The invention relates to a self-resetting single-valve double-
piston hydraulic driving device and method for an overhead
cam engine. The self-resetting single-valve double-
piston hydraulic driving method comprises the steps that a driving main
piston and a driving auxiliary piston are correspondingly arranged on a
rocker arm body and a valve bridge body, the driving auxiliary piston is connected with an
exhaust valve, and a driving oil way communicates with the driving main piston, the driving auxiliary piston and a driving control valve; when the driving control valve opens the driving oil way, the driving main piston and the driving auxiliary piston achieve hydraulic linkage, the
rocker arm body and the valve bridge do not move during lift driving, and the driving auxiliary piston opensthe
exhaust valve; when the main lift starts, a main piston body oil way and an auxiliary piston oil way are disconnected, and the driving auxiliary piston automatically resets; and when the driving oil way is disconnected, in the integrated
cam driving lift process, the driving main piston absorbs the driving lift of an integrated
cam assembly to the
rocker arm body, the rocker arm body does notmove, and the integrated cam driving lift is not transmitted to one side of the
exhaust valve. The self-resetting single-valve double-piston hydraulic driving method is simple in principle and compactin structure, and the reliability and durability of engine driving operation are improved.