JP2001216862A - Axle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axle sensor, capable of stably detecting the passage of an axle of a vehicle, without being affected by the changes in temperature. SOLUTION: As a communication conduit 17 for communicating both tubes 16, 16 has a diameter smaller than the tubes 16, 16, the resistance is low when the air flows slowly in the communication conduit 17 and is increased, when the air flows quickly. The differential pressure is solved by the flow of the air from one tube to the other tube 16 via the communication conduit 17 when a temperature around an axle sensor is gradually changed and the difference in internal pressure is found between both tubes 16, 16. In contrast, when a vehicle has passed through the axle sensor and the difference in internal pressure is suddenly generated between both tubes 16, 16, the resistance is increased, when the air flows into the communication tube 17, and the pressure difference cannot dissolved, but detected by a differential pressure sensor 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axle sensor for detecting passage of an axle of a vehicle.

[0002]

2. Description of the Related Art When a vehicle passes through a gate, there is a system which counts the number of axles of the vehicle and discriminates the type of the vehicle based on the number of axles. Used for The conventional axle sensor includes one tube disposed on a road and a pressure detector that detects the pressure of air sealed in the tube, and the internal pressure of the tube is set to a predetermined reference value. It was detected whether or not the vehicle had stepped on the tube and passed through based on whether or not it was larger.

[0003]

However, the conventional axle sensor described above has a problem that the use environment is limited because the internal pressure of the tube is changed not only by the treading pressure by the vehicle but also by a temperature change. there were.
If temperature correction is to be performed, a temperature sensor and an arithmetic circuit for calculating a correction value are required, which increases costs.

The present invention has been made in view of the above circumstances, and has as its object to provide an axle sensor capable of stably detecting the passage of an axle of a vehicle without being affected by a temperature change.

[0005]

In order to achieve the above object, an axle sensor according to the first aspect of the present invention extends in parallel in a direction crossing a road, and is provided with a pair of movable sensors which are sequentially pressed on wheels of a vehicle. A flexible conduit, a pair of pressure detectors for detecting the internal pressure of each flexible conduit, and one of the internal pressures of both flexible conduits receiving the detection result of both pressure detectors The present invention is characterized in that a reversal detection unit is provided for determining that the state of the other has been switched from the state higher than the internal pressure to the state higher than the internal pressure of the other.

According to a second aspect of the present invention, in the axle sensor according to the first aspect, the two flexible conduits are connected to each other by a communication conduit narrower than the flexible conduits.

[0007] The third aspect of the present invention is the first or second aspect.
In the axle sensor described above, when the reversal detection unit detects that one of the internal pressures of both flexible conduits has been switched from a state higher than the other internal pressure to a state where the other is higher than the one internal pressure. When the inversion detection unit detects that the number of axles that have passed through the axle sensor has been switched from a state in which the other is greater than the internal pressure to a state in which one is greater than the other, the vehicle passes the axle sensor. The present invention is characterized in that an axle counting unit for counting the number of axles minus is provided.

According to a fourth aspect of the present invention, in the axle sensor according to any one of the first to third aspects, the peak value of one of the internal pressures of the two flexible pipes and the other internal pressure are used. It is characterized in that an abnormality detecting means for performing an abnormality detection is provided based on whether or not the difference from the peak value is equal to or more than a predetermined reference value.

[0009]

When the wheel of the vehicle passes over the axle sensor, the flexible conduit located on the near side in the traveling direction of the vehicle is first crushed and then the other. Are crushed, the peak values of the internal pressures of both flexible pipes are out of timing with each other. Then, the reversing detection unit determines that one of the states has been switched from the state in which the internal pressure is higher than the other to the state in which the other is higher than the internal pressure, and detects the passage of the axle of the vehicle. As described above, in the present invention, the passage of the axle is detected based on the relative change in the internal pressure of the two flexible pipes. This is canceled when the internal pressure of the road is compared, and is hardly affected by a temperature change, so that it is possible to stably detect the passage of the axle.

<Invention of Claim 2> Since the diameter of the connecting pipe communicating the two flexible pipes is smaller than that of the flexible pipe, the resistance is small when air flows slowly through the connecting pipe.
If the air is going to flow quickly, there will be great resistance. As a result, the temperature around the axle sensor gradually changes,
When a pressure difference occurs between the internal pressures of the two flexible pipes, air flows from one to the other flexible pipe via the communication pipe, and the pressure difference is eliminated. On the other hand, when the vehicle passes through the axle sensor and suddenly generates a large differential pressure between the internal pressures of the two flexible conduits, the resistance increases when air flows through the connecting conduit, and the differential pressure is eliminated. This is not detected by the pressure detection unit.

<Invention of Claim 3> In the structure of Claim 3,
Depending on the traveling direction of the vehicle passing through the axle sensor, whether to count the axle to be counted up or down is switched, so even if the wheels move back and forth through the axle sensor, the number of axles can be accurately calculated. Can be counted.

<Invention of Claim 4> When air leaks due to a hole in one of the two flexible pipes, one of the internal pressures of the two flexible pipes when the wheel passes. The peak value of the internal pressure is different from the peak value of the other internal pressure. Then, the abnormality detecting means determines that the difference between the values of these peak values is equal to or greater than a predetermined reference value, and an abnormality is detected.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the axle sensor according to the present invention will be described below with reference to FIGS. This axle sensor is used in the above-described vehicle type discriminating system.
A groove-shaped recess 11 extends in a direction perpendicular to the traveling direction of the vehicle, and an axle sensor is housed therein (see FIG. 1).

The axle sensor has an elastic body 13 formed of, for example, a resin such as rubber. The elastic body 13 extends in the horizontal direction corresponding to the recess 11, and as a whole, the recess 11
And the elastic body 1
3 is in a state of slightly protruding above the upper end surface of the recess 11 (see FIG. 3A).

The elastic body 13 has a pair of holes 13A, 13A.
Are parallel to each other and penetrate in the longitudinal direction of the elastic body 13 so as to move back and forth in the traveling direction of the vehicle. A pair of tubes 16, 16 are inserted into the holes 13A, 13A, respectively.

Each of the tubes 16 is made of a material having elasticity such as rubber, for example.
A, as shown in FIG. 2, is a connecting pipe 17 having an inner diameter smaller than the tube 16, both of which are located at one end face of the elastic body 13.
Are connected to each other. On the other hand, the starting ends 16B of both tubes 16 are both led out from the other end surface of the elastic body 13, and
It is connected to a pressure detector 18.

As shown in FIG. 3, the pressure detector 18 has a pair of detecting portions 18 each having a space communicating with each tube 16.
A and 18B, and a differential pressure sensor 19 is provided on a partition wall between the two detection units 18A and 18B. The differential pressure sensor 19 includes, for example, a variable resistance circuit fixed to a diaphragm, and the diaphragm includes both detection units 18A, 1A.
When deformed by the differential pressure of 8B, the resistance value of the variable resistance circuit changes, whereby the output voltage from the differential pressure sensor 19 is output as a voltage signal corresponding to the differential pressure between the internal pressures of both tubes 16, 16. Is done.

An output signal from the differential pressure sensor 19 is amplified by an amplifier 23, is converted into a digital signal by an A / D converter 24, and is taken into a CPU 25.
The CPU 25 operates as described below to detect whether or not the axle of the vehicle has passed and to count how many times the wheel has passed before one vehicle passes through the gate. Be programmed. Then, an output signal of the CPU 25 is output from the axle sensor via the output circuit 26.

Next, the operation of this embodiment having the above configuration will be described. As the vehicle enters and exits the gate, the vehicle wheels step over the axle sensor. At this time, FIG.
As shown in FIGS. 3A and 3B, a tube 16 (a tube on the right side in FIG. 3; hereinafter, appropriately referred to as “tube 16 </ b> R”) located on the near side in the traveling direction of the vehicle is first attached to the wheel 40. Crushed (see FIG. 3A), and then
The other tube 16 (hereinafter, “tube 16L” as appropriate)
Is crushed. Therefore, both tubes 16R,
As shown in FIG. 4, the timing of the peak of the internal pressure of 16L is shifted from each other, and a differential pressure is generated between the two detection units 18A and 18B provided in the pressure detector 18.

Then, as shown in FIG.
The diaphragm of the differential pressure sensor 19 provided between A and 18B is initially bent to one side, and the differential pressure sensor 19 outputs, for example, a positive signal. Next, as shown in FIG. 3 (B), when the wheel 40 evenly presses the tubes 16R, 16L, the pressure difference between the detection units 18A, 18B disappears, and the output signal from the pressure difference sensor 19 is lost. Becomes 0 [V] (the state indicated by reference numeral P1 in FIG. 5). Next, after the wheel has passed the center of the axle sensor in the width direction, the differential pressure sensor 1
9 outputs a negative signal.

The CPU 25 takes in the output signal from the differential pressure sensor 19 via the amplifier 23 and the A / D converter 24, and from the state where the signal exceeds the predetermined threshold value Vrf to the positive side, changes to the negative side. When it is determined that the vehicle has become smaller than the predetermined threshold value Vrf, it is detected that the axle of the vehicle has passed from the right side to the left side in FIG. At this time, for example, an area sensor (not shown) provided at a position higher than the road surface detects that the vehicle has passed the axle sensor, and the CPU 25 receives this detection signal, and one vehicle passes through the axle sensor. During the period, every time the detection operation is performed, the number of passing axles is counted up.

On the other hand, the CPU 25 determines from the state that the output signal from the differential pressure sensor 19 has decreased from exceeding the predetermined threshold value Vrf to the negative side, and has increased from the state exceeding the predetermined threshold value Vrf to the positive side. When it is determined, the number of passing axles is counted down.

Now, when the temperature around the axle sensor gradually changes and a pressure difference occurs between the internal pressures of the tubes 16, 16, the tubes 16, 16 are connected to each other by the connecting pipe 1.
7, the tube 16 from one side to the other
The air flows slowly through the communication line 17 to eliminate the pressure difference. Here, since the connecting conduit 17 has a smaller diameter than the tube 16, the resistance is small when the air flows slowly as in the case where the air flows due to the differential pressure caused by the temperature change, but the air flows rapidly. Attempting to do so results in a large resistance. Therefore, when the vehicle passes through the axle sensor,
When a large differential pressure is suddenly generated in the internal pressures of the tubes 16, 16, the resistance of the air flowing through the communication conduit 17 increases, and the differential pressure is not eliminated, but is detected by the differential pressure sensor 19.

When a hole is opened in one of the tubes 16 and 16 and air leaks, when the output signal from the differential pressure sensor 19 changes, FIGS.
As shown in (B), the peak value on the positive side and the peak value on the negative side are different values. Then, the CPU 25 outputs the positive peak value (Vp in FIG. 6) of the output signal of the differential pressure sensor 19.
1) and the negative peak value (Vp2 in FIG. 6) (= | V
(p1-Vp2 |) is detected, and when the difference exceeds a predetermined reference value, a warning signal indicating that the tube 16 is abnormal is output via the output circuit 26.

As described above, in this embodiment, the axle sensor detects the passage of the vehicle through the axle of the vehicle based on the relative change in the internal pressure of both tubes 16, so that the change in the internal pressure due to the temperature change is small. When the internal pressures of the tubes 16 and 16 are compared with each other, they are canceled out, and are hardly affected by a temperature change, so that it is possible to stably detect the passage of the axle.
In addition, since the tubes 16 are communicated with each other through the communication line 17, the internal pressures of the tubes 16 always have the same value, and an accurate detection operation can be performed. Furthermore, since the axle to be counted is counted up or down depending on the traveling direction of the vehicle passing through the axle sensor, for example, even if the vehicle wheels move back and forth through the axle sensor, the axle can be accurately calculated. Numbers can be counted.

<Other Embodiments> The present invention is not limited to the above embodiments. For example, the following embodiments are also included in the technical scope of the present invention.
In addition to the following, various changes can be made without departing from the scope of the invention.

(1) The detection of the air leak by the CPU 25 may be performed, for example, by detecting the difference between the peak values of the internal pressure, for example, when the output signal of the differential pressure sensor 19 is one of the positive side and the negative side. After the predetermined threshold value Vrf is exceeded, the other side may not detect the predetermined threshold value Vrf, and the abnormality of the air leak may be detected.

(2) In the above embodiment, both tubes 1
6 and 16 were communicated at the end by a communication line 17,
For example, a configuration in which the two tubes are communicated with each other through a thin conduit at a middle portion in the longitudinal direction may be employed.

(3) Even if the two tubes are not connected by the connecting pipe, the change in the internal pressure due to the temperature change is the same for both tubes if the internal space of both tubes is the same volume. The same effect as the above embodiment can be obtained.

(4) In the above embodiment, the axle sensor is
Although the configuration is such that the number of axles is counted, the axle sensor of the present invention may detect only whether or not the axle has passed.

(5) The present invention also provides a system for detecting the speed of a vehicle by arranging a pair of axle sensors at predetermined intervals and measuring the time when the front wheels of the vehicle pass through both axle sensors. May be used.

[Brief description of the drawings]

FIG. 1 is a perspective view of an axle sensor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the axle sensor.

FIG. 3 is a perspective view showing a state where the axle sensor is depressed;

FIG. 4 is a graph showing changes in the internal pressure of both tubes.

FIG. 5 is a graph showing an output of a differential pressure sensor.

FIG. 6 is a graph showing an output of a differential pressure sensor when an abnormality occurs.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Road 16 ... Tube (flexible pipe) 17 ... Connection pipe 18A, 18B ... Detection part (pressure detection part) 19 ... Differential pressure sensor 25 ... CPU (inversion detection part, axle counting part, abnormality detection means) 40 ... wheels

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G006 AA07 LG02 5G055 DB01 DD06 DD21 DD30 DD34 DG02 DG07 5G056 DA01 DB02 DB11 DC07 DE02 DE20 DG05

Claims (4)

[Claims] 1. A pair of flexible conduits extending in parallel in a direction crossing a road and sequentially pressed on wheels of a vehicle, and a pair of pressures for detecting an internal pressure of each of the flexible conduits. A detecting unit, receiving the detection results of the two pressure detecting units, from a state in which one of the internal pressures of both the flexible conduits is larger than the other internal pressure, and a state in which the other is larger than the one internal pressure. An axle sensor comprising: an inversion detection unit that determines that the vehicle has been switched. 2. The axle sensor according to claim 1, wherein the two flexible conduits are connected to each other by a communication conduit narrower than the flexible conduits. 3. The inversion detection unit detects that one of the internal pressures of the two flexible pipes has been switched from a state higher than the other internal pressure to a state higher than the other internal pressure. In some cases, the axle sensor counts the number of axles that have passed through the axle sensor, and when the inversion detection unit detects that one of the axles has switched from a state in which one is greater than the internal pressure to a state in which one is greater than the other. The axle sensor according to claim 1 or 2, further comprising an axle counting unit that counts down the number of axles that have passed through the axle. 4. A method according to claim 1, wherein a difference between a peak value of one of the internal pressures of the two flexible pipes and a peak value of the other internal pressure is equal to or greater than a predetermined reference value. The axle sensor according to any one of claims 1 to 3, further comprising abnormality detection means for performing abnormality detection based on the abnormality.