JPS637631B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle detector used in a control device for railway signals and traffic signals, and in particular, when a vehicle enters an area where a transmitting coil and a receiving coil are installed, the degree of electromagnetic coupling between the transmitting coil and receiving coil increases. The present invention relates to a vehicle detector that detects a vehicle by utilizing changes in the vehicle.

As shown in FIG. 1A, the transmitting coil 1 and the receiving coil 2 are placed on a track or road at a predetermined distance l, and an alternating current signal Va of V ₁ sinωt is supplied from the transmitting circuit 3 to the transmitting coil 1. When the receiving circuit 4 processes the signal Vb of V ₂ sin (ωt + φ) received by the receiving coil 2, a train or a car (these are referred to as vehicles in the present invention) appears in the installation area of both coils (between both coils, Vehicles are detected by utilizing the fact that the degree of electromagnetic coupling between both coils changes by, for example, 10% or more when the vehicle enters the upper side of the coil (so-called detection area), and the reception level changes accordingly. be able to.

However, as shown in FIG. 1A, if the configuration is only made up of the transmitting coil 1, receiving coil 2, transmitting circuit 3, and receiving circuit 4, the characteristics of the transmitting circuit 3 and receiving circuit 4 will fluctuate (drift) depending on the temperature. , Moreover, since the drift may be 10% or more, the fluctuation may cancel out the change in the degree of electromagnetic coupling due to the vehicle entering the installation area of both coils, and conversely, the drift may Therefore, there is a risk that vehicle detection information may be erroneously output.

Therefore, in order to detect vehicle flow using an electronic circuit using changes in the degree of electromagnetic coupling caused by vehicles entering the installation area of both coils, it is essential to reduce disturbances caused by temperature fluctuations. As shown in FIGS. 1B, C, and D, interference caused by temperature fluctuations is reduced by differentially extracting signals caused by a vehicle entering the installation area of both coils.

The vehicle detector shown in FIG. 1B is provided with a differential coil 5 near the receiving coil 2, and a part of the AC signal Va supplied from the transmitting circuit 3 to the transmitting coil 1 is passed through an attenuation phase shift circuit 6 to a predetermined value. attenuated and phase shifted by the value
The AC signal Vc of V ₃ sin (ωt-φ) is applied to the differential coil 5.
This coil 5 is used to obtain an alternating current signal Vd, which is V ₄ sin (ωt−φ), which is in the opposite phase to the coupling between the coils 1 and 2 (the received voltage Vb of the receiving coil), to the receiving coil 2. The input to the receiving circuit 4 is (Vb-Vd). In this vehicle detector, if the coupling between the coils 1 and 2 is small, it is necessary to reduce the current supplied to the coil 5, so the attenuation in the attenuation phase shift circuit 6 must be increased. The coupling between the input line of the attenuation phase-shifting circuit 6 and the lead wires of the coil 5 and the coil 2 cannot be ignored, which not only makes a practical configuration difficult, but also temperature fluctuations of the attenuation phase-shifting circuit 6 cannot be ignored.

The vehicle detector shown in Fig. 1C has a differential coil 5 provided on the transmitting coil 1 side, and the signal Vc of this coil 5 is passed through an attenuation phase shift circuit 6' to a signal of V ₄ sin (ωt - φ).
Convert this signal Vd to coil 2 signal Vb
are combined in the differential circuit 7 so that the input to the receiving circuit 4 becomes (Vb-Vd).
Similarly to the vehicle detector shown in FIG.
Coupling between the lead wire between the attenuated phase shifter 6' and the attenuated phase shifter 6', the lead wire between the attenuated phase shifter 6' and the differential circuit 7, and the lead wire of the coil 2 can be ignored. This not only makes practical configuration difficult, but also causes temperature fluctuations in the attenuation phase shift circuit 6 that cannot be ignored. This vehicle detector can be used as a wheel detector in which the coupling between the coils 1 and 2 is relatively large (see, for example, Japanese Patent Publication No. 45-4157).

The vehicle detector shown in FIG. 1D converts the signal Va into a signal Vd of V ₄ sin (ωt−φ) with an attenuation phase shift circuit 6″,
This signal Vd and signal Vb are transferred to a transformer 8 using an iron core.
The input signal to the receiving circuit 4 is (Vb-Vd). This vehicle detector is
While the coils 1 and 2 are coupled spatially, the signal Vd is electrically coupled (using the transformer 8 with an iron core), so the environmental characteristics do not match.

In addition to the drawbacks mentioned above, the conventional vehicle detectors described above are expensive because they all use complex attenuating phase shift circuits.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle detector that can maintain spatial coupling without using a complicated attenuation phase shift circuit and obtain a differential output even when the coupling between transmitting and receiving coils is small. shall be.

As shown in FIG.
1 is provided, and a second auxiliary coil 12 is provided near the receiving coil 2. The auxiliary coils 11 and 12 are
The AC signal Vd induced into the coil 2 via the coils 11 and 12 is the AC signal Vb induced directly from the coil 1 to the coil 2 so that the coupling is in reverse phase with respect to the coupling between the coils 1 and 2. are connected to each other so that they are in opposite phase to each other. To connect the auxiliary coils 11 and 12 in this way, for example, when the magnetic fields of coils 1 and 2 are in the directions of arrows 1' and 2', the magnetic field of coil 12 is in the direction of arrow 1.
It is sufficient to connect them in the direction of 2'.

The size, number of turns, and position of the auxiliary coils 11 and 12 relative to the coils 1 and 2 are such that the AC signal Vd in the conventional vehicle detector shown in FIG.
In particular, it is preferable to provide the auxiliary coils 11 and 12 in a loop formed by the coils 1 and 2 as shown in FIG. It may be provided outside the loop, or it may be provided at a location between coils 1 and 2.

Here, the coils 1 and 2, 1 and 11, and 2 and 12 are spatially connected, and their physical connections are the same.

In the above-mentioned vehicle detector, the AC signal Vd induced into the coil 2 via the coils 11 and 12 is connected to the coil 1.
AC signal induced in coil 2 by the combination of and 2
Since the phase is opposite to Va, the input to the receiving circuit 4 becomes differential with Va-Vd. Therefore, when a vehicle enters the installation area of coils 1 and 2, if coils 1 and 11 and coils 2 and 12 are sufficiently close, the coupling between them will not be affected by the vehicle.
The rate of change (△Va) due to the approach of the vehicle is △Va/Va−Vd, which is significantly larger than the rate of change (△Va/Va) when the auxiliary coils 11 and 12 are not provided.

As described above, in the present invention, auxiliary coils are provided in the vicinity of the transmitting coil and the receiving coil, and both auxiliary coils are connected so as to affect the coupling between the transmitting coil and the receiving coil by coupling in opposite phase. , even though the coupling between each coil is a spatial coupling.
Differential output can be obtained even when the coupling between the transmitting and receiving coils is small without using an attenuated phase shift circuit or a transformer with an iron core. The vehicle detector can be used without worrying about leakage from the wire.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional device, FIG. 2 is a diagram showing an example of a wheel detector according to the present invention, and FIG. 3 is a diagram showing an example of the positional relationship between the transmitting/receiving coil and the auxiliary coil. 1: transmitting coil, 2: receiving coil, 3: transmitting circuit, 4: receiving circuit, 11, 12: auxiliary coil.

Claims (1)

[Claims] 1. In a vehicle detector that detects a vehicle by utilizing a change in the degree of electromagnetic coupling between the transmitting coil and the receiving coil when the vehicle enters the installation area of the transmitting coil and the receiving coil, which are provided at locations apart from each other, A first auxiliary coil is provided near the coil, a second auxiliary coil is provided near the receiving coil, and both auxiliary coils are influenced by coupling in opposite phase to the coupling between the transmitting coil and the receiving coil. A vehicle detector characterized in that it is connected to