JP7601577B2 - Sheet Feeding Device - Google Patents

Description

The present invention relates to a sheet feeding device that feeds sheets.

Conventionally, in a sheet feeding device that feeds sheets one by one from a stacking tray, a separation member is provided to separate the sheets one by one so that multiple sheets are not fed into the conveying path while overlapping. As an example, a separation pad made of a sheet-like friction member is used as the separation member, and the sheets are separated by pressing the separation pad against the sheet stack.

Although compression springs are sometimes used as a means for pressing the separation pad against the sheets, small sheet transport devices use sponges to save space. Compression springs have a small spring constant and can adjust the force applied to thin and thick paper, but sponges have a large spring constant and a large difference in the force applied to thin and thick paper. As a result, small sheet transport devices can transport sheets of normal thickness, such as copy paper, but when transporting thick paper such as postcards, they can sometimes have problems feeding the paper. Therefore, a technology for optimizing the separation load on sheets is proposed in Patent Document 1.

Patent No. 5378085

However, in the sheet feeding device described in Patent Document 1, the separation load varies depending on the thickness of the sheet, so some papers may not be separated sufficiently.

In view of the above problems, a sheet feeding device according to the present invention has:
A feed roller that feeds a plurality of sheets stacked on a stacking table;
a separation pad disposed at a position facing the feed roller and configured to separate the sheets fed by the feed roller one by one;
the separation pad has a first separation portion that sandwiches and separates the sheet between the first separation portion and the feed roller, a second separation portion that contacts and separates the sheet at a position outside the feed roller in the width direction of the sheet, and a biasing portion that is provided outside the second separation portion in the width direction and biases the sheet toward the feed roller in the thickness direction of the sheet,
The biasing portion protrudes toward the sheet side from the second separation portion .

By optimizing the separation load on the separation pad, it is possible to provide a sheet feeding device that can separate a wide range of papers, from thin to thick.

FIG. 1 is a schematic cross-sectional view of an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a control unit of the image reading apparatus according to the embodiment. FIG. 4 is an enlarged perspective view of the separation pad and the feed roller according to the embodiment; FIG. 4 is a diagram showing the separation pad according to the embodiment as viewed from the direction of arrow A in FIG. 3 . 4 is a cross-sectional view of the separation unit according to the embodiment, as viewed in the direction of the arrow C in FIG. 3 . 5 is a cross-sectional view of the separation unit according to the embodiment, seen from the direction of the arrow B in FIG. 4 (when thin paper is being conveyed). 5 is a cross-sectional view of the separation unit according to the embodiment, seen from the direction of arrow B in FIG. 4 (when conveying thick paper); FIG. 4 is a view of a separation pad according to a second embodiment, as viewed in the direction of arrow A in FIG. 3 .

Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are examples for realizing the present invention, and the present invention is not limited to the following embodiments. The dimensions, materials, shapes, relative positions, etc. of the components of the present embodiment should be appropriately modified or changed depending on the configuration and various conditions of the device to which the present invention is applied, without departing from the spirit of the present invention.
FIG. 1 is a schematic diagram of an image reading apparatus 10 as an example of a sheet feeding apparatus according to the present embodiment.

<Apparatus Configuration>
The image reading device 10 is a device that transports one or more sheets S loaded on a loading platform 12 into the device one by one from a paper feed port, reads the images on the sheets, and discharges the sheets S to the outside of the device by a drive roller 20 and a driven roller 21. The sheets S to be read are, for example, office paper, checks, business cards, cards, etc., and may be thick or thin sheets.

<Paper feeding>
A first transport unit 50 is provided as a sheet feeding mechanism that feeds the sheet S along the path RT. In this embodiment, the first transport unit 50 includes a feed roller 14 (feed roller) and a separation pad 30 disposed opposite the feed roller 14, and sequentially transports the sheets S on the stacking table 12 one by one in a feed direction D. A driving force is transmitted from a drive unit 15 constituted by a motor or the like to the feed roller 14 via a transmission unit (not shown), and the feed roller 14 is driven to rotate in the direction of the arrow in the figure (the direction in which the sheet S is transported).

<Drive unit>
In the present embodiment, for example, the transmission unit connecting the drive unit 15 and the feed roller 14 is in a state in which the drive force is normally transmitted, and the drive force is interrupted when the sheet S is stopped. When the transmission of the drive force is interrupted by the transmission unit, the feed roller 14 is in a state in which it can rotate freely.

<Isolation structure>
The separation pad 30, which is disposed opposite the feed roller 14, is a member for separating the sheets S one by one, and is in pressure contact with the feed roller 14. To ensure this pressure contact state, a compressible sponge member 35 (elastic member) is provided on the separation pad 30. The sponge member 35 is configured to urge a first friction member 31 and a second friction member (described later) toward the feed roller 14 by the elastic force of the sponge member 35.

<Conveyor structure>
The second conveying section 51, which serves as a conveying mechanism located downstream of the first conveying section 50 in the conveying direction, has a drive roller 16 and a driven roller 17 driven by the drive roller 16, and conveys the sheet S conveyed from the first conveying section 50 downstream. A driving force is transmitted from the drive section 15 to the drive roller 16, and the drive roller 16 is driven to rotate. The driven roller 17 is in contact with the drive roller 16 with a constant pressure, and rotates together with the drive roller 16. The driven roller 17 may be configured to be biased against the drive roller 16 by a biasing unit (not shown) such as a spring.

The third conveying section 52, which is located downstream of the second conveying section 51 in the conveying direction, includes a drive roller 20 and a driven roller 21 that is driven by the drive roller 20, and discharges the sheet S conveyed from the second conveying section 51 to the outside of the device. In other words, the third conveying section 52 functions as a discharge mechanism.

The driving force is transmitted from the driving unit 15 to the driving roller 20, which is driven to rotate. The driven roller 21 is pressed against the driving roller 20 with a constant pressure, and rotates along with the driving roller 20. The driven roller 21 may be configured to be biased against the driving roller 31 by a biasing unit (not shown) such as a spring.

<Image reading structure and control>
In the image reading device 10 of the present embodiment, the second conveying section 51 and the third conveying section 52 convey the sheet S at a constant speed in order to read the image by the image reading units 18 and 19 disposed between the second conveying section 51 and the third conveying section 52. By always setting the conveying speed at this time to be equal to or higher than the conveying speed of the first conveying section 50, it is possible to reliably prevent the succeeding sheet S from catching up with the preceding sheet S. For example, in the present embodiment, the reduction ratio of the transmission section that transmits the drive from the drive section 15 to the first conveying section 50 is set to be greater than the reduction ratio of the transmission section that transmits the drive from the drive section 15 to the second conveying section 51 and the third conveying section 52 so that the conveying speed of the sheet S by the second conveying section 51 and the third conveying section 52 is faster than the conveying speed of the sheet S by the first conveying section 50.

Even if the conveying speed of the sheet S by the second conveying unit 51 and the third conveying unit 52 and the conveying speed of the sheet S by the first conveying unit 50 are the same, it is possible to form a minimum gap between the preceding sheet S and the succeeding sheet S by controlling the drive unit 15 to control only the drive of the first conveying unit 50 and intermittently shifting the timing at which the feed of the succeeding sheet S starts.

<Registration sensor>
The medium detection sensors 41 and 42 arranged downstream of the first transport unit 50 in the transport direction are examples of detection sensors (sensors that detect the behavior and state of a sheet) arranged upstream of the image reading units 18 and 19 and downstream of the first transport unit 50 on the upstream side of the transport path RT, and detect the position of the sheet S transported by the first transport unit 50, more specifically, whether the end of the sheet S has reached or passed the detection position of the medium detection sensors 41 and 42. Various types of medium detection sensors 41 and 42 can be used, but in this embodiment, they are optical sensors that have a light emitting portion and a light receiving portion and detect the sheet S based on the principle that the intensity of received light (amount of received light) changes when the sheet S reaches or passes through. Note that the medium detection sensors 41 and 42 are not limited to the optical sensors described above, and may be, for example, sensors (image sensors, etc.) that can detect the end of the sheet S, or may be lever-type sensors protruding into the path RT.

<CIS placement>
The image reading units 18, 19 located downstream of the medium detection sensors 41, 42, for example, optically scan and convert the image data into an electrical signal to read the image data, and are equipped with a light source such as an LED, an image sensor, a lens array, etc. In the present embodiment, the image reading units 18, 19 are arranged one on each side of the path RT and read the front and back sides of the sheet S. However, it is also possible to arrange one on only one side of the path RT and read only one side of the sheet S. Also, in this embodiment, the image reading units 18, 19 are arranged opposite each other across the path RT, but they may be arranged with an interval between them in the transport direction of the path RT, for example.

<Block diagram explanation>
The control unit 80 will be described with reference to Fig. 2. Fig. 2 is a block diagram of the control unit 80 of the image reading device 10.

The control unit 80 includes a CPU 81, a memory unit 82, an operation unit 83, a communication unit 84, and an interface unit 85. The CPU 81 controls the entire image reading device 10 by executing a program stored in the memory unit 82. The memory unit 82 is composed of, for example, a RAM, a ROM, etc. The operation unit 83 is composed of, for example, a switch, a touch panel, etc., and accepts operations from the operator.

The communication unit 84 is an interface that communicates information with an external device. If the external device is a PC (personal computer), the communication unit 84 can be, for example, a USB interface or a SCSI interface. In addition to such a wired communication interface, the communication unit 84 can also be a wireless communication interface, or it can have both wired and wireless communication interfaces.

The interface unit 85 is an I/O interface that inputs and outputs data to and from the actuator 86 and the sensor 87. The actuator 86 includes the drive unit 15, a transmission unit, etc. The sensor 87 includes the media detection sensors 41, 42, and the image reading units 18, 19, etc.

<Driven by receiving a start command from a PC>
The following describes the basic operation of the image reading device 10. When the control unit 80 receives an instruction to start image reading from, for example, an external personal computer to which the image reading device 10 is connected, the control unit 80 starts driving the first conveying unit 50 to the third conveying unit 52. The sheets S stacked on the stacking tray 12 are conveyed one by one starting from the bottommost sheet S.

As described below, image reading may be started by pressing a start key provided on the operation unit 83 of the image reading device 10, and then the start of image reading may be notified to an external computer.

<Start of reading according to the output of the registration sensor>
The control unit 80 starts reading the image on the sheet S by the image reading units 18 and 19 at a timing based on the detection results of the medium detection sensors 41 and 42, temporarily stores the read images, and sequentially transmits them to the external computer. The sheet S from which the image has been read is discharged outside the apparatus by the third conveying unit 52, and the image reading process of the sheet S is completed.

<Separation pad details>
FIG. 3 is a perspective view for explaining the arrangement of the separation pad 30 and the feed roller 14 according to the first embodiment of the present invention. FIG. 3(a) shows the separation pad 30 and the feed roller 14 as viewed from the upstream side, and FIG. 3(b) shows the separation pad 30 alone as viewed from the downstream side. FIG. 4 shows the separation pad 30 as viewed from the direction of the arrow A in FIG. 3. FIG. 5 is a cross-sectional view of the separation unit as viewed from the direction of the arrow C in FIG. 3. FIG. 6 is a cross-sectional view of the feed roller 14, the separation pad 30, and the sheet S as viewed from the direction of the arrow B in FIG. 4 when thin paper is conveyed, and FIG. 7 is a cross-sectional view of the feed roller 14, the separation pad 30, and the sheet S as viewed from the direction of the arrow B in FIG. 4 when thick paper is conveyed.

As shown in FIG. 3(a), the feed roller 14 has multiple (two in the figure) roller members 14a spaced apart in the axial direction on a roller shaft 14b.

As shown in FIG. 4, the separation pad 30 includes a first friction member 31 and a second friction member 32 that separate the sheet S, and a biasing portion 33 that biases the sheet S toward the feed roller 14. The first friction member 31 has two roller contact portions 31b that respectively contact the two roller members 14a of the feed roller 14. The second friction member 32 is disposed outside the first friction member 31 in the axial direction of the roller shaft 14b, and contacts the sheet S together with the roller contact portion 31b.

As shown in FIG. 3(a), the second friction members 32 are arranged in two locations on the axially outer side of the two roller members 14a, at positions axially spaced from the roller members 14a so as to overlap (overlap) the roller members 14a in the axial direction.

As shown in Fig. 3(b) and Fig. 4, the first friction member 31 and the second friction member 32 are formed by making four notches in a single flat rectangular friction member (rubber, for example). In addition, a pressing part 33 made of a flat rectangular low-friction member (a film member made of Mylar, for example) with four notches is attached to it. The outer part of the pressing part 33 in the axial direction of the roller member 14a, i.e., the part attached to the second friction member 32, protrudes less downstream in the feed direction D shown in Fig. 4 than the second friction member 32, and a step is provided so that the protrusion amount on the inside is smaller than the outside in the axial direction.

As shown in FIG. 3B, in this embodiment, a sponge member 35 is attached to the first friction member 31 and the second friction member 32 on the side opposite the feed roller 14 in the thickness direction of the sheet S (back side). The surface of the sponge member 35 opposite the first friction member 31 and the second friction member 32 is attached with double-sided tape 38 so as to abut against the holder 36.

As described above, the restoring force (elastic force) of the sponge member 35 biases the first friction member 31 and the second friction member 32 toward the feed roller 14, forming a nip between the first friction member 31 and the feed roller 14, and the second friction member 32 protrudes in the axial direction to a position where it overlaps with the roller member 14a of the feed roller 14.

The biasing portion 33, the first friction member 31, and the second friction member 32 on the upstream side in the feed direction D are fixed to the holder 36 by clamping the holder 36 and the biasing portion 33, the first friction member 31, and the second friction member 32 with a fixing metal plate 37. Note that, although double-sided tape 38 is used to attach the sponge member 35 to the holder 36 and fixing the biasing portion 33, the first friction member 31, and the second friction member 32 on the upstream side to the holder 36 using a fixing metal plate 37, this is not limited to this.

As shown in FIG. 4, the biasing portion 33, the second friction member 32, and the first friction member 31 are continuously arranged to form a comb-tooth shape. The biasing portion 33 is made of a material having a smaller friction coefficient than the first friction member 31 and the second friction member 32, and is attached to the feed roller 14 side in the thickness direction of the second friction member 32 as shown in FIG. 5.

In the portion between the two first friction members 31 (the central portion in the width direction), the biasing portion 33 protrudes downward in FIG. 4 (the direction of the feeding direction D) to the same extent as the second friction member 32.

In the width direction, in the portion where the second friction member 32 is provided, the biasing portion 33 is provided so as to protrude halfway up the second friction member 32 toward the tip side of the second friction member 32, and a step is provided so that the outer side protrudes further downward (downstream in the feeding direction D) in Figure 4 than the inner side in the axial direction of the feed roller 14.

In this way, the biasing portion 33 is positioned to come into contact with the sheet S when the sheet S is separated one by one by the first friction member 31 and the second friction member 32.

Next, the separation operation of the sheet S by the feed roller 14 and the separation pad 30 will be described with reference to Figures 5, 6, 7, and 8.

As shown in Figures 4 and 5, the leading edge of the multiple sheets S stacked on the stacking tray 12 abuts against the urging portion 33. When the feed roller 14 is rotated in the feeding direction by a driving means (not shown), the lower layer of the multiple sheets S abutting against the urging portion 33 advances to the nip between the roller member 14a of the feed roller 14 and the roller contact portion 31b of the first friction member 31. At that time, the first friction member 31 or the second friction member 32 and the base portion of the urging portion 33 guide the leading edge of the stack of sheets S to the nip between the roller member 14a and the roller contact portion 31b of the first friction member 31 while sorting so that the leading edge is slanted.

At the same time as or after the sheet S passes through the nip between the roller member 14a and the roller contact portion 31b, the sheet S comes into contact with the second friction member 32 and the tip side (free end side) of the biasing portion 33. At this time, the sheet S separated by the first friction member 31 comes into contact with the biasing portion 33 and the second friction member 32, so that the sheets S in the lower layer are separated one by one and transported downstream in the feeding direction.

The contact pressure causes the second friction member 32 and the biasing portion 33 to bend. In addition, a sheet separating portion is formed by installing an elastically deforming member such as a sponge behind the member that contacts the sheet S (on the opposite side of the feed roller 14 in the thickness direction), and the sheet separating portion is bent and deformed by the contact pressure.

The separation operation of the sheet S by the feed roller 14 and the separation pad 30 when transporting thin paper and thick paper will be described with reference to Figures 5, 6, and 7.

When the thin paper sheet S reaches the nip with the roller contact portion 31b of the first friction member 31, it is separated one by one by contact between the second friction member 32, the roller contact portion 31b of the first friction member 31, and the urging portion 33, as shown in FIG. 6. The thin paper sheet S is weak in stiffness and is wavy in the width direction, so it comes into sufficient contact with the second friction member 32 and a large separation load acts on it. On the other hand, when the thick paper sheet S reaches the nip with the roller contact portion 31b of the first friction member 31, it is separated one by one by contact between the roller contact portion 31b of the first friction member 31 and the urging portion 33, as shown in FIG. 7. The thick paper sheet S is strong in stiffness and does not flex easily, so it is difficult to come into contact with the second friction member 32, and the separation load is smaller for the thick sheet S than for the thin sheet S.

As a result, a large separation load acts on a thin sheet S because the contact area of the second friction member 32 is large, and a small separation load acts on a thick sheet S because the contact area of the second friction member 32 is small. Therefore, even for a thick sheet S, it is possible to avoid an excessive separation load acting, and the separation load is optimized according to the thickness of the sheet S.

The configuration of the present invention is not limited to the above embodiment, and the material, shape, size, form, number, arrangement, etc. can be changed as appropriate within the scope of the present invention. For example, in the above embodiment, the root portion of the second friction member 32 in the urging portion 33 is made to protrude toward the tip side (free end side) of the second friction member 32 on the outside rather than the inside in the axial direction, so that the friction by the second friction member 32 is large for thin paper with low stiffness and the friction by the second friction member 31 is small for thick paper with high stiffness, but any other configuration that can achieve a similar effect is acceptable. As an example, the number of linearly formed urging portions 33 on the outside may be greater than on the inside, or the urging portions 33 may be wave-like and protrude from the outside toward the inside.

The base portion of the second friction member 32 in the biasing portion 33 is shaped to extend downstream with the same width, but it is also possible to make the downstream end narrower as it approaches downstream in the feed direction, as shown in FIG. 8. Specifically, the outer side protrudes downward (downstream in the feed direction D) in FIG. 8 more than the inner side in the axial direction of the feed roller 14. In other words, the inner end of the biasing portion 33 in the width direction is positioned outward as it approaches downstream in the feed direction D.

The present invention has been described above based on one embodiment, but the present invention is not limited to the above-mentioned embodiment. In the above-mentioned embodiment, an image reading device having a separation pad 30 has been described as one example, but the present invention is of course not limited to this, and may be, for example, a sheet feeding device (such as a sheet feeder) that separates and feeds sheets, and can be widely applied to general office machines such as image processing devices (printers, multifunction devices, fax machines, etc.) other than image reading devices that are equipped with such a sheet feeding device.

S: sheet D: feeding direction 10: image reading device 12: loading platform 14: feed roller 14a: roller shaft 14b: roller member 30: separation pad 31: first separation portion 31b: roller contact portion 32: second separation portion 33: urging portion

Claims (5)

A feed roller that feeds a plurality of sheets stacked on a stacking table;
a separation pad disposed at a position facing the feed roller and configured to separate the sheets fed by the feed roller one by one;
the separation pad has a first separation portion that sandwiches and separates the sheet between the first separation portion and the feed roller, a second separation portion that contacts and separates the sheet at a position outside the feed roller in the width direction of the sheet, and a biasing portion that is provided outside the second separation portion in the width direction and biases the sheet toward the feed roller in the thickness direction of the sheet,
The sheet feeding device, wherein the biasing portion protrudes toward the sheet from the second separation portion . the second separation portion has an elastic member having an elastic force directed toward the feed roller, and the biasing portion is a flat-plate-shaped biasing portion attached to the elastic member on the feed roller side,
2. The sheet feeding device according to claim 1, wherein an area of a surface of the urging portion that contacts the sheet is larger on an outer side than on an inner side in the width direction. The sheet feeding device according to claim 2, characterized in that the friction coefficient of the surface of the biasing portion that contacts the sheet is smaller than the friction coefficient of the surface of the elastic member that contacts the sheet. The sheet feeding device according to claim 2 or 3, characterized in that the biasing portion is a film member attached to the surface of the elastic member. The sheet feeding device according to any one of claims 1 to 4, characterized in that the inner end of the biasing portion in the width direction is positioned outward in the width direction as it moves downstream in the sheet feeding direction.

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