Patent ID: 7766779

Claim:
A device for power transmission between a shaft of a heat engine and a shaft of wheels, this device having at least one electric machine that has a machine shaft, the shaft of the engine, the shaft of wheels and the machine shaft being connected through a mechanical assembly, this transmission device further having a switching device that includes a dog clutch, as well as a first and a second gear connected to the mechanical assembly, the dog clutch being capable of being displaced to selectively connect a first shaft among the shaft of the engine, the shaft of wheels and the machine shaft, with one of the first and second gears, the dog clutch having protrusions extending parallel to an axis of the first shaft, the gears having projections, these projections extending parallel to the axis of the first shaft, the protrusions of the dog clutch being designed to fit into the spaces between the projections of the gears, the dog clutch and the gears being such that they allow the dog clutch to engage simultaneously with both the first and second gears, the protrusions of the dog clutch being able to fit simultaneously into the spaces between the projections of the first gear and into the spaces between the projections of the second gear, such that two gear ratios of the transmission device can be engaged simultaneously, wherein said device comprises means to zero out the torque of a dog shaft carrying the dog clutch when the two gear ratios are engaged simultaneously.