Control apparatus of an automatic transmission with a lock-up clutch

Claim 1

A control apparatus in an automatic transmission which defines four speed ranges and includes a fluid pressure source and a lock-up clutch which is lockable in response to a signal pressure to establish the fourth range, said lock-up clutch being lockable solely in the fourth range, said control apparatus comprising: first and second solenoid valves, first and second shift valves operably connected to said first and second solenoid valves, respectively, to be shifted thereby into opened and closed conditions, separate fluid supply passages connecting said fluid pressure source to said first and second shift valves, respectively, and an interconnecting passage interconnecting said first and second shift valves, said first and second solenoid valves being independently actuatable such that said first and second shift valves together define four distinct states corresponding to said four ranges, respectively, said second shift valve being hydraulically operably connected to said transmission in the third of said four states to shift said transmission from said second range to said third range while said first shift valve is hydraulically operably disconnected from said transmission, said first and second shift valves being interconnected by said interconnecting passage to conduct a fluid flow therebetween in the fourth of said four states such that said first and second shift valves and said interconnecting passage define a signal pressure passage connected to said pressure source for conducting said signal pressure to establish said fourth range.