| 摘要 |
PROBLEM TO BE SOLVED: To provide a four-stroke engine 1 mountable to a portable working machine or backpack type working machine usable in various directions while enhancing lubrication performance.SOLUTION: Cam driving parts are operatively connected with rotation of a crankshaft 24, a driving chamber 51 and a rocker chamber 42 are connected to each other, the rocker chamber 42 is connected to a crank chamber 23 and a gas-liquid separator 81, oil accumulated in a tank 62 is sucked up into the crank chamber 23, the oil is circulated through each part of the engine, the crank chamber 23 and the driving chamber 51 are connected to each other via a communicating passage 67 and a return passage 68, the connection between the crank chamber 23 and the driving chamber 51 via the return passage 68 communicates only at timing where a piston 11 is located in the vicinity of the top dead center. The oil is circulated by utilizing pressure fluctuation of the crank chamber 23 due to reciprocating motion of the piston 11 to lubricate the driving parts such as the crankshaft 24 and valve system members. |
