| 摘要 |
A valve drive mechanism 100 for internal combustion engines having two cams 33A, 33B mounted on a rotatable spined shaft 34. The cams 33A, 33B have closed path grooves 36A, 36B in their respective planar ends. The valve 21 is connected to the follower 27 by the valve stem 22 and the pin 31 which is received by and in bearing engagement with either groove 36A or groove 36B to obtain first and second reciprocating motions respectively. A cylindrical collar 102, a linkage 104 and a drive 105 are configured to the change the cam 33A, 33B to which the valve 21 is coupled when the rotational speed of the shaft 34 crosses a threshold value which is monitored by a tachometer and sensor element mounted on cam 33B.
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