Selective permeability rotor structure for built-in permanent magnet motor

Abstract

A radial flux electric motor includes a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface. The motor also includes a rotor mounted inside the stator and configured to rotate relative to the stator about an axis. The rotor has a rotor core comprised of a ferromagnetic material having a relatively high magnetic permeability and defined by a rotor exterior surface that establishes an air gap between the rotor and the stator. The rotor also has a plurality of magnetic poles disposed in the rotor core and configured to generate a magnetic flux. The rotor additionally has an insert made of a material having a relatively low magnetic permeability in at least one geometric direction. Each insert is mechanically secured to the rotor core to thereby control magnetic flux distribution and minimize magnetic flux leakage inside the rotor.

Description

Technical Field

[0001] introduction

[0002] The present disclosure relates to a selective permeability rotor structure for an interior permanent magnet electric machine. Background Art

[0003] An electric motor is an electrical machine that converts electrical energy into mechanical energy. Electric motors can be configured as either alternating current (AC) or direct current (DC) types. 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 motor. Based on the direction of the magnetic field, electric motors are generally divided into two categories - axial flux motors and radial flux motors.

[0004] An interior permanent magnet (IPM) electric motor is an AC synchronous brushless motor in which permanent magnets are encased in the rotor core. IPM motors are typically characterized by a favorable ratio of output torque relative to the physical size of the motor, and reduced input voltage. Electric motor torque is typically generated by the flux linkage between the field of the rotor permanent magnets and the electromagnetic field of the stator. IPM motors can augment such permanent magnet torque with reluctance torque that allows the use of thinner rotor magnets. Summary of the invention

[0005] A radial flux electric motor includes a stator having a radial inner stator surface and a stator winding arranged on the radial inner stator surface. The motor also includes a rotor mounted inside the stator and configured to rotate relative to the stator about an axis. The rotor has a rotor core, which is composed of a ferromagnetic material with a relatively high magnetic permeability and is defined by a rotor outer surface, which establishes an air gap between the rotor and the stator. The rotor also has a plurality of magnetic poles, which are arranged in the rotor core and are configured to generate magnetic flux. The rotor additionally has an insert, which is composed of a paramagnetic material with a relatively low magnetic permeability in at least one geometric direction. Each insert is mechanically fixed (e.g., welded) to the rotor core to thereby control the magnetic flux distribution and minimize flux leakage inside the rotor.

[0006] Each insert may be arranged on the outer surface of the rotor, between adjacent poles or opposite an individual pole.

[0007] Each insert may have a hollow body or a solid body configuration.

[0008] The ratio of the relatively high magnetic permeability of the ferromagnetic material to the relatively low magnetic permeability of the insert material may be greater than 100 to 1, and further may be greater than 10,000 to 1.

[0009] Each magnetic pole may include at least one rotor pocket having at least one permanent magnet housed therein and configured to generate magnetic flux. Each rotor pocket may have at least a portion thereof disposed adjacent at least one of the inserts.

[0010] Each insert may be configured to define a structural bridge extending from at least one of the rotor pockets to the rotor outer surface. Such structural bridges defined by the inserts may be used to strengthen the rotor core and minimize leakage of magnetic flux inside the rotor.

[0011] The ferromagnetic material may be ferrous steel and the insert material may be paramagnetic, such as austenitic steel.

[0012] Alternatively, the insert material may be grain oriented steel. In such embodiments, the orientation of the grains may be perpendicular to the leakage direction of the magnetic flux between the rotor and the stator, and parallel to the direction of linkage of the magnetic flux between adjacent magnetic poles.

[0013] Each insert may be configured to inhibit the closing of a magnetic flux loop inside the rotor.

[0014] The rotor core may include a plurality of adjacent rotor laminations arranged along an axis of rotation. For example, adjacent rotor laminations may be constrained or fixed together by an interference fit with the rotor core or by being pressed together via rotor end plates. In such embodiments, the inserts of adjacent rotor laminations may be arranged out of phase with respect to each other.

[0015] Adjacent rotor laminations may be electrically insulated from each other via a dielectric element, such as a thin dielectric material strip or coating.

[0016] Each insert may define a radial magnetic permeability and a circumferential magnetic permeability relative to the axis of rotation. In such embodiments, the magnitude of the radial magnetic permeability gradient may be different from the magnitude of the circumferential magnetic permeability gradient.

[0017] Radial flux electric motors can be either interior permanent magnet (IPM) or surface mounted permanent magnet (SPM) synchronous motors.

[0018] A motor vehicle having a radial flux electric motor of the type described above is also disclosed.

[0019] The present invention also discloses the following technical solutions:

[0020] 1. A radial flux electric motor comprising:

[0021] a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface; and

[0022] a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor comprises:

[0023] a rotor core constructed of a ferromagnetic material having a relatively high magnetic permeability and defined by a rotor exterior surface that establishes an air gap between the rotor and the stator;

[0024] a plurality of magnetic poles disposed in the rotor core and configured to generate magnetic flux; and

[0025] Inserts are formed of a material having relatively low magnetic permeability in at least one geometric direction, wherein each insert is mechanically fixed to the rotor core to thereby control magnetic flux distribution and minimize magnetic flux leakage inside the rotor.

[0026] 2. A radial flux electric motor according to technical solution 1, wherein each insert is arranged on the outer surface of the rotor, between adjacent poles or opposite to a separate pole.

[0027] 3. A radial flux electric motor according to solution 1, wherein each insert has one of a hollow body and a solid body structure.

[0028] 4. A radial flux electric motor according to technical solution 1, wherein each magnetic pole includes at least one rotor pocket, the rotor pocket having at least one permanent magnet, the permanent magnet being loaded into the rotor pocket and configured to generate magnetic flux, and wherein each rotor pocket has at least a portion thereof arranged near at least one of the inserts.

[0029] 5. A radial flux electric motor according to Technical Solution 1, wherein each insert is configured to define a structural bridge extending from at least one of the rotor pockets to the outer surface of the rotor, thereby strengthening the rotor core and minimizing leakage of magnetic flux inside the rotor.

[0030] 6. A radial flux electric motor according to technical solution 5, wherein the insert material is grain-oriented steel, and wherein the orientation of the grains is perpendicular to the leakage direction of the magnetic flux between the rotor and the stator, and parallel to the connection direction of the magnetic flux between adjacent magnetic poles.

[0031] 7. A radial flux electric motor according to technical solution 1, wherein each insert is configured to minimize the closure of the magnetic flux loop inside the rotor.

[0032] 8. A radial flux electric motor according to technical solution 1, wherein the rotor core includes a plurality of adjacent rotor laminations arranged along the rotation axis, and wherein the inserts of adjacent rotor laminations are arranged out of phase with respect to each other.

[0033] 9. A radial flux electric motor according to technical solution 8, wherein the adjacent rotor laminations are electrically insulated from each other via a dielectric element.

[0034] 10. A radial flux electric motor according to technical solution 1, wherein each insert defines a radial magnetic permeability gradient and a circumferential magnetic permeability gradient relative to the rotation axis, and wherein the magnitude of the radial magnetic permeability gradient is different from the magnitude of the circumferential magnetic permeability gradient.

[0035] 11. A motor vehicle comprising:

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

[0037] a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface; and

[0038] a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor comprises:

[0039] a rotor core constructed of a ferromagnetic material and defined by a rotor exterior surface that establishes an air gap between the rotor and the stator;

[0040] a plurality of magnetic poles disposed in the rotor core and configured to generate magnetic flux; and

[0041] Inserts are formed of a material having relatively low magnetic permeability in at least one geometric direction, wherein each insert is mechanically fixed to the rotor core to thereby control magnetic flux distribution and minimize magnetic flux leakage inside the rotor.

[0042] 12. A motor vehicle according to technical solution 11, wherein each insert is arranged on the outer surface of the rotor, between adjacent poles or opposite to a separate pole.

[0043] 13. A motor vehicle according to technical solution 11, wherein each insert has one of a hollow body and a solid body structure and is configured to minimize the closure of the magnetic flux loop inside the rotor.

[0044] 14. A motor vehicle according to technical solution 11, wherein each magnetic pole includes at least one rotor pocket, the rotor pocket having at least one permanent magnet, the permanent magnet being loaded into the rotor pocket and configured to generate magnetic flux, and wherein each rotor pocket has at least a portion thereof arranged near at least one of the inserts.

[0045] 15. A motor vehicle according to technical solution 11, wherein each insert is configured to define a structural bridge extending from at least one of the rotor recesses to the outer surface of the rotor, thereby strengthening the rotor core and minimizing leakage of magnetic flux inside the rotor.

[0046] 16. A motor vehicle according to technical solution 15, wherein the insert material is grain-oriented steel, and wherein the orientation of the grains is perpendicular to the leakage direction of the magnetic flux between the rotor and the stator, and parallel to the connection direction of the magnetic flux between adjacent magnetic poles.

[0047] 17. A motor vehicle according to technical solution 11, wherein the rotor core includes a plurality of adjacent rotor laminations arranged along the rotation axis, and wherein the inserts of adjacent rotor laminations are arranged out of phase with each other.

[0048] 18. A motor vehicle according to technical solution 17, wherein the adjacent rotor laminations are electrically insulated from each other via a dielectric element.

[0049] 19. A motor vehicle according to technical solution 11, wherein each insert defines a radial magnetic permeability and a circumferential magnetic permeability relative to the rotation axis, and wherein the magnitude of the radial magnetic permeability is different from the magnitude of the circumferential magnetic permeability.

[0050] 20. A radial flux electric motor comprising:

[0051] a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface; and

[0052] a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor comprises:

[0053] a rotor core constructed of a ferromagnetic material having a relatively high magnetic permeability and defined by a rotor outer surface that establishes an air gap between the rotor and the stator, wherein:

[0054] The rotor core includes a plurality of adjacent rotor laminations arranged along the rotation axis; and

[0055] The adjacent rotor laminations are electrically insulated from each other via a dielectric element;

[0056] a plurality of magnetic poles disposed in each of the adjacent rotor laminations and configured to generate magnetic flux; and

[0057] An insert composed of a material having a relatively low magnetic permeability in at least one geometric direction, wherein:

[0058] Each insert is mechanically fixed to the rotor core to thereby control magnetic flux distribution and minimize magnetic flux leakage inside the rotor; and

[0059] The inserts of adjacent rotor laminations are arranged out of phase with each other.

[0060] The above features and advantages and other features and advantages of the present disclosure will become apparent from the following detailed description of the embodiment(s) and best mode(s) for carrying out the described disclosure when taken in conjunction with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a schematic illustration of a motor vehicle having a powertrain that employs a radial flux motor-generator for propulsion.

[0062] Figure 2 According to the present disclosure Figure 1 A schematic close-up, partially cut-away perspective view of a radial flux dynamoelectric machine shown in , depicting a rotor having a ferromagnetic core and inserts of paramagnetic material, wherein the rotor is constructed from a plurality of adjacent rotor laminations.

[0063] Figure 3 According to the embodiment of the present disclosure Figure 2 Schematic front view of a rotor embodiment shown in , having a solid paramagnetic material insert.

[0064] Figure 4 According to the embodiment of the present disclosure Figure 2 Schematic front view of a rotor embodiment shown in , having a hollow paramagnetic material insert.

[0065] Figure 5 According to the embodiment of the present disclosure Figure 2 Schematic front view of another embodiment of a rotor shown in , the rotor having V-shaped poles with rotor pockets having permanent magnets enclosed therein and inserts of paramagnetic material arranged to retain the magnets.

[0066] Figure 6 According to the embodiment of the present disclosure Figure 2Schematic front view of another embodiment of a rotor shown in , having multiple layers of permanent magnets and paramagnetic material inserts arranged in pockets inside the rotor. DETAILED DESCRIPTION

[0067] The embodiments of the present disclosure described herein are intended to be examples. Other embodiments may take various and alternative forms. In addition, the drawings are generally schematic and are not necessarily drawn to scale. Some features may be enlarged or reduced to show the details of specific components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but only as a representative basis for teaching those skilled in the art to use the present disclosure in a variety of ways.

[0068] Certain terms may be used in the following description for reference purposes only 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," "side," "upward," "downward," "top," and "bottom" describe the orientation and / or position of parts of a component or element in a consistent but arbitrary reference system, which becomes clear by reference to the text and related drawings describing the component or element in question.

[0069] 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 meanings, and are used descriptively for the purposes of the drawings and do not represent limitations on the scope of the present disclosure as defined by the appended claims. In addition, the present teachings may be described herein in terms of functional and / or logical block components and / or various processing steps. It should be recognized that such block components may include multiple hardware, software, and / or firmware components configured to perform the specified functions.

[0070] refer to Figure 1 , depicting a motor vehicle 10 having a powertrain 12. The motor vehicle 10 may include, but is not limited to, a commercial vehicle, an industrial vehicle, a passenger vehicle, an aircraft, a watercraft, a train, etc. It is also contemplated that the motor vehicle 10 may be a mobile platform, such as an airplane, an all-terrain vehicle (ATV), a boat, a personal mobility device, a robot, etc., for purposes of the present disclosure. The powertrain 12 includes a first power source 14, which is depicted as an electric generator and is configured to generate a first power source torque T1 (e.g., Figure 1 ), for propelling the motor vehicle 10 relative to a road surface via driven wheels 16. The motor generator 14 may be configured as a radial flux electric motor, in which the magnetic flux is generated perpendicular to the motor's axis of rotation, and the air gap between the rotor and stator of the motor is arranged concentrically with the axis of rotation.

[0071] like Figure 1 As shown in , the powertrain 12 may also include a second power source 20, such as an internal combustion engine configured to produce a second power source torque T2. The power sources 14 and 20 may work together to provide power to the motor vehicle 10 and may be operably connected to a transmission assembly 22. The transmission assembly 22 may be configured to transmit the first and / or second power source torques T1, 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 an electric generator or electric motor in the remainder of this disclosure) may be mounted to the second power source 20, to (or coupled to) the transmission assembly 22, to the final drive unit 24, or may be a separate component mounted to the structure of the vehicle 10, for example. As shown, the motor vehicle 10 additionally includes: a programmable electronic controller 26, which is configured to communicate via a high voltage bus 27 and control the powertrain 12 to produce a predetermined amount of power source torque (the sum of T1 and T2); and various other vehicle systems. Motor vehicle 10 additionally includes an energy storage system 28 , such as one or more batteries, that is configured to generate and store electrical energy to power power sources 14 and 20 .

[0072] Figure 2 The radial flux dynamoelectric machine 14 is shown in general cross-section. As shown, the dynamoelectric machine 14 includes a rotationally fixed stator 30 having a generally cylindrical core 32 and winding slots 34. For example, Figure 2 , the stator core 32 also has a radially inner stator core surface 32A. The motor generator 14 also includes a rotor 36 disposed on a shaft defining an axis of rotation X and thereby mounted for rotation within the stator 30. The stator 30 may include a multi-phase AC winding or pole 34A disposed within winding slots 34, wherein the winding receives multi-phase AC from a power inverter to establish a rotating magnetic field that exerts a torque on the rotor 36. The stator winding 34A is generally contained within the winding slots 34, wherein the end turns of the winding extend beyond the confines of the cylindrical core 32 at axially opposite stator ends (first end 32-1 and second end 32-1).

[0073] The rotor 36 has a ferromagnetic rotor core 38. The rotor core 38 has axially opposite rotor core ends, a first end 38-1 and a second end 38-2, and is defined by a radially outer rotor surface 38A. The rotor core 38 may be constructed of a relatively soft magnetic material, such as laminated silicon steel or ferrous steel. The rotor 36 also includes a plurality of poles 40, each of which is configured to generate a magnetic flux 42. Specifically, the stacked rotor laminations may include voids forming an internal pocket 46, wherein one or more permanent magnets 48 are disposed or encased in the internal pocket 46, collectively defining the poles 40. As will be appreciated by those skilled in the art, the radial flux electric motor 14 may be an interior permanent magnet (IPM) or surface mounted permanent magnet (SPM) synchronous motor.

[0074] Prior art electric generator constructions typically include a substantially homogeneous ferromagnetic rotor core structure that facilitates a magnetic flux 42 leakage path in a radially outer region of the corresponding rotor core. For example, in such prior art rotor structures, a bridge region between an edge or corner portion of an interior pocket and an outer surface of the rotor may define or act as a magnetic flux leakage region, allowing the magnetic flux of the rotor to pass through into the stator. As will be described in detail below, the present electric generator 14 has a selective magnetic permeability structure of the rotor 36. The selective magnetic permeability structure of the rotor 36 is specifically designed to minimize or inhibit magnetic flux 42 leakage in the bridge region of the rotor core 38.

[0075] The rotor core 38 has a relatively high magnetic permeability, and its rotor outer surface 38A establishes an air gap 50 (eg, Figure 2 ). Figures 2 to 5 As shown in FIG. 1 , the rotor 36 additionally includes a plurality of inserts 52 formed of a material having a relatively low magnetic permeability in at least one geometric direction. For example, the inserts 52 may be formed of a paramagnetic material such as austenitic steel. Each insert 52 may be disposed on, within, or below the rotor outer surface 38A, or between adjacent magnetic poles 40 (e.g., Figures 2 to 5 ), or opposite to a separate magnetic pole, such as within the interior recess 46, adjacent to a corresponding permanent magnet 48 disposed in the interior recess (as shown in Figure 6 ). Each insert 52 is mechanically fixed to the rotor core 38. Therefore, the number of inserts 52 in the rotor 36 assembly is at least equal to the number of poles 40. Due to their low magnetic permeability, the inserts 52 act to change the direction of the magnetic flux 42 of the poles 40, control the magnetic flux distribution across the rotor 36, and generally suppress eddy current losses in the generator 14. Specifically, each insert 52 is intended to minimize or suppress the leakage of the magnetic flux 42 inside the rotor core 38 and facilitate the closure of the magnetic flux loop 42A, which is connected to the corresponding magnetic pole 34A on the stator 30.

[0076] Inserts 52 may be laser or MIG welded to rotor core 38. Corresponding welds 53 that retain inserts 52 may be applied along the plane of rotor core 38 and along exterior surface 38A to ensure a permanent and reliable connection between the insert and rotor core. Rotor core 38 may also include sections 38B configured to radially capture and retain individual inserts 52 within corresponding laminations. Figures 3 to 5 , at least one insert 52 is disposed on the left side of each pole 40 and at least one insert is disposed on the right side of each pole 40. Such incorporation of relatively low permeability inserts 52 into the rotor core 38 is intended to produce a net-formed rotor structure, eliminating the need for additional machining and / or assembly of the rotor 36.

[0077] Each insert 52 may have a solid body 52A (eg Figure 3 ) or hollow body 52B (as shown in Figure 4 ) construction, where solid inserts can provide enhanced structural support, while hollow inserts can reduce mass and material. Although not shown, the insert 52 can be divided into separate insert sections in the axial direction (along the axis of rotation X), for example, arranged in discrete rotor laminations. In such embodiments, dielectric separators can be installed between the separate insert sections to minimize the effects of induced eddy currents. Each insert 52 can have a relative magnetic permeability of less than 10 and further less than 1.2. The ratio of the relatively high magnetic permeability of the ferromagnetic material of the rotor core 38 to the relatively low magnetic permeability of the insert 52 can be greater than 100 to 1, and further can be greater than 10,000 to 1.

[0078] Each rotor pocket 46 has at least a portion 46A disposed adjacent to at least one of the inserts 52. Each insert 52 may be configured to define a structural bridge 54 extending from at least one of the rotor pockets 46 to the rotor exterior surface 38A that holds the corresponding magnetic pole 40 within the rotor core 38. Although each of the inserts 52 is shown as spanning two adjacent structural bridges 54, separate inserts for each respective bridge are also contemplated. So positioned, the corresponding insert 52 acts to strengthen the rotor core 38 in addition to minimizing leakage of the magnetic flux 42 within the rotor 36.

[0079] like Figure 2 As shown in FIG. 4 , the individual magnetic poles 40 may include adjacent permanent magnets 48 arranged in corresponding adjacent rotor pockets 46. In such a structure, the rotor core 38 may include a structural web 58 positioned between adjacent rotor pockets. A particular arrangement of the permanent magnets 48 may have a generally “V” shape, with the structural web 58 positioned at the tip of the “V”, such as Figure 5As shown in . Adjacent inserts 52 can be arranged to align with small edges or corners of corresponding nearby positioned permanent magnets 48 forming a V-shaped arrangement, thereby retaining the target permanent magnet within the rotor core 38. So positioned, the inserts 52 also block the magnetic flux 42 from passing through the structural connecting plate 58 to change the direction of the magnetic flux so that it passes through the air gap 50 to the stator 30. Figures 2 to 5 In FIG. 4 , a single layer of permanent magnets 48 is shown arranged within the rotor 36 , but additional layers of permanent magnets, such as Figure 6 as shown in .

[0080] like Figure 5 As shown in , the material of the insert 52 may be a grain-oriented austenitic steel. The orientation of the grains in such insert material may be specifically selected to be perpendicular to the leakage direction of the magnetic flux 42 between the rotor 36 and the stator 30. Such orientation of the material grains will also be aligned parallel to the connection direction of the magnetic flux between adjacent poles 40, and thereby redistribute and close the magnetic flux loop 42A between the corresponding permanent magnets 48. The rotor core 38 may include a plurality of adjacent rotor laminations 60 stacked along the rotation axis X, each lamination having a corresponding set of inserts 52. As described above, a dielectric separator may be installed between the insert segments 52 encased in adjacent laminations to minimize the effects of induced eddy currents. The rotor laminations 60 may be constrained or fixed together by an interference fit with the rotor core or by being pressed together via a rotor end plate (not shown).

[0081] Continue to refer Figure 2 , the inserts 52 of adjacent rotor laminations 60 may be arranged out of phase with respect to each other, i.e., strategically shifted or misplaced in phase angle. Thus, the poles 40 and inserts 52 of the rotor laminations 60 will also be shifted along the axis of rotation X, and thus out of phase with respect to the poles and inserts on their immediately adjacent (i.e., neighboring) rotor laminations. Such a shifted arrangement of adjacent rotor laminations 60 is intended to enhance the efficient operation of the generator 14 by reducing the slotting effect on the facing surfaces of the rotor 36 and the stator 30. Adjacent rotor laminations 60 may be electrically insulated from each other via respective dielectric elements 62, such as thin strips of dielectric material or dielectric coatings applied therebetween.

[0082] The material of the insert 52 may have a relatively low magnetic permeability in a particular geometric direction. For example, each insert 52 may define a radial magnetic permeability 64A and a circumferential magnetic permeability 64B relative to the rotation axis X. In addition, the magnetic permeability of each insert 52 may be different in the corresponding radial and circumferential directions. In other words, the size of the radial magnetic permeability 64A may be different from the size of the circumferential magnetic permeability 64B, and the circumferential magnetic permeability 64B may be used to advantageously guide the flow of the magnetic flux 42 inside the rotor 36. In general, the relatively low magnetic permeability material insert 52 blocks the magnetic flux 42 from passing through the rotor bridge and / or the connecting plate to limit the magnetic flux leakage inside the rotor, change the direction of the magnetic flux, and control the magnetic flux distribution across the rotor to promote the magnetic flux to pass through the air gap to the stator. In addition, the insert 52 incorporated into the rotor assembly strengthens the rotor structure and keeps the permanent magnets in the rotor core.

[0083] The detailed description and the accompanying drawings or figures are used to support and describe the present disclosure, but the scope of the present disclosure is limited only by the claims. Although some best modes and 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 attached claims. In addition, the embodiments shown in the drawings or the features of the various embodiments mentioned in this specification do not have to be understood as embodiments independent of each other. On the contrary, it is possible that each of the features described in one of the examples of the embodiments can be combined with one or more other desired features from other embodiments, thereby producing other embodiments that are not described in words or with reference to the drawings. Therefore, such other embodiments fall within the framework of the scope of the attached claims.

Claims

1. A radial flux electric motor comprising: a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface; and a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor comprises: a rotor core constructed of a ferromagnetic material having a relatively high magnetic permeability and defined by a rotor exterior surface that establishes an air gap between the rotor and the stator; a plurality of magnetic poles disposed in the rotor core and configured to generate magnetic flux; and Inserts are formed of a material having relatively low magnetic permeability in at least one geometric direction, wherein each insert is mechanically fixed to the rotor core to thereby control magnetic flux distribution and minimize magnetic flux leakage inside the rotor.

2. The radial flux electric motor according to claim 1, wherein: Each insert is arranged on the outer surface of the rotor, between adjacent poles or opposite an individual pole.

3. The radial flux electric motor according to claim 1, wherein: Each insert has one of a hollow body and a solid body configuration.

4. The radial flux electric motor according to claim 1, wherein: Each magnetic pole includes at least one rotor pocket having at least one permanent magnet housed therein and configured to generate magnetic flux, and wherein each rotor pocket has at least a portion thereof disposed adjacent at least one of the inserts.

5. The radial flux electric motor according to claim 1, wherein: Each insert is configured to define a structural bridge extending from at least one of the rotor pockets to the rotor exterior surface, thereby strengthening the rotor core and minimizing leakage of magnetic flux inside the rotor.

6. The radial flux electric motor according to claim 5, wherein: The insert material is grain-oriented steel, and wherein the orientation of the grains is perpendicular to the leakage direction of the magnetic flux between the rotor and the stator, and parallel to the joining direction of the magnetic flux between adjacent magnetic poles.

7. The radial flux electric motor of claim 1, wherein: Each insert is configured to minimize the closure of a magnetic flux loop inside the rotor.

8. The radial flux electric motor of claim 1, wherein: The rotor core includes a plurality of adjacent rotor laminations arranged along the rotational axis, and wherein inserts of adjacent rotor laminations are arranged out of phase with respect to each other.

9. The radial flux electric motor according to claim 8, wherein: The adjacent rotor laminations are electrically insulated from each other via a dielectric element.

10. The radial flux electric motor of claim 1, wherein: Each insert defines a radial magnetic permeability gradient and a circumferential magnetic permeability gradient relative to the rotational axis, and wherein a magnitude of the radial magnetic permeability gradient is different than a magnitude of the circumferential magnetic permeability gradient.

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