Hydraulic control system for four-wheel drive torque tranfer mechanism for vehicle

摘要

A hydraulic control system for a four-wheel drive torque transfer mechanism for a vehicle, including an automatic transmission, a transfer mechanism having a two-wheel drive direct-coupling gear (H2), a four-wheel drive direct-coupling gear (H4) and a reduced-speed four-wheel drive gear (L4) and a hydraulic control circuit for controlling the transmission and the transfer mechanism. The transfer mechanism includes a reduction gear mechanism, a first output shaft, a second output shaft connected to the first output shaft by means of a linkage, a four-wheel drive clutch for rotatably connecting and disconnecting the first and second output shafts, a direct-coupling clutch for connecting and disconnecting the input shaft of the reduction gear mechanism and the first output shaft and a reduction brake for shifting the reduction gear mechanism into the reduced-speed mode. The hydraulic control circuit includes a modulator valve capable of supplying a fluid of a reduced pressure when the transfer mechanism is established in the four-wheel drive direct-coupling gear so that the coupling torque of the four-wheel drive clutch is reduced and supplying a fluid of an increased pressure when the transfer mechanism is established in the reduced-speed four-wheel drive gear so that the coupling torque of the four-wheel drive clutch is increased.