For more than a century the gearbox kept us jumping up and down from one ratio to the next
An upgrade was overdue
The DifferentialCVT is a combination of a differential with a CVT. It is a new solution to many problems
- No need to jump from one gear ratio to the next.
- Better use of the electric motor
- The system is reversible. Possibility to use dynamic braking.
- The output speed goes down to zero speed.
- Better gas mileage
- Less pollution. The CO2, CO and NOx are reduced to the strict minimum.
- Higher torque at low speed. Fully loaded trucks will be able to climb very steep hills fully loaded.
- Smaller and much cheaper to build.
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How it works
We start with a CVT (Continuously Variable Transmission)
By changing the distance between the pullies, we change the diameter of the belt and the speed ratio.
CVTs are used in many cars to move from one gear ratio to the next.
The CVT has a problem. Its speed range is very limited. It could make the speed of your car vary between 20 and 40 and that's not enough.
Moreover the output speed does not go down to zero.
To increase the range of the CVT we combine it with a differential.
- The input power from the motor (left) is divided into two channels
One channel in RED goes directly to the differential:
Va = Vinput
- The other channel in BLUE goes through a CVT (ratio K) and a set of gears (ratio G)
Vb = V input . K . G
- The differential recombines the two channels.
Vc = 2 Vb - Va
Vc = Vinput (2KG - 1)
Gear ratio G = 0.5 Output Speed Vc = V input (K-1)
When the CVT's ratio varies between 1 and 2 the output speed varies between zero and full speed.
The input from the motor is divided into two channels
- One channel goes directly to the differential
- The other channel goes through the CVT
The differential reconnect the two channels
Many different implementations
There are many ways to combine a CVT with a differential.
The CVT and the set of gears can be between the shafts A and B or between the shafts A and C
The gear ratio and the CVT's ratio can be adapted to any specific application.
Q: How come nobody thought of that before?
A: The simple ideas are the most difficult to find
Q: The paradox - How can you have an output shaft that does not turn when the input turns at 3000 RPM and all the mechanical parts stay connected.
A: The answer is in the differential. When the satellite gear move at half the speed on a sun gear (and in the same direction) the other sun gear does not move. The satellite gear just rolls over the sun gear without transmitting any torque.
Patents US 8,771,127 B2 - US 9,109,681 B2 - US 11,028,913 B2