US Patent 7942123 Variable valve system for internal combustion engine

A variable valve system has a drive shaft having a drive cam, a rockable cam opening/closing an engine valve, a transmission mechanism converting torque of the drive cam into a rocking motion and transmitting it to the rockable cam, a control shaft, and a control cam. When the variable valve system varies a valve lift amount of the engine valve by changing the rocking fulcrum of the transmission mechanism, the rocking fulcrum during a small valve lift control is set in an area outside an arc locus drawn with the drive shaft being a center of the arc and passing through a rocking fulcrum position positioned at a maximum valve lift and also inside an arc locus drawn with a pivot of the one end side of the transmission mechanism being a center of the arc and passing through the rocking fulcrum position positioned at the maximum valve lift.