JP2023077831A - Spark plug for internal combustion engine and manufacturing method of the same - Google Patents

Abstract

To provide a spark plug capable of improving productivity, and a manufacturing method of the same.SOLUTION: In a spark plug 1, a plug cover 5 is provided with a ground electrode 6. A discharge gap G is formed by a center discharge surface 41 of a center electrode 4 and a ground discharge surface 61 of the ground electrode 6 opposite to each other in a plug axial direction Z. A tip end part of a housing 2 includes a housing fixing part 21 and an opposite surface 22. The housing fixing part 21 is opposite to a cover base end part 51 of the plug cover 5 in a plug radial direction. The opposite surface 22 is opposite to a base end surface 52 of the plug cover 5 in the plug axis direction Z on a side closer to the base end than the housing fixing part 21. The housing fixing part 21 and the cover base end part 51 are bonded to each other. Further, the base end surface 52 of the plug cover 5 is arranged at a position separated from the opposite surface 22 in the plug axis direction Z.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spark plug for internal combustion engines and a method of manufacturing the same.

For example, as disclosed in Patent Document 1, a spark plug for an internal combustion engine is known which has a sub combustion chamber at its tip. The spark plug disclosed in Patent Document 1 has a ground electrode fixed to the tip of the housing, and after adjusting the discharge gap, the discharge gap is arranged inside the plug cover that covers the sub-combustion chamber. can be assembled.

JP 2020-009747 A

However, in the spark plug disclosed in Patent Document 1, when the ground electrode is deformed to form the discharge gap, so-called springback may occur in the ground electrode. Therefore, it may be difficult to adjust the discharge gap to a desired length. Therefore, there is a problem in terms of spark plug productivity.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object thereof is to provide a spark plug capable of improving productivity and a method of manufacturing the same.

A first aspect of the present invention is a tubular insulator (3),
a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side;
a cylindrical housing (2) that holds the insulator on the inner peripheral side;
a ground electrode (6) forming a discharge gap (G) with the center electrode;
a plug cover (5) fixed to the front end of the housing so as to cover the auxiliary combustion chamber (50) in which the ground electrode is provided and the discharge gap is arranged;
The ground electrode protrudes from the inner wall surface (53) of the plug cover into the sub-combustion chamber, and is provided along the radial direction of the plug when viewed from the axial direction (Z) of the plug,
The discharge gap is formed by the center discharge surface (41) of the center electrode and the ground discharge surface (61) of the ground electrode facing each other in the axial direction of the plug,
The distal end portion of the housing includes a housing fixing portion (21) facing a cover proximal end portion (51) of the plug cover in the radial direction of the plug, and a proximal end surface of the plug cover on the proximal side of the housing fixing portion. (52) and a facing surface (22) facing in the axial direction of the plug,
The housing fixing portion and the cover base end portion are joined to each other,
The base end surface of the plug cover is in a spark plug (1) for an internal combustion engine, which is arranged at a position spaced apart from the opposing surface in the axial direction of the plug.

A second aspect of the present invention is a cylindrical insulator (3),
a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side;
a cylindrical housing (2) that holds the insulator on the inner peripheral side;
a plug cover (5) fixed to the tip of the housing so as to form a discharge gap (G) with the center electrode and cover a sub-combustion chamber (50) in which the discharge gap is disposed; have
In the discharge gap, the center discharge surface (41) of the center electrode and the ground discharge surface (611) which is part of the inner wall surface (53) of the plug cover face each other in the axial direction (Z) of the plug. It is formed by
The front end portion of the housing includes a housing fixing portion (21) facing the cover base end portion (51) of the plug cover in the plug radial direction, and a base end surface ( 52) and a facing surface (22) facing in the axial direction of the plug,
The housing fixing portion and the cover base end portion are joined to each other,
The base end surface of the plug cover is in a spark plug (1) for an internal combustion engine, which is arranged at a position spaced apart from the opposing surface in the axial direction of the plug.

A third aspect of the present invention is a method of manufacturing a spark plug (1) for an internal combustion engine, comprising:
The spark plug includes a cylindrical insulator (3), a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side, and the insulator on the inner peripheral side. a cylindrical housing (2) that is held in the body, a ground electrode (6) that forms a discharge gap (G) between the center electrode and the ground electrode, and the discharge gap is arranged. a plug cover (5) fixed to the tip of the housing so as to cover the sub-combustion chamber (50),
The ground electrode protrudes from the inner wall surface (53) of the plug cover into the sub-combustion chamber, and is provided along the radial direction of the plug when viewed from the axial direction (Z) of the plug,
The discharge gap is formed by the center discharge surface (41) of the center electrode and the ground discharge surface (61) of the ground electrode facing each other in the axial direction of the plug,
The distal end portion of the housing has a housing fixing portion (21) facing the cover base end portion (51) of the plug cover in the radial direction of the plug,
In manufacturing the above spark plug,
a preparation step of respectively producing the housing in which the insulator and the center electrode are assembled, and the plug cover in which the ground electrode is provided;
After the preparatory step, the housing fixing portion and the cover base end portion are overlapped in the radial direction of the plug, and the central discharge surface and the ground discharge surface are brought into contact with each other in the axial direction of the plug. a gap abutting step of placing the plug cover against
a separation step of separating the ground discharge surface from the central discharge surface by moving the plug cover in the plug axial direction with respect to the housing after the gap abutment step;
In the method of manufacturing a spark plug for an internal combustion engine, a bonding step of bonding the housing fixing portion and the cover base end portion to each other is performed after the separating step.

A fourth aspect of the present invention is a method of manufacturing a spark plug (1) for an internal combustion engine, comprising:
The spark plug includes a cylindrical insulator (3), a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side, and the insulator on the inner peripheral side. A discharge gap (G) is formed between the cylindrical housing (2) held in the center electrode and the center electrode. a plug cover (5) secured to
In the discharge gap, the center discharge surface (41) of the center electrode and the ground discharge surface (611) which is part of the inner wall surface (53) of the plug cover face each other in the axial direction (Z) of the plug. It is formed by
The distal end portion of the housing has a housing fixing portion (21) facing the cover base end portion (51) of the plug cover in the plug radial direction,
In manufacturing the above spark plug,
a preparatory step of fabricating the housing assembled with the insulator and the center electrode and the plug cover;
After the preparatory step, the housing fixing portion and the cover base end portion are overlapped in the radial direction of the plug, and the central discharge surface and the ground discharge surface are brought into contact with each other in the axial direction of the plug. a gap abutting step of placing the plug cover against
a separation step of separating the ground discharge surface from the central discharge surface by moving the plug cover in the plug axial direction with respect to the housing after the gap abutment step;
In the method of manufacturing a spark plug for an internal combustion engine, a bonding step of bonding the housing fixing portion and the cover base end portion to each other is performed after the separating step.

In the spark plug of the first aspect, the discharge gap is formed by the center discharge surface and the ground discharge surface of the ground electrode provided on the plug cover facing each other in the axial direction of the plug. Also, the base end surface of the plug cover is arranged at a position spaced apart from the facing surface in the axial direction of the plug. Therefore, the discharge gap can be adjusted without deforming the ground electrode. Therefore, a discharge gap having a desired length can be easily formed. As a result, the productivity of spark plugs can be improved.

In the spark plug of the second aspect, the discharge gap is formed by the central discharge surface and the grounded discharge surface of the plug cover facing each other in the axial direction of the plug. Also, the base end surface of the plug cover is arranged at a position spaced apart from the facing surface in the axial direction of the plug. Therefore, a discharge gap having a desired length can be easily formed. As a result, the productivity of spark plugs can be improved.

A method of manufacturing a spark plug according to the third aspect includes a preparation step, a gap abutment step, a separation step, and a joining step. Therefore, the discharge gap can be adjusted without deforming the ground electrode. As a result, the discharge gap can be easily adjusted, and the spark plug can be manufactured efficiently.

A method of manufacturing a spark plug according to the fourth aspect includes a preparation step, a gap abutment step, a separation step, and a joining step. Therefore, the discharge gap can be easily adjusted. As a result, spark plugs can be efficiently manufactured.

As described above, according to the above aspect, it is possible to provide a spark plug and a method of manufacturing the same that can improve productivity.
It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

FIG. 3 is a cross-sectional view along the axial direction of the spark plug in the vicinity of the tip portion of the spark plug according to the first embodiment, taken along the line II of FIG. 2; FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1; FIG. 2 is a cross-sectional view showing the length of the discharge gap and the like in the first embodiment; FIG. 5 is a cross-sectional view showing how the plug cover is moved to the base end side with respect to the housing in the gap abutting step in the first embodiment; FIG. 4 is a cross-sectional view showing a state in which the central discharge surface and the ground discharge surface are brought into contact with each other according to the first embodiment; 1 is a cross-sectional view of an internal combustion engine in which a spark plug is installed according to Embodiment 1; FIG. FIG. 5 is a cross-sectional view of the vicinity of the tip portion of the spark plug in the second embodiment along the axial direction of the plug; FIG. 8 is a cross-sectional view showing a state in which the central discharge surface and the ground discharge surface are brought into contact with each other in the second embodiment; FIG. 11 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug according to the third embodiment; FIG. 11 is a cross-sectional view showing a state in which the central discharge surface and the ground discharge surface are brought into contact with each other according to the third embodiment; FIG. 11 is a view of the vicinity of the tip portion of the spark plug in Embodiment 4, viewed from a direction orthogonal to the axial direction of the plug; FIG. 16 is a view of the plug cover viewed from the base end side in Embodiment 4, and is a view in the direction of arrow XII in FIG. 15; FIG. 16 is a view of the housing as seen from the distal end side in Embodiment 4, and is a view along arrow XIII in FIG. 15 ; FIG. 12 is an enlarged view of the vicinity of the stairs in Embodiment 4; FIG. 14 is a diagram showing how the plug cover is moved to the base end side with respect to the housing in the gap abutting step in the fourth embodiment; FIG. 11 is a diagram showing a state in which the central discharge surface and the ground discharge surface are brought into contact with each other in the fourth embodiment; FIG. 14 is a diagram showing a state in which the plug cover is moved to the distal end side with respect to the housing in the separating step according to the fourth embodiment; FIG. 15 is a view showing a state in which the convex portion is brought into contact with the stepped portion in the plug circumferential direction in the cover contacting step according to the fourth embodiment; FIG. 11 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug in Embodiment 5; FIG. 11 is a cross-sectional view along the axial direction of the spark plug near the tip of the spark plug in Embodiment 6; FIG. 12 is a cross-sectional view orthogonal to the plug axial direction of the tip of the spark plug in Embodiment 7; FIG. 11 is a cross-sectional view for explaining the direction of a swirl flow formed in an auxiliary combustion chamber according to Embodiment 7;

(Embodiment 1)
An embodiment of a spark plug for an internal combustion engine and a method of manufacturing the same will be described with reference to FIGS. 1 to 6. FIG.
In this embodiment, a spark plug 1 for an internal combustion engine comprises a cylindrical insulator 3, a center electrode 4, a cylindrical housing 2, a ground electrode 6 and a plug cover 5, as shown in FIGS. and have The center electrode 4 is held on the inner peripheral side of the insulator 3 and protrudes from the insulator 3 toward the tip side. The housing 2 holds the insulator 3 on the inner peripheral side. The ground electrode 6 forms a discharge gap G with the center electrode 4 . A ground electrode 6 is provided on the plug cover 5 . Also, the plug cover 5 is fixed to the front end of the housing 2 so as to cover the auxiliary combustion chamber 50 in which the discharge gap G is arranged.

The ground electrode 6 protrudes into the auxiliary combustion chamber 50 from the inner wall surface 53 of the plug cover 5 . 2, the ground electrode 6 is provided along the radial direction of the plug when viewed from the axial direction Z of the plug. The discharge gap G is formed by the center discharge surface 41 of the center electrode 4 and the ground discharge surface 61 of the ground electrode 6 facing each other in the axial direction Z of the plug, as shown in FIG.

Further, the distal end portion of the housing 2 has a housing fixing portion 21 and a facing surface 22 . The housing fixing portion 21 faces the cover base end portion 51 of the plug cover 5 in the plug radial direction. The facing surface 22 faces the base end surface 52 of the plug cover 5 in the plug axial direction Z on the base end side of the housing fixing portion 21 . Moreover, the housing fixing portion 21 and the cover base end portion 51 are joined to each other. The base end surface 52 of the plug cover 5 is arranged at a position away from the facing surface 22 in the axial direction Z of the plug.

The spark plug 1 of this embodiment can be used, for example, as ignition means in internal combustion engines such as automobiles. As shown in FIG. 6, the spark plug 1 is attached to the internal combustion engine 10 by screwing the threaded portion 24 of the housing 2 into the female threaded portion of the plug hole 711 of the cylinder head 71 .

Internal combustion engine 10 includes a piston 74 that reciprocates within cylinder 70 . The volume of the main combustion chamber 101 changes due to the reciprocating motion of the piston 74 . An intake port 721 and an exhaust port 731 are formed in the internal combustion engine 10, and an intake valve 72 and an exhaust valve 73 are provided, respectively.

One end of the spark plug 1 in the axial direction Z is arranged in the main combustion chamber 101 of the internal combustion engine 10 . In the axial direction Z of the spark plug 1, the side exposed to the main combustion chamber 101 is called the tip side, and the opposite side is called the base end side. Further, the axial direction Z of the spark plug 1 is also referred to as the plug axial direction Z or simply the Z direction as appropriate. It should be noted that the plug central axis C means the central axis C of the spark plug 1 . Further, the plug radial direction means the radial direction of a circle centered on the plug center axis C on a plane perpendicular to the plug center axis C. As shown in FIG. The circumferential direction of the plug is the direction along the circumference centered on the central axis C of the plug. The plug center axis C is also the center axis of the center electrode 4 in this embodiment.

When the spark plug 1 is attached to the internal combustion engine 10 , the plug cover 5 faces the main combustion chamber 101 and separates the auxiliary combustion chamber 50 from the main combustion chamber 101 .

Further, the plug cover 5 is formed with an injection hole 55 that communicates the auxiliary combustion chamber 50 with the outside. In this embodiment, the plug cover 5 is formed with four injection holes 55 as shown in FIG. The injection hole 55 is formed such that the injection hole axis 55L extends along the radial direction of the plug when viewed from the Z direction. Further, the injection hole 55 is opened so as to be inclined with respect to the Z direction so as to extend outward in the radial direction of the plug toward the distal end side. In a state where the spark plug 1 is attached to the internal combustion engine 10 , the injection hole 55 allows the sub combustion chamber 50 and the main combustion chamber 101 to communicate with each other.

Also, the ground electrode 6 is joined to the plug cover 5 by welding or the like. The ground electrode 6 has a substantially quadrangular prism shape. The ground electrode 6 has four flat sides, one of which is the proximal side 62 . A proximal side surface 62 of the ground electrode 6 faces the central discharge surface 41 of the central electrode 4 in the Z direction. That is, part of the base end side surface 62 serves as the ground discharge surface 61 .

The ground discharge surface 61 and the central discharge surface 41 are flat surfaces and formed substantially perpendicular to the Z direction. As shown in FIG. 1 , the central discharge surface 41 is located on the tip side of the housing 2 . In other words, the discharge gap G is formed closer to the tip than the tip of the housing 2 .

Moreover, the front end of the housing 2 has a housing fixing portion 21 and a facing surface 22 and is formed in a stepped shape. A cover base end portion 51 is joined to the outer peripheral side of the housing fixing portion 21 .

Also, the proximal end surface 52 of the plug cover 5 is positioned on the distal end side of the facing surface 22 . The facing surface 22 and the base end surface 52 face each other in the Z direction without contacting each other. That is, a gap g1 is formed between the facing surface 22 and the base end surface 52. As shown in FIG. As shown in FIG. 3, the distance D1 from the facing surface 22 in the axial direction Z of the plug to the base end surface 52 of the plug cover 5 is equal to or greater than the length D2 of the discharge gap G in the axial direction Z of the plug.

Also, the distance D3 from the facing surface 22 to the central discharge surface 41 in the Z direction is greater than or equal to the distance D4 from the base end surface 52 of the plug cover 5 to the ground discharge surface 61 in the Z direction.

Next, a method for manufacturing the spark plug 1 of this embodiment will be described with reference to FIGS. 4 and 5. FIG.
In manufacturing the spark plug 1, a preparation process, a gap contact process, a separation process, and a joining process are performed. In the preparatory step, the housing 2 with the insulator 3 and the center electrode 4 assembled therein, and the plug cover 5 with the ground electrode 6 provided thereon are respectively produced. In the gap abutting step, after the preparation step, as shown in FIG. 5, the housing fixing portion 21 and the cover base end portion 51 are overlapped in the radial direction of the plug, and the central discharge surface 41 and the ground discharge surface 61 are aligned in the axial direction of the plug. The plug cover 5 is arranged with respect to the housing 2 so that they abut each other on Z. In the separation process, after the gap abutting process, the ground discharge surface 61 is separated from the central discharge surface 41 by moving the plug cover 5 in the plug axial direction Z with respect to the housing 2 . In the joining step, the housing fixing portion 21 and the cover base end portion 51 are joined to each other after the separating step. A detailed description will be given below.

In this embodiment, the outer peripheral surface of the housing fixing portion 21 and the inner peripheral surface of the cover base end portion 51 are formed along the Z direction. From the gap abutment step to the joining step, the plug cover 5 is fitted to the housing 2 . In other words, each step is performed while the outer peripheral surface of the housing fixing portion 21 and the inner peripheral surface of the cover base end portion 51 are in contact with each other in the radial direction of the plug. However, a slight clearance may be provided between the outer peripheral surface of the housing fixing portion 21 and the inner peripheral surface of the cover base end portion 51 to enable smooth sliding therebetween.

First, in the preparation step, the plug cover 5 provided with the ground electrode 6 is manufactured by joining the ground electrode 6 which is a member separate from the plug cover 5 to the plug cover 5 .

Next, in the gap abutment step, the plug cover 5 is fitted to the housing 2 to which the center electrode 4 and the like are assembled. Then, as shown by an arrow M in FIG. 4, a robot arm is used to slide the plug cover 5 toward the base end side with respect to the housing 2, thereby forming a central discharge surface 41 and a ground discharge surface as shown in FIG. 61 are brought into contact with each other. In other words, in the gap abutting step, the discharge gap G is not formed between the central discharge surface 41 and the ground discharge surface 61 . A gap g2 is formed between the base end surface 52 of the plug cover 5 and the facing surface 22 when the ground discharge surface 61 is in contact with the central discharge surface 41 .

Next, in the separating step, the robot arm is used to move the plug cover 5 toward the front end side of the housing 2 in the Z direction, as indicated by arrow M in FIG. slide to At this time, the plug cover 5 is slid in the Z direction by the length of the discharge gap G with respect to the housing 2 . Thereby, the length of the discharge gap G can be set to a desired length. That is, the amount of movement of the plug cover 5 with respect to the housing 2 in the separating process corresponds to the length of the discharge gap G. As shown in FIG.

Next, in the joining step, the housing fixing portion 21 and the cover base end portion 51, which are in contact with each other in the radial direction of the plug, are joined together by welding or the like. In addition, in the joining step, the cover base end portion 51 is joined to the outer peripheral side of the housing fixing portion 21 . Thereby, as shown in FIGS. 1 and 2, the spark plug 1 of this embodiment can be produced.

Next, the effects of this embodiment will be described.
In the spark plug 1 of this embodiment, the discharge gap G is formed by the central discharge surface 41 and the ground discharge surface 61 of the ground electrode 6 provided on the plug cover 5 facing each other in the axial direction Z of the plug. there is Also, the base end surface 52 of the plug cover 5 is arranged at a position away from the facing surface 22 in the axial direction Z of the plug. Therefore, the discharge gap G can be adjusted without deforming the ground electrode 6 . Therefore, a discharge gap G having a desired length can be easily formed. As a result, productivity of the spark plug 1 can be improved.

In other words, the spark plug 1 of this embodiment can be manufactured by performing the preparation process, the gap contact process, the separation process, and the joining process. Therefore, the discharge gap G can be adjusted without deforming the ground electrode 6 . Therefore, the desired length of the discharge gap G can be formed without readjustment of the discharge gap G. FIG. As a result, productivity of the spark plug 1 can be improved. Also, the defect rate of the spark plug 1 can be suppressed.

Also, the distance D1 is greater than or equal to the length D2 (see FIG. 3). Therefore, when manufacturing the spark plug 1, the ground discharge surface 61 can be reliably brought into contact with the central discharge surface 41 in the gap contact process. Therefore, a discharge gap G having a desired length can be reliably and easily formed. As a result, the productivity of the spark plug 1 can be reliably improved.

A cover base end portion 51 is joined to the outer peripheral side of the housing fixing portion 21 . Therefore, the width of the plug cover 5 in the plug radial direction can be increased. Therefore, the volume of the space inside the plug cover 5 can be increased. Therefore, the volume of the sub-combustion chamber 50 can be increased. Therefore, the flame jet ejected from the auxiliary combustion chamber 50 to the main combustion chamber through the injection holes 55 can be strengthened. As a result, ignitability can be improved.

The method for manufacturing the spark plug 1 of this embodiment includes a preparation step, a gap contact step, a separation step, and a joining step. Therefore, the discharge gap G can be adjusted without deforming the ground electrode 6 . As a result, the discharge gap G can be easily adjusted, and the spark plug 1 can be manufactured efficiently.

In this embodiment, from the gap abutting step to the joining step, the plug cover 5 is fitted to the housing 2 . Therefore, when performing each step, the position of the plug cover 5 in the plug radial direction with respect to the housing 2 is less likely to shift. Therefore, the spark plug 1 can be manufactured more efficiently.

The outer peripheral surface of the housing fixing portion 21 and the inner peripheral surface of the cover base end portion 51 are formed along the Z direction. Therefore, the plug cover 5 can be slid in the Z direction with respect to the housing 2 while the cover base end portion 51 is fitted to the housing fixing portion 21 . Therefore, while the housing fixing portion 21 and the cover base end portion 51 have simple shapes, the steps from the gap abutting step to the bonding step can be efficiently performed. Therefore, the spark plug 1 can be manufactured more efficiently.

Further, in the present embodiment, the length D2 of the discharge gap G is the moving distance of the plug cover 5 in the Z direction with respect to the housing 2 in the separating step. Therefore, the length of the discharge gap G can be adjusted without directly checking the discharge gap G by adjusting the moving distance of the plug cover 5 in the Z direction with respect to the housing 2 .

In the joining step, the cover base end portion 51 is joined to the outer peripheral side of the housing fixing portion 21 . Therefore, the plug cover 5 can be assembled to the housing 2 so that the volume of the auxiliary combustion chamber 50 is increased. As a result, it is possible to manufacture a spark plug 1 capable of improving ignitability.

The ground electrode 6 is provided along the radial direction of the plug when viewed from the axial direction Z of the plug. Further, the injection hole 55 is opened so as to be inclined with respect to the Z direction so as to extend outward in the radial direction of the plug toward the distal end side. Therefore, the airflow introduced into the sub-combustion chamber 50 through the injection hole 55 is easily directed toward the discharge gap G by being guided by the base end side surface 62 of the ground electrode 6 . Therefore, the discharge formed in the discharge gap G tends to extend. As a result, ignitability can be improved.

As described above, according to the present embodiment, it is possible to provide the spark plug 1 and the method of manufacturing the same that can improve productivity.

(Embodiment 2)
In this embodiment, as shown in FIGS. 7 and 8, a part of the plug cover 5 constitutes the ground electrode 6. FIG.

The plug cover 5 forms a discharge gap G with the center electrode 4 as shown in FIG. The discharge gap G is formed by the center discharge surface 41 of the center electrode 4 and the ground discharge surface 611 that is part of the inner wall surface 53 of the plug cover 5 facing each other in the axial direction Z of the plug.

In this embodiment, the center electrode 4 forms a discharge gap G with the inner wall surface 53 of the plug cover 5 by extending the tip portion to the vicinity of the inner wall surface 53 of the plug cover 5 . That is, in this embodiment, the ground electrode 6 does not protrude from the inner wall surface 53 into the sub-combustion chamber 50 .

Next, a method for manufacturing the spark plug 1 of this embodiment will be described.
In the preparatory step, the housing 2 to which the insulator 3 and the center electrode 4 are assembled, and the plug cover 5 are produced. In the gap abutting step, as shown in FIG. 8, the central discharge surface 41 and the ground discharge surface 611 are brought into contact with each other in the plug axial direction Z while the housing fixing portion 21 and the cover base end portion 51 are overlapped in the radial direction of the plug. The plug cover 5 is arranged with respect to the housing 2 in such a manner as to In the separating step, the ground discharge surface 611 is separated from the central discharge surface 41 by moving the plug cover 5 in the plug axial direction Z with respect to the housing 2, as indicated by an arrow M in FIG.
Others are the same as those of the first embodiment. Note that, of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the previous embodiments represent the same constituent elements as those in the previous embodiments, unless otherwise specified.

In the spark plug 1 of this embodiment, the discharge gap G is formed by the center discharge surface 41 and the ground discharge surface 611 of the plug cover 5 facing each other in the axial direction Z of the plug. Also, the base end surface 52 of the plug cover 5 is arranged at a position away from the facing surface 22 in the axial direction Z of the plug. Therefore, a discharge gap G having a desired length can be easily formed. As a result, productivity of the spark plug 1 can be improved.

The method for manufacturing the spark plug 1 of this embodiment includes a preparation step, a gap contact step, a separation step, and a joining step. Therefore, the discharge gap G can be easily adjusted. As a result, the spark plug 1 can be manufactured efficiently.

In this embodiment, a part of the plug cover 5 constitutes the ground electrode 6. As shown in FIG. Therefore, the spark plug 1 can be manufactured without fixing the ground electrode to the plug cover 5 . As a result, the spark plug 1 can be manufactured more efficiently.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 3)
In this embodiment, as shown in FIGS. 9 and 10, the plug cover 5 is fixed to the housing 2 by screwing.

In this embodiment, the housing fixing portion 21 and the cover base end portion 51 are fixed to each other by screwing the male screw portion 11 and the female screw portion 12 that screw together with the male screw portion 11, as shown in FIG. In addition, a threaded portion is formed. Specifically, the plug cover 5 is fixed to the housing 2 by screwing the female threaded portion 12 formed on the cover base end portion 51 and the male threaded portion 11 formed on the housing fixing portion 21 .

Next, a method for manufacturing the spark plug 1 of this embodiment will be described.
In the gap abutting step, the plug cover 5 is rotated in one direction in the plug circumferential direction with respect to the housing 2 while the male threaded portion 11 and the female threaded portion 12 are screwed together. As a result, as shown in FIG. 10, the plug cover 5 is moved proximally with respect to the housing 2 until the central discharge surface 41 and the ground discharge surface 61 abut each other.

In the separation step, the male threaded portion 11 and the female threaded portion 12 are screwed together, and the plug cover 5 is attached to the housing 2 on the other side in the plug circumferential direction as indicated by the arrow M in FIG. rotate to As a result, the plug cover 5 is moved toward the front end side with respect to the housing 2 to separate the ground discharge surface 61 from the central discharge surface 41 .
Others are the same as those of the first embodiment.

The housing fixing portion 21 and the cover base end portion 51 form a threaded portion. Therefore, the plug cover 5 can be efficiently assembled with the housing 2 . That is, after setting the discharge gap G to a desired length in the separation step, when performing the joining step, the cover base end portion 51 is welded to the housing fixing portion 21 without holding the plug cover 5 with a robot arm or the like. etc. can be joined. Therefore, the tact time of the work performed by the robot arm can be shortened. As a result, productivity of the spark plug 1 can be improved.

The method of manufacturing the spark plug 1 of this embodiment includes the above-described gap contact step and separation step. Therefore, the discharge gap G can be easily adjusted. That is, for example, the pitch of the male threaded portion 11 and the female threaded portion 12 is set to 1.25 mm, and the length D2 (see FIG. 3) of the discharge gap G is set to 0.6 mm. In this case, the length D2 can be set to 0.6 mm by rotating the plug cover 5 with respect to the housing 2 by 0.48 in the plug circumferential direction in the separating step. As a result, the spark plug 1 can be manufactured efficiently.
In addition, it has the same effects as those of the first embodiment.

(Embodiment 4)
As shown in FIGS. 11 to 18, this embodiment is a form in which the shapes of the cover base end portion 51 and the facing surface 22 are changed from those of the first embodiment.

As shown in FIGS. 11, 12, and 15 to 18, the base end portion 51 of the cover has a plurality of protrusions 54 formed by protruding a portion of the base end surface 52 toward the base end side. As shown in FIGS. 11 and 13 to 18, the facing surface 22 has a stepped portion 23 formed stepwise along the circumferential direction of the plug. Further, as shown in FIG. 11, the convex portion 54 abuts on a part of the stepped portion 23 in the axial direction Z of the plug.

In this embodiment, two protrusions 54 are formed on the base end portion 51 of the cover, as shown in FIG. The two protrusions 54 are formed so as to face each other in the radial direction of the plug. Further, each convex portion 54 is arranged so as to be sandwiched between the two base end surfaces 52 in the plug circumferential direction.

As shown in FIG. 11, the projection 54 has a projection side surface 541 facing the plug circumferential direction and formed along the Z direction, and a projection base end surface 542 formed substantially orthogonal to the Z direction. have Protrusion base end surfaces 542 of the two protrusions 54 are in contact with the stepped portion 23 in the Z direction. In addition, in this embodiment, the base end faces 542 of the projections are positioned at the same position in the Z direction.

Two stepped portions 23 are formed at the tip of the housing 2 in accordance with the number of protrusions 54 . As shown in FIG. 13, when the front end of the housing 2 is viewed from the Z direction, the two stepped portions 23 are symmetrical with respect to the central axis C of the plug. In this embodiment, a step portion 23 is formed on a portion of the facing surface 22 .

The stepped portion 23 has a plurality of stepped portions 231 formed in a stepped shape. Each of the stepped portions 231 has a circumferential contact surface 232 that faces the plug circumferential direction and is formed along the Z direction, and an axial contact surface 233 that is substantially perpendicular to the Z direction. have.

As shown in FIG. 14, the length D5 of each stepped portion 231 in the Z direction is equal to or less than the discharge gap G tolerance. That is, for example, the reference value of the length D2 (see FIG. 3) of the discharge gap G is 0.6 mm, the maximum allowable value of the length D2 is 0.65 mm, and the minimum allowable value of the length D2 is 0.55 mm. In this case, since the tolerance of the discharge gap G is 0.1 mm, the length D5 is 0.1 mm or less. In this embodiment, the length D5 is equal to the tolerance of the discharge gap G. As shown in FIG. The length D5 is also the length of the circumferential contact surface 232 in the Z direction.

Further, as shown in FIG. 15, the length D6 of the stepped portion 23 in the Z direction is longer than the length D2. Further, as shown in FIG. 11, the distance D7 from the central discharge surface 41 in the Z direction to the facing surface 22 located closest to the base end is the distance from the ground discharge surface 61 in the Z direction to the convex base end surface 542 of the convex portion 54. is greater than or equal to D8.

Next, a method for manufacturing the spark plug 1 of this embodiment will be described with reference to FIGS. 15 to 18. FIG.
In this embodiment, the gap abutting step is performed so that the convex portion 54 and the stepped portion 23 do not abut against each other in the Z direction. Specifically, when viewed from the Z direction (not shown), the plug cover 5 is arranged with respect to the housing 2 so that the projection 54 does not overlap the stepped portion 23, and the housing is moved as shown by an arrow M in FIG. 2, the plug cover 5 is slid to the base end side. Note that the direction of arrow M in FIG. 15 is vertically downward.

In the separating step, the plug cover 5 is slid forward with respect to the housing 2 as indicated by arrow M in FIG. Further, in the separating step, the plug cover 5 is moved toward the leading end side along the Z direction with respect to the housing 2 by a distance equivalent to the maximum allowable value of the length D2.

Further, in this embodiment, the cover contacting step is performed after the separating step and before the joining step. In the cover abutment step, the plug cover 5 is rotated in the plug circumferential direction with respect to the housing 2 as indicated by an arrow M in FIG. Thereafter, as indicated by arrow M in FIG. 18, the plug cover 5 is moved toward the proximal end side along the axial direction Z of the plug with respect to the housing 2 so that the projection 54 abuts against the stepped portion 23 in the axial direction Z of the plug. Let

Specifically, in the cover abutting step, the plug cover 5 is rotated in the plug circumferential direction with respect to the housing 2 as indicated by arrow M in FIG. 17 while maintaining the position of the plug cover 5 with respect to the housing 2 in the Z direction. Let As a result, as shown in FIG. 18, the projection side surface 541 of the projection 54 is brought into contact with the circumferential contact surface 232 of the stepped portion 231 in the plug circumferential direction. 18, the plug cover 5 is moved to the base end side with respect to the housing 2, and as shown in FIG. It is brought into contact with the contact surface 233 in the Z direction. Here, the length D5 (see FIG. 14) is a length equal to or less than the discharge gap G tolerance. Therefore, the amount of movement of the plug cover 5 toward the base end side with respect to the housing 2 in the cover abutting process is equal to or less than the tolerance of the discharge gap G. As shown in FIG. Further, as described above, in the separation step, the plug cover 5 is moved toward the front end side along the Z direction with respect to the housing 2 by a distance equivalent to the maximum allowable value of the length D2. Therefore, in the cover abutment step, when the convex base end surface 542 is abutted against the axial abutment surface 233, the distance from the central discharge surface 41 to the ground discharge surface 61 in the Z direction is the length of the discharge gap G The distance is within the allowable range of D2. That is, it is possible to set the discharge gap G to a desired length.
Others are the same as those of the first embodiment.

The cover base end portion 51 has a plurality of protrusions 54 . The facing surface 22 has a step portion 23 . Further, the convex portion 54 abuts on a part of the stepped portion 23 in the axial direction Z of the plug. Therefore, a discharge gap G having a desired length can be efficiently formed. As a result, the productivity of the spark plug 1 can be further improved.

Further, in this embodiment, the cover contacting step is performed after the separating step and before the joining step. Therefore, the spark plug 1 can be manufactured more efficiently.

Specifically, in the cover contact step, the plurality of protrusions 54 are brought into contact with the stepped portion 23 in the Z direction, thereby maintaining the length of the discharge gap G at a desired length. , the plug cover 5 can be placed on the tip of the housing 2 . In other words, even if the robot arm is separated from the plug cover 5 after the cover abutting step, the discharge gap G is maintained at a desired length, and the state where the plug cover 5 is placed on the housing 2 is maintained. can do. Therefore, in the joining process, the plug cover 5 can be joined to the housing 2 without holding the plug cover 5 by the robot arm. Therefore, the tact time of the work performed by the robot arm can be shortened. As a result, the productivity of the spark plug 1 can be further improved.

Length D6 (see FIG. 15) is longer than length D2. Therefore, even if the position of the central discharge surface 41 with respect to the housing 2 varies in the Z direction, the convex portion 54 can be reliably brought into contact with the stepped portion 23 in the cover contacting step. Therefore, it is possible to reliably form the discharge gap G having a desired length. As a result, the spark plug 1 can be reliably and efficiently manufactured.

Distance D7 (see FIG. 11) is greater than or equal to distance D8 (see FIG. 11). Therefore, the ground discharge surface 61 can be reliably brought into contact with the center discharge surface 41 in the gap contact process. As a result, the spark plug 1 can be reliably and efficiently manufactured.
In addition, it has the same effects as those of the first embodiment.

In Embodiment 4, the cover base end portion 51 has two convex portions 54 . However, it is also possible to form three or more protrusions on the base end of the cover. In this case, by forming steps corresponding to the number of protrusions, the plug cover can be stably placed on the front end of the housing during the joining process.

(Embodiment 5)
In this embodiment, as shown in FIG. 19, the base end portion 51 of the cover is joined to the inner peripheral side of the fixing portion 21 of the housing.

In this embodiment, the gap contact step to the joining step are performed in a state in which the inner peripheral surface of the housing fixing portion 21 and the outer peripheral surface of the cover base end portion 51 are in contact with each other in the radial direction of the plug.
Other configurations and effects are the same as those of the first embodiment.

(Embodiment 6)
In this embodiment, as shown in FIG. 20, the shape of the base end portion 51 of the cover is changed from that of the fifth embodiment.

The base end portion 51 of the cover has a cylindrical thin portion 511 as shown in FIG. The thin portion 511 is thinner than other portions of the plug cover 5 . Here, "thinner than other portions" means that the average thickness of thin portion 511 is thinner than the average thickness of portions of plug cover 5 other than thin portion 511 .

Further, the plug cover 5 is fixed to the housing 2 by joining the thin portion 511 to the inner peripheral side of the housing fixing portion 21 .

The plug cover 5 also has a cover facing surface 56 that faces the housing fixing portion 21 in the Z direction. The cover facing surface 56 is formed along the tip of the outer peripheral surface of the thin portion 511 .
Others are the same as those of the fifth embodiment.

The base end portion 51 of the cover has a thin portion 511 . Therefore, the volume of the sub-combustion chamber 50 can be increased. As a result, ignitability can be improved.
In addition, it has the same effects as those of the fifth embodiment.

(Embodiment 7)
As shown in FIGS. 21 and 22, this embodiment is a form in which the opening direction of the nozzle hole 55 is changed from that of the first embodiment.

In this embodiment, as shown in FIG. 21, when viewed from the Z direction, the injection hole 55 has an injection hole axis 55L with respect to an imaginary straight line VL passing through the injection hole 55 and the plug central axis C and extending in the radial direction of the plug. is slanted at an acute angle. In the plurality of injection holes 55, the inclination direction of the injection hole axis 55L with respect to the imaginary straight line VL in each injection hole 55 is on the same side in the plug circumferential direction.

Due to such a formation mode of the injection holes 55 , a swirl flow (see dashed arrow SF in FIG. 22 ) is formed in the sub-combustion chamber 50 by the air flow introduced into the sub-combustion chamber 50 via the injection holes 55 . In the case of this embodiment, the swirl flow SF is generated in a counterclockwise spiral in FIG. 22 around the central axis C of the plug.
Others are the same as those of the first embodiment.

The injection hole 55 is formed such that the air flow introduced into the sub-combustion chamber 50 through the injection hole 55 produces a swirl flow SF in the sub-combustion chamber 50 . Therefore, the initial flame formed by the discharge generated in the discharge gap G is likely to spread within the sub-combustion chamber 50 by the swirl flow SF. Therefore, combustion in the sub-combustion chamber 50 is likely to be promoted. As a result, the ignitability of the auxiliary combustion chamber 50 can be improved.
In addition, it has the same effects as those of the first embodiment.

In Embodiments 1 to 7 described above, the plug cover 5 is formed with four injection holes 55 . However, five or more injection holes may be formed in the plug cover. Also, the number of injection holes formed in the plug cover can be three or less.

In Embodiments 1, 3 to 7 described above, the ground electrode 6 which is a separate member from the plug cover 5 is fixed to the plug cover 5 . However, the plug cover and the ground electrode may be integrally formed.

In Embodiments 1 and 3 to 7, the injection hole axes 55L of all the injection holes 55 are inclined with respect to the projecting direction of the ground electrode 6 when viewed from the Z direction. However, for example, the injection holes may be formed so that the injection hole axes of some of the injection holes are aligned with the projecting direction of the ground electrode when viewed from the Z direction.

Also, a tip can be joined to each of the tip of the center electrode forming the discharge gap and the ground electrode. That is, a discharge gap can be formed between the tip joined to the tip of the center electrode and the tip joined to the ground electrode. The tip can be made of, for example, noble metals such as iridium or platinum, or alloys based on these metals.

The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1... Spark plug 2... Housing 21... Housing fixed part 22... Opposing surface 3... Insulator 4... Center electrode 41... Center discharge surface 5... Plug cover 50... Sub-combustion chamber 51... Cover Base end portion 52 Base end surface 53 Inner wall surface 6 Ground electrode 61 Ground discharge surface G Discharge gap Z Plug axial direction

Claims (11)

a cylindrical insulator (3);
a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side;
a cylindrical housing (2) that holds the insulator on the inner peripheral side;
a ground electrode (6) forming a discharge gap (G) with the center electrode;
a plug cover (5) fixed to the front end of the housing so as to cover the auxiliary combustion chamber (50) in which the ground electrode is provided and the discharge gap is arranged;
The ground electrode protrudes from the inner wall surface (53) of the plug cover into the sub-combustion chamber, and is provided along the radial direction of the plug when viewed from the axial direction (Z) of the plug,
The discharge gap is formed by the center discharge surface (41) of the center electrode and the ground discharge surface (61) of the ground electrode facing each other in the axial direction of the plug,
The distal end portion of the housing includes a housing fixing portion (21) facing a cover proximal end portion (51) of the plug cover in the radial direction of the plug, and a proximal end surface of the plug cover on the proximal side of the housing fixing portion. (52) and a facing surface (22) facing in the axial direction of the plug,
The housing fixing portion and the cover base end portion are joined to each other,
A spark plug (1) for an internal combustion engine, wherein the base end surface of the plug cover is arranged at a position separated from the opposing surface in the axial direction of the plug. a cylindrical insulator (3);
a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side;
a cylindrical housing (2) that holds the insulator on the inner peripheral side;
a plug cover (5) fixed to the tip of the housing so as to form a discharge gap (G) with the center electrode and cover a sub-combustion chamber (50) in which the discharge gap is disposed; have
In the discharge gap, the center discharge surface (41) of the center electrode and the ground discharge surface (611) which is part of the inner wall surface (53) of the plug cover face each other in the axial direction (Z) of the plug. It is formed by
The front end portion of the housing includes a housing fixing portion (21) facing the cover base end portion (51) of the plug cover in the plug radial direction, and a base end surface ( 52) and a facing surface (22) facing in the axial direction of the plug,
The housing fixing portion and the cover base end portion are joined to each other,
A spark plug (1) for an internal combustion engine, wherein the base end surface of the plug cover is arranged at a position separated from the opposing surface in the axial direction of the plug. The base end portion of the cover has a plurality of protrusions (54) formed by protruding a portion of the base end face toward the base end side, and the facing surface is formed in a stepped shape along the circumferential direction of the plug. 3. A spark plug for an internal combustion engine according to claim 1 or 2, having a stepped portion (23), wherein said projection abuts a part of said stepped portion in the axial direction of said plug. The housing fixing portion and the cover base end portion are fixed to each other by screwing a male threaded portion (11) and a female threaded portion (12) that screws together with the male threaded portion. 3. A spark plug for an internal combustion engine as claimed in claim 1 or 2, forming. 5. The distance (D1) from the facing surface in the plug axial direction to the base end surface of the plug cover is equal to or greater than the length (D2) of the discharge gap in the plug axial direction. A spark plug for an internal combustion engine as described in . The spark plug for an internal combustion engine according to any one of claims 1 to 5, wherein the cover base end portion is joined to the outer peripheral side of the housing fixing portion. A method of manufacturing a spark plug (1) for an internal combustion engine, comprising:
The spark plug includes a cylindrical insulator (3), a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side, and the insulator on the inner peripheral side. a cylindrical housing (2) that is held in the body, a ground electrode (6) that forms a discharge gap (G) between the center electrode and the ground electrode, and the discharge gap is arranged. a plug cover (5) fixed to the tip of the housing so as to cover the sub-combustion chamber (50),
The ground electrode protrudes from the inner wall surface (53) of the plug cover into the sub-combustion chamber, and is provided along the radial direction of the plug when viewed from the axial direction (Z) of the plug,
The discharge gap is formed by the center discharge surface (41) of the center electrode and the ground discharge surface (61) of the ground electrode facing each other in the axial direction of the plug,
The distal end portion of the housing has a housing fixing portion (21) facing the cover base end portion (51) of the plug cover in the radial direction of the plug,
In manufacturing the above spark plug,
a preparation step of respectively producing the housing in which the insulator and the center electrode are assembled, and the plug cover in which the ground electrode is provided;
After the preparatory step, the housing fixing portion and the cover base end portion are overlapped in the radial direction of the plug, and the central discharge surface and the ground discharge surface are brought into contact with each other in the axial direction of the plug. a gap abutting step of placing the plug cover against
a separation step of separating the ground discharge surface from the central discharge surface by moving the plug cover in the plug axial direction with respect to the housing after the gap abutment step;
A method of manufacturing a spark plug for an internal combustion engine, further comprising: a joining step of joining the housing fixing portion and the cover base end portion to each other after the separating step. A method of manufacturing a spark plug (1) for an internal combustion engine, comprising:
The spark plug includes a cylindrical insulator (3), a center electrode (4) held on the inner peripheral side of the insulator and protruding from the insulator to the tip side, and the insulator on the inner peripheral side. A discharge gap (G) is formed between the cylindrical housing (2) held in the center electrode and the center electrode. a plug cover (5) secured to
In the discharge gap, the center discharge surface (41) of the center electrode and the ground discharge surface (611) which is part of the inner wall surface (53) of the plug cover face each other in the axial direction (Z) of the plug. It is formed by
The distal end portion of the housing has a housing fixing portion (21) facing the cover base end portion (51) of the plug cover in the plug radial direction,
In manufacturing the above spark plug,
a preparatory step of respectively fabricating the housing in which the insulator and the center electrode are assembled, and the plug cover;
After the preparatory step, the housing fixing portion and the cover base end portion are overlapped in the radial direction of the plug, and the central discharge surface and the ground discharge surface are brought into contact with each other in the axial direction of the plug. a gap abutting step of placing the plug cover against
a separation step of separating the ground discharge surface from the central discharge surface by moving the plug cover in the plug axial direction with respect to the housing after the gap abutment step;
A method of manufacturing a spark plug for an internal combustion engine, further comprising: a joining step of joining the housing fixing portion and the cover base end portion to each other after the separating step. The distal end portion of the housing has a facing surface (22) facing the proximal end surface (52) of the plug cover in the plug axial direction on the proximal side of the housing fixing portion, and the cover proximal end portion A plurality of protrusions (54) are formed by protruding a part of the base end face to the base end side, and the facing face has a stepped part (23) formed in a stepped shape along the circumferential direction of the plug. have
After the separating step and before the bonding step,
After rotating the plug cover with respect to the housing in the plug circumferential direction so that the protrusion contacts the stepped portion in the plug circumferential direction, the plug cover is rotated with respect to the housing along the plug axial direction. 9. The method of manufacturing a spark plug for an internal combustion engine according to claim 7 or 8, wherein a cover abutting step is performed in which the convex portion is brought into contact with the stepped portion in the axial direction of the plug by moving the convex portion toward the base end side. The housing fixing portion and the cover base end portion are fixed to each other by screwing a male threaded portion (11) and a female threaded portion (12) that screws together with the male threaded portion. is forming
In the gap abutting step, the plug cover is rotated in one circumferential direction with respect to the housing while the male threaded portion and the female threaded portion are screwed together. moving the plug cover proximally with respect to the housing until the discharge surface and the ground discharge surface abut each other;
In the separating step, the plug cover is rotated in the other circumferential direction with respect to the housing while the male threaded portion and the female threaded portion are screwed together. 9. The method of manufacturing a spark plug for an internal combustion engine according to claim 7 or 8, wherein the plug cover is moved toward the distal end side by a force to separate the ground discharge surface from the center discharge surface. The method of manufacturing a spark plug for an internal combustion engine according to any one of claims 7 to 10, wherein in the joining step, the cover base end portion is joined to the outer peripheral side of the housing fixing portion.

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