Illumination – Supported by vehicle structure – Condition responsive
Reexamination Certificate
1999-08-11
2001-12-25
O'Shea, Sandra (Department: 2875)
Illumination
Supported by vehicle structure
Condition responsive
C362S466000, C701S049000, C701S036000
Reexamination Certificate
active
06332698
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic leveling apparatus which automatically tilts the light axis of a headlamp in such a direction as to offset a pitch angle (an inclination of a vehicle in the longitudinal direction thereof). More particularly, the present invention relates to an automatic leveling apparatus for automatically controlling the alignment of the light axis of the headlamp in a vertical direction on the basis of a pitch angle obtained while the vehicle is stationary.
2. Related Art
A headlamp of this type is built such that, for example, a reflector equipped with a light source is supported on a lamp body so as to be tiltable about a horizontal axis, and such that the light axis of the reflector (headlamp) can be pivoted about the horizontal axis by means of an actuator.
A known automatic leveling apparatus comprises pitch angle detection means and a vehicle speed sensor, both of which are mounted on a vehicle, and a control section for controlling operation of an actuator on the basis of detection signals output from the detection means and the sensor. The light axis of a headlamp (reflector) is controlled so as to constantly remain in a predetermined position relative to the road surface.
Automatic leveling comprises dynamic automatic leveling for constantly effecting an automatic leveling operation either while the vehicle is travelling or stationary, and static automatic leveling for effecting an automatic leveling operation while the vehicle is stationary.
During the dynamic automatic leveling operation, a leveling operation is performed in real time in response to a change in the orientation of a vehicle stemming from acceleration and deceleration during travel, as well as to a change in the weight of the vehicle stemming from loading and unloading of cargo on or from the vehicle during halts. For this reason, the actuator is operated a very large number of times, thus consuming a large amount of power. Further, components constituting a drive mechanism, such as a motor and gears, are required to have great durability, thus adding to cost.
In contrast, the static automatic leveling operation is basically directed toward a leveling operation performed during stoppage of the vehicle. For this reason, a correct pitch angle can easily be detected. Since the number of times the actuator is operated is small, power consumption is correspondingly low. Components constituting a drive mechanism, such as a motor and a gear, do not require great durability. Hence, the conventional automatic leveling apparatus is advantageously inexpensive. Such an automatic leveling apparatus has received attention from the headlamp industry.
When a vehicle stops while facing downhill or such that the wheels on one side of the vehicle are on the curb, the orientation of the vehicle is changed regardless of loads imposed on the vehicle (i.e., the sum of the weights of passengers and cargo). If the automatic leveling operation is carried out while the vehicle is stationary, the light axis of the headlamp may be changed excessively upward or downward, thus resulting in improper leveling.
SUMMARY OF THE INVENTION
The present invention has been conceived in view of the foregoing drawbacks in the related art, and the object of the present invention is to provide an apparatus capable of automatically leveling automobile headlamps by employing, for automatic static leveling, some of the components normally used for automatic dynamic leveling.
To achieve this object, the present invention provides an automobile headlamp automatic leveling apparatus comprising:
a headlamp whose light axis is tilted upward and downward in relation to a vehicle body by means of an actuator;
a control unit for controlling the operation of the actuator;
vehicle speed detection means for detection of the speed of the vehicle; and
pitch angle detection means for detecting a pitch angle of the vehicle, wherein the control unit controls the operation of the actuator on the basis of a detected pitch angle such that the light axis of the headlamp maintains a constant, predetermined angle in relation to the road surface, the apparatus being characterized in that
the control unit controls the operation of the actuator only when the vehicle is stationary and when the vehicle is in a stable traveling state. Accordingly, the number of times the actuator is operated is small, which in turn results in power conservation. Further, the constituent members of a drive mechanism undergo less wear.
During travel, the orientation (i.e., pitch angle) of the vehicle changes frequently. In contrast, the orientation (i.e., pitch angle) of the vehicle while the vehicle is in a stable traveling state is stable and can be readily detected. Further, the pitch angle detected while the vehicle is in a stable traveling state is substantially equal to that obtained while the vehicle is stationary.
Preferably, the control unit controls the operation of the actuator on the basis of the pitch angle obtained while the vehicle is stationary, and in a case where the pitch angle detection means detects a pitch angle while the vehicle is in a stable traveling state, the control unit controls the operation of the actuator in consideration of the thus-detected pitch angle.
Since the pitch angle obtained while the vehicle is in a stable traveling state is taken into consideration, an automatic leveling operation is prevented from being effected on the basis of a false pitch angle obtained while the vehicle is stationary.
Preferably, the control unit controls the operation of the actuator on the basis of the pitch angle obtained while the vehicle is in a stable traveling state in place of the pitch angle obtained while the vehicle is stationary.
As a result, an automatic leveling operation is prevented from being performed on the basis of a false pitch angle obtained while the vehicle is stationary.
Preferably, when a difference between the pitch angle obtained while the vehicle is in a stable traveling state and the pitch angle obtained while the vehicle is stationary exceeds a predetermined value, the control unit controls the operation of the actuator on the basis of the pitch angle obtained while the vehicle is in a stable traveling state in place of the pitch angle obtained while the vehicle is stationary.
A correct pitch angle is detected while the vehicle is stationary rather than while the vehicle is in a stable traveling state. If the pitch angle obtained while the vehicle is in a stable traveling state is analogous to the pitch angle obtained while the vehicle is stationary, the pitch angle obtained while the vehicle is stationary is considered more accurate and is used as control data. If a large difference exists between the pitch angles, the pitch angle obtained while the vehicle is stationary has a great possibility of being in error. Since the pitch angle obtained while the vehicle is in a stable traveling state is used as control data, an automatic leveling operation is prevented from being effected on the basis of the false pitch angle obtained while the vehicle is stationary.
In one preferred mode of the present invention, when a difference between the pitch angle obtained while the vehicle is in a stable traveling state and the pitch angle obtained while the vehicle is stationary exceeds a predetermined value, the operation of the actuator is controlled on the basis of a mean value of pitch angles obtained by the pitch angle detection means at a plurality of times during which the vehicle travels stably, or on the basis of the pitch angle value which most frequently occurs.
If a large difference exists between the pitch angle obtained while the vehicle is stationary and the pitch angle obtained while the vehicle is in a stable traveling state, the pitch angle obtained while the vehicle is in a stable traveling state may be false. Hence, the pitch angle while the vehicle is in a stable traveling state is obtained several additional times, and a mean pitch angle of the thus-detec
Izawa Makoto
Takeuchi Hideaki
Toda Atsushi
Koito Manufacturing Co. Ltd.
Negron Ismael
O'Shea Sandra
Sughrue & Mion, PLLC
LandOfFree
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