Patent ID: 6953012

Claim:
A forced opening and closing valve operating system comprising: a camshaft including a low speed valve-opening cam, a low speed valve-closing cam, a high speed valve-opening cam, and a high speed valve-closing cam, the low speed valve-opening cam and the low speed valve-closing cam having profiles corresponding to low speed running of an engine, the high speed valve-opening cam and the high speed valve-closing cam having profiles corresponding to high speed running of the engine; a rocker shaft having an axis parallel to the camshaft; a low-speed free rocker arm supported on the rocker shaft so as to swing by following the low speed valve-opening cam and the low speed valve-closing cam; a high-speed free rocker arm supported on the rocker shaft so as to swing by following the high speed valve-opening cam and the high speed valve-closing cam; a valve operating rocker arm swingably supported by the rocker shaft between the low-speed and high-speed free rocker arms, and connected to an engine valve so as to drive the engine valve in both valve-opening and valve-closing directions; and connection switching means provided in the rocker arms, the connection switching means switching so that the valve operating rocker arm is connected alternatively to the low-speed and high-speed free rocker arms.