Stator for axial flux machines cooled by dielectric liquid

Abstract

The present invention relates to an axial flux motor (1), comprising: a stator (2), a rotor (3) fixed to a rotating shaft (34), and a housing (22) housing the stator (2), the housing (22) comprising a main wall (20) through which the rotating shaft (34) passes, and two concentric sidewalls (21, 23), the first ends of the two concentric sidewalls being fixed to the main wall (20), the stator comprising: a plurality of teeth (24) fixed to the main wall (20) and projecting axially toward the rotor (3); a winding support (25) disposed on the teeth (24) and housing a stator winding (28); the motor (1) comprising a membrane (27) fixed to the second ends of the sidewalls (21, 23), the membrane (27) and the housing (22) forming a sealed chamber for cooling the stator winding (28).

Description

Technical Field

[0001] This invention relates to the fields of electrical engineering and mechanics, and more particularly to an axial flux motor. Background Technology

[0002] Currently, electric or hybrid vehicles use electric traction or propulsion motors, which are typically radial flux motors, meaning that the stator windings of such machines generate a magnetic field in a radial direction relative to the axial direction corresponding to the machine's axis of rotation.

[0003] To reduce the size of the electric traction or propulsion motors in such vehicles, axial flux motors are considered instead of radial flux motors. In fact, the latter type of machine is generally more compact, at least in the axial direction corresponding to the machine's axis of rotation, thus giving it a disc-like appearance.

[0004] The power density provided by axial flux motors designed for traction or propulsion in motor vehicles means that strong currents flow through the active parts of the machine, causing them to heat up. Typically, these active parts include stator windings, which should be effectively cooled so that the temperature rise caused by the current flowing through them does not damage them.

[0005] Effective cooling of the stator windings can be achieved through a cooling jacket in which a cooling liquid flows; however, such a jacket occupies space around the machine housing, which may be incompatible with some architectures of electric or hybrid powertrains. Another solution involves spraying a dielectric heat-transfer fluid, such as oil, onto the stator windings and then connecting the motor to a cooling circuit where the dielectric heat-transfer fluid is cooled. However, this solution has the disadvantage of reduced machine performance because the presence of heat-transfer fluid in the air gap generates friction with the rotor of the axial flux motor. Summary of the Invention

[0006] The present invention aims to overcome at least some of the above-mentioned disadvantages by providing an axial flux motor and an electric or hybrid vehicle including such a motor, which allows for effective cooling of the stator windings of the motor without degrading the motor's performance and eliminates the need for a cooling jacket.

[0007] Therefore, the present invention proposes an axial flux motor, comprising:

[0008] stator,

[0009] The rotor fixed to the rotating shaft, and

[0010] A housing that accommodates the stator includes a main wall and two concentric side walls. The rotation shaft passes through the main wall, and the first ends of the two concentric side walls are fixed to the main wall.

[0011] The stator includes:

[0012] Multiple teeth, which are fixed to the main wall and project axially in the direction of the rotor.

[0013] The winding support member is provided on the tooth, and

[0014] The stator winding is housed within the winding support.

[0015] The motor is characterized in that it includes a membrane fixed to a second end of the sidewall, the membrane and the housing forming a sealed chamber for cooling the stator windings.

[0016] It should be noted that in this patent application, unless otherwise stated, the term "axial" refers to a direction parallel to the axis of rotation of the motor's rotor. Similarly, unless otherwise stated, the term "radial" refers to a direction orthogonal to and tangential to the axis of rotation of the motor's rotor, while unless otherwise stated, the terms "angular" or "orthogonal radial" refer to directions orthogonal to both the axial and radial directions, which actually rotate around the axis of rotation of the rotor.

[0017] The motor according to the invention comprises at least one stator and at least one rotor, for example, it comprises two stators on either side of the rotor in the axial direction. In the latter case, the two stators are preferably manufactured similarly, i.e., the motor according to the invention then specifically comprises two sealed chambers. Of course, the sealed chambers (multiple) comprise at least one heat transfer fluid inlet and one heat transfer fluid outlet.

[0018] For example, the housing that houses the stator is part of the motor housing, or a housing specifically for the stator, which includes, for example, this dedicated stator housing. For instance, the main wall is a wall of the motor housing orthogonal to the rotor's axis of rotation, or a plate made of magnets fixed to the motor housing wall and serving as a stator yoke when side walls are fixed to the plate. Teeth can be fixed to the main wall via a plate, which is generally planar on the sides of the teeth, but may, of course, include fastening grooves or ribs for securing the teeth or plates. For example, the main wall includes cooling channels on the opposite side of the teeth, using a different heat transfer fluid than that used in the sealed chamber.

[0019] For example, the sidewalls of the housing are cylindrical or formed by multiple concentric cylindrical walls, for example, to allow the rotor hub to be partially housed in the motor, especially when the sidewalls are also the central sidewalls of the motor housing.

[0020] Because of this invention, during motor operation, the heat transfer fluid present in the sealed chamber cannot exit the sealed chamber except through the oil outlet connected to the cooling circuit used to cool the heat transfer fluid. Therefore, the heat transfer fluid will not permeate into the air gap and will not interfere with the rotor's rotation. Furthermore, the membrane is thin, for example, within half a millimeter, which allows for a reduced air gap between the stator and rotor, thus not reducing the motor's magnetic properties. The membrane is flexible enough that its positioning can tolerate varying gaps between the sidewalls of the motor to which it is fastened. Preferably, the membrane is made of a composite synthetic material, such as a polymer reinforced with glass or carbon fiber. For example, the membrane is overmolded onto the second end of the sidewall.

[0021] For example, the membrane is in the form of a flat crown, with its rounded end fixed to a countersunk hole formed at a second end of the sidewall. For example, the membrane is bonded to these countersunk holes or overmolded onto them.

[0022] The membrane must withstand axial forces, particularly due to the pressure of the heat transfer fluid within the sealed chamber, and the negative pressure generated by the rotation of the rotor. This resistance is achieved specifically by securing it to the motor's mounting elements, which helps prevent the membrane from being pulled out or deformed. Such pulling out or deformation could lead to heat transfer fluid leakage and / or friction with the rotor, thereby degrading the performance of both the membrane and the motor.

[0023] In one embodiment of the invention, the membrane is fixed to at least one of the axial end surfaces of the teeth. For example, the membrane is bonded to each axial end surface of the tooth on the air gap side. This allows for prevention of membrane deformation in the region radially located at the level of the stator teeth, while allowing for the selection of a softer membrane than if it were only fixed to the second end of the sidewall.

[0024] Preferably, the axial flux motor according to the invention includes fixing devices for securing the diaphragm to at least one of the winding supports disposed on one of the teeth. These fixing devices are complementary to the fixing of the diaphragm to the sidewall of the housing and may also be complementary to the fixing of the diaphragm to at least one of the stator teeth. These fixing devices allow for prevention of deformation of the diaphragm at the periphery of the teeth, and thus allow for the selection of a softer diaphragm than if it were only fastened to the second end of the sidewall. For example, these fixing devices include adhesive or attachment devices integrally formed with or fastened to the diaphragm.

[0025] The winding support includes a retaining wall for holding one of the stator windings, the retaining wall being configured to contact a diaphragm. The retaining device includes, for example, at least one fastening pin capable of holding the diaphragm and the retaining wall abutting each other, and a channel hole for allowing the fastening pin to pass through the retaining wall. The retaining wall is a first retaining wall orthogonal to the rotor's axis of rotation and surrounding teeth fitted onto the winding support. The winding support includes a second retaining wall on the opposite side of the winding relative to the first retaining wall. For example, the fastening pin is attached to the diaphragm or integrally formed as a single piece with the diaphragm. Using a fastening pin instead of attaching the diaphragm to the retaining wall allows for the avoidance of requiring equal axial clearances, both between the axial end surfaces of the teeth and the diaphragm, and between the retaining wall and the diaphragm.

[0026] The retaining wall forms a frame around the axial end surface of the tooth, and the fixing device preferably includes at least one fastening pin on each side of the frame. For example, the diaphragm is secured to the periphery of each tooth by four fastening pins, each pin being held in the retaining wall to retain the winding support. A large number of pins, evenly distributed around each tooth, further ensures a minimum distance between the rotor and the diaphragm. For example, each pin is angularly and radially centered on one side of the frame formed by the retaining wall.

[0027] For example, a fastening pin includes a foot, a head, and a body connecting the foot and the head. The head is elastically deformable within a channel hole to position the retaining wall between the foot and the head. The use of a pin whose head elastically passes through the channel hole of the retaining wall allows for easier removal of the membrane for replacement during motor maintenance or repair.

[0028] Preferably, the foot is secured to a surface of the membrane positioned opposite the retaining wall. For example, the foot is secured to this surface or within the thickness of the membrane without forming a hole in the membrane, thus maintaining the seal of the sealing chamber. Alternatively, the foot is secured to the other side of the membrane, with the body extending through the membrane. In this variation, an additional sealing device, such as a flat annular seal, can be provided between the foot and the membrane, particularly if the latter is not an elastomer. Similarly, in a variation where the pin is in the form of a screw, such a sealing device can be added between the screw head and the membrane if the screw head is secured relative to the retaining wall on the other side of the membrane.

[0029] More preferably, the foot is secured to the surface of the membrane by adhesive or by gripping it in the membrane's woven structure. Similarly, in variations where the pin is in the form of a screw, the screw head is preferably secured to the surface of the membrane by adhesive or by gripping it in the membrane's woven structure. "Gripping" should be understood as wedging, i.e., the foot or screw head is interwoven into the membrane's fibers. If the membrane does not include fibers, it includes, for example, a non-penetrating receptacle into which the foot or screw head can be resiliently inserted.

[0030] The present invention also relates to an electric or hybrid vehicle including an electric motor according to the present invention. Attached Figure Description

[0031] Other features and advantages of the invention will become more apparent, both in the description which follows and from several embodiments given for non-limiting and indicative purposes with reference to the accompanying schematic diagrams, wherein:

[0032] [ Figure 1 [This is a half-sectional view of the stator and rotor of the electric motor according to the invention, mounted on a rotating shaft, in one embodiment of the invention.]

[0033] [ Figure 2 ]yes Figure 1 A front view of the stator and rotating shaft, where the motor's sealing film has been made transparent, and

[0034] [ Figure 3 [This is in conjunction with the corresponding embodiments] Figure 2 A cross-sectional view of the fastening pin in a portion of the mentioned sealing membrane. Detailed Implementation

[0035] According to embodiments of the present invention, such as Figure 1 As shown, the axial flux motor 1 according to the present invention includes at least one stator 2 and a rotor 3, the rotor 3 being fixed to a rotation shaft 34 movably mounted about a rotation axis X. Only half of the stator 2 and half of the rotor 3 are shown in the cross-sectional view, the other half of which are symmetrical with respect to the rotation axis X.

[0036] The motor 1 also includes a housing (not shown) that houses the stator 2, the rotor 3, and another stator (not shown) located axially on the opposite side of the rotor 3 relative to the stator 2. This other stator is arranged symmetrically with respect to the rotor 3 and has the same structure as the stator 2. Alternatively, however, the motor 1 may include a single stator.

[0037] In this embodiment of the invention, the stator 2 includes a dedicated housing 22, which includes a main wall 20 orthogonally disposed to the rotation axis X and fastened to the wall of the motor housing. The main wall 20 is a plate made of magnets, in the form of a flat crown, to which stator teeth 24 (also called stator teeth), also made of magnets, are engaged or fastened by nesting. The main wall 20 has a hole at its center for the passage of the rotation shaft 34. Alternatively, the teeth and the main wall 20 are integrally formed as a single piece.

[0038] In this embodiment of the invention, each tooth 24 has a trapezoidal shape, and the teeth are distributed at an angle and uniformly around the rotation axis X, such as... Figure 2As shown. The teeth 24 are shaped as right prisms with their height parallel to the axial direction. Winding supports 25, made of an insulating synthetic material (e.g., a polymer), are fitted onto each of the teeth 24. The winding supports 25 include trapezoidal hollow bodies whose shape is complementary to the teeth 24 on which the hollow bodies are fitted, and include two retaining walls 252, 254 of the stator windings 28, which are orthogonal to the axis of rotation X and each connected to an axial end different from the hollow body. Thus, the stator windings 28 are arranged around each hollow body fitted onto the stator teeth 24. For example, each stator winding is formed of a coil of copper wire. Each end of the stator windings 28 is electrically connected to a phase conductor (not shown) inside or outside the housing 22.

[0039] The housing 22 also includes two concentric sidewalls 21, 23, each sidewall being secured to the main wall 20 via its first end. In this embodiment of the invention, the sidewalls 21, 23 are cylindrical, but may alternatively have different shapes. For example, the sidewalls 21, 23 may be welded to the main wall 20 or integrally formed as a single piece with the main wall 20. For example, they may be made of steel or aluminum. The sidewall 23 is located close to the rotation axis 34, and the sidewall 21 is located away from the rotation axis 21. The main wall 20 and the sidewalls 21, 23 are dimensioned to accommodate the teeth 24, the stator windings 28, and the winding supports 25, wherein these elements accommodated therein do not extend axially beyond the second ends of the sidewalls 21, 23.

[0040] A membrane 27, made of a glass or carbon fiber reinforced polymer, such as so-called PA6GF35 or PA12GF35 polyamide, is fastened to the second ends of the sidewalls 21 and 23 by overmolding into countersunk holes arranged on the second ends of the sidewalls 21 and 23. The membrane 27, the main wall 20, and the sidewalls 21 and 23 form a sealed chamber in which the active portion of the stator 2 can be immersed in a heat-transfer dielectric cooling liquid such as oil. The oil enters the sealed chamber through a heat-transfer liquid inlet 222 and exits through a heat-transfer liquid outlet 224, which are orifices arranged in the main wall 20. The inlet 222 and the outlet 224 are connected to a cooling circuit (not shown). The oil entering or exiting through these orifices is controlled by… Figure 1 The arrows passing through these openings indicate this.

[0041] It should be noted that other channel holes can be provided in the main wall 20 for the passage of electrical connectors of the stator windings or phase conductors outside the housing 22. Sealing devices can be provided at these holes to prevent leakage of the coolant contained in the sealed cavity. For example, an overmolding of all electrical connectors can be provided behind these channel holes for the passage of electrical connectors or phase conductors, and the overmolding can also cover the periphery of these holes on the main wall 20. Alternatively, the electrical connectors or phase conductors can pass through one of the side walls 21 or 23 of the housing 22.

[0042] The rotor 3 is in the form of a disc with an opening at its center to allow the rotation shaft 34 to pass through. It includes a fastening hub (not shown) that is fastened to the rotation shaft 34. The rotor 3 includes a body 32 made of a composite material, such as reinforced with glass or carbon fiber, which includes a circular portion connected to the fastening hub and branches of a circular hoop 36 extending radially from the circular portion to the rotor 3.

[0043] The rotor 3 includes trapezoidal magnetic poles 30, each housed between branches of the body 32. The dimensions of the surfaces of these magnetic poles 30 are at least equal to the dimensions of the axial end surfaces 240 of the teeth 24, in order to receive most of the magnetic field generated by the stator windings 28. Of course, if the teeth have a shape different from a trapezoid, the magnetic poles 30 preferably have the same shape as that different shape. For example, the magnetic poles 30 are formed by small permanent magnets bonded together by resin possibly filled with magnetic powder, or the magnetic poles 30 themselves are bonded magnets. Although the rotation of the rotor 3 exerts a centrifugal force during operation of the motor 1, the clamps 36 allow the magnetic poles 30 to be held in the housings between the branches of the body 32.

[0044] To prevent the membrane 27 from deforming, for example due to the pressure of the cooling liquid in the sealed cavity or the vibration of the motor 1 during operation, the membrane 27 is attached to the axial end surface 240 of each tooth 24, which is configured to contact the membrane 27.

[0045] Furthermore, in this embodiment of the invention, the fastening pin 4 is fastened to the membrane 27 on one hand, and to the retaining wall 252 of each winding support 25 on the other hand, these retaining walls 252 being close to the membrane 27 relative to the retaining wall 254. Figure 2 As shown, the membrane 27 is secured to each retaining wall 252 by four fastening pins 4, which are located on each side of the trapezoidal frame formed by the retaining walls 252, i.e., on each side of the teeth 24 surrounded by the retaining walls 252. Furthermore, each fastening pin 4 is centered on the side of the trapezoidal frame and is radially and angularly secured to the side of the trapezoidal frame. Of course, other positioning and other numbers of fastening pins are possible. Figure 3 An example of a fastening pin 4 used in this embodiment of the invention is shown. The fastening pin 4 includes a foot 40, a body 42, and a head 44 having a tapered overall shape. The body 42 connects the tapered base of the head 44 to the foot 40. The foot 40 is, for example, shaped as a disc with a diameter larger than that of the cylindrical body 42. For example, the fastening pin 4 is made of polyamide.

[0046] like Figure 3 As shown, each fastening pin 4 is fastened to the membrane 27 without forming a hole in the membrane 27, so as to maintain the seal of the sealing chamber. For example, the foot 40 of each fastening pin 4 is bonded or wedged into the fibers of the membrane 27.

[0047] like Figure 1 As shown, each retaining wall 252 includes a channel hole for fastening the pin 4. Each channel hole is formed in a countersunk hole of the retaining wall 252 located on the side of the stator winding 28. Therefore, when the fastening pin 4 is fastened to the diaphragm 27 on the side of the retaining wall 252 opposite to the channel hole via its foot 40, the head 44 of the pin is elastically inserted into the channel hole, and the countersunk hole holds the base of the head 44 of the pin 4. Thus, the pin 4 holds the diaphragm 27 against the retaining wall 252 and prevents its deformation.

[0048] Of course, the present invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, features of different variations of the invention considered in this application can be combined to implement the invention, provided that these variations do not contradict each other.

Claims

1. An axial flux motor (1), comprising: Stator (2); The rotor (3) is fixed to the rotating shaft (34), and The housing (22) houses the stator (2), the housing (22) includes a main wall (20) and two concentric side walls (21, 23), the rotating shaft (34) passes through the main wall (20), and the first ends of the two concentric side walls (21, 23) are fixed to the main wall (20). The stator includes: Multiple teeth (24) are fixed to the main wall (20) and protrude axially in the direction of the rotor (3). The winding support (25) is provided on the tooth (24), and The stator winding (28) is housed in the winding support (25). The motor (1) is characterized in that it includes a membrane (27) fixed to a second end of the sidewalls (21, 23), the membrane (27) and the housing (22) forming a sealed chamber for cooling the stator windings (28).

2. The axial flux motor (1) according to claim 1, wherein, The membrane (27) is in the form of a flat crown, and the circular end of the membrane is fixed to a countersunk hole formed at the second end of the sidewall (21, 23).

3. The axial flux motor (1) according to claim 1 or 2, wherein, The membrane (27) is fixed to at least one of the axial end surfaces (240) of the tooth (24).

4. The axial flux motor (1) according to any one of claims 1 to 3, comprising a fixing device for fixing the diaphragm (27) to at least one of the winding supports (25) fitted onto one of the teeth (24).

5. The axial flux motor (1) according to claim 4, wherein, The winding support (25) includes a retaining wall (252) for retaining one of the stator windings (28), the retaining wall being configured to contact the membrane (27), and the fixing device including at least one fastening pin (4) capable of holding the membrane (27) and the retaining wall (252) against each other, and a channel hole for the fastening pin (4) to pass through the retaining wall (252).

6. The axial flux motor (1) according to claim 5, wherein, The retaining wall (252) forms a frame around the axial end surface (240) of the tooth (24), and the fixing device includes at least one fastening pin (4) on each side of the frame.

7. The axial flux motor (1) according to claim 5 or 6, wherein, The fastening pin (4) includes a foot (40), a head (44), and a body (42) connecting the foot (40) and the head (44). The head (44) is elastically deformable in the channel hole to place the retaining wall (252) between the foot (40) and the head (44).

8. The axial flux motor (1) according to claim 7, wherein, The foot (40) is fastened to the surface of the membrane (27) that is positioned opposite to the retaining wall (252).

9. The axial flux motor (1) according to claim 8, wherein, The foot (40) is secured to the surface of the membrane (27) by adhesive or by gripping in the woven structure of the membrane (27).

10. An electric or hybrid vehicle, comprising an electric motor (1) according to any one of claims 1 to 9.

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