Speed-responsive retarder control system providing for overheat prevention

摘要

In response to the actuation of a speed control lever by the vehicle operator, a potentiometer puts out a speed setting signal indicative of a desired vehicle speed. A control circuit responds to this speed setting signal, as well as signals representative of the actual vehicle speed and of the temperature of the retarder fluid, by putting out a first braking signal, corresponding to the difference between the desired and actual vehicle speeds, and a second braking signal corresponding to the difference between the actual acceleration of the vehicle and a preset acceleration. Under the control of the control circuit a selector normally passes the first braking signal and, when either the temperature of the retarder fluid or its temperture rise gradient exceeds a preset maximum, the second braking signal. The first or second braking signal is proportionately translated into a hydraulic pressure for actuation of a retarder. The second braking signal is intended to prevent the overheating of the retarder as when the vehicle is traveling down a long or steep slope.