The present invention relates to a wind energy recovery device for motor vehicles and a motor vehicle comprising at least one wind energy recovery device according to the invention.

Various types of wind energy recovery devices for motor vehicles have been known to the art for some time, at least in concept. The purpose of these devices is to convert the kinetic energy of an air flow generated by the relative motion between a motor vehicle and the air of the surrounding environment, in particular during travel of the motor vehicle, into electric power. The electric power produced can advantageously be used, for example, to contribute to charging battery power packs for electric or hybrid powered motor vehicles, in order to increase their autonomy, or also to at least partially supply autonomous electric devices installed in motor vehicles with conventional internal combustion engines or also electric or hybrid powered vehicles, reducing the reliance on a service battery commonly provided for this purpose.

A general type of prior art wind energy recovery devices for motor vehicles essentially comprises a duct through which an air flow can flow and at least one rotor or fan arranged inside the duct, which is made to rotate by the air flow and is operatively connected to electric power generation means.

Within this general type, by way of example CN205589003U describes a wind power generation system for electric vehicles comprising a duct having a funnel shaped air flow inlet portion that opens toward a front air intake of a vehicle. A fan is arranged in the funnel shaped air flow inlet portion, mounted on a rotation shaft whose rotation axis coincides with the central axis of the duct. The rotation shaft is connected to a generator located outside the duct and electrically connected to a battery bank of the vehicle with the interposition of a transformer.

US 3,374,849 describes an electric powered motor vehicle comprising an electric motor, two battery banks to alternately power the electric motor and an air turbine to alternately charge one of the battery banks while the other is supplying the electric motor. The air turbine comprises an enclosure that extends longitudinally for the full length of the vehicle and comprises an air intake at the front side of the vehicle and two discharge ducts terminating at the rear side of the vehicle. The enclosure of the turbine is formed by several longitudinal sections having a progressively smaller diameter in the direction of the discharge ducts and inside it a shaft, on which two pairs of turbine rotors or fans are mounted axially spaced from each other, is rotatably supported. By means of a coupling and of two belt drives the shaft is selectively connectable to two distinct pairs of alternators located outside the enclosure, each connected to one of the battery banks.

Regardless of the specific configuration, wind energy recovery devices of the aforesaid general type for motor vehicles that have found concrete application are generally designed to operate optimally with speeds of the air flow flowing through them that are relatively high, above a given threshold. Below this threshold, the electric power produced decreases considerably until practically reaching zero. In these conditions, the presence of wind energy recovery devices on motor vehicles does not provide any significant contribution to improving their performance, or can even worsen it due to the additional weight.

US 6,138,781A describes a system for generating electricity in a vehicle by means of wind energy conversion. The system is based on a multi-stage rotor assembly comprising a high speed rotor and a low speed rotor mounted on two independent shafts, which drive respective generators. The two rotors are supported in a rotor assembly casing, in which an air flow coming from air intakes at the front side of the vehicle is fed through specific ducts or tunnels extending along the vehicle. The air flow is selectively sent to the high speed rotor or to the low speed rotor, based on a signal coming from a speed sensor that measures the speed of the air that reaches the multi-stage rotor assembly.

The main object of the present invention is to provide an improved wind energy recovery device for motor vehicles of the aforesaid general type, which allows extension of the speed range in which energy can be effectively extracted from an air flow flowing through it.

Another object of the present invention is to provide a wind energy recovery device for motor vehicles with a structure that is as compact as possible and easily integrated in existing motor vehicles, and which can be manufactured cost-effectively.

According to the invention, these objects are achieved by a wind energy recovery device for motor vehicles comprising:

- a tubular duct configured to receive an air flow generated by a relative motion between the wind energy recovery device and air of the surrounding environment when the wind energy recovery device is mounted on a motor vehicle, the tubular duct having an air flow inlet portion and an air flow outlet portion;

- a primary rotor and a secondary rotor arranged in the tubular duct, which can be made to rotate by said air flow and are operatively connected with electric power generation means,

The primary rotor and the secondary rotor can be made to rotate independently from each other and are configured and/or installed in the tubular duct so that when the air flow in the tubular duct has a speed higher than a predetermined threshold value at least said primary rotor is made to rotate and when the air flow in the tubular duct has a speed lower than said predetermined threshold value at least the secondary rotor is made to rotate.

The primary rotor and the secondary rotor have respective rotation axes coinciding with a longitudinal center axis of the tubular duct.

The primary rotor and the secondary rotor are operatively connected with the electric power generation means by means of respective coaxial shafts and the shaft of the primary rotor is at least partially rotatably received within the shaft of the secondary rotor.

The electric power generation means comprise at least one first rotor unit rotatably integral with the primary rotor, at least one second rotor unit rotatably integral with the secondary rotor, and corresponding stator units arranged around said at least one first and at least one second rotor units.

Advantageously, the use of two independent rotors, suitable to be activated respectively below and above a predetermined threshold value of the speed of the air flow flowing in the wind energy recovery device allows energy to be effectively extracted from the air flow not only in the presence of relatively high flow speeds, as typically occurs in the prior art devices, but also in the presence of lower flow speeds. This increases the speed range of the air flow within which the wind energy recovery device can operate efficiently and consequently contribute positively to the energy balance of the motor vehicle in which kit is installed. Due to extension of the useful speed range of the air flow, in particular to lower values, the wind energy recovery device according to the invention is advantageously capable of operating effectively even when a motor vehicle on which it is installed is travelling at low speed, as is often the case in urban traffic.

Moreover, due to the construction solutions in accordance with the invention it is possible to produce wind energy recovery devices with two independent rotors operating as described above which also have a particularly compact and lightweight structure, and are therefore easily integrated in motor vehicles, and can be manufactured relatively cost- effectively.

Preferred features of the wind energy recovery device of the invention are defined in the appended claims 2-6, the content of which is fully incorporated herein for reference.

The invention also relates to a motor vehicle, in particular an electric or hybrid powered motor vehicle, comprising at least one wind energy recovery device having the aforesaid features.

Further features and advantages of the invention will be more apparent from the following detailed description of preferred embodiments thereof, set forth below by way of non-limiting example, with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic perspective view of a preferred embodiment of a wind energy recovery device for motor vehicles according to the invention;

Fig. 2 is a schematic perspective view of the wind energy recovery device of Fig. 1, in which the tubular duct is represented in transparency to show the inner components of the device;

Fig. 3 is a schematic longitudinal sectional view of the wind energy recovery device of Fig. i;

Fig. 4 is a schematic front view of the wind energy recovery device of Fig. 1, and

Fig. 5 is a schematic perspective view of a motor vehicle comprising a plurality of wind energy recovery devices of the type shown in Fig. 1.

In Figs. 1-4 a wind energy recovery device according to the invention for motor vehicles is indicated as a whole with the reference numeral 1.

The wind energy recovery device 1 comprises a tubular duct 2, which preferably forms an outer enclosure of the device. The tubular duct 2 can be flowed through by an air flow A, indicated with arrows in Figs. 2 and 3, which is generated following a relative motion between the wind energy recovery device 1 and air of the surrounding environment.

To this end, the tubular duct 2 comprises an air flow inlet portion 21, at which the air flow A enters the tubular duct 2 and an air flow outlet portion 22, at which the air flow A exits the tubular duct 2, which are connected to each other through an intermediate portion 23 of the tubular duct 2. The tubular duct 2 can be made in one piece or can be formed of several portions, which may be coincident with the above-mentioned portions 21, 22, 23, which can be assembled to one another in a removable manner.

The tubular duct 2 preferably has a rectilinear longitudinal center axis X-X and has, as a whole, a preferably symmetrical shape in rotation with respect to the longitudinal center axis X-X.

The air flow inlet portion 21 of the tubular duct 2 comprises a preferably funnel shaped air intake 210, convergent in the flow direction of the air flow A, and preferably a convex curvilinear wall, when observing the surface of the tubular duct 2 from the inside. This configuration facilitates the collection of air and increases the speed of the air flow A at the entrance to the wind energy recovery device 1.

The air flow outlet portion 22 of the tubular duct 2 preferably also terminates with a funnel shaped air discharge end 220, convergent in the flow direction of the air flow A, preferably with a rectilinear wall, i.e., truncated cone shaped. A coupling element 221 can advantageously be provided at the air discharge end 220, to facilitate, where desired, connection of a duct for collecting the exiting air flow A to the wind energy recovery device 1.

As is visible in particular in Figs. 2 and 3, a primary rotor or fan 3 and a secondary rotor or fan 4, which can be made to rotate by the air flow A independently from each other, are arranged in the tubular duct 2.

The primary rotor 3 and the secondary rotor 4 are also configured and/or installed in the tubular duct 2 so that when the air flow A in the tubular duct has a speed higher than a predetermined threshold value at least the primary rotor 3 is made to rotate and when the air flow A in the tubular duct 2 has a speed lower than said predetermined threshold value at least the secondary rotor 4 is made to rotate.

In the case of use of the wind energy recovery device 1 on motor vehicles, the aforesaid threshold value of the speed of the air flow A flowing through the tubular duct 2 can advantageously be between around 15 m/s and around 20 m/s. Assuming the air surrounding the motor vehicle to be stationary, these values correspond to a travelling speed of the motor vehicle ranging from around 50 km/h to around 70 km/h, which typically characterize the passage from slow urban travel to fast urban or suburban travel. In this case, the primary rotor 3 ensures an effective energy extraction from the air flow A at higher travelling speeds of the motor vehicle, while the secondary rotor 4 ensures an effective energy extraction from the air flow A at lower travelling speeds of the motor vehicle, preferably up to at least around 20 km/h, corresponding to a speed of the air flow A in the tubular duct 2 of around 5 m/s, assuming the surrounding air to be stationary.

The operation described above can be obtained by appropriately selecting the construction parameters of the primary rotor 3 and of the secondary rotor 4, such as mass, diameter, number and shape of the blades.

Preferably, the primary rotor 3 has a moment of inertia greater than the moment of inertia of the secondary rotor 4. More preferably, the primary rotor 3 has a diameter greater than the diameter of the secondary rotor 4.

Alternatively or in addition to an appropriate configuration of the primary rotor 3 and of the secondary rotor 4, the operation described above can be obtained through an appropriate mounting of the rotors in the tubular duct 2.

In particular, the wind energy recovery device 1 can advantageously be provided with braking means (not show) acting on the primary rotor 3 so as to prevent rotation thereof when the air flow A has a speed lower than said predetermined threshold value.

The primary rotor 3 and the secondary rotor 4 have respective rotation axes coinciding with the longitudinal center axis X-X of the tubular duct 2. Consequently, the primary rotor 3 and the secondary rotor 4 are arranged and rotate in the tubular duct 2 perpendicularly to the longitudinal axis X-X thereof.

The primary rotor 3 is preferably located in the air flow inlet portion 21 of the tubular duct 2, close to the air intake 210 and is directly facing it. The secondary rotor 4 is preferably arranged in the tubular duct 2 downstream of the primary rotor 3 with respect to the flow direction of the air flow A, in particular in the intermediate portion 23 of the tubular duct 2.

Preferably, in the section between the primary rotor 3 and the secondary rotor 4 the tubular duct 2 has a shape convergent in the flow direction of the air flow A, more preferably a concave curvilinear wall, when observing the surface of the tubular duct 2 from the inside.

Through the arrangement of the rotors 3, 4 and the shape of the tubular duct 2 described above, a section operating as nozzle, which increases the speed of the air flow A reaching the secondary rotor 4, is advantageously created in the wind energy recovery device 1. This further contributes to the capacity of this latter to extract energy from air flows A at low speeds.

The primary rotor 3 and the secondary rotor 4 are mounted on, or formed in one piece with, respective coaxial shafts 5, 6. As can be seen in particular in Fig. 3, the shaft 5 of the primary rotor 3 is at least partially rotatably received within the shaft 6 of the secondary rotor 4. This configuration allows implementation of the functional features of the wind energy recovery device 1 described above in a particularly compact form.

In particular, the shaft 6 of the secondary rotor 4 preferably also projects from the front side of said secondary rotor 4, preferably until reaching the axial position of the primary rotor 3, and is supported in rotation by means of supporting fins 61 projecting radially from the inner surface of the tubular body 2 with the operational interposition of a plurality of bearings 62. For example, in the preferred embodiment illustrated here two arrays of supporting fins 61 are provided, respectively upstream and downstream of the secondary rotor 4 with respect to the flow direction of the air flow A and each comprising four supporting fins 61 arranged substantially in the shape of a cross. For reasons of clarity, in Fig. 2 only some of the supporting fins 61 are indicated with the respective reference numerals. The shaft 5 of the primary rotor 3 is in turn supported in rotation inside the shaft 6 of the secondary rotor 4 by means of a plurality of bearings 52 (Fig. 3).

By means of the respective shafts 5, 6 the primary rotor 3 and the secondary rotor 4 are operatively connected to electric power generation means, visible in particular in Figs. 2 and 3. The electric power generation means can indifferently be of direct current or alternating current type. Preferably, the electric power generation means comprise at least one first rotor unit 71 rotatably integral with the primary rotor 3 by means of the shaft 5, at least one second rotor unit 72 rotatably integral with the secondary rotor 4 by means of the shaft 6, and corresponding stator units (not shown in the figures) arranged around the rotor units 71 and 72. The stator units could also be structurally and/or electrically connected to each other so as to form a single stator unit.

In any case, all the components of the electric power generation means are preferably fully received within the tubular duct 2. In this way the wind energy recovery device 1 is completely autonomous from a functional viewpoint and also particularly compact and easily installable as single component on a motor vehicle.

The wind energy recovery device 1 can advantageously comprise heating means 8, which can preferably be operated selectively, for heating the air flow A flowing in the tubular duct 2. The air flow A exiting from the wind energy recovery device 1 at a higher temperature can be used, for example, to heat a battery compartment of a motor vehicle during cold weather, so as to counter the negative effects of low temperatures on the batteries, in particular their lower charge duration.

The heating means 8 can be arranged inside the tubular duct 2, as schematically shown in Figs. 2 and 3, preferably downstream of the secondary rotor 4 and of the electric power generation means, in particular in the area of the air flow outlet portion 22 of the tubular duct 2. However, it would also be possible for the heating means 8 to be arranged in other positions along the tubular duct 2 and/or outside the tubular duct 2, in contact with its walls or integrated therein.

The wind energy recovery device 1 is advantageously made of lightweight materials. In particular, metal materials such as magnesium, aluminium and their alloys can preferably be used for the tubular duct 2, while hard plastic materials, such as PTFE, PEEK or other suitable technopolymers, in the case reinforced with fibers, can be used for the rotors 3, 4 and the respective shafts 5, 6.

Fig. 5 shows a motor vehicle 100 in which wind energy recovery devices 1 according to the invention, having the structural and functional features described above, are installed.

The motor vehicle 100 is preferably an electric or hybrid powered motor vehicle, in which the wind energy recovery devices 1 are mainly used as an aid for charging the batteries that power the motor vehicle 100, thus contributing to increasing its autonomy. However, the motor vehicle 100 could also be a motor vehicle powered by a conventional internal combustion engine and in this case the wind energy recovery devices 1 could advantageously be used to at least partially power autonomous electric devices installed in the vehicle, reducing the consumption of the conventional service battery of the motor vehicle.

In the example shown, the wind energy recovery devices 1 are preferably arranged in a front area of the motor vehicle 100, more preferably in an engine compartment, at a front air intake thereof. However, according to the type and shape of the motor vehicle 100, the wind energy recovery devices 1 could also be installed at other air intakes, for example provided on the hood, close to the front headlamps or along the sides of the motor vehicle, although preferably always inside the body of the motor vehicle 100.

In the case in which the wind energy recovery devices 1 are provided with heating means 8 that can be operated selectively as described previously, the motor vehicle 100 can also be provided with ducts, collectors or other conveying means for placing the air discharge end 220 of each wind energy recovery device 1 in fluid communication with a compartment containing the power batteries or service battery of the motor vehicle 100, so as to heat this compartment with the heated air flow A exiting each wind energy recovery device 1.

Naturally, a person skilled in the art may make modifications and variations to the wind energy recovery device 1 described above in order to satisfy specific and contingent application requirements, without said modifications and variations departing from the scope of protection defined by the following claims.

In particular, the wind energy recovery device 1 could comprise more than two rotors made to rotate independently from each other, and each of these rotors could be configured and/or installed in the tubular duct 2 so as to be made to rotate in a corresponding predetermined speed range of the air flow A flowing in the tubular duct 2.