Fly-by-wire electro-hydraulic control mechanism for a six speed transmission

A fly-by-wire electro-hydraulic control mechanism for a power transmission having a plurality of torque transmitting devices selectively engageable by said control mechanism to provide six forward speed ratios including four lower speed ratios and two higher speed ratios, a neutral condition, and a reverse speed ratio, said electro-hydraulic control mechanism comprising:

• a main source of hydraulic fluid pressure including a variable pressure regulator valve having at least one bias area;
• a control source of control pressure receiving fluid from said main source and delivering a reduced control pressure;
• an electrical source of electrical control signals;
• a plurality of solenoid valves communicating with said control source and being selectively operable in response to signals from said electrical source trim control pressures, at least two of said solenoids being normally open to supply hydraulic pressure from said control source during a discontinuance of said electrical control signals and when said main source is supplying fluid;
• a first trim valve operable in response to said trim control pressure from one of said normally open solenoid valves to direct fluid from said main source to a first of said torque transmitting devices and to maintain said first torque transmitting device engaged during a discontinuance of electrical control signals when said transmission is in any of the six forward speed ratios and said main source is supplying hydraulic fluid;
• a second trim valve operable in response to said trim control pressure from another of said normally open solenoid valves to direct fluid from said main source;
• a third trim valve operable in response to said trim control pressure from a third of said solenoid valves for supplying a variable fluid pressure;
• a first logic valve having a spring set position and a pressure set position, said first logic valve being connected in fluid communication between said third trim valve and a second and a third of the torque transmitting devices;
• a second logic valve having a spring set position and a pressure set position, said second logic valve being in fluid communication between said second trim valve and a fourth of said torque transmitting devices, and also being in fluid communication with said main source, said control source, said first logic valve, and said bias area on said variable pressure regulator valve, said second logic valve being operable to direct hydraulic fluid from said control source to said bias area during said pressure set position, and being operable to deliver a variable fluid pressure from said third trim valve to said bias area when said first logic valve is in said pressure set position and said second logic valve is in said spring set position.