JPH069074B2 - Multi-lane vehicle detector - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a vehicle detector used, for example, to measure the number of vehicles passing through a road or to measure the traveling speed of the vehicle. In particular, it relates to a multi-lane compatible vehicle detector for sensing vehicles traveling in multiple lanes.

(Summary of the Invention) In the present invention, when a sensor is configured to detect a vehicle traveling in multiple lanes, both the configuration and installation work are simple, and the vehicle detection is good without impairing aesthetics. It is designed to be able to do.

(Prior Art and Problems Thereof) The following are known as conventional vehicle detectors.

(I) First Conventional Example A loop coil is buried under the road surface so as to cover almost the entire width direction of the road, and the impedance change associated with the passage of a vehicle, which is a metal body, is detected on the loop coil, and the impedance is measured. The vehicle detection signal was output based on a predetermined amount of level change due to the change.

(Ii) Second Conventional Example A pole is erected on one side of a vehicle on a road, an arm is extended from the upper end of the pole, and an oscillator that projects ultrasonic waves and a receiver that receives reflected ultrasonic waves are provided on the arm. The ultrasonic sensor is attached and the vehicle detection signal is output based on the time difference between the time when the ultrasonic wave is transmitted and the time when the ultrasonic wave is reflected depending on whether the ultrasonic wave is reflected from the road surface or reflected from the vehicle traveling on the road.

However, the conventional example having such a configuration has the following drawbacks.

Disadvantages of the first conventional example In order to detect a vehicle accurately with a loop coil, a large one of about 2 m × 2 m is usually required, and this loop coil must be buried under the road surface. There is no choice but to cut the road over a wide area. For this reason, there are drawbacks that it takes time and effort for cutting the road, the period of traffic regulation becomes long, and the construction cost becomes expensive.

Disadvantages of Second Conventional Example Since a large pole is erected on the road, there is a drawback that the installation work is time-consuming and the construction cost is high, similarly to the first conventional example. It had a drawback that it was unaesthetic because it protruded onto the road.

(Object of the Invention) The present invention has been made in view of such circumstances, and the installation work can be performed at a low cost and at a low cost, and the sensor can be installed without impairing the aesthetic appearance. An object of the present invention is to reduce the number of vehicles so that a vehicle with a plurality of lanes can be detected well.

(Structure and Effect of the Invention) In order to achieve such an object, the present invention provides a receiving coil having a magnetic body as a magnetic core, which is arranged at a boundary between adjacent lanes, and a receiving current of the receiving coil. An output circuit that outputs a vehicle detection signal in response to a level change, and first and second transmission coils having a magnetic core as a magnetic core, which is arranged on a side of the adjacent lane opposite to the boundary. A high-frequency oscillator circuit for outputting an exciting current to the first and second transmitting coils, and a switching means for causing the first transmitting coil and the second transmitting coil to output the exciting current in a time sharing manner. And is configured.

According to this configuration, when the excitation current is output from the high-frequency oscillation circuit to the first transmission coil and the second transmission coil in a time-sharing manner, the first transmission coil or the first transmission coil to which the excitation current is output is output. 2 A magnetic field is formed from the transmitting coil to the receiving coil, and the magnetic field induces a current in the receiving coil. When the vehicle approaches the magnetic field, the magnetic flux passes through the vehicle and the magnetic resistance on the receiving coil side decreases, increasing the density of the magnetic flux linking the receiving coil and increasing the receiving current, or eddy current. The level changes depending on whether the receiving current of the receiving coil decreases due to the loss.In any case, the level of the receiving current changes compared to when the vehicle is not approaching, The approach of the vehicle in each lane can be detected based on the divided configuration.

Therefore, since a magnetic field is formed between each of the first and second transmitting coils and the receiving coil, each of the first and second transmitting coils and the receiving coil is different from the conventional loop coil. If they are installed in the median strip or on the roadside and the sensor body is installed in one place, it is enough to bury the cable connecting the coil and the sensor body under the road surface. Moreover, even if all of the coils are buried, the space for burying them is small, cutting work on the road can be simplified, installation work can be done with less effort, and the period of traffic regulation can be shortened, and the construction cost can be reduced. It's cheaper.

Further, unlike the ultrasonic type, since the pole is not installed upright, it can be installed without impairing the aesthetics.

Further, in order to detect a vehicle on two lanes, by adopting a time-division configuration, a magnetic excitation current is output to the first and second transmission coils at set time intervals, and the transmission coil on the output side and both lanes are connected. Since the vehicle detection signal is output from the receiving coil in a corresponding state and the receiving coil is also used, compared to the case of installing a pair of transmitting coil and receiving coil as a set for each lane, The number of coils can be reduced by one, and vehicle detection in multiple lanes can be performed more inexpensively by reducing the number of constituent members.

(Description of Embodiments) Hereinafter, the present invention will be described in detail based on embodiments illustrated in the drawings. FIG. 1 is a schematic configuration diagram of a multi-lane vehicle detector according to an embodiment of the present invention, FIG. 2 is a schematic plan view showing an installed state, and FIG. 3 is a circuit diagram. In these figures, 1
Is a first transmitting coil, and 2 is a second transmitting coil, which are wound around magnetic bodies 1a and 2a such as ferrite as magnetic cores. The reference numeral 3 designates a receiving coil wound around a magnetic core 3a, which is also ferrite, and which is wound around the magnetic core 3a. In a road having two lanes, a first lane 4a and a second lane 4b, a first lane 4a 2 lanes 4b
It is embedded in the boundary part 4c with the. Further, the first transmitting coil 1 is on the road side opposite to the boundary portion 4c of the first lane 4a, and the second transmitting coil 2 is on the second lane 4b.
Are buried on the road side opposite to the boundary portion 4c. Each of the first and second transmitting coils 1 and 2 and the receiving coil 3 may be fixedly installed on the road surface.

Reference numeral 5 denotes a sensor main body that houses an electric circuit section. The sensor main body 5, the first and second transmitting coils 1 and 2, and the receiving coil 3 are embedded in a power transmission cable 5 below the road surface.
It is connected via a.

The first transmission coil 1 and the second transmission coil 2 are connected to an excitation means 8 including a high frequency oscillation circuit 6 that outputs an excitation current and an amplification circuit 7 that amplifies the excitation current.

An output circuit 9 that outputs a vehicle detection signal in response to a change in the level of the received current is connected to the receiving coil 3. The output circuit 9 includes an amplifier 10, a band pulse filter 11, a detection circuit 12, and a determination unit 13, and amplifies the reception current from the reception coil 3 and then removes a noise component by the band pass filter 11 for detection. The circuit 12 detects the wave and inputs it to the first and second decision units 13a and 13b. Each of the determination units 13a and 13b includes a switch circuit 14 and a first switch circuit 14 of the switch circuit 14.
A first capacitor 15 connected to the contact, a second capacitor 16 connected to the second contact of the switch circuit 14, and a differential amplifier circuit 17 connected to the positive terminals of the first and second capacitors 15 and 16, respectively. A comparator 18 connected to the output terminal of the differential amplifier circuit 17, a constant voltage power supply 19 for determining the threshold voltage Vref of the comparator 18, and a timing for outputting a switch switching pulse signal to the switch circuit 14. And a circuit 20.

The timing circuit 20 outputs a pulse signal to the switch circuit 14 when the output of the comparator 18 is "L" level, and stops the output of the pulse signal when the output of the comparator 18 is "H" level. ing. The switch circuit 14 connects the detection circuit 12 to the first capacitor 15 when the pulse signal from the timing circuit 20 is at “H” level, and conversely, when the pulse signal is at “L” level. The second capacitor 1
6 is connected.

A transmission switching circuit 21 is interposed between the first and second transmission coils 1 and 2 and the excitation means 8, and the transmission switching circuit 21 is driven by a switching pulse signal from a switching control signal generating circuit 22. It is configured to be switched every set time. That is, when the switching pulse signal is at the "H" level, the exciting means 8 receives the first transmission coil 1
On the contrary, the exciting means 8 is connected to the second transmitting coil 2 when the switching pulse signal is at the "L" level.

Further, the detection circuit 12 and the first and second determination units 13
A reception switching circuit 23 is interposed between a and 13b, and when the switching pulse signal from the switching control signal generating circuit 22 is at "H" level, the detection circuit 12 is connected to the first judging section 13a. The detection circuit 12 is connected to the second determination unit 13b when the switching pulse signal is at the "L" level.

A transmission switching circuit 21, a switching control signal generation circuit 22, and a reception switching circuit 2 for detecting a vehicle in a time-sharing manner in a manner contrary to each of the first and second lanes 4a and 4b. And is referred to as switching means.

Reference numeral 24 denotes a third capacitor interposed between the reception switching circuit 23 of each of the first and second determination sections 13a and 13b and the switch circuit 14, and even when the reception switching circuit 23 is switched to the other side. , For holding the signal level at the level before the switching.

The configuration of the second determination unit 13b is the same as that of the first determination unit 13a, and is omitted in the drawing.

Next, the operation of this embodiment will be described based on the time chart of FIG.

The exciting current from the high frequency oscillating circuit 6 is amplified by the amplifying circuit 7, and the exciting current is responded to the switching control signal a from the switching control signal generating circuit 22 in response to the first transmitting coil 1 and the second transmitting coil 2. And output in a time-divisional manner, and the first and second transmitting coils 1 and 2 are excited in accordance with the exciting currents b and c, and the first transmitting coil 1 or the second transmitting coil 2 A magnetic field is formed between the receiving coil 3 and the receiving coil 3.

The reception current received by the reception coil 3 is amplified by the amplifier 10, the noise component is removed by the bandpass filter 11, and the signal d is detected by the detection circuit 12 to become the signal e.

In response to the switching control signal a from the switching control signal generation circuit 22, the signal e from the detection circuit 12 is alternately output to the first determination unit 13a and the second determination unit 13b in a time-sharing manner. To be done.

Looking at the signal f output to the first determination unit 13a, when the vehicle travels on the first lane 4a and reaches the magnetic field, the time t ₂ at which a minute time has elapsed from the time t ₁ at which the magnetic field is reached Until then, the pulse signal g is output from the timing circuit 20 to the switch circuit 14, and the switching of the switch circuit 14 is repeated. The first capacitor 15 is
The second capacitor 16 is charged by the input signal h when the pulse signal g is “H” level, and is charged by the input signal i when the pulse signal g is “L” level.
These input signals h and i have the same level as the output signal f from the reception switching circuit 23. First and second capacitors 15 and 16, to repeat the both alternately charged and discharged in response to the switching operation, the charging voltage V ₁ of the first capacitor 15 and the charging voltage V ₂ of the second capacitor 16, typically , Stay substantially equal.

By the way, as the vehicle reaches the magnetic field, the magnetic flux concentrates on the metal portion of the vehicle, and the mutual inductance between the first transmitting coil 1 and the receiving coil 3 changes. That is, the amplitude of the output signal d of the bandpass filter 11 starts to increase, and along with that, the levels of the output signal e of the detection circuit 12 and the output signal f from the reception switching circuit 23 also start to increase. At this time, when the pulse switching signal g rises at time t ₁ and the reception switching circuit 23 is connected to the first capacitor 15, the level of the input signal h to the first capacitor 15 is
The output signal f from the reception switching circuit rises by the amount corresponding to the rise, and accordingly, the level of the output signal j of the differential amplifier circuit 17 rises by a minute amount. However, since the rising amount of the output signal j is very small, the output signal j is
It is lower than the threshold voltage Vref of 8 and the output signal k of the comparator 18 maintains the “L” level, and the vehicle detection signal S ₁ is not output.

There is a fall of the pulse signal g at time t _2, the when the reception switching circuit 23 is connected to the second capacitor 16, in this case, the vehicle has penetrated largely into the magnetic field, the output signal f from the reception switching circuit 23 The level of the input signal i to the second capacitor 16 is higher than that at the time t ₁ to the time t ₂ .
The input signal h to the capacitor 15 rises sufficiently larger than the rise. Therefore, in the first capacitor 15,
The charging voltage V ₁ is kept constant, but in the second capacitor 16, the charging voltage V ₂ is changed to the input signal i to the charging voltage V _2.
Level, that is, the level of the output signal f from the reception switching circuit 23 changes. As a result, the output signal j of the differential amplifier circuit 17 also rises, its level exceeds the threshold voltage Vref, and the output signal k of the comparator 18 becomes "H" level. As a result, the vehicle detection signal S ₁ is output to an external device (not shown), and the “H” level output signal k is input to the timing circuit 20 to output the pulse signal g from the timing circuit 20. Is stopped.

As the vehicle passes through the magnetic field, the level of the output signal f from the reception switching circuit 23 decreases accordingly.
As a result, when the level of the output signal j of the differential amplifier circuit 17 becomes lower than the threshold voltage Vref, the output signal k from the comparator 18 becomes the “L” level and the vehicle detection signal S ₁ is not output. Also. Output signal k
As a result, the pulse signal g is output from the timing circuit 20 to the switch circuit 14 and the switching is restarted. As a result, the levels of the input signals h and i to the first and second capacitors 15 and 16, respectively, are low corresponding to the level of the output signal f from the reception switching circuit 23, and the output signal from the differential amplifier circuit 17 is low. j also stabilizes at the “L” level.

According to the present invention, one lane on each side can be applied to roads having different passage directions adjacent to each other with the median strip as a boundary portion, in short, regardless of the traffic direction. , As long as the roads are adjacent to each other and have 2n (n: integer) lanes, the method can be applied to all roads.

Further, these sensors may be installed at a set distance in the vehicle running direction, and the sensing time difference may be divided by the set distance to measure the running speed of the vehicle.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a multi-lane vehicle detector according to an embodiment of the present invention, FIG. 2 is a schematic plan view showing an installation state, and FIG.
The figure is a circuit diagram and FIG. 4 is a time chart. DESCRIPTION OF SYMBOLS 1 ... 1st transmission coil, 1a ... 1st transmission coil magnetic body, 2 ... 2nd transmission coil, 2a ... 2nd transmission coil magnetic body, 3 ... reception coil, 3a ... reception coil magnetic, 4a, 4b ... lane, 4c ... boundary, 6 ... frequency oscillation circuit, 9 ... output circuit, 21, 22, 23 ... switching means, _{S 1,} S 2 _... vehicle sensing signal.

Claims (1)

[Claims] 1. A receiving coil having a magnetic body as a magnetic core, which is arranged at a boundary between adjacent lanes, and an output circuit which outputs a vehicle detection signal in response to a change in a level of a receiving current of the receiving coil. First and second transmission coils having magnetic bodies as magnetic cores, which are arranged on a side opposite to the boundary between adjacent lanes, and an excitation current is output to the first and second transmission coils. And a switching means for causing the first transmitting coil and the second transmitting coil to output exciting current in a time-sharing manner, which is contrary to the above.