U.S. patent number RE45,015 [Application Number 13/692,479] was granted by the patent office on 2014-07-15 for image heating apparatus using flexible sleeve.
This patent grant is currently assigned to Canon Kabushiki Kaisha. The grantee listed for this patent is Canon Kabushiki Kaisha. Invention is credited to Kazushi Ino, Yuusuke Shimizu, Michio Uchida.
United States Patent |
RE45,015 |
Uchida , et al. |
July 15, 2014 |
Image heating apparatus using flexible sleeve
Abstract
An image heating apparatus includes a flexible sleeve, a sliding
member for sliding on the inner periphery of the sleeve, and a
back-up member for forming a nip portion together with the sliding
member through the sleeve. A recording material for bearing an
image is heated while being held and conveyed by the nip portion,
and a regulation member is set by facing the edge surface of the
sleeve in the generatrix direction to regulate the movement of the
sleeve in the generatrix direction, the regulation member having a
regulation surface with which the edge surface of the sleeve
contacts when the sleeve moves in the generatrix direction. The
regulation surface of the regulation member has a curved-surface
area in which a line when the regulation surface is cut at a
virtual plane almost parallel with the nip portion is a curved line
expanded toward the edge surface of the sleeve. Thereby, an image
heating apparatus is provided which is able to restrain
deterioration of the durability of the flexible sleeve.
Inventors: |
Uchida; Michio (Susono,
JP), Shimizu; Yuusuke (Susono, JP), Ino;
Kazushi (Sunto-gun, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Canon Kabushiki Kaisha |
Tokyo |
N/A |
JP |
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|
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
37108600 |
Appl.
No.: |
13/692,479 |
Filed: |
December 3, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
11400410 |
Apr 10, 2006 |
7283780 |
Oct 16, 2007 |
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Foreign Application Priority Data
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Apr 14, 2005 [JP] |
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2005-117199 |
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Current U.S.
Class: |
399/329 |
Current CPC
Class: |
G03G
15/2053 (20130101); G03G 2215/2016 (20130101); G03G
2215/00151 (20130101); G03G 2215/2035 (20130101) |
Current International
Class: |
G03G
15/20 (20060101) |
Field of
Search: |
;399/329
;198/806,810.03,807 ;193/37 ;492/47 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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63-313182 |
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Dec 1988 |
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JP |
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63-313182 |
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Dec 1988 |
|
JP |
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4-44075 |
|
Feb 1992 |
|
JP |
|
4-44075 |
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Feb 1992 |
|
JP |
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4-204980 |
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Jul 1992 |
|
JP |
|
4-204980 |
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Jul 1992 |
|
JP |
|
5-208750 |
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Aug 1993 |
|
JP |
|
5-208750 |
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Aug 1993 |
|
JP |
|
10-10893 |
|
Jan 1998 |
|
JP |
|
10-10893 |
|
Jan 1998 |
|
JP |
|
11-15303 |
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Jan 1999 |
|
JP |
|
11-15303 |
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Jan 1999 |
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JP |
|
2002-231419 |
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Aug 2002 |
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JP |
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2002-231419 |
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Aug 2002 |
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JP |
|
2003-45615 |
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Feb 2003 |
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JP |
|
2003-45615 |
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Feb 2003 |
|
JP |
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2003-156954 |
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May 2003 |
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JP |
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2003-156954 |
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May 2003 |
|
JP |
|
2006065056 |
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Mar 2006 |
|
JP |
|
Primary Examiner: Lee; Susan
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. An image heating apparatus comprising: a flexible sleeve; a
sliding member for sliding on an inner periphery of said flexible
sleeve; a back-up member for forming a nip portion together with
said sliding member through said flexible sleeve; wherein a
recording material for bearing an image is heated while being held
and conveyed .Iadd.in a moving direction of the recording material
.Iaddend.by the nip portion; and a regulation member provided
opposing .[.the.]. .Iadd.an .Iaddend.edge surface of said sleeve in
a generatrix direction of said sleeve, for regulating a movement of
said sleeve in the generatrix direction of said sleeve without
rotating, wherein said regulation member has a regulation surface
with which the edge surface of said sleeve contacts when said
sleeve moves in the generatrix direction, wherein the regulation
surface of the regulation member is substantially perpendicular to
a .[.vertical.]. .Iadd.virtual .Iaddend.plane including .Iadd.all
of .Iaddend.the nip portion .Iadd.parallel to the moving
direction.Iaddend., and wherein the regulation surface of said
regulation member has a curved-surface area in which a line when
the regulation surface is cut in a virtual plane substantially
parallel to the nip portion is a curved line convexed toward the
edge surface of said sleeve.
2. An image heating apparatus according to claim 1, wherein the
curved-surface area of the regulation surface has a shape obtained
by cutting a part of a periphery of a virtual elliptic
cylinder.
3. An image heating apparatus according to claim 1, wherein the
curved-surface area faces the edge surface of an area farthest from
an area surrounded by the nip portion of said flexible sleeve in a
peripheral direction of said flexible sleeve.
4. An image heating apparatus according to claim 1, wherein said
sliding member is a heat generating member.
5. An image heating apparatus according to claim 1, wherein said
sleeve has a metallic layer.
6. An image heating apparatus according to claim 1, wherein said
back-up member is a driving roller for driving said flexible
sleeve.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image heating apparatus for
heating an image borne by a recording material by passing the
recording material through a fixing nip portion N between a heat
member and a pressuring member to cause the material to be held and
conveyed. Particularly, the present invention relates to an image
heating apparatus to be preferably mounted on an image forming
apparatus such as a copying machine or printer as an image
heating-fixing device.
More minutely, the present invention includes a flexible
sleeve-shaped rotor, a sliding member set to the inside of the
rotor to slide on the inner periphery of the rotor, a pressuring
member for forming a nip portion together with the sliding member
by holding the rotor and a regulation member set by facing the end
of the rotor to regulate movement of the rotor in a generatrix
direction, which heats a recording material bearing an image by the
nip portion while conveying the recording material.
2. Related Background Art
The heating roller system shown in FIG. 15 has been used so far as
an image heating apparatus to be mounted on a copying machine or
printer as a fixing device. This system is basically constituted of
a metallic heating roller 202 including a halogen heater 201 and an
elastic pressuring roller 203 pressure-welded to the heating roller
202. Moreover, a recording medium S bearing an unfixed toner image
t as a member to be heated is introduced into the fixing nip
portion N (fixing nip portion) of the roller pair 202 and 203 to
hold, convey and pass the recording medium S. Thereby, the toner
image t is heated, pressured and fixed.
However, the fixing device according to the heating roller system
requires a lot of time in order to raise the temperature of roller
surface up to a fixing temperature because the rollers respectively
have a large heat capacity. Therefore, to quickly execute the image
output operation, it is necessary to keep the roller surface at a
certain degree of temperature also when the apparatus is not
used.
Therefore, a film-heating-system heating apparatus for fixing a
developer to a recording medium by using a film heated by a heater
is proposed as an on-demand type heating apparatus.
This film-heating-system heating apparatus normally has a thin
heat-resistant film (e.g. polyimide) and a heater (heat generation
member) fixed to one side of the film. Moreover, the apparatus has
a pressure roller set to the other side of the film by facing a
heater to contact a member to be heated with the heater through the
film.
Moreover, when using the pressure roller as a fixing device, a
recording medium making the fixing nip portion N (fixing nip
portion) formed by pressure welding between the heater and pressure
roller at both sides of the film form and bear a toner image is
introduced and passed. Thereby, the visualized image bearing body
face of the recording medium is heated by the heater through the
film, heat energy is supplied to an unfixed image, toner is
softened and melted and the image is heated and fixed.
In the case of the above film-heating-system heating apparatus, it
is possible to use a low-heat-capacity heater as a heat generation
member. Therefore, it is possible to save power and shorten the
wait time compared to the case of a conventional heat-roller-system
or belt-heating-system apparatus.
Moreover, it is recently proposed to prevent luster irregularity of
an image by setting an elastic layer to the outside of a fixing
film and uniforming the contact between a recording material having
minute irregularity and the film. Furthermore, an apparatus is
proposed which secures the on-demand property of a fixing device by
using a metallic film having a heat conductivity higher than that
of the polyimide film (e.g. stainless steel) in order to prevent
deterioration of heat conductivity caused as a harmful result of
setting the elastic layer.
In the case of these film-heating-system fixing devicees, lateral
shift to the generatrix direction (thrust direction) may occur in a
film and it is difficult to regulate the lateral shift force.
Particularly, when a displacement of the parallelism between a
pressure roller and the film or the right-left difference of
applied pressure increases, a strong hook-approach force is
generated and a strong stress is applied to the end of the film.
Therefore, the end of the film may be damaged.
Therefore, it is proposed to regulate lateral shift by loosely
winding a film, decreasing the lateral shift force of the film, and
receiving the film end by the film-edge part regulation surface
(hereafter also referred to as "regulation face") of a flange in
Japanese Patent Application Laid-Open No. H04-044075 and Japanese
Patent Application Laid-Open No. H04-204980. When a fixing film is
flexible enough and loose pulling is possible, it is possible to
avoid film damage by the configuration disclosed in the above
documents. However, in the case of a fixing belt using a metallic
film, the fixing film itself has a high stiffness and lacks in
flexibility. Therefore, when the shift of parallelism between the
above pressure rollers and film or the difference between right and
left applied pressures arises and a strong lateral shift force is
generated and a film locally receives a stress on the lateral shift
regulation surface, cracks may arise from an end.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above problem
and its object is to provide an image heating apparatus capable of
preventing deterioration of the durability of a flexible
sleeve.
Another object of the present invention is to provide an image
heating apparatus including a flexible sleeve, a sliding member for
sliding on an inner periphery of said flexible sleeve, a back-up
member for forming a nip portion together with said sliding member
through said flexible sleeve, wherein a recording material for
bearing an image is heated while being held and conveyed by the nip
portion, and a regulation member provided with opposing to the edge
surface of said sleeve in a generatrix direction of said sleeve,
for regulating a movement of said sleeve in the generatrix
direction of said sleeve, said regulation member having a
regulation surface with which the edge surface of said sleeve
contacts when said sleeve moves in the generatrix direction,
wherein the regulation surface of said regulation member has a
curved-surface area in which a line when the regulation surface is
cut in a virtual plane substantially parallel to the nip portion is
a curved line convexed toward the edge surface of said sleeve.
A further object of the present invention is to provide an image
heating apparatus including a flexible sleeve, a sliding member for
sliding on the inner periphery of said sleeve, a back-up member for
forming a nip portion together with said sliding member through
said sleeve, wherein a recording material for bearing an image is
heated while being held and conveyed by the nip portion, and a
regulation member provided opposing to the edge surface of said
sleeve in a generatrix direction of said sleeve, for regulating a
movement of said sleeve in the generatrix direction of said sleeve,
said regulation member having a regulation surface with which the
edge surface of said sleeve contacts when said sleeve moves in the
generatrix direction, wherein the regulation surface of said
regulation member has a curved-surface area in which the generatrix
direction of the regulation member intersects with a virtual plane
including the nip portion.
A still further object of the present invention will become
apparent by reading detailed description while referring to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an image forming apparatus which
mounts an image heating apparatus of the present invention;
FIG. 2 is an enlarged crossing side schematic view of an essential
portion of a fixing device;
FIG. 3 is an enlarged longitudinal front schematic view of a fixing
device in which a part of the fixing device in the longitudinal
direction is omitted;
FIG. 4 is a sectional schematic view showing the layer
configuration of a flexible sleeve;
FIG. 5 is a perspective schematic view showing a state of
separating a fixing flange 40 from a reinforcement stay 39;
FIG. 6 is a perspective schematic view showing an engagement
relation between a longitudinal groove portion 40a formed on the
fixing flange 40 and the longitudinal marginal portion 34b of a
longitudinal guide slit 34a formed on the side plate 34 of an
apparatus frame;
FIG. 7A is a perspective view of a fixing flange in which a sleeve
edge part regulation surface is a curved face;
FIG. 7B is a perspective view of a fixing flange in which a sleeve
edge part regulation surface is a part of an elliptic cylinder
surface and the sleeve edge part regulation surface is a curved
surface;
FIG. 7C is an illustration for explaining a fixing flange in which
the shape of a circular arc when cutting a sleeve edge part
regulation surface at a plane almost parallel with a fixing nip is
approximate to an ellipse or circle and the sleeve edge part
regulation surface is a curved surface;
FIG. 8 is an enlarged longitudinal section schematic view of a
fixing device using a fixing flange whose sleeve edge part
regulation surface is a curved surface at one edge surface;
FIG. 9 is an illustration viewed from the direction of the arrow V1
in FIG. 8, which shows how the force of a flexible sleeve is
applied to the edge part regulation surface of a flange when the
reinforcement stay 39 is curved;
FIG. 10 is an illustration when viewing the
longitudinal-directional edge surface of a fixing device from the
direction of the arrow V1 in FIG. 8, which shows how the force of a
flexible sleeve is applied to the edge part regulation surface of a
flange when a flexible sleeve and a pressure roller have a crossing
angle;
FIG. 11 is a perspective view of a conventional fixing flange whose
sleeve edge part regulation surface is a plane;
FIG. 12 is an enlarged longitudinal section schematic view of a
fixing device using a fixing flange whose sleeve edge part
regulation surface is a plane at one edge surface;
FIG. 13 is an illustration viewed from the direction of the arrow
V1 in FIG. 12, which shows how the force of a flexible sleeve is
applied to the edge part regulation surface of a flange when the
reinforcement stay 39 is curved;
FIG. 14 is an illustration viewing the longitudinal-directional
edge surface of a fixing device from the direction of the arrow V1
in FIG. 12, which shows how the force of a flexible sleeve is
applied to the edge part regulation surface of a flange when a
flexible sleeve and a pressure roller have a crossing angle;
and
FIG. 15 is a schematic view of a configuration of a
heat-roller-system fixing device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
(1) Embodiment of Image Forming Apparatus
An embodiment of an image forming apparatus using an image heating
apparatus of the present invention as a fixing device is described
below by referring to FIG. 1.
The image forming apparatus of this embodiment is a full-color
image forming apparatus using an electrophotographic system. The
apparatus has four process stations 1a to 1d arranged on an
substantial straight line in a substantial vertical direction to
the setting face of the apparatus to form four different color
images (magenta, cyan, yellow and black) and a conveying route 20
for conveying sheets S serving as recording materials (recording
media).
The process stations 1a to 1d have photosensitive drums 2a to 2d
for bearing a latent image. Moreover, the process stations 1a to 1d
have electrification rollers 3a to 3d for uniformly electrifying
the photosensitive drums 2a to 2d and exposure devices 4a to 4d for
applying a laser beam on the photosensitive drums 2a to 2d to form
a latent image. Furthermore, the process stations 1a to 1d have
developing means 5a to 5d for developing the latent image formed on
the photosensitive drums 2a to 2d by toners of corresponding colors
(magenta, cyan, yellow and black) to visualize it. Furthermore, the
process stations 1a to 1d have cleaning devices 6a to 6d for
removing remaining toners from the photosensitive drums 2a to 2d.
These are arranged around the photosensitive drums 2a to 2d.
The developing means 5a to 5d have developing sleeves 50a to 50d
for bearing toners. The developing sleeves 50a to 50d are supported
by keeping predetermined intervals from corresponding
photosensitive drums 2a to 2d. A developing bias is applied between
the photosensitive drums 2a to 2d and developing sleeves 50a to
50d.
An intermediate transfer belt 7 is suspended and strained on a
driving roller 8, a driven roller 9 and belt tension rollers 10 and
11 under tension and rotated in the direction shown by arrows in
FIG. 1. The intermediate transfer belt 7 is conveyed along the
arrangement direction of the process stations 1a to 1d. Toner
images of various colors on the photosensitive drums 2a to 2d are
successively transferred to the surface of the intermediate
transfer belt by primary transfer means 14a to 14d through the
stations. Thereby, an unfixed full-color toner image is synthesized
and formed on the outer face of the intermediate transfer belt
7.
The sheets S are stored in a sheet feed cassette 15 set to the
lower portion of the apparatus. Then, the sheets S are separated
and sent one by one from the sheet feed cassette 15 by a sheet feed
roller 16 and fed to a pair of registration rollers 17. The pair of
the registration rollers 17 sends the fed sheets S between the
intermediate transfer belt 7 and a secondary transfer roller
12.
The secondary transfer roller 12 set so as to face the driven
roller 9 contacts with the lowermost surface of the intermediate
transfer belt 7. The secondary transfer roller 12 holds and conveys
the sheets S passing between the roller 12 and the intermediate
transfer belt 7. A bias is applied to the secondary transfer roller
12 from a high-voltage power supply 13 (bias means). Thereby, a
toner image on the intermediate transfer belt is
secondary-transferred to the sheets S passing between the secondary
transfer roller 12 and the intermediate transfer belt.
The sheets S to which a toner image is transferred are sent to a
fixing device 18. In the fixing device 18, the above sheets S are
thermally pressured and the toner image is fixed on the sheets S as
a permanent fixed image.
The sheets S to which an image is fixed by the fixing device 18 are
discharged to a discharge tray 19 at the outside of the fixing
device 18 from the fixing device 18.
(2) Fixing Device (Image Heating Apparatus) 18
FIG. 2 is an enlarged crossing side schematic view of an essential
portion of the fixing device 18 and FIG. 3 is an enlarged
longitudinal front schematic view of the fixing device 18 whose
middle portion is omitted. For apparatus component members in the
following description, a longitudinal direction or horizontally
long denotes a direction orthogonal to the moving direction of a
recording material in a recording-material conveying face. Width
direction or width denotes the moving direction of a recording
material.
In the fixing device 18, a film assembly 31 as a heating member (a
fixing member) and a pressure roller 32 serving as a backup member
are arranged in vertically parallel between right and left side
plates 34 of an apparatus frame 33.
The pressure roller 32 is constituted of a cored bar 32a and an
elastic layer 32b of silicone rubber or fluorocarbon rubber formed
like a roller concentrically around the cored bar. It is also
possible to form a mold release layer of PFA, PTFE or FEP on the
elastic layer 32. In the case of this pressure roller 32, both edge
surfaces of the cored bar 32a are rotatably supported between right
and left side plates 34 of the apparatus frame 33 through a bearing
member 35. Reference character G denotes a drive gear fixed to one
edge surface of the cored bar 32a of the pressure roller. A torque
is transferred to the drive gear G from a not-illustrated driving
mechanism portion and the pressure roller 32 is rotated.
The film assembly 31 is an assembly of a flexible sleeve 36 serving
as a flexible rotor, guide member 37 for guiding the flexible
sleeve from the inside, ceramic heater 38 (hereafter referred to as
heater) serving as heating means for heating the flexible sleeve
36, reinforcement stay (fixing stay) 39 and right and left fixing
flanges 40 serving as regulation members for regulating the
generatrix (thrust) directional movement of the flexible sleeve
36.
In the case of this embodiment, as shown by the layer configuration
schematic view in FIG. 4, the flexible sleeve 36 is flexible and
constituted of a metallic film layer 36a, elastic layer 36b and
mold release layer 36c from the inside toward the outside. The heat
capacity of the flexible sleeve 36 for unit area is approx. 0.1
J/cm.sup.2K.
The guide member 37 is a horizontally long member having a tube
shape with a generally semicircular cross section and having
rigidity, heat resistance, and heat insulating property, and is
formed of liquid-crystal polymer, phenol resin, PPS or PEEK. The
guide member 37 serves as a rotational guide of the flexible sleeve
36 loosely outer-fitted to the guide member 37. Moreover, the guide
member 37 also serves as a heater holder for heat-insulating and
holding the heater 38. Furthermore, the guide member 37 serves as a
pressure member.
The heater 38 has a high-insulating and preferable heat-conductive
ceramic substrate such as alumina or aluminum nitride (AlN) or high
heat-resistant resin substrate of polyimide, PPS or liquid-crystal
polymer as a heater substrate. Moreover, a current-carrying
heat-generating resistor layer made of silver palladium (Ag/Pd),
RuO.sub.2 or Ta.sub.2N is formed like a line or thin band having a
thickness of approx. 10 .mu.m and a width of approx. 1-5 mm through
screen printing or the like on the surface of the heater substrate
along the longitudinal direction. The heater 38 is set along the
longitudinal direction of the guide member below the guide member
37. The temperature of the heater 38 quickly rises when power is
supplied from a not-illustrated power feed portion to the
current-carrying heat-generating resistor layer. Then, the heater
temperature is detected by a not-illustrated temperature sensor and
supply of power from the power feed portion to the current-carrying
heat-generating resistor layer is controlled so that the heater is
maintained at a predetermined temperature by a control portion (not
illustrated).
The reinforcement stay 39 is a horizontally-long rigid member
having a U-shaped cross section.
Then, the flexible sleeve 36 is loosely applied to the outside of
the guide member 37 to whose lower face the heater 38 is set and
the reinforcement stay 39 is inserted into the guide member 37.
Right and left fixing flanges 40 are fitted to right and left
outward extension arm portions 39a of the reinforcement stay 39.
Thus, the film assembly 31 is assembled.
FIG. 5 is a perspective view of the fixing flange 40 at one edge
surface and right and left outward extension arm portions 39a of
the reinforcement stay 39.
The film assembly 31 is set to the upper side of the pressure
roller 32 in substantial parallel with the pressure roller 32 with
the heater 38 side facing down to set the film assembly 31 between
right and left side plates 34 of the apparatus frame 33. In the
case of the right and left fixing flanges 40, the longitudinal
groove portions 40a set to the right and left flanges 40 are
engaged with longitudinal marginal portions 34b of longitudinal
guide slits 34a set to the right and left side plates 34 of the
apparatus frame 33 (refer to FIG. 6).
Then, a pressure spring 42 is set between pressure portions 40b of
the right and left fixing flanges 40 and the pressure arm 41.
Thereby, the heater 38 is pressured at a predetermined pressure
against the upper face of the pressure roller 32 at both sides of
the flexible sleeve 36 through the right and left fixing flanges
40, the reinforcement stay 39 and the guide member 37. The fixing
nip portion (nip portion) N having a predetermined width is formed
by the pressure because the heater 38 is pressure-welded to the
upper face of the pressure roller 32 at both sides of the flexible
sleeve 36 against the elasticity of the flexible sleeve 36 and
elasticity of the pressure roller 32. In the case of the fixing nip
portion N, the flexible sleeve 36 is held between the heater 38 and
the elastic pressure roller 32 and bent in accordance with the flat
face at the lower face of the heater 38 and the inside of the
flexible sleeve 36 closely contacts with the flat face at the lower
face of the heater 38.
Thus, a torque is transferred to the drive gear G of the pressure
roller 32 from a not-illustrated driving mechanism portion and the
pressure roller 32 is rotated at a predetermined speed clockwise in
FIG. 2. A torque acts on the flexible sleeve 36 in accordance with
the friction force between the pressure roller 32 and the flexible
sleeve 36 at the fixing nip portion N in accordance with the
rotation of the pressure roller 32. Thereby, the inside of the
flexible sleeve 36 rotates by following the rotation of the
pressure roller 32 counterclockwise in FIG. 2 around the guide
member 37 while closely contacting with and sliding on the lower
face of the heater 38 (pressure roller driving type).
In the case of the fixing device of this embodiment, the above
heater 38 is set inside the flexible sleeve 36 serving as a rotor,
and is a sliding member for forming the nip portion together with
the pressure roller 32 serving as a pressure member at both sides
of the flexible sleeve 36.
When the flexible sleeve 36 is rotated in accordance with the
rotation of the pressure roller 32, the heater 38 is turned on, the
heater temperature is raised to a predetermined temperature and the
temperature is controlled, the sheet S serving as a recording
material is introduced. That is, the sheet S bearing unfixed toner
image t is introduced between the flexible sleeve 36 of the fixing
nip portion N and the pressure roller 32 and the toner-image
bearing side of the sheet S closely contacts with the outer face of
the flexible sleeve 36 at the fixing nip portion N and the fixing
nip portion N is held and conveyed together with the flexible
sleeve 36. In this holding and conveying process, the sheet S is
heated by the heat of the flexible sleeve 36 heated by the heater
38 and the unfixed toner image t on the sheet S is heated and
pressured on the sheet S and melted and fixed. The sheet passing
through the fixing nip portion N is curvature-separated from the
face of the flexible sleeve 36 and discharged and conveyed.
(3) Fixing Flange 40
The pressure roller 32 and flexible sleeve 36 to be set to the
fixing device are not always parallel to each other but a crossing
angle may be present between the two due to a tolerance for
fabrication. For example, component tolerances of right and left
pressure springs 41 are also one of the causes of generating the
crossing angle and lead to the imbalance between right and left
pressures applied to the fixing nip portion and a crossing angle
arises between the pressure roller 32 and the flexible sleeve 36.
When fabricating components used for the fixing device and
assembling these components, various tolerances are overlapped
other than the component tolerance of the pressure spring 41.
Therefore, a crossing angle easily arises between the flexible
sleeve 36 and the pressure roller 32 and a phenomenon (lateral
shift) arises in which the flexible sleeve 36 rotates and slowly
moves in the thrust direction due to the crossing angle. The
lateral shift of the flexible sleeve 36 is received by the
regulation surface A of a edge part (an edge surface) of the
flexible sleeve of the fixing flange 40 to regulate the flexible
sleeve position in the generatrix direction of the flexible
sleeve.
The case of a conventional fixing flange 40 is described below by
referring to FIGS. 11 to 14. In the case of the conventional fixing
flange 40, the edge part regulation surface A is plane as shown in
FIG. 11. The edge part regulation surface A is not set nearby the
fixing nip portion in the sleeve circumferential direction but it
is set to an area farthest from the fixing nip portion. The portion
of the fixing flange 40 corresponding to the vicinity of the
sleeve-circumference-directional nip portion is more concaved than
the regulation surface A as shown in FIG. 11B so that it does not
contact with the flexible-sleeve edge surface E (refer to FIG. 12).
This is because the flexible sleeve 36 is strongly constrained by
the nip portion formed by the pressure roller 32 and heater 38 at
the nip portion but it has no flexibility. Therefore, when the
flexible sleeve 36 is pressed against the flange 40 at this
portion, a local deforming stress arises and edge-surface breakdown
of the sleeve easily occurs.
By the above reason, the flange 40 has the regulation surface A in
only a portion facing a circular-arc area opposite to the fixing
nip portion when almost halving the circular edge surface E on a
virtual plane almost parallel with the face of the fixing nip
portion N, that is, a circular-arc area farthest from the fixing
nip portion in the sleeve circumference direction in the
edge-surface E (circular) of the flexible sleeve 36.
However, there is a case in which not only a crossing angle to the
pressure roller 32 of the flexible sleeve 36 but also the curvature
of the reinforcement stay 39 due to the pressure of the pressure
spring 42 or tilt of the fixing flange 40 may be present. In this
case, it is found that a range in which the edge part regulation
surface A contacts with the sleeve edge surface E is narrow and
local as shown in FIGS. 12, 13, and 14 and edge-surface breakdown
of the sleeve may occur. FIG. 12 shows a state in which the
reinforcement stay 39 is deflected by the force of the pressure
spring 42. Under this state, the edge surface E of the sleeve 36
and regulation surface A of the flange 40 become a state close to
point contact. FIG. 13 is an illustration viewed from the direction
of the arrow V1 in FIG. 12. FIG. 14 shows a state in which the
sleeve 36 does not vertically contact with the regulation surface A
of the flange 40 because the crossing angle .theta. is present
between the flexible sleeve 36 and the pressure roller 32 when
viewed from the direction of the arrow V1 in FIG. 12.
Then, a mechanism is described in which edge-surface breakdown of
the flexible sleeve 36 occurs.
As described above, because of the crossing angle between the
flexible sleeve 36 and the pressure roller 32, a force approaching
to the generatrix direction to the flexible sleeve 36 is generated
and the flexible sleeve 36 is sent to right or left generatrix
direction while rotating. The flexible sleeve 36 contacts with the
planar edge part regulation surface A of the fixing flange 40 shown
in FIG. 11, generatrix-directional movement stops and flexible
sleeve 36 continuously rotates while receiving a certain force from
the contact face.
FIG. 12 shows an illustration in which the fixing flange 40 fitted
and fixed to the reinforcement stay 39 due to the curvature of the
reinforcement stay 39 tilts from the flexible sleeve 36 and under
this state, the flexible sleeve 36 rotates while receiving a
certain force F from the edge part regulation surface A. In this
case, when the fixing flange 40 tilts as shown in FIG. 12, the
planar edge part regulation surface A tilts, the contact between
the flexible sleeve 36 and the edge part regulation surface A
becomes local as shown in FIG. 12 and contacts in the
circumferential direction at a minute length.
FIG. 13 viewed from the V1 direction in FIG. 12 shows a state in
which the regulation surface A of the flange locally contacts with
two places of the edge surface of the flexible sleeve 36. When a
force acting in the thrust direction of the flexible sleeve 36 is
locally received by the regulation surface A, apprehensiveness that
the flexible-sleeve edge surface is broken increases.
Moreover, FIG. 14 shows a contact state between the flexible sleeve
36 and the edge part regulation surface A when a crossing angle
occurs between the flexible sleeve 36 and the pressure roller 32.
In FIG. 13, the flexible sleeve 36 contacts with the edge part
regulation surface A at two places. However, because the flexible
sleeve 36 tilts from the pressure roller 32, the number of contact
places becomes one. Therefore, a local internal stress arises at
the sleeve edge surface compared to the case of FIG. 13 and
apprehensiveness of edge-surface breakdown of the flexible sleeve
36 increases.
Moreover, also when the fixing flange 40 tilts from the
longitudinal direction of the pressure roller due to assembling
backlash of the fixing flange 40, pressure is locally received at
one point similarly to the case of FIG. 14 (illustration is
omitted).
Therefore, this embodiment uses a configuration in which a local
force does not easily act by curving the flexible-sleeve edge part
regulation surface A of the fixing flange 40 like a circular arc
(convex curved surface to flexible sleeve edge surface).
That is, the edge part regulation surface A of the fixing flange 40
is formed like a circular arc as shown in FIGS. 5 to 10. The flange
is different from that shown in FIG. 11 only in the shape of the
regulation surface A.
FIG. 7A is a perspective view of the fixing flange 40, showing edge
part regulation surface A curved like a circular arc, contactable
width w, and curved value d. FIG. 7B shows that the edge part
regulation surface A is a part of the surface of an elliptic
cylinder. That is, FIG. 7B shows that the shape of the edge part
regulation surface is a part of a circular cylinder or elliptic
cylinder almost vertically standing on a recording-sheet passing
face (virtual plane including nip portion). FIG. 7C shows a cross
section Pf obtained by cutting the regulation surface at a plane P
(plane parallel with virtual plane) almost parallel with the face
of the nip portion N shown in FIG. 7B. That is, FIG. 7C shows that
the cross section obtained by cutting the edge part regulation
surface A at virtual plane almost parallel with the nip portion N
is a part of the circumferential face of the circle B or ellipse C.
The circular arc of the edge part regulation surface A shown by the
cross section is approximate to a part of the ellipse C or circle B
as shown in FIG. 7C and is constituted so as to coincide with a
state when diagonally viewing the flexible sleeve 36. Thus, the
regulation surface A of the regulation flange (regulation member)
40 has a curved-surface area in which a line when cutting the
regulation surface A at a virtual plane substantially parallel with
the nip portion N becomes a curved line inflated toward the edge
surface E of the flexible sleeve 36. Moreover, the regulation
surface A of the regulation flange 40 has a curved-surface area
whose generatrix direction intersects with a virtual plane
including the nip portion N.
By using this configuration, even when the reinforcement stay 39 is
curved and the fixing flange 40 tilts as shown in FIGS. 8 and 9 or
the flexible sleeve 36 has a crossing angle from the pressure
roller 32 as shown in FIG. 10, it is possible to widen the contact
range between the sleeve edge surface E and the regulation surface
A. Therefore, the risk that the flexible sleeve 36 locally receives
a stress decreases and it is possible to avoid the local
deformation of flexible sleeve edge surface and prevent edge
surface breakdown from occurring.
Therefore, to set the curved value, experiments are performed.
Table 1 shows experiment results.
TABLE-US-00001 TABLE 1 Curved value d Number of durable sheets (mm)
reaching edge part breakdown Contactable 0 30k to 50k width w = 20
(mm) 0.1 70k to 120k 0.2 200k to 250k 0.3 150k to 200k 0.4 100k to
150k
Table 1 shows a relation between the curved value d when setting
the contactable width w to 20 mm and the service life of a fixing
device until reaching edge part destruction of a sleeve. Reference
characters w and d denote the lengths shown in FIGS. 7A to 7C. To
clarify the effect by an experiment, the curved value of the
reinforcement stay 39, tilt of the fixing flange 40, and crossing
angle with the pressure roller 32 of the flexible sleeve 36 are set
to values larger than those of a product fabricated in accordance
with the normal quality standard.
From these results, it is clarified that a configuration curved
like a circular arc realizes a more preferable service life to edge
part destruction than a case where the edge part regulation surface
A is a plane. However, a curved value depends on one of the
contactable range w and curved value d, contour of the flexible
sleeve 36, deflection value of the reinforcement stay 39 due to
pressure of a pressure spring and crossing angle with the pressure
roller 32 generated in the flexible sleeve 36 and changes in
accordance with one of these conditions. Moreover, when the curve
value is too large, it is shown that the durability of a sleeve may
lower and is excluded from values shown in this table.
Moreover, it is shown by an embodiment that the edge part
regulation surface A is a part of the surface of a circular
cylinder or elliptic cylinder. However, the edge part regulation
surface A can be applied to a part of a conical surface and a part
of a spherical surface. Also in the case of these shapes, the
regulation surface A of the regulation flange (regulation member)
40 has a curve-surface area in which a line when the regulation
surface A is cut at a virtual plane almost parallel with the nip
portion N becomes a curved line inflated toward the edge surface E
of the flexible sleeve 36.
Moreover, in the case of the above embodiment, the flexible sleeve
36 uses a sleeve having a heat capacity for unit area of approx.
0.1 J/cm.sup.2K. However, the flexible sleeve 36 is not restricted
to the above sleeve. It is also possible to use a polyimide film
having a very small heat capacity (for example, thickness of 50
.mu.m and heat capacity for unit area of 0.01 J/cm.sup.2K). Also in
this case, it is possible to realize a long service life to sleeve
edge part destruction.
[Others]
(1) The heating means 37 for heating the flexible sleeve 36 serving
as a rotor is not restricted to the ceramic heater of the above
embodiment. It is also possible to use heating means such as a
nichrome wire, an electromagnetic-induction heat generating member
such as an iron piece, or a PTC heat generating member. It is not
always necessary to set the heating means 37 to the fixing nip
portion N. The flexible rotor 35 can be heated by optional heating
means from the inside or outside of the rotor 35. It is also
possible to constitute the flexible rotor 35 itself so as to
generate heat through electromagnetic induction.
(2) The pressure rotor 32 serving as a pressure member is not
restricted to a roller. It is also possible to use a rotating
endless belt.
(3) An image heating apparatus of the present invention is not
restricted to use as the image heating-fixing device of the
embodiment. The image heating apparatus is also effective as a
temporary fixing device for temporarily fixing an unfixed image to
a recording material or image heating apparatus such as a surface
reforming apparatus for reforming the image surface property such
as luster by reheating a recording material bearing a fixed image.
Moreover, it is a matter of course that the image heating apparatus
is also effective as a heating apparatus for heating a member to be
heated such as a heat press apparatus for removing creases from
paper currency, heat laminate apparatus, heating drying apparatus
for evaporating moisture from paper currency, or drying heating
apparatus used for an ink-jet printer.
The present invention is not restricted to the above embodiment but
it includes modifications within technical idea.
This application claims priority from Japanese Patent Application
No. 2005-117199 filed Apr. 14, 2005, which is hereby incorporated
by reference herein.
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