JPH0548596B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to an improvement in the core of a center electrode of a spark plug having a composite structure. (Prior Art) Conventionally, a center electrode of a spark plug is known which has a composite structure in which a core portion and an outer peripheral portion are made of separate components. The reason for having this composite structure is that it is required not only to have excellent spark consumption resistance and heat resistance, but also to have excellent thermal conductivity to quickly release generated heat. In other words, in order to make the outer periphery of the center electrode spark abrasion resistant and heat resistant,
A Ni alloy made by adding Cr, Si, Mn, Al, Fe, etc. to Ni was used, and the core was made of Cu, which has good thermal conductivity. However, with the recent improvements in engine performance, spark plugs are required to be used for long periods of time under harsh conditions, and under such conditions, the center electrode is made of Cu in the core and Ni alloy in the outer periphery. Thermal stress generated by the difference in thermal expansion causes deformation, resulting in a decrease in ignition and discharge performance, and the performance of the spark plug is deteriorated. (Problems to be Solved by the Invention) Therefore, the present invention aims to improve the above-mentioned drawbacks of the conventional ones and to obtain a constituent material that can prevent deformation of the center electrode. (Means for Solving the Problems) For this purpose, the present invention adds Fe, Ni, and Si to phosphorus-deoxidized copper, which is a constituent material of the core of the center electrode, and
The center electrode is made by adding Si, Cr, Mn, Al, and Fe to Ni. (Function) By configuring in this way, the heat resistance of the core portion is improved, which means that the growth of crystal grains of the constituent materials at high temperatures is suppressed. In this case, the phosphorus compound that suppresses grain growth is
Add 0.015 or less. Note that addition of 0.015% or more of a phosphorus compound impairs thermal conductivity and reduces the deformation prevention effect of the center electrode. (Example) To explain this with an example shown in the figure, 1 indicates a spark plug, 2 is an insulator made of alumina porcelain, and the tip end surface 2 is inserted into the shaft hole 2a of the insulator 2.
The center electrode 3 exposed from b is inserted, and the shaft hole 2
A conductive glass seal 4 is held at the rear end of the center electrode 3, and a resistor 5 and a terminal electrode 6 are integrally heat-sealed by a known method. The ground electrode 3 protruding from the tip of the center electrode 3 and the mounting bracket 7 has a core part 10 and an outer peripheral part 11.
As mentioned above, the core portion 10 is made of Fe, Ni,
0.01 to 1.0 of one or two types of Si
%, P, 0.015% or less, and the outer peripheral portion 11 is made of a Ni alloy to which Si, Cr, Mn, Al, Fe, etc. are added. Note that since the present invention relates to the center electrode, it goes without saying that the other configurations of the spark plug are not limited to the embodiments. The following table shows that the outer peripheral part 11 of the center electrode 3 is Si, Cr,
The center electrode is made of a heat-resistant Ni alloy with 1 to 2% Mn added, the core part 10 is configured as shown in the table below, and a long-term durability test is carried out by attaching it to each cylinder of a 6-cylinder gasoline engine. indicates the time at which deformation occurs.

[Table] In the table above, the total amount added shall not exceed 1.0%. If it exceeds 1.0%, the thermal conductivity properties will decrease,
This will cause plug performance problems. As described above, it is clear that the present invention can significantly delay the deformation occurrence time compared to the deformation occurrence time of oxygen-free copper wire, and has excellent heat resistance. Furthermore, the center electrode 3 is made by fitting a base material that will become the core part 10 having a downwardly protruding part onto a base material that has a concave hole on the upper surface that will become the outer peripheral part 11, and heating it in an inert atmosphere or vacuum. The two bonding surfaces are bonded by mutual diffusion, and then the center electrode 3 having a composite structure is formed by plastic molding. (Effects of the Invention) As described above, by configuring the core component as in the present invention, a center electrode with a composite structure that not only has excellent spark wear resistance and heat resistance but also excellent thermal conductivity can be obtained. Therefore, it has an excellent effect of preventing performance deterioration of the spark plug due to thermal deformation.

[Brief explanation of the drawing]

FIG. 1 shows a partially longitudinal side view of a spark plug equipped with a center electrode according to the present invention, and FIG. 2 shows an enlarged view of the center electrode. 1...Spark plug, 2...Insulator, 2a...
...Shaft hole, 2b...Tip surface, 2c...Step, 3...
Center electrode, 10... core portion, 11... outer peripheral portion.

Claims (1)

[Claims] 1. The core is composed of phosphorus-deoxidized copper to which one or two of Fe, Ni, and Si are added at 0.01 to 1.0% and P, 0.015% or less, and the outer periphery is mainly composed of Ni. Center electrode of a spark plug made of Ni alloy.