JPH0517866Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention is mainly connected to the power line of electronic equipment to remove noise from commercial power supply and to prevent noise from leaking from inside the electronic equipment to the outside. This invention relates to the structure of a line filter coil.

[Prior art and its problems]

As shown in the cross-sectional view of FIG. 3, a conventional filter coil of this type has a core 1 passed through a synthetic resin bobbin 2, and a wire 3 and a wire 4 forming two coils.
It is wrapped around. The core 1 is a combination of E-type ferrite from above and below, and is also present on the outside of the wire rods 3 and 4 wound around the bobbin 2. Therefore, the wire rod 3 and the wire rod 4 are wound in a window frame-shaped gap 5 surrounded by the bobbin 2 and the core 1.

In such a line filter coil,
A synthetic resin insulating film is baked on the surface of the wire 3 and wire 4, but as shown in the equivalent circuit diagram in Fig. 4, a line capacitance C exists in each wire through the insulating film. ing. This line capacitance C causes deterioration of high frequency characteristics, and weakens the ability as a filter against high frequency noise. Conventionally, the wire capacitance C was reduced by increasing the number of winding grooves on the bobbin, dividing it into different winding grooves, and continuously winding the same wire rod. The area on the bobbin where the wire can be wound is reduced,
There was a drawback that the specified inductance could not be obtained due to the limited coil size. Furthermore, in order to improve the insulation between the core 1 and the wire 3 and the wire 4 and between the different wires 3 and 4, the wire 3 and the wire 4 cannot be wound until the gap 5 is completely filled. It was necessary to maintain a sufficient distance L between wire rod 1, wire rod 3, and wire rod 4.

〔the purpose〕

An object of the present invention is to provide a line filter coil that can improve high frequency characteristics by reducing line capacitance without substantially reducing inductance, and also improve insulation properties.

[Technical means to solve problems]

In the line filter coil of the present invention, a wire rod having an insulating film with different thickness in the length direction is wound around a bobbin 2 with the thinner part on the inside and the thicker part on the outside. It is characterized by

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the line filter coil of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view, and FIG. 2 is an equivalent circuit diagram of the wire. Note that the same parts as in FIG. 3 are given the same reference numerals.

In FIG. 1, the shapes of the core 1 and bobbin 2 are the same as in FIG.
0 and wire rod 11 are wound respectively. However, the third
Unlike wire rod 3 and wire rod 4 in the figure, wire rod 10 and wire rod 1
The thickness of the insulating film 1 is not uniform in the length direction of the wire, and the wire is wound around the bobbin 2 such that the thicker part is on the outside and the thinner part is on the inside.

10A and 11A shown in FIG. 1 are portions of the wire 10 and the wire 11 where the insulating film is thin, and are inner layer portions wound inside. Also, 10B,
11B is a thicker insulating film portion of the wire 10 and the wire 11, and is an outer layer portion wound on the outside. Specifically, the outer layer portion 10B and the outer layer portion 11B have thicker insulating films by passing the respective wire rods through a cylindrical insulating coating made of synthetic resin. The inner layer portion 10A and the inner layer portion 11A are only insulating films of wire rods.

By winding the wire 10 and the wire 11 in this manner, each wire can be represented equivalently as shown in FIG. The part where the line capacitance C' is connected in parallel corresponds to the inner layer part 10A or 11A, and the part where the line capacitance C' is not connected corresponds to the outer layer part 10B or 11B, respectively. Of course, the outer layer portion and the inner layer portion may be formed by connecting wires with varying thicknesses of insulating films that are directly coated and baked. Further, the ratio of the wire rods in the outer layer and the inner layer, and the thickness of the insulating film in the outer and inner layers may be set in consideration of the inductance value and insulation properties.

In the embodiment, a filter coil in which two wires are wound is described, but it goes without saying that a single-wound coil also exists and the present invention can be applied thereto. Also,
The core may be U-shaped.

〔effect〕

As mentioned above, in the line filter coil of the present invention, the insulation film of the wire in the outer layer is thicker than that in the inner layer, so the insulation between the wire and the outer core is improved. From this point on, the wire can be wound until the void is almost filled. Then, as shown in Figure 1, the distance L' between the wire rod and the outer core 1 of the wire rod is
It can be made smaller than the distance L of the corresponding part in the figure. Further, there is almost no decrease in the number of turns of the wire rod caused by partially increasing the thickness of the insulating film. Furthermore, as shown in FIG. 2, the line capacitance C' can be ignored in the outer layer portion, so its value is also small. Therefore, the high frequency characteristics can be improved without substantially reducing the inductance, and the filter function against noise can be maintained up to high frequencies. Furthermore, a thicker insulating film on the outer layer is equivalent to having a thicker insulating film on the exposed surface of the wound wire, which improves insulation with other wires. Therefore, in combination with the above-mentioned effects, the present invention can provide a desirable line filter coil.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the line filter coil of the present invention, Fig. 2 is an equivalent circuit diagram of the wire,
FIG. 3 is a sectional view of a conventional line filter coil, and FIG. 4 is an equivalent circuit diagram of the wire shown in FIG. 10, 11... Wire rod, 10A, 11A... Inner layer part, 10B, 11B... Outer layer part.

Claims (1)

[Scope of utility model registration request] In line filter coils where the core is inside the bobbin and outside the wire wound around the bobbin, the wire has different insulating film thicknesses in the length direction, with the thinner part on the inside and the thicker part in the coil. A coil for a line filter, characterized in that the coil is wound on the bobbin so as to be on the outside.