Method for creating tire model

Abstract

To provide a model for creating a tire model capable of specifying coefficients constituting the tire model from a design parameter without creating a tire.SOLUTION: A method for creating a tire model being a mathematical model including a characteristic value of a tire and a plurality of coefficients includes a first step S1 for acquiring design parameter information of the tire, a second step S2 for calculating a characteristic estimate of the tire on the basis of the design parameter information set in the first step S1, a third step S3 for acquiring a characteristic estimate of the existing tire in which a characteristic value and coefficients in the tire model are known, and a fourth step S4 for specifying coefficients of the tire on the basis of the characteristic estimate of the existing tire, the characteristic estimate of the tire, and a characteristic value in a tire model of the existing tire.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for creating a tire model, which is a mathematical model including characteristic values of a tire and a plurality of coefficients.

Background Art

[0002] Conventionally, a technique for expressing the motion of a vehicle using a tire model has been known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The coefficients (parameters) constituting the tire model are calculated by curve regression using the measured characteristic values of the tire.

[0005] However, when measuring the characteristic values, it is necessary to manufacture tires, which incurs high costs and time.

[0006] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a method for creating a tire model that can specify the coefficients constituting the tire model from the design parameters of the tire without manufacturing the tire.

Means for Solving the Problems

[0007] The present invention relates to a method for creating a tire model. The tire model is a mathematical model including characteristic values of a tire and a plurality of coefficients. The creation method includes: a first step of obtaining design parameter information of the tire; a second step of calculating an estimated value of the characteristics of the tire based on the design parameter information set in the first step; a third step of obtaining an estimated value of the characteristics of an existing tire in which the characteristic values and the coefficients in the tire model are known; and a fourth step of specifying the coefficients of the tire based on the estimated value of the characteristics of the existing tire, the estimated value of the characteristics of the tire, and the characteristic values in the tire model of the existing tire.

Effect of the Invention

[0008] Since the method for creating a tire model of the present invention has the above configuration, it is possible to specify the coefficients constituting the tire model from the design parameters of the tire without creating the tire.

Brief Description of the Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The tire model created by the creation method of this embodiment is a mathematical model including tire characteristic values and a plurality of coefficients. The tire model is created for each tire and includes a plurality of coefficients with different values for each tire.

[0011] In the present application, the tire T for which the tire model is created is simply referred to as "tire T". The tire T does not necessarily have to be an actual existing tire, but it is necessary that the design parameter information is specified. The "design parameter information" is information regarding the parameters for designing the tire T, and a plurality of design parameter information is determined for one tire T.

[0012] Also, the tire referred to when creating the tire model is denoted as "existing tire RT". The existing tire RT is a tire in which the mathematical formula of the tire model, that is, the above characteristic values and a plurality of coefficients in the tire model are known.

[0013] By using the data obtained by actually measuring the existing tire RT, the characteristic values of the existing tire RT are acquired. The above characteristic values of the tire include, for example, at least one of cornering power, cornering force, overtuning moment, rolling resistance moment, self-aligning moment, longitudinal force (braking force, driving force), camber thrust, and friction coefficient. There are various tire models according to the above characteristic values of the tire.

[0014] As an example of the tire model created in this embodiment, when D, C, B, and E are coefficients, the measurement condition is the slip parameter x, and the force or moment from which the characteristic value of the tire is obtained is y, it is represented by the following formula (1). y = D·sin { C·arctan [ Bx - E·( Bx - arctan ( Bx ) ) ]} (1)

[0015] As another example of the tire model, when α, β, and C are coefficients, the measurement condition is the load W, and the characteristic value of the tire is the cornering power CP, the following formula (2) can be cited. CP / W = α·cos { β·arctan ( W - C ) ) (2)

[0016] It is desirable that the characteristic values of the existing tire RT be obtained based on a plurality of internal pressure conditions. Further, it is desirable that the characteristic values of the existing tire RT be obtained based on a plurality of load conditions. Furthermore, it is desirable that the characteristic values of the existing tire RT be obtained based on a plurality of speed conditions.

[0017] Based on the characteristic values obtained under various measurement conditions, a plurality of coefficients in the tire model of the existing tire RT are specified by using a method such as curve fitting. As the internal pressure condition, load condition, or speed condition in the actual measurement of the existing tire RT increases, the accuracy of the mathematical formula of the tire model of the existing tire RT improves, contributing to the development of the tire and the vehicle.

[0018] FIG. 1 shows the procedure of the method for creating the tire model of the present embodiment. The method for creating the tire model includes a first step S1 of obtaining the design parameter information of the tire T, a second step S2 of calculating the estimated characteristic values of the tire T, a third step S3 of obtaining the estimated characteristic values of the existing tire RT, and a fourth step S4 of specifying the coefficients of the tire T.

[0019] In the first step S1, the design parameter information of the tire T is obtained. The design parameter information of the tire T is set by, for example, the designer of the tire T.

[0020] Examples of the design parameter information include, for example, parameter information regarding the tire size, parameter information regarding the usage conditions, parameter information regarding the structural design, parameter information regarding the rubber compounding, and the like.

[0021] Examples of the parameter information regarding the tire size include information regarding the outer diameter, maximum width, cross-sectional height, etc. of the tire.

[0022] Examples of parameter information regarding usage conditions include information regarding the used rim, internal pressure, load, etc.

[0023] The used rim preferably includes a standard rim. The "standard rim" is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim". A rim different from the standard rim may be used.

[0024] The internal pressure preferably includes a standard internal pressure. The "standard internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire is based. In the case of JATMA, it is the "maximum air pressure", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "INFLATION PRESSURE". When the tire is for a passenger car, the standard internal pressure is, for example, 180 kPa.

[0025] The load preferably includes a standard load. The "standard load" is the load defined for each tire in a standard system including the standards on which the tire is based. In the case of JATMA, it is the "maximum load capacity", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY". When the tire is for a passenger car, the standard load is, for example, a load corresponding to 88% of the above load.

[0026] Examples of parameter information related to structural design include information regarding the case structure, belt angle, cord twist structure, thickness of each part of the tire, tread rigidity, etc. The thickness of each part of the tire refers to, for example, the thickness of the tread part at the tire equator, the thickness of the shoulder part, the thickness of the sidewall part at the maximum width position of the tire, the maximum thickness of the bead part, etc. Tread rigidity refers to the rigidity in the front - rear, lateral, and longitudinal directions of the tread part with various patterns applied.

[0027] Examples of parameter information related to rubber compounding include information regarding the complex elastic modulus of the rubber constituting each part of the tire, the presence or absence of fillers, etc.

[0028] Note that the above - mentioned parameter information is for illustration, and the design parameter information obtained in the first step S1 is not limited to these.

[0029] The obtained parameter information is input into a computer.

[0030] Figure 2 is a perspective view showing a computer 1 into which the design parameter information obtained in the first step S1 is input. The computer 1 of this embodiment includes, for example, a main body 11, a keyboard 12, a mouse 13, and a display device 14. In this main body 11, for example, an arithmetic processing unit (CPU), a memory, and a storage device are provided (not shown). Also, in the storage device, software for executing the creation method of this embodiment (for example, information regarding the mathematical formulas constituting the tire model) is stored in advance. Hereinafter, the second step S2 to the fourth step S4 are executed using the computer 1.

[0031] In the second step S2, an estimated value of the characteristics of the tire T is calculated based on the design parameter information obtained in the first step S1. The estimated value of the characteristics of the tire T is the characteristics of the tire T estimated by calculation.

[0032] The characteristics of the tire T for which the estimated value is calculated in the second step S2 correspond to the characteristics obtained for the existing tire RT. For example, when the characteristic value obtained for the existing tire RT is the cornering power (in other words, when creating a tire model for the tire T regarding the cornering power), in the second step S2, the estimated value of the cornering power of the tire T is calculated.

[0033] In the second step S2, for example, the characteristic value of the tire T incorporated in the standard rim, filled with the standard internal pressure, and loaded with the standard load is calculated.

[0034] In the second step S2, the characteristic value of the tire T incorporated in a rim different from the standard rim may be calculated. Also, in the second step S2, the characteristic value of the tire T filled with an internal pressure different from the standard internal pressure may be calculated. Further, in the second step S2, the characteristic value of the tire T loaded with a load different from the standard load may be calculated.

[0035] In the second step S2, it is desirable that the characteristic value of the tire T is calculated based on a plurality of load conditions. Furthermore, it is desirable that the characteristic value of the tire T is obtained based on a plurality of speed conditions.

[0036] In the second step S2, the estimated characteristic value of the tire T is calculated by numerical analysis such as the finite element method, for example. In the finite element method, based on the design parameter information obtained in the first step S1, a tire model discretized into finite elements (different from the tire model created in the present invention) is applied, and the estimated characteristic value of the tire T is calculated.

[0037] In the third step S3, the estimated characteristic value of the existing tire RT is obtained. The estimated characteristic value of the existing tire RT is the characteristic of the existing tire RT estimated by calculation.

[0038] The characteristics of the existing tire RT for which the estimated value is calculated in the third step S3 correspond to the characteristics for which the estimated value is calculated for the tire T in the second step S2. For example, when the characteristic for which the estimated value is calculated for the tire T is the cornering power (in other words, when creating a tire model regarding the cornering power for the tire T), in the third step S3, the estimated value of the cornering power of the existing tire RT is obtained.

[0039] In the third step S3, for example, the characteristic values of the existing tire RT incorporated in the standard rim, filled with the standard internal pressure, and loaded with the standard load are calculated.

[0040] In the third step S3, the characteristic values of the existing tire RT incorporated in a rim different from the standard rim may be calculated. Also, in the third step S3, the characteristic values of the existing tire RT filled with an internal pressure different from the standard internal pressure may be calculated. Further, in the third step S3, the characteristic values of the existing tire RT loaded with a load different from the standard load may be calculated.

[0041] In the third step S3, it is desirable that the characteristic values of the existing tire RT are calculated based on a plurality of load conditions. Furthermore, it is desirable that the characteristic values of the existing tire RT are obtained based on a plurality of speed conditions.

[0042] The estimated characteristic values of the existing tire RT are also calculated by numerical analysis such as the finite element method, similar to the estimated characteristic values of the tire T in the second step S2. If the estimated value of the cornering power of the existing tire RT has already been calculated, that value is applied.

[0043] In the fourth step S4, based on the estimated characteristic values of the existing tire RT, the estimated characteristic values of the tire T, and the characteristic values in the tire model of the existing tire RT, the coefficient in the tire model of the tire T is specified.

[0044] This makes it possible to identify the coefficients for constructing the tire model from the design parameters of the tire T without creating the tire T.

[0045] FIG. 3 is a flowchart showing an example of the third step S3.

[0046] The third step S3 includes a step S31 of extracting an existing tire RT1 that is the same as or similar to the tire T from among a plurality of existing tires RT, and a step S32 of obtaining an estimated value of the characteristics of the extracted existing tire RT1. In the computer 1 of the present embodiment or a server (not shown) connected to the computer 1 by wire or wirelessly, etc., information regarding the tire models and estimated values of characteristics of a plurality of existing tires RT is stored.

[0047] In step S31, an existing tire RT1 that is the same as or similar to the tire T is extracted from among a plurality of existing tires RT stored in the computer 1 or the like. The determination of similarity is made, for example, based on the category (use) and size.

[0048] For example, a snow tire and a summer tire are treated as non-similar categories. Also, a road tire and a racing tire are treated as non-similar categories. The similarity of the sizes is determined, for example, taking into account the nominal width, aspect ratio, and rim diameter. Tires that have the same or similar category and the same or similar size as the tire T are extracted as the same or similar existing tires RT1.

[0049] The extraction of the existing tire RT1 is performed by the computer 1 or the developer of the tire T. The developer of the tire T may further select from among the existing tires RT1 extracted by the computer 1.

[0050] In step S32, the estimated characteristic values of the extracted existing tire RT1 are obtained. More specifically, in step S32, the estimated characteristic values of the existing tire RT are searched for in a storage means (such as a hard disk) of the computer 1 or the like, the estimated characteristic values of the extracted existing tire RT1 are retrieved, and are copied to the memory in the computer 1. As a result, the estimated characteristic values of the existing tire RT1 become available in the fourth step S4.

[0051] Since the estimated characteristic values of the existing tire RT1 calculated in the third step S3 are estimated values obtained by numerical analysis such as the finite element method, they do not necessarily match the characteristic values in the tire model of the existing tire RT1 based on measured values. Similarly, since the estimated characteristic values of the tire T calculated in the second step S2 are estimated values obtained by numerical analysis such as the finite element method, they generally do not match the characteristic values in the tire model of the tire T.

[0052] However, since the existing tire RT1 extracted in step S31 has the same or similar category and size as the tire T, the relative value between the estimated characteristic values of the tire T and those of the existing tire RT1, and the relative value between the characteristic values in the tire model of the tire T and those in the tire model of the existing tire RT1 are highly likely to approximate with the same tendency.

[0053] Based on the above considerations, the inventor of the present application has found that by executing the fourth step S4 as follows, the coefficients in the tire model of the tire T can be specified without creating the tire T.

[0054] FIG. 4 is a flowchart showing an example of the fourth step S4.

[0055] The fourth step S4 includes a step S41 of calculating the relative value of the estimated characteristic values, a step S42 of calculating the characteristic values in the tire model of the tire T, and a step S43 of calculating the coefficients in the tire model of the tire T.

[0056] The relative value calculated in step S41 is represented by the ratio between the characteristic estimate value of the existing tire RT1 obtained in the third step S3 and the characteristic estimate value of the tire T calculated in the second step S2. That is, in step S41, the relative value of the characteristic estimate value of the tire T with respect to the characteristic estimate value of the existing tire RT1 is calculated by the arithmetic processing unit of the computer 1.

[0057] In step S42, by multiplying the relative value calculated in step S41 by the characteristic value in the tire model of the existing tire RT1, the characteristic value in the tire model of the tire T is calculated without creating the tire T.

[0058] That is, by executing the third step S3 shown in FIG. 3 and the fourth step S4 shown in FIG. 4, the characteristic value in the tire model of the tire T can be accurately calculated without creating the tire T.

[0059] In step S43, the coefficient in the tire model of the tire T is calculated by curve regression. More specifically, in step S43, while changing the coefficient in the tire model of the existing tire RT1, the coefficient in the tire model of the tire T is calculated by bringing the characteristic value in the tire model of the existing tire RT1 closer to the characteristic value in the tire model of the tire T.

[0060] FIG. 5 shows the relationship between the characteristic value CP1 in the tire model of the existing tire RT1 extracted in step S31 and the characteristic value CP in the tire model of the tire T calculated in step S42. In the figure, the transition of the cornering power under the load conditions in five steps is shown for each characteristic value.

[0061] In Equation (2), by changing the coefficients α, β, and C, CP / W varies. Therefore, in step S43, the coefficients α, β, and C that bring CP1 in the tire model of the existing tire RT1 closest to CP in the tire model of the tire T at each load W are calculated by regression analysis.

[0062] For the regression analysis, for example, spreadsheet software having a solver function or the like is used, and a method such as the least squares method is applied.

[0063] In step S43, for example, in the tire model shown in formula (2), when the coefficients α, β, and C are specified, the tire model of the tire T is specified. According to the verification by the inventor, the time required for the fourth step S4 was only a few minutes.

[0064] As described above, the method for creating a tire model of the present invention has been described in detail. However, the present invention is not limited to the above specific embodiments and can be implemented in various modes.

[0065] [Appendix] The present invention includes the following aspects.

[0066] [Invention 1] A method for creating a tire model, wherein the tire model is a mathematical model including characteristic values of a tire and a plurality of coefficients, and the creation method includes: a first step of obtaining design parameter information of the tire; a second step of calculating an estimated value of the characteristics of the tire based on the design parameter information set in the first step; a third step of obtaining estimated values of characteristics of an existing tire in which characteristic values and the coefficients in the tire model are known; and a fourth step of specifying the coefficients of the tire based on the estimated value of the characteristics of the existing tire, the estimated value of the characteristics of the tire, and the characteristic values in the tire model of the existing tire. A method for creating a tire model. [Invention 2] The method for creating a tire model according to Invention 1, wherein the third step includes a step of extracting existing tires having the same or similar category and size as the tire from among a plurality of the existing tires. [Invention 3] The method for creating a tire model according to claim 1 or 2 of the present invention, wherein the fourth step includes calculating a relative value between the estimated value of the characteristics of the tire and the estimated value of the characteristics of the existing tire with respect to the estimated value of the characteristics of the existing tire. [Invention 4] The method for creating a tire model according to claim 3 of the present invention, wherein the fourth step includes calculating the characteristic value in the tire model of the tire by multiplying the relative value by the characteristic value in the tire model of the existing tire. [Invention 5] The method for creating a tire model according to claim 4 of the present invention, wherein the fourth step includes calculating the coefficient of the tire by curve fitting. [Invention 6] The method for creating a tire model according to claim 5 of the present invention, wherein the fourth step includes calculating the coefficient of the tire by bringing the characteristic value in the tire model of the existing tire closer to the characteristic value in the tire model of the tire while changing the coefficient of the existing tire. [Invention 7] The method for creating a tire model according to any one of claims 1 to 6 of the present invention, wherein the characteristic value includes at least one of cornering power, cornering force, longitudinal force, camber thrust, and friction coefficient. [Invention 8] The method for creating a tire model according to any one of claims 1 to 7 of the present invention, wherein the characteristic value is obtained based on a plurality of internal pressure conditions. [Invention 9] The method for creating a tire model according to any one of claims 1 to 8 of the present invention, wherein the characteristic value is obtained based on a plurality of load conditions. [Invention 10] The method for creating a tire model according to any one of claims 1 to 9 of the present invention, wherein the characteristic value is obtained based on a plurality of speed conditions.

Description of Reference Numerals

[0067] 1: Creation method RT: Existing tire RT1: Existing tire S1: First step S2: Second step S3: Third step S31: Step S32: Step S4: Fourth step S41: Step S42: Step S43: Step T: Tire D: Coefficient C: Coefficient B: Coefficient E: Coefficient α: Coefficient β: Coefficient

Claims

1. A method for creating a tire model, comprising the steps of: the tire model is a mathematical model including a tire characteristic value and a plurality of coefficients, The method for producing the same comprises the steps of: A first step of obtaining design parameter information of the tire; a second step of calculating the estimated tire characteristic value based on the design parameter information set in the first step; a third step of acquiring estimated values ​​of characteristics of an existing tire, the estimated values ​​being known for the characteristic values ​​and the coefficients in the tire model; and a fourth step of determining a coefficient of the tire based on the characteristic estimate value of the existing tire, the characteristic estimate value of the tire, and the characteristic value in the tire model of the existing tire. How to create a tire model.

2. 2. The tire model creation method according to claim 1, wherein the third step includes a step of extracting, from a plurality of the existing tires, the existing tires that are the same or similar in category and size as the tire.

3. 2. The tire model creation method according to claim 1, wherein the fourth step includes a step of calculating a relative value of the estimated characteristic value of the tire with respect to the estimated characteristic value of the existing tire.

4. 4. The tire model creation method according to claim 3, wherein the fourth step includes a step of multiplying the relative value by the characteristic value in the tire model of the existing tire to calculate the characteristic value in the tire model of the tire.

5. 2. The method of claim 1, wherein said fourth step comprises calculating said coefficients of said tire by curve regression.

6. 6. The tire model creation method according to claim 5, wherein the fourth step includes a step of calculating the coefficients of the tire by changing the coefficients of the existing tire while bringing the characteristic values ​​in the tire model of the existing tire closer to the characteristic values ​​in the tire model of the tire.

7. The tire model creating method according to claim 1 , wherein the characteristic values ​​include at least one of cornering power, cornering force, longitudinal force, camber thrust, and friction coefficient.

8. 2. The method for creating a tire model according to claim 1, wherein the characteristic values ​​are obtained based on a plurality of internal pressure conditions.

9. The tire model creation method according to claim 1 , wherein the characteristic values ​​are obtained under a plurality of load conditions.

10. The tire model creation method according to claim 1 , wherein the characteristic values ​​are obtained based on a plurality of speed conditions.

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