JP4586436B2 - How to create a tire model - Google Patents

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 uses a computer to create a finite element model of the tire, uses the created tire model to reproduce the stationary or rolling state of the tire, and at this time the specific material properties that act on the tire model The tire characteristics are evaluated by calculating the value. By using this tire characteristic, a tire having excellent tire characteristics can be designed without actually manufacturing the tire.

As a method of creating a tire model used for such a tire simulation, the tire body part element model is set by dividing the two-dimensional shape of the tire body part in the circumferential direction and dividing the element, and more detailed than the tire body part element model. There is proposed a method of creating a finite element model of a tire by setting a tread pattern part element model divided into elements and combining the tread pattern part element model with a tire body part element model (see, for example, Patent Document 1). .)
Japanese Patent No. 3314082

By the way, the actual tire manufacturing process generally includes a first molding process for molding the green tire casing 100 and a second molding process for molding the finished green tire 108 (green tire) (see the broken line in FIG. 9B). , A vulcanization step of vulcanizing the green tire 108 is included.
In the first molding step, as shown in FIGS. 9A and 9B, a carcass member P, a pair of bead core members Bd, a pair of bead filler members Bf, and a pair of side tread members S are rotated. A body-shaped raw tire casing 100 is formed.
In the second forming step, a tread / belt portion 106 having a rotating body shape having a tread member T and a belt member Be is formed, and the central axis of the rotating body is aligned with the inner peripheral surface side of the formed tread / belt portion 106. In this state, the raw tire casing 100 is disposed, and in this state, the raw tire casing 100 is expanded, and the green tire 108 is molded by pressing the raw tire casing 100 onto the inner peripheral surface of the tread / belt portion 106.

In the vulcanization process, the green tire 108 is placed in a vulcanization mold (mold), and a vulcanization bladder (not shown) that can be expanded and contracted from the inner peripheral surface side of the green tire 108 is inflated. The tire 108 is expanded so as to conform to the shape of the inner surface of the vulcanization mold, and then the temperature of the vulcanization mold and the vulcanization bladder is increased to vulcanize the expanded green tire 108.
Therefore, in the second molding step, the tire casing 100 is expanded, and in the vulcanization step, pressure is applied from the inner peripheral surface side of the green tire 108 using the vulcanization bladder, and the green tire 108 is expanded.
In particular, when organic fibers are used as the reinforcing cord in the tire, the tire cross-sectional shape is the level of tension applied to the reinforcing cord or the ground contact shape (tread surface shape) of the tire when the tire is grounded to the ground surface. It has a big impact. Further, the tension and the ground contact shape applied to the reinforcing cord have a great influence on tire characteristics such as rolling resistance characteristics, wear characteristics, durability characteristics, steering stability, vibration riding comfort characteristics, wet characteristics and noise characteristics.

Therefore, in order to design a tire having excellent tire characteristics, it is important to accurately reproduce the tire cross-sectional shape and reproduce the initial stress applied to the reinforcing cord in consideration of the tire manufacturing process. In particular, the initial stress applied to the belt layer and the belt reinforcing layer has a great influence on the tire ground contact characteristics.
The present invention has been made in view of such problems, and a tire capable of appropriately reproducing the initial stress of the tire reinforcement cord, particularly the belt layer and / or the belt reinforcement layer, and accurately simulating the tire characteristics. The purpose is to provide a model creation method.

In order to achieve the above object, a tire model creation method according to the present invention is a tire model creation method for creating a tire model in consideration of a tire manufacturing process for analyzing tire characteristics by simulation in a simulation device. A step of creating a two-dimensional cross-sectional model in which the simulation device reproduces a plurality of members including at least a carcass portion, a bead portion, and a reinforcing cord layer constituting a tire by dividing a mesh into a plurality of elements; but with deploying the two-dimensional cross-sectional model linearly with mesh divided into elements of a predetermined number of the deployment direction element, the step of creating a three-dimensional linear model comprising a plurality of three-dimensional finite element, the simulation device, the said 3-dimensional linear model about a predetermined straight line Is deformed in order to give a forced displacement for each node of the plurality of finite elements of the three-dimensional linear model from the edge, rounded to the 3-dimensional linear model about said predetermined straight line, deformation annularly a deformation step of creating a three-dimensional model by the simulation device, and a coupling step of creating a tire model by combining both end surfaces of the three-dimensional model deformed in an annular, said simulation apparatus, said tire The model includes an initial stress applying step of applying an initial stress acting on the reinforcing cord layer as an initial stress generated in the reinforcing cord in the tire manufacturing process .
Here, the deformation step includes the initial stress applying step, performs a deformation analysis in which each node of the plurality of finite elements is deformed in order by applying a forced displacement, and calculates a stress generated in the reinforcing cord layer. Preferably, the initial stress acting on the reinforcing cord layer applied in the initial stress applying step is calculated based on the calculated stress.
Moreover, it is preferable that the said initial stress provision step provides the initial stress which acts on the said reinforcement cord layer after the said coupling | bonding step.
The reinforcing cord layer preferably includes at least one of a belt layer and a belt reinforcing layer.
Further, in the deformation step, a material property value is given to a member model of the member including at least the reinforcing cord layer in the three-dimensional linear model, and the three-dimensional linear model is annularly formed by executing a simulation. It is preferable to be deformed.
Moreover, it is preferable that the material property value is set only in the reinforcing cord layer .
The physical property value of the material preferably includes at least one of specific gravity and tensile elastic modulus, bending elastic modulus and Poisson's ratio indicating mechanical properties .

The present invention creates a two-dimensional cross-sectional shape of a tire model, develops it in a straight line, and then transforms it into an annular shape (toroidal shape) as in the tire manufacturing process. At this time, by deforming the linear tire model, stress acts on the member model including the tire reinforcing cord constituting the tire model.
According to the present invention, it is possible to provide a tire model creation method capable of appropriately reproducing the initial stress of the tire reinforcement cord, particularly the belt layer and the belt reinforcement layer, and accurately simulating the tire characteristics.

Hereinafter, the tire model creation method of the present invention will be described in detail based on the preferred embodiments 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. A memory 3 for storing processing results of the processing program to be executed, various data, and the like is provided, and the CPU 2 and the memory 3 are connected via a bus.
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 the I / O interface 4, and exchanges data with them.
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.

  Such a simulation apparatus 1 creates a tire analysis model (hereinafter referred to as a tire model) by a finite element method in accordance with an input from an operator, sets simulation conditions, and then simulates a tire characteristic test. By analyzing the tire characteristics.

FIG. 2 is a perspective view showing an example of a tire secondary cross-section model. 2 dimensional section model is a two-dimensional cross-sectional shape of the tire model to be created in three-dimensional space, the tread portion, a belt portion, a carcass portion, a bead portion, the tire circumferential of the tire model which includes a support Idogomu portion and the belt reinforcing layer It reproduces the cross section perpendicular to the direction.
The two-dimensional cross-sectional model is mesh-divided into a plurality of elements in response to operator input. Each element is represented by defining a vertex with a node, and data indicating the correspondence between the element number and the node number is stored in the storage device. The node coordinates are defined by three-dimensional space coordinates, and the node numbers and the space coordinates are stored in the storage device.

  The two-dimensional section created here is not limited to a plane perpendicular to the tire circumferential direction when a tire model is created. For example, considering that the tire model is mesh-divided by inclining at a constant angle with respect to the tire circumferential direction, a cross section inclined with respect to the tire circumferential direction may be assumed in advance to be a two-dimensional cross section.

FIG. 3 is a perspective view showing an example of a tire three-dimensional linear model. The tire three-dimensional linear model is a three-dimensional finite element model created by developing the tire two-dimensional cross-sectional model shown in FIG. 2 in a predetermined linear direction (Z direction). When the two-dimensional section model is developed in a straight line, the mesh is divided in the Z direction. The tire three-dimensional straight line model created in this way is represented by a plurality of elements such as a solid element, a membrane element or a shell element.
The number of elements divided in the Z direction is preferably set by calculating in advance the number of elements in the circumferential direction of the final tire model in order to omit the process of resetting the number of elements later.
Note that the length in the Z direction set here is the length of the reference portion (reference portion for deformation) in the process of creating a tire model by deforming a tire three-dimensional linear model described later.

FIG. 4 is a diagram showing how the tire three-dimensional linear model is deformed. After the material physical property values are given to the tire three-dimensional linear model according to the input from the operator, a forced displacement is given to each node from one end with the straight line O as the center, and the tire three-dimensional linear model in turn. Is deformed, the tire three-dimensional linear model is rounded in a toroidal shape (annular).
This process is executed by performing a simulation calculation on a tire three-dimensional linear model given material property values.

Specifically, for example, a translational motion is performed on all nodes that give a forced displacement, excluding nodes on the joint surface at the other end, and rounded in order from a point that exceeds a predetermined reference line. Thus, the stress generated in the reinforcing cord is calculated by performing deformation analysis.
Based on this stress, an initial stress acting on the reinforcing cord is calculated. The initial stress can be calculated by applying a predetermined mathematical process such as adding a numerical value to the generated stress.

  Here, the circumferential length at the reference portion of the tire model is the length in the linear direction (Z direction) of the tire three-dimensional linear model shown in FIG. Therefore, the tread side that is outside the tire radial direction from the reference portion of the tire model is extended by deformation, and the bead core side that is inside the tire circumferential direction is contracted.

However, in the actual tire manufacturing process, the initial stress applied to each member of the tire is due to the pressure applied to the green tire by inflating the bladder in the vulcanization process, and the initial stress is only tensile stress. Therefore, no compression force acts in the actual tire manufacturing process.
In addition, the initial stress of the members other than the tire reinforcing cord has less influence on the tire characteristics than that of the reinforcing cord.
Therefore, the material property values need not be set for members other than the reinforcing cord.

  On the other hand, the material property value of the tire reinforcement cord is set based on the actual value, and the elastic modulus of the rubber part and the bead core is set to a small value less than the elastic modulus of the unvulcanized rubber. The Poisson's ratio is set to zero.

By doing so, it is possible to appropriately reproduce the initial stress of the tire reinforcing cord, particularly the belt layer and the belt reinforcing layer.
However, the method for setting the material physical property value is not limited to the above. For example, assuming that the initial stress applied to the tire reinforcing cord, particularly the belt layer and / or the belt reinforcing layer is important, the material physical property value is Only the belt reinforcing layer (reinforcing cord) is set, and the members other than the reinforcing cord have little influence on the tire characteristics, so that the material property value does not need to be set.

  Examples of such material property values include specific gravity, tensile elastic modulus showing mechanical properties, bending elastic modulus, Poisson's ratio, and the like.

FIG. 5 is a perspective view showing an example of a tire three-dimensional finite element model. The tire three-dimensional linear model deformed into a toroid has cross sections (discontinuous portions) that are not joined. That is, in the tire three-dimensional straight line model, both cross-sections which were end portions are in contact with each other by being deformed into a toroidal shape, but the nodes on this surface are doubly present and are not constrained to each other.
Therefore, discontinuous parts are joined by merging overlapping node coordinates to form a shared node. Since the tire model created in this manner appropriately reproduces the initial stress applied to the tire reinforcement cord, the tire characteristics can be accurately simulated.
FIG. 6 is a diagram illustrating an example of an initial stress distribution applied to the belt layer and the belt reinforcing layer. 5 is an example of an initial stress distribution acting on a tire reinforcing layer in the deformation analysis shown in FIG. 4.

FIG. 7 is a diagram showing a processing flow of a method for creating a tire three-dimensional finite element model.
A tire two-dimensional section model is set (step S101). Tread portion, a belt portion, a carcass portion, a bead portion, a two-dimensional cross-sectional shape perpendicular to the tire circumferential direction of the tire model which includes a support Idogomu portion and the belt reinforcing layer, as a two-dimensional cross-sectional model created.
The two-dimensional section model is mesh-divided into a predetermined number of elements in accordance with an input operation by the operator.

  The tire two-dimensional cross-sectional model is developed linearly, and a three-dimensional straight tire model is set (step S102). The two-dimensional cross-sectional model created in step S101 is developed in the linear direction to create a tire three-dimensional linear model. The length in the linear direction of the three-dimensional tire model set here is the length of the deformation reference portion in step S103.

  The three-dimensional straight line model is deformed (step S103). After assigning material property values to the tire three-dimensional linear model created in step S102, a forced displacement is applied to each node from one end, and the tire three-dimensional linear model is deformed into a toroidal shape. . Here, the material property values need not be set for all the member models of the tire model, and may be set for members that affect the tire characteristics, such as tire reinforcement cords, for example.

The discontinuous portions are combined (step S104). In the tire model created in step S103, the nodes in the cross section (discontinuous portion) corresponding to both ends exist in a double state and are not constrained to each other. To connect discontinuous parts.
Thus, the created tire model is a model to which an initial stress is applied in advance, and an accurate analysis result can be obtained by simulating tire characteristics using this tire model.

By following the above procedure, it is possible to appropriately set the initial stress applied to the belt portion reinforcing cord layer in the actual tire manufacturing process, and it is possible to accurately simulate various performances of the tire.
The tire characteristics in the simulation using such a tire model include the slip characteristics (friction force, slip ratio, etc.) in the contact surface when simulating the braking state and acceleration state, and the carcass when the tire is inflated. Such stress characteristics, wet grip performance when simulating hydroplaning, snow performance on snow tires, cornering characteristics (lateral spring characteristics) when simulating vehicle cornering, tire deflection by applying a load to the tire (load load) Vertical spring characteristics and ground pressure when simulating (deformation of time), and vibration riding comfort characteristics (envelope characteristics) when simulating how to absorb vibration transmitted from the road surface in tire rolling conditions .

Moreover, in the said embodiment, although forced displacement was given to each node of a tire three-dimensional linear model, it was made to deform | transform in order and rounded to a toroid shape, However, the method of deformation | transformation of a tire three-dimensional straight line is not limited to this, One end A tire model may be created by fixing the other end and applying a forced displacement according to a specific functional expression (for example, a cycloid curve).
In addition, the discontinuous part was joined by merging overlapping node coordinates on the joint surface to make a common node, but the constraint condition was set so that the relative position of the joint surface and the node was constant. You may join a discontinuous part.

In the above embodiment, a tread portion, a belt portion, a carcass portion, a bead portion, to create a two-dimensional cross-section of the tire model which includes a support Idogomu portion and the belt reinforcing layer has been created the tire model, the present invention will now It is not limited to.
For example, as shown in FIG. 8, a tread part model (FIG. 8 (b)) and a casing part model (FIG. 8 (a)) including other than the tread part model are created, and the casing part model and the tread part model are created. A tire model (FIG. 8C) may be created by combining the tire models.
Casing section model, members other than the tread portion, i.e. the belt portion, a carcass portion, a bead portion, which reproduces the like Sa Idogomu unit and the belt reinforcing layer, is prepared by creating method described above.
The tread portion includes a tread pattern, and the creation method is not particularly limited, and is created by a well-known method. In the tread portion, unlike the initial stress applied to the belt layer and the belt reinforcing layer, the initial stress that affects the tire ground contact characteristics is not applied, and therefore, the tread portion can be formed by a known method.

  The tire model creation 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 gist of the present invention. May be.

It is the schematic which shows the outline of the simulation apparatus for implement | achieving this invention. It is a perspective view showing an example of a tire secondary section model. It is a perspective view which shows an example of a tire three-dimensional linear model. It is a figure which shows a mode that a tire three-dimensional linear model deform | transforms. It is a perspective view showing an example of a tire three-dimensional finite element model. It is a figure which shows an example of initial stage stress distribution. It is a figure which shows the flow of a process of the preparation method of a tire three-dimensional finite element model. It is a figure which shows the modification of the tire model creation method of this invention. It is a figure for demonstrating shaping | molding of the tire in a tire manufacturing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Simulation apparatus 2 Central processing part 3 Memory 4 I / O interface 5 Input device 6 Output device 7 External storage device 100 Tire casing 106 Belt part 108 Green tire

Claims (7)

In a simulation device, a tire model creation method for creating a tire model considering a tire manufacturing process for analyzing tire characteristics by simulation,
A step of creating a two-dimensional cross-sectional model in which the simulation apparatus reproduces a plurality of members including at least a carcass portion, a bead portion, and a reinforcing cord layer constituting a tire by dividing a mesh into a plurality of elements ;
The simulation apparatus develops the two-dimensional cross-sectional model in a straight line and divides the mesh into elements having a predetermined number of elements in the development direction to create a three-dimensional linear model composed of a plurality of three-dimensional finite elements ; ,
The simulation apparatus sequentially deforms the three-dimensional linear model by applying a forced displacement to each node of the plurality of finite elements of the three-dimensional linear model from one end thereof with a predetermined straight line as a center. A deformation step of rounding the dimensional straight line model around the predetermined straight line and deforming it into an annular shape to create a 3D model ;
The simulation device, and a coupling step of creating a tire model by combining both end surfaces of the three dimensional model which is deformed in a ring shape,
The simulation apparatus includes an initial stress applying step of applying, to the tire model, an initial stress acting on the reinforcing cord layer as an initial stress generated in the reinforcing cord in the tire manufacturing process. Tire model creation method. The deformation step includes the initial stress application step, performs a deformation analysis in which a forced displacement is applied to each node of the plurality of finite elements and sequentially deforms, calculates a stress generated in the reinforcing cord layer, and calculates The tire model creation method according to claim 1, wherein an initial stress acting on the reinforcing cord layer applied in the initial stress applying step is calculated based on the applied stress. The initial stress applying step, after said coupling step, the tire model generating method according to claim 1 is intended to impart an initial stress acting on the reinforcing cord layer. The tire model creation method according to claim 1, wherein the reinforcing cord layer includes at least one of a belt layer and a belt reinforcing layer. In the deforming step, a material property value is given to a member model of the member including at least the reinforcing cord layer in the three-dimensional linear model, and the three-dimensional linear model is deformed into an annular shape by executing a simulation. The tire model creation method according to any one of claims 1 to 4 . The tire model creation method according to any one of claims 1 to 5, wherein the material property value is set only in the reinforcing cord layer. The tire material creation method according to any one of claims 1 to 6, wherein the material property value includes at least one of a specific gravity and a tensile elastic modulus, a bending elastic modulus, and a Poisson's ratio indicating mechanical properties.

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