Self-adjustable camshaft drive mechanism

A self-adjustable camshaft drive mechanism of an internal combustion engine having a camshaft rotatable about an axis for driving intake and exhaust valves of the engine, comprising a camshaft drive means rotatable relative to the camshaft about an axis substantially in line with the axis of rotation of the camshaft and adapted to be driven from the crankshaft of the engine, a differential reduction gear unit means coaxially rotatable in its entirety with said camshaft drive means and operatively connected to the camshaft, drive means coaxially rotatable in its entirety with said camshaft drive means and said reduction gear unit means and having an output shaft drivingly connected to said reduction gear unit and rotatable relative to the camshaft and the camshaft drive means about an axis in line with the axis of rotation of the camshaft, said gear unit means being operative to transmit therethrough driving torque from said output shaft of the drive means to said camshaft drive means with reduction of speed of revolution at a predetermined ratio for producing relative rotation between the camshaft and the camshaft drive means by an angle and in a direction which are related to the angle and direction of rotation of the output shaft of the drive means, sensing means associated with the camshaft and the camshaft drive means for detecting an angle and direction of relative rotation between the camshaft and the camshaft drive means and producing an output signal substantially representative of the angle and direction of the detected relative rotation between the camshaft and the camshaft drive means, and control means responsive to said output signal of the sensing means and to preselected operational parameters of the engine for producing a control signal effective to actuate said drive means for causing the output shaft of the drive means to rotate a number of turns and in a direction which are dictated by said control signal.