JP2013067184A - Tire simulation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire simulation method designed to precisely simulate tire performance on a soft mud road surface, while reducing calculation time.SOLUTION: A tire simulation method for simulating tire performance on a soft mud road surface includes: a tire model setting step S1 for setting a tire model formed by modeling a tire having at least a tread pattern with a numerically analyzable element; a road surface model setting step S2 for setting a soft road model formed by modeling the mud road surface with the numerically analyzable element; and a simulation step S4 for bringing the tire model into contact with the soft road model and performing deformation calculation of the soft road model by use of a computer for each minute time increment. In the tire model setting step S1, the tire model is set as an undeformable rigid body, while in the simulation step S4, the deformation calculation of the tire model is not performed.

Description

  The present invention relates to a tire simulation method capable of accurately simulating tire performance on a soft road surface while reducing calculation time.

  Pneumatic tires mounted on multi-purpose vehicles such as four-wheel drive vehicles and SUVs have the opportunity to travel on soft road surfaces such as mud road surfaces. Is sometimes called “mud performance”). Conventionally, the tire mud performance has been evaluated by the driver's feeling by running on a muddy road surface with an actual vehicle equipped with a test tire. However, in such an evaluation method, variations are likely to occur due to changes in the condition of the mud road surface due to the weather or the like, and the ability of the driver, and it is difficult to quantitatively grasp the mud performance.

  Therefore, in recent years, a method for predicting and analyzing tire running performance on a mud road surface by computer simulation using a numerical analysis method such as a finite element method has been proposed. As related technologies, there are the following Patent Documents 1 and 2.

JP 2003-315236 A JP 2009-3000278 A

  However, in the simulation method described above, a tire model in which the tire is modeled as an elastic body and a mud road surface model in which the mud road surface is modeled are set and brought into contact with each other. It was necessary to perform deformation calculation for each minute time increment using a computer, which required a lot of time.

  The present invention has been devised in view of the above problems, and it is a main object of the present invention to provide a tire simulation method capable of accurately simulating tire performance on a soft road surface while reducing calculation time. It is said.

  The invention according to claim 1 of the present invention is a tire simulation method for simulating tire performance on a soft road surface, and is a tire model in which a tire having at least a tread pattern is modeled as an element capable of numerical analysis. A tire model setting step for setting the road surface, a road surface model setting step for setting the soft road model in which the road surface is modeled by an element capable of numerical analysis, and the tire model and the soft road model are brought into contact with each other and the soft road model is deformed. A simulation step in which calculation is performed for each minute time increment using a computer. In the tire model setting step, the tire model is set as a non-deformable rigid body, and in the simulation step, deformation calculation of the tire model is performed. It is characterized by not performing.

  According to a second aspect of the present invention, in the simulation step, the tire model is rolled with respect to the soft road model based on a predetermined condition.

  The invention according to claim 3 is characterized in that the soft road model setting step sets the soft road model with a thickness that the tread pattern does not contact in the simulation step.

  On a soft road surface, for example, a muddy road surface having a sufficient depth, the tire usually travels while receiving buoyancy while floating from the bottom without touching the bottom of the mud road surface. Often, the load does not act. In the present invention, attention is paid to the tire running condition on such a soft road. That is, the present invention is characterized in that the tire model is set as a rigid body that cannot be deformed, and in the simulation step, only the deformation calculation of the soft road model is performed and the deformation calculation of the tire model is not performed. Therefore, according to the present invention, since the deformation calculation of the tire model is eliminated, the calculation time can be greatly shortened. On the other hand, on soft roads, as described above, tire deformation remains in a very small range, so there is no significant difference in the tendency of mud performance even if the tire model is handled as a rigid body. Can be used.

It is a perspective view which shows an example of the computer apparatus used by this embodiment. It is a flowchart which shows the process sequence of this embodiment. It is a perspective view which visualizes and shows a tire model. It is sectional drawing which shows the relationship between a mud road surface model and the tire model made to contact with it. It is a graph which shows the relationship between the longitudinal load and time of the tire model obtained in the simulation step. In the graph of FIG. 5, it is sectional drawing which shows the relationship between the tire model of 0-0.30s, and a soft road model. In the graph of FIG. 5, it is sectional drawing which shows the relationship between the tire model of 0.30s-0.35s, and a soft road model. In the graph of FIG. 5, it is sectional drawing which shows the relationship between the tire model of 0.35 s-0.40 s, and a soft road model. In the graph of FIG. 5, it is sectional drawing which shows the relationship between the tire model after 0.40 s, and a soft road model.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The tire simulation method of the present invention can evaluate the running performance of a tire when running on a soft road surface having a sufficient thickness. A typical example of a soft road surface is a mud road surface filled with mud. Embodiments of the present invention will be described below using a mud road surface as an example.

  In this specification, mud is at least clay (particle size: less than 0.005), silt (particle size: 0.005 to 0.075 mm), fine sand (particle size: 0.075 to 0.250 mm), Medium sand (particle size: 0.250-0.850 mm), coarse sand (particle size: 0.850-2.00 mm), fine gravel (2.00 mm-4.75 mm) and medium gravel (4.75 mm-19) 0.001 mm) or a mixture containing two or more particles and moisture (10 to 50%).

  Although not particularly limited, as a preferable soft mud road surface, the particle diameter is 5.0 mm or less, and the moisture content (% by weight of moisture in the entire mud) is greater than 0% and 100% or less, preferably A road surface of about 10 to 50%, more preferably 20 to 40%, and still more preferably about 20 to 30% can be assumed.

  FIG. 1 shows a computer apparatus 1 for carrying out the simulation method of the present invention. The computer device 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with an arithmetic processing unit (CPU), a ROM, a working memory, a mass storage device such as a magnetic disk (all not shown), and drive devices 1a1, 1a2 such as a CD-ROM. . The large-capacity storage device stores a processing procedure (program) necessary for executing a simulation method described later.

  FIG. 2 shows an embodiment of the procedure of the simulation method of the present invention performed using the computer apparatus 1. First, in the present embodiment, a tire model setting step of setting a tire model obtained by modeling a tire having at least a tread pattern as an element capable of numerical analysis is performed (step S1). Here, that numerical analysis is possible means that it can be handled by a numerical analysis method such as a finite element method, a finite volume method, a difference method or a boundary element method. In this example, the finite element method and the finite volume method are used. Adopted.

  FIG. 3 shows an example of the tire model 2 visualized in three dimensions. The tire model 2 is modeled by representing a tire to be analyzed using a finite number of small elements 2a, 2b, 2c. The substance of the tire model 2 is numerical data that can be handled by the computer device 1. Specifically, the node coordinate value, element number, and node number of each element 2a, 2b, 2c... Are defined. Although not particularly limited, each of the elements 2a, 2b, 2c... Is preferably a three-dimensional tetrahedral solid element suitable for expressing a complicated tread pattern including vertical grooves and horizontal grooves, for example. Thereby, in the tire model 2 of FIG. 3, the tread pattern shape including the vertical groove and the horizontal groove on the tread surface is faithfully reproduced. However, other than this, a pentahedron or a hexahedron solid element may be used.

  The tire model 2 of the present embodiment is characterized by being defined as a rigid body from the beginning. Such a tire model 2 does not deform even when a load is applied. Therefore, such a tire model 2 can be modeled by omitting the internal structure of the tire (for example, a carcass, a belt, and various rubber members) except that the tread pattern is reproduced. This helps reduce model creation time. The tire model 2 made of a rigid body can be easily set by defining the elements 2a, 2b... With rigid elements that do not deform. However, the tire model 2 is defined according to the tire to be analyzed, except that the tire model 2 is not deformed and the internal structure becomes unnecessary.

  Next, a mud road surface model 3 in which the mud road surface is modeled with elements that allow numerical analysis is set (step S2).

  FIG. 4 shows a side view of the mud road surface model 3 visualized. The mud road surface model 3 of this embodiment is modeled with Euler elements that can be handled by the finite volume method. In the present embodiment, the mud road surface model 3 is fixed in a space above the plane rigid element 4 and a mud model 3b (gray) that can move in a lattice-shaped mesh 3a and a space partitioned by the mesh 3a. A colored portion). Physical quantities such as pressure and flow velocity of the mud model 3b are sequentially calculated and stored at each intersection of the grid-like mesh or at the center of gravity of each grid.

  The mud model 3b simulates mud on an actual road surface, and is closed at the bottom and the periphery except for the upper part of the mud road surface model 3. That is, the mud model 3b is equivalent to, for example, mud put in a box whose upper part is opened. Since the thickness H of the mud model 3b corresponds to the mud thickness of the actual mud road surface to be analyzed, in the present embodiment, the mud model 3b has a sufficient size so that the influence of the plane rigid element 4 can be ignored. It is done.

  Further, the mud road surface model 3 of the present embodiment has a three-dimensional space provided with a width and a length necessary and sufficient to contact and roll the tire model 2. Here, the rolling of the tire model 2 may be a rotation amount smaller than one rotation as long as the mud performance can be evaluated.

  Furthermore, as shown in FIG. 4, the mud road surface model 3 takes into account the contact with the surface of the tire model 2. In the deformation calculation (described later) of the mud road surface model 3, the intersection J between the tire model 2 and the mud road surface model 3 is calculated from the mutual position information. The tire model 2 and the mud model 3b are handled as being in contact with each other via the boundary JL of the intersecting portion J (that is, the surface of the tread pattern of the tire model 2). That is, the mud model 3b applies pressure or the like to the tire model 2 via the boundary JL. Conversely, the tire model 2 gives its surface as a “wall” (coupling surface) to the mud model 3b and deforms the mud model 3b.

  Further, the mud model 3b defines physical properties approximate to actual mud, and in this embodiment, elasto-plastic characteristics, collapse characteristics, and adhesive strength are defined.

  The elasto-plastic property means that the physical property of the mud model 3b differs based on the stress state.

  In addition, the collapse characteristic is that the mud model 3b does not break even if plastic strain occurs under compressive stress (average compressive stress), while the equivalent plastic strain is specified under tensile stress (average tensile stress). It is a characteristic that destroys when the value of is reached. The equivalent plastic strain that the mud model 3b breaks exhibits a substantially constant value regardless of the restraint pressure. Therefore, by defining the collapse characteristic and the elasto-plastic characteristic in the mud model 3b, the mud road surface condition when the tire travels on the mud road surface is accurately captured by the simulation result.

  Furthermore, an adhesive force is defined in the mud model 3b. When the tire travels on the mud road surface, the mud adheres to the tire surface. Therefore, mud adhering to the tire surface fills the tread pattern and causes a reduction in tire traction. However, such a reduction in traction can be minimized if the tread pattern groove has good soil removal. Therefore, the simulation method of the present invention is useful for evaluating the soil removal performance of tire grooves.

  Each of the above characteristics defined in the mud model 3b is set according to the mud road surface particles and moisture content to be analyzed. In addition, about the definition of each characteristic etc., based on the mud road surface etc. of analysis handling, the method described in the patent document 2 shown previously can be used suitably, for example.

  Next, in the present embodiment, conditions necessary for performing a simulation step described later, such as boundary conditions, are defined (step S3). The set conditions include, for example, the rim on which the tire model 2 is mounted, the internal pressure, the friction coefficient between the mud road surface model 3 and the tire model 2, the slip angle, the camber angle, the rolling speed, and the tire model of the tire model 2. 2 and the initial time increment when the mud road surface model 3 is deformed and conditions such as the initial positions of the models 2 and 6 are included.

  Further, as the boundary condition, the mud road surface model 3 includes the outflow / inflow condition of the mud model 3b. In the mud road surface model 3 of the present embodiment, for the mud layer in which the mud model 3b exists, a condition is defined in which the bottom and side portions excluding the upper surface are surrounded by walls. That is, with respect to the mud layer, the mud model 3b does not enter or exit except the upper surface. The mud model 3b is not supplied from the outside. Furthermore, a space layer 3c having a certain height is provided above the mud model 3b of the mud road surface model 3 so that the mud model 3b can move. All the surfaces of the space layer 3c are released.

  Furthermore, the thickness (that is, the thickness of the mud layer) H of the mud model 3b is defined. The thickness H is defined as a mud thickness at which the tread pattern of the tire model 2 does not contact the planar rigid element 4 that is the bottom surface of the mud road surface model 3 in a simulation step described later. This thickness H can be appropriately determined depending on the viscosity of the mud model 3b, the longitudinal load of the tire model 2, and the like.

  Next, as shown in FIG. 4, the computer apparatus 1 makes a simulation in which the tire model 2 and the mud model 3b of the mud road model 3 are brought into contact with each other and the deformation calculation of the mud road model 3 is performed at every minute time increment. A step is performed (step S4). In the simulation step of the present invention, only the deformation calculation of the mud road surface model 3 is performed, and the deformation calculation of the tire model 2 which is a rigid body is not performed.

  As described above, on a muddy road surface that is soft and has a sufficient depth, the tire usually runs in a floating state without touching the bottom of the muddy road surface, so a load that greatly deforms the tire is almost effective. do not do. In the present invention, the tire model 2 is set as a non-deformable rigid body by paying attention to the situation when the tire travels on a muddy road surface. In the simulation step, only the deformation calculation of the mud road surface model 3 is performed, and the deformation calculation of the tire model 2 is not performed. As a result, in the present invention, the calculation time required for the simulation can be greatly reduced since the deformation calculation of the tire model 2 is eliminated as well as the creation time of the tire model 2 is shortened. Further, on the mud road surface, since the deformation of the tire is limited to a very small range as described above, even if the tire model 2 is handled as a rigid body, the mud performance can be simulated without a large decrease in accuracy.

  The deformation calculation of the mud road surface model 3 is performed by various methods. In this embodiment, the deformation calculation is performed by the explicit method. In the explicit method, the moment when a load or the like is applied to each of the models 2 and 3 is set to time 0, the time is divided for each set time increment Δt, and the displacement of the models 2 and 3 at each time is obtained. Therefore, although convergence calculation is not necessary, the time increment Δt is set so as to satisfy the Courant condition in order to stabilize the calculation. Such calculation is performed, for example, using general-purpose finite element analysis application software (for example, MSC-Dytran manufactured by MSC).

When the simulation step is finished, a necessary physical quantity is output (step S5). In FIG. 5, the vertical load acting on the tire model 2 is output as time on the horizontal axis and physical quantity on the vertical axis. The calculation conditions of this simulation are as follows.
<Actual mud with reference to the characteristics of the mud model>
Collection location: Nara Prefecture Gravel (particle size 2 to 75mm): 0%
Sand content (particle size 0.075-2mm): 44.8%
Sand particle content (particle diameter: less than 0.075 mm): 55.2%
Moisture content: 26.3%
Ground material classification: sandy viscosity (low viscosity)
Classification symbol (CLS)

<Calculation conditions>
Tire size: 285 / 60R18
Mud thickness H: 15cm
Subsidence amount of tire model to mud road surface model D: 8cm
Speed when rotating tire model: 1rps

<Examples 1 and 2>
In Examples 1 and 2, the tire model is formed of a rigid body, and the deformation calculation of the tire model is not performed in the simulation. In the simulation of the first embodiment, the tire model is started at the rotational speed at the time of 0.3 seconds. In the simulation of Example 2, the tire model is made to contact only the mud road surface model by applying only the longitudinal load, and is not rotated.

<Comparative Examples 1 and 2>
In Comparative Examples 1 and 2, the tire model is made of an elastic body. That is, these tire models are modeled to the internal structure, and the material properties of the tire model to be analyzed are defined for each element. In the simulation, tire model deformation calculation is also performed. Furthermore, in the simulation of the comparative example 1, the tire model is started at the rotational speed at the time of 0.3 seconds. In the simulation of Comparative Example 2, the tire model is caused to act only on the longitudinal load and contact the mud road surface model, and is not rotated.

[Examination of simulation results]
Next, Comparative Example 2 and Example 2 which are not rotated in FIG. 5 will be examined. As shown in FIGS. 6 and 7, in Comparative Example 2, the tire model 2 was subtracted with a subsidence amount D of 8 cm over 0 to 0.3 seconds. In the course, the reaction force R of the mud road surface model 3 reached its maximum in about 0.15 seconds. The tire model 2 is supported by the reaction force from the mud road surface model 3, and after 0.4 seconds, the mud model 3b removed by the tire model 2 slowly flows around and reacts (longitudinal load). Gradually decreases. In Example 2, since the tire model is a rigid body, it can be seen that there is no vibration in the waveform because it is not elastically deformed. As is clear from FIG. 5, in Example 2, the increase in reaction force is smaller than that in Comparative Example 2. However, it can be seen that Example 2 shows almost the same tendency as Comparative Example 2 when the transition of the longitudinal load is observed.

  Next, Comparative Example 1 and Example 1 will be examined. In Comparative Example 1, as shown in FIGS. 6 to 7, after the tire model 2 was sunk for 8 cm over 0 to 0.3 seconds, from 0.3 seconds to 1 rps as shown in FIGS. The tire model 2 was rotated. Accordingly, Comparative Example 1 follows the same process as Comparative Example 2 until 0.3 seconds, while mud is dug along with rotation of the tire model 2 after 0.3 seconds, and the longitudinal load R is suddenly applied. It turns out that it decreases. With respect to such a change in the longitudinal load, it can be seen that Example 2 also shows a tendency similar to that of Comparative Example 2.

  Next, the time required for each simulation of Example 2 and Comparative Example 2 was examined. With respect to the tire model creation time, assuming that the creation time of Comparative Example 2 was 100, Example 2 was 25, a 75% reduction. The simulation time was 29 in Example 2 when Comparative Example 2 was set to 100, which was a significant reduction of 71%.

  As is clear from the above examples, it has been confirmed that the calculation results are greatly shortened without impairing the tendency of the mud performance in the present invention.

1 Computer device 2 Tire model 3 Mud road surface model 3a Mesh 3b Mud model

Claims (3)

A tire simulation method for simulating tire performance on a soft road surface,
A tire model setting step for setting a tire model obtained by modeling a tire having at least a tread pattern as an element capable of numerical analysis;
A road surface model setting step for setting a soft road model in which the road surface is modeled with an element capable of numerical analysis;
A simulation step of contacting the tire model with the soft road model and performing a deformation calculation of the soft road model for each minute time increment using a computer,
In the tire model setting step, the tire model is set as a non-deformable rigid body,
In the simulation step, a tire simulation method is characterized in that deformation calculation of the tire model is not performed.   The tire simulation method according to claim 1, wherein, in the simulation step, the tire model rolls with respect to the soft road model based on a predetermined condition.   3. The tire simulation method according to claim 1, wherein the soft road model setting step sets the soft road model with a thickness at which the tread pattern does not contact in the simulation step.

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