Patent ID: 8037989

Claim:
A hydraulic control system for actuating a torque transmitting device in a transmission, the hydraulic control system comprising: a sump for receiving a hydraulic fluid; a piezoelectric pump for pumping the hydraulic fluid from the sump to the torque transmitting device; a first fluid flow path that communicates the hydraulic fluid from the sump to the piezoelectric pump; a second fluid flow path that communicates the hydraulic fluid directly from the piezoelectric pump directly to the torque transmitting device; a third fluid flow path that communicates the hydraulic fluid directly from the second fluid flow path to the sump; an exhaust device within the third fluid flow path for selectively preventing the hydraulic fluid from communicating from the second fluid flow path to the sump; and an orifice located downstream of the exhaust device in the third fluid flow path, the orifice having a reduced cross-sectional area in order to control the flow of the hydraulic fluid from the torque transmitting device when the exhaust device is open.