MAGNETIC PART

A magnetic part used with a non-contact power transmitting/receiving coil has an appropriate shape and size and decreases power loss of the magnetic part. A power transmitting/receiving coil unit includes four flat magnetic bodies disposed over a power transmitting coil that is flatly wound in a rectangular shape. The magnetic bodies are disposed at vertices of the power transmitting coil. Each magnetic body includes a pair of magnetic pieces, with the magnetic pieces being disposed symmetrically about an imaginary line extending from the center toward the vertex of the power transmitting coil and expanding from the inside to outside of the power transmitting coil.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2017-089925 filed on Apr. 28, 2017, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to magnetic parts for vehicles and, in particular, to a magnetic part used with a non-contact power transmitting coil.

BACKGROUND

Electric vehicles, such as electric cars with external charging devices mounted thereon, or hybrid vehicles, have come into wide use. The external charging devices that have been put into practical use receive power from a commercial power source via electrical outlets. Other examples of the external charging devices that have been proposed for non-contact charging are those that charge electricity from power supply units provided at, for example, general households, or parking lots or service stations of community facilities and amusement facilities.

As disclosed in PATENT DOCUMENT1, a power supplying device for non-contact charging includes a power transmitting coil that generates a magnetoelectric field for power transmission. An electric vehicle includes a power receiving coil that receives the electromagnetic field for power transmission. Power transmission is enabled by resonance between the circuit on the power transmitting coil side and the circuit on the power receiving coil side.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

The power transmitting coil and the power receiving coil, both for non-contact charging, (these coils will hereinafter be collectively referred to as a non-contact power transmitting/receiving coil hereinafter) include a conductive wire that is wound flatly.FIG. 6illustrates an example of a non-contact power transmitting/receiving coil40formed by winding a conductive wire44in a rectangular shape. The conductive wire44starts looping from an internal end S until it finishes at the external other end E by being wound one pitch outward every time a single winding of the conductive wire44is finished. The conductive wire44is wound around a rectangular region having a void in the center of the region. A magnetic plate42is disposed opposite to the region where the conductive wire44is wound for decreasing leakage of the magnetic flux and increasing the transmission power.FIG. 6schematically illustrates the non-contact power transmitting/receiving coil40disposed directly over the magnetic plate42, but the non-contact power transmitting/receiving coil40is, in practice, often fixed on a bobbin which is made of an insulator such as plastic resin and is disposed over the magnetic plate42via the bobbin.

Various sizes and shapes of the magnetic plate have been manufactured, but the manufacture is sometimes difficult depending on the shape or size of the non-contact power transmitting/receiving coil, and perhaps causes an increase of the manufacturing cost. To solve this problem, the magnetic plate may be formed to a desired shape and size by combining small pieces of a magnetic body, but in this case a gap is formed between the pieces of the magnetic body and causes power loss.

An object of the present disclosure is to achieve an appropriate shape and size of a magnetic part used with a non-contact power transmitting/receiving coil, and decrease power loss of the magnetic part.

Solution to Problem

The present disclosure provides a magnetic part for a vehicle, including a plurality of flat magnetic bodies disposed over a non-contact power transmitting/receiving coil that is flatly wound, in which the magnetic bodies are disposed over the non-contact power transmitting/receiving coil at a plurality of positions along a winding direction of the non-contact power transmitting/receiving coil, and the magnetic bodies each expand from the inside to the outside of the non-contact power transmitting/receiving coil.

Preferably, the magnetic bodies each include a pair of magnetic pieces, with the magnetic pieces disposed symmetrically about an imaginary line extending outward from the inside of the non-contact power transmitting/receiving coil.

Preferably, the non-contact power transmitting/receiving coil is wound in a polygonal shape, and includes a pair of magnetic pieces, with the magnetic pieces disposed symmetrically about an imaginary line extending toward a vertex of the polygonal shape from the inside of the non-contact power transmitting coil.

Advantageous Effects of Invention

The present disclosure can achieve an appropriate shape and size of the magnetic part used with the non-contact power transmitting/receiving coil, and decrease power loss of the magnetic part.

DESCRIPTION OF EMBODIMENTS

FIG. 1is an exploded schematic view of a power transmitting coil unit10used in a power supply apparatus for non-contact charging. The power transmitting coil unit10includes an electric circuit housing12, magnetic pieces14, a bobbin16, a power transmitting coil18, and a resin cover20. The bobbin16is made of a plastic resin or the like, with its top and bottom surfaces recessed or projecting depending on the necessity. The bobbin16includes a coil groove22for receiving the power transmitting coil18formed by winding a conductive wire into a flat rectangular shape. Thus, the power transmitting coil18is accommodated in the coil groove22and fixed on the bobbin16.

The electric circuit housing12receives an electric circuit for non-contact charging. A pair of magnetic pieces14is fixed at each of the four corners of the upper surface of the electric circuit housing12. The magnetic pieces14are made of ferrite, permalloy, iron, or the like and formed into the flat plate-like shape. By covering the electric circuit housing12by the bobbin16from above, the magnetic pieces14of each pair face each other via the bobbin16at the respective corners of the power transmitting coil18.

The four pairs of magnetic pieces14and the electric circuit housing12are covered by the bobbin16on which the power transmitting coil18is fixed, and the bobbin16is covered by the resin cover20from above. Thus, the power transmitting coil unit10is assembled.

The power transmitting coil unit10is installed in a parking lot, for example. When the electric vehicle capable of non-contact charging stops over the power transmitting coil unit10, the power transmitting coil18comes to face a power receiving coil mounted on the electric vehicle to enable non-contact charging from the power transmitting coil18to the power receiving coil.

FIG. 2is a plan view of four pairs of magnetic pieces14. The four pairs of magnetic pieces14are disposed over the power transmitting coil at four positions along the winding direction of the power transmitting coil. Specifically, a pair of magnetic pieces14extend toward each corner of the four corners of the transmitting coil from the inside of the transmitting coil, so that each pair of magnetic pieces14extends from the inside to the outside of the transmitting coil and spans over the inside and outside of the power transmitting coil. A pair of magnetic pieces14forms a magnetic body24which is symmetrical about an imaginary line26extending from the center0toward the outside. A gap is formed between the pair of magnetic pieces14in which the magnetic pieces14are disposed symmetrically about the imaginary line26.

The magnetic pieces14are shaped, for example, by the steps illustrated inFIG. 3AtoFIG. 3D. Specifically,FIG. 3Ais the step of forming an octagonal hole30in the center of a rectangular magnetic plate28,FIG. 3Bis the step of dividing the magnetic plate28by dividing lines32each extending outward from each vertex of the octagonal hole30, where each diving line32extends in a direction equally dividing each vertex,FIG. 3Cis the step of forming a notch34of an isosceles triangle shape on each side of the magnetic plate28, andFIG. 3Dis the step of forming holes36for the production or installation process on each magnetic piece14.

FIG. 4illustrates the power transmitting coil18disposed over the individual magnetic pieces14. Each magnetic piece14is shown by a broken line, as it is covered by the transmitting coil18via the bobbin16inFIG. 4.

FIG. 5is a cross-sectional view schematically illustrating a portion where the power transmitting coil18overlaps the magnetic pieces14. A magnetic flux38is generated in the vicinity of the transmitting coil18to surround the transmitting coil18, allowing the magnetic flux38to pass through a magnetic path formed by the magnetic pieces14. The magnetic flux is concentrated in the magnetic pieces14that have a magnetic permeability greater than that of air.

This structure forms the magnetic path through the magnetic pieces14at each of the four corners of the power transmitting coil18. Usually, the magnetic flux expands more easily in the vicinity of the four corners of the rectangular coil than in straight line sections. Since the magnetic pieces14of the present embodiment are disposed at positions corresponding to the four corners in the power transmitting coil unit10, the magnetic flux is concentrated in the magnetic pieces14in the vicinity of the four corners of the power transmitting coil18. As a result, leakage of the magnetic flux decreases and the transmitting power to the power receiving coil increases.

Meanwhile, the magnetic flux generated around the power transmitting coil18is often directed to surround the conductive wire that forms the power transmitting coil18. This means that few magnetic flux crosses the gap between the magnetic pieces of the pair of the magnetic pieces14, thereby decreasing the electromagnetic loss due to the gap. In addition, each magnetic piece14is small, as the magnetic pieces14are disposed only at positions corresponding to the four corners of the transmitting coil18. Further, the magnetic pieces14are identical in shape, as they are formed symmetrically about the gap at the four corners of the transmitting coil18, so that the number of types of required parts can be reduced.

The power transmitting coil formed by winding the conductive wire rectangularly has been described. Alternatively, the power transmitting coil may be wound in a different polygonal shape. In that case, the shape of the magnetic pieces can be derived also from similar steps as illustrated inFIG. 3AtoFIG. 3D. For example, assume that the power transmitting coil is wound in an equilateral n-angle polygon (where n is an integer not smaller than 3), then the magnetic pieces can be shaped by the following steps of: (i) forming a 2n-polygonal hole in the center of the magnetic plate of an equilateral polygon, (ii) dividing the magnetic plate by divisional lines extending outward from each vertex of the 2n-polygonal hole, (iii) forming a notch in the center part of each side of the magnetic plate, and (iv) forming holes for the production or installation step in each magnetic piece.

Although the magnetic pieces used for the power transmitting coil have been described, the magnetic pieces may also be used for the power receiving coil.