Valve driving mechanism for double overhead camshaft engine

A valve drive mechanism for an internal combustion engine, comprising:

• an intake overhead camshaft having one cam for driving each intake valve of the internal combustion engine;
• an exhaust overhead camshaft, in juxtaposition with said intake overhead camshaft, having one cam for driving each exhaust valve of the internal combustion engine, said exhaust overhead camshaft being operationally coupled to said intake overhead camshaft;
• camshaft drive means for transmitting engine output from a crankshaft of the internal combustion engine to one of said intake and exhaust overhead camshafts;
• gear means for connecting rotation of said one of said intake and exhaust overhead camshafts to another of said intake and exhaust overhead camshafts, said gear means comprising helical gears in mesh with each other;
• and
• variable valve timing means for varying a valve timing at which one of said intake and exhaust valves is driven relative to a valve timing at which the other of said intake and exhaust valves is driven;
• said variable valve timing means having slidable means, mounted on said one of said intake and exhaust overhead camshafts for axial displacement, for operationally coupling said one of said intake and exhaust overhead camshafts to said camshaft drive means so as to cause a relative rotational displacement therebetween when said slidable means causes axial displacement with respect to said one of said intake and exhaust overhead camshafts,
• said slidable means comprising cylindrical piston means with internal and external helical coupling means for coupling with said one of said intake and exhaust overhead camshafts and said camshaft drive means, respectively,
• said internal and external helical coupling means, respectively, comprising helical splines cut in opposite directions,
• said camshaft drive means including internal helical splines cut in a direction opposite to helical threads of one of said helical gears mounted on said one of said intake and exhaust overhead camshafts.