JP2006018422A - Tire finite element modelling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for more efficiently modelling a tire finite element having a complicated tread pattern as well as changing a design than usual. <P>SOLUTION: This is a method for generating a tire finite element model having a concave-and-convex form in its tread. In addition, the method includes a step which acquires a finite element model including a tread which reproduces a tire tread, a step which acquires a boundary surface model on which a convex-and-concave part corresponding to the concave-and-convex form of the tread is formed, a step which regulates the concave-and-convex form of the tread by arranging the boundary surface model in at least partial area of the tread of the finite element model, and a resetting step which resets a finite element constituting the tread of the tire finite element model in accordance with the regulated concave-and-convex form of the tread. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of creating an analysis model when evaluating tire characteristics by a finite element method.

Various methods for predicting tire characteristics using a finite element method and designing tires based on the tire characteristics have been proposed. Each of these methods creates a finite element model of the tire using a computer, reproduces the stationary state or rolling state of the tire using the created tire model, and determines specific physical quantities that act on this tire model. The tire characteristics are calculated and evaluated.
Thus, by evaluating tire characteristics on a computer, a tire having excellent tire characteristics can be designed without actually manufacturing the tire.

By the way, the tire tread pattern is difficult to model due to the complexity of its configuration, and much time and effort have been spent on modeling the tread pattern.
In addition, the tread pattern has a great influence on the hydroplaning performance, tire wear performance, or cornering performance of the tire. Therefore, the tread pattern needs to be modeled as faithfully as possible.

Conventionally, for tread pattern modeling, mesh is divided based on the CAD data of the tread pattern drawn on a two-dimensional plane, and it is swept in the thickness direction while matching the curvature in the tire circumferential direction and cross-sectional direction. A method of creating a finite element model of a tread portion has been proposed (see, for example, Patent Document 1).
Also, a two-dimensional plane model of the tread pattern divided into meshes is created, the groove bottom line is set, the groove depth direction is calculated, the two-dimensional plane model is transferred to the surface of the tire tread portion, and the tread pattern is finite A method for creating an element model has been proposed (see, for example, Patent Document 2).
JP 2001-282873 A JP 2002-283816 A

  However, in the method described in Patent Document 1 and Patent Document 2, the tread part including the tread pattern is modeled by dividing a block having a complicated shape into a two-dimensional plane and then aligning it with the tire surface. It is necessary to sweep. The tire surface shape is generally formed of a curved surface having a plurality of curvatures. Sweeping the mesh created on the two-dimensional plane by recognizing the surface is the normal direction calculation and tread pattern edge. Part processing is required. Further, when a design change such as a change in the shape of a tread pattern is performed, a process of regenerating a mesh on a two-dimensional plane and sweeping it again is necessary. Furthermore, since the conventional technology is based on the premise that the tread pattern and the tire body part are individually modeled, it is not always an efficient method. It wasn't.

In order to solve the above problems, the present invention provides a tire finite element model creation method in which a tread portion is provided with an uneven shape, the step of obtaining a finite element model including a tread portion reproducing a tire tread, and a tread. Obtaining a boundary surface model having an uneven shape corresponding to the concavo-convex shape of the portion on the surface, and disposing the boundary surface model in at least a partial region of the tread portion of the finite element model, A step of defining the uneven shape of the portion, and a resetting step of resetting the finite elements constituting the tread portion of the tire finite element model according to the specified uneven shape of the tread portion. To do.
Further, the resetting step can reset the finite element constituting the tread portion by newly generating a node along the specified uneven shape of the tread portion.
Further, the resetting step can be reset by moving a node inside the finite element constituting the tread portion.
Furthermore, the resetting step can reset the shape of the finite element by integrating one node among the plurality of nodes of the finite element constituting the tread portion by overlapping with another node. .

The present invention also includes a determination step for determining whether or not a finite element constituting the reset tread portion satisfies a predetermined condition, and the reset tread portion is configured as a result of the determination. Preferably, when the finite element does not satisfy a predetermined condition, the method further includes resetting the finite element and repeating until the finite element satisfies the predetermined condition.
The predetermined condition is set based on at least one of the size of the finite element, the internal angle of the finite element, the aspect ratio of the finite element, and the twist of the finite element.

The present invention obtains a finite element model including a tread portion reproducing a tire tread and a boundary surface model having a rugged shape corresponding to the rugged shape of the tread portion on the surface, and at least one of the tread portions of the finite element model. By arranging the boundary surface model in the region of the portion, the uneven shape of the tread portion is defined, and the finite elements constituting the tread portion of the tire finite element model are reset.
Therefore, according to the present invention, the boundary surface model can be created using CAD data of the vulcanization mold at the time of tire manufacture, and the tire finite having a tread pattern having a complicated shape using the boundary surface model. An element model can be created efficiently.
In addition, when changing the design of the tread pattern, the tread part can be changed according to the changes made to the interface model, so the tire finite element model can be changed efficiently even when the design of the tread pattern is changed. can do.
Furthermore, in the present invention, the tread pattern and the tire body portion do not necessarily need to be individually modeled, and a smooth tire model (a tire model having no groove at all) or a tire model having only a circumferential groove, A tread pattern with a complicated shape can also be created. In particular, in such a case, since the process of combining the tread pattern and the tire body portion is unnecessary, the man-hour for creating the tire model is greatly reduced, and efficient model creation can be realized.

  A tire finite element model creation method according to the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

  FIG. 1 is a schematic diagram showing an outline of a simulation apparatus that executes a tire model creation method of the present invention, simulates an actual tire characteristic test, and executes an analysis of tire characteristics.

The simulation apparatus 1 executes various arithmetic processes and centrally controls each part, and functions as a work area of the CPU 2, processing programs executed by the CPU 2, and the CPU 2. The CPU 2 and the memory 3 are general-purpose computers connected via a bus. The memory 3 stores processing results of the processing program to be executed and various data.
As the memory 3, a DRAM (Dynamic Random Access Memory) that stores information by storing electricity in a capacitor, a SRAM (Static Random Access Memory) that uses a logic circuit without using a capacitor, a CPU, There is a semiconductor storage device such as a nonvolatile read-only ROM (Read Only Memory) that stores an execution program or the like.

The simulation apparatus 1 is connected to an input device 5, an output device 6, and an external storage device 7 via an I / O interface 4, and exchanges data with these devices.
The input device 5 inputs various conditions such as model creation conditions, processing conditions, or characteristic calculation conditions, and representative examples include a keyboard and a mouse. The output device 6 displays an input result from the input device 5, an analysis result of tire characteristics, and the like, and representative examples include a display and a printer.
Examples of the external storage device 7 include a magnetic disk such as a flexible disk and an optical disk such as a CD and a DVD.

This simulation device 1 uses a Finite Element Method (FEM) software to create a tire analysis model (hereinafter referred to as a tire model) by a Finite Element Method, and after setting boundary conditions, The tire characteristics are analyzed by simulating a characteristic test.
Moreover, the simulation apparatus 1 creates a CAD model using CAD (Computer Aided Design) software.
The tire model creation method of the present invention is realized by such a simulation apparatus.

  In the present embodiment, a method for generating a tire model with a tread pattern by forming a tread pattern on a smooth tire model that is a finite element model using a mold model 104 of a tread pattern that is a CAD model is described. Apply.

  2 is a perspective view showing an example of a finite element model of a smooth tire, FIG. 3 is a partial perspective view showing an example of a mold model 104 by CAD, and FIG. 4 is a finite element model of a tire with a tread pattern. It is a perspective view which shows an example.

As shown in FIG. 2, the smooth tire model 100 is a finite element model including a tread portion, a belt portion, a carcass portion, a bead portion, a tread rubber portion, a side rubber portion, and a belt reinforcing layer. A tire model having a smooth shape.
The smooth tire model 100 includes a plurality of elements such as solid elements, membrane elements, or shell elements for each member. Each element divided into meshes is defined by defining each vertex of the element with a node, and data indicating a correspondence relationship between the element number and the node number defining the element is stored in the storage device. Each node is defined by three-dimensional space coordinates, and the node number and its space coordinates are stored in the storage device.
Such a smooth tire model 100 can be created by creating a three-dimensional model reproducing each member and combining the three-dimensional models. Further, the smooth tire model 100 may be created by creating a two-dimensional cross-sectional model of the smooth tire model 100 including each member and developing it. The method for creating the smooth tire model is not limited to these methods, and other methods may be used.

As shown in FIG. 3, the mold model 104 is a boundary surface model for forming a tread pattern shape on the smooth tire model 100. The boundary surface model is not particularly limited as long as it can represent the shape of the tread pattern. However, it is convenient to use a CAD model having a three-dimensional shape created by CAD software for ease of model creation.
The CAD model is represented by points, lines, surfaces, solids, etc., and has geometric information. In particular, recently, with the advancement of hardware, software functions have been expanded, and the improvement of the CAD software's geometric model creation function is particularly remarkable. For this reason, the use range of CAD software has been expanded even in the tire industry, and it can be used to create a tread pattern model relatively easily.

By the way, in actual vulcanization molding of a pneumatic tire, an unvulcanized tire is placed in a vulcanization molding die composed of an upper mold and a lower mold, and is placed inside the unvulcanized tire (green tire). A bladder made of an inflatable elastic hollow body is inserted. When the pressure heat medium for vulcanization (for example, high-temperature and high-pressure steam) is blown into the bladder, the bladder expands and the unvulcanized tire is pressed against the inner walls of the upper mold and the lower mold for a predetermined time. Heat.
In order to form a groove-like tread pattern on the outer peripheral surface of the tread portion of the tire, both molds are provided with irregularities corresponding to the tread pattern.

In the present invention, when the unvulcanized tire is vulcanized, a model in which the tire tread has an uneven portion corresponding to the tread pattern is referred to as a mold model 104, and straight grooves, lug grooves, and sipes are formed. Because of unevenness.
Therefore, in the present embodiment, the mold model 104 is illustrated as a three-dimensional structure model having a predetermined thickness, but may be a surface model having only irregularities corresponding to the tread pattern.

The tread pattern is formed by repeating a certain pattern on the tread portion 102 serving as a ground contact surface. The tread pattern is related to all characteristics such as driving, braking, turning performance, riding comfort, noise, rolling resistance, and wear, which are basic functions of the tire. Therefore, the shape of the tread pattern is an important design element, and in order to create a simulation model that can appropriately express the effect, modeling of the tread pattern is important.
Typical tread patterns include a rib-type pattern with excellent maneuverability and stability, low rolling resistance, low tire noise, excellent driving and braking power, and excellent traction on unpaved roads. There are a rib lug type pattern combining a rib type and a lug type, a snowy road, a block type pattern which is excellent in driving force and braking force and used for a muddy road.

In the present embodiment, since the tread pattern is formed by repeating a certain shape, the mold model 104 is partially created. However, the mold model 104 may have an annular structure that makes one round in the tire circumferential direction. .
As for the tread pattern of the tire, the tread pattern constituting the minimum unit (pitch) is repeatedly arranged in the circumferential direction. This repetition is generally called pitch variation. The pitch variation is a tread pattern design technique in which only a single frequency does not protrude in the circumferential direction by preparing pitches of several sizes and arranging them in various combinations in the circumferential direction. In a simulation in which this pitch variation is modeled faithfully and pattern noise is predicted, a die model over the entire circumference of the tire is required.
However, since cornering characteristics and wear characteristics are not easily affected by pitch variations, tire models are often modeled by arranging pitches of the same size in the circumferential direction. Therefore, the above-described mold model only needs to have a part in the tire circumferential direction, and does not necessarily require the entire circumference.

As shown in FIG. 4, the tire model 106 with a tread pattern has a tread pattern formed by straight grooves, lug grooves, and sipes in the tread portion 102 of the smooth tire model. Corresponds to the irregularities formed on the surface.
That is, the tire model 106 with a tread pattern is a model in which a tread pattern is formed by pressing the mold model 104 against the tread portion 102 of the smooth tire model 100.

In the present invention, a tire model with a tread pattern is created by correcting the tread portion of the smooth tire model 100 based on the mold model 104. Therefore, a tire finite element model having a tread pattern with a complicated shape is efficiently created. Can do.
A method for creating the tire model with a tread pattern will be described in detail later.

The tire model 106 with a tread pattern is a model of an actual tire and can be used for analysis of tire characteristics using the tire model.
As such tire characteristics, slip characteristics (frictional force, slip ratio, etc.) in the contact surface when simulating braking and acceleration conditions, stress characteristics on carcass when the tire is inflated, and hydroplaning are simulated. When simulating the wet grip performance when snowing, the snow performance of snow tires, cornering characteristics when simulating vehicle cornering (lateral spring characteristics), and tire deflection (deformation under load) when a load is applied to the tire Vertical spring characteristics, contact pressure, and vibration vibration comfort characteristics (envelope characteristics) when simulating how to absorb vibration transmitted from the road surface in the rolling state of the tire.

Next, a method for creating a tire model with a tread pattern will be described with reference to FIGS. 5 and 6 are diagrams for explaining a tire finite element model creation method according to the present invention, and FIG. 5 shows a case where the boundary surface and the tire model overlap and there is a portion where they overlap each other. FIG. 6 shows a case where there is a gap between the boundary surface and the tire model.
The boundary surface 108 is a boundary when the mold model 104 is superimposed on the smooth tire model 100. At this time, the mold model 104 moves into the inner region of the smooth tire model 100 to define the uneven shape of the tread portion.

FIG. 5 shows a case where the boundary surface exists inside the smooth tire model 100, and partially shows a cross-sectional view taken along the line AA of the smooth tire model 100 shown in FIG.
5A shows a state immediately before the mold model 104 overlaps the smooth tire model 100, and FIG. 5B shows a state where the mold model 104 overlaps the smooth tire model 100. FIG. c) shows a state in which the elements of the smooth tire model 100 are reset.

The smooth tire model 100 includes a cap 122, a belt 124, and a carcass 124, has node information and element information, and material property values corresponding to each material are given according to the analysis type. Since the smooth tire model 100 is an object to be analyzed by the finite element method, it is created using FEM software.
On the other hand, the mold model 104 has geometric information such as lines and surfaces. The mold model 104 is created by CAD software in order to easily create a tread pattern shape.

As shown in FIG. 5B, the boundary when the mold model 104 is moved to the inner region of the smooth tire model 100 and overlapped is the boundary surface 108, which corresponds to the tread pattern unevenness.
In this state, among the elements of the smooth tire model 100, elements located outside the boundary surface 108, that is, on the mold model 104 side are deleted (indicated by a dotted line in the figure), and a tread pattern shape is formed on the tread surface. Is done.
Further, when the boundary surface 108 crosses the element, the node located on the metal model 104 side of this element is deleted, and the outline is deleted.

After that, as shown in FIG. 5C, among the elements of the smooth tire model 100, the elements inside the boundary surface 108 are reset using newly generated nodes.
Here, when the node of the element is reset, the element shape collapses and causes a decrease in analysis accuracy. In the simulation analysis by the explicit method, the time increment at the time of executing the calculation is determined by the representative length of the element, the rigidity and density of the material. Therefore, when the shape of the element is distorted, for example, when a part of the side of the element is shortened, the representative element length is reduced and the analysis time increases. Therefore, sufficient consideration is required for the element shape after resetting the nodes.

6 shows a case where a part of the boundary surface exists outside the smooth tire model 100, and partially shows a cross-sectional view of the smooth tire model 100 shown in FIG.
6A shows a state immediately before the mold model 104 overlaps the smooth tire model 100, and FIG. 6B shows a state where the mold model 104 overlaps the smooth tire model 100. FIG. c) shows a state in which the elements of the smooth tire model 100 are reset. Although FIG. 5 shows the case where the boundary surface 108 exists inside the tire model 100, FIG. 6 shows the case where the boundary surface 108 exists outside the tire model 100.

A smooth tire model 100 created using FEM model creation software includes a cap 122, a belt 124, and a carcass 124, and has node information and element information. On the other hand, the mold model 104 is created using CAD software, and has geometric information.
As shown in FIG. 6B, the boundary surface 108 is a boundary surface when moving to the inner region of a part of the mold model 104 and moving to the inner region of the smooth tire model 100 and superimposing them. In FIG. 6B, since the recess of the mold model 108 is located outside the smooth tire model 100, a gap is formed between the recess of the mold model 104 and the surface of the smooth tire model 100.
In this state, among the elements of the smooth tire model 100, the elements of the smooth tire model 100 existing outside the boundary surface 108 are deleted, and the outline of the element is deleted (indicated by a dotted line in the figure).

As shown in FIG.5 (c), a node and an element are newly produced | generated in the clearance gap produced between the smooth tire surfaces. That is, the elements are reset so as to fill a gap formed between the boundary surface 108 and the smooth tire model 100 surface.
As the elements are reset, the elements outside the boundary surface 108 are deleted, and the shape of the tread pattern is formed on the tread surface.

Next, with reference to FIG. 7 to FIG. 12, a method for resetting the elements constituting the tread pattern when the boundary surface 108 exists inside the smooth tire model 100 will be described in detail using a two-dimensional model. To do.
Here, the surface shape of the smooth tire model 100 is changed to a surface shape along the surface of the mold model 104. That is, the node position and the element shape on the surface of the smooth tire model 100 are changed based on the mold model 104 that models the shape of the tread pattern.

FIG. 7 shows a state in which the mold model 104 is superimposed on the smooth tire model 100 in two dimensions. The interference state between the mold model 104 and the smooth tire model 100 is examined, and unnecessary elements of the smooth tire model 100 are checked. Is deleted.
By superimposing the mold model 104 on the smooth tire model 100, the boundary surface 108 between the smooth tire model 100 and the mold model 104 having a tread pattern shape is recognized.
Based on the boundary surface 108, nodes outside the smooth tire model 100 (shown in black in FIG. 7) such as nodes included in the mold model 104 are detected, and elements (elements A, A, and B) including those nodes are detected. Element B, element C, element F) are deleted.
Here, the outer nodes of the smooth tire model 100 are nodes that are not included in the smooth tire model 100 and are nodes existing on the mold model 104 side with the boundary surface 108 as a boundary.

FIG. 8 shows a state in which the outer nodes of the tire model are deleted, and a state in which new nodes are generated.
In such a state, first, elements (element A, element B, element C, element F) composed of nodes outside the smooth tire model 100 located outside the boundary surface 108 are deleted, and along the boundary surface 108. A new node is created. This node is a node necessary for an element constituting the tread pattern, and is an intersection of the contour line of the element included in the smooth tire model 100 and the boundary surface 108, or a connection point between the line segment and the line segment of the boundary surface 108. Is generated.
In addition, after a new node is generated, the remaining nodes (indicated by black in FIG. 8) outside the detected smooth tire model 100 are deleted.

FIG. 9 shows a state in which elements are reset according to new nodes. The remaining nodes (indicated by black in FIG. 8) of the detected tire model are deleted, and the elements (element D, element E, element H, element I) defined by the deleted nodes are newly added. Redefined as an element containing a node.
By resetting the elements of the tread portion, the element shape is changed, and a ridge line corresponding to the tread pattern shape is formed.

FIG. 10 shows a state where inappropriate elements among the reset elements are detected and these elements are changed. The element reset includes not only redefinition of an element including a new node, but also an inappropriate element change or element shape correction.
Inappropriate elements are elements that have a shape that may increase the processing time or decrease the analysis accuracy when finite element analysis is performed. For example, the size of the element, the inner angle of the element, etc. This is appropriately determined based on the aspect ratio of the element, the twist of the element, and the like.
The elements D and H shown in FIG. 9 are originally composed of four nodes when the boundary between the initial element shape and the mold model is recognized and cut out, and the elements are composed of five nodes. It is an example that has become an element. In general, since a two-dimensional finite element is defined by a three-node element or a four-node element, simulation cannot be executed as it is. In such a case, the inner angle of the element D or the element H is divided into two to divide the element. That is, element D and element H are divided into element D1 and element D2, or element H1 and element H2.

Hereinafter, a method for determining whether an element is appropriate or inappropriate will be exemplified.
When an appropriate element is determined based on the size of the element, the representative length of the element is used, and the representative length of the element is 0.2 times that of the element group adjacent to the element. Elements that are in the range of 2.0 times are appropriate elements, and other elements are inappropriate elements. The representative length is a value obtained by dividing the element volume by the maximum area of the element surface.
Judging whether the element is appropriate based on the element size is because the accuracy of physical quantity distribution such as stress distribution deteriorates in the vicinity when the element size is changed suddenly. This is to prevent the size of the element from changing extremely compared to the group.
Note that the representative length of the appropriate element is preferably set in the range of 0.5 to 1.5, and more preferably in the range of 0.8 to 1.2.

Among the simulation methods based on the finite element method, in particular, in the explicit method, the stable time increment is determined by Equation (1).
Δt ≦ L / √ (E / ρ) (1)
Where Δt is the time increment, L is the representative length of the element, E is the stiffness of the element, and ρ is the material density.
At this time, if the time increment Δt is small, the analysis time increases. Therefore, it is necessary to increase L / √ (E / ρ), which is the upper limit of the time increment Δt in the formula (1), and the range of the representative length of an appropriate element is related to the rigidity and material density of the element. Must be set according to
For example, in the case of a tire, the belt and the bead core have higher rigidity than other members made of a rubber material. Therefore, in many cases, the time increment is determined at the belt edge portion or the bead core. However, when the element size is small even in a tread portion made of a rubber material having low rigidity, the upper limit of the time increment is determined by the element of the tread portion. In such a case, it is necessary to set the range of the representative length of the appropriate element according to the relationship with the rigidity and material density of the element, and to increase the upper limit of the time increment Δt in the equation (1). It becomes.

When an appropriate element is determined based on the internal angle of the element, an element having an internal angle of 30 ° to 150 ° as an appropriate element is set as an appropriate element, and other elements are set as inappropriate elements.
The reason why the element is appropriate based on the inner angle of the element is that the analysis error increases when the inner angle of the element exceeds 180 ° or approaches 0 °. Therefore, it is preferable that the angle is 90 ° for a quadrilateral element and 60 ° for a triangular element. In the present invention, it is preferable that the inner angle of a suitable element is in the range of 60 ° to 120 °.
If the inner angle of the element exceeds 180 ° or 180 °, the element is subdivided by dividing the inner angle into two.

If an appropriate element is determined based on the aspect ratio of the element, an element having an aspect ratio in the range of 0.2 to 5.0 is set as an appropriate element, and other elements are set as inappropriate elements. .
The reason why the element is appropriate based on the element aspect ratio is that the analysis error increases as the element aspect ratio increases. Therefore, the aspect ratio is preferably closer to 1, and in the present invention, the aspect ratio of an appropriate element is preferably in the range of 0.5 to 2.0.
Further, when it is determined that the element is inappropriate based on the aspect ratio of the element, the shape of the element is changed. For example, in the case of an inappropriate hexahedron element, the shape is changed to a pentahedron or is changed to two elements of a pentahedron and a tetrahedron.

  If the appropriate element is determined based on the twist of the element, the element having the twist in the range of 0 to 45 °, preferably the element in the range of 0 to 20 ° is regarded as the appropriate element, and the other elements Is an inappropriate element. Such a twist of an element can be calculated by a known method using an element area and an element volume.

  Thus, by resetting the elements, it is possible to avoid an increase in time increment and a decrease in analysis accuracy when the finite element analysis is executed.

11 and 12 show another method for resetting inappropriate elements. In FIG. 10, the interior angle of an inappropriate element is divided into two and the element is divided. However, the resetting of the element is not limited to this, and a node located on the boundary surface 108 is moved or a smooth tire model is used. The shape of the element may be modified by moving the nodes included in 100.
In FIG. 11, the nodes located on the boundary surface 108 move along the boundary surface 108, so that inappropriate elements are reset. As shown in FIG. 10, when an inappropriate element (element D2, element H2) is detected even after the inappropriate element is subdivided by dividing the interior angle into two, the element is configured. A node on the boundary surface 108 moves along the boundary surface.

In FIG. 12, the nodes located on the boundary surface 108 move, and the nodes included in the smooth tire model 100 also move and are rearranged, and inappropriate elements are reset.
As shown in FIG. 11, when a small element (element E) is detected as compared with an adjacent element even after a node located on the boundary surface moves along the boundary surface 108, a smooth tire model is detected. The node included in 100 moves.

13 and 14 show an example of a method for resetting in the three-dimensional element. In the above description, a method for resetting inappropriate elements using a two-dimensional model has been described. However, a method for setting three-dimensional elements will be described below. The inappropriate element reset described here is reset by changing, dividing, or deleting elements by integrating moving nodes.
FIG. 13 shows two hexahedral elements made up of eight nodes as an example, and FIG. 14 shows a pentahedron element made up of six nodes as an example.

  As shown in FIG. 13A, the first element is composed of nodes (13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h), and the second element is a node (13e, 13f, 13g, 13h, 13i, 13j, 13k, 13l). Note that the nodes that move here are only the nodes that constitute the first element.

FIG. 13B and FIG. 13C show the resetting of the element when one node 13b included in the first element moves beyond the element thickness. That is, when the node 13b moves along the line segment 13b-13j and moves beyond the node 13f to a position closer to the node 13j, the node 13b is integrated (merged) with the node 13f as shown in FIG. )
At this time, the first element is composed of four tetrahedral elements (node 13a, node 13d, node 13e, node 13f, node 13d, node 13e, node 13f, node 13h, node 13cd, node 13f, An element composed of a node 13g, an element composed of a node 13d, a node 13f, a node 13g, and a node 13h).
Alternatively, as shown in FIG. 13C, the node 13b is merged with the node 13f, and the first element is an element composed of one pentahedron element (node 13a, node 13d, node 13e, node 13f, node 13h). ) And two tetrahedral elements (elements consisting of nodes 13c, 13d, 13f and 13g, elements consisting of nodes 13d, 13f, 13g and 13h).

  FIG. 13 (d) shows the resetting of the element when the two nodes (13b, 13c) included in the first element move beyond the element thickness. If two nodes (13b, 13c) exceed the element thickness, node 13b is merged with node 13f, node 13c is merged with node 13g, and the first element is one pentahedral element (node 13a, node 13d, node 13e, node 13f, node 13g, node 13h).

  FIG. 13E shows the resetting of the element when the three nodes (13a, 13b, 13c) included in the first element move beyond the element thickness. If three nodes (node 13a, node 13b, node 13c) exceed the element thickness, node 13a is merged with node 13e, node 13b is merged with node 13f, and node 13c is merged with node 13g. It is changed to one pentahedron element (node 13d, node 13e, node 13f, node 13g, node 13h).

  FIG. 13 (f) shows the resetting of the element when the four nodes (13a, 13b, 13c, 13d) of the first element move beyond the element thickness. If the four nodes (13a, 13b, 13c, 13d) exceed the element thickness, the first element is deleted.

As shown in FIG. 14A, the third element is composed of nodes (14a, 14b, 14c, 14d, 14e, 14f), and the fourth element is a node (14d, 14e, 14f, 14g, 14h, 14i). Note that the nodes that move here are only the nodes that constitute the third element.
FIG. 14B shows element resetting when one node 14b included in the first element moves beyond the element thickness. That is, when the node 14b moves along the line segment 14b-14h and moves to a position that approaches the node 14h beyond the node 14e, the node 14b is merged with the node 14e as shown in FIG.
At this time, the first element is divided into two tetrahedron elements (an element composed of a node 14a, a node 14d, a node 14e, and a node 14f, an element composed of a node 14a, a node 14c, a node 14e, and a node 14f).

FIG. 14C shows the resetting of the element when the two nodes (14b, 14c) included in the first element move beyond the element thickness.
If two nodes (13b, 13c) exceed the element thickness, node 13b is merged with node 13e, node 13c is merged with node 13f, and the first element is a tetrahedral element (node 13a, node 13d, node 13e, and node 13f).

FIG. 14D shows the resetting of the element when three nodes (13a, 13b, 13c) included in the first element move beyond the element thickness.
If the three nodes (14a, 14b, 14c) exceed the element thickness, the third element is deleted.

Thus, by resetting the elements, it is possible to avoid an increase in time increment and a decrease in analysis accuracy when the finite element analysis is executed.
As examples of element resetting, an example of changing and splitting an element by creating a new node, an example of modifying an element shape by moving a node, and an example of changing, splitting, and deleting an element by merging nodes However, the resetting of the elements is not limited to these, and the resetting may be appropriately combined.

FIG. 15 is a flowchart illustrating an example of a flow of a method for creating a tire model with a tread pattern.
The smooth tire model 100 and the mold model 104 are set (step S101). A smooth tire model 100 that forms a tread pattern and a mold model 104 having irregularities corresponding to the tread pattern are read and displayed on the display (output device 6) of the simulation apparatus 1.
The smooth tire model 100 and the mold model 104 are not limited to models created by the simulation apparatus 1, and model data created by other apparatuses may be read via the I / O interface 4.

The mold model 104 is overlaid on the smooth tire model 100 to recognize the boundary surface 108 (step S102).
The mold model 104 is moved to a position where the tread pattern of the tread portion of the smooth tire model is to be formed, and a surface corresponding to the unevenness of the tread pattern is detected. That is, the surface shape of the tread pattern is read based on the mold model 104.

It is determined whether or not a node exists outside the boundary surface 108 among the elements of the smooth tire model 100 (step S103). The outside of the boundary surface 108 refers to the mold model 104 side with the boundary surface 108 as a boundary.
Here, it is determined whether or not the node defined by the three-dimensional space coordinates is on the mold model 104 side with the boundary surface 108 as a boundary.

  In step S103, when it is determined that the nodes of the smooth tire model 100 exist outside the boundary surface 108, the elements of the smooth tire model 100 including only the nodes outside the boundary surface 108 are deleted (step S104). An element defined only by a node outside the boundary surface 108 is an element that is unnecessary for forming a tread pattern.

  A new node is generated along the boundary surface 108 (step S105). A new node is generated at the intersection of the element included in the tire model and the boundary surface 108, or at the connection point between the line segment and the line segment of the boundary surface 108, and this node is used to construct a tread pattern. .

  On the other hand, if it is determined in step S103 that no smooth tire model node exists outside the boundary surface, a new node is generated in a region between the boundary surface 108 and the smooth tire model (step S106). For example, when changing the groove width of the tread pattern to be narrow, a new element is created in the groove of the existing tread pattern to reduce the groove width. At that time, a node for defining the element is generated.

  The element is reset (step S107). The resetting is executed based on a newly generated node or the like, and a tread pattern is formed on the surface of the tread portion. The element resetting may be modification of the element shape and change of the element type.

  It is determined whether the reset element satisfies a predetermined condition (step S108). Predetermined conditions are set according to the element size, element interior angle, element aspect ratio, and element twist, and by setting the predetermined conditions, the time increment when performing finite element analysis is increased. And degradation of analysis accuracy can be avoided.

  If it is determined in step S108 that the reset element satisfies a predetermined condition, the process ends.

On the other hand, if it is determined in step S108 that the reset element does not satisfy the predetermined condition, the element is reset (step S107), and the process is repeated until the element satisfies the predetermined condition.
In the element resetting, the element shape is modified and the element type is changed so that the element size, the element inner angle, the element aspect ratio, and the element twist satisfy predetermined conditions.
The modification of the element shape is performed by moving the node, and the element is modified without changing the element type. For example, in the case of a hexahedral element, the node is moved as it is in the hexahedron and reset so as to be corrected so as to satisfy a predetermined condition.
On the other hand, the element type is changed by dividing elements or merging nodes. For example, in the case of a hexahedral element, it is divided into a pentahedron and a hexahedron, and is reset so as to satisfy a predetermined condition.

  Next, another embodiment will be described with reference to FIGS. In the above-described embodiment, the embodiment in which the longitudinal groove, the lateral groove, and the tread pattern are formed in the smooth tire model 100 having a smooth tread surface has been described, but the present invention is not limited thereto, and in the tire model with a tread pattern, The present invention can also be applied when changing the tread pattern.

FIG. 16A shows a simplified two-dimensional shape of the tread pattern of the tire before the change, and FIG. 16B schematically shows the two-dimensional shape of the tread pattern of the tire after the change. .
The tire tread pattern before the change includes five straight grooves 130, three lug grooves 132, and a plurality of sipes 140.
In the mold model, the groove width of the straight groove 130 is expanded, the number of sipes 140 is increased, and the tread pattern is corrected based on the mold model. When this mold model is created by CAD software or the like, the shape can be corrected relatively easily, so that the design change of the tread pattern can be performed more efficiently than in the past.

  FIG. 17A shows a simplified shape of the tread surface before the change, and FIG. 17B shows a simplified shape of the tread surface after the change. This is an example in which a groove is added to the hexahedral shape by changing the inclination angle of the groove wall.

  Therefore, changes in the tread pattern include a change in groove width, a change in groove wall angle, and addition or deletion of grooves and sipes.

  As described above, according to the present invention, a plurality of mold models having different tread patterns can be created, and the tread portion can be corrected based on the mold models. A tire model for analyzing changes and the like can be created in a short period of time. Therefore, simulation of the tire model can be repeatedly performed, and tire development can be performed more quickly through such simulation.

  The tire model generation method according to the present invention has been described in detail above. However, the present invention is not limited to the above embodiment, and various improvements and modifications are made without departing from the scope of the present invention. May be.

It is the schematic which shows the outline of the simulation apparatus which performs analysis of a tire characteristic. It is a perspective view which shows an example of the finite element model of a smooth tire. It is a partial perspective view which shows an example of the metal mold | die model by CAD. It is a perspective view which shows an example of the finite element model of a tire with a tread pattern. It is a figure which shows the case where a boundary surface exists in the inside of a smooth tire model. It is a figure which shows the case where a boundary surface exists in the exterior of a smooth tire model. It is a figure which shows the state with which the metal mold | die model was piled up on the smooth tire model. It is a figure which shows the state from which the node outside the tire model was deleted, and the state where a new node is produced | generated. It is a figure which shows the state in which an element is reset according to a new node. It is a figure which shows the state in which an inappropriate element is reset. It is a figure which shows the other method of resetting an inappropriate element. It is a figure which shows the other method of resetting an inappropriate element. It is a figure which shows an example of the method of resetting in a three-dimensional element. It is a figure which shows an example of the method of resetting in a three-dimensional element. It is a flowchart which shows an example of the flow of the preparation method of a tire model with a tread pattern. It is a figure for demonstrating other embodiment which changes a tread pattern. It is a figure for demonstrating other embodiment which changes a tread pattern.

Explanation of symbols

1 Simulation device 2 CPU
3 memory 4 interface 5 input device 6 output device 7 external storage device 100 smooth tire model 102 tread part 104 mold model 106 tire model with tread pattern 108 boundary surface 122 cap 124 carcass 124 belt 130 straight groove 132 lug groove 140 sipe

Claims (6)

A method for creating a tire finite element model in which an uneven shape is provided in a tread portion,
Obtaining a finite element model including a tread portion reproducing a tire tread;
Obtaining a boundary surface model having an uneven surface corresponding to the uneven shape of the tread on the surface;
Defining the concavo-convex shape of the tread portion by disposing the boundary surface model in at least a partial region of the tread portion of the finite element model;
And a resetting step of resetting the finite elements constituting the tread portion of the tire finite element model in accordance with the concavo-convex shape of the tread portion defined.   2. The tire finite element model creating method according to claim 1, wherein the resetting step resets a finite element constituting the tread portion by newly generating a node along the specified uneven shape of the tread portion.   The tire finite element model creation method according to claim 1 or 2, wherein the resetting step is reset by moving a node inside the finite element constituting the tread portion.   The resetting step resets the shape of the finite element by integrating one of the plurality of nodes of the finite element constituting the tread portion with another node. 4. The tire finite element model creation method according to any one of items 3. A determination step of determining whether or not the finite element constituting the reset tread portion satisfies a predetermined condition;
If the finite element constituting the reset tread portion does not satisfy a predetermined condition as a result of the determination, the step of resetting the finite element and repeating until the finite element satisfies a predetermined condition is further performed. The tire finite element model creation method according to any one of claims 1 to 4.   The tire finite element creation method according to claim 5, wherein the predetermined condition is set based on at least one of a finite element size, a finite element interior angle, a finite element aspect ratio, and a finite element twist.

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