Hydraulic control system in automatic transmission and hydraulic control method in same

摘要

In a hydraulic control system for an automatic transmission comprising a hydraulic servomotor C-2 for a clutch or brake adapted to engage and disengage necessary rotary components of a planetary gear mechanism, and a select valve for selectively supplying hydraulic pressure to the hydraulic servomotor C-2 dependent on two transmission states, the select valve has two input ports selectively supplied with hydraulic pressure dependent on the two transmission states and one output port for outputting hydraulic pressure to the hydraulic servomotor C-2, a first orifice is disposed between the output port and the hydraulic servomotor C-2, and a second orifice is disposed on the same side as either of the two input ports. Upon an upshift from the 2nd to the 3rd speed in the D range condition, a shift valve is changed over such that the line pressure is supplied to one input port of the select valve via a line pressure output port and the second orifice to move a ball valve body in the select valve. Thus, the line pressure is supplied to the hydraulic servomotor C-2 via the output port of the select valve and the first orifice. In the R range condition, a manual valve is changed over such that its ports p and d are communicated with each other, while its port a is blocked off. The line pressure is hence supplied from the line pressure output port to another input port of the select valve for moving the ball valve body, so that the line pressure is supplied to the hydraulic servomotor C-2 via the first orifice. Therefore, at the time of an upshift from the 2nd to the 3rd speed, since the line pressure is supplied to the hydraulic servomotor C-2 while being restricted through both the second orifice and the first orifice, the clutch is gradually connected so as to prevent the occurrence of a shift shock. At the time of a shift into the reverse position, since the line pressure is supplied to the hydraulic servomotor C-2 while being restricted through only the first orifice, the clutch is more quickly connected so as to prevent a time lag in speed change.