Coolant sump with abutment member and magnetic element retention feature

Abstract

A coolant sump 100, for an electric drive unit (102, Fig. 2), comprising at least one member 104, 106 for abutting a magnetic element 124, and at least one feature 112, 114 for retaining the magnetic

Description

TECHNICAL FIELD The present disclosure relates to a coolant sump for an electric drive unit (EDU). Aspects of the invention relate to a coolant sump for an EDU, to an EDU comprising a coolant sump, and to a vehicle comprising an EDU having a coolant sump. BACKGROUND An electric drive unit (EDU) of a vehicle comprises mechanical and electronic components for accepting a drive current from an inverter and generating torque in one or more output shafts for driving road wheels, thereby causing the vehicle to move. A coolant, which can also act as a lubricant, is circulated within the EDU. A sump can be provided, into which the coolant drains. The sump can be a separate component that is attached to the EDU. 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 coolant sump for an electric drive unit (EDU), an EDU comprising such a coolant sump, and a vehicle comprising such a EDU, as claimed in the appended claims According to an aspect of the present invention there is provided a coolant sump for an electric drive unit, EDU, the coolant sump comprising: at least one abutment member for abutting, in use, a magnetic element, thereby to maintain a space between the magnetic element and a base wall of the coolant sump, so as to allow, in use, coolant to flow between the magnetic element and the base wall of the coolant sump; and at least one retention feature for retaining, in use, the magnetic element within the coolant sump. By maintaining a space between the magnetic element and the base wall, a greater proportion of the magnetic element’s surface area is exposed to the coolant, which may improve capture of metallic particles The retention feature may comprise a clip. The at least one abutment member may comprise at least one formation extending upwardly from the base wall. The at least one formation can comprise, for example: at least one post; and / or at least one rib or wall extending along a portion of the base wall. The coolant sump may comprise at least two of the ribs or walls, the ribs orwalls being disposed and configured to abut, in use, opposite sides of the magnetic element. By extending upwardly from the base wall, the at least one formation assists in maintaining a lateral position of the magnetic element relative to the base wall. At least one of the at least one abutment member and / or at least one of the at least one retention feature is defined or formed by one or more elements extending from the base wall of the sump. At least one of the at least one abutment member and at least one of the at least one retention feature define a unitary element extending from the base wall. Providing an abutment member and retention feature as a unitary element rather than as separate elements may reduce material usage and / or allow for reduced surface area, which may allow improved coolant flow around the magnetic element. The at least one abutment member and the at least one retention feature may be moulded as part of the coolant sump. This may simplify manufacture and / or assembly of the coolant sump. At least one abutment member and / or at least one retention feature may extend from and / or be supported by, a sidewall of the coolant sump. The coolant sump may comprise the magnetic element retained in position relative to the base wall by the at least one abutment member and the at least one retention feature. The at least one abutment member may be positioned and configured such that it allows, when the coolant sump is in use, movement of a coolant fluid into one or more recesses and / or apertures formed on or through the magnetic element. The at least one retention feature may comprise a pawl configured to engage, in use, the magnetic element so as to retain it within the coolant sump. For example, the at least one retention feature may comprise a flexible portion comprising the pawl. The use of a pawl may simplify installation of the magnetic element into the coolant sump, and / or may allow the magnetic element to be retained without fasteners. The coolant sump may comprise at least one locating feature for laterally positioning, in use, the magnetic element relative to the base wall. For example, the or each locating feature may comprise a post extending from the base wall for engaging, in use, an aperture or recess in the magnetic element. The posts, and corresponding apertures in the magnet element, may be different in shape to other apertures in the magnetic element. Advantageously, this may reduce the likelihood of the magnetic element being installed incorrectly. According to a further aspect of the present invention there is provided a coolant sump for an electric drive unit, EDU, the coolant sump comprising at least one abutment member for abutting, in use, a magnetic element, thereby to maintain a space between the magnetic element and a base wall of the coolant sump, so as to allow, in use, coolant to flow between the magnetic element and the base wall of the coolant sump. According to a further aspect of the present invention there is provided a coolant sump for an electric drive unit, EDU, the coolant sump comprising: at least one retention feature for retaining, in use, a magnetic element within the coolant sump. According to a further aspect of the present invention there is provided an electric drive unit, EDU, comprising the coolant sump of any aspect. According to a further aspect of the present invention there is provided a vehicle comprising the electric drive unit, EDU, of any aspect. 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 is a perspective view of a vehicle; Figure 2 is a side elevation of an electric drive unit (EDU in accordance with an embodiment of the invention; Figure 3 a detail perspective view of a coolant sump in accordance with a further embodiment of the invention; Figure 4 is a vertical section through part of the coolant sump of Figure 3; Figure 5 is a perspective view of a magnetic element for use with the coolant sump of Figures 3 and 4; Figures 6 to 8 show, in vertical section, an installation sequence of the magnetic element of Figure 5 into the coolant sump of Figures 3 and 4; Figure 9 is a detail perspective view of a coolant sump in accordance with a further embodiment of the invention; Figure 10 is a vertical section through part of the coolant sump of Figure 9; Figure 11 is a perspective view of a magnetic element for use with the coolant sump of Figures 9 and 10; Figures 12 to 14 show, in vertical section, an installation sequence of the magnetic element of Figure 11 into the coolant sump of Figures 9 and 10; Figure 15 is a detail perspective view of the magnetic element of Figure 11 installed into the coolant sump of Figures 9 and 10; Figure 16 is a detail perspective view of a coolant sump in accordance with a further embodiment of the invention; Figure 17 is a vertical section through part of the coolant sump of Figure 16, with a magnetic element installed; Figure 18 is a vertical section through a coolant sump with a magnetic element installed, in accordance with a further embodiment of the invention; Figure 19 is a vertical section through a coolant sump with a magnetic element installed, in accordance with a further embodiment of the invention; Figure 20 is a vertical section through part of coolant sump in accordance with a further embodiment of the invention; Figure 21 is a vertical section through a magnetic element for use with the coolant sump of Figure 20; and Figure 22 is a vertical section of the coolant sump of Figure 20, with the magnetic element of Figure 21 installed. DETAILED DESCRIPTION With reference to Figure 2, there is illustrated a coolant sump 100 in accordance with an embodiment of the invention. The coolant sump 100 forms part of an electric drive unit (EDU) 102. The EDU 102 is configured for installation onto a vehicle 200, as shown in Figure 1. The EDU 102 comprises mechanical and electronic components for accepting a drive current from an inverter (not shown) and generating torque in one or more output shafts (not shown) for driving road wheels (not shown), thereby causing the vehicle 200 to move. To this end, the EDU 102 typically includes an electrical machine (e.g., a multi-phase electric motor, not shown), a reduction gearbox (not shown), and a differential gear (not shown). The specific functional components of an EDU, such as EDU 102, are well known to the skilled person, and will therefore not be described in detail. The EDU 102 comprises a housing 144. The coolant sump 100 is attached to a lower region of the housing 144. The coolant sump 104 is formed from one or more components that are moulded, stamped, machined, additively manufactured, or otherwise formed from a suitable material or materials, such as aluminium alloy and / or a polymer, and defines an internal volume for holding coolant. During operation, the EDU 102 generates heat due to, for example, friction and electrical machine winding losses. One way of removing such heat is to circulate a coolant within the EDU. The coolant can be, for example, oil that is used to lubricate moving parts such as gears within the gearbox or differential. The coolant is pumped around the EDU, where it absorbs heat generated by various components. The heated coolant is cooled by a heat exchanger, where the heat is rejected to the atmosphere or repurposed (e.g., for cabin heating) before the cooled coolant is returned to the EDU. The heat exchanger can be a separate component, or can be integrated into the housing 144 or the sump 100, by way of cooling fins (not shown) for example. As shown in Figure 3, the coolant sump 100 comprises a base wall 136 and an upwardly extending peripheral sidewall 104. The coolant sump 100 comprises a first abutment member 106 and a second abutment member 108, each of which extends upwardly from the base wall 136. The first abutment member 106 comprises a formation in the form of a wall extending upwardly from, and along a portion of, an upper (that is, interior) surface of the base wall 136. The first abutment member 106 terminates at a flat upper surface 110 that is generally parallel with the upper surface of the base wall 136. The second abutment member 108 is similar to the first abutment member 106, and has flat upper surface 110 similar to that of the first abutment member 106. The first abutment member 106 and the second abutment member 108 are generally parallel to each other. The coolant sump 100 also comprises a first retention feature 112 and a second retention feature 114. The first retention feature 112 comprises an elongate portion 116 that extends upwardly from the base wall 136 and terminates at a pawl 118. The elongate portion 116 is flexible, which allows the pawl 118 to be moved laterally relative to the base wall 136, as indicated by arrow 122. As best shown in Figure 4, each pawl 118 has an upper ramped surface 160 and a lower ramped surface 162, the function of which is described below with reference to Figures 6 to 8. The second retention feature 114 is similar to the first retention feature 112, and has like features indicated with like reference signs. The first retention feature 112 and the second retention feature 114 are positioned opposite each other, so that they can bend away from each other as described in more detail below. In use, the first and second abutment members 106,108 and the first and second retention features 110, 112 interact with a magnetic element 124 (see Figure 5) to retain and hold the magnetic element 124 in position relative to the base wall 136 of the coolant sump 100. As best shown in Figure 5, the magnetic element 124 is generally rectangular in plan, with rounded corners, opposite short sides 126, 128, and opposite long sides 130, 132. An array of through holes 120 is formed vertically through the magnetic element 124. It will be appreciated that the magnetic element 124 can take other shapes and configurations in other embodiments. Turning to Figures 6 to 8, there is shown a sequence of steps involved in installing the magnetic element 124 in the coolant sump 100. In Figure 6, the edges of the magnetic element 124 adjacent to the short sides 126, 128 initially engage the upper ramped surfaces 160 of the pawls 118. Since the elongate portions 116 are flexible, further downward movement of the magnetic element 124 causes the pawls 118 to be pushed away as the magnetic element 124 slides down the upper ramped surfaces 160, until the pawls 118 start to traverse the short sides 126, 128 as shown in Figure 7. Yet further downward movement causes the upper edges of the short sides 126, 128 to engage the lower ramped surfaces 162 of the pawls 118. The inwardly directed restorative forces on the pawls 118, provided by the resilience of the elongate portions 116, cause the lower ramped surfaces 162 to push the magnetic element 124 downwards, until it reaches the position shown in Figure 8. Once installation of the magnetic element 124 is complete as shown in Figure 8, the underside surface of the magnetic element 124 engages the upper surfaces 110 of the first and second abutment members 106, 108. In this position, the lower ramped surfaces 162 hold the magnetic element 124 against the upper surfaces 110 of the first and second abutment members 106, 108. The magnetic element 124 is therefore retained in a position above the base wall 136. A space 138 formed between the lower surface of the magnetic element 124 and the corresponding upper surface of the base wall 136 allows, in use, coolant to flow between the magnetic element 124 and the base wall 136 of the coolant sump 100. The positions and configurations of the abutment members 106,108 are such that they allow, when the coolant sump is in use, movement of coolant into and through the holes 126. This is assisted by ensuring that none of the holes 126 is covered by the abutment members 106, 108. In other embodiments, it may be acceptable for some of the holes to be partly or wholly covered by the abutment members 106, 108. The magnetic element 124 captures ferromagnetic particles that are distributed through the coolant. Such particles can arise from wear of steel components within the EDU 144, for example. The particles can increase component wear rates, and so it is desirable to remove them from the coolant. The holes 120 in the magnetic element 124 increase its surface area. By spacing the magnetic element 124 off the base wall 136, coolant can contact both ends of the holes 120, which increases contact with passing fluid. This may, in turn, increase the rate at which wear particles are removed from the coolant. Turning to Figures 9 to 15, there is shown a coolant sump 202, in accordance with a further embodiment of the invention. The coolant sump 202 shares several features with the coolant sump 100, and like features are indicated with like reference signs in the coolant sump 100 and the coolant sump 202. Coolant sump 202 is configured for use with a magnetic element 224, as best shown in Figure 11. The magnetic element 224 shares several features with the magnetic element 124, and like features are indicated with like reference signs in the magnetic element 124 and the magnetic element 224. The coolant sump 202 comprises locating features for laterally positioning, in use, the magnetic element 224 relative to the base wall 136. In the embodiment of Figures 9 to 15, the locating feature comprises two posts 140 extending upwardly from the base wall 136. Each post 140 is stadium- orobround-shaped in cross-section, although any other cross-sectional shape may be used in other embodiments. Each post 140 terminates with a tapered portion to assist with alignment of the magnetic element 224 during installation. As best shown in Figure 11, the magnetic element 224 has alignment apertures 142 that are complementary in cross-sectional shape with the corresponding posts 140. Installation of the magnetic element 224 into the coolant sump 202 is similar to installation of the magnetic element 124 into the coolant sump 100. However, the alignment apertures 142 of the magnetic element 224 must be aligned with the posts 140 as the magnetic element 224 is lowered towards the first and second retention features 112, 114. Optionally, the size and / or shape of the posts 140, the corresponding apertures 142, and / or the holes 120, may be selected such that it is not possible to accidentally push the posts 140 through the holes 120. Once the magnetic element 224 is installed, the posts 140 prevent lateral movement of the magnetic element 224 relative to the base wall 136. This helps stabilize the magnetic element, which may reduce flexing and hence long-term fatigue of the retention features 112,114. Optionally, a single post 140 can be used. Optionally, such a single post can be non-circular in cross section, and the corresponding aperture 142 configured to key to the post 140 to constrain rotation of the magnetic element after installation into the sump. A single post can also be circular, which will still at least restrain lateral movement of the magnetic element. Alternatively, multiple posts and apertures can be provided (e.g., as shown in Figures 9 to 15), which will again constrain rotation of the magnetic element after installation into the sump. It will be appreciated that other arrangements can be used to laterally locate a magnetic element (such as magnetic element 124) installed on a coolant sump according to embodiments of the invention. For example, one or peripheral abutment features (not shown) may be provided adjacent to one or more of the sides or corners of the magnetic element, on one or more of the abutment members and / or as a separate component. In other embodiments, the at least one abutment member comprises one or more abutment posts. Figures 16 and 17 show a coolant sump 302 according to a further embodiment of the invention. Instead of the abutment members 106, 108 of other embodiments described above, the coolant sump 302 includes abutment posts 146. Each abutment post 146 is cylindrical and extends upwardly from the base wall 136. The coolant sump 302 has four abutment posts 146 (one is not visible in Figure 16 because it is behind the second retention feature 114), positioned near corners of the magnet 224, but any other suitable number and positions of abutment posts can be used in different embodiments. As with the abutment members 106,108, the abutment posts 146 can be positioned such that they allow, when the coolant sump is in use, movement of coolant into the holes 126. The process for installing the magnetic element 224 into the coolant sump 302 is similar to that described above in relation to Figures 12 to 14. However, when the magnetic element 224 reaches the installed position, it rests on the tops of the abutment posts 146. In other embodiments, the magnetic element can have more, fewer, or no holes. Alternatively, or in addition, the magnetic element may have one or more turbulating features, such as recesses, ridges, and / or other formations that tend to turbulate coolant as it passes across them. The use of holes and / or turbulating features tends to increase contact between the coolant and the surface of the magnetic element, which may increase the rate at which particles are captured from the coolant. In yet other embodiments, some or all of the surfaces of the magnetic element are flat or at least do not include holes or turbulating features. Irrespective of the presence, absence, number, and / or configuration of any holes or turbulating features, the spacing of the lower surface of the magnetic element from the base wall of the coolant sump by the one or more abutment features provides an increased area for coolant to be in contact with the magnetic element. In other embodiments, at least one of the at least one abutment member and at least one of the at least one retention feature comprise a unitary element extending from the base wall 136. Figure 18 shows a coolant sump 402 including firstand second unitary elements 168,170. Each of the unitary elements 168,170 extends upwardly from the base wall 136, and terminates at a pawl 118 having an upper ramped surface 160 and a lower ramped surface 162, similar to the pawl 118 described above in relation to other embodiments. Each of the unitary elements 168, 170 also includes an abutment member in the form of a laterally extending shelf 172 disposed between the pawl 118 and the base wall 136. As shown in Figure 18, when installed, the magnetic element 242 is retained between the shelf 172 and the lower ramped surface 162. It will be appreciated that unitary and non-unitary elements can be used together in the same embodiment. For example, Figure 19 shows a further embodiment of a coolant sump 502 including a unitary element 168 similar to that shown in Figure 18, and an abutment post 146. Many other combinations of unitary and non-unitary elements will suggest themselves to the skilled person. Figures 20 to 22 show a further embodiment of a coolant sump 602 including a unitary element 152. The unitary element 152 includes a base portion 154 that extends upwardly from the base wall 136. A shelf 156 is formed at the top of the base portion 154. The shelf 156 and base portion 154 form an abutment member. The unitary element 152 includes retention features in the form of first and second laterally spaced apart members 158, 160, which extend upwardly from the shelf 156. Each of the members 158,160 terminates at a pawl 162. The members 158, 160 are flexible, such that they can move inwards towards each other as described below. A magnetic element 164 for use with the coolant sump 602 includes a central aperture 166. The magnetic element 324 is installed onto the unitary element 152 by aligning the central aperture 166 with the upper end of the members 158,160 and pushing the magnetic element downwards. Interaction between lower edges of the central aperture 166 and the pawls 162 cause the pawls 162, and hence the members 158, 160, to move towards each other. Further downward movement of the magnetic element 164 causes the pawls 162 to pass through the central aperture 166, until they exit the central aperture 166, allowing the members 158, 160 to move outwards towards their original position. This locks the magnetic element 164 into place relative to the unitary element 152, as shown in Figure 18. It will be appreciated that unitary elements having other shapes, configurations, and operating mechanisms can be employed in other embodiments. Some or all of the abutment member(s) and / or the retention feature(s) can be moulded, additively printed, and / or otherwise formed as part of the coolant sump. Alternatively, some or all of the abutment member(s) and / or the retention feature(s) can be formed separately and attached to the coolant sump, for example by way of an adhesive, one or more mechanical fasteners, welding, or the like. In alternative embodiments, one or more of the retention features and / or abutment members is supported by and / or extends from the sidewall 104. For example, an abutment member and / or a retention feature can be formed in or on the sidewall 104. While several of the embodiments described above use moveable retention features, it will be appreciated that at least some of the retention features may remain stationary during installation of the magnetic element. For example, one retention feature may remain stationary while a retention feature positioned on an opposite side of the magnetic element moves laterally during installation. 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.

Claims

1. A coolant sump for an electric drive unit, EDU, the coolant sump comprising:at least one abutment member for abutting, in use, a magnetic element, thereby to maintain a space between the magnetic element and a base wall of the coolant sump, so as to allow, in use, coolant to flow between the magnetic element and the base wall of the coolant sump; andat least one retention feature for retaining, in use, the magnetic element within the coolant sump.

2. The coolant sump of claim 1, wherein the at least one abutment member comprises at least one formation extending upwardly from the base wall.

3. The coolant sump of claim 2, wherein the at least one formation comprises:at least one post; and / orat least one rib or wall extending along a portion of the base wall.

4. The coolant sump of claim 3, comprising at least two of the ribs or walls, the ribs or walls being disposed and configured to abut, in use, opposite sides of the magnetic element.

5. The coolant sump of any preceding claim, wherein at least one of the at least one abutment member and / or at least one of the at least one retention feature are defined or formed by one or more elements extending from the base wall of the sump.

6. The coolant sump of claim 5, wherein at least one of the at least one abutment member and at least one of the at least one retention feature define a unitary element extending from the base wall.

7. The coolant sump of any preceding claim, wherein the at least one abutment member and the at least one retention feature are moulded as part of the coolant sump.

8. The coolant sump of any preceding claim, comprising the magnetic element retained in position relative to the base wall by the at least one abutment member and the at least one retention feature.

9. The coolant sump of claim 8, wherein the at least one abutment member is positioned and configured such that it allows, when the coolant sump is in use, movement of a coolant fluid into one or more recesses and / or apertures formed on or through the magnetic element.

10. The coolant sump of any one of claims 7 to 9, wherein the retention feature comprises a pawl configured to engage, in use, the magnetic element so as to retain it within the coolant sump.

11. The coolant sump of claim 10, wherein the at least one retention feature comprises a flexible portion comprising the pawl.

12. The coolant sump of any one of claims 7 to 11, comprising at least one locating feature for laterally positioning, in use, the magnetic element relative to the base wall.

13. The coolant sump of claim 12, the or each locating feature comprising a post extending from the base 5 wall for engaging, in use, an aperture or recess in the magnetic element.

14. An electric drive unit, EDU, comprising the coolant sump of any preceding claim.

15. A vehicle comprising the electric drive unit, EDU, of claim 14.

Images