A high-speed and high-current sliding current-carrying friction and wear testing machine and testing method

Abstract

The present invention discloses a high-speed and high-current sliding current-carrying friction and wear testing machine and a testing method, which include a driving device and a loading device. The output end of the driving device is connected with a first specimen, and a second specimen is installed on the loading device. The second specimen is driven by the loading device to move up and down. The first specimen and the second specimen are in contact to form a friction pair. The driving device and the loading device cooperate to make the second specimen generate different friction tracks on the surface of the first specimen. In the present invention, a spherical plain bearing is installed outside the conductive copper shaft, and a conductive lubricant is added between the two, which plays the roles of lubrication, enhancing conductivity, support, compensating angular deviation, suppressing circular runout at high speeds, and ensuring thermal expansion space. The laser displacement sensor can continuously monitor the position of the rotating crossbeam during the test. When uneven wear occurs on the surface of the friction pair, the X-axis displacement platform will actively compensate in the direction of the disc specimen, so that the end faces of the friction pair remain in close contact, reducing high temperature and ablation damage caused by electric arcs, etc.

Description

Technical Field

[0001] The invention relates to a friction and wear testing machine and a testing method, in particular to a high-speed and high-current sliding current-carrying friction and wear testing machine and a testing method. Background Art

[0002] Current-carrying friction and wear refers to the tribological behavior between friction pairs under the condition that current passes through the contact interface. It usually exists in key occasions such as the pantograph / contact network system of high-speed railways, aerospace conductive slip rings and electromagnetic railguns. The intervention of electrical factors makes the process of current-carrying friction and wear more complicated. Under the coupling effect of mechanical wear and current-carrying wear, the surface of the contact element is more susceptible to damage. The melting and splashing caused by arc erosion will further aggravate the wear state of the friction pair surface. At present, in order to improve the wear resistance and conductivity of current-carrying friction pairs, extensive research has been carried out on the materials of friction pairs and friction working conditions such as temperature, lubrication, load, speed, and current. Therefore, it has far-reaching social significance and economic benefits to study the relevant theoretical and technical issues of current-carrying tribology by developing a current-carrying friction and wear testing machine.

[0003] Patent application number 202010588717.8 discloses a current-carrying friction and wear tester and test system, which only performs insulation treatment between the slider detection devices, while ignoring the insulation measures on the drive device and one side of the turntable. This will not only cause obvious errors in the test results, but also cause great damage to the current-carrying friction and wear tester when the current is large. Patent application number 202010488327.3 discloses a current-carrying friction and wear tester, a test system and a test method thereof. The front end of the force shaft is two symmetrical specimens, which are difficult to accurately position to control the friction trajectory between the specimen and the disc, and eccentric wear is prone to occur. In addition, although a pressure sensor is provided to detect whether the loading device is damaged, it is impossible to fundamentally avoid the problem of damage to the loading device caused by long-term use, and the overall device is more complicated. The above-mentioned test device is difficult to adapt to the damage to the test machine parts and specimens caused by high temperature and electric arc under high-speed and high-current conditions.

[0004] Due to the zigzag arrangement of the contact wire, there is both longitudinal relative motion and lateral reciprocating motion between the high-speed rail contact wire and the carbon slide plate. Existing testing machines cannot simulate complex motion forms. Large currents generate high temperatures, and reliable insulation and heat insulation are required between the current-carrying circuit and other structures. The conductive structure vibrates violently during high-speed rotation, and the angular deviation increases. Existing technologies cannot solve the problem of reliable conduction under high-speed rotation and high temperature. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a high-speed, high-current sliding current-carrying friction and wear testing machine and testing method, which can meet a variety of working conditions and ensure the long-term and stable current-carrying friction and wear test.

[0006] Technical solution: The present invention includes a driving device and a loading device. The output end of the driving device is connected to a first specimen, and a second specimen is installed on the loading device. The loading device drives the second specimen to move up and down. The first specimen and the second specimen are in contact to form a friction pair. The driving device and the loading device cooperate to make the second specimen generate different friction tracks on the surface of the first specimen.

[0007] The output end of the driving device is connected to a torque sensor. The other end of the torque sensor is connected to a conductive slip ring. The other end of the conductive slip ring is connected to a first fixture. A first specimen is installed on the first fixture. The other end of the first specimen is connected to a spherical plain bearing through a copper shaft. The copper shaft and the spherical plain bearing are in clearance fit.

[0008] A fixing ring is installed on the outer cylindrical surface of the first fixture and the first specimen. The first specimen is a disc specimen.

[0009] The spherical plain bearing is installed on a conductive copper plate, and a current introduction column is arranged on the conductive copper plate.

[0010] The loading device includes a Z-axis lifting table. An X-axis displacement platform is installed above the Z-axis lifting table. A rotating crossbeam and a fixed crossbeam are installed on the top of the X-axis displacement platform. Pulleys are respectively installed at the same end of the rotating crossbeam and the fixed crossbeam. A weight is connected below the pulley on the fixed crossbeam.

[0011] A laser displacement sensor is installed above the side of the fixed crossbeam close to the pulley to monitor the position of the rotating crossbeam at all times during the friction process. Once the phenomenon of eccentric wear of the friction pair occurs, the X-axis displacement platform will advance towards the disc specimen for active compensation, so that the friction pair always maintains good contact and reduces high temperature and ablation damage caused by electric arcs, etc.

[0012] A triaxial acceleration sensor is installed at the other end of the rotating crossbeam far from the pulley to collect vibration signals in the X, Y, and Z directions during the test process.

[0013] A second fixture is installed at one end of the rotating crossbeam close to the disc specimen. A second specimen is clamped on the second fixture. The second specimen is a block specimen. A current export column is arranged at the bottom of the second fixture. A ceramic insulating plate is arranged between the second fixture and the rotating crossbeam.

[0014] A first positioning ball and a second positioning ball are installed on the top of the X-axis displacement platform to play a role in positioning and fixing.

[0015] A sliding current-carrying friction and wear test method includes the following steps:

[0016] S1: Weigh the weight of the block specimen and install the block specimen on the second fixture;

[0017] S2: Fix the rotating crossbeam at the first positioning ball, adjust the Y-axis displacement platform and the Z-axis lifting table to determine the contact position;

[0018] S3: Move the X-axis displacement platform to make the disc specimen and the block specimen in close contact. After hanging the weights for loading, turn down the first positioning ball until it no longer plays the role of positioning and fixing;

[0019] S4: According to the test requirements, set the rotation speed of the driving device and the lifting frequency of the Z-axis lifting table, apply the set current, turn on the torque sensor, and start the current-carrying friction and wear test;

[0020] S5: During the test, if it is necessary to weigh the block specimen, pause the movement of the driving device and the Z-axis lifting table, disconnect the current, lift the first positioning ball and the second positioning ball, move the rotating crossbeam to the second positioning ball, and take out the block specimen for weighing;

[0021] S6: After weighing, install the block specimen back to its original position in the second fixture, move the rotating crossbeam back to the first positioning ball and turn it down, start the driving device and the Z-axis lifting table and apply the current, and continue the current-carrying friction and wear test.

[0022] Beneficial effects:

[0023] 1) In the present invention, a spherical plain bearing is installed outside the conductive copper shaft. The spherical plain bearing and the conductive copper shaft are in clearance fit, and a conductive lubricant is added between them, so that the contact resistance between the spherical plain bearing and the conductive copper shaft is small, which plays the role of lubrication and enhancing conductivity. The spherical plain bearing also has the functions of support and alignment, can compensate for the angular deviation of the copper shaft, and suppress the outer circle runout of the copper shaft during high-speed rotation. It can realize the current-carrying test at a high speed of 6000 revolutions per minute and a current of 800 A. When the conductive copper shaft is heated, it can freely elongate axially and expand within the radial clearance in the spherical plain bearing;

[0024] 2) The laser displacement sensor of the present invention can continuously monitor the position of the rotating crossbeam during the test. When uneven wear occurs on the surface of the friction pair due to wear, the X-axis displacement platform will actively compensate towards the direction of the disc specimen, so that the rotating crossbeam is always parallel to the disc specimen, and the end faces of the friction pair remain in close contact, reducing high temperature and ablation damage caused by electric arcs, etc.;

[0025] 3) The present invention is provided with two positioning balls, which facilitates the loading, unloading and weighing of the block specimen during the test, and can accurately restore the position when the test is paused to continue the test;

[0026] 4) The motor and the Z-axis electric lifting table of the present invention can work simultaneously, and accurately design a variety of friction paths to adapt to various complex working conditions such as the high-speed rail pantograph-catenary system;

[0027] 5) In addition to transmitting torque, the coupling of the present invention is also used for insulation and heat insulation, so that the current and heat of the disc fixture will not be transmitted to the conductive slip ring and the torque sensor, playing a protective role. When the temperature at the friction interface of the first specimen and the second specimen is 400 °C and the temperature at the coupling is lower than 280 °C, the testing machine can operate stably. Brief Description of the Drawings

[0028] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 is a schematic diagram of the loading device of the present invention;

[0030] Figure 3 is a schematic diagram of the contact state of the friction pair of the present invention;

[0031] Figure 4 is a schematic diagram of the separation state of the friction pair of the present invention;

[0032] Figure 5 is a schematic diagram of the connection mode between the heat dissipation copper shaft and the disc specimen of the present invention;

[0033] Figure 6 is a schematic diagram of the "zigzag" friction track of the present invention;

[0034] Figure 7 is a schematic diagram of the "S-shaped" friction track of the present invention. Detailed Embodiment

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] As Figures 1 to 5 shown, the present invention includes a driving device 1 and a loading device 12. The output end of the driving device 1 is connected to a disc specimen 7, and a block specimen 9 is installed on the loading device 12. The block specimen 9 contacts the disc specimen 7 to form a friction pair.

[0037] As Figure 1As shown in the figure, the driving device 1 includes a motor 101. A lower pulley 102 is installed on the output shaft of the motor 101. The lower pulley 102 is in transmission connection with an upper pulley 103 through a transmission belt 104. The output shaft of the upper pulley 103 is connected to a torque sensor 2. The other end of the torque sensor 2 is connected to a slip ring 3. The torque sensor 2 is powered through the slip ring 3. The other end of the slip ring 3 is connected to a disc fixture 6 through a coupling 4. The coupling 4 is a plum blossom coupling. The middle connecting part of the coupling 4 is replaced with PEEK material, which can achieve good insulation and high-temperature resistance effects, so that the current and heat of the disc fixture will not be transmitted to the slip ring and the torque sensor, playing a protective role. A ceramic bearing seat 5 is provided between the disc fixture 6 and the coupling 4. The shaft of the disc fixture 6 passes through the ceramic bearing seat 5. The end face of the disc fixture 6 is connected to a disc specimen 7. The disc specimen 7 is fixed to the disc fixture 6 through screws and nuts. The other end of the disc specimen 7 is connected to a spherical plain bearing 8 through a conductive copper shaft 20. The spherical plain bearing 8 and the conductive copper shaft 20 are in clearance fit, and a conductive lubricant is added between them, so that the contact resistance between the spherical plain bearing and the conductive copper shaft is small, playing a role in lubrication and enhancing conductivity. The spherical plain bearing also has the functions of support and alignment, can compensate for the angular deviation of the copper shaft, and suppress the outer circle runout of the copper shaft during high-speed rotation. It can achieve a high-speed rotation of 6000 revolutions per minute and a current-carrying test under 800 A current. When the conductive copper shaft is heated, it can freely elongate axially in the spherical plain bearing and expand within the radial clearance.

[0038] As Figure 5 shown, a fixing ring 21 is installed on the outer cylindrical surfaces of the disc fixture 6 and the disc specimen 7 to prevent the disc specimen 7 from breaking during the high-speed friction process when the disc specimen 7 is a brittle material. The conductive copper shaft 20 passes through the center of the disc specimen 7. The threaded rod of the conductive copper shaft 20 is connected to the threaded hole in the center of the disc fixture 6. A spherical plain bearing 8 is installed outside the conductive copper shaft 20. There is a 0.05 mm gap between the spherical plain bearing 8 and the conductive copper shaft 20 for adding a conductive lubricant, making the contact between the spherical plain bearing 8 and the conductive copper shaft 20 closer, and playing a certain role in lubrication and enhancing conductivity. The outside of the spherical plain bearing 8 is horizontally installed on a conductive copper plate 22 through a nut. The bottom of the conductive copper plate 22 is fixed on an insulating plate 24. Current introduction columns 23 are provided on the conductive copper plate 22. The current introduction columns 23 are the inlets of the current. After flowing through the conductive copper plate 22 and the spherical plain bearing 8, it passes through three parallel circuits, then through a block specimen 9 and a block fixture 10, and finally flows out through a current outlet column 18. The three parallel circuits are respectively conductive copper shaft 20 - disc specimen 7, conductive copper shaft 20 - disc fixture 6 - disc specimen 7, and conductive copper shaft 20 - the outer cylindrical surfaces of the disc fixture 6 and the disc specimen 7 - fixing ring 21. The whole is charged and has a smaller resistance. At the same time, it avoids insulating materials and can withstand a larger current.

[0039] As Figure 2As shown, the loading device 12 includes an X-axis displacement platform 121, a Y-axis displacement platform 122 and a Z-axis electric lifting platform 123. The Y-axis displacement platform 122 is installed on the top of the Z-axis electric lifting platform 123, the X-axis displacement platform 121 is installed on the top of the Y-axis displacement platform 122, and a rotating beam 124 and a fixed beam 125 are installed on the top of the X-axis displacement platform 121. The rotating beam 124 rotates in the horizontal direction around the rotating shaft 14 and the thrust bearing 17. Pulleys 126 are installed on the same end of the rotating beam 124 and the fixed beam 125 respectively. A weight 127 is connected below the pulley 126 on the fixed beam 125. The weight 127 is wound around the pulleys 126 at the ends of the rotating beam 124 and the fixed beam 125 through the traction of a steel wire rope to apply a load to the friction pair. A laser displacement sensor 19 is installed above the fixed beam 125 near the pulley 126. The laser displacement sensor 19 can monitor the position of the rotating beam 124 at all times during the friction process. Once the friction pair wears eccentrically, the X-axis displacement platform 121 will be pushed toward the disk sample for active compensation, so that the friction pair always maintains good contact and reduces the high temperature and ablation damage caused by the arc. A three-axis acceleration sensor 13 is installed at the other end of the rotating beam 124 away from the pulley to collect vibration signals in the three directions of X, Y, and Z during the test.

[0040] A block fixture 10 is installed at one end of the rotating beam 124 close to the disk sample 7. The block fixture 10 is installed on the rotating beam 124 through a ceramic screw. The block sample 9 is clamped on the block fixture 10, and a current lead-out column 18 is provided at the bottom of the block fixture 10. A ceramic insulating plate 11 is provided between the block fixture 10 and the rotating beam 124. The block fixture 10 and the rotating beam 124 are connected by a special screw. The outer layer of the special screw is a ceramic material, and the center is an alloy steel material. It has a good insulation effect and can withstand a large torque and is not easy to be broken.

[0041] like Figure 3 and Figure 4 As shown, the top of the X-axis displacement platform 121 is equipped with a first positioning ball 15 and a second positioning ball 16, which are matched with the circular groove at the bottom of the rotating beam 124, respectively, to play the role of positioning and fixing. The rotating beam 124 is moved to the first positioning ball 15 and the second positioning ball 16 to respectively put the friction pair in a contact state and a separation state, which facilitates the loading and weighing of the block sample 9 during the test, and can accurately restore the position when the test is paused to continue the test. In this embodiment, the distance between the rotating shaft 14 and the pulley 126 at the end of the rotating beam 124 is twice the distance between the rotating shaft 14 and the block fixture 10. The pulley 126 at the end of the rotating beam 124 and the fixed beam 125 form a pulley group, and the loading force is four times the weight of the weight.

[0042] The testing machine of the present invention can simultaneously set the rotation speed of the motor 101 and the lifting frequency of the Z-axis electric lifting table 123, enabling the friction pair to complete either a single radial or tangential friction form, or both radial and tangential frictions simultaneously. By configuring appropriate motor rotation speed and the lifting frequency of the Z-axis electric lifting table, different friction trajectories can be presented by the block specimen 9 on the surface of the disc specimen 7.

[0043] The friction trajectory of the friction pair can be regarded as being composed of the compound motion of the motor rotation and the reciprocating up-and-down motion of the Z-axis electric lifting table. For the convenience of explanation in this embodiment, the motor rotation is simplified to a linear motion.

[0044] As Figure 6 shown, the method for designing a "zigzag" friction trajectory is as follows: Set the rotation speed V1 of the motor and the speed V2 of the Z-axis electric lifting table as constant values. The "zigzag" angle α is twice the θ in the figure. Since the "zigzag" angle can be obtained. By adjusting the rotation speed of the motor and the lifting speed of the Z-axis electric lifting table, the size of the "zigzag" angle α of the friction trajectory can be controlled, and the height of the "zigzag" of the friction trajectory is determined by the lifting stroke of the Z-axis electric lifting table. The "zigzag" friction path can be used to simulate the current-carrying friction and wear between the pantograph and the catenary wire in the high-speed rail pantograph-catenary system.

[0045] As Figure 7 shown, the method for designing an "S" - shaped friction trajectory is as follows: Set the rotation speed V1 of the motor as a constant value, and the speed of the Z-axis electric lifting table for lifting is: V2 = AcosT, where T is a lifting cycle, and A refers to the adjustment parameter of the lifting table speed magnitude. A determines the lifting stroke of the Z-axis electric lifting table, that is, controls the height of the "S" - shaped of the friction trajectory. At this time, the "S" - shaped friction path L is L = AsinT. The "S" - shaped friction path can be used to simulate the current-carrying friction and wear between the overhead rigid suspension and the pantograph in the overhead rigid suspension catenary system of urban rail transit subways. It should be noted that the design method of the "S" - shaped friction trajectory here is not the only method.

[0046] The test method of the present invention includes the following steps:

[0047] S1: Weigh the weight of the block specimen using an electronic analytical balance and install the block specimen on the block fixture 10;

[0048] S2: Fix the rotating crossbeam 124 at the first positioning ball 15. As Figure 3 shown, adjust the Y-axis displacement platform 122 and the Z-axis electric lifting table 123 to determine an appropriate contact position;

[0049] S3: Move the X-axis displacement platform 121 to bring the disk specimen 7 into close contact with the block specimen 9. After hanging the weight 127 for loading, turn down the first positioning ball 15 until it no longer serves the purpose of positioning and fixing.

[0050] S4: According to the test requirements, set the rotation speed of the motor 101 and the lifting frequency of the Z-axis electric lifting table 123, apply the set current, turn on the torque sensor, etc., and start the current-carrying friction and wear test.

[0051] S5: During the test, if it is necessary to weigh the block specimen, pause the movement of the motor 101 and the Z-axis electric lifting table 123, disconnect the current, lift the first positioning ball 15 and the second positioning ball 16, and move the rotating crossbeam 124 to the position of the second positioning ball 16. As Figure 4 shown, take out the block specimen and weigh it.

[0052] S6: After weighing, install the block specimen back to its original position in the block fixture 10, move the rotating crossbeam 124 back to the first positioning ball and turn it down, start the motor 101 and the Z-axis electric lifting table 123 and apply the current, and continue the current-carrying friction and wear test.

Claims

1. A high-speed and high-current sliding current-carrying friction and wear testing machine, characterized in that, It includes a driving device and a loading device. The output end of the driving device is connected to a first specimen, and a second specimen is installed on the loading device. The second specimen is driven to move up and down by the loading device. The first specimen and the second specimen are in contact to form a friction pair. The loading device includes a Z-axis electric lifting table, an X-axis displacement platform is installed above the Z-axis electric lifting table, and a rotating crossbeam and a fixed crossbeam are installed on the top of the X-axis displacement platform; The driving device and the loading device cooperate to generate different friction tracks of the second specimen on the surface of the first specimen. The friction track of the friction pair can be regarded as being composed of the rotation of the motor and the reciprocating movement of the Z-axis electric lifting table up and down: set the rotational speed V1 of the motor as a constant value, and the speed of the Z-axis electric lifting table for lifting and lowering is: V 2 =AcosT , where T is a lifting cycle, A refers to the adjustment parameter of the lifting table speed magnitude, A determines the lifting stroke of the Z-axis electric lifting table, that is, controls the height of the "S" shape of the friction track. At this time, the friction path L of the "S" shape is L=AsinT ; The output end of the driving device is connected to a torque sensor, the other end of the torque sensor is connected to a conductive slip ring, the other end of the conductive slip ring is connected to a first fixture, a first specimen is installed on the first fixture, and the other end of the first specimen is connected to a spherical plain bearing through a copper shaft. The spherical plain bearing and the copper shaft are in clearance fit, and a conductive lubricant is added between them, so that the contact resistance between the spherical plain bearing and the conductive copper shaft is small, playing a role in lubrication and enhancing conductivity; the spherical plain bearing also has the functions of support and alignment, which can compensate for the angular deviation of the copper shaft and suppress the outer circle runout of the copper shaft during high-speed rotation.

2. The high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 1, characterized in that A fixed ring is installed on the outer cylindrical surface of the first fixture and the first specimen.

3. A high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 1, characterized in that The spherical plain bearing is installed on a conductive copper plate, and a current introduction column is arranged on the conductive copper plate.

4. A high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 1, characterized in that, Pulleys are respectively installed at the same end parts of the rotating crossbeam and the fixed crossbeam, and a weight is connected below the pulley on the fixed crossbeam.

5. A high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 4, characterized in that, A laser displacement sensor is installed above the fixed crossbeam close to the pulley side.

6. The high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 4, characterized in that A three-axis acceleration sensor is installed at the other end of the rotating crossbeam far from the pulley.

7. A high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 6, characterized in that, A second fixture is installed at one end of the rotating crossbeam close to the disc specimen, a second specimen is clamped on the second fixture, and a current export column is arranged at the bottom of the second fixture.

8. A high-speed and high-current sliding current-carrying friction and wear testing machine according to claim 1, characterized in that, A first positioning ball and a second positioning ball are installed on the top of the X-axis displacement platform.

9. The test method of a high-speed and high-current sliding current-carrying friction and wear testing machine according to any one of claims 1 to 8, characterized in that, It includes the following steps: S1: Weigh the second specimen and install the second specimen on the second fixture; S2: Fix the rotating crossbeam at the first positioning ball, adjust the Y-axis displacement platform and the Z-axis lifting table to determine the contact position; S3: Move the X-axis displacement platform to make the first specimen and the second specimen in close contact. After hanging the weight for loading, screw down the first positioning ball until it no longer plays a role in positioning and fixing; S4: According to the test requirements, set the rotation speed of the driving device and the lifting frequency of the Z-axis lifting table, input the set current, turn on the torque sensor, and start the current-carrying friction and wear test; S5: During the test, if it is necessary to weigh the second specimen, pause the movement of the driving device and the Z-axis lifting table, disconnect the current, lift the first positioning ball and the second positioning ball, move the rotating crossbeam to the second positioning ball, take out the second specimen and weigh it; S6: After weighing, install the second specimen at the original position of the second fixture, move the rotating crossbeam back to the first positioning ball and screw it down, start the driving device and the Z-axis lifting table and input the current, and continue the current-carrying friction and wear test.

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