Rotor for an electric motor of a motor vehicle comprising a bi-material disc

Abstract

Rotor for an electric motor of a motor vehicle comprising a bi-material disc. Rotor (4) for an electric motor (1) of a motor vehicle, comprising a set of magnetic elements (6) and a disc (7) supporting the magnetic elements and intended to be fixed to a rotor shaft (5), characterized in that the disc (7) comprises a central part (22) and a peripheral part (23) integral with the central part and arranged around the central part, the central part being intended to be fixed to the rotor shaft and being made of a first material, the peripheral part supporting the magnetic elements and being made of a second material different from the first material, the central part and the peripheral part comprising conjugate reliefs (25) adapted to transmit a rotational torque of the electric motor. Figure for the abbreviation: Figure 2

Description

Title of the invention: Rotor for an electric motor of a motor vehicle comprising a bi-material disc. Technical field of the invention

[0001] The invention relates to a rotor 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. 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 ring. The ring is centered on the axis of rotation and extends perpendicularly to the axis of rotation. 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 transmission shaft. In particular, the rotor is fixed to the transmission 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, and in particular of the disc holding the magnetic elements, 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 for an electric motor of a motor vehicle, comprising a set of magnetic elements and a disc supporting the magnetic elements and intended to be fixed to a rotor shaft, the disc comprising a central part and a peripheral part integral with the central part and arranged around the central part, the central part being intended to be fixed to the rotor shaft and being made of a first material, the peripheral part supporting the magnetic elements and being made of a second material different from the first material, the central part and the peripheral part comprising conjugate reliefs suitable for transmitting a rotational torque from the electric motor.

[0009] The central part may include a set of radial teeth regularly distributed around a perimeter of an external surface of the central part, in particular the central part may include between six and twenty radial teeth.

[0010] Said first material may be more rigid than said second material.

[0011] Said first material may be a metallic material, and / or said second material can be 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 peripheral part can be overmolded onto the central part, or the peripheral part can be fretted onto the central part.

[0013] The central part may include a set of fixing holes, the disc being intended to be fixed to the rotor shaft by a set of fixing elements, each fixing element of the set of fixing elements passing through a fixing hole of the set of fixing holes.

[0014] The central part of the disc may include a central opening intended to accommodate the rotor shaft and to center the disc relative to the rotor shaft.

[0015] The peripheral part of the disk may include a set of slots distributed regularly on an external surface of the peripheral part, each magnetic element of the set of magnetic elements being housed in a slot of said set of slots.

[0016] The invention also relates to a rotor assembly comprising a rotor as defined above, and a rotor shaft fixed to the central part of the disc.

[0017] The invention also relates to an electric motor for a motor vehicle, in particular an axial magnetic flux electric motor, comprising a rotor assembly as defined above and a stator cooperating with the rotor assembly. 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 disk 7 extends in a plane perpendicular to the axis of rotation A1 and is centered on the axis of rotation A1. The rotor shaft 5 is intended to be coupled to the drive wheels of the The vehicle is driven 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 A1. Such a motor has the advantage of being compact in the axial direction, and therefore easier to integrate into the engine compartment of a motor vehicle. The stator 2 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 and / or oil 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. In 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 fastening 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 fastening 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 fastening hole 13. According to yet another embodiment, the fastening elements could be rivets.

[0028] Figure 2 now illustrates the rotor 4 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 7 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, and as can be more clearly seen in [Fig. 2], the disk 7 comprises two distinct parts made of different materials: a central part 22 and a peripheral part 23, integral with the central part and arranged around it. The central part 22 comprises an external surface in contact with an internal surface of the peripheral part 23. The disk 7 thus comprises a boundary line 24 at the interface between the central part 22 and the peripheral part 23. The central part 22 comprises a mounting interface for attaching the disk 7 to the rotor shaft 5. In particular, the central part 22 comprises the mounting holes 13 and the central opening 19. The peripheral part 23 comprises means for retaining the magnetic elements 17. In particular, the peripheral part 23 comprises the housings 17 in which the magnetic elements 6 are housed.

[0032] The disc 7 is therefore a bi-material disc. This allows for the consideration of a first material optimized for fixing the disc 7 to the rotor shaft 5 and a second material optimized for holding the magnetic elements 6.

[0033] Furthermore, in order to allow efficient transmission of the motor torque by the disc 7, a specific interface between the central part 22 and the peripheral part 23 is provided: the central part 22 and the peripheral part 23 comprise conjugate reliefs 25 capable of transmitting a rotational torque from the electric motor, in particular A torque of approximately 300 N·m to 400 N·m is applied. The conjugate ridges 25 are formed on the outer surface of the central part 22 and on the inner surface of the peripheral part 23. The outer surface of the central part 22 and the inner surface of the peripheral part 23 are therefore distinct from surfaces of revolution. Each ridge acts as a mechanical stop, preventing the central and peripheral parts from rotating relative to each other. The dimensions of the ridges 25 are adapted to the torque to be transmitted by the disc 7.

[0034] According to the embodiment presented, the reliefs of the central part 22 are formed by twelve radial teeth regularly distributed around a perimeter of the external surface of the central part. Alternatively, the number of teeth could be different, for example, any number between three and twenty, preferably between six and fifteen. Each tooth may have an axial cross-section with a generally trapezoidal shape. In particular, the bases of the trapezoid may extend parallel to the axis of rotation AL. The shorter base of the trapezoid may be further from the axis of rotation AL than the longer base of the trapezoid. The central part 22 can thus at least roughly have the shape of a gear wheel. The boundary line 24 thus has the shape of an annular crenellated line.Alternatively, other shapes could be considered: for example, a star shape, a cross shape, or a polygonal shape such as a square, a rectangle, a pentagon, or a hexagon.

[0035] The external surface of the central part 22 advantageously comprises a shape complementary to the internal surface of the peripheral part 23. These two surfaces are thus in contact with each other without any gap between them. This maximizes the bearing surface between the central part 22 and the peripheral part 23, thereby reducing the mechanical stresses on both the central part 22 and the peripheral part 23.

[0036] Due to its central positioning, the central part 22 is subjected to greater mechanical stresses than the peripheral part 23. Advantageously, the first material is more rigid than the second material. In particular, the first material may have a higher Young's modulus than the second material. Thus, each part 22, 23 can be made of a material optimized for the mechanical stresses it is subjected to. It is possible, in particular, to use a second material that is less expensive and / or less complex to manufacture and / or lighter than the first material.

[0037] The first material can preferably be a metallic material, for example aluminum or steel. The use of a metallic material is advantageous because it allows for high rigidity and also enables high geometric precision of the central opening 19 and the fixing holes 13. The disc 7 can thus be precisely centered on the rotor shaft 5, which reduces the imbalance of the rotor assembly. Furthermore, any necessary balancing of the rotor assembly can be easily carried out by removing material from the central section.

[0038] Alternatively, the first material could be different, for example a fiber-reinforced polymer, for example Polyether Ether Ketone (PEEK). Such a material has the advantage of being very lightweight while retaining significant rigidity.

[0039] The second material is advantageously a magnetic insulating material, so as not to disrupt the operation of the magnetic elements 6. The second material may be a composite material. A 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 to say, a binder or adhesive, for fixing the fibers. The resin may, for example, be an epoxy resin. The resin may 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 generally consisting of an amine, an anhydride, or polyamide, the hardener being capable of reacting with the epoxy groups of the resin to form a solid structure.Such a composite material is both very light and very robust. According to one embodiment, the second material could be a polymer, in particular a fiber-reinforced polymer.

[0040] According to one embodiment of the invention, the first material and the second material could be two different composite materials or two different polymers. These two materials could differ in the nature of their fibers and / or in their fiber content.

[0041] Several methods can be used to manufacture the disc 7. If the first material is metallic, the central part 22 can advantageously be made by cutting a metal sheet. The peripheral part 23 can then be overmolded onto the central part 22. In this case, the central part 22 can extend partially inside the peripheral part. The central part then forms a metallic core of the disc 7. An overmolding method makes it easy to obtain very good cohesion between the two parts 22, 23 of the disc. Advantageously, the central part 22 can be perforated to improve cohesion with the peripheral part 23.

[0042] Alternatively, the central portion 22 could be overmolded onto the peripheral portion 23. According to a third method, the disc 7 can be manufactured by bi-injection or co-injection. In bi-injection, the two materials are injected separately by two injection nozzles into the same mold. In co-injection, the two materials are injected successively by the same injection nozzle into a same mold. Injection or molding manufacturing processes are simple to implement and allow for perfect or near-perfect shape complementarity between the central and peripheral parts. According to a fourth process, the central part 22 and the peripheral part 23 can be manufactured separately and then fixed to each other, for example by shrink fitting. A shrink fitting assembly allows the two parts 22 and 23 to be pre-stressed and thus improves the overall rigidity of the disc 7. Alternatively or in addition, the central part 22 and the peripheral part 23 could be bonded and / or welded to each other.

[0043] Advantageously, the combined reliefs improve the cohesion between the two parts 22 and 23. Thus, a simple fastening method between these two parts can be envisaged. In particular, it is not necessary to use auxiliary fastening elements such as fixing screws to fasten the two parts together.

[0044] After the manufacture of the disc 7, 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 to form the rotor assembly 3. For this purpose, the fixing elements 14 are inserted through the fixing holes 13. In particular, the fixing screws are screwed into the corresponding holes 15, positioned opposite the fixing holes 13. A regular distribution of the fixing holes 13 allows for a plurality of orientations in which the rotor 4 can be assembled to the rotor shaft 5, which facilitates the assembly between the rotor 4 and the rotor shaft 5. To complete the manufacture of the rotor assembly, a balancing step can be carried out, for example by removing material from the central part 22 of the disc 7. The rotor assembly 3 can then be assembled to the stator 2 to form a motor electric for motor vehicles.

[0045] Finally, thanks to the invention, a rotor and an electric motor comprising such a rotor are obtained that are simple to manufacture, compact, lightweight, and particularly reliable and robust. When the electric motor 1 is operating and torque is transmitted between the disk 7 and the rotor shaft 5, the disk 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 1 thus operates optimally.

Claims

Demands

1. Rotor (4) for an electric motor (1) of a motor vehicle, comprising a set of magnetic elements (6) and a disk (7) supporting the magnetic elements and intended to be fixed to a rotor shaft (5), characterized in that the disk (7) comprises a central part (22) and a peripheral part (23) integral with the central part and arranged around the central part, the central part being intended to be fixed to the rotor shaft and being made of a first material, the peripheral part supporting the magnetic elements and being made of a second material different from the first material, the central part and the peripheral part comprising conjugate reliefs (25) capable of transmitting a rotational torque of the electric motor.

2. Rotor (4) according to the preceding claim, characterized in that the central part (22) comprises a set of radial teeth regularly distributed around a periphery of an external surface of the central part, in particular in that the central part comprises between six and twenty radial teeth.

3. Rotor (4) according to any one of the preceding claims, characterized in that said first material is more rigid than said second material.

4. Rotor (4) according to any one of the preceding claims, characterized in that said first material is a metallic material, and / or in that said second material is 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 (4) according to any one of the preceding claims, characterized in that the peripheral part (23) is overmolded on the central part, or in that the peripheral part (23) is swaged onto the central part.

6. Rotor (4) according to any one of the preceding claims, characterized in that: - the central part (22) comprises a set of mounting holes (13), the disc being intended to be fixed to the rotor shaft (5) by a set of fastening elements (14), each fastening element of the assembly of fasteners passing through a fixing hole of the assembly of fixing holes, and / or in that - the central part of the disc includes a central opening (19) intended to accommodate the rotor shaft and to center the disc relative to the rotor shaft.

7. Rotor (4) according to any one of the preceding claims, characterized in that the peripheral part (23) of the disk comprises a set of slots (17) distributed regularly on an external surface of the peripheral part, each magnetic element (6) of the set of magnetic elements being housed in a slot of said set of slots.

8. Rotor assembly (3) comprising a rotor (4) according to any one of the preceding claims and a rotor shaft (5) fixed to the central part of the disc.

9. Electric motor (1) for a motor vehicle, in particular axial magnetic flux electric motor, comprising a rotor assembly (3) according to the preceding claim and a stator (2) cooperating with the rotor assembly.

10. Motor vehicle comprising an electric motor (1) according to the preceding claim.

Images