Patent ID: 6319164
Filing Date: 2001-11-20
Classification: F16H,Y10T

Abstract:
An electro-hydraulic control for a transmission having a plurality of torque transmitting mechanisms for controlling the establishment of a reverse drive ratio, a neutral condition, and a plurality of forward drive ratios, said electro-hydraulic control comprising:a source of fluid pressure;first and second variable pressure solenoid valves that are controllable to establish variable output pressures;first, second, and third shift valves each having a control solenoid valve and a pressure chamber to urge the respective shift valve to a hydraulically on position when said respective control solenoid valve issues a pressure signal, and a spring member to urge each respective shift valve to a hydraulically off position when said respective control solenoid valve is not issuing a pressure signal, said first variable pressure solenoid valve being in continuous fluid communication with said first shift valve, and said second variable pressure solenoid valve being in continuous fluid communication with said second shift valve;a manual control valve moveable by an operator to a reverse position, a neutral position, and a forward position;said control solenoid valves each issuing a pressure signal to the respective shift valves to urge said shift valves to said hydraulically on position when said manual control valve is in said neutral condition and a first of the torque transmitting mechanisms being engaged by fluid pressure from said second variable pressure solenoid valve;said second shift valve having a pressure signal imposed thereon from said first variable pressure solenoid valve via said third shift valve and said manual control valve to assist said spring to urge said second shift valve to said hydraulically off position when said manual control valve is moved to said reverse position and to interchange the fluid pressure at the first torque transmitting mechanism from said first variable pressure solenoid valve to said second variable pressure solenoid valve and said first variable pressure solenoid valve being connected with a second of said torque transmitting mechanisms by a fluid flow path sequentially including said first shift valve, said third shift valve, said manual control valve, and said second shift valve when said manual control valve is in said reverse position and all of said control solenoid valves are issuing a pressure signal;said manual control valve being operable when moved from said reverse position to exhaust said pressure signal assisting said spring of said second shift valve; andsaid manual control valve being operable, when moved to said forward position, to connect said first variable pressure solenoid valve with a third of said torque transmitting mechanisms via said first shift valve, said third shift valve and said manual control valve.