JP7574573B2 - How to simulate tires - Google Patents

Description

The present invention relates to a tire simulation method.

The following Patent Document 1 describes a tire testing device that includes a support means for supporting a tire so that it can rotate freely, and a first moving means for pressing the tire against the surface of a test plate. In this testing device, the tire is passed through a protrusion provided on the test plate, and the external force applied by the protrusion is measured.

Patent No. 5745574

In general, a tire's rotation axis is attached to a vehicle via a suspension, allowing for radial and axial displacements. For this reason, in order to evaluate the vibration performance of a tire, it is important to obtain the physical quantities acting on the tire's rotation axis, which is allowed for the above-mentioned displacements.

On the other hand, although the tire of the above test device has a rotating shaft supported so that it can rotate freely, the above displacement is restricted. Therefore, the test device cannot obtain the above physical quantities, and there is a problem that the vibration performance of the tire cannot be evaluated.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to provide a tire simulation method that can evaluate the vibration performance of a tire.

The present invention is a simulation method for evaluating the vibration performance of a tire, which includes the steps of inputting a wheel model consisting of a tire model that models the tire and a support element model that models a support element that rotatably supports the rotation axis of the tire model into a computer, inputting a road surface model into the computer, and causing the computer to roll the tire model of the wheel model on the road surface model to obtain physical quantities acting on the rotation axis, and the support element model supports the tire model displaceably with six degrees of freedom in a three-dimensional orthogonal coordinate system.

In the tire simulation method according to the present invention, the support element model may include a spring model that models a spring means.

In the tire simulation method according to the present invention, the spring constant of the spring model may be 1/100 or less of the longitudinal spring constant of the tire.

In the tire simulation method according to the present invention, the step of acquiring the physical quantity may include a first step of applying a first load to the rotation axis by bringing the tire model into contact with the road surface model and bringing the rotation axis and the road surface model closer together, and a second step of elastically deforming the spring model so that the spring model applies a second load to the rotation axis in the opposite direction to and of the same magnitude as the first load.

In the tire simulation method according to the present invention, at least the second step may be performed after constraining the rotation shaft.

The tire simulation method according to the present invention may further include a step of releasing the constraint on the rotation shaft after the second step.

In the tire simulation method according to the present invention, the step of acquiring the physical quantity may include a step of vibrating the tire model or the rotating shaft, and a step of calculating the response of the rotating shaft to the vibration.

In the tire simulation method of the present invention, the tire model is supported so that it can be displaced with the six degrees of freedom. This allows the present invention to obtain the physical quantities acting on the rotation axis of the tire model in which the displacement is permitted, thereby making it possible to evaluate the vibration performance of the tire.

FIG. 1 is a perspective view showing an example of a computer for executing a tire simulation method. 1 is a flowchart showing an example of a processing procedure of a tire simulation method. FIG. 2 is a perspective view showing an example of a wheel model and a road surface model. FIG. 2 is a cross-sectional view of a tire model. 13 is a flowchart showing an example of a processing procedure of a physical quantity acquiring step. FIG. 11 is a side view of a wheel model for explaining an example of a processing procedure of the first step. FIG. 11 is a side view of a wheel model illustrating an example of a processing procedure of the second step. 13 is a graph showing the relationship between the transfer function in the X-axis translation direction (left-right direction) and frequency. 13 is a graph showing the relationship between the transfer function in the Y-axis translation direction (front-rear direction) and frequency. 13 is a graph showing the relationship between the transfer function in the Z-axis translation direction (vertical direction) and frequency. 13 is a graph showing the relationship between the transfer function in the Y-axis rotation direction (around the front-to-rear axis) and frequency. 13 is a graph showing the relationship between the transfer function in the Z-axis rotation direction (around the up-down axis) and frequency. 13 is a graph showing the relationship between the reaction force against the first load and time in Examples 1 to 3.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the tire simulation method of this embodiment (hereinafter sometimes simply referred to as the "simulation method"), the vibration performance of a tire is evaluated. The tire to be analyzed may or may not actually exist. A computer is used in the simulation method of this embodiment. FIG. 1 is a perspective view showing an example of a computer 1 for executing the simulation method.

The computer 1 is configured to include, for example, a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with, 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 software and the like for executing the simulation method of this embodiment in advance. Thus, the computer 1 is configured as a simulation device for evaluating the vibration performance of a tire.

Figure 2 is a flowchart showing an example of the processing procedure of a tire simulation method. In the simulation method of this embodiment, first, a wheel model is input to a computer 1 (step S1). Figure 3 is a perspective view showing an example of a wheel model 2 and a road surface model 3.

The wheel model 2 includes a tire model 5 and a support element model 6. In this embodiment, the wheel model 2 is defined as a three-dimensional model in a three-dimensional orthogonal coordinate system. Figure 4 is a cross-sectional view of the tire model 5.

The tire model 5 is a model of the tire (not shown) to be analyzed. As shown in FIG. 4, the tire model 5 can be defined by modeling (discretizing) the tire with a finite number of elements F(i) (i = 1, 2, ...) that can be handled by a numerical analysis method, for example.

As the numerical analysis method, for example, the finite element method, the finite volume method, the difference method, or the boundary element method (in this embodiment, the finite element method) can be appropriately adopted. For example, three-dimensional tetrahedral solid elements, pentahedral solid elements, or hexahedral solid elements are used for the elements F(i). Each element F(i) is configured to include a plurality of nodes 7 and linear edges 8 connecting adjacent nodes 7, 7. Numerical data such as the element number, the node 7 number, the coordinate values of the nodes 7, and material properties (for example, density, Young's modulus, or damping coefficient) are defined for each element F(i).

In the tire model 5, the rubber portion including the tire tread rubber (not shown), the carcass ply that forms the tire's framework, and the belt ply arranged radially outward of the carcass ply are each modeled (discretized) with elements F(i). As a result, the tire model 5 is set with a rubber member model 11, a carcass ply model 12, and a belt ply model 13.

In step S1, the tire model 5 after internal pressure filling is calculated. In this embodiment, the bead portions 5c, 5c of the tire model 5 are constrained by a rim model 14 that models the tire rim (not shown). In this embodiment, the rim model 14 is defined by rigid plane elements (not shown) that are set to be non-deformable.

In step S1 of this embodiment, the deformation of the tire model 5 is calculated based on the uniformly distributed load w that corresponds to the internal pressure condition. This allows the tire model 5 after internal pressure filling to be calculated. For the internal pressure, it is desirable to set, for example, the air pressure defined by each standard in the standard system that includes the standard on which the tire to be analyzed is based.

For deformation calculation of the tire model 5, a mass matrix, stiffness matrix, and damping matrix are created for each element F(i) based on the shape and material properties of each element F(i). These matrices are then combined to create a matrix for the entire system. Then, equations of motion are created by applying the various conditions described above, and these are calculated for each minute time (unit time T(x) (x = 0, 1, ...)). In this way, deformation calculation of the tire model 5 is performed, and the tire model 5 after internal pressure filling can be obtained.

For the deformation calculation of the tire model 5 (including the deformation calculation in the physical quantity acquisition step S3 described below), a commercially available finite element analysis application software such as LS-DYNA manufactured by LSTC may be used. The unit time T(x) may be set appropriately depending on the required simulation accuracy.

As shown in FIG. 3, the rotation axis 16 of the tire model 5 of this embodiment is defined by a line element H that is defined to be non-deformable. A pair of nodes 17, 17 are defined at both ends of the line element H of this embodiment. The rotation axis 16 may be defined by discretizing the rotation axis of the tire to be analyzed (not shown) with elements F(i). The tire radial distance L1 between the rotation axis 16 and the rim model 14 (or the bead portion 5c shown in FIG. 4) is defined to be constant. In this embodiment, the rotation of the rim model 14 and the tire model 5 is calculated along with the rotation of the rotation axis 16.

The support element model 6 is a model of a support element (not shown). The support element is for supporting the rotation axis of a tire (not shown) so that it can rotate freely. In this embodiment, the support element includes a suspension (not shown).

The support element model 6 can be set as appropriate as long as it is a model of a support element (not shown). In this embodiment, the support element model 6 includes a spring model 21 that models a spring means (coil spring), which is one of the components of the suspension (not shown).

The support element model 6 of this embodiment is composed only of a spring model 21. Therefore, in the simulation method of this embodiment, a support element model 6 that simplifies the support element (not shown) is defined, which can suppress increases in model creation time and calculation costs. Note that the support element model 6 may include, for example, a damper model (not shown) that models a damper, which is one of the components of a suspension.

The spring model 21 of this embodiment is defined by spring elements J that are set to be expandable and contractible. Such a spring model 21 does not need to be discretized (so-called mesh division) into a large number of elements, for example, and therefore it is possible to significantly reduce the model creation time.

The spring model 21 (spring element J) specifies the two points (one end 21a and the other end 21b) that are connected, but the specific volume and shape are not defined. For example, the coordinates, distance, and spring constant between the two points are defined in the spring model 21. With such a spring model 21, it is possible to calculate the force acting between the two points according to Hooke's law based on the change in the distance between the two points.

The spring constant can be set appropriately. The spring constant in this embodiment is set to 1/100 or less of the vertical spring constant of the tire (tire model 5) (not shown). This prevents the vertical spring component of the spring model 21 from affecting the natural frequency (resonance frequency) of the vertical spring component of the tire in the physical quantity acquisition process S3 described below. Therefore, the simulation method of this embodiment can improve the evaluation accuracy of the vibration performance of the tire. It is preferable that the spring constant is set to 1/500 or more of the vertical spring constant of the tire. This makes it possible to acquire physical quantities that take the suspension into account in the physical quantity acquisition process S3 described below.

The support element model 6 in this embodiment is configured to include a pair of spring models 21, 21. Note that the support element model 6 may be configured to include only one spring model 21, or may be configured to include three or more spring models 21.

One end 21a of each spring model 21 (spring element J) is connected to the rotation axis 16 of the tire model 5. In this embodiment, the one end 21a is connected to each node 17, 17 of the line element H of the rotation axis 16 by a turning pair. This allows the support element model 6 (spring model 21) to support the rotation axis 16 of the tire model 5 rotatably (in this example, rotatably in the X-axis rotation direction θx). The other end 21b of the spring model 21 is arranged on the road surface model 3 side (lower side in the figure) with respect to the one end 21a. A mass point 22 is defined on the other end 21b of the spring model 21 to apply a load (second load F2 in FIG. 7) to the road surface model 3 side to the rotation axis 16 (including the tire model 5) in the second step S33 (shown in FIG. 5) described later. In this embodiment, the spring model 21 and the mass point 22 are allowed to overlap with the road surface model 3.

The support element model 6 supports the tire model 5 so that it can be displaced with six degrees of freedom in a three-dimensional Cartesian coordinate system. "Six degrees of freedom" includes the degrees of freedom (translational degrees of freedom) in the X-axis translation direction, Y-axis translation direction, and Z-axis translation direction in the three-dimensional Cartesian coordinate system, as well as the degrees of freedom (rotational degrees of freedom) in the X-axis rotation direction θx, Y-axis rotation direction θy, and Z-axis rotation direction θz. "Displaceable with six degrees of freedom" indicates that the tire model 5 including the rotation axis 16 can be displaced with six degrees of freedom relative to the support element model 6.

In this embodiment, the six-degree-of-freedom constraint condition is set to be invalid for node 7 of each element F(i) of the tire model 5 shown in FIG. 4 and node 17 of the line element H of the rotation axis 16. This allows the support element model 6 to support the tire model 5 including the rotation axis 16 so that it can be displaced with six degrees of freedom.

In step S1 of this embodiment, as described above, the tire model 5 and the support element model 6 are defined, thereby defining the wheel model 2. The wheel model 2 is stored in the computer 1.

Next, in the simulation method of this embodiment, as shown in FIG. 2, a road surface model 3 is input to a computer 1 (shown in FIG. 1) (step S2). The road surface model 3 of this embodiment is defined as a three-dimensional model in a three-dimensional orthogonal coordinate system, similar to the wheel model 2.

As shown in FIG. 3, in step S2, the road surface is discretized using a finite number of elements G(i) (i=1, 2, ...) that can be handled by a numerical analysis method (in this embodiment, the finite element method) based on information about the road surface (not shown). As a result, in step S2, a road surface model 3 is set.

Element G(i) is defined as a rigid plane element that is defined to be non-deformable. Element G(i) has a number of nodes 23. Furthermore, element G(i) is defined with numerical data such as an element number and the coordinate values of the nodes 23.

In step S2 of this embodiment, a road surface model 3 having a smooth surface is defined, but is not limited to this. In step S2, for example, a road surface model 3 having minute irregularities, irregular steps, depressions, undulations, or irregularities approximating the actual road surface such as ruts, as in an asphalt road surface, may be defined. The road surface model 3 is input to the computer 1 shown in FIG. 1.

Next, in the simulation method of this embodiment, as shown in Figures 2 and 3, the computer 1 (shown in Figure 1) rolls the tire model 5 of the wheel model 2 on the road surface model 3 to acquire the physical quantities acting on the rotation shaft 16 (physical quantity acquisition step S3). Figure 5 is a flowchart showing an example of the processing procedure of the physical quantity acquisition step S3.

In the physical quantity acquisition step S3 of this embodiment, first, the rotation axis 16 (shown in FIG. 3) is constrained (step S31). In this embodiment, a six-degree-of-freedom constraint condition is effectively set for the node 17 of the line element H of the rotation axis 16, thereby constraining the displacement of the rotation axis 16.

Next, in the physical quantity acquisition step S3 of this embodiment, a first load is applied to the rotating shaft 16 (shown in FIG. 3) (first step S32). FIG. 6 is a side view of the wheel model 2 illustrating an example of the processing procedure of the first step S32.

The first load F1 can be set as appropriate. In this embodiment, the first load F1 is set to the load applied to the tire (not shown) to be analyzed. An example of the load applied is the load specified by each of the above standards.

In the first step S32, a first load F1 can be applied to the rotating shaft 16 based on an arbitrary procedure. In the first step S32 of this embodiment, first, the tire model 5 is brought into contact with the road surface model 3. A predetermined friction coefficient is defined between the tire model 5 and the road surface model 3. Next, in the first step S32, the rotating shaft 16 and the road surface model 3 are brought closer together while the tire model 5 and the road surface model 3 are in contact with each other. As a result, in the first step S32, a load (first load F1) can be applied to the rotating shaft 16 through the tire model 5 that is pressed against the road surface model 3 and elastically deformed. In this embodiment, the rotating shaft 16 and the road surface model 3 are brought closer together until the load applied to the rotating shaft 16 becomes equal to the first load F1.

In the first step S32 of this embodiment, the road surface model 3 is moved toward the rotation axis 16, but this is not limited to the above. For example, the rotation axis 16 may be moved relative to the road surface model 3, or both the rotation axis 16 and the road surface model 3 may be moved in directions facing each other. When moving the rotation axis 16 in the first step S32, the constraint condition for the degree of freedom of the Z-axis translation direction (up and down direction) of the rotation axis 16, among the six degrees of freedom of the rotation axis 16, may be temporarily set to invalid.

Next, in the physical quantity acquisition step S3 of this embodiment, the spring model 21 applies a second load to the rotating shaft 16 (second step S33). The second load is in the opposite direction to the first load F1 and has the same magnitude. Figure 7 is a side view of the wheel model for explaining an example of the processing procedure of the second step S33.

In the second step S33 of this embodiment, first, the spring model 21 is elastically deformed. In the second step S33, the spring model 21 can be elastically deformed based on any procedure. In this embodiment, a mass point 22 is defined to apply a load (in this example, a second load F2) in the opposite direction to the first load F1 to the other end 21b of the spring model 21.

The mass point 22 is for applying the second load F2 to the rotation axis 16 of the tire model 5 by elastically deforming the spring model 21. When there are multiple spring models 21 (in this embodiment, a pair of spring models 21, 21 shown in FIG. 3), mass points 22 are defined for applying a load (in this example, F1/2) obtained by dividing the first load F1 by the number of spring models 21 to the other end 21b of each spring model 21. As a result, in the second step S33, the spring model 21 is elastically deformed (tensile deformation) in the direction opposite to the direction in which the first load F1 acts, and a second load F2 of the same magnitude and in the opposite direction to the first load F1 can be applied to the rotation axis 16.

In this embodiment, the spring model 21 is elastically deformed (tensilely deformed) by defining a mass point 22 at the other end 21b of the spring model 21, but this is not limited to the above. For example, if the other end 21b of the spring model 21 is disposed on the opposite side of the road surface model 3 (upper side in the figure) with respect to the one end 21a, the spring model 21 may be compressively deformed (elastically deformed).

Instead of the mass point 22, a load condition may be defined for the other end 21b of the spring model 21. In this case, it is desirable to define the load condition so that the value obtained by dividing the first load F1 by the spring constant (if multiple spring models 21 are included, the value obtained by multiplying the number of spring models 21 by the spring constant) is equal to the amount of displacement of the spring model 21.

The second step S33 in this embodiment is performed after the rotating shaft 16 is restrained (after step S31). Therefore, in the second step S33, the tire model 5 and the spring model 21, which are elastically deformed, can be prevented from exerting forces on each other via the rotating shaft 16. Therefore, in the physical quantity acquisition step S3, the occurrence of coupled vibration between the tire model 5 and the spring model 21 can be suppressed.

Next, in the physical quantity acquisition process S3 of this embodiment, the state in which the tire model 5 of the wheel model 2 rolls on the road surface model 3 is calculated (process S34). In process S34, first, as shown in FIG. 3, among the six degrees of freedom of the constrained rotation axis 16, the constraint condition of the rotation direction of the rotation axis 16 (X-axis rotation direction θx) is set to be invalid. As a result, the rotation axis 16 of the tire model 5 can be supported rotatably (in this example, rotatably in the X-axis rotation direction θx) by the spring model 21 (support element model 6).

Next, in step S34 of this embodiment, an angular velocity V1 corresponding to the running speed V is defined for the rotation axis 16 of the tire model 5. Furthermore, in step S34, a translational velocity V2 corresponding to the running speed V is set for the road surface model 3. This makes it possible to calculate the tire model 5 rolling on the road surface model 3 in step S34.

In step S34 of this embodiment, five degrees of freedom of the rotation axis 16 (five degrees of freedom excluding the X-axis rotation direction θx) are constrained. Therefore, in step S34, the tire model 5 can be rolled on the road surface model 3 while suppressing the occurrence of coupled vibration between the tire model 5 and the spring model 21.

Next, in the physical quantity acquisition step S3 of this embodiment, the constraint on the rotation axis 16 is released (step S35). In step S35 of this embodiment, the six-degree-of-freedom constraint condition is set to be invalid for the node 17 of the line element H of the rotation axis 16 (in this example, the constraint condition for the X-axis rotation direction θx has already been set to be invalid). As a result, in step S35, the constraint on the rotation axis 16 is released.

In the physical quantity acquisition process S3 of this embodiment, after the second process S33 in which a second load F2 is defined on the rotating shaft 16 in the opposite direction to and of the same magnitude as the first load F1, the constraint on the rotating shaft 16 is released. As a result, in the physical quantity acquisition process S3, the reaction force R1 against the first load F1 and the reaction force R2 against the second load F2 can be balanced, so that the occurrence of coupled vibration between the rolling tire model 5 and the spring model 21 can be suppressed.

In step S35, it is desirable to release the constraint on the rotating shaft 16 at the timing when the initial micro-vibration occurring in the tire model 5 immediately after the start of rolling has damped. This makes it possible to effectively suppress the occurrence of coupled vibration between the rolling tire model 5 and the spring model 21 in the physical quantity acquisition step S3.

To effectively exert the above effect, it is desirable to release the constraint on the rotating shaft 16 0.025 seconds after the tire model 5 starts rolling in step S34. Note that even if the constraint on the rotating shaft 16 is released a long time after the tire model 5 starts rolling, there is a risk of the calculation time increasing. From this perspective, it is desirable to release the constraint on the rotating shaft 16 before 0.1 seconds have elapsed after the tire model 5 starts rolling in step S34.

Next, in the physical quantity acquisition step S3 of this embodiment, the tire model 5 or the rotating shaft 16 shown in FIG. 3 is vibrated (step S36). Any procedure can be adopted for vibrating the tire model 5 or the rotating shaft 16. For example, the tire model 5 may be vibrated by setting a convex portion (not shown) on the road surface model 3 and passing the tire model 5 through the convex portion, or an impact may be input to the tread portion 5a (shown in FIG. 4) of the tire model 5. For example, the rotating shaft 16 may be vibrated by inputting an impact that impacts the rotating shaft 16. The size of the convex portion, the magnitude of the impact, and the interval between the convex portions and the interval between the impacts can be appropriately set according to the vibration performance to be evaluated.

Next, in the physical quantity acquisition step S3 of this embodiment, the response of the rotating shaft 16 to the vibration is calculated (step S37). The response of the rotating shaft 16 can be calculated as appropriate. In this embodiment, the transfer function (accelerance and inertance) of the rotating shaft 16 is acquired as the response of the rotating shaft 16.

The tire model 5 in this embodiment is supported so that it can be displaced with six degrees of freedom, so the response of the rotating shaft 16 to the vibration can also be obtained with six degrees of freedom. Therefore, in step S37, it is possible to calculate the physical quantities acting on the rotating shaft for a tire (not shown) that is attached to the vehicle via a suspension.

In addition, in this embodiment, the spring constant of the spring model 21 is set to 1/100 or less of the vertical spring constant of the tire (not shown), so that the vertical spring component of the spring model 21 can be prevented from affecting the natural frequency (resonant frequency) of the vertical spring component of the tire. Therefore, in step S4 (shown in FIG. 2) described later, it becomes possible to evaluate the resonant frequency. The response of the rotating shaft 16 is stored in the computer 1.

Next, in the simulation method of this embodiment, as shown in FIG. 2, the vibration performance of the tire (not shown) is evaluated as to whether it is good or not (step S4). In step S4, it is determined whether the vibration performance of the tire is good or not based on the physical quantity acting on the rotating shaft 16 (shown in FIG. 3) acquired in the physical quantity acquisition step S3 (in this example, the response of the rotating shaft to vibration). Note that the quality of the vibration performance may be determined by the computer 1 (shown in FIG. 1) or by an operator.

If it is determined in step S4 that the tire has good vibration performance ("Y" in step S4), the tire is manufactured based on tire design drawings (CAD data) (not shown) and the like (step S5). On the other hand, if it is determined in step S4 that the tire has poor vibration performance ("N" in step S4), the tire design factors are changed (step S6) and steps S1 to S4 are carried out again. This makes it possible to design a tire with good vibration performance.

As shown in FIG. 5, in the previous embodiments, step S31 of constraining the rotating shaft 16 (shown in FIG. 7) was performed before the first step S32 and the second step S33, but this is not particularly limited. As long as at least the second step S33 is performed after constraining the rotating shaft 16 (i.e., after step S31), for example, step S31 may be performed after the first step S32. In this embodiment, as in the previous embodiments, the elastically deformed tire model 5 and spring model 21 can be prevented from exerting forces on each other via the rotating shaft 16.

As shown in FIG. 3, in the embodiments described above, the spring model 21 is modeled using spring elements J, but is not limited to this. The spring model 21 may be, for example, a spring means (not shown) constituting a suspension that is discretized into a finite number of elements. In such a spring model 21, the spring means is faithfully reproduced, making it possible to perform a highly accurate simulation.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways.

The vibration performance of the tire was evaluated based on the processing procedure shown in Figure 2 (Examples 1 to 3 and Comparative Example). In Examples 1 to 3, a support element model was defined that supports the tire model in a three-dimensional orthogonal coordinate system so that it can be displaced with six degrees of freedom. In Examples 1 and 2, the spring constant of the spring model was set to 1/100 of the vertical spring constant of the tire. On the other hand, in Example 3, the spring constant of the spring model was set to 1/50, which is greater than 1/100 of the vertical spring constant of the tire.

In Examples 1 and 3, based on the processing procedure shown in FIG. 5, a first step of applying a first load to the rotating shaft after restraining the rotating shaft, and a second step of applying a second load to the rotating shaft by the spring model were carried out. On the other hand, in Example 2, the first and second steps were carried out without restraining the rotating shaft. Then, for Examples 1 to 3, the physical quantities acting on the rotating shaft of the tire model rolling on the road surface model were calculated.

In the comparative example, similarly to Patent Document 1, the rotation axis of the tire model was defined in a three-dimensional orthogonal coordinate system so as to be displaceable only in the rotation direction (X-axis rotation direction). A first load and a second load were applied to the rotation axis, and physical quantities acting on the rotation axis of the tire model rolling on the road surface model were calculated. The common specifications are as follows:
Tire size: 195/65R15
Rim size: 15x6J
Internal pressure: 230 kPa
First load F1 and second load F2: 4240 N
Traveling speed V: 60km/h
Vibration on a rotating shaft (hammering):
X-axis translation direction (left/right direction)
Y-axis translation direction (back and forth direction)
Z-axis translation direction (vertical direction)
Y-axis rotation direction (around the front-rear axis)
Z-axis rotation direction (around the vertical axis)

Figure 8 is a graph showing the relationship between the transfer function in the X-axis translation direction (left-right direction) and frequency. Figure 9 is a graph showing the relationship between the transfer function in the Y-axis translation direction (front-back direction) and frequency. Figure 10 is a graph showing the relationship between the transfer function in the Z-axis translation direction (up-down direction) and frequency. Figure 11 is a graph showing the relationship between the transfer function in the Y-axis rotation direction (around the front-back axis) and frequency. Figure 12 is a graph showing the relationship between the transfer function in the Z-axis rotation direction (around the up-down axis) and frequency.

As a result of the test, in Examples 1 to 3, as shown in Figures 8 to 12, it was possible to obtain transfer functions (inertance) for all directions in which the rotation axis was vibrated. On the other hand, in the comparative example, since the rotation axis was defined so that it could only be displaced in the rotation direction (X-axis rotation direction), it was not possible to obtain the transfer functions shown in Figures 8 to 12.

Figure 13 is a graph showing the relationship between the reaction force R1 against the first load F1 and time for Examples 1 to 3. In Examples 1 and 3, the second step is performed after the rotation axis is constrained, so the reaction force R1 against the first load F1 can converge earlier than in Example 2, where the rotation axis is not constrained. As a result, Examples 1 and 3 were able to reduce the calculation time compared to Example 2.

In Examples 1 and 2, the spring constant of the spring model is set to 1/100 or less of the vertical spring constant of the tire, so compared to Example 3, where the spring constant is set to more than 1/100, it is possible to prevent the vertical spring component of the spring model from affecting the natural frequency of the vertical spring component of the tire.

2 Wheel model 3 Road surface model 5 Tire model 6 Support element model 16 Rotation axis

Claims (7)

A simulation method for evaluating vibration performance of a tire, comprising:
inputting a wheel model, which is made up of a tire model that models the tire and a support element model that models a support element that supports a rotation axis of the tire model, into a computer;
inputting a road surface model into the computer;
and a step of causing the computer to roll the tire model of the wheel model on the road surface model to obtain a physical quantity acting on the rotation shaft,
the support element model supports the tire model displaceably with six degrees of freedom, including a degree of freedom in a rotational direction of the rotation shaft , in a three-dimensional orthogonal coordinate system.
How to simulate tires. The tire simulation method according to claim 1, wherein the support element model includes a spring model that models a spring means. The tire simulation method according to claim 2, wherein the spring constant of the spring model is 1/100 or less of the longitudinal spring constant of the tire. The step of acquiring the physical quantity includes a first step of applying a first load to the rotation shaft by bringing the tire model into contact with the road surface model and bringing the rotation shaft and the road surface model closer to each other;
4. The tire simulation method according to claim 2, further comprising a second step of elastically deforming the spring model so that the spring model applies a second load to the rotation shaft in an opposite direction to and having the same magnitude as the first load. The tire simulation method according to claim 4, wherein at least the second step is performed after the rotation shaft is constrained. The tire simulation method according to claim 5, further comprising a step of releasing the constraint on the rotation shaft after the second step. The step of acquiring the physical quantity includes a step of vibrating the tire model or the rotation shaft;
7. The tire simulation method according to claim 1, further comprising the step of calculating a response of said rotating shaft to said excitation.

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