Tire characteristic model generation method, tire characteristic model generation apparatus, and tire characteristic model generation program

Abstract

This technology provides a method for easily generating a magic formula model for a new tire using a finite element analysis model. [Solution] The tire characteristic model generation method comprises an FEM model acquisition step, a feature calculation step, a ratio calculation step, and a model generation step. The FEM model acquisition step acquires an FEM model of a known tire for which an MF model has been identified, and an FEM model of a new tire with specifications different from the known tire. The feature calculation step calculates features in the tire characteristics of the known tire and the new tire based on the FEM model. The ratio calculation step calculates the ratio R of the features of the new tire to the features of the known tire. The model generation step generates an MF model of the new tire by correcting the MF model identified for the known tire based on the ratio R.

Description

Technical Field

[0001] The present invention relates to a tire characteristic model generation method, a tire characteristic model generation device, and a tire characteristic model generation program for generating a tire characteristic model configured by a magic formula.

Background Art

[0002] For example, as a tire characteristic model showing tire characteristics such as the slip angle of a tire, the camber angle, and the lateral force of the tire with respect to the vertical load, the magic formula is widely known. The magic formula is used by identifying a group of parameters in the formula based on measured values and analytical values related to tire characteristics.

[0003] Patent Document 1 discloses a vehicle design method including conventional tires. In this design method, when approximating the characteristic curves of the lateral force and self-aligning torque of the tire with the "Magic Formula", the values of parameters B to E are given to the vehicle model to perform a running simulation and performance evaluation. In this performance evaluation, when the vehicle model does not satisfy a predetermined performance, the values of parameters B to E are corrected to perform a running simulation and perform a performance evaluation of the vehicle, and at the same time, a tire characteristic curve defined by the corrected values of parameters B to E is calculated, and from this characteristic curve, tire mechanical element parameters are derived based on a tire mechanical model configured using a plurality of tire mechanical element parameters. On the other hand, when the vehicle model satisfies a predetermined performance, the tire mechanical element parameters corresponding to parameters B to E are determined as tire required characteristics.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The magic formula model representing the characteristics of a tire is identified using actual measured values ​​obtained by testing prototype tires. The inventors focused on utilizing the magic formula models of known tires that have been identified to date when generating a magic formula model for a new tire, and considered that the generation of the magic formula model could be simplified by using a finite element analysis model of the tire.

[0006] This invention has been made in view of the above circumstances, and its objective is to provide a tire characteristic model generation method, a tire characteristic model generation apparatus, and a tire characteristic model generation program that can easily generate a magic formula model for a new tire using a finite element analysis model. [Means for solving the problem]

[0007] One aspect of the present invention is a method for generating a tire characteristic model. The method for generating a tire characteristic model comprises: an FEM model acquisition step of acquiring FEM models for both a first tire for which a magic formula model representing the tire characteristics has been identified, and a second tire having different specifications from the first tire; a feature calculation step of calculating feature quantities in the tire characteristics of the first tire and the second tire based on the FEM models acquired in the FEM model acquisition step; a ratio calculation step of calculating the ratio of the feature quantities of the second tire to the feature quantities of the first tire calculated in the feature calculation step; and a model generation step of generating a magic formula model for the second tire by correcting the magic formula model identified for the first tire based on the ratio calculated in the ratio calculation step.

[0008] Another aspect of the present invention is a tire characteristic model generation device. The tire characteristic model generation device includes: an FEM model acquisition unit that acquires FEM models for both a first tire for which a magic formula model representing tire characteristics has been identified, and a second tire having different specifications from the first tire; a feature quantity calculation unit that calculates feature quantities in the tire characteristics of the first tire and the second tire based on the FEM models acquired by the FEM model acquisition unit; a ratio calculation unit that calculates the ratio of the feature quantities of the second tire to the feature quantities of the first tire calculated by the feature quantity calculation unit; and a model generation unit that generates a magic formula model for the second tire by correcting the magic formula model identified for the first tire based on the ratio calculated by the ratio calculation unit.

[0009] Another aspect of the present invention is a tire characteristic model generation program. The tire characteristic model generation program causes a computer to perform the following steps: an FEM model acquisition step of acquiring FEM models for both a first tire in which a magic formula model representing the tire characteristics has been identified, and a second tire having different specifications from the first tire; a feature calculation step of calculating feature quantities in the tire characteristics of the first tire and the second tire based on the FEM models acquired in the FEM model acquisition step; a ratio calculation step of calculating the ratio of the feature quantities of the second tire to the feature quantities of the first tire calculated in the feature calculation step; and a model generation step of generating a magic formula model for the second tire by correcting the magic formula model identified for the first tire based on the ratio calculated in the ratio calculation step. [Effects of the Invention]

[0010] According to the present invention, a magic formula model for a new tire can be easily generated using a finite element analysis model. [Brief explanation of the drawing]

[0011] [Figure 1] This block diagram shows the functional configuration of the tire characteristic model generation device according to the embodiment. [Figure 2] This flowchart shows the procedure for generating an MF model using a tire characteristic model generation device. [Figure 3] This chart shows examples of characteristic features for known and new tires. [Figure 4] This graph shows the longitudinal force characteristics of the tire using the MF model for the new tire example shown in Figure 3. [Figure 5] This graph shows the tire cornering characteristics of the new tire example shown in Figure 3, based on the MF model. [Modes for carrying out the invention]

[0012] The present invention will be described below with reference to Figures 1 to 5, based on preferred embodiments. The same or equivalent components and members shown in each drawing are denoted by the same reference numerals, and redundant explanations are omitted as appropriate. Furthermore, the dimensions of the members in each drawing are enlarged or reduced as appropriate for ease of understanding. Also, some members that are not important for explaining the embodiments are omitted in each drawing.

[0013] (Embodiment) Figure 1 is a block diagram showing the functional configuration of a tire characteristic model generation device 100 according to an embodiment. The tire characteristic model generation device 100 comprises a storage unit 10, an operation unit 31, a display unit 32, and a calculation processing unit 40. The tire characteristic model generation device 100 calculates feature quantities of tire characteristics based on a finite element analysis model (hereinafter referred to as FEM model) of a known tire 1 for which a magic formula model representing the tire characteristics has been identified, and an FEM model of a new tire 2.

[0014] The tire characteristic model generation device 100 generates a magic formula model for the new tire 2 based on the feature quantities calculated for the known tire 1 and the new tire 2. The new tire 2 has different specifications from the known tire 1, and conventionally, in order to generate a magic formula model for the new tire 2, it was necessary to prototype the new tire 2 and subject it to tire testing to obtain tire characteristic data. The known tire 1 corresponds to the first tire in the present invention, and the new tire 2 corresponds to the second tire in the present invention.

[0015] The Magic Formula model, with its identified set of parameters, is a function that calculates the longitudinal force Fx of a tire with respect to the tire slip ratio S, the lateral force Fy with respect to the tire slip angle α, and the moment Mz around the vertical axis, and is used, for example, in the motion analysis of a vehicle. The independent variables in the Magic Formula model are the slip angle α and the slip ratio S. The Magic Formula model is also referred to as the MF model.

[0016] The tire characteristic model generation device 100 is an information processing device such as a PC (personal computer). Each part of the tire characteristic model generation device 100 can be realized hardware-wise using electronic processing circuits and mechanical components, including the CPU of a computer, and software-wise using computer programs. Here, however, we are depicting functional blocks realized through the coordination of these components. Therefore, it will be understood by those skilled in the art that these functional blocks can be realized in various forms through combinations of hardware and software.

[0017] The storage unit 10 is a storage device composed of, for example, an SSD (Solid State Drive), a hard disk, a CD-ROM, a DVD, etc. The storage unit 10 stores the FEM model 11 of the known tire 1 and the FEM model 12 of the new tire 2, and newly stores the calculated feature amount data 13. The storage unit 10 stores the MF model 21 of the known tire 1, and newly stores the generated MF model 22 of the new tire 2. The storage unit 10 also stores a computer program executed by the arithmetic processing unit 40, data used for the execution of the computer program, and the like.

[0018] The storage unit 10 may take in and store the information of the FEM model 11, the FEM model 12, and the MF model 21 from an external device in which this information is stored. Note that the MF model 21 of the known tire 1 is an MF model in which a parameter group has already been identified based on the tire test data of the known tire 1.

[0019] The operation unit 31 has an operable input device such as a touch panel, a switch, a keyboard, and a mouse device, and receives a user's operation input. The operation unit 31 receives a user's operation input related to the calculation of the feature amount data 13 and the generation of the MF model 22. The display unit 32 has a display device such as a liquid crystal display, and displays a screen for receiving various data and a user's operation input in the calculation of the feature amount data 13 and the generation of the MF model 22.

[0020] The arithmetic processing unit 40 includes an FEM model acquisition unit 41, a finite element analysis unit 42, a ratio calculation unit 43, and a model generation unit 44. The FEM model acquisition unit 41 reads and acquires the FEM model 11 and the FEM model 12 stored in the storage unit 10. The finite element analysis unit 42 has a feature amount calculation unit 42a, executes finite element analysis based on the FEM model 11 and the FEM model 12 acquired by the FEM model acquisition unit 41, and obtains tire characteristics. The feature amount calculation unit 42a calculates the feature amount of the tire characteristics.

[0021] The FEM models 11 and 12 are composed of a finite number of elements obtained by dividing the tire through element division (e.g., mesh division) corresponding to the finite element method. Nodes are defined at the boundaries of each element, and the equations of motion are calculated for each node. The FEM models 11 and 12 have a tread pattern formed by main grooves and lateral grooves provided in the tread portion of the tire.

[0022] The finite element analysis unit 42 sets the friction coefficient μ between the road surface and the tire, gives the slip angle and slip ratio, analytically calculates the longitudinal force Fx, lateral force Fy, and moment Mz about the vertical axis acting on the tire, and obtains the tire characteristics. A known method can be used as the method for obtaining the tire characteristics by finite element analysis using the FEM model. For example, the method disclosed in Japanese Patent Application Laid-Open No. 2018-96785 may be used.

[0023] The finite element analysis unit 42 can obtain graphs representing tire characteristics such as the longitudinal force Fx with respect to the slip ratio S of the tire, the lateral force Fy with respect to the slip angle α, and the moment Mz about the vertical axis by the FEM models 11 and 12.

[0024] The feature calculation unit 42a of the finite element analysis unit 42 calculates the feature amounts in the graphs representing the tire characteristics for each of the known tire 1 and the new tire 2. The feature amounts calculated by the feature calculation unit 42a include at least one of the four feature amounts of the cornering power CP, the maximum cornering force CFmax, the braking stiffness BS, and the maximum friction coefficient Peakμ. The feature calculation unit 42a may calculate any two, any three, or all of the above four feature amounts.

[0025] The cornering power CP is the rising gradient of the cornering force with respect to the slip angle α of the tire. In the range where the slip angle α is small, the cornering force increases almost proportionally to the slip angle α, and thus this gradient is defined as the cornering power CP.

[0026] The maximum cornering force (CFmax) is the maximum value of the lateral force acting sideways relative to the direction of travel, which is the frictional force generated between the tire and the contact patch when a car turns.

[0027] Braking stiffness BS is represented by the μ-α characteristic diagram (friction coefficient-slip angle characteristic diagram) during braking. In the range where the slip angle α is small, the μ-α characteristic is almost linear, and BS represents the slope of this characteristic. The maximum friction coefficient Peakμ is the value at which the friction coefficient between the tire and the road surface peaks.

[0028] The feature calculation unit 42a stores the feature quantities calculated for both the known tire 1 and the new tire 2 as feature data 13 in the storage unit 10.

[0029] The ratio calculation unit 43 reads feature data 13 for known tire 1 and new tire 2 from the storage unit 10 and calculates the ratio R of the features of the new tire to the features of known tire 1. The ratio calculation unit 43 outputs the calculated feature ratio R to the model generation unit 44.

[0030] The model generation unit 44 reads the MF model 21 of the known tire 1 from the storage unit 10, modifies the MF model 21 of the known tire 1 based on the feature ratio R calculated by the ratio calculation unit 43, and generates the MF model 22 of the new tire 2. The model generation unit 44 stores the generated MF model 22 of the new tire 2 in the storage unit 10.

[0031] The MF model has a basic formula using coefficients B, C, D, and E. This basic formula of the MF model is also called the basic Pacejka formula, named after its inventor, and is written in a form that includes the following function: y=D sin[C arctan{B xE(B x-arctan(B x))}] ···(1)

[0032] In equation (1), x on the right-hand side represents an independent variable, which is either the slip angle α or the slip ratio S itself, or a value added to either the slip angle α or the slip ratio S by adding or multiplying a coefficient or the like. In the right-hand side of equation (1), the slip angle α and the slip ratio S are treated as independent variables. The notation "B x" on the right-hand side of equation (1) represents the multiplication of B and x.

[0033] The basic equation of the MF model includes a term for y, represented by equation (1), and is expressed by independently defining the longitudinal force Fx, lateral force Fy, and moment Mz of the tire, and by including terms that are further added to y and terms that are further multiplied by y. Coefficients are set for the terms that are further added to y and terms that are further multiplied by y in the basic equation of the MF model. The MF model depends, for example, on load conditions, camber angle conditions, and internal pressure conditions on the tire, and is identified by tire test data with these conditions varied. A characteristic of the basic equation of the MF model is that by including calculations using sin and arctan functions, an empirical formula that fits well to tire characteristics obtained from tire test data can be obtained.

[0034] For example, the graph of tire characteristics obtained from the FEM model 11 of known tire 1 and the graph of tire characteristics represented by the MF model 21 are not necessarily identical. The MF model 21 of known tire 1 has already been identified based on tire test data of the prototype known tire 1, and fits well to the tire characteristics of known tire 1.

[0035] The MF model 22 for the new tire 2 can be generated by comparing the feature quantities of the tire characteristics obtained by finite element analysis for the FEM model 11 of the known tire 1 and the FEM model 12 of the new tire 2, and correcting the MF model 21 of the known tire 1 based on the comparison results. The model generation unit 44 can easily generate the MF model 22 for the new tire 2 based on the feature quantity ratio R calculated by the ratio calculation unit 43.

[0036] As mentioned above, the known tire 1 has already been prototyped and tire test data has been obtained. The model generation unit 44 can estimate the MF model 22 of the new tire 2 using the method described above, even if the new tire 2 has not actually been prototyped, as long as the FEM model 12 of the new tire 2 has been constructed.

[0037] Next, the operation of the tire characteristic model generation device 100 will be described. Figure 2 is a flowchart showing the procedure for generating an FEM model by the tire characteristic model generation device 100. The FEM model acquisition unit 41 of the tire characteristic model generation device 100 reads and acquires the FEM models (FEM model 11 and FEM model 12) of the known tire 1 and the new tire 2 stored in the storage unit 10 (S1).

[0038] The finite element analysis unit 42 performs finite element analysis based on FEM models 11 and 12 to determine the tire characteristics (S2). The feature calculation unit 42a calculates the feature quantities of the tire characteristics of the known tire 1 and the new tire 2 (S3). As described above, the feature quantities calculated by the feature calculation unit 42a include cornering power CP, maximum cornering force CFmax, braking stiffness BS, and maximum friction coefficient Peakμ.

[0039] The ratio calculation unit 43 calculates the ratio R of the features of the new tire 2 to the features of the known tire 1 (S4). The model generation unit 44 modifies the MF model 21 of the known tire 1 based on the ratio R calculated in step S4 to generate the MF model 22 of the new tire 2 (S5). The model generation unit 44 stores the MF model 22 of the new tire 2 in the storage unit 10 (S6) and terminates the process.

[0040] Figure 3 is a diagram showing an example of the feature quantities for known tire 1 and new tire 2. In the example shown in Figure 3, the cornering power CP, maximum cornering force CFmax, braking stiffness BS, and maximum friction coefficient Peakμ, which are the feature quantities of the tire characteristics, are calculated under the condition of a standard load (e.g., assumed vehicle weight). In Figure 3, the feature quantities of new tire 2 are shown when the feature quantities of known tire 1 are set to 100.

[0041] For example, looking at cornering power CP, if the CP of known tire 1 is set to 100, the CP of new tire 2 is 108, and the ratio R is 1.08. Also, looking at maximum cornering force CFmax, if the CFmax of known tire 1 is set to 100, the CFmax of new tire 2 is 101, and the ratio R is 1.01.

[0042] Figure 4 is a graph showing the longitudinal force characteristics of the new tire 2, as shown in Figure 3, using the MF model. In Figure 4, the horizontal axis represents the slip ratio S, and the vertical axis represents the longitudinal force Fx of the tire. The model generation unit 44 corrects the MF model 21 of the known tire 1 based on the feature ratio R shown in Figure 3 to generate the MF model 22, thereby obtaining the longitudinal force characteristics of the new tire 2, as shown in Figure 4.

[0043] Figure 5 is a graph showing the tire cornering characteristics of the new tire 2, as shown in Figure 3, using the MF model. In Figure 5, the horizontal axis represents the slip angle α, and the vertical axis represents the tire's lateral force Fy. The model generation unit 44 corrects the MF model 21 of the known tire 1 based on the feature ratio R shown in Figure 3 to generate the MF model 22, thereby obtaining the tire cornering characteristics of the new tire 2, as shown in Figure 5.

[0044] The tire characteristic model generation method in this embodiment comprises an FEM model acquisition step, a feature calculation step, a ratio calculation step, and a model generation step. The FEM model acquisition step acquires FEM models (FEM model 11 and FEM model 12) for both a known tire 1 (corresponding to the first tire) for which an MF model 21 representing the tire characteristics has been identified, and a new tire 2 (corresponding to the second tire) with different specifications from the known tire 1. The feature calculation step calculates the features of the tire characteristics of the known tire 1 and the new tire 2 based on the FEM models 11 and FEM model 12 acquired in the FEM model acquisition step. The ratio calculation step calculates the ratio R of the features of the new tire 2 to the features of the known tire 1 calculated in the feature calculation step. The model generation step generates the MF model 22 of the new tire 2 by correcting the MF model 21 identified for the known tire 1 based on the ratio R calculated in the ratio calculation step. This method makes it possible to easily generate the MF model of the new tire 2 using an FEM model.

[0045] The feature calculation step in the tire characteristic model generation method calculates at least one of the feature quantities of the tire characteristics: cornering power CP, maximum cornering force CFmax, braking stiffness BS, and maximum friction coefficient Peakμ. Based on the values ​​of cornering power CP, maximum cornering force CFmax, braking stiffness BS, and maximum friction coefficient Peakμ calculated in the feature calculation step, the tire characteristic model generation method can easily generate an MF model for a new tire 2.

[0046] The tire characteristic model generation device 100 in this embodiment comprises an FEM model acquisition unit 41, a feature quantity calculation unit 42a, a ratio calculation unit 43, and a model generation unit 44. The FEM model acquisition unit 41 acquires an FEM model 11 of a known tire 1 whose MF model 21 representing the tire characteristics has been identified, and an FEM model 12 of a new tire 2 with different specifications from the known tire 1. The feature quantity calculation unit 42a calculates the feature quantities in the tire characteristics of the known tire 1 and the new tire 2 based on the FEM models 11 and 12 acquired by the FEM model acquisition unit 41. The ratio calculation unit 43 calculates the ratio R of the feature quantities of the new tire 2 to the feature quantities of the known tire 1 calculated by the feature quantity calculation unit 42a. The model generation unit 44 generates an MF model 22 of the new tire 2 by correcting the MF model 21 identified for the known tire 1 based on the ratio R calculated by the ratio calculation unit 43. As a result, the tire characteristic model generation device 100 can easily generate an MF model of the new tire 2 using an FEM model.

[0047] Furthermore, the tire characteristic model generation program in this embodiment causes the computer to execute the following steps: FEM model acquisition step, feature calculation step, ratio calculation step, and model generation step. The FEM model acquisition step acquires the FEM model 11 of a known tire 1, in which an MF model 21 representing the tire characteristics has been identified, and the FEM model 12 of a new tire 2 with different specifications from the known tire 1. The feature calculation step calculates the features of the tire characteristics of the known tire 1 and the new tire 2 based on the FEM models 11 and 12 acquired in the FEM model acquisition step. The ratio calculation step calculates the ratio R of the features of the new tire 2 to the features of the known tire 1 calculated in the feature calculation step. The model generation step generates the MF model 22 of the new tire 2 by correcting the MF model 21 identified for the known tire 1 based on the ratio R calculated in the ratio calculation step. According to this tire characteristic model generation program, the MF model of the new tire 2 can be easily generated using an FEM model.

[0048] The embodiments of the present invention have been described above. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes are also within the scope of the claims of the present invention. Accordingly, the descriptions and drawings herein should be treated as illustrative rather than limiting. [Explanation of Symbols]

[0049] 1. Known tire (1st tire), 2. New tire (2nd tire), 11 FEM model, 12 FEM model, 21 MF model, 22 MF model, 41 FEM model acquisition unit, 42a Feature calculation unit, 43 Ratio calculation unit, 44 Model generation unit, 100 Tire characteristic model generation device.

Claims

1. An FEM model acquisition step involves acquiring FEM models for both a first tire, for which a magic formula model representing tire characteristics has been identified, and a second tire, which has different specifications from the first tire. A feature calculation step, which calculates feature quantities in the tire characteristics of the first tire and the second tire based on the FEM model acquired in the FEM model acquisition step, A ratio calculation step for calculating the ratio of the feature quantities of the second tire to the feature quantities of the first tire calculated in the feature quantity calculation step, A model generation step in which a magic formula model for the second tire is generated by correcting the magic formula model identified for the first tire based on the ratio calculated in the ratio calculation step, A method for generating a tire characteristic model that includes the following features.

2. The tire characteristic model generation method according to claim 1, wherein the feature calculation step calculates at least one of the feature quantities of tire characteristics, namely cornering power, maximum cornering force, braking stiffness, and maximum friction coefficient.

3. An FEM model acquisition unit acquires FEM models for both a first tire, for which a magic formula model representing tire characteristics has been identified, and a second tire, which has different specifications from the first tire. A feature quantity calculation unit calculates feature quantities in the tire characteristics of the first tire and the second tire based on the FEM model acquired by the FEM model acquisition unit, A ratio calculation unit calculates the ratio of the feature quantities of the second tire to the feature quantities of the first tire calculated by the feature quantity calculation unit, A model generation unit generates a magic formula model for the second tire by correcting the magic formula model identified for the first tire based on the ratio calculated by the ratio calculation unit, A tire characteristic model generation device equipped with the following features.

4. An FEM model acquisition step involves acquiring FEM models for both a first tire, for which a magic formula model representing tire characteristics has been identified, and a second tire, which has different specifications from the first tire. A feature calculation step, which calculates feature quantities in the tire characteristics of the first tire and the second tire based on the FEM model acquired in the FEM model acquisition step, A ratio calculation step for calculating the ratio of the feature quantities of the second tire to the feature quantities of the first tire calculated in the feature quantity calculation step, A model generation step in which a magic formula model for the second tire is generated by correcting the magic formula model identified for the first tire based on the ratio calculated in the ratio calculation step, A tire characteristic model generation program that has a computer execute the following.

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