JP7528753B2 - Spark plug - Google Patents

Description

This disclosure relates to spark plugs.

A spark plug used to ignite an air-fuel mixture in an engine comprises a cylindrical insulator that houses a center electrode, resistor, terminal fittings, etc., and a cylindrical housing that is attached to the outer periphery of the insulator. The insulator prevents high voltage from being applied to anything other than the electrode by insulating between the housing and the center electrode, etc., housed inside it. The housing supports the insulator and also functions as a part for attaching the spark plug to the engine. The housing is located from the tip to the middle of the insulator.

In such spark plugs, a method is generally used in which a buckling portion is formed by buckling a thin portion provided in the middle of the housing, for example, in order to firmly secure the housing to the insulator. By forming the buckling portion, the strength of that portion is increased by work hardening, making it possible to more firmly secure the housing to the insulator. In addition, a male thread portion is formed on the outer peripheral surface of the lower end portion of the housing for attaching the spark plug to the engine head block. Between the male thread portion and the buckling portion on the outer peripheral surface of the housing, a thread steal portion and a body portion are formed in this order from the male thread portion toward the buckling portion. The body portion has an outer diameter larger than that of the male thread portion. A gasket is attached to the outer periphery of the thread steal portion.

The above spark plugs are designed to satisfy the relationship "strength of buckling part < strength of thread stealing part" before the buckling part is buckled, and to satisfy the relationship "strength of buckling part > strength of thread stealing part" after the buckling part is buckled. The former relationship is necessary to prevent the thread stealing part from buckling before the buckling part when the buckling part is buckled. The latter relationship is necessary to break the thread stealing part before the buckling part if excessive screwing force is applied when screwing the male thread of the spark plug into the female threaded hole of the engine head block. This allows the part above the thread stealing part, i.e., the body of the housing and the gasket that are in close contact with the engine head block, to be separated from the engine head block, making it possible to easily remove the remaining part of the spark plug that remains on the engine head block after fracture.

However, when a spark plug is designed so that the strength of the buckling portion and the thread stealing portion before and after buckling the buckling portion satisfies the above-mentioned relationship, there is a risk that the strength of the buckling portion cannot be ensured, especially when the spark plug is made smaller. Specifically, when making a spark plug smaller, if an attempt is made to satisfy the relationship "strength of the buckling portion < strength of the thread stealing portion" before the buckling portion is buckled, the buckling portion needs to be extremely thinned, and the strength of the buckling portion cannot be ensured. This increases the possibility that the buckling portion will break due to aging or the like. If the buckling portion breaks, there is a risk that part of the insulator housed inside the housing will fly out to the outside. An example of a spark plug that can suppress such problems is the spark plug described in Patent Document 1 below.

The spark plug described in Patent Document 1 further includes a fixed sleeve that is fastened to the outer periphery of the housing. With this configuration, even if the buckling portion of the housing is damaged, the fixed sleeve prevents the insulator from scattering to the outside.

Patent No. 6450821

The spark plug is attached to the engine head block by, for example, attaching a tool such as a hexagonal wrench to the outer periphery of the housing, and then using the tool to apply torque to the spark plug and screw the male thread of the spark plug into the female thread of the engine head block. Therefore, when a fixed sleeve is attached to the outer periphery of the housing as in the spark plug described in Patent Document 1, it is necessary to attach a tool such as a hexagonal wrench to the outer periphery of the fixed sleeve. Therefore, it is necessary to set the outer diameter of the fixed sleeve to a predetermined dimension that can engage with the tool. As a result, in the spark plug described in Patent Document 1, the thickness of the housing must be made thinner by the amount of the fixed sleeve compared to a spark plug that does not have a fixed sleeve. If this significantly reduces the strength of the housing, there is a high possibility that the buckling part, which is the weakest in terms of strength, will break when the housing is attached to the insulator.

This disclosure was made in light of these circumstances, and its purpose is to provide a spark plug that can be made smaller while still maintaining the strength of the housing.

The spark plug that solves the above problem includes a cylindrical housing (11) that is assembled to the outer periphery of an insulator (12), and a reinforcing member (60) that is attached to the outer periphery of the housing. The outer periphery of the housing is provided with a crimped portion (25) that is provided at the base end of the housing and is crimped, a tool engagement portion (24) that is provided at the tip end of the housing relative to the crimped portion and can engage with a tool, a threaded portion (20) that is provided at the tip end of the housing and has a male thread, a body portion (22) that is provided at the base end of the housing relative to the threaded portion and has an outer diameter larger than the outer diameter of the threaded portion, and a buckling portion (23) that is formed by buckling the bottom wall portion of a buckling groove portion (26) that is provided between the tool engagement portion and the body portion. The reinforcing member is inserted into the buckling groove portion and is joined to the body portion and the tool engagement portion.

With this configuration, the strength of the buckling portion can be supplemented by the reinforcing member inserted into the buckling groove portion. As a result, the strength of the housing can be ensured. Furthermore, by inserting a reinforcing member into the buckling groove portion, the reinforcing member does not protrude significantly from the outer peripheral surface of the housing, allowing the spark plug to be made smaller.

Note that the symbols in parentheses in the above means and claims are examples showing the correspondence with the specific means described in the embodiments described below.

The spark plug disclosed herein makes it possible to reduce the size of the housing while maintaining its strength.

FIG. 1 is a cross-sectional view showing a broken cross-sectional structure of a spark plug according to a first embodiment. FIG. 2 is a front view showing the front structure of the housing of the first embodiment. FIG. 3 is a cross-sectional view showing a broken cross-sectional structure of the periphery of a housing in the spark plug of the first embodiment. FIG. 4 is a perspective view showing a perspective structure of the reinforcing member of the first embodiment. FIG. 5 is a front view showing the front structure around the housing of the spark plug of the first embodiment. FIG. 6 is a perspective view showing a perspective structure of a reinforcing member according to a first modified example of the first embodiment. FIG. 7 is a front view showing an example of assembly of a reinforcing member in a spark plug according to a first modified example of the first embodiment. FIG. 8 is a front view showing a front structure around a housing of a spark plug according to a first modified example of the first embodiment. FIG. 9 is a front view showing a front structure around a housing of a spark plug according to a second modified example of the first embodiment. FIG. 10 is a front view showing the front structure around the housing of the spark plug of the second embodiment. FIG. 11 is a cross-sectional view showing a cross-sectional structure of the periphery of a housing in a spark plug of the second embodiment. FIG. 12 is a cross-sectional view showing a cross-sectional structure taken along line XII-XII in FIG. FIG. 13 is a front view showing a front structure around a housing in a spark plug according to a modification of the second embodiment.

Hereinafter, an embodiment of a spark plug will be described with reference to the drawings. In order to facilitate understanding of the description, the same components in the various drawings are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.
First Embodiment
First, a first embodiment of a spark plug will be described. A spark plug 10 of this embodiment shown in Fig. 1 is attached to an engine head of a vehicle and is used to ignite an air-fuel mixture in a cylinder of the engine by forming a spark discharge based on the application of a voltage. The spark plug 10 includes a housing 11, an insulator 12, a center electrode 13, and a ground electrode 14.

The housing 11 is made of a metal material such as carbon steel and is formed into a cylindrical shape centered on a central axis m10 of the spark plug 10. A lower end portion of an insulator 12 is coaxially inserted inside the housing 11.
The insulator 12 is made of an insulating material such as alumina and is formed into a cylindrical shape centered on a central axis m10. The housing 11 is integrally assembled to the outer periphery of the insulator 12. A center electrode 13, a glass seal 15, a resistor 16, and a terminal fitting 17 are inserted and held in a through hole 121 formed inside the insulator 12.

The central electrode 13 has an electrode base material 131 and an electrode tip 132. The electrode base material 131 is made of a nickel (Ni) alloy or the like having excellent heat resistance, and is formed into a cylindrical shape centered on the central axis m10. Specifically, the inner material of the electrode base material 131 is made of copper, and the outer material is made of a nickel alloy. The tip of the electrode base material 131 is exposed from the lower end of the insulator 12. The electrode tip 132 is joined to the tip of the electrode base material 131. The electrode tip 132 is formed into a cylindrical shape centered on the central axis m10. The electrode tip 132 is made of an iridium alloy or the like containing iridium (Ir), which has a high melting point and excellent wear resistance, and rhodium (Rh) to suppress the high-temperature volatility of iridium.

The resistor 16 can be formed by heat sealing a resistor composition containing a resistive material such as carbon or ceramic powder and glass powder, or by inserting a cartridge-type resistor. The glass seal 15 is made of copper glass, which is made by mixing copper powder into glass. A terminal metal fitting 17 is disposed on the base end side of the resistor 16 via the glass seal 15. The terminal metal fitting 17 is made of, for example, an iron alloy. The terminal metal fitting 17 is a terminal for electrically connecting the spark plug 10 to the ignition coil.

The ground electrode 14 has an electrode base material 141 and a precious metal tip 142. The electrode base material 141 is made of a nickel alloy or the like. The electrode base material 141 is attached integrally to the lower end surface of the housing 11. The electrode base material 141 is formed so as to extend in a curved manner from the lower end surface of the housing 11. The tip of the electrode base material 141 is positioned so as to face the electrode tip 132 of the center electrode 13. The precious metal tip 142 is joined to the tip of the electrode base material 141. The precious metal tip 142 is made of a precious metal alloy such as an iridium alloy or a platinum alloy, for example, a Pt-20Ir material. The precious metal tip 142 is arranged to face the electrode tip 132 of the center electrode 13 with a predetermined gap therebetween.

In this spark plug 10, an external circuit that applies a high voltage is connected to the terminal metal fitting 17. When a high voltage is applied to the terminal metal fitting 17 by the external circuit, a spark discharge is generated between the electrode tip 132 of the center electrode 13 and the precious metal tip 142 of the ground electrode 14. The spark discharge generated by this spark plug 10 ignites the air-fuel mixture in the cylinder of the engine, causing the mixture to burn.

Next, the structure of the housing 11 will be described in detail. For convenience, in the following, of both ends of the housing 11 in the direction along the central axis m10, the end located closer to the ground electrode 14 will be referred to as the tip end 111, and the opposite end will be referred to as the base end 112. In addition, the direction from the tip end 111 of the housing 11 toward the base end 112 will be referred to as the upward direction, and the opposite direction will be referred to as the downward direction.

As shown in FIG. 2, the outer peripheral surface of the housing 11 is provided with, in order from the tip end 111 to the base end 112, a threaded portion 20, a thread stealing portion 21, a body portion 22, a buckling portion 23, a tool engagement portion 24, and a crimping portion 25.
The threaded portion 20 is a male threaded portion formed on the outer circumferential surface of the housing 11 from the tip portion 111 to the middle portion. The spark plug 10 can be fixed to the engine head block by screwing the threaded portion 20 into a female threaded portion formed in the engine head block.

The thread stealing portion 21 is provided adjacent to the threaded portion 20 on the side of the base end 112 of the housing 11. The thread stealing portion 21 is a portion having an outer diameter smaller than the outer diameter of the threaded portion 20. The thread stealing portion 21 is a portion for allowing the cutting tool to escape when the cutting tool is used to form the threaded portion 20 on the outer peripheral surface of the housing 11. As shown in FIG. 3, an annular gasket 30 is inserted into the thread stealing portion 21.

As shown in FIG. 2, the body 22 is provided adjacent to the base end 112 side of the housing 11 relative to the thread stealing portion 21. The body 22 has an outer diameter larger than the outer diameter of the threaded portion 20. The body 22 is the portion that is pressed against the engine head block via the gasket 30 when the spark plug 10 is attached to the engine head block.

As shown in FIG. 3, a gap is formed between the inner peripheral surface of the base end 112 of the housing 11 and the outer peripheral surface of the insulator 12. Ring members 40, 41 such as O-rings and powdered talc 50 are housed in this gap. In detail, the ring members 40, 41 are disposed on both ends of the talc 50 in the direction along the central axis m10 of the housing 11. The ring members 40, 41 and the talc 50 seal the gap formed between the base end 112 of the housing 11 and the outer peripheral surface of the insulator 12.

The crimped portion 25 is a portion formed by crimping the base end portion 112 of the housing 11 using a specified jig. The crimped portion 25 seals and fixes the ring members 40, 41 and talc 50 in the gap formed between the inner peripheral surface of the base end portion 112 of the housing 11 and the outer peripheral surface of the insulator 12.

As shown in FIG. 2, the tool engagement portion 24 is provided adjacent to the crimping portion 25 on the side of the tip portion 111 of the housing 11. The tool engagement portion 24 is a portion with which a specified tool is engaged when fastening the spark plug 10 to the engine head block. In this embodiment, the outer peripheral surface of the tool engagement portion 24 is formed in a regular hexagonal shape so that a tool such as a hexagonal wrench can be engaged.

The buckling portion 23 is provided between the body portion 22 and the tool engagement portion 24. As shown in FIG. 3, the plate thickness of the buckling portion 23 is thinner than the plate thickness of other portions of the housing 11. The buckling portion 23 is a portion formed by buckling deformation of the bottom wall portion of the buckling groove portion 26 provided between the body portion 22 and the tool engagement portion 24, and has a shape that curves outward. By forming the buckling portion 23, the strength of the housing 11 in that portion is increased by work hardening, so that the housing 11 can be fixed to the insulator 12 more firmly.

In the spark plug 10 of this embodiment, the housing 11 is attached to the insulator 12 as follows. First, the insulator 12 is inserted into the housing 11, and then the ring members 40, 41 and talc 50 are placed in the gap formed between the inner peripheral surface of the base end 112 of the housing 11 and the outer peripheral surface of the insulator 12 as shown in FIG. 3. Then, a pressing force is applied to the base end 112 of the housing 11 in the direction indicated by the arrow F11 using a specified jig, thereby forming the crimped portion 25 at the base end 112 of the housing 11.

On the other hand, before the buckling portion 23 of the housing 11 is buckled, the buckling portion 23 has a cylindrical shape. At this time, the strengths of the thread stealing portion 21 and the buckling portion 23 satisfy the relationship "strength of buckling portion 23 < strength of thread stealing portion 21". Therefore, when a pressing force is further applied to the base end portion 112 of the housing 11 in the direction indicated by the arrow F11 using a specified jig, the buckling portion 23 buckles as shown in FIG. 3 before the thread stealing portion 21 buckles. As a result, the strength of the buckling portion 23 is increased by work hardening, and the strengths of the thread stealing portion 21 and the buckling portion 23 satisfy the relationship "strength of buckling portion 23 > strength of thread stealing portion 21".

After the manufacture of the spark plug 10 is completed in this manner, when the spark plug 10 is to be assembled to the engine head block, first, the threaded portion 20 of the housing 11 is inserted into the female threaded hole of the engine head block. Then, a tool such as a hexagonal wrench is engaged with the tool engagement portion 24 of the housing 11, and the threaded portion 20 of the housing 11 is screwed into the female threaded hole of the engine head block using the tool. This causes the spark plug 10 to be fastened and fixed to the engine head block. When the spark plug 10 is fastened to the engine head block, the gasket 30 arranged on the outer periphery of the thread stealing portion 21 of the housing 11 is deformed by being crushed between the bottom surface 220 of the body portion 22 and the engine header block. As a result, the gap formed between the bottom surface 220 of the body portion 22 of the housing 11 and the engine header block is sealed by the gasket 30.

However, in order to reduce the size of such a spark plug 10, the buckling portion 23 must be thinned. This significantly reduces the strength of the buckling portion 23, and there is a possibility that unintended deformation may occur in the buckling portion 23 when the buckling portion 23 is buckled. This reduces the strength of the buckling portion 23. If the strength of the buckling portion 23 is reduced, the buckling portion 23 becomes more susceptible to breakage, which may cause problems such as the insulator 12 housed inside the housing 11 popping out to the outside.

3, in the spark plug 10 of this embodiment, a reinforcing member 60 is attached to the buckling groove portion 26 of the housing 11 to reinforce the buckling portion 23. The reinforcing member 60 will be described in detail below.
3, the reinforcing member 60 has substantially the same outer shape as the outer shape of the tool engagement portion 24, and is formed in a hexagonal ring shape centered on a central axis m10. The reinforcing member 60 is made of the same material as the housing 11, for example, carbon steel. Note that the reinforcing member 60 may be made of a material different from that of the housing 11.

As shown in FIG. 4, the reinforcing member 60 is composed of two reinforcing pieces 61, 62. Each reinforcing piece 61, 62 has half the shape of the reinforcing member 60, i.e., half the shape of a hexagonal ring. Grooves 610, 620 are formed on the inner peripheral surface of each reinforcing piece 61, 62, respectively. The cross-sectional shape of the grooves 610, 620 perpendicular to the circumferential direction C centered on the central axis m10 is formed in an arc shape so as to correspond to the outer shape of the buckling portion 23 of the housing 11.

As shown in FIG. 3, each of the reinforcing pieces 61, 62 is inserted into the buckling groove 26. As shown in FIG. 5, the abutment portion B11 of each of the reinforcing pieces 61, 62, the abutment portions B21, B22 between each of the reinforcing pieces 61, 62 and the tool engagement portion 24, and the abutment portions B31, B32 between each of the reinforcing pieces 61, 62 and the body portion 22 are joined to each other by laser welding. With this joining structure, the reinforcing member 60 is fixed to the housing 11 while inserted into the buckling groove 26.

According to the spark plug 10 of the present embodiment described above, the following actions and effects (1) to (3) can be obtained.
(1) The strength of the buckling portion 23 of the housing 11 can be supplemented by the reinforcing member 60 inserted into the buckling groove portion 26. As a result, the strength of the housing 11 can be ensured. Furthermore, by inserting the reinforcing member 60 into the buckling groove portion 26, the reinforcing member 60 does not protrude significantly from the outer circumferential surface of the housing 11, so that the spark plug 10 can be made smaller.

(2) The reinforcing member 60 is a hexagonal ring-shaped member that is inserted into the buckling groove portion 26. According to this configuration, the buckling portion 23 can be surrounded by the reinforcing member 60, so that the strength of the buckling portion 23 can be more appropriately supplemented.
(3) The reinforcing member 60 is composed of a plurality of divided reinforcing pieces 61, 62. With this configuration, the reinforcing member 60 can be easily attached to the buckling groove portion 26.

(First Modification)
Next, a first modification of the spark plug 10 of the first embodiment will be described.
The spark plug 10 of this modified example employs a reinforcing member 60 shown in Fig. 6. As shown in Fig. 6, the reinforcing member 60 is formed in an annular shape centered on a central axis m10, and has a notch 63 in a part thereof. Thus, the reinforcing member 60 has a substantially C-shape.

In the spark plug 10 of this modified example, the buckling portion 23 of the housing 11 is inserted into the notch 63 of the reinforcing member 60, and the reinforcing member 60 is attached to the outer periphery of the buckling portion 23 as shown in FIG. 7. Then, as shown in FIG. 8, a pressing force is applied to the outer periphery of the reinforcing member 60 in the direction indicated by the arrow F12 to swage the reinforcing member 60 into the buckling groove portion 26. Furthermore, the abutting portion between the reinforcing member 60 and the tool engagement portion 24 and the abutting portion between the reinforcing member 60 and the body portion 22 are joined to each other by laser welding. The symbol B40 shown in FIG. 8 indicates a joint formed by laser welding. With such a swaging structure and joining structure, the reinforcing member 60 is fixed to the housing 11 while inserted into the buckling groove portion 26.

Even when using a reinforcing member 60 having a structure like that of this modified example, the action and effect shown in (1) above can be obtained. In addition, since the reinforcing member 60 is made of a single part, it is possible to reduce the number of parts compared to when the reinforcing member 60 of the first embodiment is used.

(Second Modification)
Next, a second modification of the spark plug 10 of the first embodiment will be described.
As shown in Fig. 9, the outer peripheral surface of the tool engagement portion 24 of this modified example is formed in a bi-hex shape. The reinforcing member 60 is composed of a plurality of reinforcing pieces 65 arranged alternately with respect to the plurality of vertices 241 of the tool engagement portion 24. Abutment portions B70 between each reinforcing piece 65 and the upper surface 221 of the body portion 22, abutment portions B71 and B72 between each reinforcing piece 65 and the buckling groove portion 26, and abutment portion B73 between the buckling groove portion 26 and the tool engagement portion 24 are joined by laser welding. Each reinforcing piece 65 is fixed to the housing 11 by this joining structure.

Even when the reinforcing member 60 having the structure of this modified example is used, the actions and effects shown in (1) and (3) above can be obtained.
Second Embodiment
Next, a second embodiment of the spark plug 10 will be described. The following description will focus on the differences from the spark plug 10 of the first embodiment.

In the spark plug 10 of this embodiment, the reinforcing member 60 is composed of a plurality of reinforcing pieces 64 as shown in FIG. 10. Each reinforcing piece 64 is formed to extend in a direction parallel to the central axis m10 from the buckling groove portion 26 to the crimping portion 25. Specifically, when the portion provided between the plurality of vertices 241 in the tool engagement portion 24 of the housing 11 is defined as a side wall 242, each reinforcing piece 64 is formed to extend across the buckling groove portion 26, the side wall 242 of the tool engagement portion 24, and the crimping portion 25.

As shown in FIG. 11, each reinforcing piece 64 abuts against the upper surface 221 of the body 22 at the buckling groove 26. Each reinforcing piece 64 also abuts against the side wall 242 of the tool engagement portion 24 and the crimping portion 25. The abutting portion between each reinforcing piece 64 and the upper surface 221 of the body 22, the abutting portion between each reinforcing piece 64 and the center of the side wall 242 of the tool engagement portion 24, and the abutting portion between each reinforcing piece 64 and the crimping portion 25 are each joined by laser welding. Reference characters B50 to B52 shown in FIG. 10 and FIG. 11 indicate joints formed by laser welding. Each reinforcing piece 64 is fixed to the housing 11 by this joining structure.

10 , the multiple reinforcing pieces 64 are provided at positions corresponding to the respective centers of the multiple side walls 242 of the tool engagement portion 24. Thus, the multiple reinforcing pieces 64 are disposed at predetermined intervals in the circumferential direction C of the housing 11.
FIG. 12 shows a cross-sectional structure taken along line XII-XII shown in FIG. 10. As shown in FIG. 12, the reinforcing piece 64 perpendicular to the central axis m10 is formed in a substantially pentagonal shape. The two-dot chain line shown in FIG. 12 shows the outer shape of the cross-sectional structure of the tool engagement portion 24 perpendicular to the central axis m10. The length L11 from the central axis m10 to the apex 640 of each reinforcing piece 64 is substantially equal to the length L12 from the central axis m10 to each apex 241 of the tool engagement portion 24. Therefore, each reinforcing piece 64, in other words, the reinforcing member 60 does not protrude outside the maximum outer diameter of the tool engagement portion 24, specifically, the circle passing through each apex 640 of the tool engagement portion 24. When the spark plug 10 is viewed from a direction parallel to the central axis m10, the tool engagement portion 24 and the reinforcing member 60 are substantially bi-hex shaped.

According to the spark plug 10 of the present embodiment described above, in addition to the action and effect of (1) above, the action and effect described in (4) below can be obtained.
(4) Since each reinforcing piece 64 is engaged not only with the buckling groove portion 26 but also with the side wall 242 of the tool engaging portion 24 and the crimping portion 25, it is possible to supplement the strength of not only the buckling portion 23 but also the tool engaging portion 24 and the crimping portion 25. As a result, the strength of the housing 11 can be further increased.

(Third Modification)
Next, a modification of the spark plug 10 of the second embodiment will be described.
As shown in FIG. 13, a reinforcing member 60 of this modified example has a shape that combines the structure of the reinforcing pieces 61 and 62 of the first embodiment and the structure of the reinforcing piece 64 of the second embodiment.

Specifically, the reinforcing member 60 of this modified example is divided into two reinforcing pieces 61, 62 as shown in FIG. 4. Each reinforcing piece 61, 62 is inserted into the buckling groove 26. Each reinforcing piece 61, 62 has an extension 611, 621 extending from its outer circumferential surface across the center of the side wall 242 of the tool engagement portion 24 and the crimping portion 25. Each extension 611, 621 is joined by laser welding at the portions abutting the upper surface 221 of the body portion 22, the center of the side wall 242 of the tool engagement portion 24, and the crimping portion 25. Reference characters B60 to B62 in FIG. 13 indicate joints formed by laser welding. The shapes of the joints B60 to B62 are substantially the same as the shapes of the joints B50 to B52 shown in FIG. 11.

By using such a reinforcing member 60, the buckling portion 23 of the housing 11 can be further reinforced compared to the case where a reinforcing member 60 as shown in FIG. 10 is used, so that the strength of the housing 11 can be further increased.
<Other embodiments>
The above embodiment can also be implemented in the following manner.

The reinforcing member 60 of the first embodiment is not limited to a two-part structure, and may be a three-part or more part structure.
Each reinforcing piece 64 in the second embodiment may be formed so as to span only the buckling groove portion 26 and the side wall 242 of the tool engagement portion 24 .

The tool engagement portion 24 of the housing 11 is not limited to a hexagonal shape, and may be any shape that allows a predetermined tool to be engaged therewith, such as a polygonal shape.
The present disclosure is not limited to the above specific examples. Any design changes made by a person skilled in the art to the above specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above specific examples, as well as their arrangements, conditions, shapes, etc., are not limited to those exemplified and can be changed as appropriate. The elements of each of the above specific examples can be combined as appropriate as long as no technical contradictions arise.

10: Spark plug 11: Housing 12: Insulator 20: Threaded portion 22: Body portion 23: Buckling portion 24: Tool engagement portion 25: Crimping portion 26: Buckling groove portion 60: Reinforcing member 61, 62, 64: Reinforcing piece

Claims (6)

A cylindrical housing (11) that is assembled to the outer periphery of an insulator (12);
a reinforcing member (60) attached to the outer periphery of the housing;
The outer circumferential surface of the housing is
a crimped portion (25) provided at a base end of the housing and crimped;
a tool engagement portion (24) provided on a tip end side of the housing with respect to the crimping portion and capable of engaging with a tool;
A threaded portion (20) provided at a tip end of the housing and having a male thread formed thereon;
a body portion (22) provided on a base end side of the housing with respect to the threaded portion and having an outer diameter larger than an outer diameter of the threaded portion;
a buckling portion (23) formed by buckling and deforming a bottom wall portion of a buckling groove portion (26) provided between the tool engagement portion and the body portion,
The reinforcing member is inserted into the buckling groove portion and joined to the body portion and the tool engagement portion. The spark plug according to claim 1 , wherein the reinforcing member is an annular member that is inserted into the buckling groove portion. The spark plug according to claim 2 , wherein the reinforcing member is composed of a plurality of reinforcing pieces (61, 62) divided in a circumferential direction . The spark plug according to claim 2 , wherein the reinforcing member is formed of a single annular part having a notch. The outer circumferential surface of the tool engagement portion is formed in a polygonal shape centered on a central axis of the housing,
When a portion provided between a plurality of vertices of the tool engagement portion is defined as a side wall,
The reinforcing member is composed of a plurality of reinforcing pieces (64) formed to extend across the side wall of the tool engagement portion and the buckling groove portion,
The reinforcing piece is joined to a side wall of the tool engagement portion, the buckling groove portion, and the body portion,
The spark plug according to claim 1 , wherein the reinforcing pieces are arranged at intervals in the circumferential direction of the housing. The spark plug according to claim 5 , wherein the reinforcing piece is formed so as to extend further from the tool engagement portion to the crimped portion and is joined to the crimped portion.

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