Vehicle headlamp

Details Vehicle headlamp Vehicle headlamp

2000-01-11

2001-09-11

Cariaso, Alan (Department: 2875)

Illumination

Supported by vehicle structure

Light modifier

C362S284000, C362S324000

Reexamination Certificate

active

06286985

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a vehicle headlamp arranged so as to switch beams between low and high beams by moving a shade.
2. Description of the Related Art
Vehicle headlamps are normally designed to send out low and high beams by making a reflector reflect light from a light source bulb forward. However, a difference in the light distribution pattern between the low and high beams required has made it customary to employ different light sources (discharge light emitting parts or filaments). However, vehicle headlamps using a single light source are also well known; in the case of a two-lamp type headlamp using a discharge bulb as a light source in particular, the single light source will have to be used very often.
In such a vehicle headlamp using a single light source, switching between low and high beams is conducted by the mechanical displacement of an optical element such as a light source, a reflector, a shade or the like. With respect to the vehicle headlamp shown in
FIG. 8
in which beam switching is conducted by moving a shade, for example, a known arrangement is to longitudinally pivot a shade
2
around a longitudinal axis extending in the lateral direction.
In this vehicle headlamp, a light distribution pattern for the low beam is formed by shading part of light incident on the reflective surface
6
a
of a reflector
6
from a light source bulb
4
when the shade
2
is positioned as shown by a solid line in
FIG. 8
, whereas a light distribution pattern for the high beam is formed by reducing the shading quantity of light incident on the reflective surface
6
a
by the shade
2
when the shade
2
is pivoted forward and positioned as shown by a chain double-dashed line therein.
When the beam switching is conducted by mechanically driving the shade
2
as mentioned above, however, the shade
2
tends to produce a backlash in the low- or high-beam forming position because the clearance or backlash is inevitably produced in the mechanical coupling portion. If this sort of backlash occurs, the shade
2
will deflect (generate minute vibrations) because of vibrations during the travel of a vehicle and this may vary the area of the reflective surface
6
a
shielded by the shade
2
. Therefore, the problem is that a light distribution pattern different from the intended light distribution pattern is formed in both cases of low and high beams.
SUMMARY OF THE INVENTION
An object of the present invention was made in view of the situation above to provide a vehicle headlamp arranged so as to switch beams between low and high beams by moving a shade whereby to prevent its light distribution pattern from deviating from the intended light distribution pattern caused by deflection of the shade.
The above object of the present invention is accomplished by arranging a predetermined displacement regulating means.
According to the present invention, a vehicle headlamp comprises: a light source bulb, a reflector having a reflective surface for emitting a predetermined beam forward by reflecting light from the light source bulb, a shade capable of shading part of light incident on the reflective surface from the light source bulb, and a beam switching device for selectively switching beams between low and high beams by moving the shade between two positions where the amount of shielding the shade relative to light incident on the reflective surface has different values, and is characterized in that
displacement regulating member is provided so as to regulate the displacement of the shade from the position by making contact with the shade while the shade is located in one of low- and high-beam forming positions.
The aforementioned ‘light source bulb’ is not limited to a specific kind of light source bulb but may be a halogen lamp, a discharge bulb or the like that is adoptable.
The aforementioned ‘beam switching device’ is not limited to a specific form as long as the shade is made movable between the two positions. For example, its driving source may be a solenoid, a motor or the like that is adoptable. Further, the power transmission mechanism may be a link mechanism, a gear train or the like that is also adoptable.
The aforementioned ‘displacement regulating member’ is not limited to a specific form as long as it is capable of regulating the displacement of the shade by contact with the shade located in the low- or high-beam forming positions.
With the arrangement above, though the vehicle headlamp according to the present invention is so constructed as to switch beams between the low and high beams by moving the shade, the displacement of the shade is regulated by bringing the displacement regulating member in contact with the shade located in the low- or high-beam forming position. The backlash of the shade located in the low- or high-beam forming position can thus be prevented whereby to prevent its light distribution pattern from deviating from the intended light distribution pattern.
The aforementioned ‘displacement regulating member’ may be such that it is brought into contact with the shade in one of the low- and high-beam forming positions. However, the light distribution pattern is prevented from deviating from the intended light distribution pattern in both cases of low and high beams on condition that the displacement regulating member is allowed to contact the shade in both positions.
Although the ‘beam switching device’ is not limited to a specific form as mentioned above, the provision of the beam switching device includes a solenoid and an elastic member for urging the movable iron core of the solenoid toward a non-excitation position, wherein the low beam is switched to the high beam by exciting the movable iron core and wherein the high beam is switched to the low beam by releasing the movable iron core from being excited ensures beams switching with a simple construction. Moreover, the elastic member may be utilized as part of means for regulating displacement in the direction of moving the shade located in the low-beam forming position by allowing the urging force for urging the movable iron core toward the non-excitation position to remain in the elastic member even when the shade is located in the low-beam forming position.
With the arrangement above, though the direction of moving the shade at the time of beam switching is not specifically restricted, the area of the reflective surface shielded by the shade can be varied with a small shade movement by pivoting the shade longitudinally so as to switch the beams. Consequently, it is possible to switch the beams efficiently and to arrange a simple power transmission mechanism in the beam switching device.
Although the ‘displacement regulating member’ is not limited to a specific form as mentioned above, since the area of the reflective surface shielded by the shade will vary greatly if the shade is deflected longitudinally because of vibrations during the travel of a vehicle, the displacement regulating member preferably has a low- or high-beam longitudinal displacement regulating structure for regulating the longitudinal displacement of the shade located in the low- or high-beam forming position. In the case of the low beam in particular, such an arrangement as mentioned above is very effective as the longitudinal deflection of the shade directly affects an increase or a decrease in the glare.
On the other hand, the lateral deflection of the shade affects the light distribution less than the longitudinal deflection thereof and the displacement regulating member preferably has a lateral displacement regulating structure for regulating the lateral displacement of the shade located in one of the low- or high-beam forming positions in view of ensuring light distribution performance, as well as preventing the shade from being damaged.
In this case, while the aforementioned lateral displacement regulating structure may be intended to regulate the lateral displacement of the shade located in one of the low- and highbeam forming positions, the lateral displacement r

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