JPS6039963Y2 - Noise prevention filter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a noise prevention filter, and more particularly to a filter that is inserted into the power supply section of electrical equipment, which is a source of noise radio wave leakage, and prevents noise radio wave leakage in a wide frequency band. It is something.

Generally, in microwave ovens and the like that utilize high frequency energy, countermeasures against radio wave leakage are an inevitable problem because they adversely affect other electrical devices such as televisions and radios.

Figures 1a and 1b show an example of a filter proposed by the inventors of the present application, which specifically blocks radio waves leaking to the outside from the heater current supply section of a magnetron used in a microwave oven over a wide band. Shows the filter for

In the figure, 1 is the magnetron main body, 2 is a shield case surrounding the input structure 3 of the magnetron main body 1, and 4
is a rod-shaped filter body that penetrates and is fixed to this shield case 2, and this filter body 4 has an outermost cylindrical conductor 5 that is grounded to the shield case 2, and a withstand voltage inside this conductor 5. A plurality of ferrite beads 7 housed through an insulator 6 and the ferrite beads 7
It is composed of two conductive wires 8a and 8b passed through the inside of the shield case 2, and both terminals of the two conductive wires inside the shield case 2 are connected to the input terminal of the input structure 3.

Further, both conductive wires 8a and 8b of each ferrite bead 7
A plate-shaped gap 9 is provided along the axial direction in the area connecting the conductive wires 8a and 8b, and a capacitor 10 is connected between the conductive wires 8a and 8b on the power supply side.

The noise prevention filter configured in this way has a large magnetic loss effect against the high frequency magnetic field of the ferrite beads, and
The dielectric loss effect of the ferrite beads on the high-frequency electric field generated between the conductor and the conductor, and the low-pass filter effect due to the fact that the filter body is a distributed constant line, combine to block radio wave leakage at the input section over a wide band. It is something that can be done.

In addition, because there is a gap in the ferrite bead, it is possible to eliminate saturation of the ferrite due to the magnetic field caused by the large current flowing through the conductor, and because the capacitor connected between the conductors causes a short circuit at high frequency. In addition, the so-called odd mode electromagnetic field concentrated in the gap can be removed, and an effective radio wave leakage prevention effect can be expected.

However, this type of noise prevention filter has various excellent features such as simple structure, broadband blocking effect, low cost, and small size. Since it is necessary to provide a hole, due to its structure, it is necessary to perform press shaping only in the axial direction of the ferrite bead, that is, in the direction of the arrow, as shown in FIG.

For this reason, when the filter body requires a certain length, it is necessary to construct a set of filters by connecting a large number of short ferrite beads in series.

As a result, there is a disadvantage that the manufacturing workability of the ferrite beads and the assembly workability of the filter body are reduced.

Therefore, it is an object of the present invention to provide a noise prevention filter in which ferrite beads of a desired length can be manufactured very easily and the assembling workability of the filter body is improved.

In order to achieve this objective, the noise prevention filter of the present invention is made by dividing a ferrite bead into two parts in the direction of conductor penetration, at least by the conductor and the wire passing through the gap. The idea will be explained in detail.

FIGS. 3a and 3b are a sectional view and a perspective view of essential parts showing an embodiment of the noise prevention filter according to the present invention, and the same or corresponding parts as in FIG. 1 are denoted by the same reference numerals.

Each conductive wire 8a, 8b is passed through a through hole of a separate cylindrical ferrite bead 18a, 18b, and each ferrite bead 18a, 18b is a single strip forming a through hole as shown in the figure. groove 12 and protrusion 1
It is composed of a semi-cylindrical ferrite core 18 having a diameter of 9.

In this case, the protrusion 19 connects the pair of ferrite beads 18.
A gap 15.15b is formed between the opposing surfaces of ferrite beads 18a and 18b, but when storing these ferrite beads 18a and 18b in the conductor 5,
The conductive wires 8a and 8b should not be located in the area connecting the two conductive wires 8a and 8b.

These two ferrite beads 18a, 18b are inserted and housed in the cylindrical conductor 5 through the insulator 6, and the two conductive wires 8a, 8b are passed through the through holes formed by the grooves 12 to eliminate noise. A prevention filter is configured.

The noise prevention filter constructed in this way is essentially different from the conventional filter shown in Fig. 1, in that the gap provided in the ferrite bead is located in a region other than the region connecting two conductive wires. I will do it.

As a result, it propagates through two conductive tubes.

The ferrite beads also act effectively against the high frequency components of the dd mode, and the leakage radio wave blocking effect can be obtained.

Capacitors that were conventionally inserted between conductors can be removed.

Also, since there is a gap in the circumferential direction of each conductor,
There is no saturation phenomenon of the ferrite beads 7, and leakage of noise radio waves is effectively prevented over a wide band.

In this way, the noise prevention filter according to this embodiment is composed of two ferrite cores in which the ferrite bead is divided into two by a conductive wire and a line passing through a gap, so the shape of the ferrite core is a simple semi-cylindrical shape. As shown in FIG. 3, it becomes possible to press and shape the ferrite beads from the axial and radial direction, that is, from the direction of the arrow.

Therefore, a long ferrite core can be easily obtained, and there is no need to connect a large number of ferrite beads 7 in series to form a filter as in the conventional case.

Moreover, since the necessary gaps can be created at the same time as pressing, the number of manufacturing steps for the ferrite beads 7 is reduced.

Furthermore, since the ferrite core has a simple shape, press work efficiency is increased and yield is reduced.

Further, in the above embodiments, the gap is formed by the protrusion, but instead of the protrusion, a spacer made of a paramagnetic or non-magnetic material can be inserted between the ferrite cores to obtain a predetermined gap.

FIG. 4 is a cross-sectional view of a main part showing another embodiment of the present invention, and FIG. In addition, the radio wave absorption properties of ferrite are further increased.

The figure shows a case where a gap is provided only in the hand portion of the ferrite bead.

As explained above, in the noise prevention filter according to the present invention, conductive wires are passed through the through holes of two ferrite beads covered with a conductor, and the outer periphery of the ferrite beads is In addition to providing a gap that reaches the through hole from the surface, the ferrite bead is divided into two parts along the direction in which the conductor passes through the gap, making it extremely easy to manufacture ferrite beads of the required length. The ease of assembling the filter is significantly improved.

Therefore, various excellent effects can be achieved, such as an inexpensive and highly reliable noise prevention filter that effectively blocks radio wave leakage over a wide band.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figures 1a and 1b are partially fragmented cross-sectional views and II-I cross-sectional views showing an example of a conventional noise prevention filter, and Figure 2 shows the manufacturing of the ferrite beads shown in Figure 1. FIGS. 3a and 3b are sectional views and perspective views of essential parts showing an embodiment of the noise prevention filter according to the present invention, and FIGS. 4a and 4b are sectional views of essential parts for explaining the method. It is a diagram. 5... Conductor, 6... Insulator, 8a,
8b...Conducting wire, 18----Ferrite core, 18a, 18b...Ferrite bead, 1
5a, 15b...Gap.

Claims (1)

[Scope of utility model registration request] The ferrite beads include a cylindrical conductor, two cylindrical ferrite beads having a through hole in the center housed in the conductor, and conductive wires penetrating each of the through holes, and the ferrite bead has the through hole in the center. Consisting of a pair of semi-cylindrical ferrite cores having grooves forming holes, the opposing surfaces of each ferrite core form a gap extending from the through hole to the outer peripheral surface, and the position of this gap is located between the two conductors. A noise prevention filter that exists outside the area connecting the two.