JPH02183989A - Spark plug with aluminum nitride insulator - Google Patents

Abstract

PURPOSE:To obtain a large heat absorption effect by providing a ring-shaped contact section in the middle barrel section direction other than a conical taper contact section in the junction between the main metal of a plug and an AIN insulator. CONSTITUTION:A ring-shaped contact section 5 with the height of about 1mm is provided other than a conical taper contact section on the junction between a main metal 1 and an AIN insulator 3. The heat flow from the insulator 5 to the main metal 1 is made very good according to this constitution, the temperature of an ignition section is reduced to allow a wide-range plug, and the heat flow to the corrugation side in the axial direction can be prevented. The deterioration of a cap due to heat is prevented, and the high-performance plug is obtained. A material with the thermal conductivity of 50W/m.k and the hardness of Hv 150 or below is used for the ring material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a spark plug for an internal combustion engine, and particularly to a spark plug for an internal combustion engine that prevents deterioration of the plug cap due to heat that occurs when aluminum nitride is used as the plug insulator. Regarding plugs.

[Conventional technology]

Conventionally, A2,0. As shown in Figure 2, the spark plug that used the insulator dissipated heat from the insulator only through the conical tapered contact part 2, with a wire packing 4 at the joint between the metal shell 1 and the insulator 5. It's here. This is At
, 03 had a thermal conductivity of only about 20 to 50 w/m-k, and the heat from the tip of the plug could not be sufficiently transferred to the contact part, so the contact part was provided at a location other than the above. There was no change in performance, etc.

However, aluminum nitride insulators, which have been considered for practical use in recent years, have good thermal conductivity (150 to 180 w/+n
-k), the high heat at the tip of the long leg is transmitted to the main metal fitting and also to the coy gation part, so the plug cap rubber that connects to the high voltage cord, which has not been a problem with alumina insulators, Deterioration due to heat has emerged as a problem.

The present invention aims to solve the above-mentioned problems.

[Means to solve the problem]

In order to transfer more heat flow in the aluminum nitride insulator of the spark plug to the metal shell side, the present invention provides a ring-shaped contact part with good thermal conductivity to the insulator in addition to the conventional wire packing. By forming it in the clearance portion of the metal shell, the above object can be achieved.

[Effect]

According to the present invention, the contact portion between the metal shell and the AtN insulator is
By expanding the spark plug further than conventional spark plugs and more actively discharging heat to the metal shell, the following effects are achieved.

■ The temperature at the end of the spark plug leg is further reduced, increasing the advance angle margin for ignition occurrence, in other words, achieving higher heat value performance.

■ By sufficiently absorbing the flow of heat in the axial direction to the corrugation part with the metal shell, the temperature of the corrugation part can be lowered and deterioration of the plug cap rubber can be prevented.

- Table 1 shows the contact area of the inner-membrane eggplant spark plug and the effect of the ring-shaped contact part.

Table 1 The present invention provides a ring-shaped contact portion 5 having a width (height) of 11, as shown in FIG. As shown by the arrow, we were able to obtain a large heat-reducing effect.

Experimentally, if the width of the ring-shaped contact part 5 is 11 or more,
It was confirmed that the effects of (■) above were sufficiently achieved.

The material of the ring 5 is selected from the following 2nd material due to thermal conductivity and hardness requirements.
The ones shown in the table are preferable.

Table 2 If the material has a thermal conductivity of 50 w/m or less, the contact part will act on the heat insulating material and have the opposite effect. It is necessary to have

If a material with a hardness higher than Hv (Vickers) 150 is used, compressive stress will be applied to the contact area due to the difference in linear expansion coefficient between the insulator 3 and the metal shell 1 during the plug tightening process and engine installation, and the insulator will Squeezing cracks (see Figure 5)
occurs.

Therefore, it is preferable that the contact portion be made of a soft material that does not have good stress transmission properties and rather serves as a buffer material.

〔Example〕

The ring-shaped contact portion 5 in the spark plug of the present invention may be formed by attaching it to the surface of the corresponding insulator 30 in advance by metallization plating, OVD, etc., or by mechanically fixing it by ultrasonic pressure welding or the like. You can leave it there. Also, the 6th
As shown in Figures (A) to (C), an integral packing 15 may be inserted and joined. Furthermore, as shown in Figure 4,
When the metal shell 1 is molded, a convex portion 16 may be locally provided on the inner wall thereof, the insulator 3 may be press-fitted, and the insulator 3 may be assembled by a conventional crimping process. Further, copper plating or the like may be applied only to the inner wall of the metal shell 1.

Example 1 Corrugation: Part 7 IAJl and Bignition resistance are shown in Table 5.

The insulator leg length of the spark plug used in the test was 2.
Q: I compared it with Owm. In addition, the preignition resistance is 4 cycles A/b9tT, cylinder 2o o.

I did it with my engine under the conditions of 5500 r, p, tn x 4/4, changing the advance angle. Furthermore, the corrugation temperature is 5500r with the same engine, p0mX4/4
This is the surface temperature at the 8 inch position from the top under the following conditions.

〔Effect of the invention〕

By layering as described above, the present invention further improves the flow of heat from the highly thermally conductive insulator to the metal shell, lowering the temperature of the ignition part and making it possible to create a wide range plug. It is also possible to prevent the flow of heat toward the corrugation side, preventing deterioration of the cap due to heat, and obtaining a spark plug with excellent performance.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a spark plug provided with a ring-shaped contact portion according to the present invention, Fig. 2 is an explanatory diagram for comparing the performance of the wire packing and the ring-shaped contact portion, and Fig. 3 (A) to ( C) is an explanatory diagram in which the ring-shaped contact part is a packing type, and Figure 4 is
FIG. 5 is an explanatory diagram of an example in which a ring-shaped contact portion is provided on a metal shell, and is an explanatory diagram showing defects caused by a ring-shaped contact portion made of an inappropriate material. 1: Metal shell, 2: Conical tapered contact portion, 3: Insulator, 4. : Wire packing, 5: Ring-shaped contact part, 6: Center electrode, 7: Outer electrode, 15 integrated packing, 16: Convex part Fig. 2 Fig. 3

Claims (4)

[Claims] (1) A spark plug having an aluminum nitride insulator, which has a ring-shaped contact part in the direction of the middle body in addition to the conical tapered contact part at the junction between the metal shell and the insulator. (2) The thermal conductivity of the ring material of the contact part is 50w/m・k
The spark plug according to claim 1, which is the above. (3) The spark plug according to claim 1 or 2, wherein the ring material has a hardness of Hv150 or less. (4) The spark plug according to claim 1, 2 or 3, wherein the ring has a width of 1 mm or more.