Comprehensive method for optimizing abrasion of subway train wheel brake

Abstract

The invention relates to the technical field of train braking control, in particular to a comprehensive optimization method for abrasion of a subway train wheel brake, and aims to solve the problems of excessive air braking input and large abrasion of the wheel brake caused by mismatching of electric braking input and actual load of an existing subway train and increase of operation and maintenance cost due to abnormal abrasion of the wheel brake. The method is optimized from the two aspects of normal abrasion and abnormal abrasion and comprises the steps that (1) an electric braking input dynamic adjustment model is established based on the linear relation between the actual load of a train and the three standard loads AW0, AW2 and AW3, when the running speed of the train is larger than 6 km / h, electric braking force is dynamically adjusted according to five working conditions, the difference value between the electric braking force and the total braking force is reduced, and air braking input is reduced; and 2) screening the brake shoe with moderate hardness, relatively low elastic modulus and relatively high density, optimizing the contact state of the brake shoe and the wheel tread, and inhibiting abnormal abrasion. Vehicle hardware does not need to be changed, the method can be realized only through software optimization and brake shoe type selection, the replacement period is remarkably prolonged, the operation and maintenance cost is reduced, and the implementation is high.

Description

Technical Field

[0001] This invention relates to the field of train braking control technology, specifically a comprehensive method for optimizing wheel brake wear in subway trains. Background Technology

[0002] With the acceleration of urbanization in my country, urban population density continues to increase, and traffic congestion is becoming increasingly serious. As a high-capacity, high-speed, and low-pollution urban rail transit system, the subway has become a core option for alleviating urban traffic pressure and occupies a crucial position in the transportation networks of major cities. The safe and efficient operation of subway trains directly affects the convenience and safety of citizens' travel, and also impacts the economic benefits of subway operating companies.

[0003] However, with the accumulation of subway train operating time and the continuous increase in the number of trains, brake wear has become increasingly prominent, becoming a key factor restricting the safety and economy of subway operations. Excessive brake wear not only leads to a decline in train braking performance and increases the risk of unsafe operation, but also significantly increases maintenance costs. Frequent replacement of brake shoes and wheelsets, as well as increased wheel refinishing, all result in substantial consumption of manpower and resources. Statistics show that one subway operating branch alone spends tens of millions of yuan annually on brake shoe and wheelset replacement costs, making brake wear a significant source of economic pressure for subway operating companies.

[0004] A thorough analysis of the root causes of excessive wear on subway train wheel brakes reveals two main issues: excessive use of air brakes and abnormal wear on the wheel brakes.

[0005] Regarding the deployment of air brakes, the electric braking system commonly used in urban rail transit vehicles currently has significant drawbacks. This system relies on the train's electric braking force curve, with the core logic being to select the electric braking force curve corresponding to the standard load closest to the actual train load based on the correspondence between the train's actual load and three standard loads: AW0 (empty), AW2 (full capacity), and AW3 (overloaded). For example, when the train's actual load is between AW0 and AW2, the electric braking force curve corresponding to AW0 is still used; when the actual load is between AW2 and AW3, the electric braking force curve corresponding to AW2 is used. This "nearest-to-lower-range matching" method results in a significant difference between the electric braking force applied during braking and the total braking force required by the train in most cases. To ensure braking effectiveness, the train must engage air brakes to compensate for this difference. However, air braking is achieved through direct friction between the brake shoes and the wheel treads. Frequent and excessive air brake engagement inevitably leads to rapid wear of the brake shoes and wheel treads, accelerating normal brake wear.

[0006] Regarding abnormal wear of wheel brakes, during subway train operation, abnormal wear phenomena such as narrow parallel grooves often appear on the wheel treads. This abnormal wear not only leads to irregular wheel tread shapes, affecting train stability, but also significantly increases wheel reworking. The reworking process cuts away the metal layer of the wheel tread, and each reworking shortens the effective service life of the wheel, thereby reducing wheel mileage and creating a vicious cycle of "abnormal wear - frequent reworking - shortened lifespan - increased costs." A survey revealed that on a certain line, the frequency of wheel reworking due to abnormal wear was more than 30% higher than normal, the wheel mileage was nearly 20% shorter than the design value, and maintenance costs increased significantly.

[0007] Although the industry has recognized the harm of brake shoe wear and conducted relevant research, existing technologies still have significant shortcomings. Current research mainly focuses on analyzing brake shoe wear patterns and predicting remaining life, with the core solution being merely "replacing brake shoes promptly based on wear patterns," without fundamentally optimizing the mechanism of wear generation. Regarding the problem of excessive air brake application, existing technologies have not established an effective dynamic adjustment mechanism for electric braking, failing to optimize electric braking force application in real time based on the actual train load, resulting in a persistent difference between electric braking force and total braking force. For the problem of abnormal brake shoe wear, existing technologies have not deeply studied the correlation between brake shoe characteristics and tread wear, lacking targeted solutions; simply replacing brake shoes routinely cannot fundamentally suppress abnormal wear.

[0008] Therefore, there is an urgent need for a comprehensive approach that can fundamentally solve the problem of wheel brake wear. This approach should reduce normal wear by optimizing the use of electric brakes to reduce the use of air brakes, and suppress abnormal wear through targeted brake shoe selection. This comprehensive optimization of wheel brake wear will provide technical support for the safe and economical operation of subway trains. Summary of the Invention

[0009] To address the problems in existing technologies, this invention provides a comprehensive method for optimizing wheel brake wear in subway trains. It addresses both normal and abnormal wear of the wheel brakes simultaneously, significantly reducing wheel brake wear, extending wheel brake lifespan, and lowering maintenance costs without affecting normal train operation or altering the vehicle's existing hardware configuration.

[0010] The technical solution adopted by this invention to solve its technical problem is: a comprehensive method for optimizing wheel brake wear in subway trains, comprising the following steps: 1) Reduce normal wear: When the train is in braking condition and the operating speed is greater than the electro-pneumatic switching point speed Vz=6km / h, based on the relationship between the actual train loads M0, M2, M3 and the preset standard loads AW0, AW2, AW3, the electric braking force F is dynamically adjusted under five operating conditions to match the electric braking force with the total braking force required by the train, reducing the need for air brakes; the five operating conditions are as follows: ①When M = M0, F = F0 (F0 is the electric braking force value matching the actual running speed of the train in the electric braking force curve under the AW0 condition of the train); ②When M0 < M < M2, according to the linear interpolation formula F = F0 + (M - M0) × (F2 - F0) / (M2 - M0), dynamic adaptation adjustment is completed in combination with the actual running speed of the train; ③When M = M2, F = F2 (F2 is the electric braking force value matching the actual running speed of the train in the electric braking force curve under the AW2 condition of the train); ④When M2 < M < M3, according to the linear interpolation formula F = F2 + (M - M2) × (F3 - F2) / (M3 - M2); ⑤When M = M3, F = F3 (F3 is the electric braking force value matching the actual running speed of the train in the electric braking force curve under the AW3 condition of the train); Among them, M0 = 225.5t, M2 = 316.5t, M3 = 340.9t, and F0, F2, F3 are preset known parameters of the train; 2) Reduce abnormal wear: Select brake shoes with a density ≥ 2.08 g / cm ,

[0013] ,

[0012] , 3 , 2 ,

[0011] , , 2 , , , ,

[0016] , ,

[0015] , ,

[0014] , an elastic modulus ≤ 986 N / mm 2 , and a hardness ≤ 77.8 HRR brake shoes, optimize the contact state between the brake shoes and the wheel tread, and suppress abnormal wear such as narrow and parallel grooves on the tread.

[0011] Specifically, in step 1), after the train arrives at each station and updates the actual load M, it is re - substituted into the corresponding formula to adjust the electric braking force.

[0012] Specifically, the thermal conductivity of the brake shoes ≥ 0.89 W / (m·K).

[0013] Specifically, the specific parameters of the brake shoes are: density 2.16 - 2.20 g / cm 3 , elastic modulus 350 - 456 N / mm 2 , hardness 30.0 - 42 HRX, thermal conductivity 1.24 - 1.35 W / (m·K).

[0014] Specifically, the dynamic adjustment model in step 1) is realized by software upgrade of the existing train braking control system without changing the hardware.

[0015] Specifically, the train is a Type B subway train, the initial thickness of the brake shoes is 45 mm, and the replacement limit thickness is 12 mm; the new wheel diameter of the wheel is 840 mm, and the wear limit diameter is 770 mm.

[0016] Specifically, in step 1), after the electric braking force is adjusted, the total amount of the train's regenerative braking energy and resistance braking energy consumption increases compared with that before adjustment, and the difference supplemented by air braking is reduced.

[0017] Specifically, in step 2), a static inspection needs to be carried out before the brake shoes are installed on the vehicle, and the friction area of ​​the new brake shoes after break-in should not be less than 75%.

[0018] Specifically, the effect of reducing air brake input was verified by monitoring the average maximum temperature of the brake shoes and wheels by attaching temperature patches.

[0019] A subway train braking system using the method described above includes a load detection module, an electric braking control module, and a brake shoe adaptation module. The load detection module collects the actual load of the train in real time, the electric braking control module executes a dynamic adjustment model, and the brake shoe adaptation module matches brake shoes with preset performance parameters.

[0020] The beneficial effects of this invention are: Significantly reduced normal wear: By dynamically adjusting the electric braking force, the use of air brakes is greatly reduced, the linear wear of brake shoes is reduced by 29.6%, the replacement cycle is extended by 39.4%, and the replacement mileage is increased by 41.7% for every 120×10 trains in operation. 4 km, brake shoe replacement costs are reduced by nearly 30%; wheelset tread wear is reduced by 43.8%, wheelset replacement cycle is extended by 76.7%, and every 220×10 km of train operation... 4 km, wheelset replacement costs reduced by 43.4%; Effectively suppresses abnormal wear: After selecting brake shoes with specific performance parameters, abnormal wear phenomena such as narrow parallel grooves on the wheel tread are completely eliminated, the amount of wheel turning is significantly reduced, and the wheel running mileage is greatly increased. High feasibility: No need to modify the vehicle's existing hardware configuration; the electric braking force can be dynamically adjusted simply by upgrading the braking control system software. The brake shoe selection is a routine replacement operation, making the modification difficult and the cost controllable. Enhanced safety: The wear of the wheel brakes is more uniform and less severe, which improves the stability of the train's braking performance, reduces braking deviation caused by uneven wear, and enhances operational safety. Energy utilization optimization: Increased use of electric braking fully recovers the kinetic energy generated during train operation, indirectly optimizing energy utilization efficiency. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Figure 1 The flowchart of the dynamic adjustment algorithm for electric braking force clearly shows the five operating conditions and corresponding electric braking force adjustment logic based on the actual load of the train. Figure 2The graph shows the electric braking force curves of the train under different operating conditions. The horizontal axis represents the train speed (km / h) and the vertical axis represents the electric braking force (kN). The graphs show the changing trend of electric braking force with speed under three standard load conditions: AW0, AW2, and AW3. Figure 3 The trend chart of electric braking force input was adjusted for the train upward model. The horizontal axis represents the stations the train passes through (station 1 to station 17), and the vertical axis represents the electric braking force (kN). The changes in electric braking force before and after the model adjustment were compared, which intuitively reflects the adjustment effect under different load conditions. Figure 4 Adjust the trend chart of electric braking force input for the train's downward model, and... Figure 3 Correspondingly, it shows the changing trend of the electric braking force of the train in the downward direction after adjustment; Figure 5 This image shows temperature patches for the brake shoes and wheels of a subway train, illustrating the placement of the temperature patches on the brake shoes and wheels to monitor temperature changes during braking. Figure 6 The graph shows the trend of changes in the heat capacity test results of the train brake shoes and wheels. The horizontal axis represents the train load range (t), and the vertical axis represents the average maximum temperature (°C). The average maximum temperature of the brake shoes and wheels before and after the model adjustment was compared, which verified the effect of reducing the use of air brakes. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0024] like Figures 1-6 As shown, the comprehensive method for optimizing wheel brake wear of subway trains according to the present invention includes two core parts: reducing normal wear and reducing abnormal wear of subway trains. The specific technical solution is as follows: 1. Reduce normal wear and tear on subway trains: Dynamically adjust electric braking force to reduce the need for air brakes. The core idea is to reduce the amount of air braking required by minimizing the difference between the applied electric braking force and the total braking force required by the train during braking, thereby reducing normal wear of the wheel brakes. This invention proposes a dynamic adjustment model for electric braking based on the actual load of the train. This model categorizes the actual load of the train into five cases according to the three load states (AW0, AW2, AW3) corresponding to the train's electric braking force curve, establishing a dynamic correlation between electric braking force and load. This ensures that the applied electric braking force is as close as possible to the actual total braking force required by the train, reducing the gap caused by insufficient electric braking force.

[0025] 1.1 Applicable Conditions of the Model When the train is in the braking condition and the running speed drops to the electro-pneumatic conversion point speed value Vz = 6 km / h, regardless of the state of the electro-braking input, the train braking system will force the switch from electro-braking to air braking. Therefore, this dynamic adjustment model is applicable to the braking condition when the train running speed is greater than 6 km / h. When the train running speed ≤ 6 km / h, the existing conventional braking logic is still executed.

[0026] 1.2 Five Working Conditions of the Dynamic Adjustment Model Let: M be the actual load of the train (unit: t); M0 be the load under the AW0 load condition (225.5 t, a fixed preset known parameter); M2 be the load under the AW2 load condition (316.5 t, a fixed preset known parameter); M3 be the load under the AW3 load condition (340.9 t, a fixed preset known parameter); F be the actual electro-braking force applied to the train (unit: kN); F0 be the electro-braking force value matching the actual running speed of the train in the electro-braking force curve of the train under the AW0 condition (known parameter); F2 be the electro-braking force value matching the actual running speed of the train in the electro-braking force curve of the train under the AW2 condition (known parameter); F3 be the electro-braking force value matching the actual running speed of the train in the electro-braking force curve of the train under the AW3 condition (known parameter).

[0027] The five working conditions are as follows: ① When the train load condition is AW0, that is, M = M0, the train applies the electro-braking force according to the AW0 electro-braking force curve, that is, F = F0; ② When the train load condition is between AW0 and AW2, that is, M0 < M < M2, the train applies the electro-braking force according to the linear interpolation formula (3): (M - M0) / (M2 - M0) = (F - F0) / (F2 - F0) (1); F = (F2 - F0) / (M2 - M0)×M - (F2 - F0) / (M2 - M0)×M0 + F0 (2); Formula (3) is obtained by simplifying Formula (1) and Formula (2): F = F0 + (M - M0)×(F2 - F0) / (M2 - M0) (3); This formula (3) is derived based on the linear difference relationship between the actual load of the train and the standard loads of AW0 and AW2, and the linear difference relationship between the actual electro-braking force and the electro-braking forces corresponding to the standard loads, ensuring that the electro-braking force changes smoothly with the load; ③ When the train load condition is AW2, that is, M = M2, the train applies the electro-braking force according to the AW2 electro-braking force curve, that is, F = F2; ④When the train load state is between AW2 and AW3, that is, M2 < M < M3, the train applies electric braking force according to the linear interpolation formula (6): (M - M2) / (M3 - M2) = (F - F2) / (F3 - F2) (4); F = (F3 - F2) / (M3 - M2)×M - (F3 - F2) / (M3 - M2)×M2 + F2 (5); Formula (6) is simplified from formula (4) and formula (5): F = F2 + (M - M2)×(F3 - F2) / (M3 - M2) (6); Similarly, this formula (6) ensures the precise matching of the electric braking force and the actual load when the load is in the range from the rated capacity to the over - capacity; ⑤When the train load state is at AW3, that is, M = M3, the train applies electric braking force according to the AW3 electric braking force curve, that is, F = F3.

[0028] After the train arrives at each next station and completes passenger boarding, the load detection module will update the actual load M of the train in real - time, substitute the new load data into the above dynamic adjustment model, recalculate and adjust the applied electric braking force, and realize the real - time dynamic optimization of the electric braking during the main - line operation.

[0029] [[ID=|18]]2. Reduce abnormal wear of subway trains: Optimize brake shoe characteristics and inhibit abnormal tread wear Aiming at abnormal wear problems such as narrow and parallel grooves on the wheel tread, the present invention deeply studies the correlation law between brake shoe characteristics and tread wear, and proposes to optimize the contact state between the brake shoe and the wheel tread by selecting brake shoes with specific performance parameters, so as to reduce abnormal wear at the source.

[0030] Through a large number of experimental verifications, the density, elastic modulus, hardness and thermal conductivity of the brake shoe are the key parameters affecting the tread wear state: when the elastic modulus is too high, the deformation of the brake shoe under the braking pressure is small, and it does not fit well with the wheel tread, which is easy to form local friction and generate instantaneous high temperature, resulting in tread thermal damage; too high hardness will exacerbate local stress concentration and further amplify the abnormal wear phenomenon; brake shoes with a relatively large density and appropriate thermal conductivity can improve the heat diffusion efficiency during friction, reduce the accumulation of local high temperature, and at the same time ensure the uniformity of frictional contact.

[0031] Based on the above rules, the present invention determines that the optimal range of brake shoe performance parameters is: density ≥ 2.08 g / cm 3 、elastic modulus ≤ 986 N / mm 2 、hardness ≤ 77.8 HRR, thermal conductivity ≥ 0.89 W / (m·K). Preferably, the brake shoe parameters are: density 2.16 - 2.20 g / cm 3 、elastic modulus 350 - 456 N / mm2 With a hardness of 30.0-42 HRX and a thermal conductivity of 1.24-1.35 W / (m·K), brake shoes within this parameter range can optimize the contact state to the greatest extent and suppress abnormal wear of the tread surface.

[0032] In addition, a static inspection must be carried out before the brake shoes are installed to ensure that there is no damage or deformation; new brake shoes need to be broken in, and the friction area after breaking in should not be less than 75% to ensure the stability of friction contact during braking.

[0033] Example 1: Practical Application and Verification of the Dynamic Adjustment Model for Electric Braking Force This embodiment uses a Type B metro train operated by a branch of a city rail transit group as an example. The original electric braking system used by the branch's operating vehicles was the conventional standard load curve matching method, which resulted in excessive air brake activation and high wheel brake wear. This embodiment verifies the effectiveness of the electric braking force dynamic adjustment model of this invention in reducing normal wear by applying it.

[0034] 1. Basic parameter settings Based on the train parameters of this branch company, the preset standard load and corresponding electric braking force parameters are as follows: AW0 (M0): 225.5t, corresponding to electric braking force F0 = 230.2kN; AW2 (M2): 316.5t, corresponding to electric braking force F2=323kN; AW3 (M3): 340.9t, corresponding to electric braking force F3=348kN; The speed at the electro-pneumatic conversion point is Vz = 6 km / h.

[0035] 2. Model Application Process After the train enters mainline operation, the load detection module collects the actual load at each station after passenger loading in real time, and the electric braking control module adjusts the electric braking force in real time according to the dynamic adjustment model. First station (initial station): The train load is AW0 (M=225.5t). When the train speed is greater than 6km / h and is in braking condition, substitute into condition (1), the electric braking force F=F0=230.2kN; After the first stop picks up passengers: the actual load of the train is updated to M=300.6t, which is between M0 (225.5t) and M2 (316.5t). Substituting this into formula (3) for calculation: F=230.2+(300.6-225.5)×(323-230.2) / (316.5-225.5) =230.2+75.1×92.8 / 91 =230.2+76.6 =306.8kN; Other stations during the morning rush hour: After the train completes passenger loading at subsequent stations (stations 2 to 17), the actual load continues to change, and the model continuously executes adjustment logic. For example, after passenger loading at station 2, M=296.8t (still between M0 and M2), and F=302.9kN is calculated; after passenger loading at station 8, M=318.2t (between M2 and M3), and the result is calculated by substituting into formula (6): F=323+(348-323)×(318.2-316.5) / (340.9-316.5) =323 + 25 × 1.7 / 24.4 =323+1.7 =324.7kN, and the system will execute this electric braking force value after adjustment.

[0036] 3. Verification of adjustment effects (1) Trend of electric braking force: The adjustment trends of electric braking force in the upward and downward directions of the train are as follows: Figure 3 , Figure 4 As shown in the figure, after the model adjustment, the electric braking force dynamically changes with the actual load. Compared with the fixed curve before the adjustment, the difference is significant. The difference is large between M0 and M2 (the maximum difference reaches 88.1kN), indicating that the model compensates for the most air braking in this load range. Between M2 and M3, the difference is relatively small (the maximum difference is about 23kN), indicating that the compensated air braking is less, which is consistent with the model design logic.

[0037] (2) Energy data verification: The regenerative braking energy (group a, group c) and resistive braking energy consumption (group b, group d) of eight traction substations before and after model adjustment were simulated for seven consecutive days using the DCTPS simulation platform for urban rail DC traction power supply. The results are shown in Table 1.

[0038] Table 1 Energy data for each traction substation before and after model adjustment (unit: kWh / day)

[0039] Analysis of the data in Table 1 shows that after model adjustment, the regenerative braking energy of each traction substation (Group C) increased slightly compared to before adjustment (Group A) (average increase of approximately 0.614%), while the energy consumption of resistance braking (Group D) increased significantly (average increase of approximately 102.85%), and the total braking energy (total value) increased by an average of approximately 13.85%. This result confirms the effectiveness of the model, demonstrating a substantial increase in the total amount of electric braking input and a significant reduction in the space for air braking supplementation, consistent with the model's design objectives.

[0040] (3) Wear data verification: By tracking and monitoring 30 trains on the line for one year, the wear parameters of brake shoes and treads before and after model adjustment were recorded, and the results are shown in Table 2.

[0041] Table 2 Calculation of brake shoe and tread parameters before and after model adjustment

[0042] Table 2 shows that the linear wear of the brake shoe is 0.27 mm / 10. 4 km decreased to 0.19 mm / 10 4 The replacement mileage decreased by approximately 29.6% from 120 km to 4.6 years, an increase of approximately 39.4% from 3.3 years to 4.6 years; the replacement cycle increased from 3.3 years to 4.6 years, an increase of approximately 39.4% from 4.6 years to 3.3 years; the replacement mileage decreased from 120 km to 10 km to 4.6 years. 4 km increased to 170×10 4 km, the increase is (170-120) / 120×100%≈41.7%; every 120×10 km of operation 4 The cost of replacing brake shoes decreased from 403,200 yuan to 283,700 yuan, a saving of nearly 30%; the wear on the wheelset tread decreased from 0.32mm / 10 km. 4 km decreased to 0.18 mm / 10 4 km, a reduction of (0.32-0.18) / 0.32×100%≈43.8%; the replacement cycle is extended from 6.0 years to 10.6 years, an extension of (10.6-6.0) / 6.0×100%≈76.7%; every 220×10 4 The cost of wheelset replacement decreased from 43 million yuan to 24.34 million yuan, a saving of 43.4%.

[0043] The above data fully demonstrates the significant effect of the electric braking force dynamic adjustment model in reducing normal wear and tear of wheel brakes and saving operation and maintenance costs.

[0044] Example 2: Heat Capacity Test and Wear Verification of Brake Shoes and Wheels This embodiment aims to verify the effect of the electric braking force dynamic adjustment model in reducing the use of air brakes through heat capacity tests, and to further confirm the optimization of brake shoe and tread wear after model adjustment.

[0045] 1. Experimental Design (1) Test subjects: Three Type B subway trains from Example 1 were selected and labeled as Train 1 (before model adjustment), Train 2 (after model adjustment), and Train 3 (after model adjustment with optimized brake shoes). (2) Test period: Each train will be tested continuously for 1 week (7 days), covering all operating hours during the morning peak, off-peak, and evening peak; (3) Load division: The train load is divided into 4 sections: 225.5≤M<280t, 280≤M<300t, 300≤M<316.5t, and 316.5≤M≤340.9t, covering the full load range from AW0 to AW3; (4) Temperature monitoring: Temperature patches are affixed to the tread surfaces of 4 sets of brake shoes and 4 pairs of wheelsets on each train (the affixing locations are as follows). Figure 5 As shown in the figure, the average maximum temperature after braking is collected in real time. (5) Wear monitoring: Measure the brake shoe thickness and wheel diameter before and after the test, and calculate the wear amount; record the train running mileage daily during the test and count the wear rate.

[0046] 2. Results of heat capacity test After the test, the average maximum temperature of the brake shoes and wheels in each load range was recorded, and the results are as follows: Figure 6 As shown.

[0047] Depend on Figure 6 It can be seen that within the same load range, the average maximum temperature of brake shoes and wheels of train 2 (after model adjustment) is significantly lower than that of train 1 (before model adjustment), with a temperature difference range of 5-15℃. The greater the load, the more obvious the temperature difference before and after adjustment. In the range of 316.5≤M≤340.9t (AW2-AW3), the average maximum temperature of brake shoes decreased from 237℃ to 223℃, a decrease of 6%; the average maximum temperature of wheels decreased from 221℃ to 209℃, a decrease of 5.4%.

[0048] This result fully validates the effectiveness of the model adjustment: reduced air braking input leads to less frictional heat generation between the brake shoes and wheel treads, resulting in a lower average maximum temperature, consistent with the logic of increased electric braking force and reduced supplemental air braking.

[0049] 3. Wear verification results After the test, the wear data of the brake shoes and treads of the three trains were collected, and the results are as follows: Train 1 (before model adjustment): Brake shoe wear 0.27mm / 10 4 km, tread wear 0.32mm / 10 4 km, consistent with the data before adjustment in Example 1; Train 2 (after model adjustment): Brake shoe wear 0.19mm / 10 4 km, tread wear 0.18mm / 10 4 km, consistent with the adjusted data in Example 1, with a significant reduction in wear; Train 3 (Model adjusted + optimized brake shoes): Brake shoe wear 0.16mm / 10 4 km, tread wear 0.10mm / 10 4km, the wear amount is further reduced compared to train 2, and there are no abnormal wear marks on the tread surface.

[0050] Furthermore, correlation analysis between temperature and wear data revealed that for every 1°C decrease in the average maximum temperature of the brake shoe, brake shoe wear decreased by approximately 1.2%, and wheel tread wear decreased by approximately 1.0%, further confirming that the reduction in air braking is the core reason for the decrease in wear.

[0051] Example 3: Comparative Test and Verification of Abnormal Wear Suppression of Brake Shoes with Different Characteristics This embodiment addresses the problem of abnormal wear caused by narrow parallel grooves on the tread of train wheels in this branch company. By comparing the performance of brake shoes with different characteristics, it verifies the effectiveness of the brake shoe selection scheme proposed in this invention in suppressing abnormal wear.

[0052] 1. Test brake shoe selection and parameters Five brake shoes with different performance parameters (numbered 1-5) were selected, and their core performance parameters are shown in Table 3.

[0053] Table 3 Performance parameters of the test brake shoes

[0054] Among them, brake shoes 1 and 2 are existing conventional brake shoes (high elastic modulus and high hardness), and brake shoes 3-5 are brake shoes selected according to the parameter range of this invention (low elastic modulus, moderate hardness, and relatively high density).

[0055] 2. Test Plan (1) Test train: Select 5 B-type subway trains with the same condition, and install brake shoes 1-5 respectively to ensure that the initial condition of the train (wheel diameter, brake shoe thickness, braking system parameters) is completely consistent; (2) Break-in process: After the new brake shoes are installed, a 500km break-in period is carried out to ensure that the friction area is not less than 75%; (3) Trial period: 6 months, covering different seasons and different operating periods (morning peak, off-peak, evening peak); (4) Data collection: Measure the brake shoe thickness and wheel diameter once a month and record the wear amount; after the test, observe the wheel tread shape through professional testing equipment to judge the abnormal wear.

[0056] 3. Experimental Results and Analysis After the test, the wear and tread morphology data of the five types of brake shoes were compiled, and the results are shown in Table 4.

[0057] Table 4. Tracking results of brake shoe, tread wear and tread morphology.

[0058] Analysis of the data in Tables 3 and 4 shows that: Brake shoes 1 and 2 (elastic modulus > 1100 N / mm) 2 (Hardness > 80HB / HRR): After use, the wheel tread still has obvious narrow parallel grooves, and the tread wear is 0.16mm / 10. 4 km, 0.13mm / 10 4 The wear level is relatively high. This is because the high elastic modulus leads to poor contact between the brake shoe and the tread surface, resulting in severe localized friction. The high hardness also exacerbates stress concentration, causing abnormal wear. Brake shoe 3 (elastic modulus = 986 N / mm) 2 (Hardness = 77.8 HRR): Only shallow grooves appeared on the tread surface, and the wear rate was reduced to 0.11 mm / 10. 4 km, abnormal wear is significantly alleviated. This indicates that when the elastic modulus and hardness drop to the lower limit value set in this invention, the fit is improved and local friction is reduced; Brake shoes 4 and 5 (elastic modulus 350-456 N / mm) 2 Hardness 30.0-42 HRX, density 2.16-2.20 g / cm³ 3 The tread surface is free of grooves, has a smooth surface, and has the lowest wear rate (0.10mm / 10). 4 This is because the brake shoe deformation within this parameter range is moderate, it fits evenly against the tread surface, and the frictional stress is evenly distributed. At the same time, the high density and high thermal conductivity reduce the accumulation of local high temperatures and completely suppress abnormal wear.

[0059] In addition, the wear of brake shoes 4 and 5 is 0.16mm / 10 mm respectively. 4 km, 0.14mm / 10 4 The wear rate was reduced by 23.8%-26.3% compared to conventional brake shoes 1 and 2, indicating that the optimized brake shoes can not only suppress abnormal wear, but also further reduce the normal wear of the brake shoes themselves, achieving "dual optimization".

[0060] 4. Long-term verification effect A two-year long-term follow-up study of trains equipped with brake shoes 5 showed that the wheel treads remained consistently flat, without any abnormal wear phenomena such as narrow parallel grooves; the brake shoe wear rate remained stable at 0.14-0.15 mm / 10. 4 The replacement cycle has been extended to 5.2 years; the number of wheel turning repairs has been reduced from twice a year to once every 3 years, saving 66.7% in turning repair costs and significantly reducing maintenance costs.

[0061] This invention comprehensively addresses the wheel brake wear problem of subway trains by employing a combined approach of dynamic adjustment of electric braking force and optimized brake shoe selection, addressing both normal and abnormal wear. The dynamic adjustment model of electric braking force optimizes the application of electric braking force in real time based on the actual train load, significantly reducing the use of air brakes and lowering normal wear. Brake shoes with specific performance parameters optimize the frictional contact state, completely suppressing abnormal wear. This method requires no hardware modifications, has low implementation costs, and yields significant results. It greatly extends the replacement cycle of brake shoes and wheelsets, significantly reduces maintenance costs, and improves train braking safety, demonstrating high engineering application value and promising prospects for widespread adoption.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A comprehensive method for optimizing wheel brake wear in subway trains, characterized in that, It includes the following steps: 1) Reduce normal wear: When the train is in the braking condition and the running speed is greater than the electro-pneumatic conversion point speed Vz = 6 km / h, based on the relationship between the actual load M0, M2, M3 of the train and the preset standard loads AW0, AW2, AW3, dynamically adjust the electric braking force F in five working conditions to make the electric braking force match the total braking force required by the train and reduce the air braking input; the five working conditions are specifically as follows: ① When M = M0, F = F0, where F0 is the electric braking force value matching the actual running speed of the train in the electric braking force curve of the train under AW0 condition; ② When M0 < M < M2, according to the linear interpolation formula F = F0 + (M - M0) × (F2 - F0) / (M2 - M0), complete the dynamic adaptation adjustment in combination with the actual running speed of the train; ③ When M = M2, F = F2, where F2 is the electric braking force value matching the actual running speed of the train in the electric braking force curve of the train under AW2 condition; ④ When M2 < M < M3, according to the linear interpolation formula F = F2 + (M - M2) × (F3 - F2) / (M3 - M2), complete the dynamic adaptation adjustment in combination with the actual running speed of the train; ⑤ When M = M3, F = F3, where F3 is the electric braking force value matching the actual running speed of the train in the electric braking force curve of the train under AW3 condition; Among them, M0 = 225.5t, M2 = 316.5t, M3 = 340.9t, and F0, F2, F3 are preset known parameters of the train; 2) Reduce abnormal wear: Select materials with a density ≥ 2.08 g / cm³ 3 Elastic modulus ≤ 986 N / mm 2 Brake shoes with a hardness ≤77.8HRR optimize the contact state between the brake shoe and the wheel tread, and suppress abnormal wear such as narrow parallel grooves on the tread.

2. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: In step 1) above, after the train updates the actual load M every time it arrives at a station, substitute it into the corresponding formula again to adjust the electric braking force.

3. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: The thermal conductivity of the brake shoe is ≥ 0.89 W / (m·K).

4. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: The specific parameters of the brake shoe are: density 2.16-2.20 g / cm³. 3 Elastic modulus 350-456 N / mm 2 Hardness 30.0-42HRX, thermal conductivity 1.24-1.35W / (m·K).

5. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: The dynamic adjustment model in step 1) is realized by software upgrade of the existing train braking control system without changing the hardware.

6. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: The train is a Type B subway train, the initial thickness of the brake shoe is 45 mm, and the replacement limit thickness is 12 mm; the new wheel diameter of the wheel is 840 mm, and the wear limit diameter is 770 mm.

7. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: In step 1) above, after the electric braking force is adjusted, the total amount of regenerative braking energy and resistive braking energy consumption of the train increases compared with before the adjustment, and the difference that needs to be supplemented by air braking is reduced.

8. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: In step 2) above, the brake shoe needs to be subjected to static inspection before being installed on the vehicle, and the friction area after the new brake shoe is run-in is not less than 75%.

9. The comprehensive method for optimizing wheel brake wear of subway trains according to claim 1, characterized in that: Monitor the average maximum temperature of the brake shoe and the wheel by pasting temperature patches to verify the effect of reducing the air braking input.

10. A subway train braking system applying the method according to any one of claims 1-9, characterized in that, It includes a load detection module, an electric braking control module and a brake shoe adaptation module. The load detection module collects the actual load of the train in real time, the electric braking control module executes the dynamic adjustment model, and the brake shoe adaptation module matches the brake shoes with preset performance parameters.

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