Method for estimating dynamic friction characteristics of vulcanized rubber components

Abstract

To provide an estimation method capable of simply estimating dynamic frictional characteristics of a vulcanized rubber member in which a large number of rigidity particles exist.SOLUTION: While grasping in advance the correlation CR between a dynamic friction coefficient of a vulcanized rubber member 1 with respect to a target surface 4 and an estimation parameter X calculated by the following formula (1), based on a storage elastic modulus Eo' of the vulcanized rubber member 1 to be estimated and an outer diameter Do of rigid particles existing therein, a projection diameter Ro and a wavelength λo of the target surface 4 to be applied, and the estimation parameter X, dynamic frictional characteristics of the vulcanized rubber member 1 to be estimated with respect to the target surface 4 to be applied are estimated: estimation parameter X=R2 / (λE'2D4) ... (1). In the formula (1), R is a projection diameter of the target surface, λ is a wavelength of the target surface, E' is a storage elastic modulus of the vulcanized rubber member, and D is an outer diameter of the rigid particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for estimating the dynamic friction characteristics of a vulcanized rubber member, and more particularly to a method for more simply estimating the dynamic friction characteristics of a vulcanized rubber member containing a large number of rigid particles. [Background technology]

[0002] Among rubber products, dynamic friction characteristics are important. For example, the dynamic friction characteristics of tires against the road surface are important, and the dynamic friction characteristics of brake pads against the brake disc are important. To understand these dynamic friction characteristics, dynamic friction tests have traditionally been conducted to measure the dynamic friction coefficient.

[0003] To improve dynamic friction characteristics, it is known that, for example, in tires, tread rubber is blended with rigid particles such as powdered eggshells or crushed seashells (see, for example, Patent Document 1). To select rubber specifications with desired dynamic friction characteristics, it is necessary to prepare many types of test samples with different rigid particles and rubber types and conduct dynamic friction tests. Therefore, there is room for improvement in order to more easily grasp the dynamic friction characteristics of vulcanized rubber components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-167410 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for more simply estimating the dynamic friction characteristics of a vulcanized rubber member containing a large number of rigid particles. [Means for solving the problem]

[0006] In order to achieve the above object, the method of estimating the dynamic friction characteristics of a vulcanized rubber member of the present invention is to estimate the dynamic friction characteristics of a vulcanized rubber member having a large number of rigid particles therein. When the rigid particle is not present, the rigid particle is present. Coefficient of kinetic friction against the target surface The increase in and the estimated parameter X calculated by the following formula (1), and based on the storage modulus Eo' of the vulcanized rubber member to be estimated and the outer diameter Do of the internal rigid particles, the protrusion diameter Ro and wavelength λo of the target surface to be applied, and the estimated parameter X, The case where the rigid particles are present compared to the case where the rigid particles are not present dynamic friction Coefficient increase A method for estimating dynamic friction characteristics of a vulcanized rubber member, comprising: Estimated parameters X=R 2 / (λ·E' 2 D 4 )···(1) Here, R is the diameter of the protrusions on the target surface, λ is the wavelength of the target surface, E′ is the storage modulus of the vulcanized rubber member, and D is the outer diameter of the rigid particle. [Effects of the Invention]

[0007] In the present invention, once the storage modulus Eo' of the vulcanized rubber member to be estimated and the outer diameter Do of the internal rigid particles, as well as the protrusion diameter Ro and wavelength λo of the target surface to be applied, are known, it becomes possible to estimate the dynamic friction characteristics of the vulcanized rubber member to be estimated with respect to the target surface to be applied by using these data and the previously determined correlation CR between the dynamic friction coefficient and the estimation parameter X. Therefore, since there is no need to perform a dynamic friction test each time the specifications of the vulcanized rubber member to be estimated or the specifications of the target surface to be applied change, the dynamic friction characteristics can be easily determined. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is an explanatory diagram illustrating a cross-sectional view of a vulcanized rubber member and a target surface. [Figure 2] 2 is an explanatory diagram showing a cross-sectional view of a sliding state between the vulcanized rubber member of FIG. 1 and a target surface. FIG. [Figure 3]FIG. 10 is a graph illustrating the correlation CR between the estimated parameters and the increase in the dynamic friction coefficient. [Figure 4] FIG. 2 is an explanatory diagram illustrating a flow of steps of a method for estimating dynamic friction characteristics of a vulcanized rubber member according to the present invention. [Figure 5] FIG. 10 is an explanatory diagram illustrating a process for calculating a dynamic friction coefficient. DETAILED DESCRIPTION OF THE INVENTION

[0009] The method for estimating the dynamic friction characteristics of a vulcanized rubber member according to the present invention will be described based on the embodiment shown in the drawings.

[0010] In this estimation method, the dynamic friction characteristics (dynamic friction coefficient μ D One end face (the lower end face in the figure) of the vulcanized rubber member 1 serves as a contact face 1 a that comes into contact with and slides on the target surface 4 .

[0011] The vulcanized rubber member 1 has vulcanized rubber 2 and a large number of rigid particles 3 present within the vulcanized rubber 2. The type of rubber used for the vulcanized rubber 2 is not particularly limited, and the vulcanized rubber member 1 can be formed from various general-purpose rubber compositions.

[0012] The rigid particles 3 are particles or aggregates that are harder than the vulcanized rubber 2 and do not substantially deform even when a frictional force acts on them. Specific examples of the rigid particles 3 include aggregates of various silica, carbon, aluminum hydroxide, calcium carbonate, metal particles, etc.

[0013] The target surface 4 is uneven with many tiny protrusions. The distance between the protrusions is expressed as wavelength λ, the radius of the protrusions is expressed as protrusion diameter R, and the height of the protrusions (size of the unevenness) is expressed as amplitude a.

[0014] First, the dynamic friction force generated in the vulcanized rubber member 1 containing a large number of rigid particles 3 will be described.

[0015] 2, when the vulcanized rubber member 1 is pressed against the target surface 4 with a predetermined pressure to bring the contact surface 1a into contact with the target surface 4, the contact surface 1a is pressed into the target surface 4. More specifically, the contact surface 1a is pressed into the protrusions on the target surface 4 (the protrusions are embedded in the contact surface 1a).

[0016] In this state, the vulcanized rubber member 1 is moved relative to the target surface 4 so that the contact surface 1a slides against the target surface 4. The direction of the relative movement is as shown by the arrow in FIG. surface 4. The vulcanized rubber member 1 moves relative to the contact surface 1a while deforming the area near the contact surface 1a (area surrounded by the broken line), and a dynamic friction force is generated as a resistance force at that time.

[0017] The rigidity of the area near the contact surface 1a is significantly different from that of the surrounding vulcanized rubber 2. Therefore, when the contact surface 1a is slid over the target surface 4, the hysteresis loss of the vulcanized rubber member 1 (the vulcanized rubber 2 in this area) becomes larger than when the rigid particles 3 are not present. As a result, heat generation is promoted around the contact surface 1a, and the kinetic friction force (kinetic friction coefficient μ D ) increases. This increase in dynamic friction caused by deformation in the area near the contact surface is called hysteresis friction, and is thought to occur mainly due to the collapse of aggregates such as silica compounded in the rubber. Recent research has revealed that in addition to the hysteresis loss caused by the collapse of aggregates mentioned above, the presence of rigid particles 3 in the rubber also increases the friction caused by deformation in the area near the contact surface.

[0018] The kinetic friction force (kinetic friction coefficient μ D The degree of increase in the parameter X can be determined by various experiments and analyses conducted by the inventors of the present application using the estimated parameter X in the following equation (1): Can It has been found that the present invention is characterized by the use of this estimation parameter X. Estimated parameters X=R 2 / (λ·E' 2 D 4 )···(1) In equation (1), R is the protrusion diameter (mm) of the target surface 4, λ is the wavelength (mm) of the target surface 4, E' is the storage modulus (MPa) of the vulcanized rubber member 1, and D is the outer diameter (μm) of the rigid particle 3.

[0019] The storage modulus E' of the vulcanized rubber member 1 can be measured using various known measuring devices (viscoelasticity measuring devices). The measurement conditions for the storage modulus E' may be set to an initial strain of 10%, an amplitude of ±2%, a temperature of 0°C, and a frequency of 20 Hz, in accordance with the provisions of JIS K6394. As long as the measurement conditions are consistently the same, the respective conditions are not limited to these and can be slightly different.

[0020] The outer diameter D of the rigid particles 3 is the average particle diameter of each rigid particle 3. The particle (aggregate) size Rss, which can be calculated by fitting the scattering profile obtained by ultra-small angle X-ray scattering measurement (USAXS) to the Unified-Guinier function of the following equation (2), is defined as the average particle diameter. For rigid particles 3 with an outer diameter D of more than 1 μm, the outer diameter D is measured using an optical microscope or the like.

[0021] I(q)=Aexp(-(q 2 Rgg 2 ) / 3)q -p +Bexp(-(q 2 Rgg 2 ) / 3)+Cexp(-(q 2 Rgg 2 ) / 3)×{erf(q·Rss / 6 1 / 2 )} 3Dm ·q -Dm +Dexp(-(q 2 Rgg 2 ) / 3)×E{erf(q·Rss / 6 1 / 2 )} 3(2d - Ds) ·q -(2d-Ds) ···(2) Here, q is the wavenumber, I(q) is the scattering intensity at wavenumber q, A, B, C, D, and E are constants (note that these constants D and E are different values ​​from the outer diameter D and elastic modulus E' mentioned above), p is the exponent, Rss is the size of the particles (aggregates) forming the hierarchical structure, Rgg is the size of the higher-order aggregates, Dm is the mass fractal dimension, Ds is the surface fractal dimension, and d is the Euclidean dimension of the space.

[0022] The rigid particles 3 may be scattered throughout the entire vulcanized rubber member 1, and as in this embodiment, it is desirable that they are scattered evenly at least in the region on the contact surface 1a side of the vulcanized rubber member 1. In this embodiment, the rigid particles 3 are not exposed at all from the contact surface 1a, but they may be exposed.

[0023] Data such as the protrusion diameter R, wavelength λ, and amplitude a of the target surface 4 can be measured using various known devices (surface roughness measuring instruments). While the target surface 4 is depicted in a simplified form in Figure 1, the actual target surface 4 has a more complex shape. Therefore, the protrusion diameter R of the target surface 4 is determined by fitting a quadratic curve to the convex portion of the profile of the surface roughness measurement data, determining the radius from the fitted quadratic curve, and using the average of these radii as a representative value. Furthermore, the wavelength λ is determined by Fourier analysis of the profile of the surface roughness measurement data, and the wavelength at which the amplitude a is maximum is used as a representative value.

[0024] Figure 3 shows the dynamic friction coefficient μ D The correlation CR between the estimated parameter X and the kinetic friction coefficient μ D This dynamic friction coefficient μ D The degree of increase in the coefficient of dynamic friction μ when the rigid particles 3 are present in the vulcanized rubber member 1 is compared to when the rigid particles 3 are not present. D In this embodiment, the dynamic friction coefficient μ D Therefore, in FIG. 3, when the rigid particles 3 are present in the vulcanized rubber member 1, the dynamic friction coefficient μ DThe larger the value, the higher the data is plotted, indicating that there is no difference between the two at the origin of the vertical axis. The vertical axis represents the coefficient of kinetic friction μ D In the present invention, the coefficient of dynamic friction μ D is measured in accordance with the test method specified in JIS K7125, but in order to eliminate the influence of adhesive friction, the value obtained by measuring with a lubricant interposed between the contact surface 1a and the target surface 4 is used.

[0025] figure 3 The coefficient of dynamic friction μ D According to the correlation CR between the estimated parameter X and the coefficient of dynamic friction μ D In other words, when the value of the estimated parameter X is approximately 1 or less, the dynamic friction coefficient μ D The increase in the coefficient of dynamic friction μ D When the value of the estimated parameter X is approximately greater than 1, the coefficient of dynamic friction μ D It can be seen that increases linearly.

[0026] When the estimated parameter X exceeds the boundary point (the value is approximately 1), it increases as the storage modulus E' decreases, the outer diameter D of the rigid particle 3 decreases, the protrusion diameter R increases, and the wavelength λ decreases, and the kinetic friction coefficient μ D The reason for this is that the smaller the storage modulus E', the more easily the vulcanized rubber 2 deforms, and therefore the more easily the rigid particles 3 penetrate into the irregularities of the target surface 4, and also the smaller the outer diameter D of the rigid particles 3, the larger the protrusion diameter R, and the shorter the wavelength λ, the more easily the rigid particles 3 penetrate into the irregularities of the target surface 4, and the greater the hysteresis loss of the vulcanized rubber member 1 (vulcanized rubber 2).

[0027] In the present invention, the dynamic friction coefficient μ of the vulcanized rubber member 1 with various specifications (the specifications of the vulcanized rubber 2 and the specifications of the rigid particles 3 are varied) against the target surface 4 with various specifications (the projection diameter R and the wavelength λ are varied) DThe data obtained by measuring the coefficient of dynamic friction μ of the vulcanized rubber member 1 shown in FIG. D The correlation CR between the estimated parameter X and the parameter X is determined in advance. This correlation CR data is input to and stored in a computing device such as a computer.

[0028] Then, by the procedure illustrated in FIG. 4, the dynamic friction characteristics (dynamic friction coefficient μ D The data required to estimate this dynamic friction characteristic are the storage modulus Eo of the vulcanized rubber member 1 to be estimated, the outer diameter Do of the rigid particles 3, the protrusion diameter Ro of the target surface 4 to be applied, the wavelength λo, and the correlation CR described above, which is known in advance.

[0029] Therefore, the storage modulus Eo and the outer diameter Do of the rigid particles 3 are determined using the vulcanized rubber member 1 to be estimated. These data are measured and determined using the method described above. In addition, the projection diameter Ro and wavelength λo are determined using the target surface 4 to be applied. These data are also measured and determined using the method described above.

[0030] Next, using the data on the storage modulus Eo, the outer diameter Do of the rigid particles 3, the protrusion diameter Ro, and the wavelength λo, and the data on the correlation CR previously determined, the dynamic friction characteristics (dynamic friction coefficient μ D ) is estimated. The data of the determined storage modulus Eo, outer diameter Do of the rigid particle 3, protrusion diameter Ro, and wavelength λo are input into a calculation device. The calculation device calculates the estimated parameter X based on the input data.

[0031] Next, as shown in FIG. 5, the calculation device substitutes the calculated value of the estimated parameter X into the data of the correlation CR stored in advance to calculate the dynamic friction coefficient μ D When grasping the data of the correlation CR, the dynamic friction coefficient μ of the vulcanized rubber member 1 with various specifications against the target surface 4 with various specifications is calculated. D The data obtained when measuring the coefficient of dynamic friction μ DTherefore, from these existing data, the dynamic friction coefficient μ D The standard data for the degree of increase (standard dynamic friction coefficient μ D ) and adding the calculated increase to this data, the dynamic friction characteristics (dynamic friction coefficient μ D ) can be estimated. D may be obtained by new measurement.

[0032] According to this embodiment, if the storage modulus Eo' of the vulcanized rubber member 1 to be estimated and the outer diameter Do of the internal rigid particles, as well as the protrusion diameter Ro and wavelength λo of the target surface 4 to be applied, are known, these data and the data of the correlation CR known in advance can be used to determine the dynamic friction characteristics (dynamic friction coefficient μ D Therefore, it is not necessary to perform a dynamic friction test every time the specifications of the vulcanized rubber member 1 to be estimated or the specifications of the target surface 4 to which it is applied change. As a result, the number of work steps is significantly reduced, and the dynamic friction characteristics can be easily grasped.

[0033] In other words, since the dynamic friction characteristics of a wider range of specifications of the vulcanized rubber member 1 can be grasped in a short period of time, the specifications of the vulcanized rubber member 1 having the desired dynamic friction characteristics can be selected more accurately and efficiently depending on the specifications of the target surface 4 to which it is applied.

[0034] The data for the storage modulus Eo, outer diameter Do, projection diameter Ro, and wavelength λo do not have to be actually measured, and may be virtual data. That is, the present invention can be used to determine the dynamic friction characteristics of the vulcanized rubber member 1 based on the set values ​​for the storage modulus Eo, outer diameter Do, projection diameter Ro, and wavelength λo.

[0035] Examples of the vulcanized rubber member 1 include tire components (tread rubber, etc.), brake pads, seals (packing), etc. Therefore, the present invention greatly contributes to the development of tires, brake pads, seals, etc. with excellent performance.

[0036] To estimate the dynamic friction characteristics of the vulcanized rubber member 1 with high accuracy, the storage modulus E' (Eo') of the vulcanized rubber member 1 should be set to, for example, 30 MPa or less. The outer diameter D (Do) of the rigid particles 3 should be set to, for example, 0.010 μm or more and 0.100 μm or less, and the number density (particles / cm) of the rigid particles 3 should be set to, for example, 0.010 μm or more and 0.100 μm or less. 3 ) is, for example, 10 14 Over 10 18 The projection diameter R (Ro) should be in the range of 0.1 mm or more, for example. The wavelength λ (λo) should be in the range of 3 mm or less, for example. [Explanation of symbols]

[0037] 1. Vulcanized rubber material 1a Contact surface 2. Vulcanized rubber 3 Rigid particles 4 Target Surface

Claims

1. A correlation between an increase in the coefficient of dynamic friction of a vulcanized rubber member containing a large number of rigid particles with respect to a target surface when the rigid particles are present compared to when the rigid particles are not present and an estimated parameter X calculated by the following formula (1) is grasped in advance, A method for estimating the dynamic friction characteristics of a vulcanized rubber member, characterized by estimating the increase in the dynamic friction coefficient when the rigid particles are present in the vulcanized rubber member to be estimated relative to when the rigid particles are not present in the vulcanized rubber member to be estimated for the target surface to be applied, based on the storage modulus Eo' of the vulcanized rubber member to be estimated and the outer diameter Do of the rigid particles present therein, the protrusion diameter Ro and wavelength λo of the target surface to be applied, and the estimation parameter X. Estimated parameters X = R 2 / (λ·E' 2 ・D 4 ) ... (1) Here, R is the diameter of the protrusions on the target surface, λ is the wavelength of the target surface, E′ is the storage modulus of the vulcanized rubber member, and D is the outer diameter of the rigid particle.

2. The method for estimating dynamic friction characteristics of a vulcanized rubber member according to claim 1 , wherein the rigid particles are scattered in a region of the contact surface of the vulcanized rubber member that contacts the target surface.

3. 3. The method for estimating dynamic friction characteristics of a vulcanized rubber member according to claim 1, wherein the storage modulus Eo' of the vulcanized rubber member 1 to be estimated is 30 MPa or less, and the outer diameter Do of the rigid particles is 0.010 μm to 0.100 μm.

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