Tire design and manufacturing method

Abstract

To provide a design method capable of reducing cost necessary for chamfering design, and a manufacturing method.SOLUTION: A tire design method and manufacturing method include: step S1 which inputs to a computer a first tire model modelling a tire whose corner part does not form substantial chamfering by using an element having a plurality of nodes; step S2 which inputs to the computer a road surface model modelling a road surface; step S3 at which the computer rotates the first tire model on the road surface model and computes the physical quantity of nodes positioned on a tread of the first tire model among a plurality of nodes; and step S4 at which the computer moves the nodes on the tread on the basis of the physical quantity and creates a second tire model the corner part forms chamfering.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for designing and manufacturing a tire. [Background technology]

[0002] The following Patent Document 1 describes a tire having a tread portion with a plurality of main grooves continuing in the tire circumferential direction and a plurality of land portions separated between the main grooves. The land portions have chamfers formed at the corners where the tread surface and the sidewall surface intersect. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6582726 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the above chamfering can prevent local concentration of ground pressure on the land portion, forming multiple chamfers or larger chamfers than necessary may lead to uneven distribution of ground pressure on the tread and a decrease in the land ratio, which may degrade running performance, etc. For this reason, designing chamfering requires, for example, repeated hand-cutting of tire prototypes and creation of simulation models to verify running performance, etc., which is problematic in that it requires a lot of cost.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a design method capable of reducing the cost required for designing chamfers. [Means for solving the problem]

[0006] The present invention provides a method for designing a tire having a plurality of land portions in a tread portion, at least one of the plurality of land portions having a chamfer formed at a corner portion where the tread surface and a sidewall surface intersect, comprising the steps of: inputting into a computer a first tire model in which a tire having no substantial chamfer formed at the corner portions is modeled using elements having a plurality of nodes; inputting into the computer a road surface model in which a road surface is modeled; the computer rolling the first tire model on the road surface model and calculating the physical quantities of the nodes among the plurality of nodes located on the tread surface of the first tire model; and the computer moving the nodes on the tread surface based on the physical quantities to create a second tire model in which a chamfer is formed at the corner portions.

[0007] In the tire design method according to the present invention, the step of creating the second tire model may include moving only nodes whose physical quantities are greater than a predetermined threshold value.

[0008] In the tire design method according to the present invention, the method may further include a step of inputting predetermined constraint conditions related to the chamfer into the computer, and the step of creating the second tire model may include moving the nodes so as to satisfy the constraint conditions.

[0009] In the tire design method according to the present invention, the rolling in the step of calculating the physical quantity may include at least one of braking, driving, and turning.

[0010] In the tire design method of the present invention, the physical quantity may be wear energy or contact pressure, and the process of creating the second tire model may include moving nodes on the tread so that distribution of the physical quantity on the tread approaches uniformity.

[0011] The present invention is characterized in that it includes a step of manufacturing the tire based on the second tire model created by the tire design method. Effect of the Invention

[0012] By employing the above steps, the tire design method of the present invention makes it possible to reduce the cost required for designing the chamfer. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an example of a computer for executing a tire design and manufacturing method. [Diagram 2] 1 is a partial cross-sectional view showing an example of a tire designed by a tire design method. [Diagram 3] 1 is a flowchart showing an example of a processing procedure of a tire design method and a tire manufacturing method. [Figure 4] FIG. 2 is a perspective view showing an example of a first tire model and a road surface model. [Diagram 5] FIG. 2 is a partial cross-sectional view showing an example of a first tire model. [Figure 6] FIG. 1A is a diagram for explaining an example of a state before a node is moved, and FIG. 1B is a diagram for explaining an example of a state after a node is moved. [Figure 7] FIG. 4 is a partial cross-sectional view showing an example of a second tire model. [Figure 8] 6 is a flowchart showing an example of a processing procedure of a tire design method and a tire manufacturing method according to another embodiment of the present invention. [Figure 9] FIG. 2A is a diagram showing an example of chamfering of a middle land portion model of an embodiment, and FIG. 2B is a diagram showing an example of chamfering of a middle land portion model of a comparative example. [Figure 10] FIG. 1A is a diagram showing the contact pressure distribution of a second tire model of an embodiment, and FIG. 1B is a diagram showing the contact pressure distribution of a tire model of a comparative example. [Figure 11] 1 is a graph showing the relationship between the friction coefficient and the slip ratio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are intended to enhance understanding of the contents of the invention, and therefore some of the drawings may be exaggerated, and the scales of the drawings may not be strictly consistent.

[0015] [computer] FIG. 1 is a perspective view showing an example of a computer 1 for executing a tire design method and a tire manufacturing method (hereinafter, sometimes referred to as a "design method" and a "manufacturing method", respectively) of the present embodiment. The computer 1 is configured to include, 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 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 design method and the manufacturing method of the present embodiment in advance. Thus, the computer 1 is configured as a tire design device and a tire manufacturing device.

[0016] [tire] 2 is a partial cross-sectional view showing an example of a tire 2 designed by the tire design method of the present embodiment. In the present embodiment, a pneumatic tire for passenger cars is shown as an example, but the tire may be of other categories such as a heavy-duty tire for trucks and buses, or an airless tire.

[0017] The tire 2 of this embodiment has a plurality of land portions 4 in a tread portion 3.

[0018] The land portion 4 in this embodiment is divided by a plurality of circumferential grooves 5 that extend continuously in the tire circumferential direction. The circumferential grooves 5 in this embodiment include a pair of center circumferential grooves 5A, 5A and a pair of shoulder circumferential grooves 5B, 5B. The pair of center circumferential grooves 5A, 5A are disposed on both outer sides of the tire equator C in the tire axial direction. The pair of shoulder circumferential grooves 5B, 5B are disposed between the center circumferential groove 5A and the tread ground contact edge 3t.

[0019] In this specification, "tread ground contact edge 3t" refers to the axially outermost end of the tread ground contact surface 6 when a tire 2 in a normal state is placed in contact with a flat surface with a normal load and a camber angle of 0 degrees. The normal state refers to a state in which the tire 2 is mounted on a normal rim (not shown), inflated to a normal internal pressure, and no load is applied. In this specification, the dimensions of each part of the tire are specified as values ​​measured in the normal state, unless otherwise specified.

[0020] "Genuine rim" refers to a rim that is determined for each tire by the standard system that includes the standard on which 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.

[0021] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system including the standard on which tire 2 is based. Therefore, the normal internal pressure is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO, but if the tire is for passenger cars, it is 180 kPa.

[0022] The "normal load" is the load that the standard specifies for each tire 2. Therefore, the normal load is the maximum load capacity for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0023] The land portion 4 of this embodiment includes a center land portion 4A, a pair of middle land portions 4B, 4B, and a pair of shoulder land portions 4C, 4C. The center land portion 4A is divided by a pair of center circumferential grooves 5A, 5A. The pair of middle land portions 4B, 4B are divided by the center circumferential groove 5A and the shoulder circumferential groove 5B. The pair of shoulder land portions 4C, 4C are divided by the shoulder circumferential groove 5B and the tread ground contact edge 3t.

[0024] In this embodiment, lateral grooves 7 extending in a direction intersecting the circumferential grooves 5 are provided at intervals in the tire circumferential direction in the center land portion 4A, the pair of middle land portions 4B, 4B, and the pair of shoulder land portions 4C, 4C. As a result, a plurality of blocks 8 divided by the lateral grooves 7 are provided in each of the center land portion 4A, the pair of middle land portions 4B, 4B, and the pair of shoulder land portions 4C, 4C.

[0025] Each of the land portions 4 (each block 8) includes a tread surface 9 and a side wall surface 10. In this embodiment, the side wall surface 10 extends from an end portion (corner portion 13) of the tread surface 9 toward the groove bottoms 11 of the circumferential grooves 5 and the lateral grooves 7, or toward the sidewall portion 12.

[0026] Corner portions 13 (indicated by two-dot chain lines in FIG. 2) where the tread surface 9 and the side wall surface 10 intersect are more susceptible to localized ground pressure concentration and uneven wear compared to other portions of the tread surface 9. For this reason, at least one of the multiple land portions 4 has a chamfer 14 formed in the corner portion 13.

[0027] The chamfer 14 in this embodiment is formed at a corner portion 13 between the tread surface 9 and a side wall surface 10 facing the circumferential groove 5. Furthermore, the chamfer 14 is formed at a corner portion (not shown) between the tread surface 9 and a side wall surface (not shown) facing the lateral groove 7. Note that the chamfer 14 is not limited to this form, and can be formed at the corner portion 13 as appropriate.

[0028] The chamfers 14 as described above are useful for preventing localized concentration of ground pressure on the land portion 4 and uneven wear. On the other hand, if a large number of chamfers 14 or a large chamfer 14 is formed more than necessary, it may cause uneven distribution of ground pressure on the tread 9 and a decrease in the land ratio, which may degrade driving performance (e.g., braking performance, driving performance, and cornering performance). For this reason, in the conventional design of the chamfers 14, for example, the tire 2 is prototyped by hand cutting and a simulation model (tire model) is repeatedly created to verify the driving performance, which has the problem of requiring a lot of cost.

[0029] [Tire design method (first embodiment)] The design method of this embodiment directly obtains the shape of the chamfer 14 that can maintain running performance while preventing local concentration of ground pressure on the land portion 4, based on the processing procedure described below. As a result, the design method of this embodiment reduces the cost required for designing the chamfer compared to the conventional design method that involves repeated prototyping of the tire 2. Figure 3 is a flowchart showing an example of the processing procedure of the tire design method and tire manufacturing method.

[0030] [First tire model input process] In the design method of this embodiment, first, a first tire model is input to a computer 1 (shown in FIG. 1) in which a tire 2 (shown by a two-dot chain line in FIG. 2) in which no substantial chamfer 14 is formed at a corner portion 13 is modeled using elements having multiple nodes (step S1). Here, "substantial chamfer" refers to the chamfer 14 (shown in FIG. 2) formed for the purpose of preventing localized concentration of ground contact pressure in the land portion 4. For this reason, chamfers that are not formed for that purpose (for example, formal chamfers (formed in a chamfered shape) for the purpose of improving aesthetics, etc.) are not included in the substantial chamfer 14.

[0031] Fig. 4 is a perspective view showing an example of the first tire model 21 and the road surface model 23. Fig. 5 is a partial cross-sectional view showing an example of the first tire model 21. Note that in Fig. 4, the element F(i) of the first tire model 21 shown in Fig. 5 is omitted.

[0032] As shown in Fig. 5, in step S1, a tire 2 (indicated by a two-dot chain line in Fig. 2) in which no substantial chamfer 14 is formed at a corner portion 13 shown in Fig. 2 is modeled (discretized) using a finite number of elements F(i) (i = 1, 2, ...) that can be handled by a numerical analysis method. As a result, in step S1, a first tire model 21 in which no chamfer is formed is set. As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method can be appropriately adopted, but in this embodiment, the finite element method is adopted.

[0033] The elements F(i) may be, for example, tetrahedral solid elements, pentahedral solid elements, or hexahedral solid elements. Each element F(i) has a plurality of nodes 24. Furthermore, each element F(i) has linear edges 25 connecting the nodes 24, 24.

[0034] Each element F(i) is defined with numerical data such as an element number, a node 24 number, and the coordinate value of the node 24. Furthermore, each element F(i) is defined with numerical data such as material properties (e.g., density, Young's modulus, damping coefficient, loss tangent (tan δ), and / or complex modulus of elasticity E*, etc.) of the tire components (e.g., tread rubber) shown in FIG.

[0035] In the tread portion 21T of the first tire model 21 of this embodiment, a circumferential groove model 26 that models the circumferential groove 5 (shown in FIG. 2) and a land portion model 27 that models the land portion 4 (shown in FIG. 2) are set.

[0036] The circumferential groove model 26 of this embodiment includes a pair of center circumferential groove models 26A, 26A and a pair of shoulder circumferential groove models 26B, 26B. The pair of center circumferential groove models 26A, 26A are models of the pair of center circumferential grooves 5A, 5A (shown in FIG. 2), respectively. The pair of shoulder circumferential groove models 26B, 26B are models of the pair of shoulder circumferential grooves 5B, 5B (shown in FIG. 2), respectively.

[0037] The land portion model 27 of this embodiment includes a center land portion model 27A, a pair of middle land portion models 27B, 27B, and a pair of shoulder land portion models 27C, 27C. The center land portion model 27A models the center land portion 4A (shown in FIG. 2). The pair of middle land portion models 27B, 27B models the pair of middle land portions 4B, 4B (shown in FIG. 2), respectively. The pair of shoulder land portion models 27C, 27C models the pair of shoulder land portions 4C, 4C (shown in FIG. 2), respectively.

[0038] In this embodiment, a lateral groove model (not shown) that models a lateral groove (shown in FIG. 7) is provided in the center land portion model 27A, the pair of middle land portion models 27B, 27B, and the pair of shoulder land portion models 27C, 27C. As a result, a plurality of block models 28 that model a plurality of blocks 8 are provided in the center land portion model 27A, the pair of middle land portion models 27B, 27B, and the pair of shoulder land portion models 27C, 27C.

[0039] The plurality of land models 27 (each block model 28) includes a tread surface 29 and a side wall surface 30, similar to the plurality of land portions 4 (each block 8) shown in Fig. 2. Furthermore, the plurality of land models 27 (each block model 28) includes corner portions 31 where the tread surface 29 and the side wall surface 30 intersect. These corner portions 31 are not substantially chamfered.

[0040] Other structures of the first tire model 21 can be set in the same manner as the conventional tire model, based on the structure of the tire 2 shown in Fig. 2. The first tire model 21 is input to the computer 1 (shown in Fig. 1).

[0041] [Road surface model input process] Next, in the design method of this embodiment, a road surface model 23 that models a road surface (not shown) is input to a computer 1 (shown in FIG. 1) (step S2). In step S2 of this embodiment, based on information about the road surface (not shown), the road surface is discretized using a finite number of elements G(i) (i=1, 2, ...) that can be handled by a numerical analysis method (in this embodiment, the finite element method). As a result, in step S2, the road surface model 23 is set.

[0042] The element G(i) is made of a rigid plane element that is set to be undeformable. The element G(i) has a plurality of nodes 32. Furthermore, for the element G(i), numerical data such as an element number and the coordinate values ​​of the nodes 32 are defined.

[0043] The road surface model 23 in this embodiment is set to a smooth surface, but as necessary, small irregularities like those on an asphalt road surface, irregular steps, depressions, undulations, or irregularities approximating those of an actual road surface such as ruts may be set. The road surface model 23 is input to the computer 1 (shown in FIG. 1).

[0044] [Physical quantity calculation process] Next, in the design method of this embodiment, the computer 1 (shown in FIG. 1) rolls the first tire model 21 on the road surface model 23, and calculates the physical quantities of the nodes 24 located on the tread surface 29 of the first tire model 21, among the multiple nodes 24 shown in FIG. 5 (step S3).

[0045] In step S3 of this embodiment, first, as shown in Fig. 4, the first tire model 21 rolling on the road surface model 23 is calculated. The rolling of the first tire model 21 can be calculated appropriately. In this embodiment, for example, as in the procedure described in the patent document (JP Patent Publication No. 2019-91302), the first tire model 21 after filling with internal pressure is calculated based on predetermined boundary conditions, and the state in which the first tire model 21 rolls on the road surface model 23 is calculated.

[0046] For deformation calculation (rolling calculation) of the first tire model 21, a mass matrix, a stiffness matrix, and a damping matrix are created for each element F(i) based on the shape and material properties of each element F(i) shown in Fig. 5. Furthermore, these matrices are combined to create a matrix for the entire system. Then, an equation of motion is created to which the various conditions are applied, and deformation calculation of the first tire model 21 is performed for each minute time (unit time T(x) (x=0, 1, ...)).

[0047] The deformation calculation (rolling calculation) of the first tire model 21 can be performed using, for example, commercially available finite element analysis application software such as LS-DYNA manufactured by LSTC, Inc. The unit time T(x) can be appropriately set depending on the required simulation accuracy.

[0048] The rolling of the first tire model 21 is appropriately set to, for example, free rolling, braking, driving, turning, etc., depending on the running state of the tire 2 (shown in FIG. 2). The rolling of the present embodiment includes at least one of braking, driving, and turning. The rolling of the first tire model 21 can be easily calculated by appropriately defining the angular velocity V1 (shown in FIG. 4) and the slip angle (not shown) for the first tire model 21.

[0049] Next, in step S3 of this embodiment, the physical quantity of the nodes 24 located on the tread 29 of the first tire model 21, among the multiple nodes 24 constituting the first tire model 21 shown in Fig. 5, is calculated. The physical quantity is not particularly limited, but is preferably one related to local concentration of ground contact pressure of the land portion 4 or uneven wear of the land portion 4. As the physical quantity of this embodiment, wear energy or ground contact pressure (wear energy in this example) is adopted.

[0050] In step S3, it is preferable to calculate the physical quantity of each node 24 on the tread 29 after the force acting on the first tire model 21 has been caused to roll until it reaches a steady state (stable state). In this embodiment, the physical quantity is calculated for each node 24 on the tread 29 of the first tire model 21 for each minute time (unit time T(x)) from when the node 24 comes into contact with the road surface model 23 until when the node 24 leaves the road surface model 23. The physical quantity of each node 24 is input to the computer 1.

[0051] [Second tire model creation process] Next, in the design method of this embodiment, the computer 1 creates a second tire model 22 in which chamfers are formed at the corner portions 31 of the first tire model 21 (step S4). In step S4, based on the physical quantities calculated in step S3, the nodes 24 on the tread surface 29 of the first tire model 21 are moved to create the second tire model 22 in which chamfers are formed at the corner portions 31. Fig. 6(a) is a diagram illustrating an example of a state before the nodes 24 are moved. Fig. 6(b) is a diagram illustrating an example of a state after the nodes 24 are moved.

[0052] The procedure for moving the node 24 on the tread surface 29 is not particularly limited, but may be, for example, the procedure described in the patent document (JP Patent Publication No. 2017-033076) or the patent document (JP Patent Publication No. 2019-91302). As a result, in step S4 of this embodiment, as shown in Figures 6(a) and 6(b), the node 24 on the tread surface 29 can be moved along the side 25 connecting the node 24 on the tread surface 29 and the node 24 located radially inward of the node 24 on the tread surface 29.

[0053] 6(a), the movement amount M of each node 24 on the tread surface 29 is determined based on the physical quantities of those nodes 24. In this embodiment, the movement amount M is determined based on the sum of the physical quantities calculated for each minute time (unit time) for each node 24 on the tread surface 29. Note that the movement amount M is not limited to this embodiment, and may be determined based on, for example, the average value of the physical quantities calculated for each minute time.

[0054] In step S4 of the present embodiment, for each node 24 on the tread 29 of the first tire model 21, the movement amount M is set to be larger as the physical amount (in this example, the sum of the physical amounts) calculated in step S3 is larger. The physical amount tends to be relatively large in the node 24 located on the corner portion 31 side. Therefore, in step S4, as shown in FIG. 6(b), the node 24 located on the corner portion 31 side can be moved significantly toward the inside of the first tire model 21 (inward in the tire radial direction). By moving the node 24 in this way, in step S4, the second tire model 22 in which the chamfer 33 is formed in the corner portion 31 of the first tire model 21 can be created.

[0055] In the second tire model 22, the physical quantity of the node 24 (the moved node 24) constituting the chamfer 33 can be made smaller than the physical quantity of the node 24 before it is moved (shown in FIG. 6(a)). As described above, the physical quantity in this embodiment (wear energy in this example) is related to the local concentration of ground contact pressure in the land portion 4. Therefore, the shape of the chamfer 33 of the second tire model 22 can prevent the local concentration of ground contact pressure in the land portion 4 that tends to occur in the corner portion 13 shown in FIG. 2.

[0056] The movement amount M of each node 24 on the tread 29 may be determined by multiplying the physical amount (sum of physical amounts) of the nodes 24 on the tread 29 by the wear progression rate, for example, in the same manner as in the procedure described in the patent document (JP Patent Publication No. 2019-91302). As a result, the design method of this embodiment can prevent the nodes 24 with large physical amounts from moving more than necessary, thereby preventing the formation of chamfers 33 that deviate from reality.

[0057] Also, in step S4, only the nodes 24 whose physical quantity (in this example, the sum of the physical quantities) is greater than a predetermined threshold value may be moved. As a result, in this embodiment, the nodes 24 whose physical quantity is less than the threshold value can be prevented from moving, and therefore, for example, all the nodes 24 located on the tread surface 29 can be prevented from moving. Therefore, in the design method of this embodiment, unintended deformation of the tread profile and formation of chamfers 33 that deviate from reality are prevented. The threshold value can be set appropriately so as to prevent the above-mentioned problems. For example, the threshold value in this embodiment can be set based on a value obtained by multiplying the average value of the physical quantities of all the nodes 24 located on the tread surface 29 by a predetermined coefficient, or a value obtained by multiplying the maximum value of the physical quantities of all the nodes 24 by a predetermined coefficient. Each coefficient can be adjusted appropriately.

[0058] 7 is a partial cross-sectional view showing an example of the second tire model 22. The second tire model 22 is stored in the computer 1 (shown in FIG. 1).

[0059] [Judgment process] Incidentally, even if the shape of the chamfer 33 (shown in FIG. 7) formed on the second tire model 22 can prevent local concentration of ground contact pressure on the land portion 4, if the distribution of the physical quantity on the tread 29 becomes non-uniform, there is a risk of degradation of running performance (e.g., braking performance, etc.). To prevent such degradation of running performance, in the design method of this embodiment, the computer 1 judges whether the distribution of the physical quantity on the tread 29 of the second tire model 22 is uniform or not (step S5).

[0060] In step S5, first, a state in which the second tire model 22 is rolled on the road surface model 23 shown in Fig. 4 is calculated based on the same procedure as in step S3 for calculating the physical quantities. Next, in step S5, the physical quantities of each of the nodes 24 located on the tread 29 of the second tire model 22 among the multiple nodes 24 constituting the second tire model 22 are calculated. Then, in step S5, it is determined whether the distribution of the physical quantities on the tread 29 of the second tire model 22 is uniform.

[0061] Whether or not the distribution of the physical quantity on the tread 29 of the second tire model 22 is uniform is determined as appropriate. In this embodiment, when the difference (dispersion) between the maximum and minimum values ​​of the physical quantities of all the nodes 24 located on the tread 29 of the second tire model 22 is smaller than a predetermined threshold, the physical quantity is determined to be uniform. The larger the numerical value of such dispersion (i.e., the difference between the maximum and minimum values ​​of the physical quantity), the greater the variation in the physical quantity, indicating that the distribution of the physical quantity is non-uniform. The threshold value can be set as appropriate as long as it is possible to determine whether or not the distribution of the physical quantity is uniform. For example, the threshold value in this embodiment can be set based on a value obtained by multiplying the average value of the physical quantities of all the nodes 24 calculated in step S5 by a predetermined coefficient for the nodes 24 located on the tread 29, or a value obtained by multiplying the dispersion of the physical quantities calculated in step S3 by a predetermined coefficient. Each coefficient can be adjusted as appropriate.

[0062] In step S5, if it is determined that the distribution of the physical quantities on the tread 29 of the second tire model 22 is uniform ("Yes" in step S5), the second tire model 22 maintains running performance while preventing local concentration of ground contact pressure on the land portion 4 (shown in FIG. 2). Therefore, in the manufacturing method (design method) of this embodiment, the tire 2 (shown in FIG. 2) is manufactured based on the second tire model 22 (step S6).

[0063] On the other hand, if it is determined in step S5 that the distribution of the physical quantity on the tread 29 of the second tire model 22 is not uniform ("No" in step S5), it is difficult to maintain the running performance of the second tire model 22 even if local concentration of ground contact pressure on the land portion 4 (shown in FIG. 2) can be prevented. For this reason, in the design method of this embodiment, the step S4 of creating the second tire model 22 and the step S5 of determining are performed again.

[0064] In step S4 of creating the second tire model 22 again, the nodes 24 on the tread 29 of the second tire model 22 are moved based on the physical quantities calculated in the judging step S4 so that the distribution of the physical quantities on the tread 29 approaches uniformity.

[0065] In this embodiment, among the nodes 24 on the tread 29, the nodes 24 having a larger physical quantity than the average value of the physical quantity are moved inward in the tire radial direction. On the other hand, among the nodes 24 on the tread 29, the nodes 24 having a smaller physical quantity than the average value of the physical quantity are moved outward in the tire radial direction. The movement of the nodes 24 is performed based on the above-mentioned procedure. As a result, in the step S4 of creating the second tire model 22, the nodes 24 on the tread 29 of the second tire model 22 can be moved so that the distribution of the physical quantity on the tread 29 becomes closer to uniform. Therefore, in the design method of this embodiment, it is possible to obtain a shape of the chamfer 14 (chamfer 33 shown in FIG. 7) that can maintain the running performance while preventing local concentration of the ground contact pressure on the land portion 4 of the tire 2 shown in FIG. 2.

[0066] In the design method of this embodiment, for example, even without repeatedly making prototype tires by hand cutting, the shape of the chamfer 14 that can maintain running performance while preventing local concentration of ground contact pressure on the land portion 4 can be directly obtained from the second tire model 22. Therefore, the design method of this embodiment makes it possible to reduce the cost required for designing the chamfer 14.

[0067] Furthermore, in the step S3 of calculating the physical quantities, if the rolling of the first tire model 21 includes braking, in the step S4 of creating the second tire model, the nodes 24 on the tread surface 29 can be moved based on the physical quantities during braking. This makes it possible to obtain a shape of the chamfer 14 (chamfer 33 shown in FIG. 7) that can maintain braking performance while preventing localized concentration of ground contact pressure on the land portion 4 during braking.

[0068] Furthermore, in the step S3 of calculating the physical quantities, if the rolling of the first tire model 21 includes driving, in the step S4 of creating the second tire model, the nodes 24 on the tread surface 29 can be moved based on the physical quantities in driving. This makes it possible to obtain a shape of the chamfer 14 (chamfer 33 shown in FIG. 7) that can maintain driving performance while preventing local concentration of ground contact pressure on the land portion 4 during driving.

[0069] Furthermore, in the step S3 of calculating the physical quantities, if the rolling of the first tire model 21 includes turning, in the step S4 of creating the second tire model, the nodes 24 on the tread surface 29 can be moved based on the physical quantities in turning. This makes it possible to obtain a shape of the chamfer 14 (chamfer 33 shown in FIG. 7) that can maintain turning performance while preventing local concentration of ground pressure on the land portion 4 during turning.

[0070] In this manner, in the design method of this embodiment, the rolling (braking, etc.) of the first tire model 21 is set based on the driving performance (braking performance, etc.) that is desired to be maintained, thereby making it possible to more reliably obtain a shape of the chamfer 14 (chamfer 33) that can maintain the driving performance.

[0071] Furthermore, in the step S3 of calculating the physical quantities, the rolling of the first tire model 21 may include all of braking, driving, and turning. In this case, in the step S3 of calculating the physical quantities, the total value of the physical quantities during braking, driving, and turning may be calculated as the physical quantities of the first tire model 21. Furthermore, in the step S4 of creating the second tire model, the nodes 24 on the tread surface 29 may be moved based on the total value of these physical quantities. In this way, the design method makes it possible to obtain a shape of the chamfer 14 (chamfer 33 shown in FIG. 7) that can maintain braking performance, driving performance, and turning performance while preventing local concentration of ground pressure on the land portion 4 during braking, driving, and turning.

[0072] [Tire manufacturing method] [Tire manufacturing process] In step S6 of manufacturing the tire 2, first, a mold (not shown) for the tire 2 is designed based on the shape (including the shape of the chamfer 33) of the second tire model 22 shown in Fig. 7. Then, an unvulcanized raw tire (not shown) is vulcanized and molded using the designed mold. As a result, the manufacturing method of this embodiment can manufacture a tire 2 equipped with a chamfer 14 that can maintain running performance while preventing local concentration of ground contact pressure in the land portion 4.

[0073] [Tire design method (second embodiment)] 8 is a flowchart showing an example of a processing procedure of a tire design method and a tire manufacturing method according to another embodiment of the present invention. In this embodiment, the same components as those in the previous embodiments are given the same reference numerals, and the description thereof may be omitted.

[0074] [Constraint condition input process] The design method of this embodiment further includes a step S7 of inputting predetermined constraint conditions related to the chamfer 14 (shown in FIG. 2) into the computer 1. The step S7 in this embodiment is performed prior to the step S4 of creating a second tire model. Then, in the step S4 of creating the second tire model, the nodes 24 on the tread surface 29 shown in FIG. 6(a) are moved so as to satisfy the constraint conditions.

[0075] The constraint conditions can be set appropriately as long as they relate to the chamfer 14. The constraint conditions in this embodiment include the maximum value of the movement amount M (shown in FIG. 6(a)) and the node 24 to be moved.

[0076] [Maximum movement amount (constraint)] The maximum value of the movement amount M is a constraint condition for determining the range within which movement of the node 24 on the tread surface 29 is permitted. Such a maximum value of the movement amount M is set based on, for example, a land ratio required to maintain the running performance of the tire 2.

[0077] 6(a) and 6(b), in the process S4 of creating the second tire model of this embodiment, the nodes 24 on the tread surface 29 are moved so as to satisfy the maximum value of the movement amount M (i.e., the nodes 24 are moved by an amount equal to or less than the maximum value). As a result, in the design method of this embodiment, it is possible to obtain the chamfer 33 that can maintain the running performance while preventing the formation of a chamfer 33 that deviates from reality.

[0078] [Nodes to be moved (constraint conditions)] The nodes 24 to be moved are used (constraint conditions) to determine the movable nodes 24 among all the nodes 24 on the tread surface 29. For example, the nodes 24 to be moved are set to the nodes 24 located on the corner portion 31 side based on the land ratio required to maintain the running performance of the tire 2.

[0079] In step S4 of creating the second tire model in this embodiment, only the nodes 24 to be moved are moved. As a result, in the design method of this embodiment, it is possible to prevent, for example, the central part of the land model 27 in the tire axial direction from being partially recessed or the formation of a chamfer 33 that deviates from reality, and it is possible to obtain a chamfer 33 that can maintain driving performance.

[0080] [Tire design method (third embodiment)] In the design method of the above embodiment, the wear energy has been exemplified as a physical quantity for moving the node 24 on the tread 29, but the wear energy may be ground pressure, or the shear force or slippage used in calculating the wear energy. Furthermore, the node 24 on the tread 29 may be moved based on a physical quantity that combines (for example, multiplies) at least two of the wear energy, the ground pressure, the shear force, and the slippage. All of these physical quantities are related to the local concentration of the ground pressure on the land portion 4 and the uneven wear of the land portion 4. Therefore, by moving the node 24 on the tread based on these physical quantities as shown in Figs. 6(a) and 6(b), it is possible to obtain a shape of the chamfer 14 (chamfer 33 shown in Fig. 7) that can prevent the local concentration of the ground pressure on the land portion 4.

[0081] 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

[0082] A tire with chamfers was designed (Example) based on the processing procedure shown in Fig. 3. In the Example, first, a first tire model that models a tire with no substantial chamfers at the corners, and a road surface model that models a road surface were input to a computer.

[0083] Next, in the embodiment, the computer rolled the first tire model on the road surface model, and among the multiple nodes, the physical quantities of the nodes located on the tread surface of the first tire model were calculated. The rolling of the first tire model was calculated based on the braking conditions (speed just before braking: 20 km / h, acceleration during braking: 0.8 G). In addition, the friction coefficient was calculated as a physical quantity.

[0084] In the embodiment, the nodes on the tread were moved based on the physical quantity when the tire rolled under braking conditions, and a second tire model with chamfered corners was created. Only nodes whose physical quantity was greater than a predetermined threshold were moved.

[0085] Fig. 9(a) is a diagram showing an example of chamfering of a middle land portion model of an embodiment. Fig. 9(a) shows a representative chamfer 33 formed at a corner portion 31 between a tread surface 29 and a sidewall surface 30 facing a lateral groove model. As shown in Fig. 9(a), the chamfer 33 of the embodiment has a radial depth of the chamfer of the middle land portion model that increases from the shoulder circumferential groove model 26B toward the center circumferential groove model 26A due to the movement of the nodes.

[0086] For comparison, a tire with chamfers was designed by an operator, and a tire model was created based on the designed tire, using elements with multiple nodes.

[0087] Fig. 9(b) is a diagram showing an example of chamfering of a middle land portion model of a comparative example. As shown in Fig. 9(b), the chamfering 33 of the comparative example is set in accordance with the convention such that the radial depth of the chamfering of the middle land portion model is uniform from the shoulder circumferential groove model 26B to the center circumferential groove model 26A.

[0088] The second tire model of the embodiment and the tire model of the comparative example were rolled under braking conditions (speed immediately before braking: 100 km / h), and their contact pressure distributions and the relationship between the friction coefficient and the slip ratio (μ-S curve) were obtained. The common specifications are as follows:

[0089] Tire size: 205 / 55R17 Internal pressure: 250kPa Load: 5kN

[0090] Fig. 10(a) is a diagram showing the contact pressure distribution of the second tire model of the embodiment. Fig. 10(b) is a diagram showing the contact pressure distribution of the tire model of the comparative example. Figs. 10(a) and (b) show the contact pressure distribution when the slip ratio is 4%. Also, Figs. 10(a) and (b) show that the darker the color, the higher the contact pressure. Fig. 11 is a graph showing the relationship between the friction coefficient and the slip ratio.

[0091] As shown in Figures 10(a) and 10(b), the Example was able to reduce the ground contact pressure near the corners compared to the Comparative Example, and was able to make the ground contact pressure distribution on the tread closer to uniform. Also, as shown in Figure 11, the Example was able to increase the maximum friction coefficient compared to the Comparative Example, and was able to improve braking performance. Therefore, the Example was able to design a tire that can improve running performance while preventing local concentration of ground contact pressure on the land area compared to the Comparative Example.

[0092] In addition, in the Comparative Example, in order to design a chamfer having the running performance, etc. of the Example, it is necessary to repeatedly produce a prototype tire by hand cutting, create a simulation model, etc. On the other hand, in the Example, the above chamfer can be directly obtained, so there is no need to repeatedly produce a prototype tire or create a simulation model. Therefore, the Example was able to reduce the cost required for designing the chamfer compared to the Comparative Example (reduced to about 20% of the Comparative Example). [Explanation of symbols]

[0093] S1: Step of inputting the first tire model S2: Road surface model input process S3: A process of calculating the physical quantities of the first tire model S4: A process of creating a second tire model with chamfers formed.

Claims

1. A method for designing a tire having a plurality of land portions in a tread portion, at least one of the plurality of land portions having a chamfer formed at a corner portion where a tread surface and a sidewall surface intersect, comprising: A step of inputting a first tire model in which a tire having no substantial chamfer formed at the corner portion is modeled using elements having a plurality of nodes into a computer; A step of inputting a road surface model, which models a road surface, into the computer; a step of causing the computer to roll the first tire model on the road surface model and calculating physical quantities of nodes located on a tread surface of the first tire model among the plurality of nodes; and generating a second tire model having chamfers formed at the corner portions by the computer moving nodes on the tread surface based on the physical quantities. How tires are designed.

2. 2. The tire design method according to claim 1, wherein the step of creating the second tire model comprises moving only nodes whose physical quantities are greater than a predetermined threshold value.

3. inputting predetermined constraints on the chamfer into the computer; 3. The tire design method according to claim 1, wherein the step of creating the second tire model comprises moving the nodes so as to satisfy the constraint conditions.

4. The tire design method according to claim 1 , wherein the rolling in the step of calculating the physical quantity includes at least one of braking, driving, and turning.

5. The physical quantity is wear energy or ground pressure, 5. The tire design method according to claim 4, wherein the step of creating the second tire model comprises moving nodes on the tire tread so that a distribution of the physical quantity on the tire tread approaches uniformity.

6. A step of manufacturing the tire based on the second tire model created by the tire design method according to any one of claims 1 to 5. A method for manufacturing tires.

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