| 摘要 |
PURPOSE:To improve engine performance with higher fidelity in follow-up movement of valves in a four-cycle internal combustion engine by constituting such that suction and exhaust valves are pushed back to be closed by means of concavely shaped cams rather than push-back springs that force those valves resiliently toward closing direction. CONSTITUTION:In a configuration where a suction or an exhaust valve 3 is depressed to be opened by swinging a rocker arm 2 about a fulcrum 12 by rotation of a cam 1 which synchronizes with engine rotation, a concavely shaped cam 6 is arranged adjacent to the above-mentioned cam 1. A rocker arm 7 is then swung about a fulcrum 13 according to the rotation of the concavely shaped cam 6 to close the suction or exhaust valve 3 which has been opened by the action of the above-mentioned cam 1. The suction or exhaust valve 3, when closed, is brought into close contact with valve seats formed in a cylinder head part 4 by means of a spring 9 fitted resiliently over a valve shaft.
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