JPH07140261A - Frozen road surface detecting device - Google Patents

Abstract

PURPOSE:To detect a frozen road surface without using special means such as a road surface moisture meter and a heater, etc. CONSTITUTION:Air temperature measured by an air temperature sensor 4 and road surface temperature measured by a temperature sensor 1 are normally varied in correlation with each other. When moisture is present near a road surface, however, the road surface temperature temporarily stops near zero degree when the moisture is solidified below zero degree. A recognition circuit 7 recognizes this phenomenon according to the air temperature and the road surface temperature stored in a storage circuit 3, thus detecting freezing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention detects the freezing of a road surface,
The present invention relates to a road surface freeze detection device that issues an alarm.

[0002]

2. Description of the Related Art In cold weather, it is necessary to detect a frozen state of a road surface and issue an alarm so that a vehicle can safely drive on a mountain road or a highway. For example, JP-A-52-1273
In Japanese Patent Publication No. 79, a temperature determination means, a moisture determination means, a heater and the like are provided. When the temperature determination means determines that the temperature is below the freezing point and the water determination means determines that there is water, a freeze prediction signal is issued. Further, in order to increase the reliability of freezing detection, when the output signal of the water content determination means changes from the presence of water to the absence of water, it is determined that the heater is energized and the output signal of the water content determination means changes to the presence of water. Send a freeze confirmation signal. Further, in JP-A-62-245180, the dew point temperature is calculated from the atmospheric temperature and the atmospheric humidity. Freezing is determined when the road surface temperature and the difference between the road surface temperature and the dew point temperature are both 0 degrees or less and the high humidity duration is a predetermined condition. Further, in Japanese Patent Laid-Open No. 5-71111, optical fiber temperature sensors are installed at a plurality of observation points to measure air temperature and road surface temperature. The road surface condition is determined from the measured data of the air temperature and the road surface temperature and the road surface moisture data of the road surface moisture detector.

[0003]

However, in these conventional road surface freezing detecting devices, a road surface moisture meter, a hygrometer and the like are used. Further, in order to improve the accuracy of freezing detection, special means such as a heater is required. In other words, improvement in accuracy could not be expected in determining the freezing of the road surface based on the presence or absence of water and the road surface temperature.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an accurate road surface freezing detecting device without using a special means such as a road surface moisture meter or a heater.

[0005]

In order to solve the above-mentioned problems, the road surface freezing detecting apparatus of the present invention utilizes the fact that when water exists on the road surface, the water freezes below zero degrees. The inventor paid attention to the phenomenon that when the water solidifies, the road surface temperature temporarily stops near zero. Specifically, the following configurations are adopted.

An air temperature sensor for measuring the air temperature, a road surface temperature sensor for measuring the road surface temperature, a memory circuit for storing the air temperature measured by the air temperature sensor and the road surface temperature measured by the road surface temperature sensor, and data stored in the memory circuit. Of the
A determination circuit that determines whether or not the road surface temperature has a stationary point near zero degree and freezes when the temperature changes monotonously.

[0007]

According to the road surface freezing detection device having such a structure, it becomes possible to detect the freezing by processing only time-series data of air temperature and road surface temperature (road temperature). The air temperature and the road surface temperature generally change while maintaining a correlation as shown in FIG. Freezing is detected using this correlation. That is,
When there is water on the road surface, the road surface temperature changes to solid by releasing the heat of solidification (80 cal / g) near zero, and a stationary point occurs until it freezes (FIG. 5 (b)).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram, FIG.
Is a flowchart of freezing determination, FIG. 3 is a conceptual diagram showing an installation example, and FIG. 5 is a diagram showing temporal changes in air temperature and road surface temperature.

(Structure) The structure of the first embodiment of the present invention will be described with reference to FIG. The infrared camera 1a captures an image of the condition of the road surface. The temperature conversion unit 1b converts the imaged screen into road surface temperature pixel by pixel. The converted road surface temperature of each pixel is converted into a digital value by the first A / D converter 2 and stored in the storage circuit 3. On the other hand, the temperature on the road is measured by the temperature sensor 4, converted into a digital value by the second A / D converter 5, and stored in the storage circuit 3. The road surface temperature and the air temperature are stored in the storage circuit 3 as write pulses output from the timer 6 at predetermined intervals (for example, 60 seconds). The determination circuit 7 determines freezing from the temporal changes in the air temperature and the road surface temperature of the storage circuit 3. When it is determined to be frozen, the transmission / reception unit 8 transmits a freeze detection signal to the center. Further, the road surface temperature data, the air temperature data, and the image data can be transmitted to the center as needed.

An infrared camera 1 is used as the road surface temperature sensor 1.
By using a, non-contact road surface temperature monitoring and road surface monitoring in a wide area can be performed. When the road surface temperature is monitored by the infrared camera 1a, the measurement may be interrupted by the passage of the vehicle, which may affect the freeze detection accuracy. As a means for removing the influence, vehicle traffic is detected by image processing, and data during the vehicle traffic and during a certain time after the vehicle traffic are excluded from the determination. Further, by averaging the data corresponding to the pixels in the block with a plurality of pixels as one block, it is possible to correct the variation in the temperature change due to the pixels.

(Operation) When there is water on the road surface and the water freezes, a stationary point near the zero temperature occurs in the road surface temperature even when the air temperature changes monotonously as shown in FIG. Further, when there is no water on the road surface, the road surface temperature also changes monotonously as the temperature changes. Hereinafter, the flow in which the determination circuit determines the freeze will be specifically described with reference to FIG.

The road surface temperature is input (S1). Input the temperature (S2). Next, it is determined whether the road surface temperature is within the same range as the previous input value (S3). Road temperature is within the same range (Ye
In the case of s), it is determined whether the temperature is within the same range as the previous input value (S4). If the temperature is outside the same range (No), it is monitored whether a predetermined time has passed (S5), and after the predetermined time has passed (Yes
s) Output an alarm (S6). Further, in each step, in the opposite case to the above, the process returns to the step (S1) and the same processing is repeated. Even when the road surface temperature rises from the frozen state, the stationary point is generated because the heat of fusion is absorbed and changed to a liquid in the vicinity of zero degree. By grasping this phenomenon, it is determined that the freeze is released.

(Example of installation) A road surface freezing detection device is installed in a freezing danger area such as a mountain area, and the data collected by the terminal equipment is transmitted to the center and also transmitted to the information display board installed in the vicinity. Freezing information and weather information can be provided. Further, the thermal image captured by the infrared camera of the terminal equipment can be transmitted to the center for remote image monitoring at the center.

[Second Embodiment] The configuration of a second embodiment of the present invention will be described with reference to FIG. Even if the temperature is higher than zero, the heat of vaporization may be taken away by wind and the water may freeze. In addition, the freezing temperature may differ due to the influence of atmospheric pressure. In order to exclude these influences, correction is added based on the data from the pressure sensor and the wind speed sensor.

[Application to Water Surface Freezing Detection] The present invention can also be used to detect water surface freezing. That is, the water surface temperature is monitored, and it can be determined to be frozen when the temperature is constantly below 0 ° C. and a certain area of the thermal image does not change.
That is, it is utilized that the movement of particles is stopped even on a thermal image when the liquid surface is solidified by freezing.

[0017]

As described above, according to the road surface freezing detection device of the present invention, it is provided with the judging circuit for judging that the road surface temperature temporarily stops near zero degrees. Therefore, it becomes possible to detect freezing by processing only time-series data of air temperature and road surface temperature, and no special sensor such as a road surface moisture meter is required.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing freeze determination according to the present invention.

FIG. 3 is a conceptual diagram showing an example in which the present invention is installed.

FIG. 4 is a diagram showing temporal changes in air temperature and road surface temperature.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Road surface temperature sensor, 2 ... 1st A / D converter, 3 ... Memory circuit, 4 ... Temperature sensor, 5 ... 1st A / D converter, 6
... timer, 7 ... determination circuit, 8 ... transmission / reception section.

Claims (1)

[Claims] 1. An air temperature sensor (4) for measuring an air temperature, a road surface temperature sensor (1) for measuring a road surface temperature, a memory for storing an air temperature measured by the air temperature sensor and a road surface temperature measured by the road surface temperature sensor. The circuit (3) and the temporal changes in the air temperature and the road surface temperature stored in the memory circuit are monitored to determine whether the road surface temperature has a stationary point when the air temperature monotonously changes, and it is determined that freezing has occurred. Road freezing detection device comprising a determination circuit (7) for