Axial magnetic flux electric machine rotor disc for high rotational speed.

Abstract

An axial flux electric machine whose rotor disk 50 carries magnetic studs 40, each consisting of elementary magnets 10 glued together in stacks 20, 21, 22, 23, 24, 25 positioned in a structure 30, characterized in that the median planes of the stacks 20 to 25 intersect along a line 42, parallel to the axis of rotation of the rotor disk 50, located outside of it, and that, thus, the magnets furthest from the axis of rotation of the disk, at the ends of the stacks, form an arch. Figure for the abbreviation: Fig. 6

Description

Title of the invention: Rotor disc of an axial magnetic flux electric machine for high rotation speed. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an electric motor or generator known as axial magnetic flux of the type comprising a discoid rotor with several permanent magnet pads framed by two flat annular stators with several coils distributed radially in a regular manner and the axis of each of which is oriented parallel to that of the rotor. More specifically, the invention relates to a rotor disc capable of reaching a very high rotation speed. STATE OF THE ART

[0002] The disc of an axial magnetic flux electric machine has a much larger diameter than the rotor of a conventional radial magnetic flux machine. Increasing the rotation speed of an axial flux machine to a value comparable to that of a rotor of a radial flux machine means being faced with a serious difficulty of mechanical strength and risk of bursting due to the centrifugal force exerted on the magnet poles.

[0003] In publication FR3064422, the rotor is composed of a central annular structure from which branches radiate radially, between which are housed blocks of highly segmented magnets. These blocks of magnets are surrounded by a hoop whose role is to oppose the centrifugal forces.

[0004] In publication FR3107999, the rotor also has a central annular structure from which branches radiate. The central annular structure and the branches form a block and preferably made of a composite material filled with glass fibers. The branches and the magnet blocks have sawtooth edges of conjugate shape. Thus, the bonding surface is increased and contributes, with the hoop, of reduced thickness, to the resistance to centrifugal forces. PRESENTATION OF THE INVENTION

[0005] Being able to achieve a very high rotation speed, beyond 15,000 or even 20,000 rpm, is only possible if we know how to counter the centrifugal forces to which the magnet blocks are subjected.

[0006] Increasing the rotation speed is also an elegant way of increasing the power delivered by the machine. Increasing the torque, the second possibility, is less advantageous because it means increasing the mass of the magnet, the current density in the windings, and therefore the cost.

[0007] Furthermore, an electric machine, whether it has axial or radial magnetic flux, to be able to reach very high speeds, has a special rotor combining magnetic flux provided by magnets and induction. We thus have an electric motor which has, in its rotor, two ways of playing with the stator magnetic flux: induction and permanent magnets. The advantage is to be able to switch from one to the other depending on the driving context, and therefore to exploit the advantages of these two ways of rotating the rotor. For low speeds the calculator will favor permanent magnets and at high speed induction. Advantageously, the need for magnets is reduced and alleviates the problem of centrifugation.

[0008] The invention proposes a rotor equipped with blocks of magnets made up of identical elementary magnets pre-assembled in stacks by gluing, electrically insulating them from each other.

[0009] Several batteries, having a different number of magnets, are assembled in a support frame made of insulating material, to form an elementary block. The interstices are, between the batteries on the one hand and with the structure on the other hand, filled with resin.

[0010] The extensions of the median planes of the stacks have a common linear intersection parallel to the rotor axis located outside the disc.

[0011] The magnets of each stack, furthest from the axis of rotation of the disc, form an arch, comparable to a hydraulic dam, suitable for supporting the centrifugal force of all the magnets constituting a block.

[0012] Each block is then inserted into the discoid structure to which it is glued.

[0013] The arch rests on the discoid structure and stresses it both in compression and in traction.

[0014] The structure of the disc is made of conductive material, with low density to limit the total inertia, of sufficient mechanical resistance, for example aluminum.

[0015] The structure surrounds the magnet blocks, allows circulation of currents providing the induction effect. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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:

[0017] [Fig-1] is the representation of the elementary magnet stacks.

[0018] [Fig.2] is the representation of the structure for receiving the magnet stacks.

[0019] [Fig.3a]is a view of a magnet pad consisting of the structure with the magnet stacks inserted.

[0020] [Fig.3b] is a view of a magnet pad consisting of the structure with the magnet stacks inserted after the resinating operation.

[0021] [Fig.4]is a front view of the rotor disk structure.

[0022] [Fig.5]is a front view of a portion of the assembled rotor disc.

[0023] [Fig.6]is the view of a magnet plot and the line of convergence, reduced to a point, median planes, reduced to lines, stacks of elementary magnets

[0024] [Fig.7]is a view of a stud mounted in the structure of the disc and its compressive and tensile stresses during rotation.

[0025] [Fig.8] is a partial view of the disk and the representation of the induced current loop.

[0026] The rotor of the electric machine is a disc comprising pads of elementary magnets 10. In a first phase, according to the representation of [Fig.l], they are assembled by gluing in stacks 20, 21, 22, 23, 24 and 25.

[0027] Then these batteries 20 to 25 are put in place in a structure 30 shown from the front only in [Fig.2]. It comprises a perimeter 31, local thickenings 32 for supporting the batteries on the perimeter 31 and lugs 33, 34, 35, 36, 37 and 38 for positioning and orienting the batteries relative to each other.

[0028] [Fig.3a] shows stacks 20 to 25 in structure 30.

[0029] [Fig.3b] shows the magnetic pad 40 after the operation of fixing by gluing the batteries 20 to 25 in the structure 30, by filling all the interstices between the batteries and with the perimeter 31.

[0030] [Fig. 4] is a front view of the bare rotor disc 50. It is composed of an electrically conductive discoid structure 51 made of a low-density material. It has a central opening 52 for centering on a hub (not shown), several holes 53 distributed regularly for the passage of the fixing screws, openings 54 for receiving the magnet pads and holes 55 intended for balancing by partial fillings.

[0031] [Fig.5] is a partial front view of the assembled disc 60. After the magnetic studs 40 have been put in place, an operation is carried out to secure it to the discoid structure 51 by gluing, by filling the gaps between the magnetic studs 40 and the discoid structure 51 with resin 61.

[0032] [Fig.6] shows, for a magnetic pad 40 in place in the discoid structure 51, the orientation planes 41 of the magnet stacks and the line 42 of convergence of these planes.

[0033] This line 42 outside the disc is the consequence of the particular orientation of the stacks of magnets 20 to 25 so that all the magnets at the outer end form a curve like a hydraulic dam arch which is very resistant to high intensity centrifugal forces at high rotation speed, due to the specific mass of the magnets.

[0034] [Fig.7] shows the impact of centrifugation and the resistance reaction of the discoid structure 51. The centrifugation forces 70 converge towards the axis of rotation of the disc. The arch shape puts the magnets in compression which bear on the discoid structure 51. the consequence for the discoid structure 51 is the application of compressive stress in the zone 56 between two magnetic stud reception zones, traction in the peripheral bridging 57 of the disc beyond each stud and traction in the radial zone 58 between each stud up to the compression zone 56.

[0035] [Fig.8] shows the induced current loop circuit 80 in the conductive discoid structure 51 around the magnetic pads 40. The circuit is the succession of zones 57, 56a, 58a, 59, 58b, 56b. Depending on the position of zones 56a, 56b, 58a, 58b in the axial stator magnetic flux, the current flows from the center to the periphery of the disc or vice versa. The induced current flowing in zones 56a, 58a is in the opposite direction to that in zones 56b, 58b.

Claims

Claims

1. Electrical machine with axial magnetic flux whose rotor disc (50) carries magnetic pads (40), each consisting of elementary magnets (10) assembled by gluing in stacks (20, 21, 22, 23, 24, 25) positioned in a structure (30), characterized in that the median planes of the stacks (20 to 25) are intersecting along a line (42), parallel to the axis of rotation of the rotor disc (50), located outside the latter and that thus, the magnets, furthest from the axis of rotation of the disc, at the ends of the stacks form an arch.

2. Electrical machine with axial magnetic flux according to claim 1 characterized in that the stacks of magnets (20 to 25) are made up of identical elementary magnets and assembled by gluing, electrically insulating them from each other.

3. An axial magnetic flux electric machine according to claim 1 or 2, characterized in that the stacks of magnets (20 to 25) are assembled in a structure (30) made of insulating material, to form a magnetic pad (40). The gaps between the stacks of magnets (20 to 25) on the one hand and with the structure (30) on the other hand are filled with resin (36).

4. Electrical machine with axial magnetic flux according to the preceding claim, characterized in that each magnetic pad (40) is inserted into the discoid structure (51) to which it is secured by filling with resin (61) the interstices between the periphery of the magnetic pad (40) and the receiving opening (54).

5. Electrical machine with axial magnetic flux according to the preceding claim, characterized in that each magnetic pad (40), subjected to centrifugation, bears on the discoid structure (51) and stresses it both in compression in the zones (56) and in traction in the zones (57, 58).

6. Electrical machine with axial magnetic flux according to claims 4 or 5 characterized in that the discoid structure (51) is made of conductive material, with low density to limit the total inertia, but with sufficient mechanical resistance to oppose the centrifugation constraints caused by the magnetic pads (40).

7. Electrical machine with axial magnetic flux according to claims 5 and 6 characterized in that the discoid structure (51) forms by the succession of zones (57, 56a, 58a, 59, 58b, 56b) a conductive loop around each magnetic pads (40), which allows circulation current (80) providing an induction effect.

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