JP6304276B2 - Coil unit, wireless power feeding device, wireless power receiving device, and wireless power transmission device - Google Patents

Description

  The present invention relates to a coil unit, a wireless power feeding device, a wireless power receiving device, and a wireless power transmission device.

  In recent years, in electric vehicles and portable devices, wireless power transmission technology for supplying power wirelessly from the outside without using a power cable has attracted attention. When this wireless power transmission technology is applied to a charging device that requires high power transmission, such as an electric vehicle, it is necessary to flow a large current through the power transmission coil. There was a possibility of adverse effects such as obstacles.

  In order to solve this problem, for example, in Patent Document 1, the primary side and the secondary side are each a coil having a flat structure wound in a spiral shape in order from the air gap side, a ferrite core having a flat plate shape, There is disclosed a non-contact power feeding device that includes an aluminum plate having a flat plate shape and shields external exposure of leakage magnetic flux by the aluminum plate.

JP 2010-93180 A

  By the way, in wireless power transmission technology, a method using a resonance phenomenon is becoming mainstream. When this resonance phenomenon is used, there is an advantage that the distance between power transmission and reception can be increased as compared with electromagnetic induction. In the wireless power transmission technology using this resonance phenomenon, it is necessary to connect a resonance reactance circuit to either the start or end of the winding of the power transmission coil. However, when the resonance reactance circuit is connected to only one of the start and end of the winding of the power transmission coil, a potential difference occurs between the start and end of the winding of the power transmission coil. Therefore, a high induced voltage between the ground and the metal part is generated through the parasitic capacitance due to the generated potential difference.

  The present invention has been made in view of the above problems, and an object thereof is to provide a coil unit, a wireless power feeding device, a wireless power receiving device, and a wireless power transmission device that can suppress a high induced voltage generated in a metal part.

  A coil unit according to the present invention includes a power transmission coil, a reactance circuit that forms a resonance circuit with the power transmission coil, and a metal portion disposed on the back side of the power transmission coil. A first reactance circuit connected to one end of the winding of the power transmission coil, and a second reactance circuit connected to the other end of the winding of the power transmission coil, the first reactance The ratio of the second reactance value of the second reactance circuit to the first reactance value of the circuit is determined from the other end of the winding with respect to the average distance between the winding and the metal portion from one end to the center of the winding. It is set based on the ratio of the average distance of the said coil | winding and metal part in the center part.

  According to the present invention, the reactance circuit includes a first reactance circuit connected to one end of the winding of the power transmission coil and a second reactance circuit connected to the other end of the winding of the power transmission coil. The ratio of the second reactance value of the second reactance circuit to the first reactance value of the first reactance circuit is such that the winding and the metal portion from one end to the center of the winding Is set based on the ratio of the average distance between the winding and the metal part from the other end of the winding to the central part. Therefore, the voltage value of the voltage induced in the metal part through the parasitic capacitance generated between the winding and the metal part in one end to the center of the winding of the power transmission coil, and the first reactance circuit The voltage difference between the voltages applied to both ends of the metal part is small, and the metal part is connected via a parasitic capacitance generated between the winding and the metal part at the other end to the center part of the winding of the power transmission coil. The difference between the voltage value of the voltage induced by the voltage and the voltage value of the voltage applied to both ends of the second reactance circuit is reduced. As a result, high voltage induced in the metal part can be suppressed.

Preferably, the ratio of the average distance between the winding and the metal part from the other end of the winding to the central part to the average distance between the winding and the metal part from one end to the center of the winding is n, power Assuming that the frequency of the alternating current flowing in the power transmission coil during transmission is f and the resonance frequency of the resonance circuit is f ₀ , the ratio M of the second reactance value to the first reactance value is expressed by the following equations (1), ( It may be set to satisfy 2).
M = (1 + α) / (1-α) Formula (1)
α = {(n-1) / (n + 1)} · (f / f 0) 2 Equation (2)
In this case, the voltage value of the voltage induced in the metal part through the parasitic capacitance generated between the winding and the metal part at one end to the center of the winding of the power transmission coil, and the first reactance Parasitic capacitance generated between the winding and the metal part between the other end and the center of the winding of the power transmission coil when the difference between the voltages applied to both ends of the circuit approaches zero as much as possible. The difference between the voltage value induced in the metal part via the voltage and the voltage value applied to both ends of the second reactance circuit approaches zero as much as possible. As a result, the high voltage induced in the metal part can be further suppressed.

  More preferably, the power transmission coil may have a winding wound continuously in layers. In this case, the inductance value of the coil can be improved while suppressing a high voltage induced in the metal part.

  A wireless power supply apparatus according to the present invention includes a power supply coil unit, and the power supply coil unit is the coil unit. ADVANTAGE OF THE INVENTION According to this invention, the wireless electric power feeder which can suppress the high induced voltage which arises in a metal part can be provided.

  A wireless power receiving apparatus according to the present invention includes a power receiving coil unit, and the power receiving coil unit is the coil unit. ADVANTAGE OF THE INVENTION According to this invention, the wireless power receiving apparatus which can suppress the high induced voltage which arises in a metal part can be provided.

  A wireless power transmission device according to the present invention includes a wireless power feeding device having a power feeding coil unit and a wireless power receiving device having a power receiving coil unit, and at least one of the power feeding coil unit and the power receiving coil unit is the coil unit. It is characterized by that. ADVANTAGE OF THE INVENTION According to this invention, the wireless power transmission apparatus which can suppress the high induced voltage which arises in a metal part can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the coil unit which can suppress the high induced voltage which arises in a metal part, a wireless electric power feeder, a wireless power receiving apparatus, and a wireless power transmission apparatus can be provided.

It is a circuit block diagram which shows the wireless power transmission apparatus with which the coil unit which concerns on suitable embodiment of this invention is applied with a load. It is the figure which showed typically the circuit structure of the coil unit which concerns on 1st Embodiment of this invention. It is the figure which planarly viewed the coil unit which concerns on 1st Embodiment of this invention. It is sectional drawing of the coil unit which follows the cutting line AA in FIG. 3a. It is the figure which planarly viewed the coil unit which concerns on 2nd Embodiment of this invention. It is sectional drawing of the coil unit which follows the cutting line BB in FIG. 4a.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  First, an overall configuration of a wireless power transmission device S1 to which a coil unit according to a preferred embodiment of the present invention is applied will be described with reference to FIG. FIG. 1 is a circuit configuration diagram showing a wireless power transmission device to which a coil unit according to a preferred embodiment of the present invention is applied together with a load. Note that the coil unit according to a preferred embodiment of the present invention can be applied to both the power feeding coil unit and the power receiving coil unit in the wireless power transmission device.

  As illustrated in FIG. 1, the wireless power transmission device S <b> 1 includes a wireless power feeding device 100 and a wireless power receiving device 200.

  The wireless power supply apparatus 100 includes a power source 110, a power conversion circuit 120, and a power supply coil unit 130. The power supply 110 supplies DC power to the power conversion circuit 120. The power source 110 is not particularly limited as long as it outputs DC power, and is a DC power source rectified and smoothed from a commercial AC power source, a secondary battery, a DC power source generated by photovoltaic power, or a switching power source device such as a switching converter. Is mentioned.

  The power conversion circuit 120 includes a power conversion unit 121 and a switch drive unit 122. The power conversion circuit 120 has a function of converting input DC power supplied from the power supply 110 into AC power. More specifically, the power conversion unit 121 includes a switching circuit in which a plurality of switching elements are bridge-connected. In this embodiment, it is a full bridge type circuit using four switching elements SW1 to SW4. Examples of the switching elements SW1 to SW4 include elements such as a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor). Each of the switching elements SW1 to SW4 performs on / off control of the switching elements SW1 to SW4 in accordance with the SW control signals SG1 to SG4 supplied from the switch driving unit 122, so that the input DC power supplied from the power supply 110 is obtained. Convert to AC power.

  The feeding coil unit 130 has a function of feeding AC power supplied from the power conversion circuit 120 to a receiving coil unit 210 described later. Note that when the wireless power transmission device S1 according to the present embodiment is used in a power supply facility for a vehicle such as an electric vehicle, the power supply coil unit 130 is disposed in the ground or in the vicinity of the ground.

  The wireless power receiving apparatus 200 includes a power receiving coil unit 210 and a rectifying unit 220.

  The power receiving coil unit 210 has a function of receiving AC power fed from the power feeding coil unit 130. When the wireless power transmission device S1 according to the present embodiment is applied to a power supply facility for a vehicle such as an electric vehicle, the power receiving coil unit 210 is mounted on the lower portion of the vehicle.

  The rectifying unit 220 rectifies the power received by the power receiving coil unit 210 and outputs the rectified power to the load RL. In this embodiment, the rectifying unit 220 includes a bridge type circuit in which four diodes (rectifying elements) D1 to D4 are connected in a full bridge, and a smoothing capacitor C0 connected in parallel to the bridge type circuit. . That is, the rectifying unit 220 has a function of full-wave rectifying the AC power supplied from the power receiving coil unit 210. The smoothing capacitor C0 smoothes the rectified voltage and generates a DC voltage.

  By providing such a configuration, the power feeding coil unit 130 of the wireless power feeding apparatus 100 and the power receiving coil unit 210 of the wireless power receiving apparatus 200 are opposed to each other so that they are magnetically coupled to each other from the power conversion circuit 120 to the power feeding coil unit 130. The supplied AC power excites the induced electromotive force in the power receiving coil unit 210 by the proximity electromagnetic field effect. That is, the wireless power transmission device S1 is realized in which power is transmitted from the wireless power feeding device 100 to the wireless power receiving device 200 in a contactless manner.

  Next, the configuration of the coil unit according to a preferred embodiment of the present invention applied to the above-described feeding coil unit 130 or the receiving coil unit 210 will be described.

(First embodiment)
The configuration of the coil unit Lu1 according to the first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 2 is a diagram schematically showing a circuit configuration of the coil unit according to the first embodiment of the present invention. FIG. 3A is a plan view of the coil unit according to the first embodiment of the present invention. FIG. 3b is a cross-sectional view of the coil unit along the cutting line AA in FIG. 3a. For convenience of explanation, the reactance circuit is omitted in FIG.

  As shown in FIG. 2, the coil unit Lu1 includes a power transmission coil L1, a metal part SD, and a reactance circuit X.

  The power transmission coil L1 is formed by winding a winding made of a litz wire obtained by twisting a plurality of thin conductor wires. Specifically, as shown in FIG. 3A, the power transmission coil L1 is a coil having a planar spiral structure having a substantially circular shape. The number of turns of the power transmission coil L1 is appropriately set based on the distance between the coils facing each other during power transmission, the desired power transmission efficiency, and the like. When the power transmission coil L1 is applied to the power feeding coil unit 130 in the wireless power transmission device S1, the power transmission coil L1 functions as a power feeding unit, and the power transmission coil L1 is used as the power receiving coil in the wireless power transmission device S1. When applied to the unit 210, the power transmission coil L1 functions as a power receiving unit.

  As shown in FIG. 3b, the metal part SD has a substantially rectangular parallelepiped shape, and is disposed on the back side of the power transmission coil L1. Specifically, when the power transmission coil L <b> 1 is applied to the power supply coil unit 130, the metal part SD is in a direction opposite to the power supply coil unit 130 and the power reception coil unit 210 than the power transmission coil unit L <b> 1. It will be arranged at a position far from. On the other hand, when the power transmission coil L1 is applied to the power receiving coil unit 210, the metal part SD is located farther from the power feeding coil unit 130 than the power transmission coil L1 in the opposing direction of the power feeding coil unit 130 and the power receiving coil unit 210. Will be placed. In other words, the metal part SD is disposed on the side opposite to the power transmission surface of the power transmission coil L1 during power transmission. That is, the coil axis of the power transmission coil L1 is orthogonal to the main surface of the metal part SD. The metal part SD is made of a conductor and has an action of absorbing electromagnetic waves. That is, the metal part SD plays a role as a shielding member. Examples of the metal part SD include aluminum, copper, and silver. Further, the metal part SD may be non-magnetic, and its electrical conductivity is preferably as high as possible. With this configuration, as shown in FIG. 2, a parasitic capacitance C12 is formed between one end of the winding of the power transmission coil L1 and the metal part SD, and the winding of the power transmission coil L1 is performed. A parasitic capacitance C13 is formed between the other end of the line and the metal part SD. In the present embodiment, an insulating member IL is interposed between the power transmission coil L1 and the metal part SD. In this case, insulation between the power transmission coil L1 and the metal part SD is ensured, and it is possible to prevent both ends of the power transmission coil L1 from being short-circuited. Instead of the insulating member IL, a gap may be provided between the power transmission coil L1 and the metal part SD.

  The reactance circuit X forms a resonance circuit with a power transmission coil. The reactance circuit X has a function of adjusting the resonance frequency of the resonance circuit. Specifically, the reactance circuit X includes a first reactance circuit X10 and a second reactance circuit X11.

  The first reactance circuit X10 is connected to one end of the winding of the power transmission coil L1, as shown in FIG. That is, the first reactance circuit X10 is connected in series with the power transmission coil L1. The first reactance circuit X10 includes a resonance capacitor C10. In the present embodiment, the first reactance circuit X10 includes the resonance capacitor C10. However, the present invention is not limited to this, and an inductor may be connected in series or in parallel to the resonance capacitor C10.

  As shown in FIG. 2, the second reactance circuit X11 is connected to the other end of the winding of the power transmission coil L1. That is, the second reactance circuit X11 is connected in series to the power transmission coil L1. The second reactance circuit X11 includes a resonance capacitor C13. In the present embodiment, the second reactance circuit X11 includes the resonance capacitor C13. However, the present invention is not limited to this, and an inductor may be connected in series or in parallel to the resonance capacitor C13.

  Incidentally, as described above, the parasitic capacitances C12 and C13 are formed between the power transmission coil L1 and the metal part SD. If the parasitic capacitances C12 and C13 are different, the induced voltage generated via the parasitic capacitance C12 between one end of the winding of the power transmission coil L1 and the metal part SD and the other winding of the power transmission coil L1. There is a potential difference between the induced voltage generated through the parasitic capacitance C13 between the end and the metal part SD. As a result, a high voltage is generated in the metal part SD. An object of the present invention is to suppress a high voltage induced in the metal part SD.

  As a result of intensive studies by the present inventors, by adjusting the ratio of the reactance values of the first reactance circuit X10 and the second reactance circuit X11, the induced voltage generated in the metal part SD due to variations in the parasitic capacitances C12 and C13. It was found that the potential difference could be canceled out. Specifically, in the present embodiment, the ratio of the second reactance value of the second reactance circuit X11 to the first reactance value of the first reactance circuit X10 is such that the one end to the center of the winding It is set based on the ratio of the average distance between the winding and the metal part SD from the other end of the winding to the central part with respect to the average distance between the winding and the metal part SD. Here, the voltage generated in the metal part SD is applied to the metal part SD via a parasitic capacitance C12 generated between the winding and the metal part SD from one end to the center of the winding of the power transmission coil L1. The difference between the voltage value of the induced voltage and the voltage value of the voltage applied to both ends of the first reactance circuit X10, and the winding from the other end to the center of the winding of the power transmission coil L1 The difference between the voltage value induced in the metal part SD via the parasitic capacitance C13 generated between the metal part SD and the voltage value applied to both ends of the second reactance circuit X11 is induced. It becomes. Therefore, the voltage value of the voltage induced in the metal part SD via the parasitic capacitance C12 generated between the winding and the metal part SD from one end of the winding of the power transmission coil L1 to the center part, Difference in voltage applied to both ends of one reactance circuit X10, and parasitic capacitance generated between the other end of the winding of the power transmission coil L1 and the metal portion SD in the central portion. When the difference between the voltage value induced in the metal part SD via C13 and the voltage value of the voltage applied to both ends of the second reactance circuit X11 is reduced, the voltage induced in the metal part SD is reduced. be able to. The average distance between the winding and the metal part SD from one end to the center of the winding is the outer surface part closest to the metal part SD of the winding and the outer surface of the metal part SD on the winding side. It is a value obtained by obtaining a plurality of shortest distances between the portions at different points from one end of the winding to the center and averaging them. Similarly, the average distance between the winding and the metal part SD from the other end of the winding to the central part is the outer surface portion closest to the metal part SD of the winding and the outside of the winding side of the metal part SD. It is a value obtained by obtaining a plurality of shortest distances from the surface portion at different locations from the other end of the winding to the central portion and averaging them.

  For example, when the parasitic capacitance C12 is larger than the parasitic capacitance C13, the average distance between the winding and the metal part SD from one end to the center of the winding is the winding from the other end to the center of the winding. It is shorter than the average distance between and the metal part SD. In this case, if the first reactance value of the first reactance circuit X10 is made smaller than the second reactance value of the second reactance circuit X11, the power reacting coil L1 has a winding from one end to the center thereof. The difference between the voltage value of the voltage induced in the metal part SD via the parasitic capacitance C12 generated between the winding and the metal part SD and the voltage value of the voltage applied to both ends of the first reactance circuit X10 is as follows. The voltage value of the voltage induced in the metal part SD via the parasitic capacitance C13 generated between the winding and the metal part SD between the other end of the winding of the power transmission coil L1 and the central part is small. The difference between the voltage values applied to both ends of the second reactance circuit X11 is reduced. Conversely, when the parasitic capacitance C12 is smaller than the parasitic capacitance C13, the average distance between the winding and the metal part SD from one end of the winding to the center is the winding from the other end of the winding to the center. This is longer than the average distance between the line and the metal part SD. In this case, if the first reactance value of the first reactance circuit X10 is made larger than the second reactance value of the second reactance circuit X11, the power reacting coil L1 has a winding from one end to the central portion. The difference between the voltage value of the voltage induced in the metal part SD via the parasitic capacitance C12 generated between the winding and the metal part SD and the voltage value of the voltage applied to both ends of the first reactance circuit X10 is as follows. The voltage value of the voltage induced in the metal part SD via the parasitic capacitance C13 generated between the winding and the metal part SD between the other end of the winding of the power transmission coil L1 and the central part is small. The difference between the voltage values applied to both ends of the second reactance circuit X11 is reduced.

  In this way, by adjusting the ratio of the reactance values of the first reactance circuit X10 and the second reactance circuit X11, the potential difference of the induced voltage generated in the metal part SD due to variations in the parasitic capacitances C12 and C13 can be canceled.

Further, the ratio of the average distance between the winding and the metal part SD from the other end of the winding to the central part to the average distance between the winding and the metal part SD from one end to the center of the winding is n, When the frequency of the alternating current flowing through the power transmission coil L1 during power transmission is f and the resonance frequency of the resonance circuit is f ₀ , the ratio M of the second reactance value to the first reactance value is expressed by the following equation (1). , (2) is preferably satisfied.
M = (1-α) / (1 + α) Formula (1)
α = {(n-1) / (n + 1)} · (f / f 0) 2 Equation (2)
In this case, the voltage value of the voltage induced in the metal part via the parasitic capacitance C12 generated between the winding and the metal part from one end to the central part of the winding of the power transmission coil L1; The difference between the voltage values applied to both ends of the reactance circuit X10 approaches zero as much as possible, and between the other end of the winding of the power transmission coil L1 and the central portion, the winding and the metal portion SD The difference between the voltage value induced in the metal part via the parasitic capacitance C13 generated therebetween and the voltage value applied to both ends of the second reactance circuit X11 approaches zero as much as possible. As a result, the high voltage induced in the metal part SD can be further suppressed.

Here, the principle by which the high voltage induced in the metal part can be further suppressed by satisfying the conditions of the above formulas (1) and (2) will be described in detail. For convenience of explanation, the first reactance circuit X10 is referred to as a resonance capacitor C10, and the second reactance circuit X11 is referred to as a resonance capacitor C11. That is, the capacitance value of the resonance capacitor C10 is C100, the capacitance value of the resonance capacitor C11 is C110, and the first reactance value X100 of the first reactance circuit X10 satisfies the following equation (3), and the second reactance The second reactance value X110 of the circuit X11 satisfies the following expression (4).
X100 = 1 / (j · ω · C100) Equation (3)
X110 = 1 / (j · ω · C110) Equation (4)
That is, from the above equations (3) and (4), the ratio M of the second reactance value X110 to the first reactance value X100 is expressed by equation (5).
M = C100 / C110 Formula (5)
In the present embodiment, the reactance ratio M is set in order to suppress the induced voltage generated in the metal part SD. Hereinafter, parameters necessary for setting the reactance ratio M will be described.

First, each characteristic of the resonance circuit will be described. When the capacitance value C100 of the resonant capacitor C10 is expressed using the above equation (5), the equation (6) is obtained. Further, the combined capacitance value C of the resonant capacitor C10 and the resonant capacitor C11 is expressed by Equation (7).
C100 = M · C110 Formula (6)
C = M / (M + 1) · C110 Formula (7)
Furthermore, the inductance values L100 of the power transmission coil L1, a resonance frequency of the resonant circuit and _{f 0,} the use of Equation (7), the equation (8).
L100 = 1 / {(2 · π · f ₀ ) ² · C} Equation (8)

Next, the parasitic capacitances C12 and C13 generated between the power transmission coil L1 and the metal part SD will be described. The capacitance values of the parasitic capacitances C12 and C13 are inversely proportional to the distance between the power transmission coil L1 and the metal part SD. Therefore, the ratio of the average distance between the winding and the metal part SD from the other end of the winding to the central part with respect to the average distance between the winding and the metal part SD from one end to the center of the winding is represented by n. Then, the capacitance value C120 of the parasitic capacitance C12 and the capacitance value C130 of the parasitic capacitance C13 have the relationship of the following formula (9).
C130 = n · C120 Formula (9)

Next, an induced voltage generated in the metal part SD will be described. The voltage value of the induced voltage is determined by the voltage across the power transmission coil L1 and the voltage dividing ratio of the parasitic capacitances C12 and C13. Therefore, when the voltage at one end of the power transmission coil L1 is Va and the voltage at the other end of the power transmission coil L1 is Vb, the induced voltage Vsd is expressed by Expression (10).
Vsd = | Vb + (Va−Vb) · C120 / (C120 + C130) | Formula (10)
Here, the voltage Va at one end of the power transmission coil L1 is V ₊ , V ₋ (where V ₊ is the voltage applied to the end of the resonance capacitor C10, and the resonance capacitor C11 is the voltage applied to the resonance capacitor C10). The voltage applied to the end of the power transmission is represented by V ₋ ), and the frequency of the alternating current flowing through the power transmission coil L1 during power transmission is represented by f.
_{Va = V - + (V +} -V -) · (ω · C100-ω 3 · L100 · C100 · C110) / (ω · C100 + ω · 110-ω 3 · L100 · C100 · C110) formula (11)
Similarly, the voltage Vb at the other end of the power transmission coil L1 is expressed by Expression (12).
_{Vb = V - + (V +} -V -) · ω · C100 / (ω · C100 + ω · C110-ω 3 · L100 · C100 · C110) formula (12)
Substituting equations (6), (8), (9), (11), and (12) into equation (10) yields equation (13).
Vsd = V ₊ · {− (n + 1) · (1 + M) · (1−ω ² / ω ₀ ² ) + 2 · (nM−1) · ω ² / ω ₀ ² } / {(n + 1) · (1 + M) · (1-ω ² / ω ₀ ² )} Formula (13)
From the equation (13), the reactance ratio M becomes the equation (14).
M = [{n + (n + 1) · Vsd / V ₊ } · {1− (f / f ₀ ) ² } + {1+ (f / f ₀ ) ² }] / [{1− (n + 1) · Vsd / V ₊ } · {1- (f / f ₀ ) ² } + n · {1+ (f / f ₀ ) ² }] Formula (14)

From the above, in order to suppress the induced voltage generated in the metal part SD, the induced voltage Vsd in the equation (14) may be set to Vsd = 0, and when Vsd = 0 is substituted into the equation (14), the equation (1) and (2). Therefore, in order to suppress the induced voltage generated in the metal part SD, it can be realized by setting the reactance ratio M so as to satisfy the expressions (1) and (2).
M = (1-α) / (1 + α) Formula (1)
α = {(n-1) / (n + 1)} · (f / f 0) 2 Equation (2)

  As described above, in the coil unit Lu1 according to this embodiment, the reactance circuit includes the first reactance circuit connected to one end of the winding of the power transmission coil and the other end of the winding of the power transmission coil. And a ratio of the second reactance value of the second reactance circuit to the first reactance value of the first reactance circuit is from the one end of the winding to the center portion. It is set based on the ratio of the average distance between the winding and the metal part from the other end of the winding to the central part with respect to the average distance between the winding and the metal part. Therefore, the voltage value of the voltage induced in the metal part through the parasitic capacitance generated between the winding and the metal part in one end to the center of the winding of the power transmission coil, and the first reactance circuit The voltage difference between the voltages applied to both ends of the metal part is small, and the metal part is connected via a parasitic capacitance generated between the winding and the metal part at the other end to the center part of the winding of the power transmission coil. The difference between the voltage value of the voltage induced by the voltage and the voltage value of the voltage applied to both ends of the second reactance circuit is reduced. As a result, high voltage induced in the metal part can be suppressed.

Further, in the coil unit Lu1 according to the present embodiment according to the present embodiment, the coil unit Lu1 from the other end of the winding to the central unit with respect to the average distance between the coil and the metal unit from one end of the winding to the central unit. When the ratio of the average distance between the winding and the metal part is n, the frequency of the alternating current flowing through the power transmission coil during power transmission is f, and the resonance frequency of the resonance circuit is f ₀ , the second reactance value relative to the first reactance value The reactance value ratio M is set so as to satisfy the following expressions (1) and (2).
M = (1 + α) / (1-α) Formula (1)
α = {(n-1) / (n + 1)} · (f / f 0) 2 Equation (2)
Therefore, the voltage value of the voltage induced in the metal part through the parasitic capacitance generated between the winding and the metal part in one end to the center of the winding of the power transmission coil, and the first reactance circuit The parasitic capacitance generated between the winding and the metal portion between the other end of the winding of the power transmission coil and the central portion thereof is as close to zero as possible. Thus, the difference between the voltage value induced in the metal part and the voltage value applied to both ends of the second reactance circuit approaches zero as much as possible. As a result, the high voltage induced in the metal part can be further suppressed.

(Second Embodiment)
Next, the configuration of the coil unit according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4A is a plan view of the coil unit according to the second embodiment of the present invention. 4b is a cross-sectional view of the coil unit along the cutting line BB in FIG. 4a. For convenience of explanation, the reactance circuits X10 and X11 are omitted in FIG. 4b. The coil unit according to the second embodiment is different from the coil unit Lu1 according to the first embodiment in that a power transmission coil L2 is provided instead of the power transmission coil L1. Hereinafter, a description will be given focusing on differences from the first embodiment. In addition, since the structure of the metal part SD and the reactance circuits X10 and X11 is the same as that of the coil unit Lu1 which concerns on 1st Embodiment, description is abbreviate | omitted.

  As shown in FIG. 4a, the power transmission coil L2 is a coil having a planar spiral structure having a substantially circular shape. The number of turns of the power transmission coil L2 is set as appropriate based on the distance between the coils facing each other during power transmission, the desired power transmission efficiency, and the like. In the present embodiment, as shown in FIG. 4b, the power transmission coil L2 is configured by winding the windings continuously in layers. Specifically, the winding is continuously wound in layers so that one end of the winding is located in the layer farthest from the metal portion. In the present embodiment, the power transmission coil L2 is a two-layered coil, and the first layer winding is wound sequentially from the metal part SD side, and then the second layer winding is wound. Composed. At this time, the end of the first-layer winding and the start of the second-layer winding are connected to form a power transmission coil L2 in which the windings are continuously wound in layers. It will be. In the present embodiment, the winding of the power transmission coil L2 is wound in the order of the first layer and the second layer from the metal part SD side. However, the present invention is not limited to this. You may wind so that the 2nd layer of the coil L2 for transmission may be located in the metal part SD side rather than the 1st layer.

  In the power transmission coil L2, a reactance circuit X10 (first reactance circuit) is connected to the end of the winding of the layer closest to the metal part SD. That is, in this embodiment, the reactance circuit X10 (first reactance circuit) is connected to the end of the first layer of the winding of the power transmission coil L2. Furthermore, in the power transmission coil L2, a reactance circuit X11 (second reactance circuit) is connected to the end of the winding of the layer farthest from the metal part SD. That is, in this embodiment, the reactance circuit X11 (second reactance circuit) is connected to the end of the second layer of the winding of the power transmission coil L2.

  As described above, in the coil unit according to the present embodiment, the power transmission coil L2 has the windings wound continuously in layers. Therefore, the inductance value of the coil can be improved while suppressing a high voltage induced in the metal part.

  Hereinafter, the suppression of the high induced voltage to the metal part SD and the adjustment of the reactance value of the reactance circuit according to the above-described embodiment will be specifically described by Examples 1 and 2 and Comparative Example 1.

  As Examples 1 and 2, the average distance between the winding and the metal part SD from the other end of the winding to the central part with respect to the average distance between the winding and the metal part SD from one end to the center of the winding The coil unit Lu1 according to the first embodiment described above having a ratio n of 1.5 is used. Here, the second reactance value of the second reactance circuit X11 of the first embodiment is the center from the other end of the winding to the average distance between the winding and the metal portion SD from one end to the center of the winding. Is set to 1.55 times the first reactance value of the first reactance circuit X10 based on the ratio n of the average distance between the winding and the metal part SD up to the first part. Further, the second reactance value of the second reactance circuit X11 of the second embodiment is such that the average distance between the winding and the metal part SD from one end of the winding to the center is from the other end of the winding to the center. Is set to 1.6 times the first reactance value of the first reactance circuit X10 on the basis of the ratio n of the average distance between the winding and the metal part SD. On the other hand, as Comparative Example 1, in order to compare the characteristics with Examples 1 and 2, the other end of the winding to the central portion with respect to the average distance between the winding and the metal portion SD from one end to the central portion of the winding. In the coil unit Lu1 according to the first embodiment in which the ratio n of the average distance between the winding and the metal part SD is 1.5 times, only the first reactance circuit X10 has one of the windings of the power transmission coil L1. A coil unit connected to the end was used. In Examples 1 and 2 and Comparative Example 1, a single-layer coil was used as the power transmission coil.

  Subsequently, the voltage applied to Examples 1 and 2 and Comparative Example 1 is an AC voltage of 400 V in which the frequency of the AC current flowing through the power transmission coil is 90 kHz during power transmission from the power conversion circuit. The induced voltage was measured. At this time, a digital multimeter was used to measure the induced voltage of the metal part SD. Here, the digital multimeter has a positive terminal connected to the metal part SD and a negative terminal connected to the ground. In addition, the voltage measurement exceeding the rated voltage of the digital multimeter was measured by resistance partial pressure.

  The measurement results of Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

  According to Table 1, the induced voltage of the metal part was applied to 2430 [V] in Comparative Example 1, whereas it was suppressed to 28.5 [V] in Example 1 and 22.2 [V] in Example 2. Yes. That is, it was confirmed that when the reactance value of the second reactance circuit X11 is set as in the first and second embodiments, the high voltage induced in the metal part SD can be suppressed.

  DESCRIPTION OF SYMBOLS 100 ... Wireless power feeder, 110 ... Power supply, 120 ... Power converter circuit, 121 ... Power converter, 122 ... Switch drive part, 130 ... Feed coil unit, 200 ... Wireless power receiver, 210 ... Power receiver coil unit, 220 ... Rectifier , C0 ... smoothing capacitor, C10, C11 ... resonance capacitor, C12, C13 ... parasitic capacitance, D1-D4 ... diode, L1, L2 ... coil for power transmission, Lu1 ... coil unit, RL ... load, S1 ... wireless power transmission device SG1 to SG4, SW control signal, SW1 to SW4, switching element, X10, first reactance circuit, X11, second reactance circuit.

Claims (5)

A power transmission coil;
A reactance circuit that forms a resonant circuit with the power transmission coil;
A metal part disposed on the back side of the coil for power transmission,
The reactance circuit includes: a first reactance circuit connected to one end of the winding of the power transmission coil; and a second reactance circuit connected to the other end of the winding of the power transmission coil. Have
The ratio of the second reactance value of the second reactance circuit to the first reactance value of the first reactance circuit is an average of the winding and the metal portion from one end to the center of the winding. It is set based on the ratio of the average distance between the winding and the metal part from the other end of the winding to the center with respect to the distance ,
The ratio of the average distance between the winding and the metal part from the other end of the winding to the central part with respect to the average distance between the winding and the metal part from one end to the center of the winding is n, Assuming that the frequency of the alternating current flowing through the power transmission coil during power transmission is f and the resonance frequency of the resonance circuit is f0, the ratio M of the second reactance value to the first reactance value is given by A coil unit that is set to satisfy 1) and (2) .
M = (1 + α) / (1-α) Formula (1)
α = {(n-1) / (n + 1)} · (f / f0) 2 Equation (2) The power transmission coil, the coil unit according to claim 1, characterized in that said windings are wound continuously in layers. Equipped with a feeding coil unit,
The feeding coil unit, the wireless power supply apparatus which is a coil unit according to claim 1 or 2. Equipped with a receiving coil unit,
The power receiving coil unit, the wireless power receiving apparatus which is a coil unit according to claim 1 or 2. A wireless power feeder having a power feeding coil unit;
A wireless power receiving device having a power receiving coil unit,
Wherein at least one of the feeding coil unit and the power receiving coil unit, the wireless power transmission device which is a coil unit according to claim 1 or 2.

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