Angular Contact Bearing Friction Torque Testing Machine Based on Magnetic Levitation Bearing and Measurement Method

Abstract

The present invention relates to an angular contact bearing friction torque testing machine and a measurement method based on a magnetic levitation bearing. The testing machine includes a testing machine main body, a magnetic levitation bearing system, a variable frequency speed regulation system, and a test monitoring system. The magnetic levitation bearing system is used to control the axial floating of the main shaft, and the variable frequency speed regulation system is used to drive the main shaft to rotate. One end of the main shaft connected to the test bearing is provided with an upper clearance adjusting pad and an upper compression nut that can move with the main shaft. An upper collision gasket is arranged between the upper compression nut and the upper clearance adjusting pad. A second adjustment clearance is left between the inner ring of the test bearing and the outer cylindrical surface of the upper clearance adjusting pad, and a third adjustment clearance is provided between one end of the inner ring and the upper clearance adjusting pad. The other end of the inner ring is in contact with the upper collision gasket for transmission or separated to form a first adjustment clearance. The test monitoring system is used to monitor the rotational speed of the inner ring and the parking time. The accurate friction torque of the test bearing can be calculated based on the rotational speed and parking time of the inner ring, providing a theoretical basis for bearing design and process improvement.

Description

Technical Field

[0001] The present invention belongs to the field of bearing testing, and particularly relates to a friction torque testing machine and a measuring method for angular contact bearings based on magnetic suspension bearings. Background Art

[0002] Friction exists between two interacting objects, including between the molecules within the objects. Generally, it is divided into internal friction and external friction. Internal friction refers to the friction force existing between the molecules of a material. For example, the viscosity of a liquid, the vibration damping and vibration absorption of a solid, etc. are the results of the internal friction of the material. External friction refers to the friction force existing when two objects are in relative motion or have a tendency of relative motion, and is divided into dynamic friction and static friction. Friction always hinders the relative motion between objects. When there is a distance between the friction force and the instantaneous absolute velocity center of the moving object, a friction torque is generated. Friction force and friction torque exist in a rotating bearing, which hinders the movement of the bearing and generates frictional heat.

[0003] The magnitude of the bearing friction torque directly affects the bearing life and is an important factor affecting the reliability and accuracy of the main engine system. It is a main factor that must be considered during bearing design. The revolution of moving objects from sliding to rolling is precisely to reduce friction and improve the life and accuracy of moving objects. Domestic and foreign research on bearing friction attaches great importance. The dynamic design of bearings starts mainly from the friction torque.

[0004] The friction torque of a ball bearing is a very complex problem. It is not only related to the structural dimensions, geometric accuracy, material and heat treatment performance of the bearing itself, but also related to the working load, assembly accuracy, lubrication conditions and environmental parameters. It is a non-stationary periodic random process. Quantitative research and measurement of bearing friction torque have always been a cutting-edge topic in the world bearing industry and main engine units. At present, countries around the world have quantitative analysis requirements for the friction torque of precision bearings. The research purpose of bearing friction torque measurement technology is to study how to reasonably evaluate and accurately measure the bearing friction torque, provide a reliable means for improving bearing design parameters, improving processing technology and analyzing the influencing factors of bearing friction torque, so as to improve bearing quality, improve the accuracy of the main engine, and meet the technical requirements of the user unit for the friction performance of the bearing. This is of great significance to the development of cutting-edge science and technology and national defense construction. Summary of the Invention

[0005] The purpose of the present invention is to provide a friction torque testing machine and a measuring method for angular contact bearings based on magnetic suspension bearings, so as to accurately obtain the friction torque of angular contact bearings, provide a reliable basis for improving bearing design parameters and improving processing technology, and be beneficial to improving bearing quality and the accuracy of the main engine, and meet the technical requirements of the user unit for the friction performance of the bearing.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: An angular contact bearing friction torque testing machine based on a magnetic levitation bearing, comprising a testing machine main body, a magnetic levitation bearing system, a variable frequency speed regulation system, and a test monitoring system. The magnetic levitation bearing system is installed on the testing machine main body and is used to control the axial floating of the main shaft of the testing machine main body. The variable frequency speed regulation system is installed on the testing machine main body and is used to drive the main shaft to rotate. One end of the main shaft connected to the test bearing is provided with an upper clearance adjusting pad and an upper compression nut that can move along with the main shaft. The outer circular surface of the upper clearance adjusting pad is a stepped shaft surface. The upper compression nut is threadedly connected to the main shaft, and an upper collision gasket that can move along with the main shaft is arranged between the upper compression nut and the upper clearance adjusting pad. A second adjustment gap L2 is left between the inner ring of the test bearing and the small diameter section of the outer circular surface of the upper clearance adjusting pad. A third adjustment gap L3 is left between one end face of the inner ring and the stepped surface of the upper clearance adjusting pad. According to different axial positions of the main shaft, the other end of the inner ring contacts and transmits with the upper collision gasket or forms a first adjustment gap L1. The test monitoring system includes a speed sensor and a timer. The speed sensor is used to monitor the rotational speed of the inner ring of the test bearing, and the timer is used to record the parking time of the inner ring.

[0007] The quantitative relationship among the first adjustment gap L1, the second adjustment gap L2, and the third adjustment gap L3 is: L3>L1 = 2L2, and L1 is 0.55 mm - 0.75 mm.

[0008] As an option, a companion test bearing is installed at the other end of the main shaft relative to the test bearing.

[0009] Further, a lower collision ring that can move along with the main shaft is installed on the main shaft, and a fourth adjustment gap L4 is left between the inner ring of the companion test bearing and the outer circular surface of the lower collision ring.

[0010] Furthermore, the following quantitative relationship exists among the first adjustment gap L1, the second adjustment gap L2, the third adjustment gap L3, and the fourth adjustment gap L4: L3>L1 = 2L2 = 2L4, and L1 is 0.55 mm - 0.75 mm.

[0011] Specifically, the magnetic levitation bearing system includes a radial magnetic levitation bearing and an axial magnetic levitation bearing.

[0012] Further, two radial magnetic levitation bearings are provided and arranged at intervals along the axial direction of the main shaft. A large diameter section is provided on the main shaft part between the two radial magnetic levitation bearings. Two axial magnetic levitation bearings are provided and are respectively arranged opposite to the two end faces of the large diameter section on the main shaft.

[0013] As an alternative, the main shaft is vertically arranged, the test bearing and the accompanying test bearing are respectively arranged at the upper and lower ends of the main shaft, and a weight adjustment component is further connected to the lower part of the main shaft to increase and adjust the counterweight of the main shaft.

[0014] A method for measuring the frictional torque of an angular contact bearing based on a magnetic levitation bearing, which uses the above-mentioned testing machine. First, the motor of the variable frequency speed regulation system in the testing machine drives the main shaft to drive the inner ring of the test bearing to rotate to a preset speed. Then, the axial magnetic levitation bearing in the magnetic levitation bearing system is energized to apply magnetic force to float the main shaft. The upper gap adjustment gasket moves upward with the main shaft and pushes up the upper collision gasket and the upper compression nut, so that the upper collision gasket is separated from the inner ring of the test bearing. At the same time, the timer starts to record the parking time of the inner ring of the test bearing; according to the rotation speed and parking time of the inner ring of the test bearing, through , F = ma and M = F·L, the frictional torque M of the test bearing is calculated, where a is the acceleration, v t is the preset speed of the inner ring of the test bearing, v0 is the parking speed, m is the mass of the test bearing, F is the frictional force, and L is the lever arm of the frictional force.

[0015] While the motor drives the main shaft to rotate, the radial magnetic levitation bearing in the magnetic levitation bearing system is energized to apply magnetic force.

[0016] The beneficial effects of the present invention are as follows: The present invention can indirectly measure the value of the bearing frictional torque through a calculation formula by directly measuring the rotation speed of the inner ring of the test bearing driven by the motor-driven main shaft and measuring the time from the peak speed to parking. In the present invention, the magnetic levitation bearing system is used to optimize the transmission mode, which can ensure good centering and stability when the main shaft rotates, and can relatively easily achieve the interchange of roller bearings within a certain range, and can achieve the purpose of simplifying control, operation, analysis, calculation, etc.; the accurate measurement of time and speed more directly affects or makes the finally indirectly calculated frictional torque more accurate.

[0017] In the present invention, different bearing inner diameters can be installed by replacing the gap adjustment component, such as the upper gap adjustment gasket (the thickness of the adjustment gasket), etc., to achieve the applicability of bearings within a certain range, and also increase the practicability of the present invention. Brief Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of the testing machine described in the present invention;

[0019] Figure 2 is a schematic structural diagram of the installation of the test bearing in the present invention;

[0020] Figure 3 is a schematic structural diagram of the upper gap adjustment component of the test bearing in the present invention;

[0021] Figure 4 Schematic diagram of the installation structure of the magnetic levitation bearing in the present invention;

[0022] Figure 5 Schematic diagram of the installation structure of the test bearing in the present invention;

[0023] Figure 6 Schematic diagram of the structure of the lower clearance adjustment assembly of the test bearing in the present invention;

[0024] Figure 7 Schematic diagram of the structure of the weight adjustment assembly in the present invention;

[0025] Markings in the figure: 1 - lower base plate; 2 - L-shaped angle iron; 3 - upper base plate; 4 - lower flange.; 5 - housing; 6 - magnetic levitation bearing mounting seat; 7 - motor seat; 8 - motor water jacket; 9 - motor stator; 10 - motor rotor; 11 - motor balance ring; 12 - test bearing mounting seat; 13 - upper sensor seat; 14 - upper compression nut; 15 - upper collision gasket; 16 - upper gland.; 17 - upper clearance adjustment pad; 18 - limit protection plate; 19 - main shaft; 20 - radial magnetic levitation bearing; 21 - adjustment ring; 22 - axial magnetic levitation bearing; 23 - axial clearance adjustment ring; 24 - counterweight disk adjustment ring; 25 - counterweight disk; 26 - lower transition ring; 27 - counterweight disk compression cap; 28 - lower collision ring; 29 - test bearing mounting seat; 30 - lower sensor seat; 31 - lower protection ring; 32 - lower gland; 33 - lower compression nut; 34 - counterweight disk taper sleeve; 100 - test bearing; 200 - test bearing. Specific embodiments

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but it is not used as a basis for any limitation of the invention.

[0027] Embodiment 1: An angular contact bearing friction torque testing machine based on a magnetic levitation bearing, comprising a testing machine main body, a magnetic levitation bearing system, a variable frequency speed regulation system, and a test monitoring system.

[0028] As Figure 1 shown, the testing machine main body mainly includes a lower base plate 1, an upper base plate 3, a magnetic levitation bearing mounting seat 6, a motor seat 7, a test bearing mounting seat 12, a main shaft 19, a test bearing mounting seat 29, and a motor. The magnetic levitation bearing system includes a radial magnetic levitation bearing 20 and an axial magnetic levitation bearing 22.

[0029] The lower base plate 1 is firmly fixed to the ground. Two L-shaped angle irons 2 are fixed on the lower base plate 1 to support the whole testing machine together. An upper base plate 3 is fixedly connected to the upper ends of the two L-shaped angle irons 2. The upper surface of the upper base plate 3 is connected to the lower flange 4. The lower end of the housing 5 of the testing machine main body is fixed on the lower flange 4, and the upper end of the housing 5 is connected to the motor base 7. The accompanying test bearing mounting seat 29 is fixedly connected to the lower flange 4 through the lower transition ring 26. An accompanying test bearing 200 for protecting and supporting the main shaft 19 is installed in the accompanying test bearing mounting seat 29. The accompanying test bearing 200 adopts a deep groove ball bearing. A motor for driving the main shaft 19 to rotate is installed in the motor base 7. The motor stator 9 is fixedly connected to the motor base 7, and the motor rotor 10 is installed in the middle of the main shaft 19. The test bearing mounting seat 12 and the upper end of the motor base 7 are fixedly connected. The test bearing 100 in the test bearing mounting seat 12 is an angular contact ball bearing and is installed at the upper end of the main shaft 19.

[0030] As Figure 1 , 4 shown, a magnetic suspension bearing mounting seat 6 is further arranged in the housing 5. The two ends of the magnetic suspension bearing mounting seat 6 are respectively connected to the lower flange 4 and the motor base 7. An axial magnetic suspension bearing 22 and a radial magnetic suspension bearing 20 are arranged in the magnetic suspension bearing mounting seat 6. Two radial magnetic suspension bearings 20 are arranged and spaced up and down. The stator mounting seat of the radial magnetic suspension bearing 20 is installed on the inner side of the magnetic suspension bearing mounting seat 6. The stator of the radial magnetic suspension bearing 20 is installed in the stator mounting seat. Taking the main shaft 19 as the rotor of the radial magnetic suspension bearing 20, after the two radial magnetic suspension bearings 20 are electrified and magnetized, good centering of the main shaft 19 can be realized, so that the main shaft 19 rotates stably without large-scale oscillation. Two axial magnetic suspension bearings 22 are also arranged, located between the two radial magnetic suspension bearings 20 and spaced up and down. A large-diameter section is arranged on the main shaft 19. The upper axial magnetic suspension bearing 22 is arranged opposite to the upper end face of the large-diameter section, and the lower axial magnetic suspension bearing 22 is arranged opposite to the lower end face of the large-diameter section. By magnetizing and demagnetizing the two axial magnetic suspension bearings 22, the main shaft 19 can complete the process of floating by magnetic force and falling by gravity.

[0031] The main shaft 19 integrates a motor rotor, a clearance adjustment component and a weight adjustment component on the axis to form a rotating shaft system required for the test. The clearance adjustment component includes an upper clearance adjustment component and a lower clearance adjustment component.

[0032] As Figure 1-3As shown, the upper clearance adjustment assembly is arranged in the test bearing mounting seat 12, including an upper clamping nut 14, an upper collision gasket 15 and an upper clearance adjustment pad 17. An upper sensor seat 13 is arranged in the test bearing mounting seat 12 as needed to install necessary sensors, such as displacement, temperature, vibration sensors, etc. In the present invention, only the friction torque of the test bearing is tested, so it is temporarily not necessary to install sensors here. The upper clearance adjustment pad 17 is installed on the main shaft 19 and moves with the main shaft 19. The upper clearance adjustment pad 17 is a hollow stepped shaft, and its outer cylindrical surface is a stepped shaft surface. The test bearing 100 is located in the small diameter section of the stepped shaft surface. The outer ring of the test bearing 100 is installed on the upper sensor seat 13, and the lower end of the outer ring is supported on the upper limit protection plate 18 between the upper clearance adjustment pad 17 and the upper sensor seat 13. The outer ring of the test bearing and the upper sensor seat 13 are pressed by the upper pressure cover 16 of the test bearing mounting seat 12; as shown Figure 3 As shown, a second adjustment gap L2 is left between the inner ring of the test bearing 100 and the outer cylindrical surface of the upper clearance adjustment pad 17, and a third adjustment gap L3 is left between the inner ring and the step surface of the upper clearance adjustment pad 17. When the axial magnetic suspension bearing 22 is magnetized and demagnetized, the main shaft 19 can move axially relative to the inner ring of the test bearing 100. An upper clamping nut 14 and an upper collision gasket 15 are installed on the main shaft 19; the upper clamping nut 14 is threadedly connected to the main shaft 19, and the upper collision gasket 15 is pressed against the inner ring of the test bearing 100 and the upper end surface of the upper clearance adjustment pad 17. The upper collision gasket 15 is pre-tightened by the pre-tightening of the upper clamping nut 14 and the deadweight of the main shaft system. At this time, the upper collision gasket 15 contacts the end surface of the inner ring of the test bearing, thereby realizing the driving of the inner ring of the test bearing by the main shaft 19, and driving the inner ring of the test bearing to rotate to the set speed. When the axial magnetic bearing 22 is powered on and magnetized, the main shaft 19 floats upward, driving the upper collision gasket 15 to separate from the end face of the inner ring of the test bearing, and a first adjustment gap L1 is formed between the upper collision gasket 15 and the end face of the inner ring of the test bearing. In order to adapt to the size specifications of different test bearings, the end face of the upper collision gasket 15 can be adjusted so that the first adjustment gap L1 can reach the axial gap required by the experiment. Similarly, by adjusting the outer diameter and end face size of the upper gap adjustment pad, the second adjustment gap L2 and the third adjustment gap L3 can reach the radial gap and axial gap required by the test. When replacing the test bearing 100, it is necessary to replace the upper gap adjustment pad 17 to ensure that the gap size between the two meets the experimental requirements.

[0033] Continue to refer Figure 2 , 3 As shown, further, the maximum outer diameters of the upper clamping nut 14 and the upper collision gasket 15 are both smaller than the maximum diameter of the inner ring of the test bearing, that is, the movement of the inner ring and even the bearing ball can be observed from the outside, so as to facilitate speed measurement by the speed sensor.

[0034] likeFigure 1 , 5 As shown in Fig. 6, the lower clearance adjustment assembly includes a lower collision ring 28, a lower protective ring 31 and a lower compression nut 33. The lower collision ring 28 is sleeved and fixed at the lower end of the main shaft 19. The outer ring of the test bearing 200 is installed in the test bearing mounting seat 29 and axially positioned by the lower compression nut 33 and the lower protective ring 31. A fourth adjustment clearance L4 is left between the inner ring of the test bearing 200 and the lower collision ring 28. By machining the outer diameter of the lower compression nut 33, the fourth adjustment clearance L4 can meet the requirement of the radial clearance specified in the index. When replacing the test bearing 200, it is necessary to replace the lower compression nut 33 to ensure that the size of the fourth adjustment clearance meets the test requirements.

[0035] In the magnetic levitation bearing system of the present invention, the size of the air gap of the axial magnetic levitation bearing and the distance between the upper clearance adjustment pad and the inner ring of the test bearing should be coordinated with each other. If the distance between the upper clearance adjustment pad and the inner ring of the test bearing is too small, when the axial magnetic levitation bearing is magnetized and the main shaft floats up, the inner ring of the test bearing may also be lifted by the upper clearance adjustment pad. At this time, due to the external friction force on the inner ring of the bearing, not only the main friction torque of the test bearing cannot be measured, but it is more likely to damage the testing machine, bringing unnecessary potential safety hazards to personal safety and property losses.

[0036] Therefore, the following quantitative relationship exists among the first adjustment clearance L1, the second adjustment clearance L2, the third adjustment clearance L3 and the fourth adjustment clearance L4: L3 > L1 = 2L2 = 2L4 = s = 0.6 mm, where s is the air gap of the axial magnetic levitation bearing.

[0037] As Figure 1 , 7 shown, the weight adjustment assembly is used to add counterweights to the main shaft 19 and adjust the counterweights according to the test requirements. The weight adjustment assembly includes a counterweight disc 25, a counterweight disc adjustment ring 24, a counterweight disc compression cap 27 and a counterweight disc taper sleeve 34, etc. The counterweight disc 25 is installed on the outer cylindrical surface of the counterweight disc taper sleeve 34. The counterweight disc compression cap 27 presses the counterweight disc 25 and the counterweight disc taper sleeve 34 against the taper surface of the main shaft 19 through threads. The taper surface is machined with matching to ensure the fitting degree. Therefore, it can ensure that the centering accuracy of the counterweight disc 25 after installation is very high. The advantage of taper surface positioning is that the accuracy will not be lost after multiple disassembly and assembly. A lock screw is installed on the counterweight disc compression cap 27, and the screw presses against the end face of the counterweight disc taper sleeve 34 to prevent the counterweight disc 25 from loosening from the taper surface after high-speed rotation. The counterweight disc adjustment ring 24 is installed on the main shaft 19 and is located between the counterweight disc 25 and the lower radial magnetic levitation bearing 20, and is used to limit the distance between the counterweight disc 25 and the radial magnetic levitation bearing 20.

[0038] Based on the above structure, there are three loading methods for the testing machine main body to apply preload to the outer ring of the test bearing: one is to apply preload through a counterweight disk, one is to apply preload through an upper compression nut, and the weights of the main shaft and each component assembly can all be used as the preload for fixing the outer ring of the bearing.

[0039] The variable-frequency speed regulation system includes a variable-frequency speed regulation motor, a frequency converter, a speed feedback system, and a computer system. This part of the structure can be connected using commercially available products, so some parts of the structure are not shown in the figure. The variable-frequency speed regulation motor is the motor installed in the motor seat of the above-mentioned testing machine main body for driving the main shaft to rotate. The computer system establishes a connection with the frequency converter through the communication and speed feedback systems, can read the parameters in the frequency converter, and can send an instruction to adjust the motor speed to the frequency converter to control the output frequency of the frequency converter to meet the adjustable speed requirement of 200 - 1000 r / min as required. The variable-frequency speed regulation motor includes a motor rotor 10, a motor stator 9, a motor water jacket 8, a motor seat 7, a motor balance ring 11, etc.

[0040] The test monitoring system includes a speed sensor, a stopwatch, etc. The speed sensor used in this testing machine is an infrared speed measurement sensor, which is erected outside the testing machine through a bracket to monitor the rotational speed of the inner ring of the test bearing. The speed sensor emits a light beam that directly touches the inner ring of the bearing through the gap between the upper collision gasket and the upper gland to obtain an accurate rotational speed value, and then the stopwatch is used to indirectly measure the time from the peak speed to the stop of the bearing.

[0041] Example 2: When measuring the friction torque of an angular contact ball bearing using the testing machine of the present invention, after the motor in the testing machine drives the main shaft 19 to drive the inner ring of the test bearing 100 to rotate to a preset speed, the axial magnetic suspension bearing 22 is energized and magnetized to float the main shaft 19. The upper clearance adjustment pad 17 moves upward with the main shaft 19, pushing up the upper collision gasket 15 and the upper compression nut 14, causing the upper collision gasket 15 to separate from the inner ring of the test bearing 100. At this time, there is no external input friction on the inner ring of the test bearing 100 except for its own friction. At the same time, the computer system automatically starts timing. Timing stops until the speed sensor measures that the speed of the inner ring of the test bearing is zero, that is, when the inner ring of the test bearing freely stops. The time consumed for free parking is obtained. The bearing friction torque, as a load torque, will consume energy, and there is a linear relationship between the consumed energy and the bearing friction torque. The bearing friction torque can be obtained by measuring the energy consumed by the drive unit.

[0042] Furthermore, according to the rotational speed and parking time of the inner ring of the test bearing, through the formula: 、F = ma (a is the acceleration, v t(Where the preset rotational speed of the test bearing inner ring is \(v_0\), the parking rotational speed is \(v_0\), the mass of the test bearing is \(m\), and the frictional force is \(F\)), the frictional force \(F\) of the test bearing itself can be calculated, and then according to the formula: \(M = F\cdot L\), the frictional torque \(M\) of the test bearing can be calculated, where \(L\) is the lever arm.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Those of ordinary skill in the art should understand that the specific implementation manners of the present invention can be modified or equivalently replaced by referring to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims pending for approval.

Claims

1. Angular contact bearing friction torque testing machine based on magnetic levitation bearings, comprising a testing machine main body, a magnetic levitation bearing system, a variable frequency speed regulation system and a test monitoring system. The magnetic levitation bearing system is installed on the testing machine main body and is used to control the axial floating of the main shaft of the testing machine main body. The variable frequency speed regulation system is installed on the testing machine main body and is used to drive the main shaft to rotate. It is characterized in that: The main shaft is vertically arranged. At one end of the main shaft connected to the test bearing, an upper clearance adjusting pad and an upper compression nut capable of moving along with the main shaft are installed. The outer circumferential surface of the upper clearance adjusting pad is a stepped shaft surface. The upper compression nut is threadedly connected to the main shaft. An upper collision gasket capable of moving along with the main shaft is arranged between the upper compression nut and the upper clearance adjusting pad. A second adjusting clearance L2 is left between the inner ring of the test bearing and the small-diameter section of the outer circumferential surface of the upper clearance adjusting pad. A third adjusting clearance L3 is left between one end face of the inner ring and the stepped face of the upper clearance adjusting pad. According to different axial positions of the main shaft, a first adjusting clearance L1 is formed between the other end of the inner ring and the upper collision gasket. The quantitative relationship among the first adjusting clearance L1, the second adjusting clearance L2, and the third adjusting clearance L3 is: L3 > L1 = 2L2, and L1 is 0.55 mm - 0.75 mm. The magnetic levitation bearing system includes a radial magnetic levitation bearing and an axial magnetic levitation bearing. Two radial magnetic levitation bearings are provided and arranged at intervals along the axial direction of the main shaft. A large-diameter section is arranged on the part of the main shaft between the two radial magnetic levitation bearings. Two axial magnetic levitation bearings are provided and respectively arranged opposite to the two end faces of the large-diameter section on the main shaft. The motor of the variable frequency speed regulation system drives the main shaft to drive the inner ring of the test bearing to rotate to a preset speed. The axial magnetic levitation bearing is electrified to apply magnetic force to float the main shaft. The upper clearance adjusting gasket moves upward along with the main shaft and jacks up the upper collision gasket and the upper compression nut, so that the upper collision gasket is separated from the inner ring of the test bearing. The test monitoring system includes a speed sensor and a timer. The speed sensor is used to monitor the rotational speed of the inner ring of the test bearing, and the timer is used to record the parking time of the inner ring.

2. The angular contact bearing friction torque testing machine based on a magnetic levitation bearing according to claim 1, characterized in that: A companion test bearing is installed at the other end of the main shaft relative to the test bearing.

3. The angular contact bearing friction torque testing machine based on a magnetic levitation bearing according to claim 2, characterized in that: A lower collision ring capable of moving along with the main shaft is installed on the main shaft. A fourth adjusting clearance L4 is left between the inner ring of the companion test bearing and the outer circumferential surface of the lower collision ring.

4. The angular contact bearing friction torque testing machine based on a magnetic levitation bearing according to claim 3, characterized in that: The following quantitative relationship exists among the first adjusting clearance L1, the second adjusting clearance L2, the third adjusting clearance L3, and the fourth adjusting clearance L4: L3 > L1 = 2L2 = 2L4, and L1 is 0.55 mm - 0.75 mm.

5. The angular contact bearing friction torque testing machine based on a magnetic levitation bearing according to claim 2, wherein: The test bearing and the companion test bearing are respectively arranged at the upper and lower ends of the main shaft. A weight adjustment component is also connected to the lower part of the main shaft to increase and adjust the counterweight of the main shaft.

6. A method for measuring the frictional torque of angular contact bearings based on magnetic levitation bearings, characterized in that: This method is carried out using the testing machine described in any one of claims 1 to 5. First, the motor of the variable frequency speed regulation system in the testing machine drives the main shaft to drive the inner ring of the test bearing to rotate to a preset speed. Then, the axial magnetic levitation bearing in the magnetic levitation bearing system is energized to generate magnetic force to lift the main shaft. The upper clearance adjustment gasket moves upward with the main shaft and jacks up the upper collision gasket and the upper compression nut, so that the upper collision gasket is separated from the inner ring of the test bearing. At the same time, the timer starts to record the stopping time of the inner ring of the test bearing. According to the rotational speed and stopping time of the inner ring of the test bearing, the frictional torque M of the test bearing is calculated through , F = ma and M = F·L, where a is the acceleration, v t is the preset speed of the inner ring of the test bearing, v0 is the stopping speed, m is the mass of the test bearing, F is the frictional force, and L is the lever arm of the frictional force.

7. The method for measuring the frictional torque of an angular contact bearing based on a magnetic levitation bearing according to claim 6, wherein: While the motor drives the main shaft to rotate, the radial magnetic levitation bearing in the magnetic levitation bearing system is electrified to apply magnetic force.

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