JPH092148A - Headlamp optical axis regulating device for automobile - Google Patents

Abstract

PURPOSE: To maintain proper regulation of an optical axis angle even when the intensity of a reflection wave is temporarily decreased up to weak value by a method wherein the angle of an automobile with a road is computed by using an arrival time of a reflection wave right before the under-mentioned time at an ultrasonic sensor at a time when a reflection wave detected by the ultrasonic sensor is decreased to a value not higher than set intensity. CONSTITUTION: A signal holding circuit 3A is added to a receiving circuit 3 and when a receiving signal (p) is decreased to a value lower than set intensity, a control circuit 6 is operated so that the level of an ultrasonic emission signal (e) right therebefore is held. Namely, when a receipt signal (p) (a rectifying output signal (s)) is decreased to a value lower than a constant voltage Vo, an output signal (v) from a comparator 31e is increased to an H-level and output signals (w) from an inverter 31f and an AND circuit 31g are at a H-level. A flip flop circuit 31h inputs a selection signal (x) for hold when an signal (w) is at an H-level, and a selection signal (x) for a sample to the sample hold circuit for a control circuit 6. As a result, even when a receipt signal (p) is weak, the level of the signal (e) right therebefore is held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a vehicle headlamp optical axis adjustment device using ultrasonic distance measurement.

[0002]

2. Description of the Related Art The angle of an automobile with respect to the road surface changes in accordance with the number of people in the automobile, the amount of load to be loaded or the distribution state thereof, and the optical axis of the headlight also changes accordingly. This means that you may unknowingly be dazzling an oncoming vehicle with your vehicle's headlight, or the headlight may be pointing too far downward, and therefore the optical axis of the headlight should be Being able to adjust automatically is extremely useful for ensuring the safety of the own vehicle and oncoming vehicles.

Therefore, various types of vehicle headlight optical axis adjusting devices for automatically adjusting the optical axis of the headlight have been devised. In this case, the angle with respect to the road surface of the vehicle, that is, the inclination of the optical axis of the headlight. As a method of determining the distance, install a distance sensor at the front and rear ends of the car, measure the distance to the road surface at each location,
There is a method of obtaining the inclination based on those values. In this method, usually, the reflection from the road surface of the measurement medium emitted (transmitted) from a predetermined position on the front and rear ends of the vehicle is detected,
Measure the distance. The medium used for distance measurement includes light, radio waves, ultrasonic waves, etc., but it is impossible to measure distance due to dirt on the light emitting surface or light receiving surface of light, and it is actually assumed that the road surface is a light reflecting surface. It is difficult, and radio waves are easily affected by external noise and are erroneously measured. From this,
Ultrasonic waves are preferable, and some techniques have been considered in which distances are actually measured using ultrasonic waves, the tilt of the optical axis of the headlight is determined, and the optical axis is adjusted.

FIG. 3 is a block diagram showing an example thereof.
In FIG. 3, reference numeral 1 is an ultrasonic sensor including a pair of ultrasonic transducers for transmission and reception, and 2 is an ultrasonic sensor 1.
By applying a pulsed high voltage signal b to the ultrasonic sensor 1
A transmitting circuit for emitting (transmitting) a predetermined pulsed ultrasonic wave from the ultrasonic wave sensor 3, a receiving circuit 3 for amplifying and shaping a signal received by the ultrasonic sensor 1, and a reference numeral 4 provided between the ultrasonic sensor 1 and the receiving circuit 3. , A selection circuit for not transmitting the signal b from the transmission circuit 2 to the reception circuit 3. Reference numeral 5 is a timing circuit, and 6 is a control circuit. Here, the timing circuit 5 sets the transmission frequency f and the transmission time τ of the ultrasonic wave, and is activated by the pulse signal (trigger pulse) a from the control circuit 6 to drive the transmission circuit 2 and the receiving circuit. The pulse signal a from the control circuit 6 is transmitted to the circuit 3. The control circuit 6 receives the signal c from the receiving circuit 3 and the signal Vs from the position sensor which will be described later as input, performs calculation, and outputs the signal a to the timing circuit 5 and the signal g to the drive circuit which will be described later according to the calculation result. It is a thing. Reference numeral 7 is a drive circuit for driving the headlamp optical axis drive device 9 by a signal g from the control circuit 6, and 8 is a position detection circuit for detecting the position of the output shaft of the headlamp optical axis drive device 9 and detecting the detected signal Vs. 6 is a position sensor that returns to 6.

Here, the transmitting circuit 2, the receiving circuit 3, the selecting circuit 4, and the timing circuit 5 are ultrasonic transmitting / receiving circuits 11.
The ultrasonic transmitter / receiver circuit 11 and the ultrasonic sensor 1 are provided as a pair, and one set (the one with the suffix F added to the reference numeral) is the front end of an automobile (not shown). The other set (the one with the suffix R attached to the code) is also for the rear end. The ultrasonic sensor 1F for the front end portion is attached to the front end portion of the automobile, for example, the lower front bumper, and the ultrasonic sensor 1R for the rear end portion is attached to the rear end portion of the automobile, for example, the lower rear bumper, while facing the road surface G. Has been.

In such an automotive headlight optical axis adjusting device, the control circuit 6 outputs a pulse signal a (aF, aR) for timing the transmission and reception of ultrasonic waves, and the timing circuit 5 (5F, 5R). To start. Transmitter circuit 2 (2F, 2
R) is a constant time τ in synchronization with the rise of the pulse signal a,
High voltage signal b to excite the ultrasonic sensor 1 (1F, 1R)
(BF, bR) is generated. The frequency f to be excited is arbitrary.

The ultrasonic wave emitted from the ultrasonic sensor 1 is reflected on the road surface G and returns to the ultrasonic sensor 1 again after T seconds.
The received signal o (oF, oR) is the selection circuit 4 (4F, 4R).
To reach the receiving circuit 3 (3F, 3R). The high voltage signal b to the transmission circuit 2 is prevented from entering the reception circuit 3 by the selection circuit 4. The reception signal p (pF, pR) that has reached the reception circuit 3 is amplified and shaped by the reception circuit 3, and as a distance signal c (cF, cR) whose time width T changes according to the distance L (LF, LR). Output control circuit 6
Sent to At this time, the temporal relationships of the signals a, b and c are as shown in FIGS. 4a, b and c.

The control circuit 6 receives the distance signal c sent from the receiving circuit 3 and converts it into a digital value or an analog value according to the width T thereof. The conversion result is stored in a memory, a sample hold circuit, or the like. Here, it is assumed that the conversion result is converted into an analog value and stored in the sample hold circuit. That is, here, the D / A conversion count is performed so that the voltage level changes depending on the width T of the distance signal c (FIG. 4).
D / A OUT). As can be seen from FIG. 4c, D / A OUT, D / A only when the distance signal c is at H level.
The A conversion count is started, and this count value is the distance signal c.
Is held at the L level. However, when the next pulse signal a comes in, the counter of the D / A converter is reset, so the counter is counted again from 0, and while the distance signal c is at the H level, counting is continued and When c goes to L level, its count value is held,
The same process is repeated thereafter. That is, D / A O in FIG.
The thick line portion of the UT waveform is represented as a change in voltage level proportional to the time width T of the distance signal c.

The ramp waveform during the D / A conversion counting (the portion indicated by the upward arrow ↑ in D / A OUT of FIG. 4) is generated in principle during the counting process, and the actual distance L Does not indicate. If the portion indicated by the upward arrow ↑ is deleted, it cannot be treated as a continuous signal. Therefore, the analog level immediately before the upward arrow ↑ is held to be a continuous signal (see FIG. 4e). When this continuous signal is referred to as a pseudo continuous signal e (eF, eR), the control circuit 6 first performs a process of obtaining the pseudo continuous signal e.

The above operation is common to the signals sent from the ultrasonic sensors 1F and 1R at the front and rear ends of the automobile, and through such operations, the pseudo continuous operation at the front and rear ends of the automobile is performed. The signals eF and eR are obtained. At this time (at a certain time t), the voltage value of the pseudo continuous signal eF of the front end ultrasonic sensor 1F: VF (t) and the voltage value of the pseudo continuous signal eR of the rear end ultrasonic sensor 1R: VR (t) Distance between front-end ultrasonic sensor 1F and road surface G: LF (= VF (t) ・ k) Distance between rear-end ultrasonic sensor 1R and road surface G: LR (= VR (t) ・ k) Proportional constant: k Distance between front and rear of ultrasonic sensors 1F and 1R: l Body inclination: θ (t), tan θ (t) = (LF−LR) / l = {k (VF (t) −VR (t))} / L ... (1), and if K = 1, then tan θ (t) = (VF (t) −VR (t)) / l (2) holds. At this time, since the range of θ (t) is practically −3 ° <θ (t) <3 °, the equation (2) is changed into k′θ (t) ≈ (VF (t) −VR (t )) / L (k ′ is a proportional constant) θ (t) ≈ (1 / k ′) × {(VF (t) −VR (t)) / l} (3)

On the other hand, to the control circuit 6, the current position signal (voltage) Vs of the output shaft of the headlamp optical axis driving device 9 is fed back from the position sensor 8. The control circuit 6 compares this voltage Vs with θ (t) according to the above equation (3), and θ (t) <Vs or θ
When (t)> Vs, the signal is output to the drive circuit 7,
The headlamp optical axis drive device 9 is driven to change the optical axis angle in a direction in which the inclination of the headlamp optical axis caused by the inclination of the vehicle with respect to the road surface G is canceled. When θ (t) = Vs, it means that the optical axis angle is appropriate, the signal g to the drive circuit 7 is not output, and the headlamp optical axis drive device 9 is not driven. Also, the signal a to the timing circuit 5 is not output.

Now, the receiving circuit 3 and the control circuit 6 will be described in more detail. FIG. 5 is a circuit diagram showing details of the receiving circuit 3. In FIG. 5, 31a and 31b are amplifiers and 3
1c is a half-wave rectifying / smoothing circuit, 31d is a flip-flop circuit, D / A IN is a D / A converter input, S / H IN
Is the sample and hold selection input, and the others are the same as in FIG. The subscript F is omitted in FIG. The following operations are common to the signals sent from the front and rear end ultrasonic sensors 1F and 1R. FIG. 6 is a signal waveform diagram of each part in FIG.

Normally, the received signal can be obtained as a distance signal c by the receiving circuit 3 shown in FIG. 5 through the operations as shown in the signal waveforms of the sections A in FIG. in this way,
As shown in the waveform of the received signal p in the section A in FIG. 6, if a signal of a sufficiently large size (a signal of a size sufficient to be amplified and used in the subsequent stage) is always input, no problem occurs. However, when mounted on an actual vehicle, the signal strength of the received signal p may fluctuate significantly, and this may be extremely weakened, and as a result, a pulse indicating the distance L may not be generated in the waveform of the distance signal c.

This state is shown in section B of FIG. In section B of FIG. 6, a is a weak reception signal p portion, and b is a distance signal c portion without a pulse indicating the distance L. According to this, D
Even at the / A conversion stage, the distance is regarded as 0 (D / A in section B
Even in the case of the pseudo continuous signal e) (see the OUT signal portion C), an incorrect level is held in the section Ba. That is, when the amplitude of the received signal p becomes extremely small, a level different from the actual level occurs in the pseudo continuous signal e,
Control proceeds with an incorrect value, and as a result, proper optical axis adjustment cannot be realized.

[0015]

As described above, a technique for measuring the distance using ultrasonic waves and detecting the inclination of the optical axis of the headlight has been conventionally known. However, the distance using ultrasonic waves is known. When the measurement is performed, since the acoustic characteristics of the road surface G that is the object to be measured are mixed, a sound wave of a constant intensity is not always reflected from the road surface G, and the intensity of the reflected wave varies. Often. Further, the acoustic characteristics of the road surface G facing the ultrasonic sensors 1 at the front and rear ends of the stopped vehicle are not always the same. Therefore, it is not always possible to perform accurate distance measurement while traveling or while stopped, and erroneous measurement due to particularly weak reflected waves is likely to occur, and proper headlight optical axis angle adjustment can be performed. There was a problem in that the safety and smoothness of driving were impaired due to the inability to do so.

An object of the present invention is to provide an automobile for which an appropriate adjustment of the headlight optical axis angle can be maintained even if the intensity of the reflected wave is temporarily weakened, and a safer and smoother driving can be realized. An object is to provide a headlight optical axis adjustment device.

[0017]

The above object is to emit predetermined pulsed ultrasonic waves from ultrasonic sensors provided on the front and rear end sides of an automobile so as to face the road surface and to reflect the reflected waves. Each ultrasonic wave is detected by the ultrasonic sensor at each ultrasonic emission, and the angle of the reflected wave to the road surface of the vehicle is calculated based on the arrival time at each ultrasonic sensor, and the headlight of the vehicle is calculated according to the calculation result. In a vehicle headlamp optical axis adjusting device for obtaining a proper optical axis angle by controlling the lamp optical axis angle, when the reflected wave detected by the ultrasonic sensor becomes less than or equal to a preset intensity, the ultrasonic wave immediately before that This can be achieved by providing a signal holding circuit that makes the reflected wave from the emission a reflected wave from the ultrasonic emission at that time and uses the arrival time at the ultrasonic sensor to calculate the angle with respect to the road surface of the automobile.

[0018]

[Function] When a reflected wave is detected each time an ultrasonic wave is emitted, an angle calculation is performed based on each arrival time of each reflected wave to the ultrasonic sensor, and normal reflected wave detection is performed when the headlight optical axis angle is controlled. If there is a remarkably weak reflected wave in the middle of the operation, the arrival time at the ultrasonic sensor will not be measured at that time, the control amount of the headlight optical axis angle control will fluctuate significantly, and after that, the normal reflected wave When the detection is performed, the control amount changes again, and the control is unstable, so that erroneous measurement is likely to occur, and the headlamp optical axis angle is not properly adjusted.

When the reflected wave detected by the ultrasonic sensor becomes less than or equal to the preset intensity, that is, when there is a remarkably weak reflected wave as described above, the signal holding circuit immediately precedes it. The reflected wave from the sound wave emission is used as the reflected wave from the ultrasonic wave emission at that time, and the angle calculation with respect to the road surface of the automobile is performed using the arrival time at the ultrasonic sensor. Therefore, the control does not become unstable due to a large change in the control amount, and erroneous measurement is eliminated. That is, even if the intensity of the reflected wave is temporarily weakened, proper headlamp optical axis angle adjustment is maintained, and safer and smoother traveling is realized.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of an embodiment of an optical axis adjusting device for a vehicle headlight according to the present invention. In FIG. 1, 31e is a comparator having a + input terminal to which a constant voltage Vo is input and a − input terminal to which a signal s is input, 31f is an inverter that inverts the signal c, 31g is an output signal of the inverter 31f (signal c Signal of the comparator 31
AND in which the output signal v of e is input to the other input end
A circuit, 31h is a flip-flop circuit that receives the output signal w of the AND circuit 31g and the pulse signal (trigger pulse) a as input signals, and these are just before that when the received signal p becomes equal to or less than a preset intensity. A signal holding circuit 3A for activating the control circuit 6 is configured to hold the level of the signal e generated by the ultrasonic wave emission as the level of the signal e generated by the ultrasonic wave emission at that time. The constant voltage Vo is a threshold voltage of whether or not to process as a valid reception signal p, and R1, R2
Is a voltage dividing resistor for setting the constant voltage Vo, and R3 is a pull-up resistor. Others are the same as in FIG. Further, the subscript F is omitted in FIG. 1 as in FIG. Further, the basic configuration of the entire device of the present invention is similar to that of FIG.

That is, the device of the present invention has the receiving circuit 3 thereof.
Is configured by adding a signal holding circuit 3A to the receiving circuit 3 shown in FIG.
The A converter input (D / A IN) is used, but the output signal x of the signal holding circuit 3A is supplied as the sample hold selection input (S / H IN).

FIG. 2 is a signal waveform diagram of each part in FIG. In FIG. 2, D / A OUT and e are not directly shown in FIG. 1, but are the D / A conversion count output signal and the pseudo continuous signal in the control circuit 6, and It is the same.

Next, the operation of the apparatus of the present invention will be described. When the received signal p has a signal strength that can be processed by the conventional apparatus, the signal waveform of each part in the section A in FIG. 2 and the section in FIG. As can be seen by comparing the signal waveforms at each part in A, the description is omitted because the operation is similar, and the reflected wave is extremely weak, and the received signal p is extremely weak so that the conventional device cannot process it. The operation in this case will be described below.

The signal waveform of each part when the signal strength of the received signal p is extremely weak as described above is shown in the section B of FIG. In section B of FIG. 2, a is a weak received signal p portion, and b is a distance signal c portion without a pulse indicating a distance. According to this, the distance is regarded as 0 even at the D / A conversion stage (see the D / A OUT signal portion C in the section B). Therefore, in the conventional device, an erroneous level is held even in the pseudo continuous signal e (see section Ba in FIG. 6).

In the device of the present invention, the signal holding circuit 3A
As a result, when the received signal p becomes equal to or lower than a preset intensity, the sample and hold circuit in the control circuit 6 holds the level of the signal e by the ultrasonic wave emission immediately before that as the level of the signal e at that time. Activate (not shown). That is, when the reception signal p, in other words, the rectified output signal s in the reception circuit 3 becomes equal to or lower than the constant voltage Vo corresponding to the preset strength, the output signal v of the comparator 31e becomes H level. At this time, since the output signal (distance signal) c of the flip-flop circuit 31d is at the L level, the output signal of the inverter 31f (the inverted signal of the signal c) is at the H level, and therefore the output signal w of the AND circuit 31g is at the H level. It is in.

The flip-flop circuit 31h outputs the output signal w.
Is applied to the sample hold circuit in the control circuit 6 as a sample hold select input (S / H IN) when the hold select signal x is at the H level and when the w is at the L level. According to this, even if the reflected wave is extremely weak and the received signal p is extremely weak to the extent that the conventional device cannot process it, immediately before the section B (section A
The final level of the signal e (the level of the signal e by the immediately preceding ultrasonic wave emission) is held as the level of the signal e by the ultrasonic wave emission at that time (see section Bb). Therefore,
Unlike the conventional device, the signal e does not have an abnormal value,
The malfunction of the optical axis adjustment is minimized, and the proper headlamp optical axis angle adjustment is maintained. The above operation is common to the signals sent from the front and rear end ultrasonic sensors 1F and 1R.

In the above embodiment, the width T of the distance signal c sent from the receiving circuit 3 is converted into an analog value and the conversion result is stored in the sample hold circuit. Convert T to a digital value,
The conversion result may be stored in a memory or the like. This is useful for making the control circuit 6 a digital circuit.

Further, in the above-mentioned embodiment, it is premised that the ultrasonic sensors 1F and 1R at the front and rear ends are mounted at the same height (the above equations (1) to (3) show that the sensors 1F and 1R have the same height). However, the present invention is not limited to this and may be attached at different heights. In this case, for example, in the calculation in the control circuit 6, the ultrasonic sensor 1
The height of F and 1R should be corrected. This eliminates the need for height adjustment when mounting the ultrasonic sensors 1F and 1R, and facilitates mounting work. Generally, the front end ultrasonic sensor 1F is attached to the lower part of the front bumper, and the rear end ultrasonic sensor 1R is attached to the lower part of the rear bumper so as to face the road surface G. In this case, the front bumper and Since the rear bumpers have almost the same height, the ultrasonic sensor 1 can be used without adjusting the height.
F and 1R can be attached.

[0029]

As described above, according to the present invention, when the reflected wave detected by the ultrasonic sensor becomes equal to or lower than the preset intensity, the reflected wave immediately before the ultrasonic wave is emitted at that time. Since the signal holding circuit that performs the angle calculation with respect to the road surface of the automobile by using the arrival time to the ultrasonic sensor as the reflected wave due to the ultrasonic wave emission of, even if the intensity of the reflected wave becomes temporarily weak, It is possible to maintain an appropriate headlight optical axis angle adjustment and to realize safer and smoother traveling.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main part of an embodiment of a device of the present invention.

FIG. 2 is a signal waveform diagram of each part in FIG.

FIG. 3 is a block diagram showing an example of a vehicle headlight optical axis adjustment device.

FIG. 4 is a signal waveform diagram for explaining the operation of the device shown in FIG.

FIG. 5 is a circuit diagram showing a main part of a conventional device.

FIG. 6 is a signal waveform diagram of each part in FIG.

[Explanation of symbols]

1 (1F, 1R) ... Ultrasonic sensor, 2 (2F, 2R) ... Transmission circuit, 3 (3F, 3R) ... Reception circuit, 3A (3AF, 3A)
R) ... signal holding circuit, 4 (4F, 4R) ... selection circuit, 5
(5F, 5R) ... Timing circuit, 6 ... Control circuit, 7 ... Drive circuit, 8 ... Position sensor, 9 ... Headlight optical axis drive device, 1
1 (11F, 11R) ... Ultrasonic wave transmitting / receiving circuit, G ... Road surface, L
... distance from ultrasonic sensor to road surface, a ... pulse signal (trigger pulse), b ... high voltage signal, c ... receiving circuit output signal (distance signal), g ... signal from control circuit (driving circuit control signal), Vs ... Output axis position detection signal of headlight optical axis drive device, o ... Selection circuit input signal, p ... Reception signal.

Claims (2)

[Claims] 1. A predetermined pulsed ultrasonic wave is emitted from ultrasonic sensors provided on the front and rear end sides of a vehicle so as to face a road surface, and the reflected wave is emitted by each ultrasonic sensor at each ultrasonic wave emission. To calculate the angle to the road surface of the vehicle based on each arrival time of each reflected wave to each ultrasonic sensor, and to control the headlight optical axis angle of the vehicle according to the calculation result In the vehicle headlight optical axis adjustment device for obtaining the axis angle, when the reflected wave detected by the ultrasonic sensor becomes equal to or lower than a preset intensity, the reflected wave immediately before the ultrasonic wave emission at that time is An optical axis adjusting device for a vehicle headlamp, comprising a signal holding circuit for performing an angle calculation with respect to a road surface of the vehicle by using a reflected wave generated by ultrasonic wave emission and its arrival time at the ultrasonic sensor. 2. An ultrasonic sensor provided on each of front and rear end sides of an automobile so as to face a road surface, a transmission circuit for emitting a predetermined pulsed ultrasonic wave from each ultrasonic sensor, and each ultrasonic sensor. By a trigger circuit and a receiving circuit that amplifies and shapes the received signal by each, and outputs a distance signal whose time width changes according to the distance from each ultrasonic sensor to the road surface for each ultrasonic emission from each ultrasonic sensor A timing circuit that drives the transmission circuit so that each ultrasonic sensor emits pulsed ultrasonic waves at a preset transmission frequency and transmission time when activated and the optical axis angle of the vehicle headlight is controlled. Headlight optical axis drive means, a position sensor for detecting the position of the optical axis angle control output shaft of the headlight optical axis drive means,
Each distance signal from the receiving circuit is received, the time width thereof is converted into a digital value or an analog value for each ultrasonic wave emission from each ultrasonic sensor and stored, and each pseudo continuous signal is obtained. The angle with respect to the road surface of the automobile is calculated by a value in time, and it is determined whether the optical axis angle is proper or not based on the calculation result and the detection signal from the position sensor. In a vehicle headlamp optical axis adjusting device comprising a control circuit for driving an axis driving means to control an optical axis angle to obtain an appropriate optical axis angle, the receiving circuit is configured so that the reception signal has a preset intensity. When the following occurs, the value of the quasi-continuous signal immediately before the ultrasonic wave emission is held as the value of the quasi-continuous signal due to the ultrasonic wave emission at that time to perform the calculation and the optical axis angle control. Automotive headlight optical axis adjustment device characterized by comprising a signal holding circuit for operating the control circuit.