Medium conveying device, image reading device, jam detection method and program

Abstract

The present application relates to a medium conveying device, an image reading device, a jam detection method and a program. In a configuration in which a plurality of conveying roller pairs are provided on a medium conveying path, if a jam detection threshold is set based on a driving load value when the medium is conveyed by the largest number of conveying roller pairs, the difference between the driving load value when the medium is conveyed by the smallest number of conveying roller pairs and the threshold becomes larger. A control unit of the medium conveying device acquires the number of the conveying roller pairs involved in the conveying of the medium based on detection information of a detection unit provided for each of the plurality of conveying roller pairs provided on the medium conveying path, and increases the threshold if the number of the conveying roller pairs involved in the conveying of the medium increases, and decreases the threshold if the number of the conveying roller pairs involved in the conveying of the medium decreases.

Description

Technical Field

[0001] The present invention relates to a medium conveying device for conveying a medium and an image reading device equipped therewith. The present invention also relates to a jam detection method for detecting a jam in a medium conveying device. The present invention also relates to a jam detection program for detecting a jam in a medium conveying device. Background Art

[0002] Some image reading devices are so-called paper-feed type devices that read while conveying a medium. In medium conveying devices that convey a medium used in such image reading devices, jam detection has been performed in various ways.

[0003] As one of them, Patent Document 1 discloses an image reading device that determines a jam when a driving load value of a motor that drives a roller that conveys a document exceeds a threshold value and stops driving the motor.

[0004] Patent document 1: Japanese Patent Application Publication No. 2019-68175.

[0005] When a plurality of conveying roller pairs are provided in the medium conveying path and the plurality of conveying roller pairs are driven by one motor, for example, between the case where the medium is conveyed by two conveying roller pairs and the case where the medium is conveyed by three conveying roller pairs, the driving load value of the motor is higher in the latter case. Therefore, the threshold value for clogging detection needs to be set based on the driving load value when the medium is conveyed by the largest number of conveying roller pairs.

[0006] However, in this case, there is a possibility that the difference between the drive load value when the medium is transported by the minimum number of transport rollers and the threshold value becomes larger, and when a jam occurs, it takes time for the drive load value to exceed the threshold value, causing the jam to develop and increasing the damage to the medium. Summary of the invention

[0007] The medium conveying device of the present invention for solving the above-mentioned technical problems is characterized in that it comprises: a medium loading portion for loading the medium before feeding; a medium conveying path for conveying the medium fed from the medium loading portion; a plurality of conveying roller pairs arranged in the medium conveying path; a motor as a power source for the plurality of conveying roller pairs; and a control portion for controlling the motor, wherein the control portion is capable of performing a blockage detection process for detecting blockage of the medium in the medium conveying path by referring to the driving load of the motor and a threshold value for the driving load, wherein a detection portion for detecting the medium is provided for each of the plurality of conveying roller pairs in the medium conveying path, and the control portion changes the threshold value based on the detection information of the detection portion.

[0008] Furthermore, the image reading device of the present invention is characterized by comprising: a reading unit that reads a surface of a medium being conveyed; and the medium conveying device that conveys the medium.

[0009] In addition, the blockage detection method of the present invention is characterized in that it is a blockage detection method for detecting blockage of the medium in the medium conveying path by referring to the driving load of the motor and the threshold value for the driving load in the medium conveying device, and the medium conveying device comprises: a medium loading portion for loading the medium before feeding; the medium conveying path for conveying the medium fed from the medium loading portion; a plurality of conveying roller pairs arranged in the medium conveying path; and the motor as a power source for the plurality of conveying roller pairs. In the blockage detection method, the number of the conveying roller pairs involved in the conveyance of the medium is obtained based on detection information of a detection portion for detecting the medium respectively arranged for the plurality of conveying roller pairs in the medium conveying path, and if the number of the conveying roller pairs involved in the conveyance of the medium increases, the threshold value is increased, and if the number of the conveying roller pairs involved in the conveyance of the medium decreases, the threshold value is decreased.

[0010] In addition, the blockage detection program of the present invention is characterized in that it is a blockage detection program for detecting blockage of the medium in the medium conveying path by referring to the driving load of the motor and the threshold value for the driving load in the medium conveying device, the medium conveying device comprising: a medium loading portion for loading the medium before feeding; the medium conveying path for conveying the medium fed from the medium loading portion; a plurality of conveying roller pairs arranged in the medium conveying path; and the motor as a power source for the plurality of conveying roller pairs, the blockage detection program comprising the following steps: obtaining the number of the conveying roller pairs involved in the conveying of the medium based on detection information of a detection portion for detecting the medium respectively arranged for the plurality of conveying roller pairs in the medium conveying path; and changing the threshold value in such a manner as to increase the threshold value when the number of the conveying roller pairs involved in the conveying of the medium increases, and to lower the threshold value when the number of the conveying roller pairs involved in the conveying of the medium decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a perspective view of the appearance of the medium conveying device as viewed from above.

[0012] Figure 2 It is a diagram showing a medium conveying path in the medium conveying device.

[0013] Figure 3 is a block diagram showing a control system in a medium transport device.

[0014] Figure 4 This is a diagram showing an example of conveying a medium in a medium conveyance path.

[0015] Figure 5This is a diagram showing an example of conveying a medium in a medium conveyance path.

[0016] Figure 6 This is a diagram showing an example of conveying a medium in a medium conveyance path.

[0017] Figure 7 This is a diagram showing an example of conveying a medium in a medium conveyance path.

[0018] Figure 8 This is a diagram showing an example of conveying a medium in a medium conveyance path.

[0019] Fig. 9 It is a diagram showing the relationship between the duty value and the threshold value of the motor drive.

[0020] Fig.10 : is a flowchart showing the flow of the congestion detection process.

[0021] Description of Reference Numerals

[0022] 1: Scanner; 2: Scanner unit; 3: Original platen glass; 4: First reading unit; 7: Operation panel; 10: Medium transport device; 11: Device body; 12: First frame; 13: Press pad; 15: Feed tray; 16A, 16B: Edge guide; 17: Open / close cover; 18: Lock release lever; 19: Driving mechanism unit; 20: Pickup roller; 21: Roller support member; 23: Separation roller pair; 24: Feed roller; 25: Separation roller; 27: First transport roller pair; 28: Driving roller; 29: Driven roller; 31: Second transport roller pair; 3 2: driving roller; 33: driven roller; 35: third conveying roller pair; 36: driving roller; 37: driven roller; 39: fourth conveying roller pair; 40: driving roller; 41: driven roller; 45: second reading section; 47: discharge tray; 50: control section; 51: CPU; 52: flash ROM; 54: program; 55: feed motor; 56: conveying motor; 61: first medium detection section; 62: second medium detection section; 63: third medium detection section; 64: fourth medium detection section; 65: fifth medium detection section; T: curved reversal path. DETAILED DESCRIPTION

[0023] The present invention is briefly described below.

[0024] The medium conveying device involved in the first aspect is characterized in that it comprises: a medium loading portion for loading the medium before feeding; a medium conveying path for conveying the medium fed from the medium loading portion; a plurality of conveying roller pairs arranged in the medium conveying path; a motor as a power source for the plurality of conveying roller pairs; and a control portion for controlling the motor, wherein the control portion is capable of performing a blockage detection process for detecting blockage of the medium in the medium conveying path by referring to the driving load of the motor and a threshold value for the driving load, wherein a detection portion for detecting the medium is provided for each of the plurality of conveying roller pairs in the medium conveying path, and the control portion changes the threshold value based on the detection information of the detection portion.

[0025] In addition, the control unit is characterized in that the number of the conveying roller pairs involved in the conveying of the medium is obtained based on the detection information of the detection unit, and the threshold is increased if the number of the conveying roller pairs involved in the conveying of the medium increases, and the threshold is lowered if the number of the conveying roller pairs involved in the conveying of the medium decreases.

[0026] According to this aspect, the control unit obtains the number of the conveying roller pairs involved in the conveying of the medium based on the detection information of the detection unit, and increases the threshold value if the number of the conveying roller pairs involved in the conveying of the medium increases, and decreases the threshold value if the number of the conveying roller pairs involved in the conveying of the medium decreases, so the threshold value is changed according to the number of the conveying roller pairs involved in the conveying of the medium, in other words, according to the driving load of the motor. Therefore, when the number of the conveying roller pairs involved in the conveying of the medium is small, it is possible to suppress the difference between the driving load of the motor and the threshold value from increasing and the time required until the clogging of the medium is detected. As a result, it is possible to suppress the development of clogging and increase the damage to the medium.

[0027] A second aspect is characterized in that, in the first aspect, the control unit changes the threshold value according to a position of the medium in the medium conveyance path.

[0028] Depending on the configuration of the medium conveying path, the driving load of the motor may change according to the position of the medium in the medium conveying path. According to this aspect, since the control unit changes the threshold value according to the position of the medium in the medium conveying path, the threshold value can be set to a more appropriate value, and the blockage of the medium can be detected more appropriately.

[0029] The third aspect is characterized in that, in the second aspect, in the medium conveying path, a separation roller pair is provided upstream of the multiple conveying roller pairs for separating the medium fed from the medium loading portion, and when the medium is not clamped by the separation roller pair, the control unit lowers the threshold value compared to a case where the medium is clamped by the separation roller pair.

[0030] In a configuration in which a separation roller pair is provided upstream of the plurality of conveying roller pairs for separating the medium fed from the medium loading section, if the medium is clamped by the separation roller pair, the separation roller pair becomes a conveying load when the medium is conveyed by the conveying roller pair, and the driving load of the motor increases. In such a configuration, if the threshold is set based on the case where the medium is clamped by the separation roller pair and the threshold is uniformly applied, the difference between the driving load of the motor when the medium is not clamped by the separation roller pair and the threshold becomes large, and it takes time to detect the clogging of the medium.

[0031] However, in this aspect, since the control unit lowers the threshold value when the medium is not clamped by the separation roller pair as compared to the case where the medium is clamped by the separation roller pair, the difference between the driving load of the motor and the threshold value when the medium is not clamped by the separation roller pair can be suppressed from increasing, and medium blockage can be quickly detected.

[0032] The fourth aspect is characterized in that, in the second aspect, the medium conveying path is a path that causes the medium fed from the medium loading portion to bend downward and then reverse in a direction opposite to the direction in which the medium is fed from the medium loading portion, and when the front end of the medium is located in a first section of the medium conveying path, the control unit lowers the threshold value compared to when the front end of the medium is located in a second section, wherein in the second section, the curvature of the medium when bent is larger than in the first section.

[0033] For example, when the front end of the medium moves along a curved path, the greater the curvature, the greater the driving load of the motor. Therefore, if the threshold is set based on the case where the front end of the medium moves along a path with a large curvature and the threshold is uniformly applied, when the front end of the medium moves along a path with a relatively small curvature, the difference between the driving load of the motor and the threshold becomes large, and it takes time to detect the clogging of the medium.

[0034] However, in the present aspect, when the front end of the medium is located in the first section of the medium conveying path, the control unit lowers the threshold value compared to when the front end of the medium is located in the second section, wherein in the second section, the curvature of the medium when bent is larger than in the first section, so that the difference between the driving load of the motor and the threshold value can be suppressed from increasing when the front end of the medium advances in the first section, and medium blockage can be quickly detected.

[0035] A fifth aspect is characterized in that, in any one of the first to fourth aspects, when a first medium is conveyed, the control unit lowers the threshold value compared to when a second medium is conveyed, wherein the second medium has a higher rigidity than the first medium.

[0036] The higher the rigidity of the medium is, the greater the driving load of the motor is. Therefore, if the threshold is set based on the medium with high rigidity and then the threshold is applied uniformly, the difference between the driving load of the motor and the threshold when conveying the medium with relatively low rigidity becomes large, and it takes time to detect the blockage of the medium.

[0037] However, according to this aspect, because the control unit lowers the threshold value when conveying the first medium as compared to when conveying the second medium, wherein the rigidity of the second medium is higher than the rigidity of the first medium, it is possible to suppress the difference between the driving load of the motor and the threshold value from becoming larger when conveying a medium with low rigidity, and it is possible to quickly detect a blockage of the medium.

[0038] An image reading device according to a sixth aspect includes: a reading unit that reads a surface of a medium being fed; and the medium feeding device according to any one of the first to fifth aspects that feeds the medium.

[0039] According to this aspect, in the image reading device, the effects of any one of the first to fifth aspects can be obtained.

[0040] The seventh aspect is characterized in that, in the sixth aspect, if the number of the conveying roller pairs involved in the conveying of the medium increases, the control unit reduces the driving speed of the motor, and if the number of the conveying roller pairs involved in the conveying of the medium decreases, the control unit increases the driving speed of the motor.

[0041] As the number of the transport roller pairs involved in transporting the medium is relatively small, the amount of medium transported becomes insufficient due to the slipping of the medium at the transport roller pairs, which may adversely affect the reading result of the reading unit.

[0042] Therefore, in this aspect, if the number of the conveying roller pairs involved in the conveying of the medium increases, the control unit reduces the driving speed of the motor, and if the number of the conveying roller pairs involved in the conveying of the medium decreases, the control unit increases the driving speed of the motor, so that an appropriate medium conveying amount corresponding to the number of the conveying roller pairs involved in the conveying of the medium can be achieved, and thus a good reading result can be obtained in the reading unit.

[0043] According to an eighth aspect, in the sixth or seventh aspect, when the rigidity of the medium is relatively higher than the rigidity of other media, the control unit increases the driving speed of the motor relatively compared with the case of the other media.

[0044] The higher the rigidity of the medium, the less the amount of medium conveyance will be due to the slipping of the medium at the conveyance roller pair, which may adversely affect the reading result of the reading unit.

[0045] Therefore, in this aspect, because the rigidity of the medium is relatively higher than that of other media, the control unit increases the driving speed of the motor relatively compared to the other media, so that an appropriate medium conveying amount corresponding to the rigidity of the medium can be achieved, and thus a good reading result can be obtained in the reading unit.

[0046] The ninth aspect involves a blockage detection method, which is characterized in that it is a blockage detection method for detecting blockage of the medium in the medium conveying path by referring to the driving load of the motor and the threshold value for the driving load in the medium conveying device, wherein the medium conveying device comprises: a medium loading portion for loading the medium before feeding; the medium conveying path for conveying the medium fed from the medium loading portion; a plurality of conveying roller pairs arranged in the medium conveying path; and the motor as a power source for the plurality of conveying roller pairs. In the blockage detection method, the number of the conveying roller pairs involved in the conveyance of the medium is obtained based on detection information of a detection portion for detecting the medium respectively arranged for the plurality of conveying roller pairs in the medium conveying path, and if the number of the conveying roller pairs involved in the conveyance of the medium increases, the threshold value is increased, and if the number of the conveying roller pairs involved in the conveyance of the medium decreases, the threshold value is decreased.

[0047] According to this aspect, the threshold value is changed according to the number of the conveying roller pairs involved in the conveying of the medium, in other words, according to the driving load of the motor. Therefore, when the number of the conveying roller pairs involved in the conveying of the medium is small, it is possible to prevent the difference between the driving load of the motor and the threshold value from increasing and the time required until the clogging of the medium is detected. As a result, it is possible to prevent the clogging from developing and increasing the damage to the medium.

[0048] The blockage detection program involved in the tenth aspect is characterized in that it is a blockage detection program for detecting blockage of the medium in the medium conveying path by referring to the driving load of the motor and the threshold value for the driving load in the medium conveying device, the medium conveying device comprising: a medium loading portion for loading the medium before feeding; the medium conveying path for conveying the medium fed from the medium loading portion; a plurality of conveying roller pairs arranged in the medium conveying path; and the motor as a power source for the plurality of conveying roller pairs, the blockage detection program comprising the following steps: obtaining the number of the conveying roller pairs involved in the conveying of the medium based on detection information of a detection portion for detecting the medium respectively arranged for the plurality of conveying roller pairs in the medium conveying path; and changing the threshold value in a manner such that the threshold value is increased when the number of the conveying roller pairs involved in the conveying of the medium increases, and the threshold value is lowered when the number of the conveying roller pairs involved in the conveying of the medium decreases.

[0049] According to this aspect, the threshold value is changed according to the number of the conveying roller pairs involved in the conveying of the medium, in other words, according to the driving load of the motor. Therefore, when the number of the conveying roller pairs involved in the conveying of the medium is small, it is possible to prevent the difference between the driving load of the motor and the threshold value from increasing and the time required until the clogging of the medium is detected. As a result, it is possible to prevent the clogging from developing and increasing the damage to the medium.

[0050] The present invention is described in detail below.

[0051] The XYZ coordinate system shown in each figure is an orthogonal coordinate system, and the X-axis direction is the width direction of the medium transported in the device, and is also the depth direction of the device. In this embodiment, the -X direction is the front side of the device, and the +X direction is the rear side of the device. In addition, the Y-axis direction is the width direction of the device. When observing the device from the -X direction, the +Y direction is the left side, and the -Y direction is the right side. The Z-axis direction is the height direction and vertical direction of the device.

[0052] exist Figure 1 The scanner 1 as an example of an image reading device in the figure is provided with a medium conveying device 10 on the upper part of a scanner unit 2 which is a flat-head type scanner. The medium conveying device 10 is provided so as to be openable and closable relative to the scanner unit 2 by a hinge (not shown) provided at the end in the +X direction, and the original platen glass 3 (see FIG. 1 ) which constitutes the upper part of the scanner unit 2 is opened and closed by opening the medium conveying device 10. Figure 2 ).

[0053] The medium transport device 10 includes a feed tray 15, an opening and closing cover 17, and a first frame 12 (see Figure 2 ) and discharge tray 47.

[0054] The medium before feeding is placed on the feed tray 15. The feed tray 15 is provided with an edge guide 16A in the +X direction to guide the edge of the placed medium in the +X direction, and the feed tray 15 is provided with an edge guide 16B in the -X direction to guide the edge of the placed medium in the -X direction. The edge guides 16A and 16B are provided to be able to slide in directions of approaching or separating from each other.

[0055] The opening and closing cover 17 is provided to be rotatable about a rotation axis (not shown) having an axis center parallel to the X-axis direction. A lock release lever 18 is provided on the opening and closing cover 17. When the user pulls up the lock release lever 18, the lock of the opening and closing cover 17 in the fully closed state can be released, and the opening and closing cover 17 can be opened. By opening the opening and closing cover 17, the inside of the medium conveying device 10, especially the curved reversing path, is exposed, and a blockage treatment can be performed.

[0056] like Figure 2As shown, the scanner unit 2 includes an original platen glass 3 , and a first reading unit 4 is provided below the original platen glass 3 so as to be movable in the Y-axis direction.

[0057] A pressing pad 13 for pressing the medium placed on the original platen glass 3 is provided on the lower surface of the medium conveying device 10. The pressing pad 13 is provided in the area in the Y-axis direction that is not in the +Y direction, and the surface of the medium can be read by conveying the medium to the first reading unit 4 that stops in the area. It should be noted that the medium conveying device 10 has a second reading unit 45 inside, and the second reading unit 45 and the first reading unit 4 can read both sides of the conveyed medium. Since the medium conveying device 10 has the second reading unit 45, the medium conveying device 10 can also be understood as an example of an image reading device alone.

[0058] The following reference Figure 2 The medium transport path inside the medium transport device 10 will be further described.

[0059] exist Figure 2 The dotted line indicated by the reference symbol T in the figure shows a curved reversing path as a medium conveying path in the medium conveying device 10. The curved reversing path T is a path from the separation roller pair 23 to the fourth conveying roller pair 39 described later. It should be noted that in this specification, the roller pair means a pair of rollers arranged opposite to each other with the curved reversing path T interposed therebetween.

[0060] The medium placed on the feed tray 15 is fed out by a pickup roller 20. The pickup roller 20 is provided at a position opposing an end region of the medium placed on the feed tray 15 in the +Y direction.

[0061] By the feed motor 55 (refer to Figure 3 ) is supported by a roller support member 21. The roller support member 21 is provided to be rotatable coaxially with a feed roller 24 described later, and the pickup roller 20 is moved forward and backward relative to the medium by rotating.

[0062] A separation roller pair 23 is provided downstream of the pickup roller 20. The separation roller pair 23 is driven by a feed motor 55 (see Figure 3 ) and a separation roller 25 to which rotational resistance is applied. The separation roller 25 is provided with rotational resistance by a torque limiter (not shown), and the medium sent out by the pickup roller 20 is separated by the separation roller 25 and sent downstream.

[0063] A first conveying roller pair 27 is provided downstream of the separation roller pair 23. The first conveying roller pair 27 is driven by a conveying motor 56 (see Figure 3 ) is composed of a driving roller 28 driven by the driving device and a driven roller 29 capable of being driven and rotated.

[0064] The medium bends downward at a position downstream of the first conveying roller pair 27. A second conveying roller pair 31 is provided downstream of the first conveying roller pair 27. In the curved reversing path T, the second conveying roller pair 31 sandwiches and conveys the medium at a position where the surface of the downward medium changes to an upward position, that is, downstream of the position closest to the +Y direction in the curved reversing path T.

[0065] The second conveying roller pair 31 is driven by the conveying motor 56 (see Figure 3 ) is composed of a driving roller 32 driven by the driving device and a driven roller 33 capable of being driven and rotated.

[0066] The medium fed from the feed tray 15 is bent downward through the curved reversing path T, and then reversed in the direction opposite to the direction in which the medium was fed from the feed tray 15, that is, in the -Y direction. Figure 2 The area facing the first reading unit 4 at the position shown is read and reaches the third conveying roller pair 35. The third conveying roller pair 35 is driven by the conveying motor 56 (see Figure 3 ) is composed of a driving roller 36 driven by the driving device and a driven roller 37 capable of being driven and rotated.

[0067] The medium conveyed by the third conveying roller pair 35 passes through the area facing the second reading unit 45, is read, and reaches the fourth conveying roller pair 39. The fourth conveying roller pair 39 is driven by the conveying motor 56 (see Figure 3 ) is composed of a driving roller 40 driven by the fourth conveying roller pair 39 and a driven roller 41 capable of being driven and rotated. The medium is discharged to the discharge tray 47 by the fourth conveying roller pair 39.

[0068] While the medium is being conveyed in the curved reversing path T, the upper surface of the medium previously placed on the feed tray 15 is read by the first reading unit 4 , and the lower surface of the medium previously placed on the feed tray 15 is read by the second reading unit 45 .

[0069] In the present embodiment, the second reading section 45 and the first reading section 4 are both constituted by a contact image sensor module (CISM).

[0070] Next, refer to Figure 3 The control system in the scanner 1 will be described. The control unit 50 as a control unit performs various controls on the scanner 1 including feeding, conveying, discharging, and reading of the medium P. In addition, a signal from the operation panel 7 is input to the control unit 50 .

[0071] It should be noted that, although the control unit 50 is provided in the scanner unit 2 in the present embodiment, it may also be provided in the medium transport device 10 .

[0072] The control unit 50 includes a CPU 51 and a flash ROM 52. The flash ROM 52 is a non-volatile memory that can be read and written. The CPU 51 performs various calculations according to the program 54 and parameters stored in the flash ROM 52 to control the operation of the entire scanner 1. Here, the program 54 does not necessarily refer to a single program, but is composed of a plurality of programs, including a jam detection program for performing the jam detection process described later, and other control programs required for feeding, conveying, and reading the medium. The jam detection program implementation is described later. Fig.10 A blockage detection method is described.

[0073] The scanner 1 is connectable to an external computer 90, and information is input from the external computer 90 to the control unit 50. The external computer 90 includes a display unit (not shown). In the display unit, a user interface (UI) is implemented by a control program stored in a storage unit (not shown) included in the external computer 90.

[0074] The read data from the first reading section 4 and the second reading section 45 are input to the control section 50 , and a signal for controlling each reading section is transmitted from the control section 50 to each reading section.

[0075] Next, the control unit 50 controls the feed motor 55 and the conveying motor 56. The feed motor 55 and the conveying motor 56 are both DC motors in this embodiment. A rotary encoder (not shown) is provided on each motor, and the control unit 50 can grasp the rotation amount and rotation speed of each motor based on the pulse signal received from the rotary encoder of each motor, and as a result, can grasp the driving amount of each roller pair.

[0076] The control unit 50 controls the voltage applied to each motor by pulse width modulation (PWM). That is, the drive of each motor is controlled by applying a voltage for a long time based on a pulse signal that is repeatedly turned on (ON) and off (OFF) in a predetermined switching cycle, in other words, by causing the current to flow. Here, the ratio of the on time in the switching cycle is called "duty value". For each motor, the duty value is adjusted along the target speed curve including the acceleration area, the constant speed area and the deceleration area to control its rotation speed.

[0077] Then, the control unit 50 performs PID (Proportional Integral Differential) control to converge the current rotation speed to the target rotation speed of each motor at each rotation position. If the difference between the target rotation speed and the current rotation speed is large, the duty value becomes larger, and if the difference between the target rotation speed and the current rotation speed is small, the duty value becomes smaller. In other words, when the driving load of each motor is large and the difference between the target rotation speed and the current rotation speed is large, the duty value as an example of the driving load of each motor becomes larger. On the contrary, when the driving load of each motor is small and the difference between the target rotation speed and the current rotation speed is small, the duty value as an example of the driving load of each motor becomes smaller. In this way, the duty value is a variable value that changes according to the driving load of each motor.

[0078] Here, when the medium is blocked in the curved reversing path T, the duty value of the conveying motor 56 increases. Then, the control unit 50 performs a blockage detection process, in which the control unit 50 refers to the duty value and the threshold value of the conveying motor 56 during the conveyance of the medium, and determines that the medium is blocked when the duty value of the conveying motor 56 exceeds the threshold value. The threshold value is hereinafter referred to as the "blockage detection threshold value". When the control unit 50 determines that the medium is blocked, it stops driving each motor and causes the operation panel 7 to display an alarm indicating that the medium is blocked.

[0079] It should be noted that, since the jam detection is performed based on the duty value of the conveying motor 56 in this embodiment, the jam detection based on the duty value is performed after the front end of the medium reaches the first conveying roller pair 27. Before the front end of the medium reaches the first conveying roller pair 27, if the front end of the medium is not detected by the second medium detection unit 62 described later even if the medium is conveyed by a predetermined conveying amount, it is determined that the medium is jammed. In addition, of course, after the front end of the medium reaches the first conveying roller pair 27, a jam detection process may be performed to determine that a jam has occurred if the medium is not detected by the third medium detection unit 63, the fourth medium detection unit 64, and the fifth medium detection unit 65 described later even if the medium is conveyed by a predetermined conveying amount, together with the jam detection process based on the duty value described later.

[0080] Next, detection signals from the first medium detection unit 61, the second medium detection unit 62, the third medium detection unit 63, the fourth medium detection unit 64, and the fifth medium detection unit 65 are also input to the control unit 50. These detection units are optical sensors having a light emitting unit (not shown) and a light receiving unit (not shown), and the control unit 50 can detect whether the front end of the medium or the rear end of the medium passes through the detection position of each detection unit based on the detection signals received from each detection unit. It should be noted that each detection unit is not limited to an optical sensor, and may also be a contact sensor that contacts the medium.

[0081] Here, if Figure 4 As shown, the first medium detection unit 61 is a detection unit provided for the separation roller pair 23. In addition, the second medium detection unit 62 is a detection unit provided for the first conveying roller pair 27. In addition, the third medium detection unit 63 is a detection unit provided for the second conveying roller pair 31. In addition, the fourth medium detection unit 64 is a detection unit provided for the third conveying roller pair 35. In addition, the fifth medium detection unit 65 is a detection unit provided for the fourth conveying roller pair 39. The control unit 50 can grasp the current position of the front end and the rear end of the medium based on the detection signals received from each detection unit.

[0082] It should be noted that, in the present embodiment, the first medium detection unit 61 detects the medium near the downstream of the medium clamping position of the separation roller pair 23. In addition, the second medium detection unit 62, the third medium detection unit 63, the fourth medium detection unit 64, and the fifth medium detection unit 65 detect the medium near the upstream of the medium clamping position of each conveying roller pair.

[0083] Next, the switching of the jam detection threshold in the jam detection process is described. In this embodiment, the control unit 50 changes the jam detection threshold according to the number of roller pairs clamping the medium, whether the separation roller pair 23 clamps the medium, the position of the front end of the medium in the curved reversing path T, etc. In addition, the motor drive speed is changed together with the change of the jam detection threshold, in other words, the predetermined conveying speed of the medium is changed.

[0084] As an example, Figures 4 to 8 FIG. 2 shows the position change of the medium P when the medium P of A4 size is conveyed with the short side direction along the conveying direction. Figures 4 to 8 , reference numeral Se1 is a section between the separation roller pair 23 and the first conveying roller pair 27 in the curved reversal path T, reference numeral Se2 is a section between the first conveying roller pair 27 and the second conveying roller pair 31 in the curved reversal path T, reference numeral Se3 is a section between the second conveying roller pair 31 and the third conveying roller pair 35 in the curved reversal path T, and reference numeral Se4 is a section between the third conveying roller pair 35 and the fourth conveying roller pair 39 in the curved reversal path T.

[0085] exist Figure 4In the state shown, since the medium P is only clamped by the separation roller pair 23, the driving load accompanying the medium transportation acts only on the feed motor 55, and the driving load accompanying the medium transportation does not act on the transportation motor 56. If the medium P is transported from this state, Figure 5 As shown, the medium P is clamped by the first conveying roller pair 27 , that is, a driving load corresponding to one roller pair acts on the conveying motor 56 .

[0086] If the medium P is further transported from this state, Figure 6 As shown, the medium P is sandwiched by the first conveying roller pair 27 and the second conveying roller pair 31 , that is, the driving loads corresponding to the two roller pairs act on the conveying motor 56 .

[0087] If the medium P is further transported from this state, Figure 7 As shown, the medium P is clamped by the first conveying roller pair 27 , the second conveying roller pair 31 , and the third conveying roller pair 35 . That is, driving loads corresponding to the three roller pairs act on the conveying motor 56 .

[0088] If the medium P is further transported from this state, Figure 8 As shown, the medium P is clamped by the second conveying roller pair 31 , the third conveying roller pair 35 , and the fourth conveying roller pair 39 , that is, driving loads corresponding to the three roller pairs act on the conveying motor 56 .

[0089] Although the subsequent illustrations are omitted, if the medium P is further transported, the driving load corresponding to the two roller pairs acts on the transport motor 56, and then, the driving load corresponding to one roller pair (the fourth transport roller pair 39) acts on the transport motor 56. Then, if the medium P is discharged, the driving load accompanying the medium transport no longer acts on the transport motor 56.

[0090] It should be noted that, when the length of the medium P is longer, a driving load corresponding to a maximum of four roller pairs acts on the transport motor 56 .

[0091] As described above, as the medium P is conveyed, the number of roller pairs involved in conveying the medium P changes, so the duty value of the conveying motor 56 also changes as the medium P is conveyed. Fig. 9 In the figure, the vertical axis A is the duty value of the conveying motor 56, and the horizontal axis t is the medium conveying distance. In the horizontal axis t, the interval shown by R1 is an interval in which the number of roller pairs involved in conveying the medium P among the roller pairs driven by the conveying motor 56 is one, and similarly, the interval shown by R2 is an interval in which the number of roller pairs involved in conveying the medium P is two, the interval shown by R3 is an interval in which the number of roller pairs involved in conveying the medium P is three, and the interval shown by R4 is an interval in which the number of roller pairs involved in conveying the medium P is four.

[0092] The solid line shown by reference numeral Cd1 is the duty value of the conveying motor 56 in section R1. Similarly, the solid line shown by reference numeral Cd2 is the duty value of the conveying motor 56 in section R2. The solid line shown by reference numeral Cd3 is the duty value of the conveying motor 56 in section R3. The solid line shown by reference numeral Cd4 is the duty value of the conveying motor 56 in section R4.

[0093] As shown in the figure, the duty value of the conveying motor 56 increases in stages as the medium P is conveyed, and then decreases in stages.

[0094] In such a configuration, if the clogging detection threshold is set based on the highest duty value Cd4 as indicated by the dashed line indicated by reference numeral S0, the difference between the other duty values ​​Cd1, Cd2, and Cd3 and the clogging detection threshold S0 becomes larger. As a result, when clogging occurs in the intervals R1, R2, and R3, it takes time for the duty value to exceed the clogging detection threshold S0, causing the clogging to develop and increasing the damage to the medium P.

[0095] Therefore, the control unit 50 changes the jam detection threshold value according to the number of roller pairs involved in conveying the medium P. The number of roller pairs involved in conveying the medium P can be determined based on the detection signals of the first medium detector 61 , the second medium detector 62 , the third medium detector 63 , and the fourth medium detector 64 .

[0096] Then, if the number of detection units that detect the medium P, that is, the number of roller pairs involved in the conveyance of the medium P, increases, Fig. 9 As shown, the control unit 50 increases the jam detection threshold. In addition, if the number of detection units that detect the medium P, that is, the number of roller pairs involved in the conveyance of the medium P decreases, the control unit 50 lowers the jam detection threshold.

[0097] exist Fig. 9 In the figure, the dotted line shown by reference numeral S1 is the congestion detection threshold in section R1, and similarly, the dotted line shown by reference numeral S2 is the congestion detection threshold in section R2, the dotted line shown by reference numeral S3 is the congestion detection threshold in section R3, and the dotted line shown by reference numeral S4 is the congestion detection threshold in section R4. Each congestion detection threshold is a value obtained by adding a predetermined value to a duty value obtained in advance by experiment, and is stored in the flash ROM 52 (refer to Figure 3 ) can be read out as needed.

[0098] The following reference Fig.10 The flow of processing of the jam detection program will be described.

[0099] When the feeding of the medium P starts (step S101), the control unit 50 then continuously monitors whether a signal change occurs in any of the second medium detection unit 62, the third medium detection unit 63, the fourth medium detection unit 64, and the fifth medium detection unit 65 (step S102). As a result, if a signal change occurs in any of the detection units ("Yes" in step S102), the number of roller pairs involved in the feeding of the medium P is acquired (step S103).

[0100] Next, the front end position of the medium P is obtained, that is, in which interval Se1, Se2, Se3, and Se4 of the curved reversing path T the front end of the medium P is located (step S104). Then, based on the results of steps S103 and S104, a jam detection threshold is obtained (step S105). The acquisition of the jam detection threshold in step S105 will be described in more detail later.

[0101] Then, based on the acquired congestion detection threshold, the congestion detection threshold is switched (step S106 ).

[0102] Next, the motor driving speed is acquired based on the results of steps S103 and S104 (step S107 ), and the driving speeds of the feed motor 55 and the transport motor 56 are switched based on the acquired motor driving speed (step S108 ).

[0103] The setting of the motor driving speed will be described again later.

[0104] The above process is performed until the medium P is discharged, specifically, until the rear end of the medium P passes through the fourth medium detection unit 64 (step S109 ).

[0105] Table 1 shows the relationship between the number of roller pairs involved in conveying the medium P, the jam detection threshold, and the motor drive speed.

[0106] Table 1

[0107] Number of roller pairs involved in conveying Blockage detection threshold Motor drive speed 1 S1 V1 2 S2 V2 3 S3 V3 4 S4 V4

[0108] As reference Fig. 9 As described, the values ​​of the congestion detection thresholds S1, S2, S3, and S4 are S1<S2<S3<S4.

[0109] In addition, regarding the motor drive speeds V1, V2, V3, and V4, speed V4 is the lowest speed and speed V1 is the highest speed. Specifically, they are set as V1>V2>V3>V4 and are stored in the flash ROM 52 (refer to Figure 3 ) can be read out as needed.

[0110] It should be noted that when the control unit 50 switches the jam detection threshold to a high value, Fig. 9 As shown in FIG. 1 , it is made to rise slowly from the time when any of the detection units has a signal change. In addition, when the clogging detection threshold is switched to a low value, as shown in FIG. Fig. 9 As shown, based on the timing of signal change in any of the detection units, the blocking detection threshold is slowly decreased from the timing of switching the number of roller pairs involved in the conveying. That is, the blocking detection threshold is set to follow the duty value of the conveying motor 56. However, this is not limited to this, and the switching of the blocking detection threshold can also be performed completely in stages.

[0111] As described above, the control unit 50 obtains the number of detection units for detecting the medium P, that is, the number of roller pairs involved in the conveyance of the medium P, based on the detection information of the plurality of detection units in the jam detection process, and increases the jam detection threshold value if the number of roller pairs involved in the conveyance of the medium P increases. In addition, the control unit 50 obtains the number of detection units for detecting the medium P, that is, the number of roller pairs involved in the conveyance of the medium P, based on the detection information of the plurality of detection units in the jam detection process, and decreases the jam detection threshold value if the number of detection units for detecting the medium P, that is, the number of roller pairs involved in the conveyance of the medium P decreases. The control unit 50 has a jam detection program that implements such a jam detection process, and implements the above-mentioned jam detection method through the jam detection program.

[0112] As described above, when the number of roller pairs involved in conveying the medium P is small, it is possible to prevent the difference between the duty value of the conveying motor 56 and the jam detection threshold from increasing and taking time to detect a jam of the medium P. As a result, it is possible to prevent the jam from progressing and causing damage to the medium P to increase.

[0113] Next, switching of the motor driving speed according to the number of roller pairs involved in conveying the medium P will be described.

[0114] The smaller the number of roller pairs involved in conveying the medium P, the less the medium conveyance amount may be due to slippage of the medium P at the roller pairs involved in conveying the medium P, which may adversely affect the reading result of the first reading unit 4 or the second reading unit 45 .

[0115] Therefore, the control unit 50 changes the motor driving speed according to the number of roller pairs involved in the conveyance of the medium P. Specifically, like the above-mentioned motor driving speeds V1, V2, V3, and V4, if the number of roller pairs involved in the conveyance of the medium P increases, the driving speed of the conveyance motor 56 is reduced, and if the number of roller pairs involved in the conveyance of the medium P decreases, the driving speed of the conveyance motor 56 is increased.

[0116] It should be noted that the control unit 50 changes the driving speed of the feed motor 55 driving the separation roller pair 23 , that is, the predetermined conveying speed of the separation roller pair 23 and the driving speed of the conveying motor 56 at the same rate of change until at least the rear end of the medium P passes through the first medium detection unit 61 .

[0117] With the above, it is possible to realize an appropriate medium transport amount according to the number of roller pairs involved in transporting the medium P, and further, to obtain a good reading result in each reading unit.

[0118] The above is the basic content of switching the jam detection threshold and the motor drive speed according to the number of roller pairs involved in the conveyance of the medium P. In this embodiment, as described later, the jam detection threshold is obtained based on other aspects ( Fig.10 Step S105) and the acquisition of the motor drive speed ( Fig.10 Step S107).

[0119] First, the control unit 50 changes the jam detection threshold value according to the position of the medium P in the curved reversing path T. Thus, the jam detection threshold value can be set to a more appropriate value, and a jam can be detected more appropriately.

[0120] This will be described in further detail below. First, if the medium P is clamped by the separation roller pair 23, when the medium P is conveyed by the roller pair downstream of the separation roller pair 23, the separation roller pair 23 becomes a conveying load, and the duty value of the conveying motor 56 increases. In such a configuration, if the jam detection threshold is set based on the case where the medium P is clamped by the separation roller pair 23, and then the jam detection threshold is uniformly applied, the difference between the duty value of the conveying motor 56 when the medium P is not clamped by the separation roller pair 23 and the jam detection threshold becomes larger, and it takes time until the jam of the medium P is detected.

[0121] Therefore, when the medium P is not nipped by the separation roller pair 23 , the control unit 50 lowers the jam detection threshold value compared to when the medium P is nipped by the separation roller pair.

[0122] Table 2 shows an example of whether or not the separation roller pair 23 sandwiches the medium P and a coefficient to be multiplied by the jam detection threshold and the motor drive speed.

[0123] Table 2

[0124] Separation roller pair Threshold Multiplier Speed ​​Multiplier With clamp Ma1 Na1 No clamping Ma2 Na2

[0125] In Table 2, the threshold multipliers Ma1 and Ma2 are multipliers for multiplying the jam detection threshold values ​​shown in Table 1, and are set to Ma1>Ma2. The threshold multipliers Ma1 and Ma2 are stored in the flash ROM 52 (see Figure 3 ) can be read out as needed.

[0126] With the above, it is possible to suppress the difference between the duty value of the conveying motor 56 and the jam detection threshold value from increasing when the medium P is not sandwiched by the separation roller pair 23 , and to promptly detect a jam in the medium.

[0127] It should be noted that the clamping force of the separation roller pair 23 on the medium P is preferably configured to be changeable according to the type of the medium P. In such a configuration, it is also appropriate to configure the threshold multiplier and speed multiplier for the "clamped" state in Table 2 to be switched according to the clamping force of the separation roller pair 23 on the medium P.

[0128] In addition, the control unit 50 switches the driving speed of the conveying motor 56 according to whether the medium P is clamped by the separation roller pair 23. That is, if the medium P is clamped by the separation roller pair 23, the medium P may slip when being conveyed by the roller pair downstream of the separation roller pair 23, resulting in insufficient conveyance of the medium, which may adversely affect the reading results of the first reading unit 4 or the second reading unit 45.

[0129] Therefore, the control unit 50 makes the driving speed of the conveying motor 56 higher when the medium P is sandwiched by the separation roller pair 23 than when the medium P is not sandwiched by the separation roller pair 23 .

[0130] The speed multipliers Na1 and Na2 in Table 2 are multipliers for multiplying the motor drive speed shown in Table 1, and are set to satisfy Na1>Na2. The speed multipliers Na1 and Na2 are stored in the flash ROM 52 (see Figure 3 ) can be read out as needed.

[0131] This makes it possible to realize an appropriate medium conveyance amount according to whether or not the separation roller pair 23 sandwiches the medium P, and further, to obtain a good reading result in each reading unit.

[0132] It should be noted that the control unit 50 changes the driving speed of the feed motor 55 driving the separation roller pair 23 , that is, the predetermined conveying speed of the separation roller pair 23 and the driving speed of the conveying motor 56 at the same rate of change until at least the rear end of the medium P passes through the first medium detection unit 61 .

[0133] Next, when the front end of the medium P advances in the curved reversing path T, the greater the curvature of the path, the greater the duty value of the conveying motor 56. This is because the driving load of the conveying motor 56 increases as the front end of the medium P and the surface edge of the medium P advance while contacting with the unillustrated guide surface of the curved reversing path T. Therefore, if the jam detection threshold is set based on the case where the front end of the medium P advances in a path with a large curvature and the jam detection threshold is uniformly applied, the difference between the duty value of the conveying motor 56 and the jam detection threshold becomes larger when the front end of the medium P advances in a path with a relatively small curvature, and it takes time to detect the jam of the medium P.

[0134] Therefore, when the front end of the medium P is located in the first section of the curved reversing path T, the control unit 50 lowers the jam detection threshold value compared to when the front end of the medium P is located in the second section, and in the second section, the curvature of the medium P is made larger than in the first section. It should be noted that the control unit 50 may also increase the jam detection threshold value when the front end of the medium P is located in the second section compared to when the front end of the medium P is located in the first section.

[0135] In the present embodiment, the sections Se1 and Se4 correspond to the first section, and the sections Se2 and Se3 correspond to the second section.

[0136] Table 3 shows an example of the relationship between the medium leading end position, the threshold multiplier, and the speed multiplier.

[0137] Table 3

[0138] Media front position Threshold Multiplier Speed ​​Multiplier Interval Se2 Mb1 Nb1 Interval Se3 MB2 Nb2 Interval Se4 MB3 Nb3 Downstream of interval Se4 MB4 Nb4

[0139] In Table 3, the threshold multipliers Mb1, Mb2, Mb3, and Mb4 are multipliers for multiplying the jam detection thresholds shown in Table 1 and are stored in the flash ROM 52 (see Figure 3 ) can be read out as needed. As an example, in this embodiment, it is set to Mb4<Mb3<Mb2=Mb1.

[0140] With the above, when the leading end of the medium P advances in a path with a relatively small curvature, the difference between the duty value of the conveyance motor 56 and the jam detection threshold value can be suppressed from increasing, and a jam of the medium can be appropriately detected.

[0141] It should be noted that when congestion is more likely to occur in interval Se3, i.e., the interval read by the first reading unit 4, than in interval Se2, in order to detect congestion more quickly, it is also appropriate to set the difference between the congestion detection threshold in interval Se3 and the duty value in the state where no congestion occurs to be smaller.

[0142] Next, the speed multipliers Nb1, Nb2, Nb3, and Nb4 in Table 3 are multipliers to be multiplied by the motor drive speed shown in Table 1, and are set to Nb4<Nb3<Nb2=Nb1. The speed multipliers Nb1, Nb2, Nb3, and Nb4 are stored in the flash ROM 52 (see Figure 3 ) can be read out as needed.

[0143] With the above, it is possible to realize an appropriate medium conveyance amount according to the position of the leading end of the medium in the curved reversing path T, and thus to obtain good reading results in each reading unit.

[0144] It should be noted that the control unit 50 changes the driving speed of the feed motor 55 driving the separation roller pair 23 , that is, the predetermined conveying speed of the separation roller pair 23 and the driving speed of the conveying motor 56 at the same rate of change until at least the rear end of the medium P passes through the first medium detection unit 61 .

[0145] In addition, the control unit 50 changes the jam detection threshold and the driving speed of the conveying motor 56 according to the rigidity of the medium P. Specifically, when conveying the first medium, the control unit 50 lowers the jam detection threshold compared to when conveying the second medium, wherein the rigidity of the second medium is higher than that of the first medium. It should be noted that the control unit 50 may also increase the jam detection threshold when conveying the second medium compared to when conveying the first medium.

[0146] That is, the higher the rigidity of the medium P, the greater the duty value of the conveying motor 56. Therefore, if the jam detection threshold is set based on the medium P with high rigidity and then the jam detection threshold is uniformly applied, the difference between the duty value of the conveying motor 56 and the jam detection threshold when conveying the medium P with relatively low rigidity becomes larger, and it takes time to detect the jam of the medium P.

[0147] Therefore, the control unit 50 lowers the clogging detection threshold for the first medium as compared with the second medium having a higher rigidity than the first medium.

[0148] Table 4 shows an example of the relationship between the medium type, the threshold multiplier, and the speed multiplier.

[0149] Table 4

[0150] Media Type Threshold Multiplier Speed ​​Multiplier Medium 1 Mc1 Nc1 Medium 2 Mc2 Nc2 Medium 3 Mc3 Nc3 Medium 4 Mc4 Nc4

[0151] In Table 4, the rigidity of medium 1, medium 2, medium 3, and medium 4 increases in this order, that is, medium 4 is the medium with the highest rigidity. The threshold multipliers Mc1, Mc2, Mc3, and Mc4 are multipliers multiplied by the jam detection threshold values ​​shown in Table 1, and are set to Mc1 < Mc2 < Mc3 < Mc4. The threshold multipliers Mc1, Mc2, Mc3, and Mc4 are stored in the flash ROM 52 (see Figure 3 ) can be read out as needed. It should be noted that the type of medium can be determined by the user using the operation panel 7 (refer to Figure 3 However, the medium type can be determined based on the duty values ​​in the interval Se1 and the interval Se2 of the curved reversal path T, or a sensor for detecting the thickness of the medium P can be set in the interval Se1 to determine the medium type based on the detection information.

[0152] Regarding the relationship between medium 1 and medium 2, medium 1 is the first medium and medium 2 is the second medium. Similarly, regarding the relationship between medium 2 and medium 3, medium 2 is the first medium and medium 3 is the second medium. Similarly, regarding the relationship between medium 3 and medium 4, medium 3 is the first medium and medium 4 is the second medium.

[0153] With the above, it is possible to suppress the difference between the duty value of the transport motor 56 and the jam detection threshold from increasing when the medium P having relatively low rigidity is transported, and the jam of the medium P can be detected promptly.

[0154] Similarly, the speed multipliers Nc1, Nc2, Nc3, and Nc4 are multipliers for multiplying the motor drive speed shown in Table 1, and are set to satisfy Nc1<Nc2<Nc3<Nc4. The threshold multipliers Nc1, Nc2, Nc3, and Nc4 are stored in the flash ROM 52 (see Figure 3 ) can be read out as needed.

[0155] That is, the higher the rigidity of the medium P is, the greater the transport load is, and the medium transport amount may be insufficient due to slippage at each roller, which has an adverse effect on the reading result in the first reading unit 4 or the second reading unit 45. However, as described above, when the rigidity of the medium P is relatively higher than that of other media P, the driving speed of the transport motor 56 is increased compared with other media P, so when the medium P with high rigidity is transported, the insufficient medium transport amount can be suppressed, and the appropriate medium transport amount corresponding to the rigidity of the medium P can be achieved, and thus a good reading result can be obtained in each reading unit.

[0156] It should be noted that the control unit 50 changes the driving speed of the feed motor 55 driving the separation roller pair 23 , that is, the predetermined conveying speed of the separation roller pair 23 and the driving speed of the conveying motor 56 at the same rate of change until at least the rear end of the medium P passes through the first medium detection unit 61 .

[0157] In the above described embodiments, Figures 4 to 8As shown, the case where a single medium P exists in the curved reversing path T is used as an example for explanation; however, even when multiple medium P exist in the curved reversing path T, the jam detection threshold and the motor drive speed can be appropriately set based on the number of roller pairs involved in the transportation of the medium P.

[0158] In addition, in the above-described embodiment, a detection unit is provided for each roller pair, and the roller pair involved in the conveyance of the medium P is grasped based on the medium detection status in each detection unit, but it is also possible to grasp the roller pair involved in the conveyance of the medium P based on the expected arrival position of the medium based on the medium conveyance amount, and change the jam detection threshold and the roller driving speed based on it. In this case, it is not necessarily necessary to provide a detection unit for detecting the medium for all roller pairs, and the method of detecting the medium is not limited to the method of detecting the medium upstream of the clamping position of the roller pair, and the medium may be detected at the clamping position or downstream of the clamping position.

[0159] The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims, and such modifications are naturally included in the scope of the present invention.

[0160] In the above embodiment, an example in which the medium transport device 10 is applied to the scanner 1 as an example of an image reading device is described, but it can also be applied to a recording device including a recording unit that records on a medium.

Claims

1. A medium conveying device, characterized in that: have: A medium loading portion for loading the medium before feeding; a medium conveying path for conveying the medium delivered from the medium loading portion; A plurality of conveying roller pairs, arranged on the medium conveying path; a motor, serving as a power source for the plurality of conveying roller pairs; as well as a control unit for controlling the motor, wherein the control unit is capable of performing a blockage detection process for detecting blockage of the medium in the medium conveying path by referring to a driving load of the motor and a duty value and a threshold value for the driving load, wherein when the duty value exceeds the threshold value, the control unit determines that a blockage has occurred in the medium conveying path, In the medium conveying path, each of the plurality of conveying roller pairs is provided with a detection unit for detecting the medium, and detection information of the detection unit includes current positions of the front end of the medium and the rear end of the medium. The control unit acquires the number of the transport roller pairs involved in transporting the medium based on the detection information of the detection unit, thereby changing the threshold value, raising the threshold value if the number of the transport roller pairs increases, and lowering the threshold value if the number of the transport roller pairs decreases.

2. The medium conveying device according to claim 1, characterized in that: The control unit changes the threshold value according to a position of a medium in the medium conveyance path.

3. The medium conveying device according to claim 2, characterized in that: In the medium conveying path, a separation roller pair is provided upstream of the plurality of conveying roller pairs for separating the medium conveyed from the medium loading portion. When the medium is not nipped by the separation roller pair, the control unit lowers the threshold value compared to when the medium is nipped by the separation roller pair.

4. The medium conveying device according to claim 2, characterized in that: The medium conveying path is a path that causes the medium fed from the medium loading portion to bend downward and then reverse in a direction opposite to the direction in which the medium is fed from the medium loading portion. When the leading end of the medium is located in a first section of the medium conveying path, the control unit lowers the threshold value compared to when the leading end of the medium is located in a second section, and in the second section, the curvature of the medium is bent larger than in the first section.

5. The medium conveying device according to any one of claims 1 to 4, characterized in that: The control unit lowers the threshold value when a first medium is conveyed, compared with a case where a second medium having a higher rigidity than the first medium is conveyed.

6. An image reading device, characterized in that: have: a reading unit that reads a surface of a medium being conveyed; and The medium conveying device according to any one of claims 1 to 5 for conveying a medium.

7. The image reading device according to claim 6, characterized in that: The control unit reduces the driving speed of the motor when the number of the transport roller pairs involved in the transport of the medium increases, and increases the driving speed of the motor when the number of the transport roller pairs involved in the transport of the medium decreases.

8. The image reading device according to claim 6 or 7, characterized in that: When the rigidity of the medium is relatively higher than the rigidity of other mediums, the control unit relatively increases the driving speed of the motor compared with the other mediums.

9. A method for detecting a blockage, characterized in that A blockage detection method for detecting blockage of a medium in a medium conveying path by referring to a driving load of a motor and a duty value and a threshold value for the driving load in a medium conveying device, and determining that a blockage occurs in the medium conveying path when the duty value exceeds the threshold value, the medium conveying device comprising: A medium loading portion for loading the medium before feeding; The medium conveying path conveys the medium delivered from the medium loading portion; A plurality of conveying roller pairs, arranged in the medium conveying path; and The motor, as a power source for the plurality of conveying roller pairs, In the blockage detection method, the number of the conveying roller pairs involved in the conveying of the medium is obtained based on the detection information of the detection unit for detecting the medium respectively set for the multiple conveying roller pairs in the medium conveying path. If the number of the conveying roller pairs involved in the conveying of the medium increases, the threshold value is increased, and if the number of the conveying roller pairs involved in the conveying of the medium decreases, the threshold value is decreased.

10. A computer program product, characterized in that The medium conveying device includes a blockage detection program, wherein the blockage detection program refers to a driving load of a motor and a duty value and a threshold value for the driving load to detect blockage of a medium in a medium conveying path, and when the duty value exceeds the threshold value, it is determined that a blockage occurs in the medium conveying path. The medium conveying device comprises: A medium loading portion for loading the medium before feeding; The medium conveying path conveys the medium delivered from the medium loading portion; A plurality of conveying roller pairs, arranged in the medium conveying path; and The motor, as a power source for the plurality of conveying roller pairs, The blockage detection program, when executed, implements the following steps: Based on detection information of a detection unit for detecting the medium provided for each of the plurality of conveying roller pairs in the medium conveying path, acquiring the number of the conveying roller pairs involved in conveying the medium; and The threshold value is changed so that the threshold value is increased when the number of the transport roller pairs involved in the transport of the medium increases, and the threshold value is decreased when the number of the transport roller pairs involved in the transport of the medium decreases.

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