Medium conveyance device, control method and control program

Abstract

To provide a medium conveyance device capable of more appropriately correcting a skew of a medium, a control method and a control program.SOLUTION: A medium conveyance device 100 includes: a plurality of feeding rollers 112 which are arranged at intervals in a direction perpendicular to a medium conveyance direction and each independently rotate and feed a medium; a plurality of brake rollers 113 which are arranged so as to face each of the plurality of feeding rollers; a rotation shaft 135e of the plurality of brake rollers; a plurality of torque limiters 139a and 139b separately provided between each of the plurality of brake rollers; a skew detection part 164 which detects a skew of a medium to be fed; and a control part 161 which corrects the skew of the medium by making peripheral speeds of the plurality of feeding rollers mutually different when the skew of the medium is detected by the skew detection part.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a medium transport device, a control method, and a control program, and more particularly to a medium transport device, a control method, and a control program that corrects skew of a medium. [Background technology]

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

[0003] A paper feeder that feeds documents using independently driven left and right forward rollers has been disclosed (see Patent Document 1). This paper feeder uses output from a sensor for detecting the leading edge of the document to activate left and right motors that drive the left and right forward rollers, respectively, to align the leading edge of the document perpendicular to the feeding direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-215499 Summary of the Invention [Problem to be solved by the invention]

[0005] In a medium transport device, when a skew of a medium occurs, it is desirable to more appropriately correct the skew of the medium.

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

[0007] A media transport device according to one aspect of the present invention comprises a plurality of feed rollers arranged at intervals in a direction perpendicular to the media transport direction, each rotating independently to feed a medium, a plurality of brake rollers arranged opposite each of the plurality of feed rollers, a plurality of torque limiters separately provided on each of the plurality of brake rollers so that each of the plurality of brake rollers can rotate independently in accordance with the plurality of feed rollers, a skew detection unit that detects skew of the media being fed, and a control unit that, when media skew is detected by the skew detection unit, corrects the media skew by making the peripheral speed of the feed roller of the plurality of feed rollers that is arranged on the side where the media is leading the way greater than 0 and lower than the peripheral speed when media skew is not detected, and the control unit performs different processing depending on whether the correction of media skew is successful or unsuccessful.

[0008] Furthermore, a control method according to one aspect of the present invention is a control method for a media transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to the media transport direction and each rotating independently to feed the media, a plurality of brake rollers arranged opposite each of the plurality of feed rollers, and a plurality of torque limiters separately provided on each of the plurality of brake rollers so that each of the plurality of brake rollers can rotate independently in accordance with the plurality of feed rollers, the control method detecting skew of the media being fed, and if media skew is detected, correcting the media skew by making the peripheral speed of the feed roller of the plurality of feed rollers arranged on the side where the media is leading the way greater than 0 and lower than the peripheral speed when media skew is not detected, and performing different processing depending on whether the correction of media skew is successful or unsuccessful.

[0009] Furthermore, a control program according to one aspect of the present invention is a control program for a media conveying device having a plurality of feed rollers arranged at intervals in a direction perpendicular to the media conveying direction and each rotating independently to feed the media, a plurality of brake rollers arranged opposite each of the plurality of feed rollers, rotation axes of the plurality of brake rollers, and a plurality of torque limiters separately provided on each of the plurality of brake rollers so that each of the plurality of brake rollers can rotate independently in accordance with the plurality of feed rollers, the control program detects skew of the media being fed, and if media skew is detected, corrects the media skew by making the peripheral speed of the feed roller of the plurality of feed rollers that is arranged on the side where the media is leading the way greater than 0 and lower than the peripheral speed when media skew is not detected, and causes the media conveying device to perform different processing depending on whether the correction of media skew is successful or unsuccessful. [Effects of the Invention]

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

[0011] [Figure 1] 1 is a perspective view showing a medium conveying device 100 according to an embodiment. [Figure 2] 2 is a diagram for explaining a transport path inside the medium transport device 100. FIG. [Figure 3] 2 is a schematic diagram for explaining a drive mechanism of the medium conveying device 100. FIG. [Figure 4] 2 is a schematic diagram for explaining a drive mechanism of the medium conveying device 100. FIG. [Figure 5] 10 is a schematic diagram for explaining the operation of the planetary gear 134b and the like. FIG. [Figure 6] 10 is a schematic diagram for explaining the operation of the planet gear 134b and the like. FIG. [Figure 7] 10 is a schematic diagram for explaining second torque limiters 139a and 139b. FIG. [Figure 8] 10A and 10B are schematic diagrams for explaining the movement of the feed roller 112 and the like. [Figure 9] FIG. 2 is a schematic diagram for explaining each sensor. [Figure 10] 1 is a block diagram showing a schematic configuration of a medium conveying device 100. FIG. [Figure 11] FIG. 2 is a diagram showing a schematic configuration of a storage device 150 and a CPU 160. [Figure 12] 10 is a flowchart illustrating an example of the operation of a medium reading process. [Figure 13] 10 is a flowchart illustrating an example of the operation of a multifeed detection process. [Figure 14] FIG. 2 is a schematic diagram for explaining characteristics of an ultrasonic signal. [Figure 15] 10 is a flowchart illustrating an example of the operation of a skew detection process. [Figure 16] 10A and 10B are schematic diagrams for explaining the relationship between the tilt of a medium and the passage time. [Figure 17] 10A and 10B are schematic diagrams for explaining a drive mechanism of another medium transport device. [Figure 18] FIG. 10 is a diagram showing a schematic configuration of a processing circuit 270 in yet another medium conveying device. DETAILED DESCRIPTION OF THE INVENTION

[0012] A medium transport device according to one aspect of the present invention will be described below with reference to the drawings. However, please note that the technical scope of the present invention is not limited to the embodiments described therein, but extends to the inventions set forth in the claims and their equivalents.

[0013] FIG. 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 may be paper, cardboard, a card, a booklet, a passport, or the like. The medium conveying device 100 may also be a facsimile machine, a copier, a multifunction peripheral (MFP), 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 also be a printer, or the like.

[0014] The medium conveying device 100 includes a lower housing 101, an upper housing 102, a loading table 103, an ejection table 104, an operation device 105, a display device 106, and the like.

[0015] The upper housing 102 is an example of the upper part of a housing, and is positioned to cover the top surface of the media conveying device 100. It is engaged with the lower housing 101 by a hinge so that it can be opened and closed when the media becomes jammed or when cleaning the inside of the media conveying device 100.

[0016] The loading platform 103 is made of a resin material and engages with the lower housing 101 so that the medium to be transported can be placed thereon. The loading platform 103 is provided so that the medium loading surface 103a is inclined with respect to the installation surface of the medium transport device 100. The ejection platform 104 engages with the lower housing 101 so that it can hold the ejected medium.

[0017] The operation device 105 has input devices such as buttons and an interface circuit for acquiring signals from the input devices, accepts input operations by a user, and outputs operation signals in response to the user's input operations. The display device 106 has a display such as a liquid crystal display, an organic EL (Electro-Luminescence) display, or the like, and an interface circuit for outputting image data to the display, and displays the image data on the display.

[0018] FIG. 2 is a diagram for explaining the transport path inside the medium transport device 100. As shown in FIG.

[0019] The transport path inside the media transport device 100 includes a media detection sensor 111, multiple feed rollers 112a, b, multiple brake rollers 113a, b, an ultrasonic transmitter 114a, an ultrasonic receiver 114b, a first center sensor 115, a first side sensor 116, a second side sensor 117, multiple first transport rollers 118a, b, multiple second transport rollers 119a, b, a second center sensor 120, a first imaging device 121a, a second imaging device 121b, multiple third transport rollers 122a, b, and multiple fourth transport rollers 123a, b.

[0020] Hereinafter, the feed rollers 112a and 112b may be collectively referred to as feed rollers 112. The brake rollers 113a and 113b may be collectively referred to as brake rollers 113. The first conveyor rollers 118a and 118b may be collectively referred to as first conveyor rollers 118. The second conveyor rollers 119a and 119b may be collectively referred to as second conveyor rollers 119. The first imaging device 121a and the second imaging device 121b may be collectively referred to as imaging device 121. The third conveyor rollers 122a and 122b may be collectively referred to as third conveyor rollers 122. The fourth conveyor rollers 123a and 123b may be collectively referred to as fourth conveyor rollers 123.

[0021] The top surface of lower housing 101 forms lower guide 107a of the medium transport path, and the bottom surface of upper housing 102 forms upper guide 107b of the medium transport path. In Figure 2, arrow A1 indicates the medium transport direction. Hereinafter, "upstream" refers to the upstream side of medium transport direction A1, and "downstream" refers to the downstream side of medium transport direction A1.

[0022] The medium detection sensor 111 is disposed upstream of the feed roller 112 and the brake roller 113. The medium detection sensor 111 has a contact detection sensor and detects whether or not a medium is placed on the placement table 103. The medium detection sensor 111 generates and outputs a medium detection signal whose signal value changes depending on whether a medium is placed on the placement table 103 or not.

[0023] The feed roller 112 is provided in the lower housing 101 and feeds the media placed on the placement table 103 from the bottom up. The brake roller 113 is provided in the upper housing 102 and is disposed opposite the feed roller 112.

[0024] The ultrasonic transmitter 114a and the ultrasonic receiver 114b are disposed downstream of the feed roller 112 and the brake roller 113. The ultrasonic transmitter 114a and the ultrasonic receiver 114b are disposed near the medium transport path, facing each other across the transport path. The ultrasonic transmitter 114a outputs ultrasonic waves. Meanwhile, the ultrasonic receiver 114b receives the ultrasonic waves emitted by the ultrasonic transmitter 114a and that have passed through the medium, and generates and outputs an ultrasonic signal, which is an electrical signal corresponding to the received ultrasonic waves. Hereinafter, the ultrasonic transmitter 114a and the ultrasonic receiver 114b may be collectively referred to as the ultrasonic sensor 114.

[0025] The first imaging device 121a is an example of an imaging unit and includes a line sensor of a reduced optical system type equipped with imaging elements based on CCDs (Charge Coupled Devices) linearly arranged in the main scanning direction. The first imaging device 121a also includes 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 121a generates and outputs an input image of the back side of the transported medium under control of a CPU (to be described later).

[0026] Similarly, the second imaging device 121b is an example of an imaging unit and has a reduction optical system type imaging sensor equipped with CCD imaging elements linearly arranged in the main scanning direction. The second imaging device 121b 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 121b generates and outputs an input image by capturing an image of the surface of the transported medium under control of a CPU (described later).

[0027] The medium conveying device 100 may be configured with only one of the first and second image capturing devices 121a and 121b to read only one side of the medium. Also, instead of a CCD, a CIS (Contact Image Sensor) with a 1:1 optical system and equipped with a CMOS (Complementary Metal Oxide Semiconductor) image capturing element may be used.

[0028] The media placed on the mounting table 103 is transported between the lower guide 107a and the upper guide 107b in the media transport direction A1 by the rotation of the feed roller 112 in the direction of arrow A2 in Figure 2, i.e., the media feed direction. When transporting the media, the brake roller 113 rotates in the direction of arrow A3, i.e., the opposite direction to the media feed direction. When multiple media are placed on the mounting table 103, the feed roller 112 and the brake roller 113 function to separate only the media placed on the mounting table 103 that are in contact with the feed roller 112. This operates to restrict the transport of media other than the separated media (preventing double feeding).

[0029] The medium is guided by lower guide 107a and upper guide 107b and fed between first conveyor roller 118 and second conveyor roller 119. The medium is fed between first imaging device 121a and second imaging device 121b as first conveyor roller 118 and second conveyor roller 119 rotate in the directions of arrows A4 and A5, respectively. The medium read by imaging device 121 is discharged onto discharge tray 104 as third conveyor roller 122 and fourth conveyor roller 123 rotate in the directions of arrows A6 and A7, respectively.

[0030] 3 and 4 are schematic diagrams for explaining the drive mechanism of the medium conveying device 100. Fig. 3 is a schematic diagram of the drive mechanism of the medium conveying device 100 as seen from the upstream side in the medium conveying direction A1 and from one end side in the direction A8 perpendicular to the medium conveying direction. Fig. 4 is a schematic diagram of the drive mechanism of the medium conveying device 100 as seen from the upstream side in the medium conveying direction A1 and from the other end side in the direction A8 perpendicular to the medium conveying direction.

[0031] As shown in Figures 3 and 4, the drive mechanism of the medium conveying device 100 includes, in addition to the above-mentioned feed roller 112 and brake roller 113, a first motor 131, a pulley 132, first to thirteenth gears 133a-m, a sun gear 134a, a planetary gear 134b, and first to fifth shafts 135a-e.

[0032] The multiple feed rollers 112a, b are arranged side by side at intervals in a direction A8 perpendicular to the medium conveying direction. Meanwhile, multiple brake rollers 113a, b are arranged opposite the multiple feed rollers 112a, b, respectively. Each feed roller 112a, b is provided with an outer circumferential surface 136a, b and a one-way clutch 136c, d. Each one-way clutch 136c, d prevents the outer circumferential surface 136a, b of each feed roller 112a, b from rotating in the direction opposite the medium feed direction A2 relative to the rotation axis of each feed roller 112a, b.

[0033] The first transport roller 118 and the second transport roller 119 transport the medium at a transport speed faster than the feed speed of the feed roller 112. Therefore, when the medium reaches the position of the first transport roller 118 and the second transport roller 119, the medium is pulled by the first transport roller 118 and the second transport roller 119 while being sandwiched between the feed roller 112 and the brake roller 113. At this time, the outer circumferential surfaces 136a, b of the feed roller 112 rotate along with the sandwiched medium due to the action of the one-way clutches 136c, d, and do not impede the transport of the medium.

[0034] A rotation shaft (shaft member) of the ninth gear 133i is provided with a first torque limiter 137. The limit value of the torque of the first torque limiter 137 is a first limit value.

[0035] The first motor 131 has a rotary shaft 131a (shaft member) and generates a driving force for rotating the feed roller 112 and the brake roller 113 via the rotary shaft 131a.

[0036] A belt 131b is stretched between the rotating shaft 131a of the first motor 131 and the pulley 132, and a first gear 133a is attached to the rotating shaft (shaft member) of the pulley 132. The first gear 133a is engaged with a gear portion having a larger outer diameter of the second gear 133b, and the gear portion having a smaller outer diameter of the second gear 133b is engaged with a third gear 133c. The third gear 133c is attached to one end of the first shaft 135a, and a fourth gear 133d is attached to the other end of the first shaft 135a. The fourth gear 133d is engaged with a fifth gear 133e. The fifth gear 133e is attached to one end of the second shaft 135b, and the feed roller 112a is attached to the other end of the second shaft 135b so that it rotates in accordance with the rotation of the second shaft 135b. The second shaft 135b is an example of a rotation shaft of the feed roller 112a.

[0037] Meanwhile, the sixth gear 133f is connected to a second motor (not shown) via a predetermined drive mechanism. The sixth gear 133f is attached to one end of a third shaft 135c, and the feed roller 112b is attached to the other end of the third shaft 135c so as to rotate in accordance with the rotation of the third shaft 135c. The third shaft 135c is an example of the rotation axis of the feed roller 112b. In this way, the feed rollers 112a and 112b are provided so as to rotate independently by separate motors. Alternatively, the feed rollers 112a and 112b may be provided so as to rotate together by a common motor.

[0038] The smaller outer diameter gear portion of the second gear 133b is further engaged with the seventh gear 133g, and the seventh gear 133g is engaged with the eighth gear 133h. The eighth gear 133h is engaged with the sun gear 134a, and the sun gear 134a is engaged with the smaller outer diameter gear portion of the planetary gear 134b. The larger outer diameter gear portion of the planetary gear 134b is engaged with the larger outer diameter gear portion of the ninth gear 133i, and the smaller outer diameter gear portion of the ninth gear 133i is engaged with the tenth gear 133j. The tenth gear 133j is attached to one end of the fourth shaft 135d, and the eleventh gear 133k is attached to the other end of the fourth shaft 135d. The eleventh gear 133k is engaged with the twelfth gear 133l, and the twelfth gear 133l is engaged with the thirteenth gear 133m. The thirteenth gear 133m is attached to one end of a fifth shaft 135e, and the brake rollers 113a and 113b are attached to the other end of the fifth shaft 135e so as to rotate in accordance with the rotation of the fifth shaft 135e. The fifth shaft 135e is an example of a rotation axis of the brake rollers 113a and 113b.

[0039] The first motor 131 generates a first driving force by rotating in a first direction, and generates a second driving force by rotating in a second direction opposite to the first direction. The rotation in the first direction rotates the rotary shaft 131a in the direction of arrow B1, and the rotation in the second direction rotates the rotary shaft 131a in the opposite direction to arrow B1. Similarly, the second motor connected to the sixth gear 133f generates a first driving force by rotating in the first direction, and generates a second driving force by rotating in the second direction opposite to the first direction.

[0040] When the first motor 131 generates a first driving force, the rotary shaft 131a rotates in the direction of arrow B1, and accordingly, the first to fifth gears 133a-e rotate in the directions of arrows B1-B5, respectively. As a result, the feed roller 112a rotates in the medium feed direction A2. When the second motor generates a first driving force, the sixth gear 133f rotates in the direction of arrow B6, causing the feed roller 112b to rotate in the medium feed direction A2. Meanwhile, as the second gear 133b rotates in the direction of arrow B2, the seventh to eighth gears 133g-h, the sun gear 134a, the planet gear 134b, and the ninth to thirteenth gears 133i-m rotate in the directions of arrows B7-B8, C1-C2, and B9-B13, respectively. As a result, the brake rollers 113a and 113b rotate in the direction A3 opposite to the medium feed direction.

[0041] Conversely, when the first motor 131 generates the second driving force, the rotary shaft 131a rotates in the direction opposite to the arrow B1, and accordingly the first to fifth gears 133a-e rotate in the directions opposite to the arrows B1-B5, respectively. As a result, the second shaft 135b rotates in the direction opposite to the medium feeding direction A2. However, the feed roller 112a is provided with a one-way clutch 136c that prevents the outer circumferential surface 136a from rotating in the direction opposite to the medium feeding direction A2 relative to the second shaft 135b. The one-way clutch 136c prevents the outer circumferential surface 136a of the feed roller 112a from rotating in the direction opposite to the arrow A2 due to the second driving force.

[0042] Similarly, when the second motor generates the second driving force, the sixth gear 133f rotates in the opposite direction of the arrow B6, causing the third shaft 135c to rotate in the opposite direction of the arrow A2. However, the feed roller 112b is provided with a one-way clutch 136d that prevents the outer circumferential surface 136b from rotating in the opposite direction of the medium feeding direction A2 relative to the third shaft 135c. The one-way clutch 136d prevents the outer circumferential surface 136b of the feed roller 112b from rotating in the opposite direction of the arrow A2 according to the second driving force.

[0043] The movement of the brake rollers 113a and 113b when the first motor 131 generates the second driving force will be described below.

[0044] 5 and 6 are schematic diagrams for explaining the operation of the sun gear 134a and the planetary gears 134b. Fig. 5 shows the state of the sun gear 134a and the planetary gears 134b when the first motor 131 generates a first driving force, and Fig. 6 shows the state of the sun gear 134a and the planetary gears 134b when the first motor 131 generates a second driving force.

[0045] As shown in FIGS. 5 and 6, the rotation shaft 138a (shaft member) of the planetary gear 134b is provided movably along a groove 138b formed in the upper housing 102. As shown in FIG. 5, when the first motor 131 generates a first driving force, the first to eighth gears 133a-h rotate in the directions of arrows B1-B8, respectively, causing the sun gear 134a to rotate in the direction of arrow C1. The planetary gear 134b engaged with the sun gear 134a moves (revolves) along the groove 138b in the direction of arrow C3 to the upper left end position of the groove 138b in accordance with the rotation of the sun gear 134a in the direction of arrow C1, and engages with the ninth gear 133i. Furthermore, the planetary gear 134b rotates (spins) in the direction of arrow C2 at the upper left end position of the groove 138b in accordance with the rotation of the sun gear 134a. As a result, as shown in FIGS. 3 and 4, the ninth to thirteenth gears 133i to 133m rotate in the directions of arrows B9 to B13, respectively, and the brake rollers 113a and 113b rotate in the direction of arrow A3.

[0046] On the other hand, as shown in FIG. 6, when the first motor 131 generates the second driving force, the first to eighth gears 133a-h rotate in the opposite directions of arrows B1-B8, respectively, causing the sun gear 134a to rotate in the opposite direction of arrow C1. As the sun gear 134a rotates in the opposite direction of arrow C1, the planetary gear 134b moves (revolves) along the groove 138b to the lower right end position of the groove 138b in the opposite direction of arrow C3, where it separates from the ninth gear 133i and engages with the tenth gear 133j. Furthermore, as the sun gear 134a rotates, the planetary gear 134b rotates (spins) in the opposite direction of arrow C2 at the lower right end position of the groove 138b. As a result, the tenth to thirteenth gears 133i-m rotate in the directions of arrows B10-B13, respectively, and the brake rollers 113a and 113b rotate in the direction of arrow A3.

[0047] In this way, the first driving force from the first motor 131 is transmitted to the brake rollers 113a, 113b via the ninth gear 133i, i.e., via the first torque limiter 137 provided on the rotation shaft of the ninth gear 133i. On the other hand, the second driving force is transmitted to the brake rollers 113a, 113b without passing through the ninth gear 133i, i.e., without passing through the first torque limiter 137.

[0048] FIG. 7 is a schematic diagram for explaining second torque limiters 139a and 139b provided on the brake rollers 113a and 113b.

[0049] As shown in FIG. 7, a plurality of second torque limiters 139a, 139b are individually provided between the fifth shaft 135e, which is the rotation axis of the brake roller 113, and each of the brake rollers 113a, 113b. That is, each of the second torque limiters 139a, 139b is provided corresponding to each of the brake rollers 113a, 113b. The torque limit value of each of the second torque limiters 139a, 139b is smaller than a first limit value, and the sum of the torque limit values ​​of the second torque limiters 139a, 139b is equal to a second limit value that is larger than the first limit value. For example, the first limit value is set to 500 gf.cm, the second limit value is set to 700 gf.cm, and the torque limit value of each of the second torque limiters 139a, 139b is set to 350 gf.cm.

[0050] It should be noted that instead of providing separate second torque limiters 139a and 139b for the brake rollers 113a and 113b, a common second torque limiter may be provided for the brake rollers 113a and 113b.

[0051] 3 and 4 are an example of a first transmission mechanism. The first transmission mechanism transmits a first driving force from the first motor 131 to the brake roller 113 via a first torque limiter 137, causing the brake roller 113 to rotate in a direction A3 opposite to the medium feeding direction.

[0052] Meanwhile, the belt 131b, pulley 132, first, second, eighth, tenth, and thirteenth gears 133a-b, h, j-m, sun gear 134a, planetary gear 134b, and fourth and fifth shafts 135d-e are an example of a second transmission mechanism. The second transmission mechanism does not include the ninth gear 133i provided with the first torque limiter 137. The second transmission mechanism transmits the first driving force from the first motor 131 to the brake roller 113 via second torque limiters 139a and 139b without passing through the first torque limiter 137, thereby rotating the brake roller 113 in the direction A3 opposite to the medium feeding direction.

[0053] As described above, the first transmission mechanism and the second transmission mechanism include the planetary gear 134b. The first transmission mechanism transmits the first driving force via the planetary gear 134b and the first torque limiter 137 to the brake roller 113. The second transmission mechanism transmits the second driving force to the brake roller 113 without passing through the first torque limiter 137 by changing the connection of the planetary gear 134b in response to switching from the first driving force to the second driving force.

[0054] Whether the first transmission mechanism or the second transmission mechanism is used, the driving forces are transmitted to the brake roller 113 via the second torque limiters 139a and 139b. However, the torque limit value (first limit value) of the first torque limiter 137 is smaller than the sum of the torque limit values ​​(second limit values) of the second torque limiters 139a and 139b. Therefore, the overall torque limit value of the first transmission mechanism, which passes through both the first torque limiter 137 and the second torque limiters 139a and 139b, is the first limit value. On the other hand, the overall torque limit value of the second transmission mechanism, which passes only through the second torque limiters 139a and 139b without passing through the first torque limiter 137, is the second limit value. That is, the brake roller 113 rotates in the direction A3 opposite to the medium feeding direction whether driven by the first driving force or the second driving force, but the torque limit value when driven by the second driving force is greater than the torque limit value when driven by the first driving force.

[0055] The first limit value is set to a value such that when there is one medium, the rotational force via the first torque limiter 137 is cut off, and when there are multiple media, the rotational force via the first torque limiter 137 is transmitted. As a result, when only one medium is transported, the brake roller 113 does not rotate according to the first driving force, but instead follows the feed roller 112. On the other hand, when multiple media are transported, the brake roller 113 rotates in the direction A3 opposite the medium feed direction, separating the medium in contact with the feed roller 112 from the other media, preventing double feeding. At this time, the outer circumferential surface of the brake roller 113 may apply a force in the direction A3 opposite the medium feed direction to the medium while it is stopped and not rotating in the direction A3 opposite the medium feed direction.

[0056] On the other hand, the second limit value is set to a value that transmits the rotational force via the second torque limiters 139a and 139b even when there are multiple media. Therefore, when the first motor 131 generates the second driving force, the brake roller 113 rotates in the direction A3 opposite to the medium feeding direction in accordance with the second driving force, and returns the media present between the brake roller 113 and the feeding roller 112 to the mounting table 103 and restores them.

[0057] FIG. 8 is a schematic diagram for explaining the movements of the feed roller 112 and the brake roller 113 when the first motor 131 generates the second driving force.

[0058] As described above, when the first motor 131 generates the second driving force, the brake roller 113 rotates in the direction A3 opposite the medium feeding direction. The limit value of the torque applied to the brake roller 113 is set so that the rotational force can be transmitted even when multiple media are being fed. Meanwhile, when the first motor 131 and the second motor generate the second driving force, the second shaft 135b and the third shaft 135c, which are the rotation axes of the feed rollers 112a and 112b, rotate in the direction opposite the medium feeding direction A2. However, due to the action of the one-way clutches 136c and 136d, the outer circumferential surfaces 136a and 136b of the feed rollers 112a and 112b do not rotate in the direction opposite the arrow A2 in response to the second driving force. Therefore, the outer circumferential surfaces 136a and 136b of the feed rollers 112a and 112b rotate in the direction opposite the medium feeding direction A2, driven by the brake rollers 113a and 113b.

[0059] The second shaft 135b and the third shaft 135c, which are the rotation axes of the feed rollers 112a and 112b, are arranged to rotate at a rotational speed faster than the rotational speed of the outer peripheral surfaces 136a and 136b of the feed rollers 112a and 112b, which rotate in response to the brake roller 113. As a result, the outer peripheral surfaces 136a and 136b of the feed rollers 112a and 112b rotate in accordance with the rotation of the outer peripheral surface of the brake roller 113 without being hindered by the one-way clutches 136c and 136d. In this way, the feed roller 112 rotates in the direction opposite to the medium feed direction A2 in response to the brake roller 113. Furthermore, the brake roller 113 rotates in the direction opposite to the medium feed direction A3 without being subjected to a load by the feed roller 112.

[0060] Therefore, the medium conveying device 100 is configured to convey a plurality of media M between the brake roller 113 and the feed roller 112. A Even if the media M are fed in a double-feed state, the first motor 131 generates the second driving force, so that the plurality of media M can be fed. A All of the media can be returned to the mounting table 103. In particular, the medium conveying device 100 can recover the media without adding a torque control device such as a hysteresis brake, thereby suppressing increases in the cost, size, and power consumption of the device.

[0061] In the medium conveying device 100, the mounting table 103 is provided so that the mounting surface 103a of the medium is inclined at a predetermined angle θ with respect to the installation surface of the medium conveying device 100, and the medium conveying device 100 uses the weight of the media placed on the mounting table 103 to feed the media in order from the bottom up. When a double feed occurs in such a so-called trade-in type medium conveying device 100, the mounting table 103 holds the double-fed media M. A On top of other media B Therefore, there is a possibility that the media M A When returning the media M to the mounting table 103, A and the medium M remaining on the mounting table 103 B The medium conveying device 100 is configured to convey the multi-fed media M A When returning the media M to the mounting table 103, the limit value of the torque applied to the brake roller 113 is increased from that when the media M are fed. A On top of other media B Even if the medium M is loaded A can be restored to good condition.

[0062] If the medium conveying device stops the feed roller and returns only the other overlapped media to the mounting table while leaving the media in contact with the feed roller in place, a friction load will also occur between the media in contact with the feed roller and the other overlapped media. On the other hand, the medium conveying device 100 of this embodiment causes the feed roller 112 to follow the brake roller 113, and returns all of the overlapped media M A Therefore, no friction load is generated between the medium in contact with the feeding roller 112 and other overlapped fed media, and instead, the fed medium M AA friction load occurs between the medium, such as paper, and the mounting surface 103a of the mounting table 103. However, the mounting table 103 is made of a resin material, and the friction load that occurs between the medium, such as paper, and the mounting surface 103a is much smaller (about 2 / 7) than the friction load that occurs between two media. Therefore, the medium conveying device 100 can return the medium to the mounting table 103 with less force than when returning only the other overlapped media to the mounting table while leaving the medium in contact with the feed roller in its position.

[0063] Furthermore, when multiple media of different sizes are placed on the placement table 103, the smaller sized media may become buried under the larger sized media, and the media may be transported without their leading edges being aligned. In particular, when a medium placed on the upper side precedes a medium placed on the lower side, the upper medium may pass between the feed roller 112 and the brake roller 113 before the lower medium, potentially resulting in a double feed. The medium transport device 100 drives the brake roller 113 located on the upper side to return the double-fed media, returning the upper medium to the placement table 103 more strongly than the lower medium. This allows the medium transport device 100 to reduce misalignment of the leading edges of the media returned to the placement table 103, thereby reducing the possibility of a double feed occurring when the media are re-fed.

[0064] In addition, in the medium conveying device 100, the multi-fed medium M A A limit value is also set for the torque applied to the brake roller 113 when returning the media to the mounting table 103. Therefore, for example, if the weight of the media remaining on the mounting table 103 is too great and the multiple-fed media cannot be returned to the mounting table 103 in a satisfactory manner, the medium conveying device 100 will not forcibly restore the media. This allows the medium conveying device 100 to prevent damage to the media.

[0065] Fig. 9 is a schematic diagram for explaining the first center sensor 115, the first side sensor 116, the second side sensor 117, and the second center sensor 120. Fig. 9 is a schematic diagram of the lower housing 101 viewed from above with the upper housing 102 removed.

[0066] 9, the first center sensor 115 is disposed downstream of the ultrasonic sensor 114 in the medium transport direction A1 and upstream of the first transport roller 118 and the second transport roller 119, approximately in the center in the direction A8 perpendicular to the medium transport direction. The first center sensor 115 includes a first center light emitter 115a and a first center light receiver 115b provided on one side (the lower housing 101) of the medium transport path. The first center sensor 115 also includes a first center reflecting member (not shown), such as a mirror, provided in a position (the upper housing 102) opposite the first center light emitter 115a and the first center light receiver 115b across the medium transport path. The first center light emitter 115a emits light toward the medium transport path. On the other hand, the first center light receiver 115b receives the light emitted by the first center light emitter 115a and reflected by the first center reflecting member, and generates and outputs a first center signal, which is an electrical signal corresponding to the intensity of the received light.

[0067] The first side sensor 116 and the second side sensor 117 are disposed at approximately the same position as the first center sensor 115 in the media transport direction A1 and outside the first center sensor 115 in the direction A8 perpendicular to the media transport direction. The first and second side sensors 116 and 117 each include a first and second side light emitter 116a and 117a and a first and second side light receiver 116b and 117b, respectively, provided on one side (lower housing 101) of the media transport path. The first and second side sensors 116 and 117 also include first and second side reflectors (not shown), such as mirrors, provided on the upper housing 102 opposite the side light emitter and side light receiver across the media transport path. The first and second side light emitters 116a and 117a emit light toward the media transport path. On the other hand, the first and second side photoreceivers 116b and 117b receive light that is irradiated by the first and second side light emitters 116a and 117a and reflected by the first and second side reflecting members, and generate and output first and second side signals, which are electrical signals corresponding to the intensity of the received light.

[0068] The second center sensor 120 is disposed downstream of the first transport roller 118 and the second transport roller 119 in the medium transport direction A1 and upstream of the imaging device 121, approximately in the center in the direction A8 perpendicular to the medium transport direction. The second center sensor 120 includes a second center light emitter 120a and a second center light receiver 120b provided on one side (the lower housing 101) of the medium transport path. The second center sensor 120 also includes a second center reflecting member (not shown) such as a mirror provided in a position (the upper housing 102) opposite the second center light emitter 120a and the second center light receiver 120b across the medium transport path. The second center light emitter 120a emits light toward the medium transport path. On the other hand, the second center light receiver 120b receives the light emitted by the second center light emitter 120a and reflected by the second center reflecting member, and generates and outputs a second center signal, which is an electrical signal corresponding to the intensity of the received light.

[0069] When a medium is present at each of the first center sensor 115, first side sensor 116, second side sensor 117, and second center sensor 120, the light emitted by the light emitter of each sensor is blocked by the medium. Therefore, the signal value generated by each sensor changes depending on whether a medium is present or not at the sensor's position. This allows first center sensor 115, first side sensor 116, second side sensor 117, and second center sensor 120 to detect whether a medium is present at that position. The light emitter and light receiver of each sensor are positioned opposite each other across the transport path, and the reflective member may be omitted.

[0070] The first center sensor 115, the first side sensor 116, and the second side sensor 117 are used to detect skew, which is the skew of the medium. The closer the first side sensor 116 and the second side sensor 117 are positioned to the center, the more easily skew can be detected for smaller-sized media. However, the closer the first side sensor 116 and the second side sensor 117 are positioned to the center, the later the timing at which the leading edge of a skewed medium passes the first side sensor 116 or the second side sensor 117, and the later the timing of skew detection. Furthermore, the closer the first side sensor 116 and the second side sensor 117 are positioned to the center, the shorter the distance between the first side sensor 116 or the second side sensor 117 and the first center sensor 115, and the lower the accuracy of skew detection. On the other hand, the closer the first side sensor 116 and the second side sensor 117 are positioned to the outside, the earlier the timing of skew detection and the higher the accuracy of skew detection, but the less likely it is that skew for smaller-sized media will be detected.

[0071] Generally, in media transport devices that support paper sizes larger than A4, skew of the media is likely to occur when A5-size paper is transported vertically or when A6-size paper is transported horizontally. Therefore, it is preferable that the distance D from the center of the media transport path to the first side sensor 116 and the second side sensor 117 in the direction A8 perpendicular to the media transport direction be equal to or less than half the length of the A5 size paper in the short direction and the A6 size paper in the long direction (148 mm). For example, taking into account a margin, it is preferable that the distance D from the center of the media transport path to the first side sensor 116 and the second side sensor 117 in the direction A8 perpendicular to the media transport direction be equal to or greater than 25 mm and equal to or less than 75 mm.

[0072] In this way, the first center sensor 115, the first side sensor 116, and the second side sensor 117 are disposed downstream of the feed roller 112 and upstream of the first transport roller 118 and the second transport roller 119. This allows the medium transport device 100 to detect skew of the medium before the medium reaches the positions of the first transport roller 118 and the second transport roller 119, and to correct the skew of the medium using the feed roller 112. Furthermore, the first center sensor 115, the first side sensor 116, and the second side sensor 117 are disposed downstream of the feed roller 112 in the medium transport direction A1, side by side at an interval in the direction A8 perpendicular to the medium transport direction. Two of the first center sensor 115, the first side sensor 116, and the second side sensor 117 are an example of two sensors disposed downstream of the feed roller 112 in the medium transport direction A1, side by side at an interval in the direction A8 perpendicular to the medium transport direction.

[0073] FIG. 10 is a block diagram showing a schematic configuration of the medium conveying device 100. As shown in FIG.

[0074] In addition to the above-described configuration, the medium conveying device 100 further includes a drive device 141, an interface device 142, a storage device 150, a CPU (Central Processing Unit) 160, a processing circuit 170, and the like.

[0075] The driving device 141 is an example of a driving force generating unit, and generates a first driving force and a second driving force. The driving device 141 has a plurality of motors including a first motor 131 and a second motor, and rotates the feed roller 112, the brake roller 113, and the first to fourth transport rollers 118, 119, 122, and 123 in response to a control signal from the CPU 160 to transport the medium.

[0076] 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 personal digital assistant, etc.) to transmit and receive input images and various information. Instead of the interface device 142, a communication unit having an antenna for transmitting and receiving wireless signals and a wireless communication interface device for transmitting and receiving signals via 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).

[0077] The storage device 150 includes a memory device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or 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 into 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 CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or the like.

[0078] CPU 160 operates based on a program stored in advance in storage device 150. Note that a DSP (digital signal processor), an LSI (large scale integration), or the like may be used instead of CPU 160. Also, an ASIC (application specific integrated circuit), an FPGA (field-programmable gate array), or the like may be used instead of CPU 160.

[0079] The CPU 160 is connected to the operation device 105, display device 106, medium detection sensor 111, ultrasonic sensor 114, first center sensor 115, first side sensor 116, second side sensor 117, second center sensor 120, imaging device 121, drive device 141, interface device 142, storage device 150, processing circuit 170, etc., and controls each of these components. The CPU 160 controls the drive of the drive device 141 and the imaging of the imaging device 121, acquires input images, and transmits them to the information processing device via the interface device 142. The CPU 160 also detects skew of the medium being fed based on a signal generated by the first side sensor 116 or the second side sensor 117, and corrects the skew of the medium based on the detection result. The CPU 160 also detects double feed of the medium being fed based on a signal generated by the ultrasonic sensor 114, and recovers the medium if double feed is detected.

[0080] The processing circuit 170 performs predetermined image processing on the image captured by the imaging device 121, and stores the processed image in the storage device 150. Note that instead of the processing circuit 170, a DSP, an LSI, an ASIC, an FPGA, or the like may be used.

[0081] FIG. 11 is a diagram showing a schematic configuration of the storage device 150 and the CPU 160. As shown in FIG.

[0082] 11, the storage device 150 stores a control program 151, an image acquisition program 152, a multifeed detection program 153, a skew detection program 154, and the like. Each of these programs is a functional module implemented by software running on a processor. The CPU 160 reads each program stored in the storage device 150 and operates in accordance with the read program. As a result, the CPU 160 functions as the control unit 161, the image acquisition unit 162, the multifeed detection unit 163, and the skew detection unit 164.

[0083] FIG. 12 is a flowchart showing an example of the operation of the medium reading process of the medium conveying device 100.

[0084] 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. 12. The operation flow described below is executed mainly by the CPU 160 in cooperation with each element of the medium conveying device 100 based on a program stored in advance in the storage device 150. The operation flow shown in Fig. 12 is executed periodically.

[0085] First, the control unit 161 waits until a user inputs an instruction to read a medium using the operation device 105 and an operation signal instructing to read a medium is received from the operation device 105 (step S101).

[0086] Next, control unit 161 acquires a medium detection signal from medium detection sensor 111, and determines whether or not a medium is placed on placement table 103 based on the acquired first medium detection signal (step S102).

[0087] If no medium is placed on the placement table 103, the control unit 161 returns the process to step S101 and waits until a new operation signal is received from the operation device 105.

[0088] On the other hand, when a medium is placed on the placement table 103, the control unit 161 drives the drive device 141 to rotate the feed roller 112, the brake roller 113, and the first to fourth transport rollers 118, 119, 122, and 123 to feed and transport the medium (step S103). The control unit 161 controls the first motor 131 and the second motor to generate a first drive force, and controls the feed roller 112 to rotate in the medium feed direction A2 and the brake roller 113 to rotate in the direction A3 opposite to the medium feed direction. That is, when feeding the medium, the control unit 161 controls the first transmission mechanism to transmit the first drive force to the brake roller 113.

[0089] Next, the control unit 161 determines whether the multi-feed flag is ON (step S104). The multi-feed flag is set to OFF when reading of each medium starts, and is set to ON when the multi-feed detection unit 163 determines that a multi-feed has occurred in the multi-feed detection process described later.

[0090] If the multiple feed flag is OFF, the image acquisition unit 162 causes the imaging device 121 to capture an image of the transported medium and acquires an input image (step S105).

[0091] The image acquisition unit 162 acquires a second center signal from the second center sensor 120 and determines whether a medium is present at the position of the second center sensor 120 based on the acquired second center signal. When the signal value of the second center signal changes from a value indicating the absence of a medium to a value indicating the presence of a medium, the image acquisition unit 162 determines that the leading edge of the medium has passed the position of the second center sensor 120 and causes the imaging device 121 to start imaging. On the other hand, when the signal value of the second center signal changes from a value indicating the presence of a medium to a value indicating the absence of a medium, the image acquisition unit 162 determines that the trailing edge of the medium has passed the position of the second center sensor 120. The image acquisition unit 162 causes the imaging device 121 to end imaging a predetermined period after determining that the trailing edge of the medium has passed the position of the second center sensor 120.

[0092] Next, the image acquisition unit 162 transmits the input image to the information processing device via the interface device 142 (step S106). Note that if the image acquisition unit 162 is not connected to an information processing device, the image acquisition unit 162 stores the input image in the storage device 150.

[0093] Next, control unit 161 determines whether or not a medium remains on mounting table 103 based on the medium detection signal obtained from medium detection sensor 111 (step S107). If a medium remains on mounting table 103, control unit 161 returns the process to step S104 and repeats the processes of steps S104 to S107.

[0094] On the other hand, if there are no media remaining on the mounting table 103, the control unit 161 stops the driving device 141 (step S108), and ends the series of steps.

[0095] On the other hand, if the double feed flag is ON in step S104, the control unit 161 stops the drive device 141 to stop feeding of the medium and sets the double feed flag to OFF as an abnormality process (step S109). Note that the control unit 161 may notify the user that an abnormality has occurred by a speaker, LED, etc. (not shown).

[0096] Next, the control unit 161 drives the drive device 141 to rotate the feed roller 112 and the brake roller 113, thereby transporting the fed medium toward the mounting table 103 (step S110). The control unit 161 controls the first motor 131 and the second motor to generate a second drive force, thereby controlling the feed roller 112 to rotate in the direction opposite to the medium feeding direction A2 and the brake roller 113 to rotate in the direction opposite to the medium feeding direction A3. As a result, the control unit 161 transports the fed medium back toward the mounting table 103 so that it returns to the mounting table 103.

[0097] That is, when a double feed of media is detected, the control unit 161 controls the second transmission mechanism to transmit the second driving force to the brake roller 113, and controls the feed roller 112 to rotate in the opposite direction to the medium feed direction A2, following the brake roller 113. As described above, the control unit 161 controls the rotation shafts (second shaft 135b and third shaft 135c) of each feed roller 112 to rotate at a rotation speed faster than the rotation speed of the outer circumferential surfaces 136a, b of each feed roller 112, which rotate following the brake roller 113.

[0098] Next, the control unit 161 rotates the feed roller 112 and the brake roller 113 for a certain time (e.g., 3 seconds) and then stops the drive device 141, thereby returning the medium to the mounting table 103 (step S108), and the series of steps ends. Note that the control unit 161 may rotate the feed roller 112 and the brake roller 113 and then stop the drive device 141 until the multi-feed detection unit 163 determines that a multi-feed has not occurred (has been resolved) in the multi-feed detection process. Furthermore, after returning the medium to the mounting table 103, the control unit 161 may return the process to step S103 and automatically re-feed the medium. This eliminates the need for the user to re-feed the medium, and the control unit 161 can improve user convenience.

[0099] FIG. 13 is a flowchart showing an example of the operation of the double feed detection process.

[0100] 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 Figure 13. The flow of the operation described below is executed mainly by the CPU 160 in cooperation with each element of the medium conveying device 100 based on a program stored in advance in the storage device 150. The flowchart shown in Figure 13 is executed periodically while the medium is being conveyed. Note that the flowchart shown in Figure 13 may be executed only during the period from when the leading edge of the medium passes the first center sensor 115 until it passes the second center sensor 120.

[0101] First, the double feed detector 163 acquires an ultrasonic signal from the ultrasonic sensor 114 (step S201).

[0102] Next, the multifeed detection unit 163 determines whether the signal value of the acquired ultrasonic signal is less than the multifeed detection threshold value (step S202).

[0103] FIG. 14 is a schematic diagram for explaining the characteristics of an ultrasonic signal.

[0104] In graph 1400 of FIG. 14, solid line 1401 shows the characteristics of the ultrasonic signal when a single sheet of paper is being conveyed as the medium, and dotted line 1402 shows the characteristics of the ultrasonic signal when a double feed of sheets has occurred. The horizontal axis of graph 1400 represents time, and the vertical axis represents the signal value of the ultrasonic signal. Due to the occurrence of a double feed, the signal value of the ultrasonic signal indicated by dotted line 1402 drops in section 1403. The multifeed detection threshold is set to a value between the signal value S1 of the ultrasonic signal when a single sheet of paper is being conveyed and the signal value S2 of the ultrasonic signal when a double feed of sheets has occurred. The multifeed detection unit 163 can determine whether a double feed of media has occurred by determining whether the signal value of the ultrasonic signal is less than the multifeed detection threshold.

[0105] If the signal value of the ultrasonic signal is equal to or greater than the multifeed determination threshold, the multifeed detection unit 163 determines that a multifeed has not occurred (step S203), and ends the series of steps.

[0106] On the other hand, if the signal value of the ultrasonic signal is less than the multifeed determination threshold, the multifeed detection unit 163 determines that a multifeed has occurred (step S204). Next, the multifeed detection unit 163 sets the multifeed flag to ON (step S205), and ends the series of steps. In this way, the multifeed detection unit 163 detects a multifeed of the fed media based on the ultrasonic signal generated by the ultrasonic sensor 114.

[0107] FIG. 15 is a flowchart showing an example of the operation of the skew detection process.

[0108] An example of the operation of the medium reading process of medium conveying device 100 will be described below with reference to the flowchart shown in Fig. 15. The flow of the operation described below is executed mainly by CPU 160 in cooperation with each element of medium conveying device 100 based on a program stored in advance in storage device 150. The flowchart shown in Fig. 15 is executed periodically.

[0109] First, the skew detector 164 acquires a first center signal, a first side signal, and a second side signal from the first center sensor 115, the first side sensor 116, and the second side sensor 117, respectively (step S301).

[0110] Next, the skew detection unit 164 detects the passing times when the leading edge of the medium passes the first center sensor 115, the first side sensor 116, and the second side sensor 117, respectively, based on the first center signal, the first side signal, and the second side signal (step S302).

[0111] The skew detection unit 164 detects the time when the signal value of each first center signal acquired to date changes from a value indicating the absence of a medium to a value indicating the presence of a medium as the passage time of the first center sensor 115. Similarly, the skew detection unit 164 detects the time when the signal value of each first side signal acquired to date changes from a value indicating the absence of a medium to a value indicating the presence of a medium as the passage time of the first side sensor 116. Similarly, the skew detection unit 164 detects the time when the signal value of each second side signal acquired to date changes from a value indicating the absence of a medium to a value indicating the presence of a medium as the passage time of the second side sensor 117.

[0112] Next, the skew detection unit 164 determines whether the skew flag is OFF (step S303). The skew flag is set to OFF when reading for each medium starts, and is set to ON when it is determined that skew has occurred in the skew detection process.

[0113] If the skew flag is OFF, the skew detection unit 164 determines whether skew of the medium has occurred based on the passage times detected in step S302 (step S304). The skew detection unit 164 determines that skew has occurred if the leading edge of the medium does not pass the first center sensor 115 within a predetermined time from the earlier of the passage time of the first side sensor 116 or the second side sensor 117. The predetermined time is set, based on prior experiments, to a value between the difference between the passage time of the first or second side sensor 116 or 117 and the passage time of the first center sensor 115 when the medium collides with a side wall of the transport path at an angle and the difference between the passage times when the medium does not collide with a side wall of the transport path. The predetermined time is set to, for example, one second. Note that the predetermined time may also be set to 0. In this case, the skew detection unit 164 determines that skew has occurred if the medium is transported at even a slight angle, and the control unit 161 corrects the skew of the medium.

[0114] In this way, the skew detection unit 164 detects the skew of the medium being fed based on the first center signal obtained from the first center sensor 115, the first side signal obtained from the first side sensor 116, and the second side signal obtained from the second side sensor 117.

[0115] If the skew detection unit 164 determines that no skew has occurred in the medium, it determines whether the medium is being transported normally based on the detected passage times (step S305). If the leading edge of the medium passes the first center sensor 115 within a predetermined time from the earlier of the first side sensor 116 and the second side sensor 117, the skew detection unit 164 determines that the medium is being transported normally. In this case, the skew detection unit 164 ends the series of steps. On the other hand, if the predetermined time has not yet passed since the earlier of the first side sensor 116 and the second side sensor 117 and the leading edge of the medium has not passed the first center sensor 115, the skew detection unit 164 returns the process to step S301. In other words, in this case, the skew detection unit 164 has not yet determined that skew has occurred or that the medium is being transported normally.

[0116] On the other hand, if the skew detection unit 164 determines that a skew of the medium has occurred, that is, if the skew of the medium has been detected, the skew detection unit 164 sets the skew flag to ON (step S306).

[0117] Next, the control unit 161 starts correcting the skew of the medium (step S307) and proceeds to step S301. The control unit 161 corrects the skew of the medium by making the circumferential velocities of the multiple feed rollers 112a, b different from each other. The control unit 161 changes the circumferential speed of each feed roller 112 so that the circumferential speed of the feed roller 112 arranged on the side where the progress of the medium is delayed is faster (higher) than the circumferential speed of the feed roller 112 arranged on the side where the progress of the medium is leading in the direction A8 perpendicular to the medium transport direction. The control unit 161 increases (increases) the circumferential speed of the feed roller 112 arranged on the side where the progress of the medium is lagging and / or decreases (decreases) the circumferential speed of the feed roller 112 arranged on the side where the progress of the medium is leading. The control unit 161 sets the circumferential speeds of the feed roller 112 arranged on the side where the progress of the medium is lagging, for example, so that the circumferential speed is three times or more and ten times or less than the circumferential speed of the feed roller 112 arranged on the side where the progress of the medium is leading.

[0118] Fig. 16 is a schematic diagram for explaining the relationship between the tilt of the medium and the time at which each sensor passes. Similar to Fig. 9, Fig. 16 is a schematic diagram of lower housing 101 viewed from above with upper housing 102 removed.

[0119] 16, when medium M is fed at an angle toward second side sensor 117, the leading edge of medium M passes first side sensor 116 and then first center sensor 115. In this case, the greater the angle of medium M, the longer the time it takes for medium M to pass first side sensor 116 and then first center sensor 115.

[0120] Therefore, if the leading edge of the medium does not pass first center sensor 115 within a predetermined time from the time the medium passes first side sensor 116, control unit 161 determines that the medium is being fed at an angle toward second side sensor 117. In this case, control unit 161 changes the circumferential speed of each feed roller 112 so that the circumferential speed of feed roller 112b arranged on the second side sensor 117 side is faster (higher) than the circumferential speed of feed roller 112a arranged on the first side sensor 116 side. This causes the medium to rotate in the direction A9 of first side sensor 116, correcting the skew of the medium.

[0121] Conversely, if the leading edge of the medium does not pass first center sensor 115 within a predetermined time from the time the medium passes second side sensor 117, control unit 161 determines that the medium is being fed at an angle toward first side sensor 116. In this case, control unit 161 changes the circumferential speed of each feed roller 112 so that the circumferential speed of feed roller 112a arranged on the first side sensor 116 side is faster (higher) than the circumferential speed of feed roller 112b arranged on the second side sensor 117 side. This causes the medium to rotate toward second side sensor 117, correcting the skew of the medium.

[0122] As described above, each feed roller 112a, b is configured to rotate independently by a separate first motor 131 and second motor to feed the medium. Meanwhile, each brake roller 113a, b is provided with a separate second torque limiter 139a, b, so each brake roller 113a, b rotates independently in accordance with the feed roller 112a, b. If each brake roller 113a, b were not independently rotated, the conveyance load (medium separation force) applied to the medium by each brake roller 113a, b in the direction A3 opposite the medium feeding direction would be approximately the same, even if the circumferential speeds of the feed rollers 112 are different. Therefore, the force rotating the medium toward the side sensor on the feed roller 112 with the slower circumferential speed (direction A9 in the example of FIG. 16 ) is reduced, making it difficult to correct the skew of the medium.

[0123] On the other hand, when the brake rollers 113a, b are driven to rotate independently, the transport load applied to the medium by each brake roller 113a, b in the direction A3 opposite the medium feed direction varies depending on the circumferential speed of the feed rollers 112a, b facing each brake roller 113a, b. That is, the transport load applied to the medium in the direction A3 opposite the medium feed direction by the brake roller 113 facing the feed roller 112 with the lower circumferential speed is smaller than the transport load applied to the medium in the direction A3 opposite the medium feed direction by the other brake roller 113. Therefore, the force that rotates the medium toward the side sensor on the side of the feed roller 112 with the lower circumferential speed (direction A9 in the example of FIG. 16) increases, making it easier to correct the skew of the medium.

[0124] The control unit 161 may set the circumferential speeds of the feed rollers 112 so that the difference in circumferential speed between them increases as the time from the passage of the first side sensor 116 or the passage of the second side sensor 117 to the passage of the first center sensor 115 increases. This allows the control unit 161 to correct the skew of the medium in a shorter time. The control unit 161 may also set the circumferential speed of the feed roller 112 arranged on the leading side to 0. This allows the leading side portion of the medium to remain in its position in the direction A8 perpendicular to the medium transport direction while the lagging side portion of the medium advances, thereby more reliably correcting the skew of the medium. Alternatively, the control unit 161 may set the circumferential speeds of both the multiple feed rollers 112a and 112b to values ​​greater than 0 but different from each other. This allows the control unit 161 to transport the medium while correcting the skew of the medium, thereby transporting the medium in a shorter time.

[0125] On the other hand, if the skew flag is ON in step S303, the control unit 161 determines whether the correction of the skew of the medium was successful based on the passage times detected in step S302 (step S308). The control unit 161 determines that the correction of the skew of the medium was successful if the leading edge of the medium passes the first center sensor 115 or the side sensor located on the side where the progress of the medium is delayed within a second predetermined time after starting the skew correction in step S307. The second predetermined time is set to, for example, one second.

[0126] If it is determined that the correction of the skew of the medium has been successful, the control unit 161 waits until a specific time has elapsed (step S309).

[0127] If the peripheral speed of the feeding roller 112 arranged on the leading side is set to a value greater than 0, the leading side medium portion also advances during the skew correction of the medium. The leading side medium portion advances at a peripheral speed V of the feeding roller 112 arranged on the leading side during the time T from when the skew correction starts until the lagging side medium portion passes the first center sensor 115, etc.A multiplied by the time T (V A × T). The difference between the delayed medium portion and the advanced medium portion is the peripheral speed V B The peripheral speed V of the feeding roller 112 arranged on the leading side from A The velocity (V B -V A ) and shrinks.

[0128] Therefore, even after the first center sensor 115 or the like detects the medium, the control unit 161 continues to correct the skew of the medium by rotating each feed roller 112 at the set peripheral speed until a specific time calculated by the following equation (1) has elapsed. (Specific time)=(V A ×T) / (V B -V A ) (1) This allows the control unit 161 to make the lagging medium portion catch up with the leading medium portion. Note that the process of step S309 may be omitted.

[0129] Next, the control unit 161 returns the peripheral speed of each feeding roller 112 to the original peripheral speed, completes the correction of the skew of the medium (step S310), and ends the series of steps.

[0130] On the other hand, if it is determined in step S308 that the correction of the medium skew has not been successful, the control unit 161 determines whether a second predetermined time has elapsed since the start of the correction of the medium skew (step S311). If the second predetermined time has not yet elapsed since the start of the correction of the medium skew, the control unit 161 proceeds to step S301.

[0131] On the other hand, if the second predetermined time has elapsed since the start of the correction of the skew of the medium, the control unit 161 determines that the correction of the skew of the medium has failed (step S312).

[0132] Next, the control unit 161 changes the imaging range of the imaging device 121 in the medium conveyance direction A1 (step S313), and ends the series of steps.

[0133] As described above, if no skew of the medium occurs, the imaging device 121 starts imaging when the leading edge of the medium passes the position of the second center sensor 120, and ends imaging a predetermined period of time after the trailing edge of the medium passes the position of the second center sensor 120. However, if skew of the medium occurs, the leading portion of the medium may have reached the position of the imaging device 121 when the leading edge of the medium passes the position of the second center sensor 120. Also, the lagging portion of the medium may remain at the position of the imaging device 121 when the predetermined period of time has passed since the trailing edge of the medium passed the position of the second center sensor 120.

[0134] Therefore, the control unit 161 increases the imaging range of the imaging device 121 in the medium conveyance direction A1 compared to the imaging range when no skew of the medium occurs. For example, the control unit 161 causes the imaging device 121 to start imaging immediately after determining that correction of the medium skew has failed, before the leading edge of the medium passes the position of the second center sensor 120. The control unit 161 also causes the imaging device 121 to end imaging after a second predetermined period, which is longer than the predetermined period, has elapsed since the trailing edge of the medium passed the position of the second center sensor 120. This allows the control unit 161 to cause the imaging device 121 to image the medium so that the entire skewed medium is included in the input image.

[0135] Note that medium conveying device 100 may omit first center sensor 115 and detect medium skew using two sensors, first side sensor 116 and second side sensor 117. In this case, in step S304, skew detection unit 164 detects medium skew if one of first side sensor 116 and second side sensor 117 detects the medium but the other sensor does not detect the medium within a predetermined time after the other sensor detects the medium. Also, in step S305, skew detection unit 164 determines that the medium is being conveyed normally if one sensor detects the medium within a predetermined time after the other sensor detects the medium.

[0136] Furthermore, in step S308, if the other sensor detects the medium within a second predetermined time after starting skew correction, the control unit 161 determines that the correction of the medium skew has been successful. Furthermore, in steps S309 and S310, the control unit 161 continues to rotate each feed roller 112 at the set peripheral speed to correct the medium skew until a specific time has elapsed after the other sensor detects the medium. Furthermore, in steps S311 and S312, if the other sensor does not detect the medium within a second predetermined time after starting skew correction, the control unit 161 determines that the correction of the medium skew has failed.

[0137] Alternatively, the medium conveying device 100 may use multiple encoders to detect the skew of the medium instead of the first side sensor 116 and the second side sensor 117. In this case, the medium conveying device 100 has multiple encoders arranged between the feed roller 112 and the first conveying roller 118 in the medium conveying direction A1 and spaced apart in a direction A8 perpendicular to the medium conveying direction. Each encoder has a disk formed with multiple slits (light-transmitting holes) and arranged to rotate in accordance with the conveyed medium, and a light emitter and a light receiver arranged opposite each other across the disk. Each light receiver detects the movement distance of the medium based on the number of times the light emitter and light receiver alternate between a state where there is a slit between them and a state where there is no slit and the light is blocked by the disk at regular intervals.

[0138] The skew detection unit 164 detects medium movement based on the movement distance detected by each encoder, and detects medium skew based on the difference in timing when each encoder first detected medium movement. Alternatively, the skew detection unit 164 may detect medium skew based on the difference in movement distance detected by each encoder. Furthermore, the skew detection unit 164 determines whether or not the correction of medium skew was successful based on the difference in timing when each encoder first detected medium movement or the difference in movement distance detected by each encoder, and ends the skew correction.

[0139] As described above in detail, in the medium conveying device 100, separate second torque limiters 139a, b are provided for each brake roller 113 facing each feed roller 112, and the medium conveying device 100 corrects medium skew by varying the peripheral speeds of the multiple feed rollers 112. This allows the medium conveying device 100 to reduce the force applied to the medium in the direction A3 opposite the medium feed direction by the brake roller 113 facing the feed roller 112 with the lower peripheral speed, making it possible to more appropriately correct medium skew.

[0140] Furthermore, when a double feed of media occurs, the medium conveying device 100 increases the limit value of the torque applied to the brake roller 113 from that when feeding the media, and rotates the feed roller 112 in response to the brake roller 113. As a result, when a double feed of media occurs, the medium conveying device 100 returns all of the media fed between the brake roller 113 and the feed roller 112 to the mounting table 103, making it possible to more appropriately recover the media.

[0141] 17 is a schematic diagram for explaining a drive mechanism of a medium transport device according to another embodiment, as viewed from the upstream side in the medium transport direction A1.

[0142] As shown in FIG. 17, the drive mechanism of the medium conveying device includes, instead of the brake roller 113 and the drive mechanism for the brake roller 113, brake rollers 213a, b, 14th to 17th gears 233n-q, 6th to 8th shafts 235f-h, a first torque limiter 237, a second torque limiter 239, etc.

[0143] The fourteenth gear 233n is connected to a third motor (not shown) via a drive mechanism including a first electromagnetic clutch and is engaged with a fifteenth gear 233o. The fifteenth gear 233o is attached to one end of a sixth shaft 235f, and the brake roller 213a is attached to the other end of the sixth shaft 235f via a first torque limiter 237 so as to rotate in accordance with the rotation of the sixth shaft 235f. Meanwhile, the sixteenth gear 233p is connected to a fourth motor (not shown) via a drive mechanism including a second electromagnetic clutch and is engaged with a seventeenth gear 233q. The seventeenth gear 233q is attached to one end of a seventh shaft 235g, and the brake roller 213b is attached to the other end of the seventh shaft 235g via a second torque limiter 239 so as to rotate in accordance with the rotation of the seventh shaft 235g.

[0144] The brake roller 213a and the brake roller 213b are connected via the eighth shaft 235h, without the intervention of the first torque limiter 237 and the second torque limiter 239, so that each brake roller rotates in accordance with the rotation of the other brake roller. The torque limit value of the first torque limiter 237 is a first limit value, and the torque limit value of the second torque limiter 239 is a second limit value.

[0145] The third motor generates a first driving force, and the fourth motor generates a second driving force. When the control unit 161 causes the third motor to generate the first driving force, it turns off the second electromagnetic clutch to interrupt the transmission of driving force between the fourth motor and the sixteenth gear 233p. As a result, the first driving force is transmitted to the brake rollers 213a and 213b via the first torque limiter 237 but not via the second torque limiter 239, and the brake rollers 213a and 213b rotate in the direction A3 opposite to the medium feeding direction. On the other hand, when the control unit 161 causes the fourth motor to generate the second driving force, it turns off the first electromagnetic clutch to interrupt the transmission of driving force between the third motor and the fourteenth gear 233n. As a result, the second driving force is transmitted to the brake rollers 213a and 213b via the second torque limiter 239 and not via the first torque limiter 237, and the brake rollers 213a and 213b rotate in the direction A3 opposite to the medium feeding direction.

[0146] As described above in detail, the media conveying device is now able to more appropriately correct media skew and more appropriately recover media in the event of multiple media feeds, even when planetary gears are not used to switch the transmission mechanism.

[0147] 18 is a diagram showing a schematic configuration of a processing circuit 270 in a medium conveying device according to yet another embodiment. The processing circuit 270 is used in place of the processing circuit 170 of the medium conveying device 100, and executes the medium reading process, the double feed detection process, and the skew detection process in place of the CPU 160. The processing circuit 270 includes a control circuit 271, an image acquisition circuit 272, a double feed detection circuit 273, and a skew detection circuit 274. Note that each of these components may be configured as an independent integrated circuit, microprocessor, firmware, or the like.

[0148] The control circuit 271 is an example of a control unit, and has the same functions as the control unit 161. The control circuit 271 receives an operation signal from the operation device 105, a medium detection signal from the medium detection sensor 111, a detection result of double feed of media from the double feed detection circuit 273, and a detection result of skew of media from the skew detection circuit 274. The control circuit 271 drives the drive device 141 in accordance with the received signals, and corrects skew of media if detected. Furthermore, if double feed of media is detected, the control circuit 271 transmits a second drive force to the brake roller 113 via the second transmission mechanism, and controls the feed roller 112 to rotate in accordance with the brake roller 113.

[0149] The image acquisition circuit 272 is an example of an image acquisition unit, and has the same function as the image acquisition unit 162. The image acquisition circuit 272 receives an input image from the imaging device 121, stores it in the storage device 150, and transmits it to the information processing device via the interface device 142.

[0150] The multi-feed detection circuit 273 is an example of a multi-feed detection unit, and has the same function as the multi-feed detection unit 163. The multi-feed detection circuit 273 receives an ultrasonic signal from the ultrasonic sensor 114, detects multi-feeding of media based on the ultrasonic signal, and outputs the detection result to the control circuit 271.

[0151] The skew detection circuit 274 is an example of a skew detection unit, and has the same function as the skew detection unit 164. The skew detection circuit 274 receives a first center signal from the first center sensor 115, a first side signal from the first side sensor 116, and a second side signal from the second side sensor 117. The skew detection circuit 274 detects the skew of the medium based on the received signals and outputs the detection result to the control circuit 271.

[0152] As described above in detail, even when using the processing circuit 270, the medium conveying device is now able to more appropriately correct medium skew and more appropriately restore the medium in the event of multiple media feeds. [Explanation of symbols]

[0153] 100 medium conveying device, 112 feeding roller, 113 brake roller, 115 first center sensor, 116 first side sensor, 117 second side sensor, 121 imaging device, 131 first motor, 131b belt, 132 pulley, 133a-m first to thirteenth gears, 134a sun gear, 134b planetary gear, 135a-e first to fifth shafts, 136a, b outer circumferential surface, 136c, d one-way clutch, 137 first torque limiter, 139a, b second torque limiter, 161 control unit, 163 double feed detection unit, 164 skew detection unit

Claims

1. a plurality of feeding rollers arranged at intervals in a direction perpendicular to the medium transport direction, each of which rotates independently to feed the medium; a plurality of brake rollers disposed opposite the plurality of feed rollers, respectively; a plurality of torque limiters provided separately on the plurality of brake rollers so that the plurality of brake rollers can be independently rotated in accordance with the plurality of feed rollers; a skew detection unit that detects skew of the medium being fed; a control unit that, when the skew of the medium is detected by the skew detection unit, corrects the skew of the medium by making the peripheral speed of the feed roller, of the plurality of feed rollers, that is arranged on the side where the advance of the medium is ahead greater than 0 and lower than the peripheral speed when the skew of the medium is not detected; the control unit executes different processes depending on whether the correction of the skew of the medium is successful or unsuccessful. A medium transport device characterized by:

2. 2. The medium transport device of claim 1, wherein when the skew detection unit detects skew in the medium, the control unit increases the peripheral speed of the feed roller among the plurality of feed rollers that is located on the side where the progress of the medium is delayed compared to the peripheral speed when skew in the medium is not detected.

3. 3. The medium transport device of claim 1, wherein when the skew detection unit detects skew of the medium, the control unit sets the peripheral speeds of the multiple feed rollers so that the greater the inclination of the medium, the greater the difference in peripheral speed between the multiple feed rollers.

4. further comprising an imaging unit that images the medium; A medium conveying device as described in any one of claims 1 to 3, wherein, when the control unit fails to correct the medium skew, the imaging range in the medium conveying direction by the imaging unit is made larger than the imaging range when no medium skew occurs.

5. The method further includes two sensors disposed at a distance from each other in a direction perpendicular to the medium transport direction downstream of the plurality of feed rollers in the medium transport direction, the skew detection unit detects a skew of the medium when one of the two sensors detects the medium but the other sensor does not detect the medium within a predetermined time; A medium transport device as described in any one of claims 1 to 4, wherein when the skew detection unit detects skew of the medium, the control unit sets the circumferential speeds of the multiple feed rollers to values ​​greater than 0 and different from each other, and rotates the multiple feed rollers at the set circumferential speeds until a specific time has elapsed after the other sensor detects the medium.

6. A control method for a media transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to a media transport direction, each of which rotates independently to feed a media, a plurality of brake rollers arranged opposite each of the plurality of feed rollers, and a plurality of torque limiters separately provided on each of the plurality of brake rollers so that each of the plurality of brake rollers can be independently rotated in response to the rotation of the plurality of feed rollers, Detecting skew of the medium being fed; When skew of the medium is detected, the circumferential speed of the feeding roller, which is arranged on the side where the medium is moving ahead, among the plurality of feeding rollers is made greater than 0 and lower than the circumferential speed when skew of the medium is not detected, thereby correcting the skew of the medium; Execute different actions depending on whether the media skew correction is successful or not, A control method comprising:

7. A control program for a medium transport device having a plurality of feed rollers arranged at intervals in a direction perpendicular to a medium transport direction and each rotating independently to transport a medium, a plurality of brake rollers arranged opposite each of the plurality of feed rollers, and a plurality of torque limiters separately provided on each of the plurality of brake rollers so that each of the plurality of brake rollers can be independently rotated in response to the rotation of the plurality of feed rollers, Detecting skew of the medium being fed; When skew of the medium is detected, the circumferential speed of the feeding roller, which is arranged on the side where the medium is moving ahead, among the plurality of feeding rollers is made greater than 0 and lower than the circumferential speed when skew of the medium is not detected, thereby correcting the skew of the medium; Execute different actions depending on whether the media skew correction is successful or not, a control program for causing the medium transport device to execute the above steps;

Images