Brushless permanent magnet motor

Abstract

A brushless permanent magnet motor is described. The brushless permanent magnet motor includes a rotor assembly rotatable to generate an airflow, a stator assembly, and a frame within which the rotor assembly and the stator assembly are housed. The frame includes an end cap and a body. The end cap and the body are separate components. The end cap is configured to attach a portion of the airflow to a portion of the body covering the stator assembly.

Description

Technical Field

[0001] The present invention relates to a brushless permanent magnet motor. Background Art

[0002] There is generally a desire to improve electric motors, such as brushless permanent magnet motors. For example, improvements may be needed in cooling brushless permanent magnet motors. Summary of the Invention

[0003] According to a first aspect of the present invention, there is provided a brushless permanent magnet motor including a rotor assembly, a stator assembly, and a frame that are rotatable to generate an air flow. The rotor assembly and the stator assembly are accommodated within the frame. The frame includes an end cap and a body, where the end cap and the body are separate components. The end cap is configured to cause a portion of the air flow to adhere to a portion of the body covering the stator assembly.

[0004] The stator assembly can be cooled by the portion of the air flow passing through the portion of the body. For example, the portion of the air flow can convectively cool the portion of the body, which in turn can conductively cool the stator assembly. Since the portion of the air flow adheres to the portion of the body, greater heat transfer may occur between the body and the portion of the air flow, which may increase the cooling of the stator assembly compared to an arrangement where the portion of the air flow detaches from the portion of the body. Cooling the stator assembly can increase the lifespan of the stator assembly. Additionally, forming the end cap and the body as separate components can increase the ease of motor assembly compared to an arrangement where the body and the end cap are integrally formed. For example, the stator assembly and the rotor assembly can be inserted into the body, and then the end cap is attached to the body. Furthermore, forming the end cap and the body as separate components can provide better control over the process of forming the end cap (e.g., molding) compared to integrally forming the end cap and the body. Greater control over the process can enable greater control over the geometry of the end cap, which can result in increased adhesion of the air flow. Optionally, the end cap is located upstream of the body.

[0005] Optionally, the end cap is configured to cause the portion of the air flow to adhere to the end cap. When the portion of the air flow travels downstream from the end cap and over the body, the portion of the air flow can remain adhered to the frame. Thus, adhering the portion of the air flow to the end cap provides a mechanism for causing the portion of the air flow to adhere to the portion of the body covering the stator assembly. Additionally, adhering the portion of the air flow to the end cap can enable the portion of the air flow to adhere along a greater portion of the frame, which is beneficial for better cooling compared to adhering the portion of the air flow at a lower position on the frame.

[0006] Optionally, the ratio of the radius of curvature of the end cap to the maximum width of the end cap is not less than 0.30. A ratio of not less than 0.30 can promote the adhesion of the portion of the air flow to the end cap and thus to the portion of the body. Optionally, the maximum width of the end cap is measured along an axis perpendicular to the central longitudinal axis of the brushless permanent magnet motor.

[0007] Optionally, the plane extends along the central longitudinal axis of the brushless permanent magnet motor, and the end cap is shaped such that when viewed in the plane, the end cap has a parabolic profile. The inventors have recognized that the parabolic profile can facilitate the attachment of a portion of the air flow to the end cap and thus to a portion of the body.

[0008] Optionally, when the frame is assembled, the maximum width of a portion of the end cap adjacent to the body is substantially the same as the maximum width of another portion of the body adjacent to the end cap. This can promote the attachment of a portion of the air flow to the portion of the body covering the stator assembly by reducing the likelihood of the portion of the air flow detaching from the frame as the portion of the air flow moves from the end cap to the body. Conversely, if the widths are significantly different, a step can be provided between the end cap and the body, which may cause the air flow to detach from the frame. Optionally, the maximum width of the portion of the end cap adjacent to the body and the maximum width of another portion of the body adjacent to the end cap are measured along an axis perpendicular to the central longitudinal axis of the brushless permanent magnet motor.

[0009] Optionally, the body includes a stator assembly cavity, the stator assembly is at least partially located within the stator assembly cavity, the body includes a stator assembly cavity inlet for allowing another portion of the air flow to enter the stator assembly cavity, and the end cap is configured to cause another portion of the air flow to attach to the body upstream of the stator assembly cavity inlet. As a result, another portion of the air flow can be directed across the stator assembly within the stator assembly cavity, which can increase the cooling of the stator assembly compared to an arrangement without a stator assembly cavity and a stator assembly cavity inlet. Additionally, by attaching another portion of the air flow to the body upstream of the stator assembly cavity inlet, the flow rate of another portion of the air flow entering the stator assembly cavity inlet can be increased compared to an arrangement where another portion detaches upstream of the stator assembly cavity inlet. Thus, the cooling of the stator assembly can be further enhanced. Optionally, the end cap is configured to cause another portion of the air flow to attach to the end cap such that another portion of the air flow attaches to the body upstream of the stator assembly cavity inlet.

[0010] Optionally, the end cap includes an inlet for allowing an additional portion of the air flow to enter the frame and an outlet for allowing an additional portion of the air flow to leave the frame. As a result, the inlet and outlet can be used to direct an additional portion of the air flow to provide cooling to the motor components located within the frame. For example, the rotor assembly can include components located between the inlet and the outlet such that an additional portion of the air flow passes over and cools the components. Cooling the motor components can increase the lifespan of the motor and / or enable the motor to operate at a higher speed compared to not cooling the motor components.

[0011] Optionally, the end cap includes a cavity located between the inlet and the outlet, and components of the rotor assembly extend into the cavity. As a result, when an air flow passes through the cavity, the components and thus the rotor assembly can be cooled by an additional portion of the air flow. For example, the components can be convectively cooled by the additional portion of the air flow, while other components of the rotor assembly can be conductively cooled by the components. In addition, the components can act as a centrifugal pump to increase the flow rate of the additional portion of the air flow through the cavity, thereby increasing the cooling of the motor.

[0012] Optionally, the minimum clearance between the components and the end cap is not less than 0.17 mm. Thus, the additional portion of the air flow can have a greater flow rate compared to a situation where the minimum clearance is less than 0.17 mm. Therefore, the cooling of the rotor assembly can be increased compared to a configuration with a clearance less than 0.17 mm.

[0013] Optionally, the outer diameter of the component is not less than 2.3 mm. Thus, the component can impart a greater velocity to the additional portion of the air flow, which can increase the centrifugal pumping performed by the component, thereby increasing the flow rate of the additional portion of the air flow to a greater extent than a component with a diameter less than 2.3 mm.

[0014] Optionally, the body includes a stator assembly cavity in which the stator assembly is at least partially located; and the brushless permanent magnet motor includes a seal configured to prevent the additional portion of the air flow from flowing from the cavity to the stator assembly cavity. Providing the seal can prevent the additional portion of the air flow that has been used to cool the rotor assembly and may thus be heated from being used to cool the stator assembly in the stator assembly cavity. Thus, another portion of the air flow (e.g., another part of the air flow), which may be cooler than the portion of the air flow that has passed through the cavity (e.g., because it was not previously used to cool the rotor assembly), can be used to cool the stator assembly in the stator assembly cavity. This can increase the cooling of the stator assembly compared to an arrangement without a seal.

[0015] Optionally, the end cap is located upstream of the stator assembly, and the rotor assembly includes a bearing located upstream of the stator assembly. Thus, the inlet and the outlet can be used to direct an additional portion of the air flow to cool the bearing. For example, the additional portion of the air flow can be directed to a component of the motor connected to the bearing to conductively cool the bearing. Therefore, the cooling of the bearing can be increased compared to an arrangement without an inlet and an outlet. Increasing the cooling of the bearing can be particularly advantageous because the life of the bearing may be particularly sensitive to excessive temperatures compared to other components of the motor (e.g., the shaft of the rotor assembly). Thus, increasing the cooling of the bearing may have a greater impact on the life of the motor compared to cooling other components of the motor that are less sensitive to temperature.

[0016] Optionally, the end cap is configured to cause a portion of the air flow to attach to the end cap upstream of the outlet and downstream of the inlet. An additional portion of the air flow entering the inlet may be decelerated, which may cause the pressure of the additional portion of the air flow at the inlet to increase relative to the pressure of the portion of the air flow attached to the end cap. Thus, by attaching the portion of the air flow to the end cap upstream of the outlet and downstream of the inlet, an attached portion of the air flow is provided at the outlet rather than the inlet, and a pressure difference can be created between the inlet and the outlet. Compared with an end that is not configured in this way, this pressure difference can increase the flow rate of the additional portion of the air flow through the cavity, thereby increasing the cooling of the rotor assembly. For example, if the portion of the air flow is attached downstream of the inlet, a region of stationary air can be provided at the outlet, which can have substantially the same pressure as the additional air flow at the inlet, thereby creating a small or no pressure difference.

[0017] Optionally, the body includes a stator assembly cavity, the stator assembly is at least partially located within the stator assembly cavity, the body includes a stator assembly cavity inlet for allowing another portion of the air flow to enter the stator assembly cavity, and the outlet surrounds the perimeter of the body and is axially offset from the stator assembly cavity inlet. As a result, compared with an arrangement where the outlet and the stator assembly cavity inlet are not offset, the cooling of the stator assembly can be increased. As described above, the additional portion of the air flow can be guided by the inlet and the outlet to cool the components within the frame. Thus, the additional portion of the air flow discharged from the outlet may be heated. If the outlet is not offset from the stator assembly cavity inlet, the previously heated additional portion of the air flow discharged from the outlet may enter the stator assembly cavity inlet and be less effective in cooling the stator assembly than the air flow that was not previously guided to cool the components within the frame. Optionally, the axial direction is parallel to the central longitudinal axis of the brushless permanent magnet motor.

[0018] Optionally, the rotor assembly includes an impeller located downstream of the stator assembly. Thus, compared with the impeller being located upstream of the stator assembly, the motor can be better cooled because when the impeller acts on the air flow, the impeller may heat the air flow, which may reduce the efficiency of the air flow in cooling the motor.

[0019] Optionally, the rotor assembly and the stator assembly are configured to rotate the rotor assembly at an operating speed of not less than 10,000 revolutions per minute in use. The flow rate of the air flow can be proportional to the operating speed. Thus, compared with an operating speed of less than 10,000 RPM, an operating speed of not less than 10,000 revolutions per minute (rpm) can increase the flow rate of the air flow, thereby increasing the cooling provided by the air flow.

[0020] Optionally, the rotor assembly and the stator assembly are configured to rotate the rotor assembly at an operating speed in use, and the operating speed is not greater than 500,000 revolutions per minute. The heat generated within the motor may be proportional to the operating speed. For example, a greater operating speed may result in more heat being generated. Thus, having an operating speed not greater than 500,000 rpm can reduce the heat generated, as compared to an operating speed less than 500,000 rpm, thereby increasing the lifespan of the motor components. Optionally, the operating speed is not greater than 400,000 rpm, 300,000 rpm, 200,000 rpm or 150,000 rpm.

[0021] According to a second aspect of the present invention, there is provided a vacuum cleaner including a brushless permanent magnet motor according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a side view of the brushless permanent magnet motor;

[0023] Figure 2 is a perspective view of the brushless permanent magnet motor;

[0024] Figure 3 is a perspective view of the stator assembly of the brushless permanent magnet motor;

[0025] Figure 4 is a perspective view of the rotor assembly of the brushless permanent magnet motor;

[0026] Figure 5 is a cross-sectional view of the brushless permanent magnet motor with the stator assembly and the rotor assembly removed;

[0027] Figure 6a is a perspective view of the top of the end cap of the brushless permanent magnet motor;

[0028] Figure 6b is a perspective view of the bottom of the end cap of the brushless permanent magnet motor;

[0029] Figure 7 is an enlarged cross-sectional view of the upstream end of the brushless permanent magnet motor;

[0030] Figure 8 is a first cross-sectional view of the brushless permanent magnet motor;

[0031] Figure 9 is a second cross-sectional view of the brushless permanent magnet motor;

[0032] Figure 10 is a third cross-sectional view of the brushless permanent magnet motor;

[0033] Figure 11 is an enlarged cross-sectional view of the upstream end of the brushless permanent magnet motor; and

[0034] Figure 12Perspective view of a vacuum cleaner equipped with a brushless permanent magnet motor. Detailed implementation

[0035] Figure 1 and Figure 2 shows a brushless permanent magnet motor (generally denoted by 10) according to the present invention, Figure 3 and Figure 4 shows the components of the brushless permanent magnet motor 10.

[0036] The brushless permanent magnet motor 10 includes a stator assembly 12, a rotor assembly 14, a frame 16, and a diffuser 18.

[0037] The stator assembly 12 is shown separately in Figure 3 and includes four stator core sub-assemblies 20 and a terminal assembly 22.

[0038] The stator core sub-assembly 20 includes a stator core (not shown), a bobbin 24, and a winding 26. The stator core has a generally C-shaped form and can be referred to as a C-core. The bobbin 24 is overmolded onto the stator core and includes a first connecting portion 28 and a second connecting portion 30. The shapes of the first connecting portion 28 and the second connecting portion 30 are complementary such that adjacent bobbins 24 in the stator assembly 12 can be connected to each other by axially sliding the associated connecting portions 28, 30 together. The winding 26 is wound around the bobbin 24.

[0039] The terminal assembly 22 includes a first upper terminal 32, a second lower terminal 34, a first terminal tab 36, and a second terminal tab 38. Each of the first terminal 32 and the second terminal 34 is generally annular, and the first terminal 32 covers the second terminal 34. The winding 26 of the stator core sub-assembly 20 is connected to the first terminal 32 and the second terminal 34. The first terminal tab 36 and the second terminal tab 38 project upward from the terminal assembly 22 and are each connected to one of the first terminal 32 and the second terminal 34. The terminal tabs 36, 38 are used to supply power to the terminals 32, 34.

[0040] Figure 4 The rotor assembly 14 is shown separately in

[0041] The rotor assembly 14 includes a shaft 40, permanent magnets 42, a first bearing 44, a second bearing 46, a first balance ring 48, a second balance ring 50, a third balance ring 52, and an impeller 54.

[0041] The shaft 40 is elongated and has an upstream end 56 and a downstream end 58, where upstream and downstream generally refer to the direction of the air flow through the brushless permanent magnet motor 10 during use. The permanent magnet 42 is typically mounted centrally along the shaft 40. The first balance ring 48 is mounted to the shaft 40 at the upstream end 56, and the first bearing 44 is mounted to the shaft 40 adjacent to the first balance ring 48. The second balance ring 50 is mounted to the shaft 40 between the first bearing 44 and the permanent magnet 42. The impeller 54 is mounted to the downstream end 58 of the shaft 40. The second bearing 46 is mounted to the shaft 40 adjacent to the impeller 54, and the third balance ring 52 is mounted to the shaft 40 between the second bearing 46 and the permanent magnet 42. The outer diameter of the first balance ring 48 is not less than 2.3 mm.

[0042] The rotor assembly 14 includes a preload spring 60 for applying a preload to the first bearing 44, and a seal in the form of an O-ring 62 located around the first bearing 44.

[0043] In Figure 1 、 2 and 5, the frame 16 can be seen, which includes a body 64, a shroud 66, and an end cap 68.

[0044] The body 64 is generally cylindrical and has four protrusions 70. The body 64 defines a first bearing seat 70 and a second bearing seat 72 for the respective first bearing 44 and second bearing 46. The body 64 also defines a channel 74, within which the rotor assembly 14 is located and into which the stator assembly 12 extends. Each protrusion 70 covers the stator core assembly 16.

[0045] The body 64 of the frame 16 includes a plurality of cooling inlets 78 and a plurality of cooling outlets 80. The plurality of cooling inlets 78 are located in the area below the first bearing seat 70 and are spaced around the perimeter of the body 64. The plurality of cooling inlets 78 are shaped to direct the air flow passing through the body 64 into the channel 74 during use, which provides a cooling effect for the stator assembly 12 and components of the rotor assembly 14 (such as the permanent magnet 42) located between the cooling inlets 78 and outlets 80. The plurality of cooling outlets 80 are located in the area of the second bearing seat 72 and are spaced around the perimeter of the body 64. The plurality of cooling outlets 80 are shaped to direct the air flow passing through the channel 74 out of the frame 16 before the air flow passes through the impeller 54.

[0046] The downstream end of the body 64 of the frame 16 defines a labyrinth seal together with the impeller 54.

[0047] The shroud 66 is axially spaced from the body 64 and has a central hole that covers the impeller 54 such that the air flow can interact with the impeller 54 during use.

[0048] As Figure 6a 、 6b7, the end cap 68 is hollow and forms the upstream end of the frame 16. The end cap 68 includes a cavity 82, an inlet 84, an outlet 86, a terminal pocket 88, a finger 90, and an adhesive groove 92.

[0049] The end cap 68 has a parabolic profile. The parabolic profile is such that the end cap 68 is substantially perpendicular to the central longitudinal axis at the apex of the profile and substantially parallel to the central longitudinal axis at the ends of the parabolic profile. The ratio of the radius of curvature of the end cap 68 to the maximum width of the end cap 68 is not less than 0.30. The maximum width occurs at the portion of the end cap 68 adjacent to and connected to the body 64.

[0050] The cavity 82 extends between an inlet 84 and an outlet 86. The inlet 84 is circular and centered at the vertex of the parabolic profile. The outlets 86 are located at either end of the parabolic profile and on opposite sides of the end cap 68. In this example, the outlets 86 are rectangular, however, other shapes of outlets 86 may also be used. The end cap 68 includes two outlets 86. However, in other examples, the end cap 68 may include a single outlet 86 or three or more outlets 86.

[0051] The terminal pocket 88 is a hole in the end cap 68 through which the terminal tabs 36, 38 extend. The fingers 90 project in a downstream direction away from the inlet 84, are elastically deformable, and when not mounted to the brushless permanent magnet motor 10, the plurality of fingers 90 are slightly flared outward from the body 64. The fingers 90 engage the interior of the passage 74 to mount the end cap 68 to the body 64. The adhesive groove 92 is located on the downstream face of the end cap 68 and contains an adhesive that secures the end cap 68 to the body 64.

[0052] Figure 8 1 shows a cross section of the brushless permanent magnet motor 10. It can be seen that the rotor assembly 14 is located within the frame 16, the first bearing 44 is located at the first bearing seat 70, the second bearing 46 is located at the second bearing seat 72, and the permanent magnet 42 is aligned with the stator core of the stator assembly 12. Therefore, the impeller 54 is located on the downstream side of the stator assembly 12, and the first bearing 44 is located on the upstream side of the stator assembly 12.

[0053] The end cover 68 is connected to the upstream end of the main body 64 so as to be located on the upstream side of the stator assembly 12 .

[0054] from Figure 7As can be seen, the O-ring 62 is located between the first bearing 44 and the body 64 and serves as a seal to prevent air flow through. Thus, the O-ring 62 divides the passage 74 into an upper part and a lower part. The second balance ring 50, the permanent magnet 42, the third balance ring 52, a part of the stator assembly 12, and the second bearing 46 are located in the lower part. A part of the first bearing 44, a part of the shaft 40, and the first balance ring 48 are located in the upper part. The end cap 68 is connected to the upstream end of the body 64 such that the cavity 82 of the end cap 68 and the upper part of the passage 74 form a single cavity.

[0055] A part of the first balance ring 48 and the shaft 40 extends into the cavity 82 of the end cap 68 such that the minimum clearance between the interior of the end cap 68 and the first balance ring 48 is not less than 0.17 mm. The maximum width of the part of the end cap 68 that abuts and is connected to the upstream end of the body 64 is substantially the same as the maximum width of the upstream end of the body 64. The maximum width of this part of the end cap 68 is 21.3 mm, and the maximum width of the upstream end of the body 64 is 21.3 mm.

[0056] As Figure 1 and 2 shown, the outlet 86 of the end cap 68 surrounds the periphery of the body 64 and is offset in the axial direction (i.e., the direction parallel to the central longitudinal axis of the brushless permanent magnet motor 10) from the cooling inlet 78.

[0057] The diffuser 18 is located downstream of the impeller 54. The diffuser 18 is attached to the shroud 66 and includes a plurality of vanes for deflecting the air flow as it passes from the impeller 54 through the diffuser 18 during use. Although described as a multi-stage diffuser, i.e., a diffuser having more than one row of vanes, it should be understood that other forms of diffusers, such as single-stage diffusers, may also be contemplated.

[0058] In use, an electric current passes through the windings 24 of the stator assembly 12 to generate a magnetic field that interacts with the permanent magnet 42, thereby causing the rotor assembly 14 to rotate. After an initial acceleration phase, the rotor assembly 14 rotates at a steady-state speed (referred to as the operating speed) between 10,000 rpm and 500,000 rpm. The rotation of the rotor assembly 14 causes the impeller 54 to rotate, and the impeller 54 generates an air flow through the brushless permanent magnet motor 10.

[0059] Now refer to Figure 9, due to the shape of the end cap 68, a first portion 94 of the air flow attaches to the end cap 68 downstream of the inlet 84 and upstream of the outlet 86. As the first portion 94 of the air flow flows from the end cap 68 towards the body 64 and around the protrusion 70, the first portion 94 of the air flow remains attached to the frame 16. Heat generated by the stator assembly 12 is transferred to the first portion 94 of the air flow through the protrusion 70. The first portion 94 of the air flow then continues to flow downstream until it enters the shroud 66 and interacts with the impeller 54 before leaving the brushless permanent magnet motor 10 via the diffuser 18.

[0060] Now refer to Figure 10 , due to the shape of the end cap 68, a second portion 96 of the air flow attaches to the end cap 68 downstream of the inlet 84 and upstream of the outlet 86. The second portion 96 of the air flow deviates from the first portion 94 of the air flow around the perimeter of the end cap 68 such that as the second portion 96 of the air flow flows downwardly beneath the frame 16 (while remaining attached to the frame 16), the second portion 96 of the air flow flows into the cooling inlet 78 and into the frame 16. The second portion 96 of the air flow then flows along the passage 74. Heat generated by the stator assembly 12 and the permanent magnet 42 is transferred to the second portion 96 of the air flow. The second air flow then exits the frame 16 through the cooling outlet 80. The second portion 96 of the air flow then continues to flow downstream until it enters the shroud 66 and interacts with the impeller 54 before leaving the brushless permanent magnet motor 10 via the diffuser 18.

[0061] Now refer to Figure 11 , a third portion 98 of the air flow enters the cavity 82 of the end cap 68 via the inlet 84. The third portion 98 of the air flow then flows through the first balance ring 48, which accelerates the third portion 98 of the air flow due to the rotation of the first balance ring 48. The third portion 98 of the air flow then exits the cavity 82 of the end cap 68 via the outlet 86. As described above, the upper portion of the passage 74 and the cavity 82 of the end cap 68 form a single cavity. As a result, some of the third portion 98 of the air flow flows through the first bearing before exiting the cavity 82 of the end cap 68 via the outlet 86.

[0062] Once the third portion 98 of the air flow has exited the outlet 86 of the end cap 68, the third portion 98 of the air flow flows along the body 64 and through the impeller 54. Since the outlet 86 of the end cap 68 is offset around the perimeter of the frame 16 from the cooling inlet 78, the heated third portion 98 of the air flow exits the outlet 86 and enters the shroud 66 without entering the cooling inlet 78.

[0063] Since the end cap 68 is configured to attach a first portion 94 of the air flow to the protrusion 70 covering the stator assembly 12, the stator assembly 12 can be cooled by the first portion 94 of the air flow passing through the protrusion 70. For example, the first portion 94 of the air flow can convectively cool the protrusion 70, which in turn can conductively cool the stator assembly 12. Since the first portion 94 of the air flow is attached to the protrusion 70, greater heat transfer can occur between the body 64 and the first portion 94 of the air flow compared to an arrangement where the first portion 94 of the air flow detaches from the protrusion 70, which can increase the cooling of the stator assembly 12. Cooling the stator assembly 12 can increase the lifespan of the stator assembly 12. Forming the end cap 68 and the body 64 as separate components can increase the ease of assembly of the brushless permanent magnet motor 10 compared to an arrangement where the end cap 68 and the body 64 are integrally formed. For example, the stator assembly 12 and the rotor assembly 14 can be inserted into the body 64, and then the end cap 68 can be attached to the body 64. Additionally, forming the end cap 68 and the body 64 as separate components can provide better control over the process (e.g., molding) of forming the end cap 68 compared to integrally forming the end cap 68 and the body 64. Greater control over the process can enable greater control over the geometry of the end cap 68, which can result in increased attachment of the air flow.

[0064] Since the end cap 68 includes an inlet 84 and an outlet 86, the inlet 84 and the outlet 86 can be used to direct a third portion 98 of the air flow to provide cooling to motor components located within the frame 16 and on the upstream side (i.e., away from the impeller 54) of the stator assembly 12. For example, a first balance ring 48 and a portion of the shaft 40 are located between the inlet 84 and the outlet 86 and can be cooled by the passage of the third portion 98 of the air flow. Cooling the first balance ring 48 and the shaft 40 can also conductively cool other components of the rotor assembly 14, such as the first bearing 44. Cooling the components of the brushless permanent magnet motor 10 can increase the lifespan of the brushless permanent magnet motor 10 and / or enable the brushless permanent magnet motor 10 to operate at higher speeds compared to not cooling the components of the brushless permanent magnet motor 10.

[0065] In the above example, the body 64 includes the protrusion 70 covering the stator assembly 12. However, in other examples, the body 64 can have other shapes such that the protrusion 70 can be omitted and other portions of the body 64 cover the stator assembly 12. Thus, in a more general sense, it can be said that a portion of the body 64 covers the stator assembly 12 and the end cap 68 is configured to attach a portion of the air flow to that portion of the body 64 covering the stator assembly 12.

[0066] In the above example, the first balance ring 48 extends into the cavity 82 of the end cap 68. However, other components of the rotor assembly 14 can alternatively extend into the cavity 82 of the end cap 68. For example, the first balance ring 48 can be omitted and the shaft 40 of the rotor assembly 14 extends into the cavity 82 of the end cap 68 without the first balance ring 48.

[0067] The brushless permanent magnet motor 10 described herein can find particular use in applications where a small form factor but high power density is desired. By way of example, Figure 12 A vacuum cleaner 100 including the brushless permanent magnet motor 10 is schematically shown.

[0068] Although combinations of features are described herein, it should be understood that embodiments of the brushless motor 10 that implement only some of the above features are also contemplated.

Claims

1. A brushless permanent magnet motor, comprising: A rotor assembly rotatable to generate an air flow; A stator assembly; And A frame, wherein the rotor assembly and the stator assembly are accommodated in the frame, and the frame includes an end cap and a body, Wherein: The end cap and the body are separate components; and The end cap is configured to cause a portion of the air flow to adhere to a portion of the body covering the stator assembly.

2. The brushless permanent magnet motor according to claim 1, wherein, The end cap is configured to cause the portion of the air flow to adhere to the end cap.

3. The brushless permanent magnet motor according to claim 2, wherein, The ratio of the radius of curvature of the end cap to the maximum width of the end cap is not less than 0.

30.

4. The brushless permanent magnet motor according to claim 2 or 3, wherein: A plane extends along the central longitudinal axis of the brushless permanent magnet motor; and The end cap is shaped such that when viewed in the plane, the end cap has a parabolic profile.

5. The brushless permanent magnet motor according to any one of claims 2 to 4, wherein, When assembling the frame, the maximum width of a portion of the end cap adjacent to the body is substantially the same as the maximum width of another portion of the body adjacent to the end cap.

6. The brushless permanent magnet motor according to any one of the preceding claims, wherein: The body includes a stator assembly cavity, and the stator assembly is at least partially located in the stator assembly cavity; The body includes a stator assembly cavity inlet for allowing another portion of the air flow to enter the stator assembly cavity; And The end cap is configured to cause the another portion of the air flow to adhere to the body upstream of the stator assembly cavity inlet.

7. The brushless permanent magnet motor according to any one of the preceding claims, wherein, The end cap includes an inlet for allowing an additional portion of the air flow to enter the frame, and an outlet for allowing the additional portion of the air flow to leave the frame.

8. The brushless permanent magnet motor according to claim 7, wherein: The end cap includes a cavity located between the inlet and the outlet; and A component of the rotor assembly extends into the cavity.

9. The brushless permanent magnet motor according to claim 8, wherein, The minimum clearance between the component and the end cap is not less than 0.17 mm.

10. The brushless permanent magnet motor according to claim 8 or 9, wherein, The outer diameter of the component is not less than 2.3 mm.

11. The brushless permanent magnet motor according to any one of claims 8 to 10, wherein: The body includes a stator assembly cavity, and the stator assembly is at least partially located in the stator assembly cavity; and The brushless permanent magnet motor includes a seal configured to prevent the additional portion of the air flow from flowing from the cavity to the stator assembly cavity.

12. The brushless permanent magnet motor according to any one of claims 7 to 11, wherein: The end cap is located upstream of the stator assembly; and The rotor assembly includes a bearing located upstream of the stator assembly.

13. The brushless permanent magnet motor according to any one of claims 7 to 12, wherein The end cap is configured to cause the portion of the air flow to adhere to the end cap upstream of the outlet and downstream of the inlet.

14. The brushless permanent magnet motor according to any one of claims 7 to 13, wherein: The body includes a stator assembly cavity, and the stator assembly is at least partially located in the stator assembly cavity; The body includes a stator assembly cavity inlet for allowing another portion of the air flow to enter the stator assembly cavity; and The outlet surrounds the perimeter of the body and is axially offset from the stator assembly cavity inlet.

15. The brushless permanent magnet motor according to any one of the preceding claims, wherein, The rotor assembly includes an impeller located downstream of the stator assembly.

16. The brushless permanent magnet motor according to any one of the preceding claims, wherein, The rotor assembly and the stator assembly are configured to rotate the rotor assembly at an operating speed of not less than 10,000 revolutions per minute in use.

17. The brushless permanent magnet motor according to any one of the preceding claims, wherein: The rotor assembly and the stator assembly are configured to rotate the rotor assembly at an operating speed in use; and The operating speed is not greater than 500,000 revolutions per minute.

18. A vacuum cleaner comprising a brushless permanent magnet motor as claimed in any one of the preceding claims.

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