A design method for a space long-life bearing assembly

Abstract

The present invention discloses a design method for a space long-life bearing assembly, comprising the following steps: S1, establishing a bearing dynamics analysis model; S2, optimizing the bearing dynamics analysis model for plastic deformation failure and long-term fatigue failure of the space bearing under harsh working conditions; S3, analyzing the wear life of the space composite material cage for wear failure of the composite material cage, and determining the cage material; S4, designing a supplementary oil supply setting for the space long-life bearing for lubrication failure caused by lubricating oil loss; S5, conducting a long-life test on the space bearing determined in the above steps to verify that the space bearing has long-life performance. The method of the present invention can improve the reliability of the space rotating mechanism, reduce mechanical system failures, improve platform operation accuracy, reduce maintenance requirements, and extend the service life of space equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite flywheel design, and in particular relates to a design method for a space long-life bearing. Background Art

[0002] With the development of my country's space technology and the improvement of earth observation requirements, satellite platform missions are becoming more and more diversified, and rotating mechanisms such as inertial actuators, torque compensation devices, and energy storage systems work simultaneously. As the core component of the rotating mechanism, the bearing characteristics, rotation accuracy, vibration characteristics, friction torque and other performance of rolling bearings are the basic guarantee for the normal operation of the space platform and the realization of the intended functions. At present, the service life of most space bearings is less than three years, and the service life of the bearings seriously restricts the long life demand of the whole machine.

[0003] The low pressure, low gravity, temperature changes, strong radiation, unmaintainable and other factors in the space environment, as well as the complex working conditions such as repeated speed changes, start / stop, swing, load mutations, coupling torque, etc. caused by the rapid maneuverability, rapid stability, and precise pointing requirements of satellite platforms, put great pressure on the bearing load characteristics and lubrication characteristics. Therefore, the failure mode of space bearings includes not only conventional fatigue failure, but also lubrication failure unique to the space environment, as well as operational instability under complex working conditions. Summary of the invention

[0004] The failure modes of existing space bearings include not only conventional fatigue failure, but also lubrication failure unique to the space environment and operational instability under complex working conditions. To address the above problems, the present invention provides a design method for a space long-life bearing assembly, comprising the following steps:

[0005] S1. Establish a bearing dynamics analysis model;

[0006] S2. Optimizing the bearing dynamics analysis model for the plastic deformation failure and long-term fatigue failure of the space bearing under harsh working conditions;

[0007] S3. Aiming at the wear failure of composite cage, the wear life analysis of space composite cage is carried out to determine the cage material;

[0008] S4. Design the supplementary oil supply setting for the space long life bearing to prevent lubrication failure caused by lubricating oil loss;

[0009] S5. Perform a long-life test on the space bearing determined in the above steps to verify that the space bearing has long-life performance.

[0010] Preferably, the bearing dynamics analysis model needs to include bearing assembly parameters, operating parameters, structural parameters, groove curvature coefficient, material parameters, and lubrication parameters.

[0011] Preferably, the step S2 further comprises the following steps:

[0012] S21. Calculate the maximum contact stress of the bearing under the severe working condition and determine that the maximum contact stress of the bearing is below the yield strength of the material of the spatial bearing.

[0013] S22. Aiming at the long-term fatigue failure of space bearings, calculate the bearing contact stress under normal working conditions to ensure that it is within the infinite life range of the bearing material.

[0014] Preferably, the step S21 further comprises the following steps:

[0015] S211, since the working load of the bearing is the largest under the severe working condition, based on the bearing dynamics analysis model established in step S1, the maximum contact stress of the bearing under the severe working condition is solved, and it is determined whether the maximum contact stress of the bearing under the severe working condition is below the yield strength of the bearing material;

[0016] S212. If the calculated maximum contact stress of the bearing under the severe working condition is less than the yield strength of the spatial bearing material, the next design step is performed; if the calculated maximum contact stress of the bearing under the severe working condition is greater than the yield strength of the spatial bearing material, the structural parameters in the bearing dynamics analysis model are optimized until the maximum contact stress of the bearing under the severe working condition is within the yield strength of the material used for the bearing.

[0017] Preferably, the severe operating conditions include the operating conditions of the entire machine under acceleration, the operating conditions when the bearing is impacted, and the operating conditions when the bearing is vibrating.

[0018] Preferably, the step S22 further comprises the following steps:

[0019] S221, based on the modified bearing dynamics analysis model in step S21, calculating the maximum contact stress of the bearing under normal operating conditions, and determining whether the maximum contact stress is within the infinite fatigue range of the bearing material;

[0020] S222. If the calculated maximum contact stress of the bearing under normal operating conditions is within the infinite life range of the bearing material, proceed to the next design step; if the calculated maximum contact stress of the bearing under normal operating conditions is not within the infinite life range of the bearing material, optimize the design of the modified bearing dynamics analysis model until the maximum contact stress of the bearing under normal operating conditions is within the infinite life range of the bearing material.

[0021] Preferably, the step S3 is specifically as follows: based on the optimized bearing dynamics analysis model described in S2, targeting the wear failure of the composite retainer, a friction and wear testing machine is used to simulate the working conditions of the retainer, a wear test is performed on the spatial composite retainer, and the retainer material is determined to be a porous polyimide composite material.

[0022] Preferably, the working condition of the cage that needs to be simulated by the friction and wear testing machine is determined by calculating the contact load, sliding speed and contact duration of the cage pocket and the guide surface.

[0023] Preferably, step S4 is specifically as follows: analyzing the lubrication state of the bearing according to the bearing dynamics analysis model determined in the above steps, determining the lubricating oil quantity requirement, and adopting a long-life oil replenishing device to ensure that the spatial bearing has sufficient lubricating oil supply during a long life cycle to meet the lubrication requirements and prevent lubrication failure.

[0024] Preferably, the oil supply supplement device is a porous oil storage ring, which is installed outside the bearing and is used to store oil and gradually release it into the bearing over a period of time.

[0025] In summary, the present invention provides a design method for a long-life bearing assembly adapted to space, and respectively targets four typical failure modes of long-life bearings in space, namely, plastic deformation failure under impact conditions of space bearings, fatigue failure under long-term operation, wear failure of composite retainers, and lubrication failure caused by loss of lubricating oil. Through dynamic simulation analysis, design parameter optimization, and tribological testing methods, a design process for long-life bearing assemblies in space is established, so that the maximum contact stress of the bearing does not exceed the yield strength of the material, ensuring that the bearing will not be plastically deformed, the bearing parameters are optimized so that the bearing material will not be fatigue-failed, the wear rate of the retainer material is tested to ensure that the retainer will not be worn, and a supplementary oil supply device is used to ensure that the bearing will not be lubricated. Through design and testing, it is ensured that the bearing will not be plastically deformed when subjected to impact loads, fatigue failure will not occur in long-term operation, composite retainers will not be worn, and lubricants can be continuously replenished, and finally it is ensured that the bearing will not produce corresponding failure forms under any working conditions, so that the space bearing can operate with high reliability for 5 to 8 years, improve the reliability of the space rotating mechanism, reduce mechanical system failures, improve the platform operation accuracy, reduce maintenance requirements, and extend the service life of space equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a design process of a design method for a space long-life bearing assembly according to the present invention;

[0027] Figure 2 It is a schematic diagram of the bearing dynamics analysis model in the present invention;

[0028] Figure 3: is a contact stress analysis diagram of a bearing under an impact load in an embodiment of the present invention;

[0029] Figure 4 This is a contact stress analysis diagram of a bearing under normal operating conditions in an embodiment of the present invention;

[0030] Figure 5 This is a diagram for analyzing the thickness of the bearing lubricating film in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention Figure 1 to Figure 5 , the technical solutions, structural features, objectives achieved and effects in the embodiments of the present invention are described in detail.

[0032] It should be noted that the drawings are in a very simplified form and use non-precise proportions. They are only used to conveniently and clearly assist in explaining the embodiments of the present invention, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention.

[0033] It should be noted that, in the present invention, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only the elements explicitly listed, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0034] A design method for long-life space bearing components is proposed. The design process of long-life space bearing components is established for four typical failure modes of long-life space bearings, namely, plastic deformation failure under harsh working conditions, fatigue failure due to long-term operation, wear failure of composite material cages, and lubrication failure caused by lubricant loss. Figure 1 As shown, the following steps are included:

[0035] S1. Establish a bearing dynamics analysis model;

[0036] like Figure 2As shown, the stress state of each rolling element in the bearing is analyzed, and a bearing dynamics analysis model under weightlessness conditions is established. The model includes bearing assembly parameters, operating parameters, structural parameters, groove curvature coefficients, material parameters, lubrication parameters, etc.; the bearing dynamics analysis model specifically includes the balance equation of each bearing rolling element, the balance equation of the bearing ring, and the oil film thickness obtained according to the Dawson-Higkinson formula. Since the design and calculation of the model can be analyzed based on existing formulas and methods, the calculation process will not be listed in detail below.

[0037] S2. Optimizing the bearing dynamics analysis model in view of the plastic deformation failure and long-term fatigue failure of the space bearing under harsh working conditions;

[0038] By optimizing the bearing dynamics analysis model, it is ensured that the designed spatial bearing will not undergo plastic deformation and the bearing material will not fail due to fatigue.

[0039] S21. Calculate the maximum contact stress of the bearing under severe working conditions to ensure that it is within the yield strength of the material;

[0040] S211. Since the working load of the bearing is the largest under severe working conditions, based on the bearing dynamics analysis model established in step S1, the maximum contact stress of the bearing under severe working conditions is solved, and it is determined whether the maximum contact stress of the bearing under severe working conditions is within the allowable stress range of the bearing material, that is, whether the maximum contact stress of the bearing under severe working conditions is less than the yield strength of the bearing material; the severe working conditions include the working conditions of the whole machine under acceleration, the working conditions when the bearing is impacted, the working conditions of the bearing when vibrating, etc.

[0041] S212, if the calculated maximum contact stress of the bearing under the bad working condition is less than the yield strength of the spatial bearing material, the next design step is performed. If the calculated maximum contact stress of the bearing under the bad working condition is greater than the yield strength of the spatial bearing material, the structural parameters in the bearing dynamics analysis model are modified; and then the maximum contact stress of the bearing under the bad working condition is calculated again until the calculated maximum contact stress of the bearing under the bad working condition is within the yield strength of the material used for the bearing.

[0042] The structural parameters include the span of the bearing assembly, the bearing ball diameter, the groove curvature coefficient, the initial clearance, the pitch circle diameter and other parameters.

[0043] This embodiment uses the impact on the bearing as a severe working condition to calculate the maximum contact stress of the bearing, such as Figure 3As shown, by modifying the structural parameters and calculating the maximum contact stress of the bearing designed in this embodiment under the impact state, the bearing is 2600MPa, while the yield strength of the spatial bearing material used in this embodiment is 3700MPa, which is greater than the calculated maximum contact stress. Therefore, it can be determined that the bearing will not undergo impact plastic deformation.

[0044] S22. Calculate the bearing contact stress under normal operating conditions to ensure that it is within the infinite life range of the bearing material;

[0045] S221, based on the bearing dynamics analysis model modified in step S21, calculating the maximum contact stress of the bearing under normal operating conditions, and determining whether the maximum contact stress is within the infinite fatigue range of the bearing material;

[0046] S222. If the calculated maximum contact stress of the bearing under normal operating conditions is within the infinite life range of the bearing material, proceed to the next design step; if the calculated maximum contact stress of the bearing under normal operating conditions is not within the infinite life range of the bearing material, then according to the material fatigue theory, the structural parameters, preload force and other parameters of the modified bearing dynamics analysis model are optimized and designed until the maximum contact stress of the bearing under normal operating conditions is within the infinite life range of the bearing material, so as to ensure that the designed spatial bearing will not suffer fatigue failure.

[0047] The infinite fatigue life threshold of the bearing material in this embodiment is 1960Mpa. Figure 4 The figure shows the maximum contact stress of the bearing under different preload forces of this embodiment. It is finally determined that the curvature coefficient of the outer ring groove and the curvature coefficient of the inner ring groove of the designed bearing are 0.525 and 0.52 respectively, the preload force is 160N, and the maximum contact stress of the bearing is calculated to be 1733MPa. The infinite fatigue life limit of the material is 1960MPa, and the maximum contact stress of the bearing of 1733MPa is within the infinite fatigue life range of the material, so it will not cause fatigue failure of the bearing material.

[0048] S3. Analyze the wear life of space composite cages and select appropriate cage materials;

[0049] Based on the optimized bearing dynamics analysis model described in S2, a friction and wear testing machine is used to simulate the working conditions of the composite cage for wear failure, and a wear test is conducted on the spatial composite cage to determine the appropriate cage material; wherein the contact load, sliding speed and contact time of the cage pocket and guide surface are calculated to determine the parameters of the friction and wear testing machine to simulate the working conditions of the cage.

[0050] The cage material is a composite material of porous polyimide. The friction and wear performance of porous polyimide cage materials with different formulations is tested by a friction and wear tester: 12mm×12mm×20mm rectangular sample materials with different formulations are used, and the friction force is measured by a Timken tester. The speed is set to 1000r / min, the load is 7.58N, the friction force is measured every 2min, and the operation is 10min. After 10min, the width of the wear scar of the sample is tested, and the influence table of different formulations on the friction and wear performance of porous polyimide cage materials as shown in Table 1 is obtained. It can be seen from Table 1 that under the same molding and sintering process conditions, as the content of polytetrafluoroethylene in the cage composite material decreases, the wear scar of the composite material becomes narrower and the wear resistance is improved; the smaller the content of polytetrafluoroethylene, the greater the friction force and the friction coefficient, but the wear scar becomes narrower and the wear resistance is enhanced. Therefore, it is determined that the formulation of 95% polyimide + 5% polytetrafluoroethylene is used as the cage material.

[0051] Table 1 Effect of different formulations on friction and wear properties

[0052]

[0053] S4. Design the supplementary oil supply setting for the space long life bearing;

[0054] Aiming at the situation that lubrication failure occurs due to loss of lubricating oil in spatial bearings after running for a period of time, a supplementary oil supply device is designed.

[0055] The lubrication state of the bearing is analyzed according to the bearing dynamics analysis model determined in the above steps to determine the amount of lubricating oil required to achieve good lubrication. A long-life oil replenishment device is used to ensure that the spatial bearing has sufficient lubricating oil supply over a long life cycle to meet lubrication needs and prevent lubrication failure.

[0056] In this embodiment, the bearing lubrication state is analyzed based on the bearing dynamics analysis model determined by S2, and the lubrication film thickness is obtained as follows: Figure 5 As shown in the figure, the horizontal axis is the film thickness ratio and the vertical axis is the film thickness. From the figure, it can be seen that the minimum film thickness of the bearing dynamics model is 0.34μm, and the minimum film thickness ratio λ is 4.2, indicating that when the lubricating oil supply is sufficient, the operating condition of the bearing friction interface can form elastohydrodynamic lubrication.

[0057] Considering the loss of lubricating oil under long service life, a porous oil storage ring is used as a supplementary oil supply device, which is installed outside the bearing to store a large amount of oil and slowly release it into the bearing over a long period of time; the porous material is porous polyimide, and the porous oil storage ring is fixed on the stationary outer spacer. In the initial operation of the control moment gyro, the lubricating oil in the bearing raceway and the retaining frame can ensure the lubrication of the bearing. After a period of time, the lubricating oil in the oil storage ring gradually enters the bearing to supplement the lubrication of the bearing, fully ensuring the life of the bearing. The initial oil content of the oil storage ring is 13% to 19%, which increases the oil atmosphere in the bearing assembly cavity. Supplementing lubrication of the bearing with a trace amount of oil atmosphere is an effective measure to ensure that the bearing always has a good lubrication state, improve the reliability of the bearing and extend the service life. The test results of the oil content of the oil storage ring are shown in Table 2.

[0058] Table 2 Test results of oil content of oil storage ring

[0059] serial number Weight before oil immersion (g) Weight after oil dumping (g) Oil content (g) Oil content (%) 1 6.1165 7.06616 0.95451 15.62 2 6.1134 7.02131 0.90997 14.90 3 6.17857 7.06395 0.88538 14.33 4 6.24921 7.26034 1.0113 16.18

[0060] S5. Conduct long life test of space bearings;

[0061] According to the actual use conditions, a 1:1 life test is carried out on the space long-life bearing assembly determined through the above steps to verify that the space bearing has long-life performance.

[0062] The spatial bearing designed by the above method can effectively avoid four failure modes: plastic deformation failure under harsh working conditions, fatigue failure due to long-term operation, wear failure of composite material cage, and lubrication failure due to lubricating oil loss. The spatial bearing can operate reliably for 5 to 8 years, which is a significant improvement compared with the existing technology.

[0063] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A design method for a space long-life bearing assembly, characterized in that: The following steps are involved: S1. Establish a bearing dynamics analysis model; S2. Optimizing the bearing dynamics analysis model for the plastic deformation failure and long-term fatigue failure of the space bearing under harsh working conditions; S3. Aiming at the wear failure of composite cage, the wear life analysis of space composite cage is carried out to determine the cage material; S4. Design the supplementary oil supply setting for the space long life bearing to prevent lubrication failure caused by lubricating oil loss; S5. Perform a long life test on the space bearing determined in the above step to verify that the space bearing has long life performance; The step S2 comprises the following steps: S21. Calculate the maximum contact stress of the bearing under the severe working condition and determine that the maximum contact stress of the bearing is below the yield strength of the material of the spatial bearing. S22. For the long-term fatigue failure of space bearings, calculate the bearing contact stress under normal working conditions to ensure that it is within the infinite life range of the bearing material; The step S21 comprises the following steps: S211, since the working load of the bearing is the largest under the severe working condition, based on the bearing dynamics analysis model established in step S1, the maximum contact stress of the bearing under the severe working condition is solved, and it is determined whether the maximum contact stress of the bearing under the severe working condition is below the yield strength of the bearing material; S212. If the maximum contact stress of the bearing under the severe working condition is calculated to be less than the yield strength of the spatial bearing material, the next step of design is performed; if the maximum contact stress of the bearing under the severe working condition is calculated to be greater than the yield strength of the spatial bearing material, the structural parameters in the bearing dynamics analysis model are optimized and designed until the maximum contact stress of the bearing under the severe working condition is within the yield strength of the material used for the bearing; The step S22 comprises the following steps: S221, based on the bearing dynamics analysis model modified in step S21, calculating the maximum contact stress of the bearing under normal operating conditions, and determining whether the maximum contact stress is within the infinite fatigue range of the bearing material; S222. If the calculated maximum contact stress of the bearing under normal operating conditions is within the infinite life range of the bearing material, proceed to the next design step; if the calculated maximum contact stress of the bearing under normal operating conditions is not within the infinite life range of the bearing material, optimize the design of the modified bearing dynamics analysis model until the maximum contact stress of the bearing under normal operating conditions is within the infinite life range of the bearing material.

2. A method for designing a spatial long-life bearing assembly as claimed in claim 1, characterized in that: The bearing dynamics analysis model must include bearing assembly parameters, operating parameters, structural parameters, groove curvature coefficients, material parameters, and lubrication parameters.

3. The design method of a spatial long-life bearing assembly according to claim 1, characterized in that: The severe working conditions include the working conditions of the whole machine under acceleration, the working conditions when the bearing is impacted, and the working conditions when the bearing is vibrating.

4. The design method of a spatial long-life bearing assembly according to claim 1, characterized in that: The step S3 is specifically as follows: based on the optimized bearing dynamics analysis model described in S2, targeting the wear failure of the composite cage, a friction and wear testing machine is used to simulate the working conditions of the cage, a wear test is performed on the spatial composite cage, and the cage material is determined to be a porous polyimide composite material.

5. A method for designing a spatial long-life bearing assembly as claimed in claim 4, characterized in that: By calculating the contact load, sliding speed and contact duration of the cage pocket and the guide surface, the parameters of the friction and wear testing machine are determined to simulate the working condition of the cage.

6. The design method of a spatial long-life bearing assembly according to claim 1, characterized in that: The step S4 is specifically as follows: analyzing the lubrication state of the bearing according to the bearing dynamics analysis model determined in the above steps, determining the lubricating oil quantity requirement, and using a long-life oil replenishing device to ensure that the spatial bearing has sufficient lubricating oil supply during a long life cycle to meet the lubrication requirements and prevent lubrication failure.

7. A method for designing a spatial long-life bearing assembly as claimed in claim 6, characterized in that: The oil supply supplement device is a porous oil storage ring, which is installed outside the bearing and is used to store oil and gradually release it into the bearing within a period of time.

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