JP2015220798A - Non-contact power transmission antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power transmission antenna whose power loss is small even in a transmission medium such as sea water without changing a planar size of an antenna.SOLUTION: The non-contact power transmission antenna for transmitting or receiving an electromagnetic wave for supplying/receiving power includes: an antenna coil, laminated at least two layers, connected in parallel; a ground coil, disposed between the two antenna coils and grounded; and a dielectric part for covering the antenna coil and the ground coil while separating a predetermined distance.

Description

  The present invention relates to a contactless power transmission antenna used when transmitting and receiving power in a contactless manner.

  In submarine exploration and the like, unmanned submersibles powered by electric power are used. However, since no power feeding means is provided in the sea, when power is supplied, it is necessary to make the submersible levitate to a place (for example, a mother ship) where there is power feeding equipment. In order to ascend and submerge a submersible craft, a long time loss occurs. Therefore, a method of supplying power between submersible divers can be considered.

  However, in order to connect submersible crafts with a power cable, for example, a connector or the like must be waterproofed and not leaked, which is unrealistic.

  Therefore, it is conceivable to transmit power by a non-contact transmission method. In Japanese Patent Laid-Open No. 2002-305121, a coil is provided on each of the power transmission side and the power reception side to transmit power by electromagnetic induction. An apparatus is disclosed.

JP 2002-305121 A

  However, when the non-contact power transmission device according to Japanese Patent Laid-Open No. 2002-305121 is used when power is transmitted through a transmission medium having a higher electrical conductivity than seawater, fresh water, or the like, the transmission efficiency is significantly reduced. There is a problem.

Generally, when the transmission medium is air, a transmission efficiency of 90% or more can be obtained even when the distance between the antennas is 10 cm. However, in the case of seawater, its electric conductivity is about 4 [S / m], which is very large compared to air. FIG. 7 is a diagram showing attenuation distances with respect to frequencies of fresh water and sea water. The attenuation distance is a distance at which energy is attenuated to 1 / (e ² ). Therefore, when the transmission medium is seawater, the power loss is large, and even a distance between antennas of 2 cm or more cannot be practically used as a power transmission means.

  Since power loss depends on the transmission frequency, it is conceivable to reduce the transmission frequency in order to achieve high transmission efficiency (suppress power loss). However, in order to reduce the transmission frequency, it is necessary to increase the inductance (L) and capacitance (C) of the antenna. For this purpose, the number of turns of the coil must be increased or the line width must be increased. . If the number of turns of the coil is increased or the line width is increased, the planar size of the antenna increases.

  Therefore, a main object of the present invention is to provide a non-contact power transmission antenna with little power loss even in a transmission medium such as seawater without changing the planar size of the antenna.

  In order to solve the above problems, at least two or more non-contact power transmission antennas that transmit or receive radio waves for power supply / reception are stacked and connected in parallel, and two antenna coils And a grounding coil that is grounded and a dielectric part that covers the antenna coil and the grounding coil while being separated from each other by a predetermined distance.

  According to the present invention, since the ground coil is provided between at least two antenna coils, power loss can be suppressed even in a transmission medium such as seawater without changing the planar size of the antenna.

It is sectional drawing of the antenna for non-contact electric power transmission. It is sectional drawing which showed the antenna of the minimum lamination number It is a top view of a 1st antenna coil, a 2nd antenna coil, and a ground coil. It is sectional drawing of a sample, (a) is the sample 1 and (b) is sectional drawing of the sample 2. FIG. It is the figure which showed the relationship between the transmission efficiency in a transmission medium (seawater), and distance dependence. It is the figure which showed a mode that the antenna was mounted in the submersible craft. It is the figure which showed the attenuation distance with respect to the frequency of freshwater and seawater.

  An embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of a contactless power transmission antenna (hereinafter abbreviated as an antenna) 2 according to the present embodiment.

  In the antenna 2, the antenna coil 11 embedded in the dielectric 21 and the grounding coil 12 embedded in the dielectric 22 are alternately stacked, and are embedded in the dielectric 23 and covered with the dielectric 24. The antenna coil 11 is laminated. Hereinafter, the dielectrics 21 to 24 are collectively referred to as a dielectric part as appropriate.

  The number of layers of the antenna coil 11 and the ground coil 12 is arbitrary, and FIG. 2 is a cross-sectional view showing the antenna 2 having the minimum number of layers. In the following description, FIG. 2 will be described as an example. At this time, in FIG. 2, the lower antenna coil 11 is referred to as a first antenna coil 11a, and the upper antenna coil 11 is referred to as a second antenna coil 11b.

  FIG. 3 is a diagram showing a top view of the first antenna coil 11a, the second antenna coil 11b, and the grounding coil 12 as described above. The first antenna coil 11a and the second antenna coil 11b have the same shape, and the ground coil 12 is also formed in substantially the same shape. The first antenna coil 11a, the second antenna coil 11b, and the ground coil 12 are made of a metal such as copper or aluminum.

  The first antenna coil 11a and the second antenna coil 11b are spiral coils wound in the same direction, and terminals 31a, 31b, 32a, 32b for connection to a power source or the like are formed at both ends. . The terminal 31a of the first antenna coil 11a and the terminal 31a of the second antenna coil 11b are connected, and the terminal 32b of the first antenna coil 11a and the terminal 31b of the second antenna coil 11b are connected. That is, the first antenna coil 11a and the second antenna coil 11b are connected in parallel when viewed from the power source.

  On the other hand, the ground coil 12 is disposed between the first antenna coil 11a and the second antenna coil 11b, and is wound in a direction opposite to the winding direction of the first antenna coil 11a and the second antenna coil 11b. It is a spiral coil. The ground coil 12 is set to ground or ground potential.

  The dielectrics 21 to 24 are formed of a dielectric having a relative dielectric constant of about 6 to 10 such as a fluororesin or a ceramic. The dielectrics 21 to 24 may be flexible dielectrics such as polyimide containing polyimide resin or carbon nanotubes. By using a flexible dielectric, the antenna 2 can be deformed according to the shape of the portion to be attached when the antenna 2 is attached.

  Thus, since the first antenna coil 11a and the second antenna coil 11b are stacked with the ground coil 12 interposed therebetween, a capacitor is formed between the first antenna coil 11a and the ground coil 12, and A capacitor is formed between the second antenna coil 11 b and the ground coil 12. That is, the two capacitors are formed without changing the planar size of the antenna 2. Therefore, even if the frequency at the time of transmitting the power wirelessly is lowered to suppress the power loss, the power obtained by being induced by the coil on the receiving side can be maintained.

  In addition, although the planar shape of the antenna coil shown in FIG. 2 etc. has illustrated the case where it is a square, you may make a corner | arc arc shape and may make the whole circle, ellipse, and ellipse shape.

In the above description, the dielectrics 21 to 24 are separate bodies, but may be integrated.
(Characteristic improvement verification)
Next, verification results of improvement in characteristics such as frequency characteristics in the antenna described above will be described. In order to verify the characteristic improvement effect, the antenna 2 according to the present embodiment was prepared as a sample 1 and a sample 2 for comparison with the sample 1 was prepared. 4 is a cross-sectional view of each sample, (a) is a cross-sectional view of sample 1 and (b) is a cross-sectional view of sample 2. FIG.

"Sample 1"
The first antenna coil 11a and the second antenna coil 11b were formed as a square having a side of 208 [mm] by winding a copper wire having a diameter of 1 [mm] 50 times with a spacing of 1 [mm]. The dimension h between the first antenna coil 11a or the second antenna coil 11b and the ground coil 12 was set to h = 0.615 [mm] (see FIG. 2).

  The dielectrics 21 to 24 are formed of a fluororesin plate having a dielectric constant of 6.15, and grooves for embedding the first antenna coil 11a, the ground coil 12, and the second antenna coil 11b are provided in the fluororesin plate. . The first antenna coil 11 a was inserted into the groove of the dielectric 21, the ground coil 12 was inserted into the groove of the dielectric 22, and the second antenna coil 11 b was inserted into the groove of the dielectric 23.

  Thus, the dielectrics 21 to 23 into which the respective coils were inserted and the dielectric 24 were laminated and pressed via the bonding sheet 26 having adhesiveness.

“Sample 2”
The sample 2 has the same configuration as the sample 1 except that the ground coil 12 and the dielectric 22 are not provided.

  Using the samples 1 and 2, the operating frequency as an antenna was determined. The operating frequency is defined as a frequency that maximizes transmission efficiency. As a result, the operating frequencies of Sample 1 and Sample 2 were 100 kHz and 140 kHz, respectively. Therefore, it was confirmed that the operating frequency of the antenna can be lowered by providing the ground coil 12.

  Next, the distance dependence of transmission efficiency was examined. FIG. 5 is a diagram showing the relationship between transmission efficiency and distance dependency in a transmission medium (seawater). Sample 1 shows higher transmission efficiency than sample 2 regardless of the transmission distance. For example, the transmission efficiency is improved by about 5% at a distance of 10 cm between the antennas. Therefore, it was proved that the transmission efficiency can be improved by lowering the frequency of the antenna.

In addition, although the said characteristic is a characteristic when seawater is used as a transmission medium, it dares to add that the predominance of the sample 1 with respect to the sample 2 is not lost even if it uses air as a transmission medium.
(Application example)
Next, the case where such an antenna 2 is mounted on a submersible craft will be described. FIG. 6 is a diagram showing how the antenna 2 is mounted on the submersible craft 28. The submersible craft 28 is generally a spindle type with a conical shape at the bow and stern and a cylindrical body.

  When attaching the antenna 2 to the body to the submersible craft 28 having such a curved surface, it is preferable to attach the antenna 2 by bending it in accordance with the shape of the attachment site from the viewpoint of transmission efficiency and ease of attachment. . Therefore, the flexible antenna 2 was formed by forming the dielectrics 21 to 24 using polyimide resin or silicone containing carbon nanotubes as a material.

  As a result, long-distance transmission is possible while suppressing power loss, so that power can be supplied without the submarine being lifted. Therefore, for example, power can be supplied and received between submersible diving boats.

2 antenna 11 antenna coil 11a first antenna coil 11b second antenna coil 12 ground coil 21-24 dielectric 26 bonding sheet

Claims (6)

A non-contact power transmission antenna that transmits or receives radio waves for power supply / reception,
At least two or more antenna coils that are stacked and connected in parallel;
A grounding coil disposed between the two antenna coils and grounded;
A dielectric portion that covers the antenna coil and the grounding coil while being separated from each other by a predetermined distance;
A non-contact power transmission antenna. The contactless power transmission antenna according to claim 1,
The winding direction of the antenna coil and the ground coil is opposite,
A non-contact power transmission antenna. The contactless power transmission antenna according to claim 1 or 2,
The dielectric part is formed by laminating a plurality of sheet-like dielectrics, and the antenna coil and the grounding coil are embedded in the dielectric.
A non-contact power transmission antenna. The contactless power transmission antenna according to claim 3,
The non-contact power transmission antenna, wherein the dielectric in which the antenna coil and the ground coil are embedded is bonded via a bonding sheet. The non-contact power transmission antenna according to any one of claims 1 to 4,
The dielectric is deformed according to the shape of the attachment site,
A non-contact power transmission antenna. The non-contact power transmission antenna according to any one of claims 1 to 4,
The antenna coil and the ground coil are spiral coils wound in a plane.
A non-contact power transmission antenna.

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