Electrophotography – Image formation – Fixing
Reexamination Certificate
2002-07-24
2004-06-08
Brase, Sandra L. (Department: 2852)
Electrophotography
Image formation
Fixing
C399S333000
Reexamination Certificate
active
06748192
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image heating apparatus suitable if used as a fixing device in an image forming apparatus such as a copying machine or a printer using a recording method such as an electrophotographic method or an electrostatic recording method.
2. Description of Related Art
Heretofore, in a fixing apparatus provided in an image forming apparatus adopting an electrophotographic method, an electrostatic recording method or the like, use has been widely made of a so-called heat fixing apparatus for causing a recording material bearing an unfixed toner image thereon to pass through a nip portion formed between a fixing roller and a pressure roller rotated while being brought into pressure contact with each other to thereby fix the toner image as a permanent image on a recording material.
An example of a conventional heat fixing apparatus is shown in
FIG. 9
of the accompanying drawings. The reference numeral
40
designates a fixing roller provided with heating means, and a halogen lamp
41
is disposed in a hollow mandrel
42
of aluminum having a thickness of the order of 1 mm to 4 mm so as to satisfy mechanical strength, and heating sufficient to fuse a toner on a recording material P from the interior of the hollow mandrel
42
is effected by the supply of electric power from a power source, not shown.
A substance generally having an absorption rate of 90% or greater for black (e.g. okitsumo or the like) is generally applied to the interior of the hollow mandrel
42
to make the absorption of radiant heat be the halogen lamp
41
good, and the inner surface of the hollow mandrel is made rough with a view to make the absorption rate high, and the roughness thereof Rz is 10 &mgr;m or greater.
Also, in order that the toner on the recording material P may be fixed on the recording material P without being offset on the fixing roller, a mold releasable layer
43
of polytetrafluoroethylene (PTFE), parfluoroalchorytetrafluoroethylene copolymer (PFA) or the like exhibiting excellent performance in mold releasability is formed on the outer side of the hollow mandrel
42
.
The mold releasable layer
43
is formed in a tube shape or formed by electrostatic spray, dipping application or the like on the hollow mandrel
42
having its outer surface subjected to blast process, etching process or the like and having its surface roughness Rz made into 5 &mgr;m or greater, and obtains an adhesive force relative to the hollow mandrel
42
.
Also, in some cases, in order to prevent offset caused by the surface of the fixing roller
40
being charged up by the conveyance of the recording material P, an electrically conductive material such as carbon black is mixed with the mold releasable layer
43
.
Further, the hollow mandrel
42
of the fixing roller
40
is electrically earth-connected or grounded through a diode element, and has a bias applied thereto by bias applying means, not shown, to thereby prevent the surface of the fixing roller from being charged up and producing an offset image.
Also, a thermistor
44
is in contact with the surface of the fixing roller
40
, and detects the temperature of the surface of the fixing roller to thereby on/off-control the supply of electric power to the halogen lamp
41
so as to heat the toner image on the recording material P at a moderate temperature.
On the other hand, the reference numeral
50
denotes a pressure roller brought into pressure contact with the fixing roller
40
in the lengthwisely opposite end portions thereof by pressure springs, not shown, to thereby nip and convey the recording material P. The pressure roller
50
comprises a mandrel
51
having applied to the outside thereof an elastic layer formed by molding silicon rubber or a sponge elastic layer
52
formed by foaming silicon rubber and further having applied to the outer layer thereof in a tube shape or as a coating a mold releasable layer
53
of PTFE, PFA, FEP or the like similar to that of the fixing roller
40
.
Consequently, a fixing nip portion N of a sufficient nip width can be formed between the two rollers
40
and
50
by the elasticity of the pressure roller
50
. The toner image on the recording material P nipped and conveyed by this fixing nip portion N can be fixed by the heating from the fixing roller
40
.
Also, particularly a method whereby electric power is not supplied to a heat fixing apparatus during standby, and electric power consumption is minimized, and more particularly an example of a heat fixing method by a film heating process for fixing a toner image on a recording material through thin film between a heater portion and a pressure roller is proposed in Japanese Patent Application Laid-Open No. 63-313182, Japanese Patent Application Laid-Open No. 2-157878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980, etc.
FIG. 10
of the accompanying drawings schematically shows the construction of an example of a fixing apparatus of the film heating type. In
FIG. 10
, the fixing apparatus has a heating member (a heating body, hereinafter referred to as the heater)
61
fixedly supported by a stay holder (supporting member)
62
, and an elastic pressure roller
50
brought into pressure contact with the heater
61
by pressure means with a fixing nip portion N of a predetermined nip width formed with heat-resistant thin film (hereinafter referred to as the fixing film)
63
interposed therebetween.
The heater
61
is heated and attempered to a predetermined temperature by electrical energization.
The fixing film
63
is a cylindrical or endless belt-shaped or rolled web-shaped member moved in the direction of arrow by the rotational force of driving means, not shown, or the pressure roller
50
while being in close contact with and sliding relative to the surface of the heater
61
in the fixing nip portion N.
When with the heater
61
heated and attempered to the predetermined temperature and the fixing film
63
moved in the direction of arrow, a recording material P bearing thereon an unfixed toner image as a material to be heated is introduced between the fixing film
63
and the pressure roller
50
in the fixing nip portion N, the recording material P is nipped and conveyed through the fixing nip portion N with the fixing film
63
while being in close contact with the surface of the fixing film
63
. In this fixing nip portion N, the recording material and the toner image thereon are heated by the heater
61
through the fixing film
63
, and the toner image on the recording material P is heat-fixed. That portion of the recording material which has passed through the fixing nip portion N is stripped from the surface of the fixing film
63
and is conveyed.
A ceramic heater is generally used as the heater
61
as a heating member. It is formed, for example, by forming an electrically energizing heat generating resistance layer of silver palladium (Ag/Pd), Ta
2
N or the like on the surface of a ceramic substrate of electrical insulativeness, good heat conductivity and low heat capacity such as alumina (that surface facing the fixing film
63
) along the lengthwise direction of the substrate (a direction perpendicular to the plane of the drawing sheet of
FIG. 10
) by screen printing or the like, and covering the heat generating resistance layer forming surface with a thin glass protective layer. This ceramic heater
61
is such that the electrically energizing heat generating resistance layer thereof is electrically energized to thereby generate heat and the entire heater including the ceramic substrate and the glass protective layer rapidly rises in temperature. This temperature rise of the heater
61
is detected by temperature detecting means
64
installed on the back of the heater and is fed back to an electrical energization controlling portion, not shown. The electrical energization controlling portion controls the electrical energization of the electrical energizing heat generating resistance layer so that the temperature
Hashiguchi Shinji
Izawa Satoru
Kanamori Akihito
Kataoka Hiroshi
Uekawa Eiji
Brase Sandra L.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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