Method for evaluating cornering performance

Abstract

We will measure the temperature dependence of cornering performance under various loads, especially low loads. [Solution] The present invention provides a method for evaluating the cornering performance of a tire T using a flat belt testing apparatus 1, comprising: a first loading step in which the tire T is pressed against the upper surface 21 of a rotating belt 20 with a first load; and a second loading step in which, after the first loading step, the tire T is pressed against the upper surface 21 of the rotating belt 20 with a second load smaller than the first load, while measuring the mechanical elements representing the cornering performance of the tire and the temperature of the tire.

Description

Technical Field

[0001] The present invention relates to a method for evaluating cornering performance.

Background Art

[0002] Conventionally, as a method for evaluating the cornering performance of a tire, a method of measuring mechanical elements representing the cornering performance of a tire, such as cornering force, using a flat belt test device is known. In this method, while pressing the tire against the upper surface of the belt with a predetermined load, the tire is rolled with a predetermined slip angle, and the cornering force corresponding to the slip angle is measured.

[0003] Patent Document 1 discloses a method of measuring the temperature dependence of cornering performance by gradually changing the swing width of the slip angle and heating the tire by frictional heat.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a vehicle turns, a lateral acceleration acts on the vehicle, so load transfer occurs between the left and right sides of the vehicle. Therefore, in order to accurately evaluate the cornering performance of a tire, it is required to measure the temperature dependence of the cornering performance at a plurality of loads including a low load. When heating the tire by frictional heat as in Patent Document 1, when the load on the tire is small, the tire cannot be sufficiently heated, and it is difficult to measure the cornering performance on the high - temperature side.

Means for Solving the Problems

[0006] The present invention provides a method for evaluating the cornering performance of a tire using a flat belt testing apparatus, comprising: a first loading step of pressing the tire against the upper surface of a rotating belt with a first load; and a second loading step, after the first loading step, of pressing the tire against the upper surface of the rotating belt with a second load smaller than the first load, while measuring mechanical elements representing the cornering performance of the tire and the temperature of the tire. [Effects of the Invention]

[0007] According to the cornering performance evaluation method of the present invention, it is possible to measure the temperature dependence of cornering performance under various loads, particularly low loads. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing the configuration of a flat belt testing apparatus, which is an example of an embodiment. [Figure 2] This is a flowchart of the measurement steps in a method for evaluating cornering performance, which is an example of an embodiment. [Figure 3] This figure shows the changes in load and slip angle in a method for evaluating cornering performance, which is one example of an embodiment. [Figure 4] This figure shows the measurement results of the inner surface temperature of the tire for each load in a method for evaluating cornering performance, which is an example of an embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, with reference to the drawings, an example of an embodiment of the method for evaluating the cornering performance of a tire according to the present invention will be described in detail. The embodiment described below is merely an example, and the present invention is not limited to the embodiments described below.

[0010] Figure 1 is a schematic diagram illustrating the configuration of the flat belt testing apparatus 1. The flat belt testing apparatus 1 comprises a pair of rollers 10 and an endless belt 20. The flat belt testing apparatus 1 further comprises a turntable 30 that is rotated around the Z-axis in Figure 1, and the rollers 10 and belt 20 are mounted on the turntable 30.

[0011] The flat belt test apparatus 1 places a tire T, which is rotatably supported on a tire axle 41, into contact with the upper surface 21 of the belt 20, and rotates the belt 20, causing the tire T to travel (roll) on the upper surface 21 of the belt 20. The flat belt test apparatus 1 then sequentially changes the slip angle by rotating the turntable 30, and measures mechanical elements representing the cornering performance of the tire T, such as tire lateral force, cornering force, and self-aligning torque, corresponding to this slip angle. Note that the flat belt test apparatus 1 is not limited to the above configuration, and known configurations can be used.

[0012] A pair of rollers 10 are arranged so that their axial directions are parallel to each other. The rollers 10 are connected to a drive unit (not shown) which includes a motor, and the motor rotates the rollers 10. As the rollers 10 rotate, the belt 20 circulates in an endless track manner.

[0013] The belt 20 is wrapped around a pair of rollers 10. The material of the belt 20 is not particularly limited. As described above, the tire T makes contact with the upper surface 21 of the belt 20. In other words, the upper surface 21 of the belt 20 acts as a substitute road surface. The upper surface 21 of the belt 20 is configured to be flat between the pair of rollers 10.

[0014] The turntable 30 is driven to rotate around the Z-axis. As the turntable 30 rotates, the rollers 10 and belt 20 installed on the turntable 30 rotate, changing the slip angle of the tire T. In other words, the turntable 30 has the function of imparting a slip angle to the tire T.

[0015] The flat belt testing apparatus 1 includes a tire support device 40 that supports the tire T. The tire support device 40 includes a tire shaft 41 that rotates with the tire T, and a support portion 42 that supports the tire shaft 41.

[0016] The support section 42 is provided with a measuring instrument (not shown) capable of measuring mechanical elements such as cornering force generated on the tire axle 41. The measuring instrument is not particularly limited as long as it is capable of measuring mechanical elements such as cornering force, and is, for example, a 6-component force gauge.

[0017] Furthermore, a load-applying device is connected to the support section 42, and a predetermined load is applied from this load-applying device while the tire T is rolling. As a result, the tire T makes contact with the upper surface 21 of the belt 20 with a predetermined ground contact load.

[0018] The tire T is provided with a temperature measuring unit (not shown) for measuring the temperature of the inner surface of the tire T. In this embodiment, the temperature dependence of the cornering performance of the tire T is determined based on the measurement results from the temperature measuring unit. The temperature measuring unit may be, for example, an infrared sensor attached to the outer surface of the wheel. Alternatively, the temperature measuring unit may be, for example, a contact-type sensor such as a thermocouple.

[0019] Next, the method for evaluating the cornering performance of this embodiment will be described with reference to Figures 2 to 4. Figure 2 is a flowchart of the measurement steps in the cornering performance evaluation method of this embodiment, Figure 3 is a diagram showing the changes in load and slip angle, and Figure 4 is a diagram showing the measurement results of the inner surface temperature of the tire T.

[0020] As shown in FIGS. 2 and 3, the method for evaluating the cornering performance of the present embodiment includes a first load step, a second load step, and a third load step of pressing the tire T against the upper surface 21 of the belt 20 with different loads. Specifically, in the first load step, the tire T is pressed against the upper surface 21 of the belt 20 with the first load. In the second load step, the tire T is pressed against the upper surface 21 of the belt 20 with a second load smaller than the first load. In the third load step, the tire T is pressed against the upper surface 21 of the belt 20 with a third load smaller than the second load. Each load step is continuously performed while sandwiching a step of changing the load.

[0021] When the tire T is pressed against the upper surface 21 of the belt 20 with a predetermined load and rolled, frictional heat is generated. As a result, the temperature of the tire T rises. And this frictional heat becomes larger as the load on the tire T increases. That is, as the load on the tire T increases, the temperature of the tire T rises.

[0022] Although it will be described in detail later, the method for evaluating the cornering performance of the present embodiment performs a first load step of pressing the tire T against the upper surface 21 of the belt 20 with a first load that is a relatively high load, before the second load step and the third load step with relatively small loads. Thereby, measurement between the second load step and the third load step can be performed in a state where the temperature of the tire T is raised. That is, according to the method for evaluating the cornering performance of the present embodiment, it is possible to measure the cornering performance on the high temperature side even under low load conditions where frictional heat is unlikely to occur and the temperature of the tire T is unlikely to rise.

[0023] Further, in the present embodiment, except while changing the load, the slip angle of the tire T continuously changes in time series. In this case, it becomes easier to raise the temperature of the tire T, and the temperature dependence of the cornering performance of the tire T can be obtained with high precision. In the present embodiment, the angular velocity of the slip angle is substantially constant. In this case, the temperature dependence of the cornering performance of the tire T can be obtained with higher precision.

[0024] As shown in Figures 2 and 3, the method for evaluating the cornering performance of this embodiment involves first setting the target load to the first load (step S1), and then performing a first load step in which the tires T are pressed against the upper surface 21 of the belt 20 with the first load (step S2). The value of the first load can be appropriately set depending on the weight of the vehicle on which the tires T are mounted, the usage conditions of the tires T, etc. The first load is, for example, a value equivalent to or greater than the maximum load expected to occur during load transfer when the vehicle turns.

[0025] As described above, rolling the tire T while pressing it with the first load generates frictional heat, causing the temperature of the tire T to rise. In other words, step S2, in which the tire T is rolled while pressing it with the first load, plays a role in raising the temperature of the tire T.

[0026] In this embodiment, in step S2, in which the tire T is rolled while being pressed with a first load, the cornering force, which is a mechanical element representing the cornering performance of the tire T, is measured for a predetermined time (for example, the time it takes for the slip angle to complete one cycle). This makes it possible to measure the cornering performance under the first load, in addition to the cornering performance under the second and third loads.

[0027] The time for rolling the tire T while being pressed with the first load can be set according to the desired temperature of the tire T and other performance characteristics such as the wear resistance of the tire T, and is not particularly limited. The time for rolling the tire T while being pressed with the first load is, for example, the time for the slip angle to complete 1 to 10 cycles, and in this embodiment it is set to the time for the slip angle to complete 3 cycles.

[0028] As shown in Figures 2 and 3, after step S2, the set load is changed to a second load that is smaller than the first load (step S3). The second load only needs to be smaller than the first load. For example, the second load may be 80% or less of the first load, or 70% or less of the first load. It is preferable that the second load is a load that does not generate much frictional heat due to the rolling of the tire T. In this embodiment, in step S3, in which the set load is changed to the second load, the slip angle is not changed and the cornering force of the tire T is not measured.

[0029] Subsequently, a second loading step is performed in which the tires T are pressed against the upper surface 21 of the belt 20 with the set second load (step S4). In step S2, the tires T are rolled while being pressed with the first load, so the temperature of the tires T rises due to frictional heat. Therefore, measurements can be taken in a higher temperature range than when the tires T are simply rolled while being pressed with the second load.

[0030] In step S4, where the tire T is rolled while being pressed with a second load, the cornering force of the tire T is measured sequentially. The time for rolling the tire T while being pressed with the second load can be set according to the index of cornering performance to be measured and the performance of the tire T, such as wear resistance, and is not particularly limited. The time for rolling the tire T while being pressed with the second load is, for example, the time for the slip angle to complete 0.5 to 5 cycles, and in this embodiment, it is set to the time for the slip angle to complete 1 cycle.

[0031] As shown in Figures 2 and 3, after step S4, the set load is changed from the second load to the first load (step S5). After step S4, step S7, which will be described later, may also be performed. In this embodiment, in step S5, when the set load is changed to the first load, the slip angle is not changed and the cornering force is not measured.

[0032] Subsequently, a first loading step is performed in which the tires T are pressed against the upper surface 21 of the belt 20 with a set first load (step S6). This generates frictional heat, which can raise the temperature of the tires T. In step S6, the time for rolling the tires T while being pressed with the first load can be set according to the desired temperature of the tires T and the performance of the tires T, such as wear resistance, and is not particularly limited. The time for rolling the tires T while being pressed with the first load is, for example, the time for the slip angle to complete 1 to 10 cycles, and in this embodiment, it is set to the time for the slip angle to complete 1 cycle. Also, in this embodiment, the cornering force is not measured in step S6.

[0033] As shown in Figures 2 and 3, after step S6, the set load is changed to a third load that is smaller than the first load and different from the second load (step S7). In this embodiment, the third load is a smaller value than the second load. The third load may be, for example, 50% or less of the first load, or 40% or less of the first load. The third load is, for example, a value equivalent to or less than the minimum load expected to occur during load transfer when the vehicle turns. In this embodiment, in step S7, when the set load is changed to the third load, the slip angle is not changed and the cornering force is not measured.

[0034] Subsequently, a third loading step is performed in which the tires T are pressed against the upper surface 21 of the belt 20 with the set third load (step S8). Since the tires T are rolled while being pressed with the first load in steps S2 and S6, the temperature of the tires T rises due to frictional heat. Therefore, measurements can be taken in a higher temperature range than when the tires T are simply rolled while being pressed with the third load.

[0035] In step S8, where the tire T is rolled while being pressed with a third load, the cornering force of the tire T is measured sequentially. The time for rolling the tire T while being pressed with the third load can be set according to the indicator of cornering performance to be measured and the performance of the tire T, such as wear resistance, and is not particularly limited, as in step S4. The time for rolling the tire T while being pressed with the third load is, for example, the time for the slip angle to complete 0.5 to 5 cycles, and in this embodiment, it is set to the time for the slip angle to complete 1 cycle. The time for rolling the tire T while being pressed with the third load may be the same as or different from the time for rolling the tire T while being pressed with the second load in step S4 described above.

[0036] The method for evaluating the cornering performance of this embodiment may involve repeating steps S1 to S8 n (n≧2) times. By repeating steps S2 to S8 multiple times, the temperature of the tire T can be further increased. In other words, by repeating steps S2 to S8 multiple times, the cornering performance of the tire T at even higher temperatures can be evaluated.

[0037] The number of times n is repeated from step S2 to step S8 above is not particularly limited, but for example, it is between 3 and 20.

[0038] As shown in Figures 2 and 3, the method for evaluating cornering performance in this embodiment involves determining after step S8 whether the number of times steps S1 to S8 have been repeated has reached a predetermined number of repetitions n (step S9). If the number of times steps S1 to S8 have been repeated has reached a predetermined number of repetitions n (step S9: Yes), this flow is terminated.

[0039] On the other hand, if the number of times steps S2 to S8 above have been repeated has not reached the predetermined number of repetitions n (step S9: No), the process returns to step S1, the set load is changed from the third load to the first load, and steps S1 to S8 above are executed again.

[0040] Figure 4 shows the measurement results of the inner surface temperature of the tire T when evaluated using the cornering performance evaluation method of this embodiment under a 25°C environment, as an example. Also in Figure 4, as Comparative Example 1, the measurement results of the inner surface temperature of the tire T when the tire T is pressed against the upper surface 21 of the belt 20 with only the first load. Also in Figure 4, as Comparative Example 2, the measurement results of the inner surface temperature of the tire T when the tire T is pressed against the upper surface 21 of the belt 20 with only the second load. Also in Figure 4, as Comparative Example 3, the measurement results of the inner surface temperature of the tire T when the tire T is pressed against the upper surface 21 of the belt 20 with only the third load. In the example shown in Figure 4, the second load was set to 62.5% of the first load, and the third load was set to 25% of the first load.

[0041] As shown in Figure 4, under each condition, the internal temperature of the tire T rises due to frictional heat as the tire T is continuously rolled. On the other hand, in Comparative Examples 2 and 3, which have small loads, and especially in Comparative Example 3, the temperature does not rise sufficiently even when the tire T is continuously rolled. In other words, under the conditions of Comparative Examples 2 and 3, it is difficult to evaluate the cornering performance at high temperatures even when the tire T is continuously rolled.

[0042] As shown in Figure 4, under the conditions of the embodiment, the internal temperature of the tire T rises significantly by continuously rolling the tire T. Therefore, it can be said that the method of this embodiment makes it possible to measure the cornering performance at high temperatures when low loads are applied, as in Comparative Examples 2 and 3.

[0043] The above embodiments can be modified as appropriate without altering the objective of the present invention. For example, in the above embodiments, in addition to the second loading step of applying a second load, there is a third loading step of applying a third load, but the second loading step alone may be used. Furthermore, the cornering performance when other loads (for example, loads lower than the third load) are applied in addition to the second and third loads may be evaluated simultaneously. Note that if the number of types of loads applied increases too much, the measurement will take longer and the tire T tends to wear down more easily. [Explanation of Symbols]

[0044] 1 Flat belt testing device, 10 Rollers, 20 Belt, 21 Top surface (Simulated road surface) ), 30 Turntable, 40 Tire support device, 41 Tire axle, 42 Support section, T Tire.

Claims

1. A method for evaluating the cornering performance of a tire using a flat belt testing device, A first load step that presses the tire against the upper surface of the rotating belt with a first load, After the first loading step, the second loading step involves pressing the tire against the upper surface of the rotating belt with a second load smaller than the first load, while measuring the mechanical elements representing the cornering performance of the tire and the temperature of the tire. A method for evaluating cornering performance, comprising the following features.

2. The method for evaluating cornering performance according to claim 1, wherein the second load is 80% or less of the first load.

3. After the second loading step, the third loading step involves pressing the tire against the upper surface of the rotating belt with a third load that is smaller than the first load and different from the second load, while measuring the mechanical elements representing the cornering performance of the tire and the temperature of the tire. The method for evaluating cornering performance according to claim 1, further comprising the above.

4. The method for evaluating cornering performance according to claim 3, wherein the third load is smaller than the second load.

5. The method for evaluating cornering performance according to claim 1, wherein in the second load step, the temperature of the tire is measured by an infrared sensor.

6. The method for evaluating cornering performance according to claim 1, wherein in the second load step, the temperature of the tire is measured by a contact sensor.

7. The method for evaluating cornering performance according to claim 1, wherein in the second loading step, the slip angle of the tire changes continuously over time.

8. The method for evaluating cornering performance according to claim 7, wherein the angular velocity of the slip angle is substantially constant.

9. The method for evaluating cornering performance according to claim 1, wherein in the first loading step, a mechanical element representing the cornering performance of the tire and the temperature of the tire are measured.

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