JP5236301B2 - Tire design method - Google Patents

Description

  The present invention relates to a tire design method, a program therefor, and a tire manufacturing method using the design method.

  Since the tread pattern of a pneumatic tire has a great influence on drainage performance, braking performance, noise, and the like, it is required to design a tire tread pattern design optimized for phase and shape.

  When designing a tire tread pattern design, a design plan that meets the required performance is designed based on conventional knowledge, experience, and design constraints, and structural analysis is used to satisfy the required performance as one means for confirmation. Confirm whether or not. If the required performance is not satisfied at this stage, the design is corrected and the structural analysis is performed again. This process is repeated until the required performance is satisfied to finalize the design plan.

  In such a conventional design method, there is no guarantee as to whether or not the design plan determined within the range based on the design constraint is the optimum value. In addition, since the design, structural analysis, and redesign process is repeated, the time required for the design may be enormous.

  When the design of a tire tread pattern is optimized by optimization calculation, a genetic algorithm is generally used (see, for example, Patent Document 1 below), but if the design area of the design is wide, an individual gene The number increases. For this reason, the calculation load is large and practically not at a level applicable to design.

Incidentally, an ECAT method (Evolutional Clustering Algorithm for Topological optimization) is known as a layout optimization method using the finite element method (see Non-Patent Documents 1 to 3 below). The ECAT method considers the target structure as one individual, classifies elements according to the size of the evaluation index determined according to the problem, grasps the distribution of the evaluation index in the structure globally, This is a method of determining the layout by considering the behavior of removing and adding small elements one after another in class units as behavior and evolving the behavior. This ECAT method has been used for layout optimization problems of mechanical structures such as cantilever beams, but its application to tire tread patterns is not known.
International Publication No. 98/29270 Pamphlet Koji Hasegawa, Keiji Kawamata “A Method for Optimizing Topology of Machine Structures Using GA (Topology Optimization Method Using Finite Element Removal and Additional Parameters as Chromosomes)”, Transactions of the Japan Society of Mechanical Engineers (A), 61 Volume 581 (1995-1), p183-p190 Satoshi Tsuruta, Koji Hasegawa, Keiji Kawamata “A Method for Optimizing Topology of Mechanical Structures Using GA (2nd Report, Examination of Convergence of Methods Using Chromosomes with Finite Element Elimination)” Proceedings of the Society (A), 63, 605 (1997-1), p170-p177 Yusaku Suzuki, Koji Hasegawa, Keiji Kawamata “A Method for Topological Optimization of Mechanical Structures Using GA (3rd Report, Definitive Method Using Single Individuals with Finite Element Removal and Additional Parameters)”, Nippon Machinery Proceedings of the Society (A), Vol. 64, No. 626 (1998-10), p49-p54

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tire design method that enables efficient design and can greatly improve tire performance by applying the ECAT method to the design of a tire tread pattern. .

The tire designing method according to the present invention includes:
(A) defining an initial layout in units of one pitch of the tire tread pattern;
(A ′) determining an objective function related to tire performance;
(B) creating a finite element model for a tire in which one pitch unit of the initial layout is developed in a plurality of pitches in the tire circumferential direction;
(C) calculating an evaluation index for each element by structural analysis using the finite element model of the initial layout;
(D) The calculated evaluation index is aggregated in units of one pitch for each corresponding element, the elements are classified according to the size of the aggregated evaluation index, and a plurality of classes to which the removal target element belongs are determined and determined Selecting an element to be removed by fuzzy division from each class;
(E) selecting an element to be restored from among the elements removed above;
(F) The current generation layout is obtained by removing and reviving the elements in the steps (d) and (e), and a finite element model of the tire is created by developing a plurality of pitch units in the tire circumferential direction in the layout. Steps,
(G) calculating an evaluation index for each element by structural analysis using the finite element model of the current generation layout;
(H) The convergence of the objective function is determined from the calculated evaluation index . When it is determined that the target function has not converged, the layout is updated to the current generation layout and the process returns to step (d) to determine that the convergence has been achieved. Sometimes determining a tire tread pattern using the current generation layout as an optimal solution.

  The present invention also provides a program for designing a tire by a computer, which causes the computer to execute the above steps. The present invention further provides a method for manufacturing a tire characterized by designing and manufacturing a tire using the above-described design method.

  In the present invention, the ECAT method is used to optimize the design (layout optimization) of the tire tread pattern. That is, as an act of classifying elements according to the size of the evaluation index calculated for the finite element model of the tire tread pattern, grasping the distribution of the evaluation index in the layout globally, and removing and adding (revitalizing) the element The final layout is determined by evolving the behavior. Since optimization is performed by globally grasping the distribution of the evaluation index, a global optimal solution can be obtained without falling into a local solution, and tire performance can be improved. In addition, the calculation load is small as compared with the case where a conventional genetic algorithm is used. Therefore, the design of the tire tread pattern can be efficiently designed.

  Further, according to the present invention, in the structural analysis using the finite element model, one pitch unit of the layout is developed in a plurality of pitches in the tire circumferential direction to calculate an evaluation index, and an objective function is calculated from the evaluation indexes for the plurality of pitches. The convergence is evaluated. On the other hand, in the process of element removal and restoration, a value obtained by collecting them in units of one pitch is used. A tire tread pattern generally constitutes a tread design by periodically arranging designs in units of one pitch in the circumferential direction. For this reason, by using an evaluation index and an objective function for a plurality of pitches, optimization in accordance with the actual situation can be performed. In addition, in the process of element removal and restoration, the values aggregated in units of one pitch are used, so that it is possible to avoid problems that are designed in different designs between pitches.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a flowchart showing a flow of a tire designing method according to the first embodiment. This embodiment optimizes the phase and shape of the tread pattern of a pneumatic tire using the ECAT method (see Non-Patent Documents 1 to 3 above) and can be implemented using a computer. .

  More specifically, the design method of this embodiment is implemented by creating a program for causing a computer to execute the following steps and using a computer such as a personal computer storing (installing) the program in a hard disk or the like. can do. In other words, the program stored in the hard disk is appropriately read into the RAM at the time of execution, and is calculated by the CPU using various data input from input means such as a keyboard, and the result is displayed by display means such as a monitor. Is displayed. Such a program can be stored in various computer-readable recording media such as a CD-ROM, DVD, MD, and MO. Therefore, a drive device for such a recording medium is provided in the computer. The program may be executed via the drive device.

  In the design method of the present embodiment, first, in step S10, an initial layout for each pitch of the tire tread pattern is determined, and an objective function related to tire performance is determined. As an initial layout, the tread has no groove at all, the tread has only a main groove extending in the circumferential direction, a main groove and a transverse groove extending in a direction intersecting with the main groove, and the main groove There is no particular limitation such as a block having a block defined by a lateral groove. In the present embodiment, an initial layout of a tread pattern is provided with only a main groove that is a circumferential groove. Therefore, in the present embodiment, the initial layout is determined by the width of the tread pattern, the length of one pitch unit, the position of the main groove in the tire width direction, and the width of the main groove.

  Examples of the objective function include physical quantities whose values change depending on the tire tread pattern. Specifically, the tire contact pressure distribution during braking and acceleration, the average contact pressure of the tire, stress, strain, and strain energy. , Friction energy, road slip speed and displacement. As an example, the objective function is the tire contact pressure dispersion, and an optimization problem is defined that minimizes the objective function.

  In the next step S12, an initial layout tire finite element model (hereinafter referred to as FEM model) is created. The FEM model is formed by dividing the tire into elements including the internal structure in a mesh shape. The tire is modeled so that the physical quantities for evaluating the tire performance can be obtained numerically and analytically by structural analysis. It has become. Here, as shown in FIG. 2, a tire FEM model including a tread pattern having only the main groove 2 on the surface of the tread 1 is created.

  In creating such an FEM model, an FEM model for one tire is created for a tire in which one pitch unit of the initial layout is developed by a plurality of pitches in the tire circumferential direction. In this example, since the initial layout is a tread pattern having only main grooves, the two-dimensional FEM model shown in FIG. 2 may be simply swept around the entire circumference of the tire. However, since FIG. 2 is a half cross-section, the entire width is swept. Further, the circumferential development at this time is made according to purposes such as equal intervals and unequal intervals. By the sweep, a tire FEM model in which an initial layout is developed by a plurality of pitches is created as a three-dimensional FEM model.

  In the next step S14, structural analysis is performed using the tire FEM model of the initial layout obtained above. The structural analysis is performed by giving the FEM model analysis conditions such as tire internal pressure, load, coefficient of friction with the road surface, physical properties of the rubber material constituting the tread pattern, etc., and calculating the ground contact surface in the tire tread pattern An evaluation index is calculated for each element. Such a structural analysis can be performed by creating a unique program using a general-purpose programming language (Fortran, etc.), and commercially available FEM analysis software can also be used. Commercially available software includes ABAQUS Inc. “ABAQUS” manufactured by the company, “MARC” manufactured by MSC Software Co., Ltd., and the like.

  The evaluation index is a physical quantity calculated for each element of the contact surface, and is a physical quantity serving as a basis for calculating the objective function as tire performance. Examples of the evaluation index include stress, strain, strain energy, ground pressure, ground pressure dispersion, friction energy, road slip speed, and displacement.

In the next step S16, the evaluation index calculated above is aggregated in units of one pitch for each corresponding element, and these elements are classified according to the size of the aggregated evaluation index .

A method for consolidating evaluation indexes in units of one pitch will be described with reference to FIGS. As shown in FIG. 3, in the case where the pitches are periodically arranged for five pitches, the function of the evaluation index of the element corresponding to each pitch is expressed as follows.

First pitch: F (i, j, 1)
Second pitch: F (i, j, 2)
Third pitch: F (i, j, 3)
-Fourth pitch: F (i, j, 4)
・ Fifth pitch: F (i, j, 5)
Therefore, when these evaluation indexes are aggregated in units of one pitch as shown in FIG. 4, the evaluation indexes of arbitrary elements in the layout in units of one pitch, that is, the function A (i, j) of the aggregated evaluation indexes is Is represented by the following formula (1).

  In addition, when collecting in 1 pitch unit, you may obtain | require an average value in this way, or you may obtain | require only a total value.

The elements included in the layout of one pitch unit are classified into classes based on the evaluation indexes collected in this way. Specifically, the size of the evaluation index is divided into a plurality of levels and classified. For example, 10 levels are set by dividing the minimum value and the maximum value of the evaluation index into 10 equal parts, and all the elements are assigned to the corresponding levels, thereby classifying into 10 classes. Note that the class may be set at regular intervals as described above, or at irregular intervals.

In the next step S18, the class to which the removal target element belongs is determined. Such a removal target class is determined according to the level of the evaluation index of each class.

That is, the evaluation index ground contact pressure distribution (i.e., relative to the average ground contact pressure squared differences of the ground pressure of the element) as in the case where, when subject to removal evaluation index is large, the large end of the evaluation index Multiple classes are determined as classes to be removed. On the other hand, when an object with a small evaluation index is to be removed (for example, when designing a pattern that increases the deflection of the tread portion, an element with a small displacement is removed in the displacement of each element), the side with a small evaluation index Are determined as classes to be removed. Specifically, the removal target class can be determined based on the following equation (2).

N _cβ = βN _cμ (2)
In the equation, N _cβ is the upper limit of the class number to which the removal target element belongs, N _cμ is the class number to which the element having the average value of the evaluation index belongs, and β is the removal coefficient. An element belonging to a class number equal to or less than N _cβ obtained by Expression (2) is a removal target. Here, when class numbers with a large evaluation index are to be removed, a small class number is assigned in order from a large evaluation index, and those with a small evaluation index are to be removed, with a small evaluation index. Assign small class numbers in order. As the removal coefficient β, a predetermined value may be used. Alternatively, as described in Non-Patent Document 1 above, together with the α-cut value and the additional coefficient γ, these parameters are used as genes for chromosomes. You may obtain | require by optimization calculation, such as the genetic algorithm to code. Here, as described in Non-Patent Document 1, the additional coefficient γ is a coefficient defined by the following equation (3).

N _pγ = γN _ps (3)
In the formula, N _pγ is the number of elements to be added, and N _ps is the number of cumulative removal elements. Instead of determining the elements to be restored based on the void ratio in steps S22 to S26 described later, the removal history is stored in the order in which the removed elements are removed, and after N _pγ obtained by the equation (3) You may make it restore all the elements of order.

  In the next step S20, an element to be removed is selected from each removal target class determined in step S18, and the selected element is removed from the layout. It is preferable that the removal element is ambiguously extracted from the class to be removed. In order to extract it ambiguously, as described in Non-Patent Document 1, a membership function is created using the fuzzy c-means method, and fuzzy division is performed. The membership function divides the elements in the removal target class into removal target elements and non-removal target elements based on the α-cut value, and the removal element is selected by obtaining the α-cut value α.

Thus, in this ECAT method, a plurality of classes are determined as removal target classes, and removal elements are selected from each removal target class by fuzzy division. Therefore, when an object with a large evaluation index is to be removed, it is better to avoid falling into a local solution than simply removing the elements of the entire class from the class with the larger evaluation index. A solution can be obtained.

  After removing the elements in this way, the elements to be restored (ie, added) are determined from the removed elements based on the constraint condition on the void ratio of the tread pattern. Specifically, first, in step S22, the void ratio of the layout after removing the elements is calculated. Here, the void ratio is the ratio of the area of the groove (non-grounding portion) to the total area of one pitch unit of the tread pattern, and is usually a void ratio as a constraint within a range of 0.25 to 0.45. An upper limit is set.

  Next, in step S24, it is determined whether the void ratio obtained by the calculation satisfies the above constraint conditions. When the constraint condition is not satisfied, that is, when the calculated void ratio exceeds the predetermined upper limit of the void ratio, the removed element is restored to compensate for the deficient element in step S26. That is, a necessary number of elements are restored from the removal elements selected in step S20 so that the void ratio constraint is satisfied. Since the evaluation index is stored for the elements removed in step S20, in order from the element that has a high possibility of remaining in the layout, that is, when an element with a large evaluation index is to be removed, the element with a small evaluation index is selected. In addition, when an object with a small evaluation index is to be removed, it is restored from an element with a large evaluation index.

  When the constraint condition is satisfied in step S24, the process proceeds to step S28, and the layout of the current generation obtained by removing and restoring the element in the above step is determined.

  In step S30, a tire FEM model of the current generation layout is created. At that time, an FEM model for the entire circumference of the tire is created for a tire in which one pitch unit of the current generation layout is developed in a plurality of pitches in the tire circumferential direction. Here, a method for pitch-developing a design in units of one pitch in the layout of the current generation will be described with reference to FIGS.

  FIG. 5 shows a design of one pitch unit of the tire tread pattern for the entire width of the tread. Reference numeral 2 indicates a main groove, reference numeral 3 indicates a lateral groove, and reference numeral 4 indicates a land portion. . X is the tire circumferential direction and Y is the tire width direction. As shown in FIG. 6, the design in units of one pitch is periodically arranged in the tire circumferential direction X by the number of a predetermined pitch. In the example of FIG. 6, they are periodically arranged for five pitches from the first pitch to the fifth pitch.

  Next, in step S32, using the obtained FEM model of the current generation layout, structural analysis is performed in the same manner as in step S14, and an evaluation index is calculated for each element of the ground contact surface in the tire tread pattern.

  In step S34, the convergence of the objective function is determined. The objective function is calculated from the evaluation index obtained by the structural analysis. For example, when the objective function is tire contact pressure dispersion, it is calculated from the contact pressure dispersion of each element as an evaluation index.

  The determination of convergence is made, for example, based on whether or not the difference between the value of the objective function in the previous generation layout and the objective function in the current generation layout is smaller than a predetermined value. Alternatively, the determination can be made based on whether the objective function in the current generation layout is greater than or equal to a predetermined value compared to the value of the objective function in the initial layout.

  If it is determined by this determination that the objective function has not converged, the layout is updated to the current generation layout, and the process returns to step S16. That is, using the current generation layout as an initial value, the elements are classified in the next step S16, the process proceeds to step S18 and the subsequent steps, and steps S16 to S34 are repeated until the objective function converges.

  If it is determined in step S34 that the objective function has converged, the layout of the current generation at that time is determined as an optimal solution (step S36), and a tread pattern is determined based on the optimal solution (step S38).

  The tire with the tread pattern designed in this way can be manufactured as an actual pneumatic tire by vulcanization molding according to a conventional method, and thereby the air performance with improved tire performance according to the objective function is improved. An inset tire is obtained.

  In this embodiment, by using the ECAT method for the optimization of the design of the tire tread pattern, a global optimum solution can be obtained without falling into the local optimum solution, and the tire performance can be improved. . In addition, since the calculation load is small compared to the case of using a conventional genetic algorithm, the design of the tire tread pattern can be efficiently designed.

  In the present embodiment, in the structural analysis using the FEM model and the convergence determination of the objective function, one obtained by developing a plurality of pitch units of the layout is used, while in the process of removing and restoring elements by the ECAT method, A value obtained by collecting these in units of one pitch is used. Therefore, optimization in accordance with the actual situation can be performed in the design of the tire tread pattern, and inconveniences designed in different designs between pitches can be avoided.

  FIG. 7 is a flowchart showing a flow of a tire designing method according to the second embodiment. In this embodiment, the tire tread pattern of the initial layout includes a lateral groove as well as a circumferential groove. When designing a design of a tire tread pattern, design constraints as a design may be imposed to some extent. For example, as shown in FIG. 5, a rough design of a design having a main groove 2 and a lateral groove 3 may be designated as a tread pattern. In this case, the designated tread pattern is optimized as an initial layout. To implement.

  In the present embodiment, the tire FEM model having the initial layout is automatically generated from the FEM model of the tire having only the main groove in order to analyze the structure of the tire FEM model having the initial layout using the specified tread pattern as an initial layout. Let Specifically, this is realized by the following steps.

  After the initial layout is determined in step S10, a tire FEM model having only main grooves is created in step S40, as in step S12 of the first embodiment. That is, the two-dimensional FEM model shown in FIG. 2 is swept around the entire tire to generate a three-dimensional FEM model.

  In step S42, input data relating to the tread pattern of the initial layout is created. Specifically, the coordinate data of each figure representing the specified tread pattern is created and input.

  In step S44, a mapping algorithm is performed using the input data in order to create a tire FEM model having the tire tread pattern of the designated initial layout from the tire FEM model having only the main groove. . The mapping algorithm is performed for a design in units of one pitch of the tread pattern.

The process by the mapping algorithm will be described. 8, which is one closed drawing of the initial layout design (m _{square) P 1 -P 2 - ... -P} i -P i + 1 - ... and -P _m, shows a relationship between the FEM model The finite element is indicated by a dotted line. Here, first, considered one N ₁ of nodes composing the finite element A. First, the outer product of the N ₁ P _i vector and the N ₁ P _{i + 1} vector is obtained, and the positive / negative of the z component of the outer product is examined. At the same time, an angle θ _i (<180 °) formed by the N ₁ P _i vector and the N ₁ P _{i + 1} vector is obtained. This is performed for each of i = 1 to m. Then, the following equation (4) is calculated, | theta _total | when> 180 °, determines that _{N 1} is in the closed figure, | theta _total | time ≦ 180 °, _{N 1} is closed figures It is determined that it is outside.

(Where ε _i is +1 if the z component of the outer product is positive and -1 if the z component of the outer product is negative)
Confirmation of such a relationship is similarly performed for the nodes N ₂ , N ₃ , and N ₄ , and the element belongs to the closed figure only when all the nodes constituting one element are all inside the closed figure. It is determined that

  Moreover, the following mapping process can also be implemented about the polygonal closed figure as shown to Fig.9 (a). FIG. 9A shows a polygon P1-P2-P3-P4-P5 as a closed figure which is one of the designs of the initial layout. Here, for example, for the node n1 constituting the finite element A, the outer product of the vector P1P2 representing one side constituting the polygon and the normal vector passing through n1 and the vector P1P2 is obtained, and the third component of the outer product is obtained. The positional relationship between the node n1 and the vector P1P2 can be understood from the sign of (z component). The confirmation of such a relationship is obtained for all vectors constituting each side for n1. This is similarly confirmed for the nodes n2, n3 and n4, and it is determined whether or not all the nodes constituting one element are inside the closed figure. FIG. 9B shows an example of the finite element B that does not belong to the closed figure.

  In this manner, the FEM model of the tread pattern in one pitch unit is created by obtaining the relationship with the design of the initial layout for all the finite elements for one pitch unit of the tread pattern, and this is generated in the circumferential direction by the predetermined pitch. The tire FEM model of the initial layout which consists of said designated tread pattern is produced by arrange | positioning in (step S46). Thereafter, as in the first embodiment, the tire tread pattern can be optimized by performing the steps after step S14.

  According to this embodiment, even when a design constraint as a design is imposed on the tire tread pattern, an analysis model can be automatically generated for the design that is desired to be defined as the initial layout. Therefore, even when design restrictions are imposed, a tread pattern can be designed efficiently.

  Hereinafter, an example of optimization of a tire tread pattern using the optimization method according to the embodiment will be described.

  In this example, the tire size was 225 / 45R17, the conditions in the structural analysis were air pressure: 220 kPa, rim used: 17 × 7.5JJ, load: 5782N, and the frictional relationship with the road surface was the slip condition. The objective function is the tire contact pressure distribution, and an optimization problem that minimizes the contact pressure distribution is defined. The evaluation index was the contact pressure dispersion of each element.

  Example 1 corresponds to the first embodiment, and the tread pattern optimization was performed from the tread pattern of only the main groove as an initial value. The initial layout is as shown in FIG. 10A (however, this figure shows the ground contact shape developed by 5 pitches in the circumferential direction), and this was developed by 5 pitches in the circumferential direction in the structural analysis. The element classification was 20 classes, the removal coefficient β = 0.8, and α-cut value α = 0.95. The upper limit of the void ratio was 0.35. The optimized final layout was as shown in FIG. 10B (however, this figure shows the ground contact shape developed by 5 pitches in the circumferential direction).

  Example 2 corresponds to the second embodiment, and tread pattern optimization from a tread pattern designated as an initial value was performed. The initial layout is as shown in FIG. 11A (however, this figure shows the ground contact shape developed by 5 pitches in the circumferential direction), and this was developed by 5 pitches in the circumferential direction in the structural analysis. The element classification was 20 classes, the removal coefficient β = 0.8, and α-cut value α = 0.95. The upper limit of the void ratio was 0.35. The optimized final layout was as shown in FIG. 11B (however, this figure shows the ground contact shape developed by 5 pitches in the circumferential direction).

  For comparison, as Comparative Example 1, a design method by trial and error by repeating conventional design → structural analysis → redesign was performed. Further, as a comparative example 2, a design method for obtaining an optimal solution from the tread pattern using a genetic algorithm using a tread pattern of only the main groove as an initial value was performed.

  The calculation costs required for optimization for Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1 below, and the effect of improving the objective function (ground pressure dispersion) for the conventional tire as a control tire is shown in Table 1 below. It was shown in 1.

As for the improvement effect of the objective function, the analysis value of the contact pressure dispersion of the conventional tire (conventional product) and the actual measurement value are 100 and 100 respectively for the analysis value by the structural analysis and the actual measurement value when actually manufacturing and measuring the tire. The index was displayed. Further, the calculation cost is expressed as an index with the calculation time required in Comparative Example 1 as 100. The smaller the value, the shorter the calculation time, and the higher the calculation cost.

  As shown in Table 1, in the case of the example according to the present invention, the contact pressure dispersion was greatly improved as compared with the conventional tire, and the calculation time was shorter than that of Comparative Example 1 and Comparative Example 2.

  The present invention can be effectively used for designing a tread pattern of various tires such as a pneumatic radial tire.

The flowchart which shows the flow of the tire design method which concerns on 1st Embodiment. The half section view of the tire which shows an example of the finite element model of a tire. The figure which shows the position which evaluates the function of the evaluation parameter | index of arbitrary elements in each pitch in the example developed 5 pitches. The figure which shows the position which evaluates the function of the evaluation index which aggregated the function of the evaluation index of each pitch about arbitrary elements in 1 pitch unit. The figure which shows an example of the design of 1 pitch unit of a tread pattern. The figure which shows the example which developed 5 pitches of designs of 1 pitch unit. The flowchart which shows the tire design method which concerns on 2nd Embodiment. The figure which shows the relationship between the closed figure with an initial layout in a mapping process, and a finite element model. (A) is a figure which shows the example in which a certain finite element belongs to a closed figure in a mapping process, (b) is a figure which shows the example in which a certain finite element does not belong to a closed figure. (A) The figure of the initial layout in Example 1, (b) The figure of the final layout optimized in Example 1. FIG. (A) The figure of the initial layout in Example 2, (b) The figure of the optimization layout of Example 2. FIG.

Explanation of symbols

  1 ... tread, 2 ... main groove (circumferential groove), 3 ... transverse groove, 4 ... land,

Claims (6)

(A) defining an initial layout in units of one pitch of the tire tread pattern;
(A ′) determining an objective function related to tire performance;
(B) creating a finite element model for a tire in which one pitch unit of the initial layout is developed in a plurality of pitches in the tire circumferential direction;
(C) calculating an evaluation index for each element by structural analysis using the finite element model of the initial layout;
(D) The calculated evaluation index is aggregated in units of one pitch for each corresponding element, the elements are classified according to the size of the aggregated evaluation index, and a plurality of classes to which the removal target element belongs are determined and determined Selecting an element to be removed by fuzzy division from each class;
(E) selecting an element to be restored from among the elements removed above;
(F) The current generation layout is obtained by removing and reviving the elements in the steps (d) and (e), and a finite element model of the tire is created by developing a plurality of pitch units in the tire circumferential direction in the layout. Steps,
(G) calculating an evaluation index for each element by structural analysis using the finite element model of the current generation layout;
(H) The convergence of the objective function is determined from the calculated evaluation index . When it is determined that the target function has not converged, the layout is updated to the current generation layout and the process returns to step (d) to determine that the convergence has been achieved. Sometimes determining the tire tread pattern with the current generation layout as an optimal solution;
Tire design method including:   The tire design method according to claim 1, wherein in step (e), an element to be restored is determined from the removed elements based on a constraint condition on a void ratio of the tread pattern.   The tire design method according to claim 1 or 2, wherein the tire tread pattern of the initial layout includes only circumferential grooves.   The tire tread pattern of the initial layout includes a lateral groove and / or a block together with a circumferential groove. In the step (b), the initial layout is performed by a mapping algorithm from a finite element model of a tire having only the circumferential groove on the tread. The tire design method according to claim 1, wherein a finite element model of a tire having a tire tread pattern is created.   A tire manufacturing method, wherein the tire is designed and manufactured using the method according to claim 1. A program for designing tires by a computer,
(A) defining an initial layout in units of one pitch of the tire tread pattern;
(A ′) determining an objective function related to tire performance;
(B) creating a finite element model for a tire in which one pitch unit of the initial layout is developed in a plurality of pitches in the tire circumferential direction;
(C) calculating an evaluation index for each element by structural analysis using the finite element model of the initial layout;
(D) The calculated evaluation index is aggregated in units of one pitch for each corresponding element, the elements are classified according to the size of the aggregated evaluation index, and a plurality of classes to which the removal target element belongs are determined and determined Selecting an element to be removed by fuzzy division from each class;
(E) selecting an element to be restored from among the elements removed above;
(F) The current generation layout is obtained by removing and reviving the elements in the steps (d) and (e), and a finite element model of the tire is created by developing a plurality of pitch units in the tire circumferential direction in the layout. Steps,
(G) calculating an evaluation index for each element by structural analysis using the finite element model of the current generation layout;
(H) The convergence of the objective function is determined from the calculated evaluation index . When it is determined that the target function has not converged, the layout is updated to the current generation layout and the process returns to step (d) to determine that the convergence has been achieved. Sometimes determining the tire tread pattern with the current generation layout as an optimal solution;
A program that causes a computer to execute.

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