Patent ID: 7172524

Claim:
An automotive vehicle transmission system rated to receive a maximum â€œfullâ€ power applied to an input, the transmission system comprising: two epicyclic gearsets, each comprising a sun member and a carrier member carrying at least one planet member which is in driving engagement with the sun member and with an annular member, the carrier member of the first epicyclic gearset constituting the input to the transmission system and the carrier member of the second gearset constituting an output from the transmission system, two members of the first epicyclic gearset being directly connected to rotate with a respective member of the second epicyclic gearset, whereby the two carrier members are not directly connected together, and wherein the ratio of the internal diameter of the annular member to the external diameter of the sun member is between 2 and 4 for each of the two gearsets, and first and second motor/generators comprising respective first and second stators connected to ground and respective first and second rotors connected to respective members of the two epicyclic gearsets other than those constituting the input and the output, one of the first and second motor/generators being connected to rotate both sun members together or to rotate both annulus members together, the carrier member of one of the gearsets being connected to that one of the sun member and the annulus member of the other gearset which is not connected to the first or second motor/generator, electrical connections of the first stator being connected to electrical connections of the second stator, whereby, in use, electrical power is transferred between the first and second motor/generators, the transmission system being so arranged that, when the full-rated power of the transmission system is applied to the input, the power transferred between the first and second motor/generators changes progressively, as the speed of the output increases, from a first maximum at a first finite speed to zero at a second speed to a second maximum at a third speed to zero at a fourth speed and then to a third maximum at a fifth speed, the ratio of the fourth speed to the second speed being greater than 2.5:1.