Stator for axial flux machine and method for manufacturing such a stator

Abstract

The invention relates to a method for manufacturing a stator (1) for an axial flux electric machine, said stator comprising a stator body (2), a plurality of teeth (5) and at least one coil (9) formed of an electrically conductive wire, each tooth being formed of a first part (52) and a second part (54), the method comprising the steps of: - obtaining a support part (7) in which the teeth are each positioned in a precise posture, - forming a sheath (30) of electrically insulating material intended to surround the second part of each tooth, - winding the electrically conductive wire around said sheath, and - fixing one end of the second part of each tooth to a face of the stator body. Figure for the abstract: Fig. 7

Description

Title of the invention: Stator for axial flux machine and method for manufacturing such a stator Technical field of the invention

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

[0002] It relates more particularly to a method of manufacturing a stator for an axial flux electric machine.

[0003] The invention also relates to a stator obtained by such a manufacturing process as well as to an engine and a motor vehicle comprising such a stator. State of the art

[0004] A conventional stator of an axial flux electric machine comprises a body with a generally annular base and teeth distributed circumferentially on one of the end faces of the base. A stator also includes coils of conducting wire arranged around the teeth. Under the influence of electric currents, the coils generate magnetic fields that allow the stator to set the rotor in motion.

[0005] Conventionally, the stator body is made by winding a metal sheet around a longitudinal axis. This metal sheet winding limits the eddy currents flowing through the stator when it is in operation and, consequently, reduces energy losses due to heating.

[0006] Following the manufacture of the stator body in this manner, three methods for making the windings of conductive wire around the teeth are known in order to form the stator coils.

[0007] According to a first method, the teeth have a generally parallelepiped shape that facilitates winding the conducting wire around each tooth. This configuration facilitates the industrial manufacture of the stator, since the space between the teeth is large enough to wind the conducting wire without difficulty. However, the use of such a tooth shape implies a degradation of the electrical properties of the electric machine.

[0008] According to a second manufacturing method, the teeth are widened at their free ends, which improves the circulation of magnetic fields. In this configuration, the conducting wire forming the coil must be inserted between the teeth, in a very narrow slot. This step is not easy to implement in an industrial process.

[0009] The third known method aims to improve upon this second method. To this end, After the metal sheet forming the stator body and teeth is wound, the teeth are cut from the stator body. Coils are then individually wound around each tooth. Finally, the teeth are reattached to the stator body. Alternatively, the teeth can each be made separately by stacking cut magnetic sheets, winding them, and then assembling them onto a stator body.

[0010] However, such a method is not easy to implement industrially, particularly because the positioning of the teeth on the stator body must be precise to guarantee the magnetic properties of the assembly. Furthermore, such a configuration alters the rigidity and mechanical strength of the stator. Presentation of the invention

[0011] The present invention proposes to improve the method of manufacturing the stator in order to form a robust stator in which the teeth are arranged in such a way as to optimize the magnetic and electrical properties of the stator.

[0012] More particularly, the invention proposes a method for manufacturing a stator for an axial flux electric machine, said stator comprising a stator body, a plurality of teeth and at least one coil formed of an electrically conductive wire, each tooth being formed of a first upper part and a second lower part, the method comprising the steps of: - obtaining a support section in which teeth are positioned, each in a precise posture, - formation of an envelope made of electrically insulating material intended to surround the second part of each tooth, - winding the electrically conductive wire around said sheath, and - fixing one end of the second part of each tooth to one face of the stator body.

[0013] Thus, thanks to the invention, a support element is formed to precisely position the teeth in orientation and spatial position. The assembly formed by the support element, the teeth, and the coils of electrically conductive wire is then fixed to the stator body, thereby allowing precise alignment of the teeth. This arrangement then optimizes the magnetic and electrical properties of the stator.

[0014] Moreover, since the support part and the teeth are assembled and then fixed onto the stator body as a single unit, this ensures the mechanical strength of the resulting stator.

[0015] Other advantageous and non-limiting features of the manufacturing process of a stator according to the invention, taken individually or in all technically possible combinations, are as follows: - it is also planned, prior to the formation of the support part, a step of positioning the teeth in pre-formed notches of a mold for manufacturing the support part; - it is also planned, prior to the winding of the electrically conductive wire around said envelope, a step of extracting the teeth from the mold; - the support part and said envelope are formed in one piece by molding; - the support part having a plurality of openings, a step is provided for placing each tooth in a corresponding opening of the support part, each opening being shaped to receive each tooth in said precise posture; - each tooth is fixed by gluing to the support part; - the support part and said casing are made of polymer material; and - the end of the second part of each tooth is fixed to the face of the stator body by gluing.

[0016] The invention also relates to a stator obtained by the manufacturing process described above.

[0017] The invention also relates to a stator housing comprising a stator as defined above and a base receiving the stator, said base comprising a bottom wall and side walls so as to form a cooling chamber. A polymer material is, for example, overmolded around the stator in the cooling chamber.

[0018] The invention further relates to an engine comprising a rotor and a stator as defined above, as well as to a motor vehicle comprising such an engine.

[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] represents a schematic front perspective view of a stator conforming to the invention;

[0023] [Fig.2] represents a schematic rear perspective view of the stator of [Fig.1];

[0024] [Fig.3] represents, in the form of a logic diagram, a first example of a method for manufacturing a stator according to the invention,

[0025] [Fig.4] schematically represents a cross-sectional view of the product obtained during step E2 of a first example of the stator manufacturing process,

[0026] [Fig.5] schematically represents a cross-sectional view of the product obtained during step E4 of the first example of the stator manufacturing process,

[0027] [Fig.6] schematically represents a cross-sectional view of the product obtained during step E8 of the first example of the stator manufacturing process,

[0028] [Fig.7] schematically represents a cross-sectional view of the product obtained during step E10 of the first example of the stator manufacturing process,

[0029] [Fig.8] represents, in the form of a flowchart, a second example of a method for manufacturing a stator according to the invention,

[0030] [Fig.9] schematically represents a cross-sectional view of the product obtained during step E22 of a second example of the stator manufacturing process,

[0031] [Fig. 10] schematically represents a cross-sectional view of the product obtained during step E24 of the second example of the stator manufacturing process,

[0032] [Fig. 11] schematically represents a cross-sectional view of the product obtained during step E26 of the second example of the stator manufacturing process,

[0033] [Fig. 12] schematically represents a cross-sectional view of the product obtained during step E28 of the second example of the stator manufacturing process,

[0034] [Fig. 13] schematically represents a motor vehicle equipped with an engine comprising a stator according to the invention,

[0035] [Fig. 14] represents a schematic perspective view of a first example of cooperation between a tooth and the upper face of a stator body,

[0036] [Fig. 15] represents a schematic perspective view of a second example of cooperation between a tooth and the upper face of the stator body, and

[0037] [Fig. 16] schematically represents a cross-sectional view of a stator housing comprising a stator according to the invention.

[0038] 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 symbols and will not be described each time.

[0039] In the following description, the terms "conductor" and "insulator" will be used to define the electrical or dielectric properties of electrically conductive and electrically insulating materials respectively.

[0040] Figures 1 and 2 schematically represent, respectively in front view and rear view, a stator 1 for an axial flux electric machine.

[0041] The stator 1 comprises a stator body 2, a plurality of teeth 5, a support portion 7 of the plurality of teeth 2 and at least one coil 9 formed of an electrically conductive wire (not visible in Figures 1 and 2).

[0042] As shown in Figures 1 and 2, the body 2 of stator 1 has a shape of a flattened ring, of height less than its diameter. The body 2 of stator 1 has a flat upper face 22, a flat lower face 24, an external peripheral face 25 and an internal peripheral face, both cylindrical of revolution.

[0043] The body 2 of the stator 1 is made of magnetic material. For example, it is made by stacking steel sheets with a thickness of half a millimeter or less. These sheets are curved and spirally wound around an axis L orthogonal to the plane of the upper face 22 and lower face 24. They extend over the entire height of the body 2 of the stator 1. Thus, the losses in the stator due to eddy currents are limited.

[0044] The stator 1 also includes the plurality of teeth 5. This plurality of teeth 5 is regularly distributed over the upper face 22 of the stator body 2 all around the axis L (Figures 1 and 2). As can be seen in [Fig. 1], each tooth 5 generally has the shape of a right prism with a trapezoidal cross-section (in a plane parallel to the upper face 22 of the stator body 2). The lateral faces of adjacent teeth 5 are parallel to each other.

[0045] Each tooth 5 here has a first part 52, or distal part 52 hereafter, and a second part 54, or proximal part 54 hereafter ([Fig. 4]). As shown, for example, in [Fig. 7], the proximal part 54 of each tooth 5 is attached to the upper face 22 of the stator body 1. In practice, each end of the proximal part 54 of each tooth 5 is fixed by bonding to the upper face 22 of the stator body 1.

[0046] Alternatively, as shown in Figures 14 and 15, the cooperation between the proximal part 54 of each tooth 5 and the upper face 22 of the stator body 2 1 can also be achieved by fitting each tooth 5 onto the upper face 22 of the stator body 2 1. More specifically, the end of the proximal part 54 of each tooth 5 has a shape complementary to a part of the upper face 22 of the stator body 2 1.

[0047] For example, in the case of [Fig. 14], the end of the proximal portion 54 of each tooth 5 has a projecting portion 540 intended to cooperate, for example by interlocking, with a groove 542 formed on the upper face 22 of the stator body 1, and having a shape complementary to the projecting portion 540. This groove may have a V-shaped dihedral cross-section ([Fig. 15]) or a U-shaped cross-section with a V-shaped bottom ([Fig. 14]). This shape has the advantage of improving the passage of magnetic flux between the base of the tooth and the portion of the yoke located between two teeth, particularly when the tooth is made of sheet metal with axially magnetically oriented grains and when the yoke is made of sheet metal with angularly magnetically oriented grains, as for example in document WO2020 / 078667.

[0048] Alternatively, the cooperation between the proximal part 54 of each tooth 5 and the upper face 22 of the stator body 2 1 can be achieved by a combination of gluing and fitting each tooth 5 onto the upper face 22 of the stator body 2 1 previously described.

[0049] Furthermore, the distal portion 52 of each tooth 5 has, at least on one side, a projecting rib 55. Here, two projecting ribs 55 are formed on either side of each tooth 5, extending from the end of the distal portion 52 of each tooth 5. As can be seen in [Fig. 1], the projecting rib 55 of one tooth 5 is opposite the projecting rib 55 of the adjacent tooth 5. These projecting ribs 55 are particularly advantageous because they reduce the available space between the teeth 5, thereby decreasing magnetic field variations at the stator 1 and reducing associated power losses. This also reduces the magnetic resistance of the air gap between the stator 1 and an associated rotor.

[0050] Advantageously, the teeth 5 are positioned in a support portion 7. This support portion 7 also has a flattened ring shape (Figures 1 and 2). The support portion 7 is shaped to support each tooth 5 in a precise posture, at least at the time of assembly of these teeth 5 onto the stator body 2 1.

[0051] In this description, "precise posture" means the positioning of each tooth 5 relative to the other teeth in a predefined, stable spatial position and according to a predetermined orientation. The use of this support portion 7 thus allows for a precise arrangement of the teeth 5 relative to each other on the stator body 2 1. This ensures the magnetic properties of the entire stator 1 by limiting losses due to misalignment and incorrect positioning of the teeth 5 relative to each other.

[0052] The support part 7 is preferably made of an electrically insulating material. For example, it is molded from a polymer material.

[0053] As shown for example in Figures 6 and 7, each tooth 5 is intended to be surrounded by a casing 30 formed from an electrically insulating material. For example, this casing is molded from a polymer material.

[0054] According to a first embodiment of the invention (figures 3 to 7), the support part 7 and the envelope 30 are formed in one piece by molding.

[0055] According to a second embodiment (figures 8 to 12), the support part 7 and the envelope 30 are formed in two separate pieces.

[0056] As can be seen for example in [Fig.6], each envelope 30 is intended to surround the proximal part 54 of the tooth 5 concerned.

[0057] The stator 1 finally comprises coils 9 formed of electrically conductive wires. As shown in Figures 7, 11 and 12, an electrically conductive wire is wound around each sheath 30 formed around the teeth 5 so as to form the coils 9. The electrically conductive wire is for example a copper wire. The coils are in practice electrically connected to an electrical connection unit 90 ([Fig. 16]).

[0058] The stator 1 according to the invention is intended to be used in an engine 110 (also comprising a rotor) of a motor vehicle 100 ([Fig. 13]).

[0059] Fig. 16 represents an example of a stator housing 200 into which the stator 1 is introduced. The stator housing 200 includes a base 202 receiving the stator 1. This base 202 has a bottom wall 204 and two side walls 205, 206 extending from the bottom wall 204.

[0060] The lower face of the stator body 2 is fixed to the bottom wall 204 of the stator housing 200, for example by gluing.

[0061] The support portion 7 is positioned in the base 202 so as to form a closed internal chamber 80. In other words, the walls of the internal chamber 80 are formed by the bottom wall 204 of the base 202, by the side walls 205, 206 of the base 202, and the support portion 7 of the stator 1. Sealing gaskets (not visible in the figures) positioned between the support portion 7 and the side walls 205, 206 of the base 202 ensure the sealing of the internal chamber 80.

[0062] Thus, once the stator 1 is fixed to the bottom wall 204 of the stator housing 200, the internal chamber 80 can advantageously form a cooling chamber. For this purpose, as shown in [Fig. 16], the base 202 includes inlet 220 and outlet 225 openings allowing the circulation of a coolant. This coolant is, for example, a dielectric coolant such as oil. Advantageously, the coolant can then circulate between the coils 9 surrounding the teeth 5, thus allowing the stator 1 to be cooled without requiring complex channel systems in the body of each tooth.

[0063] The stator housing 200 also includes a bottom element 230 positioned opposite the bottom wall 204 of the base 202, on the outside of the base 202. This bottom element 230 thus forms a closed external chamber 85. Sealing gaskets (not visible in the figures) positioned between the bottom element 230 and the bottom wall 204 of the base 202 ensure the sealing of the external chamber 85.

[0064] Advantageously, the external chamber 85 can form another cooling chamber for the stator housing 200. For this purpose, supply and discharge openings (not shown) for a coolant are provided between the bottom element 230 and the bottom wall 204 of the base 202. The coolant is here water or oil.

[0065] Finally, the cooling of the stator housing 200 can be achieved in several ways. ways thanks to the arrangements introduced: - cooling by circulating a liquid inside the internal chamber 80, or - cooling by circulating a liquid inside the external chamber 85, or - cooling by circulating one liquid inside the inner chamber 80 and another liquid inside the outer chamber 85.

[0066] As an alternative to using circulating liquid, the internal chamber 80 can be filled with a polymer material to provide cooling. The polymer material is, for example, overmolded around the stator (1) in the internal chamber 80 formed in the stator housing 200.

[0067] Fig. 3 represents, in the form of a logic diagram, a first example of a manufacturing process for stator 1.

[0068] Prior to the implementation of this method, it is assumed that the teeth 5 and the body 2 of stator 1 have been formed elsewhere (the manufacture of these elements is not considered to constitute the core of the invention and is therefore not described in detail below).

[0069] As shown in [Fig.3], the process begins at step E2. During this step, the teeth 5 are positioned in pre-formed notches 75 of a mold 70 for manufacturing the support part 7 ([Fig.4]).

[0070] As shown in [Fig. 4], only the proximal portion 54 of each tooth 5 is here transferred into the corresponding notch 75. Here, each notch 75 has dimensions slightly larger than those of the proximal portion 54 of the tooth 5 concerned, thus forming a small gap between the lateral faces of each tooth 5 and the lateral walls of the notch 75 concerned.

[0071] The manufacturing process continues in step E4. During this step, the support part 7 and the casing 30 are formed. In this first example, they are formed as a single piece by molding. In practice, the polymer material is poured into the manufacturing mold 70.

[0072] As shown in [Fig.5], the polymer material is introduced between the lateral faces of the teeth 5 and the lateral walls of the notches 75, thus forming the envelope 30 around the proximal part 54 of each tooth 5. Here, the polymer material does not completely cover the proximal part 54 of each tooth 5.

[0073] In other words, the insulating envelope 30 has openings 32. These openings 32 are for example from the positioning means which hold the teeth 5 in position during the manufacturing process (for example during the introduction of the polymer material).

[0074] As also shown in [Fig. 5], the polymer material extending between each of the distal parts 52 of each tooth 5 forms the support part 7. The part of support 7 then takes the form of a plate connecting together the protruding ribs 55 of the teeth 5.

[0075] Finally, at the end of step E4, we obtain the support part 7 in which the teeth 5 are each positioned in a precise posture and the envelope 30, formed of electrically insulating material and surrounding each proximal part 54 of each tooth 5.

[0076] During step E6, the assembly formed by the support part 7, the teeth 5 and the casing 30 is extracted from the manufacturing mold 70.

[0077] The process then continues in step E8 ([Fig.6]), during which the electrically conductive wire is wound around each sheath 30 formed in step E4 so as to obtain the coils 9. In practice, the electrically conductive wire is wound, for example in one piece, around the sheath 30.

[0078] The process concludes with step E10, in which the assembly formed by the support portion 7, the teeth 5, the casing 30, and the coils 9 is fixed to the stator body 1 2. More specifically, each free end of the proximal portions 54 of each tooth 5 is attached to the upper face 22 of the stator body 1 2. The attachment is achieved here by bonding. Alternatively, as described previously and shown in Figures 14 and 15, the attachment can be achieved by fitting the proximal portion 54 of each tooth 5 onto the upper face 22 of the stator body 1 2 or by any other suitable method.

[0079] At the end of step E10, the stator 1 is assembled and formed ([Fig.7]).

[0080] Fig. 8 represents, in the form of a logic diagram, a second example of a manufacturing process for stator 1.

[0081] Here again, prior to the implementation of this process, it is assumed that the teeth 5 and the body 2 of stator 1 have been formed elsewhere.

[0082] As shown in [Fig. 8], the process begins at step E20 of obtaining the support portion 7. According to this second embodiment, the support plate 7 is produced independently of the teeth 5. For example, it is formed by molding in polymer material from another manufacturing mold (not shown). This other manufacturing mold allows, in particular, the formation of openings 17 ([Fig. 9]), each intended to receive a tooth 5. The resulting support portion 7 therefore comprises as many openings 17 as there are teeth 5. These openings 17 are shaped to allow the positioning of each of the teeth 5 in a precise posture as defined previously. In particular, as shown in [Fig. 9], the opening 17 has a shape complementary to the distal portion 52 of the tooth 5, thus enabling it to support this distal portion 52.

[0083] The process then continues in step E22. During this step, each tooth 5 is placed in the corresponding opening 17 of the support part 7 ([Fig.9]). More specifically, the edges of each opening 17 are intended to cooperate with the distal part 52 of each tooth 5, and in particular with the projecting ribs 55 of each tooth 5.

[0084] In practice, each tooth 5 (via its distal part 52) ​​is fixed by bonding to the edges of the corresponding opening 17 of the support part 7. Alternatively, this fixing can be achieved by interlocking or any other suitable means of cooperation.

[0085] In parallel with the placement of the teeth 5 on the support part 7, the manufacturing process includes the step E24 during which the envelope 30 is formed from electrically insulating material.

[0086] According to this second embodiment, the casing 30 is formed separately from the support portion 7. The casing 30 is, for example, formed by means of a specific manufacturing mold (not shown) by molding in polymer material. The casing 30 is also shaped here to surround the proximal portion 54 of each tooth 5.

[0087] As in the first embodiment described above, the envelope 30 may (or may not) have openings 32 in its lateral parts.

[0088] Once the envelope 30 is formed, the electrically conductive wire is wound around it to form the coil 9 ([Fig. 10]).

[0089] Finally, at the end of steps E22 and E24, on the one hand, the part of the support 7 is formed in which the teeth 5 are positioned in a precise posture and, on the other hand, the sheath 30 (made of electrically insulating material) wrapped with the electrically conductive wire is formed.

[0090] Step E26 then allows the positioning of the envelope 30 equipped with the electrically conductive wire on the proximal part 54 of each tooth 5 ([Fig.1 1]).

[0091] In practice, the assembly of the envelope 30 equipped with the electrically conductive wire on the proximal part 54 of each tooth 5 is for example carried out by snapping or by gluing.

[0092] The process finally ends with step E28 (similar to step E10 described previously). During this step, the assembly formed by the support part 7, the teeth 5, the casing 30 and the coils 9 is fixed onto the stator body 2 1.

[0093] At the end of step E28, the stator 1 is assembled and formed (part of which is shown in [Fig. 12]).

[0094] Alternatively, it could have been envisaged that the envelope would simply be formed of a sheet of insulating paper.

[0095] Finalization steps, such as varnishing the assembly formed by the different elements of the stator, may be planned following the manufacturing process of the stator 1.

[0096] Once the stator 1 is obtained (by the first or second example of the process of fa (brication), the stator housing 200 can also be formed by fixing the stator 1 obtained in the bottom wall 204 of the base 202. This fixing is carried out for example by gluing.

[0097] Alternatively, the steps of each of the two examples of the process can be carried out directly in parallel with the positioning in the base 202 of the stator housing 200.

Claims

Demands

1. A method for manufacturing a stator (1) for an axial flux electric machine, said stator (1) comprising a stator body (2) (1), a plurality of teeth (5) and at least one coil (9) formed of an electrically conductive wire, each tooth (5) being formed of a first part (52) and a second part (54), the method comprising the steps of: - obtaining a support part (7) in which the teeth (5) are positioned, each in a precise posture, the first part (52) of each tooth (5) having projecting ribs (55) and the support part (7) holding each tooth (5) at the level of said projecting ribs (55), - forming a casing (30) of electrically insulating material intended to surround the second part (54) of each tooth (5), - winding the electrically conductive wire around said casing (30),and - fixing one end of the second part (54) of each tooth (5) onto a face (22) of the stator body (2) (1).

2. Method according to claim 1, also comprising steps of: - prior to the formation of the support part (7), positioning the teeth (5) in pre-formed notches (75) of a mold (70) for manufacturing the support part (7), and - prior to winding the electrically conductive wire around said sheath (30), extracting the teeth (5) from the mold.

3. Method according to claim 2, wherein the support part (7) and said envelope (30) are formed in one piece by molding.

4. Method according to claim 1, wherein, the support part (7) having a plurality of openings (17), a step is provided for placing each tooth (5) in a corresponding opening (17) of the support part (7), each opening (17) being shaped to receive each tooth (5) in said precise posture.

5. Method according to claim 4, wherein each tooth (5) is fixed by gluing to the support part (7).

6. A method according to any one of claims 1 to 5, wherein the support part (7) and said envelope (30) are formed of polymer material.

7. A method according to any one of claims 1 to 6, wherein the end of the second part (54) of each tooth (5) is fixed to

8.

9.

10.

11.

12. face (22) of the body (2) of stator (1) is made by gluing. Stator (1) for axial flux electric machine obtained by a manufacturing process according to claims 1 to 7. stator housing (200) comprising a stator (1) according to claim 8 and a base (202) receiving the stator (1), said base (202) comprising a bottom wall (204) and side walls (205, 206) so as to form a cooling chamber (80). stator housing (200) according to claim 9, wherein a polymer material is overmolded around the stator (1) in the cooling chamber (80). Motor (110) comprising a rotor and a stator (1) according to claim 8. Motor vehicle (100) comprising an engine (110) according to claim 9.

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