JPH10290137A - Noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the noise attenuation characteristic of the noise filter and to simplify the mount. SOLUTION: The noise filter is provided with a filter assembly 12 consisting of an assembly 20 being a combination of a coil core 16 and three through- capacitors 18a, 18b, 18c whose axial direction is set the same as an axial direction of the coil core 16 and of common mode coils of three metallic rods 22a, 22b, 22c that are penetrated through the assembly 20. Then the filter assembly 12 is contained in a cylindrical housing 14 whose one side is formed to be an opening 24. In this case, both ends of the three metallic rods 22a, 22b, 22c are used also for terminals and a bottom 14A of the housing 14 is used for a mount part of the housing 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise filter used for, for example, power electronics equipment.

[0002]

2. Description of the Related Art In recent years, attention has been paid to high power use efficiency, and a DC power generation circuit using a switching regulator or an inverter circuit for driving a motor has been frequently used.

[0003] Since these circuits include a switching circuit, they can be noise sources that generate conduction noise and radiation noise. For example, if the noise source is A
When directly connected via the C cord, noise generated in the switching circuit (noise generating source) returns to the AC power supply side via the AC cord as conduction noise.
Radiation noise from the C code also occurs. Conducted noise is
It affects other electric equipment (electronic equipment) connected to the AC power supply, and the radiated noise is AV (Au
dio Visuial) Affects equipment.

[0004] Therefore, the conducted noise and radiated noise generated from the noise source are referred to as so-called EMI in various standards such as the VCCI standard, the CISPR standard, and the FCC standard.
(Electromagnetic Interference) is subject to regulation, and it is required to suppress it to a level below a predetermined level.

In order to suppress this noise, various noise filters have been developed and put into practical use. As is well known, for example, an L (coil, inductor) C (capacitor) circuit, which is a passive component, is mounted on a metal case or a printed wiring board, and these LC circuits are mounted as necessary. The terminal block or the printed wiring board is shielded by a rectangular parallelepiped shield case,
It is provided on the market as a single electrical component.

[0006]

However, in such a noise filter, it is urgently required to further improve the noise attenuation characteristics and to simplify the mounting work, and various manufacturers have been developing these noise filters to realize them. ing.

SUMMARY OF THE INVENTION The present invention has been made in consideration of such problems, and has as its object to provide a noise filter capable of improving noise attenuation characteristics and simplifying a mounting operation.

[0008]

A noise filter according to the present invention comprises at least one coil core and m (m = m) coils whose axial directions are the same as the axial direction of the core.
2, 3,...) And n pairs (n = 1, 2,...), And further, m conductors penetrating through the n pairs of series. And a filter assembly formed of a common mode coil having the following.

Normally, when a current flows through a conductor penetrating the coil core, a magnetic flux is generated in the coil core. As the magnetic flux increases, the inductance decreases, and eventually magnetic saturation occurs. In this case, there is a disadvantage that only a core having a low magnetic permeability such as a dust core or a core having a reduced magnetic permeability by cutting a part of the core having a high magnetic permeability can be used as the core for the coil. Has limitations.

However, in the present invention, since m conductors are passed through at least one coil core, when signals having different phases derived from the number indicated by m are supplied, the coil core is supplied to the coil core. A magnetic flux is generated. In this case, since the magnetic flux is generated so as to cancel each other, the above-described magnetic saturation does not occur. Therefore, it is possible to use a ferrite-based, amorphous-based, or other high-permeability material as the coil core, and it is possible to further improve noise attenuation characteristics.

Moreover, in the present invention, since the combination of at least one coil core and m feedthrough capacitors is penetrated by m conductors, the structure becomes compact and the mounting area is reduced. The size can be reduced.
Further, when the noise filter is mounted on a power supply housing, a power distribution panel, or the like, the number of mounting holes for mounting the noise filter can be reduced, which greatly facilitates the mounting operation and is advantageous in reducing costs.

In the above structure, the filter assembly can be housed, and a cylindrical housing having one opening is provided, and both ends of the plurality of conductors are also used as terminal portions, The bottom of the housing may also be used as a mounting portion for the housing.

In this case, in the filter assembly, the plurality of feedthrough capacitors of each combination are positioned on the bottom side of the housing, and the coil core is positioned on the opening side of the housing. It is preferable to store in.

[0014] Further, a cap for accommodating the filter assembly in the housing may be attached near the opening of the housing. Also, a Y capacitor may be electrically connected between a plurality of terminal portions protruding through the opening of the housing and a side wall of the housing.

[0015] When there are two or more of the combination members constituting the filter assembly, it is preferable to insert a partition plate between the combination members.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows several embodiments in which the noise filter according to the present invention is applied to, for example, a noise filter used in power electronics equipment.
This will be described with reference to FIGS.

First, as shown in FIG. 1B, a noise filter 10A according to the first embodiment is, for example, a three-phase one-stage type noise filter. Have been.

The filter assembly 12 includes one coil core 16 and three feedthrough capacitors 18a, 18b whose respective axial directions are the same as the axial direction of the coil core 16.
And 18c (collectively, feed-through capacitors 18
Described above)).
And three metal rods 22a, 2
2b and 22c (collectively referred to as metal rods 22).

The housing 14 is made of, for example, metal, has a cylindrical shape with one opening 24, the bottom portion 14A is formed thick, and the cylindrical portion 14B is formed thin. . Although not shown, the housing 14 has three metal rods 22a, 22b on its bottom 14A.
And 22c are inserted through holes. The diameter of each through hole is set to be larger than the outer diameter of the corresponding metal rod 22a, 22b, and 22c.
A cylindrical insulating bush is provided for electrical insulation from 2a, 22b and 22c. Note that, for example, the insulators of the feedthrough capacitors 18a, 18b, and 18c may be extended to the through hole side and used instead of the insulating bush.

Three metal rods 22a, 22b and 22c
Penetrates the corresponding feedthrough capacitors 18a, 18b, and 18c, respectively, and is arranged on a circumference having a radius r from the center point O of the housing 14 as shown in FIG. They are arranged at an interval of 120 °. As shown in FIG. 1A, the radius r is long enough to ensure a certain distance between the feedthrough capacitors 18a, 18b and 18c, and the three metal rods 22a, 22b and 22c The length is set so as not to contact the inner wall surface of the coil core 16.

In the bottom portion 14A of the housing 14, three mounting screw holes 26a, 26
b and 26c are formed. Each screw hole 26a, 26
As shown in FIG. 1C, the arrangement relationship between b and 26c is on the circumference of a radius R (> radius r) from the center point O of the housing 14 and at an interval such that the center angle between them is 120 °. The three metal rods 22a, 22b and 22c are arranged at positions complementary to each other.

In the housing 14, a ring-shaped thin cap 28 made of, for example, synthetic resin is fitted near the opening. The inner diameter of the cap 28 is set to be slightly larger than the radius r that forms a circumference connecting the centers of the three metal rods 22a, 22b, and 22c.

As the material of the housing 14 and the cap 28, for example, copper, brass, aluminum, iron or the like can be used.
Solder plating, alumite processing (aluminum) or the like can be used.

Then, the combination body 20 is connected to the housing 1.
4, the three feed-through capacitors 18
a, 18b and 18c are positioned on the bottom 14A side of the housing 14, and the coil core 16 is
The combination 20 is housed in the housing 14 while being positioned on the side of the opening 24. At this time, one end of each of the three metal rods 22a, 22b and 22c is
4 protrudes outward from the opening 24, and the other end is
4 is projected outward from the bottom 14A, and one end and the other end projecting outward form a terminal portion of the noise filter 10A according to the first embodiment. . Each terminal portion is threaded, and a nut member 30 for connecting wiring is screwed into the terminal portion.

Further, the noise filter 10A according to the first embodiment has Y capacitors 32a and 32b between three terminals protruding outward from the opening 24 of the housing 14 and the vicinity of the opening of the housing 14, respectively. And 32c
(Collectively referred to as Y capacitors 32) are electrically connected by, for example, soldering.

Although not shown here, the filter assembly 12 may be fixed with a resin such as epoxy, silicone, or urethane.

The noise filter 1 according to the first embodiment
0A is basically configured as described above, and its operation and effect will be described next.

Normally, as shown in FIGS. 2A and 2B, when a current flows through a conductor penetrating the coil core 16 (see the arrow for the current direction), a magnetic flux is generated in the coil core 16. As the magnetic flux increases, the inductance decreases, and eventually magnetic saturation occurs. In this case, the coil core 1
As No. 6, there is an inconvenience that only a material having a low magnetic permeability such as a dust core or a material having a reduced magnetic permeability by cutting a part of a core having a high magnetic permeability can be used, and there is a limit in improving noise attenuation characteristics. .

However, in the noise filter 10A according to the first embodiment, as shown in FIG. 1, three metal rods 22a, 22b and 22c are made to pass through the coil core 16, so that When signals whose phases are different from each other by about 120 ° are supplied to the metal rods 22a, 22b and 22c, a magnetic flux is generated in the coil core 16, but in this case, as shown in FIG. Therefore, the above-described magnetic saturation does not occur. Therefore, it is possible to use a ferrite-based, amorphous-based, or other high-permeability material for the coil core 16, and further improve the noise attenuation characteristics.

Here, an experimental example will be described. In this experimental example, an example (see FIGS. 4A and 4B) having the same configuration as the noise filter 10A according to the first embodiment and three conventional single-phase one-line noise filters (comparative example) : See FIGS. 5A and 5B), and measured the respective noise attenuation characteristics. In addition, the feedthrough capacitor 1
8 and the capacity of the Y capacitor 32 are each 0.01 μm.
F and 2200 pF. FIG. 6 shows the measurement results of the example, and FIG. 7 shows the measurement results of the comparative example.

From these measurement results, in the embodiment, three single-phase one-wire noise filters are blocked to form a three-phase three-wire system. 5 to 10 dB characteristic improvement, 20 dB in 30 MHz to 60 MHz band
The more the characteristics were improved.

In the noise filter 10A according to the first embodiment, the combination 20 of the coil core 16 and the three feedthrough capacitors 18a, 18b and 18c is connected to three metal rods 22a, 22b and 22c. , The structure is compact, and the mounting area can be reduced.

Here, the effect of mounting the noise filter 10A according to the first embodiment will be described in comparison with the case where three conventional single-phase one-wire noise filters are mounted. In the case of (3), as shown in FIG. 9, since it is necessary to mount three noise filters 100 in a row, it is necessary to provide a large space for mounting the noise filter 100 on the mounting plate 50. It is necessary to make many holes 52 (when three mounting holes 52 are formed for one noise filter 100, it is necessary to provide nine mounting holes 52). Also,
The installation takes time and the installation work is complicated. Moreover, the use of a large number leads to an increase in cost.

On the other hand, in the noise filter 10A according to the first embodiment, as shown in FIG. 8, the noise filter 10A having a single structure only needs to be mounted on the mounting plate 50. The mounting area of the noise filter 10A can be reduced, and only three mounting holes 52 need to be formed in the mounting plate 50. As a result, the mounting time can be effectively reduced, and the mounting operation is also facilitated. In addition, since it can be used alone, it is advantageous for reducing costs.

Next, a noise filter 10B according to a second embodiment will be described with reference to FIG.

As shown in FIG. 10B, the noise filter 10B according to the second embodiment has substantially the same configuration as the noise filter 10A according to the first embodiment. Combination 20A, 2
0B and 20C, that is, a three-phase three-stage noise filter.

Further, in the noise filter 10B according to the second embodiment, the partition thin plates 40A and 40B made of a synthetic resin are inserted between the combined bodies 20A and 20B and between 20B and 20C, respectively. A through hole (not shown) through which three metal rods 22a, 22b and 22c are inserted is formed in 40B.

In the noise filter 10B according to the second embodiment, since the number of stages is increased as compared with the noise filter 10A according to the first embodiment, noise attenuation characteristics can be improved. In particular, it is suitable for use in equipment that requires high-frequency noise attenuation.

In the noise filters 10A and 10B according to the first and second embodiments, an example is shown in which the present invention is applied to a three-phase three-wire system. Can be applied. For example, when applying to a single-phase two-wire, two feed-through capacitors and two metal rods are prepared, and the phase difference between signals to be supplied to each metal rod is 180 °.
And it is sufficient. When applying to a three-phase four-wire system, four feedthrough capacitors and four metal bars are prepared. When one of the signals to be supplied to each metal bar has a phase difference of 0 °, another What is necessary is just to make it three angles 120 degrees.

Note that the noise filter according to the present invention
The present invention is not limited to the above-described embodiment, but can adopt various configurations without departing from the gist of the present invention.

[0041]

As described above, according to the noise filter of the present invention, at least one coil core and m (m = 2) whose respective axial directions are the same as the axial direction of the core. , 3,...) Are arranged in n sets (n = 1, 2, 2, 3).
..), And a common-mode filter assembly having m conductors penetrating the n sets of arrangements in series.

As a result, the effect of improving the noise attenuation characteristics and simplifying the mounting operation can be achieved.

[Brief description of the drawings]

FIG. 1A is a plan view of a noise filter according to a first embodiment, and FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A (a coil core is cut away). 1
C is a bottom view of the noise filter according to the first embodiment.

FIG. 2A is a diagram for explaining the action of magnetic flux generated when a current flows in one direction (left direction) to a coil core, and FIG. It is a figure for explaining an operation of a magnetic flux generated when a current flows in a direction (rightward).

FIG. 3 is an explanatory diagram schematically showing an action of a magnetic flux generated in a coil core of the noise filter according to the first embodiment.

FIG. 4A is a perspective view showing a configuration of an embodiment used for examining noise attenuation characteristics, and FIG. 4B is an equivalent circuit diagram thereof.

FIG. 5A is a perspective view showing a configuration of a comparative example used for examining noise attenuation characteristics, and FIG. 5B is an equivalent circuit diagram thereof.

FIG. 6 is a diagram showing noise attenuation characteristics of the noise filter according to the embodiment shown in FIGS. 4A and 4B.

FIG. 7 is a diagram showing a noise attenuation characteristic of the noise filter according to the comparative example shown in FIGS. 5A and 5B.

FIG. 8 is a diagram for explaining an advantage when the noise filter according to the first embodiment is mounted on a mounting plate.

FIG. 9 is a diagram for explaining a drawback when a noise filter according to a conventional example is mounted on a mounting plate.

FIG. 10A is a plan view of a noise filter according to a second embodiment, and FIG. 10B is a plan view of B in FIG. 10A.
FIG. 10C is a cross-sectional view taken along line -B (the coil core is cut away), and FIG. 10C is a bottom view of the noise filter according to the second embodiment.

[Explanation of symbols]

10A, 10B: Noise filter 12: Filter assembly 14: Housing 16: Core for coil 18a, 18b, 18c: Through capacitor 20, 20A, 20B, 20C: Combined body 22a, 22b, 22c: Metal rod 24: Opening 26a, 26b, 26c: screw hole 28: cap 30: nut member

Claims (6)

[Claims] At least one coil core, and m (m) coils each having the same axial direction as the axial direction of the core.
= 2, 3,...) Are arranged in n sets (n = 1, 2,...)
A noise filter, comprising: a filter assembly formed of a common mode coil having m conductors penetrating through the arranged n sets of combinations in series. 2. The noise filter according to claim 1, further comprising a cylindrical housing capable of housing said filter assembly and having one open end, wherein both ends of said plurality of conductors are terminals. And a bottom portion of the housing also serving as a mounting portion of the housing. 3. The noise filter according to claim 2, wherein, in the filter assembly, the plurality of feedthrough capacitors of each combination are positioned on a bottom side of the housing, and the coil core is an opening in the housing. A noise filter positioned on the side and housed in the housing. 4. The noise filter according to claim 3, wherein a cap for accommodating the filter assembly in the housing is attached near an opening of the housing. 5. The noise filter according to claim 3, wherein a Y capacitor is electrically connected between a plurality of terminal portions protruding through an opening of the housing and a side wall of the housing. Noise filter. 6. The noise filter according to claim 1, wherein there are two or more of said combination members constituting said filter assembly, and a partition plate is inserted between each combination member. A noise filter characterized by being performed.