US 12,249,809 B2
Spark plug insulator and spark plug
Hiroki Shimada, Nagoya (JP); Haruki Yoshida, Nagoya (JP); Kengo Fujimura, Nagoya (JP); and Takuto Koba, Nagoya (JP)
Assigned to Niterra Co., Ltd., Nagoya (JP)
Filed by Niterra Co., Ltd., Nagoya (JP)
Filed on Mar. 26, 2024, as Appl. No. 18/616,670.
Claims priority of application No. 2023-053309 (JP), filed on Mar. 29, 2023.
Prior Publication US 2024/0332918 A1, Oct. 3, 2024
Int. Cl. H01T 13/38 (2006.01)
CPC H01T 13/38 (2013.01) 4 Claims
OG exemplary drawing
 
1. A spark plug insulator composed of an alumina-based sintered body provided with an axial hole extending along an axial line, wherein
when a force to bend the spark plug insulator is applied to the spark plug insulator to fracture the spark plug insulator,
for a range including a starting point of the fracture out of two ranges into which a fracture surface created by the fracture is divided by a plane which is a plane perpendicular to a direction of the force and includes the axial line,
an average of areas of particles appearing in a planar image of the range is 4.4 μm2 or larger and 8.0 μm2 or smaller, and a maximum area of the particles is 600 μm2 or smaller,
the particles include large particles having an area of 60 μm2 or larger and 600 μm2 or smaller, and
as the large particles, 0.1 particles/mm2 or more are present per unit area of the planar image.