JP2021139770A - Method, device, and program for simulating tire - Google Patents

Abstract

To increase accuracy of predicting the performance of a tire on a snowy road.SOLUTION: The present invention relates to a method for simulating a tire which reproduces the behavior of a tire running on a snowy surface. The method includes the steps of: setting a tire model 50 formed by a finite number of elements on which a numerical analysis can be done; setting an Euler element model 54 including a snow model 56 in which a water film 58 is provided on at least a part of a snowy surface as an analysis model containing snow in the inside; and performing a dynamic analysis by rolling the tire model 50 on the snow model 56.SELECTED DRAWING: Figure 3

Description

The present invention relates to a tire simulation method, an apparatus and a program thereof for reproducing the behavior of a tire traveling on a snowy road surface.

By executing load load and rolling analysis on the rigid road surface of the tire, it is possible to predict the tire performance by simulation. Prediction of tire performance by such simulation has been proposed for a road surface covered with snow, that is, a snowy road surface (see Patent Documents 1 to 3).

The condition of the snowy road surface on a general public road is a mixture of snow and water, as can be seen even after the vehicle has traveled. However, in the conventional simulation of the snow road surface, the analysis using such a snow model in which snow and water are combined has not been performed, and it cannot always be said that the snow road surface of a public road is reproduced.

Japanese Unexamined Patent Publication No. 2014-210488 JP-A-2017-126272 Japanese Unexamined Patent Publication No. 2019-040559

For tire performance on snowy roads, for example, traction performance, the behavior of snow at the tire contact point is important, and in order to improve the reproducibility of actual phenomena and improve the prediction accuracy of tire performance, it is more realistic. It is desirable to build a snow model and perform a simulation.

In view of the above points, it is an object of the present invention to provide a tire simulation method, an apparatus and a program thereof, which can improve the prediction accuracy of tire performance on a snowy road surface.

The first aspect according to the present invention is a tire simulation method for reproducing the behavior of a tire traveling on a snowy road surface, in which a step of setting a tire model modeled by a finite number of elements capable of numerical analysis and a step of setting a tire model. As an analysis model in which snow is arranged inside, a step of setting an oiler element model including a snow model in which a water film is provided on at least a part of the snow surface, and a step of rolling the tire model on the snow model to move the tire model. It is a tire simulation method including a step of performing a target analysis.

A second aspect of the present invention is a tire simulation device that reproduces the behavior of a tire traveling on a snowy road surface, and is a tire model setting unit that sets a tire model modeled by a finite number of elements capable of numerical analysis. And, as an analysis model in which snow is arranged inside, an oiler element model setting unit that sets an oiler element model including a snow model in which a water film is provided on at least a part of the snow surface, and a tire model on the snow model. It is a tire simulation device including a dynamic analysis unit that rolls and performs dynamic analysis.

A third aspect of the present invention is a program for reproducing the behavior of a tire traveling on a snowy road surface, and a tire model setting for setting a tire model modeled by a finite number of elements capable of numerical analysis on a computer. An oiler element model setting function that sets an oiler element model including a function and a snow model in which a water film is provided on at least a part of the snow surface as an analysis model in which snow is arranged inside, and the tire model is the snow model. It is a tire simulation program to realize a dynamic analysis function that rolls on and performs dynamic analysis.

The first to third aspects may further include a step of performing a static analysis in which the tire model is brought into contact with the snow model with a predetermined load while the tire model is stationary, a static analysis unit, or a static analysis function. good.

Further, the thickness of the water film provided on the snow surface of the snow model may be set according to the snow quality of the simulated snow road surface. More specifically, the larger the density of snow on the simulated snow road surface, the larger the thickness of the water film may be set.

In addition, it further includes a step of obtaining the contact pressure distribution of the tire with respect to the road surface, a contact pressure distribution analysis unit or a contact pressure distribution function, and when setting the oiler element model, a position where a water film is provided based on the contact pressure distribution and a position. / Or the thickness of the water film may be set.

Further, when setting the Euler element model, a water film may be provided on the entire portion where the tire touches the snow surface.

According to the embodiment of the present invention, by arranging the water film on the surface layer of the snow model, it is possible to reproduce a phenomenon closer to the snow condition on a general public road, and to predict the accuracy of tire performance on a snowy road surface. Can be improved.

It is a block diagram of the simulation apparatus which concerns on one Embodiment. It is a flowchart of the simulation apparatus. It is a perspective view which shows the state which combined the tire model and Euler element model. It is a partially enlarged side view of the Euler element model, (A) shows an example of one mesh layer of a water film, and (B) shows an example of two mesh layers of a water film. (A) is a perspective view showing a state before the tire model is grounded on the snow model, and (B) is a perspective view showing the state where the tire model is grounded. It is a side sectional view which shows the state which the tire model is in contact with the snow model. It is a contour figure which shows an example of the contact pressure distribution of a tire. It is a perspective view of the snow model which concerns on the example which provided the water film locally.

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

The tire simulation device 10 according to the embodiment is a simulation device that reproduces the behavior of a pneumatic tire traveling on a snowy road surface, and as shown in FIG. 1, an input unit 12, a tire model setting unit 14, and a road surface model. It has a setting unit 16, an oiler element model setting unit 18, a static analysis unit 20, a dynamic analysis unit 22, an evaluation value acquisition unit 24, a tire performance prediction unit 26, and an output unit 28.

The simulation device 10 can also be realized by using, for example, a general-purpose computer having a mouse and a keyboard as basic hardware. That is, the input unit 12, the tire model setting unit 14, the road surface model setting unit 16, the oiler element model setting unit 18, the static analysis unit 20, the dynamic analysis unit 22, the evaluation value acquisition unit 24, the tire performance prediction unit 26, and The output unit 28 can be realized by causing the processor mounted on the above computer to execute the program. At this time, the simulation device 10 may be realized by installing the above program in a computer in advance, storing the above program in a storage medium such as a CD-ROM, or distributing the above program via a network. , This program may be realized by installing it on the computer as appropriate.

Hereinafter, the configurations and functions of the above parts will be described in order.

[1] Input unit 12
The input unit 12 acquires model creation conditions necessary for modeling the pneumatic tire and the snowy road surface to be analyzed, and analysis conditions for performing analysis using these models.

The model creation conditions include the shape of the model, the number of mesh divisions, and the like. For example, the tire model creation conditions include various data (tire design information) about the tire including the tire cross-sectional shape. Specifically, each dimensional specification such as the outer shape and internal structure of the tire, material properties such as Young's ratio, Poisson's ratio and specific gravity for each member such as tread, belt and carcass constituting the tire are input.

The conditions for creating the Euler element model are the size of the model according to the size of the tire model, the number of mesh divisions, the area to subdivide the mesh and the degree of subdivision, the snow quality on the road surface, the thickness of snow, and the snow. Examples include the thickness of one mesh and the thickness of one mesh of the water film.

The analysis conditions include the internal pressure and load on the tire model mounted on the rim model, the translational speed that determines the dynamic state of the tire model (that is, the running speed of the tire model), the slip angle, and other conditions related to the movement and ground contact of the tire model. In addition, the analysis time in dynamic analysis is input.

The input of such information may be performed using a keyboard, or may be performed through a recording medium such as a CD-ROM, a network, or the like.

[2] Tire model setting unit 14
The tire model setting unit 14 sets a tire model modeled by a finite number of elements capable of numerical analysis. For example, a finite element model is created for a tire having a tread pattern based on the model creation conditions input by the input unit 12.

Specifically, the tire shape in the natural equilibrium state is used as a reference shape, and this reference shape is modeled by FEM to create a three-dimensional tire model divided into a large number of finite elements by mesh division. Examples of such elements include tetrahedral solid elements, pentahedral solid elements, hexahedral solid elements, and the like, and these elements are specified one by one using three-dimensional coordinates. In FIG. 3, an example of a patterned tire model is shown as reference numeral 50.

The method for creating such a tire model itself is known, and the tire can be modeled using such a known method. A tire model created in advance may be input from the input unit 12, and in that case, the tire model setting unit 14 sets the input tire model as an analysis target.

[3] Road surface model setting unit 16
The road surface model setting unit 16 sets a road surface model that reproduces the road surface. Specifically, based on the model creation condition input by the input unit 12, a road surface model in which the surface of the road is replaced with an element capable of numerical analysis is created.

As an example of the road surface model as reference numeral 52 in FIG. 3, it may be composed of a flat rectangular rigid surface element that does not deform even when an external force acts, and a road surface model having irregularities is defined as a road surface model. You may. In the road surface model, for example, a surface friction coefficient similar to that of an asphalt road surface is defined as a boundary condition.

In the present embodiment, the tire model travels on the snow model of the Euler element model in order to reproduce the behavior of the tire traveling on the snowy road surface. Therefore, if the bottom surface of the Euler element model is fixed as a rigid body surface, the road surface model is not essential and may be omitted.

The road surface model created in advance may be input from the input unit 12, and in that case, the road surface model setting unit 16 sets the input road surface model as an analysis target. Further, one or a plurality of road surface models may be stored in advance in a storage means such as a hard disk, and the road surface model selected via a mouse, keyboard, or the like may be set as an analysis target.

[4] Euler element model setting unit 18
The Euler element model setting unit 18 creates an Euler element model as an analysis model in which snow is arranged inside based on the model creation conditions input by the input unit 12.

As shown by reference numeral 54 in FIG. 3, the Euler element model is composed of a plurality of rectangular parallelepiped elements obtained by dividing the spatial region on the road surface model 52 by an Euler mesh of eight nodes, and as a whole. It has a rectangular parallelepiped shape.

The Euler element model 54 may be provided over the entire movement range of the tire model 50 in the dynamic analysis, but in this example, in order to move the Euler element model 54 in accordance with the movement of the rolling tire model 50 in the dynamic analysis. The Euler element model 54 is created in a range including an overlapping portion with the tire model 50 and a peripheral portion in the vicinity thereof.

The oiler element model 54 is divided into a plurality of rectangular parallelepiped elements by a plurality of vertical planes parallel to the tire axial direction, a plurality of vertical planes parallel to the tire front-rear direction, and a plurality of horizontal planes having different heights. In the example shown in FIG. 3, the rectangular parallelepiped element is generated so that its volume increases as the distance from the lower surface of the Euler element model 54 arranged in contact with the road surface model 52 increases in the height direction. Further, in the Euler element model 54, the elements are subdivided in the portion overlapping with the tire model 50, that is, the area corresponding to the ground contact portion of the tire model 50 and its vicinity is more densely meshed than the area around it. It is set.

The snow model 56 is configured by arranging snow at a predetermined height inside the Euler element model 54. Further, the snow model 56 is provided with a water film 58 on at least a part of the snow surface (that is, the upper surface). In the example shown in FIG. 3, a water film 58 is provided on the entire surface layer of the snow model 56. In the Euler element model 54, an object such as snow or water moves in space without changing the shape of the element. A spatial region made of air is secured above the region where the snow model 56 and the water film 58 are arranged in the Euler element model 54. The water film 58 provided on at least a part of the snow surface may be formed by replacing the snow arranged in the oiler element model 54 on the surface layer of the snow model 56 with water, and may be formed by replacing the upper surface of the snow model 56 with water. It may be formed by adding a layer of water to the water.

The snow arranged inside the Euler element model 54 is arranged with a uniform thickness (height) over the entire lower surface region in contact with the road surface model 52 in the Euler element model 54. Snow (shown in light gray in FIG. 3) is filled from the position of the element in the third stage to the position of the element of the third stage, that is, the thickness of three layers of the mesh. Further, water (shown in dark gray in FIG. 3) is filled on the snow with a thickness of one layer of the mesh to form a water film 58.

The number of mesh layers of the snow model 56 can be obtained by dividing the thickness of snow on the simulated snow road surface by the thickness of one mesh of the snow model 56. The thickness of one mesh of the snow model 56 is preferably smaller (thinner) than the thickness of one mesh in the tread of the tire model 50 in contact with the snow model 56, which causes snow and water to be removed in dynamic and static analyzes. It is possible to avoid the occurrence of error calculation that penetrates the mesh on the surface of the tire model.

The snow model 56 is an elasto-plastic model (eg, modified Drucker-Prager / Cap plastic model) in terms of density, elastic properties (eg Young's modulus, Poisson's ratio, etc.), plastic properties (eg adhesive force, friction angle, etc.). Characterized. The water film 58 is a fluid model of water, which is a Newtonian fluid, and is characterized by density, viscosity, speed of sound in water, and the like.

In a preferred embodiment, the Euler element model 54 is configured such that the thickness of the water film 58 provided on the snow surface of the snow model 56 is set to a different size depending on the snow quality of the snow road surface to be simulated. Generally, when tires run on snow, water is generated, but the amount of water generated at that time varies depending on the snow quality. In detail, it was found that almost no water is generated even when running on fresh snow, but the amount of water generated increases according to changes in snow quality such as small snow, tight snow, and rough snow. It is known that the density increases as the snow quality changes from fresh snow to small snow to small snow to rough snow (Toshio Oda, Kiyoshi Kudo, Snow Quality and Density, Nisetsu Monthly Report 2, Showa). 2015, pp. 19-24, pp. 43-45). Therefore, it is preferable to set the thickness of the water film to be larger (specifically, to increase the number of mesh layers of the water film) as the density of snow on the simulated snow road surface is increased.

As an example, the snow quality of the simulated snow road surface is set to four types: fresh snow, small snow, tight snow, and rough snow, and the number of mesh layers of the water film is as shown in Table 1 below according to each snow quality. It is preferable to set.

図４は、雪質に応じてオイラー要素モデル５４における水膜５８の厚みを変更した例を示したものであり、図４（Ａ）は水膜５８のメッシュ層数が１つの例、図４（Ｂ）は水膜５８のメッシュ層数が２つの例を示している。

FIG. 4 shows an example in which the thickness of the water film 58 in the oiler element model 54 is changed according to the snow quality, and FIG. 4 (A) shows an example in which the number of mesh layers of the water film 58 is one, FIG. (B) shows an example in which the number of mesh layers of the water film 58 is two.

The Euler element model may be input in advance from the input unit 12, and in that case, the Euler element model setting unit 18 sets the input Euler element model as an analysis target. Further, one or a plurality of Euler element models may be stored in advance in a storage means such as a hard disk, and the Euler element model selected via a mouse, keyboard, or the like may be set as an analysis target.

[5] Static analysis unit 20
The static analysis unit 20 performs static analysis in which the tire model 50 is brought into contact with the snow model 56 with a predetermined load without rolling. In this example, in the static analysis, the road surface model 52 set above is combined with the Euler element model 54, and then the tire model 50 is grounded with respect to the snow model 56 of the Euler element model 54.

Specifically, the tire model 50 obtained by the tire model setting unit 14 is mounted on a rim model (not shown), and then static analysis is performed by a finite element analysis method. That is, the internal pressure filling process that calculates the deformation of the tire model 50 while filling the tire model 50 with a predetermined internal pressure, and the oiler element model 54 on the road surface model 52 in a stationary state without rolling the tire model 50. Specifically, while grounding the snow model 56 with a predetermined load, a ground analysis process for calculating the deformation of the tire model 50 and calculating the behavior of snow and water is performed. Such static analysis itself can be performed by a static implicit method using a general-purpose analysis program, and examples of the general-purpose analysis program include Abaqus / Standard manufactured by Dassault Systèmes.

FIG. 5A shows a state before the tire model 50 is grounded to the snow model 56 of the oiler element model 54, and from this state, the tire model 50 is grounded to the snow model 56 with a predetermined load, and FIG. It shall be in the grounded state as shown in B). In this grounded state, as shown in FIG. 6, the snow model 56 of the oiler element model 54 is deformed so that a part of the tire model 50 enters the snow model 56, and the snow model 56 and the tire model 50 The water film 58 is interposed between the tread surface and the surface of the tread. In addition, in FIG. 5 and FIG. 6, the tire model 50 is shown by omitting the mesh.

[6] Dynamic analysis unit 22
The dynamic analysis unit 22 rolls the tire model 50 on the snow model 56 to perform dynamic analysis. In this example, the tire model 50 is rolled on the snow model 56, and the oiler element model 54 is moved on the road surface model 52 in response to the movement of the rolling tire model 50. Dynamic analysis (specifically, traction analysis) is performed to calculate deformation and behavior of snow and water.

The dynamic analysis unit 22 rolls (that is, rotates) the tire model 50 forward, that is, in the direction indicated by the arrow D1 in FIG. 3 so as to translate at a predetermined acceleration, and as the tire model 50 moves. While moving the oiler element model 54 forward at the same acceleration, the dynamic analysis that performs the deformation calculation and the behavior calculation is executed. At that time, the tire model 50 and the Euler element model 54 may move at a predetermined acceleration from the stationary state to the final speed (target translation speed) at the analysis time input by the input unit 12. , The target translational speed may be input instantly to obtain the desired dynamic state.

Such dynamic analysis itself can be performed by the method described in Patent Document 3 or a dynamic explicit method using a general-purpose analysis program. Examples of the general-purpose analysis program include Abaqus / Explicit manufactured by Dassault Systèmes. Can be mentioned.

More specifically, as an analysis method, it can be carried out by using Euler-Lagrange (CEL) analysis by Abaqus / Explicit, in which the tire model is a Lagrange element and the air / water / snow model is an Euler element. As the characteristic value (physical property value) of snow, as a modified Drucker-Prager / Cap plastic model, for example, the analysis conditions are: adhesive force: d = 15,000Pa, friction angle: β = 22.53 °, cap eccentricity parameter: R = 0.001 , Cap yield surface position: ε ₀ = 0.001, Transition surface radius parameter: α = 0.0, 3-axis tensile yield stress ratio: K = 1.0, and mass density and isotropic elasticity can be set as shown in Table 1 above. good. Further, as the characteristic value (physical property value) of water, the speed of sound in water: 1483 m / s, the mass density: 1000 kg / m ³ , and the viscosity: 0.001 kg / ms may be set.

[7] Evaluation value acquisition unit 24
The evaluation value acquisition unit 24 acquires an evaluation value for evaluating tire performance on a snowy road surface, for example, traction performance, from the above dynamic analysis. For example, the contact shape, contact area, contact pressure distribution, etc. of the tire model 50 with respect to the Euler element model 54; the volume content of snow contained in each element of the Euler element model 54, the reaction force, etc.; the axial force of the tire model 50, etc. Obtained as an evaluation value.

[8] Tire Performance Prediction Unit 26
The tire performance prediction unit 26 predicts the traction performance on a snowy road surface based on the evaluation value obtained by the evaluation value acquisition unit 24, and evaluates the quality thereof.

[9] Output unit 28
The output unit 28 outputs the prediction result of the tire performance obtained as described above. The output can be performed by displaying it on a display or printing it on a printer.

Next, the simulation method according to the present embodiment will be described with reference to the flowchart of FIG.

In step S1, the tire model setting unit 14 creates the tire model 50 based on the model creation conditions input from the input unit 12. A tire model 50 created in advance may be input from the input unit 12, and the input tire model may be set as an analysis target. Then, the process proceeds to step S2.

In step S2, the road surface model setting unit 16 creates the road surface model 52 based on the model creation conditions input from the input unit 12. The road surface model 52 created in advance may be input from the input unit 12, and the input road surface model may be set as the analysis target. Then, the process proceeds to step S3.

In step S3, the Euler element model setting unit 18 creates the Euler element model 54 based on the model creation conditions input from the input unit 12. Specifically, the mesh generation unit creates an Euler element model 54 formed by dividing a spatial region on the road surface by an Euler mesh having eight nodes. Next, the object arranging portion arranges snow inside the Euler element model 54 to form the snow model 56, and provides a water film 58 on at least a part of the snow surface. At that time, characteristic values such as density and Young's modulus are given according to the snow quality to be analyzed, and a mesh layer determined according to the snow quality in order to change the thickness of the water film 58 according to the snow quality. The water film 58 is provided by the number. Then, the process proceeds to step S4.

In step S4, the static analysis unit 20 uses the tire model 50 obtained in step S1, the road surface model 52 obtained in step S2, and the Euler element model 54 obtained in step S3 to perform finite element analysis. A static analysis is performed by the method, and the tire model 50 is brought into contact with the snow model 56. Then, the process proceeds to step S5.

In step S5, the dynamic analysis unit 22 performs dynamic analysis (specifically, traction analysis) using the tire model 50 in the ground contact state and the Euler element model 54. In the dynamic analysis, the tire model 50 is rolled on the snow model 56, and the oiler element model 54 is moved on the road surface model 52 in response to the movement of the rolling tire model 50. Dynamic analysis is performed to calculate the deformation of the tire and the behavior of snow and water. Specifically, based on the boundary conditions given to the tire model 50 by the snow model 56 having the water film 58 on the surface layer, the deformation calculation of the tire model 50 is sequentially performed at a predetermined time step size, and the tire model 50 Based on the boundary conditions given to the snow model 56, the behavior of snow and water is sequentially calculated with a step size of a predetermined time.

More specifically, first, the tire model 50 and the Euler element model 54 are moved in a predetermined time step size, and the boundary surface between the tire model 50 and the snow model 56 having the water film 58 is calculated. Next, the force acting on the tire model 50 from the snow model 56 is set as a boundary condition, the deformation of the rolling tire model 50 is calculated based on this, and the displacement and stress of the tire model 50 are calculated. On the other hand, the velocity component accompanying the deformation and rolling of the tire model 50 is set as a boundary condition for the snow model 56, and the behavior of snow and water is calculated based on this. Next, mapping processing of physical quantities of snow and water in the Euler element model 54 is performed. The above steps are repeated until the predetermined analysis time elapses, and the dynamic analysis ends when the predetermined analysis time elapses.

After the dynamic analysis is completed in this way, in step S6, the evaluation value acquisition unit 24 acquires an evaluation value for evaluating the tire performance on the snowy road surface from the result of the dynamic analysis. Then, the process proceeds to step S7.

In step S7, the tire performance prediction unit 26 predicts the quality of the tire performance on a snowy road surface based on the evaluation value obtained in step S6, and the output unit 28 outputs the result.

[Action / Effect]
According to the present embodiment, by arranging the water film 58 on the surface layer of the snow model 56, it becomes possible to consider a phenomenon closer to the snow condition of a general public road. When water is generated between the tire tread and snow, the shearing force decreases due to the influence of the water intervening between the rubber and snow, and the friction coefficient decreases. By arranging the water film 58, the coefficient of friction between the tire tread and the snowy road surface can be lowered, and a situation close to the actual phenomenon can be reproduced. Therefore, it is possible to improve the prediction accuracy of tire performance on a snowy road surface.

Further, the thickness of the water film 58 was changed according to the snow quality of the simulated snow road surface, and in detail, the thickness of the water film 58 was set to be larger as the snow density was higher, so that the water generated according to the snow quality was set. Considering the amount, it is possible to reproduce a situation closer to the actual phenomenon, and the prediction accuracy can be further improved.

[Other Embodiments]
In the above embodiment, in the oiler element model 54, the water film 58 is provided on the entire surface layer of the snow model 56, but if the water film 58 is provided so as to include a portion where the tire touches the snow surface. , It is not necessary to be provided on the entire snow surface, and it may be provided on at least a part of the snow surface.

For example, in one embodiment, the position where the water film is provided and the thickness of the water film may be set based on the contact pressure distribution of the tire. In that case, a step of obtaining the contact pressure distribution of the tire with respect to the road surface is further included, and in step S3 of setting the Euler element model, the position where the water film is provided and / or the thickness of the water film is determined based on the contact pressure distribution obtained above. Just set it.

As an example, FIG. 7 shows the contact pressure distribution of the tire. After setting the tire model in step S1 and setting the road surface model in step S2, the tire model is mounted on the rim model, and then static analysis is performed by the finite element analysis method. That is, the internal pressure filling process that calculates the deformation of the tire model while filling the tire model with a predetermined internal pressure, and the deformation calculation of the tire model while grounding the road surface model with a predetermined load without rolling the tire model. Performs grounding analysis processing. As a result, the ground pressure distribution as shown in FIG. 7 can be obtained.

In FIG. 7, except for the white portion, the darker the gray color, the lower the contact pressure, and the lighter the gray color, the higher the contact pressure. Therefore, the contact pressure of the shoulder ribs on both sides of the center rib near the equator of the tire is higher than that of the center rib.

Therefore, in the example shown in FIG. 8, the water film 58 is provided only on the portion corresponding to the shoulder rib having a high contact pressure, and the water film is not provided on the other portions on the upper surface of the snow model 56. Note that FIG. 8 is a diagram showing the Euler element model 54 after the static analysis in step S4, omitting the spatial region composed of the upper air, in order to make it easier to understand the relationship between the ground contact shape and the water film 58. Is.

Instead of providing the water film 58 only in the portion having a high contact pressure as shown in FIG. 8, the thickness of the water film in the portion having a high contact pressure may be set to be larger than the thickness of the water film in the other portion. Further, both the position where the water film is provided and the thickness of the water film may be changed based on the ground pressure distribution. For example, the ground pressure is divided into three regions according to the magnitude of the ground pressure, and the ground pressure is the best. A water film of the first thickness is provided in the high part, a water film of the second thickness thinner than the first thickness is provided in the part where the contact pressure is the second highest, and a water film is provided in the part where the contact pressure is the lowest. It may be set so that it does not exist.

The amount of snow generated when the tires are running increases as the contact pressure increases. Therefore, by setting the position where the water film is provided and / or the thickness of the water film based on the ground pressure distribution in this way, it is possible to reproduce a situation closer to the actual phenomenon and further improve the prediction accuracy. ..

Further, in one embodiment, when the water film is provided on the snow model, the water film may be provided on the entire portion where the tire touches the snow surface. As a result, it is possible to perform a simulation considering the influence of snow water generation when the tire is running on the entire snow surface where the tire touches the ground.

In the above embodiment, in the dynamic analysis, the Euler element model 54 is moved according to the movement of the tire model 50, but the Euler element model 54 may be moved without moving. ..

In the above embodiment, prior to the dynamic analysis, a static analysis was performed in which the tire model 50 was brought into contact with the snow model 56 without rolling, but as described in Patent Document 2, the static analysis was performed. The dynamic analysis may be performed as it is without performing the analysis.

Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... Simulation device, 14 ... Tire model setting unit, 16 ... Road surface model setting unit, 18 ... Euler element model setting unit, 22 ... Dynamic analysis unit, 50 ... Tire model, 54 ... Euler element model, 56 ... Snow model, 58 ... Water film

Claims (8)

A tire simulation method that reproduces the behavior of tires running on snowy roads.
Steps to set a tire model modeled with a finite number of elements that can be numerically analyzed,
As an analysis model in which snow is placed inside, a step of setting an Euler element model including a snow model in which a water film is provided on at least a part of the snow surface, and
A step of rolling the tire model on the snow model to perform dynamic analysis,
Tire simulation methods, including. The simulation method according to claim 1, further comprising a step of performing a static analysis in which the tire model is brought into contact with the snow model with a predetermined load without rolling. The simulation method according to claim 1 or 2, wherein the thickness of the water film provided on the snow surface of the snow model is set according to the snow quality of the snow road surface to be simulated. The simulation method according to claim 3, wherein the thickness of the water film is set larger as the density of snow on the snow road surface to be simulated increases. 1. The step of obtaining the contact pressure distribution of the tire with respect to the road surface is further included, and in the step of setting the Euler element model, the position where the water film is provided and / or the thickness of the water film is set based on the contact pressure distribution. The simulation method according to any one of 1 to 4. The simulation method according to any one of claims 1 to 5, wherein a water film is provided on the entire portion where the tire touches the snow surface in the step of setting the Euler element model. A tire simulation device that reproduces the behavior of tires running on snowy roads.
A tire model setting unit that sets a tire model modeled with a finite number of elements that can be numerically analyzed,
As an analysis model in which snow is placed inside, an Euler element model setting unit that sets an Euler element model including a snow model in which a water film is provided on at least a part of the snow surface, and an oiler element model setting unit.
A dynamic analysis unit that rolls the tire model on the snow model to perform dynamic analysis,
A tire simulation device. It is a program to reproduce the behavior of tires running on snowy roads.
On the computer
A tire model setting function that sets a tire model modeled with a finite number of elements that can be numerically analyzed,
As an analysis model in which snow is placed inside, an Euler element model setting function that sets an Euler element model including a snow model in which a water film is provided on at least a part of the snow surface, and an oiler element model setting function,
A dynamic analysis function that rolls the tire model on the snow model to perform dynamic analysis,
Tire simulation program to realize.

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