JP4581649B2 - Operation method of simulation apparatus - Google Patents

Description

The present invention relates to an operation method of a simulation apparatus that evaluates tire characteristics by a finite element method.

In recent years, various methods for predicting tire characteristics using computer simulation such as a finite element method and designing tires based on the tire characteristics have been proposed.
In the simulation by the finite element method, a finite element model of a tire is created using a computer, and the stationary state or rolling state of the tire is simulated using the created tire model, and physical quantities generated in the tire model are obtained at this time. Tire characteristics.
By using this tire characteristic, it is possible to design a tire having excellent tire characteristics without actually manufacturing the tire, thereby improving the development efficiency of the tire.

As a method for creating such a tire model, a tire body portion continuous in the tire circumferential direction with the same cross-sectional shape is expanded in the circumferential direction to divide the elements, and a tire body portion element model is set, and the tread pattern is changed to the tire body. There has been proposed a tire finite element creation method including a process of setting a tread pattern part element model in which elements are divided in more detail than a part element model and a process of combining a tread pattern part element model with a tire body part element model ( For example, see Patent Document 1.)
Japanese Patent No. 3314082

However, the above-mentioned Patent Document 1 only discloses that the body part element model and the tread part element model are defined so that the relative positions do not change and are combined, and a means for realizing a specific combining method is disclosed. Absent.
The present invention has been made in view of such circumstances, and when a tire model is created by combining a body part model and a tread part model, the nodes constituting the tread part model to be combined with the body part model are overlooked. There is provided a method of operating a simulation apparatus capable of performing a search without any search and searching for an element of a body part model that is closest to a node constituting the tread part model.

In order to solve the above problems, the present invention is equipped with a CPU, an input device, a method of operating a simulation apparatus to create a tire model is analyzed by simulating the tire characteristic, the CPU is more A surface node search step for searching a surface node on the tire rotation axis side constituting an element surface located on the tire rotation axis side in a tread portion model reproducing a tire tread portion using an element constituted by Among the elements constituting the body part model that reproduces the tire body part in contact with the tire tread part, the element that searches for the closest element to the surface node on the tire rotation axis side of the searched tread part model According to the search step and the input from the input device by the operator , the surface node on the tire rotation axis side and the surface node closest to the surface node The tread portion model and the body portion model are combined by constraining the elements so as not to change relative positions with each other , and the element search step includes nodes constituting the element surface of the body portion model. A step of searching for a node m _s located closest to a node n _s constituting an element of the tread portion model, and a start point of the node m _s constituting the element surface of the body portion model and then, by calculating a vector c _i and c _{i + 1} to the other nodes located on the splitting line of the surface of the element that contains the node m _s and ending, a start point the node m _s, the element of the body section model the vector s and ending the projection point of the node n _s onto the surface, and calculating using the following equation (1),
s = g− (g · m) m Expression (1)
(G: a start point of the node _{m s,} vector nodal _{n s} an end _{point, m = c i × c i} + 1 / | c i × c i + 1 | (i is 1 or more N an integer, N is the plurality of sets of pairs number))
Element surfaces including the vector s, which provides an operating method of the simulation device characterized by including the step of determining the closest element to the node n _s.

Element searching step is La, in a case where the vector c _i and c _{i + 1} starting from the node m _s is plural sets extracted, calculates the vector s which satisfies the following formula (2) and (3), the the surface of the element containing the vector s, it is preferable to determine the element closest to the nodal point n _s.
(C _i × s) · (c _i × c _{i + 1} )> 0 (2)
(C _i × s) · (s × c _{i + 1} )> 0 (3)

  The surface node search step includes a step of searching for an element surface of the tread part model that is not in contact with another element surface among the element surfaces of the tread part model, and a normal line outward to the element surface. A step of calculating a vector, a step of determining whether the calculated direction of the outward normal vector is on the tire rotation axis side, and the direction of the normal vector outward to the element surface is the tire It is preferable that the method includes a step of searching for a node that constitutes a surface that is on the rotation axis side.

  Alternatively, in the surface node search step, a distance from the node of the tread part model to the intersection with the surface of the body part model on a perpendicular line from the nodes constituting the element of the tread part model to the tire rotation axis is calculated. And a step of searching for a node whose distance from the node of the tread model to the intersection with the surface of the body model is equal to or less than a threshold value.

The present invention searches for a surface node on the tire rotation axis side that constitutes an element surface located on the tire rotation axis side in the tread part model, and searches for the tread part model in the elements constituting the body part model. For each surface node on the tire rotation axis side of the tire, the closest element is searched, and the surface node on the tire rotation axis side and the element closest to the surface node are constrained, thereby the tread model and body Combine part models.
Therefore, according to the present invention, when a tire model is created by combining a body part model and a tread part model, a search is performed without overlooking the nodes constituting the tread part model to be combined with the body part model, Ru can search for elements closest body part model to the node which constitutes the tread portion model.
By doing so, it is possible as well as create a tire model is analysis models efficiently, provides a method of operating a simulation device for evaluating the tire characteristic by the finite element method.

Hereinafter, a tire model created by the method of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.
FIG. 1 is a schematic diagram illustrating an outline of a simulation apparatus that executes a tire model creation method, 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, a processing program executed by the CPU 2, and a 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, an optical disk such as an HDD, 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 operator's input, sets physical quantities and constraint conditions of the analysis model, The tire characteristics are analyzed by simulating a characteristic test.

FIG. 2 is a perspective view showing an example of a tire model created by the tire model creation method of the present invention.
The tire model 10 is obtained by combining a tread part model 12 that reproduces a tire tread part using an element constituted by a plurality of nodes and a body part model 14 that reproduces a tire body part in contact with the tire tread part. This is a created finite element model.

The tread portion model 12 is a three-dimensional model that faithfully reproduces the shape of the tread portion that is in direct contact with the road surface, and that defines the tread portion having a tread pattern with solid elements defined by a three-dimensional shape.
The tread portion model 12 includes a straight groove for improving braking force on a wet road surface, straightness and cornering properties, a lug groove for improving driving force and braking force, and shear generated by biting into snow. A sipe for improving driving force, braking force, and the like is engraved by the resistance, thereby forming a tread pattern in which a predetermined shape is repeated at a constant pitch.
The body part model 14 supports the end of a cord reinforcing material such as a carcass part which is a member constituting a skeleton of the tire, a belt part which is a cord reinforcing material positioned between the carcass part and the tread part, and a belt part. This is a model that reproduces a bead portion for fixing the tire to the rim portion of the wheel, a side portion that forms the side surface of the tire, and the like. The body part model 14 is a three-dimensional model defined by various types of elements such as a solid element defined by a three-dimensional solid shape, a shell element defined by a line or plane shape, and a membrane element.

FIG. 3 is a schematic diagram partially showing the coupling between the tread part model and the body part model. In the figure, an arrow is an imaginary line indicating that the tread part model and the body part model are combined.
As shown in FIG. 3, such a tire model has nodes (hereinafter also referred to as slave nodes) constituting the tread portion model 12 with respect to the element surface (hereinafter also referred to as a master surface) of the body portion model 14. It is created by setting the constraint conditions so that the relative position does not change and combining them. A method for setting and combining the constraint conditions will be described in detail later.

It is often difficult to divide each model into elements so that the nodes of the tread part model 12 and the body part model 14 that are created individually match each other, and the processing is complicated. Therefore, there is a risk of spending a lot of time on creating the tire model.
Therefore, by connecting the tread part model 12 and the body part model 14 by connecting and setting the constraint conditions so that the relative position does not change, the nodes of each model coincide when the elements are divided into elements. Thus, it is not necessary to divide elements, and each model can be divided into elements relatively easily.

  With reference to FIG. 4 to FIG. 8, the outline of the tire model creation method of the present invention will be described. FIG. 4 is a flowchart showing processing of the tire model creation method. As described above, the tire model is a finite element model created by connecting the tread model 12 and the body model 14 to each other, and the tread model 12 and the body model 14 are created in advance. ing.

A node on the element surface located on the tire rotation axis side is searched from the tread portion model 12 (step S101). The node on the element surface located on the tire rotation axis side is a node constituting a surface in contact with the body portion model 14 when the tread portion model 12 is coupled to the body portion model 14. That is, among the surfaces of the tread portion model 12, the surfaces are not in contact with or overlapped with other surfaces, and are directed toward the center side of the tire model that is the coupling surface side with the body portion model. It is a node that constitutes the surface.
Therefore, the nodes constituting the element surface of the groove portion of the tread pattern and the element surface that contacts the road surface are excluded from the nodes of the element surface located on the tire rotation axis side.
When the tread portion model 12 and the body portion model 14 are combined, the constraint conditions of these nodes are set based on the master surface of the body portion model 14, and these nodes are referred to as slave nodes. Details of this search process will be described separately.

From the body part model 14, the element closest to the node on the element surface of the tread part model 12 searched in step S101 is searched (step S102). The element of the body part model 14 that is closest to each node searched in step S101 is searched.
The elements closest to the nodes on the element surface of the tread model 12 located outside the body model 14 are not elements inside the body model 14 but elements on the body model surface. The element includes a master surface that is an element surface of the body part model 14. Details of this search process will be described separately.

  The node on the element surface of the tread model 12 and the element of the body model 14 are combined (step S103). By setting the node of the tread portion model 12 retrieved in step S101 as a slave node and the element surface of the body portion model 14 retrieved in step 102 as a master surface, a constraint condition that does not change the relative position of each other is set. The model 12 and the body part model 14 are combined.

  When the tire model 10 is created in this way, the tread portion model 12 and the body portion model 14 do not need to share each other's nodes. Each model can be created without considering the position. Therefore, the creation time of the tire model 10 can be shortened.

  With reference to FIG. 5 and FIG. 6, the process of searching for the node on the element surface located on the tire rotation axis side from the tread portion model in step S101 will be described in detail. FIG. 5 is a flowchart showing an example of processing for searching for a node on the element surface located on the tire rotation axis side from the tread portion model 12. FIG. 6 is a diagram for explaining a process of searching for a node on the element surface located on the tire rotation axis side from the tread part model.

  FIG. 6 schematically shows a part of a cross-sectional view of the tread portion model 12, the body portion model 14, and the tire rotation shaft 16 cut along a meridional section including the tire rotation shaft 16. Nodes on the element surface of the tread portion model 12 are indicated by black circles, and nodes on the surface elements of the body portion model 14 and nodes constituting the internal elements of the tread portion model 12 are indicated by white circles. The outward normal vector on the element surface is indicated by an arrow, and in particular, the normal vector facing the tire rotation axis 16 is indicated by a dotted line, and the others are indicated by solid lines.

  All node information of the tread part model 12 is acquired (step S201). For each element of the tread part model 12 created in advance, the node information such as the node number arbitrarily assigned to the node constituting the element and the node coordinates in the three-dimensional space is read from the external storage device 7.

  A surface formed by each node is searched (step S202). For each node constituting the element of the tread portion model 12, a surface including the node is searched, and further other node information forming the surface is acquired. By this processing, all the surfaces constituting the elements of the tread portion model 12 are searched, and these surfaces include the element surface, the surface inside the element, and the like.

A face that is an element surface of the tread portion model 12 is searched (step S203). Of the surfaces of the tread portion model 12 retrieved in step S202, the surfaces that are not in contact with or overlap with other surfaces, that is, the element surface of the tread portion model 12 are retrieved.
This search process can be determined based on whether or not the nodes constituting a certain surface are all overlapped with the nodes constituting another surface.
Two surfaces where all the nodes overlap are in contact with each other with a surface formed by all the overlapping nodes as a boundary surface. Since the finite element model is formed while a plurality of elements are in contact with each other, there are two surfaces that are formed by nodes that overlap all of the elements located inside the finite element model.
On the other hand, since the surface of the element located outside the finite element model, that is, the element surface does not contact other elements, all the nodes constituting the surface do not overlap.

A search is made for an element surface having an outward normal vector that faces the tire rotation axis (step S204). An outward normal vector is obtained with respect to the element surface of the tread portion model 12 searched in S203, and the element surface in which the normal vector faces the rotation axis 16 side of the tire model is searched. The outward normal vectors related to the element surface of the groove portion of the tread pattern and the element surface that contacts the road surface are excluded from the search process because they do not point in the direction of the rotation axis of the tire model.
By doing so, the element surface of the tread portion model 12 to be combined with the body portion model 14 is obtained.

The outward normal vector of the element surface calculates two edge vectors that detect the element surface counterclockwise from the outside and that share a certain node among the nodes forming the element surface. It can be determined by the outer product of vectors.
At this time, the direction of the normal vector is a direction perpendicular to the two ridge line vectors, and is the direction in which the screw advances when the right screw is rotated in the direction of the ridge line vector.

  The node information related to the nodes constituting the element surface whose outward normal vector of the element surface is the tire rotation axis direction is stored in the external storage device 7 (step S205). The node on the element surface whose outward normal vector searched in step S204 is the tire rotation axis direction is a node for which a constraint condition is set as a slave node when the tread model 12 is coupled to the body model 14. Yes, information about these nodes is temporarily stored in the external storage device.

With reference to FIGS. 7 and 8, the process of searching for the element closest to the node on the element surface searched in step S101 from the body part model 14 will be described.
FIG. 7 is a flowchart showing a process for searching the body part model 14 for an element closest to the node on the element surface located on the tire rotation axis side among the nodes constituting the tread part model 12. FIG. 8 is a diagram for explaining another example of the process of searching for the element of the body part model 14 that is closest to the node on the element surface located on the tire rotation axis side of the tread part model 12.

The node of the body part model 14 closest to the node acquired in step S101 is searched (step S301). With respect to the node on the element surface located on the tire rotation axis 16 side of the tread portion model 12, the node having the shortest distance between the nodes is searched among the nodes constituting the body portion model 14.
As shown in FIG. 8, in this search process, when the node on the element surface of the tread model 12 is n _s (x, y, z), the node m _s (x _i , y _i ) of the body model 14 is used. , Z _i ) can be executed by obtaining a node m _s (x _i , y _i , z _i ) when the distance l between nodes shown in the following formula (1) is minimized.
l ² = (x _i −x) ² + (y _i −y) ² + (z _i −z) ² Formula (1)

A projection vector v _j is calculated when a vector starting from the node of the body part model 14 retrieved in step S301 and ending at the node on the element surface of the tread part model 12 is projected onto the body part model 14 (step). S302).
Vector v _j is a node m _s of the body model 14 closest to the node n _s elements the surface of the tread portion model 12 a start point, the node n _s elements the surface of the tread portion model 12, the nodes of the body model 14 This is a vector whose end point is the node r _s when projected onto the plane S _j including m _s (where j = 1 in the example shown in FIG. 8).
This vector v _j can be obtained from the following equation (2). In FIG. 8, the case of j = 1 will be described, but the vector v _j is obtained by the same method not only when j = 1 but also when j = 2, 3, and 4.
v _j = g− (g · m) m Expression (2)
However, m = _cj * _{cj + 1} / | _cj * _{cj + 1} |.

Here, as shown in FIG. 8, the vector g is a vector having a node m _s of the body part model 14 as a start point and a node n _s on the element surface of the tread part model 12 as an end point. Therefore, the second term on the right side of the equation (2) (g · m) m is the start point node r _s in projecting the node n _s on the surface S _1, node n elements surface of the tread portion model 12 A vector whose end point is _s is shown.
The vector m is defined by vectors c _j and c _{j + 1} starting from the node m _s on the element surface S ₁ of the body part model 14 and ending at other nodes located on the dividing line of the element surface S _1. it is a unit vector in the direction normal to the surface S ₁ that.

In determining the vector v _j, the vector c _j which is a start point node m _s in the elements surfaces S ₁ of the body model 14, the other node located on the splitting line of the element surface S ₁ and the end _point, c j + ₁ There are several. That is, in the example shown in FIG. 8, there are four surfaces S _j including the node m _s (S ₁ , S ₂ , S ₃ , S ₄ ), and the vector c for determining the vector v _j therefrom. _j, it is necessary to select the _{c j + 1.}
Accordingly, similarly to the case of j = 1 shown in FIG. 8, v _j is obtained for j = 2, 3, and 4, and c _j and c _{j + 1} satisfying the following expressions (3) and (4) are obtained from each v _j. Is used to determine the vector v _j using equation (2).
(C _j × s) · (c _j × c _{j + 1} )> 0 (Equation 3)
(C _j × s) · (s × c _{j + 1} )> 0 (4)

If a plurality of projection vectors v _j are determined in step S302, the projection vector v _j is uniquely determined from them (step S303).
In the case of determining the projection vector v _j by using the above formulas (2) to (4), the projection vector r _s due errors due floating point may not be able to determine uniquely. In such a case, according to the following formula (5), the projection vector v _j is selected using j when the magnitude u when the node n _s is projected onto c _j is maximized.
u = g · c _j / | c _j || Formula (5)

Based on the end point r _s of the projection vector v _j , the movement direction and movement amount of the node n _s are calculated (step S304).
If the three-dimensional coordinate of the end point r _s of the projection vector v _j is (x _s , y _s , z _s ), the coordinate of the node n _{s on} the element surface is (x, y, z), so the moving direction is ( x _s −x, y _s −y, z _s −z), and the amount of movement is represented by √ ((x _s −x) ² + (y _s −y) ² + (z _s −z) ² ). Is done.
Therefore, the movement amount √ ((x _s −x) ² + in the movement direction (x _s −x, y _s −y, z _s −z) is applied to the slave node n _s that is a node constituting the tread portion model 12. (Y _s −y) ² + (z _s −z) ² ) By moving, it is possible to move to the master surface which is the element surface of the body part model 14.

The combined information including the moving direction and the moving amount is stored in the external storage device 7 (step S305). The connection information such as the movement direction and the movement amount calculated in S304 is temporarily stored in the external storage device 7, and in order to connect the tread part model 12 and the body part model 14, the nodes of the tread part model 12 which is a slave node It is used when setting a constraint condition in which the relative position does not change with the element surface of the body part model 14 which is the master surface.
The connection information includes, in addition to the movement direction and the movement amount, the node on the surface of the element located on the tire rotation axis side, the node number and the node number regarding the node forming the element surface on the body part model 14 closest to the node, and the like It is.

  In this way, the process of searching the element surface node located on the tire rotation axis side from the tread part model 12 and searching the element closest to the searched element surface node from the body part model 14 is performed. By executing the search, it is possible to search without overlooking the nodes of the tread model 12 to be coupled to the body model 14 and to search for the elements of the body model 14 closest to the nodes of the tread model 12.

  A process for coupling the slave node of the tread model 12 to the master surface of the body model 14 using information on the nodes of the tread model 12 and the element surface of the body model 14 retrieved by the above process will be described. .

The node on the element surface located on the tire rotation axis side searched from the tread portion model 12 is set as a slave node, and the element surface of the body portion model 14 closest to the node on the searched element surface is set as a master surface.
The slave node of the tread portion model 12 is moved on the master surface of the body portion model 14 based on information such as a movement amount and a movement direction. Here, if there is an intersection where the boundary of the tread portion model 12 intersects the boundary of the element of the body portion model 14, the intersection is obtained and the intersection is added as a node in the tread portion model 12 to reconstruct the element. To do.

A constraint condition for restricting the behavior of each slave node of the tread portion model 12 by the behavior of the node constituting the element on the master surface of the body portion model 14 including each node is obtained. The behavior of the tread portion model 12 is constrained by this constraint condition.
This constraint condition is determined using position information and a shape function. The shape function is a function used when converting the shape of the element on the master surface of the body portion model 14 including each slave node of the tread portion model 12 from a predetermined reference shape on the parametric space. The position information is position information of corresponding points in the reference shape of each slave node of the tread portion model 12 (Japanese Patent Application No. 2004-29195).

In the above embodiment, in the process of searching for the node on the element surface located on the tire rotation axis side from the tread portion model 12, the element surface outward normal vector is searched for the tire rotation axis. However, the present invention is not limited to this.
By searching for a node whose distance from the node on the element surface of the tread model 12 to the surface of the body model 14 is equal to or less than a predetermined threshold, the tread model 12 is positioned on the tire rotation axis side. You can also search for nodes on the element surface.

  With reference to FIG. 9 and FIG. 10, another example of the process of searching for the node on the element surface located on the tire rotation axis side from the tread portion model in step S <b> 101 will be described in detail. FIG. 9 is a flowchart showing another example of processing for searching for a node on the element surface located on the tire rotation axis side from the tread portion model 12. FIG. 10 is a diagram for explaining another example of processing for searching for a node on the element surface located on the tire rotation axis side from the tread portion model.

FIG. 10 schematically shows a part of a cross-sectional view of the tread portion model 12, the body portion model 14, and the tire rotation shaft 16 cut along a meridional section including the tire rotation shaft 16. Nodes on the element surface of the tread portion model 12 are indicated by black circles, and nodes on the surface elements of the body portion model 14 and nodes constituting the internal elements of the tread portion model 12 are indicated by white circles.
A perpendicular line extending from a node on the element surface of the tread portion model 12 to the tire rotation axis 16 is indicated by a thin line, and a distance from each node of the tread portion model 12 to an intersection with the surface of the body portion model 14 is indicated by a solid line. To express. A threshold ε used when searching for a node at a predetermined distance from the surface of the body part model 14 is indicated by a one-dot broken line.

  All node information of the tread part model 12 is acquired (step S401). For each element of the tread portion model 12, node information such as a node number arbitrarily assigned to a node constituting the element and node coordinates in a three-dimensional space is read from the external storage device 7.

  A surface formed by each node of the tread portion model 12 is searched (step S402). With respect to each node constituting the element of the tread portion model 12, a surface including the node is searched, and further other node information forming the surface is acquired. By this processing, all the surfaces constituting the elements of the tread portion model 12 are searched, and these surfaces include the element surface and the surface inside the element.

A face that is an element surface of the tread portion model 12 is searched (step S403). Of the surfaces of the tread portion model 12 retrieved in step S402, the surfaces that are not in contact with or overlap with other surfaces, that is, the element surfaces of the tread portion model 12 are retrieved.
This search process can be determined based on whether or not the nodes constituting a certain surface are all overlapped with the nodes constituting another surface.
Two surfaces where all the nodes overlap are in contact with each other with a surface formed by all the overlapping nodes as a boundary surface. Since the finite element model is formed while a plurality of elements are in contact with each other, there are two surfaces that are formed by nodes that overlap all of the elements located inside the finite element model.
On the other hand, since the surface of the element located outside the finite element model, that is, the element surface does not contact other elements, all the nodes constituting the surface do not overlap.

The distance from the node on the element surface of the tread portion model 12 to the surface of the body portion model 14 is calculated (step S404). Here, the distance to the surface of the body part model 14 is determined so that the rotation axis of the tread part model 12 and the rotation axis of the body part model 14 coincide with the tire rotation axis. In the case of the arrangement, it is the distance from the node on the element surface of the tread portion model 12 to the intersection of the perpendicular drawn on the tire rotation shaft 16 and the surface of the body portion model 14.
That is, the distance from the node of the tread portion model 12 to the intersection with the surface of the body portion model 14 on the perpendicular line extending from each node of the tread portion model 12 to the tire rotation shaft 16 is calculated.

A node whose distance calculated in S404 is equal to or smaller than a predetermined threshold is searched (step S405). A node whose distance from each node of the tread model 12 to the intersection with the surface of the body model 14 is equal to or less than a threshold is searched.
The threshold value ε is determined in a range that satisfies the following formula (6), where L _max is the maximum element length of all elements constituting the tread portion model 12. The threshold ε is defined with the surface of the body part model 14 being 0.0, the inside of the body part model 14 (tire rotating shaft side) being minus, and the outside of the body part (tread part model 12 side) being plus.
−1.0 × L _max ≦ ε ≦ 1.0 × L _max (6)
The threshold value ε is more preferably when the following equation (7) is satisfied, and further preferably when the following equation (8) is satisfied.
0.0 × L _max ≦ ε ≦ 0.5 × L _max (7)
0.0 × L _max ≦ ε ≦ 0.1 × L _max (8)

  In this way, a node whose distance from the surface of the element surface of the tread portion model 12 to the surface of the body portion model 14 is equal to or less than a predetermined threshold is retrieved, and the retrieved tread is retrieved from the body portion model 14. By executing the process of searching for the element closest to the node of the body model 12, the search is performed without overlooking the node of the tread model 12 to be coupled to the body model 14, and the node of the tread model 12 is the most. The elements of the near body part model 14 can be searched.

  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 can be made without departing from the gist of the present invention. You may go.

It is the schematic which shows the outline of the simulation apparatus which produces a tire model and performs a simulation of a tire characteristic test. It is a perspective view showing an example of a tire model created by a tire model creation method of the present invention. It is a schematic diagram which shows partially the coupling | bonding of a tread part model and a body part model. It is a flowchart which shows the outline of the tire model preparation method. It is a flowchart which shows an example of the process which searches the node of the element surface located in the tire rotating shaft side from a tread part model. It is a figure for demonstrating an example of the process which searches the node of the element surface located in the tire rotating shaft side from a tread part model. It is a flowchart which shows the process which searches the element nearest to the node of the element surface located in the tire rotating shaft side among the nodes which comprise a tread part model from a body part model. It is a figure for demonstrating the process which searches the element of the body part model nearest from the node of the element surface located in the tire rotating shaft side of a tread part model. It is a flowchart which shows the other example of the process which searches the node of the element surface located in the tire rotating shaft side from a tread part model. It is a figure for demonstrating the other example of the process which searches the node of the element surface located in the tire rotating shaft side from a tread part model.

Explanation of symbols

1 Simulation device 2 CUP
3 Memory 4 Interface 5 Input Device 6 Output Device 7 External Storage Device 10 Tire Model 12 Tread Model 14 Body Model 16 Tire Rotation Axis

Claims (4)

CPU,
An input device;
An operation method of a simulation apparatus that creates a tire model and analyzes tire characteristics by simulation, comprising:
The CPU is
A surface node search step for searching a surface node on the tire rotation axis side that constitutes an element surface located on the tire rotation axis side in a tread portion model that reproduces a tire tread portion using an element constituted by a plurality of nodes. When,
Among the elements constituting the body part model that reproduces the tire body part in contact with the tire tread part, the element search for searching for the element closest to the surface node on the tire rotation axis side of the searched tread part model Steps,
The tread part model and the body part model are combined by constraining the surface node on the tire rotation axis side and the element closest to the surface node so that their relative positions do not change according to the input from the input device by the operator. and a binding step of,
The element search step includes a step of searching for a node m _s that is an element surface of the body part model and that is closest to a node n _s that forms an element of the tread part model ; ,
Calculating vectors c _i and c _{i + 1} starting from the node m _s constituting the element surface of the body part model and having other nodes located on the dividing line of the element surface including the node m _s as an end point ; ,
The node m _s a start point of the nodal n _s vector s and ending the projected point onto the element surface of the body portion model, and calculating using the following equation (1),
s = g− (g · m) m Expression (1)
(G: a start point of the node _{m s,} vector nodal _{n s} an end _{point, m = c i × c i} + 1 / | c i × c i + 1 | (i is 1 or more N an integer, N is the plurality of sets of pairs number))
Wherein the element surface comprising the vector s, the operation method of the simulation device characterized by including the step of determining the closest element to the node n _s. When a plurality of sets of the vectors c _i and c _{i + 1} starting from the node m _s are extracted, a vector s satisfying the following expressions (2) and (3) is calculated, and an element surface including the vector s The operation method of the simulation apparatus according to claim 1 , wherein the operation is determined as an element closest to the node n _s .
(C _i × s) · (c _i × c _{i + 1} )> 0 (2)
(C _i × s) · (s × c _{i + 1} )> 0 (3) The surface node search step includes a step of searching for an element surface of the tread portion model that is not in contact with other element surfaces among the element surfaces of the tread portion model;
Calculating an outward normal vector with respect to the element surface;
Determining whether the calculated direction of the outward normal vector is on the tire rotation axis side; and
The operation method of the simulation apparatus according to claim 1, further comprising a step of searching for a node that constitutes a surface in which a direction of a normal vector outward to the element surface is a tire rotation axis side. The surface node search step calculates a distance from the node of the tread model to the intersection with the surface of the body model on a perpendicular line from the nodes constituting the element of the tread model to the tire rotation axis. And steps to
The operation method of the simulation apparatus according to claim 1, further comprising: searching for a node whose distance from the node of the tread model to the intersection with the surface of the body model is a threshold value or less.

Images