A motor

Abstract

A motor (Fig.2, 10) comprises a rotor assembly (Fig.2, 12) and a stator assembly (Fig.2, 16). The rotor assembly comprises an impeller (Fig.3, 22) for generating an airflow. The stator assembly is for

Description

BACKGROUND There is a general desire to improve electric machines, such as motors, in a number of 5 ways. For example, improvements may be desired in terms of size, weight, power density, manufacturing cost, efficiency, reliability, and noise. SUMMARY According to a first aspect of the present invention there is provided a motor comprising: a 10 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 bobbin located downstream of the impeller, a stator winding, and a stator core; the bobbin comprises: a main body about which the stator winding is located, and to which the stator core is LO connected; and a diffuser vane for interacting with the airflow generated by the impeller; CXI 15 the main body at least partially defines an airflow passage within which the diffuser vane is co located; and the main body and the diffuser vane are integrally formed. 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 20 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. 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, 25 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. 30 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 5 aerodynamic and / or acoustic performance of the motor. The rotor assembly may comprise a shaft. An axial direction of the motor may be parallel to a rotational axis of the rotor assembly, for example, in a direction parallel to a rotational axis of the shaft of the rotor assembly. A radial direction of the motor may be 10 perpendicular to the rotational axis of the rotor assembly, for example in a direction perpendicular to the rotational axis of the shaft of the rotor assembly. Optionally, the diffuser vane extends along the main body for an axial length of at least LO 40% of an axial length of the stator core. This may provide a thermal transfer path along at CXI 15 least 40% of the axial length of the stator core, which may aid with removal of heat co generated by the stator core in use. The diffuser vane may extend along the main body for an axial length of at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 100 %, at least 110%, or at least 120% of the axial length of the stator core. The axial lengths of the diffuser vane and the stator core may comprise lengths in the axial direction 20 of the motor. Optionally, the main body comprises an opening which exposes the stator core to the airflow generated by the impeller such that the stator core at least partially defines the airflow passage within which the diffuser vane is located. The airflow may thereby directly 25 cool the stator core, which may increase the cooling of the stator core relative to if the opening were not present. Optionally, the diffuser vane contacts the stator core through the opening. This may increase the amount of heat transferred from the stator core to the diffuser vane and 30 thereby increase the cooling of the stator core, when compared to the stator core being in only indirect contact with the diffuser vane via the main body. Optionally, the diffuser vane extends across the opening from a first portion of the main body to a second portion of the main body; and the diffuser vane is integrally formed with both the first portion and the second portion. As the diffuser vane is integrally formed with both portions, the diffuser vane is mechanically supported on either side of the opening. 5 This may increase the robustness and stiffness of the diffuser vane compared to if the diffuser vane projected from only one of the portions. Optionally, the bobbin is moulded. For example, the bobbin may be injection moulded. As the diffuser vane is integrally formed with both portions, the mouldability of the bobbin 10 may be increased compared to if the diffuser vane were integrally formed with only one of the portions. If the diffuser vane were integrally formed with only one of the portions, an air pocket may form within the bobbin mould during moulding which may inhibit the flow of molten material into the air pocket and thereby filling the bobbin mould. LO CXI 15 Optionally, a ratio of a radial extent of the diffuser vane to the radial extent of the stator co core is greater than or equal to 0.2. The radial extents of the diffuser vane and the stator core may comprise extents in the radial direction of the motor. 1— Optionally, the ratio of the radial extent of the diffuser vane to the radial extent of the 20 stator core is less than or equal to 1. Optionally, the radial extent of the diffuser vane is less than or equal to 10mm. Optionally, the radial extent of the diffuser vane is greater than or equal to 1mm. The 25 extent of the diffuser vane may affect the extent to which the diffuser vane can condition the airflow. Providing a heigh of greater than or equal to 1mm may enable the diffuser vane to meet the airflow conditioning requirements of applications such as a hair dryer or a vacuum cleaner. The radial extent of the diffuser vane may comprise an extent in the radial direction of the motor. 30 Optionally, the radial extent of the stator core is less than or equal to 8mm. Optionally, a radial extent of the stator core is greater than or equal to 4mm. The extent of the stator core may affect the power of the motor. Having a radial extent of greater than or equal to 4mm may therefore increase the power of the motor compared to a lesser extent of stator core. The radial extent of the stator core may comprise an extent in the radial direction of the motor. Optionally, the bobbin comprises a further diffuser vane integrally formed with the main 10 body. This may provide additional conditioning of the airflow compared to having only a single diffuser vane. Additionally, this may provide an additional thermal transfer path from the stator core, which may increase the heat transfer from the stator core. The further diffuser vane may comprise substantially the same form as the diffuser vane. Optional LO features of the diffuser vane may apply equally to the further diffuser vane where CXI 15 appropriate. co Optionally, a clearance, measured in a circumferential direction around the main body, between the diffuser vane and the further diffuser vane is greater than or equal to 3mm. Due to tooling constraints (for example, minimum tool body sizes in an injection moulding 20 tool) this may improve the manufacturability of the bobbin compared to having a clearance of less than 3mm. Optionally, the clearance is less than or equal to 8mm. A greater clearance may reduce the total number of diffuser vanes which can be accommodated for a given size of motor. 25 Reducing the total number of diffuser vanes may reduce the extent to which the airflow can be conditioning compared to a greater number of diffuser vanes. Therefore, having a clearance of less than or equal to 8mm, may improve the conditioning of the airflow compared to having a clearance of greater than 8mm, and may provide sufficient conditioning of the airflow for applications such as a hair dryer or vacuum cleaner. Having a clearance of between 3mm and 8mm may provide a good balance between manufacturability and conditioning of the airflow. Optionally, the bobbin is formed of a fibre reinforced plastic. The bobbin performs both an electrically insulative and a structural function: providing electrical insulation between the winding and the stator core, and providing a sufficiently stiff diffuser vane to interact with 5 the airflow. A fibre reinforced plastic may provide sufficient electrical insulation and mechanical properties to perform this dual function. Optionally, the bobbin is formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.2W / mK. This may provide efficient heat transfer away from 10 the stator core, via the diffuser vane and / or the main body. The bobbin may be formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.35W / mK. LO Optionally, the bobbin is formed of a material having a dielectric strength of greater than CXI 15 or equal to 15kV / mm. This may enable a higher voltage to be utilised in the stator core, co 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. 1— Optionally, the main body has a wall thickness of greater than or equal to 0.15mm. 20 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 winding to operate at a lower voltage, 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 25 provide a higher level of electrical insulation, mechanical robustness and manufacturability compared to a lower wall thickness. 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 30 whilst maintaining the same motor outer diameter. 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 (whilst maintaining the same motor outer diameter) and robustness to manufacturing defects when compared to a thicker main body. A wall thickness of between 0.15mm and 0.8mm may provide a good balance between the 5 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 diffuser vane has a root thickness of greater than or equal to 0.2mm. If the root thickness is too low, the diffuser vane may have insufficient strength and stiffness. 10 Therefore, having a root thickness of greater than or equal to 0.2mm may provide a sufficiently strong and stiff diffuser vane. Optionally, the diffuser vane has a root thickness of less than or equal to 2mm. A diffuser LO vane with a thickness of 2mm may have sufficient stiffness and strength to effectively CXI 15 interact with the airflow. Therefore, increasing the thickness beyond 2mm may not CO increase the functionality of the diffuser vane but may increase the cost of the diffuser vane. Additionally, increasing the thickness may reduce the space available for the airflow to flow around the diffuser vane. CXI 20 Having a thickness of between 0.2mm and 2mm may provide a good balance between the competing needs of providing sufficient mechanical properties on one hand and reducing the cost and the space required on the other hand. Optionally, a ratio of a wall thickness of the main body to a root thickness of the diffuser 25 vane is less than 1. The different functional requirements for the main body and the diffuser vane may result in different thicknesses being desirable. The root thickness may need to be greater than the wall thickness because the diffuser vane is interacting with the airflow and is used as rib structure, which may require a greater thickness to achieve adequate stiffness and strength for the diffuser vane. Conversely, the thickness required to 30 achieve adequate electrical insulation for the main body may be less than the thickness required for the diffuser vane. If the thicknesses were the same, then either the mechanical properties of the diffuser vane could be insufficient, or the main body could be excessively thick (and thereby reduce space for the winding). Therefore, having a lesser wall thickness than root thickness may enable the bobbin to be better optimised for both of the functional requirements. 5 Optionally, the ratio is no less than 0.3. Reducing the ratio below 0.3 may reduce the manufacturability of the bobbin. For example, excessively different thickness may impede the flow of material in the bobbin during moulding, which may reduce the mouldability of the bobbin. 10 Optionally, the stator assembly has an outer diameter of less than or equal to 100 mm. 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. Thermal management in such a size of motor may be important to enable a desired power output to be achieved, and, as LO the stator core is a heat source in use, integrally forming the main body and the diffuser CXI 15 vane may aid with such thermal management. The stator assembly may have an outer co diameter of less than or equal to 66mm, or less than or equal to 40mm. Optionally, the main body comprises a plurality of indents. The indents may act as a locating feature to improve the accuracy of the locating of the winding during winding. 20 This may improve the fill factor compared to if the main body did not comprise the indents. The stator assembly comprises a wall spaced from the main body to at least partially define the airflow passage within which the diffuser vane is located. As a result, the airflow may 25 be better directed through the motor than if the wall were omitted, which may improve the aerodynamic performance of the motor. Optionally, the wall comprises a cylindrical wall formed separately to the bobbin. Thereby, the likelihood of airflow leaking through the wall may be reduced compared to if the wall 30 was made of separate segments. This may improve the aerodynamic performance of the motor. Additionally, by being formed separately, the mouldability of the bobbin may be increased compared to if the wall were integrally formed with the bobbin. Optionally, the diffuser vane is joined to the wall. For example, the diffuser vane may be adhered or ultrasonically welded to the wall. This may reduce the likelihood of airflow passing through a gap between the wall and an end of the diffuser vane which may 5 otherwise reduce the aerodynamic performance of the diffuser. The wall is integrally formed with the bobbin. This may reduce the likelihood of airflow passing through the gap between the wall and an end of the diffuser vane which may otherwise reduce the aerodynamic performance of the motor. 10 Optionally, the stator assembly comprises, a further bobbin located downstream of the impeller, a further stator winding, and a further stator core; the further bobbin comprises: a further main body about which the further stator winding is located, and to which the LO further stator core is connected; and a further diffuser vane for interacting with the airflow CXI 15 generated by the impeller; the further main body and the further diffuser vane are integrally CO formed; the further stator core is formed separately to the stator core; and the further bobbin is formed separately to the bobbin. Forming the stator assembly from multiple separate stator cores and bobbins may facilitate winding of the windings onto the bobbins in comparison to an arrangement with a single-piece annular stator assembly. For example, 20 each bobbin may be wound and then assembled to form the complete stator assembly. Forming the stator assembly of multiple separate stator cores and bobbins may also enable a greater winding fill factor to be achieved compared to a single-piece annular stator assembly, which may lead to increased motor efficiency and / or greater power density. Furthermore, during a stamping process where laminations of the stator cores are stamped 25 from a sheet of material, less waste may be generated in stamping out laminations compared to a single-piece annular stator assembly. Additionally, as each of the bobbins comprises a respective diffuser vane, a segmented diffuser stage comprising the diffuser vanes is provided. Segmenting the diffuser stage 30 over multiple bobbins may improve the manufacturability of the diffuser stage compared to having a single piece diffuser stage. For example, segmenting the diffuser stage may simplify the tooling (such as an injection moulding mould) required to manufacture the diffuser stage. Optionally, the bobbin is overmoulded onto the stator core. Overmoulding may ensure that 5 the stator core and bobbin 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. Optionally, the motor comprises a first diffuser stage, and a second diffuser stage 10 downstream of the first diffuser stage; and the diffuser vane is part of the second diffuser stage. As a result, the airflow with which the diffuser vane interacts may have already been conditioned by the first diffuser stage. Therefore, the aerodynamic performance of the motor may be less sensitive to design changes to the diffuser vane than if the diffuser vane LO were part of the first diffuser stage. This may improve the trade-offs between performance CXI 15 and manufacturability of the bobbin and thereby improve the manufacturability of the CO bobbin whilst reducing the impacts on the aerodynamic performance of the motor. According to a second aspect of the present invention there is provided a vacuum cleaner comprising a motor according to the first aspect of the present invention. 20 According to a third aspect of the present invention there is provided a haircare appliance comprising a motor according to the first aspect of the present invention. According to a fourth aspect there is provided a motor comprising: a rotor assembly 25 comprising an impeller for generating an airflow; and a stator assembly for causing rotation of the impeller, wherein: the stator assembly comprises a bobbin located downstream of the impeller, a stator winding, and a stator core; the bobbin comprises: a main body about which the stator winding is located, and to which the stator core is connected; and a diffuser vane which is connected to the main body and is for interacting 30 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 comprises an opening which exposes the stator core to the airflow generated by the impeller such that the stator core at least partially defines the airflow passage within which the diffuser vane is located. As a result of providing the opening, the airflow may directly cool the stator core, which may increase the cooling of the stator core relative to if the opening were not present. Additionally, by connecting the diffuser vane to the main body, the diffuser vane 5 may provide a thermal transfer path to remove heat generated by the stator core and thereby increasing the cooling of the stator core relative to if the main body and diffuser vane were not connected to one another. Moreover, because the main body at least partly defines the airflow passage within which 10 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 LO space may be used to increase the size of the diffuser vane, which may increase the CXI 15 aerodynamic and / or acoustic performance of the motor. CO The rotor assembly may comprise a shaft. An axial direction of the motor may be parallel to a rotational axis of the rotor assembly, for example, in a direction parallel to a rotational axis of the shaft of the rotor assembly. A radial direction of the motor may be 20 perpendicular to the rotational axis of the rotor assembly, for example in a direction perpendicular to the rotational axis of the shaft of the rotor assembly. A circumferential direction of the motor may be parallel with the rotational direction of the rotor assembly, for example around the rotational axis of the shaft of the rotor assembly. 25 Optionally, the diffuser vane contacts the stator core through the opening. This may increase the amount of heat transferred from the stator core to the diffuser vane and thereby increase the cooling of the stator core, when compared to the stator core being in only indirect contact with the diffuser vane via the main body. 30 Optionally, the diffuser vane extends across the opening from a first portion of the main body to a second portion of the main body; and the diffuser vane is integrally formed with both the first portion and the second portion. As the diffuser vane is integrally formed with both portions, the diffuser vane is mechanically supported on either side of the opening. This may increase the robustness and stiffness of the diffuser vane compared to if the diffuser vane projected from only one of the portions. 5 Optionally, the diffuser vane extends along the main body for an axial length of at least 40% of an axial length of the stator core. This may provide a thermal transfer path along at least 40% of the axial length of the stator core, which may aid with removal of heat generated by the stator core in use. The diffuser vane may extend along the main body for an axial length of at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at 10 least 100 %, at least 110%, or at least 120% of the axial length of the stator core. The axial lengths of the diffuser vane and the stator core may comprise lengths in the axial direction of the motor. LO Optionally, a radial extent of the diffuser vane is greater than or equal to 1mm. The extent c\j 15 of the diffuser vane may affect the extent to which the diffuser vane can condition the co airflow. Providing a heigh of greater than or equal to 1mm may enable the diffuser vane to meet the airflow conditioning requirements of applications such as a hair dryer or a vacuum cleaner. The radial extent of the diffuser vane may comprise a extent in the radial direction of the motor. 20 Optionally, the radial extent of the diffuser vane is less than or equal to 10mm. Optionally, a ratio of a radial extent of the diffuser vane to the radial extent of the stator core is greater than or equal to 0.2. The radial extents of the diffuser vane and the stator 25 core may comprise extents in the radial direction of the motor. Optionally, the ratio of the radial extent of the diffuser vane to the radial extent of the stator core is less than or equal to 1. 30 Optionally, a radial extent of the stator core is greater than or equal to 4mm. The extent of the stator core may affect the power of the motor. Having a radial extent of greater than or equal to 4mm may therefore increase the power of the motor compared to a lesser extent of stator core. The radial extent of the stator core may comprise an extent in the radial direction of the 5 motor. Optionally, the radial extent of the stator core is less than or equal to 8mm. Optionally, the bobbin comprises an additional diffuser vane connected to the main body. 10 This may provide additional conditioning of the airflow compared to having only a single diffuser vane. Additionally, this may provide an additional thermal transfer path from the stator core, which may increase the heat transfer from the stator core. The additional diffuser vane may comprise substantially the same form as the diffuser vane. Optional LO features of the diffuser vane may apply equally to the additional diffuser vane where CXI 15 appropriate. co Optionally, a clearance, measured in a circumferential direction around the main body, between the diffuser vane and the additional diffuser vane is greater than or equal to 3mm. Due to tooling constraints (for example, minimum tool body sizes in an injection moulding 20 tool) this may improve the manufacturability of the bobbin compared to having a clearance of less than 3mm. The circumferential direction around the main body may be parallel to the circumferential direction of the motor. Optionally, the clearance is less than or equal to 8mm. A greater clearance may reduce the 25 total number of diffuser vanes which can be accommodated for a given size of motor. Reducing the total number of diffuser vanes may reduce the extent to which the airflow can be conditioning compared to a greater number of diffuser vanes. Therefore, having a clearance of less than or equal to 8mm, may improve the conditioning of the airflow compared to having a clearance of greater than 8mm, and may provide sufficient 30 conditioning of the airflow for applications such as a hair dryer or vacuum cleaner. Having a clearance of between 3mm and 8mm may provide a good balance between manufacturability and conditioning of the airflow. Optionally, the bobbin is formed of a fibre reinforced plastic. The bobbin performs both an 5 electrically insulative and a structural function: providing electrical insulation between the winding and the stator core, and providing a sufficiently stiff diffuser vane to interact with the airflow. A fibre reinforced plastic may provide sufficient electrical insulation and mechanical properties to perform this dual function. 10 Optionally, the bobbin is formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.2 W / mK. This may provide efficient heat transfer away from the stator core, via the diffuser vane and / or the main body. The bobbin may be formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.35 L0 W / mK. CM is CO Optionally, the bobbin is formed of a material having a dielectric strength of greater than or equal to 15kV / mm. 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. 20 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 voltage, thereby reducing the power of 25 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. 30 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 whilst maintaining the same motor outer diameter. 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 (whilst maintaining the same motor outer diameter) and robustness to manufacturing defects when compared to a thicker main body. 5 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. 10 Optionally, the diffuser vane has a root thickness of greater than or equal to 0.2mm. If the root thickness is too low, the diffuser vane may have insufficient strength and stiffness. Therefore, having a root thickness of greater than or equal to 0.2mm may provide a sufficiently strong and stiff diffuser vane. LO CXI 15 Optionally, the diffuser vane has a root thickness of less than or equal to 2mm. A diffuser CO vane with a thickness of 2mm may have sufficient stiffness and strength to effectively interact with the airflow. Therefore, increasing the thickness beyond 2mm may not increase the functionality of the diffuser vane but may increase the cost of the diffuser vane. Additionally, increasing the thickness may reduce the space available for the airflow 20 to flow around the diffuser vane. Having a thickness of between 0.2mm and 2mm may provide a good balance between the competing needs of providing sufficient mechanical properties on one hand and reducing the cost and the space required on the other hand. 25 Optionally, a ratio of a wall thickness of the main body to a root thickness of the diffuser vane is less than 1. The different functional requirements for the main body and the diffuser vane may result in different thicknesses being desirable. The root thickness may need to be greater than the wall thickness because the diffuser vane is interacting with the 30 airflow, which may require a greater thickness to achieve adequate stiffness and strength for the diffuser vane. Conversely, the thickness required to achieve adequate electrical insulation for the main body may be less than the thickness required for the diffuser vane. If the thicknesses were the same, then either the mechanical properties of the diffuser vane could be insufficient, or the main body could be excessively thick (and thereby reduce space for the winding). Therefore, having a lesser wall thickness than root thickness may enable the bobbin to be better optimised for both of the functional requirements. 5 Optionally, the ratio is no less than 0.3. Reducing the ratio below 0.3 may reduce the manufacturability of the bobbin. For example, excessively different thickness may impede the flow of material in the bobbin during moulding, which may reduce the mouldability of the bobbin. 10 Optionally, the stator assembly has an outer diameter of less than or equal to 100mm. 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. Thermal management in such LO a size of motor may be important to enable a desired power output to be achieved, and, as CXI 15 the stator core is a heat source in use, providing the opening may aid with such thermal CO management. The stator assembly may have an outer diameter of less than or equal to 66mm, or less than or equal to 40mm. 1— Optionally, the main body comprises a plurality of indents. The indents may act as a 20 locating feature to improve the accuracy of the locating of the winding during winding. This may improve the fill factor compared to if the main body did not comprise the indents. Optionally, wherein the stator assembly comprises a wall spaced from the main body to at 25 least partially define the airflow passage within which the diffuser vane is located. As a result, the airflow may be better directed through the motor than if the wall were omitted, which may improve the aerodynamic performance of the motor. Optionally, the wall comprises a cylindrical wall formed separately to the bobbin. Thereby, 30 the likelihood of airflow leaking through the wall may be reduced compared to if the wall was made of separate segments. This may improve the aerodynamic performance of the motor. Additionally, by being formed separately, the mouldability of the bobbin may be increased compared to if the wall were integrally formed with the bobbin. Optionally, the diffuser vane is joined to the wall. For example, the diffuser vane may be 5 adhered or ultrasonically welded to the wall. This may reduce the likelihood of airflow passing through a gap between the wall and an end of the diffuser vane which may otherwise reduce the aerodynamic performance of the diffuser. Optionally, the wall is integrally formed with the bobbin. This may reduce the likelihood 10 of airflow passing through the gap between the wall and an end of the diffuser vane which may otherwise reduce the aerodynamic performance of the motor. Optionally, the stator assembly comprises, a further bobbin located downstream of the LO impeller, a further stator winding, and a further stator core; the further bobbin comprises: a CXI 15 further main body about which the further stator winding is located, and to which the CO further stator core is connected; and a further diffuser vane for interacting with the airflow generated by the impeller; the further stator core is formed separately to the stator core; and the further bobbin is formed separately to the bobbin. Forming the stator assembly from multiple separate stator cores and bobbins may facilitate winding of the windings 20 onto the bobbins in comparison to an arrangement with a single-piece annular stator assembly. For example, each bobbin may be wound and then assembled to form the complete stator assembly. Forming the stator assembly of multiple separate stator cores and bobbins may also enable a greater winding fill factor to be achieved compared to a single-piece annular stator assembly, which may lead to increased motor efficiency and / or 25 greater power density. Furthermore, during a stamping process where laminations of the stator cores are stamped from a sheet of material, less waste may be generated in stamping out laminations compared to a single-piece annular stator assembly. Additionally, as each of the bobbins comprises a respective diffuser vane, a segmented 30 diffuser stage comprising the diffuser vanes is provided. Segmenting the diffuser stage over multiple bobbins may improve the manufacturability of the diffuser stage compared to having a single piece diffuser stage. For example, segmenting the diffuser stage may simplify the tooling (such as an injection moulding mould) required to manufacture the diffuser stage. The further bobbin may comprise substantially the same form as the bobbin. 5 Optionally, the main body and the diffuser vane are integrally formed. 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 10 of failure and / or reduce a cost of the motor. 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, LO thermal conduction between the main body and the diffuser vane may be increased, which CXI 15 may increase the amount of heat removed from the stator core, relative to if, for example, co 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. CXI 20 Optionally, the bobbin is overmoulded onto the stator core. Overmoulding may ensure that the stator core and bobbin 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. 25 Optionally, the motor comprises a first diffuser stage, and a second diffuser stage downstream of the first diffuser stage; and the diffuser vane is part of the second diffuser stage. As a result, the airflow with which the diffuser vane interacts may have already been conditioned by the first diffuser stage. Therefore, the aerodynamic performance of the motor may be less sensitive to design changes to the diffuser vane than if the diffuser vane 30 were part of the first diffuser stage. This may improve the trade-offs between performance and manufacturability of the bobbin and thereby improve the manufacturability of the bobbin whilst reducing the impacts on the aerodynamic performance of the motor. According to a fifth aspect there is provided a vacuum cleaner comprising a motor according to the fourth aspect. 5 According to a sixth aspect there is provided a haircare appliance comprising a motor according to the fourth aspect. According to a seventh aspect there is provided a stator assembly comprising a bobbin, a stator core, and a stator winding located about the bobbin, the bobbin comprising: a main 10 body about which the winding is located, and to which the stator core is connected; a wall spaced from the main body to define an airflow passage between the main body and the wall; and a vane extending between the main body and the wall within the airflow passage, wherein the main body, the wall, and the vane are integrally formed. By integrally forming LO the main body, the wall and the vane, a number of separate components of the stator CXI 15 assembly may be reduced relative to an arrangement where the vane, the wall and the main co body are separately formed. Reducing component count may reduce a risk of failure and / or reduce a cost of the stator assembly. 1— Additionally, the vane may provide a thermal transfer path to remove heat generated by the 20 stator core. As the main body and the vane are integrally formed, thermal conduction between the main body and the 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 vane were separate components joined by adhesive. Moreover, integrally forming the vane, the wall, and the main body may result in a more mechanically stable stator assembly than if the 25 vane, the wall, and the main body were formed separately. Moreover, because the main body at least partly defines the airflow passage within which the vane is located, the need for an additional component to define the airflow passage may be removed. Thereby, more space may be provided within a motor comprising the stator 30 assembly. 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 vane, which may increase the aerodynamic and / or acoustic performance of the motor. Optionally, the bobbin comprises a further vane integrally formed with the main body and 5 the wall; and the further vane extends between the main body and the wall within the airflow passage. This may provide additional conditioning of an airflow flowing through the airflow passage compared to having only a single vane. Additionally, this may provide an additional thermal transfer path from the stator core, which may increase the heat transfer from the stator core. The further vane may comprise substantially the same form as 10 the vane. Optional features of the vane may apply equally to the further vane where appropriate. Optionally, the bobbin is formed of a fibre reinforced plastic. The bobbin performs both an LO electrically insulative and a structural function: providing electrical insulation between the CXI 15 winding and the stator core, and providing a sufficiently stiff vane to interact with the CO airflow. A fibre reinforced plastic may provide sufficient electrical insulation and mechanical properties to perform this dual function. 1— Optionally, wherein the bobbin is formed of a material having a coefficient of thermal 20 conductivity of greater than or equal to 0.2 W / mK. This may provide efficient heat transfer away from the stator core, via the vane and / or the main body. The bobbin may be formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.35 W / mK. 25 Optionally, the bobbin is formed of a material having a dielectric strength of greater than or equal to 15kV / mm. 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. 30 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 voltage, 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 5 compared to a lower wall thickness. 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 whilst maintaining the same motor outer diameter. Additionally, a thicker main body may 10 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 (whilst maintaining the same motor outer diameter) and robustness to manufacturing defects when compared to a thicker main body. LO CXI 15 A wall thickness of between 0.25mm and 0.8mm may provide a good balance between the co competing needs of electrical insulation, mechanical robustness and manufacturability on the one hand and space and robustness to manufacturing defects on the other hand. 1— Optionally, the vane has a root thickness of greater than or equal to 0.2mm. If the root 20 thickness is too low, the vane may have insufficient strength and stiffness. Therefore, having a root thickness of greater than or equal to 0.2mm may provide a sufficiently strong and stiff vane. Optionally, the vane has a root thickness of less than or equal to 2.0mm. A vane with a 25 thickness of 2.0mm may have sufficient stiffness and strength to effectively interact with the airflow. Therefore, increasing the thickness beyond 2.0mm may not increase the functionality of the vane but may increase the cost of the vane. Additionally, increasing the thickness may reduce the space available for the airflow to flow around the vane. 30 Having a thickness of between 0.2mm and 2.0mm may provide a good balance between the competing needs of providing sufficient mechanical properties on one hand and reducing the cost and the space required on the other hand. Optionally, ratio of a wall thickness of the main body to a root thickness of the vane is less than 1. The different functional requirements for the main body and the vane may result in different thicknesses being desirable. The root thickness may need to be greater than the 5 wall thickness because the vane is interacting with the airflow, which may require a greater thickness to achieve adequate stiffness and strength for the vane. Conversely, the thickness required to achieve adequate electrical insulation for the main body may be less than the thickness required for the vane. If the thicknesses were the same, then either the mechanical properties of the vane could be insufficient, or the main body could be 10 excessively thick (and thereby reduce space for the winding). Therefore, having a lesser wall thickness than root thickness may enable the bobbin to be better optimised for both of the functional requirements. LO Optionally, the ratio is no less than 0.3. Reducing the ratio below 0.3 may reduce the CXI 15 manufacturability of the bobbin. For example, excessively different thickness may impede co the flow of material in the bobbin during moulding, which may reduce the mouldability of the bobbin. 1— Optionally, the stator assembly has an outer diameter of less than or equal to 100mm. As a 20 result, the motor may be sufficiently compact to fit within the space constrains required for handheld appliances such as hair dryers or vacuum cleaners. Thermal management in such a size of motor may be important to enable a desired power output to be achieved, and, as the stator core is a heat source in use, integrally forming the main body and the vane may aid with such thermal management. The stator assembly may have an outer diameter of 25 less than or equal to 66mm, or less than or equal to 40mm. Optionally, the main body comprises a plurality of indents. The indents may act as a locating feature to improve the accuracy of the locating of the winding during winding. This may improve the fill factor compared to if the main body did not comprise the 30 indents. Optionally, the stator assembly comprises a further bobbin, a further stator winding located about the further bobbin, and a further stator core; the further bobbin comprises: a further main body about which the further stator winding is located, and to which the further stator core is connected; a further wall spaced from the further main body to define a further 5 airflow passage between the further main body and the further wall; and an additional vane extending between the further main body and the further wall within the further airflow passage; the further main body, the further wall, and the additional vane are integrally formed; the further stator core is formed separately to the stator core; and the further bobbin is formed separately to the bobbin. Forming the stator assembly from multiple 10 separate stator cores and bobbins may facilitate winding of the windings onto the bobbins in comparison to an arrangement with a single-piece annular stator assembly. For example, each bobbin may be wound and then assembled to form the complete stator assembly. Forming the stator assembly of multiple separate stator cores and bobbins may also enable LO a greater winding fill factor to be achieved compared to a single-piece annular stator CXI 15 assembly, which may lead to increased motor efficiency and / or greater power density, co Furthermore, during a stamping process where laminations of the stator cores are stamped from a sheet of material, less waste may be generated in stamping out laminations compared to a single-piece annular stator assembly. CXI 20 Additionally, as each of the bobbins comprises a respective vane, a segmented diffuser stage comprising the vanes is provided. Segmenting the diffuser stage over multiple bobbins may improve the manufacturability of the diffuser stage compared to having a single piece diffuser stage. For example, segmenting the diffuser stage may simplify the tooling (such as an injection moulding mould) required to manufacture the diffuser stage. 25 Optionally, wherein the bobbin is overmoulded onto the stator core. Overmoulding may ensure that the stator core and bobbin 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. Optionally, the vane extends along the main body for an axial length of at least 40% of an axial length of the stator core. This may provide a thermal transfer path along at least 40% of the axial length of the stator core, which may aid with removal of heat generated by the stator core in use. The vane may extend along the main body for an axial length of at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%, at least 100 %, at least 110%, or at least 120% of the axial length of the stator core. The axial lengths of the vane 5 and the stator core may comprise lengths in an axial direction of a motor comprising the stator assembly. Optionally, the main body comprises an opening which exposes the stator core such that the stator core at least partially defines the airflow passage within which the vane is 10 located. Thereby, the stator core may be exposed to an airflow generated by an impeller of the motor. The airflow may thereby directly cool the stator core, which may increase the cooling of the stator core relative to if the opening were not present. LO Optionally, the vane contacts the stator core through the opening. This may increase the CXI 15 amount of heat transferred from the stator core to the vane and thereby increase the cooling co of the stator core, when compared to the stator core being in only indirect contact with the vane via the main body. 1— Optionally, wherein the vane extends across the opening from a first portion of the main 20 body to a second portion of the main body; and the vane is integrally formed with both the first portion and the second portion. As the vane is integrally formed with both portions, the vane is mechanically supported on either side of the opening. This may increase the robustness and stiffness of the vane compared to if the vane projected from only one of the portions. 25 Optionally, the bobbin is moulded. For example, the bobbin may be injection moulded. As the vane is integrally formed with both portions, the mouldability of the bobbin may be increased compared to if the vane were integrally formed with only one of the portions. If the vane were integrally formed with only one of the portions, an air pocket may form 30 within the bobbin mould during moulding which may inhibit the flow of molten material into the air pocket and thereby filling the bobbin mould. Optionally, a ratio of a radial extent of the vane to the radial extent of the stator core is greater than or equal to 0.2. The radial extents of the vane and the stator core may comprise extents in a radial direction of the motor comprising the stator assembly. 5 Optionally, the ratio of the radial extent of the vane to the radial extent of the stator core is less than or equal to 1. Optionally, a radial extent of the vane is greater than or equal to 1mm. The extent of the vane may affect the extent to which the vane can condition the airflow. Providing a heigh 10 of greater than or equal to 1mm may enable the vane to meet the airflow conditioning requirements of applications such as a hair dryer or a vacuum cleaner. The radial extent of the vane may comprise a extent in the radial direction of the motor LO comprising the stator assembly. CM is CO Optionally, the radial extent of the vane is less than or equal to 10mm. Optionally, a radial extent of the stator core is greater than or equal to 4mm. The extent of the stator core may affect the power of the motor. Having a radial extent of greater than or 20 equal to 4mm may therefore increase the power of the motor compared to a lesser extent of stator core. The radial extent of the stator core may comprise a extent in the radial direction of the motor comprising the stator assembly. 25 Optionally, the radial extent of the stator core is less than or equal to 8mm. Optionally, the bobbin comprises a further vane integrally formed with the main body and the wall; the further vane extends between the main body and the wall within the airflow 30 passage; and a clearance, measured in a circumferential direction around the main body, between the vane and the further vane is greater than or equal to 3mm. Due to tooling constraints (for example, minimum tool body sizes in an injection moulding tool) this may improve the manufacturability of the bobbin compared to having a clearance of less than 3mm. The circumferential direction around the main body may be parallel to a circumferential direction of the motor comprising the stator assembly. 5 Optionally, the clearance is less than or equal to 8mm. A greater clearance may reduce the total number of vanes which can be accommodated for a given size of motor. Reducing the total number of vanes may reduce the extent to which the airflow can be conditioning compared to a greater number of vanes. Therefore, having a clearance of less than or equal to 8mm, may improve the conditioning of the airflow compared to having a clearance of 10 greater than 8mm, and may provide sufficient conditioning of the airflow for applications such as a hair dryer or vacuum cleaner. Having a clearance of between 3mm and 8mm may provide a good balance between LO manufacturability and conditioning of the airflow. CM is CO According to an eighth aspect, there is provided a rotor assembly comprising an impeller for generating an airflow through the airflow passage; and a stator assembly according to the seventh aspect, wherein the stator assembly is for causing rotation of the impeller. The rotor assembly may comprise a shaft. The axial direction of the motor may be parallel to a 20 rotational axis of the rotor assembly, for example, in a direction parallel to a rotational axis of the shaft of the rotor assembly. The radial direction of the motor may be perpendicular to the rotational axis of the rotor assembly, for example in a direction perpendicular to the rotational axis of the shaft of the rotor assembly. The circumferential direction of the motor may be parallel with the rotational direction of the rotor assembly, for example around the 25 rotational axis of the shaft of the rotor assembly. Optionally, the bobbin is located downstream of the impeller; and the vane is a diffuser vane for interacting the with the airflow generated by the impeller. 30 Optionally, the motor comprises a first diffuser stage, and a second diffuser stage downstream of the first diffuser stage; and the vane is part of the second diffuser stage. As a result, the airflow with which the vane interacts may have already been conditioned by the first diffuser stage. Therefore, the aerodynamic performance of the motor may be less sensitive to design changes to the vane than if the vane were part of the first diffuser stage. This may improve the trade-offs between performance and manufacturability of the bobbin and thereby improve the manufacturability of the bobbin whilst reducing the impacts on 5 the aerodynamic performance of the motor. According to a ninth aspect there is provided a vacuum cleaner comprising a stator assembly according to the seventh aspect or a motor according to the eighth aspect. 10 According to a tenth aspect there is provided a haircare appliance comprising a stator assembly according to the seventh aspect or a motor according to the eighth aspect. According to an eleventh aspect, there is provided a motor comprising: a rotor assembly LO comprising an impeller for generating an airflow; and a stator assembly for causing CXI 15 rotation of the impeller; wherein the stator assembly comprises a circumferentially CO segmented diffuser stage for diffusing the airflow generated by the impeller. Segmenting the diffuser stage may improve the manufacturability of the diffuser stage compared to having a single piece diffuser stage. For example, segmenting the diffuser stage may simplify the tooling (such as an injection moulding mould) required to manufacture the 20 diffuser stage. The rotor assembly may comprise a shaft. An axial direction of the motor may be parallel to a rotational axis of the rotor assembly, for example, in a direction parallel to a rotational axis of the shaft of the rotor assembly. A radial direction of the motor may be 25 perpendicular to the rotational axis of the rotor assembly, for example in a direction perpendicular to the rotational axis of the shaft of the rotor assembly. A circumferential direction of the motor may be parallel with the rotational direction of the rotor assembly, for example around the rotational axis of the shaft of the rotor assembly. Optionally, the circumferentially segmented diffuser stage is segmented into no less than three segments. This may improve the manufacturability of the diffuser stage compared to segmenting the diffuser into a lesser number of segments, for example two segments. 5 Optionally, a clearance, measured in a circumferential direction around the circumferentially segmented diffuser stage, between adjacent diffuser vanes of the circumferentially segmented diffuser stage is greater than or equal to 3mm. Due to tooling constraints (for example, minimum tool body sizes in an injection moulding tool) this may improve the manufacturability of the diffuser stage compared to having a clearance of less 10 than 3mm. The circumferential direction around the circumferentially segmented diffuser stage may be parallel to the circumferential direction of the motor. Optionally, the clearance is less than or equal to 8mm. A greater clearance may reduce the LO total number of diffuser vanes which can be accommodated for a given size of motor. CXI 15 Reducing the total number of diffuser vanes may reduce the extent to which the airflow co can be conditioning compared to a greater number of diffuser vanes. Therefore, having a clearance of less than or equal to 8mm, may improve the conditioning of the airflow compared to having a clearance of greater than 8mm, and may provide sufficient conditioning of the airflow for applications such as a hair dryer or vacuum cleaner. 20 Having a clearance of between 3mm and 8mm may provide a good balance between manufacturability and conditioning of the airflow. Optionally, each diffuser vane of the circumferentially segmented diffuser stage has a root 25 thickness of greater than or equal to 0.2mm. If the root thickness is too low, the diffuser vane may have insufficient strength and stiffness. Therefore, having a root thickness of greater than or equal to 0.2mm may provide a sufficiently strong and stiff diffuser vane. Optionally, each diffuser vane of the circumferentially segmented diffuser stage has a root 30 thickness of less than or equal to 2mm. A diffuser vane with a thickness of 2mm may have sufficient stiffness and strength to effectively interact with the airflow. Therefore, increasing the thickness beyond 2mm may not increase the functionality of the diffuser vane but may increase the cost of the diffuser vane. Additionally, increasing the thickness may reduce the space available for the airflow to flow around the diffuser vane. Having a thickness of between 0.2mm and 2mm may provide a good balance between the 5 competing needs of providing sufficient mechanical properties on one hand and reducing the cost and the space required on the other hand. Optionally, each diffuser vane of the circumferentially segmented diffuser stage has a radial extent of greater than or equal to 1mm. The extent of each diffuser vane may affect 10 the extent to which the circumferentially segmented diffuser stage can condition the airflow. Providing a heigh of greater than or equal to 1mm may enable the circumferentially segmented diffuser stage to meet the airflow conditioning requirements of applications such as a hair dryer or a vacuum cleaner. LO CXI 15 The radial extent of each diffuser vane may comprise an extent in the radial direction of the co motor. Optionally, the stator assembly has an outer diameter of less than or equal to 100 mm. As a result, the motor may be sufficiently compact to fit within the space constrains required for 20 handheld appliances such as hair dryers or vacuum cleaners. Manufacturability of the diffuser stage in such a size of motor may be especially challenging. Therefore, circumferentially segmenting the diffuser stage may be especially valuable in such a size of motor. The stator assembly may have an outer diameter of less than or equal to 66mm, or less than or equal to 40mm. 25 Optionally, the motor comprises a first diffuser stage, and the circumferentially segmented diffuser stage is downstream of the first diffuser stage. As a result, the airflow with which the circumferentially segmented diffuser stage interacts may have already been conditioned 30 by the first diffuser stage. Therefore, the aerodynamic performance of the motor may be less sensitive to design changes to the circumferentially segmented diffuser stage than if the circumferentially segmented diffuser stage were the first diffuser stage. This may improve the trade-offs between performance and manufacturability of the circumferentially segmented diffuser stage and thereby improve the manufacturability of the circumferentially segmented diffuser stage whilst reducing the impacts on the aerodynamic performance of the motor. 5 Optionally, the circumferentially segmented diffuser stage is segmented into segments; each segment comprises a respective bobbin, a respective stator core and a respective stator winding; each respective bobbin comprises: a main body about which the respective stator winding is located, and to which the respective stator core is connected; and a diffuser vane 10 which is part of the circumferentially segmented diffuser stage, and is connected to the main body; and the main body at least partially defines an airflow passage within which the diffuser vane is located. By connecting the diffuser vane to the main body of the bobbin, the diffuser vane may provide a thermal transfer path to remove heat generated by LO the stator core. Moreover, because the main body at least partly defines the airflow passage CXI 15 within which the diffuser vane is located, the need for an additional component to define co 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 1“ 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 20 increase the aerodynamic and / or acoustic performance of the motor. Optionally, the main body and the diffuser vane are integrally formed. 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 25 vane and the bobbin are separately formed. Reducing component count may reduce a risk of failure and / or reduce a cost of the motor. 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 30 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. Optionally, the diffuser vane extends along the main body for an axial length of at least 5 40% of an axial length of the stator core. This may provide a thermal transfer path along at least 40% of the axial length of the stator core, which may aid with removal of heat generated by the stator core in use. The diffuser vane may extend along the main body for an axial length of at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%, at least 100 %, at least 110%, or at least 120% of the axial length of the stator core. The axial 10 lengths of the diffuser vane and the stator core may comprise lengths in the axial direction of the motor. Optionally, the main body comprises an opening which exposes the stator core to the LO airflow generated by the impeller such that the stator core at least partially defines the CXI 15 airflow passage within which the diffuser vane is located. The airflow may thereby directly co cool the stator core, which may increase the cooling of the stator core relative to if the opening were not present. 1— Optionally, the diffuser vane contacts the stator core through the opening. This may 20 increase the amount of heat transferred from the stator core to the diffuser vane and thereby increase the cooling of the stator core, when compared to the stator core being in only indirect contact with the diffuser vane via the main body. Optionally, the diffuser vane extends across the opening from a first portion of the main 25 body to a second portion of the main body; and the diffuser vane is integrally formed with both the first portion and the second portion. As the diffuser vane is integrally formed with both portions, the diffuser vane is mechanically supported on either side of the opening. This may increase the robustness and stiffness of the diffuser vane compared to if the diffuser vane projected from only one of the portions. Optionally, the bobbin is moulded. For example, the bobbin may be injection moulded. As the diffuser vane is integrally formed with both portions, the mouldability of the bobbin may be increased compared to if the diffuser vane were integrally formed with only one of the portions. If the diffuser vane were integrally formed with only one of the portions, an air pocket may form within the bobbin mould during moulding which may inhibit the flow of molten material into the air pocket and thereby filling the bobbin mould. 5 Optionally, a ratio of a radial extent of the diffuser vane to the radial extent of the stator core is greater than or equal to 0.2. The radial extents of the diffuser vane and the stator core may comprise extents in the radial direction of the motor. 10 Optionally, the ratio of the radial extent of the diffuser vane to the radial extent of the stator core is less than or equal to 1. Optionally, the radial extent of the diffuser vane is less than or equal to 10mm. LO CXI 15 Optionally, a radial extent of the stator core is greater than or equal to 4mm. The extent of co the stator core may affect the power of the motor. Having a radial extent of greater than or equal to 4mm may therefore increase the power of the motor compared to a lesser extent of stator core. CXI 20 The radial extent of the stator core may comprise an extent in the radial direction of the motor. Optionally, the bobbin comprises a further diffuser vane connected to the main body. This may provide additional conditioning of the airflow compared to having only a single 25 diffuser vane. Additionally, this may provide an additional thermal transfer path from the stator core, which may increase the heat transfer from the stator core. The further diffuser vane may comprise substantially the same form as the diffuser vane. Optional features of the diffuser vane may apply equally to the further diffuser vane where appropriate. 30 Optionally, the bobbin is formed of a fibre reinforced plastic. The bobbin performs both an electrically insulative and a structural function: providing electrical insulation between the winding and the stator core, and providing a sufficiently stiff diffuser vane to interact with the airflow. A fibre reinforced plastic may provide sufficient electrical insulation and mechanical properties to perform this dual function. Optionally, the bobbin is formed of a material having a coefficient of thermal conductivity 5 of greater than or equal to 0.2 W / mK. This may provide efficient heat transfer away from the stator core, via the diffuser vane and / or the main body. The bobbin may be formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.35 W / mK. 10 Optionally, the bobbin is formed of a material having a dielectric strength of greater than or equal to 15kV / mm. 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. LO CXI 15 Optionally, the main body has a wall thickness of greater than or equal to 0.15mm. CO 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 voltage, thereby reducing the power of the motor. Additionally, the manufacturability and the robustness of the main body may 20 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. Optionally, the wall thickness is less than or equal to 0.8mm. Increasing the thickness may 25 reduce the space within the motor to house electrical components such as the winding whilst maintaining the same motor outer diameter. 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 (whilst maintaining the same motor outer 30 diameter) and robustness to manufacturing defects when compared to a thicker main body. 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. 5 Optionally, a ratio of a wall thickness of the main body to a root thickness of the diffuser vane is less than 1. The different functional requirements for the main body and the diffuser vane may result in different thicknesses being desirable. The root thickness may need to be greater than the wall thickness because the diffuser vane is interacting with the airflow, which may require a greater thickness to achieve adequate stiffness and strength 10 for the diffuser vane. Conversely, the thickness required to achieve adequate electrical insulation for the main body may be less than the thickness required for the diffuser vane. If the thicknesses were the same, then either the mechanical properties of the diffuser vane could be insufficient, or the main body could be excessively thick (and thereby reduce LO space for the winding). Therefore, having a lesser wall thickness than root thickness may CXI 15 enable the bobbin to be better optimised for both of the functional requirements. co Optionally, the ratio is no less than 0.3. Reducing the ratio below 0.3 may reduce the manufacturability of the bobbin. For example, excessively different thickness may impede the flow of material in the bobbin during moulding, which may reduce the mouldability of 20 the bobbin. Optionally, the main body comprises a plurality of indents. The indents may act as a locating feature to improve the accuracy of the locating of the winding during winding. This may improve the fill factor compared to if the main body did not comprise the 25 indents. Optionally, the stator assembly comprises a wall spaced from the main body to at least partially define the airflow passage within which the diffuser vane is located. As a result, the airflow may be better directed through the motor than if the wall were omitted, which 30 may improve the aerodynamic performance of the motor. Optionally, the wall comprises a cylindrical wall formed separately to the bobbin. Thereby, the likelihood of airflow leaking through the wall may be reduced compared to if the wall was made of separate segments. This may improve the aerodynamic performance of the motor. Additionally, by being formed separately, the mouldability of the bobbin may be 5 increased compared to if the wall were integrally formed with the bobbin. Optionally, the diffuser vane is joined to the wall. For example, the diffuser vane may be adhered or ultrasonically welded to the wall. This may reduce the likelihood of airflow passing through a gap between the wall and an end of the diffuser vane which may 10 otherwise reduce the aerodynamic performance of the diffuser. Optionally, the wall is integrally formed with the bobbin. This may reduce the likelihood of airflow passing through the gap between the wall and an end of the diffuser vane which LO may otherwise reduce the aerodynamic performance of the motor. CM is CO Optionally, the bobbin is overmoulded onto the stator core. Overmoulding may ensure that the stator core and bobbin are in intimate contact which may improve the heat transfer between them and away from the stator core compared to other manufacturing techniques 20 such as moulding the bobbin and then inserting the stator core into the bobbin. According to a twelfth aspect there is provided a vacuum cleaner comprising a motor according to the eleventh aspect. 25 According to a thirteenth aspect there is provided a haircare appliance comprising a motor according to the eleventh aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Figure lisa perspective view of an example motor; Figure 2 is a cross-sectional view of the example motor; 5 Figure 3 is a perspective view of a rotor assembly of the example motor; Figure 4 is a perspective view of a first diffuser stage of the example motor; Figure 5 is a perspective view of a stator assembly of the example motor; Figure 6 is a top view of the stator assembly; Figure 7 is a perspective view of a stator sub-assembly of the stator assembly; 10 Figure 8 is a top view of the stator sub-assembly; Figure 9 is a perspective view of a stator core of the stator sub-assembly; Figure 10 is a perspective view of the stator sub-assembly with a winding of the stator subassembly removed; LO Figure 11 is a cross-sectional view of the stator sub-assembly with the winding removed; CXI 15 Figure 12 is a cross-sectional view of the stator sub-assembly with the winding, stator CO 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; Figure 14 is a side view of the stator sub-assembly with the winding removed; 20 Figure 15 is a cross-sectional view of the stator sub-assembly; Figure 16 is a perspective view of the stator core when assembled in the stator assembly; 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; Figure 18 is a cross-sectional view of the stator sub-assembly with the winding removed 25 and the doors in the open position; 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. DETAILED DESCRIPTION 30 Figures 1 and 2 show a motor 10 comprising a rotor assembly 12, a diffuser stage 14 and a stator assembly 16. 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 5 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. 10 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. The diffuser stage 14 is shown in isolation in Figure 4. The diffuser stage 14 comprises an LO outer wall 38, a central hub 40, and a plurality of diffuser vanes 42. The outer wall 38 has CXI 15 an annular shape and comprises a lip 44 for connecting the diffuser stage 14 to the stator co 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. CXI 20 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. The stator assembly 16 is shown in isolation in Figures 5 and 6. The stator assembly 16 has 25 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. 30 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. The stator core 56, illustrated in Figure 9, comprises a stack of laminations 57, here 5 schematically represented and not to scale, with not all individual laminations shown for sake of clarity. 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, 10 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. LO CXI 15 The first protrusion 66 and the second protrusion 68 each extend only partially along a CO 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. CXI 20 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. 25 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 61, 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. 30 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. 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. As the first protrusion 66 and the second protrusion 68 are offset along the stack of 5 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. 10 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. Figure 10 shows the bobbin 58 and stator core 56 with the winding 60 removed. The LO bobbin 58 comprises a main body 80, a first diffuser vane 82, a second diffuser vane 84, a CXI 15 wall 86, a first hinge 88, a second hinge 90, a first door 92, and a second door 94. The CO 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 20 bobbin 58 may be referred to a stator core bobbin. 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 25 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. 30 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. Referring now to Figure 12, The inner portion 98 overlies the tooth tips 76 and extends 5 circumferentially and axially from a radially inner end of the middle portion 96. 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. 10 Each indent 105 has a generally semi-circular cross-sectional shape and is dimensioned to receive a portion of the winding 60. The outer portion 100 comprises an opening 106 and a lip 108 (shown in Figure 14). The LO outer portion 100 overlies the yoke 61 and extends circumferentially and axially from a CXI 15 radially outer end of the middle portion 96. The outer portion 100 extends further CO circumferentially than the inner portion 98 and is curved slightly in a direction towards the middle portion 96. The opening 106 (shown in Figure 14) 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 20 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. When viewed in the plane which extends perpendicularly to the rotational axis 30 of the 25 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 30 second channel 118. 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. Referring now to Figure 13, the first diffuser vane 82 extends radially from the upstream 5 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 10 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. LO CXI 15 The first diffuser vane 82 extends along the outer portion 100 for an axial length 124 of CO 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 124 of greater than or equal to 40 % of the axial length 124 of the stator core 56 is also envisaged. CXI 20 The first diffuser vane 82 has a radial extent 127 of 3.1mm. A radial extent 127 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. 25 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 30 vanes 82,84 constitute part of a further diffuser stage which is located downstream of the diffuser stage 14. 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 87, a first connecting feature 126, and a second connecting feature 128. The main body 87 subtends a central angle A of 60° such that when the stator assembly 16 is assembled, the 5 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 123,126 each extend from a respective one of the circumferential ends 128,130 and overlap with corresponding connecting features 123,126 on adjacent walls 86 when assembled into the stator assembly 16. 10 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 LO passage 132. CM is CO 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 98, middle 20 96, 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 25 and 1 are also envisaged. The first hinge 88 has the minimum thickness 134 of the bobbin 58. The inner portion 98 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. 30 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. 5 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 10 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 LO 142 is measured in the plane which extends perpendicular to the rotational axis 30 of the CXI 15 rotor assembly 12. CO 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 20 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. The bobbin 58 has a radial extent 121, measured with the first 92 and second 94 doors in 25 the closed position, of 3.5mm. Radial extents 121 of between 2mm and D 20mm are also envisaged. 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 30 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 98, middle 96, and outer 100 of the main body 80 of the bobbin 58 and one of the doors 92,94. 5 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 10 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 LO stator sub-assemblies 50 collectively define a channel 101. CM is CO 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. CXI 20 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 25 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. 30 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 5 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. 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 10 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 LO the winding 60 located within the channels 116,118. CM is CO 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 20 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. 25 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 30 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. 21 08 25 A schematic illustration of a vacuum cleaner 1000 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. 5 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. 10 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, 15 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. 20 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

1. A motor comprising:a rotor assembly comprising an impeller for generating an airflow; and5 a stator assembly for causing rotation of the impeller,wherein:the stator assembly comprises, a bobbin located downstream of the impeller, a stator winding, and a stator core;the bobbin comprises:10 a main body about which the stator winding is located, and to whichthe stator core is connected; anda diffuser vane for interacting with the airflow generated by the impeller;LO the main body at least partially defines an airflow passage within which theCXI 15 diffuser vane is located; andco the main body and the diffuser vane are integrally formed;wherein the stator assembly comprises a wall spaced from the main body to at least partially define the airflow passage within which the diffuser vane is located, wherein the wall is integrally formed with the bobbin.

202. A motor as claimed in claim 1, wherein the diffuser vane extends along the main body for an axial length of at least 40% of an axial length of the stator core.

3. A motor as claimed in any preceding claim, wherein the main body comprises an 25 opening which exposes the stator core to the airflow generated by the impeller such that the stator core at least partially defines the airflow passage within which the diffuser vane is located.

4. A motor as claimed in claim 3, wherein the diffuser vane contacts the stator core 30 through the opening.

5. A motor as claimed in claim in claim 3 or 4, wherein the diffuser vane extends across the opening from a first portion of the main body to a second portion of the main body; and the diffuser vane is integrally formed with both the first portion and the second portion.

56. A motor as claimed in any preceding claim, wherein the radial extent of the diffuser vane is greater than or equal to 1mm.

7. A motor as claimed in any preceding claim, wherein a radial extent of the stator 10 core is greater than or equal to 4mm.

8. A motor as claimed in any preceding claim, wherein the bobbin comprises a further diffuser vane integrally formed with the main body.LOCXI 15 9. A motor as claimed in claim 8, wherein a clearance, measured in a circumferentialCO direction around the main body, between the diffuser vane and the further diffuser vane is greater than or equal to 3mm.1—10. A motor as claimed in any preceding claim, wherein the bobbin is formed of a fibre 20 reinforced plastic.

11. A motor as claimed in any preceding claim, wherein the bobbin is formed of a material having a coefficient of thermal conductivity of greater than or equal to 0.2 W / mK.25 12. A motor as claimed in any preceding claim, wherein the bobbin is formed of amaterial having a dielectric strength of greater than or equal to 15kV / mm.

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

14. A motor as claimed any preceding claim, wherein the diffuser vane has a rootthickness of greater than or equal to 0.2mm.

15. A motor as claimed any preceding claim, wherein a ratio of a wall thickness of the main body to a root thickness of the diffuser vane is less than 1.5 16. A motor as claimed in any preceding claim, wherein the stator assembly has anouter diameter of less than or equal to 100 mm.

17. A motor as claimed in any preceding claim, wherein: the stator assembly comprises, a further bobbin located downstream of the impeller, 10 a further stator winding, and a further stator core;the further bobbin comprises:a further main body about which the further stator winding is located, and to which the further stator core is connected; andLO a further diffuser vane for interacting with the airflow generated by theCXI 15 impeller;CO the further main body and the further diffuser vane are integrally formed;the further stator core is formed separately to the stator core; and the further bobbin is formed separately to the bobbin.CXI20 18. A motor as claimed in any preceding claim, wherein the bobbin is overmouldedonto the stator core.

19. A motor as claimed in any preceding claim, wherein: the motor comprises a first diffuser stage, and a second diffuser stage downstream 25 of the first diffuser stage; andthe diffuser vane is part of the second diffuser stage.

20. A vacuum cleaner comprising a motor according to any preceding claim.30 21. A haircare appliance comprising a motor according to any one of claims 1 to 19.

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