BREATHER STRUCTURE OF OVERHEAD-VALVE INTERNAL COMBUSTION ENGINE

摘要

In an overhead-valve internal combustion engine in which a driving force transmission chamber which houses a driving force transmission member for transmitting a rotational driving force of a crankshaft to a camshaft an d is arranged at the side of a cylinder bore is formed in a crankcase, a cylinder block and a cylinder head, and a breather chamber which is arranged below a camshaft housing chamber which houses the camshaft and is formed between the cylinder head and the cylinder block and at the side of the cylinder bore and the driving force transmission chamber is formed between a cylinder and the crankcase, the discharge of oil from the breather chamber is performed smoothly so as to enhance the vapor-liquid separation performance. A breather inlet passage 68 which has an upper end thereof communicated with the inside of a camshaft housing chamber 30 and a lower end thereof communicated with a breather chamber 60 at a position corresponding to a mating face between a cylinder block 12 and a crankcase 11 is formed in the cylinder block 12 such that the breather inlet passage 68 extends vertically, and an oil discharge hole 74 which is communicated with a lower portion of the inside of the breather chamber 60 is formed in the crankcase 11.