Illumination – Supported by vehicle structure – Projection-type headlamp
Reexamination Certificate
1998-09-24
2001-01-23
Tso, Laura K. (Department: 2875)
Illumination
Supported by vehicle structure
Projection-type headlamp
C362S538000, C362S265000
Reexamination Certificate
active
06176604
ABSTRACT:
The present invention relates in general manner to motor vehicle headlights fitted with discharge lamps.
BACKGROUND OF THE INVENTION
Discharge lamps, in particular of the metal halide type (typically sodium iodide), are being used more and more frequently as light sources in such headlights.
They benefit from the considerable advantage of being capable, for comparable power consumption, of supplying light of an intensity that is considerably greater than that of conventional halogen filament lamps.
Nevertheless, a discharge lamp suffers from the drawback of generating, at the arc, electromagnetic fields which give rise to severe problems concerning electromagnetic compatibility requirements, both in transmission and in reception, as are generally laid down in specifications. In this respect, it may be observed that because of the increasing use of electronic circuits to perform various safety functions on board a vehicle, these requirements are nowadays becoming more and more severe.
Dispositions do indeed exist for providing a discharge lamp and its power supply circuits with as much shielding as possible, however such dispositions are generally incompatible with the environment specific to a motor vehicle headlight. Thus, for example, it is not possible to place the entire headlight in a Faraday cage that surrounds it completely since it is necessary to leave free the region where the light is delivered through the glass.
Document DE 197 03 233 A discloses a motor vehicle headlight which, to shield a discharge lamp, comprises in particular a shielding plate (
14
) mounted on the housing of the headlight behind the mirror which receives the discharge lamp so as to minimize disturbances in a backwards direction. That plate extends freely in the inside volume of the housing between the housing and the mirror.
That solution nevertheless presents certain drawbacks. Firstly, it makes the headlight more complicated to assemble since it is necessary to put the plate into place and to fix it to the housing before mounting the reflector. In addition, the simplified figures of that document (in particular
FIGS. 3 and 4
) do not show details such as the means for mounting the mirror in the housing, or the means for manually or automatically adjusting the orientation of the mirror to determine the position of the light beam, etc.
FIG. 5
, which does show that kind of detail, does not show the rear shielding plate. It will be understood that implementing said shielding plate simultaneously with the above-mentioned means is difficult and runs the risks of requiring the size of the headlight to be increased and/or of leaving places where there are gaps in the shielding plate, thereby degrading the quality of the shielding.
In addition, the plate described in that document must possess a relatively large central opening for access to the lamp, so the rear cap (
7
) of the headlight must be metallized to provide full shielding, which further increases cost price and can be difficult to do if the cap is a flexible cap made of elastomer or the like.
OBECTS AND SUMMARY OF THE INVENTION
The present invention seeks to provide a motor vehicle headlight fitted with a discharge lamp and with improved shielding means, particularly at the arc of the lamp, which means are simple in structure and in implementation, and which headlight does not have the above-mentioned drawbacks.
To this end, the invention provides a motor vehicle headlight comprising a mirror in which a discharge lamp is mounted, a mask placed in front of the lamp, and a shielding plate of conductive material extending behind the mirror, the mask being made of conductive material and being connected to a fixed potential to capture the parasitic electromagnetic fields emitted forwards from the lamp, wherein the shielding plate is constituted by a cover extending behind and along the mirror and connected to said fixed potential.
Preferred, but non-limiting features of the headlight of the invention are the following:
the shielding cover is dimensioned so as to cover substantially all of the solid angle centered on the arc of the lamp that is not covered by the mask;
said cover is constituted by a conducive metal sheet pressed against the back of the mirror;
said cover is made by applying a coating to the rear face of the mirror;
said cover is incorporated in the mirror, the mirror being made by being overmolded on the cover;
the headlight includes an electrical link element fixed behind the mirror in the vicinity of the lamp, having said cover and said mask electrically connected thereto, and being itself electrically connected to vehicle ground;
a lamp retaining means is mounted on said link element;
the headlight further includes a high voltage connector for powering the lamp, and said connector includes at least one conductor element suitable for coming into contact with said link element when the connector is put into place;
said link element is connected to vehicle ground via at least one conductive element and via shielding of a lamp power supply cable which is connected to the connector;
the headlight further includes a generally annular conductive element situated in a gap between the connector and a collar of the lamp;
said conductive element is flexible;
said conductive element is connected to the cover by a tab integrally formed with said cover; and
the mask is electrically connected to the cover via at least one conductive mounting tab of said mask.
REFERENCES:
patent: 4774636 (1988-09-01), Gaugel et al.
patent: 4893218 (1990-01-01), Dilk et al.
patent: 4920459 (1990-04-01), Rothwell, Jr. et al.
patent: 4926301 (1990-05-01), Liverance et al.
patent: 5132881 (1992-07-01), Wakimizu et al.
patent: 5584559 (1996-12-01), Toda
patent: 5607228 (1997-03-01), Ozaki et al.
patent: 5879073 (1999-03-01), Hori et al.
patent: 5895113 (1999-04-01), Ozaki et al.
patent: 197 03 233 (1997-07-01), None
French Search Report dated Jun. 5, 1998.
Billot G{acute over (e)}rard
Dubrovin Alexis
Morgan & Finnegan L.L.P.
Tso Laura K.
Valeo Vision
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