A method of simulating a tire.

Abstract

To provide a simulation method of a tire capable of improving prediction accuracy of noise performance.SOLUTION: A method of simulating a tire. The tire simulation method includes a step of inputting the tire model 2 and the first road surface model 5 into the computer 1, a step of performing a rolling calculation of the tire model 2 in contact with the first road surface model 5, a step of inputting a second road surface model into the computer 1, a step of inputting the sound space domain 9 into the computer 1, a step of setting a sound absorption coefficient in the second road surface model, and a noise simulation step of calculating a physical quantity relating to noise in the sound space domain 9 based on the physical quantity relating to the displacement and the sound absorption coefficient while rotating the outer surface shape of the tire model 2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tire simulation method. [Background technology]

[0002] In recent years, simulation methods for evaluating tire noise performance using a computer have been proposed. For example, Patent Document 1 describes a tire simulation method that first includes a rolling simulation using a computer to calculate the rolling of a tire model that is in contact with an uneven road surface model, and a noise simulation that calculates physical quantities such as air pressure in a sound space region set around the tire model where air flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5662971 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the tire simulation method described above is capable of predicting the noise performance of a tire running on a road surface, further improvement in prediction accuracy is desired when comparing with actually measured noise performance.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire simulation method that can improve the prediction accuracy of noise performance. [Means for solving the problem]

[0006] The present invention is a tire simulation method including the steps of: inputting a tire model, in which a tire is modeled using a finite number of elements, into a computer; inputting a first road surface model, in which a road surface is modeled using a finite number of elements, into the computer; a rolling simulation step in which the computer performs a rolling calculation of the tire model in contact with the first road surface model; a step of inputting, in time series, physical quantities related to the displacement of nodes appearing on the outer surface of the rotating tire model calculated in the rolling simulation step into the computer; a step of inputting a second road surface model, in which a road surface is modeled using a finite number of elements, into the computer; a step of inputting, into the computer, the outer surface shape of the tire model specified based on the coordinate data, the second road surface model, and a sound space region forming an area surrounding at least a portion of each of these; a step of setting a sound absorption coefficient for the second road surface model; and a noise simulation step in which the computer calculates physical quantities related to noise in the sound space region based on the physical quantities related to the displacement and the sound absorption coefficient while rotating the outer surface shape of the tire model. [Effects of the Invention]

[0007] The tire simulation method of the present invention employs the above-described configuration, thereby improving the prediction accuracy of noise performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a computer device that performs processing according to an embodiment of the present invention. [Figure 2] 3 is a flowchart illustrating a simulation method according to the present embodiment. [Figure 3] 10 is a flowchart showing a rolling simulation process. [Figure 4] FIG. 2 is a perspective view showing a visualization of a tire model and a first road surface model. [Figure 5] 10 is a flowchart showing a noise simulation process. [Figure 6]FIG. 10 is a perspective view showing a visualization of a second road surface model. [Figure 7] 10 is a flowchart illustrating a process for inputting a sound space region. [Figure 8] FIG. 4 is a side view showing a visualization of the tire model and the second road surface model. [Figure 9] FIG. 2 is a side view illustrating a sound space region. [Figure 10] 10 is a graph showing the relationship between the frequency of noise and the sound absorption coefficient set in the second road surface model. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will now be described with reference to the drawings. The tire simulation method of this embodiment (hereinafter sometimes simply referred to as the "simulation method") is a method for predicting tire noise performance using a computer.

[0010] Fig. 1 is a perspective view of a computer 1 that performs processing according to this embodiment. As shown in Fig. 1, the computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with 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 a processing procedure (program) for executing the simulation method according to this embodiment.

[0011] 2 shows a specific processing procedure of the simulation method of this embodiment. The simulation method of this embodiment includes a rolling simulation step S1 in which a tire is rolled on a road surface, and a noise simulation step S2 in which noise generated by the rolling of the tire is reproduced. In this embodiment, the rolling simulation step S1 is carried out first.

[0012] An example of the processing procedure of the rolling motion simulation step S1 is shown in Fig. 3. As shown in Fig. 3, in the rolling motion simulation step S1 of this embodiment, first, a tire model 2 (shown in Fig. 4) that is a model of a tire is input to a computer 1 (step S11).

[0013] [Tire model input] Fig. 4 is a perspective view visualizing the tire model 2. As shown in Fig. 4, the tire model 2 is modeled (discretized) by using a finite number of elements F that can be handled by a numerical analysis method, which is the tire to be analyzed. As this numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method can be appropriately used, but in this embodiment, the finite element method is used.

[0014] The tire model 2 is provided with a tread pattern including a tread surface 3 and grooves 4 based on the shape of the tread portion of the tire to be analyzed. The grooves 4 in this embodiment include longitudinal grooves 4a and lateral grooves 4b.

[0015] Thus, in step S11, each portion of the tire is modeled using elements F in the tire model 2. Numerical data such as element numbers, node numbers, node coordinate values ​​in the global coordinate system XYZ, and material properties (e.g., density, Young's modulus and / or damping coefficient) are defined for each element F and stored in the computer 1.

[0016] [First road surface model input] Next, as shown in FIG. 3, in the rolling simulation step S1 of this embodiment, a first road surface model 5 is input to the computer 1 (step S12). FIG. 4 shows a visualized example of the first road surface model 5. As shown in FIG. 4, the first road surface model 5 of this embodiment is a numerical calculation model in which the road surface to be analyzed is modeled using a finite number of elements G. Such a first road surface model 5 may be defined as an approximation of, for example, an asphalt road surface or a road surface used in running noise tests (hereinafter simply referred to as an "ISO road surface"). The elements G are, for example, rigid surface elements set to be non-deformable, and numerical data such as element numbers and coordinate values ​​of nodes 7 are defined and stored in the computer 1. Furthermore, the first road surface model 5 of this embodiment is an uneven road surface model in which irregularities corresponding to the irregularities of the road surface are formed on its surface. However, the first road surface model 5 may also be a smooth road surface model without irregularities (for example, a single plane model).

[0017] [Rolling Simulation] Next, as shown in Fig. 3, in the rolling motion simulation step S1 of this embodiment, the computer 1 performs a rolling motion calculation of the tire model 2 in contact with the first road surface model 5 (steps S13 to S20). In this embodiment, the computer 1 calculates the state of the tire model 2 rolling on the first road surface model 5 based on predetermined conditions of the running speed v (shown in Fig. 4), internal pressure, and load (hereinafter referred to as "rolling motion calculation").

[0018] 3, in the rolling calculation of this embodiment, first, an internal pressure condition is applied to the tire model 2, and the deformation of the tire model 2 is calculated (step S13). In this step S13, the displacement of each node when the tire model 2 is inflated with internal pressure is calculated. As a result, the shape of the tire model 2 after inflation and deformation is calculated.

[0019] Next, load conditions are applied to the tire model 2 after inflation and deformation, and the deformation of the tire model 2 is calculated (step S14). In step S14 of this embodiment, as shown in Fig. 4, the tire model 2 is brought into contact with the unevenness 6 of the first road surface model 5, and a load L is applied in the direction perpendicular to the rotation axis 2s of the tire model 2. As a result, the tire model 2 that has been deformed by the load L after inflation and deformation is calculated. The value of the load L may be, for example, the standard maximum load of the tire.

[0020] Next, as shown in Fig. 3, the rotations of the tire model 2 and the first road surface model 5 are defined (step S15). In this step S15, angular velocities corresponding to the traveling speed v (shown in Fig. 4) are defined for the tire model 2 and the first road surface model 5, respectively.

[0021] Next, the computer 1 calculates the rolling state of the tire model 2 based on the rotations defined for the tire model 2 and the first road surface model 5 (step S16). This makes it possible to reproduce, in the tire model 2, the rolling state of a tire that deforms due to the unevenness of an asphalt road surface or the like.

[0022] In this rolling calculation, for example, deformation of the tire model 2 is calculated for each unit time Tx (x=0, 1, ...) (for example, every 1 μsec) according to the procedure described in the above-mentioned Patent Document 1. Such rolling calculation can be performed using commercially available finite element analysis application software such as Abaqus by Dassault Systèmes.

[0023] Next, the computer 1 stores, in chronological order, physical quantities related to the displacement of nodes appearing on the outer surface 2t (shown in FIG. 4) of the rotating tire model 2 for each unit time Tx (step S17). Here, the outer surface 2t of the tire model 2 refers to the outer surface that continues from the tread portion of the tire model 2 through the sidewall portion to the bead portion, and is intended to be the surface that comes into contact with the air flowing around the tire model 2. The "physical quantity related to displacement" is a physical quantity that can identify the displacement of nodes, and may include, for example, data on the coordinates, velocity, and / or acceleration of each node. In this embodiment, an example using "coordinate data" as the physical quantity related to displacement will be mainly described.

[0024] Furthermore, the computer 1 stores, in chronological order, deformation data, which is the difference between the coordinate data at time T(x+1) and the coordinate data at time Tx, for each node (step S18). This deformation data represents vibrations (e.g., deformations of 0.05 mm or less) occurring on the outer surface 2t of the tire model 2.

[0025] Next, the computer 1 determines whether a predetermined end time has elapsed (step S19). In step S19, if the computer 1 determines that the end time has elapsed, it ends the rolling simulation step S1. On the other hand, if it determines that the end time has not elapsed, it advances the unit time Tx by one (step S20), and performs the rolling calculation of the tire model 2 (step S16), the storage of coordinate data (step S17), and the storage of deformation data (step S18) again. This allows the computer 1 to store the coordinate data and deformation data of the tire model 2 from the start to the end of rolling as time-series data for each unit time Tx. The end time is determined appropriately depending on the simulation to be executed.

[0026] Next, in this embodiment, a noise simulation step S2 is performed as shown in Fig. 2. Fig. 5 shows a specific processing procedure of the noise simulation step S2.

[0027] [Input of the second road surface model] As shown in FIG. 5, in the noise simulation step S2 of this embodiment, first, a second road surface model 8 is input to the computer 1 (step S21). FIG. 6 is a perspective view that visualizes the second road surface model 8. As shown in FIG. 6, in this step S21, the second road surface model 8 is modeled using a finite number of elements J, which are road surfaces that can be handled by a numerical analysis method. Such a second road surface model 8 may be defined, for example, as the road surface of a drum testing machine having a cylindrical, smooth surface. Like the elements G of the first road surface model 5 shown in FIG. 4, the elements J are also made up of rigid surface elements that are set to be undeformable, and numerical data such as element numbers and coordinate values ​​of nodes 17 are defined and stored in the computer 1. Furthermore, the second road surface model 8 of this embodiment is a smooth road surface model made up of a smooth surface. However, the second road surface model 8 may also be a rough road surface model.

[0028] [Sound space area input] Next, as shown in Fig. 5, a sound space region 9 simulating an environment in which air flows inside is input to the computer 1 (step S22). Fig. 7 shows a specific processing procedure of step S22.

[0029] In step S22, a tire model 2A is first input to the computer 1 (step S221), separate from the tire model 2 in the rolling simulation step S1 shown in FIG. 2. FIG. 8 is a side view visualizing the tire model 2A and the second road surface model 8. In step S221, the tire model 2A is input using the coordinate data stored in step S17 described above (for example, coordinate data at the start time (unit time T0) of coordinate data acquisition). That is, this tire model 2A consists only of elements F that constitute the shape of the outer surface 2t that may come into contact with air in the sound space region 9, and elements of the internal structure are omitted. Therefore, the tire model 2A can have a much smaller amount of data than the tire model 2 shown in FIG. 4. In addition, for each element F of the tire model 2A of this embodiment, the deformation data stored in step S18 described above, as well as the coordinate data stored in step S17 described above, are defined.

[0030] Next, as shown in Figures 7 and 8, the tire model 2A is placed in contact with the second road surface model 8 shown in Figure 6 (step S222), and a sound space region 9 is set (step S223). The sound space region 9 constitutes the outer surface shape of the tire model 2A specified based on the coordinate data, the second road surface model 8, and a region surrounding at least a portion of each of them. In this embodiment, the sound space region 9 is determined as a space obtained by subtracting the volume occupied by the tire model 2A from the region of the curved body 10 that surrounds a portion of each of the tire model 2A and the second road surface model 8. Furthermore, since the sound space region 9 simulates an environment in which air flows inside, it is defined as a space in which sound is generated as air flows around the tire model 2A.

[0031] The curved body 10 is defined by boundary surfaces, which include an upper wall 9u, a front wall 9f, and a rear wall 9r. The upper wall 9u is formed to cover the entire tire model 2A, and has a contour shape that is a roughly ellipse cut in half in a side view. The front wall 9f extends horizontally rearward from the front end of the upper wall 9u, bending midway to connect to the second road surface model 8. The rear wall 9r extends horizontally forward from the rear end of the upper wall 9u, bending midway to connect to the second road surface model 8.

[0032] FIG. 9 is a side view illustrating the sound space region 9. FIG. 9 shows an enlarged view of the sound space region 9 at part IX in FIG. 8 where the tire model 2A comes into contact with the second road surface model 8. As partially shown in FIG. 9, the sound space region 9 is made up of an Euler mesh (Euler elements) divided using three-dimensional elements K. In this embodiment, the sound space region 9 is made up of a plurality of elements K in each of the tire radial direction, tire axial direction, and tire circumferential direction. Then, in a process described later, physical quantities related to noise in the sound space region 9 are calculated at the nodes 11 (or center of gravity 12) of each element K.

[0033] Furthermore, it is necessary to set the element size of the element K to a size large enough to adequately express the air pressure fluctuations according to the noise frequency. For this reason, the height H1 of the element K in the tire radial direction is preferably about 0.1 to 2.0 mm, for example.

[0034] From a similar viewpoint, the aspect ratio of element K, which is the ratio of the tire circumferential length L1 to the tire radial height H1, is preferably 100 or less, more preferably 10 or less, and is also preferably 0.01 or more, more preferably 0.1 or more.

[0035] 7, boundary conditions and the like of the sound space region 9 are set (step S224). Parameters such as the initial specific gravity, viscosity, pressure, and temperature of the air are assigned to each element K of the sound space region 9. In addition, the speeds of the outer surface 2t of the tire model 2A and the outer surface of the second road surface model 8 are assigned to the boundary between the tire model 2A and the second road surface model 8.

[0036] In this embodiment, the upper wall 9u, the front wall 9f, the rear wall 9r, the tire model 2A, and the second road surface model 8 are defined so that air cannot pass through the sound space region 9. As a result, regions other than the sound space region 9 are defined as being infinitely far away, which limits the calculation region of the simulation and ultimately helps to shorten the calculation time.

[0037] In this embodiment, noise performance is evaluated through bench testing of a tire model 2A. In this case, the top wall 9u, the front wall 9f, and the rear wall 9r are defined as wall surfaces that do not reflect sound. In another embodiment, when noise performance is evaluated through a running test of the tire model 2A, the inflow and outflow of element K of the top wall 9u, the front wall 9f, and the rear wall 9r are defined. Note that the inflow and outflow of element K may be defined, for example, by the inflow and outflow from the top wall 9u, the front wall 9f, and the rear wall 9r, or may be defined only by the pressure of element K.

[0038] As described above, in this embodiment, the sound space region 9 is input to the computer 1, and the coordinate data of the tire model 2 calculated by rolling using the first road surface model 5 shown in Fig. 4 is used to calculate the physical quantities of the sound space region 9. Therefore, the outer surface shape of the tire that deforms due to unevenness of the road surface can be reflected in the sound space region 9 as the tire model 2A.

[0039] Incidentally, it has been found that a portion of the air vibrations (i.e., sound) generated when a tire actually runs on a road surface is diffusely reflected depending on the properties of the road surface, i.e., the degree of unevenness, hardness, degree of porosity, etc., and is then absorbed by the road surface. In the present invention, in order to improve the prediction accuracy of noise performance, the phenomenon of sound absorption by the road surface is incorporated into the noise simulation step S2 as follows.

[0040] [Sound absorption coefficient setting] First, as shown in Fig. 5, a sound absorption coefficient based on unevenness is set for the second road surface model 8 (step S23). The sound absorption coefficient refers to the proportion of sound that is not reflected from the second road surface model 8 out of all sound that is incident on the second road surface model 8. The sound absorption coefficient indicates a value that differs depending on the properties of the road surface, such as the uneven shape of the road surface, the degree of unevenness, and surface hardness.

[0041] In this embodiment, the sound absorption coefficient is specified for each frequency of noise (sound incident on the second road surface model 8), for example. Fig. 10 is a graph showing the relationship between the frequency of noise and the sound absorption coefficient set for the second road surface model 8. As shown in Fig. 10, the sound absorption coefficient may be changed depending on the frequency of the noise. In this embodiment, the sound absorption coefficient is specified for each frequency of noise so that it increases approximately from a frequency of around 100 Hz to a frequency of around 2000 Hz.

[0042] In this embodiment, the entire second road surface model 8 is treated as one surface, and the sound absorption coefficient is set on that surface (stored in the computer 1). In another aspect, the sound absorption coefficient may be set at the node 17 (or the center of gravity 18) of each element J of the second road surface model 8. By setting the sound absorption coefficient at the node 17 (or the center of gravity 18) of each element J, it is possible to set the sound absorption coefficient according to the road surface characteristics (unevenness, hardness, etc.). In this aspect, the prediction accuracy of noise performance is further improved. However, in addition to the aspect in which the sound absorption coefficient is associated with the entire second road surface model 8 or the node 17 (or the center of gravity 18) of each element J of the second road surface model 8, for example, the sound absorption coefficient may be stored in the computer 1 as a parameter and set so that the value of (1 - sound absorption coefficient) is multiplied for each sound pressure level of each frequency of noise calculated by simulation. Note that the sound absorption coefficient may be specified for each noise frequency so that the actually measured noise and the noise calculated by noise simulation are similar to each other.

[0043] [Noise Simulation] Next, as shown in Fig. 5, in the noise simulation step S2 of this embodiment, the rotation of the second road surface model 8 is defined (step S24). In this step S24, as shown in Fig. 8, an angular velocity ω1 corresponding to the traveling speed v is defined for the rotation axis 8s of the second road surface model 8.

[0044] 5, the shape of the outer surface 2t of the tire model 2A for each unit time Tx is defined (step S25). In this step S25, the outer surface shape of the tire model 2A at any time is defined based on the coordinate data input to the computer 1 for each unit time Tx. As a result, in the noise simulation step S2, the shape of the outer surface 2t of the tire model 2A rolling on the road surface can be easily defined without separately performing a rolling calculation (deformation calculation) of the tire model 2A as in the rolling simulation step S1 described above.

[0045] Next, as shown in FIG. 5, at least the contact patch 13 of the tire model 2A is separated from the second road surface model 8 by an infinitesimal distance Ls, forming a gap 14 between the tire model 2A and the second road surface model 8 (step S26). As shown in FIG. 9, in this step S26, the contact patch 13 and portions of both sides of the contact patch 13 in the tire circumferential direction are partially deformed in the Z-axis direction, separating the contact patch 13 from the second road surface model 8 by the infinitesimal distance Ls. This makes it possible to form a gap 14 that is continuous in the tire circumferential direction across the entire width of the tread portion of the tire model 2A, not just in the recesses 15 deformed by rolling the first road surface model 5 (shown in FIG. 4). Note that, from the viewpoint of ensuring a sufficient sound space region 9, the minimum value of the infinitesimal distance Ls is preferably approximately 0.01 to 0.1 mm.

[0046] Next, as shown in Fig. 5, a sound space region 9 is set in the gap 14 between the tire model 2A and the second road surface model 8 (step S27). As shown in Fig. 9, in this embodiment, the sound space region 9 set in the gap 14 is modeled with a plurality of elements K in the tire radial direction. As a result, each element K of the sound space region 9 is modeled between the tire tread 16 of the tire model 2A and the second road surface model 8, which behave differently. In other words, the flows of the elements K on the tread 16 side and the elements K on the second road surface model 8 side can be calculated independently. This can improve the calculation accuracy of the physical quantities of the sound space region 9.

[0047] Next, as shown in FIG. 5 , the physical quantities of the sound space region 9 are calculated taking into account the above-mentioned sound absorption coefficient (step S28). The physical quantities related to noise in the sound space region 9 are calculated as physical quantities related to displacement while rotating the outer surface shape of the tire model 2, based on the coordinate data and the above-mentioned sound absorption coefficient, as follows in this embodiment: First, in this embodiment, the movement of air is expressed, for example, by the Navier-Stokes equation. This Navier-Stokes equation is converted into an approximate equation that can be calculated by the computer 1, for example, to calculate parameters that represent the state of movement of the air, i.e., the pressure and velocity at each position in the sound space region 9. Calculations of the sound space region 9 can be performed using commercially available fluid analysis application software such as WAVE6 from Dassault Systèmes.

[0048] In this embodiment, the physical quantity related to noise is a sound pressure level specified for each frequency. As described above, the sound pressure level is calculated based on the pressure and velocity calculated at each position in the sound space region 9. That is, the sound pressure level of the sound (noise) generated by the occurrence of each flow of element K in the sound space region 9 is calculated as the physical quantity related to noise. Note that the physical quantity related to noise is not limited to this embodiment, and for example, a change in sound pressure, flow velocity, air pressure, etc. may also be used.

[0049] Next, in step S28, the element K of the sound space region 9 passes through the longitudinal grooves 4a and lateral grooves 4b shown in Fig. 4, thereby reproducing so-called resonance noise caused by air columns formed in each actual groove of the tire. Furthermore, the flow and pressure fluctuations of the element K of the sound space region 9 are set within the longitudinal grooves 4a and lateral grooves 4b, thereby reproducing so-called impact noise and pumping noise.

[0050] Some or all of the sound (noise) reproduced in this way is incident on the second road surface model 8. The incident sound is reflected by each element J (shown in FIG. 6 ) of the second road surface model 8. During this reflection, the physical quantity of the sound (sound pressure level) is calculated taking into account the sound absorption coefficient stored in the node 17 (or center of gravity 18) of the entire second road surface model 8 or of each element J of the second road surface model 8. Specifically, the sound pressure level of the sound reflected by the second road surface model 8 is calculated by subtracting the sound pressure level of the sound absorbed (not reflected) by the second road surface model 8 from the sound pressure level of the sound incident on the second road surface model 8. As a result, the tire simulation method of the present invention can consider not only the phenomenon of tire vibration caused by an uneven road surface but also the phenomenon of sound absorption caused by an uneven road surface, thereby improving the prediction accuracy of noise performance.

[0051] In this embodiment, in order to evaluate noise performance, for example, a physical quantity related to noise (sound pressure level) is calculated at one or more preset observation points O (shown in FIG. 8). The observation points O can be set at any position, such as near the tread edge of the tire model 2A or on the side of the tire. In this embodiment, from the viewpoint of correctly evaluating actual noise performance, it is desirable to set the observation points O on the upper wall 9u.

[0052] [Physical quantity output in sound space domain] Next, as shown in Fig. 5, the computer 1 determines whether the end time has elapsed (step S28). In step S28, if it is determined that the end time has elapsed, the noise simulation step S2 is terminated, and the physical quantities of the sound space region 9 are output (step S3) as shown in Fig. 2.

[0053] 5, if the computer 1 determines that the end time has not yet elapsed, the unit time Tx is advanced by one (step S30), and steps S25 to S29 are performed. This makes it possible to calculate the physical quantities of the sound space region 9 while rotating the outer surface shape of the tire model 2A for each unit time Tx from the start to the end of rolling. The end time can be determined as appropriate depending on the simulation to be performed, but in this embodiment, the same end time as that of the rolling simulation step S1 is set.

[0054] 2, it is determined whether the physical quantities of the sound space region 9 are within the allowable ranges (step S4). In step S4, if the physical quantities of the sound space region 9 are within the allowable ranges, a tire is designed based on the tire model 2A (step S5). On the other hand, if the physical quantities are not within the allowable ranges, the tire model 2A is changed (step S6) and the simulation is performed again (steps S1 to S4). In this way, in this embodiment, the design of the tire model 2A is changed until the physical quantities are within the allowable ranges, making it possible to efficiently design tires with excellent performance.

[0055] [Variations] In the above embodiment, coordinate data was used as the physical quantity related to the displacement of the nodes when defining the outer surface shape of the tire model. However, instead, velocity data of each node may be used. In this case, in step S25 of FIG. 5 , for example, the outer surface shape (initial shape) of the tire model 2A at an arbitrary time (e.g., t0) is identified from the coordinate data, and then the displacement obtained by time-integrating the velocity at time (t1>t0) is added to the coordinates of each node to calculate the coordinate position of each node after time (t1). By performing this calculation sequentially, the outer surface shape of the rolling tire can be defined. Note that, instead of velocity data, acceleration data may be used as the physical quantity related to the displacement of the nodes. By time-integrating the acceleration twice, the displacement at each time can be obtained.

[0056] 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 implemented in various ways. [Example]

[0057] As an example, the sound pressure level of noise during driving was calculated for each frequency based on the processing procedure shown in Figure 2. Also, as a comparative example, in a noise simulation, the sound pressure level of noise during driving was calculated for each frequency when the sound absorption coefficient was not set for the second road surface model and sound incident on unevenness was totally reflected. Furthermore, as an actual measurement result, the sound pressure level of noise when the tire actually drove on an uneven road surface corresponding to the simulation was measured for each frequency. In the example, comparative example, and actual measurement, the calculated or measured noise frequencies were 1000 Hz, 1250 Hz, and 1600 Hz. The results of the tests are shown in Table 1.

[0058] [Table 1]

[0059] In Table 1, the sound pressure level for noise at each frequency is displayed as an index, with the actual measurement being set at 100. The closer the number is to 100, the closer it is to the actual measurement.

[0060] As a result of the test, it was confirmed that the Example was closer to the actual measurement than the Comparative Example. Therefore, it was confirmed that the tire simulation method of the present invention, by adopting the above-mentioned configuration, improves the prediction accuracy of noise performance.

[0061] [Note] The present invention includes the following aspects.

[0062] [Invention 1] 1. A tire simulation method, comprising: a step of inputting a tire model obtained by modeling a tire using a finite number of elements into a computer; inputting a first road surface model, in which the road surface is modeled using a finite number of elements, into the computer; a rolling motion simulation step in which the computer performs a rolling motion calculation of the tire model in contact with the first road surface model; a step of inputting, into the computer in time series, physical quantities related to the displacement of nodes appearing on the outer surface of the rotating tire model calculated in the rolling simulation step; inputting a second road surface model, in which the road surface is modeled using a finite number of elements, into the computer; inputting into the computer the outer surface shape of the tire model specified based on the coordinate data, the second road surface model, and a sound space region that defines a region surrounding at least a portion of each of the second road surface model and the tire model; setting a sound absorption coefficient based on the unevenness in the second road surface model; a noise simulation step in which the computer calculates a physical quantity related to noise in the sound space region based on the physical quantity related to the displacement and the sound absorption coefficient while rotating the outer surface shape of the tire model; A tire simulation method including: [Invention 2] The tire simulation method according to the first aspect of the present invention, wherein the physical quantity relating to the noise includes a sound pressure level specified for each frequency. [Invention 3] 3. The tire simulation method according to claim 1, wherein the sound absorption coefficient is specified for each frequency. [Invention 4] 4. The tire simulation method according to any one of claims 1 to 3, wherein the first road surface model is a model of a road surface on which projections and depressions are formed. [Invention 5] 4. The tire simulation method according to any one of claims 1 to 3, wherein the second road surface model is a model of a road surface consisting of a smooth surface. [Explanation of symbols]

[0063] 1. Computer 2 Tire Models 5 First road model 9 Sound spatial domain

Claims

1. 1. A tire simulation method, comprising: a step of inputting a tire model obtained by modeling a tire using a finite number of elements into a computer; inputting a first road surface model, in which the road surface is modeled using a finite number of elements, into the computer; a rolling motion simulation step in which the computer performs a rolling motion calculation of the tire model in contact with the first road surface model; a step of inputting, into the computer in time series, physical quantities related to the displacement of nodes appearing on the outer surface of the rotating tire model calculated in the rolling simulation step; inputting a second road surface model, in which the road surface is modeled using a finite number of elements, into the computer; inputting the outer surface shape of the tire model, the second road surface model, and a sound space region that defines a region surrounding at least a portion of each of the tire model and the second road surface model into the computer; setting a sound absorption coefficient for the second road surface model; a noise simulation step in which the computer calculates a physical quantity related to noise in the sound space region based on the physical quantity related to the displacement and the sound absorption coefficient while rotating the outer surface shape of the tire model; A tire simulation method including:

2. The tire simulation method according to claim 1 , wherein the physical quantity related to the noise includes a sound pressure level specified for each frequency.

3. The tire simulation method according to claim 2 , wherein the sound absorption coefficient is specified for each of the frequencies.

4. 4. The tire simulation method according to claim 1, wherein the first road surface model is an uneven road surface model having unevenness formed therein.

5. 4. The tire simulation method according to claim 1, wherein the second road surface model is a smooth road surface model consisting of a smooth surface.

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