Stator body manufacturing process

Abstract

The invention relates to a stator body (10) for an electric machine, the body comprising a disc-shaped plate (101) centered on a longitudinal axis (A1) and teeth (110) distributed on one face of the plate around the longitudinal axis. The plate comprises at least one opening, and at least one of said teeth comprises a projecting relief engaged in said opening. The invention further proposes a method for assembling such a stator body, which includes a step of inserting the relief into the opening, and a step of cold spraying a metallic material onto at least a portion of a junction zone between the relief and the edge of the opening. Figure for the abstract: Fig. 1

Description

Title of the invention: Method for manufacturing a stator body Technical field of the invention

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

[0002] It relates more particularly to a method of assembling a stator body for an electric machine, and in particular for an axial flux electric machine.

[0003] The invention finds a particularly advantageous application in electric motors for electric or hybrid motor vehicles. State of the art

[0004] An axial flux electric machine for an electric vehicle generally comprises a disc-shaped rotor, located between two stators.

[0005] A conventional stator body of such an electrical machine comprises a disc-shaped plate and teeth distributed circumferentially on the face of the plate that faces the rotor. To construct a stator from this body, coils of conductive wire are placed around the teeth. Then, under the influence of electric currents, the coils generate magnetic fields that allow the stator to set the rotor in motion.

[0006] One way to simplify the winding of the conductive wire around the teeth is to make the plate and the teeth separately, wind the conductive wire around each tooth and then fix the teeth to the plate.

[0007] Conventionally, the teeth are fixed to the plate by gluing or by means of additional fixing parts such as screws.

[0008] To improve the attachment of the teeth to the plate, a stator body is known from document WO2017121941. The plate has a plurality of radial grooves, and each tooth has a rib adapted to fit into one of the radial grooves. A slight mounting clearance is provided to allow the ribs to fit into the grooves. In this document, to ensure the permanent attachment of the teeth to the plate, it is proposed, for example, to weld the ribs into the grooves.

[0009] This solution of fixing the teeth by welding has disadvantages.

[0010] In particular, the welding operation causes displacements and deformations of the welded parts, so that the geometry of the resulting stator is never exactly identical to the initially desired shape, which has consequences on the performance of the electric machine and on the vibrations generated by the rotation of the rotor. Presentation of the invention

[0011] In order to remedy the aforementioned drawbacks of the prior art, the present invention proposes to fix the teeth on the stator body plate differently.

[0012] The invention relates to the assembly of a stator body comprising a disc-shaped plate centered on a longitudinal axis and teeth distributed on one face of the plate around the longitudinal axis, the plate comprising at least one opening, at least one of said teeth comprising a projecting relief engaged in said opening. The invention then proposes an assembly method comprising a step of inserting the relief into the opening followed by a step of cold spraying a metallic material onto at least a portion of a junction zone between the relief and the edge of the opening.

[0013] This metallization step makes it possible to firmly fix the relief of the tooth to the edge of the opening of the plate.

[0014] Thanks to the invention, the operation can be carried out "cold," that is, at temperatures much lower than those used for hot welding. This temperature is, for example, below 200°C and on the order of 100°C. In this way, the components of the stator body are not deformed by this assembly operation.

[0015] This operation can also be carried out on any metallic material, and in particular on aluminium, whereas hot welding of aluminium remains a complex and costly operation.

[0016] This operation also requires no fasteners, which represents a reduction in manufacturing costs and weight.

[0017] Finally, this operation is likely to ensure a seal around each opening of the plate. Thus, it is possible to use the plate as part of the motor's outer casing (this casing housing the rotor). Furthermore, it is possible to cool the teeth by circulating a coolant over the projected metallic material, on the side opposite the teeth, without any risk of electrical hazard.

[0018] Other advantageous and non-limiting features of the process according to the invention, taken individually or in all technically possible combinations, are as follows: - the relief includes at least one part in the form of a rib elongated radially with respect to the longitudinal axis and the opening has a radially elongated shape of the same length as the relief; - the metallic material is projected over the entire junction area between the relief and the edge of the opening; - the plateau has several openings in which the reliefs of several teeth are engaged; - the tray has inner and outer peripheral edges; - the metallic material is also projected onto the platform, between the aforementioned area of junction and one of said inner and outer peripheral edges of the tray, so as to form a partition projecting from the tray, two neighboring partitions extending one from the inner peripheral edge to a distance from the outer peripheral edge of the tray, and the other extending from the outer peripheral edge to a distance from the inner peripheral edge; - the tooth having a first face in contact with the plateau, said first face having two opposite sides which extend substantially radially with respect to the longitudinal axis, the relief extends substantially at an equal distance from the two sides; - the tooth having a first face resting against the plateau, said first face having two opposite sides which extend substantially radially with respect to the longitudinal axis, the relief has two parts which run along the two sides; - one of the two parts of the relief of the tooth and the other of the two parts of the relief of the neighboring tooth being engaged in said opening, the metallic material is projected on the entire edge of the opening as well as on the two parts engaged in said opening and between these two parts; - at least part of the edge of the opening is chamfered on the tooth side; - said metallic material is a non-magnetic powder, preferably comprising a mixture of aluminium and alumina; - the opening extends at a distance from the inner and outer peripheral edges of the tray.

[0019] 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

[0020] The following description, with reference 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 implemented.

[0021] On the attached drawings:

[0022] [Fig-1] is a schematic perspective view, viewed from below, of part of a stator conforming to a first embodiment, obtained by means of an assembly process according to the invention;

[0023] [Fig.2] is a schematic exploded perspective view of an angular sector of the body of the stator of [Fig.1], before its assembly;

[0024] [Fig.3] is a schematic perspective view of the sector shown in [Fig.2], after assembly;

[0025] [Fig.4] is a schematic perspective view of the sector shown in [Fig.2], after a sealing disc has been attached to the stator body;

[0026] [Fig.5] is a schematic exploded perspective view of an angular sector of the body of a stator according to a second embodiment, before its assembly;

[0027] [Fig.6] is a schematic perspective view of the sector shown in [Fig.5], after assembly;

[0028] [Fig.7] is a cross-sectional view of the space at the junction between two teeth of the stator body of [Fig.5];

[0029] [Fig.8] is a cross-sectional view of the space at the junction between two teeth of a stator body according to a third embodiment;

[0030] [Fig.9] is a cross-sectional view of the space at the junction between two teeth of a stator body according to a fourth embodiment;

[0031] [Fig. 10] is a cross-sectional view of the space at the junction between two teeth of a stator body according to a fifth embodiment.

[0032] As a preliminary point, it should be noted that identical or similar elements of the different embodiments of the invention shown in the different figures will, as far as possible, be referenced by the same reference signs and will not be described each time.

[0033] In [Fig.1], a body 10 of stator 1 obtained by means of an assembly process according to the invention is shown.

[0034] This stator body 10 is intended to be part of an axial flux electric machine, this machine being in this case a motor for propelling an electric or hybrid vehicle. Such an electric machine comprises at least one rotor and at least one stator. In practice, it more generally comprises a rotor located between two stators.

[0035] The rotor generally comprises an annular body housing a plurality of magnetic pole elements having the same function as permanent magnets. The magnetic pole elements are, for example, made up of small assembled permanent magnets.

[0036] The stators, for their part, have the shape of flattened rings and are equipped, on their faces oriented towards the rotor, with teeth around which coils 2 of electrically conductive wire are wound. When these windings are supplied with electric current, they generate a magnetic field so as to rotate the rotor. The two stators 1 are generally identical, so only one of them will be described here.

[0037] The invention relates more specifically to such a stator 1.

[0038] As shown in [Fig. 1], this stator 1 comprises a body 10 and coils 2 of electrical wires. The body 10 of the stator 1 comprises a support 100 and a plurality of teeth 110.

[0039] Preferably, the support 100 forms part of the outer casing of the electric machine (which houses the rotor). In other words, it is designed so that its outer face forms part of the outer face of this casing.

[0040] This support 100 comprises a disc-shaped plate 101 centered on a longitudinal axis A1. It has a central circular opening. More specifically, the plate 101 has the shape of a flattened ring delimited between an outer peripheral edge 10IB and an inner peripheral edge 101A.

[0041] Here, this plate 101 is bordered externally by an external tubular rim 109, which extends on both sides of the plate 101.

[0042] The plate 101 comprises a first face turned towards the rotor, hereinafter referred to as the upper face, and an opposite lower face.

[0043] It should be noted at this stage that in the remainder of this exposition, the terms “lower” and "Upper" will be used in relation to this rotor, the upper side of an element designating the part of that element which is turned towards the rotor and the lower side designating the part of that element which is turned away from the rotor.

[0044] The upper face of the plate is flat and perpendicular to the longitudinal axis AL

[0045] The thickness of the plate 101, that is to say its dimension along the longitudinal axis Al, is for example between 1 mm and 30 mm. The diameter of the 101 plate is preferably between 10 cm and 50 cm.

[0046] In Figures 2 to 6, for simplicity, only one angular sector of the stator body 10 is shown. Here, all the angular sectors forming the body 10 are identical and each angular sector comprises only one of the teeth 110. Therefore, only one tooth and one angular sector will be described in the following.

[0047] As shown in [Fig.2], the plate comprises a plurality of 102 elongated openings.

[0048] Here, each opening 102 extends at a distance from the peripheral edges of the plate 101. This means here that the openings do not lead to the outside or to the central opening of the plate.

[0049] Here, each opening 102 has a rectangular edge and is elongated along a radial direction A2, perpendicular to the longitudinal axis AL

[0050] The openings 102 are regularly distributed on the plate 101 around the longitudinal axis AL

[0051] In the embodiment shown in [Fig. 2], the edge of the opening is straight, meaning that its four sides extend in planes parallel to the longitudinal axis AL

[0052] In other embodiments, this edge may not be straight but inclined or chamfered. Such embodiments will be described later in this exposition.

[0053] Here, the support 100 is made from a single piece of aluminium, but alternatively it could be made of stainless steel or non-magnetic material.

[0054] The teeth 110 are also regularly distributed on the upper face of the plate 101, around the longitudinal axis Al.

[0055] Each tooth 110 generally has a right prism shape with a trapezoidal cross-section and a narrowing of the cross-section to accommodate a coil 2 of electrical wire. Each tooth 110 here has a radial plane of symmetry.

[0056] As illustrated in [Fig.2], each tooth 110 more precisely comprises a lower part, called base 117, extending opposite the plate 101 and an upper part 118 rising from the base 117 along the longitudinal axis Al.

[0057] The base 117 has a thick trapezoidal shape. It is designed to form, with the bases 117 of the other teeth 110 of the stator 1, a kind of thick ring.

[0058] The upper portion 118 also has a thick trapezoidal shape, but it is thinner than the base 117 because it is designed to support the coil 2 of conductor wire. As shown in [Fig. 2], the apex of the upper portion 118 of each tooth 110 is flared so that the coil 2, once wound around the upper portion 118, is held between this flare and the base 117.

[0059] The base 117 has a lower face 115 which is flat and orthogonal to the longitudinal axis AL. This lower face 115 is intended to apply against the upper face of the plate 101.

[0060] For its assembly on the plate 101, each tooth 110 includes a relief 112 projecting from the lower face 115 of the tooth 110.

[0061] The relief 112 of each tooth 110 is designed to fit into one of the openings 102 of the plate 101. A relief 112 and the opening 102 into which it fits will hereafter be referred to as "associated".

[0062] To cooperate with the opening 102, it is therefore envisaged that the relief 112 will also extend essentially radially. Each relief 112 thus forms a straight rib extending along a radial direction A2.

[0063] In the embodiment shown in figures 1 to 4, each relief 112 has an identical shape, in negative and to the extent of play, to that of the opening 102, so as to fill this opening 102 entirely and not to protrude on the underside of the plate 101.

[0064] Thus, in this embodiment, the relief 112 has a rectangular parallelepiped shape.

[0065] In this way, once engaged in the opening 102, the relief 112 ensures that the tooth is locked in relation to the plateau in all directions of space, except along the longitudinal axis AL

[0066] So, to permanently fix the tooth on the plate, it is then planned to carry out a cold metallization operation by blowing metallic material.

[0067] We can then describe the assembly process of the stator body 10 shown in the figures 1 to 4.

[0068] This process includes a first manufacturing step of the support 100 and the teeth 110. This step being well known to those skilled in the art, it will not be described here. It may only be stated that the teeth can be obtained by means of flat or curved sheets assembled and cut to the desired shape.

[0069] The second step consists of placing an electrical insulator around the upper part 118 of each tooth 110, and then winding the electrical wire so as to form the coils 2 around the teeth 110.

[0070] The third step consists of engaging the relief 112 of each tooth 110 in the associated opening 102 of the plateau 101.

[0071] The insertion of the relief 112 is achieved by a rectilinear translational movement in a direction parallel to the longitudinal axis AL. It ends when the lower face 115 of the tooth 110 comes to rest against the upper face of the plate 101. This final position corresponds to the position that the tooth will present when the electric machine is in operation.

[0072] The fourth step is a cold spray metallization step of a metallic material on at least part of a junction zone between the relief 112 and the edge of the opening 102. This step is carried out on the underside of the plate 101.

[0073] As shown in [Fig.3], this step preferably consists of covering the lower end face of the relief 112 and part of the lower face of the plate 101, all around the edge of the opening 102, with a strip of material 130, by projecting metallic powder onto this area.

[0074] This strip of material 130 preferentially extends over lengths and widths greater than those of the opening 102. Thus, it extends beyond the opening 102 by more than one millimeter at every point of the contour of this opening 102.

[0075] This strip has a thickness preferably between 0.3 and 3 millimeters.

[0076] This strip of material 130, once deposited on the plate 101 and the relief 112 of the tooth 110, makes it possible to create a kind of weld eliminating the only degree of freedom that the tooth 110 still had once installed on the plate 101.

[0077] Cold spray metallization is a technique more commonly known by its English name, "cold spray." It consists of projecting a metal powder at supersonic speed via a pressurized and heated gas. It is carried out using a 900 spraying apparatus.

[0078] The powder used here is preferably non-magnetic.

[0079] It is preferably chosen so as to form a water-impermeable layer. Its porosity is therefore preferably as low as possible, for example less than 1%.

[0080] For this purpose, the powder chosen here is a mixture of at least two materials, one being more ductile to apply well against the plate during the impact, and the other being less ductile so as to have a greater shock effect during the impact, which makes it possible to densify the band of material 130 and to obtain reduced porosity.

[0081] Here, the chosen mixture comprises aluminum powder and alumina powder (less ductile than aluminum).

[0082] The composition comprises a major portion, by volume, of aluminium (for example 80%). It allows a porosity of approximately 0.14% to be obtained.

[0083] This composition is also chosen to obtain a very low thermal resistance between the plate 101 and the teeth 110.

[0084] As shown in [Fig. 4], the final step consists of attaching a sealing plate 140 below the platform 101, so as to define a cooling chamber with it. This cooling chamber is watertight thanks to the material strips 130.

[0085] So, by providing two coolant inlet and outlet openings in this chamber, it is possible to circulate the coolant along the material strips 130 and the plate 101, which allows the teeth 110 and the support 100 to be cooled. These inlet and outlet openings are preferably diametrically opposite with respect to the longitudinal axis Al.

[0086] Preferably, as shown in [Fig.1], the material strips 130 extend in a staggered pattern around the central opening of the support 100, so as to force the coolant to circulate along the entire surface of the plate 101 and to dissipate the heat as homogeneously as possible.

[0087] In this embodiment, the material strips 130 protrude from the underside of the plate 101 to a height such that they come into contact with the sealing plate 140. They therefore form a kind of partition preventing the coolant from flowing directly from the inlet opening to the outlet opening.

[0088] Furthermore, in this embodiment, one band of material 130 out of two extends along the relief 112 and continues to the inner peripheral edge 101A of the plateau, while the other bands of material 130 (which are respectively intercalated between the aforementioned bands of material) each extend along one of the reliefs 112 and continue to the outer peripheral edge 101B of the plateau.

[0089] In this way, as shown by arrow Fl on [Fig.1], the coolant is forced to take a zig-zag path, which ensures homogeneous cooling of the support 100 and the teeth 110.

[0090] It should be noted here that the assembly method for the stator body 10 is advantageous in that it does not deform the components of the electrical machine, and it ensures a good assembly accuracy and that it is easily reproducible for manufacturing the electrical machine on an assembly line.

[0091] Figures 5 to 7 show a second embodiment of the body 10 of stator 1.

[0092] In this embodiment, the support 100 differs from that shown in the previous figures only by the shape of the openings 1021.

[0093] Indeed, the edges of these openings 1021 are, unlike the edges of the openings 102 described previously, not straight but partly chamfered.

[0094] More specifically, each opening 1021 has a rectangular edge which is chamfered at 45° along its two long sides, on the side of the tooth 110. This chamfer extends here over about half the thickness of the plate 101.

[0095] For their part, the teeth 110 differ from those described previously only in the shape and position of their reliefs 1121.

[0096] Indeed, in the embodiment described with reference to figures 1 to 4, the relief 112 is presented in the form of a single rib extending halfway between the radial edges 115A, 115B of the lower face 115 of the tooth 110.

[0097] On the contrary, in the embodiment described with reference to figures 5 to 7, the relief 1121 comprises two distinct parts in the form of two ribs 1121A, 1121B which run along respectively the radial edges 115A, 115B of the lower face 115 of the tooth 110, over the entire length of this lower face 115.

[0098] Each rib 1121A, 1121B has a rectangular parallelepiped shape, flanked on the inner side by a fillet inclined at 45°. This shape allows it to engage and fill half of an opening 1021.

[0099] As shown in [Fig.7], when the teeth 110 are brought onto the plate 101, two ribs 1121A, 1121B of two neighboring teeth 110 then engage in the same opening 1021, so as to fill it entirely.

[0100] It should be noted here that the notion of filling amounts, for one (or more) rib(s), to occupying the entire volume delimited by the opening which receives it (or them), except for the clearance.

[0101] A game is indeed provided to allow the ribs to be engaged without difficulty in the openings of the board.

[0102] This clearance is found between each rib 1121A, 1121B and the edge of the opening 1021, as well as between the two ribs 1121A, 1121B engaged in the opening 1021. Clearance is provided in the width and length of the opening. This cumulative clearance is preferably 40 µm, but a larger value may be used to facilitate assembly. However, this value must not be too high to ensure proper attachment of the teeth to the plate. This value is therefore preferably less than 200 µm, and it is even preferable that it not exceed 100 µm.

[0103] Therefore, to ensure the desired seal at each opening 1021, the A strip of material 130 is provided to extend beyond this opening on both sides, so as to simultaneously cover the two ribs 1121 A, 1121 B that are engaged therein.

[0104] The present invention is in no way limited to the embodiments described and illustrated, but those skilled in the art will be able to make any variation in accordance with the invention.

[0105] Thus, on [Fig.8], a third embodiment of the stator body is shown, which differs from that shown on [Fig.7] by the shape of the openings 1022 made in the plate 101 and by the shape of the ribs 1122A, 1122B carried by the tooth 110.

[0106] In this third mode, the plate is strictly identical to that shown in figures 1 to 4. The openings 1022 thus have straight edges.

[0107] The teeth 110 differ from those shown in [Fig.7] only by the shape of their ribs 1122A, 1122B, which here have rectangular parallelepiped shapes without fillets.

[0108] With reference to this figure, we can introduce the concept of "surface distance a", which corresponds to the smallest distance between the coil 2 and the conductive part of the tooth 110, measured along the surface of the insulator 150. It should be noted that this distance must be large enough to avoid current leakage.

[0109] In [Fig.9], a fourth embodiment of the stator body is shown, which differs essentially from that shown in [Fig.7] by the shape of the opening 1023 made in the plate 101.

[0110] Indeed, in this mode, the opening is chamfered not only on the upper face of the plate 101, but also on its lower face. This chamfer on the lower face has an angle of approximately 20° (with respect to this face).

[0111] Preferably, the apexes of the ribs 1123A, 1123B are also chamfered, at an equivalent angle.

[0112] Thus, the junction between each rib 1123A, 1123B and the edge of the opening 1023 forms a re-entrant bevel in which material can be deposited in order to ensure better attachment of the teeth 110 to the plate 101.

[0113] In [Fig. 10], a fifth embodiment of the stator body is shown, which differs essentially from that shown in [Fig. 7] by the shape of the opening 1024 made in the plate 101 and by that of the ribs 1124A, 1124B which are engaged in it.

[0114] Indeed, in this mode, the edge of the opening 1024 is chamfered along its entire height, at an angle of approximately 70° (relative to the underside of the plate). The ribs 1124A, 1124B then have complementary shapes (their cross-sections have right trapezoidal shapes).

[0115] In this embodiment, as in the second one illustrated in [Fig. 7], one can note that the upper face of the base 117 of the tooth 110 has, along its radial edges, a chamfer 119. This chamfer 119 allows to receive a part of the thicker insulator 150, shaped to fit into a corresponding part of the insulator of the neighboring tooth.

[0116] This configuration then makes it possible to maximize the aforementioned surface distance a compared to the embodiments shown in Figures 8 and 9.

[0117] According to other variants of the invention, it would have been possible to extend the material strips 130 on the plate 101 so as to force the coolant to circulate around the reliefs or even on the reliefs. It would also have been possible to use a material for projecting aluminum powder only, or alumina powder only. Other materials could also have been used.

Claims

Demands

1. Method of assembling a stator body (10) for an electric machine, the body (10) comprising a disc-shaped plate (101) centered on a longitudinal axis (Al) and teeth (110) distributed on one face of the plate (101) around the longitudinal axis (Al), the plate (101) comprising at least one opening (102), at least one of said teeth (110) comprising a protruding relief (112) engaged in said opening (102), said method includes a step of inserting the relief (112) into the opening (102), characterized in that said method comprises, after the insertion step, a cold spray metallization step of a metallic material on at least part of a junction zone between the relief (112) and the edge of the opening (102).

2. Assembly method according to the preceding claim, wherein the relief (112) has at least one part in the form of a rib elongated radially with respect to the longitudinal axis (Al) and the opening (102) has a radially elongated shape of the same length as the relief (112).

3. Assembly method according to any one of the preceding claims, wherein the metallic material is projected over the entire junction area between the relief (112) and the edge of the opening (102).

4. Assembly method according to claim 3, wherein: - the plate (101) having several openings (102) in which the reliefs (112) of several teeth (110) are engaged, - the plate (101) having inner (101A) and outer (101B) peripheral edges, - the metallic material is also projected between said junction zone and one of the inner (101A) and outer (101B) peripheral edges of the plate (101) so as to form a partition (130) projecting on one face of the plate (101), two adjacent partitions (130) extending one from the inner peripheral edge (101A) to a distance from the outer peripheral edge (101B) of the plate (101), and the other extending from the outer peripheral edge (101B) to a distance from the inner peripheral edge (101A) of the plate (101).

5. An assembly method according to any one of claims 1 to 4, wherein the tooth (110) has a first face (115) bearing against the plateau (101), said first face (115) having two opposite sides (115A, 115B) which extend substantially radially with respect to the longitudinal axis (Al), the relief (112) extends substantially at an equal distance from the two sides (115A, 115B).

6. Assembly method according to any one of claims 1 to 4, wherein the tooth (110) having a first face (115) bearing against the plate (101), said first face (115) having two opposite sides (115A, 115B) which extend substantially radially with respect to the longitudinal axis (Al), the relief (112) has two parts (1121A, 1121B) which run along the two sides (115A, 115B).

7. Assembly method according to the preceding claim, wherein one of the two parts (1121A, 1121B) of the relief (112) of the tooth (110) and the other of the two parts (1121B, 1121A) of the relief (112) of the adjacent tooth (110) being engaged in said opening (1021), the metallic material is projected onto the entire edge of the opening (1021) as well as onto the two parts (1121A, 1121B) engaged in said opening and between these two parts (1121A, 1121B).

8. Assembly method according to any one of the preceding claims, wherein at least a portion of the edge of the opening (102) is chamfered on the side of the tooth (110).

9. Assembly method according to any one of the preceding claims, wherein said metallic material is a non-magnetic powder, preferably comprising a mixture of aluminium and alumina.

10. Assembly method according to any one of the preceding claims, wherein the tray (101) has inner (101A) and outer (101B) peripheral edges, and the opening (102) extends at a distance from the inner (101A) and outer (101B) peripheral edges.

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