Electrophotography – Image formation – Fixing
Reexamination Certificate
2000-04-26
2001-08-07
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Fixing
C219S216000, C399S067000, C399S333000
Reexamination Certificate
active
06272308
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a roller-shaped heater which is composed of resistance heating elements in a sheet-like form and is arranged in close contact with a roller (e.g., the inner peripheral surface of the roller) and a fusing unit using the roller-shaped heater.
(2) Description of the Prior Art
In image forming apparatus using electrophotography, a photoreceptor is charged uniformly, then is illuminated by an exposure light source such as a laser beam etc., in accordance with image information so as to form a static latent image on the photoreceptor. Next, the static latent image on the photoreceptor is developed with a developer into a visual image. The developed image is then transferred to a recording medium such as recording paper etc., through a transfer station. Then the image on the recording paper is fused and fused by a fusing unit.
The fusing unit includes, for example, a pair of rollers opposing to each other, i.e., a heat roller and a pressure roller. The toner image on the recording paper is fed and pressed with heat between the two rollers onto the recording paper. The heat roller is composed of, for example, a cylindrical metallic core made up of aluminum etc., and a separation layer of a fluororesin coated on the outer peripheral surface of the metal core. The metal core generally incorporates a halogen lamp as a heater. When electric power is supplied to this halogen lamp, it generates heat and the heat makes the entire heat roller hot.
However, because there is an air layer between the halogen lamp and the metal core, the conventional heat roller using a halogen lamp has suffered a drawback in that the efficiency of heat transport to the heat roller is poor and hence the heat roller takes time until it is heated to a required temperature level.
In order to solve this problem, there is a proposed method in which a resistance heater which itself heats is arranged on the inner peripheral surface of a heat roller so that the heat roller will be heated directly with no air layer in between. A heat roller of this type is disclosed in Japanese Patent Application Laid-Open Hei 8 No.220915. In Japanese Patent Application Laid-Open Hei 8 No.220915, a resistance heating element having a predetermined pattern is formed on an insulation sheet. This is referred to as a heat generator (heat generating sheet). The heat generator (heat generating sheet) is inserted into the heat roller interior with the resistance heating element oriented toward the central axis of the heat roller. The resistance heating element has a pair of electric power supply strips disposed at both ends of the roller body and extending in the peripheral direction of the roller body and the power supply portions electrically connected to the resistance heating element is bonded, thus constituting the heat generator (heat generating sheet). A pair of electrodes are placed in frictional contact with these electric power supply portions so as to supply electric power to the resistance heating element via the power supply portions. Thus, the resistance heating element is supplied with power to heat itself and hence heat the entire roller.
In the case of using a resistance heating element of the above type, setting of a heat generator (heat generating sheet) inside the heat roller becomes difficult as the roller diameter becomes smaller. Further, in this method, when the resistance heating element on the heat generator (heat generating sheet) is supplied with electric power, the entire sheet is heated. Since heating only in the nip area is effective enough to fuse the recording medium such as recording paper etc., heating the entire heat roller is wasteful and consumes more electric power compared to a which the roller is heated only around the nip area.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the above problem and it is therefore an object of the present invention to provide a roller-shaped heater of which the heat generator can be readily set in close contact with the roller interior even the roller is small in diameter as well as providing a fusing unit using such a roller-shaped heater.
It is another object of the present invention to provide a roller-shaped heater which can be heated partially by supplying electric power to a necessary portion only as well as providing a fusing unit using such a roller-shaped heater.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a roller-shaped heater includes:
a cylindrically formed roller member; and
a heat generator composed of a heat-resisting insulation material and resistance heating elements formed on the heat-resisting insulation material, and is characterized in that the heat generator is composed of a multiple number of separated portions extending in the axial direction of the cylinder of the roller member and each portion has the resistance heating element.
In accordance with the second aspect of the present invention, a roller-shaped heater includes:
a cylindrically formed roller member; and
a heat generator composed of a heat-resisting insulation material and resistance heating elements formed on the heat-resisting insulation material, and is characterized in that the heat generator is formed with a multiple number of resistance heating elements and the multiple number of resistance heating elements are arranged in parallel with each other in the axial direction of the cylinder of the roller member.
In accordance with the third aspect of the present invention, the roller-shaped heater having the above first feature is characterized in that power receiving portions that receive electric power for the resistance heating elements formed in the heat generator are formed at one end of the heat generator.
In accordance with the fourth aspect of the present invention, the roller-shaped heater having the above second feature is characterized in that power receiving portions that receive electric power for the resistance heating elements formed in the heat generator are formed at one end of the heat generator.
In accordance with the fifth aspect of the present invention, a fusing unit includes:
a roller-shaped heater comprising: a cylindrically formed roller member; and a heat generator composed of a heat-resisting insulation material and resistance heating elements formed on the heat-resisting insulation material wherein the heat generator is composed of a multiple number of separated portions extending in the axial direction of the cylinder of the roller member and each portion has the resistance heating element; and
a pressing member disposed abutting against the roller-shaped heater, and is characterized in that fusing is performed by conveying a recording medium having an unfused toner image supported thereon through the nip between the roller-shaped heater and the pressing member.
In accordance with the sixth aspect of the present invention, a fusing unit includes:
a roller-shaped heater comprising: a cylindrically formed roller member; and a heat generator composed of a heat-resisting insulation material and resistance heating elements formed on the heat-resisting insulation material wherein the heat generator is provided with a multiple number of resistance heating elements extending in parallel with each other in the axial direction of the cylinder of the roller member; and
a pressing member disposed abutting against the roller-shaped heater, and is characterized in that fusing is performed by conveying a recording medium having an unfused toner image supported thereon through the nip between the roller-shaped heater and the pressing member.
In accordance with the seventh aspect of the present invention, the fusing unit having the above fifth feature is characterized in that the roller-shaped heater has a power receiving portion at one end of the heat generator through which electric current is supplied to the resistance heating elements formed in th
Kagawa Toshiaki
Maeda Tomohiro
Chen Sophia S.
Renner Otto Boisselle & Sklar
Sharp Kabushiki Kaisha
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