Impeller comprising blades with specific design of the leading and trailing edges

Abstract

An impeller for attachment to an electric motor includes a plurality of blades. Each of the plurality of blades includes a pressure surface, a suction surface, a leading edge extending between the pressure surface and the suction surface at a first end of the blade, and a trailing edge extending between the pressure surface and the suction surface at a second end of the blade opposite to the first end of the blade. At least one of the plurality of blades, when viewed in cross-section, comprises a curve that defines at least one of: the pressure surface and the leading edge such that a leading vertex is located at a transition between the pressure surface and the leading edge; and the suction surface and the trailing edge such that a trailing vertex is located at a transition between the suction surface and the trailing edge.

Description

[0001] IMPELLER COMPRISING BLADES WITH SPECIFIC DESIGN OF THE LEADING AND TRAILING EDGES

[0002] BACKGROUND

[0003] There is a general desire to improve electric machines, such as electric motors, in a number of ways. For example, improvements may be desired in terms of size, weight, power density, manufacturing cost, efficiency, reliability, and noise.

[0004] SUMMARY

[0005] A first aspect of the present disclosure provides an impeller for attachment to an electric motor, the impeller comprising a plurality of blades, each of the plurality of blades comprising a pressure surface, a suction surface, a leading edge extending between the pressure surface and the suction surface at a first end of the blade, and a trailing edge extending between the pressure surface and the suction surface at a second end of the blade opposite to the first end of the blade, wherein at least one of the plurality of blades, when viewed in cross-section, comprises a curve that defines at least one of: the pressure surface and the leading edge such that a leading vertex is located at a transition between the pressure surface and the leading edge; and the suction surface and the trailing edge such that a trailing vertex is located at a transition between the suction surface and the trailing edge.

[0006] Providing the at least one of the plurality of blades with such a blade geometry may facilitate manufacture of the impeller by relatively inexpensive manufacturing techniques, such as manufacturing via moulding. In particular, forming the at least one of the plurality of blades with a cross-sectional shape such that the curve defines at least one of the leading vertex and the trailing vertex may create a blade geometry that avoids intersection by a mould tool when the mould tool is opened to release the impeller. Such a blade geometry may allow for placement of a tooling parting line at an interface between an axial mould tool used to form the leading edge, and a mould tool used to form the pressure surface, at a vertex point on a pressure side or a suction side of the blade. This may enable a die lock condition to be avoided where injection moulding is utilised to form the blade. In contrast, if a smooth curve were used to define the blade geometry, then there is a risk that an axial mould tool would be unable to be used to form the respective transition region, requiring more complex and / or more expensive methods of manufacture.

[0007] The cross-section of the at least one of the plurality of blades may comprise a 2- dimensional slice taken through the at least one of the plurality of blades at a constant percentage of a span of the at least one of the plurality of blades, for example a constant percentage of span from a root of the at least one of the plurality of blades to a tip of the at least one of the plurality of blades.

[0008] The impeller may comprise a hub about which the plurality of blades are disposed, and the hub and the plurality of blades may be integrally formed. This may provide for a relatively inexpensive and simple manufacturing process compared to a manufacturing process where the blades are attached to the hub post-formation of the blades and hub.

[0009] The impeller may be a moulded impeller, for example an impeller formed by a moulding manufacturing process. The impeller may be an injection moulded impeller, for example an impeller formed by an injection moulding manufacturing process. The impeller may be formed of a plastic material.

[0010] Adjacent ones of the plurality of blades may overlap one another in a circumferential direction. Adjacent ones of the plurality of blades may overlap one another such that, when viewed in cross-section, an axis through the leading edge of a first one of the plurality of blades, the axis parallel to a rotational axis of the impeller, intersects with a camber line of a second, adjacent, one of the plurality of blades, at a distance that is at least 20% of a length of the camber line from the trailing edge of the second one of the plurality of blades.

[0011] Each of the plurality of blades may have substantially the same form. This may facilitate ease of manufacture. Each of the plurality of blades may, when viewed in cross-section, comprise a respective curve that defines at least one of: the pressure surface and the leading edge such that a respective leading vertex is located at a transition between the pressure surface and the leading edge; and the suction surface and the trailing edge such that a respective trailing vertex is located at a transition between the suction surface and the trailing edge.

[0012] Where the curve defines the pressure surface and the leading edge such that the leading vertex is located at the transition between the pressure surface and the leading edge, the leading edge may be tangential to a leading axis, the leading axis passing through the leading vertex and parallel to a rotational axis of the impeller, or the leading edge may extend away from the leading vertex toward the suction surface without being tangential to a leading axis, the leading axis passing through the leading vertex and parallel to a rotational axis of the impeller. In such a manner the leading edge may not extend past the leading axis toward the pressure side of the at least one of the plurality or blades, thereby providing a blade geometry that avoids intersection by a mould tool when the mould tool is opened to release the impeller. A tangential arrangement of the leading edge may provide improved aerodynamic and / or acoustic benefits, whilst a non-tangential arrangement may provide increased ease of manufacture. It will be appreciated that there is a compromise to be reached between these factors.

[0013] During manufacture of the impeller by an injection moulding technique, and where the curve defines the pressure surface and the leading edge such that the leading vertex is located at the transition between the pressure surface and the leading edge, a scalar product of a surface normal with an instantaneous displacement vector of a mould tool used to form the leading edge is positive everywhere on a surface of the leading edge. The surface of the leading edge may be the surface that is in contact with the mould tool that forms the leading edge. The displacement vector of the mould tool may be a vector that describes an initial linear motion of the mould tool as a die comprising the mould tool is opened and the impeller is released.

[0014] The curve may comprise a smooth portion between the suction surface and the leading edge, such that no vertices are located at a transition between the suction surface and the leading edge. In certain circumstances, smooth portions may provide improved aerodynamic and / or acoustics benefits in comparison to a portion having a vertex. By providing a smooth portion between the suction surface and the leading edge, aerodynamic and / or acoustic characteristics of the impeller may be improved, whilst retaining ease of manufacture. For example, the transition between the suction surface and the leading edge of the impeller may be exposed at the first end of the blade in the final manufactured impeller, such that an axial mould tool could be used to form the transition between the suction surface and the leading edge during moulding of the at least one of the plurality of blades without a die lock condition occurring.

[0015] Where the curve defines the pressure surface and the leading edge such that the leading vertex is located at the transition between the pressure surface and the leading edge, the curve may comprise a smooth portion between the suction surface and the trailing edge, such that no vertices are located at a transition between the suction surface and the trailing edge. Where the curve defines the pressure surface and the leading edge such that the leading vertex is located at the transition between the pressure surface and the leading edge, the curve may comprise a smooth portion between the pressure surface and the trailing edge, such that no vertices are located at a transition between the pressure surface and the trailing edge.

[0016] Where the curve defines the pressure surface and the leading edge such that the leading vertex is located at the transition between the pressure surface and the leading edge, the leading edge may be asymmetric.

[0017] Where the curve defines the pressure surface and the leading edge such that the leading vertex is located at the transition between the pressure surface and the leading edge, a region of a pressure side of the blade adjacent to the leading vertex may decrease in thickness towards the leading vertex. For example, the pressure side of the blade may comprise a first region distal from the leading vertex, and a second region proximal to the leading vertex, and the second region may decrease in thickness from the first region to the leading vertex

[0018] The at least one of the plurality of blades may comprise a blade root, and a blade tip distal from the root, and the taper angle of the second region may vary between the blade root and the blade tip. This may facilitate ease of manufacture, particularly where a moulding process, such as an injection moulding process, is utilised. In particular, this may help to avoid die lock where a mould tool is utilised to form the pressure surface. The taper angle of the second region may increase from the blade root to the blade tip.

[0019] Where the curve defines the suction surface and the trailing edge such that a trailing vertex is located at a transition between the suction surface and the trailing edge, the trailing edge is tangential to a trailing axis, the trailing axis passing through the trailing vertex and parallel to a rotational axis of the impeller, or the trailing edge extends away from the vertex toward the pressure surface without being tangential to a trailing axis, the trailing axis passing through the trailing vertex and parallel to a rotational axis of the impeller. In such a manner the trailing edge may not extend past the trailing axis toward the suction side of the at least one of the plurality or blades, thereby providing a blade geometry that avoids intersection by a mould tool when the mould tool is opened to release the impeller. A tangential arrangement of the trailing edge may provide improved aerodynamic and / or acoustic benefits, whilst a non-tangential arrangement may provide increased ease of manufacture. It will be appreciated that there is a compromise to be reached between these factors.

[0020] The curve may comprise a smooth portion between the pressure surface and the trailing edge, such that no vertices are located at a transition between the pressure surface and the trailing edge. In certain circumstances, smooth portions may provide improved aerodynamic and / or acoustic benefits in comparison to a portion having a vertex. By providing a smooth portion between the pressure surface and the trailing edge, aerodynamic and / or acoustic characteristics of the impeller may be improved, whilst retaining ease of manufacture. For example, the transition between the pressure surface and the trailing edge of the impeller may be exposed at the first end of the blade in the final manufactured impeller, such that an axial mould tool could be used to form the transition between the pressure surface and the trailing edge during moulding of the at least one of the plurality of blades without a die lock condition occurring. Where the curve defines the suction surface and the trailing edge such that the trailing vertex is located at the transition between the suction surface and the trailing edge, the curve may comprise a smooth portion between the pressure surface and the leading edge, such that no vertices are located at a transition between the suction surface and the leading edge. Where the curve defines the suction surface and the trailing edge such that the trailing vertex is located at the transition between the suction surface and the trailing edge, the curve may comprise a smooth portion between the suction surface and the leading edge, such that no vertices are located at a transition between the suction surface and the leading edge.

[0021] Where the curve defines the suction surface and the trailing edge such that the trailing vertex is located at the transition between the suction surface and the trailing edge, the trailing edge may be asymmetric.

[0022] Where the curve defines the suction surface and the trailing edge such that the trailing vertex is located at the transition between the suction surface and the trailing edge, a region of a suction side of the blade adjacent to the trailing vertex may decrease in thickness towards the trailing vertex. For example, the suction side of the blade may comprise a first region distal from the trailing vertex, and a second region proximal to the trailing vertex, and the second region may decrease in thickness from the first region to the leading vertex.

[0023] The at least one of the plurality of blades may comprise a blade root, and a blade tip distal from the root, and the taper angle of the second region of the suction surface may vary between the blade root and the blade tip. This may facilitate ease of manufacture, particularly where a moulding process, such as an injection moulding process, is utilised. In particular, this may help to avoid die lock where a generally radial mould tool is utilised to form the suction surface. The taper angle of the second region of the suction surface may increase from the blade root to the blade tip.

[0024] The impeller may be a mixed flow impeller. The impeller may be an axial impeller. The impeller may have a diameter of no more than 70mm, no more than 60mm, no more than 50mm, no more than 40mm, or no more than 30mm, for example when measured at a trailing end of the impeller. The aforementioned blade geometry may facilitate manufacture of impellers with such relatively small diameters. The diameter may be measured as a diameter of a minimally sized circle that encloses all blade tips of the blades of the impeller.

[0025] A second aspect of the present disclosure provides a system comprising an electric motor and an impeller according to the first aspect of the present disclosure.

[0026] A third aspect of the present disclosure provides an appliance comprising an impeller according to the first aspect of the present disclosure, or a system according to the second aspect of the present disclosure.

[0027] The appliance may be one of a vacuum cleaner and a haircare appliance.

[0028] Optional features of aspects of the present disclosure may be equally applied to other aspects of the present disclosure, where appropriate.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure l is a schematic perspective view of an impeller;

[0031] Figure 2 is a schematic view illustrating a cross-section through a blade of the impeller of Figure 1;

[0032] Figure 3 is a schematic view illustrating a system comprising the impeller of Figure 1 attached to an electric motor;

[0033] Figure 4 is a schematic view illustrating a vacuum cleaner comprising the system of Figure 3;

[0034] Figure 5 is a schematic view illustrating a haircare appliance comprising the system of Figure 3

[0035] Figure 6 is a schematic view of a first further blade geometry for an impeller; and Figure 7 is a schematic view of a second further blade geometry for an impeller. DETAILED DESCRIPTION

[0036] An impeller 10 is illustrated schematically in Figure 1. The impeller 10 has a hub 12 and nine blades 14 extending about the hub. The impeller 10 is integrally formed from a carbon filled Poly ether Ether Ketone (PEEK plastic material) in an injection moulding manufacturing method, as will be discussed in more detail hereinafter. The impeller 10 is thus a monolithic component, with the hub 12 and the blades 14 integrally formed.

[0037] The impeller 10 is a mixed-flow impeller, with the hub 12 having a generally frustoconical form. A leading end 16 of the impeller 10 has a smaller diameter than a trailing end 18 of the impeller 10, with a maximal diameter of the impeller 10 of around 25mm occurring at the trailing end 18. Adjacent ones of the plurality of blades 14 overlap one another such that, when viewed in cross-section, an axis through a leading edge of a first one of the blades 14, the axis parallel to the rotational axis R of the impeller 10, intersects with a camber line of second, adjacent, one of the blades 14 , at a distance that is at least 20% of a length of the camber line from a trailing edge of the second one of the blades 14.

[0038] Each of the blades 14 has the same form, having the same shape and dimensions. Each blade 14 has a blade root 20 proximal to the hub 12, a blade tip 22 distal from the hub 12, a leading edge 24, a trailing edge 26, a pressure surface 28, and a suction surface 30. A cross-sectional shape of one of the blades 14 is illustrated schematically in Figure 2, with the cross-section taken as a 2-dimensional slice at a constant percentage of span between the blade root 20 and the blade tip 22 of the blade 14. The cross-section has a co-ordinate system, as shown in Figure 2, consisting of an axial direction A, a pitch-wise direction P, and a span-wise direction S. It will be appreciated that the axial direction A can be considered to be a direction parallel to the rotational axis R of the impeller 10.

[0039] The cross-sectional shape is defined by a curve that defines the leading edge 24, the trailing edge 26, the pressure surface 28, and the suction surface 30 of the blade 14. The curve is smooth, save for at a transition between the pressure surface 28 and the leading edge 24, with a leading vertex 32 located at the transition between the pressure surface 28 and the leading edge 24. The curve may thereby be considered non-smooth overall, albeit with locally smooth portions. It will be appreciated that the leading vertex 32 is labelled as such in view of it being a vertex located at the leading end 16 of the impeller 10. The leading edge 24 is tangential to a leading axis L that extends through the leading vertex 32 and is parallel to the rotational axis R of the impeller 10, with the leading edge 24 then curving away from the leading axis L towards the suction surface 30 of the blade 14. In such a manner the leading edge 24 is located on only one side of the leading axis L, and on only one side of the transition point from the pressure surface 28 to the leading edge 24. The leading edge 24 can be considered to form a minor arc of a hypothetical circle drawn such that the leading axis L defines a tangent of the hypothetical circle at the leading vertex 32. The leading edge 24 is asymmetric between the pressure surface 28 and the suction surface 30, with its curvature changing between the pressure surface 28 and the suction surface 30.

[0040] The curve of the blade 14 in cross-section has no further vertices, such that a transition between the leading edge 24 and the suction surface 30 is smooth, a transition between the suction surface 30 and the trailing edge 26 is smooth, and a transition between the trailing edge 26 and the pressure surface 28 is smooth.

[0041] The geometry of the blade 14 described above may provide advantages during manufacture of the impeller 10. As mentioned above, the impeller 10 is formed in an injection moulding manufacturing process. The presence of the leading vertex 32 may create a blade geometry that avoids intersection by a mould tool when the mould tool is opened to release the impeller 10. For example, such a blade geometry may allow for placement of a tooling parting line at an interface between an axial mould tool used to form the leading edge 24 and a generally radial tool mould tool used to form the pressure surface 30, at the leading vertex 32. This may enable a die lock condition to be avoided where injection moulding is utilised to form the blade 14. In contrast, if a smooth curve were used to define the blade geometry, then there is a risk that an axial mould tool would be unable to be used to form the transition between the leading edge 24 and the pressure surface 30, requiring more complex and / or more expensive methods of manufacture to form the impeller 10. A system 100 comprising the impeller 10 and an electric motor 102 is illustrated schematically in Figure 3. The electric motor 102 comprises a stator assembly 104 and a rotor assembly 106. It will be appreciated that further features of the electric motor 102 are not described here for the sake of brevity. The stator assembly 104 comprises three windings 108, each wrapped around a corresponding stator core (not shown). The rotor assembly 106 comprises a shaft 110, and a permanent magnet 112 mounted to the shaft 110. The impeller 10 is also mounted to the shaft 110. When the three windings 108 are driven with an appropriate modulated voltage, the stator assembly 104 generates a magnetic field that interacts with the permanent magnet 112 to rotate the shaft 110, thereby causing rotation of the impeller 10.

[0042] Rotation of the impeller 10 generates an airflow, and in some examples the impeller 10 and the electric motor 102 are configured to spin at shaft speeds of up to 158krpm while providing an operating point of at least 12.5kPa of total to static pressure rise at a flow rate of 5.75slps. This may find utility in a range of appliances. A vacuum cleaner 200 comprising the system 100 is illustrated schematically in Figure 4, whilst a haircare appliance 300 comprising the system 100 is illustrated schematically in Figure 5.

[0043] It will be appreciated by a person skilled in the art that alternative blade geometries are also envisaged, whilst still facilitating ease of manufacture, for example via injection moulding techniques. In some examples, instead of the leading edge 24 being tangential to the leading axis L, the leading edge can instead extend away from the leading vertex 32 without being tangential to the leading axis L.

[0044] A first further example blade cross-section 400 is illustrated schematically in Figure 6. Here, just a region comprising a leading edge 402, a pressure surface 404, and a suction surface 406, of the blade geometry is shown for sake of clarity. A leading vertex 408 is again defined at the transition between the pressure surface 404 and the leading edge 402. The pressure surface 404 has a first region 410 distal from the leading vertex 408, and a second region 412 proximal to the leading vertex 408. The second region 412 decreases in thickness from the first region 410 toward the leading vertex,. Introduction of a leading vertex can, in some examples, be a compromise between manufacturability and aeroacoustic considerations. It has been found that introduction of a decrease in thickness of the pressure side of the blade toward the leading edge can, in some examples, mitigate for any negative aero-acoustic consequences introduced by introduction of the leading vertex.

[0045] Although not illustrated in Figure 6, in some examples the decrease in thickness of the second region 412 increases between a blade root and a blade tip of the blade. This may aid with manufacturability, for example where a generally radial mould tool is utilised to form the pressure surface 404.

[0046] A second further example blade cross-section 500 is illustrated schematically in Figure 7. The blade cross-section 500 shows a curve that defines a leading edge 502, a trailing edge 504, a pressure surface 506, and a suction surface 508. In a similar manner to the impeller 10 of Figure 1, the blade cross-section 500 of Figure 7 has a leading vertex 510 defined at a transition between the pressure surface 506 and the leading edge 502. The blade crosssection 500 of Figure 7, however, also has a trailing vertex 512 defined at a transition between the suction surface 508 and the trailing edge 504. It will be appreciated that the trailing vertex 512 is labelled as such in view of it being a vertex located at a trailing end of an impeller comprising the blade cross-section 500. The trailing edge 504 extends away from to a trailing axis T that extends through the trailing vertex 512 and is parallel to a rotational axis R2 of the impeller comprising the blade cross-section 500, with the trailing edge 504 curving away from the trailing axis T towards the pressure surface 502. In such a manner the trailing edge 504 is located on only one side of the trailing axis T, and on only one side of the transition point from the suction surface 508 to the trailing edge 504. The trailing edge 504 is asymmetric between the pressure surface 506 and the suction surface 508, with its curvature changing between the pressure surface 508 and the suction surface 506.

[0047] The presence of the trailing vertex 512 may create a blade geometry that intersection by a mould tool when the mould tool is opened to release an impeller having the blade crosssection 500. For example, such a blade geometry may allow for placement of a tooling parting line at an interface between a mould tool used to form the trailing edge 504 and a mould tool used to form the suction surface 508, at the trailing vertex 514. This may enable a die lock condition to be avoided where injection moulding is utilised to form such a blade. The blade cross-section 500 of Figure 7 may be utilised as part of an axial impeller.

[0048] In each of the examples described herein, presence of a vertex at either or both of a transition between a pressure surface and a leading edge, and a suction surface and a trailing edge, may facilitate manufacture of an impeller via injection moulding, thereby increasing ease of manufacture and / or decreasing costs associated with manufacture.

Claims

CLAIMS1. An impeller for attachment to an electric motor, the impeller comprising a plurality of blades, each of the plurality of blades comprising a pressure surface, a suction surface, a leading edge extending between the pressure surface and the suction surface at a first end of the blade, and a trailing edge extending between the pressure surface and the suction surface at a second end of the blade opposite to the first end of the blade, wherein at least one of the plurality of blades, when viewed in cross-section, comprises a curve that defines at least one of: the pressure surface and the leading edge such that a leading vertex is located at a transition between the pressure surface and the leading edge; and the suction surface and the trailing edge such that a trailing vertex is located at a transition between the suction surface and the trailing edge.

2. An impeller as claimed in Claim 1, wherein the impeller comprises a hub about which the plurality of blades are disposed, and the hub and the plurality of blades are integrally formed.

3. An impeller as claimed in Claim 1 or Claim 2, wherein the impeller is a moulded impeller.

4. An impeller as claimed in any one of the preceding claims, wherein the impeller is an injection moulded impeller.

5. An impeller as claimed in any one of the preceding claims, wherein adjacent ones of the plurality of blades overlap one another in a circumferential direction.

6. An impeller as claimed in any one of the preceding claims, wherein each of the plurality of blades has the same form.

7. An impeller as claimed in any one of the preceding claims, wherein the curve defines the pressure surface and the leading edge such that a leading vertex is located at a transition between the pressure surface and the leading edge, and: the leading edge is tangential to a leading axis, the leading axis passing through the leading vertex and parallel to a rotational axis of the impeller; or the leading edge extends away from the leading vertex toward the suction surface without being tangential to a leading axis, the leading axis passing through the leading vertex and parallel to a rotational axis of the impeller.

8. An impeller as claimed in any one of the preceding claims, wherein the curve comprises a smooth portion between the suction surface and the leading edge, such that no vertices are located at a transition between the suction surface and the leading edge.

9. An impeller as claimed in any one of the preceding claims, wherein the curve defines the suction surface and the trailing edge such that a trailing vertex is located at a transition between the suction surface and the trailing edge, and: the trailing edge is tangential to a trailing axis, the trailing axis passing through the trailing vertex and parallel to a rotational axis of the impeller; or the trailing edge extends away from the vertex toward the pressure surface without being tangential to a trailing axis, the trailing axis passing through the trailing vertex and parallel to a rotational axis of the impeller.

10. An impeller as claimed in any one of the preceding claims, wherein the curve comprises a smooth portion between the pressure surface and the trailing edge, such that no vertices are located at a transition between the pressure surface and the trailing edge.

11. An impeller as claimed in any one of the preceding claims, wherein the impeller is a mixed flow impeller.

12. An impeller as claimed in any one of the preceding claims, wherein the impeller has a diameter of no more than 70mm, no more than 60mm, no more than 50mm, or no more than 40mm, or no more than 30mm.

13. A system comprising an electric motor and an impeller as claimed in any one of the preceding claims.

14. An appliance comprising an impeller as claimed in any one of Claims 1 to 12, or a system as claimed in Claim 13.

15. An appliance as claimed in Claim 14, wherein the appliance is one of a vacuum cleaner and a haircare appliance.

Images