Electric heating – Heating devices – Combined with diverse-type art device
Reexamination Certificate
1996-06-06
2001-06-19
Heinrich, Samuel M. (Department: 1725)
Electric heating
Heating devices
Combined with diverse-type art device
C219S469000, C219S470000, C219S471000, C355S117000
Reexamination Certificate
active
06248978
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a heater comprising a substrate having excellent thermal conductivity, an exothermic resistive layer formed on this thermally conductive substrate, and a temperature sensing element, and also, to a fixing apparatus employing this heater.
In the past, a fixing apparatus of a heat roller type has been widely used as the image fixing thermal apparatus. This type of fixing apparatus comprises a heating roller controlled to maintain a predetermined temperature and a pressure roller having an elastic layer and being pressed on the heating roller, wherein a sheet of recording material on which an unfixed toner image has been formed is heated while it is passed between the rollers.
However, this type of fixing apparatus using the heat roller requires a large amount of electric power because of its large thermal capacity; therefore, it suffers from a long wait time. In other words, it takes a long time for the apparatus to reach a predetermined temperature after the start-up.
As a means for solving such a problem, this applicant has proposed a thermal fixing apparatus comprising a thermal heater of a small heat capacity and a piece of thin film, which has been disclosed in U.S. Pat. Nos. 5,149,941 and 444,802.
This heater comprises a resistor which generates heat as the power is supplied, and a ceramic substrate having excellent thermal conductivity, on which this resistor is formed. The power supplied to the resistor is controlled to keep constant the output of the temperature sensing element which senses the temperature of the substrate.
However, since this heater has a small heat capacity, increase in the heater temperature is fast, which amplifies the temperature ripple if the response time of the temperature sensing element is long.
Further, if the contact is poor between the temperature sensing element and the substrate, not only can a normal temperature control not be executed, but also, the temperature sometimes rises excessively.
In the fixing apparatus comprising a heater with a slow response, or a heater suffering from a poor connection, such as the above, non-uniform fixing or non-uniform glossiness occurs.
SUMMARY OF THE INVENTION
Accordingly, a principal object of the present invention is to provide a heater provided with a temperature sensing element with fast response.
Another object of the present invention is to provide a heater on which the temperature sensing element can be securely attached on the substrate.
According to an aspect of the present invention, the heater according to the present invention comprises: a substrate having excellent thermal conductivity, an exothermic resistive layer which generates heat as the power is supplied, an output electrode provided on the substrate, and a temperature sensing element, the output portions of which are placed on top of the electrodes.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.
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patent: 4350870 (1982-09-01), Nakayama et al.
patent: 4406785 (1983-09-01), Siefer
patent: 4888463 (1989-12-01), Middlebrook
patent: 4999136 (1991-03-01), Su et al.
patent: 5083168 (1992-01-01), Kusaka et al.
patent: 5149941 (1992-09-01), Hirabayashi et al.
patent: 5253024 (1993-10-01), Okuda et al.
patent: 5262834 (1993-11-01), Kusaka et al.
patent: 5285054 (1994-02-01), Barsky
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Heinrich Samuel M.
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