Patent ID: 7223201
Filing Date: 2007-05-29
Classification: B60K,B60W,F16H,Y02T,Y10S,Y10T

Abstract:
1. A method for controlling a speed ratio shift for a multiple speed ratio power transmission in a hybrid electric vehicle powertrain, the powertrain having an internal combustion engine and an electric motor for developing a total vehicle driving power source, the multiple speed ratio power transmission having multiple-ratio gearing with first and second selectively engageable fluid pressure actuated friction elements for establishing and disestablishing low speed ratio and high speed ratio torque flow paths from the driving power source to a transmission torque output member, the first friction element being applied and the second friction element being released during low speed ratio operation, the second friction element being applied and the first friction element being released during high speed ratio operation, the method comprising: increasing motor torque during an inertia phase of a speed ratio downshift as the first friction element is released; reducing motor torque when the pressure of the second friction element is increased toward a full engagement value during the speed ratio downshift whereby inertia torque disturbances due to changing engine speed during the speed ratio downshift are reduced; reducing actuating pressure for the first friction element during the inertia phase to a value that will effect a downshift as motor torque is increased during the inertia phase; and maintaining the reduced value of the actuating pressure for the first friction element using a closed-loop friction element pressure control.