Abstract: A rocker arm (210) for use in a reciprocating, internal combustion engine includes a tip (235) and a seat (240). The tip and seat are urged to move by cams (220, 225) on a shaft (230). As the shaft rotates, the cams alternately apply force to the tip and the seat, causing the rocker arm to rotate about a pivot shaft (215). A valve (100) and valve stem (110?) are attached to the rocker arm. The valve is urged to open and close by motion of the rocker arm. Thus the valve is opened and closed through the use of positive camming and reciprocating forces only. No conventional valve spring is required to close the valve. Thus valve floating at high engine speeds is prevented and engine performance is improved.

Abstract: A system for continuously varying valve-opening overlap in reciprocating internal combustion engines changes the path of the timing belt (16) that drives the intake valve camshaft (26). An idler wheel (44) mounted on a pivoted arm (48) turns against the timing belt. At low engine speeds, the sprocket wheel idles against the timing belt. At higher engine speeds, increased engine oil pressure causes a hydraulic cylinder (58) to force the sprocket wheel against the timing belt, changing its path. As the path of the belt is changed, the intake valve position is advanced with respect to the position of the crankshaft (12). The exhaust valve position remains the same relative to that of the crankshaft. Thus at above-idle speeds, intake-exhaust valve overlap is present. Since the amount of belt path deviation is related to engine oil pressure, and thus engine speed, valve overlap varies smoothly as a function of engine speed. A tensioner (30) maintains proper belt tensioning at all times.