U.S. patent application number 17/313821 was filed with the patent office on 2022-02-10 for heating device, fixing device, and image processing apparatus.
The applicant listed for this patent is TOSHIBA TEC KABUSHIKI KAISHA. Invention is credited to Sasuke ENDO.
Application Number | 20220043377 17/313821 |
Document ID | / |
Family ID | 1000005614759 |
Filed Date | 2022-02-10 |
United States Patent
Application |
20220043377 |
Kind Code |
A1 |
ENDO; Sasuke |
February 10, 2022 |
HEATING DEVICE, FIXING DEVICE, AND IMAGE PROCESSING APPARATUS
Abstract
A heating device for heating a medium on which an image can be
formed includes a cylindrical belt, a first heating unit, and a
second heating unit. The first and second heating units are inside
the cylindrical belt and face an inner circumferential surface of
the belt. A controller is configured to control the heating units
to generate heat. When the medium is to be heated to reach an image
fixing temperature at which the image can be fixed to the medium,
the controller controls the first and second heating units to both
generate heat. After the medium is heated to the image fixing
temperature, the controllers control the first heating unit to
generate heat, but not the second heating unit.
Inventors: |
ENDO; Sasuke; (Chigasaki
Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA TEC KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
1000005614759 |
Appl. No.: |
17/313821 |
Filed: |
May 6, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G 15/2039
20130101 |
International
Class: |
G03G 15/20 20060101
G03G015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2020 |
JP |
2020-133915 |
Claims
1. A heating device, comprising: a cylindrical belt; a first
heating unit and a second heating unit inside the belt, facing an
inner circumferential surface of the belt, and extending along an
axial direction of the belt, the second heating unit having a
length in the axial direction that is greater than a length of the
first heating unit in the axial direction; and a controller
configured to control the first and second heating units, wherein
when the medium is to be heated to reach an image fixing
temperature, the controller controls both the first and second
heating units to generate heat, and after the medium has been
heated to the image fixing temperature, the controller controls the
first heating unit to generate heat and the second heating unit to
not generate heat.
2. The heating device according to claim 1, wherein the first and
second heating units are arranged on a substrate extending along a
longitudinal direction that is parallel to the axial direction of
the cylindrical belt.
3. The heating device according to claim 2, wherein the first
heating unit generates heat in a first region of the cylindrical
belt at a center thereof in the axial direction, and the second
heating unit generates heat in a second region of the cylindrical
belt beyond the first region along the axial direction.
4. The heating device according to claim 3, wherein the second
heating unit also generates heat in the first region.
5. The heating device according to claim 4, wherein the first and
second heating units are arranged parallel to each other on the
substrate.
6. (canceled)
7. The heating device according to claim 1, further comprising: a
heat conduction member in contact with at least one of the first
and second heating units.
8. The heating device according to claim 7, wherein the heat
conduction member is in contact with the first heating unit.
9. The heating device according to claim 1, wherein a resistance
temperature coefficient of the first heating unit is different from
a resistance temperature coefficient of the second heating
unit.
10. The heating device according to claim 9, wherein the resistance
temperature coefficient of the second heating unit is less than the
resistance temperature coefficient of the first heating unit.
11. A fixing device for fixing an image to a sheet, comprising: a
cylindrical belt that contacts a sheet; a first heating unit and a
second heating unit inside the cylindrical belt, facing an inner
circumferential surface of the cylindrical belt, and extending
along an axial direction of the cylindrical belt, the second
heating unit having a length in the axial direction that is greater
than a length of the first heating unit in the axial direction; and
a controller configured to control the first and second heating
units, wherein when the sheet is to be heated to reach an image
fixing temperature, the controller controls both the first and
second heating units to generate heat, and after the sheet is
heated to the image fixing temperature, the controller controls the
first heating unit to generate heat and the second heating unit not
to generate heat.
12. The fixing device according to claim 11, wherein an image is
formed on the sheet with a toner.
13. The fixing device according to claim 11, wherein the first and
second heating units are arranged on a substrate extending along a
longitudinal direction that is parallel to the axial direction of
the cylindrical belt.
14. The fixing device according to claim 13, wherein the first
heating unit generates heat in a first region of the cylindrical
belt at a center thereof in the axial direction, and the second
heating unit generates heat in a second region of the cylindrical
belt beyond the first region along the axial direction.
15. The fixing device according to claim 13, wherein the second
heating unit also generates heat in the first region.
16. An image processing apparatus, comprising: an image forming
unit configured to form an image on a sheet; a conveyance roller
configured to convey the sheet to the image forming unit; a
cylindrical belt that contacts the sheet after the sheet is
conveyed to the image forming unit; a first heating unit and a
second heating unit inside the cylindrical belt, facing an inner
circumferential surface of the cylindrical belt, and extending
along an axial direction of the cylindrical belt, the second
heating unit having a length in the axial direction that is greater
than a length of the first heating unit in the axial direction; and
a controller configured to control the first and second heating
units, wherein when the sheet is to be heated to reach an image
fixing temperature, the controller controls both the first and
second heating units to generate heat, and after the sheet is
heated to the image fixing temperature, the controller controls the
first heating unit to generate heat and the second heating unit to
not generate heat.
17. The image processing apparatus according to claim 16, further
comprising: a pressure roller contacting the cylindrical belt to
form a nip.
18. The image processing apparatus according to claim 16, wherein
the first and second heating units are arranged on a substrate
extending along a longitudinal direction that is parallel to the
axial direction of the cylindrical belt.
19. The image processing apparatus according to claim 18, wherein
the first heating unit generates heat in a first region of the
cylindrical belt at a center thereof in the axial direction, and
the second heating unit generates heat in a second region of the
cylindrical belt beyond the first region along the axial
direction.
20. The image processing apparatus according to claim 18, wherein
the second heating unit generates heat in the first region.
21. The heating device according to claim 2, wherein the second
heating unit is closer to an edge of the substrate in a direction
crossing the longitudinal direction than the first heating unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2020-133915, filed on
Aug. 6, 2020, the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments described herein relate generally to a heating
device, a fixing device, and an image processing apparatus.
BACKGROUND
[0003] An image processing apparatus includes an image forming
unit, a belt, and a heating unit. The image forming unit forms an
image on a sheet. The belt is formed in a cylindrical shape. The
heating unit is provided inside the cylindrical shape of the belt.
The heating unit thus faces an inner peripheral surface of the belt
and operates to heat the belt. It is generally required to suppress
the local temperature changes or variations of the belt for image
forming operations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a schematic diagram of an image processing
apparatus according to a first embodiment.
[0005] FIG. 2 is a hardware diagram of an image processing
apparatus according to a first embodiment.
[0006] FIG. 3 is a front cross sectional view of a heating device
of a first embodiment.
[0007] FIG. 4 is a front cross sectional view of a heater unit
according to a first embodiment.
[0008] FIG. 5 is a bottom view of a heater unit according to a
first embodiment.
[0009] FIG. 6 is a plan view of a heater thermometer and a
thermostat according to a first embodiment.
[0010] FIG. 7 is a schematic circuit diagram of a heating device
according to a first embodiment.
[0011] FIG. 8 is a bottom view of a heater unit of a comparative
example.
[0012] FIG. 9 is a diagram for explaining temperature distributions
of belts according to a first embodiment and a comparative
example.
[0013] FIG. 10 is a bottom view of a heater unit of a second
embodiment.
DETAILED DESCRIPTION
[0014] In general, according to one embodiment, a heating device
for heating a medium on which an image can be formed includes a
cylindrical belt, a first heating unit, and a second heating unit.
The first and second heating units are inside the cylindrical belt
and face an inner circumferential surface of the belt. A controller
is configured to control the heating units to generate heat. When
the medium is to be heated to reach an image fixing temperature at
which the image can be fixed to the medium, the controller controls
the first and second heating units to both generate heat. After the
medium is heated to the image fixing temperature, the controllers
control the first heating unit to generate heat, but not the second
heating unit.
[0015] Hereinafter, one or more embodiments will be described with
reference to the drawings.
[0016] First, an image processing apparatus 1 according to a first
embodiment will be described with reference to FIG. 1. For example,
the image processing apparatus 1 is an image forming apparatus
configured to form an image on a sheet of paper S. The image
processing apparatus 1 includes a housing 10, a scanner unit 2, an
image forming unit 3, and a heating device 30, a sheet supply unit
4, a conveyance unit 5, a discharge tray 7, a reversing unit 9, a
control panel 8, and a controller 6.
[0017] The housing 10 houses various components of the image
processing apparatus 1 therein. The scanner unit 2 reads an image
from a sheet to be copied as a pattern of brightness and darkness
of reflected light or the like and generates an image signal. The
scanner unit 2 outputs the generated image signal to the image
forming unit 3. The image forming unit 3 forms an image with a
material such as toner based on the image signal received from the
scanner unit 2 or an image signal received from an external device.
The image initially formed by the image forming unit 3 is referred
to as a toner image. The image forming unit 3 transfers the toner
image onto the surface of the sheet S. The image forming unit 3
heats and presses the sheet S to fix the toner image to the sheet
S.
[0018] The sheet supply unit 4 supplies sheets S one by one to the
conveyance unit 5 in accordance with the timing at which the image
forming unit 3 forms the toner image. The sheet supply unit 4
includes a sheet storage unit 20 and a pickup roller 21. The sheet
storage unit 20 stores sheets S of a particular size and type. The
pickup roller 21 takes out the sheets S one by one from the sheet
storage unit 20. The pickup roller 21 supplies the taken-out sheet
S to the conveyance unit 5.
[0019] The conveyance unit 5 conveys the sheet S from the sheet
supply unit 4 to the image forming unit 3. The conveyance unit 5
includes conveyance rollers 23 and registration rollers 24. The
conveyance rollers 23 convey the sheet S from the pickup roller 21
to the registration rollers 24. The conveyance rollers 23 cause the
front end of the sheet S in the conveyance direction to touch
(abut) against a nip N1 formed by the registration rollers 24. The
registration rollers 24 serve to adjust the front end position of
the sheet S in the conveyance direction at the nip N1. The
registration rollers 24 convey the sheet S in accordance with the
timing at which the image forming unit 3 can appropriately transfer
the toner image onto the sheet S.
[0020] The image forming unit 3 includes a plurality of image
drawing units 25, a laser scanning unit 26, an intermediate
transfer belt 27, and a transfer unit 28. Each image drawing unit
25 includes a photosensitive drum 29. Each image drawing unit 25
forms a toner image on the respective photosensitive drum 29
according to an image signal received from the scanner unit 2 or
another device. Each image forming unit 25 forms the toner image
with one of yellow, magenta, cyan, and black toners.
[0021] An electrostatic charger, a developing device, and the like
are disposed around each photosensitive drum 29. The electrostatic
charger charges the surface of the photosensitive drum 29. Each
developing device contains a developer containing one of yellow,
magenta, cyan, and black toners. Each developing device develops an
electrostatic latent image formed on a photosensitive drum 29. As a
result, toner images of the respective colors are formed on the
photosensitive drums 29.
[0022] The laser scanning unit 26 scans the charged photosensitive
drums 29 with laser light L to expose the photosensitive drums 29
according to the image signal. The laser scanning unit 26 exposes
the photosensitive drums 29 of the image drawing units 25 for each
color with respective laser beams LY, LM, LC, LK. Thus, the laser
scanning unit 26 forms an electrostatic latent image on each
photosensitive drum 29.
[0023] The toner image on the surface of each photosensitive drum
is then transferred (primary transferred) to the intermediate
transfer belt 27. The transfer unit 28 then transfers the toner
images from the intermediate transfer belt 27 onto the surface of
the sheet S at a secondary transfer position. The heating device 30
heats and presses the sheet S to fix the transferred toner image
onto the sheet S.
[0024] The reversing unit 9 can operate to reverse the sheet S in
order to form an image on the back surface of the sheet S. The
reversing unit 9 reverses the sheet S discharged from the heating
device 30 by a switchback or the like. The reversing unit 9 conveys
the reversed sheet S back to the registration rollers 24. The sheet
S on which an image has already been formed and which has been
discharged can be placed on the sheet discharge tray 7.
[0025] The control panel 8 is an input unit through which an
operator (user) inputs instructions or commands related to
operating the image processing apparatus 1. The control panel 8
includes a touch panel and various hardware keys.
[0026] The controller 6 controls each unit of the image processing
apparatus 1.
[0027] FIG. 2 is a hardware diagram of the image processing
apparatus 1. The image processing apparatus 1 includes the
controller 6 including a CPU (Central Processing Unit) 91, a memory
92, and an auxiliary storage device 93 connected via a bus or the
like. The controller 6 executes one or more programs. The image
processing apparatus 1 includes a scanner unit 2, an image forming
unit 3, a heating device 30, a sheet supply unit 4, a conveyance
unit 5, and a reversing unit 9, the control panel 8, and the
communication unit 90. In one embodiment, the heating device 30 may
further include a control circuit having similar functions as those
described for the controller 6 or controller 6 may be considered as
a part of a heating device 30 in some examples.
[0028] The CPU 91 of the controller 6 executes programs stored in
the memory 92 and/or the auxiliary storage device 93. The
controller 6 controls each unit of the image processing apparatus 1
according to the programs. The auxiliary storage device 93 is a
storage device such as a magnetic hard disk device (HDD) or a
semiconductor storage device (SSD). The auxiliary storage device 93
stores various programs and data. The communication unit 90 is a
communication interface circuit to communicate with an external
device.
[0029] The heating device 30 will be described in detail. FIG. 3 is
a front cross sectional view of the heating device 30. In one
embodiment, the heating device 30 is a fixing device including a
pressure roller 101 and a heating roller 102.
[0030] The pressure roller 101 forms a nip N with the heating
roller 102. The pressure roller 101 applies pressure to the sheet S
on which the toner image has been formed and that has entered the
nip N. The pressure roller 101 rotates and conveys the sheet S. The
pressure roller 101 includes a core metal 32, an elastic layer 33,
and a release layer 34.
[0031] The core metal 32 is formed in a cylindrical shape with a
metal material such as stainless steel. Both end portions of the
core metal 32 in the axial direction are rotatably supported. The
core metal 32 is rotationally driven by a motor. The core metal 32
contacts a cam member. The cam member rotates so that the core
metal 32 is moved toward and away from the heating roller 102.
[0032] The elastic layer 33 is formed of an elastic material such
as silicone rubber. The elastic layer 33 is formed on the outer
peripheral surface of the core surface of the core metal 32. The
release layer 34 is formed of a resin material such as PFA (tetra
fluoroethylene-perfluoroalkyl vinyl ether copolymer). The release
layer 34 is formed on the outer peripheral surface of the elastic
layer 33.
[0033] For example, when the outer diameter of the pressure roller
101 is 20 mm to 40 mm, the outer diameter of the core metal 32 is
10 mm to 20 mm, the thickness of the elastic layer 33 is 5 mm to 20
mm, and the thickness of the release layer 34 is 20 .mu.m to 40
.mu.m is preferably set.
[0034] It is desirable that the hardness of the outer peripheral
surface of the pressure roller 101 is 40.degree. to 50.degree.
under a load of 9.8N on an ASKER-C hardness meter. As a result, the
area of the nip N and the durability of the pressure roller 101 are
ensured.
[0035] The pressure roller 101 can approach and separate from the
heating roller 102 by rotation of the cam member. When the pressure
roller 101 is brought close to the heating roller 102 and pressed
by a pressure spring, the nip N is formed. On the other hand, when
the jam of the sheet S occurs in the heating device 30, the sheet S
can be removed by separating the pressure roller 101 from the
heating roller 102. Further, in a state where the rotation of the
belt 35 is stopped, such as during sleep, the pressure roller 101
is separated from the heating roller 102, thereby preventing the
belt 35 from being plastically deformed.
[0036] The pressure roller 101 is rotated by a motor. When the
pressure roller 101 rotates while the nip N is formed, the belt 35
of the heating roller 102 is driven to rotate. The pressure roller
101 conveys the sheet S in the conveyance direction W by rotating
in a state in which the sheet S is disposed in the nip N.
[0037] The heating roller 102 heats the sheet S entering the nip N.
The heating roller 102 includes a belt 35, a heater unit 40, a heat
conduction member 49, a support member 36, a stay 38, a heater
thermometer 62, a thermostat 68, and a film thermometer 64.
[0038] The belt 35 is formed in a cylindrical shape. The belt 35
includes a base layer, an elastic layer, and a release layer in
this order from the inner circumferential side. The base layer is
formed of a material such as nickel (Ni) and the like. The elastic
layer is laminated on the outer peripheral surface of the base
layer. The elastic layer is formed of an elastic material such as
silicone rubber. The release layer is laminated on the outer
peripheral surface of the elastic layer. The release layer is
formed of a material such as PFA resin.
[0039] In order to shorten the warm-up time, it is preferable to
set the thicknesses of the elastic layer and the release layer so
that the heat capacities are not too large. For example, when the
inner diameter of the belt 35 is 20 mm to 40 mm, the thickness of
the base layer should be set to 30 .mu.m to 50 .mu.m, the thickness
of the elastic layer should be set to 100 .mu.m to 300 .mu.m, and
the thickness of the release layer should be set to 20 .mu.m to 40
.mu.m. The inner side of the base layer may be coated to improve
frictional sliding properties with the heater unit 40.
[0040] FIG. 4 is a front cross sectional view of the heater unit 40
taken along line IV-IV in FIG. 5. FIG. 5 is a bottom view of the
heater unit 40 viewed from +z direction. The heater unit 40
includes a substrate 41, a first heating unit 45, a second heating
unit 120, and a wiring set 55.
[0041] The substrate 41 is formed of a metal material such as
stainless steel or a ceramic material such as aluminum nitride. The
substrate 41 is formed in an elongated rectangular plate shape. The
substrate 41 is disposed radially inward of the belt 35. The
longitudinal direction of the substrate 41 is parallel to the axial
direction of the belt 35.
[0042] In this application, the x, y and z directions are defined
as follows. The y direction is the longitudinal direction of the
substrate 41 or the heater unit 40. The longitudinal direction is
orthogonal to the conveyance direction of the sheet S. As will be
described later, the +y direction is a direction from a central
heating element 110 toward a first end heating element 111. The x
direction is the lateral direction of the substrate 41. The +x
direction is the conveyance direction or downstream direction of
the sheet S. The z direction is a normal direction of the substrate
41. The +z direction is a direction in which the first heating unit
45 is disposed with respect to the substrate 41. An insulating
layer 43 made of a glass material or the like is formed on the
surface in the +z direction of the substrate 41. A surface fa in
the +z of the heater unit 40 direction is in contact with an inner
circumferential surface of the belt 35 (see FIG. 3).
[0043] The first heating unit 45 is disposed on the substrate 41.
As shown in FIG. 4, the first heating unit 45 is formed on the
surface in the +z direction of the insulating layer 43. The first
heating unit 45 is formed of a silver-palladium alloy or the like.
As shown in FIG. 5, the outer shape of the first heating unit 45 is
formed in a rectangular shape having a longitudinal direction
parallel to the y direction and a short direction parallel to the x
direction. The first heating unit 45 generates heat in a first
region Ea whose longitudinal direction is the y direction. For
example, the total length of the first heating unit 45 in the y
direction is set to be greater than or equal to 297 mm and less
than 329 mm.
[0044] The first heating unit 45 includes a plurality of heating
elements 111, 110, and 112 provided along the y direction. The
first heating unit 45 includes a first end heating element 111, a
central heating element 110, and a second end heating element 112
arranged in the y direction. The central heating element 110 is
disposed at the center of the first heating unit 45 in the y
direction. The central heating element 110 may include a plurality
of small heating elements arranged side by side along the y
direction. The first end heating element 111 is disposed on the +y
direction side of the central heating element 110 and at an end
portion of the first heating unit 45 in the +y direction. The
second end heating element 112 is arranged on -y direction side of
the central heating element 110 and at an end portion of the first
heating unit 45 in the -y direction. A boundary line between the
central heating element 110 and the first end heating element 111
is parallel to the x direction. A boundary line between the central
heating element 110 and the first end heating element 111 may cross
the x direction. The same applies to the boundary line between the
central heating element 110 and the second end heating element
112.
[0045] The first heating unit 45 generates heat by
energization.
[0046] The electric resistance value of the central heating element
110 is smaller than the electric resistance values of the first end
heating element 111 and the second end heating element 112. The
first end heating element 111 and the second end heating element
112 have substantially the same electrical resistance value. Here,
the electric resistance value of the central heating element 110 is
referred to as "central resistance value A", and the electric
resistance value of the first end heating element 111 or the second
end heating element 112 is referred to as "end resistance value B".
For example, the ratio of the central resistance value A to the end
resistance value B (A:B) is preferably in the range of 1:3 to 1:7,
and more preferably in the range of 1:4 to 1:6.
[0047] The sheet S which has a small width in the y direction
passes through the center of the heating device 30 in the y
direction. In such a case, the controller 6 causes only the central
heating element 110 to generate heat. On the other hand, the
controller 6 heats the whole of the first heating unit 45 when the
sheet S has a large width in the y direction. Therefore, the
central heating element 110 and the pair of the first end heating
element 111 and the second end heating element 112 are controlled
to generate heat independently of each other. The first end heating
element 111 and the second end heating element 112 are similarly
controlled to generate heat.
[0048] The second heating unit 120 is disposed on the substrate 41.
As shown in FIG. 4, the second heating unit 120 is formed on the
surface of the insulating layer 43 in +z direction. The second
heating unit 120 is formed of a silver-palladium alloy or the like.
The outer shape of the second heating unit 120 is formed in a
rectangular shape whose longitudinal direction is parallel to the y
direction and whose short direction is parallel to the x direction.
The first heating unit 45 and the second heating unit 120 generate
heat indifferent regions. The second heating unit 120 generates
heat in a region including a second region Eb (see FIG. 5) outside
the first heating unit 45 along the y direction. In an embodiment,
the second heating unit 120 generates heat in the first region Ea
and the second region Eb. For example, the total length of the
second heating unit 120 in the y direction is greater than or equal
to the 329 mm.
[0049] As shown in FIG. 5, the length of the second heating unit
120 in the y direction is larger than the length of the first
heating unit 45 in the y direction. The second heating unit 120 is
longer than the first heating unit 45 on both outer sides in the y
direction. The second heating unit 120 is formed by a single
heating element extending along the y direction.
[0050] The second heating unit 120 generates heat by energization.
The temperature coefficient of resistance for the first heating
unit 45 and the temperature coefficient of resistance for the
second heating unit 120 are different from each other. In the
present example, the temperature coefficient of resistance for the
second heating unit 120 is less than the temperature coefficient of
resistance for the first heating unit 45.
[0051] For example, the first heating unit 45 and the second
heating unit 120 may be formed of different heating elements. For
example, a heating element may include a "TCR material," which in
this context is a material having a large temperature coefficient
of resistance (TCR). When the heating element includes a TCR
material, the electric power used by the heating element decreases
as the temperature of the heating element increases.
[0052] Specifically, as the temperature of the heating element
rises, the electric power changes as expressed by the following
equation (1):
P=Pa/{1+(.alpha..sub.TCR/10.sup.6).times.(T-Ta)}
[0053] In the equation (1), P indicates an electric power output in
watts (W) required at a particular temperature, Pa indicates an
electric output in watts (W) required at a reference temperature T
indicates the particular temperature in .degree. C., Ta indicates a
reference temperature in .degree. C., and .alpha..sub.TCR indicates
a temperature coefficient for resistance change in parts per
million (ppm).
[0054] Since the heating element includes a TCR material, power
consumption can be reduced, and a temperature rise of the non-sheet
passing portion can be alleviated. On the other hand, the time
required for heating the heating device 30 at start up from a low
temperature may increase.
[0055] As described above, the temperature coefficient of
resistance of the second heating unit 120 is smaller than the
temperature coefficient of resistance of the first heating unit 45.
Therefore, when the temperature of the heater unit 40 is increased,
the decrease of the electric power for the second heating unit 120
is smaller than the decrease of the electric power for the first
heating unit 45. Therefore, it is possible to shorten the time
required for heating during the start-up of the heating device
30.
[0056] The wiring set 55 can be formed of a metal material such as
silver. As shown in FIG. 5, the wiring set 55 includes a central
contact 131, a central wiring 140, an end contact 132, a first end
wiring 141, a second end wiring 142, an auxiliary contact 133, an
auxiliary wiring 143, a common contact 58, and a common wiring
57.
[0057] The central contact 131 is disposed on the -y direction side
of the first heating unit 45. The central wiring 140 is disposed on
the +x direction side of the first heating unit 45. The central
wiring 140 connects the side of the central heating element 110 in
the +x direction and the central contact 131.
[0058] The end contacts 132 are disposed on the -y direction side
of the central contact 131. The first end wiring 141 is disposed on
the +x direction side of the first heating unit 45 and on the +x
direction side of the central wiring 140. The first end wiring 141
connects the side of the first end heating element 111 in the +x
direction and the end of the end contact 132 in the +x direction.
The second end wiring 142 is disposed on the +x direction side of
the first heating unit 45 and on the -x direction side of the
central wiring 140. The second end wiring 142 connects the side of
the second end heating element 112 in the +x direction and the end
of the end contact 132 in the -x direction.
[0059] The auxiliary contact 133 is disposed on the +y direction
side of the common contact 58. The auxiliary wiring 143 is disposed
on the +y direction of the second heating unit 120. The auxiliary
wiring 143 is arranged on the -x direction side of the first
heating unit 45 and on the -x direction side of the common wiring
57. The auxiliary wiring 143 connects the end portion of the second
heating unit 120 in the +y direction and the end portion of the
auxiliary contact 133 in the -x direction.
[0060] The common contact 58 is disposed on the +y direction side
of the first heating unit 45. The common wiring 57 is disposed on
the -x direction side of the first heating unit 45 and on the +x
direction side of the second heating unit 120. The common wiring 57
connects the sides in the -x direction of the central heating
element 110, the first end heating element 111, and the second end
heating element 112, the end portion of the second heating unit 120
in the -y direction, and the common contact 58.
[0061] As shown in FIG. 3, a straight line CL connecting the center
pc of the pressure roller 101 and the center hc of the heating
roller 102 is defined. The center Xa of the substrate 41 in the x
direction is located on the +x direction side of the straight line
CL. Accordingly, since the substrate 41 extends along the +x
direction of the nip N, the sheet S passing through the nip N is
easily separated from the heating roller 102.
[0062] As shown in FIG. 4, the first heating unit 45, the second
heating unit 120, and the wiring set 55 are formed on the surface
of the insulating layer 43 in the +z direction. A protective layer
46 is formed of a glass material or the like so as to cover the
first heating unit 45, the second heating unit 120, and the wiring
set 55. The protective layer 46 protects the first heating unit 45,
the second heating unit 120, and the wiring set 55. The protective
layer 46 improves the slidability between the heater unit 40 and
the belt 35.
[0063] As shown in FIG. 3, the heater unit 40 is disposed inside
the belt 35. Grease is applied to the inner peripheral surface of
the belt 35. The heater unit 40 is in contact with the inner
circumferential surface of the belt 35 via the grease.
Specifically, the grease is applied between the first surface fa
(see FIG. 4) of the heater unit 40 and the inner peripheral surface
of the belt 35. When the heater unit 40 generates heat, the
viscosity of the grease decreases. This ensures the slidability
between the heater unit 40 and the belt 35.
[0064] The heat conduction member 49 is formed of a metal material
having high heat conductivity such as copper. The outer shape of
the heat conduction member 49 is the same as the outer shape of the
substrate 41 of the heater unit 40. The heat conduction member 49
is disposed in contact with the surface of the heater unit 40 in
the -z direction (second surface fb, see FIG. 4).
[0065] The support member 36 is formed of an elastic material such
as silicone rubber or fluorine rubber, or a resin material such as
polyimide resin, PPS (Polyphenylene Sulfide), PES (Polyether
Sulfone), or liquid crystal polymer. The support member 36 is
disposed so as to cover the sides of the heater unit 40 in the -z
direction and the +x and -x directions. The support member 36
supports the heater unit 40 via the heat conduction member 49. Both
ends of the support member 36 in the x direction are rounded. The
support member 36 supports the inner circumferential surface of the
belt 35 at both ends of the heater unit 40 in the x direction.
[0066] When the sheet S passing through the heating device 30 is
heated, a temperature distribution occurs on the heater unit 40
according to the size of the sheet S. When the heater unit 40 is
locally heated to a high temperature, the temperature may exceed
the heat resistance temperature of the support member 36 formed of
a resin material. The heat conduction member 49 averages the
temperature distribution of the heater unit 40. This ensures heat
resistance of the support member 36.
[0067] The stay 38 is formed of a steel plate material or the like.
The cross section of the stay 38 perpendicular to the y direction
is formed in a U shape. For example, the stay 38 is formed by
bending a steel material having a plate thickness of 1 mm to 3 mm.
As shown in FIG. 3, the stay 38 is attached to the support member
36 in the -z direction so that the opening of the U shape is closed
by the support member 36. The stay 38 extends along the y
direction. Both end portions of the stay 38 in the y direction are
fixed to the housing of the image processing apparatus 1. Thus, the
heating roller 102 is supported by the image processing apparatus
1. The stay 38 improves the bending rigidity of the heating roller
102. Flanges for restricting the movement of the belt 35 in the y
direction are provided near both ends of the stay 38 in the y
direction.
[0068] The heater thermometer 62 is disposed on the -z direction
side of the heater unit 40 with the heat conduction member 49
interposed therebetween. For example, the heater thermometer 62 is
a thermistor. The heater thermometer 62 is attached to and
supported by the surface of the support member 36 in the -z
direction. The temperature sensing element of the heater
thermometer 62 passes through a hole penetrating the support member
36 along the z direction and comes into contact with the heat
conduction member 49. The heater thermometer 62 measures the
temperature of the heater unit 40 via the heat conduction member
49.
[0069] The thermostat 68 is disposed similarly to the heater
thermometer 62. The thermostat 68 is incorporated in an electric
circuit described later. When the temperature of the heater unit
detected via the heat conduction member 49 exceeds a predetermined
temperature, the thermostat 68 cuts off energization to the first
heating unit 45 and the second heating unit 120.
[0070] FIG. 6 is a plan view (viewed from the -z direction) of the
heater thermometer 62 and the thermostat 68. In FIG. 6,
illustration of the second heating unit 120 and the support member
36 is omitted. In the following description of the arrangement of
the heater thermometer 62, the thermostat 68, and the film
thermometer 64, the arrangement of the temperature sensing elements
will be described.
[0071] A plurality of heater thermometers 62 including a central
heater thermometer 151 and an end heater thermometer 152 are
arranged side by side along the y direction. The plurality of
heater thermometers 62 are disposed on the first heating unit 45.
The plurality of heater thermometers 62 are disposed within the
range of the first heating unit 45 in the y direction. The
plurality of heater thermometers 62 are disposed at the center of
the first heating unit 45 in the x direction. That is, when viewed
from the z direction, the plurality of heater thermometers 62 and
the first heating unit 45 at least partially overlap each other.
The plurality of thermostats 68 (171, 172) are arranged in the same
manner as the plurality of heater thermometers 62 described
above.
[0072] The plurality of heater thermometers 62 include the central
heater thermometer 151 and the end heater thermometer 152 disposed
on one side thereof in the longitudinal direction.
[0073] The central heater thermometer 151 measures the temperature
of the central heating element 110. The central heater thermometer
151 is disposed within the range of the central heating element 110
in each of the x and y directions. That is, when viewed from the z
direction, the central heater thermometer 151 and the central
heating element 110 overlap each other.
[0074] The end heater thermometer 152 measures the temperature of
the second end heating element 112. As described above, the first
end heating element 111 and the second end heating element 112 are
similarly controlled to generate heat. Therefore, the temperature
of the first end heating element 111 is equal to the temperature of
the second end heating element 112. The end heater thermometer 152
is disposed within the second end heating element 112. That is,
when viewed from the z direction, the end heater thermometer 152
and the second end heating element 112 overlap each other.
[0075] The plurality of thermostats 68 includes a central
thermostat 171 and an end thermostat 172.
[0076] When the temperature of central heating element 110 exceeds
a predetermined temperature, the central thermostat 171 cuts off
the energization to first heating unit 45 and second heating unit
120 (see FIG. 7). The central thermostat 171 is disposed within the
central heating element 110. That is, when viewed from the z
direction, the central thermostat 171 and the central heating
element 110 overlap each other.
[0077] When the temperature of the first end heating element 111
exceeds a predetermined temperature, the end thermostat 172 cuts
off energization to the first heating unit 45 and the second
heating unit 120 (see FIG. 7). As described above, the first end
heating element 111 and the second end heating element 112 are
similarly controlled to generate heat. Therefore, the temperature
of the first end heating element 111 is equal to the temperature of
the second end heating element 112. The end thermostat 172 is
disposed within the first end heating element 111. That is, when
viewed from the z direction, the end thermostat 172 and the first
end heating element 111 overlap each other.
[0078] As described above, the central heater thermometer 151 and
the central thermostat 171 are disposed on the central heating
element 110. Thus, the temperature of the central heating element
110 is measured. When the temperature of central heating element
110 exceeds the predetermined temperature, energization to first
heating unit 45 and second heating unit 120 (see FIG. 7) is cut
off. The end heater thermometer 152 is disposed on the second end
heating element 112. Thus, the temperature of the second end
heating element 112 is measured. Since the temperature of the first
end heating element 111 is equal to the temperature of the second
end heating element 112, the temperatures of the first end heating
element 111 and the second end heating element 112 are measured.
The end thermostat 172 is disposed on the first end heating element
111. When the temperatures of the first end heating element 111 and
the second end heating element 112 exceed a predetermined
temperature, energization to the first heating unit 45 and the
second heating unit 120 (see FIG. 7) is cut off.
[0079] The plurality of heater thermometers 62 and the plurality of
thermostats 68 are alternately arranged along the y direction. As
described above, the first end heating element 111 is disposed on
the +y direction side of the central heating element 110. The end
thermostat 172 is disposed within the first end heating element
111. The central heater thermometer 151 is disposed on the +y
direction side of the center of the central heating element 110.
The central thermostat 171 is disposed on the -y direction side of
the center of the central heating element 110. As described above,
the second end heating element 112 is disposed on the -y direction
side of the central heating element 110. An end heater thermometer
152 is disposed within the range of the second end heating element
112. Thus, the end portion thermostat 172, the central portion
heater thermometer 151, the central portion thermostat 171, and the
end portion heater thermometer 152 are arranged in this order from
the +y direction to the -y direction.
[0080] In general, the thermostat 68 connects and disconnects an
electric circuit by utilizing bending deformation of a bimetal
caused by a temperature change. The thermostat is formed long and
narrow in accordance with the shape of the bimetal. Terminals
extend outward from both ends of the thermostat 68 along the
longitudinal direction. A connector of external wiring is connected
to the terminal by caulking. Therefore, it is necessary to secure a
space outside the thermostat 68 in the longitudinal direction.
Since there is no spatial margin in the x direction in the heating
device 30, the longitudinal direction of the thermostat 68 is
arranged along the y direction. At this time, if the plurality of
thermostats 68 are arranged adjacent to each other along the y
direction, it becomes difficult to secure a connection space for
external wiring.
[0081] As described above, the plurality of heater thermometers 62
and the plurality of thermostats 68 are alternately arranged along
the y direction. Thus, the heater thermometer 62 is disposed
adjacent to the thermostat 68 in the y direction. Therefore, it is
possible to secure a space for connecting external wiring to the
thermostat 68. In addition, the degree of freedom of the layout of
the thermostat 68 and the heater thermometer 62 in the y direction
is increased. Thus, the temperature of the heating device 30 can be
controlled by arranging the thermostat 68 and the heater
thermometer 62 at optimum positions. Furthermore, the
alternating-current wiring connected to the plurality of
thermostats 68 and the direct-current wiring connected to the
plurality of heater thermometers 62 can be easily separated from
each other. This suppresses generation of noise in the electric
circuit.
[0082] As shown in FIG. 3, the film thermometer 64 is disposed
inside the belt 35 and on the +x direction side of the heater unit
40. The film thermometer 64 is in contact with the inner peripheral
surface of the belt 35 and measures the temperature of the belt
35.
[0083] FIG. 7 is an electric circuit diagram of the heating device
30. In FIG. 7, the bottom view of FIG. 5 is shown on the upper
side, and the plan view of FIG. 6 is shown on the lower side. In
FIG. 7, the cross section of the belt 35 and a plurality of belt
thermometers 64 are shown in the upper part of the lower plan view.
The plurality of belt thermometers 64 include a central belt
thermometer 161 and end belt thermometers 162 disposed on one side
thereof in the longitudinal direction.
[0084] The central belt thermometer 161 is in contact with the
central portion of the belt 35 in the y direction. The central belt
thermometer 161 contacts the belt 35 within the range of the
central heating element 110 in the y direction. The central belt
thermometer 161 measures the temperature of the central portion of
the belt 35 in the y direction.
[0085] The end belt thermometer 162 is in contact with the end of
the belt 35 in the -y direction. The end belt thermometer 162
contacts the belt 35 within the range of the second end heating
element 112 in the y direction. The end belt thermometer 162
measures the temperature of the end portion of the belt 35 in the
-y direction. As described above, the first end heating element 111
and the second end heating element 112 are similarly controlled to
generate heat. Therefore, the temperature of the end portion of the
belt 35 in the -y direction is equal to the temperature of the end
portion of the belt 35 in the +y direction.
[0086] A power supply 95 is connected to the central contact 131
via a central triac 181. The power supply 95 is connected to an end
contact 132 via an end triac 182. The power supply 95 is connected
to the auxiliary contact 133 via an auxiliary triac 183. The CPU 91
controls ON/OFF of the central triac 181, the end triac 182, and
the auxiliary triac 183 independently of each other. When the CPU
91 turns on the central triac 181, the central heating element 110
is energized from the power supply 95. As a result, the element 110
generates heat. When the CPU 91 turns on the end triac 182, the
first end heating element 111 and the second end heating element
112 are energized from the power supply 95. Thus, the first end
heating element 111 and the second end heating element 112 generate
heat. When the CPU 91 turns on the auxiliary triac 183, the second
heating unit 120 is energized from the power supply 95. As a
result, the second heating unit 120 generates heat. As described
above, the heat generation of the central heating element 110, the
first end heating element 111, the second end heating element 112,
and the second heating unit 120 is controlled independently of each
other. The central heating element 110, the first end heating
element 111, the second end heating element 112, and the second
heating unit 120 are connected in parallel to the power supply
95.
[0087] The power supply 95 is connected to the common contact 58
via the central thermostat 171 and the end thermostat 172. The
central thermostat 171 and the end thermostat 172 are connected in
series. When the temperature of the central heating element 110
abnormally rises, the temperature detected by the central
thermostat 171 exceeds a predetermined temperature. During this
time, the central portion thermostat 171 cuts off energization from
power supply 95 to the entire first heating unit 45 and the second
heating unit 120.
[0088] When the temperature of the first end heating element 111
abnormally increases, the temperature detected by the end
thermostat 172 exceeds a predetermined temperature. During this
time, the end thermostat 172 cuts off the energization from the
power supply 95 to the entire first heating unit 45 and the second
heating unit 120. As described above, the first end heating element
111 and the second end heating element 112 are similarly controlled
to generate heat. Therefore, when the temperature of the second end
heating element 112 rises abnormally, the temperature of the first
end heating element 111 also increases. Therefore, even when the
temperature of the second end heating element 112 abnormally rises,
similarly, the end thermostat 172 controls the power supply 95 to
supply power to the entire first heating unit 45 and the second
heating unit 120.
[0089] The CPU 91 of the control unit 6 acquires the temperature of
the central heating element 110 by the central heater thermometer
151. The CPU 91 acquires the temperature of the second end heating
element 112 with the end heater thermometer 152. The temperature of
the second end heating element 112 is equal to the temperature of
the first end heating element 111. The CPU 91 acquires the
temperature of the first heating unit 45 by the heater thermometer
62 when the heating device 30 is started. When the temperature of
the first heating unit 45 is lower than the predetermined
temperature, the CPU 91 causes the first heating unit 45 to
generate heat for a short time. Thereafter, the CPU 91 starts
rotation of the pressure roller 101. The viscosity of the grease
applied to the inner peripheral surface of the belt 35 decreases
due to the heat generation of the first heating unit 45. This
ensures the slidability between the heater unit 40 and the belt 35
at the start of rotation of the pressure roller 101.
[0090] The CPU 91 acquires the temperature of the center portion of
the belt 35 in the y direction by the central portion belt
thermometer 161. The CPU 91 acquires the temperature of the end
portion of the belt 35 in the -y direction by the end belt
thermometer 162. The temperature of the end portion of the belt 35
in the -y direction is equal to the temperature of the end portion
of the belt 35 in the +y direction. The CPU 91 acquires the
temperature of the center portion and the end portion of the belt
35 in the y direction during the operation of the heating device
30. The CPU 91 controls the phase or the wave number of the power
supplied to the first heating unit 45 by the central triac 181 and
the end triac 182. The CPU 91 controls energization to the central
heating element 110 based on the temperature measurement result of
the central portion of the belt 35 in the y direction.
[0091] Next, an example of control of the heater unit 40 will be
described. When the CPU 91 of the controller 6 increases the
temperature of the heater unit 40 to a temperature at which the
image formed by the image forming unit 3 can be fixed to the sheet
S, the CPU 91 controls to increase the temperature of the first
heating unit 45 and the second heating unit 120. Hereinafter, a
time period during which the temperature of the heater unit 40 is
increased to a temperature at which the image formed by the image
forming unit 3 can be fixed to the sheet S is also referred to as a
"start-up time". For example, the start-up time includes a start-up
time or warming-up time of the heating device 30 and a return time
from a paused (idle) state or sleep state. The CPU 91 causes the
entire first heating unit 45 and the second heating unit 120 to
generate heat during the start-up time. Accordingly, it is possible
to avoid an excessive decrease in temperature of the end portion in
the longitudinal direction of the belt 35 during the start-up
time.
[0092] The CPU 91 controls heating of the first heating unit 45
when the image formed by the image forming unit 3 is fixed to the
sheet S. The CPU 91 does not cause the second heating unit 120 to
generate heat when the image formed by the image forming unit 3 is
fixed to the sheet S. Hereinafter, a time period during which the
image formed by the image forming unit 3 is fixed to the sheet S is
also referred to as "fixing time". For example, the fixing time
includes a time period during which the sheet S is continuously
conveyed. In other words, fixing is performed during printing. The
CPU 91 causes the entire first heating unit 45 to generate heat
during the fixing time. The CPU 91 does not cause the second
heating unit 120 to generate heat during the fixing time. Thus,
excessive temperature rise of the longitudinal end portion of the
belt 35 can be suppressed during the fixing time.
[0093] Next, another example of the control of the heater unit 40
will be described. The CPU 91 controls heating of the first heating
unit 45 and the second heating unit 120 regardless of the size of
the sheet in the start-up time. The CPU 91 causes the entire first
heating unit 45 and the second heating unit 120 to generate heat
regardless of the size of sheet S.
[0094] The CPU 91 controls heating of the first heating unit 45 and
the second heating unit 120 based on the size of the sheet S during
the fixing time. For example, when the length of the sheet S in the
y direction is equal to or less than 297 mm, the CPU 91 causes the
entire first heating unit 45 to generate heat during the fixing
time. For example, when the length of the sheet S in the y
direction is less than or equal to 297 mm, the CPU 91 does not
cause the second heating unit 120 to generate heat during the
fixing time. For example, when the length of the sheet S in the y
direction exceeds 297 mm, the CPU 91 causes the entire first
heating unit 45 and the second heating unit 120 to generate heat
during the fixing time. For example, the CPU 91 may control heating
of the second heating unit 120 only when the length of the sheet S
in the y direction exceeds 297 mm.
[0095] As described above, during the start-up time, the entire
first heating unit 45 and the second heating unit 120 generate heat
regardless of the size of the sheet S. Therefore, during the
start-up time, it is possible to suppress an excessive decrease in
the temperature of the end portion in the longitudinal direction of
the belt 35 regardless of the size of the sheet S. Additionally,
during the fixing time, when the length of the sheet S in the y
direction is equal to or less than 297 mm, the entire first heating
unit 45 generates heat, but the second heating unit 120 does not
generate heat. Therefore, during the fixing time, it is possible to
avoid an excessive temperature rise of the end portion in the
longitudinal direction of the belt 35 (e.g., the portion for which
the length in the y direction exceeds 297 mm).
[0096] Next, a heater unit of a comparative example will be
described with reference to FIG. 8. FIG. 8 is a bottom view of a
heater unit of a comparative example. In the comparative example,
the heater unit includes a substrate 41, a plurality of heating
elements 110, 111, and 112, a plurality of contact points 131, 132,
58, and a plurality of wirings 140, 141, 142, 57. In the
comparative example, the heater unit does not include the second
heating unit 120, the auxiliary contact 133, and the auxiliary
wiring 143.
[0097] Next, effects of a first embodiment will be described
together with the comparative example with reference to FIG. 9.
FIG. 9 is an explanatory diagram of the temperature distribution of
the belt according to a first embodiment and the comparative
example. In the FIG. 9, the horizontal axis represents the belt
longitudinal position (that is, the position along the longitudinal
direction of the belt 35), and the vertical axis represents the
belt temperature (that is, the temperature of the belt 35). In FIG.
9, a solid line represents values during the start-up time in a
first embodiment, a one-dot chain line indicates values during the
fixing time in the first embodiment, a two-dot chain line indicates
values during the start-up time in the comparative example, and a
broken (dashed) line indicates a values during the fixing time in
the comparative example.
[0098] As described above, in the comparative example, since the
second heating unit 120 is not provided, the belt temperature
decreases at the end portion of the belt longitudinal position
during the start-up time, as indicated by the two-dot chain line in
FIG. 9. In order to suppress the temperature decrease at the end
portion of the belt longitudinal position, the heating element may
be enlarged in the longitudinal direction. However, if the heating
element is simply increased in size in the longitudinal direction,
the temperature of the belt at the non-sheet passing portion (e.g.,
the end portion of the belt longitudinal position) increases during
the fixing time, as indicated by the broken line in FIG. 9.
[0099] In first embodiment, the first heating unit 45 and the
second heating unit 120 are provided. In the start-up time, the
entire first heating unit 45 and the second heating unit 120
generate heat regardless of the size of the sheet S. Therefore, it
is possible to suppress the temperature decrease of the end portion
of the belt longitudinal position during the start-up time, as
indicated by the solid line in FIG. 9. Further, during the fixing
time, when the length of the sheet S in the y direction is equal to
or less than 297 mm, the entire first heating unit 45 generates
heat, but the second heating unit 120 does not generate heat. For
this reason, it is possible to suppress a temperature rise of an
end portion (e.g., a portion outside the range of 297 mm) of the
belt longitudinal position at the time of fixing, as indicated by
the alternate long and short dash line in FIG. 9.
[0100] As described above, the image processing apparatus 1
includes the image forming unit 3, the belt 35, the heating unit
40, and the controller 6. The image forming unit 3 forms an image
on the sheet S. The belt 35 has a cylindrical shape. The heating
unit 40 is provided inside the belt 35. The heating unit 40
includes the first heating unit 45 and the second heating unit 120
facing the inner circumferential surface of the belt 35. The
heating unit 40 heats the belt 35. The controller 6 controls the
first heating unit 45 and the second heating unit 120 to generate
heat when the temperature of the heating unit 40 is increased to a
temperature at which the image formed by the image forming unit 3
can be fixed to the sheet S. When the image formed by the image
forming unit 3 is fixed to the sheet S, the controller 6 controls
the first heating unit 45 to generate heat and controls the second
heating unit 120 to not generate heat. With the above
configuration, the following effects are achieved. When the
temperature of the heating unit 40 is increased to a temperature at
which the image formed by the image forming unit 3 can be fixed to
the sheet S, the first heating unit 45 and the second heating unit
120 generate heat, and thus it is possible to suppress a local
decrease in the temperature of the belt 35. When the image formed
by the image forming unit 3 is fixed to the sheet S, the first
heating unit 45 generates heat, but the second heating unit 120
does not generate heat. Therefore, it is possible to suppress a
local temperature rise of the belt 35. Therefore, the local
temperature drop and temperature rise of the belt 35 can be
suppressed.
[0101] The first heating unit 45 generates heat in the first region
Ea. The second heating unit 120 generates heat in a region
including a second region Eb outside the first heating unit 45
along the longitudinal direction orthogonal to the conveyance
direction of the sheet S. With the above configuration, the
following effects are achieved. In a case where the temperature of
the heating unit 40 is increased to a temperature at which the
image formed by the image forming unit 3 can be fixed to the sheet
S, the first heating unit 45 and the second heating unit 120
generate heat, and thus an excessive decrease in the temperature of
the end portion of the belt 35 in the longitudinal direction can be
suppressed. When the image formed by the image forming unit 3 is
fixed to the sheet S, the first heating unit 45 generates heat, but
the second heating unit 120 does not generate heat. Therefore, it
is possible to suppress an excessive temperature rise of the end
portion in the longitudinal direction of the belt 35. Therefore,
local temperature decrease and temperature increase of the belt 35
can be suppressed.
[0102] The second heating unit 120 generates heat in the first
region Ea and the second region Eb. With the above configuration,
the following effects are achieved. If the heating unit 40 is
raised to a temperature at which the image formed by the image
forming unit 3 can be fixed to the sheet S, then the first region
Ea can be heated by the first heating unit 45 and the second
heating unit 120. This contributes to shortening of the start-up
time.
[0103] The first heating unit 45 has a plurality of heating
elements 110, 111, and 112 along the longitudinal direction. With
the above configuration, the following effects are achieved.
Corresponding to various paper sizes, the heating temperature can
be appropriately controlled.
[0104] The image processing apparatus 1 further includes the heat
conduction member 49 provided in contact with the heating unit 40.
With the above configuration, the following effects are achieved.
The temperature gradient in the longitudinal direction of the
heating unit 40 is reduced, and local temperature drop and
temperature rise in the longitudinal direction can be
suppressed.
[0105] A temperature coefficient of resistance of the second
heating unit 120 is smaller than a temperature coefficient of
resistance of the first heating unit 45. With the above
configuration, the following effects are achieved. When the
temperature of the heating unit 40 is increased, the output
decrease of the electric power of the second heating unit 120 is
smaller than the output decrease of the electric power of the first
heating unit 45. Therefore, it is possible to shorten the time
required for heating during the start-up of the heating device
30.
[0106] Next, a second embodiment will be described with reference
to FIG. 10. In the second embodiment, description of the same
configuration as those of the first embodiment will be omitted. The
second embodiment is different from the first embodiment in that
the second heating unit generates heat in the second region Eb but
does not generate heat in the first region Ea.
[0107] FIG. 10 is a bottom view of a heater unit 240 of the second
embodiment. As shown in FIG. 10, the heater unit 240 includes a
substrate 41, a first heating unit 45, a second heating unit 220,
and a wiring set 255.
[0108] The first heating unit 45 includes a plurality of heating
elements 111, 110, and 112 provided along the y direction. The
first heating unit 45 includes a first end heating element 111, a
central heating element 110, and a second end heating element 112
arranged along the y direction.
[0109] The second heating unit 220 is disposed outside the first
heating unit 45 along the longitudinal direction. The second
heating unit 220 generates heat in the second region Eb outside the
first heating unit 45 along the y direction. The second heating
unit 220 includes a first auxiliary heating element 221 disposed on
the +y direction side of the first end heating element 111, and a
second auxiliary heating element 222 disposed on the -y direction
side of the second end heating element 112.
[0110] For example, each of the first auxiliary heating element 221
and the second auxiliary heating element 222 may be provided with a
thermometer such as a thermistor. For example, the CPU 91 may
control heating of the first auxiliary heating element 221 and the
second auxiliary heating element 222 based on the detection results
of the thermistors. For example, the first heating unit 45, the
first auxiliary heating element 221, and the second auxiliary
heating element 222 may be controlled to generate heat
independently of each other. The first auxiliary heating element
221 and the second auxiliary heating element 222 may be controlled
to generate heat in the same manner. Thus, the belt temperature at
the belt longitudinal position can be controlled finely.
[0111] The wiring set 255 includes a central contact 131, a central
wiring 140, an end contact 132, a first end wiring 141, a second
end wiring 142, an auxiliary contact 133, a first auxiliary wiring
243, a second auxiliary wiring 244, a common contact 58, and a
common wiring 57.
[0112] The first auxiliary wiring 243 connects an end portion of
the first auxiliary heating element 221 in the +x direction and an
end portion of the auxiliary contact 133 in the +x direction. The
second auxiliary wiring 244 is provided between the end portion of
the second auxiliary heating element 222 in the +x direction and
the auxiliary contact 133 in the -x direction. The common wiring 57
connects end sides in the -x direction of the central heating
element 110, the first end heating element 111, and the second end
heating element 112, end portions in the -x direction of the first
auxiliary heating element 221 and the second auxiliary heating
element 222, and the common contact 58.
[0113] A heat conduction member 249 corresponding to the heat
conduction member 49 shown in FIG. 3 and indicated by the dashed
line in FIG. 10 is in contact with the first heating 45 and is not
in contact with the second heating unit 220. The heat conduction
member 249 overlaps with the first heating unit 45 when viewed from
the z direction. The heat conduction member 249 does not overlap
with the second heating unit 220 when viewed from the z direction.
The length of the heat conduction member 249 in the x direction is
equal to the length of the substrate 41 in the x direction. The
length of the heat conduction member 249 in the y direction is
equal to the length of the first heating unit 45.
[0114] Next, an example of control of the heater unit 240 will be
described. The CPU 91 causes the entire first heating unit 45 and
the second heating unit 220 to generate heat during the start-up
time. Accordingly, it is possible to suppress an excessive decrease
in temperature of the end portion in the longitudinal direction of
the belt 35 during the start-up time.
[0115] The CPU 91 causes the entire first heating unit 45 to
generate heat during the fixing time. The CPU 91 does not cause the
second heating unit 220 to generate heat during the fixing time.
Thus, excessive temperature rise of the longitudinal end portion of
the belt 35 can be suppressed during the fixing time.
[0116] Next, another example of control of the heater unit 240 will
be described. The CPU 91 causes the entire first heating unit 45
and the second heating unit 220 to generate heat regardless of the
size of the sheet S during the start-up time.
[0117] The CPU 91 controls heating of the first heating unit 45 and
the second heating unit 220 based on the size of the sheet S during
the fixing time. For example, when the length of the sheet S in the
y direction is equal to or less than 297 mm, the CPU 91 causes the
entire first heating unit 45 to generate heat during the fixing
time. For example, when the length of the sheet S in the y
direction is less than or equal to 297 mm, the CPU 91 does not
cause the second heating unit 220 to generate heat during the
fixing time. For example, when the length of the sheet S in the y
direction exceeds 297 mm, the CPU 91 causes the entire first
heating unit 45 and the second heating unit 220 to generate heat
during the fixing time. For example, the CPU 91 may control heating
of the second heating unit 220 only when the length of the sheet S
in the y direction exceeds 297 mm.
[0118] As described above, during the start-up time, the entire
first heating unit 45 and the second heating unit 220 generate heat
regardless of the size of the sheet S. Therefore, during the
start-up time, it is possible to suppress an excessive decrease in
the temperature of the end portion in the longitudinal direction of
the belt 35 regardless of the size of the sheet S. Further, during
the fixing time, when the length of the sheet S in the y direction
is equal to or less than 297 mm, the entire first heating unit 45
generates heat, but the second heating unit 220 does not generate
heat. Therefore, during the fixing time, it is possible to suppress
an excessive temperature rise of the end portion in the
longitudinal direction of the belt 35 (e.g., the portion where the
length in the y direction exceeds 297 mm). Since a local
temperature increase in the longitudinal direction does not occur,
the heat conduction member 249 may not be disposed at a position
corresponding to the second heating unit 220 as described
above.
[0119] As described above, the second heating unit 220 is disposed
outside the first heating unit 45 along the longitudinal direction.
The second heating unit 220 generates heat in the second region Eb.
With the above configuration, the following effects are achieved.
By providing the thermistor in the second heating unit 220, it is
possible to control heating of the first heating unit 45 and the
second heating unit 220 independently of each other. Therefore, the
belt temperature at the belt longitudinal position can be
controlled more finely than in the first embodiment.
[0120] As described above, the heat conduction member 249 is in
contact with the first heating unit 45. The heat conduction member
249 is not in contact with the second heating unit 220. With the
above configuration, the following effects are achieved. The power
input to the second heating unit 220 can be reduced, and this
contributes to energy saving.
[0121] Next, a modification of the aforementioned embodiments will
be described. The first heating unit 45 and the second heating unit
120 or 220 described above generate heat in regions different from
each other. However, in some examples, the first heating unit 45
and the second heating unit 120, 220 may generate heat in the same
region. The first heating unit 45 and the second heating unit 120,
220 may be controlled in such examples to be heated at different
timings regardless of whether the heating regions are the same or
different.
[0122] The image processing apparatus 1 includes a heat conduction
member 49 (or 249) provided in contact with the heating unit 40 (or
240). However, in other examples, the image processing apparatus 1
need not include the heat conductive member 49 (or 249). In such a
case, the heater thermometer 62 and the thermostat 68 may directly
measure the temperature of the heater unit 40 (or 240).
[0123] The temperature coefficient of resistance of the second
heating unit 120 (or 220) in the above-described embodiments is
smaller than the temperature coefficient of resistance of the first
heating unit 45. However, in some examples, the temperature
coefficient of resistance of the second heating unit 120 (or 220)
may be larger than the temperature coefficient of resistance of the
first heating unit 45.
[0124] The temperature coefficient of resistance of the first
heating unit 45 and the temperature coefficient of resistance of
the second heating unit 120 (or 220) of the above-described
embodiments are different from each other. However, in some
examples, the temperature coefficient of resistance of the first
heating unit 45 and the temperature coefficient of resistance of
the second heating unit 120 (or 220) may be equal to each
other.
[0125] The first heating unit 45 of the above-described embodiments
includes three heating elements (e.g., a central heating element
110, a first end heating element 111, and a second end heating
element 112). In other examples, the number of heating elements
included in the first heating unit 45 may be one, two, or four or
more. The plurality of heater thermometers 62 of the
above-described embodiments include two heater thermometers (e.g.,
the central heater thermometer 151 and the end heater thermometer
152). However, the number of heater thermometers 62 may be three or
more in some examples. The plurality of thermostats 68 of the
above-described embodiments includes two thermostats (e.g., the
central thermostat 171 and the end thermostat 172). However, the
number of thermostats 68 may be three or more in some examples.
[0126] The second heating unit 120 of the first embodiment is
formed as a single heating element extending along the y direction.
On the other hand, in other examples, the second heating unit 120
may be formed as a plurality of heating elements. The second
heating unit 220 of the second embodiment includes a first
auxiliary heating element 221 disposed on the +y direction side of
the first heating unit 45 and a second auxiliary heating element
222 disposed on the -y direction side of the first heating unit 45.
In other examples, the second heating unit 220 may be disposed on
one side of the first heating unit 45 in the y direction but not
disposed on the other side thereof in the y direction. The number
of heating elements disposed on at least one side of the first
heating unit 45 in the y direction may be more than one.
[0127] In an embodiment, the image processing apparatus 1 may be a
decoloring apparatus, and the heating apparatus included therein
may be a decoloring unit. The decoloring device performs a process
of decoloring or erasing an image that has been formed on the sheet
S with decolorable toner. The decoloring unit heats and decolors
the decolorable toner image formed on the sheet passing through the
nip N.
[0128] According to at least one embodiment described above, the
controller 6 performs heating control of the first heating unit 45
and the second heating unit 120 when the temperature of the heating
unit 40 is being increased to a temperature at which an image
formed by the image forming unit 3 can be fixed to the sheet S.
When the image formed by the image forming unit 3 is fixed to the
sheet S, the controller 6 controls the first heating unit 45 to
generate heat and controls the second heating unit 120 to not
generate hat. As a result, local temperature variations across the
belt 35 can be suppressed.
[0129] 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.
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