Device for the wireless transmission of electrical energy

Abstract

A device (1) for the wireless transmission of electrical energy, comprising a first member (2) and a second member (3), which can be connected, respectively, to fixed or mobile elements or equipment between which the electrical energy is to be transmitted, and which can be coupled together in an operating configuration, in which the transmission of the energy takes place. The first member (2) comprises a first coil (5) of conductive material, and in which said second member (3) comprises a second coil (12) of conductive material. The device (1) also comprises a power control and conditioning circuit, to which the first coil (5) of the first member (2) is operationally connected and controlled. The first member (2) comprises a first support (4), made of ferromagnetic material, of a cylindrical or substantially cylindrical shape, which defines an annular seat (8), inside which the first coil (5) is housed. The second member (3) comprises a second support (11), of cylindrical or substantially cylindrical shape, on which the second coil (12) is wound. The seat (8) is configured to house, in the aforementioned operating configuration, the second member (3), in such a way that, in the operating configuration, the first coil (5) and the second coil (12) are arranged concentrically and coaxially, so as to be magnetically coupled at a predefined and fixed distance.

Description

[0001] “DEVICE FOR THE WIRELESS TRANSMISSION OF ELECTRICAL ENERGY”

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention concerns a device for the wireless transmission of electrical energy.

[0004] More specifically, the present invention concerns a device for the wireless transmission of electrical energy with high efficiency and low electromagnetic impact, which allows for the powering of other devices and / or the recharging of batteries, which can be used particularly, but not exclusively, in the automotive, industrial, or other fields.

[0005] BACKGROUND ART

[0006] Today, the growing diffusion of electric vehicles and systems requires the development of increasingly powerful, reliable, and versatile power supply equipment to transfer and condition ever-increasing quantities of electrical energy. Most of these vehicles and systems are equipped with energy storage devices such as batteries or supercapacitors, which must be frequently recharged.

[0007] Charging is usually done using traditional wired connections.

[0008] The above-mentioned wired connections have some not insignificant drawbacks.

[0009] First of all, such wired connections present a high electrical risk, which arises due to the presence of electrical contacts.

[0010] Furthermore, their presence entails various difficulties, for example, difficulties in operating in dusty environments filled with microdebris, or difficulties in operating in environments subject to atmospheric agents.

[0011] Additionally, it is often not possible to use these wired connections in environments subject to fire risk, or in the presence of chemical agents.

[0012] To try to overcome these drawbacks, wireless electricity transmission systems that exploit electromagnetic induction have been proposed in recent years.

[0013] To transfer power in the kW range (up to 250 kW), typical magnetically coupled systems exploit loosely coupled planar coils, leading to reduced efficiency or the need for complex compensation strategies to avoid performance degradation. In particular, in the automatic machinery field, to transfer power to moving parts, magnetically coupled coils developed on axially symmetrical cylindrical structures are sometimes used.

[0014] In these structures, however, in the operational configuration, the coil windings are simply facing each other, and the fastening between the mutually approachable or separable parts must be guaranteed by additional auxiliary systems, which are developed, from time to time, in relation to the specific type of application.

[0015] Furthermore, it is generally not possible to transfer energy in applications where the parts have a relative rotary motion, as frequently happens in many types of applications.

[0016] OBJECTS OF THE INVENTION

[0017] The technical aim of the present invention is therefore to improve the state of the art in the field of devices for the transmission of electrical energy, used, for example, in the automotive, industrial, agricultural and other fields.

[0018] Within the scope of this technical aim, it is an object of the present invention to create a device for the wireless transmission of electrical energy capable of overcoming the previously mentioned drawbacks.

[0019] Another object of the present invention is to develop a device for the wireless transmission of electrical energy that is more efficient than known solutions.

[0020] Another object of the present invention is to create a device for the wireless transmission of electrical energy that can be used to recharge vehicles or electrical systems in hostile environments and with stringent safety requirements, typical of industrial and agricultural contexts.

[0021] A further object of the present invention is to provide a device for the wireless transmission of electrical energy that can also be used between parts in relative motion with respect to each other, in particular, but not only, in relative rotary motion.

[0022] This aim and these objects are achieved by the device for the wireless transmission of electrical energy according to the attached claim 1. The device comprises a first member and a second member, which can be connected, respectively, to fixed or mobile elements or equipment, between which the electrical energy must be transmitted, and which can be moved between each other between an operating configuration, in which the energy transmission takes place, and an inactive configuration, and vice versa.

[0023] The first member comprises a first coil of electrically conductive material; similarly, the second member comprises a second coil of electrically conductive material.

[0024] The device also includes a power control and conditioning circuit, to which the first coil of the first member is operationally connected and slaved.

[0025] According to the invention, the first member comprises a first support, made of ferromagnetic material, of cylindrical or substantially cylindrical shape, which defines an annular seat, inside which the first coil is housed.

[0026] The second member comprises a second support, of cylindrical or substantially cylindrical shape, on which the second coil is wound.

[0027] The seat of the first support is configured to accommodate, in the aforementioned operating configuration, the second member, such that, in the operating configuration, the first coil and the second coil are arranged concentrically and coaxially, so as to be magnetically coupled at a predefined and fixed distance.

[0028] This solution is particularly advantageous from many points of view, such as energy efficiency, versatility, simplicity of construction and the possibility of operating in hostile and problematic environments in terms of cleaning.

[0029] The dependent claims refer to preferred and advantageous embodiments of the invention.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The characteristics of the invention will be better understood by any person skilled in the art from the following description and the attached drawings, given as a nonlimiting example, in which:

[0032] Figure 1 is a front view of the device according to the invention, in operating configuration; Figure 2 is a diametrical cross-section of the device according to the invention, in operating configuration;

[0033] Figure 3 is a diametrical cross-section of the device according to the invention, in inactive configuration;

[0034] Figure 4 is a perspective view of the device according to the invention, in operating configuration;

[0035] Figure 5 is a front view of another embodiment of the device according to the invention, in operating configuration;

[0036] Figure 6 is a diametrical cross-section of the device according to the embodiment of Figure 5.

[0037] DETAILED DESCRIPTION OF THE INVENTION

[0038] With reference to the attached Figure 1, the numeral 1 generally indicates a device for the wireless transmission of electrical energy according to the present invention. The device 1 comprises a first member 2 and a second member 3.

[0039] The first member 2 and the second member 3 can be electrically connected, respectively, to fixed or mobile elements or equipment between which the electrical energy must be transmitted.

[0040] In use, the first member 2 and the second member 3 are mutually movable between an operational configuration and an inactive configuration, and vice versa.

[0041] In particular - and as will be better explained later - the first member 2 and the second member 3 can be coupled together, in the operational or use configuration, so that there is no need for any mechanical contact between them.

[0042] The first member 2 comprises, in turn, a first support 4.

[0043] The first support 4 is made of ferromagnetic material, for example ferrite (and therefore it essentially acts as a core, or socket, in the transfer of energy).

[0044] In some embodiments of the invention, the first support 4 could be made of nanocrystalline materials, or of other magnetic materials.

[0045] The first support 4 is cylindrical, or substantially cylindrical in shape.

[0046] The first member 2 also comprises a first coil 5.

[0047] The first coil 5 (for example, having windings made with Litz wire, in order to contain the skin effect) has a cylindrical tubular shape, or a substantially cylindrical tubular shape.

[0048] The first coil 5 is made of electrically conductive material.

[0049] In more detail, the first coil 5 is made, preferably, of copper, or another electrically conductive material.

[0050] The first coil 5 is wound onto the first support 4.

[0051] In more detail, the first support 4 defines a first axis of cylindrical symmetry A.

[0052] The first support 4 also defines a front surface 6 and a rear surface 7, opposite each other.

[0053] In particular, according to one aspect of the invention, the first support 4 defines a seat 8.

[0054] The seat 8 is configured to accommodate the first coil 5.

[0055] Furthermore, the seat 8 is configured to house, in the operational (or use) configuration, also the second member 3.

[0056] The seat 8 has an annular shape, and is made coaxial to the first axis of cylindrical symmetry A of the first support 4.

[0057] The seat 8 is made open at the front surface 6 of the first support 4.

[0058] Furthermore, the seat 8 comprises an internal cylindrical surface 9 and an external cylindrical surface 10, coaxial with each other.

[0059] The seat 8 also includes a bottom 10a.

[0060] The first coil 5 is housed inside the seat 8.

[0061] In more detail, the first coil 5 is housed inside the seat 8 so as to be adhered to the aforementioned external cylindrical surface 10, or in contact with the latter.

[0062] In this way, the seat 8 defines - in correspondence with, or close to, the internal cylindrical surface 9 - a housing volume for the second member 3.

[0063] The second member 3 (which essentially acts as a pin, in coupling with the first member) comprises a second support 11.

[0064] The second support 11 is made of plastic.

[0065] The second member 3 also comprises a second coil 12.

[0066] The second coil 12 is made of electrically conductive material. In more detail, the second coil 12 is also made, preferably, of copper, or another electrically conductive material.

[0067] The second coil 12 (for example, having windings made with Litz wire) has a cylindrical annular shape, or a substantially cylindrical annular shape.

[0068] The second coil 12 is wound onto the second support 11.

[0069] The second support 11 has a cylindrical tubular, or substantially cylindrical tubular, shape.

[0070] The second support 11 defines a second axis of cylindrical symmetry B.

[0071] The second coil 12 is wound on the external cylindrical surface of the second support 11.

[0072] According to a further aspect of the invention, the device 1 comprises coupling means 13, 14 of the first member 2 to the second member 3.

[0073] The coupling means 13, 14 have, mainly, the function of facilitating the insertion of the second member 3 into the seat 8 of the first member 2, of improving the mechanical seal between the two members 2, 3, and of obtaining the centering / tightening of the second member 3 with respect to the first member 2.

[0074] In more detail, the coupling means 13, 14 comprise a plurality of first permanent magnets 13, associated with the first support 4.

[0075] Furthermore, the coupling means 13, 14 comprise a plurality of second permanent magnets 14, associated with the second support 11.

[0076] The first 13 permanent magnets are parallelepiped in shape (in other words, they are shaped like elongated plates or sheets).

[0077] The first permanent magnets 13 are fixed to the first support 4; in particular, the first permanent magnets 13 are fixed to the internal cylindrical surface 9 of the seat 8.

[0078] In more detail, the first permanent magnets 13 are inserted into respective housings made in the internal cylindrical surface 9, so as to form, with the latter, a surface substantially without irregularities.

[0079] The second permanent magnets 14 are also parallelepipedal in shape, or substantially parallelepipedal (in other words, they are in the shape of elongated plates or sheets).

[0080] Furthermore, the second permanent magnets 14 are fixed to the second support 11; in particular, the second permanent magnets 14 are fixed to the internal surface of the second support 11.

[0081] In more detail, the second permanent magnets 14 are inserted into respective housings made in the internal cylindrical surface of the second support 11, so as to form, with the latter, a surface substantially without irregularities.

[0082] The arrangement of the first and second permanent magnets 13, 14 is of fundamental importance: it is in fact important to minimize the electromotive force induced on their surface, which, being highly conductive, gives rise to non- negligible currents that could lead to losses of efficiency and overheating.

[0083] The first, second permanent magnets 13, 14 are, therefore, arranged along the axes of the coils 5, 12 (i.e., the first axis of cylindrical symmetry A and the second axis of cylindrical symmetry B), so that the magnetic field lines generated by them are substantially tangent to the surface of the aforementioned permanent magnets 13, 14.

[0084] In other words, the first permanent magnets 13 and the second permanent magnets 14 have a radial, or substantially radial, magnetization direction with reference to the longitudinal axis of the device 1.

[0085] The first support 4 may comprise a central hole 15; the central hole 15 is preferably made coaxial with the first axis of cylindrical symmetry A.

[0086] The central hole 15 can be used to fix the first support 4 to a first element (or equipment), fixed or mobile, without any limitation.

[0087] Furthermore, the central hole 15 has the effect of lightening the first support 4, so that the latter is easier to handle.

[0088] Similarly, the second support 11 can be fixed to a second element (or equipment), fixed or mobile, without any limitation.

[0089] Electrical energy must, therefore, be transmitted, wirelessly, between the first element (or device) and the second element (or device).

[0090] There can be a relative motion (translational, rotational, mixed, etc.) between the first element and the second element.

[0091] According to a further aspect of the invention, the device 1 comprises a power control and conditioning circuit (not shown in the figures), to which the first member 2 (in particular, its first coil 5) is operationally connected and served.

[0092] The control and conditioning circuit can be of any suitable type.

[0093] In particular, the power, voltages and currents (and therefore, in other words, the size) of the control and conditioning circuit are absolutely adaptable to the specific requirement (for example, from a few hundred W to a few kW, but, in theory, for any power).

[0094] Furthermore, the second coil 12 of the second member 3 can be connected, for example, to a rechargeable battery (in particular, it can be electrically connected to systems or circuits for controlling the charging / recharging of the same).

[0095] In practical use, therefore, and starting from the inactive configuration (Figure 3), the second member 3 and the first member 2 (fixed to respective fixed or mobile elements) are moved closer to each other, until the second member 3 is completely inserted into the seat 8 of the first member 2 (as shown in Figures 1, 2, 4).

[0096] In more detail, the second member 2 can come into contact with the bottom 10a of the seat 8.

[0097] In this way, the operational configuration of device 1 is obtained.

[0098] In this operating configuration, the first coil 5 of the first member 2 and the second coil 12 of the second member 3 are arranged concentrically and coaxially, so as to be magnetically coupled.

[0099] In this configuration, therefore, by activating the power control and conditioning circuit, it is possible to transfer electrical energy from the first member 2 to the second member 3.

[0100] In the inactive configuration, however, the second member 3 is moved away from the seat 8, and is therefore located outside of it, and therefore in this configuration the magnetic coupling is not achieved.

[0101] In the operating configuration, the equivalent magnetic circuit of the coupling between the two members 2, 3 has a low reluctance. It follows that a magnetic coupling is obtained that can be classified as “strong”, that is, such that the coupling coefficient k is between 0.8 and 1.

[0102] The benefits of a “strong” coupling affect not only the efficiency of energy transfer, but also the costs and complexity of control.

[0103] In fact, thanks to a high coupling coefficient, the system's power electronic circuits require fewer components, and control algorithms can be simplified.

[0104] In fact, no special compensation networks are necessary, thus drastically reducing costs.

[0105] In general, to improve transfer efficiency while preserving system stability, it is necessary to size the device so that the coupling coefficient k is close to unity.

[0106] It is therefore convenient to maximize M (mutual induction coefficient between the two windings), while Li and L2 (self-induction coefficients of each coil) can be chosen based on the desired transformation ratio.

[0107] It is therefore convenient to maximize M (mutual induction coefficient between the two windings), while Li and L2 (self-induction coefficients of each coil) can be chosen based on the desired transformation ratio.

[0108] Assuming k ~ 0.8 -M, it can be shown that the ratio n between the input and output voltages of the device corresponds to the ratio between the turns of the windings (coils):

[0109] As a possible application, the insertion of the second member 3 (plug) in an industrial vehicle charging system can be considered.

[0110] As a hypothesis, we assume an operating voltage of the second member 3 (plug) of Vrated=400Vrms, and a charging power of 7 kW.

[0111] The maximum current in the second coil 12 of the second member 3 is assumed to be Imax ~ 20 Arms, and leads to the choice of a conductor for the Litz wire windings with a total radius of rw~ 1 mm.

[0112] For systems operating at frequencies of hundreds of kHz, it is recommended to choose a diameter of the single strand that makes up the Litz wire of no more than 0.1 mm.

[0113] As a first option, you can use a commercial ferrite core of the type described, for example, on the web page https: / / www.blinzinger-elektronik.de / wp- content / uploads / ferrite cores / Ferritkern-Pl 50x30.pdf, with a radius of 10 cm.

[0114] Assuming that two concentric windings of 64 turns (NI=N2=64) each are set up, it is possible to obtain Li = 0.0016 / 7 and L2 = 0.001877 and the coupling coefficient k is 0.88.

[0115] This system, powered by a power conditioning and control circuit including an inverter (with square output voltage waveform), and with a switching frequency of 85 kHz, is capable of transferring 7kW with efficiency greater than 95%.

[0116] The larger the size of the first support 4 (core), the larger the size of the coils 5, 12 can be, with a consequent increase in the power transferable by the system.

[0117] The presence of the coupling means 13, 14 of the permanent magnet type allows the device to be handled more easily by operators, and guarantees structural stability during the charging phase, as well as efficient centering of the second member 3 with respect to the first member 2.

[0118] Since the first support 4 is designed to make the first member 2 as light as possible, the force required (at the coupling means 13, 14) for tightening is reduced to a minimum, as are the dimensions of the first, second permanent magnets 13, 14 required to develop such force (and therefore their cost is also reduced to a minimum).

[0119] The number of first, second permanent magnets 13, 14 can be any (for example four first permanent magnets 13 in the first member 2 and four second permanent magnets 14 in the second member 3: however there must be the same number of magnets 13, 14 in the first, second member 2, 3).

[0120] The resulting force of attraction is of the order of tens of Newtons, since:

[0121] - the second member 3 is rather light, being provided with a second support 11 made of plastic;

[0122] - the first member 2 and the second member 3 must be able to be easily disconnected.

[0123] Commercial neodymium magnets can be used to advantage.

[0124] Another embodiment of the device 1 according to the invention is shown in Figures 5, 6.

[0125] This embodiment differs from the one previously described, and illustrated in Figures 1-4, in that the device 1 does not include means for coupling the first member 2 to the second member 3 (i.e., in particular, the permanent magnets).

[0126] In this case, therefore, given the absence of permanent magnets, it is possible, if desired, to also obtain a rotatable coupling between the first member 2 and the second member 3, thus making this specific solution particularly advantageous, or indispensable, in certain applications.

[0127] We have thus seen how the invention achieves the proposed aims.

[0128] The proposed solution, first of all, allows avoiding electrical contact between the parts between which energy must be transferred, thus eliminating the associated risks.

[0129] The device 1 according to the invention can also operate in hostile environments, i.e. dirty and exposed to atmospheric agents, and in industrial environments with a high risk of fire, and / or flammable or explosive chemical agents.

[0130] Device 1 was developed to meet the needs of both civil and industrial infrastructures, and can be used to power different equipment.

[0131] Thanks to the solution according to the present invention, the magnetic field is substantially confined within the first support 4 of the first member 2, also improving the transmission of electrical energy.

[0132] From a modular perspective, it is possible to associate multiple pairs of first and second members 2, 3 to the same power control and conditioning circuit, which controls each pair - for example - in a synchronized or independent manner.

[0133] The range of possible applications of the device 1 according to the invention is very wide, and primarily covers the field of electric vehicles, both industrial and road, and therefore aims to replace traditional electrical sockets and plugs with metal contacts. The special geometry of the first member 2 and the second member 3 allows their easy coupling by reducing the tolerance between the parts, preserving the efficiency of the power transfer and limiting the electromagnetic impact.

[0134] The device 1 according to the invention is easy to handle and reliable, and is able to operate in any type of environment.

[0135] Device 1 is also advantageous in relation to electromagnetic compatibility issues, and human exposure to electromagnetic fields.

[0136] By avoiding direct electrical contact, the device 1 according to the invention also ensures galvanic isolation, preventing the propagation of any electrical faults through the connector.

[0137] With the appropriate sizing of the electronic circuits connected to the first member 2 and the second member 3, it is possible to create an autonomous battery charger. Thanks to the fact that the device 1 allows - in a specific embodiment - the transmission of energy even in the case of relative rotary motion between the parts, the device itself is particularly suitable for integration into automatic machines and the like.

[0138] The present invention has been described according to preferred embodiments, but equivalent variants can be conceived without departing from the scope of protection offered by the following claims.

Claims

CLAIMS1. Device (1) for the wireless transmission of electrical energy, comprising a first member (2) and a second member (3), connectable, respectively, to fixed or mobile elements or equipment between which the electrical energy must be transmitted, and coupled together in an operating configuration, in which the transmission of the energy takes place, wherein said first member (2) comprises a first coil (5) of electrically conductive material, and wherein said second member (3) comprises a second coil (12) of electrically conductive material, said device (1) also comprising a power control and conditioning circuit, to which said first coil (5) of said first member (2) is operationally connected and served, characterized in that said first member (2) comprises a first support (4), made of ferromagnetic material, of cylindrical or substantially cylindrical shape, which defines an annular seat (8) inside which said first coil (5) is housed, and in that said second member (3) comprises a second support (11), of cylindrical or substantially cylindrical shape, on which said second coil (12) is wound, said seat (8) being configured to house, in said operating configuration, said second member (3), in such a way that, in said operating configuration, said first coil (5) and said second coil (12) are arranged concentrically and coaxially, so as to be magnetically coupled at a defined and pre-set distance.

2. Device (1) according to claim 1, wherein said seat (8) is made open at the front surface (6) of said first support (4), and it comprises an internal cylindrical surface (9) and an external cylindrical surface (10), coaxial with each other, said first coil (5) being housed, inside said seat (8), so as to be adhered to said external cylindrical surface (10).

3. Device (1) according to claim 1 or 2, wherein said second support (11) is made of plastic, and wherein said second coil (12) is wound on the external cylindrical surface of said second support (11).

4. Device (1) according to one of the preceding claims, comprising coupling means (13, 14) of said first member (2) to said second member (3), which have the function of facilitating the insertion of said second member (3) into said seat (8),and of improving the mechanical seal of said first member (2) and second member (3).

5. Device (1) according to claim 4, wherein said coupling means (13, 14) comprise a plurality of first permanent magnets (13), associated with said first support (4).

6. Device (1) according to claim 5, wherein said coupling means (13, 14) comprise a plurality of second permanent magnets (14), associated with said second support (11).

7. Device (1) according to one of claims 5, 6, wherein said first permanent magnets (13) and / or said second permanent magnets (14) are of parallelepiped or substantially parallelepiped shape.

8. Device (1) according to one of claims 5 or 7, wherein said first permanent magnets (13) are fixed to said internal cylindrical surface (9) of said seat (8).

9. Device (1) according to one of claims 6-8, wherein said second permanent magnets (14) are fixed to the internal surface of said second support (11).

10. Device (1) according to claim 8, wherein said first permanent magnets (13) are inserted into respective housings made in said internal cylindrical surface (9), so as to form, with the latter, a surface substantially without irregularities.

11. Device (1) according to claim 9, wherein said second permanent magnets (14) are inserted into respective housings made in the internal cylindrical surface of said first support (11), so as to form, with the latter, a surface substantially without irregularities.

12. Device (1) according to one of claims 1-3, wherein said second member (3) is rotatable with respect to said first member (2), both in said operating configuration and in an inactive configuration in which they are separated from each other.

13. Device (1) according to one of the previous claims, wherein said first support (4) is made of ferrite, or of nanocrystalline materials, or of other magnetic materials.

14. Device (1) according to one of claims 5-13, wherein said first permanentmagnets (13) and / or said second permanent magnets (14) are commercial neodymium magnets.

15. Device (1) according to one of claims 5-14, wherein said first permanent magnets (13) and said second permanent magnets (14) have a radial, or substantially radial, magnetization direction with reference to the longitudinal axis of the device (1).

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