Lift valve drive for internal combustion engines

摘要

The valve drive comprises two cams (2) and a counter-cam (4) which make contact over mutually blocking surfaces to lock the cams against changeover, thus only allowing changes during the zero lift phase. The two cams driving the counter cam change over with axial movement of the counter cam moving parallel to the main camshaft (1) and the cams can move axially and co-rotatably on the axially locked camshaft. The counter cam is moved by a return spring (16), hydraulic or pneumatic piston or magnet power. The counter cam takes the form of a rectilinear or arcuate roller, or again a straight-line tappet or arcuate lever and through a distance shorter than the axial extent of the main cam. Cam and counter cam block each other so as to limit cam changeover to the later lift phase of the valve.