ELECTRICAL MACHINE

A stator for an electrical machine defines a central axis and has a first stator face facing parallel to the central axis and a second stator face facing parallel to the central axis, with the first stator face and the second stator face facing in opposite directions. The stator includes a plurality of ferromagnetic segments disposed about the central axis, each segment having a pair of parallel faces that face parallel to the central axis of the stator. On each stator face, faces of adjacent segments of the plurality of segments form gaps therebetween, the gaps extending radially relative to the central axis, the gaps on the first stator face being angularly offset relative to the central axis from the gaps on the second stator face.

CROSS REFERENCE TO RELATED APPLICATIONS

This disclosure claims priority to China Patent Application 202311162024.2 filed on Sep. 8, 2023, which is hereby incorporated by reference.

INTRODUCTION

The present disclosure is in the field of electrical machines.

Several configurations of electrical machines may be suitable for various applications. One configuration of electrical machine is an axial-flux permanent magnet machine. Such a machine may offer high power density and relatively small thickness, providing packaging advantages in some applications.

Axial-flux permanent magnet machines may, however, be capable of performance improvements.

SUMMARY

A stator for an electrical machine defines a central axis and has a first stator face facing parallel to the central axis and a second stator face facing parallel to the central axis, with the first stator face and the second stator face facing in opposite directions. The stator includes a plurality of ferromagnetic segments disposed about the central axis, each segment having a pair of parallel faces that face parallel to the central axis of the stator. On each stator face, faces of adjacent segments of the plurality of segments form gaps therebetween, the gaps extending radially relative to the central axis, the gaps on the first stator face being angularly offset relative to the central axis from the gaps on the second stator face. The stator also includes electrically conductive windings disposed about the segments and located in slots therebetween, the windings defining axes parallel to the central axis of the stator.

As a variation, each segment of the stator, when viewed radially inwardly toward the central axis of the stator, may form a “T” shape. As an additional variation, each segment of the stator may be identical or substantially identical in geometry.

For each segment of the stator, one face of the pair of faces may be larger than the other face of the pair of faces. Additionally, a first segment of the plurality of segments may have second and third segments of the plurality of segments adjacent thereto, with the larger face of the first segment facing in an opposite direction from the larger faces of the second and third segments.

In further variations, one face of each segment of the stator may at least partially overhang at least one slot. Further, the segments of the stator may each consist of two pieces fastened together. Yet further, the segments of the stator may comprise laminations.

An electrical machine includes a stator that defines a central axis and has a first stator face facing parallel to the central axis and a second stator face facing parallel to the central axis, with the first stator face and the second stator face facing in opposite directions. The stator includes a plurality of ferromagnetic segments disposed about the central axis, each segment having a pair of parallel faces that face parallel to the central axis of the stator. On each stator face, faces of adjacent segments of the plurality of segments form gaps therebetween, the gaps extending radially relative to the central axis, the gaps on the first stator face being angularly offset relative to the central axis from the gaps on the second stator face. The stator also includes electrically conductive windings disposed about the segments and located in slots therebetween, the windings defining axes parallel to the central axis of the stator. The electrical machine additionally includes a first rotor disposed coaxially with the central axis for rotation relative to the stator and axially spaced from the stator by a first air gap and a second rotor disposed coaxially with the central axis for rotation relative to the stator and axially spaced from the stator by a second air gap. A motor vehicle may comprise the electrical machine.

An alternative stator for an electrical machine defines a central axis. The stator includes a plurality of segments disposed about the central axis of the stator, each segment having a pair of parallel faces that face parallel to the central axis of the stator and in opposite directions. For each segment, one face of the pair of faces has a different shape than the other face of the pair of faces. The stator also includes electrically conductive windings disposed about the segments and disposed in slots therebetween, the windings defining axes parallel to the central axis of the stator.

In variations of the alternative stator, each segment, when viewed radially inwardly toward the central axis of the stator, may form a “T” shape. Additionally, the segments of the stator may be identical or substantially identical in geometry. Yet further, one face of each segment may at least partially overhang at least one slot, or exactly one face of each segment may at least partially overhang at least one slot. As an enhancement, the segments may comprise metal laminations.

As an additional enhancement of the alternative stator, one face of the pair of faces of each segment may be larger in surface area than the other face of the pair of faces. Further, a first segment of the plurality of segments may have second and third segments of the plurality of segments adjacent thereto, and the larger face of the first segment may in an opposite direction from the larger faces of the second and third segments.

The above summary does not represent every embodiment or every aspect of this disclosure. Other possible features and advantages will be readily apparent from the following detailed description of the embodiments for carrying out the disclosure when taken in connection with the accompanying drawings and appended claims. Further, combinations and subcombinations of elements described in this disclosure are expressly included in this disclosure.

DETAILED DESCRIPTION

The present disclosure is susceptible of embodiment in many different forms. Representative examples of the disclosure are shown in the drawings and described herein in detail as non-limiting examples of the disclosed principles. To that end, elements and limitations described in the Abstract, Introduction, Summary, and Detailed Description sections, but not explicitly set forth in the claims, should not be incorporated into the claims, singly or collectively, by implication, inference, or otherwise.

For purposes of the present description, unless specifically disclaimed, use of the singular includes the plural and vice versa, the terms “and” and “or” shall be both conjunctive and disjunctive, “any” and “all” shall both mean “any and all”, and the words “including”, “containing”, “comprising”, “having”, and the like shall mean “including without limitation”. Moreover, words of approximation such as “about”, “almost”, “substantially”, “generally”, “approximately”, etc., may be used herein in the sense of “at, near, or nearly at”, or “within 0-5% of”, or “within acceptable manufacturing tolerances”, or logical combinations thereof.

Referring first toFIG.1, an electrical machine10is illustrated. Electrical machine10may be an axial-flux permanent magnet machine, such as a motor. Electrical machine10may have a non-rotating stator12affixed to a housing (not shown). Stator12defines a central axis14that acts as a rotational axis for two permanent magnet rotors, rotor16and rotor18. Rotor16and rotor18may be fixed to a common shaft20for rotation therewith, with shaft20being supported by bearings in the housing of electrical machine10and suitably journaled for rotation within stator12. Rotor16is separated from stator12by an air gap17, and rotor18is separated from stator12by an air gap19. Electric machine10may be of the so-called yokeless variety; that is, stator12may not comprise a back iron through which magnetic flux flows in stator12.

Stator12is wound with electrical windings21that provide magnetic flux for interaction with the permanent magnets of rotor16and rotor18to generate mechanical rotational force from electrical machine10, in the event that electrical machine10is acting as a motor. The windings may be energized by a power inverter module (PIM)23, which converts stored electrical energy from a traction battery (B+)22into alternating current (AC) electrical energy. An electronic control unit (ECU)24, which may be integrated with power inverter module23or which may be a separate controller, controls the operation of power inverter module23. ECU24is an electronic controller that has sufficient electronic resources (microcontroller, memory, software, inputs, outputs and the like) to control electrical machine10. Electrical machine10may alternatively be operated as an electrical generator if rotor16and rotor18are rotated through the input of mechanical energy.

Electrical machine10as configured inFIG.1may be characterized as an “axial-flux” motor, because magnetic flux generated by windings21travels axially, that is, parallel to central axis14of electrical machine10. This may be contrasted from a so-called “radial flux” electrical machine, where the stator may be disposed about the rotor and flux travels radially relative to the center axis of the electrical machine. Electrical machine10may be used to power a motor vehicle13, such as an electric vehicle or a hybrid-electric vehicle.

Refer additionally toFIG.2. Rotor16may have a plurality of permanent magnets26disposed on the face of rotor16that faces stator12. Permanent magnets26may be affixed to a back iron28of rotor16by a suitable mechanical method, such as adhesive. Rotor18may have a plurality of permanent magnets30disposed on the face of rotor18that faces stator12. Permanent magnets30may be affixed to a back iron32of rotor18by a suitable mechanical method, such as adhesive. Given that rotor16and rotor18may comprise permanent magnet poles, electrical machine10may be characterized as a “permanent magnet” machine. Stator12may have a first stator face34and a second stator face36. Stator face34and Stator face36may be parallel or substantially parallel to one another. Further, stator face34and stator face36may each face parallel to central axis14and in opposite directions from one another, say to the right and left inFIG.1.

Windings21(only a portion of which are illustrated inFIG.2) may be wound around segments of stator12, such as segment40a. Adjacent segments of stator12may form slots, such as slots38and39, in which windings of stator12are disposed.

Referring additionally toFIG.3, stator12may be comprised of multiple segments40a,40b,40c,40d,40c,40f,40g,40h,40i,40j,40kand401, though the present disclosure is not limited to a stator having 12 segments. Segment40amay have a first face44and a second face46. Face44and face46may be mutually or substantially mutually parallel and, as segment40ais incorporated as part of stator12, may each face parallel to central axis14of stator12, though face44and face46may face in opposite directions. Face44and face46may be of different shapes, and face46may have a greater surface area than face44. When viewed toward the central axis of stator12(that is, for instance, from direction48), segment40amay have a “T” shape. Stator segments40a-401are suitably attached relative to one another, say by a compression ring that circumscribes stator segments40a-401, or by adhesive between stator segments40a-401and the housing of electric machine10.

When stator segments40a-401are incorporated as parts of stator12, the faces of stator segments40a-401form gaps therebetween, such as gap60in stator face34and gap62in stator face36. Gap60and gap62may be disposed radially or generally radially with respect to central axis14. It may be noted that gap60and gap62may be angularly offset from one another, in terms of angular position about central axis14.

Referring additionally toFIG.4, stator segment40ais illustrated in additional detail. Stator segment40amay be comprised of ferromagnetic material. Stator segment40amay further be comprised of laminations49of ferromagnetic material such as iron or steel. Alternatively, stator segment40amay be comprised of other ferromagnetic materials or ferromagnetic material in other forms, such as soft magnetic compound (SMC), a molded composite of ferromagnetic material in a polymer or other electrically conductive carrier. Stator segment40bthrough stator segment401may feature similar or identical construction and materials to stator segment40a.

Face44and face46of stator segment40amay be flat or substantially flat and, further, faces44and46may be mutually parallel to one another and face outward from stator12as stator segment40ais incorporated in stator12. Face44and face46may face in opposite directions and may face parallel or generally parallel to central axis14of stator12. It may be noted that face44of stator segment40amay be different in shape or size than face46of stator segment40a. Face46may be larger in surface area than face44.

Other stator segments40b-401may be of the same geometry, materials, and construction as stator segment40a. (“Geometry” refers here to size and shape of stator segments40a-401.) That is, other stator segments40b-401may be identical to stator segment40a. As shown inFIG.3, however, stator segments40a-401may be installed in stator12in an alternating fashion, with the larger face of one stator segment facing in an opposite direction from the larger faces of the two stator segments adjacent to it.

Referring additionally toFIG.5, windings21may be comprised of segments such as segment21a, which have a shape that allows segment21ato be slid over the smaller end of segment40a. Segment21amay be comprised of copper, aluminum, an alloy of the foregoing, or another suitable conductive material to effectively act as an electrical machine winding. Segment21amay be stamped and then formed into the shape shown inFIG.5for convenient installation over the smaller face44of stator segment40a. Segments21a, once similarly installed on each of stator segments40a-401, may be suitably electrically connected, such as in a WYE or DELTA configuration, to form windings21of stator12.

Segment40amay be comprised of ferromagnetic material, such as a steel that is appropriate for incorporation within the core of an electrical machine. Segment40amay be formed of laminations. Segments40b-401may be similarly constructed to segment40a.

Electrical machine10may be an 8-pole, 12-slot motor and may be operated with windings21configured in three phases, though those parameters are exemplary only and not limiting.

Electrical machine10has been demonstrated to provide certain advantageous performance characteristics. For instance, with reference toFIG.6, graph (a) shows the cogging torque for a representative axial-flux, permanent magnet electrical machine. By contrast, graph (b) shows considerably less cogging torque for an axial-flux, permanent magnet electrical machine according to this disclosure.

Further, then, with reference toFIG.7, graph (a) shows torque ripple for a representative axial-flux, permanent magnet electrical machine. On the other hand, graph (b) shows substantially reduced torque ripple for an axial-flux, permanent magnet electrical machine according to this disclosure.

The improved performance characteristics of electrical machine10illustrated inFIG.6andFIG.7may be due to the differences in geometry of faces44and46of stator segment40a(and corresponding differences in geometry between respective faces of stator segment40bthrough stator segment401). The improved performance characteristics may also be due to the gaps (such as gap62) in stator face36being angularly offset, relative to central rotation axis14, from the gaps (such as gap60) in stator face34. In each case, the magnetic flux generated by stator12is more dispersed than may be the case in alternative electrical machines, smoothing the output torque of electrical machine10. Cogging torque reduction may be accomplished for electrical machine10because of the relative offset of the gaps in stator face34and stator face36of stator12. Torque ripple reduction may be accomplished by the modulation and phase shifting of the excitation of stator12between the two air gaps, air gap17and air gap19.

Referring now toFIG.8, an alternative configuration of a segment of a stator12′ is illustrated. Here, a segment140amay be comprised of a first part142and a second part144. First part142and second part144may be joined at a joining line146to form segment140a. First part142and second part144may be made of ferromagnetic material, such as laminated iron or steel or molded ferromagnetic compound such as SMC. First part142and second part144may be assembled with a winding segment, such as winding segment21a(FIG.5), disposed between first part142and second part144. First part142and second part144may be affixed together using adhesive or another suitable joining method. Segment140amay have a first face147and a second face149.

Referring additionally toFIG.9, stator12′ may comprise segment140aand additional segments (segment140bthrough segment1401), that may be of like construction, materials, and geometry to segment140aand disposed about the central axis of stator12′. The faces of adjacent stator segments may have radially extending gaps therebetween (such as gap150and gap152in opposite faces of stator12′). Gaps such as gap150and gap152may be offset from one another in terms of their angular position relative to the central axis of stator12′.

The detailed description and the drawings or figures are supportive and descriptive of the present teachings, but the scope of the present teachings is defined solely by the claims. While some of the best modes and other embodiments for carrying out the present teachings have been described in detail, various alternative designs and embodiments exist for practicing the present teachings defined in the appended claims. For instance, while the example disclosure provided herein shows the teachings hereof in the environment of a motor vehicle, these teachings are not so limited. Moreover, this disclosure expressly includes combinations and sub-combinations of the elements and features presented above and below.