JP7056344B2 - Tire performance evaluation method and performance evaluation device - Google Patents

Description

The present invention relates to a method for evaluating the performance of a tire on a wet road surface and the like.

Conventionally, various methods have been proposed for evaluating the performance of a tire. For example, in Patent Document 1, the maximum acceleration when a vehicle traveling on a frozen road surface at a predetermined speed is braked is measured, and a plurality of maximum accelerations are measured by changing the measurement speed, and the measured speed and the maximum are measured. A technique for obtaining a linear regression equation with acceleration is disclosed.

In recent years, due to the growing safety awareness of users, there is a demand for tires that exhibit excellent performance on wet road surfaces. Then, it is desired to establish a technique for evaluating the performance of a tire regarding a hydroplaning phenomenon that occurs when a vehicle traveling at high speed passes through a wet road surface having a large water depth.

Japanese Unexamined Patent Publication No. 09-288045

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a method for evaluating the performance of a tire on a wet road surface.

The present invention is a method for evaluating the performance of a tire on a wet road surface, wherein the vehicle on which the tire is mounted is driven on a wet road surface, and the tire is suddenly braked to stop the vehicle. The step, the measurement step of measuring the speed and acceleration of the vehicle during the braking step in time series, and the time-series change of the acceleration of the vehicle measured in the measurement step, during the braking step. It includes a calculation step of estimating the hydroplaning convergence speed of the tire.

In the performance evaluation method according to the present invention, the hydroplaning convergence speed is the speed at the time when the rate of change of the acceleration function indicating the relationship between the acceleration and the time in the braking process becomes small. , Is desirable.

In the performance evaluation method according to the present invention, the calculation step calculates a first acceleration function which is a function of the acceleration and the time within a predetermined first time range at the initial stage of braking of the tire. 1 Calculation step and the average value of the acceleration within a predetermined second time range of the braking end of the tire or the second acceleration function which is a function of the acceleration and time within the second time range. It is desirable to include a second calculation step for calculation and an estimation step for estimating the velocity at the time when the first acceleration function and the second acceleration function intersect as the hydroplaning convergence velocity.

In the performance evaluation method according to the present invention, it is desirable that the first time is 10% or more of the total braking time.

In the performance evaluation method according to the present invention, it is desirable that the second time is 10% or more of the total braking time.

In the performance evaluation method according to the present invention, it is desirable that the first acceleration function is a linear approximation straight line of the acceleration in the first time.

In the performance evaluation method according to the present invention, it is desirable that the first acceleration function is a linear approximation straight line of the moving average curve of the acceleration in the first time.

In the performance evaluation method according to the present invention, it is desirable that the second acceleration function is an average value of the accelerations in the second time.

In the performance evaluation method according to the present invention, the calculation step may further include a third calculation step for calculating a third time from the start of braking to the intersection of the first acceleration function and the second acceleration function. desirable.

In the performance evaluation method according to the present invention, it is desirable that the estimation step obtains the hydroplaning convergence speed based on the speed of the vehicle after the lapse of the third time from the start of braking.

In the performance evaluation method according to the present invention, it is desirable to evaluate the performance of the tire on the wet road surface based on the hydroplaning convergence speed.

In the performance evaluation method according to the present invention, it is desirable to evaluate the performance of the tire on the wet road surface based on the acceleration after the hydroplaning has converged.

The present invention is a device for evaluating the performance of a tire on a wet road surface, in which a vehicle equipped with the tire is driven on a wet road surface and the tire is suddenly braked to stop the vehicle. It includes measuring means for measuring the speed and acceleration of the vehicle in time series, and calculating means for estimating the hydroplaning convergence speed of the tire based on the change in the acceleration of the vehicle in time series.

The performance evaluation method of the present invention includes a braking process in which a vehicle to which the tire to be evaluated is mounted and traveling on a wet road surface is suddenly braked to stop, a measurement process in which the speed and acceleration of the vehicle are measured in time series, and a tire. Includes a calculation step to estimate the high loplanning convergence rate. In the calculation process, the high-loplaning convergence speed is estimated based on the time-series changes in the acceleration of the vehicle.

For tires with hydroplaning, it is desirable to converge the hydroplaning in the high speed range and quickly recover the grip of the tire. In the present invention, by estimating the hydroplaning convergence speed in the calculation process, it is possible to accurately and accurately evaluate the performance of the tire on a wet road surface.

The performance evaluation device of the present invention is a measuring means for measuring the speed and acceleration of a vehicle in chronological order by suddenly braking and stopping a vehicle running on a wet road surface on which the tire to be evaluated is mounted, and a high-loplaning convergence of the tire. Includes computational means for estimating speed. The calculation means estimates the high-loplaning convergence speed based on the time-series changes in the acceleration of the vehicle.

For tires with hydroplaning, it is desirable to converge the hydroplaning in the high speed range and quickly recover the grip of the tire. In the present invention, the calculation means estimates the hydroplaning convergence speed, which makes it possible to accurately and accurately evaluate the performance of the tire on a wet road surface.

It is a schematic diagram which shows one Embodiment of the performance evaluation apparatus of this invention. It is a flowchart which shows the procedure of the performance evaluation method of this invention. It is a conceptual diagram which shows the process of estimating the hydroplaning convergence speed from the speed and acceleration of a vehicle. It is a flowchart which shows the detail of the calculation process of FIG. It is a figure which shows the relationship between the acceleration of a vehicle, and the 1st acceleration function calculated in the 1st calculation process. It is a figure which shows the relationship between the acceleration of a vehicle, and the 2nd acceleration function calculated in the 2nd calculation process. It is a figure which shows the velocity V at the time when the 1st acceleration function and the 2nd acceleration function intersect. The figure which shows the measured velocity and acceleration data, the calculated acceleration function, and the hydroplaning convergence velocity with respect to a tire A. The figure which shows the measured velocity and acceleration data, the calculated acceleration function, and the hydroplaning convergence velocity with respect to a tire B.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the configuration of the performance evaluation device 1 of the present embodiment. The performance evaluation device 1 is a device for evaluating the performance of the tire 2 on a wet road surface 100.

As shown in FIG. 1, the performance evaluation device 1 of the present embodiment includes a measuring means 3 and a calculating means 4. Although the measuring means 3 and the calculating means 4 of the present embodiment are mounted on the vehicle 10 to which the tire 2 to be evaluated is mounted, they may be installed outside the vehicle.

The measuring means 3 causes the vehicle 10 equipped with the tire 2 to travel straight on the wet road surface 100, suddenly brakes the tire 2 to stop the vehicle 10, and measures the speed and acceleration of the vehicle 10 in time series. The measuring means 3 of the present embodiment has a speed sensor 31 and an acceleration sensor 32.

The wet road surface 100 is intended, for example, a road surface in a wet state covered with a water film of about several mm. When a vehicle traveling at high speed passes through such a wet road surface 100, a so-called hydroplaning phenomenon may occur in which the tire 2 is lifted by the hydrodynamic pressure of water.

Hydroplaning includes complete hydroplaning, where the tires are completely lifted off the road surface, and tires are partially lifted off the road surface (for example, the tread area on the ground surface is partially lifted and the kicking area is in contact with the road surface). There is partial hydroplaning. Hereinafter, the tire in the partially hydroplaned state will be described, but the present invention is also applicable to the tire in the fully hydroplaned state.

The sudden braking is intended to be strong enough to put the tire 2 in a partially hydroplaning state. The speed of the vehicle 10 in which the tire 2 is in the partially hydroplaning state gradually decreases, and then the hydroplaning converges and recovers to the grip state.

The measuring means 3 measures the speed and acceleration of the vehicle 10 from before the start of braking to the stop in time series. Therefore, the speed and acceleration measured by the measuring means 3 include the speed and acceleration of the vehicle 10 in the partially hydroplaning state and the speed and acceleration of the vehicle 10 restored to the grip state.

The speed sensor 31 detects the speed of the vehicle being braked in chronological order. The speed sensor of the present embodiment identifies the position of the vehicle 10 at each time by receiving a signal transmitted from a GPS (Global Positioning System) satellite, and acquires the speed. The speed sensor 31 is not limited to the one using GPS as long as the speed sensor 31 can accurately detect the speed of the vehicle even when the tire 2 is locked due to sudden braking.

The acceleration sensor 32 detects the acceleration of the vehicle 10 during braking in time series. The accelerometer 32 detects acceleration by a mechanical, optical or electromagnetic (capacitance or the like) method. Since the acceleration is calculated from the speed and the speed is calculated from the acceleration, the speed and the acceleration may be measured in time series from either the speed sensor 31 or the acceleration sensor 32.

The speed detected by the speed sensor 31 and the acceleration detected by the acceleration sensor 32 are input to the calculation means 4 as electric signals.

The calculation means 4 is a computer device that estimates the hydroplaning convergence speed of the tire 2 by processing the electric signals input from the speed sensor 31 and the acceleration sensor 32. The calculation means 4 of the present embodiment estimates the hydroplaning convergence speed of the tire 2 based on the time-series change of the acceleration input from the acceleration sensor 32.

In the tire 2 in which hydroplaning has occurred, it is desirable that the hydroplaning is converged in a high speed region and the grip force of the tire 2 is quickly restored. In the present invention, the calculation means 4 estimates the hydroplaning convergence rate. This makes it possible for the performance evaluation device 1 to accurately and accurately evaluate the performance of the tire 2 on a wet road surface 100, as compared with a device that evaluates the performance by, for example, simply measuring the braking distance.

FIG. 2 shows a flowchart showing the procedure of the performance evaluation method of the present invention. This performance evaluation method is a method for evaluating the performance of the tire 2 on a wet road surface 100. The performance evaluation method includes a braking process S1, a measurement process S2, and a calculation process S3.

The braking step S1 is a step of driving the vehicle 10 on which the tire 2 is mounted on the wet road surface 100 and suddenly braking the tire 2 to stop the vehicle. In the braking step S1, the hydroplaning generated immediately after the sudden braking converges as the speed decreases, and the vehicle 10 stops after recovering to the grip state.

In the measurement step S2, the speed and acceleration of the vehicle 10 in the braking step S1 are measured in time series by the calculation means 4. As described above, the speed and acceleration measured in the measurement step S2 include the speed and acceleration of the vehicle 10 in the partially hydroplaning state and the speed and acceleration of the vehicle 10 restored to the grip state.

The calculation step S3 is a step of estimating the hydroplaning convergence speed of the tire 2 in the braking step S1. In the calculation step S3, the hydroplaning convergence speed of the tire 2 in the braking step S1 is estimated based on the time-series change of the acceleration of the vehicle 10 measured in the measurement step S2. In the present invention, the hydroplaning convergence speed is estimated in the calculation step S3. This makes it possible to accurately and accurately evaluate the performance of the tire 2 on a wet road surface 100, as compared with, for example, a method of evaluating the performance by simply measuring the braking distance.

FIG. 3 is a conceptual diagram showing a process of estimating the hydroplaning convergence speed from the speed detected by the speed sensor 31 and the acceleration detected by the acceleration sensor 32. In the figure, the horizontal axis shows time (transition of time), the vertical axis on the left side shows velocity, and the vertical axis on the right side shows acceleration.

In this example, the sudden braking is started when the vehicle 10 traveling on the wet road surface 100 reaches a predetermined speed (for example, 100 km / h). After the deceleration G (negative acceleration) rises due to sudden braking, partial hydroplaning occurs, and the deceleration G gradually increases. After that, it recovers to the grip state where a constant deceleration G is generated as the hydroplaning converges.

As shown in FIG. 3, in the region where partial hydroplaning occurs, the deceleration G tends to change slowly, while in the region where the grip state is restored, the change in deceleration G becomes smaller. Therefore, when the rate of change of the acceleration function indicating the relationship between the acceleration and the time in the braking step S1 becomes smaller than a predetermined threshold value, it can be estimated that the hydroplaning has converged and the grip state has been restored.

Therefore, in the calculation step S3, the computer device, which is the calculation means 4, derives an acceleration function indicating the relationship between the acceleration detected by the acceleration sensor 32 and the time t, and the rate of change of the acceleration function is a predetermined threshold value. When it becomes smaller than, it is estimated that the hydroplaning has converged. That is, the velocity V when the rate of change of the acceleration function becomes smaller than the predetermined threshold value is acquired as the hydroplaning convergence velocity.

FIG. 4 shows the details of the calculation step S3. The calculation step S3 includes a first calculation step S31, a second calculation step S32, and an estimation step S34.

FIG. 5 shows the relationship between the acceleration a detected by the acceleration sensor 32 and the first acceleration function a1 calculated in the first calculation step S31. In the figure, the reference time is set so that the time when braking is started is 2 seconds (the same applies to FIGS. 6 and 7 below). In the first calculation step S31, the first acceleration function a1 = f (t), which is a function of the acceleration and the time within the predetermined range of the first time T1 at the initial stage of braking of the tire 2, is calculated.

The first time T1 mainly includes the time when hydroplaning is occurring. The first time T1 is set short so as not to include the time when the hydroplaning converges. The first hour T1 is preferably 10% or more of the total braking time. As a result, the calculation means 4 can accurately derive the first acceleration function a1. The first time T1 may include a moment when sudden braking is started, but in this example, after hydroplaning occurs after the deceleration G suddenly rises due to the sudden braking (the deceleration G decreases). It is set as the time after it has settled down to a substantially constant value.

The first acceleration function a1 calculated in the first calculation step S31 is preferably a linear approximation straight line of the acceleration a in the first time T1. In this case, the first acceleration function a1 is represented by, for example, a1 = βt + γ (β and γ are constants). As a result, the calculation means 4 can accurately derive the first acceleration function a1 in a short time.

The first acceleration function a1 calculated in the first calculation step S31 is preferably a linear approximation straight line of the moving average curve of the acceleration a in the first time T1. As a result, the detection error of the acceleration sensor 32 is rounded, and the first acceleration function a1 can be accurately derived in a short time.

FIG. 6 shows the relationship between the acceleration detected by the acceleration sensor 32 and the second acceleration function a2 calculated in the second calculation step S32. In the second calculation step S32, the second acceleration function a2 = g (t), which is a function of the acceleration and the time within the predetermined range of the second time T2 at the end of braking of the tire 2, is calculated.

The second time T2 mainly includes the time in the grip state after the hydroplaning has converged. In the grip state, since the rate of change of the second acceleration function a2 is small, it may be approximated to a substantially constant value. In this case, the second acceleration function a2 = constant. Can be approximated by the average value of the accelerations within the range of the second time T2. The second acceleration function a2 may be a linear approximation straight line of the acceleration a at the second time T2.

The second time T2 is set short so as not to include the time when the hydroplaning converges. The second time T2 is preferably 10% or more of the total braking time. As a result, the calculation means 4 can accurately derive the second acceleration function a2. The second time T2 may include the moment when the vehicle 10 stops.

FIG. 7 shows the relationship between the first acceleration function a1 and the second acceleration function a2 processed in the estimation step S34. In the estimation step S34, the velocity V at the time t12 where the first acceleration function a1 and the second acceleration function a2 intersect is estimated as the hydroplaning convergence velocity.

As shown in FIG. 4, the calculation step S3 may further include a third calculation step S33 between the second calculation step S32 and the estimation step S34. The third calculation step S33 is a step in which the calculation means 4 calculates the third time T3 from the start of braking to the time t12 when the first acceleration function a1 and the second acceleration function a2 intersect.

In this case, in the estimation step S34, the calculation means 4 acquires the hydroplaning convergence speed based on the speed V of the vehicle 10 after the lapse of the third time T3 from the start of braking. For example, the calculation means 4 approximates the relationship between the speed and the time of the vehicle 10 detected by the speed sensor 31 with a linear function or a quadratic function, and after the lapse of the third time T3 from the start of braking (time t12). ), The speed V of the vehicle 10 can be calculated and used as the hydroplaning convergence speed. In the approximation by the above function, the moving average of the speed of the vehicle 10 detected by the speed sensor 31 may be calculated.

In the present invention, it is possible to evaluate the performance of the tire 2 on the wet road surface 100 based on the hydroplaning convergence speed estimated in the calculation step S3. That is, it is considered that a tire having a high hydroplaning convergence speed recovers quickly to a grip state and has high safety. Such an evaluation is particularly effective in developing a tread pattern having excellent drainage performance.

Further, in the present invention, the deceleration G in the speed range lower than the hydroplaning convergence speed estimated in the calculation step S3, that is, the acceleration after the hydroplaning has converged, is used for the tire 2 on the wet road surface 100. It is possible to evaluate the performance. That is, it is considered that a tire having a large deceleration G after the hydroplaning has converged and recovered to the grip state contributes to the deceleration of the vehicle 10 at the end of braking and has high safety. Such an evaluation is particularly effective in developing a tread rubber compound having excellent wet grip performance.

Although the performance evaluation device 1 and the performance evaluation method of the present invention have been described in detail above, the present invention is not limited to the above-mentioned specific embodiment, but is modified to various embodiments.

The performance of two different types of tires A and B on a wet road surface was evaluated using the performance evaluation device 1 and the performance evaluation method shown in FIGS. 1 to 7. The road surface used for the evaluation was an asphalt road surface having a watering facility, and the water film thickness was set to 2 mm. The sizes of the tires A and B are 215 / 45R18, and they are mounted on the four wheels of a vehicle equipped with ABS (Antilock Brake System) having a displacement of 2000 cc and a vehicle weight of 1330 kg, respectively.

FIG. 8 shows the measured velocity and acceleration data, the calculated acceleration function, and the hydroplaning convergence velocity for the tire A. FIG. 9 shows the measured velocity and acceleration data, the calculated acceleration function, and the hydroplaning convergence velocity for the tire B.

The speed of the vehicle at the start of braking was 100 km / h, and the braking distance required for the speed to decelerate to 5 km / h was also measured. Table 1 shows the test results. In Table 1, the index of the test result of the tire B with the test result of the tire A as 100 is also shown.

In this test, there was no significant difference in braking distance between tires A and B. However, it was confirmed that the tire B has a high hydroplaning convergence speed and excellent drainage performance of the tread pattern. On the other hand, it was confirmed that the tire A had a high average value of the deceleration G in the second hour T2 and was excellent in the wet grip performance of the tread rubber compound. By the performance evaluation device 1 and the performance evaluation method, it becomes possible to separately determine the influence of the tread pattern and the tread rubber composition on a plurality of types of tires on the tire performance.

1: Performance evaluation device 2: Tire 3: Measuring means 4: Calculation means 10: Vehicle 31: Speed sensor 32: Accelerometer 100: Wet road surface S1: Braking process S2: Measurement process S3: Calculation process S31: First calculation process S32 : 2nd calculation process S33: 3rd calculation process S34: Estimating process T1: 1st time T2: 2nd time T3: 3rd time V: Velocity a: Acceleration a1: 1st acceleration function a2: 2nd acceleration function

Claims (13)

A method for assessing tire performance on wet roads.
A braking process in which a vehicle equipped with the tires is driven on a wet road surface and the tires are suddenly braked to stop the vehicle.
A measurement process for measuring the speed and acceleration of the vehicle during the braking process in chronological order,
A calculation step of estimating the hydroplaning convergence speed of the tire during the braking step based on the time-series change of the acceleration of the vehicle measured in the measurement step.
Tire performance evaluation method. The performance evaluation of the tire according to claim 1, wherein the hydroplaning convergence speed is the speed at the time when the rate of change of the acceleration function indicating the relationship between the acceleration and the time in the braking process becomes small. Method. The calculation step is
A first calculation step for calculating a first acceleration function, which is a function of the acceleration and the time within a predetermined first time range at the initial stage of braking of the tire,
The second calculation to calculate the average value of the acceleration within the predetermined second time range of the braking end of the tire or the second acceleration function which is a function of the acceleration and the time within the second time range. Process and
The tire performance evaluation method according to claim 1 or 2, further comprising an estimation step of estimating the speed at the time when the first acceleration function and the second acceleration function intersect as the hydroplaning convergence speed. The tire performance evaluation method according to claim 3, wherein the first hour is 10% or more of the total braking time. The braking performance evaluation method according to claim 3 or 4, wherein the second time is 10% or more of the total braking time. The tire performance evaluation method according to any one of claims 3 to 5, wherein the first acceleration function is a linear approximation straight line of the acceleration in the first time. The tire performance evaluation method according to any one of claims 3 to 5, wherein the first acceleration function is a linear approximation straight line of the moving average curve of the acceleration in the first time. The tire performance evaluation method according to any one of claims 3 to 7, wherein the second acceleration function is an average value of the accelerations in the second time. The tire performance evaluation method according to claim 8, wherein the calculation step further includes a third calculation step of calculating a third time from the start of braking to the intersection of the first acceleration function and the second acceleration function. The tire performance evaluation method according to claim 9, wherein the estimation step acquires the hydroplaning convergence speed based on the speed of the vehicle after the lapse of the third time from the start of braking. The tire performance evaluation method according to any one of claims 1 to 10, wherein the performance of the tire on the wet road surface is evaluated based on the hydroplaning convergence speed. The method for evaluating tire performance according to any one of claims 1 to 11, wherein the performance of the tire on the wet road surface is evaluated based on the acceleration after the hydroplaning has converged. A device for evaluating the performance of tires on wet roads.
A measuring means for measuring the speed and acceleration of the vehicle in time series by driving the vehicle equipped with the tire on a wet road surface and suddenly braking the tire to stop the vehicle.
A calculation means for estimating the hydroplaning convergence speed of the tire based on the time-series change of the acceleration of the vehicle.
Tire performance evaluation device.

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