JP6896250B2 - Open coil eddy current type sensor and rail displacement measurement method using this - Google Patents

Description

The present invention relates to a vortex current type displacement sensor used when measuring a distance to a metal or measuring a displacement of a metal, and in particular, an open type coil vortex current type sensor which measures using an open type coil vortex current type sensor. And a rail displacement measuring method using this.

Conventionally, eddy current type displacement sensors are rail displacement sensors that measure shaft vibrations of equipment such as turbines and compressors for power generation and manage trajectories (rails), point detection sensors every 1 km, and HSST (High Speed Surface Transport). It is used in levitation control sensors and the like. The rail displacement sensor plays a part in track management while complementing each other with the optical type and the eddy current type.

For example, a track that supports a vehicle such as a train that passes hundreds of times a day is worn by friction with the wheels of the train. Rail wear is affected by various environmental factors such as the weight applied to the rail when the train passes, the type of train, operating conditions and rail maintenance status, the presence or absence of rail lubrication, slope, rainfall / snowfall, humidity, and temperature. It is due. In addition, the rails are displaced in the lateral direction due to the running of trains and the like. That is, the positions of the top surface and the side surface of the rail are displaced. It will be necessary to carry out track maintenance work in order to improve the safety of running trains and the like.
In this way, the rails of railway tracks are worn little by little every day. From the viewpoint of safety, it is necessary to regularly numerically control the degree of wear of the rail and effectively maintain and repair it. If the rail wears significantly, the rail needs to be replaced.

Therefore, there is an eddy current type displacement sensor as a sensor for measuring such rail wear, that is, measuring the displacement of the object to be measured. The eddy current type displacement sensor supplies a high frequency current to the sensor coil to generate a high frequency magnetic field, and the magnetic field generates an eddy current on the surface of the object to be measured, so that the impedance of the sensor coil changes due to electromagnetic induction. Is used to measure the distance (displacement) from the object to be measured. The eddy current type displacement sensor can measure the displacement of the object to be measured in a non-contact manner, and the object to be measured can be a conductor as well as a magnetic material.

Various techniques have been proposed for a method of detecting a rail deviation, that is, a displacement amount, without contacting the rail while the vehicle is running. For example, as in Japanese Patent Application Laid-Open No. 2013-238516, "Eddy current type rail left-right displacement detection method and apparatus", a pair of detection coil means installed on the left and right at regular intervals from the center line in the longitudinal direction of the rail. Is excited by a high-frequency resonance current, the impedance change of the pair of detection coil means is converted into a DC voltage, the DC voltage is converted into a digital signal, and the rail and the rail are based on the voltage value of the converted digital signal. An eddy current type rail left-right displacement detection method for detecting the left-right displacement between the pair of detection coil means has been proposed.

Japanese Unexamined Patent Publication No. 2013-238516

The eddy current type displacement sensor is a sensor that can measure the output voltage corresponding to the displacement of a target such as a rail without contact. The eddy current displacement sensor consists of a (detection) coil, a coaxial cable and an output voltage circuit. Currently, the distance from the rail (measured object) of the eddy current type displacement sensor to the sensor is generally up to about 1/2 times the outer diameter of the coil, and in the case of the rail displacement sensor, it is about 25 mm. However, at the distance (lift-off) to the object to be measured (rail top surface) of the conventional eddy current displacement sensor, the eddy current displacement sensor may malfunction or malfunction due to the influence of foreign matter such as gravel or snow or collision. It had the problem of being easy to wake up.

In addition, since the coil of the conventional eddy current type displacement sensor has a solenoid shape and the magnetic flux easily spreads, the magnetic flux interlinking with the rail is reduced by increasing the lift-off, and the change in the impedance of the coil depending on the rail displacement is reduced. However, there was a problem that the detection accuracy of rail displacement was likely to decrease.

In Patent Document 1, "Swirl current type rail left-right displacement detection method and device", the rail displacement output may be affected by the amount of wear on the top of the rail caused by friction between the rail and the rail. However, there was a problem that highly accurate measurement could not be performed. For example, at a curved portion in a railway track, the amount of wear tends to increase due to uneven distribution of the load inside the rail located outside the curve.

The inventors of the present invention have focused on making the coil structure of the eddy current type rail displacement sensor an open type. Therefore, it was considered that the rail displacement can be detected up to about 50 mm, which is twice the conventional lift-off, by raising the resonance frequency and raising the Q value.

The present invention has been devised to solve such a problem. That is, an object of the present invention is to increase the measurement distance of the eddy current type displacement sensor, so that the object to be measured (the top surface of the rail) is affected by foreign matter such as gravel or snow while mounted on a track inspection vehicle. It is an object of the present invention to provide an eddy current type sensor of an open coil capable of measuring displacement and the like quickly and accurately without collision, and a rail displacement measuring method using the eddy current type sensor.

The eddy current type displacement sensor of the open coil of the present invention is an eddy current type sensor that measures the displacement of the object to be measured (R) by passing a current through the coil to generate an eddy current in the object to be measured (R). 100)
Two coils (11, 12) of dielectric open-type coils 1 and 2 become sandwiched by (13) (Co1, Co2) has two,
Two of the open type coil 1,2 (Co1, Co2), was placed above the row with respect to the measurement surface of the measurement object (R), it is characterized.

The open coils 1 and 2 (Co1, Co2) have a structure in which the coil is wound around a ferromagnetic core (14).
The open coils 1 and 2 (Co1, Co2) are provided with a shield mechanism (15) around them.

In the rail displacement measuring method using the eddy current type sensor of the present invention, an eddy current is passed through a coil to generate an eddy current in a rail (R) to be measured, and the displacement of the rail (R) is measured. This is a rail displacement measurement method using a shape sensor.
Two coils (11, 12) by using a dielectric (13) open-type coils 1 and 2 become sandwiched by (Co1, Co2) of the eddy current type sensor (100) having two, said rails ( The impedance change that changes depending on the displacement (x) and lift-off (z) of R) is output as an output voltage (Vo), and the displacement (x) of the rail (R) is measured by measuring this output voltage (Vo). ) Is detected
The output voltage (Vo) measured by the open coil 1 (Co1) and the open coil 2 (Co2) is height-corrected and linearized between the rail (R) and the eddy current sensor (100). It is characterized in that the displacement of the rail (R) is measured.

The open coil 1 (Co1) and the open coil 2 (Co2) of the eddy current sensor (100) are arranged so as to face each other in the lateral displacement direction with respect to the longitudinal direction of the rail (R) for measurement.

In the eddy current type sensor (100) of the present invention, the output voltage corresponding to the displacement of the object to be measured (R) can be measured in a non-contact manner. A high-frequency current is supplied to the open coil 1 (Co1) and the open coil 2 (Co2) of the eddy current sensor (100) to generate an eddy current on the surface of the object (R) to be measured. Since the impedance of each of the open coil 1 (Co1) and the open coil 2 (Co2) changes due to the eddy current, a DC voltage signal corresponding to the change is output. The two coils of the open coil 1 (Co1) and the open coil 2 (Co2) of the eddy current sensor (100) are arranged so as to face each other in the lateral displacement direction with respect to the longitudinal direction of the object to be measured (R). Therefore, when one of the open coil 1 (Co1) or the open coil 2 (Co2) moves in the direction approaching the object to be measured (R), the other open coil (Co1 or Co2) moves away. It works. Therefore, the output signal of the open coil 1 (Co1) and the output signal of the open coil 2 (Co2) characteristically reversely change with the center (C) of the object to be measured (R) as the axis of symmetry.
These output signals are amplified and taken out as output signals. By arithmetically processing this signal (height correction / linearization between the object to be measured (R) and the open coil 1 (Co1) and the open coil 2 (Co2)), the center of the object to be measured (R) ( Detecting the displacement (deviation) of the object to be measured (R) by extracting it as a linear output signal with respect to the lateral displacement (x) of the open coil 1 (Co1) and the open coil 2 (Co2) with respect to RC). Can be done.

The eddy current type sensor (100) of the present invention is composed of a (detection) coil, a coaxial cable and an output voltage circuit, and the distance from the eddy current type displacement sensor (100) to the object to be measured (R) is generally a coil. By making the coil structure open as in the present invention, the coil structure that was up to about 1/2 of the outer diameter is raised, the resonance frequency is raised, the Q value is raised, and the eddy current from the object to be measured (R). The distance to the shape displacement sensor (100) can be doubled as before.
For example, when a rail detection device using the eddy current type sensor (100) of the present invention is mounted on a track inspection vehicle to measure rail displacement during traveling, the eddy current type sensor (100) is used to measure an object (measurement object (100). The distance to R) can be doubled as before. The distance (lift-off) from the eddy current type sensor (100) to the object to be measured (the top surface of the rail R) becomes long, and the influence of collision by foreign matter such as gravel or snow is eliminated. It is possible to prevent the eddy current type sensor (100) from malfunctioning or malfunctioning. When a rail displacement sensor is used, the lift-off can be greatly expanded from the conventional 25 mm to 50 mm, for example, and collision with foreign matter can be avoided.

In the rail displacement measuring method of the present invention, since the distance from the rail (R) can be secured, maintenance and management of a machine such as a rail detection device can be stably performed.
In addition, malfunctions can be eliminated in rail maintenance and management, which can contribute to safe and stable operation.

An example of an open coil constituting the eddy current type sensor of the present invention is shown, (a) is a plan view, (b) is a side view, and (c) is a plan view. It is the schematic front view of the rail explaining the method of measuring the rail displacement using the eddy current type sensor of this invention. It is the schematic plan view of the rail explaining the method of measuring the rail displacement using the eddy current type sensor of this invention. It is a circuit diagram which shows an example of the output circuit which constitutes an open coil. It is a graph which shows the impedance voltage characteristic by the eddy current type sensor (rail displacement sensor) of this invention. It is a graph which shows the output voltage characteristic of the eddy current type sensor (rail displacement sensor) of this invention. It is a graph which shows the final displacement output by the eddy current type sensor (rail displacement sensor) of this invention. It is a schematic block diagram of the rail detection apparatus using the eddy current type sensor of this invention. It is a perspective view which shows the modification 1 of the open type coil of the eddy current type sensor of this invention. It is a regular cross-sectional view which shows the modification 2 of the open type coil of the eddy current type sensor of this invention. A modification 3 of the open coil of the eddy current type sensor of the present invention is shown, where FIG. 3A is a perspective view and FIG. 3B is a plan view.

The present invention is an eddy current type sensor of an open coil that measures the displacement of a rail or the like by passing a current through the coil to generate an eddy current in an object to be measured such as a rail and outputting an impedance change as an output voltage. This is a rail displacement measuring method using this.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Eddy current type sensor configuration>
1A and 1B show an example of an open coil constituting the eddy current type sensor of the present invention, where FIG. 1A is a plan view, FIG. 1B is a side view, and FIG. 1C is a plan view. FIG. 2 is a schematic front view of a rail for explaining a method of measuring rail displacement using the eddy current type sensor of the present invention. FIG. 3 is a schematic plan view of a rail for explaining a method of measuring rail displacement using the eddy current type sensor of the present invention.
The eddy current type sensor 100 of the present invention is an eddy current type sensor used when a current is passed through a coil to generate an eddy current in an object to be measured such as rail displacement and the displacement of the object R to be measured is measured. This eddy current type sensor 100 is mounted on a track inspection vehicle and used when measuring rail displacement while traveling. When the eddy current type sensor 100 of the present invention is used as a displacement sensor, two open type coils are used.
One open type coil 1 (Co1) includes two coils 11 and 12 is sandwiched a dielectric 13 such as a synthetic resin plate. The notation of the open type is used to mean a state in which two coils are in non-contact (no connection) with the dielectric 13 sandwiched between them.

As shown in FIGS. 1A, 1B, and 1C, when the eddy current type sensor 100 of the present invention is used as a displacement sensor, two open type coils configured in this way are used. Therefore, for convenience, the first coil is referred to as an open coil 1 (Co1) and the second coil is referred to as an open coil 2 (Co2), but there is no difference in their configurations.

<Composition of open coil>
The first open coil 1 (Co1) is composed of two coils 11 and 12. As shown in the figure, the first coil 11 is a copper wire wound in a triangular shape, and the second coil 12 is also a copper wire wound in a triangular shape. These two coils 11 and 12 have a structure in which a dielectric 13 such as a plastic (engineering plastic) such as an acrylic plate is sandwiched. The two coils 11 and 12 are arranged in the same shape while being sandwiched between the dielectrics 13. However, since it is not connected, it is called an open type.

The open coil 1 (Co1) of the present invention uses, for example, a single copper wire as a conducting wire, has a conductor diameter of 0.5 mm, and has a coil winding pitch of 1 mm. An acrylic plate was used as the dielectric 13. The gap between the coils was 1 mm. The number of turns of each coil C and C'is N = 12 for both. The conductor diameter, winding pitch, or thickness of the dielectric 13 (gap between the coils) of these coils is an example, and is not limited to these values. For example, the parallel resonance frequency is adjusted by the winding pitch of the coil. Further, the material of the dielectric 13 is not limited to the acrylic plate. The open coil 2 (Co2) has a similar configuration.

<Method of measuring rail displacement using an eddy current sensor>
As shown in FIGS. 2 and 3, the eddy current sensor 100 of the present invention uses the open coil 1 (Co1) and the open coil 2 (Co2) of the rail R when the object to be measured is the rail R. It is used by arranging it so as to face the crown surface. A high-frequency current is supplied to the open coil 1 (Co1) and the open coil 2 (Co2) of the eddy current sensor 100 to generate an eddy current on the surface of the rail R. The lateral displacement of the rail is defined as the rail displacement x, and the distance from the crown surface of the rail R to the eddy current sensor 100 is defined as lift-off z. The impedance change that changes depending on the displacement x of the rail R and the lift-off z is output as the output voltage Vo, and this output voltage Vo is measured. At this time, as shown in FIG. 2, when measuring the rail displacement, the rail displacement x = 0 mm is adjusted as a value at which the impedances of the open coil 1 (Co1) and the open coil 2 (Co2) match. Lift-off z = 25 mm is used as a reference. Needless to say, the values are not limited to these values.

These output signals are amplified and taken out as output signals. This signal is converted (linearized) into an output signal having a height correction (displacement correction ) between the rail R and the eddy current type sensor 100 and a linear relationship (straightening ) with the measured amount by arithmetic processing.
When actually measuring the output voltages of the open coil 1 (Co1) and the open coil 2 (Co2), the coil and the output circuit, which will be described later, are connected by a coaxial cable 22 (FIGS. 4 and 5). reference).

As shown in the plan view of FIG. 3, the open coil 1 (Co1) and the open coil 2 (Co2) of the rail displacement sensor 2 are arranged so as to face each other in the lateral displacement direction with respect to the longitudinal direction of the rail R. ing. When one of the open coil 1 (Co1) or the open coil 2 (Co2) moves toward the rail R, the other open coil (Co1 or Co2) moves away from the rail R. Therefore, the output signal of the open coil 1 (C1) and the output signal of the open coil 2 (Co2) characteristically reversely change with the center RC of the rail R as the axis of symmetry. Therefore, the displacement x of the rail R can be measured by the rail displacement sensor 2 including the open coil 1 (Co1) and the open coil 2 (Co2).

<Structure of output circuit of rail displacement sensor>
FIG. 4 is a circuit diagram showing an example of an output circuit constituting an open coil. This circuit diagram describes the open coil 1 (Co1). Since the open coil 2 (Co2) has the same configuration, the description thereof will be omitted.
As the open coil 1 (Co1) of the eddy current sensor 100 of the present invention, for example, the one having the configuration shown in FIG. 4 is used. An open coil 1 (Co1) is incorporated in the sensor unit, and is composed of a coaxial cable 22 and a voltage doubler rectifier circuit. The capacitance generated by the winding pitch of the coils 11 and 12 is defined as Cp1 and Cp1', and the capacitance generated by the gap between the dielectrics 13 is defined as Cs.
The resistance of the coil depending on the amount of magnetic flux interlinking with the rail R was set to Rs1 and Rs2, and the inductance was set to Ls1 and Ls2. E = 10Vpp was applied as the transmitter voltage. The excitation frequencies of the open coils 1 (Co1) and 2 (Co2) were set to fo = 13.19 MHz. The output voltage Vo of the eddy current type sensor 100 is the voltage between the terminals of the capacitor C4.

The eddy current type sensor 100 outputs a voltage proportional to the distance (gap) from the rail R and responds from direct current (distance in a stationary state) to a high frequency, so that displacement / vibration is measured in a non-contact manner. Since measurement is possible by generating an eddy current on the surface of the rail R, it is limited to a metal that is a good conductor such as the rail R. Further, according to the principle, the characteristics change depending on the difference between the inherent resistance and the magnetic permeability of the rail R, that is, the difference in the material. In principle, it does not detect insulation that does not allow current to flow, so it can be measured without being affected by oil or water. However, it may adversely affect the measuring device. Therefore, in the eddy current type sensor 100 of the present invention, the distance to the rail R can be doubled as in the conventional case. That is, the distance (lift-off) from the eddy current type sensor 100 to the top surface of the rail R becomes long, and the influence of collision by foreign matter such as gravel or snow is eliminated.

<Impedance voltage characteristics of eddy current type sensor (rail displacement sensor)>
FIG. 5 is a graph showing impedance voltage characteristics by the eddy current type sensor (rail displacement sensor) of the present invention.
FIG. 5 shows the impedance z-rail displacement x characteristics. Impedance z was measured with rail displacement x = −36 to 36 mm and lift-off z = 50 mm. The excitation frequency is fo = 13.19 MHz. The excitation frequency fo was set to the frequency at which the change in the output voltage Vo depending on the rail displacement x was the largest.

<About the output voltage characteristics of the eddy current type sensor (rail displacement sensor)>
FIG. 6 is a graph showing the output voltage characteristics of the eddy current type sensor (rail displacement sensor) of the present invention.
FIG. 6 shows a standardized output voltage Vo based on the impedance characteristics shown in FIG. 5 to ± 1.5 V / ± 30 mm.

<Displacement output voltage for rail displacement sensor>
FIG. 7 is a graph showing the final displacement output by the eddy current type sensor (rail displacement sensor) of the present invention.
In FIG. 7, the output voltage Vo was used by the mathematical formula shown in Equation 1 in order to derive the desired detected displacement x'. Here, x': detected displacement (mm), a, b, α, Vave :: any constant.
The values shown in Table 1 were used as arbitrary constants for the calculation of the detected displacement. The final displacement output is as shown in FIG.

<Structure of rail detection device>
FIG. 8 is a schematic configuration diagram of a rail detection device using an eddy current type sensor.
This is an example of a rail displacement detection device used in the rail displacement measurement method using the eddy current type sensor of the present invention. The displacement of the rail R can be measured using the eddy current type sensor of the present invention. For example, a rail detection device can be equipped on a track inspection vehicle to perform non-contact measurement while traveling. Therefore, the eddy current type sensor 100 having the above-mentioned function is housed in the housing 21, and a set of two of them is attached so as to face the rail R from the bottom surface of the track inspection vehicle. At this time, the eddy current type sensor 100 is directed toward the rail R. This is for non-contact measurement. The eddy current type sensor 1 is connected to the converter 23 in the track inspection vehicle by a coaxial cable 22.

The open coil 1 (Co1) and the open coil 2 (Co2) of the eddy current sensor 100 pass a high frequency current through the rail R to generate a high frequency magnetic field for measurement. Each of the open coil 1 (Co1) and the open coil 2 (Co2) is provided with an amplifier 24 that amplifies the output signal.

The converter 23 calculates and processes the output signals of the open coil 1 (Co1) and the open coil 2 (Co2). The converter 23 obtains the displacement detection voltage VLa by taking the difference between the voltage VR related to the voltage VT related to the open coil 1 (Co1) and the open coil 2 (CO2).

<Modification example 1 of eddy current type sensor>
FIG. 9 is a perspective view showing a modification 1 of the open coil of the eddy current sensor of the present invention.
The shape of the open coil of the eddy current type sensor is not limited to the above-mentioned triangular shape. As the open coil 31 of the eddy current sensor of the first modification, circular coils 32 and 33 were used instead of the triangular coil. Open type coil of the first modification, the upper coil 32 and lower coil 33 has a structure sandwiching a dielectric 34. Even with such a circular open coil 31, the measurement distance from the eddy current sensor to the object to be measured can be about twice as long as the conventional one.

<Modification example 2 of eddy current type sensor>
FIG. 10 is a normal cross-sectional view showing a modification 2 of the open coil of the eddy current sensor of the present invention.
The open coil 41 of the eddy current type sensor of the modified example 2 includes a ferromagnetic core (core material) 35 in the open coil 31 of the modified example 1. Even in the configuration in which the coils 32 and 33 are wound around the core 35 as in the second modification, the measurement distance from the eddy current type sensor to the object to be measured can be about twice as long as the conventional one.

<Modification example 3 of eddy current type sensor>
FIG. 11 shows a modification 3 of the open coil of the eddy current type sensor of the present invention, (a) is a perspective view, and (b) is a plan view.
The open coil 51 of the eddy current sensor of the third modification has a configuration in which a plurality of thin copper foils 52 are sandwiched between a shield mechanism 53 and a core (core material) 54 instead of the copper wire coil as described above. .. Even with such a plurality of thin copper foil 52 coils, the measurement distance from the eddy current type sensor to the object to be measured can be about twice as long as the conventional one. Since the open coil 51 of the eddy current sensor of the third modification uses a coil of a square copper foil 52, a square core (core material) 54 is used to match this shape. Of course, it is not limited to.

In the present invention, by increasing the measurement distance of the vortex current type displacement sensor 100, the influence or collision of foreign matter such as gravel or snow on the object to be measured (rail top surface) while the vehicle is mounted on a track inspection vehicle and traveling. Of course, if the displacement and the like can be measured quickly and accurately without doing so, the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention.

The present invention is not limited to detecting the displacement of the rail R of a train or the like, and can be used for measuring and detecting the displacement of other rails or long metal members.

100 Eddy current type sensor 11 Coil 12 Coil 13 Dielectric Co1 Open type coil 1
Co2 open coil 2
R rail x rail displacement z rail lift off

Claims (5)

An eddy current type sensor (100) that measures the displacement of the object to be measured (R) by passing a current through the coil to generate an eddy current in the object to be measured (R).
Two coils (11, 12) of dielectric open-type coils 1 and 2 become sandwiched by (13) (Co1, Co2) has two,
Two of the open type coil 1,2 (Co1, Co2), wherein arranged in rows relative to the measurement surface of the measurement object (R), the eddy current type sensor, characterized in that. The eddy current sensor according to claim 1, wherein the open coil has a structure in which the coil is wound around a ferromagnetic core. The eddy current type sensor according to claim 1 or 2, wherein the open type coil is provided with a shield mechanism around the open type coil. This is a rail displacement measuring method using an eddy current type sensor in which a current is passed through a coil to generate an eddy current in a rail (R) to be measured and the displacement of the rail (R) is measured.
Two coils (11, 12) by using a dielectric (13) open-type coils 1 and 2 become sandwiched by (Co1, Co2) of the eddy current type sensor (100) having two, said rails ( The impedance change that changes depending on the displacement (x) and lift-off (z) of R) is output as an output voltage (Vo), and the displacement (x) of the rail (R) is measured by measuring this output voltage (Vo). ) Is detected
The output voltage (Vo) measured by the open coil 1 (Co1) and the open coil 2 (Co2) is height-corrected and linearized between the rail (R) and the eddy current sensor (100). A rail displacement measuring method using an eddy current type sensor, which measures the displacement of the rail (R). The open coil 1 (Co1) and the open coil 2 (Co2) of the eddy current sensor (100) are arranged so as to face each other in the lateral displacement direction with respect to the longitudinal direction of the rail (R) for measurement. The rail displacement measuring method using the eddy current type sensor according to claim 4, wherein the rail displacement is measured.

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