Abstract: In a system for the automatic control of form-locked clutches serving as differential lock in drive axles of a motor vehicle, in which control signals for a coupling actuator are formed by comparison of slippage signals with threshold values, both the engagement and the disengagement of the lock clutch are to be better adapted to the operating conditions which occur in practice. For this purpose, slippage sum signals (SSLR, SSFH) formed by integration of the speed differences (DFLR, DFVH) are compared with slippage sum thresholds (SSSLR1, SSSLR2, SSSVH1, SSSVH2) and the actuating time of the actuator is controlled as a function of further traveling conditions.

Abstract: A system for the control of couplings in the locking mechanisms or differentials of a drive train in an all-wheel-drive vehicle is disclosed. The drive train of a vehicle having at least two drive axles (4.times.4 vehicle) comprises, starting from the engine and transmission block 1, a power take-off with switchable coupling 2, a front axle differential with locking coupling 3, a rear axle differential with locking coupling 5, steering angle sensor 10, rotational speed sensors 11, status sensors 12 and actuators 13, 14, 15. The rotational speed sensors 11 are installed in proximity to the wheels 4, 6. To be able to automatically switch all the couplings in keeping with terrain conditions, a control system 18 having individual modules (21,24,25) for each coupling (2,3,5) is provided. The control modules (24,25) of the hierarchically lower couplings (3,5) also emit control signals for one or several hierarchically higher coupling(s) (2,5) before they actuate their own couplings (3,5).