JPS6217521A - Self-control glow plug - Google Patents

Abstract

PURPOSE:To reduce the scatter in temperature rise characteristics by connecting in series a resistance body which is a formation of a metallic film on the outer surface of a cylindrical ceramic insulator. CONSTITUTION:A round rod made of a ceramic insulator has its surface chemically plated with pure nickel to form a metal film 30 on it. On both ends of the rod metal terminals 32 are provided, and a spiral groove cut 31 in the metal film 30 in formed by laser working. One end of a metal film resistance 5B is brazed on the metal terminal shaft 9, and the other end is connected to a metal cap 25 through a low resistance lead wire 26B, and the metal film resistance 5B is electrically connected in series to the heating coil 21 embedded in a ceramic sintered element 22. Because of this connection in series of the heating coil 21 with a very small resistance temperature coefficient and the metal film resistance with a large positive resistance temperature coefficient, the scatter in the resistance values of the metal film resistances becomes smaller and also the scatter in their temperature rise characteristics can be made smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rapid heating type glow 7' lug that is mainly installed in a diesel engine and preheats the auxiliary combustion chamber etc. at the time of startup.

(Prior art) Diesel engines generally have poor starting performance at low temperatures, so a glow plug is attached to the auxiliary combustion chamber provided in the engine head, and the glow plug is energized to make it red hot, causing the fuel to be injected into the room. A method of preheating by partially burning is used, and it is required to have rapid temperature rise characteristics at the time of startup, and recently, even after startup, it is used for a long time as an afterglow to stabilize combustion. There is a growing trend toward using such devices, and there is an increasing demand for improvements in their performance.

To achieve this purpose, a self-control system has a structure in which a heating element coil whose resistance value hardly changes depending on temperature and a resistor element having a positive temperature coefficient of resistance are connected in series to control the heating current. Type glow plugs are known.

Figure 4 (a) is a vertical cross-sectional view showing an example of a conventional self-control sheathed glow plug, showing a heating element coil 1 made of a wire with an extremely small temperature coefficient of resistance, one end of this coil, and a positive resistance. Resistor coil 5A made of wire material with temperature coefficient
is welded, and the center electrode shaft 6 electrically connected to the other end of this coil is press-fitted together with a heat-resistant insulating filler 3 into a metal protection tube 2 made of heat-resistant metal and closed at one end to form a heating element. 4, and the other end of the heating element coil 1 is a metal protection tube 2.
The opening side of the metal protection tube is fitted into the tip of the hollow mounting bracket 8 and soldered to form the e-side electrode, and the center electrode shaft 6 is connected to the insulator 10. It is interposed between the mounting bracket A8 and fixedly tightened with a fixing nut 11, so that it becomes a side electrode.

FIG. 4(B) is a vertical cross-sectional view showing an example of a conventional self-control ceramic glow plug, in which a ceramic heater 23 serving as a heating element is made of a heating element coil 21 made of a wire with an extremely small temperature coefficient of resistance. It is not embedded in the body 22, but is soldered to the inner cavity of the metal outer cylinder 24, and one end 21& of the heating element coil 21 is electrically connected to this. It is soldered to the tip lumen.
The other end 21b of the heating element coil 1 is connected to a wire rod having a positive temperature coefficient of resistance through a center electrode shaft 26A which is welded to a metal cap 25 fitted to the rear end of the ceramic heater 23. The other end of the resistor coil 5A is connected to the tip of a metal terminal shaft 9 having a terminal screw. In the inner cavity of the mounting bracket 8, the metal terminal shaft 9 is fixed with a glass seal 2T so that the above-mentioned components in the inner cavity are embedded, as in the example shown in FIG. 4, 0). It is configured to serve as a side electrode.

Conventional self-control glow plugs with such a structure aim to shorten the preheating waiting time during the starting operation of a diesel engine, and the temperature of the four heating element coils and resistor rises rapidly, and then the temperature rises. It has a self-control function in which the resistance value increases as the temperature rises, thereby reducing the applied current and controlling the temperature of the heating element.

(Problems to be Solved by the Invention) However, although the conventional self-control glow plugs described above have a self-control function as described above, it is desirable that the temperature of the heating element be saturated.

To achieve this, it is necessary to adjust the resistance ratio and combined resistance of the resistor coil and heating element coil to roughly match them, but this can be done during manufacturing by welding, swaging, glass sealing, etc. between the heating element coil and the resistor coil. There was a problem in that the resistance ratio and the combined resistance varied widely.

(Means for Solving the Problems) The present invention was made to solve the above-mentioned problems, and the resistor connected in series with the heating element coil is made of Al!
A metal film resistor made by closely forming a metal film with a metal having a positive temperature coefficient of resistance on the surface of a ceramic insulator round bar by vapor deposition or plating, etc.1.
If the size and shape of the core ceramic insulator round bar are constant, it is easy to manufacture a metal film resistor that always has a constant resistance value by adjusting the thickness of the metal film.

Furthermore, on the metal film on the ceramic insulator.

If you make a spiral cut using laser processing etc.

By adjusting the length and width of this cut, it is possible to correct the variation in resistance value that occurs during film formation, so it is possible to mass-produce resistors having a constant resistance value with little variation.

In the present invention, a metal film resistor as described above is electrically connected in series with a heating element coil via a center electrode shaft, a lead wire, etc. if necessary, and these components are sealed with glass in the inner cavity of a mounting bracket. The present invention provides a self-regulating glow plug.

(Function) In the self-control glow plug in which the metal film resistor is inserted, when the engine is started, the temperature of the metal film resistor rises due to self-heating due to diesel heat over time after the start of energization.
Therefore, the resistance value increases. Therefore, the current flowing through the heating element is reduced, and as a result, the temperature rise of the heating element is alleviated. That is, it is conventional to have a self-control function. However, by selecting the resistance value of the metal film resistor, it is possible to obtain any afterglow temperature after the start of the engine, as shown by lines A and B shown in FIG. 3.

(Example) Figure 1 is a perspective view of a metal film resistor used in the self-regulating glow plug of the present invention.
A metal film 30 is formed by chemically plating pure nickel on the surface of a ceramic insulator round rod, and metal terminals 32 are provided at both ends of the rod. In Fig. 1 (b), the metal film 30 is further formed by laser processing. A spiral cut 31 is formed.

Figure 2 (a) is a longitudinal cross-sectional view showing an embodiment of a self-regulating sheath type glow plug according to the present invention, in which the same parts as in the conventional example shown in Figure 4 (0) are designated by the same reference numerals. The glow plug of this embodiment has both terminals of the metal film resistor 5B soldered to the front ends of the center electrode shaft 6 and the metal terminal shaft 9, respectively, and is installed inside the metal protection tube 2 with one end closed. It is electrically connected in series with the heating element coil 1, and is sealed with glass 7 so that these components are inserted and buried in the lumen of the mounting bracket A8.The other structure is shown in FIG. It has the same structure as the conventional example shown in (-r).

Fig. 2←) is a longitudinal cross-sectional view showing an embodiment of the self-regulating ceramic glow plug according to the present invention, and Fig. 4 (the same parts as the conventional example of the mouth 1 are indicated by the same reference numerals.This embodiment The glow plug has one end of the metal film resistor 5B) soldered to the metal terminal shaft 9.

The other end is connected to the metal cap 25 via the low resistance lead wire 26B.
The metal film resistor 58 is electrically connected in series to the heating element coil 21 embedded in the ceramic sintered body 2.The other structure is shown in FIG. 4(b) VC. It has the same structure as the conventional example.

(Effects) The self-regulating glow plug of the present invention as described above has a heating element coil with an extremely small temperature coefficient of resistance.

From VC, a metal film resistor with a large positive temperature coefficient of resistance is electrically connected in series.

Temperature rise characteristics similar to those of the conventional example can be obtained. Moreover, since the resistance value of the metal film resistor has little variation, it is possible to provide a self-regulating glove 2 with little variation in temperature rise characteristics. I

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view of a metal film resistor using the VC of the present invention, and FIG. 1(b) is a perspective view of a metal film resistor with spiral cuts formed in the metal film. A) is a longitudinal sectional view of a self-regulating sheathed glow plug according to the present invention, FIG. 2(B) is a longitudinal sectional view of a self-regulating ceramic glow plug according to the present invention, and FIG. A model diagram of the temperature rise characteristics of a self-regulating glow plug using a film resistor. Figure 4 (a) is a vertical cross-sectional view of a conventional self-regulating sheathed glow plug, and Figure 4 (0) is a conventional example. FIG. 2 is a longitudinal cross-sectional view of a self-regulating ceramic glow plug.

Claims (2)

[Claims] (1) In a self-control glow plug in which a current-limiting resistor is connected in series to a heating element coil, the resistor is a metal film formed on the outer surface of a cylindrical ceramic insulator. A self-regulating glow plug characterized by consisting of a film resistor. (2) A self-regulating glow plug according to claim 1, wherein a spiral cut is formed in the metal film of the metal film resistor.