Wound rotor of an electric machine

Abstract

The invention relates to a rotor for an electric machine comprising: - a frame which has 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 of conductive electric wire wound around the feet of the magnetic pole elements, and - in each groove, a sheet of electrically insulating paper (100), which is folded so as to present a bottom (101) against the hub, two wings (102) folded with respect to the bottom and each engaged between one of the windings and one of the feet of the magnetic pole elements, and two returns (103) 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.According to the invention, each sheet of paper further comprises at least two flaps (104) folded back from the two returns towards the bottom, between the windings. Figure for the abstract: Fig. 3.

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 sheet of electrically insulating paper, which is folded so as to present a base resting against the hub, two wings folded relative to the base and each engaged between one of the windings and one of the feet of the magnetic pole elements, and two returns folded relative 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.

[0003] The invention finds a particularly advantageous application in the realization of wound-rotor synchronous electric machines, and in particular of 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.

[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] In document FR3114702, it is proposed to use two sheets of insulating paper in each groove for this purpose. The first sheet has a U-shaped portion that extends into the bottom of the groove and up along the feet of the two poles, as well as two ends folded towards each other, under the flared heads of the poles. The second sheet has a V-shaped portion that extends against the windings, as well as two ends folded in opposite directions to overlap the ends of the first sheet of paper.

[0012] Thus, the two sheets of insulating paper surround each winding.

[0013] A wedge to lock the assembly is then placed in the V delimited by the second sheet of insulating paper.

[0014] However, installing the insulating paper sheets proves difficult. Furthermore, inserting the wedge into the V-shaped space defined by the second sheet of insulating paper sometimes causes this second sheet to shift, which is detrimental to the proper functioning of the rotor. Presentation of the invention

[0015] In order to remedy the aforementioned drawbacks of the prior art, the present invention proposes to use a single sheet of insulating paper in each groove.

[0016] More particularly, the invention proposes a rotor as defined in the introduction, in which each sheet of paper further comprises at least two flaps folded back with respect to the two returns, towards the bottom, between the windings.

[0017] Thus, thanks to the invention, a single step of setting up the insulating paper is provided, implemented before the step of winding the electric wire, which significantly simplifies the manufacture of the wound rotor.

[0018] Indeed, the winding is then carried out over the sheets of insulating paper, and then the flaps of these sheets are folded over the windings in a second step. In this way, the placement of the wedge between these flaps no longer risks causing the sheet to move, since the latter is at this stage securely held by the windings.

[0019] Furthermore, preferably, the flaps are designed such that, during the winding step, any contact between the winding needle and The insulating paper sheet pushes the flaps out of the groove. This prevents damage to the sheet and, more importantly, avoids causing unwanted folding of the sheet's flaps within the groove. Otherwise, these flaps could become trapped between the windings and their corresponding magnetic pole elements, preventing them from being folded over the windings and thus failing to perform their intended function.

[0020] 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 flap has a maximum width which is at least equal to one tenth of the width of each wing; - a folding line is provided between each flap and each return which is inclined relative to a folding line located between one of the returns and one of the wings; - there are two flaps attached to each return by two fold lines inclined to each other; - at least one wedge is planned to be placed between the two flaps.

[0021] The invention also relates to a method for manufacturing a rotor as described above, in which the following steps are provided: - for each sheet of paper, folding each wing and each return on the same first side of the sheet of paper, and each flap on the opposite side, - placing each sheet of paper in one of the grooves, - winding the conductive electric wire around the feet of the magnetic pole elements and the wings of the paper sheets using a needle, and - folding the flaps on the first side, against the windings.

[0022] Preferably, at the beginning of the winding step, the normal to each flap forms with a longitudinal axis of the needle an angle greater than strictly 45°.

[0023] Advantageously, a step is also provided for placing at least one wedge in each groove, between the two flaps.

[0024] The invention also relates to an electrical machine comprising a stator and a rotor as mentioned above.

[0025] It also relates to a motor vehicle having drive wheels adapted to be coupled to an electric machine as mentioned above.

[0026] Of course, the various features, variants, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0027] 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.

[0028] On the attached drawings:

[0029] [Fig-1] is a schematic perspective view of a rotor according to the invention;

[0030] [Fig.2] is a flat view of a sheet of insulating paper from the rotor of the [Fig.1];

[0031] [Fig.3] is a schematic perspective view of a groove in the rotor of the [Fig.1] not yet wound, in which the sheet of paper of the [Fig.2] is installed once folded;

[0032] [Fig.4] is a homologous view of that of [Fig.3], shown from another angle and on which a winding needle appears;

[0033] [Fig.5] is a homologous view of that of [Fig.3], in which the rotor is wound;

[0034] [Fig.6] illustrates an operation of placing a wedge in the rotor of the [Fig.1].

[0035] In [Fig.1], a rotor 1 of an electric machine is shown.

[0036] 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.

[0037] 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.

[0038] The rotor 1 is of the wound type.

[0039] It includes a shaft 10 mounted rotatably in the housing around the longitudinal axis Al, for example via two bearings (not shown).

[0040] 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.

[0041] The rotor 1 also includes a frame 20 which is preferably formed of a stack of identical sheets, mounted coaxially on the shaft 10.

[0042] 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.

[0043] The laminations are shrink-fitted onto the external surface of the shaft 10 of the rotor 1, so that their bases overlap and form a hub 29, and that their salient poles overlap in line with each other and form magnetic pole elements, hereafter referred to as "poles 21".

[0044] 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.

[0045] As shown in part in [Fig.3], the hub 29 has a tubular shape, of revolution around the longitudinal axis Al.

[0046] 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.

[0047] Two neighboring poles 21 delimit between them a space called a gorge 40.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] In practice, as shown in [Fig.5], 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.

[0052] Each winding 50 thus comprises several turns and forms a kind of elongated and thick ring.

[0053] 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).

[0054] Figure 5 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.

[0055] In the context of the invention, a single sheet of electrically insulating paper 100 is provided in each groove 40, making it possible to ensure insulation between the frame 20 and the two neighboring bars 51 located in this groove 40.

[0056] Before describing the shape of this piece of paper 100 once folded within the groove 40 of the wound rotor 1, we can describe this sheet flat, as illustrated in [Fig.2].

[0057] As a preliminary point, it should be noted that all the sheets of paper 100 are identical and that only one of them will be described. It should also be noted that in this [Fig. 2], the solid lines represent the edge of the sheet (i.e., the cutting lines of the sheet to the desired shape) while the dashed lines represent folding lines.

[0058] A panel is then defined as a portion of the sheet of paper 100 which is entirely delimited by cutting or folding lines on its edges, and which is internally devoid of such lines. In the following, the terms "bottom", "wing", "return" and "flap" will designate different panels.

[0059] Each fold line will be considered to form a kind of joint between two panels.

[0060] As shown in [Fig.2], the sheet of paper 100 has a rectangular shape when laid flat. It has a constant thickness, between 0.15 and 0.5 mm (here on the order of 0.25 mm).

[0061] This sheet of paper 100 has four main fold lines L2, L3 parallel to each other.

[0062] The two most central main fold lines L2 delimit between them a strip called bottom 101. On either side of these two main fold lines L2 are two wings 102 articulated with respect to the bottom 101.

[0063] On either side of the two other main folding lines L3 are two other bands called returns 103, which are articulated with respect to the wings 102.

[0064] Here, the bottom 101 also has two secondary fold lines L1 parallel to the two most central main fold lines L2.

[0065] Here, all the fold lines are distributed symmetrically with respect to a central axis A2 of the sheet of paper 100.

[0066] As shown in [Fig. 3], 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 (the two secondary folding lines L1 allowing the base to be curved against the hub 29), - 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 protruding ribs 21 IA opposite these poles 21 (the underside of these protruding ribs 21 IA being flat).

[0067] According to a particularly advantageous feature of the invention, each sheet of paper 100 further comprises at least two flaps 104 (see [Fig.2]) hinged relative to the returns 103 around folding lines L4.

[0068] It would be possible to provide only two flaps respectively located at two corners of the insulating paper sheet.

[0069] Alternatively, exactly two flaps could be provided, attached to the two returns by folding lines parallel to the main folding lines.

[0070] However, here, four flaps 104 will be provided, located at the four corners of the sheet of paper 100 and attached in pairs to the two returns 103, via four inclined folding lines L4.

[0071] These four fold lines L4 are here inclined relative to the main fold lines L2, L3 at an angle between 3 and 20°. In this way, each flap has a right-angled triangle shape.

[0072] In all embodiments of these flaps, each flap has a maximum width (measured orthogonally to the main fold lines) that is greater than one-tenth of the width of a wing, and preferably greater than one-quarter of that width. The objective is that, once folded against one of the bars 51 ([Fig. 5]), each flap provides good electrical insulation between that bar 51 and the head of the corresponding pole 21.

[0073] As shown in [Fig.3], when this sheet of paper 100 is being formed into a volume, the flaps 104 are folded around these fold lines L4 towards the outside of the groove 40.

[0074] In other words, if the wings 102 and the returns 103 are folded to the same side of the sheet of paper 100, the flaps 104 are folded to the opposite side.

[0075] Put another way, if we consider any of the flaps 104, the return 103 to which it is attached and the wing 102 to which this return 103 is attached, we can say that the wing 102 and the return 103 are folded in a first direction, while the return is folded in the opposite direction.

[0076] In this way, as clearly shown in [Fig.3], the two flaps 104 can extend between the protruding ribs 21 IA opposite the heads 211 of the two neighboring poles 21.

[0077] Each flap 104, once folded outwards from the groove 104, extends in a plane which defines a normal Fl. This normal is typically formed by the axis orthogonal to the plane of the corresponding flap 104, passing through the geometric center of this flap.

[0078] The groove 40 has a plane of symmetry PI which passes between the protruding ribs 21 IA opposite the heads 211 of the two neighboring poles 21 (see [Fig.3]).

[0079] To wind the electric wire around each pole 21, a straight rod (see [Fig. 4]) is used, fixed at its upper end to an arm that allows it to be moved, and pierced at its lower end by a hole through which the electric wire passes. This straight rod thus forms a winding needle 300 elongated along an axis A3.

[0080] During the winding of the electric wire, the winding needle 300 moves through the considered groove 40, along its plane of symmetry PI.

[0081] Each time it enters the groove 40, it is likely to come into contact with the edges of the flaps 104 (those turned towards the side of the guide flange 30 through which the needle enters).

[0082] To prevent this contact from causing the flaps 104 to fold inwards into the groove 40, these flaps 104 are folded more outwards from the groove 40 than the returns 103.

[0083] They are preferably folded so that the normals Fl are inclined at more than 45° with respect to the plane of symmetry PI of the groove 40 (i.e. with respect to the axis A3 of the winding needle 300).

[0084] Below this angle, there would indeed be a risk that the contact of the needle with the edges of the flaps would cause these flaps to fold inwards, in which case they would then be caught between the electrical wire and the corresponding pole.

[0085] At this stage, we can describe how the rotor 1 can be manufactured.

[0086] 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.

[0087] The two guide flanges 30 are then attached on either side of this stack of sheets.

[0088] The sheets of paper 100 intended to be inserted into the grooves 40 are then cut and folded in the manner described above.

[0089] Thus, each sheet of paper 100 is folded along the folding lines L2, L3 in one direction, and along the folding lines L1, L4 in the opposite direction.

[0090] The sheets of paper 100 are then brought into the grooves 40, here by a sliding movement parallel to the longitudinal axis AL

[0091] 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 the winding needle 300 illustrated in [Fig.4].

[0092] In practice, this winding needle 300, in order to form each winding 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 achieve a winding 50 such as that illustrated in [Fig.5] (in cross-section).

[0093] As explained above, during this operation, the winding needle 300 may come into contact with the sheet of paper 100. In this event, it strikes the edge of one or both of the flaps 104. Then, due to their inclinations, these flaps 104 fold outwards from the groove 40, and not inwards. Consequently, as shown in [Fig. 5], once the winding operation is complete, both flaps 104 are free.

[0094] At this stage, it is then possible to fold them against the faces opposite the neighboring bars 51. This folding operation can be carried out manually or with the aid of a tool 400, as is typically illustrated in [Fig. 5].

[0095] Thus folded, the flaps 104 contribute to the electrical insulation of the windings 50.

[0096] Next, as shown in [Fig.6], it is possible to add one or two wedge(s) 60 in the throat, 40 between the flaps, 104.

[0097] These are typically shims made of electrically insulating material.

[0098] The wedges 60 have generally identical shapes, in negative, to those of the spaces located between two adjacent bars 51. Each wedge 60 is inserted into this space by a sliding movement along an axis parallel to the longitudinal axis Al. During this operation, the sheet of paper 100 is held firmly in position by the coils 50, so that the insertion of the wedge 60 cannot cause the sheet of paper 100 to move. This insertion can therefore be carried out without any particular difficulty.

[0099] 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.

[0100] Typically, the fold line between each flap 104 and the return 103 to which it is attached might not be straight but curved. Therefore, once folded outwards from the groove, each flap 104 would not be flat. In this case, the normal to the flap would be defined as the direction perpendicular to the edge of the flap 104 facing the end of the groove through which the winding needle 300 enters. Indeed, it is the inclination of this edge relative to the winding needle that will cause the flap, upon contact with the needle, to fold outwards and not inwards from the groove.

Claims

Demands

1. 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 sheet of electrically insulating paper (100), which is folded so as to present a bottom (101) bearing against the hub (29), two wings (102) folded relative to the bottom (101) and each engaged between one of the windings (50) and one of the feet (210) of the magnetic pole elements (21),and two returns (103) folded back 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), characterized in that each sheet of paper (100) further comprises at least two flaps (104) folded back with respect to the two returns (103) towards the bottom (101), between the windings (50).

2. Rotor (1) according to claim 1, wherein each flap (104) has a maximum width which is at least equal to one tenth of the width of each wing (102).

3. Rotor (1) according to claim 1 or 2, wherein a folding line (L4) is provided between each flap (104) and each return (103) which is inclined with respect to a folding line (L3) located between one of the returns (103) and one of the wings (102).

4. Rotor (1) according to claim 3, wherein two flaps (104) are provided, attached to each return (103) by two fold lines (L4) inclined relative to each other.

5. Rotor (1) according to any one of claims 1 to 4, wherein at least one shim (60) is provided which is interposed between the two flaps (104).

6. A method for manufacturing a rotor (1) according to any one of claims 1 to 5, wherein the following steps are provided: - for each sheet of paper (100), folding of each wing (102) and each return (103) on the same first side of the sheet of paper (100), and of each flap (104) on the opposite side, - placing each sheet of paper (100) in one of the grooves (40), - winding of the electrical conductor wire around the feet (210) of the elements of the magnetic pole (21) and the wings (102) of the sheets of paper (100) by a needle (300), and - folding of the flaps (104) on the first side, against the windings (50).

7. A manufacturing method according to claim 6, wherein, at the beginning of the winding step, the normal to each flap (104) forms with a longitudinal axis of the needle (300) an angle greater than strictly 45°.

8. A manufacturing method according to any one of claims 6 and 7, further comprising a step of placing at least one shim (60) in each groove (40), between the two flaps (104).

9. An electrical machine comprising a stator and a rotor (1) according to any one of claims 1 to 5.

10. Motor vehicle comprising drive wheels adapted to be coupled to an electric machine conforming to claim 9.

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