JP7359669B2 - Friction evaluation method - Google Patents

Description

The present invention relates to a friction evaluation method.

It is known that the frictional force generated between a rubber member (for example, a tread portion of a pneumatic tire) and a friction surface (for example, a road surface) consists of an adhesive component and a hysteresis component. In recent years, there has been a demand to clarify the magnitude of the adhesion component and the hysteresis component of frictional force.

In order to meet this demand, as described in Patent Document 1, the coefficient of friction is measured when a rubber material is rubbed against a friction surface sprayed with surfactant-containing water (water containing a surfactant). A first step, a second step of measuring the coefficient of friction when a rubber material is rubbed against a friction surface sprayed with surfactant-free water (water that does not contain a surfactant), and a first step. A friction evaluation method has been proposed that includes a third step of calculating the difference between the friction coefficient measured in step 1 and the friction coefficient measured in step 2.

According to this method, the friction coefficient caused by hysteresis friction is measured in the first step, and the friction coefficient caused by sticky friction and hysteresis friction is measured in the second step, so the sticky friction component is calculated in the third step. It is said that it will be done.

Japanese Patent Application Publication No. 2016-200563

However, in reality, even if the friction surface is wetted with surfactant-containing water or the like, the adhesive component of the frictional force cannot be completely removed, and the magnitude of the hysteresis component cannot be determined. Furthermore, in recent years, there has been interest in the temperature dependence of the hysteresis component of frictional force, but this cannot be determined using the method of Patent Document 1.

Therefore, an object of the present invention is to provide a method that can clarify the temperature dependence of the hysteresis component of frictional force.

The friction evaluation method of the embodiment is a friction evaluation method that calculates an adhesion component and a hysteresis component in the friction force between a rubber or resin member and a friction surface, and reproduces the unevenness of an actual road surface as the friction surface. a step of creating a first simulated road surface made of resin, a step of creating a second simulated road surface by removing microscopic irregularities from the first simulated road surface, and adhesion between the member and the resin surface. A step of conducting a first test to examine the temperature dependence of force, and based on the results of the first test, a standard is determined as the temperature dependence coefficient of the adhesive component of the frictional force between the member and the resin surface. a step of determining each coefficient a _i at another one or more temperatures T _i with respect to the coefficient 1 at the temperature T _base ; and a step of at least adding oil and powder of a substance having a hexagonal crystal structure to the second simulated road surface. applying a second test to the lubricated surface and measuring the frictional force by sliding the member on the lubricated surface under a plurality of temperature conditions; and the lubricated surface, a step of determining each coefficient b _i at another one or more temperatures T _i with respect to coefficient 1 at the reference temperature T _base , and the member and the actual road surface at the reference temperature T _base , a friction force F2 at the reference temperature T _base between the member and the first simulated road surface, and a friction force F2 between the member and the second simulated road surface. a friction force F3 _base between the simulated road surface at the reference temperature T _base , and a respective friction force F3 _i between the member and the second simulated road surface at the one or more temperatures T _i ; F1=F1 _adh +F1 _his ...(Formula 1), F2=F2 _adh +F2 _his ...(Formula 2), F3 _base =F3 _adh +F3 _his ...(Formula 3), F3 _i = a _i ×F3 _adh + b _i ×F3 _his ... (Formula 4) (F1 _adh in formula 1 , F2 _adh in formula 2 , F3 _adh in formula 3, and a _i ×F3 _adh in formula 4 are each frictional force The _adhesion component in equation 1, F2 _his in equation 2 _, F3 _his in equation 3, and b _{i adh} and F3 _his ; assuming that F3 _adh = F2 _adh , and calculating F2-F3 _adh based on equation 2 to obtain F2 _his ; and assuming F2 _his = F1 _his , calculating F1 based on equation 1. - calculating F2 _his to obtain F1 _adh .
Further, the friction evaluation method of the embodiment is a friction evaluation method for determining an adhesion component and a hysteresis component in the friction force between a rubber or resin member and a friction surface, the unevenness of an actual road surface as the friction surface. a step of creating a first simulated road surface made of resin that reproduces the road surface; a step of conducting a first test to examine the temperature dependence of the adhesive force between the member and the resin surface; Based on the results, as the temperature dependent coefficient of the adhesion component of the frictional force between the member and the resin surface, the coefficient 1 at the reference temperature T base and the coefficient 1 at another one or more temperatures _T i are _determined . determining a coefficient a _i ; and applying at least one of oil and powder of a substance having a hexagonal crystal structure to the first simulated road surface to provide a lubricating surface, and lubricating the member under a plurality of temperature conditions. A step of performing a second test in which the frictional force is measured by sliding it on the surface, and based on the results of the second test, a standard is determined as the temperature dependent coefficient of the hysteresis component of the frictional force between the member and the lubricated surface. a step of determining each coefficient b _i at another one or more temperatures T _i with respect to coefficient 1 at the temperature T _base ; and a friction force F1 between the member and the actual road surface at the reference temperature T _base ; The frictional force F2 between the member and the first simulated road surface at the reference temperature T _base and the one or more temperatures T _i between the member and the first simulated road surface , respectively. The step of measuring the frictional force F2 _i , F1=F1 _adh +F1 _his ...(Formula 5), F2 _base =F2 _adh +F2 _his ...(Formula 6), F2 _i =a _i ×F2 _adh +b _i ×F2 _his ...(Equation 7) (F1 _adh in Equation 5 , F2 _adh in Equation 6 , a _i ×F2 _adh in Equation 7 is the adhesion component in each friction force, F1 _his in Equation 5 , F2 in Equation 6 _his , b _i ×F2 _his in Equation 7 is a hysteresis component in each friction force), and the process of calculating F2 _adh and F2 _his from Equation 6 and Equation 7, and considering F2 _his = F1 _his , and using Equation 5. The method is characterized in that it includes a step of calculating F1-F2 _his based on the method to obtain F1 _adh .

According to the above embodiment, it is possible to measure the frictional force from which the adhesive component has been removed by sliding the rubber member on the lubricated surface, and by measuring each at a plurality of different temperatures, the temperature dependence of the hysteresis component can be measured. can be revealed.

1 is a flowchart of a friction evaluation method according to an embodiment. A flowchart for confirming that an appropriate second simulated road surface has been created. A diagram showing an outline of an adhesive strength test. The figure which shows the example of the measurement result of an adhesion test. A diagram showing an outline of the second test. The figure which shows the example of the measurement result of the 2nd test. A diagram showing adhesion components and hysteresis components due to differences in road surfaces.

Embodiments will be described based on the drawings. Note that the embodiment described below is merely an example, and any modifications made as appropriate without departing from the spirit of the present invention are included within the scope of the present invention.

<Overall process>
This embodiment is an embodiment in which the magnitude of the adhesion component and the magnitude of the hysteresis component of the frictional force between the rubber member and the actual road surface is clarified.

As shown in FIG. 1, the friction evaluation method of the embodiment includes a first simulated road surface creation step (S1) of creating a first simulated road surface made of resin that reproduces the irregularities of an actual road surface, and a step of creating a first simulated road surface (S1) that reproduces the irregularities of an actual road surface. A second simulated road surface creation step (S2) of creating a second simulated road surface by removing microscopic irregularities from the first simulated road surface having Adhesion test (first test) step (S3) in which a test is conducted to investigate the temperature dependence of the adhesion component of the frictional force between the rubber member and the resin surface based on the results of the adhesion test (first test). A temperature-dependent coefficient a _i determining step (S4) for determining the coefficient a i, and measuring the frictional force by sliding a rubber member on the lubricated surface under a plurality of temperature conditions, using the second _simulated road surface as a lubricated surface. a second test step (S5) and a temperature dependent coefficient _{b i} determination step (S6 ), the frictional force of the rubber member against each of the actual road surface, the first simulated road surface, and the second simulated road surface is measured at a reference temperature, and the frictional force of the rubber member against the second simulated road surface is measured at a temperature other than the reference temperature. A frictional force measurement step (S7), and a calculation step (S8) for determining an adhesion component and a hysteresis component of the frictional force using each measured frictional force and the temperature dependent coefficients a _i and b _i . .

<First simulated road surface creation process>
In the first simulated road surface creation step, a first simulated road surface made of resin that reproduces the unevenness of an actual road surface made of asphalt or the like is created. As a specific example of the creation method, the unevenness of the actual road surface is molded using silicone rubber, a resin is poured into the silicone rubber mold, and the resin is hardened to form the first simulated road surface. Examples of the resins used include two-component mixture type resins, and more specific examples include two-component mixture type urethane resins.

Here, the reason why the first simulated road surface and the second simulated road surface (described later) are formed of resin is that the adhesive force between rubber and resin changes greatly depending on the temperature. This is because the adhesion component of the frictional force between the member and the resinous second simulated road surface changes greatly depending on the temperature. This temperature dependence is utilized in this embodiment as will be described later. That is, when the frictional force is measured while changing the temperature on the same resin surface, the frictional force changes depending on the temperature, and this change in the frictional force can be considered to be caused by the temperature change of the adhesive component. From this, the adhesion component and hysteresis component of the frictional force can be determined. Note that the temperature dependence of the adhesive force between rubber and an actual road surface made of asphalt or the like is small.

Preferably, the first simulated road surface reproduces the surface roughness of the actual road surface to an order of 1 μm when the surface roughness is measured with a contact type surface roughness meter. Further, the first simulated road surface needs to have such hardness that it does not undergo visually obvious deformation when the rubber member is pressed against it. Specifically, it is preferable that the durometer type D hardness of the first simulated road surface is 80 or more and 84 or less. Further, it is preferable that the elastic modulus of the resin forming the first simulated road surface is 10 times or more the elastic modulus of the rubber forming the rubber member. Further, the tensile strength of the resin forming the first simulated road surface measured by the method of JIS K 7113 is, for example, 55 MPa or more and 65 MPa or less.

<Second simulated road surface creation process>
In the second simulated road surface creation step, the surface of the first simulated road surface is polished to remove microscopic irregularities from the first simulated road surface, which had macroscopic and microscopic irregularities, and is used as a second simulated road surface. . A fine abrasive cloth is used for polishing.

Here, the actual road surface is formed by embedding aggregates such as pebbles in a base material such as asphalt. Macro unevenness refers to large unevenness based on the rough shape of the aggregate. Further, the term "microscopic irregularities" refers to small irregularities based on fine irregularities on the surface of a base material, fine irregularities on the surface of aggregate, or the like. It is known that microscopic irregularities have an effect on the hysteresis component of the frictional force, and by removing the microscopic irregularities from the first simulated road surface, the hysteresis component of the frictional force becomes smaller on the second simulated road surface.

<How to confirm that the second simulated road surface is appropriate>
It is confirmed by the method shown in FIG. 2 that an appropriate second simulated road surface has been created. First, as described above, microscopic irregularities are removed from the first simulated road surface to create a second simulated road surface (S2-1).

Next, the surface roughness of the first simulated road surface and the second simulated road surface are each measured using a surface roughness meter (S2-2). The measured surface roughness data is taken into a frequency analyzer and subjected to frequency analysis (S2-3).

Here, among waves obtained by frequency analysis of road surface roughness data, waves with a predetermined wavelength within the range of 0.1 mm or more and 1.0 mm or less are used as the reference, and waves with a wavelength larger than the reference wave wavelength are used as the reference. It is assumed that waves are caused by macroscopic unevenness, and waves with wavelengths smaller than the reference wave wavelength are caused by microscopic unevenness. Based on this idea, the frequency of a wave with a predetermined wavelength within the range of 0.1 mm or more and 1.0 mm or less among waves obtained by frequency analysis of road surface roughness data is set as the cutoff frequency. A filter that hardly attenuates frequency components lower than the cutoff frequency and attenuates frequency components higher than the cutoff frequency is set as a low-pass filter (S2-4). Further, a filter that hardly attenuates frequency components higher than the cutoff frequency and attenuates frequency components lower than the cutoff frequency is set as a high-pass filter (S2-4).

Next, a low-pass filter is applied to the frequency analysis result of the surface roughness of the first simulated road surface, and waves with large wavelengths are obtained. The waveform obtained by combining the waves acquired in this manner can be considered to reproduce the macroscopic unevenness of the first simulated road surface. Therefore, the surface roughness (for example, arithmetic mean roughness) is calculated from the waveforms created by the above-mentioned synthesis (S2-5). The calculation result can be regarded as surface roughness (macro surface roughness) based on the macro unevenness of the first simulated road surface. Similarly, a waveform is synthesized from the waves obtained by applying a low-pass filter to the frequency analysis result of the surface roughness of the second simulated road surface, and the surface roughness (for example, arithmetic mean roughness) is calculated from the synthesized waveform. is calculated (S2-5).

Next, the waveform surface roughness (i.e., macro surface roughness) consisting of waves obtained by applying a low-pass filter to the frequency analysis result of the surface roughness of the first simulated road surface, and the surface roughness of the second simulated road surface. The surface roughness of a waveform formed by applying a low-pass filter to the roughness frequency analysis result (that is, macroscopic surface roughness) is compared. If the difference between the two is 5% or less, that is, if the difference between the two is 5% or less of the value of either one (YES in S2-6), macroscopic unevenness is detected between the first simulated road surface and the second simulated road surface. is determined to have hardly changed, and it is determined that the macroscopic unevenness of the second simulated road surface is appropriate.

Next, a high-pass filter is applied to the frequency analysis result of the surface roughness of the second simulated road surface, and waves with small wavelengths are obtained. The waveform obtained by combining the waves acquired in this manner can be considered to reproduce the microscopic irregularities of the second simulated road surface. Therefore, the surface roughness (eg, arithmetic mean roughness) is calculated from the synthesized waveform (S2-7). The calculation result can be regarded as surface roughness (microscopic surface roughness) based on microscopic irregularities of the second simulated road surface. If this surface roughness (for example, arithmetic mean roughness) is 10 μm or less (YES in S2-8), it is determined that the second simulated road surface has microscopic irregularities removed, and the microscopic irregularities of the second simulated road surface are It is determined that the unevenness is appropriate.

If the macro unevenness or micro unevenness of the second simulated road surface is determined to be inappropriate (NO in S2-6, NO in S2-8), the second simulated road surface is created so that each unevenness is appropriate. It is fixed (S2-1).

The steps from S2-3 to S2-8 are executed by the frequency analyzer or a computer connected thereto. Note that the order of the steps from S2-5 to S2-6 and the steps from S2-7 to S2-8 may be reversed.

<Adhesive strength test process>
On the other hand, a test is conducted to examine the temperature dependence of the adhesive force between the rubber member and the resin adhesive force test surface. As shown in FIG. 3, in this test, the rubber member 1 is pressed against a resin adhesive test surface 2 with a predetermined load and then pulled apart, and the force (N) required to pull it apart is measured. Known equipment can be used for this measurement.

As the rubber member 1 in this test, the rubber member to be the final friction evaluation target is used. Moreover, the adhesive force test surface 2 is formed of the same resin as the resin that forms the first simulated road surface and the second simulated road surface. The reason for this is that if the resin is the same, the temperature dependence of the adhesion force (and the adhesion component of the frictional force) between the rubber member and the resin surface is the same. This is because the temperature dependence of the adhesive force in No. 2) can be used as the temperature dependence of the adhesive component of the frictional force on the second simulated road surface. The adhesion test surface 2 is preferably the second simulated road surface itself, but may also be the first simulated road surface, or even a resin road surface prepared separately from the first simulated road surface and the second simulated road surface. good.

As test temperatures for examining the temperature dependence of adhesive strength, it is necessary to select two or more temperatures, and more preferably three or more temperatures. Temperatures when three or more temperatures are selected include, for example, normal temperature (for example, 20 to 25 degrees Celsius) and low temperature (for example, 0° to 10°C) and high temperatures (for example, 35 to 40°C) where the adhesive component of the frictional force is expected to be about half of that at room temperature. The above measurements are then performed at each temperature. The measurement is performed in a state where the rubber member 1 and the adhesive force test surface 2 have reached the test temperature. In this embodiment, the test is performed at three points: room temperature, low temperature, and high temperature.

Since the adhesive force between the rubber member and the resin surface varies greatly depending on the temperature, measurement results that vary greatly depending on the temperature are obtained as the adhesive force test results. An example of the measurement results is shown in FIG. 4 as a bar graph.

<Temperature dependence coefficient a _i determination process>
Next, the temperature dependence coefficient a _i of the adhesive component of the frictional force between the rubber member and the resin surface is determined based on the adhesion test results.

Specifically, first, each coefficient a _i at another temperature T _i is calculated as a temperature dependent coefficient of the adhesive force between the rubber member and the adhesive force test surface, with respect to coefficient 1 at a certain reference temperature T _base .

As an example of how to obtain it, linear regression is performed using the least squares method etc. on the adhesive force data at each temperature, and the change in adhesive force with respect to temperature change is approximated (taking Figure 4 as an example, the bar graph A function (which approximates the vertices of the plurality of bars) is determined (an example of the function is shown as a straight line in FIG. 4). Then, based on the obtained function, the ratio of the adhesive force at another temperature T _i when the adhesive force at a certain reference temperature T _base is set to 1 is determined as the coefficient a _i at that temperature T _i . For example, the adhesive force at the standard temperature T _base which is room temperature is 26.0 N, the adhesive force at the low temperature T ₁ (i.e., i=1) is 48.4 N, and the adhesive force at the high temperature T ₂ (i.e., i=2). When the adhesive force is 8.8 N, the coefficient a ₁ at temperature T ₁ is 48.4/26.0 = 1.86, and the coefficient a ₂ at temperature T ₂ is 8.8/26.0 = 0.34. .

Here, as the reference temperature T _base and another temperature T _i , temperatures at the time of frictional force measurement, which will be described later, are selected. In this embodiment, it is assumed that the frictional force measurement described later is performed at the above-mentioned three points: normal temperature, low temperature, and high temperature, and normal temperature is selected as the reference temperature T _base , and low temperature T ₁ and high temperature T ₂ are selected as other temperatures T _i . shall be selected.

Here, the force referred to as adhesive force in this embodiment is the force required to separate the rubber member pressed against the resin road surface as described above, and is the concentration of frictional force when the rubber member slides against the road surface. The size is different from the clothing component. However, regarding temperature dependence, it can be considered that the adhesive force and the adhesive component are the same. Therefore, the temperature dependence coefficient a _i of the adhesion between the rubber member and the adhesion test surface determined as above is the adhesion component of the frictional force between the rubber member and the adhesion test surface. It is assumed that the temperature dependence coefficient a _i .

Further, the temperature dependence coefficient a _i of the adhesive force (or the adhesion component of the frictional force) on the adhesive force test surface can be used as is for all surfaces formed of the same resin as the adhesive force test surface. The resin forming the adhesion test surface and the resin forming the second simulated road surface are the same. Therefore, the temperature dependence coefficient a _i of the adhesion component of the friction force between the rubber member and the adhesion test surface is the temperature dependence coefficient a of the adhesion component of the friction force between the rubber member and the second simulated road surface. It can be considered to be the same as _i .

As described above, the temperature dependence coefficient a _i of the adhesion component of the frictional force between the rubber member and the resin surface (specifically, the adhesion test surface or the second simulated road surface) is determined.

By using the temperature dependent coefficient a _i , the adhesion component of the frictional force at each temperature is determined. That is, if the adhesion component of the frictional force at the reference temperature T _base is F3 _adh , the adhesion component of the frictional force at another temperature T _i is determined as a _i ×F3 _adh .

<Second test process>
In addition, a second test is conducted in which a lubricant is applied to the second simulated road surface to make it a lubricated surface, and the frictional force is measured by sliding the rubber member 1 on the lubricated surface under a plurality of temperature conditions.

First, a lubricant is applied to the second simulated road surface. As the lubricant applied to the second simulated road surface, oil or powder of a substance having a hexagonal crystal structure is used. By applying these lubricants to the second simulated road surface, adhesive components are removed from the frictional force between the rubber member 1 and the second simulated road surface, and the frictional force can be considered to consist only of hysteresis components. .

As the oil, vegetable oil, mineral oil, or silicone oil each having a viscosity of 10 cSt or more and 1000 cSt or less is suitable. When the oil is applied, an oil film is formed between the second simulated road surface and the rubber member 1, but if the viscosity of the oil is 10 cSt or more, the phenomenon in which the oil film is ruptured by the convex parts of the second simulated road surface is unlikely to occur; If it is 1000 cSt or less, the viscous resistance of the oil film will hardly affect the measurement of frictional force.

A particularly preferred oil is a vegetable oil having a viscosity of 50 cSt or more and 500 cSt or less. Examples of vegetable oils include salad oil and olive oil. Note that cSt stands for centistokes, and 1cSt=1mm ² /s. The viscosity is measured by the method of JIS Z8803.

In addition, examples of powder of a substance having a hexagonal crystal structure include graphite powder and molybdenum disulfide powder. These powders may be applied (sprayed) directly onto the second simulated road surface, or may be applied together with a solvent onto the second simulated road surface. In addition, in a substance having a hexagonal crystal structure, the bond between the layers of the crystal structure is weak, and slippage easily occurs between the layers when shear force is applied. Therefore, when powder of a substance having a hexagonal crystal structure is applied to the second simulated road surface, lubricity is generated on the second simulated road surface.

Next, a test is conducted in which the rubber member is slid on a lubricated surface and the frictional force is measured under a plurality of temperature conditions. As shown in FIG. 5, the rubber member 1 is arranged on the lubricating surface 3, and a load is applied to the rubber member 1 from above as shown by arrow A, and the rubber member 1 is moved along the lubricating surface 3 in the direction of arrow B. The rubber member 1 slides, and the frictional force at that time is measured. Known equipment can be used for this measurement. As the rubber member 1 in this test, the same rubber member 1 as that used in the adhesion test is used.

The test temperatures for the second test are room temperature, low temperature, and high temperature, which are the same as those for the adhesion test. The measurement is performed with the rubber member 1 and the lubricated surface 3 reaching the test temperature.

In the second test, the frictional force measured on the lubricated surface 3 can be considered to consist only of hysteresis components. The temperature dependence of the hysteresis component is not as great as the temperature dependence of the cohesive component, but there is some. An example of the measurement results in the second test is shown in FIG. 6 as a bar graph.

<Temperature dependence coefficient b _i determination process>
Next, the temperature dependence coefficient b _i of the hysteresis component of the frictional force between the rubber member 1 and the second simulated road surface is determined based on the results of the second test.

Here, what was obtained in the second test was the temperature dependence of the hysteresis component of the frictional force between the lubricated surface 3 and the rubber member 1, but this temperature dependence was The temperature dependence of the hysteresis component between the rubber member 1 and the rubber member 1 can be considered to be the same as the temperature dependence of the hysteresis component between the rubber member 1 and the second simulated road surface coated with water. Therefore, if the temperature dependence coefficient b _i of the hysteresis component of the frictional force between the rubber member 1 and the lubricated surface 3 is calculated, the temperature dependence coefficient _b It can be handled as the temperature dependence coefficient _bi of the hysteresis component between the rubber member 1 and the second simulated road surface coated with water, or as the temperature dependence coefficient b _i of the hysteresis component between the rubber member 1 and the second simulated road surface coated with water.

In this step, each coefficient b _i at another temperature T _i is determined as a temperature dependent coefficient of the hysteresis component of the frictional force between the rubber member 1 and the lubricated surface 3 with respect to coefficient 1 at a certain reference temperature T _base .

As an example of how to obtain it, linear regression is performed on the data of the second test for each temperature using the least squares method, etc., and a function that approximates the change in the hysteresis component with respect to temperature change is obtained (an example of this function is shown below). (shown as a straight line in Figure 6). Then, based on the obtained function, the ratio of the hysteresis component at another temperature T _i when the hysteresis component at a certain reference temperature T _base is set to 1 is determined as the coefficient b _i at that temperature T _i .

Here, as the reference temperature T _base and another temperature T _i , temperatures at the time of frictional force measurement, which will be described later, are selected. In this embodiment, it is assumed that the frictional force measurement described later is performed at the above-mentioned three points: normal temperature, low temperature, and high temperature, and normal temperature is selected as the reference temperature T _base , and low temperature T ₁ and high temperature T ₂ are selected as other temperatures T _i . shall be selected.

By using the temperature dependence coefficient b _i determined as described above, the hysteresis component at each temperature is determined. That is, if the hysteresis component of the frictional force at the reference temperature T _base is F3 _his , the adhesion component of the frictional force at another temperature T _i is determined as b _i ×F3 _his .

<Friction force measurement process>
Next, the friction force F1 between the rubber member and the actual road surface at the reference temperature T _base , the friction force F2 between the rubber member and the first simulated road surface at the reference temperature T _base , and the friction force F2 between the rubber member and the second simulated road surface are calculated. The frictional force F3 _base between the simulated road surface at the reference temperature _{T base} and the respective frictional force F3 i between the rubber member and the second simulated road surface at the temperature T _i (i is one or more than two) is measured. The measurement of the frictional forces F1, F2, F3 _base and F3 _i may be performed with no coating applied to all road surfaces (actual road surface, first simulated road surface, and second simulated road surface), or with no coating applied to all road surfaces (actual road surface, first simulated road surface, and second simulated road surface). The test may be performed with water applied to the road surface (actual road surface, first simulated road surface, and second simulated road surface).

Here, in this embodiment, the low temperature T ₁ and the high temperature T ₂ are selected as the temperature T _i as described above. Therefore, in this embodiment, the frictional force between the rubber member and the second simulated road surface is the frictional force _F3base at the reference temperature _Tbase , the frictional force F31 at the low temperature _T1 , and the frictional force _F31 at the high temperature _T2 . Frictional force _F32 is measured.

A known friction force measuring device can be used for the measurement. The measurement is performed when the rubber member and each road surface have reached their respective temperatures.

It is assumed that the measured frictional force consists of an adhesive component and a hysteresis component. That is,
F1=F1 _adh +F1 _his ...(Formula 1)
F2=F2 _adh +F2 _his ...(Formula 2)
F3 _base =F3 _adh +F3 _his ...(Formula 3)
F3 _i =a _i ×F3 _adh +b _i ×F3 _his ... (Formula 4)
(F1 _adh in Equation 1, F2 _adh in Equation 2, F3 _adh in Equation 3, and a _i ×F3 _adh in Equation 4 are the adhesion components in each friction force, F1 _his in Equation 1, F2 _his in Equation 2, Equation 3 F3 _his in and b _i ×F3 _his in equation 4 are hysteresis components in each friction force)
It is assumed that the following holds true.

As shown here, since the temperature at which the frictional force is measured is different between Equation 3 and Equation 4, the magnitudes of the adhesion component and the hysteresis component of the frictional force are different. Specifically, the adhesion component of the frictional force at the reference temperature T _base is F3 _adh (see equation 3), and the adhesion component of the frictional force at another temperature T _i is a _i ×F3 _adh (formula 4). a _i is a coefficient determined in the temperature dependent coefficient a _i determination step described above. Furthermore, the hysteresis component of the frictional force at the reference temperature T _base is F3 _his (see equation 3), and the hysteresis component of the frictional force at another temperature T _i is b _i ×F3 _his (see equation 4). . b _i is a coefficient determined in the temperature dependent coefficient b _i determination step described above.

As described above, in this embodiment, the frictional force between the rubber member and the second simulated road surface is measured at low temperature T ₁ and high temperature T ₂ in addition to the reference temperature T _base , so Equation 4 is expressed as F3 ₁ = a ₁ ×F3 _adh +b ₁ ×F3 _his ... (Formula 4-1)
F3 ₂ = a ₂ × F3 _adh + b ₂ × F3 _his ... (Formula 4-2)
It consists of two equations.

<Calculation process>
Based on the above equations 1 to 4, the adhesion component F1 _adh and the hysteresis component F1 _his of the frictional force between the rubber member and the actual road surface are calculated. This calculation is performed, for example, by a computer. The following assumptions are made for the calculation.

As shown in Table 1, the actual road surface and the first simulated road surface are made of different materials and have the same surface roughness. Since the first simulated road surface is made of resin while the actual road surface is made of asphalt, etc., if the adhesive component of the frictional force on the actual road surface is the reference value, the adhesive component of the frictional force on the first simulated road surface is the reference value. bigger. On the other hand, since it can be said that the actual road surface and the first simulated road surface have the same unevenness, it can be assumed that the hysteresis component of the frictional force is the same.

Further, as shown in Table 1, the first simulated road surface and the second simulated road surface are made of the same material but have different surface roughnesses. Since the first simulated road surface and the second simulated road surface are made of the same resin, it can be assumed that the adhesion component of the frictional force on these road surfaces is the same. On the other hand, the surface roughness of the first simulated road surface includes micro-roughness, whereas the surface roughness of the second simulated road surface does not include micro-roughness, so the frictional force on the second simulated road surface It can be assumed that the hysteresis component of is smaller than the hysteresis component of the frictional force on the actual road surface or the first simulated road surface.

The above assumption is illustrated in FIG. 7. In the bar graph of FIG. 7, the lattice-shaped portion represents the adhesion component, and the dot-shaped portion represents the hysteresis component. From the above, in Equations 1 to 4, it can be assumed that F3 _adh = F2 _adh and F2 _his = F1 _his . Utilizing this fact, the adhesion component F1 _adh and the hysteresis component F1 _his of the frictional force between the rubber member and the actual road surface can be determined.

First, F3 _adh and F3 _his are found from equations 3 and 4. As an example of a specific method for finding F3 _adh and F3 _his , all combinations of the two equations are extracted from equation 3 and a plurality of equations 4 that hold for each temperature, and a provisional method is extracted from each combination. F3 _adh and provisional F3 _his are calculated, and the median value of the plurality of provisional F3 _adhs found and the value of F3 _his when F3 _adh is the median value are the final F3 _adh and F3 _his .

As a specific example, in this embodiment, equations 3, 4-1, and 4-2 exist as equations for the frictional force on the second simulated road surface. From these three equations, there are three combinations of two equations. That is,
F3 _base =F3 _adh +F3 _his ...(Formula 3) and F3 ₁ =a ₁ ×F3 _adh +b ₁ ×F3 _his ...(Formula 4-1)
the first combination of;
F3 ₁ =a ₁ ×F3 _adh +b ₁ ×F3 _his ... (Formula 4-1) and F3 ₂ =a ₂ ×F3 _adh +b ₂ ×F3 _his ... (Formula 4-2)
and F3 _base = F3 _adh + F3 _his ... (Formula 3) and F3 ₂ = a ₂ × F3 _adh + b ₂ × F3 _his ... (Formula 4-2)
This is the third combination of

Since F3 _base , F3 ₁ and F3 ₂ have been clarified by measurement, and a ₁ , a ₂ , b ₁ and b ₂ have been determined, the first combination of simultaneous equations is solved and the provisional F3 _adh and provisional F3 _his can be determined. Similarly, provisional F3 _adh and provisional F3 _his are found from the second combination of simultaneous equations, and provisional F3 _adh and provisional F3 _his are also found from the third combination of simultaneous equations.

Ideally, the provisional F3 _adh and provisional F3 _his have the same value no matter which simultaneous equations among the first to third combinations are solved. However, in reality, the provisional F3 _adh and provisional F3 _his determined for each simultaneous equation differ due to measurement errors in the frictional force and the like.

Therefore, the median value of the three provisional F3 _adhs determined is determined as the final (in other words, official) F3 _adh . Then, F3 _his when F3 _adh is at that value (that is, the above median value) is calculated from Formula 3 (or Formula 4-1 or Formula 4-2), and is determined as the final F3 _his .

Next, since F3 _adh = F2 _adh can be considered as described above, F2 _his can be obtained by entering the value of F3 _adh as F2 _adh in equation 2 and calculating F2-F3 _adh .

Next, since F2 _his = F1 _his can be considered as described above, F1 _adh can be obtained by entering the value of F2 _his as F1 _his in Equation 1 and calculating F1 - F2 _his .

As described above, the adhesion component F1 _adh and the hysteresis component F1 _his of the frictional force between the rubber member and the actual road surface are determined.

As described above, according to the method of this embodiment, the adhesion component F1 _adh and the hysteresis component F1 _his of the frictional force between the rubber member and the actual road surface can be clarified.

<Change example 1>
An example of the change will be explained. In this modified example, the temperature dependent coefficient a _i of the adhesion component of the frictional force between the rubber member _and the resin surface is a coefficient a 1 at another temperature T 1 for a coefficient ₁ at a certain reference temperature T _base . is required. Furthermore, as the temperature-dependent coefficient b _i of the hysteresis component of the frictional force between the rubber member and the second simulated road surface, a coefficient b ₁ at another temperature T ₁ is determined with respect to coefficient 1 at a certain reference temperature T _base . Further, as the friction force between the rubber member and the second simulated road surface, a friction force F3 _base at a reference temperature T _base and a friction force F3 ₁ at another low temperature T ₁ are measured.

Therefore,
F3 _base =F3 _adh +F3 _his ...(Formula 3)
F3 ₁ =a ₁ ×F3 _adh +b ₁ ×F3 _his ... (Formula 4)
Two formulas are possible. Since F3 _base and F3 ₁ have been measured and the coefficients a ₁ and b ₁ have been determined, F3 _adh and F3 _his can be determined by solving these two simultaneous equations. Once F3 _adh and F3 _his are determined, the adhesion component F1 _adh and the hysteresis component of the frictional force between the rubber member and the actual road surface are calculated based on Equations 1 and 2 in the same way as the calculation process of the above embodiment. Find F1 _his .

If the measurement error of the frictional force is small, F3 _adh and F3 _his can be determined with sufficient accuracy just by solving the simultaneous equations of the above two equations, and F1 _adh and F1 _his can be clarified.

<Change example 2>
Another modification example will be explained. In this modification example, the friction force between the rubber member and the second simulated road surface is a friction force F3 _base at the reference temperature T _base and another temperature T _i (i=1, 2, 3, ), the respective frictional forces F3 _i (i=1, 2, 3...) are measured. Also, at each temperature, the temperature dependence coefficient a _i (i=1, 2, 3...) of the adhesive component of the frictional force between the rubber member and the resin surface, and the rubber member and the second simulated road surface. The temperature dependent coefficient b _i (i=1, 2, 3...) of the hysteresis component of the frictional force between the two is determined.

Therefore,
F3 _base =F3 _adh +F3 _his ...(Formula 3)
F3 _i =a _i ×F3 _adh +b _i ×F3 _his (i=1, 2, 3...) (Formula 4)
Four or more expressions can be created. All combinations of two formulas are extracted from these formulas, and provisional F3 _adh and provisional F3 _his are determined from each combination. Then, the median value of the plurality of provisional F3 _adhs found and the value of F3 _his when F3 _adh is the median value are set as the final F3 _adh and F3 _his .

<Change example 3>
Even without using the second simulated road surface of the above embodiment, it is possible to clarify the adhesion component and hysteresis component of the frictional force between the rubber member and the actual road surface.

Specifically, first, the same first simulated road surface creation step (S1), adhesion test step (S3), and temperature dependence coefficient a _i determination step (S4) as in the above embodiment are performed.

Next, a second test was conducted in which the frictional force was measured by sliding a rubber member under a plurality of temperature conditions on a lubricated surface coated with oil or powder of a substance having a hexagonal crystal structure. The test is performed on the first simulated road surface rather than on the second simulated road surface. That is, the frictional force is measured using the first simulated road surface as a lubricated surface. Based on the results of this second test, the temperature dependence coefficient b _i of the hysteresis component of the frictional force between the rubber member and the lubricated surface (first simulated road surface) is set to another 1 with respect to the coefficient 1 at the reference temperature T _base . Alternatively, each coefficient b _i at two or more temperatures T _i is determined.

Next, a frictional force measurement step is performed, and in this modified example, the frictional force F1 at the reference temperature T _base between the rubber member and the actual road surface and the reference temperature T between the rubber member and the first simulated road surface The friction force F2 at _{the base} and the friction force _{F2 i} at each temperature T _i (i is one or more) between the rubber member and the first simulated road surface are measured. Here, it is assumed that a low temperature T ₁ and a high temperature T ₂ are selected as the temperature T _i .

It can be assumed that the following equation holds true for the measured frictional force.

F1=F1 _adh +F1 _his ...(Formula 5)
F2 _base =F2 _adh +F2 _his ...(Formula 6)
F2 _i =a _i ×F2 _adh +b _i ×F2 _his ... (Formula 7)
(F1 _adh in Equation 5, F2 adh in Equation 6, a _i ×F2 _adh in Equation 7 is the adhesion component in each friction force, F1 _his in Equation 5, F2 _his in Equation 6 _, b _i ×F2 _his in Equation 7 is the hysteresis component of each friction force)
Next, a calculation step is performed in which the adhesion and hysteresis components of the frictional force are determined using the respective measured frictional forces and the temperature-dependent coefficients a _i , b _i . Specifically, first, F2 _adh and F2 _his are found from equations 6 and 7. The specific method is the same as the method of determining F3 _adh and F3 _his from equations 3 and 4 in the above embodiment.

Next, since F2 _his = F1 _his can be considered as described above, F1 _adh can be obtained by entering the value of F2 _his as F1 _his in equation 5 and calculating F1 - F2 _his .

As described above, the adhesion component F1 _adh and the hysteresis component F1 _his of the frictional force between the rubber member and the actual road surface are determined.

<Change example 4>
The above embodiment is an embodiment in which the magnitude of the adhesion component and hysteresis component of the frictional force between the rubber member and the actual road surface is clarified, and in the embodiment, the temperature dependence of the hysteresis component was determined. , apart from such an embodiment, only the temperature dependence of the hysteresis component may be determined independently.

If you measure the frictional force by sliding a rubber member on a lubricated surface coated with oil or a lubricated surface coated with powder of a substance with a hexagonal crystal structure, the measured frictional force will only contain the hysteresis component. It can be considered to consist of If such measurements are performed under a plurality of different temperature conditions, the temperature dependence of the measured frictional force can be considered to be equal to the temperature dependence of the hysteresis component.

This method of determining the temperature dependence of the hysteresis component can be used in various embodiments other than the above embodiments.

<Change example 5>
In the above embodiment, the friction force between the rubber member and the actual road surface was investigated, but it is also possible to investigate the friction force between not only the rubber member but also the resin member and the actual road surface in the same manner as in the above embodiment. I can do it.

<Change example 6>
In the above embodiment, oil or powder of a substance having a hexagonal crystal structure is applied as a lubricant to the second simulated road surface, but both oil and powder of a substance having a hexagonal crystal structure are used as a lubricant. may be applied to the second simulated road surface.

1...Rubber member, 2...Adhesion test surface, 3...Lubricating surface

Claims (4)

In a friction evaluation method for determining an adhesive component and a hysteresis component in the frictional force between a rubber or resin member and a friction surface,
creating a first simulated road surface made of resin that reproduces the unevenness of an actual road surface as the friction surface;
creating a second simulated road surface by removing microscopic irregularities from the first simulated road surface;
conducting a first test to examine the temperature dependence of the adhesive force between the member and the resin surface;
Based on the results of the first test, as the temperature dependent coefficient of the adhesion component of the frictional force between the member and the resin surface, one or more temperatures other than the coefficient 1 at the reference temperature T _base are determined. determining each coefficient a _i in T _i ;
The second simulated road surface is coated with at least one of oil and powder of a substance having a hexagonal crystal structure to provide a lubricated surface, and the member is slid on the lubricated surface under a plurality of temperature conditions to generate friction. a step of conducting a second test to measure the
Based on the results of the second test, as the temperature dependent coefficient of the hysteresis component of the frictional force between the member and the lubricated surface, a coefficient of 1 at the reference temperature T _base is determined at one or more other temperatures T _i , respectively. a step of determining the coefficient b _i of
a frictional force F1 between the member and the actual road surface at the reference temperature T _base ;
a frictional force F2 between the member and the first simulated road surface at the reference temperature T _base ;
a frictional force F3 _base between the member and the second simulated road surface at the reference temperature T _base ;
a step of measuring each frictional force F3 _i at the one or more temperatures T _i between the member and the second simulated road surface;
F1=F1 _adh +F1 _his ...(Formula 1)
F2=F2 _adh +F2 _his ...(Formula 2)
F3 _base =F3 _adh +F3 _his ...(Formula 3)
F3 _i =a _i ×F3 _adh +b _i ×F3 _his ... (Formula 4)
(F1 _adh in Equation 1, F2 _adh in Equation 2, F3 _adh in Equation 3, and a _i ×F3 _adh in Equation 4 are the adhesion components in each friction force, F1 _his in Equation 1, F2 _his in Equation 2, Equation 3 F3 _his in and b _i ×F3 _his in equation 4 are hysteresis components in each friction force)
and calculating F3 _adh and F3 _his from equations 3 and 4;
A step of determining F2 his by considering F3 _adh = F2 _adh and calculating F2- _{F3 adh} based on equation 2;
a step of determining F1 _adh by assuming that F2 _his = F1 _his and calculating F1 - F2 _his based on equation 1;
A friction evaluation method characterized by comprising: In a friction evaluation method for determining an adhesive component and a hysteresis component in the frictional force between a rubber or resin member and a friction surface,
creating a first simulated road surface made of resin that reproduces the unevenness of an actual road surface as the friction surface;
conducting a first test to examine the temperature dependence of the adhesive force between the member and the resin surface;
Based on the results of the first test, as the temperature dependent coefficient of the adhesion component of the frictional force between the member and the resin surface, one or more temperatures other than the coefficient 1 at the reference temperature T _base are determined. determining each coefficient a _i in T _i ;
The first simulated road surface is coated with at least one of oil and powder of a substance having a hexagonal crystal structure to provide a lubricated surface, and the member is slid on the lubricated surface under a plurality of temperature conditions to generate friction. a step of conducting a second test to measure the
Based on the results of the second test, as the temperature dependent coefficient of the hysteresis component of the frictional force between the member and the lubricated surface, a coefficient of 1 at the reference temperature T _base is determined at one or more other temperatures T _i , respectively. a step of determining the coefficient b _i of
a frictional force F1 between the member and the actual road surface at the reference temperature T _base ;
a frictional force F2 between the member and the first simulated road surface at the reference temperature T _base ;
a step of measuring each frictional force F2 _i at the one or more temperatures T _i between the member and the first simulated road surface;
F1=F1 _adh +F1 _his ...(Formula 5)
F2 _base =F2 _adh +F2 _his ...(Formula 6)
F2 _i =a _i ×F2 _adh +b _i ×F2 _his ... (Formula 7)
(F1 _adh in Equation 5, F2 adh in Equation 6, a _i ×F2 _adh in Equation 7 is the adhesion component in each friction force, F1 _his in Equation 5, F2 _his in Equation 6 _, b _i ×F2 _his in Equation 7 is the hysteresis component of each friction force)
and calculating F2 _adh and F2 _his from equations 6 and 7;
A step of determining F1 _adh by assuming that F2 _his = F1 _his and calculating F1 - F2 _his based on equation 5;
A friction evaluation method characterized by comprising: The friction evaluation method according to claim 1 or 2 , wherein the lubricated surface is a lubricated surface coated with vegetable oil having a viscosity of 50 to 500 cst. The friction evaluation method according to claim 1 or 2 , wherein the lubricated surface is a lubricated surface coated with graphite powder or molybdenum disulfide powder.

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