Illumination – Light modifier – Translucent or opaque
Reexamination Certificate
2000-05-19
2002-03-12
O'Shea, Sandra (Department: 2875)
Illumination
Light modifier
Translucent or opaque
C362S303000, C362S343000, C362S522000, C362S529000, C362S539000, C362S523000, C362S518000
Reexamination Certificate
active
06354718
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a vehicular headlamp having a light source bulb of the “H4” type.
BACKGROUND OF THE INVENTION
Many conventional vehicular headlamps employ a low-beam light distribution pattern P′ as shown in
FIG. 10
, which has a horizontal cut-off line CL
1
′ and a diagonal cut-off line CL
2
′ rising from the horizontal cut-off line CL
1
′ at an angle of 15°. In this low-beam light distribution pattern P′, the horizontal cut-off line CL
1
′ is arranged on the side of the oncoming lane and the diagonal cut-off line CL
2
′ is arranged on the side of the is lane in which the vehicle is traveling, whereby forward visibility for the driver is ensured while preventing the vision of drivers of oncoming vehicles from being dazzled by glare.
To obtain such a low-beam light distribution pattern, a light source bulb of the H4 type is often employed, which has a longitudinally extending filament
18
a
and a shade
18
c
covering the filament
18
a
around its axis at a central angle of approximately 165° so that light beams emitted from the filament
18
a
in the downward direction are blocked. Due to the light-blocking effect of the shade
18
c
, light from the filament
18
a
does not impinge on a lower zone of a reflecting surface indicated by broken lines in FIG.
10
.
In a vehicular headlamp designed to obtain the low-beam light distribution pattern described above, vertical aiming (beam adjustment) is carried out in the low-beam mode of the headlamp with respect to the horizontal cut-off line CL
1
′. For this reason, the contrast in luminosity of the horizontal cut-off line CL
1
′ should be sufficiently enhanced.
However, if the contrast in luminosity of the horizontal cut-off line CL
1
′ is enhanced excessively, long-distance visibility tends to decrease to such an extent that the driver may experience difficulty in driving in situations where the road ahead suddenly becomes dark, for example, in a case where the vehicle is approaching a flat road at the end of the descent of a slope. Also, even if the horizontal cut-off line CL
1
′ is slightly displaced upwards or downwards due to pitching of the vehicle or the like, there is a concern that oncoming drivers could be dazzled by glare.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of such circumstances. It is an object of the present invention to provide a vehicular headlamp employing an H4 type light source bulb and which is capable of providing a low-beam light distribution pattern which makes it easy for a driver to drive and reduces the possibility of oncoming drivers being dazzled by glare.
The present invention achieves the above-stated object by the provision of an improved structure for securely supporting a light source bulb on a reflector, and by providing the reflector or a front lens with a suitable downward deflective reflection zone or a downward deflective transmission zone.
More specifically, a vehicular headlamp according to a first aspect of the present invention includes a light source bulb having a longitudinally extending filament and a shade covering the filament around its longitudinal axis at a central angle of approximately 165° so that light traveling downward from the filament is blocked, a reflector securely supporting the light source bulb and having a reflecting surface forwardly reflecting light from the filament, and a front lens disposed forwardly of the reflector. The light source bulb is securely supported by the reflector so that left and right upper edges of the shade are at substantially the same height and the longitudinal axis of the filament is offset upward from the optical axis of the reflector at a predetermined angle. The reflecting surface of the reflector is provided with a downward deflective reflection zone which deflects downward and reflects light that has traveled from the filament past the vicinity of the upper edges of the shade and impinges on a traveling-lane-side reflection zone of the reflecting surface.
A vehicular headlamp according to a second aspect of the present invention includes a light source bulb having a longitudinally extending filament and a shade covering the filament around its axis at a central angle of approximately 165° so that light beam traveling downward from the filament is blocked, a reflector securely supporting the light source bulb and having a reflecting surface forwardly reflecting light beam from the filament, and a front lens disposed forwardly of the reflector. The light source bulb is securely supported by the reflector so that left and right upper edges of the shade are at substantially the same height and the longitudinal axis of the filament is offset upward from the optical axis of the reflector at a predetermined angle. The front lens is provided with a downward deflective transmission zone which downwardly deflects and transmits light that has traveled from the filament past the vicinity of the upper edges of the shade and impinges on a traveling-lane-side reflection zone of the reflecting surface.
The aforementioned “predetermined angle” means an angle is required to transform a generally sectorial light distribution pattern formed of light beams reflected from the reflecting surface of the reflector to a pattern where a pair of left and right cut-off lines constituting upper edges of the pattern at a central angle of approximately 195° are both substantially horizontal, under the condition that the reflecting surface is a paraboloid of revolution extending around the optical axis of the reflector.
In the above-described vehicular headlamp of the present invention which has the light source bulb securely supported by the reflector so that the left and right upper edges of the shade are located at substantially the same height and that the longitudinal axis of the filament is offset upward from the optical axis of the reflector at the predetermined angle, under the condition that the reflecting surface of the reflector is a paraboloid of revolution extending around the optical axis of the reflector, a low-beam light distribution pattern is obtained which has horizontal cut-off lines formed of light beams reflected from the reflecting surface on laterally opposed sides of a vertical line perpendicular to the reference axis of the lighting fixture, hereinafter referred to as “line V”.
In addition, with the reflecting surface of the reflector provided with the downward deflective reflection zone which downwardly deflects and reflects light that has traveled from the filament past the vicinity of the upper edges of the shade and impinges on the traveling-lane-side reflection zone of the reflecting surface, the front lens is provided with the downward deflective transmission zone which downwardly deflects and transmits light that has traveled from the filament past the vicinity of the upper edges of the shade and impinges on the traveling-lane-side reflection zone of the reflecting surface. Thus, in the aforementioned low-beam light distribution pattern, the oncoming-lane-side horizontal cut-off line formed of light reflected from the traveling-lane-side reflection zone is at a lower level than the traveling-lane-side horizontal cut-off line formed of light reflected from the oncoming-lane-side reflection zone.
In such a low-beam light distribution pattern, since vertical aiming can be carried out with respect to the traveling-lane-side horizontal cut-off line, the contrast in luminosity of the oncoming-lane-side horizontal cut-off line can be reduced.
This prevents long-distance visibility from being reduced when the road ahead of the vehicle suddenly darkens, for example, when the vehicle approaches a flat road after having traveled down a slope. As long as the horizontal cut-off line is just slightly displaced upward or downward due to pitching of the vehicle or the like, the luminosity of the upward light beams can be prevented from reaching a high level. Hence, the possibility of oncoming drivers be
Iwaki Takayuki
Takada Kenichi
Alavi Ali
Koito Manufacturing Co. Ltd.
O'Shea Sandra
LandOfFree
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