Wear form prediction method and program therefor

Abstract

To provide a wear form prediction method for two objects which relatively slide and move while electrifying the two objects such as a trolley wire and a slider, and a program therefor.SOLUTION: A wear form prediction method is configured to contain a wear frictional heating resultant prediction process which calculates frictional heat Qf along with a friction coefficient μ on the basis of a wear form just before a contact location and then predicts a wear form at an object contact location. The process includes a first comparison step which, when the wear form just before is a seizure wear form or an abrasive wear form, compares a contact point temperature T obtained from the frictional heat Qf with a softening temperature Ts1 of a trolley wire and a softening temperature Ts2 of a slider, and predicts either the seizure wear form, the abrasive wear form, or the softening flow wear form, and a second comparison step which, when the wear form just before is the softening flow wear form, predicts either the abrasive wear form or the softening flow wear form from the friction coefficient μ. The wear frictional heating resultant prediction process is sequentially repeated for the contact location at regular time intervals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and a program for predicting the wear mode of two objects that slide relative to each other while being electrified, and more particularly to a method and a program for predicting the wear mode of two objects such as a contact wire and a slider. [Background technology]

[0002] In developing materials for sliding components, the wear rate depends on the wear mode, so it is necessary to predict the wear mode.

[0003] Here, Patent Document 1 discloses a method for estimating the wear rate, as one type of wear, from the degree of melting of two metal parts when the metal parts are in contact and a current is applied to the two metal parts. Specifically, the potential at the contact point is calculated based on the electrical resistivity of each of the two metal parts, and the potential corresponding to the melting point of one of the metal parts is calculated based on information indicating the relationship between the voltage generated between the two metal parts when a current is applied and the potential distribution and temperature of the one of the metal parts, and the melt depth is calculated based on the potential at the contact point and the potential corresponding to the melting point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-132379 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] In electric railways, two objects that slide relative to each other while carrying an electric current, such as a contact wire and a slider, can have significantly different friction coefficients depending on the internal temperature of the sliding members and the materials that have been transferred to the sliding surfaces. For example, predicting wear patterns requires the contact point temperature, but calculating this contact point temperature generally requires the friction coefficient, making it extremely difficult to predict wear patterns under conditions where the friction coefficient changes from moment to moment.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a method and a program for predicting the wear mode of two objects that slide relative to each other while conducting electricity, such as a contact wire and a slider. [Means for solving the problem]

[0007] The method according to the present invention is a method for predicting a wear mode at a contact position at a certain time interval when a contact strip of a current collector shoe is moved in contact with a contact wire by a pantograph, the wear modes being seizure wear, abrasive wear, and softening flow wear, and a friction coefficient μ and a frictional heat Q are calculated based on the immediately preceding wear mode, which is the wear mode at the contact position immediately preceding a target contact position that is a prediction target at the contact position. f and predicting the wear type at the target contact position, and in the frictional heat-induced prediction process, if the immediately preceding wear type is a seizure wear type or an abrasive wear type, the frictional heat Q f The contact temperature T obtained from the above and the softening temperature T of the contact wire s1 and the softening temperature T s2 and a second comparison process in which, if the immediately preceding wear mode is a softening flow wear mode, the friction coefficient μ is used to predict either an abrasive wear mode or a softening flow wear mode, and the frictional heat-induced prediction process is repeated sequentially for the contact positions at the fixed time intervals.

[0008] According to this feature, it is possible to predict specific wear patterns of two objects, such as a contact wire and a contact strip, which slide relative to each other while being electrically connected, from the calculation of frictional heat.

[0009] In the above invention, the wear mode further includes a mixed melting wear mode, and a Joule heat-induced wear prediction step is included prior to the frictional heat-induced wear prediction step, in which a contact temperature T' based on Joule heat is calculated from the running speed and current collection of the pantograph, and a set of steps including the Joule heat-induced wear prediction step and the frictional heat-induced wear prediction step is repeated for the contact positions at the predetermined time intervals, and in the Joule heat-induced wear prediction step, the contact temperature T' is calculated based on the melting point T of the contact wire. m If the wear mode is greater than 1 / 2, the immediately preceding wear mode is set to a provisional wear mode, and one of the sets of steps is completed by predicting the wear mode to be a mixed melting wear mode without going through the frictional heat-induced prediction step, and in the frictional heat-induced prediction step, if the immediately preceding wear mode is a mixed melting wear mode, the provisional wear mode is processed as the immediately preceding wear mode. According to this feature, by calculating Joule heat as a premise for calculating frictional heat, a more accurate and specific wear mode prediction can be provided.

[0010] In the above-mentioned invention, in the first comparison step, the contact temperature T is equal to or lower than the softening temperature T of the contact wire. s1 When the contact temperature T is less than the softening temperature T of the contact wire, seizure wear occurs. s1 and the softening temperature T s2 When the contact temperature T is less than the softening temperature T of the contact strip, the abrasive wear occurs. s2 In the above cases, the softening flow wear mode may be predicted. In addition, in the second comparison step, the upper limit value μ of the friction coefficient in the softening flow mode set in advance is m Regarding the coefficient of friction μ, the upper limit value μ m When the friction coefficient μ is greater than the upper limit value μ m The method may be characterized in that it predicts the softening flow wear mode in the following cases: According to this feature, it is possible to more accurately predict the specific wear mode.

[0011] The wear mode prediction program of the present invention is characterized by providing the above-mentioned wear mode prediction method, and can provide a specific wear mode prediction for two objects, such as a contact wire and a contact strip, which slide relative to each other while being electrified.

[0012] In the above-mentioned invention, in the first comparison step, the contact temperature T is equal to or lower than the softening temperature T of the contact wire. s1 When the contact temperature T is less than the softening temperature T of the contact wire, seizure wear occurs. s1 and the softening temperature T s2 When the contact temperature T is less than the softening temperature T of the contact strip, the abrasive wear occurs. s2 In the above cases, the softening flow wear mode may be predicted. In addition, in the second comparison step, the upper limit value μ of the friction coefficient in the softening flow mode set in advance is m Regarding the coefficient of friction μ, the upper limit value μ m When the friction coefficient μ is greater than the upper limit value μ m The method may be characterized in that it predicts the softening flow wear mode in the following cases: According to this feature, it is possible to more accurately predict the specific wear mode. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a flow chart showing an embodiment of a wear mode prediction method according to the present invention. [Figure 2] 1 is a graph showing the relationship between contact voltage, sliding speed, and current. [Figure 3] FIG. 1 is a diagram showing an analytical model of a trolley wire and a contact strip. [Figure 4] 1 is a graph of normalized temperature by a logistic regression equation. [Figure 5] 1 is a graph showing the friction coefficient for each wear mode. [Figure 6] 1 is a graph showing an example of forced convection heat transfer coefficient versus wind speed. DETAILED DESCRIPTION OF THE INVENTION

[0014] The wear mode prediction method and the program therefor according to the present invention will be described below with reference to FIG. 1 and FIGS. 2 to 6. FIG.

[0015] Here, the wear pattern at the contact position is predicted at regular time intervals when the pantograph moves the contact strip of the current collector shoe while keeping it in contact with the contact wire. As will be described later, the method and program of this embodiment predict the wear pattern at the target contact position, which is the current contact position to be predicted, and then predicts the wear pattern at the contact position to which it moved after a regular time interval, and repeats this series of prediction steps sequentially. In this process, the current prediction is based on the wear pattern predicted at the immediately previous contact position, i.e., the target contact position one repetition before. Hereinafter, the target contact position will be referred to as the "contact point."

[0016] As shown in FIG. 1 , in the wear mode prediction method of this embodiment, various conditions are first set (S1). Here, to predict the wear mode between the contact wire and the contact strip, the material properties of the contact wire, its deviation relative to the track, the presence or absence of surface deposits, etc. are set. For the contact strip, the material properties, shape, the presence or absence of surface deposits, and the internal temperature distribution are set. Furthermore, for the contact strip, the contact force due to a pantograph or the like, the moving speed (traveling speed) relative to the contact wire, the current collection current, etc. are also set. As described above, the wear mode prediction process is repeated at regular time intervals, and the wear mode predicted in the previous process is set as the immediately preceding wear mode. Note that, for the first process, the immediately preceding wear mode is unknown, so one of the softening flow wear mode, seizure wear mode, and abrasive wear mode is set as the immediately preceding wear mode in advance. For example, it is preferable to set the wear mode according to the moving speed, such that when the moving speed is less than 20 km / h, the wear mode is a seizure wear mode, and when the moving speed is 20 km / h or more but less than 100 km / h, the wear mode is a softening flow wear mode.

[0017] Next, in the Joule heat cause prediction step (A), Joule heat is calculated from the pantograph running speed and the collected current. Then, the contact temperature T' based on the calculated Joule heat is calculated, and it is predicted whether or not the mixed melting wear mode will occur. For example, the following method can be used.

[0018] First, we will use the graph shown in Figure 2 to calculate the contact voltage V c and multiply it by the current I to get the Joule heat Q j =V c The Joule heat Q is calculated (S2). The graph in the figure differs depending on the specifications of the pantograph, such as the contact force, shape, and material, but can be obtained in advance through experiments. j is used in calculating the temperature inside the contact strip (S16) which will be described later.

[0019] Next, the contact temperature is calculated using the analytical model 10 shown in Fig. 3 (S3). The analytical model 10 is a cylinder with a radius D and a central axis on the z-axis, calculated by the finite element method. In this cylinder, the upper side of the plane at z = 0 is assumed to be the contact wire 1, and the lower side is assumed to be the contact strip 2. On the plane at z = 0, a circular area of ​​radius a from the z-axis is assumed to be the contact point 3 where the contact wire 1 and the contact strip 2 come into contact with each other. The mesh of the analytical model 10 is divided into the z-axis direction, the r-direction perpendicular to the z-axis, and the circumferential direction around the z-axis. In the figure, the right side shows a cutout portion of the cylinder on the left, cut along a plane including the z-axis and divided in the circumferential direction.

[0020] Contact temperature θ t can be calculated, for example, from the following normalized temperature formula. Here, θ0 is the bulk temperature, which can be considered to be the same value as the air temperature. ∞ is the steady-state temperature at the normalized potential. This normalized temperature equation normalizes the temperature at an arbitrary position and is a logistic regression equation with the normalized temperature as the response variable.

number

[0021] The above θ ∞ is given by the following formula, where L is the Lorentz number (=2.44×10 -8 [V 2 / K 2 ]) and V C is the contact voltage between the contact wire 1 and the contact strip 2. α is the contact boundary coefficient between the contact wire 1 and the contact strip 2, and is a constant determined by the combination of materials of the contact wire 1 and the contact strip 2 and the presence or absence of adhered matter on the surface. This formula is based on the fact that the temperature distribution and the electric potential distribution are similar when the temperature is saturated, and that the electric potential distribution reaches a steady state instantaneously (in a sufficiently short time compared with the transition of the temperature distribution to a steady state).

number

[0022] The above t * is given by the following equation: where t is the contact time of the contact point 3, λ1 and λ2 are the thermal conductivities of the contact wire 1 and the contact strip 2, respectively, c is the specific heat, ρ is the density, and a is the radius a of the contact point 3 mentioned above.

number

[0023] Also, f x is given by the following formula, where t 50 is a coefficient indicating the time it takes for the temperature to reach 50% of the normalized range, and y1 and y2 are coefficients for logistic regression. y1 and y2 are set to minimize the error from the analytical values ​​in Figure 4, which will be described later.

number

[0024] Figure 4 shows a graph of the normalized temperature change by such a logistic regression equation. By using this normalization, the temperature change over time at any position can be expressed by a single curve, even if, for example, the combination of materials for the contact wire 1 and the contact strip 2 or the radius a of the contact point 3 changes.

[0025] In this way, the contact temperature θ t Calculate the contact temperature θ t is the melting point T of the material of contact wire 1 m It is determined whether or not the temperature is equal to or higher than the melting point Tm (S4). If it is equal to or higher than the melting point Tm (S4: YES), it is predicted that the mixed fusion wear mode is electrical wear caused by a fusion bridge (S5), and the process returns to the beginning. This is because the mixed fusion wear mode generates almost no friction and does not require processing in the frictional heat-caused prediction step (B), which is a step of analyzing temperature rise due to frictional heat, described below. At this time, a temporary wear mode is set instead of the mixed fusion wear mode as the immediately preceding wear mode to be used in the next process group, so that analysis due to frictional heat is possible. As the temporary wear mode, for example, the immediately preceding wear mode may be set as the temporary wear mode from among the seizure wear mode, abrasive wear mode, and softening flow wear mode.

[0026] Contact temperature θ t is the melting point T of the material of contact wire 1 m If the temperature rise is less than 100°C (S4: NO), the frictional heat-caused wear prediction step (B) predicts that the wear mode is one of softening flow wear, seizure wear, or abrasive wear, based on the temperature rise caused by frictional heat. In the frictional heat-caused wear prediction step (B), the wear mode can be predicted by, for example, the following method.

[0027] First, the wear mode at the contact position immediately before the contact 3 is checked, and different processing is performed depending on whether the wear mode is seizure wear or abrasive wear or whether the wear mode is softening flow wear.

[0028] The first comparison step will be described when the wear mode at the contact position immediately before the contact 3 is not the softening flow wear mode (S6: NO), that is, when the immediately previous wear mode is the seizure wear mode or the abrasive wear mode.

[0029] As shown in Figure 5, the friction coefficient varies depending on the wear pattern, so the immediately preceding wear pattern is referenced and the friction coefficient μ of contact 3 is found from the relevant portion (S7). The friction coefficient is, for example, an average friction coefficient, which is calculated using a formula that depends on the speed. The relationship between speed, wear pattern, and friction coefficient, as shown in the figure, also varies depending on the specifications of the pantograph, so it is a good idea to find it in advance through experiments, etc.

[0030] Then, the frictional heat Q is calculated using the obtained friction coefficient μ (S8). f is calculated by the following formula: where ε is the heat distribution coefficient to the contact strip 2 for each wear mode, η is the heat exchange rate, N is the contact force, v is the speed, and n is the number of contact points at the contact force N.

number

[0031] And frictional heat Q f The contact temperature T is calculated by the following formula using (S9). Here, Tc is the temperature rise on the surface due to contact between the contact strip and the contact wire. 1,i is the internal temperature of the contact wire and can be considered to be equal to the air temperature, and T 2,i is the surface temperature of the contact strip. c1 and ρ1 are the specific heat and density of the contact wire, respectively, and c2 and ρ2 are the specific heat and density of the contact strip, respectively.

number

[0032] Then, the contact temperature T obtained is calculated as the softening point T of the contact wire 1. S1 and the softening point T of contact strip 2 S2 As a result of the comparison, the contact temperature T is compared with the softening point T S1When the contact temperature T is less than the softening point T of the contact wire 1, the seizure wear mode is predicted. S1 and the softening point T S2 If the contact temperature T is less than the softening point T of the contact strip 2, the abrasive wear mode is predicted. S2 In the above cases, the wear mode is predicted to be softening flow wear (S11). In the first comparison step, the wear mode can be predicted in the above manner.

[0033] On the other hand, if the wear mode at the contact position immediately before the contact point 3 is the softening flow wear mode (S6: YES), the wear mode is predicted as follows in the second comparison step.

[0034] First, the temperature increase margin ΔT due to frictional heat is calculated (S12). Here, the actual upper limit of the contact temperature in the softening flow wear mode is the softening point T S2 Therefore, the temperature rise T c Taking this into consideration, the temperature rise due to frictional heat, ΔT, can be expressed by the following formula: ΔT=T s -T c

[0035] Then, the friction coefficient μ is calculated (S13). The friction coefficient μ is a value corresponding to an increase in the contact temperature by ΔT, so it can be obtained by establishing the following equation. Here, ε is the heat distribution coefficient to the contact strip 2 according to the wear mode, η is the heat exchange rate, N is the contact force, v is the speed, and n is the number of contacts at the contact force N.

number

[0036] Then, the obtained friction coefficient μ is set to the upper limit value μ m As mentioned above, the friction coefficient μ varies depending on the wear mode. The friction coefficient in the softening flow wear mode has an upper limit. Therefore, the upper limit value μ of the friction coefficient in the softening flow wear mode is m is set in advance. Then, the friction coefficient μ is set to the upper limit value μ mWhen the wear rate is greater than the upper limit μ m The softening flow wear mode is predicted in the following cases: In the second comparison step, the wear mode can be predicted in the above manner.

[0037] Furthermore, the temperature inside the contact strip 2 is calculated (S16). First, the heat flux q to the contact strip 2 is calculated by the following equation. That is, the Joule heat Q calculated in (S2) above is j and the frictional heat Q calculated in (S8) above. f The heat flux q is calculated by adding the above values, multiplying them by the heat distribution coefficient ε to the contact strip 2, and dividing the result by the contact area A between the contact wire 1 and the contact strip 2.

number

[0038] Using the obtained heat flux q, the forced convection heat conductivity due to the counter wind corresponding to the speed, and the contact heat transfer coefficient with the contact wire 1, the internal temperature of the contact strip in the next step is calculated. For this, analysis software using the finite element method or AI that has machine-learned similar analysis can be used.

[0039] As shown in Figure 6, the forced convection heat transfer coefficient is roughly proportional to the wind speed, but it varies depending on the type of pantograph, such as its shape.

[0040] Finally, it is determined whether the process has been performed a predetermined number of times or for a predetermined period of time, or whether other termination conditions are met (S17). If it is determined that the process has not ended (S17: NO), the process returns to the beginning and repeats the above-mentioned process. If it is determined that the process has ended (S17: YES), the process ends.

[0041] The above-mentioned method can predict the wear mode of two objects, such as the contact wire 1 and the contact strip 2, which move in a sliding manner relative to each other while current is being applied. In addition, by storing this processing step as a program in a storage medium and having a computer execute it, it is possible to efficiently repeat predictions of the wear mode. Note that this method is not limited to predictions of the wear mode of a contact wire and a contact strip, but can be widely used to predict the wear mode of two objects which move in a sliding manner relative to each other while current is being applied.

[0042] However, actual wear modes can be complex and ambiguous. Here, wear modes are classified into the four types described above: mixed melting wear, seizure wear, abrasive wear, and softening flow wear. That is, wear modes are classified into mixed melting wear, in which melting of the material may occur at the contact interface, and three types: seizure wear, abrasive wear, and softening flow wear, which are classified according to the softening temperature of the material.

[0043] While the exemplary embodiments of the present invention and the accompanying modifications have been described above, the present invention is not necessarily limited thereto and can be modified as appropriate by those skilled in the art. In other words, those skilled in the art will be able to find various alternative embodiments and modifications without departing from the scope of the appended claims. [Explanation of symbols]

[0044] 1 Contact wire 2 sliders 3. Contact points A. Joule heat cause prediction process B Frictional heat-induced prediction process

Claims

1. A method for predicting a wear pattern at a contact position at regular time intervals when a contact strip of a current collector shoe of a pantograph is moved while being in contact with a contact wire, comprising: The wear mode is a seizure wear mode, an abrasive wear mode, and a softening flow wear mode, Based on the previous wear mode, which is the wear mode at the contact position immediately before the target contact position that is the prediction target at the contact position, the friction coefficient μ and the friction heat Q ｆ and a frictional heat caused prediction step of calculating the wear mode at the target contact position and predicting the wear mode at the target contact position, In the frictional heat cause prediction process, When the immediately preceding wear mode is a seizure wear mode or an abrasive wear mode, the friction heat Q ｆ The contact temperature T obtained from the above and the softening temperature T of the contact wire ｓ１ and the softening temperature T ｓ２ a first comparison step of comparing the results of the tests and predicting the wear pattern to be either a seizure wear pattern, an abrasive wear pattern, or a softening flow wear pattern; a second comparison step of predicting, when the immediately preceding wear mode is a softening flow wear mode, whether the wear mode is an abrasive wear mode or a softening flow wear mode from the friction coefficient μ; A wear mode prediction method, characterized in that the frictional heat caused prediction process is repeated sequentially for the contact positions at the fixed time intervals.

2. The wear configuration further includes a mixed melt wear configuration; a Joule heat attributed prediction step for determining a contact temperature T' based on Joule heat from the running speed and current collection of the pantograph prior to the frictional heat attributed prediction step, and repeating a set of steps including the Joule heat attributed prediction step and the frictional heat attributed prediction step for the contact positions at the fixed time intervals in sequence; In the Joule heat cause prediction step, The contact temperature T' is equal to the melting point T ｍ If the wear pattern is greater than the predetermined value, the immediately preceding wear pattern is determined as a provisional wear pattern, and the wear pattern is predicted as a mixed melting wear pattern without going through the frictional heat-induced prediction step, and one of the step sets is completed.

2. The wear mode prediction method according to claim 1, wherein, in the frictional heat-induced prediction step, if the previous wear mode is a mixed fusion wear mode, the temporary wear mode is treated as the previous wear mode.

3. In the first comparison step, The contact temperature T is the softening temperature T of the contact wire. ｓ１ If less than this, seizure wear occurs. The contact temperature T is the softening temperature T of the contact wire. ｓ１ and the softening temperature T ｓ２ Abrasive wear mode when less than The contact temperature T is the softening temperature T ｓ２ 3. The wear mode prediction method according to claim 1, wherein the wear mode is predicted to be a softening flow wear mode in the above cases.

4. In the second comparison step, the upper limit value μ of the friction coefficient in the preset softening and flow form is ｍ Regarding The friction coefficient μ is an upper limit value μ ｍ When the value is larger than the abrasive wear mode, The friction coefficient μ is an upper limit value μ ｍ 3. The wear mode prediction method according to claim 1, wherein the wear mode is predicted to be the softening flow wear mode in the following cases:

5. A wear mode prediction program that implements the wear mode prediction method according to claim 1 or 2.

6. In the first comparison step, The contact temperature T is the softening temperature T of the contact wire. ｓ１ If less than this, seizure wear occurs. The contact temperature T is the softening temperature T of the contact wire. ｓ１ and the softening temperature T ｓ２ Abrasive wear mode when less than The contact temperature T is the softening temperature T ｓ２ 6. The wear mode prediction program according to claim 5, wherein the wear mode is predicted to be a softening flow wear mode in the above cases.

7. In the second comparison step, the upper limit value μ of the friction coefficient in the preset softening and flow form is ｍ Regarding The friction coefficient μ is an upper limit value μ ｍ When the value is larger than the abrasive wear mode, The friction coefficient μ is an upper limit value μ ｍ 6. The wear mode prediction program according to claim 5, wherein the wear mode prediction is for softening flow wear in the following cases:

Images