| 摘要 |
<p>A mechanism for switching valve operation modes in an internal combustion engine has a valve operating mechanism with a high- (4) and low-speed cams (3a,3b) having different cam profiles corresponding to rotational speed ranges of the engine, a pair of valves disposed in intake or exhaust ports of a combustion chamber and normally urged to be closed by spring means, a pair of directly moving rocker arms (5,7) for imparting the list of the low-speed cams to the valves, an idling rocker arm (6) for transmitting the lift of said high-speed cam (4) to the pair of valves and a selective coupling mechanism (14) for selectively connecting the rocker arms when mutually adjacent portions of the rocker arms are in a predetermined positional relationship. The diameter (D2) of the base-circle portion of the high-speed cam (4) is smaller than the diameter (D1) of the base-circle portion of the low-speed cam (3a,3b) whereby the selective coupling mechanism may be readily operated to connect the rocker arms without compressing the valve springs.</p> |
