Patent ID: 7326144

Claim:
A transmission system for a vehicle, the transmission system including an input shaft connected to a differential mechanism, which has two output shafts, the two output shafts carrying first and second coaxially mounted sun wheels, respectively, of an epicyclic gear system which mesh with first and second sets of planet wheels, respectively, which mesh with first and second annulus wheels, respectively, gear ratios of the first sun wheel with the first set of planet wheels and the second sun wheel with the second set of planet wheels being different, each planet wheel being mounted to rotate independently about a respective planet shaft, the planet shafts being connected to a common carrier which is rotatably mounted coaxially with the first and second sun wheels, the first and second annulus wheels being connected together, the carrier being connected to a selectively operable speed changing means arranged to increase or decrease the speed of rotation of the carrier about an axis, the transmission system further including at least one sensor arranged to produce a signal indicative of an operating parameter of the vehicle or an engine and a controller connected to the sensor and to the speed changing means and arranged to operate the speed changing means in response to said signal.