Spark plug

Patent metadata

Field	Value
Publication number	US-12095234-B2
Application number	US-202218567550-A
Country	US
Kind code	B2
Filing date	Jun 14, 2022
Priority date	Jun 14, 2021
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

A spark plug 1 of the present invention includes an insulator 2 made from an alumina-based sintered body and including: a leg portion 22 provided on a front end side; a middle trunk portion 23 provided on a rear end side of the leg portion 22 and having a larger diameter than the leg portion 22; and a flange portion 24 provided on the rear end side of the middle trunk portion 23 and having a larger diameter than the middle trunk portion 23. In the spark plug 1, in a state where a cut surface 23b obtained by cutting the middle trunk portion 23 in a direction perpendicular to an axial line AX direction at an arbitrary position in the axial line AX direction is mirror-polished, when 20 observation regions X each being 185 μm×250 μm are set so as not to overlap each other, and with respect to each of a plurality of pores included in the 20 observation regions X, a square value P2 [μm2] of a length P [μm] of a circumference of the pore is obtained, an average value of the square values P2 [μm2] of top 20 pores having the largest square values P2 [μm2] is not greater than 2200 μm2, and a proportion T [%] of a total area of all pores included in the 20 observation regions X relative to a total area (100%) of the 20 observation regions X is not greater than 5%.

First claim

What is claimed is:

1. A spark plug comprising an insulator made from an alumina-based sintered body and having a tubular shape extending along an axial line direction thereof, the insulator including:
a leg portion provided on a front end side;
a middle trunk portion provided on a rear end side of the leg portion and having a larger diameter than the leg portion; and
a flange portion provided on the rear end side of the middle trunk portion and having a larger diameter than the middle trunk portion, wherein
in a mirror-polished surface obtained by mirror-polishing a cut surface obtained by cutting the middle trunk portion in a direction perpendicular to the axial line direction at an arbitrary position in the axial line direction,
when 20 observation regions each being 185 μm×250 μm are set so as not to overlap each other, and with respect to each of a plurality of pores included in the 20 observation regions, a square value P 2 [μm 2 ] of a length P [μm] of a circumference of the pore is obtained,
an average value of the square values P 2 [μm 2 ] of top 20 pores having the largest square values P 2 [μm 2 ] is not greater than 2200 μm 2 , and
a proportion T [%] of a total area of all pores included in the 20 observation regions relative to the total area (100%) of the 20 observation regions is not greater than 5%.

2. The spark plug according to claim 1 , wherein an area of cumulative 50% in a cumulative distribution of areas of the pores with respect to each of the 20 observation regions is a value exceeding 3 μm 2 .

3. The spark plug according to claim 1 , wherein the proportion T is not greater than 3%.

4. The spark plug according to claim 1 , wherein a thickness of the middle trunk portion is not greater than 2.0 mm.

Assignees

• Niterra Co Ltd

Inventors

• Sakuma Takeshi
• Yamada Yuichi
• Yoshida Haruki
• Shimada Hiroki
• KOBA Takuto

Classifications

• H01T13/22

  having two or more electrodes embedded in insulation (sparking plugs having two or more spark gaps H01T13/46) · CPC title

• H01T21/02

  of sparking plugs · CPC title

• H01T13/38 Primary

  Selection of materials for insulation · CPC title

• H01T13/20 Primary

  characterised by features of the electrodes or insulation · CPC title