I don't see such designs before. But what I'm think is that if you add another differential to one of the original differential output shaft. If all the two differentials is basic design that distribute the torque equally, then you can get three same output torque.
Sam Shen
Clutch and Driveline engineer
Drive for the future
I suspect that adding another differential to one of the original differential output shafts will result in the power being split 50% / 25% / 25%. The objective is to obtain a 33% / 33% / 33% power split.
Maybe you need to use a non-symmetry differential at the first stage. Such as the central-differential in the 4wd system. It is mainly a plant gear system. But I think it is difficult for you to find a exsiting one with 33/66 distribution.....
Sam Shen
Clutch and Driveline engineer
Drive for the future
I looked into the planetary central differential used in 4W drives. They appear to split the power 25% / 25% /25% / 25% and if any two of the outputs were combined the resultant power output would be 25% / 25% / 50%. Brakes or clutches will change the ratios but they will result in friction.
There must be some 'unusual' gearing arraignment that will output the power 33% / 33% / 33%.
I'm a little confused, because almost all the central differential in the 4WD system only have 2 way output,which distribute the power to the front axle and rear axle. For a planet gear system, there is three in/out path which usually refer to the sun gear/ring gear/carrer. Maybe this system contain 3 or 4 planet gears, but this doesn't mean that the power is split into 3 path or 4 path. The power distribution is only determined by the gear ratio of the sysytem. The most popular design maybe about 40/60 to meet the weight distribution of the vehicle. In recent years, some high lever cars use electronic magnic torque clutch to achieve more accurate and flexible distribution instand of the tranditional mechnical gear system.
Sam Shen
Clutch and Driveline engineer
Drive for the future
I was not very clear. My belief is that the central differential will split the power 50/50 between it's 2 outputs. These 2 outputs will be the inputs to 2 additional differentials, and these differentials will split the power 50/50 between their outputs. This will result in a total of 4 final outputs, with each delivering 25% of the power.
A planetary gear will act as a differential but the gearing ratio will not change the power split of 50/50.
Clutches and brakes can be used to vary the 50/50 power split, however they will consume power and generate heat if subjected to continual usage.
One thing that has always baffled me about these unequal torque split centre differentials. The only way to do it that I can see is to have unequal input/output ratios to front and rear driveshafts through a suitable planetary arrangement.
How is it then possible to optionally completely lock the centre differential ? I just cannot see how you could lock something that has other than a 50/50 torque split unlocked.
Even if you did it by having different front and rear diff ratios (really the same thing) you would then be in real trouble if the centre diff was solidly locked.
Most trucks with double rear axles have a power divider differential on the forward rear axle. The power comes in from the drive shaft but instead of going to the front pinion it goes to a differential unit that splits power between the forward and rearward axles. The rear differential is a regular unit. The rest of the front unit is gear driven off the power divider. From there on it is a regular unit. The driver can lock the power divider so power goes to the front and rear axles equally. But side to side is still split and not locked together.
