JPH10282226A - Speed meter for railroad car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed meter for a railroad car wherein the speed of the railroad car is measured with stability and precision without being effected by such environment condition as weather. SOLUTION: The device is provided with electro-magnetic ultrasonic wave probes TD1 and TD2 which are, at a predetermined interval D along the floor of a car along the direction of track, attached so that their tip end part is close to the surface of a track. Elastic ultrasonic waves are generated in the track by the electro-magnetic ultrasonic wave probes TD1 and TD2 at the same time, the elastic ultrasonic waves propagated in the track are detected by the electro-magnetic ultrasonic wave probes TD1 and TD2 , and the propagation time difference in the track or equivalent phase difference of the elastic ultrasonic waves between generation and detection of them by the electro-magnetic ultrasonic wave proves TD1 and TD2 is detected, thus car's speed is found, based on the time difference or equivalent phase difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed measuring device for a railway vehicle which is mounted on a railway vehicle and which is used in a device utilizing the ground speed of the vehicle, such as a wheel anti-spin device, an ABS device, and a mileage measuring device. About.

[0002]

2. Description of the Related Art Conventionally, as a speed measuring device for a railway vehicle, a method of measuring a vehicle speed by a wheel speed sensor mounted on a wheel of a vehicle has been generally used. However, the speed measurement device for a railway vehicle using the conventional method has a problem that when the wheels spin or slide, the accuracy of measuring the vehicle speed with respect to the ground is extremely reduced. In order to eliminate the problem of the railway vehicle speed measuring device using the wheel speed sensor, a Doppler type ground speed using aerial ultrasonic wave, millimeter wave (electromagnetic wave) or intensity-modulated light instead of the wheel speed sensor. Sensors have been proposed.

[0003] For example, in a vehicle speed measuring apparatus using aerial ultrasonic waves disclosed in Japanese Patent Application Laid-Open No. 3-269388, a single-frequency tone burst wave signal is applied to an ultrasonic transmitter / receiver, and the vehicle is driven forward or forward of the vehicle. Ultrasonic waves are emitted at a predetermined depression angle θ toward the ground in the rear or both front and rear directions. Next, the ultrasonic echo reflected from the ground and returned is received by the ultrasonic transducer, and the speed of the vehicle is determined from the difference between the signal at the time of transmission and the frequency at the time of reception (this is called Doppler frequency component). This is a calculation that is now widely known. FIG. 6 is an explanatory diagram when the Doppler ground speed sensor 3 is attached to the lower part of the vehicle 2 and emits ultrasonic waves in the direction of the railway track 1.

[0004]

However, in the above-mentioned non-contact Doppler type ground speed sensor, for example, when the ground is wet with rainwater or in a puddle as in rainy weather, Since the ground, which is the point of irradiation of these waves, is close to a so-called mirror surface for sound waves, millimeter waves or light waves, most of the energy of these waves radiated toward the ground is specularly reflected and reflected by the ground Then, the reflected echo level including the speed information that returns again becomes extremely low, which causes a problem that the measurement accuracy is reduced or the measurement becomes impossible.

[0005] In such a case, not only the reflection echo level is reduced, but also when ultrasonic waves or millimeter waves are used, the directivity of the sensors (ultrasonic transducers, antennas) in the ground direction is reduced. Due to the lobe, there is a problem in that the reflected echo level that does not include the velocity information that is specularly reflected from the ground directly below the sensor and returns again becomes large, and the velocity measurement accuracy is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and is directed to an electromagnetic ultrasonic probe (EMA).
T: Electromagnetic Acoustic Transducer) is used to generate non-contact elastic ultrasonic waves that propagate in a railway track, which is a non-contact conductor, and detect the non-contact elastic ultrasonic waves by another electromagnetic ultrasonic probe in a non-contact manner. By doing so, by measuring the required propagation time of the elastic ultrasonic waves in the railway track, the speed measurement device for railway vehicles capable of performing a stable and highly accurate vehicle speed measurement without being affected by environmental conditions such as weather. The purpose is to provide.

[0007]

According to the present invention, there is provided a speed measuring apparatus for a railway vehicle according to the present invention, wherein a predetermined distance is provided on a floor surface of a railway vehicle along a direction of a railway track, and a tip portion is close to a surface of the railway track. The two electromagnetic ultrasonic probes are installed so that elastic ultrasonic waves are generated in the railway track by one electromagnetic ultrasonic probe, and the elastic ultrasonic waves propagated in the railway track are transmitted to the other electromagnetic probe. Detected by the ultrasonic probe, the elastic ultrasonic wave from the time of the generation of the elastic ultrasonic wave by the one electromagnetic ultrasonic probe to the time of the detection of the elastic ultrasonic wave by the one electromagnetic ultrasonic probe It is characterized in that the speed of the railway vehicle is obtained based on the propagation time in the railway track.

In the speed measuring apparatus for a railway vehicle according to the present invention, elastic electromagnetic waves are generated in a non-contact manner in a railway track as a conductor by one electromagnetic ultrasonic probe, and the other electromagnetic ultrasonic probe is used. Elastic ultrasonic waves propagating in the railroad track are detected by the stylus, and the railroad from the generation of the elastic ultrasonic wave by one electromagnetic ultrasonic probe to the detection of the elastic ultrasonic wave by the other electromagnetic ultrasonic probe Based on the propagation time of the elastic ultrasonic waves in the track, the vehicle speed of the railway vehicle with respect to the rail track can be obtained without being affected by the slipping or sliding of the wheels. In addition, the use of elastic ultrasonic waves, which are generated using an electromagnetic ultrasonic probe and propagate in a railroad track, enables stable and accurate measurement without being affected by the weather such as rain, snow, and fog. The speed of the vehicle can be determined.

A speed measuring apparatus for a railway vehicle according to the present invention is mounted on a floor surface of a railway vehicle at a predetermined interval along a direction of a railroad track so that a front end portion is close to a surface of the railroad track. Equipped with multiple electromagnetic ultrasonic probes,
Elastic ultrasonic waves are simultaneously generated in the railway track by the plurality of electromagnetic ultrasonic probes, and the elastic ultrasonic waves propagated in the railway track are detected by the plurality of electromagnetic ultrasonic probes, respectively. Detect the propagation time difference or equivalent phase difference of the elastic ultrasonic wave in the railway track from the time when the elastic ultrasonic wave is generated to the time when the elastic ultrasonic wave is detected by each electromagnetic ultrasonic probe,
The speed of the railway vehicle is obtained from the time difference or the equivalent phase difference.

In the speed measuring device for a railway vehicle according to the present invention, an elastic ultrasonic wave is generated or detected in a non-contact manner in a railway track, which is a conductor, using an electromagnetic ultrasonic probe, and the elastic ultrasonic wave By measuring the intra-track propagation time difference or equivalent phase difference, the vehicle speed of the rail vehicle with respect to the rail track can be obtained without being affected by slipping or sliding of wheels. In addition, the use of elastic ultrasonic waves that are generated using an electromagnetic ultrasonic probe and propagated in railway tracks,
The speed of the vehicle can be obtained stably and with high accuracy without being affected by the weather such as snow and fog.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A railway vehicle speed measuring device according to the present invention will be described with reference to an embodiment.

FIG. 1 is a block diagram showing a configuration of a railway vehicle speed measuring device according to an embodiment of the present invention. FIG. 2 is a block diagram of a railway vehicle speed measuring device according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a state of attachment to a vehicle.

In FIGS. 1 and 2, reference numerals TD ₁ and TD ₂ denote electromagnetic ultrasonic probes, and reference numeral 100 denotes an electric circuit unit of a railway vehicle speed measuring device according to an embodiment of the present invention. .

The electromagnetic ultrasonic probes TD ₁ and TD ₂ are:
It is mounted on the floor of the vehicle 2 at a distance D along the direction of the railway track 1, and the tip portion thereof is close to the surface of the railway track 1.

The electromagnetic ultrasonic probes TD ₁ and TD ₂ are:
Not only generation of elastic ultrasonic waves 4 propagating inside the railroad track 1 but also detection of elastic ultrasonic waves are performed.

Electric circuit section 10 of speed measuring device for railway vehicle
0 includes the central processing circuit 18 and the central processing circuit 1
8 includes a transmission system circuit 101 and a reception system circuit 102 which cooperate with the central processing unit 8. The central processing unit 18 controls the entire speed measuring device for a railway vehicle and controls the electromagnetic ultrasonic probes TD ₁ and TD ₂ . Receiving the output from the thermistor 17 for detecting the ambient temperature, the temperature change of the propagation speed of the elastic ultrasonic wave is corrected, and the transmission system circuit 10 is used by using the corrected propagation speed.
1 and the reception system circuit 102 to obtain vehicle speed data and send it to the subsequent stage.

The transmission circuit 101 is a drive signal generation circuit 1
5, a power amplification circuit 16 and a transmission / reception switch 8 for generating elastic ultrasonic waves 4 in cooperation with a central processing circuit 18.

The drive signal generation circuit 15 is a central processing circuit
Frequency division ratio, pulse width Tw, repetition supplied from 18
A control signal b and a base for controlling the period To
In response to the quasi-signal a, the control signal b
Over a period of pulse width Tw, for example a reference of 20 MHz
Drive signal a at the frequency division ratio determined by control signal b.
The frequency is divided by a counter built in the motion signal generation circuit 15.
And the carrier frequency f ₀Fig. 5 showing the tone burst wave of
A drive signal p1 shown in FIG. Tone burst
The wave has a repetition period T determined by the control signal b.
repeated by o.

The driving output from the driving signal generating circuit 15
The signal p1 is power-amplified by the power amplification circuit 16 and
The amplified drive signal p2 shown in FIG.
8 through the electromagnetic ultrasonic probe TD₁And TD_TwoSupply to
And the electromagnetic ultrasonic probe TD ₁And TD_TwoThe power amplification
Driven by the drive signal p2 thus generated, the electromagnetic ultrasonic probe
TD₁, TD_TwoA high frequency current I of several A
Drive to flow. By this drive, electromagnetic ultrasonic probe
Child TD₁And TD_TwoSuper elastic in the railway track 1 close to
A sound wave 4 is generated.

The generated elastic ultrasonic wave 4 is applied to a railway track.
Electromagnetic ultrasonic probe TD in 1 ₁And TD_TwoIn the position
Propagate the corresponding interval D. Bullet that propagated in railroad track 1
Ultrasonic wave 4 is again the electromagnetic ultrasonic probe TD₁, TD_Twoso
TD detected by electromagnetic ultrasonic probe₁, TD_TwoBy
The signal is converted into an air signal, and is again transmitted through the transmission / reception switch 8 to the reception system.
Route 102.

The receiving system circuit 102 includes a transmission / reception switch 8, bandpass filters 9 ₁ and 9 ₂ , amplification circuits 10 ₁ and 1
0 ₂ , detection circuits 11 ₁ and 11 ₂ , level comparison circuit 1
2 ₁ and 12 ₂ , AND gate circuits 13 ₁ and 13
₂ , a phase difference detection circuit 14 and a central processing circuit 18. The electric signals from the electromagnetic ultrasonic probes TD ₁ and TD ₂ received via the transmission / reception switch 8 are passed through a band-pass filter 9 ₁ ,
Band-limited supplies 9 _2, it amplifies the band-limited signal by the amplifier circuit 10 _1, 10 _2. Amplifying circuit 10 ₁ , 1
0 the output signal E1, E2 from ₂ detection circuit 11 _1, 11
_2, full-wave rectification and conversion to DC, and detection circuits 11 ₁ , 1
1 output signal from the ₂ predetermined by the threshold and level comparison in the level comparing circuit 12 _1, 12 _2, together with the level comparison output G1, G2 are fed to the central processing circuit 18, the output signal E1, E2, respectively AND gate circuit 1
3 and supplies _1, 13 ₂ ANDing.

The AND gate circuits 13 ₁ and 13 ₂ further fall from the central processing circuit 18 at the same time as the pulse of the width Tw in the control signal b, and the drive signal P
2 is supplied with a low-potential signal γ having a pulse width slightly longer than the duration of the leakage component, and the AND operation output from the AND gate circuits 13 ₁ and 13 ₂ is a phase difference. The detection signal is supplied to a detection circuit 14 to detect the phase difference between the two, and a phase difference detection signal and level comparison outputs G1, G
2 is supplied to the central processing circuit 18 and the central processing circuit 18 calculates vehicle speed data by calculation.

FIG. 3 shows the electromagnetic ultrasonic probes TD ₁ and T
Is an explanatory view showing the principle of generating an elastic ultrasonic railroad track 1 which is an internal structure and the conductor D _2.

FIGS. 4A and 4B are schematic diagrams showing the relative positional relationship between the electromagnetic ultrasonic probe TD ₁ (TD ₂ ) and the railway track 1, and FIG. FIG.
(B) shows a side view.

The electromagnetic ultrasonic probes TD ₁ and TD ₂ are provided with permanent magnets 5 and 6 and a coil 7 provided between the permanent magnets 5 and 6 and the railway track 1. The permanent magnets 5 and 6 may be electromagnets.

The permanent magnets 5, 6 are brought close to the railway track 1,
A strong electrostatic magnetic field B is formed in the railway track 1. on the other hand,
When the power-amplified drive signal p2 is supplied to the coil 7 and a high-frequency current I of several tens of kHz or more flows through the coil 7, an alternating magnetic field generated by the high-frequency current I in the railway track (conductor) 1 is canceled. As described above, an eddy current I 'is generated, and electrons serving as a source of the eddy current I' receive a Lorentz force F due to the electrostatic magnetic field B, so that a distortion occurs in the railway track 1, and as a result, a high-frequency current flowing through the coil 7 Elastic ultrasonic waves 4 having the same frequency as I are generated. Further, the elastic ultrasonic waves 4 are detected by the electromagnetic ultrasonic probes TD ₁ and TD ₂ by following the reverse process.

The distance D between the electromagnetic ultrasonic probes TD ₁ and TD ₂
Ultrasonic waves 4 propagating in the interval D of the railway track 1 facing the
Are detected by the electromagnetic ultrasonic probes TD ₁ and TD ₂ , converted into electric signals, and output. Electromagnetic ultrasonic probe T
The signal converted into an electric signal by D ₁ and TD ₂ is sent to the reception circuit 102 via the transmission / reception switch 8. The electric signal based on the elastic ultrasonic wave 4 received via the transmission / reception switch 8 is supplied to bandpass filters 9 ₁ and 9 ₂ to extract only frequency components in a predetermined band, and amplify the circuits 10 ₁ and 10 _2.
, And output signals E1 and E2 are output.
The waveforms of the output signals E1 and E2 are as shown in FIG.

The output signals E1 and E2 are supplied to the detection circuits 11 ₁ and 1 1
At 1 ₂ are all-wave rectified and converted into a DC signal. The output signal levels from the detection circuits 11 ₁ and 11 ₂ are compared with predetermined thresholds in the level comparison circuits 12 ₁ and 12 ₂ ,
When the threshold value is exceeded, the high-potential level comparison outputs G1 and G
2 is sent from the level comparison circuits 12 ₁ and 12 ₂ and receives the level comparison outputs G 1 and G 2, and receives the AND gate circuit 1.
3 _1, 13 output signals F1, F2 from ₂ is sent.

Here, the output signal E1 usually includes a leak component X and an elastic ultrasonic detection signal component Y of the drive signal p2 for generating elastic ultrasonic waves to the receiving system circuit 102. However, a low-potential signal γ is further supplied to the AND gate circuits 13 ₁ and 13 ₂ from the central processing circuit 18, and the low-potential signal γ falls at the same time as the pulse of the width Tw in the control signal b, and Drive signal P2
Because it is a low potential signal is slightly longer pulse width than the existing period width of the leakage component X to the receiving system circuit 102, leakage component X to the receiving system circuit 102 is blocked by the AND gate circuit 13 _1. Further, as shown in FIG.
The gate of the AND gate circuit 13 ₁ is opened level period of the elastic ultrasound detection signal component Y of less than the threshold indicated by a broken line only. During the period in which the gate is open, the elastic ultrasonic detection signal component Y in the output signal E1 is output. That from the AND gate circuit 13 _1, so that the signal threshold or higher portions in the elastic ultrasonic signal propagating railway track 1 is extracted as shown in FIG. 5 (e) as the output signal F1.

The same applies to the output signal F2, the signal above the threshold level of the portion in the elastic ultrasonic signal propagating railway track 1 from the output signal E2 from the AND gate circuit 13 ₂ is extracted as an output signal F2 You.

The extracted output signals F1 and F2 are sent to the phase difference detection circuit 14.

The phase difference detection circuit 14 is a circuit for detecting a phase difference between the elastic ultrasonic signals detected by the electromagnetic ultrasonic probes TD ₁ and TD ₂ and includes, for example, output signals F 1 and F 2.
Is limited in amplitude by a limiter and converted into a rectangular wave signal. Before and after the rising edges of these two signals, the leading and lagging of the two phases are determined based on the relationship between the two signals, and the absolute value of the phase difference is determined by the two signals F1, The time interval Δt between rising edges of F2 is measured by a counter using, for example, a high-speed clock pulse c of several tens of MHz. The time interval Δt is taken into the central processing circuit 18. On the other hand, the level comparison outputs G1, G
The rising timing time difference T1 of 2 is also taken into the central processing circuit 18.

In FIG. 1, a control signal d is a control signal of the counter, and a high-speed clock pulse c of the counter is a reference signal, which are both sent from the central processing circuit 18 to the phase difference detection circuit 14.

Next, the speed calculation in the central processing unit 18 will be described.

The central processing circuit 18 calculates the vehicle speed v by the following formula using the time interval Δt corresponding to the phase difference.

Now, assuming that the propagation speed of the elastic ultrasonic waves on the railway track 1 is C, the electromagnetic ultrasonic probes TD ₁ to TD ₂
The required propagation time T _{1 with} respect to the interval D is as follows: T ₁ = D / (C−v) (1)

The propagation speed C of the elastic ultrasonic wave is about 3000 [m / s] for a transverse wave and about 6000 for a longitudinal wave in the case of iron.
[M / s], and the vehicle speed v
Much faster than. Therefore, assuming that C≫v in the equation (1), the required propagation time T ₁ can be approximated as in the following equation (2).

T ₁ ≒ D (1 + v / C) / C (2) Similarly, the required propagation time T ₂ from the electromagnetic ultrasonic probe TD ₂ to TD ₁ is T ₂ ≒ D (1−v / C) ) / C (3)

Since the propagation time difference ΔT = T ₁ −T ₂ between the _two is considered to be the above-mentioned time interval Δt, Δt = 2D / C × v / C (4), and solving equation (4) for v The vehicle speed v is given by the following equation (5).

V = C ² · Δt / 2D (5) If Δt exceeds the period 1 / f ₀ of the carrier frequency f ₀ , the relationship between ΔT and Δt is given by the following equation (6): ΔT = n × 1 / f ₀ + Δt (6) (n = 0, ± 1, ± 2,...), and n can be obtained from ΔT and Δt. In this case, Δt in equation (5) is n × 1 / f _The value is obtained by adding ₀ .

When calculating the vehicle speed v, the vehicle speed v can be calculated from Equation (5) by using either ΔT or Δt in principle. However, Δt is considered to be the phase difference of the carrier frequency as described above, and the measurement accuracy of this phase difference is considered to be higher than the accuracy of ΔT. Therefore, calculating the vehicle speed v from Expression (5) using Δt improves measurement accuracy.

The railway vehicle speed measuring device of the present invention is not limited to the configuration of the above-described embodiment.
Some transformation is possible.

For example, two electromagnetic ultrasonic probes TD ₁ ,
TD ₂ to may be calculated vehicle speed by solving only from (2) the measurement results required propagation time T ₁ of the electromagnetic ultrasonic transducer TD ₁ to TD ₂ for the vehicle speed v with. In this case, since the distance D between the electromagnetic ultrasonic probes TD ₁ and TD ₂ and the propagation speed C of the elastic ultrasonic wave are fixed, the electromagnetic ultrasonic probe TD ₁ is used for transmitting elastic ultrasonic waves. , The electromagnetic ultrasonic probe TD ₂ is fixed for reception, and the difference between the elastic ultrasonic transmission time from the ultrasonic probe TD ₁ and the elastic ultrasonic reception time from the ultrasonic probe TD ₂ , The vehicle speed v can be obtained, and the circuit configuration can be simplified.

[0044] The electromagnetic ultrasonic probe TD ₂ and elastic ultrasonic delivery, may be fixed and for receiving electromagnetic ultrasonic probe TD _1.

The measurement of the required propagation time difference is not a tone burst wave having a single carrier frequency of f ₀ ,
It is also possible to use a chirp signal whose frequency is swept linearly. Further, it is needless to say that the vehicle speed v can be measured even when the number of the electromagnetic ultrasonic probes is three or more. Furthermore, vehicle speed measurement becomes impossible at the joint of the railway track 1, but such inconvenience is caused, for example, by mounting a pair of electromagnetic ultrasonic probes TD ₁ and TD ₂ at the center and at the end of the vehicle, respectively. If the vehicle speed is measured independently, the vehicle speed v can be measured by one of the pair of electromagnetic ultrasonic probes TD ₁ and TD ₂ .

[0046]

As described above, according to the speed measuring apparatus for a railway vehicle according to the present invention, the electromagnetic ultrasonic probe is used to generate and detect elastic ultrasonic waves in a non-contact manner with respect to a railway track. Because the vehicle speed is measured by measuring the required propagation time difference or equivalent phase difference of the elastic ultrasonic wave,
There is an effect that the absolute absoluteness of the railcar with respect to the ground can be measured without being affected by the slipping or sliding of the vehicle.

Further, according to the speed measuring device for a railway vehicle according to the present invention, since the elastic ultrasonic wave propagating in the railway track is used, the speed measuring device is stable without being affected by the weather such as rain, snow and fog. In addition, the effect that the speed of the vehicle can be measured with high accuracy can be obtained. Further, since the electromagnetic ultrasonic probe has a simple structure, there is obtained an effect that a highly reliable and low-cost device can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a railway vehicle speed measuring device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a state in which the speed measuring device for a railway vehicle according to one embodiment of the present invention is mounted on a railway vehicle.

FIG. 3 is an explanatory diagram showing the internal structure of an electromagnetic ultrasonic probe and the principle of generating elastic ultrasonic waves in a railway track.

FIG. 4 is a schematic diagram showing a relative positional relationship between an electromagnetic ultrasonic probe and a railway track.

FIG. 5 is a waveform chart for explaining the operation of the railway vehicle speed measuring device according to the embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining a state in which a conventional Doppler type ground speed sensor is mounted on a vehicle.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Railroad track 2 ... Vehicle 3 ... Conventional Doppler type ground speed sensor 4 ... Elastic ultrasonic wave which propagates in a rail 5, 6 ... Permanent magnet 7 ... Coil 8 ... Transmission / reception switch 9 ₁ , 9 ₂ ... Bandpass filter 10 ₁ , 10 ₂ … amplifier circuit 11 ₁ , 11 ₂
... Detection circuits 12 ₁ and 12 ₂ ... Level comparison circuits 13 ₁ and 13 ₂
... AND gate circuit 14 ... phase difference detection circuit 15 ... drive signal generation circuit 16 ... power amplifier circuit 17 ... thermistor 18 ... central processing circuit TD ₁ , TD ₂
... Electromagnetic ultrasonic probe 100 ... Electrical circuit part of speed measuring device for railway vehicle 101 ... Transmission system circuit 102 ... Reception system circuit

Claims (4)

[Claims] 1. An electromagnetic ultrasonic probe mounted on a floor of a railway vehicle at a predetermined interval along a direction of a railway track and with a tip portion thereof close to a surface of the railway track. Elastic ultrasonic waves are generated in the railway track by one electromagnetic ultrasonic probe, and the elastic ultrasonic waves propagated in the railway track are detected by the other electromagnetic ultrasonic probe. Calculating the speed of the railway vehicle based on the propagation time of the elastic ultrasonic wave in the railway track from the time when the elastic ultrasonic wave is generated by the probe to the time when the elastic ultrasonic wave is detected by the one electromagnetic ultrasonic probe. Characteristic speed measuring device for railway vehicles. 2. A plurality of electromagnetic ultrasonic probes mounted on a floor of a railway vehicle at predetermined intervals along the direction of the railway track and with their tip portions close to the surface of the railway track. Provided, simultaneously generate elastic ultrasonic waves in a railway track by the plurality of electromagnetic ultrasonic probes, and detect the elastic ultrasonic waves propagated in the railway track by the plurality of electromagnetic ultrasonic probes, respectively. , Detecting the propagation time difference or equivalent phase difference of the elastic ultrasonic wave in the railway track from the generation of the elastic ultrasonic wave to the detection of the elastic ultrasonic wave by each electromagnetic ultrasonic probe, and from the time difference or the equivalent phase difference. A speed measuring device for a railway vehicle, wherein a speed of the railway vehicle is obtained. 3. The speed measuring device for a railway vehicle according to claim 1, wherein the elastic ultrasonic wave propagating in the railway track is a single frequency tone berth signal. . 4. The railway vehicle speed measuring device according to claim 1, further comprising a correcting means for correcting the propagation speed of the elastic ultrasonic wave propagating in the railway track based on a temperature change. Characteristic speed measuring device for railway vehicles.