Rail axial force measurement device, and rail axial force measurement method

Abstract

To provide a rail axial force measurement device that does not need to adhere a sensor to a rail, and can measure axial force of an average rail falling within several meters to several tens of meters.SOLUTION: A rail axial force measurement device is configured to: apply an AC current VL1 to a part between an electrode 11 electrically connected to a rail RA1 at a position PS1 and an electrode 12 electrically connected to the rail RA1 at a position PS2, and flow the AC current CR1 to the part PR1 between the electrode 11 and the electrode 12 of the rail RA1; calculate AC resistance RS1 of the part PR1 or inductance IN1 thereof by a first calculation unit 16 on the basis of a voltage value VV1 of the AC voltage VL1 and a current value CV1 of the AC current CR1; calculate magnetic permeability MP1 of the part PR1 by a second calculation unit 17 on the basis of the calculated AC resistance RS1 or a calculation value CL1 of the inductance IN1; and calculate axial force of the part PR1 by a third calculation unit 18 on the basis of a calculation value CL2 of the calculated magnetic permeability MP1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rail axial force measuring device and a rail axial force measuring method for measuring the axial force of a rail. [Background technology]

[0002] In railways, long rails made by welding rails together are used to solve problems such as increased noise when railway vehicles pass over rail joints. However, when long rails thermally expand due to temperature rise, compressive forces (axial forces or rail axial forces) are generated in the longitudinal direction (length direction) of the rail, which may cause buckling, in which the rail protrudes in the lateral direction (width direction of the rail). For this reason, it is necessary to measure the axial forces of the rail at regular intervals. It is also desirable to reduce the labor required for measuring the axial forces of the rail.

[0003] Non-Patent Document 1 describes rail axial force measurement methods for measuring the axial force of a rail, such as a method based on strain measurement, a method based on magnetic properties, a method based on X-rays, a method based on ultrasonic waves, a method based on rail vibration, and a method based on rail reaction force.

[0004] As a method based on magnetic characteristics, a method of measuring the axial force of a rail by using a magnetic anisotropy sensor is known. JP-A-60-243526 (Patent Document 1) discloses a technology in which, in a rail axial force measuring device, two sets of magnetic anisotropy sensors are adjacently arranged, with coils wound around inverted U-shaped cores arranged with legs in contact with the rail surface in two planes that are substantially perpendicular to the rail surface and perpendicular to each other, one for magnetic anisotropy detection and the other for excitation. In the technology described in the above Patent Document 1, the magnetic anisotropy detection core faces and the excitation core faces of these two sets of magnetic anisotropy sensors are parallel to each other, the magnetic anisotropy detection coils are differentially connected to each other, and the excitation coils are excited in opposite phases to each other, and by utilizing the fact that magnetic anisotropy corresponding to the rail axial force occurs in the rail, the rail axial force is measured from the output of the differentially connected magnetic anisotropy detection coils, with the influence of disturbance magnetic fields removed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 60-243526 [Non-patent literature]

[0006] [Non-Patent Document 1] Fumihiro Urakawa, "Rail Axial Force Measurement Method", RRR, 2017, Vol. 74, No. 2, pp. 28-31 Summary of the Invention [Problem to be solved by the invention]

[0007] Among the various rail axial force measurement methods described in Non-Patent Document 1, the strain measurement method requires a certain amount of work time and technical skill to attach a strain gauge, which is a sensor, to the rail. Also, in the method using a strain gauge and a magnetic anisotropy sensor, when it is desired to measure the average rail axial force in an area of ​​several meters to several tens of meters in the longitudinal direction of the rail, it is necessary to measure at multiple locations, which takes a long time to perform the measurement.

[0008] The present invention has been made to solve the problems of the conventional technology as described above, and has an object to provide a rail axial force measurement device that measures the axial force of a rail without the need to attach a sensor to the rail, and that can measure the average axial force of the rail over a range of several to several tens of meters in the longitudinal direction of the rail by measuring at one location, thereby enabling the axial force of the rail to be measured quickly. [Means for solving the problem]

[0009] Among the inventions disclosed in this application, a brief summary of representative inventions is as follows.

[0010] A rail axial force measurement device according to one embodiment of the present invention is a rail axial force measurement device for measuring a first axial force of a first rail on a track equipped with a first rail. The rail axial force measurement device has a first electrode electrically connected to the first rail at a first position in the longitudinal direction of the track, and a second electrode electrically connected to the first rail at a second position separated by a first distance from the first position in the longitudinal direction. The rail axial force measurement device also has a power source including a first terminal and a second terminal, and applies a first AC voltage between the first electrode and the second electrode in a state in which the first terminal is connected to the first electrode, the second terminal is connected to the second electrode, the first electrode connected to the first terminal is electrically connected to the first rail at the first position, and the second electrode connected to the second terminal is electrically connected to the first rail at the second position, thereby passing a first AC current through a first portion of the first rail between the first position and the second position. Moreover, the rail axial force measurement device has a first calculation unit that calculates a first AC resistance or a first inductance of the first portion based on a first voltage value of the first AC voltage and a first current value of the first AC current, a second calculation unit that calculates a first permeability of the first portion based on a first calculated value of the first AC resistance or the first inductance calculated by the first calculation unit, and a third calculation unit that measures the first axial force by calculating a first axial force of the first portion based on the second calculated value of the first permeability calculated by the second calculation unit.

[0011] In another aspect, the rail axial force measurement device may have a first measurement unit that measures a first AC voltage applied between the first electrode and the second electrode, and a second measurement unit that measures a first AC current flowing through the first portion. The first calculation unit may calculate a first AC resistance or a first inductance based on a first voltage value of the first AC voltage measured by the first measurement unit and a first current value of the first AC current measured by the second measurement unit.

[0012] In another aspect, the power supply applies a first AC voltage having a first frequency of 50 Hz or more or 1 MHz or less between the first electrode and the second electrode, and the power supply may pass a second AC current through the first portion by applying a second AC voltage having a second frequency of less than 50 Hz between the first electrode and the second electrode, with the first electrode connected to the first terminal electrically connected to the first rail at a first position and the second electrode connected to the second terminal electrically connected to the first rail at a second position, or may pass a first DC current through the first portion by applying a first DC voltage between the first electrode and the second electrode. The first measurement unit may measure a first voltage consisting of a second AC voltage or a first DC voltage applied between the first electrode and the second electrode, and the second measurement unit may measure a first current consisting of a second AC current flowing through the first portion by applying the second AC voltage between the first electrode and the second electrode, or a first DC current flowing through the first portion by applying the first DC voltage between the first electrode and the second electrode. The rail axial force measurement device may further include a fourth calculation unit that calculates a second AC resistance of the first portion when the first voltage is the second AC voltage and the first current is the second AC current, and calculates a first DC resistance of the first portion when the first voltage is the first DC voltage and the first current is the first DC current, based on a second voltage value of the first voltage measured by the first measurement unit and a second current value of the first current measured by the second measurement unit, and a fifth calculation unit that calculates a first temperature of the first portion based on a third calculated value of the first resistance calculated by the fourth calculation unit and the first DC resistance. The second calculation unit may calculate a first permeability based on the fourth calculated value of the first temperature calculated by the fifth calculation unit and the first calculated value.

[0013] In another aspect, the power supply may apply a first AC voltage having a first frequency of 1 MHz or less between the first electrode and the second electrode, and the first calculation unit may calculate the first inductance based on a first voltage value of the first AC voltage measured by the first measurement unit and a first current value of the first AC current measured by the second measurement unit. The power supply may pass a third AC current through the first portion by applying a third AC voltage having a third frequency greater than the first frequency and equal to or greater than 100 kHz between the first electrode and the second electrode in a state in which the first electrode connected to the first terminal is electrically connected to the first rail at the first position and the second electrode connected to the second terminal is electrically connected to the first rail at the second position. The first measurement unit may measure the third AC voltage applied between the first electrode and the second electrode, and the second measurement unit may measure the third AC current passed through the first portion. The rail axial force measurement device may further include a sixth calculation unit that calculates a second inductance of the first portion based on a third voltage value of the third AC voltage measured by the first measurement unit and a third current value of the third AC current measured by the second measurement unit, and a seventh calculation unit that calculates an internal inductance of the first portion by subtracting a fifth calculated value from a first calculated value based on a first calculated value of the first inductance calculated by the first calculation unit and a fifth calculated value of the second inductance calculated by the sixth calculation unit. The second calculation unit may calculate a first permeability based on the sixth calculated value of the internal inductance calculated by the seventh calculation unit.

[0014] In another aspect, the rail axial force measurement device may have a third electrode electrically connected to the first rail at a third position that is separated by a second distance from the first position on the opposite side to the second position across the first position in the longitudinal direction of the track. The power source may apply a first AC voltage between the first electrode and the second electrode and a fourth AC voltage between the first electrode and the third electrode in a state in which the first terminal is connected to the first electrode, the second terminal is connected to the second electrode and the third electrode, the first electrode connected to the first terminal is electrically connected to the first rail at the first position, the second electrode connected to the second terminal is electrically connected to the first rail at the second position, and the third electrode connected to the second terminal is electrically connected to the first rail at the third position, thereby passing a first AC current through the first portion and a fourth AC current through a second portion of the first rail between the first position and the third position. The rail axial force measurement device may further include a third measurement unit that measures a fourth AC voltage applied between the first electrode and the third electrode, and a fourth measurement unit that measures a fourth AC current flowing through the second portion. The rail axial force measurement device may also include an eighth calculation unit that calculates a third AC resistance or a third inductance of the second portion based on a fourth voltage value of the fourth AC voltage measured by the third measurement unit and a fourth current value of the fourth AC current measured by the fourth measurement unit, a ninth calculation unit that calculates a second permeability of the second portion based on a seventh calculated value of the third AC resistance or the third inductance calculated by the eighth calculation unit, and a tenth calculation unit that calculates a second axial force of the second portion based on the eighth calculated value of the second permeability calculated by the ninth calculation unit.

[0015] In another aspect, the rail axial force measuring device may be provided on a first vehicle that runs on a track and is a railway vehicle or a trolley, and may measure a first axial force when the first vehicle runs on the track. The first vehicle may include a first wheel and a second wheel that are spaced apart from each other by a first distance in the longitudinal direction of the track and roll on the first rail, and the first electrode may be electrically connected to the first wheel and the second electrode may be electrically connected to the second wheel. The power source may apply a first AC voltage between the first electrode and the second electrode in a state in which the first electrode connected to the first terminal is electrically connected to the first rail at a first position via the first wheel and the second electrode connected to the second terminal is electrically connected to the first rail at a second position via the second wheel, thereby passing a first AC current through the first portion.

[0016] In another aspect, the track may include a second rail spaced apart from the first rail in a width direction of the track. The first vehicle may include a third wheel and a fourth wheel spaced apart from each other by a first distance in a length direction and each rolling on the second rail, the third wheel being electrically connected to the first wheel via a first axle, the fourth wheel being electrically connected to the second wheel via a second axle, the first electrode being electrically connected to the third wheel, and the second electrode being electrically connected to the fourth wheel. The power supply may be configured to apply a first AC voltage between the first electrode and the second electrode in a state in which a first electrode connected to the first terminal is electrically connected to the first rail at a first position via the first wheel, a second electrode connected to the second terminal is electrically connected to the first rail at a second position via the second wheel, the first electrode connected to the first terminal is electrically connected to the second rail at the first position via the third wheel, and the second electrode connected to the second terminal is electrically connected to the second rail at the second position via the fourth wheel, thereby passing a first AC current through the first portion and passing a fifth AC current through a third portion of the second rail between the first position and the second position. The rail axial force measurement device may further include an eleventh calculation unit that calculates a fourth AC resistance or a fourth inductance of the third portion based on the first voltage value and the fifth current value of the fifth AC current, a twelfth calculation unit that calculates a third permeability of the third portion based on a ninth calculated value of the fourth AC resistance or the fourth inductance calculated by the eleventh calculation unit, and a thirteenth calculation unit that calculates a third axial force of the third portion based on a tenth calculated value of the third permeability calculated by the twelfth calculation unit.

[0017] In another embodiment, the track may include a third rail spaced apart from the first rail in the width direction of the track. The first vehicle may include a fifth wheel and a sixth wheel spaced apart from each other by a first distance in the length direction and rolling on the third rail, the fifth wheel being connected to the first wheel via a third axle, and the sixth wheel being connected to the second wheel via a fourth axle. A fourth portion of the third axle located closer to the fifth wheel than the first central portion in the width direction may be electrically insulated from a fifth portion of the third axle located closer to the first wheel than the fourth portion in the width direction, and a sixth portion of the fourth axle located closer to the sixth wheel than the second central portion in the width direction may be electrically insulated from a seventh portion of the fourth axle located closer to the second wheel than the sixth portion in the width direction.

[0018] In another aspect, the rail axial force measurement device may measure the first axial force at each of a plurality of fourth positions that are different from one another along the length direction by repeatedly executing a rail axial force measurement process, while changing a fourth position of the first vehicle on the track, in which a first calculation unit calculates a first AC resistance or a first inductance, a second calculation unit calculates a first permeability based on the first calculated value calculated by the first calculation unit, and a third calculation unit calculates the first axial force of the first portion based on the second calculated value calculated by the second calculation unit, when the first vehicle runs on the track.

[0019] A rail axial force measurement device according to one embodiment of the present invention is a rail axial force measurement device for measuring a first axial force of a first rail on a track equipped with a first rail. The rail axial force measurement device has a first electrode electrically connected to the first rail at a first position in the longitudinal direction of the track, a second electrode electrically connected to the first rail at a second position spaced a first distance from the first position in the longitudinal direction, and a capacitor including a first terminal and a second terminal, the first terminal being connected to the second electrode. The rail axial force measuring device further includes a third terminal and a fourth terminal, and has a power source that passes a first AC current through a first portion of the first rail between the first position and the second position by applying a first AC voltage having a first frequency between the first electrode and the second terminal in a state in which the third terminal is connected to the first electrode, the fourth terminal is connected to the second terminal so that the fourth terminal is connected to the second electrode via a capacitor, the first electrode connected to the third terminal is electrically connected to the first rail at a first position, and the second electrode connected to the fourth terminal via a capacitor is electrically connected to the first rail at a second position. The rail axial force measurement device also includes a first calculation unit that calculates a first AC resistance of the first portion based on a first voltage value of the first AC voltage and a first current value of the first AC current, a second calculation unit that calculates a first magnetic permeability of the first portion based on the first calculated value of the first AC resistance calculated by the first calculation unit, and a third calculation unit that measures the first axial force by calculating a first axial force of the first portion based on the second calculated value of the first magnetic permeability calculated by the second calculation unit. A first closed circuit is formed by the power source, the first portion, and the capacitor, and the first frequency is set so that a first reactance of the first closed circuit becomes 0 or is equal to or less than a first threshold value.

[0020] In another aspect, the rail axial force measurement device may have a first measurement unit that measures a first AC voltage applied between the first electrode and the second terminal, and a second measurement unit that measures a first AC current flowing through the first portion. The first calculation unit may calculate a first AC resistance based on a first voltage value of the first AC voltage measured by the first measurement unit and a first current value of the first AC current measured by the second measurement unit.

[0021] In another embodiment, the rail axial force measurement device may have a switching unit that switches whether or not to short-circuit the fourth terminal and the second electrode. The power source may apply a first AC voltage having a first frequency of 50 Hz or more between the first electrode and the second terminal in a state in which the fourth terminal and the second electrode are not short-circuited by the switching unit, and the power source may pass a second AC current through the first portion by applying a second AC voltage having a second frequency of less than 50 Hz between the first electrode and the second electrode in a state in which the first electrode connected to the third terminal is electrically connected to the first rail at a first position and the second electrode short-circuited to the fourth terminal by the switching unit is electrically connected to the first rail at a second position, or pass a first DC current through the first portion by applying a first DC voltage between the first electrode and the second electrode. The first measurement unit may measure a first voltage consisting of a second AC voltage or a first DC voltage applied between the first electrode and the second electrode, and the second measurement unit may measure a first current consisting of a second AC current flowing through the first portion by applying the second AC voltage between the first electrode and the second electrode, or a first DC current flowing through the first portion by applying the first DC voltage between the first electrode and the second electrode. The rail axial force measurement device may further include a fourth calculation unit that calculates a second AC resistance of the first portion when the first voltage is the second AC voltage and the first current is the second AC current, and calculates a first DC resistance of the first portion when the first voltage is the first DC voltage and the first current is the first DC current, based on a second voltage value of the first voltage measured by the first measurement unit and a second current value of the first current measured by the second measurement unit, and a fifth calculation unit that calculates a first temperature of the first portion based on a third calculated value of the first resistance calculated by the fourth calculation unit and the first DC resistance. The second calculation unit may calculate a first permeability based on the fourth calculated value of the first temperature calculated by the fifth calculation unit and the first calculated value.

[0022] A rail axial force measuring method according to one aspect of the present invention is a rail axial force measuring method for measuring a first axial force of a first rail on a track equipped with a first rail. The rail axial force measuring method includes the steps of (a) electrically connecting a first electrode to the first rail at a first position in the longitudinal direction of the track, and (b) electrically connecting a second electrode to the first rail at a second position separated by a first distance from the first position in the longitudinal direction. The rail axial force measuring method also includes the step of (c) applying a first AC voltage between the first electrode and the second electrode by the power source in a state in which a first terminal included in a power source including a first terminal and a second terminal is connected to the first electrode, a second terminal included in the power source is connected to the second electrode, the first electrode connected to the first terminal is electrically connected to the first rail at the first position, and the second electrode connected to the second terminal is electrically connected to the first rail at the second position, thereby passing a first AC current through a first portion of the first rail between the first position and the second position. Moreover, the rail axial force measuring method includes the step (d) of calculating a first AC resistance or a first inductance of the first portion by a first calculation unit based on a first voltage value of the first AC voltage and a first current value of the first AC current, the step (e) of calculating a first permeability of the first portion by a second calculation unit based on the first calculated value of the first AC resistance or the first inductance calculated in the step (d), and the step (f) of measuring the first axial force by calculating a first axial force of the first portion by a third calculation unit based on the second calculated value of the first permeability calculated in the step (e). Effect of the Invention

[0023] By applying one embodiment of the present invention, in a rail axial force measurement device that measures the axial force of a rail, it is not necessary to attach a sensor to the rail, and even by measuring at one location, it is possible to measure the average axial force of the rail over a range of several meters to several tens of meters in the longitudinal direction of the rail, and the axial force of the rail can be measured quickly. [Brief description of the drawings]

[0024] [Figure 1]1 is a block circuit diagram showing a rail axial force measuring device according to a first embodiment. [Diagram 2] 1 is a circuit diagram showing a measurement circuit of a rail axial force measurement device according to a first embodiment. FIG. [Diagram 3] FIG. 3 is a flow chart showing some steps of a rail axial force measuring method according to the first embodiment. [Figure 4] FIG. 4 is a flow chart showing a method of calculating temperature and axial force in the rail axial force measuring method according to the first embodiment. [Diagram 5] FIG. 4 is a diagram for explaining a change in magnetic permeability due to an axial force of a rail. [Figure 6] FIG. 4 is a diagram for explaining a change in magnetic permeability due to an axial force of a rail. [Figure 7] FIG. 2 is a diagram illustrating an analysis model constructed in an analysis of rail impedance. [Figure 8] FIG. 4 is a diagram showing a finite element model of a rail portion. [Figure 9] 1 is a graph showing frequency dependence of impedance per 1 m of rail. [Figure 10] 1 is a graph showing frequency dependence of resistance per meter of rail. [Figure 11] 1 is a graph showing frequency dependence of inductance per meter of rail. [Figure 12] 1 is a graph showing frequency dependence of values ​​of external reactance, internal reactance, and resistance components in impedance. [Figure 13] 1 is a graph showing frequency dependence of the distribution of each component of external reactance, internal reactance, and resistance in impedance. [Figure 14] 13 is a graph in which the vertical axis of FIG. 12 is enlarged. [Figure 15] 13 is a graph showing frequency dependence of the value and distribution of the amount of change in resistance value when the magnetic permeability is increased by 2.5%. [Figure 16] 13 is a graph showing frequency dependence of the value and distribution of the amount of change in inductance when the magnetic permeability is increased by 2.5%. [Figure 17]FIG. 4 is a block circuit diagram showing a rail axial force measuring device according to a first modified example of the first embodiment. [Figure 18] FIG. 4 is a circuit diagram showing a measurement circuit of a rail axial force measurement device according to a first modified example of the first embodiment. [Figure 19] FIG. 2 is a circuit diagram showing a measurement circuit and a leakage current path of the rail axial force measurement device of the first embodiment. [Figure 20] FIG. 4 is a circuit diagram showing a measurement circuit and a leakage current path of a rail axial force measurement device according to a first modified example of the first embodiment. [Figure 21] FIG. 11 is a block circuit diagram showing a rail axial force measuring device according to a second modified example of the first embodiment. [Figure 22] FIG. 11 is a circuit diagram showing a measurement circuit of a rail axial force measurement device according to a second modified example of the first embodiment. [Figure 23] FIG. 13 is a block circuit diagram showing a rail axial force measuring device according to a third modified example of the first embodiment. [Figure 24] FIG. 11 is a circuit diagram showing a measurement circuit of a rail axial force measurement device according to a third modified example of the first embodiment. [Diagram 25] FIG. 11 is a block circuit diagram showing an example of a rail axial force measuring device according to a second embodiment. [Figure 26] FIG. 11 is a circuit diagram showing a measurement circuit of a rail axial force measurement device according to a second embodiment. [Figure 27] FIG. 11 is a flow chart showing some steps of a rail axial force measuring method according to a second embodiment. [Figure 28] FIG. 11 is a block circuit diagram showing another example of a rail axial force measuring device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0026] The disclosure is merely an example, and those who are skilled in the art can easily come up with appropriate modifications that maintain the gist of the invention, and naturally, these modifications are included in the scope of the present invention. In addition, in order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0027] In addition, in this specification and each figure, elements similar to those described above with respect to the previous figures are given the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0028] Furthermore, in the drawings used in the embodiments, hatching (shading) may be omitted even in cross-sectional views in order to make the drawings easier to see, and hatching may be added even in plan views in order to make the drawings easier to see.

[0029] In the following embodiments, when a range is indicated as A to B, it means A or more and B or less, unless otherwise specified.

[0030] (Embodiment 1) <Rail axial force measurement method using rail axial force measuring device> First, a rail axial force measuring method using the rail axial force measuring device of embodiment 1 will be described with reference to Figures 1 to 4. The rail axial force measuring device of embodiment 1 is a rail axial force measuring device that measures the axial force of a rail on a track equipped with rails. Moreover, the rail axial force measuring method of embodiment 1 is a rail axial force measuring method using the rail axial force measuring device of embodiment 1, which is a rail axial force measuring method that measures the axial force of a rail on a track equipped with rails.

[0031] Fig. 1 is a block circuit diagram showing a rail axial force measurement device of the first embodiment. Fig. 2 is a circuit diagram showing a measurement circuit of the rail axial force measurement device of the first embodiment. Fig. 3 is a flow diagram showing some steps of a rail axial force measurement method of the first embodiment. Fig. 4 is a flow diagram showing a method of calculating temperature and axial force in the rail axial force measurement method of the first embodiment. Details of Fig. 4 will be described later.

[0032] 1, a rail axial force measuring device 10 of the first embodiment has an electrode (first electrode) 11, an electrode (second electrode) 12, a power source 13, a measuring unit (first measuring unit) 14, a measuring unit (second measuring unit) 15, a first calculation unit 16, a second calculation unit 17, and a third calculation unit 18. A computer 19 can be used as the first calculation unit 16, the second calculation unit 17, and the third calculation unit 18.

[0033] The electrode 11 is electrically connected to the rail (first rail) RA1 at a position (first position) PS1 in the longitudinal direction of the track TR1. The electrode 12 is electrically connected to the rail RA1 at a position (second position) PS2 spaced a distance (first distance) DS1 from the position PS1 in the longitudinal direction of the track TR1.

[0034] The power source 13 includes a terminal (first terminal) 13a and a terminal (second terminal) 13b (opposite to the terminal 13a) having a polarity opposite to that of the terminal 13a. The power source 13 also includes a control unit (not shown). In a state in which the terminal 13a is connected to the electrode 11, the terminal 13b is connected to the electrode 12, the electrode 11 connected to the terminal 13a is electrically connected to the rail RA1 at the position PS1, and the electrode 12 connected to the terminal 13b is electrically connected to the rail RA1 at the position PS2, the power source 13 applies an AC voltage (first AC voltage) VL1 between the electrode 11 and the electrode 12 by the control unit (not shown), thereby passing (passing) an AC current (first AC current) CR1 through a portion (first portion) PR1 between the positions PS1 and PS2 of the rail RA1. Note that, hereinafter, the portion PR1 may be referred to as a measurement section MS1.

[0035] The measurement unit 14 measures an AC voltage VL1 applied between the electrodes 11 and 12. The measurement unit 15 measures an AC current CR1 flowing through the portion PR1. As will be described later, the measurement unit 15 preferably includes a Rogowski coil, which is an air-core coil arranged in the vicinity of the portion PR1 of the rail RA1 so as to measure a circumferential magnetic field centered on the portion PR1 when viewed from the longitudinal direction of the track TR1.

[0036] The first calculation unit 16 calculates an AC resistance (first AC resistance) RS1 or an inductance (first inductance) IN1 of the portion PR1 based on the voltage value (first voltage value) VV1 of the AC voltage VL1 measured by the measurement unit 14 and the current value (first current value) CV1 of the AC current CR1 measured by the measurement unit 15 (from the voltage value VV1 and the current value CV1). The second calculation unit 17 calculates a magnetic permeability (first magnetic permeability) MP1 of the portion PR1 based on a calculated value (first calculated value) CL1 of the AC resistance RS1 or the inductance IN1 calculated by the first calculation unit 16. The third calculation unit 18 calculates an axial force (first axial force) AF1 (see FIG. 3) of the portion PR1 based on a calculated value (second calculated value) CL2 of the magnetic permeability MP1 calculated by the second calculation unit 17, thereby measuring the axial force AF1.

[0037] In this specification, axial force refers to the axial force of the rail, i.e., rail axial force, and rail axial force refers to the force accumulated in the rail in the longitudinal direction of the rail (the longitudinal direction of the track).

[0038] In the first embodiment, the rail axial force measurement device 10 is described by taking as an example a case where the rail axial force measurement device 10 has the measurement unit 14 and the measurement unit 15. However, when the voltage value VV1 of the AC voltage VL1 set by a control unit (not shown) included in the power source 13 is used as the voltage value VV1 of the AC voltage VL1, the rail axial force measurement device 10 of the first embodiment may not have the measurement unit 14. When the current value CV1 of the AC current CR1 measured by an ammeter (not shown) included in the power source 13 is used, the rail axial force measurement device 10 of the first embodiment may not have the measurement unit 15. In such a case, the first calculation unit 16 simply calculates the AC resistance RS1 or the inductance IN1 of the portion PR1 based on the voltage value VV1 of the AC voltage VL1 and the current value CV1 of the AC current CR1.

[0039] A computer 19 used as the first calculation section 16, the second calculation section 17 and the third calculation section 18 of the rail axial force measuring device 10 of the present embodiment 1 is composed of a central processing unit (CPU), a RAM (Random Access Memory), a storage section, a data / command input section, an image display section, an output section, etc.

[0040] Although not shown, the CPU is a part that executes arithmetic operations (addition, subtraction, multiplication and division), logical operations (logical AND, logical OR, negation and exclusive OR, etc.), data comparison, data shifting, etc., on various data. Although not shown, the storage unit has a hard disk device (Hard Disk Drive: HDD) or a ROM (Read Only Memory), etc., and is a part that stores a control program for controlling the CPU and various data used by the CPU. The ROM is generally composed of a semiconductor chip, etc.

[0041] Moreover, a computer 19 used as the first calculation unit 16, the second calculation unit 17, and the third calculation unit 18 of the rail axial force measurement device 10 of the present embodiment 1 executes a program for performing the operation and processing of each step of the rail axial force measurement method described below.

[0042] In the rail axial force measuring method using the rail axial force measuring device 10 of the first embodiment, first, the electrode 11 is electrically connected to the rail RA1 at a position PS1 in the longitudinal direction of the track TR1 (step S11 in FIG. 3). Also, the electrode 12 is electrically connected to the rail RA1 at a position PS2 spaced a distance DS1 from the position PS1 in the longitudinal direction of the track TR1 (step S12 in FIG. 3).

[0043] Next, terminal 13a included in power supply 13, which includes terminals 13a and 13b, is connected to electrode 11, terminal 13b included in power supply 13 is connected to electrode 12, electrode 11 connected to terminal 13a is electrically connected to rail RA1 at position PS1, and electrode 12 connected to terminal 13b is electrically connected to rail RA1 at position PS2. In this state, an AC voltage VL1 is applied between electrode 11 and electrode 12 by power supply 13, whereby an AC current CR1 is passed through portion PR1 of rail RA1 between positions PS1 and PS2 (step S13 in FIG. 3).

[0044] Next, the AC voltage VL1 applied between the electrodes 11 and 12 is measured by the measurement unit 14 (step S14 in FIG. 3). Also, the AC current CR1 flowing through the part PR1 is measured by the measurement unit 15 (step S15 in FIG. 3).

[0045] Next, based on the voltage value VV1 of the AC voltage VL1 measured by the measurement unit 14 in step S14 and the current value CV1 of the AC current CR1 measured by the measurement unit 15 in step S15 (from the voltage value VV1 and the current value CV1), the AC resistance RS1 of the portion PR1 (R R ) or inductance IN1 (L in Figure 4 R) is calculated by the first calculation unit 16 (step S16 in FIGS. 3 and 4). Here, when the voltage between the electrode 11 and the electrode 12 (AC voltage VL1) is taken as voltage V as shown in FIG. 2, voltage V is expressed by the following formula (1).

[0046]

number

[0047] Note that a specific method for calculating the AC resistance RS1 or the inductance IN1 is not particularly limited. However, for example, the AC resistance RS1 and the inductance IN1 can be calculated by inputting the voltage value VV1 of the AC voltage VL1 of the power supply 13 and the current value CV1 of the AC current CR1 calculated by integrating the voltage output of the Rogowski coil included in the measurement unit 15 with an integrator into an oscilloscope and measuring the amplitudes of the AC voltage VL1 and the AC current CR1 and the phase difference between the AC voltage VL1 and the AC current CR1.

[0048] In addition, the rail inductance L R (Inductance IN1) is expressed, for example, by the following formula (2).

[0049]

number

[0050] Next, in step S16, the AC resistance RS1 calculated by the first calculation unit 16 (R in FIG. 4) R ) or inductance IN1 (L in Figure 4 R Based on the calculated value CL1 of the magnetic permeability MP1 (μ in FIG. 4) of the portion PR1, the second calculation unit 17 calculates the magnetic permeability MP1 (μ in FIG. 4) of the portion PR1 (step S17 in FIG. 3 and FIG. 4). A specific method for calculating the magnetic permeability MP1 will be described later.

[0051] Next, based on the calculated value CL2 of the magnetic permeability MP1 (μ in FIG. 4) calculated by the second calculation unit 17 in step S17, the axial force AF1 (F in FIG. 4) of the portion PR1 is calculated by the third calculation unit 18, thereby measuring the axial force AF1 (step S18 in FIGS. 3 and 4). A specific method for calculating the axial force AF1 will be described later.

[0052] As described above, in the rail axial force measuring method by the rail axial force measuring device 10 of the first embodiment, an AC voltage VL1 is applied between the electrode 11 electrically connected to the rail RA1 at the position PS1 and the electrode 12 electrically connected to the rail RA1 at the position PS2, and an AC current CR1 is caused to flow through a portion PR1 of the rail RA1 between the electrode 11 and the electrode 12. Based on a voltage value VV1 of the AC voltage VL1 and a current value CV1 of the AC current CR1, an AC resistance RS1 or an inductance IN1 of the portion PR1 is calculated by a first calculation unit 16, based on a calculated value CL1 of the calculated AC resistance RS1 or inductance IN1, a magnetic permeability MP1 of the portion PR1 is calculated by a second calculation unit 17, based on a calculated value CL2 of the calculated magnetic permeability MP1, and an axial force AF1 of the portion PR1 is calculated by a third calculation unit 18, based on a calculated value CL2 of the calculated magnetic permeability MP1.

[0053] As described above, in the case where the rail axial force measurement device 10 of the present embodiment 1 does not have the measuring unit 14 and the measuring unit 15, the rail axial force measurement method by the rail axial force measurement device 10 of the present embodiment 1 does not need to have steps S14 and S15.

[0054] Here, the problems encountered when measuring the axial force of a rail will be described.

[0055] As described in the above-mentioned Non-Patent Document 1, known methods for measuring the axial force of a rail include a method based on strain measurement, a method based on magnetic properties, a method based on X-rays, a method based on ultrasonic waves, a method based on rail vibration, and a method based on rail reaction force.

[0056] However, the strain measurement method requires a certain amount of work time and technical skill to attach the strain gauge, which is a sensor, to the rail. Also, when measuring the average axial force of the rail over a range of several meters to several tens of meters in the longitudinal direction of the rail, the method using the strain gauge and magnetic anisotropy sensor requires measurement at multiple locations, which takes a long time.

[0057] Moreover, in the various rail axial force measurement methods described in Non-Patent Document 1, the sensor device needs to be close to the rail, and a method for continuously acquiring the rail axial force in the train traveling direction by scanning has not been established.

[0058] Furthermore, in the technology described in the above Patent Document 1, the magnetic anisotropy detection core surfaces and the excitation core surfaces of two sets of magnetic anisotropy sensors are parallel to each other, the magnetic anisotropy detection coils are differentially connected to each other, and the excitation coils are excited in opposite phases to each other, and by utilizing the fact that magnetic anisotropy corresponding to the rail axial force is generated in the rail, it is possible to measure the axial force of the rail from the output of the differentially connected magnetic anisotropy detection coils, removing the influence of disturbance magnetic fields. However, the technology described in the above Patent Document 1 is strongly influenced by residual stresses that are mainly generated in a process called "cold straightening" in which curves in the rail are straightened during production of the rail, so there is a problem that a measurement error occurs when the axial force is calculated based on stress measurement at one point on the rail.

[0059] On the other hand, according to the rail axial force measuring method by the rail axial force measuring device 10 of the first embodiment, an AC voltage VL1 is applied between the electrode 11 electrically connected to the rail RA1 at the position PS1 and the electrode 12 electrically connected to the rail RA1 at the position PS2, and an AC current CR1 is caused to flow through a portion PR1 of the rail RA1 between the electrode 11 and the electrode 12. Based on a voltage value VV1 of the AC voltage VL1 and a current value CV1 of the AC current CR1, an AC resistance RS1 or an inductance IN1 of the portion PR1 is calculated by a first calculation unit 16, based on a calculated value CL1 of the calculated AC resistance RS1 or inductance IN1, a second calculation unit 17 calculates a magnetic permeability MP1 of the portion PR1, based on a calculated value CL2 of the calculated magnetic permeability MP1, and a third calculation unit 18 calculates an axial force AF1 of the portion PR1.

[0060] As a result, compared to the method using strain measurement, attaching the sensor to the rail does not require much work time or special technical skills. Therefore, compared to the method using strain gauges and magnetic anisotropy sensors, the time required for measurement can be shortened even when measuring the average rail axial force at multiple points in a range of several meters to several tens of meters in the longitudinal direction of the rail. In addition, as will be described in a second modified example of the first embodiment later, it is not necessary for the sensor device to be close to the rail, and the rail axial force can be continuously obtained by scanning in the train travel direction. In addition, since the time required for measurement can be shortened, the rail axial force can be easily measured at multiple points, and measurement errors can be reduced even when the axial force is strongly affected by residual stress.

[0061] That is, according to the rail axial force measuring method using the rail axial force measuring device 10 of the first embodiment, there is no need to attach a sensor to the rail, and even by measuring at one location, it is possible to measure the average rail axial force over an area of ​​several meters to several tens of meters in the longitudinal direction of the rail, and therefore the rail axial force can be measured quickly.

[0062] Furthermore, in the rail axial force measurement method of the first embodiment, when installing the measuring device, the electrodes only need to be brought into contact with the rail so as to establish electrical continuity, so that preparation for measurement is easier than with a measurement method using a strain gauge, and rail axial force measurement can be easily performed in a short time. Furthermore, when obtaining the average axial force and temperature over a measurement section of several tens of meters, a simple device configuration is possible. Furthermore, since the temperature is calculated by passing electricity through the inside of the rail, a value close to the average temperature inside the rail can be obtained. Furthermore, since no sensors need to be brought close to the rail, it is possible to scan the axial force and temperature of the vehicle and the rail used.

[0063] Preferably, the distance DS1 is 5 to 10 m. In such a case, as will be described later, the distance DS1 can be increased to a certain extent while mounting the rail axial force measurement device 10 on one railway car.

[0064] Preferably, the rail axial force measurement device 10 of the present embodiment 1 has a fourth calculation unit 21 and a fifth calculation unit 22. As the fourth calculation unit 21 and the fifth calculation unit 22, a computer 19 can be used.

[0065] In step S13, the power supply 13 applies an AC voltage VL1 having a first frequency of 50 Hz or more or 1 MHz or less between the electrodes 11 and 12. Preferably, when the power supply 13 applies an AC voltage VL1 having a first frequency of 50 Hz or more between the electrodes 11 and 12, the first calculation unit 16 calculates an AC resistance RS1 based on the voltage value VV1 and the current value CV1. Also, preferably, when the power supply 13 applies an AC voltage VL1 having a first frequency of 1 MHz or less between the electrodes 11 and 12, the first calculation unit 16 calculates an inductance IN1 based on the voltage value VV1 and the current value CV1.

[0066] In addition, with the electrode 11 connected to the terminal 13a electrically connected to the rail RA1 at the position PS1 and the electrode 12 connected to the terminal 13b electrically connected to the rail RA1 at the position PS2, the power supply 13 applies an AC voltage (second AC voltage) VL2 having a second frequency of less than 50 Hz between the electrodes 11 and 12, thereby passing an AC current (second AC current) CR2 through the portion PR1 (step S21 in FIG. 3).

[0067] The measurement unit 14 measures a first voltage consisting of an AC voltage VL2 applied between the electrodes 11 and 12 (step S22 in FIG. 3). The measurement unit 15 measures a first current consisting of an AC current CR2 flowing through the portion PR1 by applying the AC voltage VL2 between the electrodes 11 and 12 (step S23 in FIG. 3).

[0068] The fourth calculation unit 21 calculates an AC resistance (second AC resistance) RS2 (R in FIG. 4 ) of the portion PR1 when the first voltage is the AC voltage VL2 and the first current is the AC current CR2 based on a voltage value (second voltage value) VV2 of the first voltage consisting of the AC voltage VL2 measured by the measurement unit 14 and a current value (second current value) CV2 of the first current consisting of the AC current CR2 measured by the measurement unit 15. DC ) (step S24 in Figs. 3 and 4). The fifth calculation unit 22 calculates the temperature (first temperature) TM1 (T in Fig. 4) of the portion PR1 based on the calculated value (third calculated value) CL3 of the first resistance consisting of the AC resistance RS2 calculated by the fourth calculation unit 21 in step S24 (step S25 in Figs. 3 and 4). In such a case, in step S17, the second calculation unit 17 calculates the magnetic permeability MP1 based on the calculated value (fourth calculated value) CL4 (see Fig. 1) of the temperature TM1 calculated by the fifth calculation unit 22 in step S25 and the calculated value CL1. A specific method for calculating the temperature TM1 will be described later.

[0069] When managing rail axial force, the buckling margin is judged by measuring the rail axial force or the amount of expansion and contraction, and the temperature. Although it is considered more appropriate to measure the rail temperature as the average temperature including the inside of the rail, rather than the surface temperature of the rail, when measuring temperature using a thermocouple or a thermal camera, only the surface temperature of the rail can be measured.

[0070] On the other hand, according to the rail axial force measuring method using the rail axial force measuring device of the first embodiment, an AC voltage VL2 having a frequency of less than 50 Hz, i.e., a low frequency, is applied between the electrodes 11 and 12, and an AC current CR2 is passed through the portion PR1 of the rail RA1. An AC resistance RS2 of the portion PR1 is calculated by a fourth calculation unit 21 based on a voltage value VV2 of the AC voltage VL2 and a current value CV2 of the AC current CR2, a temperature TM1 of the portion PR1 is calculated by a fifth calculation unit 22 based on a calculated value CL3 of the calculated AC resistance RS2, and a magnetic permeability MP1 of the portion PR1 is calculated by a second calculation unit 17 based on a calculated value CL4 of the temperature TM1 and a calculated value CL1 of the calculated AC resistance RS1.

[0071] This allows the rail temperature to be measured as an average temperature including the inside of the rail, rather than as the surface temperature of the rail. Therefore, when managing the axial force of the rail, the buckling margin can be determined with high accuracy by accurately measuring the axial force or the amount of expansion and contraction of the rail and the temperature. Furthermore, while DC resistance is required to calculate the temperature, it is possible to measure AC resistance equivalent to the DC resistance by applying an AC voltage with a low frequency, and therefore it is possible to calculate the DC resistance without using a DC power source.

[0072] Note that, instead of applying the AC voltage VL2 having a low frequency between the electrodes 11 and 12, a DC voltage DV1 may be applied between the electrodes 11 and 12. In such a case, the rail axial force measurement device 10 of the present embodiment 1 has a DC power supply 13c. Also, in step S21, the DC power supply 13c includes a terminal 13d switchably connected to the electrode 11 with the terminal 13a of the power supply 13, and a terminal 13e switchably connected to the electrode 12 with the terminal 13b of the power supply 13 and having a polarity opposite to that of the terminal 13d (opposite the terminal 13d), and in a state in which the terminal 13d is connected to the electrode 11, the terminal 13e is connected to the electrode 12, the electrode 11 connected to the terminal 13d is electrically connected to the rail RA1 at the position PS1, and the electrode 12 connected to the terminal 13e is electrically connected to the rail RA1 at the position PS2, a DC voltage (first DC voltage) DV1 is applied between the electrode 11 and the electrode 12 to pass a DC current (first DC current) DC1 through the portion PR1.

[0073] In such a case, in step S22, the measurement unit 14 measures a first voltage consisting of a DC voltage DV1 applied between the electrodes 11 and 12. Also, in step S23, the measurement unit 15 measures a first current consisting of a DC current DC1 flowing through the portion PR1 by applying the DC voltage DV1 between the electrodes 11 and 12.

[0074] In this case, in step S24, the fourth calculation unit 21 calculates the DC resistance DR1 of the portion PR1 when the first voltage is the DC voltage DV1 and the first current is the DC current DC1 based on the voltage value VV2 of the first voltage consisting of the DC voltage DV1 measured by the measurement unit 14 and the current value CV2 of the first current consisting of the DC current DC1 measured by the measurement unit 15. In step S25, the fifth calculation unit 22 calculates the temperature TM1 of the portion PR1 based on the calculated value CL3 of the first resistance consisting of the DC resistance DR1 (see FIG. 1) calculated by the fourth calculation unit 21. In step S17, the second calculation unit 17 calculates the magnetic permeability MP1 based on the calculated value CL4 (see FIG. 1) of the temperature TM1 calculated by the fifth calculation unit 22 and the calculated value CL1.

[0075] In addition, when the surface temperature of the rail is measured by a temperature measuring device, such as a thermocouple or a thermo camera, provided separately from the rail axial force measurement device, the rail temperature does not have to be measured by the rail axial force measurement device. Therefore, the rail axial force measurement device 10 of the first embodiment does not have to have the fourth calculation unit 21 and the fifth calculation unit 22.

[0076] In the measurement circuit shown in FIG. 2, strictly speaking, as will be described later with reference to FIG. 19, the current from the power source 13 branches into a current flowing through the rail and a current leaking to the ground through the rail. Therefore, if the power source current is applied to the current I in the above formula (1), an error may occur. As a countermeasure against this, in stationary measurement, it is desirable to measure the current flowing through the rail using a Rogowski coil or the like. Therefore, as described above, the measurement unit 15 preferably includes a Rogowski coil, which is an air-core coil arranged in the vicinity of the portion PR1 of the rail RA1 so as to measure the circumferential magnetic field centered on the portion PR1 when viewed from the longitudinal direction of the track TR1. On the other hand, in the measurement by scanning, although an ammeter that surrounds the rail cannot be used, the rail current can be estimated by measuring the leakage magnetic field caused by the measurement current generated from the rail.

[0077] Furthermore, when the rail axial force measuring device 10 of the first embodiment is used as a stationary rail axial force monitoring device for condition monitoring, a robust monitoring device that is almost free from deterioration over time can be configured by brazing the electrodes to the rail. Also, unlike strain gauges, the adhesive does not deteriorate.

[0078] <Technical concept of rail axial force measurement method> Next, the technical concept of the rail axial force measuring method according to the first embodiment will be described. Figures 5 and 6 are diagrams for explaining the change in magnetic permeability due to the axial force of the rail. Figure 5 shows the case where the axial force of the rail is compressive stress, and Figure 6 shows the case where the axial force of the rail is tensile stress.

[0079] The rail axial force measurement method of the first embodiment utilizes the phenomenon in which the magnetic permeability of ferromagnetic materials changes with stress, and measures the rail axial force and temperature in a simple manner. As described above, electrodes are attached to the rail at intervals of several meters, an alternating current is passed through the rail, and the voltage and current generated by the rail are analyzed to measure the rail axial force and temperature.

[0080] As shown in Figure 5, when an axial force AF1 is applied to a rail RA1 as a compressive stress, the magnetic permeability μ in the direction of the magnetic flux FL1 generated in the rail RA1 by the passage of an AC current CR1 by the above-mentioned measurement circuit increases. Due to this phenomenon, the internal inductance of the rail RA1 increases, which is measured, and the axial force AF1 is measured as a compressive stress. On the other hand, as shown in Figure 6, when an axial force AF1 is applied to a rail RA1 as a tensile stress, the magnetic permeability μ in the direction of the magnetic flux FL1 generated in the rail RA1 by the passage of an AC current CR1 by the above-mentioned measurement circuit decreases. Due to this phenomenon, the internal inductance of the rail RA1 decreases, which is measured, and the axial force AF1 is measured as a tensile stress.

[0081] When an AC current flows through a conductor, the current density is high on the surface of the conductor and decreases as you move away from the surface (skin effect). As the frequency increases, the current is more concentrated on the surface, and the AC resistance of the conductor increases. Here, if the thickness of the part of the conductor's surface through which current flows is defined as the skin depth δ, then skin depth δ can be expressed by the following equation (3).

[0082]

number

[0083] As shown in the above formula (3), the change in magnetic permeability due to compression (tension) also affects the skin depth δ when high frequency current is applied to the rail. Therefore, by performing steps S11 to S18 in Fig. 3, the stress can be measured from the change in AC resistance due to the change in skin depth.

[0084] On the other hand, the temperature of the rail RA1 can be measured by measuring the resistance of the rail RA1 when an AC or DC current having a low frequency is applied thereto.

[0085] <Rail impedance analysis> Next, in order to demonstrate that the rail axial force can be measured with high accuracy by the rail axial force measuring method according to the first embodiment, the results of analyzing the rail impedance will be described.

[0086] Using electromagnetic field analysis software, an analytical model was constructed in an analytical space, in which a portion PR1 of a rail RA1 and a measurement circuit of the rail axial force measurement device of the first embodiment were formed, and the frequency dependency of the rail impedance measured by the rail axial force measurement method of the first embodiment was analyzed. Fig. 7 is a diagram showing a schematic diagram of the analytical model constructed in the analysis of the rail impedance. The analytical model has the portion PR1 of the rail RA1 and wiring WR1 that is arranged at a position 200 mm above the top of the portion PR1 and that constitutes the measurement circuit of the rail axial force measurement device of the first embodiment. Fig. 8 is a diagram showing a finite element model of the rail portion, i.e., the portion PR1.

[0087] [Analysis conditions] The analysis conditions were as follows: Rail resistivity: 2.2×10 -7 Ωm Rail relative permeability: 200 Effective value of current: 1A

[0088] [Analysis results] Figure 9 shows the frequency dependence of impedance per 1m of rail. Figure 10 shows the frequency dependence of resistance, i.e., AC resistance, per 1m of rail. Figure 11 shows the frequency dependence of inductance per 1m of rail.

[0089] In Fig. 12 and Fig. 13, the external reactance X in the impedance Lo (ωL Ro ), internal reactance X Li (ωL Ri ) and resistor RR Fig. 12 shows the value of each component, and Fig. 13 shows the distribution of each component. Here, the internal reactance is calculated by treating the reactance at 1 MHz as the external reactance and subtracting the reactance at 1 MHz as the external reactance from the total reactance at each frequency.

[0090] Figure 14 shows a graph in which the vertical axis of Figure 12 is enlarged. In the range of 1 kHz to 10 kHz, the impedance is high and the distribution of resistance and internal reactance is ensured, which is considered to be a suitable frequency for measurement.

[0091] FIG. 15 shows the frequency dependence of the change in resistance and the distribution when the magnetic permeability is increased by 2.5%. FIG. 16 shows the frequency dependence of the change in inductance and the distribution when the magnetic permeability is increased by 2.5%. Here, the increase in magnetic permeability of 2.5% is the increase in magnetic permeability estimated when an axial force of 300 kN is applied. The empirical formula of SNCM439, a type of nickel-chromium-molybdenum steel, was used to estimate the increase in magnetic permeability. As shown in FIG. 15 and FIG. 16, the distribution of the resistance and inductance is approximately constant in the frequency range of several tens of Hz or more, and it is considered to be suitable for measuring resistance and inductance.

[0092] <Temperature and axial force calculation flow> Next, a suitable calculation flow for axial force and temperature derived from the analysis results of rail impedance will be described with reference to FIG.

[0093] DC resistance R DC (AC resistance RS2) is measured or calculated (step S24 in FIG. 4), and resistance R R (AC resistance RS1) is measured or calculated (step S16 in FIG. 4), and the inductance L R (inductance IN1) is measured or calculated (step S16 in FIG. 4), and the external inductance L Ro (inductance IN2) is measured or calculated (step S34 in FIG. 4), and each measured value or each calculated value is input to the arithmetic unit. Rand inductance L R It is preferable to measure or calculate the external inductance L of the rail at a frequency of about 1 kHz to 10 kHz. Ro is preferably measured or calculated at a frequency of several MHz.

[0094] In the calculation flow of axial force and temperature, DC resistance R DC The temperature T (temperature TM1) of the rail RA1 is calculated from the AC resistance RS2 (step S25 in FIG. 4). In addition, in order to take temperature dependency into consideration, the calculated temperature T is used to calculate the resistance R R Coefficient K in the equation showing the relationship between (AC resistance RS1) and magnetic permeability μ (magnetic permeability MP1) R1 and coefficient K R2 (Step S26 in FIG. 4). R , coefficient K R1 and coefficient K R2 From the magnetic permeability μ, the magnetic permeability μ is calculated (step S17 in FIG. 4), and the axial force F (axial force AF1) is calculated from the magnetic permeability μ (step S18 in FIG. 4). The calculation flow of the axial force and temperature up to this point is as already described above as the rail axial force measuring method using the rail axial force measurement device of the first embodiment.

[0095] In addition, although details will be described later, the inductance L R (Inductance IN1) to external inductance L Ro By subtracting (inductance IN2), the internal inductance L Ri (internal inductance IN21) is calculated (step S35 in FIG. 4). In addition, in order to take temperature dependency into consideration, the internal inductance L Ri Coefficient K in the equation expressing the relationship between and magnetic permeability μ (magnetic permeability MP1) L1 and coefficient K L2 (Step S27 in FIG. 4). The internal inductance L Ri , coefficient K L1 and coefficient K L2 The magnetic permeability μ is calculated using the above formula (step S17 in FIG. 4), and the axial force F is calculated from the magnetic permeability μ (step S18 in FIG. 4).

[0096] Here, the resistance R R (AC resistance RS1) vs. magnetic permeability μ (magnetic permeability MP1), and internal inductance L Ri The relationship between the internal inductance IN21 and the magnetic permeability μ depends on the cross-sectional shape of the rail RA1 and the distribution of the magnetic field inside the rail RA1, so it is difficult to express it strictly by a specific relational expression. However, the inventors have found that when the frequency is 50 Hz or more, the resistance R R Assuming that the relationship between the resistance R and the magnetic permeability μ is expressed by the following formula (4), R It was found that the relationship between the magnetic permeability μ and the impedance of the rail was consistent with the analysis results described above.

[0097]

number

[0098] In addition, the inventors have found that when the frequency is less than 0.1 Hz, the internal inductance L Ri Assuming that the relationship between (internal inductance IN21) and magnetic permeability μ (magnetic permeability MP1) is expressed by the following formula (5), the internal inductance L Ri It was found that the relationship between the magnetic permeability μ and the impedance of the rail was consistent with the analysis results described above.

[0099]

number

[0100] <How to calculate internal inductance> Next, the method of calculating the internal inductance will be described in detail with reference to FIGS.

[0101] Preferably, the rail axial force measurement device 10 has a sixth calculation unit 23 and a seventh calculation unit 24. As the sixth calculation unit 23 and the seventh calculation unit 24, the computer 19 can be used.

[0102] In step S13, power supply 13 applies AC voltage VL1 having a first frequency of 1 MHz or less between electrode 11 and electrode 12. In step S16, first calculation unit 16 calculates inductance IN1 based on voltage value VV1 of AC voltage VL1 measured by measurement unit 14 and current value CV1 of AC current CR1 measured by measurement unit 15.

[0103] In addition, with the electrode 11 connected to the terminal 13a being electrically connected to the rail RA1 at the position PS1 and the electrode 12 connected to the terminal 13b being electrically connected to the rail RA1 at the position PS2, the power supply 13 applies an AC voltage (third AC voltage) VL3 having a third frequency that is greater than the first frequency and equal to or greater than 100 kHz between the electrodes 11 and 12, thereby passing an AC current (third AC current) CR3 through the portion PR1 (step S31 in FIG. 3).

[0104] The measurement unit 14 measures the AC voltage VL3 applied between the electrodes 11 and 12 (step S32 in FIG. 3). In addition, the measurement unit 15 measures the AC current CR3 flowing through the portion PR1 (step S33 in FIG. 3).

[0105] The sixth calculation unit 23 calculates the inductance IN2 of the portion PR1 based on the voltage value (third voltage value) VV3 of the AC voltage VL3 measured by the measurement unit 14 and the current value (third current value) CV3 of the AC current CR3 measured by the measurement unit 15 (step S34 in FIG. 3). The seventh calculation unit 24 calculates the internal inductance IN21 of the portion PR1 by subtracting the calculated value CL5 from the calculated value CL1 based on the calculated value CL1 of the inductance IN1 calculated by the first calculation unit 16 and the calculated value (fifth calculated value) CL5 of the inductance IN2 calculated by the sixth calculation unit 23 (step S35 in FIG. 3). In such a case, in step S17, the second calculation unit 17 calculates the magnetic permeability MP1 based on the calculated value CL1 of the inductance IN1 calculated by the first calculation unit 16 and the calculated value (sixth calculated value) CL6 of the internal inductance IN21 calculated by the seventh calculation unit 24.

[0106] As mentioned before, the external inductance L of rail RA1 Ro It is preferable that the inductance IN2 is measured or calculated at a frequency of several MHz. Therefore, by applying an AC voltage VL3 having a third frequency of 1 MHz or more in step S31, the external inductance L Ro By applying an AC voltage VL1 having a first frequency of 50 Hz to 100 kHz, the inductance L of the rail RA1 is calculated. R Calculate the inductance IN1 and the inductance L R from the external inductance L Ro By subtracting the internal inductance L Ri (internal inductance IN21) can be reliably calculated.

[0107] <First Modification of First Embodiment> Next, a first modified example of the rail axial force measurement device of the first embodiment will be described. The rail axial force measurement device of this first modified example differs from the rail axial force measurement device of the first embodiment in that the measurement section is two sections. In the following, the parts of the rail axial force measurement device of this first modified example that differ from the rail axial force measurement device of the first embodiment will be described, and a description of the parts that are the same as those of the rail axial force measurement device of the first embodiment will be omitted (the same applies to second and third modified examples of the first embodiment and the second embodiment, which will be described later).

[0108] Fig. 17 is a block circuit diagram showing a rail axial force measurement device of a first modified example of embodiment 1. Fig. 18 is a circuit diagram showing a measurement circuit of a rail axial force measurement device of a first modified example of embodiment 1. Fig. 19 is a circuit diagram showing the measurement circuit and a leakage current path of the rail axial force measurement device of embodiment 1. Fig. 20 is a circuit diagram showing the measurement circuit and a leakage current path of the rail axial force measurement device of the first modified example of embodiment 1.

[0109] In Figs. 19 and 20, R g is the resistance to earth, C g is the capacitance to earth, R pis the resistance to the adjacent rail (rail RA2), C p is the capacitance to the adjacent rail, L IB is the inductance of the impedance bond, and I gr is the current flowing through the earth resistive element, I gc is the current flowing through the earth capacitance element, I pr is the current through the resistive element to the adjacent rail, I IB is the current through the inductance element of the impedance bond.

[0110] 17, the rail axial force measurement device 10a of the first modified example has, in addition to the parts of the rail axial force measurement device 10 of the first embodiment (see FIG. 1), an electrode (third electrode) 31, a measurement unit (third measurement unit) 32, a measurement unit (fourth measurement unit) 33, an eighth calculation unit 34, a ninth calculation unit 35, and a tenth calculation unit 36. A computer 19 can be used as the eighth calculation unit 34, the ninth calculation unit 35, and the tenth calculation unit 36.

[0111] In step S12 of FIG. 3, the electrode 31 is electrically connected to the rail RA1 at a position (third position) PS3 located opposite position PS2 across position PS1 in the longitudinal direction of the track TR1 and spaced a distance (second distance) DS2 from position PS1.

[0112] In step S13 of FIG. 3, the power supply 13 applies an AC voltage VL1 between the electrodes 11 and 12 and also applies an AC voltage (fourth AC voltage) VL4 between the electrodes 11 and 31 in a state in which the terminal 13a is connected to the electrode 11, the terminal 13b is connected to the electrodes 12 and 31, the electrode 11 connected to the terminal 13a is electrically connected to the rail RA1 at position PS1, the electrode 12 connected to the terminal 13b is electrically connected to the rail RA1 at position PS2, and the electrode 31 connected to the terminal 13b is electrically connected to the rail RA1 at position PS3, thereby passing an AC current CR1 through the portion PR1 and passing an AC current (fourth AC current) CR4 through the portion (second portion) PR2 of the rail RA1 between positions PS1 and PS3. At this time, the electrodes 11 and 31 are at the same potential, and the AC voltage VL1 applied between the electrodes 11 and 12 and the AC voltage VL4 applied between the electrodes 11 and 31 cancel each other out. Note that, hereinafter, the portion PR2 may be referred to as the measurement section MS2.

[0113] In step S14 of Fig. 3, the measurement unit 32 measures the AC voltage VL4 applied between the electrode 11 and the electrode 31. In step S15 of Fig. 3, the measurement unit 33 measures the AC current CR4 flowing through the portion PR2. Like the measurement unit 15, the measurement unit 33 preferably includes a Rogowski coil, which is an air-core coil arranged in the vicinity of the portion PR2 of the rail RA1 so as to be able to measure the circumferential magnetic field centered on the portion PR2 when viewed from the longitudinal direction of the track TR1.

[0114] 3, the eighth calculation unit 34 calculates an AC resistance (third AC resistance) RS3 or an inductance (third inductance) IN3 of the portion PR2 based on the voltage value (fourth voltage value) VV4 of the AC voltage VL4 measured by the measurement unit 32 and the current value (fourth current value) CV4 of the AC current CR4 measured by the measurement unit 33. Here, as shown in FIG. 18, when the voltage (AC voltage VL1) between the electrode 11 and the electrode 12 is taken as voltage V1, the voltage V1 is expressed by the following formula (6).

[0115]

number

[0116] Furthermore, as shown in FIG. 18, when the voltage between electrode 11 and electrode 31 (AC voltage VL4) is taken as voltage V2, voltage V2 is expressed by the following formula (7).

[0117]

number

[0118] 3, the ninth calculation unit 35 calculates the magnetic permeability (second magnetic permeability) MP2 (see FIG. 17) of the portion PR2 based on the calculated value (seventh calculated value) CL7 (see FIG. 17) of the AC resistance RS3 or the inductance IN3 calculated by the eighth calculation unit 34. In such a case, the tenth calculation unit 36 ​​measures the axial force AF2 by calculating the axial force (second axial force) AF2 (see FIGS. 5 and 6) of the portion PR2 based on the calculated value (eighth calculated value) CL8 (see FIG. 17) of the magnetic permeability MP2 calculated by the ninth calculation unit 35 in step S18 of FIG. 3.

[0119] As shown in FIG. 19, in the measurement circuit of the rail axial force measurement device of the first embodiment, a voltage V R Since a voltage VL1 (corresponding to voltage V in FIG. 2, AC voltage VL1 in FIG. 1) is applied, a potential difference is generated between electrode 11 and electrode 12 (between position PS1 and position PS2). As a result, a potential difference is also generated in the portion of rail RA1 other than portion PR1 between electrode 11 and electrode 12, i.e., in the front and rear rails other than measurement section MS1 ​​(see FIG. 1), and a current IR In addition, the leakage current I from the rail to the ground outside the measurement section MS1 l This may cause problems and affect the measurement accuracy.

[0120] On the other hand, as shown in Fig. 20, in the measurement circuit of the rail axial force measurement device of the first modified example, the voltage V1 (AC voltage VL1 in Fig. 17) applied between the electrodes 11 and 12 and the voltage V2 (AC voltage VL4 in Fig. 17) applied between the electrodes 11 and 31 cancel each other out, so no potential difference is generated between the electrodes 12 and 31 (between positions PS2 and PS3). That is, in the rail axial force measurement device of the first modified example, one of the two electrodes of the rail axial force measurement device is divided in two, and the circuit configuration is such that the measurement section is sandwiched between the divided electrodes. Therefore, the potential difference between the front and rear rails other than the measurement sections MS1 and MS2 is minimized, and leakage current I is not generated other than the current flowing in the measurement sections MS1 and MS2. l It is possible to prevent or suppress the occurrence of the noise, thereby improving the measurement accuracy.

[0121] <Second Modification of First Embodiment> Next, a description will be given of a second modified example of the rail axial force measuring device of the embodiment 1. The rail axial force measuring device of the second modified example is provided on a first vehicle that runs on a track and is made up of a railway car or a trolley, and measures the axial force when the first vehicle runs on the track.

[0122] Fig. 21 is a block circuit diagram showing a rail axial force measurement device according to a second modified example of embodiment 1. Fig. 22 is a circuit diagram showing a measurement circuit of the rail axial force measurement device according to the second modified example of embodiment 1.

[0123] As shown in Fig. 21, the rail axial force measurement device 10b of the second modified example has the same components as the rail axial force measurement device 10 of the first embodiment (see Fig. 1), and in addition, the first vehicle 40 has a wheel (first wheel) 41 and a wheel (second wheel) 42 that are spaced apart from each other by a distance DS1 in the longitudinal direction of the track TR1 and roll on the rail RA1. The electrode 11 is electrically connected to the wheel 41 in step S11 (see Fig. 3). The electrode 12 is electrically connected to the wheel 42 in step S12 (see Fig. 3).

[0124] The wheel 41 is electrically connected to an axle (first axle) 43 as a wheel axle, and the wheel 42 is electrically connected to an axle (second axle) 44 as a wheel axle. Therefore, the electrode 11 and the axle 43 are electrically connected via, for example, a ground brush (not shown) that provides electrical conduction between the gear device of the bogie and the axle 43. Similarly to the electrode 11 and the axle 43, the electrode 12 and the axle 44 are also electrically connected via, for example, a ground brush (not shown).

[0125] In step S13 (see Figure 3), the power supply 13 applies an AC voltage VL1 between the electrode 11 and the electrode 12, with the electrode 11 connected to the terminal 13a being electrically connected to the rail RA1 at the position PS1 via the wheel 41, and the electrode 12 connected to the terminal 13b being electrically connected to the rail RA1 at the position PS2 via the wheel 42, thereby passing an AC current CR1 through the part PR1.

[0126] In such a case, a railway vehicle or trolley is used, and the electrodes 11 and 12 of the rail axial force measuring device 10 (see FIG. 1) of embodiment 1 can be essentially replaced with steel wheels, so that the axial force and temperature of the rail can be scanned while changing the position of the railway vehicle or trolley (the same applies to the third modified example of embodiment 1 described below).

[0127] That is, the rail axial force measurement device 10b of the second modification calculates the AC resistance RS1 or the inductance IN1 by the first calculation unit 16 when the first vehicle 40 runs on the track TR1, calculates the magnetic permeability MP1 of the portion PR1 based on the calculated value CL1 calculated by the first calculation unit 16 by the second calculation unit 17, and calculates the axial force AF1 (see FIG. 3) of the portion PR1 based on the calculated value CL2 calculated by the second calculation unit 17 by the third calculation unit 18, thereby measuring the axial force AF1. This can be repeatedly performed while changing the position of the portion PR1 of the rail RA1 where the AC current CR1 flows from the power source 13, that is, the position (fourth position) PS4 of the first vehicle 40 on the track TR1. This makes it possible to easily measure the axial force AF1 at each of a plurality of different positions PS4 along the length direction of the track TR1 (similarly in the third modification of the first embodiment described later).

[0128] Also, consider a case where one first vehicle 40 includes a vehicle body (not shown), a rear bogie 40a supporting a rear portion of the vehicle body, and a front bogie 40b supporting a front portion of the vehicle body, with wheels 41 and 41a provided on the rear bogie 40a and wheels 42 and 42a provided on the front bogie 40b. In such a case, since the length of one first vehicle 40 is about 10 to 20 m, a distance DS1 of 5 to 10 m can be easily realized, and as described above, the distance DS1 can be increased to a certain extent while mounting a rail axial force measuring device on one first vehicle.

[0129] 21, a case will be considered in which a track TR1 includes a rail RA2 spaced apart from the rail RA1 in the width direction of the track TR1, and a first vehicle 40 includes a wheel (third wheel) 45 and a wheel (fourth wheel) 46 spaced apart from each other by a distance DS1 in the length direction of the track TR1 and each rolling on the rail RA2. Also, a case will be considered in which the wheel 45 is electrically connected to the wheel 41 via the axle 43, and the wheel 46 is electrically connected to the wheel 42 via the axle 44.

[0130] In this case, in step S11, the electrode 11 is electrically connected to the wheel 45. In addition, in step S12, the electrode 12 is electrically connected to the wheel 46. The wheel 41a and the wheel 45a connected to the wheel 41a via the axle 43a are provided on the rear bogie 40a, and the wheel 42a and the wheel 46a connected to the wheel 42a via the axle 44a are provided on the front bogie 40b.

[0131] In addition, in step S13, the power supply 13 applies an AC voltage VL1 between the electrode 11 and the electrode 12 in a state in which the electrode 11 connected to the terminal 13a is electrically connected to the rail RA1 at position PS1 via the wheel 41, the electrode 12 connected to the terminal 13b is electrically connected to the rail RA1 at position PS2 via the wheel 42, the electrode 11 connected to the terminal 13a is electrically connected to the rail RA2 at position PS1 via the wheel 45, and the electrode 12 connected to the terminal 13b is electrically connected to the rail RA2 at position PS2 via the wheel 46, thereby passing an AC current CR1 through the portion PR1 and passing an AC current (fifth AC current) CR5 through the portion (third portion) PR3 of the rail RA2 between positions PS1 and PS2.

[0132] Moreover, the rail axial force measuring device 10b of the second modified example further includes a measuring unit (eleventh measuring unit) 15a, an eleventh calculating unit 47, a twelfth calculating unit 48, and a thirteenth calculating unit 49. The eleventh calculating unit 47, the twelfth calculating unit 48, and the thirteenth calculating unit 49 can be implemented by a computer 19.

[0133] In step S15 (see FIG. 3), the measurement unit 15a measures an AC current (fifth AC current) CR5 flowing through the portion PR3. The measurement unit 15a preferably includes a magnetic sensor arranged in the vicinity of the portion PR3 of the rail RA2 so as to measure a circumferential magnetic field centered on the portion PR3 when viewed from the longitudinal direction of the track TR1.

[0134] In step S16 (see FIG. 3), the eleventh calculation unit 47 calculates the AC resistance (fourth AC resistance) RS4 or the inductance (fourth inductance) IN4 of the portion PR3 based on the voltage value VV1 of the AC voltage VL1 measured by the measurement unit 14 and the current value (fifth current value) CV5 of the AC current CR5 measured by the measurement unit 15a. In step S17 (see FIG. 3), the twelfth calculation unit 48 calculates the magnetic permeability (third magnetic permeability) MP3 of the portion PR3 based on the calculated value (ninth calculated value) CL9 of the AC resistance RS4 or the inductance IN4 calculated by the eleventh calculation unit 47. In step S18 (see FIG. 3), the thirteenth calculation unit 49 calculates the axial force (third axial force) AF3 of the portion PR3 based on the calculated value (tenth calculated value) CL10 of the magnetic permeability MP3 calculated by the twelfth calculation unit 48, thereby measuring the axial force AF3.

[0135] As a result, even when using a general railway vehicle or trolley in which the wheels on both the left and right sides are electrically connected, the axial forces of the rails on both the left and right sides can be measured simultaneously by providing a magnetic sensor on both the left and right sides. However, when a magnetic sensor (measurement unit 15 or measurement unit 15a) is provided on only one of the left and right sides, or when the power supply current is measured, the average value of the axial forces of the rails on both the left and right sides can be measured.

[0136] <Third Modification of First Embodiment> Next, a description will be given of a third modified example of the rail axial force measurement device of embodiment 1. The rail axial force measurement device of the third modified example differs from the rail axial force measurement device of the second modified example of embodiment 1 in that the wheels on both the left and right sides are insulated.

[0137] Fig. 23 is a block circuit diagram showing a rail axial force measurement device according to a third modified example of embodiment 1. Fig. 24 is a circuit diagram showing a measurement circuit of a rail axial force measurement device according to the third modified example of embodiment 1.

[0138] As shown in Fig. 23, in the rail axial force measurement device 10c of the third modified example, a part of the rail axial force measurement device 10c of the third modified example is different from the rail axial force measurement device 10b of the second modified example of the first embodiment (see Fig. 21), in that the track TR1 includes a rail (third rail) RA3 arranged at an interval from the rail RA1 in the width direction of the track TR1, and the first vehicle 40 consisting of a railway car or a trolley includes a wheel (fifth wheel) 51 and a wheel (sixth wheel) 52 arranged at an interval of a distance DS1 in the length direction of the track TR1 and rolling on the rail RA3. The wheel 51 is connected to the wheel 41 via an axle (third axle) 53 as a wheel set, and the wheel 52 is connected to the wheel 42 via an axle (fourth axle) 54 as a wheel set.

[0139] A portion (fourth portion) 53b of the axle 53 arranged closer to the wheel 51 than the center portion (first center portion) 53a in the width direction of the track TR1 is connected to a portion (fifth portion) 53c of the axle 53 arranged closer to the wheel 41 than the portion 53b in the width direction of the track TR1 via an insulating plate (first insulating plate) 53d, so that the portion is electrically insulated from the portion 53c. Also, a portion (sixth portion) 54b of the axle 54 arranged closer to the wheel 52 than the center portion (second center portion) 54a in the width direction of the track TR1 is connected to a portion (seventh portion) 54c of the axle 54 arranged closer to the wheel 42 than the portion 54b in the width direction of the track TR1 via an insulating plate (second insulating plate) 54d, so that the portion is electrically insulated from the portion 54c.

[0140] In such a case, the axial force of each of the left and right rails can be easily measured by insulating the left and right wheels. That is, when using a railcar or trolley with insulated wheels on both the left and right sides, such as a maintenance vehicle, the axial force of one of the left and right rails can be easily measured.

[0141] As with the rail axial force measuring device 10b of the second modified example of the first embodiment, a case will be considered in which one first vehicle 40 includes a rear bogie 40a and a front bogie 40b, with the wheels 41 and 41a provided on the rear bogie 40a and the wheels 42 and 42a provided on the front bogie 40b. In this case, the wheels 41a and the wheels 51a connected to the wheels 41a via the axles 53e are provided on the rear bogie 40a, and the wheels 42a and the wheels 52a connected to the wheels 42a via the axles 54e are provided on the front bogie 40b.

[0142] (Embodiment 2) <Rail axial force measurement method using rail axial force measuring device> Next, a rail axial force measurement method using the rail axial force measurement device of embodiment 2 will be described. Like the rail axial force measurement device of embodiment 1, the rail axial force measurement device of embodiment 2 is also a rail axial force measurement device that measures the axial force of a rail on a track equipped with rails, but differs from the rail axial force measurement device of embodiment 1 in that it has a capacitor. Also, the rail axial force measurement method of embodiment 2 is a rail axial force measurement method using the rail axial force measurement device of embodiment 2.

[0143] Fig. 25 is a block circuit diagram showing an example of a rail axial force measurement device of embodiment 2. Fig. 26 is a circuit diagram showing a measurement circuit of the rail axial force measurement device of embodiment 2. Fig. 27 is a flow chart showing some steps of a rail axial force measurement method of embodiment 2.

[0144] 25, the rail axial force measuring device 10d of the second embodiment has an electrode (first electrode) 11, an electrode (second electrode) 12, a capacitor CP1, a power source 13, a measuring unit (first measuring unit) 14, a measuring unit (second measuring unit) 15, a first calculation unit 16, a second calculation unit 17, and a third calculation unit 18. A computer 19 can be used as the first calculation unit 16, the second calculation unit 17, and the third calculation unit 18.

[0145] As in the first embodiment, the electrode 11 is electrically connected to the rail (first rail) RA1 at a position (first position) PS1 in the longitudinal direction of the track TR1 (step S41 in FIG. 27). As in the first embodiment, the electrode 12 is electrically connected to the rail RA1 at a position (second position) PS2 spaced a distance (first distance) DS1 from the position PS1 in the longitudinal direction of the track TR1 (step S42 in FIG. 27).

[0146] On the other hand, the capacitor CP1 differs from the first embodiment in that it includes a terminal (first terminal) CP11 and a terminal (second terminal) CP12 opposite to the terminal CP11.

[0147] Unlike the first embodiment, the power supply 13 includes a terminal (third terminal) 13f and a terminal (fourth terminal) 13g having a polarity opposite to that of the terminal 13f (opposite to the terminal 13f), and the terminal 13f is connected to the electrode 11, the terminal 13g is connected to the terminal CP12, and the terminal 13g is connected to the electrode 12 via the capacitor CP1, and the electrode 11 connected to the terminal 13f is electrically connected to the rail RA1 at the position PS1, and the electrode 12 connected to the terminal 13g via the capacitor CP1 is electrically connected to the rail RA1 at the position PS2. In this state, an AC voltage (first AC voltage) VL1 having a first frequency is applied between the electrode 11 and the terminal CP12, and an AC current (first AC current) CR1 is passed through a portion (first portion) PR1 of the rail RA1 between the positions PS1 and PS2 (step S43 in FIG. 27). Note that, hereinafter, the portion PR1 may be referred to as a measurement section MS1.

[0148] The measurement unit 14 measures the AC voltage VL1 applied between the electrode 11 and the terminal CP12 (step S44 in FIG. 27). The measurement unit 15 measures the AC current CR1 flowing through the portion PR1 (step S45 in FIG. 27). As described above, the measurement unit 15 preferably includes a Rogowski coil, which is an air-core coil arranged in the vicinity of the portion PR1 of the rail RA1 so as to measure the circumferential magnetic field centered on the portion PR1 when viewed from the longitudinal direction of the track TR1.

[0149] The first calculation unit 16 calculates the AC resistance (first AC resistance) RS1 of the portion PR1 based on the voltage value (first voltage value) VV1 of the AC voltage VL1 measured by the measurement unit 14 and the current value (first current value) CV1 of the AC current CR1 measured by the measurement unit 15 (from the voltage value VV1 and the current value CV1) (step S46 in FIG. 27). The second calculation unit 17 calculates the magnetic permeability (first magnetic permeability) MP1 of the portion PR1 based on the calculated value (first calculated value) CL1 of the AC resistance RS1 calculated by the first calculation unit 16 in step S46 (step S47 in FIG. 27). The third calculation unit 18 calculates the axial force (first axial force) AF1 of the portion PR1 based on the calculated value (second calculated value) CL2 of the magnetic permeability MP1 calculated by the second calculation unit 17 in step S47, thereby measuring the axial force AF1 (step S48 in FIG. 27).

[0150] Furthermore, a closed circuit (first closed circuit) CC1 is formed by the power supply 13, the part PR1 and the capacitor CP1, and in step S43, the first frequency is set so that the reactance (first reactance) RE1 of the closed circuit CC1 becomes 0 or is equal to or less than a first threshold value.

[0151] According to the rail axial force measuring method by the rail axial force measuring device 10d of the second embodiment, similarly to the first embodiment, there is no need to attach a sensor to the rail, and even by measuring at one location, it is possible to measure the average rail axial force over an area of ​​several to several tens of meters in the longitudinal direction of the rail, and therefore the rail axial force can be measured quickly.

[0152] The rail axial force measuring method using the rail axial force measuring device 10 of the first embodiment described above measures the axial force by measuring either the resistance or the inductance of the rail.

[0153] On the other hand, the rail axial force measurement method using the rail axial force measurement device 10d of the second embodiment is limited to the case where the axial force is measured by measuring only the rail resistance, and by adding a capacitor to the measurement circuit, it is possible to improve the measurement accuracy, particularly in the high frequency range.

[0154] In the measurement circuit shown in FIG. 26, when the voltage between the electrode 11 and the terminal CP12 (AC voltage VL1) is taken as voltage V', the voltage V' is expressed by the following formula (8).

[0155]

number

[0156] (ωL in the above formula (8) R If the measurement frequency is set to a frequency where the term (reactance) of -1 / (ωC) is zero or close to zero, the impedance becomes almost entirely resistance, improving the measurement accuracy of the rail resistance. Here, the angular frequency ω where the reactance becomes zero is expressed by the following equation (9).

[0157]

number

[0158] In the first embodiment, that is, in the measurement circuit shown in Fig. 2, when an AC voltage VL1 having a high frequency (100 kHz to 1 MHz) is applied between the electrodes 11 and 12, the external inductance is dominant in the impedance as described above with reference to Fig. 13. Therefore, when the axial force is measured by measuring the resistance of the rail, the axial force may not be measured with high accuracy.

[0159] On the other hand, in the present embodiment 2, the first frequency of the AC voltage VL1 is set so that the reactance RE1 of the closed circuit CC1 becomes 0 or is equal to or less than the first threshold value, so that the resistance becomes dominant in the impedance. Therefore, when the axial force is measured by measuring the resistance of the rail, it becomes possible to apply the AC voltage VL1 having a high frequency (10 kHz or more) at which the absolute value of the impedance is large and the SN ratio is favorable, as shown in Fig. 14.

[0160] Like the rail axial force measurement device 10 of the first embodiment (see FIG. 1), the rail axial force measurement device 10d of the second embodiment also preferably has a fourth calculation unit 21 and a fifth calculation unit 22. As the fourth calculation unit 21 and the fifth calculation unit 22, a computer 19 can be used.

[0161] Furthermore, when the rail axial force measurement device 10d of the second embodiment has the fourth calculation section 21 and the fifth calculation section 22, preferably, instead of the example of the rail axial force measurement device of the second embodiment shown in FIG. 25, another example of the rail axial force measurement device of the second embodiment shown in FIG. 28 is used as the rail axial force measurement device 10d of the second embodiment. FIG. 28 is a block circuit diagram showing another example of the rail axial force measurement device of the second embodiment. In the example shown in FIG. 28, the rail axial force measurement device 10d has a switching section 61 that switches whether or not the terminal 13g and the electrode 12 are short-circuited.

[0162] In step S43, with the switching unit 61 not shorting the terminal 13g and the electrode 12, the power supply 13 applies an AC voltage VL1 having a first frequency of 50 Hz or more between the electrode 11 and the terminal CP12.

[0163] In addition, the power supply 13 passes an AC current (second AC current) CR2 through the portion PR1 by applying an AC voltage (second AC voltage) VL2 having a second frequency of less than 50 Hz between the electrode 11 and the electrode 12 with the electrode 11 connected to the terminal 13f electrically connected to the rail RA1 at position PS1 and the electrode 12 shorted to the terminal 13g by the switching unit 61 electrically connected to the rail RA1 at position PS2 (step S51 in FIG. 27).

[0164] The measurement unit 14 measures a first voltage consisting of an AC voltage VL2 applied between the electrodes 11 and 12 (step S52 in FIG. 27). The measurement unit 15 measures a first current consisting of an AC current CR2 flowing through the portion PR1 by applying the AC voltage VL2 between the electrodes 11 and 12 (step S53 in FIG. 27).

[0165] The fourth calculation unit 21 calculates the AC resistance (second AC resistance) RS2 of the portion PR1 when the first voltage is the AC voltage VL2 and the first current is the AC current CR2 based on the voltage value (second voltage value) VV2 of the first voltage consisting of the AC voltage VL2 measured by the measurement unit 14 and the current value (second current value) CV2 of the first current consisting of the AC current CR2 measured by the measurement unit 15 (step S54 in FIG. 27). The fifth calculation unit 22 calculates the temperature (first temperature) TM1 of the portion PR1 based on the calculated value (third calculated value) CL3 of the first resistance consisting of the AC resistance RS2 calculated by the fourth calculation unit 21 in step S54 (step S55 in FIG. 27). In such a case, in step S47, the second calculation unit 17 calculates the magnetic permeability MP1 based on the calculated value (fourth calculated value) CL4 of the temperature TM1 calculated by the fifth calculation unit 22 in step S55 and the calculated value CL1. The specific method for calculating the temperature TM1 can be the same as in the first embodiment.

[0166] As a result, similarly to the first embodiment, the rail temperature can be measured not as the surface temperature of the rail but as the average temperature including the inside of the rail. Therefore, when managing the axial force of the rail, the buckling margin can be determined with high accuracy by accurately measuring the axial force or the amount of expansion and contraction of the rail and the temperature. Furthermore, while DC resistance is required to calculate the temperature, it is possible to measure AC resistance equivalent to the DC resistance by applying an AC voltage with a low frequency, and therefore it is possible to calculate the DC resistance without using a DC power source.

[0167] In the second embodiment as well, similarly to the first embodiment, instead of applying an AC voltage VL2 having a low frequency between the electrodes 11 and 12, a DC voltage DV1 may be applied between the electrodes 11 and 12 to pass a DC current DC1 through the portion PR1. In such a case, the rail axial force measurement device 10 of the second embodiment has a DC power supply 13h. Also, in step S51, the DC power supply 13h includes a terminal 13i switchably connected to the electrode 11 and a terminal 13f of the power supply 13, and a terminal 13j switchably connected to the electrode 12 and having a polarity opposite to that of the terminal 13i (opposite the terminal 13i), in which the terminal 13i is connected to the electrode 11, the terminal 13j is connected to the electrode 12, the electrode 11 connected to the terminal 13i is electrically connected to the rail RA1 at position PS1, and the electrode 12 shorted to the terminal 13j by the switching unit 61 is electrically connected to the rail RA1 at position PS2, and in this state, a DC voltage (first DC voltage) DV1 is applied between the electrode 11 and the electrode 12 to pass a DC current DC1 through the portion PR1.

[0168] In such a case, in step S52, the measurement unit 14 measures a first voltage consisting of a DC voltage DV1 applied between the electrode 11 and the electrode 12. Also, in step S53, the measurement unit 15 measures a first current consisting of a DC current (first DC current) DC1 flowing through the portion PR1 by applying the DC voltage DV1 between the electrode 11 and the electrode 12.

[0169] In this case, in step S54, the fourth calculation unit 21 calculates the DC resistance (first DC resistance) DR1 of the portion PR1 when the first voltage is the DC voltage DV1 and the first current is the DC current DC1 based on the voltage value VV2 of the first voltage consisting of the DC voltage DV1 measured by the measurement unit 14 and the current value CV2 of the first current consisting of the DC current DC1 measured by the measurement unit 15. In step S55, the fifth calculation unit 22 calculates the temperature TM1 of the portion PR1 based on the calculated value CL3 of the first resistance consisting of the DC resistance DR1 (see FIG. 28) calculated by the fourth calculation unit 21. In step S47, the second calculation unit 17 calculates the magnetic permeability MP1 based on the calculated value CL4 (see FIG. 28) of the temperature TM1 calculated by the fifth calculation unit 22 and the calculated value CL1.

[0170] Note that a modification in which the measurement section is two sections can also be applied to this embodiment 2, similar to the first modification of embodiment 1 with respect to embodiment 1. This modification provides the same effect as the first modification of embodiment 1 with respect to embodiment 1.

[0171] Also, in the present embodiment 2, similarly to the second and third modified examples of the embodiment 1 with respect to the embodiment 1, modified examples can be applied in which the device is provided on a first vehicle that runs on a track and is made of a railway car or a trolley, and the axial force is measured while the first vehicle runs on the track. These modified examples provide the same effects as the second and third modified examples of the embodiment 1 with respect to the embodiment 1.

[0172] The invention made by the inventor has been specifically described above based on the embodiment thereof. However, it goes without saying that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention.

[0173] Within the scope of the concept of the present invention, a person skilled in the art may conceive of various modifications and alterations, and it is understood that these modifications and alterations also fall within the scope of the present invention.

[0174] For example, any embodiment in which a person skilled in the art has appropriately added or deleted components or modified the design, or added or omitted steps or modified conditions, is included within the scope of the present invention as long as it satisfies the essence of the present invention. [Industrial Applicability]

[0175] The present invention is effectively applied to a rail axial force measuring device and a rail axial force measuring method for measuring the axial force of a rail. [Explanation of symbols]

[0176] 10, 10a-10d Rail axial force measuring device 11, 12, 31 electrodes 13 Power supply 13a, 13b, 13d~13g, 13i, 13j terminals 13c, 13h DC power supply 14, 15, 15a, 32, 33 Measuring section 16 First calculation section 17 Second Calculation Section 18 Third Calculation Section 19. Computers 21 Fourth Calculation Section 22 5th Calculation Section 23 6th Calculation Section 24 7th Calculation Section 34 8th Calculation Section 35 9th Calculation Section 36 10th Calculation Section 40 First car 40a Rear bogie 40b Front bogie 41, 41a, 42, 42a, 45, 45a, 46, 46a wheels 43, 43a, 44, 44a, 53, 53e, 54, 54e axles 47 11th Calculation Section 48 12th Calculation Section 49 13th Calculation Section 51, 51a, 52, 52a wheels 53a, 54a central part 53b, 53c, 54b, 54c parts 61 Switching section AF1~AF3 Axial force CC1 closed circuit CL1, CL10, CL2~CL9 calculated values CP1 Capacitor CP11, CP12 terminals CR1~CR5 AC current CV1~CV5 current value DC1 Direct current DR1 DC resistance DS1, DS2 distance DV1 DC voltage FL1 Magnetic flux IN1, IN2, IN3, IN4 inductance IN21 Internal inductance MP1~MP3 Magnetic permeability MS1, MS2 measurement section PR1~PR3 part PS1~PS4 position RA1~RA3 rails RE1 reactance RS1~RS4 AC resistance TM1 temperature TR1 orbit VL1~VL4 AC voltage VV1~VV4 voltage value WR1 Wiring

Claims

1. 1. A rail axial force measurement device for measuring a first axial force of a first rail in a track including a first rail, a first electrode electrically connected to the first rail at a first location along the length of the track; a second electrode electrically connected to the first rail at a second location spaced a first distance from the first location in the longitudinal direction; a power supply including a first terminal and a second terminal, the first terminal being connected to the first electrode, the second terminal being connected to the second electrode, the first electrode connected to the first terminal being electrically connected to the first rail at the first position, and the second electrode connected to the second terminal being electrically connected to the first rail at the second position, wherein a first AC voltage is applied between the first electrode and the second electrode to pass a first AC current through a first portion of the first rail between the first position and the second position; a first calculation unit that calculates a first AC resistance or a first inductance of the first portion based on a first voltage value of the first AC voltage and a first current value of the first AC current; A second calculation unit that calculates a first permeability of the first portion based on a first calculated value of the first AC resistance or the first inductance calculated by the first calculation unit; a third calculation unit that calculates the first axial force of the first portion based on the second calculated value of the first magnetic permeability calculated by the second calculation unit, thereby measuring the first axial force; A rail axial force measuring device having the same.

2. The rail axial force measuring device according to claim 1, A first measurement unit that measures the first AC voltage applied between the first electrode and the second electrode; A second measurement unit that measures the first AC current flowing through the first portion; having The first calculation unit calculates the first AC resistance or the first inductance based on the first voltage value of the first AC voltage measured by the first measurement unit and the first current value of the first AC current measured by the second measurement unit.

3. The rail axial force measuring device according to claim 2, the power source applies the first AC voltage having a first frequency of 50 Hz or more or 1 MHz or less between the first electrode and the second electrode; the power supply applies a second AC voltage having a second frequency less than 50 Hz between the first electrode and the second electrode to pass a second AC current through the first portion, or applies a first DC voltage between the first electrode and the second electrode, with the first electrode connected to the first terminal electrically connected to the first rail at the first position and the second electrode connected to the second terminal electrically connected to the first rail at the second position; the first measurement unit measures a first voltage, which is the second AC voltage or the first DC voltage, applied between the first electrode and the second electrode; the second measurement unit measures a first current, the first current being the second AC current caused to flow through the first portion by applying the second AC voltage between the first electrode and the second electrode, or the first DC current caused to flow through the first portion by applying the first DC voltage between the first electrode and the second electrode; The rail axial force measuring device further comprises: a fourth calculation unit that calculates a second AC resistance of the first portion when the first voltage is the second AC voltage and the first current is the second AC current, based on a second voltage value of the first voltage measured by the first measurement unit and a second current value of the first current measured by the second measurement unit, and calculates a first DC resistance of the first portion when the first voltage is the first DC voltage and the first current is the first DC current; a fifth calculation unit that calculates a first temperature of the first portion based on a third calculated value of a first resistance calculated by the fourth calculation unit, the first resistance being the second AC resistance or the first DC resistance; having the second calculation unit calculates the first magnetic permeability based on a fourth calculated value of the first temperature calculated by the fifth calculation unit and the first calculated value.

4. In the rail axial force measuring device according to claim 3, the power supply applies the first AC voltage having the first frequency of 1 MHz or less between the first electrode and the second electrode; the first calculation unit calculates the first inductance based on the first voltage value of the first AC voltage measured by the first measurement unit and the first current value of the first AC current measured by the second measurement unit; the power supply applies a third AC voltage having a third frequency greater than the first frequency and equal to or greater than 100 kHz between the first electrode and the second electrode in a state in which the first electrode connected to the first terminal is electrically connected to the first rail at the first position and the second electrode connected to the second terminal is electrically connected to the first rail at the second position, thereby passing a third AC current through the first portion; The first measurement unit measures the third AC voltage applied between the first electrode and the second electrode, The second measurement unit measures the third AC current flowing through the first portion, The rail axial force measuring device further comprises: a sixth calculation unit that calculates a second inductance of the first portion based on a third voltage value of the third AC voltage measured by the first measurement unit and a third current value of the third AC current measured by the second measurement unit; a seventh calculation unit that calculates an internal inductance of the first portion by subtracting a fifth calculated value of the second inductance calculated by the sixth calculation unit from the first calculated value, based on the first calculated value of the first inductance calculated by the first calculation unit and a fifth calculated value of the second inductance calculated by the sixth calculation unit; having the second calculation unit calculates the first magnetic permeability based on a sixth calculated value of the internal inductance calculated by the seventh calculation unit.

5. The rail axial force measuring device according to claim 2, a third electrode electrically connected to the first rail at a third position spaced a second distance from the first position on an opposite side to the second position across the first position in a longitudinal direction of the track; the power supply applies the first AC voltage between the first electrode and the second electrode and applies a fourth AC voltage between the first electrode and the third electrode in a state in which the first terminal is connected to the first electrode, the second terminal is connected to the second electrode and the third electrode, the first electrode connected to the first terminal is electrically connected to the first rail at the first position, the second electrode connected to the second terminal is electrically connected to the first rail at the second position, and the third electrode connected to the second terminal is electrically connected to the first rail at the third position, thereby passing the first AC current through the first portion and passing a fourth AC current through a second portion of the first rail between the first position and the third position; The rail axial force measuring device further comprises: a third measurement unit that measures the fourth AC voltage applied between the first electrode and the third electrode; A fourth measurement unit that measures the fourth AC current flowing through the second portion; an eighth calculation unit that calculates a third AC resistance or a third inductance of the second portion based on a fourth voltage value of the fourth AC voltage measured by the third measurement unit and a fourth current value of the fourth AC current measured by the fourth measurement unit; A ninth calculation unit that calculates a second permeability of the second portion based on a seventh calculated value of the third AC resistance or the third inductance calculated by the eighth calculation unit; and A tenth calculation unit that calculates a second axial force of the second portion based on an eighth calculated value of the second magnetic permeability calculated by the ninth calculation unit; A rail axial force measuring device having the same.

6. The rail axial force measuring device according to any one of claims 1 to 4, The rail axial force measuring device is provided on a first vehicle that runs on the track and is a rail car or a trolley, and measures the first axial force when the first vehicle runs on the track, the first vehicle includes a first wheel and a second wheel that are spaced apart from each other by the first distance in a longitudinal direction of the track and that roll on the first rail, the first electrode is electrically connected to the first wheel; the second electrode is electrically connected to the second wheel; the power supply applies the first AC voltage between the first electrode and the second electrode in a state in which the first electrode connected to the first terminal is electrically connected to the first rail at the first position via the first wheel, and the second electrode connected to the second terminal is electrically connected to the first rail at the second position via the second wheel, thereby causing the first AC current to flow through the first portion.

7. The rail axial force measuring device according to claim 6, The track includes a second rail spaced apart from the first rail in a width direction of the track, the first vehicle includes a third wheel and a fourth wheel that are spaced apart from each other by the first distance in the longitudinal direction and that each roll on the second rail; the third wheel is electrically connected to the first wheel via a first axle; the fourth wheel is electrically connected to the second wheel via a second axle; the first electrode is electrically connected to the third wheel; the second electrode is electrically connected to the fourth wheel; the power supply applies the first AC voltage between the first electrode and the second electrode in a state in which the first electrode connected to the first terminal is electrically connected to the first rail at the first position via the first wheel, the second electrode connected to the second terminal is electrically connected to the first rail at the second position via the second wheel, the first electrode connected to the first terminal is electrically connected to the second rail at the first position via the third wheel, and the second electrode connected to the second terminal is electrically connected to the second rail at the second position via the fourth wheel, thereby passing the first AC current through the first portion and passing a fifth AC current through a third portion of the second rail between the first position and the second position; The rail axial force measuring device further comprises: an eleventh calculation unit that calculates a fourth AC resistance or a fourth inductance of the third portion based on the first voltage value and a fifth current value of the fifth AC current; A twelfth calculation unit that calculates a third permeability of the third portion based on a ninth calculated value of the fourth AC resistance or the fourth inductance calculated by the eleventh calculation unit; A thirteenth calculation unit calculates a third axial force of the third portion based on a tenth calculated value of the third magnetic permeability calculated by the twelfth calculation unit; A rail axial force measuring device having the same.

8. The rail axial force measuring device according to claim 6, The track includes a third rail disposed at a distance from the first rail in a width direction of the track, the first vehicle includes a fifth wheel and a sixth wheel that are spaced apart from each other by the first distance in the longitudinal direction and that each roll on the third rail; The fifth wheel is connected to the first wheel via a third axle, The sixth wheel is connected to the second wheel via a fourth axle, a fourth portion of the third axle that is disposed closer to the fifth wheel than the first central portion in the width direction is electrically insulated from a fifth portion of the third axle that is disposed closer to the first wheel than the fourth portion in the width direction; a sixth portion of the fourth axle arranged closer to the sixth wheel than the second central portion in the width direction, and is electrically insulated from a seventh portion of the fourth axle arranged closer to the second wheel than the sixth portion in the width direction.

9. The rail axial force measuring device according to claim 6, The rail axial force measurement device measures the first axial force by repeatedly executing a rail axial force measurement process, while changing a fourth position of the first vehicle on the track, in which the first AC resistance or the first inductance is calculated by the first calculation unit, the second calculation unit calculates the first magnetic permeability based on the first calculated value calculated by the first calculation unit, and the third calculation unit calculates the first axial force of the first portion based on the second calculated value calculated by the second calculation unit, when the first vehicle runs on the track, thereby measuring the first axial force.

10. 1. A rail axial force measurement device for measuring a first axial force of a first rail in a track including a first rail, a first electrode electrically connected to the first rail at a first location along the length of the track; a second electrode electrically connected to the first rail at a second location spaced a first distance from the first location in the longitudinal direction; a capacitor including a first terminal and a second terminal, the first terminal being connected to the second electrode; a power supply including a third terminal and a fourth terminal, the third terminal being connected to the first electrode, the fourth terminal being connected to the second terminal such that the fourth terminal is connected to the second electrode via the capacitor, the first electrode connected to the third terminal being electrically connected to the first rail at the first position, and the second electrode connected to the fourth terminal via the capacitor being electrically connected to the first rail at the second position, by applying a first AC voltage having a first frequency between the first electrode and the second terminal, so that a first AC current flows through a first portion of the first rail between the first position and the second position; a first calculation unit that calculates a first AC resistance of the first portion based on a first voltage value of the first AC voltage and a first current value of the first AC current; A second calculation unit that calculates a first magnetic permeability of the first portion based on a first calculated value of the first AC resistance calculated by the first calculation unit; a third calculation unit that calculates the first axial force of the first portion based on the second calculated value of the first magnetic permeability calculated by the second calculation unit, thereby measuring the first axial force; having a first closed circuit is formed by the power source, the first part and the capacitor; the first frequency is set so that a first reactance of the first closed circuit becomes zero or is equal to or lower than a first threshold value.

11. The rail axial force measuring device according to claim 10, a first measurement unit that measures the first AC voltage applied between the first electrode and the second terminal; A second measurement unit that measures the first AC current flowing through the first portion; having The first calculation unit calculates the first AC resistance based on the first voltage value of the first AC voltage measured by the first measurement unit and the first current value of the first AC current measured by the second measurement unit.

12. The rail axial force measuring device according to claim 11, a switching unit that switches between short-circuiting the fourth terminal and the second electrode, the power supply applies the first AC voltage having the first frequency of 50 Hz or more between the first electrode and the second terminal in a state in which the fourth terminal and the second electrode are not short-circuited by the switching unit, the power supply applies a second AC voltage having a second frequency of less than 50 Hz between the first electrode and the second electrode in a state in which the first electrode connected to the third terminal is electrically connected to the first rail at the first position and the second electrode shorted to the fourth terminal by the switching unit is electrically connected to the first rail at the second position, thereby passing a second AC current through the first portion, or applies a first DC voltage between the first electrode and the second electrode, thereby passing a first DC current through the first portion; the first measurement unit measures a first voltage, which is the second AC voltage or the first DC voltage, applied between the first electrode and the second electrode; the second measurement unit measures a first current, the first current being the second AC current caused to flow through the first portion by applying the second AC voltage between the first electrode and the second electrode, or the first DC current caused to flow through the first portion by applying the first DC voltage between the first electrode and the second electrode; The rail axial force measuring device further comprises: a fourth calculation unit that calculates a second AC resistance of the first portion when the first voltage is the second AC voltage and the first current is the second AC current, based on a second voltage value of the first voltage measured by the first measurement unit and a second current value of the first current measured by the second measurement unit, and calculates a first DC resistance of the first portion when the first voltage is the first DC voltage and the first current is the first DC current; a fifth calculation unit that calculates a first temperature of the first portion based on a third calculated value of a first resistance calculated by the fourth calculation unit, the first resistance being the second AC resistance or the first DC resistance; having the second calculation unit calculates the first magnetic permeability based on a fourth calculated value of the first temperature calculated by the fifth calculation unit and the first calculated value.

13. 1. A rail axial force measurement method for measuring a first axial force of a first rail in a track including a first rail, comprising: (a) electrically connecting a first electrode to the first rail at a first location along the length of the track; (b) electrically connecting a second electrode to the first rail at a second location spaced a first distance from the first location in the longitudinal direction; (c) applying a first AC voltage between the first electrode and the second electrode by the power source, the first terminal of the power source including a first terminal and a second terminal being connected to the first electrode, the second terminal of the power source being connected to the second electrode, the first electrode connected to the first terminal being electrically connected to the first rail at the first position, and the second electrode connected to the second terminal being electrically connected to the first rail at the second position, thereby passing a first AC current through a first portion of the first rail between the first position and the second position; (d) calculating a first AC resistance or a first inductance of the first portion based on a first voltage value of the first AC voltage and a first current value of the first AC current by a first calculation unit; (e) calculating a first permeability of the first portion by a second calculation unit based on the first calculated value of the first AC resistance or the first inductance calculated in the step (d); (f) measuring the first axial force by calculating the first axial force of the first portion by a third calculation unit based on the second calculated value of the first magnetic permeability calculated in the step (e); A rail axial force measuring method comprising the steps of:

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