The present invention generally refers to a propulsion system by an electric motor in which the energy for its operation is supplied by a non- electrical source (mechanical).

More particularly, the invention relates to a propulsion system realized through the coupling of an axial flow generator and an axial flow motor, constituting a system for converting a determined amount of input energy into an output energy with a continuous variation of the torque and speed parameters.

The propeller thus realized can be applied in various fields, among which, for example, pedal assisted bicycles, propulsion systems for navigation, etc.

The object of the invention is to eliminate mechanical complexity, reduce weight and costs and increase reliability and efficiency with respect to a traditional system consisting of an engine followed by a gearbox and a transmission of the kind mechanical.

In fact, the configurations that are part of the prior art are mechanically complex, since it is necessary to use kinematic chains composed of cogs, or timing belt reductions, as well as the traditional mechanical transmission and all the associated shafts and bearings.

The complexity of traditional propulsion systems involves weights greater with respect to the invention presented here, necessity of maintenance, higher costs and overall efficiency of the inferior system. The object of the present invention, in this specific case, is to obviate the drawbacks of the prior art mentioned above and, in particular, to provide a propulsion system by means of an electric motor to be applied in situations in which it is necessary to supply the output shaft of the system the input energy with continuous variation of torque and speed according to the need. In particular, for pedal-assisted bicycles, the system allows to reduces the mechanical complexity (pedals, engine and gearbox) of known solutions, also reducing overall weight and total costs.

Another object of the present invention is to provide a propulsion system by means of an electric motor, which allows increasing the reliability of the mechanical/electrical complex, with respect to the known type of propulsion systems, at the same time increasing the overall efficiency of the system.

These and other purposes are achieved by an electric propulsion system, which can also be applied to pedal assisted bicycles, according to the attached claim 1 ; other technical features of the propulsion system according to the present invention are provided in the further dependent claims.

Advantageously, the propulsion system which is the object of the present invention is based on the coupling of an electric motor and a generator inserted both within the same group.

The energy applied to the input axle is conveyed on a high-efficiency electric generator. The electric energy thus obtained is conveyed towards the electric motor, and therefore towards the output axle, by means of an electronic circuit governed by a microcontroller and related software. The task of the circuit is to transform the energy in the components of speed and torque according to the usage of the system. In the case of the pedal assisted bicycle, the system is installed on the so- called "central movement" of the vehicle.

In this case, the axle of the pedals is directly connected to the axle of the generator. In particular, the input energy (generated by the pedalling) is sent to the motor by means of an electronic control system, which performs, through specific algorithms, the conversion in torque/speed according to the working conditions and the selected configuration.

In turn, the electric motor transmits the movement to the rear wheel by means of a chain or timing belt drive using a traditional crown and pinion.

Pedaling assistance is obtained by summing to the energy produced by the cyclist, the one coming from a rechargeable battery in the quantity required by the assistance level, which is selectable by means of appropriate commands. Again, in the specific case of pedal-assisted bicycles, the coupling of the motor to the crown is realized using a freewheel and in particular through the outer part of the freewheel.

The freewheel allows, in case of malfunctioning of the motor, to couple the input axle (in the example the axle of the pedals ) with the output axle and thus allow the use of the vehicle, even if limited to only one transmission ratio.

Further scopes and advantages of the present invention will become clear from the following description, which refers to an exemplary and preferred, but not limitative, exemplary embodiment of the propulsion system for electric vehicles in question, and from the annexed drawings, in which: - figure 1 shows a block diagram of a propulsion system for electric vehicles in general, according to the present invention;

- figure 2 shows a block diagram of a propulsion system applied in particular to pedal assisted bicycles, according to the present invention; - figure 2A shows a cross-sectional view of the propulsion system of figure 2, according to the present invention;

- figures 3, 4 and 5 show respective views in cross-section of as many other embodiments of the propulsion system as per figures 1 and 2, according to the present invention; - figures 6A, 6B and 6C show three different ways of mounting the magnets in a rotor of the propulsion system, according to the invention.

With particular reference to figure 1 , which shows a general propulsion system for vehicles, an axial flow electric generator 2 and an axial flow electric motor 3 are connected to each other by means of a programmable electronic circuit 5 through commands and settings 7.

The input axle 1 of the generator 2 is utilized to connect the mechanical energy source; in the case of a pedal assisted bicycle, for example, this axle 1 coincides with the axle connected to the bicycle pedals.

The output axle 4 of the electric motor 3 transmits the motion which realizes the propulsion and, in particular, the input energy is transmitted to the output through the intervention of appropriate algorithms for adjusting the drive parameters of the motor 3, which transform the input energy into torque and speed, just like a traditional mechanical gear; this configuration allows to obtain high yields (higher than 95%) of the two electric machines (generator 2 and motor 3) with reduced overall size. The axial flow generator 2 is composed of a rotor equipped with permanent magnets arranged according to the classic alternating configuration (North-South) or according to the configuration known as "Halbach Array". The solution of the propulsion system referred to above, applied to a pedal assisted bicycle and illustrated in figures 2 and 2A attached, provides, similarly to what has already been described, the use of an axial flow electric generator 2 and an axial flow electric motor 3.

Just like the previous description, also in this case an electronic circuit 5, at the input appropriate commands and settings 7 are sent, manages the transfer of energy from the generator 2 to the motor 3; the pedal assistance is provided by summing the energy generated by the pedaling itself to that of the battery 6 in the proportion required by the commands equivalent to those given to the traditional mechanical gear and to the assistance settings 7 (higher or lower) selectable by the cyclist.

This configuration allows obtaining high yields (equal to or greater than 95%) of the two electric machines (generator 2 and motor 3) with sizes compatible with the application.

Also, in this case, the axial flow generator 2 is composed of a rotor 16 provided with permanent magnets arranged according to the classic alternating configuration (North-South) or according to the configuration known as "Halbach Array".

Infront the rotor 16 of the generator 2, the stator 17 is positioned, which is composed of a series of copper windings and the rotor-stator interaction transforms the motion of the pedals 12, 15 into energy to be used for driving the axial flow motor 3. A freewheel 1 1 , mounted on the axle 13 of the pedals 12, 15, allows, in the absence of operation of the motor 3, to transmit the motion of the pedals 12, 15 to the rear wheel of the bicycle, by means of a crown 23, a chain or timing belt 24 and a pinion coupled to the aforesaid rear wheel. The axial flow electric motor 3 thus transmits its movement to the rear wheel of the bicycle through the outer part of the freewheel 1 1 , which allows releasing the pedals 12, 15 from the axle of the electric motor 3; in this way, a speed of the electric motor 3 just when above that of the pedaling, it is sufficient to ensure that the only contribution to the motion of the rear wheel of the bicycle is given by the electric motor 3, since the latter receives the energy produced by the pedaling through the electronic circuit 5 equipped with microcontroller and firmware.

Through the aforementioned electronic circuit 5, the power generated by the axial flow electric generator 2 is used to drive the axial flow electric motor 3.

The axial flow electric motor 3 is composed of a rotor 10 provided with permanent magnets arranged according to the classical alternate configuration (North-South) or according to the configuration known as "Halbach Array" and, in front of the rotor 10, a stator 19 is positioned composed of copper windings.

The rotor-stator interaction transforms the energy received from the axial flow electric generator 2, possibly added to that of the rechargeable battery 6, in motion transmitted to the rear wheel of the bicycle by means of the crown 23, which drives the chain or timing belt 24. It has therefore been said that the electric motor 3 receives, by means of the electronic circuit 5, equipped with appropriate software and firmware, the energy produced by the pedaling; in fact, it can be affirmed that the energy from the pedaling, converted into electricity, is again transformed into motion, to the net of the losses of the system, thus creating an electric axle equivalent to the normal mechanical axle of a traditional bicycle equipped with a crown, chain and pinion . If the cyclist requires the intervention of electric assistance (pedal- assisted), it is the task of the electronic circuit 5 to sum the energy generated by the pedaling to that of the rechargeable battery 6.

Another fundamental task of the electronic circuit 5 and the software that manages it, is that of transforming the energy of the pedaling in torque and speed according to the conditions of the route (on plain or uphill, for example), just like a normal gearbox of the mechanical type.

In fact, using the control system algorithms, the following equation is applied rWl = Nm ^* 2π ^* RPM 60 from which it is easily understood that, for example, an uphill path will require more torque.

Then fix a power value (W), given by the sum of the energy of the pedaling and that of the rechargeable battery 6, so that the speed reduction (revolutions per minute) and the increase of the torque (Nm) will allow satisfying the equation.

Vice versa, a plain or downhill path can express the power increasing the speed and reducing the torque since the latter is less necessary on a plain and/or downhill path. The electronic circuit 5, in practice, converts the energy generated by the pedaling in function of torque and speed transferred to the axial flow electric motor 3 according to the type of path made by the bicycle.

Finally, during braking or downhill, the axial flow electric motor 3 can be used as a generator and to recharge the battery used for servicing.

In fact, in the first phase of braking, only the engine brake is inserted, which recharges the battery 6 by decelerating the bicycle and then, for more precise braking, the brake acts on the normal mechanical braking system of the bicycle. Both electric machines (motor 3 and generator 2) can also be used as generators to increase the braking force; any excess of energy produced, if not absorbed by the charging system, can be accumulated instantaneously thanks to the use of adequate storage systems (supercap or other) and used both to provide starting energies (typical snap start and stop requests of the urban cycles) and to recharge the batteries in longer times (and therefore compatible with the cycles of charge and discharge of the accumulators).

According to an alternative and non-limiting embodiments, the axial flow motor 3 can be provided with two magnet-holder rotors 18, which are connected to a stator disc 9 for solenoids by means of two angular contact ball bearings 8 (Figure 3).

The use of bearings 8 guarantees an excellent precision of the space (gap) that must be maintained between magnets and solenoids; in fact, the accuracy of this gap is obtained by a simple coupling chain between the stator disk 9 supporting the solenoids, the bearing 8 and the magnet holder rotor 18. In this way, unlike a conventional external case configuration (such as the one shown in figure 2A attached), the solenoid-holder stator disk 9 is rotatably connected to the magnet-holder rotors 18, thus simplifying the constructive form and the costs of the mechanical parts. The central axle or shaft 13 is connected to the magnet-holder rotors 18 by free wheels 14; in a specific case of the application of the pedal assisted bicycle, this configuration makes the motor 3 free to disengage from the axle 13 of the pedals 12, 15 and becomes particularly useful in case it wants to exploit the motor 3 as a generator for energy recovery during deceleration (thus it is possible in fixed gear bicycles without gearbox or with gearbox but without rear freewheel).

The construction scheme described previously and illustrated in figure 3 attached also allows a modular assembly, which allows increasing the power and torque on the central axle or shaft 13, as shown in detail in the attached figure 4; in this way, given that the operating characteristics are the same as those of the single-engine, two or more electric motors 3 can be coupled in parallel simply by locking them firmly or with freewheels 14 to the shaft 13.

In figure 5 attached, a schematic representation of the coupling of a double-shaped electric motor 3, such as that shown in figure 4, with an axial flow electric generator 2, which is constituted, in particular, by two parallel units equipped with respective magnet holders rotors 20 and solenoid holders stator discs 21 .

The central shaft 13 cages the generator 2 in a fixed manner, while the motor 3 is keyed onto the shaft 13 through the freewheels 14.

In the case of application to a pedal assisted bicycle, in this way, the generator 2 is fixed to the axles 13 of the pedals 12, 15, while the motor 3 can, thanks to the free wheels 14, spin at speed higher than the speed of rotation of the pedals 12, 15; also, in this case, it can be seen that, thanks to the use of angular contact bearings 8 placed between the rotors 18, 20 and the stator 9, 21 , the system is extremely simple and economical from a mechanical point of view.

Finally, figures 6A, 6B and 6C attached show three different methods for mounting the permanent magnets 22, which are placed on special disks 25 applied to the rotors 10, 18 of the motor 3 and to the rotors 16, 20 of the generator 2. In particular, figure 6A shows a configuration of magnets 22 mounted in opposite poles sequence; usually, in this case, the support of the magnets 22 is made of ferromagnetic material to short-circuit the flow between magnet and magnet.

Figure 6B shows an assembly of magnets 22 with Halbach Array in perimetral sequence, while in figure 6C an assembly is shown with Halbach Array with the radial polar sequence.

It is recalled that a Halbach Array is a particular union or layout of permanent magnets 22 realized in a way to reinforce the magnetic field along a face of the array and, at the same time, cancel by interference, the magnetic field in the opposite face.

From the description made, the characteristics of the propulsion system for electric vehicles and, in particular, for pedal-assisted bicycles, which is the object of the present invention are made clear, so as its advantages.

In particular, the aforementioned advantages relate to: - development of a propulsion system with electronic torque and speed regulation without the use of mechanical components; - compacting the aforementioned system into a single component of reduced dimensions;

- reduction of weight, since the type of motor and generator used and the absence of a mechanical gearbox reduce the overall weight of the vehicle; - increase in reliability, since the elimination of mechanical parts and gears, has as a direct consequence of the increase in reliability of the vehicle;

- cost reduction, since the simplicity of the electric machines used (engine and generator) and the elimination of complex mechanics, reduce the cost of the solution, compared to the known ones;

- increase in efficiency, as the efficiency of the system, is higher than that of a traditional drive chain.

In the specific case of application to a pedal assisted bicycle, the advantages achieved mainly consist of the elimination of the mechanical complexity of a normal pedal assisted bicycle, as gears, reduction and consequent bearings are eliminated.

Finally, it is clear that many other variants can be made to the propulsion system in question, without departing from the novelty principles of the inventive idea as claimed in the attached claims, as it is clear that, in the practical implementation of the invention, the materials, shapes and dimensions of the illustrated details may be any according to the requirements and the same can be replaced with other equivalents.