Prediction method for tire contact shape

Abstract

To provide a method capable of predicting a ground-contact shape of a tire including grooves on a tread part.SOLUTION: Provided is a method for predicting a ground-contact shape of a tire, in which tread patterns including grooves and a land part are formed on a tread part. The method includes a first step S1 for inputting to a computer a tire model obtained by discretizing a tire with a finite number of elements, that is, a step for modeling at least part of the tread patterns as a plane pattern part by discretizing the land part with a plurality of first elements, and also discretizing groove spaces formed by the grooves with a plurality of second elements. The method includes a second step S2 for defining a physical property of each element of the tire model, that is, a step for defining physical properties of the second elements whose Young's modulus is smaller than the first elements. The method includes a fourth step S4 in which the computer forces the plane pattern part to be brought into contact with a road surface model in a predetermined condition, and a fifth step S5 for forcing the computer to calculate a ground-contact shape of the plane pattern part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for predicting the contact shape of a tire. [Background technology]

[0002] Patent Document 1 listed below describes a method for predicting tire performance using a computer. This method includes the steps of setting a tire model in which the tire is modeled using elements that can be handled by a numerical analysis method, applying a centrifugal load to the tire model based on predetermined conditions, and calculating the contact patch shape of the tire model to which the centrifugal load has been applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-075296 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a need to predict the contact patch shape of a tire model, including not only the land portion of the tread but also the grooves, in order to analyze the contact patch shape in detail.

[0005] The present invention has been devised in view of the above circumstances, and its main object is to provide a method capable of predicting the contact patch shape of a tire, including the grooves in the tread portion. [Means for solving the problem]

[0006] The present invention is a method for predicting the contact shape of a tire having a tread pattern including grooves and land areas formed in the tread portion, comprising the following steps: a first step of inputting a tire model in which the tire is discretized into a finite number of elements into a computer, the first step including a step of modeling at least a portion of the tread pattern as a plain pattern portion by discretizing the land areas into a plurality of first elements and discretizing the groove spaces formed by the grooves into a plurality of second elements; a second step of defining physical properties for each element of the tire model, the second step including a step of defining physical properties for the second elements having a smaller Young's modulus than that of the first elements; a third step of inputting a road surface model in which a road surface is discretized into a finite number of elements into the computer; a fourth step of the computer bringing the plain pattern portion of the tire model into contact with the road surface model under predetermined conditions; and a fifth step of the computer calculating the contact shape of the plain pattern portion of the tire model.

[0007] In the tire contact patch shape prediction method of the present invention, the fifth step may include a step of calculating the contact pressure received by each element of the plain pattern portion of the tire model, and a step of determining that an element for which the contact pressure is equal to or greater than a predetermined threshold value comes into contact with the road surface model.

[0008] In the tire contact shape prediction method of the present invention, the fifth step may include a step of calculating the contact pressure received by each element of the road surface model, and a step of determining that an element whose contact pressure is equal to or greater than a predetermined threshold value comes into contact with the road surface model.

[0009] In the tire contact patch shape prediction method of the present invention, the fifth step may include a step of identifying the contour of a portion of the plain pattern portion of the tire model that is in contact with the road surface model as the contour of the tire contact patch shape.

[0010] In the tire contact patch shape prediction method of the present invention, the fifth step may include a step of identifying, as the contour of the tire contact patch shape, a contour obtained by cutting the plain pattern portion of the tire model at a plane that is separated from the surface of the road surface model by a predetermined distance in the normal direction of the surface.

[0011] In the method for predicting a tire contact patch shape according to the present invention, the second step may include a step of defining the Young's modulus of the second element to be 1 / 100 or less of the Young's modulus of the first element.

[0012] In the method for predicting a tire contact patch shape according to the present invention, the second step may include a step of defining a Poisson's ratio of the second element within a range of 0.0 to 0.1. [Effects of the Invention]

[0013] The method for predicting the contact shape of a tire of the present invention employs the above steps, making it possible to predict the contact shape of a tire including the grooves of the tread portion. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing a computer 1 for executing a tire contact shape prediction method according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a tire to be evaluated according to the present embodiment. [Figure 3] FIG. 3 is a development view of the tread of FIG. 2. [Figure 4] 3 is a flowchart showing the processing steps of a method for predicting a tire contact shape according to the present embodiment. [Figure 5] FIG. 2 is a perspective view conceptually showing a tire model and a road surface model. [Figure 6] FIG. 2 is a cross-sectional view of a tire model. [Figure 7] FIG. [Figure 8] 10 is a flowchart showing the processing procedure of a fifth step. [Figure 9]FIG. 10 is a distribution diagram of contact pressure on a plain pattern portion. [Figure 10] 10 is a flowchart showing the processing procedure of the fifth step according to another embodiment of the present invention. [Figure 11] FIG. 10 is a conceptual diagram illustrating the identification of the outline of the contact shape of a tire according to still another embodiment of the present invention. [Figure 12] FIG. 10 is a distribution diagram of contact pressure in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the invention. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0016] In the tire contact patch shape prediction method of this embodiment (hereinafter sometimes simply referred to as the "prediction method"), the contact patch shape of a tire having a tread pattern including grooves and land portions formed in the tread portion is predicted. The prediction method of this embodiment uses a computer.

[0017] [computer] FIG. 1 is a perspective view showing a computer 1 for executing the tire contact patch shape prediction method of this embodiment. The computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with a central processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive devices 1a1 and 1a2. The storage device stores in advance a processing procedure (program) for executing the prediction method of this embodiment.

[0018] [tire] FIG. 2 is a cross-sectional view of a tire 2 to be evaluated in this embodiment. FIG. 3 is a development view of the tread of FIG. 2. The tire 2 is exemplified by a pneumatic tire for a passenger vehicle (in this example, an all-season tire suitable for a four-wheel drive vehicle), but may also be a tire of another category, such as a heavy-duty tire for a truck or bus, or an airless tire. Furthermore, it does not matter whether the tire 2 actually exists.

[0019] The tire 2 is provided with a carcass 6 extending from the tread portion 2a through the sidewall portion 2b to the bead core 5 of the bead portion 2c, and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2a.

[0020] The carcass 6 is composed of at least one carcass ply 6A, one carcass ply in this embodiment. Meanwhile, the belt layer 7 is composed of two inner and outer belt plies 7A and 7B in which belt cords (not shown) are arranged at an angle of, for example, 10 to 35 degrees with respect to the tire circumferential direction. These belt plies 7A and 7B are overlapped with the belt cords crossing each other.

[0021] The tread portion 2a is formed with a tread pattern 10 including grooves 8 and land portions 9. The groove 8 in this embodiment includes at least one circumferential groove 8A (in this example, multiple grooves) that extends continuously in the tire circumferential direction. As a result, the tread portion 2a is provided with the circumferential groove 8A and multiple land portions 9 that are divided by the tread ground-contacting edge 2t. As shown in FIG. 3 , each land portion 9 is divided into multiple blocks 11 by lateral grooves 8B that connect the circumferential grooves 8A, 8A. The blocks 11 may be provided with sipes (not shown). In this specification, a sipe is a cut with a width of 2.0 mm or less, and the groove 8 has a width greater than that of the sipe.

[0022] "Genuine rim" means a rim that is defined for each tire by the standard system that includes the standard on which tire 2 is based, such as "standard rim" for JATMA, "Design Rim" for TRA, and "Measuring Rim" for ETRTO.

[0023] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which tire 2 is based. Therefore, the normal internal pressure is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. Note that if the tire is for a passenger car, it is 180 kPa.

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

[0025] In this specification, unless otherwise specified, the dimensions of each part of the tire are specified as values ​​measured in a normal state, which means that the tire 2 is mounted on a normal rim (rim 12 shown in FIG. 2), inflated to a normal internal pressure, and no load is applied.

[0026] [Method for predicting tire contact shape (first embodiment)] Next, a method for predicting the contact shape of a tire will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the processing steps of the method for predicting the contact shape of a tire according to this embodiment.

[0027] [Enter tire model (first step)] In the prediction method of this embodiment, first, a tire model in which a tire 2 (shown in FIGS. 2 and 3) is discretized into a finite number of elements is input to a computer 1 (shown in FIG. 1) (first step S1). FIG. 5 is a perspective view conceptually showing a tire model 15 and a road surface model 16. FIG. 6 is a cross-sectional view of the tire model 15. FIG. 7 is a partial development view showing a plain pattern portion 24. Elements of the tire model 15 are omitted in FIG. 5.

[0028] In the first step S1 of this embodiment, the tire 2 is discretized into a finite number of elements F(i) (i=1, 2, ...) that can be handled by a numerical analysis method based on the design information (e.g., information about a mold) of the tire 2 shown in Figures 2 and 3. As a result, in the first step S1, a tire model 15 is set (modeled).

[0029] The numerical analysis method may be, for example, the finite element method, the finite volume method, the difference method, or the boundary element method. In this embodiment, the finite element method is used. For example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element may be used as the element F(i). Each element F(i) has a plurality of nodes 18. Numerical data such as the element number, the number of the node 18, and the coordinate values ​​of the node 18 are defined for each element F(i).

[0030] In the first step S1 of this embodiment, the land portions 9 (shown in FIGS. 2 and 3) are discretized into a plurality of first elements 21. Furthermore, in the first step S1, groove spaces 8s (shown in FIG. 2) formed by the grooves 8 are discretized into a plurality of second elements 22. As a result, in the first step S1, at least a portion of the tread pattern 10 (in this example, the entire tread pattern) is modeled as a plain pattern portion 24. The plain pattern portion 24 of this embodiment includes a land portion model 41 that models the land portions 9 and a groove space model 42 that models the groove spaces 8s.

[0031] The plain pattern portion 24 is a model of a tread portion (not shown) having a slick-like tread pattern in which grooves 8 (shown in FIG. 3) are not formed. If sipes (not shown) are provided in the tread pattern 10 shown in FIG. 3, sipe spaces (not shown) formed by the sipes may be discretized into a plurality of second elements 22.

[0032] In the first step S1 of this embodiment, the body portion 25 other than the plain pattern portion 24 is discretized into a plurality of third elements 23. Similar to a conventional tire model, the body portion 25 includes a carcass ply model 26 that models a carcass ply 6A (shown in FIG. 2), belt ply models 27A and 27B that model belt plies 7A and 7B (shown in FIG. 2), and the like.

[0033] The first element 21, the second element 22, and the third element 23 are distinctions of the above-mentioned element F(i). A tire model 15 having a plain pattern portion 24 is stored in the computer 1.

[0034] [Define physical properties (step 2)] Next, in the prediction method of this embodiment, physical properties are defined for each element F(i) of the tire model 15 (second step S2). In the second step S2, first, the physical properties of the discretized objects (for example, the land portion 9 (tread rubber), the carcass ply 6A, etc.) are defined for the first element 21 and the third element 23 shown in Fig. 6. The physical properties include, for example, Young's modulus, density, and / or damping coefficient.

[0035] Next, in a second step S2, a physical property is defined for the second element 22 such that the Young's modulus is smaller than that of the first element 21. As a result, the second element 22 is more easily deformed than the first element 21 in a fourth step S4 described below. The physical property of the second element 22 is set appropriately. In this embodiment, the physical property is desirably set to be soft enough not to affect the deformation of the first element 21 and within a range in which calculations can be stably solved. The physical property of the second element 22 is set, for example, to a value having a Young's modulus that is sufficiently smaller than that of the first element 21 (for example, 1 / 1000 of that of the first element 21). The physical property of each element F(i) of the tire model 15 is stored in the computer 1.

[0036] [Input road surface model (3rd step)] Next, in the prediction method of this embodiment, a road surface model 16 (shown in FIG. 5) in which the road surface is discretized into a finite number of elements G(i) is input to a computer 1 (shown in FIG. 1) (third step S3). In the third step S3, based on information about the road surface on which the tire 2 (shown in FIG. 2) comes into contact, 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). In this way, the road surface model 16 is set.

[0037] Element G(i) is defined as a rigid plane element that is defined to be undeformable. Element G(i) has a plurality of nodes 28. Furthermore, element G(i) is defined with numerical data such as an element number and the coordinate values ​​of the nodes 28.

[0038] In this embodiment, a road surface model 16 having a smooth surface is defined, but the present invention is not limited to this. For example, a road surface model 16 (not shown) may be defined that has minute irregularities, irregular steps, depressions, undulations, or irregularities similar to those of an actual road surface, such as ruts, as in an asphalt road surface. The road surface model 16 is stored in the computer 1.

[0039] [Placing the plain pattern on the road model (4th step)] Next, in the prediction method of this embodiment, the computer 1 brings the plain pattern portion 24 of the tire model 15 into contact with the road surface model 16 under predetermined conditions (fourth step S4).

[0040] In the fourth step S4 of this embodiment, first, as shown in Fig. 6, the bead portions 15c, 15c of the tire model 15 are constrained by a rim model 29 that models the rim 12 (shown in Fig. 2) of the tire 2. Furthermore, deformation of the tire model 15 is calculated based on a uniformly distributed load w that corresponds to normal internal pressure. As a result, the tire model 15 after internal pressure inflation is calculated.

[0041] Next, in the fourth step S4 of this embodiment, as shown in FIG. 5, contact between the tire model 15 after internal pressure inflation and the road surface model 16 is calculated. Then, deformation of the tire model 15 is calculated based on predetermined conditions. The conditions for contact with the ground include, for example, the applied load condition L corresponding to the normal load, a camber angle (not shown), and a friction coefficient. As a result, in the fourth step S4, the plain pattern portion 24 of the tire model 15 can be contacted with the road surface model 16.

[0042] In the deformation calculation of the tire model 15, a mass matrix, a stiffness matrix, and a damping matrix are created for each element F(i) (including the first element 21 to the third element 23 in this example) shown in FIGS. 6 and 7 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 various conditions described above, and these are calculated for each minute time (unit time T(x) (x=0, 1, ...)). In this way, the deformation calculation of the tire model 15 is performed.

[0043] Such deformation calculations can be performed using commercially available finite element analysis application software such as Abaqus manufactured by Dassault Systems, LS-DYNA manufactured by LSTC, or NASTRAN manufactured by MSC, Inc. The unit time T(x) can be set appropriately depending on the required calculation accuracy.

[0044] The second element 22 in this embodiment is defined to have a physical property with a smaller Young's modulus than the first element 21. Therefore, even if strain occurs in the second element 22 as a result of deformation calculations due to contact with the road surface model 16, the stress is calculated to be small and the second element 22 does not hinder deformation of the first element 21. As a result, the first element 21 can undergo deformation as a result of deformation calculations due to contact with the road surface model 16 in the same way as when the tread pattern 10 is formed (i.e., when the second element 22 does not exist).

[0045] [Calculate the grounding shape of the plain pattern part (5th step)] Next, in the prediction method of this embodiment, the computer 1 calculates the contact shape of the plain pattern portion 24 of the tire model 15 (fifth step S5). Fig. 8 is a flowchart showing the processing procedure of the fifth step S5 of this embodiment.

[0046] [Calculation of contact pressure (5th step)] In the fifth step S5 of this embodiment, first, the computer 1 calculates the contact pressure that each element F(i) of the plain pattern portion 24 of the tire model 15 receives (step S51). FIG. 9 is a distribution diagram of the contact pressure of the plain pattern portion 24. The tread pattern in FIG. 9 is different from the simplified tread patterns in FIGS. 3 and 7. Also, in FIG. 9, the darker the color, the greater the contact pressure.

[0047] In step S51 of this embodiment, contact pressure is calculated at each of the nodes 18 constituting the first element 21 and the second element 22 constituting the plain pattern portion 24 shown in Figures 6 and 7. In step S51, for example, the contact pressure of an arbitrary element (the first element 21 or the second element 22) may be specified as the average value of the contact pressures calculated at the multiple nodes 18 constituting that element. The contact pressure is stored in the computer 1.

[0048] [Identifying the contour of the ground surface (5th step)] Next, in a fifth step S5 of this embodiment, the computer 1 identifies the outline of the contact shape of the tire 2 (step S52). In step S52 of this embodiment, first, as shown in Fig. 5, a portion 31 of the plain pattern portion 24 of the tire model 15 that is in contact with the road surface model 16 is identified. The contacting portion 31 is identified by the first elements 21 and second elements 22 (shown in Figs. 6 and 7) that constitute the plain pattern portion 24 and that receive a contact pressure from the road surface model 16 that is greater than zero.

[0049] Next, in step S52 of this embodiment, as shown in Figures 5 and 9, a contour 32 of the portion 31 in contact with the identified road surface model 16 is identified as the contour (outer contour) of the contact shape of the tire 2 (shown in Figure 2). The contour 32 can be identified, for example, based on the coordinate values ​​of the nodes 18 (shown in Figure 7) that constitute the first element 21 and the second element 22 that are in contact with the road surface model 16. The contour 32 is stored in the computer 1.

[0050] In the prediction method of this embodiment, both the first element 21 (land portion model 41) obtained by discretizing the land portion 9 (shown in FIG. 2 ) and the second element 22 (groove space model 42) obtained by discretizing the groove space 8s (shown in FIG. 2 ) can be brought into contact with the road surface model 16. This makes it possible to easily predict the contact patch shape of the tire 2, including the grooves 8 in the tread portion 2a. On the other hand, in a conventional method using a tire model that does not include the second element 22, an operator had to interpolate the contours (outer contours) 38 (shown in FIG. 9 ) of the grooves 8 present in the contact patch based on the contours (outer contours) of the contact patch identified only by the first element 21. As a result, variations in the predicted contact patch shape of the tire 2 occurred depending on the position of the first element 21 in contact with the road surface model 16 (the contours of the contact patch shape that change with the rotation of the tire model) and the discretion of the operator. In the prediction method of this embodiment, the above-mentioned interpolation is unnecessary, making it possible to easily and accurately predict the contact patch shape of the tire 2, including the grooves 8.

[0051] [Grounding judgment (5th step)] Next, in a fifth step S5 of this embodiment, the computer 1 determines that the element F(i) having a contact pressure equal to or greater than a predetermined threshold is in contact with the road surface model 16 (step S53). In step S53 of this embodiment, the first element 21 and the second element 22 shown in FIG. 7 are identified in the portion 31 of the plain pattern portion 24 of the tire model 15 that is in contact with the road surface model 16.

[0052] The threshold value can be set appropriately as long as it is possible to determine that the element F(i) comes into contact with the road surface model 16. As described above, the physical properties of the land portion 9 (tread rubber) are defined for the first element 21 obtained by discretizing the land portion 9 (shown in FIG. 2) that comes into contact with the road surface. Therefore, a contact pressure similar to that of the actual land portion 9 can be calculated. On the other hand, the second element 22 obtained by discretizing the groove space 8s (shown in FIG. 2) that does not come into contact with the road surface is defined as having a physical property with a smaller Young's modulus than the first element 21, and is therefore more easily deformed than the first element 21. Therefore, as shown in FIG. 9, the contact pressure of the second element 22 with the road surface model 16 is calculated to be lower than that of the first element 21. Therefore, it is desirable to set the threshold value to a value smaller than the maximum contact pressure of the second element 22 among the elements (the first element 21 and the second element 22) of the plain pattern portion 24 that come into contact with the road surface model 16. In this embodiment, the threshold value is set to, for example, 50 kPa.

[0053] In step S53 of this embodiment, the element F(i) whose contact pressure is equal to or greater than a predetermined threshold is identified, thereby making it possible to distinguish the first element 21 and the second element 22 from the element F(i) of the plain pattern portion 24 that is in contact with the road surface model 16. As a result, the prediction method of this embodiment focuses on the difference in contact pressure, making it possible to easily distinguish the groove 8 and the land portion 9 (land portion model 41 and groove space model 42) of the tread portion 2a shown in FIGS. 2 and 3 from the contact shape 33 of the plain pattern portion 24 shown in FIG. 9. The element F(i) (in this example, the first element 21) that is determined to be in contact with the road surface model 16 is stored in the computer 1.

[0054] In order to reliably distinguish between the first element 21 and the second element 22, in the second step S2 of defining the physical properties, it is desirable to define the Young's modulus of the second element 22 to be 1 / 100 or less of the Young's modulus of the first element 21. This ensures that the contact pressure of the second element 22 is lower than the contact pressure of the first element 21, making it possible to reliably distinguish between the first element 21 and the second element 22. On the other hand, if the Young's modulus of the second element 22 is too small, the contact pressure of the second element 22 will be too low, and there is a risk that contact between the second element 22 and the road surface model 16 cannot be determined. Therefore, it is desirable to define the Young's modulus of the second element 22 to be 1 / 1000 or more of the Young's modulus of the first element 21.

[0055] In order to effectively exert the above-mentioned effect, in the second step S2, the density of the second element is set to 100 kg / m 3 It is desirable to set the density of the second element 22 to about 1.0 kg / m. This allows the contact pressure of the second element 22 to be relatively small. In addition, in order to prevent the contact pressure of the second element 22 from being lowered more than necessary, the density of the second element 22 is set to about 1.0 kg / m. 3 It is desirable to set it to the above.

[0056] Furthermore, in the second step S2, it is desirable to define the Poisson's ratio of the second element 22 within the range of 0.0 to 0.1 in order to prevent the second element 22 from interfering with the deformation of the first element 21. This allows the second element 22 to have a small resistance to the deformation of the first element 21 and to deform in accordance with the deformation of the first element 21.

[0057] [Evaluation process] Next, in the prediction method of this embodiment, the predicted contact patch shape of the tire 2 (shown in FIG. 2) is evaluated as to whether it is good or not (step S6). The evaluation can be performed appropriately based on the category of the tire 2, the performance required of the tire 2 (for example, wet performance, snow performance, etc.), etc.

[0058] If it is determined in step S6 that the ground contact shape is good ("Yes" in step S6), a tire 2 (shown in FIG. 2) is manufactured (step S7) based on the design factors of the tire model 15. On the other hand, if it is determined that the ground contact shape is not good ("No" in step S6), the design factors of the tire are changed (step S8), and the first step S1 to step S6 are performed again.

[0059] The prediction method of this embodiment can predict the tire's contact patch shape, including the grooves 8 (shown in FIG. 2) in the tread portion 2a, and therefore can easily and accurately predict, for example, the proportion of the grooves 8 that have a large impact on wet and snow performance, etc., in the contact patch shape (such as the sea-to-surface ratio). This makes it possible to appropriately evaluate tire performance, and efficiently and reliably design and manufacture a tire 2 with desired performance. The sea-to-surface ratio is the ratio of the total groove area to the total tread contact patch area when all grooves in the tread portion 2a are filled.

[0060] [Fifth Step (Second Embodiment)] In the embodiments described above, an element F(i) in which the contact pressure received by each element (in this example, the first element 21 and the second element 22) of the plain pattern portion 24 of the tire model 15 is equal to or greater than a threshold value is determined to be in contact with the road surface model 16, but the present invention is not limited to this. Fig. 10 is a flowchart showing the processing procedure of the fifth step S5 in another embodiment of the present invention. In this embodiment, the same components as those in the embodiments described above are denoted by the same reference numerals, and their description may be omitted.

[0061] [Calculation of contact pressure (5th step)] In the fifth step S5 of this embodiment, the contact pressure received by each element G(i) of the road surface model 16 shown in FIG. 5 is calculated (step S54). In step S54 of this embodiment, the contact pressure is calculated at each node 28 of each element G(i) constituting the road surface model 16. Note that in step S54, for example, the contact pressure of an arbitrary element may be specified as the average value of the contact pressures calculated at the multiple nodes 28 constituting that element G(i). The contact pressure is stored in the computer 1.

[0062] [Identifying the contour of the ground surface (5th step)] Next, in a fifth step S5 of this embodiment, the computer 1 identifies the outline of the contact shape of the tire 2 (step S55). In step S55 of this embodiment, first, the portion 31 of the road surface model 16 that is in contact with the plain pattern portion 24 of the tire model 15 is identified. For the contacting portion 31, the element G(i) of the road surface model 16 that receives a contact pressure of zero or more from the plain pattern portion 24 is identified.

[0063] Next, in step S55 of this embodiment, the contour 35 of the portion 34 in contact with the identified plain pattern portion 24 is identified as the contour (outer contour) of the contact shape of the tire 2. The contour 35 can be identified, for example, based on the coordinate values ​​of the element G(i) in contact with the plain pattern portion 24. The contour 35 is stored in the computer 1.

[0064] As with the previous embodiments, the prediction method of this embodiment makes it possible to easily and accurately predict the contact patch shape of the tire 2 (shown in FIG. 2) including the grooves 8.

[0065] [Grounding judgment (5th step)] Next, in the fifth step S5 of this embodiment, the element G(i) whose contact pressure is equal to or greater than a predetermined threshold is selected. By identifying Contacting the plain pattern portion 24 of the tire model 15 Road surface model 16 In this case, the first element 21 (shown in FIG. 6) Land model 41 Contact Road surface model 16 Element G(i) and the second element 22 (shown in FIG. 6) The groove space model 42 Contact Road surface model 16 The element G(i) is identified (Step S56) The threshold value can be set in the same manner as in the previous embodiments.

[0066] In step S56 of this embodiment, the element G(i) whose contact pressure is equal to or greater than the threshold value is identified, thereby making it possible to distinguish between the element G(i) that contacts the first element 21 and the element G(i) that contacts the second element 22 in the road surface model 16 that contacts the plain pattern portion 24. As a result, the prediction method of this embodiment focuses on the difference in contact pressure and can easily distinguish between the groove 8 and the land portion 9 (land portion model 41 and groove space model 42) of the tread portion 2a from the contact shape 33 (shown in FIG. 9 ) of the plain pattern portion 24. The element G(i) that is determined to be in contact with the road surface model 16 (in this example, the element G(i) that contacts the first element 21) is stored in the computer 1.

[0067] [Fifth Step (Third Embodiment)] In the fifth step S5 of the previous embodiments, the contour 32 of the portion of the plain pattern portion 24 of the tire model 15 that is in contact with the road surface model 16 is identified as the contour of the tire contact patch shape 33, but this is not limited to this. Fig. 11 is a conceptual diagram illustrating the identification of the contour of the tire contact patch shape 33 in yet another embodiment of the present invention. In this embodiment, the same components as those in the previous embodiments are assigned the same reference numerals, and their description may be omitted.

[0068] In a fifth step S5 of this embodiment, a contour (not shown) obtained by cutting the plain pattern portion 24 of the tire model 15 at a surface 37 that is a predetermined distance D1 away from the surface 16s of the road surface model 16 in the normal direction thereof is identified as the contour of the contact shape of the tire 2. The distance D1 in this embodiment is set to a value smaller than the shortest distance (groove depth) D2 between the groove bottom 8d and the land portion 9o (outer surface of the plain pattern portion 24) shown in FIG.

[0069] In this embodiment, it is possible to predict the outline of the contact shape when the tread portion 2a (shown in FIG. 2) bites into a soft road surface such as a water film on the road surface or a snowy road. In addition, by setting the distance D1 to an arbitrary value, it is possible to obtain the sea ratio at any position in the tire radial direction, which makes it possible to evaluate, for example, wet performance, snow performance, etc. in more detail.

[0070] In the tire model 15 of the embodiments described above, the entire tread pattern 10 (shown in FIGS. 2 and 3) of the tire 2 is modeled as the plain pattern portion 24, but the present invention is not limited to this. For example, in the tire model 15, only the region that contacts the road surface model 16 in the tire circumferential direction may be modeled as the plain pattern portion 24. This prevents the second element 22 from being provided in the portion of the tire model 15 that does not contact the road surface model 16, thereby improving the accuracy of calculations of deformation based on the load condition L, for example.

[0071] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways. [Example]

[0072] The tire contact patch shape was predicted (Example) based on the processing procedure shown in Fig. 4. In the Example, first, a tire model in which the tire was discretized into a finite number of elements was input to a computer. In the Example, at least a part of the tread pattern was modeled as a plain pattern portion by discretizing the land portion into a plurality of first elements and discretizing the groove space formed by the grooves into a plurality of second elements.

[0073] The second element was defined to have a physical property with a smaller Young's modulus than the first element. In the example, the plain pattern portion was placed in contact with the road surface model, and the contact shape of the plain pattern portion was calculated.

[0074] For comparison, a tire model without a second element was created (Comparative Example) as in the conventional method. Then, the tread pattern portion of the tire model of the Comparative Example was placed in contact with the road surface model, and the contact shape of the tread pattern portion was calculated. The common specifications are as follows: Tire size: 265 / 70R17 Internal pressure: 550kPa Load (load condition L): 5.69 kN Second factor: Young's modulus: 1 / 1000 of the Young's modulus of the first element Poisson's ratio: 0.001 Density: 1 / 10 of the density of the first element

[0075] FIG. 9 is a distribution diagram of contact pressure in the plain pattern portion of the example. FIG. 12 is a distribution diagram of contact pressure in the tread pattern of the comparative example. As a result of the test, in the example, both the first element discretizing the land portion and the second element discretizing the groove space were able to come into contact with the road surface model. On the other hand, in the comparative example, since there was no second element in the groove space, only the first element came into contact with the road surface model. Therefore, in the example, it was possible to predict the tire contact shape, including the grooves in the tread portion.

[0076] In the example, the second element was defined to have a smaller Young's modulus than the first element, so the deformation of the grounded first element was not hindered. As a result, the first element of the example was calculated to have the same deformation as the first element of the comparative example.

[0077] The second element in the example has a small Young's modulus and is easily deformed, so the calculated contact pressure with the road surface model was lower than that of the first element. Therefore, by focusing on the difference in contact pressure between each element, it was possible to easily distinguish the grooves and land areas of the tread from the contact shape of the plain pattern part. [Explanation of symbols]

[0078] S1 1st process S2 2nd process S4 4th process S5 5th process

Claims

1. A method for predicting a contact shape of a tire having a tread pattern including grooves and land portions formed in a tread portion, comprising: a first step of inputting a tire model in which the tire is discretized with a finite number of elements into a computer, the first step including a step of discretizing the land portions with a plurality of first elements and discretizing groove spaces formed by the grooves with a plurality of second elements, thereby modeling at least a part of the tread pattern as a plain pattern portion including a land portion model in which the land portions are modeled with the first elements and a groove space model in which the groove spaces are modeled with the second elements; a second step of defining physical properties for each element of the tire model, the second step including a step of defining a physical property for the second element that has a smaller Young's modulus than the first element; a third step of inputting a road surface model in which the road surface is discretized into a finite number of elements into the computer; a fourth step in which the computer brings the plain pattern portion of the tire model into contact with the road surface model under predetermined conditions; a fifth step in which the computer calculates a contact shape of the plain pattern portion of the tire model, the fifth step is a step of calculating a contact pressure that each element of the road surface model receives; and identifying an element of the road surface model that contacts the land model modeled with the first element and an element of the road surface model that contacts the groove space model modeled with the second element in the road surface model that contacts the plain pattern portion by identifying an element where the contact pressure is equal to or greater than a predetermined threshold value. A method for predicting tire contact shape.

2. 2. The method for predicting a tire contact patch shape according to claim 1, wherein the fifth step includes a step of identifying, as the contour of the tire contact patch shape, a contour of a portion of the road surface model that is in contact with the plain pattern portion of the tire model.

3. A method for predicting the contact shape of a tire having a tread pattern including grooves and land portions formed in the tread portion, comprising: a first step of inputting a tire model in which the tire is discretized into a finite number of elements into a computer, the first step including a step of modeling at least a part of the tread pattern as a plain pattern portion by discretizing the land portion into a plurality of first elements and discretizing a groove space formed by the grooves into a plurality of second elements; a second step of defining physical properties for each element of the tire model, the second step including a step of defining a physical property for the second element that has a smaller Young's modulus than the first element; a third step of inputting a road surface model in which the road surface is discretized into a finite number of elements into the computer; a fourth step in which the computer brings the plain pattern portion of the tire model into contact with the road surface model under predetermined conditions; a fifth step in which the computer calculates a contact shape of the plain pattern portion of the tire model, the fifth step includes a step of specifying, as the outline of the tire contact patch shape, an outline obtained by cutting the plain pattern portion of the tire model along a plane that is spaced a predetermined distance from the surface of the road surface model in a normal direction thereof. A method for predicting tire contact shape.

4. The fifth step comprises: calculating a contact pressure applied to each element of the plain pattern portion of the tire model; 4. The method for predicting a tire contact shape according to claim 3, further comprising the step of determining that an element for which the contact pressure is equal to or greater than a predetermined threshold is in contact with the road surface model.

5. A method for predicting the contact shape of a tire described in any one of claims 1 to 4, wherein the second step includes a step of defining the Young's modulus of the second element to be greater than 1 / 1000 and less than 1 / 100 of the Young's modulus of the first element.

6. A method for predicting the contact shape of a tire described in any one of claims 1 to 5, wherein the second step includes a step of defining the Poisson's ratio of the second element within the range of 0.0 to 0.1.

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