Power control system for a turbocharged internal combustion engine

Claim 1

A power control system for a supercharged internal combustion engine comprising; a supercharger including a turbine impeller rotatably disposed in an exhaust pipe of an engine and driven by exhaust gases discharged from said engine, and a compressor impeller rotatably disposed in an intake pipe of said engine and connected to said turbine impeller so that said compressor impeller is driven by said turbine impeller for compressing air and feeding the compressed air to said engine; a by-pass pipe connecting an upstream portion of said exhaust pipe and a downstream portion of said exhaust pipe for by-passing said turbine impeller; an exhaust by-pass valve disposed in said by-pass pipe for controlling the opening degree of said by-pass pipe; and means for actuating said exhaust by-pass valve in response to a depression of an acceleration pedal of said engine, so as to maintain a compressor outlet pressure at a preset value during a partial load operating range of said engine and to increase said compressor outlet pressure to another preset value higher than said first-mentioned preset value when said engine is operated in a higher load operating range, wherein said actuating means comprises: a valve actuator having a pressure chamber and a diaphragm displacable in response to the pressure in said pressure chamber, said diaphragm being operatively connected to said exhaust by-pass valve, said valve actuator having a spring for urging said diaphragm in a direction of closing said exhaust by-pass valve; a pressure pipe connecting said pressure chamber with a portion of said intake pipe downstream of said compressor impeller for supplying the compressed air from said intake pipe to said pressure chamber; a return pipe connecting said pressure chamber with a portion of said intake pipe upstream of said compressor impeller; a variable orifice valve disposed in said return pipe for controlling the opening degree of said return pipe; an acceleration pedal depression detector for detecting a depression degree of said acceleration pedal; and control means for driving said variable orifice valve in response to a signal from said acceleration pedal depression detector, said variable orifice valve being closed during the partial load operating range of said engine so that the pressure in said pressure chamber of said valve actuator is maintained at a value equal to the compressor outlet pressure and when the pressure in said pressure chamber exceeds a resisting force of said spring of said valve actuator said exhaust by-pass valve is opened for by-passing a part of exhaust gases from said engine through said by-pass pipe so as to maintain the compressor outlet pressure at said preset value, and said control means driving said variable orifice valve to open when said engine is operated in the higher load operating range, so as to actuate said exhaust by-pass valve to move in its closing direction in response to the opening degree of said return pipe so that the compressor outlet pressure is increased to said other preset value.