Variable area turbocharger turbine and control system therefor

Claim 1

In an internal combustion engine having a turbo-supercharger including a compressor and a turbine and a means for varying the effective area of the turbine, a control system comprising, an actuator for actuating said means for varying the effective area of the turbine, said actuator being responsive to fluid pressure; a control means connected to a source of fluid pressure generating a fluid pressure signal for energizing said actuator as a predetermined function, said function comprising a first portion (I) at high engine rpms beginning at and adjacent maximum engine power and extending toward the maximum engine operating RPM said first portion maintaining the effective area substantially in its maximum area condition as established by peak engine operating pressures and a second portion (II) at lower engine rpms beginning adjacent or below peak engine torque and extending toward the minimum engine operating rpm, said second portion maintaining the effective area substantially in the minimum area condition and a third portion (III) intermediate the first and second portions and having a characteristic that the effective area increases as a direct function of engine rpm; means for generating a signal as a proportional function of engine rpm and applying said signal to said control means, means for generating a feedback signal representing the actual effective area and feeding said signal back to said control means, said control means being responsive to the rpm signal generating means and to the feedback signal generating means to generate signals applied to said actuator means to correct the actuating means for varying the effective area of the turbine solely as a predetermined function of engine rpm over said third portion (III).