Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
  • F04D29/281—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for fans or blowers

Definitions

• Ventilation device in particular for a motor vehicle alternator
• the present invention relates to a ventilation device for a rotary electrical machine, in particular for a motor vehicle.
• Such a machine can be an alternator or an alternator-starter for a motor vehicle, or another type of rotating electric machine, and is described for example in documents FR-A-2,602,925 and JP-A-6,121,497, contents of which one can refer for more details.
• This machine comprises a hollow support for fixing the machine to a fixed part, a stator and a rotor carrying at least one ventilation device.
• the stator surrounds the rotor, which is integral with a rotor shaft.
• the support carries, at its outer periphery, the stator and centrally bearings, such as bearings with one or two rows of balls, for rotational mounting of the rotor shaft so that the rotor and the stator are mounted at the interior of the support comprising two parts called front bearing and rear bearing.
• the rotor and / or the stator comprise at least one winding so that, in operation, the machine heats up. Frictions mechanical also occur during operation. These frictions contribute to the heating of the machine.
• the machine In certain applications, in particular when it is an alternator or an alternator-starter for a motor vehicle, the machine carries electronic components which must be protected against excessive heating to prevent their destruction.
• This fan has a central flange from which a series of ventilation blades extend radially outward and projecting axially. To reduce the noise of the rotary electric machine while improving the ventilation thereof, it has been proposed in document FR-A-2,811,156 to provide the fan with a second series of blades.
• This type of ventilation device is satisfactory, however in some cases it can be difficult to obtain a large number of blades of the desired shape.
• a ventilation device which is suitable for being fixed on a transverse face of an axial end of a rotor of a rotary electric machine, of the type comprising:
• a first fan comprising a first central flange of transverse orientation from which extend, radially outward, first blades;
• At least a second fan comprising a second central flange of transverse orientation from which extend, radially outward, second blades; and of the type comprising means for fixing the two fans.
• each blade of the other fan is located at least one blade of the other fan and the blades are each connected to a peripheral branch that each flange has on its outer periphery.
• the blades are therefore carried by the branches.
• the central flanges are superimposed and adjacent and their fixing means consist of one or more series of fixing points, consisting of welding points, which are for example arranged in a circle (s) and which are distributed over the surface of the two superimposed flanges which are generally annular in shape.
• This fixing is for example ensured by means of a series of fixing points, such as welding points, between one of the flanges and the rotor.
• each fan has at its external periphery respectively first branches and second branches extending radially outwards, at least some of said branches carrying a blade, characterized in that at least a first branch and at least a second branch comprise a first and a second portion of mutual covering for the formation of a covering zone, and in that said means for fixing the two fans are arranged at least partially at the level of said overlap zone of these two branches.
• the branches are configured so that they have overlapping zones, which in combination with the fixing points make it possible to stiffen the ventilation device while having space at the level of the central annular part of the flanges for fixing on the rotor.
• at least one of these branches carries a blade which makes it possible to have the number and / or the size of the desired blades.
• each branch carries a blade.
• the fans can easily be dynamically balanced in advance, that is to say pre-balance, by adding or removing material in the vicinity of at least one of the attachment points of the branches and / or at the blades. Balancing means are therefore installed in the vicinity of the means for fixing the branches of the fans.
• the space between two teeth of a pole wheel of a claw rotor can be plugged at least in part to reduce noise during operation.
• one of the fans can be in several parts and that one of the fans can include a metal insert and blades with plastic branches stiffened thanks to the overlap zones and the fixing points.
• the means for fixing the two fans include for example at least one point for fixing the covering portions of the two branches.
• the aforementioned balancing means are located in the vicinity of this fixing point.
• the fixing point is made by welding or gluing.
• the fixing point is made by riveting, in particular by extrusion to reduce the number of parts.
• the fixing point is made by clinching.
• said fixing means comprise two fixing points for the covering portions of the two branches, which are in particular arranged in the vicinity of opposite ends of the two covering portions to give the greatest possible rigidity to the ventilation device. Thanks to this arrangement, the fixing points make it possible to dispense with the presence of stiffening ribs for the blades and the branches of one of the fans, or even for the two fans.
• the two fixing points are offset angularly and radially with respect to each other to obtain a robust fixing of the fans.
• Said first and second mutual overlap portions are planar portions which extend in parallel transverse planes.
• Each of said transverse planar overlapping portions extends in the same plane as the central flange from which extends the corresponding branch.
• At least one blade of one of the fans is angularly interposed between at least two consecutive blades of the other of the fans.
• At least each of the blades of one of the fans is carried by a branch provided with a covering portion with a covering portion of a branch carrying a blade of the other fan, and said means for fixing the two fans are arranged at least in part at the level of all of said branches covering portions.
• An angular indexing means intervenes between the first and second flanges to angularly position the blades of the first blades relative to the second blades.
• Each flange is perforated centrally and has, in its inner radial edge, a notch so as to obtain said relative angular positioning of the blades by bringing the notches into coincidence.
• one of the fans has a projection which penetrates in a complementary manner into a hollow or an opening of the other fan so as to constitute angular indexing means by cooperation of complementary shapes.
• the first and second flanges are superimposed.
• the first and second flanges are in direct or indirect contact with the interposition of a means of thermal insulation, such as a coating or a thermally insulating layer.
• one of the fans preferably the one furthest from the rotor, is pre-stressed on the rotor.
• Figure 1 is an axial sectional view of a standard alternator
• FIG. 2 is a perspective view, from the rear of an exemplary implementation of the principles of the invention for the production of a rear ventilation device of Figure 1;
• - Figure 3 is an axial rear view at the end of the ventilation device of Figure 2;
• Figure 3A is a detail view on a very large scale of Figure 3;
• FIG. 4 is an axial front view at the end of the ventilation device of Figure 2;
• FIG. 5 is a perspective view, from the front, of an example of implementation of the principles of the invention for the production of a front ventilation device of Figure 1;
• - Figure 6 is a perspective view from the rear of the front ventilation device of Figure 5;
• FIG. 7 is a detail view on a larger scale illustrating an alternative embodiment of a blade of the ventilation device of Figure 5;
• FIG. 8 is an axial front end view of another configuration of a ventilation device according to the invention.
• FIGS 9 to 15 are detail views in section and on a large scale which illustrate the fixing means used in the context of the invention;
• - Figure 16 is a view similar to Figure 8 with representation of the pole wheel on which is mounted the ventilation device.
• FIG. 1 is only intended to briefly recall the general structure of a polyphase alternator with internal ventilation for a heat engine of a motor vehicle, with the aim of placing the invention in its context of preferred use.
• the alternator shown essentially comprises a rotor 10 surrounded by a stator 12 and mounted for rotation with a rotor shaft 14, the front end of which rotates a pulley. drive 16 and the rear end of the slip rings (not referenced) belonging to a manifold 18.
• the pulley 16 is intended to be connected to the engine of the vehicle by a belt transmission.
• the rotor 10 is here of the claw type and comprises two pole wheels, designated by the references 20 and 21, having teeth of axial orientation angularly offset from one wheel to the other.
• Reference 22 designates the excitation winding of the rotor mounted between the front 20 and rear 21 wheels.
• the stator comprises a body 24 internally provided with notches for the passage of wires or pins of the windings 26 of the stator.
• the windings 26 pass through the body 24, constituted by a pack of sheets stacked axially, and extend in axial projection from the side and other side of the body 24 to form a front bun and a rear bun (not referenced).
• the number of windings 26 depends on the applications, in particular on the number of phases that the alternator comprises.
• the rotor shaft 14 is supported by front ball bearings 28 and rear 30 mounted in axial end bearings respectively front 32 and rear 34 here perforated with louvers 36, 38 for air circulation.
• the bearings 32, 34 have a hollow shape and are shaped to carry at their outer periphery the body 24 of the stator 12.
• the reference 40 designates the conventional diode rectifier 41 of the alternating current produced by the machine. This device is connected to the outputs of the stator windings 26 and is carried here by the rear bearing 34, which also carries a voltage regulator (not visible in Figure 1) and a brush holder (shown in part in Figure 1) .
• the brushes (not referenced), mounted to slide in the brush holder, are intended to cooperate with the slip rings of the collector 18 which are connected by wire connections to the ends of the excitation winding 22, while the brushes are connected to the voltage regulator which, in a manner known per se, thus controls the excitation winding.
• the alternator comprises front and rear ventilation devices 42, each of which is fixed in rotation on a front transverse front face 44, rear 46 respectively of the front pole wheel 20 and the rear pole wheel 21.
• Each ventilation device or fan 42 comprises an annular central flange 48 applied and fixed to the front face 44, 46 of the support pole wheel and, at its external periphery, a plurality of blades 50 projecting axially relative to the flange 48.
• the two ventilation devices or fans 42 which therefore extend in the vicinity of the front bearing 32 and the rear bearing 34, have the function of creating a circulation of a fluid cooling, in this case air, to cool the hottest active parts of the alternator such as the diodes 41 of the rectifying device 40, the bearings 28, 30, the winding of the rotor 10 and the windings 26 of the stator, passing through different suitable openings in the bearings, as illustrated by arrows.
• each bearing 32, 34 comprises, centrally in the vicinity of the associated bearing 28, 30, air inlet openings facing a portion of the blades 50 and outlet openings facing the concerned chignon of the windings 26.
• the devices ventilation or fans 42 are installed below the winding buns, knowing that the ventilation device, or rear fan, is advantageously more powerful than the ventilation device, or fan, before, because it must also cool the straightening device 40 and the voltage regulator.
• FIG. 2 illustrates a rear ventilation device according to the invention which is designed for this purpose. It bears the general reference 60 and is mounted, in the embodiment described in place of the rear fan 42 of FIG. 1, the front of the device 60 being in direct or indirect contact with the rear transverse face 46 of the wheel 21.
• This ventilation device 60 here comprises two adjacent fans 62a, 62b, hereinafter called first fan and second fan respectively.
• the second fan 62b is intended to be fixed, for example in a known manner by welding or riveting points, to the front face 46 of the axial end concerned of the rear pole wheel 21 of the rotor of FIG. 1.
• the second fan 62b is in contact with the pole wheel concerned.
• This contact is a direct or indirect contact, a means, hereinafter called third means of thermal insulation, such as a coating or a layer of electrically insulating material, being interposed at least locally between the pole wheel 21 concerned and the second fan 62b.
• each fan 62a, 62b is metallic, being economically made of sheet metal.
• Each fan 62a, 62b has a central portion in the form of an annular flange 64a, 64b substantially planar annular transverse orientation which is provided with a circular central opening 66a, 66b for the passage of the rotor shaft 14 of Figure 1, and at its outer periphery, projecting radially outward, a series of ventilation blades 68a, 68b projecting axially relative to the flange 64a, 64b. Divergent ventilation channels to the outside are thus formed on each fan.
• each fan 62a, 62b are distributed angularly so that between at least two consecutive blades 68a, 68b of one of the fans 62a, 62b is located at least one blade 68b, 68a of l other fan 62b, 62a.
• the blades are, in one embodiment, distributed angularly in a regular manner.
• the first and second blades are not distributed angularly in a regular manner to reduce the noises, the circumferential intervals between two consecutive blades 68a, 68b not being regular.
• no blade of the other fan is provided so as not to have a regular distribution and to reduce noise.
• the blades 68a, 68b are here obtained by cutting and folding from their metal flange concerned 64a, 64b and have a curved shape as best visible in FIG. 2, the ventilation device 60 here being of the centrifugal type.
• the blades 68a and 68b are therefore of the same type here.
• the blades 68a, 68b have a great length radially and are therefore very efficient with regard to ventilation.
• the blades here have a length radially greater than their axial height.
• the second blades 68b are reinforced by pairs of parallel ribs 67b, which thanks to the invention can be extended at the branches 78b, which has the fan 62b, by ribs of great length because the second fans is provided with as described below of branches 78b with second covering portions.
• the blades are planar and have a radial orientation, the fan being centrifugal.
• the blades are inclined relative to an axial and / or radial direction.
• the blades are axially higher than radially long.
• the blades can be inclined and curved relative to the plane of the flange concerned as described in the aforementioned document FR-A-2,602,925.
• the blades of this fan are in the form of a propeller, the fan being of the helico-centrifugal type.
• at least certain blades are perpendicular to the plane of the flange and of non-radial orientation. All combinations are possible, the blades of each of the fans can be of the centrifugal, helico-centrifugal or axial type.
• the distribution of the blades is determined according to the electric machine to be cooled in order to obtain the best cooling with minimum aerodynamic noise.
• An angular indexing means intervenes between the two flanges 64a, 64b for a good angular position and therefore a good orientation of the blades 68a, 68b.
• each flange 64a, 64b has, in the edge of its circular central opening 66a, 66b, a pair of notches 72a, 72b and 74a, 74b.
• the notches 72a, 72b and 74a, 74b here have a bottom of identical shape, namely a bottom with a semi-circular outline. Note that the notches 72a and 72b are deeper than the notches 74a, 74b so that this allows the two fans to be angularly indexed relative to each other.
• the fans are fixed together, for example by gluing, advantageously spot welding, or clinching or riveting, the rivets being advantageously obtained by extrusion from one of the flanges, as described below to form a manipulable and transportable assembly .
• This assembly is then fixed to the rotor, for example by spot or through welding of the laser type, by screwing or by riveting, the rivets advantageously coming from the rotor.
• the blades 68a, 68b are here all axially substantially at the same height, that is to say that the free edges 69a, 69b of the blades are in the same transverse plane. More precisely, the blades 68a have a height axially slightly less than the blades 68b, the difference in height being equal to the thickness of the second flange 64b.
• the blades 68a, 68b are axially of different heights. As a result, the free edges 69a, 69b of the blades are therefore not all in the same plane.
• the realization of the ventilation device 60 in two parts or fans having complex blade configurations giving them increased cooling power, is obtained at a relatively low cost price, while having good mechanical strength.
• attachment points 76 have a large geometric extent, thanks to the characteristics of the invention d described below, and here are six in number. These points are shown in Figures 2 to 4 by circular grid portions.
• the fixing means between the two fans 62a and 62b intervene between at least a first branch 78a and a second branch 78b comprising a first and a second portion of mutual overlap to form an overlap zone Z.
• each flange 64a, 64b has radially outwardly projecting at its outer periphery respectively branches 78a, 78b respectively called first branches 78a and second branches 78b.
• Each branch 78a, 78b therefore extends transversely in the plane of the central annular flange 64a, 64b and in this embodiment carries respectively a first blade 68a and a second blade 68b.
• the blades are formed each at the free end of a branch while being carried each by a branch.
• the branches are obtained respectively by cutting and the blades by folding at the free end of the branch concerned from the metal flange of the fan concerned. The blades are therefore each connected to a branch, being here in one piece with this branch.
• the shape of the branches depends on the applications.
• the two aforementioned branches 78a, 78b are superimposed and overlap or overlap at least in part according to an overlap zone Z which is indicated by dotted lines in FIG. 3A, and it is thus possible to make here pairs of associated fixing points 80 and 82.
• These points 80, 82 have an extent smaller than that of the fixing points 76.
• the ribs 67b here at the rate of two per blade 68b, also affect the branches 78b and extend to the vicinity of a blades 68a.
• each radially exterior fixing point 80 is also angularly offset, in the direction of the blades relative to the radially interior point 82.
• Each blade 68a is connected to a first branch 78a, which is overlapped with a second branch 78b connected to blade 68b and each overlapping zone Z has two attachment points 80 and 82.
• the attachment between the two fans 62a, 62b is thus particularly rigid, while allowing the arrangement of a large number of fixing points 76 of the ventilation device 60 on the rotor. This fixing makes it possible not to rib the blades 68a.
• the two attachment points belonging to a pair of points 80, 82 in an overlap zone Z are separated as far as possible from each other, being arranged at the limits of this zone Z of overlap of the branches 78a, 78b so to further increase this overall rigidity, as well as the rigidity of these branches, forming the roots of the blades, and the rigidity of the corresponding blades 68a, 68b.
• certain pairs of the fixing points 80, 82 or generally a part of the fixing means are in Figures 2 to 4 located in the vicinity of the fixing points on the rotor.
• the fixing points 80, 82 can be produced according to all known and suitable technologies. They can for example be made by gluing or welding to reduce costs.
• rivets which are preferably obtained by extrusion as visible at 79b in FIG. 12.
• the two flanges of the fans 62a, 62b are metallic and the head of the rivet 79b, issued by extrusion of the flange of the fan 62b, is crushed in contact with the covering portion of the branch 78a of the fan 62a having a hole for the passage of the rivet 79b.
• the head of the rivet 79b is not crushed and the assembly is performed by clinching, the hole in the covering portion of the branch 78a being dimensioned for press fit of said portion 78a on the rivet 79b.
• one of the two fans can be made of plastic.
• the first fan 62a is for example preferably made of plastic, while the second fan 62b is made of metal for making a rivet 79b by extrusion.
• a first means of thermal insulation intervenes at least for the most part between the two flanges of the fans.
• These first means advantageously are extended by second thermal insulation means acting between the covering portions of the branches 78a, 78b.
• the first fan 62a is metallic and the second fan 62b is made of plastic so that in FIG. 12 the head of the rivets 79b molded with the second fan is hot-pressed.
• the rivets 79b instead of being hollow, as in FIGS. 11 and 12, are of solid shape and advantageously a third means of thermal insulation intervenes at least for the most part between the flange of the fan 62b and the rotor.
• the first, second and third means of thermal insulation consist, for example, of a thermally insulating layer or coating, for example of a material having the properties of asbestos. All combinations are possible whatever the nature
• the second fan can be provided on one of its faces with a first thermal coating insulator to cooperate with the rotor and on the other of its faces at the branches 78b of a coating to cooperate with the branches 78a.
• the second fan is provided with three means of thermal insulation.
• the entire zone Z is in one embodiment at least in part a bonding zone.
• the fixing points can be connected to form a fixing strip, for example obtained by gluing or transparent welding, also called through welding, of the laser type. This is possible thanks to the invention.
• At least one branch may have no blade.
• a branch devoid of a blade has a covering portion with a covering portion of a branch whether or not it has a blade.
• one of the fans 62a, or the two fans in a variant may include a central stiffening flange 84a which projects axially.
• This flange 84a as a variant is extended axially to form a sleeve allowing mounting, for example by press fitting, of an annular magnetic target used in the case of an alternator-starter, as visible for example in FIG. 12 of document WO 01/69762 to which reference will be made for more details.
• This flange 84a further stiffens the first fan 62a, which thus is in an embodiment thicker than the fan 62b.
• the collar can participate in the relative centering of the two fans, in particular when it is the second fan 62b which has such a collar. In this case, the internal periphery of the first fan is in intimate contact with the external periphery of this flange.
• the invention is not limited to the fixing of two superimposed fans for the production of a ventilation device, the number of fans possibly being higher depending on the complexity of the device, and in particular depending on the number and the conformation of the blades.
• FIGS. 5 to 7 Another example is shown in FIGS. 5 to 7 for the production of a rear ventilation device, which is intended to replace the rear device 42 shown in FIG. 1 which is fixed to the front transverse face 44 of the front pole wheel. 20.
• FIG. 5 illustrates a rear ventilation device according to the invention which is designed for this purpose. It bears the general reference 60 and is mounted, in the embodiment described in place of the rear fan 42 of FIG. 1, the rear of the device 60 being in direct or indirect contact with the transverse face 46 of the wheel rear 21.
• This ventilation device 60 here again comprises two adjacent fans 62a, 62b, hereinafter called first fan and second fan respectively.
• the second fan 62b is intended to be fixed, for example in a known manner by welding points or by riveting, on the front face 44 of the axial end concerned of the rear pole wheel 21 of the rotor of FIG. 1.
• the second fan 62b is therefore in contact with the pole wheel concerned.
• This contact is a direct or indirect contact, a third means of thermal insulation, such as a coating or a layer of electrically insulating material, being interposed at least locally between the pole wheel 21 concerned and the second fan 62b.
• a third means of thermal insulation such as a coating or a layer of electrically insulating material, being interposed at least locally between the pole wheel 21 concerned and the second fan 62b.
• the second fan 62b is made in two parts, substantially in two halves so as to delimit two slots 86b arranged opposite the open faces of the grooves 86a.
• the second fan can be produced in more than two parts, for example three parts.
• This second fan 62b is in an embodiment thinner than the first fan 62a.
• the first blades 68a each have an end chamfer 88a so as to improve the mechanical resistance against the centrifugal force.
• FIG. 8 represents an alternative embodiment of a front ventilation device 60 according to the invention with non-regular blades and which comprises a single series of mutual fixing points 80 arranged in a circle and distributed in an almost regular manner.
• This device 60 is intended to be mounted in place of the front ventilation device 42 of FIG. 1.
• the central annular flanges are almost entirely free, in particular for the arrangement of the points of fixing the ventilation device 60 on the front wheel 20 of the rotor.
• At least one fixing point 76 at the level of the annular flanges 64a, 64b.
• portions of blades in mutual overlap which are not necessarily portions of the roots of transverse orientation of the blades, but for example portions of axial orientation provided for this purpose. effect or belonging to the curved active parts of the blades.
• This first example illustrated in FIG. 9 corresponds to a first fan 62a made of plastic or metal and to a second fan 62b made of metal.
• a hole or clearance 92a is provided in the first flange 64a made of plastic or metal.
• the second flange has a stamped 94b so that the welding point 76 on the rotor is of the type standard. It will be appreciated that the hole 92a in the flange 64a is large thanks to the invention.
• FIG. 10 illustrates an inversion with respect to what is shown in FIG. 9 with the second flange 64b made of plastic or metal and the first flange 64a made of metal.
• the second flange is well pressed against the rotor because it is sandwiched between the relevant face of the rotor of Figure 1 and the first flange 64a.
• the hole 92b in the flange 64b is also large thanks to the invention which allows to locally stamp the flange 64a so that it penetrates into the hole 92b.
• the flange 64a is therefore locally level so that the point solder 76 is of the standard type.
• FIG. 13 similar to FIG. 10, shows such an embodiment, the stamping in direction reverse bearing the reference 194a, the dorsal face of this stamped showing a trapezoidal imprint.
• the stamping is deeper as visible at 294a and 394a in FIGS. 14 and 15 similar to FIG. 10, the stamping 394a being of shape similar to the stamping 194a, while the stamping 294a is similar to stamped 94a.
• the ventilation device according to the invention can be mounted in a reversible alternator, called an alternator-starter, which can also operate in electric motor mode, in particular for starting the heat engine of the motor vehicle as described in document WO 01/69762.
• this ventilation device can be mounted in an alternator comprising a rotor with salient poles and / or with permanent magnets as described in document WO 02/054566.
• the rotor comprises a pack of cut sheets for forming housings, intended to receive permanent magnets, and for arm formations around which excitation windings are wound.
• the magnets housings are closed by non-magnetic holding pieces having recesses for receiving the excitation windings.
• these parts extend on either side of the sheet pack by being integral with this pack, for example using tie rods passing through the pieces and sheet packs. It is on these parts that the ventilation device is attached.
• these retaining pieces are provided with locally threaded bosses for fixing by screwing the ventilation device as in the embodiment of FIGS. 15 and 16 of this document WO 02/054566.
• the alternator can also be water-cooled and be fitted with axial fans.
• the stator windings may include conductive elements in the form of bars, such as pins generally in the shape of a U and advantageously rectangular section as described in the document FR A 2 820 896.
• the internal ventilation device according to the invention makes it possible to cool the head of the pins well because it can have the desired shape.
• the stator windings each comprise a triangle winding and a star winding of different section mounted in the same notches as described in documents US A 4,163,187 and FR A 2,737,063.
• the alternator may have only one ventilation device at the rear thanks to the power of the ventilation device according to the invention.
• the ventilation device makes it possible to obtain blades of the same configuration, in particular identical but which are very close together and thus in large number and / or blades of long or complicated shape, and which therefore cannot be made by folding from a single fan.
• at least one blade of one of the fans is provided, overhanging, with a fin extending in an inclined or perpendicular manner relative to the plane of the flange of the fan concerned as described and visible in FIGS. 11 to 13 of document FR A 2 811 156.
• At least one blade and preferably at least some of the blades at least one of the fans may be wavy or be axially of decreasing height or be plane and inclined relative to a radial direction as respectively in Figures 6, 15 and 2 of this document.
• the ventilation device makes it possible to easily and economically manufacture at least one fan provided with at least one blade, preferably with several blades, having a configuration such that the entry angle formed on the internal circle between the blade and the direction the radius at this point on the circle is substantially the same as the exit angle formed on the outer circle between the blade and the corresponding radius as described in application FR 01 14301 filed on 10/31/2001, said angle being identical to the entry and exit angles for all points between entry and exit. Thanks to this arrangement, the turbulent flows of the cooling fluid, in this case air, are minimized while having a large number of blades.
• the angle of incidence of the blades, at the level of the leading edge is between 150 ° and 175 °
• l angle of incidence of the blades, at the trailing edge is between 90 ° and 165, relative to the tangent to a circle generated during the rotation of the blades, the ratio between the average pitch of the blades and the length average of the latter is less than 0.975 as described in application FR 01 05772 filed on 04/27/2001. Thanks to this arrangement, the friction losses of the cooling fluid are reduced.
• At least one blade of at least one of the fans has perforations, such as holes or slots, for passage of the cooling fluid, here air, from one face to the other of this blade for compensate for the slowing down of the fluid vein and thus avoid the detachment of the fluid and reduce the noises.
• At least one blade of at least one of the fans extends in a variant inclined with respect to the plane perpendicular to the flange of the fan concerned.
• the blades of the fans extend axially in the same direction.
• at least one fan has at least one blade directed axially in the opposite direction with respect to the other blades so that this fan has at least two blades extending on either side of its flange. These blades in an embodiment extending in the space present between the teeth of the pole wheels 20, 21 of the rotor 10.
• At least one of the fans in one embodiment is produced by molding a plastic material on an advantageously metallic insert so that the blades can be at least partially made of plastic.
• the insert extends at least substantially over the entire extent of the fan flange or at least over two thirds of the molded part of the fan as described in the document FR
• the blade is attached at least in part to its associated branch.
• the overlapping zones Z according to the invention, in order to reduce the noises, it is possible to at least partially block the space existing between the teeth of the adjacent pole wheel as visible in FIG. 16.
• the fan being of the type of that of FIG. 8.
• overlapping zones Z are located opposite the spaces 220 for plugging here in part these.
• the cutouts 178a between two consecutive branches 78a are not identical as visible in this figure 16. This arrangement makes it possible to balance in advance (pre-balancing) the fans by adding or removing material in certain places. This is favored by the overlap zones and the fixing points according to the invention making it possible to stiffen the branches of the invention. Of course the same can be true for the fan 62b.
• Balancing is alternatively carried out by carrying out at least one drilling in at least one of the fans at a branch overlap zone as visible in 176 in FIG. 3 and in 276 in FIG. 26, the drilling in this figure being produced in an appropriate branch of the fan 62a between two fixing points 80, 82.
• material can be removed at least in the fan 62a and this in the vicinity of a point of attachment of the branches as visible at 177 in Figure 3.
• chamfers 88a also make it possible to achieve balancing. It is the same by making openings in the blades.
• Dynamic balancing can be carried out in advance by adding material as shown at 179 in Figure 16.
• the first fan 62a is pre-stressed on the rotor as described for example in document FR A 2 743 951, the faces 44 and / or 46 of the wheels 20, 21 being shaped frustoconical and fixing on the rotor made by riveting or crimping.
• the arrangements described in document FR A 2 603 142 for pre-stressing the mounting of the first flange 64a, then of convex shape in the free state, on the rotor of the machine.
• the two fans are fixed to the rotor by means of a ring which is force fitted on the grooves of the rotor shaft 14.
• the shaft is threaded and the ring consists of a nut.
• the nets of the rotor shaft is oriented in the opposite direction to the direction of rotation of the machine.
• the fan 62a comprises, as in FIG. 2, a flange force fitted on grooves of the rotor shaft.
• the ring is hooped on the rotor shaft.

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