Patent ID: 6361464
Filing Date: 2002-03-26
Classification: F16H

Abstract:
A control device of an automatic transmission, which has an automatic shift range for automatically selecting a gear position according to driving conditions of a vehicle, and manual setting ranges for manually changing gear positions and having at least a low speed engine brake range in which the vehicle is driven at a lowest speed gear position with an engine brake being operable, said control device of the automatic transmission comprising:an operating pressure control circuit for controlling an operating pressure supplied to and released from friction elements for selectively changing power transmission routes of a transmission mechanism; wherein said operating pressure control circuit comprises: a plurality of shift valves for changing supply and release channels for supplying and releasing the operating pressure to and from said friction elements according to the selected gear position; first signal pressure generating means for supplying and releasing a signal pressure for controlling shift positions of said shift valves; shift control means for controlling said first signal pressure generating means according to the selected gear position; second signal pressure generating means for supplying a low speed range signal pressure if a low speed engine brake range is manually designated; first fail range achieving means for achieving a lowest speed gear position at which the vehicle is driven with the engine brake being operable if said shift control means fails and if said second signal pressure generating means supplies a low speed range signal pressure; and second fail range achieving means for achieving a predetermined gear position other than low speed gear positions if said shift control means fails and if said second signal pressure generating means does not supply said low speed range signal pressure.