JP2011235758A - Method and apparatus for simulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for simulation that obtain a natural frequency close to that of a real tire.SOLUTION: The simulation method includes: a road surface model setting step S3 for setting a road surface model that simulates a road surface, on which a pneumatic tire hugs, by a finite number of elements; a step S4 for setting a prescribed inner pressure for a tire model; a boundary condition setting step S5 for setting a boundary condition defining a distance between the tire model and the road surface model so that a prescribed load is generated between surfaces of the tire model and the road surface model; a contact detection step S6 for detecting a node point that comes into contact with the road surface model from node points of elements comprising the tire model; a constraint step S7 for having the node point detected in the contact detection step be constrained; and a natural frequency analyzing step S8 for calculating the natural frequency of the tire model in which the node point coming into contact with the road surface model is constrained.

Description

  The present invention relates to a simulation method and a simulation apparatus for simulating tire performance of a tire model obtained by modeling a pneumatic tire with a plurality of elements.

  In recent years, in the development of tires, due to the development of numerical analysis methods such as the finite element method and the computer environment, tires are actually manufactured and installed in automobiles without running tests and multiple newly designed tires It is now possible to simulate tire performance such as driving performance and characteristics using a composite model of a tire model modeled in, and a wheel model modeled with multiple elements.

  A tire is a structure filled with air, and has a vibration characteristic (referred to as a natural frequency) unique to each tire. The natural frequency varies depending on the tire structure and tire size, and is a factor that determines tire noise, riding comfort, rolling resistance, and the like. Therefore, a method of creating a tire model suitable for analyzing the natural frequency of the tire has been proposed (see Patent Document 1). By using the tire model created by the above-described method, a natural frequency of the tire model can be calculated by executing on a computer a hammering test in which an external force is applied to the tread portion of the tire model in an ungrounded state. .

JP 2007-304657 A

  However, since the actual tire is in contact with the road surface while attached to the wheel, the natural frequency of the actual tire is the natural frequency calculated by applying an external force to the tire model in the non-ground state. Is different.

  Therefore, an object of the present invention is to provide a simulation method and a simulation apparatus that can calculate a natural frequency of a tire model that is more realistic.

  In order to solve the above-described problems, the present invention has the following features. A feature of the present invention is a simulation method for analyzing a natural frequency of a tire model in which a pneumatic tire is divided into finite elements, and a road surface model that simulates a road surface on which the pneumatic tire contacts the ground with finite elements. A road surface model setting step for setting the tire model and the road surface model so that a predetermined load is generated between the tire model and the surface of the road surface model. A boundary condition setting step for setting a boundary condition for determining a distance of the vehicle, a contact detection step for detecting a node in contact with the road surface model among nodes of elements constituting the tire model, and a contact detection step. A restraint step for bringing the joint node into a restrained state, and a tire having the joint node in contact with the road surface model in the restraint state And summarized in that having a natural frequency calculating step of calculating the natural frequency of the model.

  According to the characteristics of the present invention, a boundary condition for the tire model to contact the surface of the road surface model is set, and the nodes that are in contact with the road surface model among the nodes of the elements constituting the tire model are put into a restrained state. For this reason, it is possible to analyze the natural frequency when the tire model is in contact with the road surface. Therefore, the natural frequency in a state where the tire is used can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, when analyzing the natural frequency of a tire model, the simulation method and simulation apparatus which can obtain the natural frequency close | similar to a real tire can be provided.

FIG. 1 is a flowchart illustrating a simulation method according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a tire model set in the simulation method according to the embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a wheel model set in the simulation method according to the embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a tire model and a road surface model set in the simulation method according to the embodiment of the present invention. FIG. 5 is a diagram for explaining the nodes of the tire model in contact with the road surface model. FIG. 6 is a configuration diagram of a simulation apparatus that executes the simulation method according to the embodiment of the present invention. FIG. 7 is a schematic diagram illustrating a tire model (Example 1) obtained by analyzing the natural frequency in the ground contact state. FIG. 8 is a schematic diagram illustrating a tire model (Comparative Example 1) obtained by analyzing the natural frequency in a non-grounded state.

  An embodiment of a simulation method according to the present invention will be described with reference to the drawings. Specifically, (1) simulation method, (2) simulation apparatus, (3) operation and effect, (4) other embodiments will be described. In the following description of the drawings, the same portions are denoted by the same reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.

(1) Simulation Method FIG. 1 is a flowchart illustrating a simulation method shown as an embodiment of the invention. The simulation method described as an embodiment is natural frequency analysis using a finite element method.

  Below, the simulation method of this embodiment is demonstrated. Step S1 is a design step. In the design step, a new pneumatic tire to be evaluated by the simulation method is designed. Specifically, the tire size, shape, structure, material, etc. of the pneumatic tire are determined. Design data such as tire size, shape, structure, and material of the pneumatic tire are input.

  In step S2, a tire model 10 is set in which the shape, structure, and material of the pneumatic tire designed in step S1 are divided into a finite number of elements. In the present embodiment, the tire model 10 is created by applying a finite element method (FEM). The tire model 10 is obtained by digitizing an actual pneumatic tire into a data format that can be input to a computer program created based on a numerical / analytical method.

  The tire model 10 created in step S2 is divided into a plurality of elements. The element division is to divide a pneumatic tire, a road surface, a fluid, or the like into a finite number of small parts (referred to as elements). That is, the tire model 10 is composed of a plurality of elements. In the finite element method, for example, calculation of physical quantities such as deformation, heat, viscoelasticity, and the like is calculated individually for all elements constituting the tire model 10, and then the calculation results for all the elements are integrated to calculate the whole tire model. This is a method of calculating a physical quantity.

  FIG. 2 is a schematic diagram illustrating the tire model 10 set in the simulation method. In the tire model 10 shown in FIG. 2, a tread pattern model is set in which the basic structure of the groove and land portion formed in the tread portion 11 of the pneumatic tire is divided into a finite number of elements. In the tire model 10, elements corresponding to a bead wire, a bead portion, a side portion, an internal rubber member, a belt, a carcass ply, and an inner liner are set (not shown in FIG. 2).

  The tread portion, the side portion, and the internal rubber member are modeled by shell elements, membrane elements, river elements, and the like. A bead wire is modeled using solid elements. The rubber member is modeled using a superelastic body such as Mooney-Rivln material or Ogdcn material. The rubber member can also be modeled by a viscoelastic body taking viscosity into consideration. Viscosity is modeled using linear viscoelasticity and Prony series.

  In step S2, a composite model 30 in which the wheel model 20 is assembled to the tire model 10 may be set. In this case, a wheel model 20 is created by dividing a wheel on which a pneumatic tire is mounted into a finite number of elements (wheel model setting step), and a composite model that is a composite of the wheel model 20 and the tire model 10. Is set (complex model setting step). FIG. 3 is a schematic diagram for explaining the wheel model 20 set in the simulation method according to the present embodiment. In the wheel model 20, a rim portion 21 and a disc portion 22 are set. Moreover, the bolt hole 23 for attaching a wheel to a vehicle using a volt | bolt, a nut, etc. is set.

  In step S3, a road surface model 30 is set that simulates the road surface on which the pneumatic tire contacts the ground with a finite number of elements. Step S3 corresponds to a road surface model setting step.

  Step S4 is an internal pressure setting step. In the internal pressure setting step, a predetermined air pressure is set in the complex model created in step S2.

  In step S5, the distance between the tire model 10 and the road surface model 30 is determined such that a predetermined load is generated between the tire model 10 and the surface of the road surface model 30 while the tire model 10 and the road surface model 30 are in contact with each other. Boundary conditions are set and nonlinear analysis is performed. FIG. 4 is a diagram illustrating the tire model 10 and the road surface model 30. Steps S4 and S5 constitute a boundary condition setting step.

  In step S <b> 6, a node that is in contact with the road surface model 30 is detected from the nodes of the elements constituting the tire model 10. FIG. 5 is a diagram for explaining the nodes of the tire model in contact with the road surface model. In FIG. 5, the k-th element constituting the tire model 10 is represented as an element k. The nodes of the element k are represented as Nk1, Nk2, Nk3, and Nk4. A region that is in contact with the road surface model 30 among n elements constituting the tire model 10 is defined as a region T. At this time, the nodes in contact with the road surface model 30 among the nodes of the elements constituting the tire model 10 are nodes constituting the elements included in the region T. Note that a node that is in contact with the road surface model 30 cannot penetrate the road surface model 30, unlike a node that is not in contact with the road surface model 30. Therefore, a node remaining on the surface of the road surface model 30 is detected as a node in contact with the road surface model 30.

  In step S7, the node detected in step S6 is put into a restrained state. Here, the “restraint state” is to set a constraint condition that constrains the physical degree of freedom. That is, setting the displacement at the node to zero.

  In step S8, the natural frequency analysis of the tire model 10 in which the nodes in contact with the road surface model 30 are constrained is executed. In the embodiment, the natural frequency analysis is performed by the constraint mode method.

(2) Simulation Device FIG. 6 shows an outline of a computer 300 as a simulation device that executes the simulation method of the embodiment. As shown in FIG. 6, the computer 300 includes a main unit 310 including a storage unit (not shown) such as a semiconductor memory and a hard disk, a processing unit (not shown), an input unit 320, and a display unit 330. . The processing unit executes the simulation method described with reference to FIG.

  The computer 300 may be provided with a removable storage medium (not shown) and a driver capable of writing / reading the storage medium. A program for executing the simulation method described with reference to FIG. 1 may be recorded in a storage medium in advance, and the program read from the storage medium may be executed. The program may be stored (installed) in the storage unit of the computer 300 and executed. Although not shown, the computer 300 may be connectable to a network, for example. You may acquire the program which performs a simulation method via a network.

(3) Action / Effect The simulation method shown in the embodiment sets a road surface model 30 that sets a road surface model 30 that simulates a road surface on which a pneumatic tire contacts the ground with a finite number of elements, and sets a predetermined internal pressure in the tire model 10. In addition, a boundary condition that determines the distance between the tire model 10 and the road surface model 30 so that a predetermined load is generated between the tire model 10 and the surface of the road surface model 30 while the tire model 10 and the road surface model 30 are in contact with each other. , A contact detection step for detecting a node in contact with the road surface model 30 among nodes of elements constituting the tire model 10, and a node detected in the contact detection step is set in a restrained state. Calculation of the natural frequency of the tire model with the restraint step and the node in contact with the road surface model 30 in a restrained state And a natural frequency calculating step.

  Conventionally, it has been difficult to analyze the deformation due to the ground contact of the tire model and the natural frequency of the tire model at the same time because the types of calculation are different, and therefore a hammer that applies an external force to the tread portion of the tire model in a non-ground state. Although the ring test was performed on the computer, if a model in which the tire model 10 and the road surface model 30 are modified so as to constrain the nodes that are in contact with the road surface model 30 is used, the tire model is deformed due to contact with the road model. It was found that the frequency can be analyzed. Boundary conditions for the tire model 10 to contact the surface of the road surface model 30 are set, deformation caused by the tire model 10 contacting the road surface model 30 is calculated, and the road surface model 30 is contacted based on the calculation result. The tire model 10 and the road surface model 30 are corrected so as to constrain the nodes. The natural frequency is analyzed using the modified tire model 10 and the road surface model 30. Thus, the tire model 10 can be applied to the road surface by separately performing two types of calculations, namely, calculation of deformation of the contact surface of the tire due to contact with the road surface, which was difficult to analyze simultaneously, and calculation of the natural frequency. The natural frequency in the grounded state can be analyzed. As a result, the natural frequency in a state where the tire is actually used can be obtained.

    In the embodiment, in step S2, a wheel model setting step for setting the wheel model 20 and a complex model setting step for setting a complex model that is a complex of the wheel model 20 and the tire model 10 are executed. The Since the tire model 10 and the wheel model 20 have different natural frequencies, boundary conditions are set so that the tire model 10 that is a part of the composite model and the road surface model 30 are in contact with each other as in this embodiment. The natural frequency of the composite model can be analyzed by placing a node in contact with the road surface model 30 among the nodes of the elements constituting the tire model 10 into a restricted state.

(4) Other Embodiments As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it is understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. Should not. From this disclosure, various alternative embodiments and examples will be apparent to those skilled in the art. For example, the embodiment of the present invention can be modified as follows.

  The simulation method according to the present embodiment includes step S3 of creating a composite model 30 in which the wheel model 20 is assembled to the tire model 10. However, step S3 for creating the complex model 30 is not essential.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

The sample tire model was a pneumatic tire of size 225 / 45R17 in which grooves and land portions were formed. A tire model of this pneumatic tire was created and grounded with the following internal pressure and load set, and the natural frequency was calculated.
・ Internal pressure 220kPa
・ Load 4KN

  FIG. 7 is a schematic diagram for explaining a tire model 10 (referred to as Example 1) in which the natural frequency is analyzed in the ground contact state, and FIG. 8 is a tire model 100 in which the natural frequency is analyzed in the non-ground state (comparison). It is a schematic diagram explaining Example 1). As shown in FIG. 7, in the tire model of Example 1, the deformation due to the stress S due to contact with the ground is represented.

  An error index was calculated for Comparative Example 1 and Example 1. The results are shown in Table 1. The error index is expressed by the following formula.

  Error index = ((calculated natural frequency) / (actually measured natural frequency)) × 100

  As shown in Table 1, in Comparative Example 1 in which the natural frequency was calculated in the non-grounded state, the error index was 91, whereas in Example 1 in which the natural frequency was calculated in the grounded state, the error index was calculated. Was 99. That is, according to the method of the embodiment of the present invention, it has been found that a natural frequency closer to the natural frequency of the actual tire can be obtained.

  DESCRIPTION OF SYMBOLS 10 ... Tire model 20 ... Wheel model, 21 ... Rim part, 22 ... Disc part, 23 ... Bolt hole, 30 ... Road surface model, 300 ... Computer, 310 ... Main-body part, 320 ... Input part, 330 ... Display part

Claims (3)

A simulation method for analyzing the natural frequency of a tire model in which a pneumatic tire is divided into a finite number of elements,
A road surface model setting step for setting a road surface model simulating the road surface on which the pneumatic tire contacts the ground with a finite number of elements;
A predetermined internal pressure is set on the tire model, and boundary conditions are set to determine a distance between the tire model and the road surface model so that a predetermined load is generated between the tire model and the surface of the road surface model. A boundary condition setting step;
A contact detection step of detecting a node in contact with the road surface model among nodes of the elements constituting the tire model;
A constraining step of constraining the nodes detected in the contact detecting step;
And a natural frequency calculating step of calculating a natural frequency of a tire model in which the nodes in contact with the road surface model are in the restrained state. A wheel model setting step for setting a wheel model obtained by dividing a wheel on which the pneumatic tire is mounted into a finite number of elements;
A composite model setting step for setting a composite model that is a composite of the wheel model and the tire model;
The simulation method according to claim 1, wherein in the boundary condition setting step, boundary conditions are set so that the tire model constituting the complex model and the road surface model are in contact with each other.   The simulation apparatus which performs the simulation method as described in any one of Claim 1 or 2.

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