How to design pneumatic tires

Abstract

To provide a method for designing a pneumatic tire capable of reducing strain at inflating.SOLUTION: A method for designing a pneumatic tire reinforced with a cord ply includes: a step S1 for entering a tire model before inner pressure filling, including a cord ply model modeling a cord ply; a step S2 for defining a first parameter for the cord ply model to suppress expansion deformation of the cord ply model at a calculation of the inner pressure filling of the tire model by a computer; a step S3 for entering an inner pressure condition for filling the tire model; a step S4, in which the computer calculates a balanced shape of the tire model on the basis of the first parameter and the inner pressure condition, and a step S5 for outputting the balanced shape of the tire model.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for designing a pneumatic tire.

Background Art

[0002] Patent Document 1 below describes a method for designing a pneumatic tire. In this method, a step of determining design variables that determine a tire cross-sectional shape or a tire structure, a step of obtaining values of the design variables that give an optimal value of an objective function while considering constraint conditions, and a step of designing a tire based on the design variables that give the optimal value of the objective function are performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, in the above optimization method, by increasing the degree of freedom of design variables, pneumatic tires of various shapes can be created. However, when the degree of freedom of design variables increases, there may be cases where pneumatic tires having a distorted shape significantly deviated from the equilibrium shape are created. Such pneumatic tires have a problem that the distortion during inflation becomes large and is disadvantageous in terms of durability.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object is to provide a method capable of designing a pneumatic tire capable of reducing distortion during inflation.

Means for Solving the Problems

[0006] This disclosure relates to a method for designing a pneumatic tire reinforced with a code ply, comprising the steps of: inputting a pre-pressurized tire model, including a code ply model that models the code ply, into a computer; defining a first parameter for the code ply model so as to suppress expansion deformation of the code ply model when the computer calculates the internal pressure of the tire model; inputting internal pressure conditions for filling the tire model into the computer; the computer calculating the equilibrium shape of the tire model based on the first parameter and the internal pressure conditions; and outputting the equilibrium shape of the tire model. [Effects of the Invention]

[0007] The tire design method described herein, by employing the above-described process, makes it possible to design a pneumatic tire that can reduce deformation during inflation. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing a computer for executing a design method for pneumatic tires. [Figure 2] This is a cross-sectional view showing a pneumatic tire. [Figure 3] (a) is a partial perspective view showing the carcass ply, and (b) is a partial perspective view showing the belt ply. [Figure 4] This is a flowchart showing the processing steps for designing pneumatic tires. [Figure 5] This is a cross-sectional view showing a tire model before internal pressure filling. [Figure 6] This is a disassembled perspective view of a carcass-ply model. [Figure 7] This is an exploded perspective view of the belt ply model. [Figure 8] This flowchart shows the processing steps for the equilibrium shape calculation process. [Figure 9] This is a cross-sectional view showing the balanced shape of the tire model. [Figure 10] This is a diagram showing the resulting equilibrium shape. [Figure 11] This flowchart shows the processing steps for the equilibrium shape calculation process of another embodiment of the present disclosure. [Figure 12] This flowchart shows a design method for yet another embodiment of the present disclosure. [Figure 13] This graph shows the relationship between the internal pressure of the tire model and the amount of deformation of the tire model (maximum tire width, tire outer diameter). [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described below with reference to the drawings. It should be understood that the drawings contain exaggerations and representations that differ from the actual structural proportions in order to aid in understanding the content of the disclosure. Furthermore, the same or common elements are denoted by the same reference numerals throughout each embodiment, and redundant explanations are omitted. Moreover, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the content of this disclosure, and this disclosure is not limited to the specific configurations shown.

[0010] The design method for a pneumatic tire of this embodiment (hereinafter sometimes simply referred to as the "design method") designs a pneumatic tire reinforced with cord ply. A computer is used in the design method of this embodiment.

[0011] [computer] Figure 1 is a perspective view showing a computer for executing a design method for pneumatic tires. The computer 1 consists of a main unit 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main unit 1a is equipped with, for example, a processing unit (CPU), ROM, working memory, a storage device such as a magnetic disk, and disk drive devices 1a1 and 1a2. The storage device also has software for executing the design method of this embodiment pre-stored in it.

[0012] [Pneumatic Tire] FIG. 2 is a cross-sectional view showing a pneumatic tire (hereinafter sometimes simply referred to as "tire") 2. The tire 2 of the present embodiment is configured, for example, as a heavy-duty tire. Note that it is not limited to a heavy-duty tire, and it may be configured as, for example, a passenger car tire, a motorcycle tire, or the like.

[0013] The tire 2 includes a cord ply 3. The cord ply 3 of the present embodiment includes a carcass ply 6P and a belt ply 7P. Note that the cord ply 3 may be, for example, only one of the carcass ply 6P and the belt ply 7P, or may further include other cord plies (for example, a band ply (not shown) etc.).

[0014] The carcass ply 6P of the present embodiment constitutes a carcass 6. The carcass 6 of the present embodiment extends from the tread portion 2a through the sidewall portion 2b to the bead core 5 of the bead portion 2c and is formed in a toroidal shape. The carcass 6 is composed of at least one, and in this embodiment, one carcass ply 6P.

[0015] FIG. 3(a) is a partial perspective view showing the carcass ply 6P. The carcass ply 6P of the present embodiment includes a carcass cord 11 and a topping rubber 12 covering the carcass cord 11. The carcass cords 11 are arranged at an angle θ1 of, for example, 70 to 90 degrees with respect to the tire equator C. As the carcass cord 11, for example, an organic fiber cord such as polyester, nylon, rayon, or aramid is adopted.

[0016] As shown in FIG. 2, the belt ply 7P of the present embodiment constitutes a belt layer 7. The belt layer 7 of the present embodiment is arranged on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2a. The belt layer 7 of the present embodiment is composed of four belt plies 7P, but is not limited to such a mode.

[0017] Figure 3(b) is a partial perspective view showing the belt ply 7P. The belt ply 7P of this embodiment is composed of belt cords 13 and a topping rubber 14 covering the belt cords 13. The belt cords 13 of this embodiment are arranged at an angle θ2 of, for example, 10 to 60 degrees with respect to the circumferential direction of the tire. The orientation of the belt cords 13 can be appropriately set for each belt ply 7P. As the belt cords 13, for example, highly elastic organic fiber cords such as aramid or rayon, or steel cords can be used.

[0018] As shown in Figure 2, the tire 2 includes a rubber portion 15. In this embodiment, the rubber portion 15 includes, for example, a tread rubber 15a, a sidewall rubber 15b, an inner liner rubber 15c, a bead apex rubber 15d, and a clinch rubber 15e.

[0019] The tread rubber 15a is located on the radially outer side of the belt layer 7. The sidewall rubber 15b is located on the axially outer side of the carcass 6. The inner liner rubber 15c is located on the inside of the carcass 6. The bead apex rubber 15d extends radially outward from the bead core 5. The clinch rubber 15e is located on the axially outer side of the bead portion 2c.

[0020] Incidentally, in the above-mentioned Patent Document 1, for example, a tire 2 (shown in Figure 2, for example) is designed based on an optimization method. In such a method, tire 2 is designed based on design variables that can give the optimal value of a predetermined objective function. However, if the degree of freedom of the design variables is set high, although it is possible to create tires of various shapes that have design factors that satisfy the objective function, it is possible to create tires that have a distorted shape that is far removed from the equilibrium shape. Such tires have the problem that the distortion during inflation (when the internal pressure is filled) is large and is disadvantageous in terms of durability. Here, "equilibrium shape" is the shape of an air-filled tire that is in balance with the internal pressure being filled.

[0021] On the other hand, it is also conceivable to obtain the shape obtained by filling the designed tire 2 with internal pressure as the equilibrium shape of tire 2 before internal pressure filling. However, since such an equilibrium shape reflects the shape of the code ply 3 that has expanded and deformed due to internal pressure filling, there is a problem that the design factors of the code ply 3 obtained by the optimization method (satisfying the objective function) are changed. Furthermore, when internal pressure is filled into tire 2 before internal pressure filling, which reflects the shape of the expanded and deformed code ply 3, there is also the problem that the strain of the code ply 3 increases.

[0022] [Design method for pneumatic tires (first embodiment)] In this embodiment, the design method produces a tire 2 that can reduce deformation during inflation. Figure 4 is a flowchart showing the processing steps of the design method for a pneumatic tire.

[0023] [Enter tire model before internal pressure filling] In the design method of this embodiment, first, a tire model before internal pressure filling is input to the computer 1 (shown in Figure 1) (step S1). The tire model of this embodiment includes a code ply model that models the code ply 3 (shown in Figure 2). Figure 5 is a cross-sectional view showing the tire model 21 before internal pressure filling. Figure 6 is an exploded perspective view of the carcass ply model 26. Figure 7 is an exploded perspective view of the belt ply model 27.

[0024] In this embodiment, the tire model 21 is modeled based on a prototype tire (not shown) in which the profile of the tire components, including the code ply 3 (shown in Figure 2), has not yet been determined. The prototype tire has a structure similar to the tire 2 shown in Figure 2. Furthermore, the prototype tire in this embodiment is designed in a state before internal pressure filling.

[0025] The prototype tire (not shown) may be designed based on an optimization method such as that described in Patent Document 1, or it may be designed using general CAD or other software. Examples of optimization methods include genetic algorithms (GA) and particle swarm optimization (PSO). In this embodiment, a prototype tire is designed based on an optimization method, having design factors that satisfy a predetermined objective function (e.g., longitudinal spring constant and transverse spring constant).

[0026] In step S1 of this embodiment, a prototype tire (not shown) is discretized using a finite number of elements F(i) (i=1, 2, ...) and elements G(i) (i=1, 2, ...). This allows for the modeling of the tire model 21.

[0027] In this embodiment, the tire model 21 is defined as a three-dimensional model. However, the tire model 21 is not limited to a three-dimensional model and may also be defined as a two-dimensional model. For modeling the tire model 21, meshing software (for example, Hypermesh from Altair) is used, similar to conventional simulation methods.

[0028] Elements F(i) and G(i) can be processed using numerical analysis methods. Appropriate numerical analysis methods such as the finite element method, finite volume method, difference method, or boundary element method can be used, but in this embodiment, the finite element method is employed. Each element F(i) and G(i) is provided with multiple nodes 22. Numerical data such as the element number, node 22 number, node 22 coordinate value, and material properties (e.g., density) are defined for each such element F(i) and G(i).

[0029] As shown in Figure 5, the tire model 21 of this embodiment includes a code ply model 23 that models the code ply 3 (shown in Figure 2) and a rubber model 25 that models the rubber portion 15 (shown in Figure 2). Furthermore, the tire model 21 of this embodiment includes a bead core model 28 that models the bead core 5 (shown in Figure 2).

[0030] The rubber model 25 of this embodiment includes a tread rubber model 25a, a sidewall rubber model 25b, an inner liner rubber model 25c, a bead apex rubber model 25d, and a clinch rubber model 25e.

[0031] The rubber model 25 and bead core model 28 in this embodiment are modeled using element F(i). For example, if the tire model 21 is two-dimensional, triangular elements or quadrilateral elements suitable for representing complex shapes are used as element F(i). If the tire model 21 is three-dimensional, it is preferable to use tetrahedral solid elements, pentahedral solid elements, or hexahedral solid elements.

[0032] The code ply model 23 of this embodiment includes a carcass ply model 26 that models the carcass ply 6P and a belt ply model 27 that models the belt ply 7P.

[0033] As shown in Figure 6, the carcass ply model 26 of this embodiment is composed of a carcass cord model 31 and topping rubber models 32, 32.

[0034] The carcass code model 31 is a model of the carcass code array 11 shown in Figure 3(a) using a finite number of elements G(i). For example, the elements G(i) can be membrane elements or shell elements that can define the strength anisotropy along the longitudinal direction of the carcass code 11, and in this embodiment, membrane elements are used.

[0035] Element G(i) defines, for example, the physical quantities of the carcass code 11 shown in Figure 3(a) (e.g., tensile stiffness) and the angle θ1 with respect to the tire equator C. This allows the carcass code model 31 to reproduce the arrangement of the carcass code 11.

[0036] The topping rubber models 32, 32 are models of the topping rubber 12 of the carcass ply 6P in Figure 3(a) using a finite number of elements F(i). The carcass ply model 26 is formed by integrally fixing these topping rubber models 32, 32 to both sides (inside and outside) of the carcass cord model 31.

[0037] As shown in Figure 7, the belt ply model 27 of this embodiment is composed of a belt cord model 33 and topping rubber models 34, 34. In Figure 7, two of the four belt plies 7P shown in Figure 2 are represented by the belt ply models 27, 27.

[0038] The belt cord model 33 is a model of the belt cord array 13 shown in Figure 3(b) using a finite number of elements G(i). The elements G(i) can be, for example, membrane elements or shell elements that can define the strength anisotropy along the longitudinal direction of the belt cord 13; in this embodiment, membrane elements are used.

[0039] Element G(i) defines, for example, the physical quantities of the belt cord 13 shown in Figure 3(b) (e.g., tensile stiffness) and the angle θ2 with respect to the tire circumferential direction. This allows the belt cord model 33 to reproduce the arrangement of the belt cord 13.

[0040] The topping rubber models 34, 34 are models of the topping rubber 14 of the belt ply 7P shown in Figure 3(b) using a finite number of elements F(i). The belt ply model 27 is formed by integrally fixing these topping rubber models 34, 34 to both sides (inside and outside) of the belt cord model 33.

[0041] In step S1 of this embodiment, the tire model 21 is set up by modeling the rubber model 25, the cord ply model 23 (carcass ply model 26 and belt ply model 27), and the bead core model 28, respectively.

[0042] In this embodiment, the tire model 21 (i.e., the prototype tire) has a distorted shape that deviates significantly from the equilibrium shape, with a portion of the sidewall 21b recessed inward in the tire axial direction before internal pressure is filled. However, the tire model 21 is not limited to this shape. The tire model 21 is stored in the computer 1 (shown in Figure 1).

[0043] [Define the first parameter] Next, in the design method of this embodiment, a first parameter is defined for the code ply model 23 (shown in Figures 5-7) (step S2). The first parameter is for suppressing the expansion deformation of the code ply model 23 during the internal pressure filling calculation of the tire model 21 by the computer 1 (shown in Figure 1) (equilibrium shape calculation step S4 described later). In this embodiment, the expansion deformation of the carcass ply model 26 and the belt ply model 27 is suppressed.

[0044] The first parameter can be defined as appropriate, provided that the expansion deformation of the Codeply model 23 (shown in Figures 5 to 7) is suppressed. In this embodiment, the first parameter includes the tensile stiffness of the Codeply model 23, which is set to a value greater than the tensile stiffness of the Codeply 3 (shown in Figures 2 and 3). With such tensile stiffness, in this embodiment, a larger tensile stress can be calculated in the Codeply model 23 than in the actual Codeply 3 (shown in Figure 2) for the tensile force acting on the Codeply model 23 during the internal pressure filling calculation. Therefore, the expansion deformation of the Codeply model 23 can be suppressed.

[0045] In this embodiment, the tensile stiffness defined for each element G(i) of the carcass cord model 31 shown in Figure 6 is set to be greater than (for example, 10 to 100 times) the tensile stiffness of the actual carcass cord 11 (shown in Figure 3(a)). Furthermore, the tensile stiffness defined for each element G(i) of the belt cord model 33 shown in Figure 7 is set to be greater than (for example, 10 to 100 times) the tensile stiffness of the actual belt cord 13 (shown in Figure 3(b)). This suppresses the expansion deformation (for example, elongation in the circumferential direction of the tire) of the carcass ply model 26 and the belt ply model 27.

[0046] The first parameter of this embodiment may include the angle θ2 of the belt cord 13 of the belt cord model 33 (shown in Figure 7), which is set to be smaller (for example, 0 to 10 degrees) than the angle θ2 of the belt cord 13 with respect to the tire circumferential direction shown in Figure 3(b). Such an angle θ2 can enhance the binding effect of the belt ply model 27 compared to the belt ply 7P (shown in Figures 2 and 3), and can suppress the expansion deformation of the belt ply model 27 (tire model 21).

[0047] As the first parameter, only one of the following may be defined: the tensile stiffness of the cord ply model 23 (shown in Figures 5-7) and the angle θ2 of the belt cord model 33 shown in Figure 7, or both may be defined. In this embodiment, all of these first parameters are defined. Furthermore, other parameters capable of suppressing the expansion deformation of the cord ply model 23 may be defined as first parameters. The first parameters are input to computer 1 (shown in Figure 1).

[0048] [Enter internal pressure conditions] Next, in the design method of this embodiment, the internal pressure conditions for filling the tire model 21 are input into the computer 1 (shown in Figure 1) (step S3). The internal pressure conditions are not particularly limited as long as the equilibrium shape of the tire model 21 (shown in Figure 5) can be calculated. The internal pressure conditions in this embodiment include the normal internal pressure (maximum internal pressure) defined in the standard system on which the tire is based.

[0049] The standard internal pressure (maximum internal pressure) is "Maximum Air Pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. The internal pressure conditions (standard internal pressure) are entered into Computer 1 (shown in Figure 1).

[0050] [Calculating the equilibrium shape of the tire model (equilibrium shape calculation process)] Next, in the design method of this embodiment, the computer 1 (shown in Figure 1) calculates the equilibrium shape of the tire model 21 shown in Figure 5 based on the first parameter and the internal pressure conditions (equilibrium shape calculation step S4). The equilibrium shape of the tire model 21 can be calculated as appropriate based on the first parameter and the internal pressure conditions. Figure 8 is a flowchart showing the processing procedure of the equilibrium shape calculation step S4.

[0051] [Constrain the bead core model] In the equilibrium shape calculation step S4 of this embodiment, first, the bead core model 28 of the tire model 21 is constrained so that it cannot move (step S41). The constraints on the bead core model 28 can be set as appropriate. In step S41 of this embodiment, the coordinate values ​​of each element F(i) constituting the bead core model 28 in the computation space where the simulation is performed (for example, a space defined by a Cartesian coordinate system of the x, y, and z axes) are fixed. This constrains the bead core model 28 so that it cannot move. The tire model 21 with the constrained bead core model 28 is input to the computer 1 (shown in Figure 1).

[0052] [Calculate equilibrium shape] Next, in the equilibrium shape calculation step S4 of this embodiment, the equilibrium shape of the tire model 21 is calculated after the bead core model 28 is constrained (step S42). In step S42 of this embodiment, a first parameter is defined for the code ply model 23. Next, in step S42 of this embodiment, a uniformly distributed load w corresponding to the internal pressure condition is defined over the entire inner surface 21i of the tire model 21. As a result, in step S42, the deformation of the tire model 21 based on the internal pressure condition (uniformly distributed load w) is calculated.

[0053] The deformation calculation of the tire model 21 is performed by creating mass matrices, stiffness matrices, and damping matrices for each element F(i) and G(i) based on the shape and material properties of each element F(i) and G(i). Furthermore, these matrices are combined to create a matrix for the entire system. Then, computer 1 (shown in Figure 1) applies the various conditions to create equations of motion and performs deformation calculations of the tire model 21 at each unit time T(x) (x=0, 1, ...) of the simulation.

[0054] The deformation calculations can be performed using commercially available finite element analysis application software, such as ABAQUS from Dassault Systems. The unit time T(x) can be set appropriately depending on the required simulation accuracy.

[0055] In step S42 of this embodiment, deformation calculations of the tire model 21 are performed until equilibrium is achieved with the internal pressure conditions (uniformly distributed load w). In this embodiment, since the bead core models 28, 28 are constrained to be immovable, the positions of the bead portions 21c, 21c of the tire model 21 before internal pressure filling are maintained. This allows the equilibrium shape 29 of the tire model 21 to be calculated. Figure 9 is a cross-sectional view showing the equilibrium shape 29 of the tire model 21.

[0056] In this embodiment, the equilibrium shape 29 of the tire model 21 is calculated, causing the portion of the sidewall 21b shown in Figure 5 that is recessed inward in the tire axial direction to be pushed outward in the tire axial direction. This eliminates the distorted shape of the tire model 21.

[0057] Furthermore, in this embodiment, the expansion deformation of the code ply model 23 (shown in Figures 5-7) is suppressed by the first parameter (for example, the length in the circumferential direction of the tire is fixed), thereby suppressing the outer diameter growth of the tire model 21 due to internal pressure filling.

[0058] Thus, in the equilibrium shape calculation step S4 of this embodiment, it is possible to calculate the equilibrium shape 29 of the tire model 21, which has been freed from distorted shapes, while suppressing outer diameter growth due to internal pressure filling (increase in tire outer diameter D1 shown in Figure 5). Since the expansion deformation of the code ply model 23 and the outer diameter growth of the tire model 21 are suppressed, such an equilibrium shape 29 can be obtained as the equilibrium shape of the tire model 21 (designed tire 2) before internal pressure filling.

[0059] In this embodiment, the bead core models 28, 28 are constrained, maintaining the position of the bead portions 21c, 21c of the tire model 21 before internal pressure filling. This prevents the movement of the bead portions 21c, 21c in the tire axial direction due to internal pressure filling from being reflected in the equilibrium shape (equilibrium shape before internal pressure filling) 29. The tire model 21 (equilibrium shape 29) is stored in the computer 1 (shown in Figure 1).

[0060] [Output the balanced shape of the tire model] Next, in the design method of this embodiment, the computer 1 (shown in Figure 1) outputs the balanced shape 29 of the tire model 21 (step S5). The balanced shape 29 of the tire model 21 may be output as appropriate. The balanced shape 29 of the tire model 21 in this embodiment may be displayed on the display device 1d (shown in Figure 1) or printed on a printer or the like. This allows the balanced shape 29 of the tire model 21 to be recognized by an operator or the like through the above output.

[0061] Figure 10 shows the outputted equilibrium shape 29. The outputted equilibrium shape 29 includes, for example, the profile 29a of the tire model 21 shown in Figure 9, the profile 29b of the carcass ply model 26, and the profile 29c of the belt ply model 27. In this embodiment, elements F(i) and G(i) shown in Figure 9 are omitted, but elements F(i) and G(i) may be displayed along with profiles 29a to 29c. The equilibrium shape 29 may also include profiles (not shown) of other tire components shown in Figure 9 (for example, the bead core model 28 and the bead apex rubber model 25d).

[0062] Next, in the design method of this embodiment, the computer 1 (shown in Figure 1) determines whether the equilibrium shape 29 of the tire model 21 is good or not (step S6). The determination of whether the equilibrium shape 29 is good or not can be performed as appropriate. For example, the determination of whether the equilibrium shape 29 is good or not can be made based on physical quantities obtained by performing a conventional rolling simulation using the tire model 21 with an equilibrium shape.

[0063] In step S6, if it is determined that the equilibrium shape 29 is good (Yes in step S6), the next step S7 is performed. On the other hand, if it is determined that the equilibrium shape 29 is not good (No in step S6), at least some of the design factors of the tire 2 (shown in Figure 2) are changed (step S8), and steps S1 to S6 are performed again. As a result, the design method of this embodiment makes it possible to obtain the equilibrium shape 29 of a tire model 21 with desired performance while reducing distortion during inflation.

[0064] [Designing the shape of a pneumatic tire] Next, in the design method of this embodiment, the computer 1 (shown in Figure 1) designs the shape of the tire before internal pressure filling based on the equilibrium shape 29 of the outputted tire model 21 (step S7). In this embodiment, the equilibrium shape 29 of the tire model 21 is obtained as the shape of the tire 2 before internal pressure filling.

[0065] The shape of tire 2 before internal pressure filling can be designed as appropriate. In this embodiment, the profile of tire 2 (including the carcass ply 6P and belt ply 7P shown in Figure 2) before internal pressure filling is designed based on the equilibrium shape 29 (profiles 29a to 29c) of tire model 21 shown in Figure 10. The shape of tire 2 before internal pressure filling can be designed, for example, using software such as CAD based on the coordinate values ​​of the equilibrium shape 29 of tire model 21. This makes it possible to design a tire 2 that can reduce distortion during inflation (improving durability).

[0066] The shape of tire 2 before internal pressure filling is used, for example, in the design of the vulcanization mold for tire 2. This makes it possible to manufacture tire 2 that can reduce distortion during inflation (improving durability).

[0067] In the design method of this embodiment, in the equilibrium shape calculation step S4 described above, it is possible to calculate the equilibrium shape 29 of the tire model 21 (shown in Figures 9 and 10) which removes the distorted shape while suppressing the outer diameter growth due to internal pressure filling. Then, by designing (manufacturing) the tire 2 before internal pressure filling based on this equilibrium shape 29 of the tire model 21, the distorted shape (shown in Figure 5) of the tire 2 before internal pressure filling is removed, and thus the distortion during inflation can be reduced. Such distortion during inflation is a factor that worsens the durability of the tire 2. Therefore, the design method of this embodiment makes it possible to reliably design a tire 2 with improved durability.

[0068] Furthermore, in this embodiment, the code ply 3 of the tire 2 before internal pressure filling (shown in Figure 2) is designed based on the profiles (equilibrium shapes) 29b and 29c (shown in Figure 10) of the code ply model 23 in which expansion deformation (outer diameter growth) is suppressed. This makes it possible to suppress changes in the design factors of the code ply 3 obtained in the optimal solution (satisfying the objective function) in the designed code ply 3 before internal pressure filling, and furthermore, it is possible to prevent the strain of the code ply 3 from becoming large during inflation.

[0069] In this embodiment, prior to the equilibrium shape calculation step S4, the bead core models 28, 28 (shown in Figure 5) are fixed so as not to move. Therefore, it is possible to prevent the movement of the bead portions 21c, 21c in the tire axial direction due to internal pressure filling, and the compression deformation of the clinch rubber models 25e, 25e from being reflected in the equilibrium shape 29 (shown in Figure 10). Thus, in this embodiment, it is possible to appropriately design the tire 2 before internal pressure filling.

[0070] In the design method of this embodiment, the specifications (design factors) of the tire 2 before internal pressure filling can be easily determined based on the equilibrium shape 29 of the outputted tire model 21. Therefore, the design method of this embodiment makes it possible to reliably design and manufacture a tire 2 that can reduce distortion during inflation (improving durability).

[0071] [Design method for pneumatic tires (second embodiment)] [Equilibrium Shape Calculation Process (Second Embodiment)] In the equilibrium shape calculation step S4 of the previous embodiments, the bead core model 28 was constrained to be immovable in step S41 shown in Figure 8, but the invention is not limited to this embodiment. Figure 11 is a flowchart showing the processing procedure of the equilibrium shape calculation step S4 of another embodiment of the present disclosure.

[0072] In the equilibrium shape calculation step S4 of this embodiment, as shown in Figure 5, the rim contact regions 35, 35 of the tire model 21 are constrained to be immovable (step S43). The rim contact regions 35, 35 are the regions where the tire 2 is scheduled to contact the rim 9 when the tire 2 is assembled to the rim as shown in Figure 2. These rim contact regions 35, 35 are defined in the tire model 21.

[0073] The rim contact area 35 can be defined as appropriate, for example, based on the standard rim. The "standard rim" is the rim specified for each tire in the standards system that includes the standard on which the tire is based. Therefore, the standard rim is, for example, the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0074] Next, in step S43 of this embodiment, the coordinate values ​​of the elements F(i) of the tire model 21 that are located in the rim contact regions 35, 35 are fixed in the computational space where the simulation is performed (for example, a space defined in a Cartesian coordinate system). This constrains the rim contact regions 35, 35 so that they cannot move.

[0075] Next, in the equilibrium shape calculation step S4 of this embodiment, after the rim contact regions 35, 35 are constrained, the equilibrium shape of the tire model 21 is calculated (step S44). The calculation of the equilibrium shape 29 is performed using the same procedure as in step S42 of the previous embodiment (shown in Figure 8).

[0076] In step S44 of this embodiment, since the rim contact area 35 is fixed so as to be immovable, the compressive deformation of the clinch rubber models 25e, 25e caused by pressing the rim model is suppressed, as in previous embodiments. As a result, the movement of the bead portions 21c, 21c in the tire axial direction due to internal pressure filling, and the compressive deformation of the clinch rubber models 25e, 25e are not reflected in the equilibrium shape 29 of the tire model 21, making it possible to properly design the tire 2 before internal pressure filling.

[0077] Furthermore, in this embodiment, by fixing the rim contact region 35, the bead portions 21c, 21c can be restrained over a wider area compared to previous embodiments in which, for example, the bead core models 28, 28 are fixed. As a result, in this embodiment, partial deformation (bending) of the bead portions 21c, 21c due to internal pressure filling can be suppressed compared to previous embodiments.

[0078] [Design method for pneumatic tires (third embodiment)] In the design method of the previous embodiment, the shape of the tire model 21 (shown in Figure 9) deformed based on predetermined internal pressure conditions (e.g., normal internal pressure (maximum internal pressure)) was identified as the equilibrium shape 29 in the equilibrium shape calculation step S4, but the invention is not limited to this embodiment. For example, the shape of the tire model 21 that has reached a predetermined deformation rate with respect to the amount of deformation of the tire model 21 from before internal pressure filling until the maximum internal pressure is filled may be identified as the equilibrium shape 29. Figure 12 is a flowchart of the design method of yet another embodiment of the present disclosure.

[0079] [Calculate the deformation of the tire model] In the equilibrium shape calculation step S4 of this embodiment, the amount of deformation of the tire model 21 (shown in Figure 5) from before internal pressure filling until maximum internal pressure is filled is calculated (step S45). In this embodiment, step S45 is performed after step S41, which restrains the bead core model 28 of the tire model 21 so that it cannot move. However, instead of step S41, step S43, which restrains the rim contact regions 35, 35 shown in Figure 11 so that they cannot move, may be performed.

[0080] In step S45 of this embodiment, the deformation amount of the tire model 21 is calculated while gradually increasing the internal pressure from before internal pressure filling (internal pressure is zero) to the maximum internal pressure. The deformation calculation of the tire model 21 based on the internal pressure is carried out in the same procedure as in previous embodiments.

[0081] The amount of deformation to be calculated can be selected as appropriate. In this embodiment, the amount of deformation includes at least one (in this example, both) change in tire maximum width W1 and change in tire outer diameter D1, as shown in Figures 5 and 9. In this embodiment, the tire maximum width W1 is determined at the position (tire maximum width position) 36 where the carcass ply model 26 protrudes most outward in the tire axial direction (as shown in Figure 9) when filled with maximum internal pressure.

[0082] Figure 13 is a graph showing the relationship between the internal pressure of the tire model 21 and the amount of deformation of the tire model 21 (maximum tire width W1, tire outer diameter D1). In this graph, the deformation rate of the maximum tire width W1 from before internal pressure filling is shown, with the maximum tire width W1 before internal pressure filling (shown in Figure 5) set to 0% and the maximum tire width W1 at maximum internal pressure filling (shown in Figure 9) set to 100%. Similarly, the deformation rate of the tire outer diameter D1 from before internal pressure filling is shown, with the tire outer diameter D1 before internal pressure filling (shown in Figure 5) set to 0% and the tire outer diameter D1 at maximum internal pressure filling (shown in Figure 9) set to 100%.

[0083] In the graph in Figure 13, the maximum tire width (deformation rate) W1 of the tire model 21 increases with increasing internal pressure. This increase in the maximum tire width W1 can eliminate the distorted shape of the tire model 21 (shown in Figure 5). On the other hand, the outer diameter (deformation rate) D1 of the tire model 21 also increases with increasing internal pressure. This is because, although the expansion deformation of the code ply model 23 (shown in Figures 5-7) is suppressed by the first parameter, the outer diameter D1 increases due to the deformation of other tire component models (e.g., rubber model 25) accompanying the increase in internal pressure. The amount of deformation of the tire model 21 is stored in computer 1 (shown in Figure 1).

[0084] [Specific to tire model shape] Next, in the equilibrium shape calculation step S4 of this embodiment, the shape of the tire model 21 with a predetermined deformation rate is identified based on the amount of deformation of the tire model 21 from before internal pressure filling (internal pressure: 0 kPa) until the maximum internal pressure is filled (step S46). The deformation rate can be set appropriately based on the amount of deformation of the tire model 21.

[0085] In this embodiment, the deformation rate of the maximum tire width W1 is set to 90% or more of the change in the maximum tire width of the tire model 21 from before internal pressure filling until the maximum internal pressure is filled (100%). This makes it possible to eliminate the distorted shape of the tire model 21 (shown in Figure 5). On the other hand, in this embodiment, the deformation rate of the tire outer diameter D1 is set to 20% or less of the change in the tire outer diameter of the tire model 21 from before internal pressure filling until the maximum internal pressure is filled (100%). This makes it possible to suppress the increase in the tire outer diameter D1.

[0086] In the graph shown in Figure 13, the internal pressure at which the deformation rate (deformation rate of the tire's maximum width: 90% or more, deformation rate of the tire's outer diameter: 20% or less) of the tire model 21 is measured, relative to the deformation amount (100%) of the tire model 21 from before internal pressure filling until the maximum internal pressure is filled, is the first internal pressure A (kPa). The shape of the tire model 21 (not shown) when filled with this first internal pressure A (kPa) is identified as the equilibrium shape 29 of the tire model 21.

[0087] The identified equilibrium shape 29 of the tire model 21 eliminates the distorted shape of the tire model 21 (shown in Figure 5). Furthermore, the identified equilibrium shape 29 suppresses the increase in the tire outer diameter D1 (outer diameter growth) compared to the equilibrium shape 29 of previous embodiments when filled with maximum internal pressure (shown in Figure 9). Therefore, this embodiment enables the design of a tire 2 with further improved durability. The identified equilibrium shape 29 of the tire model 21 is stored in the computer 1 (shown in Figure 1).

[0088] Although particularly preferred embodiments of this disclosure have been described in detail above, this disclosure is not limited to the illustrated embodiments and can be modified and implemented in various ways. [Examples]

[0089] A pneumatic tire reinforced with the code ply shown in Figure 2 was designed (Examples 1-3 and Comparative Example). In Examples 1-3 and Comparative Example, a tire model before internal pressure filling, including the code ply model shown in Figure 5, was first input.

[0090] Next, in Examples 1 to 3, a first parameter for suppressing expansion deformation was defined in the code ply model based on the processing procedure shown in Figure 4. Example 1 and Examples 2 and 3 had different first parameters. Details of the first parameters are as follows.

[0091] Next, in Examples 1-3, the equilibrium shape of the tire model was calculated based on the first parameter and the internal pressure conditions. In Examples 1-3, the equilibrium shape was calculated after the rim contact region of the tire model was constrained to be immovable.

[0092] In Examples 1 and 2, the equilibrium shape of the tire model was calculated based on the maximum internal pressure. In contrast, in Example 3, the equilibrium shape was identified as the shape of the tire model at which a predetermined deformation rate was reached, relative to the amount of deformation of the tire model from before internal pressure filling until the maximum internal pressure was filled.

[0093] In the comparative example, the equilibrium shape of the tire model was calculated based on the internal pressure condition (maximum internal pressure) without defining a first parameter in the code ply model. For the calculation of the equilibrium shape in the comparative example, the bead portion of the tire model was assembled to the rim using a rim model that modeled the rim.

[0094] In Examples 1-3 and the Comparative Example, the shape of the pneumatic tire before internal pressure filling was designed based on the equilibrium shape of the output tire model. The common specifications, including the first parameter and internal pressure conditions, are as follows. Tire size: 315 / 45R22.5 Maximum internal pressure (normal internal pressure): 900 kPa Example 1: Parameter 1: The tensile stiffness of the cord ply model is Set to a value greater than the tensile stiffness of the cord ply. Example 2: Parameter 1: The tensile stiffness of the cord ply model is Set to a value greater than the tensile stiffness of the cord ply. Set the belt cord angle to a small value (0 degrees). Example 3: Parameter 1: The tensile stiffness of the cord ply model is Set to a value greater than the tensile stiffness of the cord ply. Set the belt cord angle to a small value (0 degrees). Deformation rate: Maximum tire width: 90% Tire outer diameter: 20%

[0095] The test results showed that, compared to the comparative example, Examples 1-3 were able to calculate the equilibrium shape of the tire model while suppressing outer diameter growth due to internal pressure filling and eliminating distorted shapes. As a result, Examples 1-3 were able to design pneumatic tires that could reduce distortion during inflation (improving durability) based on the equilibrium shape of the tire model.

[0096] In Examples 2 and 3, the tensile stiffness of the cord ply model was set to a high value as the first parameter, and the angle of the belt cord was set to a small value. As a result, in Examples 2 and 3, compared to Example 1 in which the belt cord angle was not set to a small value, the outer diameter growth due to internal pressure filling was effectively suppressed, and the strain during inflation was further reduced.

[0097] In Example 3, the shape of the tire model that exhibited the above-mentioned deformation ratio was identified as the equilibrium shape, relative to the amount of deformation of the tire model from before internal pressure filling until the maximum internal pressure was filled. As a result, in Example 3, compared to Examples 1 and 2 in which the equilibrium shape at maximum internal pressure was calculated, the outer diameter growth due to internal pressure filling was further suppressed, and the distortion during inflation was further reduced.

[0098] [Note] This disclosure includes the following aspects:

[0099] [Disclosure 1] A method for designing a pneumatic tire reinforced with cord ply, The process involves inputting a tire model, including a code ply model that replicates the aforementioned code ply, into a computer before internal pressure filling. The process of defining a first parameter in the code ply model so as to suppress expansion deformation of the code ply model when the computer calculates the internal pressure filling of the tire model, A step of inputting the internal pressure conditions for filling the tire model into the computer, The computer performs the steps of calculating the equilibrium shape of the tire model based on the first parameter and the internal pressure conditions, The process includes the step of outputting the equilibrium shape of the tire model, Design methods for pneumatic tires. [Disclosure 2] A method for designing a pneumatic tire according to Disclosure 1, further comprising the step of the computer designing the shape of a pneumatic tire before internal pressure filling based on the equilibrium shape of the output tire model. [Disclosure 3] A method for designing a pneumatic tire according to disclosure 1 or 2, wherein the first parameter includes the tensile stiffness of the code ply model, which is set to a value greater than the tensile stiffness of the code ply. [Disclosure 4] The pneumatic tire design method according to Disclosure 3, wherein the code ply model includes a carcass ply model that models the carcass ply. [Disclosure 5] The method for designing a pneumatic tire according to disclosure 3 or 4, wherein the code ply model includes a belt ply model that models a belt ply having a belt cord. [Disclosure 6] The method for designing a pneumatic tire according to Disclosure 5, wherein the first parameter includes the angle of the belt cord in a belt cord model, which is set to be smaller than the angle of the belt cord with respect to the tire circumferential direction. [Disclosure 7] The tire model includes a bead core model that models the bead core of the tire, A method for designing a pneumatic tire according to any one of disclosures 1 to 6, wherein the step of calculating the equilibrium shape includes the step of constraining the bead core model of the tire model so that it cannot move, and then calculating the equilibrium shape of the tire model. [Disclosure 8] The tire model has a defined rim contact region in which the tire is expected to contact the rim. A method for designing a pneumatic tire according to any one of disclosures 1 to 6, wherein the step of calculating the equilibrium shape includes the step of constraining the rim contact area of ​​the tire model to be immovable, and then calculating the equilibrium shape of the tire model. [Disclosure 9] The aforementioned internal pressure conditions include the maximum internal pressure specified in the standards system on which the tire is based. A method for designing a pneumatic tire according to any one of disclosures 1 to 8, wherein the step of calculating the equilibrium shape includes a step of identifying the shape of the tire model at a predetermined deformation rate with respect to the amount of deformation of the tire model from before the internal pressure is filled until the maximum internal pressure is filled, as the equilibrium shape. [Disclosure 10] The method for designing a pneumatic tire according to disclosure 9, wherein the amount of deformation includes at least one of the amount of change in the maximum width of the tire and the amount of change in the outer diameter of the tire. [Explanation of symbols]

[0100] S1 Process for inputting the tire model before internal pressure filling. S2 Steps to define the first parameter in the code ply model S3 Step to input internal pressure conditions S4 Process for calculating the equilibrium shape of the tire model S5 Process for outputting the balanced shape of the tire model

Claims

1. A method for designing a pneumatic tire reinforced with cord ply, The process involves inputting a tire model, including a code ply model that replicates the aforementioned code ply, into a computer before internal pressure filling. The steps include defining a first parameter in the Code Ply model so as to suppress expansion deformation of the Code Ply model when the computer calculates the internal pressure filling of the tire model, A step of inputting the internal pressure conditions for filling the tire model into the computer, The computer performs the steps of calculating the equilibrium shape of the tire model based on the first parameter and the internal pressure conditions, The process of outputting the equilibrium shape of the tire model, The computer includes the step of designing the shape of a pneumatic tire before internal pressure filling based on the equilibrium shape of the output tire model, Design methods for pneumatic tires.

2. The method for designing a pneumatic tire according to claim 1, wherein the first parameter includes the tensile stiffness of the code ply model, which is set to a value greater than the tensile stiffness of the code ply.

3. The method for designing a pneumatic tire according to claim 2, wherein the code ply model includes a carcass ply model that models the carcass ply.

4. The method for designing a pneumatic tire according to claim 2, wherein the cord ply model includes a belt ply model that models a belt ply having a belt cord.

5. The method for designing a pneumatic tire according to claim 4, wherein the first parameter includes the angle of the belt cord of a belt cord model set to be smaller than the angle of the belt cord with respect to the tire circumferential direction.

6. The tire model includes a bead core model that models the bead core of the pneumatic tire, The method for designing a pneumatic tire according to claim 1 or 2, wherein the step of calculating the equilibrium shape includes the step of constraining the bead core model of the tire model so that it cannot move, and then calculating the equilibrium shape of the tire model.

7. The tire model has a defined rim contact region in which the pneumatic tire is intended to contact the rim, The method for designing a pneumatic tire according to claim 1 or 2, wherein the step of calculating the equilibrium shape includes the step of constraining the rim contact area of ​​the tire model to be immovable, and then calculating the equilibrium shape of the tire model.

8. The internal pressure conditions include the maximum internal pressure defined in the standard system on which the pneumatic tire is based. The method for designing a pneumatic tire according to claim 1 or 2, wherein the step of calculating the equilibrium shape includes a step of identifying the shape of the tire model at a predetermined deformation rate with respect to the amount of deformation of the tire model from before the internal pressure is filled until the maximum internal pressure is filled, as the equilibrium shape.

9. The method for designing a pneumatic tire according to claim 8, wherein the amount of deformation includes at least one change in the maximum width of the tire and a change in the outer diameter of the tire.

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