JPH04106912A - Choke coil for noise prevention, and plug having it within - Google Patents

Abstract

PURPOSE:To the eliminate noise of mainly 30MHz or below by lowering the permittivity of the rubber or plastic layer applied on the coil for noise prevention, where winding is applied on the core, than that of the outer layer. CONSTITUTION:Rubber or plastic layer 30 is applied fully (without space) around a choke coil 12 for noise prevention. The rubber or plastic layer 30 is made in the double structure of the inner layer 32 surrounding winding 16 and the outer layer 34 around it, and the inner layer 32 is constituted of the material whose permittivity is lower than that of the outer layer 34. By surrounding the winding 16 of the choke coil with this rubber or plastic inner layer 32 of low permittivity, the capacitance between windings can be maintained small. Accordingly, the ratio of the impedance reduction for the cloke coil becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise prevention choke coil used for EMI (electromagnetic interference) countermeasures and a plug incorporating the same.

[Prior Art] First, a plug having a built-in noise prevention choke coil will be described.

This is used, for example, for power cord plugs for video and audio equipment. The purpose is to remove noise below 30 MHz.

Nie Ohm In FIG. 3, 10 indicates the entire plug.

12 is a choke coil.

Reference numeral 14 designates the core, for example, a toroidal ferrite core enclosed in an insulating case with an outer diameter of 19-2, a thickness of 51, and an initial AC permeability of 6000.

16A and 16B are windings each made of 35 turns of urethane enamel having a diameter of 0.6 mm, for example. The winding directions of winding @16A and winding 16B are opposite.

In the following, when there is no need to particularly distinguish between A and B regarding the windings, the reference numerals are simply indicated as 16.

18 is a power cord. Its conductors 2OA, 20B are connected in series with windings 16A, 16B, respectively.

22A and 22B are blades, and have windings 16A and 16, respectively.
Connected in series with B.

Furthermore, when there is no particular need to distinguish between A and B, the code for these is simply displayed as 20.22.

24 is a bridge body made of glass-filled nylon IF ISi, etc., and is connected to the choke coil 12 described above.
and the blade 22.

Cord 18 and choke coil 12 connected as above
, a comb or plastic layer 30 is applied over the blades 22 etc. to form the body of the plug.

This layer 30 is made of vinyl chloride, for example, and is formed without gaps by injection molding.

In the third figure of Sakusei Futatsuchibe, WL21! ! The current am flowing between 40 and load 42 flows in opposite directions through windings 16A and 16B. Since the windings 16A and 16B are wound in opposite directions, the magnetic fluxes generated in the core 14 cancel each other out, and the impedance of the choke coil 12 is extremely small.

However, since the noise 44 (common mode) flows in the same direction through the windings 16A and 16B, it is generated in the core 14 in the direction in which the magnetic fluxes 46A and 46B are added to each other. Therefore, the choke coil 12 has a large actance against the noise 44.

Therefore, by using a ferrite core with high magnetic permeability, it becomes possible to have a large impedance in a high frequency band of ~10 MHz, and to attenuate noise.

[Problems to be Solved by the Invention] As mentioned above, vinyl chloride is the mainstream material for the rubber or plastic layer 30 constituting the body of a plaque for general electronic and electrical equipment.

When this vinyl enters between the windings 16, the static 1! A capacitor is formed via the L capacitor.

Vinyl has a high frequency of 5 to 8 even for Class II cars or commercial vehicles, and it increases even more in the high frequency band of noise. for that,
The capacitance increases, the leakage 1 flow between the windings 1i16 increases, and the impedance of the choke coil 12 decreases.

As a result, the choke coil 12 alone has ~30MH
Even if it has the required impedance necessary to cut noise over the z frequency band, molding the vinyl causes a drop in characteristics.

Table 1 shows the measurement results of the circuit impedance after the choke coil 12 was molded with vinyl.

Table 1 (unit: Ω) That is, before molding, it has the required impedance characteristics, but after molding, a decrease in impedance is observed.

Especially in the high frequency band of 10MHz, it is 1/2,
The drop is very large.

Note that "after the mold has been disassembled" means that the molded vinyl is disassembled and the windings and the vinyl around them are removed. Since the characteristics recovered when this was done, it can be considered that the deterioration in characteristics after molding was due to the vinyl that had entered between the windings.

Although the above description has been made regarding the case of a plug with a built-in choke coil, similar problems occur with plugs other than plugs.

For example, this also applies to connectors with built-in choke coils.

Even if there is a choke coil, a similar problem will occur if it is sealed with vinyl or the like.

Therefore, in the present invention, the choke coil itself is claimed in claim 1, and the plug incorporating the choke coil is claimed in claims 2 and below.

[Means for solving jlM] (1) As shown in Fig. 1, the noise prevention choke coil 1
In the case where the rubber or plastic layer 30 is applied completely (without gaps) around the wire 2, (a) the rubber or plastic layer 30 is applied to the inner layer 32 surrounding the winding 16 and the outer layer 32; (a) The inner layer 32 is made of a material with a dielectric constant lower than that of the outer layer 34.

(2) Also, as shown in Fig. 2, the noise prevention coil 16
a cavity 52 in a rubber or plastic case 50.
The portion surrounding the winding 16 is made up of air 54.

[Function] Either it is a condition that the dielectric constant of the inner layer 32 is lower than that of the outer layer 34, or it is better that the dielectric constant of the inner layer 32 is as low as possible, taking into consideration molding conditions, price, etc.

By surrounding the choke coil winding 16 with this low dielectric constant rubber or plastic inner layer 32, the capacitance between the @ wires can be kept smaller than in the conventional case. Therefore, the rate at which the impedance of the choke coil decreases is also reduced.

In particular, if the portion surrounding the winding 16 is made of air, the impedance will not decrease.

[Example 1] In FIG. 1, the parts other than the rubber or plastic layer 30 are the same as in the case of FIG. 3 above.

In this case, a polybutadiene-based insulating varnish (dielectric ratio = 2.7) is used as the inner layer 3.2.

The outer layer 34 on the outside thereof is made of vinyl chloride as in the conventional case.

Table 2 shows the measurement results of the circuit impedance of the inner and outer layers of the i-pot before molding in the above case.

Table 2 (unit: Ω) It can be seen that there was little deterioration in characteristics even with molding, and that the required characteristics were maintained.

[Example 2] The rubber or plastic layer around the choke coil 12 is not solid as described above, but is made of a case 50 made of vinyl chloride, for example, with a cavity 52 inside, as shown in FIG. 2(a). has.

The choke coil 12 is installed within this cavity 52. Therefore, the portion surrounding the winding 16 of the choke coil 12 is air 54.

In this case, instead of using an insert mold for the choke coil 12 as in the first embodiment, the choke coil 12 is manufactured as follows.

That is, as shown in FIG. 5B, the case 50 is divided into upper and lower parts and manufactured in advance by injection molding.

A choke coil 12 is housed under the choke coil 12, and is fixed by connecting it to the conductor 20 of the cord and the blade 22 by soldering or the like.

Then, the upper side of the case 50 is covered and welded using, for example, a high frequency welder. Note that 56 is a welding protrusion.

Table 3 shows the measurement results of the circuit impedance before covering the case 50 and molding the plug (in the case of the choke coil 12 alone) and in the trench in the above case.

Table 3 (in Ω) It can be seen that the properties did not deteriorate even after molding, and the required properties were maintained.

[Effects of the Invention] (1) In a noise prevention choke coil in which a core is wound and a rubber or plastic layer is provided thereon, the dielectric constant of the inner layer surrounding the winding is calculated as the dielectric constant of the outer layer. If it is lower than , the impedance of the choke coil will decrease less; if the part surrounding the winding is made of air, there will be no decrease in impedance.

(2) For this purpose, it is sufficient to ensure that the impedance of the choke coil is close to the required performance.

Therefore, the choke coil can be downsized and economical.

(3) Since the choke coil can be made smaller, the plug containing it can also be made smaller.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the first embodiment of the present invention, FIG. 2(a) is an explanatory diagram of the second example of the present invention, and FIG. 2(b) is an explanatory diagram of the manufacturing method. The figure is an explanatory diagram of an example of a conventional plug with a built-in choke coil. 10 Nib Lug 12: Choke Coil 14: Core 16: Winding 18: 20: 22: 24: 30: 32 = 34: 50: 52: 54: Cord Conductor Blade Bridge Body Rubber or Plastic Layer Inner Layer Outer Layer Case Cavity Air

Claims (3)

[Claims] (1) In a choke coil for noise prevention in which a core is wound and a rubber or plastic layer is applied thereon, the rubber or plastic layer has an inner layer surrounding the winding and an outer layer outside the coil. A chiyoke coil for noise prevention, comprising two layers, the inner layer having a lower dielectric constant than the outer layer. (2) On top of the noise prevention coil whose core is wound,
In a plug provided with a rubber or plastic layer and incorporating a noise prevention coil, the rubber or plastic layer is composed of two layers, an inner layer on the inside and an outer layer on the outside thereof, and the dielectric constant of the inner layer is equal to that of the outer layer. A plug with a built-in noise prevention coil that has a lower dielectric constant. (3) In a plug that has a built-in noise prevention coil whose core is wound, the noise prevention coil is installed in a cavity in a rubber or plastic case, and the part surrounding the winding is air-filled. A plug with a built-in noise prevention coil.