JP2001313219A - Pick-up coil and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pick-up coil which is capable of keeping its output voltage constant without using an usual constant-voltage control circuit, improved in reliability, and used in the secondary receiving circuit of a non-contact load-dispatching equipment. SOLUTION: A core 1 is composed of a center 11 wound with a cable 2, side ends 12 and 13 which are disposed corresponding to each other through the intermediary of the center 11 wound with the cable 2 and whose major axes are L and equal in length to that of the center 11, and bridges 14 and 15 which form magnetic paths between the center 11 and the side ends 12 and 13. Provided that the length of the bridges 14 and 15 butting against each other through the intermediary of the center 11 is represented by (a), the length (a) is so set as to satisfy formula, a<L. By this constitution, a magnetic flux generated in an induction line 5 passes from the center 11 or the side ends 12 and 13 massively on the narrow (axis is short) bridges 14 and 15, so that a magnetic saturation phenomenon occurs, the output voltage of a pick-up coil never gets higher than a certain voltage at which the magnetic saturation occurs, and the output voltage of the pick-up coil is kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pickup coil used in a secondary power receiving circuit of a non-contact power feeding facility.

[0002]

2. Description of the Related Art An example of a secondary side power receiving circuit of a conventional contactless power feeding facility will be described with reference to FIG. The secondary-side power receiving circuit is provided with a pickup coil 72 opposed to a primary-side induction line 71 through which a high-frequency current flows, and a capacitor 73 that forms a resonance circuit that resonates with the coil 72 at the frequency of the induction line 71. And a rectifier circuit 74 is connected to the capacitor 73. Further, the output voltage _VDC is connected to the reference voltage V _E by the rectifier circuit 74.
Is connected to a constant voltage control circuit 75 for controlling the voltage. The load 76 is connected to the constant voltage control circuit 75, and the constant voltage control circuit 75 supplies power to the load 76. The above coil 72
The capacitor 73 forms a pickup unit in which an electromotive force is induced from the induction line 71.

[0003] The constant voltage control circuit 75 includes a coil 77 for limiting current, voltage generator for generating the reference voltage V _E 78
When, a comparator 79 for comparing the reference voltage V _E of the output voltage V _DC and the voltage generator 78, the output voltage V _DC reference voltage V _E
The output adjusting transistor 80 which is turned on by the comparator 79 when the voltage exceeds the limit, and a diode forming a filter
81 and a capacitor 82. Reference voltage V
_E is set to a high voltage assuming that power is supplied to the full load 76. Power of the load 76, using the voltage V _DC, that is, a large reference voltage V _E, increases.

With the configuration of the constant voltage control circuit 75, a load
When 76 decreases, the output voltage _VDC rises and the output voltage _VDC
There exceeds the reference voltage V _E, the comparator 79 the transistor 80 is turned on, is lowered output voltage V _DC is, the output voltage V _DC is maintained at the reference voltage V _E.

[0005]

However, in such a conventional secondary-side power receiving circuit of the non-contact power feeding equipment, since the above-described constant voltage control circuit 75 is used, the circuit becomes complicated and expensive. In addition, since the constant voltage control circuit 75 uses the transistor 80, there is a problem in life and reliability.

In view of the above, according to the present invention, in place of the constant voltage control circuit 75, the secondary side power receiving of the contactless power supply equipment which can maintain the output voltage of the pickup coil at a constant voltage, is highly reliable, and can be expected to have a long life. It is an object to provide a pickup coil used in a circuit.

[0007]

In order to achieve the above-mentioned object, an invention according to claim 1 of the present invention comprises a core and a cable wound around the core, and an induction for flowing a high-frequency current. A pickup coil in which an electromotive force is induced by a magnetic flux generated in a line, wherein the core is opposed to a central portion around which the cable is wound and to both side surfaces of the central portion where the cable is wound. A side end having a major axis substantially equal to the major axis of the central part, and a bridge part forming a magnetic path between the central part and both side ends, the central part of the bridge part The length of the axis facing the long axis of the center part is shorter than the length of the long axis of the central part.

According to the above configuration, when a high-frequency current flows through the induction line, the magnetic flux generated in the induction line passes through the central portion of the core, the bridge portion, and both end portions, and an electromotive force is induced in the cable. At this time, since the magnetic flux tends to concentrate on the narrow (short axis) bridge from the center or the side end, the magnetic flux is magnetically saturated, and the output voltage of the pickup coil does not rise more than the voltage that reaches the magnetic saturation. , And is maintained at a constant voltage. Heat generated by magnetic saturation is dissipated by the heat sink.

According to a second aspect of the present invention, there is provided a pickup coil including a core and a cable wound around the core, wherein an electromotive force is induced by a magnetic flux generated in an induction line through which a high-frequency current flows. A part of the core having a reduced cross-sectional area through which the magnetic flux passes is formed, and the material of the narrowed part is a material having a smaller core loss than other parts.

According to the above configuration, when a high-frequency current flows through the induction line, the magnetic flux generated in the induction line passes through the core and induces an electromotive force in the cable. At this time, the magnetic flux is
In order to concentrate on the narrowed portion, magnetic saturation occurs in this portion, and the output voltage of the pickup coil does not rise more than the voltage at which magnetic saturation occurs, and is maintained at a constant voltage.
Further, the material of the narrowed portion is made of a material having a smaller core loss than other portions, so that the magnetic loss at the time of magnetic saturation can be minimized.

The invention according to claim 3 is the invention according to claim 2, wherein the core is formed by arranging a plurality of magnetic bodies, and a part of the plurality of magnetic bodies includes:
The narrowed portion is removed.

According to the above configuration, by removing the narrowed portion, the electromotive force induced in the cable is controlled, and the rated power of the pickup coil can be freely changed.

Further, the invention according to claim 4 is the invention according to claim 2 or 3, wherein the core is formed of a magnetic material having an E-shaped cross section, and at least one of both recesses of the core. And the narrowed portion is formed.

According to the above configuration, since the magnetic flux tends to concentrate on the narrowed portion formed in at least one of the two concave portions of the core, the magnetic flux is magnetically saturated in this portion, and the output voltage of the pickup coil is magnetically saturated. It does not rise above the maximum voltage and is maintained at a constant voltage.

A fifth aspect of the present invention is the invention according to the second or third aspect, wherein the core is formed of a magnetic material having a C-shaped cross section, and the protrusions at both ends of the core are provided. Characterized in that the narrowed portion is formed on at least one of them.

According to the above configuration, the magnetic flux tends to concentrate on the narrowed portion formed on at least one of the protrusions at both ends of the core. Therefore, the magnetic flux is magnetically saturated in this portion, and the output voltage of the pickup coil becomes magnetic. It does not rise above the voltage that leads to saturation and is maintained at a constant voltage.

Further, the invention according to claim 6 is the invention according to any one of claims 2 to 5, wherein the narrowed portion is formed in a saddle shape, and both ends of the saddle are other ends of the core. It is characterized by being continuous with the portion.

According to the above configuration, if the shape of the narrowed portion is a saddle shape, heat due to magnetic saturation is generated in the narrowed portion, and since this generated portion has a large area exposed to the outside air, this heat is generated. It becomes easy to diverge, and the temperature can be lowered.

A seventh aspect of the present invention is the invention according to any one of the first to sixth aspects, wherein a heat sink is attached to the core. According to the above configuration, the heat generated by the magnetic saturation generated in the narrowed portion is radiated by the heat sink.

An eighth aspect of the present invention is a method of manufacturing a pickup coil comprising a core and a cable wound around the core, wherein an electromotive force is induced by a magnetic flux generated in an induction line through which a high-frequency current flows. Then, a plurality of magnetic bodies having a cross section of H-shape or H-shape are arranged, a cable is wound over both concave portions of these magnetic bodies, and one of the protrusions of the magnetic body around which the cable is wound is formed. A heat sink is fixed to the side surface, and a magnetic material of a material having less core loss than the convex portion is fixed on the heat sink continuously to both ends of the one convex portion, respectively. A magnetic material combined with an L-shaped or L-shaped material of the same material as the H-shaped magnetic material is fixed on the heat sink.

According to the above method, a portion having a reduced area for magnetic flux is formed in a part of the core having the E-shaped cross section, and a pickup coil in which a cable is wound is formed in the center of the core.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a plan, front and side view of a pickup coil according to Embodiment 1 of the present invention, and FIG. 2 is an exploded perspective view of a core of the pickup coil.

As shown in FIG. 1, the pickup coil P
Is a core 1 made of ferrite (an example of a magnetic material)
And a cable 2 composed of a litz wire wound around the core 1 and a heat radiating plate 4 also serving as a plate of a non-magnetic material (also a magnetic field blocking member; aluminum or copper material) to which the core 1 is fixed by screws 3 And an electromotive force is induced at both ends of the cable 2 by a magnetic flux generated in the induction line 5 through which a high-frequency current flows.

The core 1 has a central portion 11 around which the cable 2 is wound, and a length L of a major axis of the central portion 11 which is opposed to both sides of the center portion 11 around which the cable 2 is wound. Side ends 12 and 13 having the same major axis as that of, and connected to the lower part of the center part 11 and both end parts 12 and 13 respectively, and the magnetic force between the center part 11 and both end parts 12 and 13 is provided. It is formed of bridge portions 14 and 15 that form a path, and a guiding portion 16 that is fixed to the upper surface of the central portion 11 along the long axis and forms a part of a magnetic path. In addition, the length a of the bridge portions 14 and 15 facing the long axis of the central portion 11 is shorter than the length L of the long axis of the central portion 11 (about one-several;
= L / 6). The length Q of the pickup coil P perpendicular to the long axis of the central portion 11 is substantially the same as the length L of the long axis of the central portion 11.

As shown in FIG. 2, the core 1 has a central body 21 having a cross section having a chevron shape, a major axis having the length Q, and a minor axis having the length a. Six first rectangular parallelepipeds 22 having the same height as the section and the length of the short axis, and the length of the long axis being (La) / 2, the central projection of the central body 21 and the outside thereof Are formed on three second rectangular bodies 23 having a major axis length of L / 3 and fixed to the upper parts of the two first rectangular bodies 22.

The pickup coil P is formed in the following procedure. 1. The first on each side of the central chevron of the central body 21
The rectangular body 22 is arranged, and the cable 2 is wound over both sides of the central body 21 and the first rectangular body 22. 2. On top of the central body 21 and the first rectangular body 22, three second
The rectangular body 23 is arranged and fixed to the heat sink 4 with the screws 3. 3. Subsequently, the first rectangular bodies 22 are arranged on both sides of the mountain-shaped projections at both ends of the central body 21, respectively, and are fixed to the heat radiating plate 4 with the screws 3.

According to the above configuration, when a high-frequency current is applied to the induction line 5 laid between the two concave portions of the core 1, the magnetic flux generated in the induction line 5 is generated by the central portion 11 of the core 1, the bridge portion 14, and the bridge portion 14. An electromotive force is induced in the cable 2 through the cable 15 and both end portions 12 and 13. At this time, since the magnetic flux tends to concentrate on the narrow bridges 14 and 15 from the central portion 11 or the side ends 12 and 13, the magnetic flux is magnetically saturated, and the output voltage of the pickup coil P is higher than the voltage at which the magnetic saturation occurs. It does not rise and is maintained at a constant voltage. Heat generated by magnetic saturation is dissipated by the heat sink 4.

As described above, by providing the pickup coil P with the function of maintaining a constant voltage, the conventional constant voltage control circuit and its supporting member are not required, and further, the mounting space is not required, and the space can be saved. As a result, costs can be reduced. Further, since components such as a transistor and a capacitor required for a conventional constant voltage control circuit are not required, reliability can be improved and long life can be expected.

Further, as shown by a two-dot chain line in FIG. 1, the heat sink 4 between the central portion 11 and the side edges 12, 13 is notched in a concave shape.
By providing 25, the bending radius of the guide line 5 can be reduced, and the degree of freedom in laying the guide line 5 can be improved.

Further, since the pickup coil P is formed by fixing the core 1 to the heat radiating plate 4, it is not necessary to separately prepare a plate for fixing the core 1, and the cost can be reduced.

In the above embodiment, the first ends 12 and 13 are
A rectangular body 22 is used, and the side ends 12, 13 and the central part 11 are opposed to each other on the entire surface. As shown in FIG. 3, instead of the first rectangular body 22, a first rectangular body 22 is used. Third rectangular parallelepiped whose height is less than half
26 may be provided in accordance with the height of the guiding portion 16 of the central portion 11. At this time, the side end portions 12 and 13 have a shape provided with cutouts on both sides, that is, a T-shape when viewed from the side.

According to this, the side end portions 12 and 13 can form a magnetic path facing the guide portion 16 and the side end portions 12 and 13 can be reduced in weight, so that the entire pickup coil P can be reduced in weight. Can be achieved. Further, since the notches are provided on both sides of the side end portions 12 and 13, the bending radius of the guide line 5 can be reduced, and the degree of freedom in laying the guide line 5 can be improved. Second Embodiment FIG. 4 is a plan view and a side view of a pickup coil according to a second embodiment of the present invention.

As shown in FIG. 4, the pickup coil P
Are a core 31 formed of ferrite (an example of a ferrimagnetic material), a cable 32 composed of a litz wire wound around the core 31, and a non-magnetic material (magnetic field blocking member) to which the core 32 is fixed by screws 33. A capacitor (not shown) that is formed of a heat sink 34 also serving as a plate of aluminum or copper material, and that forms a resonance circuit that resonates with the cable 32 at the frequency of the induction line 35 at both ends 32 of the cable. And the largest electromotive force is induced by the magnetic flux generated in the induction line 35 through which the high-frequency current flows.

The core 31 has a first ferrite 41 combined with an H-shaped cross section or an H-shaped cross section, and an L-shaped or L-shaped cross section disposed opposite to both sides of the first ferrite 41, respectively. The second ferrite 42 combined with
And a plurality of unit cores 44, which are disposed between the first and second ferrites 41 and 42 and are formed of the third ferrite 43 forming a concave portion, are arranged side by side. With this configuration, the core 31 (unit core 44) has a substantially E-shaped cross section, and a recess is formed in a part thereof.

The third ferrite 43 is formed in both concave portions of the unit core 44 and has a portion where the cross-sectional area through which the magnetic flux passes is smaller than that of the first and second ferrites 41 and 42. As shown in FIG. 5, the first and second ferrites 41,
The ferrite is made of a material having a characteristic of magnetic flux density B-magnetic field strength H with a reduced coercive force and saturation magnetic flux density than 42. That is, the material of the third ferrite 43 is a material having less core loss than other portions.

The cable 32 is wound around the upper and lower surfaces of the central recess of the first ferrite 41 to form the pickup coil P. The pickup coil P is formed in the following procedure. 1. A plurality of first ferrites 41 whose cross sections are H-shaped or H-shaped are arranged side by side, and the cable 32 is wound over both concave portions of the first ferrites 41. 2. The first ferrite 41 around which the cable 32 is wound is screwed on the heat sink 34 so that the outer surface of one of the protrusions is in contact with the first ferrite 41.
Fix with 33. 3. The third ferrite 43 is adhered and fixed on both ends of the first ferrite 41 and on the heat sink 34. 4. Continuous to both ends of these third ferrites 43,
The second ferrite 42 having an L-shaped cross section or an L-shaped cross section is fixed on the heat sink 34 with screws 33.

According to the above configuration, when a high-frequency current flows through the induction line 35 laid almost at the center of both the concave portions of the core 31, the magnetic flux generated in the induction line 35 passes through the core 31 and generates an electromotive force on the cable 32. Is induced. At this time, since the magnetic flux tends to pass through the narrowed portion of the third ferrite 43 in a concentrated manner, the third ferrite 43 is magnetically saturated, and the output voltage of the pickup coil P does not increase beyond the voltage at which the magnetic saturation occurs. ,
It is maintained at a constant voltage. Also, in the narrowed third ferrite 43,
The magnetic loss at the time of magnetic saturation is minimized by providing a characteristic of magnetic flux density B-magnetic field strength H with reduced coercive force and saturation magnetic flux density. In addition, a portion e of the first and second ferrites 41 and 42 continuing to the narrowed third ferrite 43
The heat generated due to the magnetic saturation is radiated by the heat sink 34.

As described above, by providing the function of maintaining the constant voltage to the pickup coil P, the conventional constant voltage control circuit and its supporting member become unnecessary, and further, the mounting space becomes unnecessary, and the space can be saved. As a result, costs can be reduced. Further, since components such as a transistor and a capacitor required for a conventional constant voltage control circuit are not required, reliability can be improved and long life can be expected.

Further, since the pickup coil P is formed by fixing the core 31 to the heat radiating plate 34, it is not necessary to separately prepare a plate for fixing the core 31, and the cost can be reduced.

As shown in FIG. 6, when the shape of the narrowed third ferrite 43 'is a saddle shape, heat generated by the magnetic saturation generated in the portion e is generated in the third ferrite 43'. Since the area has a large area exposed to the outside air, heat is easily radiated and the temperature can be reduced. Third Embodiment FIG. 7 is a front view and a side view of a pickup coil according to a third embodiment of the present invention.

As shown in FIG. 7, the pickup coil P
Is a core 51 having a substantially C-shaped cross section formed of ferrite (an example of a magnetic material), a cable 52 made of a litz wire wound around a central concave portion of the core 51, and a core around which the cable 52 is wound. A block 53 of a non-magnetic material (aluminum or copper) forming the legs at the outer ends of the block 51;
It comprises a plate 54 of a non-magnetic material (which is also a magnetic field blocking member; aluminum or copper material) to which the (core 51) is fixed, and radiator plates 55 fixed to both outer surfaces of the core 51, respectively. At both ends 52, guide line with cable 52
A capacitor (not shown) that forms a resonance circuit that resonates at the frequency of 56 is connected to the induction line through which a high-frequency current flows.
, The largest electromotive force is induced.

The core 51 includes a first ferrite 61 combined in a U-shape or a U-shape in cross section, and a second ferrite having an L-shaped cross section disposed opposite to both protrusions of the first ferrite 61. 62 and these first and second ferrites 6
A plurality of unit cores 64 are sandwiched between the first and second ferrite members 63 and formed of a third ferrite 63 having a saddle-shaped cross section. With this configuration, the core 51
The (unit core 64) has a substantially C-shaped cross section, and a concave portion is formed in a part thereof.

The third ferrite 63 is formed in both concave portions of the unit core 64 and has a portion where the area through which the magnetic flux passes is smaller than that of the first and second ferrites 61 and 62. As shown in FIG.
The ferrite is made of a material having characteristics of magnetic flux density B-magnetic field strength H with a smaller coercive force and saturation magnetic flux density than 1,62. That is, the material of the third ferrite 63 is a material having less core loss than other portions.

The cable 62 is wound around the upper and lower surfaces of the central concave portion of the first ferrite 61 to form the pickup coil P. The pickup coil P is formed in the following procedure. 1. A plurality of first ferrites 61 combined in a U-shape or a U-shaped cross section are arranged side by side, and the cable 52 is wound around the upper and lower surfaces of the recesses of the first ferrites 61. 2. Heat sinks 55 are fixed to the outer surfaces of the first ferrite 61 around which the cable 52 is wound. 3. The third ferrite 63 is fixed on the heat sink 55 so as to be continuous with both ends of the biconvex portion of the first ferrite 61. 4. Continuous to both ends of these third ferrites 63,
The second ferrite 62 is fixed on the heat sink 55. 5. The block 53 is fixed to both ends of the first ferrite 61 around which the cable 32 is wound, and the plate 54 is fixed to the block 53.

According to the above configuration, when a high-frequency current flows through the induction line 56 laid substantially at the center of the concave portion of the core 51, the magnetic flux generated in the induction line 56 passes through the core 51 and generates an electromotive force on the cable 52. Is induced. At this time, since the magnetic flux tends to concentrate on the narrowed third ferrite 63, the magnetic flux is magnetically saturated, and the output voltage of the pickup coil P is maintained at a constant voltage without increasing beyond the voltage at which the magnetic flux reaches the magnetic saturation. Is done. Further, by giving the narrowed third ferrite 63 a characteristic of a magnetic flux density B-a magnetic field strength H in which the coercive force and the saturation magnetic flux density are reduced, the magnetic loss at the time of saturation is minimized. Also, heat is generated in the narrowed third ferrite 63 due to magnetic saturation. The heat generated by the magnetic saturation is dissipated by the heat sink 55. Further, since the third ferrite 63 is formed in a saddle shape, the area of the heat generation location exposed to the outside air is widened, heat is easily dissipated, and the temperature can be lowered.

As described above, by providing the function of maintaining the constant voltage to the pickup coil P, the conventional constant voltage control circuit and its supporting member become unnecessary, and further, the mounting space becomes unnecessary and the space can be saved. As a result, costs can be reduced. Further, since components such as a transistor and a capacitor required for a conventional constant voltage control circuit are not required, reliability can be improved and long life can be expected.

In the first, second, and third embodiments, ferrite (magnetic material) is used for the cores 1, 31, and 51. However, the present invention is not limited to the magnetic material, and a magnetic path is formed as the core. I just need.

In the second and third embodiments, the third ferrites 43 and 63 are provided on all of the unit cores 44 and 64. However, in some of the unit cores 44 and 64, the third ferrites 43 and 63 are narrowed. The three ferrites 43 and 63 can be removed. For example, a portion of the third ferrite 43 indicated by hatching in FIG.
Remove. Thereby, the electromotive force induced in the cables 32 and 52 can be controlled, and the rated power of the pickup coil P can be freely changed.

In Embodiments 2 and 3, the core 3
Although the portions (the third ferrites 42 and 62) where the area through which the magnetic flux passes are narrowed are provided at two locations 1 and 51, the number is not limited to two and may be one or three or more.

[0050]

As described above, according to the present invention, the conventional constant voltage control circuit and its supporting member are not required by providing the pickup coil with the function of maintaining the constant voltage, and the conventional constant voltage control circuit is not required. Since components such as transistors and capacitors required for the above are not required, reliability can be improved and long life can be expected.

[Brief description of the drawings]

FIG. 1 is a plan, front, and side view of a pickup coil according to Embodiment 1 of the present invention.

FIG. 2 is an assembly diagram of a core of the pickup coil.

FIG. 3 is a plan view showing another embodiment of the pickup coil;
It is a front and side view.

FIG. 4 is a plan view and a side view of a pickup coil according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram of ferrite of the pickup coil.

FIG. 6 is a side view showing another embodiment of the pickup coil.

FIG. 7 is a front view and a side view of a pickup coil according to a third embodiment of the present invention.

FIG. 8 is a plan view of a pickup coil according to another embodiment of the present invention.

FIG. 9 is a diagram of a secondary-side power receiving circuit of a conventional contactless power feeding facility.

[Explanation of symbols]

 1,31,51 core 2,32,52 cable 4,34,55 radiator plate 5,35,56 induction line 11,41,61 first ferrite 12,13,14,15,42,62 second ferrite 43, 43 ', 63 Third ferrite 44, 64 Unit core 53 Block 54 Plate P Pickup coil

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 31/00 M

Claims (8)

[Claims] 1. A pickup coil comprising a core and a cable wound around the core, wherein an electromotive force is induced by a magnetic flux generated in an induction line through which a high-frequency current flows, wherein the core is formed by winding the cable. A central portion to be turned, and a side end portion having a major axis substantially the same as the major axis of the central portion, which is opposed to both side surfaces on which the cable of the central portion is wound, and the central portion. It is formed from a bridge that forms a magnetic path between both side ends, and the length of the axis facing the long axis of the central part of the bridge is shorter than the length of the long axis of the central part. Pickup coil. 2. A pickup coil including a core and a cable wound around the core, wherein an electromotive force is induced by a magnetic flux generated in an induction line through which a high-frequency current flows. A pick-up coil characterized by forming a portion having a reduced cross-sectional area through which the material passes, and using a material having a smaller core loss than the other portion. 3. The pickup coil according to claim 2, wherein the core is formed by arranging a plurality of magnetic materials, and the narrowed portion is removed from some of the plurality of magnetic materials. 4. The core according to claim 2, wherein the core is formed of a magnetic material having an E-shaped cross section, and the narrowed portion is formed in at least one of both concave portions of the core. Pickup coil. 5. The core according to claim 2, wherein the core is formed of a magnetic material having a C-shaped cross section, and the narrowed portion is formed on at least one of the protrusions at both ends of the core. The pickup coil according to any one of the above. 6. The pickup coil according to claim 2, wherein the narrowed portion is formed in a saddle shape, and both ends of the saddle are continuous with other portions of the core. 7. The pickup coil according to claim 1, wherein a heat radiating plate is attached to the core. 8. A method for manufacturing a pickup coil comprising a core and a cable wound around the core, wherein an electromotive force is induced by a magnetic flux generated in an induction line through which a high-frequency current flows, wherein the cross section is H-shaped. Alternatively, a plurality of magnetic materials combined in an H shape are arranged, a cable is wound over both concave portions of these magnetic materials, and a heat sink is fixed to an outer surface of one convex portion of the magnetic material wound with the cable. A magnetic material made of a material having less core loss than the convex portion is fixed on the heat radiating plate continuously at both ends of the one convex portion, respectively. A method of manufacturing a pickup coil, comprising fixing an L-shaped or L-shaped magnetic body made of the same material as an H-shaped magnetic body.