Abstract: A shift control apparatus for controlling shifting actions of an automatic transmission including a hydraulically operated frictional coupling device having a hydraulic cylinder which is supplied with a working fluid when the frictional coupling device is engaged, the shift control apparatus including a transient-hydraulic-pressure control device operable to control a transient value of a hydraulic pressure in the hydraulic cylinder according to an electric signal, upon releasing of the frictional coupling device, and an accumulator having a back-pressure chamber a back pressure of which is controllable, and an accumulator chamber connected to the hydraulic cylinder of the frictional coupling device and operable to control a transient value of the hydraulic pressure in the hydraulic cylinder, when the frictional coupling device is engaged with the working fluid being supplied to the hydraulic cylinder, and a back-pressure increasing portion operable to increase the back pressure in the back-pressure chamber o

Abstract: A shift control apparatus for controlling shifting actions of an automatic transmission including a hydraulically operated frictional coupling device having a hydraulic cylinder which is supplied with a working fluid when the frictional coupling device is engaged, the shift control apparatus including a transient-hydraulic-pressure control device operable to control a transient value of a hydraulic pressure in the hydraulic cylinder according to an electric signal, upon releasing of the frictional coupling device, and an accumulator having a back-pressure chamber a back pressure of which is controllable, and an accumulator chamber connected to the hydraulic cylinder of the frictional coupling device and operable to control a transient value of the hydraulic pressure in the hydraulic cylinder, when the frictional coupling device is engaged with the working fluid being supplied to the hydraulic cylinder, and a back-pressure increasing portion operable to increase the back pressure in the back-pressure chamber o

Abstract: A hydraulic servo-mechanism for an automatic transmission, including a hydraulic servo for applying a band brake to engage a band to a drum. The hydraulic servo includes a rod which is selectively positionable to an apply position for applying the band brake, a standby position in which the rod is retracted by a predetermined extent in a release direction from the apply position, and a retracted position in which the rod is further retracted in the release direction from the standby position to release the band brake.

Abstract: An automatic transmission control apparatus has first and second hydraulic servos for engaging forward and reverse driving friction engaging elements, respectively, a fluid pressure control unit, a range shift detector, and an electronic control unit. When the forward driving range is selected, the fluid pressure control unit supplies a forward driving range pressure to the hydraulic servo via a changeover valve operated by a signal pressure from a normal open-type solenoid valve, when the signal pressure is drained. When the reverse driving range is selected, the electronic control unit outputs a signal to magnetize the solenoid valve. The solenoid valve is thus turned on to discontinue the drain. The control apparatus thus prevents low pressure in the reverse driving range pressure to prevent delay of engagement of the clutch.

Abstract: An automatic transmission control apparatus has a clutch, a hydraulic servo for the clutch, a fluid pressure control unit, a range shift detector, and an electronic control unit. The fluid pressure control unit has a manual valve, a pressure regulating valve device, and a changeover valve device. The electronic control unit controls the changeover valve device and the pressure regulating valve device. Immediately after a shift to the forward driving range, the electronic control unit holds the changeover valve device in such a state that a forward driving range pressure is supplied without passing through the pressure regulating valve device. Then, the electronic control unit shifts the changeover valve device to such a state that a regulated pressure is supplied from the pressure regulating valve device, which has been switched to a pressure regulating state by the electronic control unit. This control operation precisely sets the fluid pressure changeover timing and the initial fluid pressure.