U.S. patent application number 12/555243 was filed with the patent office on 2010-05-20 for sheet feeder and image forming apparatus.
Invention is credited to Hiroyuki Ikeuchi, Takuji Miyazawa.
Application Number | 20100123280 12/555243 |
Document ID | / |
Family ID | 42171374 |
Filed Date | 2010-05-20 |
United States Patent
Application |
20100123280 |
Kind Code |
A1 |
Miyazawa; Takuji ; et
al. |
May 20, 2010 |
SHEET FEEDER AND IMAGE FORMING APPARATUS
Abstract
There is provided a sheet feeder including: a lifting unit that
lifts a loading portion having a recording medium loaded thereon; a
position detecting unit that detects whether the uppermost surface
of the recording medium is disposed at a predetermined first
position; a sheet feed mechanism that feeds the recording medium
from the loading portion; a thickness detecting unit that detects
thickness of the recording medium fed by the sheet feeding
mechanism; and a control unit that, when the position detecting
unit detects that the uppermost surface of the recording medium is
disposed at the first position, controls the lifting unit such that
the uppermost surface of the recording medium is lifted up to a
second position that is higher than the first position by a
distance determined based on cumulative value of the thickness of
the recording medium detected by the thickness detecting unit.
Inventors: |
Miyazawa; Takuji; (Kanagawa,
JP) ; Ikeuchi; Hiroyuki; (Kanagawa, JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Family ID: |
42171374 |
Appl. No.: |
12/555243 |
Filed: |
September 8, 2009 |
Current U.S.
Class: |
271/3.09 ;
271/265.04; 271/4.01; 271/9.01 |
Current CPC
Class: |
B65H 1/14 20130101; B65H
2801/06 20130101; B65H 2511/13 20130101; B65H 2511/20 20130101;
B65H 2511/13 20130101; B65H 2511/222 20130101; B65H 2511/20
20130101; B65H 2511/222 20130101; B65H 2220/02 20130101; B65H
2220/01 20130101; B65H 2220/02 20130101 |
Class at
Publication: |
271/3.09 ;
271/265.04; 271/9.01; 271/4.01 |
International
Class: |
B65H 5/00 20060101
B65H005/00; B65H 7/02 20060101 B65H007/02; B65H 7/20 20060101
B65H007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2008 |
JP |
2008-293377 |
Claims
1. A sheet feeder comprising: a lifting unit that lifts a loading
portion having at least one recording medium loaded thereon; a
position detecting unit that detects whether the uppermost surface
of the recording medium loaded on the loading portion is disposed
at a predetermined first position; a sheet feed mechanism that
feeds the recording medium from the loading portion; a thickness
detecting unit that detects thickness of the recording medium fed
by the sheet feeding mechanism; and a control unit that, when the
position detecting unit detects that the uppermost surface of the
recording medium is disposed at the first position, controls the
lifting unit such that the uppermost surface of the recording
medium is lifted up to a second position that is higher than the
first position by a distance determined based on cumulative value
of the thickness of the recording medium detected by the thickness
detecting unit.
2. A sheet feeder comprising: a lifting unit that lifts a loading
portion having at least one recording medium loaded thereon; a
position detecting unit that detects whether the uppermost surface
of the recording medium loaded on the loading portion is disposed
at a predetermined first position; a sheet feed mechanism that
feeds the recording medium from the loading portion; a thickness
detecting unit that detects thickness of the recording medium fed
by the sheet feeding mechanism; a thickness cumulative value
calculating unit that calculates the cumulative value of thickness
of the at least one recording medium detected by the thickness
detecting unit; and a control unit that, when the cumulative value
calculated by the thickness cumulative value calculating unit is
equal to a predetermined threshold value indicating that the
uppermost surface of the recording medium loaded on the loading
portion is disposed at a second position, controls the lifting unit
such that the uppermost surface of the recording medium is lifted
up to a predetermined first position higher than the second
position.
3. The sheet feeder of claim 2, wherein: there are a plurality of
sheet feed units comprising the sheet feed mechanism and the
lifting unit; the sheet feeder further comprises a storage unit
that stores the threshold value relating to the position of the
recording medium of each of the sheet feed units, and the control
unit reads the threshold value for the recording medium fed by any
one of the plurality of sheet feed units from the storage unit and
uses the read threshold value as the predetermined threshold
value.
4. The sheet feeder of claim 2, wherein: there are a plurality of
sheet feed units comprising the sheet feed mechanism and the
lifting unit; the sheet feeder further comprises a storage unit
that stores respective threshold values of each of the sheet feed
units, and the control unit reads a threshold value for the sheet
feed mechanism of any one of the plurality of sheet feed units from
the storage unit and uses the read threshold value as the
predetermined threshold value.
5. An image forming apparatus comprising: a sheet feeder; and an
image forming unit that forms an image on at least one recording
medium fed by the sheet feeder, wherein the sheet feeder includes:
a lifting unit that lifts a loading portion having the recording
medium loaded thereon; a position detecting unit that detects
whether the uppermost surface of the recording medium loaded on the
loading portion is disposed at a predetermined first position; a
sheet feed mechanism that feeds the recording medium from the
loading portion; a thickness detecting unit that detects thickness
of the recording medium fed by the sheet feeding mechanism; and a
control unit that, when the position detecting unit detects that
the uppermost surface of the recording medium is disposed at the
first position, controls the lifting unit such that the uppermost
surface of the recording medium is lifted up to a second position
that is higher than the first position by a distance determined
based on cumulative value of the thickness of the recording medium
detected by the thickness detecting unit.
6. An image forming apparatus comprising: a sheet feeder; and an
image forming unit that forms an image on at least one recording
medium fed by the sheet feeder, wherein the sheet feeder includes:
a lifting unit that lifts a loading portion having the recording
medium loaded thereon; a position detecting unit that detects
whether the uppermost surface of the recording medium loaded on the
loading portion is disposed at a predetermined first position; a
sheet feed mechanism that feeds the recording medium from the
loading portion; a thickness detecting unit that detects thickness
of the recording medium fed by the sheet feeding mechanism; a
thickness cumulative value calculating unit that calculates
cumulative value of thickness of the at least one recording medium
detected by the thickness detecting unit; and a control unit that,
when the cumulative value calculated by the thickness cumulative
value calculating unit is equal to a predetermined threshold value
indicating that the uppermost surface of the recording medium
loaded on the loading portion is disposed at a second position,
controls the lifting unit such that the uppermost surface of the
recording medium is lifted up to a predetermined first position
higher than the second position.
7. The image forming apparatus of claim 6, wherein there are a
plurality of sheet feed units comprising the sheet feed mechanism
and the lifting unit; the sheet feeder further comprises a storage
unit that stores the threshold value relating to the position of
the recording medium of each of the sheet feed units, and the
control unit reads the threshold value for the recording medium fed
by any one of the plurality of sheet feed units from the storage
unit and uses the read threshold value as the predetermined
threshold value.
8. The image forming apparatus of claim 6, wherein there are a
plurality of sheet feed units comprising the sheet feed mechanism
and the lifting unit; the sheet feeder further comprises a storage
unit that stores respective threshold values of each of the sheet
feed units, and the control unit reads a threshold value for the
sheet feed mechanism of any one of the plurality of sheet feed
units from the storage unit and uses the read threshold value as
the predetermined threshold value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 USC 119 from
Japanese Patent Application No. 2008-293377 filed on Nov. 17,
2008.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a sheet feeder and an image
forming apparatus.
[0004] 2. Related Art
[0005] In the related art, an image forming apparatus, such as a
copier and a printer, includes a sheet feeder that feeds a
recording medium, on which images are recorded, to an image forming
unit.
[0006] The recording medium which is loaded on a bottom plate that
can be lifted up by a wire is stored in a tray of the sheet
feeder.
[0007] In the image forming apparatus, when the uppermost recording
medium in the tray is sequentially fed to the image forming unit,
the number of recording medium loaded in the tray is reduced, and
the position of the uppermost recording medium becomes lower than
the lower limit of the range in which the recording medium can be
fed to the image forming unit, the bottom plate is lifted up such
that the uppermost recording medium is adjusted to be within the
sheet feedable range.
SUMMARY
[0008] An aspect of the invention provides a sheet feeder
including:
[0009] a lifting unit that lifts a loading portion having at least
one recording medium loaded thereon;
[0010] a position detecting unit that detects whether the uppermost
surface of the recording medium loaded on the loading portion is
disposed at a predetermined first position;
[0011] a sheet feed mechanism that feeds the recording medium from
the loading portion;
[0012] a thickness detecting unit that detects thickness of the
recording medium fed by the sheet feeding mechanism; and
[0013] a control unit that, when the position detecting unit
detects that the uppermost surface of the recording medium is
disposed at the first position, controls the lifting unit such that
the uppermost surface of the recording medium is lifted up to a
second position that is higher than the first position by a
distance determined based on cumulative value of the thickness of
the recording medium detected by the thickness detecting unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a diagram schematically illustrating the structure
of an image forming system according to a first exemplary
embodiment;
[0015] FIG. 2 is a diagram schematically illustrating the structure
of a sheet feeder according to the first exemplary embodiment;
[0016] FIG. 3 is a block diagram illustrating the structure of the
image forming system according to the first exemplary
embodiment;
[0017] FIG. 4 is a flowchart illustrating the flow of a sheet feed
process according to the first exemplary embodiment;
[0018] FIG. 5 is a flowchart illustrating the flow of an initial
operation of the sheet feeder according to the first exemplary
embodiment;
[0019] FIG. 6 is a diagram schematically illustrating a sheet feed
operation according to the first exemplary embodiment;
[0020] FIG. 7 is a flowchart illustrating the flow of a sheet feed
process according to a second exemplary embodiment;
[0021] FIG. 8 is a flowchart illustrating the flow of an initial
operation of a sheet feeder according to the second exemplary
embodiment;
[0022] FIG. 9 is a diagram schematically illustrating a sheet feed
operation according to the second exemplary embodiment;
[0023] FIG. 10 is a diagram schematically illustrating the
structure of an image forming system according to a third exemplary
embodiment;
[0024] FIG. 11 is a block diagram illustrating the structure of the
image forming system according to the third exemplary
embodiment;
[0025] FIG. 12 is a flowchart illustrating the flow of a sheet feed
process according to the third exemplary embodiment;
[0026] FIG. 13 is a diagram schematically illustrating the
structure of a sheet feeder according to a modification; and
[0027] FIG. 14 is a flowchart illustrating the flow of a sheet feed
process according to a modification of the third exemplary
embodiment.
DETAILED DESCRIPTION
[0028] Hereinafter exemplary embodiments of the present invention
will be described in detail.
First Exemplary Embodiment
[0029] As shown in FIG. 1, an image forming system 10 according to
a first exemplary embodiment includes a sheet feeder 12 and an
image forming apparatus 16.
[0030] The sheet feeder 12 feeds a recording medium 14 to the image
forming apparatus 16.
[0031] For example, a sheet can be used as the recording medium 14.
However, the recording medium 14 is not limited to the sheet. Any
medium may be used as long as the image forming apparatus 16 can
form an image thereon.
[0032] The image forming apparatus 16 includes an image reading
unit 18 and an image forming apparatus main body 20.
[0033] The image reading unit 18 includes, for example, a line CCD
sensor and a scanning mechanism that scans the recording medium
with the line CCD sensor. The image reading unit 18 reads the image
of a set document in response to, for example, instructions from a
user.
[0034] The image forming apparatus main body 20 includes an image
forming unit 22. The image forming unit 22 forms an image on the
recording medium 14 fed from the sheet feeder 12.
[0035] The image forming unit 22 includes a photoconductor drum 24,
a charging unit 26, an exposure device 28, a developing unit 30, a
transfer roller 32, and a fixing unit 34.
[0036] The charging unit 26, the exposure device 28, the developing
unit 30, and the transfer roller 32 are arranged around the
photoconductor drum 24.
[0037] The photoconductor drum 24 is a cylindrical photoconductor,
and is rotationally driven at a predetermined rotation speed.
[0038] The charging unit 26 uniformly charges the surface of the
photoconductor drum 24.
[0039] The exposure device 28 exposes the photoconductor drum 24
according to image data of an image to be formed on the recording
medium 14 and forms an electrostatic latent image on the
photoconductor drum 24. The exposure device 28 may include an LED
print head obtained by arranging, for example, plural LEDs. In
addition, the exposure device 28 may be an optical scanning device
that includes a semiconductor laser, a collimator lens, a polygon
mirror, and an f.theta. lens, and performs scanning exposure based
on image data on the photoconductor drum 24.
[0040] The developing unit 30 develops the electrostatic latent
image formed on the photoconductor drum 24 with toner.
[0041] The transfer roller 32 transfers the toner image on the
photoconductor drum 24 onto the recording medium 14. The
transferred toner image is fixed when the recording medium 14
passes between a pressure roller 36 and a heating roller 38
provided in the fixing unit 34.
[0042] The recording medium 14 is discharged to a discharge tray 44
through a sheet outlet 42 provided in the side surface of the image
forming apparatus 16 by a discharge roller 40.
[0043] Next, the structure of the sheet feeder 12 will be described
with reference to FIG. 2.
[0044] The sheet feeder 12 includes a tray 46. A lifting portion on
which the recording medium 14 is loaded, for example, a bottom
plate 48 is provided in the tray 46.
[0045] One end of a wire 50 is connected to the bottom plate 48
while being suspended by a pulley 52. In addition, the other end of
the wire 50 is connected to a driving gear 56 that is rotationally
driven by a lift-up motor 54. When the driving gear 56 is rotated
in the direction of an arrow A, the wire 50 suspended by the pulley
52 is wound to lift up the bottom plate 48. When the driving gear
56 is rotated in the direction of an arrow B, the wire 50 suspended
by the pulley 52 is unwound to drop the bottom plate 48.
[0046] The sheet feeder 12 includes a sheet feed mechanism that
feeds the recording medium 14. The sheet feed mechanism includes a
sheet feed unit having, for example, a sheet transport roller 58, a
sheet transport roller rotating shaft 60, and a sheet transport
roller supporting arm 62, a position detecting unit, such as a
sheet feedable position detecting sensor 64, a feed roller 66, a
retard roller 68, a thickness detecting sensor 70, a takeaway pinch
roller 76, and a takeaway drive roller 78.
[0047] The thickness detecting unit, for example, the thickness
detecting sensor 70 is formed by mounting a thickness detecting
actuator 74 to a rotary encoder 72.
[0048] In the sheet feeder 12, when the recording medium 14 is in
the range in which the sheet can be fed, the sheet transport roller
58 is rotated in the direction of an arrow C, with the sheet
transport roller 58 contacted with the uppermost surface of the
recording medium 14 loaded on the bottom plate 48, to feed the
recording medium 14.
[0049] The sheet transport roller supporting arm 62 that supports
the vertical movement of the sheet transport roller 58 is mounted
to the sheet transport roller 58.
[0050] The sheet transport roller supporting arm 62 rotates about a
sheet transport roller supporting arm rotating shaft 65. The sheet
transport roller supporting arm 62 is rotated upward when a sheet
transport roller solenoid 87 (not shown) is turned on. The sheet
transport roller supporting arm 62 is rotated downward by the
elastic force of a spring (not shown) when the sheet transport
roller solenoid 87 is turned off. In this way, the sheet transport
roller 58 is moved in the vertical direction represented by an
arrow D.
[0051] The sheet feedable position detecting sensor 64 is arranged
close to the sheet transport roller supporting arm 62. The sheet
feedable position detecting sensor 64 detects the position of the
uppermost surface of the recording medium 14 loaded on the bottom
plate 48.
[0052] The sheet feedable position detecting sensor 64 detects the
uppermost surface of the recording medium 14, without being
affected by the vertical movement of the sheet transport roller
58.
[0053] The fed recording medium 14 are separated one by one by the
feed roller 66 and the retard roller 68 that is rotationally driven
in a direction opposite to the rotation direction of the feed
roller 66 by a torque limiter (not shown).
[0054] The separated recording medium 14 is transported to the
image forming apparatus 16 by the takeaway pinch roller (driven
roller) 76 and the takeaway drive roller 78.
[0055] The thickness detecting sensor 70 is arranged between the
feed roller 66 and the takeaway pinch roller 76.
[0056] The thickness detecting sensor 70 is arranged at a position
where the thickness detecting actuator 74 is lifted up whenever the
recording medium 14 is fed.
[0057] When the recording medium 14 is fed and the thickness
detecting actuator 74 is lifted up by a distance corresponding to
the thickness of the recording medium 14, the rotary encoder 72 is
rotated at an angle corresponding to the amount of lift. The rotary
encoder 72 outputs a signal corresponding to the rotation angle.
That is, the rotary encoder 72 outputs a signal corresponding to
the thickness of the recording medium 14.
[0058] Next, the structure of the main components of an electrical
system of the sheet feeder 12 will be described with reference to
FIG. 3.
[0059] As shown in FIG. 3, the sheet feeder 12 includes a control
unit 80, the thickness detecting sensor 70, a thickness cumulative
value calculating unit 82, a sheet feedable position detecting
sensor 64, a sheet transport roller motor 84, a feed roller motor
86, a retard roller motor 88, a takeaway drive roller motor 90, a
lift-up motor 54, a sheet transport roller solenoid 87, and an I/F
(interface) 92.
[0060] Whenever the recording medium 14 is fed, the value of the
thickness of the recording medium 14 detected by the thickness
detecting sensor 70 is input to the thickness cumulative value
calculating unit 82, and the input thickness value is accumulated
(added). Then, the thickness cumulative value calculating unit 82
outputs the calculated cumulative value to the control unit 80.
[0061] The image forming apparatus 16 transmits an instruction
signal that instructs the sheet feeder 12 to feed the recording
medium 14 to the I/F 92. The instruction signal includes, for
example, information about the number of sheets to be fed. The I/F
92 outputs the instruction signal from the image forming apparatus
16 to the control unit 80.
[0062] When receiving the instruction signal for feeding the
recording medium 14 from the image forming apparatus 16 through the
I/F 92, the control unit 80 controls the operation of the sheet
transport roller motor 84 to feed the recording medium 14 to the
image forming apparatus 16.
[0063] Next, a sheet feed process routine performed by the control
unit 80 of the sheet feeder 12 provided in the image forming system
10 according to this exemplary embodiment will be described with
reference to FIG. 4.
[0064] When the user operates the image forming apparatus 16 to
select an image forming service such as copy, the routine is
performed.
[0065] First, in Step 100, an initial operation processing routine
shown in FIG. 5 is performed. In the initial operation processing
routine, as shown in FIG. 5, in Step 120, it is determined whether
the sheet feedable position detecting sensor 64 is turned on. The
sheet feedable position detecting sensor 64 is turned on when the
uppermost surface of the recording medium 14 is in a sheet feedable
range 94 shown in FIG. 6.
[0066] The sheet feedable range 94 is defined by, for example, a
first position A, which is the lower limit of the range in which
the medium 14 can be fed, and a predetermined second position B,
which is the upper limit of the range in which the recording medium
14 can be fed and is higher than the first position A.
[0067] When the uppermost surface of the recording medium 14 is
lower than the lower limit of the range in which the recording
medium 14 can be fed, it is difficult to feed the recording medium.
When the uppermost surface of the recording medium 14 is higher
than the upper limit of the range in which the recording medium 14
can be fed, it is difficult to feed the recording medium. The first
position A is not limited to the lower limit of the range, and any
position may be used as the first position as long as it is in the
range in which the recording medium 14 can be fed.
[0068] In addition, the second position B is not limited to the
upper limit of the range, and any position may be used as the
second position as long as it is higher than the first position and
is in the range in which the recording medium 14 can be fed. That
is, the sheet feedable range 94 is not limited to between the lower
limit and the upper limit, and any range may be used as long as the
recording medium can be fed therewithin.
[0069] The sheet feedable position detecting sensor 64 is turned
off when the uppermost surface of the recording medium 14 is lower
than the first position A. Therefore, when the sheet feedable
position detecting sensor 64 is turned on, the current position of
the uppermost surface of the recording medium 14 is in the range in
which the recording medium can be fed. Therefore, it is not
necessary to lift up the bottom plate 48, and the process proceeds
to Step 102 in FIG. 4.
[0070] If it is determined in Step 120 that the sheet feedable
position detecting sensor is turned off, the process proceeds to
Step 122. In this state, the position of the uppermost surface of
the recording medium 14 is not within the sheet feedable range.
That is, since the position of the uppermost surface of the
recording medium 14 is lower than the first position A, the lift-up
motor 54 is driven to lift up the bottom plate 48 until the sheet
feedable position detecting sensor 64 is turned on. Then, the
uppermost surface of the recording medium 14 is lifted up to the
first position A in the sheet feedable range 94.
[0071] Then, the process proceeds to Step 124 to drive the lift-up
motor 54 such that the bottom plate 48 is further lifted up by a
predetermined threshold value. The threshold value corresponds to
the sheet feedable range 94 in FIG. 6. That is, the threshold value
corresponds to a thickness cumulative value when the recording
medium 14 is fed up to the first position A that is lower than the
second position B, which is the upper limit of the sheet feedable
range. Therefore, the bottom plate 48 is lifted up such that the
uppermost surface of the recording medium 14 is lifted up to the
second position B in the sheet feedable range 94. In this way, the
recording medium 14 is lifted up to the second position B.
[0072] Then, in Step 126, the control unit 80 outputs an
instruction signal to the cumulative value calculating unit 82 to
reset the thickness cumulative value calculated by the cumulative
value calculating unit 82. Then, the thickness cumulative value
calculating unit 82 resets the thickness cumulative value.
[0073] The position of the uppermost surface of the recording
medium 14 is within the sheet feedable range by the initial
operation processing routine.
[0074] Then, the recording medium is fed in Step 102 in FIG. 4.
That is, the sheet transport roller motor 84 is controlled such
that the recording medium 14 loaded on the bottom plate 48 is fed
to the image forming apparatus 16.
[0075] In Step 104, it is determined whether the sheet feedable
position detecting sensor 64 is turned off, that is, whether the
uppermost surface of the recording medium 14 is lower than the
first position A.
[0076] If it is determined in Step 104 that the sheet feedable
position detecting sensor 64 is not turned off, that is, if the
uppermost surface of the recording medium 14 is within the sheet
feedable range 94, the process proceeds to Step 110.
[0077] If it is determined in Step 104 that the sheet feedable
position detecting sensor 64 is turned off, that is, sheet feeding
is performed and the position of the uppermost surface of the
recording medium 14 is lower than the first position A, i.e.,
beyond the sheet feedable range, the process proceeds to Step 106.
In Step 106, the control unit receives the calculated thickness
cumulative value output from the cumulative thickness value
calculating unit 82.
[0078] Then, in Step 108, the lift-up motor 54 is driven such that
the bottom plate 48 is lifted up by the thickness cumulative value
input to the control unit 80. In this way, the uppermost surface of
the recording medium 14 is lifted up to the second position B.
[0079] Then, in Step 109, the control unit 80 outputs an
instruction signal to the thickness cumulative value calculating
unit 82 to reset the thickness cumulative value calculated by the
thickness cumulative value calculating unit 82. Then, the thickness
cumulative value calculating unit 82 resets the thickness
cumulative value.
[0080] Then, in Step 110, it is determined whether the number of
sheets corresponding to the instruction signal from the image
forming apparatus 16 is completely fed.
[0081] If it is determined in Step 110 that the number of sheets
corresponding to the instruction signal is not completely fed, the
process returns to Step 102, and the same operation as described
above is repeatedly performed.
Second Exemplary Embodiment
[0082] Next, a second exemplary embodiment will be described.
[0083] In this exemplary embodiment, the same components as those
in the first exemplary embodiment are denoted by the same reference
numerals, and a description thereof will be omitted.
[0084] The structures of an image forming system 10, a sheet feeder
12, and an image forming apparatus 16 are the same as those
according to the first exemplary embodiment, and a description
thereof will be omitted.
[0085] The structure of the main components of an electrical system
according to the second exemplary embodiment is the same as that
according to the first exemplary embodiment, and a description
thereof will be omitted.
[0086] However, in this exemplary embodiment, a sheet feedable
position detecting sensor 64 detects that the uppermost surface of
the recording medium 14 is disposed at the first position A. That
is, the sheet feedable position detecting sensor 64 is turned on
when the recording medium 14 is disposed at the first position A,
and is turned off when the position of the recording medium 14 is
lower than the first position A.
[0087] The first position A is not limited to the upper limit of
the sheet feedable range, and any position may be used as the first
position as long as it is in the range in which the recording
medium 14 can be fed. In addition, the second position B is not
limited to the lower limit of the sheet feedable range, and any
position may be used as the second position as long as it is lower
than the first position and is in the range in which the recording
medium 14 can be fed. That is, the first and second positions may
be in the range in which the recording medium can be fed, similar
to the first exemplary embodiment.
[0088] A sheet feed process routine performed by the control unit
80 of the sheet feeder 12 provided in the image forming system 10
according to this exemplary embodiment will be described with
reference to FIG. 7.
[0089] Similar to the first exemplary embodiment, when the user
operates the image forming apparatus 16 to select an image forming
service such as copy, the routine is performed.
[0090] First, in Step 150, an initial operation processing routine
shown in FIG. 8 is performed. A thickness cumulative value may be
forcibly reset, for example, when power is supplied to the image
forming apparatus at the beginning, when the main power supply is
turned on or off, and when the recording medium 14 is added to the
tray 46. In this case, even when the uppermost surface of the
recording medium 14 is not actually disposed at the second position
B, which is the upper limit of the sheet feedable range, the
thickness cumulative value is reset. Therefore, first, in Step 200,
it is determined whether the thickness cumulative value calculated
by the thickness cumulative value calculating unit 82 is reset.
[0091] If it is determined in Step 200 that the thickness
cumulative value is not reset, the process proceeds to Step 202. On
the other hand, if it is determined that the thickness cumulative
value is reset, the process proceeds to Step 204.
[0092] In Step 202, it is determined whether the thickness
cumulative value calculated by the thickness cumulative value
calculating unit 82 is a predetermined threshold value or more.
[0093] The threshold value corresponds to the sheet feedable range
94 shown in FIG. 9. That is, the threshold value corresponds to the
thickness cumulative value when the recording medium 14 is fed up
to the second position B that is lower than the first position A,
which is the upper limit of the sheet feedable range.
[0094] If the determination result in Step 202 is "YES", the
process proceeds to Step 204.
[0095] In Step 204, the lift-up motor 54 is driven to lift up the
bottom plate 48 until the sheet feedable position detecting sensor
64 is turned on. Then, the uppermost surface of the recording
medium 14 is lifted up to the first position A.
[0096] Further, the process proceeds to Step 206, the control unit
80 outputs an instruction signal to the thickness cumulative value
calculating unit 82 to reset the thickness cumulative value
calculated by the thickness cumulative value calculating unit 82.
Then, the thickness cumulative value calculating unit 82 resets the
thickness cumulative value.
[0097] On the other hand, if the determination result in Step 202
is "NO", the current position of the position of the uppermost
surface of the recording medium 14 is within the sheet feedable
range. Therefore, it is not necessary to lift up the bottom plate
48, and the process proceeds to Step 152 in FIG. 7.
[0098] The position of the uppermost surface of the recording
medium 14 is within the sheet feedable range by the initial
operation processing routine.
[0099] Then, the recording medium is fed in Step 152 in FIG. 7.
That is, the sheet transport roller motor 84 is controlled such
that the recording medium 14 loaded on the bottom plate 48 is fed
to the image forming apparatus 16.
[0100] In Step 154, the control unit receives the calculated
thickness cumulative value output from the cumulative value
calculating unit 82.
[0101] Then, in Step 156, it is determined whether the thickness
cumulative value received in Step 154 is a predetermined threshold
value or more. That is, it is determined whether the position of
the uppermost surface of the recording medium 14 is lower than the
second position B.
[0102] If it is determined in Step 156 that the thickness
cumulative value is less than the threshold value, i.e., if the
uppermost surface of the recording medium 14 is within the sheet
feedable range 94, the process proceeds to Step 162.
[0103] If it is determined in Step 156 that the thickness
cumulative value is the threshold value or more, i.e., if sheet
feeding is performed and the position of the uppermost surface of
the recording medium 14 is lower than the second position B, that
is, beyond the sheet feedable range, the process proceeds to Step
158. In Step 158, the lift-up motor 54 is driven to lift up the
bottom plate 48 until the sheet feedable position detecting sensor
64 is turned on. In this way, the uppermost surface of the
recording medium 14 is lifted up to the first position A.
[0104] Then, the process proceeds to Step 160, the control unit 80
outputs an instruction signal to the thickness cumulative value
calculating unit 82 to reset the thickness cumulative value
calculated by the thickness cumulative value calculating unit 82.
Then, the thickness cumulative value calculating unit 82 resets the
thickness cumulative value.
[0105] Next, the process proceeds to Step 162, it is determined
whether the number of sheets corresponding to the instruction
signal from the image forming apparatus 16 is completely fed.
[0106] If it is determined in Step 162 that the number of sheets
corresponding to the instruction signal is not completely fed, the
process returns to Step 152, and the same operation as described
above is repeatedly performed.
Third Exemplary Embodiment
[0107] Next, a third exemplary embodiment will be described with
reference to FIG. 10.
[0108] In this exemplary embodiment, the same components as those
in the first and second exemplary embodiments are denoted by the
same reference numerals, and a description thereof will be
omitted.
[0109] An image forming system 10A includes a sheet feeder 13, an
image forming apparatus 16, and an image reading unit 18.
[0110] As shown in FIG. 10, the sheet feeder 13 includes plural
sheet feed units. For example, the sheet feeder 13 includes three
sheet feed units 13A-13C in this exemplary embodiment.
[0111] The sheet feeder 13 is provided in an image forming
apparatus main body 20.
[0112] The sheet feed units 13A to 13C have the same structure as
the sheet feeder 12 shown in FIG. 2, and characters "A" to "C" are
added to ends of the reference numerals of the components having
the same structure.
[0113] The image forming apparatus 16 and the image reading unit 18
are the same as those in the first exemplary embodiment, and thus a
description thereof will be omitted.
[0114] The sheet feed units 13A to 13C feed recording medium 14A to
14C to the image forming unit 22, respectively.
[0115] The recording medium 14A to 14C are loaded in trays 46A to
46C provided in the sheet feed units 13A to 13C, respectively.
[0116] For example, the recording medium 14A to 14C may be
different types of recording medium having different
thicknesses.
[0117] In the following description, when the sheet feed units 13A
to 13C are not individually specified, they are simply referred to
as a "sheet feed unit 13". Similarly, when the recording medium 14A
to 14C are not individually specified, they are simply referred to
as a "recording medium 14".
[0118] Next, the structure of the main components of an electrical
system of the sheet feed unit 13 will be described with reference
to FIG. 11.
[0119] The same components as those according to the first
exemplary embodiment are denoted by the same reference numerals,
and a description thereof will be omitted.
[0120] In the third exemplary embodiment, sheet feedable position
detecting sensors 64A to 64C, thickness detecting sensors 70A to
70C, thickness cumulative value calculating units 82A to 82C,
lift-up motors 54A to 54C, sheet transport motors 84A to 84C, feed
roller motors 86A to 86C, retard roller motors 88A to 88C, takeaway
drive motors 90A to 90C, and sheet transport roller solenoids 87A
to 87C are provided so as to correspond to the sheet feed units 13A
to 13C, respectively.
[0121] In the third exemplary embodiment, a storage unit 81 is
provided.
[0122] The storage unit 81 stores predetermined threshold values
corresponding to the recording medium 14A and 14B respectively
loaded in the sheet feed units 13A and 13B.
[0123] Next, a sheet feed process routine performed by the control
unit 80 of the image forming system 10A according to this exemplary
embodiment will be described with reference to FIG. 12.
[0124] When the user operates the image forming apparatus 16 to
select an image forming service such as copy, the routine is
performed.
[0125] First, in Step 250, among the threshold values stored in the
storage unit 81, a threshold value corresponding to the recording
medium 14 designated by the selected image forming service is
read.
[0126] In Steps 252 to 256, the same process as that in Steps 150
to 156 according to the second exemplary embodiment is performed on
the sheet feed unit 13 having the designated recording medium 14
loaded therein.
[0127] However, in Step 258, the thickness cumulative value of the
sheet feed unit 13 corresponding to the designated one of the
recording medium 14A to 14C is read from any one of the thickness
cumulative value calculating units 82A to 82C.
[0128] In Steps 260 to 264, the same process as that in Steps 158
to 162 according to the second exemplary embodiment is performed on
the sheet feed unit 13 having the designated recording medium 14
loaded therein.
[0129] Next, a sheet feed process routine performed by the control
unit 80 of an image forming system 10A according to a modification
of the third exemplary embodiment will be described with reference
to FIG. 14.
[0130] In Step 250, predetermined threshold values corresponding to
the sheet feed units 13A to 13C are read from the storage unit 81.
In Steps 252 to 256, the same process as that in Steps 150 to 156
according to the second exemplary embodiment is performed on the
sheet feed unit 13 having the designated recording medium 14 loaded
therein. However, in Step 258, a thickness cumulative value
corresponding to the designated one of the sheet feed units 13A to
13C is read from any one of the thickness cumulative value
calculating units 82A to 82C. In Steps 260 to 264, the same process
as that in Steps 158 to 162 according to the second exemplary
embodiment is performed on the sheet feed unit 13 having the
designated recording medium 14 loaded therein.
[0131] In the first to third exemplary embodiments, it is described
the thickness detecting sensor 70 includes the rotary encoder 72
and the thickness detecting actuator 74, however, the invention is
not limited thereto. For example, as shown in FIG. 13, the
thickness detecting sensor 70 may include a laser displacement
meter 96 and a roller 98. In this case, the laser displacement
meter 96 measures the amount of movement of the roller 98 in the
vertical direction to detect the thickness of the fed recording
medium 14. In the first to third exemplary embodiments, the sensor
is provided so as to detect the position of the uppermost surface
of the recording medium 14 loaded on the bottom plate 48 without
being affected by the movement of the sheet transport roller 58 in
the vertical direction. However, a sheet feedable position
detecting sensor may be provided so as to detect the position of
the sheet transport roller supporting arm 62 in the vertical
direction, and the sheet feedable position detecting sensor may
detect the position of the sheet transport roller supporting arm 62
when the sheet transport roller 58 comes into contact with the
uppermost surface of the recording medium 14 loaded on the bottom
plate 48, thereby detecting the position of the uppermost surface
of the recording medium 14 loaded on the bottom plate 48.
[0132] The structures of the sheet feeders, the image forming
systems, and the image forming apparatuses according to the
exemplary embodiments are just examples, and various modifications
and changes of the invention can be made without departing from the
concept of the invention.
[0133] In the above-described exemplary embodiments of the
invention, the image forming unit 22 of the image forming apparatus
16 forms images by electrophotography. However, the image forming
unit may form images using other methods such as an ink jet
recording method.
[0134] In addition, the flow of the processing program according to
each of the exemplary embodiments is just an example, and various
modifications and changes of the process flow can be made without
departing from the concept of the invention. For example, the
process order of the steps may be changed, unnecessary steps may be
removed, and a new step may be added.
* * * * *