Spark plug for internal combustion engine and production method thereof

Patent metadata

Field	Value
Publication number	US-9825432-B2
Application number	US-201615261017-A
Country	US
Kind code	B2
Filing date	Sep 9, 2016
Priority date	Sep 11, 2015
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A spark plug for an internal combustion engine is provided which includes a housing, a porcelain insulator, a center electrode, and an annular ground electrode. The housing has a small-diameter portion which has a smaller inner diameter and defines a front end thereof. The ground electrode is secured to a front end surface of the small-diameter portion and forms a spark gap between itself and an outer periphery of the center electrode. The ground electrode is smaller in outer diameter than the front end surface of the small-diameter portion. A annular weld which joints the ground electrode and the small-diameter portion is formed in an annular boundary through which the front end surface of the small-diameter portion and the base end surface of the ground electrode face each other. The annular weld continuously and fully extends in a circumferential direction of the ground electrode.

First claim

What is claimed is:

1. A spark plug for an internal combustion engine comprising:
a cylindrical housing;
a cylindrical porcelain insulator which is retained inside the housing;
a center electrode which is retained inside the porcelain insulator and has a head extending outside a front end of the porcelain insulator; and
an annular ground electrode which is secured to a front end of the housing,
wherein the housing has a small-diameter portion formed on the front end thereof, the small-diameter portion having an inner diameter which is smaller than that of a rest of the housing,
wherein the ground electrode protrudes from a front end surface of the small-diameter portion and has an inner peripheral surface facing an outer peripheral surface of the center electrode,
wherein the ground electrode has an outer diameter which is smaller than an outer diameter of the front end surface of the small-diameter portion, and
wherein an annular boundary through which the front end surface of the small-diameter portion and a base end surface of the ground electrode face each other has an annular region which occupies a portion of a width thereof and fully extends in a circumferential direction thereof and in which an annular weld is formed which establishes a joint between the housing and the ground electrode, the annular weld continuously extending in a circumferential direction of the annular region.

2. A spark plug as set forth in claim 1 , wherein the annular weld has an inner circumferential edge located outside an inner circumferential edge of the front end surface of the small-diameter portion, the annular weld also having an outer circumferential edge located inside of the base end surface of the ground electrode.

3. A spark plug as set forth in claim 1 , wherein the annular weld is shaped to be embedded from the front end surface of the small-diameter portion into the ground electrode or from the base end surface of the ground electrode into the small-diameter portion.

4. A spark plug as set forth in claim 3 , wherein the annular weld is shaped so as to bite from the front end surface of the small-diameter portion into the ground electrode.

5. A spark plug as set forth in claim 1 , further comprising a material-mixed portion that is a mixture of molten materials of the ground electrode and the housing and extends from an outer peripheral edge of the ground electrode into the small-diameter portion of the housing through the annular boundary, the annular weld being formed inside the material-mixed portion.

Assignees

• Denso Corp

Inventors

• Deguchi Masataka
• Terada Kanechiyo
• Miwa Tetsuya
• Tsukamoto Yuuki

Classifications

• H01T13/38

  Selection of materials for insulation · CPC title

• H01T13/32 Primary

  characterised by features of the earthed electrode · CPC title

• H01T21/02

  of sparking plugs · CPC title

• H01T13/39

  Selection of materials for electrodes · CPC title