Clip-on annular component

Abstract

A clip-on annular component comprising: an annular body 30B; one or more clips 54 extending from the body 30B, where the clips engage with formations (58, Fig. 5) on a different component (12, Fig. 5)

Description

TECHNICAL FIELD The present disclosure relates to a clip-on annular component. Aspects of the invention relate to an assembly, to an electric machine, to a cooling fluid manifold, to a vehicle, and to a method. BACKGROUND It is known to connect two components together, e.g. two vehicle components. Such components may be subjected to high temperature and / or high pressures, and thus are required to have a robust connection therebetween. For example, there may be provided an electrical machine with a stator core having a plurality of cooling passageways which extend in a longitudinal direction through the stator core. In such an electrical machine, there may be a cooling fluid manifold which defines a chamber in fluid communication with the cooling passageways. In this way, a flow of cooling fluid passes through the chamber and through the cooling passageways to remove heat from the stator core. The cooling fluid manifold may be subject to high temperatures and / or pressures, and so a robust connection between the manifold and the stator core is required to prevent leaks and loss of cooling fluid. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a clip-on annular component, an assembly, a vehicle and a method as claimed in the appended claims. According to an aspect of the present disclosure, there is provided a clip-on annular component comprising: an annular body; one or more clips extending from the annular body, the or each clip configured to engage with a corresponding one or more formations on a different component so as to secure the annular component thereto; and one or more grooves extending in an outer radial surface of the annular body, a region of the or each groove being circumferentially aligned on the annular body with a respective clip of the one or more clips. Optionally, the or each groove defines a circumferential width that is greater than a width of the respective clip. The provision and configuration of the groove has been found to improve the reliability of the clip-on annular component and the strength of connection between the annular component and a different component. It will be understood that the clips require some degree of flexibility (e.g. to facilitate engagement with formations in a different component). The clips must be capable of flexing without breaking, and be capable of returning to substantially the same shape following any flexing. The clips must be suitably resistant to significant deformation to maintain an effective connection between the annular component and a different component. This is particularly important in arrangements in which the annular component and thus the clips are subjected to high loads and temperatures that may cause deformation. The groove provides a space for the clip to flex without snapping from the annular body. This reduces the likelihood of significant, permanent deformation or breakage of the clips, thereby reducing the risk of the clips becoming ineffective and the annular component becoming detached. In this way, the clips are more reliable and less prone to fatigue and / or failure. It should be understood that the width of a clip refers to the distance between first and second circumferential ends of the clip. In some embodiments, the or each clip follows the curvature of the annular body. In this case, the width of the clip is the circumferential width of the clip. It should be understood that the term “circumferential width” refers to the angular extent of the groove or clip in a circumferential direction with respect to a longitudinal axis of the annular body, which may otherwise be described as the distance defined between a first and a second circumferential end of the groove and / or clip. It will be appreciated that the width of the clip or groove may change, e.g. the clip may have a truncated shape with a varying circumferential width. In this case, the term “circumferential width” should be understood to refer to the greatest circumferential distance between two radially aligned points on the clip. Optionally, the circumferential width of each groove is at least double, optionally at least three-times, optionally at least four-times greater than the width of the respective clip. Configuring the groove in such a way has been found to continue to ensure sufficient flexibility of the clip while avoiding significant “cut-out” in the annular body (e.g. in the radial direction) to form the groove. Put another way, the width of the groove provides effective space for the clip to flex without significantly increasing the depth of the groove in the radial direction. Reducing the extent of “cut-out” or the depth of the groove avoids significant reduction in the strength and rigidity of the annular body, facilitating a robust component that can withstand high pressures and temperatures whilst improving the effectiveness of the clips. Optionally, the groove and the respective clip are each configured to subtend an angle with respect to the longitudinal axis, and wherein the angle subtended by the groove is greater than an angle subtended by the respective clip. It should be understood that the term “subtend” refers to the angular extent of the groove or clip in a circumferential direction with respect to the longitudinal axis of the annular body, which may otherwise be described as the angle defined between a first and a second circumferential end of the groove and / or clip. Optionally, the groove defines a maximum groove depth in the radial direction, and wherein the maximum groove depth is less than or equal to one half, optionally less than or equal to one third, optionally less than or equal to one quarter of the radial thickness of the annular body. Advantageously, the groove does not occupy a significant extent of the radial thickness of the annular body. In this way, the presence of the groove does not significantly reduce the strength and rigidity of the annular body. Optionally, the one or more grooves comprises a radially inner surface that is substantially linear. Advantageously, the groove is simple to manufacture. Optionally, a radially inner edge of the one or more grooves defines a chord of a circle defined between two points on the outer radial surface of the annular body. Advantageously, the width of the groove can be significantly increased without significantly increasing the “cutout” in the annular body to form the groove (e.g. the radial depth of the groove). In this way, the groove can provide significant space forthe clip to flex, without being significantly detrimental to the robustness or strength of the annular body. Optionally, the two points are located at opposing sides of the respective clip, e.g. such that the respective clip locates between the two points. Advantageously, the groove extends to or beyond opposite sides of the clip, thereby providing space to facilitate flexing at either end of the clip. Optionally, the one or more grooves comprises a radially inner surface that is substantially arc-shaped. Advantageously, the one or more grooves are simple to manufacture in the annular body. The arc-shape may be in the radial direction and have a radially outwardly facing concave surface. Advantageously, the groove can be simply formed using normal manufacturing techniques (e.g. by simply cutting out a region of the annular body). Optionally, the radially inner surface defines an arc of a circle having a diameter of at least 200 mm. Advantageously, such dimensions provide for a groove that provides effective support, particularly when the clip-on annular component is a vehicle component. Optionally, the or each groove is arranged such that a circumferential midpoint of the or each groove is circumferentially aligned with a midpoint of the respective clip. Advantageously, the groove extends equally about the clip so as to provide effective flexing support thereto. Optionally, the one or more clips extend such that an outer surface of the or each clip extends from a radially outer edge of a first axial surface of the annular body. In this way, there is no clearance between the clip and the radially outer edge of the first axial surface of the annular body. In such an arrangement, the extent of plastic deformation of the clip is reduced compared with a clip that extends from a radially inner position on the annular body. In this way, the clips are less susceptible to permanent deformation and can maintain a secure fit with a stator core when secured thereto. It will be understood that the outer surface of a clip is the radially outer surface thereof, e.g. the surface that is distal to the longitudinal axis of the annular body. The clip may extend axially from the first axial surface of the annular body (e.g, along a longitudinal axis defined by the annular body). Optionally, the one or more clips define an axial height between a root end and a tip end, and a radial thickness between an outer radial surface and an inner radial surface, and wherein the radial thickness is at least one eighth of the axial height. Such an arrangement reduces the extent of plastic deformation of the clip compared with a clip that may have a lower radial thickness relative to the axial length thereof. Optionally, the one or more clips each define a root end that is connected to a first axial surface of the annular body, and a tip end that is distal to the annular body. Optionally, the tip end of the one or more clips is configured to engage with a corresponding one or more formations on a different component. Optionally, the annular body comprises a first and a second recess positioned adjacent opposing ends of a respective clip, such that the clip is positioned between the first and second recesses. The recesses facilitate additional flexing of the clip. Optionally, the annular body is formed of metallic material, optionally steel or aluminium alloy material. This provides for a robust body capable of withstanding high pressures and temperatures. Optionally, the one or more clips are formed of metallic material, optionally steel or aluminium alloy material. This provides for a robust clip capable of withstanding high pressures and temperatures. Optionally, a plurality ofclips are provided, circumferentially spaced apart about the annular body; optionally, wherein at least three clips are provided. Having a plurality of clips may provide a more robust connection between the annular component and different component. Optionally, the plurality of clips are evenly distributed circumferentially about the annular body. Such an even distribution ofclips provides an effective distribution of the load when the annular component is secured to a different component. Optionally, at least four, five, six, seven, eight, nine, ten, eleven or twelve clips are provided. Optionally, between three and thirty-six clips are provided. Optionally, between three and ten clips are provided. Optionally, between four and six clips are provided. Optionally, the clip-on annular component is a vehicle electric drive unit component. Optionally, the chp-on annular component is a cooling fluid manifold. Optionally, the clip-on annular component is a cover for a stator core. According to an aspect of the invention, there is provided an assembly for an electric drive unit of a vehicle, the assembly comprising: the clip-on annular component as described herein; and a vehicle electric drive unit component comprising at least one formation for engaging with a respective one or more clips of the clip-on annular component such that the clip-on annular component is securable to the vehicle electric drive unit component. Such an assembly benefits from the advantages of the clip-on annular component outlined above. Moreover, the clip / formation arrangement provides a simple and robust means of securing two vehicle electric drive unit components together. Optionally, the vehicle electric drive unit component is a stator core for an electrical machine of a vehicle traction motor, the stator core comprising a first end, and wherein the clip-on annular component is a cover which at least partly covers the first end of the stator core. Advantageously, the cover can be secured to the stator core via a simple arrangement without the need for additional fasteners. Further, it will be understood that because a stator core generally remains static within a housing of an electric machine (in contrast to the rotating rotor), use of the clip-on annular component with improved stress characteristics may provide a suitably robust connection between the cover and the stator core. Further, because the clips (e.g., projecting part(s)) are on the cover and the formations (e.g., recessed portion(s)) are on the stator core, the stator core can be produced via normal manufacturing techniques (e.g., as a stator lamination stack). Optionally, the stator core comprises a plurality of cooling passageways which extend in a longitudinal direction through the stator core away from the first end, and wherein the cover is a cooling manifold which defines at least one cooling channel in fluid communication with the cooling passageways. Such an arrangement allows the stator core to be cooled by passing a flow of cooling fluid through the cooling manifold and cooling passageways. Implementing such a clip-on annular component in the assembly ensures that the cooling manifold is robustly secured to the stator core to maintain effective cooling. According to an aspect of the invention, there is provided an electric machine for driving one or more wheels of a vehicle, the electric machine comprising the aforementioned assembly. Such an electric machine benefits from the advantages of the assembly outlined above. According to an aspect of the invention, there is provided a vehicle comprising the assembly as described herein. Such a vehicle benefits from the advantages of the assembly outlined above. According to a further aspect of the invention, there is provided a cooling fluid manifold fora stator core of an electric machine of a vehicle traction motor, the manifold comprising: an annular body; one or more clips extending from the annular body, the or each clip configured to engage with a corresponding one or more formations on the stator core so as to secure the manifold thereto; and one or more grooves extending in an outer radial surface of the annular body, a region of the or each groove being circumferentially aligned on the annular body with a respective clip. Optionally, the or each groove defines a circumferential width that is greater than a width of the respective clip. Such a manifold benefits from the advantages of the clip-on annular component outlined above. According to a further aspect of the invention, there is provided a method of coupling an annular body to a different component, the method comprising: a) providing a component comprising an axial end surface, the component comprising one or more formations; b) positioning a clip-on annular body as described herein against the axial end surface of the component; and c) securing the clip-on annular body to the component by engaging the one or more clips with the corresponding one or more formations on the component. Such a method benefits from the advantages of the clip-on annular component outlined above. According to a further aspect of the invention, there is provided a method of coupling a cooling fluid manifold to a stator core (e.g., of an electric machine for a vehicle traction motor), the method comprising: a) providing a stator core comprising an axial end surface, the stator core comprising one or more recesses; b) positioning a cooling fluid manifold as described herein against the axial end surface of the stator core; and c) securing the cover to the stator core by engaging the one or more clips with the corresponding one or more recesses on the stator core. Such a method benefits from the advantages of the clip-on annular component outlined above. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a vehicle according to an embodiment; Figure 2 shows a longitudinal cross-sectional view of an electric machine comprising an assembly according to an embodiment; Figure 3 shows a stator core and a clip-on annular component of the assembly of Figure 2 in a disconnected state; Figure 4 shows the stator core and clip-on annular component of the assembly of Figure 2 in a secured state; Figure 5 shows a perspective view of a portion of the clip-on annular component in the assembly of Figure 2; Figure 6 shows a perspective view of a portion of a clip-on annular component according to an embodiment; Figure 7A shows a perspective view of a portion of a clip-on annular component according to an embodiment; Figure 7B shows a cross-sectional view of the clip-on annular component of Figure 7A; Figure 8A shows a perspective view of a portion of a clip-on annular component according to an embodiment; Figure 8B shows a cross-sectional view of the clip-on annular component of Figure 8A; Figure 9A shows a perspective view of a portion of a clip-on annular component according to an embodiment; Figure 9B shows a cross-sectional view of the clip-on annular component of Figure 9A; Figure 10A shows a front view of a portion of a clip-on annular component according to an embodiment; Figure 10B shows a cross-sectional view of the clip-on annular component of Figure 10A; Figure 11 shows a perspective view of a clip of a clip-on annular component according to an embodiment; Figure 12 shows a flow chart of a method of coupling a cover to a stator core according to an embodiment. DETAILED DESCRIPTION Examples of the present disclosure relate to a clip-on annular component for connecting to a different component. In the examples below, the clip-on annular component may be an electric drive unit component that is connectable to a different electric drive unit component. For example, the clip-on annular component may be a cover or a cooling fluid manifold for connecting to a stator core for an electric machine of a vehicle traction motor. While the discussion below primarily refers to components of a stator assembly, it will be appreciated that the clip-on annular component may be in any suitable form, and may be configured for connecting to any different component, including in a vehicle electric drive unit. Examples of the present invention relate to a stator assembly for an electric machine of a vehicle traction motor. Such an electric machine may be of a synchronous type or asynchronous type, for example a permanent magnet synchronous motor. Non-limiting examples will now be described with reference to accompanying Figures 1 to 12, where the figures illustrate an assembly 10, a stator core 12, cover 30A, 30B, an electric machine 100, an electric drive unit (EDU) 160 and a vehicle 200. Figure 1 illustrates a vehicle 200 having a first electric machine 100-1 which is part of a vehicle traction motor fordriving one or more front wheels of the vehicle 200. The vehicle 200 also has a second electric machine 100-2 which is part of a vehicle traction motor for driving one or more rear wheels of the vehicle 200. In other embodiments the vehicle 200 may comprise only a single electric machine 100, which is part of a vehicle traction motor, arranged or configured to drive one or more front wheels of the vehicle 200 and / or one or more rear wheels of the vehicle 200. At a vehicle axle the electric machine 100 may be arranged to drive both wheels, either directly or through other transmission components. In other arrangements there may be more than one electric machine 100 arranged to provide torque to a vehicle axle, for example, to provide torque vectoring functionality for the vehicle 200. Other arrangements may have one electric machine 100 arranged or configured to drive each wheel of the vehicle 200. The electric machine 100 comprised in the vehicle 200 may have a stator assembly 10 as described herein. For example, the electric machine 100 comprised in the vehicle 200 may be the electrical machine of Figure 2, described below. As illustrated schematically on Figure 1, the electric machine(s) 100 may be part of an electric drive unit (EDU) 160. For example, the EDU may include transmission components, lubrication and cooling components, and / or power electronics, in addition to the electric machine 100. In the vehicle 200 of Figure 1, the first electric machine 100-1 is part of a first EDU 160-1 for driving front wheels of the vehicle 200, and the second electric machine 100-2 is part of a second EDU 160-2 fordriving rear wheels of the vehicle 200. Referring to Figure 2, the electric machine 100 of the vehicle 200 is illustrated. The electric machine includes an assembly 10 (e.g. a stator assembly) which has an annular stator core 12. The stator core 12 has a cylindrical inner channel or cavity 14, which defines a central stator axis 16. The cylindrical inner channel 14 extends in a direction parallel to the central stator axis 16 from a first axial end surface 18 of the stator core 12 to a second axial end surface 20 of the stator core 12. The stator core 12 has a plurality of winding slots 22 extending radially to support electrical stator windings (not shown). A plurality of stator teeth (not shown) are provided between the winding slots 22. In other words, stator teeth are interspersed between the winding slots 22 in a circumferential direction about the stator core 12. Both the plurality of winding slots 22 and the plurality of stator teeth extend from the first axial end surface 18 to the second axial end surface 20 of the stator core 12. The electric machine 100 also includes a rotor 112. The rotor 112 is configured to fit within the cylindrical inner channel 14 of the stator core 12 with a small airgap 26 therebetween. The outside surface of the rotor 112 provides a surface concentric with a circumference of the cylindrical inner channel 14, such that as the rotor 112 rotates within the cylindrical inner channel 14 of the stator core 12, a consistent air gap 26 is maintained between the rotor 112 and the stator core 12. The electric machine 100 may have forty-eight winding slots 22 and eight rotor poles. Other combinations of winding slot numbers and rotor pole numbers are useful. As shown in Figure 2, the electric machine 100 has a housing 102 surrounding the assembly 10. In some embodiments the housing 102 is a cylindrical housing, though it will be understood that the stator core 12 may have a non-circular cross section, in particular where the outer form of the stator core 12 is oblate or has projections thereon, such that the housing 102 may be non-circular. The stator core 12 has a plurality of cooling passageways 28 which extend in a longitudinal direction (i.e., in a direction parallel to the central stator axis 16) through the stator core 12 away from the first end 18 of the stator core 12. In particular, the cooling passageways 28 extend from the first axial end surface 18 to the second axial end surface 20 of the stator core 12. The cooling passageways 28 are distributed about a circumference of the stator core 12. The electric machine 100 has a first cover 30A which at least partly covers the first axial end surface 18 of the stator core 12. In the illustrated embodiment, the first cover 30A is a first cooling manifold. The first cooling manifold 30A defines at least one cooling channel 32A in fluid communication with the plurality of cooling passageways 28. In the illustrated embodiment, the at least one cooling channel 32A defines a first chamber 32A in fluid communication with the plurality of cooling passageways 28. The first cooling manifold 30A also defines a manifold inlet 34A for connecting the first chamber 32A to a cooling fluid source. In this way, cooling fluid may pass through the manifold inlet 34A, into the first chamber 32A and then through the cooling passageways 28. In the arrangement of Figure 2, the manifold inlet 34A is defined by a radially outer edge of the first cooling manifold 30A, which is open to the housing 102 so that cooling fluid can enter the first chamber 32A through a first opening 104 in the housing 102. In other words, a radially outer edge 36A of the first chamber 32A is defined by the housing 102. The electric machine 100 also has a second cover 30E3 which at least partly covers the second axial end surface 20 of the stator core 12. In the illustrated embodiment, the second cover 30B is a second cooling manifold. The second cooling manifold 30B defines at least one cooling channel 32B in fluid communication with the plurality of cooling passageways 28. In the illustrated embodiment, the at least one cooling channel 32B is a second chamber 32B in fluid communication with the plurality of cooling passageways 28. The second cooling manifold 30B also defines a manifold outlet 34B for expelling cooling fluid from the second chamber 32B. In this way, cooling fluid may pass through the manifold inlet 34A into the first chamber 32A of the first cooling manifold 30A, through the plurality of cooling passageways 28 to the second chamber 32B and then out of the manifold outlet 34B. In the arrangement of Figure 2, the manifold outlet 34B is defined by a radially outer edge of the second cooling manifold 30B, which is open to the housing 102 so that cooling fluid can be expelled from the second chamber 32B through a second opening 106 in the housing 102. In other words, a radially outer edge 36B of the second chamber 32B is defined by the housing 102. It will be understood that, although the schematic arrows on Figure 2 show a flow of cooling fluid through the first opening 104 in the housing, through the first cooling manifold 30A, along the cooling passageways 28, into the second cooling manifold 30B and then out of the second opening 106 in the housing 102, the flow of cooling fluid could be reversed. In other words, cooling fluid could instead flow through the second opening 106 in the housing 102, through the second cooling manifold 30B, along the cooling passageways 28, into the 9 first cooling manifold 30A and then out of the first opening 104 in the housing 102. In such a configuration, the manifold inlet 34Aofthe first cooling manifold 30A would instead be a manifold outlet, and similarly the manifold outlet 34E3 of the second cooling manifold 30B would instead be a manifold inlet. In the illustrated arrangement, the first and second cooling manifolds 30A, 30B are annular. In this way, the first and second chambers 32A, 32B are also annular. The first and second cooling manifolds 30A, 30B can be considered as part of the assembly 10, along with the stator core 12. In the illustrated embodiment, the housing 102 of the electric machine 100 has a first axial end surface 102A and a second axial end surface 102B. The stator assembly 10 is positioned inside the housing 102 so that a first side of the first cooling manifold 30A faces the first axial end surface 18 of the stator core 12 and a second side of the first cooling manifold faces the first axial end surface 102A of the housing 102. Similarly, a first side of the second cooling manifold 30B faces the second axial end surface 20 of the stator core 12, and a second side of the second cooling manifold 30B faces the second axial end surface 102B of the housing 102. In the illustrated embodiment, the second side of the second cooling manifold 30B is provided adjacent to the second axial end surface 102B of the housing 102. On the contrary, although the second side of the first cooling manifold 30A faces the first axial end surface 102A of the housing 102, the first cooling manifold 30A is not provided adjacent to the first axial end surface 102A of the housing 102. In other words, the first cooling manifold 30A is spaced apart from the first axial end surface 102A of the housing 102 in an axial direction. The electric machine 100 of Figure 2 also has a cooling fluid recirculation system 120 which is configured to supply cooling fluid to the manifold inlet 34A of the first cooling manifold 30A in a cooling fluid recirculation circuit 122 (i.e., via the first opening 104 in the housing 102). The stator core 12 is defined by a stator lamination stack 44. In other words, the stator core 12 is formed of a plurality of layers. The layers are stacked one atop the other to form the stator lamination stack 44, which extends from the first axial end surface 18 of the stator core 12 to the second axial end surface 20 of the stator core 12. The layers may be stamped from sheet material (e.g., sheet metal), or formed via any other suitable process. In this way, a stator core 12 having a complex cross-sectional shape can be formed. In some arrangements the cooling passageways 28 are coated on their inner surfaces, for example with a plastic material, to provide sealing such that coolant is prevented, or resisted, from passing between the laminations of the stator lamination stack 44 under the temperatures and pressures described herein. There are different methods for producing this arrangement. The plastic may be applied to the inner surface of the cooling passageway 28 by flowing the thermoplastic through the cooling passageway 28, or by inserting a formed thermoplastic tube into the cooling passageway 28 and optionally applying pressure to the tube to blow mould the tube to the shape of the cooling passageway 28. The thermoplastic may have a complex cross-sectional shape either internally and / or externally. The external surface of the thermoplastic tube may have a simple rounded shape and the inner surface of the cooling passageway 28 may be similarly rounded. Once the plastic coating is in place the thickness of the coating of the inner surface of the cooling passageways 28 is in the region of 0.5mm, but other thicknesses are useful. The thermal conductivity of the plastic material is in the range 1 to 40 watts / mK. The functioning of electrical machines 100 and electric drive units (EDUs) 160 is known, and so will not be described here in more detail. In the arrangement of Figure 2, a first axial seal 40A is located between the first end 18 of the stator core 12 and the first cooling manifold 30A to seal a radially inner edge 38A of the first chamber 32A. In particular, the first axial seal 40A is an annular seal. The first axial seal 40A is located in a first annular recess 42A in the first cooling manifold 30A, which locates the first axial seal 40A in the correct position. Similarly, a second axial seal 40B is located between the second end 20 of the stator core 12 and the second cooling manifold 30B to seal a radially inner edge 38B of the second chamber 32B. In particular, the second axial seal 40B is an annular seal. The second axial seal 40B is located in a second annular recess 42B in the second cooling manifold 30B, which locates the second axial seal 40B in the correct position. Similarly, a third axial seal 40C is provided at an opposite side of the second cooling manifold 30B to the second axial seal 40B. The third axial seal 40C is configured to form a seal between the second cooling manifold 30B and the second axial end surface 102B of the housing 102. The third axial seal 40C is located in a third annular recess 42C in the second cooling manifold 30B, which locates the third axial seal 40C in the correct position. In the arrangement of Figure 2, a radial seal 41 is located between the radially outer edge 36A of the first cooling manifold 30Aand a radial inner surface of the housing 102. In particular, the radial seal 41 is an annular seal (e.g., an O-ring). The radial seal 41 is located In a fourth annular recess 43 in the radially outer edge 36A of the first cooling manifold 30A, which locates the radial seal 41 in the correct position. In this context, the term “axial seal” will be understood to mean a seal which is configured to have compression applied to axial ends of the seal’s cross-section. Conversely, the term “radial seal” will be understood to mean a seal which is configured to have compression applied to the inner and outer radial surfaces of the seal. Often, axial seals have a cross-section which is elongate in the axial direction, although this is not always the case. Referring now to Figures 3 to 11, the clip-on annular component will be described in more detail. In the figures, the clip-on annular component is the second cover 30B of the assembly 10. The clip-on annular component 30B is configured to connect with a different component, for example a vehicle component, e.g. a vehicle electric drive unit component. In the figures, the different component is the stator core 12. It will be appreciated that the clip-on annular component and the different component may be any components that are intended to be connected together (e.g. components of a vehicle electric drive unit). The clip-on annular component may be the first cover 30A of the assembly 10 in some arrangements. In the illustrated arrangement, the assembly 10 includes the clip-on annular component in the form of the second cover 30B which, in this embodiment, is a second cooling manifold 30B. The assembly 10 also includes the different component in the form of the stator core 12. The second cooling manifold 30B is intended to cover the second axial end surface 20 of the stator core 12. As can be seen in the figures, the chp-on annular component (e.g. the cooling fluid manifold 30B) includes an annular body 52 and one or more clips 54 extending from the annular body 52. The annular body 52 defines a longitudinal axis L. In embodiments where the clip-on annular component is a cooling fluid manifold 30A, 30B of Figure 2, the longitudinal axis L of the annular body 52 may be arranged to be coaxial with the central axis 16 of the stator core 12. The one or more clips 54 are configured to engage with a corresponding one or more formations 56 on a different component so as to secure the annular component 30B thereto. Each clip 54 includes a root end 54A (see Figures 5 and 6) that is connected to a first axial surface 52A of the annular body 52, and a tip end 54B that is distal to the annular body 52. The tip end 54B is configured to engage with a formation on a different component. In the illustrated arrangement, each clip 54 is defined by a projection extending from the first axial surface 52A of the annular body 52 (e.g. the second side of the manifold 30B as outlined in the discussion relating to Figure 2). The one or more clips 54 extend in a generally longitudinal direction from the first axial surface 52A of the annular body 52. The one or more clips 54 have an axial projection 60 and a transverse projection 62, which extends from a free end 64 of the axial projection 60. In the illustrated arrangement, the clip-on annular component 30B has a plurality of clips 54. The plurality of clips 54 are distributed circumferentially about the annular body 52. The clips 54 may be evenly distributed around the annular body 52 in some arrangements. The clip-on annular component 30B includes six clips 54 in the figures. In this way, the different component, e.g. the stator core 12 may include six formations 56. However, in other embodiments there may be a different number of clips 54 and formations 56 (e.g., one, two, three, four, five, or greater than six). At least three clips 54 may be provided. In other arrangements, at least four, five, six, seven, eight, nine, ten, eleven or twelve clips 54 are provided. Between three and thirty-six clips 54 may be provided. Between three and ten clips 54 may be provided. Between four and six clips 54 may be provided. The different component is the stator core 12 in the figures, and the one or more formations 56 on the different component are one or more recesses 56 on the stator core 12. The one or more clips 54 may be configured to engage with a corresponding one or more recesses 56 in the stator core 12. In the figures, the second cooling manifold 30B includes one or more clips 54 and the stator core 12 includes a corresponding one or more recesses 56. The second cooling manifold 30B includes a plurality of clips 54, while the stator core 12 includes a plurality of recesses 56 for receiving the clips 54. The clips 54 are distributed circumferentially about the second cooling manifold 30B and the plurality of recesses 56 are distributed circumferentially about the stator core 12. As best illustrated in Figures 3 to 5, the annular clip-on component is the second cooling manifold 30B that is configured to be secured to the stator core 12 simply by pushing the manifold 30B towards the second axial end surface 20 of the stator core 12 (as illustrated in the transition between Figures 3 and 4). In this way, the connection between the second cooling manifold 30B and the stator core 12 can be considered a snap-fit arrangement. The snap-fit arrangement provides a simple means of securing without the need for additional fasteners. Further, because the stator core 12 generally remains static within the housing 102 (in contrast to the rotating 12 rotor 112), the chp-on component 30B provides a suitably robust connection between components, e.g. between the second cooling manifold 30A and the stator core 12. In the illustrated embodiment, the second axial seal 40B, which is positioned between the stator core 12 and the second cooling manifold 30B, is compressed therebetween by the clips 54. By compressing the second axial seal 40B with the clips 54, a contact pressure between the second axial seal 40B and the stator core 12 and second cooling manifold 30B can be provided, which improves seal performance. In other words, the pressure of cooling fluid inside the second chamber 32B can be increased. It will be understood that the second axial seal 40B may be further compressed due to the second cooling manifold 30B being clamped between the second axial end surface 102B of the housing 102, and the second axial end surface 20 of the stator core 12. In some embodiments, the number of recesses 56 is less than the number ofclips 54, so that each recess 56 receives more than one clip 54. For example, the clip-on annular component 30B may include a plurality of clips 54, while a single, annular, recess 56 is provided on the stator core 12 for receiving the clips 54. Such an annular recess allows the clip-on annular component (e.g. the second cooling manifold 30B) to be pushed to form a snap-fit engagement in any angular orientation (i.e., without the need to align the clips 54 with corresponding recesses 56 first). In such embodiments, the clip-on annular component 30B and clips 54 may have the same configuration as in the illustrated embodiment. In the illustrated embodiment, the recesses 56 in the stator core 12 are recessed portions of the stator core 12 which are axially spaced apart from the second axial end surface 20 of the stator core 20 by an intermediate step 58. In this embodiment, the recesses 56 are grooves in the outer radial surface of the stator core 12. During assembly, the one or more clips 54 can be pushed over the intermediate steps 58. Following this, the transverse projections 62 sit inside the recesses 56 and engage the intermediate step 58 to form an interlocking engagement which inhibits axial separation of the clip-on annular component and the different component (e.g. the second cooling manifold 30B and the stator core 12). It will be understood that, to ease pushing the transverse projections 62 over the intermediate steps 58, each transverse projection 62 has a tapered leading edge 66. In this embodiment the tapered leading edge 66 is flat, but in other embodiments the tapered leading edge 66 may be curved. However, it is apparent from the drawings that a gap 57 can be disposed in the recess 56 adjacent the projection or intermediate step 58 of the stator core so that the manifold can be fitted by a bayonet-type of engagement. That is, by insertion of the clip 54 aligned with the gap 57 and then twisted so that the edge 66 aligns with the projection 58. Further, the gap permits easy disassembly later if required for servicing of the electric machine 100. Referring to Figure 6, the annular body 52 includes an arrangement of recesses 70A, 70B positioned adjacent opposing ends of a respective clip 54 such that the clip 54 is positioned between the recesses 70A, 70B. In the figures, the recesses 70A, 70B extend in an axial direction into the first axial surface 52A of the annular body 52. A first of the recesses 70A may be positioned adjacent a first circumferential end of the clip 54 and a second of the recesses 70B may be positioned adjacent a second circumferential end of the clip 54. In the arrangement of Figures 6 to 10B, the recesses 70A, 70B may be immediately adjacent to the ends of the respective clip 54, e.g. such that the annular body 52 includes an axial cut-out at both ends of the clip 54. The recesses 70A, 70B may extend from an outer radial edge of the first axial surface 52A of the annular body 52 such that the recesses 70A, 70B extend in an axial and a radial direction. The recesses 70A, 70B provide additional support for the clip 54 to reduce bending stresses on the clip. Referring to Figures 6 to 11, the annular clip-on component 30B will be described in more detail. As has been discussed, the illustrated arrangement depicts the annular clip-on component in the form of a cover or cooling fluid manifold 30B for connecting to a stator core 12 of an electric machine 100. It will be appreciated that the annular clip-on component 30B may be any component and may be connected to any different component. The annular clip-on component 30B includes one or more grooves 68 extending in an outer radial surface 52B of the annular body 52. A region of the or each groove 68 is circumferentially aligned on the annular body 52 with a respective clip 54 of the one or more clips 54. A plurality of grooves 68 may be provided (e.g. one groove 68 per clip 54), with each groove 68 having a region that is circumferentially aligned with a respective clip 54. The one or more grooves 68 extend in a radially inward direction from the outer radial surface 52B (e.g. toward the longitudinal axis L). The one or more grooves 68, together with the recesses 70A,70B improve the reliability of the clip-on annular component 30B by providing a space for the one or more clips 54 to flex without snapping from the annular body 52. This reduces the likelihood of significant, permanent deformation or breakage of the clips 54, thereby reducing the risk of the clips 54 becoming ineffective and the annular component 30B becoming detached. In this way, the clips 54 are more reliable and less prone to fatigue and / or failure. In the illustrated arrangement, the one or more grooves 68 extend circumferentially beyond opposing circumferential ends of the respective clip 54. In this way, the groove 68 extends circumferentially beyond the clip 54 on each side, increasing the space available for supporting the flexing of the clip 54. In some arrangements, a circumferential midpoint or centre point of the or each groove 68 is circumferentially aligned with a midpoint or centre point (e.g. a circumferential midpoint) of a respective clip 54 of the one or more clips 54. In such an arrangement, the grooves 68 extend equally about the clip so as to provide improved flexing support. As is best shown in Figures 7A, 8A and 9A, the one or more grooves 68 defines a circumferential width Wi that is greater than a width W2 of the respective clip 54 of the one or more clips 54. Configuring the one or more grooves 68 to have a circumferential width W1 greater than the width W2 of a respective clip 54 with which the groove 68 is aligned provides a larger space for the clip 54 to flex. It should be understood that the width W2 of a clip 54 refers to the distance between first and second circumferential ends of the clip 54. In some embodiments, the or each clip 54 follows the curvature of the annular body 52. In this case, the width of the clip W2 is the circumferential width of the clip 54. The term “circumferential width” refers to the angular extent of the groove 68 or clip 54 in a circumferential direction with respect to the longitudinal axis L of the annular body 52, which may otherwise be described as the distance defined between a first and a second circumferential end of the groove 68 and / or clip 54. It will be appreciated that the width of the clip 54 or groove 68 may change, e.g. the clip 54 may have a truncated shape with a varying circumferential width. In this case, the term “circumferential width should be understood to refer to the greatest circumferential distance between two radially aligned points on the clip 54. The groove 68 and the respective clip 54 with which the groove 68 is aligned are each configured to subtend an angle with respect to the longitudinal axis L. The angle subtended by the groove 68 is greater than an angle subtended by the respective clip 54. The term “subtend” refers to the angular extent of the groove 68 or clip 54 in a circumferential direction with respect to the longitudinal axis L of the annular body 52, which may otherwise be described as the angle defined between a first and a second circumferential ends of the groove and / or clip. It will be understood that the term “circumferential width” may be used interchangeably with the term “angle subtended” in relation to the groove 68 and respective clip 54. The circumferential width Wi of the one or more grooves 68 may be at least double the width W2 of the respective clip 54. In some arrangements, the circumferential width W1 of the groove 68 may be at least three-times greater, or at least four-times greater, or more than the width W2 of the respective clip 54. Dimensioning the groove 68 and / or clip 54 in such a way provides for sufficient flexibility of the clip 54 while avoiding significant radial “cut-out” in the annular body (e.g. in the radial direction) to form the groove 68. The width W1 of the groove 68 relative to the clip 54 provides effective space for the clip 54 to flex without significantly increasing the depth of the groove 68 in the radial direction, avoiding a reduction in strength and rigidity in the annular body 52. In this way, the dimensions of the groove 68 facilitate effective flexing of the clip 54 without being detrimental to the rigidity of the annular body 52. A rigid annular body 52 is particularly important when the clip-on annular component is the cooling fluid manifold 30B, as the annular body 52 may be subject to high pressures and temperatures during use in a vehicle 200. Figures 7B, 8B and 9B indicate a cross-sectional view of the groove 68 in the annular body 52. As can be seen, the groove 68 defines a maximum groove depth Di in the radial direction. The maximum groove depth Di may be defined as the maximum distance between the radially outer surface 52B of the annular body 52 and a radially inner surface 68A of the groove 68. The annular body 52 defines a radial thickness D2 between the outer radial surface 52B and an inner radial surface 52C. The maximum groove depth Di may be less than or equal to one half of the radial thickness D2 of the annular body 52. The maximum groove depth Di may be less than or equal to one third of the radial thickness D2 of the annular body 52 in some arrangements. The maximum groove depth Di may be less than or equal to one quarter of the radial thickness D2 of the annular body 52. Configuring the groove 68 to have such a depth Di relative to the thickness of the annular body D2 has been found to result in a groove that provides effective flexing to the clips 54 without occupying a significant extent of the radial thickness D2 of the annular body 52. In this way, the presence of the groove(s) 68 does not significantly reduce the strength and rigidity of the annular body 52. Examples of different configurations of the annular clip-on component 30B are shown in Figures 7A to 9B. A first example configuration is shown in Figures 7A and 7B. As can be best seen in the cross-sectional view of Figure 7B, the radially inner surface 68A of the groove 68 is substantially arc-shaped. In the figures, the arc shape is in the radial direction. The inner surface 68A of the groove 68 defines a radially outward facing concave surface. The inner surface 68A of Figures 7A and 7B defines an arc of a circle having a constant diameter. The groove 68 can be seen as a radial or curved cut in the outer radial surface 52B of the annular body 52. The arrangement of the groove 68 is simple to manufacture and provides effective flexing support to the clip 54. In alternative embodiments, the inner surface 68A may define a surface having a varying diameter. An alternative configuration of the annular clip-on component 130B is shown in Figures 8A and 8B. The annular clip-on component 130B of these figures is substantially the same as that discussed in relation to Figures 7 A and 7B, e.g. the inner surface 168A of the groove 168 may define a similar shape to the inner surface 68 of the groove 68A. The primary difference is the circumferential width Wi of the groove 68,168. As can be seen, the circumferential width Wi of the groove 168 of Figures 8A and 8B is greater than that of the groove 68 of Figures 7A and 7B. In the illustrated arrangement, the maximum groove depth Di of the grooves 68 in Figures 7A and 7B and the grooves 168 in Figures 8A and 8B is substantially same. In this way, the groove 168 of Figures 8A and 8B has been widened compared to that of the example in Figures 7A and 7B without increasing the depth Di. The inner surface 168A of the groove 168 defines an arc of a circle having a greater diameter than that defined by the inner surface 68A of the groove 68. The wider groove 168A of Figures 8A and 8B may result in improved flexing support without increasing the groove depth Di and therefore without significantly reducing the radial thickness D2 of the annular body 152. It will be understood that the inner surface 68A, 168A of the groove 68, 168 may define an arc of a circle having a diameter of at least 200 mm. Another configuration of the annular clip-on component 230B is shown in Figures 9A and 9B. Only the differences between the component 230B and that of previous arrangements will be discussed in detail. As can be best seen in the cross-sectional view of Figure 9B, the radially inner surface 268A of the groove 268 is substantially linear. The radially inner surface or edge 268A defines a chord of a circle defined between two points on the outer radial surface 52B of the annular body 52. Put anotherway, the radially inner surface 268A of the groove 268 defines a substantially straight edge between two points of the outer radial surface 52B of the annular body 52. The groove 268 can be seen as a straight cut across the outer radial surface 52B of the annular body 52. The arrangement of Figures 9A and 9B maximises the circumferential width Wi of the groove 268 without increasing the maximum groove depth Di. In this way, the depth Di of the grooves 68, 168, 268 of Figures 7 to 9 is substantially the same, with the width Wi of the groove 268 being the maximum width at the given depth Di. Increasing the width Wi of the groove 268 without increasing the depth Di provides effective support to the clip 54 without removing a significant portion of the annular body 52, thereby maintaining the robustness and strength of the annular body 52 in addition to supporting the clip 54. The two points on the outer radial surface 52B between which the groove 268 extends may be located at opposing sides of the respective clip 54. In the illustrated arrangement, the respective clip 54 locates between the two points. In this way, the circumferential midpoint of the clip 54 is the circumferential midpoint between the two points on the outer radial surface 52B. The clip 54 may be positioned so as to extend from any region of the first axial surface 52A. In the arrangement of Figures 10A and 10B, the one or more clips 54 extend such that an outer surface of the or each clip 54 extends from a radially outer edge of the first axial surface 52A of the annular body 52. It will be understood that the radially outer edge of the first axial surface 52A is defined as the edge between the first axial surface 52A and the radially outer surface 52B of the annular body 52. The outer surface of the or each clip 54 is the radially outer surface thereof, e.g. the surface that is distal to the longitudinal axis L of the annular body 52. As can be best seen in Figure 10B, the clip 54 may be positioned such that there is no clearance between the clip 54 and the radially outer edge of the first axial surface 52A. Arranging the clip 54 as shown in Figures 10A and 10B has been found to reduce the extent of deformation of the respective clip 54 in use compared with a clip 54 that extends from a radially inward position on the axial surface 52A of the annular body 52. The clips 54 may be less susceptible to permanent deformation and maintain a more secure fit with a different component. Referring to Figure 11, it can be seen that each clip 54 defines an axial height H between the root end 54A and the tip end 54B. Each clip 54 also defines a radial thickness T between an outer radial surface and an inner radial surface of the clip 54. The radial thickness T may be at least one eighth of the axial height H. The radial thickness T may be at least one quarter of the axial height H. In some arrangements, the axial height may be at least one third of the axial height. In some arrangements, the thickness T to height H ratio may be in the range of 0.125 to 0.33, optionally in the range of 0.17 to 0.25. The relation between the axial height H and radial thickness T results in a more robust clip 54 that is less susceptible to permanent deformation (e.g. compared with a clip 54 having a lower thickness compared with the height). In some arrangements, the annular body 52 is formed of metallic material, optionally steel or aluminium alloy material. In other arrangements, the annular body 52 is formed of plastic material. The clips 54 may be formed from a metallic material, e.g. steel or aluminium alloy. The clips 54 may be formed from a plastic material. In some arrangements, the clips 54 may be formed from the same material as the annular body 52. This may facilitate integrally forming the clips 54 with the annular body 52. In arrangements in which the clip-on annular component is a cooling fluid manifold, the clips 54 and annular body 52 may be formed from a metallic material, optionally steel or aluminium alloy material. In this way, the clips 54 and annular body 52 are capable of withstanding high pressures and temperatures. The clip 54 may be secured to the annular body 52 by any suitable means, e.g. clamping, adhesive, welding, or the like. It will be understood that although the annular clip-on component is described above as being a cover or cooling fluid manifold 30A for a stator core 12, the annular clip-on component may another component, e.g. for connecting to a stator core 12 or another component (e.g. another vehicle electric drive unit component). For example, in some embodiments, the annular clip-on component may be: a wire harness for electrical windings, power electronics, another type of cooling component, a lubrication or bearing component, a transmission component, a housing component, or any other electric machine component or electric drive unit component. For example, any of the components mentioned may be formed as a cover which at least partially covers a portion of the stator core 12 (e.g., one of the axial end surfaces 18, 20), regardless of any other functionality that the components perform. In some cases, the annular clip-on component may be the stator core 12 (e.g. having a series ofclips 54), and the different component may be any component to be connected to the stator core 12, having corresponding formations for engaging with the clips 54, e.g. recesses. It will be understood that the annular clip-on component may be any component required to attach to another component, for example any component in the electric drive unit 160 of a vehicle 200 that is intended to be connected to another component. Although the annular chp-on component has been described in the context of vehicle electric drive unit components, it will be appreciated that the annular clip-on component described herein is suitable for any use in connecting one part with another. For example, the annular clip-on component may be implemented in electronics and electrical components, e.g. for connecting antennas, cables, power cords, sensors, communications equipment, or the like. The annular clip-on component may be further implemented in control devices, e.g. connecting probes, sensors, cables. The annular clip-on component may be utilised in other vehicle components (e.g. external to the electric drive unit), for example, in connecting sensors, lights, electrical systems or the like. It is envisaged that the annular clip-on component may be suitable for use in any application in which a simple and robust connection that has suitable stress and / or strain characteristics to withstand various temperature and pressure fluctuations is required. A method of coupling an annular body to a different component is illustrated in Figure 12. The method includes the following steps: a) providing a component comprising an axial end surface, the component comprising one or more formations; b) positioning a clip-on annular component as described herein against the axial end surface of the component; and c) securing the clip-on annular component to the component by engaging the one or more clips with the corresponding one or more formations on the component. The component may be a stator core 12 for an electric machine 100 of a vehicle traction motor. The clip-on annular component may be a cover 30A, 30B which at least partially covers the axial end 18, 20 of the stator core 12. The one or more formations may be one or more recesses 56 on the stator core 12. Step c) may include engaging the one or more clips 54 with the corresponding one or more recesses 56 on the stator core 12. The clip-on annular component may be a cooling fluid manifold 30A, 30B. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. It should also be noted that whilst the appended claims set out particular combinations of features described above, the scope of the present disclosure is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features herein disclosed.

Claims

1. A clip-on annular component comprising:an annular body;one or more clips extending from the annular body, the or each clip configured to engage with a corresponding one or more formations on a different component so as to secure the annular component thereto; andone or more grooves extending in an outer radial surface of the annular body, a region of the or each groove being circumferentially aligned on the annular body with a respective clip of the one or more clips;wherein the or each groove defines a circumferential width that is greater than a width of the respective clip.

2. The clip-on annular component according to claim 1, wherein the circumferential width of each groove is at least double, optionally at least three-times, optionally at least four-times greater than the width of the respective clip.

3. The clip-on annular component according to claim 1 or claim 2, wherein the groove defines a maximum groove depth in the radial direction, and wherein the maximum groove depth is less than or equal to one half, optionally less than or equal to one third, optionally less than or equal to one quarter of the radial thickness of the annular body.

4. The clip-on annular component according to any preceding claim, wherein a radially inner edge of the one or more grooves defines a chord of a circle defined between two points on the outer radial surface of the annular body.

5. The clip-on annular component according to any of claims 1 to 3, wherein the one or more grooves comprises a radially inner surface that is substantially arc-shaped.

6. The clip-on annular component according to any preceding claim, wherein the one or more grooves extend circumferentially beyond opposing circumferential ends of the respective clip.

7. The clip-on annular component according to claim 6, wherein the or each groove is arranged such that a circumferential midpoint of the or each groove is circumferentially aligned with a midpoint of the respective clip.

8. The clip-on annular component according to any preceding claim, wherein the one or more clips extend such that an outer surface of the or each clip extends from a radially outer edge of a first axial surface of the annular body.

9. The chp-on annular component according to any preceding claim, wherein the one or more clips define an axial height between a root end and a tip end, and a radial thickness between an outer radial surface and an inner radial surface, and wherein the radial thickness is at least one quarter of the axial height.

10. The clip-on annular component of any preceding claim, wherein the one or more clips are formed of metallic material, optionally steel or aluminium alloy material.

11. The clip-on annular component of any preceding claim, wherein a plurality of clips are provided, circumferentially spaced apart about the annular body; optionally, wherein at least three clips are provided.

12. An assembly for an electric drive unit of a vehicle, the assembly comprising: the clip-on annular component according to any preceding claim; and a vehicle electric drive unit component comprising at least one formation for engaging with a respective one or more clips of the clip-on annular component such that the clip-on annular component is securable to the vehicle electric drive unit component.

13. The assembly of claim 12, wherein the vehicle electric drive unit component is a stator core for an electrical machine of a vehicle traction motor, the stator core comprising a first end, and wherein the clip-on annular component is a cover which at least partly covers the first end of the stator core.

14. The assembly of claim 13, wherein the stator core comprises a plurality of cooling passageways which extend in a longitudinal direction through the stator core away from the first end, and wherein the cover is a cooling fluid manifold which defines at least one cooling channel in fluid communication with the cooling passageways.

15. A vehicle comprising the assembly of claim 14.

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