JP7315824B2 - Tire initial shape design method, tire initial shape design device, and program - Google Patents

Description

The present invention provides an initial tire shape design method, an initial tire shape design apparatus, and an initial tire shape design method using shape optimization calculation results in a tire modeled with elements that can be numerically analyzed by a computer. Regarding programs to be executed, in particular, an initial tire shape designing method, an initial tire shape designing apparatus, and an initial tire shape design that take into consideration actual manufacturing restrictions without impairing the characteristics of the tire shape that satisfies the target characteristics It relates to a program that implements the method.

Currently, a method has been proposed in which a tire model or the like that can be analyzed by a computer is created and the performance of the tire or the like is simulated. Performance simulation creates a tire model obtained by dividing the tire into a finite number of elements. An optimum tire shape is obtained by performing optimization calculations using a tire model composed of finite elements. Also, the shape of a tire mold is designed using the calculation result of the optimum shape of the tire.

For example, the tire design method of Patent Document 1 includes a setting step of setting a plurality of objective functions, constraints, and design parameters used to determine the positions of a plurality of control points in the basic tire model, and optimization of the objective function. and a design parameter determination step of determining final design parameters based on the value-giving design variables. The plurality of control points enable the shape of the first member and the second member model to be changed, and the setting step moves the no-operation control point based on the operation control point when the first member model is moved. and the operation control point is included in the design parameters, and when the second member model is moved, based on the operation control point, the member spacing of the first and second member models is included in the design parameters and set. do. A curve (eg, a B-spline curve) along each control point can define the tire profile.

JP 2014-148196 A

The tire design method of Patent Document 1 also controls the position of the reinforcing layer. Patent Literature 1 states that the tire cross-sectional shape formed by each control point after movement can be formed into a gentle shape instead of a wavy shape. However, when the tire cross-sectional shape is modeled using a finite number of elements, the model becomes a set of discrete points. If it is not specified or defined, it cannot be given as highly accurate processing instruction information. Therefore, when producing a mold using the calculation result of the optimum tire shape obtained by the tire design method of Patent Document 1, for example, according to a function such as a circular arc, a straight line, or a combination of a circular arc and a straight line, It is desirable to adjust the profile of the tire. However, depending on the degree of adjustment of the contour line, the balance of characteristics of the optimum shape of the tire may be impaired. In the tire design method of Patent Document 1, there is no description regarding the above problem, and it cannot be said that the initial shape of the tire obtained based on the obtained calculation results is sufficient.
Furthermore, it cannot be said to be sufficient in the case of defining the dimensions of the mold using the calculation result of the optimum shape of the tire obtained by the tire design method of Patent Document 1.

An object of the present invention is to solve the above-mentioned problems based on the prior art, and to efficiently calculate a tire cross-sectional shape that takes into account the physical quantities affected by the contour of the tire outside without impairing the characteristics of the shape that satisfies the target characteristics. To provide a tire initial shape designing method, an initial tire shape designing device, and a program for executing the tire initial shape designing method.

In order to achieve the above-mentioned object, the first aspect of the present invention includes a shape setting step of setting a cross-sectional shape of a reference tire, and an outline of a tread portion in the cross-sectional shape of the reference tire, x, With y as a variable and a, b, p, q, x ₀ and y ₀ as parameters, the outer shape defining process is defined using a function represented by the following formula, and for the tire, design variables related to shape, purpose A problem setting process in which functions, constraints, and optimal solution judgment conditions are set; a creation process in which a tire model is created using elements that can be numerically analyzed by a computer; and design variables and objectives set in the problem setting process A computing step of performing shape optimization calculations for a tire model based on functions, constraints, and optimal solution determination conditions; and an acquisition step of obtaining information on the cross-sectional shape of the tire model corresponding to the combination of design variables that make up the extracted solution.

Thermal contraction calculation is performed on the cross-sectional shape of the tire model obtained in the acquisition process, and the shrinkage correction process to obtain information on the heat-shrink cross-sectional shape of the tire model. It is preferable to have an output step of outputting as.
an output step of obtaining a tire outline obtained by shape optimization calculation from information on the cross-sectional shape of the tire model, and outputting the tire outline obtained by the shape optimization calculation as mold shape data; However, the design variables preferably include at least one of the parameters of the function that defines the outline of the tread portion.
The creation step includes fixing at least one of the parameters a, b, p, q, x ₀ , and y ₀ of the function and including the remaining parameters in the design variables, or setting the fixed parameters to any of the remaining parameters. It is preferable to perform shape optimization calculations on the tire model in a computational step dependent on the parameters.
In the creation process, the tire model is created with a mesh composed of multiple nodes and elements that can be numerically analyzed by a computer.In the calculation process, the mesh in the tire model is subdivided to create a new tire model. However, it is preferable to perform shape optimization calculations on the new tire model.

Between the shape setting process and the outer shape defining process, a ground contact analysis process is carried out for the reference cross-sectional shape of the tire set in the shape setting process, and a ground contact area is specified. The contact area specified in the step includes at least the range from the tread center to the contact edge, and in the contour defining step, it is preferable to define the contour using a function for the contact area.
It is preferable that the design variables set in the problem setting step include shape changes in the region including the connecting point between the edge of the tread portion and the sidewall portion of the tire model.

In a second aspect of the present invention, a reference tire cross-sectional shape is set, and the outline of the tread portion in the reference tire cross-sectional shape is represented by a, b, p, q, with x and y as variables. A condition setting unit that defines using a function represented by the following formula with x0 and y0 as parameters, and sets design variables, objective functions, constraints, and optimum solution judgment conditions related to the shape of the tire. , tire models based on the design variables, objective functions, constraints, and optimal solution judgment conditions set in the model creation section, which creates a tire model with elements that can be numerically analyzed by a computer, and the condition setting section. A computing unit that performs shape optimization calculations, and a tire corresponding to a combination of design variables that extracts at least one solution from the result of the shape optimization calculations performed by the computing unit using predetermined extraction conditions, and that constitutes the extracted solution. and a data creation unit for obtaining information on the cross-sectional shape of the model, wherein the design variables include at least one parameter of a function that defines the outline of the tread portion. It provides an apparatus.

The data creation unit performs heat shrinkage calculations on the cross-sectional shape of the obtained tire model, acquires information on the heat-shrinkable cross-sectional shape of the tire model, and uses the heat-shrinkable cross-sectional shape of the tire model as the initial shape data of the tire. Output is preferred.
The data creation unit obtains the outline of the tire obtained by the shape optimization calculation from the information on the cross-sectional shape of the tire model, and outputs the outline of the tire obtained by the shape optimization calculation as mold shape data. is preferred.

In the condition setting part, at least one of the function parameters a, b, p, q, x ₀ , and y ₀ is fixed, and the remaining parameters are included in the design variables, or the fixed parameters are It is preferable that the shape optimization calculation is performed on the tire model by the computing unit depending on the parameters of .
In the model creation section, the tire model is created with a mesh composed of multiple nodes and elements that can be numerically analyzed by a computer. , the shape optimization calculations are preferably performed on the new tire model.
The condition setting section performs ground contact analysis for the standard cross-sectional shape of the tire defined by the condition setting section. Preferably, the range is included, and the condition setting unit defines the outline using a function for the ground area.
It is preferable that the design variables set by the condition setting section include shape change of the region including the connection point between the edge of the tread portion and the sidewall portion of the tire model.

A third aspect of the present invention provides a program for causing a computer to execute each step of the initial tire shape design method of the first aspect of the present invention as a procedure.

According to the present invention, by using the information on the cross-sectional shape of the tire model corresponding to the combination of the design variables that constitute the extracted solution, the outline of the outside of the tire can be influenced without impairing the characteristics of the shape that satisfies the target characteristics. It is possible to efficiently calculate the initial shape of the tire having the tire cross-sectional shape in consideration of the physical quantity to be measured.
According to the present invention, by using the information on the cross-sectional shape of the tire model corresponding to the combination of the design variables that constitute the extracted solution, the outline of the outside of the tire can be influenced without impairing the characteristics of the shape that satisfies the target characteristics. It is also possible to efficiently calculate the tire cross-sectional shape in consideration of the physical quantity to be measured as the mold shape data.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an initial tire shape designing device used in an initial tire shape designing method according to an embodiment of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows an example of the initial shape design method of the tire of embodiment of this invention to process order. (a) is a schematic diagram showing an example of a tire model used in a method for designing an initial shape of a tire according to an embodiment of the present invention, and (b) is a schematic diagram showing an example of a method for creating an elliptical arc forming a tread contour. It is a figure and (c) is a schematic diagram which shows the other example of the preparation method of the elliptical arc which comprises a tread part outline. (a) is a schematic diagram showing an example of a tire model used in the initial tire shape design method of the embodiment of the present invention, and (b) is a tire used in the initial tire shape design method of the embodiment of the present invention. It is a schematic diagram which expands and shows the principal part which shows an example of a model. FIG. 3 is a schematic diagram showing a first example of an elliptical arc based on the initial tire shape design method of the embodiment of the present invention. FIG. 4 is a schematic diagram showing a second example of an elliptical arc based on the initial tire shape design method of the embodiment of the present invention. (a) is a schematic diagram showing an example of mesh subdivision of a tread portion of a tire, and (b) is a schematic diagram showing another example of mesh subdivision of a tread portion of a tire. It is a mimetic diagram showing an example of a tire model of an embodiment of the present invention. (a) is a schematic diagram showing an example of the tire shape change parameter of the embodiment of the present invention, and (b) is a schematic diagram showing another example of the tire shape change parameter of the embodiment of the present invention. 4 is a flow chart showing another example of the initial tire shape design method according to the embodiment of the present invention in order of steps. (a) is a schematic diagram showing the ground pressure distribution of a reference example, (b) is a schematic diagram showing the ground pressure distribution of Example 1, and (c) is a schematic diagram showing the ground pressure distribution of Comparative Example 1. is.

DETAILED DESCRIPTION OF THE INVENTION An initial tire shape design method, an initial tire shape design apparatus, and a program for executing the initial tire shape design method of the present invention will be described below in detail based on preferred embodiments shown in the accompanying drawings.

[Initial tire shape design device]
FIG. 1 is a schematic diagram showing an initial tire shape designing apparatus used in an initial tire shape designing method according to an embodiment of the present invention.
An initial tire shape designing apparatus 10 shown in FIG. 1 is used to execute the initial tire shape designing method of the present embodiment. Hereinafter, the initial tire shape designing device 10 is also simply referred to as the designing device 10 .

The design device 10 is configured using hardware such as a computer. As described above, the design apparatus 10 shown in FIG. 1 is used for the initial tire shape design method of the present invention. The program is not limited to the design apparatus 10, and may be a program for causing a computer to execute each process as a procedure.

The design device 10 has a processing section 12 , an input section 14 and a display section 16 . The processing unit 12 has a condition setting unit 20 , a model creation unit 22 , a calculation unit 24 , a data creation unit 26 , a memory 28 , a display control unit 30 and a control unit 32 . In addition, although not shown, it has a ROM and the like.
The processing unit 12 is controlled by the control unit 32 . In the processing unit 12, the condition setting unit 20, the model creation unit 22, the calculation unit 24, and the data creation unit 26 are connected to the memory 28, and the condition setting unit 20, the model creation unit 22, the calculation unit 24, and the data creation unit are connected. The data of section 26 is stored in memory 28 .
In the initial tire shape design method described below, various processes are performed in each part of the processing unit 12 . In the following description, the control unit 32 performs various processes in each part of the processing unit 12, but the control unit 32 controls a series of processes in each part. The memory 28 also stores various determination conditions, which will be described later. The control unit 32 reads out the determination conditions from the memory 28, compares them with the results obtained by the calculation unit 24, determines operations of each unit based on the determination results, and operates each unit based on the determined operations.

The input unit 14 is various input devices such as a mouse and a keyboard for inputting various information according to operator's instructions. The display unit 16 displays, for example, the results obtained by the tire initial shape design method, and various known displays are used. The display unit 16 also includes a device such as a printer for displaying various information on an output medium.

The design apparatus 10 executes a program (computer software) stored in a ROM or the like with the control unit 32 to function the condition setting unit 20, the model creation unit 22, the calculation unit 24, and the data creation unit 26. to form As described above, the design apparatus 10 may be configured by a computer in which each part functions by executing a program, or may be a dedicated device in which each part is configured by a dedicated circuit.

As will be described later, the initial tire shape design method of the present embodiment uses information on the cross-sectional shape of the tire model corresponding to the combination of the design variables that make up the extracted solution to obtain the initial tire shape and mold shape data. It relates to a method for creating initial tire shape data and a method for creating mold shape data using a computer.
In the tire initial shape design method, information on the cross-sectional shape of the tire model corresponding to the combination of the design variables that make up the extracted solution is used to define the outline using a function in advance. Without impairing the characteristics of (1), the initial shape of the tire can be efficiently searched and calculated in consideration of the physical quantity affected by the contour of the tire outer side. As a result, it is possible to obtain the initial tire shape data that satisfies the target characteristics and does not impair the characteristics of the tire shape.
In addition, in the initial tire shape design method, information on the cross-sectional shape of the tire model corresponding to the combination of design variables that make up the extracted solution is used to define the outline using a function in advance, so that the target characteristics are satisfied. It is possible to efficiently search and calculate the tire cross-sectional shape as mold shape data, taking into account the physical quantity affected by the contour of the tire outside without impairing the shape characteristics of the mold. As a result, it is possible to obtain mold shape data that does not impair the characteristics of the tire shape that satisfies the target characteristics.

The condition setting unit 20 of the design device 10 sets a reference cross-sectional shape of the tire. The reference cross-sectional shape of the tire is not particularly limited, and may be graphic data represented by lines or a finite element model divided into a finite number of elements. In addition, since the optimization calculation is searched with data modeled by elements that can be numerically analyzed by a computer, in the case of graphic data, it is converted to data that is modeled by elements that can be numerically analyzed by a computer. There is a need to.

In the condition setting unit 20, a plurality of parameters defined as design variables among the parameters that define the tire and the material that constitutes the tire are set. The parameters of the design variables may include variation factors such as loads and boundary conditions, and, in the case of products, constraint conditions such as size and mass.
Also, a plurality of parameters defined as characteristic values (objective functions) among the parameters that define the tire and the material that constitutes the tire are set. The characteristic value may be an index for evaluating the tire and the material forming the tire, other than physical and chemical characteristic values such as cost.
The tire and the material that constitutes the tire may be the entire system including the tire, such as the parts that constitute the tire, the assembly form of the tire, or the like, or a part thereof, instead of the tire alone.

The condition setting unit 20 expresses the outline of the tread portion in the cross-sectional shape of the reference tire by the following formula with x and y as variables and a, b, p, q, x ₀ and y ₀ as parameters. It is specified using a function that A method for creating outlines will be described later in detail.
The profile line is a line on the outer surface side from one bead toe through the tread portion to the opposite bead toe in a tire cross section orthogonal to the tire equatorial plane.

In addition, the condition setting unit 20 sets design variables, objective functions, constraints, and optimal solution judgment conditions necessary for shape optimization calculation of the tire model. In addition, various conditions and information necessary for shape optimization calculation of the tire model are input and set. Design variables, objective functions, constraints, optimal solution determination conditions, various conditions, and information are input via the input unit 14 . The memory 28 stores design variables, objective functions, constraints, optimal solution determination conditions, various conditions, and information set by the condition setting unit 20 .
In the condition setting unit 20, it is also possible to set extraction conditions for nodes used to define outlines.

The multiple types of characteristic values set in the condition setting unit 20 are physical quantities to be evaluated, that is, objective functions. The objective function has a direction in which performance is preferable, and the value increases, decreases, or approaches a predetermined value. Moreover, regarding the objective function, there is also an unfavorable direction opposite to the preferable direction in addition to the above-mentioned preferable direction.
The objective function is a tire characteristic value. In this case, the characteristic value is a physical quantity to be evaluated as tire performance. For example, CP (cornering power), which is the lateral force near zero slip angle, which is an index of steering stability, and an index of ride comfort. Examples include the primary natural frequency of a tire, rolling resistance as an index of fuel efficiency performance, lateral spring constant as an index of steering stability, and wear energy of a tire tread portion as an index of wear resistance. Other examples of tire physical quantities include shape and dimensional values. The shape is, for example, a cross-sectional shape. The dimension values are, for example, the width of the tire, the outer diameter of the tire, and the like. Examples of tire physical quantities include deflection, contact pressure, rolling resistance, cornering characteristics, etc., in addition to shape and dimensions.

The design variables define the shape of the tire, internal structure of the tire, material properties, and the like. The design variables are multiple parameters of tire material behavior, tire shape, tire cross-sectional shape, tire natural vibration modes, and tire structure. Design variables include, for example, the radius of curvature that defines the crown shape of the tread portion of the tire, the width of the tire belt that defines the internal structure of the tire, and the like. To obtain mold shape data, the design variables are preferably related to the shape of the tire.

The design variables include at least one of the parameters of the function defining the outline of the tread portion defined by the above function. As described above, the function has x and y as variables and a, b, p, q, x ₀ and y ₀ as parameters. Specifically, for example, at least one of parameters a, b, p, and q is included as a design variable of the tread portion that affects wear performance or braking performance. For example, at least one of the parameters b, _y0 is included as a design variable that changes the tire cross-sectional shape in the radial direction. Further, for example, when targeting a tire whose rotation direction and mounting direction are specified, at least _x0 is included as a design variable for asymmetrically changing the tread portion shape in the cross-sectional width direction.

Constraint conditions are conditions for the value of the objective function to satisfy a predetermined range, and conditions for the value of the design variable to satisfy a predetermined range.
In addition, information on vehicle specifications for use in vehicle running simulations, such as tire load, running conditions such as tire rolling speed, road surface conditions on which tires run, such as uneven shape, friction coefficient, etc. set.

Information for defining nonlinear response relationships between multiple types of design variables and multiple types of characteristic values is set in the condition setting unit 20 . This non-linear response relationship includes, for example, numerical simulations such as FEM (finite element method), theoretical formulas, and the like.
The condition setting unit 20 sets a model generated by a nonlinear response relationship, boundary conditions of the model, simulation conditions in the case of performing a numerical simulation such as FEM, and constraint conditions in the simulation.

Furthermore, the conditions for determining the optimum solution are set. The optimal solution determination condition is, for example, an optimization condition for obtaining a Pareto solution, a condition for searching for a Pareto solution, and the like. The conditions for Pareto solution search are a method for searching for Pareto solutions and various conditions in Pareto solution search.
In this embodiment, for example, a genetic algorithm (GA) can be used as a method for searching Pareto solutions. It is generally known that the search capability of a genetic algorithm decreases as the characteristic value (objective function) increases. One of the ways to solve it is to increase the population.
In addition, the domain of design variables is set in the condition setting unit 20 . The domain of design variables may be discrete level values or constants. Since there are multiple types of design variables, a discrete level value is set for each design variable, and the domain of the remaining design variables is defined as a constant, and the combination of design variables is changed by a computer. It is also possible to calculate the characteristic value while performing the extraction of the Pareto solution, which will be described later.
Further, the condition setting unit 20 can also set extraction conditions for nodes used for defining outlines as described above. The node extraction conditions include, for example, the number of nodes to be extracted, the range of node extraction, and the like.

Regarding the shape optimization calculation, the output value is calculated while changing the input variable according to the optimization algorithm such as the method of sequentially searching using the nonlinear relationship (response surface) of the input variable and the output variable and the evolutionary calculation method. You can use either of the methods of searching by

The model creation unit 22 creates a tire model modeled with elements that can be numerically analyzed by a computer. The model creation unit 22 creates various calculation models based on the set nonlinear response relationship. The non-linear response relationship includes numerical simulation such as FEM as described above. In this case, the model creation unit 22 generates a mesh model corresponding to design parameters representing design variables and characteristic value parameters representing characteristic values. be done. Also, in the case of a theoretical formula, etc., a theoretical formula, etc. corresponding to design parameters and characteristic value parameters is created. A simulation calculation is performed by the calculation unit 24 using the tire model.

The tire model created by the model creation unit 22 is created using various types of design parameters set by the condition setting unit 20, but a known creation method can be used to create the tire model. . The tire model also generates at least a road surface model on which the tire model is rolled. A tire model that reproduces a rim on which a tire is mounted, a wheel, and a tire rotation axis may also be used. Also, if necessary, a model that reproduces the vehicle on which the tire is mounted may be incorporated into the tire model. At this time, it is also possible to create a model in which the tire model, rim model (wheel model), and tire rotation axis model are integrated based on preset boundary conditions.
The form of the tire model used for analysis is not particularly limited, and may be a smooth tire without grooves, a tire with only main grooves, or a tire with a pattern.

The tire model created by the model creation unit 22 is created using various types of design parameters set by the condition setting unit 20, but a known creation method can be used to create the tire model. .
For example, a tire model is created by dividing a tire into a finite number of elements each composed of a plurality of nodes.
Elements constituting a tire model include, for example, quadrilateral elements in a two-dimensional plane, solid elements such as tetrahedral solid elements, pentahedral solid elements, and hexahedral solid elements in three-dimensional bodies, and shell elements such as triangular shell elements and quadrilateral shell elements. Elements, surface elements, and other elements that can be analyzed by computer. In the process of analysis, the elements divided in this way are specified one by one using three-dimensional coordinates for a three-dimensional model and using two-dimensional coordinates for a two-dimensional model.

Each of these models may be a discretized model capable of numerical calculation, such as a finite element model for use in a known finite element method (FEM). In addition, in addition to the road surface model and the tire model, inclusions existing on the road surface are reproduced using the tire model, for example, when obtaining a tire design plan that optimizes tire performance including tire wet performance. You should generate a model. For example, as inclusion models, various models that reproduce water, snow, mud, sand, gravel, ice, and the like on the road surface may be generated as numerically calculable discretized models. Note that the road surface model is not limited to a model that reproduces a road surface with a flat surface, and may be a model that reproduces a road surface shape having an uneven surface as necessary.

The calculation unit 24 performs shape optimization calculations for the tire model created by the model creating unit 22 based on the shape-related design variables, objective functions, constraints, and optimal solution determination conditions set by the condition setting unit 20. It is. Thereby, a characteristic value (output value) for the design variable is obtained. The obtained output value (output value) is stored in the memory 28 . The calculation unit 24 functions by executing a subroutine by a known finite element solver, for example.
The calculation unit 24 uses the nonlinear response relationship to calculate output values (sampling points) in a characteristic value space composed of multiple types of design variable values and characteristic values. Further, the calculation unit 24 uses the design variables and the output values (sampling points) to create an approximate model (metamodel) with the characteristic value, which is the output value, as the objective function.
The approximate model (metamodel) described above is a mathematical model that approximates the input/output relationship, and can approximate various input/output relationships by adjusting parameters. For example, polynomial models, kriging, neural networks, radial basis functions, and the like can be used for the approximate models described above.

The calculation unit 24 also performs shape optimization calculation using an approximate model. Using a solution (which may include a Pareto solution) extracted by the data creation unit 26 from the shape optimization calculation result, actual calculation is also executed using a defined nonlinear relationship. In addition to this, the calculation unit 24 also uses the finite element method to give boundary conditions to a tire model represented by a combination of design variables without using an approximation model, and directly calculates characteristic values. As a shape optimization calculation method, for example, a genetic algorithm (GA), which is one of evolutionary calculation methods, is used. Genetic algorithms include, for example, DRMOGA (Divided Range Multi-Objective GA) and NCGA (Neighborhood Cultivation GA) in which a solution set is divided into a plurality of regions along an objective function and a multi-objective GA is performed for each divided solution set. , DCMOGA (Distributed Cooperation model of MOGA and SOGA), NSGA (Non-dominated Sorting GA), NSGA2 (Non-dominated Sorting GA-II), SPEAII (Strength Pareto Evolutionary Algorithm-II) using known methods such as the method can be done.

The calculation unit 24 searches for a Pareto solution from the shape optimization calculation result using the approximate model obtained by the calculation unit 24 according to the conditions for the Pareto solution search set by the condition setting unit 20, and finds the Pareto solution. There is also something to extract. The resulting Pareto solutions are stored in memory 28 .
Here, a Pareto solution cannot be said to be superior to any other solution in terms of multiple characteristic values (objective functions) in a trade-off relationship, but is a solution for which there is no other superior solution. say. In general, a plurality of Pareto solutions exist as a set. A Pareto ranking method, for example, is used to search for Pareto solutions.

The calculation unit 24 performs selection using, for example, Vector Evaluated Generic Algorithms (VEGA), a Pareto ranking method, or a tournament method. Other than the genetic algorithm (GA), the same evolutionary computation technique, such as simulated annealing (SA) or particle swarm optimization (PSO), may also be used.

In the present invention, the non-linear response relationship defined between design variables and characteristic values, that is, what is used when obtaining characteristic values using design variables is not limited to simulations such as FEM, and the above-mentioned A theoretical formula or the like can also be used.

The data creation unit 26 extracts at least one solution from the result of the shape optimization calculation by the calculation unit 24 using predetermined extraction conditions. Information on the cross-sectional shape of the tire model corresponding to the combination of design variables that constitute the extracted solution is obtained. Furthermore, the data creation unit 26 obtains the outline of the tire obtained by the shape optimization calculation from the information on the cross-sectional shape of the tire model corresponding to the combination of the design variables that make up the extracted solution, and performs the shape optimization calculation. The contour line of the tire obtained by is output as mold shape data.
The method of obtaining the outline of the tire obtained by the shape optimization calculation from the information of the cross-sectional shape of the tire model is not particularly limited as long as the outline of the cross-sectional shape of the tire model can be extracted. method is available.
Mold shape data is dimension data indicating the length of a straight line, the curvature of a curved line, the positional coordinates of the straight line, and the positional coordinates of the curved line. Specifically, for example, it is dimensional data required when producing a mold using an NC processing machine. As the mold shape data, in addition to the dimension data, the shape of the tire model in which the nodes forming the outline are defined by a function may be used. It may be modeled with elements that can be numerically analyzed.

The display control unit 30 causes the display unit 16 to display various parameters such as design variables and characteristic values set in the condition setting unit 20, output values obtained by the calculation unit 24, and tire models. For example, the value of the characteristic value and the result of the shape optimization calculation of the tire model are read from the memory 28 and displayed on the display unit 16 .
The display control unit 30 can also cause the display unit 16 to display various types of information input via the input unit 14, tire models, numerical calculation results, and optimal solutions. For example, the tire model and the result of shape optimization calculation of the tire model are read from the memory 28 and displayed on the display unit 16 .

The control unit 32 controls the processing unit 12 as described above, and performs various processes performed in the initial tire shape design method described below by the model generation unit 22, the calculation unit 24, and the processing unit 12. This is done by the data creation unit 26 .
In the design device 10, the input file for changing the shape or structure is divided into common parts such as boundary conditions and analysis steps, and parts that differ according to individual shapes such as node coordinate values, reinforcing material arrangement angles and initial tension. However, by automating it using a file format that incorporates it into a common part, that is, by making individual information into an include file, it is possible to easily study tire shapes even when studying a large number of tire shapes. It is possible.

In addition, the data preparation part 26 is not limited to the above-mentioned structure. The data creation unit 26 performs heat shrinkage calculation on the obtained cross-sectional shape of the tire model, and acquires information on the heat-shrinkable cross-sectional shape of the tire model. Furthermore, the heat-shrink cross-sectional shape of the tire model is output as the initial shape data of the tire. The data creation unit 26 can also obtain the outline of the tire from the heat-shrinkage cross-sectional shape of the tire model, and output the obtained outline of the tire as the initial shape data of the tire.
In the thermal shrinkage calculation, heat shrinkage during manufacturing is taken into consideration, and heat shrinkage calculation is performed based on the output mold shape. A process of expanding and correcting the shape of the mating mold side to a recessed line may be included. In the heat shrinkage calculation, a heat shrinkage rate is set in advance according to the tire shape, the composition of the tire, and the like. The set thermal shrinkage rate may be stored in the memory 28 or input by the input unit 14 . In addition, when simulating by calculation until it is cooled and stabilized, in consideration of the actual manufacturing process, it is set to calculate the state in which the deformation due to heat and the force of the internal pressure are balanced in the state where the internal pressure is filled. may
In addition, the initial shape of the tire refers to the shape in which the molded unvulcanized tire (green tire or raw tire) is vulcanized before vulcanization in the mold, and after being released from the mold, it is cooled and stabilized. It is the product shape in the folded state.

[Initial tire shape design method]
Next, the initial shape design method of the tire of this embodiment will be described.
FIG. 2 is a flow chart showing an example of the initial tire shape design method according to the embodiment of the present invention in order of steps. FIG. 3(a) is a schematic diagram showing an example of a tire model used in the tire initial shape design method of the embodiment of the present invention, and FIG. FIG. 3C is a schematic diagram showing another example of a method for creating an elliptical arc that forms the outline of the tread portion; FIG.

First, as shown in FIG. 2, a reference cross-sectional shape of a tire is set (step S10). In step S10 (shape setting step), as described above, the reference cross-sectional shape of the tire may be graphic data or a finite element model.
Next, the contour line of the tread portion in the cross-sectional shape of the reference tire is defined using the above function (step S12). That is, in step S12 (outer shape defining step), the above function is used to approximate the outer shape of the tread portion of the cross-sectional shape of the tire.
When defining the outline of the tread portion using the above function in step S12, the method of defining the outline is not particularly limited. For example, if the cross-sectional shape of the reference tire is based on a finite element model, focus on the distance between the node and the elliptical arc, a method of minimizing the residual sum of squares such as the least squares method, and each node Among the residuals in , a method of selecting an elliptical arc with the smallest maximum value can be mentioned. A specific description will be given below.

When the cross-sectional shape of the reference tire is a finite element model representing the tire model 50 having the tread portion 51 shown in FIG. For example, as shown in FIG. 3(b), six points of node 52a, node 52b, node 52c, node 52d, node 52e and node 52f are extracted.
The plurality of nodes extracted on the outer contour, that is, the plurality of nodes extracted on the outline of the extracted shape preferably include nodes at representative positions of the tire tread portion. Taking the tire cross-sectional shape as an example, it is the cap tread center position (tread central portion), the tread development width position, and the like. In addition, with respect to the plurality of extracted nodes, the node at the representative position may be unchanged, and the other nodes may be corrected on the approximate curve, or all the extracted nodes may be corrected on the approximate curve. .

Next, an elliptical arc approximating between the extracted nodes is obtained by using the above-mentioned function represented by the above formula with x and y as variables and a, b, p, q, x ₀ and y ₀ as parameters. to create. Specifically, an elliptical arc 61 that approximates the six nodes 52a, 52b, 52c, 52d, 52e and 52f extracted as shown in FIG. do. As a result, an elliptical arc representing the outline of the tread portion 51 of the tire model 50 shown in FIG. 3(a) is obtained. Note that O(x ₀ , y ₀ ) in FIG. 3B is the center of the elliptical arc 61 .
The elliptical arc 61 is an approximation to the extracted six nodes 52a, 52b, 52c, 52d, 52e and 52f. The smaller the distance δ (residual error) from each of 52c, node 52d, node 52e and node 52f, the higher the accuracy of approximation. The elliptical arc 61 preferably has high approximation accuracy.
The approximation method is not particularly limited. For example, focusing on the distance between the above-mentioned nodes and elliptical arcs, a method of minimizing the residual sum of squares like the least squares method, and the distance δ (residual error) at each node, which is the smallest A method of selecting an elliptical arc that is

For example, as shown in FIG. 3(c), an elliptical arc 61 with a minimum distance .delta. (residual error) between the extracted four nodes 56a, 56b, 56c and 56d is created. Specifically, it is an elliptical arc that satisfies the following formula. Note that the distance δ (residual) is not particularly limited, but is defined using the Euclidean distance, the Manhattan distance, or the axial component of the distance (one of the two orthogonal components of the distance) is preferred.
In the following formula, r _i is the distance from the center O(x ₀ , y ₀ ) of the elliptical arc 61 to each node 56a-56d. s _i is the distance between the intersections of the elliptical arc center O (x ₀ , y ₀ ) and the straight lines passing through the elliptical arc center O (x 0 , y 0 ) and the nodes 56a to 56d. FIG. 3(c) shows the distances s ₁ to s ₄ of the nodes 56a to 56d.

Regarding the elliptical arc 61, for example, two nodes 52 and 54 may be used as fixed points, and an elliptical arc 61 that satisfies the above formula may be searched between the two fixed points. In this case, the elliptical arc 61 may be searched while sequentially changing the values of the parameters a, b, p, q, x ₀ , and y ₀ , and either fixed point may be the major or minor axis of the ellipse. At least one of the values of the parameters a, b, x ₀ and y ₀ may be fixed so as to be positioned on the axis, and the search may be performed while changing the values of the remaining parameters and the parameters p and q.
In FIG. 3B, no fixed points are provided for the six nodes 52a to 52f, but the invention is not limited to this. For example, an elliptical arc may be created using the nodes at both ends as fixed points. .

Even when the cross-sectional shape of the reference tire is graphic data, the outline of the tread portion is represented by a set of points, and the outline of the tread portion is calculated using the same method as the finite element model described above. It can be specified using a function.
In addition, in the created elliptical arc, if there is a circumferential groove on the tire cross-sectional shape including the target node and it is divided into multiple land parts, considering the heat shrinkage during manufacturing, the output mold shape Thermal shrinkage calculation may be performed based on , and the obtained result may be used to correct the shape of each land portion of the tread to a swollen line at the end of step S18. Specifically, with the created elliptical arc as a reference, the curve that bulges to the outside of the tread from the elliptical arc and passes through both ends of the land portion is parametrically defined as a function, and parameters that minimize the difference from the line after heat shrinkage calculation. A search for is incorporated into the optimization algorithm and run by the computer to define the corrected line.

Next, for the tire, optimization conditions such as design variables, characteristic values (objective function), and constraints are set (step S14). In step S14 (problem setting step), the optimal solution determination condition and the node extraction condition are also set. For example, the tire has a size of 195/65R15.
As design variables, for example, design variables that change the shape of the tire or the cross-sectional shape of the tire are set. The setting method of the design variables is not particularly limited, and for example, the design values of the design variables are set using the Latin hypercube method (Latin hypercube method).
The characteristic values include, for example, tire physical properties such as tire rigidity, contact pressure, rolling resistance, air resistance, cornering performance, and frictional energy. For example, two tire physical characteristics, a first characteristic value and a second characteristic value, are set as objective functions. Note that the characteristic value set as the objective function may be 1, or may be 3 or more.

Design variables (input parameters) are tire cross-sectional shape parameters, and characteristic values (output parameters) are two characteristic values that are tire physical characteristics. A parameter of the cross-sectional shape of the tire and two characteristic values are set in the condition setting unit 20 .
In this embodiment, an approximate model is created by the initial tire shape design method under such setting conditions. A change in the first characteristic value and the second characteristic value due to the value of the tire cross-sectional parameter is obtained.
Using the information set in the condition setting unit 20, the model creation unit 22 creates a tire model with elements that can be numerically analyzed by a computer, for example, a tire such as a mesh model having a mesh composed of a plurality of nodes and elements. Create a model (creation process).

Next, the condition setting unit 20 is set with a nonlinear response to be used when obtaining characteristic values from the design variables. That is, the relationship between design variables and characteristic values is determined. The type of nonlinear response is stored in memory 28, for example. For example, the relationship between the parameter of the cross-sectional shape of the tire and the first characteristic value and the second characteristic value is set. When the parameter of the cross-sectional shape of the tire is input and the first characteristic value and the second characteristic value are output, the relationship to be set is, for example, that the first characteristic value is the parameter of the cross-sectional shape of the tire as a variable It is expressed using a nonlinear function such as a polynomial. Also, the second characteristic value is expressed using a non-linear function such as a polynomial having parameters of the cross-sectional shape of the tire as variables.

Next, using the nonlinear response relationship set in step S14 (problem setting step), the output value in a characteristic value space composed of multiple types of design variable values and characteristic values is calculated. That is, a sampling calculation is performed to calculate characteristic values that are outputs when design variables are input.
Next, an approximation model is created using the output values obtained by the sampling calculation. That is, the relationship between design variables and characteristic values is represented by an approximation model.
Next, the calculation unit 24 executes shape optimization calculation using the approximate model (step S16).
Regarding the shape optimization calculation in step S16 (calculation step), the output value is calculated while sequentially changing the input variable according to a search method or optimization algorithm using the nonlinear relationship (response surface) between the input variable and the output variable. You can use either of the methods of searching by The shape optimization calculation is also called multi-objective optimization calculation if a plurality of objective functions are set.

Next, from the result of the shape optimization calculation, at least one solution is extracted using predetermined extraction conditions (extraction step). In the extraction step, a shape (extracted shape) corresponding to a combination of design variables that constitute a solution is extracted from the result of the shape optimization calculation to obtain a tire model 50 (see FIGS. 4(a) and 4(b)). can be done.
In the extraction step, as the extraction condition to be set, a Pareto solution may be extracted by the Pareto solution searching unit and a Pareto solution may be obtained. Further, solutions may be extracted from all individuals (solutions), not limited to Pareto solutions, by using characteristics other than the objective function as constraint conditions.

Next, information on the cross-sectional shape of the tire model 50 (see FIGS. 4A and 4B) corresponding to the combination of design variables forming the extracted solution is obtained (step S18 (acquisition step)).
Information on the cross-sectional shape of the tire model 50 (see FIGS. 4A and 4B) includes, in the case of a finite element model, information on the size and position of each element, and information on the contour of the tire model 50. This is the information of the outer nodes. Note that FIG. 4(a) shows a state in which the tire model 50 is in contact with the ground plane BG.
If it is graphic data, it is, for example, coordinate data of points forming an outline representing the contour of the tire model 50 . In addition to this, when the outline is represented by a spline curve, the spline function is graphic data.

Next, from the information of the cross-sectional shape of the tire model corresponding to the combination of the design variables constituting the extracted solution obtained in step S18 (acquisition step), the information of the outline of the tire obtained by the shape optimization calculation. get Then, the information on the outline of the tire described above is output as mold shape data (step S20 (output step)). In this way, in the tire initial shape design method, the tire mold shape is obtained from information on the cross-sectional shape of the tire model corresponding to the combination of the design variables constituting the extracted solution obtained in step S18 (acquisition step). It is possible to obtain mold shape data necessary for design.

(grounding analysis)
Further, the contour line of the tread portion in the cross-sectional shape of the reference tire may be defined using the above-described function after the contact analysis under a predetermined load. This clarifies the range of the outline defined by the function. The contact analysis process is a process executed between step S10 (shape setting process) and step S12 (outline definition process). The ground contact analysis step is a step of performing a ground contact analysis on the cross-sectional shape of a reference tire and specifying a ground contact area. The condition setting unit 20 performs ground contact analysis on the reference cross-sectional shape of the tire defined by the condition setting unit 20, and defines the outline of the ground contact area using the above function. Specifically, grounding analysis can be performed as follows.
In the condition setting unit 20, like the tire model 50 shown in FIG. The nodes extending to the ground edge 62 can be used to create the elliptical arcs that make up the outline.
As shown in FIG. 4(b), the range from the tread center portion 60 of the tire model 50 to the ground contact edge 62 is the ground contact area 64. As shown in FIG. This ground area 64 is approximated by an outline.
In this way, the extraction range for extracting the nodes is set as the ground contact area 64, the area to be grounded is found by calculation in advance, and the contour line of the tread outer side is created by one elliptical arc, thereby connecting a plurality of elliptical arcs. is no longer required, and the adverse effects on tire characteristics caused by connection points between arcs can be improved. For this reason, the ground contact area 64 is preferably approximated by a single elliptical arc.

In the tire model 50 shown in FIG. 4(a), the node points of the tread center portion 60 and the ground contact edge 62 are fixed, and as the fixed points, the outline (tread contour) of the ground contact area 64 is smoothed by an elliptical arc. , the tread central portion 60 may not have a node (fixed point). For example, there may be no nodes (fixed points) at symmetrical positions with respect to the tread central portion 60 as an axis. Also, if the grounding end 62 is included in the elliptical arc, the grounding end 62 does not have to be a node (fixed point).
In the ground contact analysis at a predetermined load, the load is not particularly limited, but for example, the load equivalent to the maximum load capacity, the load considering the safety factor, or the axle load equivalent value in the specified vehicle is mentioned.
The connection between the end point of the elliptical arc on the side of the grounding end 62 and the outline of the sidewall portion 53 is not particularly limited, but a known method can be used. be done. In the connection between the end point of the elliptical arc on the ground contact edge 62 side and the profile line of the sidewall portion 53 , at the ground contact edge 62 , the first derivative of the tread portion profile line 58 (elliptic arc 61 ) and the first order difference of the sidewall portion 53 An example is that the derivative is consistent. That is, for example, the end point of the elliptical arc on the side of the ground end 62 and the outline of the sidewall portion 53 are connected by sharing a tangent line.

The data generation unit 26 fixes at least one of the parameters a, b, p, q, x ₀ , and y ₀ of the above function and includes the remaining parameters in the design variables, or sets the fixed parameters to the remaining parameters. It is preferable to perform shape optimization calculations on the tire model in the computational step dependent on any parameter. As a result, the number of parameters in the optimization calculation can be reduced, that is, the degree of freedom can be lowered, and the efficiency of the optimization calculation can be improved. Note that fixing a parameter means setting the parameter to a constant.
FIG. 5 is a schematic diagram showing a first example of an elliptical arc based on the initial tire shape design method of the embodiment of the present invention, and FIG. 2 is a schematic diagram showing an example of No. 2. FIG. 5 and 6, the same components as those of the tire model 50 shown in FIGS. 4(a) and 4(b) are denoted by the same reference numerals, and detailed description thereof will be omitted.
The elliptical arc 70 shown in FIG. 5 has a fixed center O, parameters a, b, p, q, x ₀ , y ₀ among parameters b, x ₀ , y ₀ are constants, and parameters a, p , q with different values. In this way the number of variables in the shape optimization calculation can be reduced.
An elliptical arc 70 in FIG. 5 approximates the contact area 64 between the tread center 60 and the contact edge 62 and defines the tread contour 58 . Reference numeral 63 indicates the node of the tread central portion 60 and reference numeral 65 indicates the node of the ground contact edge 62 . In elliptical arc 70 , parameter b is the value of the distance from center O to node 63 of tread central portion 60 . The parameters p, q and a were adjusted to approximate the grounded area 64 . Elliptical arc 70 can be constructed using the approximation method described above.

When the tire cross-sectional shape of the tire model 50 is symmetrical about the tire equatorial plane CL, the center O of the elliptical arc is preferably on the tire equatorial plane CL. In FIG. 5, the center O of the elliptical arc 70 is on the tire equatorial plane CL. The tread central portion 60 is a position where the tire cross-sectional height passing through the tire equatorial plane CL is maximized in the cross-sectional shape of the tire model 50 orthogonal to the tire equatorial plane CL. The tire equatorial plane CL is a plane perpendicular to the rotation axis (not shown) of the tire model 50 and passing through the center of the tire width of the tire model 50 .

The elliptical arc 70 in FIG. 5 has different values for the parameters a, p, and q, but is not limited to this. For example, among parameters a, b, p, q, x ₀ , and y ₀ , parameters a and b may be constants, and parameters p and q may be changed. In this case, if the parameters a and b are constants, and the tire cross-sectional shape is symmetrical about the tire equatorial plane CL, then the center O(x ₀ , y ₀ ) is fixed and, for example, the elliptical arc 72 shown in FIG. is created. In this way, the number of variables in the shape optimization calculations can also be reduced. Elliptical arc 72 defines tread contour 58 . In FIG. 6, the center O of the elliptical arc 72 is on the tire equatorial plane CL.

In the elliptical arc 72, the parameter a is the value of the distance from the center O to the node 67 at the widest point 66 of the tire. The parameter b is the value of the distance from the center O to the node 63 of the tread central portion 60 . The parameters p and q have been adjusted to approximate grounded area 64 . Elliptical arc 72 can be constructed using the approximation method described above.
In this case, instead of minimizing the residual sum of squares of all nodes and elliptical arcs between fixed points, a weight may be given to improve the accuracy of a part of the region. For example, a method of fixing the position represented by the parameter a to the maximum width position and calculating the values of p and q that minimize the residual sum of squares between the tread central portion 60 and the ground contact edge 62 (ground contact region 64). may be used.
When the parameters a and b are constants, the parameters a and b are the maximum width represented by the maximum length in the tire equatorial plane CL, the tire width direction, and the tire radial direction from the bead bottom to the tire maximum width position. It is defined by distance (tire maximum width position height) or the like.

In the above function, the domain of the order of the parameters p and q is not particularly limited, but in order to improve the search efficiency, it is desired to constrain the center of the elliptical arc to be inside the extracted node group, that is, to the axis center side. In this case, it is preferable to give constraints p>1 and q>1. If the center of the elliptical arc is outside the node group, an asteroidal curve may be used. An asteroidal curve is obtained by imposing the constraints that p<1 and q<1.

The calculation unit 24 creates a new tire model by subdividing the mesh in the tire model composed of a mesh composed of a plurality of nodes and elements, and performs shape optimization calculation on the new tire model. may That is, in the calculation step (step S16), the mesh in the tire model may be redivided to create a new tire model, and the shape optimization calculation may be performed on the new tire model.
Here, FIG. 7(a) is a schematic diagram showing an example of mesh subdivision of the tread portion of the tire, and FIG. 7(b) is a schematic diagram showing another example of mesh subdivision of the tread portion of the tire.
The above-mentioned subdivision means that, when calculating physical properties in the shape optimization calculation, the physical properties may not be reflected depending on the mesh pitch. In this case, the tread portion 51 of the tire model 50 is subdivided into small meshes 80 as shown in FIG. 7(a). As a result, the error between the outline of the tread portion defined using the function and the element model is reduced, so that the shape can be searched with high accuracy.
On the other hand, as shown in FIG. 7B, the tread portion 51 of the tire model 50 is subdivided into large meshes 82 . As a result, the time required for shape optimization calculation can be shortened.
In both FIGS. 7A and 7B, the mesh in the region of the tread portion is uniformly subdivided, but the present invention is not limited to this. For example, a tire model may be divided into a cap portion and a casing portion, and only the cap portion may be redivided and combined with the mesh of the casing portion. This is because only the region that constitutes the outline and affects the shape optimization calculation, ie the cap portion, needs to be subdivided. In order to implement the above method, the operator predetermines the size, element angle, target area, etc. as mesh quality judgment conditions, and the computer automatically judges and executes the mesh subdivision program. may be added to the calculation step (step S16).

Here, FIG. 8 is a schematic diagram showing an example of a tire model according to the embodiment of the present invention. FIG. 9A is a schematic diagram showing an example of the shape change parameter of the tire according to the embodiment of the present invention, and FIG. 9B is a schematic diagram showing another example of the shape change parameter of the tire according to the embodiment of the present invention. be.
The design variables may include the shape change of the region 59 including the connection point 68 between the ground contact edge 62 of the tread portion 51 and the sidewall portion 53 of the tire model 50, as shown in FIG. As a result, the sensitivity of the tread portion outline 58 to the objective function at the connection point 68 of the tread portion outline 58 and the sidewall portion 53 defined using the above function is clarified, and the connection according to the objective characteristics is clarified. An optimal shape for point 68 can be provided.
The change in the shape of the region 59 described above is related to the physical properties of the tire related to heat generation or stiffness. It is possible to obtain a shape with balanced characteristics by using
The connection between the ground contact end 62 of the tread portion 51 of the tire model 50 and the connection point 68 between the sidewall portion 53 can be connected by a known method. For example, a method of extending the arc of the tread portion contour line 58 (elliptic arc 61 ) contacting the ground contact end 62 to the tread portion and connecting it to the sidewall portion 53 can be used.

Note that the above-described shape change includes, for example, a change in the shape of the region 59 in the normal direction, as shown in FIG. 9A. In the case of the shape change shown in FIG. 9A, the amount of shape change in the normal direction of the region 59 is the design variable.
Moreover, the shape change described above may include a change in the volume of the region 59 as shown in FIG. 9B. Volume change includes volume increase and volume decrease. In the case of the volume change shown in FIG. 9B, the volume change amount of the region 59 is the design variable.
In any of the above-described initial tire shape designing methods, a program for executing the initial tire shape designing method can cause a computer to execute each step of the above-described initial tire shape designing method as a procedure.

[Initial tire shape design method]
Next, another example of the initial tire shape design method of the present embodiment will be described.
FIG. 10 is a flow chart showing another example of the initial tire shape design method according to the embodiment of the present invention in order of steps. In another example of the initial tire shape designing method shown in FIG. 10, detailed descriptions of the steps similar to those of the initial tire shape designing method shown in FIG. 2 will be omitted.

Compared to the initial tire shape design method, the initial tire shape design method performs heat shrinkage calculations on the cross-sectional shape of the tire model obtained in the acquisition process, and obtains information on the heat-shrink cross-sectional shape of the tire model. and an output step (step S24) of outputting the heat-shrink cross-sectional shape of the tire model as the initial shape data of the tire. Since it is the same as the initial shape design method, its detailed description is omitted.

In the initial tire shape design method, in the shrinkage correction step (step S22), heat shrinkage calculation is performed on the cross-sectional shape of the tire model obtained in step S18 to obtain information on the heat-shrink cross-sectional shape of the tire model. Thermal shrinkage calculations are as described above.
After the shrinkage correction step, the thermally shrunk cross-sectional shape of the tire model is output as the initial shape data of the tire (step S24). Thereby, the initial shape data of the tire can be obtained.
In step S24 (output step), it is also possible to obtain the contour line of the tire from the heat-shrink cross-sectional shape of the tire model and output the obtained contour line of the tire as the initial shape data of the tire.
In the above-described initial tire shape design method, a program for executing the initial tire shape design method can cause a computer to execute each step of the above-described initial tire shape design method as a procedure.

The present invention is basically configured as described above. Although the initial tire shape design method, the initial tire shape design apparatus, and the program according to the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and within the scope of the present invention, Of course, various improvements or changes may be made.

EXAMPLES Examples of the method for designing the initial shape of a tire according to the present invention will be specifically described below.
In this example, the effect of the initial tire shape design method of the present invention was confirmed using Example 1 and Comparative Example 1 shown below. Note that Example 1 and Comparative Example 1 were compared based on a reference tire.

Example 1, Comparative Example 1, and the reference tire use the same tire finite element model. The only difference is the correction method for .
In the tire model, shape optimization calculations are performed with the shape of the rim contact portion unchanged so as not to cause poor contact. Further, the first embodiment and the first comparative example differ only in the method of correcting the outline, and the same result is used for the original shape.

In Example 1, the initial tire shape design method of the present invention is applied, and an outline of a tire model is created using an elliptical arc.
In Comparative Example 1, the contour line of the tire model is created by combining two types of circular arcs that share a tangent line at the connecting portion.
As described above, in Example 1, the outline is composed of elliptical arcs, and in Comparative Example 1, the outline is composed by combining two types of arcs. They have the same configuration except for the different outlines, and the same configuration was used for the FEM analysis, except for the different outlines of the tire models.

For Example 1, Comparative Example 1, and a reference tire, maximizing the contact area and minimizing contact pressure dispersion were set as objective functions, and shape optimization calculations were performed using the finite element method (FEM). and tire characteristics were compared. The results are shown in FIGS. 11(a) to 11(c). 11(a) is a schematic diagram showing the ground pressure distribution of the reference example, (b) is a schematic diagram showing the ground pressure distribution of Example 1, and (c) is a schematic diagram showing the ground pressure distribution of Comparative Example 1. It is a schematic diagram. 11(a) to 11(c) is the tire width direction.
In addition, for Example 1, Comparative Example 1, and the reference tire, the contact area was determined, and the contact pressure distribution was determined from each contact pressure. The results of Example 1 and Comparative Example 1 are shown in Table 1 below.
The contact pressure variance is obtained by calculating the sum of the squares of the difference (deviation) between the contact pressure detected at each node of the tire model and the average value of the contact pressure at all nodes, and dividing it by the number of detected nodes. It's about value. The lower the ground pressure distribution value, the smaller the variation in the ground pressure in the ground contact area, that is, the more uniform the ground pressure.

As shown in Table 1 above, Example 1 has a larger contact area and a smaller contact pressure dispersion than Comparative Example 1. In Example 1, ground pressure is more uniform than in Comparative Example 1.
Further, as shown in FIG. 11(b), in Example 1, the ground pressure difference is small. On the other hand, in Comparative Example 1 shown in FIG. 11(c), there was a region where the ground pressure was high at the ground end.
In the present invention, it is possible to improve the local contact pressure increase that occurs near the connecting ends of the arcs that form the outer contour in the cross-sectional shape of the tire model, and the tire shape outer shape in which the contact pressure is made uniform. I was able to get the line Thus, in the present invention, it was possible to obtain die shape data that does not impair the characteristics of the tire shape that satisfies the target characteristics.

10 Tire initial shape design device (design device)
12 processing unit 14 input unit 16 display unit 20 condition setting unit 22 model creation unit 24 calculation unit 26 data creation unit 28 memory 30 display control unit 32 control unit 50 tire model 52a to 52f, 56a to 56d node 53 sidewall unit 58 tread External outline 60 Tread center 61, 70, 72 Elliptical arc 62 Ground contact edge 64 Ground contact area 63, 65, 67 Node 66 Maximum width position 80, 82 Mesh BG Ground contact CL Tire equatorial plane O Center δ Distance

Claims (15)

A shape setting step of setting the cross-sectional shape of the tire as a reference;
The outline of the tread portion in the cross-sectional shape of the reference tire is calculated using a function represented by the following formula with x and y as variables and a, b, p, q, x ₀ and y ₀ as parameters. Defined outline definition process,
a problem setting step of setting design variables, objective functions, constraints, and optimal solution determination conditions related to the shape of the tire;
A creation step of creating a tire model with elements that can be numerically analyzed by a computer for the tire;
a calculation step of performing a shape optimization calculation for the tire model based on the design variables, the objective function, the constraint conditions, and the optimum solution determination conditions set in the problem setting step;
Extracting at least one solution using a predetermined extraction condition from the result of the shape optimization calculation in the computing step, and information on the cross-sectional shape of the tire model corresponding to the combination of design variables that make up the extracted solution An initial shape design method for a tire, comprising:
a shrinkage correction step of performing heat shrinkage calculation on the cross-sectional shape of the tire model obtained in the obtaining step to obtain information on the heat-shrink cross-sectional shape of the tire model;
2. The method of designing an initial shape of a tire according to claim 1, further comprising an output step of outputting the heat-shrinkable cross-sectional shape of the tire model as initial shape data of the tire. An outline of the tire obtained by the shape optimization calculation is obtained from the information on the cross-sectional shape of the tire model, and the outline of the tire obtained by the shape optimization calculation is output as mold shape data. and an output step to
2. The method of designing an initial shape of a tire according to claim 1, wherein said design variables include at least one of said parameters of said function defining said outline of said tread portion. The creating step includes fixing at least one of the parameters a, b, p, q, x ₀ , and y ₀ of the function and including the remaining parameters in the design variables, or fixing the fixed parameters. The initial tire shape design method according to any one of claims 1 to 3, wherein the shape optimization calculation is performed for the tire model in the calculation step, depending on any remaining parameter. In the creation step, the tire model is created with a mesh composed of a plurality of nodes and elements that can be numerically analyzed by the computer,
5. The computing step according to any one of claims 1 to 4, wherein the mesh in the tire model is subdivided to create a new tire model, and the shape optimization calculation is performed on the new tire model. tire initial shape design method. Between the shape setting step and the outer shape defining step, a ground contact analysis step of performing a ground contact analysis on the reference cross-sectional shape of the tire set in the shape setting step and specifying a ground contact area is provided. death,
The ground contact area identified in the ground contact analysis step includes at least a range from the center of the tread to the ground contact edge,
The initial tire shape design method according to any one of claims 1 to 5, wherein, in said outline defining step, said outline is defined for said ground contact area using said function. 7. The design variable according to any one of claims 1 to 6, wherein the design variables set in the problem setting step include a shape change of an area including a connection point between the end of the tread portion and the sidewall portion of the tire model. A method for initial shape design of the described tire. A cross-sectional shape of a tire as a reference is set, and the outline of the tread portion in the cross-sectional shape of the tire as a reference is obtained by using x and y as variables and a, b, p, q, x0, and y0 as parameters. a condition setting unit that defines using a function expressed by a mathematical formula and sets design variables related to shape, objective functions, constraints, and optimal solution judgment conditions for the tire;
A model creation unit for creating a tire model of the tire using elements that can be numerically analyzed by a computer;
a calculation unit that performs shape optimization calculations for the tire model based on the design variables, the objective function, the constraint conditions, and the optimum solution determination conditions set by the condition setting unit;
Extracting at least one solution using a predetermined extraction condition from the result of the shape optimization calculation of the computing unit, and information on the cross-sectional shape of the tire model corresponding to the combination of design variables forming the extracted solution and a data creation unit for obtaining
An apparatus for designing an initial shape of a tire, wherein the design variables include at least one of the parameters of the function that defines the outline of the tread portion.
The data generation unit performs heat shrinkage calculation on the obtained tire model cross-sectional shape, acquires information on the heat-shrinkable cross-sectional shape of the tire model, and converts the heat-shrinkable cross-sectional shape of the tire model into a tire. 9. The initial shape design device for a tire according to claim 8, wherein the initial shape data of the tire is output as the initial shape data of the The data creation unit obtains the outline of the tire obtained by the shape optimization calculation from the information on the cross-sectional shape of the tire model, and calculates the outline of the tire obtained by the shape optimization calculation. 9. The tire initial shape designing device according to claim 8, which outputs as mold shape data. In the condition setting unit, at least one of the parameters a, b, p, q, x ₀ , and y ₀ of the function is fixed and the remaining parameters are included in design variables, or the fixed parameters are The tire initial shape design device according to any one of claims 8 to 10, wherein the calculation unit performs the shape optimization calculation for the tire model in dependence on any of the remaining parameters. The model creation unit creates the tire model with a mesh composed of a plurality of nodes and elements that can be numerically analyzed by the computer,
The computing unit according to any one of claims 8 to 11, wherein the mesh in the tire model is subdivided to create a new tire model, and the shape optimization calculation is performed on the new tire model. tire initial shape design device. The condition setting unit performs a ground contact analysis on the reference cross-sectional shape of the tire defined by the condition setting unit. It includes the range to the ground edge,
11. The tire initial shape designing apparatus according to claim 10, wherein said condition setting unit defines said outline using said function for said ground contact area. 14. The design variable according to any one of claims 8 to 13, wherein the design variables set by the condition setting section include a shape change of an area including a connection point between the end of the tread portion and the sidewall portion of the tire model. An initial shape design device for the described tire. A program for causing a computer to execute each step of the tire initial shape design method according to any one of claims 1 to 7 as a procedure.