JPH0752798B2 - Electronics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic device that blocks the emission of unnecessary radio waves or blocks the incidence of external radio waves.

[Background technology and its problems]

Conventionally, electronic devices such as video tape recorders, video tape recorders with cameras, radio receivers, television receivers, personal computers, etc. are affected by electronic elements and external radio waves that generate unnecessary radio waves during operation. An electronic device that causes a malfunction is built in.

For example, in a video tape recorder with a camera, in which CCD (Charge Coupled Device) is used as an imaging element, unnecessary radio waves are significantly emitted. In a video tape recorder using this CCD as an image pickup device, unnecessary radio waves are generated in the band of 20 MHz to 1000 MHz used for communication such as broadcasting, and it becomes an interference wave of communication. Therefore, conventionally, in order to prevent the emission of unnecessary radio waves, the CCD is covered with a shield case made of a conductive metal material and the shield case is grounded. However, the CCD installed in the lens barrel that contains the optical system
If the cover is covered with a shield case, not only the structure becomes complicated, but also the assembly becomes difficult. Further, a clock pulse signal is generated from the drive control circuit of the rotary magnetic head device in the video tape recorder, and an unnecessary radio wave is generated from the clock pulse signal in the band of 20 MHz to 1000 MHz. Therefore, the printed circuit board that constitutes the drive control circuit is covered with a shield case made of a conductive metal material, and the case is grounded. Also in this case, a shield case is further required, which complicates the structure and causes difficulty in assembly. Furthermore, since the head amplifier that amplifies the video signal from the video head in the video tape recorder processes a minute video signal, it is necessary to protect it from external radio waves. The head amplifier part is shielded. And
By providing the shield plate, the structure is complicated and the assembly is difficult.

[Object of the Invention]

Therefore, the present invention, in the frequency band of at least 20MHz ~ 1000MHz used for communication such as television broadcasting and radio broadcasting, does not generate unnecessary radio waves to the outside, and is not affected by external radio waves The purpose is to provide equipment, especially CCDs.
A videotape recorder that can reliably block unnecessary radio waves and external radio waves without covering electronic elements such as electronic elements and electronic elements that are affected by external radio waves with a shield plate, and can also guarantee sufficient mechanical strength. It is intended to provide electronic equipment such as.

[Means for achieving the purpose]

In order to achieve the above-described object, an electronic device according to the present invention has an external casing that contains an electronic element that generates radio waves of a predetermined frequency or higher, or an external casing that contains an electronic element that is affected by external radio waves. At least one of polyethylene terephthalate resin, polybutylene terephthalate resin, polycarbonate resin, nylon 66, ABS resin, AS resin It is molded from a mixed material.

By molding the outer casing with such a material, it is possible to absorb unnecessary radio waves from the electronic elements arranged inside the outer casing and also to absorb external radio waves, and to further increase the mechanical strength. Obtainable.

〔Example〕

An example in which the present invention is applied to a video tape recorder with a camera will be described below. Inside the outer casing 1 which constitutes the main body of the video tape recorder, as shown in FIG. 1, the tape cassette mounting portion is mounted. A rotary magnetic head device 4 is provided for recording the video signal on the magnetic tape 3 and reproducing the video signal recorded on the magnetic tape 3 while the magnetic tape 3 fed from the tape cassette 2 is wound and runs. In addition, a constant speed running means for the magnetic tape, which is composed of the pinch roller 5 and the capstan 6, is provided. Further, on the left front side of the outer casing 1 in the figure, a lens barrel 8 having an optical system 7 including a focus lens is provided. At a position facing the optical system 7, a CCD 9 for converting light into an electric signal and taking out the electric signal is arranged. This CCD9 is an electronic element that generates unnecessary radio waves in the band of 20MHz to 1000MHz when operating.

Further, although not shown, a control circuit for controlling the running of the rotating magnetic head device 4 and the magnetic tape 3 and a camera synchronization control circuit for outputting a camera synchronization signal are provided in the outer casing 1, and these control circuits are provided. , A clock pulse signal of 4MHz to 13.27MHz is output, and a radio wave of 100 to 250MHz is generated as a harmonic component of these clock pulse signals.

According to the present invention, the outer casing 1 and the lens barrel 8 of the video tape recorder with a camera configured as described above are made of a molding material in which a radio wave absorber such as a sintered body of silicon carbide is mixed with a synthetic resin. It is formed by injection molding.

As the molding material, 10 to 30% by weight of a sintered body of silicon carbide, which is an electromagnetic wave absorption ceramic, and 10% by weight of glass fiber are used.
~ 30% by weight, balance polyethylene terephthalate resin,
It is a mixture of at least one of polybutylene terephthalate resin, polycarbonate resin, polyacetal resin, nylon 66, ABS resin and AS resin.
The silicon carbide sinter that is confused with the molding material mixed in this way has a maximum absorption capacity of 99.2% in the frequency band of 10MHz to 12000MHz and does not lose its electromagnetic wave absorption capacity even at high temperatures of 2000 ° C or higher. I will never be told. The molding temperature of the material containing the sintered body of silicon carbide is 220 ° C.
Since it is sufficient at ~ 280 ° C, there is no loss of radio wave absorption capability. Therefore, the outer casing 1 and the lens barrel 8 formed of this material are 20 MHz to 1000 M generated from the CCD 9 and the control circuit.
It absorbs unnecessary radio waves of Hz and does not radiate it outside,
Further, it is possible to absorb a disturbance radio wave incident from the outside.

In addition, the molding material used in this example,
Since it contains glass fibers, the mechanical strength can be sufficiently increased.
In order to improve the mechanical strength, carbon fibers may be mixed in place of glass fibers, and in the case of an electronic device that does not require high mechanical strength, the glass fibers or the like need not be mixed.

Ferrite may be used as a radio wave absorber, but since ferrite is transformed at a temperature of about 250 ° C, it is not appropriate to use it as a molding material containing polyethylene terephthalate resin as a main component as described above. .

In the above-described embodiments, the video tape recorder with a camera is described as an example, but an electronic element that generates unnecessary radio waves when the video tape recorder, the radio receiver, the television receiver, the personal computer, or the like is activated, or the like. By applying to an electronic device that contains an electronic element that may be affected by external radio waves and cause a malfunction, it is possible to absorb unnecessary radio waves of 10 MHz to 12000 MHz generated from the inside of the device main body It is possible to absorb radio waves in the same frequency band from.

〔The invention's effect〕

As described above, according to the present invention, since the outer casing is formed of the molding material including the sintered body of silicon carbide as the radio wave absorber, it is generated from the electronic device such as the CCD incorporated in the main body of the electronic device. Unwanted radio waves can be absorbed by the outer casing, and electric waves from the outside can be absorbed by the outer casing. Therefore, an electronic device that does not interfere with communication radio waves and is not affected by external radio waves can be provided. Since it can be configured and there is no need to provide a shield case or the like unlike the conventional one, the structure is simple and the assembly is easy.

In addition, since the molding material forming the outer casing is confused with glass fiber or the like to improve the mechanical strength, the strength of the outer casing can be improved, and the durability can be improved when applied to a portable electronic device. Can also be achieved.

[Brief description of drawings]

 FIG. 1 is a schematic sectional view showing an embodiment of the present invention. 1 ... Outer casing 8 ... Lens barrel

Claims (1)

[Claims] 1. An outer casing containing an electronic element for generating a radio wave of a predetermined frequency or higher, or an electronic element affected by an external radio wave, a sintered body of silicon carbide being 10 to 30% by weight, and a glass. 10 to fiber
30% by weight, the balance is at least one of polyethylene terephthalate resin, polybutylene terephthalate resin, polycarbonate resin, nylon 66, ABS resin, AS resin
An electronic device made of a mixed material.