Plasma jet spark plug

Patent metadata

Field	Value
Publication number	US-9478947-B2
Application number	US-201514811160-A
Country	US
Kind code	B2
Filing date	Jul 28, 2015
Priority date	Jul 28, 2014
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

A plasma jet plug has a cavity defined by a surface of a center electrode, an inner surface of an insulator, and a surface of a ground electrode. When a volume of a portion of the cavity on a front side of a front portion of the center electrode is a first volume V 1 and a volume of a portion of the cavity on a rear side of the front end of the center electrode is a second volume V 2 , the following expression is satisfied:

V 1/ V 2≧0.20.

First claim

The invention claimed is:

1. A plasma jet plug comprising:
a tubular insulator having an inner surface that defines an axial hole that extends along an axis;
a rod-shaped center electrode that is disposed in the axial hole of the insulator and extends along the axis;
a metallic shell disposed around an outer periphery of the insulator;
a ground electrode that is electrically connected to the metallic shell, said ground electrode having a through hole and being abutted on a front side of the insulator; and
a cavity that is defined by a surface of the center electrode, the inner surface of the insulator, and a surface of the ground electrode facing a rear side of the insulator,
wherein an inner diameter of the through hole is smaller than an inner diameter of a portion of the insulator which abuts the ground electrode; and
wherein, a following expression is satisfied:
V 1 /V 2 ≧0.20, where a first volume V 1 is a volume of a portion of the cavity on the front side of a front end of the center electrode, and a second volume V 2 is a volume of a portion of the cavity on a rear side of the front end of the center electrode.

2. The plasma jet plug according to claim 1 ,
wherein the through hole has a maximum width that is smaller than or equal to 0.7 mm.

3. The plasma jet plug according to claim 1 ,
wherein the front end of the center electrode has a maximum width that is greater than or equal to 1.3 mm.

4. The plasma jet plug according to claim 1 , wherein the cavity includes;
a first portion provided at the front side of the front end of the center electrode, and
a second portion that is located on a rear side of the first portion and has a small diameter portion whose outer diameter is smaller than an inner diameter of the first portion.

5. The plasma jet plug according to claim 4 ,
wherein the second portion is located on a rear side of the front end of the center electrode.

6. The plasma jet plug according to claim 1 ,
wherein a following expression is satisfied:
V 1 /V 2 ≦0.62.

7. The plasma jet plug according to claim 2 ,
wherein the front end of the center electrode has a maximum width that is greater than or equal to 1.3 mm.

8. The plasma jet plug according to claim 2 , wherein the cavity includes;
a first portion provided at the front side of the center electrode, and
a second portion that is located on a rear side of the first portion and has an inner diameter smaller than an inner diameter of the first portion.

9. The plasma jet plug according to claim 3 , wherein the cavity includes;
a first portion provided at the front side of the center electrode, and
a second portion that is located on a rear side of the first portion and has an inner diameter smaller than an inner diameter of the first portion.

10. The plasma jet plug according to claim 2 ,
wherein a following expression is satisfied:
V 1 /V 2 ≦0.62.

11. The plasma jet plug according to claim 3 ,
wherein a following expression is satisfied:
V 1 /V 2 ≦0.62.

12. The plasma jet plug according to claim 4 ,
wherein a following expression is satisfied:
V 1 /V 2 ≦0.62.

13. The plasma jet plug according to claim 5 ,
wherein a following expression is satisfied:
V 1 /V 2 ≦0.62.

14. The plasma jet plug according to claim 4 , wherein the outer diameter of the second portion is defined by the inner surface of the insulator.

Assignees

• Ngk Spark Plug Co

Inventors

• Mukoyama Naoyuki
• Kameda Hiroyuki
• Kasahara Daisuke

Classifications

• H01T13/54

  having electrodes arranged in a partly-enclosed ignition chamber · CPC title

• H01T13/52

  characterised by a discharge along a surface · CPC title

• H01T13/32 Primary

  characterised by features of the earthed electrode · CPC title