U.S. patent application number 14/777822 was filed with the patent office on 2016-10-13 for sheet feeding device and image forming apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Takaaki Aoyagi, Takeshi Aoyama, Takashi Hiratsuka, Hiroki Kasama, Tadashi Matsumoto, Kazumasa Shibata, Yasumi Yoshida.
Application Number | 20160297633 14/777822 |
Document ID | / |
Family ID | 51689387 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160297633 |
Kind Code |
A1 |
Kasama; Hiroki ; et
al. |
October 13, 2016 |
SHEET FEEDING DEVICE AND IMAGE FORMING APPARATUS
Abstract
Provided are a sheet feeding device and an image forming
apparatus which can separately feed a sheet with safety without
causing the length of an adsorption member to be increased. One end
of a flexible adsorption member (29) is fixed to a holding member
(24) which is disposed on the upper side of a storing unit to store
the sheet and rotated in a sheet feeding direction. Then, when the
holding member (24) is rotated, the rigidity of a second region
(29b) of the adsorption member (29) is set to be lower than that of
a first region (29a) of the adsorption member (29) which comes into
surface contact with the sheet stored in the storing unit and
adsorbs the sheet by an adsorbing force by static electricity.
Inventors: |
Kasama; Hiroki;
(Kashiwa-shi, JP) ; Yoshida; Yasumi;
(Yokohama-shi, JP) ; Matsumoto; Tadashi; (Tokyo,
JP) ; Shibata; Kazumasa; (Kawasaki-shi, JP) ;
Hiratsuka; Takashi; (Kashiwa-shi, JP) ; Aoyama;
Takeshi; (Kawasaki-shi, JP) ; Aoyagi; Takaaki;
(Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
51689387 |
Appl. No.: |
14/777822 |
Filed: |
March 20, 2014 |
PCT Filed: |
March 20, 2014 |
PCT NO: |
PCT/JP2014/057765 |
371 Date: |
September 17, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 1/266 20130101;
B65H 7/02 20130101; B65H 2404/12 20130101; B65H 7/20 20130101; B65H
2404/191 20130101; B65H 1/04 20130101; B65H 5/004 20130101; B65H
3/18 20130101; B65H 2555/41 20130101 |
International
Class: |
B65H 3/18 20060101
B65H003/18; B65H 5/00 20060101 B65H005/00; B65H 7/02 20060101
B65H007/02; B65H 7/20 20060101 B65H007/20; B65H 1/04 20060101
B65H001/04; B65H 1/26 20060101 B65H001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2013 |
JP |
2013-083582 |
Claims
1. A sheet feeding device comprising: a loading portion configured
to be loaded with a sheet; a rotation member configured to be
disposed on an upper side of the loading portion; and an adsorption
member configured to have ends and to be provided such that a part
of the adsorption member is fixed to the rotation member and the
sheet loaded on the loading portion is electrically adsorbed,
wherein the adsorption member includes an adsorption portion which
comes into contact with the sheet loaded on the loading portion,
and a support portion which is provided at a position near the
rotation member from the adsorption portion and has a rigidity
lower than that of the adsorption portion with respect to a force
applied from a sheet feeding direction.
2. The sheet feeding device according to claim 1, further
comprising: a detection unit configured to detect a rotation angle
of the rotation member; a power source configured to apply a
voltage to apply an adsorbing force by static electricity onto the
adsorption member; and a control unit configured to apply a voltage
from the power source to the adsorption member when it is
determined that the adsorption portion comes into contact with the
sheet based on a signal from the detection unit
3. The sheet feeding device according to claim 1, wherein the
support portion and the adsorption portion of the adsorption member
are set to have the same thickness, and a volume of the adsorption
member of the adsorption member is set to be smaller than that of
the adsorption portion.
4. The sheet feeding device according to claim 3, wherein at least
one of a notch, a tapper, and an opening is formed in the support
portion of the adsorption member so as to make the volume of the
adsorption member smaller than that of the adsorption portion by
the amount of the notch, the tapper, and the opening which are
formed.
5. The sheet feeding device according to claim 1, wherein a
thickness of the support portion of the adsorption member is
thinner than that of the adsorption portion.
6. The sheet feeding device according to claim 1, wherein the
support portion of the adsorption member is formed of a material
having a Young's modulus lower than that of a material of the
adsorption portion.
7. The sheet feeding device according to claim 2, wherein the
adsorption member is a dielectric having two electrodes in a
surface or the inside of a flexible base material, and wherein the
power source includes a first power source which applies a positive
voltage to one of the two electrodes and a second power source
which applies a negative voltage to the other one of the two
electrodes.
8. The sheet feeding device according to claim 7, wherein the
electrode is provided in the adsorption portion.
9. The sheet feeding device according to claim 7, wherein the
rotation member is formed of a conductive material, one of the
first power source and the second power source is connected to one
of the two electrodes of the adsorption member through the rotation
member, and the other one of the first power source and the second
power source is connected to the other one of the two electrodes of
the adsorption member.
10. A sheet feeding device comprising: a loading portion configured
to be loaded with a sheet; and a flexible adsorption member
configured to include an adsorption portion which abuts on the
sheet loaded on the loading portion from an upper side and comes
into surface contact with the sheet loaded on the loading portion
to adsorb the sheet by an adsorbing force by static electricity,
and a non-adsorption portion which has a low rigidity compared to
that of the adsorption portion.
11. The sheet feeding device according to claim 10, further
comprising a rotation member configured to be provided on the upper
side of the loading portion to be rotatably in a sheet feeding
direction, wherein one end of the non-adsorption portion of the
adsorption member is fixed to the rotation member, and when the
rotation member is rotated, the adsorption portion comes into
surface contact with the sheet loaded on the loading portion to
adsorb the sheet.
12. An image forming apparatus comprising: an image forming
section; a loading portion configured to be loaded with a sheet; a
rotation member configured to be disposed on an upper side of the
loading portion; and an adsorption member configured to have ends
and to be provided such that a part of the adsorption member is
fixed to the rotation member and the sheet loaded on the loading
portion is electrically adsorbed, wherein the adsorption member
includes an adsorption portion which comes into contact with the
sheet loaded on the loading portion, and a support portion which is
provided at a position near the rotation member from the adsorption
portion and has a rigidity lower than that of the adsorption
portion with respect to a force applied from a sheet feeding
direction.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sheet feeding device and
an image forming apparatus, and particularly to a device that feeds
a sheet using an electrostatic adsorbing force.
BACKGROUND ART
[0002] An image forming apparatus such as a copying machine or a
printer in the related art is provided with a sheet feeding device
which feeds a sheet such as plain paper, coated paper, or OHP
paper. In general, the image forming apparatus conveys the sheet
fed by the sheet feeding device to the image forming section to
form an image on the sheet. As such a sheet feeding device, there
are a friction feeding method in which the uppermost sheet is
separately fed out of a cassette loaded with a sheet bundle using a
friction force of a feeding roller, and an air feeding method which
adsorbs and conveys the sheet using the air.
[0003] By the way, in recent years, noise damping is required in
the sheet feeding device, and it is important that the operation
sound is suppressed as low as possible. However, in the sheet
feeding device using the friction force by the feeding roller,
there occurs screechy noises between the sheet and the roller or
between the sheets. Further, in the air feeding method, the
apparatus is increased in size so that the operation sound is also
increased.
[0004] As a feeding method receiving the attention in recent years,
there is an electrostatic adsorption method in which the sheet is
adsorbed using static electricity and conveyed. Further, according
to the electrostatic adsorption method, the sheet can be fed
without using the friction force, so that it is advantageous for
the sound damping. As a sheet feeding device of such an
electrostatic adsorption method, the sheet is adsorbed to an
adsorption member having an electrostatic adsorption function, and
then the adsorption member horizontally moves to convey the sheet
(see Patent Literature 1).
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Patent Laid-Open No.
6-40583
SUMMARY OF INVENTION
Technical Problem
[0006] Herein, in a case where an adsorption member adsorbing the
sheet is configured to be horizontally moved likely to the sheet
feeding device disclosed in a conventional electrostatic adsorption
method, there is a need to widen a surface contact area between the
adsorption member and an uppermost sheet in order to securely
separate the sheet. However, in order to widen the surface contact
area, the length of the adsorption member is necessarily increased.
Further, when the length of the adsorption member is increased, the
apparatus is increased in size.
[0007] The invention has been made in view of the circumstances,
and an object thereof is to provide a sheet feeding device and an
image forming apparatus which can separate and feed the sheet with
safety without causing the length of the adsorption member to be
increased.
Solution to Problem
[0008] The invention provides a sheet feeding device which includes
a loading portion configured to be loaded with a sheet, a rotation
member configured to be disposed on an upper side of the loading
portion, and an adsorption member configured to have ends and to be
provided such that a part of the adsorption member is fixed to the
rotation member and the sheet loaded on the loading portion is
electrically adsorbed. The adsorption member includes an adsorption
portion which comes into contact with the sheet loaded on the
loading portion, and a support portion which is provided at a
position near the rotation member from the adsorption portion and
has a rigidity lower than that of the adsorption portion with
respect to a force applied from a sheet feeding direction.
Advantageous Effects of Invention
[0009] According to the invention, a flexible adsorption member is
configured such that a rigidity of a fixed portion of the
adsorption member is lower than that of an adsorption portion of
the adsorption member where a sheet is adsorbed, so that the sheet
can be separated and fed with safety without causing the length of
the adsorption member to be increased.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a diagram illustrating the entire configuration of
a full-color laser beam printer as an example of an image forming
apparatus provided with a sheet feeding device according to a first
embodiment of the invention.
[0011] FIG. 2 is a diagram for describing a configuration of the
sheet feeding device.
[0012] FIG. 3 is a diagram for describing a configuration of an
adsorbing and feeding section of the sheet feeding device.
[0013] FIG. 4 is a cross-sectional diagram schematically
illustrating an adsorption member included in the adsorbing and
feeding section.
[0014] FIG. 5 is a diagram for describing the bending at the time
of a cantilever state of the adsorption member.
[0015] FIG. 6 is a diagram for describing a configuration of the
adsorption member.
[0016] FIG. 7 is a diagram for describing another configuration of
the adsorption member.
[0017] FIG. 8 is a diagram for describing the bending at the time
of the cantilever sate of the adsorption member.
[0018] FIG. 9 is a control block diagram of the full-color laser
beam printer.
[0019] FIG. 10 is a diagram for describing a sheet separating and
feeding operation of the sheet feeding device.
[0020] FIG. 11 is a flowchart of the sheet separating and feeding
operation of the sheet feeding device.
[0021] FIG. 12 is a timing chart of the sheet separating and
feeding operation of the sheet feeding device.
[0022] FIG. 13 is a diagram for comparing the adsorption member
with a conventional adsorption member at the time of the sheet
separating and feeding operation.
[0023] FIG. 14 is a diagram for describing the adsorption member of
a sheet feeding device according to a second embodiment of the
invention.
[0024] FIG. 15 is a diagram for describing the adsorption member of
a sheet feeding device according to a third embodiment of the
invention.
DESCRIPTION OF EMBODIMENTS
[0025] Hereinafter, embodiments of the invention will be described
in detail using the drawings. FIG. 1 is a diagram illustrating the
entire configuration of a full-color laser beam printer as an
example of an image forming apparatus provided with a sheet feeding
device according to a first embodiment of the invention. In FIG. 1,
a full-color laser beam printer 100 and a full-color laser beam
printer body 100A (hereinafter, referred to as a printer body) are
illustrated. The printer body 100A serving as a main body includes
the image forming section 100B which forms an image on a sheet such
as a recording sheet, a plastic sheet, or cloth, and a sheet
feeding device 200 which feeds the sheet.
[0026] The image forming section 100B includes process cartridges 7
(7Y, 7M, 7C, and 7K) which form toner images of four colors
(yellow, magenta, cyan, and black). Further, the process cartridges
7 include photosensitive drums 1 (1Y, 1M, 1C, and 1K) which serve
as image bearing members rotatably driven by a driving unit (a
driving source; not illustrated) in a direction of arrow A (a
counterclockwise direction), and is mounted to be detachably
attachable to the printer body 100A.
[0027] In addition, the image forming section 100B includes a
scanner unit 3 which is disposed on the upper side of the process
cartridges 7 in a vertical direction, irradiates the photosensitive
drums 1 with laser beams based on image information, and forms
electrostatic latent images on the photosensitive drums 1. Further,
the process cartridges 7 includes, besides the photosensitive drums
1, developing units 4 (4Y, 4M, 4C, and 4K) which attach toner to
the electrostatic latent images to visualize the latent images, and
charging rollers 2 (2Y, 2M, 2C, and 2K) which evenly charge the
surfaces of the photosensitive drums.
[0028] In addition, the image forming section 100B includes an
intermediate transfer belt unit 100C, a secondary transfer portion
N2, and a fixing portion 10. The intermediate transfer belt unit
100C includes an endless intermediate transfer belt 5, and primary
transfer rollers 8 (8Y, 8M, 8C, and 8K) which are disposed inside
the intermediate transfer belt 5 to face the photosensitive drums
1. The intermediate transfer belt 5 rotates in a direction of arrow
B while abutting on all the photosensitive drums 1 and suspending
on a drive roller 16, a secondary transfer counter roller 17, and a
driven roller 18.
[0029] Herein, the primary transfer rollers 8 presses the
intermediate transfer belt 5 toward the photosensitive drum 1,
forms a primary transfer portion N1 which abuts on the intermediate
transfer belt 5 and the photosensitive drum 1, and applies a
transfer bias to the intermediate transfer belt 5 by a bias
applying unit (not illustrated). Then, a primary transfer bias is
applied to the intermediate transfer belt 5 by the primary transfer
rollers 8, and the respective color toner images on the
photosensitive drums are sequentially transferred onto the
intermediate transfer belt 5, thereby forming a full-color image on
the intermediate transfer belt.
[0030] In addition, the secondary transfer roller 9 is disposed at
a position facing the secondary transfer counter roller 17 on an
outer peripheral surface of the intermediate transfer belt 5, and
comes in press contact with the secondary transfer counter roller
17 through the intermediate transfer belt 5 to form the secondary
transfer portion N2. Then, the toner images on the intermediate
transfer belt 5 are transferred onto a sheet P (the secondary
transfer) by applying a bias having an opposite-polarity with
respect to a normal charge polarity of the toner from a secondary
transfer bias power source (a high-voltage power source) serving as
a secondary transfer bias applying unit (not illustrated) to the
secondary transfer roller 9.
[0031] The sheet feeding device 200 includes a sheet feeding
cassette 20 serving as a storing unit which is mounted to be
detachably attachable to the printer body 100A, and an adsorbing
and feeding section 12 which adsorbs a plurality of sheets P stored
in the sheet feeding cassette 20 and feeds the sheets. Then, when
the sheet P stored in the sheet feeding cassette 20 is fed, the
sheet P is adsorbed by the adsorbing and feeding section 12 and fed
out.
[0032] Next, an image forming operation of the full-color laser
beam printer 100 having such a configuration will be described.
When an image reading apparatus (not illustrated) connected to the
printer body 100A, or an image signal from a host machine such as a
personal computer is input to the scanner unit 3, the
photosensitive drum is irradiated with the laser beam corresponding
to the image signal from the scanner unit 3. At this time, the
surfaces of the photosensitive drums 1 are evenly charged with a
polarity and a voltage determined in advance by the charging
rollers 2. The electrostatic latent images are formed on the
surfaces by irradiating with the laser beams from the scanner unit
3. Thereafter, the electrostatic latent images are developed and
visualized by the developing units 4.
[0033] For example, first, the photosensitive drum 1Y is irradiated
with the laser beam by the image signal of a yellow component from
the scanner unit 3, and a yellow electrostatic latent image is
formed in the photosensitive drum. Then, the yellow electrostatic
latent image is developed by the yellow toner from the developing
unit 4Y, and visualizes the latent image into a yellow toner image.
Thereafter, the toner image reaches the primary transfer portion N1
where the photosensitive drum 1Y and the intermediate transfer belt
5 abut on each other according to the rotation of the
photosensitive drum 1Y. Then, the yellow toner image on the
photosensitive drum is transferred onto the intermediate transfer
belt in the primary transfer portion N1 by the primary transfer
bias applied to the primary transfer roller 8Y.
[0034] Next, when a portion carrying with the yellow toner image of
the intermediate transfer belt 5 moves, a magenta toner image
formed on the photosensitive drum 1M is transferred from above the
yellow toner image to the intermediate transfer belt 5 by the
method similar to the above description until this stage.
Similarly, a cyan toner image and a black toner image are
transferred onto the yellow toner image and the magenta toner image
in an overlapping manner in the respective primary transfer
portions as the intermediate transfer belt 5 moves. Therefore, a
full-color toner image is formed on the intermediate transfer
belt.
[0035] In addition, the sheet P stored in the sheet feeding
cassette 20 is fed out by the adsorbing and feeding section 12 in
parallel to the toner image forming operation, and then conveyed to
a registration roller 15. Next, the sheet P conveyed to the
registration roller 15 is conveyed to the secondary transfer
portion N2 by the registration roller 15 in synchronization with
timing. Then, in the secondary transfer portion N2, the four-color
toner image on the intermediate transfer belt 5 is secondarily
transferred onto the conveyed sheet P by applying a positive bias
to the secondary transfer roller 9. Further, after the toner image
is secondarily transferred, the toner left on the intermediate
transfer belt 5 is removed by a belt cleaner 11. Next, the sheet P
on which the toner image is transferred is conveyed to the fixing
portion 10 and heated and pressed therein, so that the full-color
toner image is fixed as a permanent image, and then discharged to
the outside of the printer body 100A.
[0036] Next, the sheet feeding device 200 according to this
embodiment will be described using FIG. 2. As illustrated in FIG.
2, the adsorbing and feeding section 12 includes an adsorption
member 29 and a holding member 24 serving as an axial holding unit
which holds the adsorption member 29. Further, in FIG. 2, a sheet
supporting plate 21 is provided in a housing 23 provided at the
bottom surface of the printer body 100A to freely rotate in the
vertical direction about a fulcrum 22. The sheet supporting plate
21 may be disposed not in the housing 23 but in the sheet feeding
cassette 20.
[0037] In addition, a conveyance guide plate 40 is provided on a
downstream side in a sheet feeding direction of an adsorbing and
feeding section 12. Then, the center portion in a width direction
perpendicular to the sheet feeding direction of the conveyance
guide plate 40 is cut off, and a width L1 of the cut-off shape of
the conveyance guide plate 40 is set to be larger than a width L2
of an adsorption member 29 (L1>L2). In this way, it is possible
to prevent that the conveyance guide plate 40 hinders the rotation
of the adsorption member 29 by setting the width L1 of the cut-off
shape of the conveyance guide plate 40, when the adsorption member
29 is rotated together with a holding member 24 as described
below.
[0038] The holding member 24 is disposed on the upper side at the
downstream end in the sheet feeding direction of a sheet feeding
cassette 20, and one end of the adsorption member 29 is fixed to
the center portion in the width direction of the holding member 24.
The holding member 24 is an axial member formed of a conductive
material (for example, SUS303), and rotatably held by a bearing 32
provided in a printer body 100A. In addition, the holding member 24
is rotated by a driving force of a servo motor M transmitted
through a drive transmission gear train G. Then, when the holding
member 24 is rotated, the adsorption member 29 is also rotated
integrally with the holding member 24.
[0039] A rotary encoder 31 having a function of detecting a home
position of the holding member 24 is attached to one end of the
holding member 24. Then, a rotation angle .theta. of the holding
member 24 can be detected by counting the number of pulses output
from an angle sensor 71 (described below) serving as a detection
unit illustrated in FIG. 9 which detects the rotation of the rotary
encoder 31. For example, in a case where a pulse number T0 output
from the angle sensor 71 is 1000 until the holding member 24 is
rotated from the home position and returns to the home position
again, when the pulse number is 250, it is possible to detect that
the rotation angle .theta. from the home position of the holding
member 24 is 90.degree..
[0040] In addition, an insulating tape 25 is attached to one of the
holding member 24 as illustrated in FIG. 3, and a power electrode
26 is formed on the insulating tape 25. Then, the power electrode
26 comes into contact with a first power brush 43a connected to a
high-voltage power source 110, and the holding member 24 comes into
contact with a second power brush 43b which is connected to a
high-voltage power source 120 and applies a voltage different from
the power electrode 26 to the holding member 24. With this
configuration, it is possible to apply different voltages to the
holding member 24 and the power electrode 26. Further, in this
embodiment, the different voltages are applied to the holding
member 24 and the power electrode 26 using the power brushes 43a
and 43b, but any method of applying the power may be employed as
long as the power can be applied to the rotating member.
[0041] One end of the adsorption member 29 in the sheet feeding
direction is fixed to the holding member 24 as illustrated in FIG.
3, and configured in a cantilever structure. The adsorption member
29 includes a first comb-tooth electrode 30a and a second
comb-tooth electrode 30b therein. The first and the second
comb-tooth electrodes 30a and 30b are configured such that two
electrodes in the adsorption member 29 are alternately disposed in
a stripe shape, so that the power can be individually supplied to
the first and the second comb-tooth electrodes 30a and 30b.
Further, in this embodiment, the first and the second comb-tooth
electrodes 30a and 30b are disposed to have an electrode width of 6
mm, and an electrode pitch of 2 mm.
[0042] In addition, the first comb-tooth electrode (a first
electrode) 30a as one of the two electrodes is wired to the power
electrode 26, and the second comb-tooth electrode (a second
electrode) 30b as the other electrode is wired to the holding
member 24. Then, in this embodiment, a negative voltage of -1 kV is
applied from the high-voltage power source (a first power source)
110 to the power electrode 26 through the first power brush 43a,
and a positive voltage of 1 kV is applied from the high-voltage
power source (a second power source) 120 to the holding member 24
through the second power brush 43b.
[0043] In this way, an electrostatic adsorbing force can be applied
between the surface of the adsorption member 29 as a dielectric
material and the sheet by applying a positive voltage V1 one of the
first and the second comb-tooth electrodes 30a and 30b, and a
negative voltage V2 to the other one. Then, the adsorption member
29 adsorbs the sheet and holds it up by the electrostatic adsorbing
force as described below. Further, the magnitude of the applying
voltage is not limited as long as it causes an adsorbing force
having the magnitude necessary for adsorbing the sheet to the
adsorption member 29 as described below.
[0044] Further, as illustrated in FIG. 4, the adsorption member 29
is generated such that the upper surface of an insulating sheet 61
as a base material is partially cut off while not passing through
the lower surface, the first and the second comb-tooth electrodes
30a and 30b are alternately disposed in the cut-off places, and a
flexible medium resistance sheet 60 is fused thereon. Herein, in
this embodiment, for example, PVDF having a volume resistivity of
1012 .OMEGA./cm or so is employed for the medium resistance sheet
60, and a polyimide material having a volume resistivity of 1016
.OMEGA./cm or so is employed for the insulating sheet 61. Further,
the material of the adsorption member 29 may be a dielectric
material, and can be preferably made using a flexible resin sheet.
In addition, the adsorption member 29 may be configured such that
the electrode may be disposed in the surface not the inside.
[0045] By the way, as illustrated in FIG. 3, the adsorption member
29 includes a first region 29a serving as an adsorption portion
coming into surface contact with the sheet as described below to
adsorb the sheet, and a second region 29b serving as a support
portion which supports the first region 29a and is easily bent
compared to the first region 29a. Further, the first and the second
comb-tooth electrodes 30a and 30b are disposed in the first region
29a.
[0046] Herein, in this embodiment, the adsorption member 29 is
formed to have a small rigidity in the second region 29b provided
on a side near the holding member (one end in the sheet feeding
direction) from the first region 29a compared to the rigidity in
the first region 29a of the adsorption member 29. Then, the second
region 29b is made to be easily bent compared to the first region
29a by setting the rigidity in the first region 29a and the second
region 29b as described above.
[0047] Further, the rigidity of the adsorption member 29 can be
evaluated by a fixed end beam on one side and a free end beam on
the other end. For example, a maximum bending amount at the time
when a load F is intensively applied on the free end of the beam
even in a width, a thickness, and a Young's modulus is expressed by
the following equation using a length l, a width b, a Young's
modulus E, and a thickness h of the beam.
[Mathematical Formula 1]
[0048] In the above equation, the width b, the thickness h, and the
Young's modulus E of the beam are the parameter affecting on the
rigidity of the beam. Therefore, when at least one of the width b,
the thickness h, and the Young's modulus E is changed, the rigidity
in the first region 29a of the adsorption member 29 can be made
different from the rigidity in the second region 29b. Herein, in
this embodiment, the flexibility of the second region 29b is
realized by narrowing the width of the second region 29b compared
to the width of the first region 29a.
[0049] Further, the area of the first region 29a for adsorbing the
sheet is determined according to an adsorption performance. For
example, in the adsorption member 29 having an adsorption
performance of 0.00095 N/mm2, in a case where 0.22 N is necessary
for peeling off a sheet, a required area becomes 232 mm2, so that
the shape of the first region 29a is set to have an area equal to
or more than the required area.
[0050] FIG. 5 is a diagram illustrating a relation between a
distance from the fixed end of the adsorption member 29 and a
bending amount. Further, in FIG. 5, the horizontal axis indicates
the distance from the fixed end, and the vertical axis indicates
the bending amount. In FIG. 5, the plotted line a indicates the
adsorption member 29 having the shape illustrated in FIG. 3
according to this embodiment. The plotted line d indicates the
adsorption member having an ideal shape for realizing a sheet
feeding sequence of the adsorption member 29 according to this
embodiment described below. The plotted line Ref indicates the
adsorption member having a shape having even rigidity in the
related art. Section AB corresponds to the second region 29b, and
section BC corresponds to the first region 29a.
[0051] Herein, the ease bending is advantageous for the adsorption
member 29 to enable the sheet surface to be adsorbed upward when
the sheet is separated. However, when the bending amount in section
BC is large, a deformation may be generated with time, and flatness
of the sheet may be not secured at the time of adsorption.
Therefore, an adsorption member which is easily bent in section AB
as depicted with the plotted line d and hardly bent in section BC
is ideal rather than an adsorption member bending in section BC as
depicted by the plotted line Ref of FIG. 5.
[0052] Since the width of the second region 29b is made narrow
compared to that of the first region 29a as described above, the
adsorption member 29 depicted with the plotted line a of FIG. 5 can
be formed not to be bent in section BC. Then, as the width of the
second region 29b becomes significantly different with respect to
the first region 29a, the shape approaches the ideal shape as
depicted with the plotted line d of FIG. 5.
[0053] For this reason, in this embodiment, the shape of the
adsorption member 29 is made as illustrated in FIG. 6. In other
words, the adsorption member 29 is configured such that a total sum
of the respective widths X2 and X3 of the second region 29b of the
shaped portion is set to be small compared to a width X1 of the
first region 29a (X1>X2+X3). Then, in this embodiment, a
rectangular shape is employed for the first region 29a to have a
width X1 of 60 mm, a length X5 of 30 mm, and a thickness of 0.1 mm.
In addition, in consideration of durability not to cause
deformation, a non-adsorption portion of the second region 29b is
configured such that the width thereof is narrower than that of the
first region 29a and both portions separated into two parts are
made in a rectangular shape having widths X2 and X3 of 15 mm, a
length X4 of 20 mm, and a thickness of 0.1 mm.
[0054] Further, the shape of the adsorption member 29 may have the
shape illustrated in (a) to (d) of FIG. 7 other than the shape
described in FIG. 6. The first region of the adsorption member
described in FIG. 5 is on a side denoted by A from the dotted line
illustrated in FIG. 7, and the second region easily bending
compared to the first region is on a side denoted by B. The
adsorption member 29 illustrated in (a) of FIG. 7 is configured
such that the width of the cross section of the round holes 55 in
the second region becomes narrow by forming a plurality of round
holes 55 as openings in the second region. In addition, the
adsorption member 29 illustrated in (b) of FIG. 7 is configured
such that the width of the cross section of the slits 56 in the
second region becomes narrow by forming slits 56 in the second
region. The adsorption member 29 illustrated in (c) of FIG. 7 has a
shape provided with notches 57 in the second region, and the
adsorption member 29 illustrated in (d) of FIG. 7 has a tapper
shape 58 such that the width becomes narrows smoothly in the second
region.
[0055] In this way, in a case where the first region and the second
region are formed to have the same thickness, the first region
corns to have a small volume compared to that of the second region
by forming at least one of the round holes 55, the slits 56, the
notches 57, and the tapper shape 58 in the second region. Herein,
when the thickness is set to be equal, the volume is proportionate
to the width of the adsorption member 29. Therefore, when the
volume of the second region is set to be small, the width of the
cross section of the second region can be made small. In other
words, in this embodiment, reducing the volume of the second region
means that the width of the second region becomes narrow.
[0056] FIG. 8 is a diagram illustrating a relation between the
distance from the fixed end and the bending amount in the
adsorption member having the shape illustrated in (a) of FIG. 6 and
(a) of FIG. 7 and the adsorption member in the related art.
Further, the horizontal axis of FIG. 8 indicates the distance from
the fixed end, and the vertical axis indicates the bending amount.
In FIG. 8, the solid line a-1 indicates the bending amount of the
adsorption member 29 having the shape illustrated in FIG. 6, the
solid line a-2 indicates the bending amount of the adsorption
member having the shape illustrated in (a) of FIG. 7, and the line
Ref indicates the bending amount of the adsorption member of the
related art. In addition, in FIG. 8, section AB corresponds to the
second region 29b, and section BC corresponds to the first region
29a.
[0057] Herein, the section formed with the holes in the second
region of the adsorption member having the shape illustrated in (a)
of FIG. 7 is easily bent compared to the section having no holes,
as depicted by the solid line a-2 of FIG. 8, the bending property
of the adsorption member having the shape illustrated in (a) of
FIG. 7 is different in each section in section AB so that the solid
line is not smooth. However, even though the solid line is not
smooth in section AB, the bending is hardly made in section BC
similarly to the solid line a-1 indicating the adsorption member
having the shape illustrated in FIG. 6. Therefore, the adsorption
member having the shape illustrated in (a) of FIG. 7 approaches the
ideal shape as the width of a second region 55b with respect to a
first region 55a is significantly increased similarly to the
adsorption member 29 having the shape illustrated in FIG. 6.
Further, the respective shapes illustrated in (b) to (d) of FIG. 7
are also formed such that the width of the second region of the
adsorption member is set to be narrow compared to that of the first
region similarly to (a) of FIG. 7, so that it is possible to form
the shapes to approach the ideal shape of the adsorption member
similarly to (a) of FIG. 7.
[0058] FIG. 9 is a control block diagram of a full-color laser beam
printer according to this embodiment. In FIG. 9, a CPU 70 is
illustrated as a control unit. The CPU 70 is connected to the
above-mentioned image forming section 100B, the servo motor M
serving as a driving unit, high-voltage power sources HV1 and HV2,
the angle sensor 71 which detects the rotation angle .theta. of the
holding member 24 by the rotary encoder 31, and an operation
portion 72.
[0059] Next, a sheet separating and feeding operation of a sheet
feeding device 200 according to this embodiment will be described
using FIG. 10, a flowchart illustrated in FIG. 11, and a timing
chart illustrated in FIG. 12. (a) of FIG. 10 is a diagram
illustrating an initial state of the sheet feeding device 200. The
rotation angle .theta. of the holding member 24 at this time is set
to an initial rotation angle .theta.0. In the initial state, the
adsorption member 29 in a non-contact state with respect to an
uppermost sheet P1 among the sheets P loaded on the sheet
supporting plate 21. In addition, the position of the uppermost
sheet P1 is regulated by the position of the sheet supporting plate
21.
[0060] Next, when a feeding job of the sheet P starts, the CPU 70
dives the servo motor M to make the holding member 24 start to
rotate from the initial state to the sheet feeding direction
indicated with arrow R (S101). Further, at this time, there is no
voltage application to the electrodes 30a and 30b as illustrated in
FIG. 12. Then, the adsorption member 29 is moved toward the
uppermost sheet P1 by rotating the holding member 24 in this way
and comes into contact with the uppermost sheet P1 as illustrated
in (b) of FIG. 10 (S102).
[0061] Thereafter, the adsorption member 29 is deformed along the
uppermost sheet P1 as illustrated in (c) of FIG. 10 as the holding
member 24 is rotated. Then, the adsorption member 29 is further
bent by rotating the holding member 24 again from this state, and
thus a surface contact area with respect to the uppermost sheet P1
is increased to enable the adsorbed sheet to be conveyed in a
direction perpendicular to the surface (S103). Thereafter, when the
holding member 24 continues to be rotated, the first region 29a of
the adsorption member 29 comes into sufficient contact with the
uppermost sheet P1 as illustrated in (d) of FIG. 10, and the
contact leading end of the first region 29a reaches a position at a
distance La from the leading end in the sheet feeding
direction.
[0062] As illustrated in (d) of FIG. 10, in this embodiment, when
the contact leading end of the first region 29a reaches this
position, the rotation angle .theta. of the holding member 24
becomes .theta.1. Then, when it is determined that the rotation
angle .theta. of the holding member 24 becomes .theta.1 (Y of
S104), the CPU 70 applies a voltage to the electrodes 30a and 30b
in the first region as illustrated in FIG. 12 (S105). Herein, in
this embodiment, when the pulse number T0 between the home
positions of the rotary encoder 31 is 1000, it is determined that
the rotation angle .theta. of the holding member 24 becomes
.theta.1 at the time when a pulse number T1 is 500, and the voltage
is applied. Further, in this embodiment, the rotary encoder 31 is
used to determine whether the rotation angle .theta. of the holding
member 24 becomes .theta.1, but a timer 73 or the like illustrated
in FIG. 9 as described above may be used to calculate the rotation
angle .theta. at which the rotation is stopped.
[0063] Then, when a voltage is applied to the electrodes 30a and
30b, a potential pattern in a stripe shape is alternately formed in
the surface of the adsorption member 29 by the electrodes 30a and
30b and causes an electric field to generate the adsorbing force,
so that the uppermost sheet P1 is adsorbed to the first region 29a
of the adsorption member 29. Herein, since the electric field is
generated only in the vicinity of the surface of the adsorption
member 29, the adsorbing force by the electric field works only on
the uppermost sheet P1. Therefore, only the uppermost sheet P1
among the loaded sheets P is adsorbed to the adsorption member
29.
[0064] Further, (a) of FIG. 13 is a diagram for describing a state
when the uppermost sheet P1 is adsorbed, and (b) of FIG. 13 is a
diagram for describing a state when the uppermost sheet P1 of an
adsorption member 53 having an even rigidity in the related art is
adsorbed. In the adsorption member 29 of this embodiment, since the
second region 29b of the support portion is aggressively bent
compared to the first region 29a by a difference in rigidity as
illustrated in (a) of FIG. 13, the second region 29b is easily bent
by the winding when the holding member 24 is rotated, and the first
region 29a is bent a little bit.
[0065] Therefore, a radius r2 of curvature at the boundary between
the first region 29a and the second region 29b becomes smaller than
the radius of curvature of the second region 29b, so that the
flatness of the first region 29a is secured and an adsorbing area
with respect to the uppermost sheet P1 can be safely secured. On
the contrary, in the case of the adsorption member 53 having an
even rigidity in the related art, a radius r1 of curvature at the
boundary of the contact surface of the uppermost sheet P1 is large
as illustrated in (b) of FIG. 13. Therefore, the flatness of the
first region is not secured, and the adsorption area with respect
to the uppermost sheet P1 is not safely secured. In other words, in
this embodiment, since the second region 29b is easily bent
compared to the first region 29a, the adsorption area with respect
to the uppermost sheet P1 can be safely secured, and the uppermost
sheet P1 can be safely adsorbed to the adsorption member 29.
[0066] In this state, when the holding member 24 is rotated, the
adsorption member 29 is pulled up by the holding member 24. Then,
as illustrated in (e) of FIG. 10, the adsorbed uppermost sheet P1
can be raised in the vertical direction by pulling up the
adsorption member 29 so as to be separated from the sheet bundle P
(S106). Thereafter, as illustrated in (f) of FIG. 10, when the
rotation of the holding member 24 is progressed, the leading end of
the portion Z (which has a length of La and is not adsorbed to the
adsorption member 29) of the raised uppermost sheet P1 on the
downstream side in the sheet feeding direction comes into contact
with a conveyance guide 40a.
[0067] Then, the uppermost sheet P1 is conveyed toward a
registration roller 15 by the conveyance guide 40a, and then
engaged into the registration roller 15. Further, in this
embodiment, when the uppermost sheet P1 is engaged into the
registration roller 15, the rotation angle .theta. of the holding
member 24 becomes .theta.2. Then, when it is determined that the
rotation angle .theta. of the holding member 24 becomes .theta.2 (Y
in S107), the CPU 70 stops the voltage application to the
electrodes 30a and 30b in the first region as illustrated in FIG.
12 (S108). Further, in this embodiment, the voltage application is
stopped at the time when a pulse number T2 of the rotary encoder 31
becomes 950.
[0068] In this way, the adsorption of the uppermost sheet P1 by the
adsorption member 29 is released by stopping the voltage
application to the electrode 30. Thereafter, as illustrated in (g)
of FIG. 10, the uppermost sheet P1 is conveyed by the rotation in a
direction S of the registration roller 15, and the voltage
application is stopped and the adsorbing force disappears, so that
the uppermost sheet P1 is separated from the adsorption member 29
(S109). Thereafter, when it is determined that a rotation position
of the holding member 24 is the home position based on the pulse
number of the rotary encoder 31 (Y in S110), the CPU 70 stops the
servo motor M as illustrated in FIG. 12, and stops the rotation of
the holding member 24 for a while (S111). Thereafter, the feeding
job of the following sheet restarts (S112).
[0069] As described above, in this embodiment, the first region 29a
can be hardly bent by making the width of the second region 29b
narrower than that of the first region 29a of the adsorption member
29 (in other words, by making the volume of the second region 29b
smaller than that of the first region 29a). Therefore, the flatness
of the first region 29a at the time when the sheet is adsorbed can
be secured, and the adsorption area required for the adsorption can
be safely secured. As a result, the sheet can be separately fed
with safety without causing the length of the adsorption member 29
to be increased.
[0070] In addition, in this embodiment, since the portion Z of the
sheet on the downstream side in the sheet feeding direction is not
adsorbed (in other words, when the sheet is adsorbed, the leading
end of the sheet is not attached to the adsorption member 29), the
sheet can be separated from the adsorption member 29 without a
neutralization mechanism. Therefore, it is possible to reliably
guide the leading end of the sheet without causing the sheet to be
folded.
[0071] The description hitherto has been made about an example in
which the width (volume) of the second region is made to be
narrower (smaller) than the width (volume) of the first region in
order to make the first region of the adsorption member hardly
bent, but the invention is not limited thereto. For example, the
first region of the adsorption member can be made to be hardly bent
by changing the thickness or the Young's modulus of the first
region and the second region of the adsorption member.
[0072] Next, the description will be made about a second embodiment
according to the invention in which the first region of the
adsorption member is made to be hardly bent by changing the
thicknesses of the first region and the second region of the
adsorption member. FIG. 14 is a diagram for describing the
adsorption member of the sheet feeding device according to this
embodiment. In (a) and (b) of FIG. 14, an adsorption member 51 is
provided, and the adsorption member 51 includes a first region 51a
on a side coming into surface contact with the sheet and a second
region 51b on a side on the holding member. In this embodiment, the
second region 51b is made to be easily bent compared to the first
region 51a by making the thickness of the first region 51a thicker
than that of the second region 51b.
[0073] Further, in FIG. 5 described above, the broken line b
indicates the adsorption member 51 according to this embodiment.
Then, with the configuration of the adsorption member 51, as
illustrated in FIG. 5, the first region 51a can be hardly bent
compared to the second region 51b in section BC. Further, as the
thickness of the second region 51b is largely different with
respect to the first region 51a, the adsorption member approaches
an adsorption member d having the ideal shape indicated by the
two-dotted chain line of FIG. 5. In addition, as illustrated in
Equation 1 above, since a thickness is generally a parameter having
much influence in a width and a thickness, the bending property of
the adsorption member can approach the adsorption member d having
the ideal shape by changing the thickness.
[0074] In consideration of the above description, in this
embodiment, the shape of the adsorption member 51 is formed as a
shape as illustrated in (a) and (b) of FIG. 14. Herein, in the
adsorption member 51 illustrated in (a) of FIG. 14, a thickness T1
of the first region 51a is configured to be thicker than a
thickness T2 of the second region (T1>T2). Further, a plurality
of sheets may be stacked in the first region 51a in order to make
the thickness of the first region 51a thick. In this embodiment,
two sheets which have a width of 60 mm, a length of 30 mm, and a
thickness of 0.1 mm and are made of the same material as the resin
sheet are stacked on the front and rear surfaces of a flexible
resin sheet having a width of 60 mm, a length of 50 mm, and a
thickness of 0.1 mm, so that the thickness of the first region 51a
is made to be thick.
[0075] In addition, the adsorption member 51 illustrated in (b) of
FIG. 14 is configured such that the thickness T1 of the first
region 51a is thicker than the thickness T2 of the second region
51b (T1>T2). However, in regions other than the first region
51a, the thicknesses are intermittently different such that the
thicknesses T1 and T2 are alternately disposed. In this case,
similarly to the solid lines a-1 and a-1 of FIG. 8, the bending
property in regions other than the first region 51a is
intermittently different, the bending is not smoothly made.
However, similarly to the solid lines a-1 and a-1, even though the
bending is hardly made in a first region 59a, the adsorption member
can approach an adsorption member having the ideal shape similarly
to FIG. 14(a).
[0076] As described above, in this embodiment, since the thickness
of the second region 51b is made to be thinner than that of the
first region 51a of the adsorption member 51, the rigidity of the
second region 51b can be lowered compared to that of the first
region 51a, and the first region 51a can be made hardly bent.
Therefore, the flatness of the first region 51a at the time when
the sheet is adsorbed can be secured, and the adsorption area
required for the adsorption can be safely secured. As a result, the
sheet can be separately fed with safety without causing the length
of the adsorption member 51 to be increased.
[0077] Further, in this embodiment, the thickness is changed by
stacking the same two sheets on the front and rear surfaces of the
flexible resin sheet, but the thickness of the sheet may be
increased by coating the sheet. In addition, the material of the
adsorption member 51 is not limited, and the second region may be
suitably manufactured using the flexible resin sheet. In this case,
the adsorption member 51 can be formed in a simply process.
Further, in the adsorption member according to the first embodiment
described above, the thickness of the first region 51a may be made
to be thicker than that of the second region 51b similarly to this
embodiment. In other words, this embodiment may be implemented by
being combined with the first embodiment.
[0078] Next, the description will be made about a third embodiment
of the invention in which the first region of the adsorption member
is made to be hardly bent by changing the Young's moduli of the
first region and the second region of the adsorption member. FIG.
15 is a diagram for describing the adsorption member of a sheet
feeding device according to this embodiment.
[0079] In FIG. 15, an adsorption member 52 is provided, and the
adsorption member 52 includes a first region 52a on a side coming
into surface contact with the sheet and a second region 52b on a
side on the holding member 24. Then, in this embodiment, by making
the Young's modulus of the first region 52a larger than that of the
second region 51b, the second region 51b is made to be easily bent
compared to the first region 51a.
[0080] Further, in FIG. 5 described above, the broken line c
indicates the adsorption member 52 according to this embodiment.
Then, with the configuration of the adsorption member 52, as
illustrated in FIG. 5, the adsorption member can be hardly bent in
section BC compared to Ref. Further, as the Young's modulus of the
second region 52b is largely different with respect to the first
region 52a, the adsorption member approaches an adsorption member d
having the ideal shape of FIG. 5. In addition, the width and the
Young's modulus are parameters having the same influence on the
bending property of the adsorption member in general, and the line
a of FIG. 5 and the line c of FIG. 5 are plotted by the same
bending graph.
[0081] In consideration of the above description, in this
embodiment, the adsorption member 52 is made by selecting materials
such that the material of the first region 52a has a Young's
modulus El which is larger than a Young's modulus E2 of the
material of the second region. Then, the adsorption member 52 is
formed by thermally fusing the selected materials having different
Young's modulus.
[0082] As described above, in this embodiment, the rigidity of the
second region 52b can be lowered than that of the first region 52a
by making the Young's modulus of the second region 52b lower than
that of the first region 52a of the adsorption member 52, and the
first region 52a can be hardly bent. Therefore, the flatness of the
first region 52a at the time when the sheet is adsorbed can be
secured, and the adsorption area required for the adsorption can be
safely secured. As a result, the sheet can be separately fed with
safety without causing the length of the adsorption member 52 to be
increased.
[0083] Further, in this embodiment, the material of the adsorption
member 52 is not limited, and the adsorption member may be
manufactured by suitably combining the flexible resin sheets used
in the respective portions to make the Young's modulus of the
second region 52b lowered compared to that of the first region 52a.
Then, the respective regions can be given with different functions
through the selection of the materials by forming the first region
and the second region with the different materials.
[0084] In addition, in the adsorption member according to the first
and the second embodiments described above, the Young's moduli of
the first regions 29a and 51a may be made to be lower than those of
the second regions 29b and 51b similarly to this embodiment. In
other words, this embodiment may be implemented by being combined
with the first and the second embodiments.
REFERENCE SIGNS LIST
[0085] 12 adsorbing and feeding section [0086] 20 sheet feeding
cassette [0087] 24 holding member [0088] 26 power electrode [0089]
29 adsorption member [0090] 29a first region [0091] 29b second
region [0092] 30a first comb-tooth electrode [0093] 30b second
comb-tooth electrode [0094] 31 rotary encoder [0095] 52 adsorption
member [0096] 51a first region [0097] 51b second region [0098] 52
adsorption member [0099] 52a first region [0100] 52b second region
[0101] 55 round hole [0102] 56 slit [0103] 57 notch [0104] 58
tapper [0105] 70 CPU [0106] 71 angle sensor [0107] 100 full-color
laser beam printer [0108] 100A full-color laser beam printer body
[0109] 100B image forming section 200 sheet feeding device [0110]
HV1, 2 high-voltage power source [0111] M servo motor [0112] P
sheet [0113] P1 uppermost sheet
* * * * *