JPH06101362B2 - Method for manufacturing spark plug for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a spark plug used in an internal combustion engine, particularly a creeping discharge spark plug.

(Prior Art) Conventionally, as shown in FIG. 3, the ignition part of a spark plug used in an internal combustion engine, in particular, a creeping discharge type spark plug has a center electrode held in a shaft hole of an insulator (B). (A)
A collar portion (C) having an outer diameter larger than the diameter of the center electrode (A) is integrally formed at the tip of the core electrode (A) to expose the collar portion (C) at the tip of the shaft hole of the insulator (B), and Center electrode (A) at the step of
Is formed by expanding the end face of V into a V shape.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional one, a flange portion having an outer diameter larger than the diameter of the center electrode is integrally formed at the tip of the center electrode held by the insulator to form an insulator shaft. Since the flange portion is exposed at the tip of the hole and the flange portion is formed at the step portion of the shaft hole, the production efficiency is remarkably reduced and the cost is increased due to the two flange portions. . Furthermore, since the inside of the collar is in close contact with the insulator, high-temperature oxidative corrosion occurs due to the insulator being heated by long-term combustion,
There was a risk of damage to the internal combustion engine due to the ignition part falling off or the like. Therefore, the present invention is intended to improve the drawbacks of the above conventional ones, and to easily obtain a method for manufacturing a spark plug having a stable ignition part.

(Means for Solving the Problem) For that purpose, a center electrode having the flange portion and the upper flange portion of the center electrode are inserted from above so as to be locked to the step portion of the shaft hole of the insulator. Along with the terminal electrode, a resistor is sandwiched between the end of the shaft hole and the end of the center electrode by sandwiching a resistor between the center electrode in the shaft hole with conductive glass, and an insulator is formed by heat sealing together with the terminal electrode. After press-fitting an annular collar made of a spark-consumable material, which is a precious metal material having an outer diameter larger than the diameter of the center electrode tip, to the exposed end portion of the center electrode, the two joints are joined by laser welding. It forms the ignition part.

(Operation) With the above-described configuration, the firing portion arranged at the tip of the center electrode is press-fitted to the center electrode with the annular collar portion, and the joint portion is joined by laser welding. In addition, a deeper penetration can be obtained, and by sequentially moving the laser irradiation position, seam welding can be performed, stable welding can be performed, and a spark plug with high production efficiency can be easily obtained. It is also possible to obtain a long-life product by using a precious metal material, which is a spark-consumable material, as the material of the annular collar portion to be joined, and preventing its consumption.

(Example) The present invention will be further described with reference to an example shown in the drawings. (1)
Is a spark plug for an internal combustion engine according to an embodiment of the present invention. The spark plug (1) for an internal combustion engine has a shaft electrode (11) with a tip of a central electrode (3) having an upper collar portion (8) exposed. ), The resistor (14) is sandwiched by the conductive glass (13) above the center electrode (3) of the central electrode (3), and heat sealed together with the terminal electrode (15). An insulator (2), a metal shell (4) having a screw part (5), a firing part (6) arranged at the tip of the center electrode (3), and an outer electrode (7). The ignition part (6) arranged at the tip of the center electrode (3) is fixed after the center electrode (3) having the upper collar part (8) is fixed in the shaft hole (11) of the insulator (2). In the exposed portion of the tip of the center electrode (3), a ring-shaped spark-consumable material having an outer diameter larger than that of the center electrode (3), for example, a collar portion (9) made of a noble metal, is used as the center of the oxidation-resistant material. In order to prevent non-bonding due to bias during welding, the electrode (3) is fitted with a clearance of 0.05 mm or less by ultrasonic press-fitting, etc. (If this clearance is large, during laser welding, during spot movement of laser welding The collar portion (9) is attracted to the first elution portion, and a gap is created.) While rotating with the insulator (2), the collar portion (9) and the collar portion (9) are overlapped so that the beads generated by laser welding overlap. Circumference along the junction of the center electrode (3) Irradiating a YAG laser of a short wavelength which is excellent in absorption of light (1.06 .mu.m) to one in which bonding. In this collar portion (9), as shown in FIG. 2, when the wall thickness is T and the difference between the outer diameter and the inner diameter of the collar portion is A, by setting T ≦ 2A, laser welding can be performed. At this time, the peripheral portion (10) of the collar portion (9) is not melted even if the energy is increased to improve the penetration of the laser, and the discharge voltage due to the sagging of the peripheral portion (10) of the collar portion (9). Can be prevented from increasing. In addition, the wall thickness T is 1.0 m in order to complete the penetration during laser welding.
It is desirable that the thickness is m or less, and the depth of penetration is 2/3 or more of the collar thickness T.

(Effects of the Invention) As described above, in the shaft hole of the insulator, the center electrode having the upper collar portion is sealed by exposing the center electrode tip from the shaft hole tip,
After press fitting the annular collar part to the exposed end of the center electrode,
The ignition part can be stably and reliably formed on the center electrode by joining the connection part by laser welding, which improves the production efficiency and the durability of the spark plug itself and reduces the cost during production. It has an excellent effect that can be obtained.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a spark plug for an internal combustion engine which is an embodiment of the present invention, FIG. 2 is an enlarged sectional view of an essential part thereof, and FIG. 3 is a sectional view of an essential part of a conventional creeping discharge type spark plug. is there. DESCRIPTION OF SYMBOLS 1 ... Spark plug for internal combustion engine, 2 ... Insulator, 3 ... Center electrode, 4 ... Metal shell, 5 ... Screw part, 6 ... Ignition part, 7 ... Outer electrode, 8 ... Upper flange part, 9 ... Annular flange part, 10 ... Edge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 59-71280 (JP, A) JP 61-277185 (JP, A) JP 62-268080 (JP, A) JP 61- 230282 (JP, A)

Claims (1)

[Claims] 1. A center electrode having an upper flange portion, the upper flange portion of the center electrode being inserted from above so as to be locked to the step portion of the shaft hole of the insulator, and the center from the tip of the shaft hole. The tip of the electrode is exposed, a resistor is sandwiched between the center electrodes in the shaft hole by conductive glass, and an insulator is integrally formed with the terminal electrode by heat sealing to form the insulator of the center electrode of the insulator. On the exposed tip, press fit an annular collar made of a spark-consumable material made of precious metal with an outer diameter larger than the diameter of the center electrode tip.
A method for manufacturing a spark plug for an internal combustion engine, comprising forming a ignited portion by joining the joined portions of the both by laser welding.