JPS6174283A - Spark plug - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is characterized in that precious metal pieces made of a Pt-gold alloy of a specific composition are installed in the spark discharge parts of the middle, b' straight poles and outer electrodes that form the entire spark gear lug. Close the spark plug.

(Prior art) Conventionally, as a method to improve the durability of spark plugs by reducing total consumption, heat-resistant and crucible oxidized electrodes were used in the spark discharge part instead of electrodes made of base metals such as nickel/I/@-gold. It is known that a small piece of noble metal electrode with excellent properties is used, and for this purpose a spark plug using a small amount of Pt-Ir alloy has been proposed.
100" CLJ, there are problems with the peelability of small precious metal pieces under external cycle loads and spark consumption due to long-term use, and we also propose a clad structure to satisfy both peeling stability and spark consumption. However, it is expensive in terms of material cost and productivity.

(@Problems that Ming tries to solve) Therefore, from the perspective of improving these problems, the patent application
In 00316, it was proposed to use a Pt-Pc1 alloy for the spark discharge part of the electrode, but a problem occurred in which intergranular cracking occurred due to grain growth during cooling and heating cycles.

(Problem, (Means for Solving)) The present invention attempts to completely solve the problem of grain boundary cracking caused by grain growth during cooling and heating cycles in Pt-Pd alloys. The material of the small metal piece is Pd.
15-60% by weight, Ni yY* to suppress grain growth
The present invention aims to provide a spark plug which is synthesized from an alloy consisting of 2 to 20% by weight of at least one of RtzRh+Mo and Pt, which has excellent durability and has a longer plug life at a lower cost. be.

(Example) The present invention will be explained in detail below.

FIG. 1 is a cross-sectional view of the main parts of the ignition part of the spark plug of the present invention, in which 1 is a metal shell with an engine-mounting screw, and 2 is made of alumina porcelain or the like sealed and fixed in the inner cavity of the metal shell 10. an insulator; 3, a center electrode made of a nickel alloy with a tip end face thereof protruding into the shaft hole of the insulator 2, and a copper core disposed inside a sealing ring; 4, a spark discharge portion 3a of the center electrode 3; 5 is an outer electrode made of a nickel alloy or the like protruding from the end surface 1a of the metal shell 1; 6 is a small precious metal piece formed in the spark discharge portion 5a of the outer electrode; Al with a spark plug with a spark plug 7 formed between the tip of the small piece 4 of the medium/○ electrode 3 mentioned above and the spark plug 7.

The material of the precious metal pieces 4 and 6 of the present invention, which are used in the spark discharge part, is Pt, which contains 15 to 60% by weight of Pd and the balance is Pt.
-NieY+Ru, Rh+ as a third element in Pd alloy
It has been found that the addition of at least one type of Mo within the range of 2 to 20% by weight is effective in inhibiting crystal grain growth and in improving spark abrasion resistance during the production process.

That is, in the examples, various third elements were blended into F't-30Pd (Pd added at 30% by weight) alloy as shown in Table 1 below.
2-90 alloy gold is used for this, 2% S of this gel alloy is used.
i+ 2% Cr, 2% AI and remaining Ni alloy) Medium L>
A complete comparison of performance was made using pieces in which 0.4 pieces of noble metal were joined to the concave portions 3b of the electrode base material 3 by electric resistance welding. Among the mortality performance evaluations, the grain growth suppression effect was determined by the grain size No. (austenite grain size) after heat treatment at 1000°C
Comparison was made by intergranular cracks after cooling and cooling cycles of 3 minutes and 3 minutes x soooa.

Table 1 This test result is 1. In the Pt-30Pd alloy with ra 1, the crystal grains grew rapidly at high temperatures and the grains e were large, and cracks were observed at the boundaries although no peeling occurred during repeated heating and cooling cycles. On the other hand, all of the alloy materials of the present invention, 2 to 7 and 9, have slow crystal grain growth and small grain size, and exhibit minimal cracking even after repeated heating and cooling cycles. It has good adhesive properties.

Next, regarding spark consumption resistance, it was conducted by arranging precious metal rods of the same material facing each other under the condition of 100 PPS (pulses per second) of sparks using all CDI power supplies.
The total amount of gap increase at that time is shown in Figure 2. The alloy material of the present invention, F62, 3, 6.9, is slightly inferior to Pt-30Pd processing, but has relatively good wear resistance.
It was confirmed that the gap increase was small in the case of 0I r, and the durability was good.

In addition, N l+ Y r Ru + of the third element of the present invention
The amount of Rh + Mo added is within the range of 2 to 20%, and if it is less than 2% by weight, no crystal grain growth suppressing effect can be obtained, and if it is more than 20% by weight, the abrasion resistance is below the practical range. The reason why the amount of A0 or Pd added is preferably 15 to 60% by weight in total for the purpose of maintaining the bond is that if it is outside the above addition range, wear resistance and hardness in the joining range that is good for welding (Brinell 160 or more) cannot be obtained. be.

Furthermore, in the spark plug of the present invention, small pieces of precious metal are placed in the spark discharge parts of both the inner, U electrode, and outer electrode in FIG. 1, but the present invention is not limited to this embodiment. One of the electrodes is made of an uninvented alloy material, gold, and the other electrode is made of a noble metal alloy other than the alloy material of the present invention, such as Pt.
-Ni, Pt-I, rPt-Pd, etc. can be used in combination with the required characteristics. Furthermore, the spark gap is not limited to spark plugs formed between the tip surface of the center electrode and the opposing outer electrode as in the embodiment, but also to spark plugs formed between the tip side surface or the tip periphery of the middle and middle electrodes. can also be applied.

(251 results of the invention) As described above, the spark plug of the present invention has Pt in the spark discharge part.
-N i + Y + Ru + as three elements in Pd alloy
By adding at least one layer of RhlMo, the alloy (goods) not only has good spark wear resistance, but also improves the performance of the nickel alloy electrode by dramatically increasing the effect of suppressing grain growth at high temperatures. The adhesion of the f'L'fc spark plug is completely improved, and a highly durable f'L'fc spark plug is obtained.
d The material cost is relatively low, and it has the remarkable effect of extending the life of the plug at a lower cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an ignition part showing an embodiment of a spark plug of the present invention, and FIG. 2 is a characteristic diagram showing spark resistance purity of an alloy material of the present invention and a comparative alloy material.

Claims (1)

[Claims] (1) In a spark plug in which durability is improved by disposing precious metal pieces in the spark discharge part of the electrode, the material of the precious metal pieces is Pd 15 to 60% by weight, Ni, Y, Ru, etc. to suppress crystal grain growth. At least one of Rh and Mo2-20
A spark plug characterized in that it is made of an alloy consisting of % by weight and the balance being Pt.