Electric motor

Abstract

An electric motor includes a stator assembly, a frame, and a rotor assembly rotatably mounted to the frame. The rotor assembly includes an impeller for generating airflow through the motor, a frame is overmolded to the stator assembly, and the frame defines a plurality of diffuser blades downstream of the impeller.

Description

Technical Field

[0001] The present invention relates to an electric motor. Background Art

[0002] It is often desirable to improve electrical machines, such as electric motors, in a variety of ways. For example, improvements may be desired in terms of size, weight, power density, manufacturing cost, efficiency, reliability, and noise. Summary of the Invention

[0003] According to a first aspect of the present invention, there is provided an electric motor comprising: a stator assembly; a frame; and a rotor assembly rotatably mounted to the frame; wherein the rotor assembly includes an impeller for generating airflow through the electric motor, the frame is overmolded onto the stator assembly, and the frame defines a plurality of diffuser blades located downstream of the impeller.

[0004] Because the frame is overmolded onto the stator assembly and defines a plurality of diffuser vanes located downstream of the impeller, the frame can serve a number of different functions, including providing structural support for components of the electric motor, providing a heat transfer path away from the stator assembly via the diffuser vanes, and providing a portion to which other components of the electric motor can be mounted. Providing a heat transfer path from the stator assembly via the diffuser vanes can avoid the need to directly cool the stator assembly using airflow generated by the impeller, which can result in increased aerodynamic and / or acoustic performance relative to an arrangement in which the stator assembly is directly cooled by airflow generated by the impeller.

[0005] Overmolding the frame to the stator assembly can reduce tolerances relative to arrangements where the frame and stator assembly are separate components fixedly attached to each other via adhesive, etc., and can achieve an increased level of concentricity between the frame and the stator assembly. Overmolding the frame to the stator assembly can also help inhibit relative movement between the frame and the stator assembly during manufacturing.

[0006] The stator assembly can include electrical connections to a power source, and the frame can encapsulate the stator assembly so that the electrical connections are the only components of the stator assembly exposed through the frame. Encapsulating the stator assembly in this manner can improve heat conduction from the stator assembly to the diffuser blades, which can enable the motor to operate at higher power levels than an unencapsulated arrangement. Such encapsulation can further help inhibit relative movement between the stator assembly and the frame.

[0007] The electrical connector may include a plurality of electrical terminals extending outwardly from the frame, for example in a direction parallel to the axis of rotation of the rotor assembly.

[0008] The frame may include an inner portion encapsulating the stator assembly and an annular outer portion spaced apart from the inner portion to define an air flow passage, and a plurality of diffuser vanes may extend within the air flow passage between the inner portion and the annular outer portion. When the diffuser vanes are positioned within the air flow passage, airflow generated by the impeller in use may pass over the diffuser vanes, thereby removing heat from the stator assembly of the electric motor.

[0009] The inner portion, the annular outer portion and the plurality of diffuser vanes may be integrally formed, for example as part of the same overmolding process.

[0010] The plurality of diffuser blades may each include a root thickness at the inner portion of at least 1 mm. This may provide improved heat transfer relative to diffuser blades having a root thickness at the inner portion of less than 1 mm. The plurality of diffuser blades may each include a root thickness at the inner portion of at least 1.2 mm or at least 1.4 mm.

[0011] The plurality of diffuser vanes may each include a ratio of a root thickness at the inner portion to a shroud thickness at the outer portion within a range of 2:1 to 3:1.

[0012] The plurality of diffuser vanes may each include a cross-sectional shape comprising a root edge at an inner portion, a shroud edge at an outer portion, and first and second side edges extending between respective ends of the root and shroud edges, wherein the first and second side edges are concave. This may provide increased surface area relative to an arrangement having straight side edges, which may provide improved heat transfer while having minimal impact on aeroacoustic performance.

[0013] The annular outer portion may have an outer diameter of no greater than 50 mm, e.g., no greater than 45 mm, no greater than 40 mm, no greater than 35 mm, or no greater than 30 mm. Thermal management in an electric motor of this size may be important to achieving the desired power output, and since the stator assembly is a source of heat in use, overmolding the frame to the stator assembly such that the frame also defines the diffuser vanes may aid in such thermal management. The annular outer portion may have an outer diameter of approximately 28.5 mm.

[0014] The inner portion may comprise an outer diameter of no greater than 30 mm, such as no greater than 25 mm, or no greater than 20 mm. The inner portion may comprise an outer diameter of approximately 19.4 mm. The air flow channel may have a width of at least 5 mm, such as a width in a radial direction, such as at least 6 mm. The air flow channel may have a width of no greater than 7 mm.

[0015] The electric motor may comprise a maximum axial length, for example in a direction parallel to the axis of rotation of the rotor assembly, of less than 60 mm or less than 50 mm. The electric motor may comprise a maximum axial length of approximately 46.5 mm.

[0016] The electric motor may be configured to generate air flow at a rate of between 5 L / s and 25 L / s in use, for example between 9 L / s and 22 L / s in use.

[0017] The stator assembly may include a stator core assembly, and each of the plurality of diffuser vanes may extend along the frame for an axial length of at least 50% of the length of the stator core assembly. This may provide a heat conduction path along at least 50% of the length of the stator core assembly, which may help remove heat generated by the stator assembly in use. Each of the plurality of diffuser vanes may extend along the frame for an axial length of at least 60%, at least 70%, at least 80% or at least 90% of the length of the stator core assembly. The axial length may include a length in a direction parallel to the axis of rotation of the rotor assembly, such as a length in a direction parallel to the longitudinal axis of the shaft of the rotor assembly. The stator core assembly may include a stack of laminations of electrical steel.

[0018] Each of the plurality of diffuser blades may extend along the frame an axial length of between 5 mm and 20 mm, such as between 8 mm and 16 mm. Each of the plurality of diffuser blades may extend along the frame an axial length of approximately 12 mm.

[0019] The stator assembly may include a coil having an upstream end and a downstream end, and each of the plurality of diffuser vanes may include a respective leading edge and a respective trailing edge. The distance between the respective trailing edge and the downstream end of the coil, measured in a direction parallel to the rotational axis of the rotor assembly, may be no greater than 30% of the distance between the upstream and downstream ends of the coil, measured in a direction parallel to the rotational axis of the rotor assembly. Thus, the trailing edges of the plurality of diffuser vanes may enable heat removal from the downstream end of the coil, which is the portion of the coil furthest from the impeller. The terms upstream and downstream may be used to indicate directionality relative to the direction of airflow through the electric motor during use. The distance between the respective trailing edge and the downstream end of the coil, measured in a direction parallel to the rotational axis of the rotor assembly, may be no greater than 20% or 10% of the distance between the upstream and downstream ends of the coil, measured in a direction parallel to the rotational axis of the rotor assembly.

[0020] The respective leading edges of the plurality of diffuser vanes may be located within a distance from the upstream end of the coil, and the distance may be between 35% and 50% of a distance between the upstream end of the coil and the downstream end of the coil.

[0021] The plurality of diffuser blades may each have a blade sweep angle of approximately zero degrees.

[0022] The plurality of diffuser blades may include at least 7 diffuser blades, at least 9 diffuser blades, at least 11 diffuser blades, or at least 13 diffuser blades. The plurality of diffuser blades may include exactly 13 diffuser blades, such as no more than 13 diffuser blades and no less than 13 diffuser blades.

[0023] The frame may be formed from a material having a thermal conductivity of at least 4 W / mK. This may provide efficient heat transfer away from the stator assembly via the plurality of diffuser vanes in use. The frame may be formed from a material having a thermal conductivity of at least 5 W / mK.

[0024] The frame can be formed from a material having a dielectric strength of at least 15 kV / mm. This can enable a relatively small size stator assembly while still meeting creepage and clearance requirements. This can enable the use of higher voltages in the stator assembly than would be possible using materials with lower dielectric strength, which can enable the motor to operate with increased efficiency and / or increased power density.

[0025] The frame may define a bearing seat, and the rotor assembly may include a bearing assembly located at the bearing seat to rotatably mount the rotor assembly to the frame. Thus, the frame may provide structural support for the bearing assembly while providing a heat dissipation path away from the stator assembly via the diffuser vanes.

[0026] The frame may define another bearing seat spaced apart from the bearing seat, and the rotor assembly may include another bearing assembly at the other bearing seat to rotatably mount the rotor assembly to the frame.

[0027] The electric motor may include a housing component attached to the frame upstream of the diffuser blades, and the housing component may include an additional plurality of diffuser blades. When the housing component is attached to the frame, e.g., the housing component is a separate component from the frame, increased design flexibility may be provided for at least one of the plurality of diffuser blades and the additional plurality of diffuser blades. For example, molding two rows of diffuser blades in an overmolding process may impose limitations on achievable geometry for the blades based on tooling requirements. By utilizing a housing component that is separate from the frame, a wider range of geometries may be achieved for the plurality of diffuser blades and the additional plurality of diffuser blades than would be achieved if the plurality of diffuser blades and the additional plurality of diffuser blades were formed as part of the same molding process. For example, the plurality of diffuser blades may be optimized to transfer heat away from the stator assembly, while the additional plurality of diffuser blades may be optimized to enhance aeroacoustic performance.

[0028] The additional plurality of diffuser blades may include diffuser blades of a different shape and / or size than the diffuser blades in the plurality of diffuser blades.

[0029] The housing member may include an additional inner portion and an additional annular outer portion spaced apart from the additional inner portion to define an additional air flow passage, and the additional plurality of diffuser blades may extend within the additional air flow passage and between the additional inner portion and the additional annular outer portion. Together, the air flow passage and the additional air flow passage may define an air passage through the electric motor. The additional plurality of diffuser blades may be located within the air passage upstream of the plurality of diffuser blades.

[0030] The additional plurality of diffuser blades may be located radially outward from a portion of the stator assembly and may at least partially axially overlap the portion of the stator assembly. Because the housing component is mounted to the frame and the additional plurality of diffuser blades at least partially axially overlap the portion of the stator assembly, the housing component may define a heat transfer path away from the stator assembly, which may enable enhanced cooling of the stator assembly relative to an arrangement without the housing component. The housing component may at least partially axially overlap a bearing assembly of the rotor assembly.

[0031] The frame may be formed from a thermosetting epoxy resin with 80% - 95% thermally conductive ceramic filler.

[0032] According to a second aspect of the present invention, there is provided a vacuum cleaner comprising the electric motor according to the first aspect of the present invention.

[0033] According to a third aspect of the present invention, there is provided a hair care appliance comprising a motor according to the first aspect of the present invention.

[0034] Where appropriate, optional features of one aspect of the invention may be equally applicable to other aspects of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic perspective view of an electric motor;

[0036] Figure 2 yes Figure 1 A schematic cross-sectional view of a motor;

[0037] Figure 3 yes Figure 1 A schematic perspective view of a stator assembly of an electric motor;

[0038] Figure 4 yes Figure 3 A schematic exploded view of a stator assembly;

[0039] Figure 5 yes Figure 3 a schematic perspective view of a stator core assembly of a stator assembly;

[0040] Figure 6 yes Figure 5A schematic exploded view of a stator core assembly;

[0041] Figure 7 yes Figure 1 A schematic cross-sectional view of a rotor assembly of an electric motor;

[0042] Figure 8 yes Figure 7 a schematic cross-sectional view of a shaft of a rotor assembly;

[0043] Figure 9 yes Figure 1 a first schematic cross-sectional view of a frame of an electric motor;

[0044] Figure 10 yes Figure 1 a second schematic cross-sectional view of a frame of the electric motor;

[0045] Figure 11 is Figure 9 a schematic diagram of the diffuser blades of the frame; and

[0046] Figure 12 yes Figure 1 A second schematic perspective view of an electric motor. DETAILED DESCRIPTION

[0047] Motor 10 Figure 1 and Figure 2 It is schematically shown in FIG.

[0048] Electric motor 10 includes a stator assembly 12 , a rotor assembly 14 , a frame 16 , a housing component 18 , and a shroud 20 .

[0049] The stator assembly 12 is Figure 3 and Figure 4 , and includes a first stator core assembly 22 , a second stator core assembly 24 , and a third stator core assembly 26 , as well as a first bus bar assembly 28 and a second bus bar assembly 30 .

[0050] The first stator core assembly is as follows Figure 5 and Figure 6 Each of the first stator core assembly 22, the second stator core assembly 24, and the third stator core assembly 26 has substantially the same form, and therefore, for the sake of brevity, the second stator core assembly 24 and the third stator core assembly 26 will not be described in detail herein. It should be understood that the same reference numerals used for features of the first stator core assembly 22 may be used for corresponding features of the second stator core assembly 24 and the third stator core assembly 26.

[0051] The first stator core assembly 22 includes a stator core segment 32 , a bobbin 34 , first, second, and third terminal connections 36 , 38 , and 40 , and a first coil 42 and a second coil 44 .

[0052] The stator core segments 32 are formed from stacks of steel laminations (not shown) and are generally arcuate, with their height being greater than their length and width. The stator core segments 32 span an arc length of approximately 120 degrees. The circumferential end faces of the stator core segments 32 are generally planar in form.

[0053] The bobbin 34 is formed of a plastic material and is overmolded to the stator core segment 32. The bobbin 34 includes a connection recess 46, a window 48, and a connection structure 50. The connection recess 46 is generally cylindrical in form and is shaped and sized to receive the corresponding first to third terminal connectors 36-40. The window 48 is generally elongated and rectangular in cross-section and provides a line of sight to the radially outer surface of the stator core segment 32. The window 48 enables appropriate magnets to hold the stator core segment 32 in place during assembly of the first stator core assembly 22. The connection structure 50 includes appropriate protrusions and / or recesses that interact with corresponding recesses and / or protrusions of the second stator core assembly 24 and the third stator core assembly 26 to hold the stator core assemblies 22, 24, 26 relative to each other.

[0054] The first through third terminal connectors 36-40 have substantially the same form and are typically elongated pins formed of a conductive material with a square cross-sectional shape. The first and second terminal connectors 36, 38 are push-fit inserted into corresponding connection recesses 46 and extend axially outward from a first end 52 of the first stator core assembly 22. The third terminal connector 40 is inserted into the corresponding connection recess 46 and extends axially outward from a second end 54 of the first stator core assembly 22, opposite the first end 52 of the first stator core assembly 22.

[0055] The first and second coils 42, 44 are formed from multiple turns of copper wire and are wound around the bobbin 34 such that the first and second coils 42, 44 cover both the radially inner and radially outer surfaces of the stator core segments 32. The stator assembly 12 is a slotless stator assembly. For clarity, the first and second coils 42, 44 are shown in block form so that the individual turns are not visible in the figure. The first and second coils 42, 44 are formed from a single piece of copper wire so that the first and second coils 42, 44 are wound using a continuous winding process. For example, the first coil 42, located at the first terminal connection 36, is wound around the bobbin 34 and, therefore, around the stator core segments 32, and is tied at the third terminal connection 40. The second coil 42 then begins at the third terminal connection 40, is wound around the bobbin 34 and, therefore, around the stator core segments 32, and is tied at the second terminal connection 38. The first coil 42 and the second coil 44 are wound in opposite directions, wherein one of the first coil 42 and the second coil 44 is wound in a right-handed manner, and the other of the second coil 44 and the first coil 42 is wound in a left-handed manner.

[0056] Together, the first, second, and third stator core assemblies 22, 24, and 26, when connected together, define an annular space having a central bore 56 for receiving the rotor assembly, wherein the stator assembly 12 has a diameter of no greater than 40 mm. When connected together, the generally circumferential surfaces of the stator core segments 32 substantially contact one another, such that a generally annular stator core is formed by the stator core segments 32. The first and second terminal connectors 36, 38 of each stator core assembly 22, 24, 26 form a first subset of terminal connectors located at a first end 58 of the stator assembly 12, and the third terminal connector 40 forms a second subset of terminal connectors located at a second end 60 of the stator assembly 12.

[0057] The first and second terminal connections 36 , 38 are evenly spaced around the circumference of the first end 58 of the stator assembly 12 , while the third terminal connections 40 are evenly spaced around the circumference of the second end 60 of the stator assembly 12 .

[0058] The first bus bar assembly 28 is located at a first end 58 of the stator assembly 10 and is connected to the first and second terminal connections 36, 38 of the stator core assemblies 22, 24, 26. Further details of the first bus bar assembly 28 are not relevant to the present invention and, for the sake of brevity, will not be described herein, except to say that the first bus bar assembly 28 includes three electrical connections 59.

[0059] The second busbar assembly 30 is located at the second end 50 of the stator assembly 10 and connects all the third terminal connections 40. Further details of the second busbar assembly 30 are not relevant to the present invention and are not described here for the sake of brevity.

[0060] The coils 42 , 44 and the first and second busbar assemblies 28 , 30 define a three-phase parallel star connection, with the first and second terminal connections 36 , 38 serving as the live connection and the third terminal connection 40 serving as the neutral connection.

[0061] The rotor assembly 14 is Figure 7 Shown in.

[0062] Rotor assembly 14 includes a shaft 62 , an impeller 64 , first and second bearing assemblies 66 and 68 , first and second balance rings 70 and 72 , and permanent magnets 74 .

[0063] Axis 62 Figure 88. The shaft 62 is shown separately in a schematic cross-section of FIG. The shaft 62 includes a first portion 76, a second portion 78 adjacent to the first portion 76, a first transition region 80 between the first portion 76 and the second portion 78, a third portion 82 adjacent to the second portion 78, and a second transition region 84 between the second portion 78 and the third portion 82. In this manner, the second portion 78 is considered to be intermediate the first portion 76 and the third portion 82. The first portion 76 defines a first end 86 of the shaft 62, and the third portion 82 defines a second end 88 of the shaft 62 opposite the first end 86. The shaft 62 is a one-piece stainless steel component such that the first portion 76, the second portion 78, and the third portion 82 are integrally formed. The shaft 62 has a relative magnetic permeability of approximately 20. In some alternative examples, the first transition region 80 and / or the second transition region 84 may be omitted.

[0064] The impeller 64 is a mixed flow impeller and is press fit to the first portion 76 such that the impeller 64 is located at the first end 86 of the shaft 62. Axial flow and / or radial flow impellers are also contemplated. The impeller 64 is injection molded using PEEK material.

[0065] The first bearing assembly 66 comprises a ball bearing assembly and is press-fitted to the first portion 76 of the shaft 62 such that the first bearing assembly 66 is partially located within the hollow interior of the impeller 64. The outer diameter of the first bearing assembly 66 is greater than the outer diameter of each of the second bearing assembly 68, the first and second gimbals 70, 72, and the permanent magnet 74.

[0066] The second bearing assembly 68 comprises a ball bearing assembly and is press-fitted to the third portion 82 of the shaft 62 such that the second bearing assembly 68 is located at the second end 88 of the shaft 62. The first bearing assembly 66 and the second bearing assembly 68 are located at points on the respective first portion 76 and third portion 82 of the shaft 62 such that the step between the first bearing assembly 66 and the second bearing assembly 68 is approximately 30 mm.

[0067] The first gimbal 70 is press-fitted to the first portion 76 of the shaft 62, and the second gimbal 72 is press-fitted to the third portion 82 of the shaft 62. The second bearing assembly 68 is located closer to the second end 82 of the shaft 62 than the second gimbal 72. The second gimbal 72 has a smaller mass than the first gimbal 70.

[0068] The permanent magnet 74 is a two-pole sintered magnet that is mounted to the second portion 78 of the shaft 62 via an adhesive.

[0069] Frame 16 Figure 9 9 and includes an inner portion 90 , an outer portion 92 and a plurality of diffuser vanes 94 .

[0070] Inner portion 90 is generally elongated in form and tapers inwardly at both ends. Inner portion 90 includes an internal passageway having a first portion 96, a second portion 98, a third portion 100, and a fourth portion 102. The diameters of first portion 96 and fourth portion 102 substantially correspond to the outer diameters of first bearing assembly 66 and second bearing assembly 68, respectively. When rotor assembly 14 is positioned relative to frame 16, first portion 96 and fourth portion 102 serve as bearing seats for first bearing assembly 66 and second bearing assembly 68. Second portion 98 is sized such that first gimbal 70 is received within second portion 98 when rotor assembly 14 is positioned relative to frame 16, and third portion 100 is sized such that permanent magnet 74 is received within third portion 100 when rotor assembly 14 is positioned relative to frame 16. Inner portion 90 has an outer diameter of approximately 19.4 mm.

[0071] The outer portion 92 is annular and has a larger diameter than the inner portion 90, so that the outer portion 92 is arranged concentrically with the inner portion 90. The outer portion has a diameter of approximately 28 mm. The outer portion 92 has a smaller axial length than the inner portion 90, so that the outer portion 92 only covers a portion of the inner portion 90. The inner portion and the outer portion 92 together define an air flow channel 93. The air flow channel 93 has a width of approximately 6.85 mm.

[0072] Diffuser vanes 94 extend between inner portion 90 and outer portion 92, and each has a leading edge 104 and a trailing edge 106. A distance D between leading and trailing edges 104, 106, measured parallel to the axis of rotation of rotor assembly R within frame 16, is approximately 12 mm.

[0073] A single diffuser blade 84 is shown in isolation in FIG11 . The cross-sectional shape of diffuser blade 84 includes a root edge 95, a shroud edge 97, a first side edge 99, and a second side edge 101. Root edge 95 has a length of approximately 1.4 mm, and shroud edge 97 has a length of approximately 0.5 mm. This results in a root edge length to shroud edge length ratio of approximately 2.8:1. First side edge 99 and second side edge 101 are concave in form.

[0074] There are thirteen diffuser blades 84 in total, and each diffuser blade 84 has a blade sweep angle of approximately zero degrees.

[0075] The frame 16 is formed via an overmolding process, wherein the frame 16 is overmolded to the stator assembly 12, wherein the combination of the frame 16 and the stator assembly 12 is formed in a Figure 9. Thus, inner portion 90, outer portion 92, and plurality of diffuser blades 94 are integrally formed, making frame 16 a unitary component. The material used to form the frame has a thermal conductivity of at least 4 W / mK and a dielectric strength of at least 15 kV / mm. One suitable material is a thermosetting epoxy resin with 80% to 95% thermally conductive ceramic filler.

[0076] The inner portion 90 encapsulates the stator assembly 12, with only three electrical connectors 59 extending outward from the frame 16. The frame 16 is formed around the stator assembly 12 such that the diffuser vanes 94 partially overlap the stator assembly 12 in the axial direction. The leading edge 104 is located a distance E from the upstream end 108 of the coils 42, 44, i.e., within 50% of the axial length of the coils 42, 44 from the upstream end 108 of the coils 42, 44, where the distance E is measured parallel to the axis of rotation R of the rotor assembly 14. The trailing edge 106 is located a distance F from the downstream end 110 of the coils 42, 44, i.e., within 10% of the axial length of the coils 42, 44 from the downstream end 110 of the coils 42, 44, where the distance F is measured parallel to the axis of rotation R of the rotor assembly 14. In this manner, the diffuser vanes 94 extend along at least 50% of the axial length of the stator core segment 32.

[0077] The housing member 18 may be Figure 12 1 and includes an inner member 112, an outer member 114, and a plurality of additional diffuser blades 116. Inner member 114 is generally annular in form and has an inner diameter corresponding to the outer diameter of inner portion 90 of frame 16 in a region of frame 16 upstream of outer portion 92 of frame 16. Inner member 114 is attached to inner portion 90 of frame 16 via an adhesive. Outer member 116 is annular and is arranged generally concentrically with inner member 114 to define an additional air flow passage 118. Together, additional air flow passage 118 and air flow passage 93 define an air passage through electric motor 10.

[0078] Additional diffuser vanes 116 extend between the inner and outer members 112, 114, and each additional diffuser vane 116 has a leading edge 120 and a trailing edge 122. The trailing edge 122 axially overlaps the location of the upstream ends 108 of the coils 42, 44.

[0079] The shell component 18 is formed as part of a molding process that is separate from the overmolding process that forms the frame 16. The inner member 112, the outer member 114, and the additional diffuser blades 116 are integrally formed so that the shell component 18 is a unitary component. The material of the shell component 18 is different from that of the frame and is 20% glass fiber reinforced PC / ABS.

[0080] The shroud 20 is generally frusto-conical and hollow, with an open end 124 defining an inlet to the electric motor 10. The shroud 20 is mounted to the housing component 18 via adhesive.

[0081] In use, a voltage is applied to the coils 42, 44 of the stator assembly 12, causing a magnetic field to be generated by the stator assembly 12. The magnetic field generated by the stator assembly 12 interacts with the permanent magnets 74 of the rotor assembly 14 to rotate the rotor assembly 14 relative to the stator assembly 12. The rotation of the rotor assembly 14 generates airflow through the air passage via the impeller 64. Depending on the operating mode of the electric motor 10, the airflow rate ranges from 9 L / s to 22 L / s.

[0082] When voltage is applied to the coils 42, 44, the stator assembly 12 generates heat. Because the stator assembly 12 is encapsulated by the frame 16 and the plurality of diffuser vanes 94 are located within the air passage, the plurality of diffuser vanes 94 effectively act as a heat sink for removing heat generated by the stator assembly 12 from the electric motor 10. Providing a heat transfer path from the stator assembly 12 via the plurality of diffuser vanes 94 can avoid the need to directly cool the stator assembly 12 using the airflow generated by the impeller 64, which can result in increased aerodynamic and / or acoustic performance relative to an arrangement in which the stator assembly 12 is directly cooled by the airflow generated by the impeller 64.

[0083] When the frame 16 is overmolded onto the stator assembly 12, the frame provides structural support for the first and second bearing assemblies 66, 68 and provides a portion to which the housing component 18 is mounted. Overmolding the frame 16 onto the stator assembly 12 may also reduce tolerances relative to an arrangement in which the frame 16 and stator assembly 12 are separate components fixedly attached to each other via an adhesive or the like, and may achieve an increased level of concentricity between the frame 16 and the stator assembly 12.

[0084] While specific examples and embodiments have been described thus far, it should be understood that these are illustrative only and that various modifications may be made without departing from the scope of the invention as defined by the following claims.

Claims

1. An electric motor, comprising: stator assembly; frame; and a rotor assembly rotatably mounted to the frame; The rotor assembly includes an impeller for generating airflow through the electric motor, the frame is overmolded onto the stator assembly, and the frame defines a plurality of diffuser blades located downstream of the impeller.

2. The electric motor according to claim 1, wherein The stator assembly includes electrical connections to a power source, and the frame encapsulates the stator assembly such that the electrical connections are the only components of the stator assembly exposed through the frame.

3. The electric motor according to claim 1 or 2, wherein: The frame includes an inner portion enclosing the stator assembly and an annular outer portion spaced from the inner portion to define an air flow channel, and the plurality of diffuser vanes extend within the air flow channel between the inner portion and the annular outer portion.

4. The electric motor according to claim 3, wherein Each of the plurality of diffuser blades includes a root thickness at the interior portion of at least 1 mm.

5. The electric motor according to claim 3 or 4, wherein: The annular outer portion has an outer diameter of no greater than 50 mm.

6. The electric motor according to any one of claims 3 to 5, wherein Each of the plurality of diffuser blades includes a cross-sectional shape comprising a root edge at the inner portion, a shroud edge at the outer portion, and first and second side edges extending between respective ends of the root edge and the shroud edge, and the first and second side edges are concave.

7. An electric motor according to any one of the preceding claims, wherein The stator assembly includes a stator core assembly, and each of the plurality of diffuser vanes extends an axial length along the frame that is at least 50% of a length of the stator core assembly.

8. An electric motor according to any one of the preceding claims, wherein The stator assembly includes a coil having an upstream end and a downstream end, each of the plurality of diffuser vanes including a respective leading edge and a respective trailing edge, the respective trailing edge being a distance measured in a direction parallel to the rotational axis of the rotor assembly from the downstream end of the coil no greater than 30% of a distance measured in a direction parallel to the rotational axis of the rotor assembly between the upstream end and the downstream end of the coil.

9. An electric motor according to any one of the preceding claims, wherein The frame is formed from a material having a thermal conductivity of at least 4 W / mK.

10. An electric motor according to any one of the preceding claims, wherein The frame is formed of a material having a dielectric strength of at least 15 kV / mm.

11. An electric motor according to any one of the preceding claims, wherein The frame defines a bearing seat, and the rotor assembly includes a bearing assembly at the bearing seat to rotatably mount the rotor assembly to the frame.

12. An electric motor according to any one of the preceding claims, wherein The electric motor includes a housing member attached to the frame upstream of the diffuser vanes, the housing member including an additional plurality of diffuser vanes.

13. The electric motor according to claim 12, wherein The additional plurality of diffuser vanes is located radially outward from a portion of the stator assembly and at least partially axially overlaps a portion of the stator assembly.

14. An electric motor according to any one of the preceding claims, wherein The frame is formed from a thermosetting epoxy resin with 80% - 95% thermally conductive ceramic filler.

15. A vacuum cleaner comprising a motor according to any preceding claim.

16. A hair care appliance comprising a motor according to any one of claims 1 to 14.

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