# US 2020/0403385 A1 · Spark plug that prevents gas turbulence in the discharge space > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0403385 A1 - Document ID: US20200403385A1 - Status: Published application - Kind: A1 - Application number: 16/905,174 - Filed: 2020-06-18 - Published: 2020-12-24 - Earliest claimed: 2019-06-19 - Assignees: Denso Corporation - Applicants: Denso Corporation - Inventors: Yuya ABE; Masamichi SHIBATA - Web page: https://patentgrep.com/patent/US20200403385A1 ## CPC - H01T 13/32: characterised by features of the earthed electrode - H01T 13/39: Selection of materials for electrodes - H01T 13/20: characterised by features of the electrodes or insulation - 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 On a base part forming a ground electrode in a spark plug, a facing surface is formed facing a distal end surface of a central electrode to have a shortest gap between the facing surface and the central electrode. A first slope surface is formed on an upper surface of the base part. A downstream-side end surface is formed parallel with a virtual plane, and connected to the first slope surface. A second slope surface is formed on a lower surface of the base part, connected to a downstream-side end surface. An opposing surface is formed on the lower surface of the base part. A width of the facing surface is wider than a width of the opposing surface. A first angle of the facing surface to the first slope surface satisfies a relationship of 10°≤θ1≤40°. ## Claims ### Claim 1 A spark plug comprising a metal shell having a cylindrical shape, a center electrode disposed in an inside of the metal shell and a ground electrode connected to the metal shell, and having a curved shape arranged facing a distal end surface of the central electrode, a virtual plane along the curved shape of the ground electrode facing a flow of a fuel mixture gas, the ground electrode comprising a base part, wherein the base part of the ground electrode comprises: a facing surface formed on an upper surface of the base part at a position facing the distal end surface of the central electrode to form a spark gap between the facing surface and the distal end surface of the central electrode; a first slope surface formed on the upper surface of the base part and connected to the facing surface, and increasingly away from the distal end surface of the central electrode in a flow direction of the fuel mixture gas, a downstream-side end surface formed at a most downstream side in the flow direction of the fuel mixture gas and parallel with the virtual plane, and connected to the first slope surface; a second slope surface formed on a lower surface of the base part and connected to the downstream-side end surface, and approaching the distal end surface of the central electrode in the flow direction of the fuel mixture gas; and an opposing surface formed on the lower surface of the base part, and farthest away from the distal end surface of the central electrode, wherein a width A1 of the facing surface of the base part is wider than a width A2 of the opposing surface of the base part, a first angle θ1 of the facing surface to the first slope surface satisfies a relationship of 10°θ1≤40°, and a first distance L1 satisfies a relationship of 0.3 mm≤L1≤0.9 mm, where the first distance is measured, in the central axis of the central electrode to which the central electrode is disposed into the metal shell, from a connection point between the second slope surface and the downstream-side end surface to the facing surface of the base part. ### Claim 2 (depends on 1) The spark plug according to claim 1, wherein in the base part of the ground electrode, the first angle θ1 satisfies a relationship of 15°≤θ1≤25°, and the first distance L1 satisfies a relationship of 0.5 mm≤L1≤0.7 mm. ### Claim 3 (depends on 1) The spark plug according to claim 1, wherein in the base part of the ground electrode, the first angle θ1 satisfies a relationship of 25°≤θ1≤40°, and the first distance L1 satisfies a relationship of 0.5 mm≤L1≤0.8 mm. ### Claim 4 (depends on 1) The spark plug according to claim 1, wherein the base part of the ground electrode further comprises: a third slope surface formed on the upper surface of the base part and connected to the facing surface, approaching the distal end surface of the central electrode in the flow direction of the fuel mixture gas; an upstream-side end surface formed connected to the third slope surface, at a most upstream side in the flow direction of the fuel mixture gas, and formed parallel with the virtual plane; and a fourth slope surface formed on the lower surface of the base part and connected to the upstream-side end surface and the opposing surface, and increasingly away from the distal end surface of the central electrode in the flow direction of the fuel mixture gas, wherein a second angle θ2 of the facing surface to the third slope surface satisfies a relationship of 10°≤θ2≤40°, and a second distance L2 satisfies a relationship of 0.3 mm≤L2≤0.9 mm, where the second distance is measured, in the central axis of the central electrode to which the central electrode is disposed into the metal shell, from a second connection point between the upstream-side end surface and the fourth slope surface to the facing surface of the base part. ### Claim 5 (depends on 4) The spark plug according to claim 4, wherein in the base part of the ground electrode, the second angle θ2 satisfies a relationship of 15°≤θ2≤25°, and the second distance L2 satisfies a relationship of 0.5 mm≤L2≤0.7 mm. ### Claim 6 (depends on 4) The spark plug according to claim 4, wherein in the base part of the ground electrode, the second angle θ2 satisfies a relationship of 25°≤θ2≤40°, and the second distance L2 satisfies a relationship of 0.5 mm≤L2≤0.8 mm. ### Claim 7 (depends on 4) The spark plug according to claim 4, wherein in the base part of the ground electrode, the first angle θ1 is equal to the second angle θ2. ### Claim 8 (depends on 1) The spark plug according to claim 1, wherein in the base part of the ground electrode, a width W of the base part of the ground electrode, measured in a direction which is perpendicular to the virtual plane, satisfies a relationship of 2.3 mm≤W≤2.9 mm. ### Claim 9 (depends on 8) The spark plug according to claim 8, wherein in the base part of the ground electrode, the width W of the base part satisfies a relationship of 2.5 mm≤W≤2.7 mm. ### Claim 10 (depends on 1) The spark plug according to claim 1, further comprising a first noble metal chip formed on the facing surface of the base part, facing the distal end surface of the central electrode.