JPS61243597A - Vehicle sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Field of the Invention) The present invention can be used, for example, in a traffic control system that detects the number of vehicles traveling on a road and controls traffic lights to facilitate vehicle passage. The present invention relates to a vehicle sensor that detects a vehicle by detecting a change in a magnetic field as the vehicle passes by.

(Summary of the Invention) The present invention makes it possible to increase the sensitivity of vehicle detection, simplify construction work such as cutting of passages during construction, and suppress the occurrence of disconnection accidents.

(Prior art and its problems) One of the main types of conventional vehicle detectors is a loop coil type vehicle detector as shown in FIG.

In FIG. 10, 50 is a loop coil buried in a passage (road) 53, 51 is a high-frequency oscillator circuit that outputs an excitation current to the loop coil 50, and 52 is when a change in the current flowing through the loop coil 50 is more than a predetermined amount. This is an output circuit that outputs a vehicle sensing signal S to the vehicle.

The operation of this loop coil type vehicle sensor is as follows.

The excitation current from the high frequency oscillation circuit 51 is transmitted to the loop coil 50.
, a magnetic field H is created by the loop coil 50. When the vehicle passes through this magnetic field H, the magnetic flux concentrates on the metal parts of the vehicle, so the inductance of the loop coil 50 changes, and the input current to the output circuit 52 changes.

The output circuit 52 outputs a vehicle sensing signal S in response to this change in input current.

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

(a) The loop coil 50 usually has a size of about 2 m x 2 m, and in order to bury such a large loop coil 50 in the passage (road) 53, the passage 53 must be cut in a large area. Such cutting work is a large-scale work, and not only is the construction cost high, but also requires a lot of time and effort.

(b) The loop coil 50 buried in the passage 53 is frequently subjected to loads caused by passing vehicles, and is therefore prone to breakage accidents. If a disconnection accident occurs, vehicle detection becomes impossible.

In addition, as a means to solve such problems, it is possible to significantly reduce the size of the loop coil and adopt a ferrite coil in which the loop coil is wound around a ferrite core. However, since the vehicle sensing area is as narrow as the diameter of a ferrite coil in a sentinel, there is a problem in that the sensitivity is low, and the reality is that it has not been put into practical use.

(Objective of the invention) The present invention has been made to address these circumstances by 9% and 1, and simplifies construction work such as cutting of passageways during construction while increasing the sensitivity of vehicle detection. At the same time, the purpose is to suppress the occurrence of disconnection accidents.

(Configuration and Effects of the Invention) In order to achieve the above object, the present invention has the following configuration.

That is, the vehicle sensor of the present invention includes a transmitting coil having a magnetic core as a magnetic material disposed on one side of the passage, a high-frequency oscillation circuit that outputs an excitation current to the transmitting coil, and a high-frequency oscillation circuit on the other side of the passage. The receiving coil includes a receiving coil whose magnetic core is an arranged magnetic material, and an output circuit that outputs a vehicle sensing signal in response to a change of a predetermined amount or more in a received signal of the receiving coil.

In this configuration, "aisle" refers to a wide area where vehicles pass, including roads, road surfaces within premises,
Also refers to the floor surface. Also, "one side of the aisle, the other side" refers to one side in the direction of crossing the aisle.

In a broad sense, it includes not only the other side, but also an example of the other side in the direction along the passage, and one side and the other side in the diagonal direction.

The effects of this configuration are as follows.

(i) When the excitation current from the high frequency oscillation circuit flows into the transmitting coil, a magnetic field is formed between the transmitting coil and the receiving coil. When the vehicle passes through this magnetic field, the mutual inductance changes, and the level of the signal received by the receiving coil changes. This received signal is input to the output circuit, and when a change in the level of the received signal is equal to or greater than a predetermined amount (that is, when a vehicle is detected), a vehicle sensing signal is output from the output circuit.

(ii) Since the transmitting coil and the receiving coil are sufficiently smaller than conventional loop coils, even if they are buried in the passage, the cutting work can be simpler than in the conventional case. Furthermore, it is not necessarily necessary to embed a transmitting coil and a receiving coil in order to detect a vehicle, and it is sufficient to simply install them on a passageway. In this case, the construction work can be further simplified.

When placing the high frequency oscillation circuit and the output circuit on one side of the aisle, it is necessary to route the power transmission line across the aisle, but even if this power transmission line is buried in the aisle,
Only the cutting of one power line is required. Furthermore, when wiring is placed above the passage, no cutting is necessary.

Further, when the high frequency oscillation circuit and the output circuit are arranged on opposite sides of the passage, there is no need to wire the power transmission line across the passage.

(iii) As described in (ii) above, the possibility of wire breakage is significantly reduced compared to the conventional case where the entire large loop coil is buried in the passage.

(iv) Since the magnetic field formed between the transmitting coil and the receiving coil is formed above the path, the vehicle sensing area is sufficiently large compared to the case of a single ferrite coil, and the vehicle sensing sensitivity is becomes high.

As described above, according to the present invention, while increasing the sensitivity of vehicle detection, it is possible to simplify construction work such as cutting of passages during construction, reduce construction costs and labor, and reduce wire breakage. This has the effect of suppressing the occurrence of accidents.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

<First Embodiment> FIG. 1 is a schematic configuration diagram of a vehicle sensor according to a first embodiment (basic embodiment) of the present invention.

〔composition〕

In FIG. 1, reference numeral 2 denotes a transmitting coil having a magnetic core 2a made of a magnetic material, and is disposed on one side of the passage (road) 1 in the width direction. 3 is a high frequency oscillation circuit that outputs an excitation current to the transmitting coil 2. 4 is a receiving coil having a magnetic core 4a made of a magnetic material, and is disposed on the other side of the passage 1 in the width direction. 5
is an output circuit that includes a determination unit that detects a change of a predetermined amount or more in the reception signal of the reception coil 4, and outputs a vehicle sensing signal S to an external device (not shown) based on the detection.

The output circuit 5 and the high frequency oscillation circuit 3 are built into a sensor main body 6 disposed on one side of the passage 1.

The power transmission line 7 connecting the receiving coil 4 and the output circuit 5 is
Wires are wired in the groove formed in passage 1 by cutting,
It is buried. Further, a transmitting coil 2 and a receiving coil 4 are also buried in the passage 1.

The receiving coil 4 is connected to the output circuit 5, and the high frequency oscillation circuit 3 is also connected thereto. Output circuit 5
A built-in determination unit constantly compares the signal level from the high-frequency oscillation circuit 3, that is, the current level output to the transmitting coil 2, and the current level input from the receiving coil 4, and determines the level between them. A vehicle sensing signal S is output when the difference is greater than or equal to a predetermined amount.

〔motion〕

Next, the operation of this first embodiment will be explained based on FIG. 2.

(2) When an excitation current flows from the high frequency oscillation circuit 3 to the transmitting coil 2, a magnetic field H is formed between the transmitting coil 2 and the receiving coil 4. As shown in FIG. 2(A), when the vehicle M is not passing through the magnetic field H, the levels of the transmitting current (excitation current) and receiving current input to the output circuit 5 are below a predetermined amount, so the vehicle is detected. There is no signal S output.

■ When the vehicle M is passing through the magnetic field H as shown in Figure 2 (B), the magnetic flux concentrates on the metal parts of the vehicle M, so
The mutual inductance between the transmitting coil 2 and the receiving coil 4 changes.

Depending on the material of the vehicle body (for example, the difference between iron and aluminum) and vehicle height, there are cases where the magnetic resistance decreases and the received current increases, and cases where the received current decreases due to eddy current loss, but in any case, this current The change is captured by the determination section of the output circuit 5. That is, while the transmitting current is constant, when the receiving current changes and the level difference between the two types of currents becomes equal to or greater than a predetermined amount -L, the output circuit 5 outputs the vehicle sensing signal S.

Note that the sensing area can be arbitrarily set by adjusting the interval between the transmitting coil 2 and the receiving coil 4. Further, the power transmission line 7 may be constructed above the passage 1, and the transmission coil 2. Either or both of the receiving coils 4 may be installed on the road surface or on a pillar erected on the road surface.

Furthermore, since the transmitting coil 2 and the receiving coil 4 are placed separately, if the vehicle M is equipped with a transmitter/receiver,
It is also easy to develop the device so that it can communicate with the transceiver.

Second Embodiment Next, a more specifically configured second embodiment will be described based on FIG. 3. FIG. 3 is a block diagram of the vehicle sensor.

〔composition〕

In FIG. 3, 8 is a power amplifier circuit inserted between the high frequency oscillation circuit 3 and the transmitting coil 2, 9 is an amplifier circuit connected to the receiving coil 4, 10 is a filter, 11 is a detection circuit, 12 is an analog switch circuit. A first contact of the switch circuit 12 is grounded via a capacitor 13, and a second contact is grounded via a capacitor 14. The capacitances of both capacitors 13 and 14 are equal to each other. The positive terminals of both capacitors 13 and 14 are input-connected to a differential amplifier circuit 15, and the output terminal of the differential amplifier circuit 15 is input-connected to a comparator 16. 17 is a constant voltage power supply for determining the threshold voltage V ref of the comparator 16.

Comparator 16 is connected to an external device (not shown). 18 outputs a pulse signal C to the switch circuit 12 when the output of the comparator 16 is "L"level;
This is a timing circuit that stops outputting the pulse signal C when the output of the comparator 16 is at the "H" level.

The switch circuit 12 connects the detection circuit 11 to the capacitor 13 when the pulse signal C from the timing circuit 18 is at the "H" level, and connects the detection circuit 11 to the capacitor 14 when the pulse signal C is at the "L" level. configured to connect.

〔motion〕

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

■ The excitation current from the high frequency oscillation circuit 3 is transmitted to the power amplifier circuit 8.
The signal is amplified and excites the transmitting coil 2.

After the reception current by the reception coil 4 is amplified by the amplifier circuit 9, noise components are removed by the filter IO and the signal a is
becomes. This signal a is detected by a detection circuit 11 and becomes a signal S.

■ Time when vehicle M reaches magnetic field H1. Until time t2 when a minute time has elapsed, the pulse signal C is output from the timing circuit 18 to the switch circuit 12 (see ■ below).
Switching of the switch circuit 12 is repeated. The capacitor 13 is charged by the input signal d when the pulse signal C is at the "H" level, and the capacitor 14 is charged by the input signal e when the pulse signal C is at the "I" level. These input signals d and e are at the same level as the output signal of the detection circuit 11.

Since both the capacitor 13 and the capacitor 14 are repeatedly charged and discharged by switching, the charging voltage v13 of the capacitor 13 and the charging voltage v14 of the capacitor 14 remain substantially equal. Therefore, the output signal f from the differential amplifier circuit 15 is at the "L" level, and the output signal g from the comparator 16 also maintains the "L" level, so that the vehicle sensing signal S is not output.

Since the output signal g is at "L" level, timing circuit 1
8 continues to output the pulse signal C, and the switching of the switch circuit 12 is repeated.

■ Time 1. When the vehicle M reaches the magnetic field H at , the amplitude of the output signal a of the filter 10 starts to increase, and the detection circuit 1
The level of the output signal S1 begins to rise. Time 1. There is a rise of the pulse signal C at , and the detection circuit 11 is connected to the capacitor 13 . Therefore, capacitor 13
The level of the input signal d to the output signal d increases by the amount of the output signal s.

Therefore, the level of the output signal f of the differential amplifier circuit 15 increases by a small amount. The increase in the output signal f is minute,
Since it is lower than the threshold voltage V ref of the comparator 16, the output signal g of the comparator 16 maintains the "L" level and no vehicle sensing signal S is output.

(2) At time t2, the pulse signal C falls, and the detection circuit 11 is connected to the capacitor 14. Time 1
．． Since the level of the output signal S of the detection circuit 11 has increased between time t2 and time t2, the level of the input signal e to the capacitor 14 has increased sufficiently larger than the increase in the input signal d at the time ①. do. As a result, the level of the output signal f of the differential amplifier circuit 15 exceeds the threshold voltage Vref, and the output signal g of the comparator 16 becomes "H" level. As a result, the vehicle sensing signal S is output, the output signal g is input to the timing circuit 18, and the output of the pulse signal C from the timing circuit 18 is stopped.

Therefore, switching of the switch circuit 12 is stopped at time t2, and the detection circuit 11 remains connected to the capacitor 4.

That is, the level of the input signal d to the capacitor 3 is held constant, the charging voltage VI3 is also kept constant, and
The level of the input signal e to the capacitor 4, that is, the charging voltage V
14 changes according to the level change of the output signal of the detection circuit 11. Further, the level of the output signal f of the differential amplifier circuit 15 changes similarly. This state continues until the vehicle M passes through the magnetic field H.

■ When the vehicle M passes through the magnetic field H, the level of the output signal of the detection circuit 11 decreases, and in response, the differential amplifier circuit 15
When the level of the output signal f becomes lower than the threshold voltage V ref at time t3, the vehicle sensing signal S is no longer output and the output signal g of the comparator 16 becomes "L" level. As a result, timing circuit 1
8, the pulse signal C is output to the switch circuit 12, and switching is restarted. Then, the level of the input signal d to the capacitor 13 and the input signal e to the capacitor 4 becomes low corresponding to the level of the output signal of the detection circuit 11, and the output signal f of the differential amplifier circuit 15 also goes to "L" level. becomes stable.

<Third example> Next, a third embodiment will be described based on FIG. 5.

In FIG. 5, the same reference numerals as those shown in FIG. 3 according to the second embodiment refer to the same parts as the two parts indicated by the reference numerals in this embodiment as well.

〔composition〕

A series circuit including an attenuator 19 and a filter 20 is inserted between the high frequency oscillation circuit 3 and the power amplifier circuit 8.

The attenuator 19 is configured to receive an attenuator value control signal from an output ink face 22 of a microcomputer 21 (hereinafter referred to as microcomputer) via a bus 23.

The circuit configuration from the receiving coil 4 to the detection circuit 11 is the second one.
This is similar to the example. An A/D conversion circuit 24 at the next stage of the detection circuit 11 is connected to an input interface 25 of the microcomputer 21.

In the microcomputer 21, 26 is a CPU, 27 is a ROM,
28 is a RAM, 29 is a timer, 30 is an output interface for communicating with an external device (not shown), and 31 is a bus.

〔motion〕

The basic operation of this embodiment will be explained.

The excitation current from the high-frequency oscillation circuit 3 is attenuated by an attenuator 19, and after unnecessary frequency components such as harmonics are removed by a filter 20, it is amplified by a power amplifier circuit 8 to excite the transmitting coil 2. By excitation of the transmitting coil 2,
A magnetic field H is formed between the transmitting coil 2 and the receiving coil 4. After the received current by the receiving coil 4 is amplified by the amplifier circuit 9, noise components are removed by the filter 10, and detected by the detection circuit 11.

The detected analog signal is converted into a digital signal by the A/D conversion circuit 24, sent to the CPU 26 via the input interface 25 and the bus 31, and sent from the CPU 26 to the RAM 28.

The CPU 26 adjusts the attenuator value of the attenuator 19 according to the program written in the ROM 27, processes the received data from the receiving coil 4, and outputs the vehicle sensing signal S in the case of vehicle sensing. 30 to an external device.

Next, the detailed operation will be explained based on the flowchart of FIG. 6, the time chart of FIG. 7, and the memory map of FIG. 8. The memory map in FIG. 8 is for the RAM 28, and has an address ADI of the received data from the A/D conversion circuit 24 and an address ATT of the attenuator value.

(1) Turn on the power at time T1 and set the attenuator value to the maximum value in step (see Figure 7 (A)).
, minimize the transmit level. This attenuator value is stored at address ATT. In step (2), the received data (see FIG. 7(B)), which is the output value of the A/D conversion circuit 24, is read. In step ■, the level of the received data is
A reference value Va corresponding to a predetermined voltage necessary to sense
Determine whether it has been reached. If NO, step■
Then, the attenuator value of the address ATT is decremented by 1, and the process returns to step (2). By repeating this process, the attenuator value decreases stepwise, and the level of the received data increases stepwise.

(2) At time T2, when the level of the received data reaches the reference value Va and the judgment in step ■ becomes YES, the process moves to step ■, where the level of the received data from the A/D conversion circuit 24 is read again, and step (2) Store it at address ADI in RAM2B. Next, in step (2), idling is performed for a certain period of time. Read the level of the received data again in step ■, and address A in step ■.
The difference from the previous received data level stored in D1 is calculated. At step [phase], the difference is the sensing reference value vt
Determine whether it exceeds h.

If No, the process moves to step (2), stores the received data level read in step (2) at address ADI, idles at step @, and then returns to step (2).

(3) When the vehicle M reaches the magnetic field ■(, and at time T3, the difference between the current received data level and the previous received data level exceeds the sensing reference value vth, and the judgment at step [phase] becomes YES. Proceeding to step 0, the vehicle sensing signal S is output to an external device via the output interface 30 (see FIG. 7(C)).

(4) Next, in step (2), the received data level is read again, and in step [phase], it is determined whether the difference between the address ADI stored in step (2) and the received data level exceeds the sensing reference value vth.

If YES, return to step ■.

(5) Vehicle M fr<Eil world ■(passes through, time T
4, if the difference between the address ADI stored in step ■ and the received data level becomes smaller than the sensing reference value vth, it is determined No in step ■, and the process moves to step [phase] to output the vehicle sensing signal S. stop.

In the present invention, as shown in FIG. 9, when there are two passages 1, a transmitting coil 2 is installed at the boundary between both roads 1.1, and a receiving coil 4.1 is installed outside each passage 1.1. Set up 4, then 1
An embodiment in which one transmitting coil 2 is used for sensing vehicles on two paths 1, 1 is also included.

[Brief explanation of the drawing]

1 and 2 relate to a vehicle sensor according to a first embodiment of the present invention, FIG. 1 is a schematic configuration diagram of the vehicle sensor, and FIG. 2 (A
), (B) are operation explanatory diagrams, FIGS. 3 and 4 relate to the vehicle sensor of the second embodiment, FIG. 3 is a block diagram, FIG. 4 is a time chart I, and FIGS. 8 relates to the third embodiment, FIG. 5 is a block diagram, FIG. 6 is a flowchart, FIG. 7 is a time chart, FIG. 8 is a memory map, FIG. 9 is a schematic diagram of another embodiment, and FIG. The figure is a schematic diagram of a conventional example. In the figure, 1 is a passage, 2 is a transmitting coil, 2a is a magnetic core,
3 is a high frequency oscillation circuit, 4 is a receiving coil, 4a is a magnetic core,
5 is an output circuit.

Claims (2)

[Claims] (1) A transmitting coil whose magnetic core is a magnetic material placed on one side of the passage, a high-frequency oscillation circuit that outputs an excitation current to this transmitting coil, and a magnetic core whose magnetic material is placed on the other side of the passage. A vehicle sensor comprising: a receiving coil; and an output circuit that outputs a vehicle sensing signal in response to a change of a predetermined amount or more in a received signal of the receiving coil. (2) The vehicle sensor according to claim (1), wherein the transmitting coil and the receiving coil are embedded in the passage.