JPH0684668A - Line filter - Google Patents

Abstract

PURPOSE:To ensure higher high frequency impedance of a line filter being employed in various electronic appliances for the purpose of noise prevention by decreasing the distributed capacity between core part and core. CONSTITUTION:A ferrite core 2 is inserted into a bobbin 1 made of a material having dielectric constant of 3-5 with at least two core supports 3 being formed on the tubular inner peripheral surface thereof. The ferrite core 2 is positioned in the center of the bobbin 1 by means of the supports 3 with the ratio between the thickness of the bobbin 1 and the distance between a coil part 4 provided on the support 3 and the core 2 being set in the range of 1:2-3.5. This constitution decreases distributed capacity between the coil part 4 and the core 2 and provides a line filter having higher high frequency impedance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line filter used in various electronic devices for noise prevention.

[0002]

2. Description of the Related Art Today, along with the progress of various technologies such as higher frequency of power supply circuits and adoption of resonance type with downsizing of electronic equipment, the problem of noise countermeasure becomes very important, and high frequency of line filters is strongly required. Is desired. Generally, a line filter is mainly used to prevent common mode noise components generated between a pair of lines in an electric wire circuit and the ground, and how to use distributed capacitance existing in the filter as a method to realize high frequency of this line filter. The issue is how to reduce it.

Among conventional line filters, there are the following ones in which the filter structure is improved in order to reduce the distributed capacitance.

A conventional line filter will be described below. FIG. 12 is a perspective view of a conventional line filter.
FIG. 13 is a sectional view of the same. FIG. 14 is a perspective view of a conventional line filter using a rectangular conductor. Figure 15
Is a sectional view of the same.

12 to 15, 9 is a split bobbin, 2 is a UU type ferrite core, 10 is a coil portion around which a round conductor wire is wound, l ₂ is a distance between the coil portion 10 and the core 2, l ₃
Indicates the air layer thickness between the bobbin 9 and the core 2. Reference numeral 11 represents a bobbin, and 12 represents a coil portion around which a rectangular conductor wire is wound.

The structure will be described with reference to FIGS. 12 and 13. After preparing two coil bobbins 9 each having a round conductor wound around the split bobbin 9 and finishing the coil portion 10, the UU type ferrite core 2 is inserted and fixed. And completed.

The structure will be described with reference to FIGS. 14 and 15. After two flat wire conductors are wound spirally around the bobbin 11 in a single layer to finish the coil portion 12, two UU type ferato cores 2 are inserted. It is fixed and completed.

[0008]

However, in the conventional configuration shown in FIGS. 12 and 13, since the split bobbin 9 is used, the coil portion 10 has a winding configuration in which the winding start and winding end are separated from each other, and the coil portion 10 It is possible to reduce the distributed capacitance C ₀ that occurs in the coil winding. Also, in the configuration shown in FIGS. 14 and 15, the flat conductor wire can be wound in one layer in a spiral shape. Therefore, the winding start and the winding end of the coil portion 12 can be reliably separated. a configuration, although the distributed capacitance C ₀ generated in the coil portion 12 is a structure of a valid line filter can be reduced, connected in series through the ferrite core 2, also combined with distributed capacitance C ₀
The distributed capacitances C ₁ and C ₂ generated between the coil section and the core, which result in the parallel connection to the coil section and consequently reduce the high frequency impedance, are generated depending on the distance between the coil section and the core. The distance l ₂ between the core and the core is determined from factors other than the manufacturing accuracy of the bobbin and the core in manufacturing, clearance, and the distribution capacity such as dielectric strength, and is suitable for a line filter that secures a higher high-frequency impedance. Not a thing.

Therefore, in the conventional configuration, even though the distributed capacitance C ₀ generated in the coil portion can be reduced, the distributed capacitances C ₁ and C ₂ generated between the coil portion and the core are determined by factors other than the distributed capacitance. Minimum, optimization has not been achieved, and higher high frequency impedance cannot be secured.

FIG. 16 shows a connection diagram of the line filter and the generation state of the distributed capacitance C ₀ generated in the coil portion and the distributed capacitances C ₁ and C ₂ generated between the coil portion and the core.

Further, in order to reduce the distributed capacitances C ₁ and C ₂ generated between the coil portion and the core, an air layer between the coil portion and the bobbin should be made large to secure a large distance between the coil portion and the core. Can be considered. However, even if a large air layer is taken indiscriminately, the distributed capacitance can be reduced, but the line filter shape becomes larger and larger, which is unrealistic.

The present invention solves the above problems, and when the inductance and DC resistance, which are important characteristics of the line filter, are constant, the distance and position between the coil and core are simple with a simple structure. By optimizing the relationship, it is possible to minimize the distributed capacitance generated between the coil portion and the core and to provide a high-quality line filter that can secure a higher high-frequency impedance.

[0013]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention has a relative dielectric constant of a material in which at least two supports for supporting a core are formed on a cylindrical inner peripheral surface around which a conductive wire is wound. A ferrite core with a diameter of 1 to 20 is inserted into a bobbin of 3 to 5, the ferrite core is positioned at the center of the bobbin by a support, and the bobbin wall thickness and the distance between the coil portion provided by the support and the core. The ratio of 1: 2 to 3.5
The line filter is configured as follows.

[0014]

With this configuration, when the inductance and DC resistance, which are important characteristics of the line filter, are fixed,
The support formed on the inner peripheral surface of the bobbin optimizes the distance and positional relationship between the coil portion and the core, and can minimize the distributed capacitance generated between the coil portion and the core. Moreover, since this support has a very simple structure, a high quality product can be realized.

For the above reasons, a line filter having a higher high frequency impedance can be provided with minimum quality.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Here, an example when the bobbin wall thickness is 1 mm will be described.

FIG. 1 is a side view of a line filter showing a first embodiment of the present invention. FIG. 2 is a sectional view of the line filter. 1 and 2, 1 is a bobbin having a relative dielectric constant of 3 to 5 and a thickness of 1 mm, and 2 is a diameter of 1 to 20.
mm UU type ferrite core, 3 support for core 2, 4 coil part in which round conductor wire is wound one layer, l ₀ is a distance between coil part 4 and core 2 of 2 to 3.5 mm, l ₁ is Bobbin 1 and core 2
The air layer between them is shown.

The structure will be described below. A round lead wire is attached to a bobbin 1 formed by projecting the support body 3 inward so that the core 2 is located at the center by the support body 3 formed on the inner peripheral surface. Two pieces are prepared by winding the layers to finish the coil portion 4. After that, the UU type ferrite core 2 is inserted and fixed to complete.

With the configuration of the line filter of this embodiment, the reason why the distributed capacitances C ₁ and C ₂ generated between the coil portion 4 and the core 2 can be most reduced when the inductance and the DC resistance are constant will be described with reference to the drawings. To do.

FIGS. 3 and 4 show the relationship between the distance between the coil portion 4 and the core 2 and the distributed capacitance in percentage when trying to obtain a line filter having the same number of windings, that is, the inductance and the same DC resistance. It is a thing. In the figure, circles indicate changes in the distributed capacitance as the distance between the coil portion 4 and the core 2 increases. On the other hand, the triangular marks show the change of the distributed capacitance that increases with the increase of the winding diameter. This is because the coil and the core are separated from each other and the winding length becomes long, and it is necessary to increase the winding diameter in order to obtain the same DC resistance.

The solid line shows the sum of the two distributed capacities. The sum of the two is that the distance between the coil portion 4 and the core 2 is 2 to
The minimum value was 3.5 mm, that is, when the length of the support 3 was 1 to 2.5 mm. Therefore, this result shows that when the relative permittivity of the material of the bobbin 1 is 3 to 5 and the diameter of the core 2 is 1 to 20 mm, the distance between the coil portion 4 and the core 2 is 2 to 3.5 mm. It is shown that the distributed capacitance generated between the core 2 and the core 2 can be reduced most.

FIG. 5 shows the percentage of the distributed capacitance between the coil portion 4 and the core 2 due to the difference in the positional relationship between the bobbin 1 and the core 2.

As a result, when the core 2 is located at the center of the bobbin 1, the distributed capacity has the smallest value. Therefore,
In order to obtain this positional relationship by the support 3,
It is shown that the distributed capacitance generated between the coil portion 4 and the core 2 can be reduced most.

As described above, according to the first embodiment, when the inductance and DC resistance, which are important characteristics of the line filter, are constant, the distributed capacitances C ₁ and C ₂ generated between the coil portion 4 and the core 2 are obtained. On the other hand, the support 3 formed on the inner peripheral surface of the bobbin 1 can optimize the distance l ₀ between the coil portion 4 and the core 2 and the positional relationship. Therefore, it is possible to provide the structure of the line filter that can minimize the distributed capacitance generated between the coil portion 4 and the core 2 and at the same time reduce the size to the smallest. Further, since the support 3 has a very simple structure, a high quality one can be realized.

Here, the diameter of the core 2 and the distance between the coil portion 4 and the core 2 were obtained with the bobbin 1 having a wall thickness of 1 mm. I can say.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a perspective view of a line filter showing a second invention example of the present invention, in which the line filter of the first embodiment of the present invention is resin-molded into a bobbin structure capable of resin-molding. FIG. 7 is an exploded perspective view of the line filter. FIG. 8 is a sectional view of the line filter. Figure 9
FIG. 4 is a cross-sectional view of a resin-molded line filter in which a rectangular conductor is spirally wound on the resin-casting bobbin structure described above. FIG. 10 is a cross-sectional view of a resin-casting line filter in which a round conductor is wound in multiple layers on a resin-casting bobbin structure. FIG. 11 is a cross-sectional view of a resin-molded bobbin structure provided with a split collar on the outer peripheral surface of a bobbin structure, and a round conductor wire divided and wound in multiple layers.

6 to 11, reference numeral 1a is a bobbin which has a structure which does not change the characteristics of the line filter shown in the first embodiment of the present invention but allows physical resin casting. Further, a bobbin capable of being separately wound around this, 4a is a coil portion obtained by winding one layer of a rectangular conductor wire, 4b is a coil portion obtained by winding a round conductor wire in multiple layers, and 4c is a coil portion obtained by making a round conductor wire in multiple layers. Is a pin terminal, 6 is a case, 7 is a casting resin, and 8 is an air layer portion between the bobbin and the core.

The structure will be described with reference to FIGS. 6 to 8. After winding the round conductor wire around the resin casting bobbin 1a in a single layer winding to finish the coil portion 4, the UU type ferrite core 2 is inserted and fixed to complete. The line filter thus made is fitted into the case 6. Further, the case 6 is cast with a casting resin 7 and cured. Since the bobbin 1a and the case 6 are fitted to each other, only the coil portion 4 of the line filter is cast.

9 to 11, the same resin casting structure as that described above is used, except that the winding portion is different. FIG. 9 shows one layer 4a of a rectangular conductor in a spiral shape, and FIG.
b, and FIG. 11 shows a winding portion structure of a multi-layer 4c in which a round conductor is divided.

In the second embodiment in which the resin is cast as described above, the case 6 and the casting resin 7 are used in order to reduce the size of the line filter due to the high heat radiation of the resin, and to improve the safety and reliability. , The bobbin 1 and the case 6 are fitted together, and the coil portion 4
The coil portion 4 according to the present invention can be formed by casting only the resin and not allowing the resin to be cast between the bobbin 1 and the core 2.
A structure that is optimal for the distributed capacitance generated between the core and the core 2 can significantly reduce the adverse effect on the high frequency impedance due to the increase in the resin dielectric constant, which was a drawback of the conventional casting resin, and the decrease in the high frequency impedance is small. Cast line filters can be obtained. Further, since the ferrite core 2 is not cast by resin, the ferrite core 2 is not stressed by the resin and has no defects such as cracks.

In the first and second embodiments, the core having the same surface area is not limited to the circular cross section and is not limited to the UU type ferrite core.

[0032]

As described above, in the line filter of the present invention, the bobbin having the relative permittivity of 3 to 5 and having the diameter of 1 is formed on the material having at least two supports for supporting the core formed on the inner peripheral surface of the cylinder. ~ 20 ferrite cores are inserted, this ferrite core is positioned at the center of the bobbin by the support, and the bobbin wall thickness and the distance between the coil portion provided by the support and the core are set to 1: 2 to 3.5. By doing so, (1) when the inductance and the DC resistance are constant, the distributed capacitance generated between the coil portion and the core can be minimized, and the shape can be minimized and a higher high-frequency impedance can be secured.

Further, even if only the coil portion is cast with the resin aiming at the effect of the resin casting, (2) the high frequency impedance, which is an adverse effect of the resin casting, is less likely to decrease. (3) There is no defect such as ferrite core crack due to resin stress.

Furthermore, since the structure of the support for ensuring the characteristics (1) is very simple, (4) the characteristics can be ensured with high quality. It is possible to provide a line filter with a simple structure and high quality, which has great effects such as the above, and can secure a high-frequency impedance, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a side view of a line filter showing a first embodiment of the present invention.

FIG. 2 is a sectional view of the line filter.

FIG. 3 is a change diagram of a distributed capacitance generated between a coil portion and a core when an attempt is made to construct a line filter having the same inductance and the same DC resistance.

FIG. 4 is a diagram showing a change in distributed capacitance generated between a coil portion and a core when an attempt is made to construct a line filter having the same inductance and the same DC resistance.

FIG. 5 is a diagram showing the influence of the positional relationship between the coil portion and the core on the distributed capacitance generated between the coil portion and the core.

FIG. 6 is a perspective view of a resin cast line filter showing a second embodiment of the present invention.

FIG. 7 is an exploded perspective view of the line filter.

FIG. 8 is a sectional view of the line filter.

FIG. 9 is a sectional view of the same line filter with different winding methods.

FIG. 10 is a cross-sectional view of the same line filter with a different winding method.

FIG. 11 is a sectional view of the same line filter with different winding methods.

FIG. 12 is a perspective view of a conventional line filter.

FIG. 13 is a sectional view of the line filter.

FIG. 14 is a perspective view of a conventional line filter.

FIG. 15 is a sectional view of the line filter.

FIG. 16 is a connection diagram of a line filter.

[Explanation of symbols]

 1 bobbin 1a bobbin (resin casting structure) 1b bobbin (divided resin casting structure) 2 UU type ferrite core 3 core support 4 coil part 4a coil part (1 layer winding) 4b coil part (multilayer winding) 4c coil part ( Multi-layer split winding) 5 pin terminals 6 Case 7 Cast resin 8 Air layer 9 Split bobbin 10 Coil 11 Bobbin 12 Coil

Claims (1)

[Claims] 1. A dielectric constant of 3 in which at least two or more supports for supporting a core are formed on a cylindrical inner peripheral surface around which a conductive wire is wound.
Insert a ferrite core with a diameter of 1 to 20 into the bobbin of the material of ~ 5, this ferrite core is positioned in the center of the bobbin by the support, and further, the thickness of the bobbin and the coil portion and core provided by the support The distance ratio of 1: 2
A line filter set to 3.5.