IT201700010847A1 - PROPULSION SYSTEM FOR ELECTRIC VEHICLES - Google Patents

Description

PROPULSION SYSTEM FOR ELECTRIC VEHICLES

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

More specifically, the invention relates to a propulsion system made by coupling an axial flux generator and an axial flux motor, constituting a system for converting a certain amount of input energy into output energy with variation continuous of the torque and speed parameters.

The engine thus created can be applied in various fields, including, for example, pedal assisted bicycles, propulsion systems for navigation, etc.

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

In fact, the configurations that are part of the known art are mechanically complex, since it is necessary to use kinematic chains composed of gears, or toothed belt reductions, as well as the traditional mechanical gearbox and all the relative shafts and bearings.

The complexity of traditional propulsion systems involves heavier weights than the invention presented here, the need for maintenance, higher costs and a lower overall system efficiency.

The purpose of the present invention is, in the specific case, 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 axis of the system the input energy with continuous variation of torque and speed according to the needs.

In particular, for pedal assisted bicycles, the system allows to reduce the mechanical complexity (pedals, motor and gearbox) of the known solutions, also reducing the overall weight and the total costs.

Another purpose of the present invention is to create a propulsion system using an electric motor, which allows to increase the reliability of the mechanical / electrical complex, compared to known propulsion systems, while 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 characteristics of the propulsion system according to the present invention are provided in the further dependent claims.

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

The energy applied to the input axis is conveyed to a high efficiency electric generator. The electricity thus obtained is conveyed to the electric motor, and then to the output axis, by means of an electronic board governed by a microcontroller and related software. The task of the board is to transform the energy into the speed and torque components according to the system usage needs.

In the case of the pedal assisted bicycle, the system is installed on the so-called “bottom bracket” of the vehicle.

In this case, the axis of the pedals is directly connected to the axis of the generator.

In particular, the input energy (generated by pedaling) is sent to the motor by means of an electronic control system, which realizes, through specific algorithms, the conversion into torque / speed depending on the working conditions and the selected configuration.

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

Pedaling assistance is obtained by adding to the energy produced by the cyclist that coming from a rechargeable battery in the amount required by the degree of assistance, which can be selected using appropriate commands.

Again in the specific case of pedal assisted bicycles, the coupling of the motor with the crown is achieved by means of a free wheel and in particular by means of the external part of the same.

The freewheel allows, in case of engine failure, to couple the input axis (in the example the pedal axis) with the output axis and thus allow the use of the vehicle, even if limited to a gear ratio only.

Further objects and advantages of the present invention will become clear from the following description, which refers to an exemplary and preferred, but not limitative, embodiment of the propulsion system for electric vehicles in question, and from the attached 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 cross-sectional views of as many embodiments of the propulsion system of 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 generic propulsion system for vehicles, an axial flux electric generator 2 and an axial flux electric motor 3 are connected to each other by means of an electronic card 5 programmable by means of commands and settings 7.

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

The output axis 4 of the electric motor 3 transmits the motion that realizes the propulsion and, in particular, the input energy is transmitted to the output through the intervention of suitable algorithms for regulating the operating parameters of the motor 3, which they transform the input energy into torque and speed, exactly as a traditional mechanical gearbox would do; this configuration allows to obtain high efficiency (higher than 95%) of the two electric machines (generator 2 and motor 3) with reduced dimensions.

The axial flux 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 the "Halbach Array". The solution of the propulsion system described above, applied to a pedal assisted bicycle and illustrated in the attached figures 2 and 2A, provides, in a similar way to what has already been described, the use of an axial flow electric generator 2 and of a axial flux electric motor 3.

As for the previous description, also in this case an electronic board 5, to whose input appropriate commands and settings 7 are sent, manages the energy transfer from generator 2 to motor 3; pedaling assistance is provided by adding to the energy generated by the pedaling itself that of the battery 6 in the proportion required by the commands equivalent to those given to the traditional mechanical gearbox and to the assistance settings 7 (greater or lesser) selectable by the cyclist.

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

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

In front of the rotor 16 of the generator 2 the stator 17 is positioned, consisting of a series of copper windings and the rotor-stator interaction transforms the motion of the pedals 12, 15 into energy to be used to drive the axial flux motor 3 .

A free wheel 11, mounted on the axis 13 of the pedals 12, 15, allows, in the absence of drive 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 belt toothed 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 by means of the external part of the free wheel 11, which allows the pedals 12, 15 to be released from the axis of the electric motor 3; in this way, a speed of the electric motor 3 just higher than that of pedaling 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 by means of the electronic board 5 equipped with microcontroller and firmware. Through the aforementioned electronic board 5, the power generated by the axial flux electric generator 2 is used to drive the axial flux electric motor 3.

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

The rotor-stator interaction transforms the energy received from the axial flux electric generator 2, possibly added to that of the rechargeable battery 6, into motion transmitted to the rear wheel of the bicycle by means of the crown 23, which drives the chain or toothed belt 24.

It has therefore been said that the electric motor 3 receives, through the electronic board 5 equipped with special software and firmware, the energy produced by pedaling; in fact, it can be said that the pedaling energy, converted into electricity, is transformed again into motion, net of the system losses, thus creating an electric axis equivalent to the normal mechanical axis of a traditional bicycle equipped with a crown, chain and pinion.

If the cyclist requires the intervention of the electrical assistance (eg assisted by the assisted person), it is the task of the electronic board 5 to add to the energy generated by pedaling that of the rechargeable battery 6.

Another fundamental task of the electronic board 5 and of the software that manages it is to transform the pedaling energy into torque and speed according to the conditions of the route (flat or uphill, for example), as would a normal mechanical change.

In fact, the following equation is applied using the algorithms of the control system

from which it is easy to understand that, for example, an uphill journey will require more torque.

Once a power value (W) has been set, given by the sum of the pedaling energy and that of the rechargeable battery 6, the reduction in speed (revolutions per minute) and the increase in torque (Nm) will allow satisfy the equation.

Conversely, a flat or downhill route can express power by increasing speed and reducing torque, the latter being less necessary on a flat and / or downhill route. The electronic board 5, in practice, converts the energy generated by pedaling into torque and speed functions transferred to the axial flux electric motor 3 depending on the type of path taken by the bicycle.

Finally, during braking or during a downhill ride, the axial flux electric motor 3 can be used as a generator and recharge the battery used for assistance.

In fact, in the first stage of braking, only the engine brake is engaged, which recharges the battery 6 by decelerating the bicycle and then, for more decisive 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 energy produced, if not absorbable by the recharging system, can be accumulated instantaneously thanks to the use of adequate storage systems (supercap or other) and be used both to provide starting energies (instantaneous requests for typical start and stop of urban cycles) and to recharge the batteries in longer times (and therefore compatible with the charge and discharge cycles of the accumulators).

According to alternative and non-limiting embodiments, the axial flux motor 3 can be equipped with two magnet-carrying rotors 18, which are connected to a solenoid-carrying stator disc 9 by means of two angular contact ball bearings 8 (fig. 3 ).

The use of bearings 8 guarantees excellent accuracy of the space (gap) that must be maintained between magnets and solenoids; in fact, the accuracy of this gap is obtained by means of a simple coupling chain between the stator disk 9 supporting the solenoids, the bearing 8 and the magnet-carrying rotor 18.

In this way, unlike a classic external casing configuration (such as that shown in the attached figure 2A), the solenoid-holder stator disc 9 is rotatably constrained to the magnet-holder rotors 18, thus simplifying the constructive form and costs of the mechanical parts. The axis or central shaft 13 is bound to the magnet-holder rotors 18 by free wheels 14; in the specific case of the application to pedal assisted bicycles, this configuration makes the motor 3 free to disengage from the axis 13 of the pedals 12, 15 and becomes particularly useful if you want to use the motor 3 as a generator for energy recovery during deceleration (this is possible in fixed gear bicycles without gearbox or with gearbox but without rear freewheel).

The construction scheme described above and illustrated in the attached figure 3 also allows a modular assembly, which allows to increase the power and torque on the axis or central shaft 13, as shown in detail in the attached figure 4; in this way, given that the operating characteristics are like those of the single motor, two or more electric motors 3 can be coupled in parallel simply by keying them fixedly or with free wheels 14 to the shaft 13.

The attached figure 5 schematically represents the coupling of an electric motor 3 with double conformation, such as the one represented in figure 4, with an axial flux electric generator 2, which is constituted, in particular, by two units in parallel equipped with respective rotors 20 magnet holders and stator discs 21 solenoid holders.

The central shaft 13 holds the generator 2 in a fixed way, while the motor 3 is keyed on the shaft 13 through the free wheels 14.

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

Finally, in the attached figures 6A, 6B and 6C three different ways of assembling the permanent magnets 22 are shown, which are placed on special discs 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 a sequence with opposite poles; usually, in this case, the support of the magnets 22 is made of ferromagnetic material to short-circuit the flux between the magnet and the magnet. Figure 6B shows a mounting of magnets 22 with a perimeter sequence Halbach Array, while Figure 6C shows a mounting with Halbach Array with a radial polar sequence.

It should be remembered that a Halbach Array is a particular union or layout of permanent magnets 22 made in such a way as to strengthen the magnetic field along one face of the array and, at the same time, cancel the magnetic field on the opposite face by interference.

From the above description 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 clear, as are the advantages.

In particular, the aforementioned advantages concern:

- creation of a propulsion system with electronic torque and speed regulation without the use of mechanical components;

- compaction of the aforementioned system into a single small component;

- weight reduction, as the type of engine and generator used and the absence of a mechanical gearbox reduce the overall weight of the vehicle;

- increase in reliability, as the elimination of mechanical parts and gears has the direct consequence of increasing the reliability of the vehicle;

- cost reduction, as the simplicity of the electrical machines used (motor 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 kinematic chain.

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

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

Barzanò & Zanardo Roma S.p.A.

Claims (10)

CLAIMS 1. Electric propulsion system with transformation of mechanical energy in input into electric energy in output, characterized by the fact of comprising an electric motor (3) with axial flow and an electric generator (2) with axial flow, in which an input axis (1) of said electric generator (2) is connected to a mechanical source of energy and in which said electric motor (3) and electric generator (2) are electrically interconnected by means of a programmable electronic card (5), which transforms, on the basis of externally supplied adjustments and commands (7), an input energy component into energy available at an output axis (4) of said electric motor (3) with continuous torque and speed adjustment. 2. Propulsion system as in claim 1, characterized in that said electric generator (2) is composed of at least one rotor (16, 20) equipped with permanent magnets (22) and at least one stator (17, 21) which carries a series of solenoids, while said electric motor (3) is composed of at least one rotor (10, 18) equipped with permanent magnets (22) and at least one stator or stator disc (9, 19) carrying a series of solenoids. 3. Propulsion system as in claim 2, characterized in that said at least one rotor (10, 18) of said electric motor (3) is rotatably constrained to said at least one stator or stator disk (9, 19) for solenoid-carrying said electric motor (3) by means of angular contact ball bearings (8), in order to maintain a correct space between said magnets (22) and said solenoids. 4. Propulsion system as per at least one of claims 2 and 3, characterized in that two or more of said electric motors (3) are coupled in parallel and keyed in a fixed way or with free wheels (14) to an axis or shaft central (13) coinciding with said input (1) and output (4) axes, while two or more of said electric generators (2) are coupled in parallel and fixedly keyed to said central shaft (13). 5. Propulsion system as per at least one of claims 2 to 4, characterized in that said permanent magnets (22) are placed on suitable discs (25) applied to said at least one rotor (10, 18) of the electric motor (3 ) and to said at least one rotor (16, 20) of the electric generator (2), said permanent magnets (22) being mounted with opposite pole sequence or according to a Halbach Array arrangement with perimeter sequence or with radial polar sequence. 6. Pedal-assisted bicycle comprising a propulsion system as per at least one of the preceding claims, characterized in that said electric generator (2) is connected to a rechargeable battery (6) and said electric motor (3) and electric generator (2) ) are mounted on said axis or central shaft (13), which is directly connected to the pedals (12, 15) of the bicycle. 7. Pedal-assisted bicycle as in claim 6, characterized in that the interaction between said at least one rotor (10, 18) and said at least one stator or stator disc (9, 19) of the electric motor (1) transforms the motion of the pedals (12, 15) of said bicycle in energy to be used for driving said electric motor (3) and the interaction between said at least one rotor (16, 20) and said at least one stator (17, 21) of the electric generator (2) transforms the energy received by said electric generator (2), possibly added to the energy of said rechargeable battery (6), into motion transmitted to a wheel of said bicycle, by means of a crown (13), which drives a toothed chain or belt (14), and a free wheel (11), mounted on said axis or central shaft (13), allows, in the absence of activation of said electric motor (3), to transmit the motion of the pedals (12 , 15) to said bicycle wheel, by means of said crown (13), said chain or toothed belt ( 14) and a pinion. 8. Pedal-assisted bicycle as in claim 7, characterized in that said electric motor (3) transmits its movement to said bicycle wheel by means of an external portion of said free wheel (11), which allows the pedals to be released (5 , 12) from said axis or central shaft (13). 9. Pedal assisted bicycle as per at least one of claims 6 to 8, characterized in that said electronic card (5) allows to drive said electric motor (3) using the power generated by said electric generator (2) and transforms the energy produced on said pedals (5, 12) in torque and speed transferred to said electric motor (3) according to the path traveled by said bicycle. 10. Electric pedal assisted bicycle as claimed in claim 9, characterized in that, during braking or during a downhill journey, said electric motor (3) is used as a generator and recharges said rechargeable battery (6). Barzanò & Zanardo Roma S.p.A.