Quote:
Originally Posted by Dean
No it doesn't. If the clutch acts between the same two axis as the planetaries and effectively locks those two axis, the planetaries are no longer rotating and therefore not transferring any torque, the clutch is! The same as if it they were welded. 0% X35/65 = 0; 100% X 50/50 = 50/50.
Depending on the level of clutch engagement, you are somewhere between the two.
Anything that limits the rotation of any of the axis relative to any other axis inside the diff is going to affect there ability of the gear ratios to split the torque...
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Imagine the open planetary differential. The power comes into the diff on the planet gears. The planetary carrier is attached to the rear wheels, the sun gear is attached to the front wheels. When there are no wheels slipping, the tooth ratio between the planetary carrier and the sun gear determines that the torque coming into the system on the planet gears goes out 65% to the planetary carrier, and 35% to the sun gear.
Now, let's say the rear wheels are slipping. In this case, the power takes the path of least resistance, and the planet gears easily accelerate the planetary carrier, effectively robbing the sun gear of it's power. i.e. in order for the front wheels to receive power, the rear wheels must be pushing against something. And of course the opposite is true, if there is no traction up front, the sun gear will spin freely and prevent power from reaching the planetary carrier.
Now we toss in the clutch. The clutch engages when there is a speed difference between the planetary carrier and the sun gear. So, in our example case, where the rear wheels have lost traction, as the planetary carrier gets faster than the sun gear, it is effectively braked by the clutch, allowing the planet gears to transfer power to the sun carrier. The clutch acts as a replacement for the lost traction at the wheels. The settings of the DCCD controller simply change how much speed difference is allowed between the planetary carrier and the sun gear before the clutch engages.
So, let's take the extreme example of 100% DCCD lock, and no rear traction: The power comes in on the planet gears, which attempt to push the planetary carrier at 65% of the input torque and the sun gear at 35% of the input torque. There is no resistance at the rear wheels, so all the power attempts to go through the planetary carrier, but because there is no speed difference between the wheels "allowed" due to the DCCD setting, the clutch engages to prevent the planetary carrier from spinning freely, thus allowing power to reach the sun gear. So, in this case, the front wheels are seeing 35% of the input, and the rear wheels 0%, and the clutch 65% of the power which is being converted into heat/clutch wear in order to act like ground traction.
In practice, this interaction between the clutch and gears is very dynamic, and ever changing, but due to the gear ratios in the gearset, you're never splitting the maximum torque differently than 35/65. At least that's the best I can understand from the documents Mike dug up.