Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
2000-08-18
2002-10-15
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C307S125000
Reexamination Certificate
active
06465906
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an alignment device for a vehicle, and particularly to an alignment device for a vehicle suitable to align an optical axis of a headlamp for an automobile.
In some vehicles such as an automobile or the like, an alignment device (auto leveling device) is mounted to prevent the direction of irradiation of light of a headlamp from becoming irregular due to changes in the running attitude of the vehicle. The alignment device corrects the direction of light irradiated by the headlamp according to the changes in the running attitude of the vehicle. For example, vehicle height sensors arranged at axle portions in the front and in the rear of the vehicle generate detection signals that correspond to the change of a pitting angle (or pitch angle) of the vehicle, and the direction of light irradiated by the headlamp is controlled according to this change.
Specifically, the alignment device shown in
FIG. 4
includes a vehicle height sensor
50
, a control unit
52
and an actuator
54
. Electric power is supplied to the control unit
52
and the actuator
54
from a vehicle power supply. The control unit
52
includes a controller
62
comprising resistances
56
and
58
, a stabilized power supply
60
and a microcomputer, and a D/A converter
64
. The stabilized power supply
60
stabilizes voltage upon reception of a supply of the electric power from the vehicle power supply, and outputs the stabilized voltage to the controller
62
and to the D/A converter
64
. The controller
62
receives the voltage divided by the resistances
56
and
58
therein, monitors the voltage change of the vehicle power supply in accordance with this voltage, converts a detection signal of the vehicle height sensor
50
to a digital signal, performs an alignment operation, for example, alignment according to the change of the pitting angle of the vehicle on the basis of the digital signal, and outputs a digital signal in accordance with this operation result to the D/A converter
64
. The D/A converter
64
converts the digital signal from the controller
62
to an analog signal and outputs this analog signal to a motor driver
66
of the actuator
54
.
The motor driver
66
compares the analog signal output from the D/A converter
64
with the rotational position of a motor detected by a potentiometer
68
, and drives a motor
70
according to the result of the comparison. Consequently, the motor driver
66
drives the motor
70
so that the output signal of the D/A converter
66
conforms to the position detected by the potentiometer
68
. The motor
70
tilts a reflector within a lamp body up and down, so that the optical axis of the lamp is aligned according to the change of the vehicle height.
In the conventional alignment device, a constant voltage is always supplied to the controller
62
by the stabilized power supply
60
. Therefore, even if the voltage of the vehicle power supply varies, no error is produced in the operation result of the controller
62
. However, since the vehicle power supply is directly supplied to the motor driver
66
and potentiometer
68
in the actuator
54
, the detection value of the potentiometer
68
is under the influence of variations of the supply voltage. The conventional alignment device includes a voltage divided by the resistances
56
and
58
that is input to the controller
62
, and thus the controller
62
monitors the voltage variation of the vehicle power supply and corrects the operation value according to the variation of the supply voltage. Therefore, in the conventional alignment device, in order to monitor the variation of the supply voltage. the resistances
56
and
58
must be provided to serve in a supply voltage monitor circuit so that the controller
52
can perform the correction operation.
Further, referring to
FIG. 5
, the D/A converter
64
of the conventional alignment device is composed of a rudder circuit
72
comprising a plurality of resistance elements and an operation amplifying circuit
74
. Consequently, the number of parts is increased and the positional accuracy of the actuator
54
is decreased by the supply voltage.
For example, in case that the supply voltage of the controller
62
is 5V, the D/A converter
64
performs a digital/analog conversion on the basis of 5V. Conversely, since the actuator
54
operates at the voltage (battery voltage) of the vehicle power supply, an operational amplifier
74
is required, which converts the analog voltage which is 5V at its maximum into the highest value of the operation voltage in the system. Such circuitry is required because, if the actuator
54
is designed to operate at 5V, the motor
70
would have to be large which is not practical. When the stroke of the actuator
54
is 0, in the case that the operational voltage range of the system is 8V to 16V in order to output a signal corresponding to the battery voltage from the D/A converter
64
, the gain of the operational amplifier
74
is 3.2 times. Since the actuator
54
operates on the basis of the battery voltage, and the amplification factor of the operational amplifier
74
is fixed, when the battery voltage is 8V, which is the lowest in the system operational voltage range, the digital value when the stroke of the actuator
54
is 0 must be half as large as one when the supply voltage is 16V. If not half, the output voltage of the D/A converter
64
does not approach that of the battery voltage. Accordingly, in case that a D/A converter of 8 bits resolution is used, the output voltage can be naturally adjusted at 256 gradations. However, the output voltage can be changed only by 128 gradations which is half of 256 gradations, so that the positional accuracy of the actuator
54
is lowered by half.
SUMMARY OF THE INVENTION
The invention has been made in view of the problem of the above prior art. In particular, presented is an alignment device for a vehicle which can align an optical axis of a light source according to the change of attitude of a vehicle without lowering the positional accuracy, and the alignment device offers a simple construction.
In order to achieve the above result, the alignment device for a vehicle according to the first aspect of the invention is designed to include a vehicle attitude detecting means for detecting an attitude of a vehicle and then outputting a vehicle attitude detecting signal of analog amount; an analog-to-digital conversion means for converting the vehicle attitude detecting signal to a digital signal; an operation means for executing alignment operation in accordance with the digital signal and outputting an alignment command signal of which the pulse duration has been modulated according to this operation result; a switching means which responds to the alignment command signal upon reception of electric power from a vehicle power supply to perform a switching operation and outputs a signal according to this switching operation; a filter means for smoothing the signal accompanying the switching operation of this switching means; an alignment means for aligning an optical axis in response to an alignment signal; a position detecting means for detecting the position of the optical axis upon reception of supply of the electric power from the vehicle power supply; and an alignment signal generating means which generates an alignment signal corresponding to the deviation between the output signal of the filter means and the detection output of the position detecting means and outputs it to the alignment means.
In a process in which the switching means performs the switching operation in response to the alignment command signal of which pulse duration has been modulated and the signal accompanying the switching operation of this switching means is smoothed by the filter means, when the supply voltage of the vehicle power supply varies, the signal accompanying the switching operation is smoothed in accordance with the variation of this supply voltage, and the variation of the supply voltage is absorbed by the smoothed signal
Takeuchi Hideaki
Toda Atsushi
Fish & Richardson P.C.
Fleming Fritz
Koito Manufacturing Co. Ltd.
Polk Sharon
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