Radial flux electric motor with air gap cooling

Abstract

The invention relates to a radial flux electric motor with air gap cooling. A radial flux electric motor includes a stator having a radially inner stator surface and a rotor mounted inside the stator. The rotor defines an axis of rotation and has axially opposing rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface to establish an air gap between the radially inner stator surface and the radially outer rotor surface. The rotor further includes a fluid circulation arrangement having at least one fluid passage extending through the rotor to a radially outer rotor surface and configured to receive liquid via a first passage and to receive gas via at least one second passage. The fluid circulation arrangement is further configured to direct liquid and gas into the air gap via centrifugal force when the rotor is sufficiently rotated inside the stator to expel the liquid and gas out of the air gap at axially opposite ends of the rotor, thereby cooling the electric motor.

Description

Technical Field

[0001] The present disclosure relates to a radial flux electric motor with air gap cooling. Background Art

[0002] An electric motor is a 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 machine. Electric motors are classified into two categories based on the direction of the magnetic field - axial flux motors and radial flux motors.

[0003] As a byproduct of the torque produced, electric motors generate heat, which can negatively impact motor performance and reliability. Therefore, cooling of electric motors can eliminate thermal stresses experienced by the motor poles or windings and provide longer motor life at or near peak loads. Additionally, electric motor cooling can generally make motor operation quieter and enhance motor operation at higher speeds, as well as facilitate reduced motor inertia and packaging. Summary of the invention

[0004] A radial flux electric motor includes a stator having a radially inner stator surface and a rotor mounted inside the stator. The rotor defines an axis of rotation and has axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface, thereby establishing an air gap between the radially inner stator surface and the radially outer rotor surface. The rotor also includes a fluid circulation arrangement having at least one fluid channel extending through the rotor to the radially outer rotor surface and configured to receive liquid via a first passage and gas via at least one second passage. The fluid circulation arrangement is further configured to direct liquid and gas into the air gap via centrifugal force when the rotor is sufficiently rotated inside the stator to discharge the liquid and gas out of the air gap at axially opposed ends of the rotor, thereby cooling the electric motor.

[0005] The fluid circulation arrangement may additionally include a rotor shaft positioned coaxially with the rotation axis, the rotor shaft being fixed to the rotor and defining a first passage configured to receive the liquid.

[0006] The rotor shaft may additionally define the at least one second passage configured to receive a gas.

[0007] The rotor may define the at least one second passage.

[0008] The fluid circulation arrangement may include a plurality of fluid passages. Each subject fluid passage may extend through the rotor to a radially outer rotor surface.

[0009] The fluid circulation arrangement may additionally include a rotor wheel defining a plurality of fluid passages.The radially outer rotor surface may define circumferentially distributed apertures fluidly connected to the respective plurality of fluid passages.

[0010] The rotor wheel can be arranged centrally in the rotor perpendicular to the axis of rotation.

[0011] The rotor may have a three-piece structure including a first lateral rotor portion and a second lateral rotor portion sandwiching the rotor wheel.

[0012] The rotor impeller may have a laminated impeller structure including a first impeller lamination and a second impeller lamination sandwiching a third impeller lamination. The first and second impeller laminations together with the first and second lateral rotor portions may define each of the fluid channels. When the third impeller lamination is sandwiched between the first and second impeller laminations, the third impeller laminations together with the first and second lateral rotor portions may define a first portion of each fluid channel. When the third impeller lamination is sandwiched between the first and second impeller laminations, the first and second impeller laminations together may define a second portion of each fluid channel.

[0013] The liquid may be pressurized oil and the gas may be air.

[0014] A motor vehicle having a radial flux electric motor as described above is also disclosed.

[0015] The present invention provides the following technical solutions.

[0016] Technical Solution 1. A radial flux electric motor, comprising:

[0017] a stator having a radially inner stator surface; and

[0018] a rotor mounted inside the stator, defining an axis of rotation, and having axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface such that an air gap is established between the radially inner stator surface and the radially outer rotor surface;

[0019] wherein the rotor includes a fluid circulation arrangement having at least one fluid passage extending through the rotor to the radially outer rotor surface and configured to receive liquid via a first passage and gas via at least a second passage, and to direct the liquid and gas into the air gap via centrifugal force when the rotor is sufficiently rotating within the stator to expel the liquid and gas from the air gap at axially opposite ends of the rotor, thereby cooling the electric motor.

[0020] Technical Solution 2. A radial flux electric motor according to Technical Solution 1, wherein the fluid circulation arrangement additionally includes a rotor shaft, which is coaxially positioned with the rotor, fixed to the rotor and defines the first passage.

[0021] Technical Solution 3. A radial flux electric motor according to Technical Solution 2, wherein the rotor shaft defines the at least one second passage.

[0022] Technical Solution 4. A radial flux electric motor according to Technical Solution 2, wherein the rotor defines the at least one second passage.

[0023] Technical Solution 5. A radial flux electric motor according to Technical Solution 1, wherein the at least one fluid channel comprises a plurality of fluid channels, and wherein each fluid channel extends through the rotor to the radially outer rotor surface.

[0024] Technical Solution 6. A radial flux electric motor according to Technical Solution 5, wherein the fluid circulation arrangement additionally includes a rotor impeller defining the multiple fluid channels, and wherein the radial outer rotor surface defines circumferentially distributed orifices that are fluidically connected to the corresponding multiple fluid passages.

[0025] Technical Solution 7. A radial flux electric motor according to Technical Solution 6, wherein the rotor impeller is centrally arranged in the rotor perpendicular to the rotation axis.

[0026] Technical Solution 8. A radial flux electric motor according to Technical Solution 7, wherein the rotor has a three-piece structure, and the three-piece structure includes a first lateral rotor part and a second lateral rotor part that sandwich the rotor impeller.

[0027] Technical solution 9. The radial flux electric motor according to technical solution 8, wherein:

[0028] The rotor impeller has a laminated impeller structure including a first impeller lamination and a second impeller lamination sandwiching a third impeller lamination and defining each of the fluid channels together with the first and second lateral rotor portions.

[0029] Technical Solution 10. A radial flux electric motor according to Technical Solution 1, wherein the liquid is pressurized oil and the gas is air.

[0030] Technical Solution 11. A motor vehicle, comprising:

[0031] A radial flux electric motor configured to generate torque for propelling the motor vehicle, the radial flux electric motor comprising:

[0032] a stator having a radially inner stator surface; and

[0033] a rotor mounted inside the stator, defining an axis of rotation, and having axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface such that an air gap is established between the radially inner stator surface and the radially outer rotor surface;

[0034] wherein the rotor includes a fluid circulation arrangement having at least one fluid passage extending through the rotor to the radially outer rotor surface and configured to receive liquid via a first passage and gas via at least a second passage, and to direct the liquid and gas into the air gap via centrifugal force when the rotor is sufficiently rotated inside the stator to discharge the liquid and gas out of the air gap at axially opposite ends of the rotor, thereby cooling the electric motor.

[0035] Technical Solution 12. A motor vehicle according to Technical Solution 11, wherein the fluid circulation arrangement additionally includes a rotor shaft, which is positioned coaxially with the rotation axis, fixed to the rotor and defines the first passage.

[0036] Technical Solution 13. A motor vehicle according to Technical Solution 12, wherein the rotor shaft defines the at least one second passage.

[0037] Technical Solution 14. A motor vehicle according to Technical Solution 12, wherein the rotor defines the at least one second passage.

[0038] Technical Solution 15. A motor vehicle according to Technical Solution 11, wherein the at least one fluid channel comprises a plurality of fluid channels, and wherein each fluid channel extends through the rotor to the radially outer rotor surface.

[0039] Technical Solution 16. A motor vehicle according to Technical Solution 15, wherein the fluid circulation arrangement additionally includes a rotor impeller defining the multiple fluid channels, and wherein the radially outer rotor surface defines circumferentially distributed orifices that are fluidically connected to the corresponding multiple fluid channels.

[0040] Technical Solution 17. A motor vehicle according to Technical Solution 16, wherein the rotor impeller is centrally arranged in the rotor perpendicular to the rotation axis.

[0041] Technical Solution 18. A motor vehicle according to Technical Solution 17, wherein the rotor has a three-piece structure, the three-piece structure comprising a first lateral rotor portion and a second lateral rotor portion that sandwich the rotor impeller.

[0042] Technical Solution 19. The motor vehicle according to Technical Solution 18, wherein:

[0043] The rotor impeller has a laminated impeller structure including a first impeller lamination and a second impeller lamination sandwiching a third impeller lamination and defining each of the fluid channels together with the first and second lateral rotor portions.

[0044] Technical Solution 20. A radial flux electric motor, comprising:

[0045] a stator having a radially inner stator surface; and

[0046] a rotor mounted inside the stator, defining an axis of rotation, and having axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface such that an air gap is established between the radially inner stator surface and the radially outer rotor surface;

[0047] in:

[0048] the rotor including a fluid circulation arrangement having a plurality of fluid passages each extending through the rotor to the radially outer rotor surface and configured to receive a liquid via a first passage and a gas via at least one second passage and to direct the liquid and the gas into the air gap via centrifugal force when the rotor rotates sufficiently inside the stator to discharge the liquid and the gas out of the air gap at axially opposite ends of the rotor to cool the electric motor;

[0049] The fluid circulation arrangement additionally comprises a rotor wheel defining the plurality of fluid passages, and wherein the radially outer rotor surface defines circumferentially distributed apertures fluidly connected to the respective plurality of fluid passages;

[0050] The rotor wheel is centrally arranged within the rotor along the rotation axis;

[0051] The rotor has a three-piece structure, the three-piece structure including a first lateral rotor portion and a second lateral rotor portion sandwiching the rotor impeller;

[0052] The rotor impeller has a laminated impeller structure, the laminated impeller structure includes a first impeller lamination and a second impeller lamination, the first impeller lamination and the second impeller lamination sandwiching a third impeller lamination and defining each of the fluid channels together with the first and second lateral rotor portions;

[0053] The third impeller laminations together with the first and second lateral rotor portions define a first portion of each fluid passage; and

[0054] The first and second impeller laminations together define a second portion of each fluid passage.

[0055] 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

[0056] Figure 1 is a schematic diagram of a motor vehicle having a powertrain employing a radial flux electric motor-generator for propulsion.

[0057] Figure 2 According to the present disclosure Figure 1 A schematic enlarged cross-sectional side view of a radial flux motor-generator shown in , depicting a stator, an internally disposed coaxial rotor, and a fluid circulation arrangement including fluid channel(s) extending radially outwardly across the rotor.

[0058] Figure 3 According to the present disclosure Figure 2 Schematic, partially cut-away perspective view of a fluid circulation arrangement shown in , the fluid circulation arrangement having an embodiment of a rotor impeller establishing a fluid channel in communication with liquid and gas passages.

[0059] Figure 4 According to the present disclosure Figure 3 A schematic perspective view of an embodiment of a rotor impeller shown in , illustrates a laminated impeller structure of the rotor impeller, the structure comprising a first impeller lamination and a second impeller lamination sandwiching a third impeller lamination.

[0060] Figure 5 According to the present disclosure Figure 3 to Figure 4 A schematic cross-sectional side view of a rotor impeller laminate impeller structure shown in , illustrating that the first and second impeller laminations together with the first and second lateral rotor portions define a fluid channel of a fluid circulation arrangement. DETAILED DESCRIPTION

[0061] 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.

[0062] 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," "up," "down," "top," and "bottom" 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.

[0063] 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 in the drawings and do not represent limitations on the scope of the present disclosure as defined by the appended claims. In addition, the teachings may be described herein in terms of functional and / or logical block components and / or various processing steps. It should be appreciated that such block components may include multiple hardware, software, and / or firmware components configured to perform the specified functions.

[0064] 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 sports device, a robot, etc., for purposes of the present disclosure. The powertrain 12 includes a first power source 14, which is depicted as a motor-generator and is configured to generate a first power source torque T 1 ( 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, wherein the magnetic flux is generated perpendicular to the axis of rotation of the motor and the air gap between the rotor and stator of the machine is arranged concentrically with the axis of rotation.

[0065] like Figure 1 As shown in FIG. 1 , the powertrain 12 may also include a second power source 20 such as an internal combustion engine, which is configured to generate a second power source torque T2 The power sources 14 and 20 can act in concert to provide power to the motor vehicle 10 and are operatively connected to a transmission assembly 22. The transmission assembly 22 can be configured to convert the first power source torque T 1 and / or the second power source torque T 2 The first power source 14 (which will be referred to as a motor-generator in the remainder of this disclosure) can 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 a separate component mounted to the structure of the vehicle 10. As shown, the motor vehicle 10 additionally includes a programmable electronic controller 26 and various other vehicle systems, 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 (T 1 and T 2 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 for powering power sources 14 and 20 .

[0066] Figure 2 A general cross-section of a radial flux motor-generator 14 is shown. Figure 3 As shown in FIG. 1 , the motor-generator 14 includes a rotationally fixed stator 30 having a generally cylindrical core 32 and winding slots 34. Figure 3 , the stator core 32 also has a radially inner stator core surface 32A. The motor-generator 14 also includes a rotor 36 that defines an axis of rotation X and is mounted for rotation inside the stator 30. The stator 30 may include a multi-phase AC winding 34A disposed within the winding slots 34, wherein the winding receives multi-phase AC from a power inverter to establish a rotating magnetic field that applies torque on the rotor 36. The stator winding 34A is generally contained within the winding slots 34, with the end turns of the winding extending beyond the limits of the cylindrical core 32 at axially opposite stator ends (first end 32-1 and second end 32-2).

[0067] like Figure 3As shown in , the rotor 36 has a ferromagnetic rotor core 38. The rotor core 38 has axially opposed rotor core ends - a first end 38-1 and a second end 38-2. The rotor core 38 can be made of a relatively soft magnetic material such as laminated silicon steel. In a permanent magnet machine, the stacked rotor laminations may include gaps forming internal pockets for carrying permanent magnets. In an induction machine, the stacked laminations may include peripheral slots for carrying conductive bars. Alternative rotor constructions are also used in the industry and may include, for example, surface mounted permanent magnets and wound rotors. The rotor core 38 has a radially outer rotor surface 38A positioned proximate to the radially inner stator core surface 32A, thereby establishing an air gap 40 ( Figure 2 and Figure 3 An air gap 40 extends between axially opposite first and second ends 38 - 1 , 38 - 2 of the rotor core.

[0068] like Figure 2 and Figure 3 As shown in , the rotor 36 also includes a fluid circulation arrangement 42 having one or more fluid passages 44, each extending radially through the rotor to the radially outer rotor surface 38A. The fluid circulation arrangement 42 is configured to receive a liquid 46 via a first passage 50-1 and to receive a gas 48 via one or more second passages 50-2 along the rotation axis X. Specifically, the liquid 46 can be pressurized oil and the gas 48 can be air. The fluid circulation arrangement 42 is also configured to direct the liquid 46 and the gas 48 into the air gap 40 via centrifugal force when the rotor 36 is fully rotated inside the stator 30 to discharge the liquid and the gas out of the air gap at the axially opposite ends 38-1, 38-2 of the rotor 36. Therefore, the fluid circulation arrangement 42 is configured to cool the motor-generator 14.

[0069] Continue to refer to Figure 2 and Figure 3 , the fluid circulation arrangement 42 may additionally include a rotor shaft 52 coaxially positioned with the rotor 36. The rotor shaft 52 may be fixed to the rotor 36 and define a first passage 50-1 for supplying the liquid 46 to the (multiple) fluid channels 44. Specifically, the first passage 50-1 may be arranged along the rotation axis X and configured to receive the pressurized liquid 46 from one end of the rotor shaft 52. The liquid 46 may flow from the first passage 50-1 into the inner rotor fluid channel 44 through a liquid inlet, which may be configured as one or more third passages 50-3. Figure 2 , Figure 3 and Figure 5 As shown in FIG. 1 , the third passage 50 - 3 may be a cross-drilled hole arranged substantially perpendicular to the first passage 50 - 1 . When the radial flux motor-generator 14 generates the first power source torque T1 When the rotor shaft 52 rotates together with the rotor 36 about the rotation axis X, the rotor shaft 52 can be rotatably supported by bearings (not shown) at both ends (the first end 38-1 and the second end 38-2) of the rotor core 38, and can transfer the first power source torque T generated by the rotor 36 to the rotor core 38. 1 Via the transmission assembly 22 ( Figure 1 ) is transmitted to the driven wheel 16.

[0070] like Figure 3 As shown in , the rotor shaft 52 may also define a second passage 50-2 for supplying the gas 48 to the (multiple) fluid channels 44. Alternatively, the rotor 36 may define (multiple) second passages 50-2 (not shown). Figure 3 In the embodiment shown in , the second passage(s) 50-2 may be arranged substantially parallel to the rotation axis X. The gas 48 may be drawn into the second passage 50-2 by the rotation of the rotor 36 using a vacuum generated in the second passage due to the second passage being in communication with the radially disposed fluid passage(s) 44. Figure 3 As shown in FIG. 4 , first passage 50-1 and second passage 50-2 are in fluid communication with each of fluid channels 44 in fluid circulation arrangement 42. Liquid fluid 46 and gaseous fluid 48 may thus combine within fluid channel(s) 44 to create a two-phase mixture that is subsequently injected into air gap 40.

[0071] Reference Figures 2 to 5 The fluid circulation arrangement 42 may additionally include a rotor wheel 54 defining a plurality of fluid passages 44. The rotor wheel 54 may be arranged perpendicular to the axis of rotation X and centrally fixed within the rotor 36. Figure 3 As shown in , the plurality of channels 44 may define a radially arranged channel pattern defined by the rotor wheel 54. Figure 3 As shown in FIG. 4 , passage 44 extends through rotor wheel 54 to radially outer rotor surface 38A. In such an embodiment, radially outer rotor surface 38A defines circumferentially distributed apertures 55 ( Figure 5 ), the orifice 55 is fluidly connected to the corresponding plurality of fluid passages 44. As such, the rotor 36 may have a three-piece structure ( Figure 3 and Figure 5 ), the structure includes a first lateral rotor portion 36 - 1 and a second lateral rotor portion 36 - 2 sandwiching a rotor impeller 54 .

[0072] like Figure 4As shown in , the rotor impeller 54 may have a laminated impeller structure 56. The laminated impeller structure 56 may have a first impeller lamination 56-1 and a second impeller lamination 56-2 sandwiching a third impeller lamination 56-3. In other words, the first impeller lamination 56-1 and the second impeller lamination 56-2 are arranged on opposite sides of the third impeller lamination 56-3. Although the first impeller lamination 56-1 and the second impeller lamination 56-2 may have the same form and structure, the third impeller lamination 56-3 is specifically formed to establish a gap in a specific area between the first and second impeller laminations when the three laminations are stacked together. This arrangement of the three laminations 56-1, 56-2, 56-3 allows a continuous path to be created for the fluid channel 44 between them.

[0073] like Figure 3 As shown in FIG. 1 , when installed between the first lateral rotor portion 36-1 and the second lateral rotor portion 36-2, the first impeller lamination 56-1, the second impeller lamination 56-2, and the third impeller lamination 56-3 create the fluid passage 44. Therefore, the first impeller lamination 56-1, the second impeller lamination 56-2, and the third impeller lamination 56-3 together with the first lateral rotor portion 36-1 and the second lateral rotor portion 36-2 can define each of the fluid passages 44 in the rotor impeller 54. Figure 5 As shown in , when the third impeller lamination is sandwiched between the first impeller lamination 56-1 and the second impeller lamination 56-2, the third impeller lamination 56-3 together with the first lateral rotor portion 36-1 and the second lateral rotor portion 36-2 define the first portion 44-1 of each fluid channel. In addition, when the third impeller lamination 56-3 is sandwiched between the first impeller lamination 56-1 and the second impeller lamination 56-2, the first and second impeller laminations together define the second portion 44-2 of each fluid channel 44. As a result, the first portion 44-1 of the channel 44 is formed around the third impeller lamination 56-3 closest to the rotor shaft 52. The second portion 44-2 of the channel 44 is then formed radially farther between the first lamination 56-1 and the second lamination 56-2. Therefore, during operation of the radial flux motor-generator 14, the first portion 44-1 and the second portion 44-2 of the channel are in continuous fluid communication and supply the liquid 46 and the gas 48 into the air gap 40.

[0074] Continue to refer to Figure 2, the radial flux motor-generator 14 also includes a motor housing 58 that defines a fluid reservoir 60. The first passage 50-1 may be defined by a fixed tube 61 mounted to the motor housing 58 and extending through the center of the rotor shaft 52 to introduce the liquid 46 along a rotation axis X that is generally parallel to the gas flow 48. The fluid reservoir 60 is configured to collect the liquid 46 after the liquid has been drained from the air gap 40 and returned to the housing 58 by gravity or returned to the fluid reservoir by the housing 58. Each of the fluid reservoir 60 and the first fluid passage 50-1 in the rotor shaft 52 is in fluid communication with a fluid pump 62. The fluid pump 62 is regulated via the electronic controller 26 and is configured to pressurize and circulate the liquid 46, that is, to supply the liquid from the fluid reservoir 60 to the first fluid passage 50-1. The fluid pump 62 may be part of an electric motor cooling system 64 operated via the electronic controller 26.

[0075] The electronic controller 26 may be programmed with an algorithm 66 to regulate the fluid pump 62 using detected (e.g., via corresponding sensors (generally indicated by numeral 68)) or calculated variables. Such variables may be, for example, motor phase currents, motor rotational speed, temperature of the stator 30 and / or temperature of the rotor 36, and flow rate of the fluid 46 in the radial flux electric motor 14. The temperature of the stator 30 and / or rotor 36 may be detected, otherwise determined, or estimated using a recent history of other sensor readings (including readings of the fluid temperature) and a motor operating map 70 programmed into the controller 26. Thus, the electric motor cooling system 64 may be configured to eliminate thermal stresses and provide longer life for the radial flux electric motor 14 at higher speeds or near peak loads (such as during propulsion of the motor vehicle 10), among other benefits.

[0076] 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. A radial flux electric motor comprising: a stator having a radially inner stator surface; and a rotor mounted inside the stator, defining an axis of rotation, and having axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface such that an air gap is established between the radially inner stator surface and the radially outer rotor surface; wherein the rotor includes a fluid circulation arrangement having at least one fluid passage extending through the rotor to the radially outer rotor surface and configured to receive liquid via a first passage and gas via at least a second passage, and to direct the liquid and gas into the air gap via centrifugal force when the rotor is sufficiently rotating within the stator to expel the liquid and gas from the air gap at axially opposite ends of the rotor, thereby cooling the electric motor.

2. The radial flux electric motor according to claim 1, wherein: The fluid circulation arrangement additionally includes a rotor shaft located coaxially with the rotor, fixed to the rotor and defining the first passage.

3. The radial flux electric motor according to claim 2, wherein: The rotor shaft defines the at least one second passage.

4. The radial flux electric motor according to claim 2, wherein: The rotor defines the at least one second passage.

5. The radial flux electric motor according to claim 1, wherein: The at least one fluid passage comprises a plurality of fluid passages, and wherein each fluid passage extends through the rotor to the radially outer rotor surface.

6. The radial flux electric motor according to claim 5, wherein: The fluid circulation arrangement additionally comprises a rotor wheel defining the plurality of fluid passages, and wherein the radially outer rotor surface defines circumferentially distributed apertures fluidly connected to the respective plurality of fluid passages.

7. The radial flux electric motor according to claim 6, wherein: The rotor wheel is arranged centrally in the rotor, perpendicular to the axis of rotation.

8. The radial flux electric motor according to claim 7, wherein: The rotor has a three-piece structure including a first lateral rotor portion and a second lateral rotor portion sandwiching the rotor wheel.

9. A motor vehicle comprising: A radial flux electric motor configured to generate torque for propelling the motor vehicle, the radial flux electric motor comprising: a stator having a radially inner stator surface; and a rotor mounted inside the stator, defining an axis of rotation, and having axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface such that an air gap is established between the radially inner stator surface and the radially outer rotor surface; wherein the rotor includes a fluid circulation arrangement having at least one fluid passage extending through the rotor to the radially outer rotor surface and configured to receive liquid via a first passage and gas via at least a second passage, and to direct the liquid and gas into the air gap via centrifugal force when the rotor is sufficiently rotated inside the stator to discharge the liquid and gas out of the air gap at axially opposite ends of the rotor, thereby cooling the electric motor.

10. A radial flux electric motor comprising: a stator having a radially inner stator surface; and a rotor mounted inside the stator, defining an axis of rotation, and having axially opposed rotor ends and a radially outer rotor surface positioned proximate the radially inner stator surface such that an air gap is established between the radially inner stator surface and the radially outer rotor surface; in: the rotor including a fluid circulation arrangement having a plurality of fluid passages each extending through the rotor to the radially outer rotor surface and configured to receive a liquid via a first passage and a gas via at least one second passage and to direct the liquid and the gas into the air gap via centrifugal force when the rotor rotates sufficiently inside the stator to discharge the liquid and the gas out of the air gap at axially opposite ends of the rotor to cool the electric motor; The fluid circulation arrangement additionally comprises a rotor wheel defining the plurality of fluid passages, and wherein the radially outer rotor surface defines circumferentially distributed apertures fluidly connected to the respective plurality of fluid passages; The rotor wheel is centrally arranged within the rotor along the rotation axis; The rotor has a three-piece structure, the three-piece structure including a first lateral rotor portion and a second lateral rotor portion sandwiching the rotor impeller; The rotor impeller has a laminated impeller structure, the laminated impeller structure includes a first impeller lamination and a second impeller lamination, the first impeller lamination and the second impeller lamination sandwiching a third impeller lamination and defining each of the fluid channels together with the first and second lateral rotor portions; The third impeller laminations together with the first and second lateral rotor portions define a first portion of each fluid passage; and The first and second impeller laminations together define a second portion of each fluid passage.

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