JP2020047614A - Wireless power transmission coil unit - Google Patents

Abstract

To provide a wireless power transmission coil unit capable of little power loss by using an inexpensive plat-plate spiral coil and skin effect or proximity effect.SOLUTION: The wireless power transmission coil unit includes a spirally wound flat-plate coil 2 and a magnetic shield 1 provided to face the coil 2. A clearance between a coil conductor of an optional winding positioned at a central peripheral part of the coil 2 and a coil conductor of a winding adjacent thereto is smaller than that between a coil conductor of any winding positioned on coil inner-peripheral side or outer-peripheral side and a coil conductor of a winding adjacent thereto.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to a wireless power transmission coil unit for wireless power transfer capable of wirelessly transmitting power.

  In recent years, use of an electromagnetic induction type wireless power supply device for charging a battery of a vehicle such as an electric vehicle or a hybrid vehicle has been studied. In the wireless power supply device, a high-frequency alternating current (approximately several 10 kHz to 200 kHz) is applied to the power transmission coil, and the power reception coil receives the high-frequency magnetic field generated from the power transmission coil, thereby transmitting power in a non-contact manner.

  In such a non-contact power supply device, the use of a planar coil having a spiral (spiral) rectangular cross section has been studied in order to reduce the thickness of the device. Further, a magnetic shield made of ferrite or the like is arranged near the coil in order to avoid occurrence of eddy current in the surrounding metal parts due to the high frequency magnetic field and abnormal heat generation (for example, Patent Document 1). As described above, the transmission coil unit is configured by the combination of the planar coil and the magnetic shield.

  Generally, in a transmission coil unit, when a coil is energized, magnetic lines of force are generated so as to surround the coil cross section. Further, the magnetic lines of force are distributed so as to flow perpendicularly from the surface of the magnetic shield because the magnetic shield has high magnetic permeability. Further, the coil is wound with a plurality of conductors (coil conductors), and the coil conductors are close to each other. For this reason, a coil has both a skin effect due to a current flowing through the coil and a proximity effect due to an eddy current generated in an adjacent coil conductor. Therefore, the current flowing through each coil conductor is biased inside the conductor, especially the current that is biased toward the inner circumference inside the coil conductor at the inner circumference of the coil and toward the outer circumference inside the coil conductor at the outer circumference. As a result, current concentrates at those portions, and the lines of magnetic force also concentrate.

  In particular, the coil disclosed in Patent Document 1 has a thin high-frequency skin because the rectangular cross section is a plane, and the above-described current flows intensively in the thin portion. As a result, copper loss occurs and the AC resistance increases, resulting in a decrease in power transmission efficiency. In a single coil or inductor that does not output magnetic flux, the copper loss can be reduced by reducing the width of the inner and outer coil conductors and increasing the width of the middle conductor in accordance with the interlinkage magnetic flux density. There is one that suppresses generation of as much as possible (Patent Document 3). However, when a coil having such a configuration is used for wireless power transmission, it is necessary to consider the influence of a magnetic shield placed face to face.

  For such a problem, it is known to use a litz wire in which a large number of insulated wires are twisted as a coil winding (for example, Patent Document 3). The litz wire is a wire formed by combining many thin wires (for example, enamel wires having a wire diameter of 0.1 mm or less) (for example, 500 wires or more), and can suppress high-frequency loss due to the skin effect and the proximity effect.

JP 2013-201296 A JP-A-11-40438 JP-A-2006-219252

However, the litz wire has a problem that the production cost is high because the wires are thin and the number of wires is large. In view of the above circumstances, the present invention reduces the high-frequency loss (copper loss) due to the skin effect and proximity effect of a planar spiral coil, suppresses the increase in AC resistance, and can be manufactured at low cost for wireless power supply. It is an object of the present invention to provide a transmission coil unit.

  A wireless power transmission coil unit according to an embodiment of the present disclosure is a wireless power transmission coil unit including a flat coil wound in a spiral shape and a magnetic shield provided to face the coil. The gap between the coil conductor of an arbitrary winding located at the middle peripheral portion of the coil and the coil conductor of the adjacent winding is changed to the coil conductor of an arbitrary winding located at the inner peripheral side or outer peripheral side of the coil. And a gap between the coil conductor and a coil conductor of a winding adjacent thereto.

  A magnetic body may be provided at least in the gap between the coil conductors of the arbitrary windings located at the inner and outer peripheral portions of the coil and the coil conductors of the windings adjacent to these.

  A magnetic body may be provided on the entire surface of the coil facing the magnetic shield.

  The magnetic body in the gap of the coil may be provided on the side opposite to the side facing the magnetic shield so as to protrude from the coil.

  A magnetic body may be provided on a part of the surface of the coil opposite to the side facing the magnetic shield.

  A magnetic material may be provided to be unevenly distributed on the inner peripheral side of the coil of an arbitrary winding on the inner peripheral part of the coil and on the outer peripheral side of the coil of the arbitrary winding on the spiral outer peripheral part.

  According to an embodiment of the present disclosure, it is possible to guide the magnetic flux lines concentrated on the surface and the side surface of the spiral coil conductor on the flat plate to the magnetic layer to reduce the number of magnetic force lines penetrating the coil conductor, thereby reducing the number of magnetic field lines inside the coil conductor. Eddy current can be suppressed to reduce the AC resistance (copper loss) of the coil, and a transmission efficiency almost equal to or higher than that in the case of using a litz wire can be obtained.

Plan view and sectional view of a general spiral coil unit Sectional view of wireless transmission coil unit according to the first embodiment of the present disclosure Sectional view of a wireless transmission coil unit according to a second embodiment of the present disclosure. FIG. 5 is an enlarged cross-sectional view of the wireless transmission coil unit according to the second embodiment of the present disclosure. Explanatory drawing showing the effect of a magnetic body in a wireless transmission coil unit Sectional view of a wireless transmission coil unit according to a first embodiment of the present disclosure. Configuration diagram of litz wire coil unit on the receiving side Configuration diagram of Litz wire coil unit on power transmission side Analysis model diagram of the wireless transmission coil unit according to the second embodiment of the present disclosure Magnetic flux and current distribution diagram of a copper plate coil in Embodiment 2 of the present disclosure Magnetic flux and current distribution diagram of the MPC coil according to the second embodiment of the present disclosure Shape and dimension diagram of MPC coil in embodiment 2 of the present disclosure Electric characteristics of various coils in Embodiment 3 of the present disclosure Transmission efficiency of various coil units in Embodiment 4 of the present disclosure

  Hereinafter, embodiments according to an aspect of the present disclosure will be described in detail with reference to the drawings.

  First, FIG. 1 shows a configuration of a general planar spiral coil type wireless transmission coil unit. It is characterized in that a coil conductor (Copper) formed in a spiral shape and a magnetic shield (Ferrite) are provided to face each other. In FIG. 1, a portion surrounded by a broken-line square is a radial cross-sectional view. Hereinafter, in the present embodiment, the structural features of the wireless transmission coil unit will be described with such a radial cross-sectional view.

  FIG. 2 is a cross-sectional view of the wireless transmission coil unit according to the first embodiment of the present disclosure. In FIG. 2, reference numeral 1 denotes a magnetic shield, which is made of a magnetic material such as ferrite. Reference numeral 2 denotes a coil, which is a coil conductor (2a) made of copper, aluminum or the like manufactured in a spiral shape and in a flat shape. As a manufacturing method, a metal plate may be cut in a spiral shape by a method such as pressing or etching, may be cast, or may be formed by winding a band-shaped conductor on a plane. Is also good. Although the magnetic shield 1 and the coil 2 are not in direct contact with each other, a nonmagnetic insulating material (resin, ceramic, or the like) may be interposed therebetween (not shown).

  In FIG. 2, a gap 2 d between a coil 2 c of an arbitrary winding located in the middle peripheral portion of the spiral coil and a coil of an adjacent winding is a coil conductor of an arbitrary winding on the inner peripheral side and the outer peripheral side of the coil. It is characterized in that it is narrower than the gap (2b, 2f) between (2a, 2e) and the coil conductor of the adjacent winding. In the present embodiment, the inner periphery refers to a region from N / 4 to N / 2 turns from the innermost to the outermost with the number of turns of the coil 2 being N (N> 8), and the outer periphery refers to the region from the outermost. A region from 1 to N / 3 turns is defined inside. The middle circumference refers to a region surrounded by the inner circumference and the outer circumference.

  By configuring the coil 2 as described above, it is possible to control the path through which the magnetic force lines pass so as to reduce copper loss. Generally, in a coil unit having a magnetic shield 1 on the back surface, an arc-shaped magnetic field line is generated from the coil 2 from the inner circumference to the outer circumference. That is, as shown in FIG. 5 (a), while passing through the magnetic shield (Ferrite), magnetic lines of force are generated upward on the inner circumference, horizontally (parallel to the coil) on the middle circumference, and downward on the outer circumference.

  Therefore, it is better to make the gap (2b) between the coil conductors adjacent to each other as small as possible in the vicinity of the middle circumference where the lines of magnetic force are horizontal, so that the magnetic flux flows parallel to the coil 2 without changing the direction (in the vertical direction) toward the magnetic shield 1 Prone. On the other hand, on the inner and outer peripheral sides of the coil in which the magnetic field lines include a vertical component, the gaps (2b and 2f) are expanded in the opposite direction to the middle so as to minimize the magnetic field lines from intersecting with the coil conductor. It is better to let a lot of magnetic flux escape to the magnetic shield 1 side.

  As described above, in the present embodiment, the gap 2d between the coil 2c of an arbitrary winding located in the middle periphery and the coil of the winding adjacent thereto is set to be equal to that of the arbitrary windings on the inner and outer circumferences. The gap between the coil conductors (2a, 2e) and the coil conductors of the adjacent windings (2b, 2f) is narrower than that of the coil conductors (2a, 2e). 1 as a result, the magnetic flux linked to the coil conductor can be reduced, and as a result, the copper loss due to the eddy current can be reduced.

  In adjusting the gaps 2b, 2d, 2f, a method of changing the width of the coil conductors 2a, 2c, 2e is adopted in FIG. 2, but the present embodiment is not limited to this method. The winding pitch may be changed by making the width of the coil conductor uniform.

  Hereinafter, a second embodiment of the present disclosure will be described. FIG. 3 is a cross-sectional view of the wireless transmission coil unit according to the second embodiment of the present disclosure. In FIG. 3, the magnetic shield 1 and the coil 2 have the same functions as those shown in FIG. In the present embodiment, the magnetic body 3 (3a, 3b, 3c) is provided at least in the gaps 2b, 2d, and 2f on the inner and outer peripheral sides of the coil 2 and the periphery thereof. Note that the magnetic body 3 may be a composite magnetic material in which magnetic powder is kneaded in a resin that is an insulator.

  FIG. 4 is a partially enlarged view of FIG. First, a magnetic body 3b is provided at least in a gap 2b between a coil conductor 2a of an arbitrary winding on the inner peripheral side and an outer peripheral side and a coil conductor of an adjacent winding. The magnetic body 3b guides the magnetic flux linking the coil 2 to the left and right by the wall of the magnetic body, thereby reducing the linking magnetic flux.

  A magnetic body 3a is provided on the entire surface of the coil 2 on the side facing the magnetic shield 1 (hereinafter, also referred to as the coil lower surface). The magnetic material guides the magnetic flux attracted to the magnetic shield to the magnetic material, thereby reducing the magnetic flux linked to the coil upper portion and the coil end.

  In addition, the magnetic body 3 in the gap except for the middle part of the coil 2 is provided on the side opposite to the side facing the magnetic shield 1 so as to protrude from the upper surface of the coil conductor 2a. Further, a magnetic body 3c is provided on a part of the surface of the coil conductor opposite to the side facing the magnetic shield 1 (hereinafter also referred to as the coil upper surface). The magnetic material is unevenly provided so as to cover only the inner peripheral side of the coil conductor 2a on the inner periphery and to cover only the outer peripheral side of the coil conductor on the outer periphery.

  With the above configuration, the magnetic flux linked to the coil can be reduced as much as possible, and the bias of the current in the coil conductor due to the proximity effect can be reduced. As a result, the configuration of the first embodiment can be reduced. The loss can be further reduced than the one.

  Examples of the configuration of the wireless transmission coil unit according to the first and second embodiments and the results of analysis and simulation will be described in the following examples.

  First, a cross section of a wireless transmission coil unit (FIG. 1) having a general structure, a current flowing therethrough, and a schematic diagram of magnetic force generated therefrom are shown in FIG. In FIG. 5, a ferrite (Ferrite) is used as the magnetic shield 1, and a copper plate (Copper) is used as the coil conductor 2a. As shown in FIG. 5A, the lines of magnetic force are formed in an arc from the inner circumference to the outer circumference of the coil through the magnetic shield. In the cross section of the coil conductor (Copper), a symbol with a cross and an open square means a current flowing through the conductor in a downward direction from above the paper surface. This current is offset in accordance with the lines of magnetic force passing through the coil conductor. In other words, in a conductor in which the lines of magnetic force cross obliquely (the inner periphery is closer to the outer periphery and the outer periphery is closer to the inner periphery), the current is concentrated at the corners. In addition, the magnetic flux is attracted to the ferrite, so that the current tends to be biased toward the upper part of the coil.

  Here, when a wall of a magnetic material is provided in the gap between the coil conductors (FIG. 5B), the flow of the lines of magnetic force changes, and the current distribution changes accordingly. That is, in the windings on the inner peripheral side and the outer peripheral side of the coil, the current is biased toward the coil end and upper part. In addition, the current flowing through the winding in the middle part of the coil tends to be shifted toward the upper part of the coil.

  Therefore, as shown in the second embodiment, when a magnetic material is provided at the position where the coil is unevenly distributed (FIG. 5C), the deviation of the end can be reduced. Further, a magnetic material is provided on the entire lower surface of the coil (the side facing the magnetic shield 1), and the magnetic flux attracted to the magnetic shield 1 (ferrite) is passed through this magnetic material, so that the current in the inner and outer windings of the coil is reduced. It flows not only on the top but also on the sides. As described above, by controlling the flow of the magnetic flux by using the magnetic material, the copper loss can be reduced, and the bias of the current can be suppressed.

(Example 1) Structure of coil unit for wireless transmission FIG. 6 shows a specific structure on the power receiving side of a coil unit for wireless transmission (hereinafter, MPC (Magnetic Path Control) coil unit) of the second embodiment. is there. 6A is a plan view, FIG. 6B is a sectional view, and FIG. 6C is a structural view. The coil 2 (Coil) has a spiral shape and the number of turns N = 10. Also, a ferrite (magnetic shield 1) is provided on the back of the coil to reduce the radiation electromagnetic field. The copper plate (coil conductor 2a) has a thickness of 1.5 mm, and magnetic members (3b, 3c) are provided between the coil windings and at a portion where the current density is shifted. The magnetic material (3a) was also used below the coil. The gap between the magnetic body and the ferrite under the coil is 3 mm, and the thickness of the ferrite is 5 mm.

(Comparative Example 1) Structure of coil unit for wireless transmission using litz wire coil FIG. 7 shows the structure of a coil unit (hereinafter, LCW coil) on the power receiving side using litz wire as a coil. 7A is a plan view, FIG. 7B is a cross-sectional view, and FIG. 7C is a structural view. The number of turns N = 10 which is the same as that of the MPC coil unit of the first embodiment. Ferrite and an aluminum plate are used to reduce the radiation electromagnetic field. As for the LCW coil wire, 4200 copper wires having a conductor diameter of 0.05 mm are stepwise twisted (FIG. 7C). The finished outer diameter is 5 mm.

  FIG. 8 shows the structure of the LCW coil on the power transmission side. FIG. 8A is a plan view, and FIG. 8B is a cross-sectional view. The overall shape is longer than the power receiving side, but the litz wire used is the same as the power receiving side coil.

(Example 2) Magnetic field analysis of coil unit In this example, a two-dimensional alternating magnetic field analysis (Ansys Maxwell) was used for analyzing the coil unit for wireless transmission. Furthermore, the resistance R, inductance L, and Q value of the receiving coil were calculated from the results of the magnetic field analysis. Further, the mutual inductance M was calculated from the three-dimensional alternating magnetic field analysis, and the transmission efficiency η _c was calculated from these values using the following equations (1) to (4). The analysis conditions are shown in Table 1. The magnetic material 3 used for the coil is a magnetic composite material using amorphous powder.


Here, Q _{1 is} the Q value of the transmitting coil, Q _{2 is} the Q value of the receiving coil, U is the performance index, and η _{c is the} transmission efficiency (%).

  FIG. 9 shows an analysis model in a two-dimensional cylindrical coordinate system. Although the actual shape of the coil is a square shape, the analysis was performed in a cylindrical coordinate system, so that the analysis was performed with the coil having the same wire length and pitch and a circular shape. 10 and 11 show the analysis in the two-dimensional cylindrical coordinate system. FIG. 10 shows the type of the first embodiment (hereinafter, referred to as a copper plate coil) in which the gap at the center portion of the coil is narrowed, and FIG. 11 shows the type of the second embodiment in which a magnetic material is provided in the gap of the copper plate coil and its periphery. (MPC coil).

  The shape and dimensions of the coil used for the magnetic field analysis will be described below. The total number of windings N was 10, and the pitch between the coil conductors was 7 mm. The gap between the coil conductors at the inner circumference (from the innermost circumference to 5 turns outward) was 2.2 mm. Regarding the outer peripheral portion (from the outermost periphery to the innermost two turns), the gap between the outermost periphery (the first winding) and the second winding coil conductor is 2.2 mm, and the second and third windings (from the outermost periphery to the middle peripheral portion) Boundary) was 1.2 mm.

  FIG. 10 (copper coil model) shows a simulation result of the magnetic field lines and the current distribution. The lines of magnetic force are neatly parallel in the middle part of the coil, but the magnetic flux interlinks perpendicular to the coil plane on the inner and outer sides of the coil. As a result, the current is shifted left and right. Note that the current distribution is shown by shading in the figure. For example, a whitish portion in the coil conductor is a portion where a large amount of current flows. Although the lines of magnetic force are also parallel at the middle part of the coil, they intersect in parallel with the coil conductor, so that current bias occurs at the upper part and the end of the coil conductor.

  FIG. 11 shows a simulation result of the MPC coil in which a magnetic material is provided around the gap between the coils in FIG. 10 and the periphery thereof. In this embodiment, the height of the magnetic body protruding from the upper surface of the coil was 1 mm, and the thickness of the magnetic body covering the entire lower surface of the coil was 0.5 mm. The length of the magnetic material that partially covers the coil upper surface was 0.4 mm to 0.6 mm. FIG. 12 shows details of the shape and dimensions of the magnetic body.

  In the MPC coil (FIG. 11), the magnetic flux interlinking perpendicularly to the coil plane inside and outside the coil winding is guided to the left and right by the wall of the magnetic body, so that the interlinkage with the coil conductor is suppressed as much as possible. I have. In addition, since the magnetic material is used in a place where the current is largely offset such as the coil end, the linkage flux is also reduced. However, at the center of the coil winding, the magnetic flux interlinks parallel to the coil plane, so that the current is biased at the top of the coil. However, by using a magnetic material on the lower surface of the coil, the magnetic flux attracted to the ferrite is guided to the magnetic material, and the magnetic flux linked to the coil upper portion and the coil end is reduced.

Example 3 Impedance Characteristics of Coil Unit In this example, the impedance characteristics of the coil units in FIGS. 10 (copper plate) and 11 (MPC) were calculated using electromagnetic field analysis. For comparison, the impedances of the LCW coil and the power transmission coil were also measured using an impedance analyzer (Agilent Technologies 4294A). The coupling coefficient k was measured under the condition that the transmission distance 1 was 150 mm. The inductance La in the in-phase series connection of the coils and the inductance Lb in the anti-phase connection were measured, and the mutual inductance M was calculated. Also, the coil coupling coefficient k was calculated from the inductance L1 of the power transmission coil, the inductance L2 of the power reception coil, and the mutual inductance M. The coil performance index U was calculated using the measured coupling coefficient k and coil Q value. Finally, the transmission efficiency η _c was calculated from the performance index U. FIG. 13 shows the impedance characteristics of each coil unit.

  In FIG. 13A, the resistances of the copper plate coil, the MPC coil, the LCW coil, and the power transmission coil at 85 kHz are indicated as 187.4 mΩ, 80.2 mΩ, 32.6 mΩ, and 29.5 mΩ, respectively. The resistance was reduced from 187.4 mΩ to 80.2 mΩ by applying the magnetic flux path control technology of the second embodiment to a general copper plate coil unit (FIG. 13B). At this time, the inductance at 85 kHz of the copper plate coil unit, the coil unit of the second embodiment, the LCW coil unit, and the power transmission coil unit was 40.1 μH, 43.6 μH, 37.7 μH, and 40.3 μH, respectively. The power transmission coil has a smaller number of turns than the power reception coil, but has a larger outer diameter and thus has a larger inductance than the power reception LCW. The coil unit according to the second embodiment has an effect of suppressing the deviation of the current density, and thus has a slightly increased inductance as compared with the copper plate coil.

  FIG. 13C shows the Q value of the copper plate coil unit, the MPC coil unit, the LCW coil unit, and the power transmission coil unit at 85 kHz. They were 114, 290, 610, and 724, respectively. Since the resistance of the MPC coil was reduced by half and the inductance was improved as compared with the copper plate coil, the Q value was increased by 2.5 times.

Table 2 collectively shows the impedance characteristics, the coupling coefficient k, and the transmission efficiency η shown in FIG. The coupling coefficient and the efficiency will be described in more detail. FIG. 14 shows the transmission efficiency of the coil in which the figure of merit U (formula (3)) is plotted on the horizontal axis. First, the mutual inductance of the copper plate coil and the MPC coil was calculated using electromagnetic field analysis software (Maxwell 3D), and the coupling coefficient was calculated from equation (2). Further, the inductance La of the LCW coil and the power transmission coil were measured in an in-phase series connection, and the inductance Lb in an anti-phase connection, and the mutual inductance M was calculated using the equation (1).

  The coupling coefficients of the copper plate coil, the MPC coil, and the LCW coil were 0.102 (measured value), 0.125 (calculated value), and 0.175 (calculated value), respectively. Since the magnetic material used for the MPC coil induces the magnetic flux from the power transmission coil to the power receiving coil, the coupling coefficient k of the MPC coil is higher than that of the copper plate coil. It is considered that by suppressing the bias of the current and flowing the current to the coil surface, the magnetic flux linked to the current increased, and the coupling coefficient k was improved.

  As shown in FIG. 14, the efficiencies of the copper plate coil, the MPC coil, and the LCW coil were 94.58% (analysis value), 97.54% (analysis value), and 97.29% (measurement value), respectively. Compared with the copper plate coil, the MPC coil uses the magnetic flux path control technology to reduce the copper loss and the resistance R. Further, since the bias of the current density was suppressed, the inductance was increased, and as a result, the Q value was improved. The MPC coil has an effect of inducing magnetic flux in the power receiving coil as compared with the copper plate coil, and has a high coupling coefficient. Accordingly, the efficiency of the copper plate coil was 94.58%, whereas the efficiency of the MPC coil was 97.54%, an improvement of 2.96 points. The MPC coil is 97.54% (analysis value) compared to the 97.29% (measurement value) of the LCW coil, and almost the same transmission efficiency is expected for the MPC coil and the LCW coil.

  The embodiment according to one aspect of the present disclosure has been described above. In the first embodiment, the line of magnetic force can be controlled so as to avoid the coil conductor as much as possible by narrowing the gap between the coil conductors at the middle portion. Further, in the second embodiment, a magnetic material wall is provided in the coil gap, and the magnetic material is unevenly arranged at the coil end, thereby reducing the current bias at the end. Further, in the second embodiment, by using a magnetic material in the lower part of the coil, the magnetic flux attracted to the ferrite is passed through the magnetic material, thereby reducing the current density flowing in the upper part of the coil. By these measures, it is possible to realize a wireless transmission coil unit having substantially the same transmission efficiency as a Litz wire, despite a structure much simpler than a Litz wire.

  INDUSTRIAL APPLICABILITY The present invention can be used in a non-contact power supply system for electric vehicles, mobile phones, home appliances, medical devices, and other devices having a built-in rechargeable battery.

Reference Signs List 1 magnetic shield 2 coil 2a, 2c, 2e coil conductor 2b, 2d, 2f gap 3 (3a, 3b, 3c) magnetic material

Claims (6)

A wireless power transmission coil unit including a flat coil wound in a spiral shape and a magnetic shield provided to face the coil,
The gap between the coil conductor of an arbitrary winding located in the middle part of the coil and the coil conductor of the winding adjacent thereto is the coil conductor of an arbitrary winding located on the inner or outer peripheral side of the coil. A wireless power transmission coil unit, wherein the gap is smaller than a gap between a coil conductor of a winding adjacent to the coil.   2. The magnetic body according to claim 1, wherein a magnetic material is provided at least in a gap between a coil conductor of an arbitrary winding located at an inner peripheral portion and an outer peripheral portion of the coil and a coil conductor of a winding adjacent thereto. Wireless power transmission coil unit.   3. The wireless power transmission coil unit according to claim 2, wherein a magnetic body is provided on the entire surface of the coil facing the magnetic shield. 4.   The wireless power transmission coil unit according to claim 2, wherein a magnetic body in a gap portion of the coil is provided so as to protrude from the coil on a side opposite to the side facing the magnetic shield.   The wireless power transmission coil unit according to claim 4, wherein a magnetic body is provided on a part of the surface of the coil opposite to the side facing the magnetic shield. A magnetic material is provided on the inner peripheral side of the coil of an arbitrary winding on the inner peripheral part of the coil and on the outer peripheral side of the coil of the arbitrary winding on the outer peripheral part of the spiral, respectively. The wireless power transmission coil unit according to claim 5.