Shift control system for automatic transmission

摘要

A hydraulic control system for an automatic transmission comprises a one-way valve arranged between a hydraulic line leading to a second speed apply chamber of a band brake and a hydraulic line leading to a fourth speed apply chamber of the band brake in such a manner as to allow fluid communication between them when a pressure dfferential takes place. The pressure differential takes place when the transmission upshifts from the first speed ratio to fourth speed ratio. Thus, during the 1-4 shift, a pressure build-up in the fourth speed apply chamber takes place in the same manner as a pressure build-up taking place in the second speed apply chamber under the control of a 1-2 accumulator valve.