| 摘要 |
PURPOSE:To aim at miniaturization in an air-cooled internal-combusion engine and improvements in sealability, by casting a push rod cover part together with a cylinder block as one body, while installing a seal material interposingly between both of them so as to surround a loose fitting part of a push rod. CONSTITUTION:A tappet 4 is reciprocated by cam 3 installed in a cam shaft 2 to be driven by a crankshaft 1. And, a push rod 8 is interposingly installed between this tappet 4 and a valve arm 7 installed inside a valve arm chamber 6 on top of a cylinder 5, and suction and exhaust valves are opened or closed by this valve arm 7. At the abovementioned, a push rod cover part 9 where the push rod 8 is loosely fitted is cast together with a cylinder block 10 as one body. And, a top surface of the cover part 9 if formed as low as a clearance (d) so as not to come into metal contact with a lower surface of the cylinder head 5, and an 0-ring 11 composed of an elastic body is interposingly installed therein so as to surround the loosely fitted part of the push rod 8, making it a seal material. |
