Spark plug and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-10447014-B1
Application number	US-201916353294-A
Country	US
Kind code	B1
Filing date	Mar 14, 2019
Priority date	Mar 26, 2018
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

A spark plug comprising: a first electrode including a tip containing 1r as a main material, and a base member to which the tip is joined; and a second electrode opposed to the tip with a spark gap therebetween. The number of crystal grains appearing in a range of 0.25 mm2 on an arbitrary cross-section of the tip in a first direction connecting the tip and the second electrode within the spark gap, is not less than 20. When a length of each of the crystal grains in the first direction is denoted by Y, and a length of each of the crystal grains in a second direction perpendicular to the first direction is denoted by X, 5 μm≤X≤100 μm and Y/X≥1.5 are satisfied.

First claim

Having described the invention, the following is claimed:

1. A spark plug comprising:
a first electrode including a tip containing Ir as a main material, and a base member to which the tip is joined; and
a second electrode opposed to the tip with a spark gap therebetween, wherein
a number of crystal grains appearing in an area of 0.25 mm 2 on an arbitrary cross-section of the tip in a first direction connecting the tip and the second electrode within the spark gap, is not less than 20 crystal grains, and
when a length of each of the crystal grains in the first direction is denoted by Y and a length of each of the crystal grains in a second direction perpendicular to the first direction is denoted by X, 5 μm≤X≤100 μm and Y/X≥1.5 are satisfied.

2. The spark plug according to claim 1 , wherein an amount of content of Ir on the cross-section of the tip is not greater than 4 mass %.

3. The spark plug according to claim 1 , wherein, when a Vickers hardness on the cross-section of the tip after heat treatment on the tip in an Ar atmosphere at 1300° C. for 10 hours is denoted by Ha, and a Vickers hardness on the cross-section of the tip before the treatment is denoted by Hb, the tip satisfies Hb≥220 HV and Hb/Ha≤1.3.

4. The spark plug according to claim 2 , wherein, when a Vickers hardness on the cross-section of the tip after heat treatment on the tip in an Ar atmosphere at 1300° C. for 10 hours is denoted by Ha, and a Vickers hardness on the cross-section of the tip before the treatment is denoted by Hb, the tip satisfies Hb≥220 HV and Hb/Ha≤1.3.

5. The spark plug according to claim 1 , wherein the tip further contains not less than 0.5 mass % of Rh.

6. The spark plug according to claim 2 , wherein the tip further contains not less than 0.5 mass % of Rh.

7. The spark plug according to claim 3 , wherein the tip further contains not less than 0.5 mass % of Rh.

8. A manufacturing method for the spark plug according to claim 1 , the manufacturing method comprising:
a preparation step of preparing a wire composed of a plurality of crystal grains and having a diameter corresponding to a diameter of the tip; and
a heating step of heating a part in a longitudinal direction of the wire, thereby forming a temperature gradient in the wire and causing the crystal grains to grow in the longitudinal direction.

9. The manufacturing method for the spark plug according to claim 8 , further comprising a cooling step of cooling a part in the longitudinal direction of the wire.

10. A manufacturing method for the spark plug according to claim 2 , the manufacturing method comprising:
a preparation step of preparing a wire composed of a plurality of crystal grains and having a diameter corresponding to a diameter of the tip; and
a heating step of heating a part in a longitudinal direction of the wire, thereby forming a temperature gradient in the wire and causing the crystal grains to grow in the longitudinal direction.

11. The manufacturing method for the spark plug according to claim 10 , further comprising a cooling step of cooling a part in the longitudinal direction of the wire.

12. A manufacturing method for the spark plug according to claim 3 , the manufacturing method comprising:
a preparation step of preparing a wire composed of a plurality of crystal grains and having a diameter corresponding to a diameter of the tip; and
a heating step of heating a part in a longitudinal direction of the wire, thereby forming a temperature gradient in the wire and causing the crystal grains to grow in the longitudinal direction.

13. The manufacturing method for the spark plug according to claim 12 , further comprising a cooling step of cooling a part in the longitudinal direction of the wire.

Assignees

• Ngk Spark Plug Co

Inventors

• Kikai Takaaki
• Sumoyama Daisuke
• Nakada Takuto

Classifications

• H01T21/02

  of sparking plugs · CPC title

• H01T13/39 Primary

  Selection of materials for electrodes · CPC title

• C22F1/14

  of noble metals or alloys based thereon · CPC title

• C22C5/04 Primary

  Alloys based on a platinum group metal · CPC title