Method and apparatus for turbocharger control

A method of controlling intake manifold pressure in a turbo-charged internal combustion engine having a turbocharger driven by flow of exhaust gases from the engine and a throttle positionable to vary power developed by the engine, comprising the steps of:

• regulating exhaust gas flow through said turbocharger to vary said intake manifold pressure by moving a member exposed to said exhaust gas flow;
• sensing said intake manifold pressure and said throttle position;
• producing a pneumatic force on said member in relation to the sensed intake manifold pressure, said pneumatic force urging said member to move in a direction decreasing intake manifold pressure;
• and
• producing a hydraulic force on said member in relation to the sensed throttle position, said hydraulic force opposing said pneumatic force and urging said member to move in a direction increasing intake manifold pressure, whereby said member moves substantially in response to the difference between said pneumatic and hydraulic forces to regulate said intake manifold pressure in relation to said throttle position.

In combination with a turbocharger, an internal combustion engine having an intake manifold, an exhaust manifold, a throttle positionable to vary power developed by the engine, and a source of fluid under pressure, said turbocharger comprising:

• a turbine operably associated with said exhaust manifold be driven by exhaust gas flow from the engine;
• a compressor driven by said turbine and having a gas inlet passage, said compressor operably associated with said intake manifold to deliver gas flow thereto at a pressure which varies with the speed of said compressor;
• a member exposed to said exhaust gas flow and movable to vary exhaust gas flow through said turbine to thereby regulate compressor speed and pressure of gas flow to the intake manifold;
• a housing receiving at least a portion of said member;
• first conduit means communicating with said intake manifold and said housing whereby the pressure developed in said intake manifold acts upon said member to urge the latter to move in a direction reducing compressor speed and pressure of gas flow to the intake manifold;
• second conduit means communicating with said source of fluid and said housing whereby fluid pressure in said housing acts upon said member to urge the latter to move in an opposite direction increasing compressor speed and pressure of gas flow to the intake manifold;
• and
• fluid pressure control means operably associated with said second conduit means and said throttle for regulating said fluid pressure acting upon said member in relation to the position of said throttle, whereby said pressure of gas flow to the intake manifold is regulated in relation to said throttle position.