Fly-by-wire limp home and multi-plex system

Abstract

An electro-hydraulic control mechanism for use with a multi-speed transmission includes a pair of logic valves, which are manipulated during the ratio interchanges and the ratio establishment by aiding in the distribution of fluid pressure from a plurality of trim valves. The logic valves are retained in specific drive ranges in the event of electrical discontinuance.

1. An electro-hydraulic apparatus for a power transmission having a plurality of torque-transmitting mechanisms selectively engageable by said apparatus to provide six forward ratio ranges, said electro-hydraulic apparatus comprising:
 a supply of electrical power to activate said electro-hydraulic apparatus;  
 first and second logic valves each positionable to a latched position and an unlatched position;  
 first and second trim valves means  for providing maximum output pressure when said electrical power is discontinued;  
 third and fourth trim valves controlled by normally closed solenoid valves that have a minimum output pressure when said electrical power is discontinued;  
 said trim valves and said logic valves cooperating to provide control of the torque-transmitting mechanisms to establish said six forward ratios wherein said first trim valve is effective to maintain said first logic valve in said latched position during the first, second, third, and fourth of said forward ratio ranges, said second trim valve is effective to maintain said second logic valve in said latched position during the fourth, fifth, and sixth forward ratio ranges;  
 said first trim valve and said first logic valve being effective to maintain a first of said torque-transmitting mechanisms engaged during an electrical power discontinuance occurring in either said third or fourth ratio range, said second trim valve and said second logic valve being effective to maintain a second of said torque-transmitting mechanisms engaged during an electrical discontinuance occurring in said third ratio range, said second trim valve and said second logic valve being effective to maintain said second logic valve stroked and a third of said torque-transmitting mechanisms engaged during an electrical discontinuance occurring in said fourth ratio range, and said first trim valve, said first logic valve in said unlatched position, and said second logic valve in said latched condition cooperating to maintain said second torque-transmitting mechanism engaged during an electrical power discontinuance in said fifth ratio range; and  
 said electro-hydraulic apparatus being effective to maintain the transmission in third ratio range in the event of an electrical discontinuance during operation in either said first, second, or third forward ratio range, in said fourth forward ratio range during an electrical discontinuance during operation in said fourth range, and in said fifth forward ratio range in the event of an electrical discontinuance during operation in either said fifth or sixth ratio range.  
 
     
     
       2. The electro-hydraulic apparatus for the power transmission having the plurality of torque-transmitting mechanisms selectively engageable by said apparatus to provide the six forward ratio ranges, said electro-hydraulic apparatus defined in  claim 1  further comprising:
 means for urging said first and second logic valves to said latched position during an interchange from a neutral condition to said first forward range.  
 
     
     
       3. The electro-hydraulic apparatus for the power transmission having the plurality of torque-transmitting mechanisms selectively engageable by said apparatus to provide the six forward ratio ranges, said electro-hydraulic apparatus defined in  claim 1  further comprising:
 means for urging said first and second logic valves to said latched position during an interchange from a neutral condition to said first forward range and said means being discontinued during a ratio interchange from said fifth forward ratio range to said sixth forward ratio range whereby said first logic valve is moved to said unlatched position.  
 
     
     
       4. The electro-hydraulic apparatus for the power transmission having the plurality of torque-transmitting mechanisms selectively engageable by said apparatus to provide the six forward ratio ranges, said electro-hydraulic apparatus defined in  claim 1  further comprising:
 means for urging said first and second logic valves to said latched position during an interchange from a neutral condition to said first forward range, and said means being inoperative during an electrical discontinuance.  
 
     
     
       5. The electro-hydraulic apparatus for the power transmission having the plurality of torque-transmitting mechanisms selectively engageable by said apparatus to provide the six forward ratio ranges, said electro-hydraulic apparatus defined in  claim 1  further comprising:
 means for urging said first and second logic valves to said latched position during an interchange from a neutral condition to said first forward range, said means being discontinued during a ratio interchange from said fifth forward ratio range to said sixth forward ratio range whereby said first logic valve is moved to said unlatched position and said means being inoperative during an electrical discontinuance.  
 
     
     
       6. An automatic transmission control apparatus comprising:
   a source of fluid pressure;        an exhaust apparatus;        a first logic valve having a spring set position and a pressure set position;        a second logic valve having a spring set position and a pressure set position;        a plurality of trim valves for supplying fluid pressure to said logic valves, one of said trim valves being operable to supply fluid pressure to said logic valves to urge said logic valves to said pressure set position, said logic valves being effective to distribute fluid pressure to a plurality of torque transmitting mechanisms, said second logic valve being urged to said spring set position when a second of said trim valves is operated to engage a first of said torque transmitting mechanisms;        a diagnostic apparatus having a spring set condition and a pressure set condition for issuing a signal dependant on the operating condition of said torque transmitting mechanisms; and        said diagnostic apparatus being urged to said pressure set condition when said second logic valve is held in said spring set position and a first of said torque transmitting mechanisms is engaged and being in said spring set position when said first torque - transmitting mechanism is not engaged.     
     
     
       7. An automatic transmission control apparatus comprising:
   a source of fluid pressure;        an exhaust apparatus;        a first logic valve having a spring set position and a pressure set position;        a second logic valve having a spring set position and a pressure set position;        a plurality of trim valves for supplying fluid pressure to said logic valves, one of said trim valves being operable to supply fluid pressure to said logic valves to urge said logic valves to said pressure set position, said logic valves being effective to distribute fluid pressure to a plurality of torque transmitting mechanisms, said second logic valve being urged to said spring set position when a second of said trim valves is operated to engage a first of said torque transmitting mechanisms;        a diagnostic apparatus having a spring set condition and a pressure set condition for issuing a signal dependant on the operating condition of said torque transmitting mechanisms; and        said diagnostic apparatus being connected with said exhaust apparatus when said first logic valve is in said spring set position and said diagnostic apparatus is in said spring set position.     
     
     
       8. An automatic transmission control apparatus comprising:
   a source of fluid pressure;        an exhaust apparatus;        a first logic valve having a spring set position and a pressure set position;        a second logic valve having a spring set position and a pressure set position;        a plurality of trim valves for supplying fluid pressure to said logic valves, one of said trim valves being operable to supply fluid pressure to said logic valves to urge said logic valves to said pressure set position, said logic valves being effective to distribute fluid pressure to a plurality of torque transmitting mechanisms, said second logic valve being urged to said spring set position when a second of said trim valves is operated to engage a first of said torque transmitting mechanisms;        a diagnostic apparatus having a spring set condition and a pressure set condition for issuing a signal dependant on the operating condition of said torque transmitting mechanisms; and        said diagnostic apparatus being urged to said pressure set condition when said second logic valve is held in said spring set position and a first of said torque transmitting mechanisms is engaged, said diagnostic apparatus being connected with said exhaust apparatus when said first logic valve is in said spring set position and said diagnostic apparatus is in said spring set position, and said diagnostic apparatus being connected with said pressure source when both of said logic valves are in said pressure set position.     
     
     
       9. The automatic transmission control apparatus defined in  claim 8  further comprising:
   said diagnostic apparatus being connected with said exhaust apparatus when said first logic valve is in said pressure set opposition and said second logic valve is in said spring set position.