Arrangement for detecting a critical driving torque in a motor vehicle

An apparatus for determining information representing a critical driving torque at a driving wheel of a motor vehicle having a plurality of driving wheels, comprising:

• driving torque sensors for determining driving torque information corresponding to the magnitude of the respective driving torque of the respective driving wheel, speed sensors for determining speed information corresponding to the magnitude of the respective speed of the respective driving wheel, a computation circuit for determining and supplying information on the critical driving torque, electric motors for individually driving the driving wheels, and torque control devices for separately controlling the electric motors,
• the computation circuit comprising means for:
• (a) causing, at least at one of the driving wheels, a temporary increase in driving torque, from its current driving torque, a predetermined guantity beyond that of the other driving wheels, wherein the predetermined quantity is selected from the group consisting of a predetermined fixed amount and a predetermined percentage of the current driving torque of this driving wheel,
• (b) determining a speed differential by comparing speed information determined from the driving wheel with increased driving torque by its respective speed sensor with the speed information determined from at least one of the other driving wheels, which have a relatively lower driving torque, by its respective speed sensor for the purpose of detecting slip,
• (c) performing a step, when the computation circuit determines the speed differential does not exceed a given permissible relative speed differential, wherein a wheel grip limit is not exceeded, selected from the group consisting of (i) transmitting a signal with the information that the temporarily increased driving torque is not critical and (ii) causing the driving torque to be increased again by a greater amount,
• (d) transmitting a signal representing the critical driving torque when the given permissible relative speed differential is determined by the computation circuit, and
• (e) determining the critical driving torque, when the computation circuit determines the speed differential exceeds the given permissible relative speed differential, wherein the wheel grip limit is exceeded, and transmitting the critical driving torque as a signal for the purpose of an iterative approximation to the permissible relative speed differential by repeated temporary increases in the driving torque wherein at least the first of the repeated increases is smaller than its respectively preceding temporary increase in the driving torque.