JP2020092039A - Manufacturing method of ignition plug and ignition plug - Google Patents

Abstract

To improve peeling resistance of a chip.SOLUTION: A ground electrode of an ignition plug comprises a body part and a chip. The body part is a rod-like member. The chip is welded to a tip of the body part and faces a tip surface of a center electrode so as to form a discharge gap. Here, by cutting a rod member which is a material of the body part, a first portion including a deformed end and serving as the tip is formed out of the rod member. Further, the chip may be welded to the first portion. The tip of the body part is provided at an end on the side opposite to a main body metal fitting side and has a protrusion protruding to the center electrode side. The chip may be located at a position closer to the main body metal fitting side than the protrusion.SELECTED DRAWING: Figure 2

Description

The present specification relates to spark plugs.

Conventionally, a spark plug has been used for ignition in a device that burns fuel (for example, an internal combustion engine). As the spark plug, a spark plug having a center electrode and a ground electrode is used. As the ground electrode, an electrode including a main body and a tip welded to the main body is used. By fixing the tip to the end of the main body, it is possible to suppress the action of extinguishing the flame by absorbing the heat by the main body of the ground electrode (also referred to as the extinction action).

JP 61-45582 A

By the way, as the ground electrode, a rod-shaped main body portion having a tip portion located on the tip end side of the center electrode, and a surface of the tip portion of the body portion on the side of the center electrode are welded and face the tip surface of the center electrode. A ground electrode comprising a tip forming a discharge gap may be utilized. Here, when the chip is fixed to the main body by welding, a portion melted during welding may flow out from the end of the main body. When the melted portion flows out, the portion that joins the chip and the main body portion becomes smaller, so that the strength of the joint between the tip and the main body portion decreases, and the chip may easily peel off.

This specification discloses the technique which can improve the peeling resistance of a chip.

The technology disclosed in this specification can be implemented as the following application examples.

[Application example 1]
An insulator having a through hole extending from the rear end side toward the front end side,
A center electrode, at least a part of which is inserted into a portion on the tip side of the through hole of the insulator,
A tubular metal shell arranged on the outer peripheral side of the insulator,
While being welded to a rod-shaped main body portion that is connected to the metal shell and has a tip end portion located on the tip end side of the center electrode, and a facing side surface that is a side surface of the tip end portion of the main body portion on the center electrode side. A ground electrode provided with a tip facing the tip surface of the center electrode to form a discharge gap;
A method of manufacturing a spark plug comprising:
By cutting the rod member, which is the material of the main body, from the second side surface side opposite to the first side surface including the portion to be the opposite side surface toward the first side surface side, A cutting step of forming a first portion including the deformed end and serving as the tip end portion from the rod member;
A welding step of welding the tip to the first side surface of the first portion formed by the cutting step;
A method for manufacturing a spark plug, comprising:

According to this structure, the protrusion is formed by the movement of the cutting blade at the end of the first side surface of the first portion which is formed by the cutting process. Then, since the tip is welded to the first side surface having the protruding portion, it is possible to suppress the portion melted during welding from flowing out from the end of the first side surface. Therefore, the peeling resistance of the chip can be improved.

[Application example 2]
A method of manufacturing an ignition plug according to Application Example 1, wherein
The welding process is
An arranging step of arranging the chip on the first side surface of the first portion at a position distant from the end of the first side surface formed by the cutting step;
A tip welding step of welding the tip and the first portion arranged on the first side surface by the arrangement step;
Including,
The tip welding step includes a step of forming a joint portion that joins the tip and the first portion between the end on the first side surface and the tip,
Spark plug manufacturing method.

According to this configuration, the portion melted during welding can remain in the portion between the end and the tip on the first side surface, so that the joint can be easily formed. Therefore, the peeling resistance of the chip can be improved.

[Application example 3]
An insulator having a through hole extending from the rear end side toward the front end side,
A center electrode, at least a part of which is inserted into a portion on the tip side of the through hole of the insulator,
A tubular metal shell arranged on the outer peripheral side of the insulator,
While being welded to a rod-shaped main body portion that is connected to the metal shell and has a tip end portion located on the tip end side of the center electrode, and a facing side surface that is a side surface of the tip end portion of the main body portion on the center electrode side. A ground electrode provided with a tip facing the tip surface of the center electrode to form a discharge gap;
A spark plug comprising:
The tip portion of the main body portion has a protruding portion that is provided on an end portion on the opposite side to the metal shell side on the facing side surface and that protrudes toward the center electrode side,
The tip is arranged closer to the metal shell than the protrusion,
Spark plug.

According to this configuration, since the tip is welded to the facing side surface having the protruding portion provided at the end portion, the portion melted during welding is prevented from flowing out from the end of the facing side surface. Therefore, the peeling resistance of the chip can be improved.

[Application example 4]
The spark plug according to application example 3,
The tip is joined to the metal shell side of the protruding portion on the facing side surface of the tip portion of the main body portion,
Between the projecting portion and the tip, a joining portion that joins the tip and the tip portion is provided.
Spark plug.

According to this configuration, since the joining portion for joining the tip and the tip portion is provided on the opposite side surface of the tip portion of the main body portion between the end of the opposite side surface and the chip, the chip is resistant to peeling. It is possible to improve the property. Further, since the tip is welded at a position away from the end on the opposite side surface, the portion melted at the time of welding the tip and the tip portion can remain at the portion between the end and the tip on the opposite side surface. Therefore, the joint portion can be easily formed.

[Application example 5]
The spark plug according to Application Example 4,
The tip portion has an end surface opposite to the metal shell side, a first lateral surface and a second lateral surface connected to the facing side surface and the end surface,
The shortest distance Da in the direction parallel to the facing side surface between the tip and the end surface is the shortest distance Db in the direction parallel to the facing side surface between the chip and the first lateral side surface and the tip and the It is larger than the average value of the shortest distance Dc in the direction parallel to the facing side surface between the second lateral side surface,
Spark plug.

According to this configuration, since the portion of the tip of the main body located near the chip is large, cooling of the chip by the main body is promoted. Therefore, chip consumption can be suppressed.

[Application example 6]
The spark plug according to Application Example 4,
The tip portion has an end surface opposite to the metal shell side, a first lateral surface and a second lateral surface connected to the facing side surface and the end surface,
The shortest distance Da in the direction parallel to the facing side surface between the tip and the end surface is the shortest distance Db in the direction parallel to the facing side surface between the chip and the first lateral side surface and the tip and the Smaller than the average value of the shortest distance Dc in the direction parallel to the facing side surface between the second lateral side surface,
Spark plug.

The tip of the body can prevent the flame generated by the discharge from spreading. According to the above configuration, since the portion of the tip portion of the main body portion located near the tip is small, such a problem can be suppressed.

The technique disclosed in the present specification can be realized in various modes. For example, a ground electrode for a spark plug, a method for manufacturing a ground electrode, a spark plug, a method for manufacturing a spark plug, and a spark plug are provided. The present invention can be implemented in the form of an ignition device used, an internal combustion engine equipped with the ignition plug, an internal combustion engine equipped with the ignition device using the ignition plug, or the like.

It is sectional drawing of the spark plug 100 as one Embodiment. FIG. 3A is a perspective view of a part of the ground electrode 30. FIG. 3B is a sectional view of the center electrode 20 and the ground electrode 30. (C) is an explanatory view of a part of the ground electrode 30. It is a flowchart which shows the example of the manufacturing method of a spark plug. (A)-(F) is explanatory drawing which shows the change of the state of the part by the side of the front direction Df of the metal shell 50. (A)-(E) is explanatory drawing which shows the change of the state of the part of the metallic shell 50 by the front direction Df side. (F) is an explanatory view when the second tip 39 is welded to the temporary first portion 34z.

A. Embodiment:
A1. Spark plug configuration:
FIG. 1 is a sectional view of a spark plug 100 as one embodiment. In the figure, a central axis CL of the spark plug 100 (also referred to as “axis line CL”) and a flat cross section including the central axis CL of the spark plug 100 are shown. Hereinafter, the direction parallel to the central axis CL will also be referred to as the “direction of the axial line CL” or simply the “axial direction”. The radial direction of the circle having the axis CL as the center is also referred to as “radial direction”. The radial direction is a direction perpendicular to the axis line CL. The circumferential direction of a circle centered on the axis CL is also referred to as "circumferential direction". Of the directions parallel to the central axis CL, the downward direction in FIG. 1 is referred to as the front direction Df or the front direction Df, and the upward direction is also referred to as the rear end direction Dfr or the rear direction Dfr. The tip direction Df is a direction from the terminal fitting 40 described later toward the center electrode 20. Further, the front end direction Df side in FIG. 1 is referred to as the front end side of the spark plug 100, and the rear end direction Dfr side in FIG. 1 is referred to as the rear end side of the spark plug 100.

The spark plug 100 includes a cylindrical insulator 10 having a through hole 12 (also referred to as a shaft hole 12) extending from the rear direction Dfr side toward the front direction Df side, and a center electrode held at the tip end side of the through hole 12. 20, a terminal fitting 40 held on the rear end side of the through hole 12, a resistor 73 arranged between the center electrode 20 and the terminal fitting 40 in the through hole 12, a center electrode 20 and a resistor 73. The first seal portion 72, which is in contact with and electrically connects the members 20 and 73, and the resistor 73 and the terminal fitting 40, and electrically connects these members 73 and 40. The conductive second seal portion 74, the tubular metallic shell 50 fixed to the outer peripheral side of the insulator 10, one end of which is joined to the annular front end surface 55 of the metallic shell 50, and the other end of which is the center electrode 20. And a ground electrode 30 arranged so as to face each other via a discharge gap g.

The insulator 10 is a tubular member that extends along the axis CL. A large-diameter portion 14 having the largest outer diameter is formed in the central portion of the insulator 10. A rear end side body portion 13 having an outer diameter smaller than the outer diameter of the large diameter portion 14 is connected to the rear side Dfr side of the large diameter portion 14. The outer diameter of the connection portion 18 between the large diameter portion 14 and the rear end side body portion 13 is gradually reduced in the rear direction Dfr (the connection portion 18 is also referred to as a reduced outer diameter portion 18).

On the front side Df side of the large diameter portion 14, a tip side body portion 15 having an outer diameter smaller than the outer diameter of the large diameter portion 14 is connected. A leg portion 19 having an outer diameter smaller than the outer diameter of the tip side body portion 15 is connected to the front side body portion 15 on the front direction Df side. The leg portion 19 is a portion including the tip of the insulator 10. The outer diameter of the connecting portion 16 between the distal end side body portion 15 and the leg portion 19 gradually decreases in the front direction Df (the connecting portion 16 may be the reduced outer diameter portion 16 or the step portion 16). Also called). Further, the tip end side body portion 15 is provided with a reduced inner diameter portion 11. The inner diameter of the reduced inner diameter portion 11 gradually decreases in the front direction Df.

The insulator 10 is preferably formed in consideration of mechanical strength, thermal strength, and electric strength. The insulator 10 is formed, for example, by firing alumina (other insulating materials can be used).

The center electrode 20 is a rod-shaped metal member extending along the axis line CL. The center electrode 20 is arranged in the through hole 12 of the insulator 10 at the end portion on the front direction Df side. The center electrode 20 has a rod portion 28 and a first tip 29 joined (for example, laser welded) to the tip of the rod portion 28. The rod portion 28 has a head portion 24, which is a portion on the rear direction Dfr side, and a shaft portion 27, which is connected to the front direction Df side of the head portion 24. The shape of the shaft portion 27 is a substantially cylindrical shape extending toward the front direction Df side. The front portion Df side portion of the head portion 24 forms a collar portion 23 having an outer diameter larger than the outer diameter of the shaft portion 27. The surface of the flange portion 23 on the front direction Df side is supported by the contracted inner diameter portion 11 of the insulator 10. The shaft portion 27 is connected to the front side Df side of the collar portion 23. The first tip 29 is bonded to the end of the shaft portion 27 on the front direction Df side.

The rod portion 28 has an outer layer 21 and a core portion 22 arranged on the inner peripheral side of the outer layer 21. The outer layer 21 is formed of a material (for example, an alloy containing nickel as a main component) that is more excellent in oxidation resistance than the core portion 22. Here, the main component means a component having the highest content rate (mass percent (wt %)). The core portion 22 is formed of a material having a higher thermal conductivity than the outer layer 21 (for example, pure copper, an alloy containing copper as a main component, or the like). The first tip 29 is joined to the outer layer 21 of the rod portion 28. The rod portion 28 (the outer layer 21 in the present embodiment) is an example of a base material to which the first tip 29 is joined. The first chip 29 is formed by using a material (for example, a noble metal such as iridium (Ir) or platinum (Pt)) that is more durable than the shaft portion 27 against discharge. A part of the center electrode 20 on the front direction Df side including the first chip 29 is exposed from the shaft hole 12 of the insulator 10 on the front direction Df side. A part of the center electrode 20 on the rear direction Dfr side is arranged in the shaft hole 12. Thus, a part of the center electrode 20 is inserted into the through hole 12. The first chip 29 may be omitted. Further, the core portion 22 may be omitted.

The terminal fitting 40 is a rod-shaped member extending along the axis CL. The terminal fitting 40 is formed using a conductive material (for example, a metal containing iron as a main component). A rod-shaped portion 41 of the terminal fitting 40 on the front direction Df side is inserted into a portion on the rear direction Dfr side of the shaft hole 12 of the insulator 10.

The resistor 73 in the through hole 12 of the insulator 10 is a member for suppressing electrical noise. The resistor 73 is formed of, for example, a mixture of glass, a conductive material (for example, carbon particles) and ceramic particles. The seal portions 72 and 74 are formed by using a mixture of a conductive material (for example, metal particles such as copper and iron) and glass. The center electrode 20 is electrically connected to the terminal fitting 40 by the first seal portion 72, the resistor 73, and the second seal portion 74.

The metal shell 50 is a tubular member having a through hole 59 extending along the axis line CL. The insulator 10 is inserted into the through hole 59 of the metal shell 50, and the metal shell 50 is fixed to the outer periphery of the insulator 10. The metal shell 50 is formed using a conductive material (for example, a metal such as carbon steel containing iron as a main component). A part of the insulator 10 on the front direction Df side is exposed to the outside of the through hole 59. Further, a part of the insulator 10 on the rear direction Dfr side is exposed to the outside of the through hole 59.

The metal shell 50 has a tool engagement portion 51, a middle body portion 54, and a tip side body portion 52. The tool engaging portion 51 is a portion into which a wrench (not shown) for a spark plug fits. The middle body portion 54 is a flange-shaped portion that is disposed on the front side Df side of the tool engagement portion 51 and that projects radially outward. A front surface Df-side surface 54f of the middle body portion 54 is a seating surface and forms a seal with a mounting portion (for example, an engine head) that is a portion that forms a mounting hole of the internal combustion engine (seat surface 54f). Also called). The tip side body portion 52 is a portion connected to the front body direction Df side of the middle body portion 54, and is a portion including the tip end surface 55 of the metal shell 50. On the outer peripheral surface of the distal end side body portion 52, a screw portion 57 that is a portion formed with a male screw for screwing into a mounting hole of an internal combustion engine (not shown) is provided.

An annular gasket 80 is arranged between the seat surface 54f of the middle body portion 54 and the threaded portion 57 of the tip side body portion 52. In the present embodiment, the gasket 80 is an annular metal plate. The gasket 80 is crushed and deformed when the spark plug 100 is attached to the engine head. The deformation of the gasket 80 seals the gap between the spark plug 100 and the engine head. The gasket 80 may be omitted. In this case, the seat surface 54f of the middle trunk portion 54 may directly contact the engine head.

A support portion 56 is formed on the tip end side body portion 52 of the metal shell 50 so as to project inward in the radial direction. On the surface 56r (also referred to as the rear surface 56r) on the rear direction Dfr side of the support portion 56, the inner diameter gradually decreases toward the front direction Df. The front packing 8 is sandwiched between the rear surface 56r of the support portion 56 and the reduced outer diameter portion 16 of the insulator 10. The support portion 56 indirectly supports the step portion 16 of the insulator 10 via the packing 8.

A rear end portion of the metal shell 50 is formed on the rear end side of the tool engagement portion 51 and forms a rear end of the metal shell 50 and is thinner than the tool engagement portion 51. Further, a connecting portion 58 that connects the middle body portion 54 and the tool engagement portion 51 is formed between the middle body portion 54 and the tool engagement portion 51. The wall thickness of the connecting portion 58 is smaller than the wall thickness of each of the middle body portion 54 and the tool engaging portion 51. An annular ring is provided between the inner peripheral surface of the metal shell 50 from the tool engaging portion 51 to the rear end portion 53 and the outer peripheral surface of the reduced outer diameter portion 18 of the insulator 10 on the rearward Dfr side. The members 61 and 62 are inserted. Further, powder of talc 70 is filled between the ring members 61 and 62. In the process of manufacturing the spark plug 100, when the rear end portion 53 is bent inward and caulked, the connecting portion 58 is deformed, and as a result, the metal shell 50 and the insulator 10 are fixed. The talc 70 is compressed during this caulking process, and the airtightness between the metal shell 50 and the insulator 10 is enhanced. Further, the packing 8 is pressed between the reduced outer diameter portion 16 of the insulator 10 and the support portion 56 of the metal shell 50, and seals between the metal shell 50 and the insulator 10.

The ground electrode 30 is a metal member and has a rod-shaped main body 37. The end portion 33 (also referred to as the base end portion 33) of the main body portion 37 is joined to the front end surface 55 of the metal shell 50 (for example, resistance welding). The main body portion 37 extends from the base end portion 33 joined to the metal shell 50 in the distal direction Df, bends toward the central axis CL, extends in the direction intersecting the axis CL, and reaches the distal end portion 34. The second tip 39 is joined to the rear surface Dfr side surface of the tip portion 34 (details will be described later). The second tip 39 of the ground electrode 30 and the first tip 29 of the center electrode 20 form a discharge gap g. The second tip 39 of the ground electrode 30 is disposed on the front side Df side of the first tip 29 of the center electrode 20, and the front side Df side surface of the first tip 29 (that is, the tip end surface of the center electrode 20). And a gap g.

The main body portion 37 has an outer layer 31 and an inner layer 32 arranged on the inner peripheral side of the outer layer 31. The outer layer 31 is formed of a material having a higher oxidation resistance than the inner layer 32 (for example, an alloy containing nickel as a main component). The inner layer 32 is formed of a material having a higher thermal conductivity than the outer layer 31 (for example, pure copper, an alloy containing copper as a main component, or the like). The second tip 39 is joined to the outer layer 31 of the body portion 37. The second chip 39 is formed using a material (for example, a noble metal such as iridium (Ir) or platinum (Pt)) that is more durable than the body portion 37 against discharge. The main body portion 37 (the outer layer 31 in the present embodiment) is an example of a base material to which the second tip 39 is joined. The inner layer 32 may be omitted.

A2. Structure of the ground electrode 30:
FIG. 2A is a perspective view of a part of the ground electrode 30. In the figure, the second tip 39 and the tip portion 34 of the main body portion 37 are shown. In the present embodiment, the main body portion 37 is a rod-shaped member having a rectangular cross section. The tip portion 34 of the main body portion 37 forms an end surface 371 and four side surfaces 372 to 375. The end surface 371 is an end surface of the end portion (that is, the tip end portion 34) of the main body portion 37 opposite to the end portion 33 (FIG. 1) on the metal shell 50 side. The four side surfaces 372 to 375 are connected to the end surface 371.

A side surface 374 of the tip portion 34 of the main body portion 37 is a side surface on the side of the center electrode 20 (FIG. 1) and faces the center electrode 20 (also referred to as a facing side surface 374). The side surface 375 is a side surface opposite to the opposite side surface 374 (also referred to as an opposite side surface 375). The opposite side surface 375 is approximately parallel to the opposite side surface 374. The side surface 372 is a rear side surface of the main body portion 37 in the figure, and is a side surface connected to the end surface 371, the facing side surface 374, and the opposite side surface 375 (also referred to as a first lateral side surface 372). The side surface 373 is a front side surface of the main body portion 37 in the figure, and is a side surface opposite to the first lateral side surface 372 (also referred to as a second lateral side surface 373). The second lateral side surface 373 is also connected to the end surface 371, the opposite side surface 374, and the opposite side surface 375. The second lateral surface 373 is substantially parallel to the first lateral surface 372. The lateral sides 372, 373 are approximately perpendicular to the opposing side surface 374.

The second tip 39 of the ground electrode 30 is welded to the facing side surface 374 of the tip portion 34 of the body portion 37. In the present embodiment, the shape of the second chip 39 is a square pole.

Although not shown, the four side surfaces 372 to 375 extend from the end surface 371 to the base end portion 33 (FIG. 1). As shown in FIG. 1, the body portion 37 is bent between the distal end portion 34 and the proximal end portion 33. Therefore, the four side surfaces 372 to 375 are also bent between the distal end portion 34 and the proximal end portion 33.

FIG. 2B is a cross-sectional view of a portion of the center electrode 20 and the ground electrode 30 in the vicinity of the gap g. The illustrated cross section is a cross section that includes the axis line CL and is parallel to the lateral side surfaces 372 and 373 (FIG. 2A). The second tip 39 of the ground electrode 30 is welded to the facing side surface 374 of the tip portion 34 of the body portion 37. The second tip 39 forms a discharge gap g so as to face the front end surface 20f which is the end surface of the center electrode 20 on the front direction Df side. In the present embodiment, the tip surface 20f of the center electrode 20 is the end surface of the first tip 29 on the front direction Df side.

The joining portion 380 is a portion that joins the second tip 39 and the tip portion 34. The joint portion 380 is a portion where the melted portion of the second tip 39 and the tip portion 34 is cooled and solidified during welding (also referred to as a melted portion 380). Such a joint 380 includes the components of the second tip 39 and the tip 34. The joining portion 380 includes a first portion 381 and a second portion 382. The first portion 381 is a portion located between the second tip 39 and the tip portion 34, and the second portion 382 is a portion located around the second tip 39 on the facing side surface 374.

An end portion of the facing side surface 374 of the tip portion 34, which is connected to the end surface 371, forms a protrusion 35. The projecting portion 35 projects toward the center electrode 20. As shown in FIG. 2A, the protrusion 35 is formed over the entire end 374e of the facing side surface 374 (specifically, the end 374e at which the facing side surface 374 and the end surface 371 are connected). There is. In the present embodiment, the protruding portion 35 is formed by cutting the rod member that is the material of the main body portion 37 at the time of manufacturing the spark plug 100 (details will be described later). The second tip 39 is arranged closer to the metal shell 50 than the protruding portion 35. That is, the second tip 39 is arranged on the facing side surface 374, closer to the base end portion 33 side than the projecting portion 35.

In the present embodiment, the peripheral portion 374s of the facing side surface 374, which is the peripheral portion of the second chip 39, forms a substantially flat surface. The direction 374d is the normal direction of the peripheral portion 374s (also referred to as the normal direction 374d). In this embodiment, the normal direction 374d is substantially parallel to the axis line CL. As described later, the positional relationship between the second tip 39 and the tip portion 34 is examined using this normal direction 374d.

FIG. 2C is an explanatory diagram of a part of the ground electrode 30 viewed in the direction opposite to the normal direction 374d. In the figure, the tip portion 34, the second tip 39, and the joint portion 380 are shown. In the present embodiment, a part of the second portion 382 of the joint portion 380 is formed on the surface of the protrusion 35. Further, the projecting portion 35 and the peripheral portion 374s are hatched. As the peripheral portion 374s, a flat portion that is connected to the joint portion 380 is adopted. When the joining portion 380 is not formed on the facing side surface 374, a portion that is connected to the second chip 39 and is flat is used as the peripheral portion 374s.

The first distance Da in the figure is the shortest distance in the direction parallel to the facing side surface 374 between the second tip 39 and the end surface 371. The second distance Db is the shortest distance in the direction parallel to the facing side surface 374 between the second chip 39 and the first lateral surface 372. The third distance Dc is the shortest distance in the direction parallel to the facing side surface 374 between the second chip 39 and the second lateral surface 373. In order to specify the distances Da, Db, Dc, the direction parallel to the facing side surface 374 is the direction parallel to the peripheral portion 374s (that is, the direction perpendicular to the normal direction 374d). For example, the facing side surface 374 of the curved portion of the body portion 37 (FIG. 1) is not referenced. Further, in order to specify the distances Da, Db, Dc, as the second chip 39, a portion of the second chip 39 exposed to the outside is used. For example, the portion of the second chip 39 hidden by the joint portion 380 is not referred to.

When the portion of the tip end portion 34 on the end surface 371 side of the second tip 39 is larger, the portion of the tip end portion 34 located near the second tip 39 is larger, so that the tip end portion 34 and, by extension, the main body portion 37 The cooling of the two chips 39 is promoted. Therefore, the consumption of the second chip 39 can be suppressed. For example, the first distance Da may be larger than the average value of the second distance Db and the third distance Dc (Da>(Db+Dc)/2).

Further, the tip end portion 34 of the main body portion 37 can prevent the flame generated by the discharge from spreading. When the portion of the tip portion 34 on the end face 371 side of the second tip 39 is smaller, such a problem can be suppressed. For example, the first distance Da may be smaller than the average value of the second distance Db and the third distance Dc (Da<(Db+Dc)/2).

A3. Spark plug manufacturing method:
FIG. 3 is a flowchart showing an example of a method for manufacturing the spark plug. In the figure, a code that is a combination of the character "S" and a number following the character "S" is used as the code indicating the process.

In S110, the members of the spark plug 100 are prepared. Specifically, the center electrode 20, the terminal fitting 40, the metallic shell 50, the rod member that is the material of the main body portion 37 and is not bent, and the second tip 39 are the known methods. Manufactured in. Further, the respective material powders of the seal parts 72 and 74 and the material powder of the resistor 73 are prepared.

In S120, an assembly including the insulator 10, the center electrode 20, the first seal portion 72, the resistor 73, the second seal portion 74, and the terminal fitting 40 is created by a known method. For example, the center electrode 20, the material of the first seal part 72, the material of the resistor 73, and the material of the second seal part 74 are inserted into the through hole 12 of the insulator 10 from the opening on the rear side Dfr side in this order. To do. Then, the assembly is manufactured by inserting the terminal fitting 40 from the rear direction Dfr side of the through hole 12 while the insulator 10 is heated.

Next, the remaining portion of the spark plug 100 including the ground electrode 30 is manufactured. 4(A) to 4(F) and FIGS. 5(A) to 5(E) are explanatory views showing changes in the state of the portion of the metal shell 50 on the front direction Df side. As the manufacture of the spark plug 100 progresses, the state changes in the order of FIGS. 4(A) to 4(F) and 5(A) to 5(E).

In S130 of FIG. 3, the rod member that is the material of the main body 37 is fixed to the metal shell 50. FIG. 4A is an explanatory diagram of the rod member 37x and the metal shell 50. In the drawing, a part of the metal shell 50 on the front direction Df side and the rod member 37x viewed in a direction perpendicular to the axis CL are shown. The rod member 37x is a square rod that is not bent. The length of the rod member 37x is longer than the length of the main body portion 37 of the ground electrode 30. The rod member 37x has an end portion corresponding to the base end portion 33 of the completed main body portion 37 (the same reference numeral is used to call the end portion 33). The end 33 of the rod member 37x is joined to the front end surface 55 of the metal shell 50 (for example, resistance welding, laser welding, electron beam welding, etc.). In addition, in FIG. 4A, the side surfaces 372x, 374x, and 375x of the rod member 37x are shown. These side surfaces 372x, 374x, 375x respectively include portions to be the side surfaces 372, 374, 375 of the completed main body portion 37. The side surface 374x is a side surface including a portion that should be the facing side surface 374 (referred to as a first side surface 374x). The side surface 375x is a side surface opposite to the first side surface 374x (referred to as a second side surface 375x). FIG. 4A shows the rod member 37x and the metal shell 50 viewed in a direction parallel to the side surfaces 374x and 375x.

In S140 of FIG. 3, the assembly (including the insulator 10) manufactured in S120 is fixed to the metal shell 50 (FIG. 1). 4B shows a state in which the assembly is fixed to the metal shell 50 of FIG. 4A. In the present embodiment, the distal packing 8, the assembly prepared in S120, the ring member 62, the talc 70, and the ring member 61 are arranged in the through hole 59 of the metal shell 50. The tip side packing 8 is sandwiched between the step portion 16 of the insulator 10 and the support portion 56 of the metal shell 50. The metal shell 50 and the insulator 10 are assembled by crimping the rear end portion 53 of the metal shell 50 so as to be bent inward.

In S150 of FIG. 3, the rod member 37x is cut. 4C to 4E show how the rod member 37x of FIG. 4B is cut. First, as shown in FIG. 4C, the movable blade 910 is disposed on the second side surface 375x side of the rod member 37x. The blade edge 911 of the movable blade 910 is arranged at a predetermined position on the second side surface 375x of the rod member 37x. For example, the cutting edge 911 is arranged at a position separated from the tip surface 55 of the metal shell 50 by a predetermined first distance in the front direction Df. The fixed blade 920 is disposed on the side of the first side surface 374x of the rod member 37x. The cutting edge 921 of the fixed blade 920 is arranged at a predetermined position on the first side surface 374x of the rod member 37x. For example, the cutting edge 921 is arranged at a position away from the front end surface 55 of the metal shell 50 by a predetermined second distance in the front direction Df. A predetermined clearance is provided between the position of the cutting edge 911 of the movable blade 910 (first distance) and the position of the cutting edge 921 of the fixed blade 920 (second distance). The blade edge 921 of the fixed blade 920 is arranged closer to the metal shell 50 side than the blade edge 911 of the movable blade 910.

Next, as shown in FIG. 4D, the movable blade 910 is moved from the second side surface 375x side toward the first side surface 374x side. As a result, the rod member 37x is cut. In the present embodiment, the movable blade 910 is moved in a direction substantially perpendicular to the axis line CL and from the second side surface 375x side toward the first side surface 374x side. As a result, the portion 37z of the rod member 37x on the front direction Df side is cut off. This portion 37z is a portion of the rod member 37x on the front direction Df side from the contact position with the blade edge 911. And the main-body part 37 before bending is formed. In this way, the main body 37 before being bent is formed by shearing.

FIG. 4E shows the state after cutting. The cut surface of the rod member 37x by the movable blade 910 is the end surface 371. The end portion 34x of the rod member 37x including the end surface 371 is a portion that should be the tip portion 34 (also referred to as a first portion 34x). The first portion 34x is formed from the rod member 37x by cutting the rod member 37x.

FIG. 4(F) is an enlarged view of the first portion 34x of the rod member 37x of FIG. 4(E). As described in FIG. 4D, the movable blade 910 cuts the rod member 37x from the second side surface 375x side toward the first side surface 374x side. At the time of this cutting, the portion of the rod member 37x where the end surface 371 is to be formed is in contact with the moving movable blade 910. Therefore, the portion including the end surface 371 of the rod member 37x (particularly, the portion on the front direction Df side from the contact position of the fixed blade 920 with the cutting edge 921) is in the cutting direction (that is, from the second side surface 375x to the first side surface 375x). (Direction toward 374x). As a result, the end 34xe of the first portion 34x after cutting is deformed in the cutting direction. The end 374xe of the first side surface 374x after cutting forms the protrusion 35. In addition, a bent portion 36 that is bent toward the first side surface 374x is formed at the end of the second side surface 375x. The size of the protruding portion 35 is adjusted by adjusting the clearance amount between the position (first distance) of the blade edge 911 of the movable blade 910 and the position (second distance) of the blade edge 921 of the fixed blade 920, and the movable blade. It can be adjusted by adjusting the moving speed of 910.

In S160 of FIG. 3, the second tip 39 is welded to the first side surface 374x of the first portion 34x. S160 includes S163 and S166. In S163, the second tip 39 is arranged on the first side surface 374x of the first portion 34x of the rod member 37x. FIG. 5A shows a state in which the second chip 39 is arranged on the first side surface 374x of the first portion 34x of FIG. 4E. FIG. 5B is an enlarged view of the first portion 34x and the second chip 39 of FIG. 5A. As shown in the drawing, the second chip 39 is arranged on the first side surface 374x of the first portion 34x at a position apart from the end 374xe of the first side surface 374x (that is, the end 374xe formed by the cutting process). .. In the present embodiment, the second chip 39 is placed on the flat portion 374sx of the first side surface 374x. This portion 374sx includes a peripheral portion 374s (FIG. 2C). The second chip 39 is supported by a support member (not shown).

In S166 of FIG. 3, the second chip 39 is joined to the first portion 34x. FIG. 5C is an explanatory diagram of the bonding between the second chip 39 and the first portion 34x of FIG. 5B. In the present embodiment, the contact portion between the second tip 39 and the first side surface 374x is irradiated with the laser beam Lz. The direction of irradiation with the laser beam Lz is not particularly limited. Although the laser beam Lz is emitted from the Df side and the Dfr side of the second chip in FIG. 5C, even if the laser beam Lz is emitted from the side surface 372x side or a side surface opposite to the side surface 372x. Good. Thus, the second tip 39 and the first portion 34x are joined by laser welding. FIG. 5D shows a state in which the second chip 39 and the first portion 34x of FIG. 5C are joined. By welding, a part of the second tip 39 and a part of the first part 34x are melted. Then, the melted portion is cooled and solidified to form the joint 380. Here, when a part of the joint portion 380 is formed on the surface of the protrusion 35, the fusion portion 380 (that is, the fusion portion 380 before being cooled and solidified) that is trying to spread toward the protrusion 35 is the protrusion portion. It is returned to the second chip 39 side by 35. This makes it possible to thicken the joint 380 after it has cooled and solidified. Therefore, forming a part of the bonding portion 380 on the surface of the protruding portion 35 (that is, including the portion where the bonding portion 380 is formed on the surface of the protruding portion 35) makes the second chip 39 resistant to peeling. It is preferable from the viewpoint of improving. As the surface of the protrusion 35, a portion of the facing side surface 374 that forms the protrusion 35 is adopted. As the surface of the protrusion 35, a portion of the facing side surface 374, which is provided closer to the center electrode 20 than the plane including the flat peripheral portion 374s may be adopted.

In S180 of FIG. 3, the rod member 37x is bent to form the discharge gap g. FIG. 3(E) shows a state in which the rod member 37x is bent. Here, the rod member 37x is bent so that the distance of the discharge gap g becomes a predetermined distance. As described above, the ground electrode 30 is completed and the spark plug 100 is completed. Then, the processing of FIG. 3 ends.

As described above, the spark plug 100 (FIG. 1) of this embodiment includes the insulator 10, the center electrode 20, the metal shell 50, and the ground electrode 30. The insulator 10 has a through hole 12 extending from the rear direction Dfr side toward the front direction Df side. At least a part of the center electrode 20 is inserted into a portion of the through hole 12 of the insulator 10 on the front direction Df side. The metal shell 50 is a tubular member arranged on the outer peripheral side of the insulator 10. The ground electrode 30 has a main body portion 37 and a second tip 39. The main body portion 37 is a rod-shaped member that is connected to the metallic shell 50 and has the tip portion 34 located on the front direction Df side of the center electrode 20. The second tip 39 is welded to the facing side surface 374 of the tip portion 34 of the body portion 37. The facing side surface 374 is a side surface on the side of the center electrode 20. The second chip 39 (FIG. 2B) forms a discharge gap g facing the tip surface 20f of the center electrode 20.

Then, as described with reference to FIGS. 2A to 2C, the tip end portion 34 of the main body portion 37 has the protruding portion 35. The projecting portion 35 is provided on the opposite side surface 374 at the end opposite to the metal shell 50 side and projects toward the center electrode 20 side. The second tip 39 is arranged closer to the metal shell 50 than the protrusion 35. In this way, the second tip 39 is welded to the facing side surface 374 having the protruding portion 35 provided at the end portion. Therefore, the melted portion during welding is suppressed from flowing out from the end 374e of the facing side surface 374 (specifically, the end where the facing side surface 374 and the end surface 371 are connected). As a result, the peeling resistance of the second chip 39 can be improved.

The second tip 39 is joined to the metal shell 50 side of the protruding portion 35 on the facing side surface 374 of the tip end portion 34 of the main body portion 37. Then, between the protruding portion 35 and the second tip 39, a joint portion 380 (specifically, a part of the second portion 382) for joining the second tip 39 and the tip portion 34 is provided. .. Therefore, the peeling resistance of the second chip 39 can be improved. Further, since the second tip 39 is welded on the opposite side surface 374 at a position away from the end 374e, the portion of the second tip 39 and the tip portion 34 melted at the time of welding is melted at the end 374e on the opposite side surface 374. Can remain in the portion between the second chip 39 and the second chip 39. Therefore, the joint portion 380 (specifically, a part of the second portion 382) can be easily formed.

The spark plug 100 of this embodiment can be manufactured by various methods. For example, the manufacturing method of FIG. 3 includes a step S150 of cutting the rod member 37x, which is a material of the main body 37, and a step S160 (S163, S166) of welding the second tip 39. As described in FIGS. 4C to 4D, the rod member 37x includes the first side surface 374x from the second side surface 375x side opposite to the first side surface 374x including the portion to be the facing side surface 374. Cut towards the side. As a result, as described with reference to FIG. 4E, the first portion 34x to be the tip portion 34 is formed from the rod member 37x. As described in FIG. 4F, the first portion 34x includes the end 34xe that is deformed in the cutting direction (that is, the direction from the second side surface 375x to the first side surface 374x). In addition, as described in FIGS. 5A to 5D, the second tip 39 is welded to the first side surface 374x of the first portion 34x formed by the cutting step (S150). According to this method, the movable blade is provided at the end of the first side surface 374x of the first portion 34x (FIG. 4(F)) that is formed by the cutting process (that is, the portion including the end 374xe). The movement of 910 forms the protrusion 35. Then, as shown in FIGS. 5A to 5D, the second tip 39 is welded to the first side surface 374 x having the protrusion 35.

FIG. 5F is an explanatory diagram in the case where the second tip 39 is welded to the temporary first portion 34z having no protruding portion 35. The difference from the first portion 34x of FIG. 5D is that the protruding portion 35 is omitted from the first side surface 374z of the first portion 34z. In FIG. 5F, the first side surface 374z of the first portion 34z is flat. In this case, the portion melted during welding can move on the first side surface 374z and flow out from the end 374ze of the first side surface 374z. As a result, a part of the joint portion 380z can be formed outside the first side surface 374z (referred to as an outer portion 380zo). The external component 380zo is not in direct contact with either the first portion 34z or the second chip 39. Therefore, the contribution of the outer portion 380zo to the bonding strength between the first portion 34z and the second tip 39 is small. As a result, when the molten portion flows out from the end 374ze of the first side surface 374z during welding, the bonding strength of the second tip 39 may be reduced.

On the other hand, in the present embodiment, as described with reference to FIG. 5C, the second tip 39 is welded to the first side surface 374x having the protrusion 35. Therefore, the portion melted during welding is suppressed from flowing out from the end 374xe of the first side surface 374x. As a result, the peeling resistance of the second chip 39 can be improved.

Further, the step S160 for welding the second tip 39 includes S163 in which the second tip 39 is arranged and S166 in which the second tip 39 is welded. In S163, as described in FIGS. 5A and 5B, on the first side surface 374x of the first portion 34x, the first side surface 374x formed by the cutting step (S150) is separated from the end 374xe. The second chip 39 is arranged at the open position. Then, in S166, as described with reference to FIGS. 5C and 5D, the second tip 39 arranged on the first side surface 374x and the first portion 34x are welded in S163. By this welding, a joining portion 380 (specifically, one end of the second portion 382) that joins the second tip 39 and the first portion 34x between the end 374xe on the first side surface 374x and the second tip 39. Part) is formed. Thus, S166 includes the step of forming the joint 380 between the end 374xe on the first side surface 374x and the second chip 39. In the manufacturing method of the present embodiment, the molten portion during welding can remain on the first side surface 374x in the portion between the end 374xe and the second tip 39. Therefore, the joint portion 380 (specifically, a part of the second portion 382) can be easily formed between the end 374xe on the first side surface 374x and the second chip 39. As a result, the peeling resistance of the second chip 39 can be improved.

B. Modification:
(1) The configuration of the ground electrode may be various other configurations instead of the configuration of the above-described embodiment described with reference to FIG. For example, in the embodiment of FIGS. 2A to 2C, the shape of the second chip 39 is a square pole. Instead of this, the shape of the second tip 39 may be various shapes such as a cylinder and a truncated cone. In any case, it is preferable that the distances Da, Db, Dc described with reference to FIG. 2C are all greater than zero. According to this structure, the bonding portion 380 can be easily formed around the second chip 39 on the facing side surface 374. Therefore, the peeling resistance of the second chip 39 can be improved. The second distance Db may be zero. Further, the third distance Dc may be zero. Further, the normal direction 374d of the peripheral portion 374s of the facing side surface 374 (FIGS. 2A to 2C) may be an oblique direction with respect to the axis CL. In any case, the shortest distances in the direction parallel to the peripheral portion 374s of the facing side surface 374 are used as the distances Da, Db, and Dc (FIG. 2C).

(2) As a method for joining the tip portion 34 (and thus the first portion 34x) and the second tip 39, various welding methods such as resistance welding and electron beam welding may be adopted instead of laser welding. For example, when the second tip 39 contains iridium, proper joining can be realized by using laser welding. When the second tip 39 contains platinum, laser welding may be adopted, and instead of this, resistance welding may be adopted. In any case, when the first portion 34x and the second tip 39 are joined by welding, the melted portion of the first portion 34x and the second tip 39 is the second tip 39 on the first side surface 374x. A joint 380 may be formed around the. Here, if the first portion 34x has the protrusion 35, the portion melted during welding is prevented from flowing out of the first side surface 374x. As a result, the peeling resistance of the second chip 39 can be improved.

It should be noted that the bonding portion 380 may not be formed on the first side surface 374x (and by extension, the facing side surface 374) in at least a part of the entire circumference of the second chip 39. For example, the bonding portion 380 may not be formed between the second tip 39 and the end surface 371 on the first side surface 374x. As described above, the shape of the joint portion 380 on the first side surface 374x does not have to be the intended shape. Further, the melted portion at the time of welding may move on the first side surface 374x, so that the joint portion 380 may be unintentionally formed on the first side surface 374x. Here, if the first portion 34x has the protrusion 35, the portion melted during welding is prevented from flowing out of the first side surface 374x. As a result, the peeling resistance of the second chip 39 can be improved.

(3) The method of forming the main body having the protrusions (for example, the protrusions 35 in FIGS. 2A to 2C) may be any method instead of shearing. For example, the protrusion may be formed by cutting or forging. Further, the member including the protrusion may be fixed (welding, fitting, etc.) to the bar member that is the material of the main body. Further, the shape of the protruding portion may be any shape such as a triangular prism or a quadrangular prism extending parallel to the opposite side surfaces. In addition, the protrusion may be provided only on a part of the end of the facing side surface (for example, the end 374e of the facing side surface 374 in FIG. 2A). Further, the cross-sectional shape of the rod-shaped main body of the ground electrode may be various other shapes instead of being rectangular. In general, the shape of the tip of the main body is such that the side surface on the side of the center electrode is opposite to the side surface and the end on the side opposite to the metal shell side is a protrusion protruding toward the side of the center electrode. And may have various shapes. In addition, the tip may be bonded to the metal shell side of the opposing side surface rather than the protruding portion.

(4) The method for manufacturing the spark plug may be various other methods instead of the method described in FIG. For example, the order of S130, S140, S150, S163, and S166 may be any order (provided that S166 is performed after S163 and S163 is S150.
Later than). S120 may be performed at any timing before S140.

(5) The configuration of the spark plug may be various other configurations instead of the configuration described in FIG. For example, the tip packing 8 may be omitted. That is, the support portion 56 of the metal shell 50 may directly support the step portion 16 by contacting the step portion 16 of the insulator 10. Further, a magnetic body may be arranged between the terminal fitting 40 in the shaft hole 12 of the insulator 10 and the center electrode 20. Further, the entire center electrode may be arranged in the through hole of the insulator. Further, the through hole of the insulator may be inclined with respect to the axis CL. In general, the insulator may have a through hole that extends from the rear direction Dfr side toward the front direction Df side. Generally, the structure of the spark plug is such that an insulator, a center electrode at least a part of which is inserted into a portion of a through hole of the insulator at a tip side, and a cylindrical main body arranged on an outer peripheral side of the insulator. It may have various configurations including a metal fitting and a ground electrode. Here, the structure of the ground electrode includes a rod-shaped main body portion which is connected to the metallic shell and has a tip portion located on the tip end side of the center electrode, and an opposite side surface which is a side surface of the tip portion of the body portion on the center electrode side. And a tip that is welded and forms a discharge gap facing the tip surface of the center electrode.

Although the present invention has been described based on the embodiments and the modifications, the embodiments of the present invention described above are intended to facilitate understanding of the present invention and do not limit the present invention. The present invention can be modified and improved without departing from the spirit thereof, and the present invention includes equivalents thereof.

8... Tip side packing, 10... Insulator, 11... Reduced inner diameter portion, 12... Through hole (shaft hole), 13... Rear end side body portion, 14... Large diameter portion, 15... Tip side body portion, 16... Reduced Outer diameter portion (step portion, connection portion), 18... Reduced outer diameter portion (connection portion), 19... Leg portion, 20... Center electrode, 20f... Tip surface, 21... Outer layer, 22... Core portion, 23... Collar portion , 24... Head part, 27... Shaft part, 28... Rod part, 29... First tip, 30... Ground electrode, 31... Outer layer, 32... Inner layer, 33... Proximal end part, 34... Tip part, 34x... First part Part (end part), 34z... First part, 34xe... End, 35... Projection part, 36... Bent part, 37... Main body part, 37x... Bar member, 37z... Part, 39... Second chip, 40... Terminal fitting , 41... Portion, 50... Metal shell, 51... Tool engaging section, 52... Tip side body section, 53... Rear end section, 54... Middle body section, 54f... Seat surface, 55... Tip surface, 56... Support section , 56r... Rear surface, 57... Screw part, 58... Connection part, 59... Through hole, 61, 62... Ring member, 70... Talc, 72... First seal part, 73... Resistor, 74... Second seal part, 80... Gasket, 100... Spark plug, 371... End surface, 372... First lateral side surface, 373... Second lateral side surface, 374... Opposing side surface, 375... Opposite side surface, 372x... Side surface, 374x, 374z... First side surface, 375x ... 2nd side surface, 374d... Normal direction, 374e... End, 374s... Peripheral part, 374xe... End, 374ze... End, 374sx... Part, 380... Joined part (fusion part), 381... 1st part, 382... 2 parts, 380z... Joined part, 380zo... Outer part, 910... Movable blade, 911... Blade edge, 920... Fixed blade, 921... Blade edge, g... Discharge gap, CL... Central axis (axis), Df... Forward direction (tip) Direction), Lz... laser beam, Dfr... rear end direction (rear direction)

Claims (6)

An insulator having a through hole extending from the rear end side toward the front end side,
A center electrode, at least a part of which is inserted into a portion on the tip side of the through hole of the insulator,
A tubular metal shell arranged on the outer peripheral side of the insulator,
While being connected to the metal shell and welded to a rod-shaped main body portion having a tip portion located on the tip end side of the center electrode, and a facing side surface that is a side surface of the tip portion of the body portion on the center electrode side. A ground electrode having a tip facing the tip surface of the center electrode to form a discharge gap;
A method of manufacturing a spark plug comprising:
By cutting the bar member, which is the material of the main body, from the second side surface side opposite to the first side surface including the portion to be the opposite side surface toward the first side surface side, in the cutting direction. A cutting step of forming a first portion including the deformed end and serving as the tip end portion from the rod member;
A welding step of welding the tip to the first side surface of the first portion formed by the cutting step;
A method for manufacturing a spark plug, comprising: A method of manufacturing the spark plug according to claim 1, wherein
The welding process is
An arranging step of arranging the chip on the first side surface of the first portion at a position distant from the end of the first side surface formed by the cutting step;
A tip welding step of welding the tip and the first portion arranged on the first side surface by the arrangement step;
Including,
The tip welding step includes a step of forming a joint portion that joins the tip and the first portion between the end on the first side surface and the tip,
Spark plug manufacturing method. An insulator having a through hole extending from the rear end side toward the front end side,
A center electrode, at least a part of which is inserted into a portion on the tip side of the through hole of the insulator,
A tubular metal shell arranged on the outer peripheral side of the insulator,
While being welded to a rod-shaped main body portion that is connected to the metal shell and has a tip end portion located on the tip end side of the center electrode, and a facing side surface that is a side surface of the tip end portion of the main body portion on the center electrode side. A ground electrode provided with a tip facing the tip surface of the center electrode to form a discharge gap;
A spark plug comprising:
The tip portion of the main body portion has a protruding portion that is provided on an end portion on the opposite side to the metal shell side on the facing side surface and that protrudes toward the center electrode side,
The tip is arranged closer to the metal shell than the protrusion,
Spark plug. The spark plug according to claim 3, wherein
The tip is joined to the metal shell side of the protruding portion on the facing side surface of the tip portion of the main body portion,
Between the projecting portion and the tip, a joining portion that joins the tip and the tip portion is provided.
Spark plug. The spark plug according to claim 4, wherein
The tip portion has an end surface opposite to the metal shell side, a first lateral surface and a second lateral surface connected to the facing side surface and the end surface,
The shortest distance Da in the direction parallel to the facing side surface between the tip and the end surface is the shortest distance Db in the direction parallel to the facing side surface between the chip and the first lateral side surface and the tip and the It is larger than the average value of the shortest distance Dc in the direction parallel to the facing side surface between the second lateral side surface,
Spark plug. The spark plug according to claim 4, wherein
The tip portion has an end surface opposite to the metal shell side, a first lateral surface and a second lateral surface connected to the facing side surface and the end surface,
The shortest distance Da in the direction parallel to the facing side surface between the tip and the end surface is the shortest distance Db in the direction parallel to the facing side surface between the chip and the first lateral side surface and the tip and the Smaller than the average value of the shortest distance Dc in the direction parallel to the facing side surface between the second lateral side surface,
Spark plug.

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