JP7487567B2 - Tire simulation method and tire simulation device - Google Patents

Description

The present invention relates to a tire simulation method, etc.

The following Patent Document 1 proposes a method for creating a tire model with advanced wear using a computer. This creation method involves a process of acquiring the wear energy of the contact area through rolling analysis using a tire model, and a process of changing the tire model to one with advanced wear based on the amount of wear obtained from the wear energy. Predetermined material properties are defined for the tire model.

Patent No. 5098711

Although the above method takes into account the change over time in the material properties of the tire model, the specific method for doing so was not described.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to provide a tire simulation method that can accurately calculate the state of a tire's tread contact surface after wear.

The present invention is a tire simulation method for calculating the state of a tire tread surface after wear, which includes inputting a tire model in which the tire has multiple nodes and is discretized using a finite number of elements for which predetermined material properties are defined, into a computer, and the computer executes the following steps: a first step of calculating physical quantities associated with wear of the tread surface for multiple tread nodes that constitute the tread surface of the tire model among the nodes; a second step of determining a movement amount for expressing wear of each of the tread nodes based on the physical quantities; a third step of moving each of the tread nodes based on the movement amount; and a fourth step of updating the material properties based on the movement amount.

In the tire simulation method according to the present invention, the computer may repeatedly perform the first to fourth steps until a predetermined condition is satisfied.

In the tire simulation method according to the present invention, the fourth step may include a first calculation step of calculating at least one of the travel distance and travel period of the tire based on the amount of movement, and a second calculation step of calculating the material properties that have changed over time based on at least one of the travel distance and travel period.

In the tire simulation method according to the present invention, the first calculation step may include a step of inputting a wear rate that defines the amount of wear of the tire per unit distance traveled into the computer, and a step of calculating the distance traveled by dividing the amount of movement by the wear rate.

In the tire simulation method according to the present invention, the first calculation step may include a step of calculating the total number of rotations of the tire based on the amount of movement, and a step of calculating the traveled distance by multiplying the total number of rotations of the tire by the circumference of the tire model.

In the tire simulation method according to the present invention, the step of calculating the total number of rotations of the tire may include a step of inputting a unit wear development rate that defines the amount of wear per unit wear energy for the tread rubber of the tire into the computer, a step of inputting a wear energy development rate that defines the wear energy for one tire rotation into the computer, and a step of calculating the total number of rotations of the tire by dividing the amount of movement by the unit wear development rate and the wear energy development rate.

In the tire simulation method according to the present invention, the step of calculating the traveled distance may include a step of calculating the circumference based on at least one of the rolling speed and the angular velocity of the tire model.

In the tire simulation method according to the present invention, the step of calculating the circumference may calculate the circumference based on at least one of the rolling speed and the angular velocity that occurs most frequently while the tire is running.

In the tire simulation method according to the present invention, the first calculation step may include a step of inputting an actual vehicle distance rate that defines the travel distance of the tire per unit period into the computer, and a step of calculating the travel period by dividing the travel distance by the actual vehicle distance rate.

In the tire simulation method according to the present invention, the second calculation step may include a step of inputting into the computer a material property change rate that defines the relationship between at least one of the actual driving distance and the actual driving period of the tire and the material properties of the tread rubber of the tire, and a step of calculating the material properties that have changed over time based on at least one of the driving distance and the driving period and the material property change rate.

The present invention is a simulation device having a processing device that calculates the state of a tire tread contact surface after wear, and the processing device may include a tire model acquisition unit that acquires a tire model in which the tire has a plurality of nodes and is discretized using a finite number of elements for which predetermined material properties are defined, a physical quantity calculation unit that calculates physical quantities associated with the wear of the tread contact surface for a plurality of tread nodes that constitute the tread contact surface of the tire model among the nodes, a movement amount determination unit that determines a movement amount for expressing the wear of each of the tread nodes based on the physical quantity, a movement unit that moves each of the tread nodes based on the movement amount, and a material property update unit that updates the material properties based on the movement amount.

The tire simulation method of the present invention, having the above configuration, can update the material properties based on the amount of movement, making it possible to accurately calculate the state of the tire tread contact surface after wear.

FIG. 2 is a block diagram showing an example of a computer (tire simulation device) on which a tire simulation method is executed. FIG. 1 is a cross-sectional view showing an example of a tire. 1 is a flowchart showing an example of a processing procedure of a tire simulation method. FIG. 2 is a perspective view showing an example of a tire model and a road surface model. FIG. 2 is a cross-sectional view showing an example of a tire model. FIG. 6 is a partially enlarged view of the tread portion of FIG. 5 . 11 is a flowchart showing an example of a processing procedure of a pre-processing step. FIG. 4A is a diagram illustrating an example of a state before each tread node moves, and FIG. 4B is a diagram illustrating an example of a state after each tread node moves. 13 is a flowchart showing an example of a processing procedure of a fourth step. 13 is a flowchart showing an example of a processing procedure of a first calculation step. 13 is a flowchart showing an example of a processing procedure of a second calculation step. 1 is a graph showing an example of a material property change rate. 13 is a flowchart showing an example of a processing procedure of a first calculation step according to another embodiment of the present invention. 13 is a flowchart showing an example of a processing procedure of a rotation speed calculation step. 13 is a flowchart showing an example of a processing procedure of a travel distance calculation step. 13 is a flowchart showing an example of a processing procedure of a first calculation step according to still another embodiment of the present invention. 10 is a flowchart showing an example of a processing procedure of a second calculation step in this embodiment. 13 is a graph showing an example of a material property change rate according to another embodiment of the present invention. 1 is a graph showing the relationship between actual vehicle mileage and material properties. 1 is a graph showing the relationship between wear amount and mileage.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the tire simulation method of the present 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 an example of a computer (tire simulation device) that executes the tire simulation method.

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

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 device 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.

The storage unit 4B is a non-volatile information storage device, such as a magnetic disk, an optical disk, or an SSD. The storage unit 4B includes a data unit 5 and a program unit 6.

The data section 5 includes an initial data section 5A in which information (e.g., CAD data, etc.) relating to the tire and road surface to be evaluated is stored, a tire model input section 5B, and a road surface model input section 5C to which a road surface model is input. The data section 5 further includes a boundary condition input section 5D to which boundary conditions of the simulation are input, a physical quantity input section 5E to which physical quantities calculated by the calculation section 4A, etc. are input, and a condition input section 5F to which termination conditions of the simulation, etc. are input.

The program unit 6 is a program executed by the calculation unit 4A. The program unit 6 includes a tire model acquisition unit 6A that acquires a tire model, a road surface model acquisition unit 6B that acquires a road surface model, and an internal pressure filling calculation unit 6C that calculates the shape of the tire model after internal pressure filling. The program unit 6 includes a load load calculation unit 6D that defines a load on the tire model after internal pressure filling, a rolling motion calculation unit 6E that calculates the rolling motion of the tire model, and a physical quantity calculation unit 6F that calculates a physical quantity associated with the wear of the tread contact surface of the tire model. The program unit 6 includes a movement amount determination unit 6G that determines the movement amount for expressing the wear of each tread node of the tire model, a movement unit 6H that moves each tread node, and a material property update unit 6J that updates the material properties. The program unit 6 includes a judgment unit 6K that evaluates the end condition of the simulation and the state of the tread contact surface after wear.

Figure 2 is a cross-sectional view showing an example of a tire 11 whose wear amount is predicted by a tire simulation method (using simulation device 1A (shown in Figure 1)). In this embodiment, a pneumatic tire for a passenger vehicle is shown as an example, but other categories of tires, such as heavy-duty tires for trucks and buses, and airless tires, may also be used.

The tire 11 of this embodiment is provided with a carcass 16 that extends from the tread portion 12 through the sidewall portion 13 to the bead core 15 of the bead portion 14, and a belt layer 17 that is disposed radially outside the carcass 16 and inside the tread portion 12.

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

The belt layer 17 is composed of two belt plies, inner and outer, 17A and 17B, in which belt cords (not shown) are arranged at an angle of, for example, 10 to 35 degrees relative to the tire circumferential direction. These belt plies 17A and 17B are overlapped so that the belt cords cross each other.

The tire 11 is provided with a rubber member 11G including a tread rubber 12G arranged on the outside of the belt layer 17 in the tread portion 12 and a sidewall rubber 13G arranged on the outside of the carcass 16 in the sidewall portion 13.

The tread portion 12 (tread rubber 12G) is provided with main grooves 18 that extend continuously in the tire circumferential direction. As a result, the tread portion 12 is provided with a plurality of land portions 19 that are divided by the main grooves 18. Each land portion 19 may be provided with blocks that are separated by lateral grooves (not shown), for example.

The main groove 18 of this embodiment is configured to include a pair of center main grooves 18A, 18A arranged on both axially outer sides of the tire equator C, and a pair of shoulder main grooves 18B, 18B arranged between the center main groove 18A and the tread ground edge 12t. On the other hand, the land portion 19 of this embodiment is configured to include a center land portion 19A divided between the pair of center main grooves 18A, 18A, and a pair of middle land portions 19B, 19B divided between the center main groove 18A and the shoulder main groove 18B. Furthermore, the land portion 19 includes a pair of shoulder land portions 19C, 19C divided between the shoulder main groove 18B and the tread ground edge 12t.

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

A "genuine rim" is a rim that is determined for each tire by the standard system that includes the standard on which the tire 11 is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

"Normal internal pressure" refers to the air pressure set for each tire by each standard in the standard system, including the standard on which tire 11 is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE," but if the tire is for a passenger car, it is 180 kPa.

"Normal load" refers to the load that the standard specifies for each tire 11; for JATMA, it is the maximum load capacity; for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is "LOAD CAPACITY."

In this specification, unless otherwise specified, the dimensions of each part of the tire are specified as values measured in a normal state. A normal state is when the tire 11 is mounted on a normal rim (not shown), filled to the normal internal pressure, and unloaded.

Figure 3 is a flowchart showing an example of the processing procedure of a tire simulation method. In the simulation method of this embodiment, first, a tire model in which the tire 11 (shown in Figure 2) is discretized using a finite number of elements having multiple nodes and having predetermined material properties defined is input to the computer 1 (shown in Figure 1) (step S1).

In step S1 of this embodiment, first, as shown in FIG. 1, information (e.g., contour data, etc.) regarding the tire 11 (shown in FIG. 2) input to the initial data section 5A is input to the working memory 4C. Furthermore, the tire model acquisition section 6A is read into the working memory 4C. Then, the tire model acquisition section 6A is executed by the calculation section 4A.

Figure 4 is a perspective view showing an example of a tire model 21 and a road surface model 25. Figure 5 is a cross-sectional view showing an example of a tire model 21. Figure 6 is a partially enlarged view of the tread portion 22 in Figure 5. Note that in Figure 4, the mesh (element F(i)) of the tire model 21 shown in Figures 5 and 6 is omitted.

As shown in FIG. 5, in step S1 of this embodiment, based on the information about the tire 11 shown in FIG. 2, the tire 11 is discretized using a finite number of elements F(i) (i=1, 2, ...) that can be handled by a numerical analysis method. As a result, in step S1, a tire model 21 is set. 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, but in this embodiment, the finite element method is adopted.

5 and 6, for example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element is used for the element F(i). 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, and the coordinate value of the node 31 are defined for each such element F(i). Furthermore, numerical data such as the material properties (e.g., density, Young's modulus, damping coefficient, loss tangent (tan δ), and/or complex elastic modulus E*, etc.) of the tire components (e.g., tread rubber 12G) shown in FIG. 2 are defined for each element F(i).

In the tread portion 22 of the tire model 21, a main groove model 28 that reproduces the main groove 18 (shown in FIG. 2) and a land model 29 that reproduces the land portion 19 (shown in FIG. 2) are set. In the land model 29, for example, a block model separated by a lateral groove model (not shown) may be set.

The main groove model 28 of this embodiment includes a pair of center main groove models 28A, 28A and a pair of shoulder main groove models 28B, 28B, similar to the main groove 18 of the tire 11 shown in FIG. 2. On the other hand, the land portion model 29 of this embodiment includes 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, similar to the land portion 19 of the tire 11 shown in FIG. 2.

In the tire model 21, a carcass ply model 41 that models the carcass ply 16A (shown in FIG. 2), and belt ply models 41A and 41B that model the belt plies 17A and 17B (shown in FIG. 2), respectively, are set. In addition, in the tire model 21, a rubber model 21G including a tread rubber model 22G that models the tread rubber 12G (shown in FIG. 2), and a sidewall rubber model 23G that models the sidewall rubber 13G (shown in FIG. 2) is set. The tire model 21 is input to the computer 1 (tire model input unit 5B) shown in FIG. 1.

Next, in the simulation method of this embodiment, a road surface model 25 (shown in FIG. 4) that models the road surface (not shown) is input to the computer 1 (shown in FIG. 1) (step S2). In step S2 of this embodiment, first, information about the road surface (not shown) input to the initial data section 5A shown in FIG. 1 is input to the working memory 4C. Furthermore, the road surface model acquisition section 6B is read into the working memory 4C. Then, the road surface model acquisition section 6B is executed by the calculation section 4A.

As shown in FIG. 4, in step S2, the road surface is discretized using 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) based on information about the road surface (not shown). As a result, in step S2, a road surface model 25 is set.

Element G(i) is made up of a rigid plane element that is set to be undeformable. This element G(i) has a number 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.

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

Next, in the simulation method of this embodiment, the computer 1 (shown in FIG. 1) calculates the tire model 21 during rolling (pre-processing step S3). FIG. 7 is a flowchart showing an example of the processing procedure of the pre-processing step S3.

In the pre-processing step S3 of this embodiment, first, as shown in FIG. 4 and FIG. 5, boundary conditions for bringing the tire model 21 into contact with the road surface model 25 are defined (step S31). As the boundary conditions, for example, the internal pressure condition of the tire model 21, the load condition L, the camber angle, and the friction coefficient between the tire model 21 and the road surface model 25 are set. Furthermore, as boundary conditions, the angular velocity V1 corresponding to the running speed (rolling speed V3), the translational velocity V2, and the turning angle (not shown) are set. Note that the running speed and the translational velocity V2 are the velocities at the surface where the tire model 21 is in contact with the road surface model 25. These conditions are input to the computer 1 (boundary condition input unit 5D) shown in FIG. 1.

Next, in the pre-processing step S3 of this embodiment, the tire model 21 after internal pressure filling (shown in FIG. 5) is calculated (step S32). In step S32, as shown in FIG. 1, the tire model 21 inputted to the tire model input section 5B and the internal pressure conditions inputted to the boundary condition input section 5D are read into the working memory 4C. Furthermore, the internal pressure filling calculation section 6C is read into the working memory 4C. Then, the internal pressure filling calculation section 6C is executed by the calculation section 4A.

In step S32, first, as shown in FIG. 5, the bead portions 24, 24 of the tire model 21 are constrained by a rim model 27 that models the rim 26 (shown in FIG. 2) of the tire 11. Furthermore, the deformation of the tire model 21 is calculated based on a uniformly distributed load w that corresponds to the internal pressure condition. In this way, the tire model 21 after filling with internal pressure is calculated. For example, it is desirable to set the internal pressure to the air pressure stipulated by each standard in a standard system including the standard on which the tire 11 (shown in FIG. 2) is based.

For deformation calculation of the tire model 21, a mass matrix, stiffness matrix, and 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. Then, equations of motion are created by applying the above-mentioned various conditions, and these are calculated for each minute time (unit time T(x) (x = 0, 1, ...)). This allows deformation calculation of the tire model 21 to be performed. Such deformation calculation of the tire model 21 (including rolling calculation, which will be described later) can be calculated using commercially available finite element analysis application software such as LS-DYNA made by LSTC. The unit time T(x) can be set appropriately depending on the required simulation accuracy.

Next, in the pre-processing step S3 of this embodiment, the tire model 21 after loading is calculated (step S33). In step S33, as shown in FIG. 1, the load condition L, camber angle (not shown), and friction coefficient input to the boundary condition input unit 5D are read into the working memory 4C. Furthermore, in step S33, the load calculation unit 6D is read into the working memory 4C. Then, the load calculation unit 6D is executed by the calculation unit 4A.

In step S33, first, as shown in FIG. 4, the contact between the tire model 21 after internal pressure filling and the road surface model 25 is calculated. Next, in step S33, the deformation of the tire model 21 is calculated based on the load condition L, the camber angle (not shown), and the friction coefficient. As a result, in step S33, the tire model 21 after the load is applied and in contact with the road surface model 25 is calculated.

Next, in the pre-processing step S3 of this embodiment, the tire model 21 during rolling is calculated (step S34). In step S34, first, as shown in FIG. 1, the angular velocity V1 and translational velocity V2 input to the boundary condition input unit 5D are read into the working memory 4C. Furthermore, in step S34, the rolling calculation unit 6E is read into the working memory 4C. Then, the rolling calculation unit 6E is executed by the calculation unit 4A.

In step S34, first, as shown in FIG. 4, an angular velocity V1 is set for the tire model 21. Furthermore, a translational velocity V2 is set for the road surface model 25. This makes it possible to calculate the tire model 21 rolling on the road surface model 25.

The rolling conditions of the tire model 21 can be set as appropriate, for example, free rolling, braking, driving, turning, etc., depending on the running state of the tire 11 (shown in FIG. 2). These rolling conditions can be easily set by appropriately defining the angular velocity V1 and slip angle (not shown) in the tire model 21. In addition, when setting the rolling conditions, longitudinal forces and lateral forces may be appropriately defined in the tire model 21.

Next, in the simulation method of this embodiment, the computer 1 (shown in FIG. 1) calculates physical quantities associated with wear of the tread contact surface 20 (shown in FIG. 2) (first step S4). In the first step S4, physical quantities (hereinafter sometimes simply referred to as "physical quantities") associated with wear of the tread contact surface 20 are calculated for a plurality of tread nodes 35 constituting the tread contact surface 33 of the tire model 21, among the nodes 31 of the tire model 21 shown in FIGS. 5 and 6.

In the first step S4 of this embodiment, first, as shown in FIG. 1, the physical quantity calculation unit 6F is loaded into the working memory 4C. Then, the physical quantity calculation unit 6F is executed by the calculation unit 4A.

The physical quantity calculated in the first step S4 is the wear energy at each tread node 35 (shown in FIG. 6). In the first step S4 of this embodiment, as shown in FIG. 4, the tire model 21 is rolled (one rotation in this example) on the road surface model 25, and the wear energy E of each tread node 35 (shown in FIG. 6) is calculated. Note that in the first step S4, it is preferable to calculate the wear energy E after rolling the tire model 21 until the force acting on the tire model 21 reaches a steady state (stable state).

In the first step S4 of this embodiment, the shear force P and slippage Q (not shown) are calculated for each unit time T(x) of the simulation at the tread nodes 35 (shown in FIG. 6) that come into contact with the road surface model 25. Then, in the first step S4, the wear energy E at each tread node 35 is calculated based on the shear force P and slippage Q. Details of the calculation method of the shear force P, slippage Q, and wear energy E are as described in, for example, JP 2019-91302 A. The wear energy E of each tread node 35 is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the simulation method of this embodiment, the computer 1 determines the amount of movement M for expressing the wear of each tread node 35 (second step S5). In the second step S5, first, as shown in FIG. 1, the wear energy E of each tread node 35 (shown in FIG. 6) input to the physical quantity input unit 5E is read into the working memory 4C. Furthermore, in the second step S5, the movement amount determination unit 6G is read into the working memory 4C. Then, the movement amount determination unit 6G is executed by the calculation unit 4A. FIG. 8(a) is a diagram illustrating an example of a state before each tread node 35 moves. FIG. 8(b) is a diagram illustrating an example of a state after each tread node 35 moves.

In the second step S5 of this embodiment, the wear progression rate A (not shown) is determined based on the degree of dispersion V (not shown) of the physical quantity of the tread nodes 35, similar to the procedure of JP 2019-91302 A. Then, the wear progression rate A is multiplied by the wear energy E to determine the movement amount M (shown in FIG. 8(a)) of each tread node 35. In this embodiment, the movement amount M is treated as the amount of wear (mm) in the actual tire 11 (shown in FIG. 2). The movement amount M of each tread node 35 is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

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 FIG. 8(a)) (third step S6). In the third step S6, first, as shown in FIG. 1, the movement amount M of each tread node 35 inputted to the physical quantity input unit 5E is read into the working memory 4C. Furthermore, in the third step S6, the movement unit 6H is read into the working memory 4C. Then, the movement unit 6H is executed by the calculation unit 4A.

The procedure for moving each tread node 35 is not particularly limited. In this embodiment, based on the description of JP 2019-91302 A, as shown in FIG. 8(b), the tread node 35 is moved along the edge 32 connecting the tread node 35 and the inner node 36 located radially inward of the tread node 35.

As shown in FIG. 8(a), in the third step S6, 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. 8(b), the coordinate value 40 after the movement (shown in FIG. 8(a)) is updated as the coordinate value of the tread node 35. In this way, in the third step S6, each tread node 35 can be moved based on the movement amount M (shown in FIG. 8(a)).

In the third step S6 of this embodiment, as shown in FIG. 8(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 portion 22 to be further accelerated in the third step S6. The threshold value of the distance L1 can be set as appropriate, for example, depending on the required simulation accuracy.

Next, in the third step S6, a worn tire model 21 is constructed based on the element F(i) including the moved tread node 35 and the newly set tread node 35. In this embodiment, the edge 32 of the element F(i) is reset based on the moved tread node 35 and the newly set tread node 35. As a result, in the third step S6, a worn tire model 21 (shown in FIG. 8(b)) is set. The worn tire model 21 is input to the computer 1 (tire model input unit 5B) shown in FIG. 1.

Next, in the simulation method of this embodiment, the computer 1 updates the material properties based on the movement amount M (fourth step S7). In the fourth step S7, first, as shown in FIG. 1, the movement amount M (shown in FIG. 8(a)) of each tread node 35 inputted to the physical quantity input unit 5E is read into the working memory 4C. Furthermore, in the fourth step S7, the worn tire model 21 (shown in FIG. 8(b)) inputted to the tire model input unit 5B and the material property update unit 6J are read into the working memory 4C. Then, the material property update unit 6J is executed by the calculation unit 4A. FIG. 9 is a flowchart showing an example of the processing procedure of the fourth step S7.

The material properties to be updated are not particularly limited. In this embodiment, the material properties to be updated include the complex modulus of elasticity E* and the loss tangent tan δ.

In the fourth step S7 of this embodiment, first, at least one of the travel distance and the travel period of the tire 11 (shown in FIG. 2) is calculated based on the movement amount M (shown in FIG. 8(a)) of each tread node 35 (first calculation step S21). In this embodiment, the travel distance and the travel period are the distance or period that the tire 11 is estimated to have traveled until the shape of the tire 11 before wear shown in FIG. 2 becomes the shape of the currently worn tire model 21 (for example, shown in FIG. 8(b)). In the first calculation step S21 of this embodiment, the travel distance is calculated. FIG. 10 is a flowchart showing an example of the processing procedure of the first calculation step S21.

In the first calculation step S21 of this embodiment, first, a wear rate that defines the amount of wear of the tire 11 per unit travel distance is input to the computer 1 (step S41). The wear rate can be set appropriately. In step S41 of this embodiment, first, a vehicle equipped with the tire 11 (shown in FIG. 2) is driven a predetermined travel distance (km), and then the amount of wear (mm) from when the tire was new is measured. Then, as shown in the following formula, the amount of wear (mm) is divided by the travel distance (km) to obtain a wear rate (mm/km) that defines the amount of wear of the tire 11 per unit travel distance.
Wear rate (mm/km) = wear amount (mm) / mileage (km)

The amount of wear of the tire 11 can be measured as appropriate. For example, the amount of wear of the tire 11 can be determined by measuring the amount of wear at multiple locations (e.g., 3 to 10 locations) around the tire circumference of the center land portion 19A (shown in FIG. 2) and calculating the average of these amounts of wear. The amount of wear of the center land portion 19A can be easily determined, for example, by subtracting the groove depth of the center main groove 18A of the tire 11 after wear from the groove depth of the center main groove 18A of the tire 11 before wear.

In this embodiment, the wear rate is calculated based on the measurement results of the amount of wear of one tire 11, but the present invention is not limited to this. For example, the wear rate may be calculated based on the measurement results of the amount of wear of multiple tires 11 (shown in FIG. 2) having the same configuration. In this case, after the wear rates of the multiple tires 11 are calculated, the average of these wear rates can be specified as the wear rate. In this way, the wear rate is calculated from the measurement results of the amount of wear of the multiple tires 11, making it possible to take into account the wear rate of the tires 11, which tends to vary depending on the actual driving conditions of each tire 11. The wear rate is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the first calculation step S21 of this embodiment, the travel distance (km) of the tire 11 is calculated by dividing the movement amount (mm) by the wear rate (mm/km) as shown in the following formula (step S42).
Mileage (km) = Distance traveled (mm) / Wear rate (mm/km)

In this embodiment, the movement amount M (shown in FIG. 8(a)) obtained in the second step S5 is calculated based on the wear energy when the tire model 21 makes one rotation. On the other hand, the travel distance is the estimated distance traveled by the tire 11 until the shape of the tire 11 before wear shown in FIG. 2 becomes the shape of the current worn tire model 21 (for example, as shown in FIG. 8(b)). For this reason, the movement amount used in calculating the travel distance is the total value of the movement amount M calculated up to the current worn tire model 21 for each tread node 35 of the tire model 21 before wear shown in FIG. 6 (hereinafter, sometimes referred to as the "total movement amount N"). Note that when the original tread node 35 is deleted, the total value of the movement amount M of the deleted tread node 35 and the movement amount M of the new tread node 35 is used as the total movement amount N.

In addition, since the movement amount M (shown in FIG. 8A) determined in the second step S5 is calculated for each tread node 35, the total movement amount N (total value of the movement amount M) of each tread node 35 is also different. For example, if these total movement amounts N are divided by the wear rate, multiple travel distances are calculated for one tire 11. For this reason, in step S42 of the present embodiment, one movement amount is determined based on the total movement amount N of each tread node 35 so that one travel distance is calculated for one tire 11. This movement amount can be calculated, for example, as the average value, median value, minimum value, maximum value, etc. (average value in this example) of the total movement amount N of each tread node 35, and is treated as the wear amount (representative wear amount) of the actual tire 11 (shown in FIG. 2). In addition, the movement amount may be corrected taking into account the temperature and the rain rate.

In step S42, the amount of movement (in this example, the average value (mm) of the total amount of movement N of each tread node 35) is divided by the wear rate (mm/km) determined in step S41. As a result, in step S42, the distance (mileage) that the tire 11 is estimated to have traveled until the shape of the tire 11 before wear shown in FIG. 2 becomes the shape of the currently worn tire model 21 (for example, as shown in FIG. 8(b)) is calculated. The calculated tire mileage is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the fourth step S7 of this embodiment, the material properties that have changed over time are calculated based on at least one of the mileage and the running period of the tire 11 (second calculation step S22). In the second calculation step S22 of this embodiment, the material properties that have changed over time are calculated based on the mileage calculated in the first calculation step S21. FIG. 11 is a flowchart showing an example of the processing procedure of the second calculation step S22.

In the second calculation step S22 of this embodiment, first, the material property change rate of the tread rubber 12G of the tire 11 is input to the computer 1 (step S51). The material property change rate specifies the relationship between the material properties and at least one of the actual vehicle travel distance and the actual vehicle travel period of the tire (in this example, the actual vehicle travel distance). Figure 12 is a graph showing an example of the material property change rate. In Figure 12, the change rate of the complex elastic modulus E* is shown as a representative example.

In step S51 of this embodiment, first, multiple vehicles equipped with tires 11 (shown in FIG. 2) having the same configuration are driven so that the actual vehicle mileage differs from one another. After each vehicle has been driven, the material properties (including the complex elastic modulus E* and loss tangent tan δ in this example) of the tread rubber 12G shown in FIG. 2 are measured. Each tire 11 is mounted on the same type of vehicle under the same conditions (internal pressure, load, etc.).

The material properties (including the complex elastic modulus E* and loss tangent tan δ in this example) of the tread rubber 12G (shown in FIG. 2) of each tire 11 are measured under the same measurement conditions. For example, a known viscoelasticity tester (not shown) is used to measure the material properties in accordance with the provisions of JIS-K6394. As the viscoelasticity tester in this embodiment, a dynamic viscoelasticity measuring device "Eplexer 4000N" manufactured by Netzig Gabo is used. An example of the measurement conditions is as follows:
Initial distortion: 10%
Dynamic strain amplitude: ±1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70°C

Then, in step S51, the relationship between the actual vehicle travel distance and the material properties (i.e., the material property change rate) is obtained for the tread rubber 12G (shown in FIG. 2) of each tire 11. In this embodiment, the material property change rate including the complex elastic modulus E* and the loss tangent tan δ is obtained. In FIG. 12, the material property (complex elastic modulus E*) increases as the actual vehicle travel distance increases. The material property change rate is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the second calculation step S22 of this embodiment, the material properties that have changed over time are calculated based on at least one of the mileage and the mileage period, and the material property change rate (step S52). In step S52 of this embodiment, the material properties (complex modulus of elasticity E* in FIG. 12) are acquired at the actual vehicle mileage that matches the mileage calculated in the first calculation step S21, among the material property change rates shown in FIG. 12. The acquired material properties (including complex modulus of elasticity E* and loss tangent tan δ in this example) are identified as the material properties that have changed over time until the shape of the tire 11 before wear (shown in FIG. 2) becomes the shape of the currently worn tire model 21 (for example, shown in FIG. 8(b)). The identified material properties are input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the second calculation step S22 of this embodiment, the material properties of each element F(i) of the tire model 21 are updated (step S53). In step S53, the material properties (including the complex elastic modulus E* and the loss tangent tan δ in this example) of each element F(i) of the tread rubber model 22G of the currently worn tire model 21 are updated to the material properties calculated in step S52. The tire model 21 with the updated material properties is input to the computer 1 (tire model input unit 5B) shown in FIG. 1.

In this way, the simulation method (simulation device 1A) of this embodiment can update the material properties (including the complex modulus E* and loss tangent tan δ in this embodiment) based on the movement amount M (in this embodiment, the average value (mm) of the total movement amount N of each tread node 35). Therefore, in the simulation method (simulation device 1A) of this embodiment, the updated material properties are used, and the wear energy and movement amount M can be calculated with high accuracy in the first step S4 to the fourth step S7 that are performed next. As a result, in this embodiment, it is possible to accurately calculate the state of the tread contact surface 33 after wear.

Next, in the simulation method of this embodiment, the computer 1 judges whether or not a predetermined condition is satisfied (step S8). In step S8 of this embodiment, first, as shown in FIG. 1, the condition for terminating the simulation stored in the condition input unit 5F is read into the working memory 4C. Furthermore, in step S8, the judgment unit 6K is read into the working memory 4C. Then, the judgment unit 6K is executed by the calculation unit 4A.

The conditions can be set as appropriate, for example, the calculation end time and the amount of wear of the tread portion 22 shown in FIG. 8(b) (for example, total movement amount N, not shown). The conditions in this embodiment are input to the condition input unit 5F (shown in FIG. 1) before the simulation method is performed.

If it is determined in step S8 that the condition is satisfied ("Y" in step S8), the next step S9 is performed. On the other hand, if it is determined that the condition is not satisfied ("N" in step S8), the tire model 21 is redefined based on the worn tire model 21 and the updated material properties (step S1). Then, the computer 1 performs steps S2 to S8 (including the first step S4 to the fourth step S7) again. In this embodiment, the first step S4 to the fourth step S7 are repeatedly performed until the above condition is satisfied, so that the worn state of the rolling tread contact surface 33 can be simulated while updating the material properties. Note that, if the worn tire model 21 constructed in the third step S6 and whose material properties have been updated in the fourth step S7 is used as is, steps S1 to S3 may be omitted and the first step S4 to S8 may be repeatedly performed.

Next, in the simulation method of this embodiment, the computer 1 evaluates whether the condition of the tread contact surface 33 after wear is good or not (step S9). In step S9 of this embodiment, as shown in FIG. 1, the worn tire model 21 (for example, as shown in FIG. 8(b)) stored in the tire model input unit 5B is loaded into the working memory 4C. Furthermore, in step S9, the judgment unit 6K is loaded into the working memory 4C. Then, the judgment unit 6K is executed by the calculation unit 4A.

The evaluation criteria for whether the condition after wear is good or not can be set appropriately based on, for example, the amount of wear of the tread portion 22, the number of calculation steps (number of steps of wear progression) until a predetermined amount of wear is reached, etc. In this embodiment, for example, based on the description in JP2019-91302A, whether the condition after wear is good or not is evaluated based on the amount of uneven wear (heel-and-toe wear) of the block model (not shown) formed on the land model 29 shown in FIG. 5.

In step S9, if it is determined that the condition of the tread contact surface 33 after wear is good ("Y" in step S9), the tire 11 is manufactured based on the design drawing (CAD data) of the tire 11 shown in FIG. 2 (step S10). On the other hand, in step S9, if it is determined that the condition of the tread contact surface 33 after wear is not good ("N" in step S9), the tire 11 (shown in FIG. 2) is redesigned (step S11), and steps S1 to S9 are performed again. As a result, the simulation method of this embodiment (simulation device 1A (shown in FIG. 1)) can take into account material properties that change over time, so that the tire 11 shown in FIG. 2 in which the condition of the tread contact surface 20 after wear is good can be reliably designed.

The tire model 21, in which the state of the tread contact surface 33 after wear has been calculated, may be used, for example, by contacting or rolling on the road surface model 25 to calculate rolling resistance and to evaluate the shape of the contact surface, braking performance, drainage performance, etc. Based on these results, the tire 11 is designed (improved), making it possible to manufacture a tire 11 that can maintain good performance for a long period of time from when it is new.

In the previous embodiment, in the first calculation step S21 shown in FIG. 10, the travel distance of the tire is calculated by dividing the movement amount (in this example, the average value of the total movement amount N of each tread node 35) by the wear rate, but this is not limited to the above. For example, the travel distance (km) may be calculated by multiplying the total number of rotations (times) of the tire 11 by the circumference (mm) of the tire model 21. FIG. 13 is a flowchart showing an example of the processing procedure of the first calculation step S21 in another embodiment of the present invention. In this embodiment, the same components as those in the previous embodiment are given the same reference numerals and may not be described.

In this embodiment, in the first calculation step S21, the total number of revolutions of the tire 11 is calculated based on the amount of movement of each tread node 35 (revolution number calculation step S43). Figure 14 is a flowchart showing an example of the processing procedure of the revolution number calculation step S43.

In the rotation speed calculation step S43 of this embodiment, first, for the tread rubber 12G of the tire 11 shown in FIG. 2, a unit wear progression rate (mm/(J/m ² )) that specifies the wear amount per unit wear energy is input to the computer 1 (step S61). The unit wear progression rate can be calculated appropriately. In step S61 of this embodiment, a known wear tester is used to measure the wear amount and wear energy of the tread rubber 12G of the tire 11 that has rolled a predetermined distance. Then, as shown in the following formula, the wear amount (mm) of the tread rubber 12G is divided by the wear energy (J/m ² ) to calculate the unit wear progression rate (mm/(J/m ² )). The unit wear progression rate is input to the computer 1 (physical quantity input unit 5E).
Unit wear progression rate = wear volume/wear energy

Next, in the rotation number calculation step S43 of this embodiment, the wear energy progress rate ((J/ ^m2 )/time) that specifies the wear energy for one tire rotation is input to the computer 1 (step S62). The wear energy progress rate can be determined as appropriate. In this embodiment, the tire 11 is rotated at least once using the above-mentioned wear energy measuring device, and the wear energy for that one rotation (i.e., the wear energy progress rate) is measured. The wear energy progress rate is input to the computer 1 (physical quantity input unit 5E).

Next, in the rotation count calculation process S43 of this embodiment, the total number of tire rotations (times) is calculated by dividing the movement amount (mm) by the unit wear progression rate (mm/(J/ ^m2 )) and the wear energy progression rate ((J/ ^m2 )/time) as shown in the formula below (step S63).
Total number of revolutions = movement amount / unit wear progress rate / wear energy progress rate

The amount of movement can be determined as appropriate. As in the previous embodiments, the amount of movement in this embodiment is the average value (mm) of the total amount of movement N of each tread node 35 (shown in Figures 8(a) and (b)).

In step S63, first, the movement amount (average value (mm) of the total movement amount N of each tread node 35) is divided by the unit wear progression rate (mm/(J/ ^m2 )) as shown in the above formula. As a result, in step S63, the total wear energy required for the shape of the tire 11 before wear shown in FIG. 2 to change to the shape of the currently worn tire model 21 (for example, as shown in FIG. 8(b)) is calculated. Then, as shown in the above formula, the total wear energy (J/ ^m2 ) is divided by the wear energy progression rate ((J/ ^m2 )/time) to calculate the total number of rotations (times) of the tire 11. The total number of rotations is input to the computer 1 (physical quantity input unit 5E).

Next, in the first calculation step S21 of this embodiment, the total number of rotations (times) of the tire 11 is multiplied by the circumference (km/time) of the tire model 21 to calculate the mileage (km) (mileage calculation step S44). The circumference is specified as the distance traveled by the tire model when it rotates once. Such a circumference is not constant, and tends to be smaller when driving and larger when braking, for example. By calculating the mileage based on such a circumference, it is possible to calculate the mileage taking into account the rolling conditions of the tire 11, including driving and braking. FIG. 15 is a flowchart showing an example of the processing procedure of the mileage calculation step S44.

In the travel distance calculation step S44 of this embodiment, first, as shown in Fig. 4, the circumference of the tire model 21 is calculated based on at least one of the rolling speed V3 and the angular speed V1 of the tire model 21 (step S71). The rolling speed V3 (km/sec) of the tire model 21 is defined as the distance traveled per unit time (second). In this embodiment, as shown in the following formula, the rolling speed V3 (km/sec) is divided by the angular speed V1 (rad/sec) of the tire model 21, and the result is further multiplied by 2π (rad/cycle), thereby calculating the circumference of the tire model (km/cycle).
Circumference of tire model = rolling speed V3 / angular speed V1 x 2π

In step S71, the circumference may be calculated based on at least one of the most frequent rolling speed and angular velocity during the running of the tire 11. As a result, in step S71, the most frequent rolling speed V3 and angular velocity V1 are used among the constantly changing rolling speeds V3 and angular velocity V1, so that the running distance can be calculated with high accuracy. In addition, in the simulation method of this embodiment, when the state of the drive wheel after wear is calculated, the rolling speed V3 and angular velocity V1 when the driving force is generated are the most frequent. When the driving force is generated, air resistance and rolling resistance also act on the vehicle (not shown) on which the tire 11 shown in FIG. 2 is mounted. Therefore, by using such rolling speed V3 and angular velocity V1, the circumference (km/time) of the tire when the driving force is generated and when air resistance and rolling resistance act can be calculated with high accuracy.

Next, in a mileage calculation step S44 of this embodiment, the total number of tire revolutions calculated in the rotation number calculation step S43 is multiplied by the circumference of the tire model 21 calculated in step S71 to calculate the mileage of the tire 11 (step S72), as shown in the following formula.
Mileage (km) = Total number of revolutions (times) x circumference of tire model (km/time)

As a result, in the travel distance calculation step S44, the travel distance until the shape of the tire 11 before wear shown in FIG. 2 becomes the shape of the currently worn tire model 21 (for example, as shown in FIG. 8(b)) is calculated. The calculated travel distance of the tire is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

In the second calculation step S22 (shown in FIG. 11) of this embodiment, in step S52, the material properties (complex modulus of elasticity E*) at the actual vehicle travel distance that matches the travel distance calculated in step S72 (shown in FIG. 15) are obtained from the material property change rate shown in FIG. 12. The travel distance in this embodiment is calculated based on the rolling speed V3 and angular speed V1 that occur most frequently among the rolling speed V3 and angular speed V1 (shown in FIG. 4) that change from moment to moment, so that the material properties can be calculated with high accuracy.

In the second calculation step S22 of the embodiments described above, the aged material properties are calculated based on the mileage calculated in the first calculation step S21 (shown in FIG. 9), but the present invention is not limited to this. For example, in the second calculation step S22 (shown in FIG. 9), the aged material properties may be calculated based on the mileage calculated in the first calculation step S21. FIG. 16 is a flowchart showing an example of the processing procedure of the first calculation step S21 in yet another embodiment of the present invention. In this embodiment, the same components as in the embodiments described above are given the same reference numerals, and the description may be omitted.

In the first calculation step S21 of this embodiment, the actual vehicle distance rate (km/year) that defines the distance traveled per unit period of the tire 11 is input to the computer 1 (step S45). Step S45 of this embodiment is performed after the above-mentioned steps S41 and S42.

The actual vehicle distance rate can be set appropriately. In step S45 of this embodiment, first, the travel distance (km) of a vehicle (not shown) equipped with the tire 11 (shown in FIG. 2) is measured when the vehicle is driven for a predetermined driving period (years). Then, as shown in the following formula, the travel distance (km) is divided by the driving period (years) to obtain the actual vehicle distance rate (km/year) that specifies the travel distance of the tire 11 per unit period.
Actual vehicle distance rate = distance traveled / driving period

In this embodiment, the actual vehicle distance rate is calculated based on the travel distance of one vehicle (not shown), but this is not limited to the above. For example, the actual vehicle distance rate may be calculated based on the travel distance of multiple vehicles. In this case, after the actual vehicle distance rates of multiple vehicles are calculated, the average of these actual vehicle distance rates may be specified as the actual vehicle distance rate. The actual vehicle distance rate is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the first calculation step S21 of this embodiment, the running period of the tire 11 (shown in FIG. 2) is calculated based on the running distance (km) calculated in step S42 (step S46). In step S46, as shown in the following formula, the running period of the tire 11 is calculated by dividing the running distance (km) calculated in step S42 by the actual vehicle distance rate (km/year) obtained in step S45. The running period is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.
Driving period (years) = mileage (km) / actual vehicle distance rate (km/year)

Figure 17 is a flow chart showing an example of the processing procedure of the second calculation step S22 of this embodiment. In the second calculation step S22 of this embodiment, a material change rate that specifies the relationship between the actual vehicle running period of the tire 11 and the material properties is input to the computer 1 (step S54). Figure 18 is a graph showing an example of a material property change rate of another embodiment of the present invention. In Figure 18, the change rate of the complex elastic modulus E* is shown as a representative example.

In step S54 of this embodiment, first, multiple vehicles equipped with tires 11 (shown in FIG. 2) having the same configuration are driven for different driving periods. Then, the material properties (including the complex elastic modulus E* and loss tangent tan δ in this example) of the tread rubber 12G shown in FIG. 2 are measured. Each tire 11 is mounted on the same type of vehicle under the same conditions (internal pressure, load, etc.).

The material properties can be measured using the same procedures as in the previous embodiments. Then, in step S54, the relationship between the actual vehicle running period and the material properties (i.e., the material property change rate) is obtained for these tread rubbers 12G. In this embodiment, the material property change rate including the complex elastic modulus E* and the loss tangent tan δ is obtained. In FIG. 18, the material property (complex elastic modulus E*) increases as the actual vehicle running period increases. The material property change rate is input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1.

Next, in the second calculation step S22 of this embodiment, the material properties (complex modulus of elasticity E* in FIG. 18) during the actual vehicle running period that coincides with the running period calculated in step S46 (shown in FIG. 16) are calculated (step S55) from among the material property change rates shown in FIG. 18. The acquired material properties are identified as the material properties that have changed over time since the product was new. The identified material properties are input to the computer 1 (physical quantity input unit 5E) shown in FIG. 1. Then, in step S53, the material properties identified in step S55 are updated as the material properties of each element F(i) of the tread rubber model 22G of the tire model 21.

In this embodiment, even if the material change rate shown in FIG. 12 (which specifies the relationship with the actual vehicle driving distance) cannot be obtained, the material change rate shown in FIG. 18 (which specifies the relationship with the actual vehicle driving period) is used, and the material properties that have changed over time can be obtained from the calculated driving period.

In the above embodiment, the material properties of each element F(i) of the tread rubber model 22G shown in FIG. 8(b) are updated, but the present invention is not limited to this. For example, the material properties of each element F(i) of other rubber models 21G such as the sidewall rubber model 23G, the carcass ply model 41, and the belt ply models 41A and 41B may be updated. In this case, for each component of the tire 11 (shown in FIG. 2) whose material properties are updated, the material property change rate, for example, as shown in FIG. 12 and FIG. 18, is obtained.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways.

The state of the tire tread contact surface after wear was calculated based on the processing procedure shown in Figure 3 (Examples 1 and 2). In Examples 1 and 2, the material properties of the elements of the tire model were updated based on the amount of movement of the tread nodes based on the processing procedure shown in Figures 9 to 11. Then, in Examples 1 and 2, steps 1 to 4 were repeated until the predetermined conditions were met.

Figure 19 is a graph showing the relationship between the actual vehicle mileage and material properties. As shown in Figure 19, the tire model of Example 1 was defined with a tread rubber that had a smaller rate of change in material properties than the tire model of Example 2.

For comparison, the state of the tread contact surface of the tire after wear was calculated based on the description of JP 2019-91302 A (Comparative Example). In the Comparative Example, similar to Examples 1 and 2, the first to fourth steps were repeatedly performed until the predetermined conditions were satisfied. In the Comparative Example, the state of the tread contact surface after wear was calculated without taking into account the change in material properties over time (i.e., the material property change rate was zero), as shown in FIG. 19. The common specifications are as follows.
Tire size: 215/55R17
Rim size: 17x7J
Internal pressure: 230kPa
Load: 3.51kN

Figure 20 is a graph showing the relationship between the amount of wear and the distance traveled. As shown in Figure 20, in Examples 1 and 2, the calculated state of wear was earlier than in the Comparative Example, which does not take into account the change over time in the material properties. The state after wear in Examples 1 and 2 shows the same tendency as an actual tire. Therefore, in Examples 1 and 2, the state after wear of the tire tread contact surface could be calculated more accurately than in the Comparative Example.

As shown in FIG. 19, the tire model of Example 1 defines tread rubber with a smaller rate of change in material properties compared to the tire model of Example 2, and therefore, as shown in FIG. 20, Example 1 was able to calculate a smaller amount of wear relative to the distance traveled compared to Example 2. In this way, Example 1 and Example 2 were able to appropriately take into account the difference in the change over time in the material properties of the tread rubber, and therefore were able to accurately calculate the state of the tire tread contact surface after wear.

S4 First step S5 Second step S6 Third step S7 Fourth step

Claims (11)

A tire simulation method for calculating a state of a tire tread contact surface after wear, comprising the steps of:
inputting a tire model into a computer by discretizing the tire using a finite number of elements having a plurality of nodes and having predetermined material properties defined therein;
The computer,
a pre-processing step of calculating said tire model during rolling;
a first step of calculating a physical quantity associated with wear of the tread contact surface for a plurality of tread nodes constituting the tread contact surface of the tire model among the nodes;
a second step of determining a movement amount for representing wear of each of the tread nodes based on the physical quantity;
a third step of moving each of the tread nodes based on the movement amount;
and a fourth step of updating the material properties based on the amount of movement .
The rolling conditions of the tire model include driving and braking,
The circumference of the tire model includes a circumference during driving and a circumference during braking that is greater than the circumference during driving,
The fourth step includes a first calculation step of calculating at least one of a travel distance of the tire based on the movement amount and a travel period based on the travel distance;
and a second calculation step of calculating the aged material properties based on at least one of the mileage and the duration of the run,
the first calculation step includes a step of calculating a total number of rotations of the tire based on the movement amount;
and calculating the travel distance based on the total number of rotations of the tire, the circumference during driving, and the circumference during braking.
How to simulate tires.
The tire simulation method according to claim 1, wherein the computer repeatedly performs the first step through the fourth step until a predetermined condition is satisfied. The first calculation step includes inputting a wear rate that defines a wear amount of the tire per unit traveling distance into the computer;
3. The tire simulation method according to claim 1, further comprising the step of: calculating the travel distance by dividing the amount of movement by the wear rate.
The tire simulation method according to claim 3 , wherein the wear rate is specified by an average value of wear rates of a plurality of tires having the same configuration .
5. The tire simulation method according to claim 1, wherein the step of calculating the traveled distance calculates the traveled distance by multiplying a total number of rotations of the tire by a circumference of the tire model including the circumference during driving and the circumference during braking .
The step of calculating the total number of rotations of the tire includes inputting a unit wear growth rate, which defines a wear amount per unit wear energy, for a tread rubber of the tire into the computer;
inputting a wear energy progress rate that defines the wear energy for one rotation of the tire into the computer;
6. The tire simulation method according to claim 1, further comprising the step of: calculating a total number of rotations of the tire by dividing the amount of movement by the unit wear progression rate and the unit wear energy progression rate.
7. The tire simulation method according to claim 1 , wherein the step of calculating the traveled distance includes the step of calculating the circumference based on at least one of a rolling speed and an angular velocity of the tire model.
The tire simulation method according to claim 7, wherein the step of calculating the circumference calculates the circumference based on at least one of the rolling speed and the angular velocity that is most frequent while the tire is running. The first calculation step includes inputting an actual vehicle distance rate that defines a travel distance of the tire per unit period into the computer;
9. The tire simulation method according to claim 1 , further comprising the step of calculating the driving period by dividing the driving distance by the actual vehicle distance rate.
The second calculation step includes inputting a material property change rate for a tread rubber of the tire, the change rate defining a relationship between at least one of an actual vehicle running distance and an actual vehicle running period of the tire and the material property, into the computer;
10. The tire simulation method according to claim 1 , further comprising a step of calculating the material characteristics that have changed over time based on at least one of the travel distance and the travel period, and the material characteristic change rate.
A simulation device having a processor for calculating a state of a tire tread surface after wear,
The arithmetic processing device includes a tire model acquisition unit that acquires a tire model by discretizing the tire using a finite number of elements having a plurality of nodes and having predetermined material properties defined therein;
A rolling motion calculation unit for calculating the rolling motion of the tire model;
a physical quantity calculation unit that calculates a physical quantity associated with wear of the tread contact surface for a plurality of tread nodes that constitute the tread contact surface of the tire model among the nodes;
a movement amount determination unit that determines a movement amount for expressing wear of each of the tread nodes based on the physical quantity;
a moving unit that moves each of the tread nodes based on the movement amount;
a material property update unit that updates the material property based on the movement amount ,
The rolling conditions of the tire model include driving and braking,
The circumference of the tire model includes a circumference during driving and a circumference during braking that is greater than the circumference during driving,
a first calculation step of calculating at least one of a travel distance of the tire based on the movement amount and a travel period based on the travel distance;
A second calculation step of calculating the material properties that have changed over time based on at least one of the mileage and the running period;
the first calculation step includes a step of calculating a total number of rotations of the tire based on the movement amount;
and calculating the travel distance based on the total number of rotations of the tire, the circumference during driving, and the circumference during braking.
Tire simulation device.

Images