Five-speed automatic transmission and hydraulic control system thereof

Abstract

A five-forward speed automatic transmission, includes: a torque convertor connected to an output shaft of an engine for changing and transmitting engine torque; an input shaft connected to an output member of the torque convertor; first, second and third planetary gearsets disposed between the input and output shafts so as to shift power transmitted to the input shaft in five-forward speeds and one reverse speed; a first clutch selectively connecting a sun gear of the second planetary gearset to the input shaft; a second clutch selectively connecting a sun gear of the first planetary gearset to the input shaft; a third clutch selectively connecting a planet pinion gear carrier of the first planetary gearset to the input shaft; a fourth clutch selectively connecting a sun gear and a planet pinion gear carrier of the third planetary gearset with each other; a first one-way clutch for ensuring that the sun gear of the first planetary gearset and a ring gear of the second planetary gearset rotate in a single direction; a second one-way clutch for ensuring that the sun gear of the third planetary gearset rotates in a single direction; a first brake for fixing the sun gear of the first planetary gearset relative to a housing; a second brake for fixing both the ring gear of the second planetary gearset and the sun gear of the first planetary gearset relative to a housing; and a third brake for fixing the sun gear of the third planetary gearset relative to a housing.