Patent Application
20240296986
The present invention relates to a wireless power transmission coil used in a wireless power transmission system in which the electric power is transmitted from a power supply circuit to a load over a space.
A wireless power transmission system, which does not use a power cable or a power transmission cable, has been proposed as disclosed in Patent Document 1. In the wireless power transmission system, power is transmitted wirelessly from the power transmitting coil in the power transmitter to the power receiving coil in the power receiver by resonating an alternating current (AC) magnetic field of the power transmitting coil on the transmitter side and an AC magnetic field of the power receiving coil of the resonant circuit on the receiver side.
When wireless power is transmitted by widening the distance between the power transmitting coil on the power transmitter side and the power receiving coil on the power receiver side, the loss at the power transmitting coil and the power receiving coil must be minimized in order to increase the wireless power transmission efficiency. Therefore, it is necessary to reduce the AC resistance of the power transmitting coil and the power receiving coil.
When spiral coils, in which a conductor pattern is spirally wound flat, are used as the power transmitting coil and the power receiving coil, there is a portion where the current density is higher in the inner windings of the spiral coil. Which causes the problem of increasing the AC resistance of the coil due to the large non-uniformity of the current density flowing through the windings. For a solution to this problem, Patent Document 2 proposes the following coil. That is, the innermost winding of the spiral coil is divided into strip conductors, the windings of the strip conductors are exchanged, and the windings of the strip conductors are meandered so that the windings of the strip conductor are alternately arranged on the innermost circumference to average out the non-uniformity of the current within the windings. As a result, non-uniformity in the density of the current flowing through the windings of the coil is reduced, the influence of the proximity effect is suppressed, and the AC resistance of the coil is reduced.
When helical coils are used as the power transmitting coil and the power receiving coil, there are the following problems.
As described above, when a helical coil is used, there is the problem that the AC resistance cannot be reduced because the non-uniformity in the density of the current flowing through the windings cannot be eliminated by the meandering of the windings of the coil.
Therefore, the problem of the present invention is to reduce the current non-uniformity in the windings of a helical coil to reduce the AC resistance of the coil.
In order to solve the problem, an aspect in accordance with the present invention is a wireless power transmission coil comprising: a first helical coil portion, a first spiral coil portion, a second helical coil portion, a second spiral coil portion, and a third helical coil portion, wherein the first helical coil portion, the first spiral coil portion, the second helical coil portion, the second spiral coil portion, and the third helical coil portion have windings that share a central axis, wherein an inner end of the first spiral coil portion is connected to an upper end of the first helical coil portion, an upper end of the second helical coil portion is connected to an outer end of the first spiral coil portion, an inner end of the second spiral coil portion is connected to an lower end of the first helical coil portion, and an lower end of the third helical coil portion is connected to an outer end of the second spiral coil portion.
With this configuration, the present invention has the effect of eliminating non-uniformity of the current density in the windings of the coil and reducing the AC resistance of the coil.
An aspect in accordance with the present invention is a wireless power transmission coil, a doughnut-shaped cylindrical space surrounding an central axis of the coil, an surface of the doughnut-shaped cylindrical space being covered with multi-turn winding wires wound around the central axis, an area of the surface of the cylindrical space being divided into an even number of annular regions which have a predetermined width and make one turn around the central axis of the coil, each annular region being covered with series of the multi-turn winding wires around the central axis, and wherein a first annular region is covered with an first series of the multi-turn winding wires and a second annular region is covered with a second series of the multi-turn wining wires, and an end of the first series of the multi-turn winding wires and an adjacent end of the second series of the multi-turn winding wires are electrically connected in parallel to a same terminal of the coil, and wherein the first series of the multi-turn winding wires and the second series of the multi-turn winding wires are wired in parallel in a same direction from the same terminal of the coil, whereby the series of multi-turn winding wires of each of the annular region are connected in parallel between the terminals of the coil, and the ends of the series of the multi-turn winding wires connecting to a different terminal of the coil are spaced apart by at least the width of the annular region.
An aspect in accordance with the present invention is a wireless power transmission coil according to claim 2, a doughnut-shaped cylindrical space surrounding an central axis of the coil, an surface of the donut-shaped cylindrical space being covered with a series of multi-turn winding wires wound around the central axis of the coil, an area of the surface of the cylindrical space being divided into a first annular region and a second annular region which have a predetermined width and making one turn around the central axis of the coil, each annular region being covered with series of the multi-turn winding wires around the central axis, wherein the first annular region is covered with first series of multi-turn winding wires and the second annular region is covered with second series of multi-turn winding wires, and an end of the first series of the multi-turn winding wires and an adjacent end of the second series of the multi-turn winding wires are electrically connected in parallel to a same terminal of the coil, and wherein the first series of the multi-turn winding wires and the second series of the multi-turn winding wires are wired in a same direction in parallel from the same terminal of the oil, whereby the series of multi-turn winding wires of each of the annular region are connected in parallel between the first terminal and the second terminal of the coil, and the end of the series of the multi-turn winding wires connecting the first terminal and the end of the series of the multi-turn winding wires connecting the second terminal are spaced apart by at least the width of the annular region.
A wireless power transmission coil of the present invention has a first helical coil portion, a first spiral coil portion, a second helical coil portion, a second spiral coil portion, and a third helical coil portion, having windings sharing a central axis. The inner end of the first spiral coil portion is connected to the upper end of the first helical coil portion. The upper end of the second helical coil portion is connected to the outer end of the first spiral coil portion. The inner end of the second spiral coil portion is connected to the lower end of the first helical coil portion. The lower end of the third helical coil portion is connected to the outer end of the second spiral coil portion.
With this configuration, the present invention has the effect of eliminating non-uniformity of the current density in the windings of the coil and reducing the AC resistance of the coil.
The embodiments are described with reference to
The first spiral coil portion 3 is arranged on a first horizontal plane which is a plane perpendicular to the central axis 1 of the coil. The second spiral coil portion 5 is arranged on a second horizontal plane parallel to the first horizontal plane. The inner end of the first spiral coil portion 3 is connected to the upper end of the first helical coil portion 2. The outer end of the first spiral coil portion 3 is connected to the upper end of the second helical coil portion 4. A first terminal of the coil is provided at the lower end of the second helical coil portion 4.
The inner end of the second spiral coil portion 5 is connected to the lower end of the first helical coil portion 2. The lower end of the third helical coil portion 6 is connected to the outer end of the second spiral coil portion 5. A second terminal of the coil is provided at the upper end of the third helical coil portion 6.
Thus, the coil is made up of a series of windings w from the first terminal to the second terminal. The first terminal of the coil is connected to the lower end of the winding of second helical coil portion 4 and the coil winding w is wound from the lower end to the upper end of the second helical coil portion 4. Next, the coil winding w is wound from the outer end to the inner end of the first spiral coil portion 3. Next, the coil winding w is wound from the upper end to the lower end of the first helical coil portion 2. Next, the coil winding w is wound from the inner end to the outer end of the second spiral coil portion 5. Next, the coil winding w is wound from the lower end to the upper end of the third helical coil portion 6 and leads to the second terminal of the coil. Thereby, a coil having a shape in which most of the surface of the donut-shaped cylindrical space 7 is covered with winding wires w is formed.
The mechanisms by which the AC resistance of the wireless power transmission coil is generated will be described with reference to
As shown in
That is, the current is reversed on the lower side of the windings w1, w2 and w3 and the forward current is strengthened on the upper side, causing non-uniformity of the current density on the surface of the winding w. Thus, non-uniformity of the current density in each winding w increases the AC resistance of each winding w. The AC resistance of the winding w3 is greater than that of the winding w1.
In the second helical coil portion 4, an external magnetic field Hb is applied to the windings w7 and w8. Due to the induction of this external magnetic field Hb, the current is reversed on the lower side of the winding w8, and the forward current is strengthened on the upper side.
On the other hand, since the external magnetic field applied to the lower side of the winding w8 is weaker than the external magnetic field applied to the upper side of the winding w8, the effect of the reverse current flow on the lower side of the winding w8 is reduced. As a result, the current non-uniformity in the winding w8 is reduced. Therefore, it has the effect of reducing the increase in the AC resistance of the winding w8 at the ends of the coil.
The first helical coil portion 2 is a 5-turn coil with an inner diameter of 470 mm and a height of 25 mm. The first spiral coil portion 3 and the second spiral coil portion 5 are three-turn coils with an inner diameter of 470 mm and an outer diameter of 500 mm. The second helical coil portion 4 and the third helical coil portion 6 are single-turn coils with an outer diameter of 500 mm.
The reason why the thickness of the winding wire w is set to 35 μm is to exclude the influence of the skin thickness due to the skin effect on the AC resistance of the coil. For the wireless power transmission coil of the present embodiment, it is desirable to use a winding wire w having a thickness equal to or greater than the thickness of the skin thickness due to the skin effect.
In this wireless power transmission coil, coil windings w are sequentially wound from the lower side of the second helical coil portion 4 toward the upper side. Next, a coil windings w are sequentially wound from the outside to the inside of the first spiral coil portion 3. Next, coil windings w are sequentially wound from the upper side to the lower side of the first helical coil portion 2. Next, the coil windings w are sequentially wound from the inside to the outside of the second spiral coil portion 5. Next, coil windings w are sequentially wound from the lower side to the upper side of the third helical coil portion 6. In the first simulation, the AC resistance of a coil with these windings w connected in parallel was calculated.
In this helical coil, as shown in the cross-sectional view of
For comparison,
The coil model for the second simulation was a coil model in which each winding w was connected in series to form a single multi-turn coil. The AC resistance of the coil was calculated in a second simulation.
In
From these, it is considered that the difference in the magnitude of the external magnetic field applied to the winding wire w for each winding w is reduced in the wireless power transmission coil of the present embodiment. The wireless power transmission coil of the present embodiment has the doughnut-shaped cylindrical space 7 surrounding the central axis of the coil. The surface of the doughnut-shaped cylindrical space 7 is covered with winding wires w of the first helical coil portion 2, the first spiral coil portion 3, the second helical coil portion 4, the second spiral coil portion 5, and the third helical coil portion 6. It is assumed that the magnetic field in the doughnut-shaped cylindrical space 7 covered with winding wires is weakened by them. Thus, the wireless power transmission coil of this embodiment has the effect of reducing the AC resistance more than the helical coil.
Thus, the wireless power transmission coil that has coil windings w sequentially wound from the lower side of the second helical coil portion 4 toward the upper side, coil windings w sequentially wound from the outside to the inside of the first spiral coil portion 3, coil windings w sequentially wound from the upper side to the lower side of the first helical coil portion 2, coil windings w sequentially wound from the inside to the outside of the second spiral coil portion 5, coil windings w sequentially wound from the lower side to the upper side of the third helical coil portion 6. This coil has the effect of suppressing an increase in the AC resistance of the coil with frequency.
Furthermore, the wireless power transmission coil of the first embodiment can reduce the height of the conventional helical coil from 65 mm to 25 mm. This has the effect of reducing the size of the structure in which the coil is installed.
The first terminal T1 of the coil is electrically connected to the end of the winding wire s1 of the first group of multi-turn winding wires covering the annular region 8a, which is on the farthest side from the central axis 1 of the coil. And the end of the winding wire s11 parallel to the winding wire s1 is electrically connected to the first terminal T1 and in the same direction as s1. The winding wire s11 is furthest from the central axis 1 of the coil and belongs to the second group of multi-turn winding wires that covers the annular region 8b. Then, the winding wires s1 and s11 are connected in parallel in the same direction to the first terminal T1 of the coil.
Similarly, the second terminal T2 of the coil is electrically connected to the end of the winding wire s7 of the first group of multi-turn winding wires covering the annular region 8a, which is on the side closest to the central axis 1 of the coil. And the end of the winding wire s17 parallel to the winding wire s7 is electrically connected to the second terminal T2 and in the same direction as s7. The winding wire s17 is on the side closest to the central axis 1 of the coil and belongs to the second group of multi-turn winding wires that covers the annular region 8b. Then, the winding wires s7 and s17 are connected in parallel in the same direction to the second terminal T2 of the coil.
In this way, the first series of multi-turn winding wires and the second series of multi-turn winding wires are electrically connected in parallel to the first terminal T1 and the second terminal T2 of the coil. Then, the first series of seven-turn winding wires covers the annular region 8a, the second series of seven-turn winding wires covers the annular region 8b, and the entire surface of the doughnut-shaped cylindrical space 7 is covered with the winding wires w.
As a result of simulating the AC resistance of the coil of the second embodiment of this structure, the AC resistance of the coil was reduced as in the first embodiment. In the wireless power transmission coil of the present embodiment, the magnetic field in the doughnut-shaped cylindrical space 7 surrounded by the first series of seven-turn winding wires and the second series of seven-turn winding wires is weakened. As a result, the wireless power transmission coil according to the present embodiment has the effect of reducing the AC resistance more than the helical coil.
In this embodiment, the windings s1 and s11 electrically connected to the first terminal T1 of the coil and the windings s7 and s17 electrically connected to the second terminal T2 of the coil are not adjacent and separated. An insulating material of the coil insulates the winding wire w connected to the first terminal T1 and the winding wire w connected to the second terminal T2. Since the first terminal T1 and the second terminal T2 are separated, it is possible to reduce the influence of the dielectric loss of the insulating material of the coil, which causes the AC resistance of the coil.
In the third embodiment, similarly to the second embodiment, the surface of a doughnut-shaped cylindrical space 7 surrounding the central axis 1 of the coil is covered by the multi-turn winding wires w around the central axis 1 of the coil. The difference between the third embodiment and the second embodiment is as follows. In the second embodiment, the surface of the doughnut-shaped cylindrical space 7 is divided into two annular regions, each of which is covered with multi-turn winding wires. In the third embodiment, the surface of the doughnut-shaped cylindrical space 7 is divided into four or more annular regions, and each region is covered with multi-turn winding wires.
That is, in the third embodiment, surface area of the donut-shaped cylindrical space 7 is divided into even number of annular regions. They are parallel to the central axis 1 of the coil and have a predetermined width. Then, for each annular region, the annular region is covered with a series of multi-turn winding wires w parallel to the annular region around the central axis 1 of the coil. One end of the series of multi-turn winding wires in each annular region is connected to the first terminal T1 of the coil and the other end of the series of multi-turn winding wires is connected to the second terminal T2 of the coil.
A first end of a second series of multi-turn winding wires on the second annular region is provided adjacent a first end of the first series of multi-turn winding wires on the first annular region. The first end of the first series of multi-turn winding wires on a first annular region and the first end of a second series of multi-turn winding wires are connected in parallel in the same direction to the first terminal T1 of the coil.
A second end of the third series of multi-turn winding wires on the third annular region is provided adjacent a second end of the first series of multi-turn winding wires on the first annular region. The second end of the first series of multi-turn winding wires on a first annular region and the second end of the third series of multi-turn winding wires are connected in parallel in the same direction to the second terminal T2 of the coil.
Similarly, a first end of the fourth series of multi-turn winding wires on the fourth annular region is provided adjacent a first end of the third series of multi-turn winding wires on the third annular region. The first end of the third series of multi-turn winding wires on the third annular region and the first end of the fourth series of multi-turn winding wires are connected in parallel in the same direction to the first terminal T1 of the coil. The first end of the third series of multi-turn winding wires on a third annular region and the first end of the fourth series of multi-turn winding wires are connected in parallel in the same direction to the first terminal T1 of the coil. The second end of the fourth series of multi-turn winding wires are connected to the second terminal T2 of the coil.
In this way, an even number of series of multi-turn winding wires such as the first series of multi-turn winding wires, the second series of multi-turn winding wires, the third series of multi-turn winding wires, and the fourth series of multi-turn winding wires are electrically connected in parallel to the first terminal T1 and the second terminal T2 of the coil. The first ends of these series of multi-turn winding wires connected to the first terminal T1 of the coil and the second ends of these series of multi-turn winding wires connected to the second terminal T2 of the coil are spaced apart by the width of the annular region.
Since the first ends of them connected the first terminal T1 and the second ends of them connected the second terminal T2 are spaced apart, it is possible to reduce the influence of the dielectric loss of the insulating material of the coil, which causes the AC resistance of the coil.
In addition, this embodiment has the effect of reducing the number of turns of the series of the multi-turn winding wires to a number divided by the number of the series of the multi-turn winding wires, which is the number of the annular regions. That is the number of turns of the coil. Reducing the number of turns of the coil in this way has the effect of reducing the inductance of the coil.
The difference between the fourth embodiment and the second embodiment is as follows. The end of the winding wire s5 at the second end of the first group of series of multi-turn winding wires is connected to the third terminal T3, and the end of the winding wire s6 at the first end of the second group of series of multi-turn winding wires is connected to the fourth terminal T4. The third terminal T3 and the fourth terminal T4 are connected to the terminals of the resonance capacitor C for wireless power transmission. Then, the first group of multi-turn winding wires, the resonance capacitor C, and the second group of multi-turn winding wires are connected in series and wiring in the same direction. And there is a gap between windings s5 and s6. Therefore, the end winding s5 of the first group of multi-turn windings connected to the third terminal T3 is not adjacent to the end winding s6 of the second group of multi-turn windings connected to the fourth terminal T4.
The end of the winding wire s1 at the first end of the first group of series of multi-turn winding wires is connected to the first terminal T1, and the end of the winding wire s10 at the second end of the second group of series of multi-turn winding wires is connected to the second terminal T2. The first terminal T1 and the second terminal T2 are connected to the terminals of the AC power supply for the wireless power transmission system.
In the case shown in
On the other hand, the amplitude of the voltage applied between the third terminal T3 and the fourth terminal T4 of the coil to which the terminals of the resonance capacitor C are connected is high. Therefore, a gap is required to separate the winding wire s5 at the end of the first group of multi-turn winding wires and the winding wire s6 at the end of the second group of multiple winding wires.
The coil for wireless power transmission according to the present invention is applicable for non-contact power feeding to moving objects such as electric vehicles and aircraft, and for supplying electric power to an electronic device installed on a desk across a desk plate. Also, it can be applied to supply electric power to in vivo electronic devices buried in the human body through skin without power lines.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-003969 | Jan 2021 | JP | national |
| 2021-105261 | Jun 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/000808 | 1/13/2022 | WO |
