JPH0582304A - Ceramic heater unit - Google Patents

Abstract

PURPOSE:To obtain a ceramic heater unit having a low thermal capacity by forming a pectinated electrode opposed to one surface of a ceramic plate made of a semiconductor material having positive resistance temperature characteristics. CONSTITUTION:Al base is screen printed on one side surface of a platelike PTC sintered material made of barium titanate series semiconductor porcelain, and baked to form an opposed pectinated electrode 4. Electrodes are so formed on both side surfaces of the material as to connect to the electrode 4 thereby to form a PTC element 1. Then, input/output terminals 5 are adhered and longitudinally output from ends. Further, the lower surface of the PTC element and the terminals 5 are coated with silicon compound 3, and the element 1 is supported to a supporting base 2 through an insulation sheet 6 to be adhesively supported. Thus, since only the surface of the electrode 4 becomes a heat transfer surface and the other part becomes a heat insulator, a ceramic heater unit having excellent temperature rising characteristic and small power consumption can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power saving type ceramic heater unit which is suitable as a heater for fixing toner in a copying machine or a facsimile machine and has excellent temperature rising characteristics.

[0002]

2. Description of the Related Art Conventionally, a halogen lamp or a heating wire has been used as the heater for fixing the toner. However, it takes time for the halogen lamp and the heating wire to reach a predetermined temperature, and it is necessary to always turn on the heater power source for practical use, and a temperature control means is required, and a partial It was difficult to cope with temperature changes.

In recent years, it has been proposed to use a ceramic (hereinafter abbreviated as PTC) element having a positive resistance temperature characteristic as a heat roll. The characteristics of the PTC element are suitable for solving the above problems. However, when the PTC element was used as a heat roll, there was a problem in terms of dimensional accuracy of the sintered body, and mechanical workability was poor. On the other hand, it has been proposed that a thick film in which PTC powder is dispersed in a resin is provided on the roll.
The resistance temperature characteristic is inferior, and heat is taken by the base material such as resin, and as a result, the temperature rising characteristic has not been significantly improved.

To solve the above-mentioned problems, Japanese Patent Laid-Open No. 2-158782 discloses an image forming apparatus in which a linear heating section and a PTC heating element are integrally formed as a heating element. When a toner image is heat-fixed by using a heating body as disclosed in FIG. 6 of the publication, heat transfer is improved and pressure contact width (nip width) is improved as compared with the conventional product.
By using the narrow linear heating element, the heat capacity is lowered and the self-temperature control type heating element with good response is obtained, but the fixing speed is about 50 mm / sec at most.

However, there is a market demand for an image forming apparatus that operates instantaneously, consumes less power, and is compatible with high speeds.
Even in the image forming apparatus disclosed in this publication, it is difficult to say that these characteristics are sufficient. In the high-speed machine as described above, when the pressure contact width is narrowed, the amount of heat received from the heating body per unit time is small, so that the toner temperature does not rise. Therefore, in order to improve these characteristics, in the case of FIG. 6 of the publication, it is necessary to widen the pressure contact width, thin the heating plate, and further reduce the heat capacity of the PTC heating element. For this purpose, it is conceivable to reduce the heat capacity by reducing the thickness of the PTC element to 1 mm or less. However, in this case, it is difficult to process the PTC ceramic and there is a risk of cracking, resulting in poor assembly workability. Moreover, it is difficult and practical to form an electrode on a thin side surface (thickness portion) and take it out. Furthermore, if the electrodes of the PTC element are counter electrodes as shown in FIG. 4 of the publication, the electrodes can be easily formed and taken out even if the thickness is reduced, but heat radiation on one side and heat insulation on the other side are required. A temperature distribution occurs in the PTC element, the high temperature part and the low temperature part are in series, and are blocked by the high resistance of the high temperature part,
There was a problem that power could not be obtained. Particularly in a high-speed machine, since the amount of heat from the heating element per unit time to the toner is small, it is necessary to increase the surface area of the heating element, but in that case, the volume of the heating element increases and the heat capacity increases, resulting in poor responsiveness. It is necessary to resolve the contradiction.

[0006]

SUMMARY OF THE INVENTION The present invention provides a ceramic heater unit which can solve the above problems.

[0007]

According to the present invention, a comb-teeth-shaped electrode is formed on one surface of a ceramic plate made of a semiconductor material having a positive resistance temperature characteristic, and the comb-teeth-shaped electrode is formed only on the surface. The present invention relates to a ceramic heater unit having a low heat capacity, which is used as a heating source, has a comb-teeth-shaped electrode portion surface as a heat transfer surface, and uses a portion other than the comb-teeth-shaped electrode portion surface of the ceramic plate as a heat insulating material and is integrated with a support base. ..

The present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of a ceramic heater unit of the present invention,
FIG. 2 is a sectional view thereof. In the figure, 1 is a PTC element, 2 is a support base made of metal, 3 is an insulating adhesive such as silicon resin, 4 is a comb-shaped electrode, 5 is an input / output terminal, and 6 is an insulating sheet. A plurality of PTC elements 1 are connected and supported by a support base 2. It is also possible to use a long, integral body as the PTC element. Although not shown, a comb-shaped electrode is formed on the surface of the PTC element 1 in FIG. The surface of the PTC element 1 is usually coated with heat-resistant glass or the like to improve smoothness, but it is omitted in FIGS. 1 and 2. The support base 2 is not particularly limited, but metal or heat resistant resin is preferably used. FIG. 3 is a perspective view of the plate-shaped PTC element 1 which constitutes the present invention, and the comb-shaped electrodes 4 facing each other are formed on one surface of the PTC element 1.

The ceramic heater unit having the structure of the present invention has a very small heat capacity because heat is mainly generated on the surface of the PTC element, and the temperature can be instantly raised to a desired temperature. Moreover, it has excellent temperature stability because it is well suited to thermal loads, and power can be saved. Also P
Since the TC element has a heat conductivity several orders of magnitude smaller than that of metal, the portion other than the heat generating portion on the surface provided with the comb-shaped electrodes acts as a heat insulating material. Furthermore, it can also serve as an insulator. In a high-speed machine, the amount of heat received from the heating element per unit time is reduced, so it is necessary to widen the pressure contact width for heating the toner to reach the toner fixing temperature, but even in this case, if the heat capacity is not so large In addition, it can sufficiently support high-speed fixing and consumes less power.

[0010]

EXAMPLES The present invention will be described more concretely with reference to the following examples. A plate-like PTC sintered body made of barium titanate-based semiconductor porcelain is screen-printed with A1 paste on one surface in a pattern capable of obtaining predetermined characteristics and baked to face the comb-teeth-shaped electrodes 4 as shown in FIG. , And electrodes for electrically connecting to the comb-teeth-shaped electrodes were formed on both side surfaces of the sintered body by roller transfer to prepare a PTC element. The input / output terminal 5 is attached thereto and taken out from the end in the longitudinal direction. Silicon compound 3 was applied to the lower surface of this PTC element and the surface of the input / output terminal, and a plurality of PTC elements were interposed and connected to an insulating sheet 6 on a support base 2 made of stainless steel to be adhesively supported. The input / output terminal 5 is provided with a projection, and the projection electrically contacts the electrode.

[0011]

As described above, according to the present invention, it is suitable for a heater for a toner image heating and fixing device, which has excellent temperature rising characteristics, does not require a power supply control means, can perform high-speed fixing, and consumes less power. A ceramic heater unit that can be used is obtained.

[Brief description of drawings]

FIG. 1 is an external perspective view of a ceramic heater unit of the present invention.

FIG. 2 is a vertical sectional view of FIG.

FIG. 3 is a perspective view of a plate-shaped PTC element 1 that constitutes the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PTC element 2 Support stand 3 Adhesive 4 Comb-shaped electrode 5 Input / output terminal 6 Insulation sheet

Claims (1)

[Claims] 1. A comb-teeth-shaped electrode in which comb-teeth-shaped electrodes facing each other are formed on one surface of a ceramic plate made of a semiconductor material having a positive resistance temperature characteristic, and only the comb-teeth-shaped electrode formation surface is used as a heating source. A low-heat-capacity ceramic heater unit that is integrated with a support by using the surface of the ceramic plate as a heat transfer surface and using a portion other than the comb-teeth-shaped electrode surface of the ceramic plate as a heat insulating material.