A Solving Method for Grease Lubrication Contact Characteristics of In-Wheel Motor Bearings

Abstract

The present invention relates to a method for solving the grease lubrication contact characteristics of a hub motor bearing, belonging to the field of automation technology. Based on the unbalanced magnetic pull of the motor bearing and the operating conditions in a wide speed range and wide temperature range, this method calculates the normal force and entrainment velocity of the maximum load-carrying rolling elements of the bearing, accelerates the calculation of the comprehensive elastic deformation of the rolling elements and the outer raceway by using the FFT algorithm, solves the grease lubrication Reynolds equation to obtain the grease film pressure, solves the distribution of the grease solidified layer, solves the VonMise stress on the subsurface of the bearing, and solves the thermal deformation and temperature rise on the surface of the bearing. The present invention can consider the influence of the air gap caused by the machining and installation of the hub motor on the unbalanced magnetic pull of the motor bearing, is applicable to the grease lubrication state, and can quickly and accurately calculate the grease lubrication contact characteristics of the hub motor bearing based on the motor theory and the elastohydrodynamic lubrication theory through different grease lubrication models.

Description

Technical Field

[0001] The invention belongs to the technical field of automation and relates to a method for solving the grease lubrication contact characteristics of a hub motor bearing. Background Art

[0002] In the hub motor, the motor bearing is a key component of the hub motor, and most of them are also lubricated with grease. This type of bearing is widely used in electric drive hub transmission systems due to its small size, high operating speed, and low leakage. The hub motor bearing is lubricated with grease, which can reduce friction and wear during operation and play a certain supporting role. The lubrication performance directly affects the efficiency, fatigue life and dynamic characteristics of the hub motor bearing. However, the hub motor bearing is currently affected by the rotor unbalanced magnetic pull brought by the motor itself and the lubrication performance of the grease during operation. Due to the unclear coupling between the grease lubrication mechanism of the hub motor bearing and the unbalanced magnetic pull of the motor, it is easy to produce intensified vibration and excessive contact stress under harsh working conditions such as high speed and unbalanced magnetic pull of the motor, causing common failure forms such as wear and pitting on the rolling surface. In addition, the lubrication performance of the solidified layer and the flowing layer of the lubricating film in the contact area of ​​the hub motor bearing under grease lubrication conditions is quite different. The thickness of the solidified layer in the contact area will have a great influence on its lubrication performance. Under high speed and large unbalanced magnetic pull of the motor, the temperature of the contact area of ​​the hub motor bearing will change greatly, which will directly affect the early failure and fatigue life of the hub motor bearing.

[0003] Traditional hub motor bearing contact characteristics are mostly calculated using mature commercial finite element software, ignoring the unbalanced magnetic pull brought by the hub motor itself, the influence of the coupling effect of hub motor bearing grease lubrication, and the temperature field change under lubrication. Although this treatment has brought great convenience to the research of hub motor bearing contact stress, deformation, etc., it cannot accurately and truly reflect the contact characteristics of hub motor bearings under real working conditions, and thus cannot accurately provide guidance for the working speed, ambient temperature and grease parameters of hub motor bearings in actual production and use. In addition, the calculation of hub motor bearing contact characteristics considering the influence of unbalanced magnetic pull and thermal elastic hydrodynamic lubrication involves iterative calculations of lubricating film pressure and load, temperature increment and thermal deformation. The amount of calculation is undoubtedly very large. The use of traditional calculation methods seriously consumes calculation time and resources, and even cannot be solved. Therefore, the traditional calculation method of hub motor bearing grease lubrication contact characteristics is more statistical and empirical, and its accuracy is not accurate enough and its efficiency is not efficient enough. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for solving the grease lubrication contact characteristics of a hub motor bearing, which can consider the unbalanced magnetic pull force brought by the motor and the influence of grease lubrication conditions on the contact characteristics of the hub motor bearing, and can accurately and quickly calculate the contact characteristics in the contact area of the hub motor bearing.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for solving the grease lubrication contact characteristics of a hub motor bearing, the method comprising the following steps:

[0007] S1: Calculate the air-gap fundamental magnetic potential f(α m , t) of the motor based on electrical machinery theory and Maxwell's law, and solve the radial electromagnetic force per unit area q(α m , t) on the rotor surface under different eccentric states, perform integral operation to obtain the unbalanced magnetic pull force F of the rotor, and couple the unbalanced magnetic pull force F with the solution of the grease lubrication contact characteristics of the hub motor bearing through a grease lubrication analysis model of rolling bearings;

[0008] S2: Calculate the range F in of the unbalanced magnetic pull force of the rotor based on the motor structure and design parameters, and at the same time take the temperature range T in of the hub motor bearing under the operating conditions to be considered and the speed range n in as inputs;

[0009] S3: Iteratively solve the normal force F c of the maximum load-carrying rolling element of the bearing and the entrainment velocity U by the Newton-Raphson method;

[0010] S4: Solve the comprehensive elastic deformation V m between the rolling element and the outer raceway and the film thickness h by using the influence coefficient method ICM, the Green's function method, and the FFT algorithm;

[0011] S5: Solve the pressure distribution P (i,j) and the load distribution Q (i,j) in the contact area between the outer raceway and the rolling element of the hub motor bearing based on the H-B rheological model and the Ostwald rheological model;

[0012] S6: Judge whether the pressure P and the load Q converge. If they do not converge, update the initial values of the pressure P and the central film thickness h c and return to S4. If they converge, end the iteration and transfer to step S7;

[0013] S7: Based on the H-B rheological model, use ICM and the fast Fourier transform FFT to solve the thickness and range H p(x, y) and the von Mises stress distribution ζ(x, y) of the rolling elements and the outer raceway;

[0014] S8: Based on the Ostwald rheological model and the moving heat source method ITD, combined with the heat conduction equation and the energy equation, use the ICM and FFT methods to solve the temperature distribution T in the contact area of the in-wheel motor bearing (i,j) and the thermal deformation V t(i,j) ;

[0015] S9: Judge whether the temperature T converges. If it does not converge, update the initial temperature value and return to S4. If it converges, end the iteration and output the analysis results of the grease lubrication contact characteristics of the in-wheel motor bearing.

[0016] Optionally, the specific content of S1 is:

[0017] S101: According to the electrical machinery theory, through the input motor structure and design parameters, solve the air-gap fundamental wave magnetomotive force f(α m , t) = F1 cos(ω r t - pα m ) at any attitude angle and any moment of the motor;

[0018] S102: According to different eccentric conditions of the motor rotor, use the Maxwell's law and the Gauss method to solve the air-gap length δ i (α m , t) = δ[1 - ε1 cosα m - ε2 cos(α m - θ)] under the working conditions including no eccentricity i = 0, static eccentricity i = 1, dynamic eccentricity i = 2, and combined eccentricity i = 3;

[0019] S103: According to the electromagnetic theory, solve the unit air-gap permeance Λ i = μ0 / δ i ;

[0020] S104: Solve the air-gap magnetic density B i (α m , t) at any attitude angle and any moment under different eccentricities according to the unit air-gap permeance and the air-gap fundamental wave magnetomotive force, where B m (α i , t) = f(α i , t)Λ m i (α m , t) on the rotor surface per unit area of the radial electromagnetic force q i (α 2 , t) = B m i (α m, t) / (2μ0);

[0022] S106: The radial force q per unit area on the surface of the integral rotor i (α m , t), calculate the unbalanced magnetic pull force under various eccentricity conditions, and divide the magnetic pull force into two directions, x and y, which can be expressed as Therefore, the radial unbalanced magnetic pull force is

[0023] S107: Couple the unbalanced magnetic pull force with the centrifugal force and other loads, and perform quasi-static analysis based on the thermal analysis model between the rolling elements and the outer raceway in the rolling bearing. Obtain the normal load F through the Newton-Raphson method c and the entrainment velocity U.

[0024] Optionally, in the S1, calculate and solve the air gap length δ, the air gap magnetic density B, the radial electromagnetic force q per unit area, and the unbalanced magnetic pull force F r while considering the following four air gap conditions: (1) no eccentricity; (2) static eccentricity; (3) dynamic eccentricity; (4) compound eccentricity.

[0025] Optionally, in the S1, perform quasi-static analysis based on the grease lubrication analysis model between the rolling elements and the outer raceway in the rolling bearing, and couple the unbalanced magnetic pull force F r with the solution of the grease lubrication contact characteristics of the hub motor bearing;

[0026]

[0027]

[0028] Optionally, in the S7, based on the pressure partial derivative obtained from the H-B rheological model, through the flow field stratification equation calculate the thickness and range H of the solidified layer p (x, y).

[0029] Optionally, the S8 is specifically:

[0030] S801: Calculate the pressure distribution P and the load distribution Q in the contact area between the outer raceway and the rolling elements under the grease lubrication condition of the hub motor bearing through the Ostwald rheological model (i,j) and the load distribution Q (i,j) ;

[0031] S802: Based on the heat conduction equation and the energy equation, solve the temperature distribution T in the contact area between the outer raceway and the rolling elements of the hub motor bearing through the pressure distribution in the contact area and the grease movement velocity (i,j) ;

[0032] S803: Obtain the thermal deformation influence coefficient K of the contact interface in the rolling elements and raceways according to the rectangular approximation method c ;

[0033] S804: Based on the ICM method and the moving heat source method, quickly solve the thermal deformation caused by each temperature layer

[0034] The beneficial effects of the present invention are as follows: This method accurately obtains the distribution of the grease solidification layer, its working temperature rise and thermal deformation of the hub motor bearing under grease lubrication conditions by using the Reynolds equation under different lubricant rheological models. In addition, it can also be used to calculate the contact characteristics such as elastic deformation, von Mises stress, and lubricating film pressure of the hub motor bearing under grease lubrication conditions. The method proposed by the present invention can provide theoretical guidance for the optimal design and use of hub motors and their bearings in engineering practice, which is beneficial to extending the service life of hub motor bearings and improving the reliability of mechanical systems. The technical content of the present invention, a method for solving the grease lubrication contact characteristics of hub motor bearings, mainly aims at the hub motor bearings affected by the unbalanced magnetic pull force brought by the hub motor, and at the same time couples the thermo-elastohydrodynamic lubrication theory to quickly solve the contact characteristics under its grease lubrication conditions; the present invention discloses a calculation method and process for the unbalanced magnetic pull force affected by the air gap of the hub motor, and also discloses a coupling calculation method and process for the unbalanced magnetic pull force of the motor and the grease lubrication contact characteristics of the hub motor bearing, which has certain theoretical guiding significance when applied to the actual production and use of hub motor bearings.

[0035] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in preferred detail below in conjunction with the drawings, where:

[0037] Figure 1 It is a schematic diagram of the structure of an electric drive hub;

[0038] Figure 2 It is a schematic diagram of the grease lubrication quasi-static analysis model;

[0039] Figure 3 It is a schematic diagram of the distribution of the grease solidification layer of the motor bearing;

[0040] Figure 4 It is a schematic diagram for explaining the solution of the contact characteristics of the hub motor; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The following specific examples are used to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0042] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams rather than actual diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0043] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] In an electric drive hub, the motor bearing is generally on the high-speed output shaft of the motor. Due to the air-gap eccentricity generated during the machining and installation of the motor rotor, there will be an unbalanced magnetic pulling force acting on the motor bearing, as Figure 1 shown.

[0045] Schematic diagrams of various working conditions of the air-gap eccentricity of the in-wheel motor are as Figure 1 shown. In the figure, o is the center of the stator circle, o s is the center of the rotor shape, o s o is the static eccentricity of the rotor, oo r is the dynamic eccentricity of the rotor, and θ is the direction angle between the geometric center of the rotor and the x-axis. Since the motor rotor rotates continuously, the air-gap length of the rotor is not only a function of the relative position between the stator and the rotor, but also a function of time. Calculating the unbalanced magnetic pulling force of various air-gap eccentricity working conditions of the in-wheel motor requires first calculating the air-gap fundamental magnetic potential at any attitude angle and any moment of the motor, that is:

[0046] f(α m, t) = F1 cos(ω r t - pα m ) (1)

[0047] Wherein, f is the air-gap fundamental magnetic potential at any attitude angle of the motor at any moment; α m is the attitude angle of the motor at any time; t is any moment of the motor; F1 is the amplitude of the fundamental magnetic potential of the motor, ω r is the angular frequency of the electronic rotor, and p is the rotor frequency.

[0048] According to different eccentric conditions of the motor rotor, based on Maxwell's law, the air-gap lengths under conditions including no eccentricity, static eccentricity, dynamic eccentricity, and combined eccentricity are solved respectively by the Gauss method:

[0049] δ s (α m ) = δ(1 - ε s cosα m ) (2a)

[0050] δ d (α m , t) ≈ δ - r0·cos(α m - θ) = δ[1 - ε d cos(α m - θ)] (2b)

[0051] δ e (α m , t) = δ[1 - ε s cosα m - ε d cos(α m - θ)] (2c)

[0052] Wherein, δs is the air-gap size under static eccentricity, δ d is the air-gap size under dynamic eccentricity; δ e is the air-gap size under combined eccentricity; δ is the air-gap size under no eccentricity; θ is the angle of the eccentric position from the origin; α m is the stator mechanical angle. The air-gap unit permeance under each eccentric condition can be obtained from the air-gap length and the vacuum permeance:

[0053]

[0054]

[0055]

[0056]

[0057] Wherein, Λ ois the air-gap unit permeance without eccentricity, Λ s is the air-gap unit permeance with static eccentricity, Λ d is the air-gap unit permeance with dynamic eccentricity; Λ e is the air-gap unit permeance with compound eccentricity; μ0 is the permeability of free space.

[0058] Therefore, the radial electromagnetic force per unit area on the rotor surface under the conditions of no eccentricity, static eccentricity, dynamic eccentricity, and compound eccentricity of the air gap is obtained through Maxwell's law:

[0059]

[0060]

[0061]

[0062]

[0063] where q o is the radial electromagnetic force without eccentricity, q s is the radial electromagnetic force with static eccentricity, q d is the radial electromagnetic force with dynamic eccentricity; q e is the radial electromagnetic force with compound eccentricity; B is the air-gap magnetic flux density; Λ is the unit permeance; μ0 is the permeability of free space.

[0064] Integrating the radial electromagnetic force per unit area on the rotor surface under each eccentricity condition in Equation 4, the unbalanced magnetic pull force on the rotor under different eccentricity conditions can be obtained:

[0065]

[0066] In Equation (5), L and R are the effective length of the rotor and the surface radius of the rotor, respectively.

[0067] Based on the grease lubrication analysis model, a quasi-static analysis is carried out, as Figure 2 shown. According to the structural parameters of the in-wheel motor bearing and the unbalanced magnetic pull force (taking the maximum value), centrifugal force, and other radial forces acting on the bearing, a non-linear equation system with δ0 and as unknowns is formed:

[0068]

[0069]

[0070] where F, F b are the unbalanced magnetic pull force and other radial forces, respectively; is the centrifugal force at the azimuth angle θ; is the normal displacement between the raceways at the azimuth angle θ; δ0 is the radial movement of the bearing ring at the azimuth angle θ = 0°; P d is the radial clearance of the bearing; K i is the load-displacement coefficient of the inner raceway; K o is the load-displacement coefficient of the outer raceway. Furthermore, the normal loads between the rolling elements and the inner and outer raceways at the azimuth angle θ are solved through the load-displacement coefficients of the inner and outer raceways and complete the coupling of the theoretical calculation of unbalanced magnetic pull in electrical machinery theory and the solution algorithm for the grease lubrication contact characteristics of bearings.

[0071]

[0072]

[0073] Taking the unbalanced magnetic pull on the rotor under different eccentric conditions as the input quantity, and considering the ambient temperature and the motor speed, a method for solving the grease lubrication contact characteristics of in-wheel motor bearings based on electrical machinery theory and thermo-elastohydrodynamic lubrication theory is realized through the following steps:

[0074] S1: Calculate the air-gap fundamental magnetic potential f(α m , t) of the motor based on electrical machinery theory and Maxwell's law, and solve the radial electromagnetic force per unit area q(α m , t) on the rotor surface under different eccentric states. The integral operation is used to obtain the unbalanced magnetic pull F of the rotor, and the unbalanced magnetic pull F is coupled with the solution of the grease lubrication contact characteristics of in-wheel motor bearings through the grease lubrication analysis model of rolling bearings;

[0075] S2: Calculate the range F in of the unbalanced magnetic pull of the rotor based on the motor structure and design parameters. At the same time, the temperature range T in of the in-wheel motor bearings to be considered and the speed range n in are used as inputs;

[0076] S3: Iteratively solve the normal force F c of the maximum load-bearing rolling element of the bearing and the entrainment speed U through the Newton-Raphson method;

[0077] S4: Use the ICM, Green's function method, and FFT algorithm to solve the comprehensive elastic deformation V m between the rolling element and the outer raceway and the film thickness h;

[0078] S5: Based on the H-B rheological model and the Ostwald rheological model, solve the pressure distribution P (i,j) and the load distribution Q (i,j) in the contact area between the outer raceway and the rolling element of the in-wheel motor bearing;

[0079] S6: Determine whether the pressure P and the load Q converge. If they do not converge, update the initial values of the pressure P and the central film thickness h and return to S4. If they converge, end the iteration and proceed to step S7; c The initial values and return to S4. If they converge, end the iteration and proceed to step S7;

[0080] S7: Based on the H-B rheological model, use ICM and FFT to solve and obtain the von Mises stress distribution ζ(x,y) of the rolling element and the outer raceway, and based on the partial derivative of the contact zone pressure between the rolling element and the raceway obtained from the H-B rheological model, use the flow field stratification equation to calculate the thickness and range H of the solidified layer p (x,y), as Figure 3 shown.

[0081] S8: Based on the Ostwald rheological model and the moving heat source method, combine the heat conduction equation and the energy equation, and use the ICM and FFT methods to solve the temperature distribution T (i,j) and the thermal deformation V t(i,j) ;

[0082] S9: Determine whether the temperature T converges. If it does not converge, update the initial temperature value and return to S4. If it converges, end the iteration and output the analysis results of the grease lubrication contact characteristics of the in-wheel motor bearing.

[0083] The above process can be represented by Figure 4 the flow chart for solving the grease lubrication contact characteristics of the in-wheel motor bearing shown.

[0084] In step S8, the specific method for solving the temperature distribution and thermal deformation of the outer raceway is as follows:

[0085] S801: Based on the Ostwald rheological model, use the Gauss elimination method to calculate the pressure distribution P (i,j) and the load distribution Q (i,j) in the lubrication calculation domain. For the Ostwald fluid, its Reynolds equation can be expressed as

[0086]

[0087] where h is the grease film thickness, p is the grease film pressure, η is the grease viscosity, ρ is the grease density, and u e is the velocity of the grease fluid layer.

[0088] S802: Based on the heat conduction equation and the energy equation, solve the temperature distribution T (i,j) of the contact zone between the outer raceway and the rolling element of the in-wheel motor bearing through the pressure distribution and the grease movement velocity. Without considering the action of the grease body force and heat radiation, and ignoring the heat conduction effect of the grease along the x and y directions, the energy equation of the grease is:

[0089]

[0090] In the formula, c f is the specific heat capacity of the grease, k f is the thermal conductivity of the grease, and η is the equivalent viscosity. u and v represent the velocities of the grease in the x and y directions, and represent the velocity gradients of the grease in the x and y directions, respectively.

[0091] The heat conduction equations of the rolling elements and the outer raceway in the rolling bearing are respectively:

[0092]

[0093]

[0094] In the formula, c1 (c2), ρ1 (ρ2), and k1 (k2) respectively refer to the specific heat capacity, density, and thermal conductivity of the rolling element 1 and the outer raceway 2. z1 and z2 are the coordinates of the rolling element 1 and the outer raceway 2 in the film thickness direction, and their positive directions are consistent with the positive direction of the film thickness direction z.

[0095] S803: The numerical calculation range of the present invention is taken as: x in ≤x≤x out , y in ≤y≤y out , 0≤z≤h t , and the corresponding grid system is: NX×NY×NL, where h t is the temperature penetration layer thickness from the solid-liquid interface to the inside of the rolling element / raceway of the hub motor bearing. K c (x i -x s , y j -y t , z k ) is the comprehensive thermal deformation influence coefficient of the contact interface caused by the k-th temperature layer in the rolling element / raceway of the hub motor bearing, briefly denoted as K c (x, y).

[0096] According to the rectangular approximation method, the thermal deformation influence coefficient of the contact interface caused by the k-th temperature layer in the rolling element / raceway of the reducer bearing can be obtained, that is:

[0097]

[0098] In the formula, x m , x p , y m and y p are related to the thermal deformation influence coefficient.

[0099] S804: To better combine with the internal temperature of the rolling elements / raceways of the in-wheel motor bearing obtained from the thermo-elastohydrodynamic lubrication calculation, the present invention proposes a moving heat source method for calculating the surface thermal deformation based on the internal temperature distribution of the solid. The specific implementation process is described as follows. When a half-space with an initial temperature of T0 undergoes a temperature rise of ΔT at the point (x′, y′, z′) under the action of an external heat source, thermal deformation will occur at the surface point (x, y, 0) of the half-space under the action of the internal temperature rise. Based on the principle of linear elastic superposition, the thermal deformation of the contact interface of the rolling elements / raceways of the in-wheel motor bearing caused by each temperature layer is discretized, that is:

[0100]

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for solving the grease lubrication contact characteristics of a hub motor bearing, characterized in that: The method includes the following steps: S1: Calculate the air-gap fundamental magnetic potential f(α m , t) of the motor based on the theory of electrical machinery and Maxwell's law, and solve the radial electromagnetic force q(α m , t) per unit area on the rotor surface under different eccentric states. Integrate to obtain the unbalanced magnetic pull F of the rotor, and couple the unbalanced magnetic pull F with the solution of the grease lubrication contact characteristics of the in-wheel motor bearing through the grease lubrication analysis model of the rolling bearing; S2: Calculate the range of the rotor unbalanced magnetic pull force F based on the motor structure and design parameters in , and at the same time, take the hub motor bearing temperature range T in to be considered and the rotational speed range n in as inputs; S3: Iteratively solve for the normal force F of the maximum load-bearing rolling element of the bearing by the Newton-Raphson method c and the entrainment velocity U; S4: Solve the comprehensive elastic deformation V of the rolling elements and the outer raceway using the Influence Coefficient Method (ICM), Green's function method, and FFT algorithm m and the film thickness h; S5: Solve the pressure distribution P (i,j) (i,j) and the load distribution Q (i,j) (i,j) ; S6: Determine whether the pressure P and the load Q converge. If they do not converge, update the initial values of the pressure P and the central film thickness h and return to S4. If they converge, end the iteration and proceed to step S7; c The initial values and return to S4. If they converge, end the iteration and proceed to step S7; S7: Based on the H-B rheological model, the thickness and range H of the grease solidified layer are solved by using ICM and the fast Fourier transform FFT p (x, y) and the von Mises stress distribution ζ(x, y) of the rolling element and the outer raceway; S8: Based on the Ostwald rheological model and the moving heat source method ITD, combined with the heat conduction equation and the energy equation, use the ICM and FFT methods to solve the temperature distribution T of the contact area of the in-wheel motor bearing (i,j) and the thermal deformation V t(i,j) ; S9: Determine whether the temperature T converges. If it does not converge, update the initial temperature value and return to S4. If it converges, end the iteration and output the analysis results of the grease lubrication contact characteristics of the in-wheel motor bearing.

2. The grease lubrication contact characteristic solving method for a hub motor bearing according to claim 1, characterized in that: Specifically, S1 is as follows: S101: According to the theory of electrical machinery, by inputting the structure and design parameters of the motor, solve the air-gap fundamental magnetic potential f(α m , t) = F1cos(ω r t - pα m ) at any attitude angle and any moment of the motor; S102: According to different motor rotor eccentricity conditions, by Maxwell's law, the air-gap length δ is solved respectively by the Gauss method for working conditions including no eccentricity (i = 0), static eccentricity (i = 1), dynamic eccentricity (i = 2), and combined eccentricity (i = 3). i (α m , t) = δ[1 - ε1cosα m - ε2cos(α m - θ)]; S103: Solve for the per-unit air-gap permeance Λ of the motor according to electromagnetic theory i = μ0 / δ i ; S104: Solve the air-gap magnetic density B at any attitude angle and any time under different eccentricities according to the unit air-gap permeance and the fundamental air-gap magnetomotive force i (α m , t) = f(α m , t)Λ i ; S105: Air-gap permeance δ under no eccentricity, static eccentricity, dynamic eccentricity, and combined eccentricity i (α m , t) Radial electromagnetic force per unit area on the rotor surface S106: Radial force q per unit area on the surface of the integral rotor i (α m , t), the unbalanced magnetic pull under each eccentricity condition is obtained, and the magnetic pull can be divided into two directions, x and y, and can be expressed as Therefore, the radial unbalanced magnetic pull is S107: Couple the unbalanced magnetic pull force with the centrifugal force and other loads, perform a quasi-static analysis based on the thermal analysis model between the rolling elements and the outer raceway in the rolling bearing, and obtain the normal load F by the Newton-Raphson method c and the entrainment velocity U.

3. A method for solving the grease lubrication contact characteristics of a hub motor bearing according to claim 1, characterized in that: In S1, calculate and solve for the air-gap length δ, air-gap magnetic flux density B, radial electromagnetic force q per unit area, and unbalanced magnetic pull F r When considering the following four air-gap conditions: (1) no eccentricity; (2) static eccentricity; (3) dynamic eccentricity; (4) combined eccentricity.

4. The grease lubrication contact characteristic solving method for a hub motor bearing according to claim 1, characterized in that: In S1, quasi-static analysis is carried out based on the grease lubrication analysis model between the rolling elements and the outer raceway in the rolling bearing, and the unbalanced magnetic pull F r is coupled with the solution of the grease lubrication contact characteristics of the in-wheel motor bearing; 5. The method for solving the grease lubrication contact characteristics of a hub motor bearing according to claim 1, wherein: In the above S7, the pressure partial derivative obtained based on the H-B rheological model is used to obtain the thickness and range H of the solidified layer through the flow field stratification equation to calculate the thickness and range H of the solidified layer p (x, y).

6. The method for solving the grease lubrication contact characteristics of a wheel hub motor bearing according to claim 1, wherein: Specifically, S8 is as follows: S801: Calculate the pressure distribution P of the contact area between the outer raceway and the rolling elements in the case of grease lubrication of the in-wheel motor bearing through the Ostwald rheological model (i,j) and the load distribution Q (i,j) ; S802: Based on the heat conduction equation and the energy equation, solve for the temperature distribution T in the contact area between the outer raceway of the hub motor bearing and the rolling elements through the pressure distribution in the contact area and the movement speed of the grease (i,j) ; S803: Calculate the thermal deformation influence coefficient \(K\) of the contact interface in the rolling elements and raceways according to the rectangular approximation method c ; S804: Based on the ICM method and the moving heat source method, quickly solve the thermal deformation caused by each temperature layer

Images