JP2008034393A - Spark plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spark plug and its manufacturing method capable of surely ensuring a joint strength between an electrode member and a chip. <P>SOLUTION: A chip 1 is manufactured, in a first process S10, comprising a flange section 1b, and a projecting section 1a protruding from one surface 1c of the flange section 1b. The other surface 1d of the flange section 1b is, in a second process S20, temporarily stopped to a discharge gap side joint surface 32, 42 of an electrode matrix of at least one of a central electrode 30 and an earthed electrode 40. The flange 1b is, in a third process S30, welded to the joint surface 32, 42 in such a manner that a molten portion 3 exits, on the other surface 1d, inside an intersection between an imaginary extension of a side surface of the projecting section 1a and the other surface 1d of the flange section 1b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a spark plug and a manufacturing method thereof.

  Conventionally, the spark plug of patent document 1 is known. The spark plug includes a cylindrical metal shell, and a cylindrical insulator extending in the axial direction of the metal shell and having both ends projecting from both ends of the metal shell is fixed in the metal shell. ing. The central electrode extends in the axial direction of the metal shell, the tip of the center electrode protrudes from the tip of the insulator, and the rear end of the center electrode is fixed in the insulator. On the other hand, one end of the ground electrode is fixed to the metal shell, and a discharge gap is formed between the other end of the ground electrode and the center electrode. The center electrode and the ground electrode are each made of an electrode base material made of Ni alloy or the like such as Inconel (registered trademark) 600 and a chip made of a spark consumable material such as Pt alloy containing Ir at a position forming the discharge gap side. Have.

  The center electrode of this spark plug is manufactured as follows. First, a chip having a flange portion and a convex portion protruding from one surface of the flange portion is manufactured. Then, the other surface opposite to the convex portion of the tip is laser welded to the joint surface on the discharge gap side of the electrode base material to form a center electrode. At this time, a melted portion is formed between the flange portion of the chip and the electrode base material.

  In this spark plug, since the diameter of the flange portion of the tip is larger than the diameter of the convex portion, the melted portion is formed in a wider range than a general cylindrical tip. Moreover, since a fusion | melting part is formed between a flange part and an electrode base material, the diameter reduction of the welding part by scattering of the electrode base material which arises by laser welding can be prevented. Thus, with this spark plug, the bonding strength between the electrode base material and the tip can be ensured.

JP 2001-244042 A

  However, in the above-described conventional spark plug, since the melted portion is merely a certain distance or more in the inner direction from the outer periphery of the flange portion, the bonding strength between the electrode base material and the tip is ensured depending on the shape of the tip. Can be difficult. That is, for example, when a chip composed of a flange portion and a columnar convex portion is adopted and the diameter of the convex portion is relatively large, the melted portion is formed only near the outer periphery of the flange portion, and in the vicinity of the center portion of the flange portion. In this case, a portion where no melted portion exists is present in a wide range. Therefore, in such a case, the bonding strength between the electrode base material and the tip cannot be sufficiently ensured, and it becomes difficult to maintain the durability of the spark plug for a long period of time.

  The present invention has been made in view of the above-described conventional situation, and it is a problem to be solved to provide a spark plug capable of reliably ensuring the bonding strength between an electrode base material and a chip and a manufacturing method thereof. It is said.

  The spark plug manufacturing method of the present invention includes a cylindrical metal shell, and a cylindrical metal shell that extends in the axial direction of the metal shell and is fixed in the metal shell with both ends projecting from both ends of the metal shell. An insulator, a central electrode that extends in the axial direction of the metal shell, has a tip protruded from the tip of the insulator, and a rear end is fixed in the insulator; one end is fixed to the metal shell; A ground electrode that forms a discharge gap between the end and the center electrode, and at least one of the center electrode and the ground electrode is formed from a spark consumable material at a position where the discharge gap is formed with the electrode base material, respectively. In a method for manufacturing a spark plug having a chip,

As the chip, a first step of manufacturing a flange portion and a convex portion protruding from one surface of the flange portion;
A second step of temporarily fixing the other surface of the flange portion opposite to the convex portion to the joint surface on the discharge gap side of the electrode base material in at least one of the center electrode and the ground electrode by resistance welding;
The melted portion exists in the electrode base material and the chip so as to pass through the inside of the other surface from the intersection of the virtual extension line of the bus line constituting the side surface of the convex portion and the other surface of the flange portion. And a third step of welding the flange portion to the joint surface by laser.

  In the spark plug manufacturing method of the present invention, in the first step, a chip including a flange portion and a convex portion protruding from one surface of the flange portion is manufactured. Next, in the second step, the other surface of the flange portion is temporarily fixed to the bonding surface on the discharge gap side of the electrode base material in at least one of the center electrode and the ground electrode by resistance welding. In the third step, the flange is welded to the joint surface of the electrode base material by a laser in the third step. At this time, welding is performed so that a melted portion exists in the electrode base material and the tip through the inner side on the other surface from the intersection of the virtual extension line of the bus bar constituting the side surface of the convex portion and the other surface of the flange portion. . Here, the generatrix refers to the center of the convex portion of the chip extending on the side surface of the convex portion when the convex portion of the chip is cylindrical, prismatic, conical, pyramidal, truncated cone or truncated pyramid. A line that can form the same plane as the axis. Thereby, it can prevent that the part which does not have a fusion | melting part exists widely in the center part vicinity of a flange part. Therefore, the flange portion is reliably bonded to the bonding surface of the electrode base material.

  Therefore, according to the spark plug manufacturing method of the present invention, the bonding strength between the electrode base material and the chip can be reliably ensured.

  In this spark plug manufacturing method, the joining surface can be on the discharge gap side of the electrode base material in the ground electrode. That is, this manufacturing method can be used not only when the tip is welded to the electrode base material in the center electrode, but also when the tip is welded to the electrode base material in the ground electrode that must be welded more firmly.

  In this spark plug manufacturing method, the maximum distance between the intersections of the virtual extension line of the bus bar constituting the side surface of the convex portion and the other surface of the flange portion is D, and the inner side on the other surface is passed by D / 5 or more from the intersection point. It is preferable that a melting part exists. This is because, according to the test results of the inventors, the flange portion is reliably bonded to the bonding surface of the electrode base material.

  In this spark plug manufacturing method, in the first step, a plate-shaped intermediate member having an intermediate melting point or linear expansion coefficient between the electrode base material and the chip and having a surface larger than the other surface of the flange portion is manufactured. In the two steps, it is preferable to provide an intermediate member between the bonding surface and the chip. In this case, the intermediate member, the electrode base material, and the tip can be easily combined with each other by laser irradiation, and the thermal stress difference generated between the intermediate member, the electrode base material, and the tip can be reduced. For this reason, peeling hardly occurs between the electrode base material and the intermediate member or between the intermediate member and the chip.

  In the second step, it is preferable that the intermediate member is temporarily fixed to the joint surface by resistance welding, and then the other surface of the flange portion is temporarily fixed to the intermediate member by resistance welding. As a result, the intermediate member and the tip can be prevented from moving during laser welding, and the electrode base material and the tip can be reliably welded.

  In this spark plug manufacturing method, when the joining surface is on the discharge gap side of the electrode base material in the ground electrode, the tip is used as the ground electrode in a state where the ground electrode is bent in the direction opposite to the one end side of the center electrode. It is preferable to weld. Thereby, since the restriction | limiting of a laser irradiation angle can be avoided, a chip | tip can be welded to a ground electrode with an optimal laser irradiation angle.

  The spark plug of the present invention includes a cylindrical metal shell and a cylindrical insulating member that extends in the axial direction of the metal shell, and that is fixed in the metal shell with both ends protruding from both ends of the metal shell. A body electrode, a central electrode extending in the axial direction of the metal shell, the tip protruding from the tip of the insulator, and a rear end fixed to the insulator, and one end fixed to the metal shell And a ground electrode that forms a discharge gap between the center electrode and the center electrode, and at least one of the center electrode and the ground electrode is composed of an electrode base material and a spark-resistant consumable material at a position where the discharge gap is formed. In a spark plug having a tip,

  The tip includes a flange portion and a convex portion protruding from one surface of the flange portion, and at least one of the center electrode and the ground electrode has a flange on a joint surface on the discharge gap side of the electrode base material. The other surface of the portion opposite to the convex portion is temporarily fixed by resistance welding, and on the other surface from the intersection of the virtual extension line of the bus forming the side surface of the convex portion and the other surface of the flange portion The flange portion is welded by a laser so that a melted portion exists in the electrode base material and the tip through the inside of the electrode.

  In the spark plug of the present invention, the tip is composed of a flange portion and a convex portion, and by laser welding, the inner side on the other surface from the intersection of the virtual extension line of the bus bar constituting the side surface of the convex portion and the other surface of the flange portion. As described above, a melted portion exists in the electrode base material and the tip. Therefore, there is no wide area in the vicinity of the center portion of the flange portion where no melted portion exists. In this way, since the flange portion is securely joined to the joining surface of the electrode base material, the joining strength between the electrode base material and the tip can be secured, and the durability of the spark plug can be maintained over a long period of time. It becomes.

  The melting part preferably contains 20 to 80% by mass of the components of the chip. According to the test results of the inventors, when the component of the tip in the melted portion is less than 20% by mass or more than 80% by mass, the electrode base material and the tip are difficult to be combined, and are generated between the electrode base material and the tip. Since the thermal stress difference is large, there is a possibility that the bonding strength between the electrode base material and the chip cannot be ensured. On the other hand, if the melted portion contains 20 to 80% by mass of the component of the tip, the electrode base material and the tip are easily compatible, and the difference in thermal stress generated between the electrode base material and the tip is small. It is easy to ensure the bonding strength between the material and the chip. In particular, it is more preferable that the melting part contains 30 to 60% by mass of the chip components. In this case, the bonding strength between the electrode base material and the tip can be reliably ensured.

  Hereinafter, embodiments and tests embodying the spark plug of the present invention and the manufacturing method thereof will be described with reference to FIGS.

(Embodiment)
First, as shown in FIG. 1, in a first step S10, 1 to 20 mass% of Rh, 1 to 10 wt% of Pt, any at least 5 wt% of Y ₂ O ₃ and Ni1~20 wt% Or a chip 1 made of a spark consumable material made of a Pt alloy containing at least one of 20-60 mass% Rh, 10-40 mass% Ir, and 1-20 mass% Ni. To do. When the chip 1 is attached to both the center electrode 30 and the ground electrode 40 (see FIG. 9), the chip 1 made of the same material may be used, or the chip 1 made of a different material may be used. As shown in FIG. 2, the chip 1 includes a flange portion 1b and a convex portion 1a protruding from one surface 1c of the flange portion 1b. The flange portion 1b has a disk shape with a diameter L = 1 (mm) and a thickness of 0.2 (mm), and the convex portion 1a has a diameter R = 0.6 (mm) and a thickness of 0.5 (mm). It has a cylindrical shape.

  Further, as shown in FIG. 3, an intermediate member 2 made of an Ir alloy containing 40% by mass of Ni is manufactured. The intermediate member 2 has a disk shape with a diameter L = 1.2 (mm) and a thickness of 0.2 (mm).

  In the second step S20 shown in FIG. 1, the intermediate member 2 is temporarily welded to the center electrode 30 by resistance welding as shown in FIG. The center electrode 30 has a diameter of 2.5 (mm) using a Ni alloy of Inconel (registered trademark) 600 as an electrode base material. At that time, the intermediate member 2 is first disposed on the joint surface 32 of the center electrode 30 on the discharge gap side. Then, the first electric resistance welder 50 is provided on the intermediate member 2, and a predetermined current is applied under a predetermined pressure, whereby the intermediate member 2 is resistance-welded to the center electrode 30 and temporarily fixed.

  Subsequently, as shown in FIG. 4, the flange portion 1 b of the chip 1 is disposed on the intermediate member 2 temporarily fixed to the center electrode 30. Then, the second electric resistance welder 60 is provided on the one surface 1c of the flange portion 1b, and a predetermined current is applied under a predetermined pressure. The second electric resistance welder 60 has a structure that does not contact the tip surface of the tip 1. This prevents the tip surface of the tip 1 from being affected by resistance welding. And the other surface 1d of the flange part 1b is temporarily fixed to the intermediate member 2 by resistance welding. Thus, the intermediate member 2 and the chip 1 are temporarily fixed to the center electrode 30.

  Next, in the third step S <b> 30 shown in FIG. 1, laser irradiation is performed as indicated by the arrow in FIG. At this time, as shown in FIG. 6, a virtual extension line of a bus line that extends on the side surface of the cylindrical convex portion 1a and can form the same plane as the central axis of the convex portion 1a, and the flange portion 1b When the maximum distance between the intersections with the surface 1d is D and the distance from the intersection to the deepest part on the other surface 1d of the melted part 3 is a, the size of a is set to D / 5 or more. And it is made for a fusion | melting part to exist in an electrode base material and the chip | tip 1. FIG. Thereby, the fusion | melting part 3 contains 30-60 mass% of the component of the chip | tip 1. FIG. In this embodiment, D and the diameter R of the convex portion 1 coincide.

  Thereafter, as shown in FIG. 9, the center electrode 30 is incorporated into the insulator 62 so that the tip protrudes, and the terminal 63 is inserted into the rear end of the center electrode 30 in the insulator 62. These are incorporated into the metal shell 60.

  Next, in the fourth step S40 shown in FIG. 1, as shown in FIG. 9, the ground electrode 40 previously welded to the metal shell 60 is manufactured. The ground electrode 40 has a width of 2.5 (mm) using a Ni alloy of Inconel (registered trademark) 600 as an electrode base material, like the center electrode 30. As shown in FIG. 7 or FIG. 8, the ground electrode 40 is bent in the direction opposite to the one end side of the center electrode 30.

  Then, as shown in FIG. 3, the intermediate member 2 is resistance-welded to the ground electrode 40 and temporarily fixed. At that time, the intermediate member 2 is first disposed on the bonding surface 42 of the ground electrode 40 on the discharge gap side. Then, the first electric resistance welder 50 is provided on the intermediate member 2, and a predetermined current is applied under a predetermined pressure, whereby the intermediate member 2 is resistance-welded to the ground electrode 40 and temporarily fixed.

  Subsequently, as shown in FIG. 4, the flange portion 1 b of the chip 1 is disposed on the intermediate member 2 temporarily fixed to the ground electrode 40. Then, the second electric resistance welder 60 is provided on the one surface 1c of the flange portion 1b, and a predetermined current is applied under a predetermined pressure, whereby the other surface 1d of the flange portion 1b is resistance-welded to the intermediate member 2. Temporarily fix with. Thus, the intermediate member 2 and the chip 1 are temporarily fixed also to the ground electrode 40.

  Next, in the fifth step S50 shown in FIG. 1, laser irradiation is performed as indicated by the arrow in FIG. At this time, as shown in FIG. 6, a virtual extension line of a bus line that extends on the side surface of the cylindrical convex portion 1a and can form the same plane as the central axis of the convex portion 1a, and the flange portion 1b When the maximum distance between the intersections with the surface 1d is D and the distance from the intersection to the deepest part on the other surface 1d of the melted part 3 is a, the size of a is set to D / 5 or more. And it is made for a fusion | melting part to exist in an electrode base material and the chip | tip 1. FIG. Thereby, the fusion | melting part 3 contains 30-60 mass% of the component of the chip | tip 1. FIG. In this embodiment, D coincides with the diameter R of the convex portion 1.

  Then, as shown in FIGS. 7 and 8, one end of the electrode base material of the ground electrode 40 to which the tip 1 is welded is bent toward the center electrode 30 side. In this way, the spark plug shown in FIG. 9 is obtained.

  In this spark plug manufacturing method, a virtual extension line of a bus bar that extends on the side surface of the cylindrical convex portion 1a and can form the same plane as the central axis of the convex portion 1a, and the other surface 1d of the flange portion 1b. The melted portion 3 exists on the inner side of the other surface 1d by D / 5 or more with respect to the maximum distance D between the intersections. For this reason, it can prevent that the part which the fusion | melting part 3 does not exist in the vicinity of the center part of the flange part 1b exists in a wide range. Therefore, the flange portion 1b is reliably bonded to the bonding surfaces 32 and 42 of the electrode base material.

  Further, in this spark plug manufacturing method, since the intermediate member 2 has an intermediate melting point and linear expansion coefficient between the electrode base material and the chip 1, the intermediate member 2, the electrode base material and the chip 1 become familiar by laser irradiation. In addition, the thermal stress difference generated between the intermediate member 2 and the electrode base material and the chip 1 can be reduced. For this reason, separation between the electrode base material and the intermediate member 2 or between the intermediate member 2 and the chip 1 hardly occurs.

  In this spark plug manufacturing method, the intermediate member 2 is temporarily fixed to the joint surfaces 32 and 42 by resistance welding, and then the other surface 1d of the flange portion 1b is temporarily fixed to the intermediate member 2 by resistance welding. Sometimes, the intermediate member 2 and the tip 1 can be prevented from moving, and the electrode base material and the tip 1 can be reliably welded.

  Therefore, in the spark plug manufacturing method of the present embodiment, the bonding strength between the electrode base material and the chip 1 can be reliably ensured.

  Further, in this spark plug manufacturing method, the tip 1 is welded to the ground electrode 40 in a state where the ground electrode 40 is bent in the direction opposite to the one end side of the center electrode 30. For this reason, the limitation of the laser irradiation angle can be avoided, and the chip 1 can be welded to the ground electrode 40 with the optimum laser irradiation angle.

  As shown in FIG. 9, the spark plug thus obtained includes a cylindrical metal shell 60. The metal shell 60 extends in the axial direction of the metal shell 60, and both ends are connected to the metal shell 60. A cylindrical insulator 62 protruding from both ends is fixed. Further, the center electrode 30 extends in the axial direction of the metal shell 60, the tip of the center electrode 30 protrudes from the tip of the insulator 62, and the rear end of the center electrode 30 is fixed in the insulator 62. On the other hand, one end of the ground electrode 40 is fixed to the metal shell 60, and a discharge gap is formed between the other end of the ground electrode 40 and the center electrode 30. The chip 1 is provided opposite to the center electrode 30 and the ground electrode 40 while maintaining a discharge gap.

  In this spark plug, the tip 1 is composed of a flange portion 1b and a convex portion 1a, and extends on the side surface of the cylindrical convex portion 1a by laser welding, and is a line that can form the same plane as the central axis of the convex portion 1a. The melting part 3 exists in the electrode base material and the chip 1 through the inner side on the other surface 1d from the intersection of the virtual extension line of a certain bus line and the other surface 1d of the flange portion 1b. Therefore, a portion where the melted portion 3 does not exist in the vicinity of the center portion of the flange portion 1b does not exist in a wide range. In this way, since the flange portion 1b is reliably joined to the joining surfaces 32 and 42 of the electrode base material, the joining strength between the electrode base material and the chip 1 can be secured, and the durability of the spark plug can be maintained over a long period of time. Can be maintained.

  Moreover, in this spark plug, since the fusion | melting part 3 contains 30-60 mass% of the component of the chip | tip 1, it is easy to adapt an electrode base material and the chip | tip 1, and it arises between an electrode base material and the chip | tip 1. FIG. Since the thermal stress difference is small, the bonding strength between the electrode base material and the chip 1 can be ensured reliably.

(test)
A test was conducted to confirm the effect of the method for manufacturing the spark plug of the embodiment. First, the chip 1 and the intermediate member 2 which are the same alloy as the embodiment and have the same shape were manufactured. However, as shown in FIG. 6, the chip 1 extends on the side surface of the columnar convex portion 1a and is a virtual extension line of a bus that is a line that can form the same plane as the central axis of the convex portion 1a, and a flange portion. 1b, the maximum distance between the intersections with the other surface 1d is D (same as the diameter R of the convex portion 1; hereinafter referred to as “the diameter R of the convex portion 1”), and D = 0.6 (mm), 0. Four types of 8 (mm), 1.0 (mm), and 1.2 (mm) were manufactured. Moreover, the diameter of the flange part 1b is 0.4 mm larger than the diameter R of each convex part 1. FIG.

  The chip 1 was laser-welded to an electrode base material of the same alloy as the center electrode 30 and the ground electrode 40 of the embodiment by the same method as in the embodiment. However, the test was performed for the case where the intermediate member 2 was used as in the embodiment and the case where the chip 1 was directly laser welded to the electrode base material without using the intermediate member 2.

  The test contents are shown below. First, when laser welding the tip 1 to the electrode base material, from the intersection of the virtual extension line constituting the side surface of the convex portion 1a and the other surface 1d of the flange portion 1b to the deepest portion on the other surface 1d of the melted portion 3 A distance (hereinafter referred to as “melting depth”) is a, and a melting portion 3 having a predetermined melting depth a is formed for each type of chip 1. And after heating the fusion | melting part for 2 minutes with the burner, it annealed for 1 minute at normal temperature. After repeating this for 50 hours, the length of the oxide scale was examined. Here, the oxide scale refers to a crack generated in the cross section of the chip 1 due to a thermal stress difference or peeling of the chip 1. The burner temperature was 900 ° C and 950 ° C.

  Test results are shown in Tables 1-4. Table 1 shows the test results for the convex portion 1 having a diameter R = 0.6 (mm), and Table 2 shows the test results for the convex portion 1 having a diameter R = 0.8 (mm). Table 3 shows the test results for the convex portion 1 having a diameter R = 1.0 (mm), and Table 4 shows the test results for the convex portion 1 having a diameter R = 1.2 (mm). In each table, assuming that the diameter of the flange portion 1b is L, ○ indicates that the scale length b is smaller than L / 3, and Δ indicates that the oxidized scale length b is not less than L / 3 and smaller than L / 2. X indicates that the length b of the oxide scale is L / 2 or more.

  According to Tables 1 to 4, if the melting depth a is D / 5 or more, the test results are all ◯, and the scale length b is smaller than L / 3. From this test result, it can be seen that if the melting depth a of the melted portion 3 is D / 5 or more, the bonding strength between the electrode base material and the chip 1 can be reliably ensured.

  In the manufacturing method of the embodiment, for example, as shown in FIGS. 10A to 10C, chips 71 to 73 having various shapes can be employed. A chip 71 shown in FIG. 10A has a convex portion 71a having a tapered surface. A tip 72 shown in FIG. 10B has a flange portion 72b having a tapered surface. In the chip 73 shown in FIG. 10C, the convex portion 73a has a tapered surface, and the diameter of the bottom surface 73c of the convex portion 73a and the diameter of the flange portion 72b are the same. Even if it is such chips 71-73, the effect of the present invention can be produced.

  In the manufacturing method of the embodiment, both the convex portion and the flange portion have a circular shape. However, the present invention is not limited to this, and a polygonal chip (for example, a triangle or a square) may be used. Moreover, a convex part and a flange part do not need to be the same shape.

  In the manufacturing method of the embodiment, the electrode base material of the center electrode and the ground electrode is Inconel (registered trademark), but is not limited thereto, and may be Ni or Ni alloy, Fe or Fe alloy, or the like.

  The present invention is applicable to a spark plug.

It is process drawing of the manufacturing method of a spark plug concerning embodiment. 1 is a side view of a chip according to an embodiment. It is a side view of the intermediate member at the time of resistance welding according to the embodiment. It is a side view of the tip and intermediate member during resistance welding according to the embodiment. FIG. 4 is a side view of the tip and the intermediate member during laser welding according to the embodiment. It is sectional drawing of the center electrode or ground electrode after laser welding concerning embodiment. FIG. 4 is a partially enlarged side view of the spark plug according to the embodiment. FIG. 4 is a partially enlarged side view of the spark plug according to the embodiment. It is a side view of a partial cross section of the spark plug according to the embodiment. It is a side view of another chip according to the embodiment.

Explanation of symbols

60 ... metal shell 62 ... insulator 30 ... center electrode 40 ... ground electrode 1 ... tip 1a ... convex part 1b ... flange part 2 ... intermediate member 3 ... melting part 32, 42 ... joining surface S10 ... first step S20 ... second Process S30 ... 3rd process

Claims (9)

A cylindrical metal shell, a cylindrical insulator that extends in the axial direction of the metal shell, protrudes from both ends of the metal shell, and is fixed in the metal shell, and an axial direction of the metal shell A center electrode with a tip projecting from the tip of the insulator and a rear end fixed in the insulator, and one end fixed to the metal shell, between the other end and the center electrode. A spark plug manufacturing method comprising: a ground electrode forming a discharge gap, wherein at least one of the center electrode and the ground electrode each has an electrode base material and a chip made of a spark-resistant consumable material at a position where the discharge gap is formed In
As the chip, a first step of manufacturing a flange portion and a convex portion protruding from one surface of the flange portion;
A second step of temporarily fixing the other surface of the flange portion opposite to the convex portion by resistance welding to a joint surface on the discharge gap side of the electrode base material in at least one of the center electrode and the ground electrode;
The melted portion exists in the electrode base material and the chip so as to pass through the inside of the other surface from the intersection of the virtual extension line of the bus line constituting the side surface of the convex portion and the other surface of the flange portion. And a third step of welding the flange portion to the joint surface by laser.   The method for manufacturing a spark plug according to claim 1, wherein the joining surface is on the discharge gap side of the electrode base material in the ground electrode.   The spark plug manufacturing method according to claim 1 or 2, wherein the maximum distance between the intersection points is D, and the melted portion that passes through the inside of the other surface by D / 5 or more from the intersection point exists. In the first step, an intermediate melting point or linear expansion coefficient between the electrode base material and the tip is produced, and a plate-like intermediate member having a surface larger than the other surface of the flange portion is manufactured,
4. The spark plug manufacturing method according to claim 1, wherein, in the second step, the intermediate member is provided between the joint surface and the chip. 5.   The said 2nd process WHEREIN: After temporarily fixing the said intermediate member to the said joint surface by resistance welding, this other surface of this flange part is temporarily fixed to this intermediate member by resistance welding. Spark plug manufacturing method.   The joining surface is on the discharge gap side of the electrode base material in the ground electrode, and the tip is welded to the ground electrode in a state where the ground electrode is bent in a direction opposite to one end side of the center electrode. A method for manufacturing a spark plug according to any one of claims 1 to 5, wherein: A cylindrical metal shell, a cylindrical insulator that extends in the axial direction of the metal shell, protrudes from both ends of the metal shell, and is fixed in the metal shell, and an axial direction of the metal shell A center electrode with a tip projecting from the tip of the insulator and a rear end fixed in the insulator, and one end fixed to the metal shell, between the other end and the center electrode. A spark plug comprising a ground electrode forming a discharge gap, wherein at least one of the center electrode and the ground electrode each has an electrode base material and a tip made of a spark-resistant consumable material at a position where the discharge gap is formed,
The tip includes a flange portion and a convex portion protruding from one surface of the flange portion, and at least one of the center electrode and the ground electrode has a flange on a joint surface on the discharge gap side of the electrode base material. The other surface of the portion opposite to the convex portion is temporarily fixed by resistance welding, and on the other surface from the intersection of the virtual extension line of the bus forming the side surface of the convex portion and the other surface of the flange portion The spark plug is characterized in that the flange portion is welded by a laser so that a melted portion exists between the electrode base material and the tip.   The spark plug according to claim 7, wherein the melting portion contains 20 to 80% by mass of a component of the chip.   The spark plug according to claim 8, wherein the melting portion contains 30 to 60 mass% of the components of the chip.

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