Active oil replenishment method and system for space momentum wheel bearing based on oil film thickness

Abstract

The present invention provides a method and system for actively replenishing oil for a space momentum wheel bearing based on oil film thickness, comprising: according to the target oil film thickness h of the momentum wheel bearing to achieve lubrication under all possible service conditions L Establish a target oil film thickness database; obtain the current oil film thickness h by monitoring or calculation L , at the current oil film thickness h L Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h L Reach target oil film thickness h L The present invention can actively replenish oil according to the lubricating oil film thickness required by the operating conditions of the bearing, thereby ensuring that the momentum wheel is in a low friction torque and meets the long service life performance.

Description

Technical Field

[0001] The present invention relates to the field of automation control, and in particular to an active oil replenishment method and system for a space momentum wheel bearing based on oil film thickness. Background Art

[0002] The regulation of the lubrication performance of the momentum wheel bearing is of great significance to the satellite attitude control. Its means mainly include passive oil replenishment and active oil replenishment. Among them, the passive oil replenishment method mainly includes seepage and diversion. During service, it relies on centrifugal action, temperature gradient or adjustment of the surface energy of the lubricating oil channel to drive the lubricating oil to move to the lubrication area to provide lubrication. This oil replenishment method depends on the operating conditions such as the bearing speed and temperature. It is difficult to control and there are problems such as untimely oil supply or premature exhaustion of stored lubricating oil. Active oil replenishment uses an active (forced) lubrication system to provide controllable lubricating oil to the bearing under external command. The current active oil replenishment strategy is determined according to the temperature or energy consumption of the system. When the friction torque increases, resulting in the temperature rise of the momentum wheel bearing and the increase of the motor rotation energy consumption, the active lubrication system is driven to provide lubrication to the bearing through an actuator (such as an electromagnetic generator, a stepper motor, etc.) (Sathyan K, Gopinath K, Hsu HY, et al. Development of a positive lubrication system for space application [J]. Tribology Online, 2010, 5 (1): 40–45.). However, the increase in friction torque is not entirely caused by insufficient lubrication. For example, when the bearing is fully lubricated, an increase in load will also lead to an increase in friction torque. At this time, active lubrication cannot reduce the friction torque, but will lead to premature consumption of lubricating oil, which is not conducive to the long-term lubrication performance requirements of the momentum wheel bearing. For this reason, considering the limited lubricating oil reserves of the bearing assembly, it is necessary to consider the effective lubrication of the bearing, and propose an active oil replenishment strategy for the momentum wheel bearing, while ensuring the low friction torque and long service life of the momentum wheel. Summary of the invention

[0003] In view of the defects in the prior art, an object of the present invention is to provide a method and system for actively replenishing oil of a spatial momentum wheel bearing based on oil film thickness.

[0004] According to the present invention, a method for actively replenishing oil for a space momentum wheel bearing based on oil film thickness comprises:

[0005] Database establishment steps: According to the target oil film thickness h of the momentum wheel bearing under all possible service conditions L Establish target oil film thickness database;

[0006] The first oil replenishment step: When the momentum wheel bearing has the ability to monitor the oil film thickness in real time, the current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L ;

[0007] Second oil replenishment step: When the momentum wheel bearing does not have the ability to monitor the oil film thickness in real time, the current oil film thickness h under the current service condition is calculated in real time. t , the calculated current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L .

[0008] Preferably, the method for calculating the current oil film thickness includes: calculating the lateral flow rate Q of all rolling element raceway contact areas at a certain moment s , Rolling lubricant evaporation rate Q E , the flow rate Q of lubricating oil return during the interval R and the lubricating oil supply rate Q of the porous cage under centrifugal and thermal effects PS ;

[0009] Current oil film thickness h t The calculation method is:

[0010]

[0011] Among them, h t0 is the oil film thickness at the center of the contact area between the raceway and the rolling element at the initial moment, Q AS is the active oil supply flow, S ci and S co are the contact areas of the inner and outer ring raceways and rolling elements of the bearing, respectively, and S i , S o It refers to the area where lubricating oil is distributed on the inner and outer raceways of the bearing.

[0012] Preferably, the evaporation rate of the raceway lubricating oil Q E The calculation method is:

[0013] Q E =(S i +S o )m evp

[0014] Among them, S i , S oare the raceway surface areas of the inner and outer rings of the bearing, m evp It is the evaporation rate of the lubricating oil at the operating temperature and the corresponding service environment vacuum.

[0015] Preferably, the flow rate Q of the lubricating oil return during the interval time is R The calculation method is:

[0016]

[0017] S c is the contact area between the raceway and rolling element of the inner and outer rings of the bearing, Δt is the interval time, h Δt is the oil film thickness in the contact center area after the reflux interval time Δt, h0 is the oil film thickness in the contact center area before reflux, and the summation symbol represents the need to calculate the distribution change of the oil film thickness of the corresponding raceways of the inner and outer rings respectively, and then sum them up to get the reflux flow rate.

[0018] Preferably, the lubricating oil supply rate Q of the porous cage under centrifugal and thermal effects is PS The calculation method is:

[0019]

[0020] f(λ) is the pore size distribution density per unit area of ​​the porous cage, S1 is the outer ring area of ​​the porous cage, S2 is the contact area between the cage and the rolling element, Centrifugal action capillary oil flow rate with diameter λ, is the oil flow rate of a capillary tube with a diameter of λ under thermal effect.

[0021] According to the present invention, a spatial momentum wheel bearing active oil replenishment system based on oil film thickness is provided, comprising:

[0022] Database establishment module: Target oil film thickness h for lubrication under all possible service conditions of momentum wheel bearings L Establish target oil film thickness database;

[0023] The first oil replenishment module: When the momentum wheel bearing has the ability to monitor the oil film thickness in real time, the current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L ;

[0024] The second oil replenishment module: when the momentum wheel bearing does not have the ability to monitor the oil film thickness in real time, the current oil film thickness h under the current service condition is calculated in real time t , the calculated current oil film thickness ht Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L .

[0025] Preferably, the current thickness calculation module includes: calculating the lateral flow rate Q of all rolling element raceway contact areas at a certain moment s , Rolling lubricant evaporation rate Q E , the flow rate Q of lubricating oil return during the interval R and the lubricating oil supply rate Q of the porous cage under centrifugal and thermal effects PS ;

[0026] Current oil film thickness h t The calculation method is:

[0027]

[0028] Among them, h t0 is the oil film thickness at the center of the contact area between the raceway and the rolling element at the initial moment, Q AS is the active oil supply flow, S ci and S co are the contact areas of the inner and outer ring raceways and rolling elements of the bearing, respectively, and S i , S o It refers to the area where lubricating oil is distributed on the inner and outer raceways of the bearing.

[0029] Preferably, the evaporation rate of the raceway lubricating oil Q E The calculation method is:

[0030] Q E =(S i +S o )m evp

[0031] Among them, S i , S o are the raceway surface areas of the inner and outer rings of the bearing, m evp It is the evaporation rate of the lubricating oil at the operating temperature and the corresponding service environment vacuum.

[0032] Preferably, the flow rate Q of the lubricating oil return during the interval time is R The calculation method is:

[0033]

[0034] S c is the contact area between the raceway and rolling element of the inner and outer rings of the bearing, Δt is the interval time, h Δtis the oil film thickness in the contact center area after the reflux interval time Δt, h0 is the oil film thickness in the contact center area before reflux, and the summation symbol represents the need to calculate the distribution change of the oil film thickness of the corresponding raceways of the inner and outer rings respectively, and then sum them up to get the reflux flow rate.

[0035] Preferably, the lubricating oil supply rate Q of the porous cage under centrifugal and thermal effects is PS The calculation method is:

[0036]

[0037] f(λ) is the pore size distribution density per unit area of ​​the porous cage, S1 is the outer ring area of ​​the porous cage, S2 is the contact area between the cage and the rolling element, Centrifugal action capillary oil flow rate with diameter λ, is the oil flow rate of a capillary tube with a diameter of λ under thermal effect.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention considers the factors affecting the lateral flow, evaporation, reflux of the lubricating oil in the raceway of the space momentum wheel bearing, as well as the oil supply and active oil supply of the porous cage, and can predict the change of the raceway oil film thickness during the operation of the bearing;

[0040] (2) The active oil replenishment strategy of the momentum wheel bearing based on the target oil film thickness of the present invention can meet the lubrication requirements of the raceway / rolling element contact area without causing the lubricating oil to be exhausted too quickly, thereby ensuring the long-life lubrication requirements of the bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0042] Figure 1 It is a schematic diagram of rolling element raceway contact;

[0043] Figure 2 Schematic diagram of initial oil film thickness and oil film thickness after confluence;

[0044] Figure 3 This is a flow chart of the active oil replenishment strategy. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0046] The purpose of the active oil replenishment strategy is to ensure that the rolling element / raceway of the momentum wheel bearing is in the (elastic-hydrodynamic) hydrodynamic lubrication state during service. The corresponding indicator is that the lubricating oil film thickness on the raceway surface should be greater than or equal to the minimum film thickness required for (elastic-hydrodynamic) hydrodynamic lubrication during the rolling element / raceway motion contact process. Considering that the factors affecting the oil film thickness of the raceway of the spatial momentum wheel bearing mainly include lateral flow, raceway lubricating oil evaporation, lubricating oil reflux, porous cage oil supply, and active oil supply, the present invention proposes an active oil replenishment strategy for the spatial momentum wheel bearing based on the oil film thickness. By monitoring or predicting the current oil film thickness in the rolling element / raceway contact area, the target oil film thickness h required for the current bearing operating condition is calculated. L And compare it with the current oil film thickness to determine whether to actively replenish oil and the corresponding amount of oil replenishment. Among them, the target oil film thickness h L The contact load and relative motion speed information between the rolling element and the raceway can be calculated according to the bearing service conditions, and then obtained by solving the Reynolds equation.

[0047] In the case of limited lubricating oil reserves, in order to meet the long-life lubrication requirements of space momentum wheel bearings, the present invention proposes an active oil replenishment method for space momentum wheel bearings based on oil film thickness. The specific implementation method is shown in the attached Figure 3 As shown, the description is as follows:

[0048] Step 1: Obtain all possible service conditions of the momentum wheel bearing, calculate the relative motion speed and contact load between the rolling element / raceway, solve the Reynolds equation of the rolling element / raceway contact area based on elastohydrodynamic lubrication and hydrodynamic lubrication, obtain the minimum oil film thickness for lubrication, and thus establish a target oil film thickness database, so that the controller can quickly obtain the bearing target oil film thickness h from the database according to the momentum wheel speed, output torque and other operating condition information L .

[0049] Step 2: Determine whether the momentum wheel bearing assembly has the ability to monitor the raceway oil film thickness in real time during service. If yes, proceed to the next step; otherwise, jump to step 5.

[0050] Step 3: Monitor the current raceway oil film thickness h t .

[0051] Step 4: Input the current momentum wheel speed, output torque and other operating condition information to obtain the target oil film thickness h L , and the current raceway oil film thickness h t If the target oil film thickness h L Greater than h t , the controller gives an active oil replenishment instruction, drives the active oil replenishment device to perform active oil replenishment, and then jumps to step 3.

[0052] Step 5: For all possible operating conditions of the bearing during the service of the momentum wheel, calculate the lubricating oil flow rate Q under the operating conditions according to equations (2), (3), (5), and (8): s , Q E , Q R , Q PS , establish a lubricating oil flow database.

[0053] Step 6: Combine the information of momentum wheel speed, output torque, initial oil film thickness, cage oil storage capacity, and active oil replenishment information during the service process, and quickly calculate the current raceway oil film thickness h according to formula (9): t .

[0054] Step 7: Input the current momentum wheel speed, output torque and other operating condition information to obtain the target oil film thickness h L , and the current raceway oil film thickness h t If the target oil film thickness h L Greater than h t , calculate the volume of lubricating oil that needs to be replenished, then control the active oil replenishment device to replenish the oil according to the given lubricating oil volume, and record the active oil replenishment information, and jump to step 6.

[0055] (1) Lateral flow

[0056] As attached Figure 1 As shown in the figure, when the rolling element passes through the raceway contact area, the lubricating oil in the middle area of ​​the raceway will move in the lateral direction under the combined effect of the dynamic pressure effect and the velocity flow, that is, lateral flow. For any rolling element, the lateral flow rate generated is calculated as:

[0057]

[0058] Where ρ is the density of the lubricating oil, η is the dynamic viscosity of the lubricating oil, V is the speed of the rolling element relative to the raceway in the oil film area, h is the oil film thickness distribution, and p is the oil film pressure distribution, which can be calculated by elastohydrodynamic lubrication; y - ,y + are the upper and lower boundaries of the lubrication area at different x positions along the y direction, x0, x e are the two boundaries of the lubricating oil along the x direction. Then the lateral flow rate of all rolling element raceway contact areas at a certain moment is:

[0059]

[0060] Where N is the number of rolling elements.

[0061] (2) Evaporation of raceway lubricating oil

[0062] The evaporation rate of the raceway lubricant can be calculated as:

[0063] Q E =(S i +S o )m evp (3)

[0064] Among them, S i , S o are the raceway surface areas of the inner and outer rings of the bearing, m evp It is the evaporation rate of the lubricating oil at the operating temperature and the corresponding service environment vacuum, which can be measured through ground tests.

[0065] (3) Lubricating oil reflux

[0066] After the rolling element passes through the raceway of the bearing surface, it will leave an oil film distribution with a low center and high sides in the original area. Figure 2 As shown in the gray curve, the oil film thickness in the contact center area before reflux is h0. The volume force and surface tension in the height direction will drive the oil film thickness to redistribute, that is, the lubricating oil refluxes. The control equation of the oil film thickness during the lubricating oil reflux process is as follows:

[0067]

[0068] Among them, f z is the acceleration corresponding to the volume force acting on the unit mass of fluid particles along the z direction, p a is the ambient gas pressure, and σ is the surface tension coefficient of the lubricating oil. According to the interval time Δt between two adjacent rolling elements in the same raceway area, the oil film thickness in the raceway contact center area after Δt is obtained by solving equation (4): Δt , then the flow rate of lubricating oil return during the interval is Q R It can be calculated as:

[0069]

[0070] Among them, S c is the area of ​​the contact area between the raceway and the rolling element corresponding to the inner and outer rings of the bearing, which can be approximated as the product of the arc circumference of the center of the raceway contact area and the distribution length of the contact area along the y direction. The summation symbol in the above formula represents the need to calculate the distribution change of the oil film thickness of the raceway corresponding to the inner and outer rings respectively, and then sum them to get the reflux flow rate.

[0071] (4) Oil supply to porous cage

[0072] The porous cage contains interconnected holes that can be used to store lubricating oil, so it is used in the lubrication system of aerospace bearing components. The hole structure inside the porous cage can be regarded as a combination of many capillaries. Due to the centrifugal effect, the oil supply flow rate of the capillary with a diameter of λ is calculated as follows:

[0073]

[0074] The first term on the right side of the above equation represents the centrifugal effect, and the second term represents the surface tension effect. τ(λ) represents the tortuosity of the capillary, m λ is the mass of lubricating oil contained in the capillary, and a is the centrifugal acceleration generated by the rotation of the cage at the capillary position.

[0075] When the lubricating oil completely fills the capillary at a certain temperature T, When the temperature rises, the lubricant will precipitate outward due to the inconsistency between the thermal expansion coefficients of the lubricant and the porous cage material. The corresponding capillary lubricant supply flow rate is:

[0076]

[0077] Among them, l λ is the capillary length, ρ T is the density of the lubricating oil at temperature T, α T is the volume thermal expansion coefficient of lubricating oil, It is considered that when the lubricating oil precipitates in the capillary tube, the same mass will be precipitated along both ends of the tube, and only the end in contact with the rolling element can be effectively lubricated. The premise of the application of formula (7) is that the lubricating oil completely fills the capillary tube at the current moment and the temperature of the lubricating oil is on the rise, otherwise the oil supply flow rate of the porous cage due to the thermal effect is 0.

[0078] In summary, combined with the density distribution characteristics of the cage capillary pore diameter f(λ), the lubricating oil supply rate of the porous cage under centrifugal and thermal effects is calculated as:

[0079]

[0080] Among them, f(λ) is the pore size distribution density per unit area of ​​the porous cage, S1 is the area of ​​the outer ring of the porous cage, that is, under the centrifugal effect, the lubricating oil will move in the radial direction and be supplied to the raceway through the outer ring of the cage; and S2 is the contact area between the outer ring of the cage and the rolling element, that is, the oil supply under the thermal effect can only be effectively delivered to the raceway when the cage and the rolling element are in contact.

[0081] (5) Changes in bearing raceway oil film thickness

[0082] The factors that affect the oil film thickness of the bearing raceway of the space momentum wheel mainly include lateral flow, evaporation of lubricating oil in the raceway, reflux of lubricating oil, oil supply from porous cages, and active oil supply. The oil film thickness h of the contact area between the center of the bearing raceway and the rolling element at time t is t It can be calculated as:

[0083]

[0084] Among them, h t0 is the oil film thickness at the center of the contact area between the raceway and the rolling element at the initial moment, Q AS is the active oil supply flow, S ci and S co are the contact areas of the inner and outer ring raceways and rolling elements of the bearing, respectively, and S i , S o It refers to the area where lubricating oil is distributed on the inner and outer raceways of the bearing.

[0085] (6) Active oil replenishment strategy

[0086] Evaluate all possible operating conditions of the bearing during the service life of the momentum wheel and calculate the target oil film thickness h under the operating conditions L A database is established so that the controller can obtain the target bearing oil film thickness h from the database according to the operating conditions such as the momentum wheel speed and output torque. L .

[0087] During the rotation of the momentum wheel, when the sensor can monitor the current oil film thickness h in real time, t When , the active oil replenishment device compares the target oil film thickness h according to the current momentum wheel service condition L and the current oil film thickness h t If the film thickness of any contact area of ​​the inner / outer raceway is less than the target film thickness, active oil replenishment is performed until the current oil film thickness h t Reach target oil film thickness h L .

[0088] When the momentum wheel is in service, there is no sensor that can monitor the current oil film thickness h in real time. t When the bearing is used in the momentum wheel service process, it is necessary to calculate the lubricating oil flow rate Q under the operating conditions according to equations (2), (3), (5), and (8) for all possible operating conditions of the bearing during the momentum wheel service process. s , Q E , Q R , Q PS , so that the controller can combine the information of momentum wheel speed, output torque, initial oil film thickness, cage oil storage capacity, and active oil replenishment information during the service process, and quickly calculate the current raceway oil film thickness h during the service process according to formula (9): t , and thus the target oil film thickness h L If the film thickness of any contact area of ​​the inner / outer raceway is less than the target film thickness, the volume of lubricating oil to be replenished is calculated, and then the active oil replenishment device is controlled to replenish the oil according to the given lubricating oil volume, so that the theoretical oil film thickness of the raceway is greater than the target oil film thickness h L .

[0089] The present invention also provides an active oil replenishment system for a space momentum wheel bearing based on oil film thickness. The active oil replenishment system for a space momentum wheel bearing based on oil film thickness can be realized by executing the process steps of the active oil replenishment method for a space momentum wheel bearing based on oil film thickness, that is, those skilled in the art can understand the active oil replenishment method for a space momentum wheel bearing based on oil film thickness as a preferred implementation of the active oil replenishment system for a space momentum wheel bearing based on oil film thickness.

[0090] An active oil replenishment system for a space momentum wheel bearing based on oil film thickness, comprising:

[0091] Database establishment module: Target oil film thickness h for lubrication under all possible service conditions of momentum wheel bearings L Establish a target oil film thickness database.

[0092] The first oil replenishment module: When the momentum wheel bearing has the ability to monitor the oil film thickness in real time, the current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L .

[0093] The second oil replenishment module: when the momentum wheel bearing does not have the ability to monitor the oil film thickness in real time, the current oil film thickness h under the current service condition is calculated in real time t , the calculated current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L .

[0094] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0095] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for actively replenishing oil in a space momentum wheel bearing based on oil film thickness, characterized in that: include: Database establishment steps: According to the target oil film thickness h of the momentum wheel bearing under all possible service conditions L Establish target oil film thickness database; The first oil replenishment step: When the momentum wheel bearing has the ability to monitor the oil film thickness in real time, the current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L ; Second oil replenishment step: When the momentum wheel bearing does not have the ability to monitor the oil film thickness in real time, the current oil film thickness h under the current service condition is calculated in real time. t , the calculated current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L ; The method for calculating the current oil film thickness is: Calculate the lateral flow rate Q of all rolling element raceway contact areas at a certain moment s , Rolling lubricant evaporation rate Q E , the flow rate Q of lubricating oil return during the interval R and the lubricating oil supply rate Q of the porous cage under centrifugal and thermal effects PS ; Current oil film thickness h t The calculation method is: Among them, h t0 is the oil film thickness at the center of the contact area between the raceway and the rolling element at the initial moment, Q AS is the active oil supply flow, S ci and S co are the contact areas of the inner and outer ring raceways and rolling elements of the bearing, respectively, and S i , S o It refers to the area where lubricating oil is distributed on the inner and outer raceways of the bearing.

2. The active oil replenishment method for a space momentum wheel bearing based on oil film thickness according to claim 1 is characterized in that: Rolling lubricant evaporation rate Q E The calculation method is: Q E =(S i +S o )m evp Among them, S i , S o are the raceway surface areas of the inner and outer rings of the bearing, m evp It is the evaporation rate of the lubricating oil at the operating temperature and the corresponding service environment vacuum.

3. The active oil replenishment method for a space momentum wheel bearing based on oil film thickness according to claim 1 is characterized in that: The flow rate Q of lubricating oil return during the interval R The calculation method is: S c is the contact area between the raceway and rolling element of the inner and outer rings of the bearing, Δt is the interval time, h Δt is the oil film thickness in the contact center area after the reflux interval time Δt, h0 is the oil film thickness in the contact center area before reflux, and the summation symbol represents the need to calculate the distribution change of the oil film thickness of the corresponding raceways of the inner and outer rings respectively, and then sum them up to get the reflux flow rate.

4. The active oil replenishment method for a space momentum wheel bearing based on oil film thickness according to claim 1 is characterized in that: Lubricating oil supply rate Q of porous cage under centrifugal and thermal effects PS The calculation method is: f(λ) is the pore size distribution density per unit area of ​​the porous cage, S1 is the outer ring area of ​​the porous cage, S2 is the contact area between the cage and the rolling element, Centrifugal action capillary oil flow rate with diameter λ, is the oil flow rate of a capillary tube with a diameter of λ under thermal effect.

5. An active oil replenishment system for a space momentum wheel bearing based on oil film thickness, characterized in that: include: Database establishment module: Target oil film thickness h for lubrication under all possible service conditions of momentum wheel bearings L Establish target oil film thickness database; The first oil replenishment module: When the momentum wheel bearing has the ability to monitor the oil film thickness in real time, the current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L ; The second oil replenishment module: when the momentum wheel bearing does not have the ability to monitor the oil film thickness in real time, the current oil film thickness h under the current service condition is calculated in real time t , the calculated current oil film thickness h t Less than the target oil film thickness h under the current service condition L When the oil is replenished, the current oil film thickness is h t Reach target oil film thickness h L ; The method of calculating the current oil film thickness includes: calculating the lateral flow rate Q of all rolling element raceway contact areas at a certain moment s , Rolling lubricant evaporation rate Q E , the flow rate Q of lubricating oil return during the interval R and the lubricating oil supply rate Q of the porous cage under centrifugal and thermal effects PS ; Current oil film thickness h t The calculation method is: Among them, h t0 is the oil film thickness at the center of the contact area between the raceway and the rolling element at the initial moment, Q AS is the active oil supply flow, S ci and S co are the contact areas of the inner and outer ring raceways and rolling elements of the bearing, respectively, and S i , S o It refers to the area where lubricating oil is distributed on the inner and outer raceways of the bearing.

6. The active oil replenishment system for space momentum wheel bearing based on oil film thickness according to claim 5 is characterized in that: Rolling lubricant evaporation rate Q E The calculation method is: Q E =(S i +S o )m evp Among them, S i , S o are the raceway surface areas of the inner and outer rings of the bearing, m evp It is the evaporation rate of the lubricating oil at the operating temperature and the corresponding service environment vacuum.

7. The active oil replenishment system for space momentum wheel bearing based on oil film thickness according to claim 5 is characterized in that: The flow rate Q of lubricating oil return during the interval R The calculation method is: S c is the contact area between the raceway and rolling element of the inner and outer rings of the bearing, Δt is the interval time, h Δt is the oil film thickness in the contact center area after the reflux interval time Δt, h0 is the oil film thickness in the contact center area before reflux, and the summation symbol represents the need to calculate the distribution change of the oil film thickness of the corresponding raceways of the inner and outer rings respectively, and then sum them up to get the reflux flow rate.

8. The active oil replenishment system for space momentum wheel bearing based on oil film thickness according to claim 5 is characterized in that: Lubricating oil supply rate Q of porous cage under centrifugal and thermal effects PS The calculation method is: f(λ) is the pore size distribution density per unit area of ​​the porous cage, S1 is the outer ring area of ​​the porous cage, S2 is the contact area between the cage and the rolling element, Centrifugal action capillary oil flow rate with diameter λ, is the oil flow rate of a capillary tube with a diameter of λ under thermal effect.

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