JP2021002480A - Spark plug - Google Patents

Abstract

To provide a technology to prevent wear of a ground electrode due to spark discharge.SOLUTION: A spark plug comprises: a center electrode; a ground electrode that has an opposite surface opposite to the center electrode; a first chip that is provided on the opposite surface; and a second chip that is provided on a surface of the ground electrode, the surface being a side face continuing from the opposite surface. The ground electrode is formed of nickel as a main component. The first chip and the second chip are formed of precious metal as a main component. The first chip and the second chip are separated from each other. Since the first chip projects toward the second chip beyond the side face, when the first chip and the second chip are projected on a surface perpendicular to a direction along the axis of the center electrode, part of the first chip overlaps at least part of the second chip.SELECTED DRAWING: Figure 4

Description

The present invention relates to a spark plug.

As a spark plug for ignition used in an internal combustion engine, for example, a gasoline engine, a spark plug that generates sparks by applying a voltage between a center electrode and a ground electrode is known (for example, Patent Document 1).

In Patent Document 1, in order to suppress a short circuit of spark discharge even under the condition that a tumble flow exists in the combustion chamber, a chip is provided on the surface of the ground electrode facing the center electrode and facing the center electrode. A spark plug provided with a chip is disclosed in terms of not being provided.

JP-A-2018-147617

However, in the spark plug described in Patent Document 1, since the formation position of the discharge path is changed by the tumble flow, the portion of the ground electrode that is not covered with the chip may be consumed by the spark discharge. Therefore, a technique for suppressing consumption of the ground electrode due to spark discharge has been desired.

The present invention has been made to solve the above problems, and can be realized as the following forms.

(1) According to one embodiment of the present invention, a spark plug is provided. The spark plug is a surface of the center electrode, a ground electrode having a facing surface facing the center electrode, a first chip provided on the facing surface, and a surface of the ground electrode, which is connected to the facing surface. The ground electrode is provided with a second chip provided, and the ground electrode is formed with nickel as a main component, and the first chip and the second chip are formed with a noble metal as a main component. The first chip and the second chip are separated from each other by a spark plug, and the first chip protrudes toward the second chip from the side surface, so that the first chip and the first chip are separated from each other. When the two chips are projected onto a plane perpendicular to the direction along the axis of the center electrode, a part of the first chip overlaps with at least a part of the second chip. A tumble flow flows between the center electrode and the first chip from the side surface of the ground electrode opposite to the side surface where the second chip is provided toward the side surface where the second chip is provided. In this case, according to the spark plug of this form, since the first chip projects toward the second chip side with respect to the side surface, it is possible to suppress the consumption of the ground electrode due to the spark discharge.

(2) In the spark plug of the above-described embodiment, the ground electrode has a base end portion extending from the base end along the axis of the center electrode, a facing portion on which the facing surface is formed, and the base end portion facing the base end portion. The side surface may be a surface along the direction from the bent portion to the facing portion, which is provided with a bent portion having a bent shape and connected to the portion. According to this type of spark plug, when the tumble flow flows so that the second tip is located downstream of the ground electrode in the flow direction of the tumble flow, it is possible to suppress the consumption of the ground electrode due to spark discharge.

(3) In the spark plug of the above-described embodiment, the length of the portion where the position of the first chip and the position of the second chip overlap may be equal to or less than the thickness of the second chip. According to this type of spark plug, as the discharge path becomes longer due to the tumble flow, the discharge path tends to reach the second chip, so that the discharge path becomes longer and the fuel consumption is improved.

(4) In the spark plug of the above-described embodiment, the second tip may protrude toward the tip side of the ground electrode in the direction along the axis. According to this type of spark plug, it is possible to suppress the consumption of the ground electrode due to spark discharge.

The present invention can be realized in various forms, for example, in the form of an engine head to which a spark plug is attached.

Explanatory drawing which shows the partial cross section of a spark plug. The perspective view which shows the positional relationship between the 1st chip and the 2nd chip. The figure which projected the 1st chip and the 2nd chip on the plane perpendicular to the direction along the axis. The figure for demonstrating the case where the spark discharge is generated. The figure which shows the comparative example. The schematic diagram of the spark plug of the 2nd Embodiment. The figure which shows the modification which provided the 2nd chip on the surface different from the side surface.

A. First Embodiment:
FIG. 1 is an explanatory view showing a partial cross section of the spark plug 100. In FIG. 1, the external shape of the spark plug 100 is shown on the right side of the paper, and the cross-sectional shape of the spark plug 100 is shown on the left side of the paper, with the axis CA, which is the axis of the spark plug 100, as a boundary. In the description of the present embodiment, the lower side of FIG. 1 is referred to as the front end side of the spark plug 100, and the upper side of FIG. 1 is referred to as the rear end side of the spark plug 100.

The spark plug 100 includes an insulator 10 having a shaft hole 12 along the axis CA, a center electrode 20 provided in the shaft hole 12, a tubular main metal fitting 50 arranged on the outer periphery of the insulator 10, and a main body. A ground electrode 30 having a base end 32 fixed to the metal fitting 50 is provided. The axis of the spark plug 100 is the same as the axis of the center electrode 20.

The insulator 10 is an insulator formed by firing a ceramic material such as alumina. The insulator 10 is a member arranged on the inner circumference of the main metal fitting 50, and has a shaft hole 12 on the front end side for accommodating a part of the center electrode 20 and on the rear end side for accommodating a part of the terminal metal fitting 40. It is a tubular member formed in the center. A central body portion 19 having a large outer diameter is formed at the center of the insulator 10 in the axial direction. A rear end side body portion 18 having an outer diameter smaller than that of the central body portion 19 is formed on the rear end side of the central body portion 19. On the tip end side of the central body portion 19, a tip side body portion 17 having an outer diameter smaller than that of the rear end side body portion 18 is formed. On the tip side of the tip side body portion 17, a leg length portion 13 whose outer diameter becomes smaller toward the center electrode 20 side is formed.

The main metal fitting 50 is a tubular metal fitting that surrounds and holds a portion extending from a part of the rear end side body portion 18 of the insulator 10 to the leg length portion 13. The main metal fitting 50 is made of, for example, low carbon steel, and is entirely plated with nickel plating, galvanization, or the like. The main metal fitting 50 includes a tool engaging portion 51, a seal portion 54, and a mounting screw portion 52 in this order from the rear end side. A tool for attaching the spark plug 100 to the engine head 90 is fitted into the tool engaging portion 51. The mounting screw portion 52 is a portion where a male screw is formed on the entire circumference of the outer circumference of the main metal fitting 50, and is a portion screwed into the mounting screw hole 93 of the engine head 90. The seal portion 54 is formed in a brim shape at the base of the mounting screw portion 52. An annular gasket 65 formed by bending a plate body is fitted between the seal portion 54 and the engine head 90. The end surface 57 on the tip end side of the main metal fitting 50 has a hollow circular shape, and the tip end of the leg length portion 13 of the insulator 10 and the tip end of the center electrode 20 project from the center thereof.

A thin crimping portion 53 is provided on the rear end side of the main metal fitting 50 with respect to the tool engaging portion 51. Further, between the seal portion 54 and the tool engaging portion 51, a compression deformation portion 58 having a thin thickness is provided as in the crimping portion 53. An annular ring members 66 and 67 are interposed between the inner peripheral surface of the main metal fitting 50 from the tool engaging portion 51 to the crimping portion 53 and the outer peripheral surface of the rear end side body portion 18 of the insulator 10. Further, talc 69 powder is filled between these ring members 66 and 67. At the time of manufacturing the spark plug 100, the compression deformation portion 58 is compression-deformed by pressing the crimping portion 53 inward so as to bend it toward the tip end side. Due to the compression deformation of the compression deformation portion 58, the insulator 10 is pressed toward the tip side in the main metal fitting 50 via the ring members 66, 67 and the talc 69. Then, by this pressing, the talc 69 is compressed in the axial direction CA direction, so that the airtightness inside the main metal fitting 50 is enhanced.

The main metal fitting 50 is formed with a metal fitting inner stage portion 56 overhanging the inner circumference. Further, the insulator 10 is formed with an insulator step portion 15 located at the rear end of the leg length portion 13 and projecting to the outer periphery. On the inner circumference of the main metal fitting 50, the metal fitting inner step portion 56 is in contact with the insulator step portion 15 via an annular packing 68. The packing 68 is a member that maintains airtightness between the main metal fitting 50 and the insulator 10 and prevents the outflow of combustion gas. In the present embodiment, plate packing is used as the packing.

The center electrode 20 is a rod-shaped member in which a core material 22 having higher thermal conductivity than the electrode member 21 is embedded inside the electrode member 21. The electrode member 21 is formed of a nickel alloy containing nickel as a main component, and the core material 22 is formed of copper or an alloy containing copper as a main component. A noble metal chip formed of, for example, an iridium alloy may be bonded to the tip end of the center electrode 20.

A flange portion 23 overhanging the outer peripheral side is formed in the vicinity of the end portion on the rear end side of the center electrode 20. The flange portion 23 is in contact with the shaft hole inner step portion 14 projecting to the inner peripheral side in the shaft hole 12 of the insulator 10 from the rear end side, and positions the center electrode 20 in the insulator 10. The center electrode 20 is electrically connected to the terminal fitting 40 via the seal body 64 and the ceramic resistor 63 on the rear end side of the center electrode 20.

The base end 32 of the ground electrode 30 is fixed to the end surface 57 of the main metal fitting 50. The ground electrode 30 connects the base end portion 36 extending from the base end 32 to the tip end side, the facing portion 33 on which the facing surface S1 is formed, and the base end portion 36 and the facing portion 33, and has a bent shape. 38 and. The ground electrode 30 is formed mainly of nickel. In the present specification, the "main component" means a component contained in an amount of 50% by mass or more. The ground electrode 30 is provided with a first chip 31 and a second chip 35. The first chip 31 and the second chip 35 are separated from each other.

FIG. 2 is a perspective view showing the positional relationship between the first chip 31 and the second chip 35. The ground electrode 30 includes a facing surface S1 facing the tip of the center electrode 20. The first chip 31 is provided on the facing surface S1 of the ground electrode 30. A gap for spark discharge is formed between the first chip 31 and the center electrode 20.

The second chip 35 is provided on the side surface S2 which is the surface of the ground electrode 30 and is connected to the facing surface S1. In the present embodiment, the side surface S2 is a surface along the first direction D1 from the bent portion 38 toward the facing portion 33. The first chip 31 projects toward the second chip 35 side with respect to the side surface S2 of the ground electrode 30. The tip of the second chip 35 is provided at the same position as the tip of the ground electrode 30 in the direction along the axis CA.

The first chip 31 and the second chip 35 are formed mainly of a precious metal. Examples of the noble metal include platinum, iridium, ruthenium, rhodium, and alloys thereof. In the present embodiment, the first chip 31 and the second chip 35 contain the same precious metal as the main component, but the first chip 31 and the second chip 35 may contain different precious metals as the main components.

The method of attaching the first chip 31 and the second chip 35 to the ground electrode 30 is not particularly limited. Examples of the mounting method include a method in which the second chip 35 is mounted on the ground electrode 30 and then the first chip 31 is mounted on the ground electrode 30. This method is preferable because it can prevent the protruding portion of the first chip 31 from becoming an obstacle when the second chip 35 is installed.

FIG. 3 is a view in which the first chip 31 and the second chip 35 are projected onto a plane F perpendicular to the direction along the axis CA. When the first chip 31 and the second chip 35 are projected onto the surface F, a part of the first chip 31 overlaps with at least a part of the second chip 35. Specifically, when the first chip 31 and the second chip 35 are projected onto the surface F, the first chip 31 and the second chip 35 overlap in the region J.

FIG. 4 is a diagram for explaining a case where a spark discharge is generated. If a spark discharge is generated in a windless state in the combustion chamber, the discharge path P is formed in a straight line connecting the center electrode 20 and the first chip 31 of the ground electrode 30. However, in reality, a tumble flow is generated in the combustion chamber, and the discharge path P is stretched to the downstream side of the direction D in which the tumble flow flows by the tumble flow. By extending the discharge path P by the tumble flow, the flame comes into contact with a wide range of combustion gas, and the ignitability is improved, so that the fuel consumption is improved.

From the viewpoint of improving fuel efficiency, in the present embodiment, the spark plug 100 is installed in the combustion chamber so that the base end portion 36 of the ground electrode 30 is arranged at a position that does not obstruct the tumble flow. More specifically, the spark plug 100 is installed in the combustion chamber so that the first direction D1 and the direction D are orthogonal to each other. Therefore, the center electrode 20 and the first surface of the ground electrode 30 are directed from the side surface of the ground electrode 30 opposite to the side surface S2 where the second chip 35 is provided toward the side surface S2 where the second chip 35 is provided. A tumble flow will flow between the chip 31 and the chip 31. In such a case, the discharge path P is effectively stretched by the tumble flow.

Further, in the present embodiment, when the first chip 31 and the second chip 35 are projected onto the plane F perpendicular to the direction along the axis CA, at least a part of the second chip 35 is one of the first chips 31. It is a mode that overlaps with the part. According to this aspect, as a result of the discharge path P being stretched to the downstream side of the tumble flow by the tumble flow, the discharge path P extends to the second chip 35 instead of the first chip 31. By doing so, as the discharge path P becomes longer due to the tumble flow, the spark comes into contact with a wide range of combustion gas. As a result, according to the present embodiment, the ignitability is improved and the fuel consumption is improved. In particular, this embodiment is effective under the conditions that the flow velocity of the tumble flow is high and the voltage applied to the center electrode 20 is high.

In the present embodiment, the first chip 31 and the second chip 35 contain noble metal as a main component, whereas the ground electrode 30 contains nickel as a main component. Therefore, the ground electrode 30 is more likely to be consumed by spark discharge than the first chip 31 and the second chip 35. However, by adopting the above-described embodiment, it is possible to prevent the portion of the ground electrode 30 not covered by the first chip 31 from being consumed by the spark discharge, and the durability of the spark plug 100 is improved. This mechanism will be described below.

FIG. 5 is a diagram showing a comparative example. Compared with the present embodiment, the comparative example is the same as the embodiment except that the first chip 31x does not protrude toward the second chip 35 side with respect to the side surface S2.

When a spark discharge is generated in a state where a tumble flow is generated in the direction D, the discharge path P is stretched to the downstream side of the tumble flow by the tumble flow. Therefore, in the case of the comparative example, the discharge path P may extend to the region R1 at the corner of the upper surface of the ground electrode 30 instead of the first chip 31x. In this case, the area R1 is consumed.

On the other hand, in the present embodiment, as shown in FIG. 4, since the first chip 31 projects toward the second chip 35 side from the side surface S2, the first chip 31 and the second chip 35 are aligned along the axis CA. When projected onto a plane perpendicular to the vertical direction, a part of the first chip 31 overlaps with at least a part of the second chip 35. Therefore, according to the present embodiment, even when the discharge path P is stretched, the discharge path P extends to the second chip 35 instead of the ground electrode 30, and the ground electrode 30 is consumed by the spark discharge. It can be suppressed. As a result, the durability of the spark plug 100 is improved.

Further, in the present embodiment, the second chip 35 is provided on the side surface S2 along the first direction D1 from the bent portion 38 toward the facing portion 33. Therefore, when the tumble flow flows so that the second chip 35 is located downstream of the ground electrode 30 in the flow direction D of the tumble flow, consumption of the ground electrode 30 due to spark discharge can be suppressed.

Further, in the spark plug 100 of the present embodiment, the length L of the portion where the first chip 31 and the second chip 35 overlap is equal to or less than the thickness T of the second chip 35. By doing so, as compared with the case where the length L is made longer than the thickness T of the second chip 35, the discharge path P reaches the second chip 35 as the discharge path P becomes longer due to the tumble flow. This is likely to result in a longer discharge path P. As a result, the flame comes into contact with a wide range of combustion gases, improving fuel economy. In the present specification, the "length L of the portion where the first chip 31 and the second chip 35 overlap" is the first chip in the second direction D2 orthogonal to the first direction D1 and the direction along the axis CA. The length of the portion where 31 and the second chip 35 overlap is shown. Further, the "thickness T of the second chip 35" indicates the maximum length in the direction perpendicular to the side surface S2.

Further, in the spark plug 100 of the present embodiment, the first chip 31 and the second chip 35 are separated from each other. Therefore, as compared with the configuration in which the first chip 31 and the second chip 35 are integrated, the heat generated in the first chip 31 when the discharge path P extends to the first chip 31 is the second chip. It is possible to suppress transmission to 35. Similarly, as compared with the configuration in which the first chip 31 and the second chip 35 are integrated, the heat generated in the second chip 35 when the discharge path P extends to the second chip 35 is the first chip. It is possible to suppress the transmission to 31. Therefore, the spark plug 100 of the present embodiment can suppress overheating of the first chip 31 and the second chip 35.

B. 2nd Embodiment FIG. 6 is a schematic view of the spark plug 100a of the 2nd embodiment. Compared with the first embodiment, the second embodiment differs in that the second chip 35a protrudes toward the tip side of the ground electrode 30 in the direction along the axis CA, but other than that, the first embodiment It is the same as the form.

According to the present embodiment, as a result of the discharge path P being stretched to the downstream side of the direction D, the discharge path P is stretched to the tip of the second chip 35a. The fact that the discharge path P is extended to the tip of the second chip 35 is synonymous with the spark approaching the center of the combustion chamber. As a result, sparks come into contact with a wide range of combustion gases, improving fuel efficiency.

From the viewpoint of improving fuel efficiency, the length of the second chip 35a in the portion protruding toward the tip side of the ground electrode 30 in the direction along the axis CA is 1% or more of the total length of the second chip 35a. It is preferably 3% or more, and even more preferably 5% or more. On the other hand, from the viewpoint of suppressing the peeling of the second chip 35a, the length of the second chip 35a in the portion protruding toward the tip side of the ground electrode 30 in the direction along the axis CA is the length of the entire second chip 35a. The length is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less.

Further, in the present embodiment, since the second chip 35a protrudes toward the tip side of the ground electrode 30 in the direction along the axis CA, the second chip is not the region R2 at the lower surface corner of the ground electrode 30. The discharge path extends to 35a. As a result, it is possible to suppress the consumption of the ground electrode 30 due to the spark discharge, so that the durability of the spark plug 100a is improved.

C. Other embodiments:
The present invention is not limited to the above-described embodiment, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments corresponding to the technical features in each form described in the column of the outline of the invention may be used to solve some or all of the above-mentioned problems, or one of the above-mentioned effects. It is possible to replace or combine as appropriate to achieve a part or all. Further, if the technical feature is not described as essential in the present specification, it can be appropriately deleted.

In the above-described embodiment, the second chip 35 is provided on the side surface S2 along the first direction D1 from the bent portion 38 toward the facing portion 33. However, it is not limited to this.

FIG. 7 is a diagram showing a modified example in which the second chip 35b is provided on a surface different from the side surface S2. As shown in FIG. 7, the second chip 35b may be provided on the plane S3 orthogonal to the first direction D1.

In the above-described embodiment, the length L of the portion where the first chip 31 and the second chip 35 overlap is not limited to the thickness T of the second chip 35, but is not limited to this, and the first chip 31 and the second chip 35 are not limited to this. The length L of the portion where the portion 35 overlaps may be larger than the thickness T of the second chip 35.

In the above-described embodiment, the shapes of the first chip 31 and the second chips 35, 35a, 35b are square columnar, but the shape is not limited thereto. For example, the shapes of the first chip 31 and the second chips 35, 35a, 35b may be cylindrical.

In the above-described first embodiment, the tip of the second chip 35 is provided at the same position as the tip of the ground electrode 30 in the direction along the axis CA, but the present invention is not limited to this. In the direction along the axis CA, the tip of the second chip 35 may project toward the tip side of the tip of the ground electrode 30, or may be provided at the rear end side of the tip of the ground electrode 30.

10 ... Insulator 12 ... Shaft hole 13 ... Leg length 14 ... Shaft hole inner step 15 ... Insulator step 17 ... Tip side body 18 ... Rear end side body 19 ... Central body 20 ... Center electrode 21 ... Electrode Member 22 ... Core material 23 ... Flange portion 30 ... Ground electrode 31, 31x ... First chip 32 ... Base end 33 ... Opposing portion 35, 35a, 35b ... Second chip 36 ... Base end portion 38 ... Bending portion 40 ... Terminal fitting 50 ... Main metal fitting 51 ... Tool engaging part 52 ... Mounting screw part 53 ... Clamping part 54 ... Seal part 56 ... Metal fitting inner stage part 57 ... End face 58 ... Compressive deformation part 63 ... Ceramic resistance 64 ... Seal body 65 ... Gasket 66 , 67 ... Ring member 68 ... Packing 69 ... Tarku 90 ... Engine head 93 ... Mounting screw hole 100 ... Spark plug 100a ... Spark plug F ... Surface CA ... Axis D ... Direction D1 ... First direction D2 ... Second direction J ... Area L ... Length P ... Discharge path R1 ... Region R2 ... Region S1 ... Facing surface S2 ... Side surface S3 ... Surface T ... Thickness

Claims (4)

With the center electrode
A ground electrode having a facing surface facing the center electrode and
The first chip provided on the facing surface and
A second chip, which is a surface of the ground electrode and is provided on a side surface connected to the facing surface, is provided.
The ground electrode is formed mainly of nickel.
The first chip and the second chip are formed mainly of a precious metal.
The first chip and the second chip are separated from each other.
It ’s a spark plug,
The first chip protrudes toward the second chip from the side surface, whereby
When the first chip and the second chip are projected onto a plane perpendicular to the direction along the axis of the center electrode, a part of the first chip overlaps with at least a part of the second chip. A featured spark plug. The spark plug according to claim 1.
The ground electrode is
A base end portion extending from the base end along the axis of the center electrode and
With the facing portion on which the facing surface is formed,
A bent portion having a bent shape by connecting the base end portion and the facing portion is provided.
A spark plug, characterized in that the side surface is a surface along a direction from the bent portion to the facing portion. The spark plug according to claim 1 or 2.
A spark plug, wherein the length of a portion where the position of the first chip and the position of the second chip overlap is equal to or less than the thickness of the second chip. The spark plug according to any one of claims 1 to 3.
A spark plug, characterized in that the second tip projects toward the tip end side of the ground electrode in a direction along the axis.

Images