JP2006072896A - Tire model generation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire model generation method for efficiently analyzing the influence of a side wall part on a tire characteristic. <P>SOLUTION: The tire model generation method for analyzing the tire characteristic with the use of a simulation includes a step for generating a tire body element model which reproduces a tire body comprising a cord reinforcing material, a step for generating a rubber element model which reproduces a rubber comprising at least a side wall, and a step for coupling the tire body element with the rubber element model. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for creating an analysis model when evaluating tire characteristics by computer simulation such as a finite element method.

Various methods for predicting tire characteristics using computer simulation such as a finite element method and designing tires based on the tire characteristics have been proposed. In the simulation using the finite element method, a finite element model of the tire is created using a computer, and the stationary state or rolling state of the tire is simulated using the created tire model. The tire characteristics are evaluated by calculating the value.
By using the tire characteristics, it is possible to design a tire having excellent tire characteristics without actually manufacturing the tire, and to improve the development efficiency of the tire.

  As a method of creating a tire model used for such tire simulation, the tire body part element model is set by dividing the two-dimensional shape of the tire body part in the circumferential direction and dividing it into meshes, and more detailed than the tire body part element model A tread part element model with a tread pattern divided into meshes is set, and a tread part element model is combined with a tire body part element model to create a tire finite element model (for example, Patent Documents) 1).

By the way, tire characteristics such as steering stability, riding comfort, friction wear characteristics, etc. are greatly influenced not only by the tread part but also by the rigidity of the sidewall part, and it is efficient to grasp these influences through simulation analysis in advance. Is essential to a successful design.
Japanese Patent No. 3314082

However, as described above, conventionally, in the tire model with a tread pattern, the tire body portion and the tread portion are separately modeled and coupled to each other. Therefore, when analyzing the influence of the sidewall portion, the tire body portion has to be remodeled.
Further, since the side wall portion has a large strain at the time of ground deformation, the elements must be divided in detail. However, in the conventional modeling, since the side portion is adjacent to a highly rigid cord reinforcing layer such as a carcass layer or a belt layer, there is a problem that only the side cannot be divided into elements in detail.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a tire model creation method capable of efficiently analyzing the influence of sidewall portions on tire characteristics.

  In order to solve the above-mentioned problems, the present invention provides a tire model creation method for analyzing tire characteristics by simulation, and a tire body part for creating a tire body part element model that reproduces a tire body part including a cord reinforcing material An element model creating step; a rubber part element model creating step for creating a rubber part element model that reproduces at least a rubber part including a sidewall part; and a step of combining the tire body part element model and the rubber part element model. The present invention provides a tire model creation method characterized by including the tire model.

The rubber part element model is a finite element model that reproduces a rubber part including a sidewall part and a tread part with a tread pattern, and the rubber part element model creation step includes a sidewall part element model that reproduces the sidewall part. It is preferable to create the rubber part element model by combining the tread part element model reproducing the tread part with the tread pattern.
The tire body part element model is a finite element model that reproduces the tire body part including the carcass and the belt, and the tire body part element model creation step includes the carcass part element model that reproduces the carcass and the belt part that reproduces the belt. Preferably, the tire body part element model is created by individually creating and combining element models.
Furthermore, it is preferable that the rubber part element model is a model in which mesh division is performed in more detail than the tire body part element model.

  The step of combining the element models described above is preferably combined in such a way that the relative positions of the element models do not change at the boundary surfaces of the element models to be combined.

In the tire body part element model creation step, the time increment for each constituent element is calculated by the following formula (1), and the element of the member not including the element with the smallest time increment or the smallest time increment is calculated. It is good to divide elements other than elements. Furthermore, when dividing an element other than the element with the smallest time increment, the dimension of the element can be set to be approximately equal to the time increment of the element with the smallest time increment. In this way, it is possible to divide the elements in detail without reducing the time increment more than necessary at the site where the elements should be divided more finely.
Δt ≦ L / √ (E / ρ) (1)
(Δt: time increment, L: representative element size, E: elastic modulus, ρ: density)

The present invention creates a tire body part element model that reproduces a tire body part including a cord reinforcing material, and creates a rubber part element model that reproduces a rubber part including a sidewall part. Then, a tire model is created by combining the tire body element model and the rubber element model.
Therefore, according to the present invention, the influence of the sidewall portion on the tire characteristics can be efficiently analyzed.

Hereinafter, a tire model creation method of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.
FIG. 1 is a schematic diagram showing an outline of a simulation apparatus that executes a tire model creation method of the present invention, simulates an actual tire characteristic test, and executes an analysis of tire characteristics.

The simulation apparatus 1 executes various arithmetic processes and centrally controls each part, and functions as a work area of the CPU 2, processing programs executed by the CPU 2, and the CPU 2. A memory 3 for storing processing results of the processing program to be executed, various data, and the like is provided, and the CPU 2 and the memory 3 are connected via a bus.
As the memory 3, a DRAM (Dynamic Random Access Memory) that stores information by storing electricity in a capacitor, a SRAM (Static Random Access Memory) that uses a logic circuit without using a capacitor, a CPU, There is a semiconductor storage device such as a nonvolatile read-only ROM (Read Only Memory) that stores an execution program or the like.

The simulation apparatus 1 is connected to an input device 5, an output device 6, and an external storage device 7 via the I / O interface 4, and exchanges data with them.
The input device 5 inputs various conditions such as model creation conditions, processing conditions, or characteristic calculation conditions, and representative examples include a keyboard and a mouse. The output device 6 displays an input result from the input device 5, an analysis result of tire characteristics, and the like, and representative examples include a display and a printer.
Examples of the external storage device 7 include a magnetic disk such as a flexible disk and an optical disk such as a CD and a DVD.

  Such a simulation apparatus 1 creates a tire analysis model (hereinafter referred to as a tire model) by a finite element method (hereinafter referred to as a tire model) according to an operator input, sets simulation conditions, and then simulates a tire characteristic test. By analyzing the tire characteristics.

In the present embodiment, a finite element model (hereinafter referred to as a tire model with a pattern) that reproduces a tire with a tread pattern is created using the tire model creation method of the present invention. FIG. 2 is a perspective view showing an example of a tire model with a tread pattern.
The tire model 10 with a tread pattern is a model of an actual tire and can be used for analysis of tire characteristics using the tire model. This tire model 10 with a tread pattern includes a tire body model 14 that reproduces a tire body part including a cord reinforcing material such as a carcass and a belt, and a thick rubber part model 12 that reproduces a thick rubber part including a sidewall part. The thick rubber part model 12 is mesh-divided in more detail than the tire body part model 14.

  The sidewall portion is a member corresponding to the flank of the tire between the tread portion and the bead, and receives the load of the tire while being bent at the time of ground contact. Therefore, one of the members that are greatly distorted in the ground contact state of the tire is the sidewall portion. This sidewall portion is made of rubber that is flexible and excellent in weather resistance and aging resistance.

  Therefore, in order to analyze the tire characteristics such as steering stability, riding comfort, and frictional wear characteristics that cannot be ignored by the effects of strain at the time of ground deformation, for example, a sidewall portion having a large strain at the time of ground deformation is used. The analysis result is closer to the actual value by using a tire model that is meshed in detail.

  In addition, tire characteristics that can be analyzed in a simulation involving ground contact deformation of a tire using this tire model include cornering characteristics (lateral spring characteristics) when simulating vehicle cornering, and tires by applying a load to the tire. Longitudinal spring characteristics when simulating the degree of deflection (deformation under load), ground contact shape and pressure, and vibration vibration ride characteristics when simulating how to absorb vibration transmitted from the road surface in the rolling state of the tire (Envelope characteristics), slip characteristics (frictional force, slip ratio, etc.) in the contact surface when simulating braking and acceleration conditions, stress characteristics on the carcass when the tire is inflated, and hydroplaning Wet grip performance, snow There is such as snow performance of the tire.

The tire model with a pattern shown in FIG. 2 is created by joining the thick rubber part model 12 and the tire body part model 14 by a joining method described later.
FIG. 3 is a perspective view showing an example of a thick rubber part model, and FIG. 4 is a perspective view showing an example of a tire body part model.

The thick rubber part model 12 is a model reproducing a thick rubber including a tread part and a sidewall part, and is created by integrating the tread part model and the sidewall part model.
As described above, since the sidewall portion is a member that is largely distorted during ground deformation, the analysis accuracy can be improved by dividing the mesh in detail.

In addition, the tread pattern of the tire carved on the tread is related to various tire characteristics such as driving, braking, turning performance, riding comfort, noise, rolling resistance and wear, which are the basic performance of the tire. It is preferable that the part model is also divided into meshes in the same manner as the sidewall part model. In the present embodiment, the tread part model is created together with the sidewall part model, and is divided into meshes in detail.
There is no particular limitation on the method of creating such a thick rubber part model 12.

The mesh size of the tire body part model 14 does not need to be as fine as the thick rubber part in consideration of the time required for calculation processing in the analysis and the influence on the analysis accuracy of the tire characteristics.
Accordingly, the tire body part model 14 only needs to be easily created. Therefore, the tire body part model 14 is created by creating a two-dimensional cross-sectional shape and developing the cross-section in the circumferential direction with the center axis of the tire as the center of rotation. It is preferable to do.
However, the method of creating the tire body part model 14 is not limited to this, and may be created by other methods.

  FIG. 5 is a cross-sectional view for explaining a tire model in the present embodiment. As a method of connecting the thick rubber part model 12 and the tire body part model 14, there are a nodal sharing type and a nodal sharing type.

The joint sharing type joint method is a method in which elements are divided at the boundary surface between the thick rubber part model 12 and the tire body part model 14 so that the respective joint positions are the same, and the same joints are integrated. is there.
On the other hand, the node non-covalent coupling method defines one as a coupling surface and the other as a coupled surface, and the nodes of elements located on the coupled surface are connected to the coupled surface that is the surface to be coupled. In this method, a constraint condition that does not change relatively is applied to the nodes.

The node non-shared type coupling method is such that when the rubber part model 12 is arranged in the region of the tire body part model 14 and there is an intersection where the rubber part model 12 intersects the boundary of the elements of the tire body part model 14, this intersection point The intersection is added as a node in the rubber part model 12 to reconstruct the element.
Next, a constraint condition for restricting the behavior of each node of the rubber model 12 by the behavior of the node of the element of the tire body model 14 including each node is obtained, and the behavior of the rubber model 12 is constrained by this constraint condition. To do.
This constraint condition is determined by defining the shape of the element of the tire body part model 14 including each node of the rubber part model 12 as a shape converted from a predetermined reference shape in the parametric space using a shape function. The position information of the corresponding points in the reference shape of each node of the partial model 12 is obtained and determined using the position information and the shape function (for details, refer to the specification of Japanese Patent Application No. 2004-29195).

In many cases, it is difficult to divide each model into elements so that the nodes on the boundary surface between the thick rubber part model 12 that is divided into elements in detail and the tire body part model 14 that is divided into elements roughly are the same. Processing becomes complicated, and there is a risk that a lot of time may be spent on creating the tire model.
Therefore, in the present invention, the thick rubber part model 12 and the tire body part model 14 are joined by a joint method that does not share the nodes. By doing so, each model can be divided into elements relatively easily without matching each node at the same position on the boundary surface when dividing each model into elements.
Note that, not only when the thick rubber part model 12 and the tire body part model 14 are coupled, but also when a finite element model is coupled, the jointing method is performed using a no-node sharing method.

When the tire body part model 14 is created, the time increment for each constituent element is calculated by the following formula (1), and the element of the member not including the element with the smallest time increment or the smallest time increment is calculated. Divide elements other than the element.
Δt ≦ L / √ (E / ρ) (1)
Where Δt is the time increment, L is the representative length of the element, E is the stiffness of the element, and ρ is the material density.
Alternatively, when creating the tire body part model, the time increment for each constituent element is calculated by the above formula (1), and the element of the member not including the element with the smallest time increment, or the most time increment is Elements other than the smaller elements may be divided by representative element dimensions that result in substantially equal time increments. Here, the time increment is substantially equal means that the time increment is within a range of ± 10% with respect to the value calculated by the equation (1).

In the simulation analysis using the explicit method, for example, in the case of a tire, the belt and bead core are more rigid than other members made of rubber material, so in many cases when a tire model is simulated, the belt edge and bead core are reproduced. The time increment is determined based on the elements forming the model.
Therefore, the degree of detail (representative element dimensions, etc.) when the rubber part model 12 is divided into elements in detail is a value smaller than the time increment Δt determined based on the elements forming the model reproducing the highly rigid member. It is a range that does not become.
By doing so, the analysis accuracy can be improved without increasing the time required for the analysis.

In the above-described embodiment, the sidewall portion and the tread portion are reproduced as one piece, and the elements are divided with the same level of detail to create the thick rubber portion model, but the present invention is not limited to this. In other embodiments, a tread part model and a sidewall part model are individually created and combined to create a thick rubber part model.
FIG. 6 is a perspective view showing an example of the tread portion model, and FIG. 7 is a perspective view showing an example of the sidewall portion model. FIG. 8 is a cross-sectional view for explaining a tire model in another embodiment.

As described above, the sidewall portion is a large strain member during contact deformation, so the analysis accuracy can be improved by dividing the mesh in detail, and the tire tread pattern is related to various tire characteristics. Therefore, the tread portion is also divided into meshes in detail.
It is often difficult to divide each other's model so that the nodes on the boundary surface of the finite element model divided into elements with different mesh sizes are the same, making the process complicated and creating a finite element model May spend a lot of time.
Therefore, in the present embodiment, the tread part model 16 and the sidewall part model 18 are joined by a joint method that does not share nodes.

In the present embodiment, a thick rubber part model is created by creating a tread part model and a sidewall part model individually and combining them. Therefore, a plurality of sidewall models that modeled the shapes of multiple molds used in actual tire manufacturing are created in advance, and only the sidewall model is replaced, and tire models with different sidewall models Therefore, the tire model creation time can be shortened.
In addition, the node non-shared type coupling method makes it relatively easy to divide the tread part model 16 and the sidewall part model 18 into elements without dividing each node into the same position on the boundary surface. can do.

  The mesh size (representative element dimensions, etc.) when the tread portion model 16 and the sidewall portion model 18 are divided into elements is determined by the above equation (1) based on the elements that form the model that reproduces the highly rigid member. This is a range that does not become smaller than the time increment Δt.

  According to other embodiments, the side wall part model 18 that increases in strain at the time of ground deformation is created separately from the tread part model 16, so that the mesh size of the side wall part model 18 can be made more detailed, and bending deformation can be achieved. It is possible to improve the accuracy when analyzing the part where the stress gradient is increased by the finite element method.

  In the above-described other embodiments, the thick rubber part model is created by individually creating the tread part model and the sidewall part and combining them, but the present invention is not limited to this. As shown in FIG. 9, not only the tread part model and the sidewall part, but also the filler part model is individually created, and the thick part model can be created by combining them. Further, as shown in FIG. 10, a tire body model may be created by individually creating a belt part model and a carcass part model and combining them.

FIG. 9 shows an example in which rubber part models are individually created according to differences in rigidity and strength and are combined. In FIG. 9, the filler part model 20 is individually created in the same manner as the tread part model and the sidewall part model.
The rigidity around the bead has a great influence on the handling of the vehicle, and the bead filler is made of hard rubber in order to improve the rigidity around the bead.
Therefore, by modeling the bead filler formed of hard rubber as the filler part model 20 and combining it with the tread part model 16 and the sidewall part model 18, the rubber part model can be created more faithfully. Can be reproduced.

  FIG. 10 shows an example in which tire body portions are individually created according to differences in rigidity and strength and are combined. In FIG. 10, a finite element model that reproduces the belt portion, the carcass portion, and the bead portion is individually created.

The belt portion is a steel member provided between the tread portion and the carcass portion. The belt portion further improves the stability at the time of high speed traveling by further improving the rigidity of the tread portion.
In FIG. 10, the belt portion is modeled as a single piece, but depending on the type of tire, there may be two belt pieces or three pieces.

  The carcass portion is a tire skeleton, and is a member that withstands loads, impacts, and filled air pressure to hold the tire structure. The carcass portion is wound up so as to wrap the bead wire, and the rigidity changes according to the length of the winding.

A bead part is a member which tightens a wheel moderately and prevents a tire from shifting. If the strength of the bead portion is insufficient, the shape of the tire changes due to the load of the vehicle and the tire is detached or only the wheel is idle.
The bead portion is greatly related to the roundness of the tire, and is composed of a steel wire.

  Thus, the belt portion, the carcass portion, and the bead portion are members that affect the rigidity of the tire. Therefore, in the tire body portion, the belt portion, the carcass portion, and the bead portion are individually modeled, and the tire portion portion model 22 is created by combining the belt portion model 22, the carcass portion model 24, and the bead portion model 26. The tire body can be reproduced more faithfully.

  As described above, according to the present invention, a tire model capable of efficiently analyzing the influence of the sidewall portion on the tire characteristics can be created in a short period of time. Therefore, simulation of the tire model can be repeatedly performed, and tire development can be performed more quickly through such simulation.

  The tire model creation method according to the present invention has been described in detail above. However, the present invention is not limited to the above embodiment, and various improvements and modifications are made without departing from the gist of the present invention. May be.

It is the schematic which shows the outline of the simulation apparatus for implement | achieving this invention. It is a perspective view which shows an example of a tire model with a pattern. It is a perspective view which shows an example of a thick rubber part model. It is a perspective view which shows an example of a tire body part model. It is sectional drawing for demonstrating the tire model in embodiment of this invention. It is a perspective view which shows an example of a tread part model. It is a perspective view which shows an example of a sidewall part model. It is sectional drawing for demonstrating the tire model in other embodiment. It is sectional drawing for demonstrating the tire model in other embodiment. It is sectional drawing for demonstrating the tire model in other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Simulation apparatus 2 Central processing part 3 Memory 4 I / O interface 5 Input device 6 Output device 7 External storage device 10 Tire model with a tread pattern 12 Thick rubber part model 14 Tire body part model 16 Tread part model 18 Side wall part Model 20 Filler part model 22 Belt part model 24 Carcass part model 26 Bead part model

Claims (7)

A tire model creation method for analyzing tire characteristics by simulation,
A tire body part element model creation step for creating a tire body part element model that reproduces the tire body part including the cord reinforcement,
A rubber part element model creating step for creating a rubber part element model that reproduces a rubber part including at least the sidewall part,
A tire model creating method comprising: combining the tire body part element model and the rubber part element model. The rubber part element model is a finite element model that reproduces a rubber part including a sidewall part and a tread with a tread pattern,
The rubber part element model creating step creates the rubber part element model by combining a sidewall part element model reproducing a sidewall part and a tread part element model reproducing a tread with a tread pattern. The tire model creation method according to 1. The tire body part element model is a finite element model reproducing a tire body part including a carcass and a belt,
The tire body part element model creating step creates the tire body part element model by individually creating and combining a carcass part element model reproducing a carcass and a belt part element model reproducing a belt. The tire model creation method according to 1 or 2.   4. The tire model creation method according to claim 1, wherein the rubber part element model is a model in which mesh division is performed in more detail than the tire body part element model. 5.   The tire model creation method according to any one of claims 1 to 4, wherein the step of combining the element models is performed in such a manner that the relative positions of the element models do not change at the boundary surfaces of the element models to be combined. For the tire model created by the method according to any one of claims 1 to 5, in the tire body part element model creating step, a time increment for each constituent element is calculated by the following formula (1): A tire model creation method including a step of dividing an element of a member that does not include an element with the smallest time increment or an element other than an element with the smallest time increment.
Δt ≦ L / √ (E / ρ) (1)
(Δt: time increment, L: representative element size, E: elastic modulus, ρ: density) For the tire model created by the method according to any one of claims 1 to 5, in the tire body part element model creating step, a time increment for each constituent element is calculated by the following formula (1): A tire model creation method including a step of dividing an element of a member that does not include an element having the smallest time increment or an element other than an element having the smallest time increment by a representative element dimension having substantially the same time increment.
Δt ≦ L / √ (E / ρ) (1)
(Δt: time increment, L: representative element size, E: elastic modulus, ρ: density)

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