JP2022015939A - Spark plug - Google Patents

Abstract

To provide a spark plug which can prevent the detachment of an electrode chip.SOLUTION: By applying a voltage between a center electrode 13 and a ground electrode 14, a spark plug 10 creates a spark discharge. The ground electrode 14 has a ground electrode chip 141 and a ground electrode base material 140. The ground electrode chip 141 has an electrode member 30 and a bonding member 31. The electrode member 30 is formed in a cup shape. The bonding member 31 is disposed between the electrode member 30 and the ground electrode base material 140 so as to bond the electrode member 30 to the ground electrode base material 140. The electrode member 30 has: a constant diameter part 30a which has a constant outer diameter; and an enlarged diameter part 30b which is formed such that its outer diameter enlarges toward a predetermined direction Z. A base end part 301 of the electrode member 30 is spaced away from the ground electrode base material 140.SELECTED DRAWING: Figure 3

Description

This disclosure relates to spark plugs.

Conventionally, there is a spark plug described in Patent Document 1 below. This spark plug includes a center electrode and a ground electrode arranged with a predetermined gap from the center electrode. The ground electrode has an electrode base material formed in a substantially L shape and an electrode tip provided on the base material surface facing the center electrode in the electrode member. The electrode tip is formed so as to project from the base material surface of the electrode base material toward the center electrode. The base end of the electrode tip is joined to the electrode base material by laser welding. A molten portion melted by laser welding is formed around the base end portion of the electrode chip. The molten portion is formed so that the height gradually decreases from one side surface of the electrode chip located on the tip side of the electrode base material toward the other side surface of the electrode chip located on the bending portion side of the electrode base material. Has been done.

In the spark plug described in Patent Document 1, when a voltage is applied between the center electrode and the ground electrode, a spark discharge is first formed between the center electrode and the tip of the electrode tip. After that, the end of the spark discharge on the electrode tip side moves toward the tip of the electrode base material along the side surface of the electrode tip due to the flow of the air flow in the cylinder of the engine. Therefore, since the spark discharge can be guided to the outside of the center electrode and the ground electrode, the air-fuel mixture can be ignited outside the center electrode and the ground electrode. As a result, it is possible to suppress the heat of the flame from being absorbed by the center electrode and the ground electrode, so that the ignitability can be improved.

Japanese Patent No. 5980247

By the way, in the spark plug described in Patent Document 1, the molten portion formed at the base end portion of the electrode chip is a noble metal such as platinum which is a material for forming the electrode chip and nickel which is a material for forming the electrode base material. It is a part where metal such as alloy is melted. Therefore, the molten portion is inferior in wear resistance to spark discharge as compared with the electrode chip made of a single precious metal. Therefore, when the spark discharge is repeatedly formed, the molten portion is more likely to be consumed in a scoop-like shape than the electrode tip. If the molten portion is consumed, the electrode tip may fall off from the electrode base material.

The present disclosure has been made in view of such circumstances, and an object thereof is to provide a spark plug capable of suppressing the falling off of an electrode tip.

The spark plug (10) that solves the above problems forms a spark discharge by applying a voltage between the center electrode (13) and the ground electrode (14). The ground electrode has an electrode tip (141) arranged so as to face the center electrode with a gap, and a ground electrode base material (140) to which the electrode tip is bonded. The electrode tip has an electrode member (30) and a joining member (31). The electrode member is formed in a cup shape so as to have an opening at a base end portion (301) facing the ground electrode base material. The joining member is provided so as to be inserted into the inside through the opening of the electrode member, and is arranged between the electrode member and the ground electrode base material to join the electrode member to the ground electrode base material. The electrode member has the same outer diameter as the same diameter portion (30a) when the direction from the tip portion (300) facing the center electrode to the proximal end portion (301) facing the ground electrode is a predetermined direction. , A diameter-expanded portion (30b) formed so that the outer diameter becomes larger toward a predetermined direction, and a diameter-expanded portion (30b), which are formed in order from the tip portion to the base end portion. The base end portion of the electrode member is separated from the ground electrode base material.

Another spark plug (10C) that solves the above problems forms a spark discharge by applying a voltage between the center electrode (13) and the ground electrode (14). The ground electrode has an electrode tip (141) arranged so as to face the center electrode with a gap, and a ground electrode base material (140) to which the electrode tip is bonded. The electrode tip has an electrode member (30) and a joining member (31). The electrode member is formed in a cup shape so as to have an opening at a base end portion (301) facing the ground electrode base material. The joining member is provided so as to be inserted into the inside through the opening of the electrode member, and is arranged between the electrode member and the ground electrode base material to join the electrode member to the ground electrode base material. The electrode member is formed so that the outer diameter becomes smaller toward the predetermined direction when the direction from the tip portion (300) facing the center electrode to the proximal end portion (301) facing the ground electrode is a predetermined direction. It has a reduced diameter portion (30c) to be formed and an enlarged diameter portion (30b) formed so that the outer diameter increases toward a predetermined direction, in order from the tip end portion to the base end portion. The base end portion of the electrode member is separated from the ground electrode base material.

According to this configuration, after a spark discharge is formed between the center electrode and the tip of the electrode member of the ground electrode, one end of the spark discharge is from the tip of the electrode member due to the flow of airflow near the spark flag. The side surface of the electrode member is moved toward the base end portion. At that time, since the base end portion of the electrode member is separated from the ground electrode base material, one end of the spark discharge moves to the base end portion of the electrode member, but it becomes difficult to move to the ground electrode base material. Therefore, as compared with the structure in which the electrode tip and the ground electrode base material are connected via the molten portion as in the conventional spark plug, the phenomenon that the portion other than the electrode tip is consumed by the spark discharge is less likely to occur. As a result, it is possible to prevent the electrode tip from falling off from the ground electrode base material.

The reference numerals in parentheses described in the above means and claims are examples showing the correspondence with the specific means described in the embodiments described later.

According to the spark plug of the present disclosure, it is possible to prevent the electrode tip from falling off.

FIG. 1 is a cross-sectional view showing a broken cross-sectional structure of the spark plug of the first embodiment. FIG. 2 is a front view showing a frontal structure around a center electrode tip and a ground electrode tip of the spark plug of the first embodiment. FIG. 3 is a cross-sectional view showing a cross-sectional structure of the ground electrode chip of the first embodiment. 4 (A) and 4 (B) are diagrams schematically showing a method of joining a ground electrode tip to the ground electrode base material of the first embodiment. FIG. 5 is a perspective view showing an operation example of the spark plug of the first embodiment. FIG. 6 is a graph showing changes in the required voltages of the spark plugs of the first embodiment, the spark plugs of the first comparative example, and the spark plugs of the second comparative example. FIG. 7 is a cross-sectional view showing a cross-sectional structure of the ground electrode tip of the spark plug of the second embodiment. FIG. 8 is a graph showing changes in the required voltages of the spark plugs of the first embodiment, the spark plugs of the second embodiment, and the spark plugs of the comparative example.

Hereinafter, embodiments of the spark plug will be described with reference to the drawings. In order to facilitate understanding of the description, the same components are designated by the same reference numerals as possible in the drawings, and duplicate description is omitted.
<First Embodiment>
The spark plug 10 shown in FIG. 1 is arranged in a cylinder of an internal combustion engine. The spark plug 10 ignites the air-fuel mixture in the cylinder by forming a spark discharge based on the application of a voltage. The spark plug 10 includes a housing 11, an insulating insulator 12, a center electrode 13, and a ground electrode 14.

The housing 11 is made of a metal material such as iron and is formed in a cylindrical shape around the axis LM. A threaded portion 11a is formed on the outer periphery of the lower portion of the housing 11. The spark plug 10 can be fixed to the cylinder block by screwing the screw portion 11a into a screw hole formed in the cylinder block of the internal combustion engine. A gasket 17 is provided at the upper end of the threaded portion 11a of the housing 11 to seal the gap formed between the internal combustion engine and the spark plug. Inside the housing 11, the lower end of the insulating insulator 12 is coaxially inserted.

The insulating insulator 12 is formed in a cylindrical shape around the axis LM by an insulating material such as alumina. A housing 11 is integrally assembled to the outer peripheral portion of the insulating insulator 12. The center electrode 13 is inserted and held in the through hole 12a formed in the lower part of the insulating insulator 12.

The center electrode 13 has a center electrode base material 130 and a center electrode tip 131. The center electrode base material 130 is formed of a nickel (Ni) alloy or the like having excellent heat resistance in a columnar shape centered on the axis LM. Specifically, the inner material of the center electrode base material 130 is made of copper, and the outer material thereof is made of a nickel alloy. The tip portion 130a of the center electrode base material 130 is exposed from the lower end of the insulating insulator 12. The central axis of the center electrode base material 130 coincides with the central axis LM of the spark plug 10. The center electrode tip 131 is joined to the tip portion 130a of the center electrode base material 130 by a joining process such as laser welding or resistance welding. The center electrode tip 131 is formed in a columnar shape about the axis LM. The center electrode tip 131 is made of iridium (Ir), which has a high melting point and excellent wear resistance, as a main material, and is made of an iridium alloy containing rhodium (Rh) in order to suppress high-temperature volatility of iridium. The center electrode tip 131 is not limited to the iridium alloy, and may be formed of a noble metal such as a platinum alloy containing platinum (Pt) as a main material.

The ground electrode 14 has a ground electrode base material 140 and a ground electrode tip 141. The ground electrode base material 140 is made of a nickel alloy or the like. The ground electrode base material 140 is integrally formed on the lower end surface of the housing 11. The ground electrode base material 140 is formed so as to be curved and extend from the lower end surface of the housing 11. The tip portion 140b of the ground electrode base material 140 is located so as to face the center electrode tip 131. The ground electrode tip 141 is joined to the tip portion 140b of the ground electrode base material 140 by resistance welding. The ground electrode tip 141 is also made of a noble metal such as an iridium alloy or a platinum alloy. The ground electrode chip 141 has a predetermined gap 18 and is arranged so as to face the center electrode chip 131. Hereinafter, the gap 18 formed between the center electrode tip 131 and the ground electrode tip 141 will be referred to as a “spark discharge gap 18”.

In the spark plug 10, the central shaft member 15 and the terminal portion 16 are electrically connected to the upper portion of the central electrode 13. An external circuit that applies a high voltage is connected to the terminal portion 16. When a high voltage is applied to the terminal portion 16 by an external circuit, a spark discharge is formed between the center electrode chip 131 of the center electrode 13 and the ground electrode chip 141 of the ground electrode 14. The spark discharge formed by the spark plug 10 ignites the air-fuel mixture in the cylinder of the internal combustion engine, so that the air-fuel mixture burns.

Next, the structure of the ground electrode 14 of the spark plug 10 will be specifically described.
As shown in FIG. 2, the ground electrode tip 141 is joined to the upper surface 140a of the ground electrode base material 140. The upper surface 140a of the ground electrode base material 140 is a flat surface facing the center electrode chip 131 in the ground electrode base material 140. The ground electrode tip 141 has an electrode member 30 and a joining member 31.

As shown in FIG. 3, the electrode member 30 is formed in a cup shape so as to have an opening in a base end portion 301 facing the ground electrode base material 140. The electrode member 30 is made of a noble metal such as an iridium alloy. The electrode member 30 has the same diameter portion 30a and the diameter expansion portion 30b in order from the tip portion 300 facing the center electrode tip 131 toward the proximal end portion 301 facing the ground electrode base material 140. .. Hereinafter, the direction from the tip portion 300 of the electrode member 30 toward the proximal end portion 301 is referred to as a “predetermined direction Z”. The same diameter portion 30a is a portion having the same outer diameter centered on the axis LM. The enlarged diameter portion 30b is a portion formed so that the outer diameter centered on the axis Lm becomes larger toward the predetermined direction Z.

The joining member 31 is a member for joining the electrode member 30 to the ground electrode base material 140. The joining member 31 is made of a material having a melting point lower than that of the electrode member 30, for example, a nickel alloy. The joining member 31 is provided so as to be inserted into the inside of the electrode member 30 through the opening. The lower end portion 310 of the joining member 31 is exposed from a gap provided between the base end portion 301 of the electrode member 30 and the ground electrode base material 140, and is arranged so as to intervene between them. As a result, the base end portion 301 of the electrode member 30 is separated from the ground electrode base material 140. Hereinafter, the lower end portion 310 of the joining member 31 is also referred to as an “exposed portion 310”. The exposed portion 310 of the joining member 31 is arranged inside the outer edge of the base end portion 301 of the joining member 31. Therefore, a gap is formed between the base end portion 301 of the electrode member 30 and the ground electrode base material 140.

Next, a method of joining the ground electrode tip 141 to the ground electrode base material 140 will be described.
In the manufacturing process of the spark plug 10, as shown in FIG. 4A, a bottomed cylindrical electrode member 30 and a cylindrical joining member 31 are formed. When joining the ground electrode tip 141 to the ground electrode base material 140, first, the joining member 31 is inserted from the opening portion of the base end portion 301 of the electrode member 30 as shown by an arrow C in FIG. 4 (A). To. Then, as shown in FIG. 4B, the assembled products of the electrode member 30 and the joining member 31 are installed on the upper surface 140a of the ground electrode base material 140, and then they are joined by resistance welding. Specifically, while applying the load in the direction indicated by the arrows F1 and F2 in FIG. 4B, that is, the load in the direction of compressing the electrode member 30, the joining member 31, and the ground electrode base material 140, those members. Apply current to. As a result, Joule heat is generated in the electrode member 30, the joining member 31, and the ground electrode base material 140. The Joule heat softens the electrode member 30 and the joining member 31.

When the electrode member 30 and the joint member 31 are softened while the compressive loads F1 and F2 as shown in FIG. 4B are applied to the electrode member 30, the joint member 31, and the ground electrode base material 140, the electrode member The joining member 31 located near the base end portion 301 of 30 is deformed so as to spread outward in the radial direction. Along with the deformation of the joining member 31, a force F3 in the radial direction is applied to the base end portion 301 of the electrode member 30. As a result, the base end portion 301 of the electrode member 30 can be deformed from a cylindrical shape to a divergent shape as shown in FIG.

After that, when the temperatures of the electrode member 30, the bonding member 31, and the ground electrode base material 140 are further increased by Joule heat, the bonding member 31 having a melting point lower than that of the electrode member 30 and the ground electrode base material 140 is melted first. The electrode member 30 and the ground electrode base material 140 are melt-bonded via the bonding member 31. Then, by cooling them, the joining of the ground electrode tip 141 to the ground electrode base material 140 is completed.

Next, an operation example of the spark plug 10 of the present embodiment will be described.
In the spark plug 10, when a high voltage is applied to the terminal portion 16 from the external circuit, first, as shown by the solid line D1 in FIG. 5, the tip portion 131a of the center electrode chip 131 and the electrode member of the ground electrode chip 141 A spark discharge is formed between the tip portion 300 of 30 and the tip portion 300. After that, the spark discharge is extended by the flow of the air flow in the cylinder of the internal combustion engine.

Specifically, the starting point P on the ground electrode chip 141 side in the spark discharge moves from the tip portion 300 of the electrode member 30 toward the proximal end portion 301 along the side surface of the electrode member 30 as indicated by an arrow. After that, when the starting point on the ground electrode chip 141 side of the spark discharge flows to the proximal end portion 301 of the electrode member 30, there is no more movable portion of the starting point of the spark discharge. That is, the corner of the base end portion 301 of the electrode member 30 becomes one electric field concentration point, and the starting point on the ground electrode chip 141 side in the spark discharge stops at the base end portion 301 of the electrode member 30, so that the spark discharge is the ground electrode. It is possible to suppress the movement to the base metal 140.

When the starting point P on the ground electrode chip 141 side in the spark discharge stops at the base end portion 301 of the electrode member 30, the spark discharge reaches a position away from the spark discharge gap 18 as shown by the solid line D2 in FIG. Moving. Therefore, when the air-fuel mixture is ignited by the spark discharge, the initial flame is formed at a position separated from the spark discharge gap 18, so that the heat of the initial flame is transferred to the center electrode chip 131, the ground electrode chip 141, and the ground electrode base material. It becomes difficult to be absorbed by 140. Therefore, the ignitability of the air-fuel mixture can be improved.

Further, if the electrode member 30 is formed with the same diameter portion 30a and the diameter expansion portion 30b as in the spark plug 10 of the present embodiment, the life of the spark plug 10 can be extended.
Specifically, the required voltage Vr of the spark plug of the present embodiment changes with the passage of time, for example, as shown by a solid line in FIG. The required voltage Vr of the spark plug is the minimum voltage required to be applied to the spark plug 10 from an external circuit in order to form a spark discharge. In FIG. 6, the transition of the required voltage Vr of the spark plug 10A of the first comparative example in which the ground electrode tip is formed only in the enlarged diameter portion is shown by a one-point chain line, and the ground electrode tip is formed only in the same diameter portion. The transition of the required voltage Vr of the spark plug 10B of the second comparative example is shown by a two-point chain line, and the transition of the required voltage Vr of the spark plug of the present embodiment is shown by a solid line. In the spark plug 10A of the first comparative example and the spark plug 10B of the second comparative example, the ground electrode tip is joined to the ground electrode base material by laser welding as in the conventional spark plug.

For example, if the use of the spark plug is started at time t10, the corner portion of the tip of the ground electrode chip is consumed at the initial stage, and the corner portion changes from the pin angle shape to the R shape. The time t11 indicates the time when the corner portion of the tip of the ground electrode chip is consumed to the R shape. In this case, the required voltage Vr of the spark plug rises sharply during the period from time t10 to time t11. The change in the required voltage Vr of the spark plug during the period from the time t10 to the time t11 is substantially the same in any of the spark plugs 10A and 10B of the first comparative example and the second comparative example, and the spark plug 10 of the present embodiment. ..

After time t11, in the spark plug 10B of the second comparative example in which the ground electrode tip is formed only in the same diameter portion, the required voltage Vr gradually increases until discharge cannot be performed, as shown by the alternate long and short dash line. This is because the spark discharge gap expands due to the consumption of the ground electrode chip with the passage of time, and the required voltage Vr rises as the spark discharge gap expands.

On the other hand, in the spark plug 10A of the first comparative example in which the ground electrode tip is formed only by the enlarged diameter portion, as shown by the alternate long and short dash line, after time t11, the inclination is larger than that of the spark plug 10B of the second comparative example. The required voltage Vr rises. This is because not only the spark discharge gap expands with the passage of time, but also the outer diameter of the tip of the ground electrode chip gradually increases due to wear, so that the initial spark discharge is formed in the ground electrode chip. This is because the outer diameter is substantially expanded.

On the other hand, in the spark plug 10 of the present embodiment, as shown by the solid line, the period from the time t11 to the time t12 when the same diameter portion 30a is consumed is the spark plug of the second comparative example shown by the alternate long and short dash line. As with 10B, the required voltage Vr gradually rises. Then, when the enlarged diameter portion 30b begins to wear out after the time t12, the required voltage Vr of the spark plug 10 of the present embodiment begins to rise with a larger inclination.

As the required voltage Vr of the spark plug increases, the voltage required to be applied to the spark plug from the external circuit increases. When the required voltage Vr of the spark plug exceeds a predetermined value, spark discharge is not formed even if a voltage is applied to the spark plug from an external circuit. Therefore, it can be said that the life of the spark plug becomes shorter as the degree of increase in the required voltage Vr of the spark plug increases.

Considering this, the spark plug 10B of the second comparative example shown by the alternate long and short dash line is excellent in terms of life. However, in the spark plug 10B of the second comparative example, since the ground electrode tip is formed only in the same diameter portion, it is difficult to guide the spark discharge to the outside of the center electrode tip and the ground electrode tip. Therefore, it is inferior in terms of ignitability.

On the other hand, the spark plug 10A of the first comparative example shown by the alternate long and short dash line is inferior in terms of life. However, in the spark plug 10A of the first comparative example, since the ground electrode tip is formed only by the enlarged diameter portion, it is easy to guide the spark discharge to the outside of the center electrode tip and the ground electrode tip. Therefore, it is excellent in terms of ignitability.

As described above, there are advantages and disadvantages in the spark plugs 10A and 10B of any of the first comparative example and the second comparative example.
In this respect, the spark plug 10 of the present embodiment has excellent ignitability while realizing a life close to that of the spark plug 10B of the second comparative example. In other words, the spark plug 10 of the present embodiment can achieve both life and ignitability.

According to the spark plug 10 of the present embodiment described above, the actions and effects shown in the following (1) to (4) can be obtained.
(1) The ground electrode tip 141 has an electrode member 30 formed in a cup shape and a joining member 31 for joining the electrode member 30 to the ground electrode base material 140. The electrode member 30 has the same diameter portion 30a having the same outer diameter and the enlarged diameter portion 30b formed so that the outer diameter increases toward a predetermined direction Z from the tip portion 300 toward the base end portion 301. Have in order. The base end portion 301 of the electrode member 30 is separated from the ground electrode base material 140. According to this configuration, when a spark discharge is formed between the center electrode chip 131 and the electrode member 30, one end of the spark discharge moves to the base end 301 of the electrode member 30 of the ground electrode chip 141. However, it becomes difficult to move to the ground electrode base material 140. Therefore, as compared with the structure in which the electrode tip and the ground electrode base material are connected via the molten portion as in the conventional spark plug, the phenomenon that the portion other than the ground electrode tip 141 is less likely to be consumed by the spark discharge is less likely to occur. As a result, it is possible to prevent the ground electrode chip 141 from falling off from the ground electrode base material 140. Further, the life of the spark plug 10 and the ignitability can be compatible with each other.

(2) A gap is formed between the outer edge of the base end portion 301 of the electrode member 30 of the ground electrode chip 141 and the ground electrode base material 140. According to this configuration, when the spark discharge moves due to the flow of the airflow in the cylinder of the internal combustion engine, one end of the spark discharge on the ground electrode chip 141 side stops at the base end 301 of the electrode member 30. , The ground electrode base material 140 is less likely to be consumed by the spark discharge.

(3) The exposed portion 310 provided between the base end portion 301 of the electrode member 30 and the ground electrode base material 140 in the joining member 31 is located inside the outer edge of the base end portion 301 of the electrode member 30. .. According to this configuration, for example, a phenomenon in which one end of the spark discharge that has moved to the base end 301 of the electrode member 30 moves to the ground electrode base material 140 via the joining member 31 is unlikely to occur. The material 140 is less likely to be consumed.

(4) The material forming the electrode member 30 is a material having a melting point lower than that of the member forming the joining member 31. More specifically, the material forming the electrode member 30 is a noble metal such as an iridium alloy or a platinum alloy. The material forming the joining member 31 is, for example, a nickel alloy. According to this configuration, the electrode member 30 can be easily joined to the ground electrode base material 140 by using resistance welding.

<Second Embodiment>
Next, the spark plug of the second embodiment will be described. Hereinafter, the differences from the spark plug 10 of the first embodiment will be mainly described.
As shown in FIG. 7, in the spark plug 10C of the present embodiment, the electrode member 30 is provided with a reduced diameter portion 30c and a diameter expanded portion 30b in order from the tip end portion 300 toward the base end portion 301. There is. The reduced diameter portion 30c is a portion formed so that the outer diameter centered on the axis Lm becomes smaller toward the predetermined direction Z.

Next, an operation example of the spark plug 10C of the present embodiment will be described.
When the spark plug 10C of the present embodiment is used, the required voltage Vr changes with the passage of time as shown by the solid line in FIG. In FIG. 8, for reference, the transition of the required voltage Vr of the spark plug 10 of the first embodiment is shown by a alternate long and short dash line, and the spark of the comparative example in which the ground electrode tip is formed only by the same diameter portion. The transition of the required voltage Vr of the plug 10B is shown by the alternate long and short dash line.

As shown by the solid line in FIG. 8, in the spark plug 10C of the present embodiment, the reduced diameter portion 30c having an outer diameter smaller than that of the same diameter portion 30a is consumed during the period from the time t11 to the time t12. Therefore, in the spark plug 10C of the present embodiment, the required voltage Vr is increased with a smaller inclination than the spark plug 10 of the first embodiment shown by the alternate long and short dash line and the spark plug 10B of the comparative example shown by the alternate long and short dash line. Become. Therefore, as compared with the spark plug 10 of the first embodiment and the spark plug 10B of the comparative example, the spark plug 10C of the present embodiment can significantly suppress the required voltage Vr.

According to the spark plug 10C of the present embodiment described above, in addition to the actions and effects shown in the above (2) to (4), the actions and effects alternative to the above (1) are described in the following (5). The indicated actions and effects can be obtained.
(5) The ground electrode tip 141 has an electrode member 30 formed in a cup shape and a joining member 31 for joining the electrode member 30 to the ground electrode base material 140. The electrode member 30 has a reduced diameter portion 30c and an enlarged diameter portion 30b in order from the tip end portion 300 toward the base end portion 301. The base end portion 301 of the electrode member 30 is separated from the ground electrode base material 140. According to this configuration, as in the spark plug 10 of the first embodiment, one end of the spark discharge is difficult to move to the ground electrode base material 140, so that the members other than the ground electrode tip 141 are consumed by the spark discharge. Is less likely to occur. Therefore, it is possible to prevent the ground electrode chip 141 from falling off from the ground electrode base material 140. Further, the required voltage Vr of the spark plug 10C can be suppressed.

<Other embodiments>
In addition, each embodiment can also be carried out in the following embodiments.
-The material forming each component of the spark plugs 10 and 10C, such as the material forming the ground electrode base material 140 and the ground electrode chip 141, can be arbitrarily changed.

-The present disclosure is not limited to the above specific examples. Specific examples described above with appropriate design changes by those skilled in the art are also included in the scope of the present disclosure as long as they have the characteristics of the present disclosure. Each element included in each of the above-mentioned specific examples, and their arrangement, conditions, shape, and the like are not limited to those exemplified, and can be appropriately changed. The combinations of the elements included in each of the above-mentioned specific examples can be appropriately changed as long as there is no technical contradiction.

10, 10C: Spark plug 13: Center electrode 14: Ground electrode 30: Electrode member 30a: Same diameter part 30b: Diameter expansion part 30c: Diameter reduction part 31: Joining member 141: Electrode tip 140: Ground electrode base material 300: Tip Part 301: Base end part 310: Exposed part

Claims (7)

A spark plug (10) that forms a spark discharge by applying a voltage between the center electrode (13) and the ground electrode (14).
The ground electrode has an electrode tip (141) arranged so as to face the center electrode with a gap, and a ground electrode base material (140) to which the electrode tip is bonded.
The electrode tip is
An electrode member (30) formed in a cup shape so as to have an opening at a base end portion (301) facing the ground electrode base material, and
A joining member (which is provided so as to be inserted into the inside through the opening of the electrode member, is arranged between the electrode member and the ground electrode base material, and joins the electrode member to the ground electrode base material. 31) and
The electrode member is
When the direction from the tip portion (300) facing the center electrode toward the proximal end portion facing the ground electrode base material is set as a predetermined direction.
The same diameter portion (30a) having the same outer diameter and the enlarged diameter portion (30b) formed so that the outer diameter increases toward a predetermined direction are provided in order from the tip portion to the base end portion. death,
The base end portion of the electrode member is a spark plug separated from the ground electrode base material. A spark plug (10C) that forms a spark discharge by applying a voltage between the center electrode (13) and the ground electrode (14).
The ground electrode has an electrode tip (141) arranged so as to face the center electrode with a gap, and a ground electrode base material (140) to which the electrode tip is bonded.
The electrode tip is
An electrode member (30) formed in a cup shape so as to have an opening at a base end portion (301) facing the ground electrode base material, and
A joining member (which is provided so as to be inserted into the inside through the opening of the electrode member, is arranged between the electrode member and the ground electrode base material, and joins the electrode member to the ground electrode base material. 31) and
The electrode member is
When the direction from the tip portion (300) facing the center electrode toward the proximal end portion facing the ground electrode base material is set as a predetermined direction.
The tip of the reduced diameter portion (30c) formed so that the outer diameter becomes smaller toward the predetermined direction and the enlarged diameter portion (30b) formed so that the outer diameter becomes larger toward the predetermined direction. Hold in order from the part to the base end,
The base end portion of the electrode member is a spark plug separated from the ground electrode base material. The spark plug according to claim 1 or 2, wherein a gap is formed between the outer edge of the base end portion of the electrode member and the ground electrode base material. Claim 1 in which the exposed portion (310) provided between the base end portion of the electrode member and the ground electrode base material in the joining member is located inside the outer edge of the base end portion of the electrode member. The spark plug according to any one of 3 to 3. The spark plug according to any one of claims 1 to 4, wherein the material forming the electrode member has a melting point lower than that of the material forming the joining member. The spark plug according to any one of claims 1 to 5, wherein the material forming the electrode member is an iridium alloy or a platinum alloy. The spark plug according to any one of claims 1 to 6, wherein the material forming the joining member is a nickel alloy.

Images