| 摘要 |
A valve operation changing system of an internal combustion engine, comprises a rocker arm (3, 3') to operate an intake or exhaust valve (2, 11), and a control device (19A, 19B, 22, 23, 24, 25, 26) for axially moving the rocker arm so as to selectively cause the rocker arm (3, 3') to engage with first or second cam (12, 13; 45A, 45B) in accordance with an engine operating condition. The control device includes an actuator having first and second hydraulic pressure chambers (19A, 19B; 50a, 50b) whose pressures move the rocker arm (3, 3') to engage with the first and second cams (12, 13; 45A, 45B), respectively. A flow direction changing valve (23) is provided to selectively supply the first or second hydraulic pressure chambers (19A, 19B; 50a, 50b) with oil from an oil pressure source (21), in accordance with the engine operating condition. A stopper device (26) is provided to restrict the movement of the rocker arm (3, 3'). Additionally, a timing lifter (25) is provided to release the rocker arm (3, 3') from the restriction by the stopper device in timed relation to the rotation of the first and second cams (12, 13; 45A, 45B), thereby accomplishing the axial movement of the rocker arm (3, 3') at a predetermined suitable timing and at a higher speed.
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