JPS59203389A - 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 electrode material for a spark plug, and an object thereof is to provide a plug electrode material with excellent durability.

The conventional plug electrode material is Ni, which is a heat-resistant metal.
Although an alloy type plug is used, the plug needs to be replaced periodically because it wears out due to discharge at high temperature and pressure inside the engine cylinder, causing the distance between the electrodes to change and ignitability to deteriorate. Particularly in today's world, after exhaust gas regulations were passed, the combustion inside the engine is now finely controlled through various controls, and the wear and tear of the plugs itself has a large effect on combustion, and the emergence of plugs with less wear and tear is expected. desired.

For this reason, a proposal has been made to use a ceramic center electrode made of a ceramic material with a high melting point mixed with a high melting point metal material (Japanese Patent Publication No. 34-965.3, Japanese Unexamined Patent Publication No. 55-15
0579). Ceramics include high melting point substances such as carbides, borides, and silicides. From these facts, the idea of constructing the plug electrode from a ceramic with an extremely high melting point was easily generated.

However, it has been found through experiments that even if the plug electrode is made of these high melting point ceramics, it is not very effective in improving the wear resistance of the plug.

Therefore, as a result of intensive research, the present inventor discovered the following points. (1) There are two types of high melting point ceramics: those with oxidation wear resistance and those with discharge wear resistance.
I can't find it. (2) Furthermore, in order to reduce plug wear, it is effective to mix oxidation wear-resistant ceramics and discharge wear-resistant ceramics, and this is truly effective when they have a certain special structure.

The present invention has been proposed based on the above points, and will be explained in detail below.

The causes of plug wear were divided into two: oxidation at high temperatures and discharge wear due to discharge energy, and the degree of wear of various high melting point materials was measured. Figure 1 shows the results of the oxidation test. For the oxidation test, each sample was heated at 1000°C
The test pieces were left in an electric furnace in an air atmosphere, and their weight was measured after a durability test of 1Iil. Figure 2 shows the results of the discharge test. The discharge test used an ignition coil with an outer diameter of 62 mm, and the test conditions were a discharge interval of 60 m5 and a discharge energy of 40 mJ. This discharge was continuously endured for 3011 r, and weight changes before and after were examined.

As a comparison product, Ni-C, which is currently a commercially available plug electrode material,
An r-Mn-3i Ni alloy was subjected to comparable durability. The dimensions of the test product are 5x for both oxidation test and discharge test samples.
The size was unified to 5x20m. In the oxidation test, the change in weight was large, so it was shown as a rate of change, and in the discharge test, the change in weight was small, so it was shown in units of mg. In the oxidation test shown in Figure 1, Mo5i2 and S showed oxidation resistance.
iC, while TiC, TiNXZrB2 had the least discharge wear in the discharge test shown in Figure 2, and Mo
``S i 2 does not have as much discharge wear and tear, but SiC
shows very large discharge loss. From the above, no material has been found that causes very little wear in both oxidation and discharge wear, and it is not possible to provide a plug electrode material with little wear even if the high melting point substances tested this time, such as carbides, silicates, and borides, are used alone. .

Therefore, we investigated whether it is possible to create a material that is resistant to wear and tear by mixing oxidation wear-resistant materials and discharge wear-resistant materials. SiC and MoSi2 are used as oxidation wear-resistant materials, and as discharge wear-resistant materials.
I"1Cs-FiN, using ZrB2, SiC, MoS
30 mol% of any of i2, T i C1T'iN,
Figures 3 and 4 show the results of carbonizing discharge durability test using ZrB2 mixed at a ratio of 70 mol%. Figure 3 shows oxidation durability, Figure 4 shows discharge durability, and each test condition is
．． It is the same as Figure 2. Mixing shows better results in terms of oxidation discharge durability than when using SiC alone, but in the case of SiC, the effect is small, and in the case of a mixture of M o Si 2, the results vary depending on the firing strip 1. The M o S i 2 mixture calcined under these conditions shows very good results.

The α group in Figure 3.4 is fired under a pressure of 300 kg/cffl at a firing temperature of 1800"C, and the β group is fired under a pressure of 300 kg/crA at a firing temperature of 1600"C.
Pressure is applied, T group is 300K with firing temperature of 1800℃
Firing was performed under pressure conditions of g/eJ. FIG. 5 shows the results of observing the structures after each firing using an electron microscope. Figure 5(1) shows 5iC-TiC1 of the α group.
@5 (Figure 21 shows β glue 7”17) Mo S i 2
-T i C, Figure 5 (3) shows the γ group (D*Mo
S i 2 T' i C (7) organization, E,
By P, M, and A analysis, it was confirmed that ■ is Sic, 2 is TiC, and 3 is Mo Si 2. Fifth (
In Figure 1) and Figure 5 (2), particles of 5iC1 and MOS i 23 are dispersed in spots in T i C2, whereas in Figure 5 (3), particles of 5iC1 and MOS i 23 are scattered around T i C particle 2. It was found that M o S i 23 was present in such a way as to surround it. It is thought that the reason why the γ group shows good results in FIG. 3.4 is because it has such a structure. Such structures include not only TiCM o 3 i 2 but also γ group ZrB2-MoSi2, TiN-
MoSi2 also showed a similar structure. In order to obtain such a structure, in the case of a Mo, Si 2 mixture, it must be fired in an inert atmosphere at a temperature of 1700 °C or higher (preferably 1700 to 2100 °C) and under pressure (200 to 600 kg/cn+17). It is essential to do so. In addition,
' SIC mixtures have never had such a structure regardless of temperature and pressure conditions.

Next, we will show the results of actual engine durability tests on plugs. Figure 6.7 shows a structure in which a ceramic electrode material is made into a plug.
The tube 4 is machined into a two-cut tube 4 and assembled into a metal tube 6 made of a Ni-based heat-resistant alloy so that its tip is exposed, and an internal conductor 5 made of copper is packed inside the tube 6. The reason for this configuration is to prevent the plug heat value from occurring if the entire center electrode is made of ceramic material, which would result in a pre-ignition phenomenon.
In order to avoid this, copper, which has good thermal conductivity, is packed inside the plug in contact with the ceramic, thereby making the heat value close to that of commercially available plugs. Of course, if bracing can be avoided by other means, the entire structure may be made of ceramic material.

The center electrode of FIG. 6 is assembled into the plug of FIG. 7. That is, the plug includes an insulator 10, a center electrode rod 9, conductive glass 8, a ground electrode 7, a housing 11, and the like. Note that 12 indicates a spark discharge gap. This plug was installed in the engine and the engine was tested for durability. Figure 8 shows the results, and the test conditions were 2 displacements.
Using a 000cc engine, rotation speed 400Orpm,
-120 + tn + 1 g under continuous operation, the ignition timing was alternately repeated 50 times at 85° - → 40° BTDC, and the durability test time was 5011 r. From the results in Figure 8, Mo5i2-TiC showing the structure of T group
It can be seen that the wear of the center electrode made of aluminum is the least. In FIG. 8, the material compositions of the α, β, and γ groups and the manufacturing conditions are the same as those described above.

In the present invention, the ground electrode in addition to the center electrode may be made of the above-mentioned material, and both electrodes may be made of the same material. Also,
Three of Tic, ZrB2, and TiN may be mixed with MOSi2.

[Brief explanation of the drawing]

Figures 1 to 4 are characteristic diagrams for explanation, Section 5 (1)
Figures 5(3) to 5(3) are schematic organization diagrams of electrode materials provided for explanation of the present invention, Figures 6 and 7 show an embodiment of the spark plug of the present invention, and Figure 6 shows the center electrode. FIG. 7 is a half sectional view showing the overall configuration, and FIG. 8 is a characteristic diagram for explaining the present invention in detail. 4... Ceramic chip of center electrode, 7... Ground electrode, 12... Spark discharge gap. Representative Patent Attorney Takashi Okabe Figure 1 Ni TiCSiCZrB2 MoB2 ZrSi2
MoSi2 TiNFigure 2Figure 4Figure 5

Claims (3)

[Claims] (1) An ignition plug comprising a center electrode and side electrodes, and configured to generate a spark discharge in a spark discharge gap formed between the two electrodes, wherein at least one of the electrodes is electrically conductive. This ceramic material is made of a mixed material of a material with discharge wear resistance and a material with oxidation wear resistance, and furthermore, the particles of the discharge wear resistance material are surrounded by the oxidation resistance. A spark plug that is coated with a layer of wearable material. (2) The oxidation wear-resistant material is molybdenum disilicide, and the discharge wear-resistant material is any one of titanium carbide, titanium nitride, and zirconium boride. spark plug. (3) The amount of the oxidation wear resistant material in the total amount of the oxidation wear resistant material and the discharge wear resistant material is 10 to 5.
The spark plug according to claim 2, wherein the content is 0 mol%.