Tire noise evaluation method

Abstract

To provide a tire noise evaluation method capable of evaluating tire noise during accelerated running in a short time and reducing the labor and cost required for the noise evaluation.SOLUTION: A tire noise evaluation method disclosed herein is a method for evaluating tire noise during accelerated running. The tire noise evaluation method disclosed herein estimates a driving force sensitivity based on tire characteristics, which is based on a value obtained by dividing an amount of change in noise when the driving force of the vehicle changes by the amount of change in the driving force, and evaluates noise during accelerated running based on the estimated driving force sensitivity.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a tire noise evaluation method. [Background technology]

[0002] Conventionally, a method for evaluating tire noise during tire rotation, as disclosed in Patent Document 1, is known in which tire noise generated by running a tire in contact with a rotating drum having a simulated road surface on its outer circumferential surface is measured using a noise meter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-134213 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the tire noise evaluation method of Patent Document 1, the tire must be installed on a testing machine to collect the noise, so tire noise evaluation cannot be performed in a short time, and the labor and cost required for tire noise evaluation are large. In addition, it is known that tire noise increases during acceleration when a driving force is applied. Therefore, there is a demand for accurately evaluating acceleration noise during acceleration of a vehicle. Therefore, an object of the present disclosure is to provide a tire noise evaluation method that can perform noise evaluation during acceleration of a tire in a short time and reduce the labor and cost required for the noise evaluation. [Means for solving the problem]

[0005] In order to solve the above problems, the tire noise evaluation method disclosed herein is a method for evaluating tire noise when a vehicle is accelerating, which estimates a driving force sensitivity based on the characteristics of the tire and is based on a value obtained by dividing the amount of change in noise when the driving force of the vehicle changes by the amount of change in the driving force, and evaluates the noise when the vehicle is accelerating based on the estimated driving force sensitivity.

[0006] According to the present disclosure, tire noise during accelerated running is estimated and evaluated without testing based on driving force sensitivity estimated without testing due to tire characteristics, so that noise evaluation during accelerated running can be performed in a short time, and the labor and cost required for the noise evaluation can be reduced.

[0007] In addition, a third noise obtained by adding a first noise generated when the vehicle is coasting to a second noise obtained by multiplying the driving force sensitivity by the driving force may be estimated as the noise when the vehicle is accelerating with the driving force.

[0008] According to this configuration, when estimating the third noise (corresponding to tire noise during accelerating driving) for a specific driving force, the third noise can be instantly estimated for that driving force simply by substituting the driving force into a linear equation for calculating the third noise, the linear equation having the driving force as a variable.

[0009] The drive force sensitivity may also be estimated based on one or more design factors.

[0010] According to this configuration, it is easy to systematically and objectively estimate the driving force sensitivity using design factors.

[0011] In addition, the driving force sensitivity may be estimated based on a plurality of the design factors, and the contribution of each of the design factors to the driving force sensitivity may be evaluated based on an experimental design method.

[0012] According to this configuration, it is easy to efficiently and accurately evaluate the contribution of each tire design factor to the driving force sensitivity, and it is also easy to accurately estimate tire noise during accelerating driving. Effect of the Invention

[0013] According to the tire noise evaluation method according to the present disclosure, tire noise evaluation during accelerating driving can be performed in a short time, and the labor and cost required for the noise evaluation can also be reduced. [Brief description of the drawings]

[0014] [Figure 1] This is an L8 orthogonal array of four design factors in a bench noise test. [Diagram 2] 4 is a graph showing the relationship between driving force and noise for each tire. [Diagram 3] 1 is a graph showing the slope of the linear equation applied to each tire and the coefficient of determination R2. [Figure 4] This is an analysis of variance table based on a test conducted by the present inventor, and is an example of an analysis of variance table when the design factors are A, B, C, D, A and B, and A and C. [Diagram 5] 13 is a graph showing the change in the slope of the linear expression when only each design factor is changed from a reference value. [Figure 6] 13 is a graph showing an analysis of variance table regarding noise of tires of other basic specifications in an actual vehicle test. [Figure 7] FIG. 6 is a graph corresponding to FIG. 5 for the basic specification tire showing a variance analysis table of noise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In addition, when multiple embodiments and modified examples are included below, it is assumed from the beginning that new embodiments will be constructed by appropriately combining the characteristic parts of those. In addition, in the following examples, the same components are given the same reference numerals in the drawings, and duplicated explanations will be omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios of the length, width, height, etc. of each member between different drawings do not necessarily match. In addition, in this specification, coasting noise refers to tire noise when a vehicle is coasting, and acceleration noise refers to tire noise when a vehicle is accelerating. In addition, among the components described below, components that are not described in the independent claims showing the highest concept are optional components and are not essential components.

[0016] The inventors conducted numerous bench tests and vehicle tests on numerous tires with different design factors (design elements, design variables) to investigate the relationship between vehicle driving force and tire noise. Some of these tests will be described below. As disclosed in Patent Document 1, the bench test is a test in which a tire is made to contact a rotating drum with a simulated road surface on its outer periphery and run on it, and the tire noise generated is measured with a noise measuring device.

[0017] Figure 1 shows an L8 orthogonal array of four design factors in a bench noise test. By using an L8 orthogonal array, two different combinations of the four design factors can be calculated. 4 It is possible to identify the combination of design factors that contribute significantly to noise with only eight tires, without testing every tire, and with significantly less effort. In the example shown in Figure 1, the identification of each tire is determined by four design factors (design elements) A, B, C, and D.

[0018] The design factors include the effective contact area [contact area excluding grooves] (the area of ​​an axially divided area can be used, and the ratio of these is also a design factor). Here, examples of the axially divided area include the center, quarter, and shoulder. Other design factors include, for example, the area ratio of the land part of the contact area to the whole including grooves (the area of ​​an axially divided area can be used, and the ratio of these is also a design factor), the effective contact ratio of the rib, the pitch number [the number of blocks in the circumferential direction of one circumference of the tire], the hardness of the tread rubber, the belt width [the axial width of the belt when viewed in cross section], the belt angle [the angle with respect to the circumferential direction of the belt ply], the number of belt ends [the number of cords per inch of the belt ply], the Young's modulus of the tread rubber, the elastic modulus of the tread rubber, the tan δ (loss tangent) of the tread rubber, the material of the carcass ply, the Young's modulus of the carcass ply, the number of carcass ply ends, the hardness of the bead filler, the Young's modulus of the bead filler, and the height of the bead filler [the radial length of the bead filler].

[0019] FIG. 1 shows the results of an analysis of four design factors among the design factors listed in paragraph 0018. In FIG. 1, each design factor is configured to select one of two. In addition, "base" in the design factor column indicates that the design factor is a reference value, "+" in the design factor column indicates that the design factor is a value greater than the reference value, and "-" in the design factor column indicates that the design factor is a value less than the reference value. As shown in FIG. 1, Tire 1 is a tire in which all four design factors are reference values. Tire 2 is a tire in which design factors A and B are reference values, while design factor C is less than the reference value and design factor D is greater than the reference value.

[0020] Tire 3 is a tire in which design factor A and design factor C are reference values, while design factor B is smaller than the reference value and design factor D is larger than the reference value. Tire 4 is a tire in which design factor A and design factor D are reference values, while design factor B is smaller than the reference value and design factor C is smaller than the reference value. Tire 5 is a tire in which design factor B and design factor C are reference values, while design factor A is larger than the reference value and design factor D is larger than the reference value.

[0021] Tire 6 is a tire in which design factor B and design factor D are reference values, while design factor A is greater than the reference value and design factor C is smaller than the reference value. Tire 7 is a tire in which design factor C and design factor D are reference values, while design factor A is greater than the reference value and design factor B is smaller than the reference value. Tire 8 is a tire in which design factor A is greater than the reference value, design factor B is smaller than the reference value, design factor C is smaller than the reference value, and design factor D is greater than the reference value.

[0022] FIG. 2 is a graph showing the relationship between driving force and noise for each tire. The noise on the vertical axis of FIG. 2 is the noise measured by a microphone, and is the sum of the power of the power spectrum of the measured sound pressure in the frequency band from 500 kHz to 1500 Hz. The inventor fitted the relationship between driving force and noise for each tire to a linear equation, Y=aX+b, based on the measured values ​​of each tire. The fitting to the linear equation was performed using the least squares method. In order to determine whether this fitting is appropriate, the inventor used the calculated linear equation for each tire to calculate the coefficient of determination R shown in the following equation (1): 2 was calculated.

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[0023] In formula 1, y i is the measured noise level, and y i Hat is y i The noise value of the linear equation at the same driving force as is shown in Fig. 1. The y bar is the average of the measured noise values. The coefficient of determination R 2is an index with a maximum value of 1 that is used to determine whether the fit is adequate or not. The coefficient of determination R 2 The closer the value is to 1, the more appropriate the fit is. Roughly speaking, if the value is greater than about 0.7, the fit can be determined to be appropriate.

[0024] In Equation 1, if all of the measurements fall on the fitted linear equation, then for each i, y i From y i The value obtained by subtracting the hat is 0. Therefore, the coefficient of determination R shown in formula (1) is 2 is 1. This also means that the coefficient of determination R 2 It can be seen that the closer to 1 the value is, the more appropriate the fit is.

[0025] Figure 3 shows the slope of the fitted linear equation for each tire and the coefficient of determination R 2 As shown in FIG. 3, six tires, which represent 75% of the eight tires tested, had a R 2 The coefficient of determination R 2 The values ​​of were 0.98 and 0.99, which were approximately 1. Therefore, from the tests on these eight tires, it became clear that, for tires, there is a proportional relationship between the amount of change in driving force and the amount of change in noise, and that the noise can be expressed as a linear function with driving force as a variable. The inventors also confirmed in actual vehicle tests that there is a proportional relationship between the amount of change in driving force and the amount of change in noise, and that the noise can be expressed as a linear function with driving force as a variable.

[0026] FIG. 4 is an analysis of variance table based on a test conducted by the present inventor, and is an example of the analysis of variance table when the design factors are A, B, C, D, A and B, and A and C. In the analysis of variance table shown in FIG. 4, SS (Sum of Square) is the sum of squares, df (Degrees of Freedom) is the degree of freedom, and is the rank of the variation. MS (Mean square) is the mean sum of squares, and F is the variance ratio, which is the value obtained by dividing the MS of the factor variation by the MS of the error. P-value is the risk rate obtained from the probability function of the F distribution, and is the probability of an incorrect judgment. P-value is usually determined to be significant if it is 5% or less. ρ is the contribution rate, which is calculated by (SS-df x mean sum of squares of error) / (total sum of squares x 100).

[0027] The analysis of variance table is a well-known method and will not be described in detail, but it is a method of analyzing the average value by using the variance for each design variable, and is a method for analyzing whether or not the design variable has an effect when the design variable is varied. By performing the analysis of variance, it is possible to analyze the extent to which the variation due to the design variable is compared with the variation due to the measurement error, and it is possible to identify whether the variation due to the design variable is greater than the measurement error, or whether the effect of varying the design variable is within the range of the measurement error.

[0028] The variance ratio in the analysis of variance table is an index showing how large the variance of the design factors is compared to the variance of the error. The contribution rate is an index showing the power relationship between the design factors, and roughly shows the contribution of the sum of squares of each design factor to the total sum of squares. The contribution rate is an index used in the field of statistics or statistical data analysis, and shows the proportion of each variable's contribution to a certain criterion when there are multiple variables in an analysis model. The contribution rate takes values ​​from 0 to 1, and a contribution rate of 1 means that all of the information expressed by the original feature is expressed. In the example shown in Figure 4, the contribution rate of design factor D is 77%, which is outstanding compared to the other design factors. From this, it can be seen that in this case, among A, B, C, and D, design factor D has a large contribution to noise.

[0029] Figure 5 is a graph investigating the change in the slope of the linear equation when only each design factor is changed from the reference value. In each graph, the slopes for A1, B1, C1, and D1, which are subscripted with 1, indicate the slope at the reference value. Also, in each graph, the slopes for A2, B2, C2, and D2, which are subscripted with 2, indicate the slope when the values ​​of design factors A and D are increased above the reference value, and for design factors B and C, indicate the slope when the values ​​are increased above the reference value.

[0030] As shown in Fig. 5, the change in slope is greater when design factor D is changed than when the other design factors A, B, and C are changed. This is consistent with Fig. 4, in which the contribution rate of design factor D is 77%, which is significantly greater than the contribution rates of the other design factors A, B, and C. From this, it can be concluded that in this test example, for tires with the same basic specifications, design factor D contributes greatly to noise.

[0031] Therefore, for tires with the same basic specifications, by evaluating tire design and estimated acceleration noise at driving force with focus on design factor D, it is possible to efficiently design a tire with low noise, and also to accurately and efficiently evaluate the estimated noise at driving force of the designed tire. More specifically, by focusing on design factor D and performing multiple further tests with different values, it is possible to grasp the tendency of the change (amount of change) in driving force sensitivity (slope of the linear expression) that changes when design factor D is changed for tires with the same basic concept and basic specifications. As a result, for another tire with the same basic concept and basic specifications, it is easy to accurately estimate the change in driving force sensitivity when design factor D is changed, and easy to accurately estimate the noise value relative to driving force.

[0032] FIG. 6 is a graph showing an analysis of variance table for noise of tires with other basic specifications in an actual vehicle test, and FIG. 7 is a graph corresponding to FIG. 5 for a tire with basic specifications showing an analysis of variance table for noise in FIG. 6. As shown in FIG. 6, in this tire with basic specifications, the design factor A has an outstanding contribution rate of 56%, and in order to match this, the slope of the design factor A becomes large when the value is increased from the reference value. In this example, the contribution rate of the design factor D is 28%, which is a value that cannot be ignored. Therefore, by focusing on the design factors A and D, and particularly on the design factor A, and conducting multiple further tests with different values, it is easy to accurately estimate the change in noise when at least one of the design factors A and D is changed for tires with the same basic concept and the same basic specifications. Therefore, it is possible to efficiently design tires with low noise, and it is also easy to accurately and efficiently evaluate the estimated noise at the driving force of the designed tire.

[0033] In this way, by analyzing and investigating the relationship between design factors and acceleration noise using at least one of experimental design methods, such as an orthogonal array, an analysis of variance table, a D-optimal design, a full factorial design, a fractional factorial design table, a Latin hypercube, Fisher's three rules, and a factorial effect diagram, it becomes easy to efficiently design a tire with low noise, and it also becomes easy to accurately and efficiently estimate the acceleration noise of the designed tire at a specific driving force.

[0034] As described above, it has been confirmed and found that it is possible to calculate the quantitative sensitivity (driving force sensitivity) to the slope of the linear equation that expresses noise and driving force from the relationship between the range of design factors and the factor effects regarding tire design specifications, and to estimate the acceleration noise [dB(A)] at any acceleration (driving force) using this linear equation. The estimation formula can be the following formula (2), and the estimation of acceleration noise at driving force can be performed by the following procedure. Estimate formula:

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[0035] Steps to follow: (1) For the design standard tires, obtain the driving force sensitivity = noise increase [dB(A)] / driving force during acceleration (rotating shaft torque [Nm]) and tire coasting noise using at least one of bench tests and actual vehicle tests. (2) The effect of the specification change on the coasting noise and the driving force sensitivity (changes in the coasting noise and the driving force sensitivity) is evaluated and compiled into a database. In this case, it is preferable to evaluate the changes in the coasting noise and the driving force sensitivity in association with the design factors using an experimental design method. The database may also store a function for calculating the changes (amounts of change) in the coasting noise and the driving force sensitivity. (3) Based on the specification changes between the design standard tires and the estimated tires, the changes in coasting noise and driving force sensitivity are calculated based on the above database. (4) Using the above formula (2), calculate the acceleration noise at the target acceleration (driving force).

[0036] When the driving force sensitivity includes the contribution of rubber hardness, the estimation accuracy is improved by incorporating temperature correction, which can be performed, for example, by multiplying the coasting noise and the driving force sensitivity by a temperature coefficient.

[0037] The noise level to be evaluated may be the overall noise level. Alternatively, the noise level to be evaluated may be the partial overall noise level including the 1 kHz band, for example, the partial overall noise level of a frequency band included in the frequency band of 500 Hz to 1.5 kHz. The overall noise level is the sum of the power of each frequency band of the analyzed power spectrum, and the partial overall noise level is the sum of the power of each frequency band of the power spectrum in an arbitrary frequency range.

[0038] The inventors have found through numerous tests that the contribution of acceleration noise is prominent in the frequency band between 500 Hz and 1.5 kHz. Therefore, by performing a partial overall analysis of noise in the frequency band between 500 Hz and 1.5 kHz, acceleration noise can be evaluated effectively and with high accuracy.

[0039] Noise evaluation during testing can be carried out using the following methods: Coasting noise assessment method: JASO C 606:1981, ISO 10844:1994 Acceleration noise assessment method: ISO362, UN-ECE R51-03, JIS D 1024, ISO 10844:1994

[0040] As described above, the tire noise evaluation method disclosed herein is a method for evaluating tire noise when a vehicle is accelerating, in which a driving force sensitivity based on the tire characteristics is estimated based on the value obtained by dividing the change in noise when the driving force of the vehicle changes by the change in the driving force, and the noise when accelerating is evaluated based on the estimated driving force sensitivity.

[0041] According to the present disclosure, tire noise during accelerated running is estimated and evaluated without testing based on driving force sensitivity estimated without testing due to tire characteristics, so that noise evaluation during accelerated running can be performed in a short time, and the labor and cost required for the noise evaluation can be reduced.

[0042] In addition, a third noise obtained by adding a second noise obtained by multiplying the driving force sensitivity by the driving force to a first noise generated when the vehicle is coasting may be estimated as the noise generated when the vehicle is accelerating using the driving force.

[0043] According to this configuration, when estimating the third noise (corresponding to tire noise during accelerating driving) for a specific driving force, the third noise can be instantly estimated for that driving force simply by substituting the driving force into a linear equation for calculating the third noise, the linear equation having the driving force as a variable.

[0044] Additionally, the drive force sensitivity may be estimated based on one or more design factors.

[0045] According to this configuration, it is easy to systematically and objectively estimate the driving force sensitivity using design factors.

[0046] In addition, the driving force sensitivity may be estimated based on a plurality of design factors, and the contribution of each design factor to the driving force sensitivity may be evaluated based on an experimental design method.

[0047] According to this configuration, it is easy to efficiently and accurately evaluate the contribution of each tire design factor to the driving force sensitivity, and it is also easy to accurately estimate tire noise during accelerating driving. [Explanation of symbols]

[0048] A,B,C,D Design factors.

Claims

1. A method for evaluating tire noise during acceleration of a vehicle, comprising the steps of: A tire noise evaluation method comprising: estimating a driving force sensitivity based on a value obtained by dividing an amount of change in the noise when the driving force of the vehicle changes by the amount of change in the driving force based on characteristics of the tire; and evaluating the noise during accelerating driving based on the estimated driving force sensitivity.

2. 2. The tire noise evaluation method according to claim 1, wherein a third noise obtained by adding a first noise generated when the vehicle is coasting to a second noise obtained by multiplying the driving force sensitivity by the driving force is estimated as the noise when the vehicle is accelerating with the driving force.

3. The tire noise evaluation method according to claim 1 or 2, wherein the driving force sensitivity is estimated based on one or more design factors.

4. estimating the driving force sensitivity based on a plurality of the design factors; The tire noise evaluation method according to claim 3 , wherein the contribution of each of the design factors to the driving force sensitivity is evaluated based on an experimental design method.

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