EGR system and improved actuator therefor

An exhaust gas recirculation system for an internal combustion engine, said system having a valve including a valve stem, said valve being moveable between a closed position, blocking communication from an engine exhaust gas passage to an engine intake passage, and an open position;

• said system comprising housing means, and actuator means operable to move said valve between said closed and open positions, in response to changes in an electrical input signal;
• characterized by:
• (a) said valve stem including an input portion disposed within said housing means;
• (b) said actuator means including an electric motor operably associated with said housing means and operable to provide a low torque, high speed rotary output in response to said electrical input signal;
• (c) said actuator means further including a gear train comprising at least an input gear, adapted to receive said low torque, high speed rotary output of said electric motor, and an output gear providing a high torque, low speed rotary output;
• (d) linkage means operable to translate said high torque, low speed rotary output into axial movement of said input portion of said valve stem, to move said valve between said closed and open positions;
• (e) said gear train including a motor pinion gear comprising said input gears, and at least one intermediate sear assembly comprising a relatively larger gear member in toothed engagement with said motor pinion gear, and a relatively smaller pinion, normally operable to rotate with said larger gear, and operable to provide a reduction in speed of rotation, and an increase in torque from said input gear to said output gear;
• and
• (f) gear train including torque limiting clutch means operable to limit the amount of torque transmitted to said output gear as said valve approaches an open stop and a closed stop.