Drive for gas exchange valves, preferably inlet valves for reciprocating internal combustion engines

摘要

PCT No. PCT/DE93/00357 Sec. 371 Date Oct. 14, 1994 Sec. 102(e) Date Oct. 14, 1994 PCT Filed Apr. 22, 1993 PCT Pub. No. WO93/22543 PCT Pub. Date Nov. 11, 1993A valve drive for controlling gas exchange valves of an internal combustion engine having a cylinder head, a valve stem and a longitudinal tappet axis including a camshaft having a first cam with a first cam profile and a second cam with a second cam profile greater than the first cam profile. The second cam has two cam members which abut both sides of the first cam. A cup-shaped tappet is slidably disposed within the cylinder head for engaging the two cam members. A central tappet is disposed within the cup-shaped tappet for engaging the first cam. A lash adjuster is disposed within the central tappet and supported against the valve stem. A hydraulic switching arrangement is disposed between the cup-shaped tappet and the central tappet for selectively moving the valve stem according to the first and second cam profiles. The switching arrangement includes contours within one of the tappets oriented transverse to the longitudinal tappet axis, and radially-displaceable convex drivers within the other of the tappets for selectively engaging the concave contours when the cams are positioned at their base circles. A hydraulically-driven locking element movably supported in a plane oriented transverse to the tappet longitudinal axis selectively displaces the drivers into the concave contours to lock the tappets together and move the valve stem according to the second profile. The locking element also displaces the drivers out of the concave contours to unlock the tappets from each other and move the valve stem according to the first cam profile.