| 摘要 |
A hydraulic control system for an automatic transmission including a plurality of frictional elements associated with respective transmission speeds. The hydraulic control system includes a hydraulic fluid source, a line pressure/reducing pressure producer, a shift controller for controlling a shift mode, a hydraulic controller for converting line pressure fed from the shift controller into duty-controlled drive pressure or duty-controlled reverse pressure to improve shift quality and responsiveness, and a pressure distributer for selectively distributing line pressure from the shift controller and duty-controlled drive or reverse pressure from the pressure controller to each frictional element for each speed ratio while being controlled by line pressure from the shift controller. The pressure distributer includes a control switch valve which supplies duty-controlled drive pressure from the pressure controller to one of frictional elements operated in fourth speed ratios as operating pressure during a shift control, and switches the duty-controlled drive pressure to line pressure from the shift controller after the shift control is completed.
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