Patent ID: 6159128
Filing Date: 2000-12-12
Classification: B60W,F16H,Y10T

Abstract:
An automatic transmission control system for selectively activating friction coupling elements to change a power transmission path of a transmission gear mechanism and controlling locking pressure supplied to the friction coupling elements to provide a desired gear ratio between an engine speed of rotation and a speed of rotation of drive wheels, said automatic transmission control system comprising:pressure regulating means for regulating a locking pressure level of locking pressure to be supplied to a specific one of said frictional coupling elements;torque monitoring means for monitoring input torque transmitted to the transmission gear mechanism from an engine;gear shift monitoring means for monitoring an occurrence of an up-shift of the automatic transmission; andcontrol means for determining first, second and third target locking pressure appropriate to prevent the automatic transmission from causing a shift shock according to said input torque during said occurrence of an up-shift, said first target locking pressure being determined by a first function such as to increase with an increase in said input torque, said second target locking pressure being determined by a second function such as to be lower than said first target locking pressure for every said input torque while said input torque is in a first range greater than a first specified torque, and said third target locking pressure being determined by a third function such as to be higher than said first target locking pressure while said input torque is in a second range smaller than a second specified torque smaller than said first specified torque, controlling said pressure regulating means to provide said first target locking pressure during said occurrence of an up-shift when said torque monitoring means monitors said input torque indicating that the engine stays in a loaded state, controlling said pressure regulating means to regulate said locking pressure to said second target locking pressure lower than said first target locking pressure during said occurrence of an up-shift when said torque monitoring means monitors said input torque indicating an operational change of the engine from a no-loaded state to said loaded state and being greater than said first specified torque, and controlling said pressure regulating means to regulate said locking pressure to said third target locking pressure when said torque monitoring means monitors said input torque indicating an operational change of the engine from said no-load state to said load state and being smaller than said second specified torque.