FR3083389A1 - POLAR ROTOR WHEEL FOR ROTATING ELECTRIC MACHINE - Google Patents

Abstract

The present invention provides a pole wheel (31) for a rotary electric machine rotor, comprising a plate (32) extending transversely with respect to an axis (X) of rotation of the pole wheel and a plurality of claws (33) s extending from the tray in a substantially axial direction. The plate (32) has at least one cavity (39) intended to receive and cooperate with a fixing element (51) to fix a fan (25, 26) on the pole wheel (31).

Description

POLAR ROTOR WHEEL FOR ROTATING ELECTRIC MACHINE

The invention relates in particular to a polar rotor wheel for a rotary electrical machine, in particular of a motor vehicle.

The invention finds a particularly advantageous application in the field of rotating electrical machines such as alternators, alternator-starters or even reversible machines or electric motors. It is recalled that a reversible machine is a rotary electrical machine capable of working in a reversible manner, on the one hand, as an electric generator in alternator function and, on the other hand, as an electric motor for example for starting the heat engine of the motor vehicle .

A rotating electrical machine includes a rotor that rotates about an axis and a fixed stator surrounding the rotor. In alternator mode, when the rotor is rotating, it induces a magnetic field on the stator which transforms it into electric current in order to supply the electric consumers of the vehicle and to recharge the battery. In motor mode, the stator is electrically supplied and induces a magnetic field driving the rotor in rotation.

The rotor has a shaft extending in a direction defining an axis of rotation of the rotor and two pole wheels mounted on the shaft. Each pole wheel has a plate extending transversely to the shaft and a plurality of claws extending axially from the plate. Each plate has a first axial end face and a second axial end face from which the claws extend. The pole wheels are arranged so that their second axial end faces face each other in an axial direction and so that each claw of one of the pole wheels extends in a space defined between two adjacent claws of the other pole wheel.

The rotor also has two fans each mounted on the first axial end face of one of the pole wheels. The fans are mounted respectively on the pole wheels by welding and in particular by resistance welding. This method of fixing the fans to the rotor requires high electrical power and requires on the one hand to have dedicated electrical transformers and on the other hand to regularly change the electrodes which wear out quickly due to strong electric currents. In addition, the tests carried out at the end of assembly on some of the rotors of a production batch to guarantee the correct fixing of the fans in said batch are destructive. The rotors tested are therefore no longer usable. These constraints mean that this means of fixing the fans to the pole wheels by welding is very expensive.

However, any means of attachment cannot be used to attach a fan to a pole wheel. In fact, the attachment must be strong enough to support the speed of rotation of the rotor and the centrifugal force generated by this rotation and to generate a flow of cooling air driven by the fan without disturbing the magnetic field generated in the wheels. polar.

The present invention aims to avoid the drawbacks of the prior art.

To this end, the subject of the present invention is a pole wheel for a rotor of a rotary electric machine, the pole wheel comprising a plate extending transversely with respect to an axis of rotation of the pole wheel; and a plurality of claws extending from the tray in a substantially axial direction. According to the present invention, the plate has at least one cavity intended to receive and cooperate with a fixing element for fixing a fan on the pole wheel.

The present invention makes it possible to propose a means of fixing the fan to the pole wheel which is simple, inexpensive, does not require high electrical power, does not require destructive testing, allows good resistance to centrifugal force and does not disturb the magnetic flux of the rotor.

According to one embodiment, the cavity is located on a first axial end face of the plate opposite to a second axial end face of the plate from which extend the claws.

According to one embodiment, the pole wheel has several cavities. This improves the retention of the fan on the pole wheel and adapts it to different configurations of the pole wheel. For example, the pole wheel has as many cavities as there are claws.

According to one embodiment, the plate is divided into several delimited angular sectors, each by two straight lines passing respectively through the center of the plate and the two circumferential ends of the same claw or the two circumferential ends facing two adjacent claws, the sectors forming an alternation, in a circumferential direction, of angular sector with claw and of angular sector without claw. In this embodiment, the cavity is arranged in an angular sector devoid of claw. This makes it possible not to reduce the passage section of the magnetic flux towards the claw and thus to avoid saturation of the magnetic flux which can lead to a decrease in performance.

According to one embodiment, the cavities are located on the same circumference. This facilitates the manufacturing process of the pole wheel by simplifying the tool making the cavities. This also allows better balancing of the pole wheel.

According to one embodiment, the cavities are angularly spaced from one another at the same angle. This also improves the balancing of the pole wheel and simplifies its manufacture.

The cavity is located between an outer periphery and an inner periphery of the tray. The inner periphery of the plate is defined by an opening intended to receive a rotor shaft. The outer periphery of the plate is defined by the circumference of larger diameter of said plate, this circumference is here discontinuous. For example, the cavity is located closer to the outer periphery of the pole wheel than to the inner periphery. This increases the diameter of the cavity and thus improves the mechanical strength of the fan on the pole wheel.

According to one embodiment, the cavity is located in the part of the pole wheel having the smallest thickness in an axial direction.

In other words, the cavity is located in a portion of the plate arranged radially between a portion of the plate being in contact with a core and a portion of the plate being in contact with one of the claws of the pole wheel. This simplifies the manufacturing process of the pole wheel by facilitating the production of a counter support on a surface axially opposite the surface comprising the cavity when the latter is produced by forging.

According to one embodiment, the cavity has a cylindrical shape. This shape allows a cavity to be produced in a simple manner. Alternatively, the cavity can have any other type of shape such as a rectangular shape. This rectangular shape may include, in addition to a holding function, an anti-rotation function of the fan on the pole wheel. For example, the same cavity can have different shapes such as a cylindrical shape in its bottom part and a rectangular shape in its inlet part.

According to one embodiment, the cavity has a depth in an axial direction of between 5% to 100% of the thickness of the plate taken at the level of said cavity and preferably between 30% and 60% of said thickness. When this depth is equal to 100% of the thickness of the plate, the cavity is through, that is to say that it extends over an entire axial thickness of the plate so as to lead to the two end faces. axial of said plate.

According to one embodiment, the cavity has a maximum diameter between 0.02 and 0.2 times the external diameter of the pole wheel and preferably between 0.03 and 0.08.

According to one embodiment, the cavity extends along an axis which is parallel to the axis of rotation of the pole wheel.

According to one embodiment, the cavity is formed by a bottom and a side wall. The side wall has a first axial end defining an entrance opening of the cavity and a second axial end opposite to said first end which connects the side wall with the bottom.

According to one embodiment, the side wall of the cavity extends in a direction which forms an angle between 0 and 30 degrees with the axis of the cavity. For example, the cavity has a bottom diameter and an inlet diameter, the bottom diameter being smaller than the inlet diameter. This simplifies the manufacturing process of the cavity. Alternatively, the bottom diameter can be greater than the inlet diameter.

According to one embodiment, the side wall extends linearly, that is to say that a section in an axial plane of the wall has a straight shape. Alternatively, the section can have a concave or convex curve shape.

According to one embodiment, the cavity has a shoulder forming an axial abutment against which a portion of the fixing element located in the cavity is intended to be pressed to maintain the fan on the pole wheel.

According to one embodiment, the shoulder extends transversely, relative to the axis of the cavity, from the side wall.

According to one embodiment, the shoulder extends over the entire circumference of the side wall or alternatively over only a portion of said circumference. According to the last alternative, the side wall may have several shoulders.

According to one embodiment, the shoulder defines an opening whose diameter is less than the largest diameter of the side wall.

In one embodiment, the shoulder extends over a height, in an axial direction, of at least 30% of the depth of the cavity.

According to one embodiment, the shoulder extends over a length, in a radial direction relative to the axis of the cavity, between 10% and 30% of the maximum diameter of the cavity, the maximum diameter being comprised axially between the bottom and shoulder of the cavity. The length of the shoulder must not be too small to ensure good support for the fan and must not be too large so as not to overly constrain the fixing element when it is inserted into the cavity.

According to one embodiment, the shoulder extends away from the first axial end face of the plate. Alternatively, the shoulder extends from the first axial end face of the plate.

According to one embodiment, the polar wheel comprises a core extending axially from the second axial end face of the plate and centrally around the central opening, the core also having an opening allowing the passage of a rotor shaft .

The present invention also relates to a rotor of a rotary electrical machine, the rotor comprising a pole wheel as defined above and a fan comprising a plate extending transversely and at least one blade projecting from the plate, the fan being mounted on the pole wheel by at least one fixing element cooperating with an associated cavity of the pole wheel.

According to one embodiment, the fastening element is force fitted or screwed or snapped into the cavity.

According to one embodiment, the fan plate has an opening arranged opposite the associated cavity.

In one embodiment, the fan plate includes a groove surrounding the opening to partially accommodate the fastener. This is to prevent the fastening element from protruding axially from the fan plate, thereby reducing ventilation noise.

In one embodiment, the fan has a projection extending into the cavity. In particular, the projection extends into the upper part of the cavity when the latter has a shoulder. This makes it possible to block the fan in rotation relative to the cavity.

According to a first embodiment, the fixing element is an element added relative to the fan.

According to a second embodiment, the fixing element extends from the fan plate, that is to say that the fan and the fixing element are in one piece.

The present invention also relates to a rotary electrical machine comprising a rotor as defined above. The rotating electric machine can advantageously form an alternator, an alternator-starter, a reversible machine or an electric motor.

The present invention can be better understood on reading the detailed description which follows, of non-limiting examples of implementation of the invention and of the examination of the appended drawings, in which:

FIG. 1 represents, diagrammatically and partially, a sectional view, in a plane not including a cavity, of a rotary electrical machine according to a first example of implementation of the invention,

FIG. 2 schematically represents a perspective view of a pole wheel of FIG. 1,

FIG. 3 schematically represents a sectional view of the pole wheel of FIG. 2,

FIG. 6 represents a zoom of the cavity of FIG. 3,

FIG. 5 schematically represents a sectional view of a second example of a polar wheel,

FIG. 6 schematically represents a sectional view of a third example of a polar wheel,

FIGS. 7a and 7b represent zooms of the cavity in FIG. 6 according to two alternative embodiments,

FIG. 8 schematically represents a sectional view of the pole wheel of FIG. 2 on which a fan is fixed,

- Figures 9a and 9b show zooms of the fixing of Figure 8 according to two alternative embodiments.

Identical, similar or analogous elements keep the same references from one figure to another. It will also be noted that the different figures are not necessarily on the same scale.

FIG. 1 represents an example of a compact and multi-phase rotary electrical machine 10, in particular for a motor vehicle. This machine 10 transforms mechanical energy into electrical energy, in alternator mode, and can operate in motor mode to transform electrical energy into mechanical energy. This rotary electric machine 10 is, for example, an alternator, an alternator-starter, a reversible machine or an electric motor.

In this example, the machine 10 comprises a casing 11 and, inside thereof, a shaft 13, a rotor 12 integral in rotation with the shaft 13 and a stator 15 surrounding the rotor 12. The rotational movement of the rotor 12 takes place around an axis X corresponding to the axis of extension of the shaft. In the following description, the axial, radial, exterior and interior designations refer to the X axis passing through the shaft 13 at its center. For radial directions, the exterior or interior designations are assessed relative to the same axis X, the internal designation corresponding to an element oriented towards the axis, or closer to the axis with respect to a second element, the external designation designating a distance from the axis.

In this example, the casing 11 has a front flange 16 and a rear flange 17 which are assembled together. These flanges 16, 17 are hollow in shape and each carry centrally a bearing coupled to a respective ball bearing 18, 19 for the rotational mounting of the shaft 13. In addition, the casing 11 comprises fixing means 14 allowing the mounting of the rotary electrical machine 10 in the vehicle.

A pulley 20 is fixed to a front end of the shaft 13, at the level of the front flange 16. In the following description, the front / rear designations refer to the pulley 20. Thus a front face is a face oriented in direction of the pulley while a rear face is a face facing the opposite direction of the pulley.

The rear end of the shaft 13 carries, here, slip rings 21 belonging to a collector 22. Brushes 23 belonging to a brush holder 24 are arranged so as to rub on the slip rings 21. The brush holder 24 is connected to a voltage regulator (not shown).

In this exemplary embodiment, the stator 15 comprises a body 27 in the form of a sheet pack with notches and an electric coil 28 which passes through the notches of the body 27 and form a front bun 29 and a rear bun 30 and on the other side of the stator body. Furthermore, the winding 28 is formed of one or more phases electrically connected to an electronic assembly 36 forming a voltage rectifier bridge.

In this example, the rotor 12 is a claw rotor. It has two pole wheels 31, each formed by a plate 32 and a plurality of claws 33 extending from the plate and forming magnetic poles. The plate 32 is of transverse orientation and has, for example, a substantially annular shape. The plate 32 has a first axial end face 37 and a second axial end face 38 opposite to said first face, the claws extending from the second face 38.

This rotor 12 further comprises a cylindrical core 34 which is interposed axially between the pole wheels 31. Here, this core 34 is formed by two half cores each belonging to one of the pole wheels. The rotor 12 comprises, between the core 34 and the claws 33, a coil 35 comprising, here, a winding hub and an electric winding on this hub. For example, the slip rings 21 belonging to the collector 22 are connected by wire connections to the said coil 35. The rotor 12 may also include magnetic elements interposed between two adjacent claws 33.

The flanges 16, 17 may have openings for the passage of a flow of cooling air from the rotary electrical machine. The air flow is generated by the rotation of a front fan 25 fixed on the front axial face of the rotor 12 and a rear fan 26 fixed on the rear axial face of the rotor.

As illustrated in the example of FIG. 2, the plate 32 has cavities 39 extending from the first axial end face 37 to allow the fixing of the fan on the pole wheel. The pole wheel 31 comprises in particular between two and eight cavities. In the example illustrated here, the pole wheel has as many cavities as there are claws 33.

In this example, the cavities 39 are located on the same circumference of the plate 32, that is to say that a circle traced on the first axial end face 37 and having as center the axis X crosses at least one portion of each cavity. Preferably, the respective distances between the axis X and the centers of the cavities 39 are equal for the same pole wheel 31. In addition, the cavities 39 are angularly spaced from one another at the same angle. A symmetrical polar wheel is then obtained. In addition, the cavities 39 are located closer to the outer periphery A of the pole wheel 31, defined by the circumference of larger diameter of the plate 32, than to the inner periphery B, defined by the opening traversed by the tree 13.

The plate 32 is divided into several angular sectors each delimited by two straight lines and forming an alternation of angular sectors with claw Z1 and of angular sectors devoid of claw Z2. An angular sector with claw Z1 is delimited by a first straight line passing through the center C of the plate and by one of the two circumferential ends of a claw and by a second straight line passing through the center C and by the other circumferential end of the same claw. An angular sector devoid of claw Z2 is delimited by a first straight line passing through the center C and by a circumferential end of a claw and by a second straight line passing through the center C and by the circumferential end of the adjacent claw, both circumferential ends facing each other. The cavities are preferably arranged in the angular sectors devoid of claw Z2 in order to disturb the magnetic field passing through the plate as little as possible.

This distribution of the cavities depends on the application and is applicable in particular for the front pole wheel because the rear pole wheel has different design constraints due to the passage of the connection wires of the rotor coil 35. Thus, the rear pole wheel may include cavities 39 arranged astride two angular sectors or in angular sectors with claw Z1 to allow the passage of the supply wires from the coil 35 to the collector 22.

As shown in Figure 3, the cavities 39 are arranged in the part of the plate 32 which is neither in contact with the core 34 nor with one of the claws 33, that is to say in the part of the pole wheel with the smallest axial thickness.

Each cavity 39 extends along an axis Y which is parallel to the axis X of rotation of the pole wheel 31 and has a cylindrical or conical shape.

Each cavity 39 has a depth P1 in an axial direction of between 5% to 100% of the thickness E1 of the plate 32 taken at the level of said cavity and preferably between 30% and 60%. For example, the cavity has a depth P1 of between 3 and 20 mm.

Each cavity 39 has a maximum diameter between 0.02 and 0.2, and in particular between 0.03 and 0.08, times the external diameter of the pole wheel.

A cavity 39, as illustrated in FIG. 4, is formed by a bottom 40 and a side wall 41 having a first axial end defining an inlet opening 42 of the cavity and a second axial end opposite to said first end which connects the side wall with the bottom. Leave radii can be provided between for the side wall 41 and the bottom 40 and between the side wall and the first axial end face 37 of the plate.

In the following description, various embodiments will be presented, the general characteristics set out above are applicable whatever the embodiment.

In the first embodiment illustrated in Figures 3 and 4, the side wall 41 extends linearly, that is to say that a section in an axial plane of the wall has a straight shape. For example, the side wall 41 extends in a direction which forms an angle between 0 and 30 degrees with the axis Y of the cavity. In particular, the cavity 39 has an inlet diameter taken at the inlet opening 42 and a bottom diameter taken at the bottom 40, the bottom diameter being smaller than the inlet diameter.

In a variant of this first embodiment illustrated in FIG. 5, the cavities 39 pass through so as to lead both to the first axial end face 37 and to the second axial end face 38 of the plate 32.

Figures 7, 7a and 7b illustrate an example of a second embodiment in which the cavities 39 have a shoulder 43 extending from the side wall 41 to form a stop. The shoulder 43 extends substantially transversely, relative to the axis Y of the cavity 39, over the entire circumference of the side wall. The shoulder defines an opening 44 whose diameter is less than the largest diameter of the side wall 41.

For example, the shoulder 43 extends over a height H1, in an axial direction relative to the axis Y, of at least 30% of the depth P1 of the cavity 39. Still for example, the shoulder 43 extends over a length L1, in a radial direction relative to the axis Y, between 10% and 30% of the maximum diameter of the cavity taken axially between the bottom 40 and the shoulder 43.

In a first variant of the second embodiment illustrated in FIG. 7a, the shoulder 43 extends from the first axial end face 37 of the plate 32. The opening 44 formed by the shoulder then corresponds to the entry opening 42 of the cavity 39.

In a second variant of the second embodiment illustrated in FIG. 7b, the shoulder 43 extends at a distance from the first axial end face 37 of the plate 32. In other words, there is a non-zero axial distance between the first connecting portion 37 and the shoulder 43. The opening 44 formed by the shoulder is then distinct from the inlet opening 42 of the cavity 39. For example, an axial height H2 between the shoulder 43, in particular the apex 57 of said shoulder, and the first axial end face 37 of the plate is at least 15% of the depth P1 of the cavity. The apex 57 of the shoulder is the point from which the shoulder has the smallest diameter D3.

For example, in this alternative embodiment, the cavity 39 has an upper part 45 located axially between the first axial end face 37 and the shoulder 43 and a lower part 46 located axially between the shoulder 43 and the bottom 40 of the cavity. The parts 45, 46 are independent of one another and may have characteristics such as a shape, dimensions or an angle of inclination relative to the axis Y of the cavity, which are different. For example, a maximum diameter of the upper part 45 is greater than a maximum diameter of the lower part 46. Still for example, the upper part 45 may have a shape different from the lower part 46. Thus, the lower part 46 may have a cylindrical shape and the upper part 45 may have a rectangular shape. This rectangular shape allows the fan to block in rotation relative to the pole wheel.

The shoulder has a first portion 47 and a second portion 48, said positions being separated from each other by the apex 57 of the shoulder defining the opening 44. The first portion 47 extends opposite the upper part 45 and the second portion 48 extends opposite the lower part 46. For example, the first portion 47 extends substantially radially with respect to the axis Y and the second portion 48 forms a curvature.

The cavity 39 can be obtained by a forging process, in particular by hot stamping, or by machining.

FIGS. 8, 9a and 9b illustrate the attachment of a fan 25, 26 to a pole wheel 31. The fan 25, 26 comprises a plate 49 extending transversely and at least one blade 50 extending projecting from the plaque. The fan is mounted on the pole wheel 31 associated by at least one fixing element 51 cooperating with an associated cavity 39. The plate 49 is in contact with the first axial end face 37 of the associated pole wheel 31.

The plate 49 has an opening 54 disposed opposite the associated cavity 39 to allow the passage of the fixing element 51. Preferably, the opening 54 of the fan is slightly larger than the inlet opening 42 of the cavity so as not to deform the fan when inserting the fixing element 51.

The fastening element 51 may have a head 52 in contact with the plate 49 of the fan and a body 53 projecting from the head 52. The body 53 is disposed through the opening of the fan and cooperates with the cavity 39 for holding the fan on the pole wheel.

For example, an adhesive such as resin can be placed in the cavity 39 in order to improve the retention of said fan on the pole wheel.

FIG. 8 represents a pole wheel according to the first embodiment of FIGS. 3 and 4. In this embodiment, the fixing element51 is force fitted into the cavity 39.

As a variant, the fixing element 51 could be screwed into the cavity 39. The side wall 41 of the cavity could then comprise a complementary tapping of a threaded part formed on the body 53 of the fixing element 51.

Figure 9a shows a pole wheel according to the second embodiment of Figure 7a. In this embodiment, the fixing element51 is snapped into the cavity 39. In other words, the shoulder 43 forms an axial stop against which the fixing element 51 comes to bear to hold the fan.

For example, as illustrated in FIG. 9a, the plate 49 includes a groove 55 surrounding the opening 54 to accommodate the head 52 of the fixing element. This groove is also applicable to the first embodiment illustrated in FIG. 8.

Figure 9b shows a pole wheel according to the second embodiment of Figure 7b. In this embodiment, the fixing element 51 is snapped into the cavity 39.

In the example of FIG. 9b, the plate 49 of the fan 25, 26 has a projection 56 extending in the upper part 45 of the cavity 39 making it possible to block the fan 25, 26 in rotation relative to the pole wheel 31 This projection is also applicable to the first embodiment illustrated in FIG. 8.

The embodiment of the pole wheel in FIG. 5 is compatible with one or the other of the fixing methods described above.

In an exemplary embodiment compatible with any of the embodiments described above, the fixing element 51 is an element relative to the fan 25, 26. Thus, the fixing element 51 is for example a nail, a rivet, a screw or a clip cooperating with the shoulder 43.

In another exemplary embodiment compatible with any of the embodiments described above, the fixing element 51 extends from the plate 49 of the fan 25, 26. In other words, the fan and the fixing element are monoblocs.

For example, the fan 25, 26 is formed from a plastic material. Alternatively, the fan 25, 26 is formed from a metallic material such as steel or aluminum or copper or brass or from a composite material.

For example, the fastening element 51 is made of metallic or plastic material. When the fixing element is in one piece with the fan, said element can be made from one piece with the fan or molded onto the fan.

The present invention finds applications in particular in the field of rotors for alternator or reversible machine, but it could also be applied to any type of rotary machine.

Of course, the foregoing description has been given by way of example only and does not limit the field of the present invention from which one would not depart by replacing the various elements with any other equivalent. For example, a pole wheel can have identical cavities with each other in order to simplify the manufacture of the pole wheel as well as its balancing. In the same way, the pole wheels of a rotor can have identical cavities as well as an identical distribution of said cavities. It will however be understood that each cavity, of the same polar wheel or of a different polar wheel of the same rotor, can have its own shape, its own dimensions and its own location as long as the associated fixing element is adapted accordingly for keep the fan on the pole wheel.

Claims (10)

1. Polar wheel for rotary electric machine rotor, the polar wheel (31) comprising: - a plate (32) extending transversely with respect to an axis (X) of rotation of the pole wheel; - A plurality of claws (33) extending from the plate in a substantially axial direction, the pole wheel being characterized in that the plate (32) has at least one cavity (39) intended to receive and cooperate with an element fixing (51) for fixing a fan (25, 26) on the pole wheel (31). 2. Polar wheel according to the preceding claim, characterized in that the plate (32) is divided into several delimited angular sectors, each by two straight lines passing respectively through the center (C) of the plate and the two circumferential ends of the same claw (33) or the two circumferential ends facing two adjacent claws (33), the sectors forming an alternation, in a circumferential direction, of angular sector with claw (Z1) and of angular sector without claw (Z2), the cavity (39) being disposed in an angular sector devoid of claw (Z2). 3. Polar wheel according to claim 1 or 2, characterized in that the cavity (39) has a shoulder (43) forming an axial stop against which a portion of the fixing element (51) located in the cavity is intended to be pressed to maintain the fan (25, 26) on the pole wheel (31). 4. Polar wheel according to the preceding claim, characterized in that the shoulder (43) extends away from a first axial end face (37) of the plate (32). 5. Rotor of a rotary electrical machine, the rotor (12) comprising: a polar wheel (31) according to any one of the preceding claims and - a fan (25, 26) comprising a plate (49) extending transversely and at least one blade (50) projecting from the plate, the fan being mounted on the pole wheel by at least one element fixing (51) cooperating with a cavity (39) associated with the pole wheel. 6. Rotor according to the preceding claim, characterized in that the fixing element (51) is force fitted or screwed or snapped into the cavity (39). 7. Rotor according to claim 5 or 6, characterized in that the plate (49) of the fan (25, 26) has an opening (54) disposed opposite the cavity (39) associated. 8. Rotor according to the preceding claim, characterized in that the plate (49) comprises a groove (55) surrounding the opening (54) to partially accommodate the fixing element (51). 9. Rotor according to any one of claims 5 to 8, characterized in that the fan (25, 26) has a projection (56) extending in the cavity (39). 10. Rotating electric machine comprising a rotor according to claim 8 or 9.