U.S. patent application number 16/165930 was filed with the patent office on 2019-05-02 for image forming apparatus and feeding apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Miho Kaiga, Junichi Ochi, Yohei Suzuki.
Application Number | 20190127166 16/165930 |
Document ID | / |
Family ID | 66245156 |
Filed Date | 2019-05-02 |
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United States Patent
Application |
20190127166 |
Kind Code |
A1 |
Ochi; Junichi ; et
al. |
May 2, 2019 |
IMAGE FORMING APPARATUS AND FEEDING APPARATUS
Abstract
A feeding apparatus includes a feeding member to feed a
recording material stacked on a stacking portion, a first
conveyance member, a separation member to form a nip portion with
the first conveyance member and separate a plurality of recording
materials at the nip portion, a second conveyance member, a
detection unit, and a control unit. The control unit controls to
feed a stacked first recording material and, after a first
recording material rear end passes through the feeding member, the
control unit controls to feed a stacked second recording material
while partially overlapped with the first recording material and
thereby the first recording material rear end passes through the
nip portion after a second recording material leading end passes
through the nip portion. The control unit controls so that the
second recording material is stopped before the second recording
material leading end reaches the second conveyance member.
Inventors: |
Ochi; Junichi; (Mishima-shi,
JP) ; Suzuki; Yohei; (Mishima-shi, JP) ;
Kaiga; Miho; (Suntou-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
66245156 |
Appl. No.: |
16/165930 |
Filed: |
October 19, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65H 7/12 20130101; B65H
2403/724 20130101; B65H 2513/53 20130101; B65H 2403/732 20130101;
B65H 3/5215 20130101; B65H 2511/528 20130101; B65H 5/062 20130101;
B65H 7/06 20130101; B65H 5/24 20130101; B65H 3/0669 20130101; B65H
2701/1311 20130101; B65H 2701/1313 20130101; B65H 2513/514
20130101; B65H 2701/1311 20130101; B65H 2220/01 20130101; B65H
2701/1313 20130101; B65H 2220/01 20130101; B65H 2513/53 20130101;
B65H 2220/03 20130101; B65H 2511/528 20130101; B65H 2220/03
20130101; B65H 2513/514 20130101; B65H 2220/02 20130101 |
International
Class: |
B65H 7/12 20060101
B65H007/12; B65H 3/06 20060101 B65H003/06; B65H 5/06 20060101
B65H005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2017 |
JP |
2017-207963 |
Claims
1. A feeding apparatus comprising: a feeding member configured to
feed a recording material stacked on a stacking portion; a first
conveyance member configured to convey the recording material fed
by the feeding member; a separation member configured to form a nip
portion with the first conveyance member and separate a plurality
of recording materials at the nip portion; a second conveyance
member configured to convey the recording material conveyed by the
first conveyance member; a detection unit configured to be disposed
between the first conveyance member and the second conveyance
member and to detect the recording material; and a control unit
configured to control the feeding member and the first conveyance
member so that a first recording material that is stacked on the
stacking portion is fed by the feeding member and, after a rear end
of the first recording material passes through the feeding member,
a second recording material that is stacked on the stacking portion
is fed by the feeding member while being partially overlapped with
the first recording material and thereby the rear end of the first
recording material passes through the nip portion after a leading
end of the second recording material passes through the nip
portion, and control the feeding member and the first conveyance
member so that the second recording material is stopped before the
leading end of the second recording material reaches the second
conveyance member, wherein, after the first recording material is
conveyed by the second conveyance member and the first recording
material and the second recording material that are partially
overlapped are separated from each other, the control unit changes
a feeding condition for the feeding member and the first conveyance
member to feed the stopped second recording material in accordance
with a detection result of the second recording material by the
detection unit.
2. The feeding apparatus according to claim 1, wherein a timing at
which feeding of the second recording material is started is the
feeding condition and the control unit changes the timing at which
feeding of the second recording material is started.
3. The feeding apparatus according to claim 2, wherein the control
unit starts the feeding of the second recording material at a
predetermined timing in a case where the detection unit detects the
second recording material, and starts the feeding of the second
recording material at a timing earlier than the predetermined
timing in a case where the detection unit does not detect the
second recording material.
4. The feeding apparatus according to claim 1, wherein a feeding
speed of the second recording material is the feeding condition and
the control unit changes the feeding speed of the second recording
material.
5. The feeding apparatus according to claim 4, wherein the control
unit feeds the second recording material at a predetermined speed
in a case where the detection unit detects the second recording
material, and feeds the second recording material at a speed faster
than the predetermined speed in a case where the detection unit
does not detect the second recording material.
6. The feeding apparatus according to claim 1, further comprising:
a motor configured to drive the feeding member, the first
conveyance member, and the second conveyance member; and an
electromagnetic clutch configured to transmit or intercept driving
force from the motor with respect to the feeding member and the
first conveyance member.
7. The feeding apparatus according to claim 1, further comprising:
a first motor configured to drive the feeding member and the first
conveyance member; and a second motor configured to drive the
second conveyance member.
8. The feeding apparatus according to claim 1, wherein the
detection unit includes a sensor arm configured to rotate by being
in contact with a recording material that is conveyed and includes
an encoder configured to detect a rotation angle of the sensor arm,
and wherein the control unit obtains a position of the leading end
of the stopped second recording material from the rotation angle of
the sensor arm, which is detected by the encoder, and changes the
feeding condition in accordance with the position of the leading
end of the second recording material.
9. The feeding apparatus according to claim 1, wherein the
detection unit includes a transmission unit configured to transmit
an ultrasonic wave and includes a reception unit configured to
receive the ultrasonic wave that is transmitted by the transmission
unit and passes through plural recording materials, wherein the
detection unit is configured to detect, based on the ultrasonic
wave received by the reception unit, a timing at which the leading
end of the second recording material that is conveyed while being
partially overlapped with the first recording material passes
through the detection unit, and wherein the control unit is
configured to obtain a position of the leading end of the second
recording material from the timing at which the leading end of the
second recording material passes through the detection unit, and to
change the feeding condition in accordance with the position of the
leading end of the second recording material.
10. The feeding apparatus according to claim 1, wherein, in a case
where the first recording material is fed to the nip portion by the
feeding member, the separation member rotates in a predetermined
direction to feed the first recording material, wherein, in a case
where the second recording material is fed to the nip portion by
the feeding member while the first recording material is held by
the nip portion, the separation member rotates in the predetermined
direction to feed the second recording material, and wherein, in a
case where a third recording material that is stacked on the
stacking portion is fed while the first recording material and the
second recording material are held by the nip portion, the
separation member stops rotating or rotates in a direction opposite
to the predetermined direction to prevent the third recording
material from being fed.
11. The feeding apparatus according to claim 1, wherein, in a case
where the first recording material is fed, the control unit stops
drive of the feeding member before the rear end of the first
recording material passes through the feeding member after a
leading end of the first recording material reaches the second
conveyance member and, after the rear end of the first recording
material that is conveyed by the second conveyance member passes
through the feeding member, drives the feeding member again to feed
the second recording material by the feeding member while being
partially overlapped with the first recording member.
12. The feeding apparatus according to claim 1, wherein, in a case
where the first recording material is fed, the control unit
continuously drives the feeding member without stopping the drive
of the feeding member before the rear end of the first recording
material passes through the feeding member after a leading end of
the first recording material reaches the second conveyance member,
and feeds the second recording material by the feeding member while
being partially overlapped with the first recording material, after
the rear end of the first recording material passes through the
feeding member.
13. An image forming apparatus comprising: a feeding member
configured to feed a recording material stacked on a stacking
portion, a first conveyance member configured to convey the
recording material fed by the feeding member, a separation member
configured to form a nip portion with the first conveyance member
and separate a plurality of recording materials at the nip portion,
a second conveyance member configured to convey the recording
material conveyed by the first conveyance member, an image forming
unit configured to form an image on the recording material conveyed
by the second conveyance member, a detection unit configured to be
disposed between the first conveyance member and the second
conveyance member and to detect the recording material, and a
control unit configured to control the feeding member and the first
conveyance member so that a first recording material that is
stacked on the stacking portion is fed by the feeding member and,
after a rear end of the first recording material passes through the
feeding member, a second recording material that is stacked on the
stacking portion is fed by the feeding member while being partially
overlapped with the first recording material and thereby the rear
end of the first recording material passes through the nip portion
after a leading end of the second recording material passes through
the nip portion, and control the feeding member and the first
conveyance member so that the second recording material is stopped
before the leading end of the second recording material reaches the
second conveyance member, wherein, after the first recording
material is conveyed by the second conveyance member and the first
recording material and the second recording material that are
partially overlapped are separated from each other, the control
unit changes a feeding condition for the feeding member and the
first conveyance member to feed the stopped second recording
material in accordance with a detection result of the second
recording material by the detection unit.
14. A method for a feeding apparatus having a feeding member
configured to feed a recording material stacked on a stacking
portion, a first conveyance member configured to convey the
recording material fed by the feeding member, a separation member
configured to form a nip portion with the first conveyance member
and separate a plurality of recording materials at the nip portion,
a second conveyance member configured to convey the recording
material conveyed by the first conveyance member, and a detection
unit configured to be disposed between the first conveyance member
and the second conveyance member and to detect the recording
material, the method comprising: controlling the feeding member and
the first conveyance member so that a first recording material that
is stacked on the stacking portion is fed by the feeding member;
feeding, by the feeding member, while being partially overlapped
with the first recording material and after a rear end of the first
recording material passes through the feeding member, a second
recording material that is stacked on the stacking portion to be
fed such that the rear end of the first recording material passes
through the nip portion after a leading end of the second recording
material passes through the nip portion; controlling the feeding
member and the first conveyance member so that the second recording
material is stopped before the leading end of the second recording
material reaches the second conveyance member; and changing, after
the first recording material is conveyed by the second conveyance
member and the first recording material and the second recording
material that are partially overlapped are separated from each
other, a feeding condition for the feeding member and the first
conveyance member to feed the stopped second recording material in
accordance with a detection result of the second recording material
by the detection unit.
15. A non-transitory computer-readable storage medium storing a
program causing a feeding apparatus to perform the method according
to claim 14.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present disclosure relates to an image forming
apparatus, such as a copier or a printer, and control of feeding of
a recording material in a feeding apparatus used in the image
forming apparatus.
Description of the Related Art
[0002] Conventionally, an image forming apparatus, such as a copier
or a printer, includes a feeding apparatus that feeds, toward
conveyance rollers on a downstream side, a sheet stacked on a
stacking portion such as a cassette. In a feeding apparatus
described in Japanese Patent Laid-Open No. 10-167494, a sheet
stacked in the stacking portion is drawn out by a pickup roller.
Here, when a plurality of sheets are drawn out in an overlapped
manner due to influence of friction, a feed roller and a separation
roller separate the plurality of sheets into a preceding sheet and
a following sheet on a one-by-one basis. The feeding apparatus is
configured such that, when the preceding sheet reaches conveyance
rollers on the downstream side from the feed roller, drive of the
pickup roller and the feed roller is stopped and the preceding
sheet is pulled out by the conveyance rollers. Thus, the following
sheet is prevented from being fed toward the downstream side from a
separation nip portion formed by the feed roller and the separation
roller.
[0003] FIG. 18A illustrates an enlarged view of a separation nip
portion 111a formed by a feed roller 110 and a separation roller
111. Here, when a preceding sheet S1 drags a following sheet S2 and
the two sheets are drawn out to the separation nip portion 111a,
the following sheet S2 is not fed toward the downstream side from
the separation nip portion 111a by the aforementioned control.
However, as illustrated in FIG. 18B, there is a case where the
following sheet S2 enters a vicinity of the separation nip portion
111a. In this state, when a rear end of the preceding sheet S1
passes through the separation nip portion 111a, the rear end of the
preceding sheet S1 bounces in a direction of an arrow F due to a
step caused by a thickness E of the following sheet S2 and sudden
sound is generated.
[0004] FIG. 18C illustrates a state of a cassette at a time point
when feeding of the preceding sheet S1 is completed. As described
above, at a time when the preceding sheet S1 is drawn out by a
pickup roller 112, the following sheet S2 may also be drawn out due
to influence of friction in some cases. At the time point when the
feeding of the preceding sheet S1 is completed, a position of a
leading end of the following sheet S2 varies within a range from an
initial position Pa of a leading end of a sheet stacked on the
cassette to a position Pb of the separation the nip portion 111a.
Therefore, when feeding of the following sheet S2 is started, a
sheet feeding start timing or a sheet feeding speed is set to
secure a predetermined sheet interval between sheets (interval
between the rear end of the preceding sheet S1 and the leading end
of the following sheet S2), by taking the variation into
consideration. However, when a sheet feeding start timing of the
following sheet S2 is set to secure the predetermined sheet
interval in a state where the leading end of the following sheet S2
is at the position Pb, a sheet interval is expanded more than
necessary in a state where the leading end of the following sheet
S2 is at the position Pa. As a result, productivity (the number of
sheets subjected to image formation/the number of fed sheets per
unit time) of an image forming apparatus or the feeding apparatus
is decreased.
SUMMARY OF THE INVENTION
[0005] The disclosure works towards providing an image forming
apparatus and a feeding apparatus whose productivity is refined
while reducing sudden sound when a rear end of a recording material
passes through a separation nip portion.
[0006] According to an aspect of the present disclosure, a feeding
apparatus includes a feeding member configured to feed a recording
material stacked on a stacking portion, a first conveyance member
configured to convey the recording material fed by the feeding
member, a separation member configured to form a nip portion with
the first conveyance member and separate a plurality of recording
materials at the nip portion, a second conveyance member configured
to convey the recording material conveyed by the first conveyance
member, a detection unit configured to be disposed between the
first conveyance member and the second conveyance member and to
detect the recording material, and a control unit configured to
control the feeding member and the first conveyance member so that
a first recording material that is stacked on the stacking portion
is fed by the feeding member and, after a rear end of the first
recording material passes through the feeding member, a second
recording material that is stacked on the stacking portion is fed
by the feeding member while being partially overlapped with the
first recording material and thereby the rear end of the first
recording material passes through the nip portion after a leading
end of the second recording material passes through the nip
portion, and control the feeding member and the first conveyance
member so that the second recording material is stopped before the
leading end of the second recording material reaches the second
conveyance member, wherein, after the first recording material is
conveyed by the second conveyance member and the first recording
material and the second recording material that are partially
overlapped are separated from each other, the control unit changes
a feeding condition for the feeding member and the first conveyance
member to feed the stopped second recording material in accordance
with a detection result of the second recording material by the
detection unit.
[0007] Further features of the present invention will become
apparent from the following description of embodiments with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a sectional view of a printer in Embodiment 1.
[0009] FIG. 2 illustrates a configuration of a conveyance sensor in
Embodiment 1.
[0010] FIG. 3 is a perspective view illustrating appearance of the
printer in Embodiment 1.
[0011] FIG. 4 is a control block diagram of the printer in
Embodiment 1.
[0012] FIG. 5 is a timing chart of control at a time of sheet
feeding in Embodiment 1.
[0013] FIGS. 6A to 6F are views for explaining a motion of a sheet
in Embodiment 1.
[0014] FIG. 7 is a view for explaining distribution of a position
of a leading end of a sheet in Embodiment 1.
[0015] FIG. 8 is a graph for explaining a positional relation
between a preceding sheet and a following sheet in a comparative
example.
[0016] FIG. 9 is a graph for explaining a positional relation
between a preceding sheet and a following sheet in Embodiment
1.
[0017] FIG. 10 is a view illustrating an example of an arrangement
position of the conveyance sensor in Embodiment 1.
[0018] FIGS. 11A and 11B illustrate a flowchart of control at a
time of sheet feeding in Embodiment 1.
[0019] FIG. 12 is a control block diagram of a printer in
Embodiment 2.
[0020] FIG. 13 is a graph for explaining a positional relation
between a preceding sheet and a following sheet in Embodiment
2.
[0021] FIGS. 14A and 14B illustrate a flowchart of control at a
time of sheet feeding in Embodiment 2.
[0022] FIG. 15 is a graph for explaining a positional relation
between a preceding sheet and a following sheet in Embodiment
3.
[0023] FIG. 16 illustrates a configuration of a conveyance sensor
in a modification example 1.
[0024] FIG. 17 illustrates a configuration of a conveyance sensor
in a modification example 2.
[0025] FIGS. 18A to 18C are views for explaining an issue in a
related art.
DESCRIPTION OF THE EMBODIMENTS
Embodiment 1
<Configuration>
[0026] Embodiments will be described below with reference to
drawings. Note that, the same reference signs are assigned to
components common among the drawings.
[0027] FIG. 1 is a sectional view schematically illustrating a
full-color laser beam printer 100 (hereinafter, referred to as a
printer 100) as an example of an image forming apparatus that
includes a feeding apparatus in Embodiment 1.
[0028] In FIG. 1, the printer 100 includes photosensitive drums 1,
serving as image bearing members, in process cartridges 7. The
process cartridges 7 are provided correspondingly to four colors in
total of yellow (Y), magenta (M), cyan (C), and black (B). In FIG.
1, any one of reference signs (Y, M, C, K) that represent colors is
added after a reference sign of a corresponding one of the members
to thereby represent a member with a specific color. For example, a
photosensitive drum for yellow is represented by 1Y. Hereinafter,
when representing a member with a specific color is not required,
each of the reference signs (Y, M, C, K) that represent colors is
omitted. A charging roller (not illustrated) provided in each of
the process cartridges 7 charges a surface of a corresponding one
of the photosensitive drums 1. A laser scanner unit 2 radiates
laser light L to each of the photosensitive drums 1 based on image
information so that an electrostatic latent image is formed on the
photosensitive drum 1. The latent image formed on the
photosensitive drum 1 is visualized with toner by a development
roller (not illustrated) which is provided in the process cartridge
7. In this manner, toner images of the respective colors that are
formed on the photosensitive drums 1 are transferred on an
intermediate transfer belt 9 by primary transfer rollers 5 while
sequentially being superimposed. The intermediate transfer belt 9
is rotated by a driving roller 8 and a color toner image formed on
the intermediate transfer belt 9 is transferred onto a sheet S by a
secondary transfer belt 6. These process members function as image
forming units configured to form an image on the sheet S.
[0029] The feeding apparatus is composed of a cassette 10 and a
roller unit 19. In the cassette 10, a sheet stacking plate 22 that
is a stacking portion on which a plurality of sheets S are stacked
is provided. In a standby state, a sheet S is moved up to a
drawn-out position by the sheet stacking plate 22 and a sheet
(preceding sheet) S that is positioned at the uppermost position is
in contact with a pickup roller 15 (hereinafter, referred to as a
pick roller 15). When a print signal is input, the pick roller 15
(feeding member) feeds the sheet S1 among the sheets S stacked on
the sheet stacking plate 22. A feed roller 16 (first conveyance
member) further feeds the sheet S1 fed by the pick roller 15 toward
a downstream side. A separation roller 17 (separation member) is
fixed to a chassis or the like of the printer 100 via a torque
limiter (not illustrated). An operation of the separation roller 17
will be described in detail later.
[0030] The sheet S1 fed by the feed roller 16 is conveyed by a pair
of registration rollers 3 and 4 (second conveyance member). A
conveyance sensor 23 and a top sensor 24 detect the sheet S1 that
is conveyed. Onto the sheet S1 conveyed by the pair of the
registration rollers 3 and 4, the toner image is transferred by the
aforementioned secondary transfer roller 6. After that, a fixing
unit 12 fixies the toner image, which is transferred onto the sheet
S1, on the sheet S1 with heat and pressure. The sheet S1 on which
the toner image is fixed is discharged to a sheet discharge try 13
by a pair of discharge rollers 11.
[0031] FIG. 2 illustrates a configuration of the conveyance sensor
23 in the present embodiment. In the present embodiment, the
conveyance sensor 23 in which a rotation-type sensor arm 30 and a
photo-interrupter 31 are combined is used. The sensor arm 30 is
configured to be rotatable about a rotation shaft 34 as a center
and an arm portion 30a enters a conveyance path of a sheet S. The
arm portion 30a comes into contact with the sheet S that is
conveyed, so that the sensor arm 30 is rotated by passage of the
sheet S. When the sensor arm 30 is rotated, a sensor flag 30b that
is integrally provided with the sensor arm 30 is also rotated so
that a light transmitting state and a light shielding state of the
photo-interrupter 31 are switched. By a signal output from the
photo-interrupter 31, it is possible to detect presence or absence
of the sheet S and a timing when a leading end or a rear end of the
sheet S passes. Additionally, the top sensor 24 also has the same
configuration as that of the conveyance sensor 23.
[0032] FIG. 3 is a perspective view illustrating appearance of the
printer 100. The cassette 10 is configured to be pullable toward a
front surface side of a main body of the apparatus. A user pulls
out the cassette 10 and supplies a sheet S for the cassette 10. In
addition, a door for jam processing 20 is configured on a side
surface side of the main body of the apparatus to be
openable/closable. When a sheet S remains in the middle of the
conveyance path, that is, when a jam occurs, the user is able to
remove the sheet S remaining inside by opening the door for jam
processing 20. Additionally, an operation panel 29 is provided on
the printer 100. The operation panel 29 provides guidance of each
operation to the user through a liquid crystal screen. The
operation panel 29 also displays an error or a button or an icon
for performing a manual operation. For example, when a jam occurs,
based on information of each sensor, it is determined at which part
in the apparatus the jam occurs, and how to perform jam processing
is notified to the user in an easy-to-understand manner through the
operation panel 29. Note that, simple notification by, for example,
an LED may be performed without the liquid crystal screen. For
example, an LED may be arranged in each of the cassette 10 and the
door for jam processing 20, and the LED to be accessed by the user
for the jam processing may be turned on.
[0033] FIG. 4 is a control block diagram of the printer 100 in the
present embodiment. An engine control unit 26 that controls an
operation of the printer 100 includes a CPU, a ROM, a RAM, and the
like therein and executes processing based on a program stored in
the ROM in advance. In FIG. 4, for example, description related to
a process other than a sheet feeding operation, such as an image
forming process, is omitted. A motor 27 is connected to the engine
control unit 26. The motor 27 drives and rotates the pick roller 15
and the feed roller 16 through an electromagnetic clutch 28. The
electromagnetic clutch 28 transmits or intercepts driving force of
the motor 27 with respect to the pick roller 15 or the feed roller
16. One-way clutches (not-illustrated) are built in the pick roller
15 and the feed roller 16, and when the electromagnetic clutch 28
is turned OFF, the pick roller 15 and the feed roller 16 are
brought into a state of being rotatable only in a direction in
which a sheet S is fed. Additionally, the motor 27 drives and
rotates the pair of the registration rollers 3 and 4. It is
configured that detection results of the conveyance sensor 23 and
the top sensor 24 are notified to the engine control unit 26 to
display information such as occurrence of a jam on the operation
panel 29.
<Operation>
[0034] A sheet feeding operation of the present embodiment will be
described in detail by using FIG. 5. FIG. 5 is a timing chart of
control at a time of the sheet feeding and a view schematically
illustrating a positional relation between a rear end of a sheet S1
that is being fed and each of the rollers. Here, the rear end of
the sheet S1 indicates an end of the sheet S1 on an upstream side
in the feeding direction.
[0035] When a print signal is input, the engine control unit 26
rotates the pair of the registration rollers 3 and 4 by the motor
27. Almost at the same time, the engine control unit 26 turns the
electromagnetic clutch 28 ON to rotate the pick roller 15 and the
feed roller 16 (at a timing when the rear end of the sheet S1 is at
a position d in FIG. 5).
[0036] The sheet S1 drawn out by the pick roller 15 passes through
a separation nip portion 17a formed by the feed roller 16 and the
separation roller 17 and reaches the pair of the registration
rollers 3 and 4. When a leading end of the sheet S1 reaches the top
sensor 24 positioned immediately after the pair of the registration
rollers 3 and 4, the engine control unit 26 turns the
electromagnetic clutch 28 OFF. At this time, the rear end of the
sheet S1 does not pass through the pick roller 15 (at a timing when
the rear end of the sheet S1 is at a position e in FIG. 5).
[0037] The pair of the registration rollers 3 and 4 convey the
sheet S1 toward the downstream side so that the sheet S1 is pulled
out from the separation nip portion 17a. At this time, since the
electromagnetic clutch 28 is turned OFF, the driving force from the
motor 27 is not transmitted to the pick roller 15 and the feed
roller 16. However, the two rollers are driven to rotate by
following the conveyance of the sheet S1 by the one-way clutches
(not-illustrated). Then, at a timing when a predetermined time has
elapsed since the rear end of the sheet S1 had passed through the
pick roller 15, the engine control unit 26 turns the
electromagnetic clutch 28 ON again (at a timing when the rear end
of the sheet S1 is at a position fin FIG. 5).
[0038] The electromagnetic clutch 28 is turned ON again and the
pick roller 15 and the feed roller 16 are rotated. At this time,
since the sheet S1 has already passed through the pick roller 15, a
sheet (following sheet) S2 to be fed next after the sheet S1 is in
contact with the pick roller 15 and is fed. This operation is
expressed as "pre-feeding". Here, the sheet S1 and the sheet S2 are
conveyed while being partially overlapped. Then, at a timing when
the sheet S2 is conveyed by the pick roller 15 by a predetermined
distance B illustrated in FIG. 5, the engine control unit 26 turns
the electromagnetic clutch 28 OFF again. At this time, the sheet S1
is also conveyed by the feed roller 16 and the pair of the
registration rollers 3 and 4 by a predetermined distance C (=B)
illustrated in FIG. 5 (at a timing when the rear end of the sheet
S1 is at a position g in FIG. 5). A purpose for performing such
pre-feeding is to take a countermeasure against sound during
conveyance of a sheet, and a content thereof will be described in
detail later.
[0039] At a time point when a pre-feeding operation of the sheet S2
ends, the rear end of the sheet S1 has passed through the
separation nip portion 17a. Although detailed description will be
given later, at the time point when the pre-feeding operation of
the sheet S2 ends, the leading end of the sheet S2 has passed
through the separation nip portion 17a. But the leading end of the
sheet S2 does not reach the pair of the registration rollers 3 and
4. Accordingly, the sheet S2 is stopped in a state where the
electromagnetic clutch 28 is turned OFF. That is, the pick roller
15 and the feed roller 16 are not rotated by the sheet S2 and stop.
The sheet S1 is conveyed toward a further downstream side by the
pair of the registration rollers 3 and 4, and image formation is
performed. As above, the sheet feeding operation of the sheet S1
ends.
[0040] The engine control unit 26 calculates a start timing (f in
FIG. 5) of the pre-feeding operation or an end timing (g in FIG. 5)
of the pre-feeding operation of the sheet S2 based on a timing when
the sheet S1 reaches the top sensor 24. The engine control unit 26
calculates these timings by taking a length of the sheet S1 and a
conveyance speed of the sheet S1 into consideration. A time lag of
responsiveness of the electromagnetic clutch 28 or delay due to a
space between driving columns (not illustrated) arises until the
pick roller 15 rotates after the electromagnetic clutch 28 is
turned ON, so that the engine control unit 26 calculates the
timings also by taking the time lag or the delay into
consideration.
[0041] Note that, the start timing or the end timing of the
pre-feeding operation may be calculated based on a timing when the
sheet S1 reaches the conveyance sensor 23 instead of the top sensor
24 or may be calculated based on a timing when feeding of the sheet
S1 stacked on the cassette 10 is started by the pick roller 15 and
the feed roller 16.
[0042] Moreover, when a plurality of sheets S are continuously fed,
the motor 27 may be continuously rotated so that ON and OFF of the
electromagnetic clutch 28 are repeatedly switched.
[0043] Here, before the pick roller 15 comes in contact with the
following sheet S2, that is, before the pre-feeding of the
following sheet S2 is performed, the sheet S2 is moved due to
frictional force between the preceding sheet S1 and the following
sheet S2 (hereinafter, expressed as "being dragged") in some cases.
The sheet S2 may not be dragged at all, or may be dragged to a
position before the separation nip portion 17a, or may be dragged
to the separation nip portion 17a. Description of being dragged
will be given below by using FIGS. 6A to 6F.
[0044] FIG. 6A illustrates a state where the sheet S2 is not
dragged at all. FIG. 6B illustrates a state where the sheet S2 is
separated from the sheet S1 at the position before the separation
nip portion 17a and stopped after being slightly dragged. FIG. 6C
illustrates a state where the sheet S2 is separated from the sheet
S1 and stopped at the separation nip portion 17a after being
completely dragged. In FIGS. 6A to 6C, the electromagnetic clutch
28 is turned OFF. In addition, the sheet S1 is conveyed by the pair
of the registration rollers 3 and 4 (not illustrated in FIGS. 6A to
6F), and the feed roller 16 is driven to rotate by the sheet S1.
The pick roller 15 that is in contact with the sheet S2 stops. A
position of the leading end of the sheet S2 advances by a distance
F in FIG. 6B and by a distance G in FIG. 6C when FIG. 6A is set as
a reference.
[0045] In the present embodiment, "being dragged" indicates a
phenomenon that the following sheet S2 is moved due to influence of
the friction with the preceding sheet S1, that is, a phenomenon
that the following sheet S2 is moved although the following sheet
S2 and the pick roller 15 are not in contact with each other.
Whereas, "pre-feeding" indicates an operation that the following
sheet S2 is moved by a predetermined distance in advance by the
pick roller 15 while a feeding operation of the preceding sheet S1
is performed. That is, in the pre-feeding, the following sheet S2
and the pick roller 15 are in contact with each other.
[0046] FIGS. 6D, 6E, and 6F indicate states where pre-feeding of
the sheet S2 is completed after start of the pre-feeding from the
states of FIGS. 6A, 6B, and 6C, respectively. In each of the states
where the pre-feeding is completed, amounts of being dragged F and
G are maintained as they are and the position of the leading end of
the sheet S2 is moved by the predetermined distance B. As
illustrated in FIGS. 6D, 6E and 6F, the leading end of the sheet S2
passes through the separation nip portion 17a in any cases.
[0047] Here, an operation of the separation roller 17 will be
described. First, when there is no sheet S in the separation nip
portion 17a, force received by the separation roller 17 due to
friction with the feed roller 16 that is rotating is set to exceed
a rotational load of the torque limiter. Thus, the separation
roller 17 is rotated in a feeding direction of the sheet S. When
one sheet S1 is conveyed to the separation nip portion 17a, force
received by the separation roller 17 due to friction with the one
sheet S1 is set to exceed the rotational load of the torque
limiter. Thus, the separation roller 17 is rotated in the feeding
direction of the sheet S1. When one sheet S1 is conveyed to the
separation nip portion 17a and a sheet S2 is dragged due to
influence of friction with the sheet S1, the rotational load of the
torque limiter is set to exceed force received by the separation
roller 17 due to friction with the two sheets S1 and S2. Thus,
rotation of the separation roller 17 is stopped.
[0048] On the other hand, when the one sheet S1 is conveyed to the
separation nip portion 17a and the sheet S2 is further conveyed by
the pick roller 15, the force received by the separation roller 17
due to the friction with the two sheets S1 and S2 is set to exceed
the rotational load of the torque limiter. Thus, the separation
roller 17 is rotated in the feeding direction of the sheet S1. When
the two sheets S1 and S2 are conveyed to the separation nip portion
17a and a sheet S3 is dragged due to influence of friction with the
sheet S2, the rotational load of the torque limiter is set to
exceed force received by the separation roller 17 due to friction
with the three sheets S1 to S3. Thus, the rotation of the
separation roller 17 is stopped.
[0049] A purpose of subjecting the sheet S2 to the pre-feeding
after the rear end of the sheet S1 passes through the pick roller
15 is to reduce sound at a moment when the rear end of the sheet S1
passes through the separation nip portion 17a. The countermeasure
against the sound will be described below in detail.
[0050] FIG. 7 illustrates distribution of a position of the leading
end of the following sheet S2. Distribution of the position of the
leading end of the sheet S2 in a case where the pre-feeding
operation is not performed is illustrated in (a) of FIG. 7. The
distribution of the position of the leading end of the sheet S2 has
two peaks at a position j of setting in the cassette 10 and a
position m of the separation nip portion 17a, and frequency thereof
is high. Then, frequency at which the leading end of the sheet S2
is positioned within a range k therebetween is low. In a case of a
paper type which is difficult to be dragged, the sheet S2 is hardly
moved due to the influence of the friction with the sheet S1. On
the other hand, in a case of a paper type which is easy to be
dragged, the sheet S2 is moved due to the influence of the friction
with the sheet S1, separated from the sheet S1 by the separation
nip portion 17a, and stopped. Thereby, distribution of the position
of the leading end of the sheet S2 has peaks at two positions.
[0051] As described in FIG. 18B, in a case where, when the rear end
of the sheet S1 being fed passes through the separation nip portion
17a, the leading position of the following sheet S2 is at the
position m of the separation nip portion 17a, the rear end of the
sheet S1 being fed bounces due to a step caused by a thickness of
the following sheet S2 and sudden sound is generated. In a case
where the pre-feeding operation is not performed, since frequency
at which the leading end of the following sheet S2 exists at the
position m of the separation nip portion 17a is high, frequency at
which the sudden sound is generated when the rear end of the sheet
S1 being fed passes through the separation nip portion 17a is also
high.
[0052] Distribution of the position of the leading end of the sheet
S2 in a case where the pre-feeding operation is performed is
illustrated in (b) of FIG. 7. The distribution of the position of
the leading end of the sheet S2 is shifted to a position advanced
by the predetermined distance B to the downstream side of the
feeding direction as a whole compared to (a) of FIG. 7 in the case
where the pre-feeding operation is not performed. In the present
embodiment, the predetermined distance B by which the sheet S2 is
moved by the pre-feeding operation is set to be longer than a
distance A from the position j at which a leading end of a sheet S
is set in the cassette 10 to the position m of the separation nip
portion 17a. Thus, peaks of the position of the leading end of the
sheet S2 are shifted to a position n and a position o that are on
the downstream side of the separation nip portion 17a. Then, since
frequency at which the leading end of the sheet S2 exists at the
position m of the separation nip portion 17a is low (range p),
frequency at which the sudden sound is generated when the rear end
of the sheet S1 being fed passes through the separation nip portion
17a is low. That is, the sudden sound is able to be reduced.
[0053] When the leading end of the following sheet S2 reaches the
pair of the registration rollers 3 and 4 by the pre-feeding
operation, the following sheet S2 is conveyed while being
overlapped with the sheet S1 being fed. In order to prevent this,
the predetermined distance B by which the sheet S2 is conveyed by
the pre-feeding operation is set to be shorter than a distance D
from the separation nip portion 17a to the pair of the registration
rollers 3 and 4. That is, this may be addressed by satisfying a
relation of distance A<distance B<distance D.
[0054] Next, a timing when feeding of the following sheet S2 is
started again after the pre-feeding is completed will be described.
In order to enhance productivity of continuous printing, a sheet
interval (interval between the rear end of the preceding sheet S1
and the leading end of the following sheet S2) may be made as short
as possible. The sheet interval is set in advance in accordance
with a size or a paper type of a sheet S. At a time point when the
pre-feeding is completed, as illustrated in FIGS. 6D, 6E, and 6F,
there is a possibility that the position of the leading end of the
sheet S2 varies. The variation should be considered on deciding a
feeding timing of the following sheet S2.
[0055] First, the feeding timing of the following sheet S2 in a
comparative example will be described by using FIG. 8. A graph of a
thick solid line indicates the position of the rear end of the
sheet S1 and a graph of a thin solid line indicates the position of
the leading end of the sheet S2. A case where the position of the
leading end of the sheet S2 is most advanced (FIG. 6F) and a case
where the position of the leading end of the sheet S2 is most
delayed (FIG. 6D) are drawn by two lines, positions of the leading
end of the sheet S2 are all distributed between the aforementioned
two lines. As illustrated in FIG. 8, when the sheet S2 is most
advanced, a sheet interval between the sheet S1 and the sheet S2 is
the same as a set sheet interval, and when the sheet S2 is most
delayed, the sheet interval is a sheet interval obtained by adding
the distance G to the set sheet interval. Note that, as illustrated
in FIG. 6C, the distance G is a distance from an initial position
of a leading end of a sheet S stacked on the cassette 10 to the
separation nip portion 17a.
[0056] Here, in FIG. 8, since the leading end of the sheet S2 in
the state of FIG. 6F is advanced to the most downstream side,
response delay of the electromagnetic clutch 28 or delay due to a
space between gears or a backlash thereof is estimated based on the
state and the feeding timing of the sheet S2 is set. As a method of
setting the timing, for example, a method of obtaining a timing T3
when a predetermined time has elapsed since a timing when the
leading end of the sheet S1 had been detected by the top sensor 24
is taken. Note that, the sheet feeding timing may be obtained based
on the conveyance sensor 23 instead of the top sensor 24.
[0057] Next, the feeding timing of the following sheet S2 in the
present embodiment will be described by using FIG. 9. In the
present embodiment, in a case where the conveyance sensor 23 does
not detect the stopped sheet S2, after the pre-feeding is
completed, the feeding of the sheet S2 is started at a timing T4
that is earlier than the timing T3 illustrated in FIG. 8 so that
the sheet interval is shortened. The timing T4 is calculated from a
conveyance speed, a position of the conveyance sensor 23, or the
like. Here, it is most effective in a case where a position of the
conveyance sensor 23 is set on the upstream side by a distance G/2
from a position H (FIG. 6F) in a case where the sheet S2 is most
advanced after the pre-feeding (after the electromagnetic clutch 28
is turned OFF). A configuration thereof is indicated in FIG. 10. In
the case where the conveyance sensor 23 does not detect the stopped
sheet S2 after the pre-feeding is completed, that is, in a case
where the leading end of the sheet S2 is stopped on the upstream
side from the conveyance sensor 23, a timing when the
electromagnetic clutch 28 is turned ON is uniformly made earlier as
illustrated in FIG. 9. Thereby, even in a case where the sheet S2
is most delayed, the sheet interval between the sheet S1 and the
sheet S2 is a sheet interval obtained by adding the distance G/2 to
the set sheet interval, so that variation in the sheet interval is
refined by at most G/2 compared to that in the comparative
example.
[0058] As described above, according to the present embodiment, a
variation amount between a minimum sheet interval and a maximum
sheet interval is able to be reduced by G/2 unless restriction of a
configuration of the apparatus or the minimum sheet interval to be
set is taken into consideration.
[0059] FIGS. 11A and 11B illustrate a flowchart in which the sheet
feeding operation in the present embodiment is summarized. The
engine control unit 26 executes control based on the flowchart in
FIGS. 11A and 11B based on a program stored in a ROM or the
like.
[0060] First, on reception of a print instruction, the engine
control unit 26 determines whether or not a feeding timing of a
sheet S from the cassette 10 arrives (S400). When determining that
the feeding timing of the sheet S arrives, the engine control unit
26 starts a feeding operation of a sheet S1 (S401). Specifically,
as described above, the engine control unit 26 causes the motor 27
to drive so that the electromagnetic clutch 28 is turned ON.
Thereby, the pick roller 15, the feed roller 16, and the pair of
the registration rollers 3 and 4 are rotated.
[0061] Next, the engine control unit 26 determines whether or not
the conveyance sensor 23 or the top sensor 24 detects the sheet S1
(S402, S403). When determining that the top sensor 24 detects a
leading end of the sheet S1, the engine control unit 26 turns the
electromagnetic clutch 28 OFF (S404). Thereby, the sheet S1 is
conveyed by the pair of the registration rollers 3 and 4, so that
the pick roller 15 and the feed roller 16 are driven by conveyance
of the sheet S1. Here, when the engine control unit 26 determines
that the sheet S1 being fed is a final sheet of a print job (S405),
the engine control unit 26 stops the motor 27 after the feeding of
the sheet S1 (S413) and ends the sheet feeding operation. On the
other hand, when the engine control unit 26 determines that the
sheet S1 is not the final sheet, the engine control unit 26
proceeds to processing at S406.
[0062] When the sheet S1 is not the final sheet, that is, a next
sheet S2 is continuously fed, the engine control unit 26 obtains at
least a timing when a rear end of the sheet S1 has passed through
the pick roller 15. In the present embodiment, the engine control
unit 26 determines whether or not a timing when a predetermined
time T1 has elapsed since the top sensor 24 had detected the
leading end of the sheet S1 arrives (S406). In a case where
determining that the timing when the predetermined time T1 has
elapsed arrives, the engine control unit 26 turns the
electromagnetic clutch 28 ON to start a pre-feeding operation of
the sheet S2 (S407).
[0063] Next, the engine control unit 26 determines whether or not a
timing when the sheet S2 is conveyed by the predetermined distance
B, that is, a timing when a predetermined time T2 has elapsed since
the top sensor 24 had detected the leading end of the sheet S1
arrives (S408). In a case of determining that the timing when the
predetermined time T2 has elapsed arrives, the engine control unit
26 turns the electromagnetic clutch 28 OFF to end the pre-feeding
operation of the sheet S2 (S409).
[0064] As already described by using FIGS. 6A to 6F or FIG. 7, the
position of the leading end of the sheet S2 at a time point when
the pre-feeding operation of the sheet S2 ends and the feeding of
the sheet S2 is started again varies within the range of the
distance G. The conveyance sensor 23 is arranged within the range
of the variation and detects presence or absence of the stopped
sheet S2 (S410). In the case where the conveyance sensor 23 detects
the sheet S2, the leading end of the sheet S2 is on the downstream
side from the conveyance sensor 23, and in the case where the
conveyance sensor 23 does not detect the sheet S2, the leading end
of the sheet S2 is on the upstream side from the conveyance sensor
23. Then, in the case where the conveyance sensor 23 detects the
sheet S2, the engine control unit 26 turns the electromagnetic
clutch 28 ON at the timing T3 when a predetermined time has elapsed
since the top sensor 24 had detected the leading end of the sheet
S1 (S411). Additionally, in the case where the conveyance sensor 23
does not detect the sheet S2, the engine control unit 26 turns the
electromagnetic clutch 28 ON at the timing T4 when a predetermined
time has elapsed since the top sensor 24 had detected the leading
end of the sheet S1 (S412). Here, the timing T4 is earlier than the
timing T3 and is a timing for reducing a variation amount to at
most 1/2. In this manner, when the leading end of the sheet S2 is
on the upstream side from the conveyance sensor 23, by setting a
sheet feeding start timing earlier compared to a case where the
leading end of the sheet S2 is on the downstream side, it is
possible to shorten the sheet interval between the sheet S1 and the
sheet S2 compared to a case where sheet feeding is always started
at a fixed timing.
[0065] Note that, processing at 410 by which the conveyance sensor
23 detects presence or absence of the sheet S2 is executed at a
timing after a time required for the rear end of the sheet S1 to
pass through the conveyance sensor 23 has elapsed at least. A start
point at which the engine control unit 26 counts the time may be a
timing when the conveyance sensor 23 detects the leading end of the
sheet S1 or may be a timing when the top sensor 24 detects the
leading end of the sheet S1.
[0066] Next, a method of specifying a jam position by using the
conveyance sensor 23 will be described. When determining, at S402,
that the conveyance sensor 23 does not detect the sheet S1, the
engine control unit 26 determines whether or not a threshold time
Tth1 has elapsed since the feeding operation of the sheet S1 had
been started (S414). Here, the threshold time Tth1 is longer than
at least the predetermine time T1. In a case of determining that a
timing when the threshold time Tth1 has elapsed arrives, the engine
control unit 26 displays, on the operation panel 29 provided on the
printer 100, a message indicating that a jam occurs. Furthermore,
it is determined that the leading end of the sheet S1 has not
reached the conveyance sensor 23 (not passed through the separation
nip portion 17a), and display is performed on the operation panel
29 to urge pulling out the cassette 10 to perform jam processing
(S415).
[0067] When determining, at S403, that the top sensor 24 does not
detect the sheet S1, the engine control unit 26 determines whether
or not a timing when a threshold time Tth2 has elapsed since the
conveyance sensor 23 had detected the sheet S1 arrives (S416). In a
case where determining that the timing when the threshold time Tth2
has elapsed arrives, the engine control unit 26 displays, on the
operation panel 29 provided on the printer 100, a message
indicating that a jam occurs. At this time, it is determined that
the leading end of the sheet S1 has passed through the conveyance
sensor 23 and stopped at a position not reaching the top sensor 24,
and display is performed on the operation panel 29 to urge opening
the door for jam processing 20 to perform jam processing
(S417).
[0068] Since a conventional apparatus does not include the
conveyance sensor 23 as in the present embodiment, it is difficult
to determine whether a leading end of a jammed sheet that does not
reach the top sensor 24 remains in the cassette 10 or stops in a
conveyance path on the upstream side of the top sensor 24. Thus,
there is a case where it is difficult for a user to find the jammed
sheet by opening the door for jam processing 20 in a state where
the jammed sheet remains in the cassette 10 or the jammed sheet is
torn out because the cassette 10 is pulled out with the jammed
sheet positioned over the cassette 10 and the conveyance path.
According to the configuration in the present embodiment, it is
possible to guide an appropriate method of jam processing by
accurately detecting a jam position without adding a new sensor for
detecting a jam. Then, control of the flowchart ends.
[0069] As above, according to the present embodiment, it is
possible to provide an image forming apparatus and a feeding
apparatus whose productivity is refined while reducing sudden sound
when a rear end of a recording material passes through a separation
nip portion.
Embodiment 2
[0070] Next, Embodiment 2 will be described. In Embodiment 2, a
difference from Embodiment 1 will be mainly described and
description of components similar to those of Embodiment 1 will be
omitted.
<Configuration>
[0071] In Embodiment 1, the motor 27 drives the pair of the
registration rollers 3 and 4, the pickup roller 15, and the feed
roller 16. On the other hand, as illustrated in a block diagram of
FIG. 12, a motor 37 drives the pair of the registration rollers 3
and 4, and a motor 36 drives the pickup roller 15 and the feed
roller 16 in the present embodiment. Thus, no electromagnetic
clutch is required, and the motor 36 is caused to rotate or stop in
the present embodiment instead of the operation of turning the
electromagnetic clutch 28 ON or OFF in Embodiment 1. Note that, the
motor 37 may also serve as drive of the photosensitive drum 1 or
the like. Other configurations are similar to those in Embodiment
1.
<Operation>
[0072] The pre-feeding operation of the sheet S2 is similar to that
of Embodiment 1 except for a difference of the electromagnetic
clutch and the motor described above. In Embodiment 1, after the
pre-feeding ends, "timing" at which feeding of the sheet S is
started is changed by changing a timing when the electromagnetic
clutch 28 is turned ON in accordance with a detection result by the
conveyance sensor 23, but in the present embodiment, a "conveyance
speed" of the sheet S2 is changed.
[0073] An operation of the present embodiment will be described by
using a graph of FIG. 13. In FIG. 13, a graph of a thick solid line
indicates the position of the rear end of the sheet S1 and three
graphs of thin solid lines each indicate the position of the
leading end of the sheet S2. The three graphs indicate a case where
the position of the leading end of the sheet S2 is most advanced, a
case where the position of the leading end of the sheet S2 is at a
middle position, and a case where the position of the leading end
of the sheet S2 is most delayed. In the case where the leading end
of the sheet S2 is most advanced, the sheet interval between the
sheet S1 and the sheet S2 becomes the set sheet interval, so that
no special operation is performed. At this time, a timing when the
leading end of the sheet S2 reaches the pair of the registration
rollers 3 and 4 is set as T5. Next, in the case where the position
of the leading end of the sheet S2 is at the middle position,
specifically, when the motor 36 stops, the leading end of the sheet
S2 is at a position immediately before the conveyance sensor 23 on
the upstream side. That is, in this case, the conveyance sensor 23
does not detect the stopped sheet S2. Here, the motor 36 starts
rotating at the timing T3 and the motor 36 is driven so that a
conveyance speed of the sheet S2 by the pick roller 15 and the feed
roller 16 is faster than a conveyance speed of the sheet S1 by the
pair of the registration rollers 3 and 4. Thereby, the leading end
of the sheet S2 is to reach the pair of the registration rollers 3
and 4 at the timing T5. Note that, in a case where the conveyance
speed is not changed, a timing when the leading end of the sheet S2
reaches the pair of the registration rollers 3 and 4 is T7, so that
delay occurs. When the position of the leading end of the sheet S2
is most delayed, since the conveyance speed is made faster in the
same manner as above, a timing when the leading end of the sheet S2
reaches the pair of the registration rollers 3 and 4 is T6. Note
that, in a case where the conveyance speed is not changed, a timing
when the leading end of the sheet S2 reaches the pair of the
registration rollers 3 and 4 is T8, so that delay occurs. By the
aforementioned operation, the sheet interval between the sheet S1
and the sheet S2 is able to be reduced also in the present
embodiment.
[0074] FIGS. 14A and 14B illustrate a flowchart of the present
embodiment. Processing of S500 to S510 and S514 to S517, which is
described in FIGS. 14A and 14B, is basically the same as the
processing of S400 to S410 and S414 to S417, which is described in
FIGS. 1A and 11B. In the processing, processing of
rotating/stopping the motor 36 at S504, S507, or S509 is one
obtained by replacing processing of turning the electromagnetic
clutch 28 ON/OFF at S404, S407, or S409, respectively. A difference
from the flowchart described in FIGS. 11A and 11B lies at S518 and
S519. In a case where the conveyance sensor 23 detects the sheet S2
at a feeding start timing of the sheet S2, the engine control unit
26 rotates the motor 36 so that the sheet S2 is conveyed at a
normal conveyance speed V1 (S518). On the other hand, in a case
where the conveyance sensor 23 does not detect the sheet S2, the
engine control unit 26 rotates the motor 36 so that the sheet S2 is
conveyed at a conveyance speed V2 that is faster than the
conveyance speed V1 (S519).
[0075] In Embodiment 1, the timing when the sheet S2 reaches the
pair of the registration rollers 3 and 4 is made earlier by setting
the feeding start timing of the sheet S2 to be earlier. In the
present embodiment, the timing when the sheet S2 reaches the pair
of the registration rollers 3 and 4 is made earlier by increasing a
speed at which the sheet S2 is conveyed. The present embodiment is
effective in a case where a sheet interval that is set in advance
is very short and it is therefore difficult to set the feeding
start timing of the sheet S2 to be earlier, for example.
[0076] As above, according to the present embodiment, it is
possible to provide an image forming apparatus and a feeding
apparatus whose productivity is refined while reducing sudden sound
when a rear end of a recording material passes through a separation
nip portion.
Embodiment 3
[0077] Next, Embodiment 3 will be described. In Embodiment 3, a
difference from Embodiment 1 and Embodiment 2 will be mainly
described and description of components similar to those of
Embodiment 1 or Embodiment 2 will be omitted.
<Configuration>
[0078] A configuration of Embodiment 3 is similar to that of
Embodiment 2.
<Operation>
[0079] The pre-feeding operation of the sheet S2 is similar to that
of Embodiment 2. In the present embodiment, the conveyance speed of
the sheet S2 is changed while changing the feeding start timing of
the sheet S2 depending on a detection result by the conveyance
sensor 23. Additionally, a difference lies in that, although the
conveyance speed of the sheet S2 is increased in Embodiment 2, the
conveyance speed of the sheet S2 is reduced in the present
embodiment.
[0080] An operation of the present embodiment will be described by
using a graph of FIG. 15. In FIG. 15, a graph of a thick solid line
indicates the position of the rear end of the sheet S1 and three
graphs of thin solid lines each indicate the position of the
leading end of the sheet S2. The three graphs indicate a case where
the position of the leading end of the sheet S2 is most advanced, a
case where the position of the leading end of the sheet S2 is at a
middle position, and a case where the position of the leading end
of the sheet S2 is most delayed. A graph of a broken line indicates
an operation before the control of the present embodiment is
applied. Before the application of the control of the present
embodiment, timings when the leading end of the sheet S2 reaches
the pair of the registration rollers 3 and 4 in the respective
cases are T5, T7, and T8, and there is variation of T8 to T5 at
maximum. Note that, a graph indicated as the middle of the
variation indicates a case where the leading end of the sheet S2 is
at the position immediately before the conveyance sensor 23 on the
upstream side, specifically, when the motor 36 is stopped. That is,
in this case, the conveyance sensor 23 does not detect the stopped
sheet S2.
[0081] In the present embodiment, in a case where the conveyance
sensor 23 does not detect the sheet S2 when the motor 36 is caused
to stop, the feeding start timing of the sheet S2 is changed from
T3 to T9. Here, T9 is a timing when a timing when the leading end
of the sheet S2 in a case of being most delayed reaches the pair of
the registration rollers 3 and 4 is just at T5. On the other hand,
also in the case where the leading end of the sheet S2 is at the
middle position, the feeding start timing of the sheet S2 is
changed to T9. In this case, the timing of reaching the pair of the
registration rollers 3 and 4 is made earlier from T7 to T11 as
illustrated by a two-dot chain line in FIG. 15. Then, the leading
end of the sheet S2 reaches the pair of the registration rollers 3
and 4 at a timing earlier than the set sheet interval, so that
there is a possibility that inconvenience, such as a sheet interval
being too short to perform image forming in time, occurs.
Therefore, a rotation speed of the motor 36 is set to be slow by a
predetermined amount calculated from time until the conveyance
sensor 23 detects the leading end of the sheet S2 after starting
feeding of the sheet S2. Thereby, the leading end of the sheet S2
is to reach the pair of the registration rollers 3 and 4 at the
timing T5.
[0082] Note that, adjustment of the sheet interval is to be
completed before the leading end of the sheet S2 reaches the pair
of the registration rollers 3 and 4 here, but the adjustment of the
sheet interval may be completed before the leading end of the sheet
S2 reaches the secondary transfer roller 6 at the latest. In this
case, a speed of the pair of the registration rollers 3 and 4 also
may be set to be variable.
[0083] By the aforementioned operation, the timing when the leading
end of the sheet S2 reaches the pair of the registration rollers 3
and 4 is able to be uniformized to be T5. The configuration of the
present embodiment makes it possible to minimize or eliminate
variation in the sheet interval and is able to be used even when
the conveyance speed is not able to be made faster because of an
issue, for example, such as a rated performance of the motor 36 or
operation sound thereof.
[0084] As above, according to the present embodiment, it is
possible to provide an image forming apparatus and a feeding
apparatus whose productivity is refined while reducing sudden sound
when a rear end of a recording material passes through a separation
nip portion.
Modification Example 1
[0085] Description has been given by using the sensor having the
configuration described in FIG. 2 as the conveyance sensor 23 in
Embodiment 1 to Embodiment 3 described above. However, there is no
limitation thereto. As illustrated in FIG. 16, a type that detects
a rotation angle of the sensor arm 30 in detail by providing a
rotary encoder wheel 32 on a rotation shaft 34 may be used.
[0086] In FIG. 16, the sensor arm 30 is configured to be rotatable
about the rotation shaft 34 as a center and the arm portion 30a
enters an inside of a conveyance path of a sheet S. The arm portion
30a is in contact with the sheet S that is conveyed so that the
sensor arm 30 is rotated by passage of the sheet S. As the sensor
arm 30 is rotated, the rotary encoder wheel 32 that is integrally
formed with the sensor arm 30 is also rotated. A wheel detecting
unit 33 is able to detect the rotation angle of the sensor arm 30
based on a rotational amount of the rotary encoder wheel 32. In a
case where a conveyance sensor 35 detects the sheet S2, the
rotation angle of the sensor arm 30 becomes larger as a stop
position of the sheet S is at a position further on the downstream
side. That is, according to the conveyance sensor 35 that has the
configuration of FIG. 16, it is possible to detect the position of
the leading end of the sheet S2 more in detail compared to the
conveyance sensor 23 that has the configuration described in FIG.
2.
[0087] After the pre-feeding operation of the following sheet S2 is
completed, and the sheet S1 is conveyed by the pair of the
registration rollers 3 and 4, and the sheet 1 and the sheet 2 that
are partially overlapped are separated from each other, the engine
control unit 26 determines whether or not the conveyance sensor 35
detects the sheet S2. In the case where the conveyance sensor 35
detects the sheet S2, the engine control unit 26 further obtains
the position of the leading end of the sheet S2 based on the
rotation angle of the sensor arm 30. Then, the engine control unit
26 changes a feeding condition such as the feeding start timing of
the sheet S2 or the feeding speed thereof in accordance with the
obtained position of the leading end of the sheet S2.
Modification Example 2
[0088] Description has been given by using the sensor having the
configuration described in FIG. 2 as the conveyance sensor 23 in
Embodiment 1 to Embodiment 3 described above. However, there is no
limitation thereto. As illustrated in FIG. 17, even when the
preceding sheet S1 and the following sheet S2 are overlapped, the
leading end of the following sheet S2 may be detected by using an
ultrasonic wave sensor 40.
[0089] In FIG. 17, the ultrasonic wave sensor 40 includes a
transmission unit 38 that transmits an ultrasonic wave and a
reception unit 39 that receives the ultrasonic wave transmitted
from the transmission unit 38. The transmission unit 38 and the
reception unit 39 are disposed to hold a conveyance path of a sheet
S therebetween and the reception unit 39 receives the ultrasonic
wave that is attenuated through the sheet S. Here, by an amplitude
value of the ultrasonic wave received by the reception unit 39,
whether or not the sheet S exists between the transmission unit 38
and the reception unit 39 or how many sheets S exist therebetween
when the sheet S exists is able to be detected. That is, as
illustrated in FIG. 17, even in a state where the preceding sheet
S1 and the following sheet S2 are conveyed while the rear end of
the preceding sheet S1 and the leading end of the following sheet
S2 are overlapped, it is possible to detect a timing when the
leading end of the following sheet S2 passes between the
transmission unit 38 and the reception unit 39. The ultrasonic wave
sensor 40 is disposed between the separation nip portion 17a and
the pair of the registration rollers 3 and 4.
[0090] After the pre-feeding operation is completed and the
electromagnetic clutch 28 is turned OFF or the motor 36 is caused
to stop, an ON timing of the electromagnetic clutch 28 or a
conveyance speed by the motor 36 is changed depending on whether or
not the conveyance sensor 23 detects the sheet S2, in Embodiment 1
to Embodiment 3. In the present embodiment, the position of the
leading end of the sheet S2 is able to be determined even in a
state where the sheet S1 and the sheet S2 are overlapped. Thus, the
engine control unit 26 obtains the position of the leading end of
the sheet S2 from a timing when the ultrasonic wave sensor 40
detects the leading end of the sheet S2 during the pre-feeding and
a timing when the electromagnetic clutch 28 is turned OFF or the
motor 36 is caused to stop so that the sheet S2 is temporarily
stopped. Then, the engine control unit 26 changes a feeding
condition such as the feeding start timing of the sheet S2 or the
feeding speed thereof in accordance with the obtained position of
the leading end of the sheet S2.
[0091] In this manner, according to the configuration of the
modification example, the position of the leading end of the sheet
S2 is determined more accurately, so that it is possible to reduce
variation in the sheet interval between the sheet S1 and the sheet
S2 by finely controlling the feeding start timing of the sheet S2
or the feeding speed thereof.
[0092] As illustrated in FIG. 5, in the pre-feeding operation in
Embodiment 1 to Embodiment 3 described above, the electromagnetic
clutch 28 is turned OFF or the motor 36 is caused to stop for a
while before the rear end of the preceding sheet S1 passes through
the pick roller 15. Then, the electromagnetic clutch 28 is turned
ON or the motor 36 is caused to rotate again after the rear end of
the preceding sheet S1 passes through the pick roller 15. However,
there is no limitation thereto. The pick roller 15 and the feed
roller 16 may be continuously rotated to perform the pre-feeding
operation, without turning the electromagnetic clutch 28 OFF or
stopping the motor 36.
[0093] By continuously rotating the pick roller 15 and the feed
roller 16, for example, an effect that influence of backward
tension caused by turning the electromagnetic clutch 28 OFF is able
to be suppressed is obtained, resulting in that the conveyance
speed of the sheet S1 by the pair of the registration rollers 3 and
4 is stabilized. The electromagnetic clutch 28 is not turned OFF
during a time when the pick roller 15 and the feed roller 16 are in
contact with the sheet S1, so that states of the pick roller 15 and
the feed roller 16 are not shifted into driven states. Thus, it is
possible to prevent the conveyance speed of the sheet S1 from
changing due to occurrence of backward tension caused by influence
of the pick roller 15 and the feed roller 16.
[0094] Also in a case of executing control of Embodiment 1
described above, the configuration of Embodiment 2 (Embodiment 3)
may be adopted. That is, the electromagnetic clutch 28 may not be
arranged but the motor 36 and the motor 37 may be arranged.
[0095] Additionally, in Embodiment 1 to Embodiment 3 described
above, the separation roller 17 is used for separating one sheet S
from a plurality of sheets S, but there is no limitation thereto. A
retard roller by which one sheet S is separated from a plurality of
sheets S by rotating in a direction opposite to the feeding
direction of the sheet S may be used.
[0096] Additionally, in Embodiment 1 to Embodiment 3 described
above, the description has been given by using a feeding apparatus
that is provided in the printer 100 in a fixed manner. But there is
no limitation thereto. The disclosure may be applied to an optional
sheet feeding apparatus that is detachably attachable to the
printer 100. The optional sheet feeding apparatus includes a
control unit and has a configuration similar to the block diagram
described in FIG. 4. It may be configured that the optional sheet
feeding apparatus is not mounted with the control unit, and the
engine control unit 26 of a side of the printer 100 performs
control of each roller provided in the optional sheet feeding
apparatus.
[0097] While the present disclosure has been described with
reference to embodiments, it is to be understood that the
disclosure is not limited to the disclosed embodiments. The scope
of the following claims is to be accorded the broadest
interpretation to encompass all such modifications and equivalent
structures and functions.
[0098] This application claims the benefit of Japanese Patent
Application No. 2017-207963 filed Oct. 27, 2017, which is hereby
incorporated by reference herein in its entirety.
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