Wheel model preparation method and simulation method

Abstract

To provide a wheel model preparation method and a simulation method for assembling a wheel and a tire, capable of preparing a wheel model approximating vibration characteristics of an actual wheel in a short time.SOLUTION: A method of preparing a wheel model for numerical analysis of a wheel on which a tire is mounted performs: a step of inputting a natural frequency of the wheel; inputting the wheel model in which the wheel is discretized by a finite number of elements; a step of defining a material property as a rigid body in a first element constituting a first part of the wheel model; a step of defining a material property as an elastic body in a second element constituting a second part of the wheel model; a first calculating step of calculating the natural frequency of the wheel model; a second calculating step of calculating the difference between the natural frequency of the wheel and the natural frequency of the wheel model; and a correcting step of changing the material property of the second element so that the difference between the natural frequencies is reduced.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for creating and simulating a wheel model. [Background technology]

[0002] The following Patent Document 1 proposes a method for modeling a structure such as a wheel. This method includes the steps of creating a structure model by dividing the structure into a finite number of elements, and changing at least one of the elastic modulus and mass density of each element or element group so that the natural frequencies in a predetermined vibration mode of the structure and the structure model are approximately the same. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-153739 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above method, a structure model that approximates the vibration characteristics of an actual structure can be created by changing the elastic modulus, etc. so that the natural frequency is approximately the same. However, there is a problem in that it takes a lot of time to adjust the elastic modulus, etc.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a method capable of creating, in a short period of time, a wheel model that approximates the vibration characteristics of an actual wheel. [Means for solving the problem]

[0006] The present invention is a method for creating a wheel model for numerical analysis of a wheel on which a tire is mounted, comprising the steps of: inputting the natural frequency of the wheel into a computer; inputting a wheel model in which the wheel is discretized into a finite number of elements into the computer; defining material properties as a rigid body for a first element of the finite number of elements that forms a first part of the wheel model; and defining material properties as an elastic body for a second element of the finite number of elements that forms a second part of the wheel model, wherein the computer executes a first calculation step of calculating the natural frequency of the wheel model with the material properties defined for the finite number of elements; a second calculation step of calculating the difference between the natural frequency of the wheel and the natural frequency of the wheel model; and a modification step of changing the material properties of the second element so as to reduce the difference. Effect of the Invention

[0007] By employing the above steps, the method for creating a wheel model of the present invention makes it possible to create a wheel model that approximates the vibration characteristics of an actual wheel in a short period of time. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of a computer 1 for executing a method for creating a wheel model. [Diagram 2] FIG. 2 is a perspective view showing an example of a wheel. [Diagram 3] FIG. [Figure 4] 10 is a flowchart showing a processing procedure of a wheel model creating method. [Diagram 5] 1 is a graph showing the relationship between acceleration response and frequency. [Figure 6] FIG. 2 is a perspective view showing a wheel model. [Figure 7] 13(a) and 13(b) are diagrams showing the deformation state of a wheel model in the secondary bending mode of the rim portion. [Figure 8]13(a) and 13(b) are diagrams showing the deformation state of a wheel model in a collapse mode of the rim portion. [Figure 9] FIG. 11 is a perspective view showing a deformation state of the wheel model in a left-right translation mode of the rim flange portion. [Figure 10] 10 is a flowchart showing a processing procedure of a wheel model creation method according to another embodiment of the present invention. [Figure 11] 2 is a tire meridian cross-sectional view including a tire rotation axis in a normal state of an assembly. FIG. [Figure 12] 1 is a flowchart showing a processing procedure of a simulation method for a wheel and tire assembly. [Figure 13] FIG. 2 is a cross-sectional view showing an example of an assembly model. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be understood that the drawings include exaggerated expressions and expressions different from the dimensional ratio of the actual structure in order to help understand the contents of the invention. Furthermore, the same or common elements are given the same reference numerals throughout the embodiments, and duplicated explanations are omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for understanding the contents of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0010] In the method for creating a wheel model according to the present embodiment (hereinafter sometimes referred to as the "creation method"), a wheel model for numerical analysis of a wheel on which a tire is mounted is created. This wheel model can be used, for example, in a computer-based simulation to calculate vibration characteristics of an assembly of a wheel and a tire.

[0011] The tire mounted on the wheel is exemplified as a pneumatic tire for a passenger car, but is not particularly limited thereto. For example, tires of other categories such as heavy-duty tires for trucks and buses, and airless tires may be adopted. A computer is used in the creation method of this embodiment.

[0012] [computer] FIG. 1 is a perspective view showing an example of a computer 1 for executing a method for creating a wheel model. The computer 1 includes, for example, a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a includes, for example, a central processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive devices 1a1 and 1a2. The storage device stores in advance software for executing the creation method of this embodiment and a simulation method described later. Therefore, the computer 1 is configured as a device for creating a wheel model and a device for executing a simulation.

[0013] [wheel] Fig. 2 is a perspective view showing an example of the wheel 2. Fig. 3 is a partial cross-sectional view of the wheel 2. The wheel 2 of this embodiment is configured to include a hub portion 3, a rim portion 4, and spoke portions 5, similar to a conventional wheel.

[0014] The hub portion 3 is disposed on the center (axis) side of the wheel 2 and is attached to a hub axle (not shown) of a vehicle. The rim portion 4 includes a well portion 4a, a pair of bead seat portions 4b, 4b, and a pair of rim flange portions 4c, 4c.

[0015] 2, the spoke portions 5 extend between the rim portion 4 and the hub portion 3. In this embodiment, a plurality of spoke portions 5 are spaced apart in the tire circumferential direction. Due to such spoke portions 5, the wheel 2 has a non-uniform shape in the wheel circumferential direction (i.e., the shape of the meridian cross section including the rotation axis in the wheel circumferential direction is not uniform).

[0016] The wheel 2 of this embodiment is provided with five spoke portions 5, but is not limited to this. For example, four or less spoke portions 5, or six or more spoke portions 5, may be provided depending on the rigidity required of the wheel 2. Also, in this embodiment, the outer ends 5o of the multiple spoke portions 5 are each fixed to one rim flange portion 4c in the wheel radial direction.

[0017] [Method of creating a wheel model (first embodiment)] Next, a method for creating a wheel model according to this embodiment will be described with reference to a flowchart shown in FIG.

[0018] [Enter the wheel natural frequency] In the creation method of this embodiment, first, the natural frequency of the wheel 2 shown in Figures 2 and 3 is input to the computer 1 (shown in Figure 1) (step S1). The natural frequency is a natural resonance frequency of the wheel 2. Such a natural frequency changes depending on the shape, restraint position, material properties, etc. of the wheel 2, and is useful for identifying the vibration characteristics of the wheel 2.

[0019] The natural frequency is measured based on a predetermined mode. The modes may include, for example, various modes described in the above-mentioned Patent Document 1 and Patent Document 2 (JP Patent Publication 2007-102623 A). The modes in this embodiment include at least one of a secondary bending mode of the rim portion, a tilt mode of the rim portion, and a left-right translation mode of the rim flange portion.

[0020] In the secondary bending mode of the rim portion, the natural frequency of the wheel 2 is obtained when the rim portion 4 vibrates in the wheel radial direction. In the tilting mode of the rim portion, the natural frequency of the wheel 2 is obtained when the spoke portions 5 and the rim portion 4 vibrate so as to tilt relative to the hub portion 3. In the left-right translation mode of the rim flange portion, the natural frequency of the wheel 2 is obtained when the rim flange portion 4c (rim portion 4) vibrates in the left-right direction (axial direction) relative to the spoke portions 5 and hub portion 3. In these modes, unlike conventional modes that vibrate in the wheel circumferential direction, for example, it is possible to obtain natural frequencies based on non-uniform shapes in the wheel circumferential direction (for example, differences in the number and shape of the spoke portions 5).

[0021] In this embodiment, the natural frequencies are measured for all of the secondary bending mode of the rim portion, the tilt mode of the rim portion, and the lateral translation mode of the rim flange portion.

[0022] The natural frequency can be measured appropriately based on a conventional procedure. In this embodiment, the natural frequency of each mode can be measured by vibrating the wheel 2 with an impulse hammer while the hub portion 3 of the wheel 2 is restrained.

[0023] Figure 5 is a graph showing the relationship between acceleration response and frequency. In Figure 5, the natural frequency of the secondary bending mode of the rim is A1 (Hz). The natural frequency of the tilt mode of the rim is A2 (Hz). The natural frequency of the left-right translation mode of the rim flange is A3 (Hz). The natural frequencies of the wheel are input to computer 1 (shown in Figure 1).

[0024] [Enter wheel model] Next, in the creation method of this embodiment, a wheel model in which the wheel 2 is discretized into a finite number of elements is input to the computer 1 (shown in FIG. 1) (step S2). FIG.

[0025] In step S2 of this embodiment, the wheel 2 is discretized into a finite number of elements F(i) (i=1, 2, ...) based on the information on the wheel 2 shown in Figures 2 and 3. This sets a wheel model 12 that can be handled by a numerical analysis method. As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method is appropriately adopted. In this embodiment, the finite element method is adopted.

[0026] The wheel model 12 of this embodiment is created as a three-dimensional model. The wheel model 12 may be created as a two-dimensional model. For example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element is used as the element F(i). Each element F(i) has a plurality of nodes 6. Numerical data such as an element number, the number of the node 6, and the coordinate value of the node 6 are defined for each element F(i).

[0027] The wheel model 12 of this embodiment includes a hub portion 13, a rim portion 14, and spoke portions 15, similar to the wheel 2 shown in FIG.

[0028] The hub portion 13 is modeled after the hub portion 3 (shown in FIG. 2) of the wheel 2. The rim portion 14 is modeled after the rim portion 4 (shown in FIG. 2) of the wheel 2. Like the rim portion 4 of the wheel 2, the rim portion 14 includes a well portion 14a, a pair of bead seat portions 14b, 14b, and a pair of rim flange portions 14c, 14c.

[0029] The spoke portions 15 are modeled after the spoke portions 5 (shown in FIG. 2) of the wheel 2. The spoke portions 15 extend between the rim portion 14 and the hub portion 13 and are spaced apart in the tire circumferential direction. Furthermore, outer ends 15o of the spoke portions 15 are each fixed to one of the rim flange portions 14c.

[0030] For example, commercially available mesh creation software (for example, "ICEM CFD" by ANSYS, Inc.) is used for modeling the wheel model 12. The wheel model 12 is stored in a computer 1 (shown in FIG. 1).

[0031] [Define rigid body material properties for the first element of the wheel model] In the creation method of this embodiment, among the finite number of elements F(i) constituting the wheel model 12, the material properties as a rigid body are defined for the first element 17 forming the first portion 16 of the wheel model 12 (step S3).

[0032] In the first portion 16 of the wheel model 12, in which the material properties as a rigid body are defined, deformation (vibration) is not calculated in the first calculation step S5 described below. Therefore, the first portion 16 does not affect the natural frequency of the wheel model 12. Therefore, it is preferable that the first portion 16 corresponds to a portion of the actual wheel 2 shown in FIG. 2 that has a relatively small effect on the natural frequency.

[0033] In the actual wheel 2 shown in FIG. 2, a portion that has a relatively small effect on the natural frequency can be appropriately selected. As described above, the hub portion 3 of the wheel 2 is attached to the hub axle (not shown) of the vehicle. Therefore, the hub portion 3 has a higher rigidity and is less likely to deform (vibrate) than the rim portion 4 and the spoke portion 5, and therefore has a relatively small effect on the natural frequency of the wheel 2. Therefore, as shown in FIG. 6, it is preferable that at least a part of the hub portion 13 of the wheel model 12 that models the hub portion 3 (shown in FIG. 2) is included in the first portion 16. In this embodiment, the entire hub portion 13 is included in the first portion 16. Then, among the finite number of elements F(i) that constitute the wheel model 12, the material properties as a rigid body are defined for the first element 17 that forms the first portion 16 (hub portion 13).

[0034] The material properties as a rigid body can be appropriately defined so that the first element 17 does not deform even if an external force is applied to the first element 17. Such material properties can be easily defined, for example, by using a function (procedure) included in a commercially available finite element analysis application software (for example, ABAQUS manufactured by Dassault Systems). The material properties as a rigid body defined for the first element 17 are stored in the computer 1 (shown in FIG. 1).

[0035] [Define elastic material properties for the second element of the wheel model] Next, in the creation method of this embodiment, among the finite number of elements F(i) constituting the wheel model 12, material properties as an elastic body are defined for the second element 19 forming the second portion 18 of the wheel model 12 (step S4).

[0036] In the second portion 18 of the wheel model 12, in which the material properties as an elastic body are defined, deformation (vibration) is calculated in a first calculation step S5 described later, unlike the above-mentioned first portion 16. Therefore, the second portion 18 affects the natural frequency of the wheel model 12. Therefore, it is preferable that the second portion 18 corresponds to a portion of the actual wheel 2 shown in FIG. 2 that has a relatively large effect on the natural frequency.

[0037] In the actual wheel 2 shown in FIG. 2, the part that has a relatively large effect on the natural frequency can be appropriately selected. Unlike the hub portion 3, the rim portion 4 and the spoke portion 5 are not attached to the hub axle (not shown) of the vehicle. Therefore, the rim portion 4 and the spoke portion 5 have a lower rigidity and are more likely to deform (vibrate) than the hub portion 3, and therefore have a relatively large effect on the natural frequency of the wheel 2. Therefore, as shown in FIG. 6, it is preferable that at least a part of the rim portion 14 modeled on the rim portion 4 (shown in FIG. 2) and at least a part of the spoke portion 15 modeled on the spoke portion 5 (shown in FIG. 2) are included in the second portion 18. In this embodiment, the entire rim portion 14 and the entire spoke portion 15 are included in the second portion 18. Then, of the finite number of elements F(i) that make up the wheel model 12, the material properties as an elastic body are defined for the second element 19 that forms the second portion 18 (the rim portion 14 and the spoke portion 15).

[0038] The material properties of the second element 19 as an elastic body can be appropriately defined so that the second element 19 can elastically deform when an external force is applied to the second element 19. In this embodiment, numerical data of the material properties of the actual wheel 2 (rim portion 4 and hub portion 3) shown in FIG. 2 is defined in the second element 19. The material properties include, for example, elastic modulus and density. For example, the above-mentioned finite element analysis application software is used to define such material properties. The material properties of the second element 19 as an elastic body defined are stored in the computer 1 (shown in FIG. 1).

[0039] [Calculate the natural frequency of the wheel model (first calculation step)] Next, in the creation method of this embodiment, the computer 1 (shown in FIG. 1) calculates the natural frequency of the wheel model 12 (first calculation step S5). In the first calculation step S5, the natural frequency is calculated for the wheel model 12 in which material properties (i.e., material properties as a rigid body and an elastic body) are defined for the finite number of elements F(i) in steps S3 and S4.

[0040] The natural frequency is calculated based on a predetermined mode. In this embodiment, similar to the natural frequency of the wheel 2 shown in FIG. 2, the natural frequency is calculated based on at least one of the secondary bending mode of the rim portion, the tilt mode of the rim portion, and the left-right translation mode of the rim flange portion. As described above, unlike the conventional modes that vibrate in the circumferential direction of the wheel, these modes make it possible to obtain natural frequencies based on non-uniform shapes in the circumferential direction of the wheel (for example, differences in the number and shapes of the spoke portions 15 shown in FIG. 6).

[0041] In this embodiment, the natural frequencies are calculated for the secondary bending mode of the rim portion, the tilt mode of the rim portion, and the lateral translation mode of the rim flange portion.

[0042] The natural frequencies can be calculated appropriately based on conventional procedures. In this embodiment, the natural frequencies of each mode can be calculated under the condition that the hub portion 13 of the wheel model 12 shown in Fig. 6 is constrained. These natural frequencies can be easily calculated using, for example, the functions (procedures) of the above-mentioned finite element analysis application software.

[0043] Fig. 7 is a diagram showing the deformation state of wheel model 12 in the secondary bending mode of the rim portion. Fig. 7(a) is a side view of wheel model 12. Fig. 7(b) is a front view of wheel model 12. Note that Fig. 7 illustrates a wheel model 12 having a greater number of spokes 15 than the wheel model 12 shown in Fig. 6. In this secondary bending mode of the rim portion, the rim portion 14 vibrates (deforms) in the radial direction of the wheel.

[0044] Fig. 8 is a diagram showing the deformation state of the wheel model 12 in the rim portion collapse mode. Fig. 8(a) is a side view of the wheel model 12. Fig. 8(b) is a front view of the wheel model 12. Note that Fig. 8 illustrates a wheel model 12 having a greater number of spokes 15 than the wheel model 12 shown in Fig. 6. In this rim portion collapse mode, the spokes 15 and rim portion 14 vibrate so as to collapse (bend) relative to the hub portion 13.

[0045] Fig. 9 is a perspective view showing the deformation state of the wheel model 12 in the left-right translation mode of the rim flange portion. Note that Fig. 9 illustrates a wheel model 12 having a greater number of spoke portions 15 than the wheel model 12 shown in Fig. 6. In this left-right translation mode of the rim flange portion, the rim flange portion 14c (rim portion 14) vibrates (deforms) in the left-right direction (axial direction (y-axis direction)) relative to the spoke portions 15 and hub portion 13.

[0046] Unlike the conventional modes that vibrate in the circumferential direction of the wheel, the secondary bending mode of the rim, the tilt mode of the rim, and the left-right translation mode of the rim flange make it possible to obtain natural frequencies based on the non-uniform shape of the wheel in the circumferential direction. The natural frequencies of the wheel model 12 are stored in a computer 1 (shown in FIG. 1).

[0047] [Calculate the difference in natural frequencies (second calculation step)] Next, in the creation method of this embodiment, the computer 1 (shown in Figure 1) calculates the difference between the natural frequency of the wheel 2 shown in Figure 2 and the natural frequency of the wheel model 12 shown in Figures 6 to 9 (second calculation step S6).

[0048] In this embodiment, as shown in Fig. 5, the natural frequencies A1 to A3 of the wheel 2 are measured for each of the predetermined modes (in this example, the secondary bending mode of the rim portion, the tilt mode of the rim portion, and the left-right translation mode of the rim flange portion). Furthermore, as shown in Figs. 7 to 9, the natural frequency (not shown) of the wheel model 12 is calculated for each of these modes. Then, in the second calculation step S6 of this embodiment, the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12 is calculated for each of these modes. The calculated difference in the natural frequencies of each mode is stored in the computer 1 (shown in Fig. 1).

[0049] [Change material properties of the second element (correction process)] Next, in the creation method of this embodiment, the computer 1 (shown in FIG. 1) changes the material properties of the second element 19 shown in FIG. 6 so as to reduce the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12 (modification process S7).

[0050] As described above, the natural frequency changes depending on the shape, restraint position, material properties, etc. of the wheel 2 (wheel model 12). In this embodiment, the shape of the wheel 2 shown in Fig. 2 matches the shape of the wheel model 12 shown in Fig. 6, and further, the restraint position (hub portion 3) of the wheel 2 matches the restraint position (hub portion 13) of the wheel model 12. For this reason, in order to reduce the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12, it is necessary to change (adjust) the material properties of the wheel model 12.

[0051] In this embodiment, as shown in Fig. 6, material properties as an elastic body are defined for the second element 19 forming the second portion 18 (rim portion 14 and spoke portion 15) which has a relatively large effect on the natural frequency. Therefore, in the modification step S7, the material properties of the second element 19 are changed so as to reduce the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12. In this embodiment, of the material properties (such as elastic modulus and density) defined for the second element 19, the elastic modulus which has a large effect on the natural frequency is changed.

[0052] In this embodiment, when the natural frequency of the wheel model 12 is smaller than the natural frequency of the wheel 2, the elastic modulus of the second element 19 is increased. This increases the natural frequency of the wheel model 12, making it possible to approach the natural frequency of the wheel 2. On the other hand, when the natural frequency of the wheel model 12 is larger than the natural frequency of the wheel 2, the elastic modulus of the second element 19 is decreased. This decreases the natural frequency of the wheel model 12, making it possible to approach the natural frequency of the wheel 2.

[0053] In this way, in the creation method of this embodiment, the material properties (including the elastic modulus) of the second element 19 are changed so that the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12 is reduced. As a result, in the creation method of this embodiment, it is possible to create a wheel model 12 that approximates the vibration characteristics of the actual wheel 2. Furthermore, since the material properties of the second element 19 that forms the second portion 18, which has a relatively large effect on the natural frequency, are changed, it is not necessary to change the material properties of the first element 17 that forms the first portion 16, which has a relatively small effect on the natural frequency. Therefore, in the creation method of this embodiment, it is possible to create a wheel model 12 that approximates the vibration characteristics of the actual wheel 2 in a short time.

[0054] The first element 17 forming the first portion 16, which has a relatively small effect on the natural frequency, is defined with material properties as a rigid body, and therefore does not affect the natural frequency of the wheel model 12. For this reason, in the modification step S7, it is preferable to change only the material properties of the second element 19. This allows the wheel model 12, which is close to the vibration characteristics of the actual wheel 2, to be created in a shorter time.

[0055] [Method of creating a wheel model (second embodiment)] In the creation method of the above-mentioned embodiments, in the correction step S7, the material property of the second element 19 is changed so as to reduce the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12, but the present invention is not limited to such an embodiment. For example, the material property of the second element 19 may be changed until the difference in the natural frequency reaches a predetermined threshold value. Fig. 10 is a flowchart showing the processing procedure of the wheel model creation method of another embodiment of the present invention.

[0056] [Determine whether the difference in natural frequency is below the threshold] In the creation method of this embodiment, after the second calculation step S6, the computer 1 judges whether or not the difference (in this example, the absolute value of the difference) between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12 is equal to or less than a predetermined threshold value (step S8). The threshold value can be set appropriately depending on the calculation accuracy required for the wheel model 12 (approximation to the vibration characteristics of the actual wheel 2). In this embodiment, the threshold value is set to 5% of the natural frequency of the wheel 2.

[0057] If it is determined that the difference between the natural frequencies (in this example, the absolute value of the difference) is equal to or less than the threshold value ("Yes" in step S8), the series of processes in the creation method ends. On the other hand, if it is determined that the difference between the natural frequencies is greater than the threshold value ("No" in step S8), the correction step S7, the first calculation step S5, and the second calculation step S6 are performed again.

[0058] In this manner, in this embodiment, the material properties of the second element 19 are changed (i.e., the first calculation step S5, the second calculation step S6, and the correction step S7 are repeated) until the difference between the natural frequency of the wheel 2 and the natural frequency of the wheel model 12 becomes equal to or less than the threshold value. As a result, in this embodiment, it becomes possible to more reliably create the wheel model 12 that is close to the vibration characteristics of the actual wheel 2.

[0059] [Simulation method for wheel and tire assembly] Next, a method for simulating an assembly of a wheel 2 and a tire mounted on the wheel 2 (hereinafter, sometimes referred to as a "simulation method") will be described. In the simulation method of the present embodiment, vibration characteristics of the assembly are evaluated, but are not particularly limited.

[0060] [Assembly] Fig. 11 is a tire meridian cross-sectional view including the tire rotation axis (not shown) of the assembly 21 in a normal state. The hub portion 3 and spoke portion 5 of the wheel 2 are omitted in Fig. 11. The assembly 21 is configured to include the wheel 2 and a tire 22 mounted on the wheel 2. The wheel 2 may be the same as that in the previous embodiments shown in Figs. 2 and 3.

[0061] [tire] The tire 22 to be evaluated may be one in the above-mentioned categories. In this embodiment, a pneumatic tire for a passenger vehicle is exemplified.

[0062] The tire 22 of this embodiment is provided with a carcass 24 extending from the tread portion 22a through the sidewall portion 22b to the bead core 23 of the bead portion 22c, and a belt layer 25 disposed radially outside the carcass 24 and inside the tread portion 22a.

[0063] The carcass 24 is composed of at least one carcass ply 24A, one carcass ply in this embodiment. The carcass ply 24A has carcass cords (not shown) arranged at an angle of, for example, 75 to 90 degrees with respect to the tire equator C. In this embodiment, a tread pattern is provided on an outer surface 22s of the tread portion 22a.

[0064] The belt layer 25 includes two inner and outer belt plies 25A and 25B in which belt cords (not shown) are arranged at an angle of, for example, 10 to 35 degrees with respect to the tire circumferential direction. These belt plies 25A and 25B are overlapped with the belt cords crossing each other.

[0065] In this specification, unless otherwise specified, the dimensions of each part of the tire are indicated as values ​​measured in a normal state, which means that the tire 22 is mounted on a normal rim (rim portion 4), inflated to the normal internal pressure, and unloaded.

[0066] A "genuine rim" is a rim that is determined for each tire by a standard system that includes the standard on which the tire 22 is based. Therefore, a genuine rim is, for example, a "standard rim" for JATMA, a "Design Rim" for TRA, and a "Measuring Rim" for ETRTO.

[0067] The "normal internal pressure" is the air pressure that is determined for each tire by each standard in a system of standards that includes the standard on which the tire 22 is based. Therefore, the normal internal pressure is, for example, the "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO.

[0068] Next, a specific procedure of the simulation method for the assembly 21 will be described. Fig. 12 is a flowchart showing the procedure of the simulation method of this embodiment.

[0069] [Enter wheel model] In the simulation method of this embodiment, first, the wheel model 12 (shown in FIG. 6) is input to the computer 1 (shown in FIG. 1) (step S11). Figure 13 is a cross-sectional view showing an example of the assembly model 31. In Figure 13, the hub portion 13 and the spoke portion 15 of the wheel model 12 shown in Figure 6 are omitted.

[0070] In step S11 of this embodiment, a wheel model 12 (shown in Figs. 6 and 13) for numerical analysis of the wheel shown in Figs. 2 and 3 is created based on the processing procedure (shown in Fig. 7 or 10) of the creation method of the previous embodiment. This makes it possible to create a wheel model 12 that is close to the vibration characteristics of the actual wheel 2 in a short period of time. The wheel model 12 is stored in the computer 1 (shown in Fig. 1).

[0071] [Enter tire model] Next, in the simulation method of this embodiment, a tire model 32 obtained by discretizing the tire 22 shown in FIG. 11 into a finite number of elements is input to the computer 1 (shown in FIG. 1) (step S12).

[0072] As shown in Fig. 13, in step S12 of this embodiment, the tire 22 is discretized using a finite number of elements G(i) (i = 1, 2, ...) that can be handled by a numerical analysis method, based on the information about the tire 22 shown in Fig. 11. As a result, in step S12, a tire model 32 is set. As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method is appropriately adopted. In this embodiment, the finite element method is adopted.

[0073] For example, a tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element is used as the element G(i). Each element G(i) has a plurality of nodes 26. For each element G(i), numerical data such as an element number, the number of the node 26, and the coordinate values ​​of the node 26 are defined. Furthermore, for each element G(i), numerical data such as material properties (e.g., density, Young's modulus, damping coefficient, loss tangent (tan δ), and / or complex modulus of elasticity E*, etc.) of members (shown in FIG. 11) constituting the tire 22 are defined.

[0074] In the tire model 32, a carcass ply model 34A that models the carcass ply 24A (shown in FIG. 11) and belt ply models 35A and 35B that model the belt plies 25A and 25B (shown in FIG. 11), respectively, are set. In addition, the tread pattern shown in FIG. 11 is reproduced on an outer surface 32s of the tread portion 32a. The tire model 32 is stored in the computer 1 (shown in FIG. 1).

[0075] [Set Assembly Model] Next, in the simulation method of this embodiment, the computer 1 (shown in FIG. 1) sets an assembly model 31 in which the tire model 32 is mounted on the wheel model 12 (step S13).

[0076] In step S13, a fitting simulation is performed to mount the tire model 32 on the wheel model 12, for example, based on the same procedure as in Patent Document 3 (JP Patent Publication 2002-350294 A). As a result, the tire model 32 is mounted on the wheel model 12, and an assembly model 31 filled with internal pressure (normal internal pressure) is set. For example, the above-mentioned finite element analysis application software is used for the fitting simulation. The assembly model 31 is stored in the computer 1 (shown in FIG. 1).

[0077] [Calculate the vibration characteristics of the assembly] Next, in the simulation method of this embodiment, computer 1 (shown in FIG. 1) performs rolling analysis using assembly model 31 to calculate vibration characteristics of assembly 21 (shown in FIG. 11) (step S14). The vibration characteristics can be calculated appropriately based on the rolling analysis of assembly model 31. In this embodiment, for example, based on a procedure similar to that of Patent Document 4 (JP Patent Publication No. 2017-125816), assembly model 31 is rolled on a road surface model (not shown) having a protrusion model to calculate physical quantities related to the vibration characteristics.

[0078] A physical quantity related to vibration characteristics (hereinafter, sometimes referred to as "physical quantity") can be appropriately set according to the vibration performance evaluated in the assembly 21 (shown in FIG. 11). One example of the physical quantity is the vibration acceleration in the tire circumferential direction at the excitation point by a protrusion model (not shown).

[0079] In this embodiment, the wheel model 12 that approximates the vibration characteristics of the actual wheel 2 is used to calculate the vibration characteristics of the assembly 21, improving the calculation accuracy of the vibration characteristics of the assembly 21 (tire 22). Furthermore, in the wheel model 12 of this embodiment, the material characteristics as a rigid body are defined for the first element 17 that forms the first portion 16, making it possible to reduce the cost required for rolling analysis. Physical quantities related to the vibration characteristics are stored in a computer 1 (shown in FIG. 1).

[0080] [Evaluate the vibration characteristics of the assembly] Next, in the simulation method of the present embodiment, it is evaluated whether the vibration characteristics of the assembly 21 are good or not (step S15). The vibration characteristics are evaluated appropriately. In the present embodiment, when a physical quantity related to the vibration characteristics (such as vibration acceleration) is equal to or less than a predetermined threshold value, the vibration characteristics of the assembly 21 can be evaluated as good.

[0081] If it is determined that the vibration characteristics are good ("Yes" in step S15), the assembly 21 is manufactured (step S16) based on the design factors, etc. of the wheel 2 and tire 22 shown in Fig. 11. On the other hand, if it is determined that the vibration characteristics are good ("No" in step S15), the design factors, etc. of the wheel 2 or tire 22 are changed (step S17), and steps S11 to S15 are performed again. This makes it possible to reliably design and manufacture the assembly 21 with good vibration characteristics.

[0082] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and carried out in various forms.

[0083] [Note] The present invention includes the following aspects.

[0084] [Invention 1] 1. A method for creating a wheel model for a numerical analysis of a wheel on which a tire is mounted, comprising the steps of: inputting the natural frequency of the wheel into a computer; inputting a wheel model obtained by discretizing the wheel into a finite number of elements into the computer; defining material properties as a rigid body for a first element forming a first portion of the wheel model among the finite number of elements; and defining material properties as an elastic body for a second element forming a second part of the wheel model among the finite number of elements; The computer, a first calculation step of calculating the natural frequencies of the wheel model having the material properties defined for the finite number of elements; a second calculation step of calculating the difference between the natural frequency of the wheel and the natural frequency of the wheel model; and performing a modification step of changing a material property of the second component so that the difference is reduced. How to create a wheel model. [Invention 2] The method for creating a wheel model according to aspect 1, wherein the computer repeats the first calculation step, the second calculation step, and the correction step until the difference becomes equal to or less than a predetermined threshold value. [Invention 3] The wheel includes a hub portion that is attached to a hub axle of a vehicle; 3. The method for creating a wheel model according to claim 1 or 2, wherein the first portion includes at least a part of the hub portion. [Invention 4] The wheel includes a rim portion to which a bead of the tire is attached, and a spoke portion extending between the rim portion and the hub portion, A method for creating a wheel model according to claim 3, wherein the second portion includes at least a part of the rim portion and at least a part of the spoke portion. [Invention 5] A method for creating a wheel model according to any one of claims 1 to 4, wherein the modification step changes only the material properties of the second element. [Invention 6] A method for simulating an assembly of the wheel and the tire mounted on the wheel, comprising the steps of: inputting the wheel model created by the creation method according to any one of the first to fifth aspects of the present invention into the computer; inputting a tire model obtained by discretizing the tire into a finite number of elements into the computer; The computer, setting an assembly model in which the tire model is mounted on the wheel model; and performing a rolling analysis using the assembly model to calculate vibration characteristics of the assembly. A method for simulating a wheel and tire assembly. [Explanation of symbols]

[0085] 12 Wheel Models 16 Part 1 17 First Element 18 Part 2 19 Second Element

Claims

1. 1. A method for creating a wheel model for a numerical analysis of a wheel on which a tire is mounted, comprising the steps of: inputting the natural frequency of the wheel into a computer; inputting a wheel model obtained by discretizing the wheel into a finite number of elements into the computer; defining material properties as a rigid body for a first element of said finite number of elements forming a first portion of said wheel model; and defining material properties as an elastic body for a second element forming a second part of the wheel model among the finite number of elements; The computer, a first calculation step of calculating the natural frequencies of the wheel model having the material properties defined for the finite number of elements; a second calculation step of calculating the difference between the natural frequency of the wheel and the natural frequency of the wheel model; and performing a modification step of changing a material property of the second component so that the difference is reduced. How to create a wheel model.

2. 2. The method for creating a wheel model according to claim 1, wherein the computer repeats the first calculation step, the second calculation step, and the correction step until the difference is equal to or less than a predetermined threshold value.

3. The wheel includes a hub portion that is attached to a hub axle of a vehicle; The method for creating a wheel model according to claim 1 , wherein the first portion includes at least a part of the hub portion.

4. The wheel includes a rim portion to which a bead of the tire is attached, and a spoke portion extending between the rim portion and the hub portion, The method for creating a wheel model according to claim 3 , wherein the second portion includes at least a part of the rim portion and at least a part of the spoke portion.

5. The method for creating a wheel model according to claim 1 , wherein the modifying step changes only the material properties of the second element.

6. A method for simulating an assembly of the wheel and the tire mounted on the wheel, comprising the steps of: a step of inputting the wheel model created by the creation method according to any one of claims 1 to 5 into the computer; inputting a tire model obtained by discretizing the tire into a finite number of elements into the computer; The computer, setting an assembly model in which the tire model is mounted on the wheel model; and performing a rolling analysis using the assembly model to calculate vibration characteristics of the assembly. A method for simulating a wheel and tire assembly.

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