Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2000-08-21
2002-08-06
Hilten, John S. (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C362S465000
Reexamination Certificate
active
06430521
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a vehicle headlamp leveling device for estimating a pitch angles of a vehicle in its longitudinal direction and automatically tilting the axes of headlamps to cancel the pitch angle.
BACKGROUND OF THE INVENTION
In a headlamp, a reflector, in which a light source is securely inserted, is tilted around a horizontal tilting shaft relative to the body of the headlamp. The optical light axis of the reflector (or the headlamp) is arranged to be tilted by an actuator around the horizontal tilting shaft.
When luggage is loaded in or unloaded from the vehicle or occupants in the vehicle get in or out while the vehicle is at a stop or stationary, the load acting on the vehicle changes and the pitch angle of the vehicle may change. However, in most cases, both the front and the rear of the vehicle sinks or is lowered. When a vehicle height at the rear (a distance between the axle and the body) detected with a vehicle height sensor provided on a rear suspension and a pitch angle are correlated, an approximate line can be estimated, with the assumption that the front of the vehicle is lowered. Then, a pitch angle can be calculated based on an output from the vehicle sensor and the estimated approximate line.
A conventional vehicle headlamp leveling device comprises a vehicle height sensor provided on either the left or right suspension of either the front or rear of the vehicle for detecting a distance between the axle and the body, a storage part in which a correlation function (an approximate line) between outputs from the vehicle height sensor and pitch angles of the vehicle is entered and set as control data, and an operation control part for controlling the driving of actuators based on an output from the vehicle height sensor. The control data (the approximate line) is stored in the storage part such that a predetermined inclined state of the optical light axes of the headlamps is maintained relative to a road surface.
When a load on the vehicle changes, the vehicle height sensor detects the change and outputs the change to the operation control part. The operation control part then calculates a vehicle pitch angle corresponding to the output from the vehicle height sensor based on the correlation function (the approximate line which is entered and set in advance) between outputs from the vehicle height sensor and pitch angles of the vehicle. The control part then drives the actuators (tilts the optical light axes of the headlamps) only to an extent corresponding to the calculated pitch angle.
The correlation function between outputs from the vehicle height sensor and pitch angles of the vehicle, which is stored in the storage part in advance, is specified by a single approximate line with the assumption that the vehicle is lowered also at the front. However, if luggage is put into a protruding section of the vehicle such as a trunk, the front of the vehicles rises (or lowers less) compare to the rear, and the actual pitch angle deviates far from the approximate line. Hence, an appropriate pitch angle of the vehicle cannot be obtained, and the headlamps cannot be appropriately leveled.
FIG. 2
is a chart showing a correlation between outputs from the vehicle height sensor (abscissa) and pitch angles of the vehicle (ordinate). D denotes that the driver is seated in the driver's seat, P denotes that the front passenger is seated in the front passenger seat, R denotes that a rear seat passenger is seated in the rear seat, and L denotes that luggage is loaded in the loading space such as a trunk (for example, a load of 100 kg). For example, DPR shows data taken when the driver, front sea passenger and rear seat passenger are seated in their respective seats. DPRRL shows data taken when the driver, front seat passenger and two rear seat passengers are seated in the respective seats with luggage loaded in the loading space to its given or maximum loading capacity. Furthermore, full loading (DPRRRL) shows data taken when the driver, front seat passenger and three rear seat passengers are seated in the respective seats with luggage loaded in the luggage space to its maximum loading capacity. Full loading (D) shows data taken when only the driver is seated in the driver's seat with luggage loaded to the maximum loading capacity.
In the conventional automatic headlamps leveling device, the correlation between outputs from the vehicle height sensor and pitch angles of the vehicle is specified by an approximate line (linear) designated by reference character A for use as control data, with the assumption that the front of the vehicle is lowered.
Although the correlation between outputs from the vehicle height sensor and pitch angles of the vehicle shows a characteristic of increasing linearly as shown in
FIG. 2
, there is variation of data in the direction of the ordinate axis. If the output from the vehicle height sensor shows −2 mm, the operation control part calculates an angle of 0.45 degree as the posture (the pitch angle) of the vehicle. This angle corresponds to an output of the vehicle sensor (−2 mm) derived from the approximate linear line designated by A. However, in actuality the vehicle posture (the pitch angle) of the vehicle should be about 0.6 degree (position DL in
FIG. 2
) but the operation control part controls the driving of the actuators to an extent that corresponds to the value of 0.45 degree and not 0.6 degree, as it should be.
SUMMARY OF THE INVENTION
An object of the invention is to provide a vehicle headlamp leveling device for enabling the compensation of optical light axes of headlamps of a vehicle with high accuracy by specifying two or more control lines (approximate lines stored in a storage part) with different slopes that correlates outputs from a vehicle height sensor and pitch angles of the vehicle. An optimum control line (approximate line) from the two or more control lines is selected based on a change in an absolute pitch angle obtained from an output of an auxiliary sensor. The auxiliary sensor detects the absolute pitch angle of the vehicle relative to a horizontal plane.
A vehicle headlamp leveling device according to a first embodiment of the invention comprises headlamps adapted to be driven by actuators such that light axes thereof are tilted up and/or down relative to the body of a vehicle, a vehicle speed sensor provided on the body, a vehicle height sensor provided either on a left or right suspension of either the front or rear of the vehicle for detecting a distance between an axle and the body, a storage part in which control data is entered and set in advance which comprises a correlation function between outputs from the vehicle height sensor and relative pitch angles of the vehicle relative to a road surface, and an operation control part for determining from an output from the vehicle sensor whether the vehicle is at a stop or moving and controlling the driving of the actuators based on an output from the vehicle speed sensor. The control data can be stored in the storage part. With the above embodiment, the optical light axes of the headlamps can stay in a predetermined inclined state relative to the surfaces of roads at all times. The control data in the storage part can be specified by at least two or more control lines that are inclined differently. An auxiliary sensor can be provided on the body for detecting an absolute pitch angle of the vehicle relative to a horizontal plane. The operation control part compares a difference between a variation added pitch angle, which is obtained by adding a variation in the absolute pitch angle to a relative pitch angle calculated from control lines previously selected, and a relative pitch angle calculated from respective control lines based on a current output of the vehicle height sensor. The control part then selects a control line with the smallest difference and controls the driving of the actuators based on a relative pitch angle calculated from the selected control line.
If the relative pitch angle calculated fr
Cherry Stephen J.
Hilten John S.
Koito Manufacturing Co. Ltd.
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