# US 10,865,667 B2 · Internal combustion engine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,865,667 B2 - Document ID: US10865667B2 - Status: Granted - Kind: B2 - Application number: 16/572,617 - Filed: 2019-09-17 - Published: 2020-05-21 - Granted: 2020-12-15 - Earliest claimed: 2018-11-15 - Assignees: Toyota Jidosha Kabushiki Kaisha - Applicants: Toyota Jidosha Kabushiki Kaisha - Inventors: Manabu Tateno - Web page: https://patentgrep.com/patent/US10865667B2 ## CPC - F01L 3/04: Coated valve members or valve-seats - F01L 3/20: Shapes or constructions of valve members, not provided for in preceding subgroups of this group - F01L 1/185: {Overhead end-pivot rocking arms} - F01L 1/2405: {by means of a hydraulic adjusting device located between the cylinder head and rocker arm} - F01L 2301/00: Using particular materials - F01L 2303/00: Manufacturing of components used in valve arrangements - F01L 2305/00: Valve arrangements comprising rollers - F01L 2810/01: Cooling - F01L 2820/01: Absolute values - F01L: CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES ## Abstract An internal combustion engine includes: intake and exhaust ports; an intake valve including an intake valve shaft and an intake valve head; and an exhaust valve including an exhaust valve shaft and an exhaust valve head. The surface of the intake valve includes an intake-valve-head front surface exposed in a combustion chamber when the intake valve is closed and an intake-valve-head back surface exposed in the intake port when the intake valve is closed. The surface of the exhaust valve includes an exhaust-valve-head front surface exposed in the combustion chamber when the exhaust valve is closed and an exhaust-valve-head back surface exposed in the exhaust port when the exhaust valve is closed. The arithmetic mean roughness of the whole exhaust-valve-head back surface is greater than the arithmetic mean roughness of each of the whole intake-valve-head front surface, the whole intake-valve-head back surface and the whole exhaust-valve-head front surface. ## Claims ### Claim 1 An internal combustion engine, comprising: an intake port and an exhaust port which communicates communicate with a combustion chamber; an intake valve including an intake valve shaft and an intake valve head, the intake valve head being arranged at an end of the intake valve shaft and opening and closing the intake port; and an exhaust valve including an exhaust valve shaft and an exhaust valve head, the exhaust valve head being arranged at an end of the exhaust valve shaft and opening and closing the exhaust port, wherein the intake valve has a surface including an intake-valve-head front surface exposed in the combustion chamber when the intake valve is closed and an intake-valve-head back surface exposed in the intake port when the intake valve is closed, wherein the exhaust valve has a surface including an exhaust-valve-head front surface exposed in the combustion chamber when the exhaust valve is closed and an exhaust-valve-head back surface exposed in the exhaust port when the exhaust valve is closed, wherein an arithmetic mean roughness of the whole exhaust-valve-head back surface is greater than an arithmetic mean roughness of each of the whole intake-valve-head front surface, the whole intake-valve-head back surface and the whole exhaust-valve-head front surface, wherein the arithmetic mean roughness of the whole exhaust-valve-head back surface is greater than 0.5 μm, and wherein the arithmetic mean roughness of each of the whole intake-valve-head front surface, the whole intake-valve-head back surface and the whole exhaust-valve-head front surface is equal to or less than 0.5 μm. ### Claim 2 (depends on 1) The internal combustion engine according to claim 1, wherein at least one groove is formed in the exhaust-valve-head back surface. ### Claim 3 (depends on 2) The internal combustion engine according to claim 2, wherein the at least one groove includes a plurality of grooves that are formed in the exhaust-valve-head back surface so as to extend radially in a radial direction of the exhaust valve head. ### Claim 4 (depends on 3) The internal combustion engine according to claim 3, wherein each of the plurality of grooves is formed so as to become deeper at a portion of the exhaust valve head located radially outward than at a portion of the exhaust valve head located radially inward. ### Claim 5 (depends on 1) The internal combustion engine according to claim 1, wherein the arithmetic mean roughness of the whole of the exhaust-valve-head front surface and the exhaust-valve-head back surface is greater than the arithmetic mean roughness of the whole of the intake-valve-head front surface and the intake-valve-head back surface. ### Claim 6 (depends on 1) The internal combustion engine according to claim 1, wherein the arithmetic mean roughness of the whole exhaust-valve-head back surface is greater than the arithmetic mean roughness of the whole intake-valve-head back surface. ### Claim 7 (depends on 1) The internal combustion engine according to claim 1, wherein the arithmetic mean roughness of the whole intake-valve-head back surface is greater than the arithmetic mean roughness of the whole intake-valve-head front surface. ### Claim 8 (depends on 1) The internal combustion engine according to claim 1, wherein the arithmetic mean roughness of the whole exhaust-valve-head front surface is less than the arithmetic mean roughness of the whole intake-valve-head front surface. ### Claim 9 (depends on 1) The internal combustion engine according to claim 1, wherein an arithmetic mean roughness of a portion of the intake-valve-head front surface located radially outward of the intake valve head is greater than an arithmetic mean roughness of a portion of the intake-valve-head front surface located radially inward of the intake valve head. ### Claim 10 (depends on 1) The internal combustion engine according to claim 1, wherein an arithmetic mean roughness of a portion of the intake-valve-head back surface located radially outward of the intake valve head is less than an arithmetic mean roughness of a portion of the intake-valve-head back surface located radially inward of the intake valve head. ### Claim 11 (depends on 1) The internal combustion engine according to claim 1, wherein an arithmetic mean roughness of a portion of the exhaust-valve-head front surface located radially outward of the exhaust valve head is less than an arithmetic mean roughness of a portion of the exhaust-valve-head front surface located radially inward of the exhaust valve head. ### Claim 12 (depends on 1) The internal combustion engine according to claim 1, wherein an arithmetic mean roughness of a portion of the exhaust-valve-head back surface located radially outward of the exhaust valve head is greater than an arithmetic mean roughness of a portion of the exhaust-valve-head back surface located radially inward of the exhaust valve head. ### Claim 13 (depends on 1) The internal combustion engine according to claim 1, wherein the intake valve includes an intake front-surface coating layer which covers at least a part of the intake-valve-head front surface and an intake back-surface coating layer which covers at least a part of the intake-valve-head back surface, and wherein the intake front-surface coating layer is thinner than the intake back-surface coating layer. ### Claim 14 (depends on 13) The internal combustion engine according to claim 13, wherein a thickness of the intake front-surface coating layer is equal to or less than the arithmetic mean roughness of the whole intake-valve-head front surface. ### Claim 15 (depends on 13) The internal combustion engine according to claim 13, wherein a thickness of the intake back-surface coating layer is equal to or less than the arithmetic mean roughness of the whole intake-valve-head back surface. ### Claim 16 (depends on 1) The internal combustion engine according to claim 1, wherein the exhaust valve includes an exhaust front-surface coating layer which covers at least a part of the exhaust-valve-head front surface, and wherein the exhaust-valve-head back surface is not covered by a coating layer. ### Claim 17 (depends on 16) The internal combustion engine according to claim 16, wherein a thickness of the exhaust front-surface coating layer is equal to or less than the arithmetic mean roughness of the whole exhaust-valve-head front surface.