Suction unit

Abstract

There is provided a suction unit comprising a frame, wherein an inner surface of the frame forms an axial stop that extends at least partially around an inner circumference of the frame such that at least a portion of the frame has a larger inner diameter and is radially thinner before the axial stop and has a smaller inner diameter and is radially thicker after the axial stop. A shroud is provided configured to at least partially cover an impeller when the impeller is assembled within the frame. The shroud is located within the frame relative to the position of the axial stop.

Description

[0001] SUCTION UNIT

[0002] BACKGROUND

[0003] Suction units may be used in appliances such as vacuum cleaners to generate an air flow. For example, the suction unit may comprise an impeller that generates suction to enable dirt and debris to be removed from a surface to be cleaned.

[0004] SUMMARY

[0005] According to a first aspect there may be provided a suction unit comprising a frame, wherein an inner surface of the frame forms an axial stop that extends at least partially around an inner circumference of the frame such that at least a portion of the frame has a larger inner diameter and is radially thinner before the axial stop and has a smaller inner diameter and is radially thicker after the axial stop. The suction unit comprises a shroud configured to at least partially cover an impeller when the impeller is assembled within the frame, wherein the shroud is located within the frame according to the position of the axial stop. As the frame is thinner at the position of the shroud, the overall thickness of the shroud and the frame can be reduced. The reduced thickness can allow more space for the impeller and fluid passages around the impeller, which may allow a more efficient and / or more powerful suction unit to be constructed.

[0006] The suction unit may be configured to suck air. For example, the suction unit may be a vacuum device e.g. an air vacuum device.

[0007] In some cases, the axial stop extends around the inner circumference of the frame at every circumferential location that the shroud contacts the frame. In some examples, the axial stop extends all the way around the inner circumference of the frame. Accordingly, the combined thickness of the frame and the shroud can be reduced at all relevant circumferential locations.

[0008] The frame may have an inner diameter after the axial stop that is smaller than an outer diameter of the shroud. Accordingly, the shroud will not easily pass the axial stop when inserted axially within the frame. The frame may be cylindrical and the shroud may be axisymmetric. In this way, a rotating impeller can be conveniently housed.

[0009] The shroud may have a cone-like shape with a profile that complements the profile of the impeller. In this way, the shroud can form a fluid flow path to funnel fluid, such as air, past the impeller.

[0010] The shroud may form a lip at an outer circumferential extent. The lip may contact the inner surface of the frame. Further the lip may be located within the frame according to the position of the axial stop. In this way, a larger contact area may be provided between the shroud and the frame for securing the shroud to the frame using adhesive.

[0011] The lip may abut the axial stop. In such examples, the axial stop may allow accurate positioning of the shroud within the frame. In other implementations, spacers or other components may be provided between the lip and the axial stop.

[0012] The suction unit may comprise adhesive located where the lip contacts the inner surface of the frame on an opposite side of the lip from the axial stop.

[0013] A portion of the lip on the opposite side of the lip from the axial stop may form a recess shaped to receive adhesive. In this way, adhesive may be inserted from one side of the shroud when the shroud is positioned within the frame.

[0014] The recess may be stepped. The recess may be arranged to receive adhesive on an outer step of the recess. In this way, adhesive may be tidily received in contact with both the shroud and the frame.

[0015] The lip may form a cavity that accommodates an adhesive between the lip and the frame. In this way, the shroud and frame can be secured together by adhesive, and the adhesive can be tidily accommodated. The cavity may be a circumferential groove. In this way, the shroud can be secured to the frame all the way around the circumference of the frame thereby providing a secure attachment.

[0016] The frame may form one or more inlets through which adhesive is inserted into the cavity. This allows insertion of adhesive between the frame and the lip of the shroud. The frame may further comprise an outlet by which air may escape when the adhesive is inserted into the cavity via an inlet.

[0017] The adhesive may be curable when exposed to ultraviolet (UV) light, i.e. the adhesive may be a UV-curable adhesive. In this way, the adhesive may be quickly cured when it has been applied to secure the shroud to the frame.

[0018] The shroud may be transparent to UV light. In this way, the shroud may transmit UV light that is used to cure a UV-curable adhesive.

[0019] The dimensions of the frame may taper inwardly from an end of the frame to the axial stop. The shroud may be interference fit within the frame. In this way, the shroud may be push-fit within the frame.

[0020] The frame may be a front frame with respect to fluid flow through the suction unit (e.g. upstream). The suction unit may comprise at least two frame portions. The use of multiple frame portions may allow components to be more easily arranged within the suction unit during manufacture of the suction unit.

[0021] In some implementations, the suction unit may be an electric motor comprising the impeller and components that drive the impeller. The electric motor may comprise a stator assembly. The stator assembly may comprise a plurality of winding portions. The electric motor may comprise a rotor assembly comprising the impeller and a rotor core secured to a shaft. The electric motor may comprise a rear frame with respect to fluid flow through the suction unit. The rear frame may comprise a plurality of diffuser vanes. The stator assembly may be positioned relative to the rear 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. 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 may surround the rotor core. The rotor core may comprise a permanent magnet.

[0022] There may be provided an appliance comprising the suction unit according to the first aspect. The appliance may be one of a haircare appliance, vacuum cleaner, and an air processing appliance such as a fan or humidifier.

[0023] According to a second aspect there may be provided a method of manufacturing a suction unit according to the first aspect, comprising inserting the shroud within the frame along an axis of the frame such that the shroud is located relative to the axial stop. In this way, the shroud may be properly located within the frame. The combined thickness of the shroud and the frame at the position of the axial stop may provide strength to the frame of the suction unit.

[0024] The method may comprise applying a UV-curable adhesive between the shroud and the frame and the exposing the UV-curable adhesive to UV light from a UV light source.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is an exploded perspective view of a suction unit.

[0027] Figure 2 is perspective view of the assembled suction unit.

[0028] Figure 3 is a cross-sectional perspective view of the suction unit.

[0029] Figure 4A is a cross-sectional view of the suction unit.

[0030] Figure 4B is a sectional slice view of the suction unit.

[0031] Figure 4C is a cross-section showing how parts of the suction unit are assembled.

[0032] Figure 4D is a cross-section showing the suction unit of Figure 4C after assembly.

[0033] Figure 4E is a cross-section showing a second example of assembly of parts of the suction unit.

[0034] Figure 4F shows the parts of the suction unit in Figure 4E prior to application of adhesive. Figure 4G shows the assembled suction unit of Figure 4E following application of adhesive. Figure 4H is a cross-section showing parts for interference attachment of a shroud to a frame within the suction unit according to a third example.

[0035] Figure 41 is a cross-section showing the assembled suction unit of Figure 4H.

[0036] Figure 5A is a perspective view of a stator assembly of the suction unit.

[0037] Figures 5B is an end view of the stator assembly.

[0038] Figure 6A is a cross-sectional perspective view of a rear frame, the stator assembly and a rotor assembly of the suction unit.

[0039] Figure 6B is a further cross-sectional view of the rear frame, the stator assembly and the rotor assembly.

[0040] Figure 7A is a further cross-sectional perspective view of the rear frame, the stator assembly and the rotor assembly.

[0041] Figure 7B is a further cross-sectional view of the rear frame, the stator assembly and the rotor assembly.

[0042] Figure 8 is a further cross-section perspective view of the suction unit.

[0043] Figure 9 is a further cross-sectional perspective view of the suction unit.

[0044] Figure 10 shows a simulation of fluid flow along fluid flow paths of the suction unit.

[0045] Figure 11 shows a vacuum cleaner comprising the suction unit.

[0046] DETAILED DESCRIPTION

[0047] Figure 1 is an exploded perspective view of a suction unit 10 that comprises an electric motor. The suction unit 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 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 of an electric motor when the suction unit 10 is assembled.

[0048] 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 18 comprises three segments. The stator assembly 18 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.

[0049] 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.

[0050] 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.

[0051] 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, the shroud 20 and the impeller 48 define a fluid flow path through which air is drawn into the first frame 14 in use.

[0052] Figure 2 is a perspective view of the assembled suction unit 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 suction unit 10. Air exits the suction unit 10 via the opposing end of the rear frame 12. The rear frame 12 is at a downstream end of the suction unit 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.

[0053] Figure 3 is a cross-sectional perspective view of the suction unit 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.

[0054] 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.

[0055] 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. Figure 4A is a cross-sectional view of the suction unit 10 taken through the plane ‘A’ from Figure 3. Figure 4B is a slice view of the suction unit taken through the same plane.

[0056] The assembled suction unit 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.

[0057] Figures 4A and 4B show the shroud 20 fitted inside the main wall 50 of the front frame 14. Figures 4C and 4D are more detailed views of a portion of Figure 4A that shows how the shroud 20 is secured to the main wall 50. Figure 4C shows how the shroud 20 is inserted into the front frame 14 and adhesive 70 is applied afterwards. The adhesive applied using a first method of attaching the shroud 20 to the main wall 50 can be seen in Figures 3, and 4A to 4D. The arrows in Figure 4C shows the direction of insertion. Figure 4D shows the assembled suction unit with the shroud 20 fixed within the main wall 50 by the adhesive 70.

[0058] The shroud 20 forms a lip 201 at an outer circumferential extent of the shroud 20. An outer surface of the lip 201 contacts the inner surface of the main wall 50.

[0059] An inner surface of the main wall 50 forms an axial stop 501. The axial stop 501 extends at least partially around an inner circumference of the main wall 50 such that at least a portion of the main wall 50 has a larger inner diameter and is radially thinner before the axial stop 501 and has a smaller inner diameter and is radially thicker after the axial stop 501. In the suction unit shown in Figure 4C, the axial stop 501 extends around the inner circumference of the main wall 50 at every circumferential location that the shroud 20 contacts the main wall 50. More specifically, both the axial stop 501 and the lip 201 of the shroud 20 extend all the way around the inner surface of the front frame 14. The lip 201 may abut the axial stop 501. In other implementations, the frame may slightly deform as the shroud 20 is inserted and the additional thickness of the axial stop may cause the shroud 20 to stop just before the axial stop when inserted with a predetermined level of force. In other implementations, one or more additional components or spacers may be provided between the shroud 20 and the axial stop 501. In further implementations, leaving a gap between the end of the lip 201 of the shroud 20 and the axial stop 501 may leave space in case any adhesive passes from the outside to the inside of the shroud during fixing. The suction unit shown in figures 2 to 4D show the shroud fixed relative to the axial stop at a position slightly separated from the axial stop for the reasons just explained, but this is by way of example only.

[0060] In further examples, the shroud could have arms such that the arms contact the inner surface of the main wall 50 in some but not all circumferential locations. In such cases, the main wall 50 may be thicker where the arms of the shroud 20 do not make contact and thinner where the arms of the shroud 20 contact the inner surface of the main wall 20. The difference in thickness could be used to guide the insertion of the arms of shroud 20 into the front frame 14 during manufacture.

[0061] The shape of the lip 201 may allow a larger contact area to be provided between the shroud 20 and the main wall 50 both for positioning and for securing the shroud 20 to the front frame 14 using adhesive. As shown in Figures 4C and 4D, the shroud 50 is located within the frame 14 and is positioned relative to the axial stop 501. As the main wall 50 is thinner prior to the location of the shroud 20, the overall thickness of the shroud 20 and the frame 50 can be made thinner. This allows more space for the impeller 48 and fluid passages around the impeller 48, which may allow a more efficient and / or more powerful suction unit to be designed for a given overall suction unit size.

[0062] The main wall 50 has an inner diameter after the axial stop 501 that is smaller than an outer diameter of the shroud 20 at the base of the lips 201. Accordingly, the shroud 20 will not easily pass the axial stop 501 when inserted axially within the frame 14. As shown in Figure 4D, the suction unit has adhesive 70 applied where the lip 201 contacts the inner surface of the main wall on an opposite side of the lip 201 from the axial stop 501. A portion of the lip 201 on the opposite side of the lip 201 from the axial stop 501 forms a recess shaped to receive the adhesive 70. The recess is stepped so that adhesive can be applied to the outer step. Accordingly, the adhesive 70 may be inserted from the front side of the shroud through the front frame 14 when the shroud 20 is positioned within the front frame 14 relative to the axial stop 501.

[0063] Figures 4E to 4G are cross-sections that shows details of a second method of attaching the shroud 20 to the main wall 50. Figure 4E illustrates insertion of the shroud 20 into the front frame 14. The arrows show the direction of insertion. Figure 4F illustrates the shroud positioned within the front frame 14 read to receive adhesive 70 and Figure 4G shows the shroud 20 fixed within the front frame 14 by the adhesive 70.

[0064] As can be seen from Figure 4E, the lip 201 forms a cavity 202 that accommodates adhesive between the lip 201 and the inner surface of the main wall 50 of the front frame 14. The cavity 202 is a circumferential groove formed in the outer surface of the lip 201 of the shroud 20. The main wall 50 includes one or more inlets 502 through which adhesive 70 is inserted into the cavity 202. The inlets 502 allow insertion of adhesive between the main wall 50 and the lip 201 of the shroud 20. The main wall 50 may further comprise an outlet 503 by which air may escape when the adhesive 70 is inserted into the cavity 202 via the inlet 502. In this way, the shroud 20 can be secured to the main wall 50 all the way around the circumference providing a secure attachment.

[0065] The adhesive 70 described above may be ultraviolet (UV) curable adhesive. In some cases, the shroud 20 may be transparent to UV light, for example, the shroud 20 may be made of transparent plastic. In this way, the shroud 20 may transmit UV light that is used to cure the UV-curable adhesive making it easier to cure the adhesive.

[0066] Figures 4H and 41 shows a further implementation in which the shroud 20 is interference fit within the front frame 14. In this example, no adhesive is required. The dimensions of the main wall 50 of the front frame 14 taper inwardly from a front end, via which the shroud 20 is received, towards the axial stop. In other words, the inner diameter of the main wall 50 is greater at the end where the shroud 20 is inserted than at the axial stop 501. The direction of insertion of the shroud 20 is shown by the arrows in Figure 4H. The shroud 20 interference fits within the front frame 14 and should have the appropriate tightness when it is located against the axial stop 501. As shown in Figure 41, this implementation illustrates and example in which the shroud 20 abuts the axial stop 501. In this way, the shroud 20 may be push-fit within the front frame 14 during manufacture of the suction unit to a precise location.

[0067] Attachment of the shroud 20 to the main frame 14 of suction unit as shown above may be performed by locating the shroud 20 within the front frame 14 such that the shroud 20 has a position determined by the axial stop 501. The axial stop 501 ensures that the shroud 20 is properly located within the front frame 14. The combined thickness of the shroud 20 and the front frame 14 at the position of the axial stop 501 may provide appropriate strength to the front frame 14 of the suction unit.

[0068] In implementations that use adhesive 70, applying a UV-curable adhesive between the shroud 20 and the front frame 14 and then exposing the UV-curable adhesive to UV light from a UV light source may allow for fast and convenient manufacture. In particular, there is no need to wait for the adhesive to dry. High viscosity UV-curable adhesives such as a high viscosity epoxy resin may be used to provide a strong bond with reduced risk that adhesive is applied other than in the intended locations. Implementations that use the circumferential groove 202 described in connection with Figures 4E to 4G may use a low viscosity adhesive to allow the adhesive to flow around the circumferential groove 202.

[0069] Figures 5A 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 over moulded onto the stator cores 30. The windings 34 are would about the bobbins 32.

[0070] Figure 6 A 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.

[0071] Figure 6B is a cross-sectional view of the suction unit 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.

[0072] 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. Figure 7 A 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.

[0073] Figure 7B is a cross-sectional view of the suction unit 10 taken through the plane ‘C’ from Figure 7A. 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.

[0074] Figure 8 is a further cross-section perspective view of the suction unit 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 common longitudinal axis, which is aligned with the axis of rotation of the suction unit 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.

[0075] 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 suction unit 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.

[0076] 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.

[0077] Figure 9 is a further cross-sectional perspective view of the suction unit 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 suction unit 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 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.

[0078] 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.

[0079] 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 suction unit 10.

[0080] 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.

[0081] 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 suction unit 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.

[0082] 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 suction unit 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.

[0083] 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.

[0084] 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.

[0085] The specific combination of diffuser pitch, diffuser vane curvature and stagger angle will be determined for a give suction unit 10 based on the specific design and requirements of the suction unit 10.

[0086] 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 suction unit 10.

[0087] A vacuum cleaner 100 comprising the suction unit 10 is shown in Figure 11. The vacuum cleaner 100 benefits from reduced size and increased cooling described above. The suction unit 10 may be incorporated with other appliances which require an suction unit to generate an air flow, such as a fan or pump.

[0088] A first further example of this 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.

[0089] 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. 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.

[0090] 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.

[0091] 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 adjacent diffuser vanes. This enables the maximum efficiency gains in terms of frame size and motor power.

[0092] 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.

[0093] The winding portions may generate heat in use. Therefore, the winding portions benefit from placement within the airflow channels formed between adjacent diffuser vanes.

[0094] 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.

[0095] 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. 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.

[0096] 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.

[0097] 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 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.

[0098] 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.

[0099] 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.

[0100] 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. A circumferential distance between adjacent diffuser vanes having a winding portion disposed therebetween may be greater than a circumferential distance between adjacent diffuser vanes having no stator portion therebetween.

[0101] 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.

[0102] 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°.

[0103] The plurality of diffuser vanes may comprise a further circumferential row of diffuser vanes disposed upstream of the circumferential row of diffuser vanes.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] The plurality of groups of diffuser vanes may be symmetrically arranged around the circumferential row of diffuser vanes.

[0108] 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.

[0109] There may be at least three winding portions and at least three groups of diffuser vanes.

[0110] The electric motor may have three winding portions. In such an arrangement, the diffuser vanes are also arranged in three groups.

[0111] 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.

[0112] 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.

[0113] Each of the plurality of winding portions may extend through a respective recess in the annular inner wall. 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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. 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] In a second further example there is provided an appliance comprising the electric motor according to the first further example. 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.

[0126] The diffuser vanes may be configured to guide a fluid from an upstream end to a downstream end, in a substantially longitudinal direction. 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.

Claims

CLAIMS1. A suction unit comprising: a frame, wherein an inner surface of the frame forms an axial stop that extends at least partially around an inner circumference of the frame such that at least a portion of the frame has a larger inner diameter and is radially thinner before the axial stop and has a smaller inner diameter and is radially thicker after the axial stop; and a shroud configured to at least partially cover an impeller when the impeller is assembled within the frame, wherein the shroud is located within the frame according to the position of the axial stop.

2. A suction unit according to claim 1, wherein the axial stop extends around the inner circumference of the frame at every circumferential location that the shroud contacts the frame.

3. A suction unit according to claim 1 or claim 2, wherein the frame has an inner diameter after the axial stop that is smaller than an outer diameter of the shroud.

4. A suction unit according to any preceding claim, wherein the frame is cylindrical and the Stroud is axisymmetric.

5. A suction unit according to claim 4, wherein the shroud has a cone-like shape with a profile that complements the profile of the impeller.

6. A suction unit according to any preceding claim, wherein the shroud forms a lip at an outer circumferential extent, the lip contacts the inner surface of the frame, and the lip is located within the frame according to the position of the axial stop.

7. A suction unit according to claim 6, wherein the lip abuts the axial stop.

8. A suction unit according to claim 6 or claim 7, comprising adhesive located where the lip contacts the inner surface of the frame on an opposite side of the lip from the axial stop.

9. A suction unit according to claim 8, wherein a portion of the lip on the opposite side of the lip from the axial stop forms a recess shaped to receive adhesive.

10. A suction unit according to claim 9, wherein the recess is stepped and arranged to receive adhesive on the outer step of the recess.

11. A suction unit according to claim 6 or claim 7, wherein the lip forms a cavity that accommodates an adhesive between the lip and the frame.

12. A suction unit according to claim 11, wherein the cavity is a circumferential groove.

13. A suction unit according to claim 11 or claim 12, wherein the frame forms one or more inlets through which adhesive is inserted into the cavity.

14. A suction unit according to any of claims 8 to 13, wherein the adhesive is a UV- curable adhesive.

15. A suction unit according to any preceding claim, wherein the shroud is transparent to UV light.

16. A suction unit according to any of claims 1 to 7, wherein the dimensions of the frame taper inwardly from an end of the frame to the axial stop and the shroud is interference fit within the frame.

17. A suction unit according to any preceding claim, wherein the frame is a front frame with respect to fluid flow through the suction unit and the suction unit comprises at least two frame portions.

18. An appliance comprising the suction unit according to any preceding claim.

19. A method of manufacturing a suction unit according to any of claims 1 to 17, comprising inserting the shroud within the frame along an axis of the frame such that the shroud is located relative to the axial stop.

20. A method according to claim 19, further comprising applying a UV-curable adhesive between the shroud and the frame and the exposing the UV-curable adhesive to UV light from a UV light source.

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