JPH10135044A - Inductance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize with large capacity and to prevent occurrence beat in driving frequency in audible frequency band by allowing an internal core to extend, at a center part where an external core is almost divided into two, along the entire width of the external core, with the internal core wound with a coil. SOLUTION: An external core 21 is formed into a square frame-shape comprising an opening 21a, with recessed cut parts 24a and 24b formed at each center part of facing two sides, while being held with insulating holding members 25a and 25b. The internal core 22 is so held that its both end parts are coupled magnetically to the cur parts 24a and 24b of the external core 21 through air gaps 26a and 26b, while provided over the entire width of the external core 21. A coil 23 is wound around a bobbin, whose both end parts are combined to the holding members 25a and 25b so as to be positioned at the outer periphery, at a center part of the internal 22. The external core 21 and the internal core 22 are, combined magnetically together through the air gaps 26a and 26b, and no beat due to magneto-striction is generated since there is no contacting of parts with each other exists.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an inductance element such as a coil and a transformer, and more particularly to an improvement in a core structure of a winding type inductance element.

[0002]

2. Description of the Related Art As a core structure of a winding type inductance element, for example, a separation type element such as an EE type or an EI type is known. In recent years, this type of inductance element has been required to have a small size and a large capacity as electronic devices have become smaller and lighter.

In order to meet such demands, for example,
As in the case of a planar transformer using a multilayer printed wiring board, a drive frequency is increased, or a gap is formed at a joint between an EE-type or EI-type core and the core to increase the magnetic resistance, thereby increasing the magnetic resistance. There is known a device capable of supplying a drive current.

[0004]

However, in the conventionally proposed inductance element, when the size is reduced, the magnetic path length becomes shorter and the magnetic flux density is saturated with a small magnetomotive force. There is a problem that a large capacity cannot be obtained.

[0005] Further, in an inductance element having a conventionally proposed EE type core structure, for example,
Generally, as shown in FIG. 5, an air gap 2 is formed at the center leg of the E-shaped cores 1a and 1b.
Is wound around the coil 3 and a drive current is passed through the coil 3 to form magnetic paths 4a and 4b as indicated by arrows in the cores 1a and 1b. In such a configuration, focusing on one magnetic path 4a,
a and four cores 1a, 1b
Since the magnetic resistance is increased at a total of six portions including the coupling portion and the air gap 2, a large output capacity can be expected in a magnetic circuit.

However, when the inductance element having the structure shown in FIG. 5 is driven as an electronic component, the temperature of the element rises due to the heat generated by the element itself, so that an output capacity as expected cannot be obtained. There is a problem. It is considered that the cause of the temperature rise is heat generation due to iron loss, which is a characteristic of the element itself, and increase in magnetomotive force, that is, heat generation due to copper loss caused by flowing a large current through the coil. In this case, the limit of the temperature rise of the inductance element is said to be room temperature + 45 ° C.

In the conventionally proposed inductance element having an EI type core structure, generally,
As shown in FIG. 6, the E-shaped core 11 and the I-shaped core 13 are joined so that the air gap 12 is formed at the end of the center leg of the E-shaped core 11, and the center leg is attached to the center. Coil 14
To form magnetic paths 15a and 15b as indicated by arrows. In this configuration, focusing on one magnetic path 15a, the magnetic resistance increases at the four portions 16a to 16d where the magnetic path 15a is curved, and the two curved portions 16c and 16d have the cores 11 and 1 attached thereto.
3 joints 17 and air gaps 12 are included, respectively. Therefore, the magnetoresistance as a whole is equal to E in FIG.
Since the size becomes large like the E type, a large output capacity can be expected.

[0008] However, even in the case of the EI type, as in the case of the above-mentioned EE type, the output capacity as expected due to temperature rise cannot be obtained at present. It is said that the cause of the temperature rise in this case is copper loss caused by the core shape. That is, in the case of the EI type, since the E-type core 11 and the I-type core 13 are configured by a combination of open magnetic paths, the magnetic distribution of the I-type core 13 is particularly complicated, and the curvature of the magnetic path 15a is particularly large. In the portions 16c and 16d, the magnetic flux flows in a short-cut manner so as to bite into the coil 14 due to the magnetic resistance of the coupling portion 17 and the air gap 12. For this reason, a so-called orthogonal magnetic field is applied to the current flowing through the coil 14, whereby the current flowing through the conductor is biased to one side of the conductor due to the proximity effect, and the effective cross-sectional area of the conductor is reduced. As a result, the current density is reduced. As a result, the copper loss increases, and the temperature of the coil 14 increases.

Further, in the case of the EI type, since the leakage magnetic flux from the I-type core 13 having a complicated magnetic flux distribution tends to cause a problem such as generation of induction noise in other electronic parts, the output capacity is also reduced from this point. There is a problem of being restricted.

On the other hand, as described above, when an air gap is formed in the inductance element, the temperature distribution in the air gap becomes non-uniform due to the demagnetizing field. That is, since the demagnetizing field is inversely proportional to the distance, it is difficult to be magnetized at the inner peripheral portion of the closed magnetic circuit and easily magnetized at the outer peripheral portion from the principle that the number of magnetic fluxes does not change. Therefore, the magnetization at the outer periphery becomes larger as compared with the magnetization at the inner periphery, and the iron loss generally increases in proportion to the magnitude of the magnetization, so that heat is locally generated near the air gap. Part will occur. Moreover, for example, ferrite, which constitutes the core material, has a large specific resistance and poor heat conduction, unlike a metal material, so that a locally high temperature state is maintained. In addition, when the inductance element is miniaturized, the wire diameter of the coil becomes thinner and the resistance value becomes higher, which increases copper loss and raises the temperature of the coil.

For this reason, in a configuration in which the coil is wound so as to cover the air gap portion as in the above-described conventional EE type or EI type, the coil is affected by the temperature rise due to the demagnetizing field in the air gap. As a result, the temperature of the coil is further increased, so that there is a problem that an expected output capacity cannot be obtained.

Further, in the above-mentioned conventional EE-type or EI-type inductance element, since both cores are brought into contact with each other at a portion other than the air gap, when the driving frequency is in the audible frequency band. Also, there is a problem that a growling due to magnetostriction occurs.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of such a conventional problem, and has an inductance which is small in size and has a large capacity and which is appropriately configured so as not to produce groans even at a driving frequency in an audible frequency band. It is intended to provide an element.

[0014]

In order to achieve the above object, an inductance element according to the present invention comprises an outer core and a center which magnetically couples the outer core to the outer core through a gap and substantially divides the outer core into two. In this case, the part includes a middle core extending over the entire width of the outer core, and a coil wound around the middle core.

When the average magnetic path length of the magnetic path passing through the outer core and the middle core is l and the sectional area of the middle core is S, l / l
It is preferable that S is 1.0 (m ^-1 ) or more, for example, in order to reduce the size of an inductance element having an output capacity of 50 W or less.

The outer core is formed in a frame shape having a rectangular opening, and a concave cutout is formed at the center of each of the two opposing sides thereof. It is preferable in terms of weight reduction that both ends of the middle core are magnetically coupled to the notched portions via gaps.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the present invention with a part cut away. This inductance element comprises an outer core 21, a middle core 22, and a coil 2
3 The outer core 21 is formed in a rectangular frame shape having a rectangular opening 21a, and concave notches 24a and 24b are formed at the center of each of two opposing sides.
The outer core 21 is provided with the sides having the notches 24a and 24b held by insulating holding members 25a and 25b, respectively.

The middle core 22 is held by holding members 25a and 25b such that both ends thereof are magnetically coupled to the notches 24a and 24b of the outer core 21 via air gaps, respectively. And is provided to extend over the entire width of the outer core 21. In this embodiment, the outer core 21 is magnetically attached to each end of the middle core 22 such that an air gap 26a with an interval t1 is formed on both sides of the middle core 22 and an air gap 26b with an interval t2 is formed on the upper portion. Join. Preferably, the air gaps 26a, 26
b is in the range of t2 / t1 = 0.1 to 2. t2 / t
This is because if 1 = 0, the effect of the present invention is lost.

The coil 23 is provided by being wound around a bobbin (not shown) made of, for example, phenol resin and having both ends joined to the holding members 25a and 25b so as to be located on the outer periphery of the central portion of the middle core 22. In FIG. 1, a part of the coil 23 is not shown in order to clearly show the cutout portion 24a of the outer core 21. The coil 23 is composed of, for example, a primary winding and a secondary winding,
Are connected to the connection terminals 27a to 27d provided in the.

In this way, by passing a current through the coil 23, magnetic paths 28a and 28b passing through the outer core 21 and the middle core 22, as indicated by arrows in FIG. 2, are formed. Here, when the average magnetic path length in each of the magnetic paths 28a and 28b is 1 and the sectional area of the middle core 22 is S,
Preferably, it is configured such that l / S is 1.0 (m ^-1 ) or more.

When attention is paid to one magnetic path 28a in the inductance element having the configuration shown in FIG. 1, four parts 29 where the magnetic path 28a is curved are the parts where the magnetic resistance is high.
a to 29d, of which two curved portions 2
Since the air gaps 26a are respectively included in 9a and 29d, there are four places as a whole. Therefore, when the magnetic path length is the same as that in FIG. 5, the magnetoresistance can be increased, so that the magnetomotive force can be increased, and thus a large capacity can be obtained. Further, when a capacitor having the same capacity as that of FIG. 5 is obtained, the magnetic path length can be shortened, so that the size can be further reduced.

Further, since the air gaps 26a and 26b are located outside the portion around which the coil 23 is wound, the high temperature portion due to the demagnetizing field in the air gaps 26a and 26b does not increase the temperature of the coil 23. Therefore, if the size is the same as that of FIG. 5, a large-capacity device can be obtained. Further, the coil 23 has an air gap 26a,
Since the temperature of the portion 26b is not affected, the temperature of the coil 23 can be increased accordingly, that is, the copper loss can be increased. Therefore, the wire diameter of the coil 23 can be reduced and the coil 23 can be reduced in size. . The outer core 21 and the middle core 2
2 is magnetically coupled via the air gaps 26a and 26b, and there is no portion that abuts each other. Therefore, even when the drive frequency is in the audible frequency band, no growling due to magnetostriction occurs.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given of a comparative example of a temperature rise test between the inductance element having the structure shown in FIG. 1 and the conventional EE-type inductance element shown in FIG. In FIG. 1, t2 / t1 = 1. (Comparative Example 1) t1, t2 in FIG. 1 and air gap 2 (interval t3) in FIG. 5 were 0.1, 0.2, 0.3, 0.5.
And the driving frequency of 100 (mm)
The difference (ΔT) between the coil temperature and room temperature was measured under the measurement conditions of kHz and magnetic flux density change ΔBm = 200 mT. The result is shown in FIG. In the configuration shown in FIG. 1, 1 / S =
2.0 (m ^-1 ). As is clear from FIG.
According to the inductance element having the configuration shown in FIG. 5, the temperature rise can be significantly suppressed as compared with the conventional inductance element shown in FIG.

(Comparative Example 2) t1, t2, and t3 were set to 0.2 mm
ΔT was measured by applying copper loss and iron loss. The result is shown in FIG. The other conditions are the same as in Comparative Example 1. As is apparent from FIG. 4, when the total loss × 10 is evaluated as the output capacitance, according to the inductance element having the configuration shown in FIG. Can be larger.

(Comparative Example 3) In the conventional configuration shown in FIG.
The cross-sectional area of the central leg of the E-shaped cores 1a, 1b is S ',
When the average magnetic path length of each of the magnetic paths 4a and 4b is l ′,
l '/ S' is 0.5, 1.0 and 2.0 (m^-1),Respectively
In the case of the above, the interval (t3) of the air gap 2 is 0.1 mm
1 and in the configuration shown in FIG.
And 2.0 (m ^-1), T1, t2 in each case is 0.2 m
Table 1 shows the result of comparison with ΔT when m is set. What
The measurement conditions were the same as in Comparative Example 1.

[0026]

[Table 1] As is clear from Table 1, according to the inductance element having the configuration shown in FIG. 1, the temperature rise can be significantly suppressed as compared with the conventional inductance element shown in FIG.

Note that the present invention is not limited to the above-described embodiment, and various modifications or changes can be made. For example, in the above-described embodiment, the middle core 22 is held by the holding members 25a, 25b. However, the middle core 22 is bonded and held so that a magnetic gap is formed in the cutouts 24a, 24b of the outer core 21. You can also. In FIG. 1, the holding members 25a, 25b and the outer core 21
Although the middle core 22 is disposed between the outer core 21 and the outer core 21, the notch portions 24 a and 24 b may be formed on the upper surface side of the outer core 21 to arrange the middle core 22. Further, the outer core 21 is not limited to a rectangular shape, but may have an arbitrary shape such as a circular shape or an elliptical shape. Further, a long groove is formed over the entire width at the center of the outer core so as to divide the flat outer core into two, and the middle core is magnetically coupled to the long groove via a magnetic gap. Can also.

[0028]

As described above, according to the present invention, the middle core around which the coil is wound extends over the entire width of the outer core at the center portion where the outer core is substantially divided into two. To be provided by magnetically coupling through a gap,
It is possible to obtain an inductance element which is small, has a large capacity, and does not generate groan even at a drive frequency in an audible frequency band.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention with a part cut away.

FIG. 2 is a diagram for explaining the operation.

FIG. 3 is a diagram showing a comparative example of a temperature rise between an inductance element according to the present invention and a conventional inductance element.

FIG. 4 is a diagram showing a comparative example of a temperature rise between the inductance element according to the present invention and a conventional inductance element.

FIG. 5 is a view for explaining a conventional EE-type inductance element.

FIG. 6 is a diagram for explaining a conventional EI-type inductance element.

[Explanation of symbols]

 21 outer core 21a opening 22 middle core 23 coil 24a, 24b notch 25a, 25b holding member 26a, 26b air gap 27a-27d connection terminal 28a, 28b magnetic path

Claims (3)

[Claims] 1. An outer core, a middle core magnetically coupled to the outer core through a gap, and extending over the entire width of the outer core at a central portion substantially dividing the outer core into two parts. And a coil wound around a middle core. 2. When the average magnetic path length of the magnetic path passing through the outer core and the middle core is l and the sectional area of the middle core is S,
The inductance element according to claim 1, wherein / S is configured to be 1.0 (m ^-1 ) or more. 3. The outer core is formed in a frame shape having a rectangular opening, and a concave notch is formed at the center of each of the two opposing sides. 3. The inductance element according to claim 1, wherein both ends of the middle core are magnetically coupled to the notch portion through gaps. 4.