JPH05100025A - Car-to-car distance measuring device - Google Patents

Abstract

PURPOSE:To provide a car-to-car distance measuring device capable of measuring the distance from the car ahead accurately even though the car body makes pitching in the advancing direction. CONSTITUTION:When a car wheel gets on a projection on a road surface to cause the car body to pitch in the advancing direction, vibration sensing means 20, 30 sense the pitching situation. On the basis of the sensed situation, a driving means 40 drives the electromagnetic wave emission from a measuring means 10 to the direction opposite to the inclination of the car body. This motion absorbs the pitch of the car body, and the electromagnetic waves emitted by the measuring means 10 are cast to the car ahead at all times, and the distance from the car ahead is measurable from the reflected waves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-vehicle distance measuring device for measuring a distance to a vehicle ahead.

[0002]

2. Description of the Related Art In recent years, rear-end collisions have increased with the increase in the number of vehicles running on highways. This is because a sufficient inter-vehicle distance cannot be secured as the number of vehicles increases. In order to avoid such an accident, the distance between the vehicle running ahead and the own vehicle is measured using a pulse laser, and an alarm is issued when the distance between vehicles becomes narrower than a certain value under the condition of a certain speed or more. An inter-vehicle distance measuring device that emits light has been developed. FIG. 4 shows an example of measuring the inter-vehicle distance using this device. As shown in the figure, the inter-vehicle distance measuring device 110 mounted on the vehicle 100 of the vehicle 100 until the laser beam 102 emitted from the laser projector 101 is reflected by the vehicle 120 ahead and returns to the light receiver 103 to be detected. Time is measured. The inter-vehicle distance is calculated by multiplying the measured time by the speed of light and halving it.

In the laser projector 101 provided in the vehicle distance measuring device 110, an optical system having a sharp directivity is used in order to irradiate as far as possible without reducing the optical power. On the other hand, the following distance detection device 11
Since 0 is fixed to the vehicle 100, the vertical movement of the vehicle body in the traveling direction due to the unevenness of the road surface causes the field of view of the laser projector 101 and the laser beam to be vertically swung. When the inter-vehicle distance is short, even if the detection range is shaken due to pitching, there is no inconvenience because a part of the vehicle 120 traveling ahead can be supplemented. However, when the inter-vehicle distance is long, as shown in FIG.
As shown in FIG. 5, the light flux is removed from the vehicle 120 ahead, or the removed portion becomes large. Therefore, the light receiver 1
03, the amount of light reflected from the vehicle 120 ahead of the vehicle becomes insufficient, and normal distance measurement cannot be performed.

Therefore, conventionally, a plurality of laser light beams are projected in a fan shape, or the light beams are mechanically and optically scanned to catch the preceding vehicle as continuously as possible, and the effective measurement distance of the inter-vehicle distance measuring device is measured. Has been devised to expand.

[0005]

By the way, an inter-vehicle distance detecting apparatus using the above method uses a light projector equipped with a plurality of laser light sources and a light projector equipped with a drive unit for moving the laser light sources to scan a light beam. Because you need
The device became complicated and was a problem. Further, even the inter-vehicle distance detecting device using the above method has a problem because the non-detection time and the non-detection space exist.

In addition to the above method, a method has also been studied in which a shock absorber is provided between the inter-vehicle distance detecting device and the vehicle to absorb longitudinal vibration of the vehicle. However, this method causes resonance,
There was a problem that the inter-vehicle distance could not be measured sufficiently.

An object of the present invention is to solve such a problem and to provide an inter-vehicle distance measuring device capable of accurately measuring an inter-vehicle distance with a vehicle in front even if the vehicle vertically shakes in a traveling direction.

[0008]

In order to solve the above-mentioned problems, an inter-vehicle distance measuring device of the present invention radiates an electromagnetic wave toward a vehicle ahead and measures the inter-vehicle distance from the reflected wave. Based on the vibration detection means for detecting the pitching of the vehicle body in the traveling direction, and the situation of the pitching of the vehicle body detected by the vibration detection means, the radiation direction of the electromagnetic wave from the measuring means is driven in the direction opposite to the pitching of the vehicle body. And a driving means for driving.

[0009]

According to the inter-vehicle distance measuring apparatus of the present invention, when the wheel rides on the convex portion on the road surface and the vehicle body vertically sways, the vibration detecting means detects the vertical swaying state of the vehicle body in the traveling direction. Based on this situation, the drive means drives the radiation direction of the electromagnetic wave from the measurement means in the direction opposite to the inclination of the vehicle body. By this operation, the longitudinal vibration of the vehicle body is absorbed, and the electromagnetic waves emitted from the measuring means are always applied to the vehicle in front, so that the distance between the vehicle and the vehicle in front can be measured from the reflected wave.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the inter-vehicle distance measuring device of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an inter-vehicle distance measuring device according to the present embodiment. As shown in FIG. 1, an inter-vehicle distance measuring device is an inter-vehicle distance detecting device 10 that is a measuring unit that measures an inter-vehicle distance from a vehicle in front of the vehicle, and an inclination detector 20 that is a vibration detecting unit that detects a vertical pitch in a traveling direction of a vehicle body.
Also, the signal processor 30 and the drive unit 4 that is a drive unit that drives the inter-vehicle distance detection device 10 in the direction opposite to the vertical vibration of the vehicle body.
0 and are provided. The inter-vehicle distance measuring device is the vehicle body 1
The inter-vehicle distance can be measured by irradiating the vehicle ahead with the laser beam 50 from the inter-vehicle distance detecting device 10. Then, even if the wheels ride on the convex portions on the road surface and the vehicle body vertically sways in the traveling direction, the drive unit 40 works so that the emission direction of the electromagnetic waves from the inter-vehicle distance detection device 10 does not shift. Therefore, the laser beam 50 from the inter-vehicle distance detecting device 10 can always irradiate the preceding vehicle.

Next, details of each device constituting the inter-vehicle distance measuring apparatus of this embodiment will be described.

First, the structures of the inter-vehicle distance detecting device 10 and the drive unit 40 will be described with reference to the perspective view of FIG. As shown in FIG. 1, an inter-vehicle distance detecting device 10 includes a laser projector 11 that emits a laser beam, a projecting lens 12 that adjusts the beam diameter of the laser beam, a Fresnel lens 13 that narrows down reflected light from a vehicle ahead, and a Fresnel lens. Light receiver for receiving the reflected light focused by 13 (large area Pin-PD)
And 14 are provided. The inter-vehicle distance detecting device 10 includes
A vertical force is applied from the drive unit 40, and the support member 1
Rotational motion centering around 5, 16 is performed. This rotational movement adjusts the emission angle of the laser beam from the laser projector 11. The drive unit 40 includes an output shaft 41 using a piezo element that expands and contracts instantaneously when an electric field is applied, and a control unit 42 that receives a signal from the signal processor 30 and applies a necessary electric field to the output shaft 41. Has been. Drive unit 4
0 directly on top of the output shaft 41 of the zero distance sensor 10
Is fixed, the output shaft 41 can obtain a high response performance with an extremely small expansion / contraction amount. In addition to the method of rotating the entire inter-vehicle distance detecting apparatus 10 by the drive unit 40 as in the present embodiment, a method of rotating the laser projector 11 and the projector lens 12 by the output shaft 41, or outputting only the laser projector 11 is performed. A method of rotating the shaft 41 may be used. Further, by moving the inter-vehicle distance detecting device 10 in the left-right direction according to the steering direction, it is possible to more reliably irradiate the vehicle ahead with the laser beam.

Next, the inclination detector 20 will be described.
The inclination detector 20 uses an optical type or electrostatic capacitance type high-speed sensor. The function of the inclination detector 20 is to output an electric signal of a voltage or a current that is exactly proportional to the deviation angle when the installation state of the inclination detector 20 deviates from the horizontal posture. The structure of the optical tilt detector 20 will be described with reference to the plan view of FIG. As shown in the figure, the inclination detector 20 includes an LED 21 that emits light from above, a split photodiode 22 that detects the light intensity of the emitted light from the LED 21, and an LE.
A single concave lens 23 arranged between the D21 and the split photodiode 22 and a mercury ball 24 placed on the concave surface of the single concave lens 23 are provided. The principle of inclination detection of the inclination detector 20 is as follows. First, the inclination detector 20
Is horizontal, the mercury bulb 24 does not move at the center of the one-sided concave lens 23. Since the irradiation light from the LED 21 is blocked by the mercury bulb 24, a shadow is formed on the split photodiode 22. Since the divided photodiode 22 can detect this shaded portion from the difference in light intensity, it can be seen that it is currently horizontal. Next, when the tilt detector 20 tilts, the mercury ball 24 rolls on the concave surface of the one-sided concave lens 23, and the position of the shadow formed on the split photodiode 22 also moves. The current tilt angle can be known by detecting the position of the shadow after the movement with the split photodiode 22. The information on the tilt angle of the vehicle body detected in this way is sent to the signal processor 30.

Next, the signal processor 30 will be described.
The signal processor 30 amplifies an electric signal from the inclination angle signal from the inclination detector 20 excluding a DC component and an unnecessary low frequency component, and sends the amplified electric signal to the driving unit. The electrical cutoff frequency of this filter is set to be equal to or slightly higher than the natural frequency of the vehicle shock absorber. By using such an electrical high-pass filter, it is possible to remove the signal of the inclination angle due to the inclination of the vehicle body on a slope. In other words, since the posture of the vehicle deviates from the horizontal plane on the uphill or downhill road, the tilt detector produces a DC offset. If this signal is sent to the drive unit 40, the output shaft 41 always applies a force in the direction opposite to the inclination of the road surface so that the inter-vehicle distance detecting device 10 becomes horizontal. With this, it is not possible to irradiate the laser beam to the vehicle ahead traveling on the slope. Therefore, it is devised that the high-pass filter removes the DC offset that occurs when the road surface continues to incline, such as on a slope, and the inter-vehicle distance detection device 10 inclines in accordance with the inclination of the vehicle body due to pitching.

As described above, the inter-vehicle distance detecting device 10 based on the pitching of the traveling vehicle in the traveling direction is realized by the cooperation of the respective devices.
The change in posture is canceled out by the expansion and contraction of the drive unit 40 in the opposite direction. As a result, the detection area of the inter-vehicle distance detection device 10 can be fixed to the average inclination direction of the road surface on which the vehicle apparently travels, without being shaken by pitching.

[0016]

According to the inter-vehicle distance measuring device of the present invention, the radiation direction of the electromagnetic wave is swung up and down in accordance with the pitching in the traveling direction of the vehicle body. Therefore, even if the wheels run on the convex portion on the road surface and the vehicle body leans, it is possible to always measure the inter-vehicle distance to the vehicle ahead.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inter-vehicle distance measuring device according to an embodiment.

FIG. 2 is a perspective view showing a structure of an inter-vehicle distance detecting device and a driving unit.

3 is a plan view showing the structure of the tilt detector 20. FIG.

FIG. 4 is a schematic diagram showing an example of measuring an inter-vehicle distance using a conventional inter-vehicle distance measuring device.

FIG. 5 is a schematic diagram showing an example of measuring an inter-vehicle distance using a conventional inter-vehicle distance measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vehicle main body 10 ... Inter-vehicle distance detection apparatus 20 ... Inclination detector 30 ... Signal processor 40 ... Drive part 50 ... Laser beam

Claims (5)

[Claims] 1. An inter-vehicle distance measuring device which is mounted on a vehicle body and measures an inter-vehicle distance to a vehicle in front, which emits electromagnetic waves toward the vehicle in front and measures an inter-vehicle distance from a reflected wave thereof. Vibration detecting means for detecting pitching in the traveling direction of the vehicle body, and based on the situation of the vehicle body pitching detected by the vibration detecting means, the radiation direction of the electromagnetic wave from the measuring means is set in the opposite direction of the vehicle body pitching. An inter-vehicle distance measuring device comprising: a driving unit that drives the vehicle. 2. The inter-vehicle distance measuring device according to claim 1, wherein the inter-vehicle distance is measured by the measuring means by detecting a time until a reflected wave returns. 3. The inter-vehicle distance measuring device according to claim 1, wherein the inter-vehicle distance is measured by the measuring means based on a phase difference between the radiated electromagnetic wave and the reflected wave. 4. The inter-vehicle distance measuring apparatus according to claim 2, wherein the measuring means uses a laser beam as an electromagnetic wave. 5. The inter-vehicle distance measuring device according to claim 1, wherein the drive unit uses a piezoelectric element to drive the measuring unit.