| 摘要 |
PURPOSE:To provide the smooth returning of lubricant oil in a crankchamber to an oil pan by a method wherein the passage area of pressure communicating passage is made large and the balance of pressure between the crankchamber and the cam chamber is kept under a good condition and the splashing of the lubricant oil from the crankchamber to the pressure communicating passage is prevented. CONSTITUTION:A cylinder case 20 and a cylinder head 22 are formed with a pressure communicating passage 66 for communicating a crankchamber 28 with a cam chamber 35. The pressure communicating passage 66 is extended substantially in a non-tangential direction of the rotation of a crankshaft 29 with its opening at the crankchamber 28 being not oppositely faced substantially to the tangential direction of the rotation of the crankshaft 29. Therefore, even if the passage area of the pressure communicating passage 66 is of a large value, the lubricant oil rotated in the rotating direction of the crankshaft 29 is prevented to flow by the inner surfaces of the cylinder case 20 and the crankcase 21 without having an opening of the pressure communicating passage 66 in its rotating direction, and so it may not be flashed directly into the pressure communicating passage 66. |
