Method for measuring and calculating friction coefficient of magnetic rail brake

Abstract

The application discloses a kind of magnetic rail brake friction coefficient's measurement method, comprising: initial parameter is obtained by testing: the brake mass of track car, empty distance and average deceleration are calculated;The effective braking distance and average braking force of track car are calculated;The equivalent deceleration of track car and the average braking force borne by each set of magnetic rail brake are calculated;The average friction coefficient of magnetic rail brake is calculated, and the equivalent braking force of track car is calculated;The equivalent braking force borne by each set of magnetic rail brake is calculated;The equivalent friction coefficient of magnetic rail brake is calculated.The measurement method of the application can truly and accurately reflect the actual friction coefficient of magnetic rail brake under different working conditions of vehicle, bring convenience to track car braking calculation, braking distance test, also provide scientific basis for the friction coefficient of magnetic rail brake under different initial speed, different load, different braking distance, different response time of similar projects in design and development stage, shorten related test verification period.

Description

Technical Field

[0001] This invention belongs to the technical field of magnetic track brakes for rail transit vehicles, and specifically relates to a method for calculating the friction coefficient of a magnetic track brake. Background Technology

[0002] Magnetic rail brakes are a new type of brake developed to adapt to the popularization and high speed of rail vehicles. When braking, the electromagnet uses electromagnetic attraction to press the rail tightly. The braking force is generated by the sliding friction between the pole shoes on the electromagnet and the rail, and the kinetic energy of the rail vehicle is converted into heat energy and dissipated into the atmosphere, thereby slowing down the vehicle.

[0003] Currently, there is no 1:1 braking power test bench in the industry that simulates the actual working conditions of a whole vehicle for testing the friction coefficient of magnetic track brakes. As a result, it is impossible to accurately determine the actual friction coefficient of magnetic track brakes. The friction coefficient of magnetic track brakes can only be predicted and inferred based on experience. However, the value of the friction coefficient of magnetic track brakes predicted and inferred based on experience is often distorted, which brings difficulties and inconvenience to the braking calculation and braking distance test of railcars.

[0004] Therefore, there is an urgent need for a method to calculate the friction coefficient of magnetic track brakes. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the friction coefficient of a magnetic track brake, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a method for calculating the friction coefficient of a magnetic track brake. The magnetic track brake is installed below the two side frames of the bogie and between the two wheels on the same side of the railcar. Each railcar has n sets of the magnetic track brake installed at its bottom. The method includes the following steps:

[0007] Step 1: Obtain initial parameters through testing: The initial parameters include the mass m of the railcar, the rotational mass mr, the measured braking distance S3 of the railcar, and the measured response and idle time t of the magnetic track brake. e ;

[0008] Step 2: Based on the given initial parameters, calculate the braking mass M, the unloaded distance S1, and the average deceleration a of the railcar. The calculation formulas are as follows:

[0009] M = m + mr

[0010] S1=V0t e

[0011]

[0012] Where V0 is the actual speed measured during the test of the railcar;

[0013] Step 3: Calculate the effective braking distance S2 and average braking force F of the railcar. The calculation formula is as follows:

[0014] S2 = S3 - S1

[0015] F = M × a

[0016] Step 4: Calculate the equivalent deceleration 'a' of the railcar. e and the average braking force F borne by each magnetic track brake ' The calculation formula is as follows:

[0017]

[0018] F′=F / n

[0019] Step 5: Calculate the average friction coefficient of the magnetic track brake. And calculate the equivalent braking force F of the railcar e The calculation formula is as follows:

[0020]

[0021] F e =M×a e

[0022] Where Q is the design value of the suction force for each set of magnetic track brakes;

[0023] Step 6: Calculate the equivalent braking force F borne by each set of magnetic track brakes. e The calculation formula is as follows:

[0024] F e ′=F e / n

[0025] Step 7: Calculate the equivalent friction coefficient μ of the magnetic track brake. The calculation formula is as follows:

[0026] μ = F e ′ / Q.

[0027] Furthermore, the specific steps for obtaining the initial parameters in step 1 are as follows:

[0028] The test track vehicle was in a ready state and underwent six complete weighing operations in a row, three times in each of the forward and backward directions. The arithmetic mean of the six measurements was taken as the mass m of the track vehicle.

[0029] The rotational mass mr is calculated as 8% to 8.2% of the mass m of the test track vehicle;

[0030] The measured braking distance S3 was determined on a straight track, under the load required by the design, and at least 3 tests were conducted for each braking condition.

[0031] Furthermore, the test method for the actual braking distance of the railcar is as follows: the power supply of the traction motor should be disconnected before the test railcar passes the braking mark point, the speed of the test railcar should be close to the specified speed, and the required braking method should be applied when it reaches the mark point.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention discloses a method for calculating the friction coefficient of a magnetic track brake. First, relevant data of the railcar is acquired or measured. Then, calculations are performed using the method described in this invention. The calculation results accurately reflect the actual friction coefficient of the magnetic track brake under different initial velocities, loads, braking distances, and response times. This facilitates railcar braking calculations and braking distance testing, and provides a scientific basis for calculating the friction coefficient of magnetic track brakes under different initial velocities, loads, braking distances, and response times in similar projects during the design and development phase, thus shortening the relevant verification cycle. Furthermore, this invention solves the problem of lacking a 1:1 braking power testing platform simulating actual vehicle operating conditions to test the friction coefficient of magnetic track brakes. Compared to traditional empirical predictions of magnetic track brake friction coefficients, this invention significantly improves the authenticity and accuracy of the data.

[0034] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0036] Figure 1 This is a flowchart illustrating a method for calculating the friction coefficient of a magnetic track brake according to the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent transformations or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0038] Please see Figure 1This embodiment provides a method for calculating the friction coefficient of a magnetic track brake. The magnetic track brake is installed below the two side frames of the bogie and between the two wheels on the same side of the railcar. Each railcar has n sets of the magnetic track brake installed at its bottom. The calculation method includes the following steps:

[0039] Step 1: Obtain initial parameters through testing: Initial parameters include the mass m of the railcar, the rotating mass mr, the measured braking distance S3 of the railcar, and the measured response and idle time t of the magnetic track brake. e The test track vehicle was in a ready state and underwent six complete weighing operations, with three tests in each of the forward and backward directions. The mass m of the track vehicle was taken as the arithmetic mean of the six records. The rotational mass mr was calculated as 8% to 8.2% of the mass m of the test track vehicle. The measured braking distance S3 was determined on a straight track under the design load, and each braking condition was tested at least three times.

[0040] The test of the actual braking distance S3 of the track vehicle includes: 1) Disconnecting the traction motor power supply before the track vehicle passes the braking mark point, and applying the required braking method when the track vehicle reaches the mark point; 2) Measuring the braking distance of each test, and the difference between the initial braking speed and the specified speed should not exceed ±3km / h; 3) If the braking distance test cannot be carried out on an absolutely straight track, the gradient of the selected straight track should not exceed ±4‰, and the measured braking distance should be converted into the corrected actual braking distance using the standard formula.

[0041] Measured response and idle time t of magnetic track brake e For the magnetic rail brake, it is operated at the rated voltage and rated air gap. The time from the initial state to the magnetic rail brake being attracted to the rail is tested. The judgment criterion for being attracted to the rail is that the excitation current reaches 90% of the rated value.

[0042] Step 2: Based on the given initial parameters, calculate the braking mass M, the unloaded distance S1, and the average deceleration a of the railcar. The calculation formulas are as follows:

[0043] M = m + mr

[0044] S1=V0t e

[0045]

[0046] Where V0 is the actual speed measured during the test of the railcar;

[0047] Step 3: Calculate the effective braking distance S2 and average braking force F of the railcar. The calculation formula is as follows:

[0048] S2 = S3 - S1

[0049] F = M × a

[0050] Step 4: Calculate the equivalent deceleration 'a' of the railcar. e and the average braking force F borne by each magnetic track brake ' The calculation formula is as follows:

[0051]

[0052] F′=F / n

[0053] Step 5: Calculate the average friction coefficient of the magnetic track brake. And calculate the equivalent braking force F of the railcar e The calculation formula is as follows:

[0054]

[0055] F e =M×a e

[0056] Where Q is the suction force of each magnetic track brake;

[0057] Step 6: Calculate the equivalent braking force F borne by each set of magnetic track brakes. e The calculation formula is as follows:

[0058] F e ′=F e / n

[0059] Step 7: Calculate the equivalent friction coefficient μ of the magnetic track brake. The calculation formula is as follows:

[0060] μ = F e ′ / Q.

[0061] Example

[0062] This embodiment takes a certain type of magnetic track brake as an example and provides a method for calculating the friction coefficient of a magnetic track brake, which specifically includes the following steps:

[0063] Step 1: Obtain initial parameters through testing; where: train mass m is 59200kg, rotating mass mr = m × 8.16% = 59200 × 8.16% = 4831kg, the measured braking distance S3 of the railcar is 2.25m, and the measured response and idle time t of the magnetic track brake are... e It is 0.035s.

[0064] Step 2, with the actual target speed V0 set to 10 km / h:

[0065] Calculate the braking mass of the railcar M = m + mr = 64031 kg; calculate the unloaded travel distance of the railcar S1 = V0t. e = (10 / 3.6) × 0.035 = 0.097m; and calculate the average deceleration of the railcar. S3 represents a measured braking distance of 2.25m.

[0066] Step 3: Calculate the effective braking distance of the railcar S2 = S3 - S1 = 2.25 - 0.097 = 2.15m; calculate the average braking force F = M × a = 64031 × 1.715 = 109793N.

[0067] Step 4: Calculate the equivalent deceleration of the railcar. S2 represents an effective braking distance of 2.15m; calculate the average braking force F borne by each magnetic track brake system. ' =F / n, =109793 / 8 =13724N, where F is the average braking force of the train (109793N) and n is the number of magnetic track brakes on the train (8 sets).

[0068] Step 5: Calculate the average friction coefficient of the magnetic track brake. Where F' is the average braking force of each magnetic track brake set (13724 N), and Q is the suction force of each magnetic track brake set (70000 N); calculate the equivalent braking force F of the railcar. e =M×a e =64031×1.79=114751N.

[0069] Step 6: Calculate the equivalent braking force F borne by each set of magnetic track brakes. e '=F e / n=114751 / 8=14344N.

[0070] Step 7: Calculate the equivalent friction coefficient μ = F of the magnetic track brake. e / Q = 14344 / 70000 = 0.205.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the friction coefficient of a magnetic track brake, wherein the magnetic track brake is installed below two side frames of a railcar bogie and between two wheels on the same side of the railcar, and n sets of the magnetic track brake are installed at the bottom of each railcar, and the design value Q of the suction force of each set of magnetic track brakes is characterized in that, The calculation method includes the following steps: Step 1: Obtain initial parameters through testing: The initial parameters include the mass m of the railcar, the rotational mass mr, the measured braking distance S3 of the railcar, the measured response of the magnetic track brake, and the idle travel time t. e The measured speed V0 during the test of the railcar; the measured response and idle time t of the magnetic track brake. e The calculation method is as follows: The magnetic rail brake is operated at its rated voltage and rated air gap. The time it takes for the magnetic rail brake to adhere to the rail from its initial state is tested. The criterion for adhering to the rail is that the excitation current reaches 90% of its rated value. The sub-step for obtaining the initial parameters in step 1 is as follows: The test track vehicle was in a ready state and underwent six complete weighing operations in a row, three times in each of the forward and backward directions. The arithmetic mean of the six measurements was taken as the mass m of the track vehicle. The rotational mass mr is calculated as 8% to 8.2% of the mass m of the test track vehicle; The measured braking distance S3 was determined on a straight track, under the load required by the design, and at least 3 tests were conducted for each braking condition. Step 2: Based on the initial parameters obtained from the test, calculate the braking mass M, the unloaded distance S1, and the average deceleration a of the railcar. The calculation formulas are as follows: M = m + mr S1=V0t e Step 3: Calculate the effective braking distance S2 and average braking force F of the railcar. The calculation formula is as follows: S2 = S3 - S1 F = M × a Step 4: Calculate the equivalent deceleration 'a' of the railcar. e The average braking force F' borne by each set of magnetic track brakes is calculated using the following formula: F′=F / n Step 5: Calculate the average friction coefficient of the magnetic track brake. And calculate the equivalent braking force F of the railcar e The calculation formula is as follows: F e =M×a e Step 6: Calculate the equivalent braking force F borne by each set of magnetic track brakes. e The calculation formula is as follows: F e ′=F e / n Step 7: Calculate the equivalent friction coefficient μ of the magnetic track brake. The calculation formula is as follows: μ=F e ′ / Q。 2. The calculation method according to claim 1, characterized in that, The test method for the actual braking distance of the railcar is as follows: the power supply of the traction motor should be disconnected before the test railcar passes the braking mark point, and the difference between the speed of the test railcar and the specified speed should not exceed ±3km / h; when the test railcar reaches the braking mark point, the required braking method is applied.

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