JPH0668956A - Manufacture of spark plug - Google Patents

Abstract

PURPOSE:To prevent the generation of dislocation at the time of welding to obtain a center electrode having a regular shape by fitting a disc-shape electrode member in a hole part formed in the center electrode, and irradiating the laser to weld the electrode member to the center electrode. CONSTITUTION:The discharge side tip surface 14 of a center electrode 1 made of nickel alloy is formed with a hole part 15 having a diameter larger than the of a disc-shape electrode member 2. A small-diameter straight bar member 1A having a diameter larger than that of the hole part 15 and smaller than that of a barrel part 17 of the center electrode 1 and a comical part 1B for connecting the small- diameter straight bar member 1A to the barrel part 17 are formed by cutting. Furthermore, the bottom part of the member 2 is fitted in the hole part 15 so as to cover the discharge tip surface 14 of the center electrode 1 with the member 2. The member 2 is pushed by a jig 4, and the laser beam is irradiated to the bottom surface of the hole part 15 from the horizontal direction, rotating the electrode 1, to form a molten solidification alloy part 3, where the base material 11 and the component of the member 2 are dissolved each other, to weld the member 2 to the electrode 1. Generation of the blowhole is thereby restricted to obtain a center electrode having a regular shape without dislocation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a spark plug in which a tip of a center electrode is joined to an electrode member such as a noble metal having excellent spark consumption resistance.

[0002]

2. Description of the Related Art For a center electrode of a spark plug, a composite material in which a core of a good heat conductive metal such as copper (Cu) is embedded in a base material mainly composed of nickel (Ni), which is corrosion resistant and heat resistant, is used. A noble metal electrode member is welded to the tip for the purpose of reducing spark consumption and further improving durability. As its manufacturing method, by resistance welding applying heat and pressure, after welding the noble metal electrode member to the tip of the base material of the center electrode,
A method for manufacturing a spark plug in which the tip of a base material is cut to a small diameter has been proposed (Japanese Patent Publication No. 59-2152).

[0003]

However, when the noble metal electrode member is resistance-welded to the center electrode, the noble metal member is embedded in the base metal while being deformed so that its edge portion is rounded due to heating and pressure during resistance welding. Will be done. If the tip portion of the center electrode is then cut for the purpose of reducing the discharge voltage and improving ignitability, the precious metal member may also be cut, and expensive precious metal cannot be effectively used. In addition, since the edge of the buried noble metal member is rounded, when the Ni part of the base material is consumed by the use of the spark plug, the tip of the noble metal member is exposed after a short use time or running time, and the discharge voltage The rise became remarkable. The problem to be solved by the present invention is to weld a noble metal electrode member to the tip of the center electrode with a laser so that the noble metal electrode member is not buckled and the shape is adjusted, and the discharge voltage characteristic is stable and the spark plug is stable. To provide a manufacturing method of.

[0004]

According to a first aspect of the present invention, there is provided a spark plug manufacturing method, wherein a center electrode made of a nickel alloy has a small diameter portion at a discharge side end portion having a diameter smaller than that of a body portion thereof. A spark plug manufacturing method comprising a disc-shaped electrode member having excellent spark consumption resistance joined to the small-diameter portion, wherein (a) a diameter of the disc-shaped electrode member is larger than that of the disc-shaped electrode member at a discharge-side end face of the center electrode; A first step of forming a large hole portion of
(Ii) A second small straight rod portion having a diameter larger than that of the hole portion and smaller than that of the body portion of the center electrode, and a conical portion connecting the small diameter straight rod portion and the body portion. And (3) a third step of fitting the bottom of the disk-shaped electrode member into the hole and placing the disk-shaped electrode member so as to cover the discharge-side end surface of the disk-shaped electrode member, and (e) the circle. While pressing the plate-shaped electrode member in the longitudinal axis direction of the center electrode, and rotating the center electrode, from the horizontal direction to the bottom surface of the hole, a laser beam is irradiated to the outer peripheral wall side surface of the hole, Forming a melt-solidified alloy portion over substantially the entire circumference or the entire circumference of the outer peripheral wall,
And a fourth step of joining the disk-shaped electrode member to the center electrode.

The method of manufacturing a spark plug according to a second aspect of the present invention is characterized in that the order of the first step and the second step according to the above-mentioned first aspect is reversed.

According to a third aspect of the present invention, there is provided a spark plug manufacturing method, wherein the disc-shaped electrode member has a diameter D, a thickness T, and a hole diameter. Where A is the depth, B is the depth, d is the diameter of the small diameter straight rod portion, and L is the length, 0.5 mm ≦ D ≦ 1.5 mm, 0.3 mm ≦ T ≦
0.6 mm, 0.01 mm ≦ (A−D) ≦ 0.1 mm,
0.05 mm ≤ B ≤ 0.2 mm, 0.05 mm ≤ (d-
A) /2≦0.2 mm, 0.2 mm ≦ L ≦ 0.5 mm.

According to a fourth aspect of the present invention, the spark plug manufacturing method is characterized in that the disk-shaped electrode members according to the first, second and third aspects are made of a noble metal.

[0008]

According to the method of manufacturing a spark plug according to claim 1 or 2, welding is performed by welding a disk-shaped electrode member to the tip of the small-diameter straight rod portion of the center electrode that has been formed in advance by a laser beam. The center electrode of the spark plug having a stable shape can be obtained by suppressing the deformation of the disk-shaped electrode member at that time. Further, the shape of the center electrode after laser welding is stabilized by providing a guide hole for restricting the displacement between the base material and the disk-shaped electrode member at the discharge side tip of the small diameter straight rod portion of the center electrode. . In addition, by inserting a disk-shaped electrode member into the hole,
Welding of components having different absorptance of laser light (for example, a noble metal electrode member having a high reflectance and a Ni base material having a high absorptivity) by irradiating a laser beam through the outer peripheral wall of the guide hole made of an i alloy. Stable laser welding can be performed by relaxing the blow holes and variations in the penetration depth that tend to occur.

In the spark plug manufacturing method of the present invention, the shape of the disk-shaped electrode member, the shape of the small-diameter straight rod portion of the center electrode, and the welded portion between the disk-shaped electrode member and the small-diameter straight rod portion. Since the size and hole shape are specified, the center electrode and the disk-shaped electrode member are joined firmly, deformation of the center electrode does not easily occur, and there are variations in the depth of blow holes and penetration in the welded part. Laser welding can be performed with less.

In the invention of claim 4, since the disk-shaped electrode member is formed of a noble metal having high heat resistance and corrosion resistance, the center electrode of the spark plug is consumed by spark discharge for a long period of time. It is possible to obtain a spark plug having a long life.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention will be described below with reference to FIG. In the first step shown in FIG. 1A, the center electrode 1 is made of a Ni alloy containing silicon (Si), manganese (Mn), chromium (Cr), Inconel 600 containing Cr, iron (Fe), or the like. The collar portion 13 is formed in the step of integrally forming the core material 12 such as copper (Cu) or silver (Ag), which is a good heat conductive metal, on the disk-shaped base material 11 made of Ni alloy by plastic working. At some times, a press pin (not shown) for pressing the discharge-side tip surface 14 was provided with a convex portion and a hole portion 15 was provided by press working.

As shown in FIG. 1B, in the second step, a small diameter straight rod portion 1A and a conical portion 1B are formed at the discharge side tip by cutting.
In the step of providing and, it is essential that the diameter of the small diameter straight rod portion 1A is larger than the diameter of the hole portion 15 formed in the first step,
Further, the diameter is smaller than the diameter of the body portion 17 of the center electrode 1, and the conical portion 1B is a connecting portion for connecting the small diameter straight rod portion 1A and the body portion 17.

In the third step, the disc-shaped electrode member 2 is fitted into the hole 15, and the bottom portion 21 of the disc-shaped electrode member 2 is fitted into the hole 15, as shown in FIG. The center electrode 1 is placed so that the discharge tip of the center electrode 1 is covered with the disk-shaped electrode member 2.
As described above, the center electrode 1 includes the base material 11, the core material 12,
The disk-shaped electrode member 2 is a thin disk-shaped member made of gold (Au), platinum (Pt), Iridium (Ir),
Ir added rare earth oxide, or Pt-Ir
It is made of alloy material.

As shown in FIG. 1D, the fourth step is a step of laser welding while pressing the disk-shaped electrode member 2 with the pressing jig 4, and the welding of the disk-shaped electrode member 2 is a single heat quantity. The YAG (yttrium, aluminum, garnet) laser beam LB of 2.0 J is intermittently applied to the side surface of the outer peripheral wall 16 of the hole 15 from the horizontal direction to the bottom surface 18 of the hole 15. At this time, by rotating the center electrode 1, the laser beam LB is irradiated a plurality of times at an interval where the irradiation surfaces L1 overlap each other over substantially the entire circumference or the entire circumference of the outer peripheral wall 16 of the hole 15. By this welding,
On the irradiation surface L1, the melt-solidified alloy part 3 in which the components of the base material 11 and the components of the disk-shaped electrode member 2 are melted is generated. In addition,
The melt-solidified alloy portion 3 is formed over substantially the entire circumference or the entire circumference of the outer peripheral wall 16.

In this laser welding, it is difficult to evenly melt different members at the same time since the Ni base material 11 has a high laser light absorptivity and the noble metal has a low absorptivity. However, the disc-shaped electrode member 2 is welded to the base material 11 made of Ni.
Since welding is performed with the laser beam LB through the outer peripheral wall 16 made of, it is possible to suppress the occurrence of blow holes and the variation in the penetration depth due to the difference in properties of both members.

Further, in the melt-solidified alloy portion 3 produced by this laser welding, the components of the base material 11 and the components of the disk-shaped electrode member 2 are melted, so that the physical properties between the two, such as the coefficient of linear expansion. It has characteristics. Therefore, the spark plug having the melt-solidified alloy portion 3 has a characteristic that peeling or the like due to a difference in thermal expansion between the base material 11 and the disk-shaped electrode member 2 does not easily occur.

At the time of laser welding in the fourth step, as shown in FIG.
As shown in (b), the tip end surface 22 of the disk-shaped electrode member 2 is somewhat deformed in the longitudinal direction due to the extension of the small diameter straight rod portion 1A of the center electrode 1, but the pressing jig 4 applies a load of 1 kg. When added, the deformation can be suppressed as shown in FIG. 2A, and the disk-shaped electrode member 2 can be fixed so as not to move within the hole 15 during laser welding.

FIG. 3 is a graph showing the relationship between the pressing load and the deformation amount 1 of the disk-shaped electrode member 2 in the longitudinal direction. As can be seen from the graph, when the pressing load is 500 g or less, the deformation amount 1 is slightly recognized, and when the pressing load is 3000 g or more, the load is too large and the indentation of the presser 4 causes the tip end surface of the disk-shaped electrode member 2. 22 will remain. Therefore, the amount is preferably 600 g to 2500 g.

As shown in FIG. 4, the diameter of the disk-shaped electrode is D, the thickness is T, the diameter of the hole is A, the depth of the hole is B, and the diameter of the small diameter straight bar is. d, where L is the length of the small diameter straight rod portion, 0.5 mm ≦ D ≦ 1.5 mm, 0.3 mm ≦ T
≤0.6 mm, 0.01 mm ≤ (A-D) ≤0.1 m
m, 0.05 mm ≤ B ≤ 0.2 mm, 0.05 mm ≤
(D−A) /2≦0.2 mm, 0.2 mm ≦ L ≦ 0.5
mm.

FIG. 5 shows changes in the spark discharge gap increase amount when a durability test was conducted for 300 hours at a 2000 cc, 6-cylinder gasoline engine, 5000 rpm fully open. As can be seen from this graph, the diameter D of the disk-shaped electrode member 2
Is less than 0.5 mm, the spark discharge is concentrated and the gap increase amount is rapidly increased. That is, the smaller the diameter D of the disk-shaped electrode member 2 is, the easier it is to fly and the discharge voltage is lowered, but on the other hand, the concentration of spark discharge becomes remarkable, and the electrode consumption is accelerated. Also, the diameter D is 1.5
If it exceeds mm, the amount of increase in the gap hardly changes, but the spark discharge surface becomes large and the ignitability deteriorates. In addition, the amount of expensive precious metal member used increases, resulting in high cost.

FIG. 6 shows a cross-sectional portion of the center electrode 1 after manufacture when the thickness T of the disk-shaped electrode member 2 is smaller than 0.3 mm. Thus, the thickness T of the disk-shaped electrode member 2 is 0.3 m.
If the thickness T is less than m, the edge portion 23 of the tip end surface 21 of the disk-shaped electrode member 2 is melted and rounded when the laser beam LB is irradiated, and the discharge voltage becomes high. It should be 0.3 mm or more.
If the thickness T of the disk-shaped electrode member 2 is thicker than 0.6 mm, the amount of precious metal used increases and the cost increases, so the thickness T
Must be 0.6 mm or less.

The diameter A of the hole 15 is 0.85.
mm, the depth B is 0.15 mm, and is preferably 0.01 mm or more larger than the diameter D of the disk-shaped electrode member 2 described later.
At this time, if it is smaller than 0.01 mm, the disk-shaped electrode member 2 is not stably inserted into the hole portion 15, and if it is larger than 0.1 mm, the disk-shaped electrode member 2 is displaced from the axial center of the tip surface 14. It is easy and cannot serve as a guide for positioning the tip end surface 14 of the disk-shaped electrode member 2. Therefore, the hole portion 15 has a diameter of 0.05 to 0.
It is desirable that it is about 07 mm larger.

If the depth B of the hole 15 is too shallow, the disc electrode member 2 fitted in the hole 15 is likely to be displaced, and cannot serve as a positioning guide. If the depth B of the hole 15 is too deep, the life of the press pin will be shortened. Therefore, the depth B of the hole 15 is 0.05 mm to 0.2 mm, preferably 0.1 mm to 0.15 mm.

A dimension corresponding to the thickness of the outer peripheral wall 16 (D-
A) / 2 needs to be 0.05 mm or more and 0.2 mm or less, and if the thickness is less than 0.05 mm, the strength becomes insufficient and the hole 1
5 is easily deformed and mass productivity cannot be maintained. Also, 0.2
If the thickness is larger than mm, it is difficult to obtain a sufficient penetration depth up to the disk-shaped electrode member 2 by melting the base material 11 and the disk-shaped electrode member 2 with the laser beam LB, and variations in the penetration depth itself increase. .

The length L of the small-diameter straight rod portion 1A of the center electrode 1 is set to 0.2 mm or more when the disc-shaped electrode member 2 and the base material 11 are welded to each other. If the length is short, the heat generated during laser welding to the outer peripheral wall 16 will be changed from the base metal 11 to the core 12.
The disk-shaped electrode member 2 is insufficiently melted, and the components of the base material 11 and the disk-shaped electrode member 2 cannot be expected to be uniformly melted in the melt-solidified alloy part 3. Because. Further, the length L of the small diameter straight rod portion 1A is set to 0.5 mm or less because when the length L is longer than 0.5 mm, the base material 11 that is more likely to be changed by heat than the disc-shaped electrode member 2 is This is because the heat of the laser beam LB is absorbed too much, and blowholes and cracks are likely to occur in the melt-solidified alloy portion 3.

The discoid electrode member 2 of the present invention includes
Au, Pt, Ir, or the like was used as a material having a higher spark wear resistance than the Ni alloy base material 11, but an alloy such as ruthenium (Ru), tungsten (W), or chromium (Cr) was used. Is also good.

In this embodiment, after the hole 15 is formed in the discharge-side tip surface 14 of the center electrode 1 in the first step, the small diameter straight rod portion 1A and the cone are formed in the center electrode 1 in the second step. Part 1B
Was cut. However, the small diameter straight rod portion 1A and the conical portion 1B may be cut in the first step, and the hole portion 15 may be provided in the discharge-side tip surface 14 in the second step. Then, the hole 15, the small diameter straight rod portion 1A, and the conical portion 1B may be formed by cutting at the same time, and the first step and the second step may be one step.

[0028]

According to the method of manufacturing a spark plug of the present invention, since the center electrode and the disc-shaped electrode member are joined only by laser welding, the disc-shaped electrode member is free from buckling deformation. It is possible to obtain a center electrode of a regular spark plug. Further, by providing a hole, positional deviation that occurs during welding between the electrode member and the center electrode is suppressed, and by inputting the heat of the laser beam through the outer peripheral wall made of Ni, a blow hole in the melt-solidified alloy part is formed. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for manufacturing a spark plug according to the present invention.

FIG. 2 is a sectional view of the center electrode tip of the spark plug of the present invention and a sectional view of the center electrode tip when the welding is performed without using a presser.

FIG. 3 is a graph showing the relationship between the pressing load of the electrode tip during laser welding and the amount of deformation of the electrode.

FIG. 4 is a cross-sectional view of an electrode tip before welding by the spark plug manufacturing method of the present invention.

FIG. 5 is a graph showing the relationship between the diameter of the electrode member of the spark plug of the present invention and the increase amount of the spark discharge gap.

FIG. 6 is a cross-sectional view of the center electrode tip of a spark plug when manufactured with a thin electrode member.

[Explanation of symbols]

 1 Center electrode 2 Disc-shaped electrode member 3 Melt-solidified alloy part 4 Holding jig 14 Discharge side tip surface 15 Hole part 16 Outer peripheral wall 17 Center electrode body part 18 Bottom part of hole 21 Bottom part of disk-shaped electrode member 1A Diameter Small straight rod 1B cone LB laser beam

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Sasa, No. 14-18 Takatsuji-cho, Mizuho-ku, Nagoya

Claims (4)

[Claims] 1. A center electrode made of a nickel alloy has a small diameter portion having a diameter smaller than that of a body portion at an end portion on a discharge side, and a disc-shaped electrode member excellent in spark wear resistance is joined to the small diameter portion. In the method for manufacturing a spark plug comprising: (a) a first step of forming a hole portion having a diameter larger than that of the disk-shaped electrode member on the discharge-side end surface of the center electrode; A second step of forming a small diameter straight rod portion having a diameter larger than the diameter and smaller than the body portion of the center electrode, and a conical portion connecting the small diameter straight rod portion and the body portion; The third step of fitting the bottom of the disk-shaped electrode member into the hole and placing the disk-shaped electrode member on the discharge-side tip surface so as to cover the disk-shaped electrode member, and (e) centering the disk-shaped electrode member. While pressing in the longitudinal axis direction of the electrode and rotating the center electrode, move it horizontally with respect to the bottom surface of the hole. Irradiating a laser beam on the side surface of the outer peripheral wall of the hole to form a melt-solidified alloy portion over substantially the entire circumference or the entire circumference of the outer peripheral wall, and joining the disk-shaped electrode member to the center electrode A method of manufacturing a spark plug, comprising the steps of: 2. A method of manufacturing a spark plug, wherein the order of the first step and the second step according to claim 1 is reversed. 3. The disk-shaped electrode member according to claim 1 has a diameter D, a thickness T, a hole diameter A, a depth B, and a small diameter straight rod portion. When the diameter is d and the length is L, 0.5 mm ≦ D ≦ 1.5 mm, 0.3 mm ≦ T ≦ 0.6
mm, 0.01 mm ≤ (A-D) ≤ 0.1 mm, 0.05 mm
≦ B ≦ 0.2 mm, 0.05 mm ≦ (d−A) /2≦0.2 mm, 0.2 m
A method of manufacturing a spark plug, wherein m ≦ L ≦ 0.5 mm. 4. A method of manufacturing a spark plug, wherein the disk-shaped electrode member according to claim 1, claim 2 or claim 3 is made of a noble metal.