CN113284715A

CN113284715A - Magnetic coupling inductor

Info

Publication number: CN113284715A
Application number: CN202011093719.6A
Authority: CN
Inventors: 山口乔之
Original assignee: Sumida Group Co ltd
Current assignee: Sumida Group Co ltd; Sumida Corp
Priority date: 2020-02-19
Filing date: 2020-10-14
Publication date: 2021-08-20
Also published as: JP2021132120A; JP7373119B2

Abstract

The magnetic coupling inductor provided by the invention has a 2in1 structure which actually acts as two independent inductors, thereby realizing miniaturization of the external dimension; the magnetic coupling inductor includes: a first magnetic core (1) and a second magnetic core (2) having a center leg part (11), (21), an outer leg part (12), (22), and a connecting part (13), (23), a bobbin (4), (5) through which the center leg part (11), (21) is inserted and disposed outside each of the center leg parts (11), (21), a first coil winding (6) and a second coil winding (7) wound around the bobbin (4), (5), respectively, and a third magnetic core (3) sandwiched by the two bobbin (4), (5) and having a ring shape into which the center leg part (11), (21) is inserted; the corresponding foot parts of the first magnetic core (1) and the second magnetic core (2) are mutually butted through a gap; the directions of magnetic fluxes generated by the respective currents flowing through the first coil winding (6) and the second coil winding (7) and passing through the third magnetic core (3) are the same as each other; when the thickness of the third core (3) is defined as a and the gap between the outer leg parts (12, 22) of the first core (1) and the second core (2) is defined as b, a is equal to or greater than b.

Description

Magnetic coupling inductor

Technical Field

The present invention relates to a magnetic coupled inductor (magnetic coupled inductor) having a 2in1(2 in 1) configuration, wherein the 2in1 configuration of the coupled inductor is configured to sandwich a toroidal core between a pair of PQ cores (including E-cores and the like).

Background

In recent years, a PFC magnetic coupling inductor has been proposed which realizes a 2in1 structure that actually functions as two independent high-voltage transformers as disclosed in patent document 1 below, and which can reduce the external dimensions of the product.

Patent document 2 discloses a transformer configured to sandwich a pair of PQ cores between a toroidal core.

[ Prior art documents ]

[ patent document ]

Patent document 1: japanese patent, Japanese patent No. 5062439

Patent document 2: japanese patent, Japanese examined patent publication No. 4-14487

However, the forms of these patent documents have the following problems: in the combined structure of the pair of PQ cores and the core sandwiched therebetween, the cross-sectional area of the core is increased to allow the synthesized magnetic flux to pass therethrough, and the size of the magnetic coupling inductor is increased, which makes it impossible to sufficiently reduce the size thereof.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic coupling inductor in which: with the 2in1 configuration that actually functions as two independent inductors, the layout conditions for the combination of the cores are optimized, and the outer dimensions can be further reduced.

In order to solve the above problem, the magnetic coupled inductor of the present invention has the following features.

The magnetic coupling inductor of the present invention includes: a first magnetic core and a second magnetic core each having a center leg portion, outer leg portions positioned on at least both sides of the center leg portion, and a connecting portion connecting the center leg portion and the outer leg portions; a bobbin through which the leg portions of the first and second magnetic cores are inserted, the bobbin being disposed outside the leg portions; a first coil winding and a second coil winding wound around the respective bobbins, respectively; and a third magnetic core which is annular and is sandwiched by the two coil bobbins, and in which the middle leg portion is inserted.

The first magnetic core and the second magnetic core have corresponding leg portions butted against each other, and gaps are provided between the corresponding leg portions; directions of magnetic fluxes generated by the respective currents flowing through the first coil winding and the second coil winding and passing through the third core are the same as each other; the magnetic coupling inductor is configured to: when the thickness of the third core is a and the gap between the outer leg portions of the first core and the second core is b, a condition (1) a ≧ b is satisfied.

Here, it is preferable that: when the thickness of the third core is a and the thickness of the connecting portion between the first core and the second core is c, a condition (2) a ≧ c is satisfied.

Further, it is preferable that: the magnetic coupling inductor includes a positioning and fixing member that fixes a thickness direction intermediate portion of the third core at an intermediate position between front end surfaces of the two middle leg portions.

Further, it is preferable that the positioning and fixing member is configured to: a vertical piece extending upward is erected at the center of a flat plate-shaped base portion, slit-shaped engagement grooves are formed on both sides of the inner side edge of the base portion, and the extension portions of the two inner flange portions of the bobbin can be engaged with the engagement grooves.

(effect of the invention)

According to the magnetic coupling inductor according to the present invention, the external dimensions of the core assembly formed by combining a plurality of cores can be reduced, and the 2in1 structure that actually functions as two independent inductors can be realized.

Further, by optimizing the arrangement conditions for the combination of the cores, the outer dimensions can be further reduced, and the installation space can be reduced.

Drawings

Fig. 1 is an overall perspective view of a magnetically coupled inductor according to a first embodiment of the present invention.

Fig. 2 is an exploded perspective view of fig. 1 with the tape omitted.

Fig. 3 is a sectional view for explaining a core portion of the magnetic circuit.

Fig. 4 is a partial plan view illustrating the arrangement condition of the magnetic core structure.

Fig. 5 is a partial plan view illustrating another arrangement condition of the magnetic core structure.

Fig. 6 is a sectional view for explaining the dimensional relationship of the magnetic core structure of the first embodiment.

Fig. 7a is a front view showing a core portion of another embodiment.

Fig. 7b is a perspective view of fig. 7 a.

Fig. 7c is a perspective view showing one PQ core in fig. 7a omitted.

Fig. 8 is a perspective view showing a combination of two bobbins and a positioning and fixing member.

Fig. 9 is a perspective view showing a combined structure of two bobbins.

Fig. 10 is a perspective view showing a combination structure of a PQ core and a positioning and fixing member.

Fig. 11 is a front view of the main part in a middle section.

Fig. 12a is an overall perspective view of the magnetically coupled inductor as viewed from above.

Fig. 12b is a perspective view of a process of winding a coil around a bobbin.

Fig. 12c is a perspective view of a process of fixing and positioning the fixing member.

Fig. 12d is a partial perspective view of a process of combining the magnetic core member and the bobbin.

Fig. 12e is a bottom perspective view illustrating the final bonding process.

(symbol description)

1 first magnetic core

2 second magnetic core

3. 31 third magnetic core

4. 5 coil framework

6 first coil winding

7 second coil winding

8 positioning and fixing component

9 terminal pin

10 adhesive tape for fixation

11. 21 middle foot part

12. 22 outer foot part

13. 23 connecting part

41. 51 terminal board

42. 52 barrel part

43. 53 outer flange portion

44. 54 inner flange part

81 base part

82 longitudinal pieces

83 engagement groove

100 magnetic coupling inductor

G1, G2 gap

Detailed Description

Hereinafter, a configuration of a magnetic coupled inductor (magnetic coupled inductor) according to an embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is an external perspective view of a magnetic coupling inductor 100 as a product, and fig. 2 is an exploded perspective view of fig. 1 with adhesive tapes omitted.

The magnetic coupled inductor 100 of the present embodiment includes: a first core 1 and a second core 2 made of PQ cores, a third core 3 made of a ring core (ring core), two coil bobbins (bobbin)4 and 5, a first coil winding (coil winding)6 and a second coil winding 7, two positioning and fixing

members

8 and 8, 8 terminal pins (terminal pins) 9 having 8 terminals on both sides, and a fixing tape 10 wound around the outer periphery.

The pair of PQ cores, i.e., the first core 1 and the second core 2, is made of, for example, ferrite cores (ferrite cores) and has the same outer dimensions, and the first core 1 has: a middle leg 11, outer legs 12 positioned on both sides of the middle leg 11, and a flat plate-like connecting portion 13 connecting the middle leg 11 and the outer legs 12, and the second magnetic core 2 includes: a middle leg portion 21, outer leg portions 22 positioned on both sides of the middle leg portion 21, and a flat plate-like connecting portion 23 connecting the middle leg portion 21 and the outer leg portions 22, and the first core 1 and the second core 2 are arranged to face each other.

The

middle leg portion

11, 21 is formed in a cylindrical shape and has a length of approximately 1/2 of the distance between the connecting portion 13 and the connecting portion 23 which are opposed to each other, and the

outer leg portion

12, 22 is formed such that: the inner side surface of the plate is in a shape of a circular arc and the outer side surface is in a plane shape.

The third core 3 is made of, for example, a ferrite core, and is formed in a ring shape (disc shape) having a rectangular cross section.

The two

bobbin

4, 5 shown in fig. 8 are made of insulating resin, the two

bobbin

4, 5 are formed in a symmetrical shape, and are combined into one body as shown in fig. 9, the two

bobbin

4, 5 are respectively provided with

wiring boards

41, 51 on the end portions thereof, and 4

wiring pins

9, 9 are respectively provided on the

respective wiring boards

41, 51.

Cylindrical portions

42 and 52 extending in the axial direction are disposed above the

terminal plates

41 and 51, respectively. Disc-shaped

outer flanges

43 and 53 are provided at one end of the

tubular portions

42 and 52 on the

connection plate

41 and 51 side, respectively, and disc-shaped

inner flanges

44 and 54 are provided at the opposite end, respectively,

extension portions

44a and 54a of the

inner flanges

44 and 54 extending downward are engaged with positioning and fixing

members

8 and 8 described later, and

projections

44b and 54b are formed at the lower end portions of the

extension portions

44a and 54a, respectively (see fig. 9). Further, the structure is:

butterfly projections

45 and 55 are provided on upper and lower ends of the

outer flanges

43 and 53 of the

bobbin

4 and 5, respectively, and the

butterfly projections

45 and 55 abut on upper and lower inclined surfaces of the connection portion 13 of the first magnetic core 1 and the connection portion 23 of the second magnetic core 2, respectively.

By providing the butterfly-shaped

projections

45 and 55 on the upper and lower ends of the

outer flange portions

43 and 53 of the

bobbins

4 and 5, respectively, the insulation between the first coil winding 6 (including the lead wire) and the first magnetic core 1 and the insulation between the second coil winding 7 (including the lead wire) and the second magnetic core 2 are improved, and the respective

magnetic cores

1, 2 and 3 and the

respective bobbins

4 and 5 can be fixed to each other stably.

The end portions of the

tubular portions

42 and 52 of the

bobbins

4 and 5 are configured to: the recessed portion 42b of one bobbin 4 provided in a symmetrical concavo-convex shape for engagement engages with the raised portion 52a (see fig. 8) of the other bobbin 5, whereby the axial centers of the

cylindrical portions

42 and 52 of both bobbins coincide with each other.

The inner leg 11 of the first core 1 is inserted from one end side into the connected

tubular portions

42 and 52 of the

bobbins

4 and 5, and the inner leg 21 of the second core 2 is inserted from the other end side into the connected

tubular portions

42 and 52 of the

bobbins

4 and 5, whereby the

bobbins

4 and 5 are disposed outside the respective

inner legs

11 and 21.

The corresponding

middle legs

11 and 21 of the first and

second cores

1 and 2 are butted against each other, the corresponding

outer legs

12 and 22 on both sides are butted against each other, gaps G1 and G2 (see fig. 3) are provided between the corresponding legs, and the sizes b (substantially the same size) of the gaps G1 and G2 are defined by a positioning and fixing member 8 (so-called spacer) described later.

In the above-described

bobbin

4, 5 structure, the first coil winding 6 is wound between the outer flange portion 43 and the inner flange portion 44 of one bobbin 4, and the second coil winding 7 is wound between the outer flange portion 53 and the inner flange portion 54 of the other bobbin 5 (see fig. 2). The first coil winding 6 has its end connected to a predetermined terminal pin 9, and the second coil winding 7 has its end connected to the predetermined terminal pin 9.

Further, the annular third core 3 is disposed between the inner flange portion 44 of the one bobbin 4 and the inner flange portion 54 of the other bobbin 5. The third core 3 is sandwiched between the two

bobbins

4 and 5, most of the

center legs

11 and 21 of the first and

second cores

1 and 2 are inserted into the inner ring of the third core 3, and the gap G1 is formed between the end faces of the

center legs

11 and 21.

When the first to third magnetic cores 1 to 3 and the two

bobbin

4 and 5 are assembled, positioning and fixing

members

8 and 8 are disposed on both sides of the lower portions of the two

bobbins

4 and 5, respectively. As shown in fig. 8, 10, and 11, the positioning and fixing

members

8 and 8 are configured to:

vertical pieces

82, 82 extending upward are erected at the centers of flat plate-shaped base portions 81, and

engagement grooves

83, 83 in the shape of slits (slit) are formed on both sides of the inner side edge of the base portion 81.

The

extension portions

44a, 54a of the two

inner flange portions

44, 54 of the

bobbins

4, 5 are engaged with the engagement grooves 83, respectively. Thereby, the positions in the axial direction and the center positions of the

inner flange portions

44 and 54 of the two

bobbins

4 and 5 are defined.

Further, the

vertical pieces

82 and 82 are sandwiched between the distal end surfaces of the outer leg portions 12 of the first core 1 and the distal end surfaces of the outer leg portions 22 of the second core 2, respectively, and the size b of the gap G2 between the distal end surfaces of the outer leg portions 12 of the first core 1 and the distal end surfaces of the outer leg portions 22 of the second core 2 is defined by the thickness dimensions of the

vertical pieces

82 and 82 of the positioning and fixing

members

8 and 8.

As shown in fig. 10, the

vertical pieces

82, 82 of the positioning and fixing

members

8, 8 have a shape similar to the cross-sectional shape of the

outer legs

12, 22, and they are in full-face contact without being displaced. Further, triangular openings 84 are formed in the upper and lower portions of the vertical pieces 82, respectively, and when the

vertical pieces

82, 82 are assembled, the adhesive is filled in the openings 84, whereby the

vertical pieces

82, 82 are fixed to the distal end surfaces of the

outer leg portions

12, 22 of the first and second

magnetic cores

1, 2.

By combining the positioning and fixing

members

8, 8 and the third core 3 between the first core 1 and the second core 2in this manner, the position of the gap G1 between the

leg portions

11, 21 can be accurately set at the intermediate position between the first coil winding 6 and the second coil winding 7 wound around the

respective bobbins

4, 5, and therefore, in the 2in1 type magnetic coupling inductor, the inductances (inductances) of the respective inductors can be set equal to each other.

Thus, the following disadvantages and the like in the prior art can be eliminated: magnetic saturation occurs in any of the inductors due to a variation in the distance from each inductor to the magnetic gap (magnetic gap).

As shown in fig. 9, the tips of the

projections

44b and 54b formed at the lower end portions of the

inner flange portions

44 and 54 of the two

bobbins

4 and 5 respectively come into contact with the substrate surface and the like, thereby serving to stabilize the posture during manufacturing in an assembly process and the like.

As described above, the magnetic coupling inductor 100 according to the present embodiment is configured to include the coupling inductor (coupled inductor) having the 2in1(2 in 1) structure, and the coupling inductor having the 2in1 structure is configured to sandwich the third core 3 formed of the toroidal core between the bobbin 4 assembled to the first core 1 and the bobbin 5 assembled to the second core 2. The directions of magnetic fluxes generated by the respective currents flowing through the first coil winding 6 and the second coil winding 7 and passing through the third core 3 are the same as each other.

Specifically, as shown in fig. 3, the first and second

magnetic cores

1 and 2 are separated from each other by forming a gap G1 between the

center leg portions

11 and 21 and a gap G2 between the

outer leg portions

12 and 22. Therefore, in the first core 1, the magnetic fluxes passing through the

connection portions

13 and 13 from the

outer leg portions

12 and 12 on both sides join at the center leg portion 11 and flow toward the distal end surface of the center leg portion 11.

On the other hand, in the second core 2, magnetic fluxes passing through the

connection portions

23 and 23 from the

outer leg portions

22 and 22 on both sides join at the center leg portion 21 and flow toward the distal end surface of the center leg portion 21. The magnetic fluxes flowing through the two

center legs

11 and 21 collide with each other at the front end surfaces of the

center legs

11 and 21, and then flow while being divided into left and right portions, and reach the

outer legs

12 and 22 of the first and

second cores

1 and 2 after passing through the third core 3.

As a result, magnetic loops (magnetic loops) L1, L2 circulating in the direction shown in fig. 3 are formed in the first and

second cores

1, 2 and the third core 3.

The magnetically coupled inductor 100 according to the embodiment described above is configured such that: as shown in fig. 4, when the thickness of the third core 3 is "a" and the gap amount of the gap G2 between the

outer leg portions

12 and 22 of the first and

second cores

1 and 2 is "b", the following condition (1) is satisfied.

a≥b (1)

By establishing the above condition (1), the magnetic coupling inductor can be downsized.

That is, when a < b, the coupling coefficient, which is an important parameter of the coupled inductor, becomes small. When the coupling coefficient is small, a large current cannot be allowed without enlarging the size of the coupling inductor.

Therefore, it is preferable to configure to satisfy the condition (1) of a.gtoreq.b, thereby realizing miniaturization of the product.

Further, the magnetic coupled inductor 100 is configured such that: as shown in fig. 5, when the thickness of the third core 3 is a and the thicknesses of the

connection portions

13 and 23 of the first and

second cores

1 and 2 are c, the following condition (2) is satisfied.

a≥c (2)

By establishing the condition (2), the magnetic coupling inductor can be downsized.

That is, when a < c, the circulating magnetic flux is generally saturated at the position referred to by a (the position of the gap G1 between the distal end surfaces of the

center legs

11 and 21 of the first and second cores 1 and 2), but not at the position referred to by c (the position of the connecting

portions

13 and 23 of the first and second cores 1 and 2), and therefore, it is difficult to ensure the function as the coupling inductor.

When the duty (ON/OFF ratio of the switch) is set to a predetermined value, the magnetic fluxes flowing through the first and

second cores

1 and 2 merge and flow into a (the gap G1), whereby the third core 3 is easily saturated, and therefore a is set to c or more (the cross-sectional area of the third core 3 is set to c or more (the cross-sectional area of the

connection portion

13 or 23 is set to c or more) (when the output voltage Vout/the input voltage Vin is equal to or greater than 2).

Therefore, it is most preferable to configure the circuit to satisfy the condition (2) of a ═ c, thereby achieving miniaturization of the product.

However, in the above condition (2), even if there is a tolerance portion of c (± 5% or so), the effect of downsizing the inductor can be confirmed, and therefore, as an actual numerical range, the following condition (2') can be satisfied.

a≥0.95c(2’)

Further, the magnetic coupled inductor 100 is configured to: when the amount of clearance between the inner peripheral surface of the annular core in the third core 3 and the outer peripheral surfaces of the

leg portions

11 and 21 is f or the amount of clearance between the outer peripheral surface of the annular core in the third core 3 and the inner peripheral surfaces of the

leg portions

12 and 22 is G as shown in fig. 6, the following condition (3) or (4) is satisfied between the sum (substantially 3b) of the amount of clearance b between the gap G1 between the

leg portions

11 and 21 of the first and

second cores

1 and 2 and the two gaps G2 and G2 between the

leg portions

12 and 22 on both sides and f and G.

3b≥f (3)

Or

3b≥g (4)

By establishing the above condition (3) or (4), the magnetic coupling inductor can be miniaturized.

That is, when 3b < f and 3b < g, the coupling coefficient, which is an important parameter of the coupled inductor, becomes small as in the case where the above condition (1) is not satisfied. When the coupling coefficient is small, a large current cannot be allowed without enlarging the size of the coupling inductor.

Therefore, it is preferable to configure the structure so as to satisfy the condition (3) of 3b ≧ f or the condition (4) of 3b ≧ g, thereby achieving miniaturization of the product.

The physical integration of the

cores

1, 2, and 3 is performed using the fixing tape 10 in the above embodiment, but the cores may be integrated using an adhesive, an adhesive tape, a clip, or the like.

The direction of the current flowing through the first coil winding 6 and the second coil winding 7 and the winding direction of the coil may be configured as described below, and may be arbitrarily selected as long as the following operational effects can be exhibited.

That is, when the two

cores

1 and 2 are arranged to face each other as shown in fig. 3, magnetic flux passing through the center leg 11 from the

outer leg portions

12 and 12 on both sides in the first core 1 formed by the first coil winding 6 and magnetic flux passing through the center leg 21 from the

outer leg portions

22 and 22 on both sides in the second core 2 formed by the second coil winding 7 collide with each other in opposite directions between the front end surfaces of the

center leg portions

11 and 21.

In fig. 3, the magnetic circuit L1 and the magnetic circuit L2 are in a relationship of canceling magnetic fluxes in opposite directions between the end surfaces of the

center legs

11 and 21, and exhibit an operational effect of forming a magnetic structure (flow of magnetic fluxes) that allows a large current, in which the magnetic circuit L1 is formed by magnetic fluxes formed by the first coil winding 6 and passing through the center leg 11 from the

outer legs

12 and 22 on both sides in the first core 1, and the magnetic circuit L2 is formed by magnetic fluxes formed by the second coil winding 7 and passing through the center leg 21 from the

outer legs

22 and 22 on both sides in the second core 2.

In addition, according to the present embodiment, since the first magnetic coupling inductor portion formed by the first coil winding 6 and the core portion around the first coil winding 6 and the second magnetic coupling inductor portion formed by the second coil winding 7 and the core portion around the second coil winding are configured in a state of being coupled to each other, a magnetic structure (flow of magnetic flux) that allows a large current can be formed as compared with a case where two independent inductors are configured.

Fig. 7a to 7c show another embodiment in which the size in the vertical direction in the drawing is reduced by removing a part of the outer periphery of the third core 31. That is, the upper and lower arcuate portions of the annular shape of the third core 31 that do not face the inner circumferential surfaces of the

outer legs

12 and 22 of the first and

second cores

1 and 2 are removed by the cut surface 3A (see fig. 7a and 7 b).

In this case, it is preferable that: when the surface area of the arc surface 3B of the outer peripheral surface of the third core 31 facing the arc-shaped inner surfaces of the

outer leg portions

12 and 22 through the minute gap is d and the surface area of the distal end surface of the

outer leg portions

12 and 22 of the first or

second core

1 and 2 is e (see fig. 7c), the following condition (5) is satisfied.

d≥e (5)

By establishing the condition (5), the magnetic coupling inductor can be miniaturized.

Since d in the condition (5) can be replaced with a in the condition (2) or e in the condition (5) can be replaced with c in the condition (2), when d < e, the coupling coefficient, which is an important parameter of the coupling inductor, becomes small as in the case where the condition (2) is not satisfied.

That is, when the coupling coefficient is small, a large current cannot be allowed without increasing the size of the coupling inductor. Therefore, when d < e, miniaturization of the product is difficult to achieve.

Next, the manufacturing process of the magnetic coupled inductor 100 according to the above embodiment will be described with reference to fig. 12a to 12 e.

First, a finished state is shown in fig. 12 a. When manufacturing the finished product, first, as shown in fig. 12b, the second coil winding 7 is wound on the bobbin 5. Similarly, although not shown, the first coil winding 6 is wound around the other bobbin 4. Then, the ends of the

coil windings

6 and 7 are soldered and fixed to predetermined terminal pins 9 of the

terminal plates

41 and 51.

Next, as shown in fig. 12c, the positioning and fixing

members

8, 8 are prepared, and the adhesive is filled and applied in each opening 84 of the longitudinal pieces 82. Then, as shown in fig. 12d, the

bobbins

4, 5 around which the

coil windings

6, 7 are respectively wound are assembled uniaxially in such a manner that the third core 3 is sandwiched between the two

bobbins

4, 5 and the uneven shapes of the end portion of the cylindrical portion 42 of one bobbin 4 and the end portion of the cylindrical portion 52 of the other bobbin 5 are aligned (see fig. 9).

At the same time, the

lower extension portions

44a, 54a of the

inner flange portions

44, 54 of the bobbins are engaged with the engagement grooves 83 of the positioning and fixing

members

8, 8 on both sides, respectively, and the first core 1 and the second core 2 are further assembled by being opposed to both end portions of the assembled

bobbins

4, 5, respectively, inserting the

center leg portions

11, 21 into the

tube portions

42, 52, respectively, and positioning the

outer leg portions

12, 22 on the outer side surfaces of the

bobbins

4, 5, respectively (see fig. 8, 9).

At this time, the positioning and fixing

members

8 and 8 are sandwiched between the distal end surfaces of the

outer leg portions

12 and 22 of the two

cores

1 and 2, and fixed by the adhesive applied before. In fig. 12d, the first core 1 is not shown.

Next, as described above, in a state where the first to third cores 1 to 3 are assembled to the

bobbin

4, 5, as shown in fig. 12e, the fixing tape 10 is wound around the outer peripheries of the first core 1 and the second core 2, and the whole is temporarily fixed. Further, an adhesive is applied to the contact portion P between the base portion 81 of the positioning and fixing

members

8, 8 and the outer peripheral surface of the third magnetic core 3 at the bottom surface, thereby fixing both, and then drying them, thereby completing the manufacturing. In this case, it is preferable to perform an inspection of electrical characteristics before applying the adhesive.

Instead of the pair of PQ cores used in the above embodiments, EE cores, EER cores, or a pair of pot cores (outer legs surrounding the middle leg) may be used.

In addition, various shapes may be adopted for the shape of the bobbin.

Claims

1. A magnetically-coupled inductor, characterized in that,

the disclosed device is provided with:

a first magnetic core and a second magnetic core each having a center leg portion, outer leg portions located on at least both sides of the center leg portion, and a connecting portion connecting the center leg portion and the outer leg portions;

a bobbin through which the leg portions of the first and second magnetic cores are inserted, the bobbin being disposed outside the leg portions;

a first coil winding and a second coil winding wound around each of the bobbin, respectively; and

a third magnetic core which is annular and is clamped by the two coil frameworks, and the middle foot part is embedded in the third magnetic core,

the corresponding leg portions of the first and second magnetic cores are butted against each other with a gap provided therebetween,

directions of magnetic fluxes generated by the respective currents flowing through the first coil winding and the second coil winding and passing through the third magnetic core are the same as each other,

the magnetically coupled inductor is configured to: when the thickness of the third core is a and the gap between the outer leg portions of the first and second cores is b, a condition (1) a ≧ b is satisfied.

2. The magnetically-coupled inductor of claim 1,

the magnetically coupled inductor is configured to: when the thickness of the third core is a and the thickness of the connecting portion between the first core and the second core is c, a condition (2) a ≧ c is satisfied.

3. A magnetically coupled inductor according to claim 1 or 2,

the magnetic coupling inductor includes a positioning and fixing member that fixes a thickness direction intermediate portion of the third core at an intermediate position between front end surfaces of the two intermediate leg portions.

4. A magnetically-coupled inductor according to claim 3,

the positioning and fixing member is constituted by: a vertical piece extending upward is erected at the center of a flat plate-shaped base portion, slit-shaped engagement grooves are formed on both sides of the inner side edge of the base portion, and the extension portions of the two inner flange portions of the bobbin can be engaged with the engagement grooves.