# US 2014/0152170 A1 · Spark plug > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0152170 A1 - Document ID: US20140152170A1 - Status: Published application - Kind: A1 - Application number: 14/235,468 - Filed: 2012-05-15 - Published: 2014-06-05 - Earliest claimed: 2011-08-03 - Assignees: Ngk Spark Plug Co., Ltd. - Inventors: Yuji Kasuya; Yoshikazu Kataoka - Web page: https://patentgrep.com/patent/US20140152170A1 ## CPC - H01T 13/06: Covers forming a part of the plug and protecting it against adverse environment - H01T 13/32: characterised by features of the earthed electrode - H01T 13/39: Selection of materials for electrodes - 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 An object is to provide a technique for improving welding strength between an intermediate member and an electrode member. In a section of a spark plug cut by a plane which passes through the center of gravity of the intermediate member and is in parallel with the facing direction between a center electrode and an extending portion of a ground electrode, the spark plug satisfies the relational expression S1/(D1×H1)≧0.005, where S1 is the total area of nuggets, H1 is the height of the end surface of a noble metal tip from the disposition surface of an electrode base metal, and D1 is the maximum width of the noble metal tip. ## Claims ### Claim 1 A spark plug comprising: a center electrode extending in a direction of an axis; a ceramic insulator having an axial bore extending in the direction of the axis and holding the center electrode in the axial bore; a metallic shell provided externally of an outer circumference of the ceramic insulator; and a ground electrode having an extending portion extending in the direction of the axis, attached to the metallic shell at one end, and forming, at the other end, a gap in cooperation with the center electrode, at least one of the center electrode and the ground electrode has an electrode base metal, a columnar noble metal tip disposed in such a manner as to face the other electrode, and an intermediate member disposed between the electrode base metal and the noble metal tip; the intermediate member has a first surface in contact with the noble metal tip and a second surface being in contact with the electrode base metal, located opposite the first surface, and having an area greater than that of a cross section of the noble metal tip cut by a plane parallel to the first surface; a nugget is formed through fusion and solidification resulting from welding at least a portion of a boundary between the intermediate member and the electrode base metal; and in a section of the spark plug cut by a plane which passes through the center of gravity of the intermediate member and is in parallel with a facing direction between the extending portion and the center electrode, a relational expression S1/(D1×H1)≧0.005 is satisfied, where S1 is a total area of the nugget, H1 is a height of an end surface of the noble metal tip from a disposition surface of the electrode base metal where the intermediate member is disposed, and D1 is a maximum width of the noble metal tip. ### Claim 2 (depends on 1) A spark plug according to claim 1, wherein when the noble metal tip and the nugget are projected vertically onto a plane parallel with the disposition surface, the nugget includes a portion located inside an outline of the projected noble metal tip. ### Claim 3 (depends on 1, 2) A spark plug according to claims 1 or 2, wherein in the section, the nugget is formed on opposite sides of a centerline which passes through the center of gravity and is perpendicular to the end surface. ### Claim 4 (depends on 3) A spark plug according to claim 3, wherein in the section, the nugget is further formed at a location on the centerline. ### Claim 5 (depends on 1, 2) A spark plug according to claims 1 or 2, wherein a relational expression S1/(D1×H1)≧0.029 is satisfied. ### Claim 6 (depends on 2) A spark plug according to claim 2, wherein in the vertical projection, the nugget further includes a portion located outside the outline of the projected noble metal tip. ### Claim 7 (depends on 6) A spark plug according to claim 6, wherein the intermediate member has an attachment portion greater in an area of a cross section cut by a plane parallel to the first surface than the noble metal tip; the attachment portion ranges from the disposition surface to a height of 0.2×H1; and in the section, a relational expression S3/(H2×D2)≧0.030 is satisfied, where H2 is a height of the attachment portion from the disposition surface, D2 is a maximum width of the attachment portion, and S3 is a total area of those portions of the nugget which are formed between the attachment portion and the electrode base metal and are located outside the range of the noble metal tip with respect to the width direction of the attachment portion. ### Claim 8 (depends on 1, 2) A spark plug according to claims 1 or 2, wherein the nugget is formed internally in such a manner as to not be exposed at an outer surface of the intermediate member, and in the section, a relational expression L1≧0.10 mm is satisfied, where L1 is a shortest distance between the nugget and outlines of the intermediate member and the noble metal tip. ### Claim 9 (depends on 1, 2) A spark plug according to claims 1 or 2, wherein in the section, the nugget is formed along the overall boundary between the electrode base metal and the intermediate member.