Patent ID: 8052563
Filing Date: 2011-11-08
Classification: F16H

Abstract:
1. An electro-hydraulic control system for a multi-speed transmission having a plurality of torque-transmitting mechanisms including a selectively engagable torque-transmitting mechanism engagable by application of fluid pressure to a dual-area piston with a first piston area and a second piston area, and a source of pressurized fluid, comprising: a shift valve movable between a stroked position and an unstroked position and including a spring urging the shift valve to the unstroked position; wherein the shift valve permits pressurized fluid in fluid communication with the first piston area to the second piston area when in the unstroked position such that pressurized fluid is applied to both of the piston areas to engage the torque-transmitting mechanism; and wherein the shift valve blocks pressurized fluid from the second piston area when in the stroked position such that the pressurized fluid is applied only to the first piston area to engage the torque-transmitting mechanism; a solenoid valve in fluid communication with the shift valve and energizable to thereby direct pressurized fluid to the shift valve acting on the shift valve with the spring to further urge the shift valve to the unstroked position; wherein the shift valve is urged by pressurized fluid acting on the shift valve against the spring to the stroked position only when the solenoid valve is not energized; and wherein the spring maintains the shift valve in the unstroked position when pressurized fluid is directed to the shift valve to act on the shift valve both against and with the spring.