A stator core bobbin

Abstract

A stator core bobbin comprises a main body and a door. The main body at least partially defines a channel. The door is moveable from an open position, in which a portion of a stator winding is moveable into the channel, to a closed position, in which the portion of the stator winding is surrounded by the main body and the door.

Description

[0001] A STATOR CORE BOBBIN

[0002] BACKGROUND

[0003] There is a general desire to improve electric machines, such as 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] According to a first aspect of the present invention there is provided a stator core bobbin comprising: a main body at least partially defining a channel; and a door moveable from an open position, in which a portion of a stator winding is moveable into the channel, to a closed position, in which the portion of the stator winding is surrounded by the main body and the door.

[0006] As a result, the door may be in the open position during manufacture to facilitate winding of the winding around the main body (and thereby movement of the portion of the winding into the channel). After winding, the door may be moved to the closed position to surround the portion of the winding. This may provide electrical insulation between the portion of the winding and a stator core connected to the stator core bobbin or another winding of the stator assembly, which may reduce the likelihood of shorting between these components. Thereby, the safety and ability to meet compliance standards of the stator assembly may be improved compared to a bobbin which does not have such a door.

[0007] Additionally, if the door were omitted, an airgap may need to be provided between the winding and an adjacent winding of the stator assembly to provide sufficient electrical insulation between the windings. By providing the door, the door may provide the electrical insulation previously provided by the airgap, which may enable the airgap to be omitted or reduced. Omitting or reducing the airgap may enable the space previously occupied by the airgap to be filled with additional winding material which may increase the fill factor of the windings. Increasing the fill factor may increase the power density of a motor comprising the bobbin compared to a lower fill factor. Optionally, the stator core bobbin comprises a hinge connecting the door to the main body; and the main body, the hinge, and the door are integrally formed. As a result, the part count of the bobbin may be reduced which may reduce the complexity of manufacturing the bobbin compared with having multiple different components, which may require multiple operations to manufacture and assemble. For example, the bobbin could be moulded as a single piece and then the hinge bent to move the door into the closed position.

[0008] Optionally, a ratio of a thickness of the hinge to a wall thickness of the main body is less than or equal to 1. A greater wall thickness of the main body may be desirable to increase the electrical insulation provided between the stator core and the winding and increase the robustness of the main body to being crushed by the winding when it is wound around the main body. Conversely, a lesser thickness of hinge may be desirable to make the hinge more flexible, which may make the hinge easier to bend and reduce the likelihood of the hinge breaking when it is bent. Having a ratio of less than or equal to 1, may therefore improve the performance of the hinge and the main body compared with a greater ratio.

[0009] Optionally, the ratio of the thickness of the hinge to the wall thickness of the main body is greater than or equal to 0.2. Having an excessively small ratio (below 0.2) may result in the differences in the thicknesses of the main body and the hinge become excessively large which may reduce the manufacturability (for example, the mouldability) of the bobbin.

[0010] Optionally, the hinge has a thickness of less than or equal to 0.4mm. Reducing the thickness of the hinge may make the hinge more flexible, which may make the hinge easier to bend and reduce the likelihood of the hinge breaking when it is bent. Therefore, having a thickness of less than or equal to 0.4mm may improve the manufacturability and robustness of the bobbin.

[0011] Optionally, the hinge has a thickness of greater than or equal to 0.1mm. Increasing the thickness of the hinge may result in the hinge providing a greater amount of electrical insulation. This may enable a higher voltage to be utilised in the stator core, compared to where a thinner hinge were used, which may enable the stator assembly to operate with increased efficiency and / or increased power density. The hinge having a thickness of between 0.4mm and 0.15mm may provide a good balance between manufacturability and robustness on one hand, and electrical insulation on the other hand.

[0012] Optionally, the door is moveable through at least 60° between the open position and the closed position. As a result, an open space provided for the windings to move into the channel in the open position may be greater than if the door were moveable through a lesser angle. This may improve the ease of winding the windings around the main body.

[0013] Optionally, the hinge comprises a material having a strain at breaking of greater than or equal to 2%. As a result, the likelihood of the hinge fracturing for a given amount of movement between the open position and the closed position may be reduced compared to using a material with a lesser strain at breaking.

[0014] Optionally, wherein a ratio of a maximum thickness of the stator core bobbin to a minimum thickness of the stator core bobbin is greater than or equal to 1 and less than or equal to 15. Large differences in the thicknesses of the parts of the bobbin may reduce the manufacturability (for example the mouldability) of the bobbin. Therefore, having a ratio of greater than or equal to 1 and less than or equal to 15, may improve the manufacturability of the bobbin compared with having a ratio of greater than 15 or less than 1. Optionally the stator core bobbin is moulded. For example, the stator core bobbin may be injection moulded.

[0015] Optionally, the stator core bobbin is formed of a material having a dielectric strength of greater than or equal to 15kV / mm. This may enable the stator core bobbin to provide a greater amount of electrical insulation for a given thickness than if it was formed of a material having a lesser dielectric strength. This may enable a higher voltage to be utilised in the stator core, compared to where a material of lower dielectric strength is used, which may enable the motor to operate with increased efficiency and / or increased power density. Optionally, the stator core bobbin is formed of a fibre reinforced plastic. The bobbin performs both an insulative and a structural function: providing electrical insulation between the winding and the stator core, and providing sufficient strength to prevent the winding crushing the main body when the winding is wound around the main body. A fibre reinforced plastic may provide sufficient electrical insulation and mechanical properties to perform this dual function.

[0016] Additionally, in examples comprising a hinge, fibres of the fibre reinforced plastic may reduce the likelihood of the hinge snapping compared to using a plastic without fibres.

[0017] Optionally, the main body has a wall thickness of greater than or equal to 0.15mm. Reducing the wall thickness of the main body may decrease the amount of electrical insulation between the stator core and the winding. This may reduce the safety of the motor and / or require the stator core to operate at a lower power, thereby reducing the power of the motor. Additionally, the manufacturability and the robustness of the main body may decrease. Therefore, providing a wall thickness of greater than or equal to 0.15mm may provide a higher level of electrical insulation, mechanical robustness and manufacturability compared to a lower wall thickness.

[0018] Optionally, the wall thickness is less than or equal to 0.8mm. Increasing the thickness may reduce the space within the motor to house electrical components such as the winding, which may reduce the performance of the motor. Additionally, a thicker main body may be more susceptible to manufacturing defects, such as shrinkage, than a thinner main body. Therefore, providing a wall thickness of less than or equal to 0.8mm may provide an increased amount of space within the motor and robustness to manufacturing defects when compared to a thicker main body.

[0019] A wall thickness of between 0.15mm and 0.8mm may provide a good balance between the competing needs of electrical insulation, mechanical robustness and manufacturability on the one hand and space and robustness to manufacturing defects on the other hand. Optionally, the door has a thickness of greater than or equal to 0.1mm. Increasing the thickness of the door may increase the amount of electrical insulation the door is able to provide between the winding and other components of the stator assembly. Therefore, having a thickness of greater than or equal to 0.1mm may increase the safety of the stator assembly, and may enable the stator assembly to operate at a higher voltage, compared to a lower thickness.

[0020] Optionally, the door has a thickness of less than or equal to 1mm. Reducing the thickness of the door may increase the space available within the stator assembly for components of the stator assembly such as windings, this may enable a greater winding fill factor to be used which may increase the power of the stator assembly. Therefore, having a thickness of less than or equal to 1mm may increase the winding fill factor and thereby the power of the stator assembly compared with a greater door thickness.

[0021] A door thickness of between 0.1mm and 1mm may provide a good balance between the competing needs of increasing the safety of the stator assembly and increasing the power of the stator assembly.

[0022] According to a second aspect of the present invention there is provided a motor comprising: a rotor assembly comprising an impeller for generating an airflow; and a stator assembly for causing rotation of the impeller, wherein: the stator assembly comprises a stator core bobbin according the first aspect of the present invention; a portion of the stator winding is located in the channel; and the door is in the closed position such that the portion of the winding is surrounded by the main body and the door.

[0023] The rotor assembly may comprise a shaft. A radial direction of the motor may be perpendicular to a rotational axis of the rotor assembly, for example in a direction perpendicular to a rotational axis of the shaft of the rotor assembly. An axial direction of the motor may be parallel to the rotational axis of the rotor assembly, for example in a direction parallel to the rotational axis of the rotor assembly. Optionally, the door extends along a full axial length of the main body. Optionally, the door extends along a full axial length of the channel.

[0024] Optionally, the door is fixed to the main body. As a result, the door may be better secured than if the door were not fixed to the main body, which may reduce the likelihood of the door being moved out of the closed position during operation (for example, due to vibrations), which may expose the windings to other components of the motor and reduce the safety of the motor. Optionally, the door is glued or welded to the main body.

[0025] Optionally, the stator core bobbin is located downstream of the impeller; the main body comprises a diffuser vane for interacting with the airflow generated by the impeller; the main body at least partially defines an airflow passage within which the diffuser vane is located; and the main body and the diffuser vane are integrally formed.

[0026] By integrally forming the main body of the bobbin with the diffuser vane, a number of separate components of the motor may be reduced relative to an arrangement where the diffuser vane and the bobbin are separately formed. Reducing component count may reduce a risk of failure and / or reduce a cost of the motor.

[0027] Additionally, the diffuser vane may provide a thermal transfer path to remove heat generated by the stator core. As the main body and the diffuser vane are integrally formed, thermal conduction between the main body and the diffuser vane may be increased, which may increase the amount of heat removed from the stator core, relative to if, for example, the main body and diffuser vane were separate components joined by adhesive. Moreover, integrally forming the diffuser vane and main body may result in a more mechanically stable stator assembly than if the diffuser vane and main body were formed separately.

[0028] Moreover, because the main body at least partly defines the airflow passage within which the diffuser vane is located, the need for an additional component to define the airflow passage may be removed. Thereby, more space may be provided within the motor. This space may be used to increase the quantity of electrical components, such as the winding, within the motor, which may increase the performance of the motor. Alternatively, this space may be used to increase the size of the diffuser vane, which may increase the aerodynamic and / or acoustic performance of the motor.

[0029] Optionally, the stator core bobbin has a radial extent of less than or equal to 20mm. As a result, the motor may be sufficiently compact to fit within the space constrains required for handheld appliances such as hair dryers or vacuum cleaners. Reducing the likelihood of shorting between components may be especially important in such small motors. Therefore, providing a closed position where the windings are surrounded by the door and the main body may be especially beneficial in such motors.

[0030] The radial extent of the stator core bobbin may comprise an extent in the radial direction of the motor.

[0031] Optionally, the radial extent of the stator core bobbin is greater than or equal to 2mm. The extent of the bobbin may dictate the maximum extent of the stator core, which may affect the power of the motor. Having a radial extent of greater than or equal to 2mm may therefore increase the power of the motor compared to a lesser extent of bobbin.

[0032] Optionally, the stator assembly comprises a stator core and the main body is overmoulded onto the stator core. Overmoulding may ensure that the stator core and main body are in intimate contact which may improve the heat transfer between them and away from the stator core compared to other manufacturing techniques such as moulding the bobbin and then inserting the stator core into the bobbin.

[0033] Optionally, the stator assembly comprises a further stator core bobbin according to the first aspect of the present invention, and the further stator core bobbin is formed separately to the stator core bobbin. Forming the stator assembly from multiple separate stator core bobbins may facilitate winding of windings onto the bobbins in comparison to an arrangement with if the bobbins were integrally formed. For example, each bobbin may be wound separately and then assembled to form the stator assembly. Optionally, the motor is configured to operate at 300V. For a given motor power, operating at 300V may reduce the current in the windings which may reduce the resistance losses within the windings and thereby the heat generated in the windings when compared with a lesser voltage. However, this may increase the likelihood of shorting between the windings and other components of the stator assembly. Therefore, providing a closed position where the windings are surrounded by the door and main body may be especially beneficial when operating at 300V.

[0034] According to a third aspect of the present invention there is provided a vacuum cleaner comprising a stator core bobbin according to the first aspect of the present invention or a motor according to the second aspect of the present invention.

[0035] According to a fourth aspect of the present invention there is provided a haircare appliance comprising a stator core bobbin according to the first aspect of the present invention or a motor according to the second aspect of the present invention.

[0036] BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure l is a perspective view of an example motor;

[0038] Figure 2 is a cross-sectional view of the example motor;

[0039] Figure 3 is a perspective view of a rotor assembly of the example motor;

[0040] Figure 4 is a perspective view of a first diffuser stage of the example motor;

[0041] Figure 5 is a perspective view of a stator assembly of the example motor;

[0042] Figure 6 is a top view of the stator assembly;

[0043] Figure 7 is a perspective view of a stator sub-assembly of the stator assembly;

[0044] Figure 8 is a top view of the stator sub-assembly;

[0045] Figure 9 is a perspective view of a stator core of the stator sub-assembly;

[0046] Figure 10 is a perspective view of the stator sub-assembly with a winding of the stator subassembly removed;

[0047] Figure 11 is a cross-sectional view of the stator sub-assembly with the winding removed;

[0048] Figure 12 is a cross-sectional view of the stator sub-assembly with the winding, stator vanes of the stator sub-assembly, and a wall of the stator sub-assembly removed; Figure 13 is a cross-sectional view of the stator sub-assembly with the winding and a main body of a bobbin of the stator sub-assembly removed;

[0049] Figure 14 is a side view of the stator sub-assembly with the winding removed;

[0050] Figure 15 is a cross-sectional view of the stator sub-assembly;

[0051] Figure 16 is a perspective view of the stator core when assembled in the stator assembly;

[0052] Figure 17 is a perspective view of the stator sub-assembly with the winding removed and doors of the stator sub-assembly in an open position;

[0053] Figure 18 is a cross-sectional view of the stator sub-assembly with the winding removed and the doors in the open position;

[0054] Figure 19 is a perspective view of a vacuum cleaner comprising the example motor; and Figure 20 is a side view of a haircare appliance comprising the example motor.

[0055] DETAILED DESCRIPTION

[0056] Figures 1 and 2 show a motor 10 comprising a rotor assembly 12, a diffuser stage 14 and a stator assembly 16.

[0057] The rotor assembly 12 is shown in isolation in Figure 3. The rotor assembly 12 comprises a shaft 18, a magnet 20 and an impeller 22. The shaft 18 is elongate in form, having an upstream end 24 and downstream end 26. Upstream and downstream refer generally to a direction of airflow through the motor 10 in use. The shaft 18 defines a rotational axis 30 of the rotor assembly 12. An axial direction 32 of the motor 10 is parallel to the rotational axis 30 of the rotor assembly 12. A radial direction 34 of the motor 10 is perpendicular to the rotational axis 30 of the rotor assembly 12. References to axial and radial herein refer respectively to the axial 32 and radial 34directions of the motor 10.

[0058] The magnet 20 is mounted generally centrally along the shaft 18. The impeller 22 is mounted to the upstream end 24 of the shaft 18.

[0059] The diffuser stage 14 is shown in isolation in Figure 4. The diffuser stage 14 comprises an outer wall 38, a central hub 40, and a plurality of diffuser vanes 42. The outer wall 38 has an annular shape and comprises a lip 44 for connecting the diffuser stage 14 to the stator assembly 16. The central hub 40 defines a bore 27. An airflow passage 46 is defined between the central hub 40 and the outer wall 38. The diffuser vanes 42 extend between the central hub 40 and the outer wall 38 within the airflow passage 46.

[0060] The diffuser vanes 42 are circumferentially offset from one another such that a clearance 43, measured in a circumferential direction around the hub 40, is 6mm. The clearance 42 could conceivably be between 3mm and 8mm.

[0061] The stator assembly 16 is shown in isolation in Figures 5 and 6. The stator assembly 16 has an annular shape. The stator assembly 16 is circumferentially segmented into six stator sub-assemblies 50. The stator sub-assemblies 50 are formed separately to each other. An outer diameter 54 of the stator assembly 16 is 65mm. Outer diameters 54 of less than or equal to 100mm are also envisaged.

[0062] The stator sub-assemblies 50 are identical, so only one stator sub-assembly 50 will be described for the sake of brevity. A stator sub-assembly 50 is shown in isolation in Figures 7 and 8. The stator sub-assembly 50 comprises a stator core 56, a bobbin 58, and a winding 60.

[0063] The stator core 56, illustrated in Figure 9, comprises a stack of laminations 57, here schematically represented and not to scale, with not all individual laminations shown for sake of clarity.

[0064] Collectively the laminations 57 define a yoke 61 and a tooth 62. The yoke 61 has a first end 63 and a second end 65. The yoke 61 comprises a first protrusion 66 at the first end 63, and a second protrusion 68 at the second end 65. A dashed plane 67 at the first end 63 is depicted from which the first protrusion 66 protrudes. The second protrusion 68 protrudes from an equivalent plane at the second end 65, which is not shown for sake of clarity. The first 66 and second 68 protrusions extend from their respective planes by the same extent.

[0065] The first protrusion 66 and the second protrusion 68 each extend only partially along a height H of the stack of laminations 57, with the extent Pl of the first protrusion 66 being roughly half of the height H of the stack of laminations 57. Similarly, the extent of the second protrusion 68 is roughly half of the height H of the stack of laminations 57.

[0066] To achieve this, two stacks of laminations 57 with a height of Pl, each with a protrusion 66, are assembled, and fixed together such that one of the two stacks of laminations 57 is turned by 180° relative to the other stack of laminations 57. This results in the form of the stator core 56 discussed above.

[0067] The first 66 and second 68 protrusions are offset along the stack of laminations 57, at the first end 63 and the second end 65 of the yoke 106, respectively. In such a manner, the first protrusion 66 is located on a first side 69 of a plane A that bisects the stack of laminations 57, with the second protrusion 68 located on a second side 70 of the plane A.

[0068] The stator core 56 comprises a first channel 71 extending through the first protrusion 66 and a second channel 73 extending through the second protrusion 68.

[0069] The tooth 62 extends radially inwardly from the yoke 61 and comprises tooth tips 76 that extend circumferentially outwardly from a radially inner end of the tooth 62.

[0070] As the first protrusion 66 and the second protrusion 68 are offset along the stack of laminations 57, and each have a height less than a height H of the stack of laminations 57, the first 66 and second 68 protrusions may allow for the stator core 56 to overlap with further stator cores 56. In such a manner the first 66 and second 68 protrusions may permit a lap joint to be formed with adjacent stator cores 56.

[0071] The stator core 56 has a radial extent 78 of 5.7mm. The stator core 56 having a radial extent 78 of between 4mm and 8mm is also envisaged.

[0072] Figure 10 shows the bobbin 58 and stator core 56 with the winding 60 removed. The bobbin 58 comprises a main body 80, a first diffuser vane 82, a second diffuser vane 84, a wall 86, a first hinge 88, a second hinge 90, a first door 92, and a second door 94. The bobbin 58 is overmoulded onto the stator core 56 such that the bobbin 58 is connected to the stator core 56. The main body 80, the first diffuser vane 82, the second diffuser vane 84, the wall 86, the first hinge 88, the second hinge 90, the first door 92, and the second door 94 are integrally formed such that the bobbin 58 is a monolithic component. The bobbin 58 may be referred to a stator core bobbin.

[0073] The bobbin 58 is formed of PBT-30GF, which is an example of a fibre reinforced plastic. PBT-30GF has a coefficient of thermal conductivity of 0.37 W / mK and a dielectric strength of 36.0kV / mm. Other types of bobbin material having a coefficient of thermal conductivity of greater than or equal to 0.2 W / mK and / or a dielectric strength of greater than or equal to 15kV / mm are also envisaged. Additionally, PBT-30GF has a strain at breaking of 2.1%. Other bobbin materials having a strain at breaking of greater than or equal to 2% are also envisaged.

[0074] Referring now to Figure 11, which show the bobbin 58 and stator core 56 with the winding 60 removed in a plane which extends perpendicularly to the rotational axis 30 of the rotor assembly 12. The main body 80 comprises three portions: an inner portion 98, a middle portion 96, and an outer portion 100, and has a first circumferential side 102 and a second circumferential side 104.

[0075] Referring now to Figure 12, The inner portion 98 overlies the tooth tips 76 and extends circumferentially and axially from a radially inner end of the middle portion 96.

[0076] The middle portion 96 overlies the tooth 62. The middle portion 96 comprises a plurality of indents 105. The indents 105 extend axially along the first 102 and second 104 circumferential sides of the middle portion 96 for an axial length of the middle portion 96. Each indent 106 has a generally semi-circular cross-sectional shape and is dimensioned to receive a portion of the winding 60.

[0077] The outer portion 100 comprises an opening 106 and a lip 108 (shown in Figure 14). The outer portion 100 overlies the yoke 61 and extends circumferentially and axially from a radially outer end of the middle portion 96. The outer portion 100 extends further circumferentially than the inner portion 98 and is curved slightly in a direction towards the middle portion 96. The opening 106 (shown in Figure 12) is in a radially outer side 110 of the outer portion 100 through which the yoke 61 is exposed. The opening 106 extends for 100% of the outer circumference of the outer portion 100 such that the outer portion 100 is split into an upstream portion 112 and a downstream portion 114. The further lip 108 is located on the upstream portion 112 and overlaps with the lip 44 of the outer wall 38 of the diffuser stage 14.

[0078] When viewed in the plane which extends perpendicularly to the rotational axis 30 of the shaft 18, the middle portion 96, the inner portion 98, and the outer portion 100 on the first circumferential side 102 of the main body 80 collectively define a U-shaped first channel 116, as shown in Figure 12. When viewed in the plane which extends perpendicularly to the rotational axis 30 of the shaft 18, the middle portion 96, the inner portion 98, and the outer portion 100 on the second circumferential side 104 of the main body 80 define a second channel 118.

[0079] The middle portions 96 of the main body 80 has a minimum wall thickness 99 of 0.25mm. Wall thicknesses 99 of between 0.15mm and 0.8mm are also envisaged.

[0080] Referring now to Figure 13, the first diffuser vane 82 extends radially from the upstream portion 112 and the downstream portion 114 of the outer portion 100 of the main body 80. The first diffuser vane 82 extends across the opening 106 from the upstream portion 112 to the downstream portion 114. The first diffuser vane 82 contacts the yoke 61 of the stator core 56 through the opening 106. The first diffuser vane 82 tapers between a root 120 of the first diffuser vane 82 to a tip 122 of the first diffuser vane 82. The root 120 of the first diffuser vane 82 connects to the outer portion 100 of the main body 80. The root 120 has a thickness of 0.5mm. Root thicknesses of between 0.2mm and 2mm are also envisaged. A ratio of the wall thickness 99 of the middle portion 96 main body 80 to the root thickness of the first diffuser vane 82 is 0.5. Ratios of between 0.3 and 1 are also envisaged.

[0081] The first diffuser vane 82 extends along the outer portion 100 for an axial length 122 of 140 % of an axial length 124 of the stator core 56. The first diffuser vane 82 extending along the outer portion 100 for axial lengths 122 of greater than or equal to 40 % of the axial length 124 of the stator core 56 is also envisaged.

[0082] The first diffuser vane 82 has a radial extent 127 of 3.1mm. A radial extent 126 of between 1mm and 10mm is also envisaged. A ratio of the radial extent 127 of the first diffuser vane 82 to the extent 78 of the stator core 56 is 0.54. Ratios of between 0.2 and 1 are also envisaged.

[0083] The second diffuser vane 84 is identical to the first diffuser vane 82 except that the second diffuser vane 84 is circumferentially offset from first diffuser vane 82 such that a clearance 125, measured in a circumferential direction around the outer portion 100 of the main body 80, between the first diffuser vane 82 and the second diffuser vane 84 is 5mm. The clearance 125 could conceivably be between 3mm and 8mm. The first and second diffuser vanes 82,84 constitute part of a further diffuser stage which is located downstream of the diffuser stage 14.

[0084] The wall 86 has an arcuate shape. A radially inner circumference of the wall 86 is connected to the tips 122 of the diffuser vanes 82,84. The wall 86 comprises a main body 124, a first connecting feature 126, and a second connecting feature 128. The main body 124 subtends a central angle A of 60° such that when the stator assembly 16 is assembled, the main bodies of the walls 86 of the stator sub-assemblies 50 form a cylinder. The main body comprises a first circumferential end 128 and a second circumferential end 130. The connecting features 124,126 each extend from a respective one of the circumferential ends 128,130 and overlap with corresponding connecting features 124,126 on adjacent walls 86 when assembled into the stator assembly 16.

[0085] An airflow passage 132 is defined between the radially inner circumference of the wall 86 on one side and the outer portion 100 of the main body 80 and the exposed yoke 61 of the stator on the other. The first and second diffuser vanes 82,84 are located within the airflow passage 132. The first hinge 88 comprises a first end 129 and a second end 131. The first end 129 is integrally formed with the first circumferential side 102 of the inner portion 98 of the main body 80. The second end 131 is internally formed with a first end 138 of the first door 92. The first hinge 88 enables movement of the first door 92 relative to the inner 96, middle 98, and outer 100 portions of the main body 80. The first hinge 88 has a thickness 134 of 0.15mm. Thicknesses of between 0.1mm and 0.4mm are also envisaged. The thickness 134 is measured in the plane which extends perpendicular to the rotational axis 30 of the rotor assembly 12. A ratio of the thickness 134 of the first hinge 88 to the wall thickness 99 of the middle portions 96 of the main body 80 of the bobbin 58 is 0.4. Ratios of between 0.2 and 1 are also envisaged. The first hinge 88 has the minimum thickness 134 of the bobbin 58. The inner portion 100 of the main body 80 has the maximum thickness 137 (shown in Figure 10) of bobbin 58 of 1.5mm. Therefore, a ratio of the maximum thickness 137 of the bobbin 58 to the minimum thickness 134 of the bobbin 58 is 10. Ratios of between 15 and 1 are also envisaged.

[0086] The second hinge 90 is identical to the first hinge 88 except for the following. The first end of the second hinge 90 is integrally formed with the second circumferential side 104 of the inner portion 98 of the main body 80. The second end of the second hinge 90 is internally formed with a first end of the second door 94. The second hinge 90 enables movement of the second door 94 relative to the portions of the main body 80.

[0087] The first door 92 comprises the first end 138 and a second end 140. The first end 138 is integrally formed with the first hinge 88. As described below in more detail, prior to assembly into the stator assembly 16, the first door 92 is moveable from an open position to a closed position. When the stator sub-assemblies 50 are assembled into the stator assembly 16, the first door 92 is in the closed position. When in the closed position, the first door 92 extends between the inner portion 98 and the outer portion 100 on the first circumferential side 102 of the main body. The second end 140 of the first door 92 is fixed to the outer portion 100 of the main body 80 by adhesive. The first door 92 has a thickness 142 of 0.2mm. Thicknesses of between 0.1mm and 1mm are also envisaged. The thickness 142 is measured in the plane which extends perpendicular to the rotational axis 30 of the rotor assembly 12. The second door 94 is identical to the first door 92 except for the following differences. The first end of the second door 94 is integrally formed with the second hinge 90. The second door 94 extends between the inner portion 98 and the outer portion 100 on the second circumferential side 104 of the main body 80. The second end of the second door 94 is fixed to the second circumferential side 104 of the outer portion 100 of the main body 80.

[0088] The bobbin 58 has a radial extent 121, measured with the first 92 and second 94 doors in the closed position, of 3.5mm. Radial extents 121 of between 2mm and D 20mm are also envisaged.

[0089] The winding 60 comprises a copper wire having a circular cross-sectional shape. The winding 60 is wound around the middle portion 96 of the main body 80 such that a first portion 144 of the winding 60 is located in the first channel 116, and a second portion 146 of the winding 60 is located in the second channel 118. As shown in Figure 13, when viewed in the plane which extends perpendicular to the rotational axis 30 of the rotor assembly 12, each channel 116,118 and thereby each portion 144,146 of the winding 60 located within each channel 116,118 is surrounded by the inner 96, middle 98, and outer 100 of the main body 80 of the bobbin 58 and one of the doors 92,94.

[0090] A schematic representation of the stator cores 56, when assembled in the stator assembly 50 is shown in Figure 16. The stator assembly comprises the stator 56 and a neighbouring second stator core 95 of the same type. The first protrusion 66 of the stator core 56 overlaps with a second protrusion 97 of the neighbouring second stator core 95. The first channel 71 aligns with a second channel (not shown) which extends through the second protrusion 97 of the neighbouring second stator core 95. A pin 111 is located in the first channel 71 and the second channel of the second motor stator core component 95. The pin 111 acts to fasten together the stator core 56 and the neighbouring second stator core 95. When the stator assembly 50 is assembled, the tooth tips 76 and inner portions 98 of the stator sub-assemblies 50 collectively define a channel 101. When the motor is assembled, the shaft 18 is located within the bore 27 and the channel 101. The diffuser stage 14 is located downstream of the impeller 22. The stator assembly 16 is located downstream of the impeller 22 and the diffuser stage 14.

[0091] In use, a voltage of 300V is applied to the windings 60 of the stator assembly 16 such that a magnetic field is created by the stator assembly 16. The magnetic field created by the stator assembly 16 interacts with the magnet 20 of the rotor assembly 12 to rotate the rotor assembly 12 relative to the stator assembly 16. Rotation of the impeller 22 of the rotor assembly 12 generates an airflow. The airflow passes through the airflow passage 46 of the first diffuser vane 82 and interacts with the diffuser vanes 42 of the diffuser stage 14. The airflow then passes through the airflow passages 132 of the stator sub-assemblies 50 and interacts with the first and second diffuser vanes 82,84 of the stator sub-assemblies 50. Additionally, the airflow flows over the yokes 61 of the stators 56 which are exposed to the airflow via the openings 106 of the bobbins 58.

[0092] Prior to assembly of the stator sub -assemblies 50 into the stator assembly 16, the doors 92,94 of the bobbins 58 are moveable from the open position (shown in Figures 16 and 17) to the closed position. In contrast to the closed position, when in the open position, the second end 140 of each door is not attached to a respective circumferential side 102,104 of the outer portion 100 of the main body 80. In the open position, the doors 92,94 extend away from the middle 96 and outer 100 portions of the main body 80 such that the doors 92,94 are moveable through an angle 148 of 150° from the open position to the closed positions. Moving through an angle 148 of at least 60° is also envisaged.

[0093] When in the open position and viewed in the plane which extends perpendicular to the rotational axis 30 of the rotor assembly 12 (as shown in Figure 18), the channels 116,118 each have an open side 150,152. These open sides 150,152 facilitate movement of the winding 60 into the channels 116,118 during winding of the winding 60 around the main body 80. After the winding 60 has been wound around the main body 80 of the bobbin 58, the doors 92,94 can be moved to their closed positions to surround the portions 144,146 of the winding 60 located within the channels 116,118. In the above example, the stator assembly 16 is circumferentially segmented into the six stator sub-assemblies 50, and the diffuser vanes 82,84 of each sub-assembly 50 form the further diffuser stage. Thereby, the further diffuser stage may be regarded as a circumferentially segmented diffuser stage with each stator sub-assembly 50 constitutes a segment of the circumferentially segmented diffuser stage. It is also envisaged that the stator assembly 16 could be circumferentially segmented into no less than three subassemblies 50 such that the circumferentially segmented diffuser stage is segmented into no less than three segments.

[0094] In the above example, each of the six stator sub-assembly 50 comprises a wall 86 which is integrally formed with the other components of the bobbin 58 and, when the stator assembly 16 is assembled, the six walls 86 form a cylinder. In other examples, the six walls 86 may be replaced with a single cylindrical wall which is formed separately to the other components of the bobbins 58. The tips 122 of the first and second diffuser vanes 82,84 may be joined to the single cylindrical wall. For example, the first and second diffuser vanes 82,84 may be adhered or ultrasonically welded to the single cylindrical wall.

[0095] A schematic illustration of a vacuum cleaner 100 comprising the motor 10 is shown in Figure 19, whilst a schematic illustration of a hair care appliance 200 comprising the motor 10 is shown in Figure 20.

[0096] In the above example, the stator assembly 50 is downstream of the impeller 22. In other examples, the stator assembly 50 is located upstream of the impeller 22. In these examples the first 82 and second 84 diffuser vanes do not diffuse the airflow generated by the impeller 22, and instead are guide vanes for guiding the airflow generated by the impeller 22.

[0097] In the above example, the main body 80, the first diffuser vane 82, the second diffuser vane 84, the wall 86, the first hinge 88, the second hinge 90, the first door 92, and the second door 94 are integrally formed such that the bobbin 58 is a monolithic component. In other examples, the main body 80, the first diffuser vane 82, the second diffuser vane 84, the wall 86, the first hinge 88, the second hinge 90, the first door 92, and the second door 94 may instead by formed separately and connected to one another, for example, using adhesive. In particular, embodiments are envisaged where the wall 86 is formed separately as a discrete cylindrical component, and the remaining components of the stator assembly are housed within the wall 86.

[0098] Whilst particular examples and embodiments have thus far been described, it should be understood that these are illustrative only and that various modifications may be made without departing from the scope of the invention as defined by the claims.

Claims

CLAIMS1. A stator core bobbin comprising: a main body at least partially defining a channel; and a door moveable from an open position, in which a portion of a stator winding is moveable into the channel, to a closed position, in which the portion of the stator winding is surrounded by the main body and the door.

2. A stator core bobbin as claimed in claim 1, wherein: the stator core bobbin comprises a hinge connecting the door to the main body; and the main body, the hinge, and the door are integrally formed.

3. A stator core bobbin as claimed in claim 2, wherein a ratio of a thickness of the hinge to a wall thickness of the main body is less than or equal to 1.

4. A stator core bobbin as claimed in claim 2 or 3, wherein the hinge has a thickness of less than or equal to 0.4mm.

5. A stator core bobbin as claimed in claim in claim 2 to 4, wherein the door is moveable through at least 60° between the open position and the closed position.

6. A stator core bobbin as claimed in claim in claim 2 to 5, wherein the hinge comprises a material having a strain at breaking of greater than or equal to 2%.

7. A stator core bobbin as claimed in any preceding claim, wherein a ratio of a maximum thickness of the stator core bobbin to a minimum thickness of the stator core bobbin is greater than or equal to 1 and less than or equal to 15.

8. A stator core bobbin as claimed in claim in any preceding claim, wherein the stator core bobbin is formed of a material having a dielectric strength of greater than or equal to 15kV / mm.

9. A stator core bobbin as claimed in claim in any preceding claim, wherein the stator core bobbin is formed of a fibre reinforced plastic.

10. A stator core bobbin as claimed in claim in any preceding claim, wherein the main body has a wall thickness of greater than or equal to 0.15mm.

11. A stator core bobbin as claimed in claim in any preceding claim, wherein the door has a thickness of greater than or equal to 0.1mm12. A motor comprising: a rotor assembly comprising an impeller for generating an airflow; and a stator assembly for causing rotation of the impeller, wherein: the stator assembly comprises a stator core bobbin according to any preceding claim and a stator winding; a portion of the stator winding is located in the channel; and the door is in the closed position such that the portion of the winding is surrounded by the main body and the door.

13. A motor as claimed in claim in claim 12, wherein the door is fixed to the main body.

14. A motor as claimed in claim 12 or 13, wherein: the stator core bobbin is located downstream of the impeller; the main body comprises a diffuser vane for interacting with the airflow generated by the impeller; the main body at least partially defines an airflow passage within which the diffuser vane is located; and the main body and the diffuser vane are integrally formed.

15. A motor as claimed in claim 12 to 14, wherein the stator core bobbin has a radial extent of less than or equal to 20mm.

16. A motor as claimed in claims 12 to 15, wherein the stator assembly comprises a stator core and the main body is overmoulded onto the stator core.

17. A motor as claimed in claims 12 to 16, wherein the stator assembly comprises a further stator core bobbin according to claims 1 to 12, and the further stator core bobbin is formed separately to the stator core bobbin.

18. A motor as claimed in claims 12 to 17, wherein the motor is configured to operate at 300V.

19. A vacuum cleaner comprising a stator core bobbin according to claims 1 to 11 or a motor according to claims 12 to 18.

20. A haircare appliance comprising a stator core bobbin according to claims 1 to 11 or a motor according to claims 12 to 18.

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