English term or phrase: e-motoring | As indicated above, the method according to the invention also provides for, among the various operating modes, an operating mode of the so-called e-motoring type, i.e. in which the vehicle is solely operated by one electric engine, without any contribution of the internal combustion engine. In such phase, the internal combustion engine is off and the shaft thereof serves as a transmission shaft between the BAS unit, which is connected through the belt transmission to the upstream end of the internal combustion engine shaft, and the transmission of the vehicle downstream of the internal combustion engine, connecting the output end of the drive shaft with the wheels of the vehicle. In the known art of the mild-hybrid systems, such operating mode is generally avoided, in that it is deemed that the driving of the internal combustion engine shaft, with ensuing passive actuation of the pistons thereof, leads to a pumping effect which determines excessive losses and low performance. However the application of such solution to an internal combustion engine provided with a system for variable actuation of the intake valves, preferably of the MULTIAIR system described above, allows reducing the aforementioned pumping losses to a level sufficient to guarantee an operation with suitable performance Returning to the systems illustrated in figures 1 and 2, in both embodiments it is provided for that, in given operating conditions, the vehicle be solely operated by the electric machine EM ("e-motoring" condition). In a particularly preferred variant of the invention, which is described herein with reference to figure 6, the system is also capable of further reducing the losses due to the pumping effect during the e-motoring phase, causing a supplementary opening of the intake valves during the phase theoretically corresponding to the conventional exhaust phase. The use of the MULTIAIR system for obtaining an additional opening of the intake valves during the conventional exhaust phase is per se known for example from the previous document EP-A-1 936 132 of the applicant. The e-motoring condition is activated, according to the invention, in a condition in which the motor vehicle is stationary, to execute an "e-launch" strategy, i.e. a vehicle start in stationary condition using the electric propulsion alone and with the internal combustion engine off and driven by the BAS unit. Entry into the e-motoring condition with the vehicle moving is actuated in case of specific conditions of the vehicle (for example covering road sections with constant power delivered to the ground), the internal combustion engine (for example operation in low efficiency conditions), the electrical system (for example accumulators ACC1 and ACC2 with suitable charge conditions). Still according to the invention, when the aforementioned e-motoring operating condition is activated, the switching off of the engine is accelerated, with the aim of being able to promptly restart it in case of a change-of-mind of the driver. |
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