Vehicle headlamp leveling device

Details Vehicle headlamp leveling device Vehicle headlamp leveling device

2000-08-16

2002-09-03

Fleming, Fritz (Department: 2836)

Electrical transmission or interconnection systems

Vehicle mounted systems

Automobile

C315S079000

Reexamination Certificate

active

06445085

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a vehicle headlamp leveling device for automatically tilting the headlamps of a vehicle, and more particularly to a vehicle headlamp leveling device for vertically tilting the light axes of the headlamps based on pitch angles of the vehicle mainly when it is stationary.
BACKGROUND OF THE INVENTION
A known automatic vehicle headlamp leveling device comprises a pitch angle detection sensor, a vehicle speed sensor and a controller for controlling the driving of actuators based on detected signals from the actuators which are mounted on a vehicle for adjusting the light axes of the headlamps (the reflectors) such that they stay in a given state relative to the surface of a road.
The known automatic vehicle headlamp leveling device is, however, constructed to level the headlamps of a vehicle in real time whether it is running or is at a stop. The device responds to a change in vehicle posture, which occurs when the vehicle accelerates or decelerates, or when luggage is loaded or unloaded or when occupants of the vehicle get in or out of the vehicle. Hence, the number of times the actuators are activated is high and consumption of power is also increased. Moreover, components of driving mechanism such as motors, gears and the like require tremendously high durability, which leads to increase in production costs.
An automatic headlamp leveling device was proposed in JP-A-2000-85458 that reduced the frequency at which the actuators are driven. The proposed device was constructed to control the actuators at certain intervals while the vehicle is at a stop, whereas when the vehicle is in motion, the driving of the actuators is controlled only once as long as the vehicle runs stably.
With the proposed device, when the vehicle turns, slaloms or runs on an irregular surface of a road at a constant speed, a vehicle height sensor, which is a pitch angle detection sensor, detects changes in pitch angle while the vehicle is running. However, when the vehicle is constantly running (i.e. running for a period of time during which the speed is equal to or more than a given value and the acceleration is equal to or less than a given value), the controller determines this condition as stable. Therefore, the headlamps can be inappropriately leveled based on pitch angle data detected during an unstable running condition such as turning, slaloming or running on irregular road surfaces.
When the vehicle turns left at a constant speed, the right-hand side suspension shortens or contracts because of a gravitational acceleration caused by the turn (hereinafter, referred to as turning G), and the vehicle height sensor attached to this suspension on the rear right wheel detects the sinking of the suspension as a tilt along the length of the vehicle as a change in pitch angle. On the other hand, when the vehicle turns right while running at a constant speed, the right-hand side suspension lengthens or expands because of a gravitational acceleration caused by the turn (hereinafter, referred to as turning G), and the vehicle height sensor attached to the suspension detects the expansion or floatation of the suspension as a tilt along the length of the vehicle as a change in pitch angle. A pitch angle data of turns is different from a pitch angle data detected during a stable running condition in which the vehicle runs on a flat surface of a road at a constant speed (which may be close to a pitch angle data detected while the vehicle is at a stop) and is inappropriate for use in leveling the headlamp.
However, the headlamp leveling device determines that a stable running condition is achieved when a speed of the vehicle is equal to or more than a given value and an acceleration of the vehicle is equal to or less than a given value for a predetermined period of time. Then the leveling (controlling) of the headlamps is carried out. If the leveling of the headlamps is carried out to lower the light axes, the visual distance in front of the vehicle is shortened. In terms of safety, this is not a preferable condition. Alternatively, if the leveling (controlling) of the headlamps is carried out to raise the light axes, on-coming vehicles may be subject to glare.
SUMMARY OF THE INVENTION
An object of the invention is to provide a headlamp leveling device that is inexpensive to produce, that provides a long service life by reducing the frequency at which actuators are activated, and that avoids inappropriate leveling of the headlamps while the vehicle is running.
A first implementation of a headlamp leveling device 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, control means for controlling the driving of the actuators, vehicle speed detection means for detecting the speed of the vehicle, pitch angle detection means provided on either of left and right suspensions of either of front and rear wheels for detecting a pitch angle of the vehicle, and a storage part for storing pitch angle data of the vehicle detected by the pitch angle detection means, the control means being adapted to control the driving of the actuators based on pitch angle data detected by the pitch angle detection means such that the light axes of the headlamps always stay in a predetermined tilted state relative to the surface of a road, wherein the control means determines whether the vehicle is being at a stop or is running based on outputs from the vehicle speed detection means and controls the driving of the actuators at certain intervals while the vehicle is being at a stop, whereas while the vehicle is running, only when the vehicle is running stably where a state continues for a given length of time in which the speed of the vehicle is equal to or more than a given value, while the acceleration of the vehicle is equal to or less than a given value, the control means controls the driving of the actuators based on pitch angle data taken during the stable running of the vehicle, the headlamp leveling device is adapted to control the driving of the actuators only in a case where respective mean pitch angle data of a plurality of different cycle periods come to coincide with one another after the state continues for a given length of time in which the speed of the vehicle is equal to or more than a given value, while the acceleration of the vehicle is equal to or less than a given value.
In addition, according to a second implementation of the invention, a headlamp leveling device 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, control means for controlling the driving of said actuators, vehicle speed detection means for detecting the speed of the vehicle, pitch angle detection means provided on either of left and right suspensions of either of front and rear wheels for detecting the pitch angle of the vehicle, and a storage part for storing pitch angle data of the vehicle detected by the pitch angle detection means, the control means being adapted to control the driving of the actuators based on pitch angle data detected by the pitch angle detection means such that the light axes of the headlamps always stay in a predetermined tilted state relative to the surface of a road, wherein said control means determines whether the vehicle is being at a stop or is running based on outputs from said vehicle speed detection means and controls the driving of the actuators at certain intervals while the vehicle is being at a stop, whereas while the vehicle is running, only when the vehicle is running stably where a state continues for a given length of time in which the speed of the vehicle is equal to or more than a given value, while the acceleration of the vehicle is equal to or less than a given value, the control means controls the driving of the actuators based on pitch angle data taken during the stable running of the vehicle, the headlamp leveling device is adapted to control the driving of the actuators only in a ca

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