Electro-pneumatic actuator for a turbocharger waste gate, and a turbocharger and a method employing same

An electro-pneumatic actuator for a waste gate includes an electric actuator to impart linear motion to an actuator shaft, and a pneumatic chamber defining a passage extending therethrough, the actuator shaft extending through the passage, the pneumatic chamber being sealed with respect to the actuator shaft. A piston is disposed in the pneumatic chamber and arranged for movement in the pneumatic chamber, the piston being affixed to the actuator shaft such that the actuator shaft and the piston move together as a unit. There is a port into the pneumatic chamber for feeding a gas into the pneumatic chamber or exhausting the gas therefrom so as to exert a pressure force on the piston and thereby provide a pneumatic assist to the force exerted on the actuator shaft.