Medium feeding device

Abstract

To provide a medium feeding device capable of more successfully feeding a medium.SOLUTION: A medium feeding device has a feed roller for feeding a medium, a separation roller made of a resin and disposed to face the feed roller, and a pressing part for pressing one of the feed roller and the separation roller against the other so that a nipping region is formed at a position where the feed roller and the separation roller come in contact with each other. A plurality of grooves arranged perpendicular to the feeding direction of the medium are formed on the surface of the feed roller. A pitch of the plurality of grooves is set such that at least one groove is always present in the nipping region during feeding of the medium. A width of the plurality of grooves is set to 0.5 mm or more, and a contact area ratio S is set to 0.5 or more, where the contact area ratio S is [(surface area of the feed roller in the nipping region)-(area of the grooves of the feed roller in the nip region)] / (surface area of the feed roller in the nip region).SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a media feeding device. [Background technology]

[0002] Generally, a medium feeding device such as a scanner uses a feeding roller and a separation roller to feed a medium while separating the medium. The medium fed by such a medium feeding device may have foreign matter such as paper dust, fillers, coating agents (pigments), powder, etc. When such a medium is fed, the foreign matter adhered to the surface of the medium may adhere to the feeding roller, reducing the coefficient of friction of the surface of the feeding roller and decreasing the feeding performance. For this reason, feeding rollers formed with grooves capable of accommodating foreign matter have been developed in recent years.

[0003] A paper feed roller made of a rubber composition and having projections and recesses on the roller surface has been disclosed (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-106067 Summary of the Invention

[0005] There is a demand for media feeding devices that can feed media better.

[0006] The medium feeding device according to the embodiment aims to feed the medium better.

[0007] A medium feeding device according to one aspect of an embodiment has a feed roller for feeding a medium, a separation roller formed of resin and arranged opposite the feed roller, and a pressing portion for pressing one of the feed roller and the separation roller against the other so that a nip area is formed at a position where the feed roller and the separation roller contact each other, and a plurality of grooves are formed on the surface of the feed roller and arranged perpendicular to the medium feeding direction, and the pitch of the plurality of grooves is set so that at least one groove is always present in the nip area during medium feeding, the width of the plurality of grooves is 0.5 mm or more, and the contact area ratio S is set to 0.5 or more, and the contact area ratio S is {(surface area of ​​the feed roller in the nip area-area of ​​the grooves of the feed roller in the nip area)} / (surface area of ​​the feed roller in the nip area).

[0008] According to this embodiment, the medium feeding device can feed the medium more effectively.

[0009] The objects and advantages of the invention will be realized and obtained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory but are not restrictive of the invention as claimed. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a medium feeding device 100 according to an embodiment. [Diagram 2] 2 is a diagram for explaining a transport path inside the medium feeding device 100. FIG. [Diagram 3] 5A and 5B are schematic diagrams for explaining forces applied to each roller. [Figure 4] 5A to 5C are schematic diagrams for explaining the surfaces of the rollers. [Diagram 5] 1A and 1B are schematic diagrams for explaining the grooves of each roller. [Figure 6] Graphs (A) and (B) are graphs for explaining the contact area ratio S. [Figure 7] 1 is a graph for explaining a contact area ratio S. [Figure 8] 1A, 1B, and 1C are schematic diagrams for explaining a separation roller 113. [Figure 9] 1 is a graph showing the relationship between medium movement speed and amplitude. [Figure 10] Graphs (A) and (B) are graphs for explaining the contact area ratio P. [Figure 11] 1 is a graph showing the relationship between frequency and sound pressure; [Figure 12] 1 is a block diagram showing a schematic configuration of a medium feeding device 100. FIG. [Figure 13] FIG. 2 is a diagram showing a schematic configuration of a storage device 140 and a processing circuit 150. [Figure 14] 10 is a flowchart illustrating an example of the operation of a medium reading process. [Figure 15] 13 is a schematic diagram for explaining another separation roller 213. FIG. [Figure 16] FIG. 13 is a diagram showing a schematic configuration of another processing circuit 350. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a medium feeding device, a control method, and a control program according to one aspect of the present disclosure will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions described in the claims and their equivalents.

[0012] FIG. 1 is a perspective view showing a medium feeding device 100 configured as an image scanner. The medium feeding device 100 feeds and conveys a medium, which is an original, and captures an image. The medium is paper, thin paper, thick paper, a card, a booklet, an envelope, or the like. The medium being fed has foreign matter attached thereto, such as paper dust, fillers attached when the paper is produced, coating agents (pigments) attached to coated paper, and powder attached during color printing. The medium feeding device 100 may be a facsimile, a copier, a multifunction printer (MFP, Multifunction Peripheral), or the like. Note that the medium being conveyed may not be an original but may be a printed object, and the medium feeding device 100 may be a printer, or the like.

[0013] Medium feeding device 100 includes a lower housing 101, an upper housing 102, a loading stand 103, an ejection stand 104, an operation device 105, and a display device 106. In Fig. 1, arrow A1 indicates the medium transport direction, arrow A2 indicates the width direction perpendicular to the medium transport direction, and arrow A3 indicates the height direction perpendicular to the medium transport surface. In the following, upstream refers to the upstream side of the medium transport direction A1, and downstream refers to the downstream side of the medium transport direction A1.

[0014] The upper housing 102 is positioned to cover the top surface of the medium feeding device 100, and is rotatably engaged with the lower housing 101 by a hinge so that it can be opened and closed when the medium is jammed, when the inside of the medium feeding device 100 is cleaned, etc.

[0015] The placement stage 103 engages with the lower housing 101 and places thereon the media to be fed and transported. The ejection stage 104 engages with the upper housing 102 and places thereon the ejected media. Note that the ejection stage 104 may also engage with the lower housing 101.

[0016] The operation device 105 has an input device such as a button and an interface circuit for acquiring a signal from the input device, accepts an input operation by a user, and outputs an operation signal according to the input operation by the user. The display device 106 has a display including a liquid crystal, an organic EL (Electro-Luminescence), or the like, and an interface circuit for outputting image data to the display, and displays the image data on the display.

[0017] FIG. 2 is a diagram for explaining the transport path inside the medium feeding device 100. As shown in FIG.

[0018] The transport path inside the medium feeding device 100 includes a medium sensor 111, a feeding roller 112, a separation roller 113, a first transport roller 114, a first opposing roller 115, an imaging device 116, a second transport roller 117, and a second opposing roller 118.

[0019] The number of each of the feed roller 112, separation roller 113, first conveyor roller 114, first opposing roller 115, second conveyor roller 117, and / or second opposing roller 118 is not limited to one, and may be more than one. In this case, the feed roller 112, separation roller 113, first conveyor roller 114, first opposing roller 115, second conveyor roller 117, and / or second opposing roller 118 are arranged at intervals in the width direction A2 perpendicular to the medium conveying direction.

[0020] The top surface of the lower housing 101 forms a lower guide 101a of the medium transport path, and the bottom surface of the upper housing 102 forms an upper guide 102a of the medium transport path.

[0021] The media sensor 111 is disposed upstream of the feed roller 112 and the separation roller 113. The media sensor 111 has a contact detection sensor, and detects whether or not a medium is placed on the placement table 103. The media sensor 111 generates and outputs a media signal whose signal value changes depending on whether or not a medium is placed on the placement table 103. Note that the media sensor 111 is not limited to a contact detection sensor, and any other sensor capable of detecting the presence or absence of a medium, such as a light detection sensor, may be used as the media sensor 111.

[0022] The feed roller 112 is provided in the lower housing 101, and separates and feeds the media placed on the placement table 103 from the bottom. The feed roller 112 is made of resin such as rubber or plastic, or metal such as iron. The separation roller 113 is a so-called brake roller or retard roller, and is provided in the upper housing 102 and disposed opposite to the feed roller 112. The separation roller 113 is provided so as to be rotatable or stoppable in the direction opposite to the medium feeding direction. The separation roller 113 is made of resin such as rubber or plastic, or metal such as iron. Note that the feed roller 112 may be provided in the upper housing 102 and the separation roller 113 in the lower housing 101, and the feed roller 112 may feed the media placed on the placement table 103 from the top.

[0023] The first conveying roller 114 and the first opposing roller 115 are disposed downstream of the feed roller 112 and the separation roller 113 in the medium conveying direction A1. The first conveying roller 114 is provided in the upper housing 102, and conveys the medium fed by the feed roller 112 and the separation roller 113 to the imaging device 116. The first conveying roller 114 is formed of a resin such as rubber or plastic, or a metal such as iron. The first opposing roller 115 is provided in the lower housing 101 below the first conveying roller 114 and faces the first conveying roller 114, and rotates following the first conveying roller 114. The first opposing roller 115 is formed of a resin such as rubber or plastic, or a metal such as iron. The first conveying roller 114 may be provided in the lower housing 101, and the first opposing roller 115 may be provided in the upper housing 102.

[0024] The imaging device 116 is an example of an imaging section, and is disposed downstream of the first transport roller 114 and the first opposed roller 115 in the medium transport direction A1, and captures an image of the medium transported by the first transport roller 114 and the first opposed roller 115. The imaging device 116 includes a first imaging device 116a and a second imaging device 116b disposed opposite each other across the medium transport path.

[0025] The first imaging device 116a has a line sensor using a CIS (Contact Image Sensor) of a life-size optical system type having imaging elements using CMOS (Complementary Metal Oxide Semiconductor) linearly arranged in the main scanning direction. The first imaging device 116a also has a lens that forms an image on the imaging elements, and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging elements. The first imaging device 116a captures the surface of the medium being conveyed under the control of a processing circuit described later, generates an input image, and outputs it.

[0026] Similarly, the second imaging device 116b has a line sensor using a CIS of a life-size optical system type having CMOS imaging elements arranged in a line in the main scanning direction. The second imaging device 116b 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 116b captures the back side of the medium being conveyed under the control of a processing circuit described later, generates an input image, and outputs it.

[0027] The medium feeding device 100 may have only one of the first imaging device 116a and the second imaging device 116b arranged to read only one side of the medium. Also, instead of a CIS line sensor of an equal magnification optical system type having a CMOS imaging element, a CIS line sensor of an equal magnification optical system type having a CCD (Charge Coupled Device) imaging element may be used. Also, a reduction optical system type line sensor having a CMOS or CCD imaging element may be used.

[0028] The second conveying roller 117 and the second opposing roller 118 are disposed downstream of the imaging device 116 in the medium conveying direction A1, that is, downstream of the feed roller 112 and the separation roller 113. The second conveying roller 117 is provided in the upper housing 102, and conveys the medium conveyed by the first conveying roller 114 and the first opposing roller 115 further downstream and discharges the medium to the discharge tray 104. The second conveying roller 117 is formed of a resin such as rubber or plastic, or a metal such as iron. The second opposing roller 118 is provided in the lower housing 101 below the second conveying roller 117 and faces the second conveying roller 117, and rotates following the second conveying roller 117. The second opposing roller 118 is formed of a resin such as rubber or plastic, or a metal such as iron. The second conveying roller 117 may be provided in the lower housing 101, and the second opposing roller 118 may be provided in the upper housing 102.

[0029] The medium placed on the mounting table 103 is transported between the lower guide 101a and the upper guide 102a in the medium transport direction A1 by the rotation of the feed roller 112 in the direction of the arrow A4, i.e., the medium feed direction. The separation roller 113 rotates or stops in the direction of the arrow A5, i.e., the opposite direction to the medium feed direction. When multiple media are placed on the mounting table 103, the feed roller 112 and the separation roller 113 function to separate only the media placed on the mounting table 103 that is in contact with the feed roller 112. This limits the transport of media other than the separated media (preventing double feeding).

[0030] The medium is fed between first conveyor roller 114 and first opposing roller 115 while being guided by lower guide 101a and upper guide 102a. The medium is fed between first imaging device 116a and second imaging device 116b as first conveyor roller 114 rotates in the direction of arrow A6. The medium read by imaging device 116 is discharged onto discharge tray 104 as second conveyor roller 117 rotates in the direction of arrow A7.

[0031] FIG. 3 is a schematic diagram for explaining the forces applied to the feed roller 112 and the separation roller 113. As shown in FIG.

[0032] As shown in FIG. 3, the medium feeding device 100 further includes a pressing member 119 .

[0033] The pressing member 119 is an example of a pressing portion, and is provided with one end on the upper housing 102 and the other end on a shaft that is a rotation axis of the separation roller 113, and presses the separation roller 113 toward the feed roller 112. The pressing member 119 includes an elastic member such as a torsion coil spring, and generates a pressing force W that presses the separation roller 113 toward the feed roller 112. The pressing member 119 forms a nip area at a position where the feed roller 112 and the separation roller 113 contact each other. The pressing member 119 may include other spring members such as a leaf spring, or a rubber member. The pressing member 119 may also be provided so as to press the feed roller 112 toward the separation roller 113. In this way, the pressing member 119 presses one of the feed roller 112 and the separation roller 113 against the other so that a nip area is formed at a position where the feed roller 112 and the separation roller 113 contact each other.

[0034] Fig. 4 is a schematic diagram for explaining the surfaces of the feed roller 112 and the separation roller 113. Fig. 4 is a perspective view of the feed roller 112 and the separation roller 113 as viewed from the downstream side.

[0035] As shown in FIG. 4, a surface 112a of the feed roller 112 has a plurality of grooves 112b arranged in a width direction A2 perpendicular to the medium transport direction, i.e., perpendicular to the medium feeding direction (parallel to the shaft that is the rotation axis of the feed roller 112). That is, the plurality of grooves 112b are arranged in a line at intervals from each other in the medium feeding direction so that they each extend in a direction perpendicular to the medium feeding direction. Note that "perpendicular to the medium feeding direction" is not limited to an angle of 90° with the medium feeding direction, but also includes an angle of a predetermined angle (for example, an angle within a range of ±5°) with respect to 90°. By arranging the grooves 112b perpendicular to the medium feeding direction on the surface 112a of the feed roller 112, the feed roller 112 can more efficiently peel off (scrape off) foreign matter adhering to the medium, and can more efficiently accommodate the foreign matter in the grooves 112b.

[0036] In addition, a plurality of grooves 113b are formed on the surface 113a of the separation roller 113 in the medium conveying direction A1, i.e., parallel to the medium feeding direction (perpendicular to the shaft that is the rotation axis of the separation roller 113). That is, the plurality of grooves 113b are arranged side by side at intervals in a direction perpendicular to the medium feeding direction so as to extend in the medium feeding direction. Note that "parallel to the medium feeding direction" is not limited to an angle of 0° with the medium feeding direction, but also includes an angle of a predetermined angle (for example, an angle within a range of ±5°) with respect to 0°. By arranging the grooves 113b on the surface 113a of the separation roller 113, the force with which the separation roller 113 pushes back the medium is increased, and the medium feeding device 100 can suppress the occurrence of double feeding of media. In particular, by arranging grooves 113b parallel to the medium feeding direction on surface 113a of separation roller 113, the position of grooves 113b in nip region N does not change during rotation of separation roller 113, and the separating force is kept constant. This allows medium feeding device 100 to prevent the occurrence of double feeding of media.

[0037] In addition, the extension direction of the groove 112b of the feeding roller 112 is different from the extension direction of the groove 113b of the separation roller 113, which prevents the groove 112b and the groove 113b from interfering with each other and causing the separation roller 113 to bound (vibrate). This allows the medium feeding device 100 to prevent the occurrence of double feeding of media.

[0038] In addition, since the extension direction of the groove 112b of the feed roller 112 and the extension direction of the groove 113b of the separation roller 113 are perpendicular to each other, foreign matter that frays from the medium and extends in various directions will be contained in one of the grooves with a high probability.

[0039] Fig. 5(A) is a schematic diagram for explaining the groove 112b of the feed roller 112. Fig. 5(A) is a schematic diagram of the periphery of the nip region between the feed roller 112 and the separation roller 113 as viewed from the side.

[0040] 5(A), a plurality of grooves 112b are formed at a constant pitch L1 along the circumferential direction on the surface 112a of the feed roller 112. The pitch L1 of the plurality of grooves 112b is set so that at least one groove 112b is always present within the nip region N during medium feeding. Furthermore, the width L2 of each groove 112b of the feed roller 112 is set to be 0.5 mm or more.

[0041] As a result of observing rollers that had become slippery in the user's environment and that had become slippery in the accelerated test, more than 90% of the clumps of paper fibers attached to the rollers were 0.5 mm or less. That is, it was found that when feeding a medium, it is unlikely that all the fibers contained in the medium such as paper will come off, and it is highly likely that some of the fibers will fray and rise to the surface of the medium, and rub against the roller and come off. The medium feeding device 100 can efficiently accommodate the fibers attached to the surface 112a of the feed roller 112 in the groove 112b by setting the width L2 of the groove 112b of the feed roller 112 to be 0.5 mm or more. As a result, the medium feeding device 100 can prevent the fibers from adhering to the surface 112a of the feed roller 112, reducing the coefficient of friction between the surface 112a of the feed roller 112 and the medium, and thus preventing the medium from slipping. Therefore, the medium feeding device 100 can prevent the medium from jamming.

[0042] Fig. 5(B) is a schematic diagram for explaining the groove 113b of the separation roller 113. Fig. 5(B) is a schematic diagram of the periphery of the nip region between the feed roller 112 and the separation roller 113 as viewed from the downstream side.

[0043] 5(B), a plurality of grooves 113b are formed at a constant pitch L3 along the width direction A2 on the surface 113a of the separation roller 113. Furthermore, the width L4 of each groove 113b of the separation roller 113 is set to be 0.5 mm or more.

[0044] As described above, when a roller on which medium slippage had occurred was observed, more than 90% of the clumps of paper fibers adhering to the roller were 0.5 mm or less. The medium feeding device 100 can efficiently accommodate the fibers adhering to the surface 113a of the separation roller 113 in the groove 113b by setting the width L4 of the groove 113b of the separation roller 113 to be 0.5 mm or more. This allows the medium feeding device 100 to prevent the fibers from adhering to the surface 113a of the separation roller 113, reducing the coefficient of friction between the surface 113a of the separation roller 113 and the medium, causing medium slippage. Therefore, the medium feeding device 100 can prevent the occurrence of medium jams.

[0045] Furthermore, the contact area ratio S is set to be 0.5 or more on the surface 112a of the feed roller 112. The contact area ratio S of the feed roller 112 is calculated by the following formula (1). Contact area ratio S={(surface area of ​​the surface 112a of the feed roller 112 in the nip region N−area of ​​the groove 112b of the feed roller 112 in the nip region N)} / (surface area of ​​the surface 112a of the feed roller 112 in the nip region N) (1)

[0046] 6A, 6B, and 7 are graphs for explaining the contact area ratio S of the feed roller 112. In FIG.

[0047] FIG. 6(A) is a graph showing the relationship between the number of media fed by the feed roller and the friction coefficient between the media and the feed roller that fed that number of media. The horizontal axis of FIG. 6(A) shows the number of media fed by the feed roller, and the vertical axis shows the friction coefficient between the media and the feed roller that fed that number of media. This feed roller is a roller that does not have grooves and has a friction coefficient of about 3.0 between the media and the feed roller in the initial state (a state in which no media has been fed yet). As shown in FIG. 6(A), the more the number of media fed, the lower the friction coefficient between the feed roller and the media, and the higher the possibility of media slippage. In particular, as a result of an accelerated test in which a large amount of media with foreign matter attached was fed, it was found that the frequency of media slippage increases sharply when the friction coefficient becomes less than 1.4.

[0048] The maximum static friction between two objects is calculated by multiplying the shear strength (which is a constant if the objects are made of the same material) by the area where the two objects are actually in contact. In other words, the friction between two objects is proportional to the contact area.

[0049] FIG. 6B is a graph showing the relationship between the contact area ratio S of the feed roller having grooves and the friction coefficient between the feed roller and the medium. The horizontal axis of FIG. 6B shows the contact area ratio S of the feed roller, and the vertical axis shows the friction coefficient between the feed roller and the medium. As shown in FIG. 6B, there is a proportional relationship between the contact area ratio S and the friction coefficient. As described above, when the friction coefficient is less than 1.4, the frequency of medium slippage is high, so the friction coefficient is preferably 1.4 or more. Since there is a proportional relationship between the contact area ratio S and the friction coefficient, it is preferable that the contact area ratio S is equal to or greater than the value (1.4 / 3.0≒0.5) obtained by dividing the friction coefficient threshold value (1.4) at which the frequency of medium slippage increases by the initial value (3.0). By setting the contact area ratio S of the feed roller 112 to 0.5 or more, the medium feeding device 100 can reduce the frequency of medium slippage during medium feeding.

[0050] Fig. 7 is a graph showing the relationship between the number of media fed by the feed roller and the media feeding force (feed force) of the feed roller that fed that number of media in an accelerated test in which a large amount of media having foreign matter attached thereto is fed. The horizontal axis of Fig. 7 shows the number of media fed by the feed roller, and the vertical axis shows the media feeding force of the feed roller that fed that number of media. The media feeding force of the feed roller 112 is the force applied to the media fed by the feed roller 112 in the media feeding direction, and is measured by attaching a tension gauge to the upstream end of the media fed by the feed roller 112.

[0051] Graph 701 shows a graph for a feed roller with a contact area ratio S of 0.35. Graph 702 shows a graph for a feed roller with a contact area ratio S of 0.50. Graph 703 shows a graph for a feed roller with a contact area ratio S of 0.60. Graph 704 shows a graph for a feed roller with a contact area ratio S of 0.90. Graph 705 shows a graph for a feed roller with a contact area ratio S of 0.95.

[0052] In order to feed the medium appropriately, a feeding force of 200 [gf] or more was required. As shown in graph 701, the feed roller with a contact area ratio S of 0.35 was able to generate sufficient feeding force and feed the medium well in the initial state (a state in which the medium has not yet been fed). However, with this feed roller, the feeding force rapidly decreased every time the medium was fed, and when about 200 sheets of medium were fed, the feeding force became less than 200 [gf] and the medium could not be fed properly. Also, as shown in graphs 702, 703, and 704, the feed roller with a contact area ratio S of 0.50, 0.60, or 0.80 was able to generate sufficient feeding force and feed the medium well in the initial state and in a state in which 1000 or more media had been fed. On the other hand, as shown in graph 705, the feed roller with a contact area ratio S of 0.95 was already unable to generate sufficient feeding force in the initial state and was unable to feed the medium properly.

[0053] Therefore, as described above, by setting the contact area ratio S to 0.5 or more, the feed roller 112 can feed the medium well for a long period of time. Also, it is preferable to set the contact area ratio S to 0.9 or less. This allows the feed roller 112 to continue to feed the medium well for a long period of time from the initial state.

[0054] Further, the contact area ratio S of the feed roller 112 is defined as the following formula (2) from formula (1), and the pitch L1 of the grooves 112b of the feed roller 112 is defined as the following formula (3) from formula (2). Contact area ratio S={(pitch L1 of groove 112b of feed roller 112-width L2 of groove 112b of feed roller 112)} / (pitch L1 of groove 112b of feed roller 112) (2) Pitch L1 of groove 112b of feed roller 112=(width L2 of groove 112b of feed roller 112) / (1-contact area ratio S) (3)

[0055] Since the minimum value of the width L2 of the groove 112b of the feed roller 112 is 0.5 mm and the minimum value of the contact area ratio S is 0.5, from formula (3), the minimum value of the pitch L1 of the groove 112b of the feed roller 112 is 1.0 mm. Generally, the width of the nip area between the feed roller and the separation roller is set in the range of 4.0 mm to 6.0 mm. The pitch L1 of the groove 112b of the feed roller 112 is set so that at least one groove 112b is always present in the nip area N during medium feeding, so the maximum value of the pitch L1 is 4.0 mm. Therefore, the pitch L1 of the multiple grooves 112b of the feed roller 112 is 1.0 mm to 4.0 mm.

[0056] The width L2 of the groove 112b of the feed roller 112 is defined by the following formula (4) from formula (3). Width L2 of groove 112b of feed roller 112=(pitch L1 of groove 112b of feed roller 112)×(1−contact area ratio S) (4)

[0057] Since the maximum value of the pitch L1 of the groove 112b of the feed roller 112 is 4.0 mm and the minimum value of the contact area ratio S is 0.5, the maximum value of the width L2 of the groove 112b of the feed roller 112 is 2.0 mm from formula (4). Therefore, the width L2 of the groove 112b of the feed roller 112 is 2.0 mm or less. Note that the fiber length of 95% or more of the hardwood pulp used as paper is 2.0 mm or less, and the fiber length of 50% or more of the softwood pulp used as paper is 2.0 mm or less. Therefore, by setting the width L2 of the groove 112b of the feed roller 112 to 2.0 mm, the medium feeding device 100 can accommodate most of the fibers of the hardwood pulp and softwood pulp in the groove 112b of the feed roller 112.

[0058] As a result, the feed roller 112 can efficiently collect foreign matter adhering to the medium being fed in the grooves 112b, and can continue to feed the medium satisfactorily for a long period of time from the initial state.

[0059] Figures 8(A), (B), and (C) are schematic diagrams for explaining surface 113a of separation roller 113. Figure 8(A) is a schematic diagram of surface 113a of separation roller 113 viewed from above, Figure 8(B) is a cross-sectional diagram along line A-A' in Figure 8(A), and Figure 8(C) is a cross-sectional diagram along line B-B' in Figure 8(A).

[0060] As shown in Fig. 8(A), (B), and (C), a surface 113a of the separation roller 113 has a plurality of flat portions 113c disposed between the plurality of grooves 113b. A plurality of openings 113d are formed in each of the flat portions 113c. Each opening 113d is formed by hollowing out a part of the flat portion 113c in a hemispherical (dome-like) shape. That is, each opening 113d is formed in a circular shape when viewed from above. Each opening 113d may be formed in any shape, such as an elliptical shape, a rectangular shape, or a triangular shape.

[0061] When the medium is fed, the surface 113a of the separation roller 113 vibrates due to the separation operation of the separation roller 113, generating abnormal noise (so-called squealing noise, slip-stick noise) around the separation roller 113. The squealing noise is a sound in a specific frequency band (for example, 3 kHz to 4 kHz, 6.5 kHz to 8 kHz, etc.).

[0062] For the vibration system on the surface 113a of the separation roller 113, the vibration frequency f ss is calculated using the following equation (5), and the vibration amplitude A ss is calculated using the following formula (6). f ss =kv / {2(μ s -μ k )W} (5) A ss =(μ s -μ k )W / k (6) Here, k is the stiffness (spring constant) of the surface 113a of the separation roller 113. v is the moving speed at which the medium moves relative to the surface 113a of the separation roller 113. μ s is the static friction coefficient between the surface 113a of the separation roller 113 and the medium. k is the dynamic friction coefficient between the surface 113a of the separation roller 113 and the medium. W is the normal load applied to the surface 113a of the separation roller 113. Frequency f ss and amplitude A ss For the calculation of this, please refer to "Takeshi Nakano, Satoru Maekawa, Soft Materials and Frictional Vibration, 177th Rubber Technology Symposium, The Society of Rubber Industry, Japan, p1-10 (2012)".

[0063] From equations (5) and (6), the amplitude of vibration A ss is calculated using the following formula (7). A ss =v / 2f ss (7) As shown in the formula (7), the amplitude A of the surface 113a of the separation roller 113 ss is proportional to the moving speed v of the medium relative to the surface 113 a of the separation roller 113 .

[0064] FIG. 9 shows the relationship between the moving speed (processing speed) of the medium relative to the surface 113a of the separation roller 113 and the amplitude A of the surface 113a of the separation roller 113. ss 1 is a graph showing the relationship between

[0065] The horizontal axis of FIG. 9 indicates the moving speed (processing speed) [ppm] of the medium relative to the surface 113a of the separation roller 113, and the vertical axis indicates the amplitude A of the vibration of the surface 113a of the separation roller 113. ss Graph 901 shows the frequency f ss When the amplitude A is 3kHz ss Graph 902 shows the frequency f ss When the amplitude A is 4kHz ss Graph 903 shows the frequency f ss When the amplitude A is 5kHz ss Shows.

[0066] Generally, the moving speed (processing speed) of the medium in the medium feeding device is 90 ppm or less. Therefore, as shown in FIG. 9, the frequency f ss The amplitude A of the surface 113a of the separation roller 113 when the frequency is 3 kHz or more and 5 kHz or less ss is 0.10 mm or less. By making the diameter (maximum width) d of the multiple openings 113d 0.10 mm or more, the medium feeding device 100 can block (reduce) the sound generated by vibration of the surface 113a of the separation roller 113 from propagating over the surface 113a.

[0067] Generally, in order to separate the media well, the width L5 (see FIG. 5(b)) of the flat portions 113c arranged between the grooves 113b on the surface 113a of the separation roller 113 is set to 1.0 mm or more. On the other hand, if the diameter d of the opening 113d is too large, the media is not separated well. An experiment was conducted to feed the media using a plurality of separation rollers with flat portions each having a width of 1.0 mm and openings each having a different diameter. As a result, the media was separated well when the opening diameter was 0.35 mm or less, but the media was not separated when the opening diameter was larger than 0.35 mm. Therefore, it is preferable that the diameter d of the openings 113d is 0.35 mm or less.

[0068] Therefore, the diameter d of the plurality of openings 113d is set to be equal to or greater than 0.10 mm and equal to or less than 0.35 mm, which enables the medium feeding device 100 to effectively separate the media while suppressing the generation of squealing noise.

[0069] Furthermore, it is preferable that the depth H of the plurality of openings 113d is 0.2 mm or more so that the openings 113d remain even when the surface 113a of the separation roller 113 is worn down.

[0070] Generally, the separation roller is formed as an annular elastic body around a shaft, which is a rotation axis. The annular elastic body includes two layers, an outer layer made of a non-foamed layer and an inner layer made of a foamed layer. In such a separation roller, the thickness (depth) of the outer layer is generally set to 1.0 mm or more and 1.5 mm or less. It is preferable that the depth H of the multiple openings 113d is 1.0 mm or less so that the multiple openings 113d are formed in the outer layer of the separation roller 113.

[0071] Therefore, the depth H of the multiple openings 113d is set to 0.2 mm or more and 1.0 mm or less. This allows the medium feeding device 100 to form the openings 113d only in the outer layer of the separation roller 113, and to continue to hold the openings 113d even if the surface 113a is worn.

[0072] Further, the contact area ratio P is set to be 0.4 or more on the surface 113a of the separation roller 113. The contact area ratio P of the separation roller 113 is calculated by the following formula (8). Contact area ratio P = {(surface area of ​​surface 113a of separation roller 113 in nip region N - area of ​​groove 113b of separation roller 113 in nip region N - total area of ​​opening 113d of separation roller 113 in nip region N)} / (surface area of ​​surface 113a of separation roller 113 in nip region N) (8)

[0073] 10A, 10B, and 11 are graphs for explaining the contact area ratio P of the separation roller 113. In FIG.

[0074] Fig. 10(A) is a graph showing the relationship between the load rate applied to the medium fed by the feed roller 112 and the separation roller 113 and the slip rate between the feed roller 112 and the medium. The horizontal axis of Fig. 10(A) shows the load rate applied to the medium fed by the feed roller 112 and the separation roller 113, and the vertical axis shows the slip rate between the feed roller 112 and the medium. Graph 1001 shows the slip rate when the contact area ratio P of the separation roller 113 is 0.37, and graph 1002 shows the slip rate when the contact area ratio P of the separation roller 113 is 0.40.

[0075] The load factor η applied to the medium fed by the feeding roller 112 and the separation roller 113 is calculated by the following formula (9). η=F / W (9) Here, W is the force with which the pressing member 119 presses the separation roller 113 toward the feed roller 112. F is the force applied by the pressing force W to the fed medium in the opposite direction to the medium transport direction A1.

[0076] The slip ratio R between the feed roller 112 and the medium is calculated by the following formula (10). R = {(V r -V p ) / V r}×100 (10) Here, Vr is the peripheral speed of the feed roller 112 (the moving speed of the surface 112a of the feed roller 112). p is the moving speed of the surface of the medium.

[0077] When the slip ratio is 0%, the medium is fed without slipping against the feed roller 112, and when the slip ratio is 100%, the medium is stopped even though the feed roller 112 is rotating. The load ratio η when the slip ratio is 100%, i.e., the load ratio η when the medium is stopped, indicates the friction coefficient between the feed roller 112 and the medium and the friction coefficient between the separation roller 113 and the medium. That is, as shown in graph 1001, when the contact area ratio P of the separation roller 113 is 0.37, the friction coefficient between the separation roller 113 and the medium is about 0.9. Also, as shown in graph 1002, when the contact area ratio P of the separation roller 113 is 0.40, the friction coefficient between the separation roller 113 and the medium is about 1.0.

[0078] A driving force from a motor, which will be described later, is transmitted to the separation roller 113 via a torque limiter. The limit value of the torque limiter is set to a value such that when there is one medium, the rotational force via the torque limiter is cut off, and when there are multiple media, the rotational force via the torque limiter is transmitted. As a result, when only one medium is transported, the separation roller 113 does not rotate according to the driving force from the motor, but follows the feed roller 112. On the other hand, when multiple media are transported, the separation roller 113 rotates or stops in the opposite direction to the medium feeding direction, and separates the medium in contact with the feed roller 112 from the other media, thereby preventing double feeding. When only one medium is transported, the separation roller 113 follows the feed roller 112, thereby preventing wear caused by only a specific area continuing to face the feed roller 112.

[0079] However, in order for the separation roller 113 to follow the feed roller 112, the coefficient of friction between the separation roller 113 and the medium must be 1.0 or greater, and therefore the contact area ratio P of the separation roller 113 must be 0.40 or greater.

[0080] FIG. 10B is a graph showing the relationship between the contact area ratio P of the separation roller 113 and the friction coefficient between the separation roller 113 and the medium. The horizontal axis of FIG. 10B shows the contact area ratio P of the separation roller 113, and the vertical axis shows the friction coefficient between the separation roller 113 and the medium. As shown in FIG. 10B, a proportional relationship is established between the contact area ratio P and the friction coefficient. As described above, if the friction coefficient is less than 1.0, the separation roller 113 does not follow the feed roller 112 when only one medium is transported, so that the contact area ratio P of the separation roller 113 is preferably 0.40 or more so that the friction coefficient is 1.0 or more. By setting the contact area ratio P of the separation roller 113 to 0.40 or more, the medium feeding device 100 can suppress wear of only a specific area of ​​the separation roller 113 when feeding the medium.

[0081] Fig. 11 is a graph showing the relationship between frequency and sound pressure for sounds generated around separation roller 113. The horizontal axis of Fig. 11 indicates frequency, and the vertical axis indicates sound pressure. Graph 1101 shows a graph when a medium is fed by a separation roller with a contact area ratio S of 0.70. Graph 1102 shows a graph when a medium is fed by a separation roller with a contact area ratio S of 0.65. Graph 1103 shows a graph when a medium is fed by a separation roller with a contact area ratio S of 0.60. Graph 1104 shows a graph when no medium is fed.

[0082] As shown in graphs 1101 and 1102, when a separation roller has a contact area ratio S of 0.70 or 0.65, loud abnormal noises (squeaks) occur in a frequency band R1 of 3 kHz to 4 kHz and in a harmonic frequency band R2 of 6.5 kHz to 8 kHz when feeding a medium. On the other hand, as shown in graph 1103, when a separation roller has a contact area ratio S of 0.60, loud abnormal noises (squeaks) do not occur in the frequency bands R1 and R2 when feeding a medium. In other words, by setting the contact area ratio P of separation roller 113 to 0.60 or less, medium feeding device 100 can suppress the generation of squeals.

[0083] Therefore, it is preferable that the opening 113d of the separation roller 113 is set so that the contact area ratio P of the separation roller 113 is 0.4 or more and 0.6 or less. This allows the medium feeding device 100 to suppress wear of the separation roller 113 during medium feeding, while suppressing the generation of squealing noise.

[0084] In addition, it is preferable that two or more openings 113d are arranged in any line along the circumferential direction in the nip region N in the flat portion 113c of the separation roller 113. This allows the medium feeding device 100 to more effectively suppress the generation of squealing noise.

[0085] Similarly to surface 112a of feeding roller 112, surface 113a of separation roller 113 preferably has contact area ratio P set to 0.5 or more. Setting contact area ratio S of separation roller 113 to 0.5 or more enables medium feeding device 100 to reduce the frequency of medium slippage during separation of the medium.

[0086] Moreover, the openings 113d may be omitted from the surface 113a of the separation roller 113. In that case, the contact area ratio P of the separation roller 113 is calculated by the following formula (11). Contact area ratio P={(surface area of ​​surface 113a of separation roller 113 in nip region N−area of ​​groove 113b of separation roller 113 in nip region N)} / (surface area of ​​surface 113a of separation roller 113 in nip region N) (11)

[0087] Further, the contact area ratio P of the separation roller 113 is defined as the following formula (12) from formula (11), and the pitch L3 of the grooves 113b of the separation roller 113 is defined as the following formula (13) from formula (12). Contact area ratio P={(pitch L3 of groove 113b of separation roller 113-width L4 of groove 113b of separation roller 113)} / (pitch L3 of groove 113b of separation roller 113) (12) Pitch L3 of groove 113b of separation roller 113=(width L4 of groove 113b of separation roller 113) / (1-contact area ratio P) (13)

[0088] Since the minimum value of width L4 of groove 113b of separation roller 113 is 0.5 mm and the minimum value of contact area ratio P is 0.5, the minimum value of pitch L3 of grooves 113b of separation roller 113 is 1.0 mm. Therefore, pitch L3 of the multiple grooves 113b of separation roller 113 is 1.0 mm or more.

[0089] This allows the separation roller 113 to efficiently collect foreign matter adhering to the fed medium in the grooves 113b, while continuing to separate the medium satisfactorily for a long period of time from the initial state.

[0090] Similarly to the groove 112b of the feed roller 112, the width L4 of the groove 113b of the separation roller 113 may be set to 2.0 mm or less. As described above, the fiber length of 95% or more of the hardwood pulp used as paper is 2.0 mm or less, and the fiber length of 50% or more of the softwood pulp used as paper is 2.0 mm or less. Therefore, by setting the width L4 of the groove 113b of the separation roller 113 to 2.0 mm, the medium feeding device 100 can accommodate most of the fibers of the hardwood pulp and softwood pulp in the groove 112b of the feed roller 112. Similarly to the groove 112b of the feed roller 112, the pitch L3 of the groove 113b of the separation roller 113 may be set to 4.0 mm or less.

[0091] FIG. 12 is a block diagram showing a schematic configuration of the medium feeding device 100. As shown in FIG.

[0092] In addition to the above-mentioned components, the medium feeding device 100 further includes a motor 131, an interface device 132, a storage device 140, a processing circuit 150, and the like.

[0093] The motor 131 has one or more motors, and rotates the feed roller 112, the separation roller 113, the first conveyor roller 114, and / or the second conveyor roller 117 to convey the medium in response to a control signal from the processing circuit 150. Note that the first opposing roller 115 and / or the second opposing roller 118 may be provided so as to rotate according to the driving force of the motor 131, rather than being driven by the first conveyor roller 114 or the second conveyor roller 117.

[0094] The interface device 132 has an interface circuit conforming to a serial bus such as USB, and is electrically connected to an information processing device (not shown, for example, a personal computer, a mobile information terminal, etc.) to transmit and receive input images and various information. Also, instead of the interface device 132, a communication unit having an antenna for transmitting and receiving wireless signals and a wireless communication interface device for transmitting and receiving signals through a wireless communication line in accordance with a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network). The communication unit may have a wired communication interface device for transmitting and receiving signals through a wired communication line in accordance with a communication protocol such as a wired LAN.

[0095] The storage device 140 includes a memory device such as a random access memory (RAM) or a read only memory (ROM), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or an optical disk. The storage device 140 also stores computer programs, databases, tables, and the like used for various processes of the medium feeding device 100. The computer programs may be installed in the storage device 140 from a computer-readable portable recording medium using a known setup program or the like. The portable recording medium is, for example, a compact disc read only memory (CD-ROM), a digital versatile disc read only memory (DVD-ROM), or the like.

[0096] The processing circuit 150 operates based on a program previously stored in the storage device 140. The processing circuit is, for example, a CPU (Central Processing Unit). The processing circuit 150 may be, for example, a DSP (digital signal processor), an LSI (large scale integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array).

[0097] The processing circuit 150 is connected to the operation device 105, the display device 106, the medium sensor 111, the imaging device 116, the motor 131, the interface device 132, the storage device 140, etc., and controls each of these components. The processing circuit 150 performs drive control of the motor 131, imaging control of the imaging device 116, etc., based on a medium signal received from the medium sensor 111. The processing circuit 150 acquires an input image from the imaging device 116, and transmits it to the information processing device via the interface device 132.

[0098] FIG. 13 is a diagram showing a schematic configuration of the storage device 140 and the processing circuit 150. As shown in FIG.

[0099] 13, the storage device 140 stores a control program 141, an image acquisition program 142, and the like. Each of these programs is a functional module implemented by software that runs on a processor. The processing circuitry 150 reads each program stored in the storage device 140 and operates according to the read program. In this way, the processing circuitry 150 functions as a control unit 151 and an image acquisition unit 152.

[0100] FIG. 14 is a flowchart showing an example of the operation of the medium reading process of the medium feeding device 100.

[0101] An example of the operation of the medium reading process of the medium feeding device 100 will be described below with reference to the flowchart shown in Fig. 14. Note that the flow of the operation described below is executed mainly by the processing circuit 150 in cooperation with each element of the medium feeding device 100 based on a program stored in advance in the storage device 140.

[0102] First, the control unit 151 waits until a user inputs an instruction to read a medium using the operation device 105 or an information processing device, and an operation signal instructing the user to read a medium is received from the operation device 105 or the interface device 132 (step S101).

[0103] Next, control unit 151 acquires a medium signal from medium sensor 111, and determines whether or not a medium is placed on mounting table 103 based on the acquired medium signal (step S102). If no medium is placed on mounting table 103, control unit 151 ends the series of steps.

[0104] On the other hand, when a medium is placed on the placement table 103, the control unit 151 drives the motor 131 to rotate the feeding roller 112, the separation roller 113, the first conveying roller 114 and / or the second conveying roller 117 (step S103). As a result, the control unit 151 causes each roller to feed and convey the medium.

[0105] Next, the control unit 151 causes the imaging device 116 to capture an image of the medium, acquires an input image from the imaging device 116, and outputs the acquired input image by transmitting it to the information processing device via the interface device 132 (step S104).

[0106] Next, control unit 151 determines whether or not a medium remains on mounting table 103 based on the medium signal received from medium sensor 111 (step S105). If a medium remains on mounting table 103, control unit 151 returns the process to step S104, and repeats the processes of steps S104 to S105.

[0107] On the other hand, if there are no media remaining on the placement table 103, the control unit 151 controls the motor 131 to stop the feed roller 112, the separation roller 113, the first conveyor roller 114, and / or the second conveyor roller 117 (step S106). Then, the control unit 151 ends the series of steps.

[0108] As described above in detail, in the medium feeding device 100, the groove 112b is formed in the feeding roller 112 so as to suppress the occurrence of slippage of the medium and to properly accommodate foreign matter. This enables the medium feeding device 100 to more effectively feed the medium.

[0109] Furthermore, in the medium feeding device 100, the groove 113b and the opening 113d are formed in the separation roller 113 so as to suppress squealing noise while suppressing wear of the separation roller 113. This makes it possible for the medium feeding device 100 to reduce the frequency of component replacement and to improve usability, thereby improving user convenience.

[0110] In particular, medium feeding device 100 suppresses squealing noise by providing openings 113d (recesses) on flat portion 113c rather than providing protrusions on surface 113a of separation roller 113. Even if separation roller 113 wears out, it takes a long time for flat portion 113c to entirely wear down and for openings 113d to disappear, so medium feeding device 100 can suppress squealing noise for a long period of time.

[0111] FIG. 15 is a schematic diagram for explaining a surface 213a of a separation roller 213 in a medium feeding device according to another embodiment.

[0112] The separation roller 213 shown in FIG. 15 is used in place of the separation roller 113 of the medium feeding device 100. The separation roller 213 has a similar configuration to the separation roller 113. However, in the surface 213a of the separation roller 213, a plurality of flat portions 213c arranged between the plurality of grooves 213b each have a plurality of openings 213d formed therein. The plurality of openings 213d are arranged in a staggered pattern. This enables the medium feeding device to efficiently arrange the openings 213d at a high density on the surface 213a of the separation roller 213, thereby making it possible to further suppress the generation of squealing noise.

[0113] As described above in detail, the medium feeding device is now able to feed the medium more satisfactorily even when the multiple openings 213d are arranged in a staggered pattern.

[0114] 16 is a diagram showing a schematic configuration of a processing circuit 350 in a medium feeding device according to yet another embodiment. The processing circuit 350 is used in place of the processing circuit 150 of the medium feeding device 100, and executes medium reading processing and the like in place of the processing circuit 150. The processing circuit 350 has a control circuit 351, an image acquisition circuit 352, and the like. Each of these components may be formed of an independent integrated circuit, microprocessor, firmware, and the like.

[0115] The control circuit 351 is an example of a control unit, and has the same functions as the control unit 151. The control circuit 351 receives an operation signal from the operation device 105 or the interface device 132, and a medium signal from the medium sensor 111. The control circuit 351 controls the motor 131 based on each piece of received information.

[0116] The image acquisition circuit 352 is an example of an image acquisition section, and has the same function as the image acquisition section 152. The image acquisition circuit 352 acquires an input image from the imaging device 116, and outputs it to the interface device 132.

[0117] As described above in detail, the medium feeding device is now able to feed the medium better even when the processing circuit 350 is used.

[0118] The following supplementary notes are further disclosed regarding the above-described embodiment.

[0119] (Appendix 1) a feed roller for feeding the medium; a separation roller made of resin and disposed opposite the feed roller; a pressing portion that presses one of the feed roller and the separation roller against the other such that a nip region is formed at a position where the feed roller and the separation roller contact each other, A surface of the separation roller is formed with a plurality of grooves arranged parallel to a feeding direction of the medium, and a plurality of flat portions respectively arranged between the plurality of grooves, A plurality of openings are formed in each of the flat portions, The opening is set so that a contact area ratio P is 0.4 or more and 0.6 or less, The contact area ratio P is {(surface area of ​​the separation roller in the nip region)-(area of ​​the grooves of the separation roller in the nip region-total area of ​​the openings of the separation roller in the nip region)} / (surface area of ​​the separation roller in the nip region); A medium feeding device comprising:

[0120] (Appendix 2) 2. The medium feeding device of claim 1, wherein the plurality of openings are arranged in a staggered pattern.

[0121] (Appendix 3) 3. The medium feeding device of claim 1 or 2, wherein a diameter of the plurality of openings is greater than or equal to 0.10 mm and less than or equal to 0.35 mm.

[0122] (Appendix 4) 4. The medium feeding device according to claim 1, wherein a depth of the plurality of openings is not less than 0.2 mm and not more than 1.0 mm.

[0123] (Appendix 5) 5. The medium feeding device according to claim 1, wherein a surface of the feeding roller is formed with a plurality of grooves that are arranged perpendicular to a feeding direction of the medium.

[0124] (Appendix 6) a pitch of the grooves of the feed roller is set such that at least one groove is always present within the nip region during media feeding; the width of the grooves of the feed roller is set to be 0.5 mm or more, and the contact area ratio S is set to be 0.5 or more; 6. The medium feeding device of claim 5, wherein the contact area ratio S is {(surface area of ​​the feed roller in the nip region - area of ​​the groove of the feed roller in the nip region)} / (surface area of ​​the feed roller in the nip region). [Explanation of symbols]

[0125] 100 medium feeding device, 112 feeding roller, 112a surface, 112b groove, 113 separation roller, 113a surface, 113b groove, 119 pressing member

Claims

1. a feed roller for feeding the medium; a separation roller disposed opposite the feed roller; a pressing portion that presses one of the feed roller and the separation roller against the other such that a nip region is formed at a position where the feed roller and the separation roller contact each other, A plurality of grooves are formed on the surface of the feed roller, the grooves being arranged perpendicular to the medium feed direction, the pitch of the grooves is set such that at least one groove is always present within the nip region during media feeding; The width of the plurality of grooves is set to be 0.5 mm or more, and a contact area ratio S is set to be 0.5 or more and 0.9 or less, the contact area ratio S is {(surface area of ​​the feed roller in the nip region−area of ​​the grooves of the feed roller in the nip region)} / (surface area of ​​the feed roller in the nip region); A plurality of grooves are formed on the surface of the separation roller, the grooves being arranged parallel to the medium feeding direction. A medium feeding device comprising:

2. The medium feeding device according to claim 1 , wherein the separation roller is made of resin.

3. The width of the grooves of the separation roller is set to be 0.5 mm or more, and a contact area ratio P is set to be 0.5 or more, 3. The medium feeding device of claim 2, wherein the contact area ratio P is {(surface area of ​​the separation roller in the nip region - area of ​​the groove of the separation roller in the nip region)} / (surface area of ​​the separation roller in the nip region).

4. The width of the grooves of the feed roller is 2.0 mm or less, 4. The medium feeding device according to claim 1, wherein the pitch of the grooves of the feeding roller is 1.0 mm or more and 4.0 mm or less.

Images