How to simulate tires

Abstract

To provide a simulation method capable of precisely analyzing braking performance.SOLUTION: Provided is a simulation method for a tire. In the method, a computer executes a rolling step P3 for rolling a tire model on a road surface model so that a slip ratio of the tire model to the road surface model increases, and a step P4 for calculating a physical amount concerning tire brake performance on the basis of the tire model in the process of increasing the slip ratio. The rolling step P3 includes a step for increasing the slip ratio by, while maintaining one of a rotational speed of the tire model and a movement speed of the road surface model, reducing the other of the rotational speed of the tire model and the movement speed of the road surface model.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The following Patent Document 1 describes a longitudinal force simulation method including tire braking analysis. In this method, a tire FEM model in which the tire is divided into multiple elements is brought into contact with the ground and rolled under a predetermined load under predetermined analysis conditions including road speed and tire rotation speed. Then, by changing the road speed and rotation speed, the slip ratio determined by them is changed, and the relationship between the slip ratio and the friction coefficient is obtained. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-96783 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in FEM simulations, vibrations that are not seen in reality may occur in the tire model and road surface model. Such vibrations tend to cause the calculated physical quantities to deviate from the actual physical quantities of the tire. The above method tends to easily cause such vibrations, and there is room for further improvement in the accuracy of the analysis of braking performance.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a simulation method capable of analyzing braking performance with high accuracy. [Means for solving the problem]

[0006] The present invention is a tire simulation method comprising the steps of: inputting a tire model that models the tire into a computer; and inputting a road surface model that models the road surface on which the tire rolls into the computer, wherein the computer executes a rolling step of rolling the tire model on the road surface model so as to increase the slip ratio of the tire model relative to the road surface model; and a step of calculating physical quantities related to the braking performance of the tire based on the tire model in the process of increasing the slip ratio, wherein the rolling step includes a step of increasing the slip ratio by maintaining one of the rotation speed of the tire model and the moving speed of the road surface model while reducing the other of the rotation speed of the tire model and the moving speed of the road surface model.

[0007] In the tire simulation method according to the present invention, the step of increasing the slip ratio may include decreasing the rotation speed while maintaining the moving speed.

[0008] In the tire simulation method according to the present invention, the step of increasing the slip ratio may include decreasing the moving speed while maintaining the rotation speed.

[0009] In the tire simulation method according to the present invention, the rolling step may include a step of setting the rotation speed and the moving speed based on a predetermined first running speed, a step of setting a dynamic friction coefficient at a second running speed higher than the first running speed between the tire model and the road surface model, and a step of simulating the tire model rolling at the second running speed based on the rotation speed, the moving speed, and the dynamic friction coefficient.

[0010] The tire simulation method according to the present invention may further include a step in which the computer evaluates the braking performance at the second traveling speed based on the physical quantity.

[0011] In the tire simulation method according to the present invention, the physical quantity may include a μ-S curve indicating a relationship between a dynamic friction coefficient μ and a slip ratio S of the tire model. Effect of the Invention

[0012] By employing the above steps, the tire simulation method of the present invention makes it possible to analyze braking performance with high accuracy. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an example of a computer for executing a tire simulation method. [Diagram 2] 1 is a flowchart showing an example of a processing procedure of a tire simulation method. [Diagram 3] FIG. 2 is a perspective view showing an example of a tire model and a road surface model. [Figure 4] FIG. 2 is a cross-sectional view showing an example of a tire model. [Diagram 5] 13 is a flowchart showing an example of a processing procedure of a rolling step. [Figure 6] 1 is a graph showing an example of a relationship between a dynamic friction coefficient μ and a sliding speed. [Figure 7] 1 is a graph showing an example of a μ-S curve showing the relationship between the dynamic friction coefficient μ and the slip ratio. [Figure 8] FIG. 1A is a graph showing the ground contact pressure distribution in Example 1, and FIG. [Figure 9] FIG. 2A is a diagram showing the braking force distribution in the first embodiment, and FIG. 2B is a diagram showing the braking force distribution in the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are intended to enhance understanding of the contents of the invention, and therefore some of the drawings may be exaggerated, and the scales of the drawings may not be strictly consistent.

[0015] [Tire simulation method (first embodiment)] In the tire simulation method of this embodiment (hereinafter sometimes simply referred to as the "simulation method"), physical quantities related to the braking performance of the tire are calculated using a computer.

[0016] 1 is a perspective view showing an example of a computer 1 for executing a tire simulation method. 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 software and the like for executing the simulation method of this embodiment in advance. Therefore, the computer 1 is configured as a tire simulation device.

[0017] [Tire model input process] Fig. 2 is a flowchart showing an example of a processing procedure of a tire simulation method. In the simulation method of this embodiment, first, a tire model in which a tire is modeled is input to a computer 1 (step P1). Fig. 3 is a perspective view showing an example of a tire model 2 and a road surface model 3. Fig. 4 is a cross-sectional view showing an example of the tire model 2. Note that in Fig. 3, the tire model 2 is shown in a simplified manner, and the tread pattern of the tread portion 2a, the element F(i) shown in Fig. 4, and the like are omitted.

[0018] The tire model 2 is a model of a tire (not shown) to be analyzed. The tire to be analyzed may or may not actually exist. The tire to be analyzed may be, for example, a pneumatic tire for a passenger vehicle, but may be a tire of another category, such as a heavy-duty tire for a truck or bus, or an airless tire.

[0019] As shown in FIG. 4, the tire model 2 can be defined, for example, by modeling (discretizing) a tire to be analyzed (not shown) with a finite number of elements F(i) (i=1, 2, ...) that can be handled by a numerical analysis method.

[0020] 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, a three-dimensional tetrahedral solid element, a pentahedral solid element, or a hexahedral solid element is used as the element F(i). Each element F(i) is configured to include a plurality of nodes 4. For each element F(i), numerical data such as an element number, a node 4 number, coordinate values ​​of the node 4, and material properties (for example, density, Young's modulus, damping coefficient, thermal conductivity, and heat transfer coefficient) are defined.

[0021] In the process P1 of the present embodiment, for example, a rubber portion including tread rubber, etc., of a tire (not shown) to be analyzed, a carcass ply, and a belt ply are each discretized (modeled) by elements F(i). As a result, a rubber member model (e.g., a tread rubber model, etc.) 5, a carcass ply model 6, and a belt ply model 7 are set in the tire model 2.

[0022] Next, in step P1 of this embodiment, the bead portions 2c, 2c of the tire model 2 are constrained by a rim model 11 that models a tire rim (not shown). Then, the deformation of the tire model 2 is calculated based on a uniformly distributed load w that corresponds to a predetermined internal pressure condition.

[0023] The internal pressure condition can be set as appropriate. For example, it is preferable that the air pressure defined for each tire by each standard in a standard system including the standard on which the tire is based is set as the internal pressure condition.

[0024] For deformation calculations of the tire model 2 (including rolling calculations described below), 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 infinitesimal time (unit time) T(x) (x=0, 1, ...). In this way, deformation calculations of the tire model 2 are performed.

[0025] For the deformation calculation (including the rolling calculation described later) of the tire model 2, a commercially available finite element analysis application software such as LS-DYNA manufactured by LSTC is used. The infinitesimal time T(x) is appropriately set (for example, 1 μsec) based on the required simulation accuracy.

[0026] In this manner, in the process P1 of this embodiment, the tire model 2 after internal pressure filling is calculated. The tire model 2 is stored in the computer 1.

[0027] [Road surface model input process] Next, in the simulation method of this embodiment, as shown in Fig. 3, a road surface model 3 that models a road surface (not shown) on which a tire rolls is input to the computer 1 (step P2). In step P2, based on information about the road surface, 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). As a result, in step P2, a road surface model 3 that models the road surface is set.

[0028] Element G(i) is defined as a rigid plane element that is defined to be undeformable. Element G(i) has a plurality of nodes 8. Furthermore, element G(i) is defined with numerical data such as an element number and the coordinate values ​​of the nodes 8.

[0029] In this embodiment, a road surface model 3 having a smooth surface is defined, but is not limited to this. For example, a road surface model 3 (not shown) may be defined that has minute irregularities, irregular steps, depressions, undulations, or irregularities such as ruts that resemble the actual road surface. The road surface model 3 is stored in the computer 1.

[0030] [Rolling process (first embodiment)] Next, in the simulation method of this embodiment, the computer 1 rolls the tire model 2 on the road surface model 3 so as to increase a slip ratio S (not shown) of the tire model 2 with respect to the road surface model 3 (rolling step P3). Fig. 5 is a flowchart showing an example of a processing procedure of the rolling step P3.

[0031] In the rolling step P3 of this embodiment, first, the number of rotations (rotational speed) N1 of the tire model 2 and the moving speed M1 of the road surface model 3 are set based on a predetermined first running speed V1 (step P31). The first running speed V1 can be appropriately set based on, for example, the category of the tire to be evaluated, the braking performance to be evaluated, etc. (for example, 10 to 80 km / h in the first embodiment).

[0032] The rotational speed N1 of the tire model 2 and the moving speed M1 of the road surface model 3 are set so that the tire model 2 can roll (freely roll) at the first running speed V1. The rotational speed N1 and the moving speed M1 are stored in the computer 1.

[0033] Next, in the rolling step P3 of this embodiment, an initial kinetic friction coefficient μ is defined between the tire model 2 and the road surface model 3 (step P32). In this embodiment, a kinetic friction coefficient μ is defined for each element F(i) constituting the contact portion 10 between the tire model 2 and the road surface model 3. The kinetic friction coefficient μ can be specified as appropriate. In this embodiment, the kinetic friction coefficient μ is defined based on a predetermined relationship between the kinetic friction coefficient μ and the sliding speed J.

[0034] 6 is a graph showing an example of the relationship between the dynamic friction coefficient μ and the sliding speed J. As shown in this graph, the dynamic friction coefficient μ decreases as the sliding speed J increases. In this way, the dynamic friction coefficient μ has a sliding speed dependency.

[0035] The relationship shown in Fig. 6 can be obtained as appropriate. In this embodiment, first, a rubber piece (not shown) having the same compounding as the tread rubber of the tire to be evaluated is obtained. Next, the dynamic friction coefficient μ of the rubber piece is measured at a plurality of sliding speeds. As a result, the relationship shown in Fig. 6 can be obtained.

[0036] The dynamic friction coefficient μ of the rubber piece can be measured at a predetermined contact pressure and temperature. These contact pressures and temperatures can be appropriately set based on, for example, the rolling conditions given to the tire model 2. Note that the relationship in FIG. 6 may be obtained by a simulation using a computer 1 instead of an actual measurement using a rubber piece.

[0037] In step P32 of this embodiment, the dynamic friction coefficient μ of the tire model 2 freely rolling at the first running speed V1 is defined. During free rolling, the rotation speed N1 and the moving speed M1 are equal to each other. Therefore, the slip speed J during free rolling (i.e., |rotation speed (rotation speed) N1-moving speed M1|) is "0". Therefore, in step P32, in FIG. 6, the dynamic friction coefficient μ when the slip speed J is "0" is defined for the element F(i) constituting the contact portion 10 shown in FIG. 3. The initial dynamic friction coefficient μ is stored in the computer 1.

[0038] Next, in the rolling process P3 of this embodiment, the tire model 2 is freely rolled on the road surface model 3 (process P33).

[0039] In step P33 of this embodiment, first, the tire model 2 is brought into contact with the road surface model 3. Similar to conventional simulations, conditions for preventing slip-through are defined in advance between the tire model 2 and the road surface model 3.

[0040] Next, in step P33 of this embodiment, the deformation of the tire model 2 is calculated based on the predetermined load condition L and camber angle. As a result, in step P33, the tire model 2 after the load is applied and the tire comes into contact with the road surface model 3 is calculated. The load condition L can be set appropriately. In this embodiment, for example, it is desirable to set the normal load defined for each tire by each standard in a standard system including the standards on which the tire is based as the load condition L.

[0041] Next, in step P33 of this embodiment, a rotation speed N1 is set for the rotation axis 2s of the tire model 2. Furthermore, in step P33, a moving speed M1 is set for the road surface model 3. Note that the dynamic friction coefficient μ is sequentially set for the contact portion 10 that changes every minute time T(x). As a result, in step P33, the tire model 2 can be made to freely roll on the road surface model 3 so that the slip ratio S becomes 0%. Note that a slip angle, lateral force, etc. (not shown) may be defined for the tire model 2.

[0042] Next, in the rolling step P3 of this embodiment, the slip ratio S of the tire model 2 is increased (step P34). In step P34 of this embodiment, one of the rotation speed (rotational speed) L1 of the tire model 2 and the moving speed M1 of the road surface model 3 is maintained, while the other of the rotation speed N1 of the tire model 2 and the moving speed M1 of the road surface model 3 is reduced, thereby increasing the slip ratio S.

[0043] In this way, in the rolling process P3 of this embodiment, one of the rotational speed (rotational velocity) L1 and the moving velocity M1 is maintained, so that it is possible to suppress an increase in vibration of the tire model 2 accompanying a change in the rotational speed L1, or an increase in vibration of the road surface model 3 accompanying a change in the moving velocity M1. As a result, in the rolling process P3, it is possible to suppress the vibrations of both the tire model 2 and the road surface model 3 from amplifying each other, and it is possible to prevent the tire model 2 and the road surface model 3 from experiencing vibrations that are not seen in reality. Therefore, in the simulation method of this embodiment, it is possible to analyze the braking performance with higher accuracy than, for example, Patent Document 1 in which both the rotational speed L1 and the moving velocity M1 are changed.

[0044] In this embodiment, in process P34, the number of revolutions (rotational speed) L1 of the tire model 2 is reduced while maintaining the moving speed M1 of the road surface model 3. This makes it possible to prevent an increase in vibration of the road surface model 3 in the rolling process P3, and therefore to reproduce an actual road surface that hardly vibrates compared to a tire. Therefore, in this embodiment, it becomes possible to analyze the braking performance with high accuracy.

[0045] In step P34, the moving speed M1 of the road surface model 3 may be decreased while maintaining the rotation speed L1 of the tire model 2. Even in this case, the amplification of the vibration can be suppressed, so that it is possible to prevent the tire model 2 and the road surface model 3 from experiencing vibrations that are not observed in reality.

[0046] In this embodiment, in step P34, the slip ratio S of the tire model 2 is gradually increased for each minute time (unit time) T(x). As a result, in step P34, physical quantities such as the slip ratio S and the dynamic friction coefficient μ that vary for each minute time T(x) can be calculated. Note that the gradual increase in the slip ratio S can be achieved by either a gradual decrease in the rotation speed N1 of the tire model 2 or a gradual decrease in the moving speed M1 of the road surface model 3.

[0047] In step P34, the kinetic friction coefficient μ is updated based on the sliding velocity J at the infinitesimal time T(x) and the relationship between the kinetic friction coefficient μ and the sliding velocity J shown in Fig. 6. This allows physical quantities such as the slip ratio S to be calculated with high accuracy in step P34 based on the kinetic friction coefficient μ having sliding velocity dependency. The physical quantities calculated in step P34 are stored in the computer 1.

[0048] Next, in the rolling step P3 of this embodiment, it is determined whether or not the slip ratio S of the tire model 2 is equal to or greater than a predetermined threshold value (step P35). The threshold value can be set appropriately (for example, 5% to 20%) based on, for example, the category and braking performance of the tire to be evaluated.

[0049] If it is determined in step P35 that the slip ratio S is equal to or greater than the threshold value ("Y" in step P35), the series of processes in the rolling step P3 ends. On the other hand, if it is determined in step P35 that the slip ratio S is less than the threshold value ("N" in step P35), steps P34 and P35 are executed again. As a result, in the rolling step P3, the physical quantities of the tire model 2 in the process in which the slip ratio S increases from 0% to the threshold value can be acquired for each minute time T(x).

[0050] In this embodiment, since a threshold value (upper limit value) of the slip ratio S is set in advance, the above physical quantities can be calculated within a realistic range of the slip ratio S while maintaining either the rotation speed N1 of the tire model 2 or the moving speed M1 of the road surface model 3.

[0051] [Process of calculating physical quantities related to tire braking performance] Next, in the simulation method of this embodiment, the computer 1 calculates physical quantities related to the braking performance of the tire based on the tire model 2 in the process of increasing the slip ratio S (step P4). In this embodiment, the physical quantities related to the braking performance of the tire are calculated using the above physical quantities (e.g., the dynamic friction coefficient μ and the slip ratio S, etc.) of the tire model 2 calculated in the process of increasing the slip ratio S from 0% to the threshold value.

[0052] The physical quantities related to the braking performance of the tire can be calculated as appropriate as long as they can evaluate the braking performance. In this embodiment, a μ-S curve showing the relationship between the dynamic friction coefficient μ and the slip ratio S of the tire model 2 is included. Such a μ-S curve can be easily obtained by using the slip ratio S calculated in the rolling process P3 and the dynamic friction coefficient μ corresponding thereto. The physical quantities related to the braking performance of the tire may include the contact pressure distribution and the braking force distribution of the tire model 2. Such physical quantities related to the braking performance are stored in the computer 1.

[0053] [Evaluation process] Next, in the simulation method of this embodiment, the computer 1 evaluates the braking performance of the tire based on physical quantities related to the braking performance of the tire (step P5). The evaluation of the braking performance is performed appropriately. In this embodiment, when the physical quantities (e.g., μ-S curve) satisfy a predetermined target value, the braking performance is evaluated (determined) to be good. The target value is set appropriately according to the braking performance required of the tire.

[0054] If it is determined in step P5 that the tire has good braking performance ("Y" in step P5), the tire is designed and manufactured (step P6) based on the tire design factors (information about the tire) used in creating the tire model 2. On the other hand, if it is determined that the braking performance is not good ("N" in step P5), at least one of the tire design factors is changed (step P7), and steps P1 to P5 are performed again.

[0055] In this way, in the simulation method of the present embodiment, the design factors of the tire are changed until the braking performance is determined to be good, so that a tire with good braking performance can be reliably designed and manufactured.

[0056] [Rolling process (second embodiment)] In the rolling step P3 of the above-described embodiments, the tire model 2 rolling at the first running speed V1 is calculated, but the present invention is not limited to this. For example, the tire model 2 rolling (rolling at high speed) at the second running speed V2 higher than the first running speed V1 may be calculated. Note that the tire model 2 rolling at high speed tends to deform more and vibrate more than the tire model 2 rolling at low speed. For this reason, there is room for improvement in the accuracy of the analysis of the braking performance at the second running speed V2.

[0057] In order to suppress the vibration, in the rolling process P3 of this embodiment, a tire model rolling at a first running speed V1 is calculated, and a dynamic friction coefficient μ at a second running speed V2 is defined, thereby simulating a tire model 2 rolling at a second running speed V2. In this embodiment, the same components as those in the previous embodiments are denoted by the same reference numerals, and the description thereof may be omitted.

[0058] The first running speed V1 and the second running speed V2 are set appropriately. In this embodiment, the second running speed V2 can be set appropriately based on, for example, the category of the tire to be evaluated, the braking performance to be evaluated, etc. (e.g., 80 to 120 km / h). On the other hand, the first running speed V1 can be set appropriately (small) from the viewpoint of preventing vibration of the tire model 2 (e.g., 10 to 30 km / h).

[0059] In step P32 (defining the initial dynamic friction coefficient μ) of this embodiment, as in the previous embodiments, the dynamic friction coefficient μ when the sliding speed J is "0" is defined for the element F(i) constituting the contact portion 10 shown in Fig. 3 in Fig. 6. This is because the dynamic friction coefficient μ is equal during free rolling when the sliding speed J is "0", regardless of the magnitude of the running speed (first running speed V1 and second running speed V2).

[0060] Meanwhile, in step P34 (increasing the slip ratio S of the tire model 2) in this embodiment, a kinetic friction coefficient μ2 at the second running speed V2 (hereinafter sometimes referred to as the "second kinetic friction coefficient") is set between the tire model 2 and the road surface model 3. This is because the slip velocity J and the kinetic friction coefficient μ have running speed dependency (i.e., they tend to differ depending on the first running speed V1 and the second running speed V2).

[0061] In step P34 of this embodiment, the second kinetic friction coefficient μ2 is determined based on the relationship between the kinetic friction coefficient μ and the sliding speed J shown in Fig. 6. In general, the sliding speed J tends to increase in proportion to the running speed. Therefore, the sliding speed J2 at the second running speed V2 (hereinafter sometimes referred to as the "second sliding speed") is greater than the sliding speed J1 at the first running speed V1 (hereinafter sometimes referred to as the "first sliding speed").

[0062] The second slip velocity J2 is approximated to a value (i.e., J1(V2 / V1)) obtained by multiplying the ratio (V2 / V1) between the first running speed V1 and the second running speed V2 by the first slip velocity J1. Therefore, the second kinetic friction coefficient μ2 is specified as a kinetic friction coefficient corresponding to the second slip velocity J2 (i.e., an approximate value obtained from J1(V2 / V1)) in FIG. 6. As a result, in this embodiment, even if the tire model 2 rotating at high speed at the second running speed V2 is not calculated, the second kinetic friction coefficient μ2 can be specified for each small time T(x) based on the first slip velocity J1 of the tire model 2 rotating at low speed at the first running speed V1.

[0063] In step P34 of this embodiment, a second dynamic friction coefficient μ2 is set between the tire model 2 and the road surface model 3. As a result, in step P34 of this embodiment, a relatively large slip ratio S (not shown) is calculated in the tire model 2 rolling at the first running speed V1 compared to when rolling at the first running speed V1. Such a slip ratio S is approximate to the slip ratio S in the tire model 2 (tire) rolling at high speed at the second running speed V2. Therefore, in the rolling step P3 of this embodiment, it is possible to stably calculate the tire model 2 rolling at low speed based on the first running speed V1 (i.e., suppress vibration of the tire model 2) while pseudo-calculating the tire model 2 rolling at high speed at the second running speed V2.

[0064] In step P34 of this embodiment, the physical quantities (such as the slip ratio S and the dynamic friction coefficient μ) of the tire model 2 during rolling are acquired as the physical quantities of the tire model 2 at the second running speed V2 based on the rotation speed N1 and moving speed M1 at the first running speed V1 and the second dynamic friction coefficient μ2. Then, in step P4 shown in FIG. 2, these physical quantities are used to calculate the physical quantities (μ-S curve) related to the braking performance of the tire.

[0065] [Evaluation process (second embodiment)] In step P5 of this embodiment, the computer 1 evaluates the braking performance at the second running speed V2 based on the physical quantities related to the braking performance of the tire. In this embodiment, the tire model 2 rolling at a high speed at the second running speed V2 can be pseudo-calculated while the tire model 2 rolling at a low speed at the first running speed V1 can be stably calculated, so that the physical quantities at the second running speed V2 can be stably acquired. Therefore, in this embodiment, it is possible to accurately analyze the braking performance at the second running speed V2.

[0066] 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. EXAMPLES

[0067] Based on the processing procedure shown in FIG. 2, a tire model was rolled on a road surface model so as to increase the slip ratio of the tire model, and physical quantities related to the braking performance of the tire were calculated (Example 1, Example 2, and Comparative Example).

[0068] In the first and second embodiments, based on the processing procedure shown in FIG. 5, one of the moving velocities of the road surface model is maintained while the rotation speed of the tire model is set to be small, thereby increasing the slip ratio of the tire model.

[0069] In Example 1, the rotation speed of the tire model, the moving speed of the road surface model, and the dynamic friction coefficient were set based on the first running speed set to 100 km / h. In Example 1, the tire model rotating at the first running speed (100 km / h) was simulated.

[0070] On the other hand, in Example 2, the rotation speed of the tire model and the moving speed of the road surface model were set based on the first running speed set to 20 km / h. Furthermore, in Example 2, the dynamic friction coefficient was set based on the second running speed set to 100 km / h. Then, in Example 2, the tire model rotating at the second running speed was simulated.

[0071] In the first and second embodiments, based on the processing procedure shown in FIG. 5, one of the moving velocities of the road surface model is maintained while the rotation speed of the tire model is set to a small value, thereby increasing the slip ratio of the tire model.

[0072] In the comparative example, the rotation speed of the tire model, the moving speed of the road surface model, and the dynamic friction coefficient were set based on the first running speed set to 100 km / h, similarly to Example 1. In the comparative example, the slip ratio of the tire model was increased by changing both the rotation speed of the tire model and the moving speed of the road surface model, similarly to Patent Document 1. The common specifications are as follows. Tire size: 205 / 55R17 Internal pressure: 250kPa Load: 5kN Slip Threshold: 10%

[0073] FIG. 7 is a graph showing an example of a μ-S curve showing the relationship between the dynamic friction coefficient μ and the slip ratio. In FIG. 7, the μ-S curves of Example 1 and the comparative example are shown as representatives. FIG. 8(a) is the ground contact pressure distribution of Example 1. FIG. 8(b) is a diagram showing the ground contact pressure distribution of the comparative example. FIG. 9(a) is the braking force distribution of Example 1. FIG. 9(b) is a diagram showing the braking force distribution of the comparative example. In FIG. 8 and FIG. 9, the distribution when the slip ratio is 10% is shown. Note that the braking force is the tire traveling direction component of the contact reaction force (calculated by contact determination between the tire model and the road surface model) that the tire model receives from the road surface model.

[0074] As a result of the test, as shown in Fig. 7, the fluctuation range of the dynamic friction coefficient μ in Example 1 is smaller than that in the Comparative Example. This is because Example 1, unlike the Comparative Example, was able to prevent the occurrence of vibrations that are not seen in reality in the tire model and road surface model. Furthermore, Example 2 stably calculated the tire model during low-speed rotation while pseudo-calculating the tire model during high-speed rotation, and therefore was able to prevent the occurrence of vibrations more effectively than Example 1, which calculated the tire model during high-speed rotation.

[0075] In Example 1, the ground contact pressure and braking force were stably calculated with the same distribution as that of an actual tire, as shown in Figures 8(a) and 9(a). Although not shown, in Example 2, the ground contact pressure and braking force were more stably calculated than in Example 1.

[0076] On the other hand, in the comparative example, as shown in Fig. 8(b) and Fig. 9(b), the ground contact pressure and braking force were locally small at the center of the distribution, and it was not possible to stably obtain the ground contact pressure and braking force. This is because the deformation of the tire model was larger in the comparative example than in Examples 1 and 2, and the above-mentioned vibration occurred.

[0077] In this way, in Examples 1 and 2, the physical quantities related to the braking performance of the tire could be determined more stably than in the comparative example, and therefore the braking performance could be analyzed with high accuracy. [Explanation of symbols]

[0078] P3 Rolling process P4: Process for calculating physical quantities related to braking performance

Claims

1. 1. A tire simulation method, comprising: inputting a tire model obtained by modeling the tire into a computer; inputting a road surface model, which models the road surface on which the tire rolls, into the computer; The computer, a rolling step of rolling the tire model on the road surface model so as to increase a slip ratio of the tire model with respect to the road surface model; and calculating a physical quantity related to the braking performance of the tire based on the tire model during the process of the slip ratio increasing. The rolling step includes: setting a rotation speed of the tire model and a moving speed of the road surface model based on a predetermined first running speed; setting a dynamic friction coefficient between the tire model and the road surface model at a second traveling speed higher than the first traveling speed; and increasing the slip ratio by decreasing one of the rotation speed and the moving speed while maintaining the other of the rotation speed and the moving speed, The step of increasing the slip ratio includes a step of simulating a tire model rotating at the second traveling speed based on the rotation speed, the traveling speed, and the dynamic friction coefficient. How to simulate tires.

2. The tire simulation method according to claim 1 , wherein the step of increasing the slip ratio comprises decreasing the number of rotations while maintaining the moving speed.

3. The tire simulation method according to claim 1 , wherein the step of increasing the slip ratio comprises decreasing the moving speed while maintaining the rotation speed.

4. A tire simulation method as described in any one of claims 1 to 3, further comprising a step in which the computer evaluates the braking performance at the second driving speed based on the physical quantity.

5. A tire simulation method according to claim 1, wherein the physical quantity includes a μ-S curve showing the relationship between the dynamic friction coefficient μ and slip ratio S of the tire model.

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