| 摘要 |
PURPOSE:To effectively prevent always the jumping action of a valve, by urging intake and exhaust valves with the used of valve springs, and by providing an oil chamber so that the hydraulic pressure in the chamber selectively urges the intake and exhaust valves in their closing directions. CONSTITUTION:When the rotational speed of an engine is lower than a predetermined value, a control device 17 closes a shut-off valve 15 but open a shut-off valve 16, and therefore, the hydraulic oil in an oil chamber 8 flows into an oil pan 11 through a drain passage 14. Accordingly, the urging force of a valve spring 10 alone acts upon a movable member 5. Meanwhile the shut-off valve 15 is opened but the shut-off valve 16 is closed upon high speed operation, and therefore the hydraulic oil from an oil pump 12 is fed into the oil chamber 8 through an oil supply passage 13. Accordingly, a movable member 5 is exerted with an urging force by hydraulic pressure in addition to the urging force of a valve spring 10 so that the movable member 5 is made into press-contact with a cam 7 under great urging force, thereby it is possible to restrain the jumping action of valves. |
