Wound disc rotor for axial flux electric machine.

Abstract

Wound discoid rotor 1 for electric machine 100 with axial magnetic flux consisting of: two flanges 10a, 10b made of composite material and a steel ring 20, assembled by two series of rivets 50, 51 and forming an annular chamber 10c; rotor cores 30, in even number, supported at each end by the flanges 10a, 10b, and each carrying a coil 40 arranged in the annular chamber 10c; two collectors 41, 42 connected one to the end of the wire 40a of each coil 40 and the other to the end of the wire 40b of each coil;of two electric current supply wires 43,44 connected one to the external collector 41, the other to the internal collector 42, characterized in that: each flange 10a,10b is pierced with as many inclined air inlet ducts 17a,17b as there are coils, close to the internal diameter 10d of the annular chamber 10c, connecting this annular chamber with the internal ambient space of the electric machine 100 contained in the casing 110 closed by the closing flange 111; the ring 20 has as many air outlet openings 21 as there are coils, creating a second communication between the annular chamber 10c and the internal ambient space of the electric machine 100 contained in the casing 110 closed by the closing flange 111, creating, during rotation of the discoid rotor a flow of cooling air from coils 40 entering through the inclined air inlet ducts 17a, 17b and exiting through the air outlet openings 21. Figure for abstract: Fig.2;

Description

Title of the invention: Wound disc rotor for axial flux electric machine. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an axial flux electric machine comprising a disc-shaped rotor framed by two stators.

[0002] More precisely, the particularity of the rotor is that it has no permanent magnet. The magnetic flux is obtained by metal cores each surrounded by a coil. This rotor can be described as a wound rotor. STATE OF THE ART

[0003] There are many publications disclosing an axial flux electric machine.

[0004] In the architecture comprising a central stator and two lateral rotors, one can cite as an example the publication WO2022 / 185403. In all the publications, the rotors are discs on which permanent magnets are attached.

[0005] In the architecture comprising a central rotor framed by two lateral stators, we can cite publication FR3064422. The rotor is equipped with highly segmented magnet blocks.

[0006] Radial flux wound rotor electric machines have been marketed by very few electric motor vehicle manufacturers and among the few axial magnetic flux electric machines on the market, there are none with wound discoid rotors.

[0007] However, this type of machine has the advantage of not requiring permanent magnets and therefore rare earths and the magnetic field generated by the rotor coils is adjustable.

[0008] In all publications concerning axial magnetic flux electrical machines, with a few rare exceptions, the rotors are discs on which permanent magnets are attached.

[0009] Among the exceptions is publication CN218678605U. The only figure in this publication shows a rotor consisting of three discs with two notches, each carrying two coils in the shape of this spiral, which, after a particular stacking, angularly at 60°, forms a set with six coils distributed regularly. The only figure is not explicit about the circulation of the electrical current and the supply of the coils. PRESENTATION OF THE INVENTION

[0010] the object of this invention is a discoid rotor, for an axial flux electric machine, equipped with coils.

[0011] The coils being supplied with electric current, the specific device for supplying electric current is described, without being the object of the invention.

[0012] The axial magnetic flux electric machine that can operate with a wound discoid rotor is of central rotor and lateral stator architecture. The rotor is confined between two annular heat-emitting elements and the rotor has its own losses by Joule effect and eddy currents. The object of the invention deals with the cooling mode which depends on the structure of the machine and requires its description.

[0013] According to a first characteristic, the discoid rotor comprises a base, carrying rotor cores each surrounded by a coil, consisting of two flanges made of composite material and a peripheral reinforcing ring made of steel forming with the flanges an annular chamber containing the coils, the two flanges being secured by a first series of rivets, equal in number to that of the cores, arranged on a diameter smaller than the internal diameter of the annular chamber, the two flanges and the reinforcing ring being secured by a second series of rivets, equal in number to that of the cores, arranged on the external diameter of the annular chamber.

[0014] According to a second characteristic, the flanges have trapezoidal type openings corresponding precisely to the section of the rotor cores which pass through the wall and are flush with the outer surface of the flanges.

[0015] According to a third characteristic, the rotor cores, conductors of the magnetic fields generated by the coils and also by those generated by the stator pads, are made of SMC (Soft Magnetic Composite), or are laminates of electrically insulated iron sheets, or are bundles of electrically insulated iron wires.

[0016] According to a fourth characteristic, the rotor cores are externally overmolded with an electrically insulating material over their entire length and according to two distinct thicknesses: • the strongest, in the center, serves as a cradle for a coil and axially holds the core because its external dimensions are greater than those of the openings in the flanges and its length is equal to the width of the annular chamber; • the thinner one at each end gives the core the same final external dimensions as the openings in the flanges and its length is equal to the thickness of the flange fabric.

[0017] According to a fifth characteristic, in the space of the annular chamber closest to the axis of rotation, two closed circular collectors supply the coils, in even number, the two ends of the conductive wire of these coils of which are secured, for example by welding, to each of the two collectors, so that: the connections give coils connected in parallel; • the connections of two consecutive coils are reversed to create reversed magnetic fields.

[0018] According to a sixth characteristic, from each circular collector there departs a supply wire which passes through the wall of the same flange through a hole close to the internal diameter of the annular chamber.

[0019] According to a seventh characteristic, in each flange, close to the internal diameter of the annular chamber, and under each coil, an inclined bore places the annular chamber in communication with the ambient environment of the discoid rotor. The inclination of the bores is that which favors the entry of air into the annular chamber when the discoid rotor rotates in the main direction. In other words, if the machine is fitted to a motor vehicle, the main direction is its forward movement.

[0020] According to an eighth characteristic, in the reinforcing hoop, opposite each coil, an opening puts the annular chamber in communication with the ambient environment of the discoid rotor and under the centrifugal effect promotes the extraction of air from the annular chamber.

[0021] According to a ninth characteristic, the coils, carried by the rotor cores, are set back from the inner and outer diameters of the annular chamber, spaced from each other and thus a circulation of cooling air is established coming from the inclined holes in the flanges towards the openings in the reinforcing ring and it is all the more intense as the rotation speed of the rotor is high. DETAILED DESCRIPTION OF THE INVENTION

[0022] These characteristics, aims and advantages of the present invention will appear on reading the detailed description which follows and with regard to the appended drawings given as non-limiting examples and in which:

[0023] [Fig-1] is a front view of the assembled disc.

[0024] [Fig.2] is a front view of the incomplete disc, without the peripheral reinforcing ring and without the front flange.

[0025] [Fig.3] is a first AA section of the assembled disc.

[0026] [Fig.4] is a second BB section of the assembled disc.

[0027] [Fig.5] is a third CC section of the assembled disc.

[0028] [Fig.6] is a set of front views of the rotor pad, zooms on the material component and a partial sectional view of the rotor disc zooming in on the overmolding of the rotor stud.

[0029] [Fig.7] is a sectional view of the electric machine.

[0030] [Fig.8] is a sectional view of the device for supplying electric current to the rotor.

[0031] [Fig.9]is a view of the cooling air circulation in the rotor disc.

[0032] [Fig. 10]is a view of the rotor cooling air circulation in the com closed compartment of the electric machine and a partial view of the stator cooling device.

[0033] [Fig.l] is a front view of the discoid rotor 1 for an electric machine 100 with axial magnetic flux. This rotor comprises 2 flanges, the flange 10a is from the front in this view.

[0034] It has trapezoidal type openings 1 la, always even in number but variable according to the performance required for the electric machine, which carry one of the ends of the magnetically conductive rotor cores 30.

[0035] We have a circular centering opening 12a which serves to position the discoid rotor 1 on its guide bearing.

[0036] On a first diameter, we have a series of drillings. These are the screw passage holes 13a for fixing the discoid rotor 1 and the pin passage holes 14a contributing to the transmission of the torque.

[0037] On a second diameter we have circular withdrawal zones 15a relative to the surface, of the same number as the rotor cores 30, occupied by the heads of the rivets 50 securing the two flanges.

[0038] On a slightly larger diameter, we have a series of inclined air inlet ducts 17a, from the air inlet 17al on the external surface of the flange 10a to the air outlet 17a2 on the internal surface (specified later). The air inlet ducts will only be effective for the direction of rotation 2. This direction of rotation, for an electric machine equipping a vehicle, must be that corresponding to forward motion.

[0039] Finally, on a diameter at the periphery, we have semi-circular zones 16a set back from the surface, of the same number as the rotor cores 30, occupied by the heads of the rivets 51.

[0040] These rivets 51 secure the two flanges with the peripheral strapping 20 locally on its internal protrusions 20a, narrower than the strapping itself and on which the two flanges are pressed (see [Fig.3]).

[0041] The role of this strapping 20, on which the flanges can be centered with radial tightening, is to significantly increase the opposition of the flanges to the centrifugal forces generated by the rotor cores 30 which each carry a coil and to allow a higher limit rotation speed.

[0042] Air inlet ducts 17a mean internal air circulation in the discoid rotor 1. This circulation will be natural because the air outlet openings 21 are on the periphery in the ring 20 and facing each rotor core 30.

[0043] [Fig.2] is a front view of the discoid rotor 1 without the ring 20 and the flange 10a present in [Fig.l]. This figure shows a view of the interior of the discoid rotor 1.

[0044] We see the inner face of the flange 10b, and find the same orifices, a centering opening 12b which is used to position the discoid rotor 1 on its bearing guide, the screw passage holes 13b for fixing the discoid rotor and the pin passage holes 14b contributing to the transmission of the torque.

[0045] On a second diameter we have the holes 15b for the passage of the interior rivets 50 for securing the two flanges.

[0046] On a slightly larger diameter, we have a series of air ducts 17b inclined from the external air inlet 17b 1 to the internal air outlet 17b2.

[0047] The rotor cores 30 each carry a coil 40, connected to the outer collector 41 by the end of the winding wire 40a and connected to the inner collector 42 by the end of the winding wire 40b. The coils are connected in parallel.

[0048] Each coil produces a magnetic field always oriented in the same direction. But two consecutive coils must produce fields in opposite directions. Also, the connections of the ends of the winding wires 40a, 40b to the collectors 41, 42 are made in such a way as to obtain this alternation of field direction. For two adjacent coils, either two connections of the end of winding wire 40a, or two connections of the end of winding wire 40b are adjacent.

[0049] These collectors are connected to an external electrical supply by a supply wire 43 from the external collector 41 and a supply wire 44 from the internal collector 42. These supply wires 43, 44 pass through the wall of the flange 10b.

[0050] Finally, on a diameter at the periphery, we have semi-circular withdrawal zones 16b relative to the external surface of the flange 10b, of the same number as the rotor cores 30, occupied by the heads of the rivets 51 (not shown) implanted in the holes 18b.

[0051] [Fig.3] is the section AA of the discoid rotor 1. The two flanges 10a, 10b are joined and secured internally by the rivets 50. Externally, the rivets 51 secure the two flanges 10a, 10b with the strapping 20 at the level of each internal protrusion 20a.

[0052] The rotor core 30 passes through the two flanges and is flush externally. The coil 40 occupies the entire axial space of the annular chamber 10c formed by the flanges 10a, 10b.

[0053] the annular chamber 10c of the flanges extends towards the axis of rotation under the coils for the passage of the outer 41 and inner 42 collectors.

[0054] Close to the diameter 10d, the smallest of the annular chamber 10c, is located the inclined air inlet duct 17b, and in the ring 20 the air outlet opening 21 of width slightly less than that of the annular chamber 10c.

[0055] [Fig.4] is the section BB of the discoid rotor 1. In the annular chamber 10c formed the outer 41 and inner 42 collectors are arranged by the two flanges 10a, 10b and reinforcement ring 20.

[0056] These collectors are connected to an external power supply, the collector outer 41 by the power wire 43 and the inner collector 42 and the power wire 44.

[0057] These supply wires 43,44 pass through the wall of the flange 10b through openings 10b1 and 10b2 located at the level of the smallest diameter 10d of the annular chamber 10c.

[0058] [Fig.5] is the CC section of the discoid rotor 1. In the annular chamber 10c each coil is connected to the two collectors 41,42 by the two ends of winding wire 40a and 40b.

[0059] [Fig.6] includes three front views of the rotor core, two zooms on the structure of the material, and also a partial section of the discoid rotor 1 zooming the overmolding outside the metal core.

[0060] The core of the rotor core is made of a material with the lowest possible reluctance and which must generate the least possible loss by eddy current.

[0061] The core 30a is made of SMC. The core 30b is a stack of thin sheets electrically insulated from each other, of several widths to form a figure close to a trapezoid and arranged horizontally as shown in the zoom. The core 30c is a bundle of wires electrically insulated from each other and tangent to each other as shown in the zoom.

[0062] Each type of core is surrounded by a peripheral overmolding 31. This overmolding 31 covers the entire length of the core 30a, 30b, 30c. At the ends 31a, the thickness of the overmolding gives the core the final dimension corresponding to the trapezoidal type openings 11a and 11b of the flanges 10a, 10b.

[0063] In the central part, the overmolding 31b is thicker and has two roles. The first is to axially block the core. Indeed, by having a perimeter larger than that of the trapezoidal type openings 11a, 11b and a length equal to the width of the annular chamber 10c, the overmolding 31b rests laterally on the flanges 10a and 10b. The second role of this overmolding 31b in insulating material is to serve as a cradle for the coil 40, this cradle being completed laterally by the flanges 10a, 10b and the shim 45 locally filling the empty conductor space.

[0064] [Fig.7] is a sectional view of the axial magnetic flux electrical machine 100, equipped with the wound discoid rotor 1. It is contained in the casing 110 closed by the closing flange 111 fixed to the casing using the screws 112.

[0065] The electric machine 100 is of the axial magnetic flux type with a single discoidal rotor 1. It is framed by the stators 120, 130.

[0066] The stators 120, 130 are constructed on the basis of a carcass 121, 131 provided with a series of openings bordered by an axial extension 121 a, 131 a for receiving the stator pads 122, 132 glued over their entire length.

[0067] Externally, these axial extensions 121a, 131a carry the coils 123, 133.

[0068] The magnetic circuit is looped behind the stator pads 122,132 by the annular yokes 124,134 made of rolled sheet metal and glued to the stator pads 122,132.

[0069] The frames 121, 131 have the outer axial extensions 121b, 131b and the inner axial extensions 121c, 131c which form hollow annular bodies closed by the annular covers 125, 135. These stator chambers 127, 137 are occupied by the stator pads 122, 132, the coils 123, 133 and the yokes 124, 134 and the remaining free volume allows the circulation of a cooling liquid which will be in direct contact with the coils and the yokes.

[0070] The covers 125, 135 are fixed on their internal diameter by the screws 126 and on their external diameter by the screws 139, a means of fixing common with the carcasses of the stators on the central spacer 140.

[0071] This central annular spacer 140 is the intermediate element between the stators 120, 130 and the casing 110. On the periphery it has several ears 140a crossed by the screws 141 for placement on the support surfaces 110a.

[0072] In the inner zone of this annular central spacer 140, the discoid rotor 1 is arranged. It carries on either side and at a precise distance the two stators 120, 130. The thickness of the spacer 140 is precisely equal to the sum of the thicknesses of the discoid rotor 1 and the two air gaps 128.

[0073] Between two consecutive ears 140a, the spacer 140 is set back relative to the casing fabric 110 and provides a passage 145 for air circulation in the internal space formed by the casing 110 and the closing flange 111.

[0074] The casing 110 has a general shape close to a slightly conical cylinder (casting draft) closed on one side by a canvas 110b. In the center of this canvas, in the boss 110c, an axis 150 is fitted, without play.

[0075] On its free part extending beyond the boss 110c, the axis 150 carries a bearing 160 with double rows of angular contact balls.

[0076] This bearing 160 is made up of an outer ring 161, two inner rings 162, 163 between which the balls 164 are interposed. The inner rings 162, 163 are pressed into contact with each other. This bearing 160 is characterized by an absence of internal play and a slight preload. The ring 163 is indirectly in axial support on the casing 110, because between the latter and the ring 163 is interposed the balancing washer 170 of the air gaps 128. The whole is held tight by the screw 152 and the pressure washer 151.

[0077] The outer ring 161 has an annular radial extension 161a. On one side of this is supported the discoid rotor 1, centered on the outer diameter of the ring 161. On the opposite side, the rotor current supply device 200 is arranged, secured by the screws 201.

[0078] Against the discoid rotor is supported a power transmission hub 180, also centered on the outer diameter of the ring 161 of the bearing 160. The screws 185 pass through the radial extension 161a, the discoid rotor 1 and secure them with the power transmission hub 180.

[0079] The power transmission hub 180 externally carries the rotor 191 of the resolver, the stator 190 of which is positioned on the closing flange 111. In its hollow part, the power transmission hub 180 accommodates the grounding device 187, protecting the bearing 160 from possible parasitic currents and a ball slide 182 and its grooved ring 181, protecting the machine from external axial stresses harmful to the stability of the air gaps 128.

[0080] [Fig.8] is a sectional view of the current supply device 200. It comprises a first support element 210, made of insulating material, for the other elements which make up this device.

[0081] The first support element 210 is centered by its diameter 210a and is supported by its face 210b on the radial extension 161a of the outer ring 161 of the bearing 160. It is secured in rotation with this ring by the screws 201 (see [Fig.7]) and is therefore linked in rotation to the discoid rotor 1.

[0082] On the support element 210 is mounted a complementary element 220, also made of insulating material and driven in rotation by the grooves 210c.

[0083] The support element 210 and the complementary element 220, integral in rotation, frame a fixed element 230 in rotation, made of insulating material.

[0084] The fixed element 230 in the form of a crown, is centered on the support element 210, has a protrusion 230a which cooperates with a pin 260, for locking in rotation, screwed into the casing 110 of the electric machine.

[0085] The fixed element 230, made of insulating material, carries on either side the crown-shaped plates 231 and 232 made of conductive material.

[0086] Similarly, the support elements 210 and complementary 220 carry opposite crown-shaped plates 231, 232 respectively crown-shaped plates 211 and 221 also made of conductive material.

[0087] Between the crown-shaped plates 211, 231 on the one hand and 221, 232 on the other hand are interposed identical transmitter discs 250a and 250b, the first 250a centered by its outer diameter in the support element 210, the second 250b centered by its outer diameter in the complementary element 220, and free to rotate.

[0088] These two transmitting discs 250a, 250b are similar to those of the needle thrust bearings, but play a very different role. They are composed of an annular disc 251 made of insulating material which has, on two concentric circles, a large quantity of rectangular openings in which are inserted rollers 252, cylindrical and all identical, made of conductive material, copper or copper alloy, with a diameter greater than the thickness of the annular disc 251.

[0089] These rollers are subjected to a very low axial load which ensures the contact of the largest possible proportion of rollers 252 with on the one hand the crown-shaped plates 211, 231 (transmitter disc 250a) and on the other hand the crown-shaped plates 221, 232 (transmitter disc 250b) in order to transmit the electric current from the fixed element 230, connected to an external power supply, to the support element 210 and the complementary element 220 in rotation, connected to the coils of the discoid rotor 1.

[0090] For this, the complementary element 220, the fixed element 230, as well as the transmitting discs 250a, 250b are pressed against each other and against the support element 210 by a spring of the corrugated washer type 225, mounted in a circular groove 220b of the complementary element 220, put under tension by the washer 226 held by the stop ring 227 engaged in a groove of the support element 210.

[0091] The choice of a very large number of rollers 252 is the way of splitting the electric current and limiting it, for each contact, to a low intensity level reducing the risks of electric arcing and damage.

[0092] The crown-shaped plates 211, 221 have tabs 211a and 221a for connection with the rotor coils. In the embodiment described by this [Fig.8], the tab 211a is welded to the supply wire 43 of the external collector 41, and the tab 221a is welded to the supply wire 44 of the collector 42.

[0093] The crown-shaped plates 231, 232 carried by the fixed element 230 each have a tab 231a, 232a for connection with an external current supply device (not shown).

[0094] The tabs 23la, 232a exit the casing towards the external supply by passing through the tab guide 240 made of insulating material engaged in the opening 115 of the casing 110 and retained by the stop ring 241.

[0095] To ensure the longevity of the current supply device 200, the rollers 252 will be coated with bearing grease. This grease will be kept confined by the felt seals 255.

[0096] [Fig.9], is a partial front view of the discoid rotor 1. On the flange 10a, below each coil 40, that is to say the part closest to the axis of rotation we have an air inlet duct 17a inclined relative to the axis of rotation of the discoid rotor 1. This bore is an air circulation duct between the unoccupied volume internal to the casing and the unoccupied volume internal to the annular chamber 10c. For the direction of rotation 2 indicated, the introduction of air towards the annular chamber 10c is favored by an air inlet 17al, in relation to the internal volume of the casing in angular advance on the air outlet 17a2, in relation to the internal volume of the annular chamber 10c. The air outlet 17a2 is centered relative to the coil 40.

[0097] In the strapping 20, the air outlet openings 21 are conversely a conduit of air circulation from the annular chamber 10c to the volume internal to the casing, the openings are centered relative to the coils 40.

[0098] Arranged in this way, the circulation of air between the air inlets 17a, 17b and the air outlet 21 of the annular chamber 10c is as follows: • suction through the air inlets 17a 1, 17b 1 and expulsion through the air outlets 17a2, 17b2 of the air inlet ducts 17a, 17b inclined along the path 60; • the incoming flows are shared at the bottom of the coils 40, equally or not, and bypass them according to the paths 61,62; • the two flows come together at the top of each coil and exit the annular chamber 10c through the air outlet opening 21 along the path 63.

[0099] [Fig. 10], is a sectional view of the electrical machine 100 having the double cooling system. The half-section above the axis of rotation shows the loop circulation of the air in the closed space constituted by the casing 110 and the closing flange 111. The half-section below the axis of rotation shows the cooling device 300 of the stators 120, 130 because it also participates in the cooling of the air circulating in the closed space constituted by the casing 110 and the closing flange 111.

[0100] The cooling of the air passing inside the discoid rotor 1 is obtained by a double heat exchange: • with the ambient air outside the machine 100 along the canvases of the casing 110 and the closing flange 111; • with the cooling liquid of the stators 120,130 along the radial fins 125a,135a of the covers 125,135 of the frames 121,131.

[0101] The air expelled from the annular chamber 10c of the discoid rotor 1, through the air outlet openings 21 along the path 63, makes the following symmetrical loops: • along the paths 70a, is divided into two flows; • according to the 70b routes, cross the carcasses 121,131 in passages premises 121d, 13 Id made by material removal; • according to the paths 70c, bypasses the stators 120,130 between the periphery of the stators and the casing fabric 110; • according to the paths 70d, moves towards the center of the machine 100, housing, on one side, the radial fins 125a of the cover 125 and the casing fabric 110 and on the other side the radial fins 135a of the cover 135 and the fabric of the closing flange 111; • according to the 70th routes, bypasses the stators 120,130 in their internal openings; • is re-sucked, along path 60 through the air inlets 17a 1, 17b 1 of the discoid rotor 1.

[0102] During the paths 70d, the cooling device 300 of the stators 120, 130 therefore participates in the cooling of the air circulating in the annular chamber 10c of the discoid rotor 1.

[0103] The cooling of the stators, and therefore of the covers 125,135, is achieved by the circulation of a liquid in the unoccupied space in the stator chambers 127,137 while being in contact with the coils 123,133 and the yokes 124,134.

[0104] The liquid arrives via a conduit 301 carried by the central spacer 140 then, via a radial conduit 302 in the spacer, feeds the axial conduits 303 in the axial external extensions 121b, 131b of the carcasses 121, 131.

[0105] An opening 304 at the end of the axial conduits 303 allows liquid to enter the stator chambers 127,137.

[0106] An equivalent device arranged on the electrical machine 100, diametrically opposite it (not shown) allows the liquid to be evacuated to an external circuit comprising an exchanger.

Claims

Claims

1. Wound discoid rotor (1) for an electric machine (100) with axial magnetic flux consisting of: • two flanges (10a, 10b) made of composite material and a steel ring (20), assembled by two series of rivets (50, 51) and forming an annular chamber (10c); • rotor cores (30), in even number, supported at each end by the flanges (10a, 10b), and each carrying a coil (40) arranged in the annular chamber (10c); • two collectors (41, 42) connected one to the end of the wire (40a) of each coil (40) and the other to the end of the wire (40b) of each coil; • two electric current supply wires (43, 44) connected one to the external collector (41), the other to the internal collector (42), characterized in that: • each flange (10a, 10b) is pierced with inclined air inlet ducts (17a, 17b) close to the internal diameter (10d) of the annular chamber (10c), connecting this annular chamber with the ambient internal space of the electrical machine (100) contained in the casing (110) closed by the closing flange (111); • the hoop (20) has air outlet openings (21) creating a second communication between the annular chamber (10c) and the ambient internal space of the electrical machine (100) contained in the casing (110) closed by the closing flange (111), creating, during rotation of the discoid rotor, a flow of coil cooling air (40) entering through the inclined air inlet ducts (17a, 17b) and exiting through the air outlet openings (21).

2. Wound discoid rotor (l) according to claim 1 characterized in that the rotor cores (30), conductor of the magnetic fields generated by the coils and also those generated by the stator pads, are made of SMC (30a), or are a stack of thin sheets electrically insulated from each other, of several widths to form a figure close to a trapezoid and arranged horizontally (30b), or are a bundle of wires electrically insulated iron bars tangent to each other (30c).

3. Wound discoid rotor (l) according to claim 1 characterized in that the rotor cores (30) are externally covered with an overmolding (31) of electrically insulating material over their entire length and according to two distinct thicknesses: • the strongest (31b), in the center, serves as a cradle for a coil (40) and axially holds the rotor core (30) because its external dimensions are greater than those of the trapezoidal type openings (11a), (11b) in the flanges (10a, 10b) and its length is equal to the width of the annular chamber (10c); • the less thick (31a) at each end gives the rotor core (30) the same external dimensions as the trapezoidal type openings (11a), (11b) in the flanges (10a, 10b) and its length is equal to the local thickness of the flange fabric, so that the face of the core is flush with the external surface of the flange on the air gap side.

4. Wound discoid rotor (l) according to claim 1 characterized in that all the ends of the wires (40a) of the coils (40) are attached to the outer collector (41) and all the ends of the wires (40b) of the wire of the coils (40) are attached to the inner collector (42), which means that the coils are connected in parallel and so that the identical coils produce, alternately, magnetic fields of opposite direction, two connections of the ends of the wires (40a) are adjacent between two consecutive coils, alternating with two adjacent connections of the ends of the wires (40b).

5. Wound discoid rotor (l) according to claim 1 characterized in that the inclined air ducts (17a, 17b) are in communication with the ambient space of the machine by the air inlets (17a 1, 17b 1), and in communication with the annular chamber (10c) by the air outlets (17a2, 17b2) located below each coil (40). The inclination of the holes is that favoring the entry of air into the annular chamber when the discoid rotor rotates in the main direction, that is to say, if the machine equips a motor vehicle, the forward gear of the latter, the air inlets (17al, 17b 1), angularly precede the air outlets (17a2, 17b2).

6. Wound discoid rotor (l) according to claim 1 characterized in that the air outlet openings (21) in the ring (20) are located opposite each coil (40), that the cooling air flow in the annular chamber (l0c) is then as follows: • suction through the air inlets (17a 1, 17b 1) and expulsion through the air outlets (17a2, 17b2) along the route (60); • the incoming flows are shared at the bottom of the coils (40), equally or not, and bypass them according to the paths (61,62); • the two flows combine at the top of each coil into a single one which leaves the annular chamber (10c) through the air outlet opening (21) along the path (63).

7. Wound discoid rotor (l) according to the preceding claims characterized in that it is part of an axial flux electrical machine (100) contained in a closed space consisting of a casing (110) and a closing flange (111) allowing the air flow leaving the rotor through the air outlet openings (21) to be cooled in the ambient space of the machine whose stators (120, 130) are cooled by a cooling device (300) for circulating a liquid. From the air outlet openings (21) along the path (63), the air makes the following symmetrical loops: • depending on the route (70a), it is divided into two flows; • according to the routes (70b), cross the carcasses (121,131) in local passages (12Id, 13 Id) made by local removal of material; • according to the paths (70c), bypasses the stators (120,130) between the periphery of the stators and the casing fabric (110); • according to the paths (70d), moves towards the center of the electric machine (100) by housing, on one side the radial fins (125a) of the cover (125) (in contact with the cooling liquid of the stator (120)) and the casing fabric (110) and on the other side the radial fins (135a) of the cover (135) (in contact with the cooling liquid of the stator (130)) and the fabric of the closing flange (111); • according to the routes (70th), bypasses the stators (120,130) in their internal openings; is re-sucked, along the path (60) by the inclined air inlet ducts (17a, 17b) of the discoid rotor (1).

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