公开(公告)号：US12095235B2

公开(公告)日：2024-09-17

申请号：US18567558

申请日：2022-06-14

Applicant: NITERRA CO., LTD.

Inventor： Shoma Tsumagari ,  Haruki Yoshida ,  Hiroki Shimada ,  Tomoya Kukino ,  Takuto Koba ,  Noriyuki Tamura

IPC: H01T13/38

CPC classification number: H01T13/38

Abstract: In a spark plug 1 of the present invention, in a mirror-polished surface 230a obtained by mirror-polishing a cut surface 230 obtained by cutting an insulator 2 in a direction perpendicular to an axial line AX direction, at a position separated by 2 mm from a portion having a maximum diameter of a diameter-enlarged portion 31a to a rear end side along the axial line AX direction, when 20 first observation regions X each being 192 μm×255 μm are set so as to each overlap a reference position m1 being a position 0.2 mm in a radial direction from an inner peripheral surface 2a side of the insulator 2 and so as not to overlap each other, a proportion (porosity) of an area of all of pores included in the 20 first observation regions X relative to a total area (100%) of the 20 first observation regions X is not greater than 3.5%, and in a thermally etched surface 230b obtained by subjecting the mirror-polished surface 230a to thermal etching, when 20 second observation regions Y each being 32 μm×43 μm are set so as to each overlap the reference position m1 and so as not to overlap each other, a particle size distribution of alumina particles included in the 20 second observation regions Y is regarded as a normal distribution, an average particle diameter of the alumina particles is defined as A, and a standard deviation of a particle diameter of the alumina particles is defined as σ, A is not less than 1.9 μm and not greater than 2.8 μm, and (A+3σ) is not greater than 3.0 μm.