JP2023055246A - Spark plug - Google Patents

Abstract

To provide a spark plug capable of reducing the generation of falling of an intermediate member.SOLUTION: A spark plug comprises: an intermediate member containing a chip that has a discharge surface and has a precious metal as a main body, a main body part in which both parts of the discharge surface of the chip and a part on the opposite side are bonded to one end part, and a flange part that is expanded to the circumference of the other end part of the main body part; and a ground electrode that includes a base material bonded to the other end part side of the intermediate member via a fusion zone part. When viewing a cross section containing a shaft line of the chip passing through a center of the discharge surface, a gap opening toward a direction where the flange part is expanded is provided between the base material and the flange part.SELECTED DRAWING: Figure 2

Description

The present invention relates to spark plugs.

A spark plug for igniting an air-fuel mixture in a combustion chamber includes a ground electrode having a tip mainly made of precious metal, an intermediate member to which the tip is joined, and a base material to which the intermediate member is joined via a fusion zone. things are known. In the prior art disclosed in Patent Literature 1, the entire end surface of the intermediate member, including the collar portion, is in close contact with the base material.

WO2009/084565

In the prior art, since the deformation of the end face including the collar portion of the intermediate member is constrained by the base material, heating due to the combustion of the air-fuel mixture and cooling due to the air-fuel mixture flowing into the combustion chamber cause deformation of the intermediate member and the melted portion. The resulting thermal stress can crack the weld. When the fusion zone breaks, the intermediate member falls off from the base material together with the chip.

SUMMARY OF THE INVENTION An object of the present invention is to solve this problem, and to provide a spark plug capable of reducing the occurrence of falling off of the intermediate member.

To achieve this object, the spark plug of the present invention comprises: a tip having a discharge surface and mainly made of noble metal; a ground electrode having an intermediate member including an intermediate member including a brim extending around the other end; When looking at a cross section including the axis of the passing chip, there is a gap between the base material and the flange that opens in the direction in which the flange protrudes.

According to the first aspect, when a cross section including the axis line of the chip passing through the center of the discharge surface is viewed, there is a direction in which the flange protrudes between the base material of the ground electrode and the flange of the intermediate member. There is a gap to open towards. Compared to a ground electrode in which the entire end surface of the intermediate member, including the collar portion, is in close contact with the base material to restrict deformation of the intermediate member, deformation of the intermediate member due to thermal expansion or contraction is allowed by the amount of the gap. As a result, the thermal stress of the intermediate member and the fusion zone can be reduced, so that the occurrence of cracks in the fusion zone can be reduced, and the occurrence of detachment of the intermediate member can be reduced.

According to a second aspect, in the first aspect, the gap extends from between the base material and the flange to between the base material and the other end. Since the intermediate member can be deformed by the amount of the gap, the thermal stress of the intermediate member and the melted portion can be further reduced. Therefore, it is possible to further reduce the occurrence of detachment of the intermediate member due to cracks in the fusion zone.

According to a third aspect, in the first or second aspect, the gap extends from between the base material and the flange to the fusion zone. Since the intermediate member can be deformed by the amount of the gap, the thermal stress of the intermediate member and the melted portion can be further reduced. Therefore, it is possible to further reduce the occurrence of detachment of the intermediate member due to cracks in the fusion zone.

1 is a half sectional view of a spark plug in a first embodiment; FIG. FIG. 4 is a cross-sectional view of a ground electrode; FIG. 3 is a cross-sectional view of a component and a base material in which a chip is joined to an intermediate member; FIG. 5 is a cross-sectional view of a ground electrode of a spark plug in a second embodiment; FIG. 11 is a cross-sectional view of a ground electrode of a spark plug according to a third embodiment;

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a half sectional view of the spark plug 10 of the first embodiment taken along the axis O. As shown in FIG. In FIG. 1, the lower side of the page is called the front end side of the spark plug 10, and the upper side of the page is called the rear end side of the spark plug 10 (the same applies to FIGS. 2 to 5). As shown in FIG. 1, the spark plug 10 has a center electrode 13 and a ground electrode 18. As shown in FIG. The center electrode 13 is arranged on the insulator 11 and the ground electrode 18 is connected to the metal shell 16 arranged on the insulator 11 .

The insulator 11 is a substantially cylindrical member having an axial hole 12 along the axis O. As shown in FIG. The insulator 11 is made of ceramics such as alumina, which has excellent mechanical properties and insulating properties at high temperatures. A center electrode 13 is arranged in the axial hole 12 . The center electrode 13 is a conductive bar-shaped metal member. In the center electrode 13, for example, a bottomed cylindrical base material containing Ni as a main component covers a core material containing copper as a main component. It is possible to omit the core material. A tip mainly composed of a noble metal such as Pt, Rh, Ir, and Ru is provided at the tip of the center electrode 13 . A tip surface 14 (discharge surface of the tip) of the center electrode 13 is arranged outside the axial hole 12 .

The center electrode 13 is electrically connected to the terminal fitting 15 inside the shaft hole 12 . The terminal fitting 15 is a rod-shaped member to which a high-voltage cable (not shown) is connected, and is made of a conductive metal material (for example, low carbon steel). The terminal fitting 15 is fixed to the rear end of the insulator 11 in a state in which the tip side thereof is inserted into the shaft hole 12 .

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

The ground electrode 18 includes a rod-shaped base material 19 made of a conductive metal material (eg, Ni-based alloy, etc.). The base material 19 extends from one end 19a connected to the metal shell 16 toward the other end 19b. A cross section of the base material 19 perpendicular to the direction in which the base material 19 extends is exemplified by a square, an ellipse, and a semicircle. The base material 19 is bent between one end 19a and the other end 19b. The base material 19 may be embedded with a core material having a high thermal conductivity (for example, a material containing copper as a main component). A discharge is generated between the ground electrode 18 and the tip surface 14 of the center electrode 13 .

FIG. 2 is a cross-sectional view of the ground electrode 18. As shown in FIG. FIG. 2 omits illustration of part of the base material 19 (the same applies to FIGS. 3 to 5). A chip 20 is connected via an intermediate member 22 to the other end portion 19 b (see FIG. 1) of the base material 19 . The material of the tip 20 is mainly composed of noble metals such as Pt, Rh, Ir and Ru, and contains one or more of the noble metals such as Pt, Rh, Ir and Ru. % or more.

A discharge surface 21 of the tip 20 faces the tip surface 14 of the center electrode 13 (see FIG. 1). The tip 20 extends along an axis A passing through the center 20 a of the discharge surface 21 . A cross section of the chip 20 perpendicular to the axis A may be circular, rectangular, or the like. 2 is a cross-sectional view of ground electrode 18 including axis A. FIG.

The intermediate member 22 includes a body portion 23 extending along the axis A and a collar portion 26 projecting around the body portion 23 . A cross section of the main body 23 perpendicular to the axis A may be circular, rectangular, or the like. The material of the intermediate member 22 is, for example, an alloy containing Ni as a main component.

The tip 20 is joined to one axial end 24 of the main body 23 via a first fusion zone 27 . In the first melted portion 27, the component of the tip 20 and the component of the intermediate member 22 are melted and solidified. In this embodiment, the first fusion zone 27 is provided over the entire circumference of the main body part 23 and the tip 20, and the fusion zone 27 is also formed at a position where the axis A intersects.

The other axial end portion 25 of the body portion 23 is joined to the base material 19 via a second fusion portion 28 . The collar portion 26 protrudes around the other end portion 25 of the body portion 23 . In the second melted portion 28, the component of the base material 19 and the component of the intermediate member 22 are melted and solidified. In this embodiment, the fusion zone 28 is located at a position where it intersects the axis A. As shown in FIG. A fusion zone 28 is not provided in the collar part 26 .

A gap 29 is provided between the base material 19 and the flange 26 and opens in the direction in which the flange 26 protrudes. In this embodiment, the gap 29 extends from between the base material 19 and the collar portion 26 to between the base material 19 and the other end portion 25 . The gap 29 appears on both sides of the axis A in a cross section including the axis A. As shown in FIG. Furthermore, the gap 29 extends from between the base material 19 and the collar portion 26 to the fusion portion 28 . The gap 29 is provided over the entire circumference of the collar portion 26 .

An example of a method for manufacturing the ground electrode 18 will be described with reference to FIG. FIG. 3 is a cross-sectional view of the base material 19 and the part 30 in which the chip 20 is joined to the intermediate member 22. As shown in FIG. The component 30 has the chip 20 joined to the body portion 23 of the intermediate member 22 via the fusion portion 27 . The fusion zone 27 is made by laser welding. The part 30 is provided with a protrusion 31 at the center of the axial end face 25 a of the other end 25 of the main body 23 . A plurality of protrusions 31 may be provided.

The fusion zone 28 (see FIG. 2) is made by resistance welding. When the protrusions 31 of the component 30 are pressed against the base material 19 and energization is started, current flows between the component 30 and the base material 19, and the protrusions 31 are heated and softened by Joule heat. As the projections 31 are softened, a melted portion 28 is formed. By controlling the position and size of the protrusion 31, the magnitude of the current flowing between the part 30 and the base material 19, and the pressure force with which the part 30 is pressed against the base material 19, the outer periphery of the collar portion 26 and the inner side of the gap 29 can be The distance between the ends and the size of the fusion zone 28 can be set.

Returning to FIG. 2, description will be made. Since the ground electrode 18 has the intermediate member 22, the distance between the discharge surface 21 of the tip 20 and the base material 19 is lengthened by the axial length of the intermediate member 22 without lengthening the tip 20. be able to. Since the flame-extinguishing effect of the base material 19 can be reduced by the intermediate member 22, extinction of the flame kernel caused by the discharge between the center electrode 13 and the discharge surface 21 of the tip 20 can be reduced. Thereby, the ignition performance of the spark plug 10 can be improved.

On the other hand, since the intermediate member 22 and the tip 20 of the spark plug 10 protrude from the base material 19, the spark plug 10 is heated by the combustion of the air-fuel mixture in the combustion chamber of the engine (not shown), and is heated by the air-fuel mixture flowing into the combustion chamber. The temperature change of the intermediate member 22 and the tip 20 due to cooling and the temperature difference between the tip 20 and the base material 19 are large and severe compared to a spark plug without the intermediate member 22 . Therefore, the thermal stress generated in the intermediate member 22 and the melted portion 28 due to the thermal expansion and contraction of the ground electrode 18 is greater than in a ground electrode without the intermediate member 22 .

The spark plug 10 is provided with a gap 29 that opens in the direction in which the flange 26 protrudes between the flange 26 of the intermediate member 22 and the base material 19, which are in a severe environment. As a result, the flange portion 26 of the intermediate member 22 and the end surface 25a (see FIG. 3) of the other end portion 25 (excluding the melted portion 28) are in close contact with the base material 19, and the deformation of the intermediate member 22 is restrained. Compared to the ground electrode, deformation of the intermediate member 22 due to thermal expansion and contraction is allowed by the amount of the gap 29 . Since the thermal stress of the intermediate member 22 and the fusion zone 28 can be reduced, the occurrence of cracks in the fusion zone 28 can be reduced. As a result, it is possible to reduce the occurrence of falling off of the intermediate member 22 due to breakage of the fusion zone 28 .

A gap 29 between the base material 19 and the intermediate member 22 extends from between the base material 19 and the collar portion 26 to between the base material 19 and the other end portion 25 . As a result, the intermediate member 22 can be largely deformed by the amount of the gap 29, compared to the case where the gap existing between the base material 19 and the flange portion 26 does not extend to the gap between the base material 19 and the other end portion 25.例文帳に追加Since the thermal stress of the intermediate member 22 and the fusion zone 28 due to thermal expansion and contraction can be further reduced, the occurrence of cracks in the fusion zone 28 can be further reduced.

Gap 29 extends from between base material 19 and flange 26 to fusion zone 28 . As a result, the intermediate member 22 can be greatly deformed by the gap 29 compared to the case where the gap existing between the base material 19 and the collar portion 26 does not extend to the fusion zone 28 . Since the thermal stress of the intermediate member 22 and the fusion zone 28 due to thermal expansion and contraction can be further reduced, the occurrence of cracks in the fusion zone 28 can be further reduced.

Since the gap 29 extends from between the base material 19 and the collar portion 26 to the fusion zone 28, the gap 29 releases residual stress due to resistance welding. Since the tensile residual stress of the intermediate member 22 and the fusion zone 28 can be reduced, cracking of the fusion zone 28 due to the tensile residual stress can be prevented.

The gap 29 exists between the base material 19 and the two flanges 26 appearing on both sides of the axis A in a cross section including the axis A, and extends from between the base material 19 and the flange 26 to the fusion zone 28. Since it extends, the intermediate member 22 can swing around the fusion zone 28 by the gap 29 . As a result, cracks in the fusion zone 28 and the intermediate member 22 that may occur due to transmission of engine vibration to the spark plug 10 can be reduced.

The gap 29 is provided over the entire circumference of the collar portion 26 . Since the thermal stress can be reduced over the entire circumference of the fusion zone 28, the occurrence of cracks in the fusion zone 28 can be further reduced.

A second embodiment will be described with reference to FIG. In the first embodiment, the case where the gap 29 between the base material 19 and the intermediate member 22 extends from between the base material 19 and the flange portion 26 to the fusion zone 28 has been described. In the second embodiment, the case where the gap 29 extends from between the base material 19 and the collar portion 26 to between the other end portion 25 of the intermediate member 22 and the base material 19 will be described. In the second embodiment, the same reference numerals as in the first embodiment are assigned to the same parts as those described in the first embodiment, and the following description is omitted.

FIG. 4 is a cross-sectional view including the axis A of the ground electrode 40 of the spark plug in the second embodiment. The ground electrode 40 is connected to the metal shell 16 (see FIG. 1) instead of the ground electrode 18 of the spark plug 10 in the first embodiment.

Between the base material 19 of the ground electrode 40 and the flange 26 of the intermediate member 22, a gap 29 is provided that opens in the direction in which the flange 26 protrudes. In this embodiment, the gap 29 extends from between the base material 19 and the collar portion 26 to between the base material 19 and the other end portion 25 of the body portion 23 . The gap 29 appears on one side of the axis A in a cross section including the axis A. As shown in FIG. The gap 29 is not in contact with the fusion zone 28 .

Since the gap 29 is provided in the ground electrode 40 , deformation of the intermediate member 22 due to thermal expansion or contraction is allowed by the gap 29 . As a result, the thermal stress of the intermediate member 22 and the fusion zone 28 can be reduced, so that the occurrence of cracks in the fusion zone 28 can be reduced. Therefore, it is possible to reduce the occurrence of falling off of the intermediate member 22 due to breakage of the fusion zone 28 .

A third embodiment will be described with reference to FIG. 2nd Embodiment demonstrated the case where the clearance gap 29 between the base material 19 and the intermediate member 22 extended to the main-body part 23 from between the base material 19 and the collar part 26. FIG. In the third embodiment, a case where the gap 29 is provided between the base material 19 and the flange portion 26 will be described. In the third embodiment, the same reference numerals as in the first embodiment are assigned to the same parts as those described in the first embodiment, and the following description is omitted.

FIG. 5 is a cross-sectional view including the axis A of the ground electrode 50 of the spark plug according to the third embodiment. The ground electrode 50 is connected to the metal shell 16 (see FIG. 1) instead of the ground electrode 18 of the spark plug 10 in the first embodiment.

Between the base material 19 of the ground electrode 50 and the flange 26 of the intermediate member 22, a gap 29 is provided that opens in the direction in which the flange 26 protrudes. In this embodiment, the gap 29 existing between the base material 19 and the flange 26 does not extend between the base material 19 and the other end 25 . The gap 29 appears on one side of the axis A in a cross section including the axis A. As shown in FIG.

Since the ground electrode 50 is provided with the gap 29 , deformation of the intermediate member 22 due to thermal expansion or contraction is allowed by the gap 29 . As a result, the thermal stress of the intermediate member 22 and the fusion zone 28 can be reduced, so that the occurrence of cracks in the fusion zone 28 can be reduced. Therefore, it is possible to reduce the occurrence of falling off of the intermediate member 22 due to breakage of the fusion zone 28 .

Although the present invention has been described above based on the embodiments, it should be understood that the present invention is not limited to the above-described embodiments, and that various improvements and modifications are possible without departing from the scope of the present invention. It can be easily guessed. For example, the shapes of the ground electrodes 18, 40, and 50 are examples and can be set appropriately.

In the embodiment, the case where the discharge surface 21 of the tip 20 of the ground electrodes 18, 40, 50 and the center electrode 13 face each other in the direction of the axis O has been described, but this is not necessarily the case. It is of course possible to provide the ground electrode such that the discharge surface 21 of the ground electrode tip 20 and the center electrode 13 face each other in the direction intersecting the axis O.

In the embodiment, the case where the fusion zone 28 that joins the base material 19 and the intermediate member 22 is provided in the body part 23 of the intermediate member 22 and is not provided in the flange part 26 has been described. It is not limited. Depending on the size and position of the fusion zone 28 provided in the body part 23 , a part of the fusion zone 28 may protrude into the collar part 26 .

In the first embodiment, the case where the gap 29 appears on both sides of the axis A in the cross section including the axis A has been described, but it is not necessarily limited to this. A gap 29 extending from between the base material 19 and the collar portion 26 to the fusion portion 28 may appear on only one side of the axis A. The gap 29 may or may not appear on the other side of the axis A. When the gap 29 appears on the other side of the axis A, the gap 29 may extend between the base material 19 and the body portion 23, or may extend between the base material 19 and the flange portion 26. may exist only.

In the second and third embodiments, the case where the gap 29 appears only on one side of the axis A in the cross section including the axis A has been described, but it is not necessarily limited to this. A gap 29 may appear on the other side of the axis A. When the gap 29 appears on the other side of the axis A, the gap 29 may extend between the base material 19 and the body portion 23, or may extend between the base material 19 and the flange portion 26. may exist only.

REFERENCE SIGNS LIST 10 spark plug 18, 40, 50 ground electrode 19 base material 20 tip 21 discharge surface 22 intermediate member 23 main body 24 one end 25 other end 26 flange 28 second fusion zone (fusion zone)
29 Gap A Axis

Claims (3)

a chip that has a discharge surface and is mainly composed of a noble metal;
an intermediate member including a main body having one end joined to a portion of the chip opposite to the discharge surface; and a flange projecting around the other end of the main body;
and a base material joined to the other end side of the intermediate member via a welded portion, the ground electrode comprising:
A spark plug having a gap opening in a direction in which the flange protrudes between the base material and the flange when viewed in a cross section including the axis of the tip passing through the center of the discharge surface. . 2. The spark plug according to claim 1, wherein said gap extends from between said base material and said flange portion to between said base material and said other end portion. 3. The spark plug according to claim 1, wherein the gap extends from between the base material and the flange to the fusion zone.

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