Hydraulic control for automatic transmissions

摘要

The automatic transmission described for motor vehicles has a plurality of friction devices for the alternative interconnection of a plurality of rotating elements in a planetary gear train and a hydraulic circuit for controlling the friction device change-over process. The hydraulic circuit contains a control valve for generating the line pressure, a manually operated valve for optional change-over of the line pressure to the hydraulic circuit, a plurality of switching solenoids for direct control of the hydraulic pressure for the actuation of the friction devices on the basis of the operating conditions, when changing over, and a plurality of relay valves, which are controlled by the solenoid valves; the solenoid valves are controlled independently of one another on the basis of the operating conditions. With an arrangement of this type one accumulator suffices and the number of valves can be reduced so that the valve body can be of more compact design. In addition, a highly precise impact control is possible in all change-over conditions.