JPS59186017A - Case structure - Google Patents

Abstract

PURPOSE:To decrease leakage of noise generated in a case to the outside of the case and at the same time to lower leakage of electromagnetic wave by providing ventilating holes in an outer case containing an active element, arranging plural waveguides at the openings of the ventilating holes and providing a noise absorbing material at the inside of these waveguides. CONSTITUTION:A unit 2 containing electronic parts such as an active element, etc. is provided in the outer case 1 of an electronic equipment etc. and ventilating holes 3 are provided in the upper part and the lower part of the outer case 1. Cooling fans 4 are arranged in correspondence to the ventilating holes 3, and at the same time, plural waveguides 6 are provided. The waveguides are arranged at right angles to the longitudinal direction of the ventilating holes, and the length is made 1/2 or more of the maximum dimension of the opening. A sound absorbing material 7 is stuck firmly to the inner walls of the wave guides 6 and the waveguides are used as fills at frequency band lower than the cut-off frequency determined by sectional dimension. Leakage of electromagnetic wave and noise generated at the inside of the outer case 1 is decreased simultaneously.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is directed to electronic devices such as computers, which contain active elements or other parts, and which generate magnetic waves and noise when forced cooling air is stained inside the device. The present invention relates to a housing structure of a device, and particularly to a housing structure that reduces electromagnetic waves and noise.

[Background technology]

Conventionally, as shown in FIG. 1, a housing IJlc of an analog or digital device is usually provided with a ventilation hole 3 for heat dissipation from the active elements and other components 2 therein. and,
A wire mesh or perforated metal 4 is fitted into the ventilation hole 3 to shield electromagnetic waves generated inside the housing. However, in order to increase the shielding effect with this method, it is necessary to make the mesh thinner when using a wire mesh, or to increase the diameter of the strands, and when using perforated metal, it is necessary to make the mesh thinner. It was necessary to reduce the opening area by reducing the diameter.

On the other hand, power consumption of units containing electronic active elements is increasing due to high output and high speed, and the resulting increase in internal temperature is prevented by high-speed ventilation of cooling air. There is. In this way, the wire mesh or perforated metal of the ventilation hole and the electronic active element housed within the outer housing,
The disadvantage is that the high-speed air flow hits the electronic and electrical parts and the devices for holding and fixing them, producing a large amount of noise. In order to reduce this noise, it is necessary not only to reduce the noise of the unit including the electronic active elements, but also to increase the aperture ratio of the wire mesh or perforated metal of the ventilation opening.

In other words, in order to improve the shielding of electromagnetic waves, the opening ratio of the ventilation openings must be made small, while in order to reduce noise, the opening ratio of the ventilation openings must be made large. Conflicting and contradictory responses were needed to the ventilation openings in the area.

[Disclosure of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is provided with an air vent for cooling the active elements, etc. in the outer casing of an electronic device, etc. that houses active elements and other electronic/electrical parts. A waveguide having a length of 1/2 or more of the maximum dimension of the opening is arranged in the direction perpendicular to the longitudinal direction of the ventilation opening, in other words, in the opening direction of the ventilation opening, and By fixing a sound-absorbing material to each inner wall or filling the inside of each of these waveguides with an air-permeable sound-absorbing material, electromagnetic waves generated inside the outer casing can be suppressed. The purpose is to simultaneously absorb sound and noise and disclose the structure of the housing.

[Explanation of Examples]

Embodiments of the present invention shown in FIGS. 2 to 4 will be described below.

FIG. 2 shows a first embodiment of the present invention, where 1 is an outer casing of an electronic device, and 2 is an electronic active element and other electronic devices.
A unit accommodating electrical components, 3 are ventilation holes provided at the upper and lower parts of the outer housing 1, 4 is a cooling fan arranged corresponding to the ventilation hole 3, and 6 is arranged at the ventilation hole 3. The plurality of waveguides 7 are sound absorbing materials fixed to the inner wall of each waveguide 6. The waveguide 6 is arranged in a direction perpendicular to the longitudinal direction of the ventilation port 3, that is, in the opening direction, and its length is 1/! of the maximum dimension of the opening. That's all for now.

On the other hand, the waveguide 6 is a good transmission path for electromagnetic waves in a frequency range higher than the cutoff frequency determined by its cross-sectional dimension, and is widely used for very short waves or extremely short waves by taking advantage of this property. ing. However, in the frequency range lower than this cutoff frequency, it has the characteristic of not transmitting or propagating electromagnetic waves. That is, in a frequency range lower than the cut-off frequency, the waveguide functions not as a transmission path for electromagnetic waves but as a filter. The amount of attenuation of electromagnetic waves when used as a filter is approximately 27 dB for a rectangular waveguide whose length is the same as the long side of the cross section in the case of a frequency that is much lower than the cutoff frequency.
, for a circular waveguide with the same length as the diameter, approximately 30 dB
You can get a rank. By arranging a plurality of such waveguides in a direction perpendicular to the longitudinal direction of the ventilation opening as described above, the passage for the cooling air can be widened. Note that this assembled waveguide is connected to the outer casing in a high frequency manner.

On the other hand, a sound absorbing muffler is known as one method for reducing noise. This absorbs acoustic energy within the conduit and reduces the energy radiated from the outlet. With this structure, electromagnetic waves and noise generated inside the housing are simultaneously shielded and absorbed.

Note that the cross-sectional shape of the waveguide 6 may be any shape such as a rectangular, circular or hexagonal shape, and the sound absorbing material 7 is attached over the entire inner wall of the waveguide 6 as in the first embodiment. Alternatively, it may be fixed to a part of the inner wall of the Km wave tube 6 as in the second embodiment shown in FIG. Also, the fourth
As shown in the third embodiment of the figure, a similar effect can be obtained by filling the inside of the waveguide 6 with a sound absorbing material 8 having air permeability. Furthermore, it is possible to line the inner wall of the waveguide with a sound absorbing material, or insert a sound absorbing material in the middle.
This is exactly the same as when a sound absorbing material is fixed inside a waveguide.

〔Effect of the invention〕

As described above, according to the present invention, by arranging a plurality of waveguides in the opening direction of the ventilation port of the outer casing, and providing a sound absorbing material inside each of these waveguides. Furthermore, leakage of electromagnetic waves and noise generated inside the housing to the outside of the housing can be reduced at the same time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the conventional case structure, Fig. 2 is a block diagram of the first embodiment of the book-required case structure, Fig. M3 is a block diagram of main parts of the second embodiment, and Fig. 4 is a block diagram of the FIG. 2 is a configuration diagram of main parts of an embodiment. 1...Outer casing 2...Unit 3...Ventilation port 6...Waveguide 7.8-...Sound absorbing material Applicant NEC Corporation Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] An air vent for cooling the active element, etc. is provided in the outer casing that houses the active element, etc., and a waveguide having a length of 172 mm or more, which is the maximum dimension of the opening, is provided in the opening direction of the vent. A housing structure characterized in that a plurality of pipes are arranged and a sound absorbing material is provided inside each of these waveguides.