Hydraulic circuit for automatic transmission having area controlled shift actuator valve with flow force compensation

An automatic transmission (10) that is adapted to translate torque from a prime mover to an output shaft, said automatic transmission (10) comprising:

• a plurality of gear sets and a plurality of synchronizers (24) that are adapted to coordinate the engagement of selected gear sets;
• a hydraulic circuit (88) including a source of pressurized fluid (82);
• a shift actuation valve (96) including a valve body (102) having a valve bore (104) and at least one inlet (108) in fluid communication with said source of pressurized fluid (82) and at least one outlet (110) in fluid communication with at least one synchronizer (24) for selectively controlling gear engagement, a valve member (114) moveably supported in said valve bore (104), a solenoid (104);
• said valve member (114) including at least one valve element (122) having an outer diameter (162) and a metering face (164), said metering face (164) adapted to control the flow of pressurized fluid between said inlet (108) and said outlet (110) of said valve body (102), said metering face (164) including a flow force compensating annular void (166) disposed adjacent said outer diameter (162) and defined by a lead angle α measured between said outer diameter (162) and a line intersecting said outer diameter (162) and tangential to said annular void (166);
• said solenoid (104) adapted to move said valve member (114) to produce a flow area through said shift actuation valve (96) that is a function of the current delivered to said solenoid (104) to deliver a predetermined amount of pressurized fluid to at least one synchronizer (24) to selectively control the actuation of the synchronizer (24) to select a predetermined one of the plurality of gear sets in the transmission.