JP2012171477A - Tire model making method, tire model making device and tire model making program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately perform an analysis such as the deformation calculation of a bead of a tire.SOLUTION: This tire model making method includes a step 140 of setting the rigidity of the bead based on the ratio of the cross-sectional area of the whole bead of the tire and the cross-sectional area of a cord for constituting the bead by making a cross-sectional model of dividing a cross section of the tire into a plurality of elements, and a step 144 of making a tire model of dividing the tire into a plurality of elements by deploying the cross-sectional model in the circumferential direction of the tire.

Description

  The present invention relates to a tire model creation method, a tire model creation device, and a tire model creation program. More specifically, the present invention relates to a tire model creation method, a tire model creation device, and a tire model for analyzing tire performance by a finite element method. Regarding creation program.

  The analysis of tire behavior is based on the results of measuring the tires actually designed and manufactured and using the performance test results obtained by mounting them on automobiles. Can now be realized. As a main method for analyzing the tire behavior by simulation, a numerical analysis method such as a finite element method (FEM) is mainly used. FEM is a technique of modeling a structure with a finite number of elements and analyzing the behavior of the structure using a computer, and divides the structure into a finite number of elements from its features (hereinafter referred to as mesh division or Element division).

  In order to simulate tire behavior with high prediction accuracy, how to produce a tire model for simulation (consisting of numerical data) composed of a finite number of elements in the same way as the actual tire shape is important. The same applies to the bead portion of the tire, and a modeling method for the bead portion has been proposed (see, for example, Patent Document 1).

JP 2006-62554 A

  However, when a tire is modeled, it is general to model with an isotropic material having a Young's modulus of a cord (for example, a steel cord) forming the bead portion itself in the cross section of the bead portion.

  Also, a tire-wheel assembly finite element model (FEM model) based on a tire modeling method is modeled with an isotropic material having a Young's modulus of a cord (for example, a steel cord) forming a bead portion itself. Is common. When the above modeling is performed on a cross section of a bead portion of a tire, it is difficult to reproduce a deformation like an actual bead. For this reason, when a tire is pressed against the road surface under a load, the deformation of the side portion including the periphery of the bead portion does not match the deformation of the actual tire, and there is a case where high-precision simulation cannot be performed.

  Further, the bead portion is generally configured by bundling several metal wires, and it is complicated to carefully model each metal wire one by one using a finite element model. In addition, the number of finite elements is increased, resulting in a high calculation cost (a long calculation time).

  That is, in the tire-rim analysis using the finite element method, it is common to simplify the bead portion and model it as a finite element model. In this case, each metal wire constituting the bead is accurately modeled. Therefore, a state different from the state in which the actual bead portion is deformed may be simulated in the analysis. In particular, if a finite element modeled with an isotropic material having the Young's modulus of the cord forming the bead portion itself (for example, a steel cord) is used for the simplified bead portion, the model is harder than the actual bead portion. It tends to be. For this reason, in the actual tire, although the bead portion is slightly deformed, the result of the simulation may result in almost no deformation.

  The present invention has been made in view of the above facts, and in a tire analysis by a numerical analysis method such as a finite element method (FEM), a tire capable of performing analysis such as deformation calculation of a bead portion with high accuracy. It is an object to provide a model creation method, a tire model creation device, and a tire model creation program.

  In order to achieve the above object, in the tire model creating method according to the first aspect of the present invention, the step of creating a cross-sectional model in which a cross-sectional model creating unit divides a tire cross-section into a plurality of elements, and the setting unit include: A step of setting the rigidity of the bead portion based on a ratio of a cross-sectional area of the entire bead portion of the tire and a cross-sectional area of a cord constituting the bead portion; Creating a tire model in which the tire is divided into a plurality of elements by developing in a circumferential direction.

  According to the present invention, the rigidity of the bead portion is set based on the ratio of the cross-sectional area of the entire bead portion to the cross-sectional area of all the cords instead of accurately modeling each cord constituting the bead portion. Thus, the bead portion can be easily modeled, and a tire model including a bead portion having a tensile rigidity substantially equivalent to that of the actual bead portion can be created. Thereby, the analysis precision of tire performance can be raised.

  According to a second aspect of the present invention, a Young's modulus obtained by multiplying the ratio by a Young's modulus of an isotropic material constituting the cord may be set as the rigidity of the bead portion.

  A tire model creating apparatus according to a third aspect of the present invention comprises a section model creating means for creating a section model in which a section of a tire is divided into a plurality of elements, a sectional area of the entire bead portion of the tire, and the bead portion. A tire model in which the tire is divided into a plurality of elements by developing setting means for setting the rigidity of the bead portion based on the ratio to the cross-sectional area of the cord, and developing the cross-sectional model in the circumferential direction of the tire. And a tire model creating means to create.

  According to the present invention, the rigidity of the bead portion is set based on the ratio of the cross-sectional area of the entire bead portion to the cross-sectional area of all the cords instead of accurately modeling each cord constituting the bead portion. Thus, the bead portion can be easily modeled, and a tire model including a bead portion having a tensile rigidity substantially equivalent to that of the actual bead portion can be created. Thereby, the analysis precision of tire performance can be raised.

  According to a fourth aspect of the present invention, there is provided a tire model creation program comprising: a step of creating a cross-sectional model in which a cross section of a tire is divided into a plurality of elements; a cross-sectional area of the entire bead portion of the tire; Setting a rigidity of the bead portion based on a ratio to an area; and creating a tire model in which the tire is divided into a plurality of elements by developing the cross-sectional model in a circumferential direction of the tire; The computer is caused to execute processing including

  According to the present invention, the rigidity of the bead portion is set based on the ratio of the cross-sectional area of the entire bead portion to the cross-sectional area of all the cords instead of accurately modeling each cord constituting the bead portion. Thus, the bead portion can be easily modeled, and a tire model including a bead portion having a tensile rigidity substantially equivalent to that of the actual bead portion can be created. Thereby, the analysis precision of tire performance can be raised.

  According to the present invention, there is an effect that analysis such as deformation calculation of a bead portion of a tire can be performed with high accuracy.

It is the schematic of the computer for implementing performance prediction of a tire. It is a schematic block diagram of a computer. It is a flowchart of a tire performance simulation program. It is a flowchart of tire model creation. It is a figure which shows the cross-sectional model of a tire. It is sectional drawing of a bead part. It is a figure for demonstrating a deformation | transformation of the side part of a tire.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an outline of a computer as a tire performance simulation device for creating a tire model of a pneumatic tire and performing performance prediction as an example. This computer displays a keyboard 10 for inputting data and the like, a computer 12 for creating a three-dimensional tire model and predicting performance according to a pre-stored processing program, calculation results and various screens by the computer 12, etc. And a mouse 16 for performing an operation of moving the cursor displayed on the display 14 to a desired position, selecting, deselecting, or dragging a menu item or object at the cursor position. It consists of

  As shown in FIG. 2, the computer 12 includes a CPU (Central Processing Unit) 12A, a ROM (Read Only Memory) 12B, a RAM (Random Access Memory) 12C, a non-volatile memory 12D, and an input / output interface (I / O) 12E. Are connected to each other via a bus 12F.

  Connected to the I / O 12E are a keyboard 10, a display 14, a mouse 16, a hard disk 18, and a CD-ROM drive 22 into which a CD-ROM 20 as a recording medium can be inserted and removed.

  The hard disk 18 stores various programs to be described later, various parameters and data necessary for executing them. The CPU 12A reads and executes a tire performance simulation program stored in the hard disk 18.

  Note that various programs described later can be read from and written to the CD-ROM 20 using, for example, the CD-ROM drive 22, and therefore various programs described later are recorded in the CD-ROM 20 in advance and stored in the CD-ROM 20. -Various programs recorded on the CD-ROM 20 via the ROM drive 22 may be read and executed. Further, the recording medium is not limited to the CD-ROM, but includes an optical disk such as a DVD-ROM and a magneto-optical disk such as an MD or MO. A DVD-ROM drive, MD drive, MO drive or the like may be used.

  Next, as an operation of the present embodiment, a processing routine of a program executed by the computer 12 will be described with reference to flowcharts shown in FIGS.

  First, in step 100, a design plan (tire shape, structure, material, etc.) of a tire to be subjected to behavior analysis is determined. For example, design data such as CAD data (design data of tire shape, structure, material, etc.) of a plurality of types of tires is stored in the hard disk 18 in advance, and the design data of a tire to be subjected to behavior analysis is selected. By reading, it is possible to set a tire to be subjected to behavior analysis.

  Note that the setting in step 100 is not limited to the tire design plan, but includes the case of analyzing an existing tire. That is, the existing tire itself may be set as the target model.

  In the next step 102, a tire tire model for creating a tire design plan into a numerical analysis model is created. The creation of the tire model differs slightly depending on the numerical analysis method used. In this embodiment, a finite element method (FEM) is used as a numerical analysis method.

  Accordingly, the tire model created in step 102 is divided into a plurality of elements by element division corresponding to the finite element method (FEM), that is, mesh division, and the tire is created based on a numerical / analytical method. This is the numerical value of the input data format for the program. This element division means dividing an object such as a tire and a road surface (described later) into several small (finite) small parts, that is, elements. After calculating each element and calculating all the elements, the whole response can be obtained by adding all the elements.

  In the creation of the tire model in step 102, a tire model creation routine shown in FIG. 4 is executed.

  First, in step 140, a division condition in the tire circumferential direction of element division corresponding to the finite element method (FEM) is set. The tire circumferential direction (rotation direction) is divided radially from the rotation center of the tire. In the present embodiment, one round of the tire is set to be divided by, for example, several tens or more.

  In step 142, a tire radial section model (ie, tire section data) is created. As the tire cross-section data, for example, a value obtained by measuring the tire outer shape with a laser shape measuring instrument or the like can be used. In addition, an accurate value such as a design drawing and actual tire cross-section data can be used for the structure inside the tire. In addition, rubber in the tire cross section and supplementary teaching materials (belt, ply, etc., which is a bundle of reinforcing cords made of iron / organic fibers, etc.) are modeled according to the modeling method of the finite element method.

  FIG. 5 shows an example of a tire cross-sectional model. The tire cross-sectional model shown in the figure is a cross-sectional model of a tire having a structure in which one carcass ply 40, two reinforcing cross belts 42A and 42B, and a tire bead portion 44 are provided outside the carcass ply 40. .

  In practice, the bead portion 44 is formed by twisting one or a plurality of cords (for example, a metal wire such as a steel cord) and covering them with a rubber material.

  Conventionally, when creating a tire model, the bead portion 44 is generally modeled with an isotropic material having the Young's modulus of a cord (for example, a steel cord) itself forming the bead portion 44 in its entire cross section. there were. However, if the bead portion 44 is modeled by such a method, it is modeled harder than the actual bead portion, and may not match the deformation in the actual tire.

  Therefore, in the present embodiment, when creating tire cross-section data, the rigidity of the bead portion 44 of the tire is set as follows.

  In this embodiment, based on the ratio of the cord cross-sectional area of all cords in the cross section of the bead portion 44 and the bead portion cross-sectional area of the entire bead portion 44 including the rubber material covering the cord, the actual bead portion is The material property (Young's modulus) of the isotropic material is defined as the rigidity of the bead portion 44 so that the rigidity is close.

  Specifically, as shown in FIG. 6, the cross-sectional area of one cord 46 constituting the bead portion 44 is A, the number of the cords 46 is n (10 in FIG. 6), and the bead portion of the entire bead portion 44. The cross-sectional area is S, the ratio of the cross-sectional area of all the cords 46 to the cross-sectional area of the bead portion (all 10 cords in FIG. 6) is Vf, and the Young's modulus of the cord 46 as an isotropic material is E. The Young's modulus E1 of the part 44 is defined. These parameters can be obtained from tire design data.

E1 = Vf × E (1)

Vf = A × n / S (2)

  Here, the cross-sectional shape of the cord 46 constituting the bead portion 44 includes a circle, an ellipse, a triangle, a quadrangle, and other geometric shapes. If the cord can constitute the bead portion 44, the shape is particularly It is not limited.

  As described above, in the present embodiment, the plurality of cords 46 constituting the bead portion 44 are not accurately modeled, but the cord 46 is set to the ratio of the cross-sectional area of the cord 46 to the entire cross-sectional area of the bead portion 44. The bead part 44 is modeled by multiplying the Young's modulus. Therefore, the bead portion 44 can be easily modeled, and a tire model including a bead portion having a tensile rigidity substantially equivalent to the actual bead portion can be created. Thereby, the analysis precision of tire performance can be raised.

  In step 144, the tire cross-section data (tire radial cross-section model), which is two-dimensional data, is developed by one turn (360 degrees) in the circumferential direction to create a three-dimensional (3D) model of the tire. At this time, the tire cross-section data is developed so that one tire is divided by the division number set in step 140. In this way, a three-dimensional tire model is created. Although a three-dimensional tire model is created here, a simple calculation such as an internal pressure filling calculation or a load load calculation may be performed by setting an axially symmetric boundary condition with the two-dimensional cross-sectional model.

  After the tire model including the finite element model (analysis model) of the tire 20 created as described above is created, the process proceeds to step 104 in FIG. 3 where road surface setting, that is, creation of the road surface model and input of the road surface state are made. The In this step 104, the road surface is modeled and input for setting the modeled road surface to an actual road surface state. The road surface is modeled by dividing the road surface shape into elements and selecting the road surface friction coefficient μ and inputting the road surface state. For example, depending on the road surface condition, there is a road friction coefficient μ corresponding to dry (DRY), wet (WET), on ice, snow, unpaved, etc., so by selecting an appropriate value for the friction coefficient μ, The road surface condition can be reproduced.

  A fluid model may be created and provided between the road surface and the tire model. The fluid model divides and models a part (or all) of a tire, a ground contact surface, and a fluid region including a region where the tire moves and deforms.

  In this way, when the road surface condition is input, the boundary condition is set in the next step 106. The boundary conditions are necessary for analysis of the tire model, that is, for simulating the behavior of the tire, and are various conditions given to the tire model. In setting the boundary condition in step 106, first, an internal pressure is applied to the tire model. Next, a rotational displacement and a straight displacement (displacement may be force or speed), a predetermined load load, or the like is applied to the tire model according to desired calculation conditions.

  Next, a deformation calculation of the tire model as an analysis is performed based on the numerical model created and set up to step 106. That is, when the setting of the boundary condition is completed in step 106, the process proceeds to step 108, and the tire model is calculated for deformation. In this step 108, deformation calculation of the tire model is performed based on the finite element method from the tire model and the given boundary conditions.

  In the next step 110, the calculation result is output. This calculation result uses a physical quantity at the time of tire deformation. Specifically, the amount of side deflection, contact shape, contact pressure distribution, lateral force acting on the center of the tire, moment, eccentric eigenvalue in the vertical direction of the tire, and the like.

  The calculation result may be output by visualizing the value or distribution of the shape of the contact portion of the tire, the distribution of contact pressure, the force acting on the center of the tire, or the like. These can be derived from the calculation result value, amount or rate of change, force direction (vector), and distribution, and can be presented in an easy-to-understand manner by representing them with a diagram etc. along with the tire model and pattern periphery. Visualization is possible.

  As described above, in the present embodiment, the plurality of cords 46 constituting the bead portion 44 are not accurately modeled, but the cord 46 is set to the ratio of the cross-sectional area of the cord 46 to the entire cross-sectional area of the bead portion 44. Since the bead portion 44 is modeled by multiplying the Young's modulus, the bead portion 44 can be easily modeled, and a tire model including a bead portion having a tensile rigidity substantially equivalent to the actual bead portion is created. be able to. Thereby, the analysis precision of tire performance can be raised.

  (Example)

  Next, examples of the present invention will be described. A passenger tire with a tire size of 195 / 65R15 is loaded with an internal air pressure of 210 kPa, a camber angle of 0 degrees, a slip angle of 0 degrees, a vertical load of 4.5 kN, a friction coefficient of 1.0 with a road surface and a speed of 50 km / h. The result of calculating the deformation (surface shape) of the tire side part by performing rolling analysis was compared with the case of the actual tire.

As shown in FIG. 7, the calculation results are the surface positions of the side portion deformation shape in the actual tire and the side portion deformation shape calculated by the FEM simulation using the tire model using the finite element method described in the above embodiment. The amount of deviation at Δ was defined as Δdi, and Δdi ² integrated over all the side regions was defined as ΣΔdi ^2, and comparison was performed using an index with the conventional example as 100. Note that ΣΔdi ² is an index indicating a difference from the actual tire, and the smaller this value, the better the calculation accuracy.

  As shown in FIG. 5, the tire is a tire model having a structure in which one carcass ply 40, two reinforcing cross belts 42A and 42B, and a bead portion 44 are provided on the outer layer side of the ply. This was developed 360 degrees in the tire circumferential direction to create a three-dimensional model.

  The results are shown below.

ここで、「従来例」は、ビード部４４のヤング率Ｅ１をコード４６（スチールコード）のヤング率Ｅそのもので定義したタイヤモデルである。すなわち、ビード部４４のヤング率Ｅ１は、スチールコードのヤング率Ｅに等しく、その値は２１００００［ＭＰａ］である。

Here, the “conventional example” is a tire model in which the Young's modulus E1 of the bead portion 44 is defined by the Young's modulus E itself of the cord 46 (steel cord). That is, the Young's modulus E1 of the bead portion 44 is equal to the Young's modulus E of the steel cord, and its value is 210000 [MPa].

  In addition, as described in the above embodiment, the “example” is a tire model in which the Young's modulus E1 of the bead portion 44 is defined by the above equations (1) and (2). Vf was 0.91. Accordingly, the Young's modulus E1 = Vf × E = 0.91 × 210000 = 191100 [MPa] of the bead portion 44.

  As shown in Table 1 above, in the conventional example, the entire cross section of the bead portion 44 is modeled with an isotropic material having the Young's modulus of the cord 46 (steel cord) itself forming the bead portion 44, so It is modeled harder than the bead, resulting in a large difference from the actual tire and low accuracy.

  On the other hand, in the embodiment, it can be seen that the accuracy of the side portion deformation calculation is greatly improved. Moreover, there was no difference in the calculation time between the conventional example and the example.

  As described above, according to the present invention, it has been found that the accuracy of the side portion deformation calculation can be improved without affecting the calculation time.

10 Keyboard 12 Computer 14 Display 16 Mouse 18 Hard Disk 20 Tire 22 CD-ROM Drive

Claims (4)

A step of creating a cross-sectional model in which the cross-section model creating means divides the tire cross-section into a plurality of elements;
A step of setting the rigidity of the bead portion based on a ratio of a cross-sectional area of the entire bead portion of the tire and a cross-sectional area of a cord constituting the bead portion;
A tire model creating means creating the tire model by dividing the tire into a plurality of elements by expanding the cross-sectional model in the circumferential direction of the tire;
Tire model creation method including. The tire model creation method according to claim 1, wherein a Young's modulus obtained by multiplying the ratio by a Young's modulus of an isotropic material constituting the cord is set as the rigidity of the bead portion. A cross-section model creation means for creating a cross-section model in which a tire cross-section is divided into a plurality of elements;
Setting means for setting the rigidity of the bead part based on the ratio of the cross-sectional area of the entire bead part of the tire and the cross-sectional area of the cord constituting the bead part;
Tire model creating means for creating a tire model by dividing the tire into a plurality of elements by developing the cross-sectional model in the circumferential direction of the tire;
Tire model creation device including Creating a cross-sectional model in which a tire cross-section is divided into a plurality of elements;
Setting the rigidity of the bead portion based on the ratio of the cross-sectional area of the entire bead portion of the tire and the cross-sectional area of the cord constituting the bead portion;
Creating a tire model in which the tire is divided into a plurality of elements by developing the cross-sectional model in the circumferential direction of the tire;
Tire model creation program for causing a computer to execute processing including

Images