JP2002022620A - Method for simulating performance of tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simulate the performance of a tire with high accuracy. SOLUTION: A tire to be evaluated is approximated by a finite element model divided into a large number of finite elements and the performance of the tire is simulated from the finite element model using a finite element method. The method for simulating the performance of a tire includes an imaginary rim arrangement for restricting the rim contact region of the finite element model and forcibly displacing the distance at the bead part of the finite element model in the axial direction of tire to the rim width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire performance simulation method and apparatus capable of 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.

An object of the present invention is to provide a tire performance simulation method capable of simulating highly accurate tire performance applicable to actual development.

[0006]

According to the first aspect of the present invention, a tire to be evaluated is approximated by a tire finite element model obtained by dividing a tire into a finite number of elements, and the tire is evaluated using a finite element method. A tire performance simulation method for simulating tire performance from the tire finite element model, wherein a rim contact area of the tire finite element model is restricted and a tire axial distance of a bead portion of the tire finite element model is forced to a rim width. It is characterized by including a virtual rim assembling process for displacing.

According to a second aspect of the present invention, the tire finite element model is connected and fixed so that the rotation axis of the tire finite element model is always constant relative to the rim restraint area. It is a simulation method of the described tire performance.

[0008]

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, which are arranged in parallel 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.
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 that is largely bent when the tire rolls, and protects the side portion of the tire T even when it comes into contact with the curb on the road surface. For example, the sidewall rubber 21 has a more complex elasticity than the tread rubber 20. 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 intersecting 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 embodiment, a display capable of displaying input results and simulation results, Output means 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 the processing procedure of the simulation as shown in FIG. 7 in advance 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 portion 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, quadrilateral elements, and three-dimensional elements are preferably computer-usable elements such as tetrahedral solid elements, pentahedral solid elements, and hexahedral solid elements. 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 as follows.
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 portion 1B are subjected to a process of modeling with, for example, 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 with a single plane shoulder element as in the conventional case, but is made in accordance with 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, by modeling the pattern element model 4 separately from the tire body part element model 3, it is possible to elementize (mesh) in more detail than the tire body part element model 3, for example, 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, grounded on a virtual road surface 7, and made to contact or relatively move with the virtual road surface under predetermined running conditions.

The above "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. Therefore, the actual rim assembly state can be easily and accurately reproduced on a simulation.

The predetermined running conditions in the running simulation process 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, a 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 analyzing the cornering characteristics and the like, 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 that the slip angle α is obtained and the two are 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 the present embodiment, information acquisition processing 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 including the tread portion base rubber 20a in the tread pattern portion.

[0041]

[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, a cornering simulation was performed by setting the slip angle α to 0, 1, 2, and 4 deg. The result is shown in FIG.

As is apparent from FIG. 10, the cornering force is 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-state 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 analyzing the stress distribution at the center of the ground 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.

[0047]

As described above, according to the first and second aspects of the present invention, in the tire performance simulation method, the rim contact area of the tire finite element model is restricted and the tire shaft of the bead portion of the tire finite element model is provided. By including virtual rim assembling processing that forcibly displaces the directional distance to the rim width, the rim assembling state can be easily and accurately reproduced in simulation, and accurate tire performance that can be applied to actual development can be simulated. Help.

[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

Claims (2)

[Claims] 1. A tire performance simulation method for approximating a tire to be evaluated by a tire finite element model obtained by dividing the tire into a finite number of elements, and simulating the tire performance from the tire finite element model using a finite element method. And a virtual rim assembly process for constraining a rim contact area of the tire finite element model and forcibly displacing a tire axial direction distance of a bead portion of the tire finite element model to a rim width. Simulation method. 2. The tire performance simulation method according to claim 1, wherein the tire finite element model is connected and fixed so that the rotation axis of the tire finite element model is always constant relative to the rim restraint area. .