CN110350321B

CN110350321B - Antenna for wireless power transmission and method of manufacturing the same

Info

Publication number: CN110350321B
Application number: CN201810281558.XA
Authority: CN
Inventors: 姚斌
Original assignee: Valeo Comfort and Driving Assistance SAS
Current assignee: Valeo Comfort and Driving Assistance SAS
Priority date: 2018-04-02
Filing date: 2018-04-02
Publication date: 2024-04-12
Anticipated expiration: 2038-04-02
Also published as: CN110350321A

Abstract

The invention provides an antenna for wireless power transmission and a method of manufacturing the same. The antenna comprises a coil of flat wire coiled on a coil plane (P), the height (H) of the flat wire being greater than the width (W) of the flat wire. In the coil, the direction of the height (H) of the flat wire is perpendicular to the coil plane (P). In the antenna, the direction of the induced magnetic field is almost perpendicular to the coil plane (P), each flat wire is in an elongated shape along the direction of the magnetic field, and the irradiation area of the flat wire under the magnetic field is smaller, so that the antenna is less influenced by the proximity effect in the high-frequency working state, thereby having a higher quality factor and realizing higher transmission efficiency. Moreover, the cross section area of the flat wire is larger, so that the internal resistance of the flat wire is smaller, and the flat wire is favorable for realizing larger transmission power and low-cost manufacture.

Description

Antenna for wireless power transmission and method of manufacturing the same

Technical Field

The present invention relates to the field of wireless power transmission technology. In particular, the present invention relates to an antenna for wireless power transmission, and a method for manufacturing the same.

Background

Unlike conventional wired transmission, wireless power transmission (wireless power transfer, WPT) uses radio to achieve contactless power transmission. The wireless power transmission equipment has the advantages of compact structure, convenient operation, high environmental tolerance and the like, and is widely applied to the fields of mobile electronic equipment charging, high-pollution environmental power supply and the like. However, improvement in power and transmission efficiency of wireless power transmission is demanded. Whether short-range transmission based on electromagnetic induction or medium-range transmission based on electromagnetic resonance coupling, an antenna in the form of an inductor coil is necessary, which serves as a transmitter and/or receiver of radio waves. Therefore, the structure and performance of the antenna have an important influence on the performance of wireless power transmission.

The quality factor Q (Quality Factor) of the inductor is used to evaluate the level of loss that occurs in the inductor itself. Specifically, a larger Q value indicates a smaller loss of the coil itself. Since the quality factor Q is inversely proportional to the internal resistance R of the coil, a lower internal resistance of the coil contributes to higher transmission efficiency. Furthermore, a lower internal resistance R of the coil can also carry a larger excitation current, thereby increasing the transmission power. It can be seen that it is advantageous to use a high Q, low R value inductor as the wireless power transfer antenna.

For this reason, the use of stranded wires to form coils has been proposed in the prior art. As shown in fig. 1A, the strands are twisted from a large number of strands, up to hundreds of strands, where the diameter of each strand is very fine. Therefore, the process of processing fine strands and coating or twisting is very complex, which makes the wire coil very costly and unfavorable for large-scale use. In addition, while forming the coil from a single wire can significantly reduce cost, a circular cross-section wire as shown in FIG. 1B. However, due to the significant skin effect and proximity effect at high frequencies, current in the wire may be concentrated on the surface of the wire, particularly on the surface area of the wires of adjacent turns opposite to each other, and at this time, the conductor may not be fully utilized, so that the internal resistance R of the coil may be significantly increased, and the quality factor Q may be lowered, thereby failing to achieve satisfactory wireless power transmission performance.

Therefore, it is practically desired to obtain a wireless power transmission antenna having both a high quality factor Q and a low manufacturing cost.

Disclosure of Invention

The present invention aims to solve at least one of the problems caused by the prior art. More specifically, the present invention aims to provide a wireless power transmission antenna having high transmission efficiency, high transmission power and low manufacturing cost.

To this end, in an aspect of the present invention, there is provided an antenna for wireless power transmission, the antenna including a coil formed by coiling a flat wire on a coil plane (P), a height (H) of the flat wire being greater than a width (W) of the flat wire. In the coil, the direction of the height (H) of the flat wire is perpendicular to the coil plane (P). Since the coil extends flat along the coil plane (P), the direction of its induced magnetic field is made almost perpendicular to the coil plane (P). The flat conductor is configured to be in an elongated shape along the direction of the magnetic field, so that the irradiation surface of the conductor subjected to the magnetic field is relatively small, the influence of the proximity effect on the antenna in a high-frequency working state is small, the quality factor is high, and high transmission efficiency can be realized. Moreover, the cross section area of the flat wire is larger, so that the internal resistance of the flat wire is smaller, and the flat wire is favorable for realizing larger transmission power and low-cost manufacture.

Alternatively, the flat wire is vertically placed on the coil plane (P), and a cross section of the flat wire in a vertical direction of the coil plane (P) has an elongated shape.

Optionally, the height (H) and the width (W) have a relationship of H > k x W, wherein k is equal to or greater than 2. In particular, the larger k, the better the performance of the antenna.

Optionally, in the coil, an insulating strip is provided between the flat wires of adjacent turns. The insulating strip is made of insulating materials such as paper and plastic, has good bending flexibility and is easy to process and manufacture.

Further, the width (T) of the insulating strip defines the spacing (S) between the flat wires of adjacent turns. And, this pitch is similar to the width (W) of the flat wire, and may be equal to or greater than the width (W) of the flat wire, for example. Thus, in practice, the spacing (S) between the flat wires, or the overall size of the coil, can be controlled by adjusting the width (T) of the insulating strips.

Alternatively, all or part of the outer circumference of the flat wire is coated with an insulating coating. The flat wire with the insulating coating is easy to coil and the resulting coil is compact.

Optionally, the coil is wound by a winding unit comprising a plurality of flat wires stacked on each other, wherein the direction of the height (H) of the plurality of flat wires is perpendicular to the coil plane (P). Such a wound unit including a plurality of flat wires allows further reduction in the width of each flat wire with a limited coil height and number of turns, improving H: the ratio of W, thereby enabling the coil to have better alternating current performance.

Optionally, the coil has an intermediate cavity for receiving an iron core. An iron core placed in the intermediate cavity may enhance the coil inductance. This intermediate cavity may have a square, round, rectangular with rounded corners, etc. shape. Accordingly, the coil wound around the intermediate cavity may also have a square, round, rectangular with rounded corners, etc. shaped profile.

Alternatively, the coil may be placed on a bottom plate of magnetically permeable material (e.g., ferrite sheet) for reducing unnecessary magnetic radiation and enhancing the magnetic field strength at the upper side.

In another aspect of the present invention, there is provided a method of manufacturing an antenna for wireless power transmission, including: providing a flat wire having a height (H) greater than a width (W) thereof; and winding the provided flat wire in a coil plane (P) to form a coil. In the formed coil, the height (H) of the flat wire is perpendicular to the coil plane (P).

Optionally, the method further comprises: providing an insulating strip such that the height of the insulating strip overlaps the height (H) of the flat wire; and, the step of forming the coil includes simultaneously coiling the provided flat wire and the insulating strip such that the insulating strip insulates adjacent two turns of the flat wire from each other.

Optionally, in the method, the providing a flat wire includes providing a flat wire having its outer circumference fully or partially coated with an insulating coating.

Optionally, in the method, the step of providing the flat wire includes providing a wound unit having a plurality of flat wires, wherein heights (H) of the plurality of flat wires overlap each other; and, the step of forming the coil includes coiling the provided wound unit to form the coil.

In a further aspect of the invention, there is provided a wireless power transfer apparatus comprising an antenna according to the above.

The present invention also provides a vehicle comprising a wireless power transmission apparatus according to the above.

The invention also provides a magnetic induction heating apparatus comprising a wireless power transfer device according to the above.

Drawings

Reference is now made to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the invention. Like reference numerals designate identical or corresponding parts throughout the several views. The dimensions and proportions in the figures are also for illustration only and should not be interpreted as limiting the invention, these dimensions being possibly exaggerated relative to the actual product. In the drawings:

fig. 1A is a wire cross-sectional view of a prior art twisted wire antenna;

fig. 1B is a wire cross-sectional view of a prior art circular section wire antenna;

fig. 2 is a schematic cross-sectional view of a flat wire of a wireless power transmission antenna according to the present invention;

fig. 3 is a schematic top view of a wireless power transfer antenna according to an embodiment;

FIG. 4 is a cross-sectional view of the embodiment shown in FIG. 3, taken along line A-A;

fig. 5 is a schematic top view of a wireless power transfer antenna according to another embodiment;

FIG. 6 is a cross-sectional view of the embodiment shown in FIG. 5, taken along line B-B;

fig. 7 is a cross-sectional view of a wound unit of a wireless power transfer antenna according to yet another embodiment.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that those skilled in the art can easily implement them. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. For clarity, parts not relevant to describing the present invention are omitted. Unless otherwise indicated, the terms used herein have the usual meaning in the art. The terms "left", "right", "upper" and "lower" are used herein to describe the relative positions of various components in the figures. The use of these and similar terms is for convenience only and should not be construed to limit the scope of the present invention.

In the present invention, the induction coil is wound using a flat wire to obtain both good quality factor and economy. Such coils may be used for radio transmit or receive antennas of wireless power transfer devices. Wireless power transfer devices including such antennas may be used to wirelessly charge electronic devices such as mobile phones, wearable devices, tablet computers, and the like. In particular, the wireless power transmission apparatus of the present invention may be installed in a vehicle for wirelessly charging an in-vehicle electronic apparatus.

Fig. 2 shows a partial cross-sectional view of an antenna according to the principles of the present invention, wherein wires 1A and 1B are different portions of the same wire in adjacent turns in a coil. As shown, this wire has a flat cross-sectional shape, for example, a rectangular cross-section. Herein, as shown in fig. 2, a length extending in a vertical direction in fig. 2, i.e., a wider side of the wire, is defined as "height (H)", and a length extending in a horizontal direction in fig. 2, i.e., a narrower side of the wire, is defined as "width (W)". The width W of the wire is significantly smaller than its lateral height H. For example, the ratio of the height H and the width W of the wire may preferably be greater than or equal to 2, 5, 10, 20, or more. In particular, the larger the ratio of the height H and the width W of the wire, the better the performance of the coil. In other words, the height H and the width W have a relationship of H > k×w, where k is equal to or greater than 2. In particular, the larger k, the better the performance of the antenna. For example, in one embodiment, the wire has a lateral height H of 2.0mm and a width W of 0.3mm. As shown, after being wound into a coil, the flat wires 1A and 1B are adjacent to each other in a face-to-face manner, i.e., the flat surfaces of the wires defining the height in one turn are arranged opposite to each other with respect to the flat surfaces defining the height in the other turn. In addition, there is a spacing S between the wires in adjacent turns that is comparable to, e.g., slightly equal to or greater than, the width W of the wires. For example, the spacing S of the wires may be 1mm.

This wire structure and its way of winding is particularly advantageous because the surface of the largest area of the coil conductor is parallel to the induced magnetic field of the coil. In operation, therefore, the bias current due to proximity effects is distributed over the facing surface rather than being concentrated in a localized region of the conductor (as is the case with the prior art of fig. 1B), improving the current carrying capacity of the conductor. As a result, the coil wound with this flat wire can carry a high-frequency current without causing a significant increase in the internal resistance of the coil, thus ensuring a high quality factor Q. On the other hand, the winding method of the flat wire of the present invention gives the coil conductor a significantly larger effective current carrying cross-sectional area with respect to each of the strands shown in fig. 1B, thus allowing for carrying of a larger current without causing significant resistive heating effects.

In addition, the flat wire as shown is very convenient to manufacture and is readily available through conventional extrusion processes. In various embodiments, the conductive material forming the wire of the coil antenna may be copper, aluminum, tin, etc. metals and alloys thereof, as long as it has good conductivity and ductility.

Fig. 3 shows a top view of a coil antenna wound from a flat wire 100 according to an embodiment of the present invention. As shown, the flat wire 100 is coiled in two halves around the intermediate chamber 400. It should be understood that the two turns are for illustrative purposes only, and that in practice tens, hundreds or even more turns may be wound as desired. The intermediate cavity 400 may house an iron core to enhance coil inductance. The intermediate cavity 400 may be approximately square, e.g., having dimensions of 25mm x 25 mm. In addition, the intermediate cavity may have other shapes (e.g., circular) and sizes. In addition, the wound coil may be placed on a bottom plate of magnetically permeable material (e.g., ferrite sheet) for reducing unnecessary magnetic radiation and enhancing the magnetic field strength at the upper side. In particular, during the winding process, the wires of adjacent turns are arranged with their flat surfaces facing each other, in other words, the heights of the flat wires of adjacent turns overlap each other, so as to reduce the adverse effect of proximity effects at high frequency currents. Also, in order to avoid short-circuiting the wires of adjacent turns to each other, an insulating strip 200 may be provided between the adjacent turns. The insulating strip 200 may be made of insulating paper, plastic or the like, having a height similar to and overlapping the flat wire to be wound, and having flexibility suitable for being deformed in cooperation with the flat wire. In the winding process, the flat wire 100 and the insulating strip 200 are simultaneously provided and are wound around the coil center while overlapping each other.

Fig. 4 shows a cross section of the wound coil antenna along the line A-A of fig. 3. As shown, the wound coil is a flat coil that extends along a coil plane P. Also, the direction of the height H of each flat wire 100 forming the coil is perpendicular to the coil plane P. Adjacent flat wires 100 are separated by insulating strips 200. The height of the insulating strip 200 is approximately the same as the height H of the wire 100. In addition, the thickness T of the insulating strip 200 separates the coils of adjacent turns by a desired distance S. For example, the thickness T of the insulating strip 200 may be approximately equal to or greater than the width W of the wire 100.

Although only one flat wire and one layer of insulating strip associated therewith is shown in the figures, the invention is not limited thereto. In order to meet specific coil performance and improve winding efficiency, a plurality of flat wires separated by insulating strips may be wound simultaneously, for example, two flat wires are wound simultaneously, or three flat wires are wound simultaneously.

Fig. 5 shows a top view of an antenna wound from a flat wire 500 according to another embodiment of the invention. As shown, the flat wire 500 is coiled in two halves around the intermediate chamber 400. It should be understood that the two turns are for illustrative purposes only, and that in practice tens, hundreds or even more turns may be wound as desired. The intermediate cavity 400 may house an iron core to enhance coil inductance. The intermediate cavity 400 may be square or circular. In addition, the wound coil may be placed on a bottom plate of magnetically permeable material (e.g., ferrite sheet) for reducing unnecessary magnetic radiation and enhancing the magnetic field strength at the upper side. Similar to fig. 4, in the coil of the present embodiment, the flat wires 500 of adjacent turns are also arranged with their side flat surfaces facing each other so as to reduce the adverse effect of the proximity effect at high frequency current. The embodiment of fig. 5 differs from the embodiment of fig. 4 in that: to avoid shorting adjacent turns of wire to each other, an insulating coating is applied to the outside of each wire. In this way, the insulating strips between the wires of adjacent turns are omitted, making the antenna more compact.

Fig. 6 shows a cross-sectional view of the antenna of fig. 5 along line B-B. As shown, the wound coil is a flat coil that extends along a coil plane P. Also, the direction of the height H of each flat wire 500 forming the coil is perpendicular to the coil plane P. Further, with the flat wire 500 forming the coil, the insulating coating 502 is coated on the entire outer periphery of the intermediate conductor 501. However, this is not restrictive, and in an embodiment not shown, the insulating coating 502 may be coated only on the left and right flat surfaces of the intermediate conductor 501, not the upper and lower end surfaces, in order to further simplify the process and reduce the cost. In another possible embodiment, the insulating coating 502 may be coated on only one of the left and right flat surfaces of the intermediate conductor 501. Thus, after the wire 500 is wound into coils, the coils of adjacent turns are insulated from each other by the insulating coating 502 therebetween.

Although only one flat wire is shown to be included per turn of the coil in the figures, the invention is not limited thereto. In order to meet specific performance requirements and further to exert the effect of the invention on the configuration of the winding conductor shape, a plurality of flat wires may be wound simultaneously. That is, a plurality of flat wires are parallel to each other, constituting a wound unit, wherein the respective flat surfaces of the flat wires are also opposed to each other and are separated by an insulating coating or insulating strip. During the winding process, this winding unit including a plurality of flat wires is provided and wound around the center to form a coil. For example, fig. 7 shows a cross-sectional view of a wound unit of a coil according to an embodiment, wherein the wound unit includes four flat wires 511 arranged side by side, and an insulating coating 512 is surrounding each flat wire 511 for providing insulation and defining a suitable pitch. During the winding process, the wire monomer shown in fig. 7 is provided as a whole. Note that in practice, the overall height of the coil and the number of turns wound are generally limited, and the number of wires in each turn of the coil can be increased and the width of the wires in each turn of the coil reduced in the manner shown in fig. 7, thereby significantly improving the ac performance of the coil and improving the compactness of the structure.

In addition, although the embodiments of fig. 3 to 6 show coils of rectangular outline, the present invention is not limited thereto. In other embodiments, the coil may have a circular, square, oval, rectangular with rounded corners, etc. shape, which may all employ the flat wire configuration taught by the present invention and the face-to-face stacked winding of the flat wires.

In an embodiment of the present invention, a coil having the above-described exemplary features may be used in a wireless power transmission apparatus to serve as a transmitting or receiving antenna for a radio. Thus, the wireless power transfer device can wirelessly charge a mating electronic device (e.g., mobile phone, wearable electronic device, tablet computer, etc.) with high efficiency and high power. In particular, such wireless power transfer devices may be installed inside a motor vehicle, for example, in a vehicle dashboard, center console, roof panel, etc., for a user to charge their electronic devices. Such wireless power transfer devices may also be used in locations where it is difficult to successfully deploy a wired power transmission line, such as high vibration or high oil contamination. In addition, the wireless power transmission device of the invention can also be used in magnetic induction heating devices to improve the power and efficiency of magnetic induction heating.

While certain preferred and other embodiments for carrying out the invention have been described in detail above, it should be understood that such embodiments are merely illustrative of the invention, and are not intended to limit the scope, applicability, or configuration of the invention in any way. The scope of the invention is defined by the appended claims and equivalents thereof. Those skilled in the art can make numerous modifications to the above-described embodiments, which fall within the scope of the present invention, given the teachings of the present invention.

Claims

1. An antenna for wireless power transmission, characterized in that,

the antenna comprises a coil formed by coiling a flat wire on a coil plane (P), wherein the height (H) of the flat wire is larger than the width (W) of the flat wire;

in the coil, the direction of the height (H) of the flat wire is perpendicular to the coil plane (P), the coil is placed on a bottom plate of magnetically permeable material, and the coil is parallel to the bottom plate, and the coil has an intermediate cavity for receiving an iron core;

the antenna is installed in a vehicle and used for wirelessly charging vehicle-mounted electronic equipment.

2. An antenna according to claim 1, characterized in that the flat wire is placed vertically with respect to the coil plane (P) and that the flat wire has an elongated shape in cross section in the vertical direction of the coil plane (P).

3. The antenna according to claim 2, wherein the ratio of the height (H) of the flat wire to its width (W) is greater than or equal to 2, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 20.

4. An antenna according to any one of claims 1 to 3, wherein the coil comprises a plurality of turns of flat wire, and an insulating strip is provided between each adjacent two turns of flat wire.

5. An antenna according to claim 4, characterized in that the thickness (T) of the insulating strip defines the spacing (S) between the flat conductors of every adjacent two turns.

6. An antenna according to any one of claims 1 to 3, wherein the outer circumference of all or part of the flat wire is coated with an insulating coating.

7. An antenna according to any one of claims 1-3, characterized in that the coil is wound from a winding unit comprising a plurality of flat wires stacked on top of each other, wherein the heights (H) of the plurality of flat wires are each oriented perpendicularly to the coil plane (P).

8. A method of manufacturing an antenna for wireless power transfer according to any one of claims 1-7, comprising:

providing a flat wire having a height (H) greater than a width (W) thereof; and

winding the provided flat wire in a coil plane (P) to form a coil;

in the coil formed, the height (H) of the flat wire is perpendicular to the coil plane (P);

the coil is placed on a base plate of magnetically permeable material, and the coil is parallel to the base plate, and the coil has an intermediate cavity for receiving an iron core.

9. The method of claim 8, wherein a ratio of a height (H) of the flat wire to a width (W) thereof is greater than or equal to 2, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 20.

10. The method as recited in claim 8, further comprising:

providing an insulating strip such that the height of the insulating strip overlaps the height (H) of the flat wire;

and, the step of forming the coil includes simultaneously coiling the provided flat wire and the insulating strip such that the insulating strip insulates each adjacent two turns of the flat wire from each other.

11. The method of claim 8, wherein providing a flat wire comprises providing a flat wire having its outer circumference fully or partially coated with an insulating coating.

12. The method according to claim 10 or 11, wherein,

the step of providing the flat wire includes providing a wound unit having a plurality of flat wires, wherein,

the heights (H) of the plurality of flat wires overlap each other; and, in addition, the processing unit,

the step of forming a coil includes coiling the provided wound unit to form the coil.

13. A wireless power transfer apparatus comprising the antenna according to any one of claims 1 to 7.

14. A vehicle comprising the wireless power transfer apparatus according to claim 13.

15. A magnetic induction heating apparatus comprising the wireless power transfer device of claim 13.