half value.   The transmission side transmission unit, the plurality of transmission side openings, the reception side transmission unit, and the plurality of reception side openings are each configured by a voice tube. The skew detection device according to any one of the above.   The skew detection device according to any one of claims 1 to 7, further comprising a notification unit that notifies the presence / absence of skew of the sheet based on a determination result of the determination unit. The skew detection device according to any one of claims 1 to 8,
A sheet conveying apparatus comprising: a conveyance unit configured to convey the sheet. The conveying unit is a pair of conveying units that are arranged to face each other in a direction intersecting the surface of the sheet and convey the sheet by extruding the sheet in the conveying direction while sandwiching the sheet,
The transport unit is located between at least two of the plurality of transmission side openings, and receives at least two ultrasonic waves via the at least two transmission side openings. The sheet conveying apparatus according to claim 9, wherein the sheet conveying apparatus is located between the receiving side openings. A sheet conveying device according to claim 9 or 10,
An image reading apparatus comprising: a reading unit that reads an image of the sheet conveyed by the conveyance unit. The sheet conveyance speed by the conveyance unit, the time difference in which the ultrasonic wave is received by the ultrasonic wave reception unit through the plurality of reception side openings, and the ultrasonic wave generation unit in the transmission side wave transmission unit, respectively A determination unit that determines a skew angle of the sheet based on a distance to the transmission-side opening,
The image reading apparatus according to claim 11, further comprising: an image processing unit that corrects an inclination of the image of the sheet based on the skew angle determined by the determination unit.