EP3678883A1

EP3678883A1 - An electric vehicle, chassis and a vehicle cooling assembly

Info

Publication number: EP3678883A1
Application number: EP18769434.4A
Authority: EP
Inventors: Philip STANTON
Original assignee: Williams Advanced Engineering Ltd
Current assignee: Fortescue Zero Ltd
Priority date: 2017-09-05
Filing date: 2018-09-05
Publication date: 2020-07-15
Also published as: GB201714226D0; WO2019048848A1

Abstract

An electric vehicle includes a pair of lower sills, each extending longitudinally along an opposing side of the vehicle and providing crash protection in the event of a side impact to the vehicle.A first one of the sills has a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air,anda heat exchanger is located within the first sill in a position whereby,in use,cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger,in use,transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.The heat exchanger may form an integral part of the vehicle crash structure to help mitigate damage in a side impact.

Description

AN ELECTRIC VEHICLE, CHASSIS AND A VEHICLE COOLING ASSEMBLY

This invention relates to electric vehicles, and in particular to a cooling assembly for a vehicle.

The term electric vehicle used within the scope of the present invention refers to a vehicle, typically a road vehicle, in which the primary or sole means of propulsion is from an electric motor that is powered by electricity stored in a battery carried by the vehicle. It has been established that an electric vehicle needs to provide a large range of at least 500km or more for the majority of consumers to consider the EV as a replacement for a conventional vehicle propelled by an internal combustion engine. Battery technology is continually improving, but at the time of writing a battery pack that is large enough to store the 50kWh- 100kWh of energy required to achieve this sort of range is rather heavy and bulky. Taking account of the desire to place the large mass of the battery low down in the vehicle, the most convenient place to locate the battery pack is in a recess on the underside of the vehicle passenger compartment in between the wheels of the vehicle .

In one convenient and highly flexible arrangement, the batteries may be arranged in a flat battery pack that fits into a recess in a base of the vehicle below the passenger compartment floor. The base may form part of a self supporting lower frame which may include reinforcing lower sills along the sides and one or more cross beams, forming what is commonly referred to as a skateboard design because it has the general appearance of a skateboard. An upper body defining a passenger compartment and other parts of the vehicle may be located on top of this skateboard lower frame. The passenger compartment may simply be bolted onto the skateboard. An example of a vehicle with a skateboard form of chassis in the Tesla Model S manufactured by Tesla Inc, Palo Alto, California, USA. The skateboard may form a rolling chassis which is "married" to an upper body of the vehicle during assembly. Alternatively the body may be of a unibody construction with a recess formed in the underside of the floorpan of the unibody to locate the battery pack, so that the skateboard chassis is an integral part of the unibody. Placing the battery pack in a recess accessed from under the floorpan of the passenger compartment brings benefits of safety because the battery is protected from impacts by the front and rear of the vehicle and also by the sides of the vehicle, in particular the vehicle sills. It provides a flexible design as the vehicle designer has almost complete freedom of expression in designing the body that fits onto the floorpan. One common skateboard arrangement could underpin a vehicle with a saloon body style, a hatchback, an estate or a convertible.

Although the body can be in many shapes there will usually be at least one door on each side, with the skateboard like floorpan or floorpan of an unibody design defining longitudinal structural sills on each side which extends along the lower part of the body below the doors to provide some side impact protection. This both protects the passenger compartment but importantly also protects the battery pack. The applicant has appreciated that high capacity battery packs pose stringent requirements on cooling, especially when feeding current to a powerful electric motor or to multiple electric motors, due to their location in a confined recess underneath the vehicle passenger compartment. Conventional cooling of the batteries of the battery pack by passing a chilled fluid through or around the battery pack and through a front mounted radiator is possible but this introduces limitations on the form factor of the vehicle which, acceptable on a vehicle with an internal combustion engine, may limit the creative freedom of the designer of an EV.

According to a first aspect, the invention provides an electric vehicle comprising a body that defines at least the passenger compartment of the vehicle, and a battery pack, the battery pack in use supplying power to at least one electric motor that provides propulsion to the vehicle,

in which the electric vehicle includes a pair of lower sills, each extending longitudinally along an opposing side of the vehicle and providing crash protection in the event of a side impact to the vehicle, a first one of the sills having a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air,

characterised in that a heat exchanger is located within the first sill in a position whereby, in use, cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger, in use, transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.

The battery pack may be located at the bottom of the vehicle, in between the sills such that the sills provide side impact protection for the battery pack.

The heat exchanger may transfer heat from a heat transfer fluid that flows through the component that is to be cooled into the cooling air that flows through the sill. One or more pipes or other conduits may transport the cooling fluid to or from the component part that is to be cooled.

The heat exchanger may include one or more passages interconnecting at least one fluid inlet to at least one fluid outlet along which the heat transfer fluid may flow and one or more additional passages through which the cooling air flows.

The inlet to the sill may be connected to a front impact structure of the vehicle, the frontal impact structure comprising at least one hollow longeron defining an enclosed flow path for cooling air entering an inlet to the longeron located towards the front of the vehicle that flow rearwards out of the an outlet of the longeron and into the inlet to the first one of the lower sills.

Preferably the front impact structure comprises two elongate hollow members which may be considered to be longerons, each of which defines a respective enclosed flow path for cooling air entering an inlet to the longeron located towards the front of the vehicle that flow rearwards out of the an outlet of the longeron and into the inlet to a respective one of the lower sills.

The front impact structure may comprise a hollow member having a box or other hollow cross section. It may comprise a thin walled structure formed from metal sheet or a fibre reinforced composite sheet material.

The inlet of the front impact structure may be located proximate to the front bumper of the vehicle. It may face towards the front of the vehicle . The front impact structure and sill may be connected to form a continuous rigid elongate structure . The front impact structure may include one or more sacrificial portions that are preferentially crushed during a frontal impact. These may be located at or close to the forwardmost end of the front impact structure .

The outlet of the sill may be located in an area which has a relatively low pressure relative to the pressure of the cooling air entering the sill when the vehicle is moving forwards.

The component of the vehicle that is cooled by the cooled fluid may comprise a part of the vehicle drivetrain. This may comprise the battery pack, with the heat transfer fluid circulating around or through passages in the battery pack.

Alternatively, or additionally, the component may comprise an inverter of the vehicle that connects the battery to the motor. Alternatively, or additionally, the component may comprise an electric motor, or multiple electric motors.

In a preferred arrangement a heat exchanger may also be located within a second one of the two sills, the second sill also having an inlet for cooling air towards the front and an outlet towards the rear of the sill with the heat exchanger located so that cooling air flowing through the second sill extracts heat from the heat exchanger in the second sill.

Thus, in use, two distinct flows of cooling air may be provided, one through each sill, the air flowing over the respective heat exchangers on passing from the inlet to the outlet.

As with the first heat exchanger, the second heat exchanger may, in use, transfer heat energy from a fluid that flows through or around a component part of the vehicle into the cooling air flowing through the sill. One of the heat exchangers may cool fluid that in turn cools the battery pack, the other may cool a fluid that cools the motor and the inverter. Where there are more than one heat exchanger, they may cool different heat transfer fluids selected according to the cooling requirements of the component they are cooling.

The fluid may comprise any suitable coolant that has a dielectric property, meaning it will readily undergo a phase change from liquid to gas at useful temperatures. An exemplary coolant that may be used in an electric vehicle is the haloalkane 1 , 1 , 1 ,2- tetrafluoroethane .

The fluid can be any liquid such as a mix of water and an additive that lowers the freezing point of the mixture such as glycol. In the first loop, the fluid will remain in a liquid phase for all the time during use. It could be a simple water-glycol solution or, for safety reasons, is better to use dielectric oil (with a slightly lower cooling performance compared to the water-glycol fluid). The heat transfer fluid may be an oil.

It is within the scope of this invention for one sill to house more than one independent heat exchanger, with cooled air that flows through the sill passing across both heat exchangers or dividing into two airflows, each one flowing across a respective heat exchanger within a sill.

The heat exchanger may be elongate and may extend along substantially the whole of the sill, and the the inlet and the outlet may be positioned at the end of the sill. The heat exchanger may comprise a passive heat exchanger, commonly known as a heat sink, which includes a plurality of plates or fins that extend within the sill and which are connected to a base portion which is in turn in thermal contact directly or indirectly with the or each component to be chilled or with the heat transfer fluid. The base portion may, for example, define an outer part of the sill that contacts a part of the battery pack when the pack is installed in the recess in the vehicle body. A thermal matching material may be located between the outer part and the battery pack to enhance the conduction of energy from the battery pack into the heat exchanger.

However, for greatest cooling efficiency and design flexibility, it is preferred that the heat exchanger comprises an active type heat exchanger having at least one conduit through which a heat transfer fluid flows and at least one further conduit through which the cooling air flows on passing through the sill, the two conduits being in thermal contact.

The heat exchanger may comprise baffles which extend along the sill and define a passage therebetween for the heat transfer fluid, with a plurality of plate-like cooling fins extending outwards from the baffles into the cooling air flow.

The baffles may extend vertically from a top inner wall of the sill to a bottom inner wall. The baffles may lie in a respective plane which is close to or on opposing sides of a longitudinal centre line of the sill, with a first set of plates extending away from one of the baffles to contact one side of the sill and the second set of plates extending away from the other baffle to contact the opposing side of the sill.

It is preferred that the baffles are located within the sill in a position that is offset from the centre of the sill in a direction towards the centre line of the vehicle . The applicant considers that this may be beneficial in some instances in giving increased protection to the baffles in the event of a side impact.

The heat exchanger may include a plurality of plates which may be in thermal contact with the side of the sills so that heat is transferred from the plates into the side of the sills. In addition to the cooling air drawing away heat from the plates, some heat can also be drawn into the sill which may then radiate the heat into the air outside of the sill.

The plates may be oriented in a range of different orientations depending on the application. For instance, one or more or all of the plates may be substantially horizontal. There may alternatively be one or more plates that are substantially vertical.

The plates may interleave to form a grid when viewed in cross section.

In an alternative to two baffles, a tube may be provided for carrying the heat transfer fluid, the tube having the plates projecting from opposing sides of it.

Whether passive or a plate-type heat exchanger or other form of heat exchanger, the plates may be arranged to define a crash structure that is configured to provide a controlled path for side impacts which deform the side sill, such that the side load is shared in a defined and controlled manner between the sill and the heat exchanger.

Using the heat exchanger as part of the crash management structure of the vehicle may help reduce overall weight, as it allows one component to provide a dual function. This also reduces the component count. Selection of the number, shape and orientation of the parts of the heat exchanger allows for a very precise control of the paths along which energy is flowed in an impact. This can enable the sill and heat exchanger to provide a high degree of protection of the battery pack, or to carefully control the path along which energy flows into the battery pack in a side impact.

The plates of the heat exchanger may comprise deformable plates of relatively rigid thermally-conductive material such as metal, in particular aluminium or aluminium alloy.

The baffles may extend along a major length of the sill. They may, for example, extend along the whole length of the sill from the inlet to the outlet.

The ends of the passage defined by the baffles may terminate with a coupler which enables the baffle to be coupled into a flow path for the heat transfer fluid.

The plates may be spaced apart vertically to define a set of elongate channels that extend longitudinally along the sill, the channels permitting the cooling air to flow from the inlet to the outlet of the sill through the heat exchanger. The heat exchanger plates may be integrally formed with the inner wall of the sill. They may be bonded to the inner surface of the sill. The plates therefore help reinforce the wall of the sill, allowing a thinner material to be used for the sill than may otherwise be used if the sill is not reinforced by the plates.

Rather than being bonded, the heat exchanger and the sill may be integrally formed, for instance as an elongate extrusion. The skilled person will appreciate that a variety of different techniques and materials may be used during the manufacture of the sills and heat exchanger.

The heat exchanger plates may be arranged in opposed pairs, each pair defining an enclosed space therebetween through which the heat transfer fluid flows. This arrangement may be preferable where the space inside the sill is limited as it may prove more efficient at transferring heat than use of the central baffles alone .

Where the heat exchanger includes opposed pairs of plates, the baffles may be omitted. A manifold may instead be provided at each end of the heat exchanger to connect the enclosed spaces between pairs of baffles together. Of course, it is within the scope of the invention to provide multiple flow paths for heat transfer fluid through the heat exchanger which are independent of one another, i.e. to give parallel flow paths through the heat exchanger.

The plates may be wavy in cross section to increase the overall surface area of the plate that can be fitted within the sill compared to a perfectly flat plate .

Where the plates are wavy, they may be arranged such that, when a horizontal side load is applied to the sill, the plates buckle in a concertina manner to exaggerate the magnitude of one or more of the waves thereby absorbing energy in a controlled manner. However, the plates need not buckle in this way and may simply transfer side loads from the outer surface of the sill through to the inner surface of the sill.

It is preferred that the baffles deform under high side loads in preference to the plates, coming together such that a continuous load path is then formed form the plates on the side of the baffles furthest from the vehicle centre line through to the plates on the sides of the baffles nearest to the centre line.

It is possible for the plates to also deform under load.

As well as cooling a heat transfer fluid, the heat exchanger may directly cool a part of the battery pack by including a base part which is in thermal contact with an inner wall of the sill, or integral to the inner wall of the sill, which is in turn in thermal contact with a longitudinal side of the battery pack to draw heat energy away from the battery pack into the sill and in turn into flow of cooling air.

The vehicle may include a lower structure having a skateboard form which comprises a frame defined at least in part by one or more cross members that extend transversely across the frame, the frame defining a recess into which the battery pack is located.

The sills may form a part of the lower structure and the body may be fixed onto the lower structure.

In an alternative, the sills may form a part of the body that is fixed onto the lower structure, so the sills are not part of the skateboard form but located outboard of the skateboard form.

The lower support may include a plurality of mounting points for the motor and for the suspension that supports the road wheels of the vehicle. It may also include a plurality of mounting points for an upper body of the vehicle .

The vehicle may include a pair of rear wheel wells that enclose at least partially a respective rear wheel of the vehicle and the outlet of the sill, or sills, may be is located within the rear wheel well of the vehicle.

According to a second aspect, the invention provides a unibody assembly for an electric vehicle comprising:

a passenger compartment having a floorpan and a pair of side sills, each extending along an opposing lower side of the unibody assembly, at least a first one of the sills having a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and

in which a heat exchanger is located within the first sill in a position whereby, in use, cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger in use transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.

The second one of the sills may also have a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and

in which a heat exchanger is located within the second sill in a position whereby in use cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger in use transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.

The unibody assembly may include any of the features described in relation to the first aspect of the invention.

In accordance with a third aspect, the invention provides a rolling chassis structure having a skateboard form factor which in use supports a passenger compartment of a vehicle, the chassis structure comprising a pair of side sills, each extending along an opposing lower side of the unibody assembly, at least a first one of the sills having a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and

in which a heat exchanger is located within the first sill in a position whereby in use cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger in use transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill. According to a fourth aspect, the invention provides a cooling assembly for an electric vehicle comprising:

at least one sill having a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and in which a heat exchanger is located within the sill in a position whereby in use cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger in use transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.

The sill and the heat exchanger may be integrally formed as a single item.

The skilled person will appreciate that the invention of the fourth aspect, like the preceding aspects, may include any of the features described in relation to the first aspect of the invention.

There will now be described, by way of example only, one embodiment of the present invention with reference to and as illustrated in the accompanying drawings of which: Figure 1 is a simplified representation in elevation of an electric vehicle in accordance with the present invention;

Figure 2 is top view of the vehicle shown in Figure 2 showing key parts of the vehicle relevant to the present invention with other parts omitted;

Figure 3 is a perspective view of a lower frame of the vehicle of Figure 1 ;

Figure 4 is a view of one of the side sills; Figure 5(a) is a perspective view in cross section of the sill opened up along the line A-A marked in Figure 4;

Figure 5(b) is a perspective view of the sill of Figure 5(b) after an impact, with the baffles contacting each other;

Figure 5(c) is a perspective view in cross section of the sill opened up along the line A-A marked in Figure 4 for an alternative heat exchanger;

Figure 6 shows a suitable cooling circuit for the motors using one of the heat exchangers in a sill; and Figure 7 shows a suitable cooling circuit from the inverters and chargers using the other of the heat exchangers. As shown in Figure 1 an electric vehicle 100 comprises a unitary body that has an upper body part 102 that defines a passenger compartment of the vehicle, and a lower body part 104 that defines a chassis. As shown in Figure 1 and Figure 2, a battery pack 106 is located below the passenger compartment within the wheelbase of the vehicle 100. This provides a power supply for three electric motors 108, one at the front of the vehicle and two at the rear. Although not shown, an inverter and control electronics will be provided to control the flow of power to the motors 108 from the battery 106. The skilled person will understand how to connect a battery 106 to a motor 108 of an electric vehicle so this will not be described in further detail in this description.

The reader will also understand, of course, that the invention is not to be limited to an arrangement with three motors 108, and that in its simplest form only one electric traction motor 108 needs to be provided. Also, whilst the vehicle 100 shown has four wheels it could have as few as three or may have more than four wheels.

The body 102, 104 can be made in any of a variety of materials, in particular using one or more of steel, aluminium or composite panels as is known in the art. A preferred arrangement is shown in Figure 3 of the drawings in which a frame 1 10 is formed from two cross members 1 12 and two elongate longitudinal side sills 1 14. A space 1 16 is formed between the cross members 1 12 and sills 1 14 into which the battery pack 106 is located. The cross members 1 12 and side sills 1 14 are hollow sections which give strength to the frame 1 10.

The reader will understand that the term sill in this document means a structural member that is located towards the side of the vehicle and which both provides rigidity to the vehicle chassis or body, and also provides some protection against a side impact when functioning in combination with a heat exchanger located within the sill as will be described. The sill may be visible from the outside of the vehicle, or may be covered with a protective or cosmetic sill cover as is known in the art. These covers generally only provide a cosmetic benefit, but may also give some aerodynamic advantage to the vehicle.

The cross members 1 12 and side sills 1 14 may be formed from a rigid cured composite material, such as a carbon reinforced plastic material. In addition, metal castings are used to form connectors 1 18 which are located at the corners of the frame where the ends of the side sills 1 14 meet the cross members 1 12. Extending forward from each side sill 1 14 is a frontal crash structure in the form of two elongate hollow metal sections that form longerons 120. Of course, other materials could be used for the sills 1 14 and longerons 120 and the connecting pieces 1 18.

Each longeron 120 has an opening 122 at the forwardmost end to allow cooling air to flow into the longeron 120, where it is then able to flow onwards through the longeron 120 to exit from the longeron 120 and flow through an inlet 124 at the front end of the respective sill 1 14. This air flows through the inside of the sill 1 14 to eventually exit from a rear outlet 126 in the rearmost end of the sill 1 14 in a region of low pressure in the rear wheel well 128 of the vehicle 100. This can best be seen in Figure 5 of the drawings, with the rear outlet 126 also clearly visible in Figure 2. The air can be pumped through the sill 1 14 by a fan, or may be rammed into the sill 1 14 as the vehicle 100 is driving along. This may allow a sufficient airflow to be achieved without the use of a fan.

Figure 3 shows in perspective the lower chassis and clearly shows a central recess or space 1 16 into which a battery pack 106 is located underneath the passenger compartment.

The sills 1 14 provide strength to the vehicle body, stopping it bowing or twisting as loads are applied to the road wheels 130. They also provide crash protection in the event of a side impact to the vehicle 100, helping to prevent damage to the battery pack 106.

As shown in Figure 2, both of the sills 1 14 having a forward inlet 124 for cooling air to enter the sill 1 14 and a rearward outlet 126 further towards the rear of the vehicle 100 for egress of the cooling air, and both sills 1 14 house a respective heat exchanger 132 is located in a position whereby in use cooling air flowing from the inlet 124 to the outlet 126 passes through the heat exchanger 132, the heat exchanger 132 in use transferring heat energy directly or indirectly from a component part of the vehicle 100 into the cooling air flowing through the sill 1 14.

In the illustrated example, the heat exchangers 132 in both sills 1 14, and the sills 1 14 themselves, are identical mirror images of each other. Figure 5(a) is a cross section through one of the sills 1 14 and the heat exchanger 132 within that sill 1 14. The heat exchanger 132 has a constant cross section along the whole of the length L of the sill 1 14 that is shaded dark grey in Figure 4, albeit with an inlet connector at one end (not shown) and an outlet connected at the other end (not shown) .

As can be seen, the heat exchanger 132 comprises two vertical baffles 134 which extend along the sill 1 14 and define a passage 136 therebetween for the heat transfer fluid to flow along. A plurality of plate-like cooling fins 138 extend horizontally outwards from the baffles 134 into the cooling air flow. The baffles 134 extend vertically from a top inner wall 140 of the sill 1 14 to a bottom inner wall 142, close to a vertical centre line of the sill 1 14. A first set of plates or fins 138 extend generally horizontally away from one of the baffles 134 to thermally contact one side of the sill 1 14 and the second set of plates or fins 138 extend generally horizontally away from the other baffle 134 to thermally contact the opposing side of the sill 1 14.

It can also be seen that there are some shorter fins 144, located between the plates or fins 138, which do not extend all the way to the side of the sill 144.

The plates 138, baffles 134 and fins 144, are made of a metal such as aluminium which is excellent at transferring heat energy into the cooling air flowing through the sill 1 14. The aim is to efficiently draw energy from the heat transfer fluid that passes through the space between the baffles 134 out into the cooling air or the sill 1 14. As shown, the plates 138 have a wavy cross section, each having three crests and three troughs. Of course, they may have more or less troughs, and there may be more or fewer plates 138, but the provision of the waves enables the plates 138 to have a greater surface area for a given width (measured across the sill) to improve the transfer of heat into the cooling air. A notable feature of the heat exchanger 132 shown in Figure 5(a) is that the plates 138 are arranged to define a crash structure that is configured to provide a controlled path for side impacts which deform the side sill 1 14, such that the side load is shared in a defined and controlled manner between the sill 1 14 and the heat exchanger 132.

To aid the absorption of side impact energy, the plates 138 are located directly opposite each other on the baffles 134, and the two baffles 134 are relatively flexible so that on a side impact the baffles 134 are pushed into contact by the side load flowing through the outermost plates, the load then passing into the aligned innermost plates. An example of a deformed side sill 1 14, with the baffles 134 pushed into contact with one another, is shown in Figure 5(b).

In an alternative arrangement of a sill 214, shown in Figure 5(c), the plates 238 are arranged as opposed pairs to define an enclosed space 246 therebetween through which the heat transfer fluid can flow. As shown, these spaces are connected to the fluid between the two central baffles 234, but the skilled person would understand that they may not be connected to the baffle 234 and indeed the baffle 234 could be omitted completely. The heat exchangers 132 in the two sills 1 14 can be used in a variety of cooling configurations. Figures 6 shows one illustrative example of how they can be used to cool the three motors 108 shown in Figure 2.

Figure 6 shows the cooling arrangement for the motors 108. The three motors 108 are connected in series, or parallel, in a fluid flow path. A pump 148 drives the fluid around the flow path and through the heat exchanger 132 in the nearside sill 1 14 of the vehicle 100. In the depicted cooling arrangement, the fluid passes through the heat exchanger 132 twice, once after running through the first motor 108 and again after passing through the second motor 108 and third motor 108. Of course, the fluid may alternatively pass through the heat exchanger 132 only a single time, or further times.

Figure 7 shows the cooling circuit for the inverter 150, the battery charger 152 and any associated DC-DC converter 154 for use in rapid charging of the battery 106. The charger 152 and DC-DC converter 154 are connected in parallel with the inverter 150 in a flow path for a heat transfer fluid. The fluid outlet from the three components flows into the heat exchanger 132 in the offside sill 1 14, and on to a condenser 156. It then optionally flows through a further inverter 158 before passing through the heat exchanger 132 for a second time and being pulled by a pump 160 that sends it on to complete the loop. The fluid used in this circuit is a heat change fluid as is known generally in the art of refrigerant circuit design. As with the arrangement of Figure 6, the fluid may make one or more passes through the heat exchanger 132.

The skilled person will appreciate that various modifications may be made within the scope of the invention and that the embodiment shown is not intended to be limiting to the scope of the invention which is defined by the claims. For instance, various valves may be incorporated into the cooling circuits to control the rate of flow of fluid through the heat exchangers and the components that are being cooled.

Claims

1. An electric vehicle comprising a body that defines at least the passenger compartment of the vehicle, and a battery pack, the battery pack in use supplying power to at least one electric motor that provides propulsion to the vehicle,

2. An electric vehicle according to claim 1 , in which the heat exchanger in use transfers heat from a heat transfer fluid that flows through the component that is to be cooled into the cooling air that flows through the sill.

3. An electric vehicle according to claim 1 or claim 2, in which the heat exchanger includes one or more passages interconnecting at least one fluid inlet to at least one fluid outlet along which the heat transfer fluid may flow and one or more additional passages through which the cooling air flows.

4. An electric vehicle according to any preceding claim, in which the inlet to the sill is connected to a front impact structure of the vehicle, the frontal impact structure comprising at least one hollow longeron defining an enclosed flow path for cooling air entering an inlet to the longeron located towards the front of the vehicle that flow rearwards out of the an outlet of the longeron and into the inlet to one of the lower sills.

5. An electric vehicle according to claim 4, in which the front impact structure comprises a hollow member having a box or other cross section.

6. An electric vehicle according to any one of claims 4 or 5, in which the inlet of the front impact structure is located proximate to the front bumper of the vehicle .

7. An electric vehicle according any preceding claim, in which the at least one longeron of the front impact structure and a respective sill are connected to form a continuous rigid elongate structure .

8. An electric vehicle according to any preceding claim, which the outlet of the sill is located in an area which has a relatively low pressure relative to the pressure of the cooling air entering the sill when the vehicle is moving forwards.

9. An electric vehicle according to any preceding claim, in which the component of the vehicle that is cooled by the cooled fluid is one or more of: the battery pack, an inverter of the vehicle that connects the battery to the motor, and an electric motor.

10. An electric vehicle according to any preceding claim, which further comprises an additional heat exchanger located within a second one of the two sills, the second sill also having an inlet for cooling air towards the front and an outlet towards the rear of the sill with the heat exchanger located so that cooling air flowing through the second sill extracts heat from the heat exchanger in the second sill.

1 1. An electric vehicle according to claim 10, in which one of the heat exchangers cools fluid that in turn cools the battery pack, and the other cools a fluid that cools the motor and the inverter.

12. An electric vehicle according to any preceding claim, in which at least a first heat exchanger comprises a passive heat exchanger which includes a plurality of plates or fins that extend within the sill and which are connected to a base portion which is in turn in thermal contact directly or indirectly with the or each component to be chilled or with the heat transfer fluid.

13. An electric vehicle according to any preceding claim, in which the or at least one of the heat exchangers includes at least one conduit through which a heat transfer fluid flows and at least one further conduit through which the cooling air flows on passing through the sill, the two conduits being in thermal contact.

14. An electric vehicle according to claim 13, in which the heat exchanger comprises a pair of baffles which extend along the sill and define a passage therebetween for the heat transfer fluid, with a plurality of plate-like cooling fins extending outwards from the baffles into the cooling air flow.

15. An electric vehicle according to claim 14, in which the baffles extend vertically from a top inner wall of the sill to a bottom inner wall, close to a centre line of the sill, with a first set of plates extending away from one of the baffles to contact one side of the sill and the second set of plates extending away from the other baffle to contact the opposing side of the sill.

16. An electric vehicle according to any preceding claim, in which the heat exchanger includes a plurality of plates that are in thermal contact with the side of the sills so that heat is transferred from the plates into the side of the sills.

17. An electric vehicle according to any preceding claim, in which the heat exchanger includes a plurality of plates, each of which lies generally in a horizontal plane.

18. An electric vehicle according to any preceding claim, in which the heat exchanger includes a plurality of plates which each comprise deformable plates of relatively rigid thermally conductive material such as metal, in particular aluminium or aluminium alloy.

19. An electric vehicle according to any preceding claim, in which the heat exchanger includes a plurality of plates which each are integrally formed with the inner wall of the sill.

20. An electric vehicle according to any preceding claim, in which the heat exchanger includes a plurality of plates which each are wavy in cross section.

21. A unibody assembly for an electric vehicle comprising:

in which a heat exchanger is located within the first sill in a position whereby, in use, cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger, in use, transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.

22. A unibody assembly according to claim 21 , in which the second one of the sills also has a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and

in which a heat exchanger is located within the second sill in a position whereby, in use, cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger, in use, transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.

23. A rolling chassis structure having a skateboard form factor which, in use, supports a passenger compartment of a vehicle, the chassis structure comprising a pair of side sills, each extending along an opposing lower side of the unibody assembly, at least a first one of the sills having a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and

24. A cooling assembly for an electric vehicle comprising:

at least one sill having a forward inlet for cooling air to enter the sill and a rearward outlet further towards the rear of the vehicle for egress of the cooling air, and

in which a heat exchanger is located within the sill in a position whereby in use cooling air flowing from the inlet to the outlet passes through the heat exchanger, the heat exchanger in use transferring heat energy directly or indirectly from a component part of the vehicle into the cooling air flowing through the sill.