JP2010191612A - Tire model formation method and tire simulation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately form a tire model. <P>SOLUTION: A method of forming a tire model for evaluating the performance of a vulcanized tire which is formed using a metal mold by numerical calculation by a computer is characterized by including: a step S1 of determining a cross-sectional shape of the tire in the metal mold; a step S2 of forming an initial tire model based on the cross-sectional shape; and a transformation step S3 of obtaining the tire model by deforming the initial tire model by imparting a thermal contraction condition thereto accompanied by the lowering of a temperature decrease from a vulcanization temperature to an ordinary temperature. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire model creation method and a tire simulation method used for tire computer simulation using a finite element method.

  In recent years, various computer simulations for analyzing various performances of tires using a finite element method have been performed (for example, see Patent Documents 1 to 3 below).

  In this simulation, first, a tire model (also referred to as “finite element model” or “mesh model”) is created by dividing a tire to be evaluated by a finite number of elements. Next, various material properties are defined for each element of the tire model. Then, for example, various conditions approximate to the actual running state are given to the tire model, and various physical quantities such as the deformation state and reaction force of the tire model at that time are calculated. Therefore, by evaluating these physical quantities, it is possible to roughly grasp the performance without actually making a trial tire.

Japanese Patent No. 3314082 Japanese Patent No. 3498064 JP 2006-123644 A

  By the way, in many cases, a conventional tire model has a cross-sectional shape determined based on a mold (mold drawing) for vulcanizing and molding a tire. That is, the cross-sectional shape of the conventional tire model is based on the tire cross-sectional shape in a state of being restrained in the mold.

  However, at the time of vulcanization, the temperature of the tire rises to about 140 to 180 ° C., but is finally cooled to room temperature after being taken out from the mold. For this reason, shrinkage occurs in the rubber material and / or fiber cord material constituting the tire, and the cross-sectional shape of the tire is different from the state of being restrained in the mold. That is, the cross-sectional shape of the tire model used in the conventional simulation is different from the actual cross-sectional shape of the tire. This difference in shape appears as an error in the simulation calculation result, resulting in a problem that the simulation accuracy is lowered.

  The present invention has been devised in view of the above problems, and an initial tire model is created based on the cross-sectional shape of a mold, and this initial tire model is reduced in temperature from the vulcanization temperature to room temperature. A tire model creation method and simulation method useful for performing accurate simulation by approximating the actual tire cross-sectional shape and the tire model cross-sectional shape on the basis of deforming by applying the accompanying heat shrinkage condition The main purpose is to propose.

  The invention according to claim 1 of the present invention is a method for creating a tire model for numerically calculating and evaluating the performance of a tire vulcanized by a mold using a computer, A step of determining a tire cross-sectional shape in a mold, a step of creating an initial tire model based on the cross-sectional shape, and applying a heat shrink condition to the initial tire model in accordance with a temperature decrease from a vulcanization temperature to a normal temperature to be deformed And a deformation step of obtaining a contracted tire model.

  According to a second aspect of the invention, in the tire model according to the first aspect, the initial tire model includes a rubber element that models rubber, and in the deformation step, the rubber element contracts isotropically in volume. It is a creation method.

  According to a third aspect of the present invention, the initial tire model includes a fiber material element obtained by modeling a fiber cord, and the fiber element contracts along a longitudinal direction of the fiber cord in the deformation step. A tire model creation method according to 1 or 2.

  The invention according to claim 4 is characterized in that at least one physical quantity is obtained by applying a predetermined condition to the contracted tire model obtained by any one of claims 1 to 3 and deforming it. This is a tire simulation method.

  According to the first aspect of the invention, first, an initial tire model is created based on the tire cross-sectional shape in the mold. Next, a contracted tire model is obtained by applying and deforming the initial tire model with heat shrinkage conditions accompanying a temperature drop from the vulcanization temperature to room temperature. Therefore, the change in the cross-sectional shape due to the heat shrinkage deformation of the tire after vulcanization is taken into the shrink tire model and reflected. Therefore, it is possible to obtain a shrink tire model approximated by a cross-sectional shape of an actual tire.

  Further, as in the invention described in claim 2, the deformation step contracts the volume of the rubber element or contracts the fiber material element along the longitudinal direction of the fiber cord as in the invention described in claim 3. By including the treatment, it is possible to incorporate more accurate heat shrink deformation into the tire model, and to bring it closer to the actual tire cross section.

  Further, as in the invention according to claim 4, a highly accurate simulation is obtained by applying at least one physical quantity by applying boundary conditions to the shrink tire model obtained by the production method according to any one of claims 1 to 3. The result can be obtained.

It is a block diagram of the computer apparatus for implementing the simulation method of this embodiment. It is a flowchart which shows an example of the process sequence of the preparation method and simulation method of the tire model of this embodiment. It is a meridian sectional view of a tire showing a tire sectional shape in a mold. FIG. 4 is a cross-sectional view visualizing and showing an initial tire model set based on the tire cross-sectional shape of FIG. 3. It is sectional drawing which visualized the shrink tire model. It is a flowchart which shows an example of the process sequence of the step which deform | transforms an initial tire model by heat contraction. It is sectional drawing explaining the deformation | transformation calculation which loaded the rim | limb assembly and the internal pressure. It is the diagram which visualized the result of grounding shape simulation, (a) shows a conventional example and (b) shows a result of an example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a computer apparatus 1 for carrying out the present invention. The computer device 1 includes a main body 1a, a keyboard 1b as an input means, a mouse 1c, and a display device 1d as an output means. The main body 1a is appropriately provided with an arithmetic processing unit (CPU), a working memory and a magnetic disk, as well as CD-ROM and flexible disk drives 1a1 and 1a2. The magnetic disk stores a program for executing the method according to the present invention for tires.

  FIG. 2 shows an example of a processing procedure of a tire simulation method suitable for optimizing the contact shape as an embodiment of the present invention.

  In the present embodiment, first, a mold / tire structure design is performed (step S1). In this step, as shown in FIG. 3, at least the cross-sectional shape (that is, the cross-sectional shape before heat shrinkage) and the internal structure of the pneumatic tire 2 vulcanized and molded by a mold are set (designed). This work is performed by a designer using, for example, the computer apparatus 1 and CAD software.

  The pneumatic tire 2 includes, for example, a tread portion 3, a pair of sidewall portions 4 extending inward in the tire radial direction from both sides thereof, and a bead in which a bead core 6 is embedded in each sidewall portion 4. Part 5. The pneumatic tire 2 includes a carcass 7 formed of a carcass cord layer extending across a pair of bead cores 6 and 6 and a metal cord layer disposed outside the tire radial direction and inside the tread portion 3. A belt layer 8; Further, in the tread portion 2, on the outer side in the tire radial direction of the belt layer 8, a tread rubber Tg that is in contact with the road surface and is provided with a plurality of grooves g is provided. Further, in the sidewall portion 4, sidewall rubber Sg is disposed outside the carcass 7 in the tire axial direction.

  By this mold / tire structure design, a two-dimensional tire cross-sectional shape in the mold is determined. Further, the fiber cord materials used for the carcass 7 and the belt layer 8, the cord angles thereof, and detailed specifications of various structural materials such as the rubber material of the tread rubber Tg are determined.

  Next, based on the tire cross-sectional shape in the mold set in the above steps, in this embodiment, as visualized and shown in FIG. 4, a two-dimensional initial tire model comprising a finite number of elements e. 10 is set (step S2). Such model setting (modeling) can be easily performed by using, for example, design data (for example, CAD data) of the tire cross-sectional shape set in step S1 and meshing software.

  The above "based on" means that the initial tire model 10 does not need to exactly match the tire cross-sectional shape in the mold, and details that do not affect the running performance of the tire (for example, lettering of the sidewall portion) Or the like) means that the initial tire model 10 may be created by being simplified or omitted as appropriate.

  The initial tire model 10 includes a finite number of elements e (numerical data) that can be numerically analyzed by the computer apparatus 1. The possibility of numerical analysis means that calculation is possible according to a numerical analysis method such as a finite element method, a finite volume method, a difference method, or a boundary element method. Specifically, for each element e..., Nodal coordinate values, shapes, material properties (for example, density, elastic modulus, loss tangent or damping coefficient) are defined as numerical data. These elements e are stored in the computer device 1 and calculated and visualized using numerical analysis software.

  The initial tire model 10 includes a tread rubber model portion 11 that models the tread rubber Tg, a sidewall rubber model portion 12 that models the sidewall rubber Sg, and a carcass model portion 13 that models the carcass 7. The belt model part 14 which modeled the belt layer 8 and the bead core model part 15 which modeled the bead core 6 are included. Each model part is composed of a set of elements e having nodes. As the element e, various elements such as a 3 to 4 node element having an area and a 2 node element (representing a cross section of a shell element) representing a cord material or the like are employed.

  Next, in the present embodiment, the initial tire model 10 is deformed by applying a heat shrink condition, thereby setting a two-dimensional shrink tire model 20 as visualized in FIG. S3). Therefore, the change in the cross-sectional shape due to the heat shrink deformation of the tire after vulcanization is taken into the shrink tire model 20 and reflected in the cross-sectional shape. That is, the contracted tire model 20 is obtained as an approximation of the actual tire cross-sectional shape. As is clear from the comparison between FIG. 4 and FIG. 5, it can be seen that the tread shoulder portion of the contracted tire model 20 is greatly deformed due to the contraction of the carcass cord as compared with the initial tire model 10.

  An example of the step of applying the heat shrink condition to the initial tire model to deform it is shown in FIG. In this embodiment, first, the temperature of each element e of the initial tire model 10 is set to a predetermined vulcanization temperature by the computer device 1 (step S31). In numerical calculation, vulcanization temperatures are defined at the nodes of all elements e. The temperature at the time of vulcanization can be arbitrarily determined based on the vulcanization conditions of the tire to be designed, but is generally 140 to 180 ° C.

  Next, the computer device 1 performs a process of reducing the temperature of each element e (step S32). For example, the temperature change decrement is determined in advance, and the temperature of each element e can be lowered by subtracting this decrement from the vulcanization temperature. This temperature change decrement can also be determined arbitrarily, and the temperature can be lowered by multiplying by a decrement rate or the like instead of decrement.

  Next, the contraction force of each element due to the temperature drop is calculated by the computer device 1 (step S33). This heat shrinkage force is calculated based on the shrinkage rate calculated from the thermal expansion rate. For example, for the rubber elements included in the tread rubber model part 11 and the sidewall rubber model part 12, the isotropic expansion rate is predefined. Therefore, in this deformation step, the rubber element is The volume contracts isotropically without depending on the direction. On the other hand, the fiber material elements constituting the carcass model portion 13 and the belt model portion 14 have a predetermined anisotropic expansion coefficient along the longitudinal direction of the cord. Therefore, in this deformation step, the fiber material element Contracts along the longitudinal direction of the cord.

  Next, the computer device 1 uses the rigidity of each element and the contraction rate of each element to calculate the displacement amount of the node of each element so that they are balanced (step S35). Thereby, each node position of the initial tire model when the temperature decreases due to the temperature change decrement is set, and each coordinate value is stored (step S35).

  Next, the computer apparatus 1 determines whether or not the temperature of each node of the current tire model is normal temperature (step S36). If the result is negative, the temperature of each element is determined from step S32. Repeat until the temperature reaches room temperature. On the other hand, if the result of step S36 is affirmative, the process returns to step S4. 6 can be performed using various kinds of software, for example, analysis application software (“ABAQUS”) or the like.

  Next, deformation calculation is performed on the obtained two-dimensional contracted tire model 20 by applying conditions related to the rim and the internal pressure (step S4). That is, an unloaded state in which an actual tire is incorporated in the rim and filled with air pressure is reproduced by the shrink tire model 20.

  As shown in FIG. 7, the rim-related conditions are such that the rim contact areas B and B of the shrink tire model 20 are restrained so as not to be displaced, and the rim contact area B is deformed to a width W corresponding to the rim size to be mounted. The condition to be set is set. A virtual rotation axis (hereinafter simply referred to as “rotation axis”) CL of the shrink tire model 20 is connected and fixed so that the relative distance r to the rim contact region B is always constant.

  Further, as a condition relating to air pressure, as shown in FIG. 7, for example, an evenly distributed load w corresponding to the maximum air pressure defined by the standard is set over the entire inner surface of the shrinkable tire model 20.

  Then, by performing a balance calculation of the shrink tire model 20 under these conditions, the displacement of each node when the shrink tire model 20 is assembled into the rim and filled with air pressure is calculated.

  Next, in this embodiment, the process which expand | deploys the two-dimensional shrinkable tire model 20 obtained above in three dimensions is performed (step S5). Specifically, each node of the shrink tire model 20 is continuously copied in the tire circumferential direction at a predetermined angular pitch, and adjacent nodes in the tire circumferential direction are connected to each other so that a two-dimensional element is planar or three-dimensional. By re-elementizing (re-meshing), a three-dimensional shrinkage tire model 20 can be obtained.

  For example, the rubber element e1 constituting the tread rubber model unit 11 and the like is remeshed into a three-dimensional solid element. Similarly, the fiber material elements constituting the carcass 7 and the belt layer 8 can be modeled as three-dimensional solid elements or planar elements. In addition, about these fiber material elements, the shell element etc. in which the strength anisotropy along the longitudinal direction of the cord was defined are used.

  In addition, the angle pitch when the two-dimensional shrinkage tire model 20 is developed in three dimensions is not particularly limited. However, if it is too large, the calculation accuracy is lowered when performing deformation calculation described later, and conversely, it is too small. Is also not practical because it takes a lot of time for deformation calculation. From such a viewpoint, the angular pitch is preferably 0.1 degrees or more, more preferably 0.25 degrees or more, and preferably 2 degrees or less, more preferably 1 degree or less.

  As described above, in the creation method of the present embodiment, the three-dimensional initial tire model 10 is not subjected to heat shrink deformation, but the two-dimensional initial tire model 10 is subjected to heat shrink deformation to obtain the shrink tire model 20 first. Thus, the three-dimensional shrinkable tire model 20 is set by simply developing the two-dimensional shrinkable tire model 20 in the tire circumferential direction. Such a method is desirable in that the amount of calculation can be greatly reduced as compared with the case where the three-dimensional initial tire model is subjected to heat shrink deformation, and the three-dimensional shrink tire model 20 can be obtained in a short time. The tread portion 3 of the pneumatic tire 2 is provided with a belt layer 8 of a metal cord, and it has been found as a result of various experiments that a large error does not occur even when contracted as in the present embodiment. is doing.

  Next, in this embodiment, a load is applied to the three-dimensional shrinkable tire model 20 obtained above, and the ground contact shape is calculated (step S6). In the calculation of the ground contact shape, the conditions set include a vertical load to be applied, a condition regarding a road surface, and the like.

  Further, as a condition regarding the vertical load, as shown in FIG. 7, a value of a load F that pushes down the rotation axis CL of the shrink tire model 20 vertically downward is set. Although the value of this vertical load can be determined arbitrarily, for example, the standard maximum load of the tire 2 which is the basis of the shrink tire model 20 is used. In addition, as conditions regarding the road surface, those according to the actual road surface condition to be known, such as a flat surface, an uneven surface, and a soft road surface, are set.

  When the above conditions are set, deformation calculation of the shrink tire model 20 is started. In the present embodiment, the contracted tire model 20 is statically grounded on the road surface, and the grounding shape (node displacement) is calculated. In the present embodiment, the road surface is not displaced, and a predetermined friction coefficient is given to the contracted tire model 20. The calculation of the ground contact shape is performed using, for example, general-purpose finite element analysis application software (for example, application software “LS-DYNA” manufactured by Livermore Software Technology (LSTC), USA).

  FIG. 8A shows a ground contact shape obtained from the shrink tire model 20 as an example. For comparison, FIG. 8B shows a ground contact shape of the initial tire model 10 (before heat shrinkage) under the same conditions as a conventional example.

  Comparing FIGS. 8A and 8B, the contact shape of the example is substantially the same in the tire circumferential direction length and the tire axial direction length, and has a smooth contact contour shape excellent in wear resistance. It has become. On the other hand, the contact shape of the conventional example has an angry shoulder at the tread shoulder portion compared to the contracted tire model 20, and therefore, in the contact shape, the tire axial direction length is larger than the tire circumferential direction length and is angular. Contour shape. Such a difference in the ground contact shape is caused by a change in the tire cross-sectional shape after heat shrinkage. It has been confirmed by other experiments that the example is closer to the tire of the mold / structure design. Therefore, according to the present invention, designers can further evaluate and develop the performance of various tires based on an accurate ground contact shape.

  Next, in this embodiment, it is determined whether or not the contact shape obtained from the shrink tire model 20 has achieved the development goal (step S7). This determination can be made by the computer device 1 or an operator (human). If it is determined that the target has not been achieved (N in Step S7), Step S1 and subsequent steps are repeated again. That is, in the mold / structure design step S1, for example, at least 1 such as the profile shape of the carcass 7, the width or rigidity of the belt layer, the radius of curvature of the tread surface, the profile shape of the ground contact, the elastic modulus of the cord material or rubber material, etc. The above changes.

  On the other hand, if it is determined that the grounding shape has been achieved (Y in step S7), the process is terminated, and the product is obtained using the dimensions, material characteristics, tread pattern, etc. of each part obtained by the mold / structural design, for example. Tire design is done quickly.

  The present invention can be suitably used in a tire simulation method when designing or developing a tire.

DESCRIPTION OF SYMBOLS 1 Computer apparatus 2 Pneumatic tire 10 Initial tire model 20 Shrink tire model e Element e1 Rubber element e2 Textile element

Claims (4)

A method for creating a tire model for evaluating the performance of a tire vulcanized by a mold by numerical calculation using a computer,
Determining a tire cross-sectional shape in the mold;
A step of creating an initial tire model based on the cross-sectional shape; and a deformation step of obtaining a contracted tire model by applying a thermal contraction condition to the initial tire model with a temperature decrease from a vulcanization temperature to a normal temperature. A method for creating a tire model, comprising: The initial tire model includes a rubber element that models rubber,
The tire model creating method according to claim 1, wherein in the deforming step, the volume of the rubber element isotropically contracts. The initial tire model includes a fiber material element that models a fiber cord;
The tire model creation method according to claim 1 or 2, wherein in the deformation step, the fiber element shrinks along a longitudinal direction of a fiber cord.   4. A tire simulation method, wherein a predetermined condition is applied to a contracted tire model obtained by the production method according to claim 1 to deform the tire model to obtain at least one physical quantity.

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