公开(公告)号：US12095233B1

公开(公告)日：2024-09-17

申请号：US18567541

申请日：2022-06-14

Applicant: NITERRA CO., LTD.

Inventor： Noriyuki Tamura ,  Haruki Yoshida ,  Hiroki Shimada ,  Tomoya Kukino ,  Takuto Koba ,  Kengo Fujimura

IPC: H01T13/34

CPC classification number: H01T13/34

Abstract: A spark plug 1 of the present invention includes: an insulator 2 made from an alumina-based sintered body; a center electrode being a bar-like electrode inserted in the insulator 2 and having, on a rear end side of the center electrode, a diameter-enlarged portion enlarged in a radial direction and engaged with an inner wall of the insulator; and a conductive sealing material provided on the rear end side of the center electrode 3 inside the insulator. In a mirror-polished surface obtained by mirror-polishing a cut surface obtained by cutting the insulator in a direction perpendicular to the axial line direction, at a position 2 mm from a portion having a maximum diameter of the diameter-enlarged portion to the rear end side along the axial line direction, when 20 observation regions each being 192 μm×255 μm are set so as to each overlap a reference position being a center position between an inner peripheral surface and an outer peripheral surface of the insulator and so as not to overlap each other, an average of a proportion (porosity) of pores included in each observation region is not greater than 3.5% and, with respect to a variation in the proportion (porosity), when a standard deviation is defined as σ, σ is not greater than 0.36.

公开(公告)号：US12249809B2

公开(公告)日：2025-03-11

申请号：US18616670

申请日：2024-03-26

Applicant: Niterra Co., Ltd.

Inventor： Hiroki Shimada ,  Haruki Yoshida ,  Kengo Fujimura ,  Takuto Koba

IPC: H01T13/38

Abstract: When a force to bend a 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.

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.

公开(公告)号：US12095234B2

公开(公告)日：2024-09-17

申请号：US18567550

申请日：2022-06-14

Applicant: NITERRA CO., LTD.

Inventor： Takeshi Sakuma ,  Yuichi Yamada ,  Haruki Yoshida ,  Hiroki Shimada ,  Takuto Koba

IPC: H01T13/38 ,  H01T13/22

CPC classification number: H01T13/38 ,  H01T13/22

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%.