Stator including a cooling channel for an electric machine.

Abstract

Stator comprising a cooling channel for an electrical machine. The invention relates to a stator (10) for an axial flux electrical machine comprising teeth (11), an electrical wire (12) encircling each tooth (11) several times to form a coil (13) around each tooth (11), an electrical connection means (14) for supplying power to the electrical wire (12), the stator (10) comprising an annular portion (20) having a principal axis (A20) coinciding or substantially coinciding with the axis of revolution (A10) of the stator (10), the annular portion (20) comprising the electrical connection means (14) and at least one cooling channel (30) for the stator (10). Figure for the abstract: Fig. 3

Description

Title of the invention: Stator comprising a cooling channel for an electrical machine.

[0001] The invention relates to a stator for an axial flux electric machine, the stator comprising an annular portion including an electrical connection means and at least one stator cooling channel. The invention further relates to an electric machine comprising such a stator. The invention further relates to a vehicle comprising such a stator or such an electric machine.

[0002] An axial flux electric machine generally comprises a stator, i.e., a fixed element, and at least one rotor, i.e., a movable element near the stator. Such a stator comprises teeth extending radially or generally radially. A metal wire is wound around each tooth so as to form a coil at each tooth. Generally, a single wire constitutes a winding extending around each tooth to form such coils. Such an electric wire carries an electric current having a high voltage and / or a high current. Such a voltage is, for example, on the order of 800 volts and such a current is, for example, on the order of 250 amperes.

[0003] Since such an electrical wire carries such a current, and consequently the coils that the electrical wire forms at each tooth, the wire and the wound teeth therefore heat up considerably. In order to maximize the performance and reliability of such an electrical machine, it is necessary to cool these heated elements.

[0004] However, such teeth, including the winding, are generally coated with a resin to ensure its electrical insulation, particularly with respect to a housing containing the rotor and stator. Such a resin also thermally insulates the winding, thus limiting heat dissipation by convection.

[0005] The objective of the present invention is to provide a stator that overcomes the above drawbacks. Furthermore, the solution improves the reliability of an electrical machine incorporating such a stator. Summary of the invention

[0006] To achieve this objective, the invention relates to a stator for an axial flux electric machine comprising: - teeth, in particular teeth extending radially with respect to an axis of revolution or substantially of revolution of the stator so as to form an overall star shape, - an electrical wire wrapped several times around each tooth to form a coil around each tooth, - an electrical connection means for supplying electrical power to the electric wire, the stator comprising an annular part having a principal axis coincident or substantially coincident with the axis of revolution of the stator, the annular part comprising the electrical connection means and at least one cooling channel for the stator.

[0007] The annular part can extend at the level of an inner radius of the stator or at the level of an outer radius of the stator.

[0008] At least one cooling channel can be provided within the annular part by forming a helical coil having an axis coincident or substantially coincident with the main axis of the annular part.

[0009] At least one cooling channel can be obtained by molding simultaneously with obtaining the annular part, in particular by molding a plastic material.

[0010] The annular part can be at least partially overmolded on at least one cooling channel, in particular overmolded with a plastic material.

[0011] At least one cooling channel can be arranged near each coil of electric wire, in particular at a distance of between 0 mm and 5 mm.

[0012] The stator may include an insulator, in particular resin, the insulator being able to encase at least each coil of electrical wire.

[0013] The annular part can be fixed to the insulation, in particular by clipping onto and / or against the insulation, in particular inside a cylindrical envelope having as its radius the inner radius of the stator or outside a cylindrical envelope having as its radius the outer radius of the stator.

[0014] At least one cooling channel may be traversed by a heat transfer fluid, in particular oil.

[0015] The invention further relates to an electric machine, in particular an electric motor for a vehicle, in particular for a motor vehicle, comprising a rotor having an axis of rotation, the electric machine comprising at least one stator as defined above, in particular a stator on either side of the rotor, the axis of at least one stator being coincident or substantially coincident with the axis of rotation of the rotor.

[0016] The invention further relates to a vehicle, in particular a motor vehicle, comprising an electrical machine as defined above or a stator as defined above. Presentation of the figures

[0017] These objects, features and advantages of the present invention will be described in detail in the following non-limiting description of the embodiment in relation to the accompanying figures, among which:

[0018] Fig. 1 is a schematic view of a vehicle according to one embodiment of the invention.

[0019] The [Fig.2] is a partial schematic perspective view of an electrical machine according to an embodiment of the invention.

[0020] Figure 3 is a schematic partial cross-sectional view of a stator along a plane passing through the axis of revolution of the stator according to an embodiment of the invention. Detailed description

[0021] As illustrated in [Fig. 1], a vehicle 1, preferably a motor vehicle, comprises at least one electric machine 2. The electric machine 2 is advantageously an electric motor. The vehicle 1 comprises, for example, a hybrid propulsion and / or traction means, i.e., equipped with at least one internal combustion engine (not shown) and at least one electric motor 2. Alternatively, the vehicle 1 comprises, for example, an electric propulsion and / or traction means comprising at least one electric motor 2. Thus, preferably, the electric machine 2 is a traction and / or propulsion motor for the vehicle. Preferably, the vehicle 1 comprises a battery 4 for storing electrical energy. The vehicle 1, or the electric machine 2, comprises at least one stator 10. Note that the electric machine 2 is axial flux.

[0022] As illustrated in [Fig. 2], the electrical machine 2 comprises a rotor 3. The rotor 3 comprises a rotation axis A3. Preferably, the electrical machine 2 comprises two stators 10. Each stator 10 is then preferably arranged on either side of the rotor 3. In other words, each face 5, 6 of the rotor 3 extending perpendicularly to the rotation axis A3 of the rotor 3 is opposite a stator 10. Preferably, each stator 10 comprises a revolution axis or an axis substantially of revolution A10. The axis A10 of the stator, or of each stator 10, coincides, or is substantially coincident, with the rotation axis A3 of the rotor 3.

[0023] More specifically, as illustrated in [Fig. 3], the stator 10 comprises teeth 11. Preferably, the teeth 11 extend radially, or substantially radially, with respect to the axis A10 of the stator. The teeth 11 then form an overall star shape. Preferably, the number of teeth 11 is a multiple of three (related to the three-phase power of the traction battery 4), the teeth 11 being distributed regularly at an angle around the axis A10. For example, the stator 10 comprises eighteen teeth 11. More or fewer teeth may also be suitable.

[0024] As illustrated in [Fig. 3], the stator 10 further comprises an electrical wire 12 surrounding, winding several times around each tooth 11. The electrical wire 12 is shown only partially in [Fig. 3]. Thus, once the electrical wire 12 is wound around a tooth 11, a coil 13 is formed around that tooth 11.

[0025] The stator 10 further includes an electrical connection means 14 for supplying electrical energy to the electrical wire 12. Preferably, the electrical connection means 14 includes two lugs, or plugs, or connections 121, 122 for connecting, for attaching the electrical wire 12.

[0026] As illustrated in the cross-section of [Fig. 3], the stator 10 further comprises an annular portion, a ring, a bushing 20 of cylindrical or substantially cylindrical shape. The annular portion 20 has a principal axis, an axis of revolution, or an axis of revolution, A20. The axis A20 of the annular portion 20 coincides, or is substantially coincident, with the axis A10 of the stator 10. The annular portion 20 includes the electrical connection means 14. In particular, the annular portion 20 includes at least one cooling channel, a conduit, a tube 30 for cooling the stator 10. More specifically, the cooling channel or channels 30 are intended to cool the winding 13 of electrical wire 12 carrying an electric current, as will be seen subsequently.

[0027] In the embodiment illustrated in [Fig. 3], the annular portion 20 extends at an inner radius RI of the stator 10. More precisely, as schematically illustrated in [Fig. 2], the stator 10 comprises a cylindrical or substantially cylindrical cavity 16, a cylindrical recess, or even a hole with a circular or substantially circular cross-section passing through the stator in the axial direction. The axis of the cylindrical cavity or hole 16 coincides or substantially coincides with the axis A10 of the stator.

[0028] Note that this cavity 16 extends between the axis A10 of the stator 10 and the coils 13 comprising the teeth 11 wound with the electric wire 12.

[0029] Thus, by "inner radius RI" of the stator 10, we mean the radius of the cavity 16. In this embodiment, the annular part 20 is housed within the cavity 16 by being in contact with the cylindrical, or substantially cylindrical, surface of this cavity or hole 16. Preferably, the annular part 20 has an outer radius just smaller than the inner radius RI of the cavity 16 within the stator 10 so that it can be inserted into the cavity 16. In this embodiment illustrated in [Fig. 3], the annular part 20 promotes the cooling of the area of ​​each coil 13 closest to the axis A10 of the stator 10.

[0030] Alternatively, in an embodiment not shown, the annular portion extends at an outer radius RE of the stator. More precisely, by "outer radius RE" is meant the radius of a cylindrical or substantially cylindrical envelope 17 (partially illustrated in dashed lines in [Fig. 3]) encompassing all the teeth, including their respective coils. In this case, the annular portion has an inner radius slightly larger than the outer radius RE of the stator so that it can be inserted onto the stator casing 17. In this embodiment, not shown, the annular portion promotes cooling of the area of ​​each coil furthest from the stator axis.

[0031] Indeed, the presence of the annular portion 20 in contact, or at least in close proximity, with the coils 13 facilitates their cooling because the annular portion 20 includes a cooling channel 30. For example, the same channel 30 is formed within the annular portion 20, creating a helical coil. The helical coil then has, for example, its axis coincident, or substantially coincident, with the axis A20 of the annular portion 20. Optionally, the annular portion 20 includes two channels, or even more, so that two, or even more, coils are arranged within the annular portion 20. For example, the helical coils are coaxial and / or have the same or different helical pitch.

[0032] For example, the channel or channels 30 are obtained by molding, simultaneously or substantially simultaneously, with obtaining the annular part 20. Advantageously, the annular part 20 is made of plastic material.

[0033] Alternatively, the annular portion 20 is at least partially overmolded onto the cooling channel(s) 30. In this case, for example, each channel is a coil made of a first material, and the remainder of the annular portion is overmolded with a second material, possibly different from the first. The first and / or second material is, for example, plastic. Preferably, the materials constituting the annular portion have good thermal conductivity to facilitate the transfer of heat from the coils 13 to the annular portion.

[0034] The cooling channel or channels 30 are preferably traversed by a heat transfer fluid so as to extract, evacuate, and remove the heat produced during the passage of the electric current within the coils 13 to the outside of the stator. For example, the heat transfer fluid is oil or glycol water.

[0035] Optionally, a pump is provided to circulate the heat transfer fluid, creating a substantial flow rate within each cooling duct 30 and thus maximizing heat removal. Each cooling circuit or duct includes at least one fluid inlet or inlet configured to allow the heat transfer fluid to enter the duct and at least one fluid outlet or discharge configured to allow the heat transfer fluid to exit the duct. For example, the fluid always circulates in the same direction. Optionally, a radiator is also provided to create a heat exchange from the Heat transfer fluid is transferred to the external environment, for example, the ambient environment. If several ducts or circuits are planned, preferably the ducts join at a single inlet and a single outlet to facilitate connection to a single pump and, if necessary, a single radiator. This is therefore a closed cooling circuit, possibly supplemented by a means of controlling or limiting the fluid pressure. Alternatively, fluid circulation is not forced and may be generated by temperature differences within the annular section.

[0036] For example, the cooling channel 30 is arranged in the immediate vicinity of each coil 13 of electrical wire 12. For example, the distance D separating a coil 13 from the channel 30 is between 0 mm and 5 mm. Thus, dimension D is greater than 0 mm. In the event of a distance D that is too great, a conductive element can be inserted between the ring 20 and the coil 13.

[0037] Preferably, the stator 10 includes an insulator 15. Advantageously, the insulator 15 is resin, poured onto the stator before the annular portion 20 is installed. Alternatively, the stator, including its winding, is immersed in the resin. In any case, the resin 15, at a minimum, encases all the coils 13 of electrical wire 12. The thickness of the resin 15 is, for example, a few tenths of a millimeter, or even less than 0.1 mm.

[0038] Preferably, the annular part 20 is fixed to the insulation 15, for example by clipping onto and / or against the insulation 15. As illustrated in [Fig.3], the annular part 20 is fixed, fits into the cylindrical hole or cavity 16 of internal radius RI. Preferably, a shoulder 18 is provided on the side of the electrical terminals 121, 122 of the electrical wire 12. Preferably, the entry and exit points of the electrical wire 12 at the stator are indeed on the same side via the connections 121, 122. Optionally, at least one hook, a stop 19, extends on the side opposite the shoulder 18 so as to retain the annular portion inserted in the cavity 16. The interaction of at least one hook 19 with a face opposite to that which contacts the shoulder 18 ensures that the annular portion 20 is retained within the stator. For example, two hooks 19 are arranged at 180 degrees or three hooks 19 are arranged at 120 degrees.Thus, the annular part 20 is inserted until the shoulder 18 makes contact with the stator, in this case with an electrical insulator 7 of the winding where present. The insulator 7 preferably extends between the winding and the teeth 11, and / or between each metallic part of the stator and the winding. For example, each tooth 11 is made of steel, for example obtained from a thin sheet wound in a spiral.

[0039] In summary, the solution makes it possible to cool an axial flux electric machine, more particularly to cool the coils of a stator magnetic circuit of the axial flux electric machine. More specifically, the solution relates to a ring 20 comprising both a power supply 14 for the wire 12 running through the windings of the stator teeth 11 and an integrated cooling circuit.

[0040] Thus, the solution allows the winding to be cooled, although compliance with dielectric distances makes contact between the electrical machine housing and the winding difficult, if not impossible, for the purpose of cooling the winding. Furthermore, although the stator 10 was embedded in resin 15 after the winding was completed, the close proximity of the cooling channels 30 to the winding allows for heat dissipation, particularly by conduction within the heat transfer fluid. Heat transfer occurs by conduction when there is contact between the heat source, namely the resin-coated winding 15, and the annular portion 20. If there is a gap between the annular portion 20 and the winding, heat transfer occurs by convection. Thanks to the integration of at least one cooling channel 30 within the annular part 20 close to, or even in contact with, the coils 13, the cooling circuit is as close as possible to the heat source.Thus, as mentioned previously, the annular part 20, which includes the electrical connection system 14, incorporates the cooling circuit. The cooling circuit or system is separate from the electrical circuit or power supply.

[0041] As a reminder, during the operation of the electric machine 2, the stator winding 10 carries an electric current with a high voltage and / or high current, which generates heat. For example, the voltage is on the order of 800 V and the current is on the order of 250 A. The heat, in other words, the calories, are then dissipated via the electrical connection system, which is divided into two parts or zones: a zone for the electrical connections 14 and a zone for cooling 30. The cooling zone comprises the channels, pipes, and conduits attached to the ring 20 used for the electrical connections. As mentioned previously, the ring is preferably made of plastic, or at least of a material that is electrically insulating. Preferably, as illustrated in [Fig. 3], the ring 20 is held in place by clips onto the insulator 15 covering the winding.In other words, the ring 20 is fixed and inserted within the hollow cylinder or hole 16 of radius RI extending between the coils. The ring 20, which dissipates heat via the channel(s) 30, is therefore close to, or even touches, the stator winding, which must be cooled. Cooling is thus facilitated, optimized, and maximized, thereby extending the lifespan of the electrical machine by preventing overheating. Consequently, the reliability of the electrical machine is increased, as the lifespan of the materials used in its components is extended. The ring 20, which includes the phase connections of the electrical wire 12 and the integrated cooling, therefore offers a gain in the reliability of the electrical machine. Furthermore, the installation and fixing of ring 20 on the stator is particularly simple and easy, preferably by a simple clip.

[0042] The manufacture of the annular part 20, preferably of plastic, for example by injection molding, does not present any particular difficulty. As mentioned, preferably the conduits 30 are obtained simultaneously with the rest of the annular part.

[0043] Thus, although the teeth comprising the winding are coated with resin for its electrical insulation, in particular with respect to a housing housing the rotor and the stator, the solution allows the teeth to be cooled.

[0044] In remark, the solution therefore achieves the desired objective of improving the cooling of the teeth of a stator of an axial flux electrical machine and makes it possible to increase the life of the electrical machine on which the stator is mounted, and can be used on all types of axial flux electrical machines.

Claims

Demands

1. Stator (10) for an axial flux electric machine (2) comprising: - teeth (11), in particular teeth (11) extending radially with respect to an axis of revolution (A10) or substantially of revolution of the stator (10) so as to form overall a star, - an electric wire (12) encircling several times each tooth (11) to form a coil (13) around each tooth (11), - an electrical connection means (14) for electrically supplying the electric wire (12), the stator (10) comprising an annular portion (20) having a principal axis (A20) coinciding or substantially coinciding with the axis of revolution (A10) of the stator (10), the annular portion (20) comprising the electrical connection means (14) and at least one cooling channel (30) of the stator (10).

2. Stator (10) according to the preceding claim, characterized in that the annular part (20) extends at the level of an inner radius (RI) of the stator (10) or at the level of an outer radius (RE) of the stator (10).

3. Stator (10) according to any one of the preceding claims, characterized in that at least one cooling channel (30) is provided within the annular part (20) by forming a helical coil having an axis coincident or substantially coincident with the main axis (A20) of the annular part (20).

4. Stator (10) according to any one of the preceding claims, characterized in that at least one cooling channel (30) is obtained by molding simultaneously with obtaining the annular part (20), in particular by molding of a plastic material.

5. Stator (10) according to any one of claims 1 to 3, characterized in that the annular part (20) is at least partially overmolded on at least one cooling channel (30), in particular overmolded with a plastic material.

6. Stator (10) according to any one of the preceding claims, characterized in that at least one cooling channel (30) is arranged near each coil (13) of electrical wire (12), in particular at a distance (D) between 0 mm and 5 mm.

7. Stator (10) according to any one of the preceding claims, characterized in that the stator (10) comprises an insulator (15), in particular of the resin, the insulator (15) encasing at least each coil (13) of electrical wire (12).

8. Stator (10) according to the preceding claim, characterized in that the annular part (20) is fixed to the insulator (15), in particular by clipping onto and / or against the insulator (15), in particular inside a cylindrical envelope (16) having as its radius the inner radius (RI) of the stator (10) or outside a cylindrical envelope (17) having as its radius the outer radius (RE) of the stator (10).

9. Stator (10) according to any one of the preceding claims, characterized in that at least one cooling channel (30) is traversed by a heat transfer fluid, in particular oil.

10. Electric machine (2), in particular electric motor for vehicle, in particular for motor vehicle (1), comprising a rotor (3) having an axis of rotation (A3), characterized in that it comprises at least one stator (10) according to any one of the preceding claims, in particular a stator (10) on either side of the rotor (3), the axis (A10) of the at least one stator (10) being coincident or substantially coincident with the axis of rotation (A3) of the rotor (3).

11. Vehicle, in particular motor vehicle (1), characterized in that it comprises an electrical machine (2) according to the preceding claim or a stator (10) according to any one of claims 1 to 9.

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