U.S. patent application number 12/111347 was filed with the patent office on 2008-11-13 for duplex image forming apparatus with feeding roller with at least three different speeds.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Masaya Arakawa, Kazumasa YASUI.
Application Number | 20080277865 12/111347 |
Document ID | / |
Family ID | 36970005 |
Filed Date | 2008-11-13 |
United States Patent
Application |
20080277865 |
Kind Code |
A1 |
YASUI; Kazumasa ; et
al. |
November 13, 2008 |
DUPLEX IMAGE FORMING APPARATUS WITH FEEDING ROLLER WITH AT LEAST
THREE DIFFERENT SPEEDS
Abstract
The present invention has been made to provide an image forming
apparatus capable of suppressing occurrence of a problem caused by
misalignment of the feeding speed at the time of delivery and
receipt in the intermediate feeding roller with a simple
configuration without increasing cost. The image forming apparatus
according to the present invention comprises a drive controller 101
that controls the drive speed of an intermediate feeding roller 38
that feeds a sheet to a regist roller 37 that performs skew
correction for the sheet, and a feeding speed information
acquisition section 102 that acquires information relating to the
feeding speed of the sheet to be fed to the intermediate feeding
roller 38. The drive controller 101 drives the intermediate feeding
roller 38 at least three different speeds based on the information
relating to the feeding speed acquired by the feeding speed
information acquisition section 102.
Inventors: |
YASUI; Kazumasa;
(Arakawa-ku, JP) ; Arakawa; Masaya; (Kanagawa-ken,
JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
TOSHIBA TEC KABUSHIKI KAISHA
|
Family ID: |
36970005 |
Appl. No.: |
12/111347 |
Filed: |
April 29, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11260387 |
Oct 28, 2005 |
7370863 |
|
|
12111347 |
|
|
|
|
Current U.S.
Class: |
271/226 ;
270/1.01; 271/10.13 |
Current CPC
Class: |
B65H 2513/10 20130101;
B65H 2404/7231 20130101; B65H 2301/512125 20130101; B65H 2513/10
20130101; B65H 2220/02 20130101; B65H 2220/01 20130101; B65H
2220/02 20130101; B65H 2220/01 20130101; B65H 9/106 20130101; B65H
9/006 20130101; B65H 2513/10 20130101; B65H 9/14 20130101; B65H
7/00 20130101 |
Class at
Publication: |
271/226 ;
271/10.13; 270/1.01 |
International
Class: |
B65H 9/16 20060101
B65H009/16 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2005 |
JP |
2005-68014 |
Claims
1. An image forming apparatus, comprising: a drive controller that
controls the drive speed of an intermediate feeding roller that
feeds a sheet to a regist roller that performs skew correction for
the sheet; and a feeding speed information acquisition section that
acquires information relating to the feeding speed of the sheet to
be fed to the intermediate feeding roller, wherein the drive
controller drives the intermediate feeding roller at least three
different speeds based on the information acquired by the feeding
speed information acquisition section, the at least three different
speeds including a first speed at which a sheet passes a sheet
feeding path having a first curvature and a second speed at which a
sheet passes another sheet feeding path having a second curvature
lower than the first curvature, and the drive controller controls
the intermediate feeding roller such that the first speed becomes
lower than the second speed.
2. The image forming apparatus according to claim 1, wherein the
intermediate feeding roller is driven by a pulse motor.
3. The image forming apparatus according to claim 1, wherein the
motive force for driving a feeding roller that supplies the
intermediate feeding roller with a sheet is transferred by a
clutch.
4. An image forming apparatus, comprising: a drive controller that
controls the drive speed of an intermediate feeding roller that
feeds a sheet to a regist roller that performs skew correction for
the sheet; and a feeding speed information acquisition section that
acquires information relating to the feeding speed of the sheet to
be fed to the intermediate feeding roller, wherein the drive
controller drives the intermediate feeding roller at least three
different speeds based on the information acquired by the feeding
speed information acquisition section, the at least three different
speeds including a first speed at which a sheet passes a sheet
feeding path having a first curvature and a second speed at which a
sheet passes another sheet feeding path having a second curvature
lower than the first curvature, and a third speed at which a sheet
is passed through the regist roller and a toner image is formed
thereon, and the drive controller controls the intermediate feeding
roller such that the first speed becomes higher than the third
speed.
5. The image forming apparatus according to claim 4, wherein the
intermediate feeding roller is driven by a pulse motor.
6. The image forming apparatus according to claim 4, wherein the
motive force for driving a feeding roller that supplies the
intermediate feeding roller with a sheet is transferred by a
clutch.
7. An image forming apparatus according to claim 4, wherein the
drive controller controls the intermediate feeding roller such that
the first speed becomes lower than the second speed.
8. An image forming method, comprising: controlling the drive speed
of an intermediate feeding roller that feeds a sheet to a regist
roller that performs skew correction for the sheet; and acquiring
information relating to the feeding speed of the sheet to be fed to
the intermediate feeding roller, wherein the controlling step
drives the intermediate feeding roller at least three different
speeds based on the information acquired by the acquiring step, the
at least three different speeds including a first speed at which a
sheet passes a sheet feeding path having a first curvature and a
second speed at which a sheet passes another sheet feeding path
having a second curvature lower than the first curvature, and
wherein the intermediate feeding roller is controlled such that the
first speed becomes lower than the second speed.
9. The image forming method of claim 8, wherein the third speed is
a speed at which a sheet is passed through the regist roller and a
toner image is formed thereon, and the controlling step controls
the intermediate feeding roller such that the first speed becomes
higher than the third speed.
10. The image forming method according to claim 8, wherein the
intermediate feeding roller is driven by a pulse motor.
11. The image forming method according to claim 8, wherein the
motive force for driving a feeding roller that supplies the
intermediate feeding roller with a sheet is transferred by a
clutch.
12. An image forming method, comprising: controlling the drive
speed of an intermediate feeding roller that feeds a sheet to a
regist roller that performs skew correction for the sheet; and
acquiring information relating to the feeding speed of the sheet to
be fed to the intermediate feeding roller, wherein the controlling
step drives the intermediate feeding roller at least three
different speeds based on the information acquired by the acquiring
step, the at least three different speeds including a first speed
at which a sheet passes a sheet feeding path having a first
curvature, a second speed at which a sheet passes another sheet
feeding path having a second curvature lower than the first
curvature, and a third speed at which a sheet is passed through the
regist roller and a toner image is formed thereon, and the
controlling step controls the intermediate feeding roller such that
the first speed becomes higher than the third speed.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is continuation of U.S. application
Ser. No. 11/260,387, filed Oct. 28, 2005, the entire contents of
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an image forming apparatus
that forms an image on a sheet to be supplied and, more
particularly, to control of the drive speed of an intermediate
feeding roller that feeds a sheet to a regist roller.
[0004] 2. Description of the Related Art
[0005] In an image forming apparatus, an intermediate feeding
roller that feeds a sheet to a regist roller (roller that performs
skew correction or timing adjustment for a sheet being fed) has
roles of performing sheet feeding operation at the time when an
image is formed onto the sheet in cooperation with the regist
roller and receiving a sheet supplied from a sheet supply cassette
or sheet, onto the first surface of which an image has already been
formed, fed for image forming on the second surface thereof (fed
for duplex printing).
[0006] It is preferable that the sheet feeding speed of the
intermediate feeding roller having the above roles be synchronized
with the sheet feeding speed of a feeding roller or regist roller
which is a partner for the sheet feeding operation. The sheet
feeding speed with which the intermediate feeding roller should be
synchronized includes a sheet supply speed (speed at which a sheet
supplied from the cassette is fed to the regist roller), a process
speed (sheet feeding speed when a sheet is fed through the regist
roller at the time of toner image forming) and an ADU speed
(feeding speed of a sheet to be resupplied for image forming onto
the second surface thereof).
[0007] As a method for allowing the intermediate feeding roller to
realize a plurality of different sheet feeding speeds, one in which
a pulse motor is used a lot for the drive of feeding rollers that
perform sheet feeding in an apparatus and one in which a plurality
of clutch mechanisms are used for them can be taken. However, these
methods may increase cost.
[0008] Further, even in the configuration in which the clutch
mechanism is adopted to drive the intermediate feeding roller, only
two different sheet feeding speeds have been realized so far (refer
to, for example, Jpn. Pat. Appln. Laid-Open Publication No.
2001-130811).
[0009] In recent years, in order to increase sheet feeding
efficiency, intervals between sheets tend to be short in the sheet
feeding operation in which a plurality of sheets are sequentially
fed. It is difficult to perform connection or stop of the clutch
mechanism at a fraction of the time while performing the sequential
sheet feeding operation with short sheet interval as described
above. Further, misalignment in the feeding speed at the time of
delivery and receipt of the sheet between rollers or the like may
cause roller surface wear and sheet jamming.
SUMMARY OF THE INVENTION
[0010] The present invention has been made to solve the above
problem, and an object thereof is to provide an image forming
apparatus capable of suppressing occurrence of a problem caused by
misalignment of the feeding speed at the time of delivery and
receipt in the intermediate feeding roller with a simple
configuration without increasing cost.
[0011] To solve the above problem, according to an aspect of the
present invention, there is provided an image forming apparatus
comprising: a drive controller that controls the drive speed of an
intermediate feeding roller that feeds a sheet to a regist roller
that performs skew correction for the sheet; and a feeding speed
information acquisition section that acquires information relating
to the feeding speed of the sheet to be fed to the intermediate
feeding roller, wherein the drive controller drives the
intermediate feeding roller at least three different speeds based
on the information relating to the feeding speed acquired by the
feeding speed information acquisition section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view showing the entire
configuration of an image forming apparatus according to an
embodiment of the present invention;
[0013] FIG. 2 is a view for explaining a sheet feeding operation at
the portion in front of a regist roller and shows the area
surrounded by the dotted line in FIG. 1 in an enlarged manner;
[0014] FIG. 3 is a block diagram for explaining the functional
configuration of the image forming apparatus according to the
embodiment;
[0015] FIG. 4 is a timing chart showing sheet feeding timing at the
time when duplex printing is performed for A4 size sheet and A3
size sheet;
[0016] FIG. 5 is a view for explaining a sheet feeding path in the
image forming apparatus according to the embodiment; and
[0017] FIG. 6 is a timing chart showing drive timing of a regist
roller 37, intermediate feeding roller 38, and feeding rollers
other than the intermediate feeding roller 38 in the image forming
apparatus according to the embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] An embodiment of the present invention will be described
below with reference to the accompanying drawings.
[0019] FIG. 1 is a cross-sectional view showing the entire
configuration of an image forming apparatus according to an
embodiment of the present invention.
[0020] An image forming apparatus according to the embodiment of
the present invention includes: cassettes 31, 32, 33, 34 in which
sheets are stacked; pick-up rollers 31b, 32b, 33b, 34b for picking
up the sheets; sheet supply rollers 31a, 32a, 33a, 34a and
separating rollers 31c, 32c, 33c, 34c for feeding the sheets while
separating them one by one; a sheet feeding path 35; feeding
rollers 36a to 36d (motive energy for which is transferred by a
clutch) for feeding the sheet from the sheet feeding path 35 to an
intermediate feeding roller 38; an ADU (Automatic Duplexing Unit)
5; feeding rollers 5a to 5d (motive energy for which is transferred
by a clutch) for feeding the sheet in the ADU 5; an intermediate
feeding roller 38 driven by a pulse motor; a regist roller 37 for
performing skew correction and timing adjustment for the sheet; a
photoconductor drum 20 that forms a toner image onto the sheet; a
fixing section 24 that fixes the formed toner image to the sheet; a
reverse feeding path 28 to which the sheet onto which the toner
image has been fixed is guided; reverse rollers 29, 30 for feeding
the sheet that has been introduced in the reverse feeding path 28
in a switchback manner; a CPU 108; and a memory 109.
[0021] The following processing is performed in the image forming
apparatus shown in FIG. 1. Firstly, paper sheets stacked in
cassettes 31, 32, 33, or 34 are sequentially picked up by the
pick-up rollers 31b, 32b, 33b, or 34b. The picked up paper sheets
are fed to the sheet feeding path 35 while being separated one by
one by sheet supply rollers 31a, 32a, 33a, or 34a and separating
rollers 31c, 32c, 33c, or 34c. The paper sheet that has been fed to
the sheet feeding path 35 is then fed to the portion in front of
the intermediate feeding roller 38 by feeding rollers 36a, 36b,
36c, or 36d. The intermediate feeding roller 38 has a role of
guiding the sheet that has been fed along the sheet feeding path 35
or sheet that has been fed by the ADU 5 (to be described later) to
the regist roller 37 that performs skew correction or timing
adjustment for the sheet.
[0022] The sheet that has been guided to the regist roller 37
through the intermediate feeding roller 38 is subjected to the skew
correction or timing adjustment. After that, a toner image formed
on the photoconductor surface of the photoconductor drum 20 is
transferred onto the sheet. The toner image that has been
transferred onto the sheet is fixed to the sheet in the fixing
section 24. In the case of one-side printing, the sheet onto which
the toner image has been fixed is directly discharged outside the
apparatus. In the case where the duplex printing is performed or
one-side printed sheet is reversed before being discharged outside,
the sheet is guided to the reverse feeding path 28.
[0023] In the case of the duplex printing, the sheet that has been
guided to the reverse feeding path 28 is fed to the ADU 5 in a
switchback manner by reverse rollers 29 and 30. The sheet that has
been fed to the ADU 5 is then fed to the intermediate feeding
roller 38 again by feeding rollers 5a to 5d. After that, image
forming processing is performed for the other surface of the sheet
that has been fed through the ADU 5 by the photoconductor drum 20
and fixing section 24. Thus, the duplex printing for the sheet has
been completed.
[0024] FIG. 2 is a view for explaining a sheet feeding operation at
the portion in front of a regist roller and shows the area
surrounded by the dotted line in FIG. 1 in an enlarged manner.
[0025] As shown in FIG. 2, in the image forming apparatus having
the above configuration, in the case where image forming processing
is sequentially performed for a plurality of sheets (in the case
where a plurality of sheets are sequentially fed to the regist
roller 37), a succeeding sheet P2 is temporarily put on standby at
a predetermined position S in front of the intermediate feeding
roller 38 until aligning of a preceding sheet P1 has been completed
by the regist roller. Similarly, a sheet to be fed through the ADU
5 to the regist roller again is temporarily put on standby at a
predetermined position SA in the ADU 5 in front of the intermediate
feeding roller 38.
[0026] FIG. 3 is a block diagram for explaining the functional
configuration of the image forming apparatus according to the
embodiment. The image forming apparatus according to the present
embodiment has a drive controller 101 and a feeding speed
information acquisition section 102 in addition to the
configuration shown in FIGS. 1 and 2.
[0027] The drive controller 101 has a role of controlling the drive
speed of the intermediate feeding roller 38 for feeding a sheet to
the regist roller 37 for performing skew correction for the sheet
to be fed.
[0028] The feeding speed information acquisition section 102 has a
role of acquiring information relating to the feeding speed of a
sheet to be fed to the intermediate feeding roller 38.
[0029] The CPU 108 has a role of performing various processing in
the image forming apparatus and another role of executing a program
stored in the memory 109 to realize various functions. The memory
109 is constituted by, for example, a ROM or RAM and has a role of
storing various information and programs utilized in the image
forming apparatus.
[0030] Further, the drive controller 101 drives the intermediate
feeding roller 38 at least three different speeds based on the
information (information indicating which path the sheet is fed
through, etc.) relating to the feeding speed that has been acquired
by the feeding speed information acquisition section 102.
[0031] FIG. 4 is a timing chart showing sheet feeding timing at the
time when duplex printing is performed for A4 size sheet and A3
size sheet. The upper half of FIG. 4 shows a timing chart in the
case where five A4 size sheets are fed in a switchback manner (85
PPM (Print Per Minute)), and the lower half shows a timing chart in
the case where five A3 size sheets are fed in a switchback manner
(42 PPM). Further, in the timing charts of the respective sheet
sizes, upper halves show the case where the one-side printed sheet
is reversed before being discharged outside, and lower halves show
the case where duplex printing is performed.
[0032] In the case of the duplex printing for A4 size sheets,
images are formed in the order of: front (1) of first sheet, front
(2) of second sheet, front (3) of third sheet, back <1> of
first sheet, front (4) of fourth sheet, back <2> of second
sheet, front (5) of fifth sheet, back <3> of third sheet,
back <4> of fourth sheet, and back <5> of fifth
sheet.
[0033] In the case of the duplex printing for A3 size sheets,
images are formed in the order of: front (1) of first sheet, front
(2) of second sheet, back <1> of first sheet, front (3) of
third sheet, back <2> of second sheet, front (4) of fourth
sheet, back <3> of third sheet, front (5) of fifth sheet,
back <4> of fourth sheet, and back <5> of fifth
sheet.
[0034] When the productivity at the time of duplex printing is
calculated based on the configuration and feeding speed of the
image forming apparatus according to the embodiment, the following
result is obtained. FIG. 5 is a view for explaining a sheet feeding
path in the image forming apparatus according to the embodiment.
Here, as an example, the sheet feeding speed and distance are set
as shown in FIG. 5. In FIG. 5, LP represents process speed feeding
distance in process speed area, Lr represents acceleration/reverse
feeding distance (switchback distance) in acceleration/reverse
area, and La represents duplex speed feeding distance in duplex
feeding speed area.
[0035] In order to realize, at the duplex printing time, sheet
feeding efficiency (duplex productivity 100%) equivalent to the
case where one-side printed sheet is reversed before being
discharged outside, the starting time of the drive of the regist
roller 37 can be described as below and circulation time until the
regist roller 37 is restarted for feeding a sheet to the ADU 5 can
be represented by the following expression, in the case of, for
example, 72 PPM or 85 PPM.
TN5=60/PPM*5: circulation time
{4.16 sec(72 PPM),3.53 sec(85 PPM)}
Tat: duplex feeding total time [sec]=Ta+Tp+Tr+Tra+Tr PPM: one side
productivity (PPM for A4/LT size) 72, 85 PPM Vp: process speed
[mm/sec] 340 mm/sec, (410 mm/sec) Vr: Reverse speed [mm/sec] 800
mm/sec Va: ADU feeding speed [mm/sec] 385 mm/sec, (465 mm/sec) Lp:
process speed feeding distance [mm] about 367 mm Lr:
acceleration/reverse feeding distance (switchback distance) [mm]
about 296 mm La: Duplex speed feeding distance [mm] about 692 mm
Ta: Duplex speed feeding time [mm] 1797 sec, (1488 sec) Lpe: sheet
length [mm] 216 mm (LT) Tpe: sheet reverse feeding time [sec] 0.369
sec Tp: process speed feeding time [sec] 1.079 sec, (0.895 sec) Ts:
switchback time (reverse time) [seq] about 0.1 sec Tra: regist
aligning time [sec] about 0.07 sec Tr: acceleration/reverse feeding
time [sec] about 0.27 sec To: other required time (including loss
at acceleration/deceleration time and the like: 100 msec) about
0.10 sec Note that numerical values in the parentheses represent
feeding data obtained in the case of 85 PPM.
[0036] It can be seen from the above that, in the case of a 72-PPM
machine with a process speed of 340 mm/sec, duplex feeding total
time Tat is 3.79 sec, which is smaller than 4.16 sec of circulation
time TN5 of five sheets. Therefore, the processing for the five
sheets satisfies the circulation condition, with the result that
duplex productivity of 100% can be obtained. Similarly, in the case
of an 85-PPM machine with a process speed of 410 mm/sec, duplex
feeding total time Tat is 3.29 sec, which is smaller than 3.53 sec
of circulation time TN5 of five sheets. Thus, in both above cases,
high duplex productivity can be obtained.
[0037] In the present embodiment, the ratio between the process
speed and duplex feeding speed is set at 1:1.13 and the CPU 108
changes only the rotation number of the motor to thereby realize
two process speeds. As a result, the control that satisfies duplex
productivity of 100% can be realized.
[0038] Further, when a setting that satisfies the above conditions
in terms of the sheet feeding distance, sheet feeding speed,
printing speed (PPM) is performed, duplex productivity of 100% can
be realized.
[0039] In the case where there is a restriction from sheet interval
at the time of sheet supply or reverse feeding speed, it is
possible to cope with it by accelerating the feeding speed at the
time of duplex printing and, further, factors such as the feeding
speed, process speed, PPM, duplex feeding speed, reverse feeding
distance are used to easily make a calculation selection.
[0040] In the present embodiment, the drive of the motor that
drives the fixing section 24 is divided, and a clutch mechanism is
used to turn ON/OFF the transfer of the drive force. In the case
where one side printing is sequentially performed, the clutch is
turned OFF so as not to drive the feeding rollers in the ADU 5.
Further, a change in the ratio of the drive force divided from the
motor for the fixing section 24 at the input time can realize speed
change. In addition, a change in the drives of the feeding rollers
36a to 36d after the input can also realize a change in the sheet
feeding speed.
[0041] The image forming apparatus according to the present
embodiment employs alternating circulation mode of "one side-both
sides-one side-both sides" to perform sheet feeding control at the
time of duplex printing, so that it is only necessary for the
reverse feeding section or duplex feeding section to perform sheet
control for the printing section one time per two sheets.
Therefore, the image forming apparatus according to the present
embodiment does not use a pulse motor a lot for the drive of the
feeding rollers in the ADU 5 but utilizes the clutch mechanism.
Even in the case where the feeding rollers in the ADU 5 are driven
by the clutch mechanism, if the intermediate feeding roller 38 is
driven by, for example, a pulse motor, it is possible to realize a
plurality of types of feeding speeds (for example, three feeding
speeds of process speed (third speed), sheet supply speed (second
speed), and duplex feeding speed (first speed)) by simply changing
the drive frequency of the motor. Here, the intermediate feeding
roller is constituted by a roller pair. Alternatively, however, it
may be constituted by a plurality of roller pairs.
[0042] An example of the ratio of process speed: sheet supply
speed: duplex feeding speed is shown below.
72 PPM mode 1:1.235:1.13 85 PPM mode 1:1.122:1.13
[0043] As described above, by setting the sheet supply speed and
duplex feeding speed to a speed higher than (1 to 1.3 times) the
process speed, it is possible to reduce noise and stabilize the
sheet feeding control.
[0044] The intermediate feeding roller 38 according to the
embodiment can realize the following three sheet feeding
speeds.
[0045] (1) Sheet supply speed 420 mm/sec
[0046] (2) Process speed 340 mm/sec
[0047] (3) Duplex feeding speed 385 mm/sec
[0048] As described above, by setting the sheet supply speed to a
speed higher than the process speed, it is possible to shorten
intervals between sheets to be sequentially fed and thereby to
increase the number of sheets that can be fed in a given period
time. Further, by setting the duplex feeding speed of the ADU 5 to
a speed higher than the process speed, it is possible to realize
high duplex productivity.
[0049] FIG. 6 is a timing chart showing drive timing of the regist
roller 37, intermediate feeding roller 38, and feeding rollers
other than the intermediate feeding roller 38 in the image forming
apparatus according to the embodiment.
[0050] A sheet supplied from the cassette is fed by the
intermediate feeding roller 38 to the regist roller 37 at a sheet
supply speed of 420 mm/sec. The leading head of the sheet hits
against a nip portion of the stopped regist roller 37, where
aligning is performed. After that, the sheet is fed by the
intermediate feeding roller 38 and regist roller 37 at a process
speed of 340 mm/sec.
[0051] Subsequently, a succeeding sheet that has been temporarily
put on standby for image forming onto one side thereof is fed by
the intermediate feeding roller 38 to the regist roller 37 at a
sheet supply speed of 420 mm/sec.
[0052] A case where image forming processing is performed for one
side of the three sheets (in FIG. 6, timing chart relating to the
first sheet is omitted) will be described. In order to form an
image onto one side of a sheet, onto the other side of which an
image has already been formed, the sheet is fed in a switchback
manner. After the switchback, the sheet is fed in an accelerated
manner to the portion in front of the ADU 5, where the feeding
speed is slightly reduced to the ADU speed of 385 mm/sec, and the
sheet is fed to the regist roller at that speed. It can be seen
from FIG. 6 that at least three sheet feeding speeds are realized
by the intermediate feeding roller 38.
[0053] In the sheet feeding timing chart shown in FIG. 6, a
pre-regist SW serving as a sensor functions as a trigger for
turning OFF the clutch. It is preferable to switch the pre-regist
SW depending on the setting speed and stop time. This is because
there is a possibility that a sheet bends between rollers other
than those for sheet feeding, which are disposed in the so-called
an aligning section and perform skew correction and timing
adjustment for the sheet.
[0054] The setting of the sheet feeding speed will next be
described. In general, a clutch mechanism is used for the pick-up
rollers for picking-up sheets from the cassettes 31 to 34. In such
a case, the sheet feeding operation may get delayed more often than
that performed by ordinary rollers. For example, a sheet feeding
loss is generated due to delay of clutch connection time and a
sheet feeding delay of the pick-up rollers 31b to 34b is generated.
Such a delay in the sheet feeding time may cause jam or decrease in
copy speed. In such a case, in order to ensure a margin for the
sheet feeding delay and recover the sheet feeding delay, a setting
may be made to make the sheet feeding speed and process speed at
the time of printing an image different from each other in some
cases.
[0055] However, it is not preferable to further increase the sheet
feeding speed in an apparatus that feeds a sheet at high speed
because friction noise between a sheet and guide at the sheet
feeding time, drive noise, noise due to hitting of a sheet to a
guide at the sheet feeding time, and the like are increased.
Therefore, the sheet feeding speed is set in a range in which the
sheet feeding operation can be stably performed.
[0056] The setting of the sheet feeding speed at the duplex feeding
time (sheet feeding operation in the ADU 5) will next be described.
The setting of the sheet feeding speed at the duplex feeding time
is often made individually in each machine according to the machine
type or printing speed (PPM). If a higher sheet feeding speed than
necessary is set, the temperatures of a drive motor and clutch are
increased or it becomes difficult to perform stop control for a
sheet. In the case where configuration that uses a pulse motor a
lot is employed, although stable sheet feeding operation can be
performed, manufacturing cost becomes increased.
[0057] In the case where two types of clutches are used to control
the drive of the feeding rollers on the upstream side relative to
the intermediate feeding roller 38 (in the case where a dedicated
motor for driving ADU feeding rollers is not provided, and the
drive force for the ADU feeding rollers is transferred from fixing
drive motor or the like), the sheet feeding speed realized by the
feeding rollers needs to be made equal to the process speed or
needs to be changed by a drive ratio. Also in this case, by
allowing the sheet feeding speed realized by the intermediate
feeding roller 38, process speed, and sheet feeding speed at the
time of duplex printing to change in tandem with one another,
stable sheet feeding operation can be realized.
[0058] When the sheet feeding speed in the ADU 5 is made equal to
the sheet supply speed, the speed of the ADU 5 needs to be
increased more than required, thereby increasing noise level at the
sheet supply time. Therefore, the image forming apparatus according
to the present embodiment is configured to reduce the noise by
driving the respective speeds in an optimum manner.
[0059] In the present embodiment, only one pulse motor is used to
drive the sheet feeding rollers disposed upstream of the regist
roller to thereby realize the above three sheet feeding speeds,
that is, the sheet supply speed required for feeding a sheet from
the cassette; process speed for elongating the life of the
photoconductor or consumable supply such as a development material;
and duplex feeding speed for obtaining optimum sheet feeding speed
of state productivity 100% (a state in which there is no difference
in speed between one side printing and duplex printing, that is, at
the time when the efficiency is maximum at the alternating
circulation between them: except for the feeding time of the first
and second sheets and the last two sheets after the completion of
the duplex printing) with high duplex productivity.
[0060] The configuration obtained by adding only one pulse motor to
the conventional configuration as described above satisfies three
capabilities of stability in paper feeding operation, increase in
the life of consumable supply (or increase in copy speed can be
achieved), and high duplex productivity required in the image
forming apparatus. At the time of duplex printing, sheet feeding
speed can freely be set without the need of setting unnecessary
sheet feeding speed.
[0061] As described above, in the embodiment of the present
invention, the drive controller 101 drives the intermediate feeding
roller 38 at least three different speeds including the first speed
at which a sheet, which is to be resupplied to the intermediate
feeding roller 38 for image forming onto the second surface thereof
after it has been passed through the regist roller 37 and a toner
image has been formed onto the first surface thereof, is received
by the intermediate feeding roller 38 and the second speed at which
a sheet, which is to be newly fed to the intermediate feeding
roller 38, is received by the intermediate feeding roller 38.
Further, the drive controller 101 controls the intermediate feeding
roller 38 such that the first speed becomes lower than the second
speed. Although the PPM is taken as an example of the printing
speed in the present embodiment, the same applies to CPM (Copy Per
Minute) used in copy processing.
[0062] While the present invention has been described in detail
according to the specific embodiment, it will be apparent to those
skilled in the art that variations and modifications are possible
without deviating from the broad principles and spirit of the
present invention.
[0063] As has been described in detail, according to the present
invention, it is possible to provide an image forming apparatus
capable of suppressing occurrence of a problem caused by
misalignment of the feeding speed at the time of delivery and
receipt in the intermediate feeding roller with a simple
configuration without increasing cost.
[0064] This application claims priority from Japanese Patent
Application Number 2005-68014, filed Mar. 10, 2005, which is
incorporated herein by reference in its entirety.
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