An electric motor

Abstract

An electric motor comprising a frame comprising a plurality of diffuser vanes and a stator assembly comprising a plurality of winding portions. The stator assembly is positioned relative to the frame such that each of the plurality of winding portions is disposed at least partially between respective adjacent diffuser vanes of the plurality of diffuser vanes.

Description

[0001] 1 P004759-W001

[0002] AN ELECTRIC MOTOR

[0003] BACKGROUND

[0004] Electric motors may be used in appliances such as vacuum cleaners to generate an air flow. For example, the electric motor may comprise an impeller that generates suction to enable dirt and debris to be removed from a surface to be cleaned.

[0005] SUMMARY

[0006] In a first aspect, the present disclosure provides an electric motor comprising: a frame comprising a plurality of diffuser vanes; and a stator assembly comprising a plurality of winding portions, wherein the stator assembly is positioned relative to the frame such that each of the plurality of winding portions is disposed at least partially between respective adjacent diffuser vanes of the plurality of diffuser vanes.

[0007] By positioning at least part of each winding portion between adjacent diffuser vanes, the size of the frame may be decreased. In particular, the diameter of the frame may be decreased without decreasing the size of the stator assembly or the power output of the electric motor. Alternatively, for a given frame diameter, the size of the stator assembly may be increased, maximising the power output of the electric motor.

[0008] In addition, by placing the winding portions between the diffuser vanes, the winding portions are placed within airflow channels that are formed between adjacent diffuser vanes. In use, when air flows between the diffuser vanes and along the airflow channels, the airflow cools the winding portions. Heat generated by the electric motor is therefore dissipated more easily.

[0009] The plurality of winding portions may each comprise a stator core and a winding wound around the stator core, and at least a portion of the winding of each winding portion may be disposed between the respective adjacent diffuser vanes.

[0010] The windings of a stator assembly may be the part of the stator assembly that protrudes to the greatest extent in the radial direction. Therefore, the windings may be disposed between the 2 P004759-W001 adjacent diffuser vanes. This enables the maximum efficiency gains in terms of frame size and motor power.

[0011] Each pair of adjacent diffuser vanes may define a fluid flow channel therebetween, and each of the plurality of winding portions is disposed at least partially within a respective fluid flow channel.

[0012] The winding portions may generate heat in use. Therefore, the winding portions benefit from placement within the airflow channels formed between adjacent diffuser vanes.

[0013] The plurality of diffuser vanes may be arranged about a central, longitudinal axis. As a result, the fluid flow channels are likewise arranged about the longitudinal axis. Each of the fluid flow channels may then be said to have a height that extends radially, a width that extends circumferentially, and a length that extends axially relative to the longitudinal axis.

[0014] Each of the plurality of winding portions may extend radially into the respective fluid flow channel by a radial extent of at least 20% of a radial height of the respective fluid flow channel, wherein optionally the radial extent is at least 40% of the radial height, or at least 60% of the radial height.

[0015] Each of the plurality of winding portions may extend circumferentially within the respective fluid flow channel by a circumferential extent of at least 35% of a circumferential width of the respective fluid flow channel, wherein optionally the circumferential extent is at least at least 50% of the circumferential width.

[0016] Each of the plurality of winding portions may extend axially along the respective fluid flow channel by an axial extent of at least 30% of an axial length of the respective fluid flow channel, wherein optionally the axial extent is at least 50% of the axial length, or at least 70% of the axial length.

[0017] Each of the plurality of winding portions extends within a respective fluid flow channel in the radial, circumferential and axial directions. The benefit of this is that more of each winding 3 P004759-W001 portion is disposed within the respective fluid flow channel, thereby enabling a reduction in the size of the motor to be maximised. Furthermore, because more of each winding portion is exposed to the fluid flow, cooling is improved.

[0018] These benefits may be maximised when each of the plurality of winding portions extends radially into the respective fluid flow channel by a radial extent of 70% of the radial height of the respective fluid flow channel. They may be further maximised when each of the plurality of winding portions extends circumferentially within the respective fluid flow channel by a circumferential extent of 55% of a circumferential width of the respective fluid flow channel. They may also be further maximised when each of the plurality of winding portions extends axially along the respective fluid flow channel by an axial extent of 80% of an axial length of the respective fluid flow channel.

[0019] The plurality of diffuser vanes may comprise a circumferential row of diffuser vanes, and the respective adjacent diffuser vanes form part of the circumferential row of diffuser vanes.

[0020] By placing the winding portions between adjacent diffuser vanes of a circumferential row of diffuser vanes, the electric motor may be relatively compact in an axial direction. The diffuser vanes and the winding portions are all positioned in the same circumferential row, reducing the length of the electric motor in the axial direction.

[0021] A circumferential distance between adj acent diffuser vanes having a winding portion disposed therebetween may be greater than a circumferential distance between adjacent diffuser vanes having no stator portion therebetween.

[0022] The diffuser vanes may be arranged so that those that have winding portions placed between them are further apart than those that do not have winding portions between them. This enables a greater number of diffuser vanes to be included than would the case if the diffuser vanes were distributed axis-symmetrically. This also allows the diffuser vanes to be configured to manage airflow through the frame, depending on whether winding portions are present. The circumferential distance may also be referred to as circumferential pitch. 4 P004759-W001

[0023] A pitch angle of the adjacent diffuser vanes having a winding portion disposed therebetween may be from 35° to 75°, or optionally may be from 45° to 65°. A pitch angle of the adjacent diffuser vanes having no winding portion disposed therebetween may be from 15° to 55°, or optionally may be from 25° to 45°.

[0024] The plurality of diffuser vanes may comprise a further circumferential row of diffuser vanes disposed upstream of the circumferential row of diffuser vanes.

[0025] The plurality of diffuser vanes may be arranged in a plurality of groups of diffuser vanes, and each of the plurality of winding portions may be disposed between adjacent diffuser vanes of different groups, and a circumferential distance between adjacent diffuser vanes within a group may be less than a circumferential distance between the respective adjacent diffuser vanes of different groups.

[0026] The diffuser vanes may be arranged in groups. The adjacent diffuser vanes of different groups may be placed further apart than adjacent diffuser vanes within a group. This enables a greater number of diffuser vanes to be included than would the case if the diffuser vanes were not formed in groups. This also allows the groups of diffuser vanes to be configured to manage airflow through the frame, depending on whether winding portions are present. The arrangement of the diffuser vanes is designed to increase motor efficiency and to increase the static pressure generated by the motor.

[0027] Each group of diffuser vanes may include at least three diffuser vanes, and a circumferential distance between a first pair of adjacent diffuser vanes may be different to a circumferential distance between a second pair of adjacent diffuser vanes of each respective group. This enables the efficiency and static pressure rise of the electric motor to be optimised.

[0028] The plurality of groups of diffuser vanes may be symmetrically arranged around the circumferential row of diffuser vanes.

[0029] This makes the design of the frame more straight-forward, as the groups are placed axis- symmetrically. Placing the groups in this way also ensures the frame is aerodynamically balanced. Air will flow through the airflow channels in a similar manner within each group. 5 P004759-W001

[0030] There may be at least three winding portions and at least three groups of diffuser vanes.

[0031] The electric motor may have three winding portions. In such an arrangement, the diffuser vanes are also arranged in three groups.

[0032] The frame may comprise an annular inner wall and an annular outer wall, and the plurality of diffuser vanes may extend between the annular inner wall and the annular outer wall.

[0033] The annular inner wall may support the stator assembly. The inner wall also provides an inner periphery to fluid flow channels defined between adjacent diffuser vanes. The inner walls are shorter, in an axial direction, than the outer walls. The inner walls extend only partially along the radially inner edges of the diffuser vanes.

[0034] Each of the plurality of winding portions may extend through a respective recess in the annular inner wall.

[0035] The annular outer wall and the annular inner wall may extend along a longitudinal axis, and an extent of the annular outer wall may be greater than an extent of the annular inner wall in a longitudinal or axial direction.

[0036] By using an inner wall which is longitudinally shorter than the outer wall, the inner wall does not block the winding portions from extending between the diffuser vanes. This enables an inner wall to be used which provides structural strength to the frame, while also enabling the winding portions to extend between the diffuser vanes.

[0037] Each of the plurality of diffuser vanes may extend at least in the longitudinal direction, and an extent of each of the plurality of diffuser vanes in the longitudinal direction is greater than the longitudinal extent of the annular inner wall.

[0038] The inner wall does not extend along the entire longitudinal length of the diffuser vanes. Therefore, a region is formed beyond an edge of the inner wall in which the winding portions can extend radially between the diffuser vanes. 6 P004759-W001

[0039] Each of the plurality of winding portions may be disposed at least partially between a portion of the respective adjacent diffuser vanes that extends longitudinally past the annular inner wall.

[0040] The winding portions are located in gaps which are formed between the diffuser vanes and the inner wall. This enables the stator assembly to protrude into the gaps formed between the diffuser vanes, while also allowing the inner wall to be user to retain the stator assembly.

[0041] Each diffuser vane may be curved in the longitudinal direction, and each of the diffuser vanes of the plurality of diffuser vanes may have a curvature selected from at least a first and a second curvature, wherein at least a first diffuser vane of the plurality of diffuser vanes may have the first curvature and at least a second diffuser vane of the plurality of diffuser vanes may have the second curvature.

[0042] Each diffuser vane may have a stagger angle, and at least one of the diffuser vanes may have a stagger angle different to the stagger angle of the remaining diffuser vanes.

[0043] The curvature and stagger angle of the diffuser vanes may be selected to optimise the efficiency and static pressure rise of the electric motor. The curvature and stagger angle of each diffuser vane may be the same. Alternatively, every diffuser vane may have a different curvature and stagger angle. In one example, the curvature and stagger angle are different for each diffuser vane of a given group, with the curvature and stagger being repeated across each group.

[0044] Each of the plurality of diffuser vanes may be curved along its length. Curved diffuser vanes result in fluid flow channels which are aerodynamically configured to allow air to pass efficiently through the frame, and to increase the static pressure generated by the electric motor. The curvature of each diffuser vane may be designed to improve the fluid flow through each fluid flow channel to account for the presence of the winding portions. The diffuser vanes may all have identical curvatures, or some diffuser vanes may have different curvatures, depending on the fluid flow requirements around the winding portions. 7 P004759-W001

[0045] Each of the plurality of diffuser vanes may extend longitudinally and circumferentially about an axis. As well as being curved, the diffuser vanes extend both longitudinally and circumferentially. This aerodynamically defines the airflow channels to ensure efficient airflow through the frame.

[0046] Each of the plurality of diffuser vanes may have a stagger angle of between 20 and 40 degrees. The configuration of the diffuser vanes is optimised to ensure efficient airflow through the fluid flow channels.

[0047] The electric motor may comprise a rotor assembly comprising an impeller and a rotor core secured to a shaft. The plurality of diffuser vanes may act on a fluid flow generated by the impeller in use. The stator assembly and the plurality of diffuser vanes surround the rotor core. The rotor core may comprise a permanent magnet.

[0048] In a second aspect, the present disclosure provides an appliance comprising the electric motor according to any preceding clause.

[0049] The annular inner wall may have an upstream circumferential edge and a downstream circumferential edge, and the downstream circumferential edge may have a plurality of notches formed therein, each notch being configured to receive a portion of a winding portion of a stator assembly.

[0050] The diffuser vanes may be configured to guide a fluid from an upstream end to a downstream end, in a substantially longitudinal direction.

[0051] Each of the plurality of diffuser vanes may form an arc, each arc having a chord extending from one end of the arc to the other end of the arc and having a circumferential and longitudinal extent.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is an exploded perspective view of an electric motor. 8 P004759-W001

[0054] Figure 2 is perspective view of the assembled electric motor.

[0055] Figure 3 is a cross-sectional perspective view of the electric motor.

[0056] Figure 4A is a cross-sectional view of the electric motor.

[0057] Figure 4B is a sectional slice view of the electric motor;

[0058] Figure 5A is a perspective view of a stator assembly of the electric motor.

[0059] Figures 5B is an end view of the stator assembly.

[0060] Figure 6A is a cross-sectional perspective view of a rear frame, the stator assembly and a rotor assembly of the electric motor.

[0061] Figure 6B is a further cross-sectional view of the rear frame, the stator assembly and the rotor assembly.

[0062] Figure 7A is a further cross-sectional perspective view of the rear frame, the stator assembly and the rotor assembly.

[0063] Figure 7B is a further cross-sectional view of the rear frame, the stator assembly and the rotor assembly.

[0064] Figure 8 is a further cross-section perspective view of the electric motor.

[0065] Figure 9 is a further cross-sectional perspective view of the electric motor.

[0066] Figure 10 shows a simulation of fluid flow along fluid flow paths of the electric motor. Figure 11 shows a vacuum cleaner comprising the electric motor.

[0067] DETAILED DESCRIPTION

[0068] Figure 1 is an exploded perspective view of an electric motor 10. The motor electric motor 10 comprises a rear frame 12, a front frame 14, a rotor assembly 16, a stator assembly 18 and a shroud 20. The rear frame 12 comprises an inner wall 22 and an outer wall 24, both of which are annular. The longitudinal axes of the inner wall 22 and the outer wall 24 are aligned. The outer wall 24 surrounds the inner wall 22. A first row of diffuser vanes 26 extend between the inner wall 22 and the outer wall 24. The first row of diffuser vanes 26 is a circumferential row, extending around the inner wall 22 in a circumferential direction. The first row of diffuser vanes 26 defines a plurality of fluid flow channels 28, with each fluid flow channel 28 being disposed between adjacent diffuser vanes 26. In the longitudinal direction, the inner wall 22 is shorter in length than the outer wall 24. The inner wall 22 is positioned such that the outer wall 24 extends longitudinally beyond the inner wall 22 in a downstream direction. In the longitudinal direction, the first row of diffuser vanes 26 are longer than the inner wall 9 P004759-W001

[0069] 22, and shorter than the outer wall 24. A recess is therefore formed between adjacent diffuser vanes 26 and the inner wall 22. The inner wall 22 is cylindrical and defines a bore that can support the stator assembly 18 when the electric motor 10 is assembled.

[0070] The stator assembly 18 comprises a plurality of segments, which will be described in more detail below in connection with Figures 5 A and 5B. In this example, stator assembly comprises three segments. The stator assembly is not limited to three segments, and any number of segments greater than one may be used. Each stator segment includes a stator core 30, a bobbin 32 and a winding 34. The bobbin 32 is overmoulded onto the stator core 30. The winding 34 is wound about the bobbin 32. The stator assembly 18 also includes a busbar carrier 36 and a busbar 38 for enabling electrical coupling of the windings 34 to a power source and motor controller. When the segments of the stator assembly 18 are assembled, the bobbins 32 form a plurality of stator mountings 40. The stator mountings 40 are configured to be disposed within the bore formed by the inner wall 22 of the rear frame 12 when assembled. When assembled, the plurality of segments form a bore within which the rotor assembly 16 is disposed.

[0071] The rotor assembly 16 comprises a shaft 42, a magnet 44, a bearing assembly 46 and an impeller 48. When assembled, the rotor assembly 16 is disposed within the bore formed by the plurality of stator segments. The rotor assembly 16 is positioned such that the magnet 44 is disposed between the windings 34. The bearing assembly 46 is supported by the front frame 14, as will be described in more detail below.

[0072] The front frame 14 includes a main wall 50 and a rotor assembly support frame 52. The front frame 14 also includes a second row of diffuser vanes (not shown), which will be described in more detail in connection with Figure 3. The second row of diffuser vanes extend between the main wall 50 and the rotor assembly support frame 52. The rotor assembly support frame 52 defines a bore which supports the rotor assembly 16, when assembled.

[0073] The shroud 20 fits within the main wall 50 of the front frame 14. The shroud 20 has a conelike shape with a profile that complements the profile of the impeller 48. When assembled, 10 P004759-W001 the shroud 20 and the impeller 48 define a fluid flow path through which air is drawn into the first frame 14 in use.

[0074] Figure 2 is a perspective view of the assembled electric motor 10. In use, air enters the front frame 14 via an opening in the shroud 20. The front frame 14 is at an upstream end of the electric motor 10. Air exits the electric motor 10 via the opposing end of the rear frame 12. The rear frame 12 is at a downstream end of the electric motor 10. The rear frame 12 and the front frame 14 are coupled together using suitable fastenings such as glue or bolts, with a downstream end of the front frame 14 abutting an upstream end of the rear frame 12. The shroud 20 may be seen through the upstream opening in the front frame 14. The shaft 42 and impeller 48 may be seen though an upstream opening in the shroud 20.

[0075] Figure 3 is a cross-sectional perspective view of the electric motor 10. The bearing assembly 46 of the rotor assembly 16 is mounted within the bore of the rotor assembly support frame 52. The rotor assembly support frame 52 is fastened to the bobbin 32 by a labyrinth seal 54. The rotor assembly support frame 52 and the bobbin 32 may be sealed using any appropriate fastening means, such as glue, bolts or screws. By fastening the rotor assembly support frame 52 and bobbin 32 in this way, the front frame 14 and rear frame 12 are coupled together. The rotor assembly support frame 52 is connected to the main wall 50 of the front frame 14 by the second row of diffuser vanes 56. The second row of diffuser vanes extend radially from the rotor assembly support frame 52 to the main wall 50. When assembled, the second row of diffuser vanes 56 are positioned downstream from the impeller 48 and upstream from the first row of diffuser vanes 26.

[0076] As described above, the first row of diffuser vanes 26 define a plurality of fluid flow channels 28, with each fluid flow channel 28 being disposed between adjacent diffuser vanes 26. When assembled, the windings 34 are partially disposed within respective fluid flow channels 28. Further details of the manner in which the windings 34 are arranged within the fluid flow channels will be described below.

[0077] In Figure 3, profile ‘A’ is the plane through which the cross section is taken. This is the cross section used in Figures 4A and 4B. 11 P004759-W001

[0078] Figure 4A is a cross-sectional view of the electric motor 10 taken through the plane ‘A’ from Figure 3. Figure 4B is a slice view of the electric motor taken through the same plane.

[0079] The assembled electric motor 10 defines a number of fluid flow paths 58 through the front frame 14 and rear frame 12, shown by the arrows in Figure 4B. In the front frame 14, the fluid flow paths 58 are defined by the impeller 48 and the shroud 20. Downstream of the impeller 48 and shroud 20, the fluid flow paths 58 are defined by the rotor assembly support frame 52, the main wall 50 and the second row of diffuser vanes 56. In the rear frame 52, the fluid flow paths 58 are defined by the fluid flow channels 28. Figure 4B shows the windings 34 partially disposed within the fluid flow channels 28, and hence in the fluid flow paths 58.

[0080] Figures 5 A and 5B respectively show a perspective view and end view of the stator assembly 18. The stator assembly 18 includes three segments, with each segment including a stator core 30, bobbin 32, and winding 34. The bobbins 32 are overmoulded onto the stator cores 30. The windings 34 are would about the bobbins 32.

[0081] Figure 6A is a cross-sectional perspective view of the assembled rear frame 12, stator assembly 18 and rotor assembly 16. The cross section is taken through plane ‘B’. The first row of diffuser vanes 26 are shown extending circumferentially around the inner wall 22 of the rear frame 12. The windings 34 are disposed between adjacent diffuser vanes 26 of the first row of diffuser vanes, within the fluid flow channels 28. There are three windings 34, each of which is located between adjacent diffuser vanes 26 of the first row of diffuser vanes. There are nine diffuser vanes 26 in total, arranged in three groups of three. The pitch, or circumferential distance, between adjacent diffuser vanes, is greater for the diffuser vanes between which the windings 34 are disposed, than for the adjacent diffuser vanes between which there are no windings. As such, the pitch of the diffuser vanes 26 in a group is less than the circumferential distances between diffuser vanes of adjacent groups. This arrangement allows enough space between diffuser vanes to accommodate the windings 34, while maximising the number of diffuser vanes within the rear frame 12. 12 P004759-W001

[0082] Figure 6B is a cross-sectional view of the electric motor 10 taken through the plane ‘B’ from Figure 6A. Figure 6B shows the nine diffuser vanes 26, arranged in three groups of three. The pitch between adjacent diffuser vanes belonging to the same group is Pl . The windings 34 are not formed between these diffuser vanes. The pitch between adjacent diffuser vanes 26 of different groups is P2, which is greater than Pl. The windings 34 are disposed between these diffuser vanes. Figure 6B also shows a pitch P3, which is the distance between another pair of adjacent diffuser vanes 26. In some examples, P3 may be the same as Pl. However, in order to optimise efficiency and static pressure, Pl and P3 may be different.

[0083] Pitches Pl, P2 and P3 may be defined in terms of circumferential distance. Additionally, they may be defined in terms of pitch angle. That is, the angle formed between the radii extending from the central axis to adjacent diffuser vanes 26. In this example, the pitch angle for Pl and P3 may be from 15° to 55°. Alternatively, the pitch angle for Pl and P3 may be from 25° to 45° or from 30° to 40°. In this example, the pitch angle for P2 may be from 35° to 75°. Alternatively, the pitch angle for P2 may be from 45° to 65° or from 50° to 60°. In each example, the pitch angle of Pl and P3 is selected to be less than the pitch angle of P2.

[0084] Figure 7A is a further cross-sectional perspective view of the assembled rear frame 12, stator assembly 18 and rotor assembly 16. In Figure 7A, the cross section ‘C’ is taken downstream from plane ‘B’ of the cross section of Figure 6A. As such, the stator core 30 and the bobbin 32 are also shown in cross section.

[0085] Figure 7B is a cross-sectional view of the electric motor 10 taken through the plane ‘C’ from Figure 7 A. Because of the location of the plane ‘C’, the positional relationship between the windings 34, the stator core 30, the bobbin 32 are all clearly shown. Furthermore, the arrangement of the diffuser vanes 26, and the pitches Pl, P2 and P3 are also clearly shown.

[0086] Figure 8 is a further cross-section perspective view of the electric motor 10. Figure 8 is similar to Figure 3 in that the cross-section is taken through plane ‘A’. However, in Figure 8, the stator assembly 18, the rotor assembly 16 and the shroud 20 are omitted for clarity. The inner wall 22 and outer wall 24 both form respective cylinders, being open at both the upstream and downstream ends. The cylinders formed by the inner wall 22 and outer wall 24 share a 13 P004759-W001 common longitudinal axis, which is aligned with the axis of rotation of the electric motor 10. The space between the inner wall 22 and the outer wall 24 defines the fluid flow channels 28, together with the first row of diffuser vanes 26. The upstream ends of the inner wall 22 and outer wall 24 are aligned in the longitudinal direction. The outer wall 24 is longer than the inner wall 22 in the longitudinal direction. In this example, the outer wall 24 is around four times longer than the inner wall 22. In other examples, the outer wall 24 is at least twice as long as the inner wall 22 in the longitudinal direction. Alternatively, it may be at least three times as long.

[0087] The diffuser vanes 26 of the first row are curved and have an extent in both the longitudinal and circumferential direction. In this example, all of the diffuser vanes 26 have a common shape, however different diffuser vanes may have different degrees of curvature, depending on the requirements of the fluid moving through the electric motor 10. The diffuser vanes 26 extend in the longitudinal direction to a greater extent that the longitudinal length of the inner wall 22. In this example, the diffuser vanes 26 extend in the longitudinal direction beyond the inner wall 22 at least the longitudinal length of the windings 34. The enables the windings to be positioned between adjacent diffuser vanes 26, and to be at least partially positioned radially outwards of the inner wall, and hence within the fluid flow channels 28.

[0088] The longitudinal extent of the outer wall 24 is greater than the longitudinal extent of the diffuser vanes 26. In this example, the outer wall 24 is around twice the length of the diffuser vanes in the longitudinal direction. In other examples, the outer wall 24 may extend at least 50% further, in the longitudinal direction, than the diffuser vanes 26.

[0089] Figure 9 is a further cross-sectional perspective view of the electric motor 10. In this case, the cross section is taken though plane ‘D’ which is a longitudinal plane, parallel to the central rotational axis of the electric motor 10 but offset from the central rotational axis. This gives a view of the first row of diffuser vanes 26 and the relative position of the windings 34. It also gives a view of the second row of diffuser vanes 56. In Figure 9, the stator assembly 18, the rotor assembly 16 and the shroud 20 also shown. In this example, the length of the windings 34 in the longitudinal direction is greater than the extent to which the diffuser vanes 26 extend in the longitudinal direction beyond the inner wall 22. This enables enough of the windings 14 P004759-W001

[0090] 34 to be located in the fluid flow channel 28, to reduce the size of the motor and to increase the cooling effect. However, in some examples, the diffuser vanes 26 may extend beyond the windings 34 in the longitudinal direction.

[0091] Figure 10 shows a simulation of the fluid flow along the fluid flow paths 58 and the fluid flow channels 28. The first row of diffuser vanes 26, the second row of diffuser vanes 56 and the windings 34 are all shown flattened for ease of viewing. The components shown in Figure 10 represent the entire circumferential arrangement shown in the previous Figures.

[0092] The first row of diffuser vanes 26 is arrange in three groups of three diffuser vanes. The windings 34 are positioned between adjacent diffuser vanes of two adjacent groups. As described in connection with Figures 6B and 7B, the circumferential distance between adjacent diffuser vanes within a group is Pl or P3. In this example, Pl and P3 are the same. This is also referred to as the diffuser vane pitch. The circumferential distance between adjacent diffuser vanes of different groups is P2. P2 is greater than Pl and P3 to enable the windings to be positioned between the diffuser vanes of two different groups. In an alternative example, Pl and P3 may be different, depending on the efficiency and static pressure optimisation requirements of the electric motor 10.

[0093] Faster fluid flow is represented in Figure 10 by lighter shading, and slower fluid flow is represented by darker shading. The fluid flow between the diffuser vanes 26 is generally fast, whereas the fluid flow downstream from the windings 34 is generally slow, having been impeded by the windings 34.

[0094] The benefit of using a reduced pitch for the diffuser vanes within a group is that a greater number of diffuser vanes may be accommodated within the electric motor 10. In an alternative example, the pitch of the diffuser vanes 26 of the first row may be the same. In order to provide enough space for the windings 34, the pitch of the diffuser vanes which do not have windings between them will be greater. This makes for a simpler design, but one which includes fewer diffuser vanes 26. 15 P004759-W001

[0095] The pitch, curvature and stagger angle of the diffuser vanes 26 are selected in order to optimise the efficiency and static pressure rise of the electric motor 10. In particular, given the need to at least partially accommodate the winding portions between the diffuser vanes, the efficiency of the motor and the static pressure rise are impacted, because the winding portions disrupt the fluid flow through the fluid flow channels 28.

[0096] In the above example, the pitch (Pl, P3) of the diffuser vanes 26 of a given group may be the same, while the distance (P2) between diffuser vanes of different groups may be greater, in order to accommodate the winding portions. In other examples, Pl, P2 and P3 may be the same. This makes for a simpler design, but one which may not be as efficient. Alternatively, Pl, P2 and P3 may all be different. For example, using different pitches for Pl and P3 may improve motor efficiency in some circumstances.

[0097] In this example, the curvature and stagger angle of the diffuser vanes 26 is the same for all of the diffuser vanes. This may provide a simple design that is easy to manufacture. However, the curvature of each diffuser vane can also be varied to improve each fluid flow channel 28, to account for the presence of the winding portions. Furthermore, each diffuser vane of in a group can have a unique curvature depending on its position in the group, with the arrangement being repeated across the different groups.

[0098] The specific combination of diffuser pitch, diffuser vane curvature and stagger angle will be determined for a give electric motor 10 based on the specific design and requirements of the electric motor 10.

[0099] The second row of diffuser vanes 56 may be arranged using the same pitch for all of the diffuser vanes. Because the second row of diffuser vanes 56 do not have windings between them, a smaller pitch may be used without impacting the ability to locate the windings 34. However, as shown in Figure 10, the diffuser vanes 56 of the second row which are upstream of the windings 34, may have a larger pitch than those that are not upstream of the windings 34. This may encourage a greater degree of fluid flow though the diffuser vanes 56 upstream from windings 34. This may increase the cooling ability of the electric motor 10. 16 P004759-W001

[0100] A vacuum cleaner 100 comprising the electric motor 10 is shown in Figure 11. The vacuum cleaner 100 benefits from reduced size and increased cooling described above. The electric motor 10 may be incorporated with other appliances which require an electric motor to generate an air flow, such as a fan or pump.

Claims

17 P004759-W001CLAIMS1. An electric motor comprising: a frame comprising a plurality of diffuser vanes; and a stator assembly comprising a plurality of winding portions, wherein the stator assembly is positioned relative to the frame such that each of the plurality of winding portions is disposed at least partially between respective adjacent diffuser vanes of the plurality of diffuser vanes.

2. The electric motor according to claim 1, wherein the plurality of winding portions each comprise a stator core and a winding wound around the stator core, and at least a portion of the winding of each winding portion is disposed between the respective adjacent diffuser vanes.

3. The electric motor according to claim 1 or 2, wherein each pair of adjacent diffuser vanes defines a fluid flow channel therebetween, and each of the plurality of winding portions is disposed at least partially within a respective fluid flow channel.

4. The electric motor according to claim 3, wherein each of the plurality of winding portions extends radially into the respective fluid flow channel by a radial extent of at least 20% of a radial height of the respective fluid flow channel, wherein optionally the radial extent is at least 40% of the radial height.

5. The electric motor according to claim 3 or 4, wherein each of the plurality of winding portions extends circumferentially within the respective fluid flow channel by a circumferential extent of at least 35% of a circumferential width of the respective fluid flow channel, wherein optionally the circumferential extent is at least at least 50% of the circumferential width.

6. The electric motor according to any one of claims 3 to 5, wherein each of the plurality of winding portions extends axially along the respective fluid flow channel by an axial extent18 P004759-W001 of at least 30% of an axial length of the respective fluid flow channel, wherein optionally the axial extent is at least 50% of the axial length.

7. The electric motor according to any preceding claim, wherein the plurality of diffuser vanes comprises a circumferential row of diffuser vanes, and the respective adjacent diffuser vanes form part of the circumferential row of diffuser vanes.

8. The electric motor according to claim 7, wherein a circumferential distance between adjacent diffuser vanes having a winding portion disposed therebetween is greater than a circumferential distance between adjacent diffuser vanes having no winding portion therebetween.

9. The electric motor according to claim 8, wherein a pitch angle of the adjacent diffuser vanes having a winding portion disposed therebetween is from 35° to 75°, or optionally is from 45° to 65°.

10. The electric motor according to claims 8 or 9, wherein a pitch angle of the adjacent diffuser vanes having no winding portion disposed therebetween is from 15° to 55°, or optionally is from 25° to 45°.

11. The electric motor according to claims 7, 8, 9 or 10, wherein the plurality of diffuser vanes comprises a further circumferential row of diffuser vanes disposed upstream of the circumferential row of diffuser vanes.

12. The electric motor according to any one of claims 7 to 11, wherein the plurality of diffuser vanes are arranged in a plurality of groups of diffuser vanes, and each of the plurality of winding portions is disposed between adjacent diffuser vanes of different groups, and a circumferential distance between adjacent diffuser vanes within a group is less than a circumferential distance between the respective adjacent diffuser vanes of different groups.

13. The electric motor according to claim 12, wherein each group of diffuser vanes includes at least three diffuser vanes, and a circumferential distance between a first pair of19 P004759-W001 adjacent diffuser vanes is different to a circumferential distance between a second pair of adjacent diffuser vanes of each respective group.

14. The electric motor according to claims 12 or 13, wherein the plurality of groups of diffuser vanes are symmetrically arranged around the circumferential row of diffuser vanes.

15. The electric motor according to claim 14, wherein there are at least three winding portions and at least three groups of diffuser vanes.

16. The electric motor according to any preceding claim, wherein the frame comprises an annular inner wall and an annular outer wall, and the plurality of diffuser vanes extend between the annular inner wall and the annular outer wall.

17. The electric motor according to claim 16, wherein each of the plurality of winding portions extends through a respective recess in the annular inner wall.

18. The electric motor according to claim 16 or 17, wherein the annular outer wall and the annular inner wall extend along a longitudinal axis, and an extent of the annular outer wall is greater than an extent of the annular inner wall in a longitudinal direction.

19. The electric motor according to claim 18, wherein each of the plurality of diffuser vanes extends at least in the longitudinal direction, and an extent of each of the plurality of diffuser vanes in the longitudinal direction is greater than the longitudinal extent of the annular inner wall.

20. An electric motor according to claim 19, wherein each of the plurality of winding portions is disposed at least partially between a portion of the respective adjacent diffuser vanes that extends longitudinally past the annular inner wall.

21. An electric motor according to any preceding claim, wherein each diffuser vane is curved in the longitudinal direction, and each of the diffuser vanes of the plurality of diffuser vanes has a curvature selected from at least a first and a second curvature, wherein at least a20 P004759-W001 first diffuser vane of the plurality of diffuser vanes has the first curvature and at least a second diffuser vane of the plurality of diffuser vanes has the second curvature.

22. An electric motor according to any preceding claim, wherein each diffuser vane has a stagger angle, and at least one of the diffuser vanes has a stagger angle different to the stagger angle of the remaining diffuser vanes.

23. The electric motor according to any preceding claim, wherein: the electric motor comprises a rotor assembly comprising an impeller and a rotor core secured to a shaft; the plurality of diffuser vanes act on a fluid flow generated by the impeller in use; and the stator assembly and the plurality of diffuser vanes surround the rotor core.

24. An appliance comprising the electric motor according to any preceding claim.

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