Spark plug

Patent metadata

Field	Value
Publication number	US-10153620-B2
Application number	US-201615565776-A
Country	US
Kind code	B2
Filing date	Mar 28, 2016
Priority date	Apr 17, 2015
Publication date	Dec 11, 2018
Grant date	Dec 11, 2018

Abstract

A spark plug having a ceramic insulator held by a crimp portion of a metallic shell. The crimp portion satisfies a relation of A≥1.7 mm and a relation of t≥1.20 mm in a cross section of the crimp portion taken along a plane containing the axial line, where A is the distance between a closest point which is a point within the cross section closest to the ceramic insulator and an intersection at which a first orthogonal line passing through the closest point and orthogonal to the axial line intersects with an outer circumference of the crimp portion, and t is a thickness of the proximal end of the crimp portion.

First claim

Having described the invention, the following is claimed:

1. A spark plug comprising:
a ceramic insulator having a generally tubular shape and a through hole extending in a direction of an axial line, the ceramic insulator including a center electrode on a forward end side of the through hole in the direction of the axial line; and
a metallic shell formed in a generally tubular shape and having a crimp portion at a rear end of the metallic shell in the direction of the axial line, the crimp portion holding the ceramic insulator in a state in which the ceramic insulator is inserted into the metallic shell,
wherein the crimp portion satisfies a relation of A≥1.7 mm and a relation of t 1 ≥1.20 mm in a cross section of the crimp portion taken along a plane containing the axial line, where A is a distance between a closest point N which is a point within the cross section closest to the ceramic insulator and a point of intersection at which a first orthogonal line passing through the closest point and orthogonal to the axial line intersects with an outer circumference of the crimp portion, and t 1 is a thickness of a proximal end of the crimp portion.

2. A spark plug according to claim 1 , wherein the crimp portion satisfies a relation of 0.7≤C/B≤1.5, where C/B is the ratio of a distance C to a distance B in the cross section, the distance B being a distance between the closest point and a parallel line which passes through a proximal point of the outer circumference of the crimp portion and which is parallel to the axial line, and the distance C being a maximum distance between the outer circumference of the crimp portion and a second orthogonal line which passes through the proximal point of the outer circumference of the crimp portion and which is orthogonal to the axial line.

Assignees

• Ngk Spark Plug Co

Inventors

• Kiuchi Kentaro
• Mori Kazuhiko
• Mizutani Hironobu
• Teranishi Yuusuke

Classifications

• H01T13/36 Primary

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

• H01T13/02

  Details · CPC title

• H01T21/02 Primary

  of sparking plugs · CPC title

• H01T13/32

  characterised by features of the earthed electrode · CPC title