The present invention relates to the technical field of
engine valve driving devices, and in particular, to a special driving
cam-based combined
engine valve driving device, including a valve bridge, a special driving
cam, a driver, and a driving oil circuit. The driving oil circuit allows a master
piston hole and a secondary
piston hole to be in intermittent fluid communication with each other by its own on- and off-states. According to the present invention, the driver is fixed on a rocker shaft, so that the structure is simple, and the cost is low; there is no kinematic friction between the driver and the rocker shaft, and the special driving
cam is separated from a master
piston when the driver is not working, thereby effectively reducing the abrasion between the special driving cam and the master piston as well as the
noise, and improving the
utilization rate of
engine power; when the driver is working, the special driving cam automatically adjusts an actuated valve by means of a
hydraulic clearance, and the driving lift is not affected by initial clearance setting; and moreover, every time a positive work cam rotates by one circle, the driving oil circuit automatically drains oil once, and thus the circularly flowing engine oil does not cause
impurity accumulation even when the engine oil is too dirty, which improves working stability and reliability.