Spoilers are commonly used on motor vehicles in order to influence the vehicle aerodynamic characteristics. In particular,'front dam'spoilers are fitted to the front of a vehicle underbody and are used to reduce the air mass flow rate under the vehicle and thereby reducing the lift and the induced drag associated with the lift. The spoiler is used to restrict the area between the vehicle and the ground, through which oncoming air may flow. This reduces the air mass flow rate under the vehicle, lowering the pressure on the vehicle underbody. This reduction in pressure helps to reduce the lift force on the vehicle, particularly in the locality of the front spoiler. The restricted area through which air can flow reduces the inflow of air to the underbody, weakening the lift force on the vehicle and thereby reducing the induced drag.

The spoiler also directs airflow away from under-vehicle obstructions such as fuel tanks, exhaust pipes and structural members. Airflow over these relatively rough components generates pressure drag. A spoiler therefore creates a more laminar flow under the vehicle, reducing pressure drag. The main advantage of reducing the drag force on a vehicle is economic in that it improves the fuel consumption of a vehicle, whilst lift force reduction is desirable for road handling, stability and performance.

Known spoilers for use at the front of a vehicle are generally either static spoilers or active spoilers. Static spoilers are fixed to the vehicle in a fully

deployed position and thus restrict the airflow under the vehicle at all times.

This type of spoiler has the drawback of requiring sufficient ground clearance at all times to accommodate the spoiler and as such it can be easily damaged.

Known active spoilers are activated at high speeds but remain retracted a-t low speeds. This avoids the need for large ground clearances at low vehicle speeds or when the vehicle is stationary. Such active spoilers may be motor driven or biased in a retracted position by the use of a spring, torsion element or other such component which provides a biasing force that must be overcome if the spoiler is to be deployed. However, a drawback of such spoilers is that the motor or extra biasing component presents an additional cost to the vehicle and can add to warranty costs. A further drawback of the biasing component is that it is difficult to provide a'spring'device that can withstand the range of environmental conditions to which it would be exposed in day to day use of the vehicle.

The present invention aims to alleviate the problems of the prior art in a simple yet effective manner.

According to a first aspect of the present invention, there is provided a spoiler for aerodynamically influencing the airflow surrounding a vehicle, the spoiler having an upper surface and a lower surface arranged for being movably secured to the vehicle to be moveable between at least a first stowed position and a second deployed position in which at least a part of the spoiler protrudes from the bodywork into the airflow surrounding the vehicle; wherein it is adapted to be moveable towards the second deployed position by a difference in pressure between the upper surface and the lower surface that is large enough to overcome the biasing force thereon. The advantage of this arrangement is that

the spoiler is activated towards the deployed position by air pressure at higher vehicle speeds and then as the speed is reduced it retracts of its own accord without a spring/torque device or motor being required. This helps to kcey the cost of the spoiler down and is a simple arrangement.

According to a second aspect, the invention provides a spoiler having an upper surface and a lower surface and arranged for being movably secured to the vehicle to be moveable between at least a first stowed position at which it is substantially stowed within the bodywork of the vehicle and a second deployed position in which at least a part of the spoiler protrudes from the bodywork into the airflow surrounding the vehicle; the spoiler being arranged to be maintainable in the stowed position by a biasing force and wherein it is adapted to be moveable towards the second deployed position by a difference in pressure between the upper surface and the lower surface that is large enough to overcome the biasing force thereon. The main advantage of this arrangement is that the maximum ground clearance is achievable beneath the spoiler. This is particularly advantageous for use on delivery vehicles that frequently encounter small ground clearances. In addition, the risk of damage to the spoiler from loose chippings or grounding on steep slopes or the like is minimised.

In an embodiment, the spoiler comprises an elongate profile having an aerofoil cross-section. An aerofoil is desirable as it provides a continuous surface having no sharp edges facing the oncoming flow. The aerofoil cross- section may be symmetric about its chord, the upper and lower surfaces being substantially opposed. The spoiler may have a rounded leading edge and a trailing edge. This ensures that when the spoiler is in the deployed position, the air stream flowing over the spoiler remains attached to the surface of the

aerofoil, minimising pressure drag on the vehicle.

The spoiler may be pivotally mounted to the vehicle. This enables the spoiler to rotate from the stowed position towards the deployed position and vice versa. The spoiler may also have a centre of rotation about which it pivots.

The mass of the spoiler can be equally distributed forward and aft of the centre of rotation such that under gravity it will tend towards a retracted position, thus avoiding the need for an extra biasing force. The spoiler may have a centre of gravity that is in spaced relation from the centre of rotation. The centre of rotation may lie between the centre of gravity and the trailing edge. An advantage of this configuration is that it minimises the obstruction of air flowing to the radiator core of the vehicle when the spoiler is used as a front dam'.

The spoiler may optionally comprise a further biasing means such as an additional mass balance, spring or elastic torque member. Such further biasing means can assist the return of the spoiler to the stowed position and ensure that the spoiler is not deployed at low vehicle speeds. An additional mass balance may assist the spoiler centre of rotation to lie between the centre of gravity and the trailing edge.

The spoiler may be adapted for use at the front of a vehicle underside.

Thus it may act as a'front dam'to restrict the quantity of airflow entering the vehicle underbody channel. The spoiler is preferably stowed behind the vehicle front bumper fascia. An advantage of this configuration is that the spoiler does not protrude from the vehicle bodywork, thus maintaining maximum clearance between the spoiler and the ground when in the stowed position.

According to a further aspect of the invention, a motor vehicle includes a spoiler according to a first aspect of the invention mounted thereon.

A still further aspect of the invention comprises a method of deploying a spoiler for a vehicle from a first stowed position in which it is substantially stowed within the bodywork of the vehicle, to a second deployed position, the spoiler having a substantially symmetric cross-section comprising an upper surface and a lower surface and a rounded leading edge, the vehicle being situated in an oncoming airflow; the method comprising the step of disposing the spoiler into a position in which its lower surface is exposed to a first air stream having a greater speed than a second slower air stream flowing over its top surface such that the speed difference creates a pressure differential between the lower surface and the top surface which causes the spoiler to pivot such that its leading edge protrudes into the said oncoming airflow.

According to a yet further aspect of the invention, a motor vehicle includes a spoiler that is deployable according to the inventive method mounted thereon.

Another aspect of the invention comprises an aerofoil for deployment into an oncoming airflow, the aerofoil having a leading edge and being deployable from a first stowed position in which it is shielded from the oncoming airflow by a shielding means, towards a second deployed position in which at least a portion of the leading edge protrudes into the oncoming airflow, the aerofoil being arranged to be maintainable in the stowed position by the biasing force of its own mass under gravity, and wherein it is adapted to be

moveable towards the second deployed position by a difference in pressure between the upper surface and the lower surface that is large enough to overcome the biasing force thereon.

Exemplary embodiments of the present invention will now be explained in more detail by the following non-limiting description and with reference to the accompanying drawings, in which; Figure la is a schematic view of part of a vehicle showing a first example of a spoiler embodying the invention; Figure lb is a schematic view of part of a vehicle showing a second example of a spoiler embodying the invention; Figure 2 is a schematic of the spoiler of Figure 1 in a stowed position; Figure 3 is a schematic of the spoiler of Figure 1 in a deployed position; Figure 4a is a schematic of the spoiler of Figure 1 and showing a first example of a further biasing means; Figure 4b is a schematic of the spoiler of Figure 1 and showing a second example of a further biasing means, and; Figure 4c is a schematic of the spoiler of Figure 1 and showing a third example of a further biasing means.

Figure la is a schematic of part of a vehicle 1 showing a front bumper fascia 10 at the front end thereof and a radiator core 20 aft of the bumper fascia 10 and forward of the vehicle front wheel 30. The vehicle 1 is disposed upon a ground plane 40. A spoiler 50 has an elongate profile having an aerofoil shaped

cross-section. The spoiler 50 is pivotally mounted to the vehicle such that the profile extends across the front of the car, in the gap between the bumper fascia 10 and the radiator core 20. The aerofoil cross-section is symmetrical about a chord 52. However, the aerofoil can also be of asymmetric cross-section. The aerofoil comprises a rounded leading edge 54, an upper surface 56 that is substantially opposed to a lower surface 58, the upper 56 and lower 58 surface converging to a point at trailing edge 60. The spoiler 50 is shown in Figure la in the stowed position, in which it does not have any significant effect on an oncoming airflow entering the channel between the vehicle underbody and the ground (denoted by the arrows in Figure 2).

The spoiler 50 has a centre of gravity 62 that lies on the chord 52 between the leading edge 54 and trailing edge 60. The centre of gravity 62 of the spoiler 50 is at approximately half-chord distance from the leading edge 54.

The spoiler 50 also has a centre of rotation 64 that also lies on the chord 52, aft of the centre of gravity and forwards of the trailing edge 60. The spoiler is mounted to the vehicle bodywork, for example a side panel of the front bumper. fascia 10, via a pivot pin 55 such that the centre of rotation 64 coincides with the pivot point. In this configuration, the majority of the spoiler 50 cross-section lies ahead of the pivot pin 55, leaving a gap between the spoiler trailing edge 60 and the radiator core 20 through which air entering the vehicle underbody channel can flow in order to cool the radiator.

However, an extra means of biasing the spoiler 50 in the stowed position may be required. In one embodiment where such a biasing force is needed an additional mass 70 is secured towards the rear of the spoiler as shown in Figure 4a. The additional mass 70 may be affixed to both ends of the spoiler 50 profile

such that it has a flush fit with the profile cross-section, maintaining the continuity of the aerofoil shape. The additional mass 70 would provide the means to balance the mass of the spoiler 50 about its centre of rotation 64 such that no spring device would be necessary to bias the spoiler 50 in the stowed position.

In another embodiment, the extra biasing force is obtained by the usa of a spring device such as an elastomer torque element 72 as shown in Figure 4b or a leaf spring 74 as shown in Figure 4c. An example of a torque element 72 comprises a generally cylindrical rod that is adapted to be fitted over the pivot pin 55 as shown in Figure 4b. The rod extends towards a side panel of the front bumper fascia 20 and is non-rotatably attached thereto.

The leaf spring 74 has a metal strip wound into a'G'shape in which the top end thereof is extended as a straight portion 75 such that the extended portion 75 thereof can be fitted through an elongate slot 76 formed on the front bumper fascia 10 for retention thereof. The leaf spring 74 extended portion 75 is then fitted to spoiler 50 via an elongate slot 78 formed through the pivot pin 55.

It will be apparent to the skilled man that any other such suitable device may provide the extra biasing force required.

In a further embodiment, shown schematically in Figure lb, the spoiler 50 centre of rotation 64 coincides with the axis of the pivot pin 55 and the centre of gravity 62 such that the mass of the spoiler 50 is balanced about its centre of rotation. In this configuration the gap between the spoiler 50 and the

radiator core 20 is reduced, allowing less air to reach the radiator cor-C 20.

However, no extra biasing means is required for biasing the spoiler 50 in the stowed position.

In a still further embodiment (not shown) the centre of gravity 62 of the spoiler 50 lies aft of the centre of rotation 64, such that it is between the centre of rotation 64 and the trailing edge 60. In this embodiment, the spoiler is biased toward the stowed position and requires a larger downforce to activate it toward the deployed position than either the first or second embodiments.

The spoiler 50 also has a centre of pressure 66 as seen in Figure 2. The centre of pressure 66 is located on the chord 52 between the leading edge 54 and centre of gravity 62.

Located in the stowed position as shown in figures 1 and 2, the lower surface of the spoiler 50 is exposed to oncoming air entering the vehicle underbody channel at the front of the vehicle 1. If the vehicle is stationary or is travelling at low speeds, the spoiler 50 is maintained in the stowed position by the biasing force, whether this is the force of its own mass under gravity, or by a further biasing means.

In order to deploy the spoiler 50 a force must be applied to it that is sufficient to overcome the biasing force thereon. In Figure 2, the arrows underneath the vehicle front bumper fascia 10 denote the oncoming airflow.

The operation of the spoiler 50 is realised as the vehicle accelerates to a pre- determined high speed. As the lower surface 58 of the spoiler 50 is exposed to the increasingly high-speed oncoming airflow, a speed differential is created

whereby the air moving over the lower surface 58 is faster than the air moving over the upper surface 56. The speed differential creates a lower pressure at the lower surface 58 than at the upper surface 56. The result is that a downforce acts on the spoiler 50 to pull it downwards. As the downforce becomes larger than the biasing force, the spoiler 50 starts to deploy. As the centre of pressure 66 is forward of the centre of rotation 64, the downforce acts to rotate the spoiler 50 about the centre of rotation 64 such that the leading edge 54 is deployed into the oncoming airflow as shown in Figure 3. At high speeds the downforce created by the pressure difference on the upper and lower surfaces of the spoiler 50 deploys the spoiler into the fully deployed position. In this position the spoiler 50 forces the oncoming airflow to flow around the leading edge 54. The restricted gap between the deployed spoiler 50 and the ground 40 accelerates the flow locally, reducing the lift force on the vehicle and thereby reducing the vortex drag associated with the lift force.

The fully deployed position of the spoiler 50 is ideally at an angle of approximately 30 degrees anticlockwise of its stowed position.

In the embodiments described above the centre of rotation and centre of gravity lie on the chord of an aerofoil having a symmetric cross-section. It is also envisaged that an aerofoil having an asymmetric cross-section can be used.

Whether the aerofoil cross-section is symmetric or asymmetric, the centre of gravity 62 and/or centre of rotation 64 can lie off-chord. For example, the centre of gravity and centre of rotation can lie along a line that is perpendicular to the chord, the former lying below the chord and the latter lying above the chord.

The couple created by such an arrangement can assist in restoring the spoiler 50 to the stowed position after deployment.

It is further envisaged that the invention can be used to alter the =mass flow of air to other parts of the vehicle other than the underbody, such as the engine.

Various modifications may be made to the embodiment described without departing from the scope of the invention as defined by the claims.