U.S. patent application number 14/493666 was filed with the patent office on 2015-03-26 for sheet feeding apparatus and image forming apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Kazuhiro Hosohara.
Application Number | 20150084267 14/493666 |
Document ID | / |
Family ID | 52690267 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150084267 |
Kind Code |
A1 |
Hosohara; Kazuhiro |
March 26, 2015 |
SHEET FEEDING APPARATUS AND IMAGE FORMING APPARATUS
Abstract
A sheet feeding apparatus includes a stacking portion on which a
sheet is stacked, a drive source configured to generate a driving
force, a pick-up member rotatable with the driving force and
configured to rotate in contact with the stacked sheet to feed the
sheet, a feed member configured to feed the sheet fed by the
pick-up member, an elevating unit configured to raise and lower the
stacking portion with the driving force to bring the sheet and the
pick-up member into contact with each other, and a control unit
configured to control the elevating unit, when a trailing edge of a
first sheet fed to the pick-up member is upstream of the feed
member and downstream of the pick-up member, to bring a second
sheet stacked on the stacking portion and to be fed subsequently to
the first sheet and the pick-up member into contact with each
other.
Inventors: |
Hosohara; Kazuhiro;
(Kawasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
52690267 |
Appl. No.: |
14/493666 |
Filed: |
September 23, 2014 |
Current U.S.
Class: |
271/110 ;
271/117; 271/155 |
Current CPC
Class: |
B65H 2513/40 20130101;
B65H 3/0669 20130101; B65H 2701/1313 20130101; B65H 2513/514
20130101; B65H 3/0684 20130101; B65H 2513/40 20130101; B65H 7/02
20130101; B65H 2403/72 20130101; B65H 2513/514 20130101; B65H
2701/1313 20130101; B65H 1/14 20130101; B65H 2220/02 20130101; B65H
2220/01 20130101; B65H 2220/02 20130101 |
Class at
Publication: |
271/110 ;
271/117; 271/155 |
International
Class: |
B65H 3/06 20060101
B65H003/06; B65H 7/02 20060101 B65H007/02; B65H 1/14 20060101
B65H001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2013 |
JP |
2013-198162 |
Claims
1. A sheet feeding apparatus comprising: a stacking portion on
which a sheet is stacked; a drive source configured to generate a
driving force; a pick-up member provided to be rotatable with the
driving force of the drive source and configured to rotate in
contact with the sheet stacked on the stacking portion to feed the
sheet; a feed member configured to feed the sheet fed by the
pick-up member; an elevating unit configured to raise and lower the
stacking portion or the pick-up member with the driving force from
the drive source to bring the sheet stacked on the stacking portion
and the pick-up member into contact with each other; and a control
unit configured to control the elevating unit, wherein at least in
a state where a predetermined number or more of sheets are stacked
on the stacking portion, the control unit controls the elevating
unit, at a timing of when a trailing edge in a feeding direction of
a first sheet fed to the pick-up member is upstream of the feed
member and downstream of the pick-up member, to bring a second
sheet stacked on the stacking portion and to be fed subsequently to
the first sheet and the pick-up member into contact with each
other.
2. The sheet feeding apparatus according to claim 1, further
comprising a clutch mechanism configured to transmit the driving
force from the drive source to the pick-up member so that the
pick-up member rotates after the sheet stacked on the stacking
portion and the pick-up member come into contact with each
other.
3. The sheet feeding apparatus according to claim 2, wherein the
clutch mechanism rotates the pick-up member after a trailing edge
of the second sheet passes through the feed member.
4. The sheet feeding apparatus according to claim 2, wherein the
clutch mechanism includes: a clutch input portion configured to
rotate when the driving force of the drive source is input thereto:
a clutch output portion configured to transmit the driving force
from the drive source to the pick-up member by engaging with the
clutch input portion; and a movement mechanism configured to move
the clutch input portion between a disengagement position where the
clutch input portion disengages from the clutch output portion and
an engagement position where the clutch input portion engages with
the clutch output portion.
5. The sheet feeding apparatus according to claim 1, further
comprising a shaft provided to be rotatable, wherein the pick-up
member feeds the sheet when the shaft rotates, wherein the
elevating unit raises and lowers the stacking portion or the
pick-up member when the shaft rotates, and wherein the clutch input
portion rotates when the shaft rotates.
6. The sheet feeding apparatus according to claim 5, wherein the
elevating unit includes an elevating cam configured to raise and
lower the stacking portion when the shaft rotates, and wherein the
clutch input portion moves between the disengagement position and
the engagement position while the shaft rotates once.
7. The sheet feeding apparatus according to claim 4, wherein the
movement mechanism includes: a cam provided on the clutch input
portion; an elastic member configured to urge the clutch input
portion toward the clutch output portion; and a clutch restriction
member configured to lock the clutch input portion at the
disengagement position by coming into contact with the cam urged by
the elastic member, wherein, when the drive source is driven to
rotate the clutch input portion, a locked state between the cam and
the clutch restriction member is released so that the clutch input
portion moves from the disengagement position to the engagement
position, and wherein, when the clutch input portion further
rotates, the cam and the clutch restriction member are locked again
so that the clutch input portion moves to the disengagement
position.
8. The sheet feeding apparatus according to claim 1, wherein the
elevating unit separates the sheet stacked on the stacking portion
and the pick-up member from each other after the sheet stacked on
the stacking portion is fed to the pick-up member.
9. The sheet feeding apparatus according to claim 1, further
comprising a separation member provided at a position opposing the
feed member and configured to separate sheets with a frictional
force.
10. The sheet feeding apparatus according to claim 1, further
comprising a detection unit provided downstream of the feed member
and configured to detect the sheet, wherein the control unit
controls the elevating unit based on a result of detection by the
detection unit.
11. The sheet feeding apparatus according to claim 1, further
comprising a size acquisition unit configured to acquire
information about a length in a conveyance direction of the sheet
to be fed, wherein the control unit controls the elevating unit
based on a result of detection by the detection unit.
12. A sheet feeding apparatus comprising: a stacking portion on
which a sheet is stacked; a pick-up member configured to come into
contact with the sheet stacked on the stacking portion to feed the
sheet; a feed member configured to feed the sheet fed by the
pick-up member; a drive source configured to generate a driving
force; an elevating unit configured to raise and lower the stacking
portion or the pick-up member with the driving force from the drive
source to bring the sheet stacked on the stacking portion and the
pick-up member into contact with each other; and a control unit
configured to control the elevating unit, wherein the control unit
controls the elevating unit, at a timing of when a trailing edge in
a feeding direction of a first sheet fed to the pick-up member is
upstream of the feed member and downstream of the pick-up member,
to bring a second sheet stacked on the stacking portion and to be
fed subsequently to the first sheet and the pick-up member into
contact each other.
13. A sheet feeding apparatus comprising: a stacking portion on
which a sheet is stacked; a pick-up member configured to come into
contact with the sheet stacked on the stacking portion to feed the
sheet; a feed member configured to feed the sheet fed by the
pick-up member; a drive source configured to generate a driving
force; an elevating unit configured to raise and lower the stacking
portion or the pick-up member with the driving force from the drive
source to bring the sheet stacked on the stacking portion and the
pick-up member into contact with each other; and a control unit
configured to control the elevating unit, wherein the elevating
unit is configured, after a leading edge in a feeding direction of
a first sheet fed by the pick-up member reaches the feed member, to
separate the sheet stacked on the stacking portion and the pick-up
member from each other, and wherein the control unit controls the
elevating unit, at a timing of when a trailing edge in the feeding
direction of the first sheet fed by the pick-up member is upstream
of the feed member and downstream of the pick-up member, to bring a
second sheet stacked on the stacking portion and to be fed
subsequently to the first sheet and the pick-up member into contact
each other.
14. The sheet feeding apparatus according to claim 13, further
comprising a clutch mechanism configured to transmit the driving
force from the drive source to the pick-up member, wherein the
clutch mechanism includes: a clutch input portion configured to
rotate when the driving force of the drive source is input thereto;
a clutch output portion configured to transmit the driving force
from the drive source to the pick-up member by engaging with the
clutch input portion, and a movement mechanism configured to move
the clutch input portion between a disengagement position where the
clutch input portion disengages from the clutch output portion and
an engagement position where the clutch input portion engages with
the clutch output portion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sheet feeding apparatus,
and an image forming apparatus including the sheet feeding
apparatus.
[0003] 2. Description of the Related Art
[0004] Conventionally, an image forming apparatus, which forms an
image on a sheet, has been provided with a sheet feeding apparatus
that feeds stacked sheets by bringing the uppermost sheet and a
feed roller separated therefrom into contact with each other every
time a single feeding operation is performed. In such a
configuration, in order to make an interval between the preceding
sheet and the subsequent sheet (hereinafter referred to as a sheet
feed interval) as small as possible during continuous printing to
improve productivity, Japanese Patent No. 4249050 discusses a
configuration in which the stacked uppermost sheet and the feed
roller are brought into contact with each other before a trailing
edge of the preceding sheet passes through the feed roller.
[0005] However, in a sheet feeding apparatus discussed in Japanese
Patent No. 4249050, while an image is formed on or transferred onto
sheets, the trailing edge of the preceding sheet is sandwiched
between the feed roller and the stacked uppermost sheet, thereby
causing a side effect of distorting the image. Further, a
contact/separation operation between the uppermost sheet and the
feed roller, and the timing of when driving of the feed roller is
started need to be controlled independently of each other by
different electronic components (a solenoid, a clutch, etc.),
causing a cost increase.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to a sheet feeding
apparatus that is low in cost and high in productivity.
[0007] According to an aspect of the present invention, a sheet
feeding apparatus includes a stacking portion on which a sheet is
stacked, a drive source configured to generate a driving force, a
pick-up member provided to be rotatable with the driving force of
the drive source and configured to rotate in contact with the sheet
stacked on the stacking portion to feed the sheet, a feed member
configured to feed the sheet fed by the pick-up member, an
elevating unit configured to raise and lower the stacking portion
or the pick-up member with the driving force from the drive source
to bring the sheet stacked on the stacking portion and the pick-up
member into contact with each other, and a control unit configured
to control the elevating unit. At least in a state where a
predetermined number or more of sheets are stacked on the stacking
portion, the control unit controls the elevating unit, at a timing
of when a trailing edge in a feeding direction of a first sheet fed
to the pick-up member is upstream of the feed member and downstream
of the pick-up member, to bring a second sheet stacked on the
stacking portion and to be fed subsequently to the first sheet and
the pick-up member into contact with each other.
[0008] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A and 1B illustrate an overall configuration of an
image forming apparatus according to an exemplary embodiment of the
present invention.
[0010] FIG. 2 illustrates a sheet feeding apparatus according to
the exemplary embodiment of the present invention.
[0011] FIG. 3 is a schematic perspective view of a feeding
cassette.
[0012] FIGS. 4A and 4B illustrate an elevating unit that raises and
lowers a stacking plate.
[0013] FIG. 5 illustrates a drive transmission path from a drive
source.
[0014] FIG. 6 is a schematic perspective view of a clutch
mechanism.
[0015] FIGS. 7A, 7B, and 7C respectively illustrate operations to
engage and disengage the clutch mechanism.
[0016] FIG. 8 is a timing chart of a feeding operation.
[0017] FIGS. 9A, 9B, and 9C respectively illustrate continuous
feeding operations when sheets are fully stacked.
[0018] FIG. 10 is a flowchart of the continuous feeding operation
according to a first exemplary embodiment.
[0019] FIG. 11 is a block diagram of a control unit according to
the first exemplary embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0020] Various exemplary embodiments, features, and aspects of the
invention will be described in detail below with reference to the
drawings.
[0021] FIGS. 1A and 1B illustrate a color digital printer as an
example of an image forming apparatus to which a sheet feeding
apparatus according to an exemplary embodiment of the present
invention is applied. FIG. 1A is a perspective view of an external
appearance of an image forming apparatus 100, and FIG. 1B is a
schematic sectional view of the image forming apparatus 100. The
image forming apparatus 100 is a full four-color laser printer
using an electrophotographic process. More specifically, an image
is formed on a sheet (a recording medium) S based on an image
signal input to a controller unit (control unit) from an external
host apparatus such as a personal computer, an image reader, or a
counterpart facsimile apparatus.
[0022] An operation for an image forming unit 101 to form an image
will be described below. A drum 1 of each of first to fourth
cartridges PY, PM, PC, and PK is rotationally driven at a
predetermined control speed in a counterclockwise direction
indicated by an arrow illustrated in FIG. 1B. A belt 4 is also
rotationally driven at a speed corresponding to the speed of the
drum 1 in a clockwise direction (a forward direction in drum
rotation) indicated by an arrow illustrated in FIG. 1B. A scanner
unit 5 is also driven.
[0023] In synchronization with the above driving, a charging roller
2 in each of the cartridges uniformly charges a surface of the drum
1 to a predetermined polarity/potential at each predetermined
control timing. The scanner unit 5 scans and exposes the surface of
each of the drums 1 with a laser beam modulated according to an
image signal for each of the colors.
[0024] Thus, an area on the surface of each of the drums 1, which
has been scanned and exposed with the laser beam, becomes an
electrostatic latent image corresponding to the image signal. A
development unit 3 develops the electrostatic latent image formed
on the surface of each of the drums 1 as a toner image. By an
electrophotographic image formation process operation, as described
above, a toner image is formed on the drum 1, and the toner image
formed thereon is primarily transferred onto the belt 4.
[0025] A feeding cassette 9 is detachably attached to the image
forming apparatus 100 on the front side thereof (on the side on
which an operator operates the apparatus and on the right side of
the apparatus illustrated in FIG. 1B), and is configured to allow a
user to easily stack sheets and perform jam handling
processing.
[0026] A pick-up roller 6 serving as a sheet feeding unit comes
into contact with the sheets stacked on a stacking plate (stacking
unit) 16 (see FIG. 2) in the feeding cassette 9 to feed the sheets.
The sheets fed by the pick-up roller 6 are fed one by one while
being separated from one another by a feed roller 7 and a
separation roller 8, and are conveyed to a secondary transfer nip
portion between a secondary transfer roller 12 and the belt 4 via a
registration roller pair 11. The separation roller 8 is attached to
a main body of the image forming apparatus 100 via a torque limiter
(not illustrated), and is brought into pressure contact with the
feed roller 7 by an urging unit such as a spring (not illustrated).
An exemplary embodiment of the present invention is not limited to
the separation roller 8. Alternatively, a separation pad may be
used. In an exemplary embodiment of the present invention, any
separation unit may be used as long as it can separate, when one or
more sheets are fed together, the sheets from one another with a
frictional force.
[0027] The sheet on which a toner image has been transferred in the
secondary transfer nip portion is heated and pressurized by a
fixing unit 13 so that the toner image is fixed thereto. The sheet
to which the toner image has been fixed is discharged onto a sheet
discharge tray 15 by a sheet discharge roller pair 14.
[0028] Next, the sheet feeding apparatus will be described below.
FIG. 2 is a schematic perspective view of a sheet feeding apparatus
10. The stacking plate 16 can be raised and lowered with the sheets
stacked thereon. An elevating operation of the stacking plate 16
will be described with reference to FIGS. 3, 4A, and 4B. FIG. 3 is
a schematic perspective view of the feeding cassette 9, FIG. 4A is
a schematic perspective view illustrating a lowered state of the
stacking plate 16 in the present exemplary embodiment, and FIG. 4B
is a schematic perspective view illustrating a raised state of the
stacking plate 16 in the present exemplary embodiment.
[0029] As illustrated in FIG. 3, the stacking plate 16 is rotatably
positioned using a stacking plate rotation support portion 36 as a
rotation center. The stacking plate 16 is raised and lowered by an
elevating unit (stacking unit elevating unit) 50. The elevating
unit 50 urges the stacked sheets against the pick-up roller 6 by
raising the stacking plate 16, and separates the stacked sheets
from the pick-up roller 6 by lowering the stacking plate 16.
[0030] Even when the sheets are slightly stacked on the stacking
plate 16, the elevating unit 50 raises the stacking plate 16 until
the sheets are sufficiently urged against the pick-up roller 6.
[0031] The elevating unit 50 includes elevating levers 18,
elevating lever rotation support portions 37, a pair of elevating
cams 19, and a connecting shaft 20 for connecting the elevating
cams 19 to each other.
[0032] The elevating levers 18 are provided on both sides of the
feeding cassette 9, and are rotatably fixed to a casing of the
image forming apparatus 100 using the elevating lever rotation
support portion 37 as the rotation center. The elevating levers 18
are urged in a direction (upward direction) closer to the pick-up
roller 6 by an urging member such as a spring (not illustrated).
Engaging portions 17 with the elevating levers 18 are provided at
both ends of the stacking plate 16. While the feeding cassette 9 is
mounted and aligned on the image forming apparatus 100, the
engaging portions 17 and the elevating levers 18 engage with each
other, and the stacking plate 16 is raised in conjunction with
rotation of the elevating levers 18. The rotation of the elevating
levers 18, which are urged in the direction closer to the pick-up
roller 6, is restricted by the elevating cams 19 arranged above the
elevating levers 18. As illustrated in FIGS. 4A and 4B, when the
connecting shaft 20 rotates upon receiving a driving force from a
drive unit (to be described below), the elevating cams 19 rotate so
that the elevating levers 18 rotate up and down, and the stacking
plate 16 is raised and lowered via the engaging portions 17.
[0033] A drive unit 80 will be described below with reference to
FIG. 5. The drive unit 80 transmits a driving force to the
elevating unit 50 to raise and lower the stacking plate 16. The
drive unit 80 rotates the pick-up roller 6 via a driving
transmission unit.
[0034] A drive source 21 is, for example, a motor of the drive unit
80 provided in the main body of the image forming apparatus 100. A
driving force generated by the drive source 21 is transmitted from
a first drive gear 22 to a second drive gear 23 and from the second
drive gear 23 to a chipped tooth gear 24. A solenoid (see FIG. 11)
restricts the chipped tooth gear 24 and releases the restriction.
Thus, the chipped tooth gear 24 selectively engages with the second
drive gear 23. When the solenoid releases the restriction of the
chipped tooth gear 24, the chipped tooth gear 24 engages with the
second drive gear 23 so that the driving force is transmitted.
Thus, the chipped tooth gear 24 starts to rotate. When the solenoid
restricts the chipped tooth gear 24 at a position where the chipped
tooth gear 24 rotates once and a chipped tooth portion of the
chipped tooth gear 24 opposes the second drive gear 23, the driving
force is not transmitted. The chipped tooth gear 24 and the
elevating cams 19 are fixed to the connecting shaft 20, which is
rotatably supported on the main body of the image forming apparatus
100, and rotate integrally with the connecting shaft 20. When the
solenoid operates to release the restriction of the chipped tooth
gear 24 based on an electric signal from a control unit (not
illustrated), the chipped tooth gear 24 engages with the second
drive gear 23, the driving force generated by the drive source 21
is transmitted to the connecting shaft 20 via the chipped tooth
gear 24, and the connecting shaft 20, together with the elevating
cams 19, rotates once.
[0035] An idler gear 31 serving as a drive transmission unit
transmits a driving force to the pick-up roller 6 and the feed
roller 7 via a clutch mechanism 60. Each of the pick-up roller 6
and the feed roller 7 has a tooth surface formed therein, which
engages with the idler gear 31, and is rotationally driven in
response to the rotation of the idler gear 31.
[0036] A clutch input gear 26 serving as a clutch input portion
rotates when the driving force of the drive unit 80 is input
thereto, and a clutch output gear 27 serving as a clutch output
portion transmits the driving force from the drive unit 80 to the
pick-up roller 6 by engaging with the clutch input gear 26. The
idler gear 31 is arranged to engage with the clutch output gear 27.
Thus, while the clutch input gear 26 engages with the clutch output
gear 27, the rotation of the connecting shaft 20 is transmitted to
the idler gear 31 so that the pick-up roller 6 and the feed roller
7 are driven. While the clutch input gear 26 does not engage with
the clutch output gear 27, the rotation of the connecting shaft 20
is not transmitted to the idler gear 31.
[0037] When the connecting shaft 20 rotates once, the pick-up
roller 6 and the feed roller 7 rotate. A conveyance distance of the
sheet by the rotation is set to a distance that allows the sheet to
be conveyed to the registration roller pair 11 on a downstream
side.
[0038] Next, the clutch mechanism 60 will be described in detail
below. The clutch input gear 26 in the clutch mechanism 60 engages
with the clutch output gear 27 after the elevating unit 50 raises
the stacking plate 16 to bring the stacked sheets into pressure
contact with the pick-up roller 6. Thus, the pick-up roller 6
starts to rotate after the sheets stacked on the stacking plate 16
come into pressure contact with the pick-up roller 6. Therefore,
the sheet feed interval does not vary. Even if the number of the
sheets stacked on the stacking plate 16 changes and the timing of
when the sheets and the pick-up roller 6 come into contact with
each other deviates, the timing of when the pick-up roller 6 starts
to feed the sheets is constant regardless of the amount of stacked
sheets.
[0039] FIG. 6 is a schematic perspective view of the clutch
mechanism 60 according to the present exemplary embodiment, FIG. 7A
is a schematic view illustrating a state where the clutch mechanism
60 is disengaged, FIG. 7B is a schematic view illustrating a state
where the clutch mechanism 60 is engaged, and FIG. 7C is a
schematic view illustrating switching of the clutch mechanism 60
from an engaged state to a disengaged state.
[0040] As illustrated in FIG. 6, a clutch bearing 25 is fixed to
the connecting shaft 20, and rotates integrally with the connecting
shaft 20. The clutch bearing 25 includes keys 30. A clutch input
gear 26 includes key grooves 29, a cam surface 32, and an
input-side gear tooth surface 35. The clutch input gear 26 is
retained in the clutch bearing 25 when the keys 30 in the clutch
bearing 25 engage with the key grooves 29, and is fixed in a
rotational direction of the clutch bearing 25 and is movable in a
longitudinal direction (rotational axis direction) of the
connecting shaft 20. The clutch output gear 27 includes a tooth
surface 39 that engages with the idler gear 31 and an output-side
gear tooth surface 38, and is rotatably retained in the clutch
bearing 25. The clutch output gear 27 in the longitudinal direction
of the cam connecting shaft 20 is fixed to the main body of the
image forming apparatus 100. As illustrated in FIG. 7A, a clutch
pressing spring 28 serving as an elastic member urges the clutch
input gear 26 toward the clutch output gear 27.
[0041] An operation to engage and disengage the clutch mechanism 60
will be described below with reference to FIGS. 7A to 7C.
[0042] As illustrated in FIG. 7A, while the cam surface 32 provided
in the clutch input gear 26 is locked by a clutch restriction rib
33 provided in the main body of the image forming apparatus 100,
the input-side gear tooth surface 35 of the clutch input gear 26
separates from the output-side gear tooth surface 38 of the clutch
output gear 27. With the clutch mechanism 60 thus disengaged, the
driving force is not transmitted.
[0043] As illustrated in FIG. 7B, the input-side gear tooth surface
35 of the clutch input gear 26 engages with the output-side gear
tooth surface 38 of the clutch output gear 27 so that the clutch
mechanism 60 is engaged. With the clutch mechanism 60 thus engaged,
the driving force is transmitted to the pick-up roller 6 and the
feed roller 7 from the connecting shaft 20 via the idler gear 31.
Thus, the engagement and the disengagement of the clutch mechanism
60 is switched by the cam surface 32, which rotates integrally with
the connecting shaft 20, and the clutch restriction rib 33.
[0044] When the connecting shaft 20 rotates in the disengaged state
of the clutch mechanism 60 illustrated in FIG. 7A, the clutch
bearing 25 fixed to the connecting shaft 20 rotates, and the clutch
input gear 26 also rotates via the key grooves 29 and the keys 30.
The clutch restriction rib 33 is fixed to the main body of the
image forming apparatus 100, and when the clutch input gear 26
rotates, a relative position between the clutch restriction rib 33
and the cam surface 32 is shifted.
[0045] When the clutch input gear 26 rotates by a predetermined
amount, the cam surface 32 is released from the restriction by the
clutch restriction rib 33. An urging force of the clutch pressing
spring 28 brings the input-side gear tooth surface 35 of the clutch
input gear 26 into contact with the output-side gear tooth surface
38 of the clutch output gear 27. Thus, the clutch mechanism 60
enters the engaged state illustrated in FIG. 7B.
[0046] A slope surface 40 is formed in the cam surface 32. When the
clutch input gear 26 further rotates, the clutch restriction rib 33
runs onto the slope surface 40, as illustrated in FIG. 7C. The cam
surface 32 is locked by the clutch restriction rib 33 again. Thus,
the input-side gear tooth surface 35 and the output-side gear tooth
surface 38 separate from each other.
[0047] When the connecting shaft 20 further rotates in the state
illustrated in FIG. 7C, the clutch mechanism 60 enters the
disengaged state illustrated in FIG. 7A. As described above, a
movement mechanism 70 for moving the clutch input gear 26 including
the clutch pressing spring 28, the cam surface 32, and the clutch
restriction rib 33 moves the clutch input gear 26 between an
engaged position where it engages with the clutch output gear 27
and a disengaged position where it disengages therefrom. More
specifically, the movement mechanism 70 moves, by using the cam
surface 32 and the clutch restriction rib 33, the clutch input gear
26 to a position along an axial direction of the cam connecting
shaft 20 according to a rotational angle of the clutch input gear
26.
[0048] The elevating cams 19 provided in the connecting shaft 20
and the clutch input gear 26 rotate in synchronization with each
other. The cam surface 32 in the movement mechanism 70 is formed so
that the movement mechanism 70 moves the clutch input gear 26 to
the engaged position after the stacking plate 16 is raised by the
elevating cams 19 to urge the sheets stacked thereon against the
pick-up roller 6.
[0049] The timing of a feeding operation of the sheet feeding
apparatus 10 will be described below.
[0050] FIG. 8 is a timing chart of the feeding operation according
to the present exemplary embodiment, where a rising edge and a
falling edge of a line represent the start and the end of each of
operations, respectively.
[0051] When a sheet feed signal is input to a control unit in
response to an instruction from a user, the control unit starts to
drive the drive source 21. When a predetermined timing is reached
based on a count value of a timer, the above-described solenoid is
sucked in based on an electric signal from the control unit so that
the chipped tooth gear 24 and the second drive gear 23 engage with
each other. Thus, the driving force generated by the drive source
21 is transmitted to the connecting shaft 20 via the chipped tooth
gear 24, and the connecting shaft 20 starts to rotate together with
the elevating cams 19 and the clutch bearing 25.
[0052] When the elevating cams 19 rotate, the elevating levers 18
rotate, and the stacking plate 16 also starts to be raised and
lowered via the engaging portions 17 with the elevating levers 18.
As illustrated in FIG. 8, the timing of when a sheet S and the
pick-up roller 6 come into pressure contact with each other
deviates depending on the amount of sheets S stacked on the
stacking plate 16 (hereinafter, cases where the sheet stacking
amount is large and small are referred to as "fully stacked" and
"slightly stacked", respectively).
[0053] In the present exemplary embodiment, the clutch mechanism 60
is engaged by the cam surface 32 and the clutch restriction rib 33
after the timing of when the sheet S on the stacking plate 16 and
the pick-up roller 6 come into contact with each other even when
the sheets S are fully stacked. Therefore, even if the sheet S and
the pick-up roller 6 come into contact with each other, the feeding
of the sheet S is not immediately started. As illustrated in FIG.
8, the feeding of the sheet S is not started until the clutch
mechanism 60 is engaged. More specifically, the timing of when the
clutch mechanism 60 is engaged is in a predetermined position
during one rotation of the connecting shaft 20. Thus, the timing of
when the pick-up roller 6 feeds the sheet S is constant.
[0054] Thus, even if the timing of when the sheet S and the pick-up
roller 6 come into contact with each other differs, the timing of
when the pick-up roller 6 feeds the sheet S is constant regardless
of the amount of the stacked sheets S. After the connecting shaft
20 rotates once, the cam surface 32 and the clutch restriction rib
33 disengage the clutch mechanism 60 so that the clutch mechanism
60 enters the disengaged state, as illustrated in FIG. 7A. With the
clutch mechanism 60 disengaged, the pick-up roller 6 and the feed
roller 7 can be driven to rotate. Thus, the registration roller
pair 11 on a downstream side does not have a conveyance resistance
without back tension being applied to the sheet S. A conveyance
distance of the sheet S by the pick-up roller 6 and the feed roller
7 can be freely set depending on a speed reduction ratio between
the gears 27 and 31 corresponding to the one rotation of the
connecting shaft 20 and a speed reduction ratio based on the
diameters of the rollers. Therefore, the outer diameters of the
pick-up roller 6 and the feed roller 7 do not need to be increased
even if a configuration according to the present exemplary
embodiment is used to eliminate a variation in the sheet feed
interval.
[0055] A feeding operation performed when feeding is continuously
performed will be described below with reference to FIGS. 9A to 9C.
FIGS. 9A to 9C illustrate a continuous feeding operation performed
when the sheets S are fully stacked on the stacking plate 16. FIG.
9A illustrates a state where the preceding sheet (first sheet) S1
is fed by the above-mentioned feeding operation, reaches the
registration roller pair 11 on a downstream side, and is conveyed
by the registration roller pair 11.
[0056] In the first exemplary embodiment, as illustrated in FIG.
9B, before a trailing edge of the preceding sheet S1 passes through
the feed roller 7 after passing through the pick-up roller 6, the
subsequent sheet (second sheet) S2 to be fed subsequently to the
preceding sheet S1 and the pick-up roller 6 are brought into
contact with each other. In a state illustrated in FIG. 9B where
the subsequent sheet S2 and the pick-up roller 6 come in contact
with each other, the clutch mechanism 60 has not yet been engaged.
Thus, the feeding of the subsequent sheet S2 is not started.
[0057] As illustrated in FIG. 9C, after the trailing edge of the
preceding sheet S1 conveyed by the registration roller pair 11
passes through the feed roller 7, the clutch mechanism 60 is
engaged. Thus, the pick-up roller 6 feeds the subsequent sheet
S2.
[0058] The above-mentioned feeding operation of the preceding sheet
S1 and the subsequent sheet S2 will be described below with
reference to FIG. 10. FIG. 11 is a block diagram of a control unit
according to the first exemplary embodiment. As illustrated in FIG.
11, a central processing unit (CPU) 100 is connected to a drive
source (motor) 21, a registration sensor 90, a solenoid 91, and a
size acquisition unit 92. The CPU 100 is also connected to a
read-only memory (ROM) and a random access memory (RAM) and uses
the RAM as a work memory to execute a program that is stored in the
ROM and corresponds to a procedure illustrated in FIG. 10. In the
first exemplary embodiment, the CPU 100, the ROM, and the RAM
constitute the control unit.
[0059] First, in step S101, a print job is executed from an
operation unit 93 in the image forming apparatus 100 or from a
computer 94 connected to the image forming apparatus 100 directly
or via a network. When the print job has been executed, then in
step S102, the control unit drives (turns on) the drive source 21.
In step S103, the control unit sucks in (turns on) the solenoid 91
at a predetermined timing.
[0060] When the solenoid 91 is sucked in, the driving force from
the drive source 21 is transmitted to the connecting shaft 20. In
step S104, the control unit starts to raise the stacking plate 16.
In step S105, the control unit brings the uppermost sheet S (the
preceding sheet S1) stacked on the stacking plate 16 into contact
with the pick-up roller 6. At this time, the clutch mechanism 60
has not been engaged. Thus, the pick-up roller 6 and the feed
roller 7 have not rotated.
[0061] In step S106, when the connecting shaft 20 further rotates
with the driving force from the drive source 21, the clutch
mechanism 60 becomes engaged and the pick-up roller 6 and the feed
roller 7 start to rotate, allowing the preceding sheet S1 to be
fed. A profile of the elevating cams 19 is configured so that the
stacking plate 16 starts to move down after a leading edge of the
preceding sheet S1, which the pick-up roller 6 has started to feed,
reaches the feed roller 7. Thus, the uppermost sheet S stacked on
the stacking plate 16 and the pick-up roller 6 separate from each
other.
[0062] In step S107, the registration sensor 90 detects the
preceding sheet S1 that has been fed by the pick-up roller 6 and
the feed roller 7. The control unit determines a timing of when the
solenoid 91 for starting an operation to feed the subsequent sheet
S2 is turned on based on a timing of when the registration sensor
90 has detected the preceding sheet S1 (a detection result) and on
length information of the preceding sheet S1 in a conveyance
direction (acquired by the size acquisition unit 92). More
specifically, the control unit determines the timing of when the
solenoid 91 is turned on so that a timing of when the subsequent
sheet S2 and the pick-up roller 6 come into contact with each other
is a timing of when the trailing edge of the preceding sheet S1 is
downstream of the pick-up roller 6 and upstream of the feed roller
7. It is not desirable to bring the subsequent sheet S2 and the
pick-up roller 6 into contact with each other before the trailing
edge of the preceding sheet S1 passes through the pick-up roller 6.
Since the feed roller 7 and the pick-up roller 6 are connected to
the same gear train, the pick-up roller 6 may get driven to rotate
by the feed roller 7 that is driven to convey the preceding sheet
S1.
[0063] In step S108, the control unit sucks in (turns on) the
solenoid 91 based on the above-mentioned timing to start the
operation to feed the subsequent sheet S2. In step S109, the
control unit thus starts to raise the stacking plate 16, similarly
to the above. In step S110, the control unit brings the uppermost
sheet S (the subsequent sheet S2) on the stacking plate 16 being
raised and the pick-up roller 6 into contact with each other at the
timing of when the trailing edge of the preceding sheet S1 is
downstream of the pick-up roller 6 and upstream of the feed roller
7. At this time, the clutch mechanism 60 has not been engaged.
Thus, the pick-up roller 6 and the feed roller 7 have not
rotated.
[0064] In step S111, when the connecting shaft 20 further rotates
with the driving force from the drive source 21, the clutch
mechanism 60 is engaged and the pick-up roller 6 and the feed
roller 7 start to rotate, allowing the subsequent sheet S2 to be
fed. When the pick-up roller 6 and the feed roller 7 are to start
to rotate, the trailing edge of the preceding sheet S1 has passed
through the feed roller 7. The reason for this is that in the first
exemplary embodiment, the separation roller 8 separates from the
feed roller 7. Even in a configuration in which the separation
roller 8 does not separate from the feed roller 7, to prevent the
leading edges of the sheets S from being turned over or prevent the
sheets S from being doubly fed, it is desirable to start rotating
the pick-up roller 6 after the trailing edge of the preceding sheet
S1 passes through the feed roller 7.
[0065] As described above, in the first exemplary embodiment, in a
state where the trailing edge of the preceding sheet S1 is
downstream of the pick-up roller 6 and upstream of the feed roller
7, the pick-up roller 6 and the subsequent sheet S2 are brought
into contact with each other. Further, in the first exemplary
embodiment, after the trailing edge of the preceding sheet S1
passes through the feed roller 7, the pick-up roller 6 starts to
rotate. In the first exemplary embodiment, a profile of the
elevating cams 19, a timing of when the clutch mechanism 60 is
engaged, and an external size of the pick-up roller 6 are designed
to satisfy the above two conditions.
[0066] In the above-mentioned exemplary embodiment of the present
invention, the timing of when the subsequent sheet S2 and the
pick-up roller 6 come into contact each other may be controlled
only when the number of sheets S stacked on the stacking plate 16
is large, i.e., a predetermined number or more. Conversely, if the
number of sheets S stacked on the stacking plate 16 is less than
the predetermined number, the subsequent sheet S2 and the pick-up
roller 6 may be brought into contact with each other at a timing of
when the trailing edge of the preceding sheet S1 is downstream of
the feed roller 7. More specifically, in the exemplary embodiment
of the present invention, at least when the predetermined number or
more of sheets S are stacked on the stacking plate 16, the
subsequent sheet S2 and the pick-up roller 6 are brought into
contact with each other at the timing of when the trailing edge of
the preceding sheet S1 is upstream of the feed roller 7.
[0067] An interval L between the trailing edge of the preceding
sheet S1 and the leading edge of the subsequent sheet S2 is made
constant by the action of the clutch mechanism 60 regardless of the
stacked amount of the sheets S by making the timing of starting the
feeding operation of the subsequent sheet S2 relative to the
preceding sheet S1 (timing of sucking in the solenoid 91 to start
rotating the connecting shaft 20) constant. When the subsequent
sheet S2 is conveyed to the registration roller pair 11, the clutch
mechanism 60 enters the state illustrated in FIG. 9A. The foregoing
operation is repeated so that the sheets S are continuously
fed.
[0068] As described above, according to the first exemplary
embodiment, one electronic component (the solenoid 91) can control
the timing of when the pick-up roller 6 and the uppermost sheet S
on the stacking plate 16 come into contact with each other and the
timing of when the pick-up roller 6 starts to rotate. Further, when
the trailing edge of the preceding sheet S1 is positioned between
the pick-up roller 6 and the feed roller 7, the pick-up roller 6
can be brought into contact with the subsequent sheet S2. Thus, a
sheet feed interval (interval L between the trailing edge of the
preceding sheet S1 and the leading edge of the subsequent sheet S2)
can be kept small. Therefore, a sheet feeding apparatus, which is
low in cost and high in productivity, can be provided.
[0069] While the solenoid 91 controls an engagement between the
chipped tooth gear 24 and the second drive gear 23 in the
above-mentioned first exemplary embodiment, an electromagnetic
clutch may be used to control the engagement.
[0070] While the configuration in which the clutch input gear 26
and the clutch output gear 27 engage with each other in a tooth
surface shape has been described above in the first exemplary
embodiment, any configuration that can transmit a driving force may
be used. For example, the clutch input gear 26 and the clutch
output gear 27 may come into contact with each other using a
friction member having a high sliding resistance.
[0071] While the configuration in which one cam surface 32 and one
clutch restriction rib 33 are provided has been described above in
the first exemplary embodiment, a plurality of cam surfaces 32 and
a plurality of clutch restriction ribs 33 may be provided in a
rotational direction of the clutch input gear 26 so that the clutch
mechanism 60 is engaged and disengaged a plurality of times with
the rotation of the clutch input gear 26. Further, a plurality of
cam surfaces 32 and a plurality of clutch restriction ribs 33 may
be provided in a diameter direction of the clutch input gear 26 so
that the clutch mechanism 60 is engaged and disengaged
simultaneously by the plurality of lock portions.
[0072] While a configuration in which the pick-up roller 6 is fixed
and the stacking plate 16 is raised and lowered to bring the sheet
S stacked on the stacking plate 16 and the pick-up roller 6 into
contact with each other has been described above in the first
exemplary embodiment, the exemplary embodiment of the present
invention is not limited to this. The exemplary embodiment of the
present invention may have a configuration in which the stacking
plate 16 is fixed and the pick-up roller 6 is raised and
lowered.
[0073] Embodiments of the present invention can also be realized by
a computer of a system or apparatus that reads out and executes
computer executable instructions recorded on a storage medium
(e.g., non-transitory computer-readable storage medium) to perform
the functions of one or more of the above-described embodiment(s)
of the present invention, and by a method performed by the computer
of the system or apparatus by, for example, reading out and
executing the computer executable instructions from the storage
medium to perform the functions of one or more of the
above-described embodiment(s). The computer may comprise one or
more of a central processing unit (CPU), micro processing unit
(MPU), or other circuitry, and may include a network of separate
computers or separate computer processors. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blu-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
[0074] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0075] This application claims the benefit of Japanese Patent
Application No. 2013-198162 filed Sep. 25, 2013, which is hereby
incorporated by reference herein in its entirety.
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