Illumination – Supported by vehicle structure – Condition responsive
Reexamination Certificate
2000-11-02
2003-12-16
O'Shea, Sandra (Department: 2875)
Illumination
Supported by vehicle structure
Condition responsive
C362S465000, C362S466000, C362S467000, C362S468000, C362S271000, C362S272000
Reexamination Certificate
active
06663268
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an automatic automotive headlamp leveling device and more particularly to an automatic automotive headlamp leveling device for automatically adjusting the optical axes of the headlamps based on a pitch angle of the vehicle detected generally while the vehicle is not moving.
BACKGROUND OF THE INVENTION
In constructing a headlamp, a reflector in which a light source is securely inserted can be supported tiltably about a horizontal tilting axis relative to a lamp body. The optical axis of the reflector (headlamp) can be tilted about the horizontal tilting axis.
While the vehicle is stationary, a pitch angle of the vehicle may change relative to a reference position when a load is placed in or unloaded from the vehicle or when passengers get in or out of the vehicle. However, in most cases the vehicle lowers both at the front and rear. Because of this, a single vehicle height sensor of a one-sensor system is provided, for example, on a rear suspension to correlate the vehicle height (a vertical distance between a rear axle and the vehicle body) at the rear with the pitch angle of the vehicle. Thus, an approximate straight line, which comprises control data that correlate an output from the vehicle height sensor with the pitch angle of the vehicle, is obtained. The assumption associated with the line is that the front of the vehicle is also lowered. A pitch angle is then calculated based on an output from the vehicle height and the approximate straight line (control data).
As shown in
FIG. 9
, a conventional automatic automotive headlamp leveling device comprises the following: an actuator
102
for vertically tilting an optical axis L of a headlamp
100
relative to the vehicle body for adjustment, a vehicle height sensor
104
provided on a suspension on either the left or right rear wheel for detecting a distance between an axle and the vehicle body, and a control unit
106
. Data from the vehicle height sensor
104
and pitch angles data of the vehicle reside in the control unit
106
as correlation functions (control data that are represented approximately as straight lines). The control data therein are used to calculate a pitch angle of the vehicle based on an output from the vehicle height sensor
104
. The actuator
102
is controlled by an amount corresponding to the calculated pitch angle.
When A static load that acts on the vehicle is changed, the vehicle height sensor
104
detects and sends the change to the control unit
106
. The control unit
106
calculates a vehicle pitch angle based on the correlation function that correlates vehicle height sensor outputs with vehicle pitch angles that are already entered and set in the unit
106
. The unit
106
also drives the actuator
102
(tilts the optical axis about the horizontal tilting axis) by an amount corresponding to the calculated vehicle pitch angle and adjusts the optical axis L of the headlamp
100
such that the optical axis stays in a predetermined inclined or tilted angle relative to the road surface at all times.
In a two sensor system, a vehicle height sensor is provided on the front and rear suspensions, respectively. The control unit
106
calculates a vehicle pitch angle from &THgr;=tan
−1
(h/D), where &THgr; is the vehicle pitch angle, h (=H
1
−H
2
) is the difference between the output H
1
from the front vehicle height sensor and the output H
2
from the rear vehicle height sensor, and D is the distance corresponding to the wheel base of the vehicle.
With the conventional automatic headlamps leveling device described above, the vehicle pitch angle is set to 0 when only the driver is in the vehicle. Also the optical axis L is inclined to a predetermined angle relative to the road surface when the actuator
102
(a longitudinal driving member thereof) is positioned at a front-most end position P
1
. Since the vehicle pitch angle (the optical axis of the headlamp) changes upwardly only when the static load of the vehicle increases because of, for example, additional passengers, the optical axis of the headlamp only has to be tilted downwardly for adjustment. Therefore, the actuator (the longitudinal driving member thereof) is constructed to move only rearwardly where the front-most end position P
1
is set as the initial position. The driving of the actuator is controlled on the assumption that the front-most end position P
1
of the longitudinal stroke of the actuator coincides with the initial position P
0
at which the vehicle pitch angle is 0. Note that reference numeral P
2
denotes a rear-most end position of the longitudinal stroke of the actuator.
However, the front-most end position of the actuator may not necessarily match the initial position PO because of vehicle assembling error, mounting error of the vehicle height sensor on the suspension, or output voltage-related error of the vehicle height sensor itself (hereinafter, these errors are referred to in general as the mounting errors of a vehicle height sensor or the like). If the optical axis L is adjusted to a proper position L
0
by tilting the reflector using the aiming mechanism
108
, the assembling error of the mounting errors of the vehicle height sensor or the like can be corrected. However, offer errors such as errors associated with the mounting of vehicle height sensor to the suspension or the output voltage-related error of the vehicle height sensor itself (hereinafter, referred to as the mounting tolerance of the vehicle height sensor itself) remain uncorrected.
FIG. 10
shows a case where the signal voltage of the vehicle height sensor is offset in a direction in which the optical axis is raised (V
1
→V
0
) because of the mounting tolerance of the vehicle height sensor. The same figure shows the optical axis position at which the vehicle pitch angle is zero (0) when only the driver is in the vehicle. This position corresponds to a position P
0
, which is further ahead of the front-most end position P
1
of the longitudinal stroke of the actuator. Even if the optical axis is adjusted to the proper position L
0
using the aiming mechanism
108
, the positional relationship between the front-most end position P
1
of the longitudinal stroke of the actuator and the initial position P
0
of the vehicle pitch angle &THgr; remains unchanged. The issue of the mounting tolerance of the vehicle height sensor itself still exists. Therefore, between signal voltages V
0
and V
1
of the vehicle height sensor, the optical axis always constitutes a dead zone corresponding to the front-most position P
1
of the actuator, preventing the proper leveling of the headlamp.
The actuator is constructed such that it operates only in the direction in which the optical axis is lowered. However, since the front-most end position P
1
of the longitudinal stroke of the actuator is not properly set (the front-most end position P
1
of the longitudinal stroke of the actuator does not coincide with the initial position P
0
) when the rear of the vehicle is lowered, a dead zone is produced while signal voltages V
0
to V
1
of the vehicle height sensor are outputted. Thus, the pulling-in operation of the actuator is interrupted. Because of this, an operation of lowering the optical axis is started after the optical axis is tilted upward by an angle &Dgr;&THgr;′ corresponding to the mounting tolerance of the vehicle height sensor, which is an angle corresponding to the signal voltages V
0
to V
1
of the vehicle height sensor. Hence, the driver of a on-coming vehicle may suffer from glaring lights.
The present invention was made in view of the problem described above. An object of the present invention is to provide an automatic automotive headlamp leveling device for enabling a highly accurate optical axis correction by controlling the driving of an actuator without being affected by the mounting tolerance of the vehicle height sensor.
SUMMARY OF THE INVENTION
To attain the above object, according to a first embodiment of the invention, there is provided an automat
Takeuchi Hideaki
Toda Atsushi
Koito Manufacturing Co. Ltd.
O'Shea Sandra
Tsidulko Mark
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