JP2001097005A - Pneumatic tire for abs mounted vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for an ABS-mounted vehicle which can reduce the braking distance in the ABS-mounted vehicle by a method other than increasing the peak μ value of the tire. SOLUTION: In a pneumatic tire for an ABS-mounted vehicle, the brake rigidity ratio which is the μ value at the slip ratio of 3% divided by the peak μvalue in the μ-S characteristic of the tire measured on a dry road surface is 0.47 or over, or the offset gradient expressed by the formula is 0.18 or under. The offset gradient=(peak μ value -μ value at the slip ratio of 50%)/(50 -slip ratio corresponding to the peak μ value)×100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a vehicle equipped with an ABS (anti-lock brake system), which is effective for shortening a braking distance of the vehicle.

[0002]

2. Description of the Related Art In recent years, various safety devices have been developed for the purpose of improving the driving safety of automobiles. In the case of a braking device, there is a case where an ABS device is mounted in order to enhance safety during braking. It has increased. This ABS device
As shown in FIG. 1, this is a device for controlling a braking state at the time of braking so that a slip ratio is maintained substantially constant except immediately before stopping. At this time, the slip ratio is controlled so that the μ value in the μ-S characteristic (friction coefficient-slip ratio characteristic) of the tire is close to the peak μ value at which the μ value becomes maximum. The μ value (friction coefficient) of the tire is a value obtained by dividing a longitudinal force generated from the tire during braking by a vertical load, and the slip ratio is expressed by the following equation 1.

Slip ratio (%) = (Vr−Vt) / Vr × 100 (1) [Vr: body speed, Vt: peripheral speed of wheels] And there has been no concept of a tire suitable for a vehicle equipped with ABS. Regardless of the presence or absence of the ABS device, a tire having a high frictional force on the tread rubber was considered to be effective for shortening the braking distance.

[0004]

It is considered effective to increase the peak μ value of a tire even for an ABS-equipped vehicle. However, a tire using a rubber having a high frictional force for a tread rubber generally has a high wear resistance. There is a problem in that the braking distance is reduced by increasing the frictional force due to poor performance and high rolling resistance.

On the other hand, as shown in FIG.
In the operating characteristics of the device, a large number of slips occur at a slip rate lower than the slip rate corresponding to the peak μ value of the tire, and the most frequent slip rate is also smaller than the slip rate corresponding to the peak μ value. It turned out to be somewhat lower. In other words, it has been found that, in a general ABS device, the conventional tire does not always effectively use the vicinity of the peak μ value of the tire, and there is room for further shortening the braking distance.

[0006] Further, as shown in FIG.
In the operating characteristics of the device, if the slope of the curve in the μ-S characteristic of the tire (the degree of inclination at a portion exceeding the slip ratio corresponding to the peak μ value) is large, the frequency of occurrence of the high slip ratio increases, It has been found that the braking distance increases.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a pneumatic tire for an ABS-equipped vehicle that can reduce a braking distance in an ABS-equipped vehicle by a method other than increasing the peak μ value of the tire.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies on the relationship between the μ-S characteristics of the tire and the operation characteristics of the ABS device based on the above findings. The rising slope of the -S characteristic is above a certain value,
The inventors have found that the above object can be suitably achieved when the drop gradient of the μ-S characteristic is equal to or less than a certain value, and have completed the present invention. That is, the pneumatic tire for an ABS-equipped vehicle of the present invention relates to the following first to third inventions.

The pneumatic tire for an ABS-equipped vehicle of the first invention has a brake rigidity, which is a value obtained by dividing a μ value of a slip ratio of 3% by a peak μ value in a μ-S characteristic of a tire measured on a dry road surface. , 0.47 or more.

The pneumatic tire for an ABS-equipped vehicle according to the second invention has the following formula in the μ-S characteristic of a tire measured on a dry road surface: drop slope = (peak μ value−μ at a slip ratio of 50%)
Value) / (50-slip ratio corresponding to peak μ value) × 1
The depression gradient represented by 00 is 0.18 or less.

The pneumatic tire for an ABS-equipped vehicle according to the third invention has a brake rigidity, which is a value obtained by dividing a μ value of a slip ratio of 3% by a peak μ value in a μ-S characteristic of a tire measured on a dry road surface. , 0.45 or more, and the following equation: Depth slope = (Peak μ value−μ at a slip rate of 50%)
Value) / (50-slip ratio corresponding to peak μ value) × 1
The depression gradient represented by 00 is 0.20 or less.

Each numerical value relating to the μ-S characteristic of the tire described above is a value measured as follows.

For the measurement, a measuring device as shown in FIG. 4 is used. First, the tire pressure and the load are adjusted in the same manner as in the actual vehicle braking test, and the test tires 11a and 11b and the load cells 12a and 12b for detecting the load are used by using a standardized dry road surface for testing. A towed vehicle 16 having braking disc brakes 13a and 13b and speed detectors 14a and 14b for detecting speed from an axle.
Is pulled by the tractor 15 at a speed of 64 km / h. At this time, braking is applied to only one of the disc brakes 13a, the peripheral speed Vt of the wheel on the test tire 11a side is measured by the speed detector 14a, and the peripheral speed of the wheel on the test tire 11b side to which no braking is applied is measured. The vehicle speed is measured by the detector 14b and set as the vehicle speed Vr. The tire slip ratio is calculated from these values using the above-described formula 1, and the μ value is calculated by dividing the longitudinal force detected by the load cell 12a during braking by the vertical load. From the relationship between the μ value and the slip ratio, the μ-S characteristics of the tire on a dry road surface are determined, and the above-mentioned numerical values related to the μ-S characteristics are specified.

[Operation and Effect] According to the pneumatic tire for an ABS-equipped vehicle of the first invention, since the brake rigidity corresponding to the rising gradient of the μ-S characteristic is equal to or higher than a certain value, AB
As the operating characteristics of the S device, for a large number of slips occurring at a slip ratio lower than the slip ratio of the peak μ value, the braking loss can be reduced by the larger μ value, so that the total braking distance can be reduced. it can.

According to the pneumatic tire for an ABS-equipped vehicle according to the second aspect of the present invention, since the drop gradient of the μ-S characteristic is equal to or less than a predetermined value, it is possible to reduce the frequency of occurrence of a high slip ratio in the operation characteristic of the ABS device. As a result, the total braking distance can be reduced.

According to the pneumatic tire for an ABS-equipped vehicle of the third invention, since the brake rigidity of the μ-S characteristic is equal to or more than a certain value and the descent gradient is equal to or less than a certain value, According to the operation of the second aspect, the total braking distance can be reduced.

It was confirmed that the brake rigidity and the drop gradient had a high correlation with the braking distance of the ABS-equipped vehicle as follows in relation to the actually measured values.
That is, test tires having various μ-S characteristics were mounted on vehicle types A to D having different tire sizes to which the ABS device was mounted, and a braking distance from 100 km / h per hour to a stop was measured. Based on this measured value, multiple regression analysis was performed using the brake rigidity, the drop gradient, and the peak μ value as variables,
The multiple regression coefficient shown in FIG. 5, that is, a regression equation was obtained. From this regression equation, the predicted braking distance in the combination of each vehicle type and each test tire was calculated. As a result, FIG.
As shown in the graph of (d), it was confirmed that there was a high correlation between the predicted braking distance and the actually measured braking distance.
That is, it was confirmed from the relationship with the actually measured values that the brake rigidity and the drop gradient had a high correlation with the braking distance of the vehicle equipped with ABS.

On the other hand, the lower limit value of the brake rigidity and the upper limit value of the drop gradient in the present invention are values determined from the results of the examples described later, and are compared with the most common braking distances of tires. This is a value set so that the braking distance is reduced by 3% or more. A more preferable range of the brake rigidity and the drop gradient is a value set so that the braking distance is reduced by 5% or more as compared with the most common tire. .56 or more, and in the second invention, the drop gradient is 0.08
Preferably, the third aspect has a brake rigidity of 0.50 or more and a drop gradient of 0.14 or less.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The pneumatic tire for an ABS-equipped vehicle according to the present invention has a tread pattern and tread as long as it has a μ-S characteristic which falls within the range of the above-described brake rigidity and / or drop gradient. The rubber composition, the reinforcing material and structure of the tire, the manufacturing method, and the like are not limited at all. Therefore, the pneumatic tire of the present invention can be manufactured by adjusting the brake rigidity and the drop gradient in the following manner according to various known techniques.

That is, in order to increase the brake rigidity, there are a method of increasing the rigidity of the tread and a method of increasing the rigidity by using a tire reinforcing material or a reinforcing structure. As the former, there are a method of making the block shape of the tread pattern vertically long in the circumferential direction, and a method of increasing the elastic modulus of the tread rubber itself.
As the latter, there are a method of increasing the rigidity of the carcass layer by changing the material and the like, and a method of increasing the elastic modulus of the bead filler.

On the other hand, in order to reduce the drop gradient, a method of increasing the amount of carbon black or an oil component (plasticizer),
Examples thereof include a method using carbon black having a small particle diameter, a method using SBR of high styrene and SBR of high vinyl, and the like.

Each of the above-mentioned techniques is a known or well-known technique as an element technique for controlling the characteristics of a tire, and does not require any detailed description when a person skilled in the art implements the present invention. The outline of a pneumatic tire to which the above-described elemental technology is applied is as follows. However, the following description does not limit the present invention in any way.

Generally, a pneumatic tire is shown in FIG.
As shown in the sectional view of FIG. 1, a pair of annular bead portions 1 and side wall portions 2 each extending from the bead portion 1 to the outer peripheral side.
And a tread portion 4 that connects the outer peripheral ends of the sidewall portions 2 to each other via a shoulder portion 3. The bead portion 1 is provided with a bead wire bundle 1a and a bead filler 1b surrounded by the carcass layer 5, and the bead portion 1 locks the end of the carcass layer 5 so that the tire is mounted on the rim R. Fit firmly on top. Rubber layers are formed on both sides of the carcass layer 5, and in a tubeless tire, an inner liner layer is formed on the innermost layer. FIG.
As shown in the partially cutaway view of FIG. 2B, a belt layer 6 for reinforcing by a hoop effect is arranged on the outer peripheral portion of the carcass layer 5, and a tread pattern 4a is formed on the outer peripheral surface by tread rubber.

The raw rubber for the rubber layer and the like includes natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR) and the like. These rubbers are reinforced with fillers such as carbon black and silica, and are appropriately compounded with a vulcanizing agent, a vulcanization accelerator, a plasticizer, an antioxidant and the like.

As a bead wire, a steel wire or the like is used, and as a constituent material of the carcass layer 5 or the belt layer 6, steel, organic fiber, or the like is used. Each of these materials is usually subjected to a surface treatment, an adhesive treatment, or the like in order to enhance the adhesiveness to rubber.

The pneumatic tire of the present invention is used for a vehicle equipped with ABS. Although the operating characteristics of the ABS device are basically as described above, slight changes may occur in the operating characteristics due to differences in the detection means, control method, braking device, and the like. The present invention is basically applicable to any ABS device that can have the above-mentioned problem regardless of the presence or absence of the change.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below.

EXAMPLES AND COMPARATIVE EXAMPLES First, in the known tire manufacturing method, 20 types of test tires having various μ-S characteristics were manufactured by changing the manufacturing method based on the above-mentioned index. This test tire is
Vehicles A to D with different tire sizes equipped with a BS device were mounted, and the braking distance from 100 km / h per hour to a stop was measured.

Tables 1 to 3 show combinations of the measured values thus obtained, in which the braking distance can be easily compared directly. Table 1 shows the effect on the braking distance due to the difference in the brake rigidity, Table 2 shows the effect due to the difference in the drop gradient, and Table 3 shows the effect due to the difference in the brake rigidity and the drop gradient. The lower limit value of the brake rigidity and the upper limit value of the drop gradient in the present invention are values determined from this result and other similar results, and are compared with the braking distance of the most common tire. Is set to be reduced by 3% or more.

[0030]

[Table 1]

[Table 2]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a graph showing the operating characteristics of an ABS device over time.

FIG. 2 is a graph showing operating characteristics of an ABS device in relation to a slip ratio.

FIG. 3 is a graph showing the operating characteristics of the ABS device for different tires.

FIG. 4 is a schematic configuration diagram showing a measuring device used for measuring μ-S characteristics.

FIG. 5 is a graph showing a correlation between an actually measured value and a predicted value of a braking distance of a vehicle equipped with ABS.

FIG. 6 shows an example of a general pneumatic tire.

[Explanation of symbols]

 4 Tread portion 4a Tread pattern 5 Carcass layer 11a Test tire 11b Test tire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiko Kawamura 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. (72) Makoto Kimura 1-17-18 Edobori, Nishi-ku, Osaka, Osaka No. Toyo Tire & Rubber Co., Ltd. (72) Inventor Yoshiyuki Yasui 2-1-1 Asahi-cho, Kariya-shi, Aichi Prefecture Aisin Seiki Co., Ltd. (72) Inventor Hirofumi Nita 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Within Seiki Co., Ltd. (72) Inventor Tsuyoshi Yoshida 2-1-1 Asahicho, Kariya City, Aichi Prefecture Inside Aisin Seiki Co., Ltd.

Claims (3)

[Claims] An AB having a brake rigidity of 0.47 or more, which is a value obtained by dividing a μ value of a slip ratio of 3% by a peak μ value in a μ-S characteristic of a tire measured on a dry road surface.
Pneumatic tire for S-equipped vehicles. 2. A drop slope represented by the following equation in a μ-S characteristic of a tire measured on a dry road surface is 0.1.
A pneumatic tire for an ABS-equipped vehicle which is 8 or less. Fall slope = (Peak μ value-μ at 50% slip rate)
Value) / (50-slip ratio corresponding to peak μ value) × 1
00 3. A brake rigidity, which is a value obtained by dividing a μ value of a slip ratio of 3% by a peak μ value in a μ-S characteristic of a tire measured on a dry road surface, is 0.45 or more, and the following: A pneumatic tire for an ABS-equipped vehicle having a drop gradient represented by a formula of 0.20 or less. Fall slope = (Peak μ value-μ at 50% slip rate)
Value) / (50-slip ratio corresponding to peak μ value) × 1
00