Wound rotor of an electric machine

Abstract

The invention relates to a rotor for an electric machine, the rotor comprising: - a frame (20) comprising a hub (29) and also magnetic pole elements (21) distributed about a longitudinal axis, which elements extend up from the hub (29) and are separated, in pairs, by grooves (40), each magnetic pole element comprising a foot (210) and a flared head (211); - windings (50) of electrically conductive wire which are wound around the feet of the magnetic pole elements; and - in each groove, a wedge (60) comprising 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 comprises an apex (64) which is flared relative to the base such that it has two wings (65, 66) which are respectively inserted between the two windings and the flared heads of the magnetic pole elements separated by said groove.

Description

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 specifically 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 which extends between the two windings wound around the feet of the magnetic pole elements separated by said groove and which has two main faces in contact with the two windings.

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

[0004] An electrical machine typically consists of 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 to cause the rotor to rotate.

[0005] In practice, permanent magnet rotors or wound rotors can be used. The latter are more advantageous for several reasons, notably because their efficiency is often better and they do not use rare earth elements, which are expensive and often produced through environmentally unfriendly extraction processes.

[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 consists of a shaft that rotates around 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 top. Two adjacent poles define a groove between them.

[0009] The windings of electric wire, called coils, 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, we wish to place an electrical insulator in order to respect a sufficient electrical insulation distance and to prevent the electrical wires of the winding from being damaged 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 afterward, between the windings. This second sheet has a V shape.

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

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

[0014] It is therefore clear 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 being interposed 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 shims are thinner than their tops, so that the windings have more space in the grooves and can be thicker, thus improving rotor performance. The tops of the shims, on the other hand, are wider than the bases, in order to maintain a good bearing surface for the shims 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 described above.

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

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

[0022] The description that follows, 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] Regarding 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 part of the rotor of [Fig.1] located at the 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 hold of [Fig.3].

[0028] Figure 1 shows a rotor 1 of an electric machine.

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

[0030] This motor has different 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] Rotor 1 is of the wound type.

[0032] It includes a shaft 10 mounted to rotate 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 which rise radially from the base and which are regularly distributed around the longitudinal axis Al.

[0036] The sheets are fitted by shrink fitting onto 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 around the longitudinal axis Al.

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

[0040] Two neighboring poles 21 delimit between them a space called 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 50 winding thus has 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 in cross-section two bars 51 of two neighboring windings 50 located in the same groove 40. Two bars 51 will thus be referred to as neighbors in the following days 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 pattern, 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 shown in [Fig.2], seven superimposed layers are planned.

[0050] Each groove 40 is fitted with a shim 60. 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 designed 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] Figure 2 shows a cross-sectional view of such a wedge 60, according to a first 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 on the outside by a peak 64.

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

[0057] This wedge 60 is designed 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 60 wedge is made from an electrically insulating material, for example by molding a plastic material.

[0060] Its base 61, in order to be placed 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 placed 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 feature raised surfaces. More precisely, these main faces 62 and 63 form a series of contoured waves. The troughs of these waves create cradles for the turns of the last layer of electrical wire, thus ensuring that these turns are held securely.

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

[0067] By "flaring out", we mean that the width of the top 64, at the level of its junction with the base 61, grows 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 presents 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] Put another way, each wing 65, 66 forms an overthickness in relation to the main face 65, 66 in cantilever 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, specifically the one located on the outermost and final layer of the corresponding winding 50. Figure 2 clearly shows that the wedge then forms a kind of recessed indentation to accommodate this final 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 to be able to accommodate an additional layer of coils.

[0073] Alternatively, the extra thickness formed by each wing could be greater, equal to twice the diameter of the electrically conductive wire, within 25%. The wedge would then 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 outer 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 inner faces 21 IB of the projecting ribs 211 A 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 inner faces 21 IB of the projecting ribs 211 A 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 211 A. 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 low enough that the wedge 60 is entirely situated within the groove 40.

[0082] Put another way, 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 intended in each throat, 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 100 paper, when flat (before folding), has a rectangular shape. It has a constant thickness, between 0.15 and 0.5 mm (here around 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 three-dimensional shape, the sheet of paper 100 can be inserted into one of the grooves 40 such 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 throat 40, and that - its returns 103 apply under the flat parts of the internal faces of the protruding ribs 211 A 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 shown in [Fig.2], the two flaps 104 can extend between the wings 65, 66 of the wedge 60 and the protruding ribs 211 A opposite the heads 211 of the two neighboring poles 21.

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

[0093] In this way, as 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 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 hole 67.

[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, in particular, 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 rotor 1 can be assembled.

[0099] The first operation consists of assembling the chassis 20 by bringing a stack of sheet metal 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 100 sheets of paper intended to be inserted into the grooves 40 are then cut and folded in the manner described above.

[0102] The 100 sheets of paper 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 in order to form the coils 50. This operation is carried out using a winding needle (not shown).

[0104] In practice, this winding needle, 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 the one illustrated in [Fig. 2].

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

[0106] It should be noted here that in each groove 40 a single long wedge 60, of similar length to that of the groove, can be used 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. Rotor (1) for an electric machine, comprising: - a chassis (20) which includes a hub (29) and, distributed around a longitudinal axis (Al), magnetic pole elements (21) which rise from the hub (29) and which are 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) which extends between the two coils (50) wound around the feet (210) magnetic pole elements (21) separated by said groove (40) and which has two main faces (62, 63) bearing against said two windings (50), characterized in that said wedge (60) has a top (64) which flares out in relation to the base (61) so as to present two wings (65, 66) cantilevered in relation to 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) extends 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 a sheet of electrically insulating paper (100) is provided, which is folded so as to present: - a base (101) against the hub (29), - two wings (102) folded relative 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 back on themselves relative to the wings (102), one towards the 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 in relation 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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