FR2908941A1 - METHOD FOR PRODUCING A FAN DEVICE FOR A ROTATING ELECTRIC MACHINE AND A FAN DEVICE FOR CARRYING OUT SAID METHOD - Google Patents

Abstract

The invention relates to a method for producing a fan device for a rotating electrical machine, such as an alternator, for a given application.The method is characterized in that it consists in producing the fan device (18) by assembly. at least two fans (22, 23) of specific properties so that the addition of their properties provides a standardization, adaptation or optimization for the given application.The fan device for the implementation of the method is characterized in that it comprises at least two individual fans which are superimposed or fixed to one another in their axial direction.The invention is usable by motor vehicles.

Description

1 Method for producing a fan device for a machine

  TECHNICAL FIELD The invention relates to a method for producing a fan device for a rotary electric machine, such as an alternator or an alternator, for an application. data and a fan device for the implementation of this method. State of the Art It is known for each new development of a rotating electrical machine to create a new fan device by giving it an appropriate individual configuration. Thus for rotating electrical machines produced at large volume, a specific fan device is created. The same is true for rotating electrical machines produced at small volume, especially for more severe applications than those with large volume. This does not cover several ranges of rotating electrical machine. These known methods are therefore not satisfactory solutions to the problem of adaptation and optimization of fan devices for several ranges of rotating electrical machine. OBJECT OF THE INVENTION The object of the invention is to overcome this drawback. In order to achieve this object, the method according to the invention is characterized in that it consists in producing the fan device by assembling at least two fans of specific properties so that the addition of their properties provides a standardization, adaptation or optimization for the given application. According to a characteristic of the invention, the method is characterized in that the assembly is done by superposition and fixing the fans one over the other, in their axial direction. According to another characteristic of the invention, the method is characterized in that, in order to reduce the noise produced by the fan device, it consists in producing the fan device by assembling a first fan with a larger diameter and a second fan with a smaller diameter, to reduce the overall noise and to keep the harmonics away from the overall noise.

  More precisely, the second fan of smaller diameter is intended to reduce the overall noise, while the first fan of a larger diameter is intended to keep the harmonics away from the overall noise.

  According to yet another characteristic of the invention, the method is characterized in that, for the purpose of standardization, the fan device is composed from at least two fans of different diameter, namely a first fan optimized for a current power range and an additional fan for higher power ranges, smaller in diameter or equal to the diameter of the first fan. The fan device for the implementation of the method is characterized in that it comprises at least two individual fans which are superimposed or fixed to one another in their axial direction.

According to one characteristic of the invention, the fan device is characterized in that the upper fan has a smaller outer diameter than the lower fan intended to be fixed on a front face of the rotor of the rotating electrical machine. According to a characteristic of the invention, the fan device is characterized in that the two fans are fixed to each other at least in part by riveting. According to one characteristic of the invention, the fan device is characterized in that the fans are fixed to one another at least partly by crimping, in particular by stapling.

According to one characteristic of the invention, the fan device is characterized in that the fans are assembled to each other at least partly by welding. According to one characteristic of the invention, the fans comprise centrally perforated flanges carrying at their outer periphery blades, the fans being assembled to one another by spot welding in different zones distributed over the flanges of the fans and / or on the blades of the 25 fans. According to one characteristic of the invention, the lower fan comprises a plurality of welding pads for fixing it to the rotor of the rotating electrical machine, a plurality of welding points being made at least around a welding stud of the lower fan. .

Of course these characteristics are to be considered singly or in combination. Thanks to these characteristics, the second additional and optional fan can be used for the 5 ranges of higher power and low volume rotating electrical machines, the first fan being a fan of the standard type used in particular for rotating electrical machines produced at high volume. .

This second fan can be used to provide additional ventilation for more severe applications or more demanding specifications, especially with regard to higher temperatures. This optimizes the fan device. Thanks to the second fan it is possible to bring the machine closer to a hot source or to confine a little more the machine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and other objects, features, details and advantages thereof will become more clearly apparent from the following explanatory description made with reference to the accompanying diagrammatic drawings given solely for the purpose of illustration. example illustrating several embodiments of the invention and in which: - Figure 1 is an axial sectional view of a rotating electrical machine with internal ventilation equipped with a fan device according to the invention; FIG. 2 is a perspective view of a fan device for a first embodiment according to the invention; FIG. 3 is a perspective view of a fan device for a second embodiment according to the invention; FIG. 4 is a partial view in axial section illustrating the mounting of the fan device of FIG. 3 on the rear polar wheel of the rotor of FIG. 1; FIG. 5 is a partial view of FIG. 4 showing on a larger scale, without the blades, the central part of the fan device of FIG. 3; - Figures 6, 7, 8 are views similar to Figures 3, 4, 5 for a third embodiment of the ventilation device according to the invention; Figures 9, 11 are views similar to Figures 3, 4, 5 for a fourth embodiment of the ventilation device according to the invention; - Figure 12 is a partial axial sectional view showing the attachment of the lower fan of the fan device on the rear pole wheel of the rotor of Figure 1; Figure 13 is a view similar to Figure 6 for a fifth embodiment of the invention; - Figure 14 is a partial front view around a welding pad for mounting welding points of the laser type obtained by successive shots.

DESCRIPTION OF THE INVENTION In the figures, identical or similar elements will be assigned the same reference signs. FIG. 1 shows a rotating electrical machine with internal ventilation, equipped with a fan device 18 according to the invention. In this figure, the rotating electrical machine consists of a polyphase compact alternator 35 for a motor vehicle with a heat engine. This alternator comprises a housing 1 and, inside thereof, a rotor 2 of annular shape 2908941 6 integral with a central shaft 3 and a stator 5 of annular shape, which surrounds the rotor 2. The rotor 2 is here a claw rotor comprising two pole wheels 7, 8 each having a transverse flange of annular shape provided at its outer periphery with claws 9. A winding 10 is implanted in the space delimited radially by the nested claws 9 of the wheels 7, 8 and a central core. This central core is here in two parts each belonging to the flange of one of the wheels 7, 8. In a variant, the core is distinct from the flanges of the wheels 7, 8. The ends of the winding 10 are connected by wire bonds to slip rings (not referenced) belonging to the rear end of the shaft 3. Brushes (not referenced) belonging to a brush holder 14 are allowed to rub. on the slip rings. The brush holder 14 is connected to a voltage regulator, here forming an assembly with the brush holder. Permanent magnets can be implanted between the axially oriented teeth, which have the claws 9 at their outer periphery. In a variant, the rotor 2 is a rotor with salient poles. The stator 5 comprises a body 50, in the form of a bundle of sheets, carrying a polyphase winding 51. The outputs of this coil, one of which 52 is visible in the lower part of FIG. 1, are connected to at least one rectifier bridge 53 of ac current, carrying rectifier elements, such as diodes or MOSFET transistors. The alternator is, for example, in one embodiment of the three-phase type or alternatively in the three-phase or six-phase type; The number of phases depending on the applications.

The front end of the shaft 3 is secured to a drive member 12 connected by a transmission device to the engine of the vehicle. The member 12 is in one embodiment a gear, the transmission device having at least one chain. Here the drive member consists of a pulley 12 belonging to a transmission device comprising at least one belt. The casing 1 is in at least two parts, namely a front bearing 11 adjacent to the pulley 12 and a rear bearing 13 carrying the brush holder 14, the voltage regulator and the rectifier bridge (s) 53. A cover 54 here the brush holder 14, the voltage regulator and the rectifier bridge or bridges.

This cover is integral with the rear bearing 13 and is perforated for passage of air. The bearings 11 and 13 each centrally carry a ball bearing for the rotational mounting of the shaft 3.

In a variant, the alternator is brushless and without a slip ring. The alternator also comprises means for cooling its components, in particular the winding 51, the rectifier bridge (s) 53 and the voltage regulator. For this purpose, the bearings 11 and 13, here of hollow form, are perforated to allow the cooling of the machine by internal circulation of a cooling fluid, here of air, and the rotor 2 carries a front fan 16 on the front end face of the front pole wheel 7 and a rear fan assembly 18 according to the invention. The device 18 is here more powerful than the fan 16 and is mounted on the rear end face 20 of the rotor, that is to say on the outer face of the rear polar wheel 8.

In general, the front fan 16 and the rear fan assembly 18 are mounted on the front and rear end faces, respectively, which constitute the axial end faces of the rotor 2. These faces are of transverse orientation relative to each other. to the axis XX 'of the shaft 3. This axis XX' is the axis of the machine.

This fan 16 and the fan device 18 each carry blades and are here of the centrifugal type. FIG. 1 shows by arrows the flow of air generated by the front fan 16.

In a variant, the fan 16 and the device 18 are of the centripetal or helical centrifugal or axial type. The blades of the fan 16 and the device 18 are therefore configured according to the applications. Since the invention relates specifically to the fan device 18 and not to the general structure of the machine, it is not necessary to describe it in more detail and all the more so since it is known per se. . As a reminder, this alternator with or without brushes 20 converts mechanical energy into electrical energy when the member 12 is rotated by the engine of the vehicle via the motion transmission device. Alternatively the alternator is reversible and is called alternator-starter. This alternator-starter also transforms electrical energy into mechanical energy to drive the engine and in particular start it. Figure 2 shows a fan device 18 according to the invention according to a first embodiment. This device 18 comprises two fans axially superimposed and assembled to each other, namely an upper fan 22 and a lower fan 23, which is here intended to be assembled for example with the pole wheel 8.

The fans 22 and 23 are here metallic and each comprise a flange respectively 24, 25, which is centrally perforated for the passage of the shaft 3 and is provided, distributed around its outer periphery, 5 blades respectively 26, 27 These blades 26, 27 are here distributed unevenly for reducing noise. The through hole 28 of the upper fan 22 is delimited by an annular collar 29 10 axially oriented relative to the axis X-X 'of the machine. This collar is directed axially in the opposite direction to the flange 25 of the fan 23, which has no flange at its hole and thus has a simplified planar shape. The flange 29 makes it possible to stiffen the fan device 18 centrally, in particular when it is turned over so as to assemble the two fans 22, 23 together, for example by bonding points or by welding points, in particular welding points of the device. laser type, as described below. It should also be noted that the edge of each central hole of the flanges 24, 25 has a pair of notches 32 of identical shape with semicircular bottom. These notches are diametrically opposed and of different depth and belong to angular indexing means for angularly indexing the two fans 22, 23 with respect to each other, for example by means of pins (not shown). , penetrating complementary manner in the superimposed notches.

The modular structure of the fan device 18 according to the invention, which consists of at least two individual fans, such as fans 22 and 23, has the advantage of allowing standardization, adaptation of the fan device to applications various and an optimization of these performance with respect to these applications.

According to the invention, in order to achieve standardization, the lower fan 23 is a fan optimized for a series of large series while the upper fan 22 is additional 5 and optional for higher power and manufacturing ranges less large number. The diameter of the lower fan 23 is generally greater than the diameter of the upper fan 22. The fan 22 can also be used to provide additional ventilation on more severe applications or more demanding specifications. Therefore, the fan 22 will only be mounted in this case. This fan 22 may comprise in one embodiment only one blade to create an asymmetry and reduce noise. Here the fan 22 has several blades 26 each circumferentially interposed between two blades 27 of the lower fan 23 adjacent the pole wheel 8. As a variant, between certain consecutive blades 27, no blade 26 can be provided. The lower fan 23 is here thicker than the fan 22, lighter. Alternatively the two fans 22, 23 have the same thickness.

The material of the two fans 22, 23 may be identical. Alternatively the fan 22 is less noble material. It all depends on the applications. The invention also allows an acoustic optimization of the fan device. In this case, the two fans 22, 23 will have a different diameter, the diameter of the lower fan 23 being greater than that of the upper fan 22 as can be seen in FIG. 13. The invention takes advantage of the fact that a fan of a smaller diameter produces a lower overall noise but more emergent rotor harmonics, while a larger diameter fan produces a stronger overall noise, but less noticeable harmonics. Thus, the solution proposed by the invention to produce the fan device by assembling at least two fans of different outside diameters makes it possible to have a global noise and harmonics of an intermediate intensity and therefore less important compared to a single fan of a suitable large diameter.

It will be appreciated from the foregoing that for the optional and optional fan 22 there is a wide range of features including thickness, material, number of blades and diameter. These characteristics depend on the applications.

It is the same in the other examples of embodiment. In the embodiment of Figures 1 and 2 the flanges 24, 25 are of planar shape and are in mechanical and electrical contact with each other.

Figures 3 to 12 illustrate several possibilities of assembling the two fans 22, 23, one superimposed on the other. These fans are fixed to one another in the axial direction. According to the embodiment of FIGS. 3 to 5, the two fans 22, 23 are assembled by riveting at 34, the lower fan 23 being fixed on the support face 20 of the rotor 8 of the rotor 2 by welding as described in FIG. In order to do this, the flanges 24, 25 each have a central portion 124, 125 (FIG. 5) of transverse orientation with respect to the axis XX 'and axially offset in the opposite direction to the rotor 2. These portions 124 and 125 are annular and 35 are axially offset relative to the rest of the flanges 24, 25, also of transverse orientation, carrying the blades 26, 27 to accommodate the feet of the rivets 34 and avoid interference with the rotor 2. It is thus formed a cavity housing the feet of the rivets 34.

The portions 124 and 125 are in contact with each other and are each connected to the remainder of the respective flange 24, 25 by non-referenced rounded areas. Note that the portion 125 may be provided in advance with holes for the passage of the rivets 34, the fan 23 being equipped or not with the fan 22. Of course when the fan 22 is associated with the fan 23 can in one embodiment use a fan 23 flat flange and then make the portion 125. It is the same in Figures 9 to 11 described below. Of course, it is possible to carry out the portion 125 in advance when the fan 22 is mounted at the front in place of the front fan 16 provided with such a portion.

It is therefore possible to use a front fan. The flanges 24, 25 are in contact with each other. The angular indexing means between the two fans 22, 23 here consist of holes 132, here diametrically opposed. The portions 124, 125 make it possible to stiffen the flanges 24, 25 of the fans 22, 23. FIGS. 6 to 11 show an assembly of the two fans by crimping, the inner edge of a flange 24, 25 of one of the fans. 22, 23 having clamping tabs bent and folded over or under the adjacent inner edge of the flange of the other fan. In the embodiment of FIGS. 6 to 8, the radially inner edge of the flange 25 of the lower fan 23 has tabs 36 directed towards the outer periphery of the fans 23 and folded over the outer face 37 of the inner edge of the flange 24. the upper fan 22 thus ensuring a clamping assembly. For this purpose the flange 24 of the fan 22 5 comprises openings 136 for the passage of the tabs 36 obtained by cutting and bending from the flange 25. More precisely the tabs 36 are initially radially oriented being in the plane of the flange 10 25 of the fan 23 of the standard type. When it is desired to mount the fan 22, in a first step, the tabs 36 are folded in an axial direction so that they pass through the openings 136 subsequently.

The tabs 36 being folded axially, in a second step the fan 22 is mounted on the tabs 36 by means of the openings 136, and then the tabs 36 are folded radially inward towards the axis XX 'and this at contact of the outer face 37 of the flange 24 to clamp the flanges 24, 25 against each other. In one embodiment, the clamping tabs 36 are made only when the fan 22 needs to be mounted.

Alternatively, the fan 23 can be made with radial tabs 36 cut in the plane of the flange 25 of the fan 23, said fan 23 being intended or not to be equipped with the fan 22. In a variant, it is possible to fold the tabs 30 axially, see even then twist in the case where the fan 23 is not equipped with the fan 22. The axial tabs 36, twisted in one embodiment, then constitute additional blades.

Alternatively, the non-folded axial tabs 36 may be fitted with blades. For example one can weld additional blades on the free axial end of the tabs 36. The flanges 24, 25 have a flat shape and are in contact, here mechanical and electrical, with each other.

In the embodiment of FIGS. 9 to 11, the inner radial edge of the flange 24 of the upper fan 22 has clamping lugs 39 directed radially inward towards the X-X 'axis. The tabs 39 thus extend initially projecting inside the hole 28 through which the shaft 3 passes and are derived from the material drop produced to create the central hole 28 for passage of the shaft 3. The legs 39 are then axially folded to mount the portion 124 on the tabs 39. Then the tabs 15 are folded radially outward in the opposite direction relative to the axis XX 'under the inner periphery of the inner edge of the fan 23 to come in clamping contact with the underside 40 of the lower fan 23.

Of course, as in the embodiment of FIGS. 3 to 5, the flanges 24, 25 each comprise a central portion of transverse orientation, respectively 124, 125, offset axially in a direction opposite to the rotor in order to create a cavity for housing the 25 legs 39 folded. The internal edges of the fans are therefore constituted by the annular central portions 124, 125. In the embodiments of FIGS. 3 to 11, a stitching assembly is thus produced; the tabs 36, 39 constituting the staples. Of course in all cases the fan device 18 is alternatively mounted on the front face of the front pole wheel 7 as shown in FIG. 11.

The machine is alternatively cooled by circulation of liquid, such as the coolant of the engine of the motor vehicle. For this purpose at least one of the bearings 5 comprises a coolant circulation chamber. For example, the chamber belongs to the rear bearing 13 so that the fan device 18 according to the invention is secured to the front wheel 10 7 and the rotor has no fan at its rear wheel 8. The reverse is also possible, that is to say no fan at the front wheel 7, the front bearing having the coolant circulation chamber, while the rear polar wheel carries the device 18. As a variant the bearing the front bearing is of flat shape, as in FR 2,749,109, the rear bearing comprising the liquid circulation chamber, while the rear polar wheel carries the device 18 with axial action, the blades 26, 27 being configured accordingly. . In a variant, the front fan 16 is eliminated and the device 18 conserved, the cooling being air-circulating as in FIG. 1. This is made possible by the presence of the optional fan 22. The fan 23, of the standard type comprises for example a plurality of welding pads, advantageously regularly distributed, for its assembly by electric welding, for example to the pole wheel 8 or alternatively to the wheel 7. Thus, FIG. 12 illustrates a welding assembly method 35 both of the fans 22 and 23 and the device 18 assembled to the rotor 8 of the rotor 2. The assembly is performed at a certain number of zones such as the zone 139 of FIG. 12, regularly distributed over the surface of the flanges of the fans. In each weld joint zone 139, the flange 25 of the lower fan 23 is deformed by stamping to form a plurality of welding studs 140 each having an annular bead 41 having a generally V-shaped cross-section with a vertex rounded 42 in contact with the lower face of the flange 24 of the upper fan 22. The annular top of the bead 41 is in contact with the face 20 of the pole wheel 8. In a first assembly step, the two fans 22, 23 are joined to each other by spot welding. Thus, a certain number of welding points 43 are created around each stud 140. The spot welding is in one embodiment of the laser type. This type of laser welding is used in the embodiment of FIG. 2, whereas in the other embodiments, riveting or crimping is used. Then, as shown in Figure 12, the fan device is fixed by electric welding on the pole wheel 8 by means of welding electrodes 45. During the electric welding, is exerted with each electrode 45 a pressure 25 on the outer face of the flange 24 of the fan 22 and the electric current is transmitted to the flange 25 of the fan 23 and the studs 140. Each stud 140, in contact by its bead 41 with the face of the pole wheel melts, and soda on the wheel 8 which, of course, must be of a weldable material. Here the wheels 7, 8 are made of metal made of ferromagnetic material, for example mild steel. The fans 22, 23 are also made of metal and of weldable material. The fans are made of steel, for example. It will be noted that laser welding is stopped here in the raz of the upper face of the fan 22.

The assembly of the fans 22, 23 of Figure 2 is for example carried out using a fixed support and a pressing member. In a first step, the two superimposed fans are mounted upside down on a protuberance of the fixed support, the upper face of the flange 24 of the fan 22 being in contact with this protuberance. In a second step, the pressing member is used on the lower face of the flange 25 of the fan 23 to clamp the two fans between the protuberance of the fixed support and the pressing member. Then the two fans are laser welded as shown at 43 in FIG. 12. After formation of the fan device 18, electrical welding is carried out as described in FIG. 12. Of course, any other method of assembling the fans can be used. for example by riveting, the rotor having extruded rivets for assembling the correspondingly perforated fans. Of course the number of tabs 36, 39, rivets 34 and pads 140 depends on the applications. In the embodiments four rivets 34 and four legs 36, 39 are used.

This of course depends on the diameters. Thus one can realize achievements with 2 or 3 attachment points, or more than four attachment points, for example 6 attachment points. All combinations are possible.

Thus, in FIGS. 9 to 11, two lugs 39 can be replaced by an assembly with two rivets 34 as in FIGS. 3 to 5 or by two bonding or welding points, for example of the laser type. In FIGS. 6 to 8, two tabs 36 and two openings 136 may be replaced by two welding points, for example of the laser type.

As can be seen from the description and the drawings, the embodiment of FIG. 2 with welding points of the laser type can be combined with those of the other figures.

Thus, in FIG. 3 or in FIG. 9, additional laser-type welding points or glue attachment points of the two flanges are added outside the portions 124, 125. In these figures the welding studs 140 are therefore 10 implanted on a circumference of diameter greater than that of the rivets 34 or tabs 39. The same is true in FIG. 6, the additional fixing points being situated away from the tabs 36 and the openings 136.

In this FIG. 6, the welding pads 140 are implanted on a circumference with a diameter greater than or equal to that of the ends of the tabs 36. Of course, depending on the applications, the blades 26 of the additional and optional fans 22 may be modified for a larger diameter. better adaptation or better performance optimization. Thus in the embodiment of FIG. 13 the blades of the fan 22 are shortened. In this figure, the blades 126 of the fan 22 are shorter so that the external diameter of the fan 22, which corresponds to the external diameter of its blades 126, is lower than that of the fan 23. This provision is applicable to other embodiments.

In all cases additional fixing points by gluing or welding can be added in particular at the covering areas of the blades 26-27 or 126-27. In a variant, the flange 24 of the upper fan 35 is perforated at the level of each solder pad 140 for direct access of the electrodes 45 and supports them on the upper face of the solder pads 140.

In this case the fan 22 may be based on plastic or a thermally insulating layer may be interposed between the two flanges.

Fast and accurate laser spot welding can be achieved using at least two successive shots to decrease laser power and reduce laser costs.

Indeed, the metal is still hot between two successive shots. A good compromise is achieved by performing spot welding 43 using three successive rapid shots arranged at the top of a triangle as shown in Figure 14. This reduces the number of shots while having a good fixation. mechanical. Of course, welding points can be made away from the welding pads, for example at the blades of the fans and / or at the inner periphery of the flanges. In a variant, a plurality of additional welding points 43 of the successive shot laser type can be made at least around a welding pad 140. The number of points 43 is four in FIG. 14. As a variant, this number is different. of four, for example equal to 2, 3 or 5. Of course, in another embodiment the fan 22 is divided into at least two parts 30 each reported on the flange 25, for example by spot welding 43. It is it should be noted that the standardization and optimization of the fan device 18, instead of being made by assembling two individual fans, possibly split into two parts, could also be carried out using a larger number of individual fans.

Claims (14)

  1. A method of producing a fan device for a rotating electrical machine, such as an alternator or an alternator-starter, for a given application, characterized in that it consists in producing the fan device (18) by assembling at least two fans (22, 23) of specific properties so that the addition of their properties provides a standardization, adaptation or optimization for the given application.   2. Method according to claim 1, characterized in that the assembly is done by superposition and fixing the fans (22, 23) one on the other, in their axial direction.   3. Method according to claim 2, characterized in that, to reduce the noise produced by the fan device (18), it consists in producing the fan device by assembling a fan (22) of a smaller diameter, for reduce the overall noise, and a fan (23) of larger diameter, intended to remove the harmonics of the overall noise.   4. Method according to claim 2 or 3, characterized in that, for the purpose of standardization, the fan device (18) is composed of at least two fans (22, 23), namely a first fan optimized for a current power range and a second additional fan for higher power ranges, smaller in diameter or equal to the diameter of the first fan. 20 2908941 21   5. Fan device for the implementation of the method according to one of claims 1 to 4, characterized in that it comprises at least two individual fans (22, 23), respectively 5 upper and lower, which are superimposed or fixed one on the other in their axial direction.   6. Fan device according to claim 5, characterized in that the upper fan (22) has a smaller outer diameter than the lower fan (23) intended to be fixed on a front face of the rotor (2) of the electric machine. rotating. 15   7. Fan device according to one of claims 5 or 6, characterized in that the two fans (22, 23) are fixed to each other at least partly by riveting. 20   8. Fan device according to any one of claims 5 to 7, characterized in that the fans (22, 23) are fixed to each other at least partly by crimping. 25   9. Fan device according to claim 8, characterized in that the fans are fixed to each other at least partly by stapling.   10. Fan device according to claim 8 or 9, characterized in that the fans (22, 23) comprise centrally perforated flanges (24, 25) and that the inner edge of a flange (24, 25) of one of the fans (22, 23) has clamping tabs (36, 39) bent and folded over or under the adjacent inner edge of the flange (25, 24) of the other fan. 2908941 22   11. Fan device according to any one of claims 5 to 10, characterized in that the fans (22, 23) comprise centrally perforated flanges (24, 25) and in that the flanges (24, 25) of the fans (22, 23) each have a central portion (124, 125) of transverse orientation axially offset in the opposite direction to the lower fan (23) and assembled with each other at least in part by riveting and / or 10 crimping.   12. Fan device according to any one of claims 5 to 11, characterized in that the fans (22, 23) are assembled to each other at least partly by welding.   Fan device according to claim 12, characterized in that the fans (22, 23) comprise centrally perforated flanges (24, 25) and at their outer periphery have blades (26, 27), and that fans (22, 23) are connected to each other by spot welding in different zones distributed over the flanges and / or the blades of the fans. 25   14. Fan device according to any one of claims 5 to 13, characterized in that the lower fan (23) comprises a plurality of welding studs (140) for attachment to the rotor of the rotating electrical machine and in that a plurality of welding points is made at least around a welding pad of the lower fan (23).