U.S. patent application number 10/029454 was filed with the patent office on 2002-06-27 for non-contact charger.
Invention is credited to Abe, Shigeo, Kojima, Hideki.
Application Number | 20020079863 10/029454 |
Document ID | / |
Family ID | 18862908 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020079863 |
Kind Code |
A1 |
Abe, Shigeo ; et
al. |
June 27, 2002 |
Non-contact charger
Abstract
A non-contact charger wherein a battery-driven electronic device
containing a secondary battery is provided in a power supply
section and electrical power is supplied thereto by non-contact,
the non-contact charger including: a primary side coil and a
secondary side coil, the primary side coil supplying power to the
secondary side coil by electromagnetic induction, the primary side
and secondary side coils being provided to face each other with a
case therebetween; the primary side coil containing a U-shaped
magnetic core having a leg at each end thereof, and windings which
are wound around the magnetic legs; and the secondary side coil
containing a U-shaped magnetic core having a leg at each end
thereof, and a winding which is wound around a common magnetic core
of the U-shaped magnetic core; the cross-sectional area of the
magnetic legs of the primary side coil being greater than the
cross-sectional area of the magnetic legs of the secondary side
coil.
Inventors: |
Abe, Shigeo;
(Tsurugashima-Shi, JP) ; Kojima, Hideki;
(Tsurugashima-Shi, JP) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
18862908 |
Appl. No.: |
10/029454 |
Filed: |
December 26, 2001 |
Current U.S.
Class: |
320/108 |
Current CPC
Class: |
H02J 50/10 20160201;
H01F 38/14 20130101 |
Class at
Publication: |
320/108 |
International
Class: |
H02J 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2000 |
JP |
2000-397836 |
Claims
What is claimed is:
1. A non-contact charger wherein a battery-driven electronic device
containing a secondary battery is provided in a power supply
section and electrical power is supplied thereto by non-contact,
the non-contact charger comprising: a primary side coil and a
secondary side coil, the primary side coil supplying power to the
secondary side coil by electromagnetic induction, the primary side
and secondary side coils being provided to face each other with a
case therebetween; the primary side coil comprising a U-shaped
magnetic core having a leg at each end thereof, and windings which
are wound around the magnetic legs; and the secondary side coil
comprising a U-shaped magnetic core having a leg at each end
thereof, and a winding which is wound around a common magnetic core
of the U-shaped magnetic core; the cross-sectional area of the
magnetic legs of the primary side coil being greater than the
cross-sectional area of the magnetic legs of the secondary side
coil.
2. The non-contact charger according to claim 1, wherein, in the
secondary side coil, the distance between the open ends of the
magnetic legs of the magnetic core is greater than the common
magnetic core.
3. The non-contact charger according to claim 1, wherein, in the
primary side coil, the base section of the cross-sectional area of
the magnetic legs of the magnetic core is wider than the tip
section thereof.
4. The non-contact charger according to claim 1, wherein a braided
wire is used as the material for the winding of at least one of the
primary side coil and the secondary side coil.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a non-contact charger which
uses electromagnetic induction to transmit electrical power between
a primary coil and a secondary coil which are independent of each
other.
[0003] 2. Description of the Related Art
[0004] A non-contact charger comprises a primary side circuit and a
secondary side circuit, which are independently mounted inside a
case, and must efficiently transmit a large amount of electrical
power from the primary side circuit to the secondary side circuit.
An important factor in accomplishing this is to increase the
magnetic transmission efficiency.
[0005] One conventional method of increasing the magnetic
transmission efficiency is to use U-shaped magnetic cores as the
primary side and secondary side coils. The coils are divided and
wound around magnetic legs at each end, thereby increasing the size
of the magnetic leg faces of the opposing magnetic cores and the
opposing faces of the coils.
[0006] With regard to magnetic transmission efficiency, it is
effective to increase the cross-sectional area of the magnetic core
and the coil in the secondary side circuit. However, due to the
demand for small-scale and portable devices, there are limits on
the size of this area, and also on the sizes of the magnetic core
and coil which can be mounted in the secondary side case,
consequently limiting the power which can be transmitted. FIG. 4
shows a conventional small-scale portable non-contact charger.
[0007] In FIG. 4, reference code A represents a primary side coil,
and reference code B represents a secondary side coil. Reference
code 11 represents one section of the case of the primary side coil
A, reference code 12 represents a U-shaped magnetic core used in
the primary side coil A, reference code 13 represents a winding
which is wound around the magnetic leg of the U-shaped magnetic
core 12 of the primary side coil A, reference code 14 represents
one section of the case of the secondary side coil B, reference
code 15 represents a U-shaped magnetic core used in the secondary
side coil B, and reference code 16 represents a winding which is
wound around the magnetic leg of the U-shaped magnetic core 15 of
the secondary side coil B. The primary side coil A and the
secondary side coil B are formed by winding the windings 13 and 16
around the magnetic legs at each end of the magnetic cores 12 and
15, and arranging the magnetic legs so as to face each other with
the cases 11 and 14 therebetween.
[0008] FIG. 5 shows the distribution of magnetic flux in this
constitution, and uses the same reference codes as those in FIG.
4.
[0009] In FIG. 5, magnetic flux is generated in the primary side
coil A, and follows a path around the magnetic legs 12a and 12b on
each side of the U-shaped magnetic core 12, around the magnetic
legs 15a and 15b at each end of the U-shaped magnetic core 15 of
the secondary side coil B, thereby forming a closed magnetic path
for transmitting power to the secondary side coil B.
[0010] One conceivable method for improving the magnetic coupling
between the primary side coil A and the secondary side coil B is to
increase the cross-sectional areas of the magnetic legs 12a, 12b,
15a, and 15b of the magnetic cores 12 and 15 of the secondary side
coil B and the primary side coil A in order to transmit as much of
the magnetic flux as possible from the primary side coil A to the
secondary side coil B. The distance between the magnetic legs 12a
and 12b (open end sides) at each end of the primary side coil A
could also be increased to prevent the magnetic flux from passing
through the secondary side coil B, thereby reducing the magnetic
flux (leaked flux) x which returns directly to the primary side
coil A.
[0011] However, since the winding 16 is wound around the magnetic
legs 15a and 15b at each end of the U-shaped magnetic core 15 of
the secondary side coil B, consideration must be given to providing
gas pace for the winding 16. For this reason, it is extremely
difficult to increase the cross-sectional areas of the magnetic
legs 15a and 15b, and to increase the distance between the magnetic
legs 15a and 15b at each end of the U-shaped magnetic core 15, in
portable electronic devices which must be made thin and small.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a
non-contact charger wherein the secondary side coil can be made
small and thin, and having increased magnetic transmission
efficiency.
[0013] In order to achieve the above objects, the present invention
provides a non-contact charger wherein a battery-driven electronic
device containing a secondary battery is provided in a power supply
section and electrical power is supplied thereto by non-contact,
the non-contact charger comprising a primary side coil, which
supplies power by electromagnetic induction, and a secondary side
coil, which receives power, the primary side and secondary side
coils provided facing each other with cases therebetween; the
primary side coil comprising a U-shaped magnetic core having a leg
at each end thereof, and windings which are wound around the
magnetic legs; and the secondary side coil comprising a U-shaped
magnetic core having a leg at each end thereof, and a winding which
is wound around a common magnetic core of the U-shaped magnetic
core; the cross-sectional area of the magnetic legs of the primary
side coil being greater than the cross-sectional area of the
magnetic legs of the secondary side coil.
[0014] In the secondary side coil, the distance between the open
ends of the magnetic legs of the magnetic core is greater than the
common magnetic core, and, in the primary side coil, the base
section of the cross-sectional area of the magnetic legs of the
magnetic core is wider than the tip section thereof. Therefore,
magnetic flux, generated in the primary side coil, is efficiently
supplied to the secondary side coil.
[0015] Further, a braided wire is used as the material for the
winding of at least one of the primary side coil and the secondary
side coil.
[0016] According to the non-contact charger of the present
invention, a battery-driven electronic device containing a
secondary battery is provided in a power supply section and
electrical power is supplied thereto by non-contact. The
non-contact charger comprises a primary side coil and a secondary
side coil, the primary side coil supplies power to the secondary
side coil by electromagnetic induction. The primary side and
secondary side coils face each other with a case therebetween. The
primary side coil comprises a U-shaped magnetic core having a leg
at each end thereof, and windings which are wound around the
magnetic legs. The secondary side coil comprises a U-shaped
magnetic core having a leg at each end thereof, and a winding which
is wound around a common magnetic core of the U-shaped magnetic
core. The cross-sectional area of the magnetic legs of the primary
side coil is greater than the cross-sectional area of the magnetic
legs of the secondary side coil.
[0017] In the secondary side coil, the distance between the open
ends of the magnetic legs of the magnetic core is greater than the
common magnetic core, and, in the primary side coil, the base
section of the cross-sectional area of the magnetic legs of the
magnetic core is wider than the tip section thereof Therefore, the
secondary side coil can be made small, light, and thin, and can
obtain the required power.
[0018] Furthermore, a braided wire, which is made by braiding
cluster wires, each comprising multiple insulated single-wires, so
that the positions of the cluster wires change alternately inside
and outside, is used as the material for the winding of at least
one of the primary side coil and the secondary side coil.
Therefore, when the magnetic flux generated by one of the coils has
intersected with the winding of the other coil without passing the
magnetic core of the other coil, loss resulting from the eddy
current of the other coil can be reduced, helping to reduce loss in
the secondary side coil and supply the required power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional view of an embodiment of a
non-contact charger of the present invention;
[0020] FIG. 2 is a cross-sectional view of another embodiment of a
non-contact charger of the present invention;
[0021] FIG. 3 is a cross-sectional view of another embodiment of a
non-contact charger of the present invention;
[0022] FIG. 4 is a cross-sectional view of a conventional
non-contact charger; and
[0023] FIG. 5 is a diagram showing magnetic flux distribution of a
conventional non-contact charger.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The non-contact charger of the present invention will be
explained using FIGS. 1 to 3. In FIGS. 1 to 3, the same parts are
represented by the same reference codes.
[0025] FIG. 1 is a cross-sectional view of an embodiment of the
non-contact charger according to the present invention.
[0026] In FIG. 1, reference code A represents a primary side coil,
and reference code B represents a secondary side coil. In the
primary side coil A, reference code 1 represents a case, reference
code 2 represents a U-shaped magnetic core, reference codes 2a and
2b represent magnetic legs at each end of the U-shaped magnetic
core, and reference code 3 represents a winding which is wound
around the magnetic legs 2a and 2b at each end. In the secondary
side coil B, reference code 4 represents a case, reference code 5
represents a U-shaped magnetic core, reference codes 5a and 5b
represent magnetic legs at each end of the U-shaped magnetic core,
and reference code 6 represents a winding which is wound around the
magnetic core at a common section of the magnetic legs 5a and 5b at
each end.
[0027] Since the primary side coil A is provided on a table or the
like, and may acceptably be larger than the secondary side coil B,
the cross-sectional area Hi of the U-shaped magnetic core 2 is
increased prior to providing the winding 3 around the magnetic legs
2a and 2b at each end. The secondary side coil B is portable and
can be carried by a person; to enable it to be made as small as
possible, the cross-sectional area H2 of the U-shaped magnetic core
5 is reduced, the winding 6 is wound around a common magnetic core,
and the distance between the magnetic legs 5a and 5b at each end
matches the distance between the magnetic legs 2a and 2b at each
end of the primary side coil A, so that the magnetic axes are
aligned. By winding the winding 3 around the common magnetic core
of the U-shaped magnetic core 5, which is thin and has a wider
distance between its magnetic legs, the charger can be made small
and thin.
[0028] The magnetic legs 2a and 2b at each end of the primary side
coil A and the magnetic legs 5a and 5b at each end of the secondary
side coil B are arranged so as to face each other with the cases 1
and 4 therebetween.
[0029] Thus, by using a small, light, and thin U-shaped magnetic
core 2 in the secondary side coil, the overall structure is made
lighter and can be used in a portable electronic device.
[0030] FIG. 2 shows a cross-sectional view of another embodiment of
the non-contact charger of the present invention. In FIG. 2, the
secondary side coil B uses a U-shaped magnetic core 7 in which the
distance L2 between open ends of the magnetic legs 7a and 7b (open
end) is greater than the distance L1 between bases of the common
magnetic core. To reduce the magnetic flux (leaked flux) which
returns directly to the magnetic core 2 of the primary side coil A
without allowing the magnetic flux, which was generated in the
primary side coil A, to enter the magnetic core 7 of the secondary
side coil B, the distance between the magnetic legs 2a and 2b of
the primary side coil A is increased, and the magnetic axes are
aligned. This increases the magnetic transmission efficiency, and
enables the charger to be made small, thin, and light.
[0031] FIG. 3 is a cross-sectional view of another embodiment of
the non-contact charger of the present invention.
[0032] In FIG. 3, the primary side coil A uses a U-shaped magnetic
core 8 in which the cross-sectional areas of the magnetic legs 8a
and 8b at each end thereof have been adjusted so that the tip
sections S2 are narrower than the base sections S1. By winding the
winding 9 so as to fit the magnetic core 8, the flow of the
magnetic flux is contained toward the open ends, thereby reducing
the magnetic flux (leaked flux) which returns directly to the
primary side coil A without allowing the magnetic flux, which was
generated in the primary side coil A, to enter the magnetic core 5
of the secondary side coil B, and increasing the magnetic
transmission efficiency by narrowing down the flow of the magnetic
flux toward the open ends of the magnetic cores 8.
[0033] Further, in each of the above embodiments, a braided wire,
which is made by braiding cluster wires, each comprising multiple
insulated single-wires, so that the positions of the cluster wires
change alternately inside and outside, is used as the material for
the winding of at least one of the primary side coil and the
secondary side coil. Therefore, when the magnetic flux generated by
one of the coils has intersected with the winding of the other coil
without passing the magnetic core of the other coil, loss resulting
from the eddy current of the other coil can be reduced, helping to
reduce loss in the secondary side coil and supply the required
power.
[0034] The non-contact charger of the present invention is not
limited to the embodiments described above. For example, the
cross-sectional shape of the U-shaped magnetic core made be round,
square, polygonal, and the like. Further, although the braided
wire, which is made by braiding cluster wires, each comprising
multiple insulated single-wires, so that the positions of the
cluster wires change alternately inside and outside, is used as the
material for the winding of at least one of the primary side coil
and the secondary side coil, a cluster wire which has been
complexly braided from single-wire cluster wires (Litz wire,
twisted wire, etc.) is an acceptable alternative.
[0035] As described above, the non-contact charger of the present
invention comprises the primary side coil and the secondary side
coil use U-shaped magnetic cores having magnetic legs at each end,
a winding is provided around the magnetic legs of the primary side
coil and a winding is provided around a common magnetic core of the
secondary side coil, thereby making the secondary side coil small,
thin, and light, and consequently enabling the overall structure to
be made light and convenient for use in a portable electronic
device. Further, by changing the shape of the magnetic legs of the
U-shaped magnetic cores which face each other from the primary side
and secondary side coils, magnetic flux which is generated in the
primary side coil can be supplied while reducing the leakage of
magnetic flux to the secondary side coil, increasing the magnetic
transmission efficiency.
* * * * *