U.S. patent application number 13/628584 was filed with the patent office on 2013-09-12 for transport device, transfer device, and image forming apparatus.
This patent application is currently assigned to FUJI XEROX CO., LTD.. The applicant listed for this patent is FUJI XEROX CO., LTD.. Invention is credited to Atsuyuki KITAMURA, Junichi MURAKAMI, Shuichi NISHIDE, Atsushi OGIHARA, Tetsuji OKAMOTO, Masahiro SATO, Wataru SUZUKI, Koichi WATANABE.
Application Number | 20130234386 13/628584 |
Document ID | / |
Family ID | 49113396 |
Filed Date | 2013-09-12 |
United States Patent
Application |
20130234386 |
Kind Code |
A1 |
MURAKAMI; Junichi ; et
al. |
September 12, 2013 |
TRANSPORT DEVICE, TRANSFER DEVICE, AND IMAGE FORMING APPARATUS
Abstract
A transport device includes a transporting member that
transports an object that is wound around an outer peripheral
surface thereof by rotating; a holding unit that is rotatably
supported by the transporting member at a first end thereof, the
holding unit holding a leading end of the object in a transport
direction by gripping the leading end between a second end thereof
and the outer peripheral surface when the object enters a space
between the second end and the outer peripheral surface; and a
positioning unit disposed on the transporting member or the holding
unit so as to be movable downstream in a direction in which the
object enters the space. The positioning unit contacts the leading
end of the object that has entered the space and positions the
object in the transport direction when the holding unit moves to
hold the object.
Inventors: |
MURAKAMI; Junichi;
(Yokohama-shi, JP) ; KITAMURA; Atsuyuki;
(Yokohama-shi, JP) ; SATO; Masahiro;
(Yokohama-shi, JP) ; OGIHARA; Atsushi; (Ebina-shi,
JP) ; OKAMOTO; Tetsuji; (Yokohama-shi, JP) ;
WATANABE; Koichi; (Yokohama-shi, JP) ; SUZUKI;
Wataru; (Ebina-shi, JP) ; NISHIDE; Shuichi;
(Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI XEROX CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
FUJI XEROX CO., LTD.
Tokyo
JP
|
Family ID: |
49113396 |
Appl. No.: |
13/628584 |
Filed: |
September 27, 2012 |
Current U.S.
Class: |
271/147 |
Current CPC
Class: |
G03G 15/1665
20130101 |
Class at
Publication: |
271/147 |
International
Class: |
B65H 1/08 20060101
B65H001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2012 |
JP |
2012-049253 |
Claims
1. A transport device comprising: a transporting member that
transports an object that is wound around an outer peripheral
surface thereof by rotating; a holding unit that is rotatably
supported by the transporting member at a first end thereof, the
holding unit holding a leading end of the object in a transport
direction by gripping the leading end between a second end thereof
and the outer peripheral surface when the object enters a space
between the second end and the outer peripheral surface; and a
positioning unit disposed on the transporting member or the holding
unit so as to be movable downstream in a direction in which the
object enters the space, the positioning unit contacting the
leading end of the object that has entered the space and
positioning the object in the transport direction when the holding
unit moves to hold the object.
2. The transport device according to claim 1, wherein the
positioning unit moves from a positioning position, in which the
positioning unit positions the object, downstream in the transport
direction when the holding unit moves toward a separated position
in which the second end of the holding unit is separated from the
outer peripheral surface, and wherein the positioning unit returns
to the positioning position when the holding unit moves from the
separated position to a gripping position in which the holding unit
grips the leading end of the object between the second end and the
outer peripheral surface.
3. The transport device according to claim 2, further comprising: a
linkage unit that transmits a driving force from a single driving
unit to the holding unit and the positioning unit and that links
movement of the positioning unit to movement of the holding
unit.
4. A transfer device that is the transport device according to
claim 1, wherein the object is a recording medium and the
transporting member is a transfer member that transfers an image
received from the outside to the recording medium.
5. An image forming apparatus comprising: the transfer device
according to claim 4; and an image carrier that carries an image
that is to be transferred by the transfer device.
6. The transport device according to claim 1, wherein the holding
unit interferes with the positioning unit when seen from an axial
direction of the transporting member, a plurality of protruding
portions are formed in the second end of the holding unit, a
plurality of protruding portions are formed in an end of the
positioning unit, and the protruding portions of the positioning
unit are arranged between the protruding portions of the holding
unit when the holding unit moves to hold the object.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2012-049253 filed Mar.
6, 2012.
BACKGROUND
Technical Field
[0002] The present invention relates to a transport device, a
transfer device, and an image forming apparatus.
SUMMARY
[0003] According to an aspect of the invention, a transport device
includes a transporting member that transports an object that is
wound around an outer peripheral surface thereof by rotating; a
holding unit that is rotatably supported by the transporting member
at a first end thereof, the holding unit holding a leading end of
the object in a transport direction by gripping the leading end
between a second end thereof and the outer peripheral surface when
the object enters a space between the second end and the outer
peripheral surface; and a positioning unit disposed on the
transporting member or the holding unit so as to be movable
downstream in a direction in which the object enters the space. The
positioning unit contacts the leading end of the object that has
entered the space and positions the object in the transport
direction when the holding unit moves to hold the object.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] An exemplary embodiment of the present invention will be
described in detail based on the following figures, wherein:
[0005] FIG. 1 is a schematic view illustrating the structure of an
image forming apparatus;
[0006] FIG. 2 is a schematic view illustrating the structure of a
leading end gripper;
[0007] FIG. 3 is a perspective view illustrating the structure of
the leading end gripper;
[0008] FIGS. 4A and 4B illustrate the structure of the leading end
gripper;
[0009] FIGS. 5A to 5D illustrate a gripping operation performed by
the leading end gripper;
[0010] FIGS. 6A to 6C illustrate the gripping operation performed
by the leading end gripper;
[0011] FIG. 7 is a schematic view illustrating an appropriate
retracted position of a positioning unit of the leading end
gripper; and
[0012] FIG. 8 is a schematic view illustrating the structure of a
leading end gripper according to a comparative example.
DETAILED DESCRIPTION
[0013] Hereinafter, an exemplary embodiment of the present
invention will be described with reference to the drawings.
Structure of Image Forming Apparatus according to Present
Exemplary Embodiment
[0014] First, the structure of an image forming apparatus according
to the present exemplary embodiment will be described. FIG. 1 is a
schematic view illustrating the structure of an image forming
apparatus 50 according to the present exemplary embodiment.
[0015] As illustrated in FIG. 1, the image forming apparatus 50
includes an image forming apparatus body 62 and various components
disposed in the image forming apparatus body 62. An image forming
unit 10, a recording medium feeder 40, and a controller 60 are
disposed in the image forming apparatus body 62. The image forming
unit 10 forms an image on a recording medium P, which is an example
of an object. The recording medium feeder 40 feeds the recording
medium P to the image forming unit 10. The controller 60 controls
the operation of each component of the image forming apparatus 50.
A recording medium output unit 63 is disposed on an upper part of
the image forming apparatus body 62. After an image has been formed
on the recording medium P by the image forming unit 10, the
recording medium P is output to the recording medium output unit
63.
[0016] The recording medium feeder 40 includes a recording medium
container 41 and a transport unit 45. The recording medium
container 41 contains the recording medium P. The transport unit 45
transports the recording medium P from the recording medium
container 41 to the image forming unit 10. The transport unit 45
includes a feed roller 42 and plural transport rollers 44. The feed
roller 42 feeds the recording medium P contained in the recording
medium container 41. The transport rollers 44 are arranged along a
transport path 51 of the recording medium P and transport the
recording medium P, which has been fed by the feed roller 42, to
the image forming unit 10.
[0017] The image forming unit 10 includes a photoconductor drum 11
and a transfer device 20. The photoconductor drum 11 is an example
of an image carrier that carries an image. The transfer device 20
transfers the image (toner image), which is carried by the
photoconductor drum 11, to the recording medium P. The
photoconductor drum 11 rotates in one direction (for example, the
direction of arrow A in FIG. 1).
[0018] A charging roller 12, an exposure device 13, a rotary
developing device 14, and a cleaner 15 are arranged around the
photoconductor drum 11 in the rotation direction of the
photoconductor drum 11. The charging roller 12, which is an example
of a charger, charges the photoconductor drum 11. The exposure
device 13 exposes the photoconductor drum 11, which has been
charged by the charging roller 12, with light, and thereby forms an
electrostatic latent image on the photoconductor drum 11. The
rotary developing device 14, which is an example of a developing
device, develops the electrostatic latent image, which has been
formed on the photoconductor drum 11 by the exposure device 13, and
thereby forms a toner image. The cleaner 15 cleans residual toner
(developer) remaining on the photoconductor drum 11.
[0019] The exposure device 13 forms an electrostatic latent image
on the basis of an image signal sent from the controller 60.
Examples of an image signal sent from the controller 60 include an
image signal received by the controller 60 from an external
apparatus.
[0020] The rotary developing device 14 includes a rotation shaft
14A; and developing units 14Y, 14M, 14C, and 14K for yellow (Y),
magenta (M), cyan (C), and black (K), which are arranged around the
rotation shaft 14A in the circumferential direction of the rotation
shaft 14A. The rotary developing device 14 rotates around the
rotation shaft 14A in the direction of arrow C. When one of the
developing units 14Y, 14M, 14C, and 14K of the rotary developing
device 14 is located at a facing position at which the developing
unit faces the photoconductor drum 11, an electrostatic latent
image formed on the photoconductor drum 11 is developed by using a
color toner corresponding to the developing unit located at the
facing position, and thereby a toner image is formed.
[0021] The transfer device 20 includes a transfer drum 21, which is
an example of a transporting member. The transfer drum transports
the recording medium P, which is wound around the outer peripheral
surface thereof, by rotating. In the transfer device 20, the
recording medium P, which has been transported by the transport
unit 45, is wound around the outer peripheral surface of the
transfer drum 21 (to be specific, the outer peripheral surface of
an elastic layer 21B described below), and rotates together with
the photoconductor drum 11. As a result, the recording medium P is
transported to a transfer position Tr (transfer region) between the
transfer drum 21 and the photoconductor drum 11, and the transfer
drum 21 transfers a toner image from the photoconductor drum 11 to
the recording medium P. That is, the transfer drum 21 also
functions as an example of a transfer member and transfers a toner
image from the photoconductor drum 11 to the recording medium P. As
described below, a leading end gripper 23 and a trailing end
gripper 27 respectively grip the leading end and the trailing end
of the recording medium P in the transport direction, and thereby
the recording medium P is wound around the outer peripheral surface
of the transfer drum 21.
[0022] The recording medium P is supplied to the transfer drum 21
at a supply position Pa shown in FIG. 1 (a holding-start position
at which the leading end gripper 23 (described below) starts
holding the recording medium P). The recording medium P is peeled
off the transfer drum 21 at a peel-off position Pb (a
holding-finish position at which the leading end gripper 23
finishes holding the recording medium P) shown in FIG. 1. The
structure of the transfer device 20 will be described below in
detail.
[0023] A fixing unit 30 is disposed downstream of (in FIG. 1,
above) the transfer position Tr along the transport path 51. The
fixing unit 30 fixes the toner image, which has been transferred to
the recording medium P by the transfer device 20, to the recording
medium P. The fixing unit 30 includes a heating roller 31 and a
pressing roller 32. The heating roller 31 heats the toner image on
the recording medium P. The pressing roller 32 presses the
recording medium P as a result of being pressed against the heating
roller 31.
[0024] In the fixing unit 30, the recording medium P is pressed and
heated by the pressing roller 32 and the heating roller 31, which
rotate with the recording medium P therebetween while transporting
the recording medium P downstream (in FIG. 1, upward) along the
transport path 51. As a result, the toner image is fixed to the
recording medium P.
[0025] Output rollers 46 are disposed downstream of the fixing unit
30 along the transport path 51. The output rollers 46 output the
recording medium P, to which the toner image has been fixed, to the
recording medium output unit 63. Structure of Transfer Device 20
according to Present
Exemplary Embodiment
[0026] Next, the structure of the transfer device 20 according to
the present exemplary embodiment will be described.
[0027] As illustrated in FIG. 1, the transfer device 20 includes
the transfer drum 21, the leading end gripper 23, and the trailing
end gripper 27. The leading end gripper 23, which is an example of
a leading end holding member, is disposed on the transfer drum 21
and grips the leading end of the recording medium P in the
transport direction. The trailing end gripper 27, which is an
example of a trailing end holding member, is disposed on the
transfer drum 21 and grips the trailing end of the recording medium
P in the transport direction.
[0028] A detection sensor 25 for detecting passage of the recording
medium P is disposed so as to face the outer peripheral surface of
the transfer drum 21. The detection sensor 25 is disposed upstream
of a standby position (described below) of the trailing end gripper
27 (the position of the trailing end gripper 27 shown in FIG. 1) in
the transport direction of the recording medium P.
Transfer Drum 21
[0029] As illustrated in FIG. 1, the transfer drum 21 is disposed
in the image forming apparatus body 62 so as to face the
photoconductor drum 11 and so as to be rotatable around a rotation
shaft 21D. The transfer drum 21 includes a base member 21A having a
cylindrical shape and the elastic layer 21B formed on the outer
peripheral surface of the base member 21A.
[0030] The base member 21A is electroconductive and is made of, for
example, a metal material. The elastic layer 21B is made of a
semi-conductive elastic material (for example, a resin material
such as a polyurethane resin).
[0031] The transfer drum 21 rotates in the direction of arrow B in
synchronism with the rotation of the photoconductor drum 11 while
the elastic layer 21B is in contact with the photoconductor drum
11. A part of the elastic layer 21B that contacts the
photoconductor drum 11 becomes elastically deformed.
[0032] A voltage (transfer bias) having a polarity opposite to that
of toner is applied to the base member 21A of the transfer drum 21,
and thereby a toner image is transferred from the photoconductor
drum 11 to the recording medium P, which is wound around the
elastic layer 21B, at the transfer position Tr.
[0033] A portion of the outer peripheral surface of the base member
21A in the circumferential direction is not covered with the
elastic layer 21B. This portion, in which the base member 21A is
exposed, will be referred to as an exposed portion 21C. Even when
the exposed portion 21C faces the photoconductor drum 11, the
exposed portion 21C does not contact the photoconductor drum
11.
[0034] In FIGS. 1 and 2, the outer periphery of the transfer drum
21 when the elastic layer 21B is elastically deformed is shown by
two-dot chain line K. For clarity, the two-dot chain line K is
drawn around the entire circumference of the transfer drum 21.
Trailing End Gripper 27
[0035] As illustrated in FIG. 1, the trailing end gripper 27
straddles the outer peripheral surface of the transfer drum 21 in
the axial direction of the transfer drum 21. The trailing end
gripper 27 is supported by support portions 27A disposed at ends of
the transfer drum 21 in the axial direction so that the trailing
end gripper 27 is capable of contacting and becoming separated from
the outer peripheral surface of the transfer drum 21.
[0036] The support portions 27A are rotatably supported by a
rotation shaft 27D, which is coaxial with the rotation shaft 21D of
the transfer drum 21. The trailing end gripper 27 rotates around
the transfer drum 21 independently of the transfer drum 21.
[0037] The trailing end gripper 27 is located at a predetermined
standby position (the position of the trailing end gripper 27 shown
in FIG. 1) on the outer periphery of the transfer drum 21 before
gripping the recording medium P. The standby position is, for
example, a position between the transfer position Tr (transfer
region) and the supply position Pa in the rotation direction of the
transfer drum 21.
[0038] The trailing end gripper 27 is made of a resin material
(such as PET, a polyimide resin, or a fluorocarbon resin) and has a
plate-like shape extending in the axial direction of the transfer
drum 21. The length of the trailing end gripper 27 in the axial
direction is larger than the maximum width of the recording medium
P (in the axial direction of the transfer drum 21), which is wound
around the transfer drum 21. Alternatively, the trailing end
gripper 27 may have a wire-like shape, a solid cylindrical shape,
or the like.
[0039] When the detection sensor 25 detects passage of the trailing
end of the recording medium P in the transport direction, the
trailing end gripper 27 moves from a position in which the trailing
end gripper 27 is separated from the transfer drum 21 to a position
in which the trailing end gripper 27 contacts the transfer drum 21,
and thereby holds the trailing end of the recording medium P by
gripping the trailing end between the trailing end gripper 27 and
the outer peripheral surface of the transfer drum 21 (to be
specific, the outer peripheral surface of the elastic layer
21B).
Leading End Gripper 23
[0040] As illustrated in FIG. 2, the leading end gripper 23 is
disposed in the exposed portion 21C of the transfer drum 21. The
leading end gripper 23 rotates together with the transfer drum
21.
[0041] The leading end gripper 23 includes a holding unit 22 and a
positioning unit 24. The holding unit 22 is rotatably supported by
the transfer drum 21 (to be specific, the base member 21A) at a
base end of the holding unit 22. The holding unit 22 holds the
leading end of the recording medium P in the transport direction by
gripping the leading end between a second end of the holding unit
22 and the outer peripheral surface of the transfer drum 21. The
positioning unit 24 is disposed on the transfer drum 21. The
positioning unit 24 contacts the leading end of the recording
medium P and positions the recording medium P in the transport
direction while the recording medium P is held by the holding unit
22.
[0042] A facing member 29, which faces the holding unit 22, is
disposed in the exposed portion 21C on the base member 21A of the
transfer drum 21. The facing member 29 has a facing surface 29A
that faces the holding unit 22. The facing surface 29A is located
inside of the outer peripheral surface of the elastic layer 21B (to
be specific, inside of the outer periphery (two-dot chain line K)
of the elastic layer 21B in an elastically deformed state). In the
present exemplary embodiment, the facing surface 29A is a part of
the outer peripheral surface of the transfer drum 21, and the
holding unit 22 grips the leading end of the recording medium P in
the transport direction between the holding unit 22 and the facing
surface 29A. Alternatively, the holding unit 22 may grip the
leading end of the recording medium P in the transport direction
between the holding unit 22 and the elastic layer 21B or between
the holding unit 22 and the base member 21A.
[0043] The holding unit 22 has a plate-like shape extending in the
axial direction of the transfer drum 21. The length of the holding
unit 22 in the axial direction is larger than the maximum width of
the recording medium P, which is wound around the transfer drum 21,
in the axial direction of the transfer drum 21. As illustrated in
FIG. 2, when seen from an end in the longitudinal direction, the
holding unit 22 has a shape that is bent so as to be convex outward
in the radial direction of the transfer drum 21 (diagonally toward
the upper left side in FIG. 2).
[0044] As illustrated in FIG. 3, at a tip end of the holding unit
22, plural protruding portions 227 are arranged in the longitudinal
direction X of the holding unit 22. The protruding portions 227
protrude upstream in the rotation direction of the transfer drum
21. The protruding portions 227 of the holding unit 22 hold the
leading end of the recording medium P in the transport direction.
Plural cutout portions 223, which extend from the tip end toward
the base end of the holding unit 22, are formed between the
protruding portions 227 so as to be arranged in the longitudinal
direction X of the holding unit 22. Due to the presence of the
cutout portions 223, the positioning unit 24 is movable toward the
base end of the holding unit 22 (downstream in the rotation
direction of the transfer drum 21).
[0045] As illustrated in FIGS. 4A and 4B, the base end of the
holding unit 22 is supported by a swing shaft 22C so as to be
swingable with respect to the base member 21A of the transfer drum
21. Thus, the holding unit 22 is movable between a contact position
(see FIG. 4A) in which the tip end of the holding unit 22 (an
upstream end in the rotation direction of the transfer drum 21)
contacts the facing surface 29A of the facing member 29 and a
separated position (see FIG. 4B) in which the tip end is separated
from the facing surface 29A of the facing member 29.
[0046] When the holding unit 22 is located in the separated
position, the holding unit 22 allows the recording medium P to
enter a space S between the holding unit 22 and the facing surface
29A of the facing member 29. When the holding unit 22 is located in
the contact position, the holding unit 22 is capable of holding the
recording medium P, which has entered the space S, by holding the
recording medium P between the holding unit 22 and the facing
surface 29A of the facing member 29. That is, the contact position
of the holding unit 22 is, in other words, a gripping position in
which the holding unit grips the recording medium P.
[0047] When the holding unit 22 is located in the gripping
position, the holding unit 22 is capable of passing the transfer
position Tr without contacting the photoconductor drum 11. That is,
when the holding unit 22 is located in the gripping position, the
holding unit 22 is located inside of the two-dot chain line K in
FIG. 2.
[0048] An attachment portion 225 is integrally formed with the base
end of the holding unit 22. A tension spring 22B, which is an
example of an elastic member (urging member), is attached to the
attachment portion 225. The attachment portion 225 extends downward
from the swing shaft 22C in FIG. 4A (toward the rotation shaft 21D
of the transfer drum 21 (see FIG. 1)). The tension spring 22B pulls
the attachment portion 225 with its elastic force, and thereby the
holding unit 22 is urged toward the gripping position (contact
position).
[0049] A cam 22D is disposed below the attachment portion 225 in
FIGS. 4A and 4B (between the attachment portion 225 and the
rotation shaft 21D of the transfer drum 21 (see FIG. 1)). The cam
22D functions to move the holding unit 22 to the separated
position. The cam 22D is fixed to a cam shaft 26, rotates together
with the cam shaft 26, contacts the attachment portion 225, and
moves the holding unit 22 to the separated position against the
elastic force of the tension spring 22B.
[0050] The positioning unit 24 has a plate-like shape extending in
the axial direction of the transfer drum 21. The length of the
positioning unit 24 in the axial direction is larger than the
maximum width of the recording medium P, which is wound around the
transfer drum 21, in the axial direction of the transfer drum 21.
As illustrated in FIG. 4A, when seen from an end in the
longitudinal direction, the positioning unit 24 has a shape that is
bent so as to be concave toward the holding unit 22 (diagonally
toward the upper left side in FIG. 4A).
[0051] As illustrated in FIG. 3, at a tip end of the positioning
unit 24, plural protruding portions 243 are arranged in the
longitudinal direction. The protruding portions 243 protrude into
the cutout portions 223 of the holding unit 22. The protruding
portions 243 are disposed so as to be substantially perpendicular
to the holding unit 22. The protruding portions 243 are movable
through the cutout portions 223 from the tip end of the holding
unit 22 toward the base end of the holding unit 22. The protruding
portions 243 of the positioning unit 24 contacts the leading end of
the recording medium P.
[0052] As illustrated in FIGS. 4A and 4B, a base end of the
positioning unit 24 (a downstream end in the rotation direction of
the transfer drum 21) is supported by a swing shaft 24C so as to be
swingable with respect to the transfer drum 21 (to be specific, the
base member 21A). Thus, the positioning unit 24 is movable between
a positioning position and a retracted position. When the holding
unit 22 is located in the contact position, the positioning unit 24
is in the positioning position and positions the recording medium P
in the transport direction (an entry direction (the rotation
direction of the transfer drum 21)). When the holding unit 22 is
located in the separated position, the positioning unit 24 is in
the retracted position, in which the positioning unit 24 is
retracted from the positioning position toward the base end of the
holding unit 22 (the downstream end in the transport direction of
the recording medium P).
[0053] As the positioning unit 24 moves from the positioning
position toward the retracted position, the recording medium P is
allowed to enter more deeply into the space S between the holding
unit 22 and the facing surface 29A of the facing member 29.
[0054] An attachment portion 245 is integrally formed with the
positioning unit 24. A tension spring 24B, which is an example of
an elastic member (urging member), is attached to the attachment
portion 245. The attachment portion 245 extends downward from the
swing shaft 24C in FIG. 4A (toward the rotation shaft 21D of the
transfer drum 21 (see FIG. 1)). The tension spring 24B pulls the
attachment portion 245 with its elastic force, and thereby the
positioning unit 24 is urged toward the positioning position.
[0055] A cam 24D is disposed on the left side the attachment
portion 245 in FIGS. 4A and 4B (on the downstream side in the
rotation direction of the transfer drum 21). The cam 24D functions
to move the positioning unit 24 to the retracted position. As with
the cam 22D, the cam 24D is fixed to the cam shaft 26, rotates
together with the cam shaft 26, contacts the attachment portion
245, and moves the positioning unit 24 to the retracted position
against the elastic force of the tension spring 24B.
[0056] Thus, the cam 24D for moving the positioning unit 24 and the
cam 22D for moving the holding unit 22 are fixed to the single cam
shaft 26, and the cam shaft 26 is rotated by the single drive motor
28 (driving unit), which is controlled by the controller 60. When
the cam shaft 26 is rotated by the drive motor 28, the cams 24D and
22D rotate together, and the cams 24D and 22D respectively contact
the attachment portion 245 of the positioning unit 24 and the
attachment portion 225 of the holding unit 22.
[0057] The phase difference between the cams 24D and 22D is set so
that the positioning unit 24 moves from the positioning position to
the retracted position when the holding unit 22 moves toward the
separated position and so that the positioning unit 24 returns to
the positioning position when the holding unit 22 moves from the
separated position to the contact position. Thus, the movement of
the positioning unit 24 is linked to the movement of the holding
unit 22. That is, the cams 24D and 22D also function as examples of
a linkage unit and link the movement of the positioning unit 24 to
the movement of the holding unit 22.
[0058] As heretofore described, the trailing end gripper 27 and the
leading end gripper 23 respectively grip the trailing end and the
leading end of the recording medium P in the transport direction,
and thereby the recording medium P is wound around the outer
peripheral surface of the transfer drum 21. The positioning unit 24
and the holding unit 22 are each made of a metal material such as a
stainless steel (SUS).
Image Forming Operation of Image Forming Apparatus 50
[0059] Next, an image forming operation of forming a toner image on
the recording medium P, which is performed by the image forming
apparatus 50 according to the present exemplary embodiment, will be
described.
[0060] Before an image forming operation is started, the trailing
end gripper 27 is located at the standby position between the
transfer position Tr and the supply position Pa in the rotation
direction of the transfer drum 21.
[0061] When the image forming operation is started, the feed roller
42 feeds the recording medium P from the recording medium container
41, and the transport rollers 44 transport the recording medium P
toward the transfer drum 21. While the recording medium P is
transported toward the transfer drum 21, the transfer drum 21
rotates and the leading end gripper 23 moves toward the supply
position Pa.
[0062] When the recording medium P has been transported to the
transfer drum 21 by the transport rollers 44, the leading end
gripper 23 grips the leading end of the recording medium P in the
transport direction at the supply position Pa. While the transfer
drum 21 rotates, the leading end of the recording medium P in the
transport direction, which is gripped by the leading end gripper
23, passes through the space Sa between the transfer drum 21 and
the trailing end gripper 27 located at the standby position. After
the leading end of the recording medium P in the transport
direction has passed through the space Sa, the trailing end gripper
27 grips the trailing end of the recording medium P in the
transport direction. Thus, the leading end gripper 23 and the
trailing end gripper 27 respectively grip the leading end and the
trailing end of the recording medium P in the transport direction,
and thereby the recording medium P is wound around the outer
peripheral surface of the transfer drum 21.
[0063] The transfer drum 21 and the trailing end gripper 27 rotate
in synchronism with each other while the recording medium P is
wound around the outer peripheral surface of the transfer drum 21,
and thereby the recording medium P is rotated. Thus, the recording
medium P is transported to the transfer position Tr.
[0064] In the image forming unit 10, the photoconductor drum 11 is
charged by the charging roller 12 (charging) and exposed to light
by the exposure device 13 (exposure), and thereby an electrostatic
latent image is formed on the photoconductor drum 11. The
electrostatic latent image is developed by the developing unit 14Y
that faces the photoconductor drum 11, and thereby a yellow toner
image is formed on the photoconductor drum 11 (development). The
yellow toner image is transferred by the transfer drum 21 to the
recording medium P, which has been transported to the transfer
position Tr.
[0065] The transfer drum 21 and the trailing end gripper 27 rotate
in synchronism with each other, and thereby rotate the recording
medium P. The rotary developing device 14 rotates to a position at
which the developing unit 14M faces the photoconductor drum 11.
Charging, exposure, and development are performed as described
above to form a magenta toner image on the photoconductor drum 11.
The magenta toner image is transferred to the recording medium P,
which is transported to the transfer position Tr again while the
transfer drum 21 and the trailing end gripper 27 rotate. Likewise,
cyan (C) and black (K) toner images are successively transferred to
the recording medium P in an overlapping manner.
[0066] After the toner images have been transferred to the
recording medium P in an overlapping manner, the leading end
gripper 23 releases the leading end of the recording medium P in
the transport direction at the peel-off position Pb, and thereby
the recording medium P is peeled off the transfer drum 21.
[0067] The recording medium P, which has been peeled off the
transfer drum 21, is transported to the fixing unit 30, and the
toner images are fixed to the recording medium P by the fixing unit
30. The recording medium P, on which the toner images have been
fixed, is output to the recording medium output unit 63 by the
output rollers 46. An image forming process is performed as
heretofore described.
Function of Present Exemplary Embodiment
[0068] Next, a gripping operation performed by the leading end
gripper 23 to hold the recording medium P, which is a function of
the present exemplary embodiment, will be described.
[0069] As illustrated in FIG. 5A, before the gripping operation is
started, the holding unit 22 is located in the contact position, in
which the holding unit 22 is in contact with the facing surface 29A
of the facing member 29 (that is, the gripping position, in which
the holding unit 22 is to grip the recording medium P). At this
time, the positioning unit 24 is located in the positioning
position, in which the positioning unit 24 is to position the
recording medium P in the transport direction.
[0070] When the gripping operation is started, the drive motor 28,
which is controlled by the controller 60, rotates the cam shaft 26
(forward) and thereby the cams 24D and 22D rotate (forward). Then,
the cams 24D and 22D respectively contact the attachment portion
245 of the positioning unit 24 and the attachment portion 225 of
the holding unit 22 (see FIG. 4B).
[0071] Thus, as illustrated in FIG. 5B, the holding unit 22 starts
moving from the contact position (see FIG. 5A) toward the separated
position, in which the holding unit 22 is separated from the facing
surface 29A of the facing member 29. At the same time, the
positioning unit 24 starts moving from the positioning position
toward the retracted position, in which the positioning unit 24 is
retracted toward the base end of the holding unit 22.
[0072] As illustrated in FIG. 5C, when the holding unit 22 reaches
the separated position, the positioning unit 24 reaches the
retracted position. At this time, the angle .theta.1 between the
holding unit 22 and an outer peripheral surface 21E of the transfer
drum 21 (to be specific, the elastic layer 21B) is smaller than 90
degrees.
[0073] As illustrated in FIG. 7, the retracted position of the
positioning unit 24 may be located further toward the base end of
the holding unit 22 (toward the center of the transfer drum 21)
from an intersection E of the holding unit 22 and the outer
peripheral surface 21E of the transfer drum (to be specific, the
elastic layer 21B). In this case, when the recording medium P
enters the space S between the holding unit 22 and the facing
surface 29A of the facing member 29, the recording medium P is more
likely to first contact the holding unit 22 than the positioning
unit 24.
[0074] As illustrated in FIG. 5D, the recording medium P enters the
space S between the holding unit 22 and the facing surface 29A of
the facing member 29 when the holding unit 22 is located in the
separated position and the positioning unit 24 is located in the
retracted position.
[0075] As illustrated in FIG. 6A, the leading end of the recording
medium P, which has entered the space S between the holding unit 22
and the facing surface 29A of the facing member 29, first contacts
the holding unit 22, because the positioning unit 24 is located in
the retracted position. Then, the leading end of the recording
medium P is guided along the holding unit 22 that is inclined at
the angle .theta.1, which is relatively small, toward the base end
of the holding unit 22.
[0076] Next, the drive motor 28, which is controlled by the
controller 60, rotates the cam shaft 26 (backward) and thereby the
cams 24D and 22D rotate together (backward). As a result, the cams
24D and 22D respectively become separated from the attachment
portion 245 of the positioning unit 24 and the attachment portion
225 of the holding unit 22 (see FIG. 4A).
[0077] Thus, as illustrated in FIG. 6B, the holding unit 22 starts
moving from the separated position toward the gripping position
(contact position). At the same time, the positioning unit 24
starts moving from the retracted position toward the positioning
position. Thus, the recording medium P is pushed back toward the
tip end of the holding unit 22.
[0078] As illustrated in FIG. 6C, when the holding unit 22 reaches
the contact position, the positioning unit 24 reaches the
positioning position. Thus, the holding unit 22 holds the recording
medium P by gripping the recording medium P between the holding
unit 22 and the facing surface 29A of the facing member 29, and the
positioning unit 24 positions the recording medium P in the
transport direction while the recording medium P is held by the
holding unit 22. The holding unit 22 holds the recording medium P
at the supply position Pa illustrated in FIG. 1.
[0079] As heretofore described, with the present exemplary
embodiment, because the positioning unit 24 moves to the retracted
position, the recording medium P is allowed to enter more deeply
into the space S between the holding unit 22 and the facing surface
29A of the facing member 29. As a result, the recording medium P is
unlikely to be unintentionally removed from the holding unit 22.
Therefore, with the structure according to the present exemplary
embodiment, occurrence of insufficient gripping of the leading end
of the recording medium P in the transport direction by the holding
unit 22 is reduced as compared with a structure in which the
positioning unit 24 does not move.
[0080] Since occurrence insufficient gripping of a recording medium
by the holding unit 22 is reduced, displacement of a transfer
position (image formation position) on a recording medium due to
such insufficient gripping by the holding unit 22 is reduced.
[0081] With the present exemplary embodiment, when the recording
medium P enters the space S between the holding unit 22 and the
facing surface 29A of the facing member 29, the leading end of the
recording medium P first contacts the holding unit 22 and then the
leading end is guided along the holding unit 22. At this time, the
leading end of the recording medium P is not likely to be bent,
because the angle .theta.1 between the holding unit 22 and the
outer peripheral surface 21E of the transfer drum 21 (to be
specific, the elastic layer 21B) is smaller than an angle .theta.2
between the positioning unit 24 and the outer peripheral surface
21E of the transfer drum 21 (to be specific, the elastic layer
21B).
[0082] FIG. 8 illustrates a comparative example in which the
positioning unit 24 does not retract and the leading end of the
recording medium P first contacts the positioning unit 24 when the
recording medium P enters the space S between the holding unit 22
and the facing surface 29A of the facing member 29. In this case,
the angle .theta.2 is larger than 90 degrees (cf. FIG. 5C), and
therefore the recording medium P rises sharply along the
positioning unit 24. As a result, the leading end of the recording
medium P is likely to become bent.
[0083] With the present exemplary embodiment, the positioning unit
24 returns to the positioning position when the holding unit 22
grips the recording medium P. Therefore, the holding unit 22 grips
a smaller portion (area) of the recording medium P than in a case
where the positioning unit 24 does not return to the positioning
position. Thus, the margin of the recording medium P is reduced,
and an image may be formed in a larger region.
[0084] With the present exemplary embodiment, a driving force is
transmitted from the single drive motor 28 to the holding unit 22
and the positioning unit 24, and thereby the movement of the
positioning unit 24 is linked to the movement of the holding unit
22. Therefore, an error in the movements of the holding unit 22 and
the positioning unit 24 is smaller than in a case where the
movements of the holding unit 22 and the positioning unit 24 are
controlled by driving the holding unit 22 and the positioning unit
24 by using different driving units.
Modifications
[0085] In the present exemplary embodiment, the positioning unit 24
is disposed on the transfer drum 21. However, this is not
necessarily the case. For example, the positioning unit 24 may be
disposed on the holding unit 22.
[0086] In the present exemplary embodiment, the movement of the
holding unit 22 is linked to the movement of the positioning unit
24. However, this is not necessarily the case. In the present
exemplary embodiment, the holding unit 22 and the positioning unit
24 start moving at the same timing. However, they may start moving
at different timings.
[0087] In the present exemplary embodiment, a driving force is
transmitted from the single drive motor 28 to the positioning unit
24 and the holding unit 22 and the movement of the positioning unit
24 is linked to the movement of the holding unit 22. However, this
is not necessarily the case. For example, the movement of the
holding unit 22 and the movement of the positioning unit 24 may be
controlled by driving the holding unit 22 and the positioning unit
24 by using different driving units.
[0088] The present invention is not limited to the exemplary
embodiment described above and may be modified, changed, and
improved in various ways. For example, the modifications described
above may be used in combination.
[0089] The foregoing description of the exemplary embodiment of the
present invention has been provided for the purposes of
illustration and description. It is not intended to be exhaustive
or to limit the invention to the precise forms disclosed.
Obviously, many modifications and variations will be apparent to
practitioners skilled in the art. The embodiment was chosen and
described in order to best explain the principles of the invention
and its practical applications, thereby enabling others skilled in
the art to understand the invention for various embodiments and
with the various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the following claims and their equivalents.
* * * * *