Wound rotor of an electric machine

Abstract

The invention relates to a rotor for an electric machine, comprising: - a frame (20) which includes a hub (29) and, distributed around a longitudinal axis, magnetic pole elements (21) which rise from the hub (29) and which are separated in pairs by grooves (40), each magnetic pole element having a foot (210) and a flared head (211), - windings (50) of electrically conductive wire wound around the feet of the magnetic pole elements, and - in each groove, a wedge (60) including a base (61) which extends between the two windings wound around the feet of the magnetic pole elements separated by said groove. According to the invention, this wedge has a top (64) that flares out relative to the base so as to present two wings (65, 66) that are interposed respectively between the two windings and the flared heads of the magnetic pole elements separated by said groove. Figure for the abbreviation: Fig. 2

Description

Title of the invention: Wound rotor of an electric machine Technical field of the invention

[0001] The present invention relates generally to electrical machines.

[0002] It relates more particularly to a rotor for an electric machine comprising: - a chassis comprising a hub and, distributed around a longitudinal axis, magnetic pole elements that rise from the hub and are separated in pairs by grooves, each magnetic pole element comprising a foot and a flared head, - windings of electrically conductive wire wound around the feet of the magnetic pole elements, and - in each groove, a wedge comprising a base extending between the two windings wound around the feet of the magnetic pole elements separated by said groove, and having two main faces bearing against the two windings.

[0003] The invention finds a particularly advantageous application in the manufacture of wound-rotor synchronous electric machines, and in particular traction motors for motor vehicles. State of the art

[0004] An electrical machine generally comprises a rotor and a stator. The rotor is a moving part that rotates, while the stator is a fixed part that generates a magnetic field enabling the rotor to rotate.

[0005] In practice, permanent magnet rotors or wound rotors can be used. The latter prove more advantageous for several reasons, notably because their efficiency is often better and they are free of rare earth elements, which are expensive and come from extraction processes that are often not very environmentally friendly.

[0006] The rotational speed of a rotor in an electric motor vehicle exceeds 10,000 revolutions per minute, which generates strong mechanical stresses.

[0007] A wound rotor capable of withstanding such stresses is described for example in document FR3114702.

[0008] In this document, the rotor comprises a shaft that rotates about its axis, and a frame formed by a stack of laminations mounted coaxially on the shaft. This frame has a tubular base and poles projecting radially from this base. Each pole has a mushroom shape, with a flared base and head. Two adjacent poles define a groove between them.

[0009] The windings of electric wire, called windings, are then located around the feet of the poles, between the base and the head of the poles.

[0010] Between the winding and the pole around which this winding is wound, an electrical insulator is to be placed in order to maintain a sufficient electrical insulation distance and to prevent the electrical wires of the winding from deteriorating during the rotation of the rotor.

[0011] Document FR3114702 proposes using two sheets of insulating paper in each groove, one placed in the groove before winding the electrical wire, and the other placed after, between the windings. This second sheet has a V shape.

[0012] It is then planned to insert an electrically insulating wedge into this V, to block this other sheet as well as the electrical wires when the rotor is rotating at high speed.

[0013] This wedge is generally intended to rest under the flared heads of the poles, so as to be blocked during the rotation of the rotor.

[0014] It is therefore understood that the windings must not be too thick, so that the shim inserted between them can bear against the flared ends of the poles. A compromise is generally sought between the thickness of the windings to maximize rotor performance and the width of the shims to ensure sufficient support for these shims under the flared ends of the poles. Presentation of the invention

[0015] The present invention therefore proposes a solution allowing the thickness of the windings to be increased without affecting the support of the shims under the flared heads of the poles.

[0016] More particularly, the invention proposes a rotor as defined in the introduction, in which the wedge has a top which flares out from the base so as to present two wings cantilevered from the two main faces of the base, these two wings interposing respectively between the two windings and the flared heads of the two magnetic pole elements (those separated by the groove in which the wedge is located).

[0017] Thus, thanks to the invention, the bases of the wedges are thinner than their tops, so that the windings have more space in the grooves and can be thicker, to the benefit of rotor performance. The tops of the wedges, on the other hand, are wider than the bases, so as to maintain a good bearing surface for the wedges under the flared pole heads.

[0018] Other advantageous and non-limiting features of the rotor according to the invention, taken individually or in all technically possible combinations, are as follows: - each winding extending vertically from the hub to the flared head of one of the magnetic pole elements, the base of said wedge extends over the entire height of said two windings; - said wedge is entirely located in the throat; - each wing forms an overthickness relative to the main cantilevered face from which it extends, with a thickness equal to one or two times the diameter of the electrically conductive wire, within 25%; - each flared head has two internal faces located on either side of the corresponding foot, said two internal faces being turned towards the longitudinal axis and each having a hollow recess which houses (entirely or at least 75% by volume) one of the wings; - the two main faces of the base of the wedge have reliefs which form cradles to accommodate said electrically conductive wire; - a sheet of electrically insulating paper is provided, which is folded so as to present: a base against the hub, two wings folded with respect to the base and each engaged between one of the windings and one of the feet of the magnetic pole elements, two returns folded with respect to the wings towards each other and each engaged between one of the windings and one of the flared heads of the magnetic pole elements, and two flaps folded with respect to the two returns; - the two flaps are folded opposite the longitudinal axis and each is placed between one of the wings and one of the flared heads of the magnetic pole elements; - Alternatively, the two flaps are folded towards the longitudinal axis and each is placed between the base of the wedge and one of the windings; - in this variant, the base of the wedge has recessed areas in its main faces which house the flaps and which have depths that are approximately equal (for example, within 30%) to the thickness of the sheet of paper.

[0019] The invention also proposes an electrical machine comprising a stator and a rotor as mentioned above.

[0020] It also proposes a motor vehicle comprising drive wheels adapted to be coupled to an electric machine as mentioned above.

[0021] Of course, the various features, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0022] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0023] On the attached drawings:

[0024] [Fig-1] is a schematic perspective view of a rotor according to the invention;

[0025] [Fig.2] is a schematic cross-sectional view of a portion of the rotor of [Fig.1] located at level of a groove of this rotor, on which appears a wedge conforming to a first embodiment;

[0026] [Fig.3] is a schematic perspective view of a second embodiment of a wedge adapted to be installed in the rotor of the [Fig.1];

[0027] [Fig.4] is a front view of the wedge of [Fig.3].

[0028] In [Fig.1], a rotor 1 of an electric machine is shown.

[0029] This electrical machine could be a current generator. In this case, it is rather a traction motor for a motor vehicle, which motor may also function as a current generator in certain operating modes of the vehicle.

[0030] This motor comprises various components, including a casing (not shown), a stator (not shown) fixed in the casing, and the rotor 1. If the stator is fixed in the casing, the rotor 1 is mounted to rotate freely around a longitudinal axis Al.

[0031] The rotor 1 is of the wound type.

[0032] It includes a shaft 10 mounted rotatably in the housing around the longitudinal axis Al, for example via two bearings (not shown).

[0033] In the following description, the term "internal" will refer to a side turned towards the longitudinal axis Al and the term "external" will refer to the opposite side.

[0034] The rotor 1 also includes a frame 20 which is preferably formed from a stack of identical sheets, mounted coaxially on the shaft 10.

[0035] The sheets of this stack each extend in a plane perpendicular to the longitudinal axis AL. In this plane, the sheets all have an identical contour, with a disc-shaped base pierced for the passage of the shaft 10, and salient poles that rise radially from the base and are regularly distributed around the longitudinal axis AL.

[0036] The sheets are mounted by shrink fitting on the external surface of the shaft 10 of the rotor 1, so that their bases overlap and form a hub 29, and their salient poles overlap in line with each other and form magnetic pole elements, hereinafter referred to as "poles 21".

[0037] In the embodiment shown, the chassis 20 has eight poles 21. However, it could have a different number of poles, at least equal to three.

[0038] As shown partially in [Fig. 3], the hub 29 has a tubular shape, of revolution about the longitudinal axis AL

[0039] Each pole 21 has a mushroom shape, with a foot 210 which rises outwards from the hub 29, radially with respect to the longitudinal axis Al, and a flared head 211 which forms two projecting ribs 211A on either side of the foot 210, in cantilever.

[0040] Two neighboring poles 21 delimit between them a space called a gorge 40.

[0041] Since the lateral faces of the poles 21 are parallel to each other, the lateral faces of two adjacent poles that define a groove 40 are inclined relative to each other. Thus, the groove 40 widens from the hub 29 towards the heads 211 of the two poles 21. However, the groove narrows between the heads 211.

[0042] As shown in [Fig.1], it is preferably provided, at each end of the chassis 20, a guide flange 30 of a shape similar to that of the sheets, i.e. in a star shape with branches located in the extension of the poles 21.

[0043] As shown in this [Fig.1], the rotor 1 further comprises windings 50 of electrically conductive wire which are each wound around one of the poles 21 of the frame 20 and the corresponding branches of the two guide flanges 30. Each turn of electrical wire around a pole forms a loop.

[0044] In practice, as shown in [Fig.2], the electric wire is wound around each pole, over the entire height of the foot (between the hub and the head of the corresponding pole) and over several thicknesses.

[0045] Each winding 50 thus comprises several turns and forms a kind of elongated and thick ring.

[0046] Each winding 50 provided around one of the poles 21 therefore comprises two longitudinal parts located on each side of the foot 210 of the pole 21, and two arc-shaped end parts located against the two guide flanges 30. The longitudinal parts form a kind of thick "bars 51" (each of these bars then being formed from a plurality of straight sections of electric wire).

[0047] Figure 2 shows a cross-section of two bars 51 of two adjacent windings 50 located in the same groove 40. Two bars 51 will thus be referred to as neighbors in the following when they are located in the same groove 40.

[0048] Preferably, the electrical wire is wound around each of the feet 210 of the poles 21 in a staggered arrangement, that is to say in such a way that: - within the first layer of electrical wire (the one in contact with foot 210), the turns are wound in contact with each other, and that - within the other layers, each turn of electrical wire fits into the hollow formed by two turns of the previous layer (except at the ends in contact with the hub 29 or the head 211 of the pole 21).

[0049] In the example illustrated in [Fig.2], seven superimposed layers are provided.

[0050] A shim 60 is provided in each groove 40. These shims 60 are all identical. Only one of them, shown in Figures 1 and 2, will be described below.

[0051] This wedge 60 is intended to be placed between two neighboring bars 51, so as to block them in particular when the rotor is turning at high speed.

[0052] Such a wedge 60 is therefore intended to be placed in support between these two bars 51 and under the flared heads 211 of the two neighboring poles 21.

[0053] In [Fig.2], a cross-sectional view of such a wedge 60 is shown, according to a first method of embodiment of the invention.

[0054] Figures 3 and 4 show a second embodiment of wedge 60.

[0055] In both modes, the wedge 60 comprises a base 61 surmounted outwards from a peak 64.

[0056] The base 61 is intended to be interposed between the two neighboring bars 51, while the top 64 is intended to extend outwards relative to the windings 50.

[0057] This wedge 60 is intended to be inserted between the two neighboring bars 51 by a sliding movement parallel to the longitudinal axis Al. Here, it therefore has an externally profiled shape (that is to say a section of uniform shape along the longitudinal axis Al).

[0058] Here, each wedge 60 has a plane of symmetry PI (see figures 2 and 4) which passes between the two bars 51.

[0059] The wedge 60 is made of an electrically insulating material, for example by molding a plastic material.

[0060] Its base 61, in order to be interposed between the two adjacent bars 51, has two main faces 62, 63 which bear directly or indirectly against these two adjacent bars 51. Here, this support is direct since no element is interposed between them. Alternatively, a sheet of insulating paper could be interposed between them.

[0061] This base 61 tapers here from its outer end (top side 62) towards its inner end (longitudinal axis side Al).

[0062] More specifically, an inner part of the base 61 has a substantially constant width, and an outer part of the base 61 flares out.

[0063] Thus, the two main faces 62, 63 have two interior zones that are substantially parallel to each other, and two exterior zones that are inclined relative to each other.

[0064] In the embodiment illustrated in [Fig.2], these four areas are flat.

[0065] In contrast, in the embodiment illustrated in Figures 3 and 4, they have raised features. More precisely, these main faces 62, 63 form a series of contoured waves. The troughs of the waves thus form cradles for the turns of the last layer of electrical wire. They therefore ensure that these turns are held securely.

[0066] The apex 64 of the wedge 60 extends the base 61 on the outside by flaring out from it so as to present two wings 65, 66 cantilevered from the two main faces 62, 63.

[0067] By "flare out", it is meant that the width of the apex 64, at the level of its junction with the base 61, increases from its inner side to its outer side more rapidly than the width of the base at the level of this junction.

[0068] Each wing 65, 66 thus forms a projecting rib above the corresponding main face 62, 63 of the base 61, which runs along this main face on its external side.

[0069] Each wing 65, 66 thus has an internal face (longitudinal axis side Al) which is more inclined with respect to the plane of symmetry PI than the part of the main face 62, 63 to which it is attached.

[0070] In other words, each wing 65, 66 forms an overthickness in relation to the main face 65, 66 cantilevered from which it extends, the thickness of which (measured perpendicular to the plane of symmetry) is equal to one times the diameter of the electrically conductive wire, to within 25%.

[0071] The inner face of each wing 65, 66 is thus designed to come into contact with a turn of the electrically conductive wire, the one located on the outermost and outermost layer of the corresponding winding 50. Figure 2 clearly shows that the wedge then forms a kind of recessed indentation to accommodate this last layer of turns. It is thanks to this recess that it is possible to wind not six, but seven layers of turns in the illustrated embodiment.

[0072] In other words, the wedge 60 is hollowed out at the level of its base 61 in order to accommodate an additional layer of turns.

[0073] Alternatively, the extra thickness formed by each wing could be greater and equal to twice the diameter of the electrically conductive wire, within 25%. Thus, the wedge would be hollowed out at its base to accommodate two additional layers of turns.

[0074] The two wings 65, 66 are interposed respectively between the two windings 50 and the flared heads 211 of the poles 21.

[0075] The two inner faces of the two wings 65, 66 are here inclined relative to each other so as to open outwards. Alternatively, they could be coplanar.

[0076] Each wing 65, 66 has an external face which rests against the internal face of the flared head 211 of one of the neighboring poles 21.

[0077] These external faces of the wings 65, 66 are inclined relative to each other so as to open inwards. The angle of inclination is identical to the angle between the internal faces 21 IB of the projecting ribs 21 IA opposite the flared heads 211 of the two 21 neighboring poles, which ensures flat supports between the external faces of the wings 65, 66 and the internal faces of the flared heads 211.

[0078] The internal faces 21 IB of the projecting ribs 21 IA opposite the flared heads 211 of the neighboring poles 21 are here flat on the side of the feet 210 of these poles 21. They are, on the other hand, hollowed on the opposite side and thus form recesses 21 IC which house the wings 65, 66.

[0079] These recesses 21 IC have a depth (along a radial axis relative to the longitudinal axis A1) substantially equal to the width of the wings (measured along this same axis). Thus, the inner faces of the wings 65, 66 extend substantially in line with the flat portions of the inner faces 21 IB of the opposing projecting ribs 21 IA. They then allow the last layer of turns of each winding 50 to be locked in a staggered position relative to the preceding layer.

[0080] The wings 65, 66 taper towards their end edges (the one furthest from the plane of symmetry PI). To ensure the strength of the wings, the thickness of this end edge (measured radially with respect to the longitudinal axis Al) is here greater than the diameter of the electrical wire.

[0081] The apex 64 of the wedge 60 finally has, between the outer faces of the two wings 65, 66, a low rib projecting outwards. Its height is sufficiently low so that the wedge 60 is entirely situated within the groove 40.

[0082] In other words, if we consider the geometric cylinder of revolution around the longitudinal axis Al within which the frame 20 is circumscribed (which therefore passes through the points of the poles 21 furthest radially from the longitudinal axis Al), each wedge 60 is located entirely inside this cylinder. As a result, the overall size of the rotor 1 remains limited.

[0083] As shown in figures 2 and 4, there is also provided in each groove 40 a sheet of electrically insulating paper 100 to ensure insulation between the frame 20 and the two neighboring bars 51 located in this groove 40.

[0084] Preferably only one leaf is provided in each groove, but alternatively more could be used.

[0085] All 100 sheets of paper are identical and only one of them will be described.

[0086] This sheet of paper 100 has, when flat (before folding), a rectangular shape. It has a constant thickness, between 0.15 and 0.5 mm (here on the order of 0.25 mm).

[0087] This sheet of paper 100 has six parallel fold lines.

[0088] The two central fold lines define a band called the base 101. On either side of these two central fold lines are two wings 102 folded relative to the base 101. On either side of these wings 102 are find two returns 103 folded relative to the wings 102. Finally, on either side of these returns 103 are two flaps 104 folded relative to the returns 103.

[0089] As shown in [Fig.2], once formed into a volume, the sheet of paper 100 can be inserted into one of the grooves 40 in such a way that: - its base 101 is applied against the hub 29 of the chassis 20, - its wings 102 are applied against the faces of the feet 210 of the poles 21 which delimit the groove 40, and that - its returns 103 are applied under the flat parts of the inner faces of the protruding ribs 21 IA opposite these poles 21.

[0090] In the embodiment illustrated in [Fig. 2], the flaps 104 are folded outwards from the groove 40. In other words, if the wings 102 and the returns 103 are folded to one side of the sheet of paper 100, the flaps 104 are folded to the opposite side. These flaps 104 are essential to ensure good electrical insulation between the winding 50 and the frame 20.

[0091] In this way, as clearly shown in [Fig.2], the two flaps 104 can extend between the wings 65, 66 of the wedge 60 and the projecting ribs 21 IA opposite the heads 211 of the two neighboring poles 21.

[0092] In the embodiment illustrated in [Fig.4], the flaps 104 are folded inwards towards the groove 40. In other words, the flaps 104, the wings 102 and the returns 103 are folded on the same side of the sheet of paper 100.

[0093] In this way, as clearly shown in [Fig.4], the two flaps 104 can extend between the main faces 62, 63 of the base 61 of the wedge 60 and the windings 50.

[0094] As clearly shown in [Fig.4], the base 61 of the wedge 60 has recesses in its main faces 62, 63 which house these flaps 104. These recesses have dimensions identical, in negative, to those of the flaps 104. In particular, they have depths equal to the thickness of the paper used.

[0095] In the embodiment illustrated in Figures 3 and 4, the wedge 60 has a hole 67 which extends parallel to the longitudinal axis Al and which opens at least at one of its ends. Here, this hole 67 is through.

[0096] It opens on one side through a circular opening visible in [Fig.4], and on the other through an opening of larger diameter. It therefore widens from one end to the other.

[0097] This hole is designed to ensure the mechanical stability of the rotor, using tie rods. These tie rods notably hold two rings (not shown) which retain the portion of the winding located within the two guide flanges 30.

[0098] At this stage, we can describe how the rotor 1 can be assembled.

[0099] The first operation consists of assembling the chassis 20 by bringing a stack of sheets cut in the desired way onto the shaft 10.

[0100] The two guide flanges 30 are then attached on either side of this stack of sheets.

[0101] The sheets of paper 100 intended to be engaged in the grooves 40 are then cut and folded in the manner described above.

[0102] The sheets of paper 100 are then brought into the grooves 40, here by a sliding movement parallel to the longitudinal axis AL

[0103] At this stage, the winding of the electrically conductive wire can begin so as to form the windings 50. This operation is carried out using a winding needle (not shown).

[0104] In practice, this winding needle, in order to form each winding 50 one after the other, enters a groove 40 at one end, follows a translational movement in this groove 40 until it exits at the opposite end, goes around the corresponding arm of one of the guide flanges 30, then enters a neighboring groove 40, follows a translational movement in this groove 40 until it exits to return to the initial position. This movement is then repeated, at a variable height, to produce a winding 50 such as that illustrated in [Fig. 2].

[0105] Next, it is possible to bring a wedge 60 into each groove 40, taking care to fold beforehand the flaps 104 of the sheets of paper 100 to the desired side.

[0106] It should be noted here that a single, long wedge 60, of similar length to that of the groove, can be used in each groove 40 by a sliding movement along an axis parallel to the longitudinal axis AL

[0107] Alternatively, two shims 60 can be used in each groove 40, successively brought into this groove 40 from the same side.

[0108] The present invention is in no way limited to the embodiments described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

Claims

Demands

1. A rotor (1) for an electric machine, comprising: - a frame (20) having a hub (29) and, distributed around a longitudinal axis (A1), magnetic pole elements (21) extending from the hub (29) and separated in pairs by grooves (40), each magnetic pole element (21) having a foot (210) and a flared head (211), - windings (50) of electrically conductive wire wound around the feet (210) of the magnetic pole elements (21), and - in each groove (40), a wedge (60) comprising a base (61) extending between the two windings (50) wound around the feet (210) of the magnetic pole elements (21) separated by said groove (40) and having two principal faces (62, 63) bearing against said two windings (50), characterized in that said wedge (60) has a summit (64) which flares out relative to the base (61) so as to present two wings (65,66) cantilevered from the two main faces (62, 63), and in that the two wings (65, 66) are interposed respectively between the two windings (50) and the flared heads (211) of the magnetic pole elements (21) separated by said groove (40).

2. Rotor (1) according to claim 1, wherein, each winding (50) extending vertically from the hub (29) to the flared head (211) of one of the magnetic pole elements (21), the base (61) of said wedge (60) extends over the entire height of said two windings (50).

3. Rotor (1) according to claim 1 or 2, wherein said wedge (60) is entirely situated in the groove (40).

4. Rotor (1) according to any one of claims 1 to 3, wherein each wing (65, 66) forms an overthickness relative to the main face (65, 66) cantilevered from which it extends, of a thickness equal to one or two times the diameter of the electrically conductive wire, within 25%.

5. Rotor (1) according to any one of claims 1 to 4, wherein each flared head (211) has two internal faces (21 IB) facing the longitudinal axis (A1) and situated on either side of the corresponding foot (210), said two internal faces (21 IB) having each one has a recess (21 IC) in the hollow which houses one of the wings (65, 66).

6. Rotor (1) according to any one of claims 1 to 5, wherein the two main faces (62, 63) of the base (61) of the wedge (60) have reliefs which form cradles for receiving said electrically conductive wire.

7. Rotor (1) according to any one of claims 1 to 6, wherein there is provided a sheet of electrically insulating paper (100), which is folded so as to present: - a base (101) against the hub (29), - two wings (102) folded with respect to the base (101) and each engaged between one of the windings (50) and one of the feet (210) of the magnetic pole elements (21), - two returns (103) folded with respect to the wings (102) towards each other and each engaged between one of the windings (50) and one of the flared heads (211) of the magnetic pole elements (21), and - two flaps (104) folded with respect to the two returns (103).

8. Rotor (1) according to claim 7, wherein the two flaps (104) are folded opposite the longitudinal axis (Al) and are each interposed between one of the wings (65, 66) and one of the flared heads (211) of the magnetic pole elements (21).

9. Rotor (1) according to claim 7, wherein the two flaps (104) are folded towards the longitudinal axis (Al) and each interpose themselves between the base (61) of the wedge (60) and one of the windings (50).

10. Rotor (1) according to claim 9, wherein the base (61) of the wedge (60) has recessed recesses in its main faces (62, 63) which house the flaps (104) and which have depths substantially equal to the thickness of the sheet of paper (100).

11. An electrical machine comprising a stator and a rotor (1) according to any one of claims 1 to 10.

12. Motor vehicle comprising drive wheels adapted to be coupled to an electric machine conforming to claim 11.

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