SPARK PLUG

• US 20150222096A1
• Filed: 08/09/2013
• Published: 08/06/2015
• Est. Priority Date: 08/09/2012
• Status: Active Grant

• Current Assignee: NGK Spark PLUG Company Limited
• Original Assignee: NGK Spark PLUG Company Limited
• Inventors: Nakayama, Katsutoshi, Kashima, Tomokatsu, Yamada, Tatsunori
• Granted Patent: US 9,306,374 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01T 13/16 Means for dissipating heat
• CPC Class Codes: H01T 13/32 characterised by features of the earthed electrode
• CPC Class Codes: H01T 13/39 Selection of materials for electrodes

Abstract

A spark plug having a metal shell, center electrode and a ground electrode. The ground electrode includes an electrode base portion extending from a front end portion of the metal shell toward the front, a bent portion connected at one end thereof to a front end of the electrode base portion and an electrode distal end portion extending from the other end of the bent portion and forming a spark discharge gap with a center electrode. The ground electrode has a base material and a coating layer applied to the base material. The coating layer is formed on at least a front end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion of the ground electrode. The base material of the ground electrode is exposed at least at a part of the electrode base portion.

Claims

1. A spark plug, comprising:

a cylindrical insulator having an axial hole formed therethrough in an axis direction of the spark plug;

a center electrode inserted in an front side of the axial hole;

a cylindrical metal shell arranged on an outer circumference of the insulator; and

a ground electrode joined to a front end portion of the metal shell so as to form a gap between the ground electrode and the center electrode,

the ground electrode including an electrode base portion extending from the front end portion of the metal shell toward the front in the axis direction;

a curved bent portion connected at one end thereof to a front end of the electrode base portion; and

an electrode distal end portion extending from the other end of the bent portion in a direction different from the direction of extension of the electrode base portion and forming the gap with the center electrode,

wherein the ground electrode comprises a base material and a coating layer applied to the base material and made of a material having higher oxidation resistance than that of the base material so as to cover at least a distal end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion; and

wherein the base material of the ground electrode is exposed at least at a part of the electrode base portion.

2. The spark plug according to claim 1, wherein the base material of the ground electrode is exposed at the entire outer surface of the electrode base portion.

3. The spark plug according to claim 1, wherein the coating layer is formed only on the electrode distal end portion;

and wherein the base material of the ground electrode is exposed at the bent portion.

4. The spark plug according to claim 1, wherein the base material of the ground electrode is a metal material containing 90 mass % or more of nickel (Ni).

5. The spark plug according to claim 1, wherein the coating layer has a thickness of 5 to 60 μ

m.

6. The spark plug according to claim 1, wherein the coating layer is formed only on the electrode distal end portion, or is formed on the electrode distal end portion and the bent portion in such a manner that a minimum thickness of the coating layer on the electrode distal end portion is larger than a minimum thickness of the coating layer on the bent portion.

7. The spark plug according to claim 1, wherein a minimum thickness of the coating layer on the distal end face of the electrode distal end portion is larger than a minimum thickness of the coating layer on the outer circumferential surface other than the center-electrode-side surface of the electrode distal end portion.

8. The spark plug according to claim 1, wherein the coating layer is formed only on the distal end face and the outer circumferential surface other than the center-electrode-side surface of the electrode distal end portion, or is formed on the entire outer surface of the electrode distal end portion in such a manner that a minimum thickness of the coating layer on the center-electrode-side surface of the electrode distal end portion is smaller than a minimum thickness of the coating layer on the distal end face and the outer circumferential surface other than the center-electrode-side surface of the electrode distal end portion.

9. The spark plug according to claim 1, wherein the material of the coating layer is a material containing Ni, cobalt (Co) and chromium (Cr).

10. The spark plug according to claim 9, wherein the material of the coating layer further contains yttrium (Y) and aluminum (Al).

11. The spark plug according to claim 1, wherein the coating layer is formed by high velocity oxygen fuel (HVOF) spraying, high velocity air fuel (HVAF) spraying, plasma spraying, cold spraying or aerosol deposition.