JPH0451880B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for transmitting signals from the ground to a vehicle using a loop vehicle sensing system.

Conventional loop-type vehicle sensing devices detect vehicles by using the change in inductance when a vehicle passes over a loop coil installed on the ground, but they only have the function of simply sensing vehicles. Nakatsuta. SUMMARY OF THE INVENTION An object of the present invention is to provide a device that can detect a vehicle and simultaneously transmit road information to the vehicle by adding a data sending function to a conventional loop-type vehicle sensing device.

Therefore, in the present invention, an oscillator is connected to a loop coil buried in the surface of a vehicle path on the ground, and a change in the oscillation frequency of the oscillator depending on the presence or absence of a vehicle on the loop coil is detected. A circuit for modulating the oscillation signal of the oscillator with a transmission signal to the vehicle is installed in a loop-type vehicle sensing device on the ground that detects equipped.

In this way, the oscillation signal of the oscillator is input to the loop coil, and the oscillation signal is radiated to the space near the loop, so when a vehicle equipped with a receiver passes over the loop, the above Oscillation signals can be detected, and information from the ground can be received by detecting and demodulating the modulated oscillation signals.

An embodiment of the present invention will be described above based on the drawings. FIG. 1 is a block diagram of the ground side device in this embodiment. In this block diagram, a loop coil 1 is provided on the road surface as shown in FIG. 4 and is connected to an oscillation circuit 2. The oscillation circuit 2 performs self-excited oscillation, and its output is applied to the loop coil 1 and is also input to means H for detecting changes in the oscillation frequency. In the means for detecting a change in oscillation frequency, a tuning circuit 3 includes a loop coil 1
It is tuned to the oscillation frequency when there is no vehicle above it. 4 is a phase comparison circuit, into which the oscillation signal that has passed through the tuning circuit 3 and the direct signal from the oscillation circuit 2 are input, and when there is no car on the loop coil 1, both inputs are input. Since the phases are in-phase, the output B of the phase comparison circuit 4 is "0".

When the vehicle comes over the loop coil 1, the inductance of the loop coil 1 changes and the oscillation frequency changes. If the oscillation frequency is different from the resonant frequency of the tuned circuit 3, there will be a phase shift between the output signal of the oscillator 2 and the signal after the same signal has passed through the tuned circuit 3. A voltage appears depending on the phase difference. This voltage is input to the level detection circuit 5, and when the voltage exceeds a certain threshold voltage, the level detection circuit 5 outputs a vehicle sensing signal C. That is, in this embodiment, the tuning circuit 3, the phase comparison circuit 4, and the level detection circuit 5 constitute a means H for detecting a change in the oscillation frequency of the oscillation circuit 2. This vehicle sensing signal C is applied to a modulation signal generation circuit M. In this embodiment, the modulation signal generation circuit M consists of a one shot circuit 8 and a modulation signal forming circuit 7. When the vehicle sensing signal C is input to the one shot circuit 8, the one shot circuit 8
A pulse D having a certain time width from the rise of the vehicle sensing signal C is outputted from the modulation signal forming circuit 7.
Activate. In this embodiment, the modulation signal forming circuit 7 is a parallel-to-serial conversion circuit that converts the road information data inputted in parallel during the pulse period outputted from the one-shot circuit 8 into serial data and outputs the serial data. That is, this circuit is a register that sequentially outputs parallel input data and converts it into serial data, and is input with digitized road information. The oscillation circuit 2 also serves as a modulation circuit, and the oscillation signal A is frequency-modulated by the output signal E of the modulation signal generation circuit M. This oscillation signal A is slightly radiated into the air from the loop coil 1, so by installing a receiver on the vehicle side, simple data can be transmitted to the vehicle equipped with the receiver on the loop coil 1. It is possible to do so. In addition, since the inductance of the loop coil 1 changes due to changes in temperature, etc., in order to prevent false detection due to this, the output B of the phase comparator circuit 4 is integrated with a large time constant via a switch element 9 such as an analog switch. Input to circuit 6 and tune circuit 3 with this output
controls the resonant frequency of. As a result, the resonant frequency follows a gradual change in the oscillation frequency and is corrected so that the oscillation frequency of the oscillation circuit and the resonant frequency of the resonant circuit 3 are always the same. When a vehicle enters the vehicle and the level detection circuit 5 senses a sudden change in frequency, the switch element 9 is opened by the output C, and this correction is no longer applied and the vehicle sensing operation is performed normally.

FIG. 2 is a time chart illustrating the operation of the ground-side equipment shown in FIG. 1. Signal A is an oscillation signal of loop coil 1. Signal B is the output of the phase comparison circuit 4. When a vehicle approaches the loop coil 1, the phase comparison output B rises as shown in the figure and passes through the level detection circuit 5, resulting in a vehicle detection signal C.
becomes. This signal is input to the one-shot circuit 8, and the output signal is a pulse signal D. During this pulse period, the data signal E is output from the modulation signal forming circuit 7.
Send out. Signal A shows how the oscillation circuit 2 is modulated by this signal E (the density of the vertical lines indicates the magnitude of the frequency).

FIG. 3 is a block diagram of the receiver 16 (see FIG. 4) mounted on a vehicle. A signal from the loop coil 1 is received by a ferrite antenna 18 mounted on a vehicle, and amplified by an amplifier circuit 10. The amplified signal is input to a band filter 11, noise components are removed, and the signal is input to a demodulation circuit 12. The signal demodulated by the demodulation circuit 12 is converted into parallel signals by the serial/parallel conversion circuit 13, and road information is transmitted to the inside of the vehicle by the display device 14.

FIG. 4 is an overview diagram showing an embodiment of the present invention. The loop coil 1 buried in the road surface is connected to a ground machine 17 comprising the aforementioned oscillation circuit 2, a means H for detecting changes in oscillation frequency, a modulation signal generation circuit M, etc., and is connected to a receiver 16 mounted on a vehicle 15. A ferrite antenna 18 is connected to the antenna.

FIG. 5 shows one method for modulating the oscillation circuit 2 with data pulses, in which a variable capacitance diode 19 is used as part of the collector-emitter capacitance of the Colpitts type oscillation circuit to generate a modulation signal. The oscillation frequency is changed by changing the signal voltage from the circuit M.

The present invention is constructed as described above, and includes a modulation signal generation circuit that modulates an oscillation signal to the loop coil according to road information as a ground side device in a conventional loop type vehicle detector. It has the advantage of being able to sense a vehicle and at the same time transmit data such as road information to the vehicle by simply installing an antenna and receiver as vehicle-side devices, making it ideal for patrol cars and emergency vehicles. This can be effective in guiding automobiles, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2 is a time chart diagram of the same as above, Figure 3 is a block diagram of the same vehicle-mounted receiver as above, Figure 4 is an overview perspective view of the same as above in use, and Figure 5 is a specific circuit diagram of the same as above oscillation circuit. It is. G...Vehicle sensing device. In G, 1... loop coil, 2... oscillation circuit, H... means for detecting changes in oscillation frequency, in H, 3... tuning circuit, 4... phase comparison circuit, 5... level detection. Circuit, 6...Integrator circuit, M...Modulation signal generation circuit, in M, 7...Modulation signal formation circuit, 8
...One-shot circuit, 9...Switch element, 1
6...Receiver. In the receiver 16, 10...
Amplifying circuit, 11...Band filter, 12...Demodulation circuit, 13...Series parallel circuit, 14...Display device,
15...Vehicle, 17...Ground machine consisting of an oscillation circuit 2, means H for detecting a change in oscillation frequency, and a modulation signal generation circuit 7, 18...Ferrite antenna.

Claims (1)

[Claims] 1. A signal transmission device having a vehicle sensing device G and a modulated signal generating circuit M, wherein the vehicle sensing device G has a loop coil 1 buried in the ground and a signal transmission device connected to the loop coil. The modulation signal generating circuit M is started by inputting the output of the means H for detecting a change in the oscillation frequency; A modulated signal is generated by modulating the output of the transmitting circuit provided in the vehicle sensing device according to information to be transmitted to the vehicle for a certain period of time, and is transmitted via the loop coil 1 of the vehicle sensing device G and the transmitting circuit 2. and radiates the generated modulated signal onto a road.