Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
2001-01-05
2003-01-07
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C315S079000
Reexamination Certificate
active
06504265
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an autoleveling device of a headlamp for an automobile which serves to automatically adjust tilting (hereinafter referred to as autoleveling) for an optical axis of the headlamp in a direction of off set equivalent to tilting in a longitudinal direction of a vehicle (hereinafter referred to as a pitch angle) based on the pitch angle, and more particularly to an autoleveling device for automatically adjusting the optical axis of the headlamp vertically based on the pitch angle of the vehicle mainly during stop.
In a headlamp of this kind, for example, a reflector having a light source inserted therein is supported to be tilted around a horizontal tilting axis with respect to a lamp body and an optical axis of the reflector (headlamp) can be tilted around the horizontal tilting axis by an actuator.
In a conventional autoleveling device, a vehicle is provided with pitch angle detecting means, a vehicle speed sensor, a control section for controlling the driving operation of the actuator based on a detection signal therefrom and the like, and an optical axis of a headlamp (reflector) is adjusted to be always set in a constant state with respect to a road.
In the conventional autoleveling device, however, leveling is carried out in real time for a change in a vehicle posture which is caused by acceleration and deceleration during running and a change in a load which is caused by loading and unloading a luggage or causing an occupant to get in and off during the stop irrespective of the running and stop of the vehicle. For this reason, the number of operations of the actuation is very large and power consumption is great. Furthermore, a great deal of durability is required for driving mechanism components such as a motor or a gear. Thus, a cost is increased.
In order to provide an inexpensive autoleveling device which has the driving frequency of an actuator reduced and can be used for a long period of time, therefore, there has been proposed an autoleveling device (Japanese Patent Application No. Hei 10-274859) in which the driving operation of an actuator is controlled at a constant interval (10 seconds) during stop.
In the autoleveling device thus proposed, the driving operations of the actuators of a pair of left and right headlamps are controlled at the same time based on pitch angle data which are previously detected corresponding to an interval time. If an amount of a change in the pitch angle data for a stop position (a position of an optical axis) of the actuator is small, there is a possibility that the actuator of one of the headlamps might be driven and the actuator of the other headlamp might not be driven (autoleveling might function in one of the headlamps and might not function in the other headlamp).
This problem is investigated. As a result, it has been found that the problem arises due to a hysteresis of an actuator driving circuit.
More specifically, a driving circuit using a DC motor M shown in
FIG. 6
is used as an actuator mechanism for tilting a reflector. A motor driver serves to control driving (rotation) of the DC motor M which is an actuator body in response to a driving signal sent from a control unit, and a signal is fed back from a potentiometer which detects a rotating position of the motor M to the motor driver. In the motor driving circuit, a pair of switches Sw
1
and Sw
4
(or switches Sw
2
and Sw
3
) are turned on to rotate the motor M and a pair of switches Sw
1
and Sw
3
on the Hi side (or switches Sw
2
and Sw
4
) are turned on to brake and stop the motor when the potentiometer reaches a target position as shown in FIG.
7
. Also after the motor is braked, it continuously rotates by inertia. Therefore, a hysteresis having predetermined widths of H
1
and H
2
shown in
FIG. 8
is provided between the braking and operation of the motor such that the motor does not carry out a hunching operation.
FIG. 8
shows a hysteresis in an actuator (motor) driving circuit. A feedback signal sent from the potentiometer indicates a current position of the actuator (motor). Therefore, a difference between an actuator driving signal and the feedback signal sent from the potentiometer indicates an operation position of the actuator. When the difference between the actuator driving signal and the feedback signal sent from the potentiometer (which will be hereinafter referred to as an actuator driving signal output) reaches almost 0 (a position indicated as the reference numeral P
2
or P
3
in FIG.
8
), the actuator driving circuit is braked and stopped. When the actuator driving signal output is increased to be equal to or less than P
1
or equal to or more than P
4
in
FIG. 6
, the actuator (motor) is operated. Thus, the hysteresis is provided in the actuator driving circuit.
However, the actuator such as a motor is an industrial product. Therefore, a hysteresis range always has an error. The hysteresis widths of the respective actuator driving circuits of the left and right headlamps are not identical to each other. For this reason, if pitch angle data detected by pitch angle detecting means and pitch angle data used for the last driving control of the motor has a small difference when the motor is to be operated in the stop state, an actuator driving signal output corresponding to the pitch angle data gets out of the hysteresis range in the actuator driving circuit of one of the headlamps and gets in the hysteresis range in the actuator driving circuit of the other headlamp. In such a case, one of the actuators is driven and the other actuator is not driven. As a result, the autoleveling functions in one of the headlamps and does not function in the other headlamp. Consequently, the positions of the optical axes of the left and right headlamps make a difference.
SUMMARY OF THE INVENTION
The invention has been made in consideration of the problems of the conventional art and has an object to provide an autoleveling device of a headlamp for an automobile which can drive left and right actuators at the same time without influence of a hysteresis of an actuator driving circuit.
In order to achieve the object, a first aspect of the invention is directed to an autoleveling device of a headlamp for an automobile comprising a pair of left and right headlamps in which optical axes are tilted in a vertical direction with respect to a body by driving operations of respective actuators, single control means for controlling the driving operations of the actuators at the same time, vehicle speed detecting means for detecting a speed of a vehicle, pitch angle detecting means for detecting a pitch angle of the vehicle, and a storage section for storing pitch angle data of the vehicle which are detected by the pitch angle detecting means, the control means controlling the driving operation of the actuator such that the optical axes of the headlamps are set in a constant tilting state with respect to a road based on the pitch angle data detected by the pitch angle detecting means, wherein the control means drives the actuator if a difference between the pitch angle data detected by the pitch angle detecting means and the pitch angle data used for the last driving control of the actuator is more than a predetermined reference value which is equal to or more than a pitch angle equivalent to a hysteresis width of each of actuator driving circuits of the left and right headlamps, and does not drive the actuator if the difference is less than the reference value.
If the difference between the pitch angle data detected at the present time by the pitch angle detecting means and the pitch angle data used for the last actuator driving control is greater than the predetermined reference value which is equal to or greater than the pitch angle equivalent to the hysteresis width of each of the actuator driving circuits of the left and right headlamps, both actuators are driven. Contrary, if the difference is less than the predetermined reference value, the actuators are not driven. Therefore, there is no drawback that only
Takeuchi Hideaki
Toda Atsushi
Fish & Richardson P.C.
Fleming Fritz
Koito Manufacturing Co. Ltd.
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