阅读说明：本技术 用于车辆的冷却风扇的双电枢运动传递装置的转子 (Rotor of double-armature movement transmission device for cooling fan of vehicle ) 是由 P·波菲利 于 2017-05-24 设计创作，主要内容包括：一种用于电磁联接器的转子,包括：-由用于传输磁通量的铁磁材料制成的环形主体(131),其具有：--)沿轴向方向(X-X)向内延伸并且适合于与支撑轴(120)联接的同轴套筒(131b)；--)连续的圆周的非磁性内部凹槽(135),其沿着稍微大于所述套筒(132)的直径的直径形成于所述环形主体(131)的前表面中；--)至少一个非磁性外部凹槽(636),其至少部分地沿着与所述内部凹槽(135)同心的圆周布置并且具有包括于所述前表面的外直径与所述内部凹槽(135)的直径之间的直径；--)至少一个非磁性中间凹槽(637),其至少部分地沿着与所述内部凹槽(135)同心的圆周布置并且具有包括于所述非磁性外部凹槽的直径与所述内部凹槽(135)的直径之间的直径；--)在径向地包括于所述环形主体的外直径与所述径向外部非磁性凹槽的直径之间的转子区域与径向地包括于所述内部凹槽(135)的直径与所述中间凹槽(637)的直径之间的转子区域之间的装置,其用于使磁通量沿填充有非磁性材料(636a,637a)的凹槽的径向方向通过。(A rotor for an electromagnetic coupling, comprising: -an annular body (131) made of ferromagnetic material for transmitting a magnetic flux, having: - -) a coaxial sleeve (131b) extending inwardly in the axial direction (X-X) and adapted to be coupled with the support shaft (120); - -) a continuous circumferential non-magnetic internal groove (135) formed in the front surface of the annular body (131) along a diameter slightly larger than the diameter of the sleeve (132); - -) at least one non-magnetic outer groove (636) arranged at least partially along a circumference concentric with the inner groove (135) and having a diameter comprised between an outer diameter of the front surface and a diameter of the inner groove (135); - -) at least one non-magnetic intermediate groove (637) arranged at least partially along a circumference concentric with the inner groove (135) and having a diameter comprised between the diameter of the non-magnetic outer groove and the diameter of the inner groove (135); - -) means between a rotor region comprised radially between the outer diameter of the ring-shaped body and the diameter of the radially outer non-magnetic groove and a rotor region comprised radially between the diameter of the inner groove (135) and the diameter of the intermediate groove (637) for passing magnetic flux in the radial direction of the grooves filled with non-magnetic material (636a, 637 a).)

1. A rotor for an electromagnetic coupling, comprising:

-an annular body (131) made of ferromagnetic material for transmitting a magnetic flux, having:

- -) a front surface integral with the coaxial sleeve (131b),

- -) a coaxial sleeve (131b) extending in a longitudinal-axial direction (X-X) towards the rear side (P) and suitable for coupling with the supporting shaft (120 a);

-a radially outer edge of the annular body extending axially towards the rear side;

- -) a continuous circumferential internal groove (135) formed in the front surface of the annular body (131) along a diameter slightly larger than the diameter of the sleeve (131);

- -) at least one continuous outer groove (636) arranged along a circumference concentric with the inner groove (135) and having a diameter comprised between an outer diameter of the front surface and a diameter of the inner groove (135);

- -) a continuous intermediate groove (637) arranged along a circumference concentric with the inner groove (135) and having a diameter comprised between the diameter of the non-magnetic outer groove (636) and the diameter of the inner groove (135);

wherein:

the non-magnetic outer and intermediate grooves are filled with a solid non-magnetic material suitable for welding,

the method is characterized in that:

the rotor comprises passage means (639, 839, 739) for the passage of magnetic flux between:

a rotor region radially comprised between the radially outer edges of the front surfaces of the radially outer non-magnetic grooves; and

-a rotor region radially comprised between said inner groove (135) and a non-magnetic intermediate groove (637, 637a), said passage means (639; 839; 739) extending in a radial direction and being integral with an annular body (131) of said rotor.

2. A rotor according to claim 1, characterized in that the passing means (639) extending in a radial direction, integral with the rotor (631) and suitable for allowing the passage of magnetic flux (F1, F2) comprise a plurality of pins (639), the pins (639) being made of ferromagnetic material and being inserted inside corresponding radial holes (638), the radial holes (638) extending inside the body (131) of the rotor from the radially outer edge to a circular area comprised between the radially innermost groove (135) and the intermediate groove (637).

3. The rotor according to claim 1, characterized in that the passing means (839) extending in a radial direction, adapted to allow the passage of magnetic flux (F1, F2), comprise a ferromagnetic annular plate (839) applied to the rear surface of the annular body (131) via fixing means, such as screws (839a), and extending radially between a radially inner surface (131c) of the axially extending outer edge of the rotor and a circular area comprised between a radially innermost groove (135) and the intermediate groove (637).

4. The rotor according to claim 1, characterized in that the passing means (739) extending in a radial direction, integral with the annular body (131) and adapted to allow the passage of magnetic flux (F1, F2) comprise an annular plate (739), the annular plate (739) extending radially between a radially inner surface (131c) of an axially extending radially outer edge of the annular body and a circular area comprised between a radially innermost groove (135) and the intermediate groove (637), and being provided with an edge (739a) extending in an axial direction and arranged in contact with the radially inner surface (131c) of the axially extending outer edge.

5. The rotor according to claim 4, characterized in that the annular plate (739) is fastened to the annular body (131) by welding (740).

6. The rotor according to claim 4, characterized in that the annular plate (739) is fastened to the annular body (131) by gluing.

7. The rotor according to any of the preceding claims, characterized in that the non-magnetic filling material (136a) of the groove (135, 136, 137) has a thickness such that a clearance is left at the front face of the annular body in the axial direction.

8. A rotor according to any of the preceding claims, characterized in that the rotor is made of tempered magnetic steel.

9. The rotor according to any of claims 1 to 8, characterized in that a radially outer surface (131a) of the axially extending radially outer edge is formed as a means for receiving a rotational movement.

10. An electromagnetic friction coupling (200) includes a stationary electromagnet (210) having a coaxial winding (220) thereinA rotor inside which said electromagnet is housed, and two armatures (33; 34) concentric to each other,it is characterized in thatThe rotor according to any one of claims 1 to 10.

11. The friction coupling according to claim 10, characterized in that said armatures (33, 34) have different diameters.

12. The friction coupling according to claim 10 or 11, characterized in that said electromagnet (232) comprises two independent and concentric windings (232a, 232 b).

13. Device for transmitting motion to a fan (1) for cooling a coolant in a motor vehicle, comprising:

-support means (120a) for supporting said fan (1) by means of an idle bell-shaped member (1 a);

-a first electromagnetic coupling (200) comprising a rotor (131), a first armature (33) connected to the idle bell-shaped member (1a) by means of a second eddy-current coupling (300), a second armature (34) directly connected to the bell-shaped member (1a) supporting the fan (1), and the second coupling (300) being arranged between the rotor (131) and the bell-shaped member (1a), a fixed electromagnet (232) being inserted in the rotor (131),it is characterized in thatThe first coupling being a friction coupling according to any one of claims 10 to 13.

14. The device according to claim 13, characterized in that the electromagnet (232) is mounted by means of a support flange (12) on a ring of bearings (11) arranged between the rotation axis and the support flange (12) joined to the base (10) of the engine.

15. The device according to any one of claims 13 and 14, characterized in that said second coupling comprises a first portion (310) engaged with a flange (40) connected to said first armature and a second portion (320) engaged with a bell-shaped member (1a) of said fan (1).

16. The device according to claim 15, characterized in that said first portion (310) of the coupling comprises a ring (313) made of magnetic material for housing a permanent magnet (214).

17. Device according to claim 15 or 16, wherein said second portion (320) of the coupling comprises a ring (321) made of conductive material and joined together with said bell-shaped member (1a), said bell-shaped member (1a) being made of non-magnetic material.

18. The device according to any one of claims 13 to 17, characterized in that the support means (120a) is stationary and the rotor (131) is mounted on the support means by means of a bearing (11) arranged between the rotor (131) and the support means.

19. A device according to any one of claims 13 to 17, characterised in that the support means forms an extension of a drive shaft of the vehicle and is locked with the rotor to transmit rotary motion to the rotor.

Technical Field

The present invention relates to a rotor of a device for transmitting motion to a fan for cooling coolant in a vehicle, and to a dual-armature motion transmission device provided with such a rotor.

Background

It is known in the art relating to cooling of coolant contained in a radiator of a motor vehicle that it is necessary to push air onto said radiator in order to dissipate heat from the liquid as quickly as possible on the outside, this forced air flow being obtained by rotating a fan, which is usually mounted on the shaft of a water pump, or on a drive shaft, or on a stationary driven shaft carrying a pulley receiving motion from a belt operated by said drive shaft.

It is also known that the fan must be made to rotate only when a certain predetermined water temperature is reached, which is detected by a thermostat operating an electromagnetic friction coupling, the closure of which causes the rotation of the fan.

In addition to conventional devices of the so-called "on/off" type, such devices are also required in the case of specific operating requirements: the device is capable of operating the fan so that it can rotate at the following speeds:

-at a lower speed than the speed of the drive shaft, to perform cooling under lower external temperature conditions;

at a speed equal to or even greater than the speed of the drive shaft, at higher external temperatures or during use under critical conditions leading to overheating of the engine;

at particularly low temperatures (in which case further cooling is useless or even harmful), at zero speed, i.e. with the fan not rotating at all and remaining in an idle state with respect to the drive shaft.

Examples of such devices are known from EP 1,746,266 in the name of the applicant, said EP 1,746,266 describing such devices: the device comprises an electromagnetic clutch arranged between an actuating rotor and a fan, said clutch transmitting motion to the fan via two armatures which can be recalled (recallable) separately and selectively for the rotor by exciting the electromagnet to activate the clutch.

With reference to fig. 1, 2 and 3, an example of a rotor 30 according to the prior art comprises an annular body 31 integral with a coaxial sleeve 31a, said coaxial sleeve 31a extending towards the rear P and being suitable for engaging with a supporting drive shaft 20a (fig. 3) for transmitting the motion to the fan 1.

Preferably, the outer surface of the radially outer edge of the annular body has an annular groove 31b formed therein, said groove 31b for forming the annular edge of the rotor in the manner of a pulley adapted to engage with a drive belt driven by the drive shaft of the vehicle for receiving the rotary motion.

The annular body 31 has in its front surface a circumferential groove 35 formed along a diameter slightly larger than that of the sleeve 31b and filled with a non-magnetic material 35 a; and radially outer slots 36, 37 adapted to form, upon suitable excitation of one or more coils of the electromagnet 32, magnetic fluxes that diverge along the respective first and second inner armatures 33, 34 (fig. 2, 3).

These devices, although functioning properly, produce some drawbacks associated with their use on certain types of engines subjected to high vibrations that cause breakages in certain areas of the rotor, leading to the breakage of the components and the interruption of the magnetic circuit, the flow of which causes the armature to be recalled against the rotor, and the stopping of the vehicle.

DE 102004042687 also discloses a rotor which, in order to solve this problem, envisages filling the circumferential slots with a non-magnetic material; however, with this solution magnetically isolated annular regions are created and these prevent the magnetic flux to follow a radial path from the outermost diameter towards the innermost diameter. Thus, this configuration prevents operation of the rotor in the case where the fan is controlled by an electromagnetic coupling having a single electromagnet and a double armature.

Disclosure of Invention

The technical problem provided is therefore that of providing a rotor for a device for transmitting a rotary motion to a fan for cooling a coolant in a motor vehicle, which rotor is not, or at least less, subject to damage caused by specific vibration conditions caused by the engine on which the motion-transmitting device is mounted; and at the same time ensure a proper passage of the electromagnetic flow from the radially outermost region to the radially innermost region.

With respect to this problem, the rotor should also conveniently have a small diametric dimension and a small axial thickness, while maintaining high torque transmission capability to operate a larger sized fan.

Another object of the present invention is to develop a device for transmitting a rotary motion to a fan for cooling a coolant in a motor vehicle, which is provided with such a rotor and which enables the fan to rotate at a speed different from the speed of the drive shaft and determinable according to the actual cooling requirements of the engine, which has compact dimensions without high and expensive projecting rotating masses and forms few expensive components.

According to the invention, these technical problems are solved by a rotor for a device for transmitting motion to a fan for cooling the coolant of a motor vehicle according to the features of claim 1 and by an electromagnetic friction coupling according to claim 10 and by a device for transmitting motion to a vehicle cooling fan equipped with such a friction coupling according to the features of claim 13.

Drawings

Further details may be obtained from the following description of non-limiting examples of embodiments of the invention, provided with reference to the accompanying drawings, in which:

FIGS. 1a-1b: a schematic perspective view, respectively from the rear and from the front, of a rotor according to the prior art, with a radially inner armature of a motion-transmitting device, schematically shown in fig. 2;

FIG. 2: a schematic view, partly in section, of a rotor according to the prior art applied to a double-armature electromagnetic friction coupling for transmitting motion via the double armature;

FIG. 3: a schematic vertical section through a motor vehicle fan with a motion transmission device according to the prior art;

FIG. 4: a front view of a rotor according to the present invention is shown;

FIG. 5: a cross-sectional view, taken along a vertical radial plane, of the rotor according to fig. 4 is shown, which shows a first embodiment of the rotor according to the invention;

FIG. 6: a cross-sectional view, taken along a vertical radial plane, of the rotor according to fig. 4 is shown, which shows a second embodiment of the rotor according to the invention;

FIG. 7: a cross-sectional view, taken along a vertical radial plane, of the rotor according to fig. 4 is shown, which shows a third embodiment of the rotor according to the invention;

FIGS. 8a-8c: a schematic partial cross-sectional view showing a first embodiment of the rotor according to the invention in partial detail associated with the armature of the electromagnetic friction coupling in idle, first rotational speed and second rotational speed states, respectively;

FIGS. 9a-9c: a schematic partial cross-sectional view showing a second embodiment of the rotor according to the invention in partial detail associated with the armature of the electromagnetic friction coupling in idle, first rotational speed and second rotational speed states, respectively;

FIGS. 10a-10b: according to the present invention is shown in idle, first rotational speed and second rotational speed states, respectivelyA schematic partial cross-sectional view showing a partial detail of the third embodiment of the rotor associated with the armature of the electromagnetic friction coupling; and

FIG. 11:a schematic vertical sectional view of a motor vehicle fan with a motion transmission device according to the invention is shown in an idle state.

Detailed Description

For the purposes of description, the layout shown below by way of example will refer to a pair of reference axes, namely a longitudinal axis X-X (coinciding with the axis of rotation of the rotor for ease of description) and a transverse/radial axis Y-Y, as well as a front side a and a rear side P opposite each other in the axial-longitudinal direction X-X.

Referring to fig. 4, 5, 6, 7, the rotor according to the present invention includes:

an annular body 131 integral with a coaxial sleeve 131b, said coaxial sleeve 131b extending towards the rear side P and being designed to couple with a fixed support shaft 120a shown by way of example in fig. 11.

Preferably, the radially outer edge of the annular body extends towards the rear portion P and has an outer surface provided with movement receiving means, for example an annular groove 131b for forming a pulley suitable for engaging with a drive belt 3 driven by the drive shaft and preferably of the toothed type.

According to the invention, it is envisaged that the annular body 131 of the rotor always comprises (fig. 4): a circumferential groove 135 formed along a diameter slightly greater than the diameter of the sleeve 131 and filled with beads 135a made of non-magnetic material, said beads 135a being applied generally by welding and suitable for interrupting the continuity of the magnetic flux passing through the rotor; as will be seen more clearly below, the groove 135 is designed to interrupt the passage of the magnetic flux generated by the electromagnet 232, which will be forced through the thickness of the rotor in such a way as to continue along the armature opposite the rotor and close the magnetic circuit for recalling said armature;

a continuous circumferential outer groove 636 arranged along a first circumference between the rotor's inner groove 135 and outer annular rim and filled with a non-magnetic material 636a providing further reinforcement;

a continuous circumferential intermediate groove 637 arranged along a circumference between the inner groove 135 and said outer groove 636 and then filled with a non-magnetic material 637a providing further reinforcement.

According to a first embodiment of the rotor of the invention (fig. 5), it is also envisaged:

the rotor annular body 131 has a plurality of radial holes 638 angularly spaced from each other to receive respective pins 639 made of ferromagnetic material and radially extending from such circular area: the circular area is comprised between the radially outer edge of the rotor and the circular area comprised between the radially innermost groove 135 and the middle groove 637.

Fig. 6 shows a second embodiment of a rotor according to the invention, comprising:

a ferromagnetic annular plate 839 applied on and fixed to the rear end surface of the annular body 131 by suitable fixing means, such as screws 839a, and extending radially between the radially inner surface 131c of the radially outer edge of the rotor and a circular area comprised between the radially innermost recess 135 and the intermediate recess 637.

The annular plate 839 is designed to short circuit the non-magnetic intermediate groove 637 and the outer groove 636 in order to close the magnetic return path F1 to recall the inner armature 33 (fig. 9 b).

The axial thickness of the annular plate is such as to determine the passage of a magnetic flux sufficient to ensure the force required for recall of the internal armature, for example equal to the passage of a magnetic flux determined by the pin 639 of the previous embodiment.

As shown in fig. 7, a third embodiment of the rotor according to the invention is envisaged, said embodiment comprising in this example an annular plate 739, which extends radially between the inner surface 131c of the radially outer edge of the rotor 130 and a circular area comprised between the radially innermost groove 135 and the intermediate groove 637; the plate 739 is provided with an edge 739a extending in the axial direction towards the rear side P and arranged in contact with the radially inner surface 131c of the axial extension of the radially outer edge of the rotor; by this configuration, the passage of the magnetic flux is further improved, which obtains a larger passage area when passing through the two axial elements in order then to continue radially along the annular plate.

Preferably, plate 739 is applied to the rotor via: this device is designed to prevent any deformation of the plate 739, thus ensuring the planarity of the plate and therefore the best possible contact between the two components for the passage of the magnetic flux. Examples of these devices are shown in fig. 6 by spot welds 740.

In the case of fig. 6 and in the case of fig. 7, annular body 131 preferably has a recess 741 extending in a radial portion comprised between outermost recess 636 and innermost recess 637; along this portion, the plates 639, 739 do not contact the rotor, and therefore the dispersion of the magnetic flux in the annular region that is not affected by the recall to the innermost armature can be reduced.

By this solution, another advantage is also obtained from the fact that: omitting the screws enables the groove 636 with the associated non-magnetic material 636a to be arranged closer to the annular edge of the rotor, allowing a better use of its front surface area, which for the same radial dimension increases the useful magnetic flux and thus the torque applicable to the armature, or for the same torque, the radial dimension of the rotor can be reduced.

Preferably, the rotor is formed of tempered magnetic steel to reduce hysteresis once excitation of the electromagnets is released.

Preferably, the beads 636, 637 filling the slots 136, 137 have a thickness such as to leave a void in axial thickness on the front face of the rotor; this therefore ensures an iron/iron contact between the surface of the rotor and the armature of the electromagnetic friction coupling 200, said electromagnetic friction coupling 200 being designed to ensure the calculated magnetic circuit and thus the torque that can be transmitted via the friction coupling.

Fig. 11 shows an embodiment of an electromagnetic coupling 200, said electromagnetic coupling 200 comprising an electromagnet 232 fixed to a fixed component 10 and having coaxial windings; the electromagnet is coaxially inserted at least partially inside the rotor 131 according to the invention.

The two armatures, namely the radially innermost armature 33 with the smaller diameter and the radially outermost armature 34 with the larger diameter, are located outside the rotor and in a position opposite the electromagnet and are connected to the load to be rotated, respectively, via respective elastic elements, in this example elastic membranes 33a, 34a with different elasticity, which will be described in detail below.

According to a preferred embodiment, the windings of the electromagnet comprise two windings, preferably concentric, namely one winding 232a and one winding 232b, suitable for conducting two different amounts of current and thus for generating two different magnetic fluxes to recall the corresponding armature against different resistances of the respective elastic membrane.

Alternatively, the electromagnet may be implemented with a single coil PWM-controlled by reducing the power supply in order to determine the correct excitation for attracting only the inner armature 33 or both armatures 33, 34.

Although not shown, it is contemplated that the membrane may be replaced by a spring.

In the device for transmitting motion to the vehicle fan 1 shown, the cooling fan 1 is attached to a support bell-shaped member 1a (arranged on a bearing 1b mounted on a fixed shaft 120a of the vehicle) so as to be coaxial with the axis of rotation of the fixed shaft 120 a.

Said fixed shaft 120a also has mounted thereon a rotor 131 according to the invention rotationally locked therewith-a third embodiment of the invention shown in fig. 7-which forms a rotating element of a first coupling 200, said first coupling 200 comprising an annular electromagnet 232 concentric with the rotor 131 and mounted on an outer ring of a bearing 11, said bearing 11 being arranged between the shaft 120a and the sleeve 131b of the rotor;

the electromagnet 232 is electrically connected by wires to a control unit having, for example, a control logic management based on the measurement of the temperature of the cooling fluid.

The first armature 33 is arranged on the side opposite to the electromagnet 232 with respect to the rotor 131 and is connected to an annular flange 40 engaged with the outer ring 21a of the bearing 21, said bearing 21 in turn being keyed onto the shaft 120 a.

The connection between the armature 33 and the flange 40 is achieved via a resilient element 33a, said resilient element 33a being designed to allow axial movement of the armature 33 but to prevent relative rotation of the armature and the flange 40.

The flange 40 also carries a first portion 310 of a second coupling 300, another portion 320 of the second coupling 300 being joined together with the bell member 1a of the fan 1.

In more detail, said first portion 310 of the coupling comprises said flange 40, which is made of magnetic material and which carries a permanent magnet 314.

The second coupling part 320 is formed by a ring 321, which ring 321 is arranged diametrically opposite the permanent magnet 314 and is made of a conductive material and is joined together with a bell-shaped member 1a, which bell-shaped member 1a is also made of a non-magnetic material, such as die-cast aluminium.

With this first configuration, the first portion 310 of the second coupling forms a rotor portion for generating the movement of said coupling, which generates eddy currents in an inductive cascade via the driven ring 321 driven in rotation by means of the flange 40 and the permanent magnets 314, causing the rotation of the bell-shaped member 1a and therefore of the fan 1.

A second armature 34, concentric with the first armature 33, is arranged radially further outwards with respect to the first armature and is connected to the bell-shaped member 1a via an elastic element, for example an elastic membrane 34a, said elastic membrane 34a being designed to allow axial movement of the armature 34 but to prevent relative rotation of the armature and the bell-shaped member.

The membrane 34a of the second armature 34 has a greater resistance in the axial direction than the resistance of the membrane 33a of the first armature, so a greater recall force is required to allow the armature to move towards the rotor.

The second armature 34 also has a radial dimension much greater than that of the first armature 33 and a plurality of circular arc-shaped slots 34b arranged along the same circumference and designed to cause a deviation of the magnetic flux, so as to increase the magnetic attraction force and therefore the torque that can be transmitted from the rotor to the armature and therefore to the fan 1.

By this configuration and by any of the embodiments of the rotor according to the invention, it is possible to obtain different desired rotation speeds of the fan 1 and in particular:

a) when the electromagnet 232 is not excited (fig. 8 a; 9 a; 10a) and therefore the friction coupling is disconnected, the movement of the drive shaft 20 is not transmitted to the armature 33 and/or 34, and therefore to the fan 1, which remains idle.

b) In a state where the electromagnet 232 is excited by the first winding 232b (fig. 8 b; 9 b; 10b) forming a circuit F1 for the magnetic flux, the magnetic flux transmitted from the electromagnet to the rotor 131 diverging from the annular groove 135 onto the first armature 33, causing only the recall of the armature 33 of the first smaller size, said armature 33 engaging the rotor 131 against the reduced resistance of the membrane 33a in the axial direction and transmitting the motion to the fan via a foucault (foucault) coupling 300; since the transmission is performed with the flange 40 and the bell member 1a sliding relative to each other, the bell member 1a rotates at a speed slower than the speed of the drive shaft 20.

c) In a state where the electromagnet 232 is excited by simultaneously exciting the first winding 232a and the second winding 232b (fig. 8 c; 9c, and (c); 10c) forming a loop F2 for the magnetic flux, the magnetic flux passing from the electromagnet through the rotor 131 being alternately deflected from the rotor to the armature 34 and again from the armature 34 back to the rotor via the series of outer slots 136 and the series of intermediate slots 137 of the rotor and the slots 34b of the second armature 34, and again closing on the first armature, as described for the first magnetic flux loop F1; in this way, the second armature 34 is also recalled and engages the rotor 31 overcoming the resistance of the associated membrane 34a, transmitting the motion of the drive shaft directly to the bell-shaped member 1a and making the rotation speed of the fan the same as that of said drive shaft.

Although described with respect to an example (fig. 11) in which motion is transmitted to the rotor via a pulley connected to the rotor, such a case is also possible: in this case, said support means (120a) form an extension of the drive shaft of the vehicle (fig. 3) and are engaged together with the rotor 131 so as to transmit the rotary motion to the rotor 131.

It is therefore clear how the rotor according to the present invention solves the technical problem posed, as the hollow slots formed on the rotor are filled with non-magnetic material, achieving greater mechanical resistance, in particular to the vibrations generated by the engine of the vehicle on which the rotor is mounted, while simultaneously maintaining a high level of magnetic flux and therefore of torque that the device can deliver, both in the case of reduced excitation to recall only the innermost armature and in the case of complete excitation to recall both armatures.

Similar characteristic features distinguish the electromagnetic friction coupling and the double-armature device according to the invention, which are designed to achieve the required operations at several speeds and in idle condition with smaller axial and radial dimensions and a lower number of components, also avoiding the use of special bearings, reducing the associated production, assembly and maintenance costs.