CN117010231A

CN117010231A - Method and device for analyzing and evaluating pitting corrosion of planetary gear of differential mechanism of electric vehicle

Info

Publication number: CN117010231A
Application number: CN202310738460.3A
Authority: CN
Inventors: 康一坡; 闫博; 张尤龙; 刘明远
Original assignee: FAW Group Corp
Current assignee: FAW Group Corp
Priority date: 2023-06-21
Filing date: 2023-06-21
Publication date: 2023-11-07

Abstract

The invention discloses a method and a device for analyzing and evaluating pitting corrosion of a planetary gear of an electric vehicle differential, comprising the following steps: constructing a differential mechanism assembly finite element model, and respectively defining material properties of the differential mechanism assembly finite element model; defining boundary conditions of a differential case, a first side gear and a second side gear in the differential assembly finite element model respectively; defining model loads for the first and second side gear finite element models, respectively; respectively defining the calculation working conditions of two planetary gear finite element models with the same structure, and respectively defining friction coefficients between the first half-shaft gear finite element model, the second half-shaft gear finite element model and the two planetary gear finite element models; and performing finite element analysis on the two planetary gear finite element models to obtain two planetary gear finite element model finite element analysis data respectively, and performing pitting corrosion analysis evaluation on the two planetary gear finite element model finite element analysis data respectively.

Description

Method and device for analyzing and evaluating pitting corrosion of planetary gear of differential mechanism of electric vehicle

Technical Field

The invention discloses a method and a device for analyzing and evaluating pitting corrosion of a planetary gear of an electric vehicle differential, and belongs to the field of auxiliary design of gear parameters.

Background

Planetary gear transmission systems are important basic components in mechanical devices, and with the continuous change of application requirements, rapid development is currently proceeding towards high power density, high reliability and long service life. Under the service conditions of high contact stress and wide rotation speed domain, the meshing tooth surface is easy to present a changeable damage form under the interweaving influence of complex factors, and a plurality of failure modes such as pitting, micro pitting, hot gluing, deep flaking, tooth surface fracture and the like are often presented. Particularly in the field of new energy electric vehicles, the electric vehicle transmission system omits a torque converter, a clutch and other torsional vibration damping elements, and is characterized by an underdamping system which directly bears the random rotation speed and torque action of a motor and wheels, so that the actual bearing load of a planetary gear in a differential mechanism also has strong timeliness and randomness, the dynamic meshing process of the planetary gear is obviously influenced, the pitting of a tooth surface is easily caused, and the normal work of the transmission system is finally influenced. Therefore, reasonably predicting the pitting corrosion of the planetary gears of the differential mechanism of the electric vehicle has important significance for the structural design of the planetary gears.

The gear pitting prediction mainly adopts three methods, namely, the prediction is carried out through tooth surface contact stress, for example, a formula method is adopted in the national standard GB/T10062.2-2003 (bevel gear bearing capacity calculation method 2 nd part: tooth surface contact fatigue (pitting) strength calculation), the tooth surface contact stress is calculated through selecting a load sharing coefficient, a bevel gear coefficient, a lubricating oil film influence coefficient and the like in the formula to carry out pitting prediction, and when the tooth surface contact stress exceeds a contact fatigue limit, metal particles of the tooth surface fall off, and the tooth surface is pitted. And secondly, predicting by calculating the film thickness ratio, for example, a semi-theoretical semi-empirical Dowson/Higginson fitting formula is adopted in paper 'research on competitive failure mechanism of micro pitting and hot gluing of gear transmission', and the oil film thickness is calculated by giving a lubricating oil characteristic correction coefficient based on temperature change test, an oil film thickness calculation load comprehensive correction coefficient, a load split coefficient and the like, so that the ratio of the minimum oil film thickness of the lubricating oil to the average roughness value of two meshed tooth surfaces, namely, the film thickness ratio is smaller than a threshold value, and pitting occurs on the tooth surfaces. Thirdly, predicting by using stress intensity factors, for example, giving the length of an initial crack and the angle of relative movement speed at the maximum value of stress of a contact position Von-mises in paper 'gear pitting abrasive particle morphological feature simulation based on extended finite elements', and performing J integral calculation on the stress intensity factors of the crack tips in the pitting crack expansion process by using an extended finite element method (XFEM), wherein when the stress intensity factors are considered to be larger than a threshold value, tooth surface materials are separated from the tooth surface, so that tooth surface pitting is formed. The three methods have the common advantages that the tooth surface pitting corrosion can be effectively predicted, and the defects that a large number of necessary coefficients are required to be given in advance based on experience before calculation, so that the calculated contact stress, the lubricating oil film thickness and the stress intensity factor are different from person to person, the predicted results of different engineers are different, the difference is large, and the method brings trouble to the gear pitting corrosion prediction engineering practice.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an analysis and evaluation method and device for the pitting corrosion of an electric vehicle differential planetary gear, which solve the problems that the prior gear pitting corrosion prediction calculation needs to be based on a large number of necessary coefficients given in advance by experience, so that the calculated contact stress, lubricating oil film thickness and stress intensity factors are different from person to person, the predicted results of different engineers are different, the difference is large, and the problem of trouble is brought to the practice of gear pitting corrosion prediction engineering.

The technical scheme of the invention is as follows:

according to a first aspect of an embodiment of the present invention, there is provided a method for analyzing and evaluating pitting corrosion of an electric vehicle differential planetary gear, including:

constructing a differential mechanism assembly finite element model, and respectively defining material properties of the differential mechanism assembly finite element model;

defining boundary conditions of a differential case, a first side gear and a second side gear in the differential assembly finite element model respectively;

defining model loads for the first and second side gear finite element models, respectively;

respectively defining the calculation working conditions of two planetary gear finite element models with the same structure, and respectively defining friction coefficients between the first half-shaft gear finite element model, the second half-shaft gear finite element model and the two planetary gear finite element models;

And performing finite element analysis on the two planetary gear finite element models to obtain two planetary gear finite element model finite element analysis data respectively, and performing pitting corrosion analysis evaluation on the two planetary gear finite element model finite element analysis data respectively.

Preferably, before the finite element analysis is performed on the two planetary gear finite element models to obtain the two planetary gear finite element model finite element analysis data, the method further includes:

and adjusting initial meshing positions of the two planetary gear finite element models and the first half-shaft gear finite element model and the second half-shaft gear finite element model respectively to enable tooth surfaces of the planetary gears and the half-shaft gears to be in a small interference state, wherein the small interference is not more than 0.001mm.

Preferably, the material properties of the differential assembly finite element model include at least: modulus of elasticity and poisson ratio;

the boundary conditions defining the differential case, the first side gear, and the second side gear in the differential assembly finite element model include:

first boundary conditions: fixing two ends of the differential shell finite element model, wherein one end of the differential shell finite element model is fixed with radial translation and axial translation, and the other end is only fixed with radial translation;

Second boundary condition: fixing the rotational freedom degree of the first half-shaft gear finite element model;

third boundary condition: fixing the rotational freedom degree of the second side gear finite element model;

fourth boundary condition: a forced angular displacement is imposed on the differential case finite element model that rotates about the differential case centerline.

Preferably, the model loads are defined for the first and second side gear finite element models, respectively, the model loads including first, second, third, fourth, fifth, and sixth loads that are each torques, wherein:

the first load, the magnitude of which is equal to 0.1 times of the maximum design torque of the differential, is applied to the first half-shaft gear along the center line of the differential shell in the direction opposite to the forced angular displacement direction;

the second load, which is equal to 0.1 times the maximum design torque of the differential, is applied to the second side gear along the center line of the differential case in a direction opposite to the direction of the forced angular displacement;

the third load, the magnitude of which is equal to 0.3 times of the maximum design torque of the differential, is applied to the first half-shaft gear along the center line of the differential shell in the direction opposite to the forced angular displacement direction;

The fourth load, which is equal to 0.3 times the maximum design torque of the differential, is applied to the second side gear along the center line of the differential case in a direction opposite to the direction of the forced angular displacement;

the fifth load, the magnitude of which is equal to 1.0 times of the maximum design torque of the differential, is applied to the first half-shaft gear along the center line of the differential housing in the direction opposite to the forced angular displacement direction;

the sixth load, which is equal to 1.0 times the differential maximum design torque, is applied to the second side gear along the differential case centerline in a direction opposite to the forced angular displacement direction.

Preferably, the calculating working conditions of the two planetary finite element models with the same structure are defined respectively, and the calculating working conditions comprise:

the first computing working condition comprises a first boundary condition, a second boundary condition and a second load;

the second computing working condition comprises a first boundary condition, a third boundary condition and a first load;

the third computing working condition comprises a first boundary condition, a second boundary condition and a fourth load;

the fourth computing working condition comprises a first boundary condition, a third boundary condition and a third load;

a fifth calculation condition comprising a first boundary condition, a second boundary condition, and a sixth load;

A sixth calculation condition including a first boundary condition, a third boundary condition, and a fifth load;

and the seventh calculation working condition comprises a fourth boundary condition.

Preferably, the finite element analysis of the two planetary gear finite element models to obtain two planetary gear finite element model finite element analysis data respectively includes:

the two planetary finite element models are analyzed according to the following analysis steps:

the method comprises the steps of a first analysis step, namely analyzing a first calculation working condition, and then analyzing a seventh calculation working condition to obtain finite element analysis data of a finite element model of a first planet gear;

a second analysis step of analyzing a second calculation working condition and then analyzing a seventh calculation working condition to obtain finite element analysis data of a second planetary gear finite element model;

a third analysis step of analyzing a third calculation working condition and then analyzing a seventh calculation working condition to obtain finite element analysis data of a third planetary gear finite element model;

a fourth analysis step of analyzing a fourth calculation condition and then analyzing a seventh calculation condition to obtain finite element analysis data of a fourth planetary gear finite element model;

a fifth analysis step of analyzing a fifth calculation condition and analyzing a seventh calculation condition to obtain finite element analysis data of a fifth planetary gear finite element model;

A sixth analysis step of analyzing a sixth calculation condition and then analyzing a seventh calculation condition to obtain finite element analysis data of a sixth planetary gear finite element model;

the first planetary gear finite element model finite element analysis data, the second planetary gear finite element model finite element analysis data, the third planetary gear finite element model finite element analysis data, the fourth planetary gear finite element model finite element analysis data, the fifth planetary gear finite element model finite element analysis data and the sixth planetary gear finite element model finite element analysis data respectively comprise: contact pressure, contact area and slip on the tooth surface of the planetary gear.

Preferably, the performing the pitting corrosion analysis and evaluation on the finite element analysis data of the planetary gear finite element model includes:

the method comprises the steps of respectively obtaining finite element analysis data of a first planetary gear finite element model, finite element analysis data of a second planetary gear finite element model, finite element analysis data of a third planetary gear finite element model, finite element analysis data of a fourth planetary gear finite element model, finite element analysis data of a fifth planetary gear finite element model and finite element analysis data of a sixth planetary gear finite element model of two planetary gear finite element models, and respectively obtaining friction work of two groups of moments through a formula (1):

W＝PAfL (1)

Wherein: f is friction coefficient, P is contact pressure on the tooth surface of the planetary gear, A is contact area, and L is slip quantity;

judging whether the friction work is smaller than or equal to 0.5J according to the friction work at each of two groups of moments:

if yes, the corresponding planetary gear cannot be pitted;

if not, the corresponding planet gears are optimized respectively with the first half shaft gear and the second half shaft gear, so that the friction work is reduced, and the pitting corrosion resistance of the planet gears is improved.

According to a second aspect of the embodiment of the present invention, there is provided an electric vehicle differential planetary gear pitting analysis and evaluation device, including:

the building module is used for building a differential mechanism assembly finite element model and respectively defining the material properties of the differential mechanism assembly finite element model;

the first defining module is used for respectively defining boundary conditions of a differential shell, a first half-shaft gear and a second half-shaft gear in the differential assembly finite element model;

a second definition module for defining model loads for the first and second side gear finite element models, respectively;

the third definition module is used for respectively defining the calculation working conditions of two planetary gear finite element models with the same structure and respectively defining the friction coefficients between the first half-shaft gear finite element model, the second half-shaft gear finite element model and the two planetary gear finite element models;

And the analysis and evaluation module is used for respectively carrying out finite element analysis on the two planetary gear finite element models to respectively obtain two planetary gear finite element model finite element analysis data, and respectively carrying out pitting corrosion analysis and evaluation on the two planetary gear finite element model finite element analysis data.

According to a third aspect of an embodiment of the present invention, there is provided a terminal including:

one or more processors;

a memory for storing the one or more processor-executable instructions;

wherein the one or more processors are configured to:

the method according to the first aspect of the embodiment of the invention is performed.

According to a fourth aspect of embodiments of the present invention, there is provided a non-transitory computer readable storage medium, which when executed by a processor of a terminal, enables the terminal to perform the method according to the first aspect of embodiments of the present invention.

According to a fifth aspect of embodiments of the present invention, there is provided an application program product for causing a terminal to carry out the method according to the first aspect of embodiments of the present invention when the application program product is run at the terminal.

The invention has the beneficial effects that:

the invention provides a method and a device for analyzing and evaluating the pitting of a planetary gear of an electric vehicle differential mechanism, which avoid a large number of experience coefficient selections during the previous gear pitting prediction, and provide the method and the steps for analyzing and evaluating the pitting of the planetary gear in detail in the aspects of finite element model construction, calculation working condition selection, result analysis and the like, and consider the influence of the relative slippage of the contact position of a tooth surface under the action of contact stress, so that the pitting analysis and evaluation are more consistent with a pitting mechanism, and the established method for analyzing and evaluating the pitting of the gear is more accurate and effective, and solves the problem that the conclusion varies from person to person in the process of analyzing and evaluating the pitting of the gear, thereby being widely applied to engineering practice;

Considering the influence of rigidity of different positions of the differential housing, the stress condition of the planetary gears in the range of the common torque used by the electric vehicle is simulated by applying different torques on the side gears; the calculated pitting evaluation parameters of the planetary gear are more comprehensive by the measures, and the pitting resistance of the gear designed by analysis is stronger; by adjusting the interference state between the planetary gear and the half-shaft gear, good convergence of the finite element model is ensured, and the model calculation efficiency is improved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart illustrating a method of evaluating an electric vehicle differential planetary gear pitting analysis according to an exemplary embodiment;

FIG. 2 is a flow chart illustrating a method of evaluating an electric vehicle differential planetary gear pitting analysis according to an exemplary embodiment;

FIG. 3 is a schematic diagram of a differential assembly in an exemplary method for evaluating a pitting analysis of an electric vehicle differential planetary gear;

FIG. 4 is a schematic illustration of RBE2 units applying differential case boundary condition definitions in an electric vehicle differential planetary gear pitting analysis evaluation method, according to an exemplary embodiment;

FIG. 5 is a schematic representation of RBE3 units applying side gear boundary condition definitions in accordance with an exemplary embodiment of an electric vehicle differential planetary gear pitting analysis evaluation method;

FIG. 6 is a schematic diagram of RBE3 unit for applying differential case torque definition in an electric vehicle differential planetary gear pitting analysis and evaluation method, according to an exemplary embodiment.

Fig. 7 is a schematic view showing a differential case structure in an electric vehicle differential planetary gear pitting analysis evaluation method according to an exemplary embodiment.

Fig. 8 is a schematic diagram showing a distribution of tooth surface contact pressure of a planetary gear at a certain moment in a method for evaluating pitting corrosion analysis of a planetary gear of a differential gear of an electric vehicle according to an exemplary embodiment.

Fig. 9 is a schematic diagram showing a distribution of tooth surface contact pressure of a planetary gear at the same timing as fig. 8 in an evaluation method of pitting analysis of a planetary gear of a differential gear of an electric vehicle according to an exemplary embodiment.

Fig. 10 is a schematic diagram showing a distribution of the tooth surface slip amount of the planetary gear at the same timing as fig. 8 in a method for evaluating the pitting corrosion analysis of the planetary gear of the differential gear of the electric vehicle according to an exemplary embodiment.

Fig. 11 is a schematic diagram showing a distribution of frictional work on a tooth surface of a planetary gear at the same timing as fig. 8 in a method for evaluating a pitting corrosion analysis of a planetary gear of a differential gear of an electric vehicle according to an exemplary embodiment.

FIG. 12 is a schematic block diagram of an electric vehicle differential planetary gear pitting analysis and evaluation device according to an exemplary embodiment;

fig. 13 is a schematic block diagram of a terminal structure according to an exemplary embodiment.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

The embodiment of the invention provides a method for analyzing and evaluating the pitting corrosion of a planetary gear of an electric vehicle differential mechanism, which is realized by a terminal, wherein the terminal can be a desktop computer or a notebook computer and the like, and at least comprises a CPU and the like.

Example 1

FIG. 1 is a flow chart illustrating a method of analyzing and evaluating pitting corrosion of an electric vehicle differential planetary gear, for use in a terminal, according to an exemplary embodiment, the method comprising the steps of:

step S101, constructing a differential mechanism assembly finite element model, and respectively defining the material properties of the differential mechanism assembly finite element model;

step S102, respectively defining boundary conditions of a differential case, a first half-shaft gear and a second half-shaft gear in a finite element model of the differential assembly;

step S103, defining model loads for the first side gear finite element model and the second side gear finite element model respectively;

step S104, respectively defining the calculation working conditions of two planetary gear finite element models with the same structure, and respectively defining the friction coefficients between the first half-shaft gear finite element model, the second half-shaft gear finite element model and the two planetary gear finite element models;

step S105, performing finite element analysis on the two planetary gear finite element models to obtain two planetary gear finite element model finite element analysis data respectively, and performing pitting corrosion analysis evaluation on the two planetary gear finite element model finite element analysis data respectively.

the method comprises the steps of respectively obtaining first planetary gear finite element model finite element analysis data, second planetary gear finite element model finite element analysis data, third planetary gear finite element model finite element analysis data, fourth planetary gear finite element model finite element analysis data, fifth planetary gear finite element model finite element analysis data and sixth planetary gear finite element model finite element analysis data of two planetary gear finite element models, and respectively obtaining friction work of two groups at each moment through a formula (1):

W＝PAfL (1)

if yes, the corresponding planetary gear cannot be pitted;

Example two

FIG. 2 is a flow chart illustrating a method of analyzing and evaluating pitting corrosion of an electric vehicle differential planetary gear, for use in a terminal, according to an exemplary embodiment, the method comprising the steps of:

The method for analyzing and evaluating the pitting corrosion of the planetary gear of the differential mechanism of the electric vehicle is characterized by comprising the following steps of:

and step S101, constructing a finite element model of the differential assembly.

As shown in fig. 3, the differential assembly includes a word shaft 1001, a first planetary gear 2001, a second planetary gear 2002, a first half-shaft gear 3001, a second half-shaft gear 3002, a pin shaft 4001, a differential case 5001, a driven gear 6001, a first shim 7001, a second shim 7002, a third shim 7003, a fourth shim 7004, a bolt 8001, a first conical bearing 9001, and a second conical bearing 9002, and the grids of the contact portions need to be finely divided, and the grids of other non-contact portions need to be roughly divided, so that the calculation scale is reduced and the calculation speed of the model is improved on the premise of not affecting the force transmission accuracy, by performing solid meshing of the word shaft 1001, the first planetary gear 2001, the second planetary gear 2002, the first half-shaft gear 3001, the second half-shaft gear 3002, the pin shaft 4001, the differential case 5001, the first shim 7001, the second shim 7002, the third shim 7003, and the fourth shim 7004 in the differential assembly; and then assembling the contacted parts together by defining a contact relationship between them;

The mesh size of the four gear tooth surfaces of the first planetary gear 2001, the second planetary gear 2002, the first side gear 3001, and the second side gear 3002 is not more than 0.2mm, so as to reduce the calculation scale while not affecting the finite element calculation accuracy.

Step S202, defining material properties of a finite element model of the differential assembly.

A linear shaft 1001, a first planetary gear 2001, a second planetary gear 2002, a first side gear 3001, a second side gear 3002, a pin shaft 4001, a first shim 7001, a second shim 7002, a third shim 7003, and a fourth shim 7004 are defined, the elastic modulus e=210000 MPa, poisson's ratio μ=0.3, and the elastic modulus e=175000 MPa, poisson's ratio μ=0.3 of the finite element model material of the differential case 5001.

In step S203, boundary conditions of the differential case, the first side gear, and the second side gear in the differential assembly finite element model are defined, respectively.

First boundary conditions: two ends of the differential housing 5001 are fixed, wherein one end 5002 is fixed with radial and axial translation, and the other end 5003 is only fixed with radial so as to simulate the supporting effect of the conical bearing on the differential housing; the boundary condition applying process is illustrated with one end 5002 as an example, and the other end 5003 is the same as it; one end 5002 is fixed by means of a RBE2 unit 5004 and a cylindrical coordinate system 5005, as shown in fig. 4, a main point 5006 of the RBE2 unit 5004 selects a point on a center line 5007 of the differential case, and a node on a surface 5008 of the differential case contacting an inner diameter surface of the first conical bearing 9001 is selected from the point; a cylindrical coordinate system 5005, whose origin o is located on the differential case centerline 5007, the Z axis coinciding with the differential case centerline 5007, the rot plane being perpendicular to the Z axis; the r-direction and Z-direction degrees of freedom of the main point 5006 of the RBE2 unit 5004 are constrained;

Second boundary condition: fixing the rotational degree of freedom of the first half shaft gear 3001 to simulate the reaction force of the half shaft to the first half shaft gear 3001; as shown in fig. 5, the rotation of the first half-shaft gear 3001 is fixed by means of the RBE3 unit 3003 and the cylindrical coordinate system 5005, the RBE3 unit 3003 selecting a point on the differential case centerline 5007 from the point 3004, the main point selecting a node on the internal spline tooth top surface of the first half-shaft gear 3001; constraining the rotational freedom of RBE3 unit 3003 from point 3004 about the Z-axis;

third boundary condition: fixing the rotational degree of freedom of the second side gear 3001 to simulate the reaction of the half shafts to the second side gear 3002; the rotational freedom of the second side gear 3002 is fixed by the RBE3 unit and the cylindrical coordinate system, and the fixing method is the same as that of the first side gear 3001;

fourth boundary condition: applying a forced angular displacement θ on the differential housing 5001 that rotates about the differential housing centerline to simulate rotation of the differential; the angular displacement theta enables the planetary gear 2001 or 2002 to rotate by one tooth angle, so that the calculation time is reduced, the simulation efficiency is improved, the whole process from the meshing-in to the meshing-out of one tooth on the planetary gear is captured, and then the pitting analysis and evaluation are carried out on the tooth in the whole process from the meshing-in to the meshing-out; in an embodiment, the first side gear and the second side gear each have 13 teeth, and the forced angular displacement θ applied at this time is of the magnitude 2pi/13×2= 0.9667; as shown in fig. 6 and 7, θ is applied to differential housing 5001 by RBE3 unit 5009, RBE3 unit 5009 selecting a point on differential housing centerline 5007 from point 5010, the main point selecting the inner surface node of bolt hole 5011 on the differential housing to which driven gear 6001 (fig. 1) is secured; θ acts on the slave point 5010 of RBE3 unit 5009 in the direction of differential case centerline 5007;

Step S204, defining model loads for the first side gear finite element model and the second side gear finite element model, respectively.

First load: the first load is torque M ₁ The differential maximum design torque, which is equal to 177.2Nm, i.e., 0.1 times, is applied to the first half-shaft gear 3001 along the differential case centerline in a direction opposite to the fourth boundary condition-forced angular displacement θ in step S203; torque M ₁ Applying the RBE3 unit 3003 defined in step S203 from the point 3004;

second load: the second load is torque M ₂ The differential maximum design torque, which is equal to 177.2Nm, i.e., 0.1 times, is applied to the second side gear 3002 along the differential case centerline in a direction opposite to the fourth boundary condition-forced angular displacement θ in step S203; torque M ₂ The RBE3 unit is established by the same method as the RBE3 unit 3003 established on the first half-axis gear, which needs to be applied to the RBE3 unit slave points by the RBE3 unit;

third load: the third load is torque M ₃ The differential maximum design torque, which is equal to 531.6Nm, i.e., 0.3 times, is applied to the first half-shaft gear 3001 along the differential case centerline in the opposite direction to the fourth boundary condition-forced angular displacement θ in step S203; torque M ₃ The application position is the same as the first load;

fourth load: the fourth load is torque M ₄ A differential maximum design torque equal to 531.6Nm, i.e., 0.3 times, is applied to the second side gear 3002 along the differential case centerline in a direction opposite to the fourth boundary condition-imposed angular displacement θ in step S203; torque M ₄ The application position is the same as the second load;

fifth load: the fifth load is torque M ₅ A differential maximum design torque of a magnitude equal to 1772Nm, i.e., 1.0 times, is applied to the first countershaft gear 3001 along the differential case centerline in a direction opposite to the fourth boundary condition-forced angular displacement θ in step S203; torque M ₅ The application position is the same as the first load;

sixth load: the sixth load is torque M ₆ The differential maximum design torque, which is equal in magnitude to 1772Nm, i.e., 1.0 times, is applied to the second side gear 3002 along the differential case centerline in a direction opposite to the fourth boundary condition-imposed angular displacement θ in step S203. Torque M ₆ The location of application is the same as the second load.

Step S205, defining friction coefficients between the first and second side gear finite element models and the two planetary gear finite element models, respectively.

For the different loads in step S204, different friction coefficients f are defined between the first planetary gear 2001 and the first side gear 3001, between the second side gear 3002, between the second planetary gear 2002 and the first side gear 3001, between the second side gear 3002, the friction coefficient f corresponding to the first load and the second load being equal to 0.002, the friction coefficient f corresponding to the third load and the fourth load being equal to 0.005, and the friction coefficient f corresponding to the fifth load and the sixth load being equal to 0.01.

Step S206, respectively defining two planetary gear finite element model calculation working conditions with the same structure.

First calculation condition: comprising a first boundary condition of step S203, a second boundary condition, and a second load of step S204;

the second calculation condition: including step S203 first boundary conditions, third boundary conditions, and step S204 first loads;

third calculation condition: including step S203 a first boundary condition, a second boundary condition, and step S204 a fourth load;

fourth calculation condition: including step S203 first boundary condition, third boundary condition, and step S204 third load;

fifth calculation condition: including step S203 first boundary condition, second boundary condition, and step S204 sixth load;

Sixth calculation condition: including step S203 first boundary condition, third boundary condition, and step S204 fifth load;

seventh calculation condition: including the fourth boundary condition of step S203.

In step S207, initial engagement positions of the two planetary gear finite element models with the first and second side gear finite element models are adjusted.

The first planetary gear 2001 and the second planetary gear 2002 are respectively rotated, so that the tooth surfaces of the first planetary gear 2001, the first half-shaft gear 3001 and the second half-shaft gear 3002 and the tooth surfaces of the second planetary gear 2002, the first half-shaft gear 3001 and the second half-shaft gear 3002 are in a small interference state, namely the interference is not more than 0.001mm, so that the transmission of force between the tooth surfaces in contact with each other can be maintained at the beginning of finite element calculation, the problem of singular calculation caused by the initial gap between the tooth surfaces can be avoided, and the established finite element model has good convergence when the calculation of the first calculation working condition to the calculation of the sixth calculation working condition is ensured.

And step S208, performing finite element analysis on the planetary gear finite element model to obtain planetary gear finite element model finite element analysis data.

Adopting a quasi-static finite element method, considering geometric nonlinearity and respectively carrying out finite element analysis of the planetary gear according to the following sequence of the first analysis step to the sixth analysis step; the calculation time of each calculation working condition is set to be 1.0 second, when the calculation result is output, the calculation results of 1.0 second at the moment are only output by other calculation working conditions except that the interval time of calculating the seventh calculation working condition is not more than 0.01 second, so that the size of a calculation result file is reduced while the meshing process of the planetary gear is accurately captured.

The two planetary finite element models were analyzed according to the following analysis steps:

a first analysis step: analyzing and calculating a first calculation working condition, and then continuing to analyze and calculate a seventh calculation working condition to obtain finite element analysis data of a finite element model of the first planet gear;

a second analysis step: analyzing and calculating a second calculation working condition, and then continuing to analyze and calculate a seventh calculation working condition to obtain finite element analysis data of a second planetary gear finite element model;

and a third analysis step: analyzing and calculating a third calculation working condition, and then continuing to analyze and calculate a seventh calculation working condition to obtain finite element analysis data of a third planetary gear finite element model;

Fourth analysis step: analyzing and calculating a fourth calculation working condition, and then continuing to analyze and calculate a seventh calculation working condition to obtain finite element analysis data of a fourth planetary gear finite element model;

fifth analysis step: analyzing and calculating a fifth calculation working condition, and then continuing to analyze and calculate a seventh calculation working condition to obtain finite element analysis data of a finite element model of the fifth planetary gear;

sixth analysis step: analyzing and calculating a sixth calculation working condition, and then continuing to analyze and calculate a seventh calculation working condition to obtain finite element analysis data of a sixth planetary gear finite element model;

the first, second, third, fourth, fifth, and sixth planetary finite element model finite element analysis data may each include: the contact pressure, the contact area and the slippage on the tooth surface of the planetary gear are reduced, so that the size of a calculation result file is reduced, and the post-treatment time is shortened.

And S209, performing pitting corrosion analysis and evaluation on the finite element analysis data of the finite element model of the planet gear.

In step S208 of extracting two finite element models of the planet gear, the contact stress P, the contact area a and the slip amount L of the tooth surface of the planet gear corresponding to each moment of the seventh calculation condition are calculated in the first finite element model, the second finite element model, the third finite element model, the fourth finite element model, the fifth finite element model and the sixth finite element model, and the friction work W at each moment of two groups is calculated by using the formula (1):

W＝PAfL (1)

wherein: f is the friction coefficient, P is the contact pressure on the tooth surface of the planetary gear, A is the contact area, and L is the slip.

Judging whether friction work at each moment of two groups is smaller than or equal to 0.5JJ:

if yes, the corresponding planetary gear cannot be pitted;

Taking the seventh calculation condition calculated in the sixth analysis step of step S208 as an example, the tooth surface pitting analysis of the first planetary gear 2001 is performed, the extracted tooth surface contact stress P distribution, contact area a and slip amount L at the 1 st moment are respectively shown in fig. 8 to 10, the friction work W calculated according to the formula (1) is shown in fig. 11, and it can be seen from fig. 11 that the maximum value of the friction work W is 0.31J and is located at the meshing print center position and is smaller than 0.5J, so that pitting does not occur at the tooth surface meshing position at the 1 st moment; and then, respectively extracting the tooth surface contact stress P distribution, the contact area A and the slip quantity L at each meshing moment of the 2 nd, the 3 rd and the 4 th … …, calculating and analyzing the corresponding friction work W, so as to make comprehensive analysis and judgment on whether the planetary gear is pitted or not.

Example III

In an exemplary embodiment, there is also provided an electric vehicle differential planetary gear pitting analysis and evaluation device, as shown in fig. 12, including:

a building module 310, configured to build a differential assembly finite element model, and define material properties of the differential assembly finite element model respectively;

a first definition module 320 for defining boundary conditions of the differential housing, the first side gear, and the second side gear, respectively, in the differential assembly finite element model;

a second definition module 330 for defining model loads for the first and second side gear finite element models, respectively;

a third definition module 340, configured to define two planetary gear finite element model calculation conditions with the same structure, and define friction coefficients between the first and second side gear finite element models and the two planetary gear finite element models;

and the analysis and evaluation module 350 is configured to perform finite element analysis on the two finite element models of the planet gear respectively to obtain finite element analysis data of the two finite element models of the planet gear respectively, and perform pitting corrosion analysis and evaluation on the finite element analysis data of the two finite element models of the planet gear respectively.

According to the method, a large amount of experience coefficient selection during conventional gear pitting prediction is avoided, the planetary gear pitting analysis and evaluation method and steps are provided in detail in the aspects of finite element model construction, calculation working condition selection, result analysis and the like, the product of tooth surface contact stress, contact area and slippage, namely tooth surface friction work is utilized to evaluate the gear pitting, the effect of the contact stress is considered, the influence of the relative slippage of the tooth surface contact position under the effect of the contact stress is considered, so that pitting analysis and evaluation are more consistent with a pitting mechanism, and the established gear pitting analysis and evaluation method is more accurate and effective; meanwhile, the problems that the conclusion is different from person to person in the process of analyzing and evaluating the pitting corrosion of the gear are solved by giving out the determined tooth surface grid size, tooth surface friction coefficients under different torques and the like, so that the method can be widely applied to engineering practice.

According to the invention, the grids are finely divided only in the contact area, and particularly, finer grids are adopted on the tooth surface, so that the calculation accuracy is ensured, and meanwhile, the calculation scale is reduced; the forced angular displacement rotating around the central line of the differential shell is applied on the differential shell to enable the planetary gear to rotate by one tooth angle, and only the calculation result in the rotating process of the differential shell is output, so that the calculation result file is ensured to be at a small level, and a foundation is laid for rapid post-treatment of the pitting of the planetary gear.

According to the application, torque is applied to the second side gear through fixing the rotation freedom degree of the first side gear, and torque is applied to the first side gear through fixing the rotation freedom degree of the second side gear, so that the influence of rigidity of different positions of the differential shell is considered, and the differential planetary gear pitting evaluation parameters during left and right turning of the electric vehicle are calculated respectively; meanwhile, by applying different torques on the half-shaft gears, the stress condition of the planetary gears in the range of the torque which is usually used by the electric vehicle is simulated; the calculated pitting evaluation parameters of the planetary gear are more comprehensive by the aid of the measures, and the pitting resistance of the gear designed through analysis is stronger.

According to the application, by adjusting the interference state between the planetary gear and the half-shaft gear, good convergence of the finite element model is ensured, and the model calculation efficiency is improved.

Example IV

Fig. 13 is a block diagram of a terminal according to an embodiment of the present application, and the terminal may be a terminal according to the above embodiment. The terminal 400 may be a portable mobile terminal such as: smart phone, tablet computer. The terminal 400 may also be referred to by other names of user equipment, portable terminals, etc.

In general, the terminal 400 includes: a processor 401 and a memory 402.

Processor 401 may include one or more processing cores such as a 4-core processor, an 8-core processor, etc. The processor 401 may be implemented in at least one hardware form of DSP (Digital Signal Processing ), FPGA (Field-Programmable Gate Array, field programmable gate array), PLA (Programmable Logic Array ). The processor 401 may also include a main processor, which is a processor for processing data in an awake state, also called a CPU (Central Processing Unit ), and a coprocessor; a coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 401 may integrate a GPU (Graphics Processing Unit, image processor) for rendering and drawing of content required to be displayed by the display screen. In some embodiments, the processor 401 may also include an AI (Artificial Intelligence ) processor for processing computing operations related to machine learning.

Memory 402 may include one or more computer-readable storage media, which may be tangible and non-transitory. Memory 402 may also include high-speed random access memory, as well as non-volatile memory, such as one or more magnetic disk storage devices, flash memory storage devices. In some embodiments, a non-transitory computer readable storage medium in memory 402 is used to store at least one instruction for execution by processor 401 to implement the electric vehicle differential planetary gear pitting analysis evaluation method provided in the present application.

In some embodiments, the terminal 400 may further optionally include: a peripheral interface 403 and at least one peripheral. Specifically, the peripheral device includes: at least one of radio frequency circuitry 404, a touch display 405, a camera 406, audio circuitry 407, a positioning component 408, and a power supply 409.

Peripheral interface 403 may be used to connect at least one Input/Output (I/O) related peripheral to processor 401 and memory 402. In some embodiments, processor 401, memory 402, and peripheral interface 403 are integrated on the same chip or circuit board; in some other embodiments, either or both of the processor 401, memory 402, and peripheral interface 403 may be implemented on separate chips or circuit boards, which is not limited in this embodiment.

The Radio Frequency circuit 404 is configured to receive and transmit RF (Radio Frequency) signals, also known as electromagnetic signals. The radio frequency circuitry 404 communicates with a communication network and other communication devices via electromagnetic signals. The radio frequency circuit 404 converts an electrical signal into an electromagnetic signal for transmission, or converts a received electromagnetic signal into an electrical signal. Optionally, the radio frequency circuit 404 includes: antenna systems, RF transceivers, one or more amplifiers, tuners, oscillators, digital signal processors, codec chipsets, subscriber identity module cards, and so forth. The radio frequency circuitry 404 may communicate with other terminals via at least one wireless communication protocol. The wireless communication protocol includes, but is not limited to: the world wide web, metropolitan area networks, intranets, generation mobile communication networks (2G, 3G, 4G, and 5G), wireless local area networks, and/or WiFi (Wireless Fidelity ) networks. In some embodiments, the radio frequency circuitry 404 may also include NFC (Near Field Communication ) related circuitry, which is not limiting of the application.

The touch display screen 405 is used to display a UI (User Interface). The UI may include graphics, text, icons, video, and any combination thereof. The touch display screen 405 also has the ability to collect touch signals at or above the surface of the touch display screen 405. The touch signal may be input as a control signal to the processor 401 for processing. The touch display 405 is used to provide virtual buttons and/or virtual keyboards, also referred to as soft buttons and/or soft keyboards. In some embodiments, the touch display 405 may be one, providing a front panel of the terminal 400; in other embodiments, the touch display screen 405 may be at least two, and disposed on different surfaces of the terminal 400 or in a folded design; in still other embodiments, the touch display 405 may be a flexible display disposed on a curved surface or a folded surface of the terminal 400. Even more, the touch display screen 405 may be arranged in an irregular pattern that is not rectangular, i.e., a shaped screen. The touch display 405 may be made of LCD (Liquid Crystal Display ), OLED (Organic Light-Emitting Diode) or other materials.

The camera assembly 406 is used to capture images or video. Optionally, camera assembly 406 includes a front camera and a rear camera. In general, a front camera is used for realizing video call or self-photographing, and a rear camera is used for realizing photographing of pictures or videos. In some embodiments, the number of the rear cameras is at least two, and the rear cameras are any one of a main camera, a depth camera and a wide-angle camera, so as to realize fusion of the main camera and the depth camera to realize a background blurring function, and fusion of the main camera and the wide-angle camera to realize a panoramic shooting function and a Virtual Reality (VR) shooting function. In some embodiments, camera assembly 406 may also include a flash. The flash lamp can be a single-color temperature flash lamp or a double-color temperature flash lamp. The dual-color temperature flash lamp refers to a combination of a warm light flash lamp and a cold light flash lamp, and can be used for light compensation under different color temperatures.

The audio circuit 407 is used to provide an audio interface between the user and the terminal 400. The audio circuit 407 may include a microphone and a speaker. The microphone is used for collecting sound waves of users and environments, converting the sound waves into electric signals, and inputting the electric signals to the processor 401 for processing, or inputting the electric signals to the radio frequency circuit 404 for realizing voice communication. For the purpose of stereo acquisition or noise reduction, a plurality of microphones may be respectively disposed at different portions of the terminal 400. The microphone may also be an array microphone or an omni-directional pickup microphone. The speaker is used to convert electrical signals from the processor 401 or the radio frequency circuit 404 into sound waves. The speaker may be a conventional thin film speaker or a piezoelectric ceramic speaker. When the speaker is a piezoelectric ceramic speaker, not only the electric signal can be converted into a sound wave audible to humans, but also the electric signal can be converted into a sound wave inaudible to humans for ranging and other purposes. In some embodiments, audio circuit 407 may also include a headphone jack.

The location component 408 is used to locate the current geographic location of the terminal 400 to enable navigation or LBS (Location Based Service, location-based services). The positioning component 408 may be a positioning component based on the united states GPS (Global Positioning System ), the chinese beidou system, or the russian galileo system.

The power supply 409 is used to power the various components in the terminal 400. The power supply 409 may be an alternating current, a direct current, a disposable battery, or a rechargeable battery. When power supply 409 comprises a rechargeable battery, the rechargeable battery may be a wired rechargeable battery or a wireless rechargeable battery. The wired rechargeable battery is a battery charged through a wired line, and the wireless rechargeable battery is a battery charged through a wireless coil. The rechargeable battery may also be used to support fast charge technology.

In some embodiments, the terminal 400 further includes one or more sensors 410. The one or more sensors 410 include, but are not limited to: acceleration sensor 411, gyroscope sensor 412, pressure sensor 413, fingerprint sensor 414, optical sensor 415, and proximity sensor 416.

The acceleration sensor 411 may detect the magnitudes of accelerations on three coordinate axes of the coordinate system established with the terminal 400. For example, the acceleration sensor 411 may be used to detect components of gravitational acceleration on three coordinate axes. The processor 401 may control the touch display screen 405 to display a user interface in a lateral view or a longitudinal view according to the gravitational acceleration signal acquired by the acceleration sensor 411. The acceleration sensor 411 may also be used for the acquisition of motion data of a game or a user.

The gyro sensor 412 may detect a body direction and a rotation angle of the terminal 400, and the gyro sensor 412 may collect a 3D (three-dimensional) motion of the user to the terminal 400 in cooperation with the acceleration sensor 411. The processor 401 may implement the following functions according to the data collected by the gyro sensor 412: motion sensing (e.g., changing UI according to a tilting operation by a user), image stabilization at shooting, game control, and inertial navigation.

The pressure sensor 413 may be disposed at a side frame of the terminal 400 and/or at a lower layer of the touch display 405. When the pressure sensor 413 is provided at a side frame of the terminal 400, a grip signal of the terminal 400 by a user may be detected, and left-right hand recognition or shortcut operation may be performed according to the grip signal. When the pressure sensor 413 is disposed at the lower layer of the touch display screen 405, control of the operability control on the UI interface can be achieved according to the pressure operation of the user on the touch display screen 405. The operability controls include at least one of a button control, a scroll bar control, an icon control, and a menu control.

The fingerprint sensor 414 is used to collect a fingerprint of a user to identify the identity of the user based on the collected fingerprint. Upon recognizing that the user's identity is a trusted identity, the user is authorized by the processor 401 to perform relevant sensitive operations including unlocking the screen, viewing encrypted information, downloading software, paying for and changing settings, etc. The fingerprint sensor 414 may be provided on the front, back or side of the terminal 400. When a physical key or vendor Logo is provided on the terminal 400, the fingerprint sensor 414 may be integrated with the physical key or vendor Logo.

The optical sensor 415 is used to collect the ambient light intensity. In one embodiment, the processor 401 may control the display brightness of the touch display screen 405 according to the ambient light intensity collected by the optical sensor 415. Specifically, when the intensity of the ambient light is high, the display brightness of the touch display screen 405 is turned up; when the ambient light intensity is low, the display brightness of the touch display screen 405 is turned down. In another embodiment, the processor 401 may also dynamically adjust the shooting parameters of the camera assembly 406 according to the ambient light intensity collected by the optical sensor 415.

A proximity sensor 416, also referred to as a distance sensor, is typically disposed on the front face of the terminal 400. The proximity sensor 416 is used to collect the distance between the user and the front of the terminal 400. In one embodiment, when the proximity sensor 416 detects a gradual decrease in the distance between the user and the front face of the terminal 400, the processor 401 controls the touch display 405 to switch from the bright screen state to the off screen state; when the proximity sensor 416 detects that the distance between the user and the front surface of the terminal 400 gradually increases, the processor 401 controls the touch display screen 405 to switch from the off-screen state to the on-screen state.

Those skilled in the art will appreciate that the structure shown in fig. 13 is not limiting of the terminal 400 and may include more or fewer components than shown, or may combine certain components, or may employ a different arrangement of components.

Example five

In an exemplary embodiment, there is also provided a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method for analyzing and evaluating pitting corrosion of an electric vehicle differential planetary gear provided by all the inventive embodiments of the present application.

Any combination of one or more computer readable media may be employed. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, either in baseband or as part of a carrier wave. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, smalltalk, C ++ and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider).

Example six

In an exemplary embodiment, an application program product is also provided that includes one or more instructions that are executable by the processor 401 of the above apparatus to perform the above method of performing an electric vehicle differential planetary gear pitting analysis evaluation.

Although embodiments of the invention have been disclosed above, they are not limited to the use listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. Therefore, the invention is not to be limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.

Claims

1. The method for analyzing and evaluating the pitting corrosion of the planetary gear of the differential mechanism of the electric vehicle is characterized by comprising the following steps:

2. The method for evaluating and analyzing the pitting corrosion of the planetary gears of the differential mechanism of the electric vehicle according to claim 1, wherein before the finite element analysis is performed on the two finite element models of the planetary gears respectively to obtain the finite element analysis data of the two finite element models of the planetary gears respectively, the method further comprises:

3. The method for evaluating the pitting corrosion analysis of the planetary gears of the electric vehicle differential mechanism according to claim 2, wherein the material properties of the differential mechanism assembly finite element model at least comprise: modulus of elasticity and poisson ratio;

4. A method of evaluating a pitting corrosion of an electric vehicle differential planetary gear according to claim 3, wherein the model loads are defined for the first and second side gear finite element models, respectively, the model loads including first, second, third, fourth, fifth and sixth loads each being a torque, wherein:

5. The method for analyzing and evaluating the pitting corrosion of the planetary gears of the differential mechanism of the electric vehicle according to claim 4, wherein the calculating working conditions of the two planetary gear finite element models with the same structure are respectively defined, and the method comprises the following steps:

6. The method for evaluating and analyzing the pitting corrosion of the planetary gears of the differential mechanism of the electric vehicle according to claim 5, wherein the finite element analysis is performed on the two finite element models of the planetary gears respectively to obtain the finite element analysis data of the two finite element models of the planetary gears respectively, and the method comprises the following steps:

7. The method for evaluating and analyzing the pitting corrosion of the planetary gear of the electric vehicle differential according to claim 6, wherein the step of performing the pitting corrosion analysis on the finite element analysis data of the planetary gear finite element model comprises the following steps:

W＝PAfL (1)

judging whether the friction work is smaller than or equal to 0.5J according to the friction work at each of the two groups of moments:

if yes, the corresponding planetary gear cannot be pitted;

8. The utility model provides an electric motor car differential mechanism planetary gear pitting analysis evaluation device which characterized in that includes:

9. A terminal, comprising:

one or more processors;

a memory for storing the one or more processor-executable instructions;

wherein the one or more processors are configured to:

a method of performing the electric vehicle differential planetary gear pitting analysis and evaluation according to any one of claims 1 to 7.

10. A non-transitory computer readable storage medium, characterized in that instructions in the storage medium, when executed by a processor of a terminal, enable the terminal to perform the electric vehicle differential planetary gear pitting analysis evaluation method of any one of claims 1 to 7.