System for transmitting motion between the shaft of an internal combustion engine of a motor vehicle and a group of auxiliary devices

1. A System for transmitting motion between the shaft of an internal combustion engine of a motor vehicle and a group of auxiliary devices provided with corresponding drive shafts and comprising an electrical machine capable of operating selectively as a generator and as a motor;

the system including:

at least one transmission belt for coupling the drive shafts of the aforesaid auxiliary devices to a pulley which can be coupled for operation to the shaft of the combustion engine; and

an electromagnetically operated clutch, for selectively controlling the coupling of the said pulley to the shaft of the internal combustion engine;

an overrunning clutch being interposed between the said pulley and the shaft of the internal combustion engine, such that when the angular velocity of the shaft of the internal combustion engine is, respectively, greater or less than that of the said pulley, said pulley is, respectively, rotated by the shaft of the internal combustion engine or made idle with respect to the said shaft;

the electromagnetically operated clutch being normally disengaged and de-energized;

the system additionally comprising control means designed to cause the energizing and engagement of the said clutch and the activation of the said electrical machine as a motor, while the internal combustion engine is stopped, in order to restart the internal combustion engine by means of the said electrical machine operating as a motor;

the said pulley having a hub fitted on an extension of the shaft of the internal combustion engine with the interposition of the said overrunning clutch; the pulley having a channel-shaped cross section with a concavity facing the internal combustion engine; the electromagnetically operated clutch comprising:

an excitation winding which is fixed to the internal combustion engine and which extends into the said concavity of the pulley, and

a ring of ferromagnetic material carried in an axially translatable way by a support element fixed with respect to rotation to the extension of the shaft of the internal combustion engine; the said ring facing an annular surface of the pulley on the opposite side of the pulley from the excitation winding; the said ring and/or the said annular surface of the pulley being capable of providing a frictional drive action;

the arrangement being such that the energizing of the said winding can cause the attraction of the said ring in the axial direction towards the said annular surface of the pulley and the consequent engagement of the electromagnetically operated clutch.

2. A motion transmission system according to claim 1 , in which at least one rotating element bearing is interposed between the hub of the pulley and the said extension of the shaft of the internal combustion engine, in parallel with the overrunning clutch.

3. A motion transmission system according to claim 2 , in which the overrunning clutch is positioned axially between two rotating element bearings fitted between the pulley and the said extension of the shaft of the internal combustion engine.

4. A motion transmission system according to claim 1 , in which the said electrical machine is a multi-phase asynchronous machine, and the said control means comprise a controlled inverter connected to the said electrical machine and to a rechargeable source of continuous voltage.