U.S. patent application number 14/100652 was filed with the patent office on 2014-10-16 for sheet feeding device and image forming apparatus.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Akio SHIMONAGA.
Application Number | 20140306403 14/100652 |
Document ID | / |
Family ID | 51666572 |
Filed Date | 2014-10-16 |
United States Patent
Application |
20140306403 |
Kind Code |
A1 |
SHIMONAGA; Akio |
October 16, 2014 |
SHEET FEEDING DEVICE AND IMAGE FORMING APPARATUS
Abstract
A sheet feeding device includes a feeding member that rotates
and feeds a sheet; a resistance member that contacts the feeding
member with the sheet interposed therebetween, the resistance
member contacting the sheet fed by the feeding member and applying
a resistance against the feeding of the sheet; a holding unit that
holds the resistance member so that the resistance member is
movable to a position where the resistance member does not contact
the feeding member; and an urging unit that urges the resistance
member held by the holding unit in a direction opposite to a
feeding direction of the sheet.
Inventors: |
SHIMONAGA; Akio; (Kanagawa,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
51666572 |
Appl. No.: |
14/100652 |
Filed: |
December 9, 2013 |
Current U.S.
Class: |
271/274 |
Current CPC
Class: |
B65H 2801/06 20130101;
B65H 2801/39 20130101; B65H 2511/524 20130101; B65H 2404/1113
20130101; B65H 2511/212 20130101; B65H 5/062 20130101; B65H
2404/1141 20130101; B65H 2511/212 20130101; B65H 3/5215 20130101;
B65H 2404/144 20130101; B65H 2220/11 20130101; B65H 2220/08
20130101; B65H 2220/01 20130101; B65H 2511/524 20130101; B65H
2701/1912 20130101; B65H 3/0638 20130101 |
Class at
Publication: |
271/274 |
International
Class: |
B65H 5/06 20060101
B65H005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2013 |
JP |
2013-085113 |
Claims
1. A sheet feeding device comprising: a feeding member that rotates
and feeds a sheet; a resistance member that contacts the feeding
member with the sheet interposed therebetween, the resistance
member contacting the sheet fed by the feeding member and applying
a resistance against the feeding of the sheet; a holding unit that
holds the resistance member so that the resistance member is
movable to a position where the resistance member does not contact
the feeding member; and an urging unit that urges the resistance
member held by the holding unit in a direction opposite to a
feeding direction of the sheet.
2. The sheet feeding device according to claim 1, wherein a surface
of the resistance member that faces the feeding member is arc
shaped in cross section, wherein the resistance member is rotatably
held by the holding unit, and wherein the urging unit is a spring
that applies a rotational force to the resistance member.
3. The sheet feeding device according to claim 1, wherein the
resistance member includes a flat surface that applies the
resistance against the feeding of the sheet.
4. The sheet feeding device according to claim 2, wherein the
holder member includes a rotation fulcrum, and wherein the rotation
fulcrum is located so that a contact force between the feeding
member and the resistance member increases when the resistance
member applies the resistance to the sheet.
5. The sheet feeding device according to claim 1, wherein the
feeding member and the resistance member are not in contact with
each other before the feeding member is rotated.
6. The sheet feeding device according to claim 1, wherein the
urging unit is disposed in a central region of the resistance
member in a width direction that crosses a movement direction of
the resistance member or on each side of the central region in the
width direction.
7. The sheet feeding device according to claim 1, wherein, when a
single sheet is nipped between the feeding member and the
resistance member, the resistance member is moved against an urging
force applied by the urging unit to the position where the
resistance member does not contact the feeding member.
8. The sheet feeding device according to claim 1, wherein, in the
case where a single sheet is nipped between the feeding member and
the resistance member, when Np is a pressing force with which the
resistance member presses the sheet against the feeding member and
.mu. is a coefficient of friction of the resistance member, a force
Fp applied to the resistance member in the feeding direction
through the single sheet is Fp=Np.times..mu., and wherein, when Fr
is an urging force applied to the resistance member by the urging
unit in the direction opposite to the feeding direction of the
sheet, Fp>Fr is satisfied.
9. An image forming apparatus comprising: the sheet feeding device
according to claim 1; and an image forming unit which forms an
image on the sheet fed by the sheet feeding device.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2013-085113 filed Apr.
15, 2013.
BACKGROUND
Technical Field
[0002] The present invention relates to a sheet feeding device and
an image forming apparatus.
SUMMARY
[0003] According to an aspect of the invention, there is provided a
sheet feeding device including a feeding member that rotates and
feeds a sheet; a resistance member that contacts the feeding member
with the sheet interposed therebetween, the resistance member
contacting the sheet fed by the feeding member and applying a
resistance against the feeding of the sheet; a holding unit that
holds the resistance member so that the resistance member is
movable to a position where the resistance member does not contact
the feeding member; and an urging unit that urges the resistance
member held by the holding unit in a direction opposite to a
feeding direction of the sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] An exemplary embodiment of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 illustrates the structure of an image forming
apparatus according to an exemplary embodiment of the present
invention;
[0006] FIG. 2 is a side view of a feeding device according to the
exemplary embodiment of the present invention;
[0007] FIG. 3 is a perspective view of a part of the feeding device
illustrated in FIG. 1;
[0008] FIG. 4 is a perspective view of a resistance roller included
in the feeding device illustrated in FIG. 1;
[0009] FIG. 5 is a side view of the feeding device illustrated in
FIG. 1 in a state immediately after the start of a recording medium
feeding process;
[0010] FIG. 6 is a side view of the feeding device in a state in
which the recording medium has been transported from the state
illustrated in FIG. 5;
[0011] FIG. 7 is a schematic side view of a feeding device
according to a first modification;
[0012] FIG. 8A is a schematic side view of a feeding device
according to a second modification;
[0013] FIG. 8B is a side view of the feeding device in a state in
which a recording medium is being fed; and
[0014] FIG. 9 is a diagram illustrating the relationship between a
force that tries to rotate a resistance roller and a force that is
applied to the resistance roller by a recording medium in a feeding
direction S.
DETAILED DESCRIPTION
[0015] An image forming apparatus according to an exemplary
embodiment of the present invention will now be described.
Overall Structure
[0016] First, the structure of an image forming apparatus 10
according to the present exemplary embodiment will be described.
FIG. 1 schematically illustrates the structure of the image forming
apparatus 10 according to the present exemplary embodiment. The
arrow UP in FIG. 1 indicates the upward vertical direction.
[0017] The image forming apparatus 10 according to the present
exemplary embodiment illustrated in FIG. 1 includes an image
forming apparatus body 11 that houses components therein. The image
forming apparatus body 11 houses a container 12 in which
sheet-shaped recording media P, such as sheets of recording paper
and OHP sheets, are stored; an image forming section 14 that forms
an image on a recording medium P; a feeding device 100 that feeds a
sheet-shaped recording medium P from the container 12; a transport
unit 16 that transports the recording medium P that has been fed to
the image forming section 14; and a controller 20 that controls the
operation of each component of the image forming apparatus 10. An
ejection unit 18, to which the recording medium P having an image
formed thereon by the image forming section 14 is ejected, is
provided in an upper section of the image forming apparatus body
11.
[0018] The image forming section 14 includes image forming units
22Y, 22M, 22C, and 22K (hereinafter denoted by 22Y to 22K) that
form toner images of respective colors, which are yellow (Y),
magenta (M), cyan (C), and black (K), respectively; an intermediate
transfer belt 24 onto which the toner images formed by the image
forming units 22Y to 22K are transferred; first transfer rollers 26
that transfer the toner images formed by the image forming units
22Y to 22K onto the intermediate transfer belt 24; and a second
transfer roller 28 that transfers the toner images, which have been
transferred onto the intermediate transfer belt 24 by the first
transfer rollers 26, onto the recording medium P from the
intermediate transfer belt 24. The structure of the image forming
section 14 is not limited to the above-described structure as long
as an image may be formed on the recording medium P.
[0019] The image forming units 22Y to 22K are arranged next to each
other in a central region of the image forming apparatus body 11 in
the vertical direction while being tilted with respect to the
horizontal direction. Each of the image forming units 22Y to 22K
includes a photoconductor 32 that rotates in a certain direction
(for example, clockwise in FIG. 1). Since the image forming units
22Y to 22K have similar structures, components of the image forming
units 22M, 22C, and 22K are not denoted by reference numerals in
FIG. 1.
[0020] A charging roller 23, an exposure device 36, a developing
device 38, and a removing member 40 are arranged around each
photoconductor 32 in that order from an upstream side in a rotation
direction of the photoconductor 32. The charging roller 23 is an
example of a charging device that charges the photoconductor 32.
The exposure device 36 performs an exposure process on the
photoconductor 32 charged by the charging roller 23 to form an
electrostatic latent image on the photoconductor 32. The developing
device 38 develops the electrostatic latent image formed on the
photoconductor 32 by the exposure device 36 to form a toner image.
The removing member 40 contacts the photoconductor 32 and removes
toner that remains on the photoconductor 32.
[0021] The exposure device 36 forms the electrostatic latent image
on the basis of an image signal transmitted from the controller 20.
The image signal transmitted from the controller 20 may be, for
example, an image signal transmitted to the controller 20 from an
external device.
[0022] The developing device 38 includes a developer supplying unit
38A that supplies developer to the photoconductor 32 and plural
transport members 38B that transport the developer to be supplied
to the developer supplying unit 38A while stirring the
developer.
[0023] The intermediate transfer belt 24 has an annular shape and
is located above the image forming units 22Y to 22K. Stretching
rollers 42 and 44, around which the intermediate transfer belt 24
is wrapped, are disposed inside the intermediate transfer belt 24.
When one of the stretching rollers 42 and 44 is rotated, the
intermediate transfer belt 24 moves (rotates) in a certain
direction (for example, counterclockwise in FIG. 1) while being in
contact with the photoconductors 32. The stretching roller 42
serves as an opposing roller that opposes the second transfer
roller 28.
[0024] The first transfer rollers 26 oppose the respective
photoconductors 32 with the intermediate transfer belt 24
interposed therebetween. The positions between the first transfer
rollers 26 and the photoconductors 32 serve as first transfer
positions at which the toner images formed on the photoconductors
32 are transferred onto the intermediate transfer belt 24.
[0025] The second transfer roller 28 opposes the stretching roller
42 with the intermediate transfer belt 24 interposed therebetween.
The position between the second transfer roller 28 and the
stretching roller 42 serves as a second transfer position at which
the toner images that have been transferred onto the intermediate
transfer belt 24 are transferred onto the recording medium P.
[0026] The feeding device 100 is configured to separate the
sheet-shaped recording media P stored in the container 12 from each
other and feed them one by one to the transport unit 16 to avoid
simultaneous feeding of two or more recording media P to the
transport unit 16. The feeding device 100 will be described in
detail below.
[0027] The transport unit 16 includes a transport path 48 along
which each recording medium P is transported and plural transport
rollers 50 that are arranged along the transport path 48 to
transport the recording medium P to the second transfer
position.
[0028] The image forming apparatus body 11 houses a fixing device
60 at a location downstream of the second transfer position in a
transport direction. The fixing device 60 fixes the toner images
that have been transferred onto the recording medium P by the
second transfer roller 28 to the recording medium P. The fixing
device 60 may be attached to and detached from the image forming
apparatus body 11 in a manufacturing process, but is not detachable
by a user. The fixing device 60 includes ejection rollers 52 that
eject the recording medium P having the toner images fixed thereto
to the ejection unit 18.
[0029] The fixing device 60 includes a heating roller 64 and a
pressing belt 66 as examples of fixing members for fixing the toner
images to the recording medium P.
[0030] The heating roller 64 includes a cylindrical member 64A that
is rotatably supported in the fixing device 60 and a heat source
64B, such as a halogen lamp, disposed in the inner space of the
cylindrical member 64A. The pressing belt 66 has an annular shape
and is rotatably supported in the fixing device 60 at a position
where the pressing belt 66 opposes the heating roller 64.
[0031] The heating roller 64 and the pressing belt 66 rotate around
a rotation axis direction, which is a width direction of the
recording medium P (hereinafter referred to simply as a width
direction) that is orthogonal to a transport direction of the
recording medium P (hereinafter referred to simply as a transport
direction), and extend in the width direction.
[0032] When the heating roller 64 is rotated and the pressing belt
66 is rotated by the rotation of the heating roller 64, the
recording medium P onto which the toner images have been
transferred is transported while being nipped between the heating
roller 64 and the pressing belt 66. The toner on the recording
medium P that is transported while being nipped between the heating
roller 64 and the pressing belt 66 is heated by the heating roller
64 and pressed by the pressing belt 66, so that the images are
fixed to the recording medium P.
[0033] The fixing device 60 is equipped with a pair of ejection
rollers 52 for ejecting the recording medium P having the toner
images fixed thereon by the heating roller 64 and the pressing belt
66 to the ejection unit 18 from the fixing device 60. The pair of
ejection rollers 52 include a driven roller 52A and a drive roller
52B disposed below the driven roller 52A.
[0034] The image forming apparatus body 11 includes a reverse
transport path 70 for returning the recording medium P having
images formed on one side thereof to the transfer position (image
forming position) with plural transport rollers 50 to allow images
to be formed on both sides of the recording medium P.
[0035] The fixing device 60 includes an introduction path 49 that
guides the recording medium P having images fixed thereto to the
reverse transport path 70. The introduction path 49 is configured
to guide the recording medium P having images fixed thereto that
has been transported backward by reverse rotation of the ejection
rollers 52 to the reverse transport path 70. Thus, in the image
forming apparatus 10, the recording medium P having the images
formed on one side thereof may be reversed and returned to the
transport path 48 by the introduction path 49 and the reverse
transport path 70.
Image Forming Operation
[0036] Next, an image forming operation performed by the image
forming apparatus 10 according to the present exemplary embodiment
to form an image on the recording medium P will be described.
[0037] In the image forming apparatus 10 according to the present
exemplary embodiment, a recording medium P is fed from the
container 12 by the feeding device 100, and is transported to the
second transfer position by the transport rollers 50.
[0038] In each of the image forming units 22Y to 22K, the
photoconductor 32 is charged by the charging roller 23 and
subjected to the exposure process by the exposure device 36, so
that an electrostatic latent image is formed on the photoconductor
32. The electrostatic latent image is developed by the developing
device 38, so that a toner image is formed on the photoconductor
32. The toner images of the respective colors formed by the image
forming units 22Y to 22K are transferred onto the intermediate
transfer belt 24 in a superimposed manner at the first transfer
positions, so that a color image is formed. The color image formed
on the intermediate transfer belt 24 is transferred onto the
recording medium P at the second transfer position.
[0039] The recording medium P onto which the toner images have been
transferred is transported to the fixing device 60, and the toner
images are fixed to the recording medium P by the fixing device 60.
In the case where an image is to be formed only on one side of the
recording medium P, the recording medium P is ejected to the
ejection unit 18 by the ejection rollers 52 after the toner images
are fixed.
[0040] In the case where images are to be formed on both sides of
the recording medium P, the recording medium P having an image
formed on one side thereof is transported from the introduction
path 49 to the reverse transport path 70 by the reverse rotation of
the ejection rollers 52. Then, the recording medium P is
transported from the reverse transport path 70 to the transport
path 48, and an image is formed on the other side of the recording
medium P by a process similar to the above-described process. Thus,
images are formed on both sides of the recording medium P. Thus,
the image forming operation is performed.
Feeding Device
[0041] The feeding device 100 will now be described. FIG. 2 is a
side view illustrating the state before or after the recording
medium P is fed, and FIGS. 5 and 6 are side views illustrating the
state in which the recording medium P is being fed.
[0042] As illustrated in FIG. 2, the feeding device 100 includes a
feeding roller 110 disposed at an upper location and a resistance
roller 120 disposed at a lower location so as to oppose the feeding
roller 110. The direction of rotation axes of these rollers may
sometimes be referred to as a width direction. As illustrated in
FIG. 5, for example, the direction in which the recording medium P
is fed by the feeding roller 110 is defined as a feeding direction
S.
[0043] The feeding roller 110 is substantially D-shaped (half moon
shaped) and the outer periphery thereof is chamfered (D-cut) to
form a substantially flat portion. The substantially flat portion
is called a D-cut portion 114. A feeding member 112, which is made
of rubber or the like, is provided on the outer periphery of the
feeding roller 110 in a region other than the D-cut portion 114.
The feeding roller 110 is rotatable in the direction of arrow K1 by
a driving mechanism (not shown).
[0044] Rotating plates (not shown) are provided on both sides of
the feeding roller 110. The rotating plates have a diameter smaller
than that of the feeding roller 110, and are configured to prevent
the feeding member 112 and the resistance roller 120 from
contacting each other in the state before and after the recording
medium P is fed. The rotating plates (not shown) are formed by
molding a resin, such as POM.
[0045] As illustrated in FIGS. 2 and 3, the resistance roller 120
is rotatably supported by the holder member 150. Shaft portions 152
are provided on both sides of the holder member 150 in the width
direction at a downstream position in the feeding direction S. The
holder member 150 is rotatably supported on a housing (not shown)
or the like by the shaft portions 152.
[0046] As illustrated in FIG. 2, a coil spring 154 is disposed
below the holder member 150. The bottom end of the coil spring 154
is fixed to the housing (not shown) or the like. The holder member
150 is urged by an urging force of the coil spring 154 so as to
rotate around the shaft portions 152. Thus, the resistance roller
120 held by the holder member 150 is urged toward the feeding
roller 110. A stopper (not shown) is provided so that the rotation
of the holder member 150 is stopped at a predetermined
position.
[0047] Referring to FIG. 5, when the feeding roller 110 is rotated
in the direction of arrow K1, a contact pressure is applied to a
contact portion (hereinafter referred to as a nip N) between the
feeding member 112 of the feeding roller 110 and a resistance
member 130 of the resistance roller 120 by the urging force of the
coil spring 154.
[0048] The shaft portions 152 of the holder member 150 are
configured such that the urging force applied to the resistance
roller 120 held by the holder member 150 is greater when the
resistance member 130 is in contact with the feeding member 112 of
the feeding roller 110 than when the resistance member 130 is not
yet in contact with the feeding member 112 of the feeding roller
110. In other words, the shaft portions 152 of the holder member
150 are positioned so that the contact force applied between the
feeding member 112 and the resistance member 130 increases when the
resistance member 130 applies a resistance to the recording medium
P.
[0049] As illustrated in FIGS. 2 to 4, the resistance roller 120
includes a roller body 122 that is rotatably held by the holder
member 150 (see FIGS. 2 and 3) and the resistance member 130 made
of rubber that is provided over a part of the outer periphery of
the roller body 122 so as to oppose the feeding roller 110. The
resistance member 130 has an arc shape in side view.
[0050] A projection 126 and a rotation shaft 124 that is rotatably
supported by the holder member 150 (see FIGS. 2 and 3) are provided
on each end of the resistance roller 120 (roller body 122) in the
width direction. The resistance roller 120 is held by the holder
member 150 so as to be rotatable in the direction of arrow K2 and
the direction of arrow K3.
The rotational range (movable range) of the resistance member 130
of the resistance roller 120 toward the upstream side in the
feeding direction (in the direction of arrow K3) is set so that an
end 132 of the resistance member 130 in the feeding direction does
not move past the nip N (see FIG. 5) between the resistance roller
120 and the feeding roller 110. In other words, the rotation of the
resistance roller 120 in the direction of arrow K3 is stopped by a
stopper (not shown) at the position shown in FIG. 2. The feeding
roller 110 and the resistance roller 120 do not become separated
from each other even when the resistance roller 120 is rotated in
the direction of arrow K3.
[0051] The rotational range (movable range) of the resistance
member 130 of the resistance roller 120 toward the downstream side
in the feeding direction (in the direction of arrow K2) is set so
that an end 134 of the resistance member 130 opposite to the end in
the feeding direction moves past the nip N (see FIG. 5) between the
resistance roller 120 and the feeding roller 110 (see FIG. 6). In
other words, the resistance roller 120 is held by the holder member
150 so that the resistance roller 120 rotates in the direction of
arrow K2 until the upstream end 134 of the resistance member 130 of
the resistance roller 120 in the feeding direction (end in the
direction of arrow K3) moves past the nip N (see FIG. 5) between
the resistance roller 120 and the feeding roller 110 (see FIG.
6).
[0052] As illustrated in FIGS. 2 and 3, a torsion coil spring is
fitted to the rotation shaft 124 of the resistance roller 120
(roller body 122). One end portion 142 of the torsion coil spring
140 is wound around the projection 126, and the other end portion
146 of the torsion coil spring 140 is retained by a retaining
portion 156 of the holder member 150. Thus, the resistance roller
120 is urged so as to rotate in the direction of arrow K3, that is,
in a direction opposite to the feeding direction S. The resistance
roller 120 receives a torque in the direction of arrow K3
(direction opposite to the feeding direction S) from the torsion
coil spring 140.
[0053] Although only one side in the width direction (axial
direction) is illustrated in FIGS. 2 and 3, the structure at the
other side is similar to that at the illustrated side, and the
rotation shaft 124, the projection 126, the torsion coil spring
140, and the retaining portion 156 are provided. More specifically,
the torsion coil spring 140 is provided at each end of the
resistance roller 120 (resistance member 130) in the width
direction (axial direction).
Operation
[0054] The operation of the present exemplary embodiment will now
be described.
[0055] As illustrated in FIG. 5, the topmost one of the recording
media P in a stacked state is fed when the substantially D-shaped
(half moon shaped) feeding roller 110 is rotated.
[0056] As described above, a nip pressure is applied to the nip N
between the feeding member 112 of the feeding roller 110 and the
resistance member 130 of the resistance roller 120 by the urging
force of the coil spring 154. In addition, the resistance roller
120 (the resistance member 130) receives a torque in the direction
of arrow K3 (direction opposite to the feeding direction) owing to
the urging force of the torsion coil spring 140.
[0057] When a single recording medium P is fed by the feeding
roller 110, the resistance roller 120 (resistance member 130)
receives a rotational force in the direction of arrow K2 through
the recording medium P, and rotates in the direction of arrow K2
(feeding direction) against the urging force of the torsion coil
spring 140.
[0058] Referring to FIG. 9, when Np is the nip pressure applied by
the resistance member 130 of the resistance roller 120 that presses
the feeding member 112 of the feeding roller 110, .mu. is the
coefficient of friction of the resistance member 130 of the
resistance roller 120, r is the radius of the resistance roller
120, and T is the torque of the torsion coil spring 140, a force Fr
that tries to rotate the resistance roller 120 in the direction of
arrow K3 is calculated as Fr=T/r.
[0059] A force Fp applied to the resistance roller 120 (resistance
member 130) by the recording medium P in the feeding direction S is
calculated as Fp=Np.times..mu..
[0060] In order for the recording medium P to be transported, that
is, in order for the resistance roller 120 to be rotated in the
direction of arrow K2, Fp>Fr needs to be satisfied.
[0061] The image forming apparatus 10 is designed so that Fp>Fr
is satisfied as long as the recording medium P is of a type that is
capable of being subjected to a printing process performed by the
image forming apparatus 10.
[0062] As illustrated in FIG. 6, when the end portion 134 of the
resistance member 130 of the resistance roller 120 in the direction
of arrow K3 (direction opposite to the feeding direction) moves
past the nip N, the resistance roller 120 is rotated in the
direction of arrow K3 by the urging force of the torsion coil
spring 140, so that the end portion 134 returns to the nip N.
However, the resistance roller 120 soon rotates in the direction of
arrow K2 (feeding direction) again owing to the frictional force
between the recording medium P and the resistance member 130, so
that the end portion 134 of the resistance member 130 of the
resistance roller 120 is moved past the nip N. In other words, the
end portion 134 of the resistance member 130 repeatedly moves past
and returns to the nip N (small motion).
[0063] In the case where plural recording media P are fed together
by the feeding roller 110 (in case of double feeding), the topmost
recording medium P that is in contact with the feeding member 112
of the feeding roller 110 is further transported by the feeding
roller 110. Since the frictional resistance between the recording
media P is small, one or more recording media P below the topmost
recording medium P are stopped owing to a transport load (transport
resistance) of the resistance member 130 of the resistance roller
120 that tries to rotate in the direction of arrow K3 (direction
opposite to the feeding direction), and are pushed backward in the
direction of arrow K3. The recording media P below the topmost
recording medium P are pushed back past the nip N toward the
downstream side in the feeding direction. Thus, the recording media
P are separated from each other and only the topmost recording
medium P is fed to the transport unit 16 (see FIG. 1). As described
above, the image forming apparatus 10 is designed so that Fp>Fr
is satisfied. Therefore, as long as the recording medium P is of a
type that is capable of being subjected to the printing process
performed by the image forming apparatus 10, the end portion 134 of
the resistance member 130 of the resistance roller 120 moves past
the nip N.
[0064] As described above, in the feeding device 100 according to
the present exemplary embodiment, the urging force (spring force)
of the torsion coil spring 140 serves as the transport load
(transport resistance) applied to the recording medium P.
Therefore, the transport load (transport resistance) may be defined
by the urging force (spring force) of the torsion coil spring 140.
Accordingly, even when the surface of the resistance member 130 has
dust or the like attached thereto, the transport load (transport
resistance) changes by a smaller amount than in the case where the
resistance member is fixed (in the case where the transport load
(transport resistance) is defined by the frictional resistance and
the nip pressure). In other words, feeding failure, double feeding,
etc., of the recording media P may be prevented or suppressed.
[0065] The torsion coil spring 140 is provided at each end of the
resistance roller 120 (resistance member 130) in the width
direction (axial direction). Therefore, compared to the case in
which the torsion coil spring 140 is provided only at one end in
the width direction, variation in transport load along the width
direction (axial direction) is reduced (the transport load is made
uniform).
[0066] The torsion coil spring may be disposed inside the
resistance roller. Also in such a case, the spring (urging unit) is
disposed on each side of a central region in the width direction
(axial direction) to reduce variation in the transport load along
the axial direction. Alternatively, the spring (urging unit) may be
disposed only in the central region in the width direction (axial
direction). In the case where plural resistance rollers are
arranged in the axial direction, spring (urging units) may be
disposed between the resistance rollers.
[0067] When the feeding process performed by the feeding roller 110
is finished, that is, when the D-cut portion 114 of the feeding
roller 110 is positioned so as to face the resistance roller 120,
the resistance roller 120 is rotated in the direction of arrow K3
by the urging force of the torsion coil spring 140, and returns to
the original position, as illustrated in FIG. 2. As a result, the
recording media P that have been separated from the topmost
recording medium P and that remain at a position near the
downstream end of the nip N in the feeding direction are pushed
back in the direction of arrow K3. Thus, displacements of the
recording media P from the predetermined position (regular
position) may be suppressed.
[0068] A comparative example will now be considered in which the
movable range (rotatable range) of the end portion 134 of the
resistance member 130 of the resistance roller 120 is such that the
end portion 134 does not move past the nip N.
[0069] When the feeding roller 110 is rotated, the recording medium
P is fed and the resistance roller 120 is also rotated. When the
end portion 134 of the resistance member 130 in the direction of
arrow K3 stops before it moves past the nip N, the frictional force
and nip pressure of the resistance member 130, instead of the
urging force of the torsion coil spring 140, serve as the transport
load (transport resistance). This is the same as the case where the
resistance member is fixed (case where the transport load
(transport resistance) is defined by the frictional resistance and
nip pressure), and the urging force (spring force) of the torsion
coil spring 140 does not serve as the transport load (transport
resistance) applied to the recording medium P.
[0070] In the present exemplary embodiment, as described above, the
rotational range of the resistance member 130 of the resistance
roller 120 toward upstream side in the feeding direction (in the
direction of arrow K2) is set such that the end portion 134 at the
end opposite to the end in the feeding direction moves past the nip
N (see FIG. 2) between the resistance roller 120 and the feeding
roller 110. Therefore, the urging force (spring force) of the
torsion coil spring 140 serves as the transport load (transport
resistance) applied to the recording medium P.
Modifications
[0071] Modifications of the present exemplary embodiment will now
be described.
First Modification
[0072] In the above-described exemplary embodiment, the urging unit
that urges the resistance roller 120 held by the holder member 150
in a direction opposite to the feeding direction is the torsion
coil spring 140. However, the urging unit is not limited to
this.
[0073] For example, in a feeding device 190 according to a first
modification illustrated in FIG. 7, an extension coil spring 141
having an end hooked on a projection 127 may be provided to rotate
a resistance roller 121 in the direction of arrow K3.
Alternatively, a compression coil or a leaf spring may be used as
the urging unit. Alternatively, an elastic member other than a
spring, such as rubber, may be used.
Second Modification
[0074] In the above-described exemplary embodiment, the transport
load (transport resistance) is applied by the arc-shaped resistance
member 130 provided on a part of the outer periphery of the roller
body 122 that is rotatably held by the holder member 150.
[0075] The present invention may also be applied to, for example, a
case where a pad-shaped resistance member is used. In a feeding
device 200 according to a second modification illustrated in FIGS.
8A and 8B, a plate-shaped resistance member 230 having a flat
surface that applies a resistance to the recording medium P is
configured to slide along a straight line. The resistance member
230 is urged in the direction of arrow J2 by a compression coil
spring 240. As illustrated in FIG. 8B, the movable range of the
resistance member 230 in the direction of arrow J1 (feeding
direction) is set so that an end portion 234 of the resistance
member 230 in the direction of arrow J2 moves past the nip N. When
the recording medium P reaches the nip N and is transported, the
end portion 234 of the resistance member 230 repeatedly moves past
and returns to the nip N (small motion).
Others
[0076] The present invention is not limited to the above-described
exemplary embodiment.
[0077] For example, the structure of the image forming apparatus is
not limited to the structure of the above-described exemplary
embodiment, and the image forming apparatus may have various
structures.
[0078] In addition, although the image forming section 14 forms an
image on the recording medium P by an electrophotographic method in
the above-described exemplary embodiment, the image forming method
is not limited to this. An image may be formed on the recording
medium P by other methods, such as an inkjet method or a heat
transfer method.
[0079] Furthermore, although the present invention is applied to
the image forming apparatus that forms an image on the recording
medium P in the above-described exemplary embodiment, the present
invention is not limited to this. The present invention may also be
applied to apparatuses other than image forming apparatuses, such
as image reading apparatuses, automatic teller machines, and cash
registers. The present invention may be applied to any type of
feeding device that separates sheets from each other and feeds them
one by one.
[0080] Furthermore, various embodiments are, of course, possible
within the scope of the present invention.
[0081] The foregoing description of the exemplary embodiment of the
present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiment was chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
* * * * *