Patent ID: 7881834

Claim:
Method of shifting gear ratios of a vehicle utilizing a power transmission device having a heat engine and an electrical machine, this electrical machine being connected firstly to the heat engine through a clutch and secondly to a shaft of wheels through a gearbox, said method comprising, in order to start the heat engine when both an order to start the heat engine and an order to perform a gear shift have been issued and the heat engine is off at a time the order to perform a gear shift is issued: (i) starting the heat engine using a starting system connected to the heat engine and mechanically independent of the electrical machine, while the vehicle is being powered by the electrical machine alone, (ii) performing the gear shift, wherein the performance of the gear shift comprises: canceling a detectable torque on the shaft of the electrical machine, making the rotation speed of the electrical machine converge toward a target speed before the new gear ratio is engaged, and engaging a new gear ratio, and (iii) coupling the heat engine and the electrical machine via the clutch after performing the gear shift, wherein, when the order to start the engine is prior to the order to shift gear ratios, and a time period between the prior order to start the heat engine and the subsequent order to shift gear ratios is less than a threshold time period (TS) corresponding to a time needed for the heat engine to start and to couple with the electrical machine, the method comprises: authorizing the heat engine to start, but delaying the coupling between the shaft of this heat engine and the shaft of the electrical machine as long as the new gear ratio has not been engaged, so that the starting system dissociates the starting of the heat engine from the gear shifting of the vehicle.