JP2022087080A - Spark plug - Google Patents

Abstract

To provide a spark plug that can avoid premature wear even if Ta is added to an electrode member.SOLUTION: In the spark plug, an angle formed by a central forge flow line (15b) along the longitudinal direction of crystal grains that configure a precious metal tip (15), which is a central electrode tip, and a ground normal (16b), which is the normal of a ground discharge surface (16a), a surface on which a ground electrode 14 faces the precious metal tip (15), is 30 degrees or less.SELECTED DRAWING: Figure 3

Description

This disclosure relates to spark plugs.

Conventionally, there is a spark plug in which an IrRh alloy obtained by adding 3 to 30 wt% of Rh (rhodium) to Ir (iridium) is used for an electrode member of a discharge portion. Such a spark plug is excellent in high temperature heat resistance and at the same time can improve wear resistance. The spark plug described in Patent Document 1 below has been proposed with the aim of further improving wear resistance.

Japanese Unexamined Patent Publication No. 2019-110114

Patent Document 1 discloses a spark plug in which an electrode member in which at least one of Ta (tantalum) and Nb (niobium) is added in a total amount of 0.3 to 7.5 wt% to an IrRh alloy is provided in a discharge portion. Has been done.

When Ta is added to the electrode member, the surface layer portion becomes brittle, and if a discharge attack occurs in the brittle portion, the surface layer portion may be consumed prematurely. Early wear of the surface layer may also promote wear of the central part other than the surface layer.

It is an object of the present disclosure to provide a spark plug that can avoid premature wear even if Ta is added to the electrode member.

The present disclosure is a spark plug, comprising a discharge portion that discharges when a voltage is applied, and the discharge portion is formed by arranging a center electrode (13) and a ground electrode (14) facing each other. The center electrode is formed by joining a center electrode tip (15) containing Ir, Rh, and Ta to the center electrode base material (13a), and is centrally forged along the longitudinal direction of the crystal grains constituting the center electrode tip. The angle formed by the streamline (15b) and the grounding normal line (16b), which is the normal line of the grounding discharge surface (16a) on which the grounding electrode faces the center electrode chip, is within 30 °.

The present disclosure is a spark plug, comprising a discharge portion that discharges when a voltage is applied, and the discharge portion is formed by arranging a center electrode (13) and a ground electrode (14) facing each other. The center electrode is formed by joining the center electrode tip (15) containing Ir, Pt, and Ta to the center electrode base material (13a), and the center electrode is forged along the longitudinal direction of the crystal grains constituting the center electrode tip. The angle formed by the streamline (15b) and the grounding normal line (16b), which is the normal line of the grounding discharge surface (16a) on which the grounding electrode faces the center electrode chip, is within 30 °.

By setting the angle between the central forging line and the ground normal to within 30 °, it is possible to reduce wear due to discharge attack.

According to the present disclosure, it is possible to provide a spark plug that can avoid premature wear even if Ta is added to the electrode member.

FIG. 1 is a half cross-sectional view of a spark plug. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is an enlarged view of the discharge portion. FIG. 4 is an enlarged view of the discharge unit. FIG. 5 is an enlarged view of the discharge unit. FIG. 6 is an enlarged view of the discharge portion. FIG. 7 is an enlarged view of the discharge unit. FIG. 8 is an enlarged view of the discharge portion. FIG. 9 is a diagram for explaining the test results. FIG. 10 is an enlarged view of the discharge unit. FIG. 11 is a diagram for explaining the test results. FIG. 12 is a diagram for explaining the test results. FIG. 13 is a diagram for explaining the test results.

Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components are designated by the same reference numerals as possible in the drawings, and duplicate description is omitted.

As shown in FIG. 1, the spark plug 10 includes a housing 11. The housing 11 has a cylindrical shape formed of a metal material such as iron. A threaded portion 11a is formed on the outer periphery of the lower portion of the housing 11.

Inside the housing 11, the lower end of the cylindrical insulating insulator 12 is coaxially inserted. The insulating insulator 12 is formed of an insulating material such as alumina. By crimping the upper end portion 11b of the housing 11 with respect to the insulating insulator 12, the housing 11 and the insulating insulator 12 are integrally coupled. A through hole 12a is provided in the lower portion of the insulating insulator 12 at one end. A center electrode 13, which is a spark plug electrode, is inserted and held in the through hole 12a.

The center electrode 13 is formed in a columnar shape using a Ni alloy having excellent heat resistance and the like as a base material. Specifically, the inner material of the center electrode 13 is made of copper, and the outer material is made of a Ni (nickel) -based alloy. The tip portion 13a of the center electrode 13 is exposed from the lower end of the lower portion of the insulating insulator 12.

At a position facing the tip end portion 13a of the center electrode 13, a ground electrode 14 extending integrally from the lower end surface of the housing 11 is arranged. The ground electrode 14 is also formed of a Ni-based alloy.

As shown in FIG. 2, the discharge portion of the spark plug 10 is configured by the tip portion 13a of the center electrode 13 and the tip portion 14a of the ground electrode 14 facing the tip portion 13a. Precious metal chips 15 and 16 are attached to the tip portion 13a of the center electrode 13 and the tip portion 14a of the ground electrode 14, respectively. Since the precious metal chip 15 is provided on the center electrode 13 side, it corresponds to the center electrode chip. Since the precious metal chip 16 is provided on the ground electrode 14 side, it corresponds to the ground electrode chip.

The precious metal chips 15 and 16 are joined to the tip portions 13a and 14a, respectively, by a joining process such as laser welding or resistance welding. The tip portions 13a and 14a correspond to the center electrode base material. In FIG. 2, the molten portions 31 and 32 are formed in the portions where the precious metal chip 15 and the tip portion 13a are joined. Although the molten portions 31 and 32 are seen apart from each other in the cross-sectional view, they are connected along the outer circumference of the precious metal chip 15.

A spark gap 17 is formed between the noble metal chip 15 and the noble metal chip 16. An electric discharge is performed between the noble metal chip 15 and the noble metal chip 16 in the spark gap 17, and a spark is formed.

The precious metal chips 15 and 16 are both formed in a columnar shape. For example, the outer diameter A = 1.0 mm and the height B = 1.5 mm of the precious metal chip 15. The outer diameter C of the precious metal chip 16 is 1.0 mm, and the height D is 0.5 mm.

Returning to FIG. 1, the central shaft 18 and the terminal portion 19 are electrically connected to the upper portion of the central electrode 13 as is well known. An external circuit that applies a high voltage for generating sparks is connected to the terminal portion 19. Further, a gasket 20 used for attachment to an internal combustion engine is provided at the upper end of the threaded portion 11a of the housing 11.

The precious metal chips 15 and 16 are formed of an IrRh alloy containing Rh (rhodium) in order to suppress high-temperature volatility of Ir based on Ir (iridium) having a high melting point and excellent wear resistance. The IrRh alloy can suppress the oxidative volatilization of Ir from the grain boundaries in a high temperature atmosphere or an oxidizing atmosphere. An IrRh alloy preferably containing 5 to 50 wt% Rh, and more preferably an IrRh alloy containing 5 to 30 wt% Rh, can suppress oxidative volatilization of Ir from grain boundaries in a high temperature atmosphere or an oxidizing atmosphere. In the IrRh alloy, the component excluding Rh and Ta is Ir.

With reference to FIG. 3, the arrangement relationship between the noble metal chip 15 provided on the center electrode 13 side and the noble metal chip 16 provided on the ground electrode 14 side will be described. Even when the noble metal chip 16 is not provided on the ground electrode 14, the same arrangement can be made between the noble metal chip 15 and the tip portion 14a of the ground electrode 14.

The precious metal chip 15 includes a surface layer portion 151 and a non-surface layer portion 152. In the hot working process, the precious metal chip 15 is made into a linear or rod-shaped material by at least one of hot forging, hot rolling, and hot wire drawing, and then the sintered body is processed in the length direction. It can be obtained by cutting to a predetermined length. Therefore, the non-surface layer portion 152 in which the crystal particles are stretched in a fibrous form and the surface layer portion 151 in which the crystal particles are not stretched in a fibrous form are formed. In the present embodiment, the portion of the non-surface layer portion 152 particularly near the center is referred to as the central chip portion 153.

The metal flow line along the longitudinal direction of the crystal grains in the central tip portion 153 is defined as the central forging flow line 15b. The surface of the noble metal chip 16 facing the noble metal chip 15 is referred to as a ground discharge surface 16a. The normal line of the grounding discharge surface 16a is defined as the grounding normal line 16b.

In the example shown in FIG. 3, the central discharge surface 15a on which the noble metal chip 15 faces the noble metal chip 16 and the ground discharge surface 16a on which the noble metal chip 16 faces the noble metal chip 15 are parallel to each other. Is located in. In this state, the central forging line 15b and the ground normal line 16b are parallel to each other.

FIGS. 4 and 5 are diagrams for explaining that the angle formed by the central forging line 15b and the ground normal line 16b is preferably 30 ° or less. As shown in FIG. 4, when the noble metal tip 15 is attached to the tip portion 13a of the center electrode 13, the noble metal tip 15 may be attached at an angle. As shown in FIG. 5, a gap G is formed between the noble metal chip 15 and the noble metal chip 16, an electric discharge is performed between the noble metal chip 15 and the noble metal chip 16, and a spark is formed. When a spark is generated in the gap G, the attack due to the electric discharge goes to the lowermost end portion of the precious metal chip 15, and to the surface layer portion 151 in FIG.

As will be described later, it is preferable that the angle formed by the central forging line 15b and the ground normal line 16b is 30 ° or less. When the angle formed by the central forging line 15b and the grounding normal line 16b is within this range, the discharge attack on the surface layer portion 151 does not become excessive, and the wear of the precious metal chip 15 can be reduced.

As shown in FIG. 6, when the noble metal tip 15 is attached to the tip portion 13a of the center electrode 13, even if the noble metal tip 15 is not tilted, the noble metal tip 16 on the ground electrode 14 side is tilted. It is also assumed that there is. Also in this case, it is preferable that the angle formed by the central forging line 15b and the ground normal line 16b is 30 ° or less.

As shown in FIG. 7, when the noble metal tip 15 is attached to the tip portion 13a of the center electrode 13, the noble metal tip 15 is tilted, and when the noble metal tip is attached to the tip portion 14a of the ground electrode 14. However, the precious metal chip 16 may be tilted. In this case, it is preferable that the angle formed by the central forging line 15b and the grounding forging line 16c along the longitudinal direction of the crystal grains constituting the noble metal chip 16 is within 30 °.

As shown in FIG. 8, when the angle formed by the central forging line 15b and the ground normal line 16b exceeds 30 ° and reaches 45 °, the discharge attack is directed to a wide area of the surface layer portion 151. FIG. 9 shows the results of an engine durability test in which the angle formed by the central forging line 15b and the ground normal line 16b is changed.

The test sample A in which the angle between the central forging line 15b and the ground normal line 16b is 0 ° corresponds to that illustrated in FIG. The test sample B having an angle of 30 ° between the central forging line 15b and the ground normal line 16b corresponds to those illustrated in FIGS. 4, 5, 6 and 7. The test sample C having an angle of 45 ° between the central forging line 15b and the ground normal line 16b corresponds to the one illustrated in FIG.

The test conditions for the engine durability test are a 2000cc 4-cylinder engine equipped with a spark plug 10 for testing, and after holding 1min of idling, holding 1min of 5600r / min as one cycle, and expanding the gap G to 200h (100,000km). Confirmed in (equivalent to running).

When the expansion amount of the gap G exceeds 0.2 mm, the required voltage becomes high, which affects other parts such as the insulator withstand voltage. Therefore, the expansion amount of the gap G of 0.2 mm is set as the boundary value of NG. As shown in FIG. 9, if the angle between the central forging line 15b and the ground normal line 16b is 30 ° or less, the expansion amount of the gap G is 0.2 mm or less in all the test samples for four cylinders. became. On the other hand, if the angle between the central forging line 15b and the ground normal line 16b is 35 ° or more, the expansion amount of the gap G is 0.2 mm or more in all the test samples for four cylinders.

As shown in FIG. 10A, the angle between the central forging line 15b and the ground normal line 16b is 35 ° or more, and when the angle is 45 °, the surface layer portion 151 falls off due to the discharge attack. When the surface layer portion 151 falls off, as shown in FIG. 10B, a hangnail phenomenon occurs in a chain on the non-surface layer portion 152, and the precious metal chip 15 is consumed. As a result, the gap GA between the noble metal chip 15 and the noble metal chip 16 expands to the gap GB. Therefore, by setting the angle between the central forging line 15b and the grounding normal line 16b to 30 ° or less, the consumption of the precious metal tip 15 can be suppressed.

FIG. 11 shows the test results in which the angle between the central forging line 15b and the ground normal line 16b is 30 ° and the aspect ratio is changed. The aspect ratio is the tangent pair of parallel tangent pairs that do not cross the inside of the particle when drawn in various positional relationships with respect to the outline of the crystal particles observed in the field of view on the defined cross section. It is specified as the ratio of the maximum interval to the minimum interval in a set.

The test conditions for the engine durability test are a 2000cc 4-cylinder engine equipped with a spark plug 10 for testing, and after holding 1min of idling, holding 1min of 5600r / min as one cycle, and expanding the gap G to 200h (100,000km). Confirmed in (equivalent to running).

As shown in FIG. 11, when the aspect ratio is 6 or more, the total number of gaps expanded is 0.2 mm or less, and it was confirmed that the influence of the gap expansion on other parts can be suppressed.

The spark plug in the present embodiment includes a discharge unit that discharges when a voltage is applied. The discharge portion is formed by arranging the center electrode 13 and the ground electrode 14 so as to face each other. The center electrode 13 is formed by joining a noble metal chip 15 as a center electrode chip containing Ir, Rh, and Ta to a tip portion 13a as a center electrode base material, and is formed in the longitudinal direction of crystal grains constituting the noble metal chip 15. The angle formed by the central forging line 15b along the line and the grounding normal line 16b, which is the normal line of the grounding discharge surface 16a on which the grounding electrode faces the center electrode chip, is within 30 °.

By setting the angle formed by the central forging line 15b and the grounding normal line 16b within 30 °, it is possible to reduce the consumption due to the discharge attack.

The ground electrode 14 is formed by joining a noble metal chip 16 as a ground electrode chip containing Ir, Rh, and Ta to a tip portion 14a as a ground electrode base material, and a ground discharge surface 16a is formed on the noble metal chip 16. ing. In the present embodiment, since the example in which the noble metal chip 16 is provided at the tip portion 14a of the ground electrode 14, the ground discharge surface 16a is formed on the noble metal chip 16. However, it is not necessary to provide the noble metal chip 16, and in that case, the surface of the tip portion 14a facing the noble metal chip 15 becomes the ground discharge surface, and the normal line of the ground discharge surface becomes the ground normal line.

In the present embodiment, the angle formed by the central forging stream line 15b and the grounding forging line 16c along the longitudinal direction of the crystal grains constituting the noble metal chip 16 as the ground electrode tip can be within 30 °. ..

In the present embodiment, it is preferable that the aspect ratio of the crystal grains forming the central forging line 15b and / or the grounding forging line 15c is 6 or more.

In the above description, the precious metal chips 15 and 16 are formed of an IrRh alloy containing Rh (rhodium) in order to suppress high-temperature volatility of Ir based on Ir (iridium) having a high melting point and excellent wear resistance. Was used. The materials for the precious metal chips 15 and 16 are not limited to this, and are based on Ir (iridium), which has a high melting point and excellent wear resistance, and in order to suppress the high-temperature volatility of Ir, an IrPt alloy containing Pt (platinum) is used. The formed one may be used.
The IrPt alloy can suppress the oxidative volatilization of Ir from the grain boundaries in a high temperature atmosphere or an oxidizing atmosphere. An IrPt alloy containing 5 to 50 wt% of Pt, and more preferably an IrPt alloy containing 5 to 30 wt% of Pt, can suppress the oxidative volatilization of Ir from the grain boundaries in a high temperature atmosphere or an oxidizing atmosphere. In the IrPt alloy, the component excluding Pt and Ta is Ir.

FIG. 12 shows the results of an engine durability test using IrPt metal. FIG. 12 shows the results of an engine durability test in which the angle formed by the central forging line 15b and the ground normal line 16b is changed.

The test sample A in which the angle between the central forging line 15b and the ground normal line 16b is 0 ° corresponds to that illustrated in FIG. The test sample B having an angle of 30 ° between the central forging line 15b and the ground normal line 16b corresponds to those illustrated in FIGS. 4, 5, 6 and 7. The test sample C having an angle of 45 ° between the central forging line 15b and the ground normal line 16b corresponds to the one illustrated in FIG.

The test conditions for the engine durability test are a 2000cc 4-cylinder engine equipped with a spark plug 10 for testing, and after holding 1min of idling, holding 1min of 5600r / min as one cycle, and expanding the gap G to 200h (100,000km). Confirmed in (equivalent to running).

When the expansion amount of the gap G exceeds 0.2 mm, the required voltage becomes high and the influence on other parts such as the insulator withstand voltage occurs. Therefore, the expansion amount of the gap G of 0.2 mm was set as the boundary value of NG. As shown in FIG. 12, if the angle between the central forging line 15b and the ground normal line 16b is 30 ° or less, the expansion amount of the gap G is 0.2 mm or less in all the test samples for four cylinders. became. On the other hand, if the angle between the central forging line 15b and the ground normal line 16b is 35 ° or more, the expansion amount of the gap G is 0.2 mm or more in all the test samples for four cylinders.

As shown in FIG. 10A, the angle between the central forging line 15b and the ground normal line 16b is 35 ° or more, and when the angle is 45 °, the surface layer portion 151 falls off due to the discharge attack. When the surface layer portion 151 falls off, as shown in FIG. 10B, a hangnail phenomenon occurs in a chain on the non-surface layer portion 152, and the precious metal chip 15 is consumed. As a result, the gap GA between the noble metal chip 15 and the noble metal chip 16 expands to the gap GB. Therefore, by setting the angle between the central forging line 15b and the grounding normal line 16b to 30 ° or less, the consumption of the precious metal tip 15 can be suppressed.

FIG. 13 shows the test results in which the angle between the central forging line 15b and the ground normal line 16b is 30 ° and the aspect ratio is changed. The aspect ratio is the tangent pair of parallel tangent pairs that do not cross the inside of the particle when drawn in various positional relationships with respect to the outline of the crystal particles observed in the field of view on the defined cross section. It is specified as the ratio of the maximum interval to the minimum interval in a set.

The test conditions for the engine durability test are a 2000cc 4-cylinder engine equipped with a spark plug 10 for testing, and after holding 1min of idling, holding 1min of 5600r / min as one cycle, and expanding the gap G to 200h (100,000km). Confirmed in (equivalent to running).

As shown in FIG. 13, when the aspect ratio is 6 or more, the total number of gaps expanded is 0.2 mm or less, and it was confirmed that the influence of the gap expansion on other parts can be suppressed.

The spark plug in the present embodiment includes a discharge unit that discharges when a voltage is applied. The discharge portion is formed by arranging the center electrode 13 and the ground electrode 14 so as to face each other. The center electrode 13 is formed by joining a noble metal chip 15 as a center electrode chip containing Ir, Pt, and Ta to a tip portion 13a as a center electrode base material, and is formed in the longitudinal direction of crystal grains constituting the noble metal chip 15. The angle formed by the central forging line 15b along the line and the grounding normal line 16b, which is the normal line of the grounding discharge surface 16a on which the grounding electrode faces the center electrode chip, is within 30 °.

By setting the angle formed by the central forging line 15b and the grounding normal line 16b within 30 °, it is possible to reduce the consumption due to the discharge attack.

The ground electrode 14 is formed by joining a noble metal chip 16 as a ground electrode chip containing Ir, Pt, and Ta to a tip portion 14a as a ground electrode base material, and a ground discharge surface 16a is formed on the noble metal chip 16. ing. In the present embodiment, since the example in which the noble metal chip 16 is provided at the tip portion 14a of the ground electrode 14, the ground discharge surface 16a is formed on the noble metal chip 16. However, it is not necessary to provide the noble metal chip 16, and in that case, the surface of the tip portion 14a facing the noble metal chip 15 becomes the ground discharge surface, and the normal line of the ground discharge surface becomes the ground normal line.

In the present embodiment, the angle formed by the central forging stream line 15b and the grounding forging line 16c along the longitudinal direction of the crystal grains constituting the noble metal chip 16 as the ground electrode tip can be within 30 °. ..

In the present embodiment, it is preferable that the aspect ratio of the crystal grains forming the central forging line 15b and / or the grounding forging line 15c is 6 or more.

The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those skilled in the art with appropriate design changes to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in each of the above-mentioned specific examples, its arrangement, conditions, a shape, and the like are not limited to those exemplified, and can be appropriately changed. The combinations of the elements included in each of the above-mentioned specific examples can be appropriately changed as long as there is no technical contradiction.

10: Spark plug 11: Housing 11a: Threaded portion 11b: Upper end portion 12: Insulator 13: Center electrode 13a: Tip portion 14: Ground electrode 14a: Tip portion 15: Noble metal chip 16: Noble metal chip 17: Spark gap 18: Center Shaft 19: Terminal 20: Gasket

Claims (6)

It ’s a spark plug,
It has a discharge section that discharges when a voltage is applied.
The discharge portion is formed by arranging the center electrode (13) and the ground electrode (14) so as to face each other.
The center electrode is formed by joining a center electrode tip (15) containing Ir, Rh, and Ta to a center electrode base material (13a).
Grounding is the normal of the central forging line (15b) along the longitudinal direction of the crystal grains constituting the center electrode chip and the grounding discharge surface (16a) on which the grounding electrode faces the center electrode chip. The angle formed by the normal line (16b) is within 30 °. The spark plug according to claim 1.
The ground electrode is formed by joining a ground electrode tip (16) containing Ir, Rh, and Ta to a ground electrode base material (14a).
The ground discharge surface is formed on the ground electrode chip. It ’s a spark plug,
It has a discharge section that discharges when a voltage is applied.
The discharge portion is formed by arranging the center electrode (13) and the ground electrode (14) so as to face each other.
The center electrode is formed by joining a center electrode tip (15) containing Ir, Pt, and Ta to a center electrode base material (13a).
Grounding is the normal of the central forging line (15b) along the longitudinal direction of the crystal grains constituting the center electrode chip and the grounding discharge surface (16a) on which the grounding electrode faces the center electrode chip. The angle formed by the normal line (16b) is within 30 °. The spark plug according to claim 3.
The ground electrode is formed by joining a ground electrode tip (16) containing Ir, Pt, and Ta to a ground electrode base material (14a).
The ground discharge surface is formed on the ground electrode chip. The spark plug according to claim 2 or 4.
The angle formed by the central forging line and the grounding streamline (16c) along the longitudinal direction of the crystal grains constituting the ground electrode tip is within 30 °. The spark plug according to any one of claims 1 to 5.
The aspect ratio of the crystal grains forming the central forging line and / or the grounding forging line is 6 or more.

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