Friction testing apparatus and friction testing method

Abstract

The present invention provides a friction testing apparatus and friction testing method that suppress increases in testing costs and enable accurate measurement of the coefficient of friction of a test rubber body on an icy road surface. [Solution] The friction testing apparatus comprises an ice road surface that contacts a test rubber body, a friction coefficient measuring unit that measures the friction coefficient of the test rubber body when the test rubber body is moved relative to the ice road surface, a temperature measuring unit that measures the temperature of the ice road surface, a regression line calculation unit that calculates a regression line from the measured friction coefficient and the corresponding road surface temperature data set, and a friction coefficient calculation unit that calculates the friction coefficient at a specific temperature from the regression line.

Description

Technical Field

[0001] The present disclosure relates to a friction testing apparatus and a friction testing method.

Background Art

[0002] Conventionally, the friction coefficient of rubber products such as automobile tires on an ice road surface has been measured by an ice friction test using a test rubber body made of the same material as the rubber product. However, in the ice friction test, since the surface temperature of the ice road surface changes due to the frictional heat between the test rubber body and the ice road surface, when measuring the friction coefficient multiple times, it takes time to adjust the surface temperature of the ice road surface.

[0003] Patent Document 1 discloses a friction testing apparatus including a measuring device to which a test rubber body is attached, an ice disk that has an ice road surface contacting the surface of the test rubber body and relatively moves with respect to the test rubber body, and a temperature adjusting device having a Peltier element attached to an ice disk frame that houses the ice of the ice disk. By using this friction testing apparatus, even when the surface temperature of the ice road surface changes due to cooling by the Peltier element, the surface temperature is controlled to a specific temperature, so that adjustment of the surface temperature of the ice road surface becomes easy.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, there is a problem that the test cost increases by preparing a friction testing apparatus having a Peltier element as in Patent Document 1 or controlling the Peltier element. Therefore, a friction testing apparatus and a friction testing method that can suppress an increase in the test cost and accurately measure the friction coefficient of a test rubber body on an ice road surface are desired.

[0006] The purpose of this disclosure is to provide a friction testing apparatus and friction testing method that can suppress increases in testing costs and accurately measure the coefficient of friction of a test rubber body on an icy road surface. [Means for solving the problem]

[0007] The friction testing apparatus of this disclosure comprises an ice road surface that contacts a test rubber body, a friction coefficient measuring unit that measures the measured friction coefficient of the test rubber body when the test rubber body is moved relative to the ice road surface, a temperature measuring unit that measures the road surface temperature of the ice road surface, a regression line calculation unit that calculates a regression line from a data set of the measured friction coefficient and the corresponding road surface temperature, and a friction coefficient calculation unit that calculates the friction coefficient at a specific temperature from the regression line.

[0008] The friction test method of this disclosure includes a friction coefficient measurement step of measuring the measured friction coefficient of a test rubber body by moving it relative to an icy road surface; a temperature measurement step of measuring the road surface temperature of an icy road surface; a regression line calculation step of calculating a regression line from a data set of the measured friction coefficient and the corresponding road surface temperature; and a friction coefficient calculation step of calculating the friction coefficient at a specific temperature from the regression line. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing an example of a friction testing apparatus. [Figure 2] (a) Plan view and (b) Sectional view of the frame member with an ice surface [Figure 3] (a) A diagram showing the path of the test rubber body and (b) the change in travel speed. [Figure 4] Graph illustrating the relationship between the first and second data sets and the regression line. [Figure 5] A flowchart illustrating an example of a friction test method.

[0010] <Friction testing equipment> First, an example of the friction testing apparatus 100 will be explained with reference to Figures 1 to 4. Note that the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, nor do the dimensional ratios between the drawings necessarily match. Figure 1 is a schematic diagram showing an example of the friction testing apparatus 100. Figure 2 shows (a) a plan view and (b) a cross-sectional view along line AA of the frame member on which the ice surface is provided.

[0011] As shown in Figure 1, the friction testing apparatus 100 is configured to be able to travel while pressing a test rubber body R against an icy road surface 1, and is used to evaluate the friction characteristics of rubber products on ice. This friction testing apparatus 100 is housed in a constant temperature chamber 20, such as a refrigerator, indicated by a dashed line, and can be used to conduct tests in a desired temperature environment, for example, at a set temperature selected from the range of -6 to 0°C.

[0012] The test rubber body R may be the rubber product itself, or it may be a piece cut from the rubber product. Alternatively, the test rubber body R may be a test rubber piece made from the same rubber material as the rubber product. Examples of rubber products include tires (pneumatic tires or studless tires) and shoe soles.

[0013] The test rubber body R is made, for example, from vulcanized rubber and has a flat surface that is pressed against the icy road surface 1. In the example shown in Figure 1, the test rubber body R is formed in a cylindrical shape, and its upper surface is bonded to the holder 4, which will be described later. Therefore, the lower surface of the test rubber body R that faces the icy road surface 1 becomes the flat surface that is pressed against the icy road surface 1. The test rubber body R may be formed in a rectangular parallelepiped shape or a hemispherical shape with a flat surface. The flat surface may have grooves or the like, similar to those found on rubber products.

[0014] The friction testing apparatus 100 includes an ice surface 1 for measuring (calculating) the coefficient of friction of a test rubber body R. The ice surface 1 is elongated in the X direction, which is the direction in which the test rubber body R travels. On the ice surface 1, the part on which the test rubber body R travels (comes into contact) is called a lane. As shown in Figure 2, the ice surface 1 is made by fixing an ice plate to a metal frame member 21. The frame member 21 is configured to be detachably attached to the table 22 (see Figure 1). The frame member 21 includes a road surface portion 21a on which the ice plate is placed, and an outer peripheral portion 21b surrounding the road surface portion 21a. The frame member 21 with the ice plate placed on the surface of the road surface portion 21a presents as a plate-like object with a uniform thickness overall.

[0015] The ice road surface 1 is created as follows. First, water is supplied to the frame member 21 and frozen to make ice. To form the ice as uniformly as possible, it is preferable to repeat the process of spreading a thin layer of water and freezing it several times (for example, four times). After ice is made, the surface is flattened with the ice polishing plate 18 (see Figure 1), which will be described later, to create the ice road surface 1.

[0016] As shown in Figure 1, the friction testing apparatus 100 comprises a holder 4 for holding a test rubber body R and a load device 5 for pressing the test rubber body R against the ice road surface 1. The holder 4 is connected to the load device 5. The load device 5 is configured to reciprocate the holder 4 along the Z direction (up and down direction in Figure 1) perpendicular to the ice road surface 1. By appropriately setting the position of the holder 4 (the distance between the holder 4 and the ice road surface 1), the load in the Z direction applied to the test rubber body R can be adjusted, and consequently, the test rubber body R can be pressed against the ice road surface 1 under predetermined pressure conditions. The load device 5 is configured with a servo motor, but other actuator mechanisms may also be used.

[0017] The friction test device 100 includes a drive device 6 that relatively moves the test rubber body R with respect to the ice road surface 1. The drive device 6 is configured to be reciprocally movable along the X direction (the left - right direction in FIG. 1) of a table 9 that supports the load device 5. By the movement of this table 9, the holder 4 moves, and it is possible to run while sliding the test rubber body R on the ice road surface 1. The actuator 10 is configured to be reciprocally movable along the Y direction (the direction perpendicular to the plane of FIG. 1) that is perpendicular to both the X direction and the Z direction, and is used for aligning the positions of the test rubber body R and the ice road surface 1 in the Y direction and for lane change. In the present embodiment, the drive device 6 and the actuator 10 are each constituted by a servo - motor, but it is not limited to this.

[0018] In the present embodiment, as shown in FIG. 3(a), the test rubber body R travels on the ice road surface 1 from the starting point SP to the ending point GP. The travel distance of the test rubber body R is, for example, 300 mm. The travel speed of the test rubber body R changes, for example, as shown in FIG. 3(b). When repeating the travel operation, the test rubber body R that has finished traveling is lifted from the ice road surface 1, moved above the starting point SP, and pressed against the ice road surface 1 again and arranged at the starting point SP. The operation related to the travel of the test rubber body R is controlled by a control device 8 described later.

[0019] As shown in FIG. 1, the friction test device 100 includes a control device 8 that controls the operations necessary for the test. The control device 8 includes an arithmetic unit 81 that performs various calculations, an operation control unit 82 that controls the operations of the load device 5, the drive device 6, etc., an input unit 83 that receives inputs from the test operator, and a display unit 84 that displays various information regarding the operation and setting of the friction test device 100 on the screen.

[0020] The friction test device 100 includes a road surface adjustment device for adjusting the smoothness of the ice road surface 1. The road surface adjustment device in this embodiment includes an ice grinding plate 18 as a grinding tool for grinding the ice road surface 1. When operating, the ice grinding plate 18 moves to the height of the ice road surface 1, and from this state, the driving device 6 moves the table 9, causing the ice grinding plate 18 to slide on the ice road surface 1. A heating wire is embedded in the ice grinding plate 18, enabling it to grind while slightly melting the surface of the ice road surface 1.

[0021] The friction test device 100 includes a friction coefficient measurement unit 7 that measures the friction coefficient (also referred to as the measured friction coefficient) of the test rubber body R when the test rubber body R is relatively moved with respect to the ice road surface 1. The friction coefficient measurement unit 7 includes a load sensor 71 that measures the load acting on the test rubber body R, and measures the measured friction coefficient from the load measured by the load sensor 71.

[0022] The load sensor 71 can measure a total of three components of load, namely the vertical component and two horizontal components, and can measure the load in the Z direction (vertical force), the load in the X direction (front-back force), and the load in the Y direction (lateral force) acting on the test rubber body R. The load sensor 71 is constituted by, for example, a load cell. In this embodiment, the load sensor 71 is attached to the upper side of the holder 4 (opposite side to the test rubber body R).

[0023] The friction test device 100 runs while pressing the test rubber body R against the ice road surface 1. At this time, the load device 5 is controlled to press the test rubber body R with the set input load, and the driving device 6 is controlled to run the test rubber body R at the set running speed. Then, the output load acting on the test rubber body R during running is measured by the load sensor 71, and the measured friction coefficient of the test rubber body R is measured. The calculation unit 81 performs calculations for load adjustment based on the measurement result of the output load as needed. Various test conditions such as the input load, running speed, number of repetitions, etc. are input and set into the control device 8 via the input unit 83.

[0024] The friction testing apparatus 100 includes a temperature measuring unit 13 for measuring the road surface temperature of the ice road surface 1. The temperature measuring unit 13 measures the road surface temperature of the ice road surface 1 in real time. The temperature measuring unit 13 includes one or more (for example, two) temperature sensors 131. Figure 1 shows an example with two temperature sensors 131. The temperature sensors 131 may be non-contact temperature sensors (for example, infrared radiation thermometers) or contact temperature sensors.

[0025] The temperature measurement unit 13 (temperature sensor 131) preferably measures the surface temperature of the upper surface of the ice road surface 1 (the contact surface with the test rubber body R). However, the temperature measurement unit 13 (temperature sensor 131) is not limited to the above, and for example, it may measure the internal temperature of the ice road surface 1.

[0026] The friction testing apparatus 100 includes a regression line calculation unit 11 that calculates a regression line from a data set of measured friction coefficients measured by the friction coefficient measurement unit 7 and corresponding road surface temperatures measured by the temperature measurement unit 13. The regression line is a regression line or regression curve, and is calculated (fitted) by, for example, the least squares method. The regression line is represented by an n-th degree function such as a linear function, quadratic function, or cubic function. The regression line calculation unit 11 may also calculate the regression line by the Gauss-Newton method.

[0027] When the regression line is a linear function, the coefficient of friction μ is expressed by the following equation (Equation 1). In equation (Equation 1), μ is the coefficient of friction, T is the road surface temperature of the ice surface 1, A is the regression coefficient (slope), and B is the intercept. μ(T)=A×T+B (Formula 1)

[0028] The regression line calculation unit 11 preferably calculates a regression line from a data set containing 10 or more measured friction coefficients. This reduces the influence of outliers and improves regression accuracy. Alternatively, the regression line calculation unit 11 may calculate a regression line from a data set containing 30 or fewer measured friction coefficients. This suppresses increases in testing costs and prevents overfitting.

[0029] This section describes an example of measurement when 30 friction coefficients are measured (30 measurements). First, the friction coefficient is measured in sets of 5, and 3 sets are performed. Then, after changing the surface temperature of the ice surface 1, the friction coefficient is measured again in 3 sets. In each set, the friction coefficient is measured 5 times consecutively. The interval between sets is, for example, 1 minute. The number of measurements in each set, the number of sets, and the interval between sets are set appropriately considering the effect of frictional heat between the test rubber body R and the ice surface 1 on the surface temperature of the ice surface 1. Note that, although not limited to the above, the friction coefficient may be measured in 6 consecutive sets without changing the surface temperature of the ice surface 1.

[0030] The measured friction coefficient in the data set is preferably a measurement value obtained under the same test conditions, such as the compound ratio of the test rubber body R, the running speed by the drive device 6, and the load by the load device 5. It is more preferably a measurement value obtained using multiple solids (multiple test rubber bodies) from the same manufacturing lot, and even more preferably a measurement value obtained using the same solid (one test rubber body). This suppresses variations in the measured friction coefficient due to individual differences.

[0031] The friction testing apparatus 100 includes a friction coefficient calculation unit 12 that calculates the friction coefficient (also called the calculated friction coefficient) at a specific temperature from a regression line. With this configuration, precise temperature control of the ice road surface 1 is unnecessary, and the increase in testing costs can be suppressed. Furthermore, by using a regression line, the friction coefficient can be calculated (measured) with greater accuracy than when measured directly by the friction coefficient measurement unit 7. This suppresses the increase in testing costs and enables the accurate calculation (measurement) of the friction coefficient of the test rubber body R on the ice road surface 1. By enabling the accurate calculation (measurement) of the friction coefficient, variations in the friction coefficient due to differences in measurement dates can be suppressed.

[0032] The specified temperature is, for example, any road surface temperature below 0°C that can be appropriately set by the test operator. Preferably, the specified temperature is -2.0°C or lower. This suppresses variations in the measured friction coefficient due to changes in the surface properties of the icy road surface 1 or water wetting, and improves the accuracy of the regression line. As a result, it becomes possible to accurately calculate (measure) the friction coefficient of the test rubber body R on the icy road surface 1.

[0033] In this embodiment, the regression line calculation unit 11 and the friction coefficient calculation unit 12 are provided within the calculation unit 81. That is, the calculation unit 81 has the functions of the regression line calculation unit 11 and the friction coefficient calculation unit 12, but is not limited to these functions.

[0034] The regression line calculation unit 11 preferably calculates the regression line from a data set in which the road surface temperature is within ±2.0°C of a specific temperature. With this configuration, the correlation between the regression line and the data set (accuracy of the regression line) is improved, and the coefficient of friction of the test rubber body R on the icy road surface 1 can be calculated (measured) with high accuracy. This is because if the road surface temperature is outside the range of ±2.0°C of the specific temperature, the correlation between the regression line and the data set may decrease due to, for example, changes in surface properties or water wetting.

[0035] The regression line calculation unit 11 more preferably calculates the regression line from a data set in which the road surface temperature is within ±1.5°C of a specific temperature, and even more preferably calculates the regression line from a data set in which the road surface temperature is within ±1.0°C of a specific temperature.

[0036] The regression line calculation unit 11 preferably calculates a regression line from a data set in which the difference between the highest and lowest road surface temperatures measured by the temperature measurement unit 13 is 1.0°C or more. With this configuration, the accuracy of the regression line can be improved by ensuring a temperature range for the data set. This makes it possible to accurately calculate (measure) the friction coefficient of the test rubber body R on the icy road surface 1.

[0037] Preferably, the data set includes at least a first data set where the road surface temperature is lower than the specified temperature, and a second data set where the road surface temperature is higher than the specified temperature. This allows the regression line calculation unit 11 to calculate the friction coefficient at the specified temperature using the interpolation method. As a result, the friction coefficient can be calculated (measured) with greater accuracy compared to the extrapolation method.

[0038] Preferably, the highest temperature in the first data group is 0.5°C or more away (lower) than the lowest temperature in the second data group. With this configuration, the accuracy of the regression line can be improved by ensuring a temperature range for the data groups by separating the first and second data groups by 0.5°C or more. This makes it possible to accurately calculate (measure) the friction coefficient of the test rubber body R on the icy road surface 1. In addition, the measurement of the friction coefficient between the first and second data groups can be omitted, reducing the number of measurements of the friction coefficient. The highest temperature in the first data group may be 0.8°C or more away from the lowest temperature in the second data group.

[0039] Figure 4 is a graph illustrating the relationship between the first data group Dg1 and the second data group Dg2 and the regression line RL. As shown in Figure 4, the specific temperature in this example is -2.5°C. The first data group Dg1 is a data group measured after adjusting the surface temperature of the icy road surface to around -3.0°C, and the second data group Dg2 is a data group measured after adjusting the surface temperature of the icy road surface to around -2.0°C. That is, the first data group Dg1 is a data group in which the surface temperature of the icy road surface is adjusted to around the specific temperature -0.5°C, and the second data group Dg2 is a data group in which the surface temperature of the icy road surface is adjusted to around the specific temperature +0.5°C. The second data group Dg2 is measured, for example, after adjusting the surface temperature of the icy road surface following the measurement of the first data group Dg1. The target temperature for adjustment in each data group Dg1 and Dg2 can be set as appropriate.

[0040] The highest temperature in the first data group Dg1 is approximately 0.6°C or more away from the lowest temperature in the second data group Dg2. The lowest temperature in the first data group Dg1 is approximately 1.5°C or more away from the highest temperature in the second data group Dg2. The difference between the highest and lowest temperatures within each data group Dg1 and Dg2 is approximately 0.4°C or more.

[0041] The regression line calculation unit calculates the regression line RL (dashed line in Figure 4) from the first data group Dg1 and the second data group Dg2 (including the outlier X1). The regression line RL (regression line) is expressed by the following (Equation 2), and the coefficient of determination R 2 This is expressed by (Equation 3) below. The friction coefficient calculation unit calculates the friction coefficient μ from the regression line RL expressed by (Equation 2). When the specific temperature is -2.5℃, the friction coefficient μ is 0.123. μ(T)=-0.016×T+0.083 (Formula 2) R 2 =0.85 (Equation 3)

[0042] The temperature measurement unit 13 shown in Figure 1 preferably measures the surface temperature of the portion (lane) in contact with the test rubber body R on the icy road surface 1. With this configuration, the accuracy of the road surface temperature corresponding to the measured friction coefficient can be improved, and the accuracy of the regression line can be improved. As a result, the friction coefficient of the test rubber body R on the icy road surface 1 can be calculated (measured) with high accuracy.

[0043] The surface temperature of the icy road surface 1 measured by the temperature measurement unit 13 is preferably the average temperature before and after contact with the test rubber body R. With this configuration, the road surface temperature can be adjusted to take into account the temperature rise due to frictional heat between the icy road surface 1 and the test rubber body R, thereby improving the accuracy of the regression line. This makes it possible to accurately calculate (measure) the coefficient of friction of the test rubber body R on the icy road surface 1. The average temperature is the average of the road surface temperature of the icy road surface 1 before contact with the test rubber body R and the road surface temperature of the icy road surface 1 after contact with the test rubber body R, as measured by the temperature sensor 131. Note that the surface temperature of the icy road surface 1 measured by the temperature measurement unit 13 is not limited to the above, and may be the surface temperature of the icy road surface 1 before or after contact with the test rubber body R.

[0044] <Friction Testing Method> Next, an example of a friction test method will be explained with reference to Figure 5. Figure 5 is a flowchart of an example of a friction test method.

[0045] As shown in Figure 5, the friction test method includes a friction coefficient measurement step S101 in which a test rubber body is moved relative to the icy road surface to measure the friction coefficient of the test rubber body (measured friction coefficient), a temperature measurement step S102 in which the road surface temperature of the icy road surface is measured, a regression line calculation step S103 in which a regression line is calculated from the measured measured friction coefficient and the corresponding road surface temperature data set, and a friction coefficient calculation step S104 in which the friction coefficient at a specific temperature (calculated friction coefficient) is calculated from the regression line.

[0046] In the friction coefficient measurement step S101, the friction coefficient is measured using the friction testing device (friction coefficient measurement unit) described above. In the temperature measurement step S102, the road surface temperature (surface temperature or internal temperature) of the icy road surface is measured using the temperature measurement unit described above. The friction coefficient measurement step S101 may be performed simultaneously with the temperature measurement step S102, or after the temperature measurement step S102.

[0047] In the regression line calculation step S103, it is preferable to calculate the regression line from a data set in which the road surface temperature is within ±2.0℃ of a specific temperature. In the regression line calculation step S103, it is preferable to calculate the regression line from a data set in which the difference between the highest and lowest road surface temperatures is 1.0℃ or more.

[0048] The data set includes at least a first data set where the road surface temperature is lower than a specific temperature, and a second data set where the road surface temperature is higher than a specific temperature, and it is preferable that the highest temperature in the first data set is 0.5°C or more away from the lowest temperature in the second data set.

[0049] In the temperature measurement step S102, it is preferable to measure the surface temperature of the portion (lane) of the icy road surface that comes into contact with the test rubber body. The surface temperature of the icy road surface measured in the temperature measurement step S102 is preferably the average temperature before and after contact with the test rubber body.

[0050] <Variation> In the example shown in Figure 4, the regression line calculation unit calculates the regression line RL from the first data group Dg1 and the second data group Dg2 (two data groups), but is not limited to this. For example, the regression line calculation unit may calculate the regression line from one or more data groups. When calculating the regression line from three data groups, the third data group is, for example, a data group measured after adjusting the road surface temperature of an icy road surface to around a specific temperature (e.g., a specific temperature ± 0.2℃). The third data group may overlap with a part of the first data group and / or a part of the second data group. The same applies to the regression line calculation process.

[0051] Furthermore, while the regression line calculation unit calculates the regression line RL including the outlier X1, it is not limited to this. For example, the regression line calculation unit may calculate the regression line excluding the outlier X1. This can improve the accuracy of the regression line. The same applies to the regression line calculation process.

[0052] Furthermore, while the regression line calculation unit calculates the friction coefficient at a specific temperature using the interpolation method, it is not limited to this. For example, the regression line calculation unit may calculate the friction coefficient at a specific temperature using the extrapolation method. Specifically, the regression line calculation unit may calculate the friction coefficient by setting the specific temperature to -4°C when the range of the data group is within -2.5°C ± 0.8°C. The same applies to the regression line calculation process.

[0053] The friction coefficient calculation unit calculates the coefficient of determination R of the regression line. 2 The coefficient of friction may be calculated when the value is 0.8 or higher. This strengthens the correlation between the regression line and the data set, making it possible to accurately calculate (measure) the coefficient of friction of the test rubber body R on the icy road surface 1. The same applies to the coefficient of friction calculation process.

[0054] The temperature measurement unit 13 (temperature sensor 131) is preferably attached to the holder 4 shown in Figure 1. This makes it possible to measure the surface temperature of the ice road surface 1 immediately before and / or immediately after contact with the test rubber body R.

[0055] Those skilled in the art will understand that the embodiments described above are specific examples of the following embodiments.

[0056] [1] As described above, the friction testing apparatus according to this embodiment comprises an ice road surface that contacts a test rubber body, a friction coefficient measuring unit that measures the friction coefficient (measured friction coefficient) of the test rubber body when the test rubber body is moved relative to the ice road surface, a temperature measuring unit that measures the road surface temperature of the ice road surface, a regression line calculation unit that calculates a regression line from a data set of the measured friction coefficient and the corresponding road surface temperature, and a friction coefficient calculation unit that calculates the friction coefficient (calculated friction coefficient) at a specific temperature from the regression line.

[0057] With this configuration, precise temperature control of the icy road surface becomes unnecessary, thus suppressing the increase in testing costs. Furthermore, by using a regression line, the coefficient of friction of the test rubber material at a specific temperature can be calculated (measured) with greater accuracy than when measured directly by the friction coefficient measurement unit. This suppresses the increase in testing costs and enables accurate calculation (measurement) of the coefficient of friction of the test rubber material on the icy road surface 1.

[0058] [2] Furthermore, in the friction testing apparatus described in [1] above, it is preferable that the regression line calculation unit calculates a regression line from a data set in which the road surface temperature is within a specified temperature ± 2.0°C.

[0059] This configuration improves the correlation between the regression line and the data set (the accuracy of the regression line), making it possible to accurately calculate (measure) the coefficient of friction of the test rubber body on an icy road surface.

[0060] [3] Furthermore, in the friction testing apparatus described in [1] or [2] above, it is preferable that the regression line calculation unit calculates a regression line from a group of data in which the difference between the highest and lowest road surface temperatures is 1.0°C or more.

[0061] With this configuration, the accuracy of the regression line can be improved by ensuring a temperature range for the data set. This makes it possible to accurately calculate (measure) the coefficient of friction of the test rubber material on an icy road surface.

[0062] [4] Furthermore, in the friction testing apparatus described in any one of [1] to [3] above, it is preferable that the data group includes at least a first data group where the road surface temperature is lower than a specific temperature, and a second data group where the road surface temperature is higher than a specific temperature, and the highest temperature in the first data group is 0.5°C or more away from the lowest temperature in the second data group.

[0063] With this configuration, the accuracy of the regression line can be improved by ensuring a temperature range for the data groups by separating the first data group and the second data group by 0.5°C or more. This makes it possible to accurately calculate (measure) the coefficient of friction of the test rubber material on an icy road surface.

[0064] [5] Furthermore, in the friction testing apparatus described in any one of [1] to [4] above, it is preferable that the temperature measuring unit measures the surface temperature of the portion that comes into contact with the test rubber body on the icy road surface.

[0065] This configuration improves the accuracy of the road surface temperature corresponding to the measured friction coefficient and enhances the accuracy of the regression line. As a result, it becomes possible to accurately calculate (measure) the friction coefficient of the test rubber material on an icy road surface.

[0066] [6] Furthermore, in the friction testing apparatus described in [5] above, it is preferable that the surface temperature is the average temperature before and after contact with the test rubber body.

[0067] With this configuration, the road surface temperature can be adjusted to include the temperature rise due to frictional heat between the icy road surface and the test rubber body, thereby improving the accuracy of the regression line. This makes it possible to accurately calculate (measure) the coefficient of friction of the test rubber body on an icy road surface.

[0068] [7] The friction test method according to this embodiment includes a friction coefficient measurement step of measuring the friction coefficient (measured friction coefficient) of a test rubber body by moving it relative to an icy road surface; a temperature measurement step of measuring the road surface temperature of an icy road surface; a regression line calculation step of calculating a regression line from a data set of the measured friction coefficient and the corresponding road surface temperature; and a friction coefficient calculation step of calculating the friction coefficient (calculated friction coefficient) at a specific temperature from the regression line.

[0069] This method eliminates the need for precise temperature control of the icy road surface, thereby suppressing increases in testing costs. Furthermore, by using regression lines, the friction coefficient of the test rubber material at a specific temperature can be calculated (measured) with greater accuracy than when measured directly in the friction coefficient metering process. This suppresses increases in testing costs while enabling accurate calculation (measurement) of the friction coefficient of the test rubber material on an icy road surface.

[0070] [8] Furthermore, in the friction test method described in [7] above, it is preferable that the regression line calculation step is performed by calculating the regression line from a data set in which the road surface temperature is within a specific temperature ± 2.0°C.

[0071] This method improves the correlation between the regression line and the data set (the accuracy of the regression line), making it possible to accurately calculate (measure) the coefficient of friction of the test rubber material on an icy road surface.

[0072] [9] Furthermore, in the friction test method described in [7] or [8] above, it is preferable that the regression line calculation step calculates the regression line from a group of data in which the difference between the highest and lowest road surface temperatures is 1.0°C or more.

[0073] This method improves the accuracy of the regression line by ensuring a consistent temperature range for the data set. This makes it possible to accurately calculate (measure) the coefficient of friction of the test rubber material on an icy road surface.

[0074]

[10] Furthermore, in the friction test method described in any one of [7] to [9] above, it is preferable that the data group includes at least a first data group where the road surface temperature is lower than a specific temperature, and a second data group where the road surface temperature is higher than a specific temperature, wherein the highest temperature in the first data group is 0.5°C or more away from the lowest temperature in the second data group.

[0075] This method allows for improved accuracy of the regression line by separating the first and second data groups by 0.5°C or more to ensure a wide temperature range for each data group. This enables accurate calculation (measurement) of the friction coefficient of the test rubber material on an icy road surface.

[0076]

[11] Furthermore, in the friction test method described in any one of [7] to

[10] above, it is preferable that the temperature measurement step involves measuring the surface temperature of the portion of the test rubber body that comes into contact with the icy road surface.

[0077] This method improves the accuracy of the road surface temperature corresponding to the measured friction coefficient and improves the accuracy of the regression line. As a result, it becomes possible to accurately calculate (measure) the friction coefficient of the test rubber material on an icy road surface.

[0078]

[12] Furthermore, in the friction test method described in

[11] above, it is preferable that the surface temperature is the average temperature before and after contact with the test rubber body.

[0079] This method allows for the road surface temperature to be calculated taking into account the temperature rise due to frictional heat between the icy road surface and the test rubber body, thereby improving the accuracy of the regression line. This makes it possible to accurately calculate (measure) the coefficient of friction of the test rubber body on an icy road surface.

[0080] It should be noted that the friction testing apparatus and friction testing method are not limited to the configuration of the embodiments described above, nor are they limited to the effects described above. Furthermore, it goes without saying that the friction testing apparatus and friction testing method can be modified in various ways without departing from the gist of this disclosure. For example, one or more of the configurations and methods related to the various modifications described above can be arbitrarily selected and adopted in the configurations and methods of the embodiments described above. [Explanation of Symbols]

[0081] 100... Friction testing apparatus, 1... Icy road surface, 4... Holder, 5... Loading device, 6... Drive device, 7... Friction coefficient measurement unit, 8... Control device, 9... Table, 10... Actuator, 11... Regression line calculation unit, 12... Friction coefficient calculation unit, 13... Temperature measurement unit, 131... Temperature sensor, 18... Plate, 20... Constant temperature chamber, 21... Frame member, 21a... Road surface section, 21b... Outer perimeter section, 22... Table, 71... Load sensor, 81... Calculation unit, 82... Operation control unit, 83... Input unit, 84... Display unit, R... Test rubber body

Claims

1. The icy road surface in contact with the test rubber body, A friction coefficient measuring unit measures the measured friction coefficient of the test rubber body when the test rubber body is moved relative to the icy road surface, A temperature measuring unit for measuring the road surface temperature of the icy road surface, A regression line calculation unit that calculates a regression line from the measured friction coefficient and the corresponding road surface temperature data set, A friction testing apparatus comprising a friction coefficient calculation unit that calculates the friction coefficient at a specific temperature from the regression line.

2. The friction testing apparatus according to claim 1, wherein the regression line calculation unit calculates the regression line from the data group in which the road surface temperature is within ±2.0°C of the specified temperature.

3. The friction testing apparatus according to claim 1, wherein the regression line calculation unit calculates the regression line from the data group in which the difference between the highest and lowest road surface temperatures is 1.0°C or more.

4. The data set includes at least a first data set in which the road surface temperature is lower than the specified temperature, and a second data set in which the road surface temperature is higher than the specified temperature. The friction testing apparatus according to claim 1, wherein the highest temperature in the first data group is 0.5°C or more away from the lowest temperature in the second data group.

5. The friction testing apparatus according to any one of claims 1 to 4, wherein the temperature measuring unit measures the surface temperature of the portion of the icy road surface that comes into contact with the test rubber body.

6. The friction testing apparatus according to claim 5, wherein the surface temperature is the average temperature before and after contact with the test rubber body.

7. A friction coefficient measurement step involves moving a test rubber body relative to an icy road surface to measure the friction coefficient of the test rubber body, A temperature measurement step for measuring the road surface temperature of the icy road surface, A regression line calculation step, which calculates a regression line from the measured friction coefficient and the corresponding road surface temperature data set, A friction test method comprising a step of calculating the coefficient of friction at a specific temperature from the regression line.

8. The friction test method according to claim 7, wherein the regression line calculation step involves calculating the regression line from the data set in which the road surface temperature is within ±2.0°C of the specified temperature.

9. The friction test method according to claim 7, wherein the regression line calculation step involves calculating the regression line from the data set in which the difference between the highest and lowest road surface temperatures is 1.0°C or more.

10. The data set includes at least a first data set in which the road surface temperature is lower than the specified temperature, and a second data set in which the road surface temperature is higher than the specified temperature. The friction test method according to claim 7, wherein the highest temperature in the first data group is 0.5°C or more away from the lowest temperature in the second data group.

11. The friction test method according to any one of claims 7 to 10, wherein the temperature measurement step involves measuring the surface temperature of the portion of the icy road surface that comes into contact with the test rubber body.

12. The friction test method according to claim 11, wherein the surface temperature is the average temperature before and after contact with the test rubber body.

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