| 摘要 |
In a 4 stroke cycle internal combustion engine 1 having intake and exhaust valves 9, 10 opened and closed by respective intake and exhaust cams 27, 28 made integral with a camshaft 13, the engine comprises a decompression cam 38 fitted on the camshaft 13 so as to rotate freely, a one-way clutch 29 fitted on the camshaft 13 capable of transmitting reverse rotation torque to the decompression cam 38 only when the camshaft 13 rotates in reverse, a torque limiter 40 inserted between the decompression cam 38 and the one-way clutch 29, and decompression cam stoppers 42, 43 provided on a fixed portion engaging with an engaging section 41 formed on the decompression cam 38 for stopping rotation of the decompression cam 38 at respective positions in normal rotational direction and reverse rotational direction. A lift of a cam section 38a of the decompression cam 38 is higher than a base circle of the exhaust cam 28 and lower than a maximum lift of a cam section 28a of the exhaust cam 28. The exhaust valve 10 is not opened by the decompression cam when the camshaft 13 rotates normally and the decompression cam stopper 43 engages with the engaging section. A decompression device that is simple in construction, small-sized and of low-cost is provided. <IMAGE> |
