Reluctance assisted axial flux electric motor
By designing alternating South and North Pole permanent magnets and phase-angle offset core convex poles on the rotor of the axial flux electric motor, the problem of torque pulsation under high loads is solved, the motor output torque and efficiency are improved, and the noise is reduced.
Patent Information
- Application Number
- CN202311285744.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-28
- Publication Date
- 2025-03-28
AI Technical Summary
Axial flux electric motors are prone to torque pulsation under high load conditions, resulting in reduced noise and efficiency.
An axial flux electric motor is designed, with its rotor including alternating South and North Pole permanent magnets and core convex poles, which are shifted with respect to the phase angle of the permanent magnet, thereby changing the magnetic resistance of the motor.
By adjusting the magnetoresistance, torque pulsation is reduced, the motor output torque and efficiency are improved, while reducing noise.
Smart Images
Figure CN119727275A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a reluctance assisted axial flux electric motor. 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 field generated by the 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 stator of the machine, located parallel to the axis of rotation in axial flux motors and radially in radial flux motors, determines the direction of the magnetic flux of the motor.
[0003] Axial and radial flux motors can be configured as switched reluctance machines. In general, a reluctance machine induces non-permanent magnetic poles on a ferromagnetic rotor. The rotor of such a machine usually has no windings, and torque is generated by reluctance. Reluctance machine subtypes include synchronous, variable speed, switched mode, and variable speed stepper motors. Reluctance motors can provide high power density, but if the reluctance is combined with the torque from the magnets, the reluctance motor may experience significant high load torque fluctuations or "torque ripple" (the difference between maximum and minimum torque during one revolution), which may also generate noise.
[0004] Typically, axial flux motors have a relatively denser and shorter flux flow path. In addition, the rotor magnets can be located farther away from the central rotational axis of the axial motor than in radial flux motors. As a result, axial flux motors generally have higher torque-to-weight and torque-to-size ratios than radial flux motors. Like all forms of AC synchronous electric motors, the magnets on the rotor of an axial flux motor are attracted to a rotating magnetic field generated by a surrounding ring of independent electromagnets in the stator. Because the switching of the magnets that causes the magnetic field to rotate is typically not completely smooth, the rotor is subject to torque pulsations. Summary of the invention
[0005] An axial flux electric motor includes a rotating fixed stator defining an axis of rotation and having a plurality of electrically conductive stator poles radially arranged about the axis of rotation. The axial flux electric motor also includes a first rotor axially spaced from the stator from one side, having a first rotor outer surface facing the stator, and rotatably mounted coaxially with the axis of rotation. The first rotor includes a first ferromagnetic rotor core and a plurality of alternating south and north pole permanent magnets (PMs) symmetrically arranged about the axis of rotation on the first ferromagnetic rotor core and facing the stator. The first ferromagnetic rotor core includes a plurality of first core salient poles extending to the outer surface of the first rotor. Each of the first core salient poles is arranged between a first south pole PM and a first north pole PM. The plurality of first core salient poles are phase-angle offset relative to the plurality of alternating south pole PMs and north pole PMs, thereby changing the magnetic resistance of the electric motor.
[0006] The axial flux electric motor may also include a second rotor axially spaced from the stator from the other side, having a second rotor outer surface facing the stator, and rotatably mounted coaxially with the axis of rotation. The second rotor includes a second ferromagnetic rotor core and a second plurality of alternating south poles PM and north poles PM, which are symmetrically arranged on the second ferromagnetic rotor core on the second rotor outer surface around the axis of rotation. The second ferromagnetic rotor core may include a plurality of second core salient poles extending to the second rotor outer surface. Each of the second core salient poles is arranged between a second south pole PM and a first north pole PM. The plurality of second core salient poles may be phase-aligned with the plurality of first core salient poles or phase-angle offset relative to the plurality of first core salient poles. The plurality of second alternating south pole PMs and north pole PMs may be phase-angle offset relative to the plurality of first alternating south pole PMs and north pole PMs, thereby further changing the magnetic resistance of the motor.
[0007] In each pair of alternating south pole PM and north pole PM of the first rotor, the corresponding first core salient pole may be disposed angularly closer to the corresponding south pole PM than to the corresponding north pole PM.
[0008] In each pair of alternating south pole PM and north pole PM of the first rotor, the corresponding core salient pole may be disposed angularly closer to the corresponding north pole PM than to the corresponding south pole PM.
[0009] Each of the plurality of alternating south pole PMs and north pole PMs of the first rotor may be a corresponding PM group including PMs of relatively high radial span and PMs of relatively low radial span.
[0010] In each PM group, PMs of relatively low radial span may be arranged radially closer to the axis of rotation than PMs of relatively high radial span.
[0011] In each PM group, PMs of relatively high radial span may be arranged radially closer to the axis of rotation than PMs of relatively low radial span.
[0012] Each of the first core salient poles may be embedded in a corresponding group of PMs adjacent to a relatively low radial span PM.
[0013] In each PM group, PMs of relatively high radial span and PMs of relatively low radial span may be radially arranged to produce a radially straight PM group edge opposite the embedded salient poles.
[0014] In each PM group, the embedded salient poles may extend to overlap an edge of at least one of a relatively high radial span PM and a relatively low radial span PM to mechanically retain the corresponding PM on the first rotor.
[0015] The present invention provides the following technical solutions.
[0016] Technical Solution 1. An axial flux electric motor, comprising:
[0017] 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;
[0018] a first rotor axially spaced from the stator from one side, having a first rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein:
[0019] The first rotor comprises a first ferromagnetic rotor core and a plurality of first alternating south pole permanent magnets PM and north pole permanent magnets, the plurality of first alternating south poles PM and north poles PM being symmetrically arranged on the first ferromagnetic rotor core around the rotation axis and facing the stator;
[0020] The first ferromagnetic rotor core includes a plurality of first core salient poles extending to an outer surface of the first rotor;
[0021] Each of the first core salient poles is arranged between a first south pole PM and a first north pole PM; and
[0022] The plurality of first core salient poles are phase angle offset relative to the plurality of first alternating south poles PM and north poles PM to vary a reluctance of the electric motor.
[0023] Technical Solution 2. The axial flux electric motor according to Technical Solution 1 further includes a second rotor, which is axially spaced apart from the stator from the other side, has a second rotor outer surface facing the stator, and is rotatably mounted coaxially with the rotation axis, wherein:
[0024] The second rotor comprises a second ferromagnetic rotor core and a plurality of second alternating south poles PM and north poles PM, wherein the plurality of second alternating south poles PM and north poles PM are symmetrically arranged on the second ferromagnetic rotor core around the rotation axis and face the stator;
[0025] The second ferromagnetic rotor core includes a plurality of second core salient poles extending to an outer surface of the second rotor;
[0026] Each of the second core salient poles is arranged between a second south pole PM and a second north pole PM;
[0027] The plurality of second core salient poles are phase-aligned with or phase-shifted relative to the plurality of first core salient poles; and
[0028] The second plurality of alternating south pole PM and north pole PM are phase angle offset relative to the first plurality of alternating south pole PM and north pole PM to further vary the electric motor reluctance.
[0029] Technical Solution 3. An axial flux electric motor according to Technical Solution 1, wherein, in each pair of first alternating south poles PM and north poles PM, the corresponding first magnetic salient pole is angularly closer to the corresponding south pole PM than to the corresponding north pole PM.
[0030] Technical Solution 4. An axial flux electric motor according to Technical Solution 1, wherein, in each pair of first alternating south poles PM and north poles PM, the corresponding first magnetic salient pole is angularly closer to the corresponding north pole PM than to the corresponding south pole PM.
[0031] Technical Solution 5. An axial flux electric motor according to Technical Solution 1, wherein each of the plurality of first alternating south pole PMs and north pole PMs is a corresponding PM group, and the corresponding PM group includes a PM with a relatively high radial span and a PM with a relatively low radial span.
[0032] Technical Solution 6. An axial flux electric motor according to Technical Solution 5, wherein, in each PM group, the PMs with relatively low radial span are arranged radially closer to the rotation axis than the PMs with relatively high radial span.
[0033] Technical Solution 7. An axial flux electric motor according to Technical Solution 5, wherein, in each PM group, the PMs with relatively high radial span are arranged radially closer to the rotation axis than the PMs with relatively low radial span.
[0034] Technical Solution 8. An axial flux electric motor according to Technical Solution 5, wherein each of the first core salient poles is embedded in the corresponding PM group adjacent to the PM with relatively low radial span.
[0035] Technical Solution 9. An axial flux electric motor according to Technical Solution 8, wherein, in each PM group, the PMs with relatively high radial span and the PMs with relatively low radial span are radially arranged to produce a radially straight PM group edge opposite to the embedded salient pole.
[0036] Technical Solution 10. An axial flux electric motor according to Technical Solution 8, wherein, in each PM group, the embedded salient pole extends to overlap with the edge of at least one of the PMs with a relatively high radial span and the PMs with a relatively low radial span, thereby mechanically fixing the corresponding PM on the first rotor.
[0037] Technical Solution 11. A rotor for mounting on a rotating axis in an axial flux electric motor, comprising:
[0038] ferromagnetic rotor core;
[0039] a plurality of alternating south pole permanent magnets PM and north pole permanent magnets arranged symmetrically around the rotation axis on the ferromagnetic rotor core;
[0040] The ferromagnetic rotor core includes a plurality of core salient poles extending to an outer surface of the rotor;
[0041] Each pair of alternating south pole PM and north pole PM includes one of the core salient poles disposed therebetween;
[0042] Each of the core salient poles is arranged between a south pole PM and a north pole PM; and
[0043] The plurality of core salient poles are phase angle offset relative to the plurality of alternating south PM and north PM poles to vary the reluctance of the electric motor.
[0044] Technical Solution 12. A rotor according to Technical Solution 11, wherein, in each pair of alternating south pole PM and north pole PM, the corresponding magnetic salient pole is angularly closer to the corresponding south pole PM than to the corresponding north pole PM.
[0045] Technical Solution 13. A rotor according to Technical Solution 11, wherein, in each pair of alternating south pole PM and north pole PM, the corresponding magnetic salient pole is angularly closer to the corresponding north pole PM than to the corresponding south pole PM.
[0046] Technical Solution 14. A rotor according to Technical Solution 11, wherein each of the plurality of alternating south pole PMs and north pole PMs is a corresponding PM group, and the corresponding PM group includes PMs with relatively high radial span and PMs with relatively low radial span.
[0047] Technical Solution 15. A rotor according to Technical Solution 14, wherein, in each PM group, the PMs with relatively low radial span are arranged radially closer to the rotation axis than the PMs with relatively high radial span.
[0048] Technical Solution 16. A rotor according to Technical Solution 14, wherein, in each PM group, the PMs with relatively high radial span are arranged radially closer to the rotation axis than the PMs with relatively low radial span.
[0049] Technical Solution 17. A rotor according to Technical Solution 14, wherein each of the core salient poles is embedded in the corresponding PM group adjacent to the PM with relatively low radial span.
[0050] Technical Solution 18. A rotor according to Technical Solution 17, wherein, in each PM group, the PMs with relatively high radial span and the PMs with relatively low radial span are radially arranged to produce a radially straight PM group edge opposite to the embedded salient poles.
[0051] Technical Solution 19. A rotor according to Technical Solution 17, wherein, in each PM group, the embedded salient pole extends to overlap with the edge of at least one of the PMs with relatively high radial span and the PMs with relatively low radial span, and thereby mechanically holds the corresponding PM on the rotor.
[0052] Technical Solution 20. An axial flux electric motor, comprising:
[0053] 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;
[0054] a first rotor axially spaced from the stator from one side, having a first rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein:
[0055] The first rotor comprises a first ferromagnetic rotor core and a plurality of first alternating south pole permanent magnets PM and north pole permanent magnets, the plurality of first alternating south poles PM and north poles PM being symmetrically arranged on the first ferromagnetic rotor core around the rotation axis and facing the stator;
[0056] The first ferromagnetic rotor core includes a plurality of first core salient poles extending to an outer surface of the first rotor;
[0057] Each of the first core salient poles is arranged between a first south pole PM and a first north pole PM; and
[0058] The plurality of first core salient poles are phase angle offset relative to the plurality of first alternating south PM and north PM poles to thereby vary the reluctance of the electric motor; and
[0059] a second rotor axially spaced from the stator from the other side, having a second rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein:
[0060] The second rotor includes a second ferromagnetic rotor core and a second plurality of alternating south poles.
[0061] PM and north pole PM, the plurality of second alternating south pole PM and north pole PM are symmetrically arranged around the rotation axis on the second ferromagnetic rotor core and face the stator;
[0062] The second ferromagnetic rotor core includes a plurality of second core salient poles extending to an outer surface of the second rotor;
[0063] Each of the second core salient poles is arranged between a second south pole PM and a second north pole PM;
[0064] The plurality of second core salient poles are phase-aligned with or phase-shifted relative to the plurality of first core salient poles; and
[0065] The second plurality of alternating south poles PM and north poles PM are phase angle offset relative to the first plurality of alternating south poles PM and north poles PM, thereby further changing the motor reluctance.
[0066] The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the embodiments and the best mode for carrying out the disclosure when taken in conjunction with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS
[0067] Figure 1 is a schematic diagram of a motor vehicle having a powertrain employing an axial flux electric motor-generator for propulsion.
[0068] Figure 2 According to the embodiment of the present disclosure Figure 1 A schematic close-up exploded partial perspective view of a motor-generator shown in , depicting a stator assembly having first and second rotors, each having alternating south and north pole permanent magnets (PMs) and core salient poles disposed therebetween.
[0069] Figure 3A According to the embodiment of the present disclosure Figure 2The schematic cross-sectional partial side view of the first rotor assembly shown in , depicts an embodiment of a phase angle offset between the first core salient poles and a plurality of alternating first south pole PM and north pole PM.
[0070] Figure 3B According to the embodiment of the present disclosure Figure 2 The schematic cross-sectional partial side view of the first rotor assembly shown in , depicts another embodiment of the phase angle offset between the first core salient poles and the first plurality of alternating south pole PMs and north pole PMs.
[0071] Figure 4A According to the present disclosure Figure 3A A graphical illustration of the effect of phase angle offset on the output torque of an electric motor is shown in FIG.
[0072] Figure 4B According to the present disclosure Figure 3B A graphical illustration of the effect of phase angle offset on the output torque of an electric motor is shown in FIG.
[0073] Figure 5A According to the present disclosure Figure 2 The schematic cross-sectional partial front view of the first rotor shown in , depicts an embodiment of alternating south pole PMs and north pole PMs configured as respective PM groups having relatively high radial span PMs and relatively low radial span PMs.
[0074] Figure 5B According to the present disclosure Figure 2 Schematic cross-sectional partial front view of the first rotor shown in , depicting another embodiment of alternating south pole PM and north pole PM groups.
[0075] Figure 5C According to the present disclosure Figure 2 The schematic cross-sectional partial front view of the first rotor shown in , depicts corresponding South Pole PM and North Pole PM groups, each of which has a radially straight PM group edge relatively aligned with the corresponding embedded salient poles, and the embedded salient poles mechanically retain the corresponding PMs.
[0076] Figure 6 According to the present disclosure Figure 2 A schematic partial perspective view of a motor-generator shown in , depicting a second core salient pole aligned in phase with a first plurality of core salient poles and a second plurality of alternating south pole PMs and north pole PMs phase angle offset relative to a first plurality of alternating south pole PMs and north pole PMs. DETAILED DESCRIPTION
[0077] The embodiments of the present disclosure described herein are intended to be used as examples. Other embodiments may take different and alternative forms. In addition, the drawings are generally schematic diagrams and are not necessarily drawn to scale. Some features may be exaggerated or minimized to show the details of specific components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to use the present disclosure in various ways.
[0078] Certain terms may be used in the following description for reference purposes and are therefore not intended to be limiting. For example, terms such as "above" and "below" refer to directions in the drawings to which reference is made. Terms such as "front," "rear," "front," "rear," "left," "right," "rear," and "side" describe the orientation and / or position of parts of a component or element within a consistent but arbitrary reference system, which becomes clear by reference to the text and associated drawings describing the component or element in question. In addition, terms such as "first," "second," "third," etc. may be used to describe individual components. Such terms may include the words specifically mentioned above, their derivatives, and words of similar meaning.
[0079] refer to Figure 1 , depicting a motor vehicle 10 having a power system 12. The vehicle 10 may include, but is not limited to, a commercial vehicle, an industrial vehicle, a passenger vehicle, an aircraft, a ship, a train, etc. It is also contemplated that the vehicle 10 may be a mobile platform, such as an airplane, an all-terrain vehicle (ATV), a boat, a personal sports device, a robot, etc., for 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 ) for propelling the vehicle 10 via driven wheels 16 (such as against a road surface). The motor-generator 14 is configured as a reluctance machine in which non-permanent magnetic poles are induced on a ferromagnetic rotor(s) of the motor as described in detail below.
[0080] like Figure 1As shown in , the power system 12 may also include a second power source 20, such as an internal combustion engine, which is configured to produce a second power source torque T2. The power sources 14 and 20 may act in concert to provide power to the vehicle 10 and are operatively connected to a transmission assembly 22. The transmission assembly 22 may be configured to transmit the first power source torque T1 and / or the second power source torque T2 to a 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 a motor-generator in the remainder of this disclosure) may be, for example, mounted to the second power source 20, mounted to (or coupled to) the transmission assembly 22, mounted to the final drive unit 24, or may be a separate component mounted to the structure of the vehicle 10. As shown, the vehicle 10 additionally includes a programmable electronic controller 26 and various other vehicle systems, which is configured to control the power system 12 to produce a predetermined amount of power source torque T. Vehicle 10 additionally includes an energy storage system 28 , such as one or more batteries, that is configured to generate and store electrical energy for powering power sources 14 and 20 .
[0081] like Figure 2 As shown in , the motor-generator 14 includes a rotationally fixed stator 30. The stator 30 defines an axis of rotation X and includes a stator core 30A and a plurality of magnetic poles 30B radially arranged around the axis of rotation. The stator 30 has two opposing sides, a first side 30-1 and a second side 30-2. The motor-generator 14 also includes a first rotor 32, which is axially spaced from the first side 30-1 of the stator 30, creating an air gap 34 therebetween. The first rotor 32 is rotatably mounted coaxially with the axis of rotation X and has a first rotor outer surface 32-1 facing the stator 30. The first rotor 32 includes a first ferromagnetic rotor core 36. The first rotor core 36 may be constructed of a relatively soft magnetic material such as laminated silicon steel, having a plurality of first core protrusions or salient poles 38 that act as magnetic poles via reluctance. Reluctance is defined as the ratio of magnetomotive force (mmf) to magnetic flux, represents resistance to magnetic flux, and generally depends on the geometry and composition of the object. As shown, the first core salient pole 38 extends to the first rotor outer surface 32-1. During operation of the motor-generator 14, non-permanent magnetic poles are continuously induced on the motor's salient poles 38 to produce motor torque.
[0082] The first rotor 32 also includes a plurality of first alternating south pole permanent magnets (PM) 40 and north pole PM 42. The south pole PM 40 and north pole PM 42 are arranged on the first ferromagnetic rotor core 36 substantially symmetrically around the rotation axis X and face the stator 30. Each pair of alternating south pole PM 40 and north pole PM 42 includes one of the first core salient poles 38 arranged therebetween. In other words, each of the first core salient poles 38 is arranged or clamped between a first south pole PM 40 and a first north pole PM 42. The plurality of first core salient poles 38 are, as a whole, phase-angle offset relative to the plurality of first alternating south pole PM 40 and north pole PM 42. The "phase offset" of the first core salient poles 38 relative to the PM 40, 42 is defined herein as each core salient pole being positioned at an uneven or unequal radial distance or angle θ from its two adjacent or surrounding PMs. For example, the angle θ1 may be greater than the angle θ2. In other words, as Figure 3A and Figure 3B As shown in , in each pair of alternating south pole PM 40 and north pole PM 42, the corresponding core salient pole 38 clamped thereby is radially asymmetrically arranged between the corresponding south pole permanent PM and the corresponding north pole PM. The subject phase angle offset of the first core salient pole 38 relative to the alternating south pole PM 40 and north pole PM 42 is configured to change the magnetic resistance of the motor-generator 14 compared to a motor-generator structure having a symmetrically arranged core salient pole relative to the corresponding alternating south pole PM and north pole PM.
[0083] Figure 3A A cross-sectional view of the rotor 32 is depicted wherein, in each alternating pair of south pole PM 40 and north pole PM 42 , the corresponding core salient pole 38 is disposed angularly closer to the corresponding south pole PM 40 than to the corresponding north pole PM 42 . Figure 3A The subject phase shift in is indicated by the distance d1 being greater than the distance d2. Alternatively, as Figure 3B As shown in , in each pair of alternating south pole PM 40 and north pole PM 42 , the corresponding core salient pole 38 may be disposed angularly closer to the corresponding north pole PM 42 than the corresponding south pole PM 40 . Figure 3B The subject phase shift in is indicated by the distance d1 being smaller than the distance d2. Figure 3A The embodiment of the first rotor 32 shown in FIG. 1 is configured to increase the total torque output of the motor-generator 14 and may also affect torque ripple, while Figure 3B The embodiment of the first rotor 32 shown in FIG. 1 is configured to reduce the total torque output. Figure 4A and Figure 4B A comparative torque diagram is shown in FIG. 1 , which depicts PM torque (T ) in a representative motor-generator relative to the angular offset between PMs 40 and 42 and the clamped salient pole 38 . 40 ,T 42 ) relative to the reluctance torque (T38 ) alignment. Figure 4A and Figure 4B Specifically, the corresponding Figure 3A The increased torque output T1 of the embodiment corresponds to Figure 3B The reduced torque output T1 of the embodiment.
[0084] like Figure 5A and Figure 5B As shown in , each of the plurality of first alternating south pole PMs 40 and north pole PMs 42 can be identified as a corresponding PM group 40A and 42A. Each PM group 40A can include a PM 40-1 with a relatively high radial span and a PM 40-2 with a relatively low radial span. Similarly, each PM group 42A can include a PM 42-1 with a relatively high radial span and a PM 42-2 with a relatively low radial span. Figure 5A As shown in FIG. 1 , in each respective PM group 40A, 42A, the PMs 40-2, 42-2 of relatively low radial span may be arranged radially closer to the rotation axis X than the corresponding PMs 40-1, 42-1 of relatively high radial span. Alternatively, as Figure 5B As shown in FIG. 1 , in each respective PM group 40A, 42A, the PMs 40-1, 42-1 of relatively high radial span may be arranged radially closer to the rotation axis X than the corresponding PMs 40-2, 42-2 of relatively low radial span. Each PM group 40A and 42A may have a configuration as shown in FIG. Figure 5A The overall T-shape shown in .
[0085] Each of the first core salient poles 38 arranged between each pair of alternating south pole PM 40 and north pole PM 42 may be embedded in the corresponding PM group 40A, 42A adjacent to the corresponding relatively low radial span PM 40-2, 42-2 ( Figure 5A and Figure 5B In each PM group 40A, 42A, the PMs 40-1, 42-1 of relatively high radial span and the PMs 40-2, 42-2 of relatively low radial span can be radially arranged to produce a corresponding PM group edge 41A opposite to the corresponding embedded salient pole 38, an edge 41B on the opposite side of the PMs 40-2, 42-2 of relatively low radial span, and an opposite edge 41C, as shown in FIG. Figure 5C As shown in the figure, the PM group edge 41A can be configured to be substantially straight in the radial direction, wherein the edges of PM 40-1, 42-1 are aligned with each other, and the edges of PM 40-2, 42-2 are similarly aligned. In addition, the opposing edges 41C of PM groups 40A, 42A can also be substantially straight and aligned with the outer edges of the corresponding embedded salient poles 38. Figure 5CAs shown in FIG. 1 , in each PM group 40A, 42A, the embedded salient pole 38 can extend to overlap with the edge 41B of the relatively low radial span PM 40-2, 42-2 and / or a portion of the adjacent relatively high radial span PM 40-1, 42-1. The subject overlap between the salient pole 38 and the nearby PM can be used to mechanically retain the corresponding PM on the first rotor 32.
[0086] Continue to refer to Figure 2 , the motor-generator 14 may additionally include a second rotor 46, which is axially spaced from the second side 30-2 of the stator 30, creating an air gap 48 therebetween. As shown, the second rotor 46 is rotatably mounted coaxially with the rotation axis X and has a second rotor outer surface 46-1 facing the stator 30. The second rotor 46 includes a second ferromagnetic rotor core 50, which is constructed to be substantially similar to the first rotor core 36 and has a plurality of second core salient poles 52. The second core salient poles 52 extend to the second rotor outer surface 46-1 and act as magnetic poles through magnetic resistance. The second rotor 46 also includes a plurality of second alternating south poles PM 54 and north poles PM 56, which are arranged substantially symmetrically around the rotation axis X on the second ferromagnetic rotor core 50 and face the stator 30.
[0087] As shown, and similar to the first rotor 32, each of the second core salient poles 52 is arranged between a second south pole PM 54 and a second north pole PM 56. The second core salient poles 52 can be phase-aligned with the plurality of second south poles PM 54 and north poles PM 56, i.e., not offset, so that Figure 3A and Figure 3B The distances d1 and d2 shown in FIG. 1 are substantially equal. When installed in the motor-generator 14, the plurality of second core salient poles 52 may also be phase-aligned with the plurality of first core salient poles 38. On the other hand, as shown in FIG. Figure 6 As shown in , the plurality of second alternating south pole PM 54 and north pole PM 56 can be phase angle offset relative to the plurality of first alternating south pole PM 40 and north pole PM 42. The phase angle offset of the alternating south pole PM 54 and north pole PM 56 relative to the alternating south pole PM 40 and north pole PM 42 produces a positional skew 58 of the first rotor PM relative to the second rotor PM along the rotation axis X, and is used to further change the reluctance of the electric motor 14.
[0088] In addition, as described above, the plurality of second core salient poles 52 may be phase-angle offset relative to the plurality of first core salient poles 38, and such an arrangement may be combined with a phase-angle offset PM. The phase-angle offset of the second core salient poles 52 relative to the first core salient poles 38 produces a positional skewness of the first rotor salient pole relative to the second rotor salient pole along the rotation axis X (not explicitly shown, but can be seen from the Figure 3A , Figure 3B and Figure 6 In another embodiment, the first rotor 32 and the second rotor 46 may be substantially identical, but when installed in the motor-generator 14, for example, the rotor 46 is Figure 3A , the phase angle offsets between the respective PMs and salient poles of the two rotors will not be aligned. In other words, when the two substantially identical first rotors 32 and second rotors 46 face each other from opposite sides of the stator 30 (e.g., Figure 2 ), the respective PM and saliency phase angle offsets of the two rotors will be out of phase with respect to each other. Such substantially identical, relatively mounted rotors can similarly be used to vary the reluctance of the electric motor 14.
[0089] In general, the axial flux motor-generator 14 can have one or two rotors. One rotor has core salient poles that are phase-angle offset relative to the south pole PM and the north pole PM to change the reluctance of the motor, thereby assisting in torque generation in the electric motor 14. The alternating south pole PM and north pole PM of the first rotor can be arranged as separate PM groups, each of which includes a PM with a relatively high radial span and a PM with a relatively low radial span. Each of the first rotor salient poles can be embedded in a corresponding PM group adjacent to a PM with a relatively low radial span, thereby achieving a desired phase angle offset. The second rotor can have core salient poles that are phase-aligned with the first core salient poles, while the alternating south pole PM and north pole PM of the second rotor can be phase-angle offset relative to the alternating south pole PM and north pole PM of the first rotor. The second rotor can thereby further change the reluctance of the electric motor.
[0090] The detailed description and the accompanying drawings or figures are support and description of the present disclosure, but the scope of the present disclosure is limited only by the claims. Although the best mode and some of the other embodiments for implementing the claimed disclosure have been described in detail, there are various alternative designs and embodiments for practicing the disclosure defined in the appended claims. In addition, the embodiments shown in the drawings or the features of the various embodiments mentioned in this specification are not necessarily to be understood as embodiments independent 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 that are 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; a first rotor axially spaced from the stator from one side, having a first rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein: The first rotor comprises a first ferromagnetic rotor core and a plurality of first alternating south pole permanent magnets PM and north pole permanent magnets, the plurality of first alternating south poles PM and north poles PM being symmetrically arranged on the first ferromagnetic rotor core around the rotation axis and facing the stator; The first ferromagnetic rotor core includes a plurality of first core salient poles extending to an outer surface of the first rotor; Each of the first core salient poles is arranged between a first south pole PM and a first north pole PM; and The plurality of first core salient poles are phase angle offset relative to the plurality of first alternating south poles PM and north poles PM to vary a reluctance of the electric motor.
2. The axial flux electric motor of claim 1 , further comprising a second rotor axially spaced apart from the stator from another side, having a second rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein: The second rotor comprises a second ferromagnetic rotor core and a plurality of second alternating south poles PM and north poles PM, wherein the plurality of second alternating south poles PM and north poles PM are symmetrically arranged on the second ferromagnetic rotor core around the rotation axis and face the stator; The second ferromagnetic rotor core includes a plurality of second core salient poles extending to an outer surface of the second rotor; Each of the second core salient poles is arranged between a second south pole PM and a second north pole PM; The plurality of second core salient poles are phase-aligned with or phase-shifted relative to the plurality of first core salient poles; and The second plurality of alternating south pole PM and north pole PM are phase angle offset relative to the first plurality of alternating south pole PM and north pole PM to further vary the electric motor reluctance.
3. The axial flux electric motor of claim 1, wherein: In each pair of first alternating south pole PM and north pole PM, the corresponding first magnetic salient pole is angularly closer to the corresponding south pole PM than to the corresponding north pole PM.
4. The axial flux electric motor of claim 1, wherein: In each pair of first alternating south pole PM and north pole PM, the corresponding first magnetic salient pole is angularly closer to the corresponding north pole PM than to the corresponding south pole PM.
5. The axial flux electric motor of claim 1, wherein: Each of the first plurality of alternating south pole PMs and north pole PMs is a respective PM group including PMs of relatively high radial span and PMs of relatively low radial span.
6. The axial flux electric motor according to claim 5, wherein: In each PM group, the PMs of relatively low radial span are arranged radially closer to the rotation axis than the PMs of relatively high radial span.
7. The axial flux electric motor of claim 5, wherein: In each PM group, the PMs of relatively high radial span are arranged radially closer to the rotation axis than the PMs of relatively low radial span.
8. The axial flux electric motor of claim 5, wherein: Each of the first core salient poles is embedded in the corresponding PM group adjacent to the relatively low radial span PM.
9. A rotor for mounting on a rotating axis in an axial flux electric motor, comprising: ferromagnetic rotor core; a plurality of alternating south pole permanent magnets PM and north pole permanent magnets arranged symmetrically around the rotation axis on the ferromagnetic rotor core; The ferromagnetic rotor core includes a plurality of core salient poles extending to an outer surface of the rotor; Each pair of alternating south pole PM and north pole PM includes one of the core salient poles disposed therebetween; Each of the core salient poles is arranged between a south pole PM and a north pole PM; and The plurality of core salient poles are phase angle offset relative to the plurality of alternating south PM and north PM poles to vary the reluctance of the electric motor.
10. 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; a first rotor axially spaced from the stator from one side, having a first rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein: The first rotor comprises a first ferromagnetic rotor core and a plurality of first alternating south pole permanent magnets PM and north pole permanent magnets, the plurality of first alternating south poles PM and north poles PM being symmetrically arranged on the first ferromagnetic rotor core around the rotation axis and facing the stator; The first ferromagnetic rotor core includes a plurality of first core salient poles extending to an outer surface of the first rotor; Each of the first core salient poles is arranged between a first south pole PM and a first north pole PM; and The plurality of first core salient poles are phase angle offset relative to the plurality of first alternating south PM and north PM poles to thereby vary the reluctance of the electric motor; and a second rotor axially spaced from the stator from the other side, having a second rotor outer surface facing the stator, and rotatably mounted coaxially with the rotation axis, wherein: The second rotor comprises a second ferromagnetic rotor core and a plurality of second alternating south poles PM and north poles PM, wherein the plurality of second alternating south poles PM and north poles PM are symmetrically arranged on the second ferromagnetic rotor core around the rotation axis and face the stator; The second ferromagnetic rotor core includes a plurality of second core salient poles extending to an outer surface of the second rotor; Each of the second core salient poles is arranged between a second south pole PM and a second north pole PM; The plurality of second core salient poles are phase-aligned with or phase-shifted relative to the plurality of first core salient poles; and The second plurality of alternating south poles PM and north poles PM are phase angle offset relative to the first plurality of alternating south poles PM and north poles PM, thereby further changing the motor reluctance.