JPS62186127A - Self-control type glow plug - Google Patents

Abstract

PURPOSE:To facilitate a manufacturing of a glow plug in which cracking is not generated and variation in resistance value is low by a method wherein a resistor coil is molded with compound having silicone rubber as its major substance. CONSTITUTION:A resistor coil 7 connected in series with a heating coil 2A of a ceramic heater 1A is buried with a molding process in a silicone rubber compound or a mixture 16 containing the silicone rubber compound and ceramic powder together with a connection between an internal shaft 8 and a central electrode shaft 6A, and an assembly 17 pressed in a column form under a heated condition is stored and held within an inner cavity of a fixing fitting 4. The compound having a major constituent of silicone rubber after pressing, heating and molding has an inner closeness and a high mechanical strength as well as no tendency of cracking and has a heat-resistant characteristic, so that the compound can suffuciently withstand a heating of the resistor coil. Further, a drawing work is not required, so that a resistance value of the resistor will not vary.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates primarily to a self-control glow plug that is installed in a diesel engine and preheats a sub-combustion chamber and the like during startup.

(Prior art) Diesel engines generally have poor startability at low temperatures, so a glow plug is attached to the auxiliary combustion chamber provided in the engine head, and electricity is applied to the glow plug to make it red-hot indoors. Fuel to be injected The method is to preheat by burning a part of the fuel, and it is required to have rapid temperature rise characteristics at the time of startup, and it is also used for a long time as an afterglow to stabilize combustion even after startup. This is why heating coils tend to have a resistance value that hardly changes depending on temperature.

Two self-regulating glow plugs are known which have a structure in which a resistor having a positive temperature coefficient of resistance is connected in series to control the heating current.

Figure 3 (a) is a vertical cross-sectional view showing the structure of a conventional glow plug in which the heating element of this type of glow plug is a ceramic heater. Two coils are embedded in a ceramic sintered body, and are brazed to the inner cavity of the metal outer cylinder 3A, and one end 2A-1 of the heating coil 2A is electrically connected (two connected), and the metal outer cylinder 3A is attached. It is soldered to the inner cavity of the tip end of the metal fitting 4 and becomes the θ side electrode, while the other end 2A- of the heating coil 2A
2 is a metal cap 5 fitted to the rear end of the heater IA
It is electrically connected to a resistor coil 7 made of a wire having a positive temperature coefficient of resistance through a center electrode shaft 6A welded to the center electrode shaft 6A, and the other end of the resistor coil 7 is connected to the tip of the center shaft 8. There is. The inner cavity of the mounting bracket 4 is filled with glass 9 so that the above-mentioned components are embedded, and the center shaft 8
The structure is such that an insulator 10 is interposed between the mounting bracket 4 and the insulator 10 is tightened and fixed with a round nut 11 to form an electrode.

FIG. 3(b) is a longitudinal sectional view showing a conventional example of a glow plug in which the heating element is a metal sheathed type, and includes a heating coil 2B made of a wire material with an extremely small temperature coefficient of resistance.

Center electrode shaft 6B electrically connected to one end of this coil
and a heat-resistant insulating filler 12 are compressed into a metal protection tube 3B made of heat-resistant metal with one end closed, forming a heating element IB, and the other end of the heating coil 2B is placed on the inner wall of the closed part of the metal protection tube 3B. It is electrically connected, and the opening side of the metal protection tube is fitted into the tip of the hollow mounting bracket 4 and soldered to become the e-side electrode, and the side opposite to the heating coil side end of the male center electrode shaft 6B. A resistor coil 7 made of a wire material having a positive temperature coefficient of resistance between the end and the tip of the center shaft 8 having a terminal screw.
are electrically connected. The rest of the structure is the same as that shown in FIG. 3(A) and will not be described here, but the same parts are designated by the same reference numerals.

FIG. 4(a) is a longitudinal cross-sectional view of another conventional example of a glow plug in which the heating element is a ceramic heater, and the same parts as in FIG. 3(a) are designated by the same reference numerals. In the figure, a resistor coil 7 is connected to the heating coil of one heater (not shown).
is inserted into the metal tube 13 including the connection part with the center shaft 8 and the center electrode shaft 6A, and insulating powder 1 such as MgQ is inserted into the gap.
4, the packing density of the powder is increased by drawing processing such as swaging or pressing, and an assembly 15 holding the resistor coil 7, the center shaft 8, and the center electrode shaft 6A is formed, and this assembly is attached to the mounting bracket. A part 4-1 of the body part is caulked from the outer periphery into the inner cavity of 4, and a part of the body part 4-1 is housed in close contact with the inner wall.

Figure 4 (b) is a longitudinal sectional view of another conventional example of a glow plug in which one heating element is a metal sheath type, and the same parts as in Figure 5 (b) or Figure 4 (a) are designated by the same reference numerals. show. In the same figure, the resistor coil 7 is inserted into the metal tube 13 including the connection part with the center shaft 8 and the center electrode shaft 6B, and the resistor coil 7 is inserted into the metal tube 13 including the connection part with the center shaft 8 and the center electrode shaft 6B. It is housed in the internal cavity.

(Problems to be Solved by the Invention) A glow plug having a structure in which the resistor coil 7 is directly embedded in the inner cavity of the mounting bracket as shown in FIG. Since the connection component of the IB is sealed in the inner cavity of the mounting bracket 4 with the glass 9, the difference in expansion coefficient between the resistor coil 1 and the glass 9 (: therefore, due to repeated heat generation and cooling of the resistor coil 7) There is a problem in that cracks occur in the glass, impairing sealing properties, and outside air enters through the cracks, causing oxidation of the resistor coil 7 and reducing durability.

Also, as shown in FIG. 4, the resistor coil 7 is made of metal.

- In the construction of the assembly 15 embedded within the pool 13.

Although there are no problems like those mentioned above, the manufacturing process is time-consuming, and short-circuiting occurs within the resistor coil due to drawing processing such as swaging or pressing, resulting in a difference in resistance value before and after processing. The disadvantage is that it is difficult to create a resistor with a

(Means for Solving the Problems) The present invention has been made to solve the above problems, and the resistor coil is made of silicone rubber compound or silicone rubber, including the connection part with the center shaft and the center electrode shaft. Compound and SiQ, , MgO.

A1. The glow plug has a structure in which an assembly is embedded in a mixture with ceramic powders such as O, 81, N4, etc., and molded under pressure and heat into a cylindrical shape and housed in the inner cavity of the mounting fitting.

(Function) As mentioned above, the compound mainly composed of silicone rubber after pressure and heat molding has a dense interior and strong mechanical strength, and there is no risk of cracking like the glass sealing (700 to 800°).
Since it has a heat resistance of C, it can withstand heat generated by the resistor coil. Also.

Unlike assemblies using metal tubes, there is no need for drawing, so the resistance value of the resistor does not change.

(Embodiment) FIG. 1 is a longitudinal cross-sectional view of an embodiment of a self-regulating glow plug according to the present invention having a ceramic heater, in which a resistor coil 7 connected in series to a heating coil 2A of a ceramic heater IA is shown. , a silicone rubber compound, including the connection part with the center shaft 8 and the center electrode shaft 6A, or a silicone rubber compound! : Sin, , MgO, Am,
o,, 81. The assembly 17 is embedded in a mixture 161 of N molding with a ceramic powder such as N, and molded under pressure and heat into a cylindrical shape. Note that the other structures other than those described above are the same as those in the conventional example shown in FIG. 3(A), so explanation thereof will be omitted, but the same parts are indicated by the same reference numerals.

FIG. 2 is a longitudinal sectional view of an embodiment of the self-regulating glow plug according to the present invention having a metal sheathed heater connected in series to the heating coil 2B of the sheathed heater IB.
, the resistor coil 7 is embedded in a silicone rubber compound or a mixture 16 of silicone rubber compound and ceramic powder together with the connection portion with the center shaft 8 and the center electrode shaft 6B in the same manner as in the embodiment shown in FIG. It is formed as an assembly 17 that is pressurized and heat-molded, and is similarly housed and held in the inner cavity of the mounting bracket 4.
Since it is the same as (b), the explanation will be omitted, but the same parts are indicated by the same reference numerals.

(Effects of the Invention) In the self-controlling glove 2 of the present invention, the resistor coil is embedded in a compound mainly made of heat-resistant silicone rubber that has strong mechanical strength and elasticity, so the heat generated by the resistor coil is ``There is no risk of cracking due to repeated cooling, and since no metal pipe is required, there is no drawing process, so the resistance value of the resistor coil does not change due to drawing process, and the resistance value at the time of coiling is maintained as it is. Therefore, glow plugs with small variations in resistance value can be easily manufactured even in mass production. In addition, since the outer surface of the assembly molded from a compound mainly made of silicone rubber is in direct contact with the inner wall of the mounting bracket, it is possible to provide a glow plug with stable heat conduction and small variations in the temperature rise characteristics of the glow plug. .

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of a self-regulating ceramic glow plug according to the present invention, FIG. 2 is a longitudinal cross-sectional view of an embodiment of a self-regulating sheathed glow plug according to the present invention, and FIG.
Figures (A) and 4 (A) are longitudinal cross-sectional views of conventional examples of self-regulating ceramic glow plugs. FIG. 3 ←) and FIG. 4 (b) are vertical cross-sectional views of conventional examples of self-regulating sheath type glow plugs. IA, iB: heating element, 2A, 28: heating coil. 4: Mounting bracket, 6A, 6B: Center electrode shaft, 7: Resistor coil, 8: Center shaft %9 Ni glass, 10: Insulator, 11: Round nut, 13: Metal tube, 17: Silicon bomber-based compound agent Patent Attorney Mamoru Takeuchi Figure 1, Figure 3 (a) Sumire 4 (a) (b)

Claims (3)

[Claims] (1) In a self-control glow plug in which a current control resistor coil connected in series to a heating coil of a heating element fixedly protruding from the tip of a hollow fitting is housed in the inner cavity of the fitting. , a self-control glow plug characterized in that the resistor coil is molded from a compound mainly composed of silicone rubber. (2) The self-control glow plug according to claim 1, wherein the heating element is a ceramic heater formed by embedding a heating coil in ceramic powder and sintering it. (3) The heating element is a sheathed heater in which the heating coil is built into a metal tube with one end closed through a heat-resistant insulating filling, and one end of the heating coil is joined to the inner wall of the closed end of the metal tube. A self-regulating glow plug according to claim 1.