Timely transfer case no-load mode thermal state estimation method based on thermal resistance network

Abstract

The invention provides a timely transfer case no-load mode thermal state estimation method based on a thermal resistance network, and the method comprises the following steps: analyzing the heat production characteristics of a timely transfer case based on the oil stirring loss and mechanical contact friction loss of an oil immersion part; based on fluid-solid heat transfer models of a rotating part and lubricating oil, the lubricating oil and a shell and the shell and air, heat dissipation characteristic analysis of each element of the timely transfer case is combined, and a thermal resistance network model of the timely transfer case is established by taking each element as an isothermal node and utilizing a lumped parameter method through a heat balance principle and is presented by using a heat balance equation; and in combination with the initial temperature and the simulation step length of each node of the thermal resistance network model and the temperature state of the timely transfer case at the previous moment, quantizing the energy flow value of each node in the thermal resistance network model under a time step length so as to solve the temperature value of each node of the timely transfer case at the current moment. The thermal state estimation method for the no-load mode thermal state of the transfer case is high in universality and simple in calculation, can meet the real-vehicle computing power, and has a real-time monitoring function.

Description

Technical Field

[0001] The invention relates to the technical field of four-wheel drive vehicles, and in particular to a method for estimating the thermal state of a timely transfer case in an unloaded mode based on a thermal resistance network. Background Art

[0002] The timely transfer case is the core component for realizing the active torque distribution between the axles of multi-wheel drive vehicles. It also has the typical characteristics of long-term continuous no-load operation (the vehicle is driven by a single axle). The thermal state of the timely transfer case in no-load mode is an important factor affecting its performance in loaded mode and an intuitive evaluation of the thermal performance of the timely transfer case during normal vehicle driving. Identifying its thermal state changes plays an important role in the thermal safety protection of components and also has guiding significance in the component design stage.

[0003] In the related technologies, obtaining the power loss and temperature field distribution during the operation of the gearbox is an important part of guiding the design of the gearbox and estimating the safe life. Accurate calculations can be achieved by establishing a numerical simulation model, but the low calculation efficiency makes it difficult to carry out real-time predictions of power generation and flow direction inside the box under actual working conditions, and it is impossible to explore the energy flow characteristics between the components to analyze the generation and changes of their transient temperatures. The research on the thermal state estimation of the internal parts of the box during the operation of the actual vehicle still needs to be supplemented.

[0004] Currently, no effective solution has been proposed to address the key issues in related technologies, such as incomplete estimation of the thermal state of the transfer case, unclear internal heat energy exchange values, and low overall calculation efficiency. Summary of the invention

[0005] In order to solve the above problems, the technical solution adopted by the present invention is: a method for estimating the thermal state of a timely transfer case in no-load mode based on a thermal resistance network, comprising the following steps:

[0006] S1: Obtain the vehicle's operating parameters and the structure parameters of the timely transfer case.

[0007] S2: Based on the working parameters of the vehicle and the structural parameters of the timely transfer case, according to the friction characteristics, the viscous power and contact friction power of the rotating parts are calculated, and the oil stirring loss and mechanical contact friction loss of the oil-immersed parts are obtained, so as to establish a heat generation power model of the timely transfer case;

[0008] S3: According to the flow velocity distribution characteristics of the lubricating oil inside the transfer case, the shell is divided into different fluid-solid convection heat transfer areas, and the different fluid-solid convection heat transfer areas all include the inner surface and the outer surface of the shell;

[0009] According to the fluid-solid convection heat transfer areas between different rotating parts and shells, the fluid-solid heat transfer model between rotating parts and lubricating oil, the fluid-solid heat transfer model between lubricating oil and shell, and the fluid-solid heat transfer model between shell and air are established respectively;

[0010] S4: Based on the oil stirring loss of the oil-immersed parts and the mechanical contact friction loss, the heat generation characteristics of the timely transfer case are analyzed. Based on the fluid-solid heat transfer model between the rotating parts and the lubricating oil, the lubricating oil and the shell, and the shell and the air, the heat dissipation characteristics of each component of the timely transfer case are analyzed. Through the principle of thermal balance, the lumped parameter method is used to establish the thermal resistance network model of the timely transfer case with each component as an isothermal node, and it is presented with a thermal balance equation;

[0011] S5: Combine the initial temperature and simulation step of each node in the thermal resistance network model and the temperature state of the timely transfer box at the previous moment, quantify the energy flow value between each node in the thermal resistance network model under one time step, so as to solve the temperature value of each node of the timely transfer box at the current moment.

[0012] Further: the structural parameters of the timely transfer case include the dimensions and physical parameters of the bearings, sprockets, chain plates, shafts and housings, and the volume and physical parameters of the lubricating oil;

[0013] The oil churning loss includes: the power loss caused by the shearing of the rotating parts and the lubricating oil;

[0014] The mechanical contact friction loss includes: chain transmission mechanism mechanical contact friction loss and bearing friction power loss.

[0015] Further: the heat generation power model of the timely transfer case includes an expression for calculating the oil stirring loss of the oil immersed component and an expression for calculating the mechanical contact friction loss;

[0016] The expression for calculating the oil stirring loss of the oil immersed component is as follows:

[0017] P D =F D v

[0018] Among them, P D F is the oil stirring loss power of the oil immersed parts, D is the shear force of the lubricating oil, v is the flow velocity of the main body of the lubricating oil;

[0019] The mechanical contact friction loss expression of the chain transmission mechanism is as follows:

[0020] P g =μNv B

[0021] Among them, P g is the mechanical contact friction loss power, μ is the meshing dynamic friction coefficient between the sprocket and the chain plate, N is the normal force at the contact point between the chain plate and the sprocket, v B is the relative sliding speed between the sprocket and the chain plate at the contact point;

[0022] The bearing friction power loss expression is as follows:

[0023]

[0024] P s2 =f2Fd m ω;

[0025] Among them, P s1 is the viscous power loss affected by the rotation speed and lubrication state, P s2 is the load power loss affected by the load, f1 is a coefficient related to the bearing type and lubrication condition; n is the bearing speed; d m is the pitch diameter of the bearing; f2 is a coefficient related to the bearing type and load; F is the equivalent dynamic load of the bearing.

[0026] Furthermore: the fluid-solid heat transfer model of the rotating parts and the lubricating oil includes a fluid-solid heat transfer model of the bearing and the lubricating oil, a fluid-solid heat transfer model of the chain transmission mechanism and the lubricating oil, and a fluid-solid heat transfer model of the optical axis and the lubricating oil.

[0027] Further: the fluid-solid heat transfer model is characterized by the convection heat transfer coefficient, wherein the fluid-solid convection heat transfer coefficient between the bearing and the lubricating oil is:

[0028]

[0029] Where: o is the thermal conductivity of the lubricating oil; C is the radial clearance between the inner ring and the cage surface. When calculating the convective heat transfer between the inner ring and the lubricating oil, R is taken as r i ; When calculating the convective heat transfer of the outer ring, R is taken as r o ;

[0030] The chain drive mechanism and lubricating oil fluid-solid heat transfer model is characterized by the heat transfer coefficient of the oil-stirring sprocket and the convective heat transfer coefficient of the non-oil-stirring sprocket.

[0031] The convective heat transfer coefficient of the end face of the oil stirring sprocket under the lubricating oil laminar flow, transitional laminar flow and turbulent flow conditions is characterized as follows:

[0032]

[0033] Where: R g is the average radius of the oil-immersed area on the sprocket end face; Pr o 、Re o are the Prandtl number and Reynolds number of the lubricant on the sprocket end face, respectively;

[0034] The non-oil stirring sprocket is usually cooled by splashing lubricating oil. The experimental correlation formula of the convection heat transfer coefficient is expressed by the following formula:

[0035]

[0036] Among them, h gou is the convective heat transfer coefficient of the non-oil-stirring sprocket;

[0037] The fluid-solid heat transfer model between the optical axis and the lubricating oil, and between the circumferential surface of the oil stirring sprocket and the lubricating oil can be characterized by a unified convection heat transfer coefficient, and the specific formula is as follows:

[0038]

[0039] Where: h goy is the convection heat transfer coefficient of the cylindrical surface, R gw is the outer diameter of the equivalent cylinder.

[0040] Further: The convective heat transfer coefficient of the fluid-solid heat transfer model between the lubricating oil and the shell is expressed by the following formula:

[0041]

[0042] Where: h oh is the convective heat transfer coefficient between the lubricating oil and the inner surface of the shell, and l is the characteristic length of the lubricating oil flowing on the inner wall of the shell.

[0043] Further: the natural convection heat transfer coefficient of the fluid-solid heat transfer model between the shell and the air is expressed by the following formula:

[0044]

[0045] Where: g is the acceleration due to gravity; α v is the volume expansion coefficient; ΔT is the fluid-solid temperature difference; ρ a is the air density, ν a is the air viscosity, c a is the specific heat capacity of air.

[0046] The forced convection heat transfer coefficient formula of the fluid-solid heat transfer model between the shell and the air is the same as the convection heat transfer coefficient formula between the lubricating oil and the shell. Further: the thermal resistance network model of the timely transfer case can be constructed according to the thermal balance equation, and the expression of the thermal resistance network includes the thermal state equation of the bearing network node, the thermal state equation of the chain drive network node, the thermal state equation of the lubricating oil network node and the thermal state equation of the shell network node;

[0047] The thermal state equation of the bearing network node is expressed by the following equation:

[0048]

[0049] Among them, ρ s is the density of the bearing, V s is the volume of the bearing, c s is the specific heat capacity of the bearing, T s is the bearing temperature;

[0050] The thermal state equation of the chain drive network node is expressed by the following equation:

[0051]

[0052] Among them, ρ g is the density of the chain, V g is the volume of the chain, c g is the specific heat capacity of the chain, T g is the temperature of the chain;

[0053] The thermal state equation of the lubricating oil network node is expressed by the following equation:

[0054]

[0055] Among them, ρ o is the density of lubricating oil, V o is the volume of lubricating oil, c o is the specific heat capacity of the lubricating oil, T o is the temperature of the lubricating oil;

[0056] The thermal state equation of the shell network node is expressed by the following equation:

[0057]

[0058] Among them, ρ h is the density of the shell, V h is the volume of the shell, c h is the specific heat capacity of the shell, T h is the temperature of the shell.

[0059] A thermal state estimation device for a timely transfer case in no-load mode based on a thermal resistance network, comprising:

[0060] Acquisition module: used to obtain the vehicle's operating parameters and the structure parameters of the timely transfer case.

[0061] Establishing module I: Based on the working condition parameters of the vehicle and the structural parameters of the timely transfer case, according to the friction characteristics, the viscous power and contact friction power of the rotating parts are calculated, and the oil stirring loss and mechanical contact friction loss of the oil-immersed parts are obtained, so as to establish the heat generation power model of the timely transfer case;

[0062] Establish Module II: According to the flow velocity distribution characteristics of the lubricating oil inside the timely transfer case, the shell is divided into different fluid-solid convection heat transfer areas, and the different fluid-solid convection heat transfer areas all include the inner surface and the outer surface of the shell; for the fluid-solid convection heat transfer areas of different rotating parts and the shell, the fluid-solid heat transfer model of the rotating parts and the lubricating oil, the fluid-solid heat transfer model of the lubricating oil and the shell, and the fluid-solid heat transfer model of the shell and the air are established respectively;

[0063] Establish Module III: Based on the oil stirring loss of the oil-immersed parts and the mechanical contact friction loss, analyze the heat generation characteristics of the timely transfer case. Based on the fluid-solid heat transfer model between the rotating parts and the lubricating oil, the lubricating oil and the shell, and the shell and the air, combined with the heat dissipation characteristics of each component of the timely transfer case, the thermal resistance network model of the timely transfer case is established by the lumped parameter method with each component as an isothermal node through the principle of thermal balance, and presented with a thermal balance equation;

[0064] Solution module: Combine the initial temperature and simulation step of each node in the thermal resistance network model, and the temperature state of the timely transfer box at the previous moment, quantify the energy flow value between each node in the thermal resistance network model under one time step, so as to solve the temperature value of each node of the timely transfer box at the current moment.

[0065] A vehicle, wherein a timely transfer case of the vehicle adopts any one of the methods for estimating the thermal state of a timely transfer case in a no-load mode based on a thermal resistance network.

[0066] The present invention provides a timely transfer case no-load mode thermal state estimation method based on a thermal resistance network, which has the following advantages:

[0067] The thermal state estimation method of the transfer case in no-load mode is highly versatile and simple to calculate. It can meet the computing power of the actual vehicle and has real-time monitoring functions. It builds the overall thermal state equation based on the quantitative characteristics of the internal energy flow. It can provide instant and comprehensive temperature estimates of the lubricating oil temperature and different areas of the housing for a wide range of targets. At the same time, the model demonstrates a high degree of practicality and accuracy: under the cyclic working conditions of random vehicle speeds, the deviation between the estimated value and the experimental measurement value is kept within 6°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0069] Figure 1 is a flow chart of a method for timely estimating thermal state of a transfer case in no-load mode according to an embodiment of the present application;

[0070] Figure 2 is a structural diagram of a timely transfer case provided according to an embodiment of the present application;

[0071] Figure 3 It is a diagram of the surface area division of the housing of the timely transfer case provided in an embodiment of the present application, wherein (a) is the inner surface of the housing, and (b) is the outer surface of the housing;

[0072] Figure 4 It is a timely transfer case thermal resistance network diagram provided according to an embodiment of the present application;

[0073] Figure 5 is a flow chart of timely transfer case temperature calculation provided according to an embodiment of the present application;

[0074] Figure 6 These are the experimental and simulation results of the short-term operating conditions of the vehicle provided in the embodiments of the present application, including (a) vehicle speed, (b) experimental and simulation values ​​of oil temperature, (c) experimental and simulation values ​​of windward side oil-immersed shell temperature, (d) experimental and simulation values ​​of leeward side oil-immersed shell temperature, and (e) experimental and simulation values ​​of non-oil-immersed shell temperature). DETAILED DESCRIPTION

[0075] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0076] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0077] Figure 1 is a flow chart of a method for timely estimating thermal state of a transfer case in no-load mode according to an embodiment of the present application;

[0078] A method for estimating the thermal state of a timely transfer case in no-load mode based on a thermal resistance network, comprising:

[0079] S1: Obtaining the vehicle's operating parameters and the structure parameters of the timely transfer case;

[0080] S2: Based on the working parameters of the vehicle and the structural parameters of the timely transfer case, according to the friction characteristics, the viscous power and contact friction power of the rotating parts are calculated, and the oil stirring loss and mechanical contact friction loss of the oil-immersed parts are obtained, so as to establish a heat generation power model of the timely transfer case;

[0081] S3: According to the flow velocity distribution characteristics of the lubricating oil inside the transfer case,

[0082] The shell is divided into different fluid-solid convection heat transfer areas, and the different fluid-solid convection heat transfer areas include the inner surface and the outer surface of the shell;

[0083] According to the fluid-solid convection heat transfer areas between different rotating parts and shells, the fluid-solid heat transfer model between rotating parts and lubricating oil, the fluid-solid heat transfer model between lubricating oil and shell, and the fluid-solid heat transfer model between shell and air are established respectively;

[0084] S4: Based on the oil stirring loss of the oil-immersed parts and the mechanical contact friction loss, the heat generation characteristics of the timely transfer case are analyzed. Based on the fluid-solid heat transfer model between the rotating parts and the lubricating oil, the lubricating oil and the shell, and the shell and the air, the heat dissipation characteristics of each component of the timely transfer case are analyzed. Through the principle of thermal balance, the lumped parameter method is used to establish the thermal resistance network model of the timely transfer case with each component as an isothermal node, and it is presented with a thermal balance equation;

[0085] S5: Combine the initial temperature and simulation step of each node in the thermal resistance network model and the temperature state of the timely transfer box at the previous moment, quantify the energy flow value between each node in the thermal resistance network model under one time step, so as to solve the temperature value of each node of the timely transfer box at the current moment.

[0086] Steps S1 / S2 / S3 / S4 / S5 are executed sequentially;

[0087] Figure 2 is a structural diagram of a timely transfer case provided according to an embodiment of the present application;

[0088] Furthermore, the structural parameters of the timely transfer case include the dimensions and physical parameters of the bearings, sprockets, chain plates, shafts and housings, and the volume and physical parameters of the lubricating oil;

[0089] The oil churning loss includes: the power loss caused by the shearing of the rotating parts and the lubricating oil;

[0090] The mechanical contact friction loss includes: chain transmission mechanism mechanical contact friction loss and bearing friction power loss;

[0091] The fluid-solid heat transfer model is established based on the structural principle of the timely transfer case and the heat dissipation characteristics of the components. The model includes:

[0092] Establish the fluid-solid heat transfer model of each rotating component, including the heat transfer model of bearing and lubricating oil, chain transmission mechanism and lubricating oil, and optical axis and lubricating oil;

[0093] Establish heat transfer models between lubricating oil and different areas of the shell inner surface;

[0094] Establish a heat transfer model between different areas of the shell's outer surface and the outside air;

[0095] The heat transfer model of the contact parts includes: heat conduction between the inner ring and the shaft, the outer ring and the bearing seat, the shaft section where the bearing is located and the optical axis, the optical axis and the sprocket, and the sprocket and the shaft section where the bearing is located;

[0096] The heat transfer capacity between each component is expressed in the form of thermal resistance.

[0097] In order to estimate the thermal state of the timely transfer case, it is necessary to first determine the heat generation power model of the timely transfer case. Optionally, in the timely transfer case thermal state estimation method provided in the example of the present application, the heat generation power of the timely transfer case is determined by the operating parameters of the vehicle and the structural parameters of the timely transfer case, including: determining the oil stirring loss of the oil-immersed components by the structural parameters of the timely transfer case; calculating the mechanical contact friction loss by the structural parameters of the timely transfer case.

[0098] Furthermore, the heat generation power model of the timely transfer case includes an expression for calculating the oil stirring loss of the oil immersed component and an expression for calculating the mechanical contact friction loss;

[0099] The expression for calculating the oil stirring loss of the oil immersed component is as follows:

[0100] P D =F D v

[0101] Among them, P D F is the oil stirring loss power of the oil immersed parts, D is the shear force of the lubricating oil, v is the flow velocity of the main body of the lubricating oil;

[0102] Specifically, through the following formula:

[0103]

[0104] To calculate the shear force of the lubricating oil, where ρ is the density of the lubricating oil; C D is the lubricating oil shear coefficient; A is the fluid-solid shear area.

[0105] Specifically, in the oil-immersed area, the viscous shear force between the circumferential surface and end surface of the rotating parts inside the transfer case and the lubricating oil can be equivalent to a cylinder of equal diameter to calculate the oil stirring loss. The circumferential surface and end surface of the rotating parts can be regarded as the side and bottom of the equivalent cylinder respectively. Through the following formula:

[0106]

[0107] To calculate the viscous shear coefficient and shear area of ​​the equivalent cylindrical bottom and lubricating oil, where: C Dr is the viscous shear coefficient between the equivalent cylindrical surface and the lubricating oil, A r is the shear area of ​​the equivalent circular surface, ω is the angular velocity of rotation; r n is the radius of rotation of the equivalent cylindrical surface; r w is the distance from the inner surface of the shell to the center of rotation, h is the oil immersion depth, and b is the thickness of the equivalent cylindrical surface.

[0108] Specifically, the lubricating oil flow on the side of the equivalent cylinder will present two states: laminar flow and turbulent flow due to the different rotation speeds of the cylinder. Through the following formula:

[0109]

[0110] To calculate the laminar viscous friction coefficient and turbulent viscous friction coefficient, where is the laminar viscous friction coefficient, is the turbulent viscous friction coefficient, μ k is the kinematic viscosity of the lubricating oil; L is the thickness of the lubricating oil laminar boundary layer, δ T is the thickness of the lubricating oil turbulent boundary layer.

[0111] By the following formula:

[0112]

[0113] To calculate the fluid-solid shear area corresponding to the bottom of the equivalent cylinder, A θ is the fluid-solid shear area corresponding to the bottom surface of the equivalent cylinder;

[0114] The mechanical contact friction loss of the chain drive mechanism is calculated by the following formula:

[0115] P g =μNv B

[0116] Among them, P g is the mechanical contact friction loss power, μ is the meshing dynamic friction coefficient between the sprocket and the chain plate, N is the normal force at the contact point between the chain plate and the sprocket, v B is the relative sliding speed between the sprocket and the chain plate at the contact point.

[0117] Specifically, through the following formula:

[0118]

[0119] To calculate the normal force at the contact point between the chain plate and the sprocket, F is the tension of the tight side of the chain; θ is the half angle of the previous link rotation, and α is the tooth profile half angle.

[0120] Optionally, regarding the friction power loss of solid contact, the friction power of the bearing includes the viscous power loss affected by the rotation speed and lubrication state and the load power loss affected by the load, and the viscous power loss affected by the rotation speed and lubrication state and the load power loss affected by the load are calculated by the following formula:

[0121]

[0122] P s2 =f2Fdm ω;

[0123] Among them, P s1 is the viscous power loss affected by the rotation speed and lubrication state, P s2 is the load power loss affected by the load, f1 is a coefficient related to the bearing type and lubrication condition; n is the bearing speed; d m is the pitch diameter of the bearing; f2 is a coefficient related to the bearing type and load; F is the equivalent dynamic load of the bearing.

[0124] Specifically, through the following formula:

[0125] F=XF r +YF a

[0126] To calculate the equivalent dynamic load of the bearing, where F r is the radial load; F a is the axial load; X and Y are the load coefficients.

[0127] According to the vehicle's operating parameters and the structural parameters of the timely transfer case, the viscous friction power loss between the oil-immersed area of ​​the rotating component and the lubricating oil and the contact friction power loss of the relative sliding between its own components can be calculated to obtain the heat generation calculation model of the timely transfer case.

[0128] The fluid-solid heat transfer model of the rotating parts and the lubricating oil includes a fluid-solid heat transfer model of the bearing and the lubricating oil, a fluid-solid heat transfer model of the chain transmission mechanism and the lubricating oil, and a fluid-solid heat transfer model of the optical axis and the lubricating oil.

[0129] Since the calculation of convective heat transfer between bearings and lubricating oil can be based on the assumption of heat transfer between two concentric thin-walled cylinders and the moving fluid in their annular space, the convective heat transfer coefficient of the fluid-solid heat transfer model between bearings and lubricating oil is calculated by the following formula:

[0130]

[0131] Where: o is the thermal conductivity of the lubricating oil; C is the radial clearance between the inner ring and the cage surface. When calculating the convective heat transfer between the inner ring and the lubricating oil, R is taken as r i ; When calculating the convective heat transfer of the outer ring, R is taken as r o Therefore, the convection thermal resistance R between the bearing and the lubricating oil can be expressed by the following formula: so :

[0132]

[0133] The chain drive mechanism and lubricating oil fluid-solid heat transfer model is characterized by the convective heat transfer coefficient of the oil-stirring sprocket and the convective heat transfer coefficient of the non-oil-stirring sprocket;

[0134] The convective heat transfer of the end face of the oil stirring sprocket needs to distinguish the flow type of the lubricating oil. The convective heat transfer coefficient of the lubricating oil in laminar flow, transitional laminar flow, and turbulent flow can be expressed by the following formula:

[0135]

[0136] Where: R g is the average radius of the oil-immersed area on the sprocket end face; Pr o 、Re o are the Prandtl number and Reynolds number of the sprocket end face lubricant, respectively.

[0137] The circumferential surface of the oil stirring sprocket and the surface of the optical axis segment can still be regarded as cylindrical surfaces. Similar to the forced convection heat transfer of a fluid sweeping a flat plate, the fluid-solid heat transfer model between the optical axis and the lubricating oil, and between the circumferential surface of the oil stirring sprocket and the lubricating oil can be characterized by a unified convection heat transfer coefficient. The specific heat transfer coefficient can be expressed by the following formula:

[0138]

[0139] Where: h goy is the convection heat transfer coefficient of the cylindrical surface, R gw is the outer diameter of the equivalent cylinder.

[0140] The convective heat transfer resistance of the oil stirring sprocket and the optical axis can be expressed by the following formula:

[0141] R go =1 / [A θ (g)h god ]+1 / [A r (g)h goy ], R ao =1 / [A r (a)h ao ],

[0142] Among them, R go is the convection heat transfer resistance of the oil stirring sprocket, R ao is the convective heat transfer resistance of the optical axis.

[0143] The non-oil stirring sprocket is usually cooled by splashing lubricating oil. The experimental correlation formula of the convection heat transfer coefficient can be expressed by the following formula:

[0144]

[0145] Among them, h gou is the convective heat transfer coefficient of the non-oil-stirring sprocket.

[0146] Therefore, the fluid-solid heat transfer thermal resistance expression is as follows:

[0147] Rgo =1 / (A g h gou )

[0148] Where: R go is the convective heat transfer resistance of the non-oil stirring sprocket, A g It is the non-oil churning gear surface area;

[0149] Figure 3 It is a diagram of the surface area division of the housing of the timely transfer case provided in an embodiment of the present application, wherein (a) is the inner surface of the housing, and (b) is the outer surface of the housing;

[0150] The shell is divided into regions, and the lubricating oil is swept on the corresponding inner surface of each region. The heat energy flow between the lubricating oil and the inner surface of the shell is characterized by the forced convection model of the swept plate; the convection heat transfer coefficient of the fluid-solid heat transfer model between the lubricating oil and the shell is expressed by the following formula:

[0151]

[0152] Where: h oh is the convective heat transfer coefficient between the lubricating oil and the inner surface of the shell, l is the characteristic length of the lubricating oil flowing on the inner wall of the shell;

[0153] According to the flow velocity distribution characteristics of the lubricating oil inside the timely transfer case, the inner and outer surfaces of the shell are divided into different heat transfer areas. On the inner surface, there are oil immersion areas a1 and a2, chain oil throwing areas a3 and a4, sprocket and clutch oil throwing areas a5, a6 and a7. According to the characteristic length of each area on the inner wall of the shell, the characteristic velocity of the lubricating oil and the convection heat transfer area, the convection heat transfer thermal resistance between different areas and the lubricating oil can be obtained. The convection heat transfer thermal resistance between the shell and the lubricating oil in different shell areas is expressed by the following formula:

[0154] R oh (a i )=1 / [h oh (a i )×A oh (a i )],

[0155] Among them, R oh is the convection heat transfer thermal resistance between the shell and the lubricating oil.

[0156] The outer surface of the shell will be air cooled according to Figure 3 The area division of the shell in the figure can be divided into forced convection and natural convection cooling according to the flow characteristics of the air at different positions on the outer surface. The swept plate model is still used in the forced convection area, and the lubricating oil parameter λ o , Pr o Replaced by the thermal conductivity of air λ a and Prandtl number Pra At the same time, according to the characteristic length l of the outer wall a and air flow velocity u a The forced convection heat transfer coefficient of the shell cooling process can be obtained. The natural convection heat transfer coefficient of the fluid-solid heat transfer model between the shell and the air can be expressed by the following formula:

[0157]

[0158] Where: g is the acceleration due to gravity; α v is the volume expansion coefficient; ΔT is the fluid-solid temperature difference; ρ a is the air density, ν a is the air viscosity, c a is the specific heat capacity of air.

[0159] The thermal resistance of convection heat transfer between the shell and air in different areas of the shell outer surface can be expressed by the following formula:

[0160] R ha (b i )=1 / [h ha (b i )×A ha (b i )],

[0161] Among them, R ha (b i ) is the convection heat transfer thermal resistance between different areas of the shell outer surface and the air.

[0162] Energy is transferred between solid contact parts by heat conduction due to the temperature gradient. Optionally, in the thermal state estimation method of the timely transfer case provided in the example of the present application, the temperature at the bearing pitch circle can be used to represent the average temperature of the bearing through the heat generation characteristics of the bearing, through the following formula:

[0163]

[0164] To calculate the thermal resistance R between the inner ring and the shaft, and between the outer ring and the housing bearing seat sdn , where λ s , B s 、r i 、r o They are the heat transfer coefficient, width, inner diameter and outer diameter of the bearing respectively; Δr n , Δr w They are the radial distances from the center of the pitch circle to the axis and the bearing seat respectively.

[0165] The heat conduction on the forward output shaft is calculated by the following formula, which mainly exists in the thermal resistance between the shaft section where the first bearing is located and the optical axis, the optical axis and the sprocket, and the sprocket and the shaft section where the second bearing is located:

[0166] R X =Δx / (A X λ X ),

[0167] Where: x is the heat transfer coefficient of the shaft; Δx, A x are the distance and cross-sectional area between each shaft segment respectively.

[0168] The present application example also provides a timely transfer case thermal resistance network model. According to the above analysis of the heat generation and heat dissipation characteristics of each component of the transfer case, the thermal resistance network model of the transfer case can be established by using the lumped parameter method with each component as an isothermal node, forming a group of thermal balance equations that can characterize the energy flow between each node. Solving the equations can obtain the macroscopic physical quantity of the node temperature. According to the established thermal resistance network, combined with the principle of thermal balance, the thermal state equations of each thermal network node can be listed, wherein establishing the timely transfer case thermal resistance network model includes: by analyzing the heat generation and heat dissipation characteristics of each component of the timely transfer case, using the lumped parameter method with each component as an isothermal node to establish the thermal resistance network model of the timely transfer case; and establishing the thermal balance equations of each node according to the principle of thermal balance.

[0169] Figure 4 It is a timely transfer case thermal resistance network diagram provided according to an embodiment of the present application;

[0170] The expression of the thermal resistance network model of the timely transfer case includes the thermal state equation of the bearing network node, the thermal state equation of the chain drive network node, the thermal state equation of the lubricating oil network node and the thermal state equation of the shell network node;

[0171] The thermal state equation of the bearing network node is expressed by the following equation:

[0172]

[0173] Among them, ρ s is the density of the bearing, V s is the volume of the bearing, c s is the specific heat capacity of the bearing, T s is the bearing temperature;

[0174] The thermal state equation of the chain drive network node is expressed by the following equation:

[0175]

[0176] Among them, ρ g is the density of the chain, V g is the volume of the chain, c g is the specific heat capacity of the chain, T g is the temperature of the chain;

[0177] The thermal state equation of the lubricating oil network node is expressed by the following equation:

[0178]

[0179] Among them, ρ o is the density of lubricating oil, V o is the volume of lubricating oil, c o is the specific heat capacity of the lubricating oil, T o is the temperature of the lubricating oil;

[0180] The thermal state equation of the shell network node is expressed by the following equation:

[0181]

[0182] Among them, ρ h is the density of the shell, V h is the volume of the shell, c h is the specific heat capacity of the shell, T h is the temperature of the shell.

[0183] Figure 5 is a flow chart of timely transfer case temperature calculation provided according to an embodiment of the present application;

[0184] According to the thermal resistance network of the timely transfer case jointly constructed by the heat generation model of the timely transfer case in the above step S2 and the heat transfer model between the timely transfer case elements in S3, the thermal state equations of the thermal resistance network nodes are established in S4. Combined with the initial temperature of each node and the simulation step, the energy flow between each node in the thermal resistance network model under one time step is calculated to solve the temperature value of each node of the timely transfer case at the current moment; further iterative cycles can calculate the temperature value of each node of the timely transfer case at each moment.

[0185] A thermal state estimation device for a timely transfer case in no-load mode based on a thermal resistance network, comprising:

[0186] Acquisition module: used to obtain the vehicle's operating parameters and the structure parameters of the timely transfer case.

[0187] Establishing module I: Based on the working condition parameters of the vehicle and the structural parameters of the timely transfer case, according to the friction characteristics, the viscous power and contact friction power of the rotating parts are calculated, and the oil stirring loss and mechanical contact friction loss of the oil-immersed parts are obtained, so as to establish the heat generation power model of the timely transfer case;

[0188] Establish Module II: According to the flow velocity distribution characteristics of the lubricating oil inside the timely transfer case, the shell is divided into different fluid-solid convection heat transfer areas, and the different fluid-solid convection heat transfer areas all include the inner surface and the outer surface of the shell; for the fluid-solid convection heat transfer areas of different rotating parts and the shell, the fluid-solid heat transfer model of the rotating parts and the lubricating oil, the fluid-solid heat transfer model of the lubricating oil and the shell, and the fluid-solid heat transfer model of the shell and the air are established respectively;

[0189] Establish Module III: Based on the oil stirring loss of the oil-immersed parts and the mechanical contact friction loss, analyze the heat generation characteristics of the timely transfer case. Based on the fluid-solid heat transfer model between the rotating parts and the lubricating oil, the lubricating oil and the shell, and the shell and the air, combined with the heat dissipation characteristics of each component of the timely transfer case, the thermal resistance network model of the timely transfer case is established by the lumped parameter method with each component as an isothermal node through the principle of thermal balance, and presented with a thermal balance equation;

[0190] Solution module: Combine the initial temperature and simulation step of each node in the thermal resistance network model, and the temperature state of the timely transfer box at the previous moment, quantify the energy flow value of each node in the thermal resistance network model under one time step, and solve the temperature value of each node of the timely transfer box at the current moment.

[0191] A vehicle, wherein a timely transfer case of the vehicle adopts any one of the methods for estimating the thermal state of a timely transfer case in an idle mode based on a thermal resistance network.

[0192] Figure 6 The experimental and simulation results of the vehicle operating conditions provided by the embodiments of the present application are as follows: (a) vehicle speed, (b) experimental and simulation values ​​of oil temperature, (c) experimental and simulation values ​​of windward oil-immersed shell temperature, (d) experimental and simulation values ​​of leeward oil-immersed shell temperature, and (e) experimental and simulation values ​​of non-oil-immersed shell temperature;

[0193] This application provides a real vehicle operating condition experiment to verify the accuracy of the thermal state estimation model established in the no-load operating mode of the transfer case. The experiment includes: the transfer case undergoes continuous operation under urban road conditions, the vehicle speed changes from low speed to high speed, and then returns to low speed. The temperature changes of the internal lubricating oil and the outer surface of the shell of the transfer case at different positions under the corresponding operating parameters of the vehicle are measured synchronously and compared with the mathematical model.

[0194] Specifically, the experimental results show that the rise and fall of the lubricating oil and housing temperatures follow the vehicle speed, and the temperature change trends of the two are approximately synchronized. The results show that the maximum calculated deviation of the lubricating oil temperature and the housing outer surface temperature does not exceed 6°C. Under random working conditions, the simulated calculated values ​​of the transfer case lubricating oil temperature and the housing outer surface temperature show a high degree of consistency with the experimental measured values.

[0195] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for estimating the thermal state of a transfer case in no-load mode based on a thermal resistance network, characterized in that The following steps are involved: S1: Obtaining the vehicle's operating parameters and the structure parameters of the timely transfer case; S2: Based on the working parameters of the vehicle and the structural parameters of the timely transfer case, according to the friction characteristics, the viscous power and contact friction power of the rotating parts are calculated, and the oil stirring loss and mechanical contact friction loss of the oil-immersed parts are obtained, so as to establish a heat generation power model of the timely transfer case; S3: According to the flow velocity distribution characteristics of the lubricating oil inside the transfer case, the shell is divided into different fluid-solid convection heat transfer areas, and the different fluid-solid convection heat transfer areas all include the inner surface and the outer surface of the shell; According to the fluid-solid convection heat transfer areas between different rotating parts and shells, the fluid-solid heat transfer model between rotating parts and lubricating oil, the fluid-solid heat transfer model between lubricating oil and shell, and the fluid-solid heat transfer model between shell and air are established respectively; S4: Based on the oil stirring loss of the oil-immersed parts and the mechanical contact friction loss, the heat generation characteristics of the timely transfer case are analyzed. Based on the fluid-solid heat transfer model between the rotating parts and the lubricating oil, the lubricating oil and the shell, and the shell and the air, the heat dissipation characteristics of each component of the timely transfer case are analyzed. Through the principle of thermal balance, the lumped parameter method is used to establish the thermal resistance network model of the timely transfer case with each component as an isothermal node, and it is presented with a thermal balance equation; S5: Combine the initial temperature and simulation step of each node of the thermal resistance network model and the temperature state of the timely transfer box at the previous moment, quantify the energy flow value between each node in the thermal resistance network model under one time step, so as to solve the temperature value of each node of the timely transfer box at the current moment.

2. The method according to claim 1, characterized in that: The structural parameters of the timely transfer case include the dimensions and physical parameters of the bearings, sprockets, chain plates, shafts and housings, and the volume and physical parameters of the lubricating oil; The oil churning loss includes: the power loss caused by the shearing of the rotating parts and the lubricating oil; The mechanical contact friction loss includes: chain transmission mechanism mechanical contact friction loss and bearing friction power loss.

3. The method according to claim 1, characterized in that: The heat generation power model of the timely transfer case includes an expression for calculating the oil stirring loss of the oil-immersed component and an expression for calculating the mechanical contact friction loss; The expression for calculating the oil stirring loss of the oil immersed component is as follows: P D =F D v Among them, P D F is the oil stirring loss power of the oil immersed parts, D is the shear force of the lubricating oil, v is the flow velocity of the main body of the lubricating oil; The mechanical contact friction loss expression of the chain transmission mechanism is as follows: P g =μNv B Among them, P g is the mechanical contact friction loss power, μ is the meshing dynamic friction coefficient between the sprocket and the chain plate, N is the normal force at the contact point between the chain plate and the sprocket, v B is the relative sliding speed between the sprocket and the chain plate at the contact point; The bearing friction power loss expression is as follows: P s2 =f2Fd m ω; Among them, P s1 is the viscous power loss affected by the rotation speed and lubrication state, P s2 is the load power loss affected by the load, f1 is a coefficient related to the bearing type and lubrication condition; n is the bearing speed; d m is the pitch diameter of the bearing; f2 is a coefficient related to the bearing type and load; F is the equivalent dynamic load of the bearing.

4. The method according to claim 1, characterized in that: The fluid-solid heat transfer model of the rotating parts and the lubricating oil includes a fluid-solid heat transfer model of the bearing and the lubricating oil, a fluid-solid heat transfer model of the chain transmission mechanism and the lubricating oil, and a fluid-solid heat transfer model of the optical axis and the lubricating oil.

5. The method according to claim 1, characterized in that The fluid-solid heat transfer model is characterized by the convective heat transfer coefficient, where the convective heat transfer coefficient between the bearing and the lubricating oil is: Where: o is the thermal conductivity of the lubricating oil; C is the radial clearance between the inner ring and the cage surface. When calculating the convective heat transfer between the inner ring and the lubricating oil, R is taken as r i ; When calculating the convective heat transfer of the outer ring, R is taken as r o ; The chain drive mechanism and lubricating oil fluid-solid heat transfer model is characterized by the convective heat transfer coefficient of the oil-stirring sprocket and the convective heat transfer coefficient of the non-oil-stirring sprocket; The convective heat transfer coefficient of the end face of the oil stirring sprocket under the lubricating oil laminar flow, transitional laminar flow and turbulent flow conditions is characterized as follows: Where: R g is the average radius of the oil-immersed area on the sprocket end face; Pr o 、Re o are the Prandtl number and Reynolds number of the lubricant on the sprocket end face, respectively; The non-oil stirring sprocket is usually cooled by splashing lubricating oil. The experimental correlation formula of the convection heat transfer coefficient is expressed by the following formula: Among them, h gou is the convective heat transfer coefficient of the non-oil-stirring sprocket; The fluid-solid heat transfer model between the optical axis and the lubricating oil, and between the circumferential surface of the oil stirring sprocket and the lubricating oil can be characterized by a unified convection heat transfer coefficient, and the specific formula is as follows: Where: h goy is the convection heat transfer coefficient of the cylindrical surface, R gw is the outer diameter of the equivalent cylinder.

6. The method according to claim 1, characterized in that The convective heat transfer coefficient of the fluid-solid heat transfer model between the lubricating oil and the shell is expressed by the following formula: Where: h oh is the convective heat transfer coefficient between the lubricating oil and the inner surface of the shell, and l is the characteristic length of the lubricating oil flowing on the inner wall of the shell.

7. The method according to claim 1, characterized in that The natural convection heat transfer coefficient of the fluid-solid heat transfer model between the shell and air is expressed by the following formula: Where: g is the acceleration due to gravity; α v is the volume expansion coefficient; ΔT is the fluid-solid temperature difference; ρ a is the air density, ν a is the air viscosity, c a is the specific heat capacity of air. The forced convection heat transfer coefficient formula of the fluid-solid heat transfer model between the shell and the air is the same as the convection heat transfer coefficient formula between the lubricating oil and the shell.

8. The method according to claim 1, characterized in that: The thermal resistance network model of the timely transfer case can be constructed according to the thermal balance equation, and the expression of the thermal resistance network includes the thermal state equation of the bearing network node, the thermal state equation of the chain drive network node, the thermal state equation of the lubricating oil network node and the thermal state equation of the shell network node; The thermal state equation of the bearing network node is expressed by the following equation: Among them, ρ s is the density of the bearing, V s is the volume of the bearing, c s is the specific heat capacity of the bearing, T s is the bearing temperature; The thermal state equation of the chain drive network node is expressed by the following equation: Among them, ρ g is the density of the chain, V g is the volume of the chain, c g is the specific heat capacity of the chain, T g is the temperature of the chain; The thermal state equation of the lubricating oil network node is expressed by the following equation: Among them, ρ o is the density of lubricating oil, V o is the volume of lubricating oil, c o is the specific heat capacity of the lubricating oil, T o is the temperature of the lubricating oil; The thermal state equation of the shell network node is expressed by the following equation: Among them, ρ h is the density of the shell, V h is the volume of the shell, c h is the specific heat capacity of the shell, T h is the temperature of the shell.

9. A thermal state estimation device for a timely transfer case in no-load mode based on a thermal resistance network, characterized in that include: Acquisition module: used to obtain the vehicle's operating parameters and the structure parameters of the timely transfer case. Establishing module I: Based on the working condition parameters of the vehicle and the structural parameters of the timely transfer case, according to the friction characteristics, the viscous power and contact friction power of the rotating parts are calculated, and the oil stirring loss and mechanical contact friction loss of the oil-immersed parts are obtained, so as to establish the heat generation power model of the timely transfer case; Establish Module II: According to the flow velocity distribution characteristics of the lubricating oil inside the timely transfer case, the shell is divided into different fluid-solid convection heat transfer areas, and the different fluid-solid convection heat transfer areas all include the inner surface and the outer surface of the shell; for the fluid-solid convection heat transfer areas of different rotating parts and the shell, the fluid-solid heat transfer model of the rotating parts and the lubricating oil, the fluid-solid heat transfer model of the lubricating oil and the shell, and the fluid-solid heat transfer model of the shell and the air are established respectively; Establish Module III: Based on the oil stirring loss of the oil-immersed parts and the mechanical contact friction loss, analyze the heat generation characteristics of the timely transfer case. Based on the fluid-solid heat transfer model between the rotating parts and the lubricating oil, the lubricating oil and the shell, and the shell and the air, combined with the heat dissipation characteristics of each component of the timely transfer case, the thermal resistance network model of the timely transfer case is established by the lumped parameter method with each component as an isothermal node through the principle of thermal balance, and presented with a thermal balance equation; Solution module: Combine the initial temperature and simulation step of each node in the thermal resistance network model, and the temperature state of the timely transfer box at the previous moment, quantify the energy flow value between each node in the thermal resistance network model under one time step, so as to solve the temperature value of each node of the timely transfer box at the current moment.

10. A vehicle, characterized in that: The vehicle's timely transfer case adopts a thermal resistance network-based no-load mode thermal state estimation method for the timely transfer case as described in any one of claims 1 to 8.

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