Oil sump

Abstract

An oil sump (100 Fig. 2) has a chamber 101 for retaining oil. The chamber has a drainage outlet 150 that includes a removable plug 140 for sealing the drainage outlet. In use, oil drawn from the sump by a pump (200 Fig. 5) is filtered by a mesh strainer 129. The mesh is removable from the oil sump through the drainage outlet, which makes it possible to remove and replace the mesh with either a new mesh or a cleaned original mesh, but without substantial disassembly of the oil sump or the need to provide an additional opening in the oil sump through which the mesh can be extracted. Therefore, in practice, the oil will be drained from the sump before or while the mesh is being removed. The mesh may be attached to the removable plug, or it may be located proximate to the drainage outlet, and the arrangement may find use beneath an electric drive unit (10 Fig. 5) of an electric vehicle (1 Fig. 1).

Description

TECHNICAL FIELD The present disclosure relates to an oil sump. Aspects of the invention relate to an oil sump, a vehicle comprising an oil sump, and a method of replacing a mesh in an oil sump. BACKGROUND An electric vehicle is provided with one or more electric drive units which receive electrical energy from a vehicle battery and generate torque for propelling the vehicle using an electric motor. The electric drive unit may be oil lubricated, with the oil being pumped into the electric drive unit from an oil sump provided below the electric drive unit, into which oil pools under gravity from the electric drive unit. Overtime, it is possible that debris may find its way into the recirculating oil. To address this problem, a mesh may be fitted into the oil sump during assembly and will accumulate debris over the life of the unit, filtering it out before the oil is pumped back into the electric drive unit. However, the mesh may also deteriorate over the life of the sump. 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 an oil sump, a vehicle comprising an oil sump, and a method of replacing a mesh in an oil sump as claimed in the appended claims. According to an aspect of the invention, there is provided an oil sump, comprising: a chamber for retaining oil, the chamber having a drainage outlet; a removable plug for sealing the drainage outlet; a mesh for filtering oil being drawn from the oil sump by a pump; wherein the mesh is removable from the oil sump through the drainage outlet. This removes makes it possible to replace the mesh, enabling the mesh to be a cleanable or disposable part distinct from the oil sump as a whole. More particularly, this makes it possible to remove the mesh without substantial disassembly of the oil sump, and without providing an additional opening in the oil sump through which the mesh can be extracted. The mesh may be disposed, in use, proximate the drainage outlet. This enables easy extraction of the mesh from the oil sump through the drainage outlet. The mesh may be attached or attachable to the removable plug. In this way, both the plug and the mesh may be removed from the oil sump in a single step, and a need to reach into the drainage outlet to retrieve the mesh may be removed. The drainage outlet and removable plug may comprise respective mating formations, the mating formation of the drainage outlet being at a mouth of the drainage outlet. The mating formations may comprise screwthreading. Compared with a drainage outlet used only to drain oil from the sump, the present technique may make use of a larger drainage outlet, to accommodate removal and insertion of the mesh (and in some cases a tool or the hand of an installer). The chamber may be defined by a top shell and a bottom shell, the top shell being disposed in use immediately beneath an electric drive unit of a vehicle, and the drainage outlet being formed in the bottom shell. The mesh may be disposed in use more proximate to the bottom shell than the top shell. The top shell and the bottom shell may be welded (or otherwise permanently joined) together. A pickup pipe for delivering oil from the chamber towards the pump may be formed in the top shell, the pickup pipe having a mouth proximate the mesh. In such a structure, retrieval of the mesh from the top of the oil sump may be difficult or impossible due to the mouth of the pickup pipe impeding access to the mesh. By withdrawing the mesh from the bottom shell, through a drainage outlet generally lined up with the mesh (and the mouth of the pickup pipe), this problem can be averted. According to another aspect, there is provided a vehicle comprising an electric drive unit and an oil sump according to the above, wherein the pump is configured to pump oil from the oil sump through the mesh and to the electric drive unit. According to another aspect of the invention, there is provided a method of replacing a mesh in an oil sump according to the above, comprising removing the removable plug from the drainage outlet, and removing the mesh from the sump through the drainage outlet. Embodiments of the present technique propose a geometry which may replace conventional sump plug designs with a design that incorporates part of the pick-up into the plug design. A larger O-ring may be used to seal the plug. The mesh may be retained with plastic clips that are built into the plug geometry. The service life of the sump could potentially be extended by having a geometry that makes the mesh a replaceable item. 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 any way 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 schematic representation of a vehicle formed having an electric drive unit to be lubricated with oil from a sump; Figure 2 shows a schematic 3D view of an oil sump; Figure 3 shows a schematic plan view of an upper shell of the oil sump of Figure 2; Figure 4 shows the schematic view of Figure 3 with a pump attached; Figure 5 shows the oil sump in situ beneath an electric drive unit; Figure 6 shows a cross-sectional schematic view through a portion of the oil sump including a pickup pipe and mesh; Figure 7 shows a more detailed schematic view of the pickup pipe, mesh and plug; Figure 8 shows a view of Figure 7 with the mesh and plug removed; and Figure 9 shows a view of Figures 7 and 8 with the mesh removed from the plug. DETAILED DESCRIPTION An oil sump, a vehicle comprising an oil sump, and a method of replacing a mesh in an oil sump in accordance with embodiments of the present invention are described herein with reference to the accompanying figures 1 to 9. With reference to Figure 1, there is illustrated a simplified top view of a vehicle 1. The vehicle 1 is an electric vehicle having an electric drive unit (EDU) 10 which receives electrical energy from a battery 20 and generates torque which is delivered via a powertrain to the wheels of the vehicle 1. The electric drive unit 10 comprises a motor for generating torque, power electronics (for drawing electrical power from the vehicle battery 20 and delivering it to the motor as an AC voltage), and a transmission including a gearbox for delivering the torque to the wheels at the most appropriate gear ratio. The electric drive unit 10 uses oil to lubricate certain moving parts of the motor and transmission. This oil is pumped into the appropriate part of the main housing of the electric drive unit 10, and in use moves under gravity to the bottom of the housing of the electric drive unit 10 to pool in a sump (described subsequently), from which it can be pumped back into the main housing of the electric drive unit 10. Shown in Figures 2, 3 and 4 is an oil sump 100, suitable for being positioned at the base of (immediately beneath) the electric drive unit 10. Figure 2 shows the exterior of the oil sump 100. The oil sump 100 can be seen from Figure 2 to comprise an upper shell 120 and a lower shell 130. These are welded together to form a chamber 101 for holding oil. The electric drive unit 10 is positioned in use above the upper shell 120. Figure 3 shows a plan view of the upper shell 120. The upper shell 130 can be seen to comprise a plurality of openings 122. These align with openings in the base of the EDU 10 not visible), and receive oil from the EDU 10, entering the openings 122 under gravity. Oil in the chamber 101 is drawn up a pickup-pipe 126 which has one end close to a base of the chamber 101 (proximate the lower shell 130) and another end which terminates at a connector 126a. As shown in Figure 4, a pump 200 is connected to the connector 126a, and is connected also to a connector 124c, which leads to a high-pressure conduit 124b integrated into the upper shell 120. A pipe 124a is a continuation of the high-pressure conduit 124b and extends upwardly from the upper shell 120, towards and into the main body of the electric drive unit 10, where it is delivered to parts of the electric drive unit 10 to be lubricated. Figure 5 shows the electric drive unit 10, the sump 100 and the pump 200 in an assembled state. It can be seen that the electric drive unit 10 is disposed immediately above the sump 100. Oil moves from the electric drive unit 10 into the sump 100 via the openings 122 under gravity (at low pressure), and from the sump 100 into the electric drive unit 10 via the pump 200 and the high-pressure conduit and pipe 124b, 124a under high pressure, as generated by the pump 200. In this way, the oil is recirculated through the electric drive unit 10. A breather pipe 128 extends upwardly from the upper shell 120, and provides an opening between the chamber within the sump 100 and atmospheric pressure, to reduce air lock forming in the sump 100. Referring to Figure 6, a cross-sectional view of a portion of the sump 100 is provided. A portion of both the top shell 120 and the bottom shell 130 are visible, and the space between these defines the chamber 101 for holding the oil. The pick-up pipe 126 can be seen to extend from a pick-up mouth 127 near the base of the chamber 101. Directional arrows A show the flow path from the main body of the chamber 101 and into the mouth 127, then along the pipe 126 and out of the sump 100 (towards and to the electric drive unit 10). A mesh 129 is provided within or at the mouth 127 to inhibit debris I solids from being drawn into the pick-up pipe 126 and carried to the pump 200. The mesh may have any shape, but in the present example has a frustoconical part which bears apertures or perforations through which the oil may pass while being filtered for solid (a peripheral part of the mesh 129 may be without apertures I perforations). Such solids could damage the pump, or reduce its pumping efficiency and / or pressure. In Figure 6 a plug 140 is present in a drainage outlet 150 in the lower shell 130. The drainage outlet 135 is sealed (and sealable) with the plug 140, which is removable. While the plug 140 is in place, the bottom portion of the chamber 101, and in particularthe drainage outlet 150, is sealed. When the plug 140 is removed, oil is able to drain from the chamber 101, emptying the sump 100 of oil. The mesh 129 is removable from the oil sump through the drainage outlet 150, at the time of or following removal of the plug 140. In practice this means that the oil will be drained from the sump 10 before or while the mesh 129 is being removed. The purpose of removing the mesh 129 is to either replace it with a new one, orclean it. After this, the replacement mesh or cleaned original mesh can be reinstated in the sump 10 through the drainage outlet 150, and the plug 140 reinserted to re-seal the drainage outlet 150. It will be appreciated that it is desirable to minimise the number of openings in the base of the sump 100, and that providing access through the upper shell 120 is not practical due to the presence of the pickup pipe (which is formed as part of the upper shell 120) immediately above the mesh 129, and due to the mesh 129 and mouth 127 of the pickup pipe 126 being closer to the lower shell 130 than the upper shell 120 (it is a requirement that oil be drawn from near the base of the chamber 101, where oil is most likely to be present). By coinciding the mesh location with the drainage outlet 150, the drainage outlet 150 can provide the dual purpose of permitting the oil to be drained from the sump 100, and permitting removal and cleaning or replacement of the mesh 129. Figure 7 shows the vicinity of the drainage outlet 150 with the plug 140 in situ. The mesh 129 can be seen to be mounted to or at the inside of the plug 140, and in use at least partially recessed into a mouth of the pickup pipe 126. In alternative embodiments the mesh 129 may be not received within the mouth of the pick-up pipe 126, but may instead be provided at or over the mouth. In any case, the mesh is disposed, in use, proximate the drainage outlet. A seal 170 is provided at the mouth of the drainage outlet 150, in this case at the mouth of the drainage outlet 150. The plug 140 engages with this seal 170 to prevent or at least inhibit oil leakage while the plug 140 is in place. Figure 8 shows the drainage outlet 150 with the plug 140 removed. As can be seen from Figure 8, the mesh 129 is attached to the plug 140, and in particular is retained in place with clips 160 that are built into the plug geometry. The clips 160 may be formed of plastic. In some implementations the mesh 129 may be permanently attached to the plug 140, with the plug 140 and mesh 129 together being a throwaway component. In other implementations the mesh 129 is removably attached / attachable to the plug 140. In still further implementations the mesh 129 is merely trapped in place between the mouth of the pickup pipe 126 and the plug 140, or between the plug 140 and an internal structure of the sump 100. In these implementations, since the plug 140 when fully inserted into the drainage outlet 150 is closely proximate to, or in contact with, or even includes, the mesh 129, the plug 140 is either at least partially hollow or bears channels for delivering oil from the chamber of the sump 110 towards and to the pickup pipe via the mesh 129. In alternative implementations the plug may be of a shallower design and not in contact with the mesh 129, permitting oil to reach the mesh 129 through a gap between the mesh 129 and the plug 140. In such a case formations or fixtures will be required in the sump to retain the mesh 129, rather than the plug 140 providing this function. For example, the clips 160 may be provided as part of the internal structure of the sump 100 rather than as part of the plug 140. In Figures 7 to 9 the end of the plug 140 proximate and facing the mesh 129 is open, or comprises one or more openings, and openings 190 are provided in at least a portion of the sides of the plug 140, to permit oil to enter the plug laterally before being drawn through the mesh 129 and into the pickup pipe 126. In Figures 8 and 9 it can be seen that the drainage outlet 150 and removable plug 140 comprise respective mating formations. In this case the mating formations comprise screw-threading. In particular, the mouth of the drainage outlet 150 comprises screw threading 172 while the plug 140 comprises screw threading 180. The plug 140 can therefore be screwed into the drainage outlet 150 using the screw threading 172,180. This provides the seal referred to above. A large O ring may also be used (not shown) to improve the seal. The O ring may be trapped between the plug 140 and the periphery of the drainage outlet, and compressed by the action of screwing the plug 140 into the drainage outlet 150 to provide a tight seal. With the structure described above, a simple method of replacing a mesh in an oil sump may be provided. In particular, the removable plug 140 may first be removed from the drainage outlet 150 of the sump 100, in the present example by unscrewing it from the drainage outlet 150. The mesh 129 either comes away with the plug 140 (if attached to or part of the plug 140), or is initially left in place within the oil sump 100, preferably until the oil has drained from the sump 100 out of the drainage outlet 150. At that point the mesh 129 is removed from the sump 100. If the mesh 129 is attached to or part of the plug 140, it may be removed from the plug 140. In either scenario, the mesh 129 may then either be cleaned, or discarded in favour of a new mesh 129. Where the mesh 129 is attachable to the plug 140, it is then attached to the plug 140 and the plug 140 reinserted into, and screwed into, the drainage outlet 150, thereby restoring the mesh 129 to its position near the mouth of the pickup pipe. Alternatively, if the mesh 129 is separate from the plug 140, it is inserted into the sump 100 through the drainage outlet and mounted in place at the mouth of the pickup pipe, with the 5 plug 140 then being reinserted into, and screwed into, the drainage outlet 150 to seal the sump 100. In some implementations the mesh may be an integral part of the plug 140. In this case, the plug 140 as a whole may be replaceable (thereby replacing the mesh 129), or the mesh 129 may be cleaned as part of the plug 140, and the plug reinserted into the drainage outlet 150. 10 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. 15

Claims

1. An oil sump, comprising:a chamber for retaining oil, the chamber having a drainage outlet;a removable plug for sealing the drainage outlet;a mesh for filtering oil being drawn from the oil sump by a pump;wherein the mesh is removable from the oil sump through the drainage outlet.

2. The oil sump according to claim 1, wherein the mesh is disposed, in use, proximate the drainage outlet.

3. The oil sump according to claim 1, wherein the mesh is attached or attachable to the removable plug.

4. The oil sump according to any preceding claim, wherein the drainage outlet and removable plugcomprise respective mating formations, and wherein the mating formation of the drainage outlet is at a mouth of the drainage outlet5. The oil sump according to claim 4, wherein the mating formations comprise screw-threading.

6. The oil sump according to any preceding claim, wherein the chamber is defined by a top shell and abottom shell, the top shell being disposed in use immediately beneath an electric drive unit of a vehicle, and the drainage outlet being formed in the bottom shell.

7. The oil sump according to claim 6, wherein the mesh is disposed in use more proximate to the bottom shell than the top shell.

8. The oil sump according to claim 6 or claim 7, wherein the top shell and the bottom shell are welded together.

9. The oil sump according to any one of claims 6 to 8, wherein a pickup pipe for delivering oil from the chamber towards the pump is formed in the top shell, the pickup pipe having a mouth proximate the mesh.

10. A vehicle comprising an electric drive unit and an oil sump according to any preceding claim, wherein the pump is configured to pump oil from the oil sump through the mesh and to the electric drive unit.

11. A method of replacing a mesh in an oil sump according to any one of claims 1 to 10, comprising removing the removable plug from the drainage outlet, and removing the mesh from the sump through the drainage outlet.

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