JPH04600A - Vehicle sensing device - Google Patents

Abstract

PURPOSE:To detect the traveling speed of a vehicle based on the measuring time of a time measuring means and a prescribed interval by arranging two earth magnetism sensors included in two earth magnetism change detectors respectively on the side of a vehicle traveling route with a prescribed interval. CONSTITUTION:Two magnetic sensors 1a, 1b consisting of semiconductor Hall elements are arranged on the side of the vehicle traveling route in parallel with the prescribed interval. When a vehicle passes the sensors in the order of 1a and 1b, respective sensors 1a, 1b detect the change of earth magnetism magnetic flux density and amplifiers 2a, 2b output prescribed outputs with a time interval determined by a vehicle speed and the interval between both sensors 1a, 1b. When these outputs reach respective levels regulated by resistors 3a, 3b, multivibrators 4a, 4b output respective pulses A, B. The pulse A allows a counter 6 to start to count up clock pulses generated from an oscillator 5 and the pulse B stops the counting. The count value is displayed on a display device 7 and the traveling speed of the vehicle is found out of the displayed count value, a clock pulse period and the interval between both sensors 1a, 1b.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a vehicle sensing device that utilizes local changes in geomagnetic field caused by the approach of a vehicle whose main constituent material is a ferromagnetic material, and particularly to a geomagnetic detection device. Equipped with two sensors, these two
The present invention relates to a vehicle sensing device configured to measure the traveling speed of an approaching vehicle based on the difference in detection times of geomagnetic changes by two sensors.

<Prior Art> There is a device that uses ultrasonic waves as a device for measuring the running speed of a vehicle, which has recently been widely used. In addition, there are devices that use microwaves instead of ultrasonic waves, and electromagnetic coils buried in two locations on the road surface along the direction of vehicle travel, to reduce the influence of the magnetic flux produced by these electromagnetic coils from vehicles. A device or the like that measures vehicle running speed by detecting a time difference may be considered.

<Problem to be solved by the invention> However, in the case of devices that use ultrasonic waves or microwaves, the work of installing balls and arms on the road to hold the transmitting/receiving heads of the devices is difficult, as well as the installation of electromagnetic coils. Equipment that requires burying the ground requires cumbersome and costly road construction.

In addition, all of these methods require a drive unit for emitting ultrasonic waves or microwaves or supplying current to an electromagnetic coil, and a receiving unit for detecting reflected waves of ultrasonic waves or microwaves or changes in magnetic flux. This requires an additional device section, which increases the complexity of the device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle sensing device capable of measuring the traveling speed of a vehicle, which eliminates the above-mentioned drawbacks associated with the prior art.

<Means for Solving the Problems> In order to solve the above problems, the vehicle sensing device according to the present invention includes a geomagnetism detection sensor, an amplifier that amplifies the output of the geomagnetism detection sensor, and outputs a predetermined reference voltage. and a signal that generates a geomagnetic change detection signal to notify that a change in magnetic flux density of the geomagnetism at the position where the geomagnetism detection sensor is placed exceeds a predetermined value when the output of the amplifier exceeds the reference voltage. two sets of geomagnetic change detection devices comprising generators, and a time measuring means for measuring the signal generation time difference of the geomagnetic change detection signals emitted by each of the signal generators included in each of the two sets of geomagnetic change detection devices; It is configured.

<Operation> By installing the respective geomagnetic sensors included in the two sets of geomagnetic change detection devices on the side of the vehicle travel road at predetermined intervals, the time measured by the time measuring means and the predetermined The running speed of the vehicle can be determined from the interval.

<Example> Next, an example of the present invention will be described based on FIG. 1, FIG. 2, and FIG. 3.

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, in which two geomagnetic change detection devices 1 and 2 consisting of the same components include a magnetic sensor la or 1b, an amplifier 2a or 2b, a monostable multi-high It consists of a break 48 or 4b and a trigger level adjustment variable resistor 3a or 3b for adjusting the trigger level of these monostable multibiflators. By setting the trigger level to a predetermined voltage, when the output of the amplifier 2a or 2b exceeds a predetermined voltage, the monostable multi-vib break-4a or 4b as a signal generator that emits a geomagnetic change detection signal generates a pulse signal. Output. The pulses output from the monostable multi-high breaks 48 and 4b, for example, respectively cent or minus cents the counter 6 at their rising edges. Thereby, the counter 6 counts the clock pulses output from the clock oscillator 5, and the result is displayed on the display 7. In this embodiment, semiconductor Hall elements having electrical connections as shown in FIG. 2 are used for the magnetic sensors 1a and 1b.

In the circuit configuration as described above, two magnetic sensors 1a and 1b made of semiconductor Hall elements are installed parallel to each other at a predetermined distance apart from each other beside the vehicle travel path. If a vehicle passes by magnetic sensors 1a and lb in this order, magnetic sensors 1a and 1b detect changes in the geomagnetic flux density at their respective positions, and amplifiers 2a and 2b detect changes in the vehicle's running speed. and the third magnetic sensor at a time T determined by the interval between both magnetic sensors.
Signals as shown by symbols a and b in the figure are output. Respective output a and trigger level adjustment resistor 3a
or monostable multibibreak upon reaching a predetermined level defined by 3b - 4a and 4b respectively
Pulse signals A and B as shown in the figure are output. The counter 6 starts counting the clock pulses C (FIG. 3) output by the clock oscillator in response to the pulse signal A, and stops counting in response to the pulse signal B. The count value of clock pulses C counted between pulse signals A and B is displayed on the display 7.

The running speed of the vehicle is determined from the count displayed on the display 7, the period of the clock pulse C, and the spacing between the magnetic sensors 1a and lb. In this case, it goes without saying that it is desirable to configure the display 7 to convert the counted value of the clock pulses into the running speed of the vehicle instead of displaying the counted value of the clock pulses.

Although a semiconductor Hall element was used as the magnetic sensor in the above embodiments, the present invention can also be implemented using other magnetic sensors such as a fluxgate type magnetic sensor.

Further, according to the present invention, by providing means for indicating which magnetic sensor outputs a signal first, it is possible to detect not only the running speed of the vehicle but also the direction in which the vehicle is running.

<Effects of the Invention> As can be seen from the above explanation, according to the present invention, the mechanism is simple because there is no need for a drive unit such as an oscillating unit that emits a search signal for vehicle detection, and initial adjustment at the time of installation is easy. It's very easy. Also, assuming that the speed of the vehicle is 1100km/h, the time required to cover a distance of 1m is 3.
6m5ec, even if a clock pulse with a frequency of about 10kHz is used, if the distance between two magnetic sensors is about 111, it is possible to measure the vehicle running speed with three-digit accuracy. Because it is small and lightweight, the entire device can be housed in one case and easily installed on roadside guardrails, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention. FIG. 2 shows a drive circuit for a semiconductor Hall element as a magnetic sensor. FIG. 3 is an explanatory diagram of the operation of the embodiment shown in FIG. 1. ■b...Magnetic sensor 2a, 2b...Amplification 3
a, 3b...variable resistance for trigger level adjustment 4a,
4b... Monostable multi-bi break -... Clock oscillator 6... Counter... Display

Claims (1)

[Claims] Each includes a geomagnetism detection sensor, an amplifier that amplifies the output of the geomagnetism detection sensor, a voltage source that outputs a predetermined reference voltage, and a position where the geomagnetism detection sensor is placed when the output of the amplifier exceeds the reference voltage. Two sets of geomagnetic change detection devices each consisting of a signal generator that emits a geomagnetic change detection signal to notify that a change in geomagnetic flux density at a location exceeds a predetermined value; A vehicle sensing device comprising time measuring means for measuring a signal generation time difference of the geomagnetic change detection signals generated by each of the signal generators.