The statements in this section merely provide background information related to the present invention and may not necessarily constitute prior art.
A conventional differential transmission compensates speed differences between the two output shafts, with the distribution of the torques resulting from the geometry, in particular from the number of teeth of the gears in the differential transmission. A differential transmission unit having an active variation of the torque distribution furthermore permits a direct influencing of the torque distribution. On use as an axle differential, for example, additional drive power can thus be supplied to the faster rotating outer corner wheel. An intervention is thus made in the driving dynamics of the vehicle. One therefore also speaks of “torque vectoring”.
Such differential transmission units can be arranged both as an axial differential (between the wheels of an axle) and as an interaxial differential (between two driven axles). An embodiment as an axial differential is known from DE 39 00 638 C2. The clutches there are arranged on a lay shaft which is driven by the input member via a first drive connection. A respective second drive connection leads to the axis shafts from each of the two clutches. Gears which effect a low step-up ratio overall serve for the drive connection, whereby an additional torque is supplied with a more or less closed clutch of the respective axial shaft. The low step-up ratio makes gears of approximately equal size necessary, of which those of the first drive connection have to be designed for a very high torque. This differential transmission unit becomes heavy and bulky due to this and due to the lay shaft arranged in parallel at some distance. It thus substantially increases the weight of a motor vehicle and cannot be accommodated in the tightly dimensioned space in the axial region.