The present invention relates to an aerodynamic device for a motorcycle, comprising at least one pair of wing portions for producing downforce, wherein said wing portions are arranged on opposite sides on a front fairing of the motorcycle, said wing portions being directly or indirectly connected to the front fairing, and are positioned in such a way that, during the running of the motorcycle, each of the wing portions is brought to be substantially in front of, and close to, a respective lower limb of a rider straddling the motorcycle, said wing portions having an anhedral angle. These wing portions may be attached to the fairing directly at the root of the wing or by means of supports or stays, known as struts.

It is known that the use of wings on motor vehicles improves the performance of a motor car both in braking and in cornering. This is due to an increase in the vertical force which improves the behaviour of the tyres, preventing inertial action from pushing the vehicle off the road.

Devices of this kind cannot be used in the motorcycling field. This is because a motorcycle takes corners at considerable banking angles. Any wing fitted to the chassis of the motor vehicle would create a force which, while having a vertical downforce component, would also be characterized by the presence of a centrifugal component which would cancel out the benefit provided.

To overcome this problem, it has been proposed that the motor vehicle be provided with movable wings that can always remain parallel to the ground during cornering. This type of device is complicated because orientation sensors, such as gyroscopes or the like, must be provided. Furthermore, in the case of competition motorcycles, moving wing devices are banned by the rules.

Configurations of aerodynamic devices for motorcycles having wing portions with an- hedral angles have also been proposed.

For example, the Japanese publication JPH04201792 describes an aerodynamic device configured so as to increase the frictional force between the tyres and the road surface, mainly during running in a straight line. This device provides wings having an anhedral angle, configured in such a way that the line of action of the resultant of the aerodynamic forces passes through a contact point between the tyre and the road surface.

The patent US 3 971 452 also describes an aerodynamic device for improving the highspeed running conditions of motorcycles; this device comprises a wing surface mounted on the motorcycle to produce a downforce approximately in the vertical plane passing through the steering axis of the front wheel.

Both of the aforesaid devices suffer from the problem discussed above concerning fixed- wing devices, namely that, during cornering, the devices produce an undesired centrifugal component in addition to the vertical downforce component. One object of the present invention is to propose an improved aerodynamic device capable of reducing the intensity of the aforesaid centrifugal component during cornering, at high speeds at least.

In view of this object, the invention proposes an aerodynamic device of the type defined initially, in which the anhedral angle of the wing portions is equal to at least 30°.

In an aerodynamic device according to this idea for a solution, the wing portions at the sides of the fairing have a differentiated behaviour in cornering, due to an effect of interaction between the wing portions and the rider's body (particularly his elbow and knee). While the vehicle is cornering at high speed, the outer wing portion is placed in a virtually horizontal position, thus maximizing the downforce produced. Furthermore, the rider's position is such that he does not obstruct the operation of the wing in any way. On the other hand, the rider, being in a position in which he leans over towards the inside of the corner, will obstruct the slipstream of the wing portion positioned on the inside, thereby practically entirely cancelling out the centrifugal force produced by this wing portion.

The asymmetric positioning of the rider while the motorcycle is cornering therefore differ- entiates the performance of the two wing portions fitted on the fairing, thus providing a resultant of the forces which acts substantially in the vertical direction. This is achieved by using wing portions which are fixed, making it unnecessary to use any sensors measuring the speed or positioning of the motor vehicle in order to control the inclination of the wing portions. Advantageously, it is possible to use standard wing profiles included in the database provided in published sources.

Further characteristics and advantages of the device according to the invention will be apparent from the following detailed description, which refers to the attached drawings, pro- vided purely by way of non-limiting example, in which:

Figure 1 is a representation of a simplified model of the forces acting on a motorcycle having an aerodynamic device according to the invention, during cornering (front view);

Figures 2a to 2i are schematic front views of a motorcycle having different em- bodiments of an aerodynamic device according to the invention;

Figure 2j is a plan view of a motorcycle having an aerodynamic device according to the invention; and

Figures 3 a and 3 b are images of a computational fluid dynamic analysis of a motorcycle having the aerodynamic device of Figure 2c, during cornering.

With reference to Figure 1 , this shows, in a front view, the profile of a motorcycle (with rider) during cornering. In this figure, the x axis points in the direction of centripetal acceleration, while the y axis represents the vertical direction. The z axis points out of the plane of the figure. To simplify the model, a rectilinear air flow in the direction of the z axis is assumed.

The vectors indicated by F represent forces in the directions x and y, while the vectors indicated by r represent the positions. The most important force components are those acting on the motorcycle and on the rider; the force vector F _m acts on the motorcycle, while the force vector F _r acts on the rider. In both of these, there is a contribution due to centrifugal acceleration and a contribution due to gravity; these vectors can therefore be expressed as follows:

where m ₀ and m _r are, respectively, the mass of the motorcycle and the rider, r _c is the radius of the corner, v is the speed of the motorcycle, and g ₀ is the gravitational acceleration.

For a conventional motorcycle, these forces would be the only forces acting in the simplified example considered here (in addition to the resultant normal forces).

In the motorcycle according to the invention, however, a pair of wing portions are pro- vided, being arranged on opposite sides on a front fairing of the motorcycle; these wing portions have an anhedral angle _W i _n5 . The term "dihedral angle" conventionally signifies the complement of the angle formed between the wing plane and the plane of symmetry of the vehicle; therefore an anhedral angle, also known as a negative dihedral angle, signifies that the dihedral angle defined between the wing plane and a plane orthogonal to the plane of symmetry of the motorcycle is positioned below this orthogonal plane.

With the aforesaid wing portions, the system of forces also comprises the contribution due to the force components F _wl and F _w2 associated with the downforce produced by the wing portions:

where C _L is the lift coefficient, p _∞ is the density of the air, A _w is the wing surface of a wing portion, and _wl and (p _w2 are the angles of inclination of the two wing portions with respect to the coordinate system x-y, these angles being given by the following expressions:

⁽ frwl = -<Plean + Φ wing 2 ^ (5) i> 2 ^— Ψΐεαη ⁽ wing ~^ (6)

where (pi _ean is the lean angle of the motorcycle.

The coefficient Cj in expression (4) is a coefficient of interference which makes allowance for the difference in behaviour between the wing portion located on the outer side relative to the corner and the wing portion located on the inner side relative to the corner, this difference being due to the asymmetric positioning of the rider during cornering; the rider's body is positioned in the slipstream of the inner wing portion and interferes with this slipstream. A value of 0 for the coefficient C _t indicates that the wing portion develops its own downforce without being disturbed. A value of 1 indicates that the wing portion in question generates no lift.

Figure 1 also shows a centre of pressure, that is to say a point where all the lift forces intersect. A vector of the resultant F _w of the lift forces is therefore applied to this point at a dis- tance r _cp from the origin of the coordinate system (coinciding with the rolling axis), forming an angle <p _cp relative to the plane of symmetry of the motorcycle. The vector F _w is a function of the lean angle and the interference coefficient:

Fw— f(Cl> <Plean - (7) A normal force having a modulus N and a static frictional force having a modulus μ _σ Ν also act at the contact point between the wheel of the motorcycle.

The resultant F _Q of the forces acting on the motorcycle is therefore given

while the rolling moment of the motorcycle is given

M ₀ = r _m x F _m + f _r x F _r + r _wl x F _wl + r _w2 x F _v (9)

At equilibrium, F ₀ = 0 and ₀ = 0. The inventors have carried out a series of calculations and simulations based on this system of equations, to verify the effect of the interference due to the rider's body on the aerodynamic operation of the wing portions fitted to the mo- torcycle. These calculations showed that it was essential, in order to provide effective interference, for these wing portions to be positioned in such a way that, during the running of the motorcycle, each of the wing portions is brought to be substantially in front of, and close to, a respective lower limb of the rider.

The provision of wing portions at an anhedral angle gives the motorcycle an additional downforce. This downforce increases the vertical normal force N. This yields a twofold benefit: for a given coefficient of static friction μ _σ , the component of the frictional force μ _σ Ν that improves cornering is increased; while, if the state of the tyres becomes degraded (a typical phenomenon occurring at the end of a race), causing a reduction in μ _σ , an adequate frictional force is still maintained.

Another important effect is that the wing portions at an anhedral angle can help to reduce the lean angle, generating a negative rolling moment. This moment opposes the moment due to the centrifugal forces acting on the centre of mass of the motorcycle and rider.

This enables the rider to take the corner at higher speed, while maintaining the same lean angle as that of a conventional motorcycle, or alternatively to stay at the same speed but with a more vertical attitude allowing a faster entry to and exit from corners. The benefit provided by the wing portions at an anhedral angle increases as the interference coefficient Cj approaches 1.

The inventors consider that the wing portions should have an anhedral angle of at least 30°. A smaller dihedral angle is not desirable, since the wing portion on the outer side of the corner would produce a certain negative lateral force component with the lean angles normally reached at high speed. It has also been calculated that the wing portions should be rather large in order to produce significant effects; a large dihedral angle also makes it possible to have a smaller lateral overall dimension for any given wing dimensions, which is desirable, in particular, in competition motorcycles, the dimensions of which are subject to stringent constraints. Figure 2a shows schematically a motorcycle 1 , the front fairing 10 of which has a pair of wing portions 20 according to the invention. In the example of Figure 2a, the wing portions 20 are directly connected to the fairing, at their upper end or root, but may also be supported by stays or struts. The wing portions 20 may also have terminal fins 23 on their free ends, to make positive use of the interaction with the vortices produced at these ends. In the example of Figure 2a, the terminal fins are free; in an alternative embodiment, they may be connected to the fairing, thus also acting as struts. These terminal fins, or struts if present, are not used for generating downforce.

One way of increasing the wing surface, and therefore the downforce effect, without further increasing the lateral overall dimension is to provide a plurality of wing portions 20'; 20"' according to the invention in a multi-plane arrangement (see Figs. 2b and 2d), that is to say a plurality of wing portions 20'; 20"' superimposed on each side of the front fairing 10. However, this arrangement would have the drawback of producing greater aerodynamic resistance for a given downforce. In the examples of Figs. 2b and 2d, the wing portions 20'; 20"' are directly connected to the fairing, but may also be supported by stays or struts. The wing portions 20'; 20"' may also have terminal fins 23'; 23"' on their free ends, to make positive use of the interaction with the vortices produced at these ends. In the examples of Figs. 2b and 2d, the terminal fins are free; in an alternative embodiment, they may be connected to the fairing, thus also acting as struts. These terminal fins, or struts if present, are not used for generating downforce. Figure 2c shows a particularly preferred embodiment of the invention. In this embodiment, each wing portion 20" comprises a plurality of wing segments 21", 22' for producing downforce, said wing segments being arranged consecutively along the longitudinal direction of the wing portion 20", and having an anhedral angle increasing from the root towards the free end of the wing portion 20". Each of the wing portions may be substantially flat, so that the wing portion to be constructed is substantially segmented, or the wing portion may extend in a curving manner, forming a concavity facing the plane of symmetry of the motorcycle (see Fig. 2i, in which the wing portions are indicated by 320; this configuration may be considered a limiting case of the preceding one, in which the wing segments have a point-like longitudinal extension).

In this arrangement, the wing portion 20" could have a minimum dihedral angle at the root or upper end of the wing portion in the range from 30° to 60°, and a maximum dihedral angle, towards the free end or lower end of the wing portion, in the range from 70° to 110°.

The embodiment of Fig. 2c combines the benefit of having multiple dihedral angles with that of having a larger wing surface in restricted lateral spaces. In the example of Figure 2c, the wing portions 20" are directly connected to the fairing, but may also be supported by stays or struts at various points along the wing portion (see Fig. 2g, in which the stays or struts are indicated by 123' and 124'). The wing portions 20" may also have terminal fins 23" on their free ends, to make positive use of the interaction with the vortices produced at these ends.

In the example of Figure 2c, the terminal fins are free; in alternative embodiments, shown in Figs. 2e and 2g, they may be connected to the fairing, thus also acting as stays or struts, indicated by 123. The terminal fins, or struts if present, are not used for generating down- force.

The example of Figure 2f is substantially similar to the example of Figure 2e, with the difference that the wing portions 220 are connected to the fairing by stays or struts 223 at their lower ends, while their upper ends are free. In this arrangement, the wing portion 220 has an upper wing segment 221 with a smaller dihedral angle, at the free end or upper end of the wing portion, in the range from 30° to 60°, and a lower wing segment 222 with a greater dihedral angle, towards the root or lower end of the wing portion, in the range from 70° to 110°. In further embodiments which are not illustrated, the aforesaid wing portions may be connected to the fairing by means of further stays. In other embodiments, the aforesaid wing portions may have more than two wing segments. In yet other embodi- ments, the aforesaid wing portions may extend in a curving manner.

The example of Figure 2h is similar to the example of Figure 2c, with the sole difference that the wing portions 20" are not connected to the fairing directly, but by means of respective supports 24" which are not used for generating downforce. In further embodi- ments which are not illustrated, these supports may also be present in the other embodiments described above. Figure 2j shows in plan view a motorcycle 1 having an aerodynamic device according to the invention, shown schematically. This aerodynamic device may conform to one of the embodiments described above or to other embodiments which may be devised by a person skilled in the art. Figure 2j shows that the wing portions of the device according to the in- vention may have a positive, negative or zero sweepback angle Λ. Figures 3a and 3b are images of a computational fluid dynamic analysis of a motorcycle having the aerodynamic device of Figure 2c, during cornering.