JP3314082B2 - How to create a tire finite element model - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely simulate the performance of a tire. SOLUTION: This method for preparing a tire finite element model for preparing a tire finite element model obtained by dividing a tire to be evaluated into a finite large number of elements includes: processing for dividing a tire body part, where a code reinforcing material including the carcass and a belt, a rubber part including side wall rubber and bead rubber and a bead core are formed continuously in the peripheral direction of the tire and in the state of the same cross section on the basis of a finite element method to set a tire body element model; processing for setting a tread pattern part element model obtained by dividing the tread pattern of the tire into the infinitely large number of elements through the whole periphery of the peripheral direction of the tire; and processing for connecting the tread pattern part element model to the tire body part element model.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for creating a tire finite element model which is useful for accurately simulating tire performance.

[0002]

2. Description of the Related Art
The development of tires was an iterative process of creating prototypes, testing them, and producing further prototypes based on the results of the experiments. This method requires a lot of cost and time for prototype production and experimentation, and thus limits the improvement of development efficiency. In order to overcome such a problem, a method of predicting and analyzing a certain level of performance without prototyping a tire by computer simulation using an approximate analysis method or the like has recently been proposed.

[0003] Various analysis methods are used in computer simulation. For example, a method using a finite element method is well known. Finite Element Metho
d) is a method in which a structure is divided into a large number of areas of finite size called finite elements, and each finite element is given relatively simple characteristics to analyze the entire system.

The conventional analysis of tire performance by the finite element method is a load analysis in a non-rolling state of a tire,
As for the tread pattern, there are many so-called plain treads without grooves, and there is no known tread pattern in which all tread patterns of a tire are modeled as finite elements. In addition, inside the tire, there is provided a reinforcing layer or the like in which cord materials such as a carcass and a belt are stacked at different angles.
Most of these analyzes were simplified models using a single plane shell element.

[0005] For this reason, in the conventional simulation, the behavior of the tire can be roughly predicted and analyzed, but the influence of the tread pattern applied to the product cannot be analyzed.

In the present invention, the finite element model of the tire to be evaluated is based on the fact that a tread pattern element model set separately from the tire body element model is connected to the tire tread pattern. It is an object of the present invention to provide a method for creating a tire finite element model that can be used to accurately simulate tire performance that can be applied to the actual development of the tire.

[0007]

According to a first aspect of the present invention, there is provided a tire finite element model creating method for creating a tire finite element model in which a tire to be evaluated is divided into a finite number of elements. A tire body part in which a cord reinforcing material including a carcass and a belt, a rubber part including a side wall rubber and a bead rubber, and a bead core are continuous with the same cross-sectional shape in a tire circumferential direction, including a rotation axis thereof.
Processing to develop a two-dimensional shape of the meridional section in the circumferential direction and divide the elements to set a tire body part element model;
A vertical groove extending in the direction and a horizontal groove extending in the direction crossing this vertical groove
The tread pattern of the tire having the tire
A process of setting a tread pattern part element model divided into a finite number of elements over the entire circumference in the tire circumferential direction in more detail than the body part element model, and the tread pattern part element model in the tire body part element model And a combining process.

According to a second aspect of the present invention, in the tread pattern portion element model, an inner surface or a node thereof has
The tire finite element model creation method according to claim 1, wherein the tire body part element model is joined by being defined so as to be forcibly displaced so that its relative position does not change with respect to a surface or a node of the tire body element model. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, an example is shown that simulates the performance of a radial tire T for a passenger car (hereinafter, may be simply referred to as a tire) T as shown in FIG. The tire T has a carcass 16 composed of a ply 16a having a cord folded from the tread portion 12 through the sidewall portion 13 around the bead core 15 of the bead portion 14 and having a cord inclined at substantially 90 degrees with respect to the tire circumferential direction. And a belt layer 17 disposed outside the tire radial direction and inside the tread portion 12.

In the present embodiment, the belt layer 17 is formed by laminating two inner and outer belt plies 17A and 17B in a direction in which the cords intersect at an angle of 20 degrees with respect to the tire circumferential direction. You. In this example, the belt layer 1
7, a band layer 19 in which nylon cords are arranged substantially parallel to the tire circumferential direction is provided on the outer side in the tire radial direction to prevent lifting of the belt layer 17 during high-speed running. The band layer 19 includes, for example, an edge band covering both end portions of the belt layer 17 and a full band covering almost the entire width of the belt layer 17.

The carcass 16 is made of, for example, an organic fiber cord such as polyester, and a belt ply 17.
A and 17B are each configured by covering a steel cord with a sheet-like topping rubber. The cord reinforcing material F includes the carcass 16 and the belt layer 1.
7. In addition to the band layer 19, a bead reinforcing filler for reinforcing the rigidity of the bead portion 14 and the like can be included as necessary.

The tire T has a tread rubber 20, a sidewall rubber 21,
A bead rubber 22 is provided. The tread rubber 20
In the present example, the tread base rubber 20a is disposed radially outside the belt layer 17 and extends substantially along the surface of the tread portion 12 through the groove bottom line of the longitudinal groove G1 in the meridional section of the tire. A two-layer structure constituted by a tread portion cap rubber 20b which is arranged and transmits various forces in contact with a road surface is illustrated.

The sidewall rubber 21 is a portion which is largely bent when the tire rolls, and protects the side portion of the tire T even when it comes into contact with a curb on a road surface. It is preferable to use a flexible rubber having a low rate. The bead rubber 22
Is disposed in the vicinity of the fitting portion in contact with the rim flange, and may be made of, for example, rubber having a relatively large elastic modulus and excellent wear resistance.

On the outer surface of the tread portion 12, a predetermined tread pattern is formed by, for example, a vertical groove G1 extending in the tire circumferential direction and a horizontal groove G2 extending in a direction crossing the vertical groove G1. This tread pattern greatly affects tire performance, and the simulation method of the present invention makes it possible to analyze the influence of this tread pattern on tire performance, as described later.

In the simulation method or apparatus of the present embodiment, such a tire T to be evaluated is divided into a finite number of elements 2a, 2b, 2c... As shown in FIG. Approximately, a tire performance is simulated from the tire finite element model 2 using a finite element method.

As shown in FIG. 6, for example, the present simulation apparatus includes a CPU as an arithmetic processing unit and a CPU.
And a RAM which is a working memory capable of temporarily storing images or numerical values.
, Input / output ports, and a data bus connecting them.

The input / output ports include input means I such as a keyboard and a mouse for inputting numerical values for setting a tire finite element model in this example, a display capable of displaying input results and simulation results, An output unit O such as a printer and an external storage device D such as a hard disk and a magneto-optical disk are connected.

The ROM stores in advance the processing procedures of the simulation as shown in FIG. 7 and will be described below. The tire finite element model 2 in which the simulation is performed includes a tire body part element model 3 and a tread pattern part element model 4.

As shown in FIGS. 1 and 2, the tire body part element model 3 is obtained by dividing the tire body part 1B based on the finite element method. The tire body portion 1B is a portion of the tire to be evaluated that is substantially the same material and has the same cross-sectional shape in the circumferential direction. In this example, the tread rubber 2
No tread portion cap rubber 20b is removed.

Specifically, the tire body 1B includes a carcass 16, a belt layer 17, and a band layer 19 of the tire.
, A rubber portion including a tread base rubber 20 a, a sidewall rubber 21, and a bead rubber 22 of the tread rubber 20, and a bead core 15.

In the simulation method of this embodiment, the tire body 1B is divided into a finite number of elements based on the finite element method. An element based on the finite element method is, for example, 2
In the three-dimensional plane, it is desirable that the three-dimensional elements be computer-usable elements such as tetrahedral solid elements, pentahedral solid elements, and hexahedral solid elements, and these elements are three-dimensional coordinates XY- It can be specified one by one using Z.

For example, an arbitrary minute area of the belt layer 17 as the cord reinforcing material F is set in the cord reinforcing element model 5 as shown in FIG. In this example, the cord material c of the cord reinforcing material F is modeled by quadrangular membrane elements 5a and 5b, and the topping rubber t is modeled by hexahedral solid elements 5c, 5d and 5e. ing.

The material definition of the tetrahedral membrane element 5a, which models the cord material c, is such that its thickness is, for example, the cord material c.
In the illustrated example, the material is treated as an orthotropic material having different stiffness in the arrangement direction of the cord material c and the direction orthogonal thereto, and the rigidity in each direction is treated as being homogenized. The hexahedral solid elements 5c to 5e representing the topping rubber t of the cord reinforcing material F can be defined and handled as a super viscoelastic material like other rubber members.

The tread base rubber portion 10a, the sidewall rubber 21, the bead rubber 22, and the bead core 14 of the tire body 1B are subjected to, for example, a process of modeling with a hexahedral solid element or a pentahedral solid element. Such modeling can be performed using the input means I. In addition, tire body part element model 3
Can relatively easily perform modeling by specifying a two-dimensional shape of a meridional section including a rotation axis of a tire and dividing the two-dimensional shape into elements that are developed in a circumferential direction.

As described above, in the present embodiment, the cord reinforcing material F is not modeled by a single plane shoulder element as in the conventional case, but is made to correspond to the characteristics of the material, such as the cord material c and the topping rubber t. By modeling
It is possible to simulate tire performance closer to an actual product. Further, when modeling each of the rubber parts 20 to 22, the cord reinforcing material F, and the bead core 14 as finite elements, the material and rigidity can be defined based on the complex elastic modulus of each rubber, cord, bead core, and the like. .

Next, the tread pattern part element model 4 is obtained by a process of setting a tread pattern element part obtained by dividing the tread pattern of the tire into a finite number of elements over the entire circumference in the tire circumferential direction. In this example, the pattern element model 4 is a model of the tread cap rubber 20b of the tread rubber. After being set separately from the tire body element model 3, the pattern element model 4 It illustrates what is combined.

In this embodiment, the pattern element model 4
Is the tread cap rubber 2 arranged in the tire circumferential direction.
0b is divided by a finite number of tetrahedral elements 4a, 4b,... And is formed over the entire circumference of the tire.
In this way, the pattern element model 4 is modeled separately from the tire body part element model 3 to form a more detailed element (mesh formation) than the tire body part element model 3 as in this example . This is preferable because the influence of the tread pattern can be analyzed in more detail. In addition, for various tires having the same internal structure and different tread patterns, only the tread pattern element model 4 is set, and the tire body element model 3 can be used in common. There is an advantage that can be improved.

In the present embodiment, the tire finite element model 2 is completed by performing processing for connecting the tread pattern part element model 4 to the tire body part element model 3. As shown in FIG. 5, the inner surface or node of the tread pattern element model 4 is defined so as to be forcibly displaced with respect to the surface or node of the tire body element model 3 so that its relative position does not change. Joined.

Next, a running simulation process in which the tire finite element model 2 is mounted on a virtual rim and is brought into contact with the virtual road surface 7 to make contact with or relative to the virtual road surface under predetermined running conditions.

The "mounting the tire finite element model 2 on the virtual rim" means, as shown in FIG. 8, that the rim contact area of the tire finite element model 2 is restricted and the bead portion of the model 2 is in the tire axial direction. This means that the distance W is forcibly displaced to the rim width. The rotation axis CL of the tire finite element model 2 is connected and fixed so that the relative distance r from the rim constraint area of the tire finite element model 2 is always constant, as shown in FIG. The virtual road surface 7 is modeled as a flat quadrilateral rigid surface.

The predetermined running conditions in the running simulation processing include, for example, the internal pressure, the axial load, the slip angle α, the camber angle of the tire finite element model 2, the friction information between the tire finite element model 2 and the virtual road surface 7. Including. The internal pressure can be set by applying an evenly distributed load corresponding to the tire internal pressure to the inner surface of the tire finite element model 2.

The "slip angle α" refers to the angle between the traveling direction of the road surface and the center line in the circumferential direction of the tire, as shown in FIG. In general, the tire in such a rolling state (during cornering) moves laterally while keeping the contact surface with the road surface over time as shown in FIG. As described above, the surface of the tread portion is pushed laterally by the road surface, and the tread portion undergoes shear deformation, thereby generating a cornering force which is a force in a direction perpendicular to the traveling direction. The camber angle is
It refers to the angle between the road surface when viewed from the front in the traveling direction and the center line in the tire circumferential direction.

When running simulation of the tire finite element model 2 is performed, for example, the bead portion of the tire finite element model is restrained and an internal pressure is applied.
The tire finite element model 2 is brought into contact with the virtual road surface 7 by pressing the virtual road surface 7 against the tire finite element model 2 or pressing the rotation axis CL of the tire finite element model 2 against the virtual road surface 7 as shown in FIG. Set various conditions such as load according to the actual use conditions.

For example, when the cornering characteristics are analyzed, the tire finite element model 2 is brought into contact with the virtual road surface 7 as described above, and the tire finite element model 2 is turned so as to have a slip angle α and relatively moved. Is simulated. At this time, the tire finite element model 2 can be rolled by the frictional force due to the movement of the virtual road surface 7 when, for example, the rotating shaft is freely supported.

When simulating a cornering force or the like, it is preferable that the tire finite element model rolls a half turn or more with respect to the virtual road surface 7 because accurate information can be analyzed. This is because the cornering force of the tire changes over time and a certain amount of rolling of the tire is required to reach a steady state.

Next, in the simulation of this example, an information acquisition process for acquiring predetermined information from the tire finite element model 2 during the running simulation is performed. In this processing, for example, information including the cornering force, the shape of the ground contact surface, or the internal stress distribution can be obtained from the tire finite element model 2 as numerical information or image information such as animation.

This simulation is performed by the finite element method. In general, a procedure for giving various boundary conditions to a finite element model and acquiring information such as force and displacement of the entire system can be performed according to a well-known example. The algorithm of the calculation in this example is an explicit method. For example, based on the shape of the element, material properties of the element, for example, density, Young's modulus, damping coefficient, etc., the element's mass matrix M, rigidity matrix K, damping matrix C
Create

The matrices of the entire system to be simulated are created by combining the above matrices. Also, by appropriately applying the boundary conditions, the following equation of motion is created.

(Equation 1)

A simulation can be performed by sequentially calculating the equation (1) every minute time t by the CPU.
It is preferable that the minute time t in the successive calculation is a time that is 0.9 times or less the minimum time of calculating the transmission time of the stress wave for all elements.

Tires are required to have many performances such as cornering force, braking performance, noise performance, abrasion performance, and rolling resistance performance. In particular, in order to analyze these tire performances, a simulation of rolling the tires is required. Becomes In this simulation, the rolling simulation can be performed because the tire body part element model 2 and the tread pattern part element model 3 are both continuous in the circumferential direction. If the cornering performance, the wear performance, and the damping effect are taken into consideration, the vibration may be reduced. Prediction and analysis of hydroplaning performance are possible by coupling with performance and fluid.

Although the present invention has been described in detail, the present invention is not limited to the above embodiment.
Can be deformed in various modes, such as up to the belt layer and including the tread base rubber 20a in the tread pattern portion.

[0042]

[Example] The tires simulated this time were 2
35 / 45ZR17LMG02 (manufactured by Sumitomo Rubber Industries, Ltd.), showing the cornering force, the tread surface during cornering, and the internal stress distribution. The finite element model of this tire is the same as that shown in FIG.
3896 and the number of elements is 76359.

The virtual road surface was modeled as a flat rigid surface. After restraining the bead part of the tire finite element model and applying the tire internal pressure load, the virtual road surface is pressed against the tire model to apply the load, and the road surface is moved so as to have a slip angle with respect to the tire, and the simulation is performed. went. The tire finite element model has a free rotation axis and rolls due to frictional force due to the movement of the road surface. The coefficient of friction between the tire and the road surface was set to 1.0 together with static friction.
The traveling speed of the road surface was 20 km / h.

In this simulation, cornering simulations were performed with the slip angles α set to 0, 1, 2, and 4 deg. The result is shown in FIG.

As is apparent from FIG. 10, the cornering force can be obtained almost stably about 0.15 seconds after the road surface is moved with the slip angle. This is less than about a half turn when converted to the number of rotations of the tire. Therefore, in order to simulate the cornering force, it is necessary to roll the tire at least to this extent, and it has been found that it is preferable to provide a tread pattern all around the tire for that purpose.

The cornering force obtained by this simulation almost coincides with the steady cornering force (experiment) actually measured using a drum tester, and the accuracy of this simulation was confirmed. In this simulation, a slight cornering force was generated at a slip angle of 0 deg. This is mainly because a belt layer was bias-laminated and the plysteer phenomenon caused by the coupling effect appeared. be able to. The simulation up to such a plysteer phenomenon is faithfully represented in the present simulation, indicating a high accuracy.

Next, FIG. 12 shows the result of analysis of the stress distribution at the center of contact at cornering at a slip angle of 4 deg.
Shown in From this, it was found that a large tensile stress (dot portion) was generated on the tire side surface inside the cornering. FIG. 11 shows the contact pressure distribution of the tread at this time.
Shown in From this, it can be seen that the deformation in the block at the center of the tire behind the tread portion is large and the contact pressure is high (dot portion). In the meantime, the contact pressure distribution during the rolling of the tire using the actual vehicle cannot be measured experimentally, but this simulation can know this.
By collecting such data, it is possible to analyze in detail what kind of force acts on which part of the tread pattern of the tire, and it is possible to efficiently design the tire pattern, which is very useful. . This simulation was conducted using a supercomputer for approximately 40 hours of CP.
U calculation time was required.

[0048]

As described above, in the present invention, the tread pattern element model in which the tread pattern is finite over the entire circumference is provided in the tire body element model having the same cross-section in the tire circumferential direction. By performing the running simulation using the tire finite element model, it is possible to simulate the tire performance with high accuracy, including the influence of the tread pattern, and to help improve the development efficiency. The tire body element model is
Expand the two-dimensional shape of the meridional section including the rotation axis in the circumferential direction
Modeling is relatively easy by dividing elements into shapes
It can be performed.

The tread pattern element model is
Modeled separately from the tire body element model ,
Also, since the pattern element model is elementized (meshed) in more detail than the tire body part element model, it is preferable in that the influence of the tread pattern can be analyzed in more detail. Furthermore, for various tires with the same internal structure and different tread patterns, only the tread pattern element model is set, and for the tire body element model, this can be shared, further improving development efficiency. There are advantages.

Further, as in the second aspect of the present invention, in the tread pattern part element model, the relative position of the inner surface or the node with respect to the surface or the node of the tire body part element model does not change. The tread pattern part element model and the tire body part element model can be integrated with high precision by defining and joining them so as to be forcibly displaced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a tire finite element model of the present invention.

FIG. 2 is a perspective view of a tire body part element model.

FIG. 3 is a conceptual diagram showing element modeling of a cord reinforcing material.

FIG. 4 is a perspective view of a tread pattern part element model.

FIG. 5 is a diagram illustrating a modification of the tire finite element model.

FIG. 6 is a block diagram showing an embodiment of a simulation device of the present example.

FIG. 7 is a flowchart illustrating a processing procedure according to the embodiment;

FIG. 8 is a conceptual diagram of a cross section in which a tire finite element model is grounded on a virtual road surface.

FIG. 9 is a conceptual diagram of a plane in which a tire finite element model is grounded on a virtual road surface.

FIG. 10 is a graph showing a simulation result of a cornering force.

FIG. 11 is a diagram showing a tread surface of a tire finite element model during cornering.

FIG. 12 is a diagram showing a cross section of a tire finite element model during cornering.

FIG. 13 is a sectional view of a tire.

FIG. 14 is a diagram illustrating a cornering force.

[Explanation of symbols]

 T tire 2 tire finite element model 3 tire body part element model 4 tread pattern part element model 5 cord reinforcement element model 7 virtual road surface

Continuation of the front page (56) References JP-A-9-91469 (JP, A) A Kamoulakos et al. , Transient Response of a Rotating Tire undermultiple Imapacts with a Load Bump Using PA M-SHOCK, Proceedings of 1996 P.A. G. FIG. Kao et al. , Tire Transient Analysis with an Exciting Finite Element Program, Tire Science and Technology, The United States, The Tire Society, vol. 25, no. 4, October-December 1997, p230-244. Gall et al. , Some Nctcs on the Finite Element Analysis of Tires, Tire Science and Technology, USA, The Tire Society, vol. 23, no. 3, Julv-Septmber 1995, p 175-188. Meschke et al. , 3D Simulations of Automobile Tires: Material Modeling, Mesh Generation and Solution Strategies, Tire Science and Technology, United States. 25, no. 3, July-September 1997, pp. 154-176 Toyo Tire & Rubber also announced “Tire Optimization Design Technology” DSOC II, Monthly Tire, Japan, Monthly Tire Company, July 1, 1995, July 1995 Monthly Issue, p54-65 Latest Tire Technology TOYO Integrated Optimization Tire Design Technology "DSOC II", MOTOR FAN, Japan, Sanei Shobo, August 1, 1995, August 1995, no. 644, p195-199 (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 17/50 612

Claims (2)

(57) [Claims] 1. A tire finite element model creating method for creating a tire finite element model in which a tire to be evaluated is divided into a finite number of elements, comprising: a cord reinforcing material including a carcass and a belt; The tire body portion in which the rubber portion including the bead rubber and the bead core are continuous with the same cross-sectional shape in the tire circumferential direction, and the two-dimensional meridional cross-section including the rotation axis thereof is formed in the circumferential direction.
Expand and divide the element to set the tire body part element model, and adjust the vertical groove extending in the tire circumferential direction and the direction
Tread pattern of the tire having a lateral groove
A process of setting a tread pattern part element model divided into a finite number of elements over the entire circumference in the tire circumferential direction in more detail than the tire body part element model; and the tread pattern part element in the tire body part element model A method of creating a tire finite element model, the method including: combining models. 2. The tread pattern part element model has an inner surface or a node whose relative position does not change with respect to a surface or a node of the tire body part element model .
2. The method for creating a tire finite element model according to claim 1, wherein the tire finite element model is defined and joined.