Patent ID: 7789795

Claim:
A method for controlling a power transmission in a powertrain for a wheeled vehicle, the powertrain having an engine and the transmission having dual power delivery paths from the engine to vehicle traction wheels, one power delivery path being defined by multiple fixed-ratio gearing and the other power delivery path being defined by infinitely variable ratio elements; the method comprising the steps of: calibrating a first relationship of powertrain variables comprising engine speed and engine power that will achieve an optimum engine efficiency for a given engine power demand and for a given engine speed, the engine efficiency decreasing when engine speed increases for the given engine power; calibrating a second relationship of powertrain variables comprising overall powertrain efficiency and vehicle speed for each of multiple gear ratios for the transmission; determining horsepower at the traction wheels for each of several engine speeds using the calibrated first and second relationships of powertrain variables; selecting an engine speed that corresponds to optimum engine efficiency; and selecting a gear ratio and a ratio for the infinitely variable ratio elements for a given demand for power at the traction wheels whereby the engine operates at the selected engine speed.