Tire wear simulation method

Abstract

To provide a simulation method capable of calculating a wear state having a high correlation with a wear state of a real vehicle.SOLUTION: A simulation method for calculating a wear state of a tread part of a tire includes a step S1 of inputting a tire model for calculation in a computer, and a simulation step S2 of making the computer calculate a wear state using the tire model. The input tire model includes an initial wear tread part in a previously slightly worn state compared to the tread part of a new tire. The form of the initial wear tread part is a form in which changes of at least one wear feature amount for specifying wear of the tread part from a new product state are converged in a previously set small range.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for simulating tire wear conditions. [Background technology]

[0002] Patent Document 1 listed below describes a method for simulating tire wear conditions. In this method, a tire model is first created according to the tire to be evaluated. Next, the tire model is rolled on a virtual road surface to acquire the wear characteristics of the tire model. Then, the tread surface is recessed based on the wear characteristics, and the tire model is corrected to a worn state. [Prior art documents] [Patent documents]

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

[0004] Although the above method calculates the state of wear as it progresses from moment to moment, there are cases where this state deviates from the state of wear on an actual vehicle.

[0005] The present disclosure has been devised in consideration of the above-described circumstances, and its main purpose is to provide a simulation method capable of calculating a wear state that is highly correlated with the wear state of an actual vehicle. [Means for solving the problem]

[0006] The present disclosure provides a simulation method for calculating the wear state of a tire tread portion, the simulation method including: a step of inputting a tire model for calculation into a computer; and a simulation step in which the computer calculates the wear state using the tire model, wherein the input tire model has an initially worn tread portion that is in a state of slight pre-wear compared to the tread portion of the tire when new, and the shape of the initially worn tread portion is a shape in which the change from when the tire was new in at least one wear feature that specifies the wear of the tread portion has converged to a predetermined small range. [Effects of the Invention]

[0007] By employing the above steps, the tire wear state simulation method of the present disclosure makes it possible to calculate a wear state that is highly correlated with the wear state of an actual vehicle. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of a computer for executing a method for simulating a tire wear state. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a tire for which a wear state is calculated. [Figure 3] 1 is a flowchart showing an example of a processing procedure of a tire wear state simulation method. [Figure 4] 10 is a flowchart showing an example of a processing procedure of a tire model input step. [Figure 5] 10 is a graph showing the relationship between wear feature amount and mileage. [Figure 6] FIG. 2 is a perspective view showing an example of a tire model and a road surface model. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a tire model. [Figure 8] 1(a) is a graph showing the relationship between the amount of wear and the position in the axial direction of the tire for the working example and the experimental example, and FIG. 1(b) is a graph showing the relationship between the amount of wear and the position in the axial direction of the tire for the comparative example and the experimental example. [Figure 9] FIG. 1 is a cross-sectional view showing a new tire. [Figure 10] 10 is a flowchart showing an example of a processing procedure of a tire model input step according to another embodiment. [Figure 11] FIG. 2 is a cross-sectional view showing a new tire model. [Figure 12] (a) is an enlarged view of a new tire model, and (b) is an enlarged view of a tire model in which the nodes on the tread have been moved. [Figure 13] 10 is a flowchart showing an example of a processing procedure of a tire model input step according to still another embodiment. [Figure 14] FIG. 2 is a cross-sectional view showing the shape of a tread portion that does not have a portion where wear progresses relatively quickly. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. Note that the drawings are intended to enhance understanding of the contents of the disclosure, and therefore, some drawings may contain exaggerated representations and the scales may not strictly match between the drawings.

[0010] In the tire wear simulation method of this embodiment (hereinafter sometimes simply referred to as the "simulation method"), the wear state of the tread portion of the tire is calculated. The simulation method of this embodiment uses a computer.

[0011] [computer] FIG. 1 is a perspective view showing an example of a computer 1 for executing a tire wear state simulation method. 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 is provided with, for example, a central processing unit (CPU), a read-only memory (ROM), 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 simulation method of this embodiment. Therefore, the computer 1 is configured as a tire wear state simulation device.

[0012] [tire] 2 is a cross-sectional view showing an example of a tire for which the wear state is calculated. In this embodiment, a tire 2 has a tread portion 3 provided with circumferential grooves 4 extending continuously in the tire circumferential direction. As a result, the tread portion 3 is provided with a plurality of land portions 5 separated by the circumferential grooves 4.

[0013] The circumferential grooves 4 of this embodiment include a pair of crown circumferential grooves 4A, 4A arranged on both axially outer sides of the tire equator C, and a pair of shoulder circumferential grooves 4B, 4B arranged between the crown circumferential groove 4A and the tread edge 3t. Note that the circumferential grooves 4 are not limited to this embodiment, and for example, some of the circumferential grooves may be omitted, or other circumferential grooves (not shown) may be further provided.

[0014] The land portion 5 of this embodiment includes a crown land portion 5A, a pair of middle land portions 5B, 5B, and a pair of shoulder land portions 5C, 5C. The crown land portion 5A is divided between a pair of crown circumferential grooves 4A, 4A. The pair of middle land portions 5B, 5B are divided by the crown circumferential groove 4A and the shoulder circumferential groove 4B. The pair of shoulder land portions 5C, 5C are divided by the shoulder circumferential groove 4B and the tread edge 3t. These shoulder land portions 5C, 5C are arranged axially outward of the crown land portion 5A and on the pair of tread edges 3t, 3t sides, respectively. Note that the land portion 5 is not limited to this embodiment. For example, some land portions may be omitted, or other land portions (not shown) may be further provided. Furthermore, each land portion 5 may be provided with, for example, a lateral groove (not shown) extending in a direction intersecting with the circumferential groove 4.

[0015] In this specification, when the tire 2 is a pneumatic tire, the "tread edge 3t" is specified as the axially outermost contact point when the tire 2 is in a normal state and 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 and inflated to a normal internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire are indicated by values ​​measured in the normal state.

[0016] A "genuine rim" is a rim that is defined 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, or a "measuring rim" for ETRTO.

[0017] The "normal internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standard on which the tire 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.

[0018] The "normal load" is the load 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.

[0019] In most actual tires 2, the wear of the tread portion 3 is not uniform from when the tire is new until the initial stage of wear when the tire has slightly progressed, and the portions that are more susceptible to wear wear relatively quickly (initial wear). Figure 2 shows the shape of the tread portion 3 in the initial stage of wear, and the cross-sectional shape 7 of the tread portion 3 when new is indicated by a two-dot chain line.

[0020] Examples of parts that are prone to wear include the contact surface 8A of the crown land portion 5A, the pair of shoulder land portions 5C, the contact surfaces 8C of the pair of shoulder land portions 5C, and corner portions 10 between the contact surface 8 of the tread portion 3 and the groove walls 9 of the circumferential grooves 4. The parts that are prone to wear vary depending on the tread pattern, etc.

[0021] As shown in Figure 2, the contact shape at the time of initial wear differs from that at the time of a new tire (shown by the two-dot chain line in Figure 2). On the other hand, after the initial wear, the change in wear of the tread portion 3 tends to converge (become uniform). This is thought to be because corners 10, which are prone to wear, wear out early during the initial wear and no longer affect the wear of the tread portion 3 after the initial wear. Therefore, incorporating wear that progresses from the shape of the tread portion 3 at the time of initial wear into the simulation is effective for obtaining calculation results that have a high correlation with the wear state of an actual vehicle. Note that, in conventional methods, the state in which wear progresses over time is calculated for a tire model (not shown) that models a new tire (shown by the two-dot chain line in Figure 2), but the shape of the tread portion 3 at the time of initial wear is not taken into account. As a result, the wear state calculated by the conventional method sometimes deviates from the wear state of an actual vehicle.

[0022] [Tire wear simulation method] In the simulation method of this embodiment, the wear state of the tread portion 3 of the tire 2 is calculated based on the shape of the tread portion 3 that has reached initial wear. Fig. 3 is a flowchart showing an example of the processing procedure of the simulation method for the tire wear state.

[0023] [Tire model input process] In the simulation method of this embodiment, first, a tire model for calculation is input to the computer 1 (tire model input step S1). Fig. 4 is a flowchart showing an example of the processing procedure of the tire model input step S1.

[0024] [Initial wear shape acquisition process (first embodiment)] In the tire model input process S1 of this embodiment, first, the shape of the tread portion 3 at the time of initial wear (shown in FIG. 2), which is a state in which the tire 2 has been slightly worn in advance compared to the tread portion 3 at the time of new (shown by the two-dot chain line in FIG. 2), is acquired (initial wear shape acquisition process S11).

[0025] The shape of the tread portion 3 at the time of initial wear can be appropriately specified. In this embodiment, the shape of the tread portion 3 at the time of initial wear is specified as a shape in which a change from a new product in at least one wear feature amount that specifies the wear of the tread portion 3 shown in FIG. 2 has converged to a predetermined small range.

[0026] Any wear characteristic amount can be appropriately adopted as long as it can identify the wear of the tread portion 3. Due to the wear of the portions that are relatively prone to wear as described above, at least one of the changes in wear of the crown land portion 5A and the shoulder land portion 5C may become large from the time of new use to the initial wear stage. Note that these changes in wear tend to resolve (the changes relatively converge) after the initial wear stage. For this reason, the wear characteristic amount may include the ratio of the wear amount of the crown land portion 5A to the wear amount of the shoulder land portion 5C.

[0027] In addition to the above-mentioned changes in wear, there may be cases where at least one of the changes in wear of one shoulder land portion 5C and the changes in wear of the other shoulder land portion 5C increases, or where the change in the radius of curvature R of the contact surface 8 of the tread portion 3 increases. Note that these changes in wear and curvature radius also tend to resolve (the changes converge relatively) after the initial wear. Therefore, the wear feature amount may include the ratio between the amount of wear of one shoulder land portion 5C and the amount of wear of the other shoulder land portion 5C, and the radius of curvature R of the contact surface 8 of the tread portion 3.

[0028] The wear amount of each of the land portions 5A to 5C and the radius of curvature R of the contact patch 8 of the tread portion 3 can be determined as appropriate. In this embodiment, the wear amount of each of the land portions 5A to 5C is determined as the average value of wear amounts measured at a plurality of measurement points (e.g., 4 to 10 points) set at equal intervals in the tire circumferential direction. The radius of curvature R in this embodiment can be determined by measuring the radius of curvature of an arc passing through the intersection 11 of the tire equator C and the contact patch 8 and the pair of tread edges 3t, 3t at the above-mentioned plurality of measurement points and averaging these radii of curvature.

[0029] In this embodiment, the ratio of the wear amount of the crown land portion 5A to the wear amount of the shoulder land portion 5C is adopted as the wear feature, but other wear feature may be adopted, or all wear feature may be adopted.

[0030] In the initial wear shape acquisition step S11 of this embodiment, the tire 2 is gradually worn from when it is new, and the shape of the tread portion 3 is acquired in which the change in the wear feature amount from when it is new converges to a predetermined small range. Fig. 5 is a graph showing the relationship between the wear feature amount and the mileage. In Fig. 5, the mileage of a new tire is "0".

[0031] In this embodiment, first, a vehicle equipped with new tires 2 is driven, and wear feature values ​​are acquired at predetermined distance intervals. Next, the ratio between the currently (most recently) acquired wear feature value and the previously acquired wear feature value (the value acquired just before that) is acquired. When the ratio of these wear feature values ​​falls within a predetermined range (e.g., 0.9 to 1.1 (90% to 110%)), it is determined that the change in the wear feature value from when the tire was new has converged to a small range. The shape of the tread portion 3 at this convergence is identified as the shape of the tread portion 3 at the time of initial wear (shown in FIG. 2 as an example). The identified shape is stored in the computer 1, for example, as data (e.g., coordinate values) that can be handled by the computer 1.

[0032] [Modeling process (first embodiment)] Next, in the tire model input step S1 of this embodiment, a tire model including an initially worn tread portion 22 is modeled based on the acquired shape (modeling step S12). Fig. 6 is a perspective view showing an example of the tire model 15 and the road surface model 16. Fig. 7 is a cross-sectional view showing an example of the tire model 15. In Fig. 6, the tread pattern of the tire model 15 is omitted.

[0033] In the modeling step S12 of this embodiment, as shown in FIG. 7, the acquired shape of the tire 2 at the time of initial wear (shown in FIG. 2) is discretized using a finite number of elements F(i) (i=1, 2, ...) that can be handled by a numerical analysis method. This results in modeling of a tire model 15. As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method can be appropriately adopted, but in this embodiment, the finite element method is adopted.

[0034] As the element F(i), it is desirable to use, for example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element. Each element F(i) has a plurality of nodes 17. Numerical data such as the element number, the node 17 number, the coordinate values ​​of the nodes 17, and material properties (e.g., density, Young's modulus and / or damping coefficient) are defined for each element F(i).

[0035] In the tread portion 21 of the tire model 15 of this embodiment, a circumferential groove model 19 and a land portion model 20 are set. The circumferential groove model 19 is a model of the circumferential groove 4 (shown in FIG. 2). On the other hand, the land portion model 20 is a model of the land portion 5 (shown in FIG. 2).

[0036] The circumferential groove model 19 includes a pair of crown circumferential groove models 19A, 19A and a pair of shoulder circumferential groove models 19B, 19B. The pair of crown circumferential groove models 19A, 19A are models of a pair of crown circumferential grooves 4A, 4A (shown in FIG. 2), respectively. The pair of shoulder circumferential groove models 19B, 19B are models of a pair of shoulder circumferential grooves 4B, 4B (shown in FIG. 2), respectively.

[0037] The land portion model 20 includes a crown land portion model 20A, a pair of middle land portion models 20B, 20B, and a pair of shoulder land portion models 20C, 20C. The crown land portion model 20A is a model of the crown land portion 5A (shown in FIG. 2). The pair of middle land portion models 20B, 20B are modeled respectively of the pair of middle land portions 5B, 5B (shown in FIG. 2). The pair of shoulder land portion models 20C, 20C are modeled respectively of the pair of shoulder land portions 5C, 5C (shown in FIG. 2).

[0038] In the modeling step S12 of this embodiment, the tire model 15 is modeled based on the shape of the tread portion 3 at the time of initial wear (shown in FIG. 2 as an example). Therefore, the tire model 15 has an initial wear tread portion 22 that is slightly worn compared to the tread portion 3 of the tire 2 when it is new (shown by the two-dot chain line in FIG. 2). The shape of this initial wear tread portion 22 is a shape in which the change from when it was new in at least one wear feature value (in this example, the ratio of the wear amount of the crown land portion 5A to the wear amount of the shoulder land portion 5C) has converged to a predetermined small range. Therefore, in the modeling step S12, it is possible to accurately model a tire 2 having a tread portion 3 that has reached initial wear (i.e., the subsequent change in wear becomes relatively uniform). The tire model 15 is stored in the computer 1 (shown in FIG. 1).

[0039] [Simulation process] Next, in the simulation method of this embodiment, the computer 1 calculates the wear state using the tire model 15 (simulation step S2). The calculation of the wear state can be performed appropriately based on the procedure of the prior art (for example, Patent Document 2).

[0040] In the simulation step S2 of this embodiment, first, the state of the tire model 15 rolling on the road surface model 16 is calculated, similar to the procedure described in the patent document (JP 2019-91302 A). The rolling calculation of the tire model 15 is not limited to the rolling conditions obtained from actual vehicle running, and can be performed under any rolling conditions. Then, in the simulation step S2, the movement of each node 17 of the tread portion 21 (initial wear tread portion 22) shown in FIG. 7 is calculated based on the wear energy calculated at each node 17. As a result, in the simulation step S2, the state of progress of wear of the tread portion 21 can be calculated.

[0041] In the simulation step S2, the wear state of the tire model 15 may be calculated (for example, calculated for each unit time T(x) of the simulation) until a termination condition is met. The termination condition may be set appropriately, for example, as a calculation end time or the amount of wear of the tread portion 21. In addition, in the simulation step S2, commercially available finite element analysis application software such as LS-DYNA manufactured by LSTC is used. The unit time T(x) may be set appropriately depending on the required simulation accuracy. The tire model 15 whose wear state has been calculated is stored in the computer 1.

[0042] In the simulation step S2 of this embodiment, the wear state of the tire model 15 is calculated based on the initially worn tread portion 22 where the change in wear has converged. As a result, the simulation method of this embodiment can incorporate wear that progresses from the shape of the tread portion 3 that has reached initial wear into the simulation. Compared to conventional methods that calculate the wear state of a tire model (not shown) that models a new tire (shown by the two-dot chain line in FIG. 2), the simulation method of this embodiment can calculate a wear state that is highly correlated with the wear state of an actual vehicle.

[0043] [Evaluation process] Next, in the simulation method of this embodiment, the wear state of the tread portion 21 is evaluated as to whether it is good or bad (step S3). The evaluation of the wear state may be performed by the computer 1 or by an operator. The wear state may be evaluated as appropriate depending on the tire 2 (shown in FIG. 2) to be evaluated. For example, the wear state may be evaluated based on the presence or absence of uneven wear of each land portion model 20.

[0044] If it is determined in step S3 that the wear state of the tread portion 21 is good ("Yes" in step S3), the tire 2 is manufactured based on the design factors of the tire 2 shown in Fig. 2 (step S4). On the other hand, if it is determined in step S3 that the wear state of the tread portion 21 is not good ("No" in step S4), the design factors of the tire 2 are changed (step S5), and the tire model input steps S1 to S3 are performed again. As a result, the simulation method of this embodiment can reliably design and manufacture a tire 2 in which the wear state of the tread portion 3 is good.

[0045] [Tire model input process (second embodiment)] In the tire model input step S1 in the embodiments described above, the tire 2 shown in FIG. 2 is gradually worn from a new tire, and the shape of the tread portion 3 in which the change in the wear feature amount from a new tire has converged to a predetermined small range is acquired. However, the present invention is not limited to this. For example, the shape of the tread portion 3 in which the change in the wear feature amount from a new tire has converged may be predicted without actually wearing the tire 2. The same components as those in the embodiments described above are denoted by the same reference numerals, and a description thereof may be omitted.

[0046] [Initial wear shape acquisition process (second embodiment)] In the initial wear shape acquisition step S11 of this embodiment, the shape of the tread portion 3 is predicted such that changes in the wear feature quantities from when the tire is new can converge within a predetermined small range. The shape prediction of the tread portion 3 can be performed as appropriate as long as the changes in the wear feature quantities can converge.

[0047] In this embodiment, the aforementioned converged shape of the tread portion 3 (shown in FIG. 2 as an example) is predicted by removing (deleting) the aforementioned parts that are prone to wear from the shape of the tread portion 3 when new (shown by the two-dot chain line in FIG. 2). The parts that are prone to wear can be identified, for example, based on a wear tendency analyzed from the shape of the tread portion 3 in the initial wear state that has been obtained so far.

[0048] In addition, in order to check whether the change in the wear feature amount from when the tire is new has converged for the predicted shape of the tread portion 3, for example, a rolling calculation of the tire model 15 may be performed prior to the simulation step S2 shown in Figure 3.

[0049] The rolling calculation is performed in the same procedure as the rolling calculation in the simulation step S2, using a tire model modeled based on the predicted shape of the tread portion 3. In this rolling calculation, for example, the wear energy of the crown land portion model 20A and the shoulder land portion model 20C is calculated.

[0050] In this embodiment, the total wear energy is calculated at predetermined intervals (travel distance in the simulation). The total wear energy is correlated with the actual wear amount of the tread portion 3. Therefore, for example, the ratio of the wear energy of the crown land portion model 20A to the wear energy of the shoulder land portion model 20C can be treated as a wear feature amount (the ratio of the wear amount of the crown land portion 5A to the wear amount of the shoulder land portion 5C shown in FIG. 2).

[0051] In this embodiment, if the ratio between the most recently calculated wear energy and the wear energy calculated just before the most recently calculated wear energy converges within the above range, it can be determined that the change in the wear feature amount from when the tire is new has converged for the predicted shape of the tread portion 3. As a result, in this embodiment, it is possible to reliably predict the shape of the tread portion 3 for which the change in the wear feature amount from when the tire is new can converge, even without actually wearing down the tire 2. The predicted shape of the tread portion 3 is stored in the computer 1.

[0052] [Modeling process (second embodiment)] In the modeling step S12 of this embodiment, a tire model 15 (shown in FIG. 7) having an early-wear tread portion 22 is modeled based on the predicted shape. As a result, in the modeling step S12 of this embodiment, as in the previous embodiments, it is possible to accurately model a tire 2 having a tread portion 3 that has reached the early wear stage shown in FIG. 2 (i.e., subsequent wear changes become relatively uniform). Note that the modeling procedure of this embodiment can employ the modeling procedures of the previous embodiments.

[0053] In the simulation step S2 of this embodiment, the wear state of the tire model 15 is calculated based on the initially worn tread portion 22 where the change in wear has converged. Therefore, the simulation method of this embodiment can increase the correlation with the wear state of an actual vehicle.

[0054] [Tire model input process (third embodiment)] In the embodiments described above, the shape of the initially worn tread portion 22 (shown in FIG. 7 ) is determined as a shape in which the change from when new of at least one wear feature that specifies the wear of the tread portion 3 converges within a predetermined small range, but the present invention is not limited to this. For example, the initially worn tread portion 22 may be a portion of the outer surface of the tread portion when new that does not have a portion where wear progresses relatively quickly. The same components as those in the embodiments described above are designated by the same reference numerals, and their description may be omitted.

[0055] FIG. 9 is a cross-sectional view showing a new tire 2. The tread portion 3 is provided with grooves 12 each having a pair of groove walls 9, 9 extending radially inward from the tread surface 13 (contact surface 8). The grooves 12 include, for example, circumferential grooves 4 and lateral grooves 6, but may include only one of these. On the outer surface of the tread portion 3 when new, corner portions 10 between the tread surface 13 and each of the pair of groove walls 9, 9 tend to wear more easily than other portions. Therefore, the corner portions 10 are included in portions 14 where wear progresses relatively quickly (portions that wear out early during initial wear).

[0056] In this embodiment, an early wear tread portion is set on the outer surface of the tread portion 3 when new, which does not have corner portions 10. If the tire includes portions 14 in addition to the corner portions 10 where wear progresses relatively quickly, the early wear tread portion is set without those portions (portions other than the corner portions 10).

[0057] 10 is a flowchart showing an example of a processing procedure of a tire model input step S1 of another embodiment. In the tire model input step S1 of this embodiment, a tire model having an initially worn tread portion is modeled using a finite number of elements F(i) having a plurality of nodes 17 shown in FIG. 7, as in the previous embodiments.

[0058] [Input of new tire model (third embodiment)] In the tire model input step S1 of this embodiment, first, a new tire model obtained by modeling a new tire 2 (shown in FIG. 9) is input to the computer 1 (step S13). FIG. 11 is a cross-sectional view showing a new tire model 25.

[0059] In step S13 of this embodiment, a new tire model 25 (shown in FIG. 9) is modeled (discretized) using elements F(i) having a plurality of nodes 17 (a finite number of elements that can be handled by a numerical analysis method). As a result, in step S13, a new tire model 25 having a tread surface 23 is set. The elements F(i) have edges 18 connecting the nodes 17, 17. In this embodiment, the edges 18 extend, for example, linearly.

[0060] In the tread portion 21 of the new tire model 25 of this embodiment, a circumferential groove model 19 and a land portion model 20 are set. Furthermore, the tread portion 21 may include a lateral groove model (not shown) that models the lateral grooves 6 (shown in FIG. 9 ).

[0061] The circumferential groove model 19 (lateral groove model (not shown)) of this embodiment is provided with a pair of groove walls 29, 29 extending radially inward from the tread surface 23. Furthermore, the tread portion 21 of this embodiment includes corner portions 30 between the tread surface 23 and each of the pair of groove walls 29, 29. Therefore, the new tire model 25 has portions 14 (corner portions 30) in the tread portion 21 where wear progresses relatively quickly. The new tire model 25 is stored in the computer 1.

[0062] [Moving the node of the tread (third embodiment)] Next, in the tire model input step S1 of this embodiment, at least some of the nodes 17 constituting the tread surface 23 of the new tire model 25 are moved radially inward to model a tire model 15 having an initially worn tread portion 22 (step S14). Fig. 12(a) is an enlarged view of the new tire model 25. Fig. 12(b) is an enlarged view of the tire model 15 after the nodes 17 of the tread surface 23 have been moved.

[0063] 12(a), in step S14 of this embodiment, some of the nodes 17 constituting the tread 23 are moved radially inward in order to eliminate the relatively fast wear portions 14 (corner portions 30) in the new tire model 25. As a result, as shown in FIG. 12(b), chamfered portions 34 are formed in the new tire model 25, and the relatively fast wear portions 14 can be eliminated from the new tire model 25.

[0064] The movement amount L1 of the node 17 (shown in FIG. 12(a)) can be determined appropriately as long as it is possible to eliminate the portions 14 (corner portions 30) where wear progresses relatively quickly from the new tire model 25. The movement amount L1 may be determined, for example, based on the operator's rule of thumb (such as the results of previous wear experiments). Alternatively, the movement amount L1 may be determined, for example, based on the shape of the tread portion 3 after a vehicle fitted with a new tire 2 has been driven a predetermined distance (for example, 100 to 2000 km). The movement amount (maximum movement amount) L1 in this embodiment is set, for example, to about 0.05 to 0.20 mm.

[0065] In this embodiment, the movement amount L1 of the node 17 is set to be the same for the corner portion 30 of the crown land portion model 20A, the corner portion 30 of the middle land portion model 20B, and the corner portion 30 of the shoulder land portion model 20C shown in Fig. 11. This makes it possible to uniformly eliminate the portions 14 (corner portions 30) where wear progresses relatively quickly from the new tire model 25 in each of the land portion models 20A to 20C, thereby enabling early modeling of a tire model 15 having an early-wear tread portion 22. Note that the movement amount L1 of the node 17 in each of the land portion models 20A to 20C may be different from one another, taking into account the ease of wear of the corner portions 10 of each of the land portions 5A to 5C.

[0066] In step S14, the node 17 to be moved can be selected appropriately depending on, for example, the size of the portion 14 where wear progresses relatively quickly. As shown in Fig. 12(a) in this embodiment, the first node 31 located at the corner portion 10 and the second node 32 adjacent to the first node 31 across the side 18 are moved in the tire radial direction, but this is not limited to this. For example, in step S14, only the first node 31 may be moved, or the third node 33 adjacent to the second node 32 across the side 18 may also be moved.

[0067] In this embodiment, the nodes 17 that form the corner portions 10 are moved radially inward along the sides 18 of the element F(i). This makes it possible to remove the portions 14 where wear progresses relatively quickly from the new tire model 25 while maintaining the contours of the groove walls 29.

[0068] In this embodiment, as shown in FIG. 12(b), by moving the nodes 17 as described above, it is possible to model a tire model 15 having an early-wear tread portion 22 (in which a chamfered portion 34 is formed) that does not have a portion 14 where wear progresses relatively quickly. As with the previous embodiments, in such an early-wear tread portion 22, subsequent changes in wear become relatively uniform. Therefore, in this embodiment, it is possible to quickly and easily model a tire model 15 (shown in FIGS. 7 and 12(b)) having an early-wear tread portion 22, without obtaining a shape in which the changes in wear feature quantities from when the tire is new have converged.

[0069] [Simulation process] In the simulation step S2 of this embodiment, the wear state of the tire model 15 is calculated based on the early-wear tread portion 22 that does not have the portion 14 where wear progresses relatively quickly. Therefore, in the simulation method of this embodiment, as in the previous embodiments, wear that progresses from the shape of the tread portion 3 that has reached early wear can be incorporated into the simulation, and therefore a wear state that is highly correlated with the wear state of an actual vehicle can be calculated.

[0070] [Tire model input process (fourth embodiment)] As shown in Figures 12(a) and 12(b), in the previous embodiment, the tire model 15 including the initially worn tread portion 22 was modeled by moving the nodes 17 of the tread surface 23 of the new tire model 25 radially inward, but the present invention is not limited to this. For example, a tire model 15 including the initially worn tread portion 22 (shown in Figures 7 and 12(b)) may be modeled from the beginning. The same components as those in the previous embodiments are designated by the same reference numerals, and their description may be omitted.

[0071] 13 is a flowchart showing an example of the processing procedure of a tire model input step S1 of yet another embodiment. In the tire model input step S1 of this embodiment, a tire model 15 having an initially worn tread portion 22 is modeled using a finite number of elements F(i) each having a plurality of nodes 17 shown in FIG. 7, as in the previous embodiments.

[0072] [Obtaining the shape of the tread portion (fourth embodiment)] In the tire model input step S1 of this embodiment, first, the shape of the tread portion 3 when new, which does not have the portion 14 where wear progresses relatively quickly, is acquired (step S15). Fig. 14 is a cross-sectional view showing the shape of the tread portion 3 which does not have the portion 14 where wear progresses relatively quickly.

[0073] In step S15 of this embodiment, first, the shape of the tread portion 3 of the tire 2 when new, as shown in Fig. 9, is acquired. The shape of the tread portion 3 can be acquired as coordinate values ​​from, for example, a design drawing (CAD data) of the tire 2 when new.

[0074] Next, in step S15 of this embodiment, as shown in Fig. 14, the portions 14 where wear progresses relatively quickly are removed from the outer surface (tread surface 13) of the tread portion 3. In this embodiment, chamfered portions 36 are set in the corner portions 10 so that the portions 14 (corner portions 10) where wear progresses relatively quickly are eliminated from the outer surface (tread surface 13) of the tread portion 3. This makes it possible to obtain the shape of the tread portion 3 that does not have the portions 14 where wear progresses relatively quickly.

[0075] The chamfered portion 36 can be set as appropriate as long as it can eliminate the portion 14 where wear progresses relatively quickly from the new tire model 25. The chamfered portion 36 can be set based on the same viewpoint as the movement amount L1 of the node 17 described above. Furthermore, the chamfered portion 36 can be easily set based on, for example, a design drawing (CAD data) of the new tire 2. The shape of the tread portion 3 is stored in the computer 1.

[0076] [Tire model modeling (fourth embodiment)] Next, in the tire model input step S1 of this embodiment, a tire model having an early wear tread portion 22 is modeled based on the shape of the tread portion 3 (shown in Figure 14) that does not have a portion 14 where wear progresses relatively quickly (step S16).

[0077] In step S16 of this embodiment, the shape of the tread portion 3 that does not have the portion 14 where wear progresses relatively quickly is discretized using a finite number of elements F(i) that can be handled by the numerical analysis method shown in Fig. 7. As a result, in step S16, a tire model 15 (shown in Fig. 7 and Fig. 12(b)) having an early-wear tread portion 22 is modeled.

[0078] In the tire model input step S1 of this embodiment, as in the previous embodiment, it is possible to model a tire model 15 having an initially worn tread portion 22 without acquiring a shape in which changes in wear feature quantities from when new converge to a predetermined small range. Therefore, the simulation method of this embodiment can easily model a tire model 15 having an initially worn tread portion 22 in a short time while calculating a wear state that is highly correlated with the wear state of an actual vehicle.

[0079] 12(a) and 12(b), a tire model 15 having an initially worn tread portion 22 can be modeled from the beginning without moving the nodes 17 of the tread surface 23 of the new tire model 25 (shown in FIG. 11). Therefore, in the tire model input step S1 of this embodiment, the time required to model the tire model 15 can be shortened compared to the previous embodiment in which the nodes 17 are moved.

[0080] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the illustrated embodiments and can be modified and implemented in various forms. [Example]

[0081] [Example A] The wear state of the tire tread was calculated based on the processing procedure shown in Fig. 3 (Example and Comparative Example). In the Example, a tire model was set up with an initially worn tread, which was in a state where it was slightly worn beforehand compared to the tread of a new tire. On the other hand, in the Comparative Example, a tire model was set up that modeled a new tire, as in the conventional case.

[0082] In the example, a tire was gradually worn from a new state based on the processing procedure shown in Fig. 4, and a shape of a tread portion was acquired in which changes in wear feature quantities from a new state converged to a predetermined small range. Then, in the example, a tire model having an initially worn tread portion was modeled based on the acquired shape of the tread portion.

[0083] In the simulation method of the example and the comparative example, the wear state after traveling about 5000 km was calculated. Then, the wear state of the example and the comparative example was compared with the wear state (experimental example) after traveling the above-mentioned traveling distance by an actual vehicle. The specifications of the example are as follows. Wear characteristics: Ratio of wear amount of crown land area to wear amount of shoulder land area Wear feature range: 0.9 to 1.1

[0084] Fig. 8(a) is a graph showing the relationship between the amount of wear and the axial position of the tire for the Example and Experimental Examples. Fig. 8(b) is a graph showing the relationship between the amount of wear and the axial position of the tire for the Comparative Example and Experimental Examples. The graphs in Fig. 8(a) and (b) respectively show the amount of wear of the crown land portion, a pair of middle land portions, and a pair of shoulder land portions, and the amount of wear at the tire axial position "0" is the amount of wear of the crown land portion located on the tire equator C.

[0085] As shown in Figure 8(a), in the Example, similar to the Experimental Example, the calculated state was such that the wear amount of one of the shoulder land portion and middle land portion was relatively larger than the wear amount of the other shoulder land portion and middle land portion. Therefore, the wear tendency of the Example was similar to that of the Experimental Example.

[0086] As shown in Figure 8(b), in the comparative example, the wear amount of the crown land portion was relatively large, while the wear amount of the middle land portion was relatively small. Therefore, the wear tendency of the comparative example was different from that of the experimental example.

[0087] In this way, the Example was able to calculate a wear state that had a high correlation with the wear state of an actual vehicle compared to the Comparative Example.

[0088] [Example B] The wear state of the tire tread portion was calculated (Examples 2 and 3) based on the processing procedure of Fig. 3. In Examples 2 and 3, a tire model was set up that had an early-wear tread portion that did not have parts (corner portions) where wear progresses relatively quickly on the outer surface of the tread portion when new.

[0089] In Example 2, first, a new tire model that models a new tire was input based on the processing procedure shown in Fig. 10. Then, in Example 2, at least some of the nodes that make up the tread surface of the new tire model were moved radially inward to model a tire model having an initially worn tread portion.

[0090] In Example 3, a tire model including an early-wear tread portion was modeled from the beginning based on the processing procedure shown in Fig. 13. In Example 3, first, the shape of the tread portion that does not have a portion where wear progresses relatively quickly was acquired. Then, in Example 3, a tire model was modeled based on the shape of the tread portion.

[0091] In the simulation methods of Examples 2 and 3, the wear state of the tread portion was calculated based on the same procedure as in Example A, and was compared with the wear state of the experimental example.

[0092] In Examples 2 and 3, similar to the experimental example and example of Example A, the calculated state was one in which the wear amount of one shoulder land portion and middle land portion was relatively greater than the wear amount of the other shoulder land portion and middle land portion. Therefore, the wear tendency of Examples 2 and 3 could be approximated to the wear tendency of the experimental example, and a wear state highly correlated with the wear state of an actual vehicle could be calculated.

[0093] Furthermore, in Examples 2 and 3, it is not necessary to acquire a shape in which the change in wear feature amount from when the tire is new converges to a predetermined small range, as in Example A. Therefore, in Examples 2 and 3, it was possible to reduce the time required to create a tire model compared to Example A. Therefore, in Examples 2 and 3, it was possible to easily create a tire model in a short time that can calculate a wear state that is highly correlated with the wear state of an actual vehicle.

[0094] [Note] The present disclosure includes the following aspects.

[0095] [Disclosure 1] A simulation method for calculating the wear state of a tire tread portion, comprising: inputting a tire model for calculation into a computer; a simulation step in which the computer calculates a wear state using the tire model, the input tire model has an initially worn tread portion that is slightly worn in advance compared to a tread portion of the tire when it is new, The shape of the initially worn tread portion is a shape in which a change from a new tire in at least one wear feature quantity that specifies the wear of the tread portion has converged within a predetermined small range. A method for simulating tire wear conditions. [Disclosure 2] the tread portion includes a crown land portion and a shoulder land portion disposed axially outward of the crown land portion, The tire wear state simulation method described in the present disclosure 1, wherein the wear feature amount includes a ratio between the wear amount of the crown land portion and the wear amount of the shoulder land portion. [Disclosure 3] the tread portion includes a pair of shoulder land portions respectively disposed on a pair of tread end sides, The tire wear state simulation method according to Disclosure 1 or 2, wherein the wear feature amount includes a ratio between the amount of wear of one shoulder land portion and the amount of wear of the other shoulder land portion. [Disclosure 4] The tire wear state simulation method according to any one of Disclosures 1 to 3, wherein the wear feature amount includes a radius of curvature of the contact surface of the tread portion. [Disclosure 5] The step of inputting the tire model includes a step of gradually wearing the tire from a new product to acquire a shape of a tread portion in which a change in the wear feature amount from a new product has converged to the range; and modeling the tire model having the initially worn tread portion based on the shape of the tread portion. [Disclosure 6] the step of inputting the tire model includes a step of predicting a shape of a tread portion in which a change in the wear feature amount from when the tire is new converges to the range; and modeling the tire model having the initially worn tread portion based on the predicted shape of the tread portion. [Disclosure 7] A simulation method for calculating the wear state of a tire tread portion, comprising: inputting a tire model for calculation into a computer; a simulation step in which the computer calculates a wear state using the tire model, the input tire model has an initially worn tread portion that is slightly worn in advance compared to a tread portion of the tire when it is new, The initially worn tread portion does not have a portion of the outer surface of the new tread portion where wear progresses relatively quickly. A method for simulating tire wear conditions. [Disclosure 8] The tread portion is provided with a groove having a pair of groove walls extending radially inward from the tread surface, The method for simulating a tire wear state described in Disclosure 7, wherein the portion where wear progresses relatively quickly includes a corner portion between the tread surface and each of the pair of groove walls. [Disclosure 9] The method for simulating a tire wear state described in Disclosure 7 or 8, wherein the step of inputting the tire model includes a step of modeling the tire model having the initially worn tread portion using a finite number of elements having a plurality of nodes. [Disclosure 10] The modeling step includes a step of modeling the new tire using the elements having the plurality of nodes to input a new tire model having a tread surface; and modeling the tire model having the initially worn tread portion by moving at least some of the nodes constituting the tread surface of the new tire model radially inward. [Disclosure 11] The method for simulating a tire wear state described in the present disclosure 9, wherein the step of inputting the tire model includes a step of modeling the tire model including the initially worn tread portion from the beginning. [Explanation of symbols]

[0096] S1: Tire model input process S2 Simulation process

Claims

1. A simulation method for calculating the wear state of a tire tread portion, comprising: inputting a tire model for calculation into a computer; a simulation step in which the computer calculates a wear state using the tire model, the input tire model has an initially worn tread portion when, for at least one wear feature value specifying wear of the tread portion, a ratio between the most recently acquired wear feature value and the wear feature value immediately before that acquired among the wear feature values ​​acquired at predetermined distances from the time the tire is new is 0.9 to 1.1; A method for simulating tire wear conditions.

2. the tread portion includes a crown land portion and a shoulder land portion disposed axially outward of the crown land portion, The method for simulating a tire wear state according to claim 1 , wherein the wear feature amount includes a ratio of a wear amount of the crown land portion to a wear amount of the shoulder land portion.

3. the tread portion includes a pair of shoulder land portions respectively disposed on a pair of tread end sides, The tire wear state simulation method according to claim 1 or 2, wherein the wear feature amount includes a ratio between the amount of wear of one shoulder land portion and the amount of wear of the other shoulder land portion.

4. The tire wear state simulation method according to claim 1 , wherein the wear feature amount includes a radius of curvature of a contact surface of the tread portion.

5. The step of inputting the tire model includes a step of gradually wearing the tire from a new product to acquire a shape of a tread portion in which a change in the wear feature amount from a new product has converged to the range; 5. The method for simulating a tire wear state according to claim 1, further comprising the step of: modeling the tire model including the initially worn tread portion based on the shape of the tread portion.

6. the step of inputting the tire model includes a step of predicting a shape of a tread portion in which a change in the wear feature amount from when the tire is new converges to the range; 5. The method for simulating a tire wear state according to claim 1, further comprising the step of: modeling the tire model including the initially worn tread portion based on the predicted shape of the tread portion.

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