JP2007131209A - Model for numerical analysis of tire, its forming method, method for analyzing rolling resistance of tire, and model for numerical analysis of rolling resistance of tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accurately simulating the rolling resistance of a tire, and further to provide a model for numerical analysis to be suitably used in this simulation, and to provide a method for forming the model. <P>SOLUTION: The analysis of the rolling state of the tire on a road surface at a constant speed has been carried out by modeling the road surface as a drum, and by modeling the rubber members of the tire as elastic bodies. The amplitudes and frequencies of the strain in the rubber members have been derived from the wave shapes of the respective rubber elements of the tire, the wave shapes having been obtained by the analysis. After that, the viscoelastic test for a rubber material has been carried out with the obtained amplitudes and frequencies of the strain, and the viscoelastic modulus of the rubber material has been calculated. A tire model has been formed using the calculated viscoelastic modulus, and a model 10 for the numerical analysis of a tire-wheel assembly body has been formed using this tire model. The value of the rolling resistance has been obtained by carrying out the analysis of the rolling. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for creating a tire numerical analysis model by dividing a tire into a finite number of elements and a method for analyzing the rolling resistance of the tire using the created numerical analysis model.

Conventionally, as a method for simulating tire performance, the tire to be evaluated is approximated by a tire finite element model obtained by dividing a tire into a finite number of elements, and characteristics such as density and elastic modulus are given to each finite element. Finite Element Method (Finite Element Method) is often used to give boundary conditions such as internal pressure and load to the model and calculate the deformation state of each of the above elements to numerically analyze the tire dynamics such as tire deformation and rolling resistance. ing.
By the way, the cause of tire rolling resistance may be due to friction between the tire and the road surface or due to air resistance, but in normal driving, the effect of hysteresis loss caused by deformation when the tire rolls is the most. It is said to be big. As a method of simulating the rolling resistance of a tire, a tire finite element model (called a tire model) in which a rubber material such as tread rubber and a bead core are modeled as a three-dimensional solid element and a fiber composite such as a carcass or a belt is used as a membrane element. ) Is grounded on a road surface model that is modeled with a flat rigid surface element and travels under predetermined driving conditions, and a history of distortion amount of each element of the tire model is obtained. Specifically, the energy loss of the rubber member is calculated by calculating the storage elastic modulus, loss (tan δ) and maximum amplitude strain of the rubber material, or determining the area surrounded by the hysteresis loop, etc. Methods for calculating rolling resistance from energy loss have been proposed (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1).

Specifically, for example, as shown in the flowchart of FIG. 10, a tire model in which a rubber material, a carcass, a belt, a bead core, and the like are continuous in the same cross-sectional shape in the tire circumferential direction is set (step S51) and the road surface A model is set (step S52), and based on boundary conditions such as longitudinal load and road friction coefficient, the tire model is grounded and deformed without rolling (step S53). The amount of strain of each rubber element constituting the tread portion of the model is calculated, and the strain distribution in the circumferential direction of the rubber element is obtained. From this strain distribution, the history of strain of the rubber element when the tire makes one revolution After calculating (steps S54 and S55), the energy loss is calculated from the strain history and the rolling resistance is simulated (step S). 6).
In this way, if the tire finite element model is grounded on the road surface model and deformed, and the magnitude of hysteresis loss caused by the deformation when the tire rolls is numerically analyzed, the tire rolling resistance can be obtained. it can.
JP 2003-118328 A JP 2005-186900 A Luchini; “Tire Rolling Loss Computation with the Finite Element Method” Tire Science Technology, Vol. 22, 4, (1994)

However, in the above conventional simulation method, when calculating the energy loss from the obtained strain amount, the rubber member is handled as a viscoelastic body. However, the tire model is grounded on the road surface model, and each element constituting the rubber member is grounded. When analyzing the amount of strain, since the rubber member is an elastic body, there is a problem that the analysis accuracy is not good.
In addition, the conventional tire model described above cannot calculate a portion that is not continuous in the tire rotation direction due to a calculation method, and a portion where the tire is in contact with the road surface due to rolling resistance proceeds in a discontinuous portion in the tire rotation direction. Since the effect of deformation so as to move backward in the direction cannot be considered, it is difficult to accurately determine the rolling resistance.
By the way, in a tire model, it is conceivable to perform simulation by giving a viscoelastic coefficient to each element constituting the rubber member from the beginning, but since the viscoelastic coefficient of rubber differs depending on the strain amount and frequency, various strain amounts and Not only is it necessary to perform viscoelastic property tests for each rubber member at the frequency, but it is not only necessary to measure a lot, but also to set the viscoelastic coefficient in the rolling state, a considerable number of simulations are required. Since it had to be repeated, there was a problem that the analysis efficiency was remarkably bad.

  The present invention has been made in view of conventional problems, and provides a method capable of accurately simulating tire rolling resistance, a numerical analysis model suitably used for this simulation, and a method for producing the same. Objective.

As a result of diligent study, the present inventor first determined from the strain amount and frequency of the tread rubber portion obtained by modeling the rubber as an elastic body and performing the rolling analysis of the tire, to the above-described strain amount and frequency. If the viscoelastic properties that give the tires are estimated, a new model is created with the estimated viscoelastic properties applied to the rubber member, and rolling analysis is performed again, the tire characteristics such as rolling resistance can be accurately measured. The inventors have found that simulation can be performed well and have arrived at the present invention.
That is, the invention described in claim 1 of the present application is a method of creating a numerical analysis model by dividing a tire into a finite number of elements, and a numerical analysis model using a rubber member constituting the tire as an elastic body. The first step of creating and analyzing the rolling of the tire on the road surface model to calculate the strain amount and the frequency of each portion of the tire, and the viscosity of the rubber member at the calculated strain amount and frequency. A second step of measuring an elastic characteristic; a third step of calculating a viscoelastic coefficient from the measured viscoelastic characteristic; and using the calculated viscoelastic coefficient, the rubber member as a viscoelastic body. And a fourth step of creating a new numerical analysis model.

According to a second aspect of the present invention, in the tire numerical analysis model creation method according to the first aspect, viscoelastic properties of the rubber member at various strain amounts and frequencies are measured in advance, and this measurement is performed. The viscoelastic coefficient of the rubber member is obtained from the viscoelastic characteristics and the calculated strain amount and frequency.
According to a third aspect of the present invention, in the tire numerical analysis model creation method according to the first or second aspect, the road surface model abuts on the tire and rotates relative to the tire. It is a drum.
According to a fourth aspect of the present invention, in the tire numerical analysis model creation method according to any one of the first to third aspects, the temperature of each part of the tire is analyzed in the first step, and the second step. Then, the viscoelastic property of the rubber member is measured according to the temperature condition.

According to a fifth aspect of the present invention, in the method for creating a numerical analysis model for a tire according to any one of the first to fourth aspects, a numerical analysis model in which the rubber member is an elastic body, and the rubber member is viscoelastic. It is characterized by using a numerical analysis model in which a tread pattern is modeled as a body numerical analysis model.
According to a sixth aspect of the present invention, in the method for creating a numerical analysis model for a tire according to any one of the first to fifth aspects, a numerical analysis model using the rubber member as an elastic body and a viscoelasticity of the rubber member. As a numerical analysis model for the body, a numerical analysis model including an analysis result of assembling a tire on a wheel is used.

The invention according to claim 7 is a method of analyzing the rolling resistance of a tire using a numerical analysis model created by dividing the tire into a finite number of elements. Using the numerical analysis model created by the method for creating a numerical analysis model for a tire described in the above, the tire is rolled on the road surface model to calculate the longitudinal force generated in the tire, and this calculation The rolling resistance of the tire is obtained from the magnitude of the applied longitudinal force.
The invention according to claim 8 is the tire rolling resistance analysis method according to claim 7, wherein the road surface model is a drum that abuts against the tire and rotates relative to the tire. is there.
According to a ninth aspect of the present invention, in the tire rolling resistance analysis method according to the seventh or eighth aspect, the analysis is performed at a constant speed.
According to a tenth aspect of the present invention, the numerical analysis model created by the method for creating a numerical analysis model for a tire according to any one of the first to sixth aspects is rolled on a road surface model and the tire is rotated. The process in which the speed decreases from the initial speed due to the rolling resistance is analyzed to determine the rolling resistance of the tire.

The invention according to claim 11 is a numerical analysis model of a tire obtained by dividing a tire into a finite number of elements, which is used for tire simulation by a finite element method, and is given to each element of a rubber member constituting the tire. Calculated from the viscoelastic characteristics of the rubber member measured based on the amount of strain and frequency of the rubber member calculated by rolling analysis using a numerical analysis model with the tire as an elastic body as the viscoelastic coefficient The viscoelasticity coefficient is used.
The invention according to claim 12 is to calculate a longitudinal force generated in the tire by rolling a tire model obtained by dividing the tire into a finite number of elements on the road surface model, and to determine a rolling resistance of the tire. An analysis model for tire rolling resistance, comprising: the tire numerical analysis model according to claim 11; and a road surface model that models a drum that contacts the tire and rotates relative to the tire. It is characterized by this.

According to the present invention, when the viscoelastic coefficient to be given to each element of the rubber member constituting the tire is obtained, a rolling analysis is performed using a numerical analysis model in which the tire is an elastic body, and the strain amount of the rubber member is determined. After calculating the frequency and the frequency, the viscoelastic property of the rubber member is measured based on the calculated strain amount and the frequency, and the viscoelastic coefficient is obtained using the measured viscoelastic property. Therefore, a tire model having characteristics close to those of an actual tire can be created.
Also, because the tire model was analyzed to roll on the road surface model, the longitudinal force generated in the tire was calculated, and the rolling resistance of the tire was determined from the calculated longitudinal force. The rolling resistance of the tire can be accurately simulated.
At this time, if a numerical analysis model in which a tread pattern is modeled is used as the numerical analysis model, and the road surface model is in contact with the tire and is a drum that rotates relative to the tire, It is possible to accurately simulate the rolling resistance of tires that are actually used.
Furthermore, if a numerical analysis model including an analysis result obtained by assembling a tire on a wheel is used as the numerical analysis model, the analysis accuracy can be further improved.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
FIG. 1A is a diagram showing an outline of a numerical analysis model 10 of a tire / wheel assembly according to the best mode, and FIG. 1B is a cross-sectional view of a tire model 11 used in the numerical analysis model 10. It is. The numerical analysis model 10 includes a tire model 11 and a wheel model, but the wheel model is omitted in FIG.
In the numerical analysis model 10 described above, for the tire model 11, the rubber member such as the tread portion 11a and the side portion 11b and the bead wire 11r are modeled as solid elements, and the reinforcing members such as the belt 11p and the carcass ply 11q are modeled as shell elements. It has become. It is also possible to model reinforcing members such as the belt 11p and the carcass ply 11q with membrane elements and river elements. The bead wire 11r is modeled by a solid element including a plurality of steel cords, but each steel cord can be individually modeled by a solid element, a river element, and a beam element.
Further, in the numerical analysis model 10 of this example, only the wheel rim portion that contacts the tire bead portion is modeled with respect to the wheel (see FIG. 9), but it is also possible to model the disc portion connected to the axle. is there. On the other hand, the road surface 20 can be modeled by a flat rigid shell element or an actual road surface unevenness can be modeled. In general, the rolling resistance measurement of an actual tire is performed by rolling the tire on a drum. On the drum, due to its curvature, the rotational length of the tire ground contact portion is different from that of a flat road surface. That is, if the length of the ground contact portion is different, it affects the stress, strain amplitude, and frequency of each portion of the tire, particularly the tread rubber portion. Therefore, in this example, in order to accurately estimate the rolling resistance value measured on the drum, the road surface 20 as shown in FIG. 2 is modeled as a road surface model using a drum used in a tire rolling test. If the drum model 20D is used and the numerical analysis model 10 of the tire / wheel assembly is rolled on the drum model 20D for numerical analysis, the estimation accuracy of the rolling resistance can be further improved.
In addition, as a method of rolling the tire, create a model such as setting boundary conditions so that the tire and wheel rotate freely around the axle, and using joint elements, etc., and either the road surface or the axle is It can be analyzed by fixing and moving the other side in the longitudinal direction of the tire. Furthermore, it is possible to give the tire a slip angle or a camber angle, or to move the road surface so that the tire has a slip angle or a camber angle.

Next, a method for determining the rolling resistance of the tire using the numerical analysis model 10 of the tire / wheel assembly will be described.
It is known that the rolling resistance of a tire is determined by the viscoelastic properties of rubber. The higher the viscosity, the higher the rolling resistance. Also, the viscoelastic properties of rubber vary with strain amplitude, frequency, and temperature. Therefore, in order to accurately analyze the actual tire rolling resistance, it is necessary to give viscoelastic characteristics corresponding to the amplitude, frequency, and temperature of the strain to each element during tire rolling.
Since the tire temperature is a steady value in the steady rotation state, the viscoelastic properties of the rubber at this steady temperature may be measured by a rubber material test, but the strain amplitude and frequency should be predicted. In this example, first, the rubber material is regarded as an elastic body, the amplitude and frequency of the strain are obtained, and the tire model 11 in which viscoelastic properties at the amplitude and frequency of the strain are given to the rubber material is created. Then, the rolling analysis is performed again using the numerical analysis model 10 using the newly created tire model 11, and the rolling resistance of the tire is numerically analyzed.
FIG. 3 is a flowchart showing an example of a tire rolling resistance analysis method according to the present invention. In this example, first, the road surface is modeled using an elastic model in which a road surface is modeled as a drum and a rubber member is modeled as an elastic body. An analysis of the rolling of the tire at a constant speed (for example, 30 km / hr) is performed to obtain a distortion waveform (time-series waveform) generated in each rubber element of the tire model 11 (step S11). The elastic model does not model the viscosity of the material, so the longitudinal force is zero.
FIG. 4 is a diagram showing temporal changes of six components (ε ₁₁ , ε ₂₂ , ε ₃₃ , ε ₁₂ , ε ₂₃ , ε ₃₁ ) of strain generated in the rubber element of the tire tread portion 11a. It can be seen that the periods are different. Further, as shown in FIG. 5, the temporal change of the six components of strain generated in the rubber element of the tire side portion 11b is greatly different from the tire tread portion shown in FIG.
As described above, since the amplitude and frequency of stress and strain at each part of the tire are different, it is necessary to carry out very many measurements when the viscoelasticity test of each rubber member is performed under the same conditions. . Therefore, in this example, after obtaining the amplitude and frequency of strain when the rubber material is regarded as an elastic body (step S12), the viscoelasticity test of the rubber material is performed with the obtained amplitude and frequency of strain ( Then, the relaxation elastic modulus (G), which is a viscoelastic material constant, is calculated from the viscoelastic property closest to the analysis result of step S11 (step S14). Thereby, the frequency | count of a viscoelastic property test can be reduced significantly. FIG. 6 is a diagram showing a method for obtaining the amplitude and frequency of the distortion. The maximum amplitude of the distortion waveform is obtained from the time waveform of each component of the distortion, and this is used as the distortion amplitude. The strain period is determined, the reciprocal of the strain period is set as the strain frequency, and the viscoelastic characteristics of the rubber member at the determined strain amplitude and frequency are measured.

When the viscoelastic property test of the rubber member is performed with both shear input and tensile input, the strain amplitude and frequency inside the tire may be obtained and used for the test for each strain. When only one of the tests is performed, the average value of the strain amplitude and the frequency within the tire of the six strain components may be used, or the strain component having the maximum strain amplitude among the six strain components. The distortion amplitude and frequency may be used. Alternatively, the average value of the strain amplitude and the frequency within the tire of the three components of the shear strain that greatly affects the rolling resistance is used, or the strain amplitude and the frequency of the strain component having the maximum strain amplitude among the three components of the shear strain are used. It may be used.
For the viscoelastic characteristics, a known time relaxation type test or frequency variation type test may be performed. The above time relaxation type test results can be easily approximated to the Prony series of relaxation modulus. On the other hand, when a frequency variation type test is performed, it is necessary to convert the storage elastic modulus (G ′) and loss elastic modulus (G ″) obtained as a result thereof into relaxation elastic modulus (G). Ninomiya's approximation represented by the following formula (1) can be used for this conversion.
G (ω) = G ′ (ω) −0.4 · G ″ (0.4ω) + 0.01 · G ″ (10ω) (1)
ω = 2πf to f: test frequency (for example, Ninomiya, K and Ferry, JD “Some Approximate Equations Useful in the Phenomenological Treatment of Linear Viscoelastic Data”, Journal of Colloid Science, 14, 36-48, 1959)
In addition, although the shear type test was assumed in the above, each elastic modulus E, E ', E "can be calculated | required similarly also with a tension type test.

In this example, the viscoelastic material constant of the rubber material is obtained by approximating the result obtained in the viscoelastic property test to the Prony series of relaxation elastic modulus, and the viscoelasticity of the rubber member having the obtained viscoelastic material constant is obtained. The tire model 11 is reconstructed as a body to create a numerical analysis model 10 of the tire / wheel assembly (step S15), and then the numerical analysis model 10 of the tire / wheel assembly is used. The same rolling analysis is performed to determine the longitudinal force and the rolling resistance value is analyzed (step S16). In the newly created numerical analysis model 10 of the tire and wheel assembly, since the viscosity is considered in the material, a longitudinal force, that is, rolling resistance is generated, and thereby the ground contact surface is displaced backward in the traveling direction. . Therefore, if the value of the longitudinal force, which is the force that gives the displacement, is the rolling resistance, the rolling resistance can be obtained with high accuracy.
The rolling analysis was performed on the assumption that the tire rolls on the drum at a constant speed. However, when the viscosity of the rubber member is taken into account, as described above, the rolling analysis is performed when the tire rolls. Therefore, if the analysis is performed with the initial speed given, the tires with different rubber properties, structures, shapes, patterns, etc. may have different speeds, making it impossible to make accurate comparisons. Because there is. Therefore, if an analysis of rolling at a constant speed is performed as in this example, a highly accurate analysis can be performed.
The analyzed displacement amount is 90 when the actually measured displacement amount is 100, and it was confirmed by the analysis according to the present invention that a result close to the actual measurement can be obtained. In addition, since the rolling resistance of the actual tire may be caused by friction between the tire and the road surface or may be generated by the air resistance of the tire, naturally, the value obtained by the analysis is smaller than the actual rolling resistance.

Thus, in this best mode, the road surface is modeled as a drum, the rubber member of the tire is modeled as an elastic body, and the tire rolls at a constant speed on the road surface, and the analysis is performed. After obtaining the amplitude and frequency of strain of the rubber material from the strain waveform generated in each rubber element of the tire, the rubber material is subjected to a viscoelasticity test of the rubber material with the obtained amplitude and frequency of strain. Since the viscoelastic modulus is calculated and a tire model is created using this viscoelastic modulus, a tire model in which the rubber member is given a viscosity close to the actual characteristic can be obtained. Also, a tire / wheel assembly numerical analysis model 10 was created using this tire model, and the rolling analysis was performed again to calculate the longitudinal force, so that the value of the rolling resistance was obtained. The resistance can be simulated accurately.
In this example, since the viscoelasticity test of the rubber material is performed based on the amplitude and frequency of strain when the rubber material is regarded as an elastic body, the viscoelastic material constant is obtained. The elastic material constant can be obtained, and the efficiency of analysis can be greatly improved.

In the best mode, the amplitude and frequency of strain when the rubber material is regarded as an elastic body are obtained, and the viscoelasticity test of the rubber material is performed with the obtained amplitude and frequency of strain, and the elasticity is obtained. The viscoelastic material constant was calculated by using the viscoelastic coefficient at the strain amplitude and frequency closest to the analysis result by the model, but the viscoelastic characteristics of the rubber member at the strain amount and frequency were measured in advance. If the viscoelasticity test results close to the above analysis results are interpolated among the measured viscoelastic properties, the analysis accuracy is further improved. Alternatively, a viscoelastic material constant is obtained from a result of measuring the amplitude and frequency of strain in each portion of the tire using the numerical analysis model 10 of the tire / wheel assembly, and this is obtained as a numerical analysis model of the tire / wheel assembly. If the numerical analysis is performed again with the viscoelastic material constant of 10, the analysis accuracy can be further improved. Moreover, if the above operation is repeated until the obtained viscoelastic material constant reaches a substantially constant value, the analysis accuracy can be further improved.
In the above example, when the viscoelastic property test of the rubber member used in the tire was performed, the strain amplitude and frequency obtained from the rolling analysis of the elastic model were used as the test conditions. It is also possible to make a determination similar to the above and perform a test with a strain component corresponding to this stress component. In this case, the main strain is calculated and the average value of the strain amplitude and frequency inside the tire having the largest absolute value is used, or the average of the three main strain components and the average of the two main strain components. It is also possible to obtain the average value of strain amplitude and frequency inside the tire from the above and use it in the viscoelastic property test. Similarly, the main stress can be the same as the main strain.
Incidentally, the rolling resistance of the tire is necessary under various speed conditions. In order to estimate the rolling resistance when the speed conditions are different as described above, the analysis of rolling the tire at the constant speed may be repeated a plurality of times, but the fastest speed to be obtained is set as the initial speed, If the analysis that decelerates by rolling resistance (coasting analysis) is performed, the rolling resistance under continuous speed conditions can be easily obtained, so that the rolling resistance at each speed can be estimated more efficiently. .
In addition, a tire with a small rolling resistance can be accelerated by adding a brake in a pseudo manner. It is desirable that the braking force be as large as the air resistance generated in the actual tire and the rotational frictional resistance of each part of the test machine such as a drum or an actual vehicle.

  In the above example, a model in which the same elements are arranged in the tire rotation direction is used. However, in a tire having a block pattern as shown in FIG. 7, the tread rubber is not continuous in the circumferential direction. It is necessary to model in consideration of the tread pattern. This is because, in the tire model 11Z in which a tire having a tread pattern is modeled, even in an element at the same position in the tire cross section, such as the element 11m and the element 11n in FIG. This is because the time histories are different. That is, as shown in FIG. 8 (a), shearing and bending deformation occur in the tread block as the tire rolls, and this deformation occurs at a position in the tread block, specifically, the element 11m located on the stepping side. And the element 11n located on the kicking side show different changes. That is, as shown in FIG. 8B, when comparing the time histories of strain, the element 11m located on the stepping side has a large distortion when stepped on, but the element 11n located on the kicking side has a larger strain than when stepping on. The distortion when kicking out is greater. Therefore, if the tire model 11Z is modeled in consideration of the tread pattern, the stress and strain at each location inside the tread pattern block can be taken into account, so that the rolling resistance is more accurate. Can be estimated well.

In the above example, it was analyzed that the tire was in a steady state and the temperature of each part of the tire was constant, but the heat generated by the viscoelasticity of the rubber accompanying the rolling of the tire was constant when transferring heat to the air or the wheel. Even when rolling at, each part reaches a steady temperature with a balance between heat generation and heat transfer. That is, the tire has a temperature distribution. Therefore, by giving viscoelasticity to the rubber member, it is possible to estimate the temperature distribution in the steady state in each part of the tire. Based on this temperature distribution, the viscoelastic characteristics of each element of the rubber member are If it is replaced with the viscoelastic property of temperature, a viscoelastic property with higher accuracy can be given, and as a result, a more accurate rolling constant can be estimated. In addition, what is necessary is just to change the viscoelastic characteristic of the said temperature by changing temperature in the viscoelastic characteristic test of said step S12.
Further, the numerical analysis model 10 models a state where the tire bead portion is in contact with the wheel rim portion. However, an analysis of assembling the tire to the wheel is performed, and a large strain or stress is generated. When the display is made so that the portion becomes bright, as shown in FIG. 9, it can be seen that large strain and stress are generated in the portion of the tire bead portion 11k that is in contact with the wheel rim portion 12. Therefore, if the analysis of assembling the tire on the wheel is performed in advance, a model in which the above part is pre-strained and strained is created, and the analysis is performed using this model, the rolling resistance can be estimated more accurately. it can.

表１から明らかなように、本発明による各ゴム要素の粘弾性係数を設定したモデルを作成し転動解析する手法（新手法１）では、従来の手法に比較して精度のよい転がり抵抗の解析を行うことができることが確認された。更に、トレッドパターンをモデル化して解析すれば（新手法２）、転がり抵抗の値を更に精度よく求めることができる。
また、予め、ホイール組み付け解析を行って、タイヤビード部に歪や応力を与えたモデルを作成し、このモデルを用いて解析すれば（新手法３）、実測に極めて近い転がり抵抗値を得ることができることが確認された。 A tire model with a tire size of PSR215 / 45R17 is incorporated into a wheel with a rim width of 6J, a model is created by rolling it on a drum, an analysis for estimating the rolling resistance of the tire is performed, and a drum tester (outer diameter 1. Table 1 below shows the result of comparison with the rolling resistance measured in accordance with ISO 8767 at 7 m (smooth steel). In addition, all the results are shown as an index with the measured rolling resistance value as 100.
The rolling speed was 80 km / hr, the tire internal pressure was set to 200 kPa, and the load was set to 4.0 N.
Conventional method: Rolling analysis was performed using an elastic model without a tread pattern to determine the amount of stress and strain, and rolling resistance was estimated considering viscoelastic characteristics.
New method 1: Rolling analysis is performed with an elastic model without a tread pattern to determine the strain amplitude and frequency of each rubber element, and a model in which the viscoelastic coefficient of each rubber element is set from the strain amplitude and frequency is created. Then, rolling analysis was performed again to determine rolling resistance. The analysis conditions were that the drum rolls at a constant speed.
New method 2: Same as New method 1 except that the tread pattern is modeled.
New method 3: Same as New method 2 except for including wheel assembly analysis.

As is apparent from Table 1, the method (new method 1) in which a model in which the viscoelastic coefficient of each rubber element is set and rolling analysis is performed according to the present invention (new method 1) has a higher rolling resistance than the conventional method. It was confirmed that analysis can be performed. Further, if the tread pattern is modeled and analyzed (new method 2), the value of the rolling resistance can be obtained with higher accuracy.
Moreover, if wheel assembly analysis is performed in advance to create a model in which strain and stress are applied to the tire bead, and analysis is performed using this model (new method 3), a rolling resistance value extremely close to actual measurement can be obtained. It was confirmed that

  Thus, according to the present invention, the rolling resistance of a tire that is actually used can be simulated efficiently and accurately, so that the design / development efficiency of the tire can be improved.

It is a figure which shows the outline | summary of the analytical model of the rolling resistance of the tire which concerns on the best form of this invention. It is a surface which shows the outline | summary of the analytical model of the rolling resistance of a tire which rolls the tire by this invention on a drum. It is a flowchart which shows an example of the analysis method of the rolling resistance of the tire by this invention. It is a figure which shows the time change of six components of the distortion which generate | occur | produces in the rubber element of a tire tread part. It is a figure which shows the time change of six components of the distortion which generate | occur | produces in the rubber element of a tire side part. It is a figure which shows the method of calculating | requiring the amplitude and frequency of a distortion component. It is a figure which shows an example of the model of the tire which has a block pattern. It is a schematic diagram which shows the deformation | transformation and distortion state of a tread block. It is a figure which shows the generation | occurrence | production state of the distortion | strain and stress of a tire bead part when the analysis which assembles | attaches a tire to a wheel is performed. It is a flowchart which shows the analysis method of the conventional rolling resistance.

Explanation of symbols

10 Numerical analysis model of tire / wheel assembly, 11 Tire model,
11a tread part, 11b side part, 11p belt, 11q carcass ply,
11r bead wire, 11k tire bead part, 12 wheel rim part, 20 road surface, 20D drum model.

Claims (12)

A method of creating a numerical analysis model by dividing a tire into a finite number of elements,
A first step of creating a numerical analysis model using a rubber member constituting the tire as an elastic body, performing an analysis of rolling the tire on a road surface model, and calculating a strain amount and a frequency of each portion of the tire When,
A second step of measuring viscoelastic properties of the rubber member at the calculated strain amount and frequency;
A third step of calculating a viscoelastic coefficient from the measured viscoelastic properties;
A fourth step of creating a new numerical analysis model using the rubber member as a viscoelastic body, using the calculated viscoelastic coefficient;
A method for creating a numerical analysis model of a tire, comprising:   The viscoelastic characteristics of the rubber member at various strain amounts and frequencies are measured in advance, and the viscoelastic coefficient of the rubber member is obtained from the measured viscoelastic characteristics and the calculated strain amount and frequency. The method for creating a numerical analysis model for a tire according to claim 1, wherein:   3. The method for creating a numerical analysis model for a tire according to claim 1, wherein the road surface model is a drum that abuts on the tire and rotates relative to the tire.   The temperature of each part of the tire is analyzed in the first step, and the viscoelastic property of the rubber member is measured in the second step according to the temperature condition. A method for creating the numerical analysis model of the described tire.   5. The tread pattern is modeled in the numerical analysis model in which the rubber member is an elastic body and the numerical analysis model in which the rubber member is a viscoelastic body. 5. A method for creating the numerical analysis model of the described tire.   6. The numerical analysis model in which the rubber member is an elastic body and the numerical analysis model in which the rubber member is a viscoelastic body include an analysis result in which a tire is assembled to a wheel. A method for creating a numerical analysis model of a tire according to claim 1.   The longitudinal force generated in the tire is calculated by performing an analysis of rolling the numerical analysis model created by the method for creating the numerical analysis model of a tire according to any one of claims 1 to 6 on a road surface model. Then, the tire rolling resistance analysis method is characterized in that the rolling resistance of the tire is obtained from the calculated magnitude of the longitudinal force.   8. The tire rolling resistance analysis method according to claim 7, wherein the road surface model is a drum that abuts on the tire and rotates relative to the tire.   The tire rolling resistance analysis method according to claim 7 or 8, wherein the analysis is performed at a constant speed.   The numerical analysis model created by the method for creating a numerical analysis model for a tire according to any one of claims 1 to 6 is rolled on a road surface model, and the rotational speed of the tire is reduced from the initial speed due to rolling resistance. The tire rolling resistance analysis method is characterized in that the rolling resistance of the tire is obtained by analyzing the process of the tire. A numerical analysis model in which a tire is divided into a finite number of elements,
As a viscoelastic coefficient to be given to each element of the rubber member constituting the tire, based on a strain amount of the rubber member and its frequency calculated by performing a rolling analysis using a numerical analysis model using the tire as an elastic body. A tire numerical analysis model using a measured viscoelastic coefficient calculated from a viscoelastic characteristic of the rubber member.   This is a tire rolling resistance analysis model for calculating the rolling resistance of the tire by rolling the tire model in which the tire is divided into a finite number of elements on the road model and calculating the longitudinal force generated in the tire. A tire rolling resistance comprising: the tire numerical analysis model according to claim 11; and a road surface model that models a drum that contacts the tire and rotates relative to the tire. Numerical analysis model.

Images