A method and system for analyzing thermal elastic instability characteristics of a heavy-duty vehicle automatic transmission friction pair

Abstract

The present invention discloses an analysis method and system for the thermoelastic instability characteristics of friction pairs of heavy vehicle automatic transmissions, which are applied to the technical field of automatic transmissions. The method includes the following steps: Based on the theory of thermoelasticity, considering the thickness of the center plate and friction material constituting the friction plate as well as the thickness of the mating steel plate, a structural thermoelastic coupling model is established; the boundary conditions of heat flux density, temperature field and stress field during the sliding friction process of the friction pair are set; based on the symmetric and anti-symmetric thermoelastic deformation modes, system matrices under four modes are constructed; the critical speeds corresponding to each mode are solved, and the main mode of the system is determined by comparison; the influence of the structural parameters and material properties of the friction pair on thermoelastic stability is analyzed. The present invention comprehensively considers the thickness of multi-layer material friction plates and various thermoelastic deformation modes, and for the friction pairs of heavy vehicle automatic transmissions, a thermoelastic instability system matrix under four deformation modes is established to determine the main mode and critical conditions of the system.

Description

Technical Field

[0001] This invention relates to the field of automatic transmission technology, and more specifically to a method and system for analyzing the thermoelastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions. Background Technology

[0002] Automatic transmissions (ATs) are widely used in heavy vehicles such as large buses, heavy trucks, and high-traffic military off-road vehicles. Heavy-duty vehicle ATs operate under heavy loads, placing extremely stringent requirements on the friction pairs in terms of stability, pressure resistance, speed response, torque supply, and thermal load resistance. An AT contains multiple sets of plate-type friction pairs. Each set consists of alternating low-thermal-conductivity friction plates and high-thermal-conductivity mating steel plates. The torque transmission and speed change function is achieved through the engagement and disengagement of different friction pairs.

[0003] High power and prolonged relative sliding friction result in significant frictional heat loss during operation. Transient heat accumulation under high energy density input leads to problems such as spalling and ablation of the friction material, irreversible hot spots, and buckling deformation of the mating steel plates. The service life of most heavy-duty vehicle transmissions is limited by friction pair failure. The primary cause of thermal failure in heavy-duty vehicle automatic transmission friction pairs is thermoelastic instability (TEI). Thermal instability and non-uniform contact at the friction pair working interface cause frictional heat to concentrate only in a portion of the interface, resulting in a thermoelastic instability state. This leads to high local temperatures, high stress, and severe wear, easily forming localized hot spots. Therefore, providing an analytical method and system for the thermoelastic instability characteristics of heavy-duty vehicle automatic transmission friction pairs is a problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides an analysis method and system for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions. By constructing an accurate thermo-elastic coupling model, the main modes and critical conditions of the system are identified, providing theoretical support for the design and stability control of friction pairs.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An analytical method for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions includes the following steps: S1. Based on the thermoelasticity theory, considering the thickness of the central plate and friction material that make up the friction plate as well as the thickness of the paired steel plate, a structural thermoelastic coupling model is established. S2. Set the heat flux density, temperature field and stress field boundary conditions during the friction pair's sliding process; S3. Based on symmetric and antisymmetric thermoelastic deformation modes, construct the system matrix under four modes; S4. Solve for the critical velocities corresponding to each mode, and determine the dominant mode of the system by comparison; S5. Analyze the influence of friction pair structural parameters and material properties on thermoelastic stability.

[0006] Optionally, the boundary conditions in S2 include: At the fixed interface between the friction material and the center plate, the temperature and heat flux density are equal at any position and time; at the sliding interface between the friction material and the mating steel plate, the temperature disturbance is equal at any time and position, and the heat flux density disturbance at the sliding interface is equal to the difference in heat flux density between the friction material and the mating steel plate; at the fixed interface between the friction material and the center plate, the thermoelastic stress and deformation of the friction material and the center plate are consistent at any position and time; during the sliding process, the contact surfaces of the friction pair do not separate during the sliding process.

[0007] Optionally, the four modes in S3 are as follows: Symmetric-antisymmetric mode: the dual plates are symmetric, and the central plate is antisymmetric; Antisymmetric-antisymmetric mode: dual steel sheet antisymmetric, central sheet antisymmetric; Symmetric-symmetric modes: dual steel plates are symmetrical, and the central plate is symmetrical; Antisymmetric-symmetric mode: Dual steel plates are antisymmetric, while the central plate is symmetric; The symmetric mode is characterized by a symmetrical distribution of disturbances along the centerline of a plane with finite thickness, while the antisymmetric mode is characterized by an antisymmetric distribution of disturbances along the centerline of a plane with finite thickness.

[0008] Optionally, the boundary conditions in S2 also include: The heat flux density perturbation at the center line of the central plate and the dual steel plate is zero in the symmetric mode, and along the center line... z thermoelastic deformation along the direction and along x The shear stress in all directions is zero; the temperature field perturbation at the centerline of the central plate and the dual steel plate is zero in the antisymmetric mode, and the temperature field perturbation along the centerline is zero. x thermoelastic deformation along the direction and along z The normal stress in all directions is zero.

[0009] Optionally, in S3, the system matrix is ​​constructed by combining the thermoelastic deformation modes of the friction pair and using the perturbation method. It is assumed that there is a cosine pressure perturbation that grows exponentially with time between the contact interface of the friction plate and the dual steel plate. The cosine form expression of the physical field perturbation of the friction pair is solved to obtain the thermoelastic unstable system matrix.

[0010] Optionally, the mode with the minimum critical velocity in S4 will first excite the system into a thermoelastic instability state, and the perturbation mode with the minimum critical velocity is defined as the dominant mode.

[0011] Optionally, S5 can verify the rationality of the thermoelastic instability characteristic model of the friction pair by building an experimental rig to compare and analyze the influence of the structural and material properties of the friction pair on the thermoelastic stability of the system.

[0012] An analysis system for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, employing the aforementioned analysis method for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, includes: The model building module is used to build a structural thermo-elastic coupling model; The condition setting module, connected to the model building module, is used to set the heat flux density, temperature field, and stress field boundary conditions during the friction pair's sliding process. The matrix construction module, connected to the condition setting module, is used to construct the system matrix under four modes; The velocity calculation module, connected to the matrix construction module, is used to solve for the critical velocities corresponding to each mode and determine the main mode of the system. The analysis and evaluation module, connected to the velocity solution module, is used to analyze the influence of friction pair structural parameters and material properties on thermoelastic stability.

[0013] As can be seen from the above technical solution, compared with the prior art, the present invention provides an analysis method and system for the thermoelastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, which has the following beneficial effects: The present invention comprehensively considers the thickness of the multi-layer material friction plate and multiple thermoelastic deformation modes, and proposes an improved method for the thermoelastic instability analytical model. For the friction pairs of heavy-duty vehicle automatic transmissions, considering the thickness of the center plate and the friction material, a thermoelastic instability model of the friction pair with the mutual coupling of physical quantities such as circumferential non-uniform temperature field, heat flux density, and thermoelastic stress is established. The thermoelastic instability system matrix under four deformation modes is obtained, and the main mode and critical conditions of the system are determined. This can more accurately predict the thermoelastic instability behavior of the friction pair under actual working conditions, and provide a theoretical basis for the design and optimization of heavy-duty vehicle automatic transmissions. Attached Figure Description

[0014] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0015] Figure 1 This is a flowchart of the analysis method for the thermoelastic instability characteristics of the friction pair of a heavy-duty vehicle automatic transmission according to the present invention. Figure 2This is a schematic diagram of the theoretical model of the thermoelastic instability characteristics of the heavy-duty vehicle automatic transmission of the present invention; Figure 3 This is a schematic diagram of the thermoelastic deformation symmetric mode of the present invention; Figure 4 This is a schematic diagram of the antisymmetric thermoelastic deformation mode of the present invention; Figure 5 The diagram shows the critical velocity curves for each mode of this invention. Detailed Implementation

[0016] 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. 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.

[0017] This invention discloses an analytical method for the thermoelastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, such as... Figure 1 As shown, it includes the following steps: S1. Based on the thermoelasticity theory, considering the thickness of the central plate and friction material that make up the friction plate as well as the thickness of the paired steel plate, a structural thermoelastic coupling model is established. S2. Set the heat flux density, temperature field and stress field boundary conditions during the friction pair's sliding process; S3. Based on symmetric and antisymmetric thermoelastic deformation modes, construct the system matrix under four modes; S4. Solve for the critical velocities corresponding to each mode, and determine the dominant mode of the system by comparison; S5. Analyze the influence of friction pair structural parameters and material properties on thermoelastic stability.

[0018] Structural thermo-elastic coupling model such as Figure 2 As shown in Table 1, the model variables in this embodiment are as follows: Table 1 Variables of the structural thermo-elastic coupling model

[0019] Furthermore, the boundary conditions in S2 include: At the fixed interface between the friction material and the center plate, the temperature and heat flux density are equal at any position and time; at the sliding interface between the friction material and the mating steel plate, the temperature disturbance is equal at any time and position, and the heat flux density disturbance at the sliding interface is equal to the difference in heat flux density between the friction material and the mating steel plate; at the fixed interface between the friction material and the center plate, the thermoelastic stress and deformation of the friction material and the center plate are consistent at any position and time; during the sliding process, the contact surfaces of the friction pair do not separate during the sliding process.

[0020] In an embodiment of the present invention, see Figure 2 Friction material and center plate in Fixed, temperature for any x , t Since all are equal, we can obtain boundary condition 1: ; In the formula, As the central film The temperature at that location For friction materials in The temperature at that location The thickness of the friction material; Heat flux density for any x , t Since they are all equal, we can obtain boundary condition 2: ; In the formula, As the central film Heat flux density at that point For friction materials in Heat flux density at that location; Friction material and mating steel sheet in Temperature field perturbation at any point x , t Since they are all equal, we can obtain boundary condition 3: ; In the formula, For the mating steel sheet in The temperature at that location It is half the thickness of the paired steel sheet (half the thickness refers to half the thickness). Friction material The temperature at the location; The energy balance relationship between the friction material and the paired steel sheet in the friction pair can be regarded as boundary condition 4: ; In the formula, For friction materials in Heat flux density at that point For the mating steel sheet in Heat flux density at that point This is a disturbance of the heat flux density on the sliding surface; Friction material and center plate in Fixed, thermoelastic stress and deformation for any x , t Since all are equal, we can obtain boundary condition 5: , ; , ; In the formula, For friction materials in place x Orientation deformation, As the central film place x Orientation deformation, For friction materials in place z Orientation deformation, As the central film place z Orientation deformation, For friction materials in place z Directional normal stress, As the central film place z Directional normal stress, For friction materials in place z Directional shear stress, As the central film place z Directional shear stress.

[0021] Based on the assumption that the contact surfaces of the friction pair do not separate during the sliding friction process, we can obtain boundary condition 6: ; ; ; In the formula, For friction materials in place z Orientation deformation, As the central film place z Orientation deformation, For friction materials in place z Directional normal stress, As the central film place z Directional normal stress, For friction materials in place z Directional shear stress, As the central film place z Directional shear stress, For disturbance pressure, f is the coefficient of friction.

[0022] Furthermore, the four modes in S3 are specifically as follows: Symmetric-antisymmetric mode: the dual plates are symmetric, and the central plate is antisymmetric; Antisymmetric-antisymmetric mode: dual steel sheet antisymmetric, central sheet antisymmetric; Symmetric-symmetric modes: dual steel plates are symmetrical, and the central plate is symmetrical; Antisymmetric-symmetric mode: Dual steel plates are antisymmetric, while the central plate is symmetric; like Figure 3 As shown, the symmetric mode is characterized by a symmetrical distribution of disturbances along the centerline of a plane with finite thickness, such as... Figure 4 As shown, the antisymmetric mode is characterized by an antisymmetric distribution of disturbances along the centerline of a plane with finite thickness.

[0023] Furthermore, the boundary conditions in S2 also include: The heat flux density perturbation at the center line of the central plate and the dual steel plate is zero in the symmetric mode, and along the center line... z thermoelastic deformation along the direction and along x The shear stress in all directions is zero; the temperature field perturbation at the centerline of the central plate and the dual steel plate is zero in the antisymmetric mode, and the temperature field perturbation along the centerline is zero. x thermoelastic deformation along the direction and along z The normal stress in all directions is zero.

[0024] In specific embodiments of the present invention: When the perturbation of the dual steel sheet is antisymmetric, the temperature field perturbation at the centerline of the dual steel sheet is zero, and the boundary condition 7 can be obtained: ; In the formula, For the mating steel sheet in Temperature at that location; When the disturbance of the paired steel plates is symmetrically distributed, the heat flux density disturbance at the centerline of the central plate is zero, and boundary condition 7 becomes: ; In the formula, For the mating steel sheet in Heat flux density at that location; When the perturbation in the central plate is antisymmetric, the temperature field perturbation at the centerline of the central plate is zero, and the boundary condition 8 can be obtained: ; In the formula, As the central film Temperature at that location; When the disturbance in the central plate is symmetrically distributed, the heat flux density disturbance at the centerline of the central plate is zero, and boundary condition 8 becomes: ; In the formula, As the central film The heat flux density at that location.

[0025] Furthermore, in S3, the system matrix is ​​constructed by combining the thermoelastic deformation modes of the friction pair and using the perturbation method. It is assumed that there is a cosine pressure perturbation that grows exponentially with time between the contact interface of the friction plate and the dual steel plate. The cosine form expression of the physical field perturbation of the friction pair is solved to obtain the thermoelastic unstable system matrix.

[0026] Furthermore, the mode with the lowest critical velocity in S4 will first excite the system into a thermoelastic instability state, and the perturbation mode with the lowest critical velocity is defined as the dominant mode.

[0027] In this embodiment of the invention, the system matrix for the four modes is specifically as follows: (1) Symmetric-antisymmetric mode: ; ; ; In the formula, Represents the system matrix. Represents a vector of unknowns. , , , , , , , These are all process parameters to be determined in solving the thermoelastic equilibrium differential equation. This represents the initial pressure disturbance amplitude. Let be the initial temperature disturbance amplitude, where ; ; ; ; ; ; ; ; ; ; In the formula, , For custom parameters, ; ; (2) Antisymmetric-antisymmetric mode: ; ; ; In the formula, Represents the system matrix. Let the vector of unknowns be denoted as , where ; ; ; ; In the formula, , For custom parameters, ; ; (3) Symmetric-symmetric modes: ; ; ; In the formula, Represents the system matrix. Let the vector of unknowns be denoted as , where ; ; ; ; (4) Antisymmetric-symmetric modes: ; ; ; In the formula, Represents the system matrix. Let the vector of unknowns be denoted as , where ; ; ; ; m For the perturbation frequency, Shear modulus of friction material For the shear modulus of the dual steel sheet, For the shear modulus of the central piece, i To represent a complex unit, , For custom parameters, , j =1,2,3 b This represents the disturbance growth coefficient. Material j thermal diffusivity, Indicates the disturbance relative to the material j The speed of movement, , , To customize material parameters, , j =1,2,3 Material j shear modulus, Material j The coefficient of thermal expansion, Material j Poisson's ratio, The thermal conductivity of the friction material, For the thermal conductivity of the paired steel sheets, The thermal conductivity of the center plate, Poisson's ratio is the friction material. For the Poisson's ratio of the dual steel sheet, Poisson's ratio is the central slice.

[0028] Under the parameter variables shown in Table 1, such as Figure 5 As shown in the figure, the mode corresponding to the curve closest to the x-axis (i.e. the mode with the minimum critical velocity) is the principal mode. For the specific case of the friction pair listed in Table 1, when the number of hot spots N < 80, the principal mode is a symmetric-symmetric mode; when the number of hot spots N ≥ 80, the principal mode is a symmetric-antisymmetric mode.

[0029] Furthermore, S5 constructed an experimental rig to assess the thermo-elastic instability of friction pairs, and compared and analyzed the influence of friction pair structural and material properties on the thermo-elastic stability of the system, thereby verifying the rationality of the thermo-elastic instability model of friction pairs in heavy-duty vehicle automatic transmissions.

[0030] and Figure 1 Corresponding to the method described above, this embodiment of the invention also discloses an analysis system for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions. The system, applying the aforementioned analysis method for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, includes: The model building module is used to build a structural thermo-elastic coupling model; The condition setting module, connected to the model building module, is used to set the heat flux density, temperature field, and stress field boundary conditions during the friction pair's sliding process. The matrix construction module, connected to the condition setting module, is used to construct the system matrix under four modes; The velocity calculation module, connected to the matrix construction module, is used to solve for the critical velocities corresponding to each mode and determine the main mode of the system. The analysis and evaluation module, connected to the velocity solution module, is used to analyze the influence of friction pair structural parameters and material properties on thermoelastic stability.

[0031] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0032] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, characterized in that, Includes the following steps: S1. Based on the thermoelasticity theory, considering the thickness of the central plate and friction material that make up the friction plate as well as the thickness of the paired steel plate, a structural thermoelastic coupling model is established. S2. Set the heat flux density, temperature field and stress field boundary conditions during the friction pair's sliding process; S3. Based on symmetric and antisymmetric thermoelastic deformation modes, construct the system matrix under four modes; S4. Solve for the critical velocities corresponding to each mode, and determine the dominant mode of the system by comparison; S5. Analyze the influence of friction pair structural parameters and material properties on thermoelastic stability.

2. The method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions according to claim 1, characterized in that, The boundary conditions in S2 include: At the fixed interface between the friction material and the center plate, the temperature and heat flux density are equal at any position and time; at the sliding interface between the friction material and the mating steel plate, the temperature disturbance is equal at any time and position, and the heat flux density disturbance at the sliding interface is equal to the difference in heat flux density between the friction material and the mating steel plate; at the fixed interface between the friction material and the center plate, the thermoelastic stress and deformation of the friction material and the center plate are consistent at any position and time; during the sliding process, the contact surfaces of the friction pair do not separate during the sliding process.

3. The method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions according to claim 1, characterized in that, The four modes in S3 are as follows: Symmetric-antisymmetric mode: the dual plates are symmetric, and the central plate is antisymmetric; Antisymmetric-antisymmetric mode: dual steel sheet antisymmetric, central sheet antisymmetric; Symmetric-symmetric modes: dual steel plates are symmetrical, and the central plate is symmetrical; Antisymmetric-symmetric mode: Dual steel plates are antisymmetric, while the central plate is symmetric; The symmetric mode is characterized by a symmetrical distribution of disturbances along the centerline of a plane with finite thickness, while the antisymmetric mode is characterized by an antisymmetric distribution of disturbances along the centerline of a plane with finite thickness.

4. The method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions according to claim 3, characterized in that, The boundary conditions in S2 also include: The heat flux density perturbation at the center line of the central plate and the dual steel plate is zero in the symmetric mode, and along the center line... z thermoelastic deformation along the direction and along x The shear stress in all directions is zero; the temperature field perturbation at the centerline of the central plate and the dual steel plate is zero in the antisymmetric mode, and the temperature field perturbation along the centerline is zero. x thermoelastic deformation along the direction and along z The normal stress in all directions is zero.

5. The method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions according to claim 1, characterized in that, In S3, the system matrix is ​​constructed by combining the thermoelastic deformation modes of the friction pair and using the perturbation method. It is assumed that there is a cosine pressure perturbation that grows exponentially with time between the contact interface of the friction plate and the dual steel plate. The cosine form expression of the physical field perturbation of the friction pair is solved to obtain the thermoelastic unstable system matrix.

6. The method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions according to claim 1, characterized in that, The mode with the smallest critical velocity in S4 will first excite the system into a thermoelastic instability state. The perturbation mode with the smallest critical velocity is defined as the dominant mode.

7. The method for analyzing the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions according to claim 1, characterized in that, S5 constructs an experimental rig to test the thermo-elastic instability characteristics of friction pairs, compares and analyzes the influence of the structural and material properties of the friction pairs on the thermo-elastic stability of the system, and verifies the rationality of the thermo-elastic instability characteristic model of friction pairs in heavy-duty vehicle automatic transmissions.

8. An analysis system for the thermo-elastic instability characteristics of friction pairs in heavy-duty vehicle automatic transmissions, characterized in that, The analytical method for the thermo-elastic instability characteristics of friction pairs in a heavy-duty vehicle automatic transmission according to any one of claims 1-7 includes: The model building module is used to build a structural thermo-elastic coupling model; The condition setting module, connected to the model building module, is used to set the heat flux density, temperature field, and stress field boundary conditions during the friction pair's sliding process. The matrix construction module, connected to the condition setting module, is used to construct the system matrix under four modes; The velocity calculation module, connected to the matrix construction module, is used to solve for the critical velocities corresponding to each mode and determine the main mode of the system. The analysis and evaluation module, connected to the velocity solution module, is used to analyze the influence of friction pair structural parameters and material properties on thermoelastic stability.

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