CONTROL SYSTEM FOR AUTOMATIC TRANSMISSION

摘要

A control system for an automatic transmission includes a main hydraulic line to which hydraulic pressure is introduced when a manual valve takes a reverse range position for reverse movement. First and second hydraulic lines are separated from the main hydraulic line, a first frictional element is connected with the first hydraulic line, and a second frictional element is connected with the second hydraulic line. An accumulator is disposed on the second hydraulic line, a shift valve is disposed on the second hydraulic line closer to the second frictional element than the accumulator, and a first drain port is formed on the manual valve for draining hydraulic fluid from the main hydraulic line when the manual valve is shifted from the reverse range to another range. A spool is disposed in the shift valve for moving to a position to shift the shift valve so that the second line is interrupted by the shift valve and divided between a second frictional element line and an accumulator line. A second drain port is formed in the shift valve for draining the hydraulic fluid in the second frictional element line when the spool moves to the position where the shift valve interrupts the second hydraulic line between the second frictional element line and the accumulator line. A shift shock can be suppressed in a shifting operation involving the reverse range.