Automatic gearbox controller has failure mode devices for setting lowest gear if change control circuit fails in low gear mode, other than low gear if low gear mode not selected

摘要

The controller has an actuating pressure control circuit with a number of valves (VA,VB,VC) for applying and removing pressure to frictional elements, a first signal pressure generator (SA,SB,SC) for controlling valve positions, a change controller (41) for controlling the signal pressure generator, a second signal pressure generator (42) for applying a low gear mode signal pressure when a low gear engine braking mode is manually selected, a first failure mode device (VD,VE,50,63,..) for setting the lowest gear if the change control circuit fails and a low gear mode signal pressure is applied and a second failure mode device (VE,50,63,..) for setting a defined gear other than a low gear if the change control circuit fails and a low gear mode signal pressure is not applied.