Thermal sagging estimation method of tire

Abstract

To provide a thermal sagging estimation method of a tire which estimates inner surface temperature of the tire to which thermal sagging generates or pneumatic pressure of the tire.SOLUTION: In thermal sagging estimation method of a tire which estimates inner surface temperature of the tire to which thermal sagging generates or pneumatic pressure of the tire, it measures the inner surface temperature of the tire and the pneumatic pressure of the tire by rolling and moving the tire in advance and estimates that the thermal sagging generates on the tire if relationship between the inner surface temperature and the pneumatic pressure is out of prescribed value or more from relationship between pressure and temperature of ideal gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for estimating the inner surface temperature of a tire or the air pressure of a tire in which heat sag occurs in the tire.

Background Art

[0002] Tire heat sag is a phenomenon in which the grip force decreases due to an increase in the temperature of the tire. For example, in the case of tires used in a race, during the race, due to heat sag, the lateral force decreases and the handling stability performance deteriorates. For example, Patent Document 1 discloses a pneumatic tire having excellent heat sag resistance performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Currently, in order to estimate whether heat sag has occurred in a tire used in a race, it depends on the qualitative sense or experience of the driver. For example, when measuring the inner surface temperature or air pressure of a tire during a race, if the inner surface temperature or air pressure at which heat sag occurs in the tire is known in advance, it is possible to quantitatively estimate whether heat sag has occurred in the tire and replace the tire at an appropriate timing.

[0005] Therefore, an object of the present invention is to provide a method for estimating tire heat sag that estimates the inner surface temperature or air pressure at which heat sag occurs in a tire.

Means for Solving the Problems

[0006] The method for estimating heat sag of a tire according to the present invention is a method for estimating the inner surface temperature of the tire or the air pressure of the tire at which heat sag occurs in the tire, which comprises rolling the tire in advance to measure the inner surface temperature of the tire and the air pressure of the tire, and estimating that heat sag has occurred in the tire when the relationship between the inner surface temperature and the air pressure deviates from the relationship between the pressure and temperature of an ideal gas by a predetermined value or more.

Advantages of the Invention

[0007] According to the method for estimating heat sag of a tire of the present invention, it is possible to estimate the inner surface temperature or the air pressure at which heat sag occurs in the tire.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, an example of an embodiment of the present invention will be described in detail. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating the understanding of the present invention and can be appropriately changed according to applications, purposes, specifications, etc.

[0010] [Tire Heat Sag and Ideal Gas] Using FIG. 1, the relationship between tire heat sag and the inner surface temperature of the tire will be described.

[0011] Tire heat sag is a phenomenon in which the grip force decreases due to an increase in the temperature of the tire. For example, in tires used in races, during the race, due to heat sag, the lateral force decreases and the handling stability performance deteriorates.

[0012] For example, FIG. 1 shows a comparison between the lap time for each lap and the inner surface temperature of the tire for each lap in a certain race. The inner surface temperature of the tire indicates the average value of the inner surface temperatures of the four wheels. As shown in FIG. 1, as the number of laps increases, the lap time tends to deteriorate. Also, as the number of laps increases, the inner surface temperature of the tire becomes higher. That is, as the inner surface temperature of the tire increases, the lap time tends to deteriorate. In particular, if the inner surface temperature exceeds a predetermined temperature, the lap time tends to deteriorate. This means that during the race, due to heat sag, the lateral force decreases and the handling stability performance deteriorates.

[0013] [Tire Heat Sag and Ideal Gas] Using FIG. 2, the relationship between tire heat sag and an ideal gas will be described.

[0014] It was found that the inner surface temperature of the tire, which tends to cause the above-described deterioration of the lap time, is an inner surface temperature at which the relationship between the inner surface temperature of the tire and the tire air pressure deviates from the relationship between the temperature and pressure of an ideal gas (the temperature is proportional to the pressure).

[0015] For example, FIG. 2 shows the relationship between the inner surface temperature of the tire and the tire air pressure in a certain race. As shown in FIG. 2, it was found that when the relationship between the inner surface temperature of the tire and the tire air pressure in a certain race deviates from the relationship between the temperature and pressure of an ideal gas (the temperature is proportional to the pressure), the lap time tends to deteriorate.

[0016] [Tire Heat Sag Estimation Method] Using FIG. 3, the tire heat sag estimation method will be described.

[0017] The method for estimating tire heat sag is a method for estimating the inner surface temperature of a tire where heat sag occurs in the tire or the air pressure of the tire. First, in step S1, the tire used in the race is rolled in advance with a test device to measure the inner surface temperature of the tire and the air pressure of the tire. In step S2, when the relationship between the measured inner surface temperature of the tire and the air pressure of the tire deviates from the relationship between the temperature and pressure of an ideal gas by a predetermined value or more, it is estimated that heat sag has occurred in the tire. In addition, during the race, when it is estimated that heat sag has occurred in the tire mounted on the driving wheels of the vehicle. It is preferable to estimate that heat sag has occurred in all the tires of the vehicle.

[0018] Conventionally, to estimate whether heat sag has occurred in the tires used in a race, it has relied on the driver's qualitative sense or experience. However, according to the method for estimating tire heat sag, the inner surface temperature of the tire where heat sag occurs or the air pressure of the tire can be estimated in advance. Thereby, for example, when measuring the inner surface temperature of the tire or the air pressure of the tire during a race, it is possible to quantitatively estimate whether heat sag has occurred in the tire and replace the tire at an appropriate timing.

[0019] Below, several patterns for calculating the case where the relationship between the measured inner surface temperature of the tire and the air pressure of the tire deviates from the relationship between the temperature and pressure of an ideal gas by a predetermined value or more will be described.

[0020] [Method for Estimating Tire Heat Sag by Difference] Using FIGS. 4 and 5, the method for estimating tire heat sag by difference will be described.

[0021] The method for estimating tire heat sag by difference is a method of approximating the relationship between the air pressure of a tire and the inner surface temperature of the tire in a state in an ideal gas relationship by a linear function, and estimating that heat sag has occurred in the tire when it deviates from this linear function by a predetermined value or more.

[0022] In step 11, approximate the relationship between the inner surface temperature and the air pressure in the first interval from the start of measurement with a linear function. Note that the first interval is an interval in which the relationship between the inner surface temperature and the air pressure is the same as the relationship between the temperature and pressure of an ideal gas (the pressure and temperature have a substantially linear relationship), and is the interval from the start of measurement to the first hour. In step 12, when the difference between the inner surface temperature and the inner surface temperature determined by the linear function at the same air pressure is equal to or greater than a predetermined value (ΔT in FIG. 5), or when the difference between the air pressure and the air pressure determined by the linear function at the same inner surface temperature is equal to or greater than a predetermined value (ΔP in FIG. 5), it is estimated that heat sag occurs in the tire.

[0023] [Method for estimating tire heat sag due to deviation] Using FIG. 6, the method for estimating tire heat sag due to deviation will be described.

[0024] The method for estimating tire heat sag due to deviation is a method of approximating the relationship between the inner surface temperature of a tire in a state in an ideal gas relationship and the air pressure of the tire with a linear function, and estimating that heat sag occurs in the tire when the deviation from this linear function is equal to or greater than a predetermined value.

[0025] In step 21, approximate the relationship between the inner surface temperature and the air pressure in the first interval from the start of measurement with a linear function. Note that the first interval is, as described above, an interval in which the relationship between the inner surface temperature and the air pressure is the same as the relationship between the temperature and pressure of an ideal gas (the pressure and temperature have a substantially linear relationship), and is the interval from the start of measurement to the first hour. In step 22, when the value obtained by dividing the absolute value of the difference between the inner surface temperature and the inner surface temperature determined by the linear function at the same air pressure by the average of the inner surface temperatures in the first interval is equal to or greater than a predetermined value, or when the value obtained by dividing the absolute value of the difference between the air pressure and the air pressure determined by the linear function at the same inner surface temperature by the average of the air pressures in the first interval is equal to or greater than a predetermined value, it is estimated that heat sag occurs in the tire.

[0026] [Method for estimating tire heat sag using two approximation lines] Using FIGS. 7 and 8, the method for estimating tire heat sag using two approximation lines will be described.

[0027] The method for estimating tire heat sag using two approximate lines approximates the relationship between the inner surface temperature of the tire on the low-temperature side and the tire air pressure in a state in the relationship of an ideal gas with a first linear function, and approximates the relationship between the inner surface temperature of the tire on the high-temperature side and the tire air pressure in a state in the relationship of an ideal gas with a second linear function, and estimates that tire heat sag occurs at the inner surface temperature or air pressure that is the intersection of the first linear function and the second linear function.

[0028] In step 31, approximate the relationship between the inner surface temperature and the air pressure in the first section from the start of measurement with a first linear function. Note that the first section is, as described above, a section where the relationship between the inner surface temperature and the air pressure is in the relationship of the temperature and pressure of an ideal gas (the pressure and temperature are in a substantially linear relationship), and is the section from the start of measurement to the first hour. In step 32, approximate the relationship between the inner surface temperature and the air pressure in the second section until the end of measurement with a second linear function. Note that the second section is a section where the relationship between the inner surface temperature and the air pressure is in the relationship of the temperature and pressure of an ideal gas (the pressure and temperature are in a substantially linear relationship), and is the section from the second hour to the end of measurement. In step S33, estimate that tire heat sag occurs at the inner surface temperature or air pressure that is the intersection of the first linear function and the second linear function.

[0029] [Method for Estimating Tire Heat Sag by Slope] Using FIG. 9, the method for estimating tire heat sag by slope will be described.

[0030] The method for estimating tire heat sag by slope calculates the increase in the inner surface temperature of the tire with respect to the increase in the tire air pressure as the slope, or calculates the increase in the tire air pressure with respect to the increase in the inner surface temperature of the tire as the slope, calculates the rate of change of the slope, and estimates that tire heat sag occurs when the rate of change is equal to or greater than a predetermined rate of change.

[0031] In step S41, calculate, using as the slope, the increase in the inner surface temperature of the tire with respect to the increase in the air pressure of the tire in the third interval, or calculate, using as the slope, the increase in the air pressure of the tire with respect to the increase in the inner surface temperature of the tire in the third interval. Note that the third interval is, for example, a time period that includes five measurement timings. In step S42, calculate the rate of change of the slope. In step S43, if the rate of change is equal to or greater than a predetermined rate of change, estimate that heat sag has occurred in the tire.

[0032] [Method for estimating heat sag of tire (temperature) using difference and two approximate lines] Using FIGS. 10 and 11, the method for estimating heat sag of a tire using difference and two approximate lines will be described.

[0033] The method for estimating heat sag of a tire using difference and two approximate lines approximates the relationship between the inner surface temperature of the tire and the air pressure of the tire in a state in relation to the ideal gas law by a first linear function, calculates the temperature difference between the inner surface temperature and the inner surface temperature determined by the first linear function, approximates the relationship between the air pressure of the tire and the temperature difference by a second linear function, and estimates that heat sag has occurred when the temperature difference becomes 0 in the second linear function.

[0034] In step S51, approximate the relationship between the inner surface temperature and the air pressure in the first interval from the start of measurement by a first linear function. Note that the first interval is, as described above, an interval in which the relationship between the inner surface temperature and the air pressure is the relationship between the temperature and the pressure of an ideal gas (the pressure and the temperature have a substantially linear relationship), and is an interval from the start of measurement to the first hour. In step S52, calculate the temperature difference between the inner surface temperature for each air pressure of the tire and the inner surface temperature determined by the first linear function. In step S53, approximate the relationship between the air pressure of the tire and the temperature difference in the second interval until the end of measurement by a second linear function. Note that the second interval is, as described above, an interval in which the relationship between the inner surface temperature and the air pressure is the relationship between the temperature and the pressure of an ideal gas (the pressure and the temperature have a substantially linear relationship), and is an interval from the second hour to the end of measurement. In step S54, estimate that heat sag has occurred when the temperature difference becomes 0 in the second linear function.

[0035] [Method for estimating tire heat sag using difference and two approximation lines (pressure)] Using FIGS. 12 and 13, another method for estimating tire heat sag using difference and two approximation lines will be described.

[0036] The method for estimating tire heat sag using difference and two approximation lines approximates the relationship between the inner surface temperature of a tire in a state in the relationship of an ideal gas and the air pressure of the tire by a first linear function, calculates the pressure difference between the air pressure and the air pressure determined by the first linear function, approximates the relationship between the inner surface temperature of the tire and the pressure difference by a second linear function, and estimates that heat sag occurs when the pressure difference becomes 0 in the second linear function.

[0037] In step S61, the relationship between the inner surface temperature and the air pressure in the first section from the start of measurement is approximated by a first linear function. Note that the first section is, as described above, a section in which the relationship between the inner surface temperature and the air pressure is the relationship between the temperature and the pressure of an ideal gas (the pressure and the temperature are in a substantially linear relationship), and is the section from the start of measurement to the first hour. In step S62, the pressure difference between the air pressure and the air pressure determined by the first linear function is calculated. In step S53, the relationship between the inner surface temperature of the tire and the pressure difference in the second section until the end of measurement is approximated by a second linear function. Note that the second section is, as described above, a section in which the relationship between the inner surface temperature and the air pressure is the relationship between the temperature and the pressure of an ideal gas (the pressure and the temperature are in a substantially linear relationship), and is the section from the second hour to the end of measurement. In step S54, it is estimated that heat sag occurs when the pressure difference becomes 0 in the second linear function.

[0038] Note that the present invention is not limited to the above-described embodiments and their modified examples, and it goes without saying that various changes and improvements can be made within the scope of the matters described in the claims of the present application.

Claims

1. A method for estimating heat sag of a tire, which estimates the inner surface temperature or the air pressure of the tire before heat sag occurs in the tire, rolling the tire in advance to measure the inner surface temperature and the air pressure of the tire, when the relationship between the inner surface temperature and the air pressure deviates from the relationship between the pressure and temperature of an ideal gas by a predetermined value or more, it is estimated that heat sag has occurred in the tire. A method for estimating heat sag of a tire.

2. A method for estimating heat sag of a tire according to claim 1, approximating the relationship between the inner surface temperature and the air pressure in a first section from the start of the measurement by a linear function, when the difference between the inner surface temperature and the inner surface temperature determined by the linear function at the air pressure becomes a predetermined value or more, or when the difference between the air pressure and the air pressure determined by the linear function at the inner surface temperature becomes a predetermined value or more, it is estimated that heat sag has occurred in the tire. A method for estimating heat sag of a tire.

3. A method for estimating heat sag of a tire according to claim 1, approximating the relationship between the inner surface temperature and the air pressure in a first section from the start of the measurement by a linear function, when the value obtained by dividing the absolute value of the difference between the inner surface temperature and the inner surface temperature determined by the linear function by the average of the inner surface temperatures in the first section becomes a predetermined value or more, or when the value obtained by dividing the absolute value of the difference between the air pressure and the air pressure determined by the linear function by the average of the air pressures in the first section becomes a predetermined value or more, it is estimated that heat sag has occurred in the tire. A method for estimating heat sag of a tire.

4. A method for estimating heat sag of a tire according to claim 1, approximating the relationship between the inner surface temperature and the air pressure in a first section from the start of the measurement by a first linear function, approximating the relationship between the inner surface temperature and the air pressure in a second section until the end of the measurement by a second linear function, It is estimated that heat sag occurs in the tire at the inner surface temperature or the air pressure that is the intersection of the first linear function and the second linear function. Tire heat sag estimation method.

5. The tire heat sag estimation method according to claim 1, Calculate the increase in the inner surface temperature of the tire with respect to the increase in the air pressure of the tire in the third section as the slope, or calculate the increase in the air pressure of the tire with respect to the increase in the inner surface temperature of the tire in the third section as the slope, Calculate the rate of change of the slope, It is estimated that heat sag occurs in the tire when the rate of change is equal to or greater than a predetermined rate of change. Tire heat sag estimation method.

6. The tire heat sag estimation method according to claim 1, Approximate the relationship between the inner surface temperature and the air pressure in the first section from the start of the measurement with a first linear function, Calculate the temperature difference between the inner surface temperature and the inner surface temperature determined by the first linear function, Approximate the relationship between the air pressure and the temperature difference in the second section until the end of the measurement with a second linear function, It is estimated that heat sag occurs when the temperature difference becomes 0 in the second linear function. Tire heat sag estimation method.

7. The tire heat sag estimation method according to claim 1, Approximate the relationship between the inner surface temperature and the air pressure in the first section from the start of the measurement with a first linear function, Calculate the pressure difference between the air pressure and the air pressure determined by the linear function, Approximate the relationship between the inner surface temperature and the pressure difference in the second section until the end of the measurement with a second linear function, It is estimated that heat sag occurs when the pressure difference becomes 0 in the second linear function. Tire heat sag estimation method.

8. A method for estimating heat sag of a tire according to any one of claims 1 to 7, when it is estimated that heat sag occurs in a tire mounted on a driving wheel of a vehicle, estimating that heat sag occurs in all tires of the vehicle; A method for estimating heat sag of a tire.

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