Coil device

Details Coil device Coil device

2002-04-19

2004-02-10

Mai, Ahn (Department: 2832)

Inductor devices

Coil or coil turn supports or spacers

Printed circuit-type coil

C336S197000, C336S210000, C336S212000

Reexamination Certificate

active

06690256

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coil device functioning as a transformer or choke coil.
2. Description of the Related Art
FIG. 10A
shows an exploded view of a conventional coil device.
FIG. 10B
shows a sectional view at the line A—A of the coil device shown in
FIG. 10A. A
coil device
1
shown in
FIGS. 10A and 10B
functions as a transformer or choke coil provided in a circuit such as a DC—DC converter and includes a substrate
2
for mounting an electronic component, a coil pattern section
3
provided on the substrate
2
, a pair of core members
4
a
and
4
b
, and a core combining member
5
.
On the substrate
2
, electronic components defining a circuit are provided along with a circuit pattern. The substrate
2
is a multi-layered substrate defined by depositing a plurality of substrates on each other, and each substrate defining the substrate
2
has a coil pattern
7
provided coaxially about a central axis. The plurality of coil patterns
7
define a coil pattern section
3
. In addition, when the coil device
1
defines a transformer device, among the plurality of coil patterns
7
, at least one coil pattern
7
defines a primary coil while the others define secondary coils.
In this conventional example, both of the pair of core members
4
a
and
4
b
are made by pressing and sintering magnetic material powder such as ferrite, and are E-shaped core members having an E-shaped section and including a flat top-plate portion
8
and core legs
9
a
,
9
b
, and
9
c
extending from the center and bilateral ends of the top-plate portion
8
.
On the substrate
2
, core-leg insertion holes
10
a
,
10
b
, and
10
c
are provided at a position of the substrate located in the central portion of the coil pattern section
3
and at positions of the substrate located outside the coil pattern section
3
, respectively. Into these core-leg insertion holes
10
a
,
10
b
, and
10
c
, the respective core legs
9
a
,
9
b
, and
9
c
of the core members
4
a
and
4
b
are inserted from the top and back surfaces of the substrate
2
, such that the core legs
9
of the topside core member
4
a
and the core legs
9
of the backside core member
4
b
abutted each other.
The core-combining member
5
is a member for fitting and combining the pair of core members
4
a
and
4
b
together and is made by bending a metallic plate to have a top plate
12
, legs
13
, and claws
14
. The top plate
12
is a plate covering a top surface
8
a
of the top-plate portion
8
of the core member
4
a
. The legs
13
a
and
13
b
are formed by bending lateral sides of the top plate
12
in an upward direction, and are arranged along the external side surfaces of the core legs
9
a
and
9
c
of the core members
4
a
and
4
b
. The claws
14
a
and
14
b
are formed by inwardly bending end sides of the legs
13
a
and
13
b
so as to abut the top surface
8
a
of the top plate
8
of the core member
4
b.
The distance h from the top surface
8
a
of the top-plate portion
8
of the core member
4
a
to the top surface
8
a
of the top-plate portion
8
of the core member
4
b
in the state that the core legs
9
of the topside core member
4
a
abut the core legs
9
of the backside core member
4
b
is substantially the same as the spacing between the top plate
12
and the claws
14
. Thereby, the core-combining member
5
is fitted to the core members
4
a
and
4
b
in the state abutting each other so as to clamp both the lateral sides of the core members
4
a
and
4
b
in the state abutting each other with the top plate
12
and the claws
14
from both the top and backsides.
By utilizing such a core-combining member
5
, the core members
4
a
and
4
b
are combined with each other in a movable state in the front and rear direction (&agr; direction). In addition, the length W in the front and rear direction of each leg-insertion hole
10
is longer than the width w of core legs
9
of the core members
4
so as to allow movement of the core members
4
in the front and rear direction.
The coil device
1
is assembled as follows. For example, first, the core member
4
a
is placed on the top surface of the substrate
2
having the coil pattern section
3
and the leg-insertion holes
10
provided thereon while the core member
4
b
is placed on the back surface. Then, the legs
9
of the topside core member
4
a
are inserted into the respective leg-insertion holes
10
from the topside of the substrate
2
. Similarly, the legs
9
of the backside core member
4
b
are inserted into the respective leg insertion holes
10
from the backside of the substrate
2
. The core legs
9
of the topside core member
4
a
and the core legs
9
of the backside core member
4
b
are thus abutted to each other.
From the upper side of the core members
4
a
and
4
b
, the left leg
13
a
of the core-combining member
5
is inserted into the left leg-insertion hole
10
a
while the right leg
13
b
of the core-combining member
5
is inserted into the right leg-insertion hole
10
c,
at locations on either side of the core legs
9
of core members
4
.
Thus, the top plate
12
of the core-combining member
5
is abutted to the top surface
8
a
of the top-plate portion
8
of the core member
4
a
while the claws
14
a
and
14
b
of the core-combining member
5
are abutted to the top surface
8
a
of the top-plate portion
8
of the core member
4
b
, such that the core members
4
a
and
4
b
that are abutted against each other are provided into the core-combining member
5
. Thereby, the core members
4
a
and
4
b
are combined with the core-combining member
5
so as to be attached to the substrate
2
. Simultaneously, the core members
4
a
and
4
b
clamp a portion of the coil pattern section
3
therebetween from the top and back sides of the substrate
2
.
Thereafter, the combined core members
4
a
and
4
b
are slid with respect to each other in the front and rear direction such that abutting portions of the core members, i.e., abutted end-faces of the core legs
9
, are rubbed together. By rubbing the end-faces of the core legs
9
together in such a manner (core rubbing), the following advantages are obtained.
That is, since the core members
4
are made by pressing and sintering magnetic material powder, the end-faces of the core legs
9
of the core members
4
have rough surfaces. During assembling the core members
4
a
and
4
b
, foreign particles often enter between the abutted end-faces of the core legs
9
. Therefore, the degree of adhesion between the end-faces, which abut each other, of the core legs
9
is reduced, whereas when the end-faces of the core legs
9
are rubbed against each other, the end-faces of the core legs
9
are polished with each other so as to be close to mirror surfaces. Simultaneously, foreign particles which have entered between the end-faces of the core legs
9
are ground and removed, such that the end faces of the core legs
9
of the topside core member
4
a
are brought into tight contact with the end faces of the core legs
9
of the backside core member
4
b
. By bringing the core members
4
a
and
4
b
into tight contact with each other in such a manner, a reduction in inductance is effectively prevented, and thus, the performance of the coil device
1
is improved.
According to the conventional configuration, since bilateral sides of the pair of core members
4
a
and
4
b
are clamped by pressing them with the core-combining member
5
from both the top and back sides, when the cores are rubbed against each other, the core members
4
a
and
4
b
cannot be slid without a large amount force applied thereto, resulting in reduced efficiency in manufacturing.
Reduced thickness is also demanded for the coil device
1
, and when the thickness of the core members
4
a
and
4
b
is reduced to meet the demand, the core members
4
a
and
4
b
are often broken by cracking or chipping, because of the large force that is applied to the core members
4
a
and
4
b
during the core rubbing. Thereby,

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