Wet clutch sliding friction state prediction method based on friction pair fluid solid heat behavior calculation and vehicle

Abstract

The invention discloses a wet clutch sliding friction state prediction method based on friction pair fluid-solid heat behavior calculation and a vehicle, and the method comprises the steps: carrying out the iterative calculation of the internal fluid-solid pressure, oil film thickness and rough contact area of a friction pair based on the structure and working condition parameters of a wet clutch through a fluid-solid bearing equation, and representing the fluid-solid coupling behavior of a friction gap; a heat-source-input-free heat balance equation and a contact temperature continuity equation are established in combination with physical property parameters, the sliding friction interface heat flow dynamic distribution proportion is calculated at the same time, and a wet clutch temperature field prediction model is established by superposing heat conduction characteristics; through a non-dominated sorting genetic algorithm, clutch dry friction test data and a rough torque model considering radial temperature difference are fused, a rough friction coefficient-temperature fitting equation is solved, and a temperature field prediction model is combined to achieve updating of rough friction coefficients under different thermal load characteristics; and rough torque and viscous torque are respectively solved by integrating fluid-solid heat behaviors of the wet clutch, and the rough torque and the viscous torque and the temperature field jointly represent the sliding friction state of the wet clutch.

Description

Technical Field

[0001] This invention belongs to the field of vehicle transmission technology, specifically proposing a method for predicting the slippage state of a wet clutch based on the calculation of the fluid-solid-thermal behavior of the friction pair, and a vehicle thereof. Background Technology

[0002] Wet clutches possess the unique advantage of continuous slippage and stepless power transmission over a wide relative speed range, making them widely used in various transmission systems of various vehicles. The complex external slippage conditions of wet clutches lead to changes in the fluid-structure-thermal micro-behavior within the friction gap, affecting the generation and evolution of slippage torque under thermal load characteristics. Predicting the slippage state of wet clutches under corresponding operating conditions is crucial for estimating the power transmission response of the transmission system and monitoring the thermal state of key components, and also provides technical guidance for the structural design and safe use of wet clutches.

[0003] In related technologies, the prediction of slip torque generation in wet clutches under thermal load characteristics can rely on finite element simulation software to simulate a detailed three-dimensional model, but the computational cost is too high and the application scenarios are limited. Alternatively, orthogonal experiments with multiple operating conditions can be used to establish the MAP relationship between the comprehensive friction coefficient of the wet clutch and multiple discrete operating condition parameters, but this requires high experimental costs and is difficult to accurately cover all operating conditions. Furthermore, existing research has failed to reveal the macroscopic slip torque variation characteristics using the internal fluid-solid-thermal micro-behavior of the wet clutch.

[0004] There are currently no effective solutions to the key problems of complex, costly, and limited application conditions in predicting the slippage state of wet clutches in related technologies. Summary of the Invention

[0005] To address the aforementioned problems, the technical solution adopted in this invention is: a method for predicting the slippage state of a wet clutch based on the calculation of the thermal behavior of the friction pair, comprising the following steps: Based on the structural and operating parameters of the wet clutch, the fluid-structure pressure distribution, oil film thickness, and rough contact area inside the wet clutch are calculated iteratively using the fluid-structure bearing equation to characterize the fluid-structure coupling behavior of the friction gap. Based on the fluid motion characteristics and solid deformation characteristics inside the wet clutch, and combined with the principles of heat transfer and friction characteristics, this paper analyzes the equivalent heat energy flow characteristics of fluid-solid convection heat transfer and solid-solid friction heat generation at the wet clutch sliding interface. Combining the physical properties of the wet clutch, a heat balance equation without heat source input is established, the circumferential temperature mean of the temperature field without heat source is extracted, a continuity equation for the contact temperature at the sliding interface is designed, the dynamic heat flow distribution ratio is calculated, and then a temperature field prediction model for the wet clutch is constructed by combining the internal heat conduction characteristics, so as to realize the prediction of the temperature field under the actual sliding state of the wet clutch. By integrating the clutch dry friction test and the full disc rough torque calculation model with a fast non-dominated sorting genetic algorithm, the rough friction coefficient-temperature fitting equation is solved to obtain the rough friction coefficient that varies with temperature. By combining the temperature field prediction model of wet clutches and the rough friction coefficient-temperature fitting equation, the rough friction coefficient of wet clutches under different thermal load conditions can be updated. The rough torque and viscous torque are solved by using the rough contact area, the updated rough friction coefficient and oil film thickness, and the lubricating oil viscosity-temperature equation, respectively. The total slip torque of the wet clutch is obtained by summing them up, and together with the clutch temperature field, it characterizes the slip state of the wet clutch under continuous operation.

[0006] Furthermore, the process of iteratively calculating the fluid-solid pressure distribution, oil film thickness, and rough contact area inside the wet clutch based on its structural and operating parameters, combined with the fluid-solid bearing model, is as follows: First, the three-dimensional momentum conservation equation of lubricating oil in grooved cavity, the flow conservation equation of lubricating oil in non-grooved friction gap, and the bearing model of micro-protrusion on rough surface are constructed respectively to characterize the mathematical relationship between different oil film thicknesses and fluid pressure in grooved cavity, fluid pressure in non-grooved area, bearing capacity of micro-protrusion and rough contact area under any sliding friction conditions. To address the interlocking deformation characteristics of the friction surface, a calculation model for the elastic deformation of grid points across the entire friction pair is established as follows:

[0007] in, , , , They are nodes ( , The coordinates of (m,n); Based on the historical oil film thickness, the deformation of each local grid point is updated according to the fluid-solid pressure to form a reconstructed friction gap. The resulting oil film thickness calculation formula is as follows:

[0008] in, For iterative calculation steps, For oil film thickness, This is the amount of deformation. This is the deformation correction factor; Based on the reconstructed friction gap, the fluid-solid pressure distribution inside the friction pair is updated until the fluid-solid pressure distribution and the reconstructed friction gap deformation state reach stable convergence. The specific formula for the convergence of fluid-solid pressure and deformation is as follows:

[0009] in, This represents the fluid pressure convergence threshold. This refers to the fluid pressure in the non-groove region. When the fluid-solid pressure and deformation state converge, the overall oil film thickness of the grid points in the entire domain is calculated iteratively based on the balance relationship between the internal and external pressures of the friction pair. The above correction steps for reconstructing the friction gap state convergence solution are repeated until the fluid-solid pressure and deformation state inside the friction pair converge again, and the internal load and external force satisfy the balance state. The specific formula for the balance of internal and external loads is as follows:

[0010] in, Due to external pressure, The convergence threshold of internal and external pressures. For the oil film bearing area, For non-groove friction gap solid pressure, This represents the actual rough contact area. After the oil film thickness correction is completed, the current oil film thickness is output, and the actual rough contact area inside the wet clutch is calculated. for: .

[0011] Furthermore, based on the fluid motion characteristics and solid deformation characteristics inside the wet clutch, combined with the principles of heat transfer and friction characteristics, the equivalent thermal energy flow characteristics of fluid-solid convection heat transfer and solid-solid friction heat generation at the wet clutch sliding interface are analyzed. The process of establishing a heat balance equation without heat source input by combining the wet clutch's physical properties, and extracting the circumferential temperature mean of the temperature field without heat source to design the continuity equation for the sliding interface contact temperature and calculate the dynamic heat flow distribution ratio is as follows: The heat dissipation on the circumferential surface of the steel sheet alternates in a cycle, and its energy flow is characterized by the equivalent convective heat transfer intensity and the equivalent slip friction heat generation intensity. The total equivalent convective heat transfer intensity at each grid position on the steel sheet surface is... With equivalent frictional heat generation intensity for:

[0012]

[0013] The surface of the non-grooved region of the friction plate is always in a state of sliding friction heat generation, while the side boundary of the grooved region is always in a state of fluid-solid convective heat transfer. The effective convective heat transfer intensity and effective sliding friction heat generation intensity at each grid location are respectively... and ; A set of thermal balance equations for a wet clutch without heat source input is established using the principle of thermal balance:

[0014]

[0015] in, The iteration time step, The oil temperature is along the radial direction of the friction pair. For the temperature field of the steel sheet; For the thermal conductivity of the steel sheet, For the Laplace operator, For the density of the steel sheet, Let the volume of the steel sheet be a infinitesimal element. Specific heat capacity of steel sheet; Temperature field of the friction plate; The thermal conductivity of the friction plate, For the density of the friction plate, Let the volume of the friction plate be a micro-element. The specific heat capacity of the friction plate; By combining the temperature rise caused by the heat sourceless temperature of the wet clutch with the temperature rise due to sliding friction heat flow, and aiming to make the average temperature of the friction plate and the steel plate equal for one groove cycle at the same radius, the following formula is established for calculating the dynamic distribution value of the total sliding friction heat flow with the history of the temperature field under continuous contact temperature constraint:

[0016] in, Let be the heat-free average temperature of the friction plate at the node in the m-th row radial direction. For the density of the friction plate, Let the volume of the friction plate be a micro-element. For the specific heat capacity of the friction plate, For the friction plate surface in the radial direction The average temperature of the row node without a heat source. The sliding friction heat flow distribution coefficient of the steel sheet; Following the principle of conservation of thermal energy flow at grid nodes, the actual input value of the sliding friction heat generation intensity of the steel sheet is substituted into the heat balance equation set without heat source input to calculate the temperature change of general nodes of the steel sheet. For the boundary nodes of the steel sheet, only the corresponding heat conduction terms need to be deleted. Similarly, the temperature of each grid node of the friction plate can be calculated by taking the physical property parameters of the heat balance equation set without heat source input and adding the actual input value of the sliding friction heat generation intensity of the friction plate.

[0017] Furthermore, the expression for the rough friction coefficient-temperature fitting equation is as follows:

[0018] in: The roughness friction coefficient; , , , These are the coefficients of the fitted equation; The temperature at a certain location on the sliding interface. Furthermore, the overall rough torque calculation model is as follows:

[0019] in: The effective friction radius of the inner circle, The effective friction radius of the outer circle. The average roughness friction coefficient of the inner circle. The average roughness friction coefficient of the outer circle. The inner diameter of the clutch is for slippage. For the clutch slippage center diameter, For the outer diameter of the clutch slippage, This is the total normal force of the clutch.

[0020] Furthermore, using the rough contact area, the updated rough friction coefficient and oil film thickness, and the lubricating oil viscosity-temperature equation, the viscous torque is obtained. Equations and rough torque The equations are as follows:

[0021]

[0022] in, For the sliding speed term, This is a comprehensive correction term for the shear stress factor. The average temperature of the lubricating oil at the m-th radial dimension of the clutch. The average temperature of the sliding surface at the m-th radial row of the clutch is given.

[0023] A vehicle wherein the wet clutch employs any one of the wet clutch slippage state prediction methods based on the fluid-solid-thermal behavior calculation of the friction pair as described in any one of the above methods.

[0024] This invention provides a method and vehicle for predicting the slippage state of a wet clutch based on the calculation of the fluid-structure thermal behavior of the friction pair. It considers the influence of the distribution of grooves in the friction gap and the properties of the friction material on fluid motion and solid deformation. It uses the fluid-structure bearing equation to iteratively calculate the internal fluid-structure pressure and the microscopic state of the fluid-structure contact area within the wet clutch, more closely reflecting the actual characteristics of the wet clutch and analyzing the fluid-structure coupling behavior of the friction gap. Following the circumferential alternating cyclic sweeping characteristics of the groove and non-groove regions of the friction pair and the continuous temperature constraint at the contact interface, it combines heat transfer principles and friction characteristics to solve for the effective thermal energy flow at the slippage interface, establishing a dynamic model of slippage heat flow. A temperature field prediction model for the distribution process is proposed to accurately calculate the temperature field under the actual slipping state of the wet clutch. A global data optimization method is proposed to combine the clutch dry friction test with the full-disc rough torque calculation model considering radial temperature differences through intelligent algorithms. This method accurately solves the coefficients of the rough friction coefficient-temperature fitting equation, enabling the updating of the rough friction coefficient with temperature under different thermal loads of the wet clutch. By integrating the rough contact area, the updated rough friction coefficient, the oil film thickness, and the lubricating oil viscosity-temperature equation, the macroscopic torque generation and temperature field changes under continuous slipping state of the wet clutch are intuitively revealed from a fluid-solid-thermal microscopic perspective. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart for predicting the slippage state of a wet clutch according to an embodiment of this application; Figure 2 This is a schematic diagram of the fluid-structure dynamics behavior of the friction gap of a wet clutch according to an embodiment of this application; (a) wet clutch, (b) groove cavity, (c) non-groove gap; Figure 3 This is a schematic diagram of the thermal energy flow in the friction gap of a wet clutch according to an embodiment of this application; (a) during rotation, (b) from before rotation to after rotation; Figure 4 This is a flowchart of the rough friction coefficient-temperature fitting of a wet clutch according to an embodiment of this application; Figure 5 The following are simulation and test results of wet clutch slippage state provided in the embodiments of this application: (a) Simulation and test results I at different position temperatures, (b) Simulation and test results II at different position temperatures, and (c) Simulation and test results of torque. Figure 6This invention provides a wet clutch slippage state prediction system based on the calculation of the fluid-solid-thermal behavior of the friction pair. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Figure 1 This is a flowchart of a method for predicting the slipping state of a wet clutch based on an embodiment of this application. A method for predicting the slippage state of a wet clutch based on the calculation of the solid-thermal behavior of the friction pair flow includes the following steps: S1: Based on the structural and operating parameters of the wet clutch, the fluid-structure pressure distribution, oil film thickness, and rough contact area distribution inside the wet clutch are calculated iteratively using the fluid-structure bearing equation to characterize the fluid-structure coupling behavior of the friction gap. S2: Based on the fluid motion characteristics and solid deformation characteristics inside the wet clutch, and combined with the principles of heat transfer and friction characteristics, we conduct an analysis of the equivalent heat energy flow characteristics of fluid-solid convection heat transfer and solid-solid friction heat generation at the wet clutch sliding interface. We establish a heat balance equation for the wet clutch without heat source input by combining the physical properties of the wet clutch, extract the circumferential average temperature of the clutch temperature field without heat source input, design a continuity equation for the contact temperature of the sliding interface to calculate the dynamic heat flow distribution ratio, and then construct a temperature field prediction model for the wet clutch by combining the heat conduction characteristics, so as to realize the prediction of the temperature field under the actual sliding state of the wet clutch. S3: By integrating the clutch dry friction test and the full disc rough torque calculation model through a fast non-dominated sorting genetic algorithm, the rough friction coefficient-temperature fitting equation is solved to obtain the rough friction coefficient that varies with temperature. S4: Combine the wet clutch temperature field prediction model and the rough friction coefficient-temperature fitting equation to update the rough friction coefficient of the wet clutch under different thermal load conditions; S5: The rough torque and viscous torque are calculated by using the rough contact area, the updated rough friction coefficient and oil film thickness, and the lubricating oil viscosity-temperature equation, respectively. The total slip torque of the wet clutch is obtained by summing them up, and together with the clutch temperature field, it characterizes the slip state of the wet clutch under continuous slip conditions.

[0030] After step S1 is executed, steps S2 / S3 are executed in parallel, and then S4 / S5 are executed sequentially.

[0031] Figure 2 This is a schematic diagram of the fluid-structure interaction dynamics of the friction pair clearance of a wet clutch according to the embodiments of this application, (a) wet clutch, (b) grooved cavity, (c) non-groove clearance; The wet clutch, during the slippage process, involves the following fluid-structure interaction dynamics description method: there is lubricating oil flow and rough micro-protrusion deformation in the friction gap.

[0032] In the groove region of the wet clutch, the lubricating oil generates driving eddies due to the relative rotational speed difference between the friction pairs. At the same time, under the combined action of the centrifugal pressure of the friction pairs and the static pressure of the supplied flow, the lubricating oil flows in from the inner diameter of the friction pairs and flows out from the outer diameter.

[0033] In the non-grooved clearance of a wet clutch, the lubricating oil undergoes laminar flow under circumferential and radial pressure; and the friction plate surface undergoes a series of deformations under fluid dynamic pressure and solid contact pressure.

[0034] This invention constructs a three-dimensional momentum conservation equation for grooved cavity lubricating oil, a flow conservation equation for non-grooved friction gap lubricating oil, and a bearing model for rough surface micro-protrusions, respectively, to characterize the mathematical relationships between different oil film thicknesses and the fluid pressure in the grooved cavity, the fluid pressure in the non-grooved area, the bearing capacity of the micro-protrusions, and the rough contact area under any sliding friction conditions.

[0035] Regarding the circumferential driving eddy current of lubricating oil within the friction clearance groove cavity of a wet clutch, for the radial section at any radius of the groove, the junction of the friction liner and the friction core plate is taken as the origin of the coordinate system, and the direction of the eddy current is defined as... x The positive axis and the thickness direction of the cavity are as follows: y Establish a rectangular coordinate system along the positive axis, such as... Figure 2 As shown in (b), the dynamic equation for the vortex flow of lubricating oil in the radial section of the groove cavity is:

[0036] in, for Directional lubricating oil flow velocity (m / s) for Directional lubricating oil flow velocity (m / s) The density of the lubricating oil (kg / m³) The dynamic viscosity of the lubricating oil (Pa·s) This refers to the dynamic pressure of the lubricating oil (Pa).

[0037] Based on the intrinsic relationship between fluid velocity and pressure, an interlaced grid is established on the coordinate plane to represent the fluid pressure values. P I,J Velocity components are stored in the mesh nodes (I,J) of the main control volume. and The dynamic equations for the vortex flow of lubricating oil in the radial section of the groove cavity are discretized using the finite volume method. Following the fundamental principle of no slippage at the fluid-structure contact wall, and following the calculation process of staggered mesh technology, the pressure of the lubricating oil in the radial section of the groove cavity at the current friction radius is solved by iterative and correction methods. The equations are stored at nodes (i,J) and (I,j) respectively, half a mesh step back from the main control node. P With speed u and v .

[0038] Similarly, by taking the velocity values ​​of the no-slip boundary nodes in the dynamic equation of the vortex flow generated in the radial section of the groove cavity when the lubricating oil is replaced, and repeating the above iterative calculation and correction steps, the vortex flow pressure of the fluid at any corresponding radius of the groove radial section of the friction pair can be obtained. P With speed u and v .

[0039] Regarding the radial pressure flow of lubricating oil within the friction clearance groove cavity of the wet clutch, the pressure gradient at different radial locations and the actual flow rate... The relationship is:

[0040] in, The centrifugal velocity (m / s) of the lubricating oil at different cross-sections of the groove. The oil film thickness (m) is at different cross-sections of the trench. Gap length The difference in static pressure (Pa) at both ends, is the radial infinitesimal element length.

[0041] Actual traffic Supply flow to the groove cavity of the wet clutch centrifugal flow rate The difference lies in the centrifugation speed; the latter depends on the centrifugation rate. wTo solve this problem, assuming that the radial shear force and centrifugal force of the lubricating oil in the groove cavity always remain equal, the momentum conservation equation for the radial flow of the lubricating oil can be established in the form of Poisson's equation in the rectangular coordinate system of the groove section:

[0042] in, The dynamic viscosity of the lubricating oil (Pa·s) The centrifugal velocity of the lubricating oil (m / s) ω is the angular velocity of the friction pair (rad / s), which is the average of the rotational speeds of the friction plate and the steel plate.

[0043] The momentum conservation equation for the radial flow of lubricating oil was discretized using the second-order finite difference method, and the centrifugal velocity of the lubricating oil was calculated using Gauss-Seidel iteration. and the corresponding centrifugal flow rate requirements for:

[0044] Similarly, by changing the sliding radius in the radial momentum conservation equation for lubricating oil, the centrifugal velocity and centrifugal flow demand of the lubricating oil at different radial positions in the groove can be calculated. In a wet clutch, the radial outlet of the lubricating oil in the friction clearance is connected to the atmosphere, and the total fluid pressure at the outer diameter of the friction pair is... Given a value of 0, based on this constraint, for each radial infinitesimal element of the clutch, the centrifugal flow rate requirement is considered. The expression calculates the static pressure distribution of the fluid in the trench sequentially from the outer diameter to the inner diameter. .

[0045] The dynamic pressure generated by the circumferential vortex flow of the superimposed groove lubricating oil The total fluid pressure at different cross-sections of the trench is calculated as follows:

[0046] In summary, the total pressure of lubricating oil at different radial positions within the groove cavity was obtained. The calculation expression for the distribution and operating parameters of the wet clutch.

[0047]

[0048] Regarding the laminar flow of lubricating oil in the non-grooving clearance of the wet clutch friction gap, a micro-element mesh is divided along the radial and circumferential directions of the friction pair on the sliding surface, such as... Figure 2 As shown in (c), with the rotation center of the friction pair as the origin, and combining the steady flow assumption of lubricating oil and the Patir-Cheng average flow model, the flow conservation equations for the lubricating oil flowing circumferentially and radially within the infinitesimal control element in cylindrical coordinates are established as follows:

[0049] in,

[0050]

[0051] in, , , For flow factor, The fluid pressure (Pa) in the non-groove region is [value missing]. The rotational angular velocity (rad / s) of the steel sheet and friction plate. The average oil film thickness (m) in the non-groove area.

[0052] Within the smaller friction clearance in the non-groove region, considering the influence of the lubricating oil viscosity-pressure relationship, induced pressure is introduced. replace The flow conservation equations for lubricating oil flowing circumferentially and radially within a micro-element control body in cylindrical coordinates are discretized using the finite volume method. Combining the periodic boundary conditions of the solution region's circumferential direction, the natural boundary conditions of the inner diameter, and the atmospheric boundary conditions of the outer diameter, the induced pressure is calculated by solving the equations using Gauss-Seidel iteration. The corresponding lubricating oil pressure is then updated to obtain this updated value. distributed.

[0053] In summary, the lubricating oil pressure in the non-groove friction clearance was obtained. The relationship between the operating parameters of the wet clutch and the average oil film thickness.

[0054]

[0055] Regarding the compressive deformation of the solid in the non-grooving friction gap of a wet clutch, a rough surface micro-protrusion bearing model is established as follows:

[0056]

[0057] in, The distribution density of micro-protrusions (units / m²) This represents the root mean square value of the joint roughness of the friction pair. Let the radius of the micro-convexity be (m). This represents the equivalent elastic modulus (MPa) of the friction plate and the steel plate.

[0058] The equivalent elastic modulus is:

[0059] in, , Let be the elastic modulus (MPa) of the friction plate and the steel plate, respectively. , These are the Poisson's ratios of the friction plate and the steel plate, respectively.

[0060] The process of iteratively calculating the fluid-solid pressure distribution, oil film thickness, and rough contact area inside the wet clutch based on its structural and operating parameters is as follows: Based on the formula for calculating the contact area of ​​a single micro-protrusion, the average clearance of the friction pair is: The actual rough contact area inside the wet clutch is obtained by calculating the number of micro-protrusions contacted based on the rough contact probability. for:

[0061] in, The nominal area (m²) of the calculation region.

[0062] Furthermore, the friction surface exhibits chain deformation; a concentrated force at a certain local location on the surface affects the compressive deformation at all locations throughout the entire domain. This is the chain characteristic of elastic surface deformation. The deformation at any node (m0, n0) is established. The calculation model is as follows:

[0063] in, , , , They are nodes ( , The coordinates of (m,n).

[0064] The presence of fluid dynamic pressure will increase the friction gap and reduce the solid bearing capacity, but the increased friction gap will in turn reduce the fluid dynamic pressure. The deformation state of the reconstructed friction gap has a conservation relationship with the fluid-structure interaction pressure. The calculation of the reconstructed friction gap includes: Using an iterative solution approach, under the initial condition that the oil film thickness is the same at the center of each micro-grid point along the radial and circumferential directions of the friction pair, the deformation of each local grid point is updated based on the fluid-solid pressure:

[0065] in, For iterative calculation steps, For oil film thickness, This is the amount of deformation. This is the deformation correction coefficient.

[0066] Based on the reconstructed friction gap, the fluid-solid pressure distribution inside the friction pair is calculated until the fluid-solid pressure distribution and the reconstructed friction gap deformation state reach stable convergence. The calculation formula is as follows:

[0067] in, For iterative calculation steps, This is the fluid pressure convergence threshold.

[0068] The thickness of the oil film at the center of the friction gap changes with the external normal pressure. Based on the steady-state relationship between the fluid-solid pressure and deformation within the friction pair in each iteration step, the total internal fluid-solid pressure is compared with the external normal pressure. When the fluid-solid pressure and deformation state converge, the overall oil film thickness of the grid points in the entire domain is corrected according to the balance relationship between the internal and external pressures of the friction pair. The above correction steps for reconstructing the friction gap state convergence solution are repeated until the fluid-solid pressure and deformation state within the friction pair converge again, and the internal load and external force satisfy the equilibrium state. The specific formula for calculating the balance of internal and external loads is as follows:

[0069] The oil film bearing area can be expressed as:

[0070] in, External pressure (N), This is the convergence threshold for internal and external pressures.

[0071] In summary, the distribution of fluid velocity, oil film thickness, and rough contact area inside the friction gap of a wet clutch is obtained under known external normal pressure and relative speed.

[0072] The analysis of the equivalent thermal energy flow characteristics of the sliding interface includes: based on the fluid velocity, oil film thickness and rough contact area inside the wet clutch, combined with the principles of heat transfer and friction characteristics, calculating the equivalent fluid-solid convective heat transfer intensity and equivalent solid-solid sliding heat generation intensity of the wet clutch sliding interface, establishing its heat balance equation without heat source input by combining the physical property parameters of the wet clutch, extracting the circumferential average temperature of the clutch's temperature field without heat source input, and designing the continuity equation of the contact temperature of the sliding interface to calculate the dynamic heat flow distribution ratio.

[0073] Figure 3 This is a schematic diagram of the thermal energy flow in the friction gap of a wet clutch according to an embodiment of this application, (a) during rotation, (b) from before rotation to after rotation; it relates to a method for obtaining the temperature field based on the energy flow intensity of the sliding surface; In the non-grooved area of ​​a wet clutch, the friction lining is in direct contact with the steel plate. During relative rotation, the heat energy generated by sliding friction is directly transferred from the surfaces of the friction lining and the steel plate into the interior. Figure 3(a) shows a curved red double-headed arrow; in the groove area of ​​the clutch, the lubricating oil in the cavity flows spirally from the inner diameter of the friction pair to the outer diameter, carrying away some of the heat energy from the surface of the friction pair in a sweeping manner, as shown by the black spiral line in the groove in the figure.

[0074] The heat generated by slippage in the non-grooving region of a wet clutch is derived from the slippage power formed by slippage torque and relative speed. The key to calculating the heat generation energy of slippage lies in determining the distribution of slippage torque across the entire friction surface of the wet clutch disc. Since the lubricating oil film in the rough gap is extremely thin and discontinuous, its own heat generation can be ignored; only the heat generated by rough contact is considered. Therefore, the heat generation energy of the target area depends on the size of the rough contact area, the corresponding slippage radius, and the relative speed of the wet clutch, combined with… Figure 2 (c) The mesh division of the wet clutch slippage area, in the radial direction of the slippage surface Total frictional heat flow The calculation expression is:

[0075] in, The contact bearing capacity of the solid (N). The actual contact area between the two planes under this gap ( ), The roughness friction coefficient, , These represent the rotational speeds (rad / s) of the driving and driven ends of the friction pair, respectively.

[0076] The convective heat transfer in the groove region of a wet clutch is closely related to the flow state of the lubricating oil itself. The local forced convection heat transfer coefficient at different locations is:

[0077] in, The thermal conductivity of the lubricating oil [W / (m·℃)], The specific heat at constant pressure of lubricating oil [J / (kg·℃)], The local characteristic length (m) of the fluid's location. The characteristic velocity of the fluid is (m / s).

[0078] according to Figure 3 (a) indicates that lubricating oil flows radially and circumferentially across the surface of the steel plate along the friction gap of the wet clutch. With friction plate groove surface ; flows radially and axially along the friction gap of the wet clutch through the friction plate groove surface , The flow of lubricating oil in different directions generates convective heat transfer. By using the superposition principle, the convective heat transfer effects generated by the lubricating oil in different flow directions on different heat dissipation surfaces of the friction pair in the groove cavity are superimposed, which is the total convective heat transfer of the lubricating oil at a certain position of the friction pair.

[0079] The convective heat transfer of the lubricating oil flowing circumferentially and axially within the grooved cavity needs to be calculated based on the flow equation of the lubricating oil driving eddies in the circumferential section on the steel sheet surface. With friction plate groove surface Circumferential flow velocity of lubricating oil and friction plate groove surface , Axial flow velocity of lubricating oil They are respectively:

[0080]

[0081] The convective heat transfer of the lubricating oil in the groove cavity requires the radial flow velocity of the lubricating oil on the groove surface. This requires a comprehensive comparison of the relationship between the supply flow rate of lubricating oil and the centrifugal demand flow rate.

[0082] If the static pressure supply flow rate at the trench cross-section can meet the centrifugal requirements, then the radial velocity at the cross-section... for:

[0083] If the hydrostatic supply of lubricating oil cannot meet the centrifugal requirements, the lubricating oil cannot fill the groove cavity, and cavitation occurs in the fluid-solid contact region where convective heat transfer occurs in the groove. Therefore, the radial velocity of the cross-section can be assumed. Centrifugal speed alone Instead. Insufficient contact in the fluid-solid region will weaken the convective heat transfer effect of the lubricating oil. This can be addressed by weighting the amount of lubricating oil filling the cavity, with the weighting value... for:

[0084]

[0085] Based on the analysis of fluid-solid heat exchange characteristics, the density of convective heat transfer at a certain location is defined as the product of the convective heat transfer coefficient, the local heat transfer area, and the weighted value of the convective heat transfer effect. The calculation formula is as follows:

[0086] So, the convective heat transfer surface of the steel sheet Total convective heat transfer density at a certain location for:

[0087] Similarly, the surface of the friction plate , , Total convective heat transfer density at a certain grid location for:

[0088]

[0089]

[0090] Furthermore, regarding Figure 3 As shown in (b), the thermal energy flow at different circumferential locations on the same position of the steel sheet surface is different due to the alternating cyclical experience of convective heat transfer and frictional heat generation. Based on the characteristic relationship between thermal energy flow and temperature generation in heat transfer, this difference is characterized by defining equivalent convective heat transfer intensity and equivalent frictional heat generation intensity.

[0091] For the surface of the steel sheet, at a fixed time step At the end of the gliding process, the definition is... The time taken for the relative sliding angular displacement of the friction pair to reach a maximum integer multiple of the groove period, at the end of this time period, the relative positions of the friction plate and the steel plate completely coincide with the initial time, and the convective heat transfer intensity and sliding heat generation intensity at each position on the contact surface are no different in the circumferential direction, as follows:

[0092]

[0093] in, Let W be the convective heat transfer density (W) corresponding to a grid point on the steel sheet. The frictional heat density (W) corresponds to a grid point on the steel sheet.

[0094] definition The remaining time after the relative sliding angular displacement of the friction pair has reached a maximum integer multiple of the groove period is considered. After the fixed-time-step sliding friction ends, the relative positions of the friction plate and the steel plate do not completely coincide with the initial time. The convective heat transfer intensity and sliding heat generation intensity at different locations on the contact surface differ circumferentially, mainly reflected in the different durations of convective heat transfer and sliding heat flow at each grid location. A rectangular coordinate system is established with time as the x-axis and thermal energy power as the y-axis to depict the convective heat transfer density and sliding heat generation density at each grid point. The changes over time. Integrating over time yields the convective heat transfer intensity and the frictional heat generation intensity at various locations on the contact surface during this time period:

[0095]

[0096] The circumferential heat dissipation on the steel sheet surface alternates in a cycle, and its energy flow is characterized by the equivalent convective heat transfer intensity and the equivalent slip friction heat generation intensity. The total equivalent convective heat transfer intensity at each grid position on the upper and lower surfaces of the steel sheet within a given time period. With equivalent frictional heat generation intensity for:

[0097]

[0098] The density of the steel sheet (kg / m³) Let the volume of the steel sheet be a infinitesimal element (m³). Specific heat capacity of steel sheet (J / (kg·℃); The surface of the non-grooved region of the friction plate is always in a state of sliding friction and heat generation, while the side boundary of the grooved region is always in a state of fluid-solid convective heat transfer. The effective convective heat transfer intensity at each grid location is... and effective friction heat generation intensity They are respectively:

[0099]

[0100] in, This represents the convective heat transfer density at a grid point on the boundary of the friction plate groove. This represents the heat flux density at a grid point on the surface of the non-groove region of the friction plate.

[0101] Furthermore, when the friction lining and steel sheet are in contact, the contact surface inherently exhibits continuous temperature characteristics. Under this constraint, the distribution of total heat flow during sliding friction between the friction pairs is an unknown physical quantity. Using the principle of thermal equilibrium, the following set of thermal equilibrium equations for a wet clutch without a heat source input is established under conditions of only convective and conductive heat transfer:

[0102]

[0103] in, The iteration time step, The oil temperature is along the radial direction of the friction pair. The temperature field of the steel sheet without a heat source; For the thermal conductivity of the steel sheet, For the Laplace operator, For the density of the steel sheet, Let the volume of the steel sheet be a infinitesimal element. Specific heat capacity of steel sheet; The temperature field of the friction plate without a heat source; The thermal conductivity of the friction plate, For the density of the friction plate, Let the volume of the friction plate be a micro-element. The specific heat capacity of the friction plate; Based on the above equations, the heat-free temperature fields of the steel plate and friction plate are solved separately. The heat-free temperature of the wet clutch is combined with the temperature rise caused by the sliding friction heat flow. With the goal of making the average temperature of the friction plate and steel plate equal for one groove cycle at the same radius, the continuity equation of the contact temperature at the sliding friction interface is designed as follows:

[0104] in, For clutch dt The sliding friction heat flow at the radially m-th row node within a time interval. The sliding friction heat flow distribution coefficient of the steel sheet. The density of the steel sheet (kg / m³) For the steel sheet in the radial direction The infinitesimal volume (m³) of a row node. Specific heat capacity of steel sheet (J / (kg·℃)) Let be the heat-free average temperature of the friction plate at the node in the m-th row radial direction. The density of the friction plate is kg / m³. For the friction plate in the radial direction The infinitesimal volume (m³) of a row node. The specific heat capacity of the friction plate [J / (kg·℃)], For the friction plate surface in the radial direction Average temperature (°C) of row nodes without heat source.

[0105] Furthermore, the dynamic distribution value of the total heat flow due to friction, which follows the historical changes of the temperature field, is solved. Following the principle of conservation of heat energy flow at grid nodes, the actual input value of the friction heat generation intensity of the steel sheet is substituted into the heat balance equations without heat source input to calculate the temperature change of general nodes of the steel sheet. For the boundary nodes of the steel sheet, only the corresponding heat conduction terms need to be deleted.

[0106] Similarly, the temperature of each grid node of the friction plate can be calculated for the heat balance equations without a heat source input.

[0107] Figure 4 This is a flowchart of the calculation of the coefficients of the wet clutch rough friction coefficient-temperature fitting equation according to the embodiments of this application, which involves the calibration method of the rough friction coefficient changing with temperature; For a given friction pair material, its rough friction coefficient is closely related to its temperature change. To accurately obtain the coefficients of the rough friction coefficient-temperature fitting equation, a continuous dry friction sliding test of the clutch was designed. A non-dominated sorting genetic algorithm was used to fuse the temperature and sliding torque data of the clutch dry friction test with the rough torque model of the clutch under radial temperature difference. The coefficients of the rough friction coefficient-temperature fitting equation were then solved based on optimization ideas.

[0108] Using the circumference of the clutch slip-off diameter as the dividing line, the rough friction area is divided into two friction rings of equal width. The average temperature of the inner ring a is represented by the temperature measured by temperature sensor 1, and the average temperature of the outer ring b is represented by the temperature measured by temperature sensor 2. The changes in the inner diameter temperature, the middle and outer diameter temperatures, and the rough torque are recorded throughout the continuous slip-off process.

[0109] The pressure of the test bench loading system is uniformly applied to the friction pair along the normal direction of the clutch surface. The normal pressure borne by the rough micro-protrusions on the inner ring a and outer ring b of the friction pair is proportional to the nominal area of ​​the region they represent. For this annular friction pair, the sliding friction torque along the radial micro-elements of the inner and outer rings is integrated to obtain the rough torque calculation model of the entire clutch disc as follows:

[0110]

[0111]

[0112] in, , The effective friction radii (m) of the inner and outer rings respectively. , These are the average roughness friction coefficients of the inner and outer rings, respectively. The clutch slippage diameter (m) This is the total normal force (N) of the clutch.

[0113] The roughness friction coefficient is an unknown equation related to temperature, and its quantitative relationship can be uniformly expressed using a high-order polynomial model as follows:

[0114] By combining the sliding torque and temperature data from clutch dry friction tests, the coefficients of the rough friction coefficient-temperature fitting equation are solved. The inner and outer ring temperatures and their corresponding full-disc sliding torques at the same sampling time point in the test are grouped into the same data set. These are then substituted into the full-disc rough torque calculation formula and the rough friction coefficient-temperature fitting equation to establish a system of equations for the coefficients to be determined. The problem of solving the oversaturated equation system coefficients is transformed into a multi-objective optimization problem, with the optimization variables being the coefficients to be determined in the fitting equations. The optimization objectives are to minimize the root mean square deviation between the torque measurements at all sampling points and the calculated values ​​from the fitting equations, and to minimize the maximum value of the fitting deviation for all sampling points. The two objective functions of the optimization algorithm are defined as follows:

[0115]

[0116] in, The torque value (Nm) was measured for the test. This represents the total number of experimental samples used in the fitting process.

[0117] The coefficients of the rough friction coefficient-temperature fitting equation were solved using the Fast Non-dominated Sorting Genetic Algorithm (NSGA-II).

[0118] Viscosity-temperature relationship of combined lubricating oil Figure 2 Calculation of oil film thickness and rough contact area distribution Figure 3 Temperature field prediction for wet clutches, establishing viscous torque under clutch thermal load characteristics. Equations and rough torque The equation is:

[0119]

[0120]

[0121] in, For the radial direction of the clutch m The average temperature (°C) of the lubricating oil at the micro-element. For the radial direction of the clutch m Average temperature (°C) of the sliding surface at the micro-element.

[0122] Figure 5 The simulation and test results of the continuous slipping state of the wet clutch provided in the embodiments of this application are as follows: (a) Simulation and test results I at different position temperatures, (b) Simulation and test results II at different position temperatures, and (c) Simulation and test results of torque. Under continuous sliding friction conditions with different relative speeds and lubrication flow rates under a given normal pressure, the actual and calculated values ​​of the sliding torque under the average temperature and thermal load characteristics of the inner and outer rings of the wet clutch were demonstrated. The torque calculations and temperature distribution calculations from the simulation and experiments showed good agreement, with the maximum torque deviation between the simulation calculations and experimental measurements not exceeding 5%.

[0123] As the slippage time progresses under various operating conditions, the overall temperature of the wet clutch continuously increases, and the slippage torque under thermal load characteristics also shows a gradual increasing trend. With the increase of relative speed, the torque generation increment of the wet clutch at the end of slippage also increases, because under the same slippage time, the increase of relative speed promotes the rate of temperature increase of the wet clutch, thereby indirectly promoting the increase of its slippage torque under thermal load characteristics.

[0124] The wet clutch slip condition prediction method involved in the embodiments of the present invention can accurately predict the generation and evolution of slip torque under thermal load characteristics for the complex continuous slip condition of wet clutches, and guide the structural design and safe use of wet clutches.

[0125] Figure 6 The figure shows a wet clutch slippage state prediction system based on the calculation of the thermal behavior of the friction pair flow, provided by an embodiment of the present invention, comprising: Parameter reading module: used to read the slip friction parameters of the wet clutch as well as its own structural and physical property parameters, providing data for fluid-structure-thermal behavior calculation; Model building module: used to calculate the fluid-structure behavior and thermal energy flow behavior in the actual friction clearance structure of the wet clutch under corresponding slip friction conditions; simultaneously correct the influence of the wet clutch's own thermal load on friction characteristics; and determine the slip friction torque under the thermal load characteristics of the wet clutch. Slippage State Output Module: Used to output the temperature field and slippage torque under continuous slippage conditions of wet clutches, for predicting the slippage state of wet clutches in practical applications.

[0126] The wet clutch slippage state prediction system involved in this invention can solve the key problems of complex wet clutch slippage state prediction methods, high costs, and limited application conditions.

[0127] A vehicle wherein the wet clutch employs any one of the wet clutch slippage state prediction methods based on the fluid-solid-thermal behavior calculation of the friction pair as described in any one of the above methods.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 predicting the slippage state of a wet clutch based on the calculation of the solid-thermal behavior of the frictional pair flow, characterized in that: Includes the following steps: Based on the structural and operating parameters of the wet clutch, the fluid-structure pressure distribution, oil film thickness, and rough contact area inside the wet clutch are calculated iteratively using the fluid-structure bearing equation to characterize the fluid-structure coupling behavior of the friction gap. Based on the fluid motion characteristics and solid deformation characteristics inside the wet clutch, and combined with the principles of heat transfer and friction characteristics, this paper analyzes the equivalent heat energy flow characteristics of fluid-solid convection heat transfer and solid-solid friction heat generation at the wet clutch sliding interface. Combining the physical properties of the wet clutch, a heat balance equation without heat source input is established, the circumferential temperature mean of the temperature field without heat source is extracted, a continuity equation for the contact temperature at the sliding interface is designed, the dynamic heat flow distribution ratio is calculated, and then a temperature field prediction model for the wet clutch is constructed by combining the internal heat conduction characteristics, so as to realize the prediction of the temperature field under the actual sliding state of the wet clutch. By integrating the clutch dry friction test and the full disc rough torque calculation model with a fast non-dominated sorting genetic algorithm, the rough friction coefficient-temperature fitting equation is solved to obtain the rough friction coefficient that varies with temperature. By combining the temperature field prediction model of wet clutches and the rough friction coefficient-temperature fitting equation, the rough friction coefficient of wet clutches under different thermal load conditions can be updated. The rough torque and viscous torque are solved by using the rough contact area, the updated rough friction coefficient and oil film thickness, and the lubricating oil viscosity-temperature equation, respectively. The total slip torque of the wet clutch is obtained by summing them up, and together with the clutch temperature field, it characterizes the slip state of the wet clutch under continuous operation.

2. The method for predicting the slippage state of a wet clutch based on the calculation of the solid-thermal behavior of the friction pair flow according to claim 1, characterized in that: The process of iteratively calculating the fluid-solid pressure distribution, oil film thickness, and rough contact area inside the wet clutch based on its structural and operating parameters, combined with a fluid-solid bearing model, is as follows: First, the three-dimensional momentum conservation equation of lubricating oil in grooved cavity, the flow conservation equation of lubricating oil in non-grooved friction gap, and the bearing model of micro-protrusion on rough surface are constructed respectively to characterize the mathematical relationship between different oil film thicknesses and fluid pressure in grooved cavity, fluid pressure in non-grooved area, bearing capacity of micro-protrusion and rough contact area under any sliding friction conditions. To address the interlocking deformation characteristics of the friction surface, a calculation model for the elastic deformation of grid points across the entire friction pair is established as follows: in, x m y n These are the coordinates of nodes (m0, n0) and (m, n), respectively. Based on the historical oil film thickness, the deformation of each local grid point is updated according to the fluid-solid pressure to form a reconstructed friction gap. The resulting oil film thickness calculation formula is as follows: h t+1 (m,n)=h t (m,n)+a×υ t (m,n) Where t is the iterative calculation step, h is the oil film thickness, υ is the deformation amount, and a is the deformation correction coefficient; Based on the reconstructed friction gap, the fluid-solid pressure distribution inside the friction pair is updated until the fluid-solid pressure distribution and the reconstructed friction gap deformation state reach stable convergence. The specific formula for the convergence of fluid-solid pressure and deformation is as follows: Where, ε p p is the fluid pressure convergence threshold. h This refers to the fluid pressure in the non-groove region. When the fluid-solid pressure and deformation state converge, the overall oil film thickness of the grid points in the entire domain is calculated iteratively based on the balance relationship between the internal and external pressures of the friction pair. The above correction steps for reconstructing the friction gap state convergence solution are repeated until the fluid-solid pressure and deformation state inside the friction pair converge again, and the internal load and external force satisfy the balance state. The specific formula for the balance of internal and external loads is as follows: Among them, F app Let A be the external pressure, ε be the convergence threshold between internal and external pressures, and A be the external pressure. h p is the area of ​​the oil film bearing capacity. a For non-groove friction gap solid pressure, A a This represents the actual rough contact area. After the oil film thickness correction is completed, the current oil film thickness is output, and the actual rough contact area A inside the wet clutch is calculated. a for:

3. The method for predicting the slippage state of a wet clutch based on the calculation of the thermal behavior of the friction pair flow, as described in claim 1, is characterized in that... Based on the fluid motion characteristics and solid deformation characteristics inside the wet clutch, combined with the principles of heat transfer and friction characteristics, this paper analyzes the equivalent thermal energy flow characteristics of fluid-solid convection heat transfer and solid-solid friction heat generation at the wet clutch sliding interface. Combining the physical properties of the wet clutch, a heat balance equation without heat source input is established. The process of extracting the circumferential temperature mean of the heat source-free temperature field, designing the continuity equation for the sliding interface contact temperature, and calculating the dynamic heat flow distribution ratio is as follows: The heat dissipation on the circumferential surface of the steel sheet alternates in a cycle. Its energy flow is characterized by the equivalent convective heat transfer intensity and the equivalent slip friction heat generation intensity. The total equivalent convective heat transfer intensity Q at each grid location is... sm With equivalent sliding friction heat generation intensity Q ss for: Q sm (m,n)=Q sm1 (m,n)+Q sm2 (m,n) Q ss (m,n)=Q ss1 (m,n)+Q ss2 (m,n) The surface of the non-grooved region of the friction plate is always in a state of sliding friction heat generation, while the side boundary of the grooved region is always in a state of fluid-solid convective heat transfer. The effective convective heat transfer intensity and effective sliding friction heat generation intensity at each grid location are Q, respectively. fm and Q fs ; A set of thermal balance equations for a wet clutch without heat source input is established using the principle of thermal balance: Where t is the iteration time step, T oil T represents the oil temperature along the radial direction of the friction pair. s For the temperature field of the steel sheet; K s For the thermal conductivity of the steel sheet, For the Laplace operator, ρ s V is the density of the steel sheet. s Let c be the volume of a infinitesimal element of the steel sheet. s T represents the specific heat capacity of the steel sheet. f Temperature field of the friction plate; K f ρ is the thermal conductivity of the friction plate. f V is the density of the friction plate. f Let c be the volume of the friction element. f The specific heat capacity of the friction plate; By combining the temperature rise caused by the heat sourceless temperature of the wet clutch with the temperature rise due to sliding friction heat flow, and aiming to make the average temperature of the friction plate and the steel plate equal for one groove cycle at the same radius, the following formula is established for calculating the dynamic distribution value of the total sliding friction heat flow with the history of the temperature field under continuous contact temperature constraint: in, Let ρ be the average temperature of the friction plate at the node in the m-th radial row without a heat source. f V is the density of the friction plate. f Let c be the volume of the friction element. f For the specific heat capacity of the friction plate, Let X be the average temperature of the friction plate surface at the node in the m-th radial row without a heat source. s (m) is the sliding friction heat flow distribution coefficient of the steel sheet; Following the principle of conservation of thermal energy flow at grid nodes, the actual input value of the friction heat generation intensity of the steel sheet is substituted into the heat balance equation set without heat source input to calculate the temperature change of general nodes of the steel sheet. For the boundary nodes of the steel sheet, only the corresponding heat conduction terms need to be deleted. Similarly, the temperature of each grid node of the friction plate is calculated for the heat balance equation set without heat source input.

4. The method for predicting the slippage state of a wet clutch based on the calculation of the thermal behavior of the friction pair flow, as described in claim 1, is characterized in that... The expression for the rough friction coefficient-temperature fitting equation is as follows: f=a3×T 3 +a2×T 2 +a1×T 1 +a0 Where: f is the rough friction coefficient; a3, a2, a1, and a0 are the coefficients of the fitting equation; and T is the temperature at a certain location on the sliding interface.

5. The method for predicting the slippage state of a wet clutch based on the calculation of the thermal behavior of the friction pair flow, as described in claim 1, is characterized in that... The overall rough torque calculation model is as follows: M=F z ×(r e 2 -r i 2 ) / (r o 2 -r i 2 )×r a ×f a +F z ×(r o 2 -r e 2 ) / (r o 2 -r i 2 )×r b ×f b Where: r a The effective friction radius of the inner circle, r b f is the effective friction radius of the outer circle. a f is the average roughness friction coefficient of the inner circle. b r is the average roughness friction coefficient of the outer circle. i r is the inner diameter of the clutch slippage. e For the clutch slippage diameter, r o F is the outer diameter of the clutch slippage. z This is the total normal force of the clutch.

6. The method for predicting the slippage state of a wet clutch based on the calculation of the thermal behavior of the friction pair flow, as described in claim 1, is characterized in that... The viscous torque is obtained using the rough contact area, the updated rough friction coefficient and oil film thickness, and the lubricating oil viscosity-temperature equation. Equations and rough torque The equations are as follows: in, For the sliding speed term, This is a comprehensive correction term for the shear stress factor. T represents the average temperature of the lubricating oil at the m-th radial dimension of the clutch. s (m) represents the average temperature of the sliding surface at the mth radial row of the clutch.

7. A vehicle, characterized in that, The wet clutch of the vehicle employs a wet clutch slippage state prediction method based on the calculation of the fluid-solid-thermal behavior of the friction pair, as described in any one of claims 1 to 6.

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