JPS6324577A - Ignition plug - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to miniaturization of a spark plug for an internal combustion engine, and more particularly to the structure of an intermediate electrode that prevents splitting of an insulator.

(Prior Art) In recent years, internal combustion engines have had complicated combustion chamber shapes due to demands for exhaust gas countermeasures and reduced fuel consumption, and as a result, the space for the spark plug installed on the cylinder head has become limited. It has been reached. For this reason, the diameter of the mounting screw of the metal shell has also been reduced, and performance similar to that of the standard type is required. By the way, in order to miniaturize a spark plug, a ignition electrode made of a PT gold alloy with a high melting point of 1600 degrees Celsius is fixed to the tip of an insulator ignition part, and is integrated with the insulator by co-firing. This is recognized as an extremely effective means as long as airtightness is good.

(Problem to be Solved by the Invention) However, when using the above-mentioned ignition electrode, the intermediate electrode connecting the ignition electrode and the glass seal part has an expansion coefficient between the insulator and the insulator because both ends are fixed. If there is a difference, the connection with the firing electrode will be severed, resulting in poor continuity.
It has been found that it is better to use a low-expansion alloy such as a pe-Ni alloy, which has a coefficient of expansion similar to that of the insulator. However, the initial airtightness may deteriorate, oxidation expansion may occur in the alloy, and cracking may occur in the insulator.

Therefore, the present invention aims to improve the above-mentioned drawbacks of the conventional spark plugs by preventing cracking of the insulator and thereby achieving an unreasonable miniaturization of the spark plug.

(Means for solving the problem) For this purpose, as shown in FIG.
For spark plugs that use a metal made by partially bonding e as an intermediate electrode, the tip temperature is 900°C x 1 minute, 2
When repeated experiments were carried out by heating and cooling with a desk burner as a cooling/heating cycle of 00℃ x 1 minute, 100%, N
In the case of i-Cr-Fe alloy, as shown in the figure,
If the junction between the ignition electrode and the intermediate electrode is made entirely of the above-mentioned alloy, poor conductivity will occur; if the proportion of the joint to the total length is reduced to 50 inches, no defective conduction will occur;
It is clear that if it is less than 5 inches, oxidation expansion will occur and cracking will occur in the insulator'), and if the bonding ratio to the whole Ni Cr Fe alloy is 25 inches to 50% of the total length, it is in the appropriate range. (Shaded area in Figure 2) It became clear. Also,
The temperature given to the intermediate electrode is 400°C or higher for the part between 5 and 10 degrees (from the ignition part), and 400°C for the part further away from that point.
It was also revealed that the temperature was below 00°C.

As a result, the parts that become hot during use of the spark plug equipped with the above-mentioned intermediate electrode are
In this case, the area starting from the firing electrode (1/4 to 1/2) is made of a heat-resistant (oxidation-resistant) alloy, the other part is made of a low thermal expansion alloy, and both alloys are joined to form an intermediate electrode. This prevents the insulator from cracking due to expansion of the intermediate electrode.

(Function) With the above structure, oxidative expansion does not occur in the range where the low thermal expansion alloy causes oxidative expansion (5 to 10 fi from the ignition electrode), and in other areas, the insulator's heat Since the intermediate electrode exhibits expansion similar to the expansion coefficient, the connection between the intermediate electrode and the ignition electrode does not separate and conduction failure occurs, and therefore, the insulator housing the intermediate electrode can be prevented from cracking due to expansion.

(Example) An embodiment of the present invention shown in the drawings will be described.

(1) is the metal shell, and (2) is the insulator inserted into the metal shell ().
, when the insulator (2) is unfired, there is P on the tip firing part side.
A firing electrode (3) made of a noble metal such as t, Pt, Ir*Pt-Pd or an alloy thereof is joined, and these are integrated by simultaneous firing. An intermediate electrode (4) is inserted and welded to the rear end of the firing electrode (3), and glass vinyl (6) is filled in the rear end of the intermediate electrode (4) and the shaft hole of the insulator (2). Furthermore, a resistor (8).

Glass seals (7) are sequentially filled and terminals (9) are connected to the glass seals (7).

The intermediate electrode (4) has a Ni
The second half (4b) is made of a low thermal expansion alloy such as Fe-Ni-Co alloy, and both (4a) and (4b) are welded together. It is something that becomes.

In the spark plug equipped with the intermediate electrode (4) configured in this manner, no conduction failure or cracking of the insulator was observed even after being subjected to over 100,000 heating and cooling cycles.

(Effects of the Invention) As described above, the spark plug can be made smaller to match the configuration of the internal combustion engine, and the insulator can be prevented from splitting due to expansion of the intermediate electrode due to miniaturization. It is effective.

[Brief explanation of the drawing]

FIG. 1 shows a partial longitudinal sectional view of one embodiment of the present invention, and FIG. 2 is a chart showing actual and experimental results of the intermediate electrode. DESCRIPTION OF SYMBOLS 1... Metal shell, 2... Insulator, 3... Ignition electrode, 4... Intermediate electrode, 5... Grounding electrode, 6, 7...
Glass seal, 8...resistor, 9...terminal. Patent applicant Representative patent attorney Miyuki Fujiki Figure 1 Figure 2

Claims (1)

[Claims] A ignition electrode is co-fired and integrated with the insulator on the ignition part side of the insulator, and the ignition electrode and the glass seal part filled in the shaft hole of the insulator are connected by an intermediate electrode, and this intermediate electrode is 5 mm from the ignition part side. An ignition plug constructed by joining a heat-resistant alloy for a portion up to 10 mm and a low thermal expansion alloy for a portion closer to the glass seal.