JPS59191281A - Spark plug for internal combustion engine and method of producing same - 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 a spark plug for internal combustion engines (hereinafter referred to as a plug) in which a tip of a noble metal or the like is bonded to the tip of a center electrode serving as an ignition part, and a method for manufacturing the same, particularly by Rede welding. The present invention relates to a plug in which a tip of noble metal or the like is bonded to the tip of a center electrode, and a method for manufacturing the same.

In recent years, there has been an increasing demand for plugs for internal combustion engines to have a longer life (improved wear resistance) and higher performance (improved flammability and ignitability). Among these, it is known that longevity can be improved by using a noble metal tip in the developing section, and performance can be improved by using thin wire electrodes.

Conventionally, a plug using a thinned noble metal electrode has been proposed.In this case, welding methods such as capacitor welding, resistance welding, and Ray+J'' welding can be used to join the thinned precious metal electrode to the center electrode. and JP-A-50-2294
A mechanical joining means as shown in Publication No. 2 has been proposed. However, conventional proposals regarding welding means, especially regarding the above-mentioned joining technology using Rede welding, do not indicate any specific means for joining the thin precious metal wire to the center electrode, but simply use Rede welding, etc. It was merely a suggestion or possibility that it could be used. In fact, at present, a plug in which a noble metal tip is bonded to a center electrode by lathe welding has not yet been put into practical use.

Plugs in internal combustion engines are used in harsh environments such as repeated rapid heating and cooling, and an oxidizing atmosphere caused by combustion gas. In the case of the above improved plug in which the thinned noble metal electrode is joined to the center electrode made of a nickel-based heat-resistant alloy, the linear expansion coefficient of the noble metal is different from that of the nickel-based heat-resistant alloy, so it cannot be used in the harsh usage environment mentioned above. In this case, the thermal stress caused by the difference in linear expansion coefficient at the joint between the thin noble metal single pole and the center electrode causes siflux, rapid crack growth, and oxidation of the joint, causing the joint to deteriorate easily. In the worst case, the noble metal fine electrode falls off. The occurrence of such defects is closely related to the manufacturing technology used during plug manufacturing.

On the other hand, laser welding has the advantage that it is possible to weld minute parts, and that the shape constraints during welding are slightly smaller than other welding methods (capacitor welding, resistance welding, etc.). However, in Rade welding, the laser beam is focused and applied as a spot to the surface of the welded part, and the weld is made by locally melting the welded part, so the minute parts of the welded part are heated and cooled rapidly. The bridge has the disadvantage that cracks are likely to occur, and the existence of air between the thinned electrode of the noble metal to be welded and the center electrode tends to cause defects such as plowholes and air blowouts. Figure 6a shows the state of this crack 5 caused by Rede welding, Figures 7a and 7'b show the blowhole 6, and Figures 8a and 8b show the air blowout 7.
are shown respectively.

When a plug with such a defect is used in an engine, the above-mentioned deterioration is likely to occur at the joint of the plug, and the deterioration is accelerated and becomes unusable in a short period of time.

The present invention provides a plug in which a thinned noble metal electrode is joined to the tip of the center electrode that serves as the ignition part, and the above-mentioned defects do not occur in the joint, and the plug has a long life and high performance that can be used in practical use. It's about getting.

Another object of the present invention is to provide a manufacturing method for manufacturing a plug by joining a thinned noble metal electrode to the tip of the center electrode by Rede welding.

The plug of the present invention is a center electrode made of a nickel-based heat-resistant alloy and having a tip that serves as an ignition part, the center electrode having a hole extending in the axial direction at the tip of the center electrode. and a thinned noble metal electrode fitted into the hole, and a melting point provided in a direction transverse to the axis passing through the gap between the tip of the center electrode and the thinned noble metal electrode. The solidified part is joined by the melted and solidified part in which the nickel-based heat-resistant alloy and the noble metal are mixed, and the gap (a) between the center electrode tip and the noble metal thinning electrode is 5 microns or less, and the noble metal thinning electrode and The wall thickness (b) of the adjacent center electrode tip is 1-0.45 mm, and the axial length c) of the center electrode tip adjacent to or connected to the noble metal thinning electrode is 0.45 mm.
Insertion depth a) of fine-cut electrodes of 7 mm or more, C+
It is characterized in that 0.05 ram≦d≦2.0 mm. It is desirable that this melted and solidified portion does not reach the central axis of the thinned noble metal electrode; if the melted and solidified portion extends to the axis, defects such as cracks and plowholes will occur.

Preferably, this melted and solidified portion extending in the radial direction of the center electrode through the gap (a) between the center electrode tip and the noble metal thinning electrode is located at at least one location in the circumferential direction of the center electrode tip. They are provided at six locations, and are provided at the intermediate portion of the axial length C) of the center electrode tip portion into which the noble metal thinned electrode is inserted. As the N1-based alloy for the center electrode material,
70% or more N1111-25% Or, 1.0% or less Mn, 1.0% or less Fe, 0.5% or less Si, 0.
The known N1-high Cr@gold, consisting of less than 15% C, and the known N1-low Or alloy, based on N-2% Cr, are used. Pt is a well-known material for thinning electrical connections of precious metals.
, Pt-Ni alloy, Pt-Ni alloy, Pt-N
i alloy, Au-Pb alloy, etc. can be used.

A method of manufacturing the plug of the present invention using the Rede welding technique will be described below. The method of the present invention includes a center electrode made of a nickel-based heat-resistant alloy and having a tip that serves as an ignition part, and a hole extending in the direction of the needle, and a circumferential surface of the hole and an outer periphery of the tip. Thickness between surface (b)
or 0.1-O645 is 5π, and the axial length of the tip is c). 7-2.0 step of providing a center electrode having the tip portion which is a cage, providing a thinned electrode made of a noble metal or noble metal alloy, and inserting the thinned electrode into the hole to determine the insertion depth of the thinned electrode. d) is C+ 0.05 plate ≦d
≦2° (] am; a step of reducing the gap (a) between the thinned electrode and the hole to 0.005 mm or less by mechanical means such as caulking; a step of irradiating a laser beam from a direction transverse to the axial direction to a substantially central position of the axial length of the electrode tip portion, thereby melting and integrating the center electrode tip portion and a portion of the thinned electrode irradiated with the laser beam; The laser irradiation is stopped before the melting caused by the irradiation reaches the center axis of the thinning electrode, and the melted portion is solidified, thereby forming a melted and solidified portion that is integrated with the tip of the center electrode and the thinning electrode. and a step of providing the melted and solidified portion at at least one location in the circumferential direction of the tip of the center electrode.

In the above numerical range, if the gap (a) between the thinned electrode and the tip of the center electrode exceeds 0.005 mm, the rate of occurrence of plowholes and air blowing during rede welding increases. If the wall thickness (b) between the inner circumferential surface of the hole at the tip of the center electrode and the outer circumferential surface of the tip of the center electrode is less than 0.1 or greater than 0.45, normal Rede welding occurs. This may result in the occurrence of cracks or the inability to bond. If the length C) of the center electrode tip is smaller than 0.7 mm, stable bonding strength cannot be obtained. If the insertion depth d) of the thinned noble metal electrode is smaller than c + 0.05 mm, defects such as plowholes and air blistering will occur at the joint, 1.2. If it is larger than Oram, the amount of unused precious metal will increase and the cost will increase.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Figure 1 is an enlarged cross-sectional view of the tip of the center electrode before bonding by radar irradiation when manufacturing the plug according to the present invention, and 1 corresponds to Inconel 60 (trade name) Al material. 15.5% by weight Or,
Mrl below 1, Fe below 7, 8 below 0.5
1. N1-QC consisting of 01 less than 1 skin and the remainder Ni
The outer diameter A of the r-alloy center electrode lever is 2.5 mm. 2
is a thin noble metal electrode made of PT-10 alloy and its diameter B is 0.7 mm. A hole 3 extending in the axial direction is provided at the tip of the center electrode 1, and the thinned electrode 2 is inserted into the hole 3 at an insertion depth a). In order to join the thinned electrode and the center electrode tip, a radar beam is irradiated almost to the center of the center electrode tip 1a having a length C), and as a result, FIG. 9a (FIG. 9b is an explanatory diagram of the photograph) and As shown in the photograph shown in FIG. 10a (FIG. 10b is an explanatory diagram of the photograph), the center electrode tip and the thinned electrode were joined. The type of reso uses Yag lede, lede output 11 joules,
The defocus distance was set to 4 mm on the underfocus side, and the radius was narrowed to 0.5 mrn at the position where the outer peripheral surface of the tip of the center electrode was irradiated with the radar, which had an initial diameter of 6 mrn. The 10th radar welding unit irradiates this radar for about 8 milliseconds.
As shown in figure a, the part irradiated with the laser beam melts and integrates the tip of the center electrode and the noble metal thinning electrode, and after subsequent cooling, a melted and solidified part 4 in the shape of a cone is formed. The thinned electrode and the center electrode tip were joined to this melted and solidified portion 4. Although the gap (a) is not shown between the center electrode 1 and the thinned electrode 2 other than the integrated melting/solidifying portion 4 in FIG. 10b, it is actually shown enlarged in FIG. There is a gap with the same distance as the gap (a). As shown in the cross section of the integrated melted and solidified portion 4 shown in FIG. 10a, the N1-high Or alloy and the PT-10% alloy are mixed in a spiral pattern to form a striped pattern. The white part was made of PT-10% alloy, and the black part was made of N1-high Or alloy, and they were provided at three equal intervals in the circumferential direction of the center and tip of the electrode.

In order to achieve a good bond when making a sieve lug by Rede welding, the gap between the center electrode 1 and the thinning electrode 2 (
The numerical ranges of a), the wall thickness of the center electrode tip ('b), the insertion depth of the thinned precious metal electrode d), and the axial length c) of the center electrode tip, as well as C and d. As a result of manufacturing various actual plugs in the above embodiments, it was found that the interrelationship between the two is an important factor.

Figure 2 shows the value of the clearance (a) between the thinned noble metal electrode inserted and joined into the hole 3 at the tip of the center electrode and the tip of the center electrode, and the value of the molten/solidified portion 4. A correlation between the resulting zoro-holes and the incidence of air blow-off was shown. From FIG. 2, it was found that the larger the gap (a), the higher the incidence of blowholes 6 and air blowouts 7 shown in FIGS. 7a, 7b, 8a, and 8b. Therefore, the gap (a) during radar welding is 0.
．． It must be less than 0.005mm.

Figure 6 is a graph showing the relationship between the thickness of the center electrode tip ('b) when the gap (a) is 0.005 mm and the energy density of the radar during laser welding. In the graph, the solid line (I) indicates the limit of bonding.

In other words, it is impossible to bond the tip of the center electrode and the thinned noble metal electrode with the energy density below the solid line (I), and in order to bond, the energy density above the solid line (I) is It was necessary to use a lede with density.

The broken line (II) indicates the limit at which cracks 5 do not occur in the melted and solidified portion caused by Rede welding. That is, the broken line (I[
) using the upper energy density lede, the 6th a.
Cracks shown in Figures 6b and 6b occurred in the melted and solidified portion 4. Therefore, in order to prevent the occurrence of cracks, it is necessary to use a radar having an energy density below the broken line (n) for bonding. According to the graph in FIG. 6, the thickness (1) of the tip of the center electrode must be between 0.1 and 0.45 mm.

Figure 4 is a graph showing the influence of the length of the center electrode tip C) and the insertion depth of the thinned noble metal electrode d) on Rade welding and joining. Indicates the limit where holes and air blow out occur, and the vertical broken line indicates the limit where stable bonding strength can be obtained.
The horizontal dashed line indicates the practical length of the noble metal attenuated electrode.

In other words, in the area below the solid line in Figure 4, blowholes or air blow-outs occur in the melting/solidifying part, which is impossible, and in the area to the left of the vertical broken line, stable bonding strength cannot be ensured. This was not possible because it would be difficult, and it was not possible in the area above the horizontal broken line because the unused precious metal portion would increase and the cost would increase. Therefore, the length C) of the tip of the center electrode is 0.7 +++ m or more, and the insertion depth a) of the thinned noble metal electrode is 2≧d≧c + 0.05 mm.
must be satisfied.

The above conclusion was obtained from a plug using a noble metal thinned electrode with a diameter of 0.7 mm.
Various center electrodes with diameters ranging from 0°5 to 1.
As a result of making and investigating plugs with thinned noble metal electrodes having various diameters up to 5a, we found that the range of appropriate values for a, b, c, and d and the relationship between C and d are 2°5.
The same results were obtained with the combination of a 0.7 fi diameter center electrode and a 0.7 fi diameter narrowed electrode.

In addition to the material equivalent to Inconel 600 as the material for the center electrode 1, there are also spark plug materials including an N1-2% Or based alloy (also containing Mn)Si, which is an N1-low Or alloy, and a fine electrode made of a noble metal. PT as the material of 2,
pt - 20% engineering rs Pt - 20% engineering r - 5% Ni p
As a result of manufacturing an actual plug for pt -2Q%N1.50%Au -5Q%Pd and investigating the relationship between a, b, c, and d, a, b, and c are the same as in the above example.

It has been found that the range of d and the relationship between C and d are necessary when producing a defect-free plug by laser welding.

Therefore, in the plug according to the present invention, the material for the center electrode may be the conventional N1-low-Or alloy for spark plugs, and the material for the thinned noble metal electrode may be F4, Pt-
It may also be a metal alloy or an alloy such as Au--Pd. Furthermore, noble metals and alloys of noble metals to which pure black such as N1 is added as necessary may be used as the material for the thinned electrode.

The 70 lug of the present invention has a shape in which the thinned electrode 2 protrudes outward from the end of the center electrode tip 1a as shown in FIGS. 1 and 1Db, but as shown in FIG. It has been found through experiments that this method is applicable even when the ends of the thinned noble metal electrode and the tip of the center electrode are in the same plane.

The plug of the present invention having the above-mentioned structural requirements does not have the above-mentioned defects in the integrated melting and solidifying part for joining, and has a 1.10 in 50,000 defect.
It was actually confirmed that it can be used under operating conditions corresponding to the mileage covered by a Manshaku car.

[Brief explanation of drawings]

Fig. 1 is an enlarged cross-sectional view showing the arrangement of the center electrode tip and the thinned noble metal electrode before laser welding when manufacturing the plug of the present invention, and Fig. 2 shows the clearance during laser welding. Gap (a)
Figure 6 is a graph showing the relationship between the rate of occurrence of defects such as blowholes or air blow-outs, and Figure 6 shows the relationship between the thickness of the center electrode tip (,b) and the Radhe energy density when joining by welding without Radhe welding. Figure 4 shows the influence of the length of the center electrode tip during Rede welding.
FIG. 5 is a cross-sectional front view showing another embodiment of the plug of the present invention; and an explanatory diagram thereof; FIG. 7a Figures 8a and 8b are explanatory diagrams for laser welding, respectively.5 1 is the tip of the center electrode, 2 is the thinned noble metal electrode, and 3 is the tip of the center electrode. The holes provided are 4, a melted and solidified portion produced by laser welding, 5 a crank, 6 a plowhole, and 7 an air blowout. Agent Asamura Kōgai 4 people, 1 picture of Fang, 1 picture of Fang? 5 pictures? Fang 2 Diagram I 1 Town η Realan Mata o (mm) 1u Humidity b (mm) Fig. 4 1. ! 3 (=394 - Base 9♂Figure 'J-IQg-Figure O9B Figure

Claims (2)

[Claims] (1) A center electrode made of a nickel-based heat-resistant alloy and having a tip that serves as an ignition part, the tip having a hole extending in the axial direction; A thinned electrode made of a noble metal or noble metal alloy is inserted, and the center electrode and the thinned electrode are joined by a melted and solidified portion that extends through the gap between the tip and the thinned electrode. and the gap (a) is not more than 0.0051++++L,
The wall thickness (b) of the tip adjacent to the thinned electrode is 0.1-
The length in the axial direction of the tip part c) is 0.7 mvt or more, and the insertion depth d) of the thinned electrode inserted into the hole is c +0.05 mm≦d≦ 2.0
m++ spark plug for internal combustion engines. (2) A center electrode made of a nickel-based heat-resistant alloy and having a tip that serves as an ignition part, with a hole extending in the axial direction and between the circumferential inner surface of the size and the outer peripheral surface of the tip. providing the center electrode having a tip having a wall thickness (b) of 0.1-0.45 mm and an axial length C) of 0.7-2.0 mm; and providing a thinned electrode made of a noble metal or a noble metal alloy, and inserting the thinned electrode made of a noble metal or a noble metal alloy into the hole so that the insertion depth d) of the thinned electrode is c 10.05 m.
a step of making m≦d≦2.0, and making the gap (a) between the thinned electrode inserted into the hole and the hole 0.005 mm or less by mechanical means such as caulking. A step of irradiating a laser beam from a direction transverse to the axial direction to approximately the center of the axial length of the center electrode tip, and melting and integrating the laser irradiated center electrode tip and a part of the thinned electrode. At the point when the melted portion due to the laser beam irradiation does not reach the axial position of the thinning electrode, the laser beam irradiation is stopped and the melted portion is solidified, thereby causing the melted portion to become integrated with the center electrode tip and the thinning electrode. A method for manufacturing a spark plug for an internal combustion engine, comprising: forming a solidified portion; and providing at least one integrated melting/solidifying portion in the circumferential direction of a tip portion.