JPH08273815A - Self-controlled ceramic heater - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable rapid temperature rise in a ceramic heater, improve thermal shock resistance, and prevent melting of a heating element by a self-control function to improve durability. It is a thing. A heating element (4) made of conductive powder having a relatively small temperature coefficient of resistance and a control resistor (5 made of conductive powder having a relatively large temperature coefficient of resistance) are provided on a ceramic sheet (12) of silicon nitride. After printing the heat pattern (3 ') composed of (1), the ceramic sheets (12) of the same shape and the same material are laminated and fired to form the ceramic heater (2). Enables rapid temperature rise of the built-in ceramic heater body,
Furthermore, the electrical resistance of the control resistor, which increases with this temperature rise, reduces the heating current that is applied to the heating element to prevent the heating element from melting and the ceramic heater body contains silicon nitride as the main component, so that heat resistance is improved. Impact resistance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a ceramic heater which is mainly used for ignition of fuel at low temperature starting of a diesel engine, ignition of combustion equipment and activation of oxygen sensor.

[0002]

2. Description of the Related Art Conventionally, silicon nitride (Si ₃ N ₃₎ has been used as a ceramic heater mainly used for ignition of fuel and ignition of combustion equipment at low temperature starting of a diesel engine.
₄ ) A paste heat pattern is printed on a ceramic sheet containing ₄ ) as a main component with a paste of a conductive metal powder such as tungsten (W) or molybdenum (Mo) or a conductive ceramic powder such as tungsten carbide (WC). After being appropriately formed into a plate shape, a cylindrical shape, or a winding shape, it is fired to form a ceramic heater, or a ceramic sheet containing aluminum oxide (Al ₂ O ₃ ) as a main component has tungsten (W) or Is molybdenum (Mo)
While printing a heat pattern with metal powder such as
It is generally known that a ceramic heater, especially for an oxygen sensor, is formed by firing after forming it into a rod shape.

[0003]

However, in the above-mentioned conventional one, in a ceramic heater mainly used for ignition of fuel and activation of oxygen sensor at low temperature starting of a diesel engine, silicon nitride (Si ₃ N ₄ ) Or aluminum oxide (Al ₂ O ₃ ) on a ceramic sheet as a main component, by using conductive metal powder such as tungsten (W) or molybdenum (Mo) or conductive ceramic powder such as tungsten carbide (WC). When a ceramic heater is formed by printing a heat pattern and appropriately forming it into a plate shape, a cylinder shape, or a winding shape, and then firing it, silicon nitride (Si ₃ N
₄ ) or a heat pattern printed on a ceramic sheet containing aluminum oxide (Al ₂ O ₃ ) as a main component,
Since only the heating element made of conductive metal powder such as tungsten (W) or molybdenum (Mo) or conductive ceramic powder such as tungsten carbide (WC) is used as the heating element, the heater temperature for continuous energization at a constant voltage Since the ceramic heater does not have a control function, that is, a self-controlling function, the saturation temperature of the ceramic heater is a conductive metal powder such as tungsten (W), molybdenum (Mo), or tungsten carbide (WC) that constitutes a heating element. It is difficult to perform rapid temperature rising because only the temperature rising characteristics that limit the heat resistant temperature of the conductive ceramic powder are obtained.

Further, conductive metal powder such as tungsten (W), molybdenum (Mo), or tungsten carbide (W) is used.
C) such as a ceramic sheet for printing a heat pattern having a heating element made of a conductive ceramic powder containing aluminum oxide (Al ₂ O ₃ ) as a main component, aluminum oxide (Al 2 ₂ O ₃ ) itself can show only low performance in thermal shock resistance, so that it rapidly rises against a heat pattern printed on a ceramic sheet containing aluminum oxide (Al ₂ O ₃ ) as a main component. When heated, the ceramic sheet may be damaged due to cracks due to its low thermal shock resistance.

Therefore, the present invention is to further improve the performance as compared with the above-mentioned conventional ones, is inexpensive, is capable of rapid temperature rise, and is excellent in thermal shock resistance having a self-controlling function of temperature. It is intended to provide a ceramic heater.

[0006]

To this end, a ceramic sheet containing silicon nitride (Si ₃ N ₄ ) as a main component is integrated with the electrode lead-out portion, and the tip end side is made of a conductive material having a relatively small temperature resistance coefficient. A heating pattern, in which a heating element made of powder and a control resistor made of conductive powder having a relatively large temperature resistance coefficient are connected in series at the rear end side, is printed, and at the same time, silicon nitride (Si ₃ N ₃₎ for printing this heating pattern is printed. ₄ ) A ceramic sheet containing silicon nitride as a main component is integrally laminated with a ceramic sheet containing silicon nitride as a main component, which does not have a heat pattern printed thereon so as to cover the heat pattern.
It is fired to form a ceramic heater.

Further, as a conductive powder having a relatively small temperature resistance coefficient used for a heating element constituting a heat pattern, the resistance temperature coefficient from room temperature to 1000 ° C. is 3 times or less, preferably 2 times or less. Tungsten carbide (W
C), tantalum nitride (TaN), tantalum carbide (Ta)
C), a paste composed of powder of molybdenum trisilicide (Mo ₅ Si ₃ ) or rhenium-tungsten alloy, or a conductive powder having a relatively large temperature resistance coefficient used for a control resistor forming a heat pattern, , From room temperature to 1
A paste powder made of powder of molybdenum disilicide (MoSi ₂ ), tungsten (W), molybdenum (Mo), or the like, which has a resistance temperature coefficient of 4 times or more up to 000 ° C., is used.

[0008]

With the above structure, silicon nitride (Si ₃ N
₄ ) A ceramic sheet mainly composed of a heating element made of conductive powder having a relatively small temperature resistance coefficient and a control resistor made of conductive powder having a relatively large temperature resistance coefficient, integrated with the electrode extraction part. The heat pattern that connects the bodies in series enables rapid temperature rise, and increases the resistance with the temperature rise of the control resistor that is connected in series to the heating element. The heating current to be applied is reduced, and the fusing of the heating element can be prevented.

Further, since the ceramic sheet on which the heat pattern is printed is a ceramic sheet containing silicon nitride having a high thermal shock resistance as a main component, the temperature is rapidly raised.
Even if a large thermal stress is applied to the ceramic sheet itself, the ceramic heater itself can be prevented from being damaged and the durability can be improved.

[0010]

The present invention will be further described with reference to the embodiments shown in the drawings. (1) is a plate-shaped self-control type ceramic heater which is an embodiment of the present invention. The plate-shaped self-control type ceramic heater (1) has a heating element (4) and a control resistor (5) inside. ), A ceramic heater body (2) containing silicon nitride (Si ₃ N ₄ ) as a main component, and a heating element (4) incorporated in the ceramic heater body (2). Electricity is applied to the positive and negative electrode lead-out portions (6) (7) derived from the surface of the self-controlled ceramic heater body (2) by the heat pattern (3) composed of the control resistor (5). It is composed of electrode plates (8) and (9) which are connected to the lead wires (10) and (11) in order to achieve electrical continuity.

Then, with respect to the ceramic sheet (12) containing silicon nitride (Si ₃ N ₄ ) as a main component, the conductive powder having a relatively small temperature resistance coefficient is integrally formed with the electrode lead-out portions (6) and (7). A heat pattern (3 ') in which a heat generating element (4) made of and a control resistor (5) made of conductive powder having a relatively large temperature resistance coefficient is connected in series is printed, and the heat pattern (3') is also printed. On the ceramic sheet (12) containing silicon nitride as a main component for printing, a ceramic sheet (13) containing silicon nitride as a main component of the same shape and the same material as the above heat pattern is integrally laminated. It is formed by press molding and firing (hot pressing). Here, the conductive powder having a relatively small temperature resistance coefficient used for the heating element (4) constituting the heat pattern (3) has a resistance temperature coefficient from room temperature to 1000 ° C. of 3 times or less, preferably 2 times. Twice or less tungsten carbide (WC), tantalum nitride (TaN), tantalum carbide (T
aC), molybdenum trisilicide (Mo ₅ Si ₃ ) or rhenium-tungsten alloy powder paste, or the temperature resistance coefficient of the control resistor (5) that constitutes the heat pattern (3). For relatively large conductive metal powder, use a paste of powder of molybdenum disilicide (MoSi ₂ ), tungsten (W), molybdenum (Mo), etc. that has a resistance temperature coefficient of 4 times or more from room temperature to 1000 ° C. It will be done. In forming the ceramic sheet (12) for printing the heat pattern (3) and the ceramic sheet (13) integrally laminated on the ceramic sheet (12), a plate-like shape is used in the embodiment of the present invention. However, if necessary, the press-molded body laminated according to the purpose or place of use of the ceramic heater may be molded into a rod shape or a winding shape and then fired.

Since the plate-shaped self-regulating ceramic heater (1) according to the embodiment of the present invention has the above-mentioned structure, the electrode plate (8) which is actually integrated with the lead wires (10) and (11). A self-regulating type that is integrated with the electrode lead-out portions (6) and (7) through positive and negative electrode lead-out portions (6) and (7) arranged at the end of the heat pattern (3) via (9). When electricity is applied to the heat pattern (3) built in the ceramic heater body (2), the heat pattern (3) built in the self-control type ceramic heater body (2) is made of silicon nitride. Electrode extraction part (6) for the ceramic sheet (12) as the main component
A heating element (4) made of conductive powder having a relatively small temperature resistance coefficient and a control resistor (5) made of conductive powder having a relatively large temperature resistance coefficient are connected in series together with (7). In addition, the temperature coefficient of resistance of the heating element (4) and the control resistor (5) is 3 times or less, preferably 2 times or less at room temperature to 1000 ° C.
Since the control resistor (5) has a large temperature resistance coefficient four times or more from room temperature to 1000 ° C., a large current can be applied to the heating element (4) to rapidly raise the temperature and the heating element ( Since the electric resistance of the control resistor (5) connected in series with the control element (4) increases remarkably, the heating current supplied to the heating element (4) decreases. It is possible to prevent melting of the heating element (4) due to overheating.

Further, integrally with the electrode take-out portions (6) and (7),
A heating pattern (3), in which a heating element (4) made of conductive powder having a relatively small temperature resistance coefficient and a control resistor (5) made of conductive powder having a relatively large temperature resistance coefficient are connected in series, is printed. Since the resulting ceramic sheet (12) is a ceramic sheet containing silicon nitride (Si ₃ N ₄ ) having high thermal shock resistance as a main component, the electrode extraction portion (6)
By rapidly energizing the heat pattern (3) composed of the heating element (4) and the control resistor (5) through (7), the self-regulating ceramic heater body (2) containing the heating element (4) and the like is rapidly mounted. Even if a large thermal stress is generated in the main body (2) of the self-controlling ceramic heater containing silicon nitride as a main component, the self-controlling ceramic heater (1) constituting the self-controlling ceramic heater (1) is heated. Since the thermal shock resistance of the heater body (2) itself is extremely high, it is possible to prevent damage to the self-controlling ceramic heater body (2) that accompanies a rapid temperature rise. The durability of the control type ceramic heater (1) can be surely improved.

[0014]

As described above, a ceramic sheet containing silicon nitride as a main component, a heating element made of conductive powder having a relatively small temperature resistance coefficient, and a relatively large temperature resistance coefficient are integrated with the electrode extraction portion. By printing a heat pattern that connects control resistors made of conductive powder in series, stacking the ceramic sheets so as to cover this heat pattern and integrating them, and by firing to form a self-controlled ceramic heater, In addition to enabling rapid temperature rise by energizing the heating element, it can have a self-control function to prevent melting of the heating element due to temperature rise of the control resistance.
By using silicon nitride as a main component for the rapid temperature rise of the ceramic heater, it is possible to sufficiently secure the thermal shock resistance of the main body of the ceramic heater, and it has an excellent effect that it can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is an enlarged partial sectional front view of a plate-shaped ceramic heater that is an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a laminated state of ceramic sheets of a plate-shaped ceramic heater that is an embodiment of the present invention.

[Explanation of symbols]

 1 Self-Controlling Ceramic Heater 2 Self-Controlling Ceramic Heater Main Body 3 Heat Pattern 3 '(Before Firing) Heat Pattern 4 Heating Element 5 Control Resistor 6 Electrode Extraction Part 7 Electrode Extraction Part 8 Electrode Plate 9 Electrode Plate 10 Lead Wire 11 Lead wire 12 (silicon nitride) ceramic sheet 13 (silicon nitride) ceramic sheet

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H05B 3/14 0380-3K H05B 3/14 A

Claims (3)

[Claims] 1. A ceramic sheet containing silicon nitride as a main component, integrally with an electrode lead-out portion, a heating element made of conductive powder having a relatively small temperature resistance coefficient on the front end side, and a temperature resistance on the rear end side. A heating pattern is formed by connecting control resistors made of conductive powder having a relatively large coefficient in series, and a ceramic sheet containing silicon nitride as a main component for printing the heating pattern is covered with the heating pattern. A self-regulating ceramic heater that is obtained by integrally laminating and firing ceramic sheets having the same shape as the main component that do not print a heat pattern. 2. The conductive powder having a relatively small temperature coefficient of resistance used for the heating element constituting the heat pattern has a resistance temperature coefficient from room temperature to 1000 ° C. of 3 times or less, preferably 2 times or less. Narita tungsten carbide (W
C), tantalum nitride (TaN), tantalum carbide (Ta)
C), molybdenum silicide (Mo ₅ Si ₃ ) or rhenium
The self-regulating ceramic heater according to claim 1, wherein a paste made of a powder of a tungsten alloy or the like is used. 3. The conductive powder having a relatively large temperature resistance coefficient used for the control resistor forming the heat pattern has a resistance temperature coefficient of 4 from room temperature to 1000 ° C.
The self-regulating ceramic heater according to claim 1, wherein a paste made of powder of molybdenum silicide (MoSi ₂ ), tungsten (W), molybdenum (Mo), etc., which is more than double the amount is used.