Axial flux motor rotor with continuous Halbach array magnets

Abstract

The invention relates to an axial flux motor rotor with continuous Halbach array magnets. A rotor for rotatable mounting on an axis of rotation of an axial flux electric motor includes a permanent magnet (PM) disk having a continuous Halbach magnetization distribution. The axial flux electric motor also includes a rotationally fixed stator having a plurality of electrically conductive stator poles arranged radially about the axis of rotation. The rotor is axially spaced from one side of the stator. A motorized vehicle employing the subject axial flux electric motor is also envisaged.

Description

Technical Field

[0001] The present disclosure relates to a rotor for an axial flux motor having a continuous Halbach array magnet. Background Art

[0002] An electric motor is a machine that converts electrical energy into mechanical energy. The operation of an electric motor is based on the electromagnetic interaction between permanent magnets and the magnetic fields generated by selectively energized coils of the machine. Electric motors are classified into two categories according to the direction of the magnetic field - axial flux motors and radial flux motors. The arrangement of the gap between the rotor and the stator of the machine, which is parallel to the axis of rotation in an axial flux motor and radially positioned in a radial flux motor, determines the direction of the magnetic flux of the motor.

[0003] Axial and radial flux motors can be configured as switched reluctance machines. Generally, a reluctance machine induces non-permanent magnetic poles on a ferromagnetic rotor. The rotor of such a machine typically does not have windings and generates torque through reluctance. Sub-types of reluctance machines include synchronous, variable speed, switched, and variable speed stepper motors. Reluctance motors can provide high power density, but if the reluctance is combined with the torque from magnets, the reluctance motor may experience significant high load torque fluctuations or "torque ripple" (the difference between the maximum and minimum torques during one revolution), which may also generate noise.

[0004] Typically, an axial flux motor has a relatively denser and shorter magnetic flux flow path. Additionally, compared to a radial flux motor, the rotor magnets can be located further away from the central axis of rotation of the axial motor. As a result, when the diameter of the rotor is significantly larger than its axial length, the axial flux motor generally has a higher torque-to-weight ratio and torque-to-size ratio compared to a radial flux motor. Like all forms of AC synchronous electric motors, the magnets on the rotor of an axial flux motor are attracted to the rotating magnetic field generated by the surrounding ring of independent electromagnets in the stator. Since the switching of the magnets that causes the magnetic field to rotate is typically not completely smooth, the rotor experiences torque ripple. Summary of the Invention

[0005] An axial flux electric motor includes a rotationally fixed stator that defines an axis of rotation and has a plurality of conductive stator poles radially arranged about the axis of rotation. The axial flux electric motor also includes a first rotor axially spaced from one side of the stator and rotatably mounted coaxially with the axis of rotation. The first rotor is characterized by a first rotor outer surface facing the stator and includes a first permanent magnet (PM) disk having a continuous (non-segmented) Halbach magnetization distribution.

[0006] The axial flux electric motor may further include a second rotor axially spaced from the stator on the other side, having a second rotor outer surface facing the stator, and rotatably mounted coaxially with the axis of rotation. The second rotor may include a second PM disk having a continuous Halbach magnetization distribution.

[0007] The continuous Halbach magnetization distribution of each of the first PM disk and the second PM disk may have a periodic pattern.

[0008] The periodic pattern of the first PM disk may be phase angle aligned with the periodic pattern of the second PM disk.

[0009] The periodic pattern of the first PM disk may be phase angle offset relative to the periodic pattern of the second PM disk.

[0010] Each of the first PM disk and the second PM disk may include a plurality of concentrically arranged rings. Each of the subject rings may have a continuous Halbach magnetization distribution.

[0011] The first rotor may additionally include a first support structure, and the second rotor may similarly include a second support structure. In such an embodiment, each of the plurality of concentrically arranged rings of the first and second PM disks may be mounted to the respective first and second support structures.

[0012] Each of the first PM disk and the second PM disk may include a helically formed structure having a continuous Halbach magnetization distribution.

[0013] The stator may be characterized by a printed circuit board (PCB) structure that defines the magnetic poles of the stator.

[0014] The stator may be characterized by a slotless structure that defines the magnetic poles of the stator.

[0015] A motor vehicle employing such an axial flux electric motor is also contemplated.

[0016] The present invention provides the following technical solutions.

[0017] Technical solution 1. An axial flux electric motor, comprising:

[0018] A rotationally fixed stator that defines an axis of rotation and has a plurality of conductive stator magnetic poles radially arranged around the axis of rotation; and

[0019] A first rotor axially spaced from one side of the stator, rotatably mounted coaxially with the axis of rotation, characterized by a first rotor outer surface facing the stator, and including a first permanent magnet PM disk having a continuous Halbach magnetization distribution.

[0020] Technical solution 2. The axial flux electric motor according to technical solution 1 further includes a second rotor axially spaced apart from the other side of the stator, characterized in that it faces the outer surface of the second rotor of the stator and is rotatably mounted coaxially with the rotation axis, and includes a second PM disk having the continuous Halbach magnetization distribution.

[0021] Technical solution 3. The axial flux electric motor according to technical solution 2, wherein the continuous Halbach magnetization distribution of each of the first PM disk and the second PM disk has a periodic pattern.

[0022] Technical solution 4. The axial flux electric motor according to technical solution 3, wherein the periodic pattern of the first PM disk is phase angle aligned with the periodic pattern of the second PM disk.

[0023] Technical solution 5. The axial flux electric motor according to technical solution 3, wherein the periodic pattern of the first PM disk is phase angle offset with respect to the periodic pattern of the second PM disk.

[0024] Technical solution 6. The axial flux electric motor according to technical solution 2, wherein each of the first PM disk and the second PM disk includes a plurality of concentrically arranged rings, and wherein each ring has the continuous Halbach magnetization distribution.

[0025] Technical solution 7. The axial flux electric motor according to technical solution 6, wherein the first rotor additionally includes a first support structure, and the second rotor additionally includes a second support structure, and wherein each of the plurality of concentrically arranged rings of the first and second PM disks is mounted to the corresponding first and second support structures.

[0026] Technical solution 8. The axial flux electric motor according to technical solution 2, wherein each of the first PM disk and the second PM disk includes a helically formed structure having the continuous Halbach magnetization distribution.

[0027] Technical solution 9. The axial flux electric motor according to technical solution 1, wherein the stator is characterized by a printed circuit board (PCB) structure defining the stator poles.

[0028] Technical solution 10. The axial flux electric motor according to technical solution 1, wherein the stator is characterized by a slotless structure defining the stator poles.

[0029] Technical solution 11. A rotor for mounting on the rotation axis of an axial flux electric motor, comprising:

[0030] A permanent magnet (PM) disk having a continuous Halbach magnetization distribution.

[0031] Aspect 12. The rotor according to Aspect 11, wherein the continuous Halbach magnetization distribution has a periodic pattern.

[0032] Aspect 13. The rotor according to Aspect 11, wherein the PM disk includes a plurality of concentrically arranged rings, and wherein each ring has the continuous Halbach magnetization distribution.

[0033] Aspect 14. The rotor according to Aspect 13, further comprising a support structure, and wherein the plurality of concentrically arranged rings of the PM disk are mounted to the support structure.

[0034] Aspect 15. The rotor according to Aspect 11, wherein the PM disk includes a helically formed structure having the continuous Halbach magnetization distribution.

[0035] Aspect 16. A motor vehicle, comprising:

[0036] An axial flux electric motor configured to generate torque for propelling the motor vehicle, the axial flux electric motor comprising:

[0037] A rotationally fixed stator defining a rotation axis and having a plurality of conductive stator poles radially arranged about the rotation axis;

[0038] A first rotor axially spaced from one side of the stator, rotatably mounted coaxially with the rotation axis, characterized by a first rotor outer surface facing the stator, and including a first permanent magnet (PM) disk having a continuous Halbach magnetization distribution; and

[0039] A second rotor axially spaced from the other side of the stator, characterized by a second rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, and including a second PM disk having the continuous Halbach magnetization distribution;

[0040] Wherein the continuous Halbach magnetization distribution of each of the first PM disk and the second PM disk has a periodic pattern.

[0041] Aspect 17. The motor vehicle according to Aspect 16, wherein the periodic pattern of the first PM disk is phase angle aligned with the periodic pattern of the second PM disk.

[0042] Aspect 18. The motor vehicle according to Aspect 16, wherein the periodic pattern of the first PM disk is phase - angle shifted relative to the periodic pattern of the second PM disk.

[0043] Aspect 19. The motor vehicle according to Aspect 16, wherein each of the first PM disk and the second PM disk includes a plurality of concentrically arranged rings, and wherein each ring has the continuous Halbach magnetization distribution.

[0044] Aspect 20. The motor vehicle according to Aspect 16, wherein each of the first PM disk and the second PM disk includes a helically formed structure having the continuous Halbach magnetization distribution.

[0045] When combined with the accompanying drawings and the appended claims, the above - mentioned features and advantages of the present disclosure, as well as other features and advantages, will become apparent from the following detailed description of the embodiments and best mode for carrying out the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic view of a motor vehicle having a power system employing an axial - flux motor - generator for propulsion.

[0047] Figure 2 is according to an embodiment of the present disclosure Figure 1 A schematic close - up exploded partial perspective view of the motor - generator shown in, depicting a stator assembly having first and second rotors, each rotor having a permanent - magnet (PM) disk with a continuous Halbach magnetization distribution.

[0048] Figure 3 is according to the present disclosure Figure 2 A schematic close - up partial side view of the motor - generator shown in, depicting a slotless embodiment of the stator structure and a phase - angle shift between the continuous Halbach magnetization distributions of the first and second PM disks.

[0049] Figure 4 is according to the present disclosure Figure 2 A schematic close - up exploded partial perspective view of the motor - generator shown in, depicting a printed - circuit embodiment of the stator - assembly magnetic poles.

[0050] Figure 5 A schematic partial front view of a representative motor - generator rotor according to an embodiment of the present disclosure, depicting the concentric - ring structure of the PM disk.

[0051] Figure 6Is a schematic partial front view of a representative motor - generator rotor according to an embodiment of the present disclosure, depicting the helically formed annular structure of the PM disk. Detailed Description

[0052] The embodiments of the present disclosure described herein are intended to be illustrative examples. Other embodiments may take different and alternative forms. Additionally, the drawings are generally schematic and are not necessarily drawn to scale. Some features may be exaggerated or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to use the present disclosure in various ways.

[0053] Certain terms may be used for reference purposes in the following description and are thus not intended to be limiting. For example, terms such as "above" and "below" refer to directions in the referenced drawings. Terms such as "front", "rear", "forward", "rearward", "left", "right", "rear portion", and "side" describe the orientation and / or position of portions of a component or element within a consistent but arbitrary reference frame, which becomes clear by reference to the text describing the component or element in question and the associated drawings. Additionally, terms such as "first", "second", "third", etc. may be used to describe separate components. Such terms may include the specifically mentioned words above, their derivatives, and words of similar meaning.

[0054] Reference Figure 1 , depicts a motor vehicle 10 having a power system 12. The vehicle 10 may include, but is not limited to, commercial vehicles, industrial vehicles, passenger vehicles, aircraft, vessels, trains, etc. It is also contemplated that the vehicle 10 may be a mobile platform, such as an airplane, all - terrain vehicle (ATV), boat, personal mobility device, robot, etc., for the purposes of the present disclosure. The power system 12 includes a first power source 14, which is depicted as an electric motor - generator and is configured to generate a first power source torque T1 ( Figure 1 shown in) for propelling the vehicle 10 via a driven wheel 16 (such as relative to a road surface). The motor - generator 14 is configured as a reluctance machine, where non - permanent magnetic poles are induced on the (multiple) ferromagnetic rotors of the motor, which will be described in detail below.

[0055] As Figure 1As shown, the powertrain 12 may further include a second power source 20, such as an internal combustion engine, configured to generate a second power source torque T2. The power sources 14 and 20 may act in concert to power the vehicle 10 and are operatively connected to the transmission assembly 22. The transmission assembly 22 may be configured to transfer the first power source torque T1 and / or the second power source torque T2 to the final drive unit 24, which in turn may be connected to the driven wheels 16. The first power source 14 (which will be referred to as the motor-generator for the remainder of the present disclosure) may be mounted, for example, to the second power source 20, to (or incorporated into) the transmission assembly 22, to the final drive unit 24, or as a separate assembly mounted to the structure of the vehicle 10. Alternatively, the respective first power sources 14 may be incorporated into each driven wheel 16 as in-wheel / hub motors. As shown, the vehicle 10 additionally includes a programmable electronic controller 26 and various other vehicle systems, the programmable electronic controller 26 being configured to control the powertrain 12 to generate a predetermined amount of power source torque T. The vehicle 10 additionally includes an energy storage system 28, such as one or more batteries, configured to generate and store electrical energy for powering the power sources 14 and 20.

[0056] As Figure 2 As shown, the motor-generator 14 includes a rotationally fixed stator 30. The stator 30 defines a rotational axis X and includes a stator core 30A and a plurality of magnetic poles 30B radially disposed about the rotational axis X. The stator 30 has two opposite sides - a first side 30-1 and a second side 30-2. The motor-generator 14 further includes a first rotor 32 axially spaced from the first side 30-1 of the stator 30, creating an operating air gap therebetween. The first rotor 32 is rotatably mounted coaxially with the rotational axis X and has a first rotor outer side or surface 32-1 facing the stator 30 and an opposite rotor outer side or surface 30-2. The first rotor 32 includes a first permanent magnet (PM) disk 36. As shown, the PM disk 36 has a continuous Halbach magnetization distribution 38, where the term "continuous" specifically describes a non-interrupted or non-segmented structure having a magnetic field vector that rotates in a repeating flow pattern along a circular path.

[0057] Generally, a "Halbach array" is a specific arrangement of discrete permanent magnets that provides a spatially rotating or alternating magnetic field vector that enhances the magnetic field on one side of the array while canceling the magnetic field to near zero on the other side. The net effect of the Halbach arrangement is a unilateral magnetic flux distribution that roughly resembles many horseshoe magnets placed adjacent to each other with like poles in contact. The most significant advantage of a Halbach array is the generation of a significantly stronger magnetic field on one side of the array with minimized stray fields on the opposite side of the array.

[0058] The continuous Halbach magnetization distribution 38 is a spatially rotating or alternating magnetic field vector that has the effect of converging and enhancing the magnetic flux on the outer surface 32-1 of the first rotor while canceling the magnetic flux on the opposing surface 32-2. As a result, the magnetic field generated by the continuous Halbach magnetization distribution 38 is very strong on the outer surface 32-1 of the first rotor. Additionally, the resulting magnetic field is significantly stronger compared to other rotor structures with a similar amount of magnet alloy (e.g., discrete alternating south and north pole permanent magnets arranged on a ferromagnetic rotor core). The motor-generator 14 can additionally include a second rotor 40 that is rotatably mounted coaxially with the axis of rotation X and is axially spaced from the second side 30-2 of the stator 30. The second rotor 40 can be characterized by an outer surface 40-1 of the second rotor facing the stator 30 and an opposing outer side or surface 40-2 of the rotor.

[0059] As Figure 2 shown, the second rotor 40 includes a second PM disk 42 having a similar continuous Halbach magnetization distribution 38. As Figure 3 shown, the stator core 30A can be characterized by a slotless structure that defines stator poles 30B. Generally, a slotted stator uses a set of electrical steel laminations assembled to form a solid stack. The outer section of each lamination includes a ring of material from which a pattern of teeth is radially arranged and extends towards the rotor. Then, electromagnetic coils are wound around the teeth or inserted into each slot between the teeth (as Figure 2 can be seen). The laminated stack and the wound copper coils form the stator assembly. A slotless stator typically enhances motor smoothness, produces a predictable motor torque output with minimal nonlinear effects, and reduces noise and vibration via a low cogging effect, enabling cooler and smoother operation and higher speeds. Such a slotless stator advantageously works with sinusoidal drives (such as PM disks 36, 42 having a continuous Halbach magnetization distribution 38) to produce reduced torque ripple and negligible distortion in the output torque. Alternatively, as Figure 4 shown, the poles 30B of the stator 30 can be defined by a printed circuit board (PCB) structure. In a PCB stator, the copper windings visible in a conventional stator are replaced by a stator having an ultra-thin printed circuit board that positions copper conductors in particularly desired locations. The PCB stator structure results in a more efficient machine that uses a fraction of the copper required by a conventional motor.

[0060] A continuous Halbach magnetization distribution 38 can extend around the circumference of the respective rotors 32, 40 such that the first PM disk 36 has a periodic or sinusoidal pattern 44-1 and the second PM disk 42 has a corresponding periodic pattern 44-2. Each of the first rotor 32 and the second rotor 40 with the respective PM disks 36, 42 can be characterized by the absence of a ferromagnetic rotor core. When installed in the motor-generator 14, the periodic pattern 44-1 of the first PM disk 36 can be phase angle aligned with the periodic pattern 44-2 of the second PM disk 42 ( Figure 2 and Figure 4 as shown in). Alternatively, the periodic pattern 44-1 of the first PM disk 36 can be rotated or phase angle offset relative to the periodic pattern 44-2 of the second PM disk 42, as Figure 3 shown in.

[0061] For example, as Figure 3 shown in, the first rotor 32 and the second rotor 40 can be substantially identical, where the PM disk 36 is essentially a replica of the PM disk 42. A phase angle offset between the respective PM disks 36, 42 will cause the periodic pattern 44-1 to be positioned misaligned relative to the periodic pattern 44-2. Such a phase angle offset of the periodic pattern 44-1 relative to the periodic pattern 44-2 can be used to reduce the cogging torque between the two PM disks 36, 42 and the stator 30 and to change the reluctance of the electric motor 14. Reluctance is generally defined as the ratio of magnetomotive force (mmf) to magnetic flux, represents the resistance to magnetic flux, and generally depends on the geometry and composition of the object. Two rotor disks 36, 42 with magnetic poles of the same or opposite magnetic polarities can be envisioned. In the case of the same polarity, two back-to-back stators 30 sharing a common back iron will be employed. In the case of opposite polarities, one common stator disk 30 can be used for the two rotor disks 36, 42 and used between the two rotor disks 36, 42.

[0062] As Figure 5 shown in, each of the first PM disk 36 and the second PM disk 42 can include a plurality of concentrically arranged rings 46. In such an embodiment, each subject ring 46 can have a continuous Halbach magnetization distribution 38. As Figure 2 shown in, the first rotor 32 can additionally include a first support structure 48-1, while the second rotor 40 can include a second support structure 48-2. The first support structure 48-1 and the second support structure 48-2 can be used to mount Figure 5 the concentric rings 46 of the respective PM disks 36, 42 shown in. The respective first support structure 48-1 and second support structure 48-2 can be made of an iron-containing material such as silicon steel or a non-iron material such as aluminum or polymer. Alternatively, as Figure 6As shown, each of the first PM disk 36 and the second PM disk 42 may include a structure 50 helically formed in the radial direction having a continuous Halbach magnetization distribution 38.

[0063] Generally speaking, the continuous Halbach magnetization distribution 38 of the PM disks 36, 42 provides an alternating or periodic magnetization field pattern for the electric motor rotor to rotate relative to the stator. This spatially rotating magnetic field converges and enhances the magnetic field on the rotor surface facing the stator. Compared with the rotor structure using alternating south and north pole permanent magnets arranged on a ferromagnetic rotor core, the net effect of the continuous Halbach magnetization distribution of the PM disks is a stronger magnetic field and motor output torque. The electric motor may also use a specific stator configuration to supplement the above characteristics of the PM disks 36, 42, and further enhance the effectiveness of the continuous Halbach magnetization distribution and the operation of the motor.

[0064] The detailed description and the drawings or figures support and describe the present disclosure, but the scope of the present disclosure is defined only by the claims. Although the best mode for implementing the claimed disclosure and some of the other embodiments have been described in detail, there are various alternative designs and embodiments for practicing the disclosure defined in the appended claims. In addition, the features of the embodiments shown in the drawings or various embodiments mentioned in this specification are not necessarily to be understood as independent embodiments of each other. On the contrary, it is possible that each feature described in one of the examples of an embodiment can be combined with one or more other desired features from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Therefore, these other embodiments fall within the framework of the scope of the appended claims.

Claims

1. An axial flux electric motor comprising: a rotationally fixed stator defining an axis of rotation and having a plurality of electrically conductive stator poles radially arranged about the axis of rotation; and A first rotor, axially spaced from one side of the stator, is rotatably mounted coaxially with the rotation axis, characterized by a first rotor outer surface facing the stator, and includes a first permanent magnet PM disk having a continuous Halbach magnetization distribution.

2. The axial flux electric motor of claim 1 further comprising a second rotor axially spaced apart from the other side of the stator, characterized in that A second rotor outer surface faces the stator and is rotatably mounted coaxially with the rotation axis and includes a second PM disk having the continuous Halbach magnetization distribution.

3. The axial flux electric motor according to claim 2, wherein: The continuous Halbach magnetization distribution of each of the first PM disk and the second PM disk has a periodic pattern.

4. The axial flux electric motor according to claim 3, wherein: The periodic pattern of the first PM disk is phase angle aligned with the periodic pattern of the second PM disk.

5. The axial flux electric motor of claim 3, wherein: The periodic pattern of the first PM disk is phase angle shifted relative to the periodic pattern of the second PM disk.

6. The axial flux electric motor of claim 2, wherein: Each of the first PM disk and the second PM disk includes a plurality of concentrically arranged rings, and wherein each ring has the continuous Halbach magnetization distribution.

7. The axial flux electric motor of claim 6, wherein: The first rotor additionally includes a first support structure, and the second rotor additionally includes a second support structure, and wherein each of the plurality of concentrically arranged rings of the first and second PM disks are mounted to the respective first and second support structures.

8. The axial flux electric motor of claim 2, wherein: Each of the first PM disk and the second PM disk includes a spirally formed structure having the continuous Halbach magnetization distribution.

9. A rotor for mounting on a rotating axis in an axial flux electric motor, comprising: Permanent magnet PM disk with a continuous Halbach magnetization distribution.

10. A motor vehicle comprising: An axial flux electric motor configured to generate torque for propelling the motor vehicle, the axial flux electric motor comprising: a rotationally fixed stator defining an axis of rotation and having a plurality of electrically conductive stator poles radially arranged about the axis of rotation; a first rotor axially spaced from one side of the stator, rotatably mounted coaxially with the rotation axis, characterized by a first rotor outer surface facing the stator, and comprising a first permanent magnet PM disk having a continuous Halbach magnetization distribution; and a second rotor axially spaced from the other side of the stator, characterized by a second rotor outer surface facing the stator and rotatably mounted coaxially with the axis of rotation, and comprising a second PM disk having the continuous Halbach magnetization distribution; Wherein, the continuous Halbach magnetization distribution of each of the first PM disk and the second PM disk has a periodic pattern.

Images