JP2007088332A - Emc shielding case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EMC shielding case by which emitted noise in a specific frequency band can be suppressed by a simple structure and with efficiency. <P>SOLUTION: An electric apparatus 1 including a circuit which emits electromagnetic noise or is affected by electromagnetic noise is mounted on the inside of the shielding case 2 from its opening 3. Conductive plates 4 are stretched across the opening 3 in positions at a distance b from the apparatus 1 wherein the plates 4 interfere with emitted noise in the specific frequency band and are fixed to the case 2. Since noise emitted from the apparatus 1 is put to interference with by the conductive plates 4, flows to the case 2 through the conductive plates 4, and reaches a ground contacting area; noise in the specific frequency band emitted from the apparatus 1 is not emitted outside. Since emitted noise from outside is put into interference with by the conductive plates 4, flows to the case 2 through the conductive plates 4, and reaches the ground contacting area; entry of noise in the specific frequency band into the case 2 is inhibited and the apparatus 1 can be protected against emitted noise. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an EMC shield case, and more particularly, to a means for realizing EMC against radiated noise in an electric device including a circuit that radiates or is affected by electromagnetic noise.

  There is an increasing demand for Electro-Magnetic Compatibility EMC (electromagnetic environment compatibility) for electrical equipment including a circuit that includes a power converter or an electronic circuit and radiates electromagnetic noise or is affected by electromagnetic noise.

  EMC is the ability to suppress / protect equipment, devices, and systems that do not give unacceptable disturbing electromagnetic waves to anything and function satisfactorily in the electromagnetic environment.

  An EMC standard is defined for various devices, and in order to comply with this standard, it is required to reduce radiation noise and ensure protection against external radiation noise.

  FIG. 4 is a perspective view showing an example of an EMC shield case provided with a conventional radiation noise reduction means of a single device.

  In the conventional single-device EMC technology for radiation noise, as shown in FIG. 4, a device 1 equipped with a power converter or electronic circuit that generates radiation noise is mounted inside a case 7, and the case 7 and the door 8. In order to reduce the radiation noise from the gap between them and prevent the entry of radiation noise from the outside, the shield packing 9 is attached to all the gaps between the case 7 and the door 8 (see, for example, Patent Document 1).

  In general, when the case 7 has a vent hole, the shield wire mesh 10 is attached in order to reduce radiation noise from the vent hole and prevent intrusion of radiation noise from the outside.

  In this way, the entire periphery of the device 1 that is the source of radiation noise is electromagnetically shielded so that the noise from the device 1 is not radiated to the outside. Protected against adverse effects.

  FIG. 5 is a perspective view showing an example of an EMC shield case provided with a radiation noise reduction means of a conventional multi-device connection part.

  When connecting a plurality of devices, as shown in FIG. 5, a device 1 equipped with a power converter or the like and a device 1a equipped with an electronic circuit or the like are connected by an electric wire 6 (for example, Patent Documents). 2).

  When a plurality of devices are connected as shown in FIG. 5, each of the devices 1 and 1a has the EMC countermeasures shown in FIG. The electric wire 6 connecting the device 1 and the device 1a prevents the noise in the devices 1 and 1a from propagating through the electric wire 6 and being radiated to the outside, and the radiation noise from the outside propagates through the electric wire 6. In order to prevent intrusion into the devices 1 and 1a, the shield tube 12 is passed.

  Further, in order to prevent the noise radiation from the openings of the cases 7 and 7a through which the electric wire 6 passes and the invasion of the external radiation noise, a shield tube base 11 is provided, a shield tube 12 is attached to the shield tube base 11, and the electric wire 6 passes therethrough. The electromagnetic gap in the part was lost.

Japanese Patent Laid-Open No. 05-218674 (pages 2 to 3 and FIGS. 1 to 3) JP-A-11-145672 (page 6 FIG. 7)

  As shown in Patent Documents 1 and 2, in the conventional shielding method against radiation noise, the entire system is shielded electromagnetically without gaps.

  This shielding method is a reliable and effective means against radiation noise in a wide frequency band.

But,
(1) A large percentage of the total cost of shielding parts
(2) The work efficiency of installing shield parts is poor
(3) Shielding against cables connecting multiple devices significantly deteriorates work efficiency when installing devices
(4) Various additions that eliminate gaps such as opening and closing parts and openings make the design margin extremely small, and are a major obstacle especially in equipment with severe restrictions on external dimensions.
(5) Since a shield wire net is used for the vent for heat dissipation, there are problems such as poor thermal efficiency.

  The subject of this invention is providing the EMC shield case which can suppress effectively the radiation noise of the frequency band to which attention is paid with a simple structure.

  In order to solve the above problems, the present invention provides a shield case in which an electrical device including a circuit that emits electromagnetic noise or is affected by electromagnetic noise is mounted from the opening, and is specified from the electrical device by the opening. An EMC shield case is proposed in which a conductive plate is stretched over a position separated by a distance b (b ≦ λ / 2) that interferes with radiation noise in the frequency band and fixed to the case.

  The present invention also includes a plurality of devices each including an electric device including a circuit that emits electromagnetic noise or is affected by the electromagnetic noise, and each of the electric devices is connected by an electric wire 6. In a certain shielding case, a conductive plate is stretched around the wiring between the plurality of devices at a position separated from the electrical equipment by a distance b (b ≦ λ / 2) that interferes with radiation noise in a specific frequency band, An EMC shield case fixed to the case is proposed.

  According to the present invention, it is possible to easily and effectively electromagnetically shield an electric device for a specific frequency band to be suppressed, and to realize EMC required in the standard. In addition, the cost can be greatly reduced, the working efficiency can be improved, and the design margin can be increased as compared with the prior art.

  Electrical equipment does not always require strict shielding across all frequency bands. Although the above prior art provides a complete shield for electrical equipment, it is a reliable and effective means against radiation noise in a wide frequency band, but there are various problems.

  Therefore, the present invention forms an effective shield against the wavelength of the maximum intensity radiation noise or the radiation noise of the frequency band desired to be suppressed at the site where the electrical equipment is installed, and sufficiently conforms to the EMC standard with a simple structure. A possible EMC shield case was realized.

  Next, with reference to FIGS. 1-3, the Example of the EMC shielding case by this invention is described.

  FIG. 1 is a perspective view showing Example 1 of an EMC shield case provided with a radiation noise reduction means for an opening according to the present invention.

  In the first embodiment, an electric device 1 that includes a power converter or an electronic circuit, radiates electromagnetic noise, or includes a circuit that is affected by electromagnetic noise is mounted inside the case 2, and the opening 3 of the case 2 is mounted. On the other hand, a conductive plate 4 is stretched over a position away from the device 1 by a distance b and attached to the case 2.

  In general, radiated noise is rarely a single frequency and includes components of various frequencies. In the present invention, the distance b is determined by the wavelength of the maximum intensity radiation noise or the frequency characteristics of the radiation noise to be suppressed.

  The distance b is set to b ≦ λ / 2, where λ is the wavelength at which radiation noise is to be suppressed. That is, the interval is shorter than a half wavelength. The wavelength λ of the radiation noise is λ = v / f where f is the frequency of the radiation noise and v is the propagation speed.

  As a result of the experiment, it has been found that the radiation noise of the device 1 does not leak outside if b ≦ λ / 2.

  If a large number of conductive plates 4 are installed side by side, the function of the conventional shield wire mesh approaches. The lower limit of this interval is determined by the cost of the member itself and the cost of the attachment work.

  If a structure like the present Example 1 is employ | adopted, the radiation noise of the apparatus 1 will be interfered by the electrically conductive plate 4, will flow into the case 2 through the electrically conductive plate 4, and will reach a grounding part. Also, radiation noise from the outside is interfered with the conductive plate 4 and flows to the case 2 through the conductive plate 4 and reaches the grounding portion. As a result, it is possible to prevent the external radiation noise from entering the case 2 and protect the device 1 from the radiation noise.

  FIG. 2 is a perspective view showing an embodiment 2 of an EMC shield case provided with a radiation noise reducing means for connecting a plurality of devices according to the present invention.

  In the second embodiment, a power converter or an electronic circuit is mounted, and an electric device 1 that includes a circuit that radiates electromagnetic noise or is affected by electromagnetic noise is mounted in the shield case 5. And a device in which an electric device 1a including a circuit that radiates electromagnetic noise or is affected by electromagnetic noise is mounted inside a shield case 5a. The device 1 and the device 1a are connected by an electric wire 6. This is a connected EMC shield case.

  In the electric wire 6 of the second embodiment, radiation noise and conduction noise of the device 1 are superimposed inside the case 5, and noise is radiated between the case 5 and the case 5a. Similarly, the radiation noise and conduction noise of the device 1a are superimposed on the electric wire 6 inside the case 5a, and noise is radiated between the case 5 and the case 5a.

  In the second embodiment, the conductive plate 4 a is attached at a distance “b” from the electric wire 6 and outside the electric wire 6.

  If a structure like the present Example 2 is employ | adopted, the radiation noise from the electric wire 6 will interfere with the conductive plate 4a, will flow through the conductive plate 4a to the case 5 and the case 5a, and will reach a grounding part. Further, radiation noise from the outside is interfered with the conductive plate 4a, flows to the case 5 and the case 5a through the conductive plate 4a, and reaches the grounding portion. As a result, the noise can be shielded by the conductive plate 4a before reaching the electric wire 6, and the device 1 and the device 1a can be protected from the noise.

  If the conductive plates 4 and 4a are attached at a distance b, the radiation noise generated by the device can be reduced easily and effectively without shielding the device 1, the device 1a, and the electric wire 6 completely, and the external radiation noise is shielded. The electromagnetic environment compatibility required by the standards can be realized.

  In the vicinity of the case opening and the connecting wire between the cases for the purpose of radiating noise generated inside the case and electromagnetically shielding the case opening and the connecting wire between the cases where external radiation noise enters By adopting a structure in which the conductive plate 4 is attached to the device, it is possible to easily and effectively electromagnetically shield the device.

  FIG. 3 is a perspective view showing an embodiment 3 of an EMC shield case provided with a radiation noise reducing means for connecting a plurality of devices according to the present invention.

  In the third embodiment, a shield case 16 for mounting the power converter 14 and a shield case 15 for mounting the electronic device 13 for controlling the power converter 14 and other devices are installed on a metal base 17, and the case 15 and the ceiling of the case 16 are fixed to the ceiling metal plate 18, for example, an elevator control device.

  Between the case 15 and the case 16, there is a control cable 19 that connects the control electronic device 13 and the power converter 14. Radiation noise and conduction noise of the power converter 14 and the like are superimposed on the control cable 19 inside the case 16, and noise is radiated to the outside between the case 15 and the case 16. Similarly, radiation noise and conduction noise of the control electronic device 13 and the like are superimposed on the control cable 19 inside the case 15, and noise is radiated to the outside between the case 15 and the case 16.

  The control cable 19 measures the noise radiated to the outside between the case 15 and the case 16, specifies the frequency band exceeding the standard value, determines the length b according to the wavelength of the radiated noise, and controls The conductive plate 4 is attached at a position away from the cable 19 by a distance b and outside the control cable 19. As a result, radiation noise in a frequency band exceeding the standard value is suppressed by being interfered with the conductive plate 4.

  If a structure like this Example 3 is employ | adopted, only by attaching the electrically-conductive board 4, the radiation noise exceeding a standard value can be reduced and it can be adapted to a specification, without shielding a control cable completely. Similarly, external radiation noise having a frequency equal to or higher than the wavelength corresponding to the distance b is shielded by the conductive plate 4 and does not propagate to the control cable 19. Therefore, the control electronic device 13 and the power converter 14 can be protected from external radiation noise.

It is a perspective view which shows Example 1 of the EMC shield case provided with the radiation noise reduction means of the opening part by this invention. It is a perspective view which shows Example 2 of the EMC shield case provided with the radiation noise reduction means of the several apparatus connection part by this invention. It is a perspective view which shows Example 3 of the EMC shield case provided with the radiation noise reduction means of the several apparatus connection part by this invention. It is a perspective view which shows the example of the EMC shield case provided with the radiation noise reduction means of the conventional apparatus single-piece | unit. It is a perspective view which shows the example of the EMC shield case provided with the radiation noise reduction means of the conventional multiple apparatus connection part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a Electric equipment 2 which includes the circuit which radiates | emits or is affected by electromagnetic noise 2 Case 3 with an opening 3 Case opening 4, 4a Conductive plate 5, 5a Shielded case 6 Electric wire 7, 7a Conventional case 8, 8a Door 9, 9a Shield packing 10 Shield wire mesh 11 Shield tube cap 12 Shield tube 13 Control electronics 14 Power converter 15 (Control electronics) Case 16 (Power converter) Case 17 Base 18 Ceiling metal plate 19 Control cable

Claims (3)

In a shield case in which electrical equipment including a circuit that radiates electromagnetic noise or is affected by electromagnetic noise is mounted from the opening,
An EMC shield case characterized in that a conductive plate is stretched across the opening at a distance b (b ≦ λ / 2) that interferes with radiation noise in a specific frequency band from the electrical device, and is fixed to the case. . In a shield case comprising a plurality of devices each including an electric device including a circuit that radiates electromagnetic noise or is affected by electromagnetic noise, and is connected to the inside of the shield case, wherein the electric devices are connected by an electric wire 6,
A conductive plate is stretched around the wiring between the plurality of devices by a distance b (b ≦ λ / 2) that interferes with radiation noise in a specific frequency band from the electrical equipment, and is fixed to the case. EMC shield case characterized by A plurality of devices each including an electric device including a circuit that emits electromagnetic noise or is affected by the electromagnetic noise is mounted inside a shield case, and the electric devices are connected by an electric wire 6. In a shield case partially fixed to each other with a metal plate,
A conductive plate is disposed at a position that is separated from the electrical equipment by a distance b (b ≦ λ / 2) that interferes with radiation noise in a specific frequency band around the wiring between the plurality of devices excluding the fixed portion by the metal plate. An EMC shield case that is stretched and fixed to the case.

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