Air cooling device for rotor of axial magnetic flux electric machine.

Abstract

Axial magnetic flux electric machine comprising a central rotor 40, and two identical lateral stators 10, 20 mounted in mirror image on a central spacer plate 30, the assembly being arranged inside a casing 70 closed by a cover 80 thus creating an isolated air circulation chamber, the spacer having on its outer periphery several fixing lugs 30a, allowing the circulation of air between the stators and the casing, characterized in that the rotor drives two air turbines 60. Figure for the abstract: Fig. 4

Description

Title of the invention: Air cooling device for rotor of axial magnetic flux electric machine. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an electric motor or generator known as axial magnetic flux motor comprising at least one discoid rotor with several permanent magnet pads and at least one flat annular stator with several coils distributed radially in a regular manner and the axis of each of which is oriented parallel to that of the rotor. STATE OF THE ART

[0002] Two main concepts are known: that comprising a central stator and two lateral rotors, illustrated by publication GB2482928, and conversely that comprising a central rotor arranged between two stators, illustrated by publication FR3064422. The invention relates to the second type.

[0003] In this concept, the rotor is confined between the stators. If there is excessive heating generated mainly by eddy currents, the magnets can lose their magnetic characteristics when the temperature exceeds a critical value. In addition, radiant heating of the stators can further increase the rotor temperature. The solution proposed in publication FR3110767 to mitigate heating is the very strong segmentation of the magnet blocks. The eddy currents are then drastically reduced.

[0004] In the first type, where the stator is central and the rotors are arranged on either side, cooling is achieved using two different means, the first relating to the stator, described in publication WO2010092403, uses the circulation of a liquid in direct contact with the windings which generate the most loss by Joule effect. The second relating to the rotors, described in publication US10630157, uses air circulation on the outer face of the rotors, the one opposite the magnets, forced by blades, and coming from outside the machine. There is no air circulation in the air gaps.

[0005] In publication FR2999359 the cooling means deployed is an exchange by conduction between the cooling liquid, running through a network in each cylinder head each supporting a stator. As regards the rotor, there is no cooling device

[0006] However, the cooling capacity determines the continuous power of the machine. To improve cooling, it is necessary to ensure that heat sources, the Joule effect in the windings, eddy currents causing iron losses in

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[0017] the stator and in the rotor magnets, are in direct contact with the flow of a cooling fluid, whether liquid or gaseous. PRESENTATION OF THE INVENTION The object of this invention is to propose a device for cooling the rotor disk by a forced air flow. According to a first characteristic, the spacer carrying the two stators: • is arranged inside a casing closed by a cover in order to create an isolated air circulation chamber; • has several fixing ears on the outer periphery; • allows air circulation between the stators and the casing. According to a second feature, the rotating outer ring of the rotor guide bearing is arranged to carry a first turbine, forcing the circulation of air in the left air gap. According to a third feature, the rotor hub carries a second turbine identical to the first, mounted in reverse to force the circulation of air in the right air gap. According to another characteristic, the circuit traveled by the air forced by each turbine is this: • radial path of air in the air gap, from the center to the outside; • expulsion of air through peripheral openings: recesses made in the frames and in the central spacer; • bypassing the stators in the gap with the casing; • radial path of hot air between the faces of the casings and the stator covers which act as an exchanger. DETAILED DESCRIPTION OF THE INVENTION 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: [Fig.l] is a front view of the right stator frame defining a section AA of the machine. [Fig.2] is a front view of the left stator frame defining a BB section of the machine. [Fig.3] is a sectional view of the complete machine along section AA of the right stator and BB of the left stator, allowing the description of the machine. [Fig.4] is the same sectional view of the complete machine, depicting the circulation of air in each air gap, and around each stator. The frame 21 shown in front view in [Fig.l] is that of the right stator. It is made of composite material and is formed of three parts: an outer crown 21e extending axially towards the rear, an inner crown 21i also extending towards the rear and the radial links 21r.

[0018] on the outer crown 21st we have different growths: • 21fe corresponds to the fixing points on the central spacer 30 of the machine; • 21d corresponds to the positioning sleeves relative to the spacer 30 and the opposite carcass 11; • 211a and 211e correspond to the supply and evacuation of the re liquid cooling of the right stator 20.

[0019] 21f is an opening in the thickness of the outer crown 21e for the passage electrical conductors of the phases.

[0020] on the inner crown 21i we have different arrangements: • 21fc corresponds to the fixing points of the cover 26 closing the coolant circulation chamber; • 21b corresponds to notches facilitating the passage of cooling air rotor disc dislocation; • 21a corresponds to areas of carcass lightening.

[0021] the zone 21r for connecting the outer 21e and inner 21i rings appears in the form of sticks because this radial zone has trapezoidal openings 21pl for receiving the stator pads 12. Around the perimeter of each opening, we have a rearward extension 21p2 which surrounds the stator pad and forms with it longitudinal channels 21p3 which will be filled with glue during the assembly process to reinforce the connection of the pads 12 with the carcass in addition to the cord 12b around the head of the pad. These extensions 21p2 are also the insulating supports of the coils 13.

[0022] the carcass 11 shown in front view in [Fig.2] is that of the left stator. It is symmetrical to the carcass 21 except for a difference which is an angular offset of a few degrees of the fixing points 1 Ife on the spacer so that the lengths of threading in engagement are sufficient without the spacer having a significant thickness, the thickness of the spacer 30 corresponds to the sum of the thicknesses of the air gaps 40a and of the rotor disc 41.

[0023] Thus the carcass 11, just like the carcass 21, is made of composite material and is formed of three parts: an outer crown 11e extending axially towards the rear, an inner crown 11i also extending towards the rear and the radial connections 11r.

[0024] On the outer crown 1 we have different growths: • 1 Ife corresponds to the fixing points on the central spacer 30 of the machine; • 1 Id corresponds to the positioning sleeves relative to the spacer 30 and the opposite carcass 21; • 1 lia and 1 lie correspond to the supply and evacuation of the re liquid left stator cooling 10.

[0025] 1 If is an opening in the thickness of the outer crown 1 le for the passage electrical conductors of the phases.

[0026] on the inner crown 1 li we have different arrangements: • 1 Ifc corresponds to the fixing points of the cover 16 closing the chamber of coolant circulation; • 11b corresponds to notches facilitating the passage of cooling air rotor disc dislocation; • lia corresponds to areas of lightening of the carcass.

[0027] the zone 1 Ir of connection of the outer 1 le and inner 1 li rings appears in the form of sticks because this radial zone has trapezoidal openings 1 Ipl for receiving the stator pads 12. On the periphery of each opening, we have an extension 1 lp2 towards the rear which surrounds the stator pad and forms with it longitudinal channels 1 lp3 which will be during the assembly process, filled with glue to reinforce the connection of the pads 12 with the carcass in addition to the cord 12b around the head of the pad. These extensions 1 lp2 are also the insulating supports of the coils 13.

[0028] The machine shown in [Fig.3] is for the right part a cut AA as specified in [Fig.1] and for the left part a cut BB as specified in [Fig.2]

[0029] The machine is composed of a motor block arranged in a casing 70 and a closing plate 80.

[0030] The engine block is essentially made up of: • of the right stator 20 linked to the spacer 30 using the screws 17 passing through the external extension 21e of the frame 21; • of the left stator 10, mirror of the right, linked in the same way to the spacer 30 by the screws 17 (not shown because they are angularly offset) passing through the external extension 11c of the carcass 11; • the central spacer plate 30, comprising several peripheral protrusions 30a, to be fixed by the screws 31 to the casing 70; • the discoid rotor 40 supported by a single double-row ball bearing 50, carried by the axle 52 fitted into the casing 70.

[0031] the stators 10, 20 comprise the frames 11, 21 described previously in composite material. They carry the stator pads 12 in stacked sheets, an example of which

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[0037] profile 12a is shown in [Fig.l] and [Fig.2]. The (functional) face of the stator pads 12 facing the rotor disc 41 is, by the assembly process, unique for all the pads and common with the support plane of the carcasses 11, 21 on the spacer 30. This gives great precision to the axial space allocated to the rotor disc 40 in the precision of the air gaps. After this precise assembly of the stator pads 12 with the frames 11,21: • coils 13 are placed; • the ends of the cradles 14 of the coils, the cradles 1 Ip2, 21p2 are integrated into the carcasses for the main part; • the carcasses 15, made of rolled sheets, are attached, preferably by gluing; • the covers 16, 26 can then be placed and fixed using the screws 18. The complementary element to the stators to form the electric machine is the rotor 40. It is made up of: • disc 41, comprising 3 distinct parts: - a supporting structure 41,a in the shape of a “sun” because it is composed of a part discoidal central structure, from which several radial branches depart. This structure can be made of non-magnetic material or a composite of fiber-filled resin; - several magnet sectors 41,b each, each housed between two branches, which can be single-piece or segmented. They are glued to the “sun” structure 41a; - a “circle” 41,c also called a hoop to counter the centrifugation of the magnets; • hub 42; • bearing 50, fitted with a collar 50a. The hub 42 and the disc 41 are centered on the outer ring of the bearing 50 and these three elements are secured by the screws 51. Bearing 50 is: • carried by the axis 52, fitted into the casing 70; • positioned axially by the air gap balancing washer 53, the thickness of which is simple to determine, but not explained here; • axially blocked by washer 54 and screw 55; • mounted, thanks to the pre-adjustment of the contact of the inner rings, without play in the rolling bodies and with slight preload. The hub 42 transmits the rotational movement and the torque to a reducer or a transmission. It can in return, via the splines, if they are cut directly into its mass, undergo external influences, that is to say axial movement and force which may disturb the balance of the air gaps 40a, detrimental to the operation of the machine and the reliability of the rotor disc 4L. Indeed, the stators and the rotor are not directly integral and do not form a block which would be insensitive to external influences.

[0038] To obtain axial decoupling, a very low coefficient of friction is required. This is achieved by inserting a ball slide 43 between the body of the hub 42 and the splines.

[0039] This ball slide 43 is made up of several rows of balls, for example 8, regularly distributed radially. The balls are positioned axially by the sleeve 44.

[0040] The outer tracks 42a of the balls are cut into the hub 42. The inner tracks 45a are cut externally to the sleeve 45 provided internally with the grooves 45b.

[0041] The ball holding sleeve 44 is stopped axially on the left by the flange 46 and on the right by the washer 47 and the stop ring 48.

[0042] The hub also carries the target 93 of the resolver, axially blocked by the washer 94, mounted tightly.

[0043] The resolver itself 91 is carried by the cover 80 to which it is fixed by the screws 92.

[0044] A grounding 56, mounted in the hub and in contact with the washer 54, protects against possible Parisite currents which could damage the bearing 50, the balls 43 and the tracks 42a, 45a of the slide.

[0045] The cover 80 is fixed to the casing 70 using the screws 81. The entire machine is fixed to a transmission (reducer or gearbox) using the screws 82.

[0046] [Fig.4] shows the circulation of the cooling air of the rotor disc on the basis of [Fig.3]

[0047] An air turbine 60, for the left stator, is mounted on a support 61 fitted onto a protrusion 50b of the bearing 50. It forces the circulation of air, from the center to the periphery, in the air gap 40a between the stator pads 12 of the stator 10 and the rotor disk 4L.

[0048] An identical air turbine 60 is mounted symmetrically on the hub 42. Thus, it forces the circulation of air, from the center to the periphery, in the air gap 40a between the stator pads 12 of the stator 20 and the rotor disk 4L.

[0049] The air follows the path 62 in a loop. Pushed into the turbine 60, along the path 60a, the air passes into the air gap 40a along the path 62b. Then, through recesses 21h, 11h, it leaves outside the air gap. The air, in the chamber formed by the casing 70 and the cover 80, bypasses the stators 20, 10 along the path 62c. Then, it runs along the covers 26, 16 along the path 62d. The latter are cooled by the stator cooling liquid. Their radial grooves 26a, 16a increase the surface area for exchange with the air. Finally, the air bypasses the lower part of the stators along the path 62e and passes back into the turbine 60.

[0050] Air can also escape from the air gap by a local reduction in thickness 30b of the central spacer plate.

Claims

Claims

1. An axial magnetic flux electric machine comprising a central rotor (40), and two identical lateral stators (10, 20) mounted in a mirror image on a central spacer plate (30), the assembly being arranged inside a casing (70) closed by a cover (80) thus creating an isolated air circulation chamber, the spacer having on the outer periphery, between the fixing lugs (30a), zones radially set back from the casing, allowing the passage of air, characterized in that the rotor drives two air turbines (60) which circulate in a loop the air contained in the interior volume of the machine, passing through the air gaps (40a), exiting at the periphery thereof through local recesses (21h, 11h) in the frames (11, 21) or through local recesses (30b) in the spacer (30), bypassing the stators (10),(20) and following the cooling space between the housing (70) or the cover (80) and the covers (16,26) stators (10,20).,

2. Electrical machine with axial magnetic flux, according to claim 1 characterized in that the turbine (60) for the circulation of air in the air gap (40a) between the right stator (20) and the rotor disc (41) is carried by the hub (42) of the rotor.

3. Electrical machine with axial magnetic flux, according to claim 1 characterized in that the turbine (60) for the circulation of air in the air gap (40a) between the left stator (10) and the rotor disc (41) is mounted on a support (61) carried by an arrangement (50b) on the rotating outer ring of the bearing (50).

4. Electrical machine with axial magnetic flux, according to one of the preceding claims, characterized in that the two turbines (60) are identical and mounted symmetrically and so as to blow the air towards the inlet of the air gap (40a) closest to the axis of rotation.

5. Electrical machine with axial magnetic flux, according to one of the preceding claims, characterized in that the air circulates in each air gap (40a) from the center towards the largest diameter and is expelled by local recesses in the carcasses (llh, 21h) forming passages with the spacer (30).

6. Electrical machine with axial magnetic flux, according to one of the preceding claims, characterized in that the air circulates in the air gap (40a) from the center towards the largest diameter and is expelled by em- brief local (30b) in the spacer (30) forming passages with the carcasses (11,21).

7. Electrical machine with axial magnetic flux, according to one of the preceding claims, characterized in that the cooling circuits for the air gap (40a) with the stator (10), and for the air gap (40a) with the stator (20) are independent.

8. Electrical machine with axial magnetic flux, according to claims 1, 5 or 6, characterized in that the air, for both of the air gaps (40a) travels through the following loop (62): • expulsion of the turbine (60), according to the route (60a) • passage in the air gap (40a), from the center to the outside, according to the route (62b); • exit from the air gap through the local recesses (21h, 11h) in the frames (11, 21) or through the local recesses (30b) in the spacer (30); • bypassing the stators (20,10) according to the route (62c). • passage in the cooling zone, that is to say between the covers (26, 16), in internal contact with the cooling liquid circulating in the chambers of the stator pads (12), covered with radial grooves (26a, 16a) increasing the heat exchange surface, and the casing (70) or the cover (80), the external face of which is in contact with the ambient external air, according to the path (62d). • Finally bypass in the central opening of the stators according to the route (62e) and return to the turbine (60).

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