JPH0140230Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the structure of an element that prevents electromagnetic interference (EMI) in signal lines in digital equipment.

[Conventional technology]

In systems using digital equipment,
EMI countermeasures are applied to the signal lines of each device, and also to the signal line cables that connect the devices to each other.
EMI countermeasures have been taken to suppress EMI as a system.

Conventional EMI countermeasures include installing ferrite beads on each of multiple signal lines (installing a normal mode inductor), and passing multiple signal lines through a cylindrical ferrite magnetic core (installing a common mode inductor). ) was normal. In other words, there is no signal line EMI prevention element that integrates both a normal mode inductor and a common mode inductor.

[Problem that the invention attempts to solve]

In order to realize the signal line EMI prevention element as described above, an element using a composite magnetic core in which a plurality of ferrite beads are inserted into a cylindrical magnetic core can be considered.
However, it is difficult to make ferrite beads thin and their outer diameter is larger than the insulating coating of the signal line, so a large cylindrical magnetic core is required.
Furthermore, since the inductance of the cylindrical magnetic core is reduced by inserting the ferrite beads, it is necessary to increase the volume of the cylindrical magnetic core in order to obtain the original inductance, resulting in a further increase in the size of the cylindrical magnetic core. Such a large composite magnetic core is not practical.

[Means for solving problems]

The present invention was developed in view of the above-mentioned situation, and uses instead of ferrite beads a tubular body made by winding an amorphous magnetic strip that has been heat-treated to have properties that can be applied up to high frequencies comparable to ferrite. By combining it with a cylindrical magnetic core, a practical composite magnetic core is constructed.

Specifically, the present invention includes a plurality of tubular bodies through which electric wires are passed through, and a tubular ferrite magnetic core inserted through these tubular bodies, and the tubular body includes an amorphous magnetic strip having a desired frequency characteristic. A signal line characterized by being formed by winding
It is an EMI prevention element.

〔Example〕

FIG. 1 is an exploded perspective view of an EMI prevention device according to the present invention.

1 is an insulated wire (signal wire), and 2 is a tubular body formed by wrapping an amorphous magnetic strip around the wire 1 so as to partially overlap it. Amorphous magnetic strips have lower magnetic permeability through heat treatment (e.g. μe = 200 at 1 MHz), and have magnetic permeability comparable to that of ferrite beads in high frequency bands (e.g. around 100 MHz) (e.g.
It is a magnetic material that has the property of maintaining μe = 50), and has a thickness of several μm to several tens of μm. Therefore,
The outer diameter of the tubular body 2 is only slightly larger than the electric wire 1.

The magnetic core 3 is a flat cylindrical ferrite magnetic core consisting of two types of divided pieces 3a and 3b, and its opening dimensions are almost the same as those of conventional common mode inductor magnetic cores, and its outer dimensions are the same as those of conventional common mode inductor magnetic cores. It is set to have a larger required inductance than the magnetic core (for example, 150% of the conventional one).

As shown in FIG. 1, an EMI prevention element is completed by lining up a plurality of tubular bodies 2 in the recesses of the divided pieces 3b of the magnetic core 3, passing the electric wire 1 through them, and abutting the other divided pieces 3b to form a cylindrical shape. .

Although this element has slightly larger external dimensions than a conventional common mode inductor, it is possible to simultaneously and simply attach a normal mode and common mode inductor to a signal line with just this element. In addition, since the tubular body 2 is formed by winding a band, even if connectors are connected to both ends of the electric wire 1, the element can be configured without removing the connectors, and it can be retrofitted.
It is useful as an EMI countermeasure.

FIG. 2 is an external view showing another embodiment of the present invention. This shows an example of the element shown in Figure 1 being completed into a board-mounted type for use as a pre-installed EMI countermeasure (determined at the equipment design stage). Here, the magnetic core 3 is of the undivided type. The electric wire 1 has a conductor 4 exposed at both ends with an insulating coating left at a length slightly shorter than the axial dimension of the magnetic core 3, and the conductor 4 is exposed at both ends. A tubular body made of an amorphous magnetic strip is provided. A plurality of such electric wires 1 are lined up and inserted into the magnetic core 3, and then placed on an insulating terminal block 5 having a plurality of plate terminals 6 arranged at equal intervals so as to vertically penetrate through the thick parts on both sides. , the conductor 4 is connected to the plate terminal 6 by spot welding. Note that a tubular body may be inserted into the magnetic core 3 in advance, and then the electric wire 1 may be inserted through this tubular body.

FIG. 3 shows an example in which the device of the present invention is made into a multi-pole connector type. An electric wire 1, a tubular body 2, and a magnetic core 3 similar to those described in FIG. This is an EMI prevention element with a structure in which the conductor 4 is connected to the connector terminal. If this element is used when connecting between devices, it will be possible to
EMI can be prevented. Since this element is easy to attach and detach, it is suitable as a symptomatic treatment for EMI.

[Effect of idea]

As explained above, according to the present invention, a tubular body formed by winding a highly elastic amorphous magnetic strip with good frequency characteristics is used as a magnetic core for a normal mode inductor, so that The dimensions may be increased in consideration of the reduction in inductance due to insertion of the tubular body, and a composite magnetic core can be constructed without enlarging the opening of the magnetic core. In addition, we have developed a new method that has the required EMI prevention effect and requires less mounting space than conventional ones.
Can provide EMI prevention elements. Furthermore, since the tubular body is easier to handle than ferrite beads, it has the advantage that elements can be easily added to existing signal lines.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view showing one embodiment of the signal line EMI prevention element according to the present invention, Fig. 2 is an external view showing another embodiment, and Fig. 3 is an exploded perspective view showing an embodiment of the signal line EMI prevention element according to the present invention. FIG. 7 is a vertical cross-sectional view showing another embodiment. 1: Insulated wire (signal line), 2: Tubular body,
3: Magnetic core, 4: Conductor, 5: Insulating terminal block, 6: Plate terminal, 7: Multipolar connector, 8: Insulating base.

Claims (1)

[Scope of utility model registration request] A combination of a plurality of tubular bodies formed by winding and molding amorphous magnetic strips having desired frequency characteristics into a tubular shape, a plurality of electric wires each having a predetermined length passing through each of the plurality of tubular bodies, and the electric wires and the tubular body. A signal line EMI with a cylindrical ferrite magnetic core inserted through the
Prevention element.