U.S. patent application number 13/232763 was filed with the patent office on 2012-03-22 for holding device of recording medium, image forming apparatus, and conveying method of recording medium.
This patent application is currently assigned to TOSHIBA TEC KABUSHIKI KAISHA. Invention is credited to Masahiro Doi, Satoshi Kaiho, Yoshiaki Kaneko, Hirofumi Kondo.
Application Number | 20120068401 13/232763 |
Document ID | / |
Family ID | 45817047 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120068401 |
Kind Code |
A1 |
Kondo; Hirofumi ; et
al. |
March 22, 2012 |
HOLDING DEVICE OF RECORDING MEDIUM, IMAGE FORMING APPARATUS, AND
CONVEYING METHOD OF RECORDING MEDIUM
Abstract
According to one embodiment, the image forming apparatus
includes, an endless device having a plurality of suction holes,
and a negative pressure chamber which communicates with the suction
holes, a rotation mechanism which rotates the endless device, a
suction mechanism which discharges air in the negative pressure
chamber, an opening and closing mechanism which has a switching
blade which opens and closes the suction holes, a driving mechanism
which moves the switching blade to a first position and a second
position, a recording head unit, a supply mechanism which supplies
the recording medium to the endless device, and a controller. If
the switching blade moves to the first position, the suction holes
are shut. If the switching blade moves to the second position, the
suction holes communicate with the negative pressure chamber. The
controller drives the opening and closing mechanism according to
the size of the recording medium.
Inventors: |
Kondo; Hirofumi;
(Kanagawa-ken, JP) ; Kaneko; Yoshiaki;
(Shizuoka-ken, JP) ; Doi; Masahiro; (Shizuoka-ken,
JP) ; Kaiho; Satoshi; (Kanagawa-ken, JP) |
Assignee: |
TOSHIBA TEC KABUSHIKI
KAISHA
Tokyo
JP
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
45817047 |
Appl. No.: |
13/232763 |
Filed: |
September 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61384074 |
Sep 17, 2010 |
|
|
|
Current U.S.
Class: |
271/18.1 ;
271/112 |
Current CPC
Class: |
B65H 2515/342 20130101;
B41J 13/226 20130101; B65H 2511/10 20130101; B65H 2406/33 20130101;
B65H 2406/3614 20130101; B65H 2511/10 20130101; B65H 2801/06
20130101; B65H 2515/342 20130101; B65H 5/226 20130101; B65H 2220/01
20130101; B65H 2220/02 20130101 |
Class at
Publication: |
271/18.1 ;
271/112 |
International
Class: |
B65H 3/10 20060101
B65H003/10; B65H 3/18 20060101 B65H003/18 |
Claims
1. A holding device of a recording medium comprising: an endless
device which includes a circumferential surface which holds the
recording medium, a plurality of suction holes which is formed on
the circumferential surface, and a negative pressure chamber which
communicates with the suction holes, and rotates in a predetermined
direction; a suction mechanism which discharges air in the negative
pressure chamber; a switching blade which is provided in the
endless device, and moves between a first position at which the
suction holes are closed and a second position at which the suction
holes are opened; and a driving mechanism which moves the switching
blade to the first position and the second position.
2. The device according to claim 1, wherein the endless device
includes the front side hole row which is formed such that a
plurality of the suction holes is formed to have a interval in a
width direction of the endless device, in a position which
corresponds to a leading end of the recording medium in a movement
direction, which is held by the endless device.
3. The device according to claim 2, wherein the endless device
includes the rear side hole row which is formed such that a
plurality of the suction holes is formed to have a internal in a
width direction of the endless device, in a position which
corresponds to a trailing end of the recording medium in a movement
direction, which is held by the endless device.
4. The device according to claim 2, wherein the endless device
includes a first rear side hole row which is formed such that a
plurality of the suction holes is formed in a position which
corresponds to a trailing end of the recording medium of a first
size, in a movement direction, and a second rear side hole row
which is formed such that a plurality of the suction holes is
formed in a position which corresponds to a trailing end of the
recording medium of a second size in the movement direction.
5. The device according to claim 4, wherein the front side hole row
is always open, and the switching blade is disposed at the first
and second rear side hole rows.
6. The device according to claim 1, wherein the endless device is a
drum, and the switching blade moves in an axial direction of the
drum.
7. The device according to claim 6 comprising: an engaging portion
in which the switching blade extends in the axial direction of the
drum, wherein the driving mechanism includes a driving member which
has the driving unit engaging with the engaging portion, and an
actuator which moves the switching blade to the first position and
the second position if the engaging portion and the driving unit
engage with each other.
8. The device according to claim 1, wherein a dielectric layer to
which a charge for electrostatically adsorbing the recording medium
is applied is provided on the circumferential surface of the
endless device.
9. The device according to claim 3, wherein the endless device
further includes a plurality of intermediate suction holes which
communicates with the negative pressure chamber between the front
side hole row and the rear side hole row.
10. The device according to claim 9, wherein the intermediate
suction holes are smaller than those of the front and rear side
hole rows.
11. An image forming apparatus comprising: an endless device which
includes a circumferential surface which holds the recording
medium, a plurality of suction holes which is formed on the
circumferential surface, and a negative pressure chamber which
communicates with the suction holes; a rotation mechanism which
rotates the endless device in a predetermined direction; a suction
mechanism which discharges air in the negative pressure chamber; a
opening and closing mechanism which has a switching blade which is
provided in the endless device, and moves between a first position
at which the suction holes are closed and a second position at
which the suction holes are opened; a driving mechanism which moves
the switching blade to the first position and the second position;
a recording head unit which is arranged to face a circumferential
surface of the endless device, and forms images on the recording
medium; a supplying mechanism which supplies the recording medium
to the circumferential surface of the endless device; and a
controller which drives the opening and closing mechanism according
to a size of the recording medium.
12. The apparatus according to claim 11, wherein the endless device
includes hole rows which are formed such that the plurality of
suction holes is formed to have a interval in a width direction of
the endless device, and wherein the controller controls the supply
mechanism so that the leading end of the recording medium which is
supplied to the endless device is positioned on the hole rows.
13. The apparatus according to claim 11 further comprising: a
dielectric layer which is provided on the circumferential surface
of the endless device, and to which a charge for electrostatically
adsorbing the recording medium, is applied; a charging roller which
applies the charge to the dielectric layer; and a neutralizing
charger which neutralizes the charge from the recording medium on
which the image is formed.
14. The apparatus according to claim 11, wherein the endless device
is a drum, and the switching blade moves in the axial direction of
the drum.
15. The apparatus according to claim 11, wherein the endless device
includes the front side hole row which is formed in a position
which corresponds to the leading end of the recording medium in a
movement direction which is held to the endless device; the rear
side hole row which is formed in a position which corresponds to
the trailing end of the recording medium in the movement direction;
and a plurality of intermediate suction holes which communicates
with the negative pressure chamber and which is formed between the
front side hole row and the rear side hole row.
16. The apparatus according to claim 15, wherein the intermediate
suction holes are smaller than those of the front side hole row and
the rear side hole row.
17. A conveying method of a recording medium comprising: generating
a negative pressure in a negative pressure chamber of an endless
device including a plurality of suction holes on a circumferential
surface; opening suction holes in a position which corresponds to a
size of the recording medium, among the plurality of suction holes;
closing at least a part of the suction holes in a position which is
not covered by the recording medium, among, the plurality of
suction holes; adsorbing the recording medium to the
circumferential surface of the endless device, by allowing the
negative pressure to act on the recording medium through the opened
suction holes; and conveying the recording medium to the recording
head unit by rotating the endless device.
18. The method according to claim 17, wherein the recording medium
is supplied to the circumferential surface of the endless device
such that the leading end and the trailing end are supposed to
position at the opened suction holes.
19. The method according to claim 17, wherein a charge is applied
to the circumferential surface of the endless device, in order to
electrostatically adsorb the recording medium, using the charge,
and wherein the recording medium is adsorbed in the electrostatic
manner to the circumferential surface of the endless device, and
the leading end and the trailing end of the recording medium are
adsorbed to the endless device using the negative pressure.
20. The method according to claim 17, wherein the leading end and
the trailing end of the recording medium in the movement direction,
are adsorbed to the endless device using the negative pressure
which acts through the suction holes, and portions between the
leading end and the trailing end of the recording medium are
adsorbed to the endless device using the negative pressure which
acts through suction holes smaller than the above suction holes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from: U.S. Provisional Application No. 61/384,074 filed on
Sep. 17, 2010, the entire contents of each of which are
incorporated herein reference.
FIELD
[0002] Embodiments described herein relate generally to a holding
device which holds a recording medium such as a sheet, an image
forming apparatus, and a conveying method of the recording
medium.
BACKGROUND
[0003] For example, an inkjet recording apparatus or the like,
includes an endless device which is formed of a rotating drum or
belt, and recording heads which are arranged along a
circumferential surface of the endless device. The sheet is
conveyed to the recording heads, when the sheet is held on the
circumferential surface of the endless device and the endless
device rotates. One example of the endless device is a drum whose
circumferential surface is provided with a plurality of suction
holes. In the interior of the drum, a negative pressure chamber
which communicates with the suction holes, is defined. A suction
fan is communicated with the negative pressure chamber. It is
possible to adsorb the sheet onto the circumferential surface of
the drum, since the negative pressure chamber has a negative
pressure when the suction fan is rotated and air in the negative
pressure chamber is discharged.
[0004] A holding device in the related art, which includes the
endless device, has a plurality of negative pressure chambers which
are formed by division of the drum in a circumferential direction
of the drum. These negative pressure chambers communicate with a
plurality of suction holes which are formed on the circumferential
surface of the drum. Shutters which open and close each of negative
pressure chambers are respectively provided to an end surface of
the drum. When the shutter is open, the air in the negative
pressure chamber with the shutter is sucked due to the suction fan,
thereby generating the negative pressure in the negative pressure
chamber. A sheet of a desired size is adsorbed onto the
circumferential surface of the drum by generating the negative
pressure in one or more negative pressure chambers, according to
the size of the sheet. However, the holding device having the
shutter in the related art is negatively affected by a shock which
is transmitted to the drum when the shutter opens and closes,
resulting in a poor image formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a side view which schematically shows the inside
of an image forming apparatus according to a first embodiment;
[0006] FIG. 2 is a cross-sectional view which shows a sheet holding
device of the image forming apparatus;
[0007] FIGS. 3A, 3B, and 3C are respective expanded views which
show a circumferential surface of a drum according to the first
embodiment and sheets of different size from each other;
[0008] FIG. 4 is a cross-sectional view which shows a part of the
drum, and a switching blade at a first position;
[0009] FIG. 5 is a cross-sectional view which shows a part of the
drum, and a state in which the switching blade moves to a second
position;
[0010] FIG. 6 is a block diagram which shows a configuration of a
controller of the image forming apparatus;
[0011] FIG. 7 is a flowchart which shows an image forming process
of the image forming apparatus;
[0012] FIGS. 8A, 8B, and 8C are respective expanded views which
show the circumferential surface of the drum according to a second
embodiment and sheets of different size from each other; and
[0013] FIG. 9 is a side view which schematically shows the image
forming apparatus according to a third embodiment.
DETAILED DESCRIPTION
[0014] In general, according to one embodiment, the image forming
apparatus includes an endless device, and a rotation mechanism
which rotates the endless device in a predetermined direction. The
endless device includes a plurality of suction holes which are
formed on the circumferential surface thereof, and a negative
pressure chamber which communicates with the suction holes.
Further, the image forming apparatus includes a suction mechanism
which discharges air in the negative pressure chamber, an opening
and closing mechanism which has a switching blade, a driving
mechanism which moves the switching blade to a first position and a
second position, a recording head unit, a supply mechanism which
supplies a recording medium toward the circumferential surface of
the endless device, and a controller. If the switching blade moves
to the first position, the suction hole is blocked. If the
switching blade moves to the second position, the suction hole
communicates with the negative pressure chamber. The controller
drives the opening and closing mechanism according to the size of
the recording medium.
[0015] Hereinafter, the image forming apparatus according to the
first embodiment will be described with reference to drawings FIGS.
1 to 7. FIG. 1 shows an inkjet printer 10 which is an example of
the image forming apparatus. The inkjet printer 10 (hereinafter
referred to as a printer) includes a housing 11, a drum 12 which is
an example of the endless device which is accommodated in the
housing 11, a sheet receiving unit 13, a supply mechanism 14, a
charging roller 15, a recording head unit 16, a neutralizing
charger 17, a sheet discharge mechanism 18, an operation unit 19
having a display device 19a, a controller 20, a power switch 21,
and the like.
[0016] The drum 12 which is an example of the endless device
includes a cylinder portion 12a, and rotates at a predetermined
circumferential speed around a rotation axis 25 in the direction
which is shown by an arrow R1, using a rotation mechanism which
includes a motor 22 (shown in FIG. 6). The position of the drum 12
in the rotation direction is detected by a rotation angle sensor 26
such as an encoder, or the like. The cylinder portion 12a of the
drum 12 is formed of a conductive material such as an aluminum
alloy, or the like. The cylinder portion 12a of the drum 12 has an
inner circumferential surface 12b, and an outer circumferential
surface 12c. A dielectric layer 27 formed of, for example, a resin
film is provided at the outer circumferential surface 12c. The
cylinder portion 12a is grounded. A potential of the cylinder
portion 12a is maintained to 0 V as a counter electrode when being
charged using the charging roller 15.
[0017] The sheet receiving unit 13 receives a plurality of sheets S
as the recording medium. An example of the sheet S is a sheet of a
regular size, and a resin film, or a label may be used. The supply
mechanism 14 includes a pick-up roller 28, a sheet feeding roller
29, a separation roller 30, a sheet conveying path 31, and a pair
of resist rollers 32. The sheet S, which is taken out one by one
using the pair of resist rollers 32, is sent to the sheet conveying
path 31. The leading end of the sheet S which is sent to the sheet
conveying path 31, is aligned using the pair of resist rollers
32.
[0018] The charging roller 15 is provided to face the
circumferential surface 12c of the drum 12. A DC power circuit 34
is connected to the charging roller 15. When a DC voltage is
applied to the charging roller 15 using the DC power circuit 34, a
charge for electrostatically adsorbing the sheet S is generated on
the circumferential surface 12c of the drum 12. The sheet S which
is adsorbed onto the drum 12 is conveyed toward the recording head
unit 16. The charging roller 15, the dielectric layer 27 of the
drum 12, the DC power circuit 34, or the like, forms an
electrostatic adsorption device for electrostatically adsorbing the
sheet S to the circumferential surface 12c of the drum 12.
[0019] The sheet discharge mechanism 18 includes a separation
member 35, a conveying guide 36, sheet discharge rollers 37, and a
sheet discharge tray 38. A cleaner 39 for cleaning the
circumferential surface 12c of the drum 12 is provided between the
separation member 35 and the charging roller 15. The charging
roller 15, the separation member 35, and the cleaner 39 include a
moving mechanism for being separated from the sheet S, in order not
to come into contact with a surface on which an image of the sheet
S is formed, when the sheet S passes through after the image
formation.
[0020] The recording head unit 16 includes inkjet head 16a, 16b,
16c, and 16d for each color which are capable of performing color
printing. These inkjet head 16a, 16b, 16c, and 16d are all line
heads which extend in the direction of the axis line X1 of the drum
12, and are attached to a frame 16e, respectively. The inkjet head
16a, 16b, 16c, and 16d include a plurality of nozzle holes (not
shown) for ejecting ink.
[0021] An example of the inkjet head 16a, 16b, 16c, and 16d
includes a piezo element as a driving member. The ink is ejected
from the nozzle hole when the piezo element is deformed by applying
a voltage to the piezo element and the ink is pressurized. In
addition, as another example of the driving member, a heating
element may be adopted. When the ink is heated using the heating
element, the ink is ejected from the nozzle hole due to the
pressure of bubble which is generated due to evaporation of
ink.
[0022] FIG. 2 is a cross-sectional view which shows the inside of
the printer 10. The printer 10 has a sheet holding device 50
including the drum 12. Hereinafter, the sheet holding device 50
will be described. The cylinder portion 12a of the drum 12 includes
a plurality of suction holes 51. These suction holes 51 pass
through over the inner circumferential surface 12b and the outer
circumferential surface 12c of the cylinder portion 12a. The
negative pressure chamber 52 is defined in the inside of the drum
12. The suction holes 51 communicate with the negative pressure
chamber 52. The drum 12 is supported by the housing 11 using the
rotation axis 25, and rotates around the axis line X1. A direction
of the axis line X1 is the width direction of the drum 12, that is,
the width direction of the endless device.
[0023] The air discharging holes 55 are formed at one end portion
of the drum 12. The air discharging holes 55 communicate with a
duct 56. A suction fan 57 is provided in the duct 56. The suction
fan 57 is rotated using a motor 57a. When the suction fan 57 is
rotated, and the air in the negative pressure chamber 52 is
discharged to the outside from the duct 56, a negative pressure
which is lower than the atmospheric pressure is generated in the
negative pressure chamber 52. The suction holes 51, the negative
pressure chamber 52, the air discharging holes 55, the suction fan
57, the duct 56, and the like form a suction mechanism 60 which
uses a negative pressure.
[0024] FIGS. 3A, 3B, and 3C are respective expanded views of the
circumferential surface 12c of the drum 12 according to the
embodiment. FIG. 3A shows two sheets S.sub.1 of a first size (for
example, A4 size). FIG. 3B shows one sheet S.sub.1 of the first
size (for example, A4 size). FIG. 3C shows two sheets S.sub.2 of a
second size (for example, the size of a postcard).
[0025] These sheets S.sub.1 and S.sub.2 respectively have a pair of
long sides which are parallel to each other and a pair of short
sides which form right angles (90.degree.) with respect to the long
sides. Here, a state where the long side of the sheet goes along
the axis line X1 of the drum 12 is referred to as a crosswise
position, and a state where the short side of the sheet goes along
the axis line X1 of the drum 12 is referred to as a lengthwise
position. FIG. 3A shows the first size sheets S.sub.1 in the
crosswise position, FIG. 3B shows the first size sheet S.sub.1 in
the lengthwise position, and FIG. 3C shows the second size sheets
S.sub.2 in the lengthwise position.
[0026] As shown in FIGS. 3A, 3B, and 3C, hole rows 51A to 51G which
are formed of a plurality of suction holes 51, are formed on the
cylinder portion 12a of the drum 12. These hole rows 51A to 51G are
formed of the plurality of suction holes 51 which is formed at
intervals in the direction of axis line X1 of the drum 12. These
hole rows 51A to 51G are formed in a position which corresponds to
the leading end or the trailing end of the sheets S.sub.1 and
S.sub.2 in the movement direction. Here, the "leading end" of the
sheet is an end which is positioned at the front side in the
rotation direction of the drum 12, that is, the front side of the
sheet S in the movement direction, and the "trailing end" of the
sheet is an end which is positioned at the rear side in the
rotation direction of the drum 12, that is, the rear side of the
sheet S in the movement direction. A sensor 65 (shown in FIG. 1)
which detects the size of the sheet is provided in the sheet
conveying path 31.
[0027] The first hole row 51A is present in a position which
corresponds to the leading end of the sheets S.sub.1 and S.sub.2,
so as to adsorb the leading end of the sheets S.sub.1 and S.sub.2
of each size. As shown in FIG. 3C, the second hole row 51B is
present in a position which corresponds to the trailing end of the
small sheet S.sub.2 of the lengthwise position. As shown in FIG.
3A, the third hole row 51C is present in a position which
corresponds to the trailing end of the sheet of S.sub.1 of the
crosswise position. As shown in FIG. 3B, the fourth hole row 51D is
present in a position which corresponds to the trailing end of the
sheet S.sub.1 of the lengthwise position. As shown in FIGS. 3A and
3C, the fifth row hole 51E is present in a position which
corresponds to the leading end of the second sheets S.sub.1 and
S.sub.2. As shown in FIG. 3C, the sixth hole row 51F is present in
a position which corresponds to the trailing end of the second
small sheet S.sub.2 of the lengthwise position. As shown in FIG.
3A, the seventh hole row 51G is present on the position which
corresponds to the trailing end of the second sheet S.sub.1 of the
crosswise position. Since the position and number of these hole
rows is set according to a specification of the printer 10, it is
needless to say that the hole rows are not limited to the hole rows
51A to 51G which are shown in FIGS. 3A to 3C.
[0028] The printer 10 includes an opening and closing mechanism 70
which opens and closes the hole rows 51B to 51G. The opening and
closing mechanism 70 includes a plurality of switching blade 71
which is provided in each hole row 51B to 51G. These switching
blades 71 are extending in the direction of the axis line X1, along
the inner circumferential surface 12b of the cylinder portion 12a
of the drum 12. The first hole row 51A which is positioned at the
foremost in the movement direction, is covered by the leading end
of the sheets S.sub.1 and S.sub.2 of each size, therefore, it is
possible to omit the switching blade 71. However, the switching
blade 71 may be provided to the hole row 51A.
[0029] Since all of the switching blades 71 are provided in the
cylinder portion 12a of the drum 12, the switching blades move
around the axis line X1 along with the drum 12. In addition, the
switching blades 71 are able to slide in the axis line X1 direction
of the drum 12, respectively. These switching blades 71 move to a
first position (a closing position) shown in FIG. 4 and a second
position (an open position) shown in FIG. 5. In the switching blade
71, through holes 72 are formed at positions which correspond to
the suction holes 51 of each row hole 51A to 51G, respectively.
When the switching blade 71 moves to the first position (shown in
FIG. 4), since the positions of the suction holes 51 and the
through holes 72 are deviated from each other, the negative
pressure chamber 52 is closed. When the switching blade 71 moves to
the second position (shown in FIG. 5), since the positions of the
suction holes 51 and the through holes 72 match each other, the
negative pressure chamber 52 and the outside (the atmospheric side)
of the drum 12 communicate with each other.
[0030] The switching blade 71 moves in the direction shown by an
arrow M1 shown in FIG. 4 and the direction shown by an arrow M2
shown in FIG. 5, along the axis line X1 of the drum 12, using the
driving mechanism 75. The driving mechanism 75 is attached to a
member on the stationary side (for example, a frame of the housing
11) with respect to the rotating drum 12. The driving mechanism 75
includes, for example, an actuator 76 which is formed of an
electric motor, a driving member 78 which includes a driving unit
77 which is driven using the actuator 76, and a power transmission
unit 79 which uses, for example, a rack and pinion. The driving
unit 77 can be engaged with an engaging portion 71a of the
switching blade 71, when the switching blade 71 of each hole row
51B to 51G moves to a position which corresponds to the driving
unit 77 by the rotation of the drum 12. It is possible to use a
solenoid in the actuator 76. The power transmission unit 79 may
adopt a suitable power transmission member if necessary, such as a
chain and sprocket, a wire and pulley, or a combination of spur
gears, or the like. The switching blade 71 moves to the drum 12 in
the direction of the axis line X1. For this reason, the driving
mechanism 75 can move the switching blade 71 between one side in
the longitudinal direction and the first and second positions. In
addition, the driving mechanism 75 may be disposed at the drum 12.
In such a case, the driving mechanism 75 rotates along with the
drum 12.
[0031] FIG. 6 is a block diagram which shows a configuration of the
controller 20 of the printer 10 according to the embodiment. The
controller 20 includes a CPU (Central Processing Unit) 80 which
functions as a processor. In the CPU 80, a ROM (Read Only Memory)
82, a RAM (Random Access Memory) 83, a communication interface unit
84, a neutralizing and separating controller 85, a discharging
roller controller 86, a cleaner driver 87, a sensor input and
output port 88, a conveying roller motor driver 90, a drum rotation
motor driver 91, a discharge roller motor driver 92, a opening and
closing mechanism driver 93, a inkjet head controller 94, a suction
fan motor driver 95, a display and operation controller 96, and the
like, are connected through a bus line 81.
[0032] A program or a variety of persistent data which controls the
CPU 80 is stored in the ROM 82. In the RAM 83, various memory areas
are formed for storing a variety of data which is necessary for
forming images. The communication interface unit 84 controls a data
communication which is performed with an external device, through
the communication line. The neutralizing and separating controller
85 controls the separation member 35 and the neutralizing charger
17. The charging roller controller 86 controls a DC voltage which
is supplied to the charging roller 15. The cleaner driver 87 drives
the cleaner 39. Various sensors (for example, a rotation angle
sensor 26 or a sheet size sensor 65) are connected to a sensor
input and output port 88.
[0033] The conveying roller motor driver 90 drives a motor 28a of
the pick-up roller 28, a motor 29a of the sheet feeding roller 29,
and a motor 32a of the pair of resist rollers 32. The drum rotation
motor driver 91 drives a motor 22 which rotates the drum 12. The
sheet discharge roller motor driver 92 drives a motor 37a which
rotates the sheet discharge roller 37. The opening and closing
mechanism driver 93 drives the actuator 76 of the opening and
closing mechanism driver 70. The inkjet controller 94 controls an
ink ejection operation of the inkjet head 16a, 16b, 16c, and 16d.
The suction fan motor driver 95 drives a motor 57a of the suction
fan 57. The display and operation controller 96 controls a display
device 19a and an operation unit 19 having a touch panel. It is
possible to store information which is necessary for image forming,
and information such as the size of the sheet, the direction of the
sheet (crosswise position, lengthwise position), or the like, in
the RAM 83 by operating the operation unit 19.
[0034] Hereinafter, actions of image forming process using the
printer 10 according to the embodiment will be described with
reference to a flowchart in FIG. 7. In Act 1 in FIG. 7, information
on the size of the sheet is obtained. It is possible to manually
input by operating the operation unit 19 to obtain size information
on the sheet. The size or direction of the sheet (crosswise
position, lengthwise position) may be detected using the sheet size
sensor 65. Further, information on the number of pages to be
printed is obtained in Act 2.
[0035] In Act 3 in FIG. 7, the drum 12 is temporarily rotated at a
low speed, and the switching blade 71 is moved according to the
size of the sheet. The initial position (its original position) of
the switching blade 71 is the first position (the closing position)
shown in FIG. 4. Among each hole row 51B to 51G, the switching
blade 71 which corresponds to a trailing end of the sheet is moved
to the second position (the open position) shown in FIG. 5, using
the opening and closing mechanism 70, according to the size of the
sheet. As shown in FIG. 3A or FIG. 3C, when holding two sheets, the
switching blade 71 of the hole row 51E which corresponds to the
leading end of the second sheet is moved to the second position
(the open position), as well. The lower pressure (the negative
pressure) than the atmospheric pressure is generated in the
negative pressure chamber 52, since the air in the negative
pressure chamber 52 is discharged to the outside from the duct 56
due to rotation of the suction fan 57. Due to this, the leading end
and the trailing end of the sheet are ready to be adsorbed to the
drum 12.
[0036] In this Act 3, it is possible to open in advance the suction
hole 51 which is present in a position corresponding to the size of
the sheet, by operating the opening and closing mechanism 70,
before forming images on the sheet S. For this reason, it is
possible to prevent a shock from occurring when forming images
using the recording head unit 16.
[0037] In Act 4 in FIG. 7, the rotation of the drum 12 returns to
its original speed, and the drum 12 rotates at a high speed. In Act
5, the DC voltage is applied to the charging roller 15 by a DC
power circuit 34. In Act 6, the sheet S is supplied between the
circumferential surface 12c of the drum 12 and the charging roller
15. That is, the sheet S which is received in the sheet receiving
unit 13 is conveyed to a nip between the circumferential surface
12c of the drum 12 and the charging roller 15, using a supply
mechanism 14. The controller 20 controls the operation time, or the
like, of the supply mechanism 14, so that the leading end of the
sheet S which is conveyed using the supply mechanism 14 is
positioned on the first hole row 51A of the rotating drum 12. The
sheet S is charged with a charge of a first polarity, and the
dielectric layer 27 of the drum 12 is charged with a charge of a
second polarity.
[0038] In Act 7, the leading end and the trailing end of the sheet
S are adsorbed to the circumferential surface 12c of the drum 12,
due to the negative pressure of the suction hole 51. In addition,
the sheet S is electrostatically adsorbed to the drum 12. For this
reason, the sheet S which is supplied to the circumferential
surface 12c of the drum 12 moves to a rotation direction R1 of the
drum 12 along with the drum 12, without separating from the
circumferential surface 12c of the drum 12.
[0039] In Act 8 in FIG. 7, the printing is started. In a case of
color printing, when the sheet S reaches the first inkjet head 16a,
the first color ink is ejected to the sheet S from the first inkjet
head 16a. The sheet S rotates while being adsorbed to the drum 12,
and reaches the second inkjet head 16b. By doing this, the second
color ink is ejected to the sheet S from the second inkjet head
16b. Further, when the drum 12 rotates, the third color ink is
ejected to the sheet S from the third inkjet head 16c. In addition,
when the drum 12 rotates, the fourth color ink is ejected to the
sheet S from the fourth inkjet head 16d. In this manner, an image
is formed on the sheet S during the rotation of the drum 12. That
is, the printer 10 performs color printing using a multi-path
process of a line head-type.
[0040] When the printing operation ends in Act 9, an AC voltage is
applied to the sheet S on which the image is formed using the
recording head unit 16, using the neutralizing charger 17. By doing
this, an adsorption force of the sheet S with respect to the drum
12 is weakened. The sheet S is separated from the drum 12 using the
separation member 35, and is discharged onto the sheet discharge
tray 38 through a conveying guide 36 and the sheet discharge roller
37.
[0041] In Act 10 in FIG. 7, it is determined whether or not the
subsequent sheet is present, using the sensor which detects the
presence of the sheet, or by information on the number of sheets to
be printed which is input to the controller 20. If there is no
subsequent sheet, the process ends. If there is a subsequent sheet,
the process returns to Act 5 again, and printing for the subsequent
sheet is performed.
[0042] According to the sheet holding device 50 of the embodiment,
the leading end and trailing end of the sheet S which are easily
separated from the drum 12 are adsorbed to the circumferential
surface 12c of the drum 12, due to the negative pressure of the
suction holes 51, in addition to the fact that the entire sheet S
is adsorbed to the circumferential surface 12c of the drum 12 due
to the electrostatic adsorption force. In addition, among each
suction hole 51, at least a part of the suction hole 51 which is
not covered by the sheet S, is closed by the switching blade 71. In
this manner, the air is prevented from being sucked into the
negative pressure chamber 52, and the negative pressure is not
decreased. For this reason, it is possible to reliably hold the
sheet S to the circumferential surface 12c of the drum 12, even
when the circumferential surface 12c which has a curvature like the
cylinder portion 12a of the drum 12 rotates at a high speed. If the
sheet S becomes wet due to the ink which is ejected to the sheet S
from the recording head unit 16, a bending stress occurs in the
sheet S. Even such a sheet S can be reliably held on the
circumferential surface 12c of the drum 12. For this reason, since
the drum 12 rotates while reliably attaching the sheet S thereon,
it is possible to form images with high quality at a high speed,
and prevent paper jamming.
[0043] FIGS. 8A to 8C are expanded views which show a cylinder
portion 12a of a drum 12 of a sheet holding device 50' according to
a second embodiment, and correspond to the first embodiment (FIGS.
3A to 3C). The sheet holding device 50' according to the embodiment
also includes a suction mechanism 60 and an opening and closing
mechanism 70, similarly to the first embodiment. The sheet holding
device 50' is configured to adsorb a sheet to the drum 12 only
using a negative pressure without performing electrostatic
adsorption. Intermediate suction holes 99 which is adsorbed between
the leading end and the trailing end of the sheet are formed in the
cylinder portion 12a of the drum 12, in addition to hole rows 51A
to 51G which are the same as those in the first embodiment. These
intermediate suction holes 99 communicate with the negative
pressure chamber 52. The intermediate suction holes 99 are smaller
than the suction holes 51 which form the hole rows 51A to 51G. For
this reason, even if the switching blade 71 is not provided in the
intermediate suction holes 99, it is possible to prevent air from
being sucked to the negative pressure chamber 52 from the outside
of the drum 12. In addition, it may be possible to open and close
the intermediate suction holes 99, by providing the switching blade
71 in the intermediate suction holes 99.
[0044] In the second embodiment, since the sheet is held to the
drum 12 only using the adsorption force due to the negative
pressure, it is not necessary to provide the dielectric layer or
the charging roller, and the DC power circuit of the first
embodiment. Accordingly, it is advantageous that the structure can
be simplified compared to a case where the electrostatic adsorption
is used together. The other configurations and operation of the
sheet holding device 50' are common to the sheet holding device 50
in the first embodiment, and will be denoted by the same reference
numerals, and a description thereof will be omitted.
[0045] FIG. 9 shows an inkjet printer 10A according to a third
embodiment. This inkjet printer 10A has a belt 100 as an example of
an endless device. The belt 100 of the sheet holding device is
stretched across a first rotation body 101 and a second rotation
body 102, and performs an endless rotation movement (a circulation
movement) in the direction of an arrow R2 using a driving mechanism
(not shown). A recording head unit 16 including inkjet heads 16a,
16b, 16c, and 16d, is disposed in the movement direction of the
belt 100. The sheet S, which is supplied by a supply mechanism 103,
is supplied between the belt 100 and a charging roller 105 through
a conveying path 104. The charging roller 105 applies a charge for
electrostatic adsorption to a dielectric layer which is provided on
a circumferential surface of the belt 100. An image is formed on
the sheet S using the inkjet heads 16a, 16b, 16c, and 16d when the
sheet S is conveyed by the belt 100 in the direction shown by an
arrow M3. The sheet S on which the image is formed is discharged
from a sheet conveying mechanism 106. A negative pressure chamber
52 is defined in the inside of the belt 100. A negative pressure is
generated in the negative pressure chamber 52, when air in the
negative pressure chamber 52 is discharged using the suction
mechanism.
[0046] Hole rows which are formed of suction holes are formed in
the belt 100 in a position which corresponds to at least the
leading end and the trailing end of the sheet S. These suction
holes communicate with the negative pressure chamber 52. In
addition, the switching blade 71 is provided in the belt 100. The
the switching blade 71 opens and closes the suction holes. A
support member 110 is provided in the vicinity of the recording
head unit 16 of the belt 100, in order to prevent the belt 100 from
bending due to the negative pressure. The switching blade 71 can
move to a first position which closes suction holes and a second
position which opens the suction holes, using a driving mechanism
75. The other configuration and operation of the printer 10A are
common to the printer 10 in the first embodiment, they will be
denoted by the same reference numeral, and a description thereof
will be omitted.
[0047] As described above, in the printer according to each of the
embodiments, sheets are adsorbed to the circumferential surface of
the endless device before forming the image, by opening and closing
suction holes in a position which corresponds to the size of the
sheet, using an switching blade. For this reason, an image forming
operation is not affected due to a vibration, and it is possible to
promptly move to the image forming operation with respect to a
recording medium which is supplied to the endless device. In
addition, since at least a part of the suction holes which are not
contributing to the adsorption of the sheet, are shut using the
switching blade, it is possible to suppress suction of the air into
the negative pressure chamber, and maintain the adsorption force of
the sheet. The embodiment can be applied to a thermal printer or a
wire dot printer, in addition to the inkjet printer.
[0048] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *