JP2001236591A - Axle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of an axle detector for detecting the number of axles of a vehicle, to improve the reliability and to quicken the response. SOLUTION: A vibration transmitting body, in which the gap of rail-shaped metals 1 and 2 formed integrally with an iron frame 5 is filled with a rubber 6, is installed on the surface of road so as to cross a lane. Transmitters T1 and T2 are provided for applying vibrations to one terminal of each of rail- shaped metals 1 and 2. The vibrations are detected by receivers 1 and R2 on the other terminal of each of rail-shaped metals. On the basis of the level of vibrations received by the receiver R1 and R2 and the change of a phase, it is detected a tire 4 steps on the rail-shaped metals 1 and 2, and the number of axles is counted. Since the tire 4 does not step on the receivers R1 and R2, the service life of the axle detector is prolonged and reliability is improved as well. By increasing the vibration frequency, the response can be quickened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an axle detector, and more particularly to an axle detector for detecting the number of axles of a traveling vehicle at a tollgate on a toll road.

[0002]

2. Description of the Related Art In an automatic toll collection system for a toll road, it is necessary to detect a type of a vehicle and calculate a toll. One of the criteria for calculating tolls is the number of axles of a vehicle. To detect the number of axles, provide an axle detector at the toll booth.

FIG. 10 shows an example of a conventional axle detector.
In FIG. 10, the pressure detecting element 7 is a sensor element such as a piezo element or a switch. The rubber 6 is a pressure sensing element 7
Is embedded in the rubber. The iron frame 5 is a frame that supports the rubber 6. The axle detector having such a configuration is embedded in a road surface so as to cross a lane. When the tire 4 steps on the rubber 6 of the axle detector, the pressure detecting element 7 such as a piezo element or a switch detects the pressure of the tire 4, and the output signal changes. The axle is detected by detecting this signal change.

[0004]

However, in the above-mentioned conventional axle detector, since tire pressure is directly applied to the sensor element, there is a problem that the life is short and the reliability is low. When the sensor element is a mechanical switch, there is a problem that response is slow.

[0005] It is an object of the present invention to solve the above-mentioned conventional problems, prolong the life of the axle detector, increase the reliability, and make the response faster.

[0006]

In order to solve the above-mentioned problems, according to the present invention, an axle detector includes a rail-shaped metal, a wave transmitting means for applying vibration to one end of the rail-shaped metal, and a rail-shaped metal. Wave receiving means for detecting vibration at the other end and signal processing means for detecting an axle based on a change in vibration state when the rail-shaped metal is stepped on by a tire are provided.

[0007] With this configuration, the life of the axle detector can be extended, the reliability can be increased, and the response can be made faster.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS.

(First Embodiment) In a first embodiment of the present invention, vibration is applied to one end of two parallel rail-shaped metals and the rail-shaped metal is stepped on by a tire. Is an axle detector that detects a change in the axle at the other end.

FIG. 1 is a plan view and a side view of an axle detector according to a first embodiment of the present invention. In FIG.
Rails 1 and 2 are elongated rectangular parallelepiped iron rails,
It is integrated with the iron frame. The tire 4 is a contact portion of the tire of the vehicle. The iron frame 5 is a plate-like iron frame that supports a rail. The rubber 6 is a vibration absorbing material for preventing transmission of vibration between rails. The transmitting elements T1 and T2 are transducers that convert an electric signal into mechanical vibration. Receiving element R
1, R2 is a transducer for converting mechanical vibration into an electric signal.

FIG. 2 is a functional block diagram of a signal processing circuit of the axle detector according to the first embodiment of the present invention.
In FIG. 2, an oscillator 11 is an oscillation circuit that generates a sine wave signal of 20 kHz or more (ultrasonic range). The driver 12 is a circuit that amplifies a sine wave signal and drives a transmitting element. The reception amplification circuit 13 is a circuit that amplifies the signal of the wave receiving element. The level detector 14 is a circuit that measures the level of the signal of the wave receiving element. The phase comparison circuit 15 is a circuit that compares the phase of the signal of the wave receiving element with the phase of the signal of the driver. The output unit 16 is a circuit that outputs an axle detection signal based on the level and phase of the signal of the wave receiving element.

FIG. 3 is a diagram showing a signal processing method of the axle detector according to the first embodiment of the present invention. In FIG. 3, an order detection circuit 17 is a circuit that detects a tire passing order from the outputs of the two signal processing circuits. The pulse generation circuit 18 is a circuit that generates a pulse indicating the number of passing axles from the sequence detection signal.

The operation of the axle detector according to the first embodiment of the present invention configured as described above will be described. As shown in FIG. 1, metal rails 1 and 2 are passed across lanes of the road. Wave transmitting element T provided at one end of rails 1 and 2
1. The surfaces of the rails 1 and 2 are vibrated by T2. This vibration wave is received by the wave receiving elements R1 and R2 provided at the opposite ends of the rails 1 and 2. When the rails 1 and 2 are stepped on by the tire 4, the levels and phases of the signals of the wave receiving elements R1 and R2 change. By detecting this, the passage of the axle is detected.

FIG. 2 is a functional block diagram of the signal processing circuit provided on the rail 1 in column A of FIG. The same signal processing circuit is provided on the rails 2 in the B column. When the signal from the oscillator 11 is amplified and the driver 12 drives the transmitting element T1 provided at one end of the rail 1, mechanical vibration occurs on the rail 1, and the vibration wave propagates along the rail 1, and Reach the other end. This is received by the receiving element R1, and the
Amplify with This received signal has a stable phase and level when the tire is not on the rail 1. When the tire steps on the rail 1, a wave transmitted on the surface of the rail is absorbed by the tire or branches off toward the tire, so that a sudden change occurs in the level and phase of the vibration. The phase comparison circuit 15 detects a change in phase. Level detector 14
Then, a level change is detected. The output section 16 detects this change and outputs an output indicating that a tire is present.

FIG. 3 is a diagram for explaining signal processing in the A and B columns. The output signals indicating the presence / absence of tires from each row are processed by the order detection circuit 17, and the axle passing signal is output only when the signals change in the correct order. Phase 1
Phase 2 is the case where the vehicle passes the axle detector in the back. Phases 3 and 4 are cases in which the vehicle backs up from the middle of the axle detector, and no passing output is performed. Thus, similarly to the conventional case, the axle detector is arranged in a plurality of rows to prevent erroneous detection. further,
The oscillation frequency of each row is made different to avoid interference between rails.

If the vibration wave is a surface wave (Rayleigh wave),
The waves travel mostly on the rail surface. In practice, it can be considered to travel through a depth within twice the oscillation wavelength. Therefore, only the state change on the rail surface caused by the tire being stepped on by the tire has a great influence on the wave transmission.

If the sound velocity V is 5000 m / s and the vibration frequency f is 1 MHz, the wavelength λ is about V / f = 5 mm. If the frequency is further increased and the wavelength is shortened to several millimeters, the rail thickness becomes several millimeters, and the rubber portion having the structure shown in FIG. 1 becomes unnecessary. This structure also has an effect of preventing tire slip.

Unlike the conventional axle detector that steps on the sensor element with the tire, the axle detector of the present embodiment can have a robust structure because the tire does not step on the wave receiving element.
Also, by increasing the vibration frequency, an axle detector with good responsiveness can be realized.

The vibration wave can be not a surface wave but a transverse wave or a longitudinal wave. In this case, since the vibration wave propagates not only on the surface of the rail but also on the entire inside, it is necessary to hold the rubber on the three sides of the rail except the surface on which the tire steps.

Although not shown, apart from the axle detector,
A vehicle detection device that detects the vehicle with an optical sensor or the like is provided. A means for storing, as a reference value, a level, a phase difference, and a transmission time of vibration detected by a wave receiving element of an axle detector when a vehicle detection device detects that a vehicle is not present is provided in a signal processing circuit. . In this way, the reference value can always be calibrated to correct the deviation of the reference value due to aging.

Further, when the level or phase change of the vibration detected by the wave receiving element is gentler than a predetermined time constant, a means for updating the reference value is provided in the signal processing circuit. Thereby, it is possible to correct a deviation of the reference value due to an environmental change such as a change in temperature.

As described above, in the first embodiment of the present invention, the axle detector is used to apply vibration to one end of the rail-shaped metal and to detect a change in the vibration state when the rail-shaped metal is stepped on by the tire. Because it was configured to detect the axle by detecting at the other end,
Longer axle detector life, increased reliability, and faster response.

(Second Embodiment) In a second embodiment of the present invention, vibration is applied to one end of an elongated U-shaped rail-shaped metal, and the rail-shaped metal is vibrated when stepped on a tire. This is an axle detector that detects a change in state at the other end of the rail and detects an axle.

FIG. 4 is a plan view and a side view of an axle detector according to a second embodiment of the present invention. In FIG.
The rails 1 and 2 are U-shaped rails. Other basic configurations such as a signal processing circuit are the same as those of the first embodiment.

The operation of the axle detector according to the second embodiment of the present invention configured as described above will be described. As shown in FIG. 4, the metal rails 1 and 2 bent in a U-shape are passed across the lane of the road. The surface of the rail is vibrated by the wave transmitting elements T1 and T2 provided at one end of the rail.
This vibration wave is transmitted to the wave receiving elements R1, R2 provided at the other end of the rail.
Receive at When the rail is stepped on by the tire 4, the receiving element R
1. The level and phase of the R2 signal change. By detecting this, the passage of the axle is detected. By folding the rail, the transmitting element and the receiving element are arranged only on one side of the lane, and wiring that crosses the lane is eliminated.

As described above, in the second embodiment of the present invention, the axle detector is used to apply vibration to one end of a U-shaped rail-shaped metal when the rail-shaped metal is stepped on a tire. Since the change in the vibration state is detected at the other end of the rail to detect the axle, the element and the circuit can be placed only on one side of the lane.

(Third Embodiment) In a third embodiment of the present invention, an elongated W-shaped rail-shaped metal is vibrated at the center end of the rail-shaped metal, and the rail-shaped metal is stepped on by a tire. The axle detector detects an axle by detecting a change in the vibration state at the end of each of the rails.

FIG. 5 is a plan view (a), a side view (b), and a left side view (c) of an axle detector according to a third embodiment of the present invention. In FIG. 5, a rail 1 is a central rail. The rails 2 and 3 are branched outer rails. FIG. 6 is a sectional view of the axle detector.

FIG. 7 is a functional block diagram of a signal processing circuit for measuring the transmission time of vibration. 7, an intermittent pulse generator 19 is a circuit that generates a pulse every predetermined period. The gate 20 is a gate circuit that drives the transmitting element according to the intermittent pulse. The delay circuit 21 is a circuit that delays the intermittent pulse by the transmission time of the vibration wave.

FIG. 8 is a time chart for detecting a signal delayed by the transmission time of the vibration wave. FIG. 9 is a time chart in the case of interpolating with intermittent pulses of different vibration frequencies.

The operation of the axle detector according to the third embodiment of the present invention configured as described above will be described. As shown in FIG. 5, the rail 1 is bifurcated at the turning point to form a two-row axle detector. With such a configuration, the transmission unit is completed with one circuit. In addition, by turning the rails back, the transmitting element and the receiving element are arranged only on one side of the lane, and wiring that crosses the lane is avoided.

Referring to FIG. 6, a countermeasure for wraparound will be described. FIG. 6 is a sectional view when the axle detector is cut along the vehicle traveling direction. The center rail 1 is the transmitting element T1
It is excited by and vibrates. Tires are rails 1 and 2
When riding on the, vibration on the rail surface is suppressed and the wave reception level is reduced. At this time, the vibration is transmitted from the rail 1 to the rail 2 through the tire to some extent, but the level is small if the material of the tire is rubber. However, if the tire is wearing a tire chain, it will be transmitted at a large level through the metal part, and although the tire is on the rail,
The receiving level may not change. Usually this can be detected by a change in phase.

However, depending on the position where the tire is stepped on, even the phase may not change. For such a short-circuit state between columns, in Embodiments 1 and 2, erroneous detection is avoided by using different frequencies between columns, but in the case of a branch structure, the frequency may be changed. Can not. Therefore, by measuring the transmission time of the vibration wave from the transmitting element to the receiving element by adding a temporal change to the vibration wave, the length of the transmission path of the vibration wave is obtained, and the short circuit state between the rails is detected. I do.

FIG. 7 is a functional block diagram of a signal processing circuit for measuring the transmission time of vibration. Transmitting element T
1 is normally stopped, and vibrates intermittently only when the drive pulse signal from the intermittent pulse generator 19 is on. This wave has a velocity of vibration transmitted on rails 1 and 2 as V,
Assuming that the distance between transmission and reception is L, the signal is received after a time t1 (= L / V).

As shown in the time chart of FIG. 8, the driving pulse is an intermittent pulse, and the transmitting element vibrates only while the driving pulse signal is on. In FIG. 8, only one cycle of the vibration is illustrated, but normally a plurality of cycles of the vibration are generated. In the first wave transmission, the tire is not stepping on the rail, and the vibration wave is received by the wave receiving element after time t1. In the next transmission, the tire is on the rail and is received at the timing after time t1 from the transmission,
The level becomes smaller. In the third transmission, a short-circuit condition occurs and the signal is received after a time t2 shorter than the time t1.

As described above, a wave received at a timing other than the time t1 after the transmission is not a regular received vibration wave, no matter how high its level is. Thereafter, it is received at a small level at the timing after time t1.

The drive pulse signal from the intermittent pulse generator 19 in FIG. 7 is delayed by the time t1 by the delay circuit 21 to be a delay pulse. By checking the reception level by the level detector 14 only during this signal, the influence of the noise signal due to the short-circuit state can be avoided. Conversely, there is also a method of detecting that a short circuit has occurred by checking the reception level at a timing other than the delay pulse, and detecting that the tire is present on the rail.

When the detection is performed intermittently as described above, the intermittent pulse cycle becomes the detection response speed. If it is desired to increase the response speed, it is possible to interpolate with intermittent pulses of different vibration frequencies as shown in FIG. Two systems of a transmitting element, a receiving element, and a signal processing circuit that use vibration waves having different frequencies are provided. A vibration wave of the second frequency is generated substantially in the middle of the rest period of the vibration wave of the first frequency. By performing received signal processing while distinguishing the frequency, the response speed can be reduced to two.
Can be doubled. Similarly, the response speed can be tripled or more.

As described above, in the third embodiment of the present invention, the axle detector applies vibration to the center rail end of the W-shaped rail-shaped metal, and the rail-shaped metal steps on the tire. Since the axle is detected by detecting a change in the vibration state when it is touched at the ends of the rails on both sides, it is robust and responsive.

[0040]

As is apparent from the above description, according to the present invention, the axle detector includes a rail-shaped metal, a wave transmitting means for applying vibration to one end of the rail-shaped metal, and a rail-shaped metal. The wave receiving means for detecting the vibration at the end and the signal processing means for detecting the axle based on the change in the state of the vibration when the rail-shaped metal is stepped on the tire are provided. The effect is that the life of the detector can be extended, the reliability can be increased, and the response can be made faster.

[Brief description of the drawings]

FIG. 1 is a plan view (a) and a side view (b) of an axle detector according to a first embodiment of the present invention;

FIG. 2 is a functional block diagram of a signal processing circuit of the axle detector according to the first embodiment of the present invention;

FIG. 3 is a processing system diagram (a) and a waveform diagram (b) showing a signal processing method of the axle detector according to the first embodiment of the present invention;

FIG. 4 is a plan view (a) and a side view (b) of an axle detector according to a second embodiment of the present invention;

FIG. 5 is a plan view (a), a side view (b), and a left side view (c) of an axle detector according to a third embodiment of the present invention;

FIG. 6 is a cross-sectional view of an axle detector according to a third embodiment of the present invention;

FIG. 7 is a functional block diagram of a signal processing circuit of an axle detector according to a third embodiment of the present invention;

FIG. 8 is a time chart of an axle detector according to a third embodiment of the present invention;

FIG. 9 is a time chart of an axle detector according to a third embodiment of the present invention;

FIG. 10 is a plan view (a) and a side view (b) of a conventional axle detector.

[Explanation of symbols]

 1, 2, 3 rails 4 Tires 5 Iron frame 6 Rubber 7 Pressure sensing element 8 Road curb 9 Road surface 10 Steel plate 11 Oscillator 12 Driver 13 Receive amplifier 14 Level detector 15 Phase comparator 16 Output 17 Sequence detector 18 Pulse Generation circuit 19 Intermittent pulse generator 20 Gate 21 Delay circuit T1, T2 Transmitting element R1, R2 Receiving element

Claims (12)

[Claims] 1. A rail-shaped metal as a vibration transmitting body, a wave transmitting means for applying vibration to one end of the rail-shaped metal, a wave receiving means for detecting vibration at the other end of the rail-shaped metal, and the rail-shaped metal An axle detector comprising: signal processing means for detecting an axle based on a change in a vibration state when a metal is stepped on a tire. 2. A plurality of rail-shaped metals, a plurality of wave transmitting means for applying vibrations of different frequencies to one ends of the plurality of rail-shaped metals, and respective vibrations at the other end of the plurality of rail-shaped metals. Axle detector, comprising: a plurality of wave receiving means for detecting axle; and a signal processing means for detecting an axle based on a change in a vibration state when the plurality of rail-shaped metals are stepped on by a tire. . 3. Two parallel rail-shaped metals connected by a U-shaped bent portion, a wave transmitting means for applying vibration to one end of the rail-shaped metal, and the other of the rail-shaped metal Axle detection, comprising: wave receiving means for detecting vibration at an end of the vehicle; and signal processing means for detecting an axle based on a change in vibration state when the rail-shaped metal is stepped on by a tire. vessel. 4. Three parallel rail-shaped metals connected by a W-shaped branch, a wave transmitting means for applying vibration to an end of the central rail-shaped metal, and ends of the rail-shaped metal on both sides. An axle detector comprising: two wave receiving means for detecting vibrations at a time; and signal processing means for detecting an axle based on a change in a vibration state when the rail-shaped metal is stepped on by a tire. . 5. The axle detector according to claim 1, wherein said transmitting means and said receiving means are arranged on a road side of a lane. 6. The wave transmitting means is provided with means for generating a modulated vibration to vibrate the rail-shaped metal, and the signal processing means is provided with a means for generating vibration from the wave transmitting means to the wave receiving means. A means for measuring a transmission time to obtain a length of a vibration transmission path, and a means for detecting a short-circuit state between the rail-shaped metals based on the length of the transmission path. The axle detector according to any one of claims 2 to 4. 7. The axle detector according to claim 2, wherein a gap between the rail-shaped metals is filled with rubber for suppressing vibration transmission between the rail-shaped metals. 8. The axle detector according to claim 1, wherein said wave transmitting means is provided with a driving means for vibrating said rail-shaped metal with a vibration of 20 kHz or more. 9. The axle detector according to claim 1, wherein the rail-shaped metal has a shape in which an iron frame is cut out only at a portion where the vibration element of the wave transmitting means is attached. . 10. The signal processing means includes means for detecting a level of the vibration detected by the wave receiving means, means for detecting a phase change of the vibration detected by the wave receiving means, and the level and the phase change. 5. An axle detector according to claim 1, further comprising means for detecting an axle based on the following. 11. The signal processing means further comprising means for updating a reference value when the level or phase change of the vibration detected by the wave receiving means is more gradual than a predetermined time constant. The axle detector according to any one of claims 1 to 4. 12. A means for detecting a vehicle by an optical sensor or the like, wherein said signal processing means includes a reference value for a level, a phase difference, and a transmission time of vibration detected by said wave receiving means when no vehicle is present. The axle detector according to any one of claims 1 to 4, further comprising means for storing the axle.