Electrophotography – Image formation – Fixing
Reexamination Certificate
2000-03-13
2001-08-28
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Fixing
C219S216000
Reexamination Certificate
active
06282398
ABSTRACT:
FIELD OF TECHNOLOGY
The present invention relates to a fixing apparatus which is used for fusing and pressing an unfixed toner carried on a recording medium to fix the toner to the recording medium in, for example, an electric image forming apparatus.
TECHNICAL BACKGROUND
Recently, a fixing apparatus for use in an electric image forming apparatus has been developed which is illustrated in
FIG. 10
of the accompanying drawings as a technology disclosed in Japanese Patent Application Laid-Open Publication HEI 6-318001, for example, not employing a conventional heating roller type fixing system. As shown in
FIG. 10
, the fixing apparatus is provided with a fixing roller R
1
, a heating roller R
3
, and an endless fixing belt B trained around the rollers R
1
and R
3
, and a pressing roller R
2
disposed below and pressed against the fixing roller R
1
with the fixing belt B interposed therebetween. In the fixing apparatus disclosed in the Laid-Open Publication, it is combined with a preheat of a recording medium D.
Since the recording medium D is preheated, the nipping region may be set to a relatively low temperature. The fixing belt B is of such a small heat capacity that when the recording medium D passes through the nipping region, the temperature of the fixing belt B is quickly lowered to increase the coherent ability of the toner which is separated from the fixing belt B at the outlet of the nipping region, for thereby allowing the toner to be easily separated from the fixing belt B. Even if the fixing belt B is free of oil or coated with a small amount of oil, a clear fixed toner image can be produced on the recording medium D without offsets. The fixing apparatus shown in
FIG. 10
is thus capable of solving the problems of toner separation and oil coating, which have not been eliminated by other fixing apparatus using only a heating roller.
Here, the conventional fixing apparatus shown in
FIG. 10
will be described in more detail. The fixing apparatus is provided with a fixing roller R
1
, a pressing roller R
2
, a heating and tensioning roller R
3
, and an endless fixing belt B trained around the rollers R
1
and R
3
. There is provided an oil coating roller R
4
disposed above the upper run of the fixing belt B, and a guide plate G for supporting the recording medium D disposed below a lower run of the fixing belt B with a predetermined gap therebetween. The gap between the guide plate B and the lower run of the fixing belt B serves as a preheating passage P for preheating the recording medium D.
There is provided a heater H which is housed in the heating and tensioning roller R
3
. Further, additional heater may be housed in fixing roller R
1
and/or pressing roller R
2
. There is also provided a thermistor T which contacts a non-passage portion of the fixing belt B in order to control the temperature of the fixing belt B.
However, in the conventional belt-type fixing apparatus having above mentioned construction, it is preferable to rotate a driving roller for endlessly traveling the fixing belt B, which is rotatable about a stationary rotating axis. From the present point, it is constructed that the fixing roller R
1
to which the pressing roller R
2
is pressed is set to be rotatably driven. When it is limited that the fixing roller R
1
is only set as the driving roller for endlessly traveling the fixing belt B, this causes certain restrictions of design for, for example, a power transmission path or route of the driving force, a location of a driving source, being thereby failing to ensure the freedom of the design. Therefore, it has been desired to obviate this drawback.
Accordingly, it is a primary object of the present invention to provide a fixing apparatus which is capable of ensuring the freedom of the design for a driving mechanism which is provided for endlessly traveling the fixing belt.
DISCLOSURE OF THE INVENTION
In order to solve the aforementioned problems and accomplish the above object, an inventive fixing apparatus comprises a fixing roller, a pressing roller being rollingly contacted the fixing roller, a heating roller positioned upstream side of said fixing roller with respect to a feeding direction in which a sheet carrying an unfixed toner image thereon is fed, a heating source being remote from said fixing roller, a fixing belt trained around said heating roller and said fixing roller for transferring heat from said heat source to preheat the unfixed toner image on said sheet before said sheet passes through a rolling contact region defined between said fixing roller and pressing roller, and driving means for rotatably driving said pressing roller to endlessly travel the fixing belt upon the rotation of said pressing roller.
In the inventive fixing apparatus, said pressing roller is movably attached along a direction crossing to said feeding direction at least.
In the inventive fixing apparatus, urging means for urging the pressing roller toward the fixing roller so as to contact thereto is further provided.
In the inventive fixing apparatus, said driving means includes a driven gear coaxially fixed to said pressing roller, and a driving gear intermeshed with said driven gear, said driven gear is constructed so as to revolve around the driving gear with maintaining the intermeshing condition between the driving gear and driven gear.
In the inventive fixing apparatus, said driving gear is rotatably supported about a predetermined stationary axis, and said driven gear is rotatably supported on the distal end of a swing arm, the proximal end of said swing arm being rotatably supported about said predetermined stationary axis.
In the inventive fixing apparatus, said fixing belt includes an endless belt base of a heat transmission material and a separating layer coated on an outer circumferential surface of the endless belt base.
In the inventive fixing apparatus, said endless belt base is made of metal belt.
In the inventive fixing apparatus, said endless belt base is made of electro-formed nickel.
In the inventive fixing apparatus, said endless belt base is made of synthetic resin.
In the inventive fixing apparatus, said synthetic resin has an electro-conductivity.
In the inventive fixing apparatus, said endless belt base is made of polyimide.
In the inventive fixing apparatus, said poly-imide has an electro-conductivity.
In the inventive fixing apparatus, said heating source is housed in said heating roller, and said fixing belt is heated by the heating roller which is heated by said heating source.
REFERENCES:
patent: 5289248 (1994-02-01), Kurokawa
patent: 5666623 (1997-09-01), Yamada et al.
patent: 5778294 (1998-07-01), Hiraoka et al.
patent: 6055390 (2000-04-01), Kurotaka et al.
patent: 3-12683 (1991-01-01), None
patent: 5-127551 (1993-05-01), None
patent: 8-262892 (1996-10-01), None
patent: 8-339133 (1996-12-01), None
Armstrong Westerman Hattori McLeland & Naughton LLP
Chen Sophia S.
Nitto Kogyo Co. Ltd.
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