Wound stator of electric machine and corresponding winding method

Abstract

Wound stator of an electric machine and corresponding winding method The present invention relates to a stator (1) of an electric machine, comprising a stator body (11) and at least one winding, the stator body (11) comprising a yoke (10) and teeth (12) angularly distributed on an internal periphery of the yoke (10) and extending axially forming winding notches (16) in pairs, the winding comprising a conductor (14_1) comprising straight portions (142) in winding notches, the straight portions (142) being connected in pairs alternately by a lower curved portion (144) of the conductor (14_1) located at a lower axial end (15) of the stator body (11) then by an upper curved portion (146) of the conductor (14_1) located at an upper axial end (17) of the stator body (11), thus drawing a corrugation, the conductor (14_1) being an unbroken Litz wire on the corrugation. (Figure 1)

Description

Title of the invention: Wound stator of an electric machine and corresponding winding method

[0001] The present invention relates to the field of electrical engineering and more specifically concerns a stator for an electrical machine and a method of winding a stator, finding particular application in the automotive field.

[0002] A wound stator of an electrical machine consists of one or more windings and a cylindrical stator body generally formed of a stack of magnetic steel sheets, stacked axially, that is to say along the axis of rotation of the rotor of the electrical machine. Such a stator is notably used in radial flux and internal rotor electrical machines, with the wound stator coaxially surrounding the rotor. In such a machine, the stator body comprises, on its internal circumference, angularly distributed notches passing axially through the stator, and in which the different conductors of the stator phases are inserted. For example, if the stator is three-phase, one or more notches out of a multiple of three consecutive notches will be filled by a distinct phase.

[0003] In thermal vehicles, alternators or electric motors operating at low voltage, that is to say at the supply voltage of the on-board network, which is of the order of 12V (Volts) or even 48V, have windings thin enough to be wound by waves in the stators of these alternators or electric motors. Such windings are called corrugated.

[0004] Today, vehicles are mostly electrified, that is to say they each have at least one electric machine capable of delivering torque to the vehicle's wheels. Such an electric machine is powered by a high-voltage battery, that is to say a voltage greater than 60V.

[0005] In order to deliver the mechanical power necessary for traction or propulsion of the vehicle, the stator of such an electrical machine must deliver a much greater current than an alternator stator of an on-board network of the vehicle. As a result, the conductors of the stator of an electrical traction or propulsion machine are thicker and less easily deformable to form corrugated windings, and insert them by corrugations into the notches of the stator.

[0006] Furthermore, in order to increase the power density of the electrical machine, and therefore reduce its size for equivalent electrical power, it is necessary to maximize the conductor filling rate of the slots in the stator of the electrical machine, which is made possible by conductors with a rectangular section.

[0007] These conductors being thick conductive bars, their insertion into the The stator slots are made axially, the conductors being for example in the shape of pins with each branch inserted into a different slot, the ends of the branches then having to be bent and then welded to the branches of another conductor.

[0008] Other methods, such as that described in document WO2015 / 159032, use thick conductors with a round cross-section which are flattened before or after insertion into the slots. In this document, the conductors used are so poorly malleable that they must first be corrugated on a flat, longitudinal winding sheet before being arranged on a cylindrical insertion tool, then allowing the conductors to be inserted into the slots of the stator body.

[0009] The use of thick conductors therefore makes it possible to maximize the filling rate of the slots, and therefore the current density in the stator, but at the cost of a complex winding process due to the number of steps required to obtain the wound stator.

[0010] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an electrical machine stator and a method of winding such a stator, making it possible to obtain a high power density without requiring a significant number of winding steps, which makes the manufacture of the stator less expensive than in the prior art.

[0011] To this end, the invention proposes an electrical machine stator, comprising a stator body and at least one winding, the stator body comprising a yoke and teeth angularly distributed on an internal periphery of the yoke and extending axially on the internal periphery, the teeth forming winding notches in pairs, the winding comprising at least one conductor comprising straight portions in winding slots, the straight portions being connected two by two alternately by a lower curved portion of the conductor located at a lower axial end of the stator body then by an upper curved portion of the conductor located at an upper axial end of the stator body, thus drawing a corrugation, the stator being characterized in that the conductor is an uninterrupted Litz wire on the corrugation.

[0012] It should be noted that in this patent application, the term "axial" (or "axial" in the plural) refers, unless otherwise stated, to a direction parallel to the axis of symmetry of the stator body, of cylindrical shape, or of another cylindrical object considered, or to a positioning along this direction. Similarly, the term "radial" (or "radial" in the plural) refers, unless otherwise stated, to a direction orthogonal to this axis of symmetry, and secant to this axis of symmetry, or to a positioning along this direction. Finally, the terms "angular" or "ortho-radial" (or "ortho-radial" in the plural) refer, unless otherwise stated, to a direction orthogonal to the axial direction and to a radial direction, or to a positioning in this direction, which is in fact rotating around the axis of symmetry of the stator body or of the other cylindrical object considered. It should be noted that in the electrical machine comprising the stator according to the invention, the axis of symmetry of the stator body coincides with an axis of a rotating shaft of the electrical machine.

[0013] The stator according to the invention comprises one winding per stator phase, the stator preferably being three-phase but may alternatively comprise more or fewer phases, for example only two phases or on the contrary six phases. In addition, the stator comprises one or more consecutive notches per pole per phase of the stator, along the internal circumference thereof. Each winding, corresponding to a phase, is formed of one or more conductors electrically connected in parallel or in series. In other words, a winding is possibly formed of several corrugations electrically connected in parallel or in series, over one or more turns of the circumference of the stator. Certain corrugations of the same phase possibly overlap in opposite directions, as in document WO2015 / 159032.

[0014] According to the invention, the conductor of the stator winding is an uninterrupted Litz wire on the corrugation, that is to say that on a corrugation, it is in one piece. The corrugation is therefore not formed of pins of Litz wire welded together. In other words, the conductor does not have any connection or welding on the corrugation. Preferably, of course, all the windings of the stator according to the invention are made of Litz wire, the windings each comprising one or more uninterrupted corrugations of Litz wire.

[0015] The Litz wire comprises several strands electrically insulated from each other by a thin layer of varnish, in order to reduce the skin effect. It therefore allows a high current density at high frequency. The strands are for example made of copper or aluminum. A Litz wire comprises for example about twenty or thirty strands, which makes it malleable and easily shaped on a cylindrical surface, unlike a thick conductor bar. Its use therefore makes it possible to limit the number of steps necessary for its winding on the stator according to the invention. In addition, being in a single piece, the Litz wire does not require the strands it comprises to be wound one by one.

[0016] This malleability also makes it possible, compared to the prior art using hairpin conductors, to obtain stator coils of small axial dimension, which reduces the size of the stator and the resistivity of its windings, resulting in fewer Joule losses.

[0017] Finally, this malleability allows the Litz wire to take the shape of the notches and to fill them completely. As an indication, two superimposed Litz wires can completely fill a winding notch where two sections of bars conductors inserted axially according to the prior art would not fill it entirely because they would not be able to match the shape of the slot, generally trapezoidal. The invention therefore allows very good thermal conductivity of the conductors of the same slot compared to conductors with a square or round section, and a filling rate maximizing the current density of the stator, while presenting very good performances at high frequency.

[0018] According to an optional feature of the invention, the conductor comprises a sheath at least on its straight portions. The Litz wire is in fact generally provided with an electrically insulating sheath, for example made of flexible polymer, surrounding the strands of the Litz wire. This sheath makes it possible to dispense with a step of insulating the winding slots with insulating paper. In addition, it is in fact kept over the entire length of the Litz wire, therefore over the entire corrugation, and is only removed on the ends of the conductor used to make electrical connections with another conductor of the winding or with a connection terminal intended to be connected to a power supply output of an inverter, for example.

[0019] According to an optional feature of the invention, the lower or upper curved portions of the conductor are rounded. These rounded shapes are linked to the process of winding by undulation of the conductor, and participate in forming a undulation without singularity, that is to say with a radius of curvature substantially constant on each curved portion. However, since the stator coils can be subject to compression after winding the conductor, the lower or upper curved portions of the conductor can ultimately be slightly twisted compared to their initial rounded shape.

[0020] According to an optional characteristic of the invention, the winding slots each comprise several layers of conductor superimposed radially and each formed of a single straight portion of conductor. Each winding slot comprises, for example, two, four, six, eight or ten layers of the same conductor or of different conductors of the same phase. In an alternative embodiment, each winding layer comprises several straight portions of conductor, for example two straight portions of conductor. In another alternative embodiment, each winding slot comprises only a single layer of winding. In yet another alternative embodiment, each winding slot comprises straight portions of conductors of two different stator phases.

[0021] In the embodiment of the invention with several layers of winding of a single straight portion of conductor, at least one winding notch has for example a trapezoidal section, an opening of the winding notch on an air gap of the electrical machine being strictly less angularly extended than a bottom of the winding notch, and a winding layer arranged at the bottom of the notch of winding is radially less extensive than a winding layer near the winding slot opening.

[0022] Of course, preferably all the winding slots have the same trapezoidal section. The winding layer at the bottom of each slot, due to the structure according to the invention of the conductor in the form of Litz wire, can be compressed to match the shape of the bottom of the slot, which reduces the radial dimension of the winding layers in the slot and therefore makes it possible to have a less bulky stator, with an equivalent slot filling rate. In addition, the shape of the winding slots makes it possible to have teeth whose end in the air gap is angularly more extended than if the winding slots had a rectangular section. As a result, the teeth are able to exchange more magnetic flux with the rotor of the electrical machine, which improves the magnetic and electrical performance thereof.

[0023] The invention also relates to an electrical machine comprising a stator according to the invention.

[0024] The invention also relates to a method for winding an electrical machine stator according to the invention, comprising a step of shaping the stator winding by continuous undulation of the Litz wire forming the conductor, around a cylindrical surface. The Litz wire being more malleable than thick conductors, it allows such shaping directly on a cylindrical surface, which may be that of a tool for inserting the straight portions of the conductor into the notches of the stator body, or that of a winding support closing the notches of the stator body, when the latter is wound from an external periphery of the stator body. The winding method according to the invention is faster and less expensive than the winding methods of the prior art, which comprise intermediate steps of arranging conductors on a flat longitudinal sheet, or of welding the ends of conductors into pins.

[0025] In a first embodiment of the winding method according to the invention, the winding method uses an insertion tool comprising the cylindrical surface, the latter being formed of axially positioned blades, capable of moving radially on the insertion tool, and angularly spaced from guides, fixed on the insertion tool and configured to come into contact with the teeth of the stator body when the insertion tool is inserted therein, leaving the openings of the winding notches free, the winding method comprising steps of: - shaping the stator winding by continuous undulation of the Litz wire forming the conductor, on the insertion tool, the straight portions of the conductor each being inserted between two adjacent guides so as to reproduce on the insertion tool, a radial configuration inverse to that intended to be mounted in the stator, - insertion of the insertion tool into the stator body, and - radial expansion of the blades, until all straight portions of the conductor are inserted into the winding slots.

[0026] In this first embodiment of the invention, a cylindrical insertion tool is used, the outer periphery of which comprises notches arranged axially, i.e. parallel to the axis of symmetry of the cylindrical insertion tool, the side walls of the notches being formed by the fixed guides of the tool and the bottom walls of the notches being formed by the blades. These blades are radially movable from an initial position allowing the insertion of all winding layers of the stator into the notches of the cylindrical tool during the shaping step, to a final position in which the blades are radially at the same level as the outer ends of the guides, these outer ends being in contact with the teeth of the stator after insertion of the insertion tool into the stator.During the extension step, the blades move from their initial position to their final position, which allows the straight portions of the stator winding conductors to be pushed into the stator slots.

[0027] The notches of the insertion tool are possibly angularly wider than the stator notches during the shaping step to facilitate the latter. In this case, an intermediate step of tightening the guides in an angular direction takes place between the shaping step and the step of inserting the insertion tool into the stator body.

[0028] Of course, the radial expansion step can be followed by a step of closing the notches, or by a step of packing the conductors into the notches so as to ensure that they are held in the notches.

[0029] In this first embodiment of the winding method according to the invention, the stator comprising a winding per phase of the electrical machine, the shaping step comprises at least as many simultaneous insertions of straight portions of Litz wires as there are phases of the electrical machine, between guides of the insertion tool. In other words, at least three conductors per phase are corrugated at the same time in the shaping step, which allows a time saving compared to phase-by-phase winding methods.

[0030] The insertion tool comprises, for example, a cylindrical flange for holding the straight portions between the guides, the flange comprising an axial opening oriented towards a tool for guiding the conductor, the shaping step comprising steps of rotating the insertion tool in the flange alternating with steps of inserting a straight portion of the conductor into the axial opening.

[0031] Thus the guide tool places, for example, straight portions of conductors in one or more notches of the insertion tool through the axial opening, by performing a movement in a first axial direction, then the insertion tool rotates by a number of notches for example equal to the number of notches having just received one or more straight portions of conductors, and the guiding tool places other straight portions of the same conductors in a second axial direction, opposite to the first axial direction, and so on. The axial movements of the guiding tool coupled with the rotation of the insertion tool make it possible to naturally obtain undulations of the conductors.

[0032] The number of straight portions placed simultaneously corresponds for example to the number of phases of the stator multiplied by the number of notches per phase and by the number of winding layers per notch. In this case the shaping step is done in a single revolution of the insertion tool. Alternatively, the number of straight portions placed simultaneously corresponds for example to the number of phases of the stator multiplied by the number of notches per phase. In this case the shaping step requires as many revolutions of the insertion tool as there are winding layers.

[0033] In a second embodiment of the winding method according to the invention, the winding method uses an insertion tool comprising a cylindrical assembly formed of blades arranged axially in this cylindrical assembly, each blade having a width corresponding at least to a number of winding notches separating two winding notches dedicated to the stator conductor, the blades being arranged on a base of the insertion tool, the latter further comprising a portion movable relative to the base and capable of sliding between the blades, the winding method comprising steps of: - shaping the stator winding by continuous undulation of the Litz wire forming the conductor, reproducing flat the configuration of the stator winding around the cylindrical surface, the undulation forming on a plane a star of which a central portion around the cylindrical surface is intended to form the upper curved portions of the conductor, and the ends of the branches of which are intended to form the lower curved portions of the conductor, - insertion of the blades of the insertion tool between the branches of the star corrugation, the plane being positioned orthogonally to the axis of the cylindrical assembly of the insertion tool, - inserting the blades of the insertion tool into the stator body from the lower axial end of the stator body to the upper axial end of the stator body, positioning the blades between the winding notches dedicated to the conductor, - sliding the movable portion of the insertion tool between the blades inserted into the stator body, from the lower axial end of the stator body to the upper axial end of the stator body, the movable portion moving with it the upper curved portions of the conductor towards the upper axial end of the stator body, and thus inserting the straight portions of the conductor into the winding notches dedicated to it, the lower curved portions of the conductor being held at the lower axial end of the stator body by the base of the insertion tool.

[0034] In this second embodiment of the winding method according to the invention, the star formed during the shaping step comprises all the winding layers of the same phase, the latter being formed from a single conductor. The flat undulation is made around a possibly unmaterialized cylindrical surface, of height equal to the thickness of the winding on the winding layers of the shaped phase.

[0035] When the blades are inserted into the stator body, they cover the notches not intended to be filled by the conductor and leave free between them the notches intended to receive the conductor. The straight portions of the branches of the star are therefore angularly positioned, during this step, at the level of the notches intended to receive the conductor, although they are, during this step, orthogonal to the axial orientation of the notches.

[0036] Then during the sliding step, the movable portion being in contact with the blades, forces the upper curved portions of the conductor to go towards the upper axial end of the stator body, the straight portions of the branches of the star, corresponding to the straight portions of the conductor, then being driven axially along the notches dedicated to them, and ending up being inserted at least partially in them. During this step, the base of the insertion tool wedges the lower curved portions of the conductor between the base and the stator body when a sufficient portion of the branches has been driven by the movable portion inside the stator body.

[0037] The steps of this winding method, in this second embodiment of the invention, are repeated for each phase of the stator, so as to wind it entirely.

[0038] The sliding step is preferably followed by a step of axially releasing the blades and then by a step of radially separating the upper curved portions from the inside of the stator towards the outside of the stator. The radial separating step makes it possible to finalize the insertion of the straight portions of the conductor into the winding notches dedicated to it, and to place the upper curved portions in the axial extension of the stator body. This radial separating step uses, for example, a tool separate from the insertion tool, which is released from the stator body by its lower axial end to remove the blades therefrom.

[0039] In a third embodiment of the winding method according to the invention, in which the stator body is segmented into the yoke and the teeth, capable of fitting into the yoke, the teeth each comprising a fitting surface opposite to a free end surface of the tooth intended to delimit an air gap of the electrical machine, the winding method comprises steps of: - holding the teeth outside the cylinder head, around a cylindrical support comprising the cylindrical surface, the teeth being positioned axially around the cylindrical support on their free end surface, - shaping the stator winding by continuous waving of the Litz wire forming the conductor, inserting the straight portions of the conductor between the teeth of the stator body from the side of the teeth's interlocking surfaces, and - interlocking the yoke onto the teeth.

[0040] In this third embodiment of the winding method according to the invention, the winding of the conductor is carried out by the external periphery of the stator body, the latter being segmented. The teeth are for example held axially by an axial holding tool, arranged on either side of the ends of the teeth. The cylindrical support is for example formed of wedges closing the winding notches and making it possible to radially block the conductor during the shaping step, or else of a single-piece cylindrical support allowing radial holding of the stator teeth.

[0041] In a similar manner to the first embodiment of the invention, a tool for holding the teeth, for example, drives them in rotation within a fixed cylindrical flange comprising an axial opening arranged opposite a conductor guide head. Preferably, several conductors are corrugated at the same time by the guide head, these conductors each corresponding to a distinct layer of winding, to a distinct phase of the stator and to a distinct notch per series of consecutive notches assigned to a phase of the stator.

[0042] This third embodiment makes it possible to have a stator with notch openings partially closed by ortho-radial fins, which angularly extend the free ends of the teeth opposite the air gap, which makes it possible to optimize the magnetic flux in the direction of the armature.

[0043] Furthermore, according to an optional characteristic of the method for winding an electrical machine stator according to the invention, the latter further comprises a step of compressing stator coils formed at least in part by the lower and upper curved portions of the conductor. This step makes it possible to reduce the size of the stator according to the invention. It can be implemented in the three embodiments of the winding method according to the invention previously mentioned.

[0044] Of course, other implementations of the winding method according to the invention, comprising a step of shaping the stator winding by continuous undulation of the Litz wire forming the conductor, around a cylindrical surface, are conceivable.

[0045] The electrical machine according to the invention and the winding method according to the invention have advantages similar to those of the stator according to the invention.

[0046] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0047] [Fig-1] represents in perspective a portion of a stator body of a stator according to the invention partially wound,

[0048] [Fig.2] represents, seen in section orthogonal to an axial direction, a notch of the stator body of [Fig.l], filled with two straight portions of Litz wire,

[0049] [Fig.3] represents steps of a method of winding a stator according to the invention, according to a first embodiment of the invention,

[0050] [Fig.4] represents an installation allowing the implementation of the method of winding of [Fig.3],

[0051] [Fig.5] shows in section a tool of the installation of [Fig.4], allowing the insertion of straight portions of conductor into the notches of the stator body of [Fig.l], wound according to the method of [Fig.3],

[0052] [Fig.6] represents a portion of the insertion tool of [Fig.5] and the stator body of [Fig.l], in a configuration in which the straight conductor portions have just been inserted into notches in the stator body,

[0053] [Fig.7] represents steps of a method of winding a stator according to the invention, according to a second embodiment of the invention,

[0054] [Fig.8] represents a star-shaped corrugated stator winding around a cylindrical surface, in relation to a step of shaping a conductor of the stator wound according to the winding method of [Fig.7],

[0055] [Fig.9] represents an insertion tool implementing an insertion of the conductor in the notches of the stator wound according to the winding method of [Fig.7],

[0056] [Fig. 10] represents steps of a method of winding a stator according to the invention, according to a third embodiment of the invention, and

[0057] [Fig. 11] represents a step of inserting straight portions of stator windings into the stator wound according to the winding method of [Fig. 10].

[0058] A stator 1 according to the invention, partially shown in [Fig.l] being partially wound with a single phase conductor 14_1, comprises a stator body 11, formed for example from a stack of magnetic steel sheets, in an axial direction X (referenced [Fig.2]) that is to say along the axis of symmetry of the stator body 11, of overall cylindrical shape.

[0059] This stack of sheets forms a cylindrical cylinder head 10, and, on the internal periphery of the cylinder head 10, teeth 12 angularly and regularly distributed on this internal periphery. The teeth 12 are arranged axially and extend from a lower axial end 15 of the stator body 11 to an upper axial end 17 of the stator body 11. They also extend radially, from the yoke 10 towards the air gap of an electrical machine according to the invention, comprising the stator 1 according to the invention. In particular, they each comprise a free end surface 122 delimiting this air gap. Winding notches 16, each between two adjacent teeth 12, are intended to receive one or more phase conductors of the stator 1.

[0060] In this exemplary embodiment of the invention, the stator 1 comprises three phases and two consecutive winding slots 16 per phase in a series of six consecutive slots. The stator comprises, for example, 48 or 96 winding slots 16. Each phase is formed of one or more conductors, referenced 14_1 for the first phase of the stator 1, 14_2 for the second phase of the stator 1 and 14_3 for the third phase of the stator 1.

[0061] Each winding notch 16 comprises, in this embodiment of the invention, two winding layers L1 and L2, as shown [Fig.2], each formed from a single portion of conductor 14_1. This is copper Litz wire, sheathed with an insulating protection 148 made of flexible polymer material, and here comprising 66 strands 145 of enameled copper wire.

[0062] A winding of the stator 1, corresponding to a first phase of the stator 1, uses for example a single conductor 14_1, that is to say a single Litz wire, undulated over four turns of the stator body 1 to fill, at each turn, a notch on the two consecutive winding notches 16 dedicated to this first phase, and a winding layer L1 or L2.

[0063] The conductor 14_1 is wound by undulation, and therefore comprises straight portions 142 in the winding notches 16 dedicated to it, connected two by two alternately by a lower curved portion 144 of the conductor 14_1 located at the lower axial end 15 of the stator body 11 then by an upper curved portion 146 of the conductor 14_1 located at the upper axial end 17 of the stator body 11. Each curved portion 144 or 146 connects more precisely a straight portion 142 in a winding notch 16 of a first series of notches, to another straight portion 142 in another winding notch 16 ordered identically in a second series of notches with respect to the winding notch 16 of the first series of notches, the second series of notches being adjacent to the first series of notches.

[0064] According to the invention, the conductor 14_1 is the same uninterrupted Litz wire on the corrugation that it forms on the stator body 11, this corrugation comprising at least three straight portions 142 of the conductor 14_1, a lower curved portion 144 and an upper curved portion 146 of the conductor 14_1. The corrugation preferably runs at least one turn of the stator body 11, i.e. at least entirely around the inner circumference of the stator body 11.

[0065] As a variant of this embodiment of the invention, the two consecutive notches dedicated to the first phase of the stator 1 are filled by two separate conductors 14_1, electrically connected in parallel or in series. The different winding layers L1 and L2 of the same winding notch 16 are furthermore, as a variant, produced by two separate conductors 14_1, electrically connected in parallel or in series. Returning to [Fig. 2], in this exemplary embodiment of the invention, the winding notches 16 have a trapezoidal section. More precisely, in a winding notch 16, the largest base of the trapezoid corresponding to this section delimits the bottom 164 of the winding notch 16. The smallest base of the trapezoid corresponding to this section delimits the opening 162 of the winding notch 16. As a result, the opening 162 of the winding notch 16 is less angularly extended than the bottom 164 of the winding notch 16. The angular direction is referenced A in [Fig. 2] and is substantially parallel to the bases of the trapezoid of the trapezoidal section of the winding notch 16 shown therein.

[0066] The free end surface 122 of each tooth 12 is therefore angularly larger than its end of attachment to the yoke 10.

[0067] The conductor 14_1 is sufficiently flexible to fit a first portion of the trapezoid in the first winding layer L1, and to fit a second portion of the trapezoid in the second winding layer L2, the two portions of the trapezoid almost entirely filling the entire winding notch 16. The surface area of ​​the section of the Litz wire forming the conductor 14_1 being of constant value over the length of the Litz wire, the conductor 14_1 in the first winding layer extends radially less than in the second winding layer. The radial direction is referenced R in [Fig.2] and is substantially parallel to the height of the trapezoid formed by the section of the winding notch 16 in this figure. The conductor filling rate 14_1 of the winding notch 16 is therefore optimized while reducing the radial dimension of the stator body 11 and promoting the exchange of magnetic flux between the stator 1 and a rotor of the electrical machine according to the invention.

[0068] A method 100 for winding a stator 1 according to the invention is now described in relation to Figures 3 to 6, in a first embodiment of the invention. The stator 1 according to the invention, in this first embodiment of the winding method, is very similar to the stator 1 described in relation to Figures 1 and 2, and is therefore referenced, as are its elements, in the same way. It does not differ in fact from the stator 1 of figures 1 and 2 only in that it has four conductors per phase, electrically connected in parallel.

[0069] A first step 102 of the winding method 100 is the shaping of the winding of the stator 1 by continuous undulations of Litz wires forming the windings of the stator 1, on a generally cylindrical insertion tool 35.

[0070] The insertion tool 35 is visible in section along a plane orthogonal to the axis of the insertion tool 35, [Fig. 5]. Its external periphery is composed of an alternation of blades 352 and guides 353 extending radially from one axial end to the other of the insertion tool 35. The guides 353 are fixed on the insertion tool 35 and also extend angularly over a distance corresponding substantially to the depth of a winding notch 16 of the stator 1.

[0071] The blades 352 are radially movable between two adjacent guides 353, each being fixed to a rod 351 connected to a mechanism 350 at the center of the insertion tool. The mechanism 350 makes it possible to radially move the rods 351 so as to move the blades 352 from a radial position located at the ends of the guides 353 proximal to the center of the insertion tool 35, to a radial position located at the ends of the guides 353 distal to the center of the insertion tool 35.

[0072] The number of blades 352 on the insertion tool 35 corresponds to the number of winding notches 16 in the stator 1, and the outer periphery of the insertion tool 35 is configured so that the tool fits perfectly into the stator body 11, the guides 353 being able to slide against the free end surfaces 122 of the teeth 12 of the stator 1, while leaving the openings 162 of the notches of the stator 1 free.

[0073] The shaping 102 of the windings of the stator 1 on the insertion tool 35 is an intermediate step before inserting the insertion tool 35 into the stator body 11 to insert the conductors forming these windings into the stator body 11. During this shaping 102, a radial configuration is reproduced on the insertion tool 35, the opposite of that intended to be mounted in the stator 1, the straight portions 142 of the conductors 14_1, 14_2 and 14_3 of the windings of the stator 1 being inserted between the guides 353 of the insertion tool 35. In order to maintain these straight portions 142 between these guides 353, a cylindrical flange 34 encloses the external periphery of the insertion tool 35, leaving only an axial opening 36 oriented vertically upwards in order to allow the insertion of the straight portions 142 between the guides 353 of the insertion tool 35.

[0074] This shaping 102 is carried out using a visible installation 3 [Fig.4]. Coils 30 each unwind Litz wires for each of the three phases of the stator 1. For simplicity, [Fig.4] shows three coils 30 and three conductors 14_1, 14_2 and 14_3 for the three phases of the stator 1, but in reality the coils 30 deliver four conductors 14_1, 14_2 or 14_3 for each phase of stator 1.

[0075] These conductors 14_1, 14_2 and 14_3 arrive in a guide head 33 connected to a mechanical arm 32 movable in the axial direction linked to the insertion tool 35, thanks to a rail 31 on which it can slide. The guide head 33 performs, in the shaping step 102, back and forth movements by unwinding the conductors 14_1, 14_2 and 14_3 above the axial opening 36 so as to drop the conductors 14_1, 14_2 and 14_3 two by two onto six consecutive blades 352, accessible from the axial opening 36.

[0076] [Fig. 5] shows the insertion tool 35 after a first movement of the guide head 33 above the axial opening 36, in a first direction. The guide head 33 has six mouths each discharging two conductors 14_1, 14_2 and 14_3, the mouths being spaced so as to be each placed above a separate blade 352.

[0077] This first movement therefore corresponds to a first sub-step 1022 of the shaping step 102 corresponding to an insertion of straight portions 142 of the conductors 14_1, 14_2 and 14_3 on the insertion tool 35 and more precisely on a cylindrical surface formed by the blades 352.

[0078] This first sub-step 1022 is followed by a first sub-step 1024 of rotation 1024 of the insertion tool 35 in the flange 34, which makes it possible to maintain the straight portions already inserted on the insertion tool 35, in the latter, and to place six other consecutive blades 352 opposite the guide head 33.

[0079] The guide head 33 being fixed in a direction orthogonal to the axial direction, this first rotation 1024 deforms the conductors 14_1, 14_2 and 14_3 orthogonally to this axial direction, in the direction of the new blades 352 opposite the guide head 33. This deformation contributes to forming the lower 144 or upper 146 curved portions which form the stator coils of the stator 1.

[0080] This first rotation sub-step 1024 is then followed by a second sub-step of inserting straight portions 142 of the conductors 14_1, 14_2 and 14_3 onto the insertion tool 35 by a second axial displacement of the guide head 33, in a second direction opposite to the first direction of the first axial displacement. This second axial displacement makes it possible to place twelve other straight portions 142 of the conductors 14_1, 14_2 and 14_3 onto the six other blades 352, and to form first lower or upper curved portions of the twelve corresponding conductors at an axial end of the insertion tool 35.

[0081] It is therefore understood that the insertion 1022 and rotation 1024 sub-steps alternate until the entire external periphery of the insertion tool 35 is filled with straight portions 142 of the conductors 14_1, 14_2 and 14_3, i.e. until the inverse radial configuration of that intended to be mounted in the stator 1 is reproduced.

[0082] The shaping step 102 has therefore continuously produced, on one revolution of the insertion tool 35, twelve undulations of distinct Litz wires, each corresponding to a conductor 14_1, 14_2 or 14_3. These undulations are continuous in the sense that they are formed without intermediate steps of welding or connections.

[0083] Step 104 following shaping step 102 is a step of inserting the insertion tool 35 into the stator body 11, the guides 353 being positioned against the free end surfaces 122 of the teeth 12 of the stator body 11, leaving the openings 162 of the winding notches 16 free. The insertion tool 35 is of course removed from the flange 34 in this step 104.

[0084] The next step 106 is the radial expansion of the blades 352 of the insertion tool 35, by deployment of the rods 351, until insertion of all the straight portions 142 of the conductors 14_1, 14_2, 14_3 into the winding notches 16, as shown [Fig.6], in which the rods are fully deployed.

[0085] Finally, the following step 108 is a compression of the stator coils formed by the lower 144 and upper 146 curved portions of the conductors 14_1, 14_2, 14_3.

[0086] The insertion tool 35 is then removed from the stator body 1, and step 108 may be preceded or followed by steps of connecting the different conductors 14_1, 14_2, 14_3 of the same phase in parallel, and other steps of finalizing the stator 1 which are not the subject of the invention, such as the insertion of notch shims or the molding of the stator coils.

[0087] A method 200 for winding a stator 1 according to the invention is now described in relation to Figures 7 to 9, in a second embodiment of the invention. The stator 1 according to the invention, in this second embodiment of the winding method, is very similar to the stator 1 described in relation to Figures 1 and 2, and is therefore referenced, as are its elements, in the same way. It differs from the stator 1 of Figures 1 and 2 only in that it comprises two conductors per phase, electrically connected in parallel. More precisely, each conductor 14_1, 14_2 or 14_3 is wound over two turns of the stator 1 in a single winding slot 16 per series of six consecutive slots of the stator 1.

[0088] A first step 202 of the winding method 200, shown [Fig.8], is the shaping of a conductor 14_1 of the stator 1 by continuous undulation of the Litz wire forming the conductor 14_1 in a plane P, the undulation forming a star around a cylindrical surface S, of height equal to the thickness of the conductor 14_1 on the two layers L1 and L2 of winding. The central portion of the star comprises the portions intended to become the upper curved portions 146 of the conductor 14_1, the branches of the star comprise the straight portions 142 of the conductor 14_1 and the ends of the branches comprise the portions intended to become the portions lower curves 144 of the conductor 14_1. The cylindrical surface S is materialized or not depending on the corrugation tool used.

[0089] This corrugating tool is for example formed of as many arms as there are curved portions of the conductor 14_1, the arms maintaining these curved portions radially in tension and rotating around the center of the star while a guide head of the Litz wire forming the conductor 14_1, performs back and forth movements in a radial direction, without moving angularly. The rotations of the arms alternate with the radial movements of the guide head, in a manner similar to the winding method 100, to form a continuous corrugation of the conductor 14_1 over two turns of the circumference of the star.

[0090] Once the shaping 202 of the conductor 14_1 has been carried out, an insertion tool 5 shown [Fig.9] is used. This insertion tool 5 comprises a base 51 on which are fixed blades 52 regularly spaced angularly and forming a cylindrical assembly, the blades 52 extending axially in the direction of this cylindrical assembly. Each blade 52 is curved so as to match the internal periphery of the stator body 11 when the cylindrical assembly is inserted into the stator 1. In addition, each blade 52 extends angularly over a distance covering five winding notches 16 of the stator 1. Thus, it is possible to angularly position the blades 52 against the internal periphery of the stator body 11 so as to leave free only one notch of each series of six consecutive notches of the stator, dedicated to one of the conductors of the windings of the stator 1.

[0091] The insertion tool 5 also comprises a movable portion 53, cylindrical and movable in the axial direction, relative to the base 51. This movable portion 53 is configured to slide in contact with the blades 52 of the insertion tool 5.

[0092] Step 204 following the shaping step 202 is the insertion of the blades 52 of the insertion tool 5 between the branches of the conductor 14_1 which has just been shaped by star-shaped undulation. For simplicity, it is assumed that the plane P is horizontal and that the insertion tool 5 is mounted vertically, for example by means of vertical rails, under the plane P, until the blades 52 are inserted between the branches of the conductor 14_1 which is star-shaped undulation.

[0093] In this step 204, the stator body 11 is further held axially in the vertical direction, above the plane P, so that the insertion of the blades 52 of the insertion tool coincides with an insertion of the blades 52 into the stator body 11 from the lower axial end 15 of the stator body 11 towards the upper axial end 17 of the stator body 11. The blades 52 are further angularly positioned, during this insertion 204, so as to leave free only the notches dedicated to the conductor 14_1. At the end of the insertion step 204, the straight portions 142 of the conductor 14_1 are held horizontal between the base 51 of the insertion tool 5 and the stator body 11, the base 51 and the stator body 11 being sufficiently close to each other to allow this holding without assistance of the arms used during the shaping step 202, which are removed from the conductor 14_L

[0094] The next step 206 is the displacement of the movable portion 53 relative to the base 51, the movable portion 53 sliding between the blades 52 from the lower axial end 15 of the stator body 11 towards the upper axial end 17 of the stator body 11, and moving with it the upper curved portions 146 of the conductor 14_1 towards the upper axial end 17 of the stator body 11, as illustrated [Fig.9].

[0095] During this movement of the movable portion 53, the straight portions 142 are driven horizontally from the outside of the stator 1 towards the inside of the stator 1 and vertically between the blades 52 of the insertion tool 5. The space between the sliding movable portion 53 and the notch openings 162 is sufficiently reduced to force the insertion of the straight portions 142 of the conductor 14_1 into the winding notches 16 during this step 206.

[0096] Step 206 continues until the upper curved portions 146 of the conductor 14_1 exceed the upper axial end 17 of the stator body IL

[0097] These upper curved portions 146 are nevertheless positioned radially at the level of the interior of the stator 1 at the end of step 206.

[0098] The next step 208 is the axial release of the blades 52, by lowering the insertion tool 5 onto the vertical rails.

[0099] Then the following step 210 is the radial spacing of the upper curved portions 146 of the conductor 14_1 from the inside of the stator 1 towards the outside of the stator 1, so as to position them in the axial extension of the stator body 1. This step 210 uses for example a spacing tool distinct from the insertion tool 5, this spacing tool being able to comprise arms fixed in height relative to the stator body 11.

[0100] Steps 202 to 210 are then repeated, in order to wind the other five conductors 14_1, 14_2, 14_3 forming the windings of the stator 1.

[0101] Once the stator 1 is fully wound, the winding method 200 comprises a step 212 of compressing the stator coils formed by the lower 144 and upper 146 curved portions of the conductors 14_1, 14_2 and 14_3.

[0102] As for the winding method 100 previously described, the winding method may further comprise a step of electrically connecting the conductors of the same phase, and be followed by steps of finalizing the stator 1 according to the invention.

[0103] Variant embodiments of the winding method 200 are of course possible, for example the blades of the insertion tool can be movable relative to a base fixed, the latter then not sliding on vertical rails. In addition, the winding process may require twelve executions of steps 202 to 210, for example if the stator 1 has four conductors per phase connected in parallel.

[0104] A method 300 for winding a stator 1 according to the invention will now be described in relation to Figures 10 and 11, in a third embodiment of the invention. The stator 1 according to the invention, in this third embodiment of the winding method, is very similar to the stator 1 described in relation to Figures 1 and 2, and is therefore referenced, as are its elements, in the same way. It differs from the stator 1 of Figures 1 and 2 only in that it comprises four conductors per phase, electrically connected in parallel, and in that it is segmented.

[0105] The yoke 10 is in fact separable from the teeth 12, in this third embodiment of the invention. The yoke 10 and / or the teeth 12 are for example made by stacking magnetic sheets, or else from compacted magnetic powder.

[0106] The teeth 12 each comprise, on the side opposite the free end surface 122, a fitting surface 124, for example forming an axial rib whose cross-section is dovetail-shaped, this axial rib being capable of sliding in an axial groove of complementary shape in the yoke 12. As a variant, the fitting surface 124 forms an axial groove whose cross-section is dovetail-shaped, this axial groove being capable of receiving by sliding an axial rib of complementary shape in the yoke 12. Other types of fixing are of course conceivable.

[0107] In a first step 302 of the winding method 300 according to the invention, the teeth 12 insulated from the yoke 10 are held around a cylindrical support 6 forming a cylindrical surface on which the conductors 14_1, 14_2 and 14_3 will be wound. The teeth 12 are for example held axially all around the cylindrical support 6 by a tool for axially holding the teeth 12, so as to position the teeth 12 between them as they would be in the stator body 11. The cylindrical support 6 closes the openings 162 of the winding notches 16 between two adjacent teeth 12.

[0108] The second step 304 of the winding method 300 is the shaping of the winding of the stator 1 by simultaneous undulations of the twelve Litz wires forming the twelve conductors 14_1, 14_2, 14_3 of the stator 1, between the teeth 12 on the cylindrical support 6.

[0109] This step is carried out in a similar manner to step 102 of shaping the winding method in the first embodiment of the invention, the insertion tool 35 being replaced by the assembly of teeth 12 and the cylindrical support 6. In particular, this assembly is for example held in a fixed cylindrical flange having an axial opening opposite a guide head capable of inserting the wires of Litz by a reciprocating movement in the axial direction through the axial opening, the assembly being rotated between two axial movements of the guide head.

[0110] Once all the winding notches 16 are filled with the conductors 14_1, 14_2 and 14_3, the yoke 10 is fitted to the teeth 12 in a third step 306 of the winding method 300, and the cylindrical support 6 is removed from the stator 1 thus formed.

[0111] Then, during a fourth step 308 of the winding method 300, the stator coils formed by the lower 144 and upper 146 curved portions of the conductors 14_1, 14_2 and 14_3 are compressed.

[0112] The winding method 300 may further comprise a step of electrically connecting the conductors of the same phase, and be followed by steps of finalizing the stator 1 according to the invention.

[0113] Variants of embodiment of the winding method 300 are of course possible, in particular the shaping step 304 requires in a variant two turns of the set of teeth 12 and the cylindrical support 6, when each phase is formed of two conductors connected in parallel, or four turns of this set, when each phase is formed of a single conductor. It should also be noted that the cylindrical support 6 is not necessary when the teeth 12 comprise ortho-radial fins for closing the winding notches 16. In this case the cylindrical surface on which the conductors are undulated is not materialized.

[0114] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of the different variants or embodiments of the invention envisaged in this application can be combined to carry out the invention, insofar as these variants or embodiments are not incompatible with each other.

Claims

Claims

1. Stator (1) of an electric machine, comprising a stator body (11) and at least one winding, the stator body (11) comprising a yoke (10) and teeth (12) angularly distributed on an internal periphery of the yoke (10) and extending axially on the internal periphery, the teeth (12) forming two by two winding notches (16), the winding comprising at least one conductor (14_1, 14_2, 14_3) comprising straight portions (142) in winding notches, the straight portions (142) being connected two by two alternately by a lower curved portion (144) of the conductor (14_1, 14_2, 14_3) located at a lower axial end (15) of the stator body (11) then by an upper curved portion (146) of the conductor ( 14_1, 14_2, 14_3) located at an upper axial end (17) of the stator body (11), thus drawing a corrugation, the stator (1) being characterized in that the conductor (14_1, 14_2,14_3) is an unbroken Litz wire on the corrugation.,

2. Stator (1) of an electric machine according to claim 1, in which the conductor (14_1, 14_2, 14_3) comprises a sheath (148) at least on its straight portions (142).

3. Stator (1) of an electric machine according to claim 1 or 2, wherein the lower (144) or upper (146) curved portions of the conductor (14_1, 14_2, 14_3) are rounded.

4. Stator (1) of an electric machine according to any one of claims 1 to 3, in which the winding notches (16) each comprise several layers (L1, L2) of conductor superimposed radially and each formed from a single straight portion (142) of conductor (14_1, 14_2, 14_3).

5. Stator (1) of an electric machine according to claim 4, wherein at least one winding slot (16) has a trapezoidal section, an opening (162) of the winding slot (16) on an air gap of the electric machine being strictly less angularly extended than a bottom (164) of the winding slot (16), and wherein a winding layer (L1) arranged at the bottom (164) of the winding slot (16) is radially less extended than a winding layer (L2) close to the opening (162) of the winding slot (16).

6. Method of winding (100, 200, 300) a machine stator (1) electrical device according to any one of the preceding claims, comprising a step of shaping (102, 202, 304) the winding of the stator (1) by continuous undulation of the Litz wire forming the conductor (14_1, 14_2, 14_3), around a cylindrical surface (S).

7. Method for winding (100) a stator (1) of an electric machine according to the preceding claim, using an insertion tool (35) comprising the cylindrical surface, the latter being formed of blades (352) positioned axially, capable of moving radially on the insertion tool (35), and angularly spaced from guides (353), fixed on the insertion tool (35) and configured to come into contact with the teeth (12) of the stator body (11) when the insertion tool (35) is inserted therein, leaving free the openings (162) of the winding notches (16), the winding method (100) comprising steps of: - shaping (102) the winding of the stator (1) by continuous undulation of the Litz wire forming the conductor (14_1, 14_2, 14_3), on the insertion tool (35), the straight portions (142) of the conductor (14_1, 14_2, 14_3) each being inserted between two adjacent guides (353) so as to reproduce on the insertion tool (35),a radial configuration opposite to that intended to be mounted in the stator (1), - insertion (104) of the insertion tool (35) into the stator body (11), and - radial expansion (106) of the blades (352), until all the straight portions (142) of the conductor (14_1, 14_2, 14_3) are inserted into the winding notches (16).,

8. Method for winding (100) a stator (1) of an electric machine according to the preceding claim, in which the stator (1) comprises a winding per phase of the electric machine, the shaping step (102) comprises at least as many simultaneous insertions of straight portions of Litz wires as phases of the electric machine, between guides of the insertion tool (35).

9. Method for winding (100) a stator (1) of an electric machine according to claim 7 or 8, in which the insertion tool (35) comprises a cylindrical flange (34) for holding the straight portions (142) between the guides (353), the flange (34) comprising an axial opening (36) oriented towards a guide tool (33) of the conductor (14_1, 14_2, 14_3), the shaping step (102) comprises steps of rotation (1024) of the insertion tool (35) in the flange (34) alternating with steps of insertion (1022) of a straight portion (142) of the conductor (14_1, 14_2, 14_3) in the axial opening (36).

10. Method for winding (300) a stator (1) of an electric machine according to claim 6, in which the stator body (11) is segmented into the yoke (10) and the teeth (12), capable of fitting into the yoke (10), the teeth (12) each comprising a fitting surface (124) opposite a free end surface (122) intended to delimit an air gap of the electric machine, the winding method (300) comprises steps of: - holding (302) the teeth (12) outside the cylinder head (10), around a cylindrical support (6) comprising the cylindrical surface, the teeth (12) being positioned axially around the cylindrical support (6) on their free end surface (122), - shaping (304) the stator winding (1) by continuous undulation of the Litz wire forming the conductor (14_1, 14_2, 14_3), by inserting the straight portions (142) of the conductor (14_1, 14_2, 14_3) between the teeth (12) of the stator body (11) from the side of the fitting surfaces (124) of the teeth (12), and - fitting (306) the yoke (10) onto the teeth (12).

11. Method for winding (200) a stator (1) of an electrical machine according to claim 6, using an insertion tool (5) comprising a cylindrical assembly formed of blades (52) arranged axially in this cylindrical assembly, each blade (52) having a width corresponding at least to a number of winding notches (16) separating two winding notches (16) dedicated to the conductor (14_1, 14_2, 14_3) of the stator (1), the blades (52) being arranged on a base (51) of the insertion tool (5), the latter further comprising a movable portion (53) relative to the base (51) and capable of sliding between the blades (52), the winding method comprising steps of: - shaping (202) the winding of the stator (1) by continuous undulation of the Litz wire forming the conductor (14_1, 14_2, 14_3), reproducing flat the configuration of the winding of the stator (1) around the cylindrical surface (S), the undulation forming on a plane (P) a star of which a central portion around the cylindrical surface is intended to form the upper curved portions (146) of the conductor (14_1, 14_2, 14_3), and the ends of the branches of which are intended to form the lower curved portions (144) of the conductor (14_1, 14_2, 14_3), - insertion (204) of the blades (52) of the insertion tool (5) between the branches of the star undulation, the plane (P) being positioned orthogo- finally to the axis of the cylindrical assembly of the insertion tool (5), - insertion (204) of the blades of the insertion tool into the stator body (11) from the lower axial end (15) of the stator body (11) towards the upper axial end (17) of the stator body (11), by positioning the blades (52) between the winding notches (16) dedicated to the conductor (14_1, 14_2, 14_3), - sliding (206) of the movable portion (53) of the insertion tool (5) between the blades (52) inserted into the stator body (11), from the lower axial end (15) of the stator body (11) towards the upper axial end (17) of the stator body (11), the movable portion (53) moving with it the upper curved portions (146) of the conductor ( 14_1, 14_2, 14_3) towards the upper axial end (17) of the stator body (11), and thus inserting the straight portions (142) of the conductor (14_1, 14_2, 14_3) into the winding notches (16) dedicated to it,the lower curved portions (144) of the conductor (14_1, 14_2, 14_3) being held at the lower axial end (15) of the stator body (11) by the base (51) of the insertion tool (5).,

12. Method of winding (200) a stator (1) of an electric machine according to claim 11, in which the sliding step (206) is followed by a step of axial release (208) of the blades then by a step of radial separation (210) of the upper curved portions (146) from the inside of the stator (1) towards the outside of the stator (1).

13. Method of winding (100, 200, 300) a stator (1) of an electrical machine according to any one of claims 6 to 12, further comprising a step of compressing (108, 212, 308) stator coils formed at least in part by the lower (144) and upper (146) curved portions of the conductor (14_1, 14_2, 14_3).

14. Electrical machine comprising a stator (1) according to any one of claims 1 to 5.

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