Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Patent
1993-03-18
1995-02-21
Picard, Leo P.
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
361765, 361748, 361816, 174 35R, 174524, 257668, H05K 900
Patent
active
053921976
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an electric device and, more particularly, to a switching and control device for a motor vehicle. Such known devices have a printed circuit board or conductor foil on which an electronic circuit is arranged. The assembled printed circuit board is accommodated in a housing to protect the circuit and/or its components against mechanical damage and various environmental influences. Particularly when such switching or control devices are used in motor vehicles the protective functions of the housing depend on the installation location and include, for example, protection against moisture, dust and mechanical damage. Also, these housings often serve as shielding or to improve electromagnetic compatibility.
Costly sealing means are required for protecting the circuit and its components, particularly against dust and especially against moisture. For this purpose, structural component parts of the housings are usually outfitted with depressions or grooves in which corresponding seals or sealing rings are inserted. Also, such switching or control devices must be provided with costly pressure equalization members or measures to compensate for fluctuations in pressure brought about by changes in temperature. However, the transporting of moisture must be prevented in this pressure compensation. Construction costs for such switching or control devices are accordingly high and such devices are therefore expensive.
SUMMARY OF THE INVENTION
According to the invention, the electric device comprises a housing; at least one printed circuit board arranged in the housing and carrying an electronic circuit; and at least one covering means for protecting the electronic circuit against moisture arranged in the housing.
The electric device, according to the invention, claim has the advantage over the prior art that a reliable protection of the printed circuit board or conductor foil and the circuit components against dust and especially against moisture is ensured in a simple and inexpensive manner. Moreover, in an advantageous embodiment of the invention it is also possible to achieve pressure compensation, e.g. during fluctuating temperatures, in a simple and inexpensive manner.
Several embodiments of the electric device according to the invention are possible. In one embodiment there is a single printed circuit board in the housing and an upper side of the printed circuit board is protected by one covering means and an underside of the printed circuit board is protected by another covering means so that all conductor paths and electronic components of the electronic circuit on the circuit board are protected against moisture by both covering means. A throughgoing duct is formed in the printed circuit board between the upper side and the underside of it to connect the spaces between the printed circuit board and the covering means so as to equalize pressure.
The covering means is advantageously a plastic cover impermeable to moisture. Alternatively it can comprise a plurality of plastic molded parts connected with the printed circuit board so as to tightly seal it against moisture. The housing can correspondingly be assembled from two parts.
In a preferred embodiment the covering means is at least partially permeable to air.
The housing can be at least partially metallic and the covering means can include insulating means for insulating the printed circuit board from the housing.
The covering means can be made electrically conductive by at least partially coating with an electrically conductive coating, advantageously electrically connected with the electronic circuit.
BRIEF DESCRIPTION OF THE DRAWING
The objects, features and advantages of the present invention will now be illustrated in more detail by the following detailed description, reference being made to the accompanying drawing in which:
The sole FIGURE is a longitudinal cross-sectional view through an electric device according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The electric switching
REFERENCES:
patent: 4661888 (1987-04-01), Jewell
Cuntz Harald
Karr Dieter
Rau Martin
Picard Leo P.
Robert & Bosch GmbH
Striker Michael J.
Whang Young
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