Wheel flatness estimation device, wheel performance evaluation device, and key control device

Abstract

To provide a wheel flat estimating device, a wheel performance testing device and a key control device for evaluating a wheel re-adhesion control method for allowing proper wheel sliding having the possibility of damaging a wheel and a rail.SOLUTION: The wheel flat estimation device 10 includes a motion analysis part 20 for calculating various parameters by analyzing the behavior between a wheel and a rail when the wheel is fixed, a frictional heat analysis part 30 for calculating the temperature of the tread of the wheel when the wheel is fixed by frictional heat analysis, and a calculation part 30 for calculating the wheel flat based on the calculated temperature of the tread and reference data. The shape estimation device includes a yield stress calculation unit 40 that calculates a wheel yield stress of a wheel, an area calculation unit 50 that calculates an area of a contact ellipse between the wheel and a rail, a comparison unit 60 that compares a magnitude relationship between a tangential stress calculated from a tangential force and the area of the contact ellipse and the wheel yield stress, and an estimation unit 70 that estimates, as a wheel flat shape, a contact ellipse having a minimum area in which the wheel yield stress is determined to be larger than the tangential stress by the comparison in the comparison unit 60.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wheel flat estimation device, a wheel performance evaluation device, and a core control device. [Background technology]

[0002] In conditions where the coefficient of friction between the wheels and rails is small, such as in rainy weather, braking can cause the wheels to slide on the rail surface, resulting in damage (wheel flats).To reduce wheel flats, wheel readhesion control devices for vehicles are being developed.

[0003] In relation to such wheel readhesion control devices, for example, Patent Document 1 discloses the following: That is, Patent Document 1 discloses a slide control test device for railway vehicles that has an actual unit having at least an air tank, an electro-pneumatic converter valve, a slide control valve, air piping, and a brake cylinder, and a computer unit having at least a vehicle model and a slide control algorithm, with the aim of providing a slide control test device for railway vehicles that can independently evaluate the performance of a slide control algorithm by clarifying adhesion conditions that are prerequisites for accurately evaluating slide control performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-9754 Summary of the Invention [Problem to be solved by the invention]

[0005] The method in Patent Document 1 has the advantage of being able to perform normal skid detection and rapid convergence evaluation without running experiments, but has the disadvantage of not being able to evaluate whether wheel flats have occurred.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a wheel flat estimation device, a wheel performance testing device, and a core control device for evaluating wheel readhesion control methods that allow moderate wheel slippage, which may cause damage to the wheel and rail. [Means for solving the problem]

[0007] [1] In order to solve the above-mentioned problems, according to a first aspect of the present invention, there is provided a wheel flat estimation device for estimating the shape of a wheel flat formed when a railway vehicle wheel slides on a rail and then sticks, the wheel flat estimation device comprising: a motion analysis unit that performs a vehicle motion analysis to analyze the behavior between the wheel and the rail from the time the wheel slides until the wheel sticks when the brakes are applied, and thereby calculates various parameters including the tangential force between the wheel and the rail; a frictional heat analysis unit that calculates the temperature of the wheel tread when the wheel sticks by analyzing frictional heat between the wheel and the rail based on a predetermined first parameter among the various parameters; and a wheel flat estimation device that estimates the shape of a wheel flat formed when the wheel slides on a rail and then sticks, the wheel flat estimation device comprising: a motion analysis unit that performs a vehicle motion analysis to analyze the behavior between the wheel and the rail from the time the wheel slides on the rail until the wheel sticks when the brakes are applied, and a frictional heat analysis unit that calculates the temperature of the wheel tread when the wheel sticks, the frictional heat analysis unit A wheel flat estimation device is provided, which comprises: a yield stress calculation unit that calculates the wheel yield stress of the wheel based on reference data relating to the relationship between the temperature of the tread and the predetermined temperature of the wheel steel and the tangential yield stress of the wheel steel; an area calculation unit that calculates the area of ​​the contact ellipse relating to the contact area between the wheel and the rail; a comparison unit that compares the magnitude relationship between the tangential stress calculated from the tangential force and the area of ​​the contact ellipse and the wheel yield stress; and an estimation unit that estimates the contact ellipse with the smallest area, where the wheel yield stress is determined to be greater than the tangential stress, as the wheel flat shape based on the comparison in the comparison unit. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a wheel flat estimation device, a wheel performance testing device, and a core control device for evaluating wheel readhesion control techniques that allow moderate wheel slippage, which may cause damage to the wheel and rail. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a diagram showing a schematic configuration of a wheel flat estimation device according to an embodiment of the present invention; [Figure 2] 2 is a diagram showing the configuration of a wheel performance testing device having the wheel flat estimation device shown in FIG. 1 and a main control device. FIG. [Figure 3] FIG. 2 is a diagram showing an example of an analytical model of a vehicle (vehicle model) and a track. [Figure 4] 1A and 1B are diagrams showing examples of wheel tread shapes and rail cross-sectional shapes, where FIG. 1A shows the basic wheel tread shape, and FIG. 1B shows the JIS 50 kgN rail shape. [Figure 5] FIG. 1 is a diagram showing a model of heat convection between a wheel and a rail. [Figure 6] FIG. 10 is a diagram illustrating an analytical model of heat conduction. [Figure 7] FIG. 1 is a diagram illustrating an analytical model of thermal radiation. [Figure 8] 1A shows the relationship between the tensile yield stress and the set temperature, and FIG. 1B shows the relationship between the tangential stress and the set temperature. [Figure 9] FIG. 1 is a schematic diagram illustrating the relationship between the overall length in the front-rear direction of the wheel / rail contact surface shape and the flat depth. [Figure 10] This figure shows the relationship between the flat depth and the overall length of the contact surface shape in the longitudinal direction, approximated by a quadratic function, for a newly manufactured wheel with a wheel diameter of 860 mm. [Figure 11] FIG. 1 is a diagram showing the contact state between the wheel and the rail when the wheelset is in the neutral position, as determined by a geometric analysis of wheel-rail contact. [Figure 12] This figure shows the relative vertical displacement between the wheel and rail when the wheel tread shape is the standard conventional line tread shape, the rail cross section shape is a JIS 50kgN rail, and a 1 / 40 tie plate is installed under the rail. [Figure 13] FIG. 10 is a diagram showing the relationship of relative displacement between the wheel and the rail in the vertical direction. [Figure 14] FIG. 10 is a diagram showing the relationship between the flat depth of a wheel flat and the contact length in the left-right direction. [Figure 15] FIG. 10 is a diagram showing the relationship between wheel / rail contact surface temperature and time. [Figure 16] FIG. 10 is a diagram showing the relationship between the total length of the contact surface shape and time. [Figure 17] FIG. 10 is a diagram showing the relationship between drag Δσ and time. DETAILED DESCRIPTION OF THE INVENTION

[0010] A wheel flat estimation device 10, a wheel performance testing device 100, and a main control device 200 according to an embodiment of the present invention will be described below with reference to the drawings.

[0011] [1. Configuration of the wheel flat estimation device 10] 1 is a diagram showing the schematic configuration of a wheel flat estimation device 10 according to this embodiment. The wheel flat estimation device 10 of this embodiment includes a motion analysis unit 20, a frictional heat analysis unit 30, a yield stress calculation unit 40, an area calculation unit 50, a comparison unit 60, and an estimation unit 70. Note that each component of the wheel flat estimation device 10 is functionally realized by the cooperation of predetermined programs and data in memory in a computer that includes, for example, a CPU, memory (ROM, RAM, non-volatile memory, etc.), and other elements.

[0012] The motion analysis unit 20 is a part that calculates the behavior between the wheels and rails when the wheels slide and when they stick by analyzing the motion of the vehicle. By analyzing the motion of the vehicle, the motion analysis unit 20 analyzes the behavior between the wheels and rails when the wheels slide and when the wheels stick during braking, and calculates various parameters including the tangential force between the wheels and rails.

[0013] The frictional heat analysis unit 30 is a unit that calculates the wheel tread temperature when the wheel is stuck. This frictional heat analysis unit 30 calculates the wheel tread temperature when the wheel is stuck by analyzing the frictional heat between the wheel and the rail based on a predetermined first parameter among the various parameters calculated by the motion analysis unit 20.

[0014] The first parameters include the wheel load of the vehicle, the friction coefficient between the wheel and the rail, and the rotational speed and translational speed of the wheel set of the vehicle. The frictional heat analysis unit 30 calculates the temperature of the wheel tread when the wheel is stuck based on the first parameters and the area of ​​the osculating ellipse calculated by the area calculation unit 50, which will be described later.

[0015] The yield stress calculation unit 40 calculates the wheel yield stress of the wheel based on reference data regarding the relationship between the wheel tread temperature calculated by the frictional heat analysis unit 30, the temperature of the wheel steel given in advance, and the tangential yield stress of the wheel steel.

[0016] The area calculation unit 50 calculates the area of ​​the contact ellipse relating to the contact area between the wheel and the rail.

[0017] The comparison unit 60 calculates the tangential stress from the tangential force calculated by the motion analysis unit 20 and the area of ​​the osculating ellipse calculated by the area calculation unit 50. The comparison unit 60 then compares the magnitude relationship between this tangential stress and the wheel yield stress calculated by the yield stress calculation unit 40.

[0018] If the comparison unit 60 determines that the wheel yield stress is equal to or less than the tangential stress, the area calculation unit 50, upon receiving a signal from the comparison unit 60 regarding the above determination, calculates the area of ​​a new contact ellipse that is enlarged by a predetermined amount from the area of ​​the previous contact ellipse (i.e., the area of ​​the contact ellipse is successively enlarged).

[0019] The estimation unit 70 estimates the wheel flat shape as the contact ellipse with the smallest area where the wheel yield stress is determined to be greater than the tangential stress through the comparison made by the comparison unit 60. Note that the estimation unit 70 can also estimate that the wheel tread does not change (no wheel flat shape is formed) if this is the case.

[0020] 2. Configuration of the wheel performance testing device 100 and the main control device 200 2 is a diagram showing the configuration of a wheel performance testing device 100 and a main control device 200 having a wheel flat estimation device 10. This wheel performance testing device 100 has the above-mentioned wheel flat estimation device 10, as well as a readhesion control device 110 and an evaluation unit 120. Note that the wheel performance testing device 100 may not have the entire wheel flat estimation device 10, but may instead have only a part of it, including, for example, the motion analysis unit 20.

[0021] The readhesion control device 110 is a control device mounted on the vehicle that appropriately controls whether or not the wheel readhesion to the rail occurs. If the readhesion control device 110 does not operate appropriately, a wheel flat shape will occur.

[0022] The evaluation unit 120 is a part that evaluates the performance of the readhesion control device 110. This evaluation unit 120 evaluates whether or not a wheel flat shape will be generated in the estimation unit 70 of the wheel flat estimation device 10 due to the control by the readhesion control device 110. If this evaluation unit 120 evaluates that a wheel flat shape will be generated, it will be evaluated that the control law of the readhesion control device 110 is inappropriate. In this case, it is possible to take measures such as changing the readhesion control device 110 to a different control law.

[0023] In the configuration shown in FIG. 2, the evaluation unit 120 and the wheel flat estimation device 10 are separate components, but the evaluation unit 120 may have the functions of the wheel flat estimation device 10.

[0024] The main control device 200 includes the wheel flat estimation device 10 and the wheel performance testing device 100 described above, as well as a damage reduction means 210 and a selection unit 220.

[0025] The damage reduction means 210 is a means for reducing damage to the wheel and rail when the estimation unit 70 estimates that a wheel flat will occur. It is preferable that there are multiple means for reducing such damage. Examples of such multiple damage reduction means 210 include a sand spreader that spreads sand, a ceramic sprayer that sprays ceramic powder, and an anti-lock brake device that releases wheel lock.

[0026] The selection unit 220 is a part that selects an appropriate damage reduction means 210 from the plurality of damage reduction means 210 based on the control of the re-adhesion control device 110, and executes the selected damage reduction means 210. The selection unit 220 may select an appropriate damage reduction means 210 from the plurality of damage reduction means 210 based on the evaluation by the evaluation unit 120. The selection unit 220 may also select an appropriate damage reduction means 210 from the plurality of damage reduction means 210 based on the estimation result of the wheel flat shape by the estimation unit 70.

[0027] [3. Details of calculations in each part of the wheel flat estimation device 10] The following describes the details of calculations performed by each part of the wheel flat estimation device 10, using specific numerical values ​​as appropriate. Note that the numerical values ​​in the following explanation are merely examples, and are of course not limited to the following numerical values.

[0028] [3-1. Overview of wheel flat shape calculation] Research results to date show that the temperature of the contact surface between the wheel and rail is highest when the wheel slides and then sticks, and therefore it is known that a quantitative assessment of the size of a wheel flat (wheel flat shape) can be made by evaluating the period after the wheel has stuck. Based on this research knowledge, the analytical model previously constructed was partially modified to cover the period from when the wheel has stuck until the vehicle has stopped, and in order to be able to quantitatively evaluate wheel flats that occur between the wheel and rail when the wheel has stuck, the mechanical properties of the wheel steel under high-temperature conditions, obtained from the results of high-temperature tensile tests of the wheel steel conducted at temperatures up to 1100°C, were implemented in the analysis of frictional heat between the wheel and rail. This makes it possible to quantitatively evaluate wheel flats that occur due to damage (thermoplastic flow) caused by frictional heat between the wheel and rail when the wheel has stuck.

[0029] In this embodiment, a scenario is created in which the coefficient of friction between the wheel and rail is used as a parameter, and braking torque is applied to all wheelsets on a straight track to force the wheels to skid and stick. When a wheel sticks, the area where the wheel tread comes into contact with the rail becomes extremely hot because frictional heat is input at a single point. This temperature is high enough to reduce the yield stress of the wheel steel, and it is presumed that the area where the wheel tread comes into contact with the rail will undergo plastic flow, causing a wheel flat. This series of phenomena is calculated using the following procedure.

[0030] First, the dynamic behavior of the vehicle during braking is calculated, for example, using vehicle motion analysis based on MBD theory (MBD software "SIMPACK ver.2019.1 build97). This calculation section corresponds to the motion analysis unit 20. Then, part of the analysis results from the vehicle motion analysis is passed to a separately constructed wheel / rail friction heat analysis unit, which calculates the temperature rise on the contact surface between the wheel and rail during braking. The section that performs the friction heat analysis corresponds to the friction heat analysis unit 30.

[0031] Next, in order to quantitatively evaluate the size of the wheel flat, the "relationship between temperature and yield stress of wheel steel" is implemented in the wheel / rail friction heat analysis. This part corresponds to the yield stress calculation unit 40.

[0032] When the temperature between the wheel and rail is high, the yield stress of the wheel steel (wheel yield stress) becomes smaller than at room temperature. Therefore, if the longitudinal tangential stress (the value obtained by dividing the longitudinal tangential force by the contact area) resulting from the tangential force acting on the contact surface (contact ellipse) exceeds the wheel yield stress, the wheel tread is thought to undergo plastic flow. To express this concept through calculation, the wheel / rail contact surface shape is enlarged to simulate the plastic flow of the wheel tread, and the equilibrium conditions for the temperature-dependent wheel yield stress and the tangential stress acting on the contact surface are considered, and the contact surface shape that results in the minimum is determined. The portion that enlarges the contact surface shape corresponds to the comparison unit 60, and the portion that determines the minimum contact surface shape corresponds to the area calculation unit 50.

[0033] When the comparison unit 60 determines that the tangential stress is below the wheel yield stress, the estimation unit 70 estimates the osculating ellipse calculated by the area calculation unit 50 at that time as the wheel flat shape, thereby quantitatively determining the size of the wheel flat shape.

[0034] [3-2. Vehicle motion analysis for estimating vehicle behavior during braking in the motion analysis unit 20] An example of an analytical model of a vehicle (vehicle model) and track is shown in Figure 3. The vehicle model considers six degrees of freedom (front-back, left-right, up-down, roll, yaw, and pitch) for each mass element.

[0035] Brake operation can be set as desired, but one example is a model in which the same brake torque is applied to all wheel sets and turned on / off in 0.1 seconds. An example of a wheel tread shape and rail cross-sectional shape is shown in Figure 4. In Figure 4, (a) shows the basic wheel tread shape, and (b) shows the JIS 50kgN rail shape. In Figure 4, the basic wheel tread shape and JIS 50kgN rail shape are used, respectively, to be similar to the analysis target. Then, a predetermined program (for example, the analysis solver "FASTSIM") is used to calculate the tangential force between the wheel and rail.

[0036] [3-3. Analysis of frictional heat between wheel and rail after wheel has stuck in frictional heat analysis section 30] The frictional heat analysis unit 30 estimates the temperature due to frictional heat generated at the contact surface (surface) between the wheel and rail. It is known that the frictional energy acting on the contact surface in the models shown in Figures 3 and 4 is equivalent to the sum of the three energies of thermal convection, thermal conduction, and thermal radiation of the wheel and rail, respectively. According to this, the frictional energy generated between the wheel and rail due to braking force is equal to the sum of the three energies of thermal convection, thermal conduction, and thermal radiation, and can be expressed as in the following equation (1).

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[0037] In equation (1), the tangential force coefficient between the wheel and rail is μ, and the wheel load is F u (N), sliding velocity is u s (m / s), thermal convection is Q1 (W), thermal conduction is Q2 (W), and thermal radiation is Q3 (W), with the subscripts W and R representing the wheel and rail, respectively, at the bottom right.

[0038] Figure 5 shows a model of thermal convection between the wheel and the rail. In the above equation (1), we first formulate the thermal convection shown in Figure 5. Let the thermal conductivity of air be k a(W / mK), the characteristic length is 2r0 (m), and the projected area of ​​the wheel is the heat transfer area, which is 4br0 (m 2 ) The surface temperature of the wheel is T b (K), the fluid temperature of the surrounding air is T a (K), the thermal convection is expressed as the following equation (2), and the thermal convection of the wheel Q 1W and the thermal convection Q of the rail 1R In theory, the equation is the same as the equation (2) below. u is the Nusselt number.

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[0039] When a wheel rolls on a rail, the wheel is subjected to a laminar flow due to forced convection. If the temperature of the airflow is uniform (Reynolds number R e < 10 5 ), Nusselt number N u can be expressed by the following formula (3). In formula (3), P r is the Prandtl number.

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[0040] Also, let the fluid velocity be u r (m / s), the wheel circumference length is L d (mm), and the density of air is ρ a (kg / m 3 ), and the viscosity coefficient of air is η a (kg / ms), specific heat is C p , the thermal conductivity of air is k a (W / mK), the Reynolds number R e and the Prandtl number P r is expressed as the following equation (4).

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[0041] Figure 6 shows an analytical model of heat conduction. As shown in Figure 6, the heat conduction of the wheel and rail is expressed as Q2W ,Q 2R Then, the following equations (5) and (6) are established from Fourier's law. In the following equations (5) and (6), the wheel radius is r1 (m), the axle radius is r2 (m), the half length of the osculating ellipse in the longitudinal direction is a, the half width of the osculating ellipse is b, and the temperature of the wheel tread is T b (K), the temperature of the axle is T2(K), and the thermal conductivity of the wheel steel is k s (W / mK), the temperature under the rail head is T r (K), and the thickness of the rail head is l. In equation (6), the area of ​​the contact ellipse πab is replaced by A.

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[0042] Figure 7 shows an analytical model of thermal radiation. In this thermal radiation, if we consider that frictional heat is radiated to the atmosphere from the entire circumferential direction of the wheel tread that is in contact with the rail, excluding the longitudinal length of the contact ellipse between the wheel and rail, the thermal radiation Q 3W ,Q 3R can be expressed by the following equations (7) and (8). In the following equations (7) and (8), the Stefan-Boltzmann constant is σ(W / (m2·K4)), the emissivity is ε(-), the half width of the contact ellipse is b(m), and the temperature of the atmosphere is T a Let's call it (K).

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[0043] From the above equations, T in equation (1) b By solving this fourth-order equation in the frictional heat analysis unit 30, the temperature T bAn example of the thermophysical property values ​​used in this calculation is shown in Table 1, but the thermophysical property values ​​are not limited to these. [Table 1]

[0044] [3-4. Calculation in the yield stress calculation section 40] Next, the calculations performed by the yield stress calculation unit 40 will be explained. In this calculation, the contact surface shape is enlarged so that a wheel flat will be generated on the wheel tread when the wheel sticks in the numerical analysis. At this time, it is necessary to clarify the relationship between the yield stress of the wheel steel at the contact surface and the tangential stress acting on the contact surface. Therefore, the relationship between the test specimen temperature and the yield stress of the wheel steel is experimentally determined, and this is implemented in the frictional heat analysis between the wheel and rail.

[0045] Table 2 shows the relationship between the test piece temperature in the high-temperature tensile test and the wheel steel's yield stress (the average value of three measurements taken under the same temperature conditions). Figure 8 also shows the measurement results for the relationship between the test piece temperature and the yield stress in the tensile direction, and the test piece temperature and the yield stress in the tangential direction. In Figure 8, (a) shows the relationship between the yield stress in the tensile direction and the set temperature, and (b) shows the relationship between the stress in the tangential direction and the set temperature. [Table 2]

[0046] In addition, in Table 2 above, taking into consideration that it is considered most appropriate to apply the shear strain energy theory to general metallic materials for mechanical structures, the tangential yield stress (see Table 1) calculated by multiplying the tensile yield stress by (1 / √3) based on the shear strain energy theory is implemented in the wheel / rail frictional heat analysis in the frictional heat analysis unit 30.

[0047] [3-5. Calculation in the area calculation unit 50 (expansion law of the contact surface shape (contact ellipse) between the wheel and rail simulating plastic flow)] When performing calculations in the area calculation unit 50, it is necessary to take into account the shape of the contact surface. Here, since the shape of the contact surface between the wheel and rail is not circular, it is thought that when a wheel flat occurs, the progression of wear tends to differ in the front-to-back and left-to-right directions depending on the degree of flat. In other words, when the contact surface shape is viewed three-dimensionally, it is thought that when the wheel is stuck, wear progresses in order from the area with the smallest relative displacement in the up-down direction between the wheel and rail. We will attempt to formulate this wear progression.

[0048] Figure 9 is a schematic diagram illustrating the relationship between the total length of the wheel / rail contact surface shape in the longitudinal direction and the flat depth. If the wheel diameter is r, the wheel flat depth is (rx), and the total length of the wheel flat in the longitudinal direction when it occurs is (2a), the relationship between the two can be calculated using the following equation (9).

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[0049] According to the above formula (9), for example, when the total length of the contact surface profile in the longitudinal direction at the time of flat generation is calculated for a newly manufactured wheel with a wheel diameter of 860 mm, the relationship between the two can be approximated by a quadratic function, as shown in Figure 10. Figure 10 is a diagram showing the relationship between the flat depth and the total length of the contact surface profile in the longitudinal direction approximated by a quadratic function for a newly manufactured wheel with a wheel diameter of 860 mm. Note that this quadratic function will be a different formula if the wheel diameter changes.

[0050] Next, we will consider the left-right direction of the contact surface shape, just as we did with the front-to-rear direction. For simplicity's sake, in this calculation, we will determine the relationship between the two geometrically. Figure 11 shows the state of contact between the wheel and rail when the wheelset is in the neutral position, as determined by a geometric analysis of wheel-rail contact. Figure 12 shows the relative displacement in the up-down direction between the wheel and rail when the wheel tread shape is the standard tread, the rail cross section is a JIS 50kgN rail, and a 1 / 40 tie plate is installed under the rail.

[0051] As can be seen from Figure 11, when the wheelset is in the neutral position, the wheel contacts the rail, centered at approximately 558 mm in the rail's lateral coordinate system. Because the size of the wheel / rail contact surface cannot be evaluated from the results of contact geometry analysis, Hertz's theory is applied to determine the wheel / rail contact surface shape (contact ellipse). When calculating the wheel / rail contact surface shape (contact ellipse) using a combination of the basic tread shape and a JIS 50kgN rail with a static wheel load of 35.56kN, the total lateral length of the contact surface shape (2b) is determined to be 8.16 mm. To reflect this in the relationship between the flat depth and the total lateral length of the contact surface shape, a horizontal line is placed at the position where the contact width in Figure 12 is 8.16 mm, resulting in Figure 13. This is the total lateral length of the contact surface shape when a load equivalent to the static wheel load acts on the wheel on the rail.

[0052] Here, assuming that when a vertical load equivalent to the static wheel load acts on a wheel on a rail, the amount of out-of-plane bulging (protrusion) of surfaces other than the contact surface between the wheel and rail is minimal, as shown in Figure 13, if horizontal lines are drawn in 0.1 mm increments in the vertical direction based on the condition where a load equivalent to the static wheel load acts (total length 2b of the contact surface shape in the lateral direction is 8.16 mm), the lateral length (total width) of the contact surface shape between the wheel and rail when a wheel flat is generated will be equal to the distance between the two intersections with the parallel lines drawn in the vertical direction.

[0053] As shown in Figure 14, if the total length of the wheel / rail contact surface shape in the lateral direction is (2b), it can be approximated by a quadratic function, just as in the longitudinal direction. Figure 14 is a diagram showing the relationship between the wheel flat depth and the lateral contact length. Note that this quadratic function will be a different formula depending on the contact conditions, such as the wheel tread shape, rail cross-sectional shape, and the presence or absence of a tie plate.

[0054] Here, the quadratic functions in Figures 12 and 14 are equations for the wheel flat depth (rx), respectively. Therefore, combining these into one equation gives us Equation (10), which is the relational expression for the longitudinal and lateral directions when the contact surface shape (contact ellipse) between the wheel and rail expands during wheel flat generation.

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[0055] As described above, in order to quantitatively evaluate the occurrence of wheel flats between the time the wheel sticks and the time the vehicle stops, it is necessary to calculate the energy balance that occurs at the contact surface between the wheel and rail when the wheel sticks due to the application of braking force, and to consider the equilibrium conditions between the temperature-dependent yield stress of the wheel steel and the tangential stress acting at the contact surface while enlarging the shape of the contact surface between the wheel and rail, and to find the contact surface shape that minimizes this. This is thought to enable a quantitative evaluation of the occurrence of wheel flats.

[0056] [4. Verification of the validity of the one-way coupling method for vehicle motion analysis and wheel / rail frictional heat analysis] Next, the validity of the one-way coupled analysis method in this embodiment was examined. For this examination, the results of the running experiment were compared with the results of calculations obtained under the same conditions as those of the running experiment. In this one-way coupled analysis, a predetermined value was used for the brake torque, which was adjusted so that the vehicle deceleration was the same as the measurement result of the running experiment. In addition, the wheel / rail friction coefficient was used as a parameter, and calculations were performed under multiple conditions within the range in which wheel slip occurs, to examine the validity of the analysis method.

[0057] [4-1. Measurement results from driving experiments] A simple measuring device was temporarily installed on a commercial DC commuter vehicle, and a long-term investigation was conducted to determine the relationship between the behavior of the vehicle when the wheels slide and the size of the wheel flat when the wheels are stuck.The results of the measurements when a wheel flat occurs are as follows. <Measurement results of driving experiment> Wheel flat size: length (front-to-back) 35mm x width (left-to-right) 20mm (Wheel flats only occurred on the 4th axle) Wheel stuck speed: 51km / h to 25km / h, 10 seconds until re-adhesion Brake cylinder pressure: 0.31MPa Train deceleration: 0.76m / s 2

[0058] [4-2. Results of one-way coupled analysis simulating driving experiment] (1) Estimation of vehicle behavior through vehicle motion analysis In this analysis, the speed at which the wheel stuck was set to 51 km / h, the same as the measured value above, so the initial braking speed in the vehicle dynamics analysis was set to approximately 58 km / h. Also, the vehicle deceleration was set to 0.76 m / s 2 To achieve this, the brake torque acting on the wheelset was set constant at 3,000 Nm for all axles. In the vehicle motion analysis, the wheel only slides on the wheelset of the fourth axle, so the model was set so that the coefficient of friction between the wheel and rail suddenly decreases to a minimum of 0.04 for the fourth axle only after 10 seconds of calculation.

[0059] Here, a vehicle dynamics analysis was performed under the condition that the coefficient of friction between the wheels and rails of the first to third axles was constant at 0.1, and was greater than the tangential force coefficient when balanced with the braking force. As a result, each wheelset of the first to third axles decelerated (adhesion running) at a speed difference where the rotational speed was slightly smaller than the translational speed.

[0060] However, to induce wheel slip, the model assumed that the coefficient of friction between the wheel and rail of only the fourth axle would suddenly decrease from 0.3 to 0.04 after 10 seconds of calculation. As a result, the frictional force between the wheel and rail became smaller than the tangential force when balanced with the braking force, and the rotational speed of the wheelset suddenly decreased relative to its translational speed. Then, at around 12.4 seconds of calculation, the wheelset rotational speed became zero, resulting in a wheel-stuck state, and the vehicle continued to run with the wheel stuck until it came to a stop.

[0061] In this case, the translational speed of the fourth axle when the wheel was stuck and the longitudinal vibration acceleration (deceleration) of the vehicle body during deceleration both matched well with the results of the running experiment. This demonstrates that this analysis provides a vehicle dynamics analysis model that matches actual phenomena.

[0062] (2) Estimation of wheel flat size through thermal analysis of the wheel / rail interface The calculation results for the fourth axis calculated in the above vehicle motion analysis were passed to a wheel / rail frictional heat analysis (calculated by the frictional heat analysis unit 30), and then the size of the wheel / rail contact surface shape when the wheel is stuck, the temperature of the contact surface when a flat is generated, and the resistance force Δσ against plastic flow (value obtained by subtracting the tangential stress from the yield stress of the wheel steel) were calculated. These calculation results are shown in Figures 15 to 17. Figure 15 shows the relationship between the wheel / rail contact surface temperature and time. Figure 16 shows the relationship between the total length of the contact surface shape and time. Figure 17 shows the relationship between the resistance force Δσ and time.

[0063] As shown in Figure 15, in the above calculation, the wheel becomes stuck at approximately 12.4 seconds after the start of the calculation, and the temperature at the wheel / rail contact surface rises to 1454°C. As already shown in Table 2, when the contact surface becomes hot due to friction between the wheel and rail, the yield stress of the wheel steel drops significantly. At this time, if the tangential stress acting on the wheel / rail contact surface exceeds the temperature-dependent yield stress of the wheel steel, the wheel tread undergoes localized plastic flow, and the shape of the wheel / rail contact surface expands.

[0064] In the above calculation, as shown in Figure 16, the total length of the contact surface shape in the longitudinal direction was expanded to approximately 39.88 mm, and the total width to 18.45 mm. Here, as shown in Figure 15, in a calculation that did not take into account the yield stress of the wheel steel at high temperatures, the maximum temperature of the wheel / rail contact surface between the wheel and rail when the wheel went from sliding to sticking exceeded 2000°C. However, when the yield stress of the wheel steel at high temperatures is taken into account, as in this embodiment, the maximum temperature is reduced to 1454°C due to the expansion of the wheel / rail contact surface shape, which is a realistic value lower than the assumed melting point of 1600°C of wheel steel. The reason for the decrease in the contact surface temperature due to the expansion of the wheel / rail contact surface shape is thought to be due to an increase in the heat conduction effect at the contact surface.

[0065] Next, we focus on the behavior from wheel skid to vehicle stop. When a wheel sticks, the rotational speed of the wheelset becomes zero, and the wheel / rail slip velocity calculated from the difference between the translational and rotational speeds of the wheelset becomes the same as the translational speed of the wheelset. In other words, when the vehicle decelerates due to braking, the frictional energy on the left side of equation (1) decreases from moment to moment. As a result, the temperature at the contact surface between the wheel and rail also decreases steadily. During this deceleration process, as shown in Table 2, the yield stress of the wheel steel decreases as the contact surface temperature decreases, increasing the resistance force Δσ against plastic flow. This is thought to make it more difficult for wheel flats to occur.

[0066] From the above considerations, it was found that the frictional energy input between the wheel and rail is greatest immediately after the wheel sticks, and that the shape of the contact surface between the wheel and rail grows rapidly immediately after the wheel sticks, resulting in a wheel flat. Furthermore, it was found that, if external forces from coupled vehicles are not taken into consideration, the size of the wheel flat does not change significantly after the wheel sticks.

[0067] In addition, using the coefficient of friction between the wheel and rail as a parameter, the size of the wheel / rail contact surface shape when the wheel is stuck, its temperature, and the resistance force against plastic flow, Δσ, were calculated under the same conditions as in the above calculation. The calculation results are shown in Table 3. [Table 3]

[0068] From Table 3 above, when the friction coefficient between the wheel and rail is 0.02, the contact surface shape between the wheel and rail when the wheel is stuck is 24.14 mm in the longitudinal direction and 11.16 mm in the lateral direction, which are smaller than the results of the running experiment. On the other hand, when the friction coefficient between the wheel and rail is 0.04, the longitudinal length of the contact surface shape between the wheel and rail is 39.88 mm and the overall width is 18.45 mm, which is equivalent to the size of the wheel flat measured in the running experiment, with a difference of about 5% in area and about 10% in length.

[0069] On the other hand, when the friction coefficient between the wheel and rail was set to a value greater than 0.04, it was found that the shape of the wheel / rail contact surface tended to deviate significantly from the results of the running experiment. Here, after the actual running experiment, the adhesion test vehicle was again put into operation on the same line where measurements were taken, and the friction coefficient between the wheel and rail was measured under the same environmental conditions as during the running experiment. When water was sprayed on the rail surface to simulate rainy weather, the friction coefficient between the wheel and rail was approximately 0.06 on average, with some localized drops to around 0.04. Taking this into consideration, the wheel / rail friction coefficient of 0.04 set in the coupled calculation is considered a realistic value.

[0070] From the above, it was found that, assuming that the friction coefficient between the wheel and rail is at the lower limit of what can be realistically expected, the size of the contact surface shape between the wheel and rail obtained by one-way coupled analysis can be accurately estimated with a difference of about 5% in area and about 10% in length from the size measured in the running experiment.

[0071] [Note] The contents of the present embodiment described above can be understood as follows, for example, and further, the following effects can be produced. [1] That is, the wheel flat estimation device 10 of this embodiment is a wheel flat estimation device that estimates the shape of a wheel flat formed when a railway vehicle wheel slides on a rail and then sticks, and includes: (1) a motion analysis unit 20 that calculates various parameters including the tangential force between the wheel and the rail by analyzing the behavior between the wheel and the rail from when the wheel slides until the wheel sticks when the brakes are applied, by performing vehicle motion analysis; (2) a frictional heat analysis unit 30 that calculates the temperature of the wheel tread when the wheel sticks by analyzing the frictional heat between the wheel and the rail based on a predetermined first parameter among the various parameters; and (3) a frictional heat analysis unit 40. (4) a yield stress calculation unit 40 that calculates the wheel yield stress of the wheel based on the tread temperature calculated by the temperature calculation unit 30 and reference data regarding the relationship between a predetermined temperature of the wheel steel and the tangential yield stress of the wheel steel; (5) an area calculation unit 50 that calculates the area of ​​the contact ellipse related to the contact area between the wheel and the rail; (6) a comparison unit 60 that compares the magnitude relationship between the tangential stress calculated from the tangential force and the area of ​​the contact ellipse and the wheel yield stress; and (7) an estimation unit 70 that estimates the contact ellipse with the smallest area, where the wheel yield stress is determined to be greater than the tangential stress through the comparison by the comparison unit 60, as the wheel flat shape.

[0072] This configuration makes it possible to estimate the wheel flat shape without conducting a running experiment in which a vehicle is actually running, thereby avoiding damage to the wheel and rail, which would occur during an actual running test.

[0073] [2] In the above-described embodiment, when the comparison unit 60 determines in item [1] that the wheel yield stress is equal to or less than the tangential stress, the area calculation unit 50 may calculate the area of ​​a new contact ellipse that is larger than the area of ​​the previous contact ellipse by a predetermined amount.

[0074] By doing this, even if it is determined that the wheel yield stress is equal to or less than the tangential stress, the area calculation unit calculates the area of ​​a new contact ellipse enlarged by a predetermined amount, thereby making it possible to properly calculate a contact ellipse with the smallest area at which the wheel yield stress is determined to be greater than the tangential stress.The shape of the contact ellipse at this time can then be estimated as the wheel flat shape.

[0075] [3] In addition to the above-described embodiment, in addition to the contents described in either [1] or [2] above, or a combination thereof, the first parameters may be the wheel load of the vehicle, the friction coefficient between the wheel and the rail, and the rotational speed and translational speed of the wheel set of the vehicle, and the frictional heat analysis unit 30 may calculate the temperature of the wheel tread when the wheel is stuck based on the first parameters and the area of ​​the contact ellipse calculated by the area calculation unit 50.

[0076] By doing this, it becomes possible to properly calculate the temperature of the wheel tread when the wheel is stuck, and based on the temperature of the wheel tread, the yield stress calculation unit 40 can properly calculate the wheel yield stress of the wheel based on the reference data.

[0077] [4] Furthermore, the wheel performance testing device 100 of this embodiment may use a wheel flat estimation device 10 described in any one of [1] to [3] above or a combination thereof, and may also be equipped with a re-adhesion control device 110 for controlling whether or not the wheel re-adhesion to the rail occurs, and an evaluation unit 120 for evaluating the performance of the re-adhesion control device 110 based on the wheel flat shape estimated by the estimation unit 70.

[0078] In this way, the performance of the re-adhesion control device 110 installed in the railway vehicle can be appropriately evaluated by the evaluation unit 120 based on the wheel flat shape.

[0079] [5] Furthermore, the core control device 200 of this embodiment may use a wheel flat estimation device 10 described in any one of [1] to [3] above or a combination thereof, and may be equipped with multiple types of damage reduction means 210 for reducing damage to the wheel tread, and may be equipped with a selection unit 220 for selecting one of the damage reduction means 210 based on the wheel flat shape estimated by the estimation unit 70 based on the vehicle's driving conditions.

[0080] In this way, damage to the wheels and rails can be appropriately reduced even while the vehicle is in motion.

[0081] <Modification> Although the embodiments of the present invention have been described above, the present invention can be modified in various other ways, which will be described below.

[0082] In the above embodiment, the analysis was performed simulating rainy weather. However, it is possible to estimate the size of the wheel flat shape in a similar manner to the above by appropriately changing the friction coefficient as needed in situations other than rainy weather, such as snowy conditions or on slopes where it is easy to slip.

[0083] In the above embodiment, for example, a friction coefficient measured by a separately provided measuring device may be input as an external signal to the wheel flat estimation device 10. This makes it possible to estimate wheel flats that may occur in the section of track that the train is about to enter while traveling, and based on the estimation results, it becomes possible to select a countermeasure from among damage reduction means. [Explanation of symbols]

[0084] 10...wheel flat estimation device, 20...motion analysis section, 30...frictional heat analysis section, 40...yield stress calculation section, 50...area calculation section, 60...comparison section, 70...estimation section, 100...wheel performance test device, 110...re-adhesion control device, 120...evaluation section, 200...core control device, 210...damage reduction means, 220...selection section

Claims

1. A wheel flat estimation device that estimates the shape of a wheel flat formed when a railway vehicle wheel slides on a rail and becomes stuck, a motion analysis unit that performs vehicle motion analysis to analyze the behavior between the wheel and the rail from wheel skid to wheel sticking during braking, and calculates various parameters including the tangential force between the wheel and the rail; a frictional heat analysis unit that calculates the temperature of the wheel tread when the wheel is stuck by analyzing frictional heat between the wheel and the rail based on a predetermined first parameter among the various parameters; and a yield stress calculation unit that calculates the wheel yield stress of the wheel based on the tread temperature calculated by the frictional heat analysis unit and reference data relating to the relationship between a predetermined temperature of the wheel steel and a tangential yield stress of the wheel steel; an area calculation unit that calculates the area of ​​a contact ellipse related to the contact area between the wheel and the rail; a comparison unit that compares the magnitude relationship between the tangential stress calculated from the tangential force and the area of ​​the contact ellipse and the wheel yield stress; an estimation unit that estimates the contact ellipse with the smallest area, where the wheel yield stress is determined to be greater than the tangential stress, as a wheel flat shape by the comparison by the comparison unit; and A wheel flat estimation device comprising:

2. 2. The wheel flat estimation device according to claim 1, When the comparison unit determines that the wheel yield stress is equal to or less than the tangential stress, the area calculation unit calculates a new area of ​​the contact ellipse that is larger than the area of ​​the previous contact ellipse by a predetermined amount. A wheel flat estimation device characterized by:

3. 2. The wheel flat estimation device according to claim 1, the first parameters are a wheel load of the vehicle, a friction coefficient between the wheel and the rail, and a rotational speed and a translational speed of a wheel set of the vehicle; the frictional heat analysis unit calculates the temperature of the wheel tread when the wheel is stuck based on the first parameter and the area of ​​the osculating ellipse calculated by the area calculation unit. A wheel flat estimation device characterized by:

4. The wheel flat estimation device according to any one of claims 1 to 3 is used, and a readhesion control device for controlling whether or not the wheel is brought into a readhesion state with respect to the rail; an evaluation unit that evaluates the performance of the re-adhesion control device based on the wheel flat shape estimated by the estimation unit; A wheel performance evaluation device comprising:

5. The wheel flat estimation device according to any one of claims 1 to 3 is used, and a plurality of types of damage reduction means for reducing damage to the wheel tread, a selection unit that selects one of the damage reduction means based on the wheel flat shape estimated by the estimation unit based on the running status of the vehicle, A core control device characterized by:

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