Rotor comprising a set of mounting holes arranged at the vertices of a star

Abstract

Rotor assembly (3) for an electric motor (1) of a motor vehicle, comprising a rotor shaft (5), a set of magnetic elements (6), and a disk (7) connecting the magnetic elements to the rotor shaft, characterized in that the disk comprises a set of mounting holes (13) arranged at the vertices of a star-shaped pattern (20), the disk being fixed to the rotor shaft by a set of fastening elements (14), including a set of fastening screws, each fastening element of the set of fastening elements passing through a mounting hole of the set of fastening holes. Figure for the abstract: Figure 2

Description

Title of the invention: Rotor comprising a set of mounting holes arranged at the vertices of a star. Technical field of the invention

[0001] The invention relates to a rotor assembly for an electric motor of a motor vehicle. The invention also relates to an electric motor, in particular an axial flux motor, comprising such a rotor assembly. The invention further relates to a motor vehicle comprising such an electric motor. Prior art

[0002] So-called "electric" or "hybrid" motor vehicles include an electric motor configured to drive the vehicle's drive wheels. Electric motors generally comprise a stator and a rotor. The rotor rotates relative to the stator about an axis of rotation and is coupled to the drive wheels via a transmission mechanism. For this purpose, the rotor generally includes a set of magnetic elements, notably magnets, held by a disk. The disk is centered on the axis of rotation and extends perpendicularly to it. The magnetic elements are designed to interact with electrical coils in the stator to convert electrical energy into mechanical energy.

[0003] The rotor of such an electric motor is coupled to the transmission mechanism via a rotor shaft. In particular, the rotor is fixed to the rotor shaft by means of the disc that supports the magnetic elements. The disc is generally fixed to the rotor shaft by a set of fixing screws passing through fixing holes formed in the disc and cooperating with a shoulder formed in the rotor shaft.

[0004] The torque that the rotor of an electric motor for a motor vehicle must transmit is very high, for example, on the order of 300 N·m to 400 N·m. This very high torque can cause deformation of the rotor, which then leads to a risk of contact between the rotor and the stator and / or misalignment of the magnetic elements relative to the stator. The mechanical stresses on the rotor generated by the transmission of high torque can even lead to separation between the disc and the rotor shaft.

[0005] Furthermore, the rotor must be as compact and lightweight as possible to form an electric motor that can be easily integrated into a motor vehicle. Presentation of the invention

[0006] The object of the invention is to provide an electric motor rotor that remedies the above disadvantages and improves upon known electric motor rotors of the prior art.

[0007] More specifically, a first object of the invention is a rotor for an electric motor that is compact, lightweight, reliable and robust. Summary of the invention

[0008] The invention relates to a rotor assembly for an electric motor of a motor vehicle, comprising a rotor shaft, a set of magnetic elements, and a disc connecting the magnetic elements to the rotor shaft, the disc comprising a set of fixing holes arranged at the vertices of a star-shaped pattern, the disc being fixed to the rotor shaft by a set of fixing elements, in particular a set of fixing screws, each fixing element of the set of fixing elements passing through a fixing hole of the set of fixing holes.

[0009] Said assembly of fixing holes may include a first circular row of fixing holes regularly distributed along a first circle centered on an axis of rotation of the rotor assembly, and a second circular row of fixing holes regularly distributed along a second circle centered on said axis of rotation, the second circle having a larger diameter than the first circle.

[0010] Said first row may include as many fixing holes as the second row, in particular the first row may include between eight fixing holes and sixteen fixing holes inclusive, and each fixing hole of the second row may be intercalated between two adjacent fixing holes of the first row.

[0011] The disc can be made of a composite material comprising on the one hand a resin and on the other hand mineral fibers and / or natural fibers and / or polymer fibers and / or glass fibers and / or carbon fibers.

[0012] The disk may comprise a set of slots distributed regularly on an external surface of the disk, each magnetic element of the set of magnetic elements being housed in a slot of said set of slots.

[0013] The rotor assembly may further include a retaining ring extending around the periphery of the disk, the retaining ring bearing against an outer edge of each magnetic element to hold said magnetic elements in their respective slots.

[0014] The rotor assembly may further include a set of tubular metal inserts, each metal insert of said set of metal inserts being positioned in a fixing hole of said set of fixing holes, each fixing element of the set of fixing elements passing through a metal insert.

[0015] The invention also relates to an electric motor for a motor vehicle comprising a rotor assembly as defined above and a stator cooperating with the rotor assembly.

[0016] The electric motor can be an axial magnetic flux electric motor.

[0017] The invention also relates to a motor vehicle comprising an electric motor as defined above. Presentation of the figures

[0018] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0019] Fig. 1 is a schematic and cross-sectional view, along a plane P identified on Fig. 2, of an electric motor for a motor vehicle according to an embodiment of the invention.

[0020] Fig. 2 is a front view of a rotor of the electric motor. Detailed description

[0021] Figure 1 schematically illustrates an electric motor 1 according to an embodiment of the invention. The electric motor 1 is intended to equip a motor vehicle, for example, a passenger car, a commercial vehicle, a truck, or even a bus. The electric motor 1 is intended to be coupled to the vehicle's drive wheels to propel the vehicle. The drive wheels can be the front and / or rear wheels of the vehicle. The electric motor 1 is intended to be powered by electrical energy, for example, by an electrochemical battery installed in the vehicle, and it is intended to convert the electrical energy into motor torque to propel the vehicle. The electric motor can also be configured to produce electrical energy to recharge an electrochemical battery from motor torque.

[0022] The electric motor 1 comprises a stator 2 and a rotor assembly 3. The stator 2 is fixed in the vehicle's frame of reference. The stator 2 may comprise a set of electrical coils intended to carry an electric current. The rotor assembly 3 is free to rotate relative to the stator 2 about an axis of rotation AL. In this document, the term "radial" refers to a direction perpendicular to the axis of rotation AL and passing through the axis of rotation AL. The term "axial" refers to a direction parallel to the axis of rotation AL.

[0023] The rotor assembly 3 comprises a rotor 4 and a rotor shaft 5 fixed to the rotor 4. The rotor 4 comprises a set of magnetic elements 6, including magnets, and a disk 7. The disk 7 is a means for retaining the magnetic elements 6 and a means for mechanically connecting the magnetic elements 6 to the rotor shaft 5. The The disc 7 extends in a plane perpendicular to the axis of rotation Al and is centered on the axis of rotation Al. The rotor shaft 5 is intended to be coupled to the vehicle's drive wheels via a transmission mechanism. For this purpose, the rotor shaft 5 includes a mounting interface 8, for example, an axially oriented opening with radial splines. Furthermore, the rotor shaft 5 is advantageously guided in rotation by two roller bearings 9, 10 positioned on either side of the disc 7.

[0024] The electric motor 1 is an axial flux type motor, meaning that the magnetic field between the stator 2 and the rotor assembly extends globally parallel to the axis of rotation AL. Such a motor has the advantage of being compact in the radial direction, and therefore easier to integrate into the engine compartment of a motor vehicle. The stator can be formed of two parts 11, 12 positioned on either side of the rotor. Two axial air gaps, in which a magnetic field is intended to be established, can thus be formed on either side of the magnetic elements 6. Furthermore, the electric motor 1 can include a water and / or air cooling system.

[0025] According to one embodiment, the stator could comprise only one of the two parts 11 or 12. According to another embodiment of the invention, the electric motor could be a radial flux electric motor, that is to say, an electric motor in which the magnetic field between the stator and the rotor extends radially, that is to say, perpendicularly to the axis of rotation AL

[0026] The disk 7 supporting the magnetic elements 6 is thus fixed to the rotor shaft 5. For this purpose, the disk 7 includes a set of mounting holes 13, each mounting hole 13 cooperating with a mounting element 14. The rotor shaft 5 includes a set of corresponding holes 15, each corresponding hole being positioned opposite a mounting hole 13. The corresponding holes 15 are formed in a shoulder 16 of the rotor shaft. The shoulder 16, or plate 16, is a radial extension of the rotor shaft 5. The shoulder 16 forms a monolithic assembly with an axial body of the rotor shaft 5. Each mounting element 14 passes through a mounting hole 13 and a corresponding hole 15. According to a preferred embodiment, the mounting elements 14 are mounting screws. The mounting screws may include a screw head bearing against the disk 7.The corresponding holes 15 may include a thread cooperating with the fixing screws to clamp the disc 7 against the shoulder 16.

[0027] According to one embodiment, all or part of the fixing screws could cooperate with nuts separate from the shoulder 16 of the rotor shaft. According to another embodiment, all or part of the heads of the fixing screws could bear against the shoulder 16 and cooperate with a nut bearing against the disc 7, or even with a thread formed in a fixing hole 13. According to another embodiment, the fixing elements could be rivets.

[0028] Figure 2 now illustrates the rotor in front view, that is, in a plane perpendicular to the axis of rotation A1. It can be seen that the disk 7 comprises a set of slots 17 distributed regularly over an external surface of the disk 7. Each magnetic element 6 is housed in a corresponding slot 17. The magnetic elements 6 may have an axial cross-section of a generally trapezoidal shape. The slots 17 have a shape complementary to the shape of the magnetic elements. According to the embodiment shown, the rotor 4 comprises twelve magnetic elements. Alternatively, this number could be different, for example, any number between three and twenty.

[0029] The rotor 4 is also equipped with a retaining ring 18 extending around the periphery of the disk 7. The retaining ring 18 bears against an outer edge of each magnetic element 6. The retaining ring 18 can in particular be shrink-fitted around the magnetic elements 6. The retaining ring 18 makes it possible to keep said magnetic elements 6 in their respective slots 17, in particular when the rotor 4 rotates at high speed and the magnetic elements 6 are subjected to a significant centrifugal force.

[0030] The disc 7 further includes a central opening 19, in particular circular in shape, intended to receive the rotor shaft 5. The disc 7 can be centered on the rotor shaft 5 by contact between the edge of the central opening 19 and a centering portion provided on the rotor shaft.

[0031] Advantageously, according to the invention, the mounting holes 13 are arranged at the vertices of a star-shaped pattern 20. The vertices of the star-shaped pattern designate the points where two consecutive sides of the star-shaped pattern meet. One half of the vertices correspond to the distal ends of the star's branches, while the other half correspond to the points of junction between two adjacent branches of the star. Such an arrangement of the mounting holes allows for reliable and efficient torque transmission between the disk 7 and the rotor shaft 5. In particular, such an arrangement makes it possible to transmit high torque, for example, on the order of 300 N·m to 400 N·m, while maintaining a limited rotor diameter and a limited rotor thickness (considered in the axial direction). The electric motor 1 can therefore remain very compact while transmitting high torque.

[0032] According to the embodiment presented, the star-shaped motif comprises twelve points. The disc 7 therefore comprises twenty-four mounting holes 13. Alternatively, the number of points of the star, and thus the number of mounting holes 13, could be different. For example, the star could comprise only three points, i.e., six mounting holes 13. Advantageously, the star comprises between four and twenty points branches included, preferably between eight branches and sixteen branches inclusive, that is to say between sixteen fixing holes and thirty-two fixing holes inclusive.

[0033] A first set of mounting holes 13 is evenly distributed along a first circle Cl centered on the axis of rotation Al, and a second set of mounting holes 13 is evenly distributed along a second circle C2 centered on the axis of rotation Al, the second circle C2 having a larger diameter than the first circle Cl. By "evenly distributed," it is understood that the holes are spaced from each other by a constant angular distance. Such an arrangement of the mounting holes allows for good balance of the rotor and facilitates the assembly of the rotor 4 with the rotor shaft 5. Said first set and said second set of mounting holes 13 each comprise the same number of mounting holes 13. Each mounting hole of the second set is preferably interposed between two adjacent mounting holes of the first set, that is to say, positioned equidistant from two adjacent mounting holes of the first set.This maximizes the distance between neighboring mounting holes and improves the robustness of disc 7.

[0034] The star-shaped arrangement of the mounting holes 13 also allows for a larger total number of mounting holes and thus distributes the mechanical forces exerted by the mounting elements 14 over a larger surface area of ​​the disc 7. The mechanical stresses borne by the disc 7 are therefore generally lower than those that would be borne by a disc 7 with fewer mounting holes and transmitting the same torque. This reduction in stress makes it possible to use lighter and / or simpler materials to construct the disc 7. Advantageously, the disc 7 can thus be made of a composite material. The composite material comprises, on the one hand, a resin and, on the other hand, fibers, including mineral fibers and / or natural fibers and / or polymer fibers and / or glass fibers and / or carbon fibers.The resin is a matrix, that is, a binder or adhesive, used to fix the fibers. For example, the resin can be an epoxy resin. The resin can be made from a mixture of a liquid polymer containing epoxy groups, generally manufactured from bisphenol A (BPA) or bisphenol F and epichlorohydrin, and a hardener usually composed of an amine, anhydride, or polyamide. The hardener is capable of reacting with the epoxy groups in the resin to form a solid structure. Such a composite material is both very lightweight and very robust. Furthermore, a composite material is a magnetic insulator, which helps prevent interference with the operation of magnetic components.

[0035] Advantageously, the rotor 4 may further comprise a set of tubular metal inserts 21 (for example, made of aluminum or steel), each insert of said set of inserts being positioned in a mounting hole 13. Each The fixing element 14 thus passes through a metal insert 21. The integration of metal inserts 21 makes it possible to reduce the mechanical stresses in the disc 7 without significantly increasing the mass of the rotor.

[0036] To manufacture the rotor assembly 3 described above, the disc 7 can first be molded, notably with a composite material. Then, the metal inserts 21 can be inserted into the mounting holes 13 of the disc 7. Alternatively, the metal inserts 21 can be overmolded during the manufacture of the disc 7. Next, the magnetic elements 6 can be placed in the slots 17, and then the retaining ring 18 can be mounted. The resulting rotor 4 is then fixed to the rotor shaft 5. For this purpose, the fixing elements 14 are inserted through the metal inserts 21 already in place in the mounting holes 13. In particular, the fixing screws are screwed into the corresponding holes 15, positioned opposite the mounting holes 13.The regular distribution of the mounting holes allows for a plurality of orientations in which the rotor 4 can be assembled to the rotor shaft 5, thus facilitating the assembly between the rotor 4 and the rotor shaft 5. To complete the manufacture of the rotor assembly, a balancing step can be provided, for example by removing material from the shoulder 16. The rotor assembly 3 can then be assembled to the stator 2 to form an electric motor for a motor vehicle.

[0037] Finally, thanks to the invention, a rotor assembly and an electric motor comprising such a rotor assembly are obtained that are simple to manufacture, compact, lightweight, and particularly reliable and robust. When the electric motor 1 is running and torque is transmitted between the disc 7 and the rotor shaft 5, the disc 7 is not at risk of deformation or damage. The magnetic elements 6 remain ideally positioned and the air gaps are not disturbed. The electric motor thus operates optimally.

Claims

Demands

1. Rotor assembly (3) for an electric motor (1) of a motor vehicle, comprising a rotor shaft (5), a set of magnetic elements (6), and a disk (7) connecting the magnetic elements to the rotor shaft, characterized in that the disk comprises a set of mounting holes (13) arranged at the vertices of a star-shaped pattern (20), the disk being fixed to the rotor shaft by a set of fastening elements (14), including a set of fastening screws, each fastening element of the set of fastening elements passing through a mounting hole of the set of mounting holes.

2. Rotor assembly (3) according to the preceding claim, characterized in that said assembly of fixing holes (13) comprises a first circular row of fixing holes regularly distributed along a first circle (Cl) centered on an axis of rotation of the rotor assembly, and a second circular row of fixing holes regularly distributed along a second circle (C2) centered on said axis of rotation, the second circle having a larger diameter than the first circle.

3. Rotor assembly (3) according to the preceding claim, characterized in that said first row comprises as many fixing holes (13) as the second row, in particular in that the first row comprises between eight fixing holes and sixteen fixing holes inclusive, and in that each fixing hole of the second row is intercalated between two adjacent fixing holes of the first row.

4. Rotor assembly according to any one of the preceding claims, characterized in that the disc (7) is made of a composite material comprising on the one hand a resin and on the other hand mineral fibers and / or natural fibers and / or polymer fibers and / or glass fibers and / or carbon fibers.

5. Rotor assembly (3) according to any one of the preceding claims, characterized in that the disk (7) comprises a set of slots (17) distributed regularly over an external surface of the disk, each magnetic element (6) of the set of magnetic elements being housed in a slot of said set of slots.

6. Rotor assembly (3) according to the preceding claim, characterized in that it further comprises a retaining ring (18) extending at the periphery of the disk (7), the retaining ring being in contact with an outer edge of each magnetic element (6) to hold said magnetic elements in their respective slot (17).

7. Rotor assembly (3) according to any one of the preceding claims, characterized in that it further comprises a set of tubular metal inserts (20), each metal insert of said set of metal inserts being positioned in a fixing hole (13) of said set of fixing holes, each fixing element (14) of the set of fixing elements passing through a metal insert.

8. Electric motor (1) for a motor vehicle comprising a rotor assembly (3) according to any one of the preceding claims and a stator (2) cooperating with the rotor assembly.

9. Electric motor (1) according to the preceding claim, characterized in that it is an axial magnetic flux electric motor.

10. Motor vehicle comprising an electric motor (1) according to one of claims 8 or 9.

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