Technical Field

The present invention relates to a brushless electric motor.

Background Art

A wide variety of brushless electric motors widely used in many technical fields is known.

In particular, among the most popular brushless electric motors we can mention permanent magnet synchronous motors which, thanks to their technical characteristics, are used for electric vehicle drive.

In fact, these types of motor make use of a rotor with permanent magnets that are set in rotation by a rotating magnetic field generated by appropriate windings mounted on the stator of the motor itself.

Specifically, the magnetic field generated by the permanent magnets mounted on the rotor chases the rotating magnetic field and causes the motor shaft to rotate.

In this way, the rotor’s magnetic field is constantly ensured by the permanent magnets and does not require any power source, thus greatly simplifying the motor’s structure and operation.

However, these types of motor do have some drawbacks.

In particular, permanent magnets are made from particularly expensive rare earths which significantly increase the costs of such motors.

In addition, permanent magnets are complex to handle safely and make the assembly operations of the motor itself extremely complex.

In fact, permanent magnets exert intense attractive forces on the other motor components, thus complicating the assembly thereof.

In addition, permanent magnets are subject to permanent demagnetization phenomena which impair the motor operation.

Still, at high rotational speeds, the electric motors benefit from the de-fluxing of the rotor magnetic field. However, the magnetic field generated by permanent magnets is constant and cannot be de-fluxed, thus limiting motor performance at high rotational speeds. These drawbacks make this type of motor particularly expensive, complex to assemble and poorly performing at high speeds.

Description of the Invention

The main aim of the present invention is to devise a brushless electric motor with reduced cost and higher performance than permanent magnet electric motors.

A further object of the present invention is to devise a brushless electric motor which allows modulation of the rotor magnetic field flux.

Another object of the present invention is to devise a brushless electric motor which can overcome the aforementioned drawbacks of the prior art within the framework of a simple, rational solution that is easy and effective to use as well as inexpensive.

The aforementioned objects are achieved by this brushless electric motor having the characteristics of claim 1.

The aforementioned objects are achieved by this power supply method having the characteristics of claim 8.

The aforementioned objects are achieved by this vehicle having the characteristics of claim 10.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a brushless electric motor, illustrated by way of an indicative, yet non-limiting example in the accompanying tables of drawings in which:

Figure 1 is an axonometric view of a first embodiment of the electric motor according to the invention;

Figure 2 is a sectional view of the first embodiment of the electric motor according to the invention;

Figure 3 is an exploded view of the first embodiment of the electric motor according to the invention;

Figure 4 is a schematic view of some components of the first embodiment of the electric motor according to the invention; Figure 5 is a sectional view of a second embodiment of the electric motor according to the invention;

Figure 6 is an exploded view of the second embodiment of the electric motor according to the invention;

Figure 7 is a schematic view of some components of the second embodiment of the electric motor according to the invention;

Figure 8 is a schematic view of the vehicle according to the invention.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally denotes a brushless electric motor.

The brushless electric motor 1 comprises at least one stator body 2 provided with a plurality of stator windings 3 electrically powered to generate a rotating stator magnetic field.

Specifically, the stator windings 3 are distributed in a circular maimer, centered around a central axis A.

Appropriately, the stator windings 3 are configured to generate a rotating stator magnetic field lying on a transverse lying plane, preferably orthogonal to the central axis A.

In addition, the motor 1 comprises at least one rotor body 4, coupled movable in rotation to the stator body 2 and provided with at least one rotor winding 5 arranged facing the stator windings 3 and electrically powered to generate a rotor magnetic field interacting with the stator magnetic field.

Specifically, the bodies 2, 4 are movable in rotation at least one with respect to the other due to the interaction between the stator magnetic field and the rotor magnetic field.

In particular, the rotor magnetic field lines tend to align with the stator field lines in rotation and therefore cause the rotation of the rotor body 4, e.g. as known with reference to synchronous brushless electric motors.

Preferably, according to the invention, the stator body 2 is stationary, e.g. mounted on a supporting frame, while the rotor body 4 is movable in rotation with respect to the stator body 2. Advantageously, the rotor magnetic field lies on a transverse lying plane, preferably orthogonal to the central axis A.

Preferably, the stator magnetic field and the rotor magnetic field lie on the same lying plane.

Conveniently, the rotor body 4 comprises a plurality of rotor windings 5.

Preferably, the rotor windings 5 are distributed in a circular maimer, centered around a central axis A.

According to the invention, the rotor body 4 comprises at least one supporting portion 6 around which the rotor winding 5 is wound to substantially define at least one electromagnet.

Preferably, the supporting portion 6 is made of ferromagnetic material.

Conveniently, the rotor body 4 comprises a plurality of supporting portions 6, where at least one rotor winding 5 is wound around each supporting portion 6. According to the invention, the motor 1 is a brushless type motor, i.e., without brushes, sliding contacts or the like.

In more detail, the motor 1 has no brushes, sliding contacts or the like employed to power the rotor winding 5.

According to the invention, the motor 1 has no permanent magnets.

In particular, the motor 1 has no permanent magnets mounted on at least one of either the stator body 2 or the rotor body 4.

According to the invention, the motor 1 comprises magnetic induction power supply means 27 configured to electrically power the rotor winding 5 and provided with: at least one first supporting element 7 separate from the rotor body 4; at least one primary winding 8 wound around the first supporting element 7 and operationally connected to a power source 9 of the rotor winding 5; at least one second supporting element 10 associated with the rotor body 4 and separate from the first supporting element 7; at least one secondary winding 11 wound around the second supporting element 10, operationally connected to the rotor winding 5 and inductively coupled to the primary winding 8 to power the rotor winding 5. Advantageously: the first supporting element 7 substantially defines a magnetic core for the primary winding 8; and/or the second supporting element 10 substantially defines a magnetic core for the secondary winding 11.

Conveniently, the first and the second supporting elements 7, 10, together with their respective windings 8, 11, define a magnetic circuit.

Specifically, the first supporting element 7 together with the primary winding 8, and the second supporting element 10 together with the secondary winding 11, define two separate parts of such a circuit.

In other words, the first and the second supporting elements 7, 10, together with their respective windings 8, 11, allow the rotor winding 5 to be powered without a physical link between the power source 9 and the rotor winding 5 itself.

In this way, the second supporting element 10 is movable independently of the first supporting element 7.

In fact, the magnetic coupling between the primary winding 8 and the secondary winding 11 allows power to be supplied to the rotor winding 5 even though the secondary winding 11 rotates and the primary winding 8 is stationary.

Specifically, according to the invention, the rotor windings 5 are powered due to the magnetic coupling between the primary and the secondary windings 8, 11, regardless of the kinetic state and/or angular position of the rotor body 4, even when the latter is stationary.

Conveniently, the first supporting element 7 comprises a holding portion 12 around which the primary winding 8 is wound and a lateral portion 13 which extends preferably parallel to the holding portion 12, alongside it.

Preferably, the holding portion 12 and the lateral portion 13 extend longitudinally by the same length.

Advantageously, the first supporting element 7 comprises a base portion 28 with which the holding portion 12 and the lateral portion 13 are associated.

Specifically, the lateral portion 13 surrounds the holding portion 12 and defines with the latter one groove 14 within which the primary winding 8 is housed. Preferably, the first supporting element 7 is symmetrical to the central axis A.

According to a possible, but not exclusive, embodiment of the motor 1, the first supporting element 7 has a substantially cylindrical conformation.

Preferably, the first and the second supporting elements 7, 10 have a substantially equal conformation.

Advantageously, the first and the second supporting elements 7, 10 are arranged facing each other.

In more detail, the first and the second supporting elements 7, 10 are arranged facing each other to align the holding portions 12 preferably centered along the central axis A.

In even more detail, the first and the second supporting elements 7, 10 are arranged facing each other to overlook the access ports of the grooves 14.

This arrangement allows the magnetic field lines generated by the primary winding 8 to be aligned with the secondary winding 11, thus maximizing energy transfer.

In particular, the first and the second supporting elements 7, 10 are close together so as to define a narrow slit 15 that divides them.

In this way, the second supporting element 10 is free to rotate with the rotor body 4, without affecting the position of the first supporting element and/or the operation of the primary winding 8.

Conveniently, the first and the second supporting elements 7, 10 are made of a ferromagnetic material.

Specifically, the slit 15 defines an air gap between the supporting elements 7, 10.

Advantageously, the first supporting element 7 is associated with the stator body 2.

Appropriately, the rotor body 4 rotates centered around an axis of rotation B.

In addition, the primary winding 8 and the secondary winding 11 are wound centered around the axis of rotation B.

Preferably, the central axis A and the axis of rotation B are coincident.

Advantageously, the stator windings 3 are operationally connected to the power source 9.

In this way, the power source 9 powers the stator windings 3 and the rotor winding 5.

Preferably, the power source 9 is a battery 16.

Conveniently, the motor 1 comprises a power supply assembly 17 of the stator windings 3.

Advantageously, the power supply assembly 17 is operationally connected between the power source 9 and the stator windings 3.

In more detail, the power supply assembly 17 is configured to generate an operating current for the stator windings 3 of predefined amplitude and frequency and to generate the stator magnetic field.

Conveniently, the power supply assembly 17 can be modulated by means of at least one operation signal.

In other words, the power supply assembly 17 is configured to vary the predefined amplitude and/or frequency of the operating current depending on the operating signal.

Appropriately, the power supply assembly 17 comprises a converter, such as a three-phase bridge, poly-phase bridge, or the like configured to generate the operating current that powers the stator windings 3.

Conveniently, the power supply means 27 comprise: at least one power signal generator 18, operationally connected between the power source 9 and the primary winding 8 and configured to generate a power supply current flowing along the primary winding 8; at least one electronic rectifier 19, operationally connected between the secondary winding 11 and the rotor winding 5 and configured to rectify the current induced in the secondary winding 11 by the power supply current, so as to supply the rotor winding 5.

Specifically, the power supply current from the power signal generator 18 is of the alternating type of predefined amplitude and frequency.

Specifically, the power signal generator 18 comprises a generator, preferably a high-frequency one, which generates the alternating power supply current flowing along the primary winding 8.

In this way, the power supply current flowing along the primary winding 8 generates a magnetic field that passes through the secondary winding 11.

In particular, such a magnetic field is a variable magnetic field. In fact, it is well known how a time-varying current, such as e.g. an alternating current, flowing within a conductor generates a time-varying magnetic field.

This magnetic field induces the induced current to flow in the secondary winding 11.

In more detail, the induced current is an alternating current. In fact, it is well known how a time-varying magnetic field passing through a winding generates a time-varying induced current within the same, such as e.g. an alternating current.

Specifically, the power signal generator 18 and the primary winding 8 are configured to induce the induced current along the secondary winding 11 regardless of the kinetic state of and/or of the angular position of the rotor body 4.

Appropriately, the induced current is rectified by the rectifier 19 and flows within the rotor winding 5, powering it.

In this way, the induced current flowing in the rotor winding 5 generates the rotor magnetic field and enables the rotation of the rotor body 4.

Conveniently, the rotor body 4 defines a housing 20 within which the rectifier 19 is arranged.

Specifically, the rotor body 4 is at least partially hollow to define the housing 20 adapted to house the rectifier 19 and/or the decoder 24.

Preferably, the rectifier 19 comprises an electronic board.

Usefully, the power signal generator 18 can be modulated by means of at least one control signal.

In other words, the power signal generator 18 is configured to vary the predefined amplitude and/or frequency of the power supply current according to the control signal.

Usefully, the power signal generator 18 is configured to start the motor 1 being stationary.

In other words, when the rotor body 4 is stationary, the power signal generator 18 is configured to supply power to the primary winding 8 and consequently to generate the rotor magnetic field. In this way, the rotor body 4 is set in rotation. Appropriately, the motor 1 comprises control means 21 of the motor itself, operationally connected to at least one of either the power supply means 27 or the power supply assembly 17 and configured to generate at least one of either the control signal or the operation signal.

Specifically, the control means 21 are configured to generate the control signal and the operating signal so as to vary the power supply current and the operating current and so as to vary the interaction between the stator magnetic field and the rotor magnetic field.

Appropriately, the motor 1 comprises at least one position sensor, not shown in the figures, configured to detect the angular position of the rotor body 4.

Advantageously, the control means 21 are configured to generate at least one of either the power signal or the operation signal depending on the angular position detected by the angular position sensor.

Preferably, the position sensor is of the type of a Hall-effect sensor.

Advantageously, the power supply means 27 comprise at least one modulator 22, positioned operationally connected between the rectifier 19 and the rotor winding 5.

Specifically, the modulator 22 is configured to modulate the rectified current to power the rotor winding 5.

In this way, the modulator 22 is configured to vary the current flowing along the rotor winding 5 and the magnetic field flux generated by the same.

This expedient allows one or more of the characteristics of the magnetic field generated by the rotor winding 5 to be varied and consequently allows the interaction between the rotor magnetic field and the stator magnetic field to be varied.

In other words, this expedient makes it possible to vary the operation of the motor 1. For example, this expedient allows the de-fluxing of the rotor magnetic field.

For example, this expedient makes it possible to increase the rotor magnetic field and/or to simply “turn off’ and “turn on” the rotor winding 5.

Appropriately, the modulator 22 is controlled by appropriate control signals to modulate the rectified current to supply the rotor winding 5.

Preferably, the modulator 22 is housed inside the housing 20.

Conveniently, the power supply means 27 comprise: at least one control signal generator 23, connected between the power source 9 and the primary winding 8 and configured to generate a control signal flowing along the primary winding 8; at least one decoder 24, connected between the secondary winding 11 and the modulator 22 and configured to decode the signal induced in the secondary winding 11 from the control signal to control the modulator 22.

Specifically, the control signal flowing along the primary winding 8 generates a magnetic field that passes through the secondary winding 11.

This magnetic field induces the induced signal to flow in the secondary winding 11.

Appropriately, the induced signal is decoded by the decoder 24 and transmitted to the modulator 22.

In this way, the induced control signal commands the operation of the modulator 22.

In other words, the modulator 22 is configured to modulate the current to power the rotor winding 5 depending on the induced control signal decoded by the decoder 24.

Specifically, the control signal generator 23 is configured to control the operation of the rotor winding 5 by means of the modulator 22.

Preferably, the decoder 24 is housed within the housing 20.

Preferably, the control signal generator 23 coincides with the power signal generator 18.

Specifically, the power supply current and the control signal flow simultaneously along the primary winding 8. Similarly, the induced current and the induced signal flow simultaneously along the secondary winding 11.

According to an alternative embodiment, the power supply means 27 comprise: at least three primary windings 8, the power signal generator 18 being a three-phase signal generator to power the primary windings 8; at least three secondary windings 11, the second supporting element 10 being set in rotation due to the powering of the primary windings 8.

What has been described about an individual primary winding 8 and an individual secondary winding 11 with reference to the embodiment of the motor described above is also considered substantially valid for each primary winding 8 and each secondary winding 11 described with reference to this embodiment. In other words, this embodiment differs from the previous one in the structure of the power supply means 27.

In fact, in this embodiment the primary windings 8 and the secondary windings define respective three-phase structures.

In this way, the power signal generator 18 supplies power to the primary windings 8 so that they generate a rotating magnetic field that induces a current in the secondary windings 11.

Specifically, the current induced in this way in the secondary windings 11 is received by the rectifier 19, which is configured to rectify this current in order to supply power to the rotor winding 5, similarly to what has been described with reference to the previous embodiment.

In more detail, in fact, the rotating magnetic field generated by the primary windings 8 generates a change in the flux in the secondary windings 11, wherein, in this way, the current useful for supplying power to the rotor winding 5 and thus allowing the rotation of the rotor body 4 is induced.

In addition, the rotation of the rotor body 4 causes the rotation of the second supporting element 10, further increasing the flux variation operating on the secondary windings 11.

In other words, in this way, the flux variation is proportional to the rotational speed of the rotating magnetic field generated by the primary windings 8 combined (preferably summed) with the rotational speed of the rotor body 4. Advantageously, in this embodiment, the primary windings 8 are distributed around a reference axis C in a circular maimer and spaced apart from each other by a separation angle 29.

In addition, the secondary windings 11 are distributed in a circular manner around the reference axis C and spaced apart from each other by an angle substantially equal to the separation angle 29, as shown in Figure 6.

Specifically, in this embodiment, the reference axis C substantially coincides with or is substantially parallel to the central axis A.

Conveniently, one of either the first supporting element 7 or the second supporting element 10 surrounds the other of either the first supporting element 7 or the second supporting element 10.

Specifically, the second supporting element 10 surrounds the first supporting element 7, as shown in Figure 5.

Further embodiments cannot however be ruled out wherein the second supporting element 10 surrounds the first supporting element 7.

Advantageously, according to the geometry just described with reference to the first supporting element 7 and to the second supporting element 10, each primary winding 8 is wound around a corresponding first axis of winding D, arranged substantially orthogonal to the reference axis C, as shown in Figure 6. In this way, the rotating magnetic field generated by the primary windings 8 is arranged in a radial pattern to the reference axis C.

Similarly, each secondary winding 11 is wound around a corresponding second axis of winding E, arranged substantially orthogonal to the reference axis C, as shown in Figure 6.

Further embodiments, not shown in the figures, cannot be ruled out wherein the first supporting element 7 and the second supporting element 10 are arranged facing each other, preferably in a manner similar to that shown in Figure 1, and wherein each primary winding 8 is wound around a corresponding first axis of winding D, arranged substantially parallel to the reference axis C and wherein each secondary winding 11 is accommodated around a corresponding second axis of winding E, arranged substantially parallel to the reference axis C.

In this way, the rotating magnetic field generated by the primary windings 8 is arranged in an axial pattern to the reference axis C.

According to a further aspect, the present invention relates to an electric vehicle 25 comprising: at least one basic chassis 26; at least one electric motor 1, mounted on the basic chassis 26 and electrically powered for the movement of the vehicle 25; at least one power supply battery 16, mounted on the basic chassis 26 and configured to electrically power the motor 1, the battery 16 coinciding with the power source 9.

Appropriately, the vehicle 25 comprises at least one driving shaft associated with the rotor body 4 and adapted to transmit the motion to appropriate movement means of the vehicle 25.

Preferably, the vehicle 25 is an automobile.

According to a further aspect, the present invention relates to a method of powering at least one motor 1 comprising at least one start-up phase, provided with at least one step of supplying power to the primary winding 8 with the power supply current to induce the induced current into the secondary winding 11 and to supply the rotor winding 5.

In this way, the rotor winding 5 generates the rotor magnetic field.

Specifically, the step of supplying power to the primary winding involves generating a power supply current having a predefined amplitude and frequency starting from the power supplied by a power source 9.

In more detail, according to the embodiment wherein the power supply means 27 comprise a plurality of primary windings 8 and a plurality of secondary windings 11, the step of supplying power involves supplying power to the primary windings 8 so that they generate a rotating magnetic field that induces a change in flux in the secondary windings 11 and then a corresponding induced current that flows in the same secondary windings and employed to power the rotor winding 5. In the case where the power supply method is carried out to power a motor 1 of an electric vehicle 25, the power source 9 is a battery 16.

Specifically, the start-up phase comprises a step of power supplying the stator windings 3.

In this way, the stator windings 3 generate the stator magnetic field.

Conveniently, the interaction of the rotor and stator magnetic field generated according to the power supply method enables the rotational motion of the rotor body 4, even when the latter starts from standstill.

Usefully, the method comprises a phase of de-fluxing, provided with a step of reducing the rotor magnetic field flux generated by the rotor winding 5.

Specifically, the de-fluxing step involves reducing the current flowing in the rotor winding 5.

Preferably, according to the invention, steps or phases comprised in the power supply method are meant as one or more of the operations carried out by one or more of the components of the motor 1 or of the vehicle 25 and which are anticipated in this disclosure by the term “configured to” or “adapted to”. Such phases or steps are preferably, but not necessarily, carried out by the same components involved.

It has in practice been ascertained that the described invention achieves the intended objects.

In particular, the fact is emphasized that the induction power supply means allow the rotor winding to be powered without contact, without the need to employ permanent magnets, thus reducing the cost of the electric motor.

In addition, the rotor windings powered in this way enable improved performance of the electric motor.