这是测试环境

Camshaft

A camshaft is a rotating object— usually made of metal— that contains pointed cams, which converts rotational motion to reciprocal motion. Camshafts are used in internal combustion engines (to operate the intake and exhaust valves), mechanically-controlled ignition systems and early electric motor speed controllers. In piston engines, the camshaft is used to operate the intake and exhaust valves. Camshafts in automobiles are made from steel or cast iron, and are a key factor in determining the RPM range of an engine's power band.