AXIAL FLUX MACHINE FOR AN ELECTRIC DRIVE UNIT OF A VEHICLE

Abstract

An axial flux machine (200) for an electric drive assembly of a vehicle comprises a stator (202), at least one rotor assembly (204) comprising a rotor (206) arranged coaxially with the stator (202) with an air gap formed therebetween, and a housing (208) accommodating the stator (202) and the at least one rotor assembly (204). The axial flux machine (200) comprises a first magnet (210) arranged in the housing (208) and a second magnet (214) arranged in the at least one rotor assembly (204). The facing surfaces (210-1, 214-1) of the first magnet (210) and the second magnet (214) have the same polarity to prevent deformation of the at least one rotor assembly (204) in the axial direction and to maintain a uniform air gap between the stator (202) and the rotor (206).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of axial flux machines. More particularly, the present disclosure relates to an improved axial flux machine comprising a rotor housing and configured to prevent deformation of the rotor housing in its axial direction. BACKGROUND

[0002] Axial flux machines (AFMs), including motors and generators, have been known for many years and are used in many practical machines. The most common types of AFMs are an axial version of a brushless permanent magnet machine with salient poles. A typical AFM, as shown in Fig. 1, comprises one or more rotors 102 with permanent magnets bonded to or embedded in an annular metal disk, and a stator 104 with a plurality of windings wound around metal poles or teeth made of stacked metal sheets. Instead of being concentric cylinders, the rotor and stator can also be disks mounted parallel to each other and perpendicular to a rotatable shaft. The different winding geometries interact with the annular disk of permanent magnets, causing alternating flux through the windings as the rotor rotates relative to the stator windings, or vice versa. Such AFMs are primarily used in the powertrain of electric vehicles.

[0003] In general, AFMs are more compact than radial flux machines of the same power. In other words, the axial flux geometry tends to result in higher power density. AFMs exhibit a significant axial force component in the electromagnetic forces generated during operation. However, this axial force component has been shown to contribute to resonant vibrations and noise in the drive system of electric vehicles. In the conventional AFM, as in Fig. 1, the rotor disk 102 is arranged coaxially with the stator disk 104, with an air gap therebetween. The rotor housing 106, in which the rotor disk 102 is housed, can deform in the axial direction due to structural loads, i.e., high centrifugal forces and thermal loads on the rotor housing 106, particularly during high-speed operation of the AFM. The deformation of the rotor housing 106 is Fig. 1 as dashed lines. As the thermal load on the rotor 102 increases, the axial deformation of the rotor housing 106 further increases. Such axial deformation of the rotor housing 106 results in an uneven air gap between the rotor disk 102 and the stator disk 104. Play in one or more of the AFM's bearings can also contribute to air gap variations due to axial movement or tilting. This significantly impacts the noise, vibration, and harshness (NVH) characteristics of the AFM and reduces its overall efficiency.

[0004] In the past, efforts have been made to improve axial flow machines. For example, patent document WO2008015776A1 discloses a motor-type magnetic bearing device in which a compressor impeller and an expansion turbine impeller are fixed to both ends of a main shaft. A radial load on the main shaft is supported by rolling bearings, and an axial load on the main shaft is supported by an electromagnet. The compressor impeller is rotated by the driving force of a motor arranged coaxially with the main shaft and the driving force of a turbine impeller. The axial load supporting electromagnet is arranged to face the thrust plate arranged perpendicularly and coaxially with the main shaft without contact. The motor is of the axial gap type and forms a motor rotor in another thrust plate provided coaxially and perpendicularly with the main shaft.A stator of the motor is arranged to face the rotor in the axial direction. Since the thrust acting on the main shaft is assisted by the electromagnet, the thrust acting on the rolling bearings is reduced. However, the magnetic bearing device of the cited reference does not reduce the effect of axial forces on the rotor, which can lead to deformation of the rotor or the rotor housing that supports the rotor in the axial direction and impair the function of adjacent components of the motor. The deformation of the rotor in the axial direction can also cause increased vibrations to be transmitted to the compressor and turbine, generating noise.

[0005] There is therefore a need to overcome the above-mentioned drawbacks, inadequacies and limitations associated with the existing axial flux machines and the associated rotor designs by providing an improved axial flux machine capable of reducing the effect of axial forces on the rotor to effectively prevent axial deformation thereof and ensure that a uniform air gap is formed between the rotor and the stator. SUBJECT OF THE PRESENT DISCLOSURE

[0006] An object of the present invention is to provide an axial flow machine configured to prevent deformation of a rotor assembly in its axial direction.

[0007] Another object of the present invention is to provide a simple and cost-effective axial flux machine for reducing the effect of axial forces on the rotor unit.

[0008] Another object of the present invention is to provide a reliable axial flux machine capable of ensuring that a uniform air gap is formed between a rotor and the stator thereof.

[0009] Another object of the present invention is to provide a reliable and efficient axial flux machine for an electric drive assembly of a vehicle with reduced NVH (Noise, Vibration and Harshness) characteristics. SUMMARY

[0010] Aspects of the present disclosure relate to an axial flux machine (AFM) for an electric drive unit of a vehicle. The AFM includes a stator, at least one rotor assembly having a rotor arranged coaxially with the stator with an air gap formed therebetween, and a housing enclosing the stator and the at least one rotor assembly. The AFM also includes a first magnet arranged in the housing and a second magnet arranged in the at least one rotor assembly. The facing surfaces of the first magnet and the second magnet have the same polarity to prevent axial deformation of the at least one rotor assembly and to maintain a uniform air gap between the stator and the rotor.

[0011] In one embodiment, the at least one rotor assembly may include a separator configured to isolate the magnetic field generated by the rotation of the rotor and the magnetic repulsion field generated by the second magnet. The separator may be formed from a diamagnetic material.

[0012] In one embodiment, the first magnet and the second magnet may be selected from permanent magnets or electromagnets.

[0013] In one embodiment, the distance between the first magnet and the second magnet may be selected based on a minimum magnetic repulsion force generated by the first magnet to prevent deformation of the at least one rotor unit in the axial direction.

[0014] In one embodiment, the facing surfaces of the first magnet and the second magnet may have the same polarity to maintain a uniform air gap between the stator and the rotor.

[0015] In one embodiment, the first magnet can be attached to a first opening of the housing. In another embodiment, the second magnet can be attached to a second opening of the at least one rotor unit. The first opening can be opposite the second opening.

[0016] Various objects, features, aspects and advantages of the subject invention will become more apparent from the following detailed description of preferred embodiments together with the accompanying drawings in which like numerals represent like components. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. Fig. Figure 1 shows a cross-sectional view of a conventional axial flow machine. Fig. 2 and Fig. 3 show exemplary representations of an axial flux machine according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0018] The following is a detailed description of embodiments of the disclosure illustrated in the accompanying drawings. The embodiments are detailed to make the disclosure clear. However, the required detail is not intended to limit the foreseeable variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

[0019] The embodiments discussed herein relate to an axial flux machine for use in an electric drive assembly of an electric vehicle or a hybrid vehicle. The axial flux machine improves the NVH (noise, vibration, and harshness) characteristics of the electric drive unit. Fig. 2 shows an exemplary representation of the axial flux machine 200 (hereinafter also referred to as "AFM 200"), which includes a stator 202 and at least one rotor assembly 204 (hereinafter also referred to as "rotor housing 204") arranged coaxially with the stator 202. In one embodiment, the AFM 200 may include two rotor assemblies 204 arranged coaxially on either side of the stator 202.

[0020] The stator 202 may be in the form of an annular disk and include a plurality of windings radially arranged on a winding support of the stator 202. The windings may be wound around a yoke or a plurality of teeth whose metallic laminations are stacked on the winding support. The windings may be formed as a printed circuit board (PCB) or stamped from copper sheet.

[0021] The rotor assembly 204 may include a rotor 206 housed therein. The rotor 206 may be configured to rotate relative to the stator 202. The rotor 206 may be in the form of an annular disk having a magnet support structure with a plurality of permanent magnets arranged radially and attached to the magnet support structure such that one permanent magnet has an opposite polarity to an adjacent permanent magnet. The support for the magnet may be arranged parallel to the support for the winding of the stator 202.

[0022] The rotor 206 of the rotor assembly 204 may be arranged coaxially with the stator 202, forming an air gap therebetween. The various winding geometries of the stator 202 interact with the permanent magnets of the rotor 206, causing a changing flux through the windings when the permanent magnets rotate relative to the windings or vice versa. The interaction between the permanent magnets and the stator windings creates an axially oriented magnetic flux. The rotor assembly 204 may also include a rotor shaft 302, as shown in Fig. 3, which is arranged perpendicular to the rotor 206, ie in the axial direction.

[0023] The AFM 200 also includes a housing 208 that houses the stator 202 and the rotor assembly 204, a first magnet 210 disposed in a first opening 212 in the housing 208, and a second magnet 214 disposed in a second opening 216 in the rotor assembly 204. The first magnet 210 may be adhesively attached to the first opening 212 of the housing 208. Similarly, the second magnet 214 may be adhesively attached to the second opening 216 of the rotor assembly 204. In one embodiment, simple machining techniques may be used to form the openings 212, 216 in the rotor assembly 204 and the housing 208. Additionally, the components of the AFM 200 can be assembled after the first magnet 210 and the second magnets 214 have been attached to the corresponding openings 212, 216. This improves the serviceability of the AFM 200.

[0024] The first opening 212 may be opposite the second opening 216. The first magnet 210 and the second magnet 214, which are arranged in the first opening 212 and the second opening 216, respectively, may be opposite each other. The first magnet 210 and the second magnet 214 may be formed of permanent magnets or electromagnets. A surface 210-1 of the first magnet 210, which is opposite to a surface 214-1 of the second magnet 214, has the same polarity to prevent deformation of the rotor housing 204 in an axial direction by balancing deflection of the rotor housing 204 in the axial direction based on a magnetic repulsion force exerted by the first magnet 210 on the second magnet 214. Preventing axial deformation of the rotor housing 204 ensures that a uniform air gap is maintained between the stator 202 and the rotor 206.

[0025] In one implementation, the first magnet 210 and the second magnet 214 may be formed from permanent magnets, with the surface 210-1 of the first magnet 210 having N-polarity and the surface 214-2 of the second magnet 214 also having N-polarity. The permanent magnets may be made from cost-effective materials such as high-quality ferrite, alnico, and the like, which are free of rare earth magnets. To this end, the first magnet 210 disposed in the housing 208 pushes the second magnet 214 disposed in the rotor unit 204 away from itself. This prevents deflection or deformation of the rotor housing 204 in the axial direction away from the stator 202.

[0026] In another embodiment, the first magnet 210 may be selected as an electromagnet, and the second magnet 214 may be formed from a permanent magnet, with surface 210-1 of the first magnet 210 having S polarity and surface 214-2 of the second magnet 214 also having S polarity. When the first magnet 210 is energized by an electric current, the first magnet 210 disposed in the housing 208 repels the second magnet 214 disposed in the rotor assembly 204 toward the stator 202, thereby preventing axial deformation of the rotor assembly 204 and ensuring that a uniform air gap is maintained between the stator 202 and the rotor 206.

[0027] The distance between the first magnet 210 and the second magnet 214 can be selected based on a minimum magnetic repulsion force generated by the first magnet 210 that is suitable for preventing axial deformation of the rotor housing 204 toward the stator 202. The minimum magnetic repulsion force generated by the interaction between the first magnet 210 and the second magnet 214 can be determined by testing the deformation of the rotor housing 204 based on the magnetic repulsion field detected by one or more Hall-effect sensors. The size of the first and second magnets 210, 214 can be optimized based on the size of the rotor 206. A suitable size constraint may be defined for the thickness of the rotor 206 such that the maximum deflection of the rotor assembly 204 is a small fraction of the length of the air gap between the stator 202 and the rotor 206.

[0028] As in Fig.3, the rotor assembly 204 may include a separator 218 separating the rotor housing 204 from the second magnet 214 disposed in the second opening 216 of the rotor assembly 204. The separator 218 may be suitably arranged to isolate the rotor housing 204 from the second magnet 214. The separator 218 may be formed from a diamagnetic material, such as plastic, ceramic, and the like, to isolate a magnetic field created by the rotation of the rotor 206 and a magnetic repulsion field created by the interaction of the first magnet 210 and the second magnet 214. The rotor assembly 204 may also include a rotor shaft 302 disposed perpendicular to the rotor 206.The rotor shaft 302 may be rotatably coupled to at least one input spindle of the vehicle's electric drive assembly to drive the input spindle based on the magnetic flux generated by the AFM 200. Because there is no physical contact between the rotor assembly 204 and the housing 208, the AFM 200 operates without a maximum speed limitation of the rotor shaft 302. The magnetic interference between the first magnet 210 and the second magnet 214 may enable adjustment of the bearing clearance and prevent tilting of the rotor 206.

[0029] Thus, the present disclosure provides an axial flux machine with a rotor assembly whose axial deformation is effectively prevented by the magnetic levitation effect. The axial flux machine also effectively maintains a uniform air gap between the stator and the rotor. This reduces the NVH characteristics and improves the efficiency and maintainability of the axial flux machine, while increasing the throughput and torque delivered to the input spindle of the vehicle's electric drive unit.

[0030] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope of the invention. The scope of the invention is determined by the following claims. The invention is not limited to the described embodiments, variations, or examples, which are included to enable a person of ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person of ordinary skill in the art. LIST OF REFERENCE SYMBOLS 200 axial flux machine 202 Stator 204 Rotor arrangement 206 Rotor 208 housings 210 First Magnet 212 First opening 214 Second magnet 216 Second Opening 218 separators 302 Motor shaft BENEFITS OF THIS DISCLOSURE

[0031] The present disclosure provides an axial flux machine configured to prevent deformation of a rotor assembly in its axial direction.

[0032] The present disclosure provides a simple and cost-effective axial flux machine for reducing the effect of axial forces on the rotor unit.

[0033] The present disclosure provides a reliable axial flux machine capable of ensuring a uniform air gap between a rotor and the stator.

[0034] The present disclosure provides a reliable and efficient axial flux machine for an electric drive unit of a vehicle with reduced noise, vibration and harshness (NVH) characteristics. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2008015776A1

[0004]

Claims

[1] Axial flux machine (200) comprising: a stator (202); at least one rotor assembly (204) comprising a rotor (206) arranged coaxially with the stator (202) and having an air gap formed therebetween; and a housing (208) accommodating the stator (202) and the at least one rotor assembly (204), wherein the axial flux machine (200) comprises a first magnet (210) arranged in the housing (208) and a second magnet (214) arranged in the at least one rotor assembly (204), and Surfaces (210-1, 214-1) of the first magnet (210) and the second magnet (214) facing each other have the same polarity to prevent deformation of the at least one rotor assembly (204) in an axial direction and to maintain a uniform air gap between the stator (202) and the rotor (206). [2] The axial flux machine (200) of claim 1, wherein the stator (202) is arranged between two rotor assemblies (204), the air gap being formed between the stator (202) and each of the two rotor assemblies (204). [3] The axial flux machine (200) of claim 1, wherein the at least one rotor assembly (204) comprises a separator (218) configured to isolate the magnetic field generated by rotation of the rotor (206) and the magnetic repulsion field generated by the second magnet (214). [4] The axial flux machine (200) of claim 3, wherein the separator (218) is formed of a diamagnetic material. [5] The axial flux machine (200) of claim 1, wherein the first magnet (210) and the second magnet (214) are permanent magnets. [6] The axial flux machine (200) of claim 1, wherein the first magnet (210) is an electromagnet and the second magnet (214) is a permanent magnet. [7] The axial flux machine (200) of claim 1, wherein a distance between the first magnet (210) and the second magnet (214) is selected based on a minimum magnetic repulsion force generated by the first magnet (210) to prevent deformation of the at least one rotor assembly (204) in the axial direction. [8] The axial flux machine (200) of claim 1, wherein the facing surfaces (210-1, 214-1) of the first magnet (210) and the second magnet (214) have the same polarity to maintain a uniform air gap between the stator (202) and the rotor. [9] The axial flux machine (200) of claim 1, wherein the first magnet (210) is attached to a first opening (212) of the housing (208) and the second magnet (214) is attached to a second opening (216) of the at least one rotor assembly (204), and wherein the first opening (212) is opposite the second opening (216). [10] An electric drive assembly of a vehicle comprising the axial flux machine (200) of claim 1.

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