JP2006175994A - Tire model producing method and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire model producing method capable of producing an accurate model, and a computer program. <P>SOLUTION: A base mode 1 is modeled while a tire meridional cross section outline shape and a meridional cross section inner structure are not restrained. Therefore, tough the base model 1 is different from an actual tire shape, and a carcass 4l, belt layers 5, 6, 8, a belt cushion 7, and a rubber layer are geometrically and accurately modeled. On the other hand, in case that tire molded article to be modeled actually exists, an outline shape as an initial shape can be measured by a laser measuring or CT scanning. At least two reference points such as a tread center portion 11 and a rim fitting portion 13 are set in the base model, the reference points thereof are displaced to reference points 10, 12 corresponding to an outline shape 9 obtained by profiling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tire model creation method and a computer program, and more particularly to a tire model creation method capable of simulating a tire before air filling, and a computer program for executing the tire model creation method.

  Tire characteristics are greatly affected by tire shape. For this reason, tire manufacturers have a desire to create a numerical model for simulation that accurately represents a tire. For example, in the case where an actual tire as a prototype exists and an improvement plan is examined based on the tire, it is necessary to accurately model the reference tire. Since an actual tire is manufactured in a shape before air filling and used by filling it with air, a tire that accurately represents the shape before air filling in the same way when simulating a tire. It is desired to create a model (hereinafter referred to as an initial shape model).

  However, an actual tire that is not filled with air is so soft that it is deformed by its own weight, and its shape is unstable. For this reason, there is a problem that it is difficult to create a highly accurate initial shape model. On the other hand, conventionally, only a method for creating an initial shape model by performing a simulation simulating a PCI process (post-cure inflation process) from an in-mold layout has been proposed (for example, Patent Document 1). No specific proposal has been made. In the PCI process, when actually manufacturing a tire, the tire cross-sectional shape is changed by cooling it while applying internal pressure to the inner surface of the tire in a high temperature state taken out from the tire vulcanization mold. A processing step that stabilizes.

Japanese Patent Laid-Open No. 2004-217075

  However, in the above method, a large amount of labor is required to determine the material characteristics used in the calculation of the PCI process, and furthermore, whether the initial shape obtained by the calculation has sufficient accuracy including the internal structure. There was a problem that can not be guaranteed. For example, as shown in FIG. 7, the shape of the initial shape tire model 40 obtained from the in-mold layout is different from the contour 41 obtained by laser measurement of an actual tire before air filling. In particular, the side tread portion 42 is significantly different.

  Therefore, the present invention has been made in view of the above, and when an actual tire is present, a tire capable of accurately constructing an initial shape model without requiring labor such as a virtual calculation in a PCI process It is an object to provide a method for creating a model and a computer program for executing the method.

  In order to achieve the above-described object, a tire model creation method according to the present invention includes a base model construction step for geometrically modeling a meridional cross-sectional contour shape and a meridional cross-section internal structure of a tire based on an actual tire cross-section. , The profiling step of measuring the meridional cross-sectional contour shape in the actual tire before the air filling, and the reference point of the base model corresponding to the same part is matched with the reference point of the meridional cross-sectional contour shape in the actual tire obtained in the profiling step And a fitting step for deforming the base model.

  The actual tire cross section can be obtained from a cut sample or an in-mold layout. Based on this, it is possible to grasp the meridional cross-sectional contour of the tire and the internal structure of the meridional cross-section, and geometrically model it, but the meridian cross-sectional contour at this point is not constrained at all, so This is different from the meridional cross-sectional contour after being molded as a tire. In particular, the shape around the rim is different.

  Using the model obtained above as a base model, next, the meridional cross-sectional contour shape in an actual tire (molded product) in a state before air filling is measured. This is the profiling process. Then, the base model is matched (fit) with the contour shape obtained in the profiling step. In order to make them coincide with each other, it is preferable that a reference point is a portion that is a characteristic of the tire, for example, a tread center point, a corner portion of a tread groove, a tread, a rim portion, or the like. The tire model obtained in this way is an ideal tire model because the internal structure of the carcass, belt, etc. is also closely reproduced, and the contour matches the tire before air filling.

A tire model creation method according to the next invention is the tire model creation method,
At least two or more reference points of the base model are set, and the reference points are made to coincide with the same number of reference points in corresponding parts of the meridional profile contour shape in the actual tire obtained in the profiling process. is there.

  When matching the base model to the actual tire contour, the more points that are used as references, the better the accuracy. Accordingly, at least two or more points are set as reference points so that the base model matches the actual contour. Furthermore, the outline of the entire tire can be expressed more accurately by using a point far away from the neighboring point as a reference point.

  A tire model creation method according to the next invention is the tire model creation method, wherein the base model is modeled using a finite element method, and the contour model is obtained from the meridional cross-sectional contour shape obtained from the actual tire. The contact with the base model is defined as a rigid surface, and the deformation of the base model is calculated by finite element analysis under the condition that uniform air pressure is applied to the inner surface of the base model. Is.

  In the finite element method, a design object is divided into elements of a finite fixed size (for example, a triangle, a tetragon, a tetrahedron, a hexahedron, etc.), and nodes and vertices that are decomposed into elements are numbered. This is an analysis method in which the acting force and the element stiffness are obtained, the external force of the object is input, and the movement amount of each node, the element deformation and the internal force are obtained. This method is a general method used for structural analysis. In this method, it is necessary to determine the force and conditions acting on the nodes as boundary conditions.In the present invention, the meridional cross-sectional contour obtained from the actual tire has the outer surface as a rigid surface. Contact with the base model is defined as a boundary condition. And the deformation | transformation state when the base model which received the uniform pressure from the inside like an actual tire contacts the said outline is calculated from a viewpoint of material mechanics and structural mechanics.

A tire model creation method according to the next invention is the tire model creation method,
The base model is such that one side of a two-dimensional axisymmetric element is modeled.

  When the tire is symmetric with respect to the equator plane, modeling one side of a two-dimensional axisymmetric element reduces the degree of freedom in deformation calculation, thereby increasing calculation efficiency. The created two-dimensional initial shape model may be developed in the circumferential direction to create a three-dimensional model.

A tire model creation method according to the next invention is the tire model creation method,
As the contour shape in the profiling step, the contour when an air pressure of 1% to 40% of the JATMA dimension measurement air pressure is applied is used.

  Originally, the air pressure is desired to be 0, but the tire is deformed by its own weight, so that it is difficult to measure accurately. Therefore, a little air pressure is actually applied in order to stabilize the state not filled with air. If the air pressure is low, deformation due to its own weight is large. If the air pressure is too high, deformation due to the air pressure occurs, and it cannot be regarded as a state before air filling. Therefore, it is advantageous to use a tire in a state where air is appropriately sealed in the profiling process.

  A computer program according to the next invention is configured to cause a computer to execute the tire model creation method according to any one of claims 1 to 5. As a result, the tire model creation method described above is realized using a computer.

  As described above, according to the method for creating a tire model according to the present invention, an initial shape tire model can be constructed with high accuracy without requiring labor such as virtual calculation in a PCI process. This method is extremely effective when an actual tire is present. The creation method can be realized by a computer program having a simple configuration.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art.

  FIG. 1 is an explanatory diagram showing an embodiment of a tire model creation method according to the present invention. The left side of the figure is a cut sample in which the meridional section of the tire appears and a base model 1 generated from an in-mold layout. The base model 1 models the meridian cross-sectional contour shape and the meridian cross-section internal structure of the tire. Thereby, the base model 1 becomes a model in which the internal structure of the tire and the member boundaries thereof are clear. Specifically, in the meridional section, the carcass 4, belt layers 5, 6, 8, belt cushion 7, and rubber layer 3, which are the internal configuration of the tire, are quantified accurately and geometrically from actual cut samples and the like. And geometrically modeled.

  Unlike the actual tire as a molded product, the cut sample of the tire is not restrained by other parts of the tire or gravity, so it is very soft, and the overall cross-sectional shape is the initial shape as a molded product (air-filled) It is different from the previous shape. Therefore, the base model 1 modeled therefrom is modeled with, for example, the bending state of the tread portion and the positions of the side tread portion and the bead portion with respect to the tread portion as approximate shapes and positions. However, the relative positions of the internal structures such as the carcass 4 and the belt layers 5, 6, and 8 with respect to the entire tire are strictly expressed.

  On the other hand, when a tire molded product to be modeled actually exists, the contour shape as an initial shape can be measured by laser measurement, CT scan, MRI (Magnetic Resonance Imaging) method, or the like. Thus, although it is difficult to accurately determine the inner member boundary, the contour itself can accurately profile (acquire the contour scan) the actual initial shape. The outer contour shape 9 thus obtained is applied to the base model 1. In addition, when the arrangement of the members such as the outer contour, the inner contour, and the belt (metal) can be measured as in the CT scan, profiling is preferably performed using them.

  Moreover, it is good to use the outline when the air pressure of 1%-40% of JATMA dimension measurement air pressure is provided as an outline shape in a profiling process. In order to further improve the reliability, it is preferable to use the contour when an air pressure of 5% to 30% of the JATMA dimension measurement air pressure is applied. It should be noted that the JATMA dimension measurement air pressure is 180 kPa for passenger car tires, and the other tires are measured with the maximum air pressure and then the working air pressure (JATMA '04G). Originally, the air pressure is desired to be 0, but since the tire is deformed by its own weight and accurate measurement is difficult, an air pressure equal to or lower than the hollow pressure is actually applied to stabilize the shape. The reason why the pressure is equal to or lower than the hollow pressure is that if the air pressure is low, deformation due to its own weight is large, and if the air pressure is too high, deformation due to air pressure occurs and it cannot be regarded as a state before air filling. The specific numerical value of the air pressure will be described later.

  When performing the profiling, the target tire may be assembled on the rim used when analyzing the tire characteristics, or may be assembled on the rim having the rim width used in the PCI process. In order to stabilize the shape of the fitting portion with the rim, it is preferable to increase the pressure above the air pressure to be analyzed once, and then reduce the pressure to the contour measurement air pressure to measure the contour.

  As can be seen when the outer contour shape 9 is applied to the base model 1, the base model 1 is a shape different from the outer contour shape 9 actually obtained by profiling. Therefore, in the present invention, the base model 1 in which the internal structure and member boundaries are clearly expressed is fitted (matched) to the outer contour shape 9 obtained in the profiling process.

  The base model 1 to be matched is transformed into the outer contour shape 9 using a reference point. Specifically, at least two or more reference points are set in the base model 1, and the reference points are displaced to corresponding reference points (coordinates) of the outer contour shape 9 obtained by profiling. When matching the base model to the actual tire contour, the more points that are used as references, the better the accuracy. Accordingly, at least two or more points are set as reference points so that the base model matches the actual contour.

  The reference point may include the fitting portion 12 (13) with the rim and the tread center portion 10 (11). In addition, the edges 14 (16) and 15 (17) of the tread main groove are also suitable. In this way, a point with a clear correspondence between the parts is preferable. However, in order to understand the correspondence with the base model 1 when measuring the contour of the tire of the initial shape, a point that becomes a reference in advance in the shoulder portion and the side portion, for example, intentional It is also possible to set unevenness on the surface.

  FIG. 2-1 is an enlarged view of FIG. 1 showing a reference point in the tread center portion. FIG. 2-2 is an enlarged view of FIG. 1 showing a reference point at the fitting portion with the rim. 2A, the reference points on the base model side are the tread center portion 11 and the edge portions 16 and 17 of the main groove. These points are made to correspond to the corresponding portions 10, 14, and 15 of the outer contour shape obtained in the profiling step, respectively. In FIG. 2B, the rim fitting portion 13 of the base model is made to coincide with the rim fitting portion 12 (corresponding position) having an outer contour shape.

  The right side of FIG. 1 shows the base model matched to the outer contour shape in this way. This model is an initial shape tire model that accurately represents a tire before air filling. This model accurately represents the internal structure of the carcass 4 and the belt layers 5, 6, 8 as well as the outer contour. By performing various simulations using this initial shape model, the performance of the tire can be predicted and verified. The base model 1 may model a three-dimensional shape, or may model a two-dimensional shape of a meridional section including a rotation axis.

  As described above, in the present invention, the outline reference point of the base model 1 is made to coincide with the outline shape obtained in the profiling process, but the displacement of the internal structure at that time assumes that the wall thickness hardly changes, Several points may be provided, and the displacement may be determined under the condition that the thickness in the direction perpendicular to the tangent line of the points is the same before and after the deformation. Further, in the profiling step, the outer contour and inner contour of the tire before air filling may be measured and acquired, and the base model 1 may be matched with the inner contour.

  Further, the displacement of the internal structure may be determined by dividing the interior of the base model 1 before deformation into finite elements and applying a finite element method. In this case, the displacement of the internal structure when the outer contour changes is theoretically determined from the viewpoint of structural mechanics and material mechanics.

  FIG. 3 is an explanatory diagram showing boundary conditions necessary when the finite element method is applied. When the finite element method is applied, environmental conditions that are definitions such as constraint conditions and the direction and magnitude of force are required. In this case, contact with the base model is defined with the outer surface of the contour shape obtained in the profiling step as the rigid surface 22. Then, the deformation calculation of the base model is performed by the finite element method analysis under the condition that the uniform air pressure 21 is applied to the inner surface of the base model. As a result, the base model 23 becomes a model having the shape of the initial shape model while maintaining the accuracy of the internal structure like the model on the right side of FIG.

  Here, since the main purpose is to adjust the shape of the base model, the friction coefficient of the contact between the outer contour shape (line) as the rigid surface 22 and the base model is preferably zero. When the carcass cord is a resin, the elastic modulus of the carcass cord of the base model may be set to a value between 20% and 100% of the elastic modulus at room temperature. This is because by slightly reducing the elastic modulus of the carcass, the base model is easily deformed without being excessively hardened.

  In a tire having a symmetrical shape with respect to the equator of the tire, the base model 23 can be modeled with a two-dimensional axisymmetric element. In this way, the degree of freedom in the deformation calculation is reduced, so that the calculation becomes efficient. Then, the created two-dimensional model can be developed in the circumferential direction to create a three-dimensional model.

  Here, the tire optimum measurement air pressure in the profiling process described above will be described. Table 1 shows the results of examining the relationship between the measured air pressure during profiling and the initial tire shape. Specifically, using a 205 / 65R15 passenger car tire, the air pressure to be measured was varied to measure the contour shape, and an initial tire model was created using this shape and the air pressure was applied to 200 kPa. Calculations were made to compare the tire radius with the actual measurements. Here, the measured air pressure (%) indicates the ratio to the JATMA dimension measured air pressure in%. If the air pressure is low, deformation due to gravity increases and the error increases, and even when the air pressure is high, deformation due to the applied air pressure increases and the error increases.

  In addition, since the shape of the tire to which air pressure is applied affects various tire characteristics, it is necessary to match the tire radius with an error of 0.05% or less in order to perform accurate simulation. That is, when the pressure is 50%, deformation due to the air pressure cannot be ignored, and as a result, the error becomes large. Therefore, the measured air pressure is preferably 40% or less. In addition, when the measurement air pressure was set to be less than 1%, the tire radius varied when the shape measurement was repeated, and stable results could not be obtained. Is preferably 1% or more. As described above, in the profiling process, it is appropriate to profile the measured air pressure according to JATMA at a hollow pressure, particularly 1% to 40% of the JATMA dimension measuring air pressure.

  Next, the steps of the present invention will be described step by step in chronological order. FIG. 4 is a flowchart showing the steps of the present invention. In the present invention, first, the actual meridional cross-sectional shape of the tire is acquired from a cut sample or the like (step S101). Also, internal structures such as a carcass and a belt layer are acquired (step S102). Then, a base model is created by geometrically digitizing them (step S103). In this state, the contour of the base model is different from the actual tire contour. On the other hand, the inner and outer contours of the actual tire are profiled by laser measurement or the like (step S104). The reference point of the base model at the position corresponding to the reference point of the contour obtained by profiling is matched (step S105). By doing so, an initial shape model with high accuracy is completed for both the tire internal structure and the contour (step S106).

  FIG. 5 is a block diagram showing a hardware configuration for executing the present invention. The execution device 30 has a configuration in which a ROM (32), a RAM (33), a user interface (34), and a video interface (35) are connected by a bus (36) with a CPU (central processing unit) 31 as a center. The execution program of the CPU 31 is stored in the ROM 32 in advance. The ROM 32 also stores a communication program with the user interface 34 and the video interface 35. A storage device such as a hard disk is also connected to the bus as appropriate.

  The user interface 34 also includes a keyboard, mouse, scanner, and serial / parallel input / output bus. Using these buses, tire coordinate data (contour coordinate data, internal structure coordinate data) required in the base model creation process and the profiling process may be sent to the RAM 33 and the storage device. A monitor is connected to the video interface 35, and it is possible to see the modeling. The CPU 31 calculates the deformation of the base model.

  FIG. 6 is a block diagram showing functional blocks of the execution device. The execution device 30 is realized by the hardware and a program stored in the ROM 32, and includes an input unit 37 and an output unit 39 with a calculation unit 38 as a center. In the input unit 37 configured by a user interface, the base model contour data, internal structure coordinate data, profiling contour coordinate data, and electrical signals are input. The calculation unit 38 performs the fitting of the data based on the reference point by the calculation of the CPU. Then, the initial shape model is finally calculated by the CPU and output to the monitor in the output unit 39. Note that if CAD, CAE, and the finite element method program are recorded in the ROM 32 and the storage device, various simulations can be performed using the calculated initial shape model, and tire performance can be predicted. Therefore, it is preferable.

  With the configuration as described above, the tire initial shape model creation step can be realized by a computer program. Then, by reading the program into a computer, a specific tire model creation device or a creation method thereof is constructed by specific means in cooperation with the computer.

  As described above, the tire model creation method and computer program according to the present invention are useful for creating a tire model before air filling, and in particular, tire creation by simulation and simulation of the tire when an actual tire exists. Suitable for grasping and verifying performance.

It is explanatory drawing which shows the Example of the tire model creation method which concerns on this invention. It is an enlarged view of FIG. 1 which shows the reference point in a tread center part. It is an enlarged view of FIG. 1 which shows the reference point in the fitting part with a rim | limb. It is explanatory drawing which shows a boundary condition required when applying a finite element method. It is a flowchart which shows the process of this invention. It is a block diagram which shows the hardware constitutions for performing this invention. It is a block diagram which shows the functional block of the said execution apparatus. It is explanatory drawing which shows the difference between the conventional model and an actual outline.

Explanation of symbols

1, 23 Base model 3 Rubber layer 4 Carcass 5, 6, 8 Belt layer 7 Belt cushion 9 Outer contour shape 10, 11 Tread center portion 12, 13 Rim fitting portion 21 Air pressure 22 Rigid surface 24, 40 Initial shape tire model 30 Execution device 31 CPU
32 ROM
33 RAM
34 User interface 35 Video interface 36 Bus 37 Input unit 38 Calculation unit 39 Output unit 41 Contour 42 Side tread unit

Claims (6)

A base model construction process for geometrically modeling the meridional cross-sectional contour shape and the internal structure of the meridional section of the tire based on the actual tire cross-section;
A profiling step of measuring the meridional cross-sectional contour shape in an actual tire in a state before air filling,
A fitting step of deforming the base model so that the reference point of the base model corresponding to the same part matches the reference point of the meridional cross-sectional contour shape in the actual tire obtained in the profiling step;
A method for creating a tire model, comprising:   At least two or more reference points of the base model are set, and the reference points are made to coincide with the same number of reference points in corresponding parts of the meridional cross-sectional contour shape in the actual tire obtained in the profiling process. The tire model creation method according to claim 1.   The base model is modeled using a finite element method, and contact with the base model is defined with a contour as a rigid surface among the meridional cross-sectional contour shapes obtained from the actual tire, and the base model The tire model creation method according to claim 1, wherein the deformation calculation of the base model is performed by a finite element method analysis under a condition in which a uniform air pressure is applied to the inner surface of the tire model.   The tire model creation method according to claim 3, wherein the base model is modeled on one side of a two-dimensional axisymmetric element.   The tire model creation method according to any one of claims 1 to 4, wherein a contour when an air pressure of 1% to 40% of a JATMA dimension measurement air pressure is applied is used as the contour shape in the profiling step. .   The computer program for making a computer perform the preparation method of the said tire model as described in any one of Claims 1-5.

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