Method and a system for controlling traction in motor vehicles with mechanical gearboxes

A system for preventing the slippage of the driving wheels (5) of a motor vehicle with a mechanical gearbox and a friction clutch, comprising:

• means (2, 3, 4, 10) for detecting the rate of rotation of the vehicle's engine, the vehicle's speed, the angular velocity of the driving wheels and the gear ratio engaged, the detector means being adapted to generate electrical signals indicative of the parameters detected,
• actuator means (7, 8, 9) for adjusting the rate of revolution of the engine, for adjusting the engagement of the friction clutch, and for applying a braking torque to one or both of the driving wheels, and
• an electronic control unit (1) supplied with the electrical signals generated by the detector means (2, 3, 4, 10) and arranged to compare these signals with corresponding reference parameters and consequently to pilot the actuator means (7, 8, 9) so as to automatically control and reduce the speed of rotation of the driving wheels (5) to below the slipping threshold by the following procedures:
• between zero speed and a first predetermined vehicle speed (V.sub.1):
• adjusting the engagement of the friction clutch, adjusting the rate of revolution of the engine, applying a suitable braking torque to one or both of the driving wheels;
• between the first predetermined speed (V.sub.1) and a second, higher predetermined vehicle speed (V.sub.2):
• adjusting the rate of revolution of the engine and applying a braking torque to one or both of the driving wheels (5);
• between the second predetermined speed (V.sub.2) and a third, higher predetermined vehicle speed (V.sub.3):
• adjusting the rate of revolution of the engine;
• between the third predetermined speed (V.sub.3) and a fourth, higher predetermined vehicle speed (V.sub.4):
• adjusting the rate of revolution of the engine with reduced sensitivity;
• the electronic unit (1) also being arranged to prevent the control being effected at speeds above the fourth predetermined vehicle speed (V.sub.4).