Spark plug

Patent metadata

Field	Value
Publication number	US-2016285242-A1
Application number	US-201615071728-A
Country	US
Kind code	A1
Filing date	Mar 16, 2016
Priority date	Mar 27, 2015
Publication date	Sep 29, 2016
Grant date	—

Abstract

A spark plug having a resistor disposed within a through hole of an insulator and between a center electrode and a metal terminal so as to be spaced apart from the center electrode in a direction of an axial line; and a conductive glass seal layer provided between the resistor and the center electrode and electrically connecting the resistor and the center electrode to each other, the conductive glass seal layer has a diameter of 3.9 mm or less, and a joined surface of the conductive glass seal layer and the resistor has a convex shape toward the center electrode side. A length α from a rear end to a front end of the joined surface and a maximum length β of the conductive glass seal layer in the direction of the axial line meets a relation of α/β≧0.4.

First claim

1 . A spark plug comprising:
a tubular metal shell; an insulator held within the metal shell and having a through hole formed therein so as to extend along a direction of an axial line of the metal shell; a center electrode inserted and fixed in a first end portion of the through hole of the insulator; a metal terminal inserted and fixed in a second end portion of the through hole of the insulator; a resistor disposed within the through hole and between the center electrode and the metal terminal so as to be spaced apart from the center electrode in the direction of the axial line; and a conductive glass seal layer provided within the through hole and between the resistor and the center electrode and electrically connecting the resistor and the center electrode to each other, wherein the conductive glass seal layer has a diameter of 3.9 mm or less, a joined surface of the conductive glass seal layer and the resistor has a convex shape toward the center electrode side, and when: α represents a length in the direction of the axial line from a rear end to a front end of the joined surface; and β represents a maximum length of the conductive glass seal layer in the direction of the axial line, a relation of α/β≧0.4 is satisfied.

2 . A spark plug according to claim 1 , wherein a shortest distance γ in the direction of the axial line from the joined surface to the center electrode is equal to or greater than 3 mm.

3 . A spark plug according to claim 1 or 2 , wherein the maximum length β is equal to or greater than 11 mm.

4 . A spark plug according to claim 1 or 2 , wherein the diameter of the conductive glass seal layer is equal to or less than 3.0 mm.

5 . A spark plug according to claim 1 or 2 , wherein a screw portion is formed on an outer periphery of the metal shell and has a diameter of M12 or less.

6 . A spark plug according to claim 3 , wherein the diameter of the conductive glass seal layer is equal to or less than 3.0 mm.

7 . A spark plug according to claim 3 , wherein a screw portion is formed on an outer periphery of the metal shell and has a diameter of M12 or less.

8 . A spark plug according to claim 4 , wherein a screw portion is formed on an outer periphery of the metal shell and has a diameter of M12 or less.

Assignees

• Ngk Spark Plug Co

Inventors

• Iwasaki Yoshitomo
• Yoshida Haruki
• Honda Toshitaka

Classifications

• H01T13/08

  Mounting, fixing or sealing of sparking plugs, e.g. in combustion chamber · CPC title

• H01T13/36

  characterised by the joint between insulation and body, e.g. using cement · CPC title

• H01T13/34 Primary

  characterised by the mounting of electrodes in insulation, e.g. by embedding · CPC title

• H01T13/20 Primary

  characterised by features of the electrodes or insulation · CPC title

• H01T13/40 Primary

  structurally combined with other devices (combined or associated with fuel injectors F02M57/06; structurally combined with other parts of internal-combustion engines F02P13/00) · CPC title