Operation

OPERATION

The front-rear torque distribution ratio is determined by the of center differential's compound planetary gears and is varied by changing the degree of engagement of the hydraulically operated multiplate clutch that connects the center differential output elements according to driving conditions and road surface conditions. The torque distribution ratio is calculated using the following equations, which include torque distribution coefficients (determined by number of gear teeth), input torque to the center differential, and torque capacity of the multi-plate clutch as factors.







1. When the front wheel speed is higher than the rear wheel speed:
TR =0.543 x TI + TC
TF =0.457 x TI - TC

where
TR: Rear wheel output torque
TI: Input torque to center differential
TC Torque capacity of multi-plate clutch
TF: Front wheel output torque
0.543: Coefficient of rear wheel torque determined by number of gear teeth
0.457: Coefficient of front wheel torque determined by number of gear teeth







2. When the rear wheel speed is higher than the front wheel speed:
TR =0.543 x TI - TC
TF =0.457 x TI + TC


If the frictional resistance resulting from meshing of the planetary gears and sliding of rotational components are ignored, the torques distributed to the front and rear wheels are expressed by the following equations:
TR =[(ZP1 x ZS2) + (ZS1 x ZP2)] x TI
TF =[1 - (ZP1 x ZS2) + (ZS1 x ZP2)] x TI
where
ZP1: Number of teeth of 1st planetary gear
ZP2: Number of teeth of 2nd planetary gear
ZS1: Number of teeth of 1st sun gear
ZS2: Number of teeth of 2nd sun gear
TI: Input torque

If the number of teeth in each component is the same as that assumed in the equations, the following ratios are the calculation results of the equations shown above.
TR =0.543 x TI
TF =0.457 x TI

As a result, the front-rear torque distribution ratio of the compound planetary gear set without an adjustment by the multi-plate clutch is 45.7 : 54.3.