Bearing lubrication state identification method based on bearing-rotor system response

Abstract

The invention relates to a lubrication state identification method based on bearing-rotor system response, and the method comprises the steps: building a calculation model of rolling bearing contact rigid connection, calculating bearing rigidities corresponding to different contact region failures in a bearing, simulating a bearing lubrication state through different bearing rigidities, and determining the influence of bearing failures on main shaft harmonic response data. Then, vibration signals are collected in real time through a vibration sensor installed on the rotating shaft, vibration characteristics are analyzed through the signal processing technology, and the lubrication state is evaluated; according to the method, continuous lubrication state feedback can be provided in the equipment operation process, and insufficient lubrication or abnormal conditions can be recognized in time, so that bearing faults are effectively prevented, the equipment reliability is improved, and the maintenance cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of bearings, and in particular to a method for identifying a bearing lubrication state based on a bearing-rotor system response. Background Art

[0002] In modern mechanical systems, the proper operation of the bearing-rotor system is critical to the overall performance and reliability of the equipment. The lubrication state of the bearing directly affects its operating characteristics, especially under high speed and high load conditions. The thickness and stiffness of the lubricating film are important indicators for evaluating the lubrication state, which are directly related to the bearing's load capacity, friction, heat generation and life.

[0003] Traditional lubrication condition monitoring methods mostly rely on oil sample analysis and offline measurement, which usually require shutdown or specialized sampling equipment, cannot provide real-time monitoring data, and are costly. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a bearing lubrication status identification method based on the response of the bearing-rotor system. By monitoring the vibration response of the rotating shaft, the lubrication status of the bearing is inferred, providing a solution for real-time monitoring of the bearing lubrication status without stopping the machine.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A bearing lubrication status identification method based on the response of the bearing-rotor system is proposed. A rolling bearing contact stiffness calculation model is established to calculate the bearing stiffness in different failure areas. The rotor system model is used for simulation to clarify the influence of the bearing stiffness in different failure areas on the change of the main shaft vibration response data. Then, the shaft system vibration signal is detected and the bearing lubrication status is predicted and identified according to the change of the main shaft vibration response data.

[0007] Furthermore, the bearing lubrication state identification method based on the bearing-rotor system response specifically comprises the following steps: (1) Establish a calculation model for the contact stiffness of rolling bearings to solve the contact stiffness between the steel ball and the inner and outer rings, the equivalent stiffness between the steel ball and the inner and outer rings, and the radial stiffness and bearing stiffness of the bearing; (2) determining the bearing contact parameters and operating conditions, and calculating the bearing stiffness under a good lubrication state and the bearing stiffness under different failure regions according to the calculation model established in step (1); (3) Simulating in a finite element model of the rotor system, setting the bearing stiffness in the harmonic response of the model to simulate the lubrication state of the bearing, inputting different bearing stiffnesses, obtaining different spindle resonance frequencies, and thus obtaining the relationship between the spindle harmonic response data and the bearing stiffness; (4) Install a vibration sensor on the rotating shaft to collect the spindle vibration signal in real time, obtain the spindle frequency domain data through signal processing, and determine whether the bearing has oil film failure in the contact area by detecting and identifying the change in resonance frequency based on the corresponding relationship between the spindle harmonic response data obtained in step (3) and the bearing stiffness, and evaluate the bearing lubrication status.

[0008] Furthermore, in the rolling bearing contact stiffness calculation model established according to step (1): The contact stiffness between the steel ball and the inner / outer ring is K c , the oil film stiffness between the steel ball and the inner / outer ring is k f , the oil film stiffness at the lubricating oil inlet area is k e ; If the contact area is well lubricated, the equivalent stiffness K of the qth steel ball and the inner / outer ring is q =(1 / K c +1 / k f ) -1 +k e ; If the lubrication of the contact area fails, K q Directly use K c Replacement; The axial and radial stiffness components of the equivalent stiffness of the qth steel ball and the inner / outer ring are: In the formula, α q is the contact angle between the qth steel ball and the inner / outer ring after loading; The axial stiffness and radial stiffness of the rolling bearing are obtained by superimposing the equivalent stiffness of the inner and outer rings of each steel ball, expressed as: Where: K a and K r are the equivalent axial stiffness and equivalent radial stiffness of the rolling bearing respectively; K r-iq and K a-iq are the radial equivalent stiffness and axial equivalent stiffness of the qth steel ball and the inner ring respectively; K r-0q and K a-0q are the radial equivalent stiffness and axial equivalent stiffness of the qth steel ball and the outer ring respectively; Z is the number of steel balls in the rolling bearing.

[0009] Further, where Γ i(e) is the complete elliptic integral of the first kind, ξ i(e)is the second kind of complete elliptic integral; ∑ρ is the sum of the principal curvatures of the contact points between the steel ball and the inner / outer ring; K is the elliptical contact ratio between the steel ball and the inner / outer ring; E′ is the equivalent elastic modulus between the steel ball and the inner / outer ring; Q is the normal contact load between the steel ball and the inner / outer ring.

[0010] Furthermore, the oil film stiffness of the Hertz contact area between the steel ball and the inner / outer ring is Among them, C j is the oil film stiffness coefficient, h min is the oil film thickness between the ball and the inner and outer rings, U is the dimensionless velocity parameter, G is the dimensionless material parameter; E′ is the equivalent elastic modulus of the steel ball and the inner / outer ring, R x is the comprehensive curvature radius of the normal center plane of the contact object, k = a / b, a is the major semi-axis of the contact ellipse, and b is the minor semi-axis of the contact ellipse.

[0011] Furthermore, the oil film stiffness at the lubricating oil inlet area is: Where η0 is the dynamic viscosity of lubricating oil at normal pressure, u y is the average bearing speed, R x is the combined radius of curvature of the normal center plane of the contact object, a is the major semi-axis of the contact ellipse, and h min is the oil film thickness between the steel ball and the inner / outer ring.

[0012] Furthermore, in step (3), it can be determined through simulation that when the oil film of the bearing fails in different contact areas, the frequency of the shaft system at the resonance point is reduced to a certain extent. The more contact areas fail, the more the resonance frequency decreases.

[0013] Furthermore, in step (4), the vibration data of the main shaft is collected in real time, and the frequency domain data of the main shaft can be directly obtained after being processed by the acceleration demodulator. When the frequency changes at each order of resonance are monitored, and the frequency changes are consistent with the data obtained by simulation in step (3), it is considered that the oil film failure occurs in the contact area inside the bearing, and it is necessary to increase the oil injection amount in time to improve the lubrication condition.

[0014] Beneficial effects:

[0015] The rolling bearing contact stiffness calculation model established by the present invention can calculate the bearing stiffness in different failure areas representing different lubrication conditions, and obtain the main shaft vibration data in different failure areas through the rotor system model, establish the corresponding relationship between the main shaft vibration data change and the bearing stiffness and the bearing lubrication condition, and identify the change of the main shaft resonance frequency by monitoring the vibration response of the rotating shaft, thereby inferring the lubrication condition of the bearing, thereby providing a bearing lubrication condition solution that does not require shutdown and real-time monitoring.

[0016] When identifying the lubrication status of a bearing according to the method of the present invention, it is only necessary to install the vibration sensor on the main shaft to collect data in real time without stopping the machine or taking samples. The detection is convenient and can capture small vibration changes caused by changes in the lubrication status. By processing and analyzing these vibration signals, the changes in the resonance frequencies of the rotating shaft at various orders can be obtained. These parameters reflect whether oil film failure occurs between the steel ball and the ring, thereby helping to predict whether the bearing is in a good lubrication state. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the relative position of the center of the steel ball and the center of curvature of the inner and outer raceways at any position of the rolling bearing;

[0018] Figure 2 Force model of rolling bearing steel ball and inner and outer raceways along the axial plane;

[0019] Figure 3 Equivalent stiffness model of inner and outer rings of bearings;

[0020] Figure 4 A schematic diagram of the composition of a detection system using the method of the present invention;

[0021] Figure 5 Harmonic response data in the radial direction of the shaft system in Example 1 (failure regions 1-4);

[0022] Figure 6 Harmonic response data in the radial direction of the shaft system in Example 1 (failure areas 5-9);

[0023] Figure 7 The resonance frequencies of various orders in the radial direction of the main shaft in Example 1.

[0024] Figure numerals: 1, rotating shaft; 2, test bearing, 3, inductive sensor, 4, demodulator, 5, PC terminal. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] The present invention proposes a lubrication status identification method based on the vibration response of the bearing-rotor system. The vibration sensor installed on the rotating shaft collects vibration signals in real time, and uses signal processing technology to analyze vibration characteristics and evaluate lubrication status. The method can provide continuous lubrication status feedback during equipment operation, and timely identify insufficient lubrication or abnormal conditions, thereby effectively preventing bearing failures, improving equipment reliability, and reducing maintenance costs. Specifically, the following steps are included:

[0027] (1) Establish a calculation model for the contact stiffness of rolling bearings to solve the contact stiffness between the steel ball and the inner and outer rings, the equivalent stiffness between the steel ball and the inner and outer rings, and the radial stiffness and bearing stiffness of the bearing;

[0028] (2) determining the bearing contact parameters and operating conditions, and calculating the bearing stiffness under a good lubrication state and the bearing stiffness under different failure regions according to the calculation model established in step (1);

[0029] (3) Simulating in a finite element model of the rotor system, setting the bearing stiffness in the harmonic response of the model to simulate the lubrication state of the bearing, inputting different bearing stiffnesses, obtaining different spindle resonance frequencies, and thus obtaining the relationship between the bearing stiffness and the spindle harmonic response data;

[0030] (4) Install a vibration sensor on the rotating shaft to collect the main shaft vibration signal in real time, obtain the main shaft frequency domain data through signal processing, and determine whether the bearing contact area oil film failure occurs by detecting and identifying the change of the resonance frequency and comparing it with the corresponding relationship established by the simulation in step (3), so as to evaluate the bearing lubrication status.

[0031] The specific method for establishing the rolling bearing contact stiffness calculation model in step (1) is as follows:

[0032] (1.1) Contact stiffness between the steel ball and the inner / outer ring

[0033] like Figure 1 As shown, it is the positional relationship between the center of a steel ball (defined as the qth steel ball) at any position of the rolling ball bearing and the center of curvature of the inner and outer grooves before and after loading. Figure 1 Point n represents the center of curvature of the outer raceway, which is assumed to be fixed in the analysis. When the rolling bearing rotates, under the combined action of load, centrifugal force and gyroscopic torque, the center of curvature of the inner raceway moves from point m before loading to point m' after loading, and the center of the ball moves from point C before loading to point C' after loading. Figure 1 For the qth steel ball shown in the figure, considering the oil film thickness and elastic deformation between the steel ball and the inner and outer rings, the distance Δ between the center of curvature of the inner and outer raceways and the center of the ball after loading iq and Δ eq They are

[0034] In the formula, r i and r e are the inner and outer raceway curvature radii respectively; D w is the diameter of the steel ball; δ iq and δ eq are the elastic deformations between the qth steel ball and the inner and outer rings respectively; h icq and h ecqare the central oil film thickness of the contact area between the qth steel ball and the inner ring and the outer ring, respectively.

[0035] The coordinates of the center of curvature of the inner channel after loading are A xq =BD w sinα0+δ a +θR i cosψ q (3) A zq =BD w cosα0+δ r cosψ q (4)

[0036] Where: R i =d m / 2+(f i -0.5)D w cosα0,B=f i +f e -1, where f i 、f e are the curvature radius coefficients of the inner and outer races, ψ q is the position angle of the qth steel ball; θ is the inclination angle of the inner ring of the bearing, δ a is the axial displacement of the bearing inner ring, δ r is the radial displacement of the bearing inner ring, and α0 is the contact angle before loading.

[0037] According to formulas (1) to (4), combined with Figure 1 The geometric relationship represented by the deformation geometry compatibility equation considering the oil film thickness can be expressed as:

[0038] Where V xq ,V zq is the position parameter of the center of the qth steel ball, which is related to the bearing stress deformation and rotation speed; A xq ,A zq is the position parameter of the inner channel curvature center after loading, α ij , α ej are the contact angles between the steel ball and the inner and outer rings respectively.

[0039] The force model of the rolling bearing steel ball and the inner and outer rings along the axial plane is as follows: Figure 2 As shown; According to the equilibrium equation of the steel ball and the inner and outer rings along the axial plane, and the equilibrium equation of the inner ring load and the external load, the contact angle between the steel ball and the inner and outer rings can be preliminarily determined. The equilibrium equation of the steel ball and the inner ring is:

[0040] In the formula, Q ij , Q ej are the contact loads between the steel ball and the inner and outer rings respectively; α ij , α ej are the contact angles between the steel ball and the inner and outer rings respectively; ij , ej are the drag coefficients of the steel ball and the inner and outer rings respectively; D w F is the diameter of the steel ball; cj is the centrifugal force of the steel ball; M gj is the gyroscopic moment of the steel ball; F a is the axial load of the inner ring; F r is the radial load of the inner ring; ψ j is the azimuth of the steel ball.

[0041] In addition, the centrifugal force F of the steel ball cj and gyroscopic moment M gj It can be expressed as M gj =Jω mj ω bj sinβ j (14)

[0042] Where m and J represent the mass and moment of inertia of the ball; d m is the bearing pitch diameter, ω mj and ω bj The angular velocity of the revolution and rotation of the steel ball is calculated by the following equation:

[0043] r ij 、r ej is a dimensionless geometric parameter

[0044] Then determine the attitude angle according to the D'Alembert principle

[0045] In the formula, a ij and a ej Indicates the semi-major axis of the contact ellipse between the ball and the inner and outer raceways; L ij and L oj They represent the second kind elliptic integrals of the contact between the ball and the inner and outer raceways respectively.

[0046] The above formulas (1)-(20) constitute a nonlinear equation group. Under the condition of known bearing geometric parameters and operating parameters, solving this equation group can obtain the load distribution of the bearing and further obtain the contact load between each steel ball and the inner / outer ring.

[0047] According to Hertz contact theory, the relationship between the contact load and elastic deformation between the steel ball and the inner and outer rings is: In the formula, Γ i(e) , i(e) are the first kind complete elliptic integral and the second kind complete elliptic integral respectively; ∑ρ is the sum of the principal curvatures of the contact points between the steel ball and the inner / outer ring; K is the elliptical contact ratio between the steel ball and the inner / outer ring; E′ is the equivalent elastic modulus between the steel ball and the inner / outer ring; Q is the normal contact load between the steel ball and the inner / outer ring.

[0048] By differentiating Q in the equation with respect to δ, we can obtain the contact stiffness between the steel ball and the inner / outer ring:

[0049] (1.2) Oil film stiffness between the steel ball and the inner / outer ring

[0050] Due to the entrainment and extrusion of the ball, the lubricating oil first flows into the Hertz contact area and then flows from this area to the outlet area. In this process, the oil film exhibits nonlinear characteristics due to extrusion. In this case, the friction pair between the ball and the inner and outer rings can be divided into three areas: the lubricating oil inlet area, the Hertz contact area, and the lubricating oil outlet area. The contact stiffness is composed of the Hertz contact stiffness and the oil film stiffness.

[0051] According to the elastic fluid dynamic theory, the dimensionless minimum oil film thickness H between the ball and the inner and outer rings under isothermal and sufficient oil supply conditions is min for H min =3.63U 0.68 G 0.49 W -0.073 (1-e -0.68k ) (twenty three)

[0052] Where k is the ellipse parameter, U is the dimensionless velocity parameter, G is the dimensionless material parameter, W is the load parameter, α1 is the viscosity coefficient (m 2 N -1 ), η0 is the dynamic viscosity of lubricating oil at normal pressure (Pa·s), E′ is the equivalent elastic modulus (pa), u y is the average bearing speed (m / s), R x is the comprehensive curvature radius of the normal center plane of the contact object (mm), Q is the contact load (N); they can be calculated by the following formulas:

[0053] The oil film thickness between the ball and the inner and outer rings is h min =Rx H min =3.63U 0.68 ×G 0.49 W -0.073 (1-e -0.68k )R x (26)

[0054] Hertz contact zone oil film stiffness k f

[0055] In the formula, C j is the oil film stiffness coefficient, which is 6.4066×10 8 ,h min is the oil film thickness between the ball and the inner and outer rings, U is the dimensionless velocity parameter, G is the dimensionless material parameter; E′ is the equivalent elastic modulus of the steel ball and the inner / outer ring, R x is the comprehensive curvature radius of the normal center plane of the contact object, k = a / b, a is the major semi-axis of the contact ellipse, and b is the minor semi-axis of the contact ellipse.

[0056] The oil film stiffness k at the lubricating oil inlet area e

[0057] Where η0 is the dynamic viscosity of lubricating oil at normal pressure, u y is the average bearing speed, R x is the combined radius of curvature of the normal center plane of the contact object, a is the major semi-axis of the contact ellipse, and h min is the oil film thickness between the steel ball and the inner / outer ring.

[0058] (1.3) Equivalent stiffness of the steel ball and inner and outer rings

[0059] like Figure 3 As shown (where Figure 3 (B) Figure 3 (A) is an equivalent model when the steel ball is equivalent to a spring. The equivalent stiffness of the inner and outer rings of the steel ball is the series connection of its contact stiffness and the oil film stiffness. In this way, the equivalent stiffness of the qth steel ball and the inner / outer ring is expressed as K q =(1 / K c +1 / k f ) -1 +k e (29)

[0060] According to the calculation formula of rolling bearing equivalent stiffness derived by Harris, the stiffness components of the equivalent stiffness of the qth steel ball and the inner / outer ring in the axial and radial directions are respectively

[0061] If the lubrication of the contact area fails, the contact stiffness of the steel ball is K c , at this time, in equations (30) and (31), the steel ball contact stiffness K q Use K c Replace, where α q is the contact angle between the qth steel ball and the inner / outer ring after loading.

[0062] For rolling bearings, the axial stiffness and radial stiffness can be obtained by superimposing the equivalent stiffness of the inner / outer ring of each steel ball, which can be expressed as

[0063] Where: K a is the equivalent axial stiffness of the bearing, K r is the equivalent radial stiffness of the bearing; K r-iq is the radial equivalent stiffness of the qth steel ball and the inner ring, K a-iq is the axial equivalent stiffness of the qth steel ball and the inner ring; K r-eq is the radial equivalent stiffness of the qth steel ball and the outer ring, K a-eq is the axial equivalent stiffness of the qth steel ball and the outer ring; Z is the number of steel balls.

[0064] There are multiple bearings on the main shaft. In the axial direction, the axial stiffness of the bearings is considered to be in series, because each bearing is arranged in sequence in the axial direction and the load must pass through each bearing. The total axial stiffness K of the bearings on the entire main shaft is A (equivalent to the axial support stiffness of the main shaft) is the reciprocal of the sum of the reciprocals of the stiffnesses of these series components.

[0065] In the radial direction, the radial stiffness of the bearings is considered to be in parallel, they bear the external force together, and each component shares part of the load. The total radial stiffness K of the bearing on the entire spindle B (equivalent to the radial support stiffness of the spindle) can be calculated by direct addition, since the stiffness represents the overall response to external forces.

[0066] Through the above formulas (1)-(35), the coupling relationship between the lubrication state of the steel ball in the bearing and the support stiffness of the shaft system is established. When the structural parameters and working conditions of the bearing are determined, according to the above-established rolling bearing contact stiffness calculation model, the contact stiffness of the steel ball and the inner ring / outer ring in the dry friction state (oil film failure) and lubrication contact state can be calculated respectively through formulas (22) and (29), and then the bearing stiffness in different failure areas can be calculated through formulas (32) and (33). The stiffness of the bearing affects the support stiffness of the shaft system, thereby affecting the vibration of the shaft system.

[0067] Therefore, the change in bearing stiffness can be reflected by monitoring the change in shaft system vibration data. The change in bearing stiffness can reflect the lubrication status between the steel balls and rings, so that the bearing lubrication status can be identified from the change in shaft system vibration data.

[0068] On this basis, the vibration data of the main shaft is collected in real time through the inductive sensor. After being processed by the acceleration demodulator, the frequency domain data of the main shaft can be directly obtained. The radial vibration data of the shaft system can be monitored in real time through the PC. When the oil film fails in the contact area of ​​the bearing, the radial and axial stiffness of the bearing is first affected, and then the radial and axial support stiffness of the shaft system is affected. Here, by monitoring the change of the vibration data of the shaft system, the change of the stiffness of the bearing is reflected. The change of the stiffness of the bearing can reflect the lubrication state between the steel ball and the ring. Because of the different axial and radial stiffness of the bearing, the harmonic response data of the shaft system is different. When the bearing structural parameters and working conditions are determined, the oil film fails in the contact area between the steel ball and the ring, and the impact on the various frequencies of the shaft system can be determined, so as to achieve the purpose of identifying and predicting whether the oil film fails in the contact area of ​​the bearing. If the lubrication failure in the contact area occurs and the bearing is poorly lubricated, the oil injection amount should be increased in time to ensure that the bearing runs in a good lubrication environment.

[0069] The technical solution of the present invention is further described below in conjunction with specific examples.

[0070] Example 1

[0071] Under specific working conditions, a radial load of 400N and an axial load of 600N are applied to the spindle. After the bearing parameters are determined, the contact stiffness K between the steel ball and the inner and outer rings at each position can be calculated using formulas (1)-(29): c and the equivalent stiffness K with oil film participation q When the lubrication of the contact area fails due to overload or abnormal working conditions inside the bearing, the contact stiffness between the steel ball and the inner ring or outer ring in this contact area is considered to be K c The contact stiffness of the steel ball in the other well-lubricated parts is calculated based on the stiffness K q, the stiffness of each steel ball is substituted into formula (32)-(33) respectively to obtain the stiffness of the entire bearing, as shown in Table 1 below, which shows the steel ball contact stiffness and bearing stiffness under dry friction and good lubrication conditions calculated according to the model established by the present invention. Table 1 Contact stiffness calculated in Example 1 Table 2 Contact stiffness

[0072] In this embodiment, when studying the failure of the bearing oil film, the most vulnerable positions of the steel ball and the outer ring are studied first, and then the oil film failure transitions from the load-bearing area to the non-load-bearing area. If one area fails, it may affect the surrounding areas, resulting in a decrease in overall performance; for example, local wear will cause uneven load distribution, thereby accelerating the failure of other areas; in general, failure usually starts from the high-load, high-temperature contact area and gradually expands to the surrounding area. In this embodiment, the failure of the bearing oil film is based on the following assumptions:

[0073] 1. The outer ring oil film fails before the inner ring oil film;

[0074] 2. Since the axial force and radial force (applied from top to bottom) are at a 0° angle, the steel ball position is the pressure concentration area. Figure 3 The steel ball at the top position in the figure fails first;

[0075] 3. When the first steel ball fails, this failure will significantly affect the areas on both sides. Therefore, if the top steel ball fails, the next affected area is the steel ball oil film area on both sides. Considering the symmetry of the bearing, it can be assumed that the steel balls on both sides fail at the same time when the inner ring and outer ring fail. This process will continue until all oil film contact areas fail.

[0076] Based on the above assumptions, the bearing failure areas 1-9 are divided into: Figure 3 As shown, there are 16 steel balls inside the bearing, which are numbered ①- Indicates the steel balls at different positions:

[0077] Failure area 1: represents the first contact area where the steel ball ① at the top of the bearing and the outer ring fail, and the rest of the contact areas are normal.

[0078] Failure area 2: represents that the topmost steel ball ① and the inner and outer rings have all experienced lubrication failure, the left and right steel balls ②-③ and the outer ring have experienced lubrication failure, and are in lubrication contact with the inner ring. The rest of the steel balls and the inner and outer rings are normal.

[0079] Failure area 3: Lubrication failure occurs in steel balls ①-③ and the inner and outer rings, lubrication failure occurs in steel balls ④-⑤ and the outer ring, and the inner ring is in lubrication contact. The rest of the steel balls and the inner and outer rings are normal.

[0080] Failure area 4: Lubrication failure occurs between steel balls ①-⑤ and the inner and outer rings. Lubrication failure occurs in the contact area between steel balls ⑥-⑦ and the outer ring, and lubrication contact occurs with the inner ring. The rest of the steel balls and the inner and outer rings are normal.

[0081] Failure area 5: Lubrication failure occurs between steel balls ①-⑦ and the inner and outer rings. Lubrication failure occurs in the contact area between steel balls ⑧-⑨ and the outer ring, and lubrication contact occurs with the inner ring. The rest of the steel balls and the inner and outer rings are normal.

[0082] Failure area 6: Lubrication failure occurs in both the steel balls ①-⑨ and the inner and outer rings. The lubrication in the contact area with the outer ring fails, and it is in lubrication contact with the inner ring. The contact between the steel ball and the inner and outer rings in other positions is normal.

[0083] Failure area 7: represents steel ball ①- Lubrication failure occurs on both the inner and outer rings, and the steel ball The lubrication in the contact area with the outer ring fails, and it is in lubrication contact with the inner ring. The contact between the steel ball and the inner and outer rings in other positions is normal.

[0084] Failure area 8: represents steel ball ①- Lubrication failure occurs on both the inner and outer rings, and the steel ball The lubrication in the contact area with the outer ring fails, and it is in lubrication contact with the inner ring. The contact between the steel ball and the inner and outer rings in other positions is normal.

[0085] Failure area 9: Representative steel ball ①- Lubrication failure occurs on both the inner and outer rings, and the steel ball The lubrication in the contact area with the outer ring fails, and it is in lubrication contact with the inner ring. The contact between the steel ball and the inner and outer rings in other positions is normal.

[0086] When the above failure areas 1-9 are divided, the contact stiffness between the steel ball and the inner ring and outer ring when the lubrication fails and when the lubrication is good can be calculated according to formulas (22) and (29), and then according to the lubrication conditions of each steel ball in different failure areas, the axial and radial stiffness of the bearing under different lubrication conditions (i.e. corresponding to different failure areas) can be calculated according to formulas (32)-(33).

[0087] For example, when the bearing is in the lubrication state represented by failure area 1, the lubrication failure occurs first in the contact area between the top steel ball ① and the outer ring inside the bearing, and the rest of the contact area is normal. At this time, the calculation formulas for the axial stiffness and radial stiffness of the bearing are:

[0088] When the bearing is in failure zone 2, it means that the top steel ball ① and the inner and outer rings have all experienced lubrication failure, the left and right steel balls ②-③ and the outer ring have experienced lubrication failure, and are in lubrication contact with the inner ring. The rest of the steel balls and the inner and outer rings are normal. At this time, the calculation formula for the bearing stiffness is:

[0089] K a_ec , K r_ec are the axial equivalent stiffness and radial equivalent stiffness of the steel ball and the outer ring when the oil film fails in the bearing contact area, K a_ic , K r_ic They are the axial equivalent stiffness and radial equivalent stiffness of the steel ball and the inner ring when the oil film in the bearing contact area fails.

[0090] Similarly, the axial and radial stiffness of the bearing in other failure areas are calculated respectively, and then simulated through the rotor system model.

[0091] When establishing the finite element model of the dynamic characteristics of the rotor system, the fixed parts such as the spindle housing and the stator are ignored, and the rotor and the rotating shaft are assumed to be a whole. In this embodiment, taking the spindle of the A050 high temperature and high life test machine as an example, since the spindle of the A050 high temperature and high life test machine will be subjected to axial force and radial force during operation, it is necessary to consider the axial stiffness and radial stiffness of the bearing, and simplify the bearing structure at the same time. First, insert a remote point on the cross section where the bearing is located, insert the bearing (A, B, C, D) in the remote point, and set its axial stiffness and radial stiffness.

[0092] Then, the bearing stiffness is set in the harmonic response of the rotor system model to simulate the lubrication state of the bearing. The above calculations are input to obtain the bearing stiffness corresponding to the lubrication state and failure areas 1-9. The harmonic response data of the main shaft under different states are obtained through the model.

[0093] The simulation data results are as follows Figure 5-6 As shown in the figure, different color curves are used to distinguish the harmonic response curves in different failure areas. The horizontal axis represents the frequency. Figure 5-6It can be seen that when the bearing fails in lubrication, the frequency of the shaft system at the resonance point (the peak of the curve in the figure) is reduced to a certain extent (in the figure, the curves are obviously separated at the peak, and the curve corresponding to the lubricated contact state is basically located at the far right position, with the highest corresponding frequency, and the more failure areas there are, the closer the corresponding curve is to the left at the peak, that is, the more the frequency is reduced), and the more failures there are in the contact area, the greater the impact on the resonant frequency of the main shaft, that is, the more the frequency at the resonance is reduced; that is to say, the larger the number of the failure area, the more oil film failures there are in the contact area between the steel ball and the ring, and the worse the lubrication state; the frequency of the shaft system at the resonance point is reduced to a certain extent, and the more failures there are in the contact area, the greater the impact.

[0094] In order to more intuitively obtain the changes in the resonance frequencies of different failure areas, Figure 5-6 Processed, such as Figure 7 As shown, the number 0 on the horizontal axis represents the lubrication contact state, and the numbers 1-9 represent the failure areas 1-9 respectively. It can be seen that the resonance frequencies of each order of the spindle gradually decrease with the increase of the failure area. The more failure areas there are, the more they decrease. It can be seen that there is a corresponding relationship between the change in the spindle resonance frequency and the bearing lubrication failure area.

[0095] Failure of the oil film will cause changes in the bearing stiffness, and the change in stiffness will affect the frequency changes at each peak in the harmonic response data of the spindle. After the bearing structure parameters and operating parameters are determined, the contact stiffness between the steel ball and the ring at each position of the bearing (oil film failure) and the coupling stiffness after the oil film is involved (good lubrication) can be calculated. Through these two different steel ball contact stiffnesses, the stiffness of the bearing in different failure areas can be calculated. Different bearing stiffnesses correspond to different harmonic response data of the spindle. The frequency changes at the resonance can be effectively identified through the PC end to determine whether the bearing has oil film failure in the contact area.

[0096] like Figure 4As shown, a plurality of test bearings 2 are installed on the rotating shaft 1, and an inductive sensor 3 is installed on the rotating shaft 1 to collect the vibration data of the spindle in real time. Then, after the vibration data is processed by the acceleration demodulator 4, the frequency domain data of the spindle can be directly obtained on the PC 5. When the spindle is running, if the bearing is in the lubrication environment of the failure area 0-9, the vibration response characteristics of the spindle are different, and the resonance frequency will change. Under normal conditions, the resonance frequency of the bearing should conform to the number 0, that is, the data under good lubrication conditions. When the bearing runs for a period of time, if it is suddenly detected that the spindle resonance frequency changes, and it conforms to the resonance frequency change of the failure area from 0-1 or 0-2 or 0-3..... or 0-9, it is determined that the bearing has oil film failure in the contact area, and the oil injection amount is increased to improve the lubrication condition, and the spindle resonance frequency is detected to be changed back to the state in the failure area 0. If yes, it means that the oil film failure in the contact area has indeed occurred. If not, the spindle may be due to other faults. The resonance frequency change caused by the spindle is determined according to the actual situation. It is necessary to stop the machine for maintenance; through such a method, the spindle vibration data changes can be monitored in real time, and the purpose of predicting and identifying the bearing lubrication state can be achieved without stopping the machine.

[0097] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A bearing lubrication state identification method based on the response of a bearing-rotor system, characterized in that: A rolling bearing contact stiffness calculation model is established to calculate the bearing stiffness in different failure areas. The rotor system model is used for simulation to clarify the impact of bearing stiffness in different failure areas on the change of spindle vibration response data. Then, the shaft system vibration signal is detected and the bearing lubrication status is predicted and identified based on the change of spindle vibration response data.

2. The bearing lubrication state identification method based on the bearing-rotor system response according to claim 1 is characterized in that: The specific steps include: (1) Establish a calculation model for the contact stiffness of rolling bearings to solve the contact stiffness between the steel ball and the inner and outer rings, the equivalent stiffness between the steel ball and the inner and outer rings, and the radial stiffness and bearing stiffness of the bearing; (2) determining the bearing contact parameters and operating conditions, and calculating the bearing stiffness under a good lubrication state and the bearing stiffness under different failure regions according to the calculation model established in step (1); (3) Simulating in a finite element model of the rotor system, setting the bearing stiffness in the harmonic response of the model to simulate the lubrication state of the bearing, inputting different bearing stiffnesses, obtaining different spindle resonance frequencies, and thus obtaining the relationship between the spindle harmonic response data and the bearing stiffness; (4) Install a vibration sensor on the rotating shaft to collect the spindle vibration signal in real time, obtain the spindle frequency domain data through signal processing, and determine whether the bearing has oil film failure in the contact area by detecting and identifying the change in resonance frequency based on the corresponding relationship between the spindle harmonic response data obtained in step (3) and the bearing stiffness, and evaluate the bearing lubrication status.

3. The bearing lubrication state identification method based on the bearing-rotor system response according to claim 2 is characterized in that: According to the rolling bearing contact stiffness calculation model established in step (1): The contact stiffness between the steel ball and the inner / outer ring is K c , the oil film stiffness between the steel ball and the inner / outer ring is k f , the oil film stiffness at the lubricating oil inlet area is k e ; If the contact area is well lubricated, the equivalent stiffness K of the qth steel ball and the inner / outer ring is q =(1 / K c +1 / k f ) -1 +k e ; If the lubrication of the contact area fails, K q Directly use K c Replacement; The axial and radial stiffness components of the equivalent stiffness of the qth steel ball and the inner / outer ring are: In the formula, α q is the contact angle between the qth steel ball and the inner / outer ring after loading; The axial stiffness and radial stiffness of the rolling bearing are obtained by superimposing the equivalent stiffness of the inner and outer rings of each steel ball, expressed as: Where: K a and K r are the equivalent axial stiffness and equivalent radial stiffness of the rolling bearing respectively; K r_iq and K a_iq are the radial equivalent stiffness and axial equivalent stiffness of the qth steel ball and the inner ring respectively; K r-0q and K a-0q are the radial equivalent stiffness and axial equivalent stiffness of the qth steel ball and the outer ring respectively; Z is the number of steel balls in the rolling bearing.

4. The bearing lubrication state identification method based on the bearing-rotor system response according to claim 3 is characterized in that: where Γ i(e) is the complete elliptic integral of the first kind, ξ i(e) is the second kind of complete elliptic integral; ∑ρ is the sum of the principal curvatures of the contact points between the steel ball and the inner / outer ring; K is the elliptical contact ratio between the steel ball and the inner / outer ring; E′ is the equivalent elastic modulus between the steel ball and the inner / outer ring; Q is the normal contact load between the steel ball and the inner / outer ring.

5. The bearing lubrication state identification method based on the bearing-rotor system response according to claim 4 is characterized in that: The oil film stiffness of the Hertz contact area between the steel ball and the inner / outer ring is Among them, C j is the oil film stiffness coefficient, h min is the oil film thickness between the ball and the inner and outer rings, U is the dimensionless velocity parameter, G is the dimensionless material parameter; E′ is the equivalent elastic modulus of the steel ball and the inner / outer ring, R x is the comprehensive curvature radius of the normal center plane of the contact object, k = a / b, a is the major semi-axis of the contact ellipse, and b is the minor semi-axis of the contact ellipse.

6. The method for identifying bearing lubrication status based on bearing-rotor system response according to claim 5, characterized in that: The oil film stiffness at the lubricating oil inlet area is: Where η0 is the dynamic viscosity of lubricating oil at normal pressure, u y is the average bearing speed, R x is the combined radius of curvature of the normal center plane of the contact object, a is the major semi-axis of the contact ellipse, and h min is the oil film thickness between the steel ball and the inner / outer ring.

7. The method for identifying bearing lubrication status based on bearing-rotor system response according to claim 2, characterized in that: In step (3), it can be determined through simulation that when the oil film fails in different contact areas of the bearing, the frequency of the shaft system at the resonance point is reduced to a certain extent. The more contact areas fail, the more the resonance frequency decreases.

8. The method for identifying bearing lubrication status based on bearing-rotor system response according to claim 2, characterized in that: In step (4), the vibration data of the main shaft is collected in real time, and the frequency domain data of the main shaft can be directly obtained through processing by the acceleration demodulator. According to the data, when the frequency of each order resonance changes, and the frequency change is consistent with the data obtained by simulation in step (3), It is believed that the oil film failure occurs in the contact area inside the bearing, and the oil injection volume needs to be increased in time to improve the lubrication condition.

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