Tire simulation method and simulation device

Abstract

To provide a simulation method capable of acquiring a calculation result approximate to a state after actual wear in a short period of time.SOLUTION: A method simulates a tire. The method includes steps for: inputting a tread model with a discretized tread part by using the finite number of elements having a plurality of tread nodes S1; calculating a physical amount related to wear about a plurality of tread nodes constituting a tread grounding surface of the tread model S4; specifying the movement amount of each tread node on the basis of the physical amount S5; and moving each tread node to deform the tread model on the basis of the movement amount S6. The step S6 for specifying the movement amount includes the steps for: calculating the degree of dispersion of the physical amount for each of multiple local regions divided by at least two tread nodes among the plurality of tread nodes; and determining the movement amount of each tread node on the basis of the degree of dispersion of each of the multiple local regions.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a tire simulation method and a simulation device. [Background technology]

[0002] Patent Document 1 below proposes a simulation method for calculating the state of a tire tread contact surface after wear using a computer. This method includes the steps of calculating physical quantities associated with wear for multiple tread nodes of a tire model, determining the amount of movement of each tread node based on the degree of dispersion of the physical quantities, and moving each tread node based on the amount of movement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-91302 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above method, the amount of movement of the tread nodes is determined based on the degree of dispersion of physical quantities covering the entire tread contact surface, thereby achieving calculation results that approximate the actual state after wear in a short time. However, for example, if the amount of movement of the nodes is set large in order to shorten the calculation time, the degree of unevenness of the tire shape may increase, and there is room for further improvement in obtaining calculation results that approximate the actual state after wear in a short time.

[0005] The present disclosure has been devised in consideration of the above-described circumstances, and its main purpose is to provide a simulation method that can obtain calculation results that approximate the actual state after wear in a short period of time. [Means for solving the problem]

[0006] The present disclosure provides a simulation method for calculating a wear state of a tread contact surface of a tire having a tread portion, the method comprising: inputting a tread model in which the tread portion is discretized using a finite number of elements having a plurality of nodes into a computer; the computer executing the following steps: calculating physical quantities associated with wear for a plurality of tread nodes constituting the tread contact surface of the tread model; specifying, based on the physical quantities, movement amounts for expressing wear of each of the tread nodes; and deforming the tread model by moving each of the tread nodes based on the movement amounts; the step of specifying the movement amounts comprising: calculating a degree of dispersion of the physical quantities for each of a plurality of local regions separated by at least two of the plurality of tread nodes; and determining the movement amounts of each of the tread nodes based on the degree of dispersion for each of the plurality of local regions. [Effects of the Invention]

[0007] By employing the above steps, the tire simulation method of the present disclosure makes it possible to obtain calculation results that approximate the actual state after wear in a short period of time. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a computer (simulation device) that executes a tire simulation method according to the present embodiment. [Figure 2] 1 is a cross-sectional view showing a tire whose wear state is calculated by the tire simulation method of the present embodiment. FIG. [Figure 3] 3 is a flowchart showing a processing procedure of a tire simulation method according to the present embodiment. [Figure 4] FIG. 2 is a perspective view showing a tire model and a road surface model. [Figure 5] FIG. 2 is a cross-sectional view showing a tire model including a tread model. [Figure 6]FIG. 6 is a partially enlarged view of the tread portion of FIG. 5. [Figure 7] 10 is a flowchart showing a processing procedure of a rolling step according to the present embodiment. [Figure 8] 1 is a graph showing the relationship between a physical quantity (wear energy) and the axial position of each tread node. [Figure 9] 1A is a diagram illustrating an example of the state before each tread node moves, and FIG. 1B is a diagram illustrating an example of the state after each tread node moves. [Figure 10] 10 is a flowchart showing a processing procedure of a movement amount specifying step of the present embodiment. [Figure 11] FIG. 10 is a partially enlarged view of a center land portion model divided into a plurality of local regions. [Figure 12] 9(a) is a graph showing the relationship between the physical quantities of the center land area model in FIG. 8 and the positions of each tread node, and FIG. 9(b) is a graph showing the relationship between the physical quantities of the shoulder land area model in FIG. 8 and the positions of the tread nodes. [Figure 13] 1 is a graph showing an example of the relationship between the wear progression rate and the degree of dispersion. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the disclosure. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are intended to facilitate understanding of the contents of the present disclosure, and the present disclosure is not limited to the specific configurations shown in the drawings.

[0010] In the tire simulation method of this embodiment (hereinafter sometimes simply referred to as the "simulation method"), the state of the tire tread contact surface after wear is calculated using a computer. Fig. 1 is a block diagram showing a computer 1 (simulation device 1A) that executes the tire simulation method of this embodiment.

[0011] [Simulation device] The computer 1 of this embodiment has an input unit 2 as an input device, an output unit 3 as an output device, and a processing unit 4 that calculates physical quantities of the tire, etc., and is configured as a tire simulation device (hereinafter sometimes simply referred to as a "simulation device") 1A.

[0012] [Input section, output section, arithmetic processing unit] The input unit 2 may be, for example, a keyboard or a mouse. The output unit 3 may be, for example, a display device or a printer. The arithmetic processing unit 4 includes a calculation unit (CPU) 4A that performs various calculations, a storage unit 4B that stores data, programs, etc., and a working memory 4C.

[0013] [Storage] The storage unit 4B is a non-volatile information storage device formed of, for example, a magnetic disk, an optical disk, an SSD, etc. The storage unit 4B includes a data unit 5 and a program unit 6.

[0014] [Data section] The data section 5 of this embodiment is for storing data etc. necessary for executing the simulation method. The data section 5 of this embodiment includes an initial data section 5A, a tread model input section 5B, a road surface model input section 5C, a boundary condition input section 5D, a physical quantity input section 5E, and a condition input section 5F.

[0015] The initial data section 5A stores information about the tire and road surface to be evaluated (e.g., CAD data, etc.). The condition input section 5F stores the simulation termination conditions, etc., which will be described later. Other data stored in the data section 5 will be explained in the simulation method, which will be described later. Furthermore, the data section 5 is not limited to this embodiment, and may include other input sections, or some of these may be omitted, as necessary.

[0016] The program unit 6 is a program (application) required to execute the simulation method. The program unit 6 is executed by the calculation unit 4A. The program unit 6 of this embodiment includes a tread model acquisition unit 6A that acquires a tread model, a road surface model acquisition unit 6B that acquires a road surface model, and a rolling calculation unit 6C that brings the tread model into contact with the road surface model and causes it to roll. The program unit 6 further includes a physical quantity calculation unit 6D that calculates a physical quantity associated with wear, a movement amount identification unit 6E that identifies the movement amount of each tread node, a movement unit 6F that deforms the tread model, and a determination unit 6G that determines the termination conditions of the simulation, etc.

[0017] The movement amount specifying unit 6E of this embodiment includes a dispersion degree calculation unit 7A that calculates the dispersion degree of a physical quantity and a movement amount determination unit 7B that determines the movement amounts of a plurality of tread nodes. The functions of each program unit 6 will be explained in each step of the simulation method described later. The program unit 6 is not limited to this embodiment, and may include other input units as needed, or some of these may be omitted.

[0018] [tire] 2 is a cross-sectional view showing a tire 11 whose wear state is calculated by the tire simulation method (simulation device 1A (shown in FIG. 1)) of this embodiment. The tire 11 of this embodiment is provided with a carcass 16 extending from a tread portion 12 through a sidewall portion 13 to a bead core 15 of a bead portion 14, and a belt layer 17 disposed radially outward of the carcass 16 and inside the tread portion 12.

[0019] [Tread] The tread portion 12 of this embodiment is provided with at least one circumferential groove 18 and a plurality of land portions 19 separated by the circumferential groove 18. However, the tread portion 12 is not limited to this embodiment, and the circumferential groove 18 may be omitted.

[0020] [Circumferential groove] The circumferential grooves 18 of this embodiment extend continuously in the tire circumferential direction. The circumferential grooves 18 of this embodiment include a pair of center circumferential grooves 18A, 18A arranged on both axially outer sides of the tire equator C, and a pair of shoulder circumferential grooves 18B, 18B arranged between the center circumferential groove 18A and the tread ground-contact edge 12t. Note that the circumferential grooves 18 are not limited to this configuration, and, for example, other circumferential grooves (not shown) may be further added or some of these may be omitted depending on the performance required of the tire 11, etc.

[0021] In this specification, the "tread contact edge 12t" refers to the axially outermost end of the tread contact surface 20 when the tire 11, mounted on a standard rim and inflated to the standard internal pressure, is placed in contact with a flat surface with a standard load and a camber angle of 0 degrees.

[0022] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which the tire 11 is based. Therefore, a genuine rim is, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0023] The "normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire 11 is based. Therefore, the normal internal pressure is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. However, if the tire is for a passenger car, the normal internal pressure is 180 kPa.

[0024] The "normal load" is the load specified by the standard for each tire 11. Therefore, the normal load is the maximum load capacity in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO.

[0025] [Rikube] The multiple land portions 19 in this embodiment include a center land portion 19A, a pair of middle land portions 19B, 19B, and a pair of shoulder land portions 19C, 19C. The center land portion 19A is divided between the pair of center circumferential grooves 18A, 18A. The pair of middle land portions 19B, 19B are divided by the center circumferential groove 18A and the shoulder circumferential groove 18B. The pair of shoulder land portions 19C, 19C are divided by the shoulder circumferential groove 18B and the tread ground-contact edge 12t.

[0026] In this embodiment, the center land portion 19A, the pair of middle land portions 19B, 19B, and the pair of shoulder land portions 19C, 19C are provided with blocks 22 separated by, for example, lateral grooves 21, but are not limited to this. These land portions 19A to 19C may also be formed as ribs that are continuous in the tire circumferential direction without being separated by, for example, lateral grooves 21.

[0027] [Carcass] The carcass 16 is made up of at least one carcass ply 16A, one carcass ply in this embodiment. The carcass ply 16A in this embodiment has carcass cords (not shown) arranged at an angle of, for example, 75 to 90 degrees with respect to the tire equator C.

[0028] [Belt layer] The belt layer 17 of this embodiment is configured to include two inner and outer belt plies 17A and 17B in which belt cords (not shown) are arranged at an angle of, for example, 10 to 35 degrees with respect to the tire circumferential direction. These belt plies 17A and 17B are overlapped with the belt cords in a direction that crosses each other.

[0029] [Tire Simulation Method (First Embodiment)] [Enter tread model] 3 is a flowchart showing the processing steps of the tire simulation method of this embodiment. In the simulation method of this embodiment, first, a tread model is input to the computer 1 (step S1).

[0030] In step S1 of this embodiment, first, as shown in Fig. 1, information about the tread portion 12 (for example, contour data of the tire 11 (shown in Fig. 2)) stored in the initial data section 5A and the tread model acquisition section 6A are read into the working memory 4C. Then, the tread model acquisition section 6A is executed by the calculation section 4A, causing the computer 1 to function as a means for inputting the tread model 26.

[0031] Fig. 4 is a perspective view showing a tire model 24 including a tread model 26, and a road surface model 25. Fig. 5 is a cross-sectional view showing the tire model 24 including the tread model 26. Fig. 6 is a partially enlarged view of the tread portion of Fig. 5. Note that Fig. 4 omits the mesh (elements F(i)) of the tire model 24 and the circumferential groove model 28 shown in Fig. 5.

[0032] In step S1 of this embodiment, similarly to Patent Document 1, the tread portion 12 (in this example, the tire 11) is discretized into a finite number of elements F(i) (i = 1, 2, ...) based on information about the tire 11 including the tread portion 12 shown in FIG. 2. In this embodiment, each tire component, such as the rubber member including the tread rubber 12g, the carcass ply 16A, and each belt ply 17A, 17B shown in FIG. 2, is discretized into a finite number of elements F(i). In this way, a tire model 24 including a tread model 26 is set. In step S1, for example, after the tire model 24 including the two-dimensional tread model 26 is set, the two-dimensional models may be copied in the tire circumferential direction at a predetermined angle pitch and expanded into three dimensions.

[0033] Each element F(i) can be handled by a numerical analysis method. As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method can be appropriately adopted. The finite element method is adopted as the numerical analysis method in this embodiment. Furthermore, it is desirable to use, for example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element as each element F(i).

[0034] 5 and 6, each element F(i) has a plurality of nodes 31. Furthermore, each element F(i) has linear edges 32 connecting the nodes 31, 31. Numerical data such as the element number, the node 31 number, the coordinate values ​​of the node 31, and material properties (e.g., density, Young's modulus and / or damping coefficient) are defined for each element F(i).

[0035] The tire model 24 of this embodiment includes a ring-shaped tread model 26 that is continuous in the tire circumferential direction, and a toroidal body model 27 that forms the inner part of the tread model 26 in the tire radial direction.

[0036] The tread model 26 of the present embodiment is provided with a circumferential groove model 28 that reproduces, for example, the circumferential groove 18 (shown in FIG. 2). The circumferential groove model 28 of the present embodiment includes a pair of center circumferential groove models 28A, 28A that reproduce the pair of center circumferential grooves 18A, 18A, and a pair of shoulder circumferential groove models 28B, 28B that reproduce the pair of shoulder circumferential grooves 18B, 18B.

[0037] The tread model 26 of this embodiment is divided into a plurality of land portion models 29 that reproduce a plurality of land portions 19 (shown in FIG. 2), for example. The plurality of land portion models 29 of this embodiment include a center land portion model 29A, a pair of middle land portion models 29B, 29B, and a pair of shoulder land portion models 29C, 29C. The center land portion model 29A is a reproduction of the center land portion 19A (shown in FIG. 2). The pair of middle land portion models 29B, 29B are a reproduction of the pair of middle land portions 19B, 19B (shown in FIG. 2). The pair of shoulder land portion models 29C, 29C are a reproduction of the pair of shoulder land portions 19C, 19C (shown in FIG. 2).

[0038] In this embodiment, the center land portion model 29A, the middle land portion model 29B, and the shoulder land portion model 29C may be set with block models 41 separated by, for example, lateral groove models (not shown). Note that these land portion models 29 may be set as ribs that are continuous in the tire circumferential direction without being separated by lateral groove models.

[0039] The body model 27 of this embodiment is configured to include a pair of sidewall portions 42, 42 and a pair of bead portions 43, 43. Furthermore, it is desirable that the interior of the body model 27 of this embodiment includes elements that resemble fiber reinforcing materials such as the carcass 16 and belt plies 17A, 17B shown in Fig. 2. This makes the deformation behavior of the tread model 26 (tire model 24) even closer to the real thing, enabling accurate simulations.

[0040] In step S1 of this embodiment, the tire model 24 including the tread model 26 is input to the computer 1 (tread model input unit 5B) shown in FIG. 1, but for example, the body model 27 may be omitted and only the tread model 26 may be input.

[0041] [Enter road surface model] Next, in the simulation method of this embodiment, as shown in FIG. 4, a road surface model 25 that models a road surface (not shown) is input to the computer 1 (step S2). In step S2 of this embodiment, first, information about the road surface (not shown) stored in the initial data unit 5A shown in FIG. 1 is input to the working memory 4C. Furthermore, the road surface model acquisition unit 6B is read into the working memory 4C. Then, the road surface model acquisition unit 6B is executed by the calculation unit 4A, causing the computer 1 to function as a means for inputting the road surface model 25.

[0042] 4, in step S2, based on information about the road surface (not shown), the road surface is discretized into a finite number of elements G(i) (i=1, 2, ...) that can be handled by a numerical analysis method (in this embodiment, the finite element method). As a result, in step S2, a road surface model 25 is set.

[0043] Element G(i) is made up of a rigid plane element that is set to be undeformable. This element G(i) has a plurality of nodes 38. Furthermore, element G(i) is defined with numerical data such as an element number and the coordinate values ​​of the nodes 38.

[0044] In this embodiment, the road surface model 25 has been exemplified as having a smooth surface, but if necessary, it may be provided with minute irregularities like those on an asphalt road surface, irregular steps, depressions, undulations, or irregularities similar to those on an actual road surface, such as ruts. The road surface model 25 is stored in the computer 1 (road surface model input unit 5C) shown in FIG.

[0045] [Rolling process] Next, in the simulation method of this embodiment, as shown in FIG. 4, the computer 1 (shown in FIG. 1) brings the tread model 26 into contact with the road surface model 25 and causes it to roll (rolling step S3). In the rolling step S3 of this embodiment, first, as shown in FIG. 1, the tread model 26 (in this example, the tire model 24) stored in the tread model input unit 5B and the road surface model 25 stored in the road surface model input unit 5C are read into the work memory 4C. Furthermore, in the rolling step S3, the rolling motion calculation unit 6C of the program unit 6 is read into the work memory 4C. Then, the rolling motion calculation unit 6C is executed by the calculation unit 4A, causing the computer 1 to function as a means for bringing the tread model 26 (in this example, the tire model 24) into contact with the road surface model 25 and causing it to roll. FIG. 7 is a flowchart showing the processing procedure of the rolling step S3 of this embodiment.

[0046] In the rolling step S3 of this embodiment, first, boundary conditions for rolling the tread model 26 shown in FIG. 4 on the road surface model 25 are defined (step S31). The boundary conditions include, for example, the internal pressure condition of the tire model 24, the applied load condition L, the camber angle, and the friction coefficient between the tread model 26 and the road surface model 25. Furthermore, the boundary conditions include an angular velocity V1 and a translational velocity V2 corresponding to the traveling speed, and a turning angle (not shown). The translational velocity V2 is the velocity at the surface where the tread model 26 contacts the road surface model 25. These boundary conditions are stored in the computer 1 (boundary condition input unit 5D) shown in FIG. 1.

[0047] Next, in the rolling step S3 of this embodiment, the tread model 26 (tire model 24) after internal pressure filling is calculated (step S32). The tread model 26 after internal pressure filling is calculated based on the internal pressure conditions stored in the boundary condition input unit 5D (shown in FIG. 1).

[0048] In step S32, first, as shown in FIG. 5, the bead portions 43, 43 of the tire model 24 are constrained by a rim model 46 that is a model of the rim 30 (shown in FIG. 2). Furthermore, in step S32, the deformation of the tread model 26 (tire model 24) is calculated based on a uniformly distributed load w that corresponds to the internal pressure condition. As a result, the tread model 26 (tire model 24) after internal pressure inflation is calculated. It is desirable to set the internal pressure to an air pressure stipulated by each standard in a standard system that includes the standard on which the tire to be evaluated (not shown) is based.

[0049] In the deformation calculation of the tread model 26 (tire model 24), a mass matrix, a stiffness matrix, and a damping matrix are created for each element F(i) based on the shape and material properties of each element F(i). These matrices are then combined to create a matrix for the entire system. A computer 1 (shown in FIG. 1) then applies the various conditions described above to create equations of motion, which are used to calculate the deformation of the tread model 26 (tire model 24) for each unit time T(x) (x = 0, 1, ...) of the simulation. Such deformation calculations (including rolling calculations, etc., described below) can be performed using commercially available finite element analysis application software, such as LS-DYNA by LSTC. The unit time T(x) can be set appropriately depending on the required simulation accuracy.

[0050] Next, in the rolling step S3 of this embodiment, the tread model 26 (tire model 24) after the load is applied is calculated (step S33). In step S33 of this embodiment, the tread model 26 (tire model 24) after the load is applied is calculated based on the applied load condition L, the camber angle, and the friction coefficient stored in the boundary condition input unit 5D (shown in FIG. 1).

[0051] In step S33, as shown in Fig. 4, the contact between the tread model 26 (tire model 24) after internal pressure inflation and the road surface model 25 is calculated. Next, in step S33, the deformation of the tread model 26 (tire model 24) is calculated based on the applied load condition L, the camber angle (not shown), and the friction coefficient. The applied load condition L is set to the rotation axis 45 of the tread model 26 (tire model 24). As a result, in step S33, the tread model 26 (tire model 24) after the load is applied and in contact with the road surface model 25 is calculated.

[0052] Next, in a rolling step S3 of this embodiment, the tread model 26 (tire model 24) is calculated (step S34) while rolling on the road surface model 25. In step S34 of this embodiment, the rolling tread model 26 (tire model 24) is calculated based on the angular velocity V1, translational velocity V2, and turning angle (not shown) stored in the boundary condition input unit 5D (shown in FIG. 1).

[0053] In step S34, first, as shown in Fig. 4, an angular velocity V1 is set to the rotation axis 45 of the tread model 26 (tire model 24). Furthermore, in step S34, a translational velocity V2 is set to the road surface model 25. This makes it possible to calculate the tread model 26 (tire model 24) rolling on the road surface model 25.

[0054] The rolling conditions of the tread model 26 (tire model 24) can be set as appropriate, such as free rolling, driving, braking, and turning, depending on the running state of the tire (shown in FIG. 2). These rolling conditions can be easily set by appropriately defining the angular velocity V1 and turning angle (not shown) for the tread model 26 (tire model 24). Furthermore, the rolling conditions can also be set by the longitudinal force and lateral force defined for the tread model 26 (tire model 24).

[0055] In this embodiment, a free rolling condition is set as the rolling condition, and thus, in the rolling step S3 of this embodiment, for example, an angular velocity V1 and a turning angle (not shown) during free rolling are defined for the tread model 26 (tire model 24), thereby making it possible to calculate the tread model 26 (tire model 24) freely rolling on the road surface model 25.

[0056] [Calculate physical quantities] Next, in the simulation method of this embodiment, the computer 1 (shown in FIG. 1) calculates physical quantities associated with wear (step S4). In step S4 of this embodiment, first, as shown in FIG. 1, the physical quantity calculation unit 6D is loaded into the working memory 4C. Then, the physical quantity calculation unit 6D is executed by the operation unit 4A, causing the computer 1 to function as a means for calculating the physical quantities.

[0057] In step S4 of this embodiment, physical quantities associated with wear (hereinafter sometimes simply referred to as "physical quantities") are calculated for each of the multiple tread nodes 35 that constitute the tread contact surface 33 of the tread model 26, among the nodes 31 of the tire model 24 shown in Figures 5 and 6.

[0058] The physical quantity is not particularly limited as long as it is related to wear. In this embodiment, the physical quantity is the wear energy at each tread node 35. In step S4 of this embodiment, as shown in Fig. 4, the tire model 24 is rolled (at least one revolution) on the road surface model 25, and the wear energy E of each tread node 35 (shown in Figs. 5 and 6) is calculated. Note that the wear energy E is preferably calculated after the tire model 24 has been rolled until the force acting on the tire model 24 reaches a steady state (stable state).

[0059] In step S4 of this embodiment, the shear force P and the slip amount Q are calculated at the tread nodes 35 (shown in FIGS. 5 and 6) that come into contact with the road surface model 25.

[0060] The shear force P includes a shear force Px in the tire axial direction x and a shear force Py in the tire circumferential direction y. The slip amount Q includes a slip amount Qx in the tire axial direction x corresponding to the shear force Px and a slip amount Qy in the tire circumferential direction y corresponding to the shear force Py. The shear forces Px, Py and slip amounts Qx, Qy of each tread node 35 (shown in FIGS. 5 and 6) are calculated for each unit time T(x) of the simulation.

[0061] In step S4, the shear forces Px(i), Py(i) of each tread node 35 are multiplied by the slip amounts Qx(i), Qy(i) corresponding to the shear forces Px(i), Py(i), and the multiplied values ​​are integrated while each tread node 35 is in contact with the ground (for one rotation of the tire model). In this way, the wear energy E at each tread node 35 is calculated.

[0062] Fig. 8 is a graph showing the relationship between the physical quantity (wear energy) and the axial position of each tread node 35. Note that Fig. 8 (including Fig. 12) shows an example of the relationship between the physical quantity and the position of the tread node, and the number and positional relationship of the tread node 35 shown in Fig. 8 are different from the number and positional relationship of the tread node 35 shown in Figs. 5 and 6.

[0063] In Fig. 8, the physical quantities of all the tread nodes 35 are plotted. These plots are displayed overlapping each other. In Fig. 8, the average values ​​of the physical quantities of the tread nodes 35 located at the same position in the tire axial direction are obtained, and these average values ​​are connected by a straight line. The physical quantity (wear energy E) of each tread node 35 is stored in the physical quantity input unit 5E (shown in Fig. 1).

[0064] [Movement amount identification process] Next, in the simulation method of this embodiment, as shown in Fig. 6, the computer 1 (shown in Fig. 1) identifies the movement amount M for expressing the wear of each tread node 35 (movement amount identifying step S5). In the movement amount identifying step S5 of this embodiment, the movement amount M for expressing the wear of each tread node 35 is identified based on the physical quantities of the multiple tread nodes 35.

[0065] 9(a) is a diagram illustrating an example of a state before each tread node 35 moves. FIG. 9(b) is a diagram illustrating an example of a state after each tread node 35 moves. In this embodiment, the procedure for moving each tread node 35 is not particularly limited, and for example, the procedure described in Japanese Patent Application Laid-Open No. 2017-033076 can be adopted. As shown in FIGS. 9(a) and 9(b), the tread node 35 in this embodiment moves by a specified movement amount M along a side 32 connecting the tread node 35 and an inner node 36 located radially inward of the tread node 35.

[0066] In the movement amount specifying step S5 of this embodiment, as shown in Fig. 1, the physical amount (wear energy E) of each tread node 35 stored in the physical amount input unit 5E and the movement amount specifying unit 6E (including the dispersion degree calculation unit 7A and the movement amount determination unit 7B) are read into the working memory 4C. The movement amount specifying unit 6E (including the dispersion degree calculation unit 7A and the movement amount determination unit 7B) is then executed by the calculation unit 4A, causing the computer 1 to function as a means for specifying a movement amount for expressing the wear of each tread node 35. Fig. 10 is a flowchart showing the processing procedure of the movement amount specifying step S5 of this embodiment.

[0067] [Calculate the dispersion of physical quantities] In the movement amount identification step S5 of this embodiment, first, the dispersion of the physical quantity (hereinafter, sometimes simply referred to as "dispersion") is calculated for each of a plurality of local regions 51 divided by at least two of the plurality of tread nodes 35 (step S51). In step S51 of this embodiment, the dispersion calculation unit 7A shown in FIG. 1 is executed by the calculation unit 4A, causing the computer 1 to function as a means for calculating the dispersion.

[0068] In step S51 of this embodiment, first, the tread contact surface 33 is divided into a plurality of local regions 51. Each local region 51 can be divided as appropriate as long as it includes at least two tread nodes 35. FIG. 11 is a partially enlarged view of the center land zone model 29A divided into a plurality of local regions 51.

[0069] In this embodiment, the tread contact patch 33 is divided into a plurality of local regions 51 so as to include a plurality of tread nodes 35 that are adjacent in the tire circumferential direction and / or the tire axial direction, for example. In this embodiment, a plurality of tread nodes 35 arranged in the tire circumferential direction are identified as one group 52, for example. Since the tread model 26 in this embodiment is defined by developing a two-dimensional model into three dimensions, the axial positions of the tread nodes 35 that make up each group 52 are set to be the same. Note that the axial positions of the tread nodes 35 in each group 52 may be offset. Three axially adjacent groups 52 are divided into one local region 51.

[0070] In each local region 51, for example, if one tread node 35 moves significantly in the tire radial direction relative to the other tread node 35, an uneven shape that deviates from the actual wear state is formed in the tread contact surface 33. Therefore, each local region 51 can be treated as a constituent unit (a collection of tread nodes 35) that can form an uneven shape in the tread contact surface 33.

[0071] The local regions 51 are not limited to the above-described form. The local region 51 may be divided into two groups 52 adjacent to each other in the tire axial direction, or into four or more groups 52. When a block model 41 is set, the local region 51 may be divided into each of the groups 52 provided in the block model 41. Fig. 12 is a graph showing the relationship between the physical quantity of the center land zone model 29A in Fig. 8 and the position of each tread node 35. In Fig. 12, the rightmost local region 51 is shown enlarged.

[0072] In step S51 of this embodiment, the maximum value E of the physical quantity is calculated for each of the local regions 51 (the local regions 51 of the center land portion model 29A to the shoulder land portion model 29C). max and the average value E ave The maximum value E max is the largest wear energy E among the wear energies E calculated at all the tread nodes 35 (shown in FIG. 6) constituting the local region 51. On the other hand, the average value E ave is the total value of the wear energy E calculated at the tread nodes 35 that make up the local region 51 divided by the total number of tread nodes 35 that make up that local region 51.

[0073] Next, in step S51 of this embodiment, the maximum value E max and the average value E ave The difference between these values ​​is calculated. As a result, the degree of dispersion V of the physical quantity is acquired for each of the local regions 51. The degree of dispersion V calculated for each of the local regions 51 is stored in the physical quantity input unit 5E.

[0074] In a local region 51 with a large degree of dispersion V, there is a large variation in the wear energy E (physical quantity) of each tread node 35 constituting the local region 51. In such a local region 51, if the movement amount M of each tread node 35 is determined based only on the magnitude of the wear energy E, for example, there is a high possibility that large irregularities that deviate from the actual wear state as described above will be formed in the tread contact patch 33 (shown in FIG. 9) of the local region 51.

[0075] On the other hand, in a local region 51 with a small degree of dispersion V, there is little variation in the wear energy E (physical quantity) of each tread node 35 constituting the local region 51. In such a local region 51, even if the movement amount M of each tread node 35 is determined based only on the magnitude of the wear energy E, it is unlikely that large irregularities that deviate from the actual wear state will be formed in the tread contact patch 33 (shown in FIG. 9) of the local region 51.

[0076] Determine the amount of tread node movement Next, in the movement amount specifying step S5 of this embodiment, the movement amount M (shown in FIG. 9(a)) of each tread node 35 is determined based on the dispersity V (shown in FIG. 12) of each of the multiple local regions 51 (step S52). In step S52 of this embodiment, the movement amount M is determined based on the largest dispersity V among the dispersity V of each of the multiple (all) local regions 51.

[0077] In step S52 of this embodiment, the movement amount determination unit 7B shown in FIG. 1 is executed by the calculation unit 4A, causing the computer 1 to function as a means for determining the movement amount M.

[0078] In step S52 of this embodiment, the product of the wear energy E and the wear progression rate A, which is determined so that its value decreases as the degree of dispersion V increases, is determined as the movement amount M of the tread node 35 (shown in FIG. 9(a)). In this embodiment, the wear progression rate A is a coefficient indicating the amount of wear per unit wear energy of the tread rubber 12g of the tire 11 shown in FIG. 2. The larger the wear progression rate A, the larger the amount of wear (i.e., the movement amount M).

[0079] The wear progression rate in this embodiment is a linear function of the dispersity, and is defined, for example, by the following formula (1): Figure 13 is a graph showing an example of the relationship between the wear progression rate A and the dispersity V. A = a V + b …(1) where: A: Wear progression rate V: Dispersity a: Inclination b: Intercept

[0080] In the above formula (1), the slope a is set to less than 0. As a result, in the above formula (1), the wear progression rate A is determined so that it decreases as the degree of dispersion V increases. Such a wear progression rate A (linear function) can be set, for example, for each tire category (e.g., for passenger cars, for heavy loads, etc.) based on experimental results using multiple tires. This is based on the fact that the absolute value of wear energy is roughly determined for each tire category. It is desirable to set the wear progression rate A in advance before implementing the simulation method of this embodiment.

[0081] In step S52 of this embodiment, first, the largest dispersity V is identified among the dispersities V of the multiple (all) local regions 51. Next, in step S52 of this embodiment, the identified dispersity V is substituted into the linear function of the wear progress rate A (the above formula (1)). As a result, in step S52, the wear progress rate A corresponding to the identified dispersity V is determined. This wear progress rate A is determined so as to decrease as the dispersity V increases.

[0082] Next, in step S52 of this embodiment, the product of the determined wear progression rate A and the physical quantity (wear energy E) of each tread node 35 is calculated. As a result, in step S52, the movement amount M (shown in FIGS. 6 and 9(a)) of the tread node 35 is calculated. In this embodiment, the movement amount M of all the tread nodes 35 is determined based on the same wear progression rate A.

[0083] As described above, the wear progression rate A is predetermined to decrease as the dispersity V increases. Therefore, in step S52, the larger the value of the largest dispersity V among the multiple local regions 51, the smaller the wear progression rate A is set, and as a result, the movement amounts M of all tread nodes 35 can be determined to be small. On the other hand, in step S52, the smaller the value of the largest dispersity V, the larger the wear progression rate A is set, and as a result, the movement amounts M of all tread nodes 35 can be determined to be large. Note that the magnitude of the movement amount M can be determined to be a different value depending on the magnitude of the physical quantity (wear energy E) calculated for each tread node 35. The movement amount M of each tread node 35 is stored in the physical quantity input unit 5E (shown in FIG. 1).

[0084] [Transform the tread model] Next, in the simulation method of this embodiment, the computer 1 moves each tread node 35 based on the movement amount M of each tread node 35 (shown in FIGS. 6 and 9(a)), thereby deforming the tread model 26 (step S6). In step S6 of this embodiment, first, as shown in FIG. 1, the movement amount M of each tread node 35 stored in the physical quantity input unit 5E and the movement unit 6F are read into the working memory 4C. Then, the movement unit 6F is executed by the calculation unit 4A, causing the computer 1 to function as a means for deforming the tread model 26.

[0085] As shown in Fig. 9(a), in step S6 of this embodiment, for each tread node 35, a coordinate value 40 is calculated when the tread node 35 is moved by the movement amount M from the tread node 35 to the inner node 36. Then, as shown in Fig. 9(b), the coordinate value of each tread node 35 is updated to the coordinate value 40 after movement (shown in Fig. 9(a)). As a result, in step S6, the tread model 26 can be deformed by moving each tread node 35 based on the movement amount M (shown in Fig. 9(a)).

[0086] In step S6 of this embodiment, as shown in FIG. 9(b), if the distance L1 between the moved tread node 35 and the inner node 36 is equal to or less than a predetermined threshold, the tread node 35 is deleted and the inner node 36 is defined as the new tread node 35. Furthermore, the node 31 located radially inward of the new tread node 35 is defined as the new inner node 36. This allows the wear of the tread model 26 to be further accelerated. The threshold value of the distance L1 can be set as appropriate depending on, for example, the required simulation accuracy.

[0087] In step S6 of this embodiment, a worn tread model 26 (tire model 24) is constructed based on the elements F(i) including the moved tread nodes 35 and the newly set tread nodes 35. In this embodiment, the edges 32 of the elements F(i) are reset based on the moved tread nodes 35 and the newly set tread nodes 35. As a result, in step S6, the worn tread model 26 (tire model 24) is set. The worn tread model 26 (tire model 24) is stored in the tread model input unit 5B (shown in FIG. 1).

[0088] [Functions of tire simulation method and simulation device] In the simulation method (simulation device 1A) of this embodiment, the magnitude of the movement amount M (shown in FIGS. 6 and 9(a)) of the tread node 35 can be controlled according to the magnitude of the dispersion V of the physical quantity (wear energy E) of the multiple local regions 51. As described above, each local region 51 can be treated as a constituent unit (an aggregate of tread nodes 35) that can form an uneven shape that deviates from the actual wear state on the tread contact surface 33. Therefore, in this embodiment, by controlling the magnitude of the movement amount M of the tread node 35 according to the magnitude of the dispersion V of the multiple local regions 51, it is possible to prevent the acquisition of calculation results that deviate from the actual wear state. As a result, in this embodiment, it is possible to obtain calculation results that approximate the actual wear state.

[0089] In the simulation method (simulation device 1A) of this embodiment, the movement amount M (shown in FIGS. 6 and 9(a)) is determined based on the largest dispersity V among the dispersities V of multiple (all) local regions 51. In this embodiment, the larger the value of the largest dispersity V, the smaller the wear progression rate A is set, and as a result, the movement amount M of all tread nodes 35 is determined to be small. This makes it possible to reliably prevent large irregularities from being formed on the tread contact surface 33 in all local regions 51. Therefore, in this embodiment, it is possible to more reliably prevent the calculation result obtained in the next calculation step (wear progression step) from deviating from the actual wear state, such as a sudden loss of contact with the ground.

[0090] On the other hand, in the simulation method (simulation device 1A) of this embodiment, the smaller the value of the largest dispersity V among the dispersities V of the multiple (all) local regions 51, the larger the wear progression rate A is set, and as a result, the larger the movement amount M of the tread node 35 is set. In this way, in this embodiment, the movement amount M of all the tread node 35 can be made large, so that the final state after wear can be calculated in a short time.

[0091] In this way, the simulation method (simulation device 1A) of this embodiment can obtain calculation results that approximate the actual state after wear in a short time.

[0092] [Determine termination] Next, in the simulation method of this embodiment, the computer 1 determines whether or not a predetermined termination condition is satisfied (step S7). The termination condition can be set as appropriate, for example, a calculation termination time or a total value of the amount of wear of the tread model 26. The termination condition of this embodiment is input to the condition input unit 5F (shown in FIG. 1) before the simulation method is performed.

[0093] In step S7 of this embodiment, first, the simulation termination conditions stored in the condition input unit 5F and the judgment unit 6G are read into the working memory 4C as shown in Fig. 1. Then, the judgment unit 6G is executed by the calculation unit 4A, causing the computer 1 to function as a means for judging whether or not the predetermined termination conditions have been satisfied.

[0094] If it is determined in step S7 that the termination condition is satisfied ("Yes" in step S7), the next step S8 is performed. On the other hand, if it is determined that the termination condition is not satisfied ("No" in step S7), the rolling steps S3 to S7 are performed again using the worn tread model 26 (tire model 24). In this way, the simulation method of this embodiment (simulation device 1A (shown in FIG. 1)) can simulate the state of the worn tread contact surface 33 that has continued to roll until the termination condition is satisfied.

[0095] [Evaluate the condition after wear] Next, in the simulation method of this embodiment, the computer 1 evaluates whether the state of the tread contact surface 33 after wear is good or not (step S8). The evaluation criteria for whether the state after wear is good or not can be set appropriately based on, for example, the amount of wear of the tread contact surface 33 (tread model 26), the number of calculation steps (number of wear progression steps) until a predetermined amount of wear is reached, etc.

[0096] In step S8 of this embodiment, the worn tread model 26 (tire model 24) stored in the tread model input unit 5B and the determination unit 6G are loaded into the working memory 4C as shown in Fig. 1. The determination unit 6G is then executed by the calculation unit 4A, causing the computer 1 to function as a means for evaluating whether the condition of the tread contact surface 33 after wear is good or not.

[0097] In step S8 of this embodiment, first, the magnitude (total value) of the wear amount of each land model 29 is calculated. If the magnitude of each wear amount is within a predetermined range (threshold value), it is determined that the condition after wear is good. The threshold value may be set for each land model 29, or may be defined commonly for all land models 29.

[0098] If it is determined in step S8 that the condition of the tread contact surface 33 after wear is good ("Yes" in step S8), the tire 11 is manufactured based on the design drawing (CAD data) of the tire 11 shown in FIG. 2 (step S9). On the other hand, if it is determined in step S8 that the condition of the tread contact surface 33 after wear is not good ("No" in step S8), the design factors of the tire 11 (shown in FIG. 2) are changed (step S10), and steps S1 to S8 are performed again. As a result, the simulation method (simulation device 1A (shown in FIG. 1)) of this embodiment can reliably design a tire 11 in which the condition of the tread contact surface 20 after wear is good.

[0099] [Tire simulation method (second embodiment)] In the above-described embodiments, the wear progression rate A (shown in FIG. 13) has been exemplified as a linear function of the dispersity V, but the present invention is not limited to this. The wear progression rate A may be a step function of the dispersity V, as in Patent Document 1. This step function, like the linear functions described above, can determine a wear progression rate whose value decreases as the dispersity increases, and therefore, it is possible to obtain calculation results that approximate the actual state after wear.

[0100] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the illustrated embodiments and can be modified and implemented in various forms. [Example]

[0101] The wear state of the tread contact surface of the tire shown in Figure 2 was calculated based on the processing procedure shown in Figure 3 (Example). In this Example, to identify the movement amount for expressing the wear of the tread node, the dispersion of the physical quantity associated with the wear was calculated for each of a plurality of local regions divided by at least two tread nodes among the plurality of tread nodes. Then, in this Example, the movement amount of each tread node was determined based on the dispersion of each of the plurality of local regions. The dispersion was calculated as the difference between the maximum value and the average value of the physical quantity calculated in each local region.

[0102] In the example, the largest dispersity among the dispersities of each of the multiple local regions was identified. Next, in the example, the identified dispersity was substituted into the linear function of the wear progression rate (the above formula (1)) to determine the wear progression rate. Then, the product of the wear energy of each tread node and the wear progression rate was determined as the movement amount of each tread node.

[0103] For comparison, the wear state of the tread contact surface of the tire shown in Figure 2 was calculated (Comparative Example) based on the same procedure as in Patent Document 1. In the Comparative Example, to identify the amount of movement of the tread nodes, the dispersion of physical quantities associated with wear was calculated for the entire tread contact surface, and the amount of movement of each tread node was determined based on the dispersion.

[0104] Unlike the dispersity of the example, the dispersity of the comparative example was calculated as the difference between the maximum value and the average value of the physical quantity for all the tread contact areas that make up the tread contact area. In the comparative example, the wear progression rate shown in Figure 13 was used to determine the larger the dispersity, the smaller the movement amount.

[0105] The wear state of the tread contact surface of the examples and comparative examples was compared with the wear state of the tread contact surface of a tire that had been driven on an actual vehicle (experimental example). The common specifications were as follows: Tire size: 215 / 55R17 Rim size: 17 x 7J Internal pressure: 230kPa Load: 3.51kN Camber angle: 1.7°

[0106] In the example, the larger the value of the largest dispersity among the multiple local regions, the smaller the wear progression rate was set, and as a result, the movement amount of all tread nodes was determined to be small. As described above, each local region 51 can be treated as a constituent unit (a collection of tread nodes) that can form an uneven shape on the tread contact surface that deviates from the actual wear state. Therefore, in the example, calculation results that are closer to the actual state after wear could be obtained compared to the comparative example in which the dispersity is calculated for the entire tread contact surface.

[0107] Furthermore, in the example, the smaller the value of the largest dispersity among the dispersities of the respective local regions, the larger the wear progression rate was set, and as a result, the larger the movement amount of all tread nodes was determined. As a result, the example was able to move each tread node by a large amount while preventing deviation from the actual state after wear compared to the comparative example. As a result, the calculation time of the example was able to be reduced by 20% compared to the calculation time of the comparative example. Therefore, the example was able to calculate calculation results that approximated the actual state after wear in a short time.

[0108] [Note] The present disclosure includes the following aspects.

[0109] [Disclosure 1] A simulation method for calculating a wear state of a tread contact surface of a tire having a tread portion provided with at least one circumferential groove and a plurality of land portions separated by the circumferential groove, the method comprising: a step of inputting a tread model divided into a plurality of land portion models by discretizing the tread portion using a finite number of elements each having a plurality of nodes into a computer; The computer calculating physical quantities associated with wear for a plurality of tread nodes constituting a tread contact surface of the tread model; determining a movement amount representing wear of each of the tread nodes based on the physical quantity; and deforming the tread model by moving each of the tread nodes based on the amount of movement. The step of specifying the movement amount includes a step of calculating a degree of dispersion of the physical quantity for each of the plurality of land models; determining the amount of movement for each of the plurality of land models based on the degree of dispersion of each of the plurality of land models; A tire simulation method including: [Disclosure 2] The tire simulation method according to Disclosure 1, wherein the step of determining the amount of movement determines the amount of movement based on the largest degree of dispersion among the degrees of dispersion of the plurality of local regions. [Disclosure 3] The physical quantity is wear energy, The tire simulation method according to Disclosure 1 or 2, wherein the step of determining the amount of movement determines the amount of movement as the product of the wear energy and a wear progression rate that is set so that the value decreases as the degree of dispersion increases. [Disclosure 4] The tire simulation method according to Disclosure 3, wherein the step of determining the movement amounts determines the movement amounts of all tread nodes based on the same wear progression rate. [Disclosure 5] The tire simulation method according to any one of Disclosures 1 to 4, wherein the degree of dispersion is the difference between the maximum value and the average value of the physical quantity calculated by each of the land models. [Disclosure 6] A simulation device having a processing unit for calculating a wear state of a tread contact surface of a tire having a tread portion, The arithmetic processing device a tread model acquisition unit that acquires a tread model in which the tread portion is discretized using a finite number of elements having a plurality of nodes; a physical quantity calculation unit that calculates physical quantities associated with wear for a plurality of tread nodes that constitute the tread contact surface of the tread model; a movement amount specifying unit that specifies a movement amount for expressing wear of each of the tread nodes based on the physical amount; a moving unit that moves each of the tread nodes based on the amount of movement to deform the tread model, The movement amount specifying unit a dispersion degree calculation unit that calculates the dispersion degree of the physical quantity for each of a plurality of local regions divided by at least two of the plurality of tread nodes; a movement amount determination unit that determines the movement amount of each of the tread nodes based on the dispersion degree of each of the plurality of local regions; A tire simulation device including: [Explanation of symbols]

[0110] S1: Tread model input process S4: Inputting physical quantities related to wear S5: Identifying the amount of movement of each tread node S6: The process of deforming the tread model by moving each tread node.

Claims

1. A simulation method for calculating a wear state of a tread contact surface of a tire having a tread portion, comprising: a step of inputting a tread model in which the tread portion is discretized using a finite number of elements having a plurality of nodes into a computer, The computer calculating physical quantities associated with wear for a plurality of tread nodes constituting a tread contact surface of the tread model; determining a movement amount representing wear of each of the tread nodes based on the physical quantity; and deforming the tread model by moving each of the tread nodes based on the amount of movement. The step of specifying the movement amount includes: calculating a degree of dispersion of the physical quantity for each of a plurality of local regions divided by at least two of the plurality of tread nodes; determining the movement amount of each of the tread nodes based on the largest dispersity among the dispersities of the plurality of local regions; A tire simulation method including:

2. The physical quantity is wear energy, 2. The tire simulation method according to claim 1, wherein the step of determining the amount of movement determines, as the amount of movement, the product of the wear energy and a wear progression rate that is determined so that the value decreases as the degree of dispersion increases.

3. A tire simulation method as described in claim 2, wherein the step of determining the amount of movement determines the amount of movement of all tread nodes based on the same wear progression rate.

4. A tire simulation method described in any one of claims 1 to 3, wherein the degree of dispersion is the difference between the maximum value and the average value of the physical quantity calculated for each of the multiple local regions.

5. A simulation device having a processing unit for calculating the wear state of a tread contact surface of a tire having a tread portion, The arithmetic processing device a tread model acquisition unit that acquires a tread model in which the tread portion is discretized using a finite number of elements having a plurality of nodes; a physical quantity calculation unit that calculates physical quantities associated with wear for a plurality of tread nodes that constitute the tread contact surface of the tread model; a movement amount specifying unit that specifies a movement amount for expressing wear of each of the tread nodes based on the physical amount; a moving unit that moves each of the tread nodes based on the amount of movement to deform the tread model, The movement amount specifying unit a dispersion degree calculation unit that calculates a dispersion degree of the physical quantity for each of a plurality of local regions divided by at least two of the plurality of tread nodes; a movement amount determination unit that determines the movement amount of each of the tread nodes based on the largest dispersion degree among the dispersion degrees of each of the plurality of local regions; A tire simulation device including:

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