Electric drive unit housing

Abstract

A housing 100a for an electric vehicle electric drive unit comprises a cast body in which a first network of tubes 125a-125e for delivering coolant and a second network of tubes 125f-125g for deliveri

Description

TECHNICAL FIELD The present disclosure relates to an electric drive unit housing. Aspects of the invention relate to an electric drive unit housing, a method of manufacturing an electric drive unit housing, an electric drive unit and a vehicle. BACKGROUND An electric vehicle may include an electric drive unit (EDU) to propel it. To this end, the EDU usually includes an electric motor and a gearbox, both of which are arranged within a housing in the form of a metal casting. The EDU is provided with a lubricant delivery system to deliver lubricant (e.g., oil) to each of the electric motor and the gearbox. The lubricant reduces friction, and hence ensures smooth operation and prolongs the lifespan of these components. The lubricant also provides cooling, thereby preventing overheating and ensuring effective performance and longevity of these components. To convey the lubricant, a first plurality of bores is defined within the metal casting housing. These bores define conduits or galleries that extend through the metal casting housing to allow lubricant to be delivered to the electric motor and the gearbox. During operation of the EDU, the lubricant is warmed by the components of the EDU. The lubricant is conveyed through a heat exchanger designed to cool the lubricant as it passes through. To ensure such cooling, the EDU is provided with a coolant delivery system that is arranged to deliver coolant to the heat exchanger to cool the heat exchanger and hence the lubricant passing through. The coolant itself may then be cooled by a radiator of the vehicle. When the heat exchanger is mounted on the EDU, a second plurality of bores may be defined within the metal casting housing to convey the coolant through the EDU and to the heat exchanger. These bores define conduits or galleries that extend through the metal casting housing to allow the coolant to be delivered to the heat exchanger. To manufacture the EDU housing with such a network of bores, two different methods have been employed up until now: (i) a high pressure die casting (HPDC) method and (ii) a low pressure die casting (LPDC) and sand mould method. Each of these methods will now be briefly overviewed. The high pressure die casting (HPDC) method begins with providing a die or mould in the shape of the EDU housing to be formed. Then, molten metal is forced under pressure into the securely locked die cavity, where it is held by a powerful press until the metal solidifies. With HPDC, the metal is injected into the mould under considerable pressure (e.g., between 1,500 and 25,400 psi). After the EDU housing is cast, bores are drilled into and through the metal casting to form the conduits of the lubricant delivery system and the coolant delivery system. To enclose the lubricant and coolant delivery systems within the EDU housing, plugs made of steel are inserted into the bores at the boundary of the metal casting. Disadvantages of this HPDC method include limited design freedom and the need for expensive tooling. The low pressure die casting (LPDC) and sand mould method also begins with providing a die in the shape of the EDU housing to be formed. Thereafter, a sand mould is constructed within the die. This sand mould is made out of a mixture of sand and a binder material (such as resin). The sand mould is constructed in the shape of the conduits of the lubricant and coolant delivery systems. To this end, different sections of the sand mould may be constructed separately and then glued together with an adhesive. To ensure the correct position of the sand mould within the EDU housing die, the sand mould is provided with legs that are also made out of the sand and binder mixture. Once the sand mould is complete, the EDU housing is cast using low pressure die casting (LPDC), by pouring molten metal into the steel mould and letting it set around the sand mould. The pressure is typically in the range 2 - 15psi. After the EDU housing is cast, heat and vibrations are applied to the sand mould, causing the resin to burn off and the sand mould to breakdown. Again, to close off the openings in the EDU housing (where the legs of the sand mould used to be), plugs made of steel are inserted into the bores formed around the outside of the EDU casting. The LPDC and sand mould method is difficult to perform because of the fragile sand mould, and it allows only simple networks and conduits and galleries with sharp bends to be produced. 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 electric drive unit housing, a method of manufacturing an electric drive unit housing, an electric drive unit and a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided an electric drive unit housing for a vehicle, the electric drive unit housing comprising: a casting; and a delivery system embedded within the casting for delivering coolant and / or lubricant around the electric drive unit housing, wherein the delivery system comprises a network of tubes through which coolant and / or lubricant are conveyed in use, and wherein, in use, the tubes provide a barrier between the metal casting around the tubes and the coolant and / or lubricant within the tubes, wherein the network is made from a first metal and the casting is made from a second metal, and wherein the first metal has a higher melting point than the second metal. The casting may be cast around the delivery system. Optionally, at least one of the tubes may be curved. In an embodiment, at least one of the tubes has a smooth bend, i.e. a bend that has a gradual and continuous change in direction, e.g., characterized by a gentle curve without any abrupt angles or points. The LPDC and sand mould method of the prior art can only produce conduits or galleries with sharp bends, i.e. bends that have an abrupt and / or distinct change in direction, due to how the sand mould is fabricated together. However, with the present invention, when the casting is cast around the delivery system, it is possible to embed tubes of any shape within the metal casting (including those that are curved or that have smooth bends). As a result, the fluid(s) passing through the tubes experience fewer pressure drops. Optionally, the electric drive unit housing may further comprise an electric motor opening defined in the casting for receiving an electric motor and the delivery system may comprise a lubricant delivery system for delivering lubricant to the electric motor opening. The lubricant delivery system may comprise at least one lubricant tube through which lubricant is conveyed in use, the at least one lubricant tube forming part of the network of tubes. In an embodiment, the electric drive unit housing further comprises a gearbox opening defined in the casting for receiving a gearbox. The lubricant delivery system may be further configured to deliver lubricant to the gearbox opening. Optionally, the electric drive unit housing may further comprise a heat exchanger mounting point on the casting for mounting a heat exchanger and the delivery system may comprise a coolant delivery system for delivering coolant to the heat exchanger mounting point. The coolant delivery system may comprise at least one coolant tube through which coolant is conveyed in use, the at least one coolant tube forming part of the network of tubes. Optionally, the lubricant delivery system and the coolant delivery system may be fluidly distinct. ‘Fluidly distinct’ means that the lubricant delivery system and the coolant delivery system are arranged in such a way that the lubricant in the lubricant delivery system cannot move ortransferto the coolant delivery system and the coolant in the coolant delivery system cannot move ortransferto the lubricant delivery system. Optionally, the delivery system may further comprise at least one arm connecting the lubricant delivery system and the coolant delivery system. Optionally, the delivery system may further comprise at least one solid metal support attached to the network. The at least one solid metal support may extend from the network, through the casting and to an outer boundary of the casting. Providing the metal network with the at least one solid metal support beneficially allows the metal network to be held in the right position during casting. In an embodiment, the at least one solid metal support is attached to and extends from at least one of the tubes. The at least one solid metal support may be made of the first metal. In an embodiment, the first metal may be mild steel or stainless steel and / or the second metal may be aluminium. According to another aspect of the present invention, there is provided a method of manufacturing an electric drive unit housing for a vehicle, the method comprising: fabricating a delivery system, wherein the delivery system comprises a network of tubes through which coolant and / or lubricant are conveyed in use; and casting a casting around the delivery system so that the delivery system is embedded within the casting, and wherein the metal network is made from a first metal and the casting is made from a second metal, and wherein the first metal has a higher melting point than the second metal. Optionally, casting the casting comprises defining an electric motor opening in the casting for receiving an electric motor. Fabricating the delivery system may comprise fabricating a lubricant delivery system comprising a motor feed tube for opening into the electric motor opening to allow delivery of lubricant to the electric motor opening. Optionally, the casting may be shaped to define an electric motor opening for receiving an electric motor. The delivery system may comprise a lubricant delivery system comprising a motor feed tube that opens into the electric motor opening to allow delivery of lubricant to the electric motor opening. In an embodiment, casting the casting comprises defining a heat exchanger mounting point on the casting for mounting a heat exchanger. Fabricating the delivery system may comprise fabricating a coolant delivery system comprising a heat exchanger coolant feed tube for opening out to the heat exchanger mounting point to allow delivery of coolant to the heat exchanger mounting point. In an embodiment, the casting is shaped to define a gearbox opening for receiving a gearbox. After lubricant is delivered to the electric motor, the electric motor may then deliver the lubricant to the gearbox opening e.g., via at least one drilling or bore in the casting of the EDU housing. Optionally, the casting may further be shaped to define a heat exchanger mounting point on the casting for mounting a heat exchanger. The delivery system may comprise a coolant delivery system comprising a heat exchanger coolant feed tube that opens out to the heat exchanger mounting point to allow delivery of coolant to the heat exchanger mounting point. In an embodiment, fabricating the delivery system comprises forming the tubes separately and subsequently joining the tubes together to form the network. The tubes may be formed by way of bending and / or cutting pre-formed tubes and the tubes may be joined together by way of furnace brazing. This avoids having to form the entire metal network in one go. Optionally, the metal network may comprise an inlet tube through which coolant and / or lubricant is conveyed into the delivery system in use, and an outlet tube through which coolant and / or lubricant is conveyed out of the delivery system in use. The delivery system may be fabricated so that each of the inlet and outlet tubes comprises a closed offend. The method may further comprise machining an inlet bore through the casting and the closed off end of the inlet tube to define an inlet of the delivery system from outside of the electric drive unit housing, and machining an outlet bore through the casting and the closed end of the outlet tube to define an outlet of the delivery system to the outside of the electric drive unit housing. The delivery system may be fabricated so that each of the inlet and outlet tubes comprises an open end opposite the closed offend. In an embodiment, the inlet tube may be the lubricant inlet tube and the outlet tube may be the lubricant outlet tube such that the inlet and outlet of the lubricant delivery system are defined thereby and / or the inlet tube may be the coolant inlet tube and the outlet tube may be the coolant outlet tube such that the inlet and outlet of the coolant delivery system are defined thereby. Optionally, the delivery system may further comprise at least one solid metal support attached to and extending from the metal network. The casting may be cast around the delivery system so that the at least one solid metal support extends through the casting and to an outer boundary of the casting. Providing the metal network with the at least one solid metal support beneficially allows the metal network to be held in the right position during casting. In an embodiment, fabricating the delivery system comprises forming the metal network and the at least one solid metal support separately and subsequently joining the metal network and the at least one solid metal support together. In an embodiment, the metal network and the at least one solid metal support may be formed by way of cutting and / or bending of preformed tubes and / or parts and the metal network and the at least one solid metal support may be joined together by way of furnace brazing. This avoids having to cast the entire delivery system in one go. In an embodiment, the delivery system may further comprise at least one arm connecting the lubricant delivery system and the coolant delivery system. Fabricating the delivery system may comprise forming the tubes of the lubricant and coolant delivery systems and the at least one arm separately and subsequently joining them together. In an embodiment, the at least one solid metal support and / or the at least one arm is made of the first metal. In an embodiment, the first metal may be mild steel or stainless steel and / or the second metal may be aluminium. According to another aspect of the present invention, there is provided to an electric drive unit for a vehicle, comprising the electric drive unit housing described above or the electric drive unit housing made according to the method described above. In an embodiment, the electric drive unit comprises an electric motor received within the electric motor opening of the casting and / or a gearbox received within the gearbox opening and / or a heat exchanger mounted on the heat exchanger mounting point. According to another aspect of the present invention, there is provided a vehicle comprising the electric drive unit housing described above, the electric drive unit housing made according to the method described above, or the electric drive unit described 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 perspective view of a first electric drive unit housing according to an embodiment of the invention; Figure 2 shows a perspective view of a second electric drive unit housing according to an embodiment of the invention; Figure 3 shows a schematic top-down view of a vehicle comprising the electric drive unit housing of Figure 1 and the electric drive unit housing of Figure 2; and Figure 4 shows a flowchart showing a method of manufacturing the electric drive unit housing. DETAILED DESCRIPTION First and second electric drive unit (EDU) housings 100a, 100b in accordance with embodiments of the present invention are described herein with reference to the accompanying Figures 1 and 2. As shown in Figure 3, the first electric drive unit housing 100a of Figure 1 is installed in the rear of a vehicle 300, while the second electric drive unit housing 100b of Figure 2 is installed in the front of the vehicle 300. Each electric drive unit housing 100a, 100b comprises a casting 105 and a delivery system 115 embedded within the casting 105 fordelivering coolant and / or lubricant around the electricdrive unit housing. The delivery system 115 comprises a network 120 of tubes 125 through which coolant and / or lubricant are conveyed in use, and, in use, the tubes 125 provide a barrier between the metal casting 105 around the tubes 125 and the coolant and / or lubricant within the tubes 125. The network 120 is made from a first metal and the casting 105 is made from a second metal, and the first metal has a higher melting point than the second metal. Hence, while the delivery systems of the prior art are provided by bores in the metal casting 105, the delivery system 115 of the invention is comprised of metal tubes 125 extending through the metal casting 105. As such, while in the delivery systems of the prior art, the coolant and / or lubricant are in direct contact with the metal casting as they are conveyed through the EDU housing, in the delivery system 115 of the invention the tubes 125 of the metal network 120 contain the coolant and / or lubricant and prevent the coolant and / or lubricant from coming into direct contact with the metal casting 105. Moreover, because the first metal of the metal network 120 has a higher melting point than the second metal of the metal casting 105, the delivery system 115 can be fabricated fully first, and the metal casting 105 can then be cast around the delivery system 115 afterto form the completed electric driving unit housing. As such, there is no need to perform extensive machining on the metal casting 105 after casting, or to make use of the difficult-to-perform sand mould method of the prior art. Furthermore, because the metal material of the network 120 is much more robust than, say, the sand mould of the prior art, it is now possible to produce a delivery system 115 with a much more complex network 120 than was ever possible before. Now the features of each electric drive unit housing 100 will be described in more detail with reference to the first electric drive unit housing 100a shown in Figure 1. The first EDU housing 100a forms part of a first electric drive unit (EDU) 130a, which is used for the propulsion of the electric vehicle 300. The primary purpose of the metal casting 105 of the first EDU housing 100a is to provide physical protection and containment for the components of the first electric drive unit (EDU) contained therein, said components including an electric motor (not shown) and a gearbox (not shown). The electric motor drives the wheels (not shown) of the vehicle 300 using electrical power from a vehicle battery (not shown) that is typically arranged outside the first EDU 130a and elsewhere in the electric vehicle 300. To this end, the electric motor comprises a stationary component known as a stator (not shown), and a rotational component known as a rotor (not shown). The stator defines an internal cavity therein, in which the rotor is rotatably arranged, and the stator contains coils of wire that coil around the rotor and that produce a magnetic field when energized by the vehicle battery. The rotor, which is connected to the drivetrain (not shown) of the electric vehicle 300, contains permanent magnets or electromagnets and is configured to rotate within the stator's magnetic field when the stator is energised, thereby generating the mechanical force needed to propel the electric vehicle 300 forward. Meanwhile, the gearbox adjusts the speed and torque of the electric motor to ensure smooth driving of the electric vehicle 300 at any speed. To enable efficient power transfer from the electric motor to the wheels of the electric vehicle 300, the gearbox contains a system of gears. The arrangement of these gears enables the motor to operate at an effective speed while adjusting torque output to suit various driving conditions. To provide lubricant to the electric motor and the gearbox, the first EDU 130a comprises a lubricant delivery system. The lubricant delivery system forms part of the delivery system 115 described above, and comprises at least some of its tubes 125. Since only lubricant is conveyed through these tubes 125, these tubes 125 can be understood as ‘lubricant tubes’ (shown as 125a-125e in Figure 1). The lubricant delivery system forms part of a larger lubricant circuit around which the lubricant circulates. The lubricant delivery system only refers to the parts of the lubricant circuit within the first EDU 130a that are responsible for delivering the lubricant through the EDU 130a and into the electric motor and the gearbox, as will be described in detail below. As well as lubricating the electric motor and the gearbox, the lubricant also acts to cool these parts as they heat up during operation. As such, in use, the temperature of the lubricant is raised as it passes around the lubricant circuit. To cool the lubricant in the lubricant circuit, the vehicle 300 is provided with a heat exchanger (not shown), which - although not part of the first EDU 130a - is mounted on the first EDU housing 100a. The heat exchanger receives warmed lubricant from the motor and gearbox, cools it down, and sends it back into the motor and gearbox at a cooler temperature. To provide cooling of the heat exchanger, the first EDU 130a further comprises a separate coolant delivery system. The coolant delivery system delivers coolant e.g., engine coolant to the heat exchanger to cool the heat exchangerand the lubricant passing therethrough. In this way, the heat exchanger can be understood as a liquid-liquid heat exchanger, e.g., an oil cooler. The coolant delivery system also forms part of the delivery system 115 described above, and comprises at least some of its tubes. Since only coolant is conveyed through these tubes, these tubes can be understood as ‘coolant tubes’ (shown as 125f-125g in Figure 1). The coolant delivery system forms part of a larger coolant circuit around which the coolant circulates. The coolant delivery system only refers to the parts of the coolant circuit within the first EDU 130a that are responsible for delivering the lubricant through the EDU and into and out of the heat exchanger, as will be described in detail below. The delivery system 115 therefore comprises both of the lubricant and coolant delivery systems, and the network 120 of tubes 125 of the delivery system 115 includes both the lubricant tubes 125a-125e and the coolant tubes 125f-125g. Moreover, the lubricant and coolant circuits are fluidly distinct, meaning that the lubricant delivery system and the coolant delivery system are arranged in such a way that the lubricant in the lubricant circuit cannot move or transfer to the coolant circuit and the coolant in the coolant circuit cannot move or transfer to the lubricant circuit. Even within the heat exchanger, the lubricant and the coolant are kept separate. To protect and contain the electric motor, the gearbox and the delivery system 115, the first EDU housing 100a is provided with the metal casting 105. To this end the metal casting 105 is shaped to define various openings for each of the EDU components, and these openings are shaped such that these components can be securely and / or snuggly arranged therewithin. Moreover, since the metal casting 105 is mostly thin, many parts of the external configuration of the metal casting 105 are also dependent on the shape of the EDU components within, as can be seen in Figure 1. The openings of the metal casting 105 include the electric motor opening 110 in which the electric motor is arranged, a gearbox opening (not shown) in which the gearbox is arranged, and delivery system opening(s) 140 in which the delivery system 115 is arranged. The electric motor opening 110 in the metal casting 105 is shaped in this way so that the stator of the electric motor can be securely arranged therewithin. The rotor is removably arranged within the stator so that it can be removed from the first EDU housing 100a as necessary for e.g., repair. The gearbox opening is also shaped so that the gearbox can be securely arranged therewithin. The gears are removably arranged within the gearbox so that they can be removed from the first EDU housing 100a as necessary for e.g., repair. Finally, the delivery system opening(s) 140 are also shaped so that the delivery system 115 can be securely arranged therewithin. Additionally, the metal casting 105 defines a heat exchanger mounting point 135 on the exterior surface thereof. The heat exchanger is securely mounted on the metal casting 105 at the heat exchanger mounting point 135. As stated above, the lubricant circuit refers to a closed circuit around which the lubricant is conveyed so as to lubricate and cool the electric motor and the gearbox. Part of the lubricant circuit is provided by the lubricant delivery system, which comprises lubricant tubes 125a-125e that convey lubricant from a lubricant sump (not shown) to the motor and the gearbox for lubrication and cooling thereof. Then the lubricant is conveyed back to the lubricant sump to begin a new circuit. In the example of Figure 1, the lubricant delivery system comprises first, second, third, fourth and fifth lubricant tubes 125a-125e. Here, the lubricant circuit begins with lubricant being conveyed from the lubricant sump arranged outside the EDU (but mounted onto the exterior of the casting 105 of the first EDU housing 100a) and into the first lubricant tube 125a, and hence inside the EDU 130a. The first lubricant tube 125a may therefore be understood as a ‘lubricant inlet tube’ since it is this tube that delivers lubricant into the lubricant delivery system. To convey the lubricant, the circuit is provided with a lubricant pump (not shown) arranged between the sump and the first lubricant tube 125a. At the end of the first tube 125a, an oil filter 142 is arranged to filter the lubricant passing through. After the filter 142, the lubricant enters into the second lubricant tube 125b. At the end of the second lubricant tube, the lubricant enters a bypass valve 150. In the bypass valve 150, the temperature of the lubricant passing therethrough is measured. If the measured temperature is above a temperature threshold, the bypass valve 150 conveys the lubricant therein via the third lubricant tube 125c to the heat exchanger mounting point 135 (and hence to the heat exchanger mounted thereon) for cooling by the heat exchanger. On the other hand, if the measured temperature is less than the temperature threshold it conveys the lubricant via the fourth lubricant tube 125d of the lubricant circuit to the motor opening 110 (and hence into the motor received therein). In this way, the lubricant can be conveyed into the stator and / or the rotor of the electric motor to cool and / or lubricate these parts. It is noted that after lubricant has been conveyed through the heat exchanger by the bypass valve 150, it then enters back into the first EDU 130a through the fifth lubricant tube 125e. The fifth lubricant tube 125e then conveys this cooled lubricant into the fourth lubricant tube 125d, which in turn conveys it into the motor. The fourth lubricant tube 125d may also be understood as a ‘motor feed tube’ since it is the tube that delivers lubricant into the motor, or indeed as a ‘lubricant outlet tube’ since it is the tube that delivers lubricant out of the lubricant delivery system. After the lubricant has passed through the motor, it enters into the gearbox opening (and hence the gearbox received therein) for lubrication and I or cooling thereof, via at least one drilling (not shown) extending between the motor opening and the gearbox opening in the casting 105 of the first EDU housing 100a. Thereafter, the lubricant in the gear box is drained back into the sump, where it begins again the lubricant circuit. As stated above, the coolant circuit refers to a closed circuit around which the coolant is conveyed so as to take heat away from the lubricant in the heat exchanger. Part of the coolant circuit is provided by the coolant delivery system, which comprises coolant tubes 125f-125g that convey coolant through the first EDU 130a and to and from the heat exchanger, as will now be explained. The coolant circuit also conveys coolant to the radiator (not shown) of the vehicle 300 to be cooled thereby, before being send back into the heat exchanger for further cooling of the lubricant circuit. In the example of Figure 1, the coolant delivery system comprises first and second coolant tubes 125f-125g. Here, the coolant circuit begins with coolant being conveyed into the first coolant tube 125f from outside the first EDU 130a. The first coolant tube 125f then conveys the coolant to the heat exchanger mounting point 135 (and hence into the heat exchanger mounted thereon). In the heat exchanger, the coolant absorbs heat from the lubricant in the separate lubricant circuit also passing through the heat exchanger. The first coolant tube 125f may therefore be understood as a ‘coolant inlet tube’ since it is this tube that delivers coolant into the coolant delivery system, as well as a ‘heat exchanger coolant feed tube’ since it is the tube that delivers coolant into the heat exchanger. Thereafter, the warmed coolant is passed from the heat exchanger and into the second coolant tube 125g. The second coolant tube 125g then conveys the coolant back out of the first EDU 130a. The second coolant tube 125g may therefore be understood as a ‘coolant outlet tube’ since it is the tube that delivers coolant out of the coolant delivery system. The coolant is then passed through the radiator of the vehicle 300 where the coolant loses heat to the atmosphere. After being cooled by the radiator, the coolant is then delivered back into first coolant tube 125f, where it begins again the coolant circuit. Despite the lubricant and coolant delivery circuits being fluidly distinct, the delivery system 115 may include one or more arms 143 (made of the same first metal as the tubes 125) that extend between the lubricant and coolant delivery systems to connect and hold the two together. Hence, while the tubes 125 of the lubricant and coolant delivery systems are not fluidly connected, they may still be structurally connected together by way of said metal arms 143 extending between e.g., two such tubes 125 thereof). Furthermore, the delivery system 115 may further comprise one or more solid (i.e., non-hollow) metal supports 145 attached to and extending out from the metal network 120, through the metal casting 105 and to an outer boundary of the metal casting 105. Providing the metal network 120 with these solid metal supports 145, allows the metal network 120 to be held in the right position during casting (explained in detail below). Moreover, the solid supports being tightly embedded within the metal casting 105 ensures a tight seal. The solid metal supports 145 may extend or project beyond the outer boundary of the casting 105. In this way, the solid metal supports 145 may partially define the outer boundary of the first EDU housing 100a. The solid metal supports 145 may be made from the same first metal as the metal network 120, such that the entire delivery system 115 can be advantageously formed from the same material. As is clear from the above, the metal delivery system 115 of the invention can have a more complex configuration than the bored delivery systems of the prior art. Indeed, at least some of the tubes 125 of the metal network 120 may be curved and may incorporate smooth bends (such as first coolant tube 125f), i.e., bends that have a gradual and continuous change in direction. The LPDC and sand mould method of the prior art can only produce conduits or galleries with sharp bends, i.e., with abrupt and / or distinct change in direction, due to how the sand mould is fabricated together. The fluid(s) passing through the curved tubes of the invention also advantageously experience fewer pressure drops. The second or front EDU 130b shown in Figure 2 has a similar configuration to the first or rear EDU 130a described above, in particular in relation to how the tubes 125 of the delivery system 115 are connected together. However, the geometry of these tubes is different in the second EDU 130b of Figure 2. These differences are due, in part, to there being different spatial limitations in the front and rear regions of the vehicle 300. Figure 3 illustrates a vehicle 300 comprising the two separate electric drive units 130a, 130b described above and illustrated in Figures 1 and 2, each being arranged at different locations in the electric vehicle 300. In other embodiments, the vehicle 300 may contain other numbers of EDUs 130 arranged in any suitable location(s) in the vehicle 300. The two electric drive unit housings 100a, 100b form part of two separate electric drive units 130a, 130b that together are responsible for driving the vehicle 300. The vehicle 300 shown in Figure 3 is an SUV, although any kind of electric or hybrid vehicle may incorporate the EDU housings 100 and EDUs 130 described above. Figure 4 illustrates a method 400 according to an embodiment of the invention. The method 400 is a method of manufacturing either of the electric drive unit housings 100a, 100b described above and illustrated in Figures 1 and 2. In the first step 405, the delivery system 115 is fabricated. In the second step 410, the metal casting 105 is cast around the delivery system 115 so that the delivery system 115 is embedded within the metal casting 105. This is made possible because the first metal of the metal network 120 has a higher melting point than the second metal of the metal casting 105. More detail about each of these steps is provided in turn. In the first step 405, the delivery system 115 is fabricated (e.g., in its final form). To this end, each of the tubes 125 of the metal network 120 may be formed separately e.g., by way of cutting and / or bending pre-formed metal tubes into the desired shape. Subsequently, the tubes 125 may then be joined together e.g., by way of furnace brazing to form the metal network 120. This beneficially avoids having to form the entire metal network 120 in one go, although this may also be performed. Similarly, the arm(s) 143 and / or the solid metal support(s) 145 of the delivery system 115 may also be formed separately to the tubes 125 during the first step 405, e.g., byway of cutting and / or bending pre-formed metal parts into the right shape. Thereafter, the arm(s) 143 and / or the solid metal support(s) 145 may be subsequently joined with the rest of the metal network 120 to form the delivery system 115. This again avoids having to form the entire delivery system 115 (which may have a very complex arrangement) in one go. After the delivery system 115 is formed during the first step 405, it may be cleaned and then pressure tested, before the second step 410. In the second step 410, the metal casting 105 is cast around the delivery system 115. To this end, a steel casting die or mould (not shown) is first provided with the right shape to ensure the metal casting 105 has the electric motor opening 110, the gearbox opening and the heat exchanger mounting point 135 in the correct positions with respect to the tubes 125 of the delivery system 115. Then the delivery system 115 is arranged in the right position and with the right orientation within the steel casting die or mould. The solid metal support(s) 145 - if present - can be used to ensure the delivery system 115 is held in the right place within the steel mould during this step 410. Then, the moulten second metal is poured into the mould and around the delivery system 115 and then left to cool around the delivery system 115, thereby casting the metal casting 105 around the delivery system 115. The casting step can be performed using LPDC, gravity casting, sandcasting or HPDC etc. In terms of materials, the first metal of the metal network 120 may be mild steel or stainless steel while the second metal of the metal casting 105 may be aluminium. Aluminium is advantageous for the metal casting 105 because it is lightweight and yet durable, and so provides adequate protection and containment for the various components contained therein. Mild steel or stainless steel are advantageous for the delivery system 115 because it is robust and because it has a higher melting temperature than the aluminium, thereby allowing the aluminium casting to be cast around the stainless-steel metal network 120. In one embodiment, the lubricant delivery system is fabricated so that each of the lubricant inlet and outlet tubes 125a, 125d comprises an open end (where it fluidly connects to the rest of the tubes in the lubricant delivery system) and a closed off end (i.e., a capped off end) opposite the open end. In this way, the lubricant delivery system is closed after the first step 405, thereby preventing the molten metal casting 105 from entering within the delivery system 115 during the subsequent casting step 410. After the second step 410, the method 400 may then comprise the following additional steps of machining an inlet bore through the metal casting 105 and the closed offend of the lubricant inlet tube 125a to define an inlet into the lubricant delivery system from outside of the electric drive unit housing 100 and machining an outlet bore through the metal casting 105 and the closed end of the lubricant outlet tube 125d to define an outlet of the lubricant delivery system to the outside of the electric drive unit housing 100. This therefore allows the lubricant delivery system to be fluidly connected to the motor, the gear box, the sump and the rest of the lubricant circuit, as described above. Additionally or alternatively, the coolant delivery system, and hence the coolant inlet and outlet tubes 125e, 125f, may be fabricated in the same manner. To form the complete electric drive unit 130: the EDU housing 100a / 100b, the electric motor, the gearbox and the heat exchanger are first provided, and then the electric motor is arranged within the electric motor opening 110 of the EDU housing, the gearbox is arranged within the gearbox opening of the EDU housing, and the heat exchanger is mounted on the heat exchanger mounting point 135 of the EDU housing. 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. For example, in some embodiments, the EDU does not include a coolant delivery system because, for example, the heat exchanger is arranged away from the EDU housing such that coolant does not need to be delivered through the EDU. Likewise, in some embodiments, the electric drive unit does not include the gearbox, and the gearbox is contained elsewhere in the vehicle. In these embodiments, the lubricant may be conveyed to the sump after passing through the motor. In some embodiments, the fluid and / or coolant delivery systems may include any number of tubes arranged in any suitable configuration.

Claims

1. An electric drive unit housing for a vehicle, the electric drive unit housing comprising: a casting; anda delivery system embedded within the casting for delivering coolant and / or lubricant around the electric drive unit housing, wherein the delivery system comprises a network of tubes through which coolant and / or lubricant are conveyed in use, and wherein, in use, the tubes provide a barrier between the metal casting around the tubes and the coolant and / or lubricant within the tubes,wherein the network is made from a first metal and the casting is made from a second metal, and wherein the first metal has a higher melting point than the second metal.

2. The electric drive unit housing of claim 1, wherein at least one of the tubes is curved.

3. The electric drive unit housing of claim 1 or claim 2, wherein the electric drive unit housing furthercomprises an electric motor opening defined in the casting for receiving an electric motor and the delivery system comprises a lubricant delivery system for delivering lubricant to the electric motor opening, and wherein the lubricant delivery system comprises at least one lubricant tube through which lubricant is conveyed in use, the at least one lubricant tube forming part of the network of tubes.

4. The electric drive unit housing of any preceding claim, wherein the electric drive unit housing further comprises a heat exchanger mounting point on the casting for mounting a heat exchanger and the delivery system comprises a coolant delivery system for delivering coolant to the heat exchanger mounting point, and wherein the coolant delivery system comprises at least one coolant tube through which coolant is conveyed in use, the at least one coolant tube forming part of the network of tubes.

5. The electric drive unit housing of claim 4 when depending on claim 3, wherein the lubricant delivery system and the coolant delivery system are fluidly distinct.

6. The electric drive unit housing of claim 4 or claim 5 when depending on claim 3, wherein the delivery system further comprises at least one arm connecting the lubricant delivery system and the coolant delivery system.

7. The electric drive unit housing of any preceding claim, wherein the delivery system further comprises at least one solid metal support attached to the network, and wherein the at least one solid metal support extends from the network, through the casting and to an outer boundary of the casting.

8. A method of manufacturing an electric drive unit housing for a vehicle, the method comprising: fabricating a delivery system, wherein the delivery system comprises a network of tubes through which coolant and / or lubricant are conveyed in use; andcasting a casting around the delivery system so that the delivery system is embedded within the casting, andwherein the metal network is made from a first metal and the casting is made from a second metal, and wherein the first metal has a higher melting point than the second metal.

9. The method of claim 8, wherein casting the casting comprises defining an electric motor opening in the casting for receiving an electric motor, and wherein fabricating the delivery system comprises fabricating a lubricant delivery system comprising a motor feed tube for opening into the electric motor opening to allow delivery of lubricant to the electric motor opening.

10. The method of claim 8 or claim 9, wherein casting the casting comprises defining a heat exchanger mounting point on the casting for mounting a heat exchanger, and wherein fabricating the delivery system comprises fabricating a coolant delivery system comprising a heat exchanger coolant feed tube for opening out to the heat exchanger mounting point to allow delivery of coolant to the heat exchanger mounting point.

11. The method of any of claims 8 to 10, wherein fabricating the delivery system comprises forming the tubes separately and subsequently joining the tubes together to form the network.

12. The method of any of claims 8 to 11, wherein:the metal network comprises an inlet tube through which coolant and / or lubricant is conveyed into the delivery system in use, and an outlet tube through which coolant and / or lubricant is conveyed out of the delivery system in use,the delivery system is fabricated so that each of the inlet and outlet tubes comprises a closed offend, andthe method further comprises machining an inlet bore through the casting and the closed off end of the inlet tube to define an inlet of the delivery system from outside of the electric drive unit housing, and machining an outlet bore through the casting and the closed end of the outlet tube to define an outlet of the delivery system to the outside of the electric drive unit housing.

13. The method of any of claims 8 to 12, wherein the delivery system further comprises at least one solid metal support attached to and extending from the metal network, and wherein the casting is cast around the delivery system so that the at least one solid metal support extends through the casting and to an outer boundary of the casting.

14. An electric drive unit for a vehicle, comprising the electric drive unit housing of any of claims 1 to 7 or the electric drive unit housing made according to the method of any of claims 8 to 13.

15. A vehicle comprising the electric drive unit housing of any of claims 1 to 7, the electric drive unit housing made according to the method of any of claims 8 to 13, or the electric drive unit of claim 14.s

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