JP2017081658A - Medium feeding device and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a medium feeding device capable of appropriately feeding various kinds of media, and an image reading device.SOLUTION: A medium feeding device comprises: a medium placing member 22 placing a medium on a medium placing surface 22a; a feed roller 26 feeding the medium to a downstream side; a first separation roller 28 nipping and separating the medium between the feed roller 26 and the first separation roller 28; and a second separation roller 30 being provided at a downstream side in a medium transportation direction of the first separation roller 28 and capable of switching between a nip state of nipping and separating the medium between feed roller 26 and the second separation roller 30 and a separated state of separating from the feed roller 26.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a medium feeding device for feeding a medium, and an image reading apparatus including the medium feeding device.

A scanner, which is an example of an image reading device, is provided with a medium feeding device (also called ADF (Auto Document Feeder)) that automatically sends a document as a medium so that a plurality of documents can be automatically fed and read. May be configured. As a configuration of such a medium feeding device, as shown in Patent Document 1, a feeding roller that feeds the document by rotating in contact with the surface of the document set on a tray on which the document is placed, and And a separation roller that is pressed against the feeding roller by a spring or the like and nips the document with the feeding roller to separate a plurality of documents into one sheet.
For example, Patent Document 1 discloses a scanner including a sheet conveying device including a sheet feeding roller 113 as the feed roller and a retard roller 114 as the separation roller.

  The feed roller is configured to sequentially feed a sheet bundle (a plurality of documents) stacked on a tray from a lower sheet, that is, a sheet on a tray mounting surface side, and the separation roller includes: Sheets other than the first sheet from the bottom of the sheet bundle (second sheet from the bottom) are dammed up, and the first sheet from the bottom of the sheet bundle is nipped between the feed roller and the separation roller and is moved downstream. Be transported.

JP 2014-051338 A

  In such a scanner, a document to be read is required not only to be a general plain paper but also to support various types of paper types from thin paper to thick paper used for business cards and the like.

  Here, the feed roller and the separation roller exhibit a paper separation effect due to a conveyance load caused by the nip of the feed roller and the separation roller. If the contact length between the feed roller and the separation roller (the length of the nip portion in the paper conveyance direction) is increased, the conveyance load is increased and the separation capability is increased. On the other hand, if the contact length is shortened, the conveyance load is reduced, so that the separation ability is lower than that when the contact length is long.

The contact length between the feed roller and the separation roller varies depending on the paper type to be fed. More specifically, the suitable contact length varies depending on the basis weight of the paper or the rigidity of the paper. The contact length varies depending on the diameter of the separation roller, for example. The larger the diameter of the separation roller, the longer the contact length.
If the contact length is increased, the separation performance is improved as described above. However, since the conveyance load is increased, there is a trade-off relationship that the possibility of non-feeding is increased. Especially when the contact length is increased, the rigidity of the cardboard or the like is increased. It becomes easy to non-feed in the case of high paper.

  Furthermore, as described above, the separation roller also has a separation effect by blocking the sheet bundle. The separation by the damming of the separation roller is performed prior to the separation by the nip between the feed roller and the separation roller, and is hereinafter referred to as “preliminary separation”. Further, the separation by the nip between the feed roller and the separation roller is hereinafter referred to as “main separation”.

  The effect of the preliminary separation varies depending on the position of the separation roller with respect to the feed roller and the diameter of the separation roller, and is also suitable depending on the type of paper to be fed, that is, the paper basis weight or the difference in paper rigidity. The position with respect to the feed roller is different.

In addition, as the diameter of the separation roller decreases, the leading edge of the sheet bundle comes into contact with the separation roller at a steep angle, so the effect of the preliminary separation is enhanced, but the contact length between the feed roller and the separation roller is shortened, The effect of this separation becomes difficult to obtain. Conversely, if the diameter of the separation roller is increased in order to obtain the effect of this separation more reliably (to ensure the contact length between the feed roller and the separation roller), the leading edge of the sheet bundle contacts the separation roller at a gentle angle. Therefore, it becomes difficult to obtain the effect of the preliminary separation.
Therefore, in consideration of dealing with many types of paper, the design freedom of the diameter of the separation roller and the position with respect to the feed roller is low.

  In view of the above problems, an object of the present invention is to provide a medium feeding apparatus and an image reading apparatus that can appropriately feed various types of media.

  In order to solve the above problems, a medium feeding device according to a first aspect of the present invention includes a medium placing member for placing a medium on a medium placing surface, a feed roller for feeding the medium to the downstream side, A first separation roller that nips and separates the medium from the feed roller and a downstream side of the first separation roller in the medium transport direction, and nips and separates the medium from the feed roller And a second separation roller capable of switching between a nip state and a separated state separated from the feed roller.

According to this aspect, since the feed roller is provided with the second separation roller in addition to the first separation roller, the contact area of the medium with respect to the feed roller can be ensured, and the separation performance can be improved. And the 2nd separation roller provided in a downstream side can reduce the conveyance load of the said medium by separating from the said feed roller. For example, when the medium having high rigidity is transported, the second separation roller takes the separated state, thereby avoiding an excessive transport load on the medium having high rigidity, that is, avoiding or suppressing non-feeding. it can.
This makes it possible to achieve good separation for media of various stiffnesses or thicknesses.

  The medium feeding device according to a second aspect of the present invention is the medium feeding device according to the first aspect, wherein the nip region by the first separation roller and the nip region by the second separation roller with respect to the feeding roller are in the medium conveyance direction of the medium. It is provided in the position which does not overlap in.

  According to this aspect, the separation by the first separation roller and the separation by the second separation roller can be performed independently.

  The medium feeding device according to a third aspect of the present invention is characterized in that, in the first aspect or the second aspect, the first separation roller is formed with a smaller diameter than the second separation roller. And

  The curvature of the outer periphery of a separation roller becomes large, so that the diameter of the "separation roller" which contacts the said feed roller becomes small. As a result, the leading end of the bundle of media abuts against the separation roller at a steep angle, and from this point of view, the number of media entering between the separation roller and the feed roller can be well regulated. That is, the “preliminary separation” described above is performed well. However, since the contact length between the feed roller and the separation roller is shortened, the separation ability when a plurality of media enter between the feed roller and the separation roller, that is, in terms of "main separation" is inferior. It will be.

According to this aspect, by forming the first separation roller provided on the upstream side in the medium conveyance direction to have a smaller diameter than the second separation roller, the number of media entering between the first separation roller and the feed roller “Preliminary separation” that regulates the above can be performed well. Then, the contact length between the second separation roller and the feed roller can be ensured by the downstream second separation roller (having a larger diameter than the first separation roller), and the medium " This separation can be performed. In addition, in the case of a medium having high rigidity, the second separation roller is separated from the feed roller, so that an excessive transport load can be avoided and non-feed can be avoided or suppressed.
As described above, the restriction (preliminary separation) of the number of media entering between the separation roller and the feeding roller (hereinafter referred to as the separation unit) and the separation performance required when a plurality of media enter the separation unit. Both (main separation) can be ensured.

  A medium feeding device according to a fourth aspect of the present invention is the medium feeding device according to any one of the first to third aspects, wherein the first biasing member biases the first separation roller toward the feeding roller. A second urging member that urges the second separation roller toward the feeding roller, and the urging force of the second urging member is smaller than the urging force of the first urging member. It is characterized by that.

  When the urging force of the second urging member that urges the second separation roller toward the feeding roller is increased, the second separation roller cannot be separated even if a medium having high rigidity enters, and non-feeding is not performed. May occur. However, according to this aspect, since the urging force of the second urging member is smaller than the urging force of the first urging member, such a problem can be avoided or suppressed.

  The medium feeding device according to a fifth aspect of the present invention is the medium feeding apparatus according to the fourth aspect, wherein the second medium having a higher rigidity than the first medium is applied to the second medium by the feeding roller. When fed, the second separation roller is pushed by the second medium and displaced in a direction away from the feed roller, and when the first medium is fed by the feed roller, the second separation roller is displaced. It is characterized by being set to a size that does not.

According to this aspect, when the medium to be fed is the second medium whose rigidity is higher than that of the first medium, the second separation roller is pushed by the second medium and the feeding is performed. Since it is displaced in the direction away from the roller, it is possible to reduce the transport load on the second medium and reduce or avoid the possibility of non-delivery.
Further, when the medium to be fed is the first medium (having lower rigidity than the second medium), the medium is reliably separated by the first separation roller and the second separation roller. Can be fed.

  In the medium feeding device according to the sixth aspect of the present invention, in any one of the first aspect to the fifth aspect, the feeding roller has a larger diameter than the first separation roller and the second separation roller. It is formed, It is characterized by the above-mentioned.

  According to this aspect, the contact area of the medium with respect to the feed roller by the first separation roller and the second separation roller can be provided more reliably.

  The medium feeding device according to a seventh aspect of the present invention is the medium feeding device according to any one of the first aspect to the sixth aspect, wherein the first separation roller is spaced by two in the direction intersecting the medium conveying direction. The second separation roller is provided between the two first separation rollers in a direction intersecting the medium conveyance direction.

  According to this aspect, by providing two first separation rollers, the medium can be more reliably separated on the upstream side. Moreover, it can be set as the structure which arrange | positions a 1st separation roller and a 2nd separation roller with sufficient balance, and feeds a medium more reliably.

  A medium feeding device according to an eighth aspect of the present invention is placed on the medium placing surface on the upstream side in the medium conveying direction of the feed roller in any one of the first to seventh aspects. There is no pickup roller that picks up the medium and sends it to the downstream side in the medium conveyance direction.

According to this aspect, in the medium feeding device in which the pickup roller is not provided on the upstream side in the transport direction of the feeding roller, the same effects as in any of the first to seventh aspects are achieved.
In addition, the apparatus can be downsized by adopting a configuration without the pickup roller.

  In the medium feeding device according to the ninth aspect of the present invention, in any one of the first to eighth aspects, the nip state and the separated state are switched according to the rigidity of the medium. It is characterized by.

  According to this aspect, since the nip state and the separation state between the feed roller and the second separation roller are switched according to the rigidity of the medium, for example, when a medium with high rigidity is conveyed The separated state can be taken to avoid an excessive transport load. Therefore, the non-delivery of the rigid medium can be avoided or suppressed.

  An image reading apparatus according to a tenth aspect of the present invention includes a reading unit that reads a medium, and the medium feeding device according to any one of the first to ninth aspects that sends the medium toward the reading unit. It is characterized by comprising.

  According to this aspect, in the image reading apparatus including the reading unit that reads the medium, when the medium is fed toward the reading unit, the same effect as any one of the first to ninth aspects. Is obtained.

1 is a perspective view showing an external appearance of an image reading apparatus according to the present invention. 1 is a perspective view showing an external appearance of a state in which a cover part of an image reading apparatus according to the present invention is opened. FIG. 3 is a side cross-sectional view illustrating a sheet conveyance path of the image reading apparatus according to the present invention. 1 is a schematic side view of a medium feeding device according to the present invention. Schematic plan view of a medium feeding device according to the present invention The figure explaining operation | movement of the 1st separation roller in the case of feeding the medium with low rigidity. The figure explaining operation | movement of the 2nd separation roller in the case of feeding the medium with low rigidity. The figure explaining operation | movement of the 1st separation roller in the case of feeding a medium with high rigidity. The figure explaining operation | movement of the 2nd separation roller in the case of feeding a medium with high rigidity.

[Example 1]
First, an outline of an image reading apparatus according to an embodiment of the present invention will be described. As an example of the image reading apparatus of the present embodiment, a document scanner (hereinafter simply referred to as a scanner 10) capable of reading at least one of the front surface and the back surface of a medium is given as an example.
FIG. 1 is a perspective view showing an appearance of an image reading apparatus according to the present invention. FIG. 2 is a perspective view showing the appearance of the image reading apparatus according to the present invention in a state where the cover portion is opened. FIG. 3 is a side cross-sectional view showing the paper conveyance path of the image reading apparatus according to the present invention. FIG. 4 is a schematic side view of the medium feeding device according to the present invention. FIG. 5 is a schematic plan view of the medium feeding device according to the present invention.

  FIG. 6A is a diagram illustrating the operation of the first separation roller when feeding a medium with low rigidity. FIG. 6B is a diagram illustrating the operation of the second separation roller when feeding a medium with low rigidity. FIG. 7A is a diagram illustrating the operation of the first separation roller when feeding a medium having high rigidity. FIG. 7B is a diagram illustrating the operation of the second separation roller when feeding a medium having high rigidity.

<Overview of the scanner>
A scanner 10 as an image reading apparatus according to the present invention includes a document feeding device 25 (FIG. 3) which is an embodiment of a “medium feeding device” according to the present invention. Further, as shown in FIG. 1, a lower unit 12, an upper unit 14, a cover portion 16, and a paper discharge tray 18 are provided.

In the XYZ coordinate system shown in each drawing, the X direction is the apparatus width direction, the paper width direction, and the Y direction is the paper transport direction. The Z direction is a direction that intersects the Y direction, and generally indicates a direction that is orthogonal to the surface of the sheet being conveyed. Further, the + Y direction side is the front side of the apparatus, and the −Y direction side is the back side of the apparatus. Also, the right side when viewed from the front side of the apparatus is the + X direction, and the left side is the −X direction. Further, the + Z direction is the upper side of the apparatus (including the upper and upper surfaces), and the −Z direction side is the lower side of the apparatus (including the lower and lower surfaces).
Further, in the scanner 10, the paper P as a medium is transported in the + Y direction in each drawing. In the following, the direction in which the paper P is conveyed (+ Y direction side) is referred to as “downstream”, and the opposite direction (−Y direction side) is referred to as “upstream”.

The upper unit 14 is attached to the lower unit 12 so as to be rotatable with respect to the lower unit 12 with the downstream side in the sheet conveying direction as a rotation fulcrum.
Further, a cover portion 16 that opens and closes the upper portion of the upper unit 14 is provided.
The cover part 16 is attached to the lower unit 12 so as to be rotatable with respect to the upper part on the back side of the lower unit 12. As shown in FIG. 1, the cover 16 covers the upper portion of the upper unit 14 and the feeding port 20 (FIG. 2), and the back side of the apparatus as shown in FIG. 2 from the non-feeding state of FIG. The feed port 20 is opened, and the back surface of the cover portion 16 (a support surface 16a described later) can be in a feed state in which the paper P is connected to the medium placement member 22.

  Further, a discharge port 24 for discharging the paper P is provided on the front side of the lower unit 12. Further, the lower unit 12 includes a paper discharge tray 18 that can be pulled out from the discharge port 24 toward the front side of the apparatus. The paper discharge tray 18 can be in a state of being housed in the bottom of the lower unit 12 (see FIG. 1) and in a state of being pulled out to the front side of the apparatus (see FIG. 2). Further, in the present embodiment, the paper discharge tray 18 is configured by connecting a plurality of tray members, and the pull-out length from the discharge port 24 can be adjusted according to the length of the paper P to be discharged.

<About the feeding route in the scanner>
Next, a paper conveyance path in the scanner 10 will be described mainly with reference to FIG. In FIG. 3 and subsequent figures, only the main components of the scanner 10 and the document feeder 25 are shown, and the components unnecessary for the description are omitted. In FIG. 3, the lower unit 12 and the upper unit 14 show only the outline of the casing by phantom lines.

  The front side (downstream side) of the paper P as the medium (original) set in the feeding port 20 is supported by the medium placement surface 22a of the medium placement member 22, and the rear end side (upstream side) is the lower part. The unit 12 is placed by being supported by a support surface 16a which is the back surface of the cover portion 16 in a posture rotated to the back side of the apparatus. A plurality of documents can be set at the feeding port 20.

The original placed on the support surface 16a of the cover portion 16 in the opened state and the medium placement surface 22a of the medium placement member 22 is the lowermost original (sheet) placed by a drive source (not shown). The sheet is fed downstream in the feeding direction by a feeding roller 26 as a “feeding roller” that is rotationally driven by a certain motor. The outer peripheral surface of the feeding roller 26 is made of a high friction material (for example, an elastomer such as rubber). Reference numeral 26 a is a rotation shaft of the feeding roller 26.
The feeding roller 26 is arranged so that a part thereof protrudes with respect to the medium placement surface 22 a of the medium placement member 22.

  In FIG. 3, a symbol G indicates a document bundle placed (set) on the cover unit 16. The front end of the bundle of documents G is held at a feeding standby position (position shown in FIG. 3) by a stopper (not shown) before the feeding is started, and the feeding roller 26 and a first separating roller 28 serving as a separating unit described later. The entry into the space is regulated.

When document feeding is started, the lowest document in the document bundle G comes into contact with the feeding roller 26, and the lowest document (paper P) is fed downstream by the rotation of the feeding roller 26.
Two separation rollers (a first separation roller 28 and a second separation roller 30) are provided at a position facing the feeding roller 26. In the present embodiment, the first separation roller 28 is provided in a state of being urged against the feeding roller 26 by the first urging member 32 (FIG. 4). Similarly, the second separation roller 30 is provided in a state of being urged against the feeding roller 26 by the second urging member 34 (FIG. 4). The outer peripheral surfaces of the first separation roller 28 and the second separation roller 30 are made of a high friction material (for example, an elastomer such as rubber) in the same manner as the feeding roller 26.

In the present embodiment, the first biasing member 32 and the second biasing member 34 are provided on the rotation shafts 28a and 30a of the first separation roller 28 and the second separation roller 30, respectively. For example, the rotation shaft 28a , 30a can be provided with a first urging member 32 and a second urging member 34.
The roles of the first separation roller 28 and the second separation roller 30 and the further detailed configuration of the document feeder 25 will be described in detail after the description of the sheet conveyance path.

  The first separation roller 28 and the second separation roller 30 include torque limiters 29 and 31, respectively. Further, via the torque limiters 29 and 31, an original is supplied from a torque applying means (not shown) or a driving source such as a motor. It is configured to receive a drive torque in a direction (counterclockwise direction in FIG. 3) opposite to the rotational direction (clockwise direction in FIG. 3) sent to the downstream side.

  In the above configuration, when the first separation roller 28 and the second separation roller 30 are in direct contact with the feeding roller 26, the rotational torque received from the feeding roller 26 exceeds the limit torque of the torque limiters 29 and 31. Then, it rotates following the feeding roller 26 (clockwise direction in FIG. 3).

Then, the feeding of the document is started, and when a plurality of documents enter between the feeding roller 26 and the first separation roller 28 or the second separation roller 30, the first separation roller 28 and the second separation roller 30 are fed. No rotation torque is received from the feed roller 26, and the rotation driven by the feed roller 26 stops. As a result, the upper document excluding the lowest document to be fed (the document to be prevented from being double-fed) is not subjected to the conveyance force for proceeding to the downstream side, and the leading end thereof is the first separation roller 28 and the second document. It is not possible to proceed downstream with the separation roller 30 in contact. As a result, double feeding of documents is prevented.
Since the lowest document to be fed is in direct contact with the feeding roller 26, the lowermost document advances downstream by the conveyance force received from the feeding roller 26.
In FIG. 3, the broken line indicated by the symbol E indicates the transport locus of the transported document (paper P).

  In the present embodiment, the feeding roller 26, the first separation roller 28, and the second separation roller 30 are provided in the central region of the document in the document width direction (X direction) as shown in FIG. Further, in the present embodiment, the feeding reference position in the document width direction (X direction) is the center, and the document fed in the above manner has a central portion in the document width direction as the first roller and the first roller regardless of the size. It contacts the separation roller 28 and the second separation roller 30.

In the present embodiment, a plurality of sets (more specifically, two sets) of feed rollers 26 are provided in the document width direction (X direction) (FIG. 5). A first separation roller 28 and a second separation roller 30 are provided.
Two first separation rollers 28 are provided at an interval in the direction intersecting the medium conveyance direction (X-axis direction) with respect to one feeding roller 26, and the second separation roller 30 is arranged in the X-axis direction. It is provided so as to be positioned between the two first separation rollers 28.

  Subsequently, on the downstream side of the feeding roller 26, the first separation roller 28, and the second separation roller 30, a document conveyance unit including conveyance rollers 35 and 36 is provided. The lowest document sent out by the feeding roller 26 receives a feeding force from the conveying rollers 35 and 36 and is further conveyed downstream.

  On the downstream side of the transport rollers 35 and 36, reading sensors 37 and 38 as “reading sections” of the document are arranged to face each other in the vertical direction. In the present embodiment, the reading sensors 37 and 38 are configured as a contact image sensor module (CISM) as an example.

After the document is read by at least one of the front surface and the back surface by the reading sensors 37 and 38, the document discharge unit 24 includes discharge rollers 39 and 40 positioned on the downstream side in the transport direction of each sensor. Discharged from.
In this embodiment, a plurality of pairs (more specifically, two pairs) of the roller pairs of the transport rollers 35 and 36 and the roller pairs of the discharge rollers 39 and 40 are provided in the document width direction (X direction).

<About the document feeder>
The above is the schematic configuration of the scanner 10, and the configuration of the document feeding device 25 will be described in further detail below with reference to FIG.
As shown in FIG. 4, the document feeder 25 includes a first separation roller 28 and a second separation roller that nip and separate the paper P between the feeding roller 26 and the feeding roller 26 as described above. 30.

  A nip region 42 (FIGS. 4 and 5) by the first separation roller 28 with respect to the feeding roller 26 and a nip region 44 (FIGS. 4 and 5) by the second separation roller 30 are in the medium conveyance direction (Y-axis direction). It is provided in a position that does not overlap.

  Since the nip region 42 by the first separation roller 28 and the nip region 44 by the second separation roller 30 do not overlap, the separation by the first separation roller 28 and the separation by the second separation roller 30 can be performed independently.

  The second separation roller 30 provided on the downstream side of the first separation roller 28 is fed in accordance with the nip state (FIG. 6B) in which the paper P is nipped and separated from the feeding roller 26 and the rigidity of the paper P. It is configured to be switchable between a separated state (FIG. 7B) separated from the feed roller 26.

Here, the operation of the first separation roller 28 and the second separation roller 30 according to the rigidity of the paper P will be described. 6A and 6B show a state where relatively thin paper, for example, plain paper, is fed as the “first medium”.
As shown in FIG. 6A, the first separation roller 28 prevents the other than the lowest document in the plain paper bundle G from entering between the first separation roller 28 and the feeding roller 26 (separation unit). After “preliminary separation” is performed, “main separation” is performed in the nip region 42 of the first separation roller 28. However, the thin paper is easily taken downstream along with the lower paper, and a plurality of originals may pass through the separation portion by the first separation roller 28 in some cases.

  In such a case, separation between the second separation roller 30 and the feeding roller 26 is performed. That is, the “preliminary separation” and the “main separation” are performed also in the separation unit by the second separation roller 30.

  As described above, by providing the feeding roller 26 with the second separation roller 30 in addition to the first separation roller 28, it is possible to ensure the contact length (nip region) of the paper P with respect to the feeding roller 26. And separation performance can be improved.

Next, in FIGS. 7A and 7B, paper thicker than plain paper (hereinafter referred to as thick paper) is fed as “second medium” having higher rigidity than plain paper as “first medium”. Indicates the state.
In the case of thick paper, as in the case of plain paper, first, “preliminary separation” and “main separation” are performed by the first separation roller 28 (FIG. 7A).
Here, the paper P having high rigidity such as thick paper is relatively easily separated from the thin paper (having low rigidity), and the contact length of the paper P with the feeding roller 26 is less, and the paper P is separated by the first separation roller 28. It may be possible to separate only by part. On the contrary, the presence of the nip region 44 by the second separation roller 30 may cause an excessive conveyance load and lead to non-feeding of the paper P.

However, in the present embodiment, when thick paper thicker than plain paper is fed, the second separation roller 30 is configured to take a separated state in which the second separation roller 30 is separated from the feeding roller 26 as shown in FIG. 7B. Yes. In FIG. 7B, the second separation roller 30 and the rotation shaft 30a indicated by the alternate long and short dash line indicate the position before the separation of the second separation roller 30 (the position of the second separation roller 30 in FIG. 7A).
As a result, it is possible to avoid an excessive transport load on the highly rigid paper P, that is, to avoid or suppress non-feeding. With the above configuration, it is possible to achieve good separation with respect to media having various rigidity or thickness.

In the present embodiment, the urging force of the second urging member 34 provided on the second separation roller 30 is set to be smaller than the urging force of the first urging member 32 provided on the first separation roller 28.
When the urging force of the second urging member 34 is increased, the second separation roller 30 cannot be separated even when the highly rigid paper P enters, and there is a possibility that non-feeding may occur. Such a problem can be avoided or suppressed by making the urging force of the second urging member 34 smaller than that of the first urging member 32.

In addition, when the diameter of the second separation roller 30 is larger than the diameter of the first separation roller 28 as in the present embodiment, the contact length between the second separation roller 30 and the feeding roller 26 is the first. The contact length between the separation roller 28 and the feeding roller 26 is longer. Therefore, if the urging force of the second urging member 34 that urges the second separation roller 30 toward the feeding roller 26 is increased, the load when the paper P passes through the separation portion increases, and non-feeding is likely to occur. Become.
However, such a problem can be avoided by reducing the urging force of the second urging member 34.

  Further, the urging force of the second urging member 34 is applied to the second separation by being pushed by the highly rigid original (thick paper) when the original (for example, thick paper) having higher rigidity than the plain paper is fed by the feeding roller 26. When the roller 30 is displaced in the direction away from the feeding roller 26 and the plain paper (having lower rigidity than the thick paper) is fed by the feeding roller 26, the size is set such that the second separation roller 30 is not displaced.

This makes it possible to easily realize a configuration in which the second separation roller 30 is displaced in the direction away from the feeding roller 26 when the fed document is thick paper having high rigidity. The risk of non-delivery can be reduced or avoided.
In addition, when the document to be fed is plain paper (stiffer than thick paper) or less rigid than plain paper, the first separation roller 28 and the second separation roller 30 ensure that the document is Can be fed separately.

In the present embodiment, the first separation roller 28 is formed to have a smaller diameter than the second separation roller 30.
As described above, the smaller the diameter of the first separation roller 28 in contact with the front end of the original bundle G, the higher the curvature of the outer periphery thereof, and the front end of the original bundle G abuts at a steep angle. And the feeding roller 26, the number of originals entering between the paper and the feed roller 26 is restricted, and thus a good “preliminary separation” capability can be obtained.

On the other hand, if the diameter of the first separation roller 28 is small, the contact length between the first separation roller 28 and the feeding roller 26 (the length of the nip region 42 in the medium conveyance direction) is shortened. Although the separation capability is low, the second separation roller 30 having a diameter larger than that of the first separation roller 28 on the downstream side of the first separation roller 28 allows the second separation roller 30 and the feeding roller 26 to be separated from each other. The contact length (the length of the nip region 44 in the medium conveyance direction) can be ensured, and the “main separation” ability to reliably separate the document is obtained.
As described above, both “preliminary separation” and “main separation” can be achieved.

Note that the contact position of the first separation roller 28 with respect to the feeding roller 26 is usually a position where the paper P is pressed downward on the downstream side of the first separation roller 28. In such a position, the closer the first separation roller 28 is to the downstream side, the easier it is for the paper P to be wound around the feed roller 26, so that the carrying load increases and the “main separation” capability increases. However, if the conveying load is too large, there is a risk that a highly rigid original such as cardboard will not be fed.
The position of the first separation roller 28 in the medium conveyance direction may be determined in consideration of, for example, a conveyance load for a highly rigid document. As a result, when the rigidity of the document is high, the second separation roller 30 is separated from the feeding roller 26, so that an excessive conveyance load can be avoided and non-feeding can be avoided or suppressed.

On the other hand, when the rigidity of the document is low, the contact length between the feeding roller 26 by the two separation rollers of the first separation roller 28 and the second separation roller 30 is secured, and “preliminary separation” is performed in the first. Since it can carry out with both the 1 separation roller 28 and the 2nd separation roller 30, more reliable separation is realizable. Particularly, in the second separation roller 30 provided on the downstream side, the leading edge of the paper P comes into contact with the first separation roller 28 at a steeper angle than in the case where the leading edge of the paper P comes into contact with the first separation roller 28. Can be demonstrated.
By these things, the design freedom of the size of the diameter of the separation roller (the 1st separation roller 28, the 2nd separation roller 30) with respect to the feeding roller 26, and a position can be raised.

  The feeding roller 26 has a larger diameter than the first separation roller 28 and the second separation roller 30, the nip region 42 between the first separation roller 28 and the feeding roller 26, and the second separation roller 30. The nip region 44 of the feeding roller 26 can be provided with certainty.

  Further, as described above, by providing two first separation rollers 28 with respect to one feeding roller 26, it is possible to more reliably separate the document on the upstream side. Further, the first separation roller 28 and the second separation roller 30 can be arranged in a well-balanced manner, so that the document can be fed more reliably.

Note that a general medium feeding apparatus may have a pickup roller that picks up the paper P placed on the medium placement surface 22a and sends it to the downstream side upstream of the feeding roller 26 in the medium conveyance direction. However, this embodiment does not have this.
By adopting a configuration without a pickup roller, the scanner 10 can be reduced in size.

  In the present embodiment, the scanner 10 as an “image reading device” including the document feeding device 25 as a “medium feeding device” has been described as an example. However, the “medium feeding device” according to the present invention is described below. It is also possible to use a plurality of media placed on the media placement member for other devices having a configuration for feeding in order from the lowest media, such as a printer or a facsimile.

  In addition, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

10 ... Scanner, 12 ... Lower unit, 14 ... Upper unit,
16 ... cover portion, 16a ... support surface, 18 ... paper discharge tray, 20 ... feeding port,
22 ... Medium placement member, 22a ... Medium placement surface, 24 ... Discharge port,
26 ... feed roller, 28 ... first separation roller, 30 ... second separation roller,
32 ... 1st biasing member, 34 ... 2nd biasing member, 35, 36 ... Conveyance roller,
37, 38 ... reading sensor, 39, 40 ... discharge roller, 42 ... nip area,
44: Nip region, P: Paper, G: Document bundle

Claims (10)

A medium mounting member for mounting a medium on the medium mounting surface;
A feed roller for feeding the medium downstream;
A first separation roller that nips and separates the medium from the feed roller;
A second side provided downstream of the first separation roller in the medium conveying direction and capable of switching between a nip state in which the medium is nipped and separated from the feed roller and a separated state in which the medium is separated from the feed roller. A separation roller;
A medium feeding device comprising:   2. The medium feeding device according to claim 1, wherein a nip region by the first separation roller and a nip region by the second separation roller with respect to the feeding roller are provided at positions that do not overlap in the medium conveyance direction of the medium. A medium feeding device characterized by that.   3. The medium feeding device according to claim 1, wherein the first separation roller has a smaller diameter than the second separation roller. 4. In the medium feeding device according to any one of claims 1 to 3,
A first biasing member that biases the first separation roller toward the feed roller;
A second biasing member that biases the second separation roller toward the feed roller,
The medium feeding device according to claim 1, wherein a biasing force of the second biasing member is smaller than a biasing force of the first biasing member. The medium feeding device according to claim 4, wherein
The urging force of the second urging member is such that when the second medium having higher rigidity than the first medium is fed by the feeding roller, the second separating roller is pushed by the second medium and the feeding is performed. The medium feeding device, wherein the medium feeding device is set to a size that is displaced in a direction away from the roller and the second separation roller is not displaced when the first medium is fed by the feeding roller. In the medium feeding device according to any one of claims 1 to 5,
The medium feeding device, wherein the feeding roller is formed to have a larger diameter than the first separation roller and the second separation roller. In the medium feeding device according to any one of claims 1 to 6,
Two first separation rollers are provided at intervals in a direction intersecting the medium conveyance direction,
The medium feeding device, wherein the second separation roller is located between the two first separation rollers in a direction intersecting the medium conveyance direction.   The medium feeding device according to any one of claims 1 to 7, wherein the medium placed on the medium placing surface is picked up and conveyed to the upstream side of the feeding roller in the medium carrying direction. A medium feeding device characterized by not having a pickup roller for feeding to the downstream side in the direction. In the medium feeding device according to any one of claims 1 to 8,
The medium feeding device, wherein the nip state and the separated state are switched according to the rigidity of the medium. A reading unit for reading a medium;
The medium feeding device according to any one of claims 1 to 9, wherein the medium is fed toward the reading unit.
An image reading apparatus.

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