阅读说明：本技术 火花塞 (Spark plug ) 是由 伴谦治 后泽达哉 于 2020-06-23 设计创作，主要内容包括：提供能够减小从主体配件起的盖构件的轴线方向的长度的偏差的火花塞。火花塞具备：筒状的主体配件；中心电极,绝缘保持于主体配件；接地电极,与中心电极形成火花间隙；及盖构件,接合于主体配件且形成副室。盖构件具有：重叠面,与主体配件沿着轴线方向重叠；内侧对向面,位于比重叠面靠副室侧处且与主体配件在轴线方向上对向；及外侧对向面,位于比重叠面靠外周侧处且与主体配件在轴线方向上对向,盖构件中的比重叠面靠副室侧的部分与主体配件分离,主体配件和盖构件在外侧对向面及重叠面的至少一方处接合。(Provided is a spark plug which can reduce the variation of the length of a cover member in the axial direction from a main body metal fitting. The spark plug is provided with: a cylindrical main body fitting; a center electrode insulated and held by the main body member; a ground electrode forming a spark gap with the center electrode; and a cover member joined to the main fitting and forming the sub-chamber. The cover member has: an overlapping surface overlapping the main body fitting in the axial direction; an inner facing surface located closer to the sub-chamber than the overlapping surface and facing the metal shell in the axial direction; and an outer facing surface located on the outer peripheral side of the overlapping surface and facing the metal shell in the axial direction, wherein a portion of the cover member on the sub-chamber side is separated from the metal shell, and the metal shell and the cover member are joined to each other at least at one of the outer facing surface and the overlapping surface.)

1. A spark plug is provided with:

a cylindrical metal shell extending along an axis from a front end side to a rear end side;

a center electrode held in an insulated manner on an inner peripheral side of the metal shell;

a ground electrode electrically connected to the metallic shell, the ground electrode forming a spark gap between the center electrode and an end thereof; and

a cover member joined to the metallic shell, covering the end portions of the center electrode and the ground electrode from the front end side to form a sub-chamber, and having a through hole,

wherein the content of the first and second substances,

the cover member has:

an overlapping surface that overlaps with the front end portion of the metal shell in the axial direction;

an inner facing surface located closer to the sub chamber side than the overlapping surface and facing the metal shell in the axial direction; and

an outer facing surface located on an outer peripheral side of the overlapping surface and facing the metal shell in the axial direction,

a portion of the lid member on the sub-chamber side with respect to the overlapping surface is separated from the metal shell,

the metal shell and the cover member are joined to each other at least one of the outer facing surface and the overlapping surface.

2. The spark plug of claim 1,

the inner facing surface is located closer to the axial rear end than the outer facing surface,

the overlapping surface is connected with the main body fitting,

the corner where the inside facing surface intersects the overlapping surface is chamfered.

3. The spark plug of claim 2,

the chamfer is an R chamfer.

Technical Field

The present invention relates to a spark plug for forming a sub-chamber in a combustion chamber of an engine.

Background

There is known a spark plug in which a cover member joined to a cylindrical metal shell extending in an axial direction is exposed to a combustion chamber of an engine to form a sub-chamber (patent document 1). Such a spark plug ignites a fuel-air mixture flowing from the combustion chamber into the sub-chamber through the through hole of the cover member, and injects an air flow including a flame from the through hole into the combustion chamber by an expansion pressure generated by combustion of the fuel-air mixture. The combustible mixture in the combustion chamber is burned by the flame jet, and therefore, the position of the sub-chamber in the combustion chamber affects the unevenness of combustion in the combustion chamber.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-130302

Disclosure of Invention

Problems to be solved by the invention

Since the cover member joined in the axial direction of the metallic shell is exposed to the combustion chamber, the spark plug is required to reduce variation in the axial length of the cover member from the metallic shell in order to suppress combustion variation in the combustion chamber.

The present invention has been made in response to the above-described demand, and an object thereof is to provide a spark plug capable of reducing variation in the length of a cover member in the axial direction from a metal shell.

Means for solving the problems

In order to achieve the object, a spark plug according to the present invention includes: a cylindrical metal shell extending along an axis from a front end side to a rear end side; a center electrode insulated and held on the inner peripheral side of the metal shell; a ground electrode electrically connected to the metallic shell and forming a spark gap between the center electrode and an end thereof; and a cover member joined to the metallic shell, covering the end portions of the center electrode and the ground electrode from the distal end side to form a sub-chamber, and having a through hole formed therein, the cover member including: an overlapping surface that overlaps the front end portion of the metal shell in the axial direction; an inner facing surface located closer to the sub-chamber than the overlapping surface and facing the metal shell in the axial direction; and an outer facing surface located on the outer peripheral side of the overlapping surface and facing the metal shell in the axial direction, wherein the portion of the cover member on the sub-chamber side is separated from the metal shell, and the metal shell and the cover member are joined to each other at least at one of the outer facing surface and the overlapping surface.

Effects of the invention

According to the spark plug of claim 1, the overlapping surface of the cover member overlaps the distal end portion of the metallic shell in the axial direction. An inner facing surface of the cover member located closer to the sub-chamber than the superimposed surface is axially opposed to the metal shell, and an outer facing surface of the cover member located closer to the outer peripheral side than the superimposed surface is axially opposed to the metal shell. The metal shell and the lid member are joined to each other at least on one of the outer facing surface and the overlapping surface.

Since the portion of the cover member closer to the sub-chamber side than the overlapping surface is separated from the metallic shell, the cover member can be joined to the metallic shell in a state where the portion of the cover member closer to the outer side than the overlapping surface is in contact with the metallic shell when the spark plug is manufactured. Since the state in which the outer portion of the lid member abuts against the metal shell can be confirmed from the outside of the lid member when the lid member is joined to the metal shell, the length of the lid member in the axial direction from the metal shell can be managed with the abutting portion as a reference. Therefore, as compared with the case where the positioning of the cover member is performed with reference to the inner facing surface of the cover member, which cannot be confirmed from the outside of the cover member, when the cover member is joined to the metal shell, the variation in the length of the cover member in the axial direction from the metal shell can be reduced.

According to the spark plug described in claim 2, since the inner facing surface is located at the axial rear end of the outer facing surface and the overlapping surface is in contact with the metallic shell, when the cover member is joined to the metallic shell, the cover member is inserted into the metallic shell while the overlapping surface and the metallic shell rub against each other. Thereby, the cover member can be temporarily fixed to the metal shell by friction.

When the cover member is inserted into the metal shell, the corner where the inner facing surface of the cover member intersects the overlapping surface rubs against the metal shell to generate chips, and the chips enter the sub-chamber to form a pre-ignition flame. However, since the corner where the inside facing surface of the cover member intersects the overlapping surface is chamfered, a space capable of accommodating chips can be formed by the chamfering. As a result, even if chips are generated, the chips can be made difficult to enter the sub chamber, and therefore, in addition to the effect of claim 1, the occurrence of pre-ignition in which chips become a fire species can be suppressed.

According to the spark plug described in claim 3, since the corner where the inner facing surface of the cover member intersects with the overlapping surface is chamfered by R, chips are less likely to be generated when the cover member is inserted into the metallic shell. Thus, in addition to the effect of claim 2, the occurrence of pre-ignition in which chips become ignition seeds can be further suppressed.

Drawings

Fig. 1 is a partial sectional view of a spark plug in a first embodiment.

Fig. 2 is a cross-sectional view of the spark plug enlarged in part shown in II of fig. 1.

Fig. 3 is a cross-sectional view of the spark plug shown in fig. 2 at III, partially enlarged.

Fig. 4 is a sectional view of the metal shell and the lid member before forming the welded portion.

Fig. 5 is a sectional view of a spark plug in a second embodiment.

Fig. 6 is a sectional view of a spark plug in a third embodiment.

Fig. 7 is a sectional view of a spark plug in a fourth embodiment.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a partial sectional view of a spark plug 10 according to an embodiment. Fig. 1 illustrates a cross section including the axis O of a portion on the front end side of the spark plug 10. In fig. 1, the lower side of the paper surface is referred to as the front end side of the spark plug 10, and the upper side of the paper surface is referred to as the rear end side of the spark plug 10 (the same applies to fig. 2 to 7). Fig. 2 is a cross-sectional view of the spark plug 10 including the axis O, partially enlarged as shown in II of fig. 1. As shown in fig. 1, the spark plug 10 includes an insulator 11, a center electrode 13, a metallic shell 20, a ground electrode 40, and a cover member 50.

The insulator 11 is a substantially cylindrical member having a shaft hole 12 formed along the axis O, and is formed of a ceramic such as alumina having excellent mechanical properties and high-temperature insulation properties. A center electrode 13 is disposed on the tip end side of the axial hole 12 of the insulator 11. The center electrode 13 is electrically connected to the terminal fitting 14 in the axial hole 12. The terminal fitting 14 is a rod-shaped member connected to a high-voltage cable (not shown), and is formed of a conductive metal material (for example, mild steel). The terminal fitting 14 is fixed to the rear end of the insulator 11.

The metallic shell 20 is a substantially cylindrical member formed of a conductive metal material (for example, mild steel). The metal shell 20 includes a front end portion 21 having a male screw 22 formed on an outer peripheral surface thereof, a seat portion 23 adjacent to a rear end side of the front end portion 21, and a tool engagement portion 24 formed on a rear end side of the seat portion 23. The male screw 22 is screwed into the screw hole 2 of the engine 1. The seat portion 23 is a portion for closing a gap between the screw hole 2 and the male screw 22 of the engine 1, and has an outer diameter larger than that of the male screw 22. The tool engagement portion 24 is engaged with a tool such as a wrench when the male screw 22 is tightened to the screw hole 2 of the engine 1.

The ground electrode 40 is a rod-shaped member formed of a metal material containing Pt or the like as a main component. In the present embodiment, the ground electrode 40 is disposed at the position of the male screw 22, penetrates the distal end portion 21, and protrudes inward of the distal end portion 21. An end 41 (see fig. 2) of the ground electrode 40 faces the center electrode 13. A cover member 50 is connected to the distal end portion 21 of the metal shell 20. The main component element of the ground electrode 40 is not limited to this, and other elements may be used as the main component. Examples of the other element include Ni and Ir.

The cover member 50 is a hemispherical member that covers the end portions 41 (see fig. 2) of the center electrode 13 and the ground electrode 40 from the front end side. The cover member 50 is formed of a metal material containing Fe or the like as a main component. A through hole 51 is formed in the cover member 50 on the front end side of the ground electrode 40. In a state where the spark plug 10 is attached to the screw hole 2 of the engine 1 by the male screw 22, the cover member 50 is exposed to the combustion chamber 3 of the engine 1. The through hole 51 communicates the sub-chamber 52 formed by the cover member 50 with the combustion chamber 3. The main component element of the cover member 50 is not limited to this, and other elements may be used as the main component. Examples of the other element include Ni and Cu.

As shown in fig. 2, a recess 25 recessed inward in the radial direction is formed in the distal end portion 21 of the metal shell 20 at the position of the male thread 22. At the distal end portion 21, a hole 26 that is narrower than the recess 25 is formed radially inside the recess 25. The hole 26 penetrates the distal end portion 21 in the radial direction. The ground electrode 40 inserted into the hole 26 is joined to the distal end portion 21 by the weld 27. A spark gap 42 is formed between the end 41 of the ground electrode 40 and the center electrode 13. Since the ground electrode 40 is joined to the male screw 22 of the metallic shell 20, heat of the ground electrode 40 is transmitted from the male screw 22 to the engine 1.

Fig. 3 is a cross-sectional view of the spark plug 10 shown in fig. 2 at III, partially enlarged. The inner surface 53 of the cover member 50 faces the sub-chamber 52, and the outer surface 54 of the cover member 50 faces the combustion chamber 3. The cover member 50 includes an overlapping surface 55 that faces the distal end portion 21 of the metal shell 20 in the axial direction (vertical direction in fig. 3), an inner facing surface 56 that faces the distal end portion 21 of the metal shell 20 in the axial direction and is located further toward the sub-chamber 52 than the overlapping surface 55, and an outer facing surface 58 that faces the distal end portion 21 of the metal shell 20 in the axial direction and is located further toward the outside (combustion chamber 3 side) than the overlapping surface 55.

The cover member 50 is joined to the metal shell 20 by a weld 59. The welded portion 59 is formed by melting the lid member 50 and the metallic shell 20. The welding portion 59 is formed over the entire circumference of the metal shell 20 and the cover member 50.

The overlapping surface 55 is a cylindrical surface facing outward of the lid member 50, and is formed over the entire circumference of the lid member 50. The overlapping surface 55 is in contact with the cylindrical first surface 28 of the metal shell 20 facing inward. The distance between the inner surface 53 of the cover member 50 and the overlapping surface 55 is, for example, 0.2mm to 0.6 mm.

The inner facing surface 56 is an annular surface facing the rear end and is formed over the entire circumference of the cover member 50. The inner facing surface 56 intersects the inner surface 53 of the cover member 50. The inner facing surface 56 is separated from the annular second surface 29 facing the distal end side of the metallic shell 20. The distance (the size of the gap) in the axial direction between the inner facing surface 56 of the lid member 50 and the second surface 29 of the metallic shell 20 is, for example, about 0.02mm to 0.8 mm.

The corner where the overlapping surface 55 of the lid member 50 and the inner facing surface 56 intersect is chamfered, and as a result, the corner is formed over the entire circumference of the lid member 50 with the inclined surface 57 cut out obliquely. The inclined surface 57 intersects the overlapping surface 55 and the inner facing surface 56.

The outer facing surface 58 is an annular surface facing the rear end and is formed over the entire circumference of the cover member 50. The outer facing surface 58 intersects the outer surface 54 of the cover member 50. The inner facing surface 56 is located on the rear end side than the outer facing surface 58. In the present embodiment, the outer facing surface 58 is an interface between the welding portion 59 and the lid member 50.

Fig. 4 is a cross-sectional view of the metal shell 20 and the lid member 50 including the axis O before the weld portion 59 is formed. Fig. 4 is a cross-sectional view of the spark plug 10 shown in fig. 2 at a partially enlarged scale including the axis O before the weld portion 59 is formed.

When the welded portion 59 (see fig. 2) is formed in the manufacturing process of the spark plug 10, the cover member 50 is inserted into the metal shell 20 while the overlapping surface 55 of the cover member 50 and the first surface 28 of the metal shell 20 rub against each other until the outer facing surface 60 of the cover member 50 abuts against the third surface 30 of the metal shell 20. The outer facing surface 60 of the cover member 50 is an annular surface of the cover member 50 that is provided on the outer side of the superposed surface 55 and faces the rear end side. The third surface 30 of the metallic shell 20 is an annular surface facing the distal end side of the metallic shell 20 provided on the outer side of the first surface 28.

In a state where the outer facing surface 60 of the lid member 50 abuts against the third surface 30 of the metallic shell 20, the inner facing surface 56 and the inclined surface 57 are separated from the second surface 29 of the metallic shell 20. The cover member 50 is temporarily fixed to the metal shell 20 by friction of the overlapping surface 55 with the first surface 28 of the metal shell 20. In this state, for example, the outer facing surface 60 of the cover member 50 and the third surface 30 of the metallic shell 20 and the periphery thereof are melted by irradiation of a laser beam to form a welded portion 59 (see fig. 2), and the cover member 50 is joined to the metallic shell 20.

The inner facing surface 56 cannot be recognized from the outside of the cover member 50, but the state where the outer facing surface 60 of the cover member 50 is in contact with the third surface 30 of the metal shell 20 can be recognized from the outside of the cover member 50. In addition to managing the positional accuracy of the third surface 30 of the metal shell 20 and the outer facing surface 60 of the cover member 50, it is confirmed from the outside of the cover member 50 that no foreign matter or the like is interposed between the third surface 30 and the outer facing surface 60, and the axial length of the cover member 50 from the metal shell 20 can be managed with reference to the outer facing surface 60 abutting against the third surface 30. Therefore, as compared with the case where the axial direction positioning of the lid member 50 before joining is performed with the inner facing surface 56, which cannot be confirmed from the outside of the lid member 50, as a reference, the variation in the axial direction length of the lid member 50 from the metal shell 20 can be reduced.

When the cover member 50 is inserted into the first surface 28 of the metal shell 20, the corner 57a where the overlapping surface 55 and the inclined surface 57 intersect may rub against the first surface 28 of the metal shell 20, thereby generating chips. When the generated chips enter the sub-chamber 52, they become a pre-ignition fire. However, since the corner where the inner facing surface 56 of the cover member 50 intersects the overlapping surface 55 is chamfered, a space 57b capable of accommodating chips can be formed between the inclined surface 57 and the metal shell 20. As a result, even if chips are generated, the chips are less likely to enter the sub-chamber 52, and therefore, the occurrence of pre-ignition in which the chips become a fire can be suppressed.

A second embodiment will be described with reference to fig. 5. In the first embodiment, a case has been described in which the inclined surface 57 is formed by obliquely cutting off the corner where the overlapping surface 55 of the cover member 50 and the inner facing surface 56 meet. In contrast, in the second embodiment, a case of the cover member 71 in which the corner where the facing overlap surface 55 and the inner facing surface 56 intersect is R-chamfered will be described.

Note that the same portions as those described in the first embodiment are denoted by the same reference numerals, and the following description is omitted. Fig. 5 is a sectional view of the spark plug 70 in the second embodiment. Fig. 5 is a cross-sectional view of the spark plug 70 shown in fig. 2 at III, which is partially enlarged, including the axis O (the same applies to fig. 6 and 7), similarly to fig. 3.

The spark plug 70 has a cover member 71 joined to the front end portion 21 of the metallic shell 20 by a weld portion 48. The corner of the cover member 71 where the overlapping surface 55 and the inner facing surface 56 intersect is chamfered by R, and a curved surface 72 smoothly connecting the overlapping surface 55 and the inner facing surface 56 is formed on the cover member 71.

When the welded portion 59 is formed in the manufacturing process of the spark plug 70, the cover member 71 is inserted into the first surface 28 of the metallic shell 20. In a state where the outer facing surface 60 (see fig. 4) of the cover member 71 abuts against the third surface 30 of the metal shell 20 and cannot be further inserted, the inner facing surface 56 and the curved surface 72 are separated from the metal shell 20. The cover member 71 is temporarily fixed to the metal shell 20 by friction of the overlapping surface 55 with the first surface 28 of the metal shell 20.

When the lid member 71 is inserted into the first surface 28 of the metal shell 20, the portion where the overlapping surface 55 and the curved surface 72 are connected rubs against the first surface 28 of the metal shell 20, but the overlapping surface 55 and the curved surface 72 are smoothly connected, so that the generation of chips can be made difficult. Since the generation of chips that become the ignition species of pre-ignition is difficult, the generation of pre-ignition can be suppressed. Even if chips are generated, since a space 73 capable of accommodating chips can be formed between the curved surface 72 and the metal shell 20, chips can be made difficult to enter the sub-chamber 52. This can suppress the occurrence of pre-ignition in which chips become ignition seeds.

A third embodiment will be described with reference to fig. 6. In the first and second embodiments, the case where the corner where the overlapping surface 55 of the opposing cover members 50 and 71 intersects the inner opposing surface 56 is chamfered has been described. In contrast, in the third embodiment, a case will be described in which the chamfering of the corner where the overlapping surface 55 of the cover member 81 and the inner facing surface 56 intersect is omitted. Note that the same portions as those described in the first embodiment are denoted by the same reference numerals, and the following description is omitted. Fig. 6 is a sectional view of a spark plug 80 in the third embodiment.

The spark plug 80 has a lid member 81 joined to the front end portion 21 of the metallic shell 20 by a welding portion 59. The inside facing surface 56 of the cover member 81 is separated from the second surface 29 of the metal shell 20. Thus, the positional accuracy of the third surface 30 (see fig. 4) of the metal shell 20 and the outer facing surface 60 of the cover member 81 is managed, and it is confirmed from the outside of the cover member 81 that no foreign matter or the like is interposed between the third surface 30 and the outer facing surface 60, and the axial length of the cover member 81 from the metal shell 20 can be managed with reference to the outer facing surface 60 abutting against the third surface 30. Therefore, as compared with the case where the axial direction positioning of the lid member 81 before joining is performed with reference to the inner facing surface 56 that cannot be confirmed from the outside of the lid member 81, it is possible to reduce the variation in the axial direction length of the lid member 81 from the metal shell 20.

When the cover member 81 is inserted into the first surface 28 of the metal shell 20, the corner 82 where the overlapping surface 55 and the inner facing surface 56 intersect may rub against the first surface 28 of the metal shell 20, thereby generating chips. However, by narrowing the gap between the inner facing surface 56 of the cover member 81 and the second surface 29 of the metallic shell 20 to about 0.02mm to 0.8mm, the gas is less likely to flow through the gap, and thus the chips in the gap are less likely to move. Even if chips are generated, the chips are less likely to enter the sub-chamber 52, and therefore, the occurrence of pre-ignition in which chips become a fire can be suppressed.

A fourth embodiment will be described with reference to fig. 7. In the first to third embodiments, the case where the inner facing surface 56 of the cover member 50, 71, 81 is located on the rear end side of the outer facing surface 58 is described. In contrast, in the fourth embodiment, a case where the inner facing surface 99 of the cover member 95 is located on the front end side of the outer facing surface 100 will be described. Note that the same portions as those described in the first embodiment are denoted by the same reference numerals, and the following description is omitted. Fig. 7 is a sectional view of a spark plug 90 in the fourth embodiment.

In the spark plug 90, a cover member 95 is joined to the front end portion 21 of the metallic shell 91 by a welded portion 101. The inner surface 96 of the cover member 95 faces the sub-chamber 52, and the outer surface 97 of the cover member 95 faces the combustion chamber 3 (see fig. 1). The welded portion 101 is formed by melting the cover member 95 and the metallic shell 91. The welded portion 101 is formed over the entire circumference of the metal shell 91 and the cover member 95.

The cover member 95 includes an overlapping surface 98 that faces the front end portion 21 of the metal shell 91 in the axial direction (vertical direction in fig. 7), an inner facing surface 99 that faces the front end portion 21 of the metal shell 91 in the axial direction and is located closer to the sub-chamber 52 than the overlapping surface 98, and an outer facing surface 100 that faces the front end portion 21 of the metal shell 91 in the axial direction and is located farther to the outside (combustion chamber 3 side) than the overlapping surface 98.

The overlapping surface 98 is a cylindrical surface facing inward of the cover member 95, and is formed over the entire circumference of the cover member 95. The overlapping surface 98 is in contact with the cylindrical first surface 92 of the metal shell 91 facing outward. The inner facing surface 99 is an annular surface facing the rear end and is formed over the entire circumference of the cover member 95. The inside facing surface 99 intersects the inner surface 96 of the cover member 95. The inner facing surface 99 is separated from the annular second surface 93 of the metallic shell 91 facing the distal end. The distance (the size of the gap) in the axial direction between the inner facing surface 99 of the lid member 95 and the second surface 93 of the metallic shell 91 is, for example, about 0.02mm to 0.8 mm.

The outer facing surface 100 is an annular surface facing the rear end and is formed over the entire circumference of the cover member 95. The outer facing surface 100 intersects the outer surface 97 of the cover member 95. The outer facing surface 100 is located on the rear end side of the inner facing surface 99.

The chamfer is formed at the corner where the first surface 92 and the second surface 93 of the metallic shell 91 intersect, so that the corner is formed over the entire circumference of the metallic shell 91 with the inclined surface 93a being obliquely cut away. The inclined surface 93a formed in the metal shell 91 facilitates insertion of the metal shell 91 into the overlapping surface 98 of the cover member 95.

When the welded portion 101 is formed in the manufacturing process of the spark plug 90, the metallic shell 91 is inserted into the cover member 95 while the first surface 92 of the metallic shell 91 and the overlapping surface 98 of the cover member 95 rub against each other until the outer facing surface 100 of the cover member 95 abuts against the third surface 94 of the metallic shell 91. The cover member 95 is temporarily fixed to the metal shell 91 by friction of the overlapping surface 98 with the first surface 92 of the metal shell 91. In this state, for example, the cover member 95 and the metallic shell 91 are melted by irradiation of a laser beam to form a welded portion 101, and the cover member 95 is joined to the metallic shell 91.

The inner facing surface 99 cannot be recognized from the outside of the cover member 95, but the state where the outer facing surface 100 of the cover member 95 is in contact with the third surface 94 of the metal shell 91 can be recognized from the outside of the cover member 95. In addition to managing the positional accuracy of the third surface 94 of the metal shell 91 and the outer facing surface 100 of the cover member 95, the axial length of the cover member 95 from the metal shell 91 can be managed with reference to the outer facing surface 100 abutting against the third surface 94 by confirming from the outside of the cover member 95 that no foreign matter or the like is interposed between the third surface 94 and the outer facing surface 100. Therefore, as compared with the case where the axial direction positioning of the lid member 95 before joining is performed with the inner facing surface 99, which cannot be confirmed from the outside of the lid member 95, as a reference, the variation in the axial direction length of the lid member 95 from the metal shell 91 can be reduced.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments at all, and it is easily assumed that various modifications and variations can be made without departing from the scope of the present invention. For example, the shape of the cover members 50, 71, 81, 95, the number, shape, size, and the like of the through holes 51 are examples, and they can be set as appropriate.

In the embodiment, the case where the ground electrode 40 penetrating the distal end portion 21 of the metal shell 20 or 91 is provided at the position of the male screw 22 has been described, but the present invention is not necessarily limited thereto. For example, it is needless to say that the inner portions of the second surfaces 29 and 93 of the metal fittings 20 and 91 protrude inward from the inner surfaces 53 and 96 of the lid members 50, 71, 81, and 95, and the ground electrode may be connected to the protruding portions of the second surfaces 29 and 93. The ground electrode may be linear or curved in shape. The ground electrode may be joined to the lid member.

In the embodiment, the description has been given of the case where the end portion 41 of the ground electrode 40 is disposed on the distal end side of the center electrode 13 and the spark gap 42 is formed on the distal end side of the center electrode 13, but the present invention is not necessarily limited thereto. For example, it is needless to say that the end portion 41 of the ground electrode 40 is disposed so as to be spaced apart from the side surface of the center electrode 13, and the spark gap 42 may be formed between the side surface of the center electrode 13 and the end portion 41 of the ground electrode 40. It is needless to say that a plurality of ground electrodes 40 may be arranged and a plurality of spark gaps 42 may be provided.

In the embodiment, the description has been given of the case where the overlapping surfaces 55, 98 of the lid members 50, 71, 81, 95 and the first surfaces 28, 92 of the metal shell 20, 91 are in contact with each other (the fitting tolerance is interference fit), but the present invention is not necessarily limited thereto. It is needless to say that the clearance can be provided between the first surface 28, 92 and the overlapping surface 55, 98 by setting the fitting tolerance of the first surface 28, 92 and the overlapping surface 55, 98 to a clearance fit, an intermediate fit relationship, and not an interference fit relationship.

In the embodiment, the case where the welding portions 59 and 101 are formed by laser welding has been described, but the present invention is not necessarily limited thereto. Of course, the welding portions 59 and 101 can be formed by other means. Examples of other means include arc welding and electron beam welding.

In the embodiment, the case where the metal fittings 20 and 91 and the lid members 50, 71, 81, and 95 are joined by forming the welding portions 59 and 101 has been described, but the present invention is not necessarily limited thereto. For example, it is needless to say that the fitting tolerance between the metal shell 20 or 91 and the cover member 50, 71, 81, or 95 is in an interference fit relationship, and the cover member 50, 71, 81, or 95 can be joined (fixed) to the metal shell 20 or 91 so that the welded portion 59 or 101 is not formed.

In the embodiment, the case where the entire outer facing surfaces 60 (see fig. 3) of the metal shell 20 and the lid members 50, 71, 81 are melted to form the welded portion 59 has been described, but the present invention is not necessarily limited thereto. For example, it is needless to say that the laser beam is irradiated to the metal shell 20 on the rear end side of the outer facing surface 60 of the cover members 50, 71, 81 substantially perpendicular to the axis O (see fig. 1) to melt the overlapping surface 55 of the cover members 50, 71, 81 to form the welded portion. The outer facing surfaces 60 of the cover members 50, 71, 81 may be partially or entirely melted to form a weld. When a part of the outer facing surface 60 of the lid member 50, 71, 81 is melted to form a welded portion, the outer facing surface 58, which is an interface of the welded portion 59, and the unmelted outer facing surface 60 are mixed in the lid member 50, 71, 81.

It is needless to say that the laser beam is irradiated to the cover members 50, 71, and 81 on the tip side of the outer facing surface 60 of the cover members 50, 71, and 81 obliquely with respect to the axis O, and the outer facing surface 60 and the overlapping surface 55 of the cover members 50, 71, and 81 are melted to form the welded portion. In this case, the outer facing surface 60 of the lid member 50, 71, 81 may be partially or entirely melted to form a welded portion. When a part of the outer facing surface 60 of the lid member 50, 71, 81 is melted to form a welded portion, the outer facing surface 58, which is an interface of the welded portion 48, and the unmelted outer facing surface 60 are mixed in the lid member 50, 71, 81.

In the fourth embodiment, the case where the welded portion 101 is formed between the first surface 92 of the metal shell 91 and the overlapping surface 98 of the cover member 95 has been described, but the present invention is not necessarily limited thereto. Of course, a welded portion can be formed by melting the third surface 94 of the metallic shell 91 and the outer facing surface 100 of the cover member 95.

In the fourth embodiment, the case where the inclined surface 93a is formed at the corner where the first surface 92 and the second surface 93 of the metallic shell 91 intersect has been described, but the present invention is not necessarily limited thereto. Of course, this corner may be chamfered by R instead of the inclined surface 93 a. In addition, it is needless to say that the corner where the overlapping surface 98 of the cover member 95 and the outer facing surface 100 intersect can be chamfered to facilitate insertion of the metal shell 91 into the cover member 95.

In the embodiment, the case where the corner where the overlapping surface 55 of the opposing cover member 50 or 71 and the inner opposing surface 56 intersect is chamfered has been described, but it is needless to say that a recess may be provided in the corner where the first surface 28 and the second surface 29 of the metal shell 20 intersect in addition to the chamfering of the cover member 50 or 71 or without chamfering the cover member 50 or 71. By providing the recess in the metal shell 20, a space (recess) capable of accommodating chips can be formed between the metal shell 20 and the cover members 50, 71, and 81, and thus the chips can be made difficult to move toward the sub-chamber 52. In particular, it is preferable to provide a recess on the second surface 29 side of the corner. This is because the path from the recess to the sub-chamber 52 through the space between the second surface 29 and the inner facing surface 56 can be curved by the recess formed in the second surface 29, and therefore chips accommodated in the recess are less likely to enter the sub-chamber 52.

Description of the reference symbols

10. 70, 80, 90 spark plug

13 center electrode

20. 91 Main body fitting

21 front end part of main body fitting

40 ground electrode

41 end of ground electrode

42 spark gap

50. 71, 81, 95 cover member

51 through hole

52 auxiliary chamber

55. 98 overlapping surfaces

56. 99 inner side opposite surface

57 inclined plane (chamfer)

58. 60, 100 outer facing surface

72 curved surface (R chamfer)

O axis