JPS58198886A - Ignition 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 The present invention relates to an improvement in a spark plug in which a noble metal tip electrode is arranged in the spark discharge portion of a center electrode or a ground electrode that forms a spark gap.

As is well known, as a method to reduce electrode wear of spark plugs, spark plugs in which a noble metal tip electrode (flake) having corrosion resistance and oxidation resistance is formed by electric welding in the spark discharge part are made of nickel alloy, etc. Compared to ignition plugs with spark discharge parts made of base metals, they have less wear and tear and can improve durability.

By the way, spark plug electrodes are not only exposed to harsh temperatures and atmospheres under the engine operating conditions, but are also considerably affected by the polarity of the voltage applied between the electrodes, especially on the negative polarity side, the electrical energy of the discharge spark is As a result, even high-melting-point precious metal alloys tend to reach higher temperatures, and the temperature rises intensively, producing spherical perspiration and causing abnormal wear.
It was found that the electrode wear was greater compared to the positive polarity side.

Furthermore, due to the discharge characteristics, most of the spark plugs used by employees are configured with negative polarity applied to the center electrode and positive polarity applied to the ground electrode, but the noble metal tip electrode of the spark discharge part of these electrodes is They are arranged without regard to the polarity of the voltage, and cannot maintain sufficient durability.

The present invention provides a spark plug in which the material of the spark discharge part is selected depending on the polarity, suppressing wear of the tip electrode and improving durability. That is, the present invention uses a crystal-grown platinum alloy for the negative polarity side spark discharge part, which is subject to large consumption. When the ground electrode is a power source with negative polarity, it is effective to arrange a platinum alloy, which is less likely to cause crystal growth, in the spark discharge portion of the ground electrode. Examples of platinum alloys in which this crystal growth is difficult to occur include Pi-Rh and Pi-Ir.

P t W+P INi pP I Rh Ni
+P+-Ir-Ni alloys are used, among which Pi-Rh (lO~40%nh, balance pt), pt
-Ir (10-30% Ir, remainder Pt), Pt
-W (2 to 10% W remaining P t ) T P t N
r (2-10% N+, remaining PL).

Pl-Rh-Ni (10~40% Rh, 2~10% Ni
, remaining Pi), Pi-Ir Ni (10-80%■r,
2 to 10% N+, balance pt) is preferably used.

The present invention will be explained below based on embodiments shown in the drawings.

FIG. 1 is a front view of the ignition part of a spark plug showing an embodiment of the present invention, in which 1 is a ceramic insulator made of alumina, etc., 2 is a Ni-8i-Mn, Ni-0r-Fe (Inconel) alloy, etc. A base metal center electrode made of base metal protrudes from the tip surface of the shaft hole of the porcelain insulator and is fixed in accordance with known specifications. Reference numeral 8 denotes a platinum alloy tip electrode made of P I-'EL h alloy, which is welded to the spark discharge portion 2a at the tip of the center electrode 2 by electric welding or the like, and is a circular plate having a thickness of 0.1 to 0.7 mm. are joined. Reference numeral 4 designates a main metal fitting for coaxially storing and fixing the above-mentioned insulator, and a ground electrode 5 having a rectangular cross section made of base metal of the same material as the center electrode is welded to the end face of the main metal fitting. This is a spark plug that is bent in between to form a spark gap 6. The spark plug shown in FIG. 1 is an embodiment in which a negative polarity voltage is applied to the center electrode 2 side and a positive polarity voltage is applied to the ground electrode 5 side.

On the other hand, in the spark plug showing another embodiment of the present invention shown in FIG. 5a, a tip electrode 7 made of P1-Ir alloy is welded to form a spark gap 6, and this spark plug has a negative polarity on the ground electrode 5 side and a positive polarity on the center electrode 2 side. Used in combinations where a voltage of

Although not shown in the drawings, in the embodiments of the present invention, in order to advantageously obtain discharge characteristics with a low discharge voltage, it is desirable that the cross-sectional area of the tip electrode on the negative polarity side be smaller than that of the opposing spark discharge section. 1. In particular, the spark plug of the present invention has a protrusion dimension of 5 to 15 W from the end face of the metal shell to the spark discharge end of the center electrode! I! When the length is relatively long, the anti-wear effect can be effectively achieved.

Example 1 As shown in FIG.
h (25% Rh), Pt-Ir (25% Ir), PI-
Welded disks of W (5% W) and Pt-N1 (5% Ni) alloys with a diameter of 2.61 ffφ and a thickness of 0.3 fin were used for the present invention 7, 1 to -rx 4 samples and the conventional one. 5 was prepared as a sample using pure Pt material, and a 2000CeX 4-cycle engine equipped with a power source with negative polarity on the center electrode side was used.
As a result of performing the rpm
There were no defects such as cracks, splits, or sweating even after 0 hr had passed, and the durability was greatly improved compared to the conventional sample with flat 5.40 mm.
Before and after h, cracks were formed due to crystal growth, and the production of perspiration was significant, resulting in a large amount of wear and tear. In this case, the amount of wear on the ground electrode side was minimal.

Example 2 Next, as shown in Fig. 2, a platinum alloy similar to that of Example 1 (diameter 2.6 mm x thickness 0.8
ff) of the present invention, pure Plj similar to KL6-9
- Using the conventional sample /610, 500 cycles of 2000 CC x 4 with the ground electrode side as a negative polarity power source.
As a result of a durability test under 0 rpm x 474 conditions, the present invention, 1G 6 to 9, and conventional sample Black 10 showed the same tendency as the results of Example 1. In this case, the wear of the spark discharge part of the center electrode was also very small.

As described above, the spark plug of the present invention uses a platinum alloy with a high crystal growth temperature (approximately 800° C. or higher) for the negative-polarity side spark discharge portion, so that the negative-polarity side spark discharge portion, which is prone to abnormal wear, can be reduced. It is possible to suppress wear and tear and maintain excellent electrode durability.

[Brief explanation of the drawing]

FIG. 1 is a front view of the ignition part of a spark plug showing one embodiment of the present invention, and FIG. 2 is a similar front view of the ignition part showing another embodiment of the invention. 2...Center electrode 2m...Spark discharge part 3,7...
・Tip electrode 5...Ground electrode 5a...Spark discharge part 6...Spark gap patent applicant NGK SPARK PLUG CO., LTD. Figure 1 Figure 2 Procedural amendment (voluntary) February 19, 1958 (Showa 57) Patent Application No. 82846 2, Name of Invention Spark Plug 3, Relationship with the Amendment Case Patent Applicant Address 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Name (
454) NGK Spark Plug Co., Ltd. Representative: Shuho Ogawa 4, Agent address: Postal code: 467 Name: 3-3, 4-cho Takada-cho, Mizuho-ku, Nagoya (63)
71) Joint venture 5. Detailed explanation of the invention in the specification to be amended. 6. Contents of amendment 1, “10%” on page 3, line 10 of the specification is changed to r40%
” is corrected.

Claims (1)

[Claims] What is claimed is: 1. A spark plug comprising a noble metal tip electrode disposed in a spark discharge part forming a spark gap, characterized in that a crystal growth temperature is high on the negative polarity side of the spark discharge part.