Differential gear and control system for motor vehicles having a single driven axle and at least one undriven axle

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An illustrative embodiment of the invention will now be described more in detail with reference to the drawing.
The driven axle 1 of a motor vehicle which has a single driven axle, which preferably consists of the front axle, is provided with a differential gear 2, which can be locked by a differential lock 3 for improving the starting behavior of the vehicle.
Because the handling of the vehicle should not adversely be affected by the differential gear 2 when it is locked, the differential lock 3 is controlled to exert a restraining torque which decreases as the speed of travel of the vehicle increases from a standstill of the vehicle to a predetermined value.
FIG.
1 is a graph in which the restraining torque M is plotted against the speed of travel v.
It is apparent from that graph that the maximum restraining torque M.
sub.
max will be exerted when the vehicle is at a standstill or has the speed of travel v=O.
The restraining torque M decreases along the curve a as the speed of travel increases to a value v.
sub.
G.
The restraining torque becomes zero when the speed of travel has reached the value v.
sub.
G because the differential lock 3 is then disabled.
Alternatively the differential lock 3 may be controlled to exert a locking torque M which decreases from the initial restraining torque M.
sub.
max, which is exerted when the vehicle is at a standstill, along the curve b to a residual restraining torque M.
sub.
Rest, which will be exerted when the speed of travel has reached the value v.
sub.
G and which will be maintained constant even when the speed of travel exceeds the value v.
sub.
G so that handling of the vehicle will be influenced by said residual restraining torque at higher speeds of travel.
If the restraining torque is varied in dependence on the speed of travel of the vehicle in accordance with curve a or b, the high restraining torque which is exerted during the starting of the vehicle will ensure that the desired higher traction will then be obtained also, the decrease of the restraining torque as the speed of travel increases and the exertion of a residual restraining torque or a zero locking torque at speeds of travel above a predetermined value ensure that the differential lock will not adversely affect the handling of the vehicle at speeds of travel in excess of V