Vehicle headlamp optical axis control system

The present application is based on and claims priority from Japanese Patent Application 2001-263077, filed Aug. 31, 2001, the contents of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates to a headlamp's optical axis control system for a vehicle.

2. Description of the Related Art

In a headlamp's optical axis control system, such as disclosed in JP-B-2950897, the headlamp's optical axis is controlled to swivel right or left according to the steering angle of a steering wheel. In such a control system, a dead zone is provided at the neutral position of the steering wheel to prevent fluctuation of the optical axis due to play of the steering wheel or due to a minute operation of the steering wheel. Although the optical axis of the head lamp of a car is controlled according to the vehicle speed and steering angle of the steering wheel, a driver may have difficulty when he or she wants to watch an object while driving the car at a curve because the illumination range of the head lamps may not always illuminate the object.

The present invention has been made in view of the above-stated problem.

It is an object of the invention to provide a headlamp's optical axis control system for a vehicle that can illuminate the object that a driver wants to watch.

According to a feature of the invention, a head lamp's optical axis control system for a vehicle includes vehicle speed detecting means, steering angle detecting means, driver's viewpoint calculating means for providing position of a driver's viewpoint that comes a predetermined time in advance according to the vehicle speed and the steering angle, and control means for controlling the optical axis so that the illumination range covers the driver's viewpoint. Preferably the control means includes a map and correction means are provided. The map provides standard positions of the driver's view points that correspond to various vehicle speeds and steering angles, and the correcting means corrects the standard position of the driver's viewpoint by multiplying the standard position by a prescribed coefficient proportional to the vehicle speed or steering angle if the vehicle speed or the steering angle is different from the speed or steering angle that corresponds to the standard position.

Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings:

FIG. 1 is a schematic diagram illustrating a vehicle headlamp's optical axis control system according to a preferred embodiment of the invention;

FIG. 2 illustrates illumination ranges formed by fixed lamps and swiveling lamps that are controlled by the headlamp's optical axis control system according to the preferred embodiment of the invention;

FIG. 3 illustrates an example of the operation of the headlamp's optical axis control system according to the preferred embodiment of the invention while driving at a curve at a certain speed;

FIG. 4 illustrates an example of the operation of the headlamp's optical axis control system according to the preferred embodiment of the invention while driving at a curve at a speed that is twice as high as the certain speed;

FIG. 5 illustrates an example of the operation of the headlamp's optical axis control system according to the preferred embodiment of the invention while driving at a curve at a speed that is half of the certain speed;

FIG. 6 is a schematic diagram showing a three-dimensional map of the headlamp's optical axis control system according to the preferred embodiment of the invention;

FIG. 7 illustrates an example of the operation of the headlamp's optical axis control system according to the preferred embodiment of the invention while driving at a curve with a certain steering angle;

FIG. 8 illustrates an example of the operation of the headlamp's optical axis control system according to the preferred embodiment of the invention while driving at a curve with a steering angle that is a half as large as the certain steering angle; and

FIG. 9 illustrates an example of the operation of the headlamp's optical axis control system according to the preferred embodiment of the invention while driving at a curve with a steering angle that is twice as large as the certain steering angle.

As shown in FIG. 1, a vehicle is equipped with right and left headlamps 10 R, 10 L, right and left swiveling lamps 11 R, 11 L, their swiveling actuators 12 R, 12 L, a steering wheel 15 , a steering angle sensor 16 , right and left wheel speed sensors 18 R, 18 L, and an electronic control unit (ECU) 20 .

The steering angle sensor 16 detects steering angle θs of the steering wheel 15 measured from the neutral position thereof. The ECU 20 includes a central processor unit (CPU) 21 , a ROM 22 , a RAM 23 , a back-up RAM 24 , I/O circuit 25 , bus lines 26 , etc. The ROM 22 includes a map that provides standard swivel angles θsw, which is determined based on a vehicle speed V and a steering angle θs, as described below in more detail with reference to FIG. 6 . The ECU 20 connects with swiveling actuators 12 R, 12 L, the steering angle sensor 16 , the wheel speed sensors 18 R, 18 L and various sensors.

The ECU 20 calculates a driver's viewpoint a predetermined time in advance based on the vehicle speed V detected by the wheel speed sensors 18 R, 18 L and the steering angle θs detected by the steering angle sensor 16 . The ECU 20 controls the swiveling actuators 12 R, 12 L according to the standard swivel angle θsw provided by the map that corresponds to the vehicle speed V and the steering angle θs, thereby to swivel the optical axis of the swiveling lamps 11 R, 11 L so that the driver's viewpoint can be covered by the illumination range of the swiveling lamps 11 R, 11 L.

When the vehicle passes a curve at a standard speed, one (e.g. left lamp 11 L while turning left) of the swiveling lamps 11 R, 11 L is controlled according to the map shown in FIG. 6 to swivel right or left so that the illumination range of the left swiveling lamp 11 L can cover a driver's view point (white circle), as shown in FIG. 3 . In this case the calculated viewpoint (dark circle) from the map overlaps a desirable driver's viewpoint.

When the vehicle runs at the speed that is twice as high as the standard speed, the calculated viewpoint (dark circle) is located twice as distant as the driver's viewpoint. Therefore, it is not possible for the swiveling lamp to cover such a long distance. In this case, the swivel angle of the optical axis of the swiveling lamp 11 L is corrected by multiplying the standard swivel angle θsw by ½ so that the illumination range of the swiveling lamp can cover the driver's view point.

When the vehicle runs at a half of the standard speed, the calculated viewpoint at the standard speed is located at as half a distance as the driver's viewpoint. In this case, the swivel angle of the optical axis of the swiveling lamp 11 L is corrected by multiplying the standard swivel angle θsw by 2 so that the illumination range of the swiveling lamp can cover a range that is twice as long as the calculated viewpoint. As a result, the distance of the driver's viewpoint can be increased to double the calculated viewpoint.

FIG. 7 shows a standard illumination range when the driver turns the steering wheel 15 by standard steering angle θs while passing a left turn curve. In this case the driver's viewpoint (white circle) and the calculated viewpoint (dark circle) overlap each other.

When the vehicle passes a left turn curve that has a twice as large turning-radius as the left turn curve shown in FIG. 7, the driver turns the steering wheel by an angle θs that is a half of the standard steering angle. In this case, the map provides a standard swiveling θsw that is the angle for the vehicle running at a speed twice as high as the standard speed. Therefore, the standard swiveling angle θsw is multiplied by 2 to provide a corrected swiveling angle, as shown in FIG. 8 .

When the vehicle passes a left turn curve that has a half as large turning-radius as the left turn curve shown in FIG. 7 , the driver turns the steering wheel by an angle θs that is double the standard steering angle. In this case, the map provides a standard swiveling θsw that is the angle for the vehicle running at a half of the standard speed. Therefore, the standard swiveling angle θsw is multiplied by ½ to provide a corrected swiveling angle, as shown in FIG. 9 .

If the steering angle or the vehicle speed changes while turning a curve, correction may be made by multiplying the swiveling angle by a coefficient that is proportional to a change in angle or a change in vehicle speed in a similar manner as described above.

In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention is to be regarded in an illustrative, rather than a restrictive, sense.