JPH0310063B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that determines the wet state of a road surface and controls braking force.

When the road surface is wet, the coefficient of friction between the road surface and the tires decreases, which can cause slippage during braking and cause the vehicle to become unbalanced. Therefore, in a car, if the road surface condition is determined and the degree of braking is changed according to the wet condition of the road surface, that is, the degree of slipperiness, it becomes possible to safely stop or decelerate.

An object of the present invention is to provide a brake control device that accurately grasps the wet state of the road surface, changes the degree of braking, and can completely stop and decelerate without contacting the road surface. be.

The present invention includes a light source means including a light source that turns on and off light at a predetermined frequency to irradiate the road surface; a first wave means for deriving only the frequency component of the output from the first detection means; and a second detection means for detecting light in a waveband not absorbed by water among the light reflected from the road surface. , second wave means for deriving only the frequency component of the output from the second detection means; and receiving outputs from the first and second wave means;
a calculation means for deriving an electrical signal corresponding to a ratio of a light level in an absorption waveband of water to a light level in a non-absorption waveband; A brake control device for a vehicle is characterized in that it comprises a brake control means that reduces the degree of braking of the vehicle as the degree of braking increases.

Embodiment FIG. 1 is a system diagram of a road surface condition determining section used in the present invention. A road surface 1 on which a car or the like travels is irradiated with light from a light source 3 of a light source means 7 energized by a DC power source 2 . The light source 3 is, for example, an incandescent light bulb. The reflected light indicated by reference numeral 4 is incident on a lens 6 via a plate-shaped light shielding member 5 that is rotationally driven. The light shielding member 5 is rotated at a predetermined rotational speed Vc, so that the image splitting prism 6 is turned on and off at the predetermined frequency.
Light that has been turned off is incident.

In the above example, the light source means 7 includes the DC power supply 2 and
Although the light source 3 is composed of a light source 3 and a light shielding member 5, in other embodiments of the present invention, the light source 3 is a fluorescent lamp, etc., and is energized by a commercial AC power source, and the light from the light source is It is also possible to irradiate the road surface and guide the reflected light from the road surface to the image splitting prism 6.

Light from the light source means 7 is guided to the first detection means 8 and the second detection means 9 via the image splitting prism 6. The first detection means 8 includes a filter 10 that blocks visible light and a light source element 11. Similarly,
The third detection means 9 includes a filter 1 that blocks visible light.
2 and a photoconductive element 13. Photoconductive element 1
The outputs from 1 and 13 are amplified by amplifier circuits 14 and 15 and guided to bandpass filters 16 and 17 shown in FIG.

FIG. 3 is a graph showing the transmittance in the near-infrared region using the thickness of condensed water vapor in the atmosphere as a parameter. Such characteristics also apply to the light level of reflected light corresponding to the wet state of the road surface 1. The reference mark Pr indicates the thickness of water condensed from water vapor. As is clear from FIG. 3, when the road surface 1 is wet, the wavelength is 1.0 to 1.1μ.
Light with a wavelength longer than m is largely absorbed,
In particular, it can be seen that light around wavelengths 1.4 and 1.9 is largely absorbed. Furthermore, it can be seen that light having a wavelength of less than 1.0 to 1.11 μm is hardly absorbed by the water on the road surface 1.

The photoconductive element 11 included in the first detection means 8 is
For example, it is PbS, which has detection characteristics that broadly cover the absorption waveband of water, as shown by line 11 in FIG. On the other hand, the photoconductive element 13 included in the second detection means 9 is realized by, for example, a silicon photodiode, and enhances the light in the non-absorption waveband of water, as shown by line l2 in FIG. It has the characteristic of detecting with high sensitivity.

The filters 10 and 12 for blocking visible light have a characteristic of transmitting light having a wavelength longer than 0.85 μm, as shown in FIG. 5, and blocking visible light shorter than that wavelength. This prevents false detection due to ambient light.

In this way, the photoconductive element 1 of the first detection means 8
From 1, the absorption waveband of water, e.g. 0.9 to 2.0 μm.
An electrical signal corresponding to the light level is derived.
From the other photoconductive element 13, an electrical signal corresponding to the light level in the non-absorption waveband of water, for example 0.9 to 1.0 μm, is derived. Bandpass filter 1
6 and 17 pass only light having a frequency that is turned on and off by the light shielding member 5 of the reflected light given to the image splitting prism 6. The output from the bandpass filter 17 is level-adjusted by a level adjustment circuit 18 , full-wave rectified by a full-wave rectifier circuit 19 , and supplied to an arithmetic circuit 21 from a line 20 . The output from the bandpass filter 16 is sent from the full-wave rectifier circuit 22 via the line 23 to the arithmetic circuit 2.
given to 1. Level of electrical signal on line 23
VA corresponds to the level of light in the water absorption waveband of reflected light. The level of the electrical signal from line 20 also corresponds to the level of light in the non-absorbing waveband of water. The arithmetic circuit 21 calculates the ratio r between the light level VA in the water absorption waveband and the light level VB in the non-absorption waveband by performing the calculation shown in the first equation.

r=VA/VB... (1) According to the inventor's experiments, as shown in Figure 6, when water is gradually poured onto the concrete road surface from time t1, the water changes from dry to wet depending on the degree of wetness. During drying before time t2 when the level ratio r changes, there is no absorption of light by water, so r=
It is 1. When road surface 1 is sufficiently wet at time t2, light is largely absorbed by water,
Therefore, the ratio r becomes zero or a value close to zero.

The display circuit 24 responds to the output from the arithmetic circuit 21 and visually displays the degree of wetness of the road surface 1 corresponding to the level ratio r expressed by the first equation.

The degree of wetness of the road surface is derived as described above.
The brake control means (not shown) is an arithmetic circuit 2.
A braking system (not shown) of the automobile is controlled in response to the output from 1, and the degree of braking is controlled to be smaller as the degree of wetness increases.

As described above, in the present invention, the degree of wetness of the road surface is determined without contacting the road surface. Furthermore, in the present invention, the wet state of the road surface is determined based on the ratio of the light level in the absorption waveband by water to the light level in the non-absorption waveband, so that the light irradiated onto the road surface is The wet condition of the road surface is detected regardless of the strength of the wetness. Therefore, the wet state can be accurately determined, and based on this, the degree of braking is controlled to be smaller as the degree of wetness increases, thereby preventing the vehicle body from bending when braking. It is possible to safely stop or decelerate. Further, since the light given from the light source means to the first and second detection means is turned on and off at a predetermined frequency, malfunctions due to ambient light can be avoided.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of the road surface condition determination unit used in the present invention, and FIG. 2 is a first detection means 8 shown in FIG. 1.
and a block diagram of an electric circuit related to the second detection means 9, FIG. 3 is a graph showing water permeability, and FIG.
The figure is a graph showing the characteristics of the photoconductive elements 11 and 13,
FIG. 5 is a graph showing the characteristics of the filter 10 that blocks visible light, and FIG. 6 is a graph showing the experimental results of the inventor of the present invention. 1...Road surface, 2...DC power supply, 3...Light source, 4
... Reflected light, 5 ... Light shielding member, 6 ... Image splitting prism, 7 ... Light source means, 8 ... First detection means, 9
...Second detection means, 14, 15...Amplification circuit, 1
6, 17... Band pass filter, 18... Level adjustment circuit, 19, 22... Full wave rectifier circuit, 21
...Arithmetic circuit, 24...Display circuit.

Claims (1)

[Claims] 1. Turn on light at a predetermined frequency toward the road surface.
a light source means including a light source that is turned off and irradiated; a first light detection means for detecting light in a water absorption waveband among light reflected from a road surface; and the frequency component of the output from the first detection means. a first wave means for deriving only the frequency component of the output from the second detecting means; a second detecting means for detecting light in a waveband that is not absorbed by water among the light reflected from the road surface; and a second detecting means for deriving only the frequency component of the output from the second detecting means. two-wave means; receiving outputs from the first and second wave means;
a calculation means for deriving an electrical signal corresponding to a ratio of a light level in an absorption waveband of water to a light level in a non-absorption waveband; 1. A brake control device for a vehicle, comprising: brake control means for reducing the degree of braking of the vehicle as the degree of braking increases.