GB2636121A

GB2636121A - Lubricant circulation system

Info

Publication number: GB2636121A
Application number: GB2318241.3A
Authority: GB
Inventors: Guarino Giuseppe
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2023-11-29
Filing date: 2023-11-29
Publication date: 2025-06-11
Also published as: WO2025114535A1; GB202318241D0

Abstract

A lubricant circulation system 200 comprises a lubricant circuit 60 which conveys lubricant from a sump 152 to a component of an electric drive unit (100, Fig. 4), and has a heat exchanger 70 between the sump and the component. A bypass valve 92 directs a flow of lubricant through the heat exchanger to remove heat from the lubricant when the valve in a first position, and directs the flow of lubricant through a bypass circuit 90 so that no heat is removed from the lubricant when the valve is in a second position. The component may be a transmission 112. A coolant circuit 80 may convey coolant from a coolant source to the heat exchanger with an inverter 26 in the coolant circuit and upstream of the heat exchanger. An electric machine 102 may be positioned between the heat exchanger and the transmission. An electric drive unit and electric vehicle (10, Fig. 1) are also claimed. The vehicle may have two electric drive units (20, 30, Fig. 2) supplying power to two sets of wheels (12, 14, Fig. 2), with each electric drive unit having a lubrication circulation system.

Description

LUBRICANT CIRCULATION SYSTEM

TECHNICAL FIELD

The present disclosure relates to a lubricant circulation system for an electric drive unit. Aspects of the invention relate to a lubricant circulation system for an electric drive unit, to an electric drive unit comprising said lubricant circulation system, and to an electric vehicle comprising said electric drive unit.

BACKGROUND

Lubricant circulation systems for modern electric vehicles typically comprise one or more cooling elements designed to cool lubricant as it circulates about the vehicle. The intention of such elements is to prevent components of the vehicle (such as the vehicle drive unit) from overheating.

However, such elements can also be detrimental to vehicle performance during engine "warm up" phases when it is often desirable to heat up components of the vehicle drive unit so that they can reach their respective operating temperatures as quickly as possible.

It is an aim of the present invention to provide a solution to this issue.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a lubricant circulation system, an electric drive unit, and an electric vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a lubricant circulation system for an electric drive unit comprising: a lubricant sump for containing a lubricant; a lubricant circuit for conveying said lubricant from the lubricant sump to a first component of the electric drive unit; a heat exchanger positioned in the lubricant circuit between the lubricant sump and the first component, said heat exchanger being configured to remove heat from the lubricant as it passes from the lubricant sump to the first component; a bypass circuit in fluid communication with the lubricant circuit upstream and downstream of the heat exchanger, said bypass circuit being configured to divert the flow of lubricant around the heat exchanger during use; and a bypass valve positioned in said bypass circuit and being controllably moveable between a first position, in which the flow of lubricant from the lubricant sump to the first component is allowed to pass through a lubricant side of the heat exchanger such that heat is removed from the lubricant as it passes from the lubricant sump to the first component, and a second position, in which the flow of lubricant is directed along the bypass circuit such that substantially no heat removal is effected on the lubricant as it passes from the lubricant sump to the first component.

During "warm up" engine phases, it is often desirable to heat components of the electric drive unit assembly (such as the transmission) to their desired operating temperature as quickly as possible.

Advantageously, the provision of the aforementioned bypass arrangement enables the cooling effects of the heat exchanger to be "switched off' during such engine phases thereby enabling components downstream of the heat exchanger to scavenge a greater amount of heat from the lubricant circulating about the lubricant circulation system.

As a consequence, components of the EDU assembly downstream of the heat exchanger (such as the transmission) can be heated to their desired operating temperature more quickly and efficiently during "warm up" engine phases.

Optionally, the lubricant may be a liquid lubricant (e.g., oil).

Optionally, the lubricant circulation system may further comprise a coolant circuit configured for conveying a coolant from a coolant source to a coolant side of the heat exchanger, and a second component of the electric drive unit may be positioned in the coolant circuit, upstream of the heat exchanger.

Advantageously, the provision of a second component positioned along the coolant circuit (upstream of the heat exchanger) allows maximum cooling to be provided to the second component thereby enabling the second component to be run at peak performance.

Optionally, the coolant may be a liquid coolant (e.g., water, mono ethylene glycol (MEG), mono propylene glycol (MPG).

Optionally, the coolant may be a gaseous coolant (e.g., air).

Optionally, the second component may be provided within a jacket having one or more coolant channels for circulating the coolant about the second component and said coolant channels may form part of the coolant circuit.

Advantageously, the provision of a jacket having one or more coolant channels which form part of the coolant circuit allows coolant to better circulate about the second component thereby further enhancing the cooling effect afforded to said component.

Optionally, the first component of the electric drive unit may be a transmission arrangement.

Optionally, the second component of the electric drive unit may be an inverter.

Optionally, a third component of the electric drive unit may be positioned in the lubricant circuit between the heat exchanger and the first component.

Advantageously, the provision of a third component which is positioned along the lubricant circuit between the first component and the heat exchanger enables heat generated by the third component to be transferred onto first component via the lubricant as it circulates about the lubricant circulation system.

As a consequence, the "warm up" speed of the first component can be further improved during engine "warm up" phases as the first component can scavenge additional heat generated by the third component during operation.

Optionally, the third component of the electric drive unit may be an electric machine.

Optionally, the electric machine may be an induction motor (IM) or a permanent magnet (PM) synchronous motor.

Optionally, the lubricant circulation system may further comprise one or more lubricant return conduits for conveying lubricant supplied to the first and/or third components back into the lubricant sump.

Advantageously, the provision of one or more lubricant return conduits enables lubricant to be recycled around the lubricant circulation system thereby helping to reduce wastage.

Optionally, the lubricant circulation system may further comprise a breather pipe in fluid communication with the first component, said breather pipe being configured to permit the ingress and egress of fluids to and from the first component.

Advantageously, the provision of a breather pipe helps to prevent the build-up of pressure within the first component.

Optionally, the lubricant circulation system may further comprise a lubricant pump positioned in the lubricant circuit between the lubricant sump and the heat exchanger.

Advantageously, the provision of a lubricant pump helps to improve the circulation of lubricant about the lubricant circulation system.

Optionally, the lubricant circulation system may further comprise a lubricant filter positioned in the lubricant circuit between the lubricant sump and the heat exchanger.

Advantageously, the provision of a filter helps to catch debris or other unwanted inclusions which may be present within the lubricant circuit, thereby helping to prevent such debris from further circulating about the system.

Optionally, the lubricant filter may be positioned downstream of the lubricant pump (i.e., between the lubricant pump and the heat exchanger.

According to another aspect of the invention, there is provided an electric drive unit comprising: an electric machine; a transmission arrangement for transmitting motive power from the electric machine to one or more wheels of an electric vehicle; and the lubricant circulation system according to the previous aspect of the invention.

Optionally, the electric drive unit may further comprise a housing for containing the electric machine and/or the transmission arrangement, and the lubricant circuit may comprise a plurality of conduits, said conduits being provided external to the housing.

Advantageously, providing the lubricant circuit as a plurality of conduits external to the housing helps to prevent the lubricant from becoming heated by the housing as it circulates around the lubricant circuit.

Optionally, the plurality of conduits may be formed of a thermally insulating material.

Advantageously, forming the plurality of conduits of a thermally insulating material (e.g., plastic) helps to further prevent unwanted heating of the lubricant during operation.

Optionally, the plurality of conduits may comprise a polymeric material.

According to yet another aspect of the invention, there is provided an electric vehicle comprising the electric drive unit according to the previous aspect of the invention.

Optionally, the electric vehicle may further comprise a plurality of wheels, and the electric drive unit may be configured to supply motive power to at least one of said plurality of wheels.

Optionally, the vehicle may have a plurality of electric drive units.

Optionally, the vehicle may comprise two electric drive units or a different number of electric drive units may be provided such as 1, 3 or 4.

Optionally, the or each electric drive unit may be configured to supply motive power to a respective wheel of the vehicle.

Optionally, the vehicle may comprise a first electric drive unit configured to supply motive to a first wheel of the vehicle, said first electric drive unit having a first lubricant circulation system according to one of the previous aspects of the invention.

Optionally, the vehicle may comprise a second electric drive unit configured to supply motive to a second wheel of the vehicle, said second electric drive unit having a second lubricant circulation system according to one of the previous aspects of the invention.

Optionally, the vehicle may comprise a third electric drive unit configured to supply motive to a third wheel of the vehicle, said third electric drive unit having a second third lubricant circulation system according to one of the previous aspects of the invention.

Optionally, the vehicle may comprise a fourth electric drive unit configured to supply motive to a fourth wheel of the vehicle, said second electric drive unit having a fourth lubricant circulation system according to one of the previous aspects of the invention.

Optionally, the first and/or second electric drive units may be associated with the rear wheels of the vehicle.

Optionally, the third and/or fourth electric drive units may be associated with the front wheels of the vehicle.

Optionally, the vehicle may further comprise: a first set of wheels; a first axle associated with said first set of wheels; and a first electric drive unit configured to supply motive power to the first set of wheels via the first axle, said first electric drive unit having a first lubricant circulation system according to one of the previous aspects of the invention.

Optionally, the vehicle may comprise a single electric drive unit, said electric drive unit being associated with the front or rear axle.

Optionally, the electric vehicle may further comprise: a second set of wheels; a second axle associated with said second set of wheels; and a second electric drive unit configured to supply motive power to the second set of wheels via the second axle, said second electric drive unit having a second lubricant circulation system according to one of the previous aspects of the invention.

Advantageously, providing a pair of lubricant circulation systems (one associated with each drive unit) helps to ensure that sufficient lubricant is supplied to the respective drive units, particularly during periods of peak operation.

Optionally, the first electric drive unit may be associated with a front axle of the vehicle and the second electric drive unit may be associated with a rear axle of the vehicle.

Optionally, the electric vehicle may further comprise a power source configured to supply electrical power to the electric machine of the electric drive unit.

Optionally, the power source may be a DC power source.

Optionally, the electric drive unit may further comprise an inverter configured for converting DC power from the DC power source into AC power for driving to the electric machine.

Optionally, the power source may comprise one or more battery modules.

According to a further aspect of the present invention there is provided a lubricant circulation system for an electric drive unit comprising: a lubricant sump for containing a lubricant; a lubricant circuit for conveying said lubricant from the lubricant sump to a first component of the electric drive unit; and a heat exchanger positioned in the lubricant circuit between the lubricant sump and the first component, said heat exchanger being configured to remove heat from the lubricant as it passes from the lubricant sump to the first component.

We consider the term "thermally insulating material" to be defined as a material having a thermal conductivity of 0.1 W m-1 K-1 or less.

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 vehicle in accordance with an embodiment of the invention; Figure 2 schematically shows functional units and a control system of the vehicle; Figure 3 shows a controller for use in the vehicle of Figure 2; Figure 4 shows a cross-sectional view of an Electric Drive Unit (EDU) assembly of the vehicle of Figures 1 and 2; Figure 5 shows an underside view of the EDU assembly of Figure 4; and Figure 6 shows a schematic representation of a lubricant circulation system for use with the electrical drive unit assembly of Figures 4 and 5.

DETAILED DESCRIPTION

Figures 1 and 2 show an example of an electric vehicle (EV) 10.

The electric vehicle 10 comprises a set of front wheels 12 at a front axle 28 and a set of rear wheels 14 at a rear axle 38. The vehicle has at least one electric drive unit (EDU) by which one or more of the wheels are driven. In the illustrated embodiment, vehicle comprises two electric drive units, each associated with one of the sets of wheels. In other embodiments, the vehicle may have a dedicated EDU for each of the front wheels 12 and/or a dedicated EDU for each of the rear wheels 14.

In the illustrated embodiment, the front wheels 12 are driven by a first electric drive unit (EDU) 20. The first EDU 20 comprises a first electric machine 22, a front transmission arrangement 24 and power electronics 26. The rear wheels 14 are driven by a second electrical drive unit (EDU) 30. The second EDU 30 comprises a second electric machine 32, a rear transmission arrangement 34 and power electronics 36. The first EDU 20 can be called a first propulsion unit and the second EDU 30 can be called a second propulsion unit. As used herein, the term "transmission" may refer to a device with a plurality of gears through which torque can be transmitted from the drive unit to one or more of the wheels. For example, this may refer to a differential, transaxle, and/or a gearbox.

The first EDU 20 and the second EDU 30 each receive a DC supply from a power source which is configured to supply electric power to the electric machines 22, 32 of the first EDU 20 and the second EDU 30 respectively. In the illustrated embodiment, the power source of the electric vehicle 10 comprises one or more battery modules (or a battery pack 40). The battery 40 may be recharged from an external electrical source.

The electric vehicle 10 has a control system with a controller 50 which controls operation of the first EDU 20 and the second EDU 30. In operation, the controller 50 controls the power output of each of the EDUs 20, 30 to supply torque to the wheels 12, 14. Power electronics 26 comprise an inverter which converts the DC supply from battery 40 to an AC supply to drive the first electric machine 22. The first electric machine 22 drives the front transmission arrangement 24 which, in turn, drives the front axle 28 to apply torque to the front wheels 12. Power electronics 36 comprise an inverter which converts the DC supply from battery 40 to an AC supply to drive the second electric machine 32. The second electric machine 32 drives the rear transmission arrangement 34 which, in turn, drives the rear axle 38 to apply torque to the rear wheels 14. One or both of the front and rear axles 28, 38 may be a continuous shaft extending through their respective EDU, or a pair of half shafts which extend from their respective EDU.

Figure 3 schematically shows the control system. The control system comprises one controller 50, although it will be appreciated that this is merely illustrative. The controller 50 comprises at least one processor 56 which may be any type of processor for executing instructions to control the operation of the system. The processor 56 is electrically connected to other components of the controller via one or more buses 57. Processor-executable instructions 48 may be provided using any data storage device or computer-readable media, such as memory 58. The processor-executable instructions 48 comprise instructions for implementing the functionality of the described methods. The storage/memory 58 is of any suitable type such as non-volatile memory, a magnetic or optical storage device. The processor 56 is configured to access the memory 58 and execute the stored instructions 48. Memory 58, or a separate memory/storage stores data 60 used by the processor 56. Data 60 may comprise data which defines a plurality of operating points of the first electric machine 22. Instructions 48 may comprise rules for selecting between plurality of operating points of the first electric machine 22. The controller 50 comprises an input interface 54. The input interface 54 is configured to receive one or more input signals 53 (e.g., a demand for acceleration or a demand for speed). The controller 50 comprises an output interface 55. The output interface 55 is configured to output outputs, such as the control signal 51 to control the first electric machine 22 (sent to power electronics 26) and the control signal 52 to control the second electric machine 32 (sent to power electronics 36). The controller 50 is configured to use one or more of the input signals 53 and stored data 60, to generate output signals 51, 52.

Optionally, the controller 50 may operate the vehicle in the following ways: (i) Rear-wheel drive (RWD). Torque is only supplied to the rear wheels 14 by operating the second electric machine 32 to drive the rear wheels 14. The front wheels 12 are not driven by the first electric machine 22; (ii) All-wheel drive (AWD). Torque is supplied to the rear wheels 14 and to the front wheels 12 by operating the second electric machine 32 to drive the rear wheels 14 and operating the first electric machine 22 to drive the front wheels 12; (iii) Front-wheel drive (FWD). Torque is only supplied to the front wheels 12 by operating the first electric machine 22 to drive the front wheels 12. The rear wheels 14 are not driven by the second electric machine 32.

In some vehicles, the controller 50 may only operate according to options (i) and (ii), and may not operate according to option (iii).

In other embodiments, the electric vehicle may include only one EDU 20, 30. For example, the second EDU 30 may be omitted in embodiments where the electric vehicle is a "front-wheel drive" vehicle, or the first EDU 20 may be omitted in embodiments where the electric vehicle is a "rear-wheel drive" vehicle. In further embodiments, one or more of the wheels may be driven individually by a dedicated EDU. For example, the front wheels 12 may each be connected to one of a pair of front EDUs and/or the rear wheels 14 may each be connected to one of a pair of rear EDUs. In a further example, the rear wheels 14 may be connected to a plurality of rear EDUs, and/or the front wheels 12 may be connected to a plurality of front EDUs.

Referring now to Figures 4 and 5, an EDU assembly is indicated at 100. The EDU assembly 100 includes an electric machine 102, a transmission arrangement 112, and a housing 150 for the electric machine 102 and the transmission arrangement 112. It will be understood that the EDU assembly 100 illustrated in Figure 4 could be, or form part of, the first EDU 20 and/or the second EDU 30 illustrated schematically in Figure 2, along with the additional power electronics 26, 36 described above (not illustrated in the EDU assembly 100 of Figures 4 and 5).

In the illustrated embodiment, the housing 150 has a first portion 150A which houses the electric machine 102, and a second portion 150B which houses the transmission arrangement 112. In the illustrated embodiment, the first and second housing portions 150A, 150B are discrete components which are coupled together (e.g., via a bolting arrangement). The housing 150 may also include a cover 150C (shown schematically in Figure 4) which closes an end of the first housing portion 150A opposite to the second housing portion 150B. The cover 150C may be a discrete component which is coupled to the first housing portion 150A (e.g., via a bolting arrangement), or may instead be integrally formed with the first housing portion 150A. In alternative embodiments, any other suitable housing configuration may be used.

The housing 150 may also have one or more mounting features 132 for mounting the EDU assembly 100 to a sub-frame of the electric vehicle 10 and/or for reacting torsional forces generated by the EDU assembly.

The illustrated EDU assembly 100 also includes seal assemblies 300 at opposite ends of the housing 150, for sealing against the half shafts of the respective axle 28, 38. Such seal assemblies 300 provide a sealed system inside the housing 150 and thereby inhibit ingress of contaminants (e.g., dirt, debris, water, etc.) inside the housing 150.

The electric machine 102 may be an induction motor (IM). An induction motor can also be called an induction machine, as it is capable of operating as a motor and as a generator. Alternatively, the electric machine 102 may be a permanent magnet (PM) synchronous motor. In either case, the electric machine 102 includes a rotor 104 and a stator 106 with electrical windings 108. The electric machine 102 is operated by suppling an AC supply to the stator windings 108 which causes movement of the rotor 104 about a rotational axis R. IM and PM motors are known and will therefore not be described in more detail. In some embodiments, the electric machine 102 may be of a different kind, such as a DC motor, a universal motor, or a non-electrical motor such as a hydraulic motor.

The rotor 104 is coupled to a motor output shaft 110. In other words, the rotor 104 and output shaft 110 are configured for co-rotation about the rotational axis R. In this way, as the rotor 104 is rotated by the AC supply to the stator windings 108, the output shaft 110 is also rotated. The output shaft 110 is supported for rotation relative to the housing 150 by an output shaft bearing arrangement 116 which, in this embodiment, includes a first bearing 116A on a first side of the output shaft 110 and a second bearing 116B on a second side of the output shaft 110. The first and second bearings 116A, 116B may be ball bearings, roller bearings or any other

suitable bearing.

The transmission arrangement 112 is responsible for transmitting motive power from the output shaft 110 of the electric machine 102 to the front or rear wheels 12, 14 of the electric vehicle 10. Optionally, the transmission arrangement 112 includes a differential 118 which allows half shafts (not shown in Figure 4 or 5) of the respective axle 28, 38 to be rotated at different speeds while receiving motive power from the electric machine 102. In some embodiments, the transmission 112 may comprise a gearbox between the output shaft 110 of the electric machine 102 and the differential 118. The differential 118 may be of any suitable configuration. The differential 118 may include one or more components which are supported for rotation relative to the housing 150 by a differential bearing arrangement (not shown) including one or more bearings.

Although not illustrated in Figures 4 and 5, the half shafts of the respective axle 28, 38 may be coupled to the differential 118 via any suitable means (e.g., by engaging external splines on the half shafts with internal splines on a component of the differential 118). The half shafts may be supported for rotation relative to the housing by one or more half shaft bearings 130, which may be ball bearings, roller bearings or any other suitable bearing.

The illustrated EDU assembly 100 includes a lubricant circulation system 200, which supplies lubricant to one or more of the rotating components of the EDU assembly 100. The lubricant circulation system 200 shall now be described in greater detail below with reference to Figure 6.

In the embodiment illustrated in Figure 6, the lubricant circulation system 200 is associated with the first EDU 20. However, it shall be appreciated that in other embodiments, the lubricant circulation system 200 may be associated with the second EDU 30. It shall also be appreciated vehicles featuring more than one EDU (such as 2, 3, 4 etc.), may comprise multiple lubricant circulation systems, each associated with a respective one of the EDUs.

The lubricant circulation system 200 illustrated in Figure 6 comprises a lubricant sump 152 for containing a lubricant (e.g., oil), a lubricant circuit 60 for conveying lubricant from the lubricant sump 152 to one or more components of the EDU assembly 100 (e.g., electric machine 102, output shaft 110, bearings 116A, 116B, 128A, 1286, 130, gears 122, 124, differential 118 andlor transmission arrangement 112 outlined above) and a heat exchanger 70 positioned in the lubricant circuit 60 for removing heat from the lubricant as is passes along the lubricant circuit 60 from the lubricant sump 152 to the one or more components of the EDU assembly 100.

The heat exchanger 70 comprises a lubricant side 70a which is in fluid communication with the lubricant circuit 60 and a coolant side 70b which is in fluid communication with a corresponding coolant circuit 80 (described in greater detail below). In other words, the lubricant circuit 60 passes through the lubricant side 70a of the heat exchanger 70 and the coolant circuit 80 passes through the coolant side 70b of the heat exchanger 70.

As shown in Figure 6, the coolant circuit 80 comprises a first portion 82 provided upstream of the heat exchanger 70 for conveying coolant from a coolant source (not shown) to the coolant side 70b of the heat exchanger 70 and a second portion 84 provided downstream of the heat exchanger 70 for conveying coolant from the coolant side 70b of the heat exchanger 70 back to the coolant source (or optionally to a different location).

In the illustrated embodiment, the coolant which is circulated around the coolant circuit 80 is a liquid coolant (e.g., water). However, it shall be appreciated that in alternative embodiments, the coolant may be a different type of liquid (such as mono ethylene glycol (MEG) or mono propylene glycol (MPG)), or may be a gaseous coolant (e.g., air).

Optionally, one or more components of the EDU assembly 100 may be positioned in the coolant circuit 80, upstream of the heat exchanger 70.

For example, in the embodiment illustrated in Figure 6, an inverter (which forms part of the power electronics 26 of the EDU assembly 100) is positioned in the first portion 82 of the coolant circuit 80 between the coolant source (not shown) and the coolant side 70b of the heat exchanger 70. However, it shall be appreciated that in other embodiments, other components of the EDU assembly 100 may be provided in the coolant circuit in place of, or in addition to, the aforementioned inverter 26.

Advantageously, by positioning one or more components of the EDU assembly 100 in the coolant circuit 80, upstream of the heat exchanger 70, coolant can be supplied to said components before it becomes heated by the lubricant which allows the coolant to provide maximum cooling to said components, thereby enabling said components to be run at peak performance.

In the illustrated embodiment, inverter 26 is provided within a jacket 86 having a plurality of channels 86a,b which form part of the first portion 82 of the coolant circuit 80. The first portion 82 of the coolant circuit 80 also comprises a first coolant conduit 82a which provides a fluid connection between the coolant source (not shown) and one or more of the channels 86a,b provided on the jacket 86 and a second coolant conduit 82b which provides a fluid connection between one or more of the channels 86a,b provided on the jacket 86 and the coolant side 70a of the heat exchanger 70.

Similarly, the second portion 84 of the coolant circuit comprises a third coolant conduit 84a which is provides a fluid connection between the coolant side 70b of the heat exchanger 70 and the coolant source (not shown) in the illustrated embodiment.

As shown in Figure 6, the plurality of channels 86a,b extend about a circumference of the component (in this instance the inverter 26) contained within the jacket 86 such that coolant passing along the first portion 82 of the coolant circuit 80 is circulated about said component prior to reaching the coolant side 70b of the heat exchanger 70. This helps to further enhance the cooling effect afforded to said component.

However, it shall be appreciated that in other embodiments, the jacket 86 may comprise a single channel or may be omitted entirely, for example in embodiments where no components of the EDU assembly 100 are provided in the coolant circuit 80 upstream of the heat exchanger 70. As such, in some embodiments the first portion 82 of the coolant circuit 80 may comprise a single coolant conduit providing a fluid connection between the coolant source (not shown) and the coolant side 70b of the heat exchanger 70.

Referring back to the lubricant circuit 60, the lubricant circuit 60 comprises a first portion 62 provided upstream of the heat exchanger 70 for conveying lubricant from the lubricant sump 152 to the lubricant side 70a of the heat exchanger 70 and a second portion 64 provided downstream of the heat exchanger 70 for conveying lubricant from the lubricant side 70a of the heat exchanger 70 to one or more components of the EDU assembly 100.

In the illustrated embodiment, the lubricant circuit 60 is configured to convey lubricant from the lubricant sump 152 to the electric machine 102 and to the transmission arrangement 112 of the EDU assembly 100. However, it shall be appreciated that in other embodiments, the lubricant circuit 60 may be configured to convey lubricant to other components of the EDU assembly 100 in addition to, or instead of, the electric machine 102 and/or the transmission arrangement 112 such as the output shaft 110, the bearings 116A, 116B, 128A, 128B, 130, the gears 122, 124 and/or the differential 118.

As shown in Figure 6, the lubricant circulation system 200 further comprises a lubricant pump 202 for circulating lubricant around the lubricant circuit 60 and a lubricant filter 204 for collecting and/or trapping debris, both of which are positioned in the first portion 62 of the lubricant circuit 60 between the lubricant sump 152 and the heat exchanger 70.

In the illustrated embodiment, the lubricant filter 204 is positioned downstream of the lubricant pump 202 (i.e., between the lubricant pump 202 and the heat exchanger 70). However, in other embodiments, the lubricant filter 204 may be positioned upstream of the lubricant pump 202 (i.e., between the lubricant pump 202 and the lubricant sump 152). It shall also be appreciated that in further alternative embodiments, the lubricant circulation system 200 may be configured to circulate lubricant under the effects of gravity only and hence the lubricant pump 202 may be omitted. Similarly, it shall also be appreciated that in some embodiments, the lubricant filter 204 may also be omitted.

Optionally, the lubricant circulation system 200 may also comprise a breather pipe 72 having a first end in fluid communication with the transmission arrangement 112 and a second end in fluid communication with the ambient atmosphere so as to permit the ingress and egress of fluids to and from the transmission arrangement 112. This helps to prevent the build-up of pressure within the transmission arrangement 112 during use. However, in other embodiments, the breather pipe 72 may be omitted.

The first portion 62 of the lubricant circuit 60 comprises a first lubricant conduit 62a which provides a fluid connection between the lubricant sump 152 and the lubricant pump 202, a second lubricant conduit 62b which provides a fluid connection between the lubricant pump 202 and the lubricant filter 204, and a third lubricant conduit 62c which provides a fluid connection between the lubricant filter 204 and the lubricant side 70b of the heat exchanger 70.

However, it shall be appreciated that in embodiments in which the lubricant pump 202 and/or the lubricant filter 204 are omitted, the first portion 62 of the lubricant circuit 60 may comprise a pair of lubricant conduits (e.g., between the lubricant sump 152 and the lubricant pump 202 / filter 204 and between the lubricant pump 202 / filter 204 and the heat exchanger 70) or, in embodiments in which both the lubricant filter 204 and the lubricant pump 202 are omitted, the first portion 62 of the lubricant circuit 60 may comprise a single lubricant conduit.

As shown in Figure 6, the electric machine 102 is positioned in the second portion 64 of the lubricant circuit 60 between the heat exchanger 70 and the transmission arrangement 112 (although it shall be appreciated that in other embodiments a different component of the EDU assembly 100 may be positioned in the lubricant circuit 60 between the heat exchanger 70 and the transmission arrangement 112 in addition to, or in place of, the electric machine 102).

As such, the second portion 64 of the lubricant circuit 60 comprises a fourth lubricant conduit 64a which provides a fluid connection between the lubricant side 70a of the heat exchanger 70 and the electric machine 102 and a fifth lubricant conduit 64b which provides a fluid connection between the electric machine 102 and the transmission arrangement 112.

However, it shall be appreciated that in other embodiments, the second portion 64 of the lubricant circuit 60 may instead convey lubricant directly to the transmission arrangement 112 (or in alternative embodiments a different component of the EDU assembly) and hence in some embodiments, the second portion 64 of the lubricant circuit 60 may comprise a single lubricant conduit.

The lubricant circulation system 200 also comprises a pair of lubricant return conduits 66, 68 for conveying lubricant supplied electric machine 102 and the transmission arrangement 112 back into the lubricant sump 152 such that used lubricant can be recirculated about the system 200.

In the illustrated embodiment, the plurality of conduits 62a-c, 64a,b which make up the first 62 and second 64 portions of the lubricant circuit 60 (and optionally the first 82 and second 84 portions of the coolant circuit 80) are provided external to the housing 150. This helps to prevent the lubricant from becoming heated by the housing 150 as it circulates around the lubricant circuit 60 (and similarly helps to prevent coolant from becoming heated by the housing 150 as it circulates around the coolant circuit 80 in embodiments wherein the first 82 and second 84 portions of the coolant circuit 80 are provided external to the housing 150).

In the illustrated embodiment, one or more of the plurality of conduits may comprise a thermally insulating material (e.g., a thermally insulating polymeric material). For example, in some embodiments the plurality of conduits may be provided as a series of polymeric hoses. However, it shall be appreciated that in other embodiments, the plurality of conduits may be of a different type and/or may be formed of a different material.

Considering now the functionality of the aforedescribed system 200, as the lubricant circulates about the lubricant circulation system 200 between the sump 152 and the one or more components of the EDU assembly 100, the lubricant become heated to a temperature which is typically greater than that of the coolant.

As such, as the lubricant within the lubricant circuit 60 passes through the lubricant side 70a of the heat exchanger 70, heat is drawn from the relatively warmer lubricant to the relatively cooler coolant passing through the coolant side 70b of the heat exchanger 70 thereby removing heat from the lubricant as is passes through the heat exchanger 70.

During periods of peak or prolonged operation, this cooling effect is extremely beneficial as it helps to prevent the lubricant from overheating which may cause the lubricant to lose its lubrication properties. However, during engine start up phases (when it is desirable to heat components of the EDU assembly 100 to their required operating temperatures as quickly as possible) the cooling effect imparted on the lubricant via the heat exchanger 70 can actually be detrimental to fast warm up since it reduces the amount of heat that can be scavenged from the lubricant by components downstream of the heat exchanger (such as the electric machine 102 and the transmission arrangement 112).

Therefore, to help address this issue, the lubricant circulation system 200 of the claimed invention features a bypass circuit 90 and a bypass valve 92 (as shall be described below) configured to divert the flow of lubricant around the heat exchanger 70 during engine "warm up" phases, thereby enabling components downstream of the heat exchanger 70 (such as the transmission 112 and the electric machine 102) to scavenge a greater amount of heat from the lubricant circulating about the lubricant circulation system 200.

As shown in Figure 6, the bypass circuit 90 comprises a first bypass conduit 94 having a first end which is in fluid communication with the lubricant circuit 60 upstream of the heat exchanger 70 (i.e., between the lubricant sump 152 and the heat exchanger 70) and a second end which is in fluid communication with the bypass valve 92. The bypass circuit 90 also comprises a second bypass conduit 96 having a first end which is in fluid communication with the bypass valve 92 and a second end which is in fluid communication with the lubricant circuit 60 downstream of the heat exchanger 70 (i.e., between the heat exchanger 70 and the one or more components of the EDU assembly 100).

In the illustrated embodiment, the bypass valve 92 is provided as a two-port, two-position valve (or a 2/2 valve) being controllably moveable between a first position and a second position. As shown in Figure 6, the inlet port of the bypass valve 92 is in fluid communication with the first bypass conduit 94 and the outlet port of the bypass valve 92 is in fluid communication with the second bypass conduit 96.

When the bypass valve 92 is in the first (or closed) position, which is typically the case when the components of the EDU assembly 100 have reached their respective operating temperatures, the flow of lubricant around the bypass circuit 90 is blocked and hence lubricant will pass through the lubricant side 70a of the heat exchanger 70 as is circulates around the lubricant circuit 60 from the lubricant sump 152 to the one or more components of the EDU assembly 100.

As such, when the bypass valve is in the first position, heat is removed the lubricant as is passes through the lubricant side 70a of the heat exchanger 70 and hence a cooling effect is imparted on the lubricant which is beneficial during peak or prolonged operating periods.

However, when the bypass valve 92 is placed in the second (or open) position, which is typically the case during "warm up" engine phases, the flow of lubricant is able to pass along the bypass circuit 90 and hence the flow of lubricant becomes diverted around the heat exchanger 70 such that substantially no heat removal is effected on the lubricant as is circulates around the lubricant circuit 60 from the lubricant sump 152 to the one or more components of the EDU assembly 100.

Advantageously, this provision enables the cooling effects of the heat exchanger to be effectively "switched off' during such engine phases thereby enabling components downstream of the heat exchanger (such as the electric machine 102 and the transmission arrangement 112) to scavenge a greater amount of heat from the lubricant circulating about the lubricant circulation system 200. As a consequence, components of the EDU assembly 100 downstream of the heat exchanger can be heated to their desired operating temperature more quickly and efficiently during "warm up" engine phases.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. It should also be noted that whilst the appended claims set out particular combinations of features described above, the scope of the present disclosure is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features herein disclosed.

Claims

CLAIMS1. A lubricant circulation system for an electric drive unit comprising: a lubricant sump for containing a lubricant; a lubricant circuit for conveying said lubricant from the lubricant sump to a first component of the electric drive unit; a heat exchanger positioned in the lubricant circuit between the lubricant sump and the first component, said heat exchanger being configured to remove heat from the lubricant as it passes from the lubricant sump to the first component; a bypass circuit in fluid communication with the lubricant circuit upstream and downstream of the heat exchanger, said bypass circuit being configured to dived the flow of lubricant around the heat exchanger during use; and a bypass valve positioned in said bypass circuit and being controllably moveable between a first position, in which the flow of lubricant from the lubricant sump to the first component is allowed to pass through a lubricant side of the heat exchanger such that heat is removed from the lubricant as it passes from the lubricant sump to the first component, and a second position, in which the flow of lubricant is directed along the bypass circuit such that substantially no heat removal is effected on the lubricant as it passes from the lubricant sump to the first component.
2. The system according to any preceding claim, wherein the lubricant circulation system further comprises a coolant circuit configured for conveying a coolant from a coolant source to a coolant side of the heat exchanger, and wherein a second component of the electric drive unit is positioned in the coolant circuit, upstream of the heat exchanger.
3. The system according to claim 2, wherein the second component is provided within a jacket having one or more coolant channels for circulating the coolant about the second component, and wherein said coolant channels form part of the coolant circuit.
4. The system according to any preceding claim, wherein the first component of the electric drive unit is a transmission arrangement.
5. The system according to any of claim 2, 3 or 4, wherein the second component of the electric drive unit is an inverter.
6. The system according to any preceding claim, wherein a third component of the electric drive unit is positioned in the lubricant circuit between the heat exchanger and the first component.
7. The system according to claim 6, wherein the third component of the electric drive unit is an electric machine.
8. The system according to any preceding claim, wherein the lubricant circulation system further comprises one or more lubricant return conduits for conveying lubricant supplied to the first and/or third components back into the lubricant sump.
9. An electric drive unit comprising: an electric machine; a transmission arrangement for transmitting motive power from the electric machine to one or more wheels of an electric vehicle; and the lubricant circulation system according to any preceding claim.
10. The electric drive unit according to claim 9, wherein the electric drive unit further comprises a housing for containing the electric machine and/or the transmission arrangement, and wherein the lubricant circuit comprises a plurality of conduits, said conduits being provided external to the housing.
11. The electric drive unit according to claim 10, wherein the plurality of conduits are formed of a thermally insulating material.
12. An electric vehicle comprising the electric drive unit according to any of claims 9 to 11.
13. The electric vehicle according to claim 12, wherein the electric vehicle further comprises a plurality of wheels, and wherein the electric drive unit is configured to supply motive power to at least one of said plurality of wheels.
14. The electric vehicle according to claim 13, wherein the vehicle further comprises: a first set of wheels; a first axle associated with said first set of wheels; and a first electric drive unit configured to supply motive power to the first set of wheels via the first axle, said first electric drive unit having a first lubricant circulation system according to any of claims 1 to 9.
15. The electric vehicle according to claim 14, wherein the electric vehicle further comprises: a second set of wheels; a second axle associated with said second set of wheels; and a second electric drive unit configured to supply motive power to the second set of wheels via the second axle, said second electric drive unit having a second lubricant circulation system according to any of claims 1 to 9.