SYSTEM AND METHOD FOR MINIMAL DRAINDOWN IN CVT

摘要

A hydraulic control system for a transmission is provided. The hydraulic control system provides a latching system to retain CVT clutch pressure and/or pulley pressure for one or more CVT torque transmitting mechanisms and/or CVT pulleys in a CVT transmission. Components of the hydraulic control system of the present disclosure may include blow off valves, such as ball check-valves, on the exhaust of the pulley control valves and the exhaust of the CVT clutch control valve(s), and a one-way valve, such as a supply ball check-valve, disposed adjacent to each of the fluid supply inlets of the pulley control valves and the fluid supply inlet of the CVT clutch control valve(s).

主权项

1. A hydraulic control system for a continuously variable transmission, the hydraulic control system comprising:
a source of pressurized hydraulic fluid configured to communicate pressurized hydraulic fluid via a supply line; a pulley control circuit configured to fill a plurality of pulleys with pressurized hydraulic fluid and axially move at least one pulley of the plurality of pulleys to adjust a speed ratio, the pulley control circuit including a pulley control valve assembly having a pulley valve inlet and a pulley valve outlet, the pulley valve inlet being in downstream fluid communication with the supply line, the pulley valve outlet being in fluid communication with the plurality of pulleys; and an inlet valve disposed in downstream fluid communication with the supply line, the inlet valve configured to selectively communicate fluid from the supply line to the pulley control valve assembly, the inlet valve being further configured to close to keep fluid pressure in the pulley control circuit when fluid pressure in the pulley control circuit exceeds fluid pressure in the supply line.