Media transport device, media transport method and control program

Abstract

To provide a media transport device capable of more easily and appropriately correct the skew of a media.SOLUTION: The media transport device includes a first roller and a second roller that rotate independently to convey the media, a first sensor disposed downstream side of the first roller, and a second sensor disposed downstream side of the second roller, a control unit that corrects, when the first sensor detects the media before the second sensor detects the media, the skew of the media by setting a circumferential speed of the first roller to a first speed and a circumferential speed of the second roller to a second speed higher than the first speed, the first sensor and the second sensor are arranged at the same positions when viewed from the direction perpendicular to the media transport direction, and an arrangement position of the first sensor in a direction perpendicular to the media transport direction is as the same as a rotation center position that the media rotate, by a speed ratio of the second speed to the first speed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a medium transport device, a medium transport method, and a control program. [Background technology]

[0002] In media transport devices such as scanners, when transporting and reading media, skew (oblique movement) may occur, causing the media to be transported at an angle, resulting in the entire media not being captured, or the media may collide with the side wall of the transport path, causing a media jam (paper jam).

[0003] A medium transport device is disclosed that has multiple feed rollers that are spaced apart in a direction perpendicular to the medium transport direction and rotate independently to feed the medium (see Patent Document 1). When skew of the medium is detected, this medium transport device corrects the skew of the medium by making the peripheral speeds of the multiple feed rollers different from each other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-100460 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a medium transport device, there is a demand for a method for correcting medium skew more easily and appropriately.

[0006] An object of the present invention is to provide a medium transport device, a medium transport method, and a control program that are capable of more easily and appropriately correcting medium skew. [Means for solving the problem]

[0007] A media transport device according to one aspect of the present invention comprises a first roller and a second roller arranged at a distance from each other in a direction perpendicular to the media transport direction and each rotating independently to transport a medium, a first sensor arranged downstream of the first roller in the media transport direction, a second sensor arranged downstream of the second roller in the media transport direction, and a control unit that corrects skew of the medium by setting the circumferential speed of the first roller to a first speed and the circumferential speed of the second roller to a second speed higher than the first speed when the first sensor detects the medium before the second sensor detects the medium, wherein the first sensor and the second sensor are arranged at the same position when viewed from a direction perpendicular to the media transport direction, and the position of the first sensor in the direction perpendicular to the media transport direction is the same as the center of rotation about which the medium rotates depending on the speed ratio of the second speed to the first speed.

[0008] A media transport method according to one aspect of the present invention includes transporting a medium by a first roller and a second roller arranged at a distance from each other in a direction perpendicular to the media transport direction and rotating independently, and when a first sensor arranged downstream of the first roller in the media transport direction detects the medium before a second sensor arranged downstream of the second roller in the media transport direction detects the medium, correcting skew of the medium by setting the peripheral speed of the first roller to a first speed and the peripheral speed of the second roller to a second speed higher than the first speed, wherein the first sensor and the second sensor are arranged at the same position when viewed from a direction perpendicular to the media transport direction, and the position of the first sensor in the direction perpendicular to the media transport direction is the same as the center of rotation about which the medium rotates with a speed ratio of the second speed to the first speed.

[0009] A control program according to one aspect of the present invention is a control program for a media transport device having a first roller and a second roller arranged at a distance from each other in a direction perpendicular to the media transport direction and each rotating independently to transport a medium, a first sensor arranged downstream of the first roller in the media transport direction, and a second sensor arranged downstream of the second roller in the media transport direction, wherein when the first sensor detects the medium before the second sensor detects the medium, the control program causes the media transport device to correct skew of the medium by setting the circumferential speed of the first roller to a first speed and the circumferential speed of the second roller to a second speed higher than the first speed, wherein the first sensor and the second sensor are arranged at the same position when viewed from a direction perpendicular to the media transport direction, and the position of the first sensor in the direction perpendicular to the media transport direction is the same as the center of rotation about which the medium rotates with a speed ratio of the second speed to the first speed. Effect of the Invention

[0010] According to the present invention, the medium transport device, the medium transport method, and the control program are capable of correcting the skew of the medium more simply and appropriately. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a medium conveying device 100. [Diagram 2] 2 is a diagram for explaining a transport path inside the medium transport device 100. FIG. [Diagram 3] FIG. 2 is a schematic diagram for explaining each sensor. [Figure 4] 2 is a schematic diagram for explaining a pick roller 112. FIG. [Diagram 5] 1 is a block diagram showing a schematic configuration of a medium conveying device 100. FIG. [Figure 6] FIG. 2 is a diagram showing a schematic configuration of a storage device 150 and a processing circuit 160. [Figure 7] 10 is a flowchart illustrating an example of the operation of a medium reading process. [Figure 8] 13 is a flowchart illustrating an example of an operation of a skew determination process. [Figure 9] 13 is a flowchart illustrating an example of an operation of a skew determination process. [Figure 10] 13 is a flowchart illustrating an example of an operation of a skew determination process. [Figure 11] 1A is a schematic diagram for explaining a medium M1, and FIG. 1B is a schematic diagram for explaining a medium M2. [Figure 12] 13A is a schematic diagram for explaining a medium M4, and FIG. 13B is a schematic diagram for explaining insufficient correction. [Figure 13] FIG. 11 is a schematic diagram for explaining overcorrection. [Figure 14] 11 is a graph for explaining the inclination of a medium. [Figure 15] 1A to 1C are schematic diagrams for explaining feeding of a medium. [Figure 16] 13A and 13B are schematic diagrams for explaining a medium M4. [Figure 17] FIG. 13 is a schematic diagram for explaining media M8 and M9. [Figure 18] FIG. 13 is a diagram showing a schematic configuration of a processing circuit 260 according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a medium conveying device, a medium conveying method, and a control program according to one aspect of the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions described in the claims and their equivalents.

[0013] 1 is a perspective view showing a medium conveying device 100 configured as an image scanner. The medium conveying device 100 conveys a medium, which is an original document, and captures an image of the medium. The medium is paper, cardboard, card, or the like. The medium conveying device 100 may be a facsimile, a copier, a multifunction printer (MFP, Multifunction Peripheral), or the like. Note that the medium being conveyed may not be an original document, but may be a print target, or the like, and the medium conveying device 100 may be a printer, or the like.

[0014] 1, arrow A1 indicates the substantially vertical direction (height direction), arrow A2 indicates the medium transport direction, arrow A3 indicates the medium discharge direction, and arrow A4 indicates the width direction perpendicular to the medium transport direction A2 or the medium discharge direction A3. In the following, upstream refers to the upstream of the medium transport direction A2 or the medium discharge direction A3, and downstream refers to the downstream of the medium transport direction A2 or the medium discharge direction A3.

[0015] The medium conveying device 100 includes a first housing 101, a second housing 102, a placement table 103, a discharge table 104, an operation device 105, a display device 106, and the like.

[0016] The second housing 102 is disposed inside the first housing 101 and rotatably engaged with the first housing 101 by a hinge so as to be openable and closable when loading media or when cleaning the inside of the media conveying device 100, for example.

[0017] The placement table 103 engages with the first housing 101 so that the medium to be transported can be placed thereon. The placement table 103 is provided on the side surface of the first housing 101 on the medium supply side so as to be movable in the height direction A1. The placement table 103 is disposed at the bottom end position so that the medium can be easily placed thereon when the medium is not being transported, and when the medium is being transported, the uppermost medium placed on the placement table 103 rises to a position where it comes into contact with a pick roller, which will be described later.

[0018] The discharge stage 104 is formed on the second housing 102. The discharge stage 104 places the media discharged from the discharge ports of the first housing 101 and the second housing 102 thereon.

[0019] The operation device 105 has an input device such as a button and an interface circuit for acquiring a signal from the input device, accepts an input operation by a user, and outputs an operation signal according to the user's input operation. The display device 106 has a display including a liquid crystal, an organic EL (Electro-Luminescence), or the like, and an interface circuit for outputting image data to the display, and displays the image data on the display. The display device 106 may be a liquid crystal display with a touch panel function. In that case, the operation device 105 has an interface circuit for acquiring an input signal from the touch panel.

[0020] FIG. 2 is a diagram for explaining a transport path inside the medium transport device 100. As shown in FIG.

[0021] The transport path inside the media transport device 100 has a loading platform sensor 111, a pick roller 112, a feed roller 113, a separation roller 114, a rotation sensor 115, a separation sensor 116, a pick sensor 117, a first skew sensor 118, a second skew sensor 119, first to sixth transport rollers 120a-f, first to sixth driven rollers 121a-f, a feed sensor 122, and an imaging device 123, etc.

[0022] The pick roller 112, the feed roller 113, the separation roller 114, the first to sixth transport rollers 120a-f, and / or the first to sixth driven rollers 121a-f are examples of rollers that transport a medium or transport rollers. Note that the number of each of the pick roller 112, the feed roller 113, the separation roller 114, the first to sixth transport rollers 120a-f, and / or the first to sixth driven rollers 121a-f is not limited to one, and may be more than one. In this case, the multiple feed rollers 113, the separation roller 114, the first to sixth transport rollers 120a-f, and / or the first to sixth driven rollers 121a-f are arranged at intervals in the width direction A4 perpendicular to the medium transport direction.

[0023] The second housing 102 is disposed opposite the first housing 101 across the medium transport path. The surface of the first housing 101 facing the second housing 102 forms a first guide 101a of the medium transport path, and the surface of the second housing 102 facing the first housing 101 forms a second guide 102a of the medium transport path. The first guide 101a and the second guide 102a have a so-called U-turn path.

[0024] The placement table sensor 111 is disposed on the placement table 103, that is, upstream of the feed roller 113 and the separation roller 114, and detects the placement state of the medium on the placement table 103. The placement table sensor 111 determines whether or not a medium is placed on the placement table 103 by using a contact detection sensor that passes a predetermined current when the medium is in contact with the placement table 103 or not. The placement table sensor 111 generates and outputs a placement table signal whose signal value changes depending on whether or not the medium is placed on the placement table 103. Note that the placement table sensor 111 is not limited to a contact detection sensor, and any other sensor capable of detecting the presence or absence of a medium, such as a light detection sensor, may be used as the placement table sensor 111.

[0025] Pick roller 112 is disposed in second housing 102, upstream of feed roller 113 and separation roller 114 in medium transport direction A2. Pick roller 112 comes into contact with the uppermost medium among the media placed on mounting table 103, which has been raised to approximately the same height as the medium transport path, and feeds (transports) the medium downstream.

[0026] The feed roller 113 is provided in the second housing 102 downstream of the pick roller 112, and feeds (transports) the medium placed on the placement table 103 and fed (transported) by the pick roller 112 further downstream. When multiple feed rollers 113 are provided, each feed roller 113 is provided so as to rotate independently by a separate motor. The multiple feed rollers 113 are an example of a first roller and a second roller. The feed rollers 113 may be provided so as to rotate together by a common motor.

[0027] The separation roller 114 is disposed in the first housing 101 facing the feed roller 113. The separation roller 114 is a so-called brake roller or retard roller, and is provided so as to be rotatable or stoppable in the direction A13 opposite to the medium feed direction. The feed roller 113 and the separation roller 114 function as a separation unit that separates the media, and separates the media and feeds them one by one. The feed roller 113 is disposed above the separation roller 114, and the medium conveying device 100 feeds the media by a so-called top-take method.

[0028] A torque limiter that specifies the limit value of the torque applied to the separation roller 114 is provided between the separation roller 114 and the motor that applies a driving force to the separation roller 114. The limit value of the torque limiter is set to a value such that the rotational force via the torque limiter is cut off when there is one medium, and the rotational force via the torque limiter is transmitted when there are multiple media. As a result, when only one medium is transported, the separation roller 114 does not rotate according to the driving force from the motor, but follows the feed roller 113. On the other hand, when multiple media are transported, the separation roller 114 rotates in the opposite direction A13 to the medium feeding direction, and separates the medium in contact with the feed roller 113 from the other media, thereby preventing double feeding. At this time, the outer circumferential surface of the separation roller 114 may apply a force in the opposite direction A13 to the medium feeding direction to the medium while it is stopped without rotating in the opposite direction A13 to the medium feeding direction.

[0029] The separation roller 114 is supported by the first housing 101 by an arm 114c. The separation roller 114 is attached to one end of the arm 114c, and the other end of the arm 114c is attached to the first housing 101. The arm 114c is provided to the first housing 101 so as to be rotatable (swingable). A biasing force is applied to the arm 114c by a biasing member (not shown) such as a spring member or a rubber member in the upward direction, that is, in the direction in which the separation roller 114 moves toward the feed roller 113 side. The arm 114c applies a pressing force to the separation roller 114 to press the separation roller 114 toward the feed roller 113 side. In addition, a rotational force for rotating (swinging) is applied to the arm 114c by a driving force from a motor described later. The medium conveying device 100 adjusts the pressing force with which the separation roller 114 presses the feed roller 113 by rotating (swinging) the arm 114c.

[0030] The rotation sensor 115 is an encoder or the like, and is provided on a shaft that is the rotation axis of the separation roller 114, and detects the rotation of the separation roller 114. The rotation sensor 115 has a disk in which many slits (light transmission holes) are formed and which is provided to rotate according to the rotation of the separation roller 114, and a light emitter and a light receiver which are provided to face each other across the disk. The light emitter is an LED (Light Emitting Diode) or the like, and emits light toward the disk (light receiver). The light receiver is a photodiode or the like, and receives the light emitted by the light emitter through the disk. The light receiver detects the number of changes in a predetermined period from a state in which there is a slit between the light emitter and the light receiver to a state in which there is no slit and the light is blocked by the disk. The light receiver detects the movement distance of the outer circumferential surface of the separation roller 114 by multiplying the detected number of changes by the distance that the outer circumferential surface of the separation roller 114 moves when the disk rotates by the distance between two adjacent slits. A fixed slit is provided between the light emitter and the light receiver to make the output signal (pulse) two-phase, and the light receiver detects the rotation direction of the disk based on the rising timing of the output signal of each phase. The rotation sensor 115 generates and outputs a rotation signal indicating the detected moving distance and the rotation direction of the disk (stop / forward / reverse).

[0031] The rotation sensor 115 is not limited to an optical encoder, but may be any encoder such as a mechanical encoder, a magnetic encoder, or an electromagnetic induction encoder.

[0032] The first to sixth conveying rollers 120a-f and the first to sixth driven rollers 121a-f are arranged facing each other downstream of the pick roller 112, the feed roller 113, and the separation roller 114 in the medium conveying direction A2. The first to sixth conveying rollers 120a-f and the first to sixth driven rollers 121a-f convey the medium fed by the feed roller 113 and the separation roller 114 downstream. The sixth conveying roller 120f and the sixth driven roller 121f discharge the medium to the discharge tray 104.

[0033] The imaging device 123 is disposed downstream of the first and second transport rollers 120a-b in the medium transport direction A2, and captures images of the medium transported by the first and second transport rollers 120a-b and the first and second driven rollers 121a-b. The imaging device 123 includes a first imaging device 123a and a second imaging device 123b disposed opposite each other across the medium transport path. The first imaging device 123a is provided in the second housing 102, and the second imaging device 123b is provided in the first housing 101.

[0034] The first imaging device 123a has a line sensor using a CIS (Contact Image Sensor) of a life-size optical system type having imaging elements using CMOS (Complementary Metal Oxide Semiconductor) linearly arranged in the main scanning direction. The first imaging device 123a also has a lens that forms an image on the imaging elements, and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging elements. The first imaging device 123a captures an image of the surface of the medium being transported, generates an input image, and outputs it.

[0035] Similarly, the second imaging device 123b has a line sensor using a CIS of a life-size optical system type having CMOS imaging elements arranged in a line in the main scanning direction. The second imaging device 123b also has a lens that forms an image on the imaging element, and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging element. The second imaging device 123b captures the back side of the medium being transported to generate an input image and output it.

[0036] The medium conveying device 100 may have only one of the first imaging device 123a and the second imaging device 123b arranged, and may read only one side of the medium. Also, instead of a CIS line sensor of an equal magnification optical system type having a CMOS imaging element, a CIS line sensor of an equal magnification optical system type having a CCD (Charge Coupled Device) imaging element may be used. Also, a reduction optical system type line sensor having a CMOS or CCD imaging element may be used.

[0037] The medium placed on the placement table 103 is transported between the first guide 101a and the second guide 102a in the medium transport direction A2 by the rotation of the pick roller 112 and the feed roller 113 in the medium feed direction A11 and A12, respectively. The medium transport device 100 has a separation mode in which the medium is separated while being fed, and a non-separation mode in which the medium is not separated and is fed. The feed mode is set by the user using the operation device 105 or an information processing device that is communicatively connected to the medium transport device 100. When the feed mode is set to the separation mode, the separation roller 114 rotates or stops in the direction of the arrow A13, i.e., in the opposite direction to the medium feed direction. This limits the feeding of media other than the separated medium (prevention of double feeding). On the other hand, when the feed mode is set to the non-separation mode, the separation roller 114 rotates in the opposite direction to the arrow A13, i.e., in the medium feed direction.

[0038] The medium is guided by the first guide 101a and the second guide 102a, and as the first and second transport rollers 120a-b rotate in the directions of arrows A14-15, the medium is sent to the imaging position of the imaging device 123 and is imaged by the imaging device 123. Furthermore, the medium is discharged onto the discharge table 104 as the third to sixth transport rollers 120c-f rotate in the directions of arrows A16-19, respectively.

[0039] Fig. 3 is a schematic diagram for explaining each sensor. Fig. 3 is a schematic diagram of the periphery of the medium transport port as viewed from above (the second housing 102 side).

[0040] In the example shown in Fig. 3, the feed roller 113 includes a first feed roller 113a and a second feed roller 113b, and the separation roller 114 includes a first separation roller 114a and a second separation roller 114b. The first feed roller 113a and the first separation roller 114a are disposed on the left side of the center position in the width direction A4 when viewed from the downstream side (the left side in Fig. 3). The second feed roller 113b and the second separation roller 114b are disposed on the right side of the center position in the width direction A4 when viewed from the downstream side (the right side in Fig. 3). The first feed roller 113a is an example of a first roller, and the second feed roller 113b is an example of a second roller.

[0041] The separation sensor 116 is disposed downstream of the nip portion N1 between the feed roller 113 and the separation roller 114 and upstream of the nip portion N2 between the first conveyor roller 120a and the first driven roller 121a in the medium conveying direction A2. In particular, the separation sensor 116 is disposed near the feed roller 113 and the separation roller 114. The separation sensor 116 is also disposed upstream of the pick sensor 117, the first skew sensor 118, and the second skew sensor 119 in the medium conveying direction A2. The separation sensor 116 is also disposed in the center in the width direction A4, particularly between the first feed roller 113a and the second feed roller 113b (between the first separation roller 114a and the second separation roller 114b). The separation sensor 116 is also disposed between the first skew sensor 118 and the second skew sensor 119 in the width direction A4.

[0042] The separation sensor 116 includes a light emitter and a light receiver provided on one side of the media transport path, and a light guide tube provided at a position facing the light emitter and the light receiver across the media transport path. The light emitter is an LED or the like, and emits light toward the media transport path. Meanwhile, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. Based on the intensity of the light received by the light receiver, the separation sensor 116 generates and outputs a separation signal whose signal value changes depending on whether a medium is present or not at the position of the separation sensor 116. In this way, the separation sensor 116 detects a medium transported to its arrangement position.

[0043] The pick sensor 117 is disposed downstream of the nip portion N1 between the feed roller 113 and the separation roller 114 and upstream of the nip portion N2 between the first conveyor roller 120a and the first driven roller 121a in the medium conveying direction A2. In particular, the pick sensor 117 is disposed downstream of the separation sensor 116 and upstream of the first skew sensor 118 and the second skew sensor 119 in the medium conveying direction A2. The pick sensor 117 may be disposed in the same position as the first skew sensor 118 and the second skew sensor 119 or downstream of the first skew sensor 118 and the second skew sensor 119 in the medium conveying direction A2. In addition, the pick sensor 117 is disposed in the center in the width direction A4, particularly between the first feed roller 113a and the second feed roller 113b (between the first separation roller 114a and the second separation roller 114b). Furthermore, the pick sensor 117 is disposed between the first skew sensor 118 and the second skew sensor 119 in the width direction A4.

[0044] The pick sensor 117 includes a light emitter and a light receiver provided on one side of the media transport path, and a light guide tube provided at a position facing the light emitter and the light receiver across the media transport path. The light emitter is an LED or the like, and emits light toward the media transport path. Meanwhile, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The pick sensor 117 generates and outputs a pick signal whose signal value changes depending on whether a medium is present or not at the position of the pick sensor 117, based on the intensity of the light received by the light receiver. In this way, the pick sensor 117 detects the medium transported to its arrangement position.

[0045] The first skew sensor 118 and the second skew sensor 119 are an example of a first sensor and a second sensor, or a plurality of sensors. The first skew sensor 118 and the second skew sensor 119 are disposed downstream of a nip portion N1 between the feed roller 113 and the separation roller 114 and upstream of a nip portion N2 between the first conveyor roller 120a and the first driven roller 121a in the medium conveying direction A2. In particular, the first skew sensor 118 and the second skew sensor 119 are disposed downstream of the separation sensor 116 and the pick sensor 117 in the medium conveying direction A2. The first skew sensor 118 and the second skew sensor 119 may be disposed in the same position as the pick sensor 117 or upstream of the pick sensor 117 in the medium conveying direction A2. The first skew sensor 118 and the second skew sensor 119 are arranged at the same position when viewed from the width direction A4 perpendicular to the medium transport direction, that is, at the same position in the medium transport direction A2, and are arranged side by side with an interval in the width direction A4.

[0046] The first skew sensor 118 is disposed downstream of the first feed roller 113a in the medium transport direction A2, and the second skew sensor 119 is disposed downstream of the second feed roller 113b in the medium transport direction A2. The first skew sensor 118 is disposed to the left of the center position in the width direction A4 when viewed from the downstream side (left side in FIG. 3), i.e., on the side of the first feed roller 113a and first separation roller 114a. The second skew sensor 119 is disposed to the right of the center position in the width direction A4 when viewed from the downstream side (right side in FIG. 3), i.e., on the side of the second feed roller 113b and second separation roller 114b.

[0047] The first skew sensor 118 includes a light emitter and a light receiver provided on one side of the media transport path, and a light guide tube provided at a position facing the light emitter and the light receiver across the media transport path. The light emitter is an LED or the like, and emits light toward the media transport path. On the other hand, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The first skew sensor 118 generates and outputs a first skew signal whose signal value changes depending on whether a medium is present or not at the position of the first skew sensor 118 based on the intensity of the light received by the light receiver. In this way, the first skew sensor 118 detects the medium transported to its arrangement position. The first skew signal is an example of an output signal of the first skew sensor 118.

[0048] The second skew sensor 119 includes a light emitter and a light receiver provided on one side of the media transport path, and a light guide tube provided at a position facing the light emitter and the light receiver across the media transport path. The light emitter is an LED or the like, and emits light toward the media transport path. On the other hand, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The second skew sensor 119 generates and outputs a second skew signal whose signal value changes depending on whether a medium is present or not at the position of the second skew sensor 119 based on the intensity of the light received by the light receiver. In this way, the second skew sensor 119 detects the medium transported to its arrangement position. The second skew signal is an example of an output signal of the second skew sensor 119.

[0049] When the first skew sensor 118 detects the medium before the second skew sensor 119 detects the medium, the medium conveying device 100 sets the peripheral speed of the first feed roller 113a to the first speed V1 and the peripheral speed of the second feed roller 113b to the second speed V2, which is higher than the first speed V1, when the first skew sensor 118 detects the medium before the second skew sensor 119 detects the medium. Similarly, when the second skew sensor 119 detects the medium before the first skew sensor 118 detects the medium, the medium conveying device 100 sets the peripheral speed of the second feed roller 113b to the first speed V1 and the peripheral speed of the first feed roller 113a to the second speed V2. In this way, the medium conveying device 100 corrects the skew of the medium. The positions of the first skew sensor 118 and the second skew sensor 119 in the width direction A4 perpendicular to the medium conveying direction are set to be the same as the rotation center position C around which the medium rotates according to the speed ratio α of the second speed V2 to the first speed V1. A speed ratio α of the second speed V2 to the first speed V1 is set to a value greater than one.

[0050] If the first skew sensor 118 detects the medium before the second skew sensor 119 detects the medium, the progress of the medium advances on the first skew sensor 118 side and delays on the second skew sensor 119 side. In this case, the peripheral speed of the first feed roller 113a is set to a first speed V1, and the peripheral speed of the second feed roller 113b is set to a second speed V2 (=α·V1). The following equations (1) and (2) hold for the rotation angle θa at which the medium rotates at the rotation center position C in a predetermined period T. tanθa=(V1·T) / L (1) tanθa=(V2·T) / (L+D)=(α·V1·T) / (L+D) (2) Here, L is the distance between the rotation center position C and the center position of the first feed roller 113a in the width direction A4, and D is the distance between the center position of the first feed roller 113a and the center position of the second feed roller 113b in the width direction A4.

[0051] From equations (1) and (2), the following equation (3) is obtained. L = D / (α-1) (3) The first skew sensor 118 is disposed within a predetermined range from a position that is a distance L calculated by formula (3) outside the first feed roller 113a in the width direction A4 perpendicular to the medium transport direction. The predetermined range is set, for example, in consideration of manufacturing errors of the medium transport device 100 (for example, within a range of 10 mm from that position). Similarly, the second skew sensor 119 is disposed within a predetermined range from a position that is a distance L calculated by formula (3) outside the second feed roller 113b in the width direction A4 perpendicular to the medium transport direction. In this case, L is the distance between the rotation center position C and the center position of the second feed roller 113b in the width direction A4.

[0052] It should be noted that the larger the speed ratio α, the shorter the time required to correct the skew of the medium. However, the larger the speed ratio α, the greater the load on the medium during skew correction. Also, as shown in formula (3), the larger the speed ratio α, the shorter the distance L, and the smaller the size of the medium for which the medium conveying device 100 can detect skew. The speed ratio α is set taking into consideration the time required to correct the skew of the medium and the thickness (strength) and size of the medium supported by the medium conveying device 100.

[0053] As a result, when the leading edge E1 of the medium conveyed at an angle passes through the first skew sensor 118, if the speed ratio of the second feed roller 113b to the first feed roller 113a is set to α, the leading edge E1 of the medium rotates around the rotation center position C. Therefore, by correcting the skew of the medium until other sensors (such as the second skew sensor 119) arranged alongside the first skew sensor 118 in the width direction A4 detect the leading edge E1 of the medium, the skew of the medium is eliminated at the position of the first skew sensor 118. Similarly, when the leading edge of the medium conveyed at an angle passes through the second skew sensor 119, if the speed ratio of the first feed roller 113a to the second feed roller 113b is set to α, the leading edge of the medium rotates around a position that is linearly symmetrical to the rotation center position C with respect to the center position in the width direction A4. Therefore, by correcting the skew of the medium until another sensor (such as the first skew sensor 118) arranged alongside the second skew sensor 119 in the width direction A4 detects the leading edge of the medium, the skew of the medium is eliminated at the position of the second skew sensor 119.

[0054] This allows the medium conveying device 100 to easily and appropriately correct the skew of the medium without adjusting the circumferential speed of each feed roller 113 according to the skew of the medium. Therefore, the medium conveying device 100 does not need to calculate the skew of the medium in order to correct the skew of the medium, and the processing load required for correcting the skew of the medium can be reduced.

[0055] The first skew sensor 118 may be disposed within a predetermined range from a position that is a distance L calculated by formula (3) outside the left or right end position of the nip portion N1 between the first feed roller 113a and the first separation roller 114a in the width direction A4. In this case, L in formula (3) is the distance between the rotation center position C and the left or right end position of the nip portion N1 between the first feed roller 113a and the first separation roller 114a in the width direction A4. Similarly, the second skew sensor 119 may be disposed within a predetermined range from a position that is a distance L calculated by formula (3) outside the left or right end position of the nip portion N1 between the second feed roller 113b and the second separation roller 114b in the width direction A4. In this case, L in formula (3) is the distance between the rotation center position C in the width direction A4 and the left or right end position of the nip portion N1 between the second feed roller 113b and the second separation roller 114b.

[0056] Furthermore, in order to start skew correction of the medium using the feed rollers 113 at the timing when the first and second skew sensors 118, 119 detect the leading edge of the medium, the leading edge of the medium needs to have passed the positions of the two feed rollers 113 at that timing. Therefore, the first skew sensor 118 and the second skew sensor 119 are disposed at positions that are a distance A downstream from the center positions of the first feed roller 113a and the second feed roller 113b in the medium transport direction A2, which satisfies the following formula (4). A ≧ (L + D) tan θb (4) Here, θb is the maximum angle of media tilt that the media conveying device 100 supports correction for.

[0057] As a result, even when the medium is transported tilted at the maximum angle that supports correction, the medium transport device 100 can calculate the tilt of the medium and easily and appropriately correct the skew of the medium without adjusting the circumferential speed of each feed roller 113 according to the calculated tilt. Therefore, the medium transport device 100 can appropriately correct the skew of the medium while reducing the processing load for correcting the skew of the medium.

[0058] In addition, the first skew sensor 118 and the second skew sensor 119 may be positioned downstream in the media transport direction A2 from the downstream or upstream end of the nip portion N1 between each feed roller 113 and each separation roller 114 by a distance A that satisfies the above formula (4).

[0059] The feed sensor 122 is disposed downstream of the nip portion N2 between the first conveyor roller 120a and the first driven roller 121a and upstream of the nip portion N3 between the second conveyor roller 120b and the second driven roller 121b in the medium conveying direction A2. The feed sensor 122 may be disposed downstream of the second conveyor roller 120b and the second driven roller 121b and upstream of the imaging device 123 in the medium conveying direction A2. The feed sensor 122 is disposed in the center, particularly between the first feed roller 113a and the second feed roller 113b (between the first separation roller 114a and the second separation roller 114b), in the width direction A4. The feed sensor 122 is disposed between the first skew sensor 118 and the second skew sensor 119 in the width direction A4.

[0060] The feed sensor 122 includes a light emitter and a light receiver provided on one side of the media transport path, and a light guide tube provided at a position facing the light emitter and the light receiver across the media transport path. The light emitter is an LED or the like, and emits light toward the media transport path. Meanwhile, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. Based on the intensity of the light received by the light receiver, the feed sensor 122 generates and outputs a feed signal whose signal value changes depending on whether a medium is present or not at the position of the feed sensor 122. In this way, the feed sensor 122 detects a medium transported to its arrangement position.

[0061] A reflective member such as a mirror may be used instead of a light guide in separation sensor 116, pick sensor 117, first skew sensor 118, second skew sensor 119 and / or feed sensor 122. In each sensor, the light emitter and the light receiver may be disposed opposite each other across the medium transport path. Each sensor may detect the presence of the medium using a contact detection sensor or the like that passes a predetermined current when the medium is in contact or when the medium is not in contact.

[0062] FIG. 4 is a schematic diagram for explaining the pick roller 112. As shown in FIG.

[0063] As shown in FIG. 4, the medium conveying device 100 has an arm 131 that supports the pick roller 112. The arm 131 is provided on the second housing 102 so as to extend in the medium conveying direction A2 and be rotatable (swingable) about a downstream end 131a. The pick roller 112 is attached to an upstream end 131b of the arm 131. A biasing member 131c is attached to the upper part of the arm 131. The biasing member 131c is a spring member such as a torsion coil spring or a rubber member, and applies a downward biasing force to the arm 131. Note that the biasing member 131c may be omitted, and only a downward force due to its own weight may be applied to the arm 131. By biasing the arm 131 downward, the pick roller 112 can appropriately convey the medium while pressing the medium placed on the placement table 103 downward.

[0064] Further, a driving force from a motor is applied to arm 131 to rotate (rotate) it upward. By rotating (swinging) arm 131, medium conveying device 100 can move pick roller 112 between a first position where pick roller 112 abuts against the medium placed on placement table 103 and a second position where pick roller 112 is separated from the medium placed on placement table 103. In this manner, pick roller 112 is provided to be movable between the first position and the second position.

[0065] FIG. 5 is a block diagram showing a schematic configuration of the medium conveying device 100. As shown in FIG.

[0066] In addition to the components described above, the medium conveying device 100 further includes a motor 141, an interface device 142, a storage device 150, a processing circuit 160, and the like.

[0067] The motor 141 includes one or more motors, and generates a driving force for rotating the pick roller 112, the feed roller 113, the separation roller 114, and the first to sixth transport rollers 120a-f in response to a control signal from the processing circuit 160, thereby feeding and transporting the medium. When a plurality of feed rollers 113 are provided, a separate motor is provided for each feed roller 113 so that each feed roller 113 rotates independently. The feed rollers 113 may be provided so as to rotate integrally with each other by a common motor. Also, the first to sixth driven rollers 121a-f may be provided so as to rotate according to the driving force of the motor 141, rather than being driven by the first to sixth transport rollers 120a-f.

[0068] Further, each motor included in motor 141 moves mounting table 103, moves pick roller 112, or swings separation roller 114 in response to a control signal from processing circuit 160. Arm 131 supporting pick roller 112, biasing member 131c, and / or a motor for moving pick roller 112 are an example of a moving mechanism for moving pick roller 112. Arm 114c supporting separation roller 114 and / or a motor for swinging arm 114c are an example of an applying mechanism for applying a pressing force to separation roller 114 to press separation roller 114 against feed roller 113.

[0069] The interface device 142 has an interface circuit conforming to a serial bus such as USB, and is electrically connected to an information processing device (not shown, for example, a personal computer, a mobile information terminal, etc.) to transmit and receive input images and various information. Also, instead of the interface device 142, a communication unit having an antenna for transmitting and receiving wireless signals and a wireless communication interface circuit for transmitting and receiving signals through a wireless communication line in accordance with a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network). The communication unit may have a wired communication interface circuit for transmitting and receiving signals through a wired communication line in accordance with a communication protocol such as a wired LAN.

[0070] The storage device 150 includes a memory device such as a random access memory (RAM) or a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. The storage device 150 also stores computer programs, databases, tables, and the like used for various processes of the medium conveying device 100. The computer programs may be installed in the storage device 150 from a computer-readable portable recording medium using a known setup program or the like. The portable recording medium is, for example, a compact disc read only memory (CD-ROM) or a digital versatile disc read only memory (DVD-ROM). The storage device 150 stores status information indicating the correction status of the skew of the medium as data.

[0071] The processing circuit 160 operates based on a program previously stored in the storage device 150. The processing circuit is, for example, a CPU (Central Processing Unit). The processing circuit 160 may be, for example, a DSP (digital signal processor), an LSI (large scale integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array).

[0072] The processing circuit 160 is connected to the operation device 105, the display device 106, the placement table sensor 111, the rotation sensor 115, the separation sensor 116, the pick sensor 117, the first skew sensor 118, the second skew sensor 119, the feed sensor 122, the imaging device 123, the motor 141, the interface device 142, the storage device 150, and the like, and controls each of these components. The processing circuit 160 performs drive control of the motor 141, imaging control of the imaging device 123, and the like, based on signals received from each sensor. The processing circuit 160 acquires an input image from the imaging device 123, and transmits it to the information processing device via the interface device 142.

[0073] FIG. 6 is a diagram showing a schematic configuration of the storage device 150 and the processing circuit 160. As shown in FIG.

[0074] 6, the storage device 150 stores a receiving program 151, a control program 152, an acquisition program 153, a determination program 154, and the like. Each of these programs is a functional module implemented by software that runs on a processor. The processing circuit 160 reads each program stored in the storage device 150 and operates according to the read program. As a result, the processing circuit 160 functions as a receiving unit 161, a control unit 162, an acquisition unit 163, and a determination unit 164.

[0075] FIG. 7 is a flowchart showing an example of the operation of the medium reading process of the medium conveying device 100.

[0076] An example of the operation of the medium reading process of the medium conveying device 100 will be described below with reference to the flowchart shown in Fig. 7. The flow of the operation described below is executed mainly by the processing circuit 160 in cooperation with each element of the medium conveying device 100 based on a program previously stored in the storage device 150. This flowchart describes the case where the feeding mode is set to the separation mode.

[0077] First, the reception unit 161 determines whether or not the user inputs settings for the medium conveying device 100 using the operation device 105 or the information processing device and the settings for the medium conveying device 100 have been received from the user (step S101). When the reception unit 161 receives a setting signal instructing settings for the medium conveying device 100 from the operation device 105 or from the information processing device via the interface device 142, the reception unit 161 determines that the settings for the medium conveying device 100 have been received from the user. The settings for the medium conveying device 100 include settings related to the circumferential speed of each feed roller 113 when correcting skew of the medium. The settings related to the circumferential speed of each feed roller 113 include the circumferential speed of each feed roller 113 itself, the number of rotations per minute (RPM) of each feed roller 113, the number of rotations per minute (RPM) of the motor that drives each feed roller 113, and the like. The setting regarding the circumferential speed of each feed roller 113 may be a ratio or difference with respect to a reference (initial) circumferential speed of each feed roller 113. Furthermore, the setting for the medium conveying device 100 may include a setting as to whether or not to perform skew correction of the medium.

[0078] By receiving from the user settings relating to the circumferential speed of each feed roller 113 when correcting skew of the medium, medium conveying device 100 can correct skew of the medium by rotating each feed roller 113 at a speed suitable for the thickness or material of the medium being conveyed. Therefore, medium conveying device 100 can appropriately correct skew of the medium for various types of media. If settings for medium conveying device 100 have not been received, receiving unit 161 proceeds to step S103 without performing any particular processing.

[0079] On the other hand, when the settings for the medium conveying device 100 are accepted, the accepting unit 161 stores the accepted settings in the storage device 150 (step S102).

[0080] Next, the control unit 162 determines whether or not an instruction to read a medium is input by the user using the operation device 105 or the information processing device and the instruction to read a medium is accepted from the user (step S103). When the control unit 162 receives an operation signal instructing to read a medium from the operation device 105 or from the information processing device via the interface device 142, the control unit 162 determines that an instruction to read a medium is accepted from the user. When an instruction to read a medium is not accepted, the control unit 162 returns the process to step S101 without executing any particular process.

[0081] On the other hand, when an instruction to read a medium is received, control unit 162 acquires a mounting table signal from mounting table sensor 111, and determines whether or not a medium is placed on mounting table 103 based on the acquired mounting table signal (step S104). If no medium is placed on mounting table 103, control unit 162 does not execute any particular process and returns the process to step S101.

[0082] On the other hand, when a medium is placed on the placement table 103, the control unit 162 drives the motor 141 to move the placement table 103 to a position where the medium can be fed, and places the pick roller 112 at the first position. The control unit 162 also drives the motor 141 to rotate the pick roller 112, the feed roller 113, the separation roller 114, and / or the first to sixth conveyor rollers 120a to f, thereby feeding and conveying the medium placed on the placement table 103 (step S105). At this time, the control unit 162 sets the circumferential speed of the first feed roller 113a and the circumferential speed of the second feed roller 113b to the same reference speed. The control unit 162 also controls the motor 141 so that the pressing force that presses the separation roller 114 against the feed roller 113 side becomes a reference value (initial value).

[0083] Next, the control unit 162 sets (initializes) the state information indicating the state of correction of the medium skew to a not-started state indicating that correction of the medium skew has not started (step S106).

[0084] Next, the acquiring unit 163 waits until the leading edge of the medium passes the position of the pick sensor 117 (step S107). The acquiring unit 163 periodically acquires a pick signal from the pick sensor 117. When the signal value of the pick signal changes from a value indicating the absence of a medium to a value indicating the presence of the medium, the acquiring unit 163 determines that the leading edge of the medium has passed the position of the pick sensor 117 and that the pick sensor 117 has detected the leading edge of the medium.

[0085] Next, the acquisition unit 163 calculates the degree of slippage between the first and second feed rollers 113a and 113b and the medium fed (conveyed) by the first and second feed rollers 113a and 113b (step S108). The degree of slippage indicates the degree to which the medium slips on the outer circumferential surface of the feed roller 113 and does not move even when the feed roller 113 is rotated. The acquisition unit 163 calculates the degree of slippage based on the drive amount of the motor 141 and the movement distance of the medium fed (conveyed) by the feed roller 113.

[0086] After starting feeding of the medium, the acquisition unit 163 periodically acquires a separation signal from the separation sensor 116. When the signal value of the separation signal changes from a value indicating the absence of a medium to a value indicating the presence of the medium, the acquisition unit 163 determines that the leading edge of the medium has passed the position of the separation sensor 116 and that the separation sensor 116 has detected the leading edge of the medium. The acquisition unit 163 monitors the drive amount of the motor 141 for rotating the feed roller 113 during the period from when the leading edge of the medium passes the position of the separation sensor 116 to when it passes the position of the pick sensor 117. The acquisition unit 163 calculates the movement distance of the outer circumferential surface of the feed roller 113 by multiplying the drive amount (number of pulses) of the motor 141 during the above period by the movement distance of the outer circumferential surface of the feed roller 113 per pulse. The acquisition unit 163 specifies the distance in the medium conveying direction A2 between the separation sensor 116 and the pick sensor 117 as the movement distance of the medium being fed during the above period.

[0087] The acquisition unit 163 calculates the degree of slippage based on the movement distance of the outer circumferential surface of the feed roller 113 and the movement distance of the fed medium according to the following formula (5), and stores the calculated degree of slippage in the storage device 150. (Slip degree)=1-(movement distance of the medium being fed) / (movement distance of the outer circumferential surface of the feed roller 113) (5)

[0088] Next, the control unit 162 waits until the rear end of the medium passes the imaging position of the imaging device 123 (step S109). The control unit 162 periodically acquires a feed signal from the feed sensor 122. When the signal value of the feed signal changes from a value indicating the presence of the medium to a value indicating the absence of the medium, the control unit 162 determines that the rear end of the medium has passed the position of the feed sensor 122 and that the feed sensor 122 has detected the rear end of the medium. The control unit 162 determines that the rear end of the medium has passed the imaging position of the imaging device 123 when a first time has elapsed since the rear end of the medium passed the position of the feed sensor 122. The first time is set to the time required for the medium to move from the position of the feed sensor 122 to the imaging position of the imaging device 123.

[0089] Next, the control unit 162 acquires an input image from the imaging device 123, and outputs the acquired input image by transmitting it to the information processing device via the interface device 142 (step S110). The control unit 162 causes the imaging device 123 to start imaging before the leading edge of the medium reaches the imaging position of the imaging device 123, such as at the timing when the leading edge of the medium passes the position of the feed sensor 122. The control unit 162 also causes the imaging device 123 to end imaging after the trailing edge of the medium passes the imaging position of the imaging device 123, such as at the timing when a first time has elapsed since the feed sensor 122 detected the trailing edge of the medium, and acquires the input image from the imaging device 123.

[0090] Next, control unit 162 determines whether or not a medium remains on mounting table 103 based on the mounting table signal received from mounting table sensor 111 (step S111). If a medium remains on mounting table 103, control unit 162 returns the process to step S106, and repeats the processes from step S106 onwards.

[0091] If there are no media remaining on the placement table 103, the control unit 162 controls the motor 141 to stop the pick roller 112, the feed roller 113, the separation roller 114, and / or the first to sixth conveying rollers 120a-f (step S112), and ends the series of steps.

[0092] 8, 9, and 10 are flowcharts showing an example of the operation of the skew determination process of the medium conveying device 100. In FIG.

[0093] An example of the operation of the skew determination process of the medium conveying device 100 will be described below with reference to the flowcharts shown in Figures 8, 9, and 10. The flow of the operation described below is executed mainly by the processing circuit 160 in cooperation with each element of the medium conveying device 100 based on a program previously stored in the storage device 150. The flow of the operation shown in Figures 8, 9, and 10 is executed during medium conveyance. The skew determination process may be executed only when the setting accepted by the accepting unit 161 in step S101 of Figure 7 is set to execute skew correction of the medium.

[0094] First, the determination unit 164 receives a rotation signal, a separation signal, a pick signal, a first skew signal, and a second skew signal from the rotation sensor 115, the separation sensor 116, the pick sensor 117, the first skew sensor 118, and the second skew sensor 119, respectively. The determination unit 164 stores the received signals in the storage device 150 (step S201).

[0095] Next, the determination unit 164 determines whether the skew condition is satisfied (step S202). The determination unit 164 determines whether the leading edge of the medium has reached the positions of the first skew sensor 118 and the second skew sensor 119. When the signal value of the first skew signal changes from a value indicating that the medium is not present to a value indicating that the medium is present, the determination unit 164 determines that the leading edge of the medium has reached the position of the first skew sensor 118 and that the first skew sensor 118 has detected the leading edge of the medium. Furthermore, when the signal value of the second skew signal changes from a value indicating that the medium is not present to a value indicating that the medium is present, the determination unit 164 determines that the leading edge of the medium has reached the position of the second skew sensor 119 and that the second skew sensor 119 has detected the leading edge of the medium.

[0096] The determination unit 164 determines that the skew condition is satisfied when the leading edge of the medium does not reach one of the positions of the first skew sensor 118 and the second skew sensor 119 within the second time after the leading edge of the medium reaches the other of the positions. That is, the determination unit 164 determines that the skew condition is satisfied when the leading edge of the medium is not detected by one of the first skew sensor 118 and the second skew sensor 119 within the second time after the other sensor detects the leading edge of the medium. The second time is set to, for example, the average, median, minimum, or maximum value of the difference in the time when the medium passes each skew sensor when a medium jam occurs or when a chip occurs in the input image, based on a prior experiment in which the medium is transported at an angle.

[0097] If the skew condition is not satisfied, the determining unit 164 determines that no skew of the medium has occurred (step S203), and the process proceeds to step S212.

[0098] On the other hand, when the skew condition is satisfied, the determination unit 164 determines that a skew of the medium has occurred (step S204). In this way, the determination unit 164 determines whether or not a skew of the medium has occurred based on the first skew signal output from the first skew sensor 118 and the second skew signal output from the second skew sensor 119. That is, the determination unit 164 determines whether or not a skew of the medium has occurred based on the detection result of the medium by the first skew sensor 118 or the second skew sensor 119. In particular, the determination unit 164 determines whether or not a skew of the medium has occurred based on the timing at which each of the first skew sensor 118 and the second skew sensor 119 detects the leading edge of the medium.

[0099] Next, the acquisition unit 163 acquires the slip degree (step S205). The acquisition unit 163 acquires the slip degree by reading from the storage device 150 the slip degree calculated in step S108 of FIG. 7 for the medium transported immediately before. That is, the acquisition unit 163 acquires the slip degree by calculating the slip degree of the medium transported immediately before. There is a possibility that the slip degree has not yet been calculated for the medium currently being transported. The acquisition unit 163 can reliably acquire the slip degree in the latest state by reading the slip degree of the medium transported immediately before.

[0100] The acquiring unit 163 may acquire the slip degree by calculating a statistical value (average value, median value, maximum value, or minimum value) of the slip degree calculated for a predetermined number of media most recently. This allows the acquiring unit 163 to calculate the slip degree with higher accuracy. The acquiring unit 163 may also acquire the slip degree for the medium currently being transported by reading out the slip degree calculated in step S108 of FIG. 7 from the storage device 150. This allows the acquiring unit 163 to acquire the slip degree corresponding to the material of the medium currently being transported. The medium transport device 100 may also calculate the slip degree in an unused state of the product and store it in advance in the storage device 150. In this case, the process of step S108 of FIG. 7 is omitted, and the acquiring unit 163 acquires the slip degree by reading out the slip degree previously stored in the storage device 150. This allows the acquiring unit 163 to acquire the slip degree with a lower load.

[0101] Next, when the medium skew occurs, the control unit 162 determines whether or not the prohibition condition for skew correction is satisfied (step S206). When the prohibition condition for skew correction is satisfied, the control unit 162 prohibits the correction of the medium skew in the process described later, and does not correct the medium skew.

[0102] For example, if the pick sensor 117 detects the leading edge of the medium before the first skew sensor 118 and the second skew sensor 119, the control unit 162 determines that the prohibition condition for skew correction is satisfied and does not correct the skew of the medium.

[0103] FIG. 11A is a schematic diagram for explaining a medium M1 that is detected by a pick sensor 117 before the first skew sensor 118 and the second skew sensor 119. FIG.

[0104] In the example shown in FIG. 11A, the medium M1 is transported at a slight angle and is detected by the pick sensor 117 before the first skew sensor 118 and the second skew sensor 119. In this case, even if the medium M1 continues to be transported in this state, even if it is tilted, it is highly likely that it will be properly imaged by the imaging device 123 and will not collide with the side wall of the transport path. The medium transport device 100 does not correct the skew of the medium when the pick sensor 117 detects the medium before the first skew sensor 118 and the second skew sensor 119, thereby suppressing an increase in the total transport time of the medium and suppressing an increase in the processing time of the medium reading process. Furthermore, the medium transport device 100 can determine whether or not to prohibit skew correction with a low load by using the timing when the first skew sensor 118, the second skew sensor 119, and the pick sensor 117 detect the medium.

[0105] The control unit 162 may determine that the prohibition condition for skew correction is satisfied if the pick sensor 117 detects the leading edge of the medium before the third time has elapsed since the first skew sensor 118 and the second skew sensor 119 detected the leading edge of the medium. The third time is set to a sufficiently short time (for example, one second). In this case, too, the inclination of the medium is likely to be sufficiently small. By not correcting the skew of the medium in this case, the control unit 162 can suppress an increase in the total transport time of the medium and suppress an increase in the processing time of the medium reading process.

[0106] Furthermore, if the first skew sensor 118 or the second skew sensor 119 detects the leading edge of the medium before the separation sensor 116, the control unit 162 determines that the prohibition condition for skew correction is satisfied and does not correct the skew of the medium.

[0107] FIG. 11B is a schematic diagram for explaining the medium M2 that is detected by the first skew sensor 118 or the second skew sensor 119 before the separation sensor .

[0108] In the example shown in FIG. 11B, media M2 and media M3 are placed on the placement table 103 with their leading edges not aligned. The left portion of the leading edge of medium M2, which is to be fed next to medium M3 to be fed, enters downstream of the feed roller 113 and is detected by the first skew sensor 118. In this way, the medium detected by the first skew sensor 118 or the second skew sensor 119 before the separation sensor 116 may not be the medium to be fed, but may be a medium placed on the placement table 103 in an inclined state. The medium not to be fed is then pushed back toward the placement table 103 by the separation roller 114. If an attempt is made to correct the skew of the medium in this state, medium M3 to be fed may rotate in the wrong direction. When the first skew sensor 118 or the second skew sensor 119 detects the leading edge of the medium before the separation sensor 116, the medium conveying device 100 does not correct the skew of the medium, thereby preventing the medium being fed from rotating in the wrong direction.

[0109] FIG. 12A is a schematic diagram for explaining a medium M4 that is tilted to a certain extent.

[0110] 12(A), medium M4 is tilted and is detected in that order by separation sensor 116, first skew sensor 118, and pick sensor 117. In this case, medium conveying device 100 corrects the skew of the medium to prevent the entire medium from being imaged by imaging device 123 and the medium from colliding with the side wall of the conveying path.

[0111] The control unit 162 may also determine whether or not the prohibition condition for skew correction is satisfied based on the degree of slip acquired in step S205. The control unit 162 determines that the prohibition condition for skew correction is satisfied when the degree of slip exceeds an upper threshold, and determines that the prohibition condition for skew correction is not satisfied when the degree of slip is equal to or less than the upper threshold. The upper threshold is set to a value between the degree of slip calculated when the skew of the medium can be well corrected and the degree of slip calculated when the skew of the medium cannot be properly corrected, based on a prior experiment in which the medium is transported using the feed roller 113 in various states.

[0112] In this way, the control unit 162 prohibits the correction of the skew of the medium based on the degree of slippage. This allows the medium conveying device 100 to suppress the load caused by the skew correction being imposed on the medium or the processing time of the medium reading process from increasing even though the skew of the medium cannot be appropriately corrected.

[0113] Furthermore, if insufficient correction occurs for a medium on which skew correction has been performed in the past, the control unit 162 may determine that the prohibition condition for skew correction has been satisfied and prohibit skew correction for media to be transported thereafter. In a process described below, the control unit 162 determines whether insufficient correction has occurred for a medium on which skew correction has been performed. For example, if the sensor that first detected the leading edge of the medium, out of the first skew sensor 118 and the second skew sensor 119, detects the trailing edge of the medium before the separation sensor 116 detects the trailing edge of the medium, the control unit 162 determines that insufficient correction has occurred.

[0114] FIG. 12B is a schematic diagram for explaining insufficient correction of the skew correction of the medium.

[0115] Figure 12(B) shows an example of the state of medium M4 shown in Figure 12(A) after skew correction. In the example shown in Figure 12(B), the inclination of medium M4 has not been eliminated, and the rear end of medium M4 is detected by first skew sensor 118 before separation sensor 116. In this case, the skew of medium M4 has not been properly corrected for some reason, and it is highly likely that the skew of media transported thereafter will not be properly corrected either.

[0116] Furthermore, if over-correction occurs for a medium on which skew correction has been performed in the past, the control unit 162 may determine that the prohibition condition for skew correction has been satisfied and prohibit skew correction for media to be transported thereafter. In a process described below, the control unit 162 determines whether over-correction has occurred for a medium on which skew correction has been performed. For example, the control unit 162 determines that over-correction has occurred if the order in which the first skew sensor 118 and the second skew sensor 119 detect the rear end of the medium has changed from the order in which they detected the front end of the medium.

[0117] FIG. 13 is a schematic diagram for explaining over-correction of the skew of the medium.

[0118] Figure 13 shows an example of the state of medium M4 shown in Figure 12(A) after skew correction. In the example shown in Figure 13, the tilt direction of medium M4 is opposite to the state before correction shown in Figure 12(A), and the rear end of medium M4 is detected by second skew sensor 119 before first skew sensor 118. In this case, the skew of medium M4 has not been properly corrected for some reason, and it is highly likely that the skew of media transported thereafter will not be properly corrected either.

[0119] In this way, the control unit 162 prohibits skew correction of a medium to be transported thereafter based on the timing at which the first skew sensor 118 and the second skew sensor 119 detect the rear end of the skew-corrected medium. This allows the medium transport device 100 to prevent the load caused by skew correction from being imposed on the medium or the processing time for the medium reading process from increasing even though the skew of the medium cannot be appropriately corrected.

[0120] When the control unit 162 determines that insufficient or excessive correction has occurred and stops the correction of the skew of the medium, it may determine that the prohibition condition for skew correction is satisfied until the transportation of all the media placed on the placement table 103 is completed, and may not resume the correction of the skew of the medium. It is highly likely that all the media placed on the placement table 103 are placed together, and all the media may be placed tilted in the same direction. When many media are placed tilted in the same direction, many media may enter only the nip portion between one of the feed rollers 113 and the separation roller 114, and a difference may occur in the separation force (back load) by the two sets of feed rollers 113 and the separation roller 114. In this case, the tilt of the medium may increase by performing the correction of the skew of the medium. When insufficient or excessive correction has occurred, the medium conveying device 100 can suppress the increase in the tilt of the medium by prohibiting the skew correction until the transportation of all the media placed on the placement table 103 is completed.

[0121] Furthermore, when the control unit 162 determines that an insufficient or excessive correction has occurred and stops the correction of the skew of the medium, it is not necessary to resume the correction of the skew of the medium until the rotation sensor 115 detects the rotation of the separation roller 114 driven by the feed roller 113. When the separation roller 114 is rotating driven by the feed roller 113, it is highly likely that there are no multiple media in the nip portion between the feed roller 113 and the separation roller 114, and the intrusion of a large number of media into the nip portion has been eliminated. When an insufficient or excessive correction has occurred, the medium conveying device 100 can appropriately correct the skew of the medium when it becomes correctable, while suppressing an increase in the skew of the medium, by prohibiting the skew correction until the separation roller 114 rotates driven by the feed roller 113.

[0122] If the conditions for prohibiting skew correction are met, the control unit 162 prohibits correction of the skew of the medium, does not correct the skew of the medium (step S207), and moves the process to step S212.

[0123] On the other hand, if the skew correction prohibition condition is not satisfied, the control unit 162 determines whether or not the correction of the medium skew has started (step S208). If the status information is set to the not yet started state, the control unit 162 determines that the correction of the medium skew has not started yet, and if the status information is set to a state other than the not yet started state, the control unit 162 determines that the correction of the medium skew has already started. If the correction of the medium skew has already started, the control unit 162 does not execute any particular process and proceeds to step S212.

[0124] On the other hand, if the correction of the medium skew has not yet started, the control unit 162 controls the motor 141 to increase the pressing force pressing the separation roller 114 toward the feed roller 113 side from the reference value (step S209). In this way, the control unit 162 controls the arm 114c supporting the separation roller 114 and the motor 141 so that the pressing force is different when the medium skew is being corrected and when the medium skew is not being corrected. This allows the medium conveying device 100 to increase the frictional force generated between the fed medium and the feed roller 113 and separation roller 114 when correcting the medium skew, thereby making it possible to more effectively correct the medium skew.

[0125] Next, the control unit 162 controls the motor 141 to move the pick roller 112 from the first position to the second position (step S210). In this way, when skew of the medium occurs, the control unit 162 controls the arm 131 supporting the pick roller 112, the biasing member 131c, and the motor 141 to move the pick roller 112 from the first position to the second position. In this case, the pick roller 112 is separated from the medium and does not interfere with the movement of the medium in the width direction A4, so that the medium conveying device 100 can more effectively correct the skew of the medium.

[0126] Next, the control unit 162 sets the state information to a start waiting state, which indicates that the control unit 162 is waiting until the correction of the skew of the medium can be started (step S211).

[0127] Next, the control unit 162 determines whether or not a condition for starting skew correction is satisfied (step S212). If the condition for starting skew correction is satisfied, the control unit 162 starts correcting the skew of the medium in the process described below.

[0128] The control unit 162 determines that the start condition of skew correction is satisfied when the fourth time has elapsed since the state information was set to the start standby state. That is, the control unit 162 determines that the start condition of skew correction is satisfied when the fourth time has elapsed since the control of the motor 141 was started so as to increase the pressing force for pressing the separation roller 114 toward the feed roller 113 side. The control unit 162 also determines that the start condition of skew correction is satisfied when the fourth time has elapsed since the control of the moving mechanism was started so as to move the pick roller 112 to the second position. The fourth time is an example of a predetermined time. The fourth time is set to the time required from the start of the control of the motor 141 until the pressing force of the separation roller 114 is switched or until the pick roller 112 actually moves to the second position. On the other hand, the control unit 162 determines that the start condition of skew correction is not satisfied when the state information is set to a state other than the start standby state or when the fourth time has not elapsed since the state information was set to the start standby state.

[0129] In this way, the control unit 162 starts correcting the skew of the medium after the fourth time has elapsed since starting to control the motor 141 to increase the pressing force that presses the separation roller 114 toward the feed roller 113. This allows the medium conveying device 100 to correct the skew of the medium in a state where the pressing force that presses the separation roller 114 toward the feed roller 113 is reliably increased, thereby suppressing the occurrence of slippage of the medium and allowing for better correction of the skew of the medium. In addition, the control unit 162 starts correcting the skew of the medium after the fourth time has elapsed since starting to control the moving mechanism to move the pick roller 112 from the first position to the second position. This allows the medium conveying device 100 to correct the skew of the medium in a state where the pick roller 112 is reliably separated from the medium, thereby preventing the movement of the medium in the width direction A4 from being hindered by the pick roller 112 and allowing for better correction of the skew of the medium.

[0130] If the condition for starting skew correction is not satisfied, the control unit 162 does not execute any particular process and moves the process to step S218.

[0131] On the other hand, when the start condition of the skew correction is satisfied, the control unit 162 sets the circumferential speed of the feed roller 113 (step S213). When the first skew sensor 118 detects the medium before the second skew sensor 119 detects the medium, the control unit 162 sets the circumferential speed of the first feed roller 113a to the first speed V1 and the circumferential speed of the second feed roller 113b to the second speed V2 higher than the first speed V1. On the other hand, when the second skew sensor 119 detects the medium before the first skew sensor 118 detects the medium, the control unit 162 sets the circumferential speed of the second feed roller 113b to the first speed V1 and the circumferential speed of the first feed roller 113a to the second speed V2. The control unit 162 sets the circumferential speed of the feed roller 113 so that the speed ratio of the second speed V2 to the first speed V1 is the speed ratio α shown in the above-mentioned formula (3).

[0132] 7, if the reception unit 161 has received a setting related to the circumferential speed of the feed rollers 113 in step S102, the control unit 162 sets the circumferential speed of each feed roller 113 to a first speed V1 and a second speed V2 according to the received setting. On the other hand, if the reception unit 161 has not received a setting related to the circumferential speed of the feed rollers 113, the control unit 162 sets the circumferential speed of each feed roller 113 to a first speed V1 and a second speed V2 determined in advance.

[0133] Next, the control unit 162 determines whether or not a correction condition for the circumferential speed of the feed roller 113 is satisfied (step S214). If the correction condition for the circumferential speed of the feed roller 113 is satisfied, the control unit 162 corrects the circumferential speed of the feed roller 113 in a process described later.

[0134] For example, the control unit 162 determines whether the correction condition is satisfied based on the slip degree acquired in step S205. If the slip degree is greater than the slip threshold, the control unit 162 determines that the correction condition is satisfied, and if the slip degree is equal to or less than the slip threshold, the control unit 162 determines that the correction condition is not satisfied. The slip threshold is preset to a value between the slip degree when the skew of the medium is corrected and the slip degree when the skew of the medium is not corrected, for example, by a prior experiment in which the circumferential speeds of the feed rollers 113 are made different so as to have a speed ratio α.

[0135] Furthermore, the control unit 162 may determine that the correction condition is satisfied when insufficient correction occurs for a medium on which skew correction has been performed in the past, particularly for a medium on which skew correction has been performed immediately before. As shown in Fig. 12(B), if the inclination of medium M4 has not been eliminated at the time when the rear end of medium M4 passes through the separation sensor 116, the first skew sensor 118, or the second skew sensor 119, it is considered that the amount of skew correction was insufficient.

[0136] In addition, the control unit 162 may determine that the correction condition is satisfied when over-correction occurs for a medium on which skew correction has been performed in the past, particularly for a medium on which skew correction has been performed immediately before. As shown in Fig. 13, when the tilt direction of the medium M4 is opposite to that before the correction started, it is considered that the amount of skew correction was too large.

[0137] If the correction condition for the circumferential speed of the feed roller 113 is not satisfied, the control unit 162 does not execute any particular process and moves the process to step S216.

[0138] On the other hand, if the correction condition for the circumferential speed of the feed roller 113 is satisfied, the control unit 162 corrects the circumferential speed of the first feed roller 113a and the circumferential speed of the second feed roller 113b (step S215). In the process described below, the control unit 162 corrects the skew of the medium by rotating the feed roller 113 at the circumferential speed set in step S213 or the circumferential speed corrected in step S215.

[0139] For example, when the degree of slippage is greater than the slip threshold, the control unit 162 corrects the circumferential speeds of the feed rollers 113 so that the speed ratio of the circumferential speeds of the feed rollers 113 is greater than the speed ratio α shown in the above-mentioned formula (3). The control unit 162 may correct the circumferential speeds of the feed rollers 113 so that the difference between the circumferential speed of the first feed roller 113a and the circumferential speed of the second feed roller 113b increases as the degree of slippage increases. When the degree of slippage is large, the feeding force from the feed roller 113 may not be transmitted to the medium, and the degree of correction of the skew may be reduced. When the degree of slippage is large, the medium conveying device 100 can more appropriately correct the inclination of the medium by increasing the difference between the circumferential speeds of the feed rollers 113.

[0140] In this way, the control unit 162 sets the circumferential speed of the first feed roller 113a and the circumferential speed of the second feed roller 113b when correcting the skew of the medium based on the degree of slippage, which allows the medium conveying device 100 to more appropriately correct the skew of the medium.

[0141] Furthermore, if insufficient correction has occurred for a medium on which skew correction has been performed in the past, the control unit 162 increases the speed ratio of the circumferential speeds of the feed rollers 113 to a value greater than the speed ratio set for the medium on which insufficient correction has occurred. As described above, if insufficient correction has occurred, it is highly likely that the amount of skew correction for that medium was insufficient. By increasing the difference in the circumferential speeds of the feed rollers 113 when insufficient correction has occurred for a medium on which skew correction has been performed in the past, the medium conveying device 100 can more appropriately correct the inclination of the medium being conveyed this time.

[0142] Furthermore, if over-correction has occurred for a medium on which skew correction has been performed in the past, the control unit 162 reduces the speed ratio of the circumferential speeds of the feed rollers 113 to a speed ratio set for the medium on which over-correction has occurred. As described above, if over-correction has occurred, it is highly likely that the amount of skew correction for that medium was too large. By reducing the difference in the circumferential speeds of the feed rollers 113 when under-correction has occurred for a medium on which skew correction has been performed in the past, the medium conveying device 100 can more appropriately correct the inclination of the medium being conveyed this time.

[0143] In this way, the control unit 162 corrects the circumferential speeds of the first feed roller 113a and the second feed roller 113b based on the timing at which the first skew sensor 118 and the second skew sensor 119 each detect the rear end of the medium on which skew correction has been performed. This allows the medium conveying device 100 to correct the skew of the medium with a correction amount appropriate for the latest state of the medium conveying device 100, and as a result, the skew of the medium can be corrected more appropriately.

[0144] Next, the control unit 162 starts correcting the skew of the medium by rotating the motor for rotating each of the feed rollers 113 at a set speed (step S216). In this manner, the control unit 162 starts correcting the skew of the medium when either the first skew sensor 118 or the second skew sensor 119 detects the medium.

[0145] In particular, when skew of the medium occurs, the control unit 162 corrects the skew of the medium using the feed roller 113. When skew of the medium occurs, the control unit 162 corrects the skew of the medium by making the circumferential speed of the first feed roller 113a and the circumferential speed of the second feed roller 113b different from each other. That is, the control unit 162 corrects the skew of the medium by making the circumferential speed of one of the multiple feed rollers 113 higher than the circumferential speed of the other feed roller. This allows the control unit 162 to appropriately correct the skew of the medium.

[0146] FIG. 14 is a graph for explaining the inclination of the medium.

[0147] 14, the horizontal axis indicates the inclination [deg] of the medium with respect to the width direction A4 before skew correction, and the vertical axis indicates the inclination [deg] of the medium with respect to the width direction A4 after skew correction. Graph G1 shows the inclination of the medium when the feed roller 113, the first skew sensor 118, and the second skew sensor 119 are arranged as described above, and the speed ratio of the peripheral speeds of the feed rollers 113 is set to α shown in formula (3). As shown in graph G1, the greater the inclination of the medium before skew correction, the greater the inclination of the medium after skew correction, but the inclination of the medium after skew correction becomes sufficiently smaller than the inclination of the medium before skew correction.

[0148] In this way, by arranging the first skew sensor 118 and the second skew sensor 119 in the width direction A4 at the center of rotation of the medium due to skew correction, the medium conveying device 100 can appropriately correct the skew of the medium while fixing the speed ratio of each feed roller 113. Therefore, the medium conveying device 100 can easily and appropriately correct the skew of the medium without adjusting the peripheral speed of each feed roller 113 according to the inclination of the medium, and can reduce the processing load required for correcting the skew of the medium.

[0149] Graph G2 in FIG. 14 shows the inclination of the medium when the skew of the medium is corrected using the feed roller 113 having a certain degree of slippage. When the skew of the medium is corrected using the feed roller 113 having a certain degree of slippage, the speed ratio of the speed at which the medium is actually moved by each feed roller 113 becomes smaller than the speed ratio of the circumferential speeds of each feed roller 113. Therefore, as shown in graph G2, the inclination of the medium after the skew correction may not be sufficiently small. As described above, the medium conveying device 100 can correct the skew of the medium so that the inclination of the medium after the correction approaches 0 by correcting the circumferential speeds of each feed roller 113 when correcting the skew of the medium based on the slippage.

[0150] Next, the control unit 162 sets the state information to a correction in progress state, which indicates that correction of the skew of the medium is being executed (step S217).

[0151] Next, the control unit 162 determines whether or not the correction of the skew of the medium is currently being performed, and whether or not the separation roller 114 has rotated in the reverse direction or stopped after rotating forward (step S218). The control unit 162 determines whether or not the correction of the skew of the medium is currently being performed, depending on whether or not the status information is set to a correction in progress status.

[0152] Furthermore, the control unit 162 determines whether the separation roller 114 is rotating forward (rotating in the medium feeding direction), reverse (rotating in the direction A13 opposite to the medium feeding direction), or stopped, based on the rotation direction indicated by the signal value of the rotation signal. The control unit 162 may further determine that the separation roller 114 is rotating in the reverse direction only when the movement distance indicated by the signal value of the received rotation signal, i.e., the movement distance of the outer circumferential surface of the separation roller 114, is equal to or greater than a predetermined distance. In this case, the control unit 162 determines that the separation roller 114 is rotating in the reverse direction only when the total movement distance when the signal value of the rotation signal indicates that the separation roller 114 is rotating in the reverse direction is equal to or greater than a predetermined distance. This makes it possible for the control unit 162 to suppress erroneous determination that the separation roller 114 is rotating in the reverse direction when slight slippage occurs.

[0153] 15(A) to (C) are schematic diagrams for explaining the feeding of media placed on the placement table 103 with their leading edges not aligned. Figures 15(A) to (C) show an example in which multiple media are placed on the placement table 103 such that the leading edge of medium M6, which is placed below medium M5, is located downstream from the leading edge of medium M5, which is placed on the uppermost side.

[0154] Fig. 15(A) shows the state of each roller immediately after the start of medium feeding. As shown in Fig. 15(A), immediately after the start of medium feeding, the pick roller 112 and the feed roller 113 rotate in the medium feeding directions A11 and A12, respectively, as driven by the motor 141, and the separation roller 114 rotates in the opposite direction A13 to the medium feeding direction. As shown in Fig. 15(A), if multiple media have not reached the separation section, the separation roller 114 rotates in the medium feeding direction A13' following the feed roller 113 due to the action of the torque limiter provided in the separation roller 114.

[0155] Fig. 15(B) shows a state in which the leading edge of medium M6 arranged on the lower side has passed through the separation section. As shown in Fig. 15(B), medium M6 arranged on the lower side, not medium M5 to be fed, comes into contact with feed roller 113, and medium M6 is fed downstream by feed roller 113. In this case as well, the torque limiter provided on separation roller 114 cuts off the driving force from motor 141, and separation roller 114 rotates in the medium feeding direction A13' following feed roller 113 without rotating according to the driving force from motor 141.

[0156] Fig. 15(C) shows a state in which the feeding of the medium continues from the state shown in Fig. 15(B). As shown in Fig. 15(C), when the medium M6 arranged on the lower side passes through the separation section first, the medium M5 arranged on the upper side (and the medium arranged between the medium M5 and the medium M6) is fed by the pick roller 112 and the feed roller 113 and passes through the separation section. When the medium M5 arranged on the upper side passes through the separation section, a plurality of media are present between the feed roller 113 and the separation roller 114, and the driving force from the motor 141 is transmitted to the separation roller 114, which rotates in the reverse direction (in the direction A13 opposite to the medium feeding direction) or stops. As a result, the medium M6 in contact with the separation roller 114 is pushed back to the upstream side.

[0157] In this way, when separation roller 114 rotates forward and then reverses or stops, it is highly likely that the media are placed on mounting table 103 with their leading edges not aligned, and multiple media are temporarily transported downstream of separation roller 114. If the leading edges of media temporarily transported downstream of separation roller 114 are detected by separation sensor 116, pick sensor 117, first skew sensor 118, or second skew sensor 119, the skew state of the media may be erroneously determined.

[0158] If the correction of the skew of the medium is not currently being performed, or if the separation roller 114 has not yet rotated in the reverse direction or stopped after rotating forward, the control unit 162 does not execute any particular process and proceeds to step S221.

[0159] On the other hand, if the medium skew correction is currently being performed and the separation roller 114 rotates forward and then reverses or stops, the control unit 162 starts reverse correction of the medium skew (step S219). The control unit 162 performs reverse correction so that a force in the opposite direction to the skew correction started in step S216 is applied to the medium in the width direction A4. For example, the control unit 162 sets the circumferential speed set for the first feed roller 113a as the circumferential speed of the second feed roller 113b, and sets the circumferential speed set for the second feed roller 113b as the circumferential speed of the first feed roller 113a. The control unit 162 then rotates each feed roller 113 at the set speed for the same amount of time as the elapsed time from the start of the skew correction in step S216 to the present.

[0160] In this way, the control unit 162 corrects the skew of the medium by making the circumferential speed of one of the multiple feed rollers 113 higher than the circumferential speed of the other feed roller 113. If the rotation sensor 115 detects the forward rotation of the separation roller 114 and then detects the reverse rotation or stop of the separation roller 114 during the correction of the skew of the medium, the control unit 162 makes the circumferential speed of the one feed roller 113 lower than the circumferential speed of the other feed roller 113. This allows the medium conveying device 100 to return the direction of the medium when it has erroneously detected the skew of the medium and rotated the medium in the wrong direction. Therefore, the medium conveying device 100 can prevent the medium from being jammed by rotating the medium in an inappropriate direction.

[0161] Next, the control unit 162 sets the status information to an inverse correction in progress state, which indicates that inverse correction of the medium skew is being performed (step S220).

[0162] Next, the control unit 162 determines whether or not a completion condition or a stop condition for the medium skew correction is satisfied (step S221). If the completion condition or the stop condition for the medium skew correction is satisfied, the control unit 162 stops the medium skew correction in the process described later.

[0163] When the sensor, either the first skew sensor 118 or the second skew sensor 119, which did not detect the leading edge of the medium in step S202, detects the leading edge of the medium, the control unit 162 determines that the condition for completing the skew correction of the medium is satisfied. As described above, the medium rotates by the skew correction around the position of the sensor, either the first skew sensor 118 or the second skew sensor 119, which detected the leading edge of the medium. Therefore, by stopping the skew correction when the sensor, which did not detect the leading edge of the medium, detects the leading edge of the medium, the medium conveying device 100 can align the leading edge of the medium with the width direction A4 and satisfactorily eliminate the skew of the medium.

[0164] When pick sensor 117 is disposed at the same position as first skew sensor 118 and second skew sensor 119 in medium transport direction A2, control unit 162 may stop skew correction of the medium based on the detection result of the medium by pick sensor 117. For example, control unit 162 determines that the completion condition for skew correction of the medium is satisfied when pick sensor 117 detects the leading edge of the medium.

[0165] The control unit 162 may determine that the condition for completing the skew correction of the medium is satisfied when a fifth time has elapsed since the skew sensor that did not detect the leading edge of the medium or the pick sensor 117 detected the leading edge of the medium. The fifth time is an example of a predetermined time. The fifth time is set, based on a prior experiment, to an average value or the like of the time required from when each sensor detects the leading edge of the medium until the inclination of the medium becomes zero (the leading edge of the medium becomes parallel to the width direction A4).

[0166] In this way, the control unit 162 stops correcting the skew of the medium when the fifth time has elapsed since the skew sensor that did not detect the leading edge of the medium or the pick sensor 117 detected the leading edge of the medium, allowing the medium conveying device 100 to more appropriately correct the skew of the medium.

[0167] The fifth time may be set based on the degree of slip acquired in step S205. For example, the fifth time is set to be longer as the degree of slip is larger and shorter as the degree of slip is smaller. When the degree of slip is large, the medium rotates while slipping during skew correction, and the position of the center of rotation of the medium shifts downstream from the position of the skew sensor (or pick sensor 117). By stopping the correction of the skew of the medium based on the degree of slip, the medium conveying device 100 can appropriately correct the skew of the medium, taking into account the slip of the medium caused by the feed roller 113.

[0168] 14 shows the inclination of the medium when the skew correction of the medium is stopped when the fifth time has elapsed since the pick sensor 117 detected the leading edge of the medium when the feed roller 113 having the characteristics shown in graph G2 is used to correct the skew of the medium. As shown in graph G3, the inclination of the medium after the skew correction can be made smaller by lengthening the time for which the skew is corrected, taking into account the slippage of the medium.

[0169] Furthermore, the control unit 162 determines that the condition for stopping the media skew correction is satisfied when reverse correction of the media skew is currently being performed and the time during which reverse correction of the media skew is performed is equal to or longer than the time during which correction of the media skew is performed. The control unit 162 can return the orientation of the media to its original position by rotating the media in the reverse direction for the same amount of time as the time during which the media was rotated in the wrong direction due to erroneous detection of the media skew.

[0170] In this way, when the rotation sensor 115 detects the forward rotation of the separation roller 114 and then detects the reverse rotation or stop of the separation roller 114, the control unit 162 stops correcting the skew of the medium. This allows the medium conveying device 100 to prevent the medium from being rotated in the wrong direction when the media are placed on the placement table 103 with their leading edges not aligned and multiple media are temporarily conveyed downstream of the separation roller 114. The user no longer needs to carefully align the media when setting multiple media together on the placement table 103, and the medium conveying device 100 can improve user convenience.

[0171] Furthermore, when either the first skew sensor 118 or the second skew sensor 119 that detected the leading edge of the medium in step S202 no longer detects the leading edge of the medium, the control unit 162 determines that the condition for stopping skew correction of the medium has been satisfied. When the signal value of the skew signal changes from a value indicating the absence of the medium to a value indicating the presence of the medium and then changes again to a value indicating the absence of the medium, the control unit 162 determines that the leading edge of the medium has returned upstream of the corresponding skew sensor. Then, the control unit 162 determines that the skew sensor no longer detects the leading edge of the medium.

[0172] FIG. 16A is a schematic diagram for explaining the medium M4 returning to the upstream side.

[0173] 16(A), the leading edge of medium M4 detected by first skew sensor 118 shown in FIG. 12(A) has returned upstream of first skew sensor 118 and is no longer detected by first skew sensor 118. In this case, it is highly likely that medium M4 is not the medium to be fed, but has moved downstream of separation roller 114 before medium M7 to be fed, and then, as medium M7 to be fed passed separation roller 114, medium M4 has been returned upstream by the separating force of separation roller 114.

[0174] When the sensor that has been detecting the leading edge of the medium, either the first skew sensor 118 or the second skew sensor 119, no longer detects the leading edge of the medium, the control unit 162 stops correcting the skew of the medium. This allows the medium conveying device 100 to prevent the medium M7 to be fed from being rotated in the wrong direction.

[0175] When the sensor of first skew sensor 118 or second skew sensor 119 that had been detecting the leading edge of the medium no longer detects the leading edge of the medium for a sixth consecutive time, control unit 162 may determine that the condition for stopping the skew correction of the medium has been satisfied and stop the correction of the skew of the medium. The sixth time is set to the time required for the medium to move the size of a typical punch hole. There is a possibility that punch holes or the like have been formed in the medium being fed. By providing a grace period before determining that the condition for stopping the skew correction of the medium has been satisfied, control unit 162 can prevent erroneous stopping of the skew correction of the medium when a punch hole formed in the medium passes the position of the skew sensor.

[0176] The control unit 162 may also determine that the stop condition for the skew correction of the medium is satisfied when one of the first skew sensor 118 and the second skew sensor 119, which had detected the leading edge of the medium in step S202, no longer detects the leading edge of the medium, and when the other of the sensors, which had not detected the leading edge of the medium in step S202, detects the leading edge of the medium. The control unit 162 may also determine that the stop condition for the skew correction of the medium is satisfied when one of the first skew sensor 118 and the second skew sensor 119, which had detected the leading edge of the medium in step S202 no longer detects the leading edge of the medium, and when the pick sensor 117 detects the leading edge of the medium. In these cases, the control unit 162 may immediately determine that the stop condition for the skew correction of the medium is satisfied, without waiting for the sixth time to elapse.

[0177] FIG. 16B is a schematic diagram for explaining a medium M4 tilted in the opposite direction.

[0178] In the example shown in Fig. 16(B), medium M4 detected by first skew sensor 118 shown in Fig. 12(A) is no longer detected by first skew sensor 118 and is instead detected by second skew sensor 119 and pick sensor 117. In this case, medium M4 is likely tilted in the opposite direction due to overcorrection of skew. When the skew sensor that was detecting the leading edge of the medium no longer detects the medium and the other skew sensor or pick sensor 117 detects the medium, medium conveying device 100 can prevent overcorrection of skew by stopping correction of the medium skew.

[0179] In addition, when the pick sensor 117 does not detect the leading edge of the medium and both the first skew sensor 118 and the second skew sensor 119 detect the leading edge of the medium, the control unit 162 may determine that the condition for stopping the skew correction of the medium is satisfied and stop correcting the skew of the medium.

[0180] FIG. 17 is a schematic diagram for explaining media M8 and M9 that are not detected by the pick sensor 117 and are detected by both the first skew sensor 118 and the second skew sensor 119. In FIG.

[0181] In the example shown in FIG. 17, media M8 and media M9 are placed on the placement table 103 with their leading edges not aligned. The left part of the leading edge of media M8 enters downstream of the feed roller 113 and is detected by the first skew sensor 118, and the right part of the leading edge of media M9 enters downstream of the feed roller 113 and is detected by the second skew sensor 119. In this way, a medium that is not detected by the pick sensor 117 and is detected by both the first skew sensor 118 and the second skew sensor 119 is likely to be a separate medium that is not aligned and placed on the placement table 103. When the pick sensor 117 does not detect the leading edge of the medium and both the first skew sensor 118 and the second skew sensor 119 detect the leading edge of the medium, the medium conveying device 100 stops correcting the skew of the medium, thereby suppressing skew correction in the wrong direction.

[0182] Furthermore, if the pick sensor 117 does not detect the medium until the seventh time has elapsed since the start of the medium skew correction, the control unit 162 may determine that the condition for stopping the medium skew correction has been satisfied and stop the medium skew correction. The seventh time is an example of a predetermined time. For example, the seventh time is set to the maximum value of the time it takes for the pick sensor 117 to detect the medium from the start of the medium skew correction when no medium jam has occurred, based on a prior experiment. If the pick sensor 117 does not detect the medium until the seventh time has elapsed since the start of the medium skew correction, the control unit 162 determines that a medium jam has occurred or is highly likely to occur, and stops the medium skew correction. This allows the medium conveying device 100 to suppress damage to the medium caused by a load being applied to the jammed medium.

[0183] If neither the completion condition nor the stop condition of the skew correction is satisfied, the control unit 162 does not execute any particular process and moves the process to step S228.

[0184] On the other hand, if the skew correction completion condition or stop condition is satisfied, the control unit 162 controls the motor 141 to temporarily stop the pick roller 112, the feed roller 113, the separation roller 114, and / or the first to sixth conveyor rollers 120a-f (step S222).

[0185] Next, the control unit 162 controls the motor 141 to return the pressure, which is increased in step S209 and presses the separation roller 114 toward the feed roller 113, to a reference value (step S223). This allows the medium conveying device 100 to set the frictional force generated between the fed medium and the feed roller 113 to an appropriate value when the skew of the medium is not corrected, and to feed the medium well.

[0186] Next, the control unit 162 controls the motor 141 to move the pick roller 112 from the second position to the first position (step S224). In this way, when the control unit 162 stops correcting the skew of the medium, it controls the arm 131 supporting the pick roller 112, the biasing member 131c, and the motor 141 to move the pick roller 112 from the second position to the first position. This allows the pick roller 112 to come into contact with the medium placed on the placement table 103 and to appropriately feed and transport the medium.

[0187] Next, the control unit 162 sets the state information to a completion waiting state, which indicates that the control unit 162 is waiting until the correction of the skew of the medium can be completed (step S225).

[0188] Next, the control unit 162 determines whether or not the stop condition of the skew correction is satisfied in step S221 (step S226). If the stop condition is not satisfied, the control unit 162 does not execute any particular process and moves the process to step S228.

[0189] On the other hand, if the stop condition is met, the control unit 162 notifies the user that the medium skew correction is to be stopped (stopped) by displaying the message on the display device 106 or transmitting the message to the information processing device via the interface device 142 (step S227). The control unit 162 may further notify the user of the reason for stopping (stopping) the medium skew correction.

[0190] Next, the control unit 162 determines whether or not the end condition of the skew correction is satisfied (step S228). If the end condition of the skew correction is satisfied, the control unit 162 stops the correction of the skew of the medium and restarts the transportation of the medium in the process described later.

[0191] The control unit 162 determines that the end condition of the skew correction is satisfied when the eighth time has elapsed since the state information was set to the end waiting state. That is, the control unit 162 determines that the end condition of the skew correction is satisfied when the eighth time has elapsed since the control of the motor 141 was started so as to return the pressing force that presses the separation roller 114 toward the feed roller 113 side. The control unit 162 also determines that the end condition of the skew correction is satisfied when the eighth time has elapsed since the control of the moving mechanism was started so as to move the pick roller 112 to the first position. The eighth time is an example of the second predetermined time. The eighth time is set to the time required from the start of the control of the motor 141 until the pressing force of the separation roller 114 is switched or until the pick roller 112 actually moves to the first position. On the other hand, the control unit 162 determines that the end condition of the skew correction is not satisfied when the state information is set to a state other than the end waiting state or when the eighth time has not elapsed since the state information was set to the end waiting state.

[0192] In this way, the control unit 162 stops the correction of the skew of the medium after the eighth time has elapsed since the control of the motor 141 is started so as to return the pressing force that presses the separation roller 114 toward the feed roller 113 side. This allows the medium conveying device 100 to resume conveying the medium in a state where the pressing force that presses the separation roller 114 toward the feed roller 113 side is reliably returned, so that the medium can be conveyed more appropriately. Furthermore, when the correction of the skew of the medium is completed, the control unit 162 controls the moving mechanism to move the pick roller 112 from the second position to the first position. Furthermore, the control unit 162 stops the conveying of the medium until the eighth time has elapsed since the control of the moving mechanism is started so as to move the pick roller 112 from the second position to the first position. If the conveying and feeding of the medium is started before the pick roller 112 abuts against the medium, there is a high possibility that the medium will be skewed. The medium conveying device 100 can suppress the occurrence of the skew of the medium by stopping the conveying of the medium until the pick roller 112 abuts against the medium reliably.

[0193] If the condition for ending the skew correction is not satisfied, the control unit 162 does not execute any particular process and moves the process to step S231.

[0194] On the other hand, if the condition for ending the skew correction is met, the control unit 162 stops the correction of the skew of the medium by returning the peripheral speed of the first feed roller 113a and the peripheral speed of the second feed roller 113b to the same reference speed (step S229).

[0195] Next, the control unit 162 drives the motor 141 to rotate the pick roller 112, the feed roller 113, the separation roller 114, and / or the first to sixth conveying rollers 120a-f again (step S230).

[0196] Next, the control unit 162 determines whether or not skew correction has been performed on the medium currently being transported (step S231). If skew correction has not been performed on the medium currently being transported, the control unit 162 does not perform any particular process and proceeds to step S234.

[0197] On the other hand, when skew correction is performed on the medium currently being transported, the control unit 162 determines whether insufficient correction of the skew of the medium has occurred (step S232). As described above, the control unit 162 determines that insufficient correction has occurred when, for example, the sensor that first detected the leading edge of the medium, out of the first skew sensor 118 and the second skew sensor 119, detects the trailing edge of the medium before the separation sensor 116 detects the trailing edge of the medium.

[0198] When the signal value of the first skew signal changes from a value indicating the presence of the medium to a value indicating the absence of the medium, the control unit 162 determines that the trailing edge of the medium has passed the position of the first skew sensor 118 and that the first skew sensor 118 has detected the trailing edge of the medium. When the signal value of the second skew signal changes from a value indicating the presence of the medium to a value indicating the absence of the medium, the control unit 162 determines that the trailing edge of the medium has passed the position of the second skew sensor 119 and that the second skew sensor 119 has detected the trailing edge of the medium. When the signal value of the separation signal changes from a value indicating the presence of the medium to a value indicating the absence of the medium, the control unit 162 determines that the trailing edge of the medium has passed the position of the separation sensor 116 and that the separation sensor 116 has detected the trailing edge of the medium. If the control unit 162 determines that insufficient correction has occurred, it stores in the storage device 150 a message indicating that insufficient correction has occurred.

[0199] Next, the control unit 162 determines whether or not overcorrection of the skew correction of the medium has occurred (step S233). As described above, the control unit 162 determines that overcorrection has occurred, for example, when the order in which the first skew sensor 118 and the second skew sensor 119 detect the rear end of the medium has changed from the order in which they detected the front end of the medium. When the control unit 162 determines that overcorrection has occurred, it stores in the storage device 150 that the overcorrection has occurred.

[0200] Next, the control unit 162 determines whether or not a skew correction abnormality has occurred (step S234). For example, if neither the completion condition nor the stop condition of the medium skew correction is satisfied within a predetermined time after the start of the medium skew correction, the control unit 162 determines that a skew correction abnormality has occurred. If a skew correction abnormality has not occurred, the control unit 162 returns the process to step S201 and repeats the processes from step S201 onward.

[0201] On the other hand, if a skew correction abnormality occurs, the control unit 162 executes abnormality processing (step S235). As the abnormality processing, the control unit 162 controls the motor 141 to stop the pick roller 112, the feed roller 113, the separation roller 114, and / or the first to sixth conveyance rollers 120a-f. As the abnormality processing, the control unit 162 notifies the user that a skew correction abnormality has occurred by displaying the occurrence on the display device 106 or transmitting the occurrence to the information processing device via the interface device 142. This allows the medium conveying device 100 to prevent the occurrence of jams and damage to the medium. Next, the control unit 162 returns the process to step S201, and thereafter repeats the processes from step S201 onward.

[0202] 7 may be omitted. In that case, the control unit 162 sets the circumferential speed of the feed roller 113 to the first speed V1 and the second speed V2 determined in advance in step S213 of FIG.

[0203] Also, the process of step S108 in Fig. 7 and the process of step S205 in Fig. 8 may be omitted. In that case, the control unit 162 does not determine whether or not the prohibition condition for skew correction is satisfied based on the degree of slip in step S206 in Fig. 8. Also, the control unit 162 does not determine whether or not the correction condition for the circumferential speed of the feed roller 113 is satisfied based on the degree of slip in step S214 in Fig. 9, and does not correct the circumferential speed of the feed roller 113 based on the degree of slip in step S215. Also, the control unit 162 does not determine whether or not the stop condition for skew correction of the medium is satisfied based on the degree of slip in step S221 in Fig. 10.

[0204] 8 may be omitted. In that case, the control unit 162 starts skew correction of the medium when the leading edge of the medium passes either the first skew sensor 118 or the second skew sensor 119, without determining whether skew of the medium has occurred.

[0205] Also, the processes of steps S206 and S207 in Fig. 8 may be omitted. Also, in step S206 in Fig. 8, the control unit 162 may determine that the prohibition condition for skew correction is satisfied when the separation roller 114 rotates in the forward direction and then in the reverse direction or stops, similarly to the process of step S218.

[0206] 8 and / or step S223 in FIG. 10 may be omitted. Instead of step S223 in FIG. 10, the control unit 162 may return the pressing force for pressing the separation roller 114 toward the feed roller 113 by automatic torque control. The processes of step S210 in FIG. 8 and S224 in FIG. 10 may be omitted. In step S212 in FIG. 9, the control unit 162 may determine that the start condition for skew correction is satisfied immediately after starting control of the motor 141 to increase the pressing force for pressing the separation roller 114 toward the feed roller 113. In step S212 in FIG. 9, the control unit 162 may determine that the start condition for skew correction is satisfied immediately after starting control of the moving mechanism to move the pick roller 112 to the second position. 10, the control unit 162 may determine that the end condition of the skew correction is satisfied immediately after starting control of the motor 141 to return the pressing force that presses the separation roller 114 toward the feed roller 113. Similarly, the control unit 162 may determine that the end condition of the skew correction is satisfied immediately after starting control of the moving mechanism to move the pick roller 112 to the first position in step S228 of FIG.

[0207] Furthermore, the processes in steps S214 and S215 in FIG. 9 may be omitted.

[0208] 9 may be omitted. In that case, the control unit 162 may determine in step S221 of FIG. 10 that the stop condition for skew correction is satisfied immediately after the separation roller 114 rotates forward and then reverses or stops. In addition, when the control unit 162 determines in step S218 that the stop condition for medium skew correction is satisfied because the separation roller 114 rotates forward and then reverses or stops, the control unit 162 may re-determine the medium skew after stopping the skew correction. In that case, the control unit 162 sets (initializes) the state information to an unstarted state after stopping the skew correction in step S229. This causes the medium skew to be corrected again, and the medium conveying device 100 can increase the possibility of appropriately correcting the medium skew.

[0209] 10. Furthermore, the control unit 162 may not need to determine whether or not the stop condition for the skew correction of the medium is satisfied in step S221. Furthermore, when the control unit 162 determines in step S221 that the stop condition for the skew correction of the medium is satisfied because the skew sensor that had been detecting the leading edge of the medium no longer detects the leading edge of the medium, the control unit 162 may stop the skew correction and then re-determine the skew of the medium. In this case, the control unit 162 sets (initializes) the status information to an unstarted state after stopping the skew correction in step S229. This allows the skew of the medium to be corrected again, and the medium conveying device 100 can increase the possibility of appropriately correcting the skew of the medium.

[0210] Furthermore, the processes of steps S222 and S230 in FIG. 10 may be omitted.

[0211] Furthermore, the processes in steps S226 and S227 in FIG. 10 may be omitted.

[0212] 10 may be omitted. In that case, the control unit 162 does not determine whether the prohibition condition for skew correction is satisfied based on insufficient correction in step S206, and does not determine whether the correction condition for the circumferential speed of the feed roller 113 is satisfied based on insufficient correction in step S214. Similarly, the process of step S233 in FIG. 10 may be omitted. In that case, the control unit 162 does not determine whether the prohibition condition for skew correction is satisfied based on over-correction in step S206, and does not determine whether the correction condition for the circumferential speed of the feed roller 113 is satisfied based on over-correction in step S214.

[0213] Furthermore, the conditions for prohibiting skew correction, the conditions for correcting the circumferential speed of the feed roller 113, and the conditions for completing or stopping skew correction of the medium do not have to include all of the conditions described above, and it is sufficient that they include at least one of the conditions.

[0214] As described above in detail, the medium conveying device 100 sets the position of the skew sensor in the width direction A4 for starting the skew correction of the medium to coincide with the rotation center position of the medium during skew correction based on the speed ratio of each feed roller 113 during skew correction. As a result, when skew of the medium occurs, the medium conveying device 100 can appropriately correct the skew of the medium by rotating each feed roller 113 at a predetermined speed regardless of the inclination of the medium. Therefore, the medium conveying device 100 can more simply and appropriately correct the skew of the medium without calculating the amount of inclination of the medium. As a result, the medium conveying device 100 can reduce the processing time and processing load of the medium reading process, and reduce power consumption.

[0215] Furthermore, since the medium conveying device 100 does not need to calculate the amount of skew of the medium, it can start correcting the skew of the medium before the leading edge of the medium passes both the first skew sensor 118 and the second skew sensor 119. This allows the medium conveying device 100 to correct the skew of the medium before the leading edge of the skewed medium comes into contact with the conveying rollers arranged downstream of the first skew sensor 118 and the second skew sensor 119, so that the skew of the medium can be corrected well. Furthermore, since the medium conveying device 100 does not need to arrange the conveying rollers sufficiently apart from the feed rollers 113 in the medium conveying direction A2, it is possible to support the conveyance of small-sized media and reduce the size of the device.

[0216] FIG. 18 is a diagram showing a schematic configuration of a processing circuit 260 of a medium conveying device according to another embodiment.

[0217] The processing circuit 260 is used in place of the processing circuit 160 of the medium conveying device 100, and executes the medium reading process, the skew determination process, and the like in place of the processing circuit 160. The processing circuit 260 includes a receiving circuit 261, a control circuit 262, an acquisition circuit 263, and a determination circuit 264. Each of these components may be configured by an independent integrated circuit, microprocessor, firmware, or the like.

[0218] The reception circuit 261 is an example of a reception unit, and has the same function as the reception unit 161. The reception circuit 261 receives a setting signal from the operation device 105 or the interface device 142, accepts settings specified by the received setting signal, and stores the settings in the storage device 150.

[0219] The control circuit 262 is an example of a control unit, and has the same functions as the control unit 162. The control circuit 262 receives an operation signal from the operation device 105 or the interface device 142. The control circuit 262 also receives a placement table signal, a rotation signal, a separation signal, a pick signal, and a feed signal from the placement table sensor 111, the rotation sensor 115, the separation sensor 116, the pick sensor 117, and the feed sensor 122, respectively. The control circuit 262 also reads out the determination results of the slip degree and skew from the storage device 150. The control circuit 262 controls the motor 141 based on each received signal and / or each read information, acquires an input image from the imaging device 123, and outputs it to the interface device 142.

[0220] The acquisition circuit 263 is an example of an acquisition unit, and has the same function as the acquisition unit 163. The acquisition circuit 263 receives a separation signal and a pick signal from the separation sensor 116 and the pick sensor 117, respectively, and calculates the degree of slippage based on each of the received signals. Alternatively, the acquisition circuit 263 reads out the degree of slippage from the storage device 150. The acquisition circuit 263 stores the calculated or read out degree of slippage in the storage device 150.

[0221] The determination circuit 264 is an example of a determination unit, and has the same function as the determination unit 164. The determination circuit 264 receives a first skew signal and a second skew signal from the first skew sensor 118 and the second skew sensor 119, respectively. The determination circuit 264 determines whether or not a skew of the medium has occurred based on each of the received signals, and stores the determination result in the storage device 150.

[0222] As described above in detail, the medium conveying device is now able to more easily and appropriately correct medium skew, even when using the processing circuit 260.

[0223] Although preferred embodiments have been described above, the embodiments are not limited to these. For example, in the width direction A4, the first skew sensor 118 and / or the second skew sensor 119 may be disposed at a position different from the rotation center position of the medium. In addition, in the width direction A4, the first skew sensor 118 and / or the second skew sensor 119 may be disposed at a position shifted to the outside or inside of the rotation center position based on the degree of slip of the medium conveying device 100 when it is not used (at the time of product shipment). In addition, in the medium conveying direction A2, the first skew sensor 118 and / or the second skew sensor 119 may be disposed at a position upstream of the distance A that satisfies the above-mentioned formula (4).

[0224] The medium conveying device may also correct the skew of the medium using any one of the first to sixth conveying rollers 120a to 120f instead of the feed roller 113. In this case, the conveying rollers for correcting the skew of the medium include a plurality of rollers that are arranged at intervals in the width direction A4 and rotate independently to convey the medium. Furthermore, sensors similar to the separation sensor 116, the pick sensor 117, the first skew sensor 118, and the second skew sensor 119 are arranged downstream of the conveying rollers for correcting the skew of the medium. Each sensor is arranged so that the positional relationship between each sensor and each conveying roller is the same as the positional relationship between the separation sensor 116, the pick sensor 117, the first skew sensor 118, and the second skew sensor 119 and each feed roller 113. An application mechanism similar to the application mechanism that applies a pressing force to the separation roller 114 is provided on each conveying roller or a driven roller facing each conveying roller. The control unit 162 determines whether or not a skew of the medium has occurred based on the output signals from each sensor, and if a skew of the medium has occurred, corrects the skew of the medium by making the circumferential speeds of the transport rollers different from each other. Also, based on the output signals from each sensor, the control unit 162 controls the transport rollers for correcting the skew of the medium instead of the feed roller 113 according to the above-mentioned processes.

[0225] The medium conveying device may use another sensor instead of the rotation sensor 115 to detect the double feeding of the medium. The medium conveying device detects the double feeding of the medium using, for example, an optical sensor. In this case, the optical sensor is arranged so as to image from below the area of ​​the fed medium that overlaps with the nip portion N1 of the feed roller 113 and the separation roller 114 when viewed from the width direction A4. The optical sensor has a light emitter and a light receiver provided on the same side of the medium conveying path, and detects the movement of the medium in the medium conveying direction A2 and the width direction A4. The light emitter is an LED or the like, and emits light toward the conveying path. The light receiver captures an image according to the light received at regular intervals, and detects a common portion between the latest image and the image immediately before. The light receiver calculates the moving direction and moving speed of the conveyed medium based on the change in the position of the detected common portion in the image, and generates and outputs a moving signal indicating the calculated moving direction and moving speed. The regular period is, for example, a period corresponding to 100 operating pulses of the motor 141. In step S218, the control unit 162 receives a movement signal from the optical sensor, and determines the movement direction of the medium based on the signal value of the received movement signal. The control unit 162 determines whether the separation roller 114 is rotating forward, reverse, or stopped based on the determined movement direction.

[0226] The medium transport device may have a so-called straight path, and may feed and transport the media placed on the mounting table from the bottom up. In this case, the feed roller is disposed below the separation roller and faces the separation roller.

[0227] The following supplementary notes are further disclosed regarding the above-described embodiment.

[0228] (Appendix 1) a first roller and a second roller that are spaced apart in a direction perpendicular to the medium transport direction and that rotate independently to transport the medium; a determination unit that determines whether or not a skew of a medium has occurred; a control unit that corrects the skew of the medium by making the peripheral speed of the first roller and the peripheral speed of the second roller different from each other when the skew of the medium occurs; a reception unit that receives, from a user, a setting regarding the circumferential speed of the first roller or the circumferential speed of the second roller when correcting a skew of a medium; A medium transport device comprising:

[0229] (Appendix 2) A roller for transporting a medium; a first sensor and a second sensor that are spaced apart in a direction perpendicular to the medium transport direction and each detects a medium; a pick sensor that is disposed upstream of the first sensor and the second sensor in a medium transport direction and between the first sensor and the second sensor in a direction perpendicular to the medium transport direction, and detects the medium; a determination unit that determines whether or not a skew of a medium has occurred based on a detection result by the first sensor or the second sensor; A control unit that corrects a skew of a medium when the skew of the medium occurs, the control unit does not correct skew of the medium when the pick sensor detects the medium before the first sensor and the second sensor. A medium transport device comprising:

[0230] (Appendix 3) A roller for transporting a medium; a first sensor and a second sensor that are spaced apart in a direction perpendicular to the medium transport direction and each detects a medium; a separation sensor that is disposed upstream of the first sensor and the second sensor in a medium transport direction and between the first sensor and the second sensor in a direction perpendicular to the medium transport direction, and detects the medium; a determination unit that determines whether or not a skew of a medium has occurred based on a detection result by the first sensor or the second sensor; A control unit that corrects a skew of a medium when the skew of the medium occurs, the control unit does not correct skew of the medium when the first sensor or the second sensor detects the medium before the separation sensor. A medium transport device comprising:

[0231] (Appendix 4) A feed roller for feeding the medium; a separation roller disposed opposite the feed roller; A rotation sensor that detects the rotation of the separation roller; a plurality of skew sensors arranged at intervals in a direction perpendicular to the medium transport direction, each of the skew sensors detecting a medium; a determination unit that determines whether or not a skew of the medium has occurred based on output signals from the plurality of skew sensors; A control unit that corrects a skew of a medium when the skew of the medium occurs, the control unit stops correcting the skew of the medium when the rotation sensor detects a reverse rotation or a stop of the separation roller after detecting a forward rotation of the separation roller. A medium transport device comprising:

[0232] (Appendix 5) The feed roller is provided in plurality. The control unit is correcting skew of the medium by making the peripheral speed of one of the plurality of feed rollers higher than the peripheral speed of the other feed roller; A media transport device as described in Appendix 4, wherein, during media skew correction, if the rotation sensor detects forward rotation of the separation roller and then detects reverse rotation or stoppage of the separation roller, the peripheral speed of one of the feed rollers is made lower than the peripheral speed of the other feed roller.

[0233] (Appendix 6) A feed roller for feeding the medium; a separation roller disposed opposite the feed roller; a pressing force applying mechanism configured to apply a pressing force to the separation roller so as to press the separation roller toward the feed roller; a determination unit that determines whether or not a skew of a medium has occurred; a control unit that corrects the skew of the medium by using the feeding roller when the skew of the medium occurs, the control unit controls the applying mechanism so that the pressing force is different when the skew of the medium is being corrected and when the skew of the medium is not being corrected. A medium transport device comprising:

[0234] (Appendix 7) A pick roller for transporting the medium; a moving mechanism that moves the pick roller between a first position in contact with the medium and a second position away from the medium; a conveying roller that is disposed downstream of the pick roller in a medium conveying direction and conveys the medium; a determination unit that determines whether or not a skew of a medium has occurred; a control unit that controls the moving mechanism to move the pick roller to the second position when skew of the medium occurs, and corrects the skew of the medium by using the transport roller; the control unit starts correcting the skew of the medium after a predetermined time has elapsed since starting to control the moving mechanism to move the pick roller to the second position. A medium transport device comprising:

[0235] (Appendix 8) The control unit is when the correction of the skew of the medium is completed, controlling the movement mechanism to move the pick roller to the first position; The medium transport device of claim 7, wherein transport of the medium is stopped until a second predetermined time has elapsed since control of the movement mechanism is started to move the pick roller to the first position.

[0236] (Appendix 9) a first roller and a second roller that are spaced apart in a direction perpendicular to the medium transport direction and that rotate independently to transport the medium; a determination unit that determines whether or not a skew of a medium has occurred; a control unit that corrects the skew of the medium by making the peripheral speed of the first roller and the peripheral speed of the second roller different from each other when the skew of the medium occurs; an acquisition unit that acquires a degree of slip between the first roller and the second roller and a medium transported by the first roller and the second roller, the control unit sets the peripheral speed of the first roller and the peripheral speed of the second roller when correcting the skew of the medium based on the degree of slip. A medium transport device comprising:

[0237] (Appendix 10) The slip degree detecting device further includes a storage unit in which the slip degree is stored in advance, 10. The medium conveying device according to claim 9, wherein the acquisition unit acquires the degree of slip by reading out a degree of slip that is pre-stored in the storage unit.

[0238] (Appendix 11) 10. The medium transport device according to claim 9, wherein the acquisition unit acquires the degree of slip by calculating the degree of slip of the medium transported immediately before.

[0239] (Appendix 12) a first roller and a second roller that are spaced apart in a direction perpendicular to the medium transport direction and that rotate independently to transport the medium; A plurality of sensors spaced apart in a direction perpendicular to the medium transport direction; a determination unit that determines whether or not a skew of the medium has occurred based on the timing at which each of the plurality of sensors detects the leading edge of the medium; a control unit that corrects the skew of the medium by making the peripheral speed of the first roller and the peripheral speed of the second roller different from each other when the skew of the medium occurs, the control unit corrects the circumferential speed of the first roller or the circumferential speed of the second roller based on the timing at which each of the plurality of sensors detects the corrected rear end of the medium. A medium transport device comprising:

[0240] (Appendix 13) A roller for transporting a medium; A plurality of sensors spaced apart in a direction perpendicular to the medium transport direction; a control unit that starts correcting a skew of the medium when any one of the plurality of sensors detects the medium, the control unit stops correcting the skew of the medium when a sensor among the plurality of sensors that has been detecting the medium stops detecting the medium. A medium transport device comprising:

[0241] (Appendix 14) The medium conveying device described in Appendix 12, wherein the control unit stops correcting the skew of the medium when a sensor among the multiple sensors that had been detecting the medium no longer detects the medium continuously for a predetermined period of time.

[0242] (Appendix 15) A roller for transporting a medium; a first sensor and a second sensor spaced apart in a direction perpendicular to the medium transport direction; a pick sensor disposed between the first sensor and the second sensor in a direction perpendicular to a medium transport direction; a control unit that starts correcting a skew of a medium when either the first sensor or the second sensor detects a medium, the control unit stops correcting the skew of the medium when the pick sensor does not detect the medium and both the first sensor and the second sensor detect the medium. A medium transport device comprising:

[0243] (Appendix 16) A roller for transporting a medium; a first sensor and a second sensor spaced apart in a direction perpendicular to the medium transport direction; a pick sensor disposed between the first sensor and the second sensor in a direction perpendicular to a medium transport direction; a control unit that starts correcting a skew of a medium when either the first sensor or the second sensor detects a medium, the control unit stops correcting the skew of the medium when a predetermined time has elapsed since the pick sensor detected the medium. A medium transport device comprising:

[0244] (Appendix 17) A roller for transporting a medium; a first sensor and a second sensor spaced apart in a direction perpendicular to the medium transport direction; a pick sensor disposed between the first sensor and the second sensor in a direction perpendicular to a medium transport direction; a control unit that starts correcting a skew of a medium when either the first sensor or the second sensor detects a medium, the control unit stops correcting the skew of the medium if the pick sensor does not detect the medium until a predetermined time has elapsed since starting to correct the skew of the medium. A medium transport device comprising:

[0245] (Appendix 18) A roller for transporting a medium; an acquisition unit that acquires a degree of slippage between the roller and a medium transported by the roller; a determination unit that determines whether or not a skew of a medium has occurred; A control unit that corrects a skew of a medium when the skew of the medium occurs, the control unit prohibits correction of skew of the medium based on the degree of slip. A medium transport device comprising:

[0246] (Appendix 19) A roller for transporting a medium; A plurality of sensors spaced apart in a direction perpendicular to the medium transport direction; a determination unit that determines whether or not a skew of the medium has occurred based on the timing at which each of the plurality of sensors detects the leading edge of the medium; A control unit that corrects a skew of a medium when the skew of the medium occurs, the control unit prohibits correction of skew of a medium to be transported thereafter based on a timing at which each of the plurality of sensors detects a rear end of the corrected medium. A medium transport device comprising:

[0247] (Appendix 20) The apparatus further includes a mounting table, 20. The medium transport device of claim 19, wherein when the control unit stops correcting the skew of the medium, the control unit does not resume correcting the skew of the medium until transport of all of the media placed on the placement table is completed.

[0248] (Appendix 21) a separation roller disposed opposite the roller; A rotation sensor that detects the rotation of the separation roller; 20. The medium conveying device of claim 19, wherein when the control unit stops correcting the skew of the medium, the control unit does not resume correcting the skew of the medium until the rotation sensor detects the rotation of the separation roller relative to the roller. [Explanation of symbols]

[0249] 100 medium conveying device, 103 placement table, 112 pick roller, 113 feeding roller, 114 separation roller, 114c arm, 115 rotation sensor, 116 separation sensor, 117 pick sensor, 118 first skew sensor, 119 second skew sensor, 120a to 120f first to sixth conveying rollers, 121a to 121f first to sixth driven rollers, 131 arm, 131c biasing member, 141 motor, 150 storage device, 161 reception unit, 162 control unit, 163 acquisition unit, 164 determination unit

Claims

1. a first roller and a second roller that are spaced apart in a direction perpendicular to the medium transport direction and that rotate independently to transport the medium; a first sensor and a second sensor disposed downstream of the first roller and the second roller in a medium transport direction; a control unit that corrects skew of the medium by setting the peripheral speed of the first roller to a first speed and the peripheral speed of the second roller to a second speed higher than the first speed when the first sensor detects the medium before the second sensor detects the medium, a position of the first sensor in a direction perpendicular to a medium transport direction is set based on a position of a rotation center around which the medium rotates at a speed ratio of the second speed to the first speed; When the second sensor detects the medium, correction of the skew of the medium is stopped. A medium transport device characterized by:

2. The first sensor is disposed within a predetermined range from a position that is a distance L calculated by the following formula outside the first roller in a direction perpendicular to the medium transport direction: L = D / (α-1) 2. The medium transport device of claim 1, wherein α is the ratio of the second speed to the first speed, and D is the distance between the first roller and the second roller.

3. The first sensor is disposed at a position downstream of the first roller in the medium transport direction by a distance A that satisfies the following formula: A≧(L+D)・tanθb 3. The medium transport device according to claim 2, wherein θb is the maximum angle of media tilt that the medium transport device supports correction for.

4. The medium is transported by a first roller and a second roller that are spaced apart in a direction perpendicular to the medium transport direction and that rotate independently of each other; correcting skew of the medium by setting the peripheral speed of the first roller to a first speed and the peripheral speed of the second roller to a second speed higher than the first speed when a first sensor located downstream of the first roller and the second roller in the medium transport direction detects the medium before a second sensor located downstream of the first roller and the second roller in the medium transport direction detects the medium; a position of the first sensor in a direction perpendicular to a medium transport direction is set based on a position of a rotation center around which the medium rotates at a speed ratio of the second speed to the first speed; When the second sensor detects the medium, correction of the skew of the medium is stopped. A medium transport method comprising:

5. A control program for a medium transport device having a first roller and a second roller that are spaced apart in a direction perpendicular to a medium transport direction and that rotate independently to transport a medium, and a first sensor and a second sensor that are located downstream of the first roller and the second roller in the medium transport direction, causing the medium transport device to correct skew of the medium by setting a peripheral speed of the first roller to a first speed and a peripheral speed of the second roller to a second speed higher than the first speed when the first sensor detects the medium before the second sensor detects the medium; a position of the first sensor in a direction perpendicular to a medium transport direction is set based on a position of a rotation center around which the medium rotates at a speed ratio of the second speed to the first speed; When the second sensor detects the medium, correction of the skew of the medium is stopped. A control program comprising:

Images