Fastening of an axial-flux electric motor stator
Patent Information
- Application Number
- EP2023728051
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-05-23
- Filing Date
- 2023-05-23
- Publication Date
- 2025-04-02
AI Technical Summary
The existing methods for fixing axial flux electric motor stators, such as screwing through the casing or using radial bars, face issues with sealing, increased mass, and complex winding impregnation, leading to magnetic imbalances and weight increases.
A fixing device with radially extending lugs and pins that cooperate with a bayonet fixing plate or screws to immobilize the stator within the motor casing, allowing for internal mounting without sealing issues and minimizing weight.
This solution enables secure stator fixation without compromising sealing or increasing the motor's weight, while simplifying the mounting process and reducing magnetic imbalances.
Smart Images
Figure 1.1
Abstract
Description
[0001] FIXING AN AXIAL FLUX ELECTRIC MOTOR STATOR
[0002] The present invention relates to the field of electric motors and more particularly to the fixing of an axial flux electric motor stator.
[0003] BACKGROUND OF THE INVENTION
[0004] A radial flux synchronous electric motor conventionally comprises a rotor mounted to rotate inside a stator which is fixed to a casing by shrink fitting or by means of screws passing through the casing. The stator generally comprises a pack of laminations forming a yoke and a plurality of teeth which extend radially around the axis of rotation of the rotor and on which are wound windings capable of interacting with permanent magnets carried by the rotor to drive said rotor in rotation.
[0005] In the case of an axial flux electric motor, the rotor does not extend inside a stator but is, for example, sandwiched by two stators extending symmetrically on either side of the rotor. The lamination stack of each stator then forms axially extending teeth on which the windings interacting with the permanent magnets of the rotor are wound. Shrink-fitting of the stators is not an option.
[0006] One solution is to screw the stators to a motor casing using screws passing through the casing. However, such a stator attachment poses problems with the casing's sealing and involves tapping or adding inserts into the stator heads, which can lead to the detachment of the sheet metal packs constituting the stator heads.
[0007] Another solution is to screw radially extending bars between two teeth. However, such a stator fixing requires in particular: - increasing the height of the teeth so as to limit the magnetic imbalances caused by the thickness of the bars, which causes an increase in the mass of the stator and therefore of the motor;
[0008] - to position the bars before the windings so as to limit deterioration and impregnation of the windings, which makes it complicated to dismantle said bars; and
[0009] - to move the fixing screws of the winding bars far enough away from the windings in order to limit dielectric and winding passage problems, which causes an increase in the mass of the stator and therefore of the motor.
[0010] SUBJECT OF THE INVENTION
[0011] The invention therefore aims to propose a device for fixing a stator of an axial flux electric motor making it possible to at least partially overcome the aforementioned drawbacks.
[0012] SUMMARY OF THE INVENTION
[0013] To this end, an electric motor is proposed comprising a casing inside which are mounted at least one stator and a rotor mobile in rotation around an axis opposite the stator, the rotor having magnetic poles and the stator comprising a ferromagnetic yoke carrying windings arranged to produce, with the magnetic poles of the rotor, an axial flux electric motor.
[0014] According to the invention, the stator is immobilized relative to the casing by means of a fixing device which comprises lugs extending radially from a surface of the cylinder head, and at least one fixing element fixed to the casing and arranged to cooperate with the lugs so as to block the stator along and around the axis. Such a fixing device allows the stator to be mounted from the inside without causing any problem of sealing the casing and while limiting the weight of the motor.
[0015] In particular, the lugs project from an internal surface of the cylinder head.
[0016] In particular, the engine comprises pins which are inserted into holes provided in the cylinder head and which have an end portion extending radially from the surface of said cylinder head to form the lugs.
[0017] In particular, the lugs are distributed angularly in a regular manner around the axis.
[0018] In particular, the stator yoke has a generally annular shape and comprises a plurality of teeth around which the windings are wound, the lugs extending in line with the teeth.
[0019] According to a particular embodiment, the fixing device comprises a single fixing element comprising a flange which includes a plate provided with bayonet fixing notches adapted to receive the lugs.
[0020] In particular, the plate comprises an external cylindrical bearing arranged to cooperate with a homologous bearing formed by an internal surface of the stator.
[0021] According to another particular embodiment, the fixing device comprises a plurality of fixing elements, each fixing element comprising a screw which passes through the casing and which screws into a thread provided in one of the lugs along the axis.
[0022] In particular, the motor comprises two identical stators extending symmetrically on either side of the rotor.
[0023] The invention also relates to an aircraft comprising at least one landing gear which comprises a leg mounted articulated on a structure of the aircraft between a deployed position and a retracted position by means of such an electric motor.
[0024] BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention will be better understood in light of the following description, which is purely illustrative and non-limiting, and must be read in conjunction with the appended drawings, among which: [Fig. 1] Figure 1 is a schematic view of an aircraft provided with an electric motor according to a particular embodiment of the invention;
[0026] [Fig. 2] Figure 2 is an exploded view of the electric motor shown in Figure 1;
[0027] [Fig. 3] Figure 3 is a perspective view of the rotor of the electric motor shown in Figure 2;
[0028] [Fig. 4A] Figure 4A is a perspective view of one of the stators of the electric motor shown in Figure 2, without winding;
[0029] [Fig. 4B] Figure 4B is a detail view of the stator shown in Figure 4A, provided with windings;
[0030] [Fig. 5] Figure 5 is a perspective view of the stator mounting plate shown in Figures 4A-4B; [Fig. 6A] Figure 6A is a detail view of the stator shown in Figure 4A, in which the stator is in an insertion position;
[0031] [Fig. 6B] Figure 6B is a view identical to Figure 6A, in which the stator is in the unlocked position; [Fig. 6C] Figure 6C is a view identical to Figure 6A, in which the stator is in the locked position;
[0032] DETAILED DESCRIPTION OF THE INVENTION
[0033] With reference to Figure 1, the invention applies to an aircraft A comprising main landing gears P which each comprise a leg J having a first end articulated around an axis Y on a structure of the aircraft A and a second end carrying wheels R. The first end of the leg J is provided with a toothed wheel sector D linked in rotation to said first end around the axis Y. The teeth of the toothed wheel sector D mesh with a pinion mounted on an output shaft 2 of an electric motor generally designated 1.
[0034] The engine 1 is fixed to the structure of the aircraft and is controlled by a control unit UC from a cockpit K of the aircraft A. An action I controlled by the control unit UC causes a rotation of the output shaft 2 of the engine 1 and therefore of the toothed wheel sector D in a first direction SI of deployment of the landing gear P or in a second direction S2 of retraction of the landing gear P. A controllable lock V maintains the toothed wheel sector D in the deployed or retracted position.
[0035] With reference to Figure 2, the motor 1 comprises a casing 10 defining a volume inside which is mounted a rotor 20 extending between a first stator 30a and a second stator 30b. The casing is here made in two parts, namely a first part 10.1 and a second part 10.2 screwed together.
[0036] The rotor 20 has a generally annular shape and is mounted to rotate about an axis X by means of ball bearings (not shown). As illustrated in FIG. 3, the rotor 20 is here connected to the output shaft 2 of the motor 1 by radial arms 21 so that a rotation of said rotor 20 about the axis X causes a rotation of said output shaft 2 about the same axis X. Such a connection makes it possible to limit the mass of the assembly formed by the rotor 20 and the output shaft 2, said assembly being conventionally made in a single piece. The rotor 20 comprises a plurality of permanent magnets 22 which are distributed angularly in a regular manner about the axis X and whose poles alternate. The permanent magnets 22 extend in a radial direction and are here made of neodymium. The first stator 30a is fixed to the first part 10.1 of the casing 10 by means of a first fixing device 40a so that said first stator 30a is stationary with respect to said first part 10.1. Similarly, the second stator 30b is fixed to the second part 10.2 of the casing 10 by means of a second fixing device 40b so that said second stator 30b is stationary with respect to said second part 10.2.
[0037] The first stator 30a and the second stator 30b are here identical and extend symmetrically on either side of the rotor 20. The first fixing device 40a is here identical to the second fixing device 40b. Also, only the first stator 30a and the first fixing device 40a will be described.
[0038] As illustrated in Figures 4A-4B, the first stator 30a comprises a stack of laminations forming a ferromagnetic yoke 31 made of soft iron. The stack of laminations is here made by winding and is arranged axially. The yoke 31 has a generally annular shape and comprises a plurality of teeth 32 which extend radially between an inner surface 31.1 and an outer surface 31.2 of the yoke 31, opposite the permanent magnets 21 of the rotor 20. The inner surface 31.1 and the outer surface 31.2 are cylindrical in shape and respectively delimit an inner circumference and an outer circumference of the yoke 31. Around each of the teeth 32 extends a winding 33 which is connected to the control unit UC so as to produce, with the permanent magnets 21 of the rotor 20, an axial flux motor.
[0039] The first fixing device 40a comprises six pins 41 each inserted by force into a through hole formed in the yoke 31 of the first stator 30. The pins 41 each extend in a radial direction of the yoke 31 and are angularly distributed in a regular manner around the axis X. Each of the pins 41 comprises a first end portion 41.1 which projects from the inner surface 31.1 of the yoke 31, and a second end portion 41.2 which is opposite the first end portion 41.1 and which projects from the outer surface 31.2 of said yoke 31. The first end portions 41.1 and the second end portions 41.2 respectively form first lugs and second lugs. The pins
[0040] 41 are here identical and generally cylindrical in shape.
[0041] The first fixing device 40a also comprises a plate 42 for receiving the first end portions 41.1 of the pins 34 (figure 5). The plate 42 is annular in shape and is attached to the first part 10.1 of the casing 10. For this purpose, the plate
[0042] 42 comprises a rear face which cooperates with a bottom of the first part 10.1 of the casing 10, and a first internal cylindrical bearing surface 42.1 which cooperates with a homologous bearing surface arranged in the bottom of said first part 10.1 of the casing 10 to center the plate 42 with respect to the axis X of rotation of the rotor 20. The plate 42 is screwed to the first part 10.1 of the casing 10 by means of screws passing through holes 42.3 provided on an internal periphery of the plate 42, so that said plate 42 is immobile with respect to said first part 10.1 of the casing 10.
[0043] The plate 42 also includes a second external cylindrical bearing surface 42.2 which extends opposite the internal surface 31.1 of the first stator 30a.
[0044] The plate 42 also has six bayonet fixing notches 43 adapted to receive the first end portions 41.1 of the pins 41. The notches
[0045] 43 are arranged on an external periphery of the plate 42 and are distributed angularly in a regular manner around the axis X. The notches 43 are here identical and comprise:
[0046] - a first section 43.1 for inserting a first end portion 41.1 of pin 41, extending radially from the second cylindrical bearing surface 42.2 of the plate 42;
[0047] - a second section 43.2 for guiding the first end portion 41.1, communicating with the first section 43.1 and extending in a circumferential direction, delimiting a guide ramp; and
[0048] - a third section 43.3 for immobilizing the first end portion 41.1, communicating with the second section 43.2 and extending axially from the rear face of the plate 42 to form a groove for receiving said first end portion 41.1.
[0049] The different stages of mounting the first stator 30a on the first part 10.1 of the casing 10 will now be detailed.
[0050] The plate 42 is first inserted, in an axial direction, into the first part 10.1 of the casing 10 until the first cylindrical bearing surface 42.1 of said plate 42 cooperates with the corresponding bearing surface of the bottom of said first part 10.1 of the casing 10, and the plate 42 is in abutment against the bottom. The plate 42 is then pre-screwed to the first part 10.1 of the casing 10 so that said plate 42 becomes linked in rotation, about the axis X, to said first part 10.1 of the casing 10 while remaining axially movable between a close position in which the rear face of the plate 42 is in abutment against the bottom of the first part 10.1 of the casing 10, and a spaced position in which said rear face is distant from said bottom. The first stator 30a is then in turn inserted, in an axial direction, into the first part 10.1 of the casing 10, the teeth 32 of said first stator 32a being turned towards the outside of said first part 10.1 of the casing 10 and the first end portions 41.1 of the pins 41 being opposite the first sections.
[0051] 43.1 of the notches 43 of the plate 42. As soon as the first end portions 41.1 of the pins 41 are received in the first sections 43.1 of the notches 43 and the first stator 30a is in abutment against the bottom of the first part 10.1 of the casing 10, said first stator 30a is pivoted by an angle a, here equal to fifteen degrees, in a determined direction adapted to make each of the first end portions 41.1 of the pins 41 pass from the first section 43.1 of notch 43 to the third section 43.3 of notch 43 via the second section 43.2 of notch 43. The pivoting of the first stator 30a causes, under the action of the first end portions 41.1 of the pins 41 exerted on the ramps of the second sections
[0052] 43.2 of notch 43, the passage of the plate 42 from the close position to the spaced position.
[0053] The plate 42 is then screwed with a predefined torque, which causes the plate 42 to move from the spaced position to the close position and the first end portions 41.1 of the pins 41 to cooperate with the grooves of the third sections 43.3 of the notch 43. The first stator 30a is then immobilized axially and angularly around the axis X by the plate 42, so that said first stator 30a is immobile with respect to the plate 42 and therefore with respect to the first part 10.1 of the casing 10. The plate 42 thus forms a flange.
[0054] It will be noted that such an arrangement of the plate 42 in contact with the first stator 30a makes it possible to limit the bending of the pins 41. Similarly, the second fixing device 40b comprises a plate 42 adapted to immobilize the second stator 30b with respect to the second part 10.2 of the casing 10.
[0055] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.
[0056] Although the invention applies here to the main landing gear P of the aircraft A, it can also apply to any mobile landing gear equipping an aircraft (front landing gear, central landing gear, etc.).
[0057] The number of pins 41 may be less than or greater than six. It depends in particular on the axial forces undergone by the stator 30a, 30b via the permanent magnets 21 of the rotor 20 when the motor 1 is in operation but also at rest.
[0058] The pins 41 are not necessarily distributed evenly around the X axis.
[0059] In the embodiment described, the pins 41 do not necessarily extend projecting from the external surface 31.2 of said cylinder head 31.
[0060] Although the plate 42 is here arranged to cooperate with the first end portions 41.1 of the pins 41, it can also be arranged to cooperate with the second end portions 41.2 of said pins 41.
[0061] The pins 41 can be replaced by any element forming lugs suitable for bayonet fixing. The lugs can, for example, be made of the same material as the yoke 31 of the stator 30a, 30b.
[0062] Preferably, the pins 41 extend, as illustrated in FIG. 4A, in the extension of the teeth 32 of the yoke 31 in order to limit the magnetic saturation of said yoke 31 generated by the holes receiving said pins 41. Another way of limiting this magnetic saturation is to make the pins 41 in a magnetic material, for example in 15-5PH or 17-4PH stainless steel.
[0063] Although the fixing device 40a, 40b of the stator 30a, 30b here comprises a single flange (formed by the plate 42) to immobilize all of the pins 41, it can also comprise as many flanges as there are pins 41.
[0064] The notches 43 formed in the plate 42 may have a simple rectilinear shape, with a single blind section to receive the end portion 41.1 of the pin 41 and to block it in translation and in rotation (the plate 42 being placed in the first part 10.1 of the casing 10 after the stator 30a).
[0065] Instead of the plate 42, the fixing device 40a, 40b may comprise screws passing through the casing and screwing into threads provided, along the axis X, in the first end portions 41.1 of the pins 41 so as to block the stator 30a along and around the axis X.
Claims
DEMANDS 1. Electric motor (1) comprising a housing (10) within which are mounted at least one stator (30a, 30b) and a rotor (20) free to rotate about an axis (X) opposite the stator, the rotor having magnetic poles and the stator comprising a ferromagnetic yoke (31) carrying windings (33) arranged to form, with the magnetic poles of the rotor, an axial flux electric motor, characterized in that the stator is immobilized relative to the housing by means of a fastening device (40a, 40b) which comprises lugs (41.1, 41.2) extending radially from a surface (42.1, 42.2) of the yoke, and at least one fastening element (42) fixed to the housing and arranged to cooperate with the lugs so as to lock the stator along and around the axis (X).
2. Electric motor (1) according to claim 1, in which the lugs (41.1) extend in projection from an internal surface (31.1) of the cylinder head (31).
3. Electric motor (1) according to any one of the preceding claims, comprising pins (41) which are inserted into holes provided in the cylinder head (31) and which have an end portion extending radially from the surface of said cylinder head to form the lugs (41.1).
4. Electric motor (1) according to any one of the preceding claims, wherein the lugs (41.1) are regularly distributed angularly around the axis (X).
5. Electric motor (1) according to any one of the preceding claims, wherein the cylinder head (31) of the stator (30a, 30b) has an overall annular shape and comprises a plurality of teeth (32) around which the windings (33) are wound, the lugs (41.1) extending in the continuation of the teeth (32).
6. Electric motor (1) according to any one of the preceding claims, wherein the fixing device (40a, 40b) comprises a single fixing element including a flange which has a plate (42) provided with bayonet fixing notches (43) adapted to receive the lugs (41).
7. Electric motor (1) according to claim 6, in which the plate (42) has an external cylindrical bearing surface (42.2) arranged to cooperate with a corresponding bearing surface formed by an internal surface (31.1) of the stator (30a, 30b).
8. Electric motor (1) according to any one of claims 1 to 5, wherein the fastening device (40a, 40b) comprises a plurality of fastening elements, each fastening element comprising a screw which passes through the housing and which screws into a thread formed in one of the lugs (41.1) along the axis (X).
9. Electric motor (1) according to any one of the preceding claims, comprising two identical stators (30a, 30b) extending symmetrically on either side of the rotor (20).
10. Aircraft (A) comprising at least one landing gear (P) which includes a leg (J) mounted articulated on a structure of the aircraft between a deployed position and a retracted position by means of an electric motor according to any one of the preceding claims.