JPH04329286A - Manufacture of spark plug - Google Patents

Abstract

PURPOSE:To accurately weld a thermal stress relaxing layer section and a discharge layer section to the center electrode and the ground electrode of a spark plug. CONSTITUTION:A long type complex wire material 1 which has the thermal stress relaxing layer section 11 and the discharge layer section 12 closely laminated is previously manufactured. In welding, the complex wire material 1 is cut into a preset-length chip 10 just before welding, and then the chip 10 is welded to the discharge plane section 31 of a center electrode 3 and/or the discharge plane section of a ground electrode.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a spark plug for internal combustion engines, and in particular a spark plug equipped with a tip having a noble metal discharge layer portion and a thermal stress relaxation layer portion in order to improve the durability of the ignition portion. Relating to a manufacturing method.

0002

2. Description of the Related Art Conventionally, in order to improve the durability of spark plugs for internal combustion engines, a tip made mainly of noble metal is provided in the ignition part where a center electrode and a ground electrode face each other. The noble metal tip and the electrode base material have different coefficients of linear expansion, and large thermal stress is exerted on the bonding interface due to high temperatures under high loads and significant changes in electrode temperature such as during sudden starts and braking. . Therefore, as a means to reduce such thermal stress, a structure has been proposed in which a discharge layer section and a thermal stress relaxation layer section are provided on the discharge surface section of the electrode. The thermal stress relaxation layer has a linear expansion coefficient between that of the electrode base material and the discharge layer. For example, JP-A-61-1
Publication No. 3588 discloses a method of cutting a noble metal plate into strips and cladding them on a ground electrode. However, in this case, the application of the precious metal plate is limited to the ground electrode, and since the composite material is used even in unnecessary places, a large amount of precious metal is required and expensive. Also, Tokuhei 2-54
No. 636 discloses a method of welding a discharge layer of a noble metal plate and a thermal stress relaxation layer of a high-temperature brazing material to an electrode base material.

0003

[Problem to be Solved] However, the method disclosed in the latter publication may cause welding misalignment between the two members when welding them together. Further, prior to welding, a recess is previously formed in the discharge surface portion, and then the thermal stress relaxation layer member, followed by the discharge layer member, is placed in the recess and welding is performed. Therefore, it is necessary that the diameter of the recess previously provided in the base material and the diameter of both members to be placed in the recess are extremely close to each other.

[0004] Therefore, the insertion of both members into the recess requires highly accurate positioning, which also requires expensive equipment and adjustment work, as well as precision of the inserted tip. Furthermore, it is necessary to control the depth dimension of the base metal recess, which has the disadvantage of deteriorating productivity. In view of these problems, the present invention provides a spark plug in which the thermal stress relaxation layer and the discharge layer can be applied to either the center electrode or the ground electrode, and which also ensures welding accuracy and is excellent in productivity. The present invention aims to provide a method for manufacturing.

[0005]

[Means for Solving the Problems] In the present invention, a center electrode and a ground electrode face each other to form a spark gap, and a discharge surface portion of at least one of the electrodes is provided with a discharge layer portion, a linear expansion coefficient of the discharge layer portion, and a spark gap. In the method for manufacturing a spark plug for an internal combustion engine, a spark plug for an internal combustion engine is manufactured by welding a chip comprising a thermal stress relieving layer having a linear expansion coefficient between that of the electrode and a thermal stress relieving layer through the thermal stress relieving layer. The chip is formed in advance into a long composite wire by laminating and bonding a discharge layer portion and a thermal stress relaxation layer portion, and the composite wire is cut into chips of a predetermined length immediately before welding. A method of manufacturing a spark plug is characterized in that the spark plug is welded to the discharge surface portion. The most noteworthy feature of the present invention is that a long composite wire rod is prepared in advance by laminating and bonding a discharge layer portion and a thermal stress relaxation layer portion, and immediately before welding, this is cut into chips. This involves welding the chip to the discharge surface. Immediately before welding refers to the time immediately before the tip is welded to the discharge surface, in other words, the composite wire is cut into chips and then the chips are welded to the discharge surface.

[0006] Furthermore, the above-mentioned composite wire rod is a band-shaped wire rod having a constant width (for example, 0.8 to 1.7 mm). The composite wire is made by joining a discharge layer portion with a thickness of 0.2 to 0.4 mm and a thermal stress relaxation layer portion with a thickness of 0.1 to 0.2 mm. Methods for joining the two include cladding by hot press bonding, brazing, and welding. Additionally, the chip cut immediately before welding is usually rectangular or cubic.

[0007] Furthermore, when welding the chip, it is also possible to arrange a guide for positioning the chip on the discharge surface, place the chip on the guide, and perform welding. The guide shall be removed after chip welding. This makes it possible to completely prevent the welding position of the tip from shifting. Also,
Composite wire rods can be made to have a trapezoidal cross-sectional shape in the direction perpendicular to the longitudinal direction, or to provide an uneven surface on either the discharge layer portion or the thermal stress relaxation layer portion, to reduce thermal stress between the discharge layer portion and the thermal stress relaxation layer portion. It is preferable to provide an identification mark to distinguish it from the relaxation layer section. Thereby, both parts can be easily distinguished and it can be confirmed that the discharge layer part is welded to the discharge surface part via the thermal stress relaxation layer part. Furthermore, during welding, there is no possibility of accidentally welding the discharge layer side to the discharge surface section.

[0008] Furthermore, the material of the discharge layer section is Pt.
(platinum), or Pt added with one or more of rare earth elements such as Ir (iridium), Rh (rhodium), W (tungsten), Ag (silver), Co (cobalt), Y (yttrium), etc. Preferably, alloys are used. In addition, for the thermal stress relaxation layer, one or more of Ni (nickel), Ag, Pd (palladium), etc. is added to Pt,
It is preferable that the linear expansion coefficient is an intermediate value between that of the electrode base material and the discharge layer portion. Additionally, the tip shall be welded to the center electrode, the ground electrode, or both. Further, the welding between the thermal stress relaxation layer portion and the discharge surface portion of the chip is preferably performed by electric welding using a welding electrode rod.

[0009]

[Operations and Effects] In the present invention, the discharge layer portion and the thermal stress relaxation layer portion are laminated and bonded in advance and are formed into a long composite wire. Then, when welding the discharge layer portion and the thermal stress relaxation layer portion to the discharge surface portion of the spark plug, the composite wire is cut into a predetermined size in the longitudinal direction immediately before welding. The cut chips are then welded to the discharge surface.

[0010] Therefore, the chip is welded onto the discharge surface part as a laminate of the discharge layer part and the thermal stress relaxation layer part at once, so that welding displacement does not occur and the welding operation is easy. Further, the chip can be cut to a size corresponding to the width required on the discharge surface of either the center electrode or the ground electrode, so that no waste material is produced in the composite wire, and no waste is generated. In addition, these factors also improve productivity and reduce costs. As described above, according to the present invention, the discharge layer portion and the thermal stress relaxation layer portion can be bonded to either the center electrode or the ground electrode, and the spark welding can be performed with high welding accuracy and excellent productivity. A method for manufacturing a plug can be provided.

[0011]

Embodiments Embodiment 1 A method for manufacturing a spark plug according to an embodiment of the present invention will be explained with reference to FIGS. 1 to 3. First, a spark plug obtained by the manufacturing method of the present invention will be described with reference to FIGS. 2 and 3. The spark plug in this example is
As shown in FIG. 3, it consists of a center electrode 3 inserted into an insulator 55 and a ground electrode 4 attached below the housing 53, and each discharge surface of the center electrode 3 and the ground electrode 4 is A chip 10 is welded thereto.

The hanging 53 has a cylindrical shape and has a threaded portion 530 at its lower end, and further has the ground electrode 4 at its lower end.
are joined. The insulator 55 is made of high-purity alumina, and is caulked and fixed to the inner hole of the housing 53 via a ring-shaped airtight packing 51 and a ring 52. The center electrode 3 is made of copper on the inside and Ni-C with excellent heat resistance on the outside.
It is made of r alloy, Ni-Cr-Fe alloy, etc. In addition, a terminal 56 is provided at the upper part of the shaft hole 551 of the cylindrical insulator 55.
A center shaft 56 having a diameter of 1 is inserted, is heated and fused with a conductive glass sealing material 54, and is integrated with the center electrode 3.

Furthermore, the ground electrode 4 is made of the same material as the outside of the center electrode 3. Further, a spark gap is formed between the upper surface of the ground electrode 4 and the lower surface of the center electrode 3. As shown in an enlarged view in FIG. 2, chips 10 are welded to the discharge surface portion 31 of the center electrode 3 and the discharge surface portion 41 of the ground electrode 4, respectively. The chip 10 is a laminated bonding material of a discharge layer section 12 and a thermal stress relaxation layer section 11, and the thermal stress relaxation layer section 11 is welded to the discharge surface sections 31 and 41.

Next, regarding the welding method of the tip 10,
This will be explained using FIG. First, the chip 10 is in the shape of a long composite wire 1 until it is cut, and is wound into a coil as shown in the figure. Further, the cutting device for cutting the composite wire 1 has a cutter stand 24 and a cutter 26, and also has a rotating mechanism for supplying the tip 10 on the cutter stand 24 to the upper surface of the center electrode 3 to be welded. It has an arm 21. The rotating arm 21 has a suction type suction portion 22 at its tip. In addition, in the welded part,
It has a fixture 28 for fixing the center electrode 3 and a welding electrode rod 27. Further, the composite wire 1 is wound so that the thermal stress relaxation layer 11 is on the outside and the discharge layer 12 is on the inside.

Further, the composite wire 1 has a discharge layer portion 1 with a thickness of 0.4 mm on a thermal stress relaxation layer portion 11 with a thickness of 0.2 mm.
2 are joined by hot press bonding, and both widths are 1.
It is 5mm. Next, when welding the tip 10 onto the discharge surface portion 31 of the center electrode 3, first the center electrode 3 is
It is fixed by a fixture 28. Next, the tip of the wound composite wire 1 is pushed forward by the roller 16 beyond the cutter 26 of the cutting device 2. This extrusion length is the length of the tip 10 to be welded onto the discharge surface portion 31 (for example, 1.
5mm). Therefore, the chip 10 is a rectangular or square piece, and when welded to the discharge surface portion 31 of the center electrode 3, its four corners are located inside the outer periphery of the center electrode 3, which has a circular cross section.

Next, the chip 10 cut as described above is
is attracted by the attraction section 22 and placed on the discharge surface section 31 of the center electrode 3 by the arm 21. Then, after returning the arm 21 to its original position, the welding electrode rod 27 is lowered to the top of the tip 10 and brought into contact with it, and electricity is applied. Thereby, the tip 10 is welded to the center electrode 3. In this example, a Pt-Ni alloy is used as the thermal stress relaxation layer section 11.
A Pt-Ir alloy was used as the discharge layer portion 12, and welding was performed by resistance welding. As mentioned above, when welding the tip 10, the wound composite wire 1 is sequentially pushed forward, cut by the cutter 26 to form the tip 10, and the tip 10 is connected to the center electrode 3 or the ground electrode by the welding electrode rod 27. Weld to 4.

Therefore, according to this example, in the chip 10, the thermal stress relaxation layer section 11 and the discharge layer section 12 are supplied as a laminate onto the discharge surface section 31 and welded at once. Therefore, the welding deviation described above does not occur and the welding accuracy is high. In addition, welding operations are easy. Further, since the chip is cut to the required width on the discharge surface of either the center electrode or the ground electrode, no waste material is generated in the composite wire 1. These also improve productivity and reduce costs. In addition, in this example, the composite wire 1 is wound so that the thermal stress relaxation layer section 11 is on the outside and the discharge layer section 12 is on the inside, and this is fed to the cutting device 2, and the cut chips 10 are left as they are. It is supplied onto the center electrode 3 by the arm. Therefore, the thermal stress relaxation layer portion 11 is always welded onto the center electrode 3, and welding errors do not occur.

Embodiment 2 This embodiment shows a method of processing the electrode base material of the center electrode 3 to which the tip 10 is welded in Embodiment 1, as shown in FIGS. 4 and 5. That is, FIG. 4 shows the tip 10 and the center electrode 3 welded in Example 1. In this state, the center electrode 3 is placed at the lower side of the chip 10.
It has a cut section 301 of. In this example, as shown in FIG. 5, after welding, the above-mentioned section 301 of the center electrode 3
is removed and a tapered surface 30 is formed. Furthermore, in the above processing, the tip 10, which was square during welding, is processed into a cylindrical shape. According to this example, the same effects as in the first embodiment can be obtained. Further, by the above-described processing, a center electrode having only the cylindrical tip 10 at the tip can be manufactured.

Example 3 In this example, as shown in FIGS. 6 and 7, in Example 1,
A guide 5 is used to position the tip 10 when welding the tip 10. As shown in FIGS. 6A (plan view) and B (cross-sectional view), the guide 5 includes a top plate 501 having a rectangular guide hole 50 for inserting the chip above, and a center electrode 3. It consists of a cylindrical body 51 having an inner diameter larger than the outer diameter. And when welding,
As shown in FIG. 6B, the discharge surface portion 31 of the chip 3 is covered with the guide 5, and then the chip 10 is placed in the guide hole 50.
Insert the lower part of. Thereafter, as shown in FIG. 7, the welding electrode rod 27 is lowered and energized as in the first embodiment. After welding, the guide 5 is removed. According to this example, the chip 10 is
Welding can be performed accurately at a predetermined position on the discharge surface portion 31 of the center electrode 3. Further, the same effects as in the first embodiment can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a method for manufacturing a spark plug in Example 1.

FIG. 2 is an enlarged cross-sectional view of the main parts of the spark plug in Example 1.

FIG. 3 is a partial cross-sectional view of the spark plug of Example 1.

FIG. 4 is an explanatory diagram after chip welding in Example 2.

FIG. 5 is an explanatory diagram of a center electrode and a chip after processing in Example 2.

FIG. 6 is an explanatory diagram before the tip welding operation in Example 3.

FIG. 7 is an explanatory diagram during tip welding in Example 3.

[Explanation of symbols]

1. ．． ．． Composite wire rod, 10. ．． ．． Chip, 11. ．． ．． Thermal stress relaxation layer portion, 12. ．． ．． discharge layer portion, 2. ．． ．． cutting equipment,
3. ．． ．． center electrode, 4. ．． ．． Ground electrode, 5. ．． ．． guide,

Claims (3)

[Claims] Claim 1: A center electrode and a ground electrode face each other to form a spark gap, and a discharge surface of at least one of the electrodes has a discharge layer, a linear expansion coefficient of the discharge layer, and a linear expansion coefficient of the electrode. A method for manufacturing a spark plug for an internal combustion engine by welding a chip comprising a thermal stress relieving layer having a linear expansion coefficient between 1 and 2 through the thermal stress relieving layer. A long composite wire is formed by laminating and bonding the layer portion and the thermal stress relaxation layer portion, and the composite wire is cut into chips of a predetermined length immediately before welding, and then the chips are welded to the discharge surface portion. A method of manufacturing a spark plug characterized by: [Claim 2] According to claim 1, a guide for positioning the chip is provided on the discharge surface portion to which the chip is to be welded, the chip is placed on the guide and welding is performed, and the guide is then removed. A method for manufacturing a spark plug characterized by: [Claim 3] The material of the composite wire is such that the discharge layer portion is P.
It is a Pt alloy in which one or more of Ir, Rh, W, Ag, Co, and Y is added to Pt or Pt, and the thermal stress relaxation layer is made by adding one or more of Ni, Ag, and Pd to Pt. A method for manufacturing a spark plug, characterized in that the material has a coefficient of linear expansion intermediate between those of the electrode base material and the discharge layer.