Method for predicting wear condition of tire

Abstract

To provide a method enabling accurate prediction of wear condition of tread rubber having multi-layer rubber structure.SOLUTION: There is provided a method for predicting wear condition of tread rubber disposed on a tread section of a tire. The tread rubber includes at least a first layer composed of a first rubber having a first physical property value, and a second layer composed of a second rubber having a second physical property value different from the first physical property value. In a first step S1, a tire model which is obtained by modeling a tire using a finite number of elements, is input into a computer. A common synthetic physical property value is defined in an element of a tread rubber model. In a second step S3, the computer calculates a physical amount related to the wear of the tread rubber. In a third step S4, the computer calculates a wear amount of the element of the tread rubber model. In a fourth step S5, the computer recalculates and updates the synthetic physical property value of the tread rubber model on the basis of the wear amount. The second step S3 or the fourth step S5 is repeated until a predetermined final condition is satisfied.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, various simulation methods for predicting tire wear conditions have been proposed (for example, see Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4460337 Summary of the Invention [Problem to be solved by the invention]

[0004] Tire tread rubber may have a multi-layer rubber structure in which multiple rubber layers with different physical properties are layered in the radial direction of the tire. When performing wear prediction simulation of such tread rubber, a method can be considered in which a single physical property value is defined in the FEM model of the tread rubber by averaging the physical property values ​​of each of the multiple rubber layers, but this method has the problem of lower calculation accuracy compared to an FEM model that defines the physical properties of each individual rubber layer.

[0005] In addition, when creating an FEM model of the above-mentioned multi-layer rubber structure in which the physical properties of each rubber layer are defined, the positions of the boundaries between the multiple rubber layers must also be accurately reproduced, which creates the problem of being unable to freely create meshes. This means that it is necessary to use elements that are smaller than necessary at the boundaries between the multiple rubber layers, which results in problems such as modeling work taking a lot of time.

[0006] The present invention has been devised in consideration of the above-described circumstances, and a primary object of the first invention is to provide a method for predicting the wear condition of a tire that is capable of accurately predicting the wear condition of tread rubber having a multi-layer rubber structure.

[0007] In addition, the main object of the second aspect of the present invention is to provide a method for predicting the wear condition of a tire that can shorten the time required for modeling work of tread rubber having a multi-layer rubber structure. [Means for solving the problem]

[0008] A first invention of the present invention is a method for predicting a wear state of tread rubber arranged in a tread portion of a tire, the tread rubber including at least a first layer made of a first rubber having a first physical property value, and a second layer made of a second rubber overlapping the first layer in the tire radial direction and having a second physical property value different from the first physical property value, the method includes a step of inputting a tire model including a tread rubber model in which the tire including the tread rubber is modeled with a finite number of elements into a computer, and inputting a rubber volume of the first layer, a rubber volume of the second layer, and a tire volume of the second layer into the elements of the tread rubber model. a first step of defining a common composite physical property value calculated based on the tire model, the first physical property value and the second physical property value; a second step of calculating physical quantities related to wear of the tread rubber by running the tire model under predetermined conditions using the computer; a third step of calculating the amount of wear of the elements of the tread rubber model based on the physical quantities using the computer; and a fourth step of recalculating and updating the composite physical property value of the tread rubber model based on the amount of wear, wherein the second step through the fourth step are repeated until a predetermined termination condition is satisfied.

[0009] A second invention of the present invention is a method for predicting a wear state of tread rubber arranged in a tread portion of a tire, the tread rubber including at least a first layer made of a first rubber having a first physical property value, and a second layer made of a second rubber overlapping the first layer in the tire radial direction and having a second physical property value different from the first physical property value, the method includes a step of inputting a tire model including a tread rubber model in which the tire including the tread rubber is modeled with a finite number of elements into a computer, the element of the tread rubber model being input with a rubber volume of the first layer, a rubber volume of the second layer, the first physical property value and the second physical property value. The method for predicting the wear state of a tire includes a first step of defining a common composite physical property value calculated based on physical property values, a second step of the computer running the tire model under predetermined conditions to calculate physical quantities related to the wear of the tread rubber, and a third step of the computer calculating the wear amounts of the elements of the tread rubber model based on the physical quantities, wherein the second step and the third step are repeated until a predetermined termination condition is satisfied, and the first step includes a step of discretizing the area occupied by the tread rubber with the elements regardless of the boundary between the first layer and the second layer to define the tread rubber model. Effect of the Invention

[0010] The method for predicting a wear state of a tire according to the first aspect of the present invention employs the above steps, making it possible to accurately predict the wear state of the tread rubber having a multi-layer rubber structure.

[0011] The method for predicting a tire wear state according to the second aspect of the invention employs the above steps, thereby making it possible to reduce the time required for modeling the tread rubber having a multi-layer rubber structure. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing an example of a computer for executing a method for predicting a tire wear state. [Diagram 2]1 is a cross-sectional view showing an example of a tire whose wear state is predicted; [Diagram 3] 3 is a flowchart showing a processing procedure of a tire wear state predicting method according to the first invention. [Figure 4] FIG. 2 is a perspective view showing an example of a tire model and a road surface model. [Diagram 5] FIG. 2 is a cross-sectional view showing an example of a tire model. [Figure 6] FIG. 6 is a partially enlarged view of the tread portion of FIG. 5. [Figure 7] 5 is a flowchart showing a processing procedure of a tire wear state predicting method according to a second aspect of the present invention. [Figure 8] 1 is a graph showing the relationship between travel distance and wear energy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the dimensional ratio of the actual structure in order to help understand the contents of the invention. Furthermore, the same or common elements are given the same reference numerals throughout the embodiments, and duplicated explanations are omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0014] The tire wear prediction method of this embodiment (hereinafter, sometimes referred to as the "prediction method") is a method for predicting the wear state of tread rubber arranged in the tread portion of a tire. In the prediction method of this embodiment, a computer is used.

[0015] [computer] FIG. 1 is a perspective view showing an example of a computer 1 for executing a method for predicting a tire wear state. The computer 1 includes, for example, a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a includes, for example, 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 software and the like for executing the prediction method of this embodiment in advance. Therefore, the computer 1 is configured as a device for predicting a tire wear state.

[0016] [tire] 2 is a cross-sectional view showing an example of a tire 2 whose wear state is predicted. The tire 2 of this embodiment is exemplified by a pneumatic tire for a passenger vehicle, but is not particularly limited thereto. The tire 2 may be, for example, a tire for heavy loads such as a truck or bus, or an airless tire, or other tire of another category.

[0017] The tire 2 of this embodiment is provided with a carcass 4 extending from the tread portion 2a through the sidewall portion 2b to the bead core 3 of the bead portion 2c, and a belt layer 5 disposed on the tire radial outer side of the carcass 4 and inside the tread portion 2a. A tread pattern is provided on an outer surface 2S1 of the tread portion 2a of this embodiment.

[0018] The tread portion 2a is provided with a tread rubber 6 disposed on the outer side of the belt layer 5. The tread rubber 6 includes at least a first layer 6A made of a first rubber 6AG and a second layer 6B made of a second rubber 6BG overlapping the first layer 6A in the tire radial direction. Therefore, the tread rubber 6 has a multi-layer rubber structure.

[0019] The tread rubber 6 of the present embodiment is configured with a first layer 6A and a second layer 6B, but is not limited to this. The tread rubber 6 may include, for example, a third layer (not shown) or more.

[0020] The first layer 6A of the present embodiment is configured as a cap rubber layer CG that constitutes the ground contact surface 2S2 of the tread portion 2a. On the other hand, the second layer 6B is configured as a base rubber layer BG disposed on the radially inner side of the first layer 6A (cap rubber layer CG).

[0021] The first rubber 6AG has a first physical property value P. On the other hand, the second rubber 6BG has a second physical property value Q. The first physical property value P and the second physical property value Q are different from each other.

[0022] The first physical property value P and the second physical property value Q can be set appropriately as long as they are different from each other. The first physical property value P and the second physical property value Q can include rubber hardness or complex modulus E*.

[0023] Rubber hardness refers to the hardness measured using a JIS-K6253 Type A durometer under a standard temperature of 23°C ± 2°C.

[0024] The complex elastic modulus E* is a value measured in accordance with JIS-K6394 using a viscoelasticity spectrometer such as "IPLEXER (registered trademark)" manufactured by GABO under the conditions shown below. Initial distortion: 10% Amplitude: ±2% Frequency: 10Hz Deformation mode: tension Temperature: 70℃

[0025] In this embodiment, the first physical property value P and the second physical property value Q include both the rubber hardness and the complex modulus E*. In addition, the first physical property value and the second physical property value may further be specified, for example, a loss tangent tan δ.

[0026] The loss tangent tan δ is a value measured in accordance with the provisions of JIS-K6394 using the above-mentioned viscoelasticity spectrometer under the conditions shown below. Initial strain: 5% Amplitude: ±1% Frequency: 10Hz Deformation mode: Stretch Temperature: 30℃

[0027] The tread rubber 6 (tread portion 2a) of this embodiment is provided with circumferential grooves 7 that extend continuously in the tire circumferential direction. As a result, the tread rubber 6 is provided with a plurality of land portions 8 separated by the circumferential grooves 7.

[0028] The circumferential groove 7 of this embodiment includes a pair of crown circumferential grooves 7a, 7a and a pair of shoulder circumferential grooves 7b, 7b. The pair of crown circumferential grooves 7a, 7a are arranged on both outer sides of the tire equator C in the tire axial direction. The pair of shoulder circumferential grooves 7b, 7b are arranged between the crown circumferential groove 7a and the tread edge 2t. Note that the circumferential grooves 7 are not limited to this embodiment, and for example, some of the circumferential grooves 7 may be omitted, or other circumferential grooves 7 may be further provided.

[0029] In this specification, in the case where the tire 2 is a pneumatic tire, the "tread edge 2t" is specified as the axially outermost contact position when the tire 2 in a normal state is placed on a flat surface with a normal load and a camber angle of 0°. The normal state refers to an unloaded state in which the tire 2 is mounted on a normal rim 9 and inflated to a normal internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire are indicated as values ​​measured in a normal state.

[0030] A "genuine rim" is a rim that is determined for each tire by a standard system that includes the standard on which the tire 2 is based. Therefore, a genuine rim is, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0031] The "normal internal pressure" is the air pressure that is determined for each tire by each standard in a system of standards including the standard on which the tire 2 is based. Therefore, the normal internal pressure is, for example, the "maximum air pressure" 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 the "INFLATION PRESSURE" in the case of ETRTO.

[0032] The "normal load" is the load that is determined for each tire by each standard in the standard system including the standard on which the tire 2 is based. Therefore, the normal load is, for example, "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.

[0033] The land portion 8 of this embodiment includes a crown land portion 8a, a pair of middle land portions 8b, 8b, and a pair of shoulder land portions 8c, 8c. The crown land portion 8a is divided between a pair of crown circumferential grooves 7a, 7a. The pair of middle land portions 8b, 8b are divided by the crown circumferential groove 7a and the shoulder circumferential groove 7b. The pair of shoulder land portions 8c, 8c are divided by the shoulder circumferential groove 7b and the tread edge 2t. Note that the land portion 8 is not limited to such an embodiment, and for example, some of the land portions 8 may be omitted, or other land portions 8 may be further provided. In addition, each land portion 8 may be provided with, for example, a lateral groove (not shown) extending in a direction intersecting with the circumferential groove 7.

[0034] The carcass 4 is composed of at least one carcass ply 4A, one carcass ply in this embodiment. The carcass ply 4A has carcass cords (not shown) arranged at an angle of, for example, 75 to 90 degrees with respect to the tire equator C.

[0035] The belt layer 5 includes two inner and outer belt plies 5A and 5B 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 5A and 5B are overlapped with the belt cords crossing each other.

[0036] [Method for predicting tire wear state (first embodiment (first invention))] Incidentally, when performing a wear prediction simulation of a tread rubber 6 having a multi-layer rubber structure like the tire 2 of this embodiment, a method can be considered in which a single physical property value, such as an average of the physical property values ​​of each of a plurality of rubber layers, is defined in an FEM (finite element method) model of the tread rubber 6. However, such a method has a problem in that the prediction accuracy of the wear state of the tread rubber 6 is lower than that of an FEM model in which the physical property values ​​of each individual rubber layer are defined.

[0037] As a result of extensive research, the inventors have found that it is possible to accurately predict the wear state of the tread rubber 6 having a multi-layer rubber structure by changing the composite property value defined in the FEM model based on the rubber volume of the first layer 6A and the rubber volume of the second layer 6B, which change from moment to moment as the wear of the tread rubber 6 progresses. Based on this finding, in the prediction method of this embodiment of the first invention, the wear state is predicted while changing the composite property value in accordance with the wear progress of the tread rubber 6.

[0038] 3 is a flowchart showing the processing steps of the method of predicting the wear state of the tire 2 according to the first aspect of the invention. The prediction method of this embodiment uses a computer 1 (shown in FIG. 1).

[0039] [Enter tire model (first step)] In the prediction method of this embodiment, first, a tire model 10M is input to a computer 1 (first step S1). Fig. 4 is a perspective view showing an example of the tire model 10M and a road surface model 11M. Fig. 5 is a cross-sectional view showing an example of the tire model 10M. Fig. 6 is a partially enlarged view of the tread portion 10a of Fig. 5. Note that the tire model 10M of Fig. 4 is shown in a simplified manner, with the tread pattern, element F(i), and the like omitted.

[0040] As shown in Fig. 3, in a first step S1 of this embodiment, the tire 2 is modeled (discretized) with a finite number of elements F(i) (i = 1, 2, ...) based on the information on the tire 2 shown in Fig. 2. As a result, in the first step S1, a tire model 10M that can be handled by a numerical analysis method is set. As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method is appropriately adopted. In this embodiment, the finite element method is adopted.

[0041] The tire model 10M of this embodiment is created as a three-dimensional model. The tire model 10M may be created as a two-dimensional model. As shown in FIG. 5 and FIG. 6, for example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element is used for the element F(i). Each element F(i) has a plurality of nodes 12. Furthermore, each element F(i) is provided with linear edges 13 connecting the nodes 12, 12. For each element F(i), numerical data such as an element number, a node 12 number, and a coordinate value of the node 12 are defined. Furthermore, for each element F(i), numerical data such as material properties (e.g., density, Young's modulus, damping coefficient, etc.) of the tire components shown in FIG. 2 may be defined.

[0042] In the tire model 10M of the present embodiment, a carcass ply model 14MA which models the carcass ply 4A shown in FIG. 2, and belt ply models 15MA and 15MB which model the belt plies 5A and 5B shown in FIG. 2, respectively, are set.

[0043] Furthermore, the tire model 10M includes a tread rubber model 16M that models the tread rubber 6. This tread rubber model 16M can be defined, for example, by dividing the region 6R (shown in FIG. 2) occupied by the tread rubber 6 by the boundary BR (shown in FIG. 2) between the first layer 6A and the second layer 6B, and discretizing each of the first layer 6A and the second layer 6B into a finite number of elements F(i). In this case, the boundary BR shown in FIG. 6 and the side 13 or face (not shown) of the element F(i) are associated with each other and discretized, so that the degree of freedom of discretization (mesh creation) is reduced, and an element F(i) that is smaller than necessary or an element F(i) with a distorted shape may be formed. When such a small element F(i) is formed, the calculation time may increase. On the other hand, when an element F(i) with a distorted shape is formed, the calculation accuracy of the wear state of the tread rubber 6 shown in FIG. 2 may decrease.

[0044] The first step S1 of this embodiment includes a step of discretizing the region 6R occupied by the tread rubber 6 shown in FIG. 2 into a finite number of elements F(i) regardless of the boundary BR (the virtual line in FIG. 2 and FIG. 6) between the first layer 6A and the second layer 6B to define the tread rubber model 16M shown in FIG. 5 and FIG. 6. This increases the degree of freedom of discretization (mesh creation), and suppresses the formation of elements F(i) that are smaller than necessary or elements F(i) that are distorted in shape. This can reduce the calculation time and improve the calculation accuracy. In addition, since the element F(i) can be easily enlarged, the number of elements F(i) to be calculated can be reduced, and the calculation time can be further reduced. In this specification, "irrelevant" means that the modeling is performed without any association between the boundary BR and the side 13 or face (not shown) of the element F(i).

[0045] The tread rubber model 16M of this embodiment is provided with a circumferential groove 17 and a land portion 18, similar to the tread portion 2a (tread rubber 6) shown in Fig. 2. The circumferential groove 17 includes a pair of crown circumferential grooves 17a, 17a and a pair of shoulder circumferential grooves 17b, 17b. The land portion 18 includes a crown land portion 18a, a pair of middle land portions 18b, 18b, and a pair of shoulder land portions 18c, 18c.

[0046] A common composite physical property value A is defined for the elements F(i) of the tread rubber model 16M. In this embodiment, the composite physical property value A is defined for the elements F(i) as the above-mentioned material property. With such composite physical property value A, for example, even if each of the first physical property value P and the second physical property value Q is not defined in the tread rubber model 16M, the physical property value of the tread rubber 6 having the multi-layer rubber structure as a whole can be defined in the tread rubber model 16M. Therefore, modeling of the tire 2 can be simplified.

[0047] The composite property value A includes the above-mentioned rubber hardness or complex elastic modulus E*, and in this embodiment, includes both the rubber hardness and the complex elastic modulus E*. The composite property value A may further include, for example, loss tangent tan δ.

[0048] The composite physical property value A is calculated based on the rubber volume α of the first layer 6A, the rubber volume β of the second layer 6B, the first physical property value P, and the second physical property value Q.

[0049] The rubber volumes α and β of the first layer 6A and the second layer 6B can be appropriately specified. In this embodiment, the rubber volumes α and β are the volumes of the first layer 6A and the second layer 6B. As a result, the rubber volumes α and β are specified for the entire circumferential area of ​​the tire where the tread rubber 6 wears, so that it is possible to accurately define the composite property value in accordance with the progress of wear of the tread rubber 6.

[0050] The rubber volumes α and β of the first layer 6A and the second layer 6B are not limited to volumes, but may be, for example, cross-sectional areas in a tire meridian cross section. Such cross-sectional areas allow each rubber volume to be determined in a short time, compared to volumes.

[0051] From a similar viewpoint, the rubber volumes α and β of the first layer 6A and the second layer 6B may be, for example, thicknesses in a tire meridian cross section. Such thicknesses allow each rubber volume to be determined in a short time compared to the volume or cross-sectional area. In this specification, the "thickness in the tire meridian cross section" is determined as the average thickness in the tire meridian cross section for each of the first layer 6A and the second layer 6B.

[0052] The composite physical property value A can be calculated appropriately based on the rubber volume α of the first layer 6A, the rubber volume β of the second layer 6B, the first physical property value P, and the second physical property value Q. In this embodiment, the composite physical property value A is specified as the average value of the first physical property value P and the second physical property value Q weighted by the rubber volumes α and β of the first layer 6A and the second layer 6B, respectively. In this embodiment, when the composite physical property value A includes rubber hardness and loss tangent tan δ, for example, the composite physical property value A is specified based on the idea of ​​a parallel spring. In this case, for example, the following formula (1) is used. A = (αP + βQ) / (α + β) … (1) Where: A: Composite property value before wear α: Volume of the first layer of rubber before wear β: Volume of rubber in the second layer before wear P: First physical property value Q: Second physical property value

[0053] In the above formula (1), αP is a value obtained by weighting the first physical property value P by the rubber volume α of the first layer 6A before wear. βQ is a value obtained by weighting the second physical property value Q by the rubber volume β of the second layer 6B before wear. α+β is the rubber volume of the entire tread rubber 6 before wear. The sum of these weighted physical properties αP+βQ is divided by the rubber volume α+β of the entire tread rubber 6 before wear, and the composite physical property value A is obtained as the average value of the first physical property value P and the second physical property value Q. In addition, when the composite physical property value A includes the complex elastic modulus E*, the composite physical property value A may be specified, for example, based on the concept of a series spring. In this embodiment, the composite physical property value A is obtained for each of the rubber hardness and the complex elastic modulus E*. These composite physical property values ​​A are defined for each element F(i) of the tread rubber model 16M.

[0054] In this embodiment, the composite physical property value A is defined using the above formula (1), but is not limited to this. For example, of the first physical property value P and the second physical property value Q, the physical property value that has a large effect on wear may be further weighted. The tire model 10M in which the composite physical property value A is defined is stored in the computer 1 (shown in FIG. 1).

[0055] [Input road surface model (road surface model input process)] Next, in the prediction method of this embodiment, a road surface model 11M (shown in FIG. 4) that models a road surface (not shown) is input to the computer 1 (road surface model input step S2). This road surface model 11M is used for running the tire model 10M in a second step S3 described later.

[0056] 4, in the road surface model input step S2, the road surface is modeled (discretized) using a finite number of elements G(i) (i=1, 2, ...) that can be handled by a numerical analysis method (in this embodiment, the finite element method) based on information about the road surface. As a result, in the road surface model input step S2, a road surface model 11M is set.

[0057] Element G(i) is a rigid plane element that is set to be undeformable. Element G(i) has a plurality of nodes 14. Furthermore, element G(i) is defined with numerical data such as an element number and the coordinate values ​​of the nodes 14.

[0058] In this embodiment, the road surface model 11M is exemplified as one having a smooth surface, but as necessary, it may be provided with minute irregularities, irregular steps, depressions, undulations, or irregularities approximating the actual road surface such as ruts, as in an asphalt road surface. The road surface model 11M is stored in the computer 1 (shown in FIG. 1).

[0059] [Run the tire model under specified conditions (step 2)] Next, in the prediction method of this embodiment, the computer 1 (shown in FIG. 1) runs the tire model 10M under predetermined conditions to calculate physical quantities related to the wear of the tread rubber 6 (second step S3).

[0060] The conditions for running the tire model 10M can be set as appropriate. Examples of the conditions include the mounting conditions of the tire model 10M, the load conditions of the tire model 10M, and the running speed of the tire model 10M. The mounting conditions include, for example, the conditions for achieving the above-mentioned normal state (normal rim 9, normal internal pressure). The load conditions include the above-mentioned normal load W. The running speed is set to, for example, a constant (for example, 60 km / h). In the second step S3 of this embodiment, similar to the procedure described in Patent Document 2 (JP Patent Publication 2019-91302), the tire model 10M is run (rolled) on the road surface model 11M based on the above-mentioned conditions. In the second step S3 of this embodiment, for example, the running of the tire model 10M is calculated in one minute time (unit time) of the simulation. By repeating this second step S3, the state in which the tire model 10M runs continuously is calculated.

[0061] Any physical quantity related to the wear of the tread rubber 6 can be appropriately adopted. The physical quantity in this embodiment includes wear energy. As shown in Fig. 5 and Fig. 6, in this embodiment, wear energy is calculated for at least one node 15 (in this example, all nodes) among all nodes 15 constituting the contact surface 16MS of the tread rubber model 16M.

[0062] The wear energy in this embodiment is calculated based on the procedure described in Patent Document 2. In the second step S3 of this embodiment, the wear energy is calculated for one small time period. Then, the second step S3 is repeated to sequentially calculate the wear energy of the running tire model 10M for each small time period in a chronological order. The calculated physical quantity (wear energy) is stored in a computer 1 (shown in FIG. 1).

[0063] [Calculate the amount of wear (3rd step)] Next, in the prediction method of this embodiment, the computer 1 (shown in FIG. 1) calculates the wear amount of the element F(i) of the tread rubber model 16M (third step S4) based on the physical amount related to the wear of the tread rubber 6. In this embodiment, the wear energy calculated in the second step S3 is used as the physical amount used in the calculation of the wear amount.

[0064] The wear amount of the element F(i) of the tread rubber model 16M can be calculated appropriately. In this embodiment, first, the wear progression rate is determined based on the procedure described in the above-mentioned Patent Document 2. Next, the wear progression rate is multiplied by the wear energy of each node 15 constituting the contact surface 16MS. As a result, the movement amount when each node 15 is assumed to be worn is determined based on the wear energy calculated for each node 15.

[0065] In the case where the rubber volumes of the first layer 6A and the second layer 6B are specified by volume as in this embodiment, the amount of reduction in volume is calculated for a plurality of elements F(i) of the tread rubber model 16M from the amount of movement of the nodes 15 constituting each element F(i). This amount of reduction in volume is calculated as the amount of wear of the element F(i). The amount of wear of the tread rubber model 16M is calculated by accumulating the amounts of wear of these elements F(i).

[0066] On the other hand, when the rubber volumes of the first layer 6A and the second layer 6B are specified by cross-sectional area, a plurality of elements F(i) of the tread rubber model 16M are specified in a predetermined tire meridian cross section of the tire model 10M, and the reduction in the cross-sectional area is calculated from the movement amount of the nodes 15 constituting each element F(i). This reduction in the cross-sectional area is calculated as the wear amount of the element F(i). The wear amounts of these elements F(i) are accumulated to calculate the wear amount of the tread rubber model 16M.

[0067] Also, when the rubber volumes of the first layer 6A and the second layer 6B are specified by thickness, a plurality of elements F(i) of the tread rubber model 16M are specified in a predetermined tire meridian cross section of the tire model 10M, and the reduction in thickness is calculated from the movement amount of the nodes 15 constituting each element F(i). This reduction in thickness is calculated as the amount of wear of the element F(i). The amount of wear of the tread rubber model 16M is calculated by accumulating the amounts of wear of these elements F(i).

[0068] In the third step S4 of this embodiment, the wear amount of each element F(i) of the tread rubber model 16M and the wear amount of the tread rubber model 16M are calculated in one micro time based on the above procedure. Then, the third step S4 is repeated, and the wear amount of each element F(i) and the wear amount of the tread rubber model 16M are calculated in chronological order for each micro time. In this embodiment, the cumulative value of the wear amount of the tread rubber model 16M calculated in chronological order is calculated as the wear amount of the tread rubber model 16M from the start of running of the tire model 10M. The wear amount is stored in the computer 1.

[0069] [Recalculate and update composite properties (step 4)] Next, in the prediction method of this embodiment, the composite property value of the tread rubber model 16M is recalculated and updated based on the amount of wear (fourth step S5). In this embodiment, the composite property value is recalculated and updated by the computer 1 (shown in FIG. 1), but the composite property value may be recalculated and updated by, for example, an operator or the like.

[0070] The composite property value can be appropriately recalculated based on the amount of wear. In the first step S1, as in this embodiment, when the composite property value A before wear is determined by the above formula (1), the recalculated composite property value B is also determined based on the idea of ​​parallel springs. In this case, for example, the following formulas (2) and (3) are used. B=((α-γ)P+βQ) / (α+β-γ) [α≧γ] …(2) B = Q [α<γ] …(3) Where: B: Recalculated composite properties α: Volume of the first layer of rubber before wear β: Volume of rubber in the second layer before wear γ: Wear amount of the tread rubber model from the start of driving (cumulative value) P: First physical property value Q: Second physical property value

[0071] The above formula (2) is used to recalculate the composite property value when the rubber volume α of the first layer 6A before wear is larger than the wear amount γ of the tread rubber model 16M since the start of driving (i.e., when the first layer 6A remains). In this formula (2), the wear amount (accumulated value) γ of the tread rubber model 16M since the start of driving is subtracted from the rubber volume α of the first layer 6A before wear and the rubber volume β of the second layer 6B before wear in the above formula (1). This allows for the acquisition of a composite property value B that corresponds to the change in the ratio (and thus the rigidity, etc.) between the rubber volume of the first layer 6A and the rubber volume of the second layer 6B, which changes from moment to moment as the wear of the tread rubber progresses.

[0072] On the other hand, the above formula (3) is used to recalculate the composite property value when the rubber volume α of the first layer 6A before wear is smaller than the wear amount γ of the tread rubber model 16M from the start of running (i.e., when the first layer 6A does not remain). In this case, since only the second layer 6B remains, the composite property value B is specified as the second property value Q of the second layer 6B.

[0073] The composite property value B recalculated based on the above formulas (2) and (3) in this embodiment is defined in the element F(i) of the tread rubber model 16M, thereby updating the composite property value of the tread rubber model 16M. Note that, when the composite property value A before wear is not specified by the above formula (1) (i.e., when the composite property value A is specified based on the concept of a series spring), the recalculated composite property value B is also specified based on the concept of a series spring.

[0074] [Determine whether the termination condition is met] Next, in the prediction method of this embodiment, the computer 1 (shown in FIG. 1) determines whether a predetermined end condition is satisfied (step S6). The end condition can be set appropriately, for example, a calculation end time, an upper limit value of the wear amount, etc. In this embodiment, the end condition is preferably input to the computer 1 (shown in FIG. 1) before the prediction method is carried out.

[0075] If it is determined in step S6 that the predetermined end condition is satisfied ("Yes" in step S6), the next step S7 may be carried out. On the other hand, if it is determined in step S6 that the predetermined end condition is not satisfied ("No" in step S6), the micro time may be advanced by one (step S8), and the second step S3 to the fourth step S5 may be carried out again. As a result, the second step S3 to the fourth step S5 are repeated until the end condition is satisfied, and the physical quantity and the amount of wear related to wear are repeatedly calculated while changing the composite physical property value in accordance with the progress of wear of the tread rubber 6. Therefore, it is possible to accurately predict the wear state of the tread rubber 6 having a multi-layer rubber structure.

[0076] In the prediction method of this embodiment, unlike Patent Document 2, the wear state is predicted without deforming the tread rubber model 16M into a worn state by movement of the node 15. This makes it possible to reduce the calculation time, for example, since it is not necessary to recalculate the contact state between the tire model 10M and the road surface model 11M at every minute time when the node 15 moves.

[0077] [Evaluate tire wear condition] Next, in the prediction method of this embodiment, the wear state of the tire model 10M (tire 2) is evaluated as to whether it is good or not (step S7). In this embodiment, the wear state is evaluated by a computer 1 (shown in FIG. 1), but is not particularly limited thereto, and may be evaluated by, for example, an operator or the like.

[0078] The wear state can be evaluated as appropriate. In this embodiment, when the wear amount γ of the tread rubber model 16M when the tire model 10M has traveled a predetermined distance from the start of travel is equal to or less than a predetermined threshold, the wear state can be determined to be good. The threshold can be set as appropriate according to the wear resistance performance required for the tire 2 shown in FIG. 2.

[0079] If it is determined in step S7 that the wear state is good ("Yes" in step S7), the tire model 10M meets the standard for wear resistance performance. In this case, for example, the tire 2 (shown in FIG. 2) is manufactured and produced based on the design factors of the tire model 10M (step S9). On the other hand, if it is determined in step S7 that the wear state is not good ("No" in step S7), the above standard is not met. For this reason, the tire 2 is redesigned (step S10). In step S10, for example, the structure or design factors of the tire 2 are changed. Then, the first step S1 to step S7 are performed again. As a result, the prediction method of this embodiment makes it possible to reliably manufacture and produce a tire 2 with excellent wear resistance performance.

[0080] [Method for predicting tire wear state (second embodiment (second invention))] In the above-mentioned first embodiment (first invention), as shown in Fig. 3, a fourth step S5 of recalculating and updating the composite property value of the tread rubber model 16M based on the wear amount is carried out, but the present invention is not limited to this. Fig. 7 is a flowchart showing the processing procedure of the method for predicting the wear state of the tire 2 according to the second invention. In the second invention, steps having the same functions as those in the above-mentioned first invention are given the same reference numerals, and the description thereof will be omitted.

[0081] In the second invention, the fourth step S5 is omitted. This is because, for example, when there is little need to consider the amount of wear (for example, when the tire has a small amount of wear or when the simulation ends at a stage when the amount of wear is small), the effect of the amount of wear on the composite property value is small, and therefore the prediction accuracy of the wear state of the tread rubber 6 is maintained even if the composite property value of the tread rubber model 16M is not recalculated and updated based on the amount of wear.

[0082] The first step S1 of the second invention includes a step of discretizing the region 6R occupied by the tread rubber 6 shown in Fig. 2 into a finite number of elements F(i) regardless of the boundary BR (the imaginary line in Fig. 2 and Fig. 6) between the first layer 6A and the second layer 6B, to define the tread rubber model 16M shown in Fig. 5 and Fig. 6. This eliminates the need to accurately reproduce the position of the boundary BR, increasing the degree of freedom in discretization (mesh creation), and suppressing the formation of elements F(i) that are smaller than necessary or elements F(i) that are distorted in shape. This makes it possible to shorten the time required for modeling the tread rubber 6 having a multi-layer rubber structure.

[0083] [Method for predicting tire wear state (third embodiment)] In the above embodiments (first invention and second invention), the physical quantity related to wear of the tread rubber 6 and the amount of wear were calculated without transforming the tread rubber model 16M into a worn state, but the present invention is not limited to such an embodiment. For example, the third step S4 may include a step of transforming the tread rubber model 16M into a worn state based on the amount of wear. The worn state is calculated by moving each node 15 (shown in FIG. 5 and FIG. 6) of the tread rubber model 16M based on the wear energy calculated at each node 15 according to the procedure of the above-mentioned Patent Document 2, for example.

[0084] In this embodiment, by deforming the tread rubber model 16M to a worn state, physical quantities related to wear can be calculated based on the shape of the worn tread rubber model 16M, similar to an actual tire 2 (shown in FIG. 2) that wears from moment to moment. This makes it possible to more accurately predict the wear state of the tread rubber having a multi-layer rubber structure.

[0085] 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 carried out in various forms. EXAMPLES

[0086] [Example A (First Invention)] A physical quantity (wear energy) related to wear of the tread rubber of a tire was calculated based on the processing procedure of the first invention shown in FIG. 3 (Example 1). In this Example 1, in the first step S1 shown in FIG. 3, the area occupied by the tread rubber was discretized into a finite number of elements regardless of the boundary between the first layer and the second layer, thereby defining a tread rubber model. A common composite property value calculated using the above formula (1) was defined for each element of this tread rubber model based on the rubber volume of the first layer, the rubber volume of the second layer, the first physical property value, and the second physical property value. Then, the second step S3 of calculating the physical quantity related to wear of the tread rubber shown in FIG. 3, the third step S4 of calculating the wear amount of the elements of the tread rubber model, and the fourth step S5 of recalculating and updating the composite property value of the tread rubber model based on the wear amount were repeated. The above formulas (2) and (3) were used for recalculating the composite property value.

[0087] In Comparative Example 1, a tread rubber model was defined in which the area occupied by the tread rubber was divided by the boundary between the first layer and the second layer, and each of the first layer and the second layer was discretized with a finite number of elements. For each element of this tread rubber model, a first physical property value was defined for each element of the first layer of the tread rubber model, and a second physical property value was defined for each element of the second layer of the tread rubber model, without defining a composite physical property value as in Example 1. Then, in Comparative Example 1, similar to Example 1, the second step S3 of calculating the physical quantity related to the wear of the tread rubber and the third step S4 of calculating the wear amount of the elements of the tread rubber model were repeated. Note that, unlike Example 1, in Comparative Example 1, the fourth step S5 of recalculating and updating the composite physical property value was omitted. The common specifications including the running conditions are as follows. The test results are shown in FIG. 7. Tire size: 215 / 50R19 Rim size: 19 x 7.5J Installation conditions: Regular rim, regular internal pressure Loading conditions Load: Normal load Traveling speed: 60km / h

[0088] FIG. 8 is a graph showing the relationship between the mileage and the wear energy. FIG. 8(a) is a graph calculated for the crown land portion, FIG. 8(b) is a graph calculated for the tire equator side of the middle land portion, and FIG. 8(c) is a graph calculated for the tread end side of the middle land portion. FIG. 8(d) is a graph calculated for the tire equator side of the shoulder land portion, and FIG. 8(e) is a graph calculated for the tread end side of the shoulder land portion. These graphs show a representative portion of the wear energy calculated for each small time period.

[0089] An approximation formula approximating the relationship between the travel distance and the wear energy was obtained for each of Example 1 and Comparative Example 1 shown in Figures 8(a) to (e). Then, the difference between the wear energy predicted by the approximation formula of Example 1 and the wear energy predicted by the approximation formula of Comparative Example 1 was obtained. This difference in wear energy was calculated as the absolute value of the difference between the wear energy predicted by the approximation formula of Example 1 and the wear energy predicted by the approximation formula of Comparative Example 1 at a distance L (shown in Figure 8) that exceeds the distance already traveled by the tire model. The distance L was set to 5000 km.

[0090] 8(a) to 8(e), the difference in wear energy was 5% or less of the wear energy at distance L predicted by the approximation formula of Example 1. Therefore, in Example 1, without dividing the tread rubber model into a first layer and a second layer and setting separate physical property values ​​for them as in Comparative Example 1, by using the above composite physical property values, it was possible to accurately predict the wear state of the tread rubber having a multi-layer rubber structure.

[0091] Moreover, in Example 1, unlike Comparative Example 1, the region occupied by the tread rubber is discretized regardless of the boundary between the first layer and the second layer, so the degree of freedom in discretization (mesh creation) is increased, and it is possible to suppress the formation of elements that are smaller than necessary or elements with distorted shapes. As a result, in Example 1, the time required for tire modeling can be reduced to 2 / 3 of that in Comparative Example 1. In this way, in Example 1, it is possible to accurately predict the wear state of the tread rubber having a multi-layer rubber structure, while reducing the time required for tire modeling.

[0092] [Example B (Second Invention)] A physical quantity (wear energy) related to wear of the tread rubber of a tire was calculated based on the processing procedure of the second invention shown in FIG. 7 (Example 2). In this Example 2, in the first step S1 shown in FIG. 7, the area occupied by the tread rubber was discretized into a finite number of elements regardless of the boundary between the first layer and the second layer, thereby defining a tread rubber model. A common composite physical property value calculated using the above formula (1) was defined for each element of this tread rubber model based on the rubber volume of the first layer, the rubber volume of the second layer, the first physical property value, and the second physical property value. Then, the second step S3 of calculating the physical quantity related to wear of the tread rubber shown in FIG. 7 and the third step S4 of calculating the wear amount of the elements of the tread rubber model were repeated.

[0093] In Comparative Example 2, similar to Comparative Example 1 described above, a tread rubber model was defined in which the area occupied by the tread rubber was divided by the boundary between the first layer and the second layer, and each of the first layer and the second layer was discretized with a finite number of elements. For each element of this tread rubber model, a first physical property value was defined for each element of the first layer of the tread rubber model, and a second physical property value was defined for each element of the second layer of the tread rubber model, without defining a composite physical property value as in Example 2. Then, in Comparative Example 2, similar to Example 2, the second step S3 of calculating the physical quantity related to the wear of the tread rubber and the third step S4 of calculating the wear amount of the elements of the tread rubber model were repeated. The common specifications including the running conditions are the same as those of Example 1 and Comparative Example 1 of Example A described above.

[0094] In Example 2, unlike Comparative Example 2, the region occupied by the tread rubber is discretized regardless of the boundary between the first and second layers, so the degree of freedom in discretization (mesh creation) is increased, and it is possible to suppress the formation of elements that are smaller than necessary or elements with distorted shapes. As a result, in Example 2, the time required for tire modeling can be reduced to 2 / 3 of that in Comparative Example 2. In this way, in Example 2, it is possible to reduce the time required for modeling work of tread rubber having a multi-layer rubber structure while maintaining the prediction accuracy of the wear state of the tread rubber.

[0095] [Note] The present invention includes the following aspects.

[0096] [Invention 1] A method for predicting a wear state of tread rubber disposed in a tread portion of a tire, comprising: The tread rubber includes at least a first layer made of a first rubber having a first physical property value, and a second layer made of a second rubber overlapping the first layer in the tire radial direction and having a second physical property value different from the first physical property value, The method comprises: A step of inputting a tire model including a tread rubber model in which the tire including the tread rubber is modeled with a finite number of elements into a computer, the first step being to define a common composite property value calculated based on the rubber volume of the first layer, the rubber volume of the second layer, the first property value, and the second property value for the elements of the tread rubber model; A second step in which the computer runs the tire model under predetermined conditions to calculate a physical quantity related to wear of the tread rubber; A third step in which the computer calculates the wear amount of the element of the tread rubber model based on the physical quantity; and a fourth step of recalculating and updating the composite property value of the tread rubber model based on the wear amount, The second step through the fourth step are repeated until a predetermined termination condition is satisfied. How to predict tire wear condition. [Invention 2] The method for predicting a tire wear state according to the first aspect of the present invention, wherein the first physical property value, the second physical property value and the composite physical property value include rubber hardness or complex modulus. [Invention 3] 3. A method for predicting the wear state of a tire as described in claim 1 or 2, wherein the composite property value is an average value of the first property value and the second property value weighted by the rubber volume of each of the first layer and the second layer. [Invention 4] 4. The method for predicting a wear state of a tire according to any one of claims 1 to 3, wherein the rubber volume of each of the first layer and the second layer is a cross-sectional area in a tire meridian cross section. [Invention 5] The method for predicting a tire wear state according to any one of claims 1 to 3, wherein the rubber volumes of the first layer and the second layer are volumes. [Invention 6] 4. The method for predicting a wear state of a tire according to any one of claims 1 to 3, wherein the rubber volumes of the first layer and the second layer are thicknesses in a tire meridian cross section. [Invention 7] 7. The method for predicting a tire wear state according to any one of claims 1 to 6, wherein the physical quantity is wear energy. [Invention 8] The method for predicting a wear state of a tire according to any one of claims 1 to 7, wherein the third step includes a step of transforming the tread rubber model into a worn state based on the amount of wear. [The present invention 9] The method for predicting the wear state of a tire according to any one of the present inventions 1 to 8, wherein the first step includes a step of discretizing the area occupied by the tread rubber with the elements regardless of the boundary between the first layer and the second layer, to define the tread rubber model. [The present invention 10] A method for predicting a wear state of tread rubber disposed in a tread portion of a tire, comprising: The tread rubber includes at least a first layer made of a first rubber having a first physical property value, and a second layer made of a second rubber overlapping the first layer in the tire radial direction and having a second physical property value different from the first physical property value, The method comprises: A step of inputting a tire model including a tread rubber model in which the tire including the tread rubber is modeled with a finite number of elements into a computer, the first step being to define a common composite property value calculated based on the rubber volume of the first layer, the rubber volume of the second layer, the first property value, and the second property value for the elements of the tread rubber model; A second step in which the computer runs the tire model under predetermined conditions to calculate a physical quantity related to wear of the tread rubber; and a third step in which the computer calculates the wear amount of the element of the tread rubber model based on the physical quantity, The second step and the third step are repeated until a predetermined termination condition is satisfied; The first step includes a step of discretizing an area occupied by the tread rubber with the elements regardless of a boundary between the first layer and the second layer to define the tread rubber model. How to predict tire wear condition. [Explanation of symbols]

[0097] S1 1st process S3 2nd process S4 3rd process S5 4th process

Claims

1. A method for predicting a wear state of tread rubber disposed in a tread portion of a tire, comprising: The tread rubber includes at least a first layer made of a first rubber having a first physical property value, and a second layer made of a second rubber overlapping the first layer in the tire radial direction and having a second physical property value different from the first physical property value, The method comprises: A step of inputting a tire model including a tread rubber model in which the tire including the tread rubber is modeled with a finite number of elements into a computer, the first step being to define a common composite property value calculated based on the rubber volume of the first layer, the rubber volume of the second layer, the first physical property value, and the second physical property value for the elements of the tread rubber model; A second step in which the computer runs the tire model under predetermined conditions to calculate a physical quantity related to wear of the tread rubber; A third step in which the computer calculates the wear amount of the element of the tread rubber model based on the physical quantity; and a fourth step of recalculating and updating the composite property value of the tread rubber model based on the amount of wear, The second step through the fourth step are repeated until a predetermined termination condition is satisfied. How to predict tire wear condition.

2. The method for predicting a tire wear state according to claim 1 , wherein the first physical property value, the second physical property value, and the composite physical property value include rubber hardness or complex modulus.

3. 2. The method for predicting the wear state of a tire according to claim 1, wherein the composite property value is an average value of the first property value and the second property value weighted by the rubber volumes of the first layer and the second layer, respectively.

4. The method for predicting a wear state of a tire according to claim 1 , wherein the rubber volume of each of the first layer and the second layer is a cross-sectional area in a meridian cross section of the tire.

5. The method for predicting a wear state of a tire according to claim 1 , wherein the rubber volume of each of the first layer and the second layer is a volume.

6. The method for predicting a wear state of a tire according to claim 1 , wherein the rubber volumes of the first layer and the second layer are thicknesses in a meridian cross section of the tire.

7. The method for predicting a wear state of a tire according to claim 1 , wherein the physical quantity is wear energy.

8. 2. The method for predicting a wear state of a tire according to claim 1, wherein the third step includes a step of transforming the tread rubber model into a worn state based on the amount of wear.

9. 2. The method for predicting a wear state of a tire according to claim 1, wherein the first step includes a step of discretizing an area occupied by the tread rubber with the elements regardless of a boundary between the first layer and the second layer to define the tread rubber model.

10. A method for predicting a wear state of tread rubber disposed in a tread portion of a tire, comprising: The tread rubber includes at least a first layer made of a first rubber having a first physical property value, and a second layer made of a second rubber overlapping the first layer in the tire radial direction and having a second physical property value different from the first physical property value, The method comprises: A step of inputting a tire model including a tread rubber model in which the tire including the tread rubber is modeled with a finite number of elements into a computer, the first step being to define a common composite property value calculated based on the rubber volume of the first layer, the rubber volume of the second layer, the first physical property value, and the second physical property value for the elements of the tread rubber model; A second step in which the computer runs the tire model under predetermined conditions to calculate a physical quantity related to wear of the tread rubber; and a third step in which the computer calculates the wear amount of the element of the tread rubber model based on the physical quantity, The second step and the third step are repeated until a predetermined termination condition is satisfied; The first step includes a step of discretizing an area occupied by the tread rubber with the elements regardless of a boundary between the first layer and the second layer to define the tread rubber model. How to predict tire wear condition.

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