# US 10,320,158 B2 · Spark plug > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,320,158 B2 - Document ID: US10320158B2 - Status: Granted - Kind: B2 - Application number: 15/453,565 - Filed: 2017-03-08 - Published: 2017-10-05 - Granted: 2019-06-11 - Earliest claimed: 2016-03-29 - Assignees: Ngk Spark Plug Co., Ltd. - Applicants: NGK Spark Plug Co., LTD. - Inventors: Susumu Imai - Web page: https://patentgrep.com/patent/US10320158B2 ## CPC - H01T 13/39: Selection of materials for electrodes - H01T 13/32: characterised by features of the earthed electrode - H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H) ## Abstract A spark plug includes an insulator having an axial hole extending along an axial line, a center electrode disposed in the axial hole, a tubular metallic shell surrounding the insulator, a ground electrode whose proximal end is fixed to the metallic shell, and a cylindrical noble metal tip fixed to the ground electrode via an intermediate tip so as to form a gap between the noble metal tip and the center electrode. A weld portion is provided between the noble metal tip and the intermediate tip. The weld portion has a diameter larger than that of a portion of the intermediate tip which is adjacent to the weld portion. The noble metal tip is located inside a virtual tapered cylindrical surface which extends from a peripheral edge of a gap-side end of the center electrode so as to contact an outer circumferential edge of the weld portion. ## Claims ### Claim 1 A spark plug comprising: an insulator having an axial hole extending along an axial line of the spark plug; a center electrode disposed in the axial hole; a tubular metallic shell surrounding the insulator; a ground electrode whose proximal end is fixed to the metallic shell; and a cylindrical noble metal tip which is fixed to the ground electrode via an intermediate tip so as to form a gap between the noble metal tip and the center electrode, wherein a weld portion is provided between the noble metal tip and the intermediate tip, the weld portion has a diameter larger than that of a portion of the intermediate tip which is adjacent to the weld portion, the noble metal tip is entirely located inside a virtual tapered cylindrical surface, which extends from a peripheral edge of a gap-side end of the center electrode so as to contact an outer circumferential edge of the weld portion, and the weld portion has a bulge portion that bulges outward in a radial direction of the spark plug from the portion of the intermediate tip. ### Claim 2 (depends on 1) The spark plug according to claim 1, wherein, over an entirety of a circumference of the weld portion, the diameter of the weld portion is larger than the diameter of the portion of the intermediate tip which is adjacent to the weld portion. ### Claim 3 (depends on 1) The spark plug according to claim 1, wherein the intermediate tip includes a flange, which is joined to the ground electrode, and a distance between a surface of the flange which faces toward the noble metal tip and the weld portion is 10% or more of a distance between the surface of the flange and a gap-side end of the noble metal tip. ### Claim 4 A spark plug comprising: an insulator having an axial hole extending along an axial line of the spark plug; a center electrode disposed in the axial hole; a tubular metallic shell surrounding the insulator; a ground electrode whose proximal end is fixed to the metallic shell; and a first noble metal tip which is fixed to a forward end of the center electrode so as to form a gap between the first noble metal tip and the ground electrode, wherein a weld portion is provided between the first noble metal tip and the center electrode, the weld portion has a diameter larger than that of the first noble metal tip and a base portion of the center electrode which is adjacent to the weld portion, and the base portion has a constant diameter and has an outer surface that extends parallel to the axial line. ### Claim 5 (depends on 4) The spark plug according to claim 4, wherein a second noble metal tip is disposed on the ground electrode, and the first noble metal tip is located inside a virtual tapered cylindrical surface, which extends from a peripheral edge of a gap-side end of the second noble metal tip so as to contact an outer circumferential edge of the weld portion. ### Claim 6 (depends on 4) The spark plug according to claim 4, wherein, over an entirety of a circumference of the weld portion, the diameter of the weld portion is larger than the diameter of the portion of the center electrode which is adjacent to weld portion. ### Claim 7 (depends on 2) The spark plug according to claim 2, wherein, over an entirety of a circumference of the weld portion, the diameter of the weld portion is larger than the diameter of the portion of the intermediate tip which is adjacent to the weld portion. ### Claim 8 (depends on 5) The spark plug according to claim 5, wherein, over an entirety of a circumference of the weld portion, the diameter of the weld portion is larger than the diameter of the portion of the center electrode which is adjacent to weld portion. ### Claim 9 (depends on 1) The spark plug according to claim 1, wherein the weld portion has a bulge portion that bulges outward in a radial direction of the spark plug. ### Claim 10 (depends on 4) The spark plug according to claim 4, wherein the weld portion has a bulge portion that bulges outward in a radial direction of the spark plug. ### Claim 11 (depends on 1) The spark plug according to claim 1, wherein the weld portion is not provided in the center electrode.