US Patent 8006659 Internal combustion engine with variable valve mechanism

An internal combustion engine including a variable valve mechanism that can avoid an unnecessary friction increase while preventing a hydraulic lash adjuster from pumping up. When a first engine speed is a critical rotation speed at which the inertia force of the variable valve mechanism exceeds the maximum load on a lost motion spring and a second engine speed is a critical rotation speed at which the inertia force of a valve and rocker arm exceeds the maximum load on a valve spring, the maximum loads are set such that the first engine speed is lower than the second engine speed.