Electrophotography – Control of electrophotography process – Control of fixing
Reexamination Certificate
1999-11-30
2002-01-01
Lee, Susan S. Y. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of fixing
Reexamination Certificate
active
06336009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image heating apparatus of a film heating system applied to image forming apparatuses such as a copying machine and a printer, particularly to a heater applied to an image heating apparatus.
2. Related Background Art
In conventional image forming apparatuses such as a printer, a copying machine and a facsimile apparatus, as a fixing apparatus (fixing device) for heating/fixing an unfixed image (toner image) formed and borne on a recording material (transfer material, photosensitive paper, electrostatic recording paper, printing sheet, and the like) by appropriate image forming means such as an electrophotographic system and an electrostatic recording system in a transfer (indirect) system or a direct system, an apparatus of a heat roller system is widely used.
The apparatus of the heat roller system has a fixing roller (thermal roller, heat roller) as a fixing member and a pressure roller as a pressurizing member which are pressed to contact each other and rotate. When a recording material with an unfixed image formed and borne thereon is introduced, nipped, conveyed, and passed via a fixing nip portion (heating nip portion) as a pressed portion of both rollers, the unfixed image can be heated/fixed as a permanent fixed image on a recording material surface by the heat of the fixing roller and the pressurizing force of the fixing nip portion.
In recent years, from the standpoint of promotion of energy saving, an apparatus of a film heating system has been placed for practical use as an on-demand image heating apparatus high in thermal conduction efficiency and fast in starting the apparatus.
As proposed in Japanese Patent Application Laid-Open Nos. 63-313182, 2-157878, 4-44075 to 4-44083, and 4-204980 to 4-204984, this has a fixed/supported heating member, a heat resistant film which slides on the heating member, and a pressurizing member contacting the heating member via this film to form a fixing nip portion. The heating member is heated/adjusted to a predetermined temperature, and a recording material with an unfixed image formed/borne thereon is introduced between the film and the pressurizing member at the fixing nip portion, and nipped/conveyed with the film through the fixing nip portion, so that the unfixed image is heated/fixed as a permanent fixed image on a recording material surface by the heat from the heating member via the film and the pressurizing force of the fixing nip portion.
In the image heating apparatus of the film heating system, a linear heating member with a low thermal capacity such as a so-called ceramic heater as the heating member, and a thin heat resistant film with a low thermal capacity as the heat transfer member can be used. The temperature of the heating member is raised in a short time, and the rising of the temperature of the heating member or the fixing nip portion to a predetermined temperature can quickly be performed. No power is supplied to the apparatus (heating member) during standby, and the power consumption can be minimized. Therefore, as compared with the other image heating apparatus of the heat roller system or the like, power can be saved and wait time can be shortened (quick start property), so that the on-demand image heating apparatus can be constituted.
FIG. 10
is a schematic view showing a main part of one example of the image heating apparatus (heating/fixing apparatus) of the film heating system.
Specifically, the image heating apparatus has a heating member
11
(hereinafter referred to as the heater) fixed/supported on a stay holder (heater supporter)
12
, and an elastic pressure roller
20
held and pressed onto the heater
11
via a heat-resistant thin film
13
(hereinafter referred to as the fixing film) to form a fixing nip portion N with a predetermined nip width.
When electricity is supplied, the heater
11
is heated to a predetermined temperature, and the temperature is adjusted.
The fixing film
13
is a cylindrical member, an endless belt-like member, or a rolled web-like member having ends. The film is attached and slid onto the surface of the heater
11
in the fixing nip portion N, and conveyed/moved in a direction of arrow a.
When the heater
11
is heated to the predetermined temperature, the temperature is controlled, and the fixing film
13
is conveyed/moved in the direction of arrow a, a recording material P with an unfixed toner image t formed/borne thereon is introduced as a material to be heated between the fixing film
13
and the pressurizing roller
20
of the fixing nip portion N. Then, the recording material P is attached to the surface of the fixing film
13
, and held/conveyed with the fixing film
13
through the fixing nip portion N.
In the fixing nip portion N, the recording material P with the toner images t is heated by the heater
11
via the fixing film
13
so that the toner images t on the recording material P are heated/fixed.
The recording material portion passed through the fixing nip portion N is peeled off from the surface of the fixing film
13
and conveyed.
A ceramic heater is usually used in the heater
11
.
FIG. 11A
is a partially cut plan model view showing the front surface side (heating surface side) of the ceramic heater
11
, and
FIG. 11B
is a plan model view of the rear surface side (surface side opposite to the heating surface).
Specifically, for example, the front surface side (surface on the side facing the fixing film
13
) of a ceramic substrate
11
a
of alumina having electric insulation properties, good thermal conductivity, and a low thermal capacity is provided with a energizing heating resistance layer (heating member)
11
b
of Ag/Pd (silver palladium), Ta
2
N, and the like formed along the longitudinal direction of the substrate by screen printing or the like. Furthermore, the surface with the energizing heating resistance layer formed thereon is covered with a thin glass protective layer
11
c
. For the heater
11
, by supplying power via a power supplying electrode portion
11
d
, the energizing heating resistance layer
11
b
is heated so that the temperature of the entire heater is rapidly raised.
The temperature rise of the heater
11
is detected by temperature detecting means
14
disposed on the heater rear surface, and fed back to a energizing controller (not shown) via electric path patterns
11
e
, through holes
11
f
, and electrode portions
11
g
for output to a temperature controller.
The energizing controller controls the energizing of the energizing heating resistance layers
11
b
so that the heater temperature detected by the temperature detecting means
14
is maintained at a substantially constant predetermined temperature (fixing temperature). Specifically, the heater
11
is heated and controlled or adjusted to the predetermined fixing temperature.
The fixing film
13
is formed to be remarkably thin as 20 to 70 &mgr;m in order to efficiently give the heat of the heater
11
to the recording material P as the material to be heated in the fixing nip portion N. This fixing film
13
is constituted of three layers, that is, a film base layer, a primer layer, and a mold release layer, the film base layer is on the side of the heater
11
, and the mold release layer is on the side of the pressurizing roller
20
. The film base layer is formed of polyimide, polyamide-imide, PEEK, or the like which is higher in insulation property than the glass protective layer
11
c
of the heater
11
, and has a heat resistance and a high elasticity. Moreover, the mechanical strengths such as tear strength of the entire fixing film
13
are kept by the film base layer. The primer layer is formed of a thin layer which has a thickness of about 2 to 6 &mgr;m. The mold release layer is a toner offset preventive layer to the fixing film
13
, and is formed by coating fluoroplastics such as PFA, PTFE and FEP in a thickness of about 10 &mgr;m.
Moreover, the stay holder
12
is formed, for example, of a heat-resistant plastic member to hold the heater
11
, and
Kanari Kenji
Miyamoto Toshio
Suzumi Masahiko
Canon Kabushiki Kaisha
Lee Susan S. Y.
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