Vehicle headlamp device

Details Vehicle headlamp device Vehicle headlamp device

2000-02-03

2002-09-03

Husar, Stephen (Department: 2875)

Illumination

Supported by vehicle structure

Condition responsive

C362S464000, C362S466000, C362S467000, C362S276000, C315S079000, C315S081000, C315S082000

Reexamination Certificate

active

06443602

ABSTRACT:

This application claims the benefit of Japanese Application No. 11-052875, filed in Japan on Mar. 1, 1999, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a vehicle lamp system, and more specifically is directed to a vehicle headlamp that uses a discharge lamp and can vary its characteristics depending on the speed and steering angle of the vehicle.
2. Discussion of the Related Art
Conventionally, filament light bulbs have been used as light sources in vehicle headlamp devices. Depending on the light bulb structure, a four-lamp or two-lamp type headlamp device is used.
An example of a four-lamp type headlamp device is shown in FIG.
9
. The four-lamp type headlamp device
1
is equipped with light bulbs
2
and
3
which are installed side by side on both sides of the front part of the vehicle (in
FIG. 9
, only the right-side headlamp device is shown). One of the light bulbs
2
emits a so-called high beam (hereafter referred to as “H beam”), while the other light bulb
3
emits a so-called low beam (hereafter referred to as “L beam”). The respective light bulbs
2
and
3
are accommodated inside a lamp body housing
4
, and are lit by electric power supplied by a lighting device (not shown in FIG.
9
). Furthermore, the light bulbs
2
and
3
are equipped with respective reflective members
2
a
and
3
a,
so that the light emitted by the respective light bulbs
2
and
3
is reflected by the reflective members
2
a
and
3
a,
and directed towards the front of the vehicle.
In the headlamp device
1
described above, only the light bulb
3
is lit when in L beam mode, while both of the light bulbs
2
and
3
are lit when in H beam mode. As a result, the H beam that is emitted towards the front of the vehicle has an increased quantity of light relative to the L beam. Accordingly, a driver can discern the increase in the quantity of light and be confident that light quantity in the forward field of vision is sufficient in H beam mode.
In
FIG. 10
, an example of a two-lamp type headlamp device is shown in which a two-lamp type headlamp device
5
is installed on either side of the front part of a vehicle (only a right side headlamp device
5
is shown in FIG.
10
). Each of these headlamp devices
5
is equipped with only a single light bulb
6
. The light bulb
6
generally has a double-filament structure equipped with two filaments
6
a
and
6
b
for emitting the L beam and H beam, respectively. Furthermore, the light bulb
6
is accommodated inside a lamp body housing
4
, and is equipped with a reflective member
6
c
that directs light towards the front of the vehicle. A lighting device (not shown in
FIG. 10
) supplies electric power to the lamp.
In the headlamp device
5
as described above, power can be switched to the filament
6
a
in the light bulb
6
so that an L beam is emitted from the filament
6
a.
In H beam mode, power is switched to the filament
6
b
so that an H beam is emitted from the filament
6
b.
In the case of a so-called H4 type halogen lamp, which is a lamp commonly used as the light bulb
6
, the lamp is constructed so that 55 W of lamp electric power is consumed by the filament
6
a
in L beam mode, and 60 W of lamp electric power is consumed by the filament
6
b
in H beam mode, at the rated voltage. As a result, the area illuminated by the H beam is larger than that illuminated by the L beam. Accordingly, the quantity of light in the forward field of vision is detectably increased by the 5 W increase in electric power.
In recent years, discharge lamps such as metal halide lamps, etc., which are advantageous in terms of brightness and longevity, etc., have begun to see practical use as light sources in vehicle headlamp devices in place of conventional halogen light bulbs. In the case of the four-lamp type headlamp device
1
, the headlamp can be constructed in the same manner as a headlamp that uses conventional halogen light bulbs, except discharge lamps are used instead of light bulbs
2
and
3
, respectively. It is also possible to change only one of the light bulbs
2
or
3
to a discharge lamp. A headlamp that includes a discharge lamp incorporated into the L beam/H beam switching feature also provides similar operator comfort when switching between the H beam and L beam modes as in the case of halogen lamps.
Because discharge lamps are more expensive than halogen light bulbs, the use of discharge lamps in a two-lamp type headlamp device
5
would make it possible to reduce costs as compared to a four-lamp type headlamp device
1
. However, discharge lamps emit light by means of an “arc light source”, in which it is physically impossible to install two arc light sources, e. g., for H beam and L beam use, inside a single discharge lamp. As shown in
FIG. 11
, a two-lamp type headlamp device
5
using discharge lamps is conventionally constructed so that L beam/H beam switching is accomplished by moving a portion
8
a
of a hood
8
to block direct light from the discharge lamp
7
, or moving the discharge lamp
7
itself. Specifically, in the case of the L beam, a portion
8
a
of the hood
8
is extended as shown in FIG.
11
(A), so that the light-blocking area is expanded. As a result, the light directed towards a reflective member region
9
a
which reflects light into the distance is blocked, and light emitted into the distance (and possibly incident to oncoming vehicles) can be avoided. When H beam mode is desired, the portion
8
a
of the hood
8
is withdrawn as shown in FIG.
11
(B), such that the light-blocking area is contracted. As a result, light is directed onto the region
9
a
of the reflective member
9
and an H beam is emitted into the distance by the reflective member
9
. The discharge lamp
7
is typically a 35 W lamp.
In the two-lamp type headlamp device
5
using a discharge lamp
7
constructed as described above, the quantity of light produced in the H beam mode may be insufficient. In order to compensate for this insufficiency in the quantity of light, an auxiliary reflective part
9
b
is installed outside of region
9
a
of the reflective member
9
, as shown by the dotted line in FIG.
11
.
As shown in
FIG. 12
, light distribution control of lamp illumination in the direction of a vehicle's travel path during cornering is accomplished by distributing a portion of the light beam generated by the headlamp device toward the direction of travel for the vehicle in accordance with the vehicle speed and steering angle. Such light distribution control is accomplished by a reflective member
9
constructed, for example, as shown in FIG.
12
. The reflective member
9
is split into two parts (upper and lower) along a horizontal direction. The lower part
9
c
of the reflective member
9
is fastened in place, while the upper part
9
d
is pivoted about a rotating shaft
9
e.
The system is arranged so that a portion of light is distributed in the direction of vehicle travel by pivoting upper part
9
d
about the rotating shaft
9
e
in accordance with the steering angle. However, in the case of such light distribution control, the illumination of the forward field of vision drops during cornering as a result of the upper part
9
d
pivoting so that a portion of the light from the discharge lamp
7
is distributed, thus resulting in an insufficient quantity of light in the forward direction of the vehicle. Furthermore, when light distribution control is used in a two-lamp type headlamp device
5
using a discharge lamp
7
, L beam/H beam switching is accomplished by means of the discharge lamp
7
equipped with a single arc light source. Accordingly, it is necessary to equip the reflective member
9
with an auxiliary reflective part
9
b
in order to compensate for the insufficient quantity of light in H beam. Consequently, the number of parts is increased such that the cost of manufacturing and the overall size of the headlamp device
5
is increased.
In light of the above points, an object of the invention is to provide a vehicle head

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