Drive line for a track-laying vehicle

Abstract

A tank engine drive shaft (1) drives respective tank track drive shaft (20, 30) by way of a continuously-variable ratio transmission variator (200), a transfer system (12, 13, 15) including coupling means (C1, C2, 16, 17), a cross shaft (18, 19) and respective summing epicyclic gears (7, 6). Steering of the tank is achieved by a steer variator (100) also driven (2, 3) by the engine, which outputs differential rotations as further inputs (82, 55) to the summing epicyclic gears (7, 6). The drive line operates in four distinct regimes: reverse, low I, low II and high, by means of an epicyclic gear brake (B), and clutches (H, C1 and C2). The two parts (16, 17) of the coupling means are made to rotate in opposite directions by the annulus (15) of the epicyclics. As the tank accelerates from rest in low I regime, with brake B applied and clutch C1 applied but clutch H disengaged, the cross shaft (18, 19) decelerates. At a predetermined forward speed, the cross shaft is stationary and the change to low II is effected synchronously. As the tank accelerates further forwards in low II regime, the cross shaft accelerates from rest in the opposite direction, with clutch C2 instead of clutch C1 engaged. The use of the same transfer system for both parts of the low regime enables the use of a smaller variator (200) for an equivalent performance.