U.S. patent application number 12/729644 was filed with the patent office on 2010-09-30 for paper feeder and image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Yoshiteru Kaida.
Application Number | 20100244353 12/729644 |
Document ID | / |
Family ID | 42769540 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100244353 |
Kind Code |
A1 |
Kaida; Yoshiteru |
September 30, 2010 |
PAPER FEEDER AND IMAGE FORMING APPARATUS
Abstract
When a recording medium is not detected even after an elapse of
a predetermined period of time since a paper feeding unit fed the
recording medium, the paper feeding unit is operated, to execute an
assisting operation for assisting conveying of the recording
medium.
Inventors: |
Kaida; Yoshiteru;
(Numazu-shi, JP) |
Correspondence
Address: |
CANON U.S.A. INC. INTELLECTUAL PROPERTY DIVISION
15975 ALTON PARKWAY
IRVINE
CA
92618-3731
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
42769540 |
Appl. No.: |
12/729644 |
Filed: |
March 23, 2010 |
Current U.S.
Class: |
271/3.08 ;
271/258.03 |
Current CPC
Class: |
B65H 2511/515 20130101;
G03G 2215/00405 20130101; B65H 2511/52 20130101; B65H 2513/512
20130101; B65H 2513/51 20130101; B65H 2513/512 20130101; B65H
2513/50 20130101; G03G 2215/00721 20130101; B65H 2801/06 20130101;
B65H 2513/51 20130101; B65H 2220/01 20130101; B65H 2220/03
20130101; B65H 2220/02 20130101; B65H 2220/01 20130101; B65H
2220/02 20130101; B65H 2513/50 20130101; B65H 2404/1112 20130101;
B65H 2220/01 20130101; B65H 3/06 20130101; B65H 2511/515 20130101;
B65H 2511/52 20130101; G03G 15/6508 20130101; G03G 2215/00548
20130101; G03G 2215/00556 20130101; B65H 2511/40 20130101; B65H
2511/40 20130101; B65H 7/20 20130101 |
Class at
Publication: |
271/3.08 ;
271/258.03 |
International
Class: |
B65H 7/02 20060101
B65H007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2009 |
JP |
2009-076768 |
Claims
1. An paper feeder comprising: a feeding unit configured to execute
an operation for feeding a recording medium and then, stop the
operation; a conveyance unit configured to convey the fed recording
medium fed by the paper feeding unit; and a detection unit
configured to detect the conveyed recording medium conveyed by the
conveyance unit, wherein when the detection unit does not detect
the conveyed recording medium at a predetermined timing, the
feeding unit executes an assisting operation for assisting
conveying of the recording medium.
2. The paper feeder according to claim 1, wherein when the
detection unit does not detect the recording medium even if the
assisting operation is executed, it is determined that defective
conveyance of the recording medium has occurred and a conveying
operation is stopped.
3. The paper feeder according to claim 1, wherein when the
assisting operation is executed while the feeding unit feeds a
plurality of recording media, it is determined whether the
execution of the assisting operation is permitted depending on
whether a trailing edge of the recording medium has passed through
the feeding unit.
4. The paper feeder according to claim 1, wherein a number of times
the assisting operation is executed is set based on a length in a
conveyance direction of the recording medium and a distance in a
conveyance path from a leading edge of the recording medium that
has not been fed, to the detection unit.
5. The paper feeder according to claim 1, wherein a number of times
the assisting operation is executed is set based on a type of the
recording medium.
6. The paper feeder according to claim 1, wherein a number of times
the assisting operation is executed is set based on a degree of
wear of the feeding unit.
7. An paper feeder apparatus comprising: a feeding unit configured
to execute an operation for feeding a recording medium and then,
stop the operation; a conveyance unit configured to convey the fed
recording medium fed by the paper feeding unit; a detection unit
configured to detect the conveyed recording medium conveyed by the
conveyance unit; and an image forming unit configured to form an
image on the detected recording medium, wherein when the detection
unit does not detect the conveyed recording medium at a
predetermined timing, the feeding unit executes an assisting
operation for assisting conveying of the recording medium.
8. The paper feeder apparatus according to claim 7, wherein when
the detection unit does not detect the recording medium even if the
assisting operation is executed, it is determined that defective
conveyance of the recording medium has occurred and a conveying
operation is stopped.
9. The paper feeder apparatus according to claim 7, wherein when
the assisting operation is executed while the feeding unit feeds a
plurality of recording media, it is determined whether the
execution of the assisting operation is permitted depending on
whether a trailing edge of the recording medium has passed through
the feeding unit.
10. The paper feeder apparatus according to claim 7, wherein a
number of times the assisting operation is executed is set based on
a length in a conveyance direction of the recording medium and a
distance in a conveyance path from a leading edge of the recording
medium that has not been fed, to the detection unit.
11. The paper feeder apparatus according to claim 7, wherein a
number of times the assisting operation is executed is set based on
a type of the recording medium.
12. The paper feeder apparatus according to claim 7, wherein a
number of times the assisting operation is executed is set based on
a degree of wear of the feeding unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a paper feeder for feeding
and conveying a recording medium on which an image is to be formed,
and an image forming apparatus including the paper feeder.
[0003] 2. Description of the Related Art
[0004] In an image forming apparatus such as a printer or a copying
machine, when a printing operation is started, an operation for
feeding paper serving as a recording medium set in a paper feeding
unit is first executed. If the paper set in the paper feeding unit
is recycled paper, defective paper feeding is more likely to occur
as compared with high quality paper (plain paper) because the
recycled paper has worse conveyance properties. When a paper
feeding roller for performing a paper feeding operation is worn-out
and is coming to the end of its life, defective paper feeding is
also likely to occur. The defective paper feeding means that paper
is not correctly fed even if a conveyance roller performs an
operation for feeding the paper.
[0005] A technique for improving such defective paper feeding is
proposed in Japanese Patent Application Laid-Open No. 11-334935,
for example. In Japanese Patent Application Laid-Open No.
11-334935, when defective paper feeding occurs, a retrying
operation for driving a paper feeding roller again is executed to
recover the defective paper feeding, to significantly reduce the
number of times of occurrence of a paper jam (also referred to as
jam) caused by the defective paper feeding.
[0006] The above-mentioned recycled paper not only has worse
conveyance properties but also more easily creates paper dust than
the high quality paper. When the paper contacts the paper feeding
roller and a conveyance path when conveyed, the paper wears out, so
that fine paper dust is created. When the conveyance roller further
conveys the paper fed by the paper feeding roller from the paper
feeding unit, a conveyance force of the paper is reduced if the
paper dust adheres to the conveyance roller. Immediately after the
paper is fed, back tension is applied due to the friction of a
separation unit (e.g., a separating pad) for separating a plurality
of papers set in the paper feeding roller or the paper feeding
unit. Therefore, the conveyance force of the paper by the
conveyance roller is further reduced, so that the paper cannot be
conveyed and may be jammed.
[0007] In order to improve the conveyance force, a conveyance
roller can be added, then pressure for nipping paper in a
conveyance roller is increased. If the conveyance roller is added,
however, the cost increases. If the pressure for nipping the paper
is increased, the paper is liable to form wrinkles although the
conveyance force is improved.
SUMMARY OF THE INVENTION
[0008] According to an aspect of the present invention, an
apparatus includes a feeding unit configured to execute an
operation for feeding a recording medium and then, stop the
operation, a conveyance unit configured to convey the fed recording
medium, and a detection unit configured to detect the conveyed
recording medium, in which when the detection unit does not detect
the recording medium at a predetermined timing, the feeding unit
executes an assisting operation for assisting conveying of the
recording medium.
[0009] Further features and aspects of the present invention will
become apparent from the following detailed description of
exemplary embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate exemplary
embodiments, features, and aspects of the invention and, together
with the description, serve to explain the principles of the
invention.
[0011] FIG. 1 is a schematic view of a laser beam printer according
to an exemplary embodiment.
[0012] FIG. 2 is a block diagram illustrating the configuration of
a control system for controlling each unit in the laser beam
printer illustrated in FIG. 1.
[0013] FIG. 3 is a block diagram within a paper feeding control
unit illustrated in FIG. 2.
[0014] FIG. 4 is a flowchart illustrating paper feeding control
according to a first exemplary embodiment.
[0015] FIG. 5 is a flowchart illustrating paper feeding control
according to a second exemplary embodiment.
[0016] FIG. 6 is a schematic view of an option cassette in a third
exemplary embodiment.
DESCRIPTION OF THE EMBODIMENTS
[0017] Various exemplary embodiments, features, and aspects of the
invention will be described in detail below with reference to the
drawings.
[0018] The configuration and the operations of a laser beam printer
according to a first exemplary embodiment will be described in
detail.
[0019] In the first exemplary embodiment, it is detected that a
conveyance force by a conveyance roller for conveying a fed
recording medium is reduced, and conveyance assist control is
executed to assist the conveyance. When the recording medium is not
normally conveyed even if the conveyance assist control is
executed, it is determined that a paper jam (also referred to as
jam) is occurring due to a factor other than the reduction in the
conveyance force. The details of the operations will be described
below.
[0020] FIG. 1 is a schematic view of a laser beam printer 1
according to the present exemplary embodiment, illustrating a main
body of the laser beam printer 1 and a paper feeder for feeding
paper serving as a recording medium.
[0021] The main body of the laser beam printer 1 includes a
photosensitive drum 110 for forming an image. A charging roller 109
for uniformly charging a surface of the photosensitive drum 110, a
developing roller 108 for developing an electrostatic latent image
formed on the photosensitive drum 110, and a transfer roller 107
for transferring a developed image on the recording medium are
arranged around the photosensitive drum 110. The main body of the
laser beam printer 1 further includes a scanner unit 113 and a
mirror 112 as an exposure unit for forming the electrostatic latent
image on the photosensitive drum 110.
[0022] As illustrated in FIG. 2, an engine control unit 201 that
has received printing information from a printer controller 200
instructs a paper conveyance control unit 203 to convey the
recording medium.
[0023] First, when a paper feeding solenoid 100 (only a flapper of
the solenoid is illustrated in FIG. 1) in a main body cassette 10
serving as a conveyance unit in the main body is pulled, a paper
feeding roller 101 starts to feed the recording medium. The
recording medium is conveyed to a conveyance path 140 via a
conveyance roller pair 102.
[0024] The recording medium that has been conveyed by the
conveyance roller pair 102 and roller pair 104 is then conveyed to
a transfer nip portion including the photosensitive drum 110 and
the transfer roller 107 after passing through a sensor 105 and a
paper width sensor 106. When the sensor 105 detects the leading
edge of the recording medium, the paper width sensor 106 starts to
measure the length of the recording medium. When the sensor 105
detects the trailing edge of the recording medium, the paper width
sensor 106 finishes measuring the length, to obtain the length of
the recording medium using a period of time elapsed from the
leading edge to the trailing edge of the recording medium divided
by the conveyance speed of the recording medium.
[0025] A paper width sensor (not illustrated) detects the size (the
width) in a direction perpendicular to a conveyance direction of
the recording medium. The size (the length and the width) of the
recording medium may be previously set if it is a standard size
(A3, A4, Letter, B5, etc.).
[0026] In the transfer nip portion including the photosensitive
drum 110 and the transfer roller 107, the image is transferred onto
the recording medium.
[0027] The recording medium then passes through a fixing device
119. The fixing device 119 includes a heater 118 that has been
heated, a thermistor 117 for detecting the temperature of the
heater 118, a fixing film 116 for conducting heat, and a pressure
roller 115 for applying pressure to the recording medium. The
recording medium passes through a fixing nip portion including the
fixing film 116 and the pressure roller 115 so that the image is
fixed on the recording medium. The recording medium on which the
image has been fixed is conveyed to a conveyance path 141 via a
conveyance roller pair 120.
[0028] In the case of one-sided printing, a paper discharge roller
122 conveys the recording medium and discharges the recording
medium out of the printer 1. In the case of two-sided printing, a
two-sided printing motor starts to rotate in a backward direction
after the trailing edge of the recording medium has passed through
the conveyance roller pair 120. The recording medium in the
conveyance path 141 is conveyed to a two-sided conveyance path 142
by the conveyance roller pair 120 that rotates in a backward
direction to do printing on its second surface, and a two-sided
conveyance roller pair 131.
[0029] The conveyance roller pair 120 includes three conveyance
rollers, and is rotatable in a driving direction (forward
direction) to discharge the recording medium and in a driving
direction (backward direction) to convey the recording medium to
the two-sided conveyance path 142. The two-sided conveyance path
142 includes a regulating plate (not illustrated) that is operated
using one side of the conveyance path as a basis. The regulating
plate regulates a position in the direction perpendicular to the
conveyance direction of the recording medium that is conveyed to
the conveyance path 142.
[0030] The recording medium is conveyed to the conveyance path 140
again via the conveyance roller pair 133. In the transfer nip
portion including the photosensitive drum 110 and the transfer
roller 107, the image is transferred onto the second surface of the
recording medium. The fixing device 119 fixes the image on the
recording medium again, and the paper discharge roller pair 122
discharges the recording medium out of the printer 1.
[0031] Option cassettes 15 and 16 are removably mounted on the
laser beam printer 1. When the recording medium is fed from the
option cassette 15, the recording medium is fed by a paper feeding
roller 151, and is conveyed to the conveyance path 140 via a
conveyance roller pair 152 and the conveyance roller pair 102. When
the recording medium is fed from the option cassette 16, the
recording medium is fed by a paper feeding roller 161, and is
conveyed to the conveyance path 140 via a conveyance roller pair
162, the conveyance roller pair 152, and the conveyance roller pair
102. Operations performed after the recording medium has been
conveyed to the conveyance path 140 are similar to the
above-mentioned operations and hence, the description thereof is
not repeated.
[0032] FIG. 2 is a block diagram illustrating the configuration of
a control system for controlling each of the units in the laser
beam printer 1 illustrated in FIG. 1. In FIG. 2, the printer
controller 200 includes a microcomputer serving as a control unit,
and rasterizes information sent from an external apparatus such as
a host computer into bit data to do printing by the printer 1. The
printer controller 200 has the function of reading internal
information of the printer 1 in communication and displaying the
internal information.
[0033] The engine control unit 201 includes a microcomputer
containing a read-only memory (ROM) and a random access memory
(ROM) (not illustrated), sends and receives information to and from
the printer controller 200 by serial communication, and controls
the operation of each unit in the printer 1 according to an
instruction from the printer controller 200. The engine control
unit 201 further sends (reports) the internal information of the
printer 1 to the printer controller 200.
[0034] A paper feeding control unit 202 controls the driving of the
paper feeding roller 101 for feeding the recording medium and the
rotation and the stop of the conveyance roller pair 102 according
to an instruction from the engine control unit 201.
[0035] The paper conveyance control unit 203 controls the
operations of the photosensitive drum 110, the transfer roller 107,
the pressure roller 115, and the paper discharge roller 122 for
conveying the recording medium that has been fed to reach the
conveyance path 140 to a paper discharge port according to the
instruction from the engine control unit 201.
[0036] A high-voltage control unit 204 controls a high-voltage
output during each of image forming operations such as charging,
development, and transfer based on the instruction from the engine
control unit 201.
[0037] An optical system control unit 205 controls the driving and
the stop of a scanner motor (not illustrated) within the scanner
unit 113 and the lighting of a laser according to the instruction
from the engine control unit 201.
[0038] A sensor input unit 206 sends information from a paper
presence/absence sensor (not illustrated), the sensor 105, the
paper width sensor 106, and a paper discharge sensor 114 to the
engine control unit 201.
[0039] A temperature control unit 207 adjusts the temperature of
the fixing unit 119 to a temperature designated by the engine
control unit 201.
[0040] A two-sided conveyance unit control unit 208 controls a
two-sided conveyance unit 130 according to the instruction from the
engine control unit 201.
[0041] FIG. 3 is a block diagram illustrating the internal
configuration of the paper feeding control unit 202.
[0042] A paper feeding control unit 301 manages and controls the
respective paper feeding rollers 151 and 161 and the respective
conveyance roller pairs 152 and 162 in the option cassettes 15 and
16, and a paper delay detection unit 302.
[0043] The paper delay detection unit 302 detects whether the fed
recording medium is detected by respective conveyance path sensors
153 and 163 in the option cassettes 15 and 16 within a
predetermined period of time elapsed since it was detected by the
conveyance path sensors 153 and 163.
[0044] A paper feeding roller driving unit 303 drives a paper
feeding solenoid 150 (FIG. 1), to rotate the paper feeding roller
151 one revolution.
[0045] A conveyance roller driving unit 304 controls the driving
and the stop of the conveyance roller pair 152.
[0046] A conveyance path sensor detection unit 305 detects the
presence or absence of the recording medium using the conveyance
path sensor 153.
[0047] A paper feeding roller driving unit 306 drives a paper
feeding solenoid 160 (FIG. 1), to rotate the paper feeding roller
161 one revolution.
[0048] A conveyance roller driving unit 307 controls the driving
and the stop of the conveyance roller pair 162.
[0049] A conveyance path sensor detection unit 308 detects the
presence or absence of the recording medium using the conveyance
path sensor 163.
[0050] The characteristic operations and processing of the laser
beam printer 1 according to the present exemplary embodiment will
be described with reference to FIG. 4. FIG. 4 is a flowchart
illustrating control for executing an operation for assisting a
conveying operation (hereinafter referred to as a conveyance assist
control) when a recording medium is fed from the option cassette
16.
[0051] In step 400, if the printer controller 200 instructs the
engine control unit 201 to feed the recording medium from the
option cassette 16 and make a print, the engine control unit 201
starts to feed the recording medium from the option cassette
16.
[0052] In step 401, the engine control unit 201 also starts to
drive the respective conveyance roller pairs 152 and 162 in the
option cassettes 15 and 16 according to the instruction.
[0053] In step 402, the engine control unit 201 drives the paper
feeding roller 161 in the option cassette 16 to make one revolution
so that the recording medium is fed.
[0054] In step 403, the engine control unit 201 waits until the
recording medium reaches the conveyance path sensor 163 in the
option cassette 16. If the recording medium has reached the
conveyance path sensor 163 in the option cassette 16 (YES in step
403), then in step 404, the engine control unit 201 starts counting
of a timer (not illustrated).
[0055] In step 405, the engine control unit 201 waits until the fed
recording medium reaches the conveyance path sensor 153 in the
option cassette 15.
[0056] If the recording medium has reached the conveyance path
sensor 153 in the option cassette 15 (YES in step 405), then in
step 406, the engine control unit 201 determines that the recording
medium has been normally conveyed, and continues to perform the
conveying operation and the subsequent printing operation. On the
other hand, if the recording medium has not reached the conveyance
path sensor 153 in the option cassette 15 (NO in step 405), then in
step 407, the engine control unit 201 determines whether a
predetermined period of time has elapsed since the timer started
counting. If the predetermined period of time has elapsed, the
engine control unit 201 determines that the conveyance roller 162
in the option cassette 16 lacks a conveyance force.
[0057] This predetermined period of time is calculated from "((the
distance from the conveyance path sensor 163 to the conveyance path
sensor 153)+(margin))/(conveyance speed)". The margin is set to 50
mm in the present exemplary embodiment. The margin can be set, as
needed, based on conveyance variations allowed in the printer 1,
for example, the conveyance speed of the recording medium and the
configuration of the conveyance path.
[0058] If the predetermined period of time has elapsed (YES in step
407), then in step 408, the engine control unit 201 confirms
whether the conveyance assist control is executed a predetermined
number of times.
[0059] If the conveyance assist control has been executed the
predetermined number of times (YES in step 408), then in step 409,
the engine control unit 201 determines that a jam is occurring, and
stops the printing operation. This jam represents defective
conveyance in which the recording medium still does not reach the
conveyance sensor 153 even if an assisting operation to control the
conveyance assist is executed. If the conveyance assist control has
been executed less than the predetermined number of times (NO in
step 408), then in step 410, the engine control unit 201 causes the
paper feeding roller 161 in the option cassette 16 to make one
revolution, to assist conveying of the recording medium.
[0060] Then, the processing is returned to step 404. In step 404,
the engine control unit 201 waits until the recording medium
reaches the conveyance path sensor 153.
[0061] In the present exemplary embodiment, if the recording medium
does not reach the conveyance path sensor 153 after an elapse of
the predetermined period of time, the conveyance assist control for
assisting conveying of the recording medium is executed.
[0062] While for each conveyance assist control executed in the
present exemplary embodiment, the paper feeding roller 161 is set
to make one revolution, the number of revolutions of the paper
feeding roller 161 is not limited to one. The number of revolutions
can be variably set according to the length of the conveyance path
and the type of the recording medium. When the conveyance path to
the conveyance roller on the downstream side is long, for example,
the number of revolutions may be set to two. When the type of the
recording medium is recycled paper, and the grammage (thickness)
thereof is high, the number of revolutions may be set to two. In
the present exemplary embodiment, the number of times the
conveyance assist control is executed (the above-mentioned
predetermined number of times) is set to two.
[0063] While in the present exemplary embodiment, the recording
medium is fed from the option cassette 16, the recording medium may
also be fed from the main body cassette 10 and the option cassette
15. When the recording medium is fed from the option cassette 15,
it is checked whether the recording medium reaches a conveyance
sensor 103. If the recording medium has not reached the conveyance
sensor 103 even after an elapse of the predetermined period of
time, the conveyance roller pair 152 may execute the conveyance
assist control.
[0064] As described above, according to the present exemplary
embodiment, when the conveyance roller 162 lacks the conveyance
force, an assisting operation for assisting the lack of the
conveyance force is executed in a low-cost configuration without
changing the conventional configuration. This enables a reduction
in the occurrence of the jam in the recording medium. A jam due to
a factor other than the lack of the conveyance force can be
detected, as in the conventional example.
[0065] The configuration and the operations of an image forming
apparatus according to a second exemplary embodiment will be
described in detail.
[0066] In the above-mentioned first exemplary embodiment, the
conveyance assist control for the recording medium whose conveyance
force is insufficient has been described. The present exemplary
embodiment differs from the first exemplary embodiment in an
operation performed when conveyance assist control is executed
while a plurality of recording media is set in a cassette to do
continuous printing.
[0067] When the conveyance assist control is executed while the
continuous printing (continuous paper feeding) is performed, if the
trailing edge of the recording medium to be subjected to the
conveyance assist control has passed through a paper feeding
roller, the subsequent recording medium may be erroneously fed. In
the present exemplary embodiment, an operation for preventing the
subsequent recording medium from being erroneously fed when the
conveyance assist control is executed while the continuous paper
feeding is performed will be described in detail.
[0068] The configuration of the image forming apparatus, the
configuration of a control block for controlling the image forming
apparatus, and the configuration of a control block for a paper
feeding control unit according to the present exemplary embodiment
are similar to those in the first exemplary embodiment and hence,
the description thereof is not repeated.
[0069] The present exemplary embodiment will be described with
reference to FIG. 5. FIG. 5 is a flowchart illustrating conveyance
assist control in continuously feeding a plurality of recording
media from an option cassette 15 and determination whether the
conveyance assist control is executed. In FIG. 5, steps in common
with those in the first exemplary embodiment are assigned the same
step numbers 400 to 409 and hence, the description thereof is not
repeated.
[0070] If the conveyance assist control is executed less than a
predetermined number of times (NO in step 408), then in step 510,
an engine control unit 201 determines whether the trailing edge of
the recording medium to be subjected to the conveyance assist
control has passed through a conveyance path sensor 163.
[0071] If the trailing edge of the recording medium to be subjected
to the conveyance assist control has passed through the conveyance
path sensor 163 (YES in step 510), then in step 409, the conveyance
assist control is not executed because the recording medium to be
subjected to the conveyance assist control has passed through a
paper feeding roller 161 even if the paper feeding roller 161 is
driven, and it is determined that a jam has occurred. If the
trailing edge of the recording medium to be subjected to the
conveyance assist control has not passed through the conveyance
path sensor 163 (NO in step 510), then in step 511, the conveyance
assist control is executed, to drive a conveyance roller pair 162
and the paper feeding roller 161.
[0072] In the conveyance assist control in the present exemplary
embodiment, assisting of conveyance is controlled by rotating the
paper feeding roller 161, similarly to the conveyance assist
control described in the first exemplary embodiment.
[0073] While in the present exemplary embodiment, the recording
medium is fed from the option cassette 16, the recording medium may
also be fed from a main body cassette 10 and an option cassette 15.
When the recording medium is fed from the option cassette 15, it is
checked whether the recording medium reaches a conveyance sensor
103. If the recording medium has not reached the conveyance sensor
103 even after an elapse of a predetermined period of time, a
conveyance roller pair 152 may execute the conveyance assist
control. By checking whether the trailing edge of the recording
medium has passed through a paper feeding roller 151, it can be
similarly determined whether the execution of the conveyance assist
control is permitted.
[0074] As described in the foregoing, according to the present
exemplary embodiment, when the conveyance assist control is
executed while the plurality of recording media is continuously
fed, the subsequent recording medium to be subjected to the
conveyance assist control can be prevented from being erroneously
fed. The occurrence of a jam in the recording medium due to the
lack of a conveyance force can be reduced in a low-cost
configuration without changing the conventional configuration, as
in the first exemplary embodiment. A jam caused by a factor other
than the lack of the conveyance force can be detected, as in the
conventional example.
[0075] The configuration and the operations of an image forming
apparatus according to a third exemplary embodiment will be
described below in detail.
[0076] The conveyance assist control has been described in the
first exemplary embodiment, and the conveyance assist control
during the continuous paper feeding and the determination whether
the execution of the conveyance assist control is permitted have
been described in the second exemplary embodiment. The third
exemplary embodiment differs from the first and second exemplary
embodiments in that the number of times conveyance assist control
is executed is variably set.
[0077] The configuration of the image forming apparatus according
to the present exemplary embodiment, the configuration of a control
block for controlling the image forming apparatus, and the
configuration of a control block for a paper feeding control unit
are similar to those in the first exemplary embodiment and hence,
the description thereof is not repeated.
[0078] The present exemplary embodiment will be described with
reference to FIG. 6. FIG. 6 is a schematic view of option cassettes
15 and 16, illustrating the conveyance distance of a recording
medium in a conveyance path. FIG. 6 illustrates a distance L1 from
the position of the leading edge of the recording medium set in a
paper feeding tray to a conveyance path sensor 163, a distance L2
from the conveyance path sensor 163 to a conveyance path sensor
153, a distance Lpap that is the length of the recording medium set
in a cassette (the length in a conveyance direction of the
recording medium), and a distance Lpick at which a paper feeding
roller 161 contacts a surface of the recording medium when it makes
one revolution.
[0079] The conveyance assist control in the present exemplary
embodiment is similar to those in the flowcharts illustrated in
FIGS. 5 and 6 described in the first and second exemplary
embodiments and hence, the description thereof is not repeated.
[0080] In the present exemplary embodiment, the number of times the
conveyance assist control is executed is variably set based on the
length in the conveyance direction of the recording medium and the
distance thereof in the conveyance path.
[0081] N is a number of times the conveyance assist control is
executed. The number of times N can be set according to the
following conditions 1, 2, and 3 relating to the length Lpap in the
conveyance direction of the recording medium, the conveyance
distances (L1 and L2) of the recording medium, and the position of
the trailing edge of the recording medium:
[0082] Condition 1: "Lpap<L1" (the trailing edge of the
recording medium has passed through the paper feeding roller 161 at
timing of the conveyance assist control)
[0083] Condition 2: "L1<Lpap<(L1+L2)" (it is unclear whether
the trailing edge of the recording medium has passed through the
paper feeding roller 161 at timing of the conveyance assist
control)
[0084] Condition 3: "(L1+L2)<Lpap" (the trailing edge of the
recording medium has not passed through the paper feeding roller
161 at timing of the conveyance assist control)
[0085] The number of times N the conveyance assist control is
executed for each of the conditions 1 to 3 will be described
below.
[0086] Under the condition 1, the number of times N the conveyance
assist control is executed is set to zero. At the timing of the
conveyance assist control, the trailing edge of the recording
medium has already passed through the paper feeding roller 161.
When the conveyance assist control is executed, therefore, the
subsequent recording medium is erroneously fed.
[0087] Under the condition 2, it is unclear whether the trailing
edge of the recording medium has passed through the paper feeding
roller 161. Therefore, it is determined whether "prevention of a
jam by the conveyance assist control" or "erroneous feeding of the
subsequent recording medium" should be selected. The number of
times N the conveyance assist control is executed is decided based
on the determination. For example, when a recording medium of a
type having bad conveyance properties has passed or when the number
of copies to be printed is increased so that it is likely that dirt
adheres to a conveyance roller, "prevention of a jam by the
conveyance assist control" is given priority, and the number of
times N is set to one. In the other cases, "erroneous feeding of
the subsequent recording medium" is given priority, and the number
of times N is set to zero.
[0088] Under the condition 3, the trailing edge of the recording
medium has not passed through the paper feeding roller 161, and the
number of times N the conveyance assist control is executed is
determined by the following equation:
N=(Lpap-(L1+L2)/Lpick+1 (1)
[0089] Although in the present exemplary embodiment, the recording
medium is fed from the option cassette 16, the number of times N
the conveyance assist control is executed may be set by the length
of the recording medium and the distance thereof in the conveyance
path when the recording medium is fed from each of the main body
cassette 10 and the option cassette 15.
[0090] As described above, according to the present exemplary
embodiment, the optimum number of times the conveyance assist
control is executed can be determined based on the length in the
conveyance direction of the recording medium and the conveyance
distance thereof in the conveyance path. The occurrence of a jam in
the recording medium due to the lack of a conveyance force can be
reduced in a low-cost configuration without changing the
conventional configuration, as in the first exemplary embodiment. A
jam caused by a factor other than the lack of the conveyance force
can be detected, as in the conventional example. When the
conveyance assist control is executed while a plurality of
recording media is continuously fed, the subsequent recording
medium to be subjected to the conveyance assist control can be
prevented from being erroneously fed, as in the second exemplary
embodiment.
[0091] The other exemplary embodiments will be then described.
[0092] In addition to the control described in the first to third
exemplary embodiments, it is also possible to switch the number of
times conveyance assist control is executed in consideration of the
type of paper and the degree of wear of a paper feeding roller, for
example.
[0093] For example, it is possible to switch the number of times
the conveyance assist control is executed between when the paper is
plain paper and when it is thick paper having a higher grammage
(weight per unit area) than the plain paper. As an example, the
number of times the conveyance assist control is executed can be
set to two for the plain paper, while the number of times is set to
three for the thick paper. A more conveyance force is applied for
the thick paper than for the plain paper. When the thick paper and
the plain paper are conveyed in a similar way, the conveyance
properties of the thick paper tend to be worse than those of the
plain paper. Therefore, the number of times the conveyance assist
control is executed is set larger for the thick paper than for the
plain paper. It is also effective to predict the degree of wear of
the paper feeding roller from the number of copies to print and
gradually increase the number of times the conveyance assist
control is executed as the cumulative number of copies to print
increases. For example, by counting the cumulative number of copies
to be printed, the number of times the conveyance assist control is
executed can be gradually switched to two when it is 0 to 5000,
three when 5001 to 10000, and four when it is 10001 or more.
[0094] The number of times the conveyance assist control is
executed can be more appropriately set and switched when thus the
number of times is switched in consideration of the type of the
paper and the degree of wear of the paper feeding roller.
[0095] While in the plurality of exemplary embodiments described
above, the paper feeding roller is in a D-cut shape, the conveyance
assist control is similarly applicable to a configuration in which
paper feeding rollers abut on and separate from each other to
perform feeding. In this case, when it is determined that a
conveyance roller lacks a conveyance force, for example, conveyance
assist control can be executed which drives paper feeding rollers
for a predetermined period of time while abutting on each
other.
[0096] 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 modifications, equivalent
structures, and functions.
[0097] This application claims priority from Japanese Patent
Application No. 2009-076768 filed Mar. 26, 2009, which is hereby
incorporated by reference herein in its entirety
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