Vehicular headlamp having improved low-beam pattern

Details Vehicular headlamp having improved low-beam pattern Vehicular headlamp having improved low-beam pattern

2003-03-10

2004-11-30

Cariaso, Alan (Department: 2875)

Illumination

Supported by vehicle structure

Light modifier

C362S297000, C362S346000

Reexamination Certificate

active

06824301

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISK APPENDIX
Not applicable
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular headlamp which produces a low-beam light distribution pattern having a horizontal cut-off line and an oblique cut-off line.
As a low-beam light distribution pattern for a vehicular headlamp, as shown in
FIG. 10
, a light distribution pattern P (L) having a horizontal cut-off line CL
1
and an oblique cut-off line CL
2
has been employed in many cases. In the low-beam light distribution pattern P (L), the horizontal cut-offline CL
1
is arranged to fall on an opposite (oncoming) lane side and the oblique cut-off line CL
2
, which extends obliquely upward from the horizontal cut-off line CL
1
, is arranged to fall in the lane in which the vehicle is traveling so as to assure front visibility for the driver of the vehicle while preventing glare for the drivers of oncoming vehicles.
In order to obtain the desired low-beam light distribution pattern P (L), a conventional vehicular headlamp is configured such that a light source
2
is provided substantially coaxially with a lamp optical axis Ax extending in the longitudinal direction of the vehicle, and light from the light source
2
is directed to strike the reflecting surface
4
a
of a reflector
4
so as to form the cut-off lines CL
1
, CL
2
from light which is reflected from reflecting zones
4
a
1
,
4
a
2
that are on right and left sides, respectively, of the lamp optical axis Ax.
In the low-beam light distribution pattern P (L), a hot zone (area of high-intensity light) HZ is formed in an area in the vicinity of the left side of an elbow point E (an intersecting point of the cut-off line CL
1
and the cut-off line CL
2
) thereof. The hot zone HZ is mainly formed by light reflected from an area close to the periphery of the reflecting zone
4
a
2
.
A zone D shown by dashed lines in
FIG. 10
is a zone where light does not strike the reflector due to the light blocking action of an inner shade
6
positioned directly below the light source
2
. Also, a light distribution pattern Po (L) shown by a chain double-dashed line in
FIG. 10
is a basic light distribution pattern which occurs if the reflecting surface
4
a
is constituted by a paraboloid of revolution whose central axis is the lamp optical axis Ax.
However, in the conventional vehicular headlamp, as shown in
FIG. 11
, if the height of the reflector
4
is reduced, the following problem arises.
The horizontal cut-off line CL
1
is formed as a reverse image of a horizontal cut-off line L
1
of the lower end edge of the reflecting zone
4
a
1
, and the oblique cut-off line CL
2
is formed as a reverse image of an oblique line L
2
of the lower end edge of the reflecting zone
4
a
2
. If the height of the reflector
4
is reduced beyond a certain amount, the oblique line L
2
falls below the lower end edge of the reflecting surface
4
a.
Accordingly, there arises a problem that the amount of light in the hot zone HZ becomes insufficient, and distant visibility in the traveling lane cannot be sufficiently assured.
BRIEF SUMMARY OF THE INVENTION
The present invention was made in consideration of these circumstances. It is an object of the present invention to provide a vehicular headlamp which produces a low-beam light distribution pattern having a horizontal cut-off line and an oblique cut-off-line, and which enhances the distant visibility in the traveling lane by assuring a sufficient amount of light in the hot zone even when the height of the reflector is small.
The present invention achieves this object by the design of the reflecting surface of the reflector.
More specifically, a vehicular headlamp according to the present invention includes a light source positioned coaxially with a lamp optical axis extending in the longitudinal direction of the vehicle on which the headlamp is mounted, and a reflector having a reflecting surface that reflects light from the light source forward and which provides a low-beam light distribution pattern having a horizontal cut-off line and an oblique cut-off line. In accordance with the invention, the reflecting surface has first reflecting zones which reflect light so as to form the horizontal cut-off line, and second reflecting zones which reflect light so as to form the oblique cut-off line. The second reflecting zones are provided at two positions on right and left sides of the lamp optical axis, arranged diagonally with respect to the lamp optical axis, and the first reflecting zones are provided at two positions on right and left sides which are closer to the periphery of the reflector than the second reflecting zones.
The light source, which is configured as part of a light source bulb, is not limited as long as the light source is mounted substantially coaxially with the lamp optical axis. For example, a filament such as that of a halogen bulb, a discharge light source of a discharge bulb, or the like can be employed. The light source bulb in some embodiments may include light blocking means, for example, an inner shade, a light blocking film or the like, for blocking part of the light directed from the light source to the reflecting surface of the reflector.
The second reflecting zones are not limited in size, outline, shape or the like as long as the second reflecting zones are provided at two positions on right and left sides of the lamp optical axis which are diagonally positioned with respect to the lamp optical axis.
The first reflecting zones are also not limited in size, outline, shape or the like as long as the first reflecting zones are provided at two positions on right and left sides which are closer to the periphery of the reflector than the second reflecting zones.
As described above, the vehicular headlamp according to the present invention provides a low-beam light distribution pattern having a horizontal cut-off line and an oblique cut-off line. The reflecting surface of the reflector has first reflecting zones which reflect light so as to form a horizontal cut-off line, and second reflecting zones which reflect light so as to form an oblique cut-off line. The second reflecting zones are provided at two positions on right and left sides of the lamp optical axis which are arranged diagonally with respect to the lamp optical axis, and the first reflecting zones are provided at two positions on right and left sides which are closer to the periphery of the reflector than the second reflecting zones. With this headlamp, the following actions and effects are obtained.
Since the second reflecting zones are provided at two positions on right and left sides of the lamp optical axis which are arranged diagonally with respect to the lamp optical axis, the amount of light in the hot zone is increased by superimposing the light distribution patterns which are formed by the light reflected from these two second reflecting zones at the two positions.
Therefore, even if the height of the reflector is small and the oblique line which is formed as a reverse image of the oblique cut-off line falls below the lower end edge of the reflecting surface, the amount of light in the hot zone is nevertheless sufficient.
Also, since the first reflecting zone is provided at two positions on right and left sides which are closer to the periphery of the headlamp than the second reflecting zones, even with the second reflecting zones provided at two positions on right and left sides of the lamp optical axis which are arranged diagonally with respect to the lamp optical axis, the desired horizontal cut-off line can be formed.
According to the inventive vehicular headlamp which provides a low-beam light distribution pattern having a horizontal cut-off line and an oblique cut-off line, even if the height of the reflector is small, distant visibility in the traveling lane is enhanced by assuring a sufficient amount of light in the

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