U.S. patent application number 14/755206 was filed with the patent office on 2015-10-22 for sheet conveying device and image forming apparatus with the same.
The applicant listed for this patent is Sharp Kabushiki Kaisha. Invention is credited to Kohji AOKI, Norichika KATSURA, Masaharu KIMURA, Yoshiyuki KOBAYASHI.
Application Number | 20150298933 14/755206 |
Document ID | / |
Family ID | 45559308 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150298933 |
Kind Code |
A1 |
KIMURA; Masaharu ; et
al. |
October 22, 2015 |
SHEET CONVEYING DEVICE AND IMAGE FORMING APPARATUS WITH THE
SAME
Abstract
A sheet conveying device (30) includes a plurality of first
conveyance rollers (31) and a plurality of second conveyance
rollers (32). The sheet conveying device (30) includes stiffening
rollers (34). The stiffening rollers (34) are disposed coaxially
with at least one conveyance rollers (32) among the first and
second conveyance rollers (31) and (32), and have diameters larger
than diameters of the conveyance rollers (32). The stiffening
rollers (34) includes first stiffening rollers (34a), which apply
conveying forces to a sheet (P), and second stiffening rollers
(34b), which apply smaller conveying forces to the sheet (P) than
the conveying forces to the sheet (P) in the first stiffening
rollers (34a).
Inventors: |
KIMURA; Masaharu; (Osaka,
JP) ; AOKI; Kohji; (Osaka, JP) ; KOBAYASHI;
Yoshiyuki; (Osaka, JP) ; KATSURA; Norichika;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sharp Kabushiki Kaisha |
Osaka |
|
JP |
|
|
Family ID: |
45559308 |
Appl. No.: |
14/755206 |
Filed: |
June 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14323034 |
Jul 3, 2014 |
9096406 |
|
|
14755206 |
|
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13813994 |
Mar 13, 2013 |
8800987 |
|
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PCT/JP2011/066105 |
Jul 14, 2011 |
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14323034 |
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Current U.S.
Class: |
271/272 |
Current CPC
Class: |
B65H 29/20 20130101;
B65H 5/068 20130101; B65H 2404/133 20130101; B65H 5/062 20130101;
B65H 29/145 20130101; B65H 29/70 20130101; B65H 2801/06
20130101 |
International
Class: |
B65H 29/70 20060101
B65H029/70; B65H 5/06 20060101 B65H005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2010 |
JP |
2010-177576 |
Claims
1. A sheet conveying device comprising: a plurality of first
conveyance rollers; a plurality of second conveyance rollers that
face, one by one, the plurality of first conveyance rollers, the
plurality of second conveyance rollers conveying a sheet while
sandwiching the sheet between the second conveyance rollers and the
first conveyance rollers; and a stiffening roller disposed
coaxially with either or both of the first and second conveyance
rollers, the stiffening roller having a diameter larger than a
diameter of either or both of the first and second conveyance
rollers that are disposed coaxially, wherein either of the first or
second conveyance rollers are fixed on a single drive roller shaft,
and the other of the first or second conveyance rollers are fixed
on a driven roller shaft and arranged in an axial direction of the
driven roller shaft.
2. The sheet conveying device according to claim 1, wherein the
stiffening roller includes a first stiffening roller and a second
stiffening roller, either of the first stiffening roller or the
second stiffening roller has a rubber surface, and the other of the
first stiffening roller or the second stiffening roller has a resin
surface.
3. The sheet conveying device according to claim 1, wherein the
stiffening roller includes a first stiffening roller and a second
stiffening roller, the first stiffening roller is configured to
integrally rotate with the conveyance rollers, and the second
stiffening roller is configured to freely rotate with respect to
the conveyance rollers.
4. The sheet conveying device according to claim 1, wherein the
stiffening roller includes a first stiffening roller and a second
stiffening roller, and the first stiffening roller and the second
stiffening roller have a same outer diameter.
5. The sheet conveying device according to claim 1, wherein the
stiffening roller includes a first stiffening roller and a second
stiffening roller, and a conveying force applied to the sheet by
the second stiffening roller due to surface friction is smaller
than a conveying force applied to the sheet by the first stiffening
roller due to surface friction.
6. The sheet conveying device according to claim 5, wherein the
first stiffening roller has a rubber surface, and the second
stiffening roller has a resin surface.
7. An image forming apparatus comprising the sheet conveying device
according to claim 1.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sheet conveying device
applicable to an image forming apparatus such as a printer, a
copying machine, and a multifunction printer, and also relates to
an image forming apparatus.
BACKGROUND ART
[0002] A sheet conveying device included in an image forming
apparatus is required to stack sheets aligned on a discharge tray
for conveyance of the sheets with high stacking quality to the
discharge tray in the case where the sheet conveying device conveys
a sheet such as an original and a recording paper, which is
processed after an image reading process or an image forming
process in the image forming apparatus.
[0003] FIGS. 9A and 9B are explanatory views illustrating an
exemplary conventional sheet conveying device A1 that degrades
stacking quality. FIG. 9A is a schematic side view illustrating a
discharged state of a sheet P conveyed to a discharge tray B4
viewed from an axial direction X of conveyance rollers B1 and B2.
FIG. 9B is a schematic side view illustrating a conveying state of
the sheet P viewed from a conveying direction Y of the sheet P.
[0004] The sheet conveying device A1 illustrated in FIGS. 9A and 9B
includes a plurality of the first conveyance rollers B1 disposed
coaxially with one another, and a plurality of second conveyance
rollers B2 disposed coaxially with one another. The second
conveyance rollers B2 face the respective plurality of first
conveyance rollers B1. The sheet conveying device A1 conveys the
sheet P while sandwiching the sheet P between the rotatably driven
first conveyance rollers (drive rollers secured to a drive roller
shaft E1) B1 and the second conveyance rollers (driven rollers
secured to the driven roller shaft E2) B2. The first conveyance
rollers B1 are rotatably driven while the second conveyance rollers
B2 rotate in association with the rotation of the first conveyance
roller B1.
[0005] This conventional sheet conveying device A1 easily causes
inconvenience such as the following. When the sheet P is conveyed
to one side Y1 in the conveying direction Y, the downstream side
end (leading end) P1 is weighed down at one side Y1 in the
conveying direction Y of the sheet P and the leading end P1 is
brought in contact with the discharge tray B4 early. This early
contact of the leading end P1 of the sheet P with the discharge
tray B4 causes an upperstream side end (the rear end) P2, which is
disposed at one side Y1 in the conveying direction Y, hooked into
the second conveyance rollers B2 after the sheet P is conveyed
(what is called rear end remaining (see a portion .alpha. in FIG.
9A)). Alternatively, the sheet P curled by a fixing process may
degrade stacking quality.
CITATION LIST
Patent Literature
[0006] PATENT LITERATURE 1: Japanese Unexamined Patent Application
Publication No. 2006-151617
SUMMARY OF INVENTION
Technical Problem
[0007] In view of this, stiffening rollers B3 may be disposed (see
FIGS. 10A and 10B) in order to prevent the leading end P1 of the
sheet P from being weighed down immediately when the sheet P is
conveyed to one side Y1 in the conveying direction Y from the sheet
conveying device A1, to prevent the rear end P2 from remaining by
the rear end P2 of the sheet P hooked into the conveyance roller
B2, or to reduce curling of the sheet P caused in the fixing
process. The stiffening rollers B3 are disposed coaxially with at
least one conveyance roller (the first conveyance rollers B1 at the
upper side in the examples illustrated in FIGS. 10A and 10B as
described below) among the first and second conveyance rollers B1
and B2. The stiffening rollers B3 have diameters larger than
diameters of the rollers B1.
[0008] FIGS. 10A and 10B are explanatory views illustrating the
exemplary conventional sheet conveying device A2 where the
stiffening rollers B3 are disposed. FIG. 10A is a schematic side
view illustrating a discharged state of the sheet P, which is
conveyed to the discharge tray B4, viewed from the axial direction
X of the conveyance rollers B1 and B2. FIG. 10B is a schematic side
view illustrating a conveying state of the sheet P viewed from the
conveying direction Y of the sheet P.
[0009] The sheet conveying device A2 illustrated in FIGS. 10A and
10B includes the stiffening rollers B3 disposed coaxially with the
first conveyance rollers B1 in the sheet conveying device A1
illustrated in FIGS. 9A and 9B. The stiffening rollers B3 have
diameters larger than diameters of the first conveyance rollers B1.
The stiffening rollers B3 are configured to integrally rotate with
the first conveyance rollers B1 (which are secured to the drive
roller shaft E1 in the drawing). That is, the individual stiffening
rollers B3 are each configured to apply conveying forces to the
sheet P.
[0010] When this conventional sheet conveying device A2 conveys the
sheet P to one side Y1 in the conveying direction Y, the stiffening
rollers B3 corrugates the sheet P in the axial direction X. This
stiffens the sheet P to maintain a conveying posture of the sheet P
as much as possible, thus preventing the leading end P1 of the
sheet P from being weighed down early, the rear end remaining of
the sheet P, or preventing a fixed curl of the sheet P.
[0011] Although this conventional sheet conveying device A2 allows
the stiffening rollers B3 to prevent the leading end P1 of the
sheet P from being weighed down early, to prevent the rear end
remaining of the sheet P, or to prevent the fixed curl of the sheet
P, another inconvenience is caused as follows. The inconvenience
relates to corrugation of the sheet P by the stiffening rollers B3.
Especially, in the case where the sheet P is guided to a curved
conveyance path D (see FIG. 11 described later) curved in the
conveying direction Y, the sheet P corrugated in the axial
direction X is conveyed to the curved conveyance path D curved in
the conveying direction Y. This causes abnormal sound.
[0012] FIG. 11 is a schematic cross-sectional view of the exemplary
conventional sheet conveying device A2 viewed from the axial
direction X. FIG. 11 illustrates a state where the sheet P
corrugated in the axial direction X is conveyed to the curved
conveyance path D curved in the conveying direction Y.
[0013] As illustrated in FIG. 11, the sheet P is conveyed (switch
backed) in the conveying direction Y2 by the conveyance rollers B1
and B2 that are reversely rotated by switchback function. In the
case where the sheet P is guided to the curved conveyance path D
(in this example, a reverse conveying path for reversing front and
back sides of the sheet P when images are formed on both sides),
the sheet P, which is corrugated in the axial direction X by the
stiffening rollers B3, is forcibly curved along the curved
conveyance path D, which is curved in the conveying direction Y.
When the corrugation is restored to the original condition,
abnormal sound (specifically, a crunching sound) may occur. That
is, a difference in circumferential speed, which is caused by a
difference in diameter between the stiffening rollers B3 and the
first conveyance rollers B1, results in a difference of the
conveyance amount of the sheet P per unit time. This difference in
conveyance amount causes a large amplitude of the corrugation of
the sheet P, thus easily causing abnormal sound.
[0014] This is especially remarkable in the configuration
(specifically, a small-sized image forming apparatus with a
comparatively short distance between the stiffening rollers B3 and
the curved conveyance path D) where the sheet P is moved to the
curved conveyance path D in a state where the corrugation is kept
to be comparatively large.
[0015] In this respect, Patent Document 1 discloses the following
configuration. In a forward rotation as a normal discharging state,
the stiffening roller is secured to the conveyance roller to
integrally rotate and convey a recording material. In a reverse
rotation, the stiffening roller is unlocked with respect to the
conveyance roller and driven to rotate by the conveyed recording
material.
[0016] However, the configuration disclosed in Patent Literature 1
has a complicated structure of the stiffening roller. This
increases in cost and has no consideration on the corrugation of
the sheet to be conveyed in a forward rotation direction.
[0017] Therefore, an object of the present invention is to provide
a sheet conveying device that has a simple and low-cost structure,
ensures stacking quality of the sheet, and suppresses the
occurrence of inconveniences (especially, abnormal sound of the
sheet conveyed to a curved conveyance path curved in a conveying
direction) related to corrugation of the sheet by a stiffening
roller regardless of a rotation direction of a conveyance roller.
Another object of the present invention is to provide an image
forming apparatus that includes this sheet conveying device.
Solutions to the Problems
[0018] The inventors conducted extensive research to achieve the
above objects, and discovered the following information. Similarly
to the conventional configuration, the configuration where all the
individual stiffening rollers applied conveying forces to the sheet
caused inconvenience (especially, abnormal sound of the sheet
conveyed to the curved conveyance path curved in the conveying
direction) related to corrugation of the sheet by the stiffening
roller. In contrast, the configuration where all the individual
stiffening rollers did not apply conveying forces to the sheet
solved the inconvenience related to the corrugation but reduced
conveying forces to the sheet. This caused rear end remaining of
the sheet and did not ensure stacking quality of the sheet.
[0019] The inventors focused on this point, and found the following
effects. A configuration where a part of the individual stiffening
rollers did not apply a conveying force or apply a reduced
conveying force to the sheet ensured a simple and low-cost
structure and avoided occurrence of rear end remaining. Therefore,
this ensures stacking quality of the sheet, and reduces amplitude
of corrugation of the sheet. This reduces occurrence of
inconveniences (especially, abnormal sound of the sheet conveyed to
the curved conveyance path curved in the conveying direction)
related to the corrugation regardless of a rotation direction of
the conveyance roller. Thus, the present invention was
accomplished.
[0020] That is, the present invention provides a sheet conveying
device. The sheet conveying device includes a plurality of first
conveyance rollers, a plurality of second conveyance rollers, and a
stiffening roller. The plurality of first conveyance rollers are
disposed coaxially with one another. The plurality of second
conveyance rollers face the respective plurality of first
conveyance rollers. The plurality of second conveyance rollers are
disposed coaxially with one another. The plurality of second
conveyance rollers are configured to convey a sheet while
sandwiching the sheet between the second conveyance rollers and the
first conveyance rollers to be rotated. The stiffening roller is
disposed coaxially with either or both of the first and second
conveyance rollers. The stiffening roller has a diameter larger
than a diameter of either or both of the first and second
conveyance rollers. The stiffening roller includes a first
stiffening roller and a second stiffening roller. The first
stiffening roller applies a conveying force to the sheet. The
second stiffening roller applies a smaller conveying force to the
sheet than the conveying force to the sheet by the first stiffening
roller.
[0021] Here, the description about the second stiffening roller
where "the sheet conveying direction is smaller than the conveying
force to the sheet by first stiffening roller" means a concept that
also includes a case where a conveying force is not applied to the
sheet.
[0022] Additionally, the present invention provides an image
forming apparatus that includes the sheet conveying device
according to the present invention and a curved conveyance path
curved in a conveying direction of a sheet. The image forming
apparatus is configured to convey a sheet from the sheet conveying
device toward the curved conveyance path.
[0023] With the present invention, the stiffening roller is
configured to include the first stiffening roller and the second
stiffening roller. This ensures a simple and low-cost structure.
The stiffening roller allows imparting a corrugated shape to the
sheet (specifically a recording paper or an original) in the axial
direction. Additionally, the stiffening roller includes the first
stiffening roller that applies a conveying force to the sheet. This
avoids occurrence of rear end remaining of the sheet, thus ensuring
stacking quality of the sheet. Furthermore, the stiffening rollers
do not have configuration where all the individual stiffening
rollers apply conveying forces to the sheet. The stiffening rollers
include the second stiffening roller that applies a smaller
conveying force to the sheet than a conveying force of the first
stiffening roller to the sheet, in addition to the first stiffening
roller that applies a conveying force to the sheet. This reduces
the difference in conveyance amount of the sheet per unit time by
the difference in circumferential speed between the stiffening
roller and the conveyance roller, which is disposed coaxially with
the stiffening roller, irrespective of the rotation directions of
the first and second conveyance rollers, thus reducing amplitude of
corrugation of the sheet. This reduces occurrence of inconveniences
(especially, abnormal sound of the sheet conveyed to the curved
conveyance path curved in the conveying direction, for example, the
curved conveyance path in the image forming apparatus according to
the present invention) related to the corrugation.
[0024] In the present invention, as specific aspects of the first
and second stiffening rollers, an aspect (a) and an aspect (b) will
be exemplarily described as follows.
[0025] That is, as the aspect (a), an exemplary aspect will be
described as follows. The first stiffening roller is configured to
integrally rotate with a conveyance roller disposed coaxially with
the first stiffening roller. The second stiffening roller is
configured to freely rotate with respect to a conveyance roller
disposed coaxially with the second stiffening roller.
[0026] In this aspect (a), the first stiffening roller is
configured to integrally rotate with the conveyance roller disposed
coaxially with the first stiffening roller. Rotation of the
conveyance roller rotates the first stiffening roller.
Additionally, the second stiffening roller is configured to freely
rotate with respect to the conveyance roller disposed coaxially
with the second stiffening roller. The second stiffening roller is
in a free state where rotation of the second stiffening roller is
not restricted together with the rotation of the conveyance roller
even if the conveyance roller rotates. Accordingly, the first
stiffening roller provides a conveying force to the sheet while the
second stiffening roller does not provide a conveying force to the
sheet. This allows reducing the difference in conveyance amount of
the sheet per unit time by the difference in circumferential speed
between the stiffening roller and the conveyance roller disposed
coaxially with the stiffening roller.
[0027] Additionally, as the aspect (b), an exemplary aspect will be
described as follows. The first stiffening roller and the second
stiffening roller are configured to integrally rotate with the
respective conveyance rollers disposed coaxially with the first and
second stiffening rollers. A friction coefficient of a surface of
the second stiffening roller is smaller than a friction coefficient
of a surface of the first stiffening roller.
[0028] In this aspect (b), the first stiffening roller and the
second stiffening roller are configured to integrally rotate with
the respective conveyance rollers disposed coaxially with the first
and second stiffening rollers. The friction coefficient of the
surface of the second stiffening roller is smaller than the
friction coefficient of the surface of the first stiffening roller.
In view of this, the sheet easily slides on the second stiffening
roller compared with the first stiffening roller. This reduces a
conveying force to the sheet in the second stiffening roller
compared with a conveying force to the sheet in the first
stiffening roller. This consequently reduces the difference in
conveyance amount of the sheet per unit time by the difference in
circumferential speed between the stiffening roller and the
conveyance roller disposed coaxially with the stiffening roller.
The friction coefficient of the surface of the second stiffening
roller may be a friction coefficient that does not provide a
conveying force to the sheet.
[0029] In the present invention, an exemplary aspect will be
described as follows. The stiffening roller and the conveyance
roller are disposed symmetrically with respect to the center
reference in the axial direction of the conveyance roller. The
conveyance roller is disposed coaxially with the stiffening
roller.
[0030] In this limitation, the stiffening roller and the conveyance
roller disposed coaxially with the stiffening roller are disposed
symmetrically with respect to the center reference in the axial
direction. This applies a conveying force to the sheet
symmetrically with respect to the center reference. This allows
preventing occurrence of skew (diagonal feed). This aspect is
preferred to be used in the configuration for sheet conveyance with
the center reference.
[0031] In the present invention, an exemplary aspect will be
described as follows. The stiffening rollers include the first
stiffening roller at the center portion in the axial direction and
the second stiffening rollers at both end portions.
[0032] In this limitation, the stiffening roller includes the first
stiffening roller at the center portion in the axial direction and
the second stiffening rollers at both end portions. This reduces
occurrence of inconveniences related to corrugation of the sheet
while ensuring stable conveyance of the sheet in the center portion
in the axial direction.
[0033] In the present invention, an exemplary aspect will be
described as follows. The first stiffening roller is a stiffening
roller positioned closest to the center position in the axial
direction among the stiffening rollers.
[0034] In this limitation, the first stiffening roller is the
stiffening roller positioned closest to the center position in the
axial direction among the stiffening rollers. This provides a
conveying force near the center position. This allows surely
conveying the sheet in a size smaller than the maximum size even in
the case where the sheets in a plurality of sizes are used.
[0035] In the present invention, an exemplary aspect will be
described as follows. A stiffening roller positioned closest to the
center position in the axial direction among the stiffening rollers
is configured to convey a sheet in a minimum size. The minimum size
is usable in an image forming apparatus with this sheet conveying
device.
[0036] In this limitation, the stiffening roller positioned closest
to the center position in the axial direction among the stiffening
rollers is configured to convey a sheet in a minimum size. The
minimum size is usable in an image forming apparatus with the sheet
conveying device. This allows surely conveying the sheet even in
the minimum size in the configuration for sheet conveyance with the
center reference. In this case, the stiffening roller positioned
closest to the center position can be disposed in a position that
allows conveying the sheet in the available minimum size.
[0037] In the present invention, the stiffening roller may be
disposed at a shaft of the conveyance roller disposed coaxially
with the stiffening roller or may disposed at the conveyance roller
itself.
[0038] For example, an exemplary aspect of the stiffening roller
will be described as follows. The stiffening roller is disposed in
one side end portion of the conveyance roller in the axial
direction. The conveyance roller is disposed coaxially with the
stiffening roller.
[0039] In this limitation, the stiffening roller is disposed in one
side end portion of the conveyance roller in the axial direction.
The conveyance roller is disposed coaxially with the stiffening
roller. Compared with a case where the stiffening roller is distant
from the conveyance roller disposed coaxially with the stiffening
roller in the axial direction (for example, a case where the
stiffening roller is provided at the center between the adjacent
conveyance rollers), this provides a large proportion of amplitude
to the difference between the diameter of the stiffening roller and
the diameter of the conveyance roller even in the case where
corrugations of the sheet have the same maximum amplitude. This
consequently reduces material cost. Furthermore, this allows
providing the stiffening roller and the conveyance roller as one
assembly part, thus ensuring reduced assembly processes for the
stiffening roller and the conveyance roller.
Advantageous Effects of Invention
[0040] As described above, with the present invention, the
stiffening roller includes the first stiffening roller and the
second stiffening roller. The first stiffening roller applies the
conveying force to the sheet. The second stiffening roller applies
the conveying force, which is smaller than the conveying force to
the sheet by the first stiffening roller, to the sheet. This
ensures a simple low-cost structure and stacking quality of the
sheet, and suppresses the occurrence of inconveniences (especially,
abnormal sound of the sheet conveyed to the curved conveyance path
curved in the conveying direction) related to corrugation of the
sheet by the stiffening roller regardless of the rotation direction
of the conveyance roller.
BRIEF DESCRIPTION OF DRAWINGS
[0041] FIG. 1 is a schematic cross-sectional view illustrating an
image forming apparatus with a sheet conveying device according to
an embodiment of the invention viewed from a front view.
[0042] FIG. 2 is a schematic cross-sectional view illustrating
conveying paths in the image forming apparatus illustrated in FIG.
1.
[0043] FIG. 3 is a schematic side view of the sheet conveying
device in the image forming apparatus illustrated in FIG. 1 viewed
from a conveying direction of a paper.
[0044] FIGS. 4A and 4B are schematic configuration views of first
and second stiffening rollers and their peripheral portions
according to the first embodiment, FIG. 4A is a schematic side view
of the first stiffening roller portions viewed from the conveying
direction, FIG. 4B is a schematic side view of the first stiffening
roller portion viewed from an axial direction, FIG. 4C is a
schematic side view of the second stiffening roller portion viewed
from the conveying direction, and FIG. 4D is a schematic side view
of the second stiffening roller portion viewed from the axial
direction.
[0045] FIGS. 5A to 5D are schematic configuration views of the
first and second stiffening rollers and their peripheral portions
according to the second embodiment, FIG. 5A is a schematic side
view of the first stiffening roller portion viewed from the
conveying direction, FIG. 5B is a schematic side view of the first
stiffening roller portion viewed from the axial direction, FIG. 5C
is a schematic side view of the second stiffening roller portion
viewed from the conveying direction, and FIG. 5D is a schematic
side view of the second stiffening roller portion viewed from the
axial direction.
[0046] FIG. 6 is a table illustrating positional relationships and
sizes of outer diameters of the stiffening rollers by a difference
in destination of the image forming apparatus.
[0047] FIG. 7 is a table illustrating results of Comparative
examples 1 and 2 and the embodiment.
[0048] FIG. 8 is a table illustrating results of examination for
occurrence of abnormal sound in a reverse conveying path by
difference in paper type in Comparative example 1 and the
embodiment, (a) is a table illustrating results of respective paper
sizes according to Comparative example 1, and (b) is a table
illustrating results of respective paper sizes according to the
embodiment.
[0049] FIGS. 9A and 9B are explanatory views illustrating an
exemplary conventional sheet conveying device that degrades
stacking quality, FIG. 9A is a schematic side view illustrating a
discharged state of a sheet conveyed to a discharge tray viewed
from an axial direction of conveyance rollers, and FIG. 9B is a
schematic side view illustrating a conveying state of the sheet
viewed from a conveying direction of the sheet.
[0050] FIGS. 10A and 10B are explanatory views illustrating an
exemplary conventional sheet conveying device with the stiffening
rollers, FIG. 10A is a schematic side view illustrating a
discharged state of a sheet conveyed to a discharge tray viewed
from an axial direction of conveyance rollers, and FIG. 10B is a
schematic side view illustrating a conveying state of the sheet
viewed from a conveying direction of the sheet.
[0051] FIG. 11 is a schematic cross-sectional view of an exemplary
conventional sheet conveying device illustrating a state where a
sheet corrugated in an axial direction is conveyed to a curved
conveyance path curved in a conveying direction viewed from the
axial direction.
DESCRIPTION OF EMBODIMENTS
[0052] Hereinafter, embodiments according to the present invention
will be described with reference to the accompanying drawings. The
embodiments described below are only examples in which the present
invention is embodied, and are not intended to limit the technical
scope of the present invention.
(Description of an Overall Configuration of an Image Forming
Apparatus)
[0053] FIG. 1 is a schematic cross-sectional view of an image
forming apparatus 100 with a sheet conveying device 30 according to
an embodiment of the present invention viewed from a front
view.
[0054] The image forming apparatus 100 illustrated in FIG. 1 is a
color image forming apparatus that forms a multicolor and a single
color image on a sheet (hereinafter referred to as a paper) P such
as a recording paper corresponding to image data transmitted from
outside. The image forming apparatus 100 includes an original
reading device 108 and a device main body 110. The device main body
110 includes an image forming portion 102 and a sheet conveying
system 103.
[0055] The image forming portion 102 includes an exposure unit 1, a
plurality of developing units 2, a plurality of photoreceptor drums
3, a plurality of cleaning portions 4, a plurality of chargers 5,
an intermediate transfer belt unit 6, a plurality of toner
cartridge units 21, and a fixing unit 7.
[0056] The sheet conveying system 103 includes a paper feeding unit
80, conveying paths (a main conveying path 76 and a reverse
conveying path 77) described later, and a discharge tray 91. The
paper feeding unit 80 includes a paper feed tray 81 and a manual
paper feed tray 82.
[0057] The device main body 110 has an upper portion that includes
an original placement plate 92 made of transparent glass on which
an original (a sheet) is placed. The original placement plate 92
has a lower portion that includes an optical unit 90 for reading
the original. The original placement plate 92 has an original
reading device 108 at an upper side. The original reading device
108 automatically conveys the original on the original placement
plate 92. The original reading device 108 is turnably mounted to
open its front side with respect to the device main body 110.
Opening an upper portion of the original placement plate 92 allows
manually placing the original.
[0058] The original reading device 108 allows reading an
automatically conveyed original, or an original placed on the
original placement plate 92. An overall image of the original,
which is read by the original reading device 108, is transmitted to
the device main body 110 of the image forming apparatus 100 as
image data. An image formed by the device main body 110 based on
the image data is recorded on a paper P.
[0059] The image data handled in the image forming apparatus 100
corresponds to a color image with a plurality of colors (here,
respective colors of black (K), cyan (C), magenta (M), and yellow
(Y)). Accordingly, a plurality (here, four of black, cyan, magenta,
and yellow) of developing units 2, photoreceptor drums 3, cleaning
portions 4, chargers 5, and toner cartridge units 21 are set to
form multiple kinds (here, four kinds) of images corresponding to
the respective colors. These members constitute a plurality (here,
four) of image stations.
[0060] The chargers 5 are charging units to uniformly charge
surfaces of the photoreceptor drums 3 to a predetermined potential.
The chargers 5 may employ a contact type charger, such as a roller
type charger and a brush type charger, as well as the type of the
charger illustrated in FIG. 1.
[0061] The exposure unit 1 is configured as a laser scanning unit
(LSU) that includes a laser emitting portion and a reflecting
mirror. The exposure unit 1 includes a polygon mirror and an
optical element such as a lens and a mirror. The polygon mirror
scans a laser beam. The optical element guides the laser light,
which is reflected by the polygon mirror, to the photoreceptor
drums 3. The exposure unit 1 can employ, in addition to this
method, a method using a write head where light emitting elements,
such as electroluminescence (EL) and a light-emitting diode (LED),
are arranged in an array.
[0062] The exposure unit 1 exposes the respective charged
photoreceptor drums 3 corresponding to the input image data in
order to form electrostatic latent images, which correspond to the
image data, on respective surfaces of the photoreceptor drums
3.
[0063] The toner cartridge units 21 are units that house toners.
The toners are supplied to developer tanks of the developing units
2. In the device main body 110 of the image forming apparatus 100,
toners supplied from the toner cartridge units 21 to the developer
tanks of the developing units 2 are controlled such that toner
concentration of the developer in the developer tank is
constant.
[0064] The developing units 2 visualize electrostatic latent images
formed on the respective photoreceptor drums 3 using toners of four
colors (Y, M, C, and K). The cleaning portions 4 remove and recover
the toners remaining on the surfaces of the photoreceptor drums 3
after development and transfer of the image.
[0065] The intermediate transfer belt unit 6 above the
photoreceptor drums 3 includes an intermediate transfer belt 61, an
intermediate transfer belt drive roller 62, an intermediate
transfer belt driven roller 63, a plurality of intermediate
transfer rollers 64, and an intermediate transfer belt cleaning
unit 65. The intermediate transfer belt 61 operates as an
intermediate transfer body.
[0066] Four intermediate transfer rollers 64 are disposed
corresponding to the respective colors of Y, M, C, and K. The
intermediate transfer belt drive roller 62 stretches the
intermediate transfer belt 61 with the intermediate transfer belt
driven roller 63 and the intermediate transfer rollers 64. The
intermediate transfer belt drive roller 62 is rotatably driven so
as to revolve the intermediate transfer belt 61 in a movement
direction (in an arrow M direction in FIG. 1). In accordance with
this revolution, the driven roller 63 and the intermediate transfer
rollers 64 are driven to rotate.
[0067] A transfer bias voltage is applied to each of the
intermediate transfer rollers 64 to transfer toner images formed on
the photoreceptor drums 3 onto the intermediate transfer belt
61.
[0068] The intermediate transfer belt 61 is disposed in contact
with the respective photoreceptor drums 3. The intermediate
transfer belt 61 has a surface on which toner images of the
respective colors, which are formed on the photoreceptor drums 3,
are sequentially transferred to be overlaid. This forms a color
toner image (multi-color toner image) on the surface of the
intermediate transfer belt 61. The intermediate transfer belt 61
is, for example, an endless belt using a film with a thickness of
about 100 .mu.m to 150 .mu.m.
[0069] Transferring the toner images from the photoreceptor drums 3
to the intermediate transfer belt 61 is performed by the
intermediate transfer rollers 64 in contact with a back side of the
intermediate transfer belt 61. High transfer bias voltages (high
voltages with reversed polarity (+) of charged polarity (-) of the
toners) are applied to the intermediate transfer rollers 64 to
transfer the toner images. The intermediate transfer rollers 64 are
rollers that each includes a metal (such as stainless steel) shaft
with a diameter of 8 mm to 10 mm as a base and a surface covered
with a conductive elastic material (for example, a resin material
such as ethylene-propylene-diene rubber (EPDM) and foamed
urethane). With this conductive elastic material, the intermediate
transfer rollers 64 function as transfer electrodes that uniformly
apply a high voltage to the intermediate transfer belt 61. While in
this embodiment the transfer electrode employs the roller-shaped
transfer electrode, a brush electrode and a similar electrode may
also be used as another type of transfer electrode.
[0070] As described above, the toner images visualized on the
respective photoreceptor drums 3 corresponding to the respective
color phases are overlaid on the intermediate transfer belt 61. The
toner image, which is overlaid on the intermediate transfer belt
61, is transferred onto the paper P by a transfer roller 10 in
accordance with the revolution of the intermediate transfer belt
61. The transfer roller 10 constitutes a secondary transfer
mechanism disposed in contact with between the paper P and the
intermediate transfer belt 61. The configuration of the secondary
transfer mechanism is not limited to the transfer roller. The
secondary transfer mechanism may employ a transfer configuration of
a corona charger, a transfer belt, and a similar member.
[0071] At this time, a voltage (a high voltage with reversed
polarity (+) of charged polarity (-) of the toner) is applied to
the transfer roller 10 in order to transfer the toner to the paper
P in a state where a transfer nip is formed between the transfer
roller 10 and the intermediate transfer belt 61. The transfer
roller 10 and the intermediate transfer belt drive roller 62 are
brought into pressure contact with each other. This forms a
transfer nip between the transfer roller 10 and the intermediate
transfer belt 61. In order to obtain the transfer nip steadily,
either one of the transfer roller 10 and the intermediate transfer
belt drive roller 62 is a hard roller made of a hard material (such
as metal) while the other is an elastic roller made of a soft
material (a resin material such as elastic rubber and foamable
resin).
[0072] When the transfer roller 10 transfers the toner image from
the intermediate transfer belt 61 onto the paper P, the toner may
remain on the intermediate transfer belt 61 without being
transferred onto the paper P. The toner remaining on the
intermediate transfer belt 61 may cause color mixture of the toners
in the subsequent process. In view of this, the toner remaining on
the intermediate transfer belt 61 is removed and recovered by the
intermediate transfer belt cleaning unit 65. Specifically, the
intermediate transfer belt cleaning unit 65 includes a cleaning
member (such as a cleaning blade) in contact with the intermediate
transfer belt 61. The driven roller 63 supports the intermediate
transfer belt 61 from the inside (a back side). The cleaning member
is in contact with the intermediate transfer belt 61 so as to press
the intermediate transfer belt 61 toward the driven roller 63 from
the outside.
[0073] The paper feed tray 81 is a tray that preliminarily houses
the paper P on which an image is formed (printed). The paper feed
tray 81 is disposed below the exposure unit 1 in the device main
body 110. On the manual paper feed tray 82, the paper P where an
image is formed (printed) is placed. The discharge tray 91 is
disposed on the upper side of the image forming portion 102 in the
device main body 110. The discharge tray 91 accumulates the paper P
on which an image has been formed (printed) face-down.
[0074] The device main body 110 includes a main conveying path 76.
The main conveying path 76 feeds the paper P, which is fed from the
paper feed tray 81 and the manual paper feed tray 82, to the
discharge tray 91 through the transfer roller 10 and the fixing
unit 7. At the proximity of the main conveying path 76, pickup
rollers 11a and 11b, a plurality of (here, first and second)
conveyance rollers 12a and 12b, a registration roller 13, the
transfer roller 10, and a heat roller 71 and a pressing roller 72
in the fixing unit 7 are disposed. At the proximity of the reverse
conveying path 77, a plurality of (here, third and fourth)
conveyance rollers 12c and 12d are disposed.
[0075] The first to fourth conveyance rollers 12a to 12d are small
rollers for accelerating and assisting conveyance of the paper P.
The pickup roller 11a is disposed at the proximity of the paper
feed tray 81 at a paper feeding side. The pickup roller 11a picks
up the paper P sheet by sheet from the paper feed tray 81 to feed
the paper P to the main conveying path 76. Similarly, the pickup
roller 11b is disposed at the proximity of the manual paper feed
tray 82 at a paper feeding side. The pickup roller 11b picks up the
paper P sheet by sheet from the manual paper feed tray 82 to supply
the paper P to the main conveying path 76.
[0076] The registration roller 13 once holds the paper P that is
being conveyed on the main conveying path 76. Then, the
registration roller 13 conveys the paper P to the transfer roller
10 at a timing when a leading end of the toner image on the
photoreceptor drums 3 is aligned with a downstream side end
(hereinafter referred to as a leading end) P1 of the paper P at one
side Y1 in the conveying direction Y.
[0077] The fixing unit 7 fixes an unfixed toner image to the paper
P. The fixing unit 7 includes the heat roller 71 and the pressing
roller 72 that operate as fixing rollers. The heat roller 71 is
rotatably driven to convey the paper P while sandwiching the paper
P with the pressing roller 72 that rotates in accordance with the
rotation of the heat roller 71. The heat roller 71 is heated by a
heater 71a disposed inside, and is maintained at a predetermined
fixing temperature based on a signal from a temperature sensor 71b.
The heat roller 71, which is heated by the heater 71a, performs
thermo-compression bonding of a multicolor toner image, which is
transferred to the paper P, on the paper P with the pressing roller
72. This melts, mixes, and presses to make a contact with the
multicolor toner image to heat-fix the multicolor toner image to
the paper P.
(Conveying Path)
[0078] FIG. 2 is a schematic cross-sectional view illustrating
conveying paths 76 and 77 in the image forming apparatus 100
illustrated in FIG. 1.
[0079] As illustrated in FIG. 1 and FIG. 2, the image forming
apparatus 100 includes, as described above, the main conveying path
76 and the reverse conveying path 77 as the conveying paths on
which the paper P is conveyed. The image forming apparatus 100 has
a configuration where the sheet is conveyed at the center
reference. The reverse conveying path 77 constitutes a curved
conveyance path curved in the conveying direction Y.
[0080] The main conveying path 76 is a conveying path for
conveyance of the paper P between the paper feeding unit 80 and the
sheet conveying device 30.
[0081] The reverse conveying path 77 is a conveying path for
conveyance of the paper P conveyed to the other side Y2 in the
opposite direction of one side Y1 in the conveying direction Y. The
reverse conveying path 77 goes through a part of the main conveying
path 76 from the sheet conveying device 30 to a bifurcating portion
Sa between the fixing unit 7 and the sheet conveying device 30. The
reverse conveying path 77 is coupled to a coupling portion Sb (see
FIG. 1), which is coupled to the main conveying path 76 between the
image forming portion 102 and the paper feeding unit 80.
Accordingly, the main conveying path 76 and the reverse conveying
path 77 share a conveying path between the sheet conveying device
30 and the bifurcating portion Sa.
[0082] The bifurcating portion Sa includes a bifurcating claw 84.
The bifurcating claw 84 is configured to take a first posture (a
posture illustrated by a solid line in FIG. 2) and a second posture
(a posture illustrated by a two-dot chain line in FIG. 2). The
bifurcating claw 84 in the first posture guides the paper P from
the fixing unit 7 toward the sheet conveying device 30. The
bifurcating claw 84 in the second posture guides the paper P to the
reverse conveying path 77 side. In this case, the paper P is
conveyed to the other side Y2 in the opposite direction of one side
Y1 in the conveying direction Y by reverse rotation (rotation
illustrated by an arrow A2 direction in FIG. 2) of conveyance
rollers 31 and 32 described later in the sheet conveying device
30.
[0083] The image forming apparatus 100 thus configured conveys the
paper P fed from each of the paper feed trays 81 and 82 to the
registration roller 13 using the first conveyance roller 12a
disposed along the main conveying path 76. The paper P is conveyed
by the transfer roller 10 at a timing when the leading end P1 of
the paper P is aligned with the leading end of the toner image on
the intermediate transfer belt 61. Then, the toner image is
transferred onto the paper P. Then, the paper P passes through the
fixing unit 7 to melt and fix the unfixed toner on the paper P with
heat.
[0084] Then, in the case where the bifurcating claw 84 is set to
the first posture to print an image on one side of the paper P, the
paper P from the fixing unit 7 is conveyed to the conveyance
rollers 31 and 32, which rotates forward (rotate in an arrow A1
direction in FIG. 2), via the second conveyance roller 12b and then
discharged to the discharge tray 91.
[0085] In the case where the paper P is printed on both sides, the
leading end P1 side of the paper P, which has passed the fixing
unit 7, is once conveyed to the outside. An upperstream side end
(hereinafter referred to as a rear end) P2 of the paper P at one
side Y1 in the conveying direction Y passes through the bifurcating
portion Sa. Subsequently, the bifurcating claw 84 is set to the
second posture and the conveyance rollers 31 and 32 are reversely
rotated. This conveys (switch backs) the paper P to the other side
Y2 in the conveying direction Y. The paper P is conveyed to the
coupling portion Sb along the reverse conveying path 77 by the
third and fourth conveyance roller 12c and 12d while front and back
sides of the paper P are reversed. Subsequently, the paper P, which
is conveyed to the transfer nip through the registration roller 13,
is printed on the back side. Then the paper P is conveyed and
discharged to the discharge tray 91 by the conveyance rollers 31
and 32 that rotate forward.
(Sheet Conveying Device)
[0086] FIG. 3 is a schematic side view of the sheet conveying
device 30 in the image forming apparatus 100 illustrated in FIG. 1
viewed from the conveying direction Y of the paper P.
[0087] As illustrated in FIG. 2 and FIG. 3, the image forming
apparatus 100 according to the embodiment includes the sheet
conveying device 30, which conveys the paper P, and the rotation
driving portion 40.
[0088] The sheet conveying device 30 includes a plurality (here,
four) of first discharging rollers (exemplary first conveyance
rollers) 31 and a plurality (here, four) of second discharging
rollers (exemplary second conveyance rollers) 32. The first
discharging rollers 31 have the same diameter, and are disposed
coaxially with one another. The second discharging rollers 32 have
the same diameter, and are disposed coaxially with one another
facing the respective first discharging rollers 31. The sheet
conveying device 30 conveys the paper P while sandwiching the paper
P between the first discharging rollers (drive rollers) 31, which
are rotatably driven, and the second discharging rollers (driven
rollers) 32, which are driven in association with the rotation of
the first discharging rollers 31. Specifically, the sheet conveying
device 30 conveys the paper P toward the discharge tray 91 when the
first and the second discharging rollers 31 and 32 rotate forward.
On the other hand, when the first and the second discharging
rollers 31 and 32 rotate reversely, the sheet conveying device 30
conveys the paper P toward the reverse conveying path 77.
[0089] The sheet conveying device 30 further includes the drive
roller shaft 31a and the driven roller shaft 32a. The first
discharging rollers 31 are secured to the drive roller shaft 31a.
The second discharging rollers 32 are secured the driven roller
shaft 32a while facing the first discharging rollers 31. The sheet
conveying device 30 further includes a biasing member (here, coil
spring) 33 that biases the second discharging rollers 32 toward the
first discharging rollers 31.
[0090] The first and second discharging rollers 31 and 32 and the
biasing member 33 are disposed at the main body frame 30a of the
sheet conveying device 30. One end portion of the drive roller
shaft 31a, where the first discharging rollers 31 are disposed, is
protruded outside in the axial direction (illustrated by an arrow X
in FIG. 3) from the main body frame 30a of the sheet conveying
device 30.
[0091] The drive roller shaft 31a here is a single member, and is
disposed pivotally around an axis line with respect to the main
body frame 30a of the sheet conveying device 30.
[0092] Here, a plurality (here, two) of driven roller shaft 32a are
arranged along the axial direction X, to which a plurality (here,
two) of second discharging rollers 32 are each secured. The driven
roller shaft 32a is disposed pivotally around the axis line with
respect to the main body frame 30a of the sheet conveying device 30
and movable back and forth along the vertical direction (an arrow Z
direction in the drawing) such that the second discharging rollers
32 face the respective first discharging rollers 31. The sheet
conveying device 30 conveys the paper P while the paper P is
sandwiched in nip portions N between the first discharging rollers
31 and the second discharging rollers 32 in a state where the paper
P is pushed by the second discharging rollers 32.
[0093] Specifically, the biasing member 33 biases the second
discharging rollers 32 toward the first discharging rollers 31.
Here, the biasing member 33 is disposed between the second
discharging rollers 32 and between positions on the opposite side
of the first discharging rollers 31 of the main body frame 30a in
the sheet conveying device 30. Pressing forces of the second
discharging rollers 32 to the first discharging rollers 31 by the
biasing members 33 are pressures that allow properly conveying the
paper P.
[0094] The sheet conveying device 30 further includes a plurality
(here, four) of stiffening rollers 34. The stiffening rollers 34
are disposed coaxially with at least one discharging roller (here,
the second discharging rollers 32) among the first and second
discharging rollers 31 and 32. The stiffening rollers 34 have
diameters larger than diameters of the second discharging rollers
32. The stiffening rollers 34 may be disposed coaxially with one of
the first and second discharging rollers 31 and 32, or may be
disposed coaxially with both the first and second discharging
rollers 31 and 32. In the case where the stiffening rollers 34 are
disposed at both the first and second discharging rollers 31 and
32, the stiffening rollers 34 at the first discharging rollers 31
side and the stiffening rollers 34 at the second discharging
rollers 32 side are disposed not to overlap one another in the
axial direction X.
[0095] In view of this, the sheet conveying device 30 allows the
stiffening rollers 34 to impart a corrugated shape in the axial
direction X to the paper P and stiffen the paper P when conveying
the paper P. This prevents the leading end P1 of the paper P from
being weighed down early, prevents the rear end remaining of the
paper P, and prevents the fixed curl of the sheet P.
[0096] Specifically, the stiffening rollers 34 are disposed at an
end portion at one side X1 or an end portion at the other side X2
of the second discharging rollers 32 in the axial direction X. The
stiffening rollers 34 may be disposed at the driven roller shaft
32a.
[0097] Here, one stiffening roller 34 may be disposed at every or
every a plurality of individual rollers 32 in the second
discharging rollers 32. A plurality of stiffening rollers 34 may be
disposed at every or every a plurality of the individual rollers 32
in the second discharging rollers 32. The configurations thus
arranged may be combined. In this embodiment, the two stiffening
rollers 34 are disposed at each of the two places between the two
rollers 32 and 32 at both ends and the other two rollers 32 and 32
at the inner side of the rollers 32 and 32 at both ends.
[0098] The rotation driving portion 40 rotatably drives the drive
roller shaft 31a where the first discharging rollers 31 are
disposed. The rotation driving portion 40 includes a conveyance
driving motor 41 (here, a stepping motor) and a drive transmission
mechanism 42, which transmits rotation drive from the conveyance
driving motor 41 to the drive roller shaft 31a.
[0099] The conveyance driving motor 41 is disposed at the device
main body 110 where the rotating shaft 41a is along the axial
direction X.
[0100] The drive transmission mechanism 42 includes, here, a gear
train where a plurality of gears are lined up, which includes a
drive gear 42a, a roller gear 42b, and an intermediate gear
42c.
[0101] The drive gear 42a is coupled to the rotating shaft 41a of
the conveyance driving motor 41. The roller gear 42b is coupled to
an end portion, which protrudes outward in the axial direction X
from the main body frame 30a of the sheet conveying device 30, of
the drive roller shaft 31a. The intermediate gear 42c is rotatably
supported by the rotating shaft 110a, which is secured to the
device main body 110. The intermediate gear 42c is meshed with the
drive gear 42a and the roller gear 42b.
[0102] The conveyance driving motor 41 is electrically coupled to
an output system of a controller (not shown) to obtain a drive
signal (ON signal) or a drive stop signal (OFF signal) from the
controller. Transmitting a rotation command signal, which commands
a rotation direction, to the conveyance driving motor 41 drives the
conveyance driving motor 41. This rotatably drives the first
discharging rollers 31 in one direction A1 (one side Y1 in the
conveying direction Y, see FIG. 2) or the other direction A2 (the
other side Y2 in the conveying direction Y, see FIG. 2).
[0103] In the sheet conveying device 30 as described above, when
the paper P, which is switch backed, is guided to the reverse
conveying path 77 (see FIG. 2), the paper P corrugated by the
stiffening rollers 34 in the axial direction X is forcibly curved
along the reverse conveying path 77 curved in the conveying
direction Y. This restores the paper P from the corrugated state to
the prior state. At this time, the stiffening rollers 34 and the
second discharging rollers 32 have different circumferential speeds
that cause a difference in conveyance amount of the paper P per
unit time. This difference in conveyance amount causes large
amplitude of the corrugation of the sheet P, thus easily causing
abnormal sound. In this embodiment, the stiffening rollers 34
include the first stiffening rollers 34a, which apply conveying
forces to the paper P, and the second stiffening rollers 34b, which
apply smaller conveying forces to the paper P than the conveying
forces of the first stiffening rollers 34a to the paper P
(including a case without applying the conveying forces to the
paper P). This results in the following configurations of a first
embodiment and a second embodiment.
First Embodiment
[0104] In the first embodiment, the first stiffening rollers 34a
are configured to rotate integrally with the two second discharging
rollers 32 at the inner side in the axial direction X. The second
stiffening rollers 34b are disposed pivotally around the axis line
with respect to the two second discharging rollers 32 outside in
the axial direction X.
[0105] FIGS. 4A and 4B include schematic configuration views of
first and second stiffening rollers 34a and 34b and their
peripheral portions according to the first embodiment. FIG. 4A
illustrates a schematic side view of the first stiffening roller
34a portion viewed from the conveying direction Y. FIG. 4B
illustrates a schematic side view of the first stiffening roller
34a portion viewed from an axial direction X. FIG. 4C illustrates a
schematic side view of the second stiffening roller 34b portion
viewed from the conveying direction Y. FIG. 4D illustrates a
schematic side view of the second stiffening roller 34b portion
viewed from the axial direction X. FIG. 4A and FIG. 4B illustrate a
portion of the two first stiffening rollers 34a, which are
illustrated in FIG. 3, represented by a portion of the first
stiffening roller 34a on the right side. FIG. 4C and FIG. 4D
illustrate the two second stiffening rollers 34b, which are
illustrated in FIG. 3, represented by a portion of the second
stiffening roller 34b on the left side. The same applies to FIGS.
5A to 5D described below.
[0106] As illustrated in FIGS. 4A to 4D, the second discharging
rollers 32 include the stiffening roller installation portion 32b
in one side end portion at one side X1 or the other side X2 in the
axial direction X.
[0107] As illustrated in FIG. 4A and FIG. 4B, the first stiffening
rollers 34a are formed in a ring shape with the same outer
diameter. The ring shape has an inner diameter approximately the
same as an outer diameter of the stiffening roller installation
portions 32b of the second discharging rollers 32. The first
stiffening rollers 34a each include an inner peripheral surface
341a that is secured to an outer peripheral surface 321a of the
stiffening roller installation portion 32b of the second
discharging rollers 32 with an adhesive F.
[0108] As illustrated in FIG. 4C and FIG. 4D, the second stiffening
rollers 34b each have a ring shape that has the same outer diameter
as the outer diameter of the first stiffening rollers 34a and
approximately the same inner diameter as the outer diameter of the
stiffening roller installation portions 32b in the second
discharging rollers 32. The second discharging rollers 32 are
inserted into the second stiffening rollers 34b such that an inner
peripheral surface 341b of the second stiffening rollers 34b slides
on the outer peripheral surface 321a of the stiffening roller
installation portion 32b in the second discharging rollers 32.
[0109] The main body frame 30a of the sheet conveying device 30
includes a cover member 36 that covers the driven roller shaft 32a
(see FIG. 4C). This provides a configuration with a surface 32c
that faces the second stiffening roller 34b in the first
discharging rollers 31 and a surface 36a that faces the second
stiffening roller 34b in the cover member 36. This configuration
restricts movements of the second stiffening rollers 34b to one
side X1 and the other side X2 in the axial direction X, thus
preventing the second stiffening rollers 34b from dropping from the
second discharging rollers 32.
[0110] In order to reduce the strain (for example, occurrence of
scratching and similar strain) on the paper P when a corrugated
shape is imparted to the paper P, the first and second stiffening
rollers 34a and 34b may be constituted of elastic members such as
foamable resin.
[0111] The foamable resin may employ a material such as
polyurethane (specifically, urethane sponge (PORON LE-20 produced
by INOAC CORPORATION), silicone rubber, ethylene propylene rubber
(EPDM). The first and second discharging rollers 31 and 32 may
employ, for example, a resin such as polyacetal (POM) that is
excellent in strength and impact resistance.
Second Embodiment
[0112] In the second embodiment, the first stiffening rollers 34a
and the second stiffening rollers 34b are each configured to
integrally rotate with the second discharging rollers 32. The
second stiffening rollers 34b includes a surface with a smaller
friction coefficient than a friction coefficient of a surface of
the first stiffening rollers 34a.
[0113] FIGS. 5A to 5D are schematic configuration diagrams of the
first and second stiffening rollers 34a and 34b and their
peripheral portion according to the second embodiment. FIG. 5A
illustrates a schematic side view of the first stiffening roller
34a portion viewed from the conveying direction Y. FIG. 5B
illustrates a schematic side view of the first stiffening roller
34a portion viewed from the axial direction X. FIG. 5C illustrates
a schematic side view of the second stiffening roller 34b portion
viewed from the conveying direction Y. FIG. 5D illustrates a
schematic side view of the second stiffening roller 34b portion
viewed from the axial direction X.
[0114] As illustrated in FIGS. 5A to 5D, the second discharging
rollers 32 include the stiffening roller installation portion 32b
in one side end portion at one side X1 or the other side X2 in the
axial direction X.
[0115] The first stiffening rollers 34a and the second stiffening
rollers 34b each have a ring shape that has the same outer
diameter. The ring shape has an inner diameter approximately the
same as an outer diameter of the stiffening roller installation
portions 32b of the second discharging rollers 32. The first
stiffening rollers 34a and the second stiffening rollers 34b each
include the inner peripheral surface 341a that is secured to the
outer peripheral surface 321a of the stiffening roller installation
portion 32b in the second discharging rollers 32 with an adhesive
F.
[0116] As illustrated in FIG. 5C and FIG. 5D, the second stiffening
rollers 34b each have a surface that is coated with a surface layer
(here, a releasable resin layer) 342b with a friction coefficient
smaller than a friction coefficient of surfaces of the first
stiffening rollers 34a.
[0117] Similarly to the first embodiment, in order to reduce the
strain (for example, occurrence of scratching and similar strain)
on the paper P when corrugating the paper P, the first and second
stiffening rollers 34a and 34b may be constituted of elastic
members such as foamable resin.
[0118] The foamable resin may employ a material such as
polyurethane (specifically, urethane sponge (PORON LE-20 produced
by INOAC CORPORATION), silicone rubber, ethylene propylene rubber
(EPDM). The resin layer 342b may employ, for example, a fluororesin
material such as Polytetrafluoroethylene. The first and second
discharging rollers 31 and 32 may employ, for example, a resin such
as polyacetal (POM) that is excellent in strength and impact
resistance.
[0119] As illustrated in FIG. 3, in the first and second
embodiments, the second discharging rollers 32 and the stiffening
rollers 34 (34a and 34b) are symmetrical with respect to the center
in the axial direction X.
[0120] Specifically, in the first and second embodiments, the
stiffening rollers 34 (34a and 34b) includes the first stiffening
rollers 34a at the center portion in the axial direction X and the
second stiffening rollers 34b at the both end portions.
[0121] Specifically, in the axial direction X of the configuration
for sheet conveyance with the center reference, the second
discharging roller 32, the first stiffening roller 34a, the second
stiffening roller 34b, and the second discharging roller 32 are
disposed in this order from the center position .beta. (see FIG. 3)
of the paper P toward the outside, which are one side X1 and the
other side X2 (toward a lateral direction in FIG. 3).
[0122] That is, the stiffening roller closest from the center
position .beta. in the axial direction X among the stiffening
rollers 34 (34a and 34b) is the first stiffening roller 34a.
[0123] The stiffening rollers that are closest from the center
position .beta. in the axial direction X among the stiffening
rollers 34 (34a and 34b) are configured to convey the paper P with
the minimum size (the minimum size such as A6 size) that is usable
in the image forming apparatus 100. Specifically, the stiffening
rollers that are closest from the center position .beta. are
disposed to have a smaller distance in the axial direction X than a
width of the paper P in the available minimum size.
[0124] With the sheet conveying device 30 described above, the
stiffening rollers 34 are constituted of the first stiffening
rollers 34a and the second stiffening rollers 34b. This ensures a
simple structure and low cost. The stiffening rollers 34 allow
imparting a shape corrugated in the axial direction X to the paper
P. Additionally, the stiffening rollers 34 include the first
stiffening rollers 34a that apply conveying forces to the paper P.
This allows avoiding occurrence of rear end remaining of the paper
P, thus ensuring stacking quality of the paper P. Additionally, the
stiffening rollers 34 do not have a configuration where all the
individual stiffening rollers 34 apply conveying forces to the
paper P. The stiffening rollers 34 include the second stiffening
rollers 34b that apply smaller conveying forces to the paper P than
conveying forces of the first stiffening rollers 34a to the paper
P, in addition to the first stiffening rollers 34a that apply
conveying forces to the paper P. This reduces the difference in
conveyance amount of the paper P per unit time by the difference in
circumferential speed between the stiffening rollers 34 and the
second discharging rollers 32 irrespective of the rotation
directions A1 and A2 of the first and second discharging rollers 31
and 32, thus reducing amplitude of corrugation of the paper P. This
reduces occurrence of inconvenience (especially, abnormal sound of
the paper P conveyed to the reverse conveying path 77) related to
the corrugation.
[0125] In the first embodiment, the first stiffening rollers 34a
are configured to integrally rotate with the second discharging
rollers 32. Accordingly, the first stiffening rollers 34a rotate
along with the second discharging rollers 32. The second stiffening
rollers 34b are disposed pivotally around the axis line with
respect to the second discharging rollers 32. In view of this, the
second stiffening rollers 34b are in a free state where rotation of
the second stiffening rollers 34b is not restricted together with
the second discharging rollers if the second discharging rollers 32
rotate. Accordingly, the first stiffening rollers 34a provide
conveying forces to the paper P while the second stiffening rollers
34b do not provide conveying forces to the paper P. This reduces
the difference in conveyance amount of the paper P per unit time
due to the difference in circumferential speed between the
stiffening rollers 34 (34a and 34b) and the second discharging
rollers 32.
[0126] In the second embodiment, the first stiffening rollers 34a
and the second stiffening rollers 34b, which integrally rotate with
the second discharging rollers 32, are configured to have the
smaller friction coefficient of the surfaces of the second
stiffening rollers 34b than the friction coefficient of the
surfaces of the first stiffening rollers 34a. Accordingly, the
paper P easily slides on the second stiffening rollers 34b compared
with the first stiffening rollers 34a. This reduces conveying
forces to the paper P in the second stiffening rollers 34b compared
with conveying forces to the paper P in the first stiffening
rollers 34a. This reduces the difference in conveyance amount of
the paper P per unit time by the difference in circumferential
speed between the stiffening rollers 34 (34a and 34b) and the
second discharging rollers 32.
[0127] In the first and the second embodiments, the stiffening
rollers 34 (34a and 34b) and the second discharging rollers 32 are
disposed symmetrically with respect to the center reference in the
axial direction X. This applies conveying forces to the paper P
symmetrically with respect to the center reference. This prevents
occurrence of skew (diagonal feed).
[0128] In the first and second embodiments, the stiffening rollers
34 include the first stiffening rollers 34a disposed at the center
portion in the axial direction X and the second stiffening rollers
34b disposed at the both end portions. This reduces occurrence of
inconveniences related to corrugation of the paper P while ensuring
stable conveyance of the paper P at the center portion in the axial
direction X.
[0129] In the first and second embodiments, the stiffening rollers
that are closest from the center position .beta. in the axial
direction X among the stiffening rollers 34 are the first
stiffening rollers 34a. This allows applying a conveying force near
the center position .beta.. Even in the case where the papers P in
a plurality of sizes such as from A3 to A6, B4, and B5 are used,
this surely conveys the paper P in a size smaller than the maximum
size.
[0130] In the first and second embodiments, the stiffening rollers
34a that are closest from the center position .beta. in the axial
direction X among the stiffening rollers 34 are configured to
convey the paper P in the minimum size usable in the image forming
apparatus 100. This allows surely conveying the paper P even in the
minimum size in the configuration for sheet conveyance with the
center reference.
[0131] In the first and second embodiments, the stiffening rollers
34 are each disposed in the stiffening roller installation portion
32b. Compared with a case where the stiffening rollers 34 are
distant from the second discharging rollers 32 in the axial
direction X (for example, a case where the stiffening rollers 34
are provided with the driven roller shaft 32a at the center between
the adjacent second discharging rollers 32), this provides a large
proportion of amplitude to the difference between the diameters of
the stiffening rollers 34 and the diameters of the second
discharging rollers 32 even in the case where the corrugations of
the paper P have the same maximum amplitude. This consequently
reduces material cost. Furthermore, this allows providing the
stiffening rollers 34 and the second discharging rollers 32 as one
assembly part, thus ensuring reduced assembly processes for the
stiffening rollers 34 and the second discharging rollers 32.
[0132] While in this embodiment the curved conveyance path (here,
the reverse conveying path 77 that constitutes the curved
conveyance path) is disposed in the portion where the paper P is
conveyed to the other side Y2 in the conveying direction Y and
switch backed, this should not be construed in a limiting sense.
The curved conveyance path may be disposed in a portion where the
paper P is conveyed to one side Y1 in the conveying direction Y.
This similarly allows avoiding inconveniences related to the
corrugation of the paper P. While in this embodiment the sheet
conveying device 30 is disposed in the portion that conveys the
paper P where an image is formed, this should not be construed in a
limiting sense. The sheet conveying device 30 may be disposed in a
portion that conveys the original where an image is read. This
similarly allows avoiding inconveniences related to the corrugation
of the original.
Embodiment
[0133] Next, the occurrence of abnormal sound in the reverse
conveying path 77 was examined for each embodiment with the
configuration of the first embodiment. The examination results will
be described below using Comparative examples 1 and 2.
[0134] In Comparative example 1, the image forming apparatus 100
illustrated in FIG. 1 has a configuration where all the individual
stiffening rollers 34 integrally rotate with the second discharging
rollers 32. In Comparative example 2, the image forming apparatus
100 illustrated in FIG. 1 has a configuration where all the
individual stiffening rollers 34 are disposed pivotally around the
axis line with respect to the second discharging rollers 32.
[0135] FIG. 6 is a table illustrating positional relationships and
sizes of outer diameters of the stiffening rollers 34 by
destination of the image forming apparatus 100.
[0136] As illustrated in FIG. 6, in Japanese (centimeter)
specification and North America (inch) specification, outer
diameters d1 to d4 of the stiffening rollers 34 were each set to 20
mm. In European (centimeter) specification, outer diameters d2 and
d3 of the two stiffening rollers 34 and 34 inside were set to 21 mm
while outer diameters d1 and d4 of the two stiffening rollers 34
and 34 outside were set to 20 mm. All the second discharging
rollers 32 had an outer diameter d set to 15 mm.
[0137] FIG. 7 illustrates results of Comparative examples 1 and 2
and the embodiment. In FIG. 7, "Poor (x)" denotes a case where
abnormal sound occurred while "Good (o)" denotes a case where
abnormal sound did not occur. Additionally, "Poor (x)" denotes a
case where the rear end remaining occurred while "Good (o)" denotes
a case where the rear end remaining did not occur. The same applies
to FIG. 8 described below. In FIG. 7, "LOCKED" means a
configuration where the second discharging roller 32 integrally
rotates with the stiffening roller 34. "FREE" means a configuration
where the stiffening roller 34 freely rotates with respect to the
second discharging roller 32.
[0138] As illustrated in FIG. 7, like Comparative example 1, the
configuration where all the individual stiffening rollers 34 apply
conveying forces to the paper P solves the rear end remaining but
causes abnormal sound of the paper P conveyed to the reverse
conveying path 77. On the other hand, like Comparative example 2,
the configuration where all the individual stiffening rollers 34 do
not apply conveying forces to the paper P solves abnormal sound of
the paper P conveyed to the reverse conveying path 77 but reduces
conveying forces to the paper P. This caused the rear end remaining
of the paper P and could not ensure stacking quality of the paper
P.
[0139] In this respect, like the embodiment, the configuration
where a part of the individual stiffening rollers 34 does not apply
a conveying force to the paper P solves abnormal sound of the paper
P conveyed to the reverse conveying path 77, and also solves the
occurrence of rear end remaining of the paper P. This ensured
stacking quality of the paper P.
[0140] In Comparative example 1 and the embodiment, the occurrence
of abnormal sound by each of different kinds of paper P in the
reverse conveying path 77 was examined. FIG. 8 illustrates results
of the examination.
[0141] In Comparative example illustrated in FIG. 8(a), abnormal
sound occurred frequently in B4 size/legal (LGL) size and A3
size/double letter (WLT) size. In contrast, in the embodiment
illustrated in FIG. 8(b), the occurrence of abnormal sound was not
observed in any size.
[0142] The present invention can be embodied and practiced in other
different forms without departing from the spirit and essential
characteristics of the present invention. Therefore, the
above-described embodiments and examples are considered in all
respects as illustrative and not restrictive. The scope of the
invention is indicated by the appended claims rather than by the
foregoing description. All variations and modifications falling
within the equivalency range of the appended claims are intended to
be embraced therein.
[0143] This application is based on and claims priority to Japanese
Patent Application 2010-177576, filed on Aug. 6, 2010, the entire
contents of which are incorporated herein by reference.
Furthermore, the entire contents of references cited in the present
specification are herein specifically incorporated by
reference.
DESCRIPTION OF REFERENCE SIGNS
[0144] 30 sheet conveying device [0145] 31 first discharging roller
[0146] 31a drive roller shaft [0147] 32 second discharging roller
[0148] 32a driven roller shaft [0149] 32b stiffening roller
installation portion (one side end portion of second discharging
roller) [0150] 34 stiffening roller [0151] 34a first stiffening
roller [0152] 34b second stiffening roller [0153] 342b surface
layer [0154] 77 reverse conveying path (exemplary curved conveyance
path) [0155] 100 image forming apparatus [0156] F adhesive [0157] P
paper (exemplary sheet) [0158] X axial direction [0159] Y conveying
direction [0160] Y1 one side in conveying direction [0161] Y2 the
other side in conveying direction [0162] .alpha. rear end remaining
portion [0163] .beta. center position
* * * * *