JP2530304Y2 - Vehicle detection device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a vehicle traveling on a road or the like.

[0002]

2. Description of the Related Art When a vehicle exists on a road or the like, a change occurs in geomagnetism in the vicinity of the vehicle. This is caused by the fact that a vehicle uses a ferromagnetic material as a main constituent material, and the ferromagnetic material disturbs the distribution of geomagnetism. Utilizing such a phenomenon, conventionally, a magnetic sensor is disposed on a road side portion of a road or the like, a change in the geomagnetism of the road is detected by this sensor, and the detected value is compared with a preset reference value. There is a device that determines the presence or absence of a vehicle from the comparison result.

[0003]

[Problems to be Solved by the Invention] By the way, when one vehicle passes through the detection area, the output signal of the magnetic sensor swings once each in the positive and negative directions, or once in both the positive and negative directions. May swing. If the output signal is compared and discriminated with a constant reference value as in a conventional device, a malfunction may occur. That is, there is no problem if the output of the magnetic sensor swings once in either the positive or negative direction as shown in FIG. 4 when one vehicle passes, but as shown in FIG. When the vehicle swings in both the positive and negative directions, a detection signal indicating that two vehicles have passed is generated, and a count error or the like of the number of vehicles passing through occurs.

[0004]

Means for Solving the Problems The present invention has been made to solve the above-mentioned conventional problems, and the configuration thereof will be described with reference to FIG. 1 corresponding to the embodiment.
A magnetic sensor S for detecting a change in geomagnetism occurring near the vehicle due to the presence of the vehicle, a first comparing means 1 for comparing an output signal of the sensor S with a first reference value Th1,
Calculating means (differentiating circuit) 5 for obtaining a differential value of the output signal of the magnetic sensor S using time as a parameter; second comparing means 2 for comparing the differential value with a second reference value Th2; A signal is generated at the same time as the signal exceeds the first reference value Th1, and thereafter, when the output signal of the sensor falls below the reference value and the above-mentioned differential value changes from above the second reference value Th2 to below. A signal generating means (for example, an AND gate 3, a flip-flop 4, and inverters 6 and 7) for stopping the output of a signal, and using the output of the signal generating means as information for determining the presence or absence of a vehicle. It is characterized by having constituted.

[0005]

The signal generating means generates a signal at the same time that the output signal of the magnetic sensor S exceeds the first reference value Th1, but even if the sensor output becomes equal to or less than the reference value Th1,
As long as the differential value of the sensor output does not fall below the second reference value Th2, the state of the signal output is maintained. Thus, as shown in FIG. 3, for example, when the output of the magnetic sensor S swings once in both positive and negative directions by passing one vehicle, when the sensor output changes from positive to negative or from negative to positive. If the output value of the first comparing means 1 falls or rises, the differential value dA of the sensor output at this time is not less than the reference value Th2, so that fact is not reflected, and the detection signal Q is, for example, H Level is retained. Then, when the output of the magnetic sensor S becomes equal to or less than the reference value Th1 and the differential value dA of the output becomes equal to or less than the reference value Th2, the detection signal Q returns to the L level. Therefore, even if the output of the magnetic sensor S swings once in both positive and negative directions by passing one vehicle, the vehicle detection signal Q is a signal indicating that one vehicle has passed.

[0006]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention. The magnetic sensor S is installed on a road side of a road or the like, and detects a change in geomagnetism caused by a vehicle passing through the road. The output signal A of the magnetic sensor S is input to each of the first comparison circuit 1 and the differentiation circuit 5. The differentiating circuit 5 differentiates the output signal of the magnetic sensor S using time as a parameter. The output signal dA of the magnetic sensor S after the differentiation is input to the second comparison circuit 2.

[0007] The first and second comparison circuits 1 and 2
Each input signal is compared with a reference value Th1 or Th2,
Output is generated only when the input signal exceeds the reference value. The polarities of the output signals A1 and dA1 of the two comparison circuits 1 and 2 are inverted by the inverters 6 and 7, respectively, and the inverted signals A2 and dA2 are input to the AND gate 3. In the comparison circuits 1 and 2, the reference values Th1 and Th2 are set on both the positive and negative sides, and when the absolute value of the output signal of the magnetic sensor S becomes larger than the reference values Th1 and Th2. Thus, each of the comparison circuits 1 and 2 generates an output.

The output of the AND gate 3 is input to the reset terminal of the flip-flop 4. The output terminal A11 of the first comparison circuit 1 is connected to the set terminal of the flip-flop 4.
Is entered. Then, the output Q of the flip-flop 4 is provided as a signal for determining the presence or absence of the vehicle. 2 and 3 are timing charts of the embodiment of the present invention, respectively, and the operation will be described below with reference to these two figures and FIG.

First, with reference to FIG. 2, a case where the output of the magnetic sensor S when one vehicle passes through the detection area swings once to one of the positive and negative sides will be described. The output signal of the magnetic sensor S is used as the reference value Th1 of the first comparison circuit 1.
At the same time, the output signal A1 of the comparison circuit 1 rises, and at this time, the flip-flop 4 is set, and the output value Q becomes H level. On the other hand, since the second comparison circuit 2 generates an output only while the differentiated output signal dA of the magnetic sensor S exceeds the reference value Th2, the signal dA1 has a waveform as shown in FIG. AND gate 3 has its second
When the inverted signal dA2 of the output of the comparison circuit 2 and the inverted signal A2 of the output of the first comparison circuit 1 simultaneously become H level, an H-level output is generated. At this time, the flip-flop 4 is reset, and its output signal becomes L level. From the output of the flip-flop 4, it can be known that one vehicle has passed the detection area.

Next, with reference to FIG. 3, a case where the output of the magnetic sensor S due to the passage of one vehicle swings once in both positive and negative directions will be described. First, as before, the comparison circuit 1
When the output signal A1 rises, the flip-flop 4 is set and its output value Q becomes H level. The second comparison circuit 2 determines that the differentiated signal dA is equal to the reference value T.
Since the output is generated only while h2 is exceeded, the signal d
A1 has a waveform as shown in the figure.

Here, since the output of the magnetic sensor S swings in both positive and negative directions, the first comparison circuit 1
As shown in the figure, the output signal A1 has a waveform signal having two pulses, and the set signal is input again to the flip-flop 4. Before the input of the second set, the first and the second signals are output. The inverted signals A2 and dA2 of the outputs of the two comparison circuits 1 and 2 do not go high at the same time, and the output of the flip-flop 4 remains at the high level. Thereafter, when the inverted signals A2 and dA2 of the two become H level at the same time, the flip-flop 4 is reset and its output signal becomes L level.

As described above, according to the embodiment of the present invention, even if the output of the magnetic sensor S fluctuates in both positive and negative directions when one vehicle passes, the detection signal becomes a one-pulse signal, This makes it possible to detect the number of passing vehicles and the like without error. In the above embodiment, the detection signal, that is, the output signal of the flip-flop 4 is maintained at the H level while the vehicle is present in the detection area. It can be used as information for calculating occupancy. Also,
When only the number of vehicles is counted, the vehicle detection signal of the embodiment of the present invention may be configured to use a rising edge and output a pulse signal having a constant width starting from the rising edge.

[0013]

As described above, according to the present invention, a signal output is generated at the same time as the output of the magnetic sensor exceeds the reference value. As long as the differential value of the sensor output is not less than a predetermined reference value, a signal generating means for holding a signal generation state is provided, and the output is used as information for determining the presence or absence of a vehicle. Even if the output of the magnetic sensor swings in both positive and negative directions due to passing of the vehicle, the vehicle detection signal does not have two or more pulse waveforms. Thus, even when the magnetic sensor outputs a different waveform signal due to a difference in the type of passing vehicle, etc., it is possible to always obtain accurate detection signals for all of the vehicles regardless of this. It becomes possible to grasp the number of vehicles traveling on the road more accurately than before.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a timing chart of the embodiment of the present invention.

FIG. 3 is a timing chart of the embodiment of the present invention.

FIG. 4 is a timing chart of a conventional vehicle detection device.

FIG. 5 is a timing chart of a conventional vehicle detection device.

[Explanation of symbols]

 S ··· magnetic sensor 1 ··· first comparison circuit 2 ··· second comparison circuit 3 ··· AND gate 4 ··· flip-flop 5 ··· differentiation circuit 6 7 ··· Inverter

Claims (1)

(57) [Scope of request for utility model registration] 1. A magnetic sensor for detecting a change in geomagnetism generated in the vicinity of the presence of a vehicle, a first comparing means for comparing an output signal of the sensor with a first reference value, and a time parameter. Calculating means for obtaining a differential value of the output signal of the magnetic sensor, second comparing means for comparing the differential value with a second reference value, and an output signal of the magnetic sensor exceeding the first reference value At the same time, a signal is generated, after which the output signal of the sensor becomes less than the reference value,
And a signal generating means for stopping the signal output when the differential value changes from the second reference value to the second reference value. The output of the signal generating means is used to determine the presence or absence of the vehicle. A vehicle detection device configured to be used as a vehicle.