JP7258791B2 - Spark plug - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spark plug in which a center electrode and a ground electrode face each other across a spark gap.

As a material for ground electrodes of spark plugs, Patent Document 1 discloses a material containing Ni as a main component and 0.031 to 0.5 wt % of Ti or the like in order to ensure strength in a high-temperature environment.

JP 2012-177140 A

However, in the technique of Patent Document 1, 0.031 to 0.5 wt % of Ti or the like is included in the vicinity of the surface of the ground electrode, so there is a problem that the ground electrode is easily worn out by spark discharge.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spark plug which can secure the strength of the ground electrode in a high-temperature environment and can improve the resistance to spark wear of the ground electrode. .

To achieve this object, the spark plug of the present invention comprises: a center electrode extending in the axial direction; a metal shell for insulating and holding the center electrode; a ground electrode facing across a spark gap, the ground electrode comprising a base material and an outer layer covering the base material, the base material containing 0.3 wt% or more Al and 0.3 wt% Ti. As described above, it contains 0.02 wt% or more of C, 0.001 wt% or more of N, and the balance is Ni and impurities. 01 wt % or less and 99 wt % or more of Ni, the base material has a cross-sectional area of 0.2 mm ² or more, and the outer layer has a thickness of 0.02 mm or more.

According to the spark plug of claim 1, the ground electrode comprises a base material and an outer layer covering the base material. The base material contains 0.3 wt% or more Al, 0.3 wt% or more Ti, 0.02 wt% or more C, 0.001 wt% or more N, and the balance is Ni and impurities, and the cross-sectional area is 0.2 mm. ² or more. Therefore, it is possible to ensure the strength of the ground electrode in a high-temperature environment. Further, the outer layer contains 0.2 wt % or less of Al, 0.2 wt % or less of Ti, 0.01 wt % or less of C, 99 wt % or more of Ni, and has a thickness of 0.02 mm or more. Therefore, the spark consumption resistance of the ground electrode can be improved.

According to the spark plug of claim 2, since the outer layer has an arithmetic mean roughness of the surface of 10 μm or less, it is possible to suppress the occurrence of cracks that progress from the unevenness of the surface of the outer layer. Therefore, in addition to the effect of claim 1, it is possible to make the ground electrode less likely to be broken.

According to the spark plug of claim 3, the side surface facing the center electrode of the first portion extending from the end of the one end portion of the ground electrode connected to the metallic shell extends in the first direction. The length of the first part along the first direction is 10 mm or less. A second portion connected to the first portion extends to the end surface of the other end portion of the ground electrode, and the second portion extends in a second direction different from the first direction at the other end portion. A portion of the second portion located closer to the other end than the first portion in the second direction has a length along the second direction of 7 mm or less. As a result, the moment of the ground electrode around the end of the one end can be suppressed. As a result, the force applied to the ground electrode due to vibration or the like can be suppressed.

According to the spark plug of claim 4, the base material is exposed on the end surface of the other end of the ground electrode. The end face is located outside the projected area through which it passes. As a result, spark discharge is less likely to occur in the base material exposed at the end surface of the other end of the ground electrode, so in addition to the effect of any one of claims 1 to 3, spark consumption of the base material of the ground electrode can be suppressed.

1 is a half cross-sectional view of a spark plug in one embodiment; FIG. 1 is a side view of a spark plug; FIG. 1 is a perspective view of a spark plug; FIG. 3 is a cross-sectional view of the ground electrode taken along line IV-IV of FIG. 2; FIG.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a half sectional view of a spark plug 10 of one embodiment taken along an axis O. FIG. In FIG. 1, the lower side of the page is called the front end side of the spark plug 10, and the upper side of the page is called the rear end side of the spark plug 10 (the same applies to FIGS. 2 and 3). As shown in FIG. 1, the spark plug 10 includes an insulator 11, a center electrode 13, a metal shell 16 and a ground electrode 18. As shown in FIG.

The insulator 11 is a substantially cylindrical member having an axial hole 12 along the axis O, and is made of ceramic such as alumina, which has excellent mechanical properties and high-temperature insulation. A center electrode 13 is arranged on the tip side of the shaft hole 12 of the insulator 11 .

The center electrode 13 is a rod-shaped member. In the center electrode 13, a bottomed cylindrical base material containing Ni as a main component covers a core material containing copper as a main component. It is possible to omit the core material. A portion of the center electrode 13 including the tip surface 14 (see FIG. 2) is exposed from the shaft hole 12 to the tip side. The center electrode 13 is electrically connected to the terminal fitting 15 inside the shaft hole 12 .

The terminal fitting 15 is a rod-shaped member to which a high-voltage cable (not shown) is connected, and is made of a conductive metal material (for example, low carbon steel). The terminal fitting 15 is fixed to the rear end of the insulator 11 in a state in which the tip side thereof is inserted into the shaft hole 12 .

The metal shell 16 is a substantially cylindrical member made of a conductive metal material (for example, low-carbon steel). The metal shell 16 surrounds the tip side of the insulator 11 and holds the insulator 11 inside. A male thread 17 is formed on the outer peripheral surface of the metallic shell 16 . The male thread 17 is a portion that is screwed into a threaded hole of an engine (not shown). A ground electrode 18 is connected to the metal shell 16 .

FIG. 2 is a side view of a portion of the spark plug 10 on the distal end side of the metallic shell 16. As shown in FIG. In FIG. 2, the illustration of the rear end side portion of the metal shell 16 is omitted. Arrow I shown in FIG. 2 indicates the first direction and arrow II indicates the second direction. The second direction is a direction different from the first direction. In this embodiment, the first direction coincides with the axial direction and the second direction is perpendicular to the first direction. However, it is not limited to this, and the first direction does not have to match the axial direction. The second direction may be a direction that obliquely crosses the first direction.

The ground electrode 18 is a rod-shaped member. One end portion 19 of the ground electrode 18 is connected to a portion of the metal shell 16 on the distal end side of the external thread 17 . The other end 21 of the ground electrode 18 faces the center electrode 13 in the axial direction with a spark gap 22 interposed therebetween. The ground electrode 18 includes a first portion 25 and a second portion 26 and is bent.

The first portion 25 is a portion where the side surface 23 of the ground electrode 18 facing the center electrode 13 extends straight in the first direction. A first portion 25 extends from the end 20 of the one end portion 19 . The first portion 25 is substantially parallel to the axis O in this embodiment. An end 20 of one end portion 19 of the ground electrode 18 is a boundary between the ground electrode 18 and the metal shell 16 . One end 19 of the ground electrode 18 includes a fusion zone (not shown) that joins the ground electrode 18 to the metal shell 16 . The length of the first portion 25 along the first direction (the length of the arrow indicating the range of the first portion 25) is 10 mm or less.

The second portion 26 connects to the first portion 25 and extends to the end surface 24 of the other end portion 21 . The second portion 26 extends in the second direction at the other end portion 21 . The other end 21 is substantially perpendicular to the axis O in this embodiment. The length along the second direction of the portion 27 of the second portion 26 located closer to the other end portion 21 than the first portion 25 in the second direction (the length of the arrow indicating the range of the portion 27) is 7 mm or less.

3 is a perspective view of the center electrode 13 and the ground electrode 18 of the spark plug 10. FIG. In FIG. 3, the illustration of the rear end portions of the center electrode 13 and the ground electrode 18 is omitted. The ground electrode 18 has a base material 29 covered with an outer layer 30 . The base material 29 is exposed on the end surface 24 of the ground electrode 18 . The ground electrode 18 has an end surface 24 located outside a projection area 31 through which the tip surface 14 passes when the tip surface 14 of the center electrode 13 is projected axially to the tip side. This makes it difficult for spark discharge to occur in the base material 29 exposed on the end surface 24 of the ground electrode 18 .

FIG. 4 is a sectional view including the axis O of the ground electrode 18 along line IV-IV in FIG. A base material 29 of the ground electrode 18 is covered with an outer layer 30 . The base material 29 contains Al, Ti, C, N and impurities, and the balance is Ni. The outer layer 30 contains Al, Ti, C and impurities. The base material 29 and the outer layer 30 are identified by quantitative analysis using a wavelength dispersive spectroscope (WDS) of an electron probe microanalyzer (EPMA) in a cross section including the axis O of the ground electrode 18 . The spark plug 10 on which the WDS analysis is performed is unused.

The boundary between the base material 29 and the outer layer 30 is identified by line analysis using WDS. The conditions for WDS analysis are an acceleration voltage of 20 kV and a probe diameter of 10 μm. FIG. 4 shows, as an example, a ground electrode 18 having a base material 29 containing 0.3 wt % Al. The base material 29 is a region containing 0.3 wt % or more of Al, 0.3 wt % or more of Ti, 0.02 wt % or more of C, and 0.001 wt % or more of N. The cross-sectional area of the base material 29 is 0.2 mm ² or more. The Al content decreases from the base material 29 toward the surface of the ground electrode 18 .

The outer layer 30 is a region containing 0.2 wt % or less of Al, 0.2 wt % or less of Ti, 0.01 wt % or less of C, and 99 wt % or more of Ni. The thickness T of the outer layer 30 is 0.02 mm or more. An intermediate layer 32 is interposed between the base material 29 and the outer layer 30 . The intermediate layer 32 is a region where the element content does not satisfy the conditions of the base material 29 and the outer layer 30 .

The composition of the base material 29 is measured by surface analysis of a square range of 0.1 mm in length and 0.1 mm in width of the base material 29 . The conditions for the WDS analysis at this time are an acceleration voltage of 20 kV and a probe diameter of 100 μm. The composition of the outer layer 30 is measured by area analysis of a square range of 0.01 mm long and 0.01 mm wide of the outer layer 30 . The conditions for the WDS analysis at this time are an acceleration voltage of 20 kV and a probe diameter of 10 μm.

Al is an effective element for enhancing the oxidation resistance of the ground electrode 18 . Ti is an effective element for increasing the strength of the ground electrode 18 in a high-temperature environment and suppressing intergranular oxidation. C is an element that affects the hardness of the ground electrode 18 .

Impurities contained in the ground electrode 18 include Fe, Mn, Ca, Mg, P, S, Cu, and the like. Fe has little effect on the spark wear resistance of the ground electrode 18 and the strength in high temperature environments. Mn has almost no effect on spark wear resistance and strength under high temperature environments, and improves the oxidation resistance of the ground electrode 18 . Ca and Mg improve the cleanliness of the alloy by deoxidizing and desulfurizing, and improve the hot workability of the alloy. P and Cu may remain in the alloy as unavoidable impurities.

For the ground electrode 18, for example, a wire made of an alloy that satisfies the compositional conditions of the base material 29 is subjected to a vacuum heat treatment to evaporate an element with a high vapor pressure contained in the vicinity of the surface of the wire to form the outer layer 30. It can be obtained by cutting to length. The vacuum heat treatment includes, for example, a treatment of heating to 950° C. under a reduced pressure of 1.5 Pa or less. In addition, a wire made of an alloy that satisfies the compositional conditions of the base material 29 is subjected to heat treatment in the atmosphere to remove the oxide film formed on the surface of the wire, and after forming an element-depleted outer layer 30, a predetermined length is formed. can be obtained by cutting into

In either method, the material for the ground electrode 18 can be obtained by heat-treating the wire and then cutting it to a predetermined length, so that it is excellent in mass productivity. Since the cut surface becomes the end face 24 of the ground electrode 18 , the base material 29 is exposed at the end face 24 .

The outer layer 30 has a surface arithmetic mean roughness of 10 μm or less. Arithmetic mean roughness Ra is measured on the tip surface 28 (see FIG. 2) of the other end 21 of the ground electrode 18 in the outer layer 30 in accordance with JIS B0601:2013. The tip surface 28 is the surface opposite to the side surface 23 of the other end 21 of the ground electrode 18 . Using a contact-type surface roughness measuring instrument, the stylus applied to the tip surface 28 is moved 4.0 mm in the second direction, and a curve obtained by applying a high-pass filter with a cutoff value of 0.80 mm. Find the arithmetic mean roughness. The spark plug 10 for which the surface roughness of the outer layer 30 is to be measured is unused.

In the ground electrode 18, the base material 29 contains 0.3 wt% or more Al, 0.3 wt% or more Ti, 0.02 wt% or more C, 0.001 wt% or more N, and the balance is Ni and impurities, The cross-sectional area of the base material 29 is 0.2 mm ² or more. Therefore, it is possible to ensure the strength of the ground electrode 18 in a high-temperature environment. The base material 29 is covered with an outer layer 30 containing 0.2 wt% or less of Al, 0.2 wt% or less of Ti, 0.01 wt% or less of C, 99 wt% or more of Ni, and having a thickness T of 0.02 mm or more. Therefore, the resistance to spark consumption of the ground electrode 18 can be improved. According to the ground electrode 18, resistance to spark consumption can be ensured without providing a tip containing a noble metal.

The surface of the outer layer 30 has small irregularities due to evaporation or deficiency of elements contained in the alloy that is the material of the ground electrode 18 . However, since the arithmetic average roughness of the surface of the outer layer 30 is 10 μm or less, the occurrence of cracks that propagate starting from the unevenness of the surface of the outer layer 30 can be suppressed. Therefore, the ground electrode 18 can be made difficult to break.

The length of the first portion 19 of the ground electrode 18 is 10 mm or less, and the length of the portion 27 of the second portion 26 located closer to the other end portion 21 than the first portion 19 is 7 mm or less. Thereby, the moment of the ground electrode 18 about the end 20 of the one end portion 19 can be suppressed. As a result, it is possible to suppress the force applied to the ground electrode 18 due to vibrations of the vehicle body or the engine, etc., so that breakage of the ground electrode 18 can be further suppressed.

Since the end surface 24 of the ground electrode 18 is positioned outside the projection area 31, spark discharge is less likely to occur in the base material 29 exposed at the end surface 24. FIG. Therefore, spark consumption of the base material 29 of the ground electrode 18 can be suppressed.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Preparation of sample)
The tester performed heat treatment on wires made of alloys with different compositions under various conditions, and then cut them into predetermined lengths to obtain ground electrodes 18 . After the metal shell 16 to which the ground electrode 18 was joined was assembled to the insulator 11, the ground electrode 18 was bent to form the spark gap 22. As shown in FIG. As a result, the sample No. shown in Table 1 of the spark plug 10 in the above embodiment was obtained. 1-24 was obtained.

In each sample, the male screw 17 of the metal shell 16 had a nominal diameter of 14 mm, the portion of the insulator 11 protruding from the metal shell 16 had an axial length of 2 mm, and the portion of the center electrode 13 protruding from the insulator 11 had a length of 2 mm. The length in the axial direction is 3 mm, the diameter of the tip surface 14 of the center electrode 13 is 0.6 mm, and the cross-sectional shape of the ground electrode 18 is 1.5 mm long and 2.8 mm wide (the width of the side surface 23 is 2.8 mm). It was rectangular.

各サンプルの接地電極１８の軸線Ｏを含む断面において、ＥＰＭＡのＷＤＳ分析（線分析）により、Ａｌを０．３ｗｔ％以上、Ｔｉを０．３ｗｔ％以上、Ｃを０．０２ｗｔ％以上、Ｎを０．００１ｗｔ％以上含み、残部としてＮｉ及び不純物（その他の微量成分）を含む領域を母材とし、Ａｌを０．２ｗｔ％以下、Ｔｉを０．２ｗｔ％以下、Ｃを０．０１ｗｔ％以下、Ｎｉを９９ｗｔ％以上含む領域を外層とした。ＷＤＳ分析の条件は加速電圧２０ｋＶ、プローブ径１０μｍとした。Ｎｏ．１－４はＡｌの含有率が０．２ｗｔ％以下の領域（外層）を特定できなかった。そのためＮｏ．１－４は外層の厚さ、及び、外層の内側の母材の断面積を算出しなかった。

In a cross section including the axis O of the ground electrode 18 of each sample, EPMA WDS analysis (line analysis) revealed that Al was 0.3 wt% or more, Ti was 0.3 wt% or more, C was 0.02 wt% or more, and N was 0.02 wt% or more. A region containing 0.001 wt% or more and the balance containing Ni and impurities (other trace components) is used as the base material, Al is 0.2 wt% or less, Ti is 0.2 wt% or less, C is 0.01 wt% or less, A region containing 99 wt % or more of Ni was used as the outer layer. The conditions for WDS analysis were an acceleration voltage of 20 kV and a probe diameter of 10 μm. No. In 1-4, a region (outer layer) with an Al content of 0.2 wt % or less could not be identified. Therefore No. 1-4 did not calculate the thickness of the outer layer and the cross-sectional area of the base material inside the outer layer.

Next, the composition of the base material was specified by WDS analysis (surface analysis) of a square range of 0.1 mm in length and 0.1 mm in width near the center of the base material. The conditions for WDS analysis were an acceleration voltage of 20 kV and a probe diameter of 100 μm. In addition, the composition of the outer layer was specified by WDS analysis (area analysis) of a square range of 0.01 mm in length and 0.01 mm in width near the center in the thickness direction of the outer layer. The conditions for WDS analysis were an acceleration voltage of 20 kV and a probe diameter of 10 μm. Fe, Mn, Ca, Mg, P, and S were contained as impurities in the base material and the outer layer.

In addition, No. In 1-4, the result of surface analysis near the center of the cross section was used as the composition of the base material, and the result of surface analysis at a position 10 μm inward from the edge of the cross section was used as the composition of the outer layer.

The surface roughness of the outer layer was measured using a contact-type surface roughness measuring machine. The stylus applied to the tip surface 28 of the ground electrode 18 is moved 4.0 mm in the second direction, and the arithmetic mean roughness Ra of the curve obtained by applying a high-pass filter with a cutoff value of 0.80 mm is obtained. rice field.

The length 1 (mm) shown in Table 1 is the length along the first direction of the first portion 25 of the ground electrode 18 . The length 2 (mm) shown in Table 1 is along the second direction of the portion 27 of the second portion 26 of the ground electrode 18 that is positioned closer to the other end portion 21 than the first portion 25 in the second direction. length. Length 1 and length 2 were measured using a projector (50x magnification).

(Evaluation of spark consumption resistance)
After installing each spark plug sample in a 1,300 cc gasoline-fueled engine, a test was conducted in which the engine was run for 200 hours at full throttle and 5,000 rpm. Each sample was taken out, the size of the spark gap was measured using a pin-type gauge, and the amount of increase in the spark gap before and after the test was calculated. Since the amount of wear of the center electrode is the same for all samples, the difference in the amount of increase in the spark gap is caused by the difference in the ground electrode of each sample. Samples with an increase in the spark gap of less than 0.10 mm were evaluated as A, and samples with an increase of 0.10 mm or more were evaluated as B.

(Evaluation of breakage resistance)
Each spark plug sample was attached to a 1,300 cc gasoline-fueled engine, and after starting the engine, a cycle of 3,500 rpm for 1 minute and idling for 1 minute was repeated as one cycle, and the engine was operated for 200 hours. .

The evaluation was E for samples with ground electrode breakage less than 50 hours after the start of the test, D for samples with ground electrode breakage at 50 hours or more and less than 100 hours after the start of the test, and 100 hours or more and less than 150 hours after the start of the test. Sample C was broken, B was broken 150 hours or more and less than 200 hours after the start of the test, and A was the sample whose ground electrode did not break 200 hours or more after the start of the test.

As shown in Table 1, No. 13-24 had a spark consumption resistance of A and a breaking resistance of any of AC. Especially No. No. 21-24 was also rated A in terms of breaking resistance. No. 21-24, the base material contains 0.3 wt% or more Al, 0.3 wt% or more Ti, 0.02 wt% or more C, 0.001 wt% or more N, and the balance is Ni and impurities, and the outer layer contains 0.2 wt% or less of Al, 0.2 wt% or less of Ti, 0.01 wt% or less of C, and 99 wt% or more of Ni, the cross-sectional area of the base material is 0.2 mm ² or more, and the thickness of the outer layer is was 0.02 mm or more. No. In Nos. 21-24, the arithmetic average roughness of the outer layer was 10 μm or less, the length 1 was 10 mm or less, and the length 2 was 7 mm or less.

It should be noted that the No. 1 length 1 is 11 mm. No. 17, 18 and length 2 of 8 mm. Nos. 19 and 20 were B in the breaking resistance. No. 1 with a length 1 of 11 mm and a surface roughness of 15-20 μm. No. 13, 14, and No. 2 having a length 2 of 8 mm and a surface roughness of 15-20 μm. Nos. 15 and 16 had C in breaking resistance.

No. 9-12 was B in spark consumption resistance and C in breaking resistance. No. 9-12, the base material contains 0.3 wt% or more Al, 0.3 wt% or more Ti, 0.02 wt% or more C, 0.001 wt% or more N, and the balance is Ni and impurities, and the outer layer contained 0.2 wt% or less of Al, 0.2 wt% or less of Ti, 0.01 wt% or less of C, and 99 wt% or more of Ni, and the cross-sectional area of the base material was 0.2 mm ² or more, but the outer layer The thickness was 0.01 mm. No. No. 9-12 has an insufficient thickness of the outer layer. It is presumed that the spark wear resistance was inferior to that of 13-24.

In addition, No. Nos. 9 and 10 have a surface roughness of 15-20 μm and a length 1 of 11 mm. 11 and 12 had a surface roughness of 15-20 μm and a length 2 of 8 mm.

No. 5-8 was B in spark consumption resistance and D in breaking resistance. No. 5-8, the base material contains 0.3 wt% or more Al, 0.3 wt% or more Ti, 0.02 wt% or more C, 0.001 wt% or more N, and the balance is Ni and impurities, and the outer layer contained 0.2 wt% or less of Al, 0.2 wt% or less of Ti, 0.01 wt% or less of C, and 99 wt% or more of Ni, and the cross-sectional area of the base material was 0.2 mm ² or more, but the outer layer The thickness was 0.01 mm. No. No. 5-8 had insufficient outer layer thickness. It is presumed that the spark wear resistance was inferior to that of 13-24.

In addition, No. Nos. 5 and 6 have a base material with a cross-sectional area of 0.05 mm ² , a surface roughness of 15-20 μm, and a length 1 of 11 mm. In 7 and 8, the cross-sectional area of the base material was 0.10 mm ² , the surface roughness was 15-20 μm, and the length 2 was 8 mm.

No. 1-4 was B in spark consumption resistance and E in breaking resistance. No. No. 1-4 does not satisfy the conditions that the outer layer contains 0.2 wt % or less of Al, 0.2 wt % or less of Ti, 0.01 wt % or less of C, and 99 wt % or more of Ni. It is presumed that the spark wear resistance was inferior to that of 13-24. Also, No. In 1-4, it is presumed that the strength of the material was insufficient in a high-temperature environment, and the ground electrode broke early.

Although the present invention has been described above based on the embodiments, it should be understood that the present invention is not limited to the above-described embodiments, and that various improvements and modifications are possible without departing from the scope of the present invention. It can be easily guessed.

Although not described in the embodiment, it is naturally possible to embed a core material containing copper as a main component in the base material 29 of the ground electrode 18 . By embedding the core material in the base material 19, the thermal conductivity of the ground electrode 18 can be improved.

Although the spark plug 10 including the bent ground electrode 18 has been described in the embodiment, the present invention is not necessarily limited to this. It is of course possible to arrange a straight ground electrode and provide a spark gap between the center electrode and the ground electrode.

10 Spark plug 13 Center electrode 14 Tip surface 16 Metal shell 18 Ground electrode 19 One end 20 End of one end 21 Other end 22 Spark gap 23 Side surface 24 End surface 25 First part 26 Second part 27 Part 28 Tip surface (surface)
29 base material 30 outer layer 31 projection area O axis

Claims (4)

an axially extending center electrode;
a metal shell that insulates and holds the center electrode;
A spark plug comprising a ground electrode having one end connected to the metal shell and having the other end opposed to the center electrode across the spark gap in the axial direction,
The ground electrode comprises a base material and an outer layer covering the base material,
The base material contains 0.3 wt% or more Al, 0.3 wt% or more Ti, 0.02 wt% or more C, 0.001 wt% or more N, and the balance is Ni and impurities,
The outer layer contains 0.2 wt% or less of Al, 0.2 wt% or less of Ti, 0.01 wt% or less of C, and 99 wt% or more of Ni,
The spark plug, wherein the base material has a cross-sectional area of 0.2 mm ² or more, and the outer layer has a thickness of 0.02 mm or more. 2. The spark plug according to claim 1, wherein said outer layer has a surface arithmetic mean roughness of 10 [mu]m or less. a first portion of the ground electrode extending from the end of the one end portion and having a side surface facing the center electrode extending in a first direction;
a second part connected to the first part and extending to the end surface of the other end,
The second part extends in a second direction different from the first direction at the other end,
The length of the first part along the first direction is 10 mm or less,
3. The length along the second direction of a portion of the second portion located closer to the other end than the first portion in the second direction is 7 mm or less according to claim 1 or 2. spark plug. the base material is exposed on the end surface of the other end of the ground electrode;
4. The spark according to any one of claims 1 to 3, wherein the end face is positioned outside a projection area through which the tip end face passes when the tip end face in the axial direction of the center electrode is projected onto the tip end side in the axial direction. plug.

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